Four Cu(I) complexes were synthesized with a family of pyridylmethylamide ligands, HLR [HLR = N-(2-pyridylmethyl)acetamide, R = null; 2,2-dimethyl-N-(2-pyridylmethyl)propionamide, R = Me3; 2,2,2-triphenyl-N-(2-pyridylmethyl)acetamide, R = Ph3)]. Complexes 1–3 were synthesized from the respective ligand and [Cu(CH3CN)4]PF6 in a 2 : 1 molar ratio: [Cu(HL)2]PF6 (1), [Cu2(HLMe3)4](PF6)2 (2), [Cu(HLPh3)2]PF6 (3). Complex 4, [Cu(HL)(CH3CN)(PPh3)]PF6, was synthesized from the reaction of HL with [Cu(CH3CN)4]PF6 and PPh3 in a 1 : 1 : 1 molar ratio. X-Ray crystal structures reveal that complexes 1, 3 and 4 are mononuclear Cu(I) species, while complex 2 is a Cu(I) dimer. The copper ions are four-coordinate with geometries ranging from distorted tetrahedral to seesaw in 1, 2, and 4. Complexes 1 and 2 are very air sensitive and they display similar electrochemical properties. The coordination geometry of complex 3 is nearly linear, two-coordinate. Complex 3 is exceptionally stable with respect to oxidation in the air, and its cyclic voltammetry shows no oxidation wave in the range of 0–1.5 V. The unusual inertness of complex 3 towards oxidation is attributed to the protection from bulky triphenyl substituent of the HLPh3 ligand. A new geometric parameter for four-coordinate compounds, τ4, is proposed as an improved, simple metric for quantitatively evaluating the geometry of four-coordinate complexes and compounds.

Structural variation in copper(I) complexes with pyridylmethylamide ligands: structural analysis with a new four-coordinate geometry index, tau4.

Structure and Spectroscopy of Copper−Dioxygen Complexes

Triazoles and tetrazoles: Prime ligands to generate remarkable coordination materials

The coordination chemistry of pyrazole-derived ligands

Mononuclear, oligonuclear and polynuclear metal coordination compounds with 1,2,4-triazole derivatives as ligands

The linear quadridentate N2S2 donor ligand 1,7-bis(N-methylbenzimidazol-2′-yl)-2,6-dithiaheptane (bmdhp) forms mono- and di-hydrate 1 : 1 copper(II) complexes which are significantly more stable toward autoreduction than those of the non-methylated analogue. The deep green monohydrate of the perchlorate salt crystallises as the mononuclear aqua-complex, [Cu(bmdhp)(OH2)][ClO4]2, in the monoclinic space group P21/n, with Z= 4, a= 18.459(3), b= 10.362(2), c= 16.365(3)A, and β= 117.14(1)°. The structure was solved and refined by standard Patterson, Fourier, and least-squares techniques to R= 0.047 and R′= 0.075 for 3 343 independent reflections with l > 2σ(l). The compound consists of [Cu(bmdhp)(OH2)]2+ ions and ClO4– counter ions. The co-ordination around copper is intermediate between trigonal bipyramidal and square pyramidal, with Cu–N distances of 1.950(4) and 1.997(4)A, Cu–O(water) 2.225(4)A, and Cu–S 2.328(1) and 2.337(1)A. In the solid state, the perchlorate dihydrate's co-ordination sphere may be a topoisomer of the monohydrate's. A new angular structural parameter, τ, is defined and proposed as an index of trigonality, as a general descriptor of five-co-ordinate centric molecules. By this criterion, the irregular co-ordination geometry of [Cu(bmdhp)(OH2)]2+ in the solid state is described as being 48% along the pathway of distortion from square pyramidal toward trigonal bipyramidal. In the electronic spectrum of the complex, assignment is made of the S(thioether)→ Cu charge-transfer bands by comparison with those of the colourless complex Zn(bmdhp)(OH)(ClO4). E.s.r. and ligand-field spectra show that the copper(II) compounds adopt a tetragonal structure in donor solvents.

Synthesis, structure, and spectroscopic properties of copper(II) compounds containing nitrogen–sulphur donor ligands; the crystal and molecular structure of aqua[1,7-bis(N-methylbenzimidazol-2′-yl)-2,6-dithiaheptane]copper(II) perchlorate

Synthesis and characterization of coordination compounds of chelating ligands containing imidazole groups. The crystal and molecular structures of the dinuclear copper(I) and copper(II) compounds

Magnetic properties of dimeric disubstituted-triazole copper(II) compounds. X-ray structure of bis[.mu.-3,5-bis(pyridin-2-yl)-1,2,4-triazolato-N',N1,N2,N"]bis[aqua(trifluoromethanesulfonato-O)copper(II)]

An unusual trimeric CuII species of formula [Cu3(OH)(pz)3(Hpz)2(NO3)2]·H2O (Hpz = pyrazole) has been prepared from air oxidation of [Cu(Hpz)2(NO3)] in the presence of moisture. The X-ray structure of the oxidation product has been determined by single-crystal diffractometer techniques, and has been compared with a few related structures, all containing the pyramidal trimeric unit Cu3(OH). The compound crystallizes in the space group P21 with a= 7.756(2), b= 17.639(3), c= 8.883(1)A, β= 91.18(1)°, and Z= 2. The intensities of 3 640 independent reflections were used to determine the structure. The structure was solved and refined using standard heavy-atom and least-squares techniques to a residual R value of 0.0241 for 3 128 reflections with I > 2σ(I). The structure consists of trimeric units Cu3(OH)(pz)3 containing an almost flat Cu3N6 ring and a pyramidal Cu3O group with Cu–O distances of 1.994 A and an (averaged) Cu–O–Cu angle of 114°. Each copper is co-ordinated by four ligands in an almost square planar manner with two nitrogens from the bridging pyrazolato-groups and one oxygen from the bridging OH group. The fourth equatorial ligand is either the N-atom of a neutral pyrazole (for two Cu atoms) or the oxygen of a unidentate co-ordinating nitrato-ligand (for the third Cu atom). The fifth axial ligand for each copper ion is another nitrato-group. This nitrato-group links trimers together in chains, with two oxygens bound to coppers of one trimer, and the third oxygen binding to the third copper of the neighbouring trimer, resulting in chains of –O2NO–CuCu2O2NO–CuCu2–O2–. The dominant magnetic exchange in the structure occurs within each trimer, resulting in a compound having only one unpaired spin per three copper ions. An additional magnetic exchange interaction occurs between the trimers, using the nitrate-bridged chain. This interaction is only evident at very low temperatures. Due to the occurrence of rapid spin-lattice relaxation no e.s.r. spectra can be obtained at ambient temperatures, but instead n.m.r. spectra have been recorded.

Synthesis, magnetic properties, and X-ray structure of catena-µ3-nitrato-O,O′,O″-[µ3-hydroxo-1-nitrato-1,2;1,3;2,3-tris(µ-pyrazolato-N,N′)-2,3-bis(pyrazole-N2)tricopper(II) monohydrate]. An unusual chain of trinuclear copper clusters

A series of dimeric copper(II) co-ordination compounds with general formula [Cu2(tmbma)2(azolate)]X3 has been prepared and characterized, where tmbma is the tripodal benzimidazole-containing ligand tris(N-methylbenzimidazol-2-ylmethyl)amine, azolate is the anion of imidazole, benzimidazole, or benzotriazole, and X = NO3–, BF4–, or ClO4–. Variable-temperature magnetic susceptibility measurements indicate antiferromagnetic interactions with J values of –10 to –18 cm–1(for the benzimidazolate and benzotriazolate compounds) and –28 cm–1(for the imidazolate compounds). Q-Band and X-band e.s.r. spectra show typical S= 1 signals; D values calculated from these spectra range from 0.08 to 0.13 cm–1. The crystal and molecular structure of the title compound has been determined by single-crystal X-ray diffraction. The compound crystallizes in the space group C2/c, with a= 16.880(2), b= 26.011(1), c= 14.686(1)A, β= 100.585(7)°, and Z= 4. The structure was solved by heavy-atom methods and refined using least-squares techniques to a residual R of 0.050 for 3 327 reflections with l > 2σ(l). The structure consists of dimeric cations, having C2 symmetry, and disordered nitrate anions; the co-ordination geometry around the copper ions can be described as distorted trigonal bipyramidal with three equatorial benzimidazole nitrogen atoms, one axial amine nitrogen atom, and the benzotriazolate ion bridging from an axial position on one copper ion to an axial position on the other copper ion, resulting in a Cu ⋯ Cu distance of 5.536(2)A.

Dimeric copper(II) compounds with a tripodal imidazole-containing ligand and bridged by imidazolate, benzimidazolate, and benzotriazolate ions. Crystal and molecular structure of µ-(benzotriazolato-N1,N3)bis{[tris(N1-methylbenzimidazol-2-ylmethyl)amine-N,N3,N3′,N3″]copper(II)} trinitrate

G. C. Verschoor

Papers

Synthesis, structure, and spectroscopic properties of copper(II) compounds containing nitrogen–sulphur donor ligands; the crystal and molecular structure of aqua[1,7-bis(N-methylbenzimidazol-2′-yl)-2,6-dithiaheptane]copper(II) perchlorate

Synthesis and characterization of coordination compounds of chelating ligands containing imidazole groups. The crystal and molecular structures of the dinuclear copper(I) and copper(II) compounds

Magnetic properties of dimeric disubstituted-triazole copper(II) compounds. X-ray structure of bis[.mu.-3,5-bis(pyridin-2-yl)-1,2,4-triazolato-N',N1,N2,N"]bis[aqua(trifluoromethanesulfonato-O)copper(II)]

Synthesis, magnetic properties, and X-ray structure of catena-µ3-nitrato-O,O′,O″-[µ3-hydroxo-1-nitrato-1,2;1,3;2,3-tris(µ-pyrazolato-N,N′)-2,3-bis(pyrazole-N2)tricopper(II) monohydrate]. An unusual chain of trinuclear copper clusters

Dimeric copper(II) compounds with a tripodal imidazole-containing ligand and bridged by imidazolate, benzimidazolate, and benzotriazolate ions. Crystal and molecular structure of µ-(benzotriazolato-N1,N3)bis{[tris(N1-methylbenzimidazol-2-ylmethyl)amine-N,N3,N3′,N3″]copper(II)} trinitrate