Diamidophosphine complexes of niobium(III) and (IV): imide formation via ancillary ligand decomposition

The diamidophosphine complexes of niobium CyPh[NPN]NbCl(DME) (2), CyPh[NPN]NbCl2 (6), and PhPh[NPN]NbCl2 (9), where RR′[NPN]=RP(CH2SiMe2NR′)2 have been prepared, isolated and characterized. Generation of RR′[NPN]NbCl(DME) species competes with the production of (RR′[NPN]NbCl)2(μ-N2) and can be controlled with N2 pressure. CyPh[NPN]NbCl2 spontaneously decomposes into CyPh[NPN]NbCl(NPh) (7), CyP(CH2SiMe2)2NPh (8), and a paramagnetic impurity. Compound 7 was characterized by an X-ray diffraction study and its structural features are discussed. The NbNimido bond length is 1.789(2) Å with a NbNimidoC bond angle of 167.9(2)° in a distorted square pyramidal structure. Reduction of PhPh[NPN]NbCl2 (9), with KC8 produced PhPh[NPN]NbCl(NPh), PhP(CH2SiMe2)2NPh, and a paramagnetic impurity.