Phosphaalkyne-bridged clusters: Synthesis, characterization, and nonlinear optical properties of Fe4Se2(mu-Se2PCBut)(CO)(11)

The reaction of Fe-2(CO)(6)(mu-Se-2) with (BuC)-C-t=P in THF solvent, in the presence of sodium hydride, yields the tetrairon cluster Fe4Se2(mu-Se2PCBut)(CO)(11). It has been characterized by IR and H-1, P-31, and Se-77 NMR spectroscopy, and its molecular structure has been established by single-crystal X-ray diffraction methods. The structure can be described as consisting of a bow-tie type Fe3Se2 unit, one face of which is capped by an unusual FeSe2P unit, in which one Se is 3-coordinate and the other a-coordinate. The second face is capped by a P-C(CH3) group such that the P atom is bonded to the middle Fe atom of the Fe3Se2 bow tie and the C atom is attached to one Fe atom and one Se atom. Nonlinear optical properties of Fe4Se2(mu-Se2PCBut)(CO)(11), measured by the Z-scan technique, indicate significant magnitudes for the third-order susceptibility