Triple-decker complexes XIV. Reactions of iron carbonyls with the triple-decker sandwich complexes (η5-C5H5)Ni(μ,η5-C2B2C)M(η5-C5H5), (M = Co, Ni). Replacement of (η5-C5H5)Ni by and insertion of the Fe(CO)3 fragment into the (η5-C5H5)-Ni bond

Article abstract of DOI:10.1016/0022-328X(90)87242-6

The reactions of Fe2(CO)9 with triple-decker sandwich complexes containing the 2-methyl-1,3,4,5-tetraethyl or the 4,5-diethyl-1,3-dimethyl derivatives of the 2,3-dihydro-1,3-diborole heterocycle C2B2C (4a,b) as a bridging ligand have been investigated.The paramagnetic triple-deckers, 32 valence electron (VE) <(η⁵-C5H5)Ni(μ,η⁵-C2B2C)5-C5H5)> (8a) and 33 VE <(η⁵-C5H5)Ni(μ,η⁵-C2B2C)Ni(η⁵-C5H5)> (9b) react with Fe2(CO)3, or insertion of Fe(CO)3 into the (η⁵-C5H5)-Ni bond.Thus, reaction of 8a with Fe2(CO)9 proceeds via Fe(CO)3 insertion into the (η⁵-C5H5)-Ni bond to yield th'etrinuclear carbonyl-bridged complex <(η⁵-C5H5)FeCO(μ-CO)2Ni(μ,η⁵-C2B2C)Co(η⁵-C5H5)> (10a), and subsequently the tetranuclear <<(η⁵-C5H5)Co(μ,η⁵-C2B2C)Ni(μ-CO)>2> (12a), and also via replacement of (η⁵-C5H5)Ni to give the triple-decker <(η⁵-C5H5)Co(μ,η⁵-C2B2C)Fe(CO)3> (13a). 33 VE 9b reacts with Fe2(CO)9 to give initially <(η⁵-C5H5)Ni(μ,η⁵-C2B2C)Fe(CO)3> (14b); subsequent reactions lead to the carbonyl-bridged <(η⁵-C5H5)Fe(CO)(μ-CO)2Ni(μ,η⁵-C2B2C)Fe(CO)3> (15b), the tetra-decker <<(CO)3Fe(μ,η⁵-C2B2C)>2Ni> (16b), and the triple-decker <(η⁵-C5H5)Fe(μ,η⁵-C2B2C)Fe(CO)3> (17b).The unsymmetrical triple-decker complexes 14a and 14b have been made independently by stacking the Ni-sandwich complexes 20a and 20b with an Fe(CO)3 fragment.A close chemical relationship between 32 VE 8a and 20 VE nickelocene has been established, and may be rationalised by consideration of electronic structures.