Synthesis and structures of bis(silylene)iron complexes containing new six-membered chelate rings

Abstract

Reaction of Cp′Fe(CO) 2SiMe 2SiMe 2Cl ( 1a: Cp′=η 5-C 5H 5 (Cp), 1b: Cp′=η 5-C 5Me 5 (Cp*)) with acetic acid in the presence of base (pyridine or Et 3N) afforded Cp′Fe(CO) 2SiMe 2SiMe 2OCOMe ( 2a: Cp′=Cp, 77%; 2b: Cp′=Cp*, 87%). Similarly, the reaction of 1b with 2-pyridone in the presence of Et 3N gave Cp*Fe(CO) 2SiMe 2SiMe 2O(2-C 5H 4N) ( 3, 43%). Photolysis of 2a, 2b, and 3 produced Cp′(CO)Fe{SiMe 2⋯OC(Me)O⋯SiMe 2} ( 4a: Cp′=Cp, 4b: Cp′=Cp*) and Cp*(CO)Fe{SiMe 2⋯O(2-C 5H 4N)⋯SiMe 2} ( 5) quantitatively, in which an acetoxy or 2-pyridyloxy group bridges two silylene ligands to form a six-membered chelate ring. 4a and 5 were structurally characterized by single-crystal X-ray diffraction experiments. All the FeSi bonds are significantly shorter than normal FeSi single bonds and are consistent with their unsaturated bond character. The six-membered chelate ring consists of two entirely different and delocalized unsaturated bond systems.