A Theoretical Approach to New Triplet and Quintet (nitrenoethynyl)alkylmethylenes, (nitrenoethynyl)alkylsilylenes, (nitrenoethynyl)alkylgermylenes

Experimentally unreachable reactive intermediates of triplet and quintet (nitrenoethynyl)-X-methylenes, (nitrenoethynyl)-X-silylenes, and (nitrenoethynyl)-X-germylenes were compared and contrasted at B3LYP, M06-2X, WB97XD, HF, MP2, MP4, CCSD, and QCISD(T) levels with 6-311++G(d,p) basis set (X–M–C≡C–N; M=C, Si, and Ge; X = H (1), Me (2), Et (3), Pr (4), i-Pr (5), and t-Bu (6)). The effect of small and bulky groups on these acetylene linked reactive intermediates were studied. All triplet (nitrenoethynyl)-X-methylene species were identified as ground states with one local open-shell singlet carbene (δ1π^1) and other local triplet nitrene moiety (π^1π^1) with 47.75-55.70 kcal/mol quintet-triplet energy gap (ΔEq-t). Silylene and germylene substitutions caused the reduction of ΔEq-t. One local closed-shell singlet silylene or germylene moiety (δ2π0) and one local triplet nitrene moiety (π^1π^1) were connected to make triplet (nitrenoethynyl)silylenes, and (nitrenoethynyl)germylenes. The species of (nitrenoethynyl)silylenes, and (nitrenoethynyl)germylenes could be applied as dipolar intermediates in mechanism identification of chemical reactions. Quintet states were found as ground states with one local triplet divalency moiety (π 1π^1) and also other local triplet nitrene moiety (π^1π^1).