SYNTHESIS AND STRUCTURES OF DPPM-BRIDGED PLATINUM-RHODIUM COMPLEXES

The platinum-rhodium A-frame complexes [RPt(mu-Cl)(mu-dppm)(2)RhCO]PF6 (R=Me, Et, Ph) have been prepared by reaction of [PtR(dppm-PP)(dppm-P )]PF6 with [Rh-2(mu-Cl)(2)(cod)(2)] in the presence of carbon monoxide . They have been isolated as yellow, air-stable solids. They add carbo n monoxide to give the double A-frame species [RPt(mu-Cl)(mu-CO)(mu-dp pm)(2)RhCO]PF6, which lose CO readily at ambient temperature unless th ey are maintained under a CO atmosphere. All the complexes have been c haracterized in solution by NMR and IR spectroscopy. The solid state s tructures of two of the A-frame complexes have been determined by X-ra y crystallography. The phenylplatinum derivative [PhPt(mu-Cl)(mu-dppm) (2)RhCO]PF6 crystallizes in the monoclinic space group P2(1)/c with a = 20.2110(2), b = 15.1192(2), c = 19.4133(2) Angstrom, beta = 94.2750( 10)degrees, V = 5915.70(12) Angstrom(3) and Z = 4. The methylplatinum species was obtained as an unexpected carbonyl-bridged form, [MePt(mu- CO)(mu-dppm)(2)RhCl]PF6. This complex crystallizes as a dihydrate in t he triclinic space group <P(1)over bar> with a = 10.6030(8), b = 15.00 51(11), c = 18.705(2) Angstrom, alpha = 68.934(5), beta = 83.312(5), g amma = 69.529(5)degrees V = 10248(5) Angstrom(3) and Z = 2. (C) 1997 E lsevier Science S.A.