Reactions of linked tetrahedron clusters [Co2(CO)6(μ-HC2CH2O)–]2R with Rh2(CO)4Cl2 to give mixed-metal linked alkyne-bridged butterfly clusters containing C2Co2Rh2 unit

The reactions of compound Rh2(CO)4Cl2, 1 with [Co2(CO)6(μ-HC2CH2O)–]2R (R = C6H4, 2; (COCH2)2, 3; C6H4-1,4-(CO)2, 4; (COCH)2, 5; (CO)2, 6) in benzene at 60 °C produce five new mixed-metal linked clusters Rh2Co2(CO)10(μ4,η2-HC2CH2O–R–OCH2C2H-μ)Co2(CO)6 (R = C6H4, 7a; (COCH2)2, 7b; C6H4-1,4-(CO)2, 7c; (COCH)2, 7d; (CO)2, 7e) and five known linked octahedral clusters [Rh2Co2(CO)10(μ4,η2-HC2CH2O–)]2R (R = C6H4, 8a; (COCH2)2, 8b; C6H4-1,4-(CO)2, 8c; (COCH)2, 8d; (CO)2, 8e), respectively. Treatment of clusters 7a–8e in benzene at room temperature under air for 24 h with stirring afford the precursor clusters 2–6, respectively. The structure of cluster 7a has been determined by single-crystal X-ray diffraction. The linked cluster 7apossesses two isomers A and B in its structures, the Rh2(CO)4 unit inserts into one of two Co–Co bonds and coordinates to the Co2C2 core forming one distorted closo-Rh2Co2C2 octahedron framework which is connected to the Co2C2 tetrahedron unit via C6H4(OCH2)2-1,4 as a bridging ligand. All clusters were characterized by C, H elemental analysis, IR and 1H NMR spectroscopy.