Synthesis and reactivity of diphosphino Pt(II) silanolate complexes as molecular models of the interaction of platinum particles with silica

A series of di- and monosubstituted cis-platinum(II) silanolate complexes, Pt(OSiR3)2(dppe) (R=Et, 1; R=Me, 2) and Pt(OSiR3)Cl(dppe) (R=Et, 3; R=iPr, 4) where dppe is 1,2-bis(diphenylphosphino)ethane, have been isolated and characterised spectroscopically. Complex 1 does not react with CO and H2 under anhydrous conditions, but the complexes Pt{C(O)OCH3)}2(dppe) (6) and Pt(CO3)(dppe) (7) have been isolated bubbling CO in methanol and CO2 in moist benzene solutions of 1, respectively. The behaviour of 1 towards water or methanol is discussed on the basis of 1H, and 31P{1H} NMR spectroscopic data. The new complex Pt{S2C(OSiEt3)2}(dppe) (8) has been isolated by reaction of 1 with CS2 in benzene solution. This reactivity would suggest a high sensitivity towards water, but not towards H2 or CO, of the bonding of slightly oxidised platinum particles with silanol groups of silica surface.