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(Si t Bu 3 ) 2 , Si i PrDis 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.