Solid state and solution structure of the hetero-dimetallic complexes [Cp(CO)(2)Re{mu-C(OMe)(Ph)}Pt(COD)] and [Cp(CO)(2)Re{mu-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(C OD)] (2), containing a bridging carbene ligand. Reaction of 2 with (Me3O)BF 4 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 ca rbon 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 comple xes 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 sym metric nature of the carbene bridge in the dimetalla-cyclopropane ring of c omplex 2 [Re-Pt 2.7188(3), Re-(mu-C) 2.166(4) and Pt-(mu-C) 2.055(4) Angstr om]. 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) intera ction [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 charac terization showed that the Pt...CO interaction is also maintained in soluti on in both complexes. In cation 3 a libration of the ReCp(CO)(2) fragment a round the Pt-Re axis, fast down to 193 K, interchanges the two carbonyl loc ations 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 b etween spectroscopic data and structural features (concerning bridging carb enes or carbynes and semi-bridging carbonyls) in the class of heterodimetal lic M-Pt complexes is discussed. (C) 2000 Elsevier Science S.A. All rights reserved.