Synthesis of 1,3-Dimetallo-1,3-diphosphetane-2,4-diones. X-ray Structure Analysis of Cp*(CO)<sub>2</sub>FeP[Cr(CO)<sub>5</sub>]C(O)P[Fe(CO)<sub>2</sub>Cp*]C(O) (Cp* = η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)

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