Showing papers on "Tetrahedral molecular geometry published in 2003"

Hg(II), Tl(III), Cu(I), and Pd(II) Complexes with 2,2'-Diphenyl-4,4'-Bithiazole (DPBTZ), Syntheses and X-Ray Crystal Structure of [Hg(DPBTZ)(SCN)2]

Abstract: Reaction of the ligand 2,2′-diphenyl-4,4′-bithiazole (DPBTZ) with Hg(SCN)2, Tl(NO3)3, CuCl, and PdCl2 gives complexes with stoichiometry [Hg(DPBTZ)(SCN)2], [Tl(DPBTZ)(NO3)3], [Cu(DPBTZ)(H2O)Cl], and [Pd(DPBTZ)Cl2]. The new complexes were characterized by elemental analyses and infrared spectroscopy. The crystal structure of [Hg(DPBTZ)(SCN)2] determined by X-ray crystallography. The Hg atom in the title monomeric complex, (2,2′-diphenyl-4,4′-bithiazole)mercury(II)bisthiocyanate, [Hg(C18H12N2S2)(SCN)2], is four-coordinate having an irregular tetrahedral geometry composed of two S atoms of thiocyanate ions [Hg-S 2.4025(15) and 2.4073(15) A] and two N atoms of 2,2′-diphenyl-4,4′-bithiazole ligand [Hg-N 2.411(4) and 2.459(4) A]. The bond angle S(3)-Hg(1)-S(4) of 147.46(5)° has the greatest derivation from ideal tetrahedral geometry. Intermolecular interaction between Hg(1) and two S atoms of two neighboring molecules, 3.9318(15) and 3.9640(18) A, make the Hg(1) distort from a tetrahedron to a disordered octahe...

Synthesis and Structural Characterization of a Novel Mixed-Valent CuIICuICuII Triangular Metallomacrocycle Using an Imine-Based Rigid Ligand

Abstract: A novel neutral mixed-valent CuICuII2 triangular metallomacrocycle [Cu3L2(HL)]·3CH3OH·2H2O (1) was assembled by reaction of the tetradentate ligand bis(N-salicylidene-4,4‘-diphenylamine), H2L, with a copper(II) salt. ESI-MS show peaks only corresponding to the triangular structural species, indicating the high stability of the trimer structure in solution. Magnetic study confirms that there are two CuII ions and one CuI ion in a discrete triangular molecule. The crystal structure of 1 reveals that the triangle is formed by three deprotonated ligands and three copper ions with a Cu···Cu separation of ca. 11.8 A. Each copper atom is coordinated by two oxygen atoms and two nitrogen atoms from two different bis-bidentate ligands in a heavily distorted tetrahedral geometry, while each ligand is bound to two metal ions in a bis-bidentate coordination mode and links the metal centers overlapping in an unprogressive manner. Strong intramolecular π···π interactions between the ligands are found to stabilize the co...

Hydrothermal synthesis, characterization and crystal structures of two new layered lead(II) diphosphonates

Abstract: Hydrothermal reactions of N-benzyliminobis(methylenephosphonic acid), C6H5CH2N(CH2PO3H2)2 (H4L), with lead(II) chloride and lead(II) acetate resulted in two novel lead(II) phosphonates, namely, Pb5(H2L)2(HL)2·2H2O (1) and Pb3(H2L)2Cl(H2O)3·Cl·2H2O (2). Compound 1 is orthorhombic, Pbca, with Z = 4. Compound 1 features a layered structure in which the lead(II) ions are bridged by phosphonate groups.Two lead(II) ions (Pb1 and Pb3) are three-coordinated with a distorted tetrahedral geometry in which one apex is occupied by the lone pair of the lead(II) ion, the third lead(II) ion (Pb2) is six-coordinated by six phosphonate oxygen atoms from six ligands. Two ligands are doubly protonated whereas the other two are singly protonated. Compound 2 crystallizes in I2/a with Z = 4. In compound 2, one lead(II) ion is six-coordinated by four phosphonate oxygen atoms from four ligands, one aqua ligand and one chloride anion in a distorted octahedral geometry; the other lead(II) ion is coordinated by four phosphonate oxygen atoms from four ligands and two aqua ligands with a severely distorted octahedral geometry. One phosphonate group of the ligand bridges with five lead(II) ions, whereas the other one is unidentate. The interconnection of the lead(II) ions through bridging phosphonate groups results in the formation of a 〈040〉 layer. In both compounds, the phenyl groups of the ligand are oriented toward the interlayer space.

Synthesis, Spectra and Crystal Structure of Two Copper(I) Complexes of Acetonethiosemicarbazone

Abstract: The reaction of copper(I) chloride with acetonethiosemicarbazone (tscac) in a copper to tscac molar ratio of 1:2 forms the cationic complex [Cu(tscac)2]Cl (1). When the ratio of the copper to tscac was reduced to 1:1, a dimeric complex [Cu2Cl2(tscac)2]2 (2) was obtained. In complex 2, two CuCl2 species act as bridging groups between two Cu(tscac)2 moieties forming an eight-membered ring, whereas in complex 1, there is no CuCl2 moiety in the structure. In both complexes the copper(I) center is coordinated in a distorted tetrahedral geometry to two tscac groups through the sulfur and the imine nitrogen atom. In dimeric complex 2, the sulfur atom in each tscac ligand coordinates weakly to copper(I) in the CuCl2 moiety giving the distorted tetrahedral geometry. For the free ligand, the νc=s vibration at 789 cm−1 appears at lower energy than in complexes 1 and 2 (754 and 744 cm−1 respectively) indicating coordination at the sulfur atom. The complexes synthesized by either electrochemical or chemical methods are identical. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Ligand Close Packing and the Geometry of the Fluorides of the Nonmetals of Periods 3, 4, and 5

Abstract: This paper discusses the geometry of the fluorides of the nonmetals of periods 3, 4, and 5 in terms of the ligand close packing (LCP) model according to which molecular geometry is determined primarily by ligand-ligand repulsions (Pauli closed shell repulsions) rather than by the bonding and lone pair Pauli repulsions of the VSEPR model. The LCP model becomes the dominant factor in determing geometry when the ligands are sufficiently crowded that they may be regarded as essentially incompressible. Ligand close packing is a modification of the VSEPR model in which ligand-ligand repulsion (Pauli closed shell repulsion) is given more emphasis than bonding and nonbonding electron pair Pauli repulsion. The nonmetals of period 3 are large enough to form octahedral six coordinated molecules in which the ligands are close packed. The larger nonmetals of period 4 also have a maximum coordination number of six and an octahedral geometry although the ligands are not close packed. Ligand radii derived from the interligand distances in the molecules of period 3 depend only on the charge of the fluorine ligands and are consistent with the previously derived radii obtained from the fluorides of the close packed tetrahedral molecules of the period 2 elements. Although the ligands in the molecules of the period 4 nonmetals are not close packed, these elements are not large enough to form molecules with a higher coordination number. However, the larger period 5 nonmetals may have coordination numbers of seven and eight. The seven coordinated molecules have a pentagonal bipyramidal geometry in which the equatorial ligands are close packed. The eight coordinated molecules have a square antiprism geometry, which is not a close packed geometry although the fluorine interligand distances are only a little larger than expected for close packing. The difference between the axial and equatorial bond lengths in the trigonal bipyramidal pentafluorides and the pentagonal bipyramidal pentafluorides can be understood on the basis of ligand close packing. Ligand packing prevents the lone pair in AF(6)E molecules from fully entering the valence shell and thereby exerting its full stereochemical effect so that these molecules have a C(3)(v)() distorted octahedral geometry rather than a geometry based on pentagonal bipyramidal seven coordination.

Crystal structures of 2,2′-bipyridine adducts of two cadmium O-alkyl dithiocarbonates: rationalisation of disparate coordination geometries based on different crystal packing environments

Abstract: Two distinct coordination geometries are found in the structures of Cd(S 2 COR) 2 (2,2'-bipyridine). For R = CH 2 CH 2 OCH 3 (1) a N 2 S 2 donor set defines a distorted tetrahedral geometry for cadmium as the xanthate ligands adopt a monodentate coordination mode. By contrast, a N 2 S 3 donor set is found in the structure where R is butyl (2) as one of the xanthate ligands is chelating. An analysis of the crystal structures shows that both lattices feature extensive C-H...π interactions and that in (1) there are C-H...O interactions that are not present in (2). In (2) there are π...π interactions that are absent in (1). A qualitative argument based on crystal packing considerations is proposed to explain the differences in molecular structures.

Examination of cobalt, nickel, copper and zinc( ii ) complex geometry and binding affinity in aqueous media using simple pyridylsulfonamide ligands

Abstract: The sixteen neutral ML2 complexes of Co, Ni, Cu and Zn(II) with the p-toluenesulfonamide and trifluoromethylsulfonamide derivatives of 2-aminomethylpyridine (L1, L2) and its 6-Me homologue (L3, L4) have been characterised by low temperature X-ray crystallography (100–120 K). Complexes of Co and Zn invariantly adopted a distorted tetrahedral geometry and whilst Cu(II) complexes of L2, L3 and L4 also took up a distorted tetrahedral geometry, that with L1 was square planar. A database survey of the distortion from limiting tetrahedral/square planar geometry has been carried out, aided by a simple geometric analysis. The trifluoromethylsulfonamide ligands (L2 and L3) were less basic, e.g. log K1 7.51(3) for L2vs. 12.23(6) for L1 (80% MeOH/H2O) and afforded a weaker ligand field, exemplified by the position of the visible d–d transition in Cu(II) complexes and the ease of reduction of the Cu(II) centre: E1//2 values (MeCN vs. Ag/AgCl) are −430, −137, +55 and −240 mV for Cu(L1)2, Cu(L2)2, Cu(L3)2 and Cu(L4)2. Ligand protonation and stepwise formation constants have been measured for L1–L3 and derived species distribution diagrams reveal that for complexes with L2 and L3, the predominant species present at pH 7.4 when zinc was in the nanomolar range was ZnL2.

Synthesis and Characterization of (THF) 3 Li(NC)CU(C 6 H 3 -2,6-Mes 2 )and Br(THF) 2 Mg(C 6 H 3 -2,6-Trip 2 ) (Mes = C 6 H 2 -2,4,6-Me 3 ; Trip = C 6 H 2 -2,4,6-i-Pr 3 ): The Structures of a Monomeric Lower-Order Lithi

Abstract: The lower-order lithium organocyanocuprate compound, (THF) 3 Li(NC)Cu(C 6 H 3 -2,6-Mes 2 ) (1), and the bulky terphenyl Grignard reagent, Br(THF) 2 Mg(C 6 H 3 -2,6-Trip 2 ) (2), have been synthesized and structurally characterized both in the solid state by single crystal x-ray crystallography and in solution by multi-nuclear NMR and IR spectroscopy. The compound (1) was isolated as a monomeric contact ion-pair in which the C (organic ipso)-Cu-CN-Li atoms are coordinated linearly. The lithium has a tetrahedral geometry as a result of solvation by three THF molecules. The compound (1) is the first example of fully characterized monomeric lower order lithium organocyanocuprate. The bulky Grignard reagent (2) was also isolated as a monomer in which the magnesium, solvated by two THF molecules, has a distorted tetrahedral geometry. The crystals of (1) possess triclinic symmetry with the space group P1, Z = 2, with a = 12.456(3) A, b = 12.508(3) A, c = 13.904(3) A, α = 99.81°, β = 103.72(3)°, and y= 119.44(3)°. The crystals (2) have a monoclinic symmetry of space group P2 1 /c, Z = 4, with a = 13.071(3) A, b = 14.967(3) A, c = 22.070(4) A, and β = 98.95(3)°.

Theozyme for antibody aldolases. Characterization of the transition-state analogue

Abstract: A theozyme for antibody aldolases has been studied at the MP2/6-31G** computational level. Formation of two cooperative hydrogen-bonds between the acidic hydrogen atoms of the enamine and of a methanol molecule with the oxygen atom of the aldol acceptor markedly favors the C–C bond-formation associated with the aldol reaction. A comparative analysis of the geometry, the charge distribution and the shape of the molecular electrostatic potential of the transition structure (TS) with the covalent adduct, resulting from the reaction of methylamine and the β-diketone used as a hapten allows us to characterize the transition-state analogue (TSA) generated at immunization. This finding allows us to propose a hapten based on a chiral β-ketosulfoxide that could give the formation of a TSA that addresses the tetrahedral geometry of the TS.

Lewis acidity of group 14 elements toward intramolecular sulfur in ortho-aryl-thioanisoles

Abstract: The series of compounds (o-CH3SC6H4)CH2EPh3 (E = Si (1), Ge (2), Sn (3), and Pb (4)) have been synthesized and characterized by NMR spectroscopy and by single crystal X-ray diffraction. Compounds 1 and 2 are isostructural with a triclinic crystal system and P-1 space group; however, morphotropic steps occur between Ge and Sn, and Sn and Pb. While the E-S distances in 1 and 2 are 3.985 and 3.974 A, respectively, ~100% of the sum of the respective van der Waals (vdW) radii, there is a notable distortion from tetrahedral geometry about E. Compound 3 is also triclinic with P-1 symmetry, but has two molecules in the unit cell that demonstrate a distorted tetrahedral geometry and intramolecular Sn-S distances of 3.699 and 3.829 A, 88% and 91% of the sum of the vdW radii. Compound 4 has a Pb-S distance of 3.953 A (91% of Σ vdW radii). The structure of the Grignard coupling product [o-(SCH3)C6H4CH2]2 is also reported.Key words: intramolecular self-assembly, silicon, germanium, tin, lead, sulfur.

X-Ray crystal structure of [Ag4(μ-dppm)2(μ-C2F5COO)4]. Synthesis and spectroscopy of silver(I) perfluorinated carboxylate complexes with bis(diphenylphosphino)methane

Abstract: Complexes of Ag(I) carboxylates with dppm = bis(diphenylphosphino)methane of general formula [Ag2(RCOO)2(dppm)], where R = CF3, C2F5, C3F7, C4F9, C6F13, C9F19, were obtained and characterized with 1H, 13C, 19F, 31P NMR and IR. The X-ray crystal structure of [Ag4(μ-dppm)2(μ-C2F5COO)4] determined at 100(1) K (R = 0.0316) revealed a centrosymmetric tetranuclear aggregate with the silver atoms bridged by two dppm and four pentafluoropropionates forming two monoatomic μ2-(η1-O) and two triple μ3-(η2-O, η1-O′) bridges. Of the two crystallographically independent Ag(I) atoms one has distorted tetrahedral geometry with one Ag–P bond and three Ag–O bonds, while the second has trigonal planar geometry with an Ag–P and two Ag–O bonds. The 31P CP MAS NMR spectra demonstrate splitting due to 1J(107,109Ag–31P) and 2J(P–P) coupling between crystallographically inequivalent phosphorus atoms. Variable-temperature 31P NMR spectra were recorded between 323 and 223 K and 1J(107Ag–31P), 3J(107Ag–31P), 1J(109Ag–31P), 3J(109Ag–31P) spin–spin coupling constants calculated. Analysis of coordination shifts and coupling constants is in favor, in solution, of binuclear trigonal Ag(I) complexes with bridging carboxylates and dppm.

The Chelating Ligand 1,3‐Bis(pyrazol‐1′‐yl)propane (Bpp) Enforces a Tetrahedral Geometry in Both CuII and CuI Species

Abstract: The ligand 1,3-bis(pyrazol-1′-yl)propane (bpp) has been prepared by reacting 1,3-dichloropropane with two equivalents of pyrazole. After reaction of bpp with copper(II) tetrafluoroborate, three different compounds were obtained, two with CuII and one with CuI as cation, depending on the preparative method. The formation of single crystals of these compounds was only observed when 1-(3-chloropropyl)pyrazole (ppc) was present in the solution. The single-crystal X-ray structures of [Cu(bpp)2](BF4)2 and [Cu(bpp)2](BF4) show that bpp acts as a didentate chelating ligand to form an uncommon eight-atom chelate ring with the copper ion. Two polymorphs of the CuII complex were characterized. In each of them, the metal atoms possess a distorted tetrahedral geometry. In the copper(I) complex the metal center is present in a less-distorted tetrahedral coordination sphere. The spectroscopic properties of the compounds are in agreement with the structural data. Cyclic voltammetry measurements showed a redox wave at 0.92 V vs. Ag/AgCl. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Crystallographic report: Triorganotin 2‐(p‐chlorophenyl)‐3‐methylbutyrates

Abstract: The crystal structures of two triorganotin butyrates were determined. Tricyclohexyltin 2-(p-chlorophenyl)-3-methylbutyrate was determined to have a distorted tetrahedral geometry. Trimethyltin 2-(p-chlorophenyl)-3-methylbutyrate, on the other hand, was found to be polymeric in nature with a trigonal bipyramidal configuration. The three methyl groups are located in the equatorial positions with the axial positions occupied by oxygen atoms from two different carboxylate groups. Copyright © 2003 John Wiley & Sons, Ltd.

Synthesis of asymmetric binuclear copper(I) complexes containing 4-vinylpyridine and bis(diphenylphosphino) methane

Abstract: The asymmetric binuclear copper(I) complex [Cu2(dppm)2(C7H7N)(μ-NO3)](NO3) (dppm = Ph2PCH2PPh2, C7H7N = 4-vinylpyridine) has been prepared and characterized. The complex is photoluminescent at room temperature. Crystals are triclinic space group , with cell parameters a = 11.638(2), b = 12.621(3), c = 18.516(4) A, α = 89.20(3), β = 83.11(3), γ = 76.04(3)°, V = 2619.5(9) A3, D c = 1.426 g cm−3, Z = 2, μ = 0.988 mm−1, R = 0.0497 for 6574 independently observed reflections with I > 2σ(I). The structure consists of [Cu2(dppm)2(C7H7N)(μ-NO3)]+ cations and nitrate anions. Copper atoms show different coordination modes; Cu(2) has a distorted trigonal and Cu(1) a tetrahedral geometry.

Crystallographic report: Bis(pyrrolinedithiocarbamato)mercury(II)

Abstract: The mononuclear structure of Hg(S2CN(CH2)4)2 has crystallographically imposed twofold symmetry and features chelating dithiocarbamate ligands that form asymmetric HgS bond distances leading to a heavily distorted tetrahedral geometry. Copyright © 2003 John Wiley & Sons, Ltd.

Diacetatobis(2-amino­benzo­thia­zole)­zinc(II)

Abstract: In the title compound, [Zn(C2H3O2)2(C7H6N2S)2], the Zn atom is four-coordinated in the ZnO2N2 form in a distorted tetrahedral geometry. The amino groups act as donors in N—H⋯O hydrogen bonds. Two intermolecular N—H⋯O hydrogen bonds interconnect the mol­ecules into a three-dimensional network. The planes of the acetate ligands are nearly orthogonal, and the Zn atom is displaced slightly from these two planes.

Crystallographic report: Crystal structure of a one‐dimensional zinc(II) coordination polymer containing 4,4′‐biphenyldicarboxylate hemihydrate

Abstract: A one-dimensional zinc(II) coordination polymer has been constructed from zinc(II), 4,4′-biphenyldicarboxylate and pyridine in which each zinc(II) atom is coordinated by two pyridine ligands and two monodentate 4,4′-biphenyldicarboxylate ligands that define a distorted tetrahedral geometry. Copyright © 2003 John Wiley & Sons, Ltd.

A zinc-lithium complex of 4,7-bis(2-aminoethyl)-1,4,7-triazacyclononane-1-acetate.

Abstract: The asymmetric unit of ([4,7-bis(2-aminoethyl)-1,4,7-triazacyclononan-1-yl]acetato)zinc(II) triaqua{μ-[4,7-bis(2-aminoethyl)-1,4,7-triazacyclononan-1-yl]acetato}lithium(I)zinc(II) chloride diperchlorate, [Zn(C 12 H 26 N 5 O 2 )][LiZn(C 12 H 26 N 5 O 2 )(H 2 O) 3 ]Cl(ClO 4 ) 2 , obtained from the reaction between the lithium salt of 4,7-bis(2-aminoethyl)-1,4,7-triazacyclononane-1-acetate and Zn(ClO 4 ) 2 , contains two Zn II complexes in which each Zn II ion is six-coordinated by five N-atom donors and one O-atom donor from the ligand. One carboxylate O-atom donor is not involved in coordination to a Zn II atom, but coordinates to an Li + ion, the tetrahedral geometry of Li + being completed by three water molecules. The two complexes are linked via a hydrogen bond between a primary amine N-H group and the carboxylate-O atom not involved in coordination to a metal.

Complexes of Nickel(II) with N,N′‐bis(4‐Antipyrylmethylidene)ethylenediamine

Abstract: Nickel(II) complexes of the Schiff base N,N′‐bis(4‐antipyrylmethylidene)‐ethylenediamine (BAME) of the general formula [Ni(BAME)2]X2 (X = ClO4, NO3, Cl, Br or I) have been synthesized and characterised by elemental analyses, electrical conductance in non‐aqueous solvents, infrared and electronic spectra as well as magnetic susceptibility measurements. In these complexes BAME acts as a neutral bidentate ligand coordinating through both the azomethine nitrogens and both the anions are not coordinated. A tetrahedral geometry around Ni(II) may be assigned for all these complexes.

Crystal Structure and Thermal Stability Study on Tetrabutylammonium Hexamolybdate [n-Bu 4 N] 2 [Mo 6 O 19 ](TBAM)

Abstract: The crystal structure of (TBAM) (n-Bu4N=tetrabutylammonium) has been determined by X-ray crystallography. It crystallizes in the monoclinic system, space group C2/c, with lattice parameters =16.314(5), b=17.288(5), c=17.776(4) =101.47(3), and Z=4. In anion, Mo atoms occupy six vertices of octahedron and each Mo atom is coordinated by six oxygen atoms to adopt distorted octahedral coordination geometry. The average bond distance of Mo-Ot (terminal), Mo-Ob (bridged) and Mo-Oc (central) are 1.680 , 1.931 and 2.325 respectively. In cation, the N atom possesses a slightly distorted tetrahedral geometry. There are some potential extensive C-H O hydrogen bonds in the lattice, by which connecte molecules and stabilize the crystal structure. Thermogravimetric analysis suggests that thermal decomposition of the title compound includes two transitions and it loses weight at 356.0 and 803.5 , respectively, and the residue presumable be . Accordingly, the title compound has high thermal stability.

On the Jahn-Teller Origin of the Phosphorus Molecule P4 Activation by One- and Two-Electron Reduction

Abstract: The quantum chemical calculations of the tetra-phosphorus P 4 q were carried out with values of charge q =0, −1, −2. It is shown that the electronic system of the P 4 molecule has equal P–P bond orders. The neutral phosphorus molecule is stable under the reduction of the symmetry from T d to C 2 v or C 3 v . Unlike the neutral molecule, the electronic states of the reduced forms of the P 4 molecule ( 2 T 1 (P 4 − ), 1 T 1 ( P 4 2− ) or 3 T 1 ( P 4 2− )) are degenerated in the T d geometry. Due to the orbital degeneracy of the electronic states, the reduced forms of the phosphorus molecules P 4 − and P 4 2− are unstable with the lowering of the symmetry from T d to C 2 v or C 3 v with unsymmetrical changes of the bond order values. On the other hand, the Jahn–Teller effect destabilizes the tetrahedral geometry of the nuclear system, resulting in the bond order's changes too. Thus the phosphorous molecule in the reduced forms is activated due to degeneracy of the electronic orbitals and to vibronic instability. The energy of such a type of activation of the free phosphorous molecule is estimated as 60–120 kcal/mol.

Synthesis and spectroscopic characterisation of some neutral tetracoordinated germanium (IV) alkoxyalkanolates

Abstract: Compounds of the type, [Ge(OPr i ) 4 - n (OCH 2 CH 2 OR) n ], (where R = Me, Et, n-Bu and n = 1-4) have been synthesised in high yields by the interactions of germanium tetraisopropoxide with alkoxyalkanols (HOCH 2 CH 2 OR) in different stoichiometries in refluxing anhydrous benzene, and are monomeric in refluxing benzene. All these compounds can be purified by distillation under reduced pressure. IR and NMR ( 1 H and 1 3 C) spectral studies indicate a tetrahedral geometry around the germanium atom.