Reactions of the s,p-furyl complex [Fe_2(CO)_6(m-Fu)(m-PFu_2)](Fu= C_4H_3O) with phosphines: Carbonyl substitution, migratory carbonyl insertion and cyclometallation-induced furan elimination

摘要

The reactivity of the σ,π-furyl complex [Fe_2(CO)_6(μ-Fu)(μ-PFu_2)] (1) towards PPh3 and a range of bidentate phosphines has been studied and a number of different reaction products have been identified. With PPh_3, carbonyl substitution affords [Fe_2(CO)_5(PPh_3)(μ-Fu)(μ-PFu_2)] (2) in which the new phosphine is coordinated to the iron center that is s-coordinated by the bridging furyl moiety. With small bite-angle diphosphines e bis(diphenylphosphino)methane (dppm) and 1,8-bis(diphenylphosphino)naphthalene(dppn) e carbonyl substitution and migratory carbonyl insertion result to give the furyleacyl complexes with bridging, [Fe_2(CO)_4(μ-dppm)(μ-O]CeFu)(μ-PFu_2)] (3), or chelating, [Fe_2(CO)_4(k~2-dppn)(μ-O]CeFu)(μ-PFu_2)] (4), diphosphines, respectively. With the more flexible diphosphines Ph_2P(CH_2)nPPh_2 (n = 2, dppe,n = 3, dppp), the cyclometallated products [Fe_2(CO)_5{μ,k2~-C_6H_4PPh(CH_2)nPPh_2}(μ-PFu_2)] (n = 2, 5; n = 3, 6) are isolated as a result of carbonyl substitution and furan elimination, and a similar complex [Fe_2(CO)5{m,k~2-C_6H_4PPh(C_6H_4)PPh_2}(μ-PFu_2)] (7) is generated from the more rigid diphosphine bis(diphenylphosphino) benzene (dppb). With bis(diphenylphosphino)-1,1-binaphthalene (1,1-BINAP) the novel tridentate phosphine complex [Fe_2(CO)_5{m,k~3-C_6H_4P(C_(20)H_(12)PPh_2)C_6H_4PFu}] (8) results from the putative coupling of cyclometallated diphosphine and difurylphosphido ligands, following elimination of two equivalents of furan. The crystal structures of 2, 3, 5 and 8 have been determined and allow a detailed insight into the overall reaction profile.