T. Neil Waters

Some observations on the structures of pyridoxal-aminoacid schiff base complexes

Abstract Structures are reported for (pyridoxylidene-DL-valinato)copper(II), a = 25.640(2), c = 13.326(2) A, γ = 120°, space group R 3 , Z = 8 and (3-methoxysalicylidene-DL-valinato)copper(II), a = 23.515(8), b = 9.194(4), c = 17.034(6) A, β = 126.41(7)°, space group C2/c, Z = 8. The former compound is polymeric with square-pyramidal co-ordination to copper involving five donor atoms of the ligand; the latter is monomeric with planar co-ordination geometry which includes a donor oxygen from water. Attention is drawn to bond length changes in the pyridoxylidene compound which, it is suggested, can be associated with reactivity.

Crystal and molecular structures of µ-oxalato-di[bisethylenediamine-nickel(II)] dinitrate, µ-oxalato-bis[di-(2-aminoethyl)aminecopper(II)] di-perchlorate, and µ-oxalato-bis[di-(3-aminopropyl)aminezinc(II)] diperchlorate

Crystal and molecular structures of the title compounds are reported. In each the complex cation is dimeric with the planar oxalate group acting as a bridge by forming five-membered chelate rings with two metal centres. Co-ordination geometries are approximately octahedral in the nickel compound (I), square pyramidal in the copper compound (II)(oxalate oxygen atoms occupying one basal and one axial site), and trigonal bipyramidal in the zinc compound (III)(oxalate oxygens occupying one apical and one equatorial site). The conformations of the co-ordinated amines are discussed and their relationships with the stereochemistry of the metal centres and with the hydrogen bonding network examined.Crystal data: (I), monoclinic a= 6·33(2), b= 12·03(2), c= 14·95(3)A, β= 91·2(3)°, Z= 2, space group P21/n; (II), orthorhombic. a= 7·02(1), b= 13·25(3), c= 25·27(4)A, Z= 4, space group Pbc2l; (III), orthorhombic, a= 13·38(2), b= 14·72(3), c= 13·30(3)A, Z= 4, space group Pna2l. The structures were solved by the heavy-atom method from photographic data and refined by least squares to R 0·105 [(I), 1936 independent reflexions], 0·101 [(II), 1948], and 0·090 [(III), 1688].

Crystal and molecular structure of the tetranuclear copper complex di-µ-chloro-bis{chloro[NN′-ethylenebis(salicylideneiminato)copper(II)]copper(II)}

The reaction product formed between NN′-ethylenebis(salicylaldiminato)copper(II), Cu(salen), and copper(II) chloride has been subjected to a three-dimensional X-ray analysis. The monoclinic cell has a= 7·791 (6), b= 16·780(6), c= 10·536(5)A, β= 100·80(9)°; space group, P21/n. The structure was solved from diffractometer data by the heavy-atom method and refined by block-diagonal least squares to R 0·069. The tetranuclear molecular structure has chlorine atoms bridging binuclear species Cu(salen)CuCl2. The copper atoms bonded by the organic ligands are four-co-ordinate with a planar donor stereochemistry; the remaining copper atoms are five-co-ordinate with donors in a distorted tetragonal pyramidal geometry.

Thiol complexes of copper as possible biological models

SummaryThe reactions and properties of 2-aminothiophenol complexes of copper have been investigated under differing conditions. Inconsistencies among earlier reports arise from previously unrealised effects of atmospheric conditions and counter ion. It is suggested that the ligand is unusual in the sense that it stabilises the cupric and cuprous states to the same extent; some of the properties of its copper complexes are thereby understood. Three ligands similar to 2-amino-thiophenol have been studied. Spectral and magnetic measurements are presented; attention is drawn to unexpected results, especially in the d-d region of electronic spectra.

Crystal and molecular structure of 4′-(acridin-9-ylamino)methanesulphonanilide hydrochloride, a compound showing antileukemic activity

The title compound (VI) has antileukemic properties. An X-ray analysis shows it to be triclinic, a= 14·074(1), b= 6·864(1), c= 10·166(1)A, α= 105·40(3), β= 101·60(2), γ= 86·07(3)°, Z= 2, space group P. The structure was solved by Patterson and Fourier methods. Refinement of 2070 diffractometer data reduced the R factor to 0·046. The acridine ring is slightly non-planar and the phenyl ring makes an angle of 77° with it. This latter appears to be a feature of the molecule rather than a crystal-packing requirement.

The crystal structures of di-µ-chloro-bis{[N-(2-aminoethyl)thiophen-2-aldimine]chlorocopper(II)} and bis[N-(2-aminoethyl)thiophen-2-aldimine]diperchloratocopper(II)

The structures of the title complexes have been investigated by single-crystal X-ray crystallography. In both the complexes the ligands are co-ordinated through nitrogen only. the thiophen sulphur atoms remaining unattached. The chloro-complex is dimeric with chloride bridges and has a distorted square-pyrimidal co-ordination polyhedron. The perchlorato-complex is monomeric with an octahedral co-ordination geometry which includes the perchlorate groups.

Conformations of diterpenoids: an X-ray determination of the molecular structure of 6α-bromo-13-hydroxy-14-isopropylpodocarpa-8,11,13-trien-7-one and of the structure and absolute configuration of methyl 6α-bromo-13-isopropyl-7-oxopodocarpa-8,11,13-trien-15-oate

The crystal and molecular structures of the title compounds have been determined by X-ray diffraction methods from photographic data by the heavy-atom method; the absolute configuration was established for the second named. Crystals of the former (II) are tetragonal, a= 12·54, c= 23·97, A, space group P41212; the structure was refined by least squares to R 0·088. The latter (III) is triclinic, a= 6·20, b= 7·73, c= 10·79 A, α= 97·0, β= 79·3, γ= 104·6°, space group P1; refined to R 0·064. In (II) ring A has a chair conformation with a trans A/B ring fusion; ring B has an approximate boat conformation and the bromine atom has the α-configuration. The bromine is in the same configuration in compound (III) and ring A also adopts the chair conformation. There is trans A/B ring fusion with ring B somewhat distorted but describable as a ‘half-boat’. The stereochemistries at asymmetric centres confirm earlier evidence. There is considerable variation in detailed conformation, however, and a comparison between these compounds and with the molecular structure of methyl 6α-bromo-12-methoxy-7-oxopodocarpa-8,11,13-trien-16-oate leads to the view that steric rather than electronic factors are largely responsible for the path of bromine attack.

Crystal and molecular structure of a donor–acceptor complex involving protonated riboflavin, quinol, and bromide ions

Black crystals of stoicheiometry riboflavin:quinol:hydrogen bromide:water 1:1:2:2 have been grown. The crystals are monoclinic, a= 20·55(5), b= 13·69(4), c= 10·18(4)A, β= 91·2(1)°, with four ‘molecules’ of this composition in a cell of space group P21. The structure was solved from photographic data by Patterson and Fourier methods, and refined by least squares to R 0·145 for 2358 independent reflections. There are charge-transfer interactions between riboflavin molecules (as acceptors) and quinol molecules and bromide ions (as donors). The riboflavin molecules are probably in the semiquinone state and their interaction with the donors is not confined to a specific region of the isoalloxazine nuclei.

Crystal and molecular structure of di-µ-[4,6,6-trimethyl-3,7-diazanon-3-ene-1,9-diolato(1—)-ONN′,µ-O′]-dicopper(II) diperchlorate

The structure of the title compound, formed by reaction of copper(II) perchlorate, 2-aminoethanol, and acetone, has been determined by X-ray diffractometry. It is monoclinic, space group P21/c, a= 8.4495(6), b= 23.612(5), c= 8.3041(8)A, and β= 115.43(1)°; R= 0.066. The compound contains centrosymmetric di-µ-oxo-bridged dimeric cations, with the copper atoms in distorted square-pyramidal co-ordination. The bridging oxo-groups, and the amine and imine donor groups, are co-ordinated in the basal plane and the hydroxyl group of the quadridentate ligand is co-ordinated in the apical site. An analogous compound with the ligand 5,7,7-trimethyl-4,8-diazaundeca-4-ene-1,11-diol has been prepared from copper(II) perchlorate, 3-aminopropan-1-ol, and acetone. This is diamagnetic, or nearly so, implying complete spin pairing via the di-µ-oxo bridge, although spin pairing of the title compound is not significant.

X-Ray crystal structure of a stable complex of copper(III); the use of deprotonated nitrogen atoms as donors

The stable blue compounds arising from the reaction of aldehydes or ketones with oxalodihydrazide in the presence of Cu2+ ions and molecular oxygen have been characterised by X-ray diffraction and e.s.r. studies and studies and are proposed as oxidase models.