Compounds of formula [Pt(PPh3)2(quinone)] where the quinone is 1,4-benzoquinone, 2,3,5,6-tetrachloro-1,4-benzoquinone-1,4-naphthoquinone, 3,4,5,6-tetrachloro-1,2-benzoquinone, 1,2-naphthoquinone, and 9,10-phenanthrenequinone have been synthetised. With 2,3,5,6-tetramethyl-1,4-benzoquinone a compound of formula {Pt(PPh3)2}2(quinone) has been obtained. The type of bonding and the factors influencing the strength of the bond between Pt(PPh3)2 and the quinone moiety have been discussed on the basis of i.r., 1H n.m.r. and electronic spectra.