Andrzej C. Skapski

Possible mode of action of anti-tumour platinum drugs: X-ray evidence for cis binding by platinum of two inosine 5′-monophosphate molecules via the N(7) positions

Abstract Action of cis -[Pt(NH 3 ) 2 (H 2 O) 2 ] 2+ on the disodium salt of inosine 5′-monophosphate produces the ion [Pt(NH 3 ) 2 (5′-IMP) 2 ] 2- . X-ray structural evidence shows that platinum binds to the two nucleotide moieties via the N(7) positions on the bases. The implications of this finding are discussed in terms of possible modes of anti-tumour action of platinum compounds.

Refined crystal structure of tetra-µ-acetato-bisaquodicopper(II)

The structure of the title compound has been refined from three-dimensional X-ray diffractometer data. Crystals are monoclinic, space group C2/c, with Z= 4 in a unit-cell of dimensions: a= 13·168(2), b= 8·564(2), c= 13·858(2)A, and β= 117·02(1)°, Full-matrix least-squares refinement, using 1280 independent reflections, has reached R 0·047.The refinement has, as expected, confirmed the original two-dimensional structure determination and much more accurate bond lengths and bond angles have been obtained: mean Cu–O(acetate) 1·969 A, Cu–O(water) 2·156, and Cu ⋯ Cu is 2·616 A. The geometry of the acetate bridges is planar and bond lengths and angles are as expected.

Crystal structure of dichlorotetra-µ-adenine-dicopper(II) chloride hexahydrate

The structure of dichlorotetra-µ-adenine-dicopper(II) chloride hexahydrate, [Cu2(ade)4Cl2]Cl2,6H2O, has been determined by three-dimensional X-ray crystal structure analysis. The crystals are orthorhombic with unit-cell dimensions a= 23·92, b= 13·844, c= 11·262 A, Z= 4, space group Cmca. Full-matrix least-squares refinement, using 870 visually estimated reflections, has reached R 0·098.The structure contains the complex ion [Cu2(ade)4Cl2]2+, chloride ions and molecules of water of solvation. The complex ion, which has 2/m crystallographic symmetry, is dimeric with pairs of copper atoms held together by four bridging adenine ligans, co-ordinated via N(3) and N(9). The copper atoms have a square pyramidal co-ordination, with chlorine in the apical position at a distance of 2·429 A. The metal is 0·33 A above the plane of four nitrogen atoms, with Cu–N distances of 2·008 and 2·041 A. The Cu ⋯ Cu non-bonded separation is 3·066 A.The chloride ions together with the water molecules and all non-donor nitrogen atoms of adenine form an intricate network of hydrogen bonds in which linkages of the type O–H ⋯ N, N–H ⋯ O, and O–H ⋯ Cl– are involved.

X-ray structure of a hydrated nickel salt of guanosine 5′-monophosphate; Evidence for the absence of direct metal-phosphate bonding

Abstract An X-ray structure determination of the complex [Ni(5′-GMP)(H2O)5]. 3H2O has shown that the metal atom coordinates to the nucleotide only at the N(7) position on the guanine moiety. There is no direct metal-phosphate bonding, although intramolecular hydrogen bonding between coordinated water molecules and the phosphate group may be an important stabilizing element in the structure.

Studies on transition-metal peroxo complexes. Part 7. Molybdenum(VI) and tungsten(VI) carboxylato peroxo complexes, and the X-ray crystal structure of K2[MoO(O2)2(glyc)]·2H2O

New complexes [MoO(O2)2L]2–[L = malate, tartrate (tart), tartronate, quinate, or glycolate (glyc)], [WO(O2)2L]2–(L = citrate, tartrate, malate, or glycolate), and [W2O2(O2)4(tart)]4– are reported, and modified preparations given for [MO(O2)2L]2– and [MO2(O2)L(H2O)]2–(M = Mo or W; L = oxalate). Raman and i.r. spectra of the solid complexes, and Raman, 13C and 95Mo n.m.r. spectra of their aqueous solutions, have been measured and are used to suggest the structures of the species in the solid state and solution. The X-ray crystal structure of K2[MoO(O2)2(glyc)]·2H2O has been determined: triclinic, space group P, with a= 7.222(4), b= 7.950(6), c= 10.450(5)A, α= 67.81(4), β= 73.72(7), γ= 64.84(4)° at 20 °C, and Z= 2; the structure has been refined to R= 0.035.

X-ray evidence for adenine N(1)-metal bonding in a cobalt-9-methyladenine complex

Abstract X-Ray investigation of the compound CoCl2 (9-methyladenine) has shown that adenine moiety utilizes N(1) and N(7) sites in binding to the metal. This involvement of the N(1) site may well be of relevance in understanding the denaturing of DNA by metal ions.

Refinement of the crystal structure of acetylacetonatodicarbonylrhodium(I)

The structure of acetylacetonatodicarbonylrhodium(I), Rh(acac)(CO)2, has been refined from three-dimensional X-ray diffractometer data. The complex crystallises in the triclinic space groupP¯1 with two molecules in a unit cell of dimensionsa = 6.5189(5),b = 7.7614(8),c = 9.2049(12)Å, α = 106.04(1), β = 91.15(1), γ = 100.21(1) °. Full-matrix least-squares refinement, using 1456 independent reflections, has reachedR = 0.038.The rhodium atom has a square-planar coordination with two Rh-O(acac) distances of 2.040 and 2.044Å, and two Rh-C(carbonyl) distances both equal to 1.831Å, the O-Rh-O angle is 90.8 ° and the C-Rh-C angle is 88.9 °. All twelve non-hydrogen atoms are closely planar, with an average deviation of 0.003Å, and a maximum deviation of 0.006Å, from the least-squares plane through the molecule. A second non-crystallographic plane of symmetry bisects the molecule, which therefore has essentiallymm2 (C2v) point symmetry. The molecules stack in such a way that the rhodium atoms of neighbouring molecules occupy the two remaining pseudo-octahedral positions, with Rh...Rh distances of 3.253 and 3.271Å.

Tropolonato complexes of osmium, iridium, platinum, molybdenum and tungsten, and the X-ray crystal structure of MoO2trop2

The new tropolonato (trop) complexes Os(trop) 3 , Ir(trop) 3 , [Pt(trop)(PPh 3 ) 2 ] BPh 4 , OsO 2 (trop) 2 , MoO 2 (trop) 2 and W 2 O 5 (trop) 2 are reported. The vibrational, 1 H and 13 C NMR spectra of the complexes have been measured and the X-ray crystal structure of MoO 2 trop 2 has been determined. The crystals are monoclinic with α = 15.485(3), b = 13.583(3), c = 14.211(3)A, β = 117.74(1)°, space group C 2/ c , Z = 8; and the structure has been refined to R = 0.033.

Staining and fixation of unsaturated membrane lipids by osmium tetroxide: Crystal structure of a model osmium(VI) di-ester

The crystal structure of a cyclic mono-ester of osmium(VI) has been determined, and is shown to be dimeric with a double oxo bridge. The relevance of this structure as a possible model for the staining and fixation of lipids by osmium tetroxide is discussed.

X-Ray crystal structure of bis(adeninium)trans-bis(adenine)tetra-aquocobalt(II) bis(sulphate) hexahydrate: a complex of unidentate adenine containing adenine–adeninium hydrogen–bonded pairs

The structure of the title compound has been determined from X-ray diffractometer data by Patterson and Fourier methods. Crystals are monoclinic, with unit-cell dimensions: a= 13·971(2), b= 7·190(1), c= 19·900(3)A, β= 101·82(2)°, space group P21/n, Z= 2. Least-squares refinement, by use of 2275 independent reflections, has reached R 0·060.The structure contains the centrosymmetric [Co(H2O)4(adenine)2]2+ ion, adeninium and sulphate ions, and molecules of water of solvation, held together by an intricate network of hydrogen bonds. In the complex cation the cobalt atom has octahedral co-ordination, and the co-ordinated adenine is unidentate, bonding viaN(9). Co–N is 2·164 A, and the two independent cobalt–water distances are 2·073 and 2·114 A.The hydrogen–bond network contains the following types of linkage: O–H ⋯ O, N–H ⋯ O, O–H ⋯ N, N–H ⋯ N, and possibly C–H ⋯ O. A feature of the structure is the presence of adenine–adeninium pairs hydrogen–bonded together via N(1)⋯ H–N(10) and N(10)–H ⋯ N(7).