Structural and solid state 31P NMR studies of the four-coordinate copper(i) complexes [Cu(PPh3)3X] and [Cu(PPh3)3(CH3CN)]X

Abstract

The tris(triphenylphosphine)copper(I) complexes [(PPh₃)₃CuX] for X = Cl (1), Br (2), I (3), ClO₄ (4), BF₄ (5), [(PPh₃)₃CuCl]·CH₃CN (1a), [Cu(PPh₃)₃(CH₃CN)]X for X = ClO₄ (6), BF₄ (7), and [Cu(PPh₃)₃(CH₃CN)]X·CH₃CN for X = SiF₅ (8), PF₆ (9) have been studied by solid state ³¹P CP/MAS NMR spectroscopy together with single crystal X-ray diffraction for compounds (6)–(9), the latter completing the availability of crystal structure data for the series. Compounds (1)–(5) form an isomorphous series in space group P3 (a ∼ 19, c ∼ 11 Å) with three independent molecules in the unit cell, all disposed about 3-fold symmetry axes. Average values (with estimated standard deviations) for the P–Cu–P, P–Cu–X bond angles and Cu–P bond lengths in compounds (1)–(3) are 110.1(6)°, 108.8(6)° and 2.354(8) Å and 115.2(6)°, 102.8(9)° and 2.306(9) Å for compounds (4) and (5). For the acetonitrile solvated compound (1a), the corresponding parameters are 115(4)°, 103(3)° and 2.309(3) Å. The solid state ³¹P CP/MAS NMR quadrupole distortion parameters, dν_Cu, for (1)–(3) and (1a) are all less than 1 × 10⁹ Hz², despite the changes in donor properties of the halide in (1)–(3), and the coordination geometry of the P₃CuX core in (1a). Change of anion to ClO₄⁻ and BF₄⁻ in compounds (4) and (5) results in a significant increase of dν_Cu to 4.4–5.2 10⁹ Hz² and 5.2–6.0 × 10⁹ Hz², respectively. Compounds (6) and (7) crystallise as isomorphous [Cu(PPh₃)₃(CH₃CN)]X salts in space group Pbca, (a ∼ 17.6, b ∼22.3, c ∼24.2 Å), while compounds (8) and (9) crystallize as isomorphous acetonitrile solvated salts [Cu(PPh₃)₃(CH₃CN)]X·CH₃CN in space group P (a ∼ 10.5, b ∼ 13.0, c ∼19.5 Å, α ∼ 104, β ∼ 104, γ ∼ 94^°). The P₃CuN angular geometries in all four compounds are distorted from tetrahedral symmetry with average P–Cu–P, P–Cu–N angles and Cu–P bond lengths of 115(4)°, 103(4)° and 2.32(1) Å, with dν_Cu ranging between 1.3 and 2.5 × 10⁹ Hz². The solid state ²⁹Si CP/MAS NMR spectrum of the pentafluorosilicate anion in compound (8) is also reported, affording ¹J(²⁹Si, ¹⁹F) = 146 Hz.