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

• Published in: Inorganica Chimica Acta 2003-07, Vol.350, p.293-298
• Main Authors: Fryzuk, Michael D., Shaver, Michael P., Patrick, Brian O.
• Format: Article
• Language: English
• Subjects: Diamidophosphine ligands; Imido; Niobium; Reduction; SiN bond cleavage
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/S0020-1693(02)01499-8

The diamidophosphine complexes of niobium CyPh[NPN]NbCl(DME) ( 2), CyPh[NPN]NbCl 2 ( 6), and PhPh[NPN]NbCl 2 ( 9), where RR′[NPN]=RP(CH 2SiMe 2NR′) 2 have been prepared, isolated and characterized. Generation of RR′[NPN]NbCl(DME) species competes with the production of ( RR′[NPN]NbCl) 2(μ-N 2) and can be controlled with N 2 pressure. CyPh[NPN]NbCl 2 spontaneously decomposes into CyPh[NPN]NbCl(NPh) ( 7), CyP(CH 2SiMe 2) 2NPh ( 8), and a paramagnetic impurity. Compound 7 was characterized by an X-ray diffraction study and its structural features are discussed. The NbN imido bond length is 1.789(2) Å with a NbN imidoC bond angle of 167.9(2)° in a distorted square pyramidal structure. Reduction of PhPh[NPN]NbCl 2 ( 9), with KC 8 produced PhPh[NPN]NbCl(NPh), PhP(CH 2SiMe 2) 2NPh, and a paramagnetic impurity. The diamidophosphine ligand RR′[NPN] ( RR′[NPN]RP(CH 2SiMe 2NR′) 2) and its chemistry with NbCl 3(DME) (DME=dimethoxyethane) and NbCl 4(THF) 2 are discussed. The complex CyPh[NPN]NbCl 2, for instance, can be generated from reaction of the dilithium salt of CyPh[NPN] and NbCl 4(THF) 2. This complex spontaneously decomposes into the Nb(V) imido complex CyPh[NPN]NbCl(NPh) by the intramolecular decomposition of the [NPN] ligand via scission of an SiN bond.