Syntheses and structures of rhodium-osmium clusters derived from the reaction of (μ-H)2Os3(CO)10 with (η5-C5H5)Rh(CO)2

Abstract The reaction between (μ-H) 2 Os 3 (CO) 10 and (η 5 -C 5 H 5 )Rh(CO) 2 in toluene at 90°C produces (η 5 -C 5 H 5 )RhOs 2 (CO) 9 (I) and (μ-H) 2 (η 5 -C 5 H 5 )RhOs 3 (CO) 10 (II), as the principal products while the pentanuclear cluster (μ-H) 2 (η 5 -C 5 H 5 )RhOs 4 (CO) 13 (III) is obtained in low yield. When added hydrogen is present during the reaction, replacement of the cyclopentadienide ligand by toluene occurs and the principal product is (μ-H) 3 (η 6 -C 6 H 5 CH 3 )RhOs 3 (CO) 9 (VI). Also produced in this reaction are (μ-H) 2 (η 5 -C 5 H 5 ) 2 Rh 2 Os 2 (CO) 7 (IV) and cluster II, but in low yields. In benzene in the presence of H 2 , an analogous reaction occurs. The cyclopentadienide ligand is replaced by benzene to give (μ-H) 3 (η 6 -C 6 H 6 )RhOs 3 (CO) 9 (VII) as the main product and clusters II and (μ-H) 4 (η 5 -C 5 H 5 )RhOs 3 (CO) 9 (V) are formed in small yields. Conversion of clusters I and II to clusters IV and V, respectively, was achieved by bubbling H 2 through toluene solutions of I and II at 90°C. Cluster V is moderately unstable in solution, with significant decomposition occurring during the reaction. The molecular structures of clusters II, III, IV, and VII have been determined by single crystal X-ray diffraction studies. Clusters II, IV, and VII have tetrahedral metal cores, while the pentanuclear cluster III has an Os tetrahedral core which is edge bridged by a Rh atom. For compound II: space group P 2 1 / n , a 8.120(3), b 14.932(3), c 16.277(3) A, β 91.29(4)°, V 1972.9 A 3 , Z = 4, mol wt = 1020.73, ρ calcd 3.434 gm cm −3 , and μ calcd 201.5 cm −1 for Mo- K α ; 3885 independent reflections ⩾ 3σ( I ); 4 ⩽ 2θ ⩽ 55° obtained at −35°C; final R f 5.7%, R wf 7.4%. For compound III: space group P 2 1 / c , a 11.134(2), b 16.649(2), c 14.015(2) A, β 109.98(1)°, V 2441.6 A 3 , Z = 4, mol wt = 1294.95, ρ calcd = 2.773 gm cm −3 , and μ calcd 162.6 cm −1 for Mo- K α ; 5695 independent reflections ⩾ 3σ( I ); 4 ⩽ 2θ ⩽ 50° at −30°C; final R f 2.95%, R wf 4.0%. For compound IV: space group P 2 1 / c , a 8.186(3), b 15.651(5), c 15.723(2) A, β 97.32°, V 1998.25 A 3 , Z = 4, mol wt = 914.49, ρ calcd 3.038 gm cm −3 , and μ calcd 143.34 cm −1 for Mo- K α ; 3619 independent reflections ⩾ 3σ( I ); 4 ⩽ 2θ ⩽ 55° at 25°C; final R f 3.3%, R wf 4.5%. For compound VII: space group R , a = b = c = 10.003(4) A, α = β = γ = 92.16(3)°, V = 998.3 A 3 , Z = 2, mol wt = 1006.5, ρ calcd 3.34 gm cm −3 , and μ calcd 214.8 cm −1 Mo- K α ; 3017 independent reflections ⩾ 3σ( I ); 4 ⩽ 2θ ⩽ 50° at 25°C; Final R f 4.4%, R wf 6.3%.