Halide and Nitrite Recognizing Hexanuclear Metallacycle Copper(II) Pyrazolates

Abstract

Halide-centered hexanuclear, anionic copper(II) pyrazolate complexes [trans-Cu(6)((3,5-CF(3))(2)pz)(6)(OH)(6)X](-), X = Cl, Br, I are isolated in a good yield from the redox reaction of the trinuclear copper(I) pyrazolate complex [μ-Cu(3)((3,5-CF(3))(2)pz)(3)] with a halide source such as PPh(3)AuCl or [Bu(4)N]X, X = Cl, Br, or I, in air. X-ray structures of the anion-centered hexanuclear complexes show that the six copper atoms are bridged by bis(3,5-trifluoromethyl)pyrazolate and hydroxyl ligands above and below the six copper atom plane. The anions are located at the center of the cavity and weakly bound to the six copper atoms in a μ(6)-arrangement, Cu-X = ~3.1 Å. A nitrite-centered hexanuclear copper(II) pyrazolate complex [trans-Cu(6)((3,5-CF(3))(2)pz)(6)(OH)(6)(NO(2))](-) was obtained when a solution of [PPN]NO(2) in CH(3)CN was added dropwise to the trinuclear copper(I) pyrazolate complex [μ-Cu(3)((3,5-CF(3))(2)pz)(3)] dissolved in CH(3)CN, in air. Blue crystals are produced by slow evaporation of the acetonitrile solvent. The X-ray structure of [PPN][trans-Cu(6)((3,5-CF(3))(2)pz)(6)(OH)(6)(NO(2))] complex shows the nitrite anion sits in the hexanuclear cavity and is perpendicular to the copper plane with a O-N-O angle of 118.3(7)°. The (19)F and (1)H NMR of the pyrazolate ring atoms are sensitive to the anion present in the ring. Anion exchange of the NO(2)(-) by Cl(-) can be observed easily by (1)H NMR.

Structural re-arrangement in two hexanuclear CuIIcomplexes: from a spin frustrated trigonal prism to a strongly coupled antiferromagnetic soluble ring complex with a porous tubular structure

“…This kind of Cu 6 ring structure with double bridges (O and -N-N-) has already been described in a few cases, [54][55][56][57][58][59] although they are all charged or contain an ion (mainly Cl À , Br À , I À or NO 2 À ). Interestingly, in 2 the Cu 6 ring structure is chargebalanced and, therefore, 2 is the rst example of a neutral Cu 6 ring of this type without any counter-ion inside.…”

Turning a “useless” ligand into a “useful” ligand: a magneto-structural study of an unusual family of CuII wheels derived from functionalised phenolic oximes

“…Of these, seven are octametallic [14][15][16][17][18][19][20] and six are hexametallic. [21][22][23][24][25][26] There are many more examples of both octametallic and hexametallic singlestranded Cu wheels which contain bridging motifs that do not feature oxygen atoms. 27 To the best of our knowledge there are no reported examples of single-stranded heterometallic wheels of nuclearity six with a Cu : M (where M is an alkali metal cation) ratio of 4 : 2.…”

Anion binding to a tetracopper resorcinarene-based complex

“…Unfortunately, attempts to fit such species failed, probably due to the small value that would likely be associated with the stepwise constant. Based on the 1:1 and the 1:4 stability constant values, the value for the addition of an additional phosphate should be in the order of 10.…”