摘要：

The reaction of Ph2PCH2PPh2 with Rh4(CO)12 gives as the major product a brown crystalline solid of composition (Ph2PCH2PPh2)2Rh 4(CO)8. The solid compound has very low solubility and 13C NMR study of its structure and possible fluctionality was not feasible. The structure has been determined by a single-crystal x-ray study. It is derived from the C3v structure of Rh4(CO)12 itself. The set of three bridging CO groups along one triangular set of edges is retained, but one terminal CO group on each rhodium atom is replaced by a phosphorus atom. The molecule is without any element of symmetry, rigorous or approximate. Some of the principal dimensions of the molecule are as follows: Rh-Rh, 2.671 (1)-2.740 (1) Å with a mean of 2.711 Å, Rh-P, 2.266 (4)-2.334 (4) Å with a mean of 2.30 Å; Rh-C(terminal), average 1.91 Å; Rh-C(bridge), average 2.09 Å. The crystallographic parameters are as follows: space group Ci2/c, a = 22.962 (6) Å, b = 17.230 (5) Å, c = 28.946 (8) Å, β = 97.42 (1)°, V = 11356 Å Z = 8, dcalcd = 1.64 g cm-3, dobsd = 1.70 ± 0.02 g cm-3. The structure of Co4(CO)12 has been reinvestigated, in order to test more rigorously the disordered model previously reported by C. H. Wei. Using a much larger and more accurate data set, refinement of Wei's model has been carried to convergence anisotropically (R1 = 0.078; R2 = 0.089). The molecular structure (C3v) and the disorder scheme proposed by Wei were confirmed and more precise dimensions have been obtained for the molecule.

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