Synthesis and reactions of CpFe(CO)2(.eta.1-CH2PEt2) and CpFe(CO)(.eta.2-CH2PEt2). Study of a photochemically induced .eta.1 to .eta.2 conversion

Displacement of chloride from CpFe-(CO) 2 CH 2 Cl by HPEt 2 followed by deprotonation yields the new η 1 -phosphinomethyl complex CpFe(CO) 2 (η 1 -CH 2 PEt 2 ). Suprisingly, thermolysis of this complex does not lead either to the CO insertion product acyl or to the cyclic CO loss product CpFe(CO) 1 (η 2 -CH 2 PEt 2 ) (5). Coordination of the phosphorus to the iron atom occurs only upon photolysis to yield the η 2 species 5, which spectroscopic data and molecular weight data confirm is a cyclic monomer