CLUSTER SYNTHESIS .28. NEW PLATINUM COBALT CARBONYL CLUSTER COMPLEXES AND PRODUCTS OBTAINED FROM THEIR REACTIONS WITH ALKYNES

The reaction of Pt(COD)2, COD = 1,5-cyclooctadiene, with Co2(CO)8in cyclohexane solvent at 25 °C has yielded the new compounds PtCo2(CO)7(COD) (1, 3%) and Pt2Co2(CO)8(COD) (2, 31%) and the known compound Co4(CO)12(3, 14%). Compounds 1 and 2 were characterized by single-crystal X-ray diffraction analyses. Compound 1 contains a triangular cluster of one platinum and two cobalt atoms with a carbonyl ligand bridging the Co-Co bond. Compound 2 consists of a tetrahedral cluster of two platinum atoms and two cobalt atoms. The Pt-Pt bond is weak, 2.9546 (6) Å. Compound 2 reacts with EtC2Et to yield the new complex Pt2Co2(CO)8(μ3-EtC2Et)2(4, 8%), and it reacts with PhC2Ph to yield the new complex Pt3Co2(CO)6-(COD)2(μ3-PhC2Ph)2(5, 22%). Compounds 4 and 5 were characterized crystallographically. Compound 4 contains a butterfly cluster of two cobalt and two platinum atoms. The two platinum atoms occupy the hinge positions and are joined by a short Pt-Pt bond, 2.4945 (7) Å. Triply bridging EtC2Et ligands bridge the two Pt2Co triangles. Compound 5 contains a bow-tie cluster of three platinum and two cobalt atoms with a platinum atom in the center. Triply bridging PhC2Ph ligands bridge the two Pt2Co triangular groupings. Crystallographic parameters for 1: space group Pbca, a = 15.076 (3) Å, b = 16.298 (3) Å, c = 14.547 (5) Å, Z = 8, R = 0.033, and Rw= 0.033 for 2149 reflections. For 2: space group P21/n, a = 8.835 (2) Å, b = 14.573 (2) Å, c = 15.377 (2) Å, β = 100.69 (1)°, Z = 4, R = 0.024, and Rw= 0.027 for 2140 reflections. For 4: space group P21/n, a = 9.430 (2) Å, b = 14.915 (4) Å, c = 17.931 (3) Å, β = 99.11 (2)°, Z = 4, R = 0.022, and Rw= 0.023 for 2236 reflections. For 5: space group C2/c, a = 34.905 (8) Å, b = 15.106 (4) Å, c = 19.028 (3) Å, β = 102.39 (2)°, Z = 8, R = 0.064, and Rw= 0.076 for 3760 reflections. © 1990, American Chemical Society. All rights reserved.