Treatment of a THF solution of copper(I) chloride with potassium diphenylphosphide in the presence of tri-tert-butylphosphine at -30 °C results in the formation of compound 1 (eq. 1) as determined by single crystal X-ray diffraction, 1 H, 31 P, 13 C NMR, and 31 P HMBC NMR spectroscopy. Compound 1 can also be synthesized by treatment of mesitylcopper(I) with diphenylphosphine in the presence of tri-tert-butylphosphine (eq.