Synthesis of triangular mixed-metal clusters by the addition of copper electrophiles to an electron-rich rhodium-rhodium bond. X-ray crystal structures of [Rh2(η-C5H5)2(μ-CO)(μ-Ph2PCH2PPh2)(μ-CuI)] and [Rh2(η-C5H5)2(μ-CO)(μ-Ph2PCH2PPh2)(μ-AgO2CCH3)]

Synthesis of triangular mixed-metal clusters by the addition of copper electrophiles to an electron-rich rhodium-rhodium bond. X-ray crystal structures of [Rh2(η-C5H5) 2(μ-CO)(μ-Ph2PCH2PPh 2)(μ-CuI)] and [Rh2(η-C5H5) 2(μ-CO)(μ-Ph2PCH2PPh 2)(μ-AgO2CCH3)]. The new Rh2Cu mixed-metal clusters [Rh2(η-C5H5) 2(μ-CO)(μ-dppm)(μ-CuX)] (X = Cl, 2; X = I, 3; dppm = bis(diphenylphosphino)methane) have been prepared by reacting [Rh2(η-C5H5) 2(μ-CO)(μ-dppm)] (1) with CuX and have been spectroscopically characterized. The structure of 3 has also been established by X-ray crystallography. The compound crystallizes in the orthorhombic space group Pnma with a = 14.002 (2) Å, b = 18.306 (2) Å, c = 13.025 (1) Å, V = 3338.5 Å3, and Z = 4. The structure has been refined to R = 0.034 and Rw = 0.039 for the 1064 reflections with I ≥ 3σ(I). Complex 3 reacts with AgO2CCF3 to yield [Rh2(η-C5H5) 2(μ-CO)(μ-dppm)(μ-AgO2CCF3)] (4) which has been structurally characterized. Crystals of 4 are also orthorhombic of space group Pnma with a = 15.133 (2) Å, b = 18.176 (3) Å, c = 12.656 (1) Å, V = 3481.0 Å3, and Z = 4. R = 0.034 and Rw = 0.034 for the 1993 reflections with I ≥ 3σ(I). In both complexes structurally characterized the three metal atoms define a triangular cluster [in 3 Rh(1)-Rh(1′) = 2.746 (1), Rh(1)-Cu = 2.588 (2) Å; in 4 Rh(1)-Rh(1′) = 2.776 (1), Rh(1)-Ag = 2.719 (1) Å] with the Rh-Rh bond bridged by the dppm and the CO ligands. The rhodium atoms are each symmetrically capped by one η-cyclopentadienyl ligand, and the interplanar angle between the cyclopentadienyl rings can be related to the bulk of the group 11 metal. In 3 the iodine atom is bonded to copper while in 4 the trifluoroacetate group is chelated to the silver atom. The structural features of 3 and 4 have been compared with those of the other compounds of this class already reported. The results show that the formation of stable Rh2Ag and Rh2Cu triangular clusters by addition of electrophiles containing the group 11 metals to 1 requires the use of silver or copper salts of coordinating anions.