Magnetic and spectroscopic properties of benzylammomium tetrahalogenochromates(II) containing mixed halides (Cl and Br)

Summary The complexes [PhCH₂NH₃]₂[CrCl_xBr_4–x], x=0, 1, 1.8, 3.3 or 4, have been prepared, and the new mixed halides characterised by magnetic and spectroscopic measurements. They are further examples of two dimensional ferromagnets. The magnitude of the magnetic interaction increases slightly with replacement of chloride by bromide.     

A facile synthesis and structure determination from 13c-nmr spectroscopy of a novel heterocycle 1,1′-ethylenebis[2,3,8,8a-tetrahydro-5,8a-dimethyl-1H-imidazo[2,1-c][1,4]thiazine], a case of transannular stabilization

The condensation of 4-thiaheptane-2,6-dione with triethylenetetramine does not produce the macrocycle 1-thia-3,14-dimethyl-4,7,10-13-tetrazacyclopentadeca-3,13-diene; instead two molecules of the dione condense with one of the amine to give the title compound.     

Structure of bis(2-acetyloximephenolato) nitrosylcobalt,a nitrosyl containing a bent Co-N-O group

The crystal and molecular structure of [Co(NO)(ketox)₂], where ketoxH is 2-hydroxyacetophenoneoxime, have been determined. This nitrosyl crystallizes in the orthorhombic system,a=14.741,b=6.853,c=32.442 A,Z=8, space groupPbca. The structure was determined by the heavy-atom method, using Mokα diffractometer data, and refined by full-matrix least squares toR=0.041 for 1768 observed reflections. The molecule excluding the nitrosyl group is approximately planar. The cobalt atom is 5-coordinate in an essentially square pyramidal arrangment with the basal plane defined bytrans bidentate oximato ligands between which are strong hydrogen bonds. The nitrosyl group occupies the apical position and the Co-N-O angle is 126.3°.     

Vanadium(II) complexes of aromatic diamines

The new vanadium(II) complexes [V(opd)₄]X₂ and [V(mopd)₄]X₂, where opd = o-phenylenediamine, mopd = 4-methyl-o-phenylenediamine, and X = Cl or Br, have been prepared by reaction of the aromatic diamine with the vanadium(II) halide in EtOH. Magnetic measurements suggest that these contain octahedral vanadium(II) complex cations, and this is confirmed by the diffuse reflectance spectra. I.r. spectra suggest that the [V(opd)₄]²⁺ cations contain two bidentate and two monodentate diamine ligands.     

Thiocyanato adducts of chromium(II) carboxylates and the molecular structure of tetraethyl-ammonium tetra-μ-propionatodiisothio-cyanatodichromate(II)

X-Ray crystallographic studies on [NEt₄]₂[Cr₂[(O₂CC₂H₅)₄(NCS)₂] show that the Cr–Cr separation (2.467Å) in the dinuclear anion is one of the longest known. The thiocyanato groups are N-bonded, and the results emphasize the known sensitivity of the quadruple Cr–Cr bond to the nature of the axial ligands. The compound crystallises in the tetragonal space group P4/mnc with two molecules per unit cell, the dimensions of which are a = b = 9.785(1), c = 21.186(2) Å. Magnetic investigations from room to liquid nitrogen temperature on the tetra-μ-propionato complex and on [NMe₄]₂ [Cr₂(O₂CCH₃)₄(NCS)₂] show that both complexes have been obtained free from paramagnetic chromium(III) impurities. Their weak paramagnetic susceptibilities (X_cr is approx. 200 x 10⁻⁶ cm³ mol⁻¹ at 295 K and 50 x 10⁻⁶cm³mol⁻¹ at 90 K) are inherent, and are ascribed to temperature independent paramagnetism at low temperature plus para-magnetism arising from slight population of the triplet state (2J 700 cm⁻¹, g = 2, N = 50 x 10⁻⁶cm³mol⁻¹) at higher temperatures.     

Structures of NN′-ethylenebis(monothioacetylacetoneiminato)nitrosylcobalt and NN′-ethylenebis(2-hydroxyacetophenoneiminato)nitrosylcobalt

The cobalt atoms in both [Co(NO)(sacacen)] and [Co(NO)(7-Mesalen)] {sacacenH₂ isNN-ethylenebis(monothioacetylacetoneimine) and 7-MesalenH₂ isNN-ethylenebis(2-hydroxyacetophenoneimine)} are 5-coordinate, with a tetragonal-pyramidal arrangement of donor atoms. The cobalt atom in [Co(NO)(sacacen)] lies just above the plane defined by the SNNS donor atoms of the quadridentate ligand, and the nitrosyl group occupies the apical position. A similar geometry is defined by the ONNO donor atoms and the NO group in [Co(NO)(7-Mesalen)]. The Co-N-O angles are strongly bent, as predicted from¹⁵N-nmr studies (127.2(6)°[Co(NO)(sacacen)] and 127.4(3)°[Co(NO)(7-Mesalen)]). Both nitrosyls crystallize in the monoclinic system. For [Co(NO)(sacacen)],a=8.501,b=12.673,c=13.866 Å,=95.00°,Z=4 and space groupP2₁/c. The structure was determined by the heavy-atom method, usingMo K diffractometer data, and refined by full matrix least squares toR=0.062 for 2920 observed reflections. For [Co(NO)(7-Mesalen)],a=9.461,b=13.053,c=13.456,=99.32°,Z=4 and space groupP2₁/c. The structure was determined as above toR=0.040 for 2461 observed reflections.     

The molecular structure of the diacetic acid adduct of guanidinium tetrabromochromate(II)

The diacetic acid adduct of guanidinium tetrabromochromate(II) crystallizes in the monoclinic crystal system:a=8.778,b=9.125,c=12.195 Å,=89.84°, space groupP2₁/n,Z=2. The structure was determined using the heavy atom method followed by Fourier methods and refined by full-matrix least-squares toR=0.061 for 2221 observed reflections. The structure contains discrete [CrBr₄(HO₂CCH₃)₂]^2– anions separated by [C(NH₂)₃]⁺ cations. The chromium(II) atom is six-coordinate withtrans pairs of Cr-Br bonds of unequal length (2.84 and 2.63 Å), and two acetic acid molecules completing the coordination.     

Structure of (1,2-diaminoethane) (1-[[2-[(2-aminoethyl)imino]propyl]thio]-2-propanone)nickel(II) nitrate

A single crystal X-ray investigation of the purple nickel (II) complex Ni[L(en)](NO₃)2, produced by condensation of 1,2-diaminoethane (en) with the thiodiketone S(CH₂COCH₃)2 in the presence of nickel (II) nitrate (L is NH₂(CH₂)₂N=C(CH₃)CH₂SCH₂COCH₃), shows that the metal ions are six coordinate. The new ligand L is tetradentate, with the N,N and S donor atoms arranged meridionally, and the coordination shell completed by the carbonyl oxygen atom of L and the nitrogen atoms of 1,2-diaminoethane. Metal-ligand bond distances are Ni-N: 2.08 av. (en), 2.10 and 2.05 (NH₂ and N=C respectively of L); Ni-O, 2.16; Ni-S, 2.45 Å. There is considerable angular distortion from regular octahedral values of the bond angles at nickel. The crystals are monoclinic,P2₁/c (No. 14),a=12.433(2),b=11.709(1),c=13.150(2) Å,=103.93(1)°,V _c=1858.2(4) ų. The structure was solved by the heavy-atom method and refined by full-matrix least squares to anR value of 0.055 for 3633 reflections.