Reactions of the σ,π-furyl complex [Fe2(CO)6(μ-Fu)(μ-PFu2)] (Fu = C4H3O) with phosphines: Carbonyl substitution, migratory carbonyl insertion and cyclometallation-induced furan elimination

• Reactions of σ,π-furyl complex with phosphines gives a variety of product types.
• CO-substitution and migratory CO insertion afford unsaturated vinyl–acyl complexes.
• Oxidative C–H addition at the diiron centre and subsequent elimination of furan.
• Novel coupling of BINAP and phosphido-bridge gives new tridentate phosphine ligand.

The reactivity of the σ,π-furyl complex [Fe2(CO)6(μ-Fu)(μ-PFu2)] (1) towards PPh3 and a range of bidentate phosphines has been studied and a number of different reaction products have been identified. With PPh3, carbonyl substitution affords [Fe2(CO)5(PPh3)(μ-Fu)(μ-PFu2)] (2) in which the new phosphine is coordinated to the iron center that is σ-coordinated by the bridging furyl moiety. With small bite-angle diphosphines – bis(diphenylphosphino)methane (dppm) and 1,8-bis(diphenylphosphino)naphthalene (dppn) – carbonyl substitution and migratory carbonyl insertion result to give the furyl–acyl complexes with bridging, [Fe2(CO)4(μ-dppm)(μ-OCFu)(μ-PFu2)] (3), or chelating, [Fe2(CO)4(κ2-dppn)(μ-OC–Fu)(μ-PFu2)] (4), diphosphines, respectively. With the more flexible diphosphines Ph2P(CH2)nPPh2 (n = 2, dppe, n = 3, dppp), the cyclometallated products [Fe2(CO)5{μ,κ2-C6H4PPh(CH2)nPPh2}(μ-PFu2)] (n = 2, 5; n = 3, 6) are isolated as a result of carbonyl substitution and furan elimination, and a similar complex [Fe2(CO)5{μ,κ2-C6H4PPh(C6H4)PPh2}(μ-PFu2)] (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 [Fe2(CO)5{μ,κ3-C6H4P(C20H12PPh2)C6H4PFu}] (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.

The reactions of the σ,π-furyl complex [Fe2(CO)6(μ-Fu)(μ-PFu2)] towards a range of phosphines yields a number of different products that are the results of several transformations, including carbonyl substitution, migratory carbonyl insertion into the metal-bound furyl ligand, reductive elimination of furan and reductive coupling of phosphorus-containing ligands.Figure optionsDownload as PowerPoint slide