Redox potential–structure relationships in metal complexes. Part 2. The influence of trans-substituents upon the redox properties of certain dinitrogen complexes of molybdenum and tungsten and some carbonyl analogues: inner-sphere versus outer-sphere electron transfer in the alkylation of co-ordinated dinitrogen
Abstract
The preparation of some new anionic dinitrogen complexes of the type trans-[M(N2)X(dppe)2]– is described (M = Mo or W; X = SCN, CN, or N3; dppe = Ph2PCH2CH2PPh2) together with their monocarbonyl analogues(M = Mo). Relationships between E½ox, ν(N2), and ν(CO) of these complexes and those of [M(N2)(NCR)(dppe)2] and the standard series [Cr(CO)5(L or X–)] have allowed us to identify the formation of a labile ammine complex [Mo(N2)(NH3)(dppe)2] in tetrahydrofuran and to predict E½ox and ν(N2) for as yet unsynthesised complexes related to those described. Furthermore, aspects of the reactivity of the co-ordinated dinitrogen ligand have been correlated with the ‘electron-richness’ of the complex (as measured by E½ox) with particular reference to (a) inner-sphere versus outer-sphere electron-transfer alkylation of co-ordinated dinitrogen to give organodiazenido-complexes and (b) the protonation of [M(N2)(NCR)(dppe)2] complexes which give the new hydrazido(2–)-salts, [M(N2H2)(NCR)(dppe)2][HSO4]2, with retention of the trans-RCN ligand.