Internally consistent assignments of the 31P-{ 1H} NMR parameters of the complexes [Pt(RCCR′)(PPh 3) 2] are proposed, based on the premise that the magnitude of 1 J(PtP) depends mainly on the nature of the moiety CR trans to P. For a given R, 2 J(PP) correlates with 1 J(PtP) for thebond trans to CR. The alkynes PhCCSnEt 3, PhCCSnPh 3, Me 3SiCCCl, Me 3SiCCBr, Et 3SiCCI and MeCCI undergo oxidative addition reactions with [Pt(C 2H 4)(PPh 3) 2]; the intermediate alkyne complex was detected for PhCCSnEt 3, Me 3SiCCCl and Me 3CCBr. The triyne Me(CC) 3Me forms platinum(0) complexes by coordination with the central or terminal CC bond and appears also to give a platinum(II) complex by oxidative addition.