Phosphine induced migratory COinsertion into the Fe–CH2 bond of the organometallic polymer -[(η5-C5H4)Fe(CO)2CH2SiMe2]n- and characterization of model iron complexes

Abstract

Thermal and photochemical treatment of 1-sila-3-ferracyclobutane, (η⁵-C₅H₄)Fe(CO)₂CH₂SiMe₂ (1) results in ring-opening polymerization (ROP). Phosphine-induced migratory CO insertion into the Fe–CH₂ bond of the preformed polymer, -[(η⁵-C₅H₄)Fe(CO)₂CH₂SiMe₂]_n- (2) results in either linear polymers, -[(η⁵-C₅H₄)Fe(CO)(PR₃)C(O)CH₂SiMe₂]_n- [R₃ = Me₂Ph (3), Ph₃ (4)] or diphosphine bridged polymers, -{[(η⁵-C₅H₄)Fe(CO)C(O)CH₂SiMe₂]₂(P–P)}_n- [P–P = dppe (5), dppp (6), dppb (7), trans-dppen (8), dmpe (9); dppe = 1,2-bis(diphenylphosphino)ethane, dppp = 1,2-bis(diphenylphosphino)propane, dppb = 1,2-bis(diphenylphosphino)butane, cis-dppen = cis-1,2-bis(diphenylphosphino)ethylene, dmpe = 1,2-bis(dimethylphosphino)ethane]. The analogous model complexes, {[(η⁵-C₅H₅)Fe(CO)C(O)CH₃]₂P–P} [P–P = dppp (10), dppb (11), trans-dppen (12), dmpe (13)] were synthesized and characterized as models of the acylated polymers. The X-ray crystal structure of 11 and 13 were determined to establish the bridging nature of the diphosphines in the model complexes and to get insight of the crystal packing.