Structural Diversity and Rare η¹ Cu-C Interactions in Cu^I Complexes of 1,2,3-Triazole-Functionalized Bisphosphines

This manuscript describes the synthesis of copper complexes of 1,2,3-triazolyl-phosphines: o-Ph₂P(C₆H₄){1,2,3-N₃CC₆H₅)C(PPh₂)} (L1), (C₆H₅){1,2,3-N₃C(C₆H₄(o-PPh₂))-C(PPh₂)} (L2), 3-Ph₂P(C₅H₃N){1,2,3-N₃C(C₆H₅)C(PPh₂)} (L3), o-Ph₂P(C₆H₄){1,2,3-N₃C(C₅H₅N)C(PPh₂)} (L4), and {(3,5-Ph₂PC₆H₄-o)₂1,2,3-N₃CCH} (L5). The reactions of L1-L3 with Cu^I salts afforded dimeric complexes having the general formula [Cu₂(μ -X)₂L₂] (L = L1, X = Cl, Br and I: 1 - 3; L= L2, X = Cl, Br and I: 4- 6; L = L3; X = Cl, Br, and I: 7-9). The reaction of L4 with CuI in a 1:2 molar ratio afforded 1D-coordination polymer [{(CuI)₂{o-Ph₂P(C₆H₄){1,2,3-N₃C(C₅H₅N)C(PPh₂)}-μ-((k¹-N)(k²-P,P))}}] (10). The reaction of L5 with cuprous halides (CuX) (X = Br, I) yielded mononuclear complexes [CuX{(3,5-Ph₂PC₆H₄-o)₂1,2,3-N₃CCH}-κ²P,P] (X = Br, 12; I, 13). Crystal structures of complexes 12 and 13 showed close interactions between Cu^I and the triazole C7 carbon. These relatively short Cu···C7 separations may be due to the η¹-C interaction (d_π-p_π bond) between the triazolic carbon atom (via p orbital) and Cu^I or three-centered two-electron interaction between Cu^I and the triazolic C-H bond. The existence of the Cu···C interaction was further evinced by the QTAIM analysis in compounds 12 and 13.