Synthesis and redox chemistry of 1,1′-bis(diphenylphosphino)ferrocene derivatives of R 2C 2Co 2(CO) 6 (R  MeO 2C, CF 3)

Abstract

Fe(C 5H 4PPh 2) 2 (dppf) undergoes facile thermal substitution reactions with R 2C 2Co 2(CO) 6 (R  MeO 2C, CF 3) to yield a variety of products. When R  MeO 2C, initial coordination gives μ 2-(MeO 2C 2) 2C 2Co 2(CO) 5( η 1-dppf); its crystal and molecular structure, monoclinic, P2 1/c, a = 8.954(3), b = 20.211(2) c = 23.836(5) A ̊ , β = 100.55(2)°, Z = 4, R1 = 0.0345 for 5764 reflections 1 > 2 σ(1), confirms the monodentate coordination mode for dppf. At low dppf/alkyne-complex ratios, oligomeric products with dppf ligands linking up to five (μ 2-MeO 2C) 2C 2Co 2 modules have been characterised but, as the proportion of the phosphine ligand increases. unstable products, which include a η 1- μ- η 1 dppf configuration, are obtained as well. In contrast, for R  CF 3, only [(CF 3) 2C 2]Co 2(CO) 4( η 2-dppf) is found in significant yield. A molecule with two different reduction centres, [ μ 2-(MeO 2C) 2C 2Co 2(CO) 5]( μ-dppf)[Co 3( μ 3-CPh)(CO) 8], was also characterised. Electrochemistry of the dppf complexes was characterised by fast ligand dissociation upon reduction of the (μ-alkyne)Co 2 redox centre and oxidation of coordinated dppf. There was no evidence for communication between redox centres.