Sandwich and Half‐Sandwich (Imido)niobium Complexes

Abstract

This review discusses the study we have carried out towards the synthesis, structure and reactivity of (imido)niobium complexes, which contain at least one cyclopentadienyl ligand. The following families of niobium complexes are described: (i) half-sandwich imido complexes; (ii) metallocene imido compounds; (iii) imido complexes containing ansa-cyclo-

Synthesis and reactivity of new mono- and dinuclear niobium and tantalum imido complexes: X-ray crystal structure of [Ta(η5-C5H4SiMe3)Cl2{NC6Me4-4-(N(SiMe3)2)}]

“…(2)) initially afforded a mixture of the dinuclear, [{Ta (g 5 -C 5 H 4 SiMe 3 )Cl 2 } 2 (l-1, Me 4 N)] (3), and mononuclear, [Ta (g 5 -C 5 H 4 SiMe 3 )-Cl 2 {@NC 6 Me 4 -4-(N(SiMe 3 ) 2 )}] (4), imido complexes along with 2. In order to favour the production of 3, the volatile SiMe 3 Cl was removed from the medium by placing the reaction mixture under reduced pressure.…”

“…The presence of imido groups in the organometallic chemistry of niobium and tantalum is well documented [3] and our contribution to this field has recently been published [4]. Part of our research work has been dedicated to the use of metal centre bridging di-imido ligands [5] and as a continuation of this, we now report the synthesis, structural characterization and reactivity of mono-and dinuclear niobium and tantalum imido complexes.…”

“…1 H NMR (400 MHz, C 6 D 6 ): d 0.14 (s, 18H, NSiMe 3 ), 0.18 (s, 9H, C 5 H 4 SiMe 3 ), 2.17 (6H), 2.54 (6H) (s, C 6 Me 4 ), 2.88 (3H), 3.60 (3H) (br, NMe 2 ), 5.93 (1H), 5.96 (1H), 6.13 (1H), 6.53 (1H) (m, C 5 H 4 ) 13. C{ 1 H} NMR (100 MHz, C 6 D 6 ): d À0.1 (C 5 H 4 SiMe 3 ), 2.6 (NSiMe 3 ), 2.7, 3.9 (PhC(NSiMe 3 ) 2 ) 17.0, 18.0 (C 6 Me 4 ), 50.1, 59.5 (NMe 2 ), 111 4,. 112.1, 112.3, 120.0, 124.0 (C 5 H 4 ), 130.9, 132.8, 141.9 (CN), 153.0 (CN) (C 6 Me 4 ).…”

Carbosilane dendrimers containing peripheral cyclopentadienyl niobium- and tantalum-imido complexes

“…1320-1340 cm À1 . A limited number of procedures for the synthesis of niobocene-imido complexes has been reported so far [13]. A straightforward method consists in the reaction of niobium-imido halide precursors with alkali or alkaline earth metal cyclopentadienides [14].…”

Isocyanide insertion reactivity of dinuclear niobium and tantalum imido complexes: X-ray crystal structure of [{Nb(η5-C5H4SiMe3)(CH2Ph)2}2(μ-1,4-NC6H4N)]

“…A review of our contribution to this field has recently been published [4]. Part of our research work has been focussed on the incorporation of di-imido ligands that bridge two metal centres and we have previously reported the preparation of metallocene, monocyclopentadienyl, alkyl, hydride and benzamidinate derivatives [5].…”