Characterization and structure of some four-coordinate methylcopper(I) compounds

Article abstract of DOI:10.1021/om00113a032

The structure and the solution behavior of the compounds MeCuL_n (L_n = (PPh₃)₃, (PMePh₂)₃, and (Ph₂PCH₂)₃CMe) have been characterized by variable-temperature ¹H and ³¹P NMR studies and (for PPh₃) X-ray diffraction. All three compounds exist as monomeric, four-coordinate, 18-electron species at low temperatures in noncoordinating solvents, but ligand dissociation is already evident for PPh₃ and PMePh₂ at -80°C. The PPh₃ complex, which crystallizes from THF/pentane as MeCu(PPh₃)₃·THF (THF is in the crystal lattice and does not coordinate to copper), is shown by X-ray diffraction to have a nearly tetrahedral structure with Cu-C = 2.043 (12) and Cu-P = 2.313 (3) A?. The crowded intramolecular packing of phenyl groups is evident from the X-ray study, which then rationalizes the tendency of this complex to dissociate PPh₃. The thermal decomposition of MeCu(PPh₃)₃ in solution is indicated to proceed via unsaturated MeCu(PPh₃)₂. Crystallographic data for MeCu(PPh₃)₃·THF (at -154°C): space group P2₁ with a = 13.153 (5) A?, b = 10.125 (3) A?, c = 18.083 (7) A?, β = 93.19 (2)°, and Z = 2.