Homocoupling of Isocyanide at the Si(II) Center of Borylaminoamidinatosilylene.

Two borylaminoamidinatosilylenes (L)[(1,5-CH)B(Ar)N]Si (L = PhC(NtBu), Ar = 2,6-PrCH ()) and (L)[(1,5-CH)B(Ar')N]Si (Ar' = 2,4,6-MeCH ()) have been prepared and utilized to investigate the reaction toward isocyanide. Reactions of with the respective CN-2,6-MeCH and CNCy (Cy = -CH) produced compounds (L)Si(NAr)C(N-2,6-MeCH)B(1,5-CH)(CN-2,6-MeCH) () and (L)Si(NAr)C(NCy)C(NCy)B(1,5-CH)(CNCy) (). Reactions of with the respective CNCy and CN-2,6-MeCH yielded compounds -(L)SiN(Ar')C(NCy)B(1,5-CH)C(NCy) () and -(L)[(1,5-CH)B(Ar')N]SiC(CN-2,6-MeCH)N(2,6-MeCH)C(N-2,6-MeCH) (). Compounds - have different compositions and structures from each other. Density functional theory (DFT) calculations suggest initial formation of (L)[(1,5-CH)B(←:CN-2,6-MeCH)(Ar)N]Si (), (L)[(1,5-CH)B(←:CNCy)(Ar)N]Si ('), (L)[(1,5-CH)B(←:CNCy)-(Ar')N]Si (″), and (L)[(1,5-CH)B(←:CN-2,6-MeCH)(Ar')N]Si () as the respective intermediates. The as-followed transition states , ', ″, and all feature probable Si:→C(═N):→B bonding with different Gibbs energies of 7.24, 2.46, 3.86, and 6.59 kcal/mol, respectively, due to variation among the Ar, Ar', 2,6-MeCH, and Cy groups in these species, and reacted in different ways.