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

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