Synthesis and spectroscopic characterization of new Cu(I) complexes containing triaryl-, tricycloalkylphosphines and heterocyclic anionic or neutral N-donor ligands. Crystal and molecular structure of [ (Cy3P)2(pzH)Cu]ClO4·CH3OH (Cy = cyclohexyl, pzH = pyrazole)

Article abstract of DOI:10.1016/0020-1693(96)05101-8

The reaction of (PPh₃)₄CuClO₄, (PPh₃)₂CuCl, (Cy₃P)₂CuNO3 and (Cy₃P)₂CuClO₄ with an excess of monodentate heterocyclic N-donor ligand (QH in general, in detail: ImH = imidazole, 1-MeimH = 1-methylimidazole, 2-MeimH = 2-methylimidazole, 4-PhimH = 4-phenylimidazole, BimH = benzimidazole, 1-BzimH= 1-benzylimidazole, pzH = pyrazole, pz′H = 3,5-dimethylpyrazole) in diethyl ether or benzene resulted in the formation of new 2:2:1 [(PPh₃)₂(QH)₂Cu]ClO₄ (QH = ImH, 1-MeimH, 2-MeimH, 4-PhimH, BimH, pzH) and [(PCy₃)₂(QH)₂Cu]NO₃ (QH = 4-PhimH, BimH), 1:3:1 [(PPh₃)(1-BzimH)₃Cu]ClO₄, [(PCy₃)(I-MeimH)₃Cu]ClO₄ and [(PCy₃)(QH)₃Cu]NO₃ (QH = ImH, 1-MeimH, pzH), 2:1:1 [(PPh₃)₂(QH)CuCl] (QH = ImH, 2-MeimH, 4-PhimH, BimH, 1-BzimH), [(PCy₃)₂(QH)Cu]NO₃ (QH= 1-BzimH, pz′H) and [(PCy₃)₂(QH)Cu]ClO₄ (QH = 2-MeimH, 4-PhimH, BimH, 1-BzimH, pzH, pz′H), 1:2:1 [(PCy₃) (2-MeimH)₂Cu]NO₃ and [(PCy₃)(ImH)₂Cu]ClO₄ and 1:1:1 [(PPh₃)(1-MeimH)CuCl] adducts. With the bidentate donors bis(pyrazol-1-yl)methane (L¹), bis(3,5-dimethylpyrazol-l-yl)methane (L²) and bis(4-methylpyrazol-l-yl)methane (L⁴), 2:1:1 [ (PPh₃)₂(L) Cu]ClO₄ and 1:1:1 [(PCy₃)(L)Cu]ClO₄ complexes were obtained, whereas the exopolydentate bis(1,2,4-triazol-1-yl) methane (L³) in similar conditions yielded 1:1:1 [(PPh₃)(L³)Cu]ClO₄ and [(PCy₃)(L³)Cu]NO₃, and 1:2:1 [(PCy₃)(L³)₂Cu]ClO₄ derivatives. Breaking of the bridging C(sp³)-N bond in the bidentate bis (pyrazol-1-yl) methane occurred when the reaction between L¹ and (PCy₃)₂CuNO₃ was carried out in diethyl ether under aerobic conditions, the derivative [ (PCy₃) (pzH)₃Cu]NO₃ being formed. In methanol in the presence of base, ImH, 2-MeimH, 4-PhimH and BimH react with (PPh₃)₂CuCl giving the sparingly soluble complexes [(PPh₃)₂(Im)Cu] · 1/2H₂O, [(PPh₃)₂(2-Meim)Cu] · H₂O, [(PPh₃)(4-PhJm)Cu] and [ (PPh₃) (Bim)Cu], respectively. Reaction of [(PPh₃)₂(ImH)₂Cu]ClO₄ with PCy₃, PBz₃ (Bz = benzyl), P(p-tolyl)₃ and (Ph₂PCH₂)₂ (abbreviated Diphos) resulted in the formation of compounds [(PPh₃)(PCy₃)(ImH)₂Cu]ClO₄, [(PPh₃)(PBz₃)(ImH)Cu]ClO₄, [(PPh₃)P(p-tolyl)₃(ImH)₂Cu]ClO₄ and [(Diphos)₂Cu]ClO₄, respectively, whereas reaction with 1,10-phenanthroline (Phen) and 2,2′-bipyridyl (Bipy) produced [ (PPh₃)₂(ImH) (Phen)Cu]ClO₄ and [(PPh₃)₂(ImH) (Bipy)Cu]ClO₄, respectively. While PCy₃, PBz₃ and P(p-tolyl)₃ were not able to displace the triphenylphosphine from [(PPh₃)₂(L¹)Cu]ClO₄, Phen and Bipy in the same conditions formed the derivatives [ (PPh₃)₂(Phen)Cu]ClO₄ and [ (PPh₃)₂(Bipy)Cu]ClO₄. All of the complexes were characterized by IR and far-IR data, conductivity, ¹H NMR and in some cases also with UV, ¹³C and ³¹P NMR and molecular weight measurements. The structure of [ (Cy₃P)₂(pzH)Cu]ClO₄ · CH₃OH was determined by single crystal X-ray diffraction: monoclinic, space group Pn, Z=2, a=9.949(7), b=13.128(4), c=16.588(8) A, β=91.15(7)°. The copper atom exhibited a distorted ideal trigonal planar geometry involving two phosphine groups (Cu-P: 2.262(9) and 2.272(6) A;P-Cu-P: 132.3(7)°) and one pyrazole ligand (Cu-N: 2.047(18) A) coordinating through a pyridine-like nitrogen atom. The pyrazole donor of one molecule was hydrogen bonded to a molecule of methanol, which in turn was hydrogen bonded to the ionic perchlorato group.