Synthesis, structure and reactivity of homobimetallic Rh(I) and Ir(I) complexes of s- and as-indacene-diide

• Published in: Journal of organometallic chemistry 2000-04, Vol.600 (1), p.94-111
• Main Authors: Ceccon, Alberto, Bisello, Annalisa, Crociani, Laura, Gambaro, Alessandro, Ganis, Paolo, Manoli, Francesco, Santi, Saverio, Venzo, Alfonso
• Format: Article
• Language: English
• Subjects: Cooperative effects; Indacene-diide complexes; Iridium complexes; Rhodium complexes; Syn/anti isomers
• ISSN: 0022-328X; 1872-8561
• DOI: 10.1016/S0022-328X(00)00034-6

The Rh(COD) and Ir(COD) homobimetallic complexes of s-indacene-diide, 2,6-dimethyl- s-indacene-diide, as-indacene-diide, and 2,7-dimethyl- as-indacene-diide have been synthesized from the di-lithium salts of the dianions and metal dimers [M(μ-Cl)L 2] 2 (M = Rh, Ir; L 2 = COD, NBD, (ethylene) 2, (CO) 2 as mixtures of syn and anti isomers. The syn/anti ratio depends on the nature of the ancillary ligands at the metal and on the s or as geometry of the bridging ligand. In the reaction of the 2,7-dimethyl- as-indacene-diide-[M(COD)] 2 species with CO, the higher reactivity of the syn isomers has been justified on the basis of a greater instability of the ground state due to steric interactions between the COD groups. Bis-η 1 metal-bonded intermediates have been identified in the carbonylation of iridium derivatives; on the other hand, the formation of the bis-η 5 mixed complexes syn and anti-{2,7-dimethyl- as-indacene-diide-[Rh(COD)][Rh(CO) 2]} and their reactivity strongly support the existence of metalmetal interaction in the rhodium derivatives.