Transition-Metal Silyl Complexes and Chemistry in the Reactions of Silanes with Transition-Metal Complexes

Abstract

Studies from the authors' group of early-transition-metal silyl complexes and pathways in the reactions of silanes with transition-metal complexes are reviewed. Cyclopentadienyl-free, group 4 alkyl silyl, group 5 alkylidene silyl, group 6 alkylidyne silyl, and groups 4 and 5 amide and imide silyl complexes have been prepared and characterized. In the reactions of silanes with alkylidene and amide complexes, the MCH− π bonds and d−p π bonds in MNR2 were found to attack Si in silanes. The mechanistic studies here help in understanding the formation of mixtures of TiN and Si3N4 from the reactions of Ti(NMe2)4 and SiH4 as microelectronic diffusion barrier materials.

Transition metal alkylidene complexes. Pathways in their formation and tautomerization between bis-alkylidenes and alkyl alkylidynes

“…Our initial interest was to study silyl alkylidene complexes (Me 3 ECH 2 ) 2 Ta(]CHEMe 3 )(SiR 3 ) (3a,b and 4a,b), silyl analogs of d 0 high-oxidation-state Schrock-type alkyl alkylidene [6,7,12,28,48], and to compare the silyl and alkyl complexes. These complexes were prepared by the reactions in Scheme 2.…”

“…In the presence of PMe 3 , the reactions give bisalkylidene complexes (Me 3 ECH 2 )Ta(]CHEMe 3 ) 2 (PMe 3 ) 2 (E ¼ C, 14a; Si, 14b) [29,30]. In the absence of PMe 3 , 4b in benzene-d 6 decomposes within minutes at room temperature to the bridging dimeric alkyl alkylidyne complex (Me 3 SiCH 2 ) 4 Ta(m-CSiMe 3 ) 2 (15) (Scheme 3) [28], an alkyl alkylidyne complex first reported by Wilkinson and Mowat [10]. In comparison, in the absence of PMe 3 , the silyl neopentylidene (Me 3 CCH 2 ) 2 Ta(]CHCMe 3 )(SiBu t Ph 2 ) (4a) decomposes to unidentified products.…”

“…In comparison, in the absence of PMe 3 , the silyl neopentylidene (Me 3 CCH 2 ) 2 Ta(]CHCMe 3 )(SiBu t Ph 2 ) (4a) decomposes to unidentified products. The preferential silane elimination could be attributed to a kinetic effect, as it is slightly thermodynamically less favored [6,28] yield the silyl alkylidene 3b or dimerizes to give 17 [28] which then reacts with Si(SiMe 3 ) 3 À to give 15. It should be pointed out that in the preparation of silyl alkylidene 3b by the reaction in Scheme 4, 15 is a minor product.…”

“…We reasoned the following: (1) The conversion of Ta(CD 2 CMe 3 ) 5 (21-d 10 (20), Ta(CH 2 CMe 3 ) 5 (21), and (Me 3 CCH 2 ) 3 Ta]CHCMe 3 (5a), we briefly studied the reaction of (Me 3 CCD 2 ) 2 TaCl 3 with LiCD 2 CMe 3 and did observe Ta(CD 2 CMe 3 ) 5 (21-d 10 ) in the formation of (Me 3 CCD 2 ) 3 Ta]CDCMe 3 (5a-d 7 ) [6].…”

“…We used both (Me 3 CCD 2 ) 3 TaCl 2 (13a-d 6 ) and (Me 3 CCD 2 ) 4 TaCl (20-d 8 ), and then focused on 13a-d 6 , as it could be directly prepared from the reaction of TaCl 5 with Zn(CD 2 CMe 3 ) 2 while the preparation of 20-d 8 requires the initial preparation of (Me 3 CCD 2 ) 3 Ta]CDCMe 3 (5a-d 7 ) and then its reaction with DCl. In addition, the substitution of two Cl À ions in (Me 3 CCD 2 ) 3 TaCl 2 (13a-d 6 ) to give Ta(CD 2 CMe 3 ) 5 (21-d 10 ) was fast, relative to the conversion of 21-d 10 to 5a-d 7 , and was essentially not affected by the deuteration.…”