Syntheses and properties of hydride–cyanamide and derived hydrogen-cyanamide complexes of molybdenum(iv). Crystal structure of [MoH2(NCNH2)2(Ph2PCH2CH2PPh2)2][BF4]2

Abstract

The first hydride–cyanamide (or –cyanoguanidine) complexes of molybdenum, [MoH₂(NCR)₂(dppe)₂][BF₄]₂ (R = NH₂1a, NMe₂1b, NEt₂1c or NC(NH₂)₂1d; dppe = Ph₂PCH₂CH₂PPh₂), have been prepared by treatment of [MoH₄(dppe)₂] in THF with the appropriate cyanamide (or cyanoguanidine) in the presence of HBF₄. Reaction of 1a with a base leads to the bis(hydrogen-cyanamide) [or bis(hydrogen-cyananoimide)] complex trans-[Mo(NCNH)₂(dppe)₂][BF₄]₂2 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 [MoH₂(NCNH)(NCNH₂)(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 NCNH₂ ligands involved in two hydrogen bonds connecting the ions in dimeric units.