A Trigonal Planar μ3-Fluorido Coinage Metal Complex from a Dicationic (Diphosphinomethane)copper(I) Dimer: Syntheses, Structures, and Bonding

Abstract
The triflate and hexafluorophosphate salts of [Cu2(μ-dtbpm)2]2+ (12+) [dtbpm = bis(di-tert-butylphosphino)methane, tBu2PCH2PtBu2] and of [Cu33-F)(μ-dtbpm)3]2+ (22+) were synthesized and characterized. Coordination of solvent or counterions to 12+ is observed neither in solution nor in the solid state. The two copper(I) centers in 12+ indicate weak d10−d10 closed-shell interactions. 12+ reacts slowly with PF6- anions in acetone or KF in CH2Cl2 to yield the μ3-fluorido complex 22+ with idealized D3 symmetry, containing a trigonal planar Cu3F core, as shown by single-crystal X-ray diffraction. Distinct structural differences are observed compared to monocationic bicapped, trinuclear copper(I) dppm halide complexes [dppm = bis(diphenylphosphino)methane, Ph2PCH2PPh2]. The average Cu−Cu, Cu−F, and Cu−P distances and the P−Cu−P' angle in 22+ are 3.85, 2.22, and 2.28 Å and 144.3°, respectively. The P2Cu units are twisted out of the Cu3F plane by an average angle of 18.4°. DFT calculations (BPW91/LANL2DZ) for the model [Cu33-F)(μ-dhpm)3]2+ (dhpm = diphosphinomethane, H2PCH2PH2) are used to explain the formation, structure, and bonding pattern of 22+.

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