Organometallic cluster complexes with face-capping arene ligands, 10. A study of the influence of substituents on the synthesis of organometallic cluster complexes of the type [{(C 5H 5)Co} 3( μ3- η2: η2: η2-alkenylarene)

Abstract

The cluster complexes [{(C 5H 5)Co} 3( μ 3- η 2: η 2: η 2-arene)] 5a– c (arene=methyl- β-methylstyrene), 6 (arene=3,5-dimethyl- β-methylstyrene), 7 (arene= o-methylstilbene), 8b,c (arene=fluoro- β-methylstyrene) and 9a (arene=2-phenylbut-2-ene) have been prepared from the alkenylbenzene or corresponding allylbenzene derivatives and [(C 5H 5)Co(C 2H 4) 2] 1 or [(C 5H 5)Co(C 6Me 6)] 2. Yields were found to depend on the arene ligands; they were generally lower than those obtained with less highly substituted derivatives. With o-, m- and p-methylallylbenzene and 1 the corresponding μ 3-arene cluster complexes [{(C 5H 5)Co} 3( μ 3- η 2: η 2: η 2-arene)] 5a– c (arene= o-, m- and p-methyl- β-methylstyrene, respectively) were formed in 5, 60 and 5% yield. In contrast, o-, m- and p-fluoroallylbenzene did not react with 1. After treatment of these arenes with 2, [{(C 5H 5)Co} 3( μ 3- η 2: η 2: η 2-arene)] 8b and 8c (arene= m- and p-fluoro- β-methylstyrene) were obtained in 37 and 30% yield. The crystal and molecular structures of 8c and 9a have been established by single crystal X-ray diffaction. Variable temperature NMR studies showed 5b and 8b to be mixtures of two exchanging diastereomers.