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

Abstract

Keywords: Niobium / Tantalum / N ligands / Cyclopentadienyl ligands / Rearrangements Convenient strategies towards the synthesis of silylimido niobium and -tantalum complexes of the metallocene and half-sandwich type are reported. Bent metallocenes [(η 5 -C 5 H 5 ) 2 M(NSiMe 3 )Cl] (M = Nb: 1a; Ta: 1b) and [(η 5 -C 5 H 5 ) 2 M(NSiMe 3 )(η 1 -C 5 H 5 )] (M = Nb: 2a; Ta: 2b) are synthesized by reaction of [M(NSiMe 3 )Cl 3 (py) 2 ] with 2 or 3 equiv. NaCp, respectively. Half-sandwich type silylimido complexes [(η 5 -C 5 Me 5 )M(NSiMe 3 )Cl 2 ] (M = Nb: 3a; Ta: 3b) cannot selectively be obtained from the (pyridine)(silylimido) precursor complexes. However, their synthesis is accomplished by reaction of [(η 5 -C 5 Me 5 )MCl 4 ] with LiN(SiMe 3 ) 2 . On the other hand pyridine silylimido complexes are perfect

Synthesis and DFT, Multinuclear Magnetic Resonance, and X-ray Structural Studies of Iminoacyl Imido Hydridotris(3,5-dimethylpyrazolyl)borate Niobium and Tantalum(V) Complexes

“…Therefore, preliminary reports in this field pointed to facile in situ decomposition of the compounds via hydrolysis and redox reactions, B–N bond cleavage, or unexpected synthesis of ionic derivatives. However, despite these difficulties, a number of group 4 and 5 metal complexes of the [MTpX 3 ] − and [MTpX 4 ] , types, respectively, with sterically crowded and electronically flexible Tp ligands have been synthesized and their reactivity toward cationic species potentially useful in polymerization processes has been studied. In this context, we have reported the synthesis and structural studies of a series of chlorido, amido, and alkyl chlorido imido hydridotris(3,5-dimethylpyrazolyl)borate niobium and tantalum(V) compounds.…”

Titanium and niobium imido complexes stabilized by heteroscorpionate ligands

“…For example, irradiation in complexes 7 or 10 of the imido tert-butyl group enhances only one of the Me 3 signals, which is clearly the Me group (Me 3 ) of the cis pyrazole ring as it is in closer spatial proximity to the imido ligand. In addition, the 13 C{H} NMR spectra of these complexes exhibit two resonances for the different pyrazole carbon atoms, C 3 , C 4 , C 5 , Me 3 , Me 5 . The most shielded signal for the bdmpza ligand appears at ca.…”

“…1 This interest has been sustained, in part, by the utility of such compounds in organic transformations and catalysis (e.g., in olefin metathesis or polymerization catalysis). 1-3 In previous studies, imido complexes of Group 4 and 5 metals have been stabilized by tris(pyrazolyl)hydroborate ligands 4, 5 and polydentate amido-donor ligands, 6 which not only meet the electronic demands of the highly Lewis acidic early transition metal centre but ideally allow the generation of low-coordinate imido species-i.e., the polydentate ligands protect the majority of the coordination sphere of the metal. We have recently been interested in the synthesis of new "heteroscorpionate" ligands 7 that contain pyrazole rings.…”

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)).…”