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The compound [Rh2(p-C0)2(-q-C5Me5)2] reacts with [Pt(C,H4)3J to give the pentanuclear cluster complex [ PtRh4(p CO) 4(y.-C5Me5) 4J, the structure of which has been established by X-ray diffraction. Crystals grown from light petroleum-dichloromethane belong to the monoclinic system but on cooling to 200 K and rewarming to room temperature undergo an irreversible phase change to the orthorhombic system. Data were collected for both phases: (I) orthorhombic, space group Pnma, with Z = 4 in a unit cell of dimensions a = 17.945( 5), b = 17.978(6), and c = 13.764(4) A; (11) monoclinic, space group A28, with 2 = 4, a = 17.826(4), b = 13.944(3), c = 18.1 12(5) A, and p = 97.1 9(2)'. Intensities were measured to 28 G 45' for (I) and to 28 G 40"for (11), and were refined for (I) to R 0.048 (R' 0.050) and for (11) to R 0.066 (R' 0.070) for 1 606 and 1 71 8 independent reflections respectively. The two molecules have very similar structures, based on the platinum atom being ' coordinated ' to two Rh2(p-C0)2(-q-C5Me5)2 fragments. The four rhodium atoms are disposed around the platinum in an essentially tetrahedral arrangement, with the dihedral angles between the PtRhz planes being 90' for (I) and 100' for (11). In both molecules the PtRh, groups form essentially equilateral triangles [Rh-Rh(mean) and Pt-Rh(mean) 2.618(2) A]. The four CO ligands, in addition to bridging the Rh-Rh vectors, weakly interact with the platinum atom, a feature which persists in solution, as deduced from ls5Pt-'3C coupling observed in the l3C n.m.r. spectrum of [PtRh4(p-C0)4(q-C5Me5)4].

Chemistry of the Metal Carbonyls. Part 81 .l Homonuclear and Heteronuclear Di-and Tri-metal Carbonyl Complexes derived from Dicarbonyl-(pentamethylcyc1opentadienyl)rhodium ; X-Ray Crystal Structureof [Mn-Rh(~-Co),(Co),(rl-C,H,)(rl-c5Me,)l t

Synthesis of p,=Alkylidynetrimetal Complexes : X-Ray Crystal Structures of [FePtW( p&C6H4Me -4) (GO),( PEt,) (q -C,H,)] and [FeRhW( p3u CC6H4Me -4) -(p2-c 0) W ) d q -C,H,) (q -C9H7)I