A Thesis entitled "FLUOROCARBON COMPLEXES OP THE TRANSITION METALS" submitted to the UNIVERSITY OF GLASGOW in fulfilment of the requirements for the degree of DOCTOR OP PHILOSOPHY * by JOHN L. DAVIDSON, B.Sc0 Department of Chemistry, University of Glasgow, GLASGOW, W2 September, 1973 ProQuest Number: 11017952 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a com plete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. uest ProQuest 11017952 Published by ProQuest LLC(2018). Copyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States C ode Microform Edition © ProQuest LLC. ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106- 1346 ACKNOWLEDGEMENTS I am especially grateful to Professor D.V.A. Sharp for his advice and encouragement during the course of this work. My thanks are also extended to the postgraduate students and staff members of the Chemistry Department for helpful and informative discussions with reference to this work. I am particularly indebted to the members of the X-ray crystallography unit mentioned in the text for undertaking and communicating the results of the X-ray studies described in this thesis. I should also like to acknowledge the assistance of Mr. Jim Gall and Mrs. F. Lawrie and her staff. The financial support of this research by the Science Research Council is gratefully acknowledged. ABSTRACT Reactions of transition metal carbonyl and cyclopentadienyl complexes with disulphides and acetylenes bearing fluorocarbon substituents have been investigated. Fhotolytic reactions of disulphides RSSR, R ■ CF^, C^F^ are considered to proceed via RS*radicals and with dimeric complexes monomers have been obtained e.g. [CpMo(C0)J2 — CpMo(CO),SR Use of closed reaction systems has enabled the identification of thermally unstable compounds such as Mn(CO)^SCF^ and CpNi(CO)SR which decarbonylate readily in an open system to di-or polymeric mercapto bridged complexes e.g. 2Mn(C0)^SCF^ [Mn(CO)4SCF5]2 + 2C0 Bie dimers in many cases exhibit isomerism due to inversion at sulphur and this has been studied by i.r. and n.m.r. spectroscopy. The photolytic reactions of disulphides and monomeric carbonyls e.g. Fe(CO)^, Mo(CO)^, gave dimeric mercapto-bridged compounds directly, e.g. [Pe(CO)3SCP3]2> [Mo (CO)4SCF3]2, but in the absence of u.v. light CpCoCCOjg and C^F^SSC^F^ gave CpCo(CO)(SC^F^)^ which can be decarbonylated to [CpCoSC^F^J^, illustrating that monomeric carbonyls can react with disulphides to give sulphur bridged dimers via an oxidative addition reaction. Possible mechanisms of these reactions and steric and electronic effects of the substituent on sulphur are discussed. Reactions of these organothic derivatives with acetylenes CF^CSCCF^ and CF^CsCH gave a variety of novel complexes. Complexes CpMo(CO)^SCF^, M m Mo, W,were observed to undergo CO substitution by CF^CgCF^ to give CpM(C0)2(CF^C2CF^)SCF^, the variable temperature n.m.r. spectra of which have been interpreted in terms of restricted rotation of the SCF, ligand. Similar complexes were obtained with j CELCsCCH* and PhC=CPh. In contrast CpMo(CO),SCF:. and CF-,CsCH gave j j j j j . the cyclopentadienone derivative CpMo(CO)[ (CF^C^H^COjSCF^ which was photochemically decarbonylated to [CpMo[(CF^C2H)2C0]SCF^]2. Insertion of CF^C^CCF^ into the Mn-S bond of [Mn(C0)4SC^F^J2 gave Mn(CO)4C(CF5)=C(CF5)SC6F5 while CF^C^CE gave Mn(CO)4 (CF_C2H)2SC6F5# With excess acetylene the former yielded Mn(CO) ^[(^(CF^^SCgFf.] which •has been shown by X-ray studies to contain a non-planar heterocyclic sulphonium ion [(^(CF^^SC^F^] bonded to an Mn(CO)^ species. Several other examples of acetylene insertion into M-S bonds were observed but with [Fe(CO)^SR]2 insertion into the Fe-Fe bond gave complexes [Fe(C0)^SR]2CF^C2R , R *= CF^, H. X-ray studies of [Fe(C0)^SCF^]2CF^C2CF^ have revealed that this results in a significant change in the Fe2S2 ring geometry which allows the formation of the syn (axial, axial) isomer not observed in the parent complexes. [CpCoSR]2 and CF^CsCCF^ in contrast gave CpCoC^(CF^)^ containing a tetrahapto hexakis(trifluoromethyl)benzene ligand. Attempts have been made to rationalise the various reaction types in terms of the properties of possible reaction intermediates. Reactions of certain cyclopentadienyl-nickel complexes with hexa- fluorobut-2-yne gave products resulting from condensation of the acetylene and a cyclopentaaienyl ligand, e.g. Cp2Ni + CFjC-CCFj— CpNi[(C5K5)C4(CF3)4 ] while in other cases cyclooligomerisation of the acetylene was observed. These reactions have been rationalised in terms of acetylene coordination promoting a n - a rearrangement of a cyclopentadienyl ligand. Several complexes were isolated in which a TT-cyclopentadienyl ligand appears to have been replaced by a nickelacyclopentadiene ring, CpHiC4(CF5)4, e. g . Cp2Ni^6(CF3)6, C p H i ^ C ^ C F j ^ C j H ^ F j C l ] and [C3H3NiC2(CF3)2]4> The crystal structure of the last has been solved and suggests that the molecule is formed by a Diels-Alder addition of the nickelacyclopentadiene ring of a dinuclear intermediate [CpNiC2(CF^)2J2 to the 1,2 positions of a cyclopentadienyl ring of a second dimeric species. The reactions of CpMo(CO)^X, X s Cl, Br, I, with acetylenes . RC=CR, R = CF^, CH^» have been found to give sixteen electron molybdenum complexes CpMo(RC2R)2X and with R « CH^ tetramethylquinone was also obtained. Variable temperature n.m.r. studies suggest that the coordinated acetylenes undergo an intramolecular exchange reaction at temperatures above -25°C, R - CF^, +15°C, R = CH^. CpMo(CO)^X and PhCsCPh gave sixteen electron complexes CpMo(C0)(FhC2Ph)X at low temperatures ( < 50°C) or on photolysis in pentane. At higher temperatures the tetraphenylcyclobutadiene derivatives CpMo(CO)(PhC^X were obtained. Brief studies of reactions of acetylenes with transition metal trifluorophosphine complexes suggest that in certain cases the latter react in a similar manner to analogous carbonyl derivatives. CpCo(PF^) and CFjOCCF^ gave CpCofC^CF^^PF^] according to mass spectral evidence and this undergoes stepwise hydrolysis to [CpCoC^CF-^PO^H] via CpCo[C4(CF_)4POF]. An X-ray study of the terminal hydrolysis product has revealed a structure containing a heterocyclic P(v) ring n-bonded to a cyclopentadienyl-cobalt moiety. This is analogous to CpCo[C4(CF^)4C0] obtained from the reaction of CpCo(C0)2 ana CF^CsCCF^. CONTENTS Introduction : Transition metal Sulphur Chemistry Chapter I Preparation and Reactions of Trifluoro- methyithio and Pentafluorophenylthio- Metallates Results and Discussion Conclusions Introduction : Transition metal Acetylene Chemistry Chapter II Reactions of Acetylenes with Some Transi tion-metal Trifluoromethylthio and Pentafluorophenylthio-Metallates Results and Discussion Conclusions Chapter III Reactions of Hexafluorobut-2-yne with Some Cyclopentadienyl-nickel Complexes Results and Discussion Conclusions Chapter IV Reactions of Acetylenes with Some Cyclopentadienyl Molybdenum Complexes Results and Discussion Conclusions Chapter V Reactions of Acetylenes with Some 225 Transition-metal Trifluorophosphine Complexes Results and Discussion 229 Conclusions 242 Appendix Reaction of CF^ChCCF^ with [Co(C0 )^SC^F^]2 244 Experimental 247 References 273 I N T R ODUCTION The emergence of organo-transition metal chemistry over the pa^t twenty years has led to a new understanding of the principles which govern structure and bonding in all classes of chemical compounds. The development of coordination chemistry has now reached the point where modern theory can give a convincing explanation for many of the new classes of compounds which have been synthesised during the period of intense activity which followed the discovery of ferrocene in 1951. Research into organo-transition-metal chemistry has necessarily been an interdisciplinary endeavour and consequently studies into the reactivity of coordinated ligands have led to organic synthesis via organo-transition-metal complexes. Many of the compounds produced by synthetic transition metal chemists have proved to be of immense use,not only in homogeneous catalysis,but to offer new routes to organic compounds, employing the principle of carbon skeleton assembly during complex formation. The many unsaturated compounds capable of forming tt-bonds with transition metals frequently re-arrange to form new ligands,sometimes organic moieties being produced which are not capable of separate existence (cyclobutadiene),while in other cases entirely new organic compounds are formed. Two areas of coordination chemistry which have attracted much attention in the past twenty years are those involving sulphide and acetylene complexes and it is with the organometallic chemistry of mercapto and acetylene ligands bearing fluorocarbon substituents, that this thesis is concerned. TRANSITION METAL SULPHUR CHEMISTRY Transition-metal Mercapto Complexes Since the early 1960 * s a rapid expansion of the literature on sulphur derivatives of the transition metals has occurred resulting in a comprehensive review in 1968.^ The following introduction is not intended to be extensive in view of this situation and is limited to the chemistry of organo-transition metal mercaptides with emphasis on their stability, since this is of relevance to the contents of Chapter I* Two basic types of mercapto complex can be described, (i) those containing terminal RS ligands(R «* organic group, e.g. CHy CFy C^Fy) which function as one electron donors to a transition-metal (ii) those containing bridging RS ligands donating three or five electrons to two or three transition-metals respectively. Structure and Bonding In valence bond terms the metal sulphur bond in terminal mercapto coniplexes is formed by overlap of a tetrahedral sp^ hybrid orbital on sulphur with a ©type orbital on the metal.