Photoinduced Fe-Cp bond cleavage and insertion reactions of strained silicon- and sulphur-bridged [1]ferrocenophanes in the presence of transition-metal carbonyls

摘要

The photochemical reactions of the moderately strained sila[1]ferrocenophane [Fe(eta-C5H4)(2)SiPh2 (1) and the highly strained thia[l]ferrocenophane [Fe(eta-C5H4)(2)S] (8) with transition-metal carbonyls ([Fe(CO)(5)], [Fe-2(CO)(9)] and [CO2(CO)(8)]) have been studied. The use of metal carbonyls has allowed the products of photochemically induced Fe-cyclopentadienyl (Cp) bond cleavage reactions in the [1]ferrocenophanes to be trapped as stable, characterisable products. During the course of these studies the synthesis of 8 from [Fe(eta-C5H4Li)(2)center dot TMEDA] (TMEDA = N,N,N',N'-tetramethylethylenediamine) and S(SO2Ph)(2) has been significantly improved by a change of reaction solvent and temperature. Photochmical reaction of I with excess [Fe(CO)5] in THF gave the dinuclear complex [Fe-2(CO)(2)(mu-CO)(2)(eta- C5H4)(2)SiPh2] (9). The analogous photolytic reaction of 8 with [Fe(CO)5] in THF gave cyclic dimer [Fe(eta-C5H4)(2)S](2) (10) and [Fe-2(CO)(2)(mu-CO)(2)(eta-C5H4)(2)S] (11), with the former being the major product. Photolysis of 1 with [CO2(CO)(8)] afforded the remarkable tetrametallic dimer [(CO)(2)CO(eta- C5H4)SiPh2(eta-C5H4)Fe(CO)(2)](2) (13). The corresponding photochemical reaction of 8 with [Co-2(CO)(8) gave a trime-tallic insertion product in high conversion, [Co(CO)(4)(CO)(2)Fe(eta-C5H4)S(eta- C5H4)Co(CO)(2)] (14). These reactivity studies show that UV light promotes Fe-Cp bond cleavage reactions of both of the [1]ferrocenophanes 1 and 8. We have found that, whereas the less strained sila[1]ferrocenophane 1 requires photoactivation for Fe-Cp bond insertions to occur, the highly strained thia[I]ferrocenophane 8 undergoes both irradiative and non-irradiative insertions, although the latter occur at a slower rate. Our results suggest that such photoinduced bond cleavage reactions may be general and applicable to other related strained organometallic rings with pi-hydrocarbon ligands.