Phosphaalkyne-bridged clusters: Synthesis, characterization, and nonlinear optical properties of Fe₄Se₂(μ-Se₂PCBu^t)(CO)₁₁

Abstract

The reaction of Fe₂(CO)₆(μ-Se₂) with Bu^tC≡P in THF solvent, in the presence of sodium hydride, yields the tetrairon cluster Fe₄Se₂(μ-Se₂PCBu^t)(CO)₁₁. It has been characterized by IR and ¹H, ³¹P, and ⁷⁷Se 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 2-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(μ-Se₂PCBu^t)(CO)₁₁, measured by the Z-scan technique, indicate significant magnitudes for the third-order susceptibility.