A computational study to determine whether substituents make E(13)[triple bond, length as m-dash]nitrogen (E(13) = B, Al, Ga, In, and Tl) triple bonds synthetically accessible

This study theoretically determines the effect of substituents on the stability of the triple-bonded L–E(13)[triple bond, length as m-dash]N–L (E(13) = B, Al, Ga, In, and Tl) compound using the M06-2X/Def2-TZVP, B3PW91/Def2-TZVP, and B3LYP/LANL2DZ+dp levels of theory. Five small substituents (F, OH, H, CH(3) and SiH(3)) and four large substituents (SiMe(SitBu(3))(2), SiiPrDis(2), Tbt ([double bond, length as m-dash] C(6)H(2)-2,4,6-{CH(SiMe(3))(2)}(3)) and Ar* ([double bond, length as m-dash]C(6)H(3)-2,6-(C(6)H(2)-2,4,6-i-Pr(3))(2))) are used. Unlike other triply bonded L–E(13)[triple bond, length as m-dash]P–L, L–E(13)[triple bond, length as m-dash]As–L, L–E(13)[triple bond, length as m-dash]Sb–L and L–E(13)[triple bond, length as m-dash]Bi–L molecules that have been studied, the theoretical findings for this study show that both small (but electropositive) ligands and bulky substituents can effectively stabilize the central E(13)[triple bond, length as m-dash]N triple bond. Nevertheless, these theoretical observations using the natural bond orbital and the natural resonance theory show that the central E(13)[triple bond, length as m-dash]N triple bond in these acetylene analogues must be weak, since these E(13)[triple bond, length as m-dash]N compounds with various ligands do not have a real triple bond.