A. J. M. Duisenberg

An intensity evaluation method: EVAL-14

A reflection intensity integration method is presented based upon ab initio calculation of three-dimensional (x, y, ω) reflection boundaries from a few physical crystal and instrument parameters. It is especially useful in challenging circumstances, such as the case of a crystal that is far from spherical, anisotropic mosaicity, α1α2 peak splitting, interference from close neighbours, twin lattices or satellite reflections, and the case of streaks from modulated structures, all of which may frustrate the customary profile-learning and -fitting procedures. The method, called EVAL-14, has been implemented and extensively tested on a Bruker Nonius KappaCCD diffractometer.

Indexing in single-crystal diffractometry with an obstinate list of reflections

An indexing method for single-crystal diffractometry is described which is applicable to especially difficult cases such as twin lattices, incommensurate structures, fragmented crystals, long axes and unreliable data. Finding the reciprocal lattice from a cloud of reciprocal-lattice points (reflections) is reduced to finding elementary periods in one-dimensional rows, obtained by projecting all observed points onto the normal to the plane formed by any three of these points. Row periodicity and offending reflections are easily recognized. Each row, by its direction and (reciprocal) spacing, defines one direct axis vector, based upon all cooperating observations. From the direct vectors so obtained a primitive direct cell is chosen and refined against the fitting reflections. The result is one main lattice, or a main lattice and a set of alien reflections. The method operates semi-automatically in the program DIRAX and has been tested, without failure, on hundreds of CAD4 reflection files, among which there were many auto-indexing-resistant lists.

Synthesis, spectroscopic and electrochemical properties and X-ray studies of bis(2,2′-bipyridyl)(3-(2-hydroxy-phenyl)-5-(pyridin-2-yl)- 1,2,4-triazole)-ruthenium(II)hexafluorphosphate

Abstract A new ruthenium(II) bis(2,2′-bipyridyl) compound with 3-(2-hydroxy-phenyl)-5-(pyridin-2-yl)- 1,2,4-triazole (H2L) as co-ligand has been prepared and characterised by X-ray structure determination, NMR spectroscopy, electrochemical measurements, and UV-Vis absorption and emission spectroscopy. The compound of formula [Ru(bpy)2(HL)]PF6· CH3COCH3 crystallises in the monoclinic space group P21/n, with a=14.242(1), b= 14.277(1), c= 17.968(1) A, β=97.27(1)° and Z=4. The Ru(bpy)2 moiety is bound to (HL) via N1 of the triazole ring (Ru-N=2.051(3) A) and N1 of the pyridine ring (Ru-N=2.085(3) A). The phenol group is connected to N4 of the triazole ring via intramolecular hydrogen bonding. pKa titrations reveal that for free H2L the pyridine ring, the triazole ring and the phenol group can be (de)protonated, but for the coordinated ligand, only a triazole- and a phenol-based protonation are observed. The cyclic voltammogram and differential pulse polarogram of the oxidation of the deprotonated compound show the presence of three oxidation steps; one ruthenium based and two phenol based. Protonation of the complex causes a large positive shift potential for oxidation of the ruthenium centre. All measurements agree with a phenolpyridyltriazole ligand having strong σ-donor properties.

The structure of dicyclopentadienylzinc

Abstract Dicyclopentadienylzinc, (C5H5)2Zn, crystallizes in the monoclinic system, space group P21/c (Z = 8). Cell dimensions are: a 14.046(1), b 8.640(1), c 15.828(2) A; β 113.03(1)°. The structure consists of infinite chains of zinc atoms with bridging cyclopentadienyl groups. In addition, each zinc atom carries a terminal cyclopentadienyl group. The chains, which run parallel to the a-axis, contain two crystallographically independent zinc atoms in the order ...12211221... The cyclopentadienyl groups bridging between zinc atoms of the same type are located over centers of symmetry and therefore disordered. The cyclopentadienyl group bridging between Zn(1) and Zn(2) is normal. It appears that both σ and π-type interactions contribute to the cyclopentadienyl—zinc bonds.

Dinuclear silver(I) and copper(I) complexes with neutral N2S2 donor ligands and their reactivities towards CO. Structure in solution (1H and INEPT 109Ag NMR) and in the solid (X-ray) of [Ag{m-(R),(S)-1,2-(thiophene-2-CH=N)2-cyclohexane}2] (O3SCF3)2

Abstract The 1/1 reactions of the neutral N2S2 donor system (R)(S)-1,2-(5-R–thiophene-2-CHN)2–cyclohexane (R = H, 1a or Me, 1b) with [M(O3SCF3)] [M = Ag(I) or Cu(I)] yielded ionic complexes, consisting of a dinuclear [M2(1)2]2+ dication and O3SCF3− monoanions. An X-ray crystallographic study characterized the molecular structure of [Ag2–(1a)2](O3SCF3)2, in the monoclinic unit cell, space group P21/n, with Z = 4; a = 17.26(1), b = 15.08(2), c = 19.960(17) A, β = 106.15(4)°, V = 4991 A3. The structure was refined to R is 0.0704. The two N2S2 ligands coor- dinate to the silver(I) centres in a bridging di- bidentate manner with short AgN(imine) [e.g. Ag(1)N(2), 2.152(10); Ag(1)N(7), 2.162(9); Ag(2)N(3), 2.153(10); Ag(2)N(6), 2.158(10) A] and long AgS(thiophene) distances [Ag(1)S(1), 2.961(4); Ag(1)S(8), 2.938(4); Ag(2)S(4), 2.928(4); Ag(2)S(5), 2.995(5) A]. The Ag(1) Ag(I) separation is 2.909(1) A. In solution the coordination properties of the N2S2 ligands to silver(I) and copper(I) have been studied by 1H and INEPT 109Ag NMR spectroscopy. The 1H NMR data revealed, by the presence of two thiophene–imine 1H patterns at 190 K, that at this temperature i) the structural features found for [Ag2(1a)2]2+ in the solid are retained in solution and ii) the silver(I) and copper(I) complexes have similar structures in solution. Furthermore, the presence of 3J(1H107,109Ag) on the imine-H resonances of the silver(I) complexes indicates that at 190 K intermolecular exchange processes are slow on the NMR time scale. From the difference in δ109Ag of the [Ag2(1)2](O3SCF3)2 complexes, R = H (δ + 678) or Me (δ + 659), it was concluded that weak thiopheneSAg(I) interactions are present, and stabilize the formation of the [M2(1)2]2+ dications. However, in the reversible reactions of [Cu2(1)2](O3SCF3)2 with carbon monoxide the thiopheneSCu(I) bonds dissociate and neutral complexes are formed having a [{CuCO(O3SCF3)}2{μ−1}2] type of structure. In these complexes both the carbon monoxide and OSO2CF3 groups are terminally coordinated to Cu(I) (R = H, ν(CO), 2089 cm−1; R = Me, ν(CO) = 2087 cm−1 in CH2Cl2).

The structure of 2-(diphenylphosphino)phenyllithium: the significance of PLi bonding

Abstract The solid state structure of 2-(diphenylphosphino)phenyllithium·Et 2 O has been determined by a single crystal X-ray diffraction study. The crystal consists of dimeric aggregates in which the Li atoms are solvated by an additional diethyl ether molecule. The compound retains the dimeric structure in an apolar solvent (toluene) but in THF it exists in monomeric form. Ab initio calculations indicate a small but significant influence of PLi interaction on the stability and structure of P-containing organolithium compounds.

Quadridentate nitrogen donor ligands acting as bridging di-bidentates; X-ray crystal and molecular structure of [Ag2{µ-(R)(S)-1,2-[(2-C5H4N)-C(H)N]2-cyclohexane}2][O3SCF3]2 and the observation of 3J(107,109Ag-1H) in the 1H n.m.r. spectrum of the dinuclear [Ag2L2]2+ cation

The quadridentate N-donor ligands (R)(S)-1,2-[(6-R-2-C5H3N)C(H)N]2–cyclohexane (R = H, Me), upon reaction with [M(O3SCF3)](M = AgI or CuI), behave as bridging di-bidentate ligands to form dimeric complexes such as the title complex for which an X-ray crystal structure was obtained; 3J(107,109Ag-1H) is observed in the 1H n.m.r. spectra of the dinuclear [Ag2L2]2+ cations.

Internally coordinated organozinc-transition metal compounds. Crystal structure of (CH3)2N(CH2)3ZnW(ν-C5H5)(CO)3

Abstract The stabilities of simple and internally coordinated organozinc-transition metal compounds towards disproportionation have been investigated by the microwave titration technique. Simple alkyl- and aryl-derivatives disproportionate to such an extent as to preclude isolation. Internal coordination was found to stabilize the asymmetric compounds, and several derivatives containing the dimethylaminopropyl group were isolated. The crystal structure of one of them, Me 2 N(CH 2 ) 3 -ZnW(Cp)(CO) 3 , was determined by a single-crystal X-ray study. The crystals are orthorhombic, space group P 2 1 2 1 2 1 , with four molecular units in a cell with parameters a 8.406(1), b 12.179(2) and c 16.642(2) A. The structure was solved by standard Patterson and Fourier techniques. The refinement, with anisotropic temperature factors for the two heavy atoms, converged at R F = 0.092 ( R wF = 0.089) for 1536 observed reflections with I >2.5σ( I ). The molecule consists of a central tungsten atom, surrounded in a tetragonal pyramidal fashion by a cyclopentadienyl group in the apical position and three carbon monoxyde molecules and a zinc atom occupying the basal positions. The zinc atom is three-coordinate, being surrounded by the tungsten atom and the chelating dimethylaminopropyl group; there is, however, a short intermolecular contact between zinc and a carbonyl oxygen atom at 2.61(3) A.

Synthesis and characterization of two isomers of Os3(CO)10(C5H4N-2-C(H)=N-R) and the conversion to ortho-metallated HOs3(C5H3N-2-C(H)=N-R)(CO)9: Part III. X-ray structure of HOs3(C5H3N-2-(C(H)=N-i-Pr)(CO)9

Abstract Os3(CO)10(MeCN)2 reacts at room temperature in MeCN or toluene with R-Pyca† to yield two isomers of Os3(CO)10(R-Pyca) that differ in the bonding of the R-Pyca ligand to the Os3(CO)10 unit. In all cases Os3(CO)10(R-Pyca(4e)) (isomer A; 4a: R = c-Pr, 4b: R = i-Pr, 4c: R = neo-Pent, 4d: R = t-Bu), containing a chelating 4e donating R-Pyca ligand and three Os S bonds, could be isolated. In the case of R = c-Pr and R = i-Pr Os3(CO)10(R-Pyca(6e)) (isomer B; 5a: R = c-Pr, 5b: R = i-Pr), in which only two Os S bonds are present and the R-Pyca ligand is bonded as a 6e donating ligand bridging two non-bonded Os atoms, could be isolated as a minor product. At 70 °C Os3(CO)10(R-Pyca(4e)) (4b and 4d) loses one carbonyl and the pyridine moiety of the R-Pyca ligand is ortho-metallated to form HOs3(C5H3N-2-C(H) N R)(CO)9 (6b: R = i-Pr and 6d: R = t-Bu). Under the same conditions Os3(CO)10(i-Pr-Pyca(6e)) (5b) reacts to Os2(CO)6(6e)) (7b) containing a bridging 6e donating ligands. The latter two reactions were followed with FT-IR spectroscopy in a high temperature IR cell. The structure of the complexes in solution have been studied by 1H and 1C NMR and IR spectroscopy. The stoichiometries of 4a and 5a were determined by FAB-mass spectrometry while an exact mass determination was carried out for 4a. The crystal structure of 6b has been determined. Crystal of 6b are monoclinic, space group P21/n, with a = 7.808(2),b = 17.613(3),c = 16.400(8)A, β = 94.09(3)° and Z = 4. The structure was refined to R = 0.039. The molecule contains a triangular array of osmium atoms [Os(1) Os(2) = 2.898(2)A, Os(1) Os(3) = 2.886(2)Aand Os(2) O(3) = 2.911(2)A] and nine terminally bonded carbonyl ligands. The C5H3N-2-C(H) N-i-Pr ligand is chelate bonded to Os(2) with the pyridine and imine nitrogens atoms axially and equatorially coordinated respectively [Os(2) N(1) = 2.00(2)Aand Os(2) N(2) = 2.11(2)A]. The i-Pr-Pyca ligand is ortho-metallated at C(1) and forms a four membered ring containing Os(2), Os(3), C(1) and N(1), the Os(3) C(1) distance being 2.12(2)A. The hydride, which could not be located unequivocally from a difference Fourier map is proposed to bridge the Os(2) (3) bond on the basis of stereochemical considerations.

Zinc enolates: C- or O-metallation?

Abstract Two methods have been used for the generation of zinc enolates: the reaction of EtZnOMe with enol acetates, and that of lithium enolates with zinc chloride. Most of the zinc compounds prepared proved to be very reactive towards carbonyl functions, and so they cannot be isolated from the EtZnOMe/enol acetate system. The final products of these reactions are polymerisation and self-condensation products and β-diketonates, the latter being formed by condensation reactions of the zinc enolates with an acetate molecule. The structure of [EtZnOMe·Zn(Pac) 2 ] 2 (HPac = pivaloylacetone, (CH 3 ) 3 CCOCH 2 COCH 3 ), isolated in 20% yield from the reaction of EtZnOMe with CH 3 COOC(t-Bu)CH 2 , was determined by X-ray diffraction analysis. The compound forms monoclinic crystals, space group P 2 1 / c , with two dimers in a cell of dimensions a 11.677(4), b 18.299(9) and c 12.719(5) A and β 117.26(3)°. The structure closely resembles that of the known complex [PhZnOPh·Zn(Pac) 2 ] 2 . The complications involving reactions of zinc enolates with enol acetates were avoided by treating lithium enolates with zinc chloride. Polymerization and self-condensation could be prevented by using the very bulky enolate LiOC(t-Bu)CMe 2 . In this way, the corresponding stable zinc enolate RZnCl·THF was obtained as a dissociating dimer. No replacement of the second chlorine atom by an enolate group occurred even when a large excess of lithium enolate was used. The reactivity of the zinc enolates suggests that they contain both zinccarbon and zincoxygen bonds. They are assumed to have a cyclic structure which resembles that of the Reformatsky reagent.