Reactions of Doubly Bridged Bis(cyclopentadienes) with Iron Pentacarbonyl

When the doubly bridged bis(cyclopentadiene) ligand (Me2C)(Me2Si)(C5H4)2 (1) reacted with
Fe(CO)5 in refluxing toluene, the unusual product [(C5H6)(Me2C)(Me2Si)(η5-C5H3)Fe(CO)]2(μ-CO)2 (2) with a hydrogenated double bond in one of the cyclopentadiene ligands, the diiron
complex (Me2C)(Me2Si)[(η5-C5H3)Fe(CO)2]2 (3), and the desilylation product 4 were obtained.
When the reaction was performed in refluxing xylene, the novel complex (Me2C)(η5-C5H3)(η5:η1-C5H3)[(Me2Si)Fe(CO)2][Fe(CO)2] (5) with an Fe−Si bond, which should be accompanied
by the cleavage of a C−Si bond in the ligand, was isolated in addition to the complexes 2∼4.
When bis(cyclopentadienyl) ligands bridged with R2C (R2C = Me2C, (CH2)5C) and Me2E
(E = Si, Ge) groups were used instead of 1, the similar novel complexes (R2C)(η5-C5H3)(η5:η1-C5H3)[(Me2E)Fe(CO)2][Fe(CO)2] (R2C = Me2C, E = Ge (7); R2C = (CH2)5C, E = Si (17), Ge
(21)) with an Fe−E bond were obtained in addition to the diiron complexes (R2C)(Me2E)[(η5-C5H3)Fe(CO)]2(μ-CO)2 (R2C = Me2C, E = Ge (8); R2C = (CH2)5C, E = Si (18), Ge (22))
and the desilylation or degermylation products. When a tert-butyl group was introduced
into the cyclopentadienyl rings, or two phenyl groups were introduced at the bridging silicon
atom instead of two methyl groups in 1, only the diiron complexes (Me2C)(Me2E)[(η5-t-BuC5H2)Fe(CO)2]2 (E = Si(10), Ge (13)) and (Me2C)(Ph2Si)[(η5-C5H3)Fe(CO)2]2 (15) were
obtained, in addition to the desilylation or degermylation products. When a methylene bridge
was used instead of an isopropylene bridge in 1 and 6, the partially hydrogenated complexes
(Me2E)(η3-CHC5H6)(η5-C5H3)Fe(CO)3Fe(CO)2 (E = Si (24), Ge (28)), the diiron complexes
(CH2)(Me2E)[(η5-C5H3)Fe(CO)]2(μ-CO)2 (E = Si (25), Ge (29)), and the desilylation or
degermylation products were obtained. The molecular structures of 2, 3, 5, 7, 8, 10, 11t, 15,
17, 18, 21, 24, 25, 28, and 29 were determined by X-ray diffraction.