A. El-Toukhy

Transmetalation of tetranuclear copper complexes with tin transmetalators. Molecular structure of cis-dichloro-bis(trans-S-methyl isopropylidenehydrazinecarbodithioato)tin(IV) and consideration of transmetalation mechanisms

Tin complexes Sn(NS)2Cl2(D) and Sn(NS)4(E) (NS is monoanionic S-methyl isopropylidenehydrazinecarbodithioate) are very good transmetalators of tetranuclear copper(I) target [NCuCl]4 (I: N is N,N-diethylnicotinamide). An X-ray crystallographic study shows that D is cis-dichloro-bis(trans-S-methyl isopropylidenehydrazinecarbodithioato)tin(IV). Evidence that I reacts with 1 or 2 mol of D via strong precursors D·I and D2·I that contain NS ligands bridging tin to copper is used to discuss the transmetalation sequence. The tin-containing transmetalation products include the remarkable air-stable copper(I)-tin(IV) complex N3Cu2Sn(NS)2Cl4 obtained from the reaction of I with equimolar E.

Transmetallation reactions of tetranuclear copper(II) complexes. I. Crystal and molecular structures of an intermediate and a final product of reaction of di-μ-oxo-tetra[chloro(DENC)copper(II)],(DENC = N,N-diethylnicotinamide) with [Zn(N2S2], (N2S2 = diacetyl-bis-hydrazonato-S-methyl-carboditithioate) in aprotic solvents

Abstract Di-μ-oxo-tetra[chloro(DENC)copper(II)],[(DENC)CuCl]4O2, (DENC) = N,N-diethylnicotinamide) reacts with two moles of dimeric [Zn(N2S2]2), (N2S2 = diacethyl-bis-hydrazonato-S-methyl-carbodithioate) to give 2 moles of [Cu(N2S2]2 and a variety of zinc containing products, including zinc(II) oxide. The crystal and molecular structures of the intermediate five-coordinate complex Zn(N2S2)(DENC), A, and a final product, di-μ-(N,N-diethylnicotinamide-O,N)-tetrachlorodizinc(II), B, from this interesting metal exchange reaction are reported. Although the ultimate products are the same, no intermediate analog of A is detected with monomeric tetrahedral Zn(NS)2 reactants. Complex A crystallizes in the triclinic space group P 1 with Z = 2 in a cell of dimensions a = 10.258(1), b = 10.708(1), c = 12.548(1) A, α = 107.69(1), β = 99.70(1), γ = 106.49(1)°. Complex B also crystallizes in space group P1 with Z = 2 but in a cell of dimensions a = 9.427(4), b = 14.106(6), c = 8.589(3) A, α = 120.87(3), β = 116.17(3), γ = 106.76(3)°.

SYNTHESIS, STRUCTURE AND PROPERTIES OF THE ISOMERIC DINUCLEAR COMPLEXES ((DENC)2CUX2)2 (DENC = N,N-DIETHYLNICOTINAMIDE; X = CL OR BR) AND THE KINETICS OF THEIR REACTIONS WITH DENC IN METHYLENE CHLORIDE

Abstract Tetrahalo - tetrakis - (N,N-diethylnicotinamide)dicopper(II) species [(DENC) 2 CuX 2 ] 2 (X = Cl or Br) differ in that while the chloro complex is bridged by two DENC molecules in the solid but two chloro groups in solution, the bromo complex is always bromo-bridged. These conclusions result from an X-ray structural determination of (DENC)Cl 2 Cu(DENC,DENC)CuCl 2 (DENC) and from spectroscopic comparisons. The kinetics of conversion of the respective dimers to monomeric (DENC) 3 CuX 2 species have been measured in methylene chloride solution.

Crystal and molecular structures of three M(NS)2 transmetalating agents (NS is a monoanionic S-methyl hydrazinecarbodithioate Schiff base; M = Co, Zn)

Abstract The crystal and molecular structures of the M(NS) 2 transmetalating agents bis-(S-methyl-isopropylidenehydrazinecarbodithioato) cobalt(II), its zinc analog and of bis-(S-methyl-benzylidenehydrazinecarbodithioato) zinc(II) are reported. Structural differences which may give rise to different mechanisms of transmetalation are noted.

The crystal and molecular structure of trimeric [L2CuCl2]3, L=N,N-diethylnicotinamide

Abstract The complex prepared with a 2:1 molar ration of L = N,N-diethylnicotinamide to anhydrous copper(II) chloride has been crystallized from ethanol as the trimeric unit [L2CuCl2]3. The crystals are monoclinic, space group P21/c with a = 16.618(1), b = 8.253(2), c = 28.194(1) A, β = 117.3(4)°. The trimeric unit utilizes a crystallographic center of symmetry. Least squares refinement of the structure using 3692 independent intensities has yielded an R factor of 0.059. Each molecule consists of two five-coordinate and one six-coordinate copper center. The μ,μ-dichloro bridging system is asymmetric with a Cu⋯Cu separation of 3.686 A. The CuN distances range from 2.004(4) to 2.027(4) A and the CuCl distances from 2.264(2) to 2.982(-) A. The copper coordination spheres are compared to that in (py2CuCl2).

Transmetalation of tetranuclear copper(I) complexes with an Fe(NS)3 reagent

Abstract Stoichiometric transmetalation of tetranuclear copper(I) complexes N4Cu4X4 (I; N = N,N-diethyl- nicotinamide; X  Cl or Br) by 1 mol or excess tris(S- methyl isopropylidenehydrazinecarbodithioato)iron- (III) (Fe(NS)3, IIa) in aprotic solvents under dinitrogen is preceded by electron transfer from copper- (I) to iron(III) and gives tetranuclear iron(II)-containing products: I + IIa → N4Cu2ICuIIFeII(NS)2X4 (III′) + Cu(NS)(s). The rates of reaction of I with M(NS)3 and M(NS)2 reagents (M = Co, Ni, Cu, Zn) decrease in the order Co(NS)3 (II) > IIa > M(NS)2. Products III′ react stoichiometrically with 1 mol of II or M(NS)2 or with 2 mols of II or M(NS)2 to give iron(III)-containing dimers N4MFe(OH)X4 (VIII′) and trimers N3M2Fe(OH)X4O (X′), respectively, after oxidation with dioxygen and isolation. Transmetalation of III′ with equimolar mixed transmetalators M(NS)2 and M′(NS)2 is selective but gives dimers N4MM′X4 instead of VIII′ because Fe(NS)2 is more thermodynamically stable than M′(NS)2. Aprotic oxidation of III′ by dioxygen proceeds in two distinct stages, the first corresponding to four-electron oxidation of the two copper(I) and two coordinated NS ligands of III′ and the second to oxidation of the iron(II) center of III′. The isolated oxidation products are (μ4-O, μ-O)N4- Cu3Fe(OH)X4 (IV′). Products IV′ characteristically lose 1 mol CuO on transmetalation with 2 mol of M(NS)2 or II to give trimers X′. Products IV′ also react with 1 or 2 mol of Fe(NS)3 to give trimers (μ3-O)N3Fe(OH)CuFe(NS)X4 (XI′) and (μ3-O)N3Fe(OH)(Fe(NS))2X4 (XII′), respectively. The major differences between Co(NS)3 and Fe(NS)3 as transmetalators of I, III′ and IV′ are (i) lack of reaction of III and III′ with excess Fe(NS)3; (ii) facile oxidation of iron(II) in transmetalated products by dioxygen; (iii) case of transmetalation of these iron(II) centers with M(NS)2; (iv) stability of Fe(NS) centers in transmetalated products XI′ and XII′.