NEW PLATINUM IRON CARBONYL CLUSTER COMPLEXES AND THEIR REACTIONS WITH ALKYNES

The reaction of Pt(COD)2with Fe(CO)5has yielded the new compounds Pt3Fe3(CO)15(1; 9%), Pt5-Fe2(CO)12(COD)2(2; 40%), and the known compound PtFe2(CO)8(COD) (3; 3%). Compounds 1 and 2 were characterized by single-crystal X-ray diffraction analyses. Compound 1 contains a planar “raft” cluster of metal atoms consisting of a central triangle of three platinum atoms with each Pt-Pt edge bridged by a Fe(CO)4group. 1 can be reduced chemically and electrochemically to the previously known anions [Pt3Fe3(CO)15]-1,2. Compound 2 consists of a tetrahedral cluster of four platinum atoms with the fifth platinum atom bridging an edge of the tetrahedron and Fe(CO)4groups bridging the Pt-Pt bonds to the edge-bridging platinum atom. Compound 2 reacts with PhC2Ph to yield the new complex Pt5Fe2(CO)7-(COD)(μ3-PhC2Ph)3(μ-PhC2Ph) (4; 36%), and it reacts with PhC2H to yield the new complex PtFe-(CO)3(COD)[μ-PhCC(H)C(H)CPh] (5; 26%). Compound 4 contains an open cluster consisting of a central square of four platinum atoms. Three of the four edges of the square are bridged by metal atoms, one Pt plus two Fe atoms. The fourth edge contains a bridging alkyne ligand. The three remaining alkyne ligands bridge the three triangular trimetal groupings formed by the edge-bridging metal atoms and the two platinum atoms in the square that they bridge. Compound 5 contains a PhCC(H)C(H)CPh ligand formed by the head-to-head coupling of two PhC2H molecules. This ligand bridges the mutually bonded Pt and Fe atoms in the usual σ-π fashion with the π-bonding to the Fe atom. Crystal data: for 1, space group C2/c, a = 15.996 (6) Å, b = 11.843 (4) Å, c = 12.796 (5) Å, β = 92.35 (3)°, Z = 4, R = 0.035, Rw= 0.041 for 1331 reflections; for 2, space group P21/n, a = 9.857 (2) Å, b = 18.802 (6) Å, c = 18.319 (3) Å, β = 91.94 (1)°, Z = 4, R = 0.036, Rw= 0.039 for 3442 reflections; for 4, space group P21/n, a = 16.514 (4) Å, b = 19.727 (3) Å, c = 21.227 (6) Å, β = 103.82 (2)°, Z = 4, R = 0.051, Rw= 0.056 for 3692 reflections; for 5, space group P21/c, a = 10.498 (5) Å, b = 15.486 (6) Å, c = 14.809 (5) Å, β = 104.15 (3)°, Z = 4, R = 0.044, Rw= 0.041 for 1365 reflections. © 1990, American Chemical Society. All rights reserved.