Electrophilic attack of proton and [Au(PPh3)]+ on an electron-rich rhodium-rhodium bond. Synthesis and structural characterization of [Rh2(η-C5H5)2(μ-CO)(μ-H)(μ-Ph2PCH2PPh2)]+ and [Rh2(η-C5H5)2(μ-CO)(μ-AuPPh3)(μ-Ph2PCH2PPh2)]+

Electrophilic attack of H+ and [Au(PPh3)]+ on an electron-rich rhodium-rhodium bond. Synthesis and structural characterization of [Rh2(η-C5H5) 2(μ-CO)(μ-H)(μ-Ph2PCH2PPh 2)]+ and [Rh2(η-C5H5) 2(μ-CO)(μ-AuPPh3)(μ-Ph2PCH 2PPh2)]+. The synthesis of compounds [Rh2(η-C5H5) 2(μ-CO)(μ-H)(μ-dppm)]X (2a, X = BF4; 2b, X = PF6) and [Rh2(η-C5H5) 2(μ-CO)(μ-AuPPh3)(μ-dppm)]X (3a, X = BF4; 3b, X = PF6) (dppm = Ph2PCH2PPh2), via the addition of H+ and [AuPPh3]+ to the electron-rich metal-metal bond of the complex [Rh2(η-C5H5) 2(μ-CO)(μ-dppm)] (1), is described. Crystals of 2a are orthorhombic of space group Pbca with a = 11.399 (1) Å, b = 17.991 (2) Å, c = 32.819 (4) Å, and Z = 8. The structure was solved and refined to R and Rw values of 0.061 and 0.064 for the 2046 reflections with I ≥ 3σ(I). The hydride ligand bridges the Rh-Rh bond [2.721 (2) Å] with Rh(1)-H and Rh(2)-H distances [1.62 (14) and 1.71 (14) Å, respectively] which do not differ significantly. The metals are also bridged by the dppm and CO ligands. Complex 3a crystallizes in the space group P212121 with a = 26.589 (3) Å, b = 16.080 (2) Å, c = 11.710 (1) Å, and Z = 4. The structure has been refined to R = 0.037 and Rw = 0.042 for the 3066 reflections with I ≥ 3σ(I). The basic trinuclear skeleton consists of an almost equilateral triangle formed by the two rhodium atoms and the gold atom [Rh(1)-Rh(2) = 2.760 (2) Å, Rh(1)-Au = 2.718 (1) Å, and Rh(2)-Au = 2.732 (1) Å] with the Rh-Rh bond bridged by the dppm and the carbonyl ligands. The structural features of the bridging dppm and CO groups in 2a and 3a remain essentially the same as in 1; the two cyclopentadienyl ligands are in the cis position with an interplanar angle of 92.7° in 2a and 93.9° in 3a. The structural modification of 1 caused by the presence of the bridging hydride and AuPPh3 groups is discussed. Spectroscopic IR and 1H and 31P NMR data for the new compounds are presented.