Solid state and solution structure of the hetero-dimetallic complexes [Cp(CO)2Re{μ-C(OMe)(Ph)}Pt(COD)] and [Cp(CO)2Re{μ-CPh} Pt(COD)]+, containing bridging carbene and carbyne ligands

The reaction of the carbene complex [Cp(CO)(2)Re=C(OMe)(Ph)] with [Pt(COD)(2)] affords in high yield the novel complex [Cp(Co)(2)Re{mu-C(OMe)(Ph)}Pt(COD)] (2), containing a bridging carbene ligand. Reaction of 2 with (Me3O)BF4 results in removal of the carbene-bound methoxy group, with formation of the cation [Cp(CO)(2)Re{mu-CPh}Pt(COD)](+) (3), in which a bridging carbyne is present. Both the complexes contain only ligands coordinated through carbon atoms and represent the highest members, as far as the Pt:Re ratio is concerned, of the small family of phosphorous-free Pt-Re mixed metal complexes containing Pt-Re bonds. Their full H-1 and C-13 NMR characterization in solution and their single-crystal solid state diffractometric analysis are reported and discussed. The X-ray analysis evidenced the substantially symmetric nature of the carbene bridge in the dimetalla-cyclopropane ring of complex 2 [Re-Pt 2.7188(3), Re-(mu-C) 2.166(4) and Pt-(mu-C) 2.055(4) Angstrom]. In complex 3 the bond length pattern within the three-membered ring is suggestive of a significant double-bond character for the Re-(mu-C) interaction [Re-Pt 2.707(1), Re-(mu-C) 1.904(9) and Pt-(mu-C) 1.981(8) Angstrom]. Both complexes show a semi-bridging CO ligand, with Pt...C distances of 2.452(4) and 2.299(9) Angstrom, in 2 and 3, respectively. The C-13 NMR characterization showed that the Pt...CO interaction is also maintained in solution in both complexes. In cation 3 a libration of the ReCp(CO)(2) fragment around the Pt-Re axis, fast down to 193 K, interchanges the two carbonyl locations observed in the solid state, as well as the environments of couples of COD carbon atoms, leading to an apparent C-s symmetry. The correlation between spectroscopic data and structural features (concerning bridging carbenes or carbynes and semi-bridging carbonyls) in the class of heterodimetallic M-Pt complexes is discussed. (C) 2000 Elsevier Science S.A. All rights reserved.