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

Abstract

The course of the reactions of Q2[cis-Pt(C6F5)2(C≡CR) 2] (Q = PPh3Me, R = Ph 1a; Q = NBu4, R = tBu 1b, SiMe3 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 (PPh3Me)[cis-Pt(C6F5)2(μ-1 kCa:η2-C≡CPh)2Rh(COD)], 2a, analogous reactions using 1b as the precursor afford only the trinuclear complex (NBu4)[{cis-Pt(C6F5)2(μ-1 kCa: η2-C≡CtBu)2}{Rh 2(μ-Cl)(COD)2}], 4b. On the other hand, related bi- and trinuclear SiMe3 derivatives (NBu4)[cis-Pt(C6F5)2(μ-1 kCa:η2-C≡CSiMe3) 2Rh(COD)], 2c, and (NBu4)[{cis-Pt(C6F5)2(μ-1 kCa:η2-C≡CSiMe3) 2}{Rh2(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)(Et2O)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 (NBu4)[cis-Pt(C6F5)2 (μ-1kCa:η2-C≡CSiMe 3)(μ-η2:2kCa-C≡ CSiMe3)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).