A Computational Study of the Mechanism of Addition of Singlet Carbene Analogues to 1,3-Butadiene to Form 1,1-Dimethylmetallacyclopent-3-enes [MMe2C4H6, M = Si, Ge, Sn] and Their Reverse Retro-addition Reactions

• Published in: Organometallics Vol. 28; no. 19; pp. 5612 - 5622
• Main Authors: Nag, Mrinmoy, Gaspar, Peter P.
• Format: Journal Article
• Language: English
• Published: American Chemical Society 12.10.2009
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/om900369e

B3LYP, MPW1K, and CCSD(T) electronic structure calculations were employed to investigate the mechanisms for the addition of singlet carbene analogues dimethylsilylene, Me2Si:, dimethylgermylene, Me2Ge:, and dimethylstannylene, Me2Sn:, to 1,3-butadiene to form 1,1-dimethylmetallacyclopent-3-enes and their reverse retro-addition reactions. The calculations suggest that silylenes and germylenes add to 1,3-butadiene to form the 1,2-adduct, vinylmetalliranes, and the 1,4-adduct, metallacyclopent-3-enes, via 1,2-addition and concerted 1,4-addition processes, respectively, while stannylenes add exclusively to form the 1,4-adduct. Our calculations also predict that direct rearrangements of vinylmetalliranes make minimal contribution to the formation of the 1,4-adducts since the retro-addition reactions of the metallylenes followed by 1,4-addition are much faster than the rearrangement reactions of vinylmetalliranes to form metallacyclopent-3-enes.