Francis Robert

Phenylimido derivatives of [Mo6O19]2−: syntheses, X-ray structures, vibrational, electrochemical, 95Mo and 14N NMR studies

Abstract Both [Mo 6 O 18 (NPh)] 2− and [Mo 6 O 17 (NPh) 2 ] 2− species are formed by reaction of (n-Bu 4 N) 2 [Mo 6 O 19 ] with either 1 or 2 equiv. of Ph 3 Pue5fbNPh in pyridine or acetonitrile and have been isolated as mixtures. Single-crystal X-ray diffraction analyses have shown that [Mo 6 O 18 (NPh)] 2− , [Mo 6 O 17 (NPh) 2 ] 2− and [Mo 6 O 19 ] 2− can be found together in the same crystal of average composition (n-Bu 4 N) 2 [Mo 6 O 19− x (NPh) x ]. The structural parameters of the averaged anions have been determined for x =1.16 (sample 1 ) and x =0.92 (sample 2 ). Crystal data for 1 : a =12.684(4), b =22.750(4), c =19.483(3) A, β=103.04(2)°, space group P 2 1 / c , Z =4, R =0.048 and R w =0.051 for 3846 reflections with I ⩾3σ( I ). Crystal data for 2 : a = 12.678(2), b =22.645(3), c =19.462(4) A, β=104.16(2)°, space group P 2 1 / c , Z =4, R =0.058 and R w =0.061 for 5243 reflections with I ⩾3σ( I ). The products have been studied in acetonitrile solution by 95 Mo and 14 N NMR spectroscopy, Raman spectrophotometry and electrochemistry. Each of these techniques has confirmed the presence of the mono- and bis-imido derivatives together with the parent species, and has allowed both the characteristics of the individual components and the composition of the solution to be determined; the results obtained by the different methods are in reasonable agreement.

Molecular architecture of copper(I) thiometallate complexes. Example of a cubane with an extra face, (NPr4)3[MS4Cu4Cl5] MMo, W)

Abstract Thiometallates MS 4 2− (M ue5fb Mo, W) form with copper(I) heterobimetallic complexes which are interesting because of the versatility of the structural types obtained. The various structures obtained by addition of copper(I) to MS 4 2− are described and illustrated by examples recently reported in the literature. The synthesis and structural characterization of (NPr 4 ) 3 [MS 4 Cu 4 Cl 5 ] are given together with the connections which exist between ‘open’ and ‘closed’ cubane structures.

Synthesis through an in situ esterification process and characterization of oxo isopropoxo titanium clusters

Three titanium oxo-isopropoxo clusters Ti 6 O 4 (OOCue5f8CH 3 ) 4 (OPr 1 ) 12 ( 1 ), Ti 12 O 16 (OPr 1 ) 16 ( 2 ) and Ti 12 O 16 (OPr 1 ) 16 ·1.4CH 2 Cl 2 ( 3 ) are obtained by refluxing Ti(OPr 1 ) 4 with 1.2 equivalents of carboxylic acids over two days. The molecular structures of Ti 6 O 4 (OOCCH 3 ) 4 (OPr 1 ) 12 ( 1 ) and Ti 12 O 16 (OPr 1 ) 16 · 1.4CH 2 Cl 2 ( 3 ) have been resolved by single crystal X-ray diffraction. The titanium oxo organo cores of these clusters are also characterized in solution by 17 O NMR spectroscopy and in solid-state by 13 C CP MAS NMR spectroscopy.

Heterobimetallic aggregates derived from the double cubane-like structure (NMe4)4[MS4(CuCl)5Cl2] (MMo, W)

Abstract Nucleophilic substitutions in the double cubane-like structures [MS4(CuCl)5Cl2]4− (M=Mo, W) are complicated by elimination reactions. With NCS− an edge-elimination process gave the [MS4(CuNCS)4]2− anion whereas a face-elimination by PPh3 led to the monocubane structure [MS4(CuPPh3)4Cl]. Substitution by bipyridine produced the lacunary [MS4Cu3.75Cl1.75bipy2]. The different species were characterized by X-ray diffraction studies.

Tricarbonyl(1-trimethylsilyl-2,3-dimethoxybenzene)chromium: A new conformation of the tricarbonylchromium entity with respect to a bulky substituent

Abstract Because of steric effects the Cr(CO) 3 group in tricarbonyl(1-trimethylsily]-2,3-dimethoxybenzene)chromium does not take up an anti-eclipsed conformation with respect to the trimethylsilyl group, but instead adopts the opposed conformation nearly eclipsing that group.

Substitution nucléophile aromatique cine en série arènetricarbonylchrome

Abstract 2-Lithio-2-phenyl-1,3-dithiane reacts with p -chlorotoluenetricarbonylchromium to give, after treatment with CF 3 CO 2 H, the sole cyclohexadiene isomer 1-methyl-4-chloro-5(2′-phenyl-1′,3′- dithiane)-1,3-cyclohexadiene, which was characterized by X-ray crystallography.

Heterobimetallic aggregates of copper(I) with thio-tungstate and -molybdate. Cation effect in aggregation of MS4Cu4Cl4 units, a crystallographic study

Reaction of [MS4]2–(M = Mo or W) with CuCl in dichloromethane or acetonitrile gives a new set of bimetallic compounds isolated with various geometries for the same 1:4:4 M:S:Cu composition. Crystals of [NBu4]2[MoS4Cu4Cl4]1a are tetragonal, space group I/m, a= 13.343(5), c= 14.113(2)A, Z= 2, R= 0.058. The crystal structure reveals discrete [MoS4Cu4Cl4]2– anions separated in the lattice by [NBu4]+ cations. The isostructural tungsten homologue 1b was isolated and characterized: space group I/m, tetragonal, a= 13.342(4), c= 14.106(5)A. The structure of [PPh4][NPr4][MoS4Cu4Cl4]2 consists of a dimeric aggregate: monoclinic, space group P21/n, a= 9.962(8), b= 36.951(5), c= 13.114(3)A, β= 105.71(6)°, R= 0.056. The salt [NPr4]2[WS4Cu4Cl4]3b is polymerized through linear chains. Crystals are triclinic, space group P, a= 10.283(1), b= 13.925(1), c= 15.245(1)A, α= 110.32(1), β= 90.64(1), γ= 102.49(1)°, Z= 2, R= 0.031. The isostructural molybdenum compound 3a was also characterized: triclinic, a= 10.275, b= 13.961, c= 15.270 A, α= 110.57, β= 90.70, γ= 102.30°. The arrangements of the mono-, di- and poly-meric aggregates in the lattice are discussed in terms of the size of the counter anion. For compounds 1b and 3a only the cell dimensions were determined.

Bimetallic biphenylene biscarbene complexes: synthesis, x-ray crystal structure and reactivity towards some nucleopphilic reagents

Abstract The reaction of p-biphenylenedilithium with hexacarbonyl-chromium or -tungsten and subsequent alkylation by triethyloxonium tetrafluoroborate yields the μ-[p-biphenylenebis[(ethoxy)]carbene]]bis(pentacarbonylmetal) complexes: (CO)5-M=C(OEt)-p,p′-(C6H4)2C(OEt)=M(CO)5 (M = Cr (1), M = W (2)). an X-ray diffraction study of 1 has shown the at the molecule is centrosymmetric; that there is practically no delocalization between the two submits of the biphenyl ligand, and that both rings are strictly coplanar. Aminolysis and insertion of ynamine into the metalue5f8carbon bond give new bis(aminocarbene) complexes.

An electrophile-mediated cyclization on the 1,6-anhydro-d-glucopyranose framework

Abstract Iodocyclization of O -tributylstannyl- d -glucal with iodine in acetonitrile gave 1,6-anhydro-2-deoxy-2-iodo-β- d -glucopyranose ( 1 ) in high yield. The 3,4-di- O -acetyl derivative of 1 could be converted into the corresponding 2-deoxy compound and into the 2- C -allyl-2-deoxy branched sugar ( 5 ) by treatment with tributylstannane and allyltributylstannane, respectively. Controlled alkaline hydrolysis of 5 gave the 4-monoacetyl derivative. Complete hydrolysis of 5 gave the 3,4-diol, which underwent a 5- exo cyclization by treatment with N -bromosuccinimide. 1 H NMR spectroscopy and X-ray analysis showed that the cyclized product has the B 3,O conformation in its pyranose ring, which is trans -fused to the newly formed tetrahydrofuran ring.

Substitution nucléophile aromatique d'aryllithiumtricarbonylchrome sur des méthoxy- et chloro-arenetricarbonylchrome

Abstract Treatment of veratroletricarbonylchromium with n-BuLi and ClSi(CHMe2)3 or para- chlorotoluenetricarbonylchromium complexes with n-BuLi yields unexpected dinuclear complexes 4 and 6 via a cine nucleophilic aromatic substitution of a methoxy or a chloro group by an aryllithiumtricarbonylchromium complex. The structure of one of these complexes 4 is reported which shows the loss of a methoxy group and a 34° torsional angle between the aromatic rings.