Iron(II) Complexes Containing the 1,2-Diphospholanoethane Ligand

Abstract

The synthesis and crystal structure of cis -Fe(BPE5) 2 Cl 2 (BPE5 = 1,2-diphospholanoethane), the first symmetrical cis -Fe(PP) 2 Cl 2 (PP = bidentate phosphine), is reported (monoclinic, P 2 1 / n, a = 12.084(3) Å, b = 14.059(2) Å, c = 17.665(2) Å, β = 101.77(1)°, Z = 4). The overall structure and Fe−P and Fe−Cl bond lengths of cis -Fe(BPE5) 2 Cl 2 more closely resemble those in Fe(PP 3 )Cl 2 complexes (PP 3 = tripodal, tetradentate phosphine ligand) than in other Fe(PP) 2 Cl 2 complexes. In solution, cis -Fe(BPE5) 2 Cl 2 exhibits temperature-dependent paramagnetic behavior due to reversible dissociation of chloride. The dissociation of chloride was exploited in the synthesis of Fe(BPE5) 2 X 2 (X = Br, I) and [Fe(BPE5) 2 (L)(Cl)] + (L = CO, PMe 3 ). The crystal structure of [ cis -Fe(BPE5) 2 (CO)(Cl)][BPh 4 ] is reported (monoclinic, P 2 1 / a, a = 12.938(3) Å, b = 29.647(4) Å, c = 13.131(3) Å, β = 107.89(2)°, Z = 4). The relative chelation strength of BPE5 in Fe(PP) 2 Cl 2 complexes is BPE5 ≈ DMPE > DEPE > DPrPE [DMPE = 1,2-bis(dimethylphoshino)ethane; DEPE = 1,2-bis(diethylphoshino)ethane; DPrPE = bis(di- n -propylphosphino)ethane].