Generation and chemical trapping of (1,2-ethanediphosphinidene)tetracarbonyltungsten

Article abstract of DOI:10.1021/om00146a025

A series of 1,n-bis(3,4-dimethylphospholyl)alkanes has been synthesized by reaction of (3,4-dimethyl-phospholyl)lithium with 1,n-dibromoalkanes. The cleavage of these bis(phospholyl)alkanes by lithium in THF generally affords pure (3,4-dimethylphospholyl)lithium that has been characterized for the first time by ¹H and ¹³C NMR spectroscopy. However, when n = 3, the cleavage of the 1,3-bis(phospholyl)propane leads to a phosphabicyclo[3.3.0]octene that results from the intramolecular cyclization of a transient 1-(3-lithiopropyl)phosphole by addition of the carbanion onto the phosphole dienic system. The 1,2-bis(3,4-dimethylphospholyl)ethane reacts with W(CO)₆ at 130°C to give the P,P′- W(CO)₄ chelate complex. This complex in turn reacts with dimethyl acetylenedicarboxylate to give cleanly the corresponding [1,2-bis-(7-phosphanorbomadien-7-yl)ethane]tetracarbonyltungsten complex through [4 + 2] cycloaddition with the dienic systems of the two phosphole rings. This new complex is an efficient generator of (1,2-ethanediphosphinidene)tetracarbonyltungsten, P-CH₂-CH₂-P=W(CO)₄, at 130°C in toluene. This diphosphinidene complex has been trapped by methanol, diethylamine, tolan, and cyclooctene to give a series of new W(CO)₄ complexes including the first known 1,2-bis(phosphirenyl)- and bis(phosphiranyl)ethane derivatives.