ChemInform Abstract: Preparation and Characterization of Molybdenum(IV)-Alkyne Complexes Containing Bulky Aryloxide or Arenethiolate Ligands.

ChemInform Abstract

Starting with the tetrachloroalkyne complexes (III) or the tetrakis(arenethiolate) complexes (VII), the title complexes (I) and (II) are prepared as shown in the scheme. Molecular and crystal structures of the crowded, distorted-trigonal-bipyramidal complex (Id) (space group P21212, Z=2) with equatorial alkyne and of the crowded trigonal-bipyramidal complex (IIb) ( P2₁/n, Z=4) with axial 3-hexyne are determined by X-ray analysis. The alkyne ligand in (II) can be substituted by another (alkyne') in a reaction that is first order in Mo and zero order in alkyne' when the alkyne is ethyne. In contrast, the alkyne ligand in (Ic), (Id) cannot be replaced by another simple alkyne. Electrochemical studies show that (Ic), (Id) and (II) can be reduced in dichloromethane, the former more easily than the latter by ∼ 0.2 V. The reduction is an irreversible EC reaction in which only 0.5 electron is consumed; the reduction products cannot be identified.