76077-65-1Relevant academic research and scientific papers
Progressive transmetalation of tetranuclear dioxocopper(II) complexes with cobalt reagents
Henary, Maher,Davies, Geoffrey,Abu-Raqabah, Atieh,El-Sayed, Mohamed A.,El-Toukhy, Ahmed
, p. 1872 - 1879 (2008/10/08)
Aprotic oxidation of tetranuclear copper(I) complexes N4Cu4X4 (I) (N is monodentate N,N-diethylnicotinamide; X is Cl or Br) with dioxygen gives tetranuclear dioxocopper(II) complexes (μ-O)2N4Cu4X4 (II). These targets are transmetalated by excess transmetalators bis(S-methyl isopropylidenehydrazinecarbodithioato)nickel(II) (A) and bis(S-methyl benzylidenehydrazinecarbodithioato)nickel(II) (B) to give isomers of (μ-O)2[NCuNi(H2O)X2]2, Te1 and Te2, respectively. However, if complexes I are first monotransmetalated by A (the metal is Co, Ni, Cu, or Zn) or tris(S-methyl isopropylidenehydrazinecarbodithioato)cobalt(III) (C) and the oxidized, the products are tetramers (μ4-O,μ-O)N3Cu3M(H2O)X 4 (IV). Complexes IV react with excess A (M = Ni) or C to give trimers (μ3-O)N3M3X4 (Tr1) or, when M in IV is Cu (specified as III), with excess A to give the six-member family (μ4-O,μ-O)N3Cu4-x(Ni(H 2O))xCl4 (Te3). It is shown that II (X = Cl) reacts with 1-4 mol of C to give the tetranuclear family (μ-O)2N4Cu4-xCoxCl4 (x = 0-4), which includes the analogue of isomer Te2. Transmetalation of (μ3-O)N3Cu3Cl4 (XIV) with 1-3 mol of C gives the family of Tr1 trimers (μ3-O)N3Cu3-xCoxCl4 (x = 1-3). Structurally different trimers (μ-O)N3(Co,Cu)3Cl4 (Tr2) are obtained by two methods: (1) transmetalation of III with 1-3 mol of C; (2) the four-step sequence (a) transmetalation of I with C and 2 mol of A (M = Cu), (b) oxidation of the product with dioxygen and (c) transmetalation with 1 or 2 mol of C. These two methods give five of the six expected members of the Tr2 family that are distinguishable from Tr1 and from each other by ESR and electronic spectral measurements and by magnetic moment determinations. A trans effect with Co > Cu across μ-oxo bridges influence the course of progressive transmetalations of II and (μ-O)N3(Co,Cu)3Cl4 isomers by C.
Transmetalation of tetranuclear copper complexes. 4. Structural implications of the kinetics of direct transmetalation of tetranuclear copper(II) complexes by Ni(NS)2 reagents
Davies, Geoffrey,El-Sayed, Mohamed A.,El-Toukhy, Ahmed
, p. 1925 - 1928 (2008/10/08)
The rate laws for direct transmetalations of excesses of tetranuclear copper(II) complexes (μ4-O) [NCu]4X6 (A) (N = monodentate N,N-diethylnicotinamide (DENC), pyridine (py); X = Cl, Br) by Ni(NS)2 reagents B and C in nitrobenzene to give (μ4- O)[N4Cu3Ni]X6 products (D) depends on the molecular geometries of B and C. For B, with cis-coordinated sulfur atoms in a distorted square-planar geometry, rate = kB[A]2[B], while C, which is a trans square-planar species, obeys rate = kc[A][C]. It is concluded that rapid exchange of nickel for copper takes place in Cu-X-Ni-S rings.
Transmetalation of tetranuclear copper complexes. 9. Stoichiometry and kinetics of transmetalation of (μ4-O)[NCu]4X6 Complexes by M(NS)2 reagents in aprotic solvents
Davies, Geoffrey,El-Sayed, Mohamed A.,El-Toukhy, Ahmed
, p. 3899 - 3903 (2008/10/08)
Tetranuclear copper(II) complexes (μ4-O)[(DENC)Cu]4X6 (A; DENC = N,N-diethylnicotinamide; X = Cl, Br) are stoichiometrically transmetalated by 1 mol of structurally characterized M(NS)2 reagents (NS is a monoanionic S-methyl hydrazine-carbodithioate Schiff base; M = Co, Ni, Zn) in aprotic solvents. The chromatographically isolated products are equimolar tetranuclear (μ4-O)[(DENC)4Cu3M(H2O)]X 6 and Cu(NS)2. Reactants A and products (μ4-O)[(DENC)4Cu3M(H2O)]X 6 have electronic spectral features at 775 and 850 nm. The rate laws for reactions of excess A with M(NS)2 in methylene chloride and nitrobenzene depend on X, M, and the structure of the NS ligand. The proposed mechanisms contain common Cu-X-M-S rings that facilitate metal replacement in A; however, metal replacement apparently is not rate-determining in the majority of the 18 systems investigated.
