J. Protas

Structure cristalline et configuration relative d'un complexe du titanocene presentant une chiralite plane et une chiralite centree sur l'atome de titane

Abstract The crystalline structure of the racemic form m.p. 164° C of the compound ( h 5 -3-MeC 5 H 3 C(Me 2 )C 6 H 5 )( h 5 -C 5 H 5 )Ti (2,6-Me 2 C 6 H 3 O)Cl has been determined by X-ray diffraction to establish the relative configuration of the two chiral moieties. This compound may be used further as a reference for studies on dynamic stereochemistry around the titanium atom. A systematic absolute nomenclature is proposed for this type of structure.

Structure cristalline et proprietes du dichlorure de bis(pentahapto-benzylcyclopentadienyl)zirconium triboluminescent

Abstract The product ( n 5 -C 5 H 4 CH 2 C 6 H 5 ) 2 ZrCl 2 is orthorhombic: a 12.05(1), b 24.12(2), c 6.99(1) A; space group Aba 2, Z 4. Final R 0.077. The Zr atom is tetrahedrally coordinated by two ZrCl σ bonds and two ZrCp π bonds. The crystal is tri-boluminescent and highly piezoelectric.

Pentacoordinate iron(III) porphyrin carboxylates: Synthesis, physicochemical characteristics and x-ray crystal structure of acetato(5, 10, 15, 20-tetraparatolylporphyrinato) iron(III)

Abstract Carboxylatoiron(III) porphyrins have been synthesised by the action of carboxylic acids on the [(por)Fe]2O dimers. 1H NMR and ESR data of the isolated products are in accordance with pentacoordinate high spin 5/2 ferric complexes, the iron atom being displaced out of the plane of the porphyrin ligand. IR spectra show ν(CO) and ν(CO) bands separated by 356–409 cm−1. The magnitude of this separation suggests coordination between the metal centre and the carboxylate group via one oxygen atom. Magnetic susceptibility measurements from 5 to 120 K lead to the value of μ = 5.88 B.M.. The X-ray structure of acetato (5, 10, 15, 20-tetra p-tolyporphyrinato) iron(III) confirms the above deductions. (tp MePP) Fe(CO2CH3). 0.5 CH3COOH crystallises in the I2/c space group with unit cell parameters a = 24.464(8), b = 9.332(3), c = 37.174(4) A, β = 90.49(2)°, V = 8485 A3, Dc = 1.27 g · cm−3 and Z = 8. The crystal structure was refined to a conventional R(F) = 0.0584 and Rw(F) = 0.0653 for 5132 unique reflections with F0 > 3σ(F0). The iron atom is pentacoordinated by the four nitrogen atoms and one oxygen atom of the acetate group. It lies at 0.520(1) A out of the porphinato plane and 0.485(1) A out of the four nitrogen plane. The FeO bond length is 1.898(4) A.

Complexes organometalliques a liaisons metal—metal : XIII. Preparation de clusters heterotetrametalliques platine—molybdene et platine—tungstene et structure cristalline de Pt2Mo2(η5-C5H5)2(CO)6[P(C2H5)3]2

Abstract The cluster compounds Pt2M2(η5-C5H5)2(CO)6L2 (M  Mo, W; L  PEt3, PPh3) have been prepared from cis-PtCl2L2 and NaM(CO)3Cp. They are characterized by a planar, triangular, centrosymmetric arrangement of the metal atoms and by strongly asymmetric carbonyl bridges, which is shown by the crystal structure determination of Pt2Mo2(η5-C5H5)2(CO)6(PEt3)2.

Problems de stereochimie dynamique en serie du titanocene ☆: II. Stereochimie dynamique de reactions déchange de ligands σ-lies

Two ligand exchange reactions at the titanium atom in quasi-tetrahedral titanocene complexes have been studied. The first is substitution of a Cl ligand by an aryloxy group starting from substrates η5-Cp-η5-Cp′Ti(Cl)OPh which have an planar chirality on the Cp′ ring. The second is the substitution of one of the aryloxy groups of the complexes η5-Cp-η5-Cp′Ti(OPh′)OPh by the action of HCl. In this case, the reaction is generally selective and has a high degree of stereo-specificity with retention at the titanium atom. This retention has been established by crystallographic analysis of two suitable substrates: diastereoisomer F. 171°C of η5-C5H5[η5-(1-Me-3-CHMe2C5H5)](2-ClC6H4O)(2,6-Me2C6H3O)Ti and diastereoisomer F. 134°C of η5-C5H5[η5-(1-Me-3-CHMe2C5H3)](2-ClC6H4O)TiCl.

Recherche d'une description structurale des de´compositions endothermique Solide 1 → Solide 2 + gaz. I. Structure cristalline de l'oxalate de baryum 2BaC2O4, H2O

Abstract 2BaC 2 O 4 · H 2 O ( M = 468.73) is triclinic, space group P 1, with a = 9.312(1) A˚, b = 9.649(1) A˚, c = 6.188(1) A˚, α = 90.13(2)°, β = 95.36(2)°, γ = 125.18(2)°, Z = 2, D m = 3.48; C x = 3.51g · cm −3 . The position of the Ba atom was determined from a Patterson function. A subsequent Fourier synthesis clearly revealed the position of all C and O atoms in the structure. Refinement of the MoKα diffractometer data by a least-squares method using full matrix gave R = 0.065. The structure presents two remarkable characteristics: (a) We distinguish two types of (C 2 O 4 ) 2− ions. The first are planar, the second are notably separated from the plane configuration (deviation = 30°); this deformation is of a steric origin. (b) The water molecules are located in channels parallel to [001]. They enter in the coordination of one of the Ba 2+ ions but do not exchange any strong hydrogen bond with oxygen atoms which surround them.

Structure cristalline des deux éthylphényl-o-méthylbenchrotrényl méthanols

Abstract The crystalline structure of the two diastereomeric ethyl-phenyl-o-methylbenchrotrenylmethanols (racemic forms) have been determined by X-ray diffraction in support of the discussion on asymmetric induction presented in J. Organometal. Chem, 59 (1973) 267.

Pseudoasymetrie dans la serie du benchrotrene II. Structure cristalline de la forme pseudoasymetrique F 144° des glycols ortho-substitutes (OC)3CrC6H4(CHOHCH3)2 ☆

Abstract The crystalline structure of one of the pseudoasymmetric forms of the benchrotrenic glycols 1,2-(CHOHCH 3 ) 2 C 6 H 4 Cr(CO) 3 (m.p. 144° C) has been determined by X-ray diffraction to provide a complete identification of these isomeric glycols.

Synthesis of niobium(V) porphyrinates. Crystal structures of tri-µ-oxo-bis[5,10,15,20-tetraphenylporphyrinatoniobium(V)] and acetato-oxo-(5,10,15,20-tetraphenylporphyrinato)niobium(V)–acetic acid (1/1)

The action of NbCl5 on a porphyrin (H2L) followed by hydrolysis leads to a complex [(NbL)2O3]. When treated with acetic acid this complex in turn yields a metalloporphyrin of general formula [NbL(O)(O2CMe)]·xMeCO2H. The crystal structures of [{Nb(tpp)}2O3]·4C2H4Cl2(1b) and [Nb(tpp)O(O2CMe)]·MeCO2H (2b)(tpp is the dianion of 5,10,15,20-tetraphenylporphyrin) have been solved by X-ray diffraction methods. Crystals of (2b) are triclinic, space group P, with a= 16.645(6), b= 11.332(4), c= 11.868(4)A, α= 105.93(6), β= 100.54(4), γ= 105.05(4)°, and Z= 2. Crystals of (1b) are orthorhombic, space group Pccn, with a= 31.802(9), b= 11.595(5), c= 23.431 (7)A, and Z= 4. Both structures have been determined from diffractometer data by direct and Fourier methods and refined by full-matrix least-squares calculations to R 0.053 for (2b)(4 038 reflections) and R 0.076 for (1b)(1 555 reflections). In both complexes the niobium atom is seven-co-ordinated by the four nitrogen atoms of the porphyrin and by three oxygen atoms; the co-ordination polyhedron is of the 4 : 3 type and the niobium atom lies 1.00(1) and 0.99(2)A respectively from the 4 N plane of (2b) and (1b). A comparative study with [{Nb(tpp)}2O3]·CHCl3 is made. A high-resolution n.m.r. study of both complexes shows the anisochrony of the methylenic protons of [{Nb(oep)}2O3] and [Nb(oep)O(O2CMe)]·MeCO2H induced by the out-of-plane position of the metal atom.

Dynamic stereochemistry of ligand substitution in quasi-tetrahedral complexes of bis(η-cyclopentadienyl)titanium. Stereospecific reaction at titanium with retention of configuration, and X-ray structures of [(η5-C5H5)(η5-1-Me,3-Pri-C5H3)(2-ClC6H4O)ClTi] and [(η5-C5H5)(η5-1-Me, 3-Pri-C5H3)(2-ClC6H4O)(2,6-Me2C6H3O)Ti]

Substitution of an OR group by a Cl ligand by the action of HCl on quasi-tetrahedral bis-cyclopentadienyltitanium complexes of the type [(cp)(cp′)Ti(OR1)(OR2)] is a stereospecific process which occurs with retention of configuration at titanium; the X-ray crystal structures of chloro- and 2,6-dimethylphenoxy-(2-chlorophenyl)-(η5-cyclopentadienyl)-(η5-1-methyl-3-isopropylcyclopentadienyl)titanium are reported.