Organometallic cluster complexes with face-capping arene ligands, 9 . Hydrogenation of the side-chain in [{(C 5H 5)Co} 3( μ3-alkenylbenzene)]: synthesis and structure of the cluster complexes [{(C 5H 5)Co} 3( μ3- η2: η2: η2-C 6H 5–CHR 1–CH 2R 2)

Abstract

Catalytic hydrogenation (1 bar H 2, 20°C, Pd/C catalyst) of the CC double bond in the side-chain of the facial alkenylbenzene ligands of the cluster complexes [{(C 5H 5)Co} 3{ μ 3-C 6H 5(CR 1)(CHR 2)}] 2b– c gave the derivatives [{(C 5H 5)Co} 3{ μ 3-C 6H 5(CHR 1)(CH 2R 2)}] 3b– d in high yield ( b, R 1=CH 3, R 2=H; c, R 1=H, R 2=Ph; d, R 1=Ph, R 2=H). The X-ray crystal and molecular structures of 3c and 3d were determined. In both derivatives a facial μ 3- η 2: η 2: η 2 coordination of one phenyl ring to the tricobalt cluster was found. Only one of two possible diastereomeric conformers is present in the crystals of 3d. The expanded μ 3-phenyl rings show a small but statistically significant Kekulé-type (trigonal) distortion. In solution hindered rotation of the μ 3-arenes on top of the [(C 5H 5)Co] 3 clusters is observed by NMR spectroscopy.