Sign determination of coupling constants nJ(M, 13C) (n = 1, 2, 3), nJ(M, 1H)(n = 3, 4), for M = 29Si, 119Sn, 207Pb, 195Pt and 199Hg and 3J(195Pt, C  CM) (M = 29Si, 119Sn and 207Pb) in representative alkynyl-silicon, -tin, -lead, -platinum and -mercury compounds

Heteronuclear double and triple resonance experiments of the type 1H{X} (X = 31P, 199Hg, 207Pb), 13C{1H, 31P}, 29Si{1H, 31P}, 207Pb{1H, 31P}, pseudo‐triple resonance experiments [e.g. 13C{1H(199Hg)}, 207Pb{1H(13C)}], together with two‐dimensional (2D) 13C/1H heteronuclear shift correlations, were carried out to determine the signs of various coupling constants [1J(M13C), 2J(MC13C), 3J(MCC13C), 3J(MCC1H), 4J(MCCC1H); M = 29Si, 119Sn, 207Pb, 195Pt, 199Hg; 3J(195PtCCM); M = 29Si, 119Sn, 207Pb] in 17 alkynyl metal compounds. In all compounds studied, the sign of the reduced coupling constants nK(M13C) (n = 1, 2, 3) is positive. The same is true for 3K(MCC1H) and 3K(195PtCCM) (M = 29Si, 119Sn, 207Pb), whereas a negative sign was found for all 4K(MCCC1H) values.