Studies of Dirhodium Tetra(trifluoroacetate). 3. Solid State Isomers of the Compound Rh₂(O₂CCF₃)₄(THF) Prepared by Sublimation

The monoadduct of dirhodium tetra(trifluoroacetate) with THF has been obtained by deposition from the vapor phase. The compound Rh2(O2CCF3)4(THF) crystallizes in two isomeric forms, 1 and 2, whose structures have been determined by X-ray crystallography. The crystallographic parameters are as follows: for 1, triclinic space group P1̄ with a = 9.557(2) Å, b = 10.126(2) Å, c = 11.840(4) Å, α = 95.97(2)°, β = 90.40(2)°, γ = 115.58(1)°, and Z = 2; for 2, triclinic space group P1̄ with a = 8.6347(3) Å, b = 9.678(1) Å, c = 13.773(4) Å, α = 73.182(5)°, β = 74.622(5)°, γ = 89.76(1)°, and Z = 2. Compound 1 is unique as the only extended structure where dirhodium carboxylate molecules are bridged by a single exogenous atom. The oxygen atom of the THF ligand coordinates to the axial positions of two Rh2 units so that a one-dimensional zigzag chain is formed. The bridging is slightly asymmetric with Rh−O(THF) distances of 2.363(6) and 2.407(6) Å, and the Rh−O(THF)−Rh angle is 111.8(3)°. The crystal structure of 2 is not polymeric. Pairs of Rh2(O2CCF3)4(THF) units are associated through O atoms of carboxylate groups to produce a dimer of dimers. The lengths of the terminal Rh−O(THF) and axial bridging Rh···O(Ac) interactions are 2.214(7) and 2.406(6) Å, respectively.四(三氟乙酸)二铑与四氢呋喃(THF)的单加合物通过气相沉积法制备得到。化合物Rh₂(O₂CCF₃)₄(THF)存在两种异构体1和2，其结构已通过X射线晶体学(X-ray crystallography)解析。晶体学参数如下：对于异构体1，属三斜晶系空间群P1̄，晶胞参数为a=9.557(2) Å，b=10.126(2) Å，c=11.840(4) Å，α=95.97(2)°，β=90.40(2)°，γ=115.58(1)°，Z=2；对于异构体2，同样属于三斜晶系空间群P1̄，晶胞参数为a=8.6347(3) Å，b=9.678(1) Å，c=13.773(4) Å，α=73.182(5)°，β=74.622(5)°，γ=89.76(1)°，Z=2。 异构体1是独一无二的，它是唯一一种羧酸二铑分子通过单个外源性原子桥联形成的扩展结构。四氢呋喃配体的氧原子配位至两个Rh₂单元的轴向位置，从而形成一维锯齿状链。该桥联作用略显不对称，Rh−O(THF)键长分别为2.363(6) Å与2.407(6) Å，Rh−O(THF)−Rh键角为111.8(3)°。 异构体2的晶体结构不具有聚合性。两个Rh₂(O₂CCF₃)₄(THF)单元通过羧酸根基团的氧原子相互缔合，形成二聚体的二聚体。端基Rh−O(THF)键与轴向桥联Rh···O(Ac)相互作用的键长分别为2.214(7) Å与2.406(6) Å。