Synthesis of Bi- and Trinuclear Bis(alkynyl) Complexes [PtM (M = Rh, Ir), PtRh2] Starting from [cis-Pt(C6F5)2(C⋮CR)2]2-

The course of the reactions of Q 2 [ cis -Pt(C 6 F 5 ) 2 (C⋮CR) 2 ] (Q = PPh 3 Me, R = Ph 1a; Q = NBu 4, R = t Bu 1b, SiMe 3 1c ) with [M(μ-Cl)(COD)] 2 (M = Rh, Ir) is strongly influenced by the metal and the substituents, as well as the stoichiometry. Thus, whereas treatment of 1a with either 0.5 or 1 equiv of [Rh(μ-Cl)(COD)] 2 gives the chelating-type binuclear highly polar compound (PPh 3 Me)[ cis -Pt(C 6 F 5 ) 2 (μ-1κ C α:η 2 -C⋮CPh) 2 Rh(COD)], 2a, analogous reactions using 1b as the precursor afford only the trinuclear complex (NBu 4 )[{ cis -Pt(C 6 F 5 ) 2 (μ-1κ C α:η 2 -C⋮C t Bu) 2 }{Rh 2 (μ-Cl)(COD) 2 }], 4b . On the other hand, related bi- and trinuclear SiMe 3 derivatives (NBu 4 )[ cis -Pt(C 6 F 5 ) 2 (μ-1κ C α:η 2 -C⋮CSiMe 3 ) 2 Rh(COD)], 2c, and (NBu 4 )[{ cis -Pt(C 6 F 5 ) 2 (μ-1κ C α:η 2 -C⋮CSiMe 3 ) 2 }{Rh 2 (μ-Cl)(COD) 2 }], 4c, are easily obtained by treating 1c with the binuclear rhodium substrate in the adequate molar ratio [1:0.5 for 2c; 1:1 for 4c ]. Complex 2b and, alternatively, 2a, c derivatives can be produced by reacting 1 with the cationic solvento species [Rh(COD)(Et 2 O) x ] + (prepared in situ). The molecular structures of 2a and 4b have been confirmed by X-ray diffraction. By contrast, whereas the reactions of 1a, b with [Ir(μ-Cl)(COD)] 2 lead to the formation of undefined products, the heterobinuclear σ,π double-alkynyl-bridged complex (NBu 4 )[ cis -Pt(C 6 F 5 ) 2 (μ-1κ C α:η 2 -C⋮CSiMe 3 )(μ-η 2:2κ C α -C⋮CSiMe 3 )Ir(COD)], 3c, (X-ray) is isolated from reaction of 1c with the dimer iridium complex regardless of the molar ratio used (1:0.5 or 1:1).