Raymond L. Martin

Synthesis and X-ray structure of bis(diethyldithiocarbamato)(µ-dichloro)-dicopper(II), Cu2(Et2dtc)2Cl2, and the X-ray structure of Cu3(Et2dtc)2Cl3, an unusual mixed valence CuII, CuI reduction product

The preparation and crystal structure of the dimeric chloro-bridged copper(II) dithiocarbamate complex, Cu2(Et2dtc)2Cl2, are described, together with the crystal structure of a related minor product, Cu3(Et2dtc)2-Cl3, which proves to be an unusual mixed valence CUII/CUI polymer.

Synthesis, structure and properties of cobalt(III) complexes of pentadentate ligands with pyridyl pendant arms

Cobalt(III) complexes of the pentadentate ligands 3-[4-(2-pyridyl)-3-azabut-3-enyl]-3-azapentane-1,5-diamine (L1), 3-[4-(2-pyridyl)-3-azabutyl]-3-azapentane-1,5-diamine (L2) and 1,4-bis(2-pyridylmethyl)-1,4,7-triazacyclononane (L4) have been synthesized. Various characterization studies have confirmed the formation of the complexes [CoL4(OH2)]3+, [Co(L4)Cl]2+, [Co(L1)Cl]2+, [Co(L2)Cl]2+ and [Co(HL3)Cl]2+(HL3= 3-{2-[hydroxy(2-pyridyl)methyleneamino]ethyl}-3-azapentane-1,5-diamine) the product of oxidation of [Co(L1)Cl]2+ in acidic solution. The structure of [CoL4(OH2)][ClO4]3·H2O has been determined by single crystal X-ray diffraction. The complex crystallizes in the orthorhombic space group P212121, with a= 15.090(3), b= 16.659(4), c= 10.192(4)A and Z= 4. Refinement gave final R and R′ values of 0.045 and 0.043, respectively, for 1708 observed reflections. The pyridyl pendant arms were found to introduce significant distortion from ideal octahedral geometry. The Co–N(tacn) distances are shorter than in related complexes of ligands derived from 1,4,7-triazacyclononane (tacn). The complex [Co(HL3)Cl][ClO4]2·H2O crystallizes in the monoclinic space group P21/c with a= 13.496(5), b= 10.253(3), c= 15.371(6)A, β= 101.65(3)° and Z= 4. Refinement gave final R and R′ values of 0.054 and 0.054, respectively, for 1686 observed reflections. The bond lengths within the amide portion of the pentadentate ligand are intermediate between keto and enol resonance forms. Protonation of the amide oxygen is implied by the number of counter ions present. No evidence of imine oxidation was observed in electrochemical studies. These studies indicated that some stabilization of the CoII state relative to CoIII arises from the presence of pyridyl and imine π acceptors.

Paramagnetic anisotropy of planar cobalt(II) and copper(II) phthalocyanine, bis(pentane-2,4-dionato)copper(II), and bis(pentane-2,4-dithionato)cobalt(II)

The principal crystalline and molecular susceptibilities, and their orientations, of cobalt(II) phthalocyanine, [Co(pc)], bis(pentane-2,4-dithionato)cobalt(II). [Co(pdt)2]. copper(II) phthalocyanine, [Cu(pc)], and bis-(pentane-2,4-dionato)copper(II), [Cu(pd)2], are reported. The diamagnetic anisotropy of the two pc derivatives makes a significant contribution to the observed anisotropy, especially in the cooper compound. The resulting paramagnetic anisotropy {and e.s.r. data in the case of [Co(pdt)2]} is then used to confirm the S=½ ground state of each compound [⋯ dz21 in both the cobalt(II) derivatives and dxy1 in both the copper(II) derivatives]. The marked in-plane anisotropy in [Co(pdt)2], compared with the in-plane isotropy of [Co(pc)], is shown to arise from both the abnormally large splitting of the dxz, dyz pair of orbitals and the mixing of the dxy and dz2 orbitals in low symmetry. An unambiguous assignment of two of the excited states in [Cu(pc)] can be made but ambiguities remain in [Cu(pd)2].

Single-crystal magnetic studies of tris(ethylenediamine)nickel(II) nitrate

The magnetic anisotropy of [Ni(en)3][NO3]2(en = ethylenediamine) has been determined from 4.58 to 300 K and the average susceptibility has been measured down to 2.01 K at field strengths ranging from 10 to 50 KG. The results are interpreted on a point-charge model for D3 symmetry using the parameters A20 =–630 cm–1, ρ4= 7 000 cm–1, α= 25°, F2= 1 350 cm–1, F4= 70 cm–1, ζ= 400 cm–1, and k= 1.0. The calculations show that a twist from octahedral toward trigonal-prismatic co-ordination has little effect on the magnetism. The magnetization and low-temperature anisotropy are consistent with the compound being weakly antiferromagnetic.

Synthesis and properties of dimeric cobalt(III) dithiocarbamate complexes [Co2(R2dtc)5]+: X-ray structural analysis of pentakis(diethyldithiocarbamato)dicobalt(III) tetrafluoroborate

The synthesis, properties, and structures of cationic dimeric dithiocarbamato-complexes (dtc) of cobalt(III) are described. The complexes [Co2(R2dtc)5]BF4 were prepared by reaction of [Co(R2dtc)3] with boron trifluoride. The crystal structure of [Co2(Et2dtc)5]BF4 was determined from three-dimensional counter data. Crystals are orthorhombic, space group P212121, with a= 14.301(5), b= 16.819(3). c= 18.048(4)A, and Z= 4. The structure was solved by conventional Patterson and Fourier techniques and refined by block-diagonal least-squares to R 0.092 for 1 141 independent reflections. The green-brown diamagnetic [Co2(R2dtc)5]+ species is comprised of an electrophilic [Co(R2dtc)2]+ fragment co-ordinated in the cis-positions by sulphur atoms from an octahedral [Co(R2dtc)3] molecule of opposite chirality. The lability of the bridging groups renders the dimer susceptible to attack by other nucleophiles and representative mixed chelates of the type [Co(R2dtc)2(chel)] have been synthesised (chel = xanthate, dithiocarbamate, acetyl-, and dithioacetyl-acetonate).