Complexes [Fe(CO)4(RPCl2)] (2) (a: R = CPh3, b: R = tBu) were used to generate the first examples of phosphinidenoid iron(0) complexes [Li(12-crown-4)(solv)n][Fe(CO)4(RPCl] (3a,b), characterized by NMR spectroscopy.

Synthesis of the first P-CPh 3 substituted oxaphosphirane iron(0) complexes was achieved, representing a more cost-efficient access to these versatile ligands. While reactions with very electron-deficient aldehydes such as pentafluoro-and 3,5-bis (trifluoromethyl)-benzaldehyde were selective to give oxaphosphirane complexes 3 a,b, those with less electronically activated benzaldehydes were very sensitive towards traces of water, and oxaphosphirane complexes 6 ad were obtained as mixtures with the hydroxyphosphane iron complex 5 in competing reactions. As a case in point, complex 3 a was converted into 1,3,4-oxazaphospholane complex 6 using an acid-induced ringexpansion protocol and acetonitrile. The formation of oxaphosphirane complexes from Li/Cl phosphinidenoid complexes and carbonyl units was studied for the first time through theoretical calculations using appropriate model species.

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After more than 160 years of oxirane (epoxide) chemistry, the first derivative of a phosphorus analogue, namely oxaphosphirane, has been synthesized. Reactions with borane sulfane, peroxy compounds and elemental sulfur,...