Carbene complexes. Part 13. The synthesis and characterisation of secondary carbene complexes of vanadium(I), chromium(0), molybdenum(0), tungsten(0), manganese(I), rhenium(I), iron(0), ruthenium(II), cobalt(I), iridium(III), and platinum(IV), and hydridorhodium(III)

Abstract

(Chloromethylene)dimethylammonium chloride [NMe₂(CHCl)]Cl (or its dibromo-analogue) is a convenient source of secondary carbenemetal complexes [M{CH(NMe₂)}L_n]. As well as three-fragment oxidative addition to d⁸ metal complexes (Ru⁰, lr^I, or Pt^II) to give d⁶ adducts, two other procedures have been developed: salt elimination from a transition-metallate dianion precursor (V^–I, Cr^–II, Mo^–II, W^–II, or Fe^–II), and salt elimination with concomitant oxidative addition using a transition-metallate monoanion precursor (Mo⁰, W⁰, Mn^–I, Re^–I, or Co^–I). The carbenerhodium(III) complex [{Rh[CH(NMe₂)](CO)Cl₃}₂] reacts with PPh₃ in ethanol to yield the hydridocarbene complex [Rh{CH(NMe₂)}Cl₂H (PR₃)₂](R = Ph) from which analogues (R₃= Et₂ or Me₂Ph) are accessible. Infrared and ¹H or ¹³C n.m.r. spectra have been used to characterise the 23 new complexes and establish their stereochemistry.