Sandwich and half-sandwich niobium imido complexes: X-ray crystal structure of [Nb(NAr)Cp′ 2Cl] (Cp′=η 5-C 5H 4SiMe 3, Ar=C 6H 4OMe-4)

Abstract

The imido niobium complexes [Nb(NAr)Cl 3(dme)] (Ar=C 6H 4Me-4 ( 1), C 6H 4OMe-4 ( 2)) have been prepared and characterised. The half-sandwich complex [Nb(NBu t )CpCl 2] ( 3) (Cp=η 5-C 5H 5) has been synthesised by a new method via the reaction of NaCp and [Nb(NBu t )Cl 3(py) 2] and in a similar manner the novel complex [Nb(NC 6H 4Me-4)CpCl 2] ( 4) was prepared by the reaction of NaCp with 1. The preparation of [Nb(NBu t )Cp ′Cl 2] ( 5) (Cp ′=η 5-C 5H 4SiMe 3) yielded an essentially inseparable mixture of 5 and [Nb(NBu t )Cp ′ 2Cl] ( 6). The imido niobocene(V) complex 6 was prepared and isolated as the unique product by a new synthetic pathway via the reaction of two equivalents of LiCp ′ and [Nb(NBu t )Cl 3(py) 2] and in a similar manner the novel complexes [Nb(NAr)Cp ′ 2Cl] (Ar=C 6H 4Me-4 ( 7), C 6H 4OMe-4 ( 8)) were prepared. The molecular structure of 8 has been determined by X-ray diffraction studies. The mixed metallocene complex [Nb(NBu t )CpCp ′Cl] ( 9) was prepared by the reaction of Li(C 5H 4SiMe 3) and 3. The alkylation of 6– 8 by ClMgCH 2CHCH 2 yielded the η 1-allyl complexes [Nb(NR)Cp ′ 2(CH 2CHCH 2)] (R=Bu t ( 10), C 6H 4Me-4 ( 11), C 6H 4OMe-4 ( 12)).