A Mononuclear and a Mixed-Valence Chain Polymer Arising from Copper(II) Halide Chemistry and the Use of 2,2′-Pyridil

Reactions of 2,2′-pyridil (pyCOCOpy) with CuCl2 · 2H2O and CuBr2 in EtOH yielded the mononuclear complex [Cu(pyCOOEt)2Cl2] · H2O (1) and the one-dimensional, mixed-valence complex [Cu2ICuII(pyCOOEt)2Br4]n (2), respectively. Both complexes crystallize in the triclinic space group P 1¯. The lattice constants are a = 8.382(2), b = 9.778(2), c = 7.814(2), α = 101.17(1), β = 114.55(1), γ = 94.14(1)° for 1 and a = 8.738(1), b = 9.375(2), c = 7.966(1), α = 79.09(1), β = 64.25(1), γ = 81.78(1)° for 2. 2,2′-pyridil undergoes a metal-assisted alcoholysis and oxidation leading to decomposition and yielding the ethyl picolinate (pyCOOEt) ligand. The autoredox process associated with the reduction of copper(II) to copper(I) in the case of complex 2 is discussed in terms of the increased redox activity of the copper(II) bromide system relative to the copper(II) chloride system

A Mononuclear and a Mixed-Valence Chain Polymer Arising from Copper(II) Halide Chemistry and the Use of 2,2'-Pyridil

Reactions of 2, 2 -pyridil (pyCOCOpy) with (2) , respectively. Both complexes crystallize in the triclinic space group P 1. The lattice constants are a = 8.382(2), b = 9.778(2), c = 7.814(2), α = 101.17(1), β = 114.55(1), γ = 94.14(1) • for 1 and a = 8.738(1), b = 9.375(2), c = 7.966(1), α = 79.09(1), β = 64.25(1), γ = 81.7

Experimental Evidence of a Haldane Gap in an S = 2 Quasi-linear Chain Antiferromagnet

The magnetic susceptibility of the $S = 2$ quasi-linear chain Heisenberg antiferromagnet (2,$2'$-bipyridine)trichloromanganese(III), MnCl_{3}(bipy), has been measured from 1.8 to 300 K with the magnetic field, H, parallel and perpendicular to the chains. The analyzed data yield $g\approx 2$ and $J\approx 35$ K. The magnetization, M, has been studied at 30 mK and 1.4 K in H up to 16 T. No evidence of long-range order is observed. Depending on crystal orientation, $M\approx 0$ at 30 mK until a critical field is achieved ($H_{c\|} = 1.2\pm 0.2 T$ and $H_{c\bot} = 1.8\pm 0.2 T), where M increases continuously as H is increased. These results are interpreted as evidence of a Haldane gap.Comment: 11 pages, 4 figure

A general synthetic route for the preparation of high-spin molecules: Replacement of bridging hydroxo ligands in molecular clusters by end-on azido ligands

Abstract A general method of increasing the ground-state total spin value of a polynuclear 3d-metal complex is illustrated through selected examples from cobalt(II) and nickel(II) cluster chemistry that involves the dianion of the gem-diol form of di-2-pyridyl ketone and carboxylate ions as organic ligands. The approach is based on the replacement of hydroxo bridges, that most often propagate antiferromagnetic exchange interactions, by the end-on azido ligand, which is a ferromagnetic coupler

Families of Polynuclear Manganese, Cobalt, Nickel and Copper Complexes Stabilized by Various Forms of Di-2-pyridyl Ketone

The synthetic and structural chemistry of polynuclear manganese, cobalt, nickel and copper carboxylate complexes, stabilized by various forms of di-2-pyridyl ketone, is discussed. The structural diversity displayed by the described complexes stems from the ability of the doubly and singly deprotonated forms of the gem-diol form of di-2-pyridyl ketone, or the monoanion of the hemiacetal form of this ligand, to adopt a variety of coordination modes. The nuclearities of the clusters vary from four to fourteen. Perhaps the most aesthetically pleasing families are the “flywheel Cu-12 clusters, and the Co-9 and Ni-9 complexes in which the nine metal ions adopt a topology of two square pyramids sharing a common apex. A means of increasing the ground-state total spin value of a polynuclear 3d-metal cluster is also proposed. The approach is based on the replacement of hydroxo bridges, that most often propagate antiferromagnetic exchange interactions in clusters, by the end-on azido ligand, which is a well known ferromagnetic coupler. This approach involves “true” reactivity chemistry on pre-isolated clusters and the products are not undergone significant structural changes, except for the azido-for-hydroxo substitution, compared to the starting materials/clusters

Variation of product identity as a function of metal ion: ligand reaction ratio, stereochemical studies and thermal investigation of Mn(II), Fe(III), N

A systematic investigation of the MX2 and FeCl3/APH reaction systems in EtOH is described, where M = Mn, Ni, Cu, Cd and Hg, X = Cl, Br, NO3, SCN, CH3COO, BF4 and 1 2SO4, and APH = 2-acetylpyridine hydrazone. Emphasis has been placed on determining the influence of the metal ion : APH ratio on the identity of the reaction products. The variation of this ratio has led to the synthesis of thirty-two new discrete complexes with general compositions M(APH)X2, M(APH)2X2, M(APH)3X2, Fe(APH)Cl3 and Fe(APH)2Cl3. The complexes were characterized by elemental analyses, conductivity measurements. X-ray powder patterns, thermal methods, magnetic susceptibilities and spectroscopie (IR, ligand field, 1H NMR, ESR) studies. Monomeric pseudo-tetrahedral and monomeric or polymeric distorted octahedral stereochemistries were assigned in the solid state. APH appears to coordinate via both the pyridine and methine nitrogen atoms. The thermal decomposition of the prepared complexes was also studied. Some Ni(II) complexes decompose via stable intermediates. Probable mechanistic paths of the decomposition reactions have been proposed. © 1989