Multiple metal-carbon bonds. 8. Preparation, characterization, and mechanism of formation of the tantalum and niobium neopentylidene complexes, M(CH2CMe3)3(CHCMe3)

Ammonia and Dinitrogen Activation by Surface Organometallic Chemistry on Silica‐Grafted Tantalum Hydrides

“…[1] In the case of silica-grafted tantalum precursors, grafting of the tantalum organometallic precursor tris(neopentyl)neopentylidenetantalum(V), Ta(=CH-tBu)Np 3 (Np = CH 2 CMe 3 ), [11] onto silica is achieved through surface organometallic procedures analogous to those employed for other metals (e.g., Hf, Zr, Ti). [12][13][14][15] Sublimation or impregnation of the volatile perhydrocarbyl precursor Ta(=CH-tBu)Np 3 onto a partially dehydroxylated silica surface leads to the formation of the grafted organometallic species [(ϵSiO)Ta(=CH-tBu)Np 2 ] (1a) and [(ϵSiO) 2 Ta(=CH-tBu)-Np] (1b) [16] [see Equations (1a,b)], whose relative distribution can be controlled by the concentration of surface silanol groups generated during the dehydroxylation step.…”

The Synthesis of Organometallic YlidesInteraction of Methylenetriphenylphosphorane with Bis(η5-cyclopentadienyl)-zirconium and -hafnium Dichlorides and the Molecular Structure of Bis(η5 -Cyclopentadienyl)chlorozirconylmethylenetriphenylphosphorane

“…The alkylidene species [(CH3)3CCH2]3Ta-CHC(CH3)3 is generated rather than substitution of the halogen [8].…”

“…In the alkylidene complexes of Ta(V), x JCH values are uncommonly small for (Ta = CHR, IJCH = 90 Hz) [8]; such small values are unreliable indicators of carbon hybridization in these compounds. Lower values than expected for !JCH in organolithium compounds [13] have also been reported due to the charge density on the carbon atoms.…”

Synthesis and characterization of tert-butylcyclopentadienyl derivatives of hafnium

“…The trimethylsilyl 1,3-di(tert-butyi)cyclopentadiene reagent was obtained by reaction of 1,3-di(tert-butyl)cyclopentadiene, synthesized as a mixture of different possible isomers, with Lin-Bu and chlorotrimethylsilane [4]. When a hexane solution of complex I was treated with a diethyl ether solution of MgCIMe, in a molar ratio 1: 3.1, an almost quantitative yield of the trimethyl hafnium compound (6). Formation of the analogous dibenzyl complex was observed when the reaction of a hexane solution of $ with MgBz 2 • 2THF was carried out under rigorously anhydrous conditions into a drybox.…”

“…LiMe (1.6 M diethyl ether solution), MgCIMe (3 M diethyl ether solution) and HfCi 4 (Aldrich) were purchased and used without further purification. Si(C s H 3-1,3 -t Bu 2)Me.~ [4], MgBz 2 • 2THF [5], LiCH2SiMe 3 [6] and TICp [7] were …”