Syntheses and properties of hydride-cyanamide and derived hydrogen-cyanamide complexes of molybdenum (IV). Crystal structure of [MoH_2(NCNH_2)_2(Ph_2PCH_2CH_2PPh_2)_2][BF_4]_2

摘要

The first hydride-cyanamide (or-cyanoguanidine) complexes of molybdenum, [MoH_2(NCR_2)(dppe)_2][BF_4]_2(R = NH_2 la, NMe_2 1b, NEt_2 1c or NC(NH_2)_2 1d; dppe = Ph_2PCH_2CH_2PPh_2), have been prepared by treatment of [MoH_4(dppe)_2] in THF with the appropriate cyanamide (or cyanoguanidine) in the presence of HBF_4. Reaction of 1a with a base leads to the bis(hydrogen-cyanamide)[or bis(hydrogen-cyananoimide)] complex trans-[Mo(NCNH)_2(dppe)_2][BF_4]_2 2 or to the bis(cyanoimide) complex trans-[Mo(NCN)_2(dppe)_2] 3, via base-catalysed or base-promoted dehydrogenation, whereas cathodically-induced dehydrogenation appears to form [MoH_2(NCHN)(NCNH)_2(dppe)_2]~+ 4. The spectroscopic properties of the complexes are also reported along with their electrochemical behaviours and the molecular structure of 1a as established by X-ray crystallography which indicates the presence of the NCNH_2 ligands involved in two hydrogen bonds connecting the ions in dimeric units.