Dimerisation of a diplatinum to a tetraplatinum complex during catalysis of the water gas shift reaction: the X-ray crystal structure of [Pt 4 (µ 2 -CO) 2 (µ 2 -Ph 2 PCH 2 PPh 2 ) 3 {Ph 2 PCH 2 P(:O)Ph 2 }]

The binuclear complex [Pt2H2(µ-dppm)2][PF6], dppm = Ph2PCH2PPh2, is an active catalyst precursor for the water gas shift reaction, especially at low pressures of carbon monoxide; the catalytic solutions are shown to contain cluster complexes such as the tetranuclear [Pt4(µ-CO)2(µ-dppm)3{Ph2PCH2P(:O)Ph2}], whose ‘butterfly’ structure has been determined by X-ray crystallography.