Synthesis of vanadium, niobium, and tantalum silylimido complexes and reactivity of their nitrogen-silicon bonds

Abstract

A series of group V transition-metal (trimethylsilyl)imido compounds has been synthesized in which the NSiMe3 groups derive from hexamethyldisilazane. Reaction of MC15 with 2 equiv of NH(SiMe3)2 produces [M(NSiMe3)Cl3(NH2SiMe3)]2 ( = Nb, Ta). Pyridine and substituted pyridine adducts, M(NSiMe3)Cl3L2 (M = Nb, L = py, 4-Mepy, or */2 4,4'-Me2bpy; M = Ta, L = py), are prepared either by addition of ligand to the niobium dimer or by direct reaction of the metal halide with a mixture of hexamethyldisilazane and pyridine. Related vanadium (trimethylsilyl)imido compounds, V(NSiMe3)Cl3L2 (L = 4-Etpy, 4-r-Bupy), are formed upon reaction of V(NSiMe3)Cl3 with added ligand in pentane. The vanadium compounds undergo fast, stoichiometric loss of chlorotrimethylsilane, yielding the nitrido derivatives V(N)C12L2, in contrast to slow, incomplete elimination of ClSiMe3 from the niobium and tantalum complexes. The reactivity of nitrogen-silicon bonds in silylimido ligands is discussed in light of these observations.

Silylimido Complexes of Niobium and Tantalum at the Limit of π‐Bond Saturation

“…The starting compounds [M(NSiMe 3 )Cl 3 (py) 2 ] (M = Nb, Ta) are readily prepared from the metal pentachlorides and (Me 3 Si) 2 NH 9. All our attempts to synthesize half‐sandwich complexes by treatment of these pyridine complex precursors with an equimolar amount of NaCp or LiCp* in THF or toluene failed.…”

“…Therefore these ligands can be envisaged as cyclopentadienyl ligand equivalents with a very high steric demand 17. According to our procedure developed for the synthesis of [Tp*M(N t Bu)Cl 2 ] (M = Nb, Ta)7 we treated [M(NSiMe 3 )Cl 3 (py) 2 ] (M = Nb, Ta)9 with 1 equiv. of KTp* in THF and isolated [Tp*M(NSiMe 3 )Cl 2 ] (M = Nb: 4a , Ta: 4b ) in good yields.…”

“…Starting materials: Niobium and tantalum pentachloride were products of H. C. Starck GmbH & Co. KG. The following compounds were prepared as described in the literature: Na(C 5 H 5 ),26 Li(C 5 Me 5 ),27 Me 3 Si(C 5 Me 5 ),28 LiN(SiMe 3 ) 2 ,29 KTp*,30 [(η 5 ‐C 5 Me 5 )MCl 4 ],14 [M(NSiMe 3 )Cl 3 (py) 2 ] (M = Nb, Ta)9.…”

“…In previous studies we and others have established the chemistry of organoimido complexes (R = alkyl, aryl) of type [(η 5 ‐C 5 R′ 5 )M(NR)X 2 ],2,5 [(η 5 ‐C 5 R′ 5 ) 2 M(NR)X]5a,5k,6 and [Tp*M(NR)Cl 2 ]7,22 (M = Nb, Ta, X = anionic ligand). Less reports are available, by far, for corresponding silylimido complexes of niobium and tantalum:8 the key compounds are [M(NSiMe 3 )Cl 3 (py) 2 ] reported by Doherty et al9, [Nb{(η 5 ‐C 5 H 4 )CMe 2 (η 5 ‐C 5 H 4 )}(NSiMe 3 )Cl], a representative of a silylimido ansa ‐metallocene complex reported by Green and co‐workers10 and [Cp*Ta(NSi t Bu 3 )Cl 2 ], which was synthesized and tested by Stryker et al4b as an interesting catalyst for olefin polymerization reactions. Our interest in developing silylimido compounds stems from their potential to act as precursors for heterobimetallic complexes containing bridging nitrido ligands 11.…”

Magnetic Properties of Magnetic Ultrafine Particles Synthesized from a Gaseous Mixture of Iron Pentacarbonyl and Trimethylsilyl Azide

“…Fe(CO) 4 + Fe(CO) 5 → Fe 2 (CO) 9 (2) When a partial pressure of TMSAz is higher than that of Fe(CO) 5 , Fe(CO) 4 reacts efficiently with TMSAz molecule to produce transient species (Fe(CO) 4 NSi(CH 3 ) 3 ) having silylimido and/or silyl nitrene structure [27][28][29] followed by further reaction with Fe(CO) 5 molecule leading to the formation of aerosol particles with terminal and bridging C-O groups (reactions (3) and (4)).…”