Reactivity of Dinuclear Copper(I)/pybox Complexes towards Isocyanides and Phosphanes†

The dinuclear complexes [Cu2(R-pybox)2][PF6]2 {R-pybox = 2,6-bis[4′-(S)-isopropyloxazolin-2′-yl]pyridine for (S,S)-iPr-pybox (1) and 2,6-bis[4′-(R)-phenyloxazolin-2′-yl]pyridine for (R,R)-Ph-pybox (2)} are very efficient precursors for the synthesis of dinuclear and mononuclear derivatives containing isocyanide or phosphane ligands. The reaction of 1 and 2 with the isocyanides (CNBn or CNCy) resulted in the synthesis of the dinuclear derivatives [Cu2(R-pybox)2(CNBn)2][PF6]2 [R-pybox = (S,S)-iPr-pybox (3), (R,R)-Ph-pybox (4)] and [Cu2(R-pybox)2(CNCy)2][PF6]2 [R-pybox = (S,S)-iPr-pybox (5), (R,R)-Ph-pybox (6)]. When the reaction was carried out with the monodentate (PMePh2, PPh3) and the bidentate phosphanes [dppm, dppf, (S)-peap] the mononuclear complexes [Cu(R-pybox)(PRPh2)2][PF6] [R-pybox = (S,S)-iPr-pybox, R = Me(7), Ph (8); R-pybox = (R,R)-Ph-pybox, R = Ph (9)], [Cu(R-pybox){(S)-peap}][PF6] [R-pybox = (S,S)-iPr-pybox (11), (R,R)-Ph-pybox (12)], and [Cu(R-pybox)(dppf)][PF6] [R-pybox = (S,S)-iPr-pybox (13), (R,R)-Ph-pybox (14)] and the dinuclear complex [Cu2{(S,S)-iPr-pybox}(μ-dppm)2][PF6]2 (10) were obtained, respectively. The structures of complexes 3, 7, 10, and 13 have been resolved by X-ray diffraction methods and by 1D, 2D, and DOSY NMR spectroscopy measurements. The 1H, 31P, and 19F DOSY NMR spectroscopic experiments provided evidence that the solid-state nuclearity of compounds 3, 7, 10, and 13 is maintained in solution and confirmed that these ionic compounds exist in solution as stable, discrete, cationic complexes.