Two Triazole-Based Phosphine Ligands Prepared via Temperature-Mediated Li/H Exchange: Cu^I and Au^I Complexes and Structural Studies

The kinetically favored triazole-based phosphine 1-(2-(diphenylphosphino)­phenyl)-4-phenyl-1H-1,2,3-triazole (2, L₁) and its thermodynamically preferred isomer, 5-(diphenylphosphino)-1,4-diphenyl-1H-1,2,3-triazole (3, L₂), were obtained by the temperature-controlled lithiation of 2-bromotriazole followed by the reaction with chlorodiphenylphosphine. The structures of phosphines 2 and 3 were determined by X-ray diffraction. Upon reaction with late transition-metal derivatives (Cu^I, Ag^I, and Au^I), phosphines 2 and 3 form complexes with monodentate (Cu^I, Ag^I, and Au^I; κ¹-P), chelate (Cu^I; κ²-P,N), bridged bidentate (Cu^I; μ²-P,N), and tridentate (Cu^I; μ²,κ²-P,N,N) modes of coordination. Reactions with copper­(I) halides produced mono-, di-, and tetranuclear complexes, whereas the reaction of 2 with [Cu­(NCCH₃)₄]­BF₄ yielded the binuclear complex [Cu₂(CH₃CN)₂{o-Ph₂P­(C₆H₄)­{1,2,3-N₃C­(Ph)­C­(H)}-μ-(κ-P,κ-N),κ-N}₂]­(BF₄)₂ (10) with the ligand acting as a six-electron donor involving phosphorus and two triazole nitrogen atoms. The copper complexes of 2 and 3 containing rhomboid Cu₂X₂ units, [(Cu)₂(μ-X)₂{o-Ph₂P­(C₆H₄)­{1,2,3-N₃C­(Ph)­C­(H)}-κ-P}₂] (4, X = Cl; 5, X = Br), on treatment with 1,10-phenanthroline and 2,2′-bipyridine gave mixed-ligand complexes of the type [(CuX)­(N∩N-κ²-N,N)­{o-Ph₂P­(C₆H₄)­{1,2,3-N₃C­(Ph)­C­(H)}-κ-P}] (N∩N = 1,10-phen and 2,2′-bipy; X = Cl, Br, and I).