P. L'Haridon

Nitrides and oxynitrides: Preparation, crystal chemistry and properties

Abstract As compared to oxides, nitride-type compounds can have specific properties and applications. The outline of this review focuses on the crystal chemistry of nitrides and oxynitrides. Given the nitride-oxynitride association, this article mainly deals with compounds which are predominantly covalent in character and does not include compounds which are metallic in character and in which nitrogen can be considered as an interstitial element. The classification which is used thus highlights the two main coordination polyhedra: nitrided or oxynitrided tetrahedra or octahedra.

Time-of-flight neutron diffraction study of the structure of the perovskite-type oxynitride LaWO0.6N2.4

The mixed-valence oxynitride LaWO/sub 0.6/N/sub 2.4/ is a new example of a conductor with the perovskite structure. The time-of-flight neutron diffraction study has shown that this compound possesses a tetragonal symmetry (space group I/anti 4/). Oxygen and nitrogen atoms are disordered and the coordination octahedra around the tungsten atoms are tilted by /plus minus/8/degrees/ along the c axis.

Transport properties of the new perovskite-type LaVO3⇔xNx Oxynitrides

A new series of oxynitrides LaVO3−xNx (0 ⪕ × ⪕ 0.9) has been synthesized and their electrical and magnetic properties studied. Contrary to the oxides involving the mixed valence VIII−VIV, no semiconductor-metal transition is observed and all the compounds remain p-type semiconductors.

Bis-cyclopentadienyl molybdenum and tungsten compounds with mercury-transition metalmercury bonds. Part I. Chemical, spectroscopic and structural studies of halogeno- and thiolato-derivatives

Abstract Cp 2 MH 2 (M = Mo and W) react with HgX 2 (X = Cl, Br, I, SCN, OAc and CN) salts, giving insoluble compounds which have the general formula Cp 2 M(HgX) 2 ·xHgX 2 (I) (x = 0, 1 3 , 1 2 , 2 3 and 1). These compounds were characterized by using IR and, for some of them, Raman spectroscopy. Frequencies of Hg-X vibrations are discussed in the light of an ‘adduct type’ structure. MoHg and WHg bands are detected in the Ramam spectra near 130–140 cm −1 . An intermediate polymeric compound (Cp 2 MoHg) n (II) was isolated and characterized by IR spectrum and unit cell parameters. All compounds (I) and (II) react with thiolates giving non-adduct: i) compounds Cp 2 M(HgSR) 2 (R = Me, Et, i Pr and n Pr) (III) soluble in organic solvents and ii) insoluble compounds [Cp 2 MHg 2 (SR)]X(X = Cl, Br) (IV). Compounds (IV) with X = Cl also crystallize from solutions of (III) in chloroform. Insoluble Cp 2 M(HgSR) 2 (R = pheynl or pyrimidine) compounds were obtained by the reaction of (I) with corresponding thiolates. IR spectra of all these derivatives were recorded showing similar features to those of the compounds (I). ( 1 H), ( 13 C) and ( 99 Hg) NMR spectra of soluble complexes (III) were recorded. The structure of [Cp 2 MoHg 2 (SEt)] Cl determined by X-ray analysis is built of infinite chains of Cp 2 MoHg 2 moieties and thiolates bridging two mercury atoms from the adjacent Cp 2 MoHg 2 units and of essentially ionic chlorides.

Transition metal-cyanocarbon chemistry: IX. Reactions of monocyanoacetylene with dicarbonylcyclopentadienylmethylthiolatoiron(II). Crystal structures of [FeC(O)C(CN)CH(SCH3) (η5-C5H5)(CO)] and of μ-η2-Fe(CCCN)(η5-C5H5)(CO)2][Co(CO)3]2

Abstract The reaction of [Fe(η5-C5H5)(SCH3)(CO)2] with monocyanoacetylene (HCCCN) in THF at room temperature gives the acetylide [Fe(CCCN)(η5-C5H5)(CO)2] (1, the acylic species [ FeC(O)C(CN)CH(S CH3)(η5-C5H5)(CO)] (2), the binuclear complex [Fe(η5-C5H5)(CO)2C(CN)C(SCH3)Fe(η5-C5H5)(CO)2] (3), and the disubstituted olefin Z-(NC)CHCH((SCH3) (4. If the HCCCN is condensed on to a frozen solution of the thiolato complex and the mixture then allowed to warm up, the acylic compound 2 is not isolated. Irradiation of 1 and 3 in the presence of PPh3 in THF gives the substituted complex [Fe(CCCN)(η5-C5H5)(CO)(PPh3)] (6)_and [Fe(η5-C5H5)(CO)2C(CN)C(SCH3)Fe(η5-C5H5)(CO)(PPh3)] (10). Cycloaddition of tetracyanoethylene on 1 and 6 gives the corresponding complexes [fe( CC(CN)C(CN) 2 C (CN)2(η5-C5H5)(CO)(L)] (L = CO (7) or PPh3 (8). Under UV irradiation 8 is converted into Fe(η 3 -C(CN) 2 C(CN)C C(CN)2(η5-C5H5)(PPh3)] by loss of CO. Complex 1 reacts with Co2(CO)8 to form the [μ-η2-Fe(CC-CN)(η5-C5H5)(CO)2][Co(CO)3]2 (5). The structures of 2 and 5 have been determined by X-ray diffraction.

Transition metal-cyanocarbon chemistry: VII. Reactions of mono- and di-cyanoacetylenes with tricarbonylcyclopentadienylmethylthiolatotungsten(II). Formation of phosphorus ylide complex [(C5H5)(CO)2W(CH(P(C6H5)3)C(CN)SCH3)]. Crystal structure of [(C5H5)(CO)2(P(C6H5)3)-W(C(O)C(CN)CHSCH3)·CH2Cl2]☆

Abstract Reactions of (C 5 H 5 )(CO) 3 W(SMe) with cyano-activated alkynes RCCCN with R  H or CN give heterometallacyclic complexes (C 5 H 5 )(CO) 2 W(C(O)C(CN)C(R)S Me) (R  H ( 2 ) or CN ( 6 )) or for R  H, an insertion σ-vinylic complex [(C 5 H 5 )(CO) 3 W(CHC(CN)SMe)] ( 3 ). Irradiation of 3 in the presence of PPh 3 in THF gives the ylide complex (C 5 H 5 )(CO) 2 W(η 2 -CH(PPh 3 )C(CN)SMe) ( 5 ), whereas 2 under such conditions gives an η 1 -acylic complex [(C 5 H 5 )(CO) 2 PPh 3 W(C(O)C-(CN)CHSMe)] ( 4 ). The structure of 4 has been determined by X-ray diffraction.

Etude cristallochimique de LiPN2: Une structure derivée de la cristobalite

LiPN2 has been prepared by reaction between Li3N and P3N5 nitrides. The unit cell is tetragonal with a = 4.567(1) and c = 7.140(4) A. The space group is I42d. The structure is related to the β cristobalite type and is isostructural with CaGeN2. It is built up from a PN4 tetrahedra framework in the holes of which the lithium atoms are localized. The values of the rotation angle ф of tetrahedra, ca ratio and θ (NPN) angle have been discussed in relation to the parameter x of the nitrogen atoms.

Complexes biscyclopentadienyles avec des liaisons metal de transitionmercure ☆: III. Structure de deux phases de (C5H5)2Mo(HgSC2H5)2; etude de la distribution electronique dans les complexes (C5H5)2MoX2 par resonance magnetique nucleaire

Abstract (C5H5)2Mo(HgSC2H5)2 crystallizes in two different forms; a red one (A) which is insoluble in the usual organic solvents, the other one (B) is orange and soluble. Their structures were determined by X-ray diffraction. A: P21/c, a 10.342(5), b 17.757(10), c 10.193(6) A, β 113.39(4)°, Z = 4; B: C2/c, a 31.503(8), b 7.986(3), c 20.843(11) A, β 97.87(3)°, Z = 12. The molecular geometry is nearly the same in the two phases (MoHg: 2.677 A (A) and 2.676 A (B); HgS: 2.43 A (A) and (B): HgMoHg; 70.8° (A) and 73.1° (B); MoHgS: 167.6° (A) and 171.2° (B); C5H5MoC5H5: 140.5° (A) and 137.8° (B), whereas the overall structure is different. “Dimeric units” exist in A. The shortest distances HgS between two different molecules in the “dimeric unit” are equal to 3.17 A. An infinite system of mercurysulfur interactions is shown to exist in the form B(HgS: 3.32–3.33 A). The electronic structure of the (C5H5)2Mo(HgSR)2 compounds is discussed on the basis of 1H, 13C, 199Hg and 95Mo NMR results and compared with the geometrical parameters. A relation between the nature of the X-ligands in the (C5H5)MoX2 complexes (X = O, Cl, S, H, Hg), the C5H5MoC5H5 angle and the 1H(C5H5) chemical shifts is evident.

Transition metal-cyanocarbon chemistry X. Reactions of monocyanoacetylene and dicyanoacetylene with organometallic compounds of cobalt(I) and nickel(II). Crystal structure of [Co(CCCN)2(η5-C5H5)(P(C6H5)3)]☆

Abstract The reaction of monocyanoacetylene (HCCCN) with [Co(η 5 -C 5 H 5 )(P(C 6 H 5 ) 3 ) 2 ] gives the vinylacetylide [Co(CCCN)(CHCH(CN))(η 5 -C 5 H 5 )(P(C 6 H 5 ) 3 )] ( 1 ) and the diacetylide [Co(CCCN) 2 (η 5 -C 5 H 5 )(P(C 6 H 5 ) 3 )] ( 2 ). The crystal structure of the latter has been established by an X-ray diffraction study. Two conformers of 1 are formed in a ratio depending on conditions. In 1 a PPh 3 ligand can be replaced by (CH 3 ) 3 SiCCSi(CH 3 ) 3 , which acts as a π-bonded ligand in the product, [Co(CCCN)(CHCH(CN))(η 5 -C 5 H 5 )(η 2 -(CH 3 ) 3 SiCCSi(CH 3 ) 3 )] ( 3 ). Treatment of 1 with I 2 gave (Co(η 5 -C 5 H 5 )(I) 2 (P(C 6 H 5 ) 3 )] ( 6 ) and CH(CN)CH-C(CN)CHI ( 5 ). The major product of the reaction of [Co(η 5 -C 5 H 5 )(P(C 6 H 5 ) 3 ) 2 ] with dicyanoacetylene (NCCCCN) was the 1,6-diphosphorane (C 6 H 5 ) 3 PC(CN)C(CN)C(CN)C(CN)C(CN)C(CN)P(C 6 H 5 ) 3 . [Co(η 5 -C 5 H 5 )(η 4 -C 5 H 5 (CCCN))] ( 7 ) was isolated from the reaction of monocyanoacetylene with [Co(η 5 -C 5 H 5 )(η 4 -C 5 H 6 )]. Cyanoalkynes bridge two nickel atoms in [μ-(HCCCN)][Ni(η 5 -C 5 H 5 )] 2 ( 8 ) and [μ-(NCCCCN)][Ni(η 5 -C 5 H 5 )] 2 ( 9 ), which were formed in the reaction of nickelocene with HCCCN and NCCCCN, respectively.

Synthesis and characterisation of a novel aluminovanadate oxynitride basic catalyst

The influence of the time and temperature of nitridation of aluminium vanadate oxide precursor prepared by the co-precipitation method is presented. The surface properties of one VAlON containing 6.4 wt% of nitrogen are evaluated using two catalytic tests: the Knoevenagel condensation and the 1-butanol dehydrogenation/dehydration. This provides evidence that the substitution of oxygen by nitrogen induces basic catalytic properties.