Crystal structure of the [(THF)Cs(μ-η⁵:η⁵-Cp')₃Yb] oligomer

The green compound poly[(tetra-hydro-furan)-tris-[μ-η⁵:η⁵-1-(tri-methyl-sil-yl)cyclo-penta-dien-yl]caesium(I)ytterbium(II)], [CsYb(C₈H₁₃Si)₃(C₄H₈O)] or [(THF)Cs(μ-η⁵:η⁵-Cp')₃Yb^II] was synthesized by reduction of a red THF solution of (C₅H₄SiMe₃)₃Yb^III with excess Cs metal and identified by X-ray diffraction. The compound crystallizes as a two-dimensional array of hexa-gons with alternating Cs^I and Yb^II ions at the vertices and cyclo-penta-dienyl groups bridging each edge. This, based off the six-electron cyclo-penta-dienyl rings occupying three coordination positions, gives a formally nine-coordinate tris-(cyclo-penta-dien-yl) coordination environment to Yb and the Cs is ten-coordinate due to the three cyclo-penta-dienyl rings and a coordinated mol-ecule of THF. The complex comprises layers of Cs₃Yb₃ hexa-gons with THF ligands and Me₃Si groups in between the layers. The Yb-C metrical parameters are consistent with a 4f ¹⁴ Yb^II electron configuration.