Studies of the co-ordination chemistry of guanidines with transition metals

Abstract

This work involves the characterisation of reaction products of transition metals from the 1st, 2nd and 3rd rows of the Periodic Table with guanidines and their lithiated derivatives. Physical methods such as infrared spectroscopy, (^1)H, (^13)C and (^19)F nuclear magnetic resonance spectroscopy, microanalysis, and conductivity measurements have been used to characterise the materials. The transition metal compounds used in this work can be divided into two groups: (i) metal carbonyls and (ii) metal halides. The metal carbonyls group consists of [M(CO)(_5)L] (M = Mn, L = Br; M = Cr, Mo, W, L = CO), [Mo(Cl)L(CO)(_3)] (L = Ƞ-C(_5)H(_5)) and [MoL(CO)(_3)][BF(_4)] (L = Ƞ-C(_7)H(_7) ), and the metal halide group consists of MCl(_2) (M = Pd, Pt), MLCl(_2) (M = Pd and L = C(_8)H(_12)), K(_2)MCl(_4) (M = Pd, Pt) and WCl(_4). Studies have involved two substituted guanidines, 1,2,3-triphenylguanidine and syn-1,2- diphenylguanidine and the Uthiated derivative of 1,2,3-triphenylguanidine.The reactions were undertaken using a variety of conditions. The type of solvent, temperature and molar ratio are important parameters, particularly for the complexes of manganese. Similar conditions were explored for the complexes of palladium, platinum, chromium, molybdenum, tungsten and arylmolybdenum derivatives. Carbonyl complexes of the type [Mn(Br)(CO)(_3)L(_2)] (L = 1,2,3- triphenylguanidine), [Mn(Br)(CO)(_4)L] (L = 1,2,3-triphenylguanidine), [Mo(Ƞ-C(_5)H(_5))L(CO)(_2)] (L = 1,2,3-triphenylguanidino) and complexes of the type [M2CI4L2] (M = Pd, Pt; L = 1,2,3-triphenylguanidine, 1,2-diphenylguanidine), [Pt(_2)Cl(_4)L(_3)] (L = syn-1,2-diphenylguanidine), [Pt(_2)Cl(_4)L(_2)L'] (L = syn-1,2-diphenylguanidine, L' = N,N'-diphenylurea), [Pt(_2)Cl(_2)L(_2)L'(_2)] (L = syn-l,2-diphenylguanidino, L(^1) = syn-l,2- diphenylguanidine ), [PtCl(_2)L] (L = HNC(Me)NHC(Me)NH) and [PdCl(_2)(C(_8)H(_12))L] (L = 1,2,3-triphenylguanidine, syn-1,2-diphenylguanidine), were isolated. A product containing BF(_3) was isolated, and the bonding of the BF(_3) studied. The guanidine ligand adopts various bonding modes towards transition metals, and studies have been directed towards determining the mode adopted in each of the new complexes synthesised. Guanidines are found to act as strong o- bonding ligands, having consequences on the remaining ligands. Comparison is made throughout with the related amidine ligands. Mechanisms of reactions, consistent with experimental data, are discussed throughout the thesis.