Phosphine addition to the sigma,pi-thienyl complex [Fe-2(CO)(6)(mu-Th)(mu-PTh2)] (Th = C4H3S): Carbonyl substitution and migratory carbonyl insertion to give the thienyl-acyl complexes [Fe-2(CO)(4)(diphosphine)(mu-O=C-Th)(mu-PTh2)]

The reactivity of the sigma,pi-thienyl complex [Fe-2(CO)(6)(mu-Th)(mu-PTh2)] (1) towards a range of phosphines has been studied. With PR3 (R = Ph, Th) carbonyl substitution affords [Fe-2(CO)(5)(PR3)(mu-Th)(mu-PTh2)] (2ab) as the major product, with smaller amounts of the thienylacyl complexes [Fe-2(CO)(5)(PR3)(mu-O=C-Th)(mu-PTh2)] (3ab) resulting from a migratory carbonyl insertion into the thienyl ligand. With diphosphines, thienylacyl complexes are the major products in all cases. With dppm, [Fe-2(CO)(4)(mu-dppm)(mu-O=C-Th)(mu-PTh2)] (4) results in which the diphosphine bridges the ironiron bond, while with other diphosphines the chelate complexes [Fe-2(CO)(4)(kappa(2)-diphosphine)(mu-O=C-Th)(mu-PTh2)] (59) are isolated, as established through crystallographic studies on [Fe-2(CO)(4)(kappa(2)-dppe)(mu-O=C-Th)(mu-PTh2)] (5) and [Fe-2(CO)(4)(kappa(2)-dppb)(mu-O=C-Th)(mu-PTh2)] (9), both of which show that the diphosphine binds selectively to the oxygen-bound metal centre with phosphorus atoms lying trans to the metalmetal bond and mu-PTh2 bridge. With 1,2-bis(diphenylphosphino)benzene (dppb), [Fe-2(CO)(5){mu,kappa(2)-C6H4PPh(C6H4)PPh2}(mu-PTh2)] (10) is isolated in low yields and results from cyclometalation of a phenyl ring and putative elimination of thiophene. In a separate experiment, it has been shown that heating 9 results in the slow formation of 10. (C) 2015 Elsevier B.V. All rights reserved.