Muhammed A. Mazid

Pentanuclear oxoalkoxide clusters of scandium, yttrium, indium and ytterbium, X-ray crystal structures of [M5(μ5-O)(μ3-OPri)4(μ2-OPri)4(OPri)5] (M = In, Yb)

Abstract Attempts to prepare the metal tri-isopropoxides M(OPri)3 (M = Sc, Y, In, Yb) by various methods always produced the pentanuclear oxoalkoxide clusters [M5(μ5-O)(μ3-OPri)4(μ2-OPri)4(OPri)5] as the stable products. X-ray single crystal diffraction showed (M = In, Yb) the presence of the μ5-oxygen atom bonded in a square pyramidal configuration to five metal atoms which had terminal isopropoxo groups trans to the oxo atom. The μ3- and μ2-isopropoxo groups contribute to the distorted octahedral coordination of each metal atom. The scandium, yttrium and ytterbium clusters could be sublimed in vacuo and gave mass spectra containing pentanuclear cluster ions.The 1H NMR spectra for each compound was consistent with the X-ray crystal structure and variable-temperature studies showed fluxionality in the indium complex.

The X-ray crystal structures of the cadmium complexes of pyridine-1-thiol and mercaptobenzothiazole, [cd(C5H4NS)2]n And [Cd(C7H4N2S2)2]n: Two unusual volatile polymeric complexes

Abstract The structures of the 2:1 complexes formed by pyridine-1-thiol (I) and mercaptobenzothiazole (II) with cadmium(II) are polymeric but both sublime at reduced pressure and decompose cleanly to CdS in air. Both structures contain approximately octahedrally-coordinated cadmium atoms (CdN2S4) and involve bridging and chelating modes for the ligand.

Sterically hindered chalcogenolato complexes. Mono- and di-meric thiolates and selenolates of zinc and cadmium; structure of [{Cd(SeC6H2But3-2,4,6)2}2], the first three-co-ordinate cadmium–selenium complex

Protolysis of M[N(SiMe3)2]2(M = Zn or Cd) with arenechalcogenols 2,4,6-R3C6H2EH (E = S or Se; R = Me, Pri or But) gives the corresponding chalcogenolato complexes M(EC6H2R3-2,4,6)2 in high yield. Complexes with R = Me form co-ordination polymers which are soluble only in strongly co-ordinating solvents. An adduct [Cd(SC6H2Me3-2,4,6)2(py)2] can be isolated which dissociates in vacuo with quantitative loss of pyridine (py). Complexes with R = Pri readily dissolve in poorly co-ordinating solvents in which they form oligomers. NMR, infrared and Raman evidence suggests that the sterically more hindered tris-tert-butylbenzenechalcogenolato complexes of zinc and cadmium are dimeric in the solid state but dissociate in hydrocarbon solution to give two-co-ordinate monomers. The compound Zn(SeC6H2But3-2,4,6)2 forms a 1:1 adduct with tetrahydrofuran. The structure of [{Cd(SeC6H2But3-2,4,6)2}2] was determined by X-ray diffraction. The molecule is an asymmetrically bridged dimer, with three-co-ordinate cadmium in a distorted trigonal-planar arrangement. The Cd–Se distances are ca. 0.1 A shorter than in comparable four-co-ordinate complexes.

Stable gold(I) complexes with chelate rings: solution studies of bis(phosphino)ethane complexes and X-ray crystal structure of bis[1,2-bis(diphenylphosphino)ethane]gold(I) hexafluoroantimonate–acetone (1/1)

Bis-chelated four-co-ordinate gold(I)–phosphine complexes of 1,2-bis(diphenylphosphino)ethane (dppe) and 1,2-bis(diethylphosphino)ethane (depe) exhibit exceptionally high thermodynamic and kinetic stability both in the solid state and in solution at ambient temperatures. Their formation in solution has been studied by conductivity and 31P n.m.r. titrations. Complexes of [Au(depe)2]+ and [Au(dppe)2]+ have been prepared and characterized. These species exist in solution even at Au : bis(phosphine) ligand ratios of 1 : 0.75. The mixed species [Au(depe)(dppe)]+ exhibited a trans-gold 31P–31P n.m.r. coupling of 52 Hz. The title complex was crystallized and shown by X-ray crystallography to contain gold(I) with a flattened tetrahedral (closely D2d) co-ordination geometry (P–Au–P, 85–130°) chelated by two dppe ligands with Au–P bond lengths of 2.39–2.42 A. Crystals are monoclinic, space group P21/n. with a= 18.685(2), b= 19.414(2), c= 15.096(1)A, β= 91.69(1)°, and Z= 4; 4 811 reflections refined to R 0.062.

A penta-indium oxo alkoxide cluster with a central 5-co-ordinate oxygen. Preparation and X-ray crystal structure of (InOPri)5(µ2-OPri)4(µ3-OPri)4(µ5-O)

The X-ray crystal structure of (InOPri)5(µ2-OPri)4(µ3-OPri)4(µ5-O) reveals a square-pyramidal arrangement of indium atoms about a central oxygen; five of the alkoxo groups are terminal, four are µ2 about the basal metals, and four are µ3 about the triangular faces of the pyramid; the geometry about each metal is highly distorted octahedral.

Synthesis and absolute stereochemistry of the two diastereoisomers of P3-1-(2-nitrophenyl)ethyl adenosine triphosphate (‘caged’ ATP)

1 -(2-Nitrophenyl)ethanol was resolved by fractional crystallisation of its diastereoisomeric (1S)-cam-phanates. The absolute stereochemistry of the (S)-alcohol was determined using the Horeau kinetic resolution procedure, and subsequently confirmed by X-ray crystallography of its (1S)-camphanate ester. The resolved alcohols were converted to (R)- and (S)-1-(2-nitrophenyl)ethyl phosphates, each of which was condensed with adenosine diphosphate to give the (R)- and (S)-1-(2-nitro-phenyl)ethyl P3-esters of adenosine triphosphate.

The constitution of a ferrocenyl diketone: Solution and solid state NMR spectroscopy. Crystal structure of 1-ferrocenyl-3-hydroxybut-2-en-1-one

Abstract The title compound has been shown by 1 H and 13 C NMR spectroscopy to exist in solution as an enol/keto mixture, with an isomer ratio at ambient temperature in chloroform of approx. 17:1. CP-MAS 13 C NMR spectroscopy shows that only the enol form occurs in the crystalline state. This conclusion was confirmed by a single crystal X-ray structure determination. The OCCCO fragment of the molecule is planar, with an asymmetric intramolecular hydrogen bond; there are noi ntermolecular hydrogen bonds.

Cyclic cobaltadisiloxane compounds. Crystal structures of a pyridinolithium [bis(cyclosiloxy)cobalt] cobalt chloride and a bis(tetramethylethylenediaminolithium)-bis(cyclosiloxy)cobaltate

Abstract Reaction of CoCl 2 and dilithio tetraphenyldisiloxanediolate Ph 4 Si 2 O(OLi) 2 in tetrahydrofuran (THF) followed by removal of the THF, extraction of the residue with toluene, and treatment of the toluene solution with tetramethylethylenediamine (TMEDA) or pyridine (Py) has given the compounds bis [tetramethylethylenediaminolithium]-μ-[octaphenyltetrasiloxyspiro[5.5]cobalt], [TMEDALi] 2 -μ-[ Co(OSiPh 2 -OSiPh 2 O ) 2 ] and bispyridinolithium-μ-[octaphenyltetrasiloxyspiro[5.5]pyridino-cobalt]-μ-pyridinocobalt chloride, [Py 2 Li]-μ-[ Co(OSiPh 2 OSiPh 2 O ) 2 ]-μ-CoPyCl. Both compounds have been characterized by X-ray crystallography.

Solid-state carbon-13 nuclear magnetic resonance investigations of bismuth citrate complexes and crystal structure of Na2[Bi2(cit)2]·7H2O

The complex Na2[Bi2(cit)2]·7H2O (H4cit = 3-carboxy-3-hydroxypentane-1,5-dioic acid) crystallized during reactions of the antiulcer drug ranitidine bismuth citrate with the tripeptide glutathione (γ-L-Glu-L-Cys-Gly) at low pH. X-Ray analysis showed one [Bi(cit)]– fragment per asymmetric unit with Bi3+ chelated to a terminal carboxylate group; citrate also binds, in tridentate mode, to the bismuth of an equivalent [Bi(cit)]– unit (related to the first by a C2 axis)via one oxygen donor from each of the remaining two carboxylate groups and the alkoxy group. Both ends of the resultant dimeric anion {Bi(µ-cit)2Bi}2– bind to adjacent dimers, related by n-glide plane symmetry, via double carboxylate bridges, to form a continuous polymeric anionic chain [{Bi(µ-cit)2Bi}n]2n– running throughout the crystal. In this way each bismuth atom achieves six-co-ordination [Bi–O 2.210(10)–2.505(10)A] with a nido-pentagonal-bipyramidal geometry, the vacant axial site providing evidence for a stereochemically active lone pair and the second axial site being occupied by the alkoxy donor. The parallel polyanionic chains are linked by anion–cation interactions [Na ⋯ O (cit) 2.37–2.50 A] and by bonds of largely ionic character (Bi ⋯ O 3.003–3.095 A) to give the overall three-dimensional solid-state structure which incorporates seven water molecules per dianionic subunit. The solid-state cross-polarization magic angle spinning 13C NMR spectrum of this complex is assigned with the aid of dipolar-dephasing and inversion-recovery cross-polarization experiments, and compared to those of ranitidine bismuth citrate and bismuth citrate Bi(Hcit). The IR and solid-state 13C NMR data suggested that the alkoxy group is protonated in Bi(Hcit) but deprotonated in ranitidine bismuth citrate, and that the latter contains similar dimeric units to Na2[Bi2(cit)2]·7H2O. The general modes of aggregration of dimeric [{Bi(µ-cit)2Bi}n]2n– units and the relevance to antiulcer activity are discussed.

Synthesis, properties and X-ray crystal structures of copper(II) and nickel(II) thiocyanate complexes with ethanolamine : a new structure for an aminoalkoxide cluster

Abstract The new antiferromagnetic polymer [Cu(NH2C2H4O)(NCS)]∞ has been prepared and shown by X-ray crystallography to contain a new polymeric linkage of pairs of copper(II) atoms linked alternately by two oxygen bridges and one weaker thiocyanate bridge. Electronic, ESR and IR spectra and temperature-variable magnetochemical data are described. [Ni(NH2C2H4OH)2(NCS)2] is fully characterized by its magnetism, electronic and IR spectra and crystal structure as a centrosymmetric octahedral monomer with nitrogen-coordinated thiocyanates.