The preparations of complexes of the type L2M(RC2R′) (where L = Ph3P, M = Ni, Pd, Pt, R = R′ = CF3; L = Ph3P, M = Ni, Pt, R = R′ = Ph, and R = Ph, R′ = Me; L = Ph3P, M = Pd, Pt, R = R′ = COOMe; and R = R′ = CF3, M = Pd, Pt, L = n-Bu3P, Mc2PhP) are described. From their nuclear magnetic resonance spectra these complexes appear to be approximately planar in solution. The VC≡C observed in their infrared spectra indicate strong bonding of the acetylene to the metal.A new approach to the bonding in metal–acetylene complexes is proposed which can be extended to other π-complexes and which allows some predictions to be made.