Dithiocarbamate stabilized molybdenum imido complexes

This thesis is concerned with the synthesis, reactivity and structure of molybdenum imido complexes stabilized by dialkyldithiocarbamate ligands. The structure of a series of bis(arylimido) complexes [Mo(NR)2(S2CNEt2)2] is reported and compared to that of the parent complex [Mo(NPh)2 (S2CNEt2)2]. The complexes are prepared via two methods, involving either the thermolysis of [Mo(O)2 (S2CNEt2)2] with an organic isocyanate, or the treatment of [Mo(NR)2Cl2 (DME)] with [NH4[S2CNEt2]. The former reaction was not as simple as expected, affording [Mo(NR)2 (S2CNEt2)2] only with bulky arylisocyanates, the disulfur complexes [Mo(NR)(S2)(S2CNEt2)2] being the only compounds formed with all isocyanates. The structure and reactivity of the latter is reported, along with an investigation into the formation of the disulfur ligand, which is proposed to be the result of replacement of an oxo for an imido ligand, and a double sulphur-carbon bond cleavage of an additionally coordinated dithiocarbamate ligand. Other products from the reaction, although all dimeric, vary with the nature of the isocyanate. As the substituent on the isocyanate is increased in steric bulk the product changes from [Mo([mu]-NR)(O)(S2CNEt2)]2 (R=Ph, p-Tol) to [Mo(NR)([mu]-NR)(S2CNEt2)]2 (R=o-Tol), with no dimeric products being recovered with very bulky substituents. When bulky alkyl isocyanates are used the second product is the dimeric complex [{Mo2 ([mu]-S)2 (O)(NR)(S2CNEt2)2]. The reactivity and structures of these complexes is discussed, including the reversible addition of an isocyanate into the bridging imido ligand in [{Mo(NPh)([mu]-NPh)(S2CNEt2)}2] affording [{Mo(NPh)2 ([mu]-PhNC(O)NPh)([mu]- NPh)(S2CNEt2)2]