Tadeusz Głowiak

X-Ray and potentiometric studies on a pentanuclear copper(II) complex with β-alaninehydroxamic acid

Potentiometric and X-ray studies on the system copper(II)–L-β-alaninehydroxamic acid have shown the formation of a very stable pentanuclear complex [Cu5A4H–4]2+ at pH around 4. In this species all donor atoms of the aminohydroxamic acid are involved in the metal ion co-ordination. Four peripheral metal ions form an almost planar structure and the central metal ion is 0.4 A above this plane. There are twelve five- and six-membered chelate rings with different conformations. The X-ray structure results support earlier suggestions based on potentiometric and spectroscopic data for the formation of oligomeric structures at relatively low pH.

The X-ray structure and spectroscopy of platinum(II) complexes with 1,2,4-triazolo[1,5-a]pyrimidines and dimethylsulfoxide

Abstract Platinum(II) complexes with 1,2,4-triazolo[1,5-a]pyrimidines of general formula trans-[PtCl2(dmso)(L)], where L=1,2,4-triazolo[1,5-a]pyrimidine (tp), 5,7-dimethyl-1,2,4-triazolo[1,5-a]pyrimidine (dmtp), 5,7-diphenyl-1,2,4-triazolo[1,5-a]pyrimidine (dptp), 5,7-ditertbutyl-1,2,4-triazolo[1,5-a]pyrimidine (dbtp) have been prepared by direct reaction between cis-[PtCl2(dmso)2] and respective 1,2,4-triazolo[1,5-a]pyrimidine in molar ratio M:L=1:1. All new platinum(II) compounds were characterized by 1H, 13C, 15N, 195Pt NMR and IR. Significant 15N NMR upfield shifts (75–87 ppm) were observed for N(3) atom indicating this nitrogen atom as a coordination site. Crystal structure of trans-[PtCl2(dmso)(dmtp)] (2) has been determinated. The molecular structure indicates that Pt(II) ion has the square-planar geometry with N(3) bonded dmtp, S-bonded dimethylsulfoxide and two trans chloride anions.

Crystal structure, phase transitions and vibrational spectra of bis(betaine) nitrate

Abstract The crystal structure of bis(betaine) nitrate (BBN) has been determined by X-ray diffraction as monoclinic, space group P2 1 / c , with a = 5.668(1), b = 11.259(2) and c = 23.073(5) A, β = 93.65(3)°, Z = 4. The crystal comprises nitrate ions, NO 3 − , and betaine dimers: two betaine moieties are joined by a very strong asymmetric hydrogen bond with an O···O distance of 2.449(2) A. Fist order type phase transitions at 394 K, 439 K and 460 K (melting and decomposition) and very likely second order type at about 448 K were discovered for the BBN sample by the Differential Scanning Calorimetry method. In the deuterated analogue they appear at 394 K, 434 K, 448 K and 459 K. The FTIR and FT-Raman spectra for the powder samples were measured at room temperature. Additionally the FTIR spectra were taken at low temperatures (till 10 K). A strong band at about 900 cm −1 arises from the ν a OHO vibration of the very strong hydrogen bond. The site symmetry of the NO 3 − anions is C 1 according to X-ray data and the vibrational spectra.

Crystal and molecular structures of eight-coordinate (CuN4O4) and six-coordinate (CuN4O2) Cu(II) complexes with 4-methyl-5-imidazole-carboxaldehyde or 1-benzyl-2-hydroxymethylimidazole, respectively: Spectroscopic and potentiometric studies

Abstract The synthesis and characterisation of two novel Cu(II) eight and six coordinate compounds with the bidentate ligands 4-methyl-5-imidazolecarboxaldehyde (4-Me-5-CHOIm) and 1-benzyl-2-hydroxymethylimidazole (1-Bz-2-CH2OHIm) are described. Single crystals of [Cu(4-Me-5-CHOIm)4](H2O)2(NO3)2 (1) and [Cu(1-Bz-2-CH2OHIm)4](NO3)2 (2) were used in structure determinations. The two compounds both crystallise in the monoclinic space group P1 with Z=2 for (1) and Z=1 for (2). The structural data for (1) indicated that Cu(II) ion is involved in a flattened tetrahedron of N(1), N(2), N(3) and N(4) atoms of imidazoles ring as well as in a more distant elongated tetrahedron of four of the z-axis oxygen atoms O(1), O(2), O(3), O(4) of aldehyde groups. The coordination scheme of the six-coordinate Cu(II) complex (2) is a slightly distorted tetragonal bipyramid and the ligands act as a monodentate and bidentate. Additionally, the coordination processes with Cu(II) were detected and characterised in solution using spectroscopic (EPR and UV–VIS) as wall as potentiometric methods.

New insights into the chemistry of oxomolybdenum(VI) complexes with N-salicylidene-2-aminoethanol

Abstract Oxomolybdenum(VI) complexes with tridentate Schiff base, N -salicylidene-2-aminoethanol (H 2 sae), has been synthesised by the reaction of Mo(O) 2 (sal) 2 (where Hsal=salicylic aldehyde) with 2-aminoethanol. This reaction leads to dimeric [MoO(μ-O)(sae)] 2 and new monomeric [Mo(O) 2 (sae){1,2-O (−) C 6 H 4 C(H)N (+) (H)C 2 H 4 OH}] ( 1 ) compounds. Also substitution of acetylacetonate ligand in Mo(O) 2 (acac) 2 by H 2 sae in EtOH leads to the same complexes (vide infra), but in MeOH monomeric compound Mo(O) 2 (sae)(MeOH) ( 2 ) was formed. The molecular structure of complexes 1 and 2 have been determined by X-ray studies, which confirm that one of the H 2 sae co-ordinates as η 3 -tridentate O,N,O′ ligand, while in complex 1 this ligand exists also in zwitterionic form with intramolecular hydrogen bonding, O⋯HN, 2.584(3) A, of phenolic oxygen bonded to the molybdenum atom. The crystals of 1 are triclinic, space group P 1 , a =8.483(2) A, b =10.187(3) A, c =11.034(3) A, α =105.26(2)°, β =95.29(2)°, γ =95.10(2)°, and D calcd =1.666(1) g cm −3 for Z =2. The crystals of 2 are monoclinic, space group P 2 1 / c , a =6.697(2) A, b =7.375(2) A, c =24.100(3) A, β =92.76(5)°, and D calcd =1.805(1) g cm −3 for Z =4.

Ligand chirality effect on the structure and its spectroscopic consequences in [Ln2(Ala)4(H2O)8] (C104)6 crystals

Abstract Single crystals of [Ln 2 (Ala) 4 (H 2 O) 8 ](Cl0 4 ) 6 (where Ln = Eu, Nd and Ala = l -, dl -alanine) were grown from aqueous solutions and the neodymium complex has been studied by single-crystal X-ray diffraction. The space groups are triclinic P 1 and monoclinic C2/c for l - and dl -alanine, respectively, and Z = 1 and 4. The crystal structures consist of non-centrosymmetric and centrosymmetric dimer units in the complexes with l and dl ligand forms. In other words, in the latter two the lanthanide ions in the dimer are equivalent but in the former they are not. Thus the chirality of the ligand is responsible for the subtle differences in the structure. Each neodymium ion is coordinated by four carboxylate oxygens of the amino acids and four water molecules. The coordination polyhedra around the neodymium ions are distorted square antiprisms. Well-resolved absorption luminescence measurements down to 5 K are reported. The probabilities of electronic transitions were investigated. An attempt has been made to elucidate the dimer (centrosymmetric and noncentrosymmetric) structure reflection in the splitting pattern of the optical lines. The temperature effect on the spectra was studied and analysed in terms of the cooperative interaction of coupled ions. It is the first, to our knowledge, X-ray evidence of the ligand chirality effect on the dimer structure of lanthanide compounds.

Photochemical reaction of W(CO)6 with SnCl4 I. Synthesis and X-ray structure of tri-μ-chloro-trichlorostannate-heptacarbonylditungsten(II) [(CO)4W(μ-Cl)3W(SnCl3)(CO)3]

The crystal structure of [(CO)4W(μ-Cl)3W(SnCl3)(CO)3] (1) formed in the photochemical reaction of W(CO)6 with SnCl4 was determined by the single-crystal X-ray diffraction method. The crystals are orthorhombic, of space group Pbca, a = 12.706(3) A, b = 16.655(4) A, c = 18.669(3) A, V = 3951(2) A3 and Z = 8. The structure solved by the heavy-atom method has been refined to R = 0.0299 for 2187 observed reflections. The tungsten atoms in the molecule are both seven-coordinate, each being bonded to three bridging chlorines, to four CO groups on one end and three CO groups and a SnCl3 group on the other. For each tungsten, there is a 4-3 geometry of ligand. Nuclear magnetic resonance, IR and electronic absorption spectroscopies were used to examine the litle compound. Compound 1 is a unique example of the halo carbonyls of Group 6 metals with an MSn bond.

Structure, spectral and magnetic behaviours of tetrakis(flufenamato)(caffeine)(aqua) di copper(II)—first example of two non-equivalent ligands at the apex

Abstract The crystal and molecular structure of the tetrakis(flufenamato)(caffeine)(aqua)(dicopper)(II) Cu 2 (fluf) 4 (caf)(H 2 O), was determined by direct methods and Fourier techniques. The two copper(II) atoms are bridged by four carboxylate group, with the apical ligand of a water molecule around Cu(1), and a caffeine molecule around Cu(2). The spectral and magnetic properties are also discussed.

METAL(II)-PROMOTED HYDROLYSIS OF PYRIDINE-2-CARBONITRILE TO PYRIDINE-2-CARBOXYLIC ACID. THE STRUCTURE OF CU(PYRIDINE-2-CARBOXYLATE)2.2H2O

Abstract Pyridine-2-carbonitrile (2-CNpy) undergoes Cu(II) or Co(II)-promoted hydrolysis to pyridine-2-carboxamide (piaH) and/or pyridine-2-carboxylic acid (pycH). The pathway of pycH formation depends on the presence of 2-amino-2-hydroxymethyl-1,3-propanediol (AL1) and on the central atom. In the absence of AL1, Co(II) or Cu(II) ions mediate piaH formation under mild reaction conditions in the first hydrolytic step. Cu(II) ions assist in piaH transformation to pycH by subsequent reflux. In the presence of AL1 and Co(II), a Co(II) complex containing pyoxaL1 (2-(2-pyridinyl)-4,4-bis(hydroxymethyl)-2-oxazoline) is formed in the first stage; subsequent decomposition of pyoxaL1 under the reflux yields pycH. Under similar conditions, no solid Cu(II) complex with pyoxaL1 can be isolated, but a Cu(II) complex with coordinated pyc− anions precipitates from the reaction mixture. The synthesis, spectral and magnetic properties of the complexes [Co(H2O)2 (piaH)2]Cl2, [Co(H2O)2(pyc)2] · 2H2O, [Cu(H2O)2(piaH)2]Cl2, [Cu(pyc)2] and [Cu(pyc)2] · 2H2O, including the structure determination of the latter one, are described.

The initiation of ring-opening metathesis polymerisation of norbornadiene by seven-coordinate molybdenum(II) compounds. X-ray crystal structure of [Mo(μ-Cl)(SnCl3)(CO)3(η4-NBD)]

Abstract The new heterobimetallic complex [Mo(μ-Cl)(SnCl 3 )(CO) 3 (η 4 -NBD)] ( 1 ) has been prepared by reaction of [(CO) 4 Mo(μ-Cl) 3 Mo(SnCl 3 )(CO) 3 ] with norbornadiene (NBD) at room temperature. The structure of complex 1 was established by X-ray crystallography. The IR, 1 H- and 13 C-NMR spectra of 1 are also described and can be correlated with the crystallographically observed geometry. In the presence of an excess of NBD compound 1 initiates the ring-opening metathesis polymerisation (ROMP). The initiation mechanism of ROMP by seven-coordinate molybdenum(II) compounds have been discussed. The microstructure of polynorbornadiene formed was determined by 1 H- and 13 C-NMR spectroscopy.