η:η-Alkynyl-Bridged W−Si Complexes:  Formation, Structure, and Reaction with Acetone

Abstract

Reactions of (eta5-C5Me4R)(CO)2(MeCN)WMe (R = Me, Et) with HPh2SiCCtBu gave the novel alkynyl-bridged W-Si complexes, (eta5-C5Me4R)(CO)2W(mu-eta1:eta2-CCtBu)(SiPh2) (R = Me, Et), whose alkynyl ligands bridge the tungsten and silicon atoms in an eta1:eta2-coordination mode. The structures of these complexes were fully characterized, including X-ray crystallography. Treatment of (eta5-C5Me5)(CO)2W(mu-eta1:eta2-CCtBu)(SiPh2) with acetone resulted in acetone insertion into the silicon-alkynyl linkage followed by intramolecular C-H activation of the tBu group to give the chelate-type alkyl-alkene complex, (eta5-C5Me5)(CO)2W(eta1:eta2-CH2CMe2C=CHSiPh2OCMe2).

Conversion of an Acetylide−Silylene Complex to an Alkenylcarbyne Complex by Consecutive Ketone Addition and Base-Induced Silanone Elimination

“…The molecular structure of 4 indicates that the silylene ligand interacts with both the metal and the acetylide fragments, similar to 2b , but significant differences are found in their W−Si and Si−C2 bond distances. The W1−Si1 distance (2.5474(16) Å) of 4 is considerably shorter than that (2.567(2) Å) of 2b , whereas the Si1−C2 distance (2.059(6) Å) of 4 is significantly longer than that (2.008(7) Å) of 2b . These differences indicate stronger silylene−metal and weaker silylene−acetylide interactions in 4 than in 2b .…”

“…Transition-metal silylene complexes have attracted much attention as possible intermediates in various metal-mediated reactions of organosilicon compounds, and recent studies have revealed the interesting reactivity of isolated silylene complexes . Recently, we reported the synthesis of the novel acetylide−silylene complexes Cp′(CO) 2 W(SiPh 2 )(CC t Bu) ( 2a , Cp′ = η 5 -C 5 Me 5 ; 2b , Cp′ = η 5 -C 5 Me 4 Et), which have unique structural features and bonding interactions (Scheme ) . In addition to the silylene−metal interaction, Sakaki’s theoretical study revealed dual charge transfer interactions between the acetylide and silylene ligands: from the π orbital of the acetylide to the empty p orbital of the silylene and from the lone pair orbital of the silylene to the π* orbital of the acetylide .…”

“…In addition to the silylene−metal interaction, Sakaki’s theoretical study revealed dual charge transfer interactions between the acetylide and silylene ligands: from the π orbital of the acetylide to the empty p orbital of the silylene and from the lone pair orbital of the silylene to the π* orbital of the acetylide . The acetylide−silylene complex 2a exhibits an interesting reactivity toward acetone, yielding chelate-type alkyl alkene complex 3 (Scheme ) . Considering the electrophilic nature of the silylene center of silylene complexes, this reaction is likely to be initiated by nucleophilic attack of the oxygen of acetone to the silylene center of 2a .…”

Hydrosilylation and Hydrogermylation of CO2 and CS2 by Al and Ga Functionalized Silanes and Germanes – Cooperative Reactivity with Formation of Silyl Formates and Disilylacetals

“…Commercially available t Bu–C≡CH and i Pr 2 Si(H)Cl were dried with molecular sieves; i PrMgCl in THF, n BuLi in n ‐hexane, CS 2 , CO 2 , i Bu 2 Al–H and Et 2 Al–H were used without further purification. t Bu 2 Al–H, [ 39 ] t Bu 2 Ga–H, [ 39 ] [(Me 3 Si) 2 CH] 2 Al‐H, [ 39 ] Me 2 Al–H [ 40 ] and Ph 2 Si(H)–C≡C‐ t Bu [ 41 ] were synthesized according to literature procedures. An optimized procedure for the synthesis of i Pr 2 GeCl 2 is given below.…”

“…Attempts of purification by column chromatography failed; substituent exchange was initiated with the formation of diisopropyl-dialkynylgermane. 1 2 (1c): [41] Compound 1c was synthesized according to the procedure described for 1a from tBu-C≡CH (1.13 mL, 0.75 g, 9.15 mmol), nBuLi (5.7 mL, 9.14 mmol, 1.6 M in nhexane) and Ph 2 Si(H)Cl (1.79 mL, 2.00 g, 9.16 mmol) in Et 2 O (40 mL). After addition of the lithium alkynide to the silane solution the mixture was warmed to room temperature and heated under reflux overnight.…”