Mixed ruthenium-rhodium carbonyl clusters. Synthesis and crystal structure of the [PPh(4)](+) salts of the anions [Ru2Rh2(CO)(7)(mu-CO)(5)](2-), [Ru2Rh2(CO)(9)(mu-CO)(3)(mu-H)](-), and [Ru2Rh2(CO)(7)(mu-CO)(5)(mu(3)-AuPPh(3))](-)

The anion [Ru2Rh2(CO)12]2- (1) has been obtained by reaction of Ru3(CO)12 with [Rh(CO)4]- as [N(PPh3)2]+ or (PPh4)+ salts; this species reacts with acids or AuPPh3Cl to give respectively [Ru2Rh2(CO)12H]- (2) and [Ru2Rh2(CO)12(AuPPh3)]- (3). The phosphonium salts (PPh4)2[Ru2Rh2(CO)12]·THF (I), (PPh4)[Ru2Rh2(CO)12H] (II), and (PPh4)[Ru2Rh2(CO)12(AuPPh3)] (III) were characterized by single-crystal X-ray diffraction:  I, space group P21/n, Z = 4, a = 11.256(2) A, b = 26.712(2) A, c = 20.048(5) A, β = 90.45(2)°, R1 = 0.048 for 4049 independent reflections with I > 3σ(I); II space group P21/a, Z = 4, a = 12.453(2) A, b = 24.074(3) A, c = 13.174(2) A, β = 90.67(1)°, R1 = 0.039 for 4034 independent reflections with I > 3σ(I); III, space group P21/n, Z = 4, a = 11.720(2) A, b = 13.133(3) A, c = 35.614(2) A, β = 95.70(1)°, R1 = 0.054 for 4231 independent reflections with I > 3σ(I). Anions 1 and 2 have a tetrahedral Ru2Rh2 metal frame, while in 3 there is a trigonal-bipyramidal frame with one ruthenium atom and the ...