M.R. Udupa

Abstract: The crystal structure of bis(N-benzoylglycinato)-triaquozinc(II) dihydrate was determined from three-dimensional X-ray data collected by counter methods. The colourless crystals are triclinic with the space group P1. The unit cell parameters are a = 5.157(2), b = 5.192(2), c = 20.092(9) A, α= 83.60(4)°, β = 86.19(4)°, γ = 83.42(3)°, V = 530.3 A 3 and Z = 1. The structure was solved from 2332 reflections and was refined to an R index of 0.043. The zinc atom in the molecule is coordinated by an oxygen atom of the carboxyl group of each N-benzoylglycinate anion and by three water molecules, resulting in a 5-coordinated, slightly distorted trigonal bipyramidal geometry with two water molecules occupying the apical positions. The mean ZnO (basal) and ZnO(apical) distances are 1.988 and 2.165 A, respectively. All metal-bonded and all free water molecules are engaged in a network of intermolecular and intramolecular hydrogen-bonding.

Abstract: The crystal and molecular structure of bis(creatinine)silver(II) perchlorate dihydrate, [Ag(C4H7N3O)2] ClO4·2H2O, was determined from single crystal three-dimensional X-ray data collected by counter methods. The compound belongs to the monoclinic system, the space group being P2/c. The unit cell parameters are a = 11.405(2), b = 6.052(2), c = 12.325(2) A, β = 95.95(1)° and Z = 2. The structure was solved by derict method and was refined by least-square methods to a conventional R factor of 0.035 for 1509 observed reflections. The [Ag(C4H7N3O)2]+ molecule si centrosymmetric with Ag being linearly coordinated through the cyclic imino nitrogen atoms of two creatinine ligands at a distance (AgN) of 2.100*3) A. The H atom of the cyclic imino group in free creatinine is found to be transferred to the exocylic imino group in the complex. The creatinine molecules are planar. There is an extensive intermolecular hydrogen bonding system in the complex involving the water molecules, the perchlorate groups and the carbonyl and the exocyclic NH2 groups of the ligands.

Abstract: The crystal structure of binuclear copper(II) N-acetylglycinate monohydrate, [Cu(OOCCH2NH- COCH3)2(H2O)]2 was determined by three-dimensional X-ray diffraction studies. The compound crystallizes in the monoclinic system with the space group P21/c. The cell parameters are a = 7.288(2), b = 8.892(2), c = 19.473(3) A, β = 103.04(3)°, V = 1229.5 A3, Z = 4, dc = 1.695 and dm = 1.69 g cm-3. Full-matrix least-squares refinement using 2059 independent reflections has reached the R value of 0.041. The two copper atoms in the molecule are held together in a dimeric unit by the four carboxylate groups, and each copper atom is further bonded to a water molecule, resulting in a square pyramidal geometry. The mean CuO(carboxylate), CO- (water) and CuCu distances are 1.971(3), 2.108(3) and 2.666(1) A, respectively. Hydrogen bonding is observed between the peptide-NH and the carboxylate groups, and the peptide-CO groups and the water molecules.

Abstract: The crystal structure of bis(N-acetyglycinato) diaquocopper(II) dihydrate was determined by X-ray diffraction studies and was refined by least-squares methods to R = 3.7% for 1565 reflections measured. The compound is monoclinic, space group C2/c. The unit cell parameters are a = 21.145(6), b= 5.046(2), c = 18.248(5) A , β =127.55(4), V = 1543.7 A ; d c = 1.582, d m = 1.57 g cm −3 , Z = 4. The molecules is centrosymmetric with the copper atom being surrounded by two oxygen atoms of the water molecules and two oxygen atoms of the carboxylate groups in a square planar arrangement with CuO distances of 1.944(2) and 1.952(2) A , respectively. Two much longer out-of-plane CuO bonds to the remaining oxygen atoms of the carboxyl groups (2.619(2) A ) complete a distorted square bipyramidal coordination of the metal atoms. The angle between this long CuO vector and the normal to the square plane is 36.4°. The remaining two water molecules are involved in hydrogen bonding with the bonded water molecules and the peptide oxygen of the ligand.

Abstract: The crystal and molecular structure of mercury(II) tetrathiocyanatobis(dimethylformamide)cobaltate(II) Hg(SCN)4Co(DMF)2 was determined from three-dimensional X-ray data collected by counter methods. The pink prismatic crystals are monoclinic, space group P21/n. The unit cell dimensions are a = 9.163(2), b = 14.057(3), c = 16.276(3) A, β = 92.88(3)° and Z = 4. The structure was solved by direct methods from 3298 reflections and refined by least-squares methods to R = 0.053. The structure is polymeric with the four sulphur atoms of the thiocyanate groups tetrahedrally coordinated around the mercury atom. The average HgS bond length is 2.525 A. The linear thiocyanate groups have a mean angle of 96.5° to the HgS bonds. The dimethylformamide molecules are bonded to the cobalt atom in cis configuration through the oxygen atoms with average CoO distance of 2.114 A and an OCoO angle of 88.2°. Octahedral six-coordination around cobalt is completed by the thiocyanate N atoms of four Hg(SCN)4 units with mean CoN bond lengths of 2.113 A.

Abstract: This review highlights various design and synthesis approaches toward the construction of ZMOFs, which are metal–organic frameworks (MOFs) with topologies and, in some cases, features akin to traditional inorganic zeolites. The interest in this unique subset of MOFs is correlated with their exceptional characteristics arising from the periodic pore systems and distinctive cage-like cavities, in conjunction with modular intra- and/or extra-framework components, which ultimately allow for tailoring of the pore size, pore shape, and/or properties towards specific applications.

Abstract: The synthetic, structural, and coordination chemistry of crown thioethers with both transition and p-block metal ions is reviewed comprehensively through December 1988. Emphasis falls upon the electronic structures and redox properties induced in metal ions by coordination to crown thioethers. Examples include stabilization of mononuclear Rh(II), Pt(III), and low-spin octahedral Co(II). A subsidiary theme concerns the influence of ligand conformation in determining both the binding efficacy and the qualitative coordination chemistry associated with a given crown thioether. The review concludes with a view toward potential future applications of crown thioethers in catalysis, in sequestration or biological delivery of heavy metal ions, and in fundamental studies directed toward rational design of ligands.

Abstract: Representative examples of ambidentate ligand chemistry, drawn primarily from studies published during the past decade, are presented. An overview of the physical methods used for structural elucidation is included, with major emphasis being placed on structures emanating from single crystal X-ray diffraction studies. A great variety of ambidentate ligands are covered, although the bulk of the review deals with the schizophrenic behaviour of the classic ambidentate ligands NO2−CN− NCO−, NCS− NCSe− and NCTe−. As usual, the thiocyanate ion is accorded the most extensive coverage. Other ambidentate ligands discussed include CNO−, CNS−, azaphospholes, aminobenzonitriles, 4,4'-bipyrimidine, cyanoborohydrides, CCO, ClC(CN)3, chloranilate ion, isonitroso(β-ketoimine), nicotinate ion, nitramines, nitrosobenzenes and -anilines, Ph2PC(S)NHR, phosphine/arsine, phosphine sulfide/methine, and phosphinethioamide hybrid ligands, pyridine-2-thione, N-(2-pyridyl)imidazole, 4,6-dimethylpyrimidine, saccharinate ion, H2NSO3−, SO32−, Me2SO, SO2, SO2−, SNO−, NSO−, S2O32−, S2CO2−, SeO32−, SC(O)NHR−, OSNH−, dithioimidodiphosphinate ion, dithiosquarate ion, triphosphate ion, and ureas. Transition metal complexes of ambidentate ligands are emphasized throughout the review.

Abstract: Zinc(II) and copper(II) complexes of two new potentially pentadentate ligands based on methyl 2-aminocyclopent-1-ene-1-dithiocarboxylate with pendent pyrazolyl groups (Me2pzCH2)2NC2H3RNHC5H6CSSCH3 (R = H, Hmmecd, and R = CH3, Hmmpcd, both having N4S donor atoms set) have been reported. The molecular structures of [Zn(mmpcd)]ClO4 (1b) and [Cu(mmpcd)]ClO4 (2b) show a distorted trigonal bipyramidal geometry for the Zn(II) ion and a square pyramidal geometry for the Cu(II) ion. 1b crystallizes in the triclinic space group P1, a = 9.900(3) A, b = 15.379(5) A, c = 8.858(2) A, α = 99.93(2)°, β = 93.62(2)°, γ = 100.38(2)°, V = 1300.5(7) A3, and Z = 2; while 2b crystallizes in the monoclinic space group P21/n, a = 12.859(6) A, b = 12.642(3) A, c = 16.503(2) A, β = 102.67(2)°, V = 2617(1) A3, and Z = 4. The structures were refined to final R = 0.042 for 1b and 0.049 for 2b. The EPR and electronic spectroscopic studies showed that the copper(II) species doped into zinc(II) complex adopts the zinc(II) trigonal bipyr...

Abstract: This review summarizes the data for over nine hundred dimeric Cu(II) coordination compounds. There are several types of the bridges, from which doubly bridges by far prevail. The most common ligands are O− and N− donors. From the stereochemical point of view, a square-pyramidal arrangement with different degrees of distortion about Cu(II), is the most common. Several relationships were found between the Cu-Cu distances and the Cu-L-Cu bridge angle and the type of bridging, between the intra-ligand L-Cu-L ring angles and coordination numbers.