Yves Dartiguenave

Methylnickel compounds with chelating anionic ligands. Crystal and molecular structures of methyl(trimethylphosphine)nickel oxinate and oxalate dimer

Abstract Several new methyl-nickel(II) compounds NiMe- X(PMe 3 ) [X=8-hydroxyquinolate, 1; X=1/2[O 2 C(CH 2 ) n CO 2 ), 2: n =0; 3: n =1; 4 : n =2; 5 : n =3; 6 : n =4] were prepared by reacting [NiMe(PMe 3 )(OMe)] 2 and the corresponding acid. Compound 1 crystallizes in the space group P 1 with a =8.868(1), b =9.303(2), c =8.452(1) A, α=94.29(1)°, β= 105.85(1)°, γ=82.63(1)°, V =671.8(1) A 3 , Z = 2. Final discrepancy indices are R =0.0291 and R w =0.0303 for 2255 independent data ( I >3σ( I )). The coordination geometry around nickel is square planar. The NiP and NiC distances of 2.125(1) and 1.917(2) A are on the shortest range of the usually observed values, while the NiO and NiN values of 1.923(2) and 1.953(2) A are on the upper one. The oxygen atom of the oxinate ligand is trans to the methyl group. Compound 2 crystallizes in the space group P 2 1 / n with a =9.266(1), b =11.113(2), c =8.169(2) A, β=93.46(2)°, V =839.5 A 3 , Z =4. The final R values are R =0.0325 and R w = 0.0334 for 1221 independent data ( I >3σ( I )). The molecule shows two nickel atoms bridged by the oxalato group acting as a bidentate ligand to both metals (NiO1=1.990(3) and NiO2=1.961(3) A). The dimer possesses a crystallographic center of symmetry, which is located in the middle of the oxalato CC bond. The geometry about each metal is square planar, the coordination sphere being completed by the methyl and trimethylphosphine ligands. Compounds 3  6 have been characterized by IR spectroscopy, together with compounds 4a  6a obtained by reaction with PMe 3 in excess.

Spectral and Electron Paramagnetic Resonance Investigations of Copper(II) Complexes of Linear-Chain Fatty Diacids

Electron paramagnetic resonance spectra of polycrystalline copper complexes of butanedioic, pentanedioic, hexanedioic, heptanedioic, and decanedioic acids are presented, together with 77 K electronic spectra. The complexes are formulated as dimeric copper carboxylate units linked into infinite chains. Monomer impurities are also present and increase in quantity with the length of the diacid. The monomer and dimer signals occur at very different field strengths, but the g values calculated from the S = 1/2 spectra are similar to those calculated from the S = 1 spectra. The EPR method can thus be used to locate copper ions in possible biological frameworks and to study the geometry around the metal sites. The distortion from axial symmetry around the copper increases with the length of the diacid, as shown by the observed zero-field splitting parameters. Gaussian analysis of the optical absorptions yields information used with EPR data to calculate covalency and Fermi contact terms. Sodium, potassium, and lithium salts transform the dimeric polymers into monomeric polymers. The presence of magnetic exchange interactions in copper dicarboxylates is discussed and thereby shown to be of interest in the study of copper ions in molecules of biological importance containing carboxylate groups.

First structural characterization of an α-diazophosphane: crystal structure of bis[bis(diisopropylamino)phosphanyl]diazomethane [(i-Pr2N)2P]2CN2

Crystals of bis[bis(diisopropylamino)phosphanyl]diazomethane P2N6C25H56, M = 502.7 belong to the monoclinic space group, C2/c with a 12.044(2), b 28.661(4) c 10.301(1) A, β 116.13(1)°, V 3192(2) A3 and Z = 4. The structure was refined by use of 1275 non zero Mo-Ka reflections to R = 0.052 at 293 K. The unit cell contains discrete monomeric molecules. The structural parameters of the CN2 group are very close to those found for other diazoalkanes. The linear diazo group C(1)N(1)N(2) lies on the crystallographic two fold axis of the unit cell. The ability of bis[bis(diisopropylamino)phosphanyl]diazomethane to act as a chelating or reducing agent is discussed.

STEREOSPECIFIC FORMATION OF A 1,2λ3 -AZAPHOSPETANE IN THE THERMOLYSIS OF BIS[BIS(DIISOPROPYLAMINO)PHOSPHANYL] DIAZOMETHANE

Abstract Heating of bis[bis(diisopropylamino)phosphanyl]diazomethane 7. in refluxing benzene for 48 hours, quantitatively led to the corresponding 1.2λ3-azaphosphetane 9 as only one diastereoisomer. This result is explained in terms of carbene insertion into a methin-CH bond of an isopropyl substituent. The regiospecificity and the stereospecificity of the ring closure is discussed. Treatment of 9 with elemental sulfur afforded the corresponding 1.2.2λ3-azathiophosphetane 10 which has been characterized b X ray crystallo raphy: C25H56N4P2S2, space group P2(l)/n, a = 13.628 (3) A, 6 = 19.369 (5) A, c 112.485 (4) A, V = 3073 (3) A3.

Nickel—nitrosyl Complexes: structure of nitrosyltris(trimethylphosphine)nickel hexafluorophosphate, {Ni(NO)(PMe3)3} PF6

Abstract The crystal and molecular structure of nitrosyltris-(trimethylphosphine)nickel(O) hexafluorophosphate, {Ni(NO)(PMe3)3}PF6, has been determined from three dimensional single crystal X-ray analysis. The compound crystallizes in the orthorhombic space group Pnma with Z = 4 and a unit cell of dimensions: a = 16.253(3), b = 10.536(1) and c = 12.228(2) A. The structure was solved by conventional heavy atom techniques and refined by least-squares methods to R1 = 0.036 and R2 = 0.048 respectively for 1085. independent reflections. The coordination geometry around the nickel is a slightly distorted tetrahedron with an average PNiP angle of 105.63° and PNiN angle 113.03°. The nickel nitrosyl group is slightly bent with an NiNO angle of 175.4(5)°. The bending occurs in the ClPlNiNO plane toward Pl. The structure is compared with other tetrahedral {MNO}10 phosphine complexes and the MNO bonding is discussed.

CoX2(NO)(PMe3)2 Complexes: an example of the influence of X (X = CI, Br, I, NO2) on the stereochemistry and electronic structure of the five-coordinate {CoNO}8 complexes

CoX 2 (NO)(PMe 3 ) 2 complexes (X = Cl, Br, I, NO 2 ) exhibit markedly different ν (NO) stretching frequencies and different geometries. The structure of CoI 2 (NO)(PMe 3 ) 2 ( 1 ) and CoCl 2 (NO)(PMe 3 ) 2 ( 2 ) have been determined by X-ray diffraction. Both crystallize in the orthorhombic system, Pnma space group with four molecules in a cell of the following dimensions: for 1 , a = 10.497(2), b = 10.694(2), c = 13.975(2) A, ν = 1568.8, A 3 ; for 2 , a = 9.607(2), b = 10.689(2), c = 13.512(3) A, ν = 1387.5 A 3 . The structures were refined to conventional R values of R = 0.040 from 1630 reflections for 1 and R = 0.033 from 976 reflections for 2 . In both cases, the coordination geometry about the five-coordinate cobalt atom is approximately trigonal bipyramidal, with the NO group sharing the equatorial positions with the halide ligands. Structure 2 is disordered, which prevents any precise structural characterization. In ( 1 ), the CoNO angle is 179.2(19)° and the Co NO distance is 1.728(23) A; v (NO) is 1753 cm −1 . CoCl 2 (NO)(PMe 3 ) 3 shows a v (NO) vibration at 1637 cm −1 . Co(NO 2 ) 2 (NO)(PMe 3 ) 2 with v (NO) = 1658 cm −1 has been proposed as a square pyramidal structure with a bent apical CoNO. These differences in NO stretching frequencies and geometries are discussed.

Synthesis and characterization of copper, manganese and zinc complexes of the bidentate diisocyano ligands 2,5-dimethyl 2,5-diisocyanohexane (TMB) and 1,2-diisocyanoethane(DHB)

Abstract By reaction of 2,5-dimethyl 2,5-diisocyanohexane (TMB) and 1,2-diisocyanoethane (DHB) with CuX2 (X = CF3SO−3, ClO−4, BF−4), three types of complexes were isolated and characterized by magnetic susceptibility and EPR spectroscopy. In the violet CuL2X2 compounds, CuII atoms are in a square-planar environment and not magnetically interacting. For the mixed-valence green complexes Cu2L3X3, the CuII and CuI metal centres both have a tetrahedral coordination, and the presence of independent CuII and CuI atoms in a 1:1 ratio was deduced from a magnetization experiment. Diamagnetic CuI complexes CuL2X were also isolated. TMB complexes were prepared with MnII and ZnII. In the former case, high-spin Mn(TMB)(CF3SO3)2·2H2O and low-spin Mn(TMB)3(PF6)2 complexes were obtained, whereas ZnII gave Zn2(TMB)3(CF3SO3)2·2H2O. The v(CN) frequency in the infrared spectra increases with the charge on the complex, and for complexes of the same charge, decreases when the diisocyanide-to-metal ratio increases. Although solubility was improved by using CF3SO−3 as counter ion, it remained low and the complexes are likely to be polymeric, with the diisocyanide ligands in extended conformations playing a bridging role.

Ni(II) complexes of trimethylphosphine: Crystal and molecular structure of NiBr2(PMe3)2. Comparison with the pentacoordinate NiBr2(PMe3)3 and NiBr(PMe3)4BF4 complexes

Abstract The crystal and molecular structure of NiBr2(PMe3)2, obtained by sublimation at 380 K (10 mm Hg), has been determined. It crystallizes in the P21/n space group, with two molecules in a unit cell of dimension, a = 8.547(1) A; b = 13.552(1) A; c = 6.031(1) A; β = 90.20(1)°. The structure (R = 0.042 for 52 variables and 446 observations) consists of discrete NiBr2(PMe3)2 molecules with a square planar geometry around the nickel atom. The main distances and angles are well within the range observed for Ni(II)PR3 square planar complexes. Comparison with the related pentacoordinate species NiBr2(PMe3)3 and [NiBr(PMe3)4]+ indicates that pentacoordination occurs with increasing of the NiBr bond distances (2.29 A in tr-square planar to 2.50 A in trigonal bipyramidal compounds), but has no effect on the NiP bond lengths. Interligands contact distances are minimum and have about the same value in the tr-square planar complex and in the trigonal bipyramid between the axial and equatorial ligands.

Reaction of [Co(PMe3)4]BPh4 with oxygen : crystal and molecular structure of [Co(MeCN)2(OPMe3)4](BPh4)2

Abstract Reaction of molecular oxygen with the cobalt(I) cationic complex [Co(PMe3)4]BPh4 in acetonitrile yields pink crystals of the cobalt(II) compound [Co(MeCN)2(OPMe3)4](BPh4)2. X-ray diffraction (P21/c, a = 12.580, b = 18.54, c = 18.684 A, β = 130.76°, R = 0.041) shows that the cation is an octahedral d7 Co(II) monomer with two trans acetonitrile ligands. This compound is one of the few examples of octahedral Co(II) complexes containing phosphine oxide ligands. The peroxocobalt(III) compound [Co(PMe3)4-(O2)]BPh4, showing an infrared v(O-O) absorption at 880 cm−1, has been obtained as an intermediate.

Mixed trimethylphosphine—trimethylphosphite pentacoordinate d8 nickel(II) complexes

Abstract The proucts of the reactions of PMe 3 or P(OMe) 3 with trigonal bipyramidal NiX 2 (PMe 3 ) 3 (X = CN, Cl, Br, I), [NiX(PMe 3 ) 4 ]BF 4 and [Ni(P(OMe) 3 ) 5 ](BF 4 ) 2 complexes have been studied in dichloromethane and chlorodifluoromethane solutions. The stereochemistries of the mixed ligand complexes have been investigated by 31 P NMR spectroscopy at low temperature. Relations between the NMR parameters (δ; 2 J pp ), the structures and stereochemistries are discussed [l].