Indian Journal of Chemistry Vol. 20A, May 1981, pp. 440-44~ Synthesis & Properties of Some Metal s-Methalloxides S. C. GOEL & R. c. MEHROTRA*t Chemistry Department. University of Delhi. Delhi 110 007 Received 8 August 1980; revised and accepted 20 November 1980 Metal derivatives of [3-methallyl alcohol having the general formulae M[OCH2C(CH3)=CH.l.. (M = B and AI); M[OCH2C(CHs)=CH2]4, (M=Ge and Ti); M[OCH.C(CH3)=CH.ls, (M = Nb and Ta) and BunSn[OCH.C- (CH3)= CH2]4_n, (n = 1,2 and 3) have been synthesized by alcohol interchange technique. Germanium tetra-p-methal- loxide has been synthesized by the reaction of germanium tetrachloride with {3-methallylalcohol in the presence of dry ammonia as hydrogen chloride acceptor. These newly synthesized [3-methalloxides are colourless liquids which can be distilled under reduced pressure. These derivatives have been characterized by elemental analyses, molecular weight determinations and IR as well as PMR spectral data. ESPITE extensive work in alkoxid.e chemistry', passed slowly for 45 min. The precipitated ammoni- the alkenoxide derivatives derived from um chloride was filtered off and the solvent removed D unsaturated alcohols have received little from the filtrate under reduced pressure. The colour- attentionv". The presence of double bond may less liquid on distillation under reduced pressure affect the basic properties of alkoxides like volatility, gave germanium tetra-Bsmethalloxide; yield 74 %; molecular association and nature of metal coordi- b. p. 95°C/0.7 mm. nation. In the present paper, we report the synthesis Reaction of ~-methallyl alcohol with aluminium and properties of some metal aiken oxides derived isopropoxide ~ Aluminium isopropoxide (6.30 g), from ,B-methallyl alcohol. The literature reports the dry benzene (70 ml) and ~-methallyl alcohol (6.80 g) preparation of boron tri-p-methalloxide by two were mixed and refluxed employing a fractionating methods: (i) by heating boric oxide with ~-methallyl column to slowly remove isopropanol-benzene alcohol in the presence of anhydrous copper sul- azeotrope. When the temperature became constant phate"; and (ii) by the interaction of boron trichlo- at 80°, heating was stopped and excess of solvent ride with ~-methallyl alcohol". removed under reduced pressure. The crude product thus isolated was distilled to give pure aluminium Materials and Methods tri-,8-methalloxide as a colour less viscous liquid. Throughout the experiments stringent precautions Other ~-methalloxides of boron, germanium, tita- were taken to exclude moisture. Aluminium, ger- nium, niobium, tantalum, mono-, di- and tri-butyltin manium, titanium, niobium, tantalum and butyltin were prepared similarly from the corresponding isopropoxides were prepared by well established metal isopropoxide (ethoxide in the case of boron). methods'. ,B-Methallyl alcohol (Fluka) was. dried Reaction of boric oxide with fJ-methallyl alcohol ~ A by keeping over anhydrous potassium carbonate mixture of boric oxide (0.5 g) and ,B-methallyl alcohol and finally SUbjected to fractional distillation (b.p. ( '" 4.0 g) in dry benzene (60 ml) was refluxed and the 112-13°). Boron, aluminium, germanium, titanium, liberated water fractionated out. Finally excess of niobium, tantalum and tin Were estimated in the benzene was removed under reduced pressure and the compounds as described earlier+s. Alcohol (isopro- crude product was distilled to give tri-,8-methallyl panol or ethanol) in azeotrope was estimated by borate; yield 91 %; b.p. 82°C/5mm. oxidimetric methods. Infrared spectra were recorded as neat liquid films Results and Discussion on a Perkin-Elmer spectrophotometer 621, and PMR The characterization data of newly prepared spectra on a Perkin-Elmer 90MHz instrument ~-methalloxides are given in Table 1. Germanium (R-32) using TMS as an internal standard. Mole- tetra -,B-methalloxide has been synthesized by passing cular weights were determined in a semimicro ebullio- a current of dry ammonia in a mixture of germanium meter (Gallankamp) using thermistor sensor and tetrachloride and ~-methallyl alcohol in dry benzene refractive indices using an Abbe refractrometer (Eq. 1) (Toshniwal). GeCl4 + 4CH •.=C(CH3)CH20H + 4NH3 -+ Reaction of germanium tetrachloride and f3-methallyl Ge[OCH2C(CH3)=('H2]4+4NH4Cl t .. (1) alcohol ~ To a solution of germanium tetrachloride (1.55 g) in dry benzene (60ml) was added ~-methallyl This method could not be adopted for the synthesis alcohol (2.21 g), and a current of dry ammonia was of ,B-methalloxides of titanium, niobium and tantalum probably due to the strong Lewis acid character of tPresent address: Chemistry Department. University of these metal chlorides, since the water formed by the Rajasthan. Jaipur 302 004. reaction of excess alcohol with the liberated hydrogen 440 I GOEL & MEHROTRA : PREPARATION OF METAL METHALLOXIDES TABLE 1 - CHARACTERISATION DATA OF THE VARIOUS ~-METHALLOXIDES OBTAINED BY THE REACTION OF METAL ALKOXIDE WITH ~-METHALLYL ALCOHOL Molar Product isolated Mol. wt 20 Alkoxide b.p. Alcohol in Metal (%) 0 D ratio (yield, %) °C/mm azeotrope (g) obs. found obs. (Calc.) (Calc.) (Calc.) B(OEth 1:3 B[OCH2C(CHs)= CH21. 82/$.. 3.26 4.74 239 1.433 (92) (3.52) (4.82) (224) Al(OPri). 1:3 Al[OCH2C(CH3) = CH21. 198/0.5 5.01 11.08 994 1.476 (88) (5.07) (11.23) (240) Ge(OPri). 1:4 Ge[OCH2C(CH3) = CHJ. 95/0.7 1.63 20.18 344 1.453 (82) (1.75) (20.32) (357) Ti(OPri). 1:4 Ti(OCH2C(CH.) =CH21. 140-41/0.5 3.01 14.23 609 1.529 (92) (3.02) (14.42) (332) Nb(OPri)~ 1:5 Nb[OCH2C(CH.) =CH21~ 174/0.4 1.85 20.85 835 1.510 (88) (1.95) (20.71) (448) Ta(OPrih 1:5 Ta[OCH2C(CH3) =CH2ls 185-88/0.5 1.84 33.28 1044 1.499 (93) (1.83) (33.72) (536) BuSn(OPri). 1:3 BuSn[OCH.C(CH3)=CH.I. 1.02 30.42 805 1.508 (98) (1.07) (30.51) (389) Bu.Sn(OPri). 1:2 Bu.Sn[OCH2C(CH3) = CH.I. 142/0.5 0.93 31.56 453 1.490 (90) (0.95) (31.60) (375) Bu.Sn(OPri) 1:1 Bu.Sn[OCH.C(CH)3 = CH.] 130/0.5 0.41 32.44 379 1.473 (95) (0.43) (32.86) (361) chloride would tend to hydrolyse the product. In ing in alkenoxy group at ~-position has no discren- the reaction of titanium tetrachloride with ~-metha- able effect on molecular complexity. Also molecular llyl alcohol ,B-methallyl chloride (b.p. 70-72°) was complexities of these ~-methalloxides are almost the isolated, indicating that hydrogen chloride liberated same as compared to those of the alkoxides derived reacts with ~-methal1yl alcohol. However, the corres- from these metals and corresponding saturated ponding derivatives of titanium, niobium, and alcohol, 2-methyl propane-l-ol-. tantalum and also of aluminium and alkyJtin were The IR spectra ('Imaxin cm-I) of these ~-methallo- synthesized by the reactions of their isopropoxides xides exhibit a sharp 'IC=C frequency in the region with ,B-methallyl alcohol in appropriate molar 1650-1665 indicating the expected retention of ratio followed by removal of liberated isopropanol carbon-carbon double bond. Absorptions in the by azeotropic fractionation with benzene (Eqs 2 regions 1805-1785, 965-955 and 900-890 further and 3) support the existence of )C=C< linkage in these i M(OPr ) ••+nCH2=C(CH )CH OH -+ a a compounds", Absorptions in the region 1100-1000 M[OCH C(CH3)=CH l .•+nPriOH t .. (2) a a may be attributed to 'IC-O vibration-". The M-O where, M=AI, n=3; M=Ge and Ti, n=4 and absorptions'P'P appear in the region 600-400, except Ms=Nb and Ta, n=5 for the boron derivative in which it appears in the Bu••Sn(OPri)4- ••+4~nCHa=C (CHa)CHaOH -+ range 1400-1300. BUnSn[OCHaC(CHa)=CHJ4_n+4-nPriOH t .. (3) PMR spectra of all the metal ~-methalloxides show where, n = 1, 2 and 3. the absence of hydroxy proton signal ( ~ 4.1 in The boron derivative could be prepared convenien- parent alkenol) indicating the formation of O-M tly either by refluxing boric oxide with ~-methalJyl bonds. Except for -OCHa protons, the chemical alcohol and removing the liberated water azeotropi- shifts observed in these alkenoxides are similar to cally with benzene or by alcoholysis of ethyl borate. those exhibited by parent alcohol (Table 2). The All the above methalloxides are colourless liquids position of -OCHz signal depends on the nature of which could be purified by distillation under reduced the element to which the alkenoxy group is bonded. pressure. They are highly sensitive to moisture and As the e1ectrophilicity of the element increases the soluble in common organic solvents. -OCHa signal shifts to down field. Molecular weight determination data in boiling In the compounds Tia[OCH:;.C(CHa)=CHz]s; benzene indicate that boron, germanium and tributyl- Nb2[OCHzC(CHa)= CHZ]lOand Ta2[OCHzC(CH3)= tin ~-methalloxides have a degree of association close CH2]lO, at room temperature, distinction could not to 1 (Found: B 1.07, Ge 0.96, BU3Sn LOS); titanium, be made between the -OCH2 resonance due to termi- niobium and tantalum (3-methalloxides show degree nal and bridging alkenoxy groups, which must have of association close to 2 (Found : 1.8, 1.9 and 1.9 both type of alkenoxy groups. However in the case for Ti, Nb and Ta respectively). Aluminium tri-,B- of freshly distilled aluminium tri-a-methalloxide the methal.loxide is found to be tetrameric (Found: PMR spectrum shows three signals at il 4.40,4.35 and 3.9). The monobutyltin tri-B-methalloxide is dimeric 4.07. The signals at ~ 4.40 and 4.35 may be due to (Found: 2.0) whereas, dibutyltin di-~-methalloxide the two types of bridging ~OCHa protons while shows a weak tendency of dimerisation.