Dinuclear Cu(I) Halides with Terphenyl Phosphines: Synthesis, Photophysical Studies, and Catalytic Applications in CuAAC Reactions

Abstract

Several dinuclear terphenyl phosphine copper­(I) halide complexes of composition [CuX­(PR2Ar′)]2 (X = Cl, Br, I; R = hydrocarbyl, Ar′ = 2,6-diarylterphenyl radical), 1–5, have been isolated from the reaction of CuX with 1 equiv of the phosphine ligand. Most of them have been characterized by X-ray diffraction studies in the solid state, thus allowing comparative discussions of different structural parameters, namely, Cu···Cu and Cu···Aryl separations, conformations adopted by coordinated phosphines, and planarity of the Cu2X2 cores. Centrosymmetric complexes [CuI­(PMe2ArXyl2)]2, 1c, and [CuI­(PEt2ArMes2)]2, 3c, despite their similar structures, show very distinct photoluminescence (PL) in powder form at room temperature. The photophysical behavior of these compounds in liquid solution, solid–solid Zeonex solution and powder samples at room temperature and 77 K have been investigated and supported by DFT calculation. Identification of vibronic coupling modes, done by group theory calculations and the technique of projection operators, shows that the manifestation of these modes is conditioned by crystal packing. Complexes [CuI­(PMe2ArXyl2)]2, 1c, and [CuI­(PEt2ArMes2)]2, 3c, display remarkable activity in copper-catalyzed azide–alkyne cycloaddition reactions involving preformed and in situ-made azides. Reactions are performed in H2O, under aerobic conditions, with low catalyst loadings and tolerate the use of iodoalkynes as substrates.

Heteroleptic Copper Complexes as Catalysts for the CuAAC Reaction: Counter-Ion Influence in Catalyst Efficiency

“…The triazole products a-i were identified by their 1 H NMR spectra, which were consistent with the data reported in the literature [41][42][43][44][45]. In the case of the new triazole derivative f, further purification through column chromatography was required prior to NMR spectroscopy characterization.…”

Tris‐isocyanide copper(I) complex enabling copper azide‐alkyne cycloaddition in neat conditions

“…[33] Thus, in this paper we report the synthesis and structural characterization of a rare example of three-coordinated Cu(I) homogeneous catalyst having formula [Cu(CNXyl) 3 ][BF 4 ], where CNXyl is 2,6-dimethylphenyl isocyanide. [34][35][36][37] Remarkable catalytic activity for CuAAC in neat conditions was verified with a wide number of substrates (Scheme 1c).…”

New copper(i) complexes of bulky 5-substituted-2-iminopyrrolyl ligands as catalysts for azide–alkyne cycloaddition

“…The catalytic results obtained with the present system led a TOF value as high as 859 h −1 for the production of 1-benzyl-4-phenyl-1 H -1,2,3-triazole, resulting from the cycloaddition of phenylacetylene with (azidomethyl)benzene, operating at concentrations of catalyst as low as 0.1 mol%. Considering the set of activities recorded for the present catalyst system, we can conclude it is less efficient than the mononuclear copper complexes bearing NHC (maximum TOF = 950 h −1 ) 20 or diimine ligands (maximum TOF = 1920 h −1 ), 22 slightly better than the catalysts bearing phosphine/phosphonite/phosphinite ligands (maximum TOF = 313 h −1 ) 21 and considerably better than the in situ prepared ones (maximum TOF = 27 h −1 ). 7…”

“…To gain mechanistic insight into CuAAC reactions and improve their activity, the study of well-defined Cu( i ) molecular systems is imperative. 19 Some examples of well-defined copper( i ) complexes capable of performing CuAAC reactions have been reported in the literature, in which the respective copper centers were supported by N-heterocyclic carbenes (Chart 1, A , maximum TOF = 950 h −1 ), 20 phosphines/phosphonites/phosphinites (Chart 1, B , maximum TOF = 313 h −1 ), 21 or nitrogen-based diimine ligands (Chart 1, C , maximum TOF = 1920 h −1 ). 22 As a representative example of the development of nitrogen-based ligands toward CuAAC reactions, Tilley and co-workers, isolated a series of dinuclear copper( i ) intermediates using the dinucleating ligand 2,7-bis(fluoro-di(2-pyridyl)-methyl)-1,8-naphthyridine (Chart 1, D ), 23 which supported the propensity of catalytic dinuclear species in CuAAC reactions, with cooperation between the two copper centers.…”