The crystal structure of a compound with a triangular palladium cluster
Date
1977
Authors
Moroney, Pearse
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Abstract
The crystal structure of µ-chloro-bis(µ-diphenylphosphido)-tris(triethylphosphine)-tri-palladium fluoroborate has been determined by the single crystal x-ray diffraction method. The data was collected automatically at room temperature on a Picker 4-circle diffractometer using MoK radiation. The structure was solved by the heavy atom method, and refined by the full matrix least squares method using only reflections where the net count was greater than 3a (σ is the estimated standard deviation of the net count).
Crystals of [Pd₃Cl(PPh₂)₂(PEt₃)₃][BF₄] are monoclinic with a = 1614(1), b = 1951.2(8), c = 1691,2(6), β = 97.66°(6), and space group P₂₁/c (no. 14). The measured and the calculated densities are 1.49 and 1.47 g cm⁻³ respectively. Over 4,000 (20ₘₐₓ = 40°) counter intensities were measured of which 2866 independent reflections were used to refine the structure to an R value of .105. The palladium atoms are arranged approximately in an equilateral triangle, with diphenylphosphido ligands bridging two of the sides and a chloro bridge on the other side. One triethylphosphine ligand is co-ordinated terminally to each palladium atom. Some of the important dimensions of the structure are given. The distance between the palladiums, which are bridged by the chlorine atom, is 289(2) pm whilst the average of the other two Pd-Pd distances is 293(2) pm. The angles in the palladium triangle are close to 60°, and the average Pd-PEt₃ distance is 230(1) pm and the Pd-Cl-PD angle is 73.8°(8). The average Pd-PPh2 distance from the palladiums with the chloro bridge is 222(2) pm as opposed to the average Pd-PPh₂ angle is 81.4°(6). The presence of metal-metal bounding in this complex is discussed in some detail and it is concluded that [Pd₃Cl(PPh₂)₂(PEt₃)₃][BF₄] is a metal cluster.