Synthesis of 1,3-Dimetallo-1,3-diphosphetane-2,4-diones. X-ray Structure Analysis of Cp*(CO)2FeP[Cr(CO)5]C(O)P[Fe(CO)2Cp*]C(O) (Cp* = η5-C5Me5)

Reaction of the lithoxy phosphaalkyne (DME)2LiOC⋮P (1) with 1 equiv of the complexes (η5-C5R5)(CO)2FeBr (2); C5R5 = C5Me5 (a), 1,3-t-Bu2C5H3 (b), 1,2,4-i-Pr3C5H2 (c)) afforded the 1,3-diferrio-1,3-diphosphetane-2,4-diones (η5-C5R5)(CO)2FePC(O)P[Fe(CO)25-C5R5)]C(O) (3ac) as red amorphous solids in 32−37% yield. By treatment with ((Z)-cyclooctene)Cr(CO)5, compound 3a was converted into the red complex Cp*(CO)2FeP[Cr(CO)5]C(O)P[Fe(CO)2Cp*]C(O) (4). Constitutions and configurations of 3ac and 4 were determined by elemental analyses and spectra (IR, 1H, 13C, and 31P NMR, MS). The molecular structure of 4 was established by a single-crystal X-ray analysis.