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Dissertations, Theses, and Masters Projects Theses, Dissertations, & Master Projects
1971
Potential Five-Coordinate Titanium-Diketonate Complexes
Pamela Bowen Barrett College of William & Mary - Arts & Sciences
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Recommended Citation Barrett, Pamela Bowen, "Potential Five-Coordinate Titanium-Diketonate Complexes" (1971). Dissertations, Theses, and Masters Projects. Paper 1539624729. https://dx.doi.org/doi:10.21220/s2-phf3-f166
This Thesis is brought to you for free and open access by the Theses, Dissertations, & Master Projects at W&M ScholarWorks. It has been accepted for inclusion in Dissertations, Theses, and Masters Projects by an authorized administrator of W&M ScholarWorks. For more information, please contact [email protected]. POTENTIAL FIVE-COORDINATE TITANIUM-
M -DIKETONATE COMPLEXES
A T h e sis
Presented to
The Faculty of the Department of Chemistry
The College of William and Mary in Virginia
In Partial Fulfillment
Of the Requirements for the Degree of
Master of Arts
By
Pamela Bo B arrett
1971 APPROVAL SHEET
This thesis is submitted in partial fulfillm ent of
the requirements for the degree of
Master of Arts
A u th o r /
Approved, May 1971
D av id W • Th omp s on , /PhTiD •
C irila D^ordjevic, Ph.D,
Melvjrn D • S o h iav elii, Ph • D •
i i
5 04110 ACKNOWLEDGMENTS
The w riter wishes to express her appreciation to
Professor David W. Thompson, under whose guidance this inves tigation was conducted, for his direction and criticism throughout the investigation. The author is indebted also to Professor C irila Djordjevic and Professor Melvin D.
Schiavelli for their careful reading and criticism of the manuscript. Finally, the author wishes to express a special note of thanks to her husband, Richard Barrett, for his invaluable encouragement and assistance.
iii TABLE OP CONTENTS
Page
ACKNOWLEDGMENTS ...... I l l
LIST OP TABLES ...... ' ...... v i l
LIST OP PIGURES...... v i l l
ABSTRACT ..o»».o. x
REACTIONS OP TITANIUM TETRAHALIDES WITH POTENTIAL t BIDENTATE UNINEGATIVE LIGANDS - LITERATURE SURVEY
A. PRELIMINARY CONSIDERATIONS 1
B. A -DIKETONE DERIVATIVES 4 X. Historical Perspective 4 2® Di-Substituted Products 6 3® Adducts of -^-Diketones with Titanium 16 4® Mono-Substituted .^-Diketonate 17 Compounds with Titanium 5® Tri-Substituted -^-Diketonate Complexes 18 with Titanium 6® Tetra-Substituted>^-Diketonate Com- 21 pounds of Titanium f 0 . COMPOUNDS WITH 8-QUINOLINOL 21 1* Adducts of 8-Quinolinol 21 2® Mono-Substituted Complexes of 8- 32 Q u in o lin o l 3® Di-Substituted Complexes of Titanium 33 with 8-Quinolinol 4® Tris-Substituted Complexes of 8- 34 Q u in o lin o l 5® Tetra-Substituted Complexes of 36 Titanium with 8-Quinolinol
D« COMPOUNDS WITH SALICYLALDEHYDJ3 41 1® Di-Substituted Complexes 41 2® Tetra-Substituted Complexes of 41 Titanium with 8-Quinolinol and Sallcylaldehyde
iv TABLE OF CONTENTS CONT'D.
E . SERIES OF OXIMES WITH TITANIUM 45 TETRAHALIDES 1. Adducts of Oximes with Titanium 45 Tetrahalides 2. Mono-Substituted Complexes of 49 Titanium with Oximes
P . COMPLEXES OP TITANIUM TETRACHLORIDE 53 WITH ACETANILIDES 1• Di-Substituted Complexes of 53 Acetanilides' with Titanium 2e Tri-Substituted Complexes of 53 Acetanilides with Titanium
G. SUMMARY 5 6
EXPERIMENTAL eeoeteeoeeceeoeooeodo 57
REAGENTS eeeoveeaooaeeaeeaeeaa 57
SOLVENTS fiea«e*oe«<»««»e««»e PREPARATIONS 53 General Reaction Procedures 58 j Preparation of 3-Cyano-2,4-pentanedione 59 Preparation of 2,2,6,6-tetramethyl-3»5- 63 heptanedione Reaction of Titanium Tetrachloride and 64 3-Cyano-2,4-pentanedione in a 1:2 Molar Ratio Reaction of Titanium Tetrachloride and 65 3-Cyano-2,4-pentanedione in a 1:3 Molar Ratio Preparation of Trichloro(3-cyano-2,4- 65 pentanedionato)titanium(IV) Preparation of Trichioro(1-phenyl-1 93 - 65 butanedionato)titanium(IV). Preparation of Tribromo(1-phenyl-1,3- 66 butanedionato)titanium(IV) v TABLE OP CONTENTS CONT’D* P a g e Preparation of Tribromo-2,2,6,6- 67 tetram ethyl-3,5-heptanedionatotitanium (IV) Preparation of Trichloro(2,4-pentane- 67 dionato)titanium(IV) Reaction of Dicyclopentadienyltitanium 68 dichloride with Acetylacetone Preparation of Trichloro(1-phenyl-1,3- 68 butanedionato)~pyridinetitanium( IV) Preparation of Trichloroacetylacetonato- 69 pyridinetitanium(IV) PHYSICAL MEASUREMENTS •••-••••••••..o'* 69 Molecular Weights 69 Conductance Measurements 71 Halide Determinations 71 Melting Points 71 Infrared Spectra 71 Nuclear Magnetic Resonance Spectra 72 Analysis 72 DISCUSSION AND RESULTS...... '•••'••-•••••73 Preparative Chemistry 73 Trihalo(^-diketonato)titanium (lV) Complexes 85 Trichloro(3-cyano-2 94-pentanedionato)- 103 titanium(lV) Conclusion 108 POOTNOTES oeeoo 1t8 vi LIST OP TABLES T a b le Page t -^-DIKETONATE COMPLEXES ...... 22 2 8-QUIN0LIN0LATE COMPLEXES ...... 37 3 SALICYLALDEHYDATO COMPLEXES ...... 46 4 OXIME DERIVATIVES ...... 51 5 ACETANILIDE DERIVATIVES ...... 54 6 ANALYTICAL DATA ...... o. 76 7 MOLECULAR WEIGHT DATA ...... 77 8 CONDUCTANCE DATA ...... 78 9 CHARACTERISTIC INFRARED ABSORPTIONS BY ^-DIKETONATE COMPLEXES CONTAINING TERMINAL METHYL GROUPS ...... 93 10 C-N STRETCHING FREQUENCY OF METAL COMPLEXES .....oe.....o«. 107 vii LIST OP FIGURES Figure Page 1 Structural Possibilities for Compounds in the TiX^-LH System ...... 3 2 Generalized reaction scheme for the interaction of titanium tetrahalides with potential uninegative bidentate ligands • • 6oo»«*«ea99«e 3 3 Isomeric possibilities for_dihalobis (1-phenyl-1.3-butanedionationato)- titanium (IV) •»osooa»**e««» 13 4 UMR Spectra of IiX 2 ( b z a c ) 2Complexes » « 15 5 Isomeric possibilities for dihalobis- (8-quinolinolato)tltanium(IV) a * * « 35 6 Diagram of apparatus for the preparation of titanium enolate complexes » e e « 60 7 Diagram of apparatus immediately prior tO filtration aaaeaaoaaoee 6 l 8 Diagram of apparatus after filtrationa a 62 9 Diagram of filtering funnel used to dry compound a « e a aaaaaaa»ae 62 10 Beckmann thermometer «»o»0a«a»a 70 11 Infrared spectrum of trichloro(2,4-pentane- dionato)titanium(lV) as a Mull In NUjOl aaaaaaoaeaaasas 79 12 Infrared spectrum of Pyridine as a Mull I n Nlljj Ol oaseoaaaeaaaao 80 13 Infrared spectrum of trichloro-( 2,4- pentanedionato)-pyridinetitanium- * (IV) as a Mull in Uujol » « a « • » 81 14 Infrared spectrum of trichloro(1-penyl- 1,3“butanedionato)pyridinetltanlum- (IV) as a Mull in Nujol • « « * • « 82 viii LIST OF FIGURES CONT'D.> Figur Page 15 The structure of (TiCl^/POCl )2 • • • • • 8? 16 Infrared spectrum of tribromo(2,2.6,6- tetram ethyl-3,5-heptanedionato)- titanium(lV) as a Mull in Nujol . * • 89 17 Infrared spectrum of tribromo(1-phenyl- 1, 3-butanedionato)titanium(IV) as a Mull in Nujol » o • • ...... « • 90 j 18 Infrared spectrum of trichioro(1-phenyl- 1, 3-butanedionato)titanium(IV) as a Mull in Nujol • • « • ••«••••• 91 19 Infrared spectrum of trichloro(1,3- diphenyl-1,3-propanedionato)titanium- (IV) as a Mull in Nu^ol ? 0 « -92 20A B, 0, D-Hmr spectra for mixtures of trichloro(1-phenyl-1,3-butanedionato)- titanium(IV) and dichlorobis(1-phenyl- 1, 3-butanedionato ) tit anium( IV) « e e> « 96 20 Nmr spectra (shifts relative to internal TMS) 97 21 Nmr spectrum of tribrom o(1-phenyl-1,3- butanedionato)titanium(IV) in methylene chloride 93 22 Nmr spectrum of tribrom o(2,2,6,6-tetram ethyl- 3 95-heptanedionato)titanium(IV) In methylene chloride 99 23 Nmr spectrum of trichloro(2,2,6,6- tetram ethyl-3,5-heptanedionato)- titanium(IV) in chloroform • e « » • « 100 24 Postulated structure for trichloro(3-cyano- 2s4-pentanedionato)titanium(lV) « • « 104 25 Infrared spectrum trichioro(3-cyano- 2,4-pentanedionato)-titanium(IV) as a Mull llu 3 ol 0»«90c»0feo«o<>e 10 6 ix ABSTRACT The intent of this work was to investigate reactions of titanium tetrachloride and titanium tetrabromide with several enolizable A-diketones. These diketones usually coordinate to metal atoms as the anion via both oxygens• Particular attention was directed toward the preparation and characterization of potentially five-coordinate com plexes of the type X 3TiL, X = Cl* Br and L = A-diketonate anion* since few five-coordinate complexes of titanium have been reported« A«x)iketones used in this study include 2,^-pentanedione * 3-cyano-2,*l'-pentanedione, l-phenyl-l*3- butanedione, 1,3-diphenyl-l*3-propanedione* and 2*2,6*6- tetramethyl-3*5-heptanedione. In addition to preparing and characterizing X^TiL complexes* attempts were made to prepare two pyridine^adducts of the potentially five coordinate complexes» x POTENTIAL FIVE-COORDINATE TITANIUM- >3-DIKETONATE COMPLEXES REACTIONS OF TITANIUM TETRAHALIDES WITH POTENTIAL BIDENTATE UNINEGATIVE LIGANDS- LITERATURE SURVEY A. PRELIMINARY CONSIDERATIONS In recent years there has been a great deal of interest in the reactions of titanium tetrahalides with potential 1 -7 bidentate uninegative ligands such as 2,^-pentanedione , o 8 1-phenyl-1*3-butanedione , 1* 3-diphenyl-l* 3-propanedione * 9 10-12 3-methyl-2»^-pentanedione * 8-quinolinol * salicylalde- 1 2 ,1 3 1** lb hyde , dimethyIglyoxime , dipehnylglyoxime , benzil lb 15-16 monoxime , benzoylacetanilides and acetoacetanilide * These potential bidentate ligands can react with the tita nium tetrahalides to give several distinct types of com- # pounds. Among these ares 1) Lewis acid-base adducts such 17 as tetrachloro(2,^-pentanedione)titanium(IV) , TiX^LH, where LH is a neutral ligandi 2) monosubstituted complexes of the type X^TiL, where L is an anionic ligand, such as J 10,11 trichloro(8-quinolinolato)titanium(IV) j 3) disubstituted XoTiLo complexes such as dichlorobis(3-methyl-2,^-pentane- 9 dionato)titanium(IV) ? k) tri-substituted complexes co n *In this paper, adduct is used to define a molecular com pound formed by the interaction of a Lewis acid and a Lewis base in which all original bonds remain intact. However, stereochemical rearrangement may, and usually does, occur in the acceptor* 1 2 taining an L^Ti+ cation* such as tris(3-methyl-2*4-pentane- Q dion«ato)titanium(IV) hexachloroantimonate(IV) % and 5) tetra- substituted compounds* TiL^* such as tetrakis(8-quinolino- 13 lato)titanium(IV) Apart from establishing stoichiometric relationships in the TiXty-LH systems* elucidation of molecular structure has been of major concemi 1) For complexes of the type Xjj.Ti*LH* there has been a question as to whether the com pounds were (a) simple Lewis acid-base adducts* or (b) ionic salt-like compounds• (See Figure 1) 2) Complexes with the empirical formula X^TiL pose the question of (a) monomeric versus (b and c) dimeric or oligiomeric struc tures. Dimers may form via halogen or oxygen bridges* as illustrated. 3) For complexes of the type XgTiLg* both monomeric and ionic structures shown are plausible. In addition* geometric isomerism is possible for the monomeric non-ionic structure. 4) In the tri-substituted complexes of the type XTiL^* a (a) six-coordinate ionic structure and a (b) seven-coordinate non-ionic structure a!re possible. 5) The tetra-substituted complexes may possess either six (a)* seven (4b) or eight (5^) coordinate titanium* as illustrated. If all ligands are bidentate* the titanium is eight coordinati? If* however* any anions bind as monodentate ligands* then six or seven coordinate structures will result. Figure 2 describes a generalized scheme for the reaction of the titanium tetrahalides with the uninegative potential bidentate ligands. Hypothetically* stepwise substitution 3 FIGURE 1 Structural Possibilities for Compounds in the TiXjj-LH System 4 may occur to form mono- through tetra-substituted complexes# with adduct formation as a preliminary, and in some cases 17 isolable, intermediate • Thus far only adducts, mono- and di-substituted complexes have been prepared by direct reaction of a titanium tetrahalide and a neutral ligand* With the exception of the halotris(8-quinolinolato)titanium (IV) com plexes, tri- and tetra-substituted products have only been prepared by indirect means, as illustrated in Figure 1. Certain steps in the reaction scheme have been shown to be reversible• B.^-DIKETONE DERIVATIVES 1 H istorical Perspective The f i r s t Jb -diketone complex of titanium was reported o in 1904 by Dilthey . From the reaction of 2,^-pentanedione with titanium tetrachloride, a product was isolated having an empirical formula TiClgCacacJg, acac = 2,^-pentanedionate anion* On the basis of a rather high melting point (191°)# the compound was postulated to be bisCtris(2,^-pentanedio- nato) titanium(IV) ] hexachlorotitanate(IV )«. These results 1 ft were confirmed by YoungAO who supported the salt-like struc ture postulated by Dilthey, on the basis of sim ilarity to tris(2,^-pentanedionato)silicon(IV) chloride• In 1961 Mehrotra and co-workers*9-2lre-examined TiC^CacacJg obtained by the method of Dilthey* Molecular weight measure ments in benzene showed the compound to be monomeric* In 5 Ti X, * LH— > XTiLH - HCl \ . Z . / / Xn Ti L n > V C / 3 1 'T iX 2 2 4 LH X LH. TiL, 3J X J i Ln 2 2 TiL FoCl 3 4 J > I FIGURE 2 Generalized. Reaction Scheme for the Interaction of Titanium Tetrahalides with PotentiallUninegative Bidentate Ligands /' ' ■ J • ' • - . \ s . 1 J 7 " 7' 6 addition to the molecular weight data# Mehrotra reported what he considered to be a low conductivity in nitrobenzene# -1 2 -1 -3 7 ohm cm mole (1.80 x 10 .^solutions). This value is somewhat high for a nonelectrolyte, but not high enough to suggest a ltl electrolyte. Mehrotra proposed the following structure as consistent with the above date. CH CH 1 3 C} 1 3 o N l . / o = - c C— 0 !x 0 — Cl CH Mehrotra also prepared TiCl2(acac)2 by reacting 20 diethoxybis(2,ty-pentanedionato)titanium(IV) with hydrogen chloride in benzene Ti(OC2H5)2(acac)2 + 2HG1 ^ TiCl2(acac)2 * 202H^0H and showed the reversibility of this process by reacting dichlorobis(2,4-pentanedionato)titanium(IV) and ethanol in the presence of anhydrous ammonia. The ease of the reverse reaction was cited as further evidence that the complex T iC l2 ( a c a c )2 had a simple monomeric structure. 2 Di-substituted Products 3 * ^ 7 # 2 2 More recent investigations by Fay and co-workers have presented conclusive evidence about the structure of the 7 dihalobis(2,4-pentanedionato)titanium(IV) complexes. These workers prepared the difluoro, dichloro, and dibromobis- (2,4-pentanedionato)titanium(IV) compounds. Molecular weight determinations by vapor pressure osmometry in benzene show the compounds to be monomeric. Conductivities in nitro- -1 2 -1 -3 benzene of less than 1 ohm cm mole for 10 M solutions demonstrated that the complexes are non-electrolytes. The r molar conductances differ according to the group of workers. Mehrotra and co-workers for example» reported values of 6.7- 8.6 ohm"*cm2mole"* for 1 x 10~3 to 3 x 10“3 m s o l u t i o n s in nitrobenzene for TiCl<>(acac)oe These values are much * * 23 larger than expected for a non-electrolyte and do not agree with the values reported by Pay and Lowry^ or Cox* Lewis and Nyholm^, who give a value of 1.2 ohm^^cm^mole”1 for a 10"3 M nitrobenzene solution. The differences in the con ductivities may be due to partial hydrolysis. Mehrotra 20-21 and co-workers did not seem to be aware of the extreme sensitivity of these compounds to moisture* since no pre cautions were reported in handling these compounds. Fay and Lowry also found that the conductivities were very time dependent, and suggested that their conductivities be regarded as upper lim its. (See Table 1 for complete list of physical properties.) Infrared spectra in the **00-2000 cm"* region show the expected bands for the oxygen-chelated 2,4-pentane- 24-26 dionate ligand . The abscence of bands in the region 1600-1800 cm"*, and the prescence of strong bands in the 1500-1600 cm"* region indicate that all the carbonyl groups 8 are coordinated via oxygen to the meta.1# All data are consistent with these compounds being mono meric , nonionic# oxygen-chelated, six-coordinated complexes« If octahedrally coordinated, the dihalobis(2,4»-pentane- dionato)titanium(IV) complexes may possess either the cis or trans structure, illustrated below. a C Ho * C H ^ X C H 3 y ^ C 1 The nmr spectra of these two geometrical isomers should, in principle, be different. 2n the trans structure (point g ro u p 1^2^) , there is only one ring proton environment and only one methyl environment.• The cis structure (point group Cg), however, possesses two distinct methyl environments . •At room temperature the proton nmr spectra1**7 of the TiX2(acac)2 X F, Cl, and Br, show only one methyl and one ring proton . resonance. As the temperature is lowered, however, the methyl resonance broadens,'and ultim ately splits into two distinct peaksj the ring proton resonance remains sharp® The coales cence temperatures for the difluoro, dichloro, gibromo are 9 O' -63°C, -26°C, and -3^ C respectively. These observations unambiguously indicate that these compounds have the cis structure, at least in solution at low temperatures. At room temperature there is rapid interchange of the methyl groups between the two non-equivalent sites of the cis 7 isomer , and thus only a single averaged methyl signal is o b s e r v e d . 7 From nmr line shape analysis, Fay and Lowry were able to determine kinetic and thermodynamic parameters for the exchange of methyl protons between the two non-equivalent methyl group sites. First order rate constants for methyl group exchange at 25° are 1.6 x 10^ sec~* (X=F), 6.7 x 102sec“* (X^Cl), and 2.3 x 10^ sec""1 (X=Br). Since the activation , —1 energies (11.6-0.5,Fj 11.2-0.6,01? 11.6io.^,Br kcal --fflole )_ appear to be identical within experimental error, the differ ence in lability was ascribed to the differences in entropy of activation (-2.^-2.3*F? -10.0-2.3,01? -6.3-1*6,Br, e.u.). Thus far a definitive mechanism can not be assigned to methyl group exchange, but several possibilities do exist. The exchange mechanism appears to be a first-order reac tion, since the mean residence time at each site is indepen dent of concentration. There are four possible exchange mechanisms* dissociation of a halide ion to give a five coordinate intermediate? rupture of an M-0 bond to give a five coordinate intermediate which has one monodentate 2,^-pentanedionate ligand? complete dissociation of one 2,**- pentanedionate ligandi and tw ist mechanisms which exchange methyl groups without metal-ligand bond rupture. Halogen dissociation can reasonably be eliminated for three reasons. First, the activation energies are indepen dent of the halide. Secondly, methyl group exchange has been reported by Bradley and Holloway for the dialkoxides, Ti(OR)2(acac)2, which exhibit sim ilar activation energies. Thirdly, nmr spectra indicate that the rate of halide inter change is slow compared with the rate of exchange of methyl groups in the equilibrium mixture of TiFgCacac)^ and TiBr2(acac) Exchange of 2,^-pentanedionate ligands with excess 2,^-pentanedione is not observed under conditions where ex change of TiX2(acac)2 methyl groups is fast. For this reason, the meohanism involving the complete dissociation of an 2, *4—pentanedionate ligand seems unlikely. Based on the cur rent data, the rupture of one of the M-0 bonds and/or the twisting of ligands are the preferred choices for the mechan ism of exchange. Diiodobis(2,^-pentanedionato)titanium(IV) is anomalous 3 in relation to the other dihalo-complexes*; Conductance, esr, and low-temperature nmr measurements indicate that T il2(acac)2 exists in dichloromethane solution as 50% c i s , trans, and approximately 10% of an electrolytic product, + - presumably [T il2(acac)2 ] I and 0,13% of a paramagnetic Ti(III) species. T il2(acac)g gives no mnr spectrum at room tempera ture i the spectrum is observed only below about 0°C« Fay 11 and Lowry ascribe disappearance of the nmr spectrum to a rapid rate process which exchanges the 2,4-pentanedionate ligands between the diamagnetic and paramagnetic species. Thompson, Somers, and Workman have prepared an analogous series of titanium compounds containing the 3-methyl-2,4- pentanedionate ligand^. By reaction of the ligand and titanium tetrahalides in 2il mole ratios, TiXgCCgH^Og^ = and Br) were obtained. Infrared, conductivity, and molecular weight data (Table 1) are consistent with the complexes containing che lated ^-diketonate ligands, and having a non-ionic, monomeric structure. Low temperature nmr studies also indicate that the dihalo complexes possess the cis octahedral structure. In 1964 Lewis et a l. allowed to react both benzoylace- tone(bzac),1-phenyl-1,3-butanedione, and dibenzoylmethane(bzbi), l,3-diphenyl-l,3-propanedione, with titanium tetrachloride and prepared the di-substituted products. This work reported only the elemental analyses, molar conductivities and molecu lar weights (Table 1), which are consistent with a non-ionic and monomeric structure. Q Fay and Serpone have re-examined0 the dichloro-complexes of 1-phenyl-1,3-butanedione, and 1,3-diphenyl-1,3-propane- dione, and extended studies to the difluoro- and dibromo- complexes. They also found that the molecular weight and conductivity data are consistent with a monomeric, non-ionic structure. In addition, they investigated the stereochemistry 12 and lability of the compounds via nmr methods. The 1-phenyl- 1 , 3-butanedionato ligand is unsymmetrical, therefore a dihalo- bis(l-phenyl- 1 , 3-butanedionato)titanium complex yields the possibility of five isomeric structures, instead of the 7 usual two for a symmetrical ligand such as 2,4-pentanedione • The five isomers are shown in Figure 3« ^lie ois-cis-cis isomer (a) has no symmetry (point group C^) and should, therefore, have two methyl, two phenyl, and two ring proton resonance lines in the nmr spectrum. The cis-cis-trans (b) (C2)> cis-trans-cis (c) (C2)» trans- cis-cis (d) (C2v), and trans-trans-trans (e) ( 03^) all possess at least a twofold axis, which thus renders each pair of protonic groups symmetry equivalent, and a single resonance for each type of group should be observed. Low temperature nmr studies have, to some extent, clarified the stereochemis try. Figure ^a shows a reproduction of the fluorine nmr Q spectra of TiF 2 ( b z a c )2 from Fay’s paper . Fay points out that "lines 1,2,5 and 6 comprise ah AB pattern due to the two nonequivalent fluorine atoms of the cis-cis-cis isomer. Lines 1 and 2 and l i n e s 5 and 6 are equally spaced and these lines exhibit the expected relative intensities. Lines 3 and k’ must arise from two of the other isomers. Since the cis- cis-cis isomer is definitely present and since the corres ponding TiX 2 ( a c a c )2 complexes exist exclusively in the cis configuration in dichloromethane solution, it is most reason able to assign lines 3 and k to the other two isomers which / \ ' ^ 7 / * x " ^ » Me Me cis-cis-cis cis-cis-trans b Me e I \ Ph K X cis-trans-ois trans-cis-cis d t r an s - tr an s - tr ans r e The first cis or trans refers to the position of the X atoms with respect to each other; the sec ond cis or trans refers to the relative orientation of the benzoyl groups; and the third cis or trans refers to the relative orientation of the acetyl ends of the benzoylacetonate ligands. FIGURE 3 Isomeric Possibilities for Dihalobis ( 1-phenyl-l,3-butanedIonationato) titanium (B?) 14 8 have the halogen atoms in cis positions . « .M . The rela tive intensities indicate that the compound exists in solu tion as a statistical mixture of the three cis isomers t ( 0.50 cis-cis-cis, 0.2 5 cis-cis-trans, and 0.25 cis-trans-cis.) The proton nmr spectrum of TiFgfbzacJg in the methyl region, at low temperatures, is also consistent with the existence of the three cis isomers in solution. Of the four peaks, (Figure 4b) two can be assigned to the cis-cis-cis isomer, and one each to the other cis isomers. The proton nmr spectrum (Figure 4c) in the methyl region of the cJhloro- and bromo- complexes unambiguously indicates the prescence of at least one cis isomer, and may be reason ably interpreted as indicating the existence of all three cis isomers in a statistical mixture. The proton nmr spectra of the TiXg^zbzJg complexes indicate that they too have the cis configuration. With decreasing temperature, the phenyl resonance broadens, presumably due to a rapid exchange between the two non-equiva lent sites of the cis isomer; the line broadening is not ex pected for a trans isomer. No low temperature spectra were reported. In general the l,3-diphenyl-l,3-propanedionates and the 1-phenyl-1,3-butanedionates behave very much the same as the 2,4-pentanedionates. All three groups are moderately soluble in dichldromethane, chloroform, acetonitrile, nitrobenzene and acetone, but nearly insoluble in ether, -H ♦34*i -if “37.5* -«6# -23* -50* -31.5* 39.5* . ^ - u LX u . -47* -60S* *7315 a 5 cpa J ' - -TTf" - 1 l £»k»l^ “24* • 3 a s > * * ^ FIGURE 4 NMR Spectra of T iJ^bzac^ Complexes 16 7 8 carbon tetrachloride, and saturated hydrocarbons • Sol ubility decreases as the halogen varies F>Cl?Br# The 1,3- diphenyl-1,3-propanedionates are less soluble than the 2,4—pentanedionates. Solubility decreases with increasing phenyl substituents. In summary, infrared, molecular weight and conductivity measurements are consistent with the formulation of the di- halobis^-diketonates as oxygen-chelated, monomeric, non ionic complexes. Furthermore, all bis 4-diketonates studied appear to have only the cis configuration, with the excep tion of diiodobis(2,4-pentanedionato)titanium(IV)^. The reasons for the predominance of the cis configuration are not clear. Bradley and Holloway^, however, suggest that "tr-bond- in g (pfT oxygen** d ft metal) is a significant factor because in the cjLs-complex, all three d* orbitals of titanium will be involved, whereas in the trans-complex only two of the d^ orbitals can participate,” even though steric considerations would seem to favor the trans isomer. In the diiodobis- (2,^-pentanedionato)titanium(IV) compound, however, the much larger size of the iodine atoms causes the steric effects to outweigh the if-bonding in contributing to the stability of the trans isomer. The physical properties of the bis-^-diketonate titanium complexes are summarized in Table 1. 3 Adducts of ^-Diketones with Titanium Only one report of a ^-diketone adduct with a titanium 17 17 tetrahalide is found in the literature • Allred and Thompson prepared the 2,^-pentanedione adduct of titanium tetrachloride in 1968 . The infrared spectrum of this com- —1 pound showed a strong peak at 1670 cm * which is the absorp tion for a perturbed carbonyl group* not a chelated enolate. Adducts of the non-enolizable 3*3-dimethyl-2,4-pentanedione were also prepared with the titanium tetrahalides* except fluoride. Although only one adduct has been isolated* it is likely that adduct formation preceeds the loss of hydro gen chloride to form enolate derivatives. Attempts were made to isolate the adduct of titanium tetrachloride and 3-methy1- 2,^-pentanedione without successes only the mono-substituted enolate complex* trichloro(3-methyl-2,*f-pentanedionato)- titanium(IV) was obtained. M ono-substituted ^-Diketonate Compounds with Titanium In the 2*^-pentanedione series* there is only one prepar ation listed for the mono-substituted product* TiCl^(acac). Trichloro(2,^-pentanedionato)titanium(IV) was prepared in 1962 by Mehrotra and co-workers * by reacting 2*4-pentanedione with titanium tetrachloride in a lil mole ratio. This com pound was not characterized beyond determing the per cent chloride and titanium. Thompson and co-workers prepared two mono-substituted 3-methyl-2**J'-pentanedionato complexes with TiX^ ( X = Cl and Br)^. The conductivity and molecular weight data are consis- 18 tent with the mono-substituted complexes having a non-ionic# monomeric structure in nitrobenzene. Infrared data show that the compounds contain only oxygen-chelated ligands. The nmr spectra of the tribromo-compound were complex# and indi cated more than one species in solution. The preparation of the X2TiL2 and X^TiL compounds are sim ilar. Since these compounds are generally moisture sen- i sitive, and hydrolyze readily in solution# extreme caution is necessary to insure that all solvents are water free. Sol vents were dried by refluxing and distilling over suitable dehydrating agents# such as phosphorous pentoxide^ o r c a l - 7 cium hydridef• Synthesis and handling of the compounds were conducted in a dry nitrogen atmosphere. The syntheses were carried out in inert solvents# such as methylene chloride or benzene. 5 Tri-substituted A-Piketonate Complexes with Titanium Although tris-substituted A-diketonate complexes can not be obtained by direct synthesis# several have been iso lated by reacting TiCl^Lg with Lewis acids such as antimony pentachloride or ferric chloride (see Figure 2). It may be that TiCl^ is not a strong enough Lewis acid to remove chloride# or that chloride itself is not a large enough anion 27 to stabilize the cation The first such product# [Ti(acac)^|[ FeCl^] # prepared from the reaction of TiC^CacacJg with ferric chloride# has 19 2*6*19*28 been the subject of several studies . There was 29 some question in itially as to whether the compound was / C1\ (acac)TiCl Fe(acac) \ 2 / 2 x c r or CTi(acac)^][FeCl^] • Fackler et a l. proved from exami nation of the ultraviolet spectrum that the latter formu- 2 lation is correct# supporting Dilthey’s original contention • In addition to the ultraviolet# Fackler# also used Moss- bauer absorption to prove the anionic species was FeClj^ by comparison with compounds known to possess the [FeGl^“] anion. The Mossbauer isomeric shift forCTi(acac)^ DCFeCl^] in the solid state compares favorably with that of (C^H^)^- AsFeCl^* which is known to contain the slightly distorted tetrahedrstl FeCljj,“ anion. It has become clear that Puri and Mehrotra based the formulation of a monomeric species AQ Z on incorredt conductance data. Neither Fackler nor Lewis has been able to duplicate Mehrotra*s2^ data# but did concur with one another. Cox# Lewis and Nyholm prepared a series of compounds + 6 containing the Ti(acac)^ cation * to further confirm the existence of that species. In addition to conductance data and ultraviolet# Lewis et a l. offer conductometrie titra tions as further confirmation of the compound as [ Ti(acac)^] [F e C l4 ] ~ . Cox et a l.^ prepared not only [Ti(acac)^][FeClj^] » [Ti(acac)^][SbCl^] * and [Ti(acac) ^-diketonate cationic species of titanium* [Ti(bzbz) 3 ] [ F e C l ^ and [Ti(bz ao)^]CFeCl^] • These workers prepared the cationic derivatives by treating the dichloro-titanium compounds with iron(III) chloride, and also by reacting the corresponding iron(III) chelate with titanium tetrachloride. The prepara* tion of the compound via the second reaction appears to be the first in which a ^-dijcetonate anion transfer from iron is involved. Thompson^ prepared two other complexes containing a tris- substituted ,£-diketonate cationic species with 3-m e th y l- 2,^-pentanedione and FeClj^“ and SbCl^*. Conductance measure ments in nitrobenzene and acetonitrile indicate that these complexes are 111 electrolytes. Fay and Serpone*^*^ prepared Ti(acac)^+ complexes w ith C l 6 j^~ and 13”* All of the tris-substituted titanium complexes appear t o be 1«1 electrolytes containing six-coordinate cations. Fay and Pinnavaia prepared some tris -substituted complexes 32 of zirconium and hafnium . The compounds prepared were MX(acac)^ ( M = Zr and Hf, X-Cl, Br, and I for Zr only). In contrast to the titanium complexes, molecular weight and conductance data indicate that all of the halo compounds are monomeric in solution. Except for the mono-iodide, molar conductances in ionizing solvents are small compared with conductances for analogous lil electrolytes, such as at the same concentrations. Fay postulates that the 21 zirconium and hafnium complexes are seven coordinated species in solution# which is in contrast to the six-coordinate Is 1 electrolytes of the titanium series, 6 Tetra-substituted A-Piketonate Compounds of Titanium There is only one attempt mentioned in the literature for a preparation of a tetra-substituted ^-diketonate complex* 13 Frazer reacted TiClgCacacJg with 2#4-pentanedione in the presence of triethylamine in hopes of isolating Ti(acac)^# but obtained the reduced product# Ti(acac)^# instead* C* COMPOUNDS WITH 8-QUINOLINOL 1 Adducts of 8-Quinolinol The i n t e r a c t i o n o f 8 - q u i n o l i n o l ( oxH# 8 -h y d ro x y - quinoline) with the titanium tetrahalides has been examined 1 0 -1 4 thoroughly by Frazer and co-workers * From the reaction of the titanium tetrahalides with 8-quinolinol in varying mole ratios# in inert solvents# at room temperature or below# several adducts and apparent adducts have been isolated* Among these ares TiX^»oxH# X * F# Cl# Br* TiX^*2oxH# X = F, Cl# Br# Is TiCl^*3oxH? TiXj^4oxH# X - Cl# Br« It is interesting to note that TiX^*2oxH are obtained by three different methods of preparation* The first reac tion involves the direct addition of titanium tetrahalide to 8-quinolinol in a Is2 molar ratio0 Secondly# one mole of 22 o n Oi' 5 o S ia S I o n g 4h -=3‘ VO vo 9 o o T3 .Q rH CM s t .=*■ rH ’« o 9 • • H vo on o O O rH o o ON ■=r ON rH o O on on CM on CM on on ■=3- g 'O O O o o CM o n .=r o ONON -=j- 0 H rH CM 8 4 . c i on 1 ONON .= f ON rH rH CM rH CM CVJ CM CM 0 § 8 8 1 1 8 CM CM CM CM rH rH rH O § § I Complex Characterization Structural Assignment Ref •H ■8 i •P Q I CO Mc ^ ^ ^ i f i f >1 s g o g o s o ft, A O I & vi rv A >1 i O ii CM s 8 e a CM £ ctf § t % & CM CM w i f B > H« O O o b CM b b b rH b s CM CM o f cF b 'o b b g ON a s >& C*- CM m« rH c o i n rH VO i n m v o OO rH r H O CM -=r LA -=r -=r -=j- on o -=r ^ on on vo vo in CO c o o n -=r .=*• -=r if in in in m vo s i n rH CO o i n o n o rH CM CM on -=r o \ i n c o c o o o CM CO CO CO -S3” c o -= r c o i n i n i n in vo O O CO $ o • O UTN v o CO in o o O O o v o a in o o CO OO O CM CM o ON ON ON rH CM I 1 CM rH rH CM in in CM I • 9 8 CO lA A ON i f CM CO o ON ON ON O o v o I — CM rH rH CM CM CM CM CM CM CM CM CM CM CM CM CM CM O CM CM O N N tsi ci N .Q .O rO 1 N . 0 N . N tsJ I 3-vo o€ 1 3 . o N o w XI «o o\ cr\ o \ co co vo oo oo oo vo oo PS$ I U ii & & § §5 i s §g § s g I I EI § g g E a> cm CM cm ^ / —■ CM ^CM CM CM CM CM CM CM CM O O CM CM O 0 *Tq N aT N B sT * € vo a a fl ■s vo o o I .O ja •Q o ^ JO ^jO CM '^CM ICM >>CM r-S ^ CM rH* rH^ _CM r5“ o S3 o Q a i EH g 1 & S XI/—•. bO^ on bO bO on on 6 i O C\J on 'o o rH I I o o s rH 0) v o o x : rH o \ ■p in v_ •> 0 CM in IE< on C"r -=3- VO O on on CT\ 184(0.979X10-3)8 156(10.0X10"3)S S CM in m CO on on < X t CD o o •H a j=r o C VOS ^ ^ in oo O <1) oo CM t5 j *90 on o on in co a vo CM r— CJ\ • • 0 t*“ e' 3 o o o en on 35.5(3.10X10-3) 82(21.5X10-3)h 30.8(3.65X10“^) 177(0.2ta0“3)g S a a a CM OJ CM CM CM ro I « e t rci o o o o g - VO e— rH vo O CM .=3- 5 | rH "8 S 3 S CO§ o o rH jO Cu CVJ o- oo vo rH on i s (D CM CM -J- -J- 0 o O © i n O in oo in t* - O rH O I CO on ■=r rH rH S7 ^=r OrH *8 O 3 OCM s & 143 CM CM OO CM CM CM CM &\ CM CM ^ o 8cd O, €■ ^ s s > > > £ vo in £ -=3* CO VO -=T CD 4> N C rH co -=r in 8 o co o - = t in ov •=r oo oo i—s cm i l in vo vo o\ n S'S CQ rH -3 r co in rH .Q in vo CO t— vo JQ O CM co CO Jf co o o O o o O CM in vo CO in rH in o oo oo n -=r i—l Jp -=r v o ^3* S— * rH rH i—i I •5T V V i„_f s CO J— 1 0 H 1 CO 1 I__1i CO ___ 1 V CO CO CO co CM ""cm CO CO o r-N .r-'* o 0 tsJ S5 II s •9 1 S'VO vo I 8 cd 1 JO JQ o o I i o ’Sh In £ s I—JS t -» fl_fl a_ a (j) dichlorcmethane 29 OOCM oo VC$ o o vo vo vo vo vo ON ON CO •a n w f i fi fi § TO VO rH v o -=r O rH rH ■=r 8 3 oo pH£ PIh Ph O i—ii_i OO oo CO OO OO o o OO CM oo y-N o 1 O tS3 hg* ^ 8 § § •s vo VO ct5 ca o 0 i v_^ 1 & S—'8 «H Eh s a. in 1 S 30 titanium tetrachloride was reacted with two moles of quin- olinolium chloride. TiCl^ + 2oxH2Cl >TiCl^*2oxH + 2HC1 In the third preparation, hydrogen chloride was reacted with dichlorobis(8-quinolinolato)titanium (IV). The mono-8-quinolinol adducts of the titanium tetra halides, TiXjj/oxH, were prepared by the above first two methods. The Itl adduct with titanium tetrachloride loses the metal tetrachloride and hydrogen chloride on heating, leav ing dihalobis(8-quinolinolato)titanium (IV). The insolubility of the lil and 1*2 adducts in non- disruptive solvents precluded molecular weight and conductance measurements. Based on low molar conductivity values for the boron trifluoride-8-quinolinol adduct, however, Frazer concludes that the adducts are non-electrolytes. The fact that boron complexes are only tetrahedrally coordinated means that the 8-quinolinol molecule must be bonded as a uni- dentate ligand. This conclusion suggests that the 8-quin- olinol is unidentate in the titanium adducts also, since the 10 infrared spectra are similar * Infrared spectral evidence indicates that the intramolecular hydrogen bond remains in tact in the adduct? this would not be the case if the che late were formed instead. The "adducts1* of composition TiX^*3oxH and TiX^^oxH appear to be mixtures of non-adduct compounds. Thermogravi- 31 metric analysis and macro-scale pyrolysis experiments showed that 8-quinolinolium chloride could be sublimed from the "adduct" TiXjj/oxH, leaving the dichlorobis( 8-quinolinolato)- titanium. The differential thermal analysis curves of the adducts contain the same peaks which are obtained by taking curves of the individual components of the mixture. The infrared spectra and the X-ray powder patterns of the solids i are the sums of these for the It2 mixtures of the dichloro- f bis(8-quinolinolato)titanium (IV) and 8-quinolinolium chloride. When the apparent adducts of composition TiCl^*3oxH were heated , hydrogen chloride was evolved and then 8-quin- olinolium chloride sublimed off# leaving a residue of di- chlorobis(8-quinolinolato)titanium(IV)• The infrared spectra of the Is3 solids indicated that they were mixtures contain ing 8-quinolinolium chloride and a compound containing the 8-quinolinolate ligand. In addition to the adducts formed by 8-quinolinol and the titanium tetrahalides, Frazer also prepared several mixed adducts containing the base pyridine as well as 8-quinolinol. Addition of pyridine (py), to TiCl^#oxH gave TiClj^*oxH»py, which was confirmed by infrared spectroscopy (800-^00 cm“*) not to be simply an equimolar mixture of TiCl^*2oxH and TiCl^»2py. No evidence was found for pyridinium tetrachloro- (8-quinolinolato)titanium (IV), [pyH^DETiCl^ox*]. This is in contrast with the ready formation of pyridinium tetrachloro- (2,^-pentanedionato)stannate(lV ), [ pyH"*tl[ SnCl^(acac)“] , 32 33 prepared by an analogous procedure^ . TiCl^#oxH*py loses hydrogen chloride at 60°C to yield TiCl^ox*py. This latter product can also be obtained by direct reaction of pyridine and trichloro(8-quinolinolato)- titanium (IV)• The reactions just presented lend credence to the idea^ that the adduct may preceed the formation of the mono-sub stituted enolate complexes» as the adducts of 8-quinolinol may be converted by heat or by reaction with excess 8-quin- 10 olinol into complexes containing the 8-quinolinolate ligand e 2 Mono-substituted Complexes of 8-Quinolinol Of the series TiX^ox* only the trichloro complex has been isolated. Due to insolubility in suitable solvents* molecular weight and conductance measurements could not be made • The facile addition of pyridine or 8-quinolinol to trichloro(8-quinolinol&.to)titanium(IV) along with the evi dence from the far-infrared spectroscopy indicate that this compound probably contains the penta-coordinate metal atom1** since the mono-substituted trichloro- complex has titanium- chlorine stretching frequencies which are higher than those in the di-substituted dihalo- complex. Compounds with hexa- coordinate metal atoms usually have lower metal-halogen stretching frequencies than the corresponding bands in com pounds with lower coordination numbers® 33 ^ Dl-afbstituted Complexes of Titanium with 8-Quinolinol In contrast to most of the bis-^diketonate complexes, the bis-8-quinolinolate complexes (TiXgOXg* X = F, Cl, Br and I) are extremely stable, both thermally and hydrolyti cally*^. Hydrolytic stability does decrease with increas ing atomic number of the halogen^*1*. In itially solids of composition TiX^'^oxH ( X 38 Cl, Br and I) were obtained by reacting solutions of TiX^ and 8-quinolinol in chloroform* Analysis showed the compound to be a mixture of dihalobis(8-quinolinolato)titanium(IV) and quinolinolium halide. By subliming off the 8-quinolinolium halide at about 200°, Frazer was able to obtain TiX2ox 2, X = Cl, Br, and I. Difluorobis(8-quinolinolato)titanium(IV) was prepared by heating TiF^°2oxH. Insolubility in non- disruptive solvents again precluded the measurement of mole cular weight and conductance. Comparison of the infrared spectrum of TiF2ox 2 with that 11 o f SnF2ox 2 affords a basis for suggesting a structure for the TiX2ox2 complexes. "The infrared spectrum of SnF2ox2 contains two intense bands at 5^7 and 5^7 cm”* which are not present in other dihalobis(8-quinolinolato)compounds, and which • . . therefore [can be assigned] to vibrations in volving tin-fluoride stretching. The prescence of two bands is consistent with the fluorine atoms being in cis positions, but the possibility that the bands arise because of splitting of degenerate modes by intermolecular forces in the solid cannot be excluded. Absence of suitable solvents prevented 34 studies in solution. In the spectrum of TiFgOx, there is — 1 —1 a sharp band at 626 cm .and the band at 6*47 cm which 11 is also present in other MX2ox2 compoundsThe band a t 6*47 cm~* is greatly increased, and may indeed encompass two bands. If this is the case, then the cis structure could be assigned to the TiF2ox2 compound as well. Although several structural isomers of TiX2ox2 (see f Figure 5) complexes are feasible, no evidence is available for elimination of any structure. Based on the structures determined for the bis-^-di- 7 .8 34 41 ketonate titanium complexes' and Me2Snox2 ( X = F» Cl and Br), which all have the cis structure, and based on the infrared spectra of the difluorobis(8-quinolinolato)titanium(IV) compound, it is tempting to assign the cis structure to all bis-8-quinolinolato complexes, except possibly the diiodo- complex. A possible experiment which might elucidate the structure more cleanly would be the nmr study of dihalo- bis(2-t-butyl-8-quinolinolato)titanium (IV) complexes. With the tertiary butyl as a probe on the ligand, nmr studies, probably at low temperature, might eliminate several of the possible structures, as in the dihalobis(benzoylacetonato)- titanium(IV) complexes (Figure 3). 4 Tris-substituted Complexes with 8-Quinolinol The series of compounds XTiox^ ( X s F, Cl, Br, and I ) 11 has been prepared . Conductance measurements in nitro- FIGURE 5 Isomeric Possibilities for Dlhalobis C8-quinolinolato ) titanium (IV) 36 benzene show that the compounds for which X = F, Cl# and Br are non-electrolytes. The compounds were too insoluble for molecular weight determinations. Infrared spectral evidence# however, shows that all ligands are bidentate anions, and is consistent with the formulation of a hepta-coordinate titanium compound. The iodo-analog, Tilox^, shows marked differences to the other compounds in the series, as does diiodobis(2,^- pentanedionato)titanium(IV) in relation to the other bis- (2,4-pentanedionato) complexes. Conductance measurements in nitrobenzene and nitromethane indicate that Tilox. is 3 a lil electrolyte? this finding is corroborated by molecular weight measurements in nitrobenzene. The anomalie in the structure of the iodo-complex may be due to the much larger size of the iodine atom, too large, in fact, to fit into the coordination sphere. There are no analogous seven-co- ordinate titanium complexes with the >$-diketonate ligands. The difference may lie in the more compact form of the 8- quinolinol ligand, which forms five instead of six-membered rings with the metal atom. These compounds can be prepared by two methods# first, by reacting 8-quinolinol with the dihalobis(8-quinolinolato)- titanium(IV) compounds, and secondly, by reacting directly TiXj^ with three moles of 8-quiriolinol. 5 Tetra-substituted Complexes of Titanium with 8-Quinolinol A tetra-substituted complex of titanium with 8-quinoli- nol is known, but w ill be discussed with the tetra-substituted salicylaldehydato complexes• 37 0,3 | i 13 C rt •H O t 3 CM O £13 U G) CO « o o O O O O nr*o O O •53" •=3- o O o p P p Q,3 Q, p . a> CO 8o o 5>s p <=r c I > t i 1 1 VO li'*— rH O in vo A I 1 IO ■3 ooo t—CM XT CM P« & « b on »cj o on • -=t *4° Q) rH rH § a h ^ ^ a o 9 £ S 40 8 o iH c\» *8 .Qa .pl O a >3 a . a> o >> *8»> s p* CO O.feT 8cn 9 -=y « b—I rH o 3 a S h k2 dehyde groups present. For this reason, titanium has been assigned a coordination number of six in tetrakis(salicylal- dehydato)titanium(IV). The infrared spectrum has a strong -1 broad absorption at 1610 cm , which on closer examination is resolved into two bands at 1622 and 1596 cm , indicating a bidentate salicylaldehyde group, while the medium-strong band at 1682 cm is assigned to the uncoordinated carbonyl group of the unidentate salicylaldehydes. Further evidence that two groups of salicylaldehyde are present in Tisal^ arise from the nmr spectra. The two distinct signals of equal intensity at 'T-1.39 and +O .78 are assigned to two pairs of aldehydic protons. There is no evidence for an -OH group in either the ir or the nmr spectra, so the data leading to the assignment of the structure is not based on accidental hydrolysis. Based on sim ilar data, bis(8-quinolinolato)bis(sali- cylaldehydato)titanium(IV) is assigned a six-coordinated s t r u c t u r e . Nmr data is available for these compounds, and a more de finitive assignment of structure may have been possible. The nmr and ir data suggest that the salicylaldehyde groups are unidentate in the bis(8-quinolinolato)bis(salicylaldehydato)- titanium(IV). In the nmr spectrum of Tiox^sal^ in deuterio- chloroform there is a signal at ^-0.66. The ratio of the intensity of this signal to the intensity of the aromatic proton signal is lislO1^. Frazer,therefore, assigns the line ^3 at -0.66 to two identical aldehydic protons. Since the complexes are most likely stereochemically non-rigid* this nmr data gives no information about structural isomerism. Conductance data showed a ll the compounds to be non electrolytes, but molecular weight data is available only for TiSal0ox . and is consistent with the formulation of * 2 a monomeric non-electrolyte in benzene. If tetrakis(salicylaldehydato)titanium(IV) is six- coordinate, then there are five structural possibilities analogous to Figures 3 and 5« In the nmr spectrum of Tisalj^ - there are two distinct signals of equal intensity at ^-1.39 and +0«78« The aldehydic proton of the free ligand in car bon tetrachloride is at T+0.16• The ratio of the combined intensities of the two signals to the intensity of the com plex aromatic proton signal is lity. Frazer, therefore, assigns the two peaks to two pairs of aldehydic protons. As for the bis-^-diketonate complexes, rapid exchange at room tempera ture may preclude detection of differences in the stereo chemistry. low temperature nmr studies may yield more alde hydic proton peaks. If the compound, Tisal^, were cis, there are again three possible stereoisomers (see below). These cis isomers would be expected to be present in the statistical ratio 1(0.25)* 2(0.25)* 3(0.50). If this were the case, four peaks for the aromatic aldehydic proton should be present in the nmr in the ratio of intensity Isliltl. If the compound were trans, there should be only two peaks (1*1) for the aromatic aldehydic proton* one for the trans- trans-trans isomer and one for the trans-cis-cis isomer. Similar possibilities exist for Tiox2sal2. The tetra(8-quinolinolato)titanium (IV) compound also poses an interesting stereochemical problem» Cotton and 37 Wilkinson point out that the most symmetrical arrangement possible for a metal with coordination number eight is the cube* with 0^ symmetry« But this structure is not known for any discrete MX q groups• The two principal ways in which the cube may be distorted are the square antiprism and the dodecahedron. "A close analysis of the energetics of M-X and X-X interactions suggests that there w ill in gen eral be little difference between the energies of the square antiprism and dodecahedral arrangements* unless other factors* such as the existence of chelate rings# energies* of pa^ti^lly filled inner shells# [and] exceptional opportunities for" orbital hybridization « « r» It appears'that metals with ^5 coordination number eight# involving chelate rings prefer the square antiprism atic structure# based on an X-ray study of tetrakis(2#i*-pentanedionato)zirconium(IV) * «. There have not been any tetra-substituted ^-diketonate complexes of titanium yet reported, E SERIES OF OXIMES WITH TITANIUM TETRAHALIDES lb In a fourth paper Frazer and co-workers report the preparation of several adducts and compounds derived from the ligands dimethylglyoxime# diphenylglyoxime# and benzil m onoxim e• 1 Adducts of Oximes with Titanium Tetrachloride The reaction of dimethylglyoxime (DMGH 2 ) with titanium tetrachloride at 20° yields both the mono- and the di-oxime adducts# when reacted in a 1*1 and a It2 molar ratio# res pectively, Due to insolubility in non-disruptive solvents# no conductance or molecular weight data are reported. The main evidence for these adducts comes from the infrared spectra and the differential thermal analysis curves. The data on the two adducts are different from each other# and from either trichloro(dimethylglyoximato)titanium(IV)# TiCl^DMGH (DMGH 38 anion of dimethylglyoxime)# or dim ethyl glyoxime itself. The ir spectra of both adducts contain -1 sharp and strong bands at 3^00 and 3^20 cm for the lil ■ adduct# and at 32^0 and JbZO cm for the 1*2 adduct# indiea- **6 0) Ov .C S o <*~S CO CO CO ro I (11 fc> t o o r t vo 00 00 OV vo OCX ov C\J rH SJ ^ Mo> -£J§ § V •§ 8 £ 0 *3 5 S ■ s £ 3 £ US 0)a m Io 3o 10 € 3 3 I Si ^7 CVS o o ■=r o 2 ting the absence of hydrogen bonding. Both complexes also exhibit two bands (weak) in the region 1500-1700 cm"1* at 1585 and 1655 for the 1*1 adduct and at 1560 and 1660 cm“* for the 1*2 adduct. These bands have been assigned to the CN stretching frequency# and indicates that the two CN groups of the ligand are in different environments. Before describing the reactions with benzil monoxime# i Frazer points out that there are two geometric isomers. Ref- erencing K.A. Kerr » Frazer states that the-cform has the -OH group trans to the carbonyl group# whereas the A iso m e r h a s the cis structure. It appears# however# that Frazer was in error# because Kerr points out that in recent years the designations have been reversed, and goes on to prove this point. For the rest of the discussion of the benzil mon oxime compounds# the designations svn and anti w ill be used instead of the incorrect^and /. When either form of benzil monoxime is reacted with titanium tetrachloride in a 1*1 molar ratio# the lil adducts are obtained. There are two forms of the svn adduct. The yellow form is obtained as a precipitate directly from the chloroform solution# and the red form appeared after con centrating the filtrate. These two adducts exhibit dif ferent bands in the ir as well as differ from the anti adduct. Both the svn and anti benzil monoximes# when reacted in a two to one molar ratio# give products of the identical composition and identical ir spectra# TiCl^a2BM0H*0. 5CHCI3 . k9 Efforts to prepare the chloroform free adduct were unsuc cessful, but resulted instead in a compound-adduct type formation of em pirical formula TiCl^BMO*BMOH (BMOH - ben zil monoxime, BMO » the anion of benzil monoxime). "The composition of the compound TiCl^*BM0H®0.5CHC1^ has been established by (i) elemental analysis, (ii) hydrolysis and identification of chloroform in the hydrolysis products, (iii) pyrolysis and identification of chloroform in the products, and (iv) ir and nmr spectroscopy which indicated the presence of chloroform." 2 M ono-substituted Complexes of Titanium with Oximes In contrast to the reaction of dimethylglyoxime at 20°, diphenylglyoxime yields the compound trichloro(diphenyl- glyoximato)titanium(IV) at 20°C« No adducts were reported for the diphenylglyoxime reaction. The corresponding dimethylglyoximato compound was formed in hexane at 45 • Both compounds are pyrolytically unstable on heating to ca. 100°C and decompose violently. Neither compound is soluble in nondisruptive solvents. No discussion was given regarding the infrared or any other definitive data about these two compounds. It is unclear whether the diphenyl and dimethyl- glyoximes bond through both oxygens, both nitrogens, or one o f e a c h . Since there is no evidence for hydrogen bonding, the ligand*s oxygen may be free enough for binding to occur 50 through the oxygen. Based on precedent , however, the dimethylglyoxime preferentially bonds through its nitrogens as in cobalt complexes. At this point, it is impossible to exclude any possibility. There is no discussion, or even report of the ir bands for the diphenyl and dimethylglyoximato compounds. Since no mention is made about the coordination of the titanium in these compounds, it is unclear whether the ligands are monodentate or bidentate, A closer study of the infrared might at least show how the ligands are bonded. If, for example, the ligands are bonded through the nitrogens, the -OH peak should presumably be present in the ir. In addition to the uncertainty about the dimethyl- and diphenylglyoximato compounds, it is not clear whether TiCl^- BM0-BM0H possesses five or six coordinate titanium . In other words, is benzil monoxime mono- or bidentate? From the data given it is impossible to make a judgment. There were no compoundsof composition TiCl^BMO or TiGl2(BIV10)2 r e p o r t e d . Lack of a suitable solvent again precluded determination of molecular weight or conductance. The composition of the compounds is established mainly by elemental analysis, hydroly sis and pyrolysis. Now that the compounds have been prepared and have empirical formulae assigned to them, the struc tures need to be elucidated. Perhaps more extensive nmr, ir, and X-ray data would prove enlightening. 51 §3 . c ON 0 0 •H S £ S 8 J o IEO -P 0 rH £ Q N0 £ S 0 •8o 8 o o 0 CO rH A 5*1 8 A I % SB o %O O 0 0 0 5 IS 0 0 0 0 Q o 8 E-*I 0 o O Q 0 Q O W 0 LTN TJ rH 0 1 I 0 O © s \ O 0 o o o o a a H HI B S S ar* s-p 0 a tS -I 0 •P s ! CO •S' s (4T* o Q >< a I § s * second isolated product LIBRARY William & Mary College 52 jg - jst -s r •=r -=r •sr -sr (HI H H rH rH rH rH rH £ 1 CO 1 to -p E Q O8 & s E a E | A OI 0000000 oo OO iH R * o O O He as g g g M l ff jf CQ| w w S a 1 <\i g 3o % O o o o o o o o g g a £ Si a a I TiCloEMD’EMOH Six coordinate monomer 53 F COMPLEXES OF TITANIUM TETRACHLORIDE WITH ACETANILIDES 1 D i-substituted Complexes of Acetanilides with Titanium 1*5 I n 1966 Sen and Omapathy reported the preparation of dichlorobis(4-anilido-2,* 1—butanedionato)titanium (IV), TiClg- (G ^ o ^ io ° 2N^2 * Sy™3-! reported two additional compounds of titanium with acetanilides, dichlorobis(benzoylacetanilide)- titanium(IV), TiClgfC^H^^N^* 2111(1 dichlorobis(benzoyl-meta- nitroacetanilide)titanium (IV), TiCl^C^H^O^Ng^ • For dichlorobis(^-anilido- 2 ,^~butanedionato)titanium (IV ), only the elemental analysis, X-ray powder pattern data, and reflectance spectra were reported, since the compound was too insoluble for either conductivity measurements or nmr s p e c t r a . The latter two complexes behave as non-electrolytes in nitrobenzene, and magnetic susceptibility measurements indi cate that the compounds are diamagnetic, as would be expected for a 3d° system1^. The infrared mull spectra indicate that the complexes contain oxygen-chelated ligands? the che late carbonyl absorptions for dichlorobis(benzoylacetanilido)- titanium(IV) and dichlorobis(benzoyl-m eta-nitroacetanilido)- titanium(IV) occur at 1610 cm*1 and 1605 respectively. The free ligands absorb at 1?00 cm“^ and 1670 em~* r e s p e c t i v e l y . 2 Tri-substituted Complexes of Acetanilides with Titanium 1*5 In an attempt to rupture a third Ti-Cl bond, Sen Table 5 ACBTAHIL3DE DERIVATIVES CT\ °T* £ •H •H I SI XI € o CO & o v CO r-8 n i u g s *1 1 o trT1 p § H1 h I- . . . . C\J u • CO -=r rH n i s s rH p O S ! O O O s s ^ s ^ r? 1 * % % — i O iH r—i H CM 0 O 0O H e\s « <■—» CO € k * *H rH 3 3 -!-> 8 O vp \0 in in r - i CVi (V -=r % °cv, ° H —i —fl 8 W w i n rH rH 3 O O o V’o j rH > § 1 5 6 refluxed the dichlorobis(^-anilido-2,*4—butanedionato)- titanium(IV) complex with excess acetylacetone• The result was a ligand exchange yielding chlorotris( Jj'-anilido^^- butanedionatoHitaniumdV) • The same product resulted when dichlorobis(2,**-pentanedionato)titanium(IV) was refluxed with ^-anilido-2,4-butanedione. Again due to Insolubility, only elemental analysis, Reflectance spectra, and X-ray data were reported® G ■ SUMMARY Several different types of ligands that are potentially uninegative and bidentate have been studied* Insolubility in suitable solvents precluded solution studies of several of the compounds prepared. By far, the most extensively studied and characterized compounds are the /^-diketonate derivatives of titanium . Even though the X^TiL2 compounds, where L is a /-diketonate* have been thoroughly characterized, the -diketonate compounds of the type X^TiL have remained relatively uninvestigated. The fact that only a few X^TiL compounds where L = >^-diketonates have been reported has given impetus to the research presented in this thesis. EXPERIMENTAL R e a g e n ts Titanium tetrachloride and tetrabromide were pur chased from Fisher Scientific Company and Alfa Inorganics respectively. 2,4-Pentanedione and 2,2,6,6-tetramethyl-3# 5-heptanedione were prepared as described below and purified by sublimation and distillation respectively. Phenyl-1,3-butanedione and l,3-diphenyl-l,3-propanedione were purchased from Eastman Organic Chemicals. 1,3-Di- phenyl-l,3-propanedione was dried for two and a half hours under vacuum, and used without any further puri fication. 1-Phenyl-l,3-butanedione was sublimed before use. 2.4-Pentanedione was purchased from Eastman Kodak Company and redistilled before use. S o lv e n ts All solvents were obtained from commercial sources, end purified and dried before use by refluxing over either phosphorous pentoxide or calcium hydride under nitrogen, and then distilling over the suitable dehydrating agent under nitrogen. The solvents were stored over 4A Linde Molecular Sieves in flasks, equipped with a side arm stopcock to admit nitrogen. Aliquots of the solvent were transferred from the storage vessel to reaction vessel 57 with a syringe, under a stream of dry nitrogen. j Nitrobenzene was purified by a modification of the 7 ,2 3 method used by Fay and Lowry • The solvent was wash ed three times with 1:1 (vol/vol) sulfuric acid, once with water, several times with 1 M sodium hydroxide until the washings were no longer colored, and then again with water. Nitrobenzene was then distilled over phosphorous r pentoxide, under reduced pressure and stored over mole cular sieves (Linde 4A). PREPARATIONS General Reaction Procedures The following general procedure was used for all reactions attempted between the titanium tetrahalides and >d-diketones• The reactions were carried out under an atmosphere of dry nitrogen In small round bottoms flasks. . (Figure 6). The flasks were equipped with a dropping funnel, nitrogen inlet, magnetic stirrer and reflux condenser. Before any reactants were added, the apparatus was thoroughly flamed under a stream of dry nitrogen. All liquid components were transferred with syringes. Titanium tetrachloride and bromide were dis solved in the solvent in the round bottom flask first, and usually cooled to G°0 by means of an Ice bath (as a precautionary measure, and in hopes of trapping the adduct interm ediate)« The ^-diketonate ligand was then dissolved in the solvent (methylene chloride) and added dropwise to a reaction flask* In a normal procedure* after refluxing the reactants* hexane was then added and the methylene chloride boiled off* The resulting solids were transferred under nitrogen to a filtration apparatus 42 / similar to that described in the literature* (Figures 7-9)• After the compounds were washed with solvent, they were dried under vacuum at room temperature* All products were found to be sensitive to atmo spheric moisture, and it was necessary to prepare all samples for analysis, molecular weight, conductivity, melting point, spectral data, and halide determinations in a moisture-free enviroment* The samples, therefore, were prepared in Vacuum Atmospheres Dri-Lab glove box, or in a nitrogen filled glove bag* Preparation of 3-0yano-294-pentanedione 3-Cyano~2,4-pentanedione was prepared according to 43 44 the procedure of Traube as reported by Fackler* Pentane-2,4-dione (51*3 ml,50 g or 0*5 mole) was added to sodium (0*5 to 2*0 g) in absolute ethanol (200 ml) which was stirred under drynitrogen and cooled at 0°0* Cyanogen prepared from CUSO 4/ 5H2O (500g) and potassium cyanide (260*5 g) was bubbled through the solution® To produce",the cyanogen, the potassium cyanide solution was allowed to drip on to finely pulverized hydrous copper sulfate in a 2-1 round-bottom flask, equipped with a FIGURE 6'’ Diagram of Apparatus far the Preparation of Titanium Enoiate Complexes 61 FIGURE 7 Diagram of Apparatus Immediately Prior to Filtration D C FIGURE 8 FIGURE 9 Diagram of Apparatus Diagram of Filtering After Filtration Funnel used to dry Compound 63 dropping funnel and a gas outlet tube* The rate of ad dition was determined by the desired rate of gas evolu tion. If the rate of evolution of cyanogen became too slow, the flask was heated to about 60°0 on a water bath. The exit gases were passed through sodium hydroxide solu tion. The l!imido-l! intermediate was filtered with suction from the alcohol and immediately treated with sodium hydroxide (60 g) in cold water (500 ml). After dis solution was complete, ice was added, and the mixture neutralized with 6n hydrochloric acid. The -diketone crystallized. Fackler points out that the yield of pro duct depended on the immediate treatment of the imido intermediate before hydrolysis. After three attempts and one explosion, fifteen grams of the B-diketone crystallized out of solution® 3-0yano-2,4-pentanedione was purified by sublimation. The infrared spectrum agrees with that reported by Wurzchowski and Shugar. © The nmr spectrum shows that the compound exists as the enol tautomer with T(GH^) = 7*63 and r(0H) = -6.76. 45* Preparation of 2.2.6.6-Tetramethyl-3.5-heptanedione Methyl pivaloate (90g) and 72g of sodium hydride dis persed in mineral oil were added to about 900 ml of dimethoxy- ethane in a 2-1 flask© The mixture was stirred with a mechan- *The author is indebted to Oynthia Hicks for the preparation of this compound. 64 ical stirrer and brought to reflux. Pinacolone (80g) in 100 ml of dimethoxyethane was added from a dropping funnel over a 2-hour period. The mixture was poured into 1500-ml of water and neu tralized with cone hydrochloric acid (pH paper neutral or slightly acidic), and 400 ml of methylene chloride were added* The organic layer was separated and the other layer washed with another 400-ml portion of 0H2012- The organic layers were combined and washed with three 500-ml portions of Ho0* d d r i e d o v e r MgSO^ and c o n c e n tr a te d by d i s t i l l a t i o n . The concentrate was fractionally distilled through a 10-in Vigreaux column. The product was collected at 68-70 mm, 103°* Literature 100-102°, 36 mm® The ir of diplvaloyl- methane indicated the existence of a keto-enol tautomeric equilibrium mixture with the enol form predominating. The nmr data also Indicated the compound exists as the enol tautomer in chloroform: T(t-butyl) = 8.955 (=CK-) = 4.535 /(-OH) = -5.91. Reaction of Titanium Tetrachloride and 5-Qyano-2 <.4-pentane- dlone in a 1:2 Molar Ratio A mixture of titanium tetrachloride (0.90 ml, 1,56 g, 8.24 x 10 mole) and methylene chloride (25 ml) was cooled -2 to 0°, and then 3-cyano-2,4-pentanedlone (2.04 g, 1.63 x 10 mole) in 10 ml of methylene chloride was added dropwise® The reaction mixture was refluxed at ca. 55° for 1i hours* An 65 orange solid was Isolated* The compound did not melt below 300°, but had darkened* Anal: Calcd* for Ti012(C6H602N)2: Cl, 19*34 . Pound: 019 22*395 20*675 21.78. Reaction of Titanium Tetrachloride and 3-0yano-2*4- ‘pentanedione in a 1:3 Molar Ratio Titanium tetrachloride (0*95 ml, 1*65 g* 8*67 x 10“^ moles) - 2 and 3-cyano-2,4-pentanedione (3®26 g, 2.6 x 10 mole) were allowed to react as above* A fluffy, fine orange precipitate o was isolated. The compound did not melt below 300 , but had darkened (192° 0)e Anal: Oalcd. for Ti012(0^H^02R)2: 01, 19®34. Pound: 01* 17®11 and 1 6 .4 8 . Preparation of Trlehloro(3-cyano-2,4-pentanedionato)- titaniumCIV) —2 Titanium tetrachloride (2.0 ml, 3®3 g, 1.7 x 10 mole) was dissolved in 25 ml of methylene chloride* 3-Cyano-2,4- pentanedione (1.09 g» 8.7 x 10 mole) dissolved in 10 ml of methylene chloride was added, dropwise, at room temperature to the titanium tetrachloride solution. After addition was complete, the reaction solution was refluxed for two hours. A yellow solid was isolated. Mp:compound did not melt below 300°0. Preparation of Trlchloro(1-phenyl-1.3-butanedlonato)- titaniumCIV) 66 —p Dibenzoylmethane (2.5 g, 1.12 x 10 mole) was dissolved in 10 ml of methylene chloride and added dropwise to a solu- tion of titanium tetrachloride (2.5 g, 1*5 ml* 1.34 x 10“ mole) and 25 ml of methylene chloride at 0°G. The reaction mix ture was allowed to come to room temperature and an oil j appeared® Hexane was added and the methylene chloride boiled off® The resulting mixture was cooled to 0°0 and stirred i under nitrogen for several hours. After stirring at room temperature over-night, a purple-brown precipitate crys- o taliized out® The color of the compound lightened at 220 . mp 229-231°0. Anal: Oalcd® for TiOl-^O^H^OgS 0, 47.72; H, 2«9l 0 1 , 28®17® Founds 0 , 47®89| H, 3 .1 0 ; 0 1 , 2 8 .1 9 and 2 8 .6 1 . Preparation of Tribromo(1-phenyl-1,3-butanedionato)- titanium ( IV) —2 Benzoylacetone (1®76 g, 1®09 x 10 mole) dissolved in 10 ml of methylene chloride was added dropwise to a solution of titanium tetrabromide (4®4 g, 1.69 ml, 1.20 x -»p 10 mole) and 25 ml of methylene chloride at room tempera ture. (Solid TiBr^ was warmed in a sealed vial, by means of a sand bath, until it melted® The vial was then opened, and the requisite amount withdrawn by a syringe, under a steady stream of nitrogen.) As the benzoylacetone dripped in, the reaction mixture turned clear, bright red. After all the ligand had been added, the reaction mixture was reddish purple. 67 o The solution was refluxed for four hours* mp 150-152 0* Anals Calcd* for TiBr^0^0H^02. C, 26*775 H, 2*02; Br, 53,43; Ti, 10*67® Pound: 0, 26*77; H, 3.21; Br, 54*40; Ti, 10*67® (Bernhardt) Preparation of Trlbromo-2«,2.6,6-tetramethyl-3»5- heptanedionato'titanium(IV) Dipivaloylmethane (1*63 g, 1*63 ml, 8*8 x tO-*^ mole) was dissolved in 15 ml of methyleneshloride and added drop- - wise at room temperature to a solution of titanium tetra- bromide and 25 ml of methylene chloride* The reaction solution was refluxed for two hours* Hexane was added and the methy lene chloride was boiled off* Ho product was obtained in hexane until the hexane was pulled off under vacuum at room temperature* The product was dried for four and a half hours under high vacuum* The compound begins to decompose at 100°0; mp 133 -1 3 6 °C . Anals Oalcd* for TiBr^Cj 0, 28*06; H, 4.075 Br, 50*91® Pound. 0, 28*27; H, 4*33; Br, 51,47® (Bernhardt) Preparation of Trichloro(2«4-pentanedionato)titanium(IV) Titanium tetrachloride (8*6 g, 5*0 ml, 4*53 x 1Q~2 mole) was dissolved in 30 ml of methylene chloride and cooled to —2 0°0 in an ice bath* Acetylacetone (4*45 ml, 4*45 x 10 mole) dissolved in 15 ml of methylene chloride was added dropwise to the reaction solution* As the acetylacetone dripped in, the supernatant liquid was red-orange, and a yellow preoipit- 68 ate formed (the adduct). The solution was refluxed for five hours; after one half-hour, the adduct had dissolved and the solution was dark purple* A dark purple product was i s o l a t e d * Reaction of M cyclopentadienyltltanlun :rdLchloride with Acetylacetone 2,4-Pentanedlone (1,5 g, 1*5 ml, 1*49 x 10“2 mole) was dissolved in 10 ml of methylene chloride and added drop- wise to a solution of dicyclopentadienyltitanium dichloride in oa. 30 ml of methylene chloride and stirred at 0°G. The reaction mixture was refluxed, under nitrogen, for thirty- six hours. The solution was filtered without boiling off methylene chloride, and the precipitate dried under high vacuum for one hour. The bright red filtrate was treated separately* Neither the initial precipitate nor the product from the filtrate showed any solids present other than the dicyclopentadienyl titanium dichloride. Subsequent attempts in different solvents failed to pro duce any product which differed from the starting m aterial, as determined by infrared spectrum. Preparation of TrichloroC1-phenyl-1.3-butanedlonato)- pyridlnetitaniumClV) ~ —3 Pyridine (0.52 g, 0.53 ml, 6.6 x 1- mole) dissolved in 10 ml of methylene chloride was dropped into a cold (0°0) slurry of methylene chloride (30 ml) and trichlbro(1-phenyl- 69 1,3-butanedlonato) titanium( IV) • 25 ml of hexane was added to the reaction mixture, and the color changed from dark red-brown to dark red-red® An oil formed® The methylene chloride was boiled off, product filtered under nitrogen, and washed with hexane. The cinnamon product was dried for four hours under vacuum. Anal: Oalcdi for TiO^OgNOl^H^. 01, 26.96. Found: 0 1 , 23 .4-7 and 2 5 .1 1 . Preparation of TrichloroacetylacetonatopyrldlnetitaniumCJST) Trichloroacetylacetonatotitanium(IV) (1.9 g» 7.45 x 10"3 mole) was suspended in 30 ml of methylene chloride and cooled to 0°0. Pyridine (0.89 g» 0.90 ml, 1.12 x 10“*2 mole) dissolved in 10 ml of methylene chloride was added dropwise to the reaction nixture. As the pyridine dripped In, the reaction mixture went into solution. The solution refluxed for one hour, and the color changed from deep purple to bright red to black. Hexane was added as the methylene chlor ide boiled off; the brown product was filtered and dried for five hours. A n a ls O a lc d . f o r TiCl^C-jQNOgHjg® 31®99® Pounds 01, 32.32 and 31.60. PHYSICAL MEASUREMENTS Molecular Weights The molecular weights were determined, where possible, FIGURE 10 Beckmann Thermometer 71 cryoscopically in benzene and/or nitrobenzene using a Beck mann Thermometer (Figure 10), The procedure was checked against resublimed naphthalene. The value for nitrobenzene was found to be 7.37 deg/molal, and the value for benzene was 5«12 deg/molalo (See Appendix for sample graphs and cal culations). Conductance Measurements Conductivities were measured in acetonitrile or nitro benzene at 22°0 with an Industrial Instruments Conductance Bridge in a Freas-type conductivity cell® Halide Determinations Percent halide was determined potentiom etrically using a Fisher Accumet Model 210 pH meter with a glass and a silver electrode. The samples were decomposed in aqueous sodium hydroxide solution. The solution was acidified with 6 m nitirc acid and titrated against standard silver nitrate solution. (See Appendix for sample graphs and calculations). Melting Points All melting points were taken in sealed capillaries in a Hoover Melting Point Apparatus, and are uncorreoted. Infrared Spectra The infrared spectra reported were taken with a Perkin- Elmer 457* The solid state spectra were run as Nujol mulls. 72 Potassium bromide cells were used. Nuclear Magnetic Resonance Spectra The spectra reported were run on a Perkin-Elmer R-20B spectrometer® Moisture sensitive samples were prepared in a dry atmosphere, and the nmr tubes were sealed under vacuum* A n a ly se s Carbon and hydrogen analyses were done by Schwartzkopf M icroanalytical Laboratory or Alfred Bernhardt Micr©analyti cal Laboratory. The correct laboratory is noted at the end of each preparation. DISCUSSION AND RESULTS Preparative Chemistry Anhydrous titanium tetrachloride reacts with 3-cyano- 2 ,if-pentanedione, 1-phenyl-l,3-butanedione, 1,3-dlphenyl- if6 1 .3-propanedione, and 2,2,6,6-tetramethyl-3»5-heptanedione (ca. 1«1 molar ratios) in dichloromethane to give trichloro- (fl -diketonato)tltanium (IV) complexes plus hydrogen chloride. Titanium tetrabromide reacts in a sim ilar manner with 1-phenyl- 1.3-butanedione and 2,2,6,6-tetram ethyl-3*5-heptanedione to yield the corresponding tribromo-complexes. In the syntheses TiX^ + LH ----- > TiX^L + HC1 of the mono-substituted trihalo-compounds, care was taken to employ a slight excess of the titanium tetrahallde in order to prevent formation of the bis- A -diketonato compound. In the preparation of the trihalo-complexes, no evidence for adduct formation, TiX^*LH, was obtained, even though adducts 17 have been reported from the reaction of 2, if-pentanedione \ with titanium tetrachloride, and from the reaction of other potential bidentate uninegative ligands, other than A -diketones with several of the titanium tetrahalides (see previous discussion). It Is reasonable to assume, however, that the adduct Is an intermediate in the formation of the enolate complex. The facile formation and isolation of the mono-substltuted, potentially five-coordinate titanium compounds is In contrast to the behavior of the group IVA if 7-*>0 metals, silicon, germanium and tin® No mono-substituted 73 -dlketonate compounds for these groups IVA elements have yet been reported, although definite attempts have been 48 made to isolate such potentially five-coordinate compounds* When 2,4-pentanedione and silicon or tin tetrachloride are reacted in a lil molar ratio# only the disubstituted products form* Even a 5*1 molar ratio of tin tetrahalide to 2,4-pentanedlone resulted in the 48 exclusive formation of dlchlorobis(2,4-pentanedionato)tin(IV)• 11 Frazer, however, has reported one apparent five-coordinate tin compound with 8-hydroxyquinoline as the ligand, SnCl^ox. A pyridine adduct of dichlorofn-butyl)-2,4-pentanedionatotin(IV) has recently been reported although the Lewis acid itself, Cl2(n-C^H^)Sn(acac) was never Isolated* There have been no corresponding five-coordinate compounds reported for zirconium or hafnium, although the isolation of a tetrahydrofuran adduct of trichloro(2,4- 51 pentanedionato)zirconlum(IV) has been reported* Except for this adduct the zirconium and hafnium tetrachlorides and tetrabromides yield di- and trl-substituted A -dlketonate c o m p le x e s. The trihalo compounds are much more moisture sensitive than the dihalo derivatives, and extreme caution must be taken to exclude atmospheric moisture* Exposure to air results in noticeable decomposition within several minutes, presumably through the hydrolytic rupture of the titanium-halogen bonds. The apparent increase in sensitivity of the trihalo derivatives can be rationalized in terms of a five-coordinate structure* 75 Such a structure would leave the compound more accessible to ■fco attack by a water molecule^give a six-coordinate Intermediate which can then lose hydrogen chloride, Trichloro(3-cyano-2,^-pentanedlonato)tItanium(IV), however, is not appreciably moisture sensitive for reasons which w ill be discussed later. All reactions were run under dry nitrogen, and samples for physical analysis were prepared i in a Vacuum Atmospheres Dri-Lab glove box. The trlchloro-complexes are insoluble in hexane, ben zene, and carbon tetrachloride? only very slightly soluble in dichioromethane and chloroform? and moderately soluble in nitrobenzene. Trichloro(3-cyano-2,**-pentanedlonato)tltanium(IV), however, is moderately soluble only in acetonltrlle. The tribromo compounds, on the other hand, are much more soluble than the trichloro analogs. Analytical data, molecular weight measurements, and conductance data for several compounds are given in Tables 6, 7, and 8 respectively. Reactions between pyridine and trichloro(2,^-pentane- dlonato)titanium(IV) and trichloro(1-phenyl-l,3-tnitanedlonato)- tltanium(IV) led to the isolation of pyridine adducts of both complexes. Both reactions were conducted at 0° in dichloromethane. The formation of these pyridine adducts is sim ilar to the reaction reported by Frazer.”*"0 When pyridine is added to trichloro(8-quinolinolato)titanium (IV), the adduct TiCl^ox*C^H^N forms. The infrared spectra (Figures 11, 12, 1 3 9 and 1*0 show definitely that pyridine is coordinated to Complex Mp Analytical Data i—I o Q s a 1 £ £ 1 -P o 6 o aj c o c C0 on * W ■ O on _ X & a _. CM vo C H CO t— rH in n i rH C\l CM on non on o 25.89 2.7 • • & O o rH § T a vo vo CO -=s- CO CO o CO 5 CM on on t— rH on t— on O no> in on CM on n i rH in on on t— CM rH CM s— h on rH O CM • • • • • • • { JIX ~non v~fn O CO -sr a ^3- oo E-« iH o W CO O o ov Mon CM CM CM vo on rH I*" 0— «H t— CM CM o\ CM rH O O rH o\ CM 1 rH in H CM • • 9 • • TP HrH ' rH 3 “n o -=r vo -=r O C CO ■=s- • i H«H c£ rH on on CM CM on on rH o in o - 0 in O OV rH o> CM 1 • e • • • • 8* -=3- vo vo -=r vo O in CM o o in t- on CM t— o iH rH n i CM in on on CM CM t— o O CM on • • • • a 10.67 • ctf Analysis by Alfred Bernhardt Mikroanalytisches Laboratorium ,0 Analysis by Schwarzkyof M icroanalytlcal Laboratory 76 Table 7 Molecular Weight Data % <8 I “3 s I $ 04 £ c 3 03 03 k g o 03 <13 03 03 I o o o o o o O I—I VO M CM CM cd CO % VO •=r oo o OO C— o o o rH o o in in LTV ON o n oo o oo o o oo o o CO n o in bO • • cd oo vo cn oo co c o o n •c o — t oo o o o ON — ' e c— n i OO n i r -y =r -= ^=r -=y -=r crv n e bO O O bQ bO bO • • ^ In n I o v o v o v o v vo CM £■— t— i o OO \ o • • VO Oin i CO CO CM n o rH oo oo o o)b0 ovo vo 4 r o oo CO £ o v o v O ON CO CM «— oo CM o C'— o M CM ON CM ON O oo OO 4 r CM o o v o o bO bo CO CM • a 1 cd oo vo CM - t— 1-4 O CM o ON in 0 • cd , OO •st s j -= = -=r o o -=r o o o c O C rH O rH t— H CO o n o o O CM CM 3 ? • ' =r ^a- r -= ' - • M CM CM n i m X> OOO OO o CO OJ ■=T C— •=a* ON NON ON bO G bO bG • • • .a „ co •=r NrH ON o CM CM • ^bO VO vo =r -= s>- CO r js o v CO in CM o Si ON in ON O oo OO ON ON O H rH o rH o I™ e • • .ON rH OO O - 3 J VO vo rH in SI CM o ON o • nitrobenzene 77 benzene Table 8 CONDUCTANCE DATA a f o o 1 p CO 0 a> CM rH I I 0) CO -=3" O VO OO CO £ 8 3 CM •H 3 C r-S LCN I | § . « ° f - r § £ d • o vo vo cm CO s CM CO o • CO ar •a r s • 'o O OJ C"- 8 d c • CM -=r oo a rH o, « 6^ \ r < CM o CM o P i t p I a> £ a o £ £ £ CO rH • CM > O W E § £ CM CM O O O ti a s s d p p P I q) £ c o go a> Infrared Spectrum of Trichloro ( 2,^«pentanediomto ) titanium (IV) as a Mull in Nujol 79 FIGURE 12 OO VO -=r oo vo O CM O O O O i - r O O rH o o o o o o o o o o o o 80 Spectrum of Pyridine as a Mull in Nujol FIGURE 13 vo CO o o o •=3" o o o o oo OJ o o vo o o o o o o o o o Infrared Spectrum of Trichloro ( 2,4-pentanedionato) pyridlnetitanium (IV) as a Mull in Nujol 81 FIGURE 14 vo oo vo •=r CO o o o •Hl o o o o o o o OJ o o o o o o o o Infrared Spectrum of Trichloro ( 1-phenyl-l, 3-butanedionato ) pyridinetitanium (IV) as a Mull in Nujol 82 the metal. In both spectra, characteristic pyridine absorptions at ca. 1 6 0 0 , 1100 to 1000, and 800-700 cm"^ were observed. Comparison of the spectra of the adducts with those for the trichloro complexes with the 2 ,*l—pentane- dionato and 1-phenyl-1,3-butanedlonato ligands also confirms the presence of coordinated pyridine. These two adducts were not characterized further since the purpose of their preparation was to demonstrate the feasibility of formation, and to provide chemical evidence for the structure of the trlhalo(-dlketonate)titanium (IV ) complexes to be discussed l a t e r . Attempts to prepare chloro(2,^-pentanedionato)bis- (cyclopentadlenyl)titanium(IV) were unsuccessful. A reaction between dichlorobis (cyclopentadienyl )titanium ( IV) and 2,**— pentanedione yielded no product different from the starting material. The infrared spectra of several recovered solids showed that there was no 2,^-pentanedlonato species in the compound. This result was disappointing in view of the <2 evidence presented by Sen and Kantak. They report cases where chelate groups have reacted with dichlorobis(cyclo pentadienyl ) titanium (IV) , replacing either one of the chlorines or one of the cyclopentadienyl groups. For example, reaction between dichlorobis(cyclopentadienyl)- titanlum(IV) and 8-qulnolinol, acetoacetanilide, and 1,3-diphenyl-1,3-propanedione yield respectively chioro(cyclo pentadienyl) bis(8-qulnolinolato)titanium (IV), chlorobis(cyclo pentadienyl )(acetoacetanllidato)titanium (IV), and chlorobis- dk (cyclopentadienyl) (1,3-diphenyl-1,3-propanedlonato)- tltanium(IV). The only other report on this class of compounds is the synthesis of several dlketonate chelates of the bis- (cyclopentadienyl)titanium(IV) moiety .$3 Compounds of the *f — type [(C^H^gTiL ][ X ] were synthesized in aqueous media starting with C (C^H^)2Ti3[ (ClO/j,)^, where L is the anion of 2,^-pentanedione, 1-phenyl-1,3-butanedione, 1,3-diphenyl- 1,3-propanedione, 2,2,6,6-tetramethyl-3,5-heptanedlone, and tropolonej and where X“ = C10^,BF^7 AsF6* sfeF6f or FeCSO^. In none of these cases, however, is there a direct substitution of the chloride. In addition to the preparation of the mono-substituted products, attempts were made to prepare dichlorobis(3-cyano- 2,^-pentanedionato)tltanlum(IV)• The success of these attempts has not been completely established. When approximately Ii2 molar ratios of titanium tetrachloride to 3-cyano-2pentane dione were reacted at reflux, yellow solids were produced and Isolated. For these preparations, however, the chloride analyses were several per cent from the theoretical values (1 per cent low to three per cent high). Furthermore, the Infrared spectra (to be discussed later In more detail) in the region of the cyanide stretching mode indicated that the product was contaminated with the trichloro(3-cyano-2,^-pentane- dionato)titanlum(lV) complex. To prevent formation of the mono-substituted complex, the reaction was carried out in a It3 molar ratio, titanium tetrachloride to ligand. This preparation yielded a yellow solid whose infrared spectrum 85 indicated the absence of any trichloro complex* The chloride analyses# however# were lower than expected (see experimental)* Although accurate chloride analyses were not obtained# the in frared spectrum and the fact that the chloride analyses are in the neighborhood of values expected for the di-substituted complex, as well as the great number of di-substituted pro ducts with analogous A -dlketonate ligands make it reasonably t certain that the di-substltuted product was prepared* There is some evidence that absorbed solvent molecules may have given rise to the low chloride analyses. T r i h a l o (A -diketonato)tltanlum(IV) Complexes There has been relatively little definitive work reported on potential five-coordinate>8-dlketonate complexes of titanium of the type X^TiL, L being a bidentate ligand. It was of interest# therefore# to determine not only whether the compounds formed and were readily isolable, but also whether they con tained oxygen-chelated ^-dlketonate ligands and possessed the five-coordinate monomeric structure# or had in fact# a six-coordinate dimeric structure with either halogen# or oxygen bridges (see Figure 1). Not only are there few trihalo(>4-diketonato)tltanium(IV) complexes known# but there are few five-coordinate titanium complexes of any kind reported. Among the few known compounds# all that have been definitively characterized as five-coordinate# have empirical formulas corresponding to four-coordinate titanium. These compounds attain a five-coordinate structure through bridging oxygen ligands. Among these compounds are 86 chloro(2,^-pentanedlonato)titanium (IV)->fc-oxo-chloro- (2,^-pentanedionato)tltanlum(IV)f^ bis(2-methylpentane- 2,*j—dioxydim ethyl titanium (IV ))»^ bis(dichlorodiphenoxy- titanium(IV)) (Figure 11),^ bis(dlchlorodiethoxy- 57 t I t a n i u m (IV)), and di(tetraethylammonium) tetrachloro- 58 oxotitanate(IV)• Two potentially five-coordinate compounds of titanium which have been well characterized are the trichlorophosphlne adduct of titanium tetrachloride, and oxobis(2,^-pentanedionato)- tltanlum(IV). A single cyrstal study, however, of Cl^Ti(0=PCl^) shows that the structure is a dimer with titanium "having a a coordination number of six, bridging occurring through the chlorides.^ 0xobis(2,^-pentanedionato)titanium(IV)^°*^ has been definitely shown to be dimeric in solution by molecular weight considerations? infrared evidence indicates that the compound is oxygen bridged and six coordinate, having no band at ca. 1085 cm"^ assignable to a Ti=0 stretching mode. Several complexes of the type (OR)oTi(acac) (RsCoH-, 3 6 2 ,6 3 ^ n-C^H^f n-C^H^, CH^, sec-C;,,Hq) have been reported. These compounds are quite analogous to the potentially five-coordinate complexes reported herein. Unfortunately the structure of these complexes, (OR)^Tl(acac), both in the solid state and in solution has not been resolved. Molecular weight studies show a concentration dependence with the monomeric structure apparently prevailing at lower concentrations. Over the entire range, the polymerization number varies from 1.0 to 1.6, consistent with an equilibrium between the monomeric and dimeric structures. i V C/Hfc C/Hfc Bis [dichlorodiphenoxytitanium (IV)] vs V*/r ' ^ c \ Cl Cl \ Tj \ / ct C l I C l Cl «-/ ACl The S tructure of (TiCl^FOClj)^ FIGURE 15 88 It has been previously pointed out (see Figure 2) that enollzable ^-dlketones can react in several ways with titanium tetrahalides* In a ltl molar ratio, the following two reactions are of major interest* *1 *1 ❖HOI In every case study herein, no adducts were visibly formed# Reaction 2 takes precedent over reaction 1, giving 5 the >8-diketonate complex and hydrogen halide* It was found that the enollzable A -diketones do lose hydrogen halidet to form a stable oxygen-chelated structure when bonded to the titanium. Identification of the A -dlketonate chelate is easily accomplished by infrared spectroscopy* The most characteristic absorptions for oxygen-chelated ligands are listed In Table 9* The spectra of several X^TiL complexes are presented In Figures 16, 17, 18/ and 19® FIGURE 16 vo CO -=r vo o o o o o o o o o o iH o o o O PI o Infrared Spectrum of Tribromo(2,2,6s6-tetramethyl-3>5-*heptanedionato)titanium(IV) as a Mull In Nujol 89 FIGURE 1? VO CO o o o o o -=r vo l r CM o o o o H o O Infrared Spectrum of Tribromo (l-phenyl~l, 3-butanedionat o) - t Itanium (I\T); as a Mull In Nujol FIGURE 18 VO oo o o o o *3 o o VO o o o a o o o o o H o 91 Infrared Spectrum of Trichloro (1-pheny 1-1,3-butanedionato) - titanium(IV) as a Mull In Nujol FIGURE 19 oo vo o o o o o O o o O rg o o Spectrum of Trlchloro (1,3-diphenyl-l, 3-propanedionato) - titanium (IV) as a Mull in Nujol 93 TABLE 9 CHARACTERISTIC INFRARED ABSORPTIONS BY A -DIKETONATE COMPLEXES CONTAINING TERMINAL METHYL GROUPS , 2 4 .2 6 .6 4 Frequency Range, cm Assignment 1500-l600 C...... 0 s t r e t c h C-.. . 0 s t r e t c h 1010-1040 -CH^ rock 9 2 0 -9 5 0 (C-CH^) + (C...0) s t r e t c h 400-500 M-0 stretch Molecular weight and conductivity measurements in nitro benzene are consistent with the X^TlL complexes having a non- ionic and monomeric# five-coordinate structure, at least in this solvent and at the concentration levels investigated., Considering the extreme moisture sensitivity of the trihalo- complexes, the molecular weight determinations agree reasonably well with empirical formula weights. These determinations are to be compared to the molecular weights found for the tri- chloro- and tribromo(3-methyl-2,4-pentanedionato)tltanium(IV) and trichloro(2,4-pentanedionato)tItanium(IV) complexes which 9 33 indicated these latter compounds to be monomeric as well. ^ Thus far molecular weight determinations for nine complexes of the type X^TlL, X= Cl and Br, and L = <4-diketonate anions have Indicated the existence of the monomeric structure only. It is important to point but that a Kf value for nitrobenzene was determined to be 7 * 27 deg/molal using resublimed naphtha lene as the solute. This value is to be compared with a value 9k of 6.81 deg/molal reported by Serpone using benzil as the 69 solute. Thus it may be considered that the molecular weights reported herein are upper lim its* since the determined molecular weights are directly proportional to the value for the solvent. Although molecular weight* conductivity* and infrared data appear entirely consistent with the X^TiL complexes containing oxygen-chelated ^-diketonate ligands and having a non-ionic* five-coordinate structure* the nmr spectra of several of the complexes in various inert solvents is not consistent with the existence of a single five-coordinate enolate complex. The nmr spectra of several complexes are shown in Figures 20* 21* 22* 2 3 * The conditions and regions of interest are designated for each spectrum. Of special importance is the fact that two major peaks in the methyl and t-butyl regions are observed for each of the four compounds studied. The existence of the two major peaks is only consistent for two discrete enolate species. That is* a trigonal bipyramidal* five-coordinate complex with a symmetrical -^-dlketonate ligand attached to one apical and one axial position would not be expected to give two terminal resonance signals* because the energy involved in exchange of apical,and axial positions is small with respect to kT at room temperature. For,example* the fluorine-19 nmr spectrum of phosphorous pentafluoride shows only one kind of fluorine atom even at low temperatures. In order to understand the presence of two major enolate species* the trichloro(l- 95 phenyl-1,3-butanedionato)titanium(IV) was examined in detail in nitrobenzene. It is believed that the two enolate species in all cases arise from the following equilibrium* 2Xr»TiIj ------^ X^TiLo + TiX,. 3 2 £ ^ Evidence for this equilibrium is derived from the following studies with the l-phenyl-l,3-butanedione-titanium tetra chloride system. First, dichlorobis(l-phenyl-l,3-butanedionato)- titanium(IV) has been independently synthesized by the method 8* of Fay and Serpone. The chemical shift of the averaged methyl signal at 3^° is -2.36 ppm relative to tetramethylsilane. Observation of the spectrum in Figure 20 (TICl0(bzac) by itself) shows that the high-field peak corresponds quite closely to the methyl resonance position for the pure dihalo complexes. Secondly, a mixture of TiCl^(bzac) and TiClgtbzac)^ shows only the two peaks observed for TiCl^(bzac) alone, but with a different intensity ratio (see Figure 20 B). Thirdly, the spectrum of TiClgfbzac^ in nitrobenzene containing excess titanium tetrachloride (1.6 ml i n 20 ml of solution) shows only a single peak whose chemical shift (-2 ,5 6 ppm) corresponds closely to that of the high-field peak observed for TiCl^(bzac) a lo n e (see Figure 20 C). Fourthly, the dissolution of TiCl~(bzac) in nitrobenzene containing titanium tetrachloride 3 (0.8 ml in 20 ml of solution) yields a single peak having a * The author is indebted to R. W. Roser for the synthesis of this compound and for technical assistance In obtaining several s p e c t r a . FIGURE 20A Nnr Spectrum in the methyl region for TiCl^bzac in nitrobenzene B, G, D-Mnr Spectra for mixtures of Trichloro(1-phenyl- 1,3-butanedionato)titanium(IV) and dichlorobis(1-pheny1-1, 3- butanedionato ) titanium (IV ) 97 FIGURE 20 Nmr Spectra (Shifts Relative to Internal TMS) See text *for further explanations JK •2*$6 ppm FIGURE 21 Methyl Region Spectrum of Tribrano (1-phenyl-I * 3-butanedionato ) - titanium (IV) in methylene chloride 99 FIGURE 22 Nmr Spectrum of Tribromo- (2,2,6,6-tetramethy 1-3 * 5-heptane- dlonato) titanium (IV) In methylene chloride. Ring Proton t-Butyl Region R e g io n J 100 FIGURE 23 R in g P r o t-Butyl Region to n R e g io n Itar Spectrum of Trichloro (2,2,6,6-tetramethy1- 3„5-heptanedionato)titanium(IV) In chloroform. 101 methyl resonance at - 2.52 ppm which corresponds to the methyl resonance for TlCl^(bzac) in pure nitrobenzene Lastly» the two peaks in Figure 20B coalesce at high temperatures to yield a single average resonance which is consistent with a relatively rapid and facile interconversion (see Figure 20 D# D*# D**)» This nmr data is consistent with a rapid equilibrium between the mono and di-substituted enolate complexes. i Chemical evidence also supports the postulated equilibrium. The reaction of TiClgfC^H^O^)2 with TlCl^ readily yields TiCl^(C^H^02). Frazer and Rimmer11 also found analogous be havior for SnClgfC^H^NO)^ C^H^NO = quinolinolato anion, i.e. 70 SnCl2(C6H9N0)2 + SnCl^ = 2SnCl3(C6H9N0). Thompson1 fo u n d evidence for the equilibrium 3SiCl2(C5H702)2 = 2S M C^H r^^Cl + SiCl/*. This equilibrium is sim ilar to the above except that the ini tial complex is substituted one degree further. A plausible mechanism for interconversion of the mono- and dl-substltuted products is illustrated below. -X and I XI XZX 102 Two monomers may have an oxygen-bridged, interm ediate (I) which can then by a dissociative process (II) form (III) which decomposes to titanium tetrahalide and the disubstituted p r o d u c t . In the solid state ir spectrum of TlCl^(bzac)f strong bands are observed at bb 6 9 (shoulder) and 391 cm"'1', the latter of which can be assigned to a Ti-Cl stretching mode. For TiC^^zacJg bands are observed at b b k 9 433* bob w -1 and 376 s br cm , the last band being assigned to a Ti-Cl 71 stretching mode. The apparent increase in the Ti-Cl frequency from 376 t o 391 cm ^ is consistent with a five- coordinate solid state structure, since lowering of the coordination number generally leads to high metal-halogen 12 stretching frequencies. A similar trend is observed with TiCl^fC^HrjOg) 9 which was found to have bands at b 7 b 9 4 1 3 , 378 with a shoulder at 389* and 317 cm""1. Again, the band at 399 cm"*1, which can be reasonably assigned, to Ti-Cl ■ ) stretching modes, is shifted to high energy,71/.e• ca® 378 ^ -1 versus 399 cm 0 Also consistent with a five-coordinate structure for TiCl^(bzac) is the fact that pyridine can 103 readily be added to this complex to give TiCl^(bzac)*py. In conclusiont all data are consistent with TiCl^(bzac) molecules in nitrobenzene, having a non-ionic, five-coordinate structure, as opposed to a dimer structure with either halo gen or oxygen-bridges. However, TiCl^(bzac) does have a ten dency to proceed to the disubstituted product. Furthermore, it Is plausible to conclude that the same type of equilibrium i exists for the other three complexes which were examined by nmr methods. It would be highly desirable to have a single crystal X-ray study on one of the potentially five-coordinate complexes to clarify the solid state structure. Trlchloro(3-cyano-2,^-pentanedlonato)tItanium(IV) Trichloro(3-cyano-2,^-pentanedionato)titanium(IV) proved to be one of the most interesting complexes studied. Due to Insolubility, molecular weight measurements and nmr studies were not possible. Based on physical evidence, and the in frared spectrum, however, a tetrameric structure for the com plex was postulated (see Figure 2^). It is reasonable to assume that the compound contains not five-coordinate titanium , but rather, six-coordinate titanium. It is possible that the sixth coordination site is filled by the cyano end of the lig and bonding to titanium of another molecule, thus leading to polymer formation. The infrared spectrum (Figure 25) supports the contention that the nitrogen of the cyano substituent does bond to titanium. Comparison of the spectrum of the free ligand, 3-cyano-2, pentanedlone, with that of the complex shows that the C-N peak has been shifted to higher energy, from 2220 to 22^7 cm“^. This Increase In the stretching io4 FIGURE 24 N?OC' Postulated Structure for Trichloro(3-cyano- 2 j 4-pentanedionato)tltanlum( IV). frequency has been explained by Walton. He points out that t h e -CZN i can bond to the metal via the lone pair on the nitrogen atom. The increase in stretching frequency is i attributed to two factorsi First, kinematic coupling suggests that the valence-field calculation shows that coupling of the C-N and M-N stretching vibrations should give rise to a small increase in the C-N stretching frequency. Secondly, if the C-N does coordinate through the nitrogen, the increased ionic bond character should give rise to a shorter, stronger bond, thus increasing the stretching f r e q u e n c y . It is interesting to note the difference between the shift in the stretching frequency of trichloro(3-cyano-2,**•- pentanedlonato)tltanlum(IV) and the shift in some transition metal complexes that Fackler prepared in which the cyano substituent is not coordinated. He reported the C-N —1 stretching frequency of the free ligand at 2220.4- cm in chloroform solution and at 2218.9 cm ^ in a KBr pellet. Table 10 gives the C-N stretching frequency of all the complexes he prepared* FIGURE 25 -=r O C vo o o o o H o O o o o o o o C\i o O O Spectrum Trichloro (3-cyano-2, 4-pentanedionato) - titanium(IV) as a Mull Nujol. 106 10? TABLE 1 0 S o lv e n t (cm-1 Com plex m ax' FeL3 CHC13 2216.0 CrL3 CHC13 2 2 1 6 .3 CoL^ CHC13 2216.6 AIL^ CHC13 2 2 1 7 .2 GaL^ CHC13 2 2 1 7 .5 InL ^ CHCI3 2 2 1 5 .^ BeL2 CHC13 2 2 2 0 .5 KBr 2 2 1 8 .7 Cu L2 c h c i 3 2 2 1 2 .5 KBr 2 1 9 6 .2 ThL^ c h c i 3 2 2 1 1 .6 KBr 2 2 1 1 .9 ZnL2 KBr 22 2 S.b Only In the zinc compound do we note an increase in the C-N stretching frequency. The other complexes show a slight decrease in the C-N stretching frequency. At any rate, the important point is that all of the changes (except in the KBr spectrum of CuL2) are only a few wave numbers. The C-N stretching frequency in trichloro(3-cyano-2,4-pentandionato)- titanium(IV) increases 27 wave numbers. Also consistent with the assignment of a polymeric structure are the facts that the compound does not melt below 300° C„ and that it is insoluble in the non-disruptive solvents commonly used for physical determinations. Models show that 108 the compound could very easily form the tetramer pictured in F ig u r e 2k. It is interesting to note that in at least one case* insuffIcient drying afforded a complex with a slightly low chloride analysis. Examination of the Infrared spectrum revealed two bands not present In Figure 2 5 • These bands are attributed to methylene chloride* the solvent used in the 1 preparation of trich i oro(3-cyano-2,*f- pentanedionato)tItanium (IV —1 —1 The bands at 1268 cm and 700 cm are at the exact frequencies for absorption of free methylene chloride. It is easy to see how a molecule of methylene chloride could become trapped in the cage structure proposed in Figure 2k, aided by hydrogen bond formation to the diketonate oxygens, There are at least two other cases In which a molecule of solvent has been trapped in the crystal lattice, Rosenthal 66 and Drago report chloroform solvates of tetrapyrldinenlckel(II) perchlorate and tetraflrouoborate. Frazer also reported a chloroform solvate of the syn and anti bisbenzilmonoxlme adducts of titanium tetrachloride. C o n c lu s io n Compounds with a stoichiometry consistent with five- coordinate titanium, X^TiL, form easily. Molecular weight, conductivity, infrared, and nmr data are consistent with the formulation of the compounds as non-ionic, oxygen-chelated monomeric species, at least in solution, at the concentrations studied® The following equilibrium, however, does play an important role in the solution chemistry of X^TiL species 9 109 2T1X^L T1X2L2 +( TiX^ The fact that pyridine readily adds to trichloro(2,*f-pentane- dionato)titanium(IV) and trlchloro(l-phenyl-l*3-tutanedlonato)- titanlum(IV) is additional chemical evidence that the compounds are indeed five-coordinate• The formation of trichloro(3- cyano-2^-pentanedionato)titanium(IV) having the cyanide entity coordiniated to a second titanium center is also indicative of a five-coordinate structure for X^TiL complexes since the nitrogen of one ligand would not bond to another titanium if there were no available bonding site. Further study is indicated on these five-coordinate complexes. A X-ray crystal study would be of tremendous value in determining the solid state structure. APPENDIX l i t SAMPLE DATA, CALCULATION AND CURVE FOR CHLORIDE ANALYSIS OF TRICHLORO( 3-CYANO-2 e4-PENTANEDIONATO)TITANIUM(IV) Ml AgN03 V o lta Calculation 0.00 0.00 5 .0 0 0.11 H o o o m equiv . 0.20 Poundt (31.73na )( 0.0969 1 )X g o f C l 1 5 .0 0 '0 .3 0 (0.035^3 mequlv ) = 17 .0 0 0 .3 8 g o f C l g of Cl X 100 ■» 1 8 .0 0 0 .4 0 g of* sample o.!8^5g 38*29 19 .0 0 0 .4 2 % C l = 23.00 0 .5 5 26 .0 0 0.68 Sample wt« = 0*28^5g« 2 8 .0 0 0 .7 9 Theoretical % Cl = 38.21. 29.00 0.88 30.02 1 .0 0 3 0 .5 0 1 .1 0 31.00 1 .22 31.20 1 .3 1 3 1 .4 0 1 .4 3 3 1 .5 0 1 .5 4 3 1 .6 2 1 .7 1 3 1 .7 3 2.12 31.80 2 .4 3 3 1 .9 0 2 .6 3 3 2.00 2 .7 5 3 3 .0 0 3 .1 6 3 4 .0 0 3 .3 0 4 o . 00 3 .6 3 112 3 8 3 6 3 4 32 3 0 28 26 24 22 20 18 16 14 12 10 8 6 4 2 1 2 3 4 VOLTS 113 SAMPLE DATA, CALCULATION AND CURVE FOR MOLECULAR WEIGHT DETERMINATION w e ig h t of flask, compound and nitrobenzene 5 2 ,8 0 6 5 g w e ig h t of flask and compound 2 1 ,9 9 8 9 S w e ig h t of flask empty 21.503** g w e ig h t of compound 0 .4 9 5 5 g w e ig h t of nitrobenzene 3 0 .8 0 7 6 g H eading °C Time Reading °C Time m in s e c m in s e c if. 00 0 00 1 .9 5 6 18 3 .8 0 0 20 2 .0 0 6 23 3.60 , 0 . 43 2 .0 5 6 33 3.if0 1 15 2.10 6 46 3 .2 0 1 45 2 .1 5 7 06 3 .0 0 2 0? 2 .1 8 7 30 2 .8 0 2 27 2 .2 0 7 50 2 .6 0 2 50 2 .2 1 5 8 10 2 .ifO 3 07 2.225 8 30 2 .2 0 3 30 2 .2 3 5 9 00 2 .0 0 3 55 2 .2 4 0 9 30 1 .8 0 4 18 2 .2 4 5 10 00 1 .6 0 4 38 2 .2 5 0 10 30 l.ifO 5 01 2 .2 5 0 11 00 l.ifO 5 34 2.252 11 30 l.* f5 5 43 2 .2 5 4 12 00 1 .6 5 5 50 2 .2 5 4 13 00 1 .7 5 5 57 2 .2 4 8 14 00 1 .9 0 6 11 2 .2 4 0 15 00 Reading °C Time m in s e c 2 .2 4 2 16 00 2 .2 4 2 17 00 2 .2 4 0 18 00 2 .2 4 0 19 00 2.232 20 00 CALCULATION FOR MOLECULAR WEIGHT OF TRICHLORO( BENZOYLACETONATO)TITANIUM( IV) Molecular Weight = sample weight X Kf X 1000 w e ig h t o f 0 -NO2 T = Q - ^ 9 5 5 x Z a 2 Z x 1 0 0 0 30.8076 97355 Molecular Weight = 333.90 Temperature (°C) 0 4 ie (min.) Time 2 6 115 116 ANIONS OP POTENTIAL BIDENTATE LIGANDS A « II H ch3 c 6H5 *1 " c 6h 5 R1 " H H b 2 = H R2 " R2 = « II c h 3 II R3 = CH3 c 6h5 acelytacetone 1-phenyl-1 *3- It3-biphenyl-1*3- butanedlone propanedlone ch 3 R± « t - b u t y l *1 R2 - C=N H2 = H H3 a CH3 Rj a t - b u t y l 3-cyano-2f4- 2 12 f 6 96-tetram ethyl-3 15- pentanedlone heptanedlone CH_ ch3 R1 = = R2 = CHo R2 = H b 3 = CH- r 3 = NHCgHc 3-m ethyl-2#^f- pentand!one B G ( 8-hydroxyquincline sallcylaldehyde D £ substituted glyoxime benzil monoxime 117 13 =rro C R d ) . ■N* Q ■N' O ✓ R2 D FOOTNOTES 1* Wo Dilthey, Ohem. Ber., 36, 922(1903)® 2. • Ibid, 37, 588(1904). 3® Robert 0. Fay and R. N. Lowry, Inors. Chem., 9, 2048 ( 1 9 7 0 ) . 4. R.O. Fay and R.N. Lowry, Inorg. Nucl. Ohem. L ett.. 3, 117(1967). 5® D .C . B ra d le y and C .E . H o llo w a y , Ohem. Qommun. , 284(1965)® 6. M. Cox, J. Lewis, and R.S. Nyholm, J. Ohem. Soo. fl 6113(1964). ~ 7® R.O. Fay and R.N.Lowry, Inorg. Ohem., 6, 1512(1967). 8. N. Serpone and R.O. Fay, Ibid. 6, 1835(1967)® 9. D. W. Thompson, W.A. Somers, and M.O. Workman, Ibida 9 , 1252(1970 ). 10. M.J. Frazer and Z. Goffer, J. Chem.Soc. (A), 544(1966). 11. M.J. Frazer and B. Rimmer, Ibid, 69(1968). 12. I. Douek, M.J. Frazer, Z. Goffer, M. Goldstein, B. Rimmer, and H.A. W illis, Spectrochim. Acta, 23A, 373(1967). 13. D. Cunningham, I. Douek, M.J. Frazer, W.E. Newton, and B. Rimmer, J. Ohem. Soc. (A), 2133(1967). 14. J. Charalambous and M.J. Frazer, Ibid. 2361(1968). 15. D.N.Sen and P. Umapathy, Indian J . Ohem., 4, 454(1966). 16. A. Syamal, J. Inorg. Nucl. Ohem.s 31, 1850(1969). 17. A.L. Allred and L.W. Thompson, Inorg. Ohem. *7, 1196 (1968). 18. R.O. Young, Inorg. Syntheses, 2. 119(1946). 19. K.D. Pande and R.O. Mehrotra, Ohem. Ind. , 1198(1958). 20. D.M. Puri and R.O. Mehrotra, J. Lesg Qommon M etals. 3, 247(1961). 118 119 21 . Ibid, 4, 481(1962). 2 2 . N. Serpone and R.O. Fay, Inorg. Ohem. , 8, 2379(1969). 2 3 . Edward G. Taylor and Oharles A. Kraus, J. Ohem. Soc®, 69, 1731(1947). 2 4 . K. Nakamoto, "Infrared Spectra of Inorganic and Co ordinate Compounds", John Wiley and Son, New York, 1963, pp. 216-225. 2 5 . K. Nakamoto, P. J. MOOarthy, A Ruby and A.E. M artell, J. Amer. Ohem. Soc., 83, 1066(1961). 2 6 . S. Pinchas, Brian L. Silver, and I. Laulicht, J. Ohem. Phys., 46, 1506(1967). ~ 2 7 . Fred Basolo, Qoord. Ohem. Rev. , 3, 213(1968). 2 8 . R.J. Woodruff, James L. Marini, and J.P. Fackler, Jr., I n o r g . Ohem®, 3 , 6 8 7 (1 9 6 4 ). 2 9 . 35.M. Puri and R.O. Mehrotra, J. Less Qommon M etals, 5, 2(1963). 3 0 . R.O. Fay and N. Serpone, J. Amer-. Ohem. Soc. , 90, 5701(1968). 3 1 . M.J. Reynolds, J .Inorg. Nucl. Ohem. , 26, 667(1964), 3 2 . T.J. Pinnavaia and R.O. Fay, Inorg. Ohem. , 7, 502(1968). 3 3 . 35.W. Thompson, unpublished results. 3 4 . E.Oo Schlemper, Inorg. Ohem. , 6, 2012(1967). 35® R.O. Mehrotra and I.D® Verma, J. Less-Common M etals, 3, 321(1961). 3 6 . I. 35ouek, M.J. Frazer, Z. Goffer, M. Goldstein, R. Rimmer, and H.A* W illis, Spectrochim Acta. , 3 7 3 (1 9 6 7 ). 3 7 . F. Albert Cotton and Geoffrey Wilkinson "Advanced Inorganic Chemistry," John Wiley and Sons, New York, 1967, PP. 136-137 3 8 . J.L. Hoard and J.V® Silverston, Inorg. Ohem., 2,235(1963). 39® J.V. Silverston and J.L® Hoard, Ibid. 243. 4 0 . K.A. Kerr, J. Monteath Robertson, and G.A. Sim, J. Ohem. Soc. (B), 1305(1967). 120 41. R.D. Gillard and G. Wilkinson, J. Ohem* Soc. , 6041 (1963). 42. D.F. Shriver, "The Manipulation of Air-Sensitive Com pounds," McGraw-Hill Book Company, New York, 1969* 43. Traube, Ber., 31, 2944(1898). 44. J.P. Fackler, Jr., J. Chem. Soc., 1957(1960). 45* K.R Kopecky, D. Nonhebel, G. Morris, and G.S. Hammond, £ • 2 £ S e Qhem. , 2 7, 1036(1962). 46. D.W. Thompson and C. Hicks, This Laboratory. 47* D.W. Thompson, Inorg; Chem., 8, 2015(1969)* 48. D.W. Thompson, Ph.D. D issertation, Northwestern University, Evanston, 111., 1968. 49® R.C. Mehrotra and V.D. Gupta, J. Ind. Ohem. Soc. » 40, 911(1962). “ 50. G.T. Morgan and H.D.K. Drew, £. Ohem. Soc. , 1261(1924). 51® E.M. Brainina and R.Kh. Friedlina, Bull. Acad. Sci. , USSR, Div. Chem. Sci., 1331(1964). 52. D.N. Sen and U.N. Kantak, J. Indian Chem. Soc. , 46, 3 5 8 (1 9 6 8 ). 53® Gerald Doyle and R. Stuart Tobias, Inorg. Chem. 6, 1111(1967). 54. R.E. C ollis, J. Chem. Soc. (A), 1969(1895). 55. A. Yoshino, Y. Shuto, and Y. Itaka® Acta. Cryst.. B® 25, 744(1970). 56. K. Watenpaugh and C.N. Caughlan, Inorg. Chem.® 5. 1782 (1966 ). ~ 57. W. Haase and H. Hoppe, Acta. Cryst. , B, 24, 281(1968). 58. Ibid, 282(1968). 59* Branden and I. Lindqvist, Acta Ohem. Scand. , 14, 726. 60« I.R. Beattie and V. Fawcett, J. Ohem. Soc. (A), 1583(1967). 61* A.N. Nesmeyanov, O.V. Nogina, and V.A* Dubouitskil, Izv. Akad. Nauk* SSR. Ser* Khim., 1045-8(1968). 121 62. D.M. Puri, K.C. Pande and R.O. Mehrotra, J. Less- Common M e t a l s 9 4 , 3 9 3 (1 9 6 2 ). 63. A. Yamamoto and S. Kambara8 J. Amer. Ohem. Soc®. 79 , 4 3 4 4 (1 9 3 7 ). ~ 64. H. Junge and H. Musso, Spectrochlmica Acta. 1219(1968), 6 §.» R.A. Walton, Quart. Rev.. 19, 126(1963). 66. M.R. Rosenthal and R.S. Drago, Inorg® Chem., 5, 492(1966), 67. K.L. Wierzchowski and D. Shugar, Spectrochlmica Acta, 21, 943(1965). 68. Akio Yamamoto and Shu Kambara, J. Amer. Ohem. Soc. , 79, 4344(1957). 6 9 ® R,N. Lowry, Ph. D. Dissertation, Cornell University, Ithaca, NeY., 1967. 70. D.W. Thompson, Inorg. Ohem. , 8, 2015(19 69 ). 71« N. Serpone, Ph. D. Dissertation, Cornell University, I t h a c a , U .Y ., 1968. VITA PAMELA BOWEN BARRETT B orn i n C h a r l o t t e s v i l l e , V i r g i n i a , May 6 , 1947® G rad uated from Lane High School, June 1965* B«S*, College of William and Mary, 1969* In January 1970, the author entered the College of William and Mary as a graduate student in the Department of Chemistry and became a Candidate for the Degree of Master of Arts in September 1970« 122