Cyano Derivatives of Bis(cyclopentadienyl)titanium(IV). The crystal and molecular structure of μ-Oxo-bis[bis(cyclopentadienyl)cyanotitanium(IV)], [(η5-C5H5)2TiCN]2O

By the reaction of KCN with Cp₂TiCl₂ (Cp = η⁵-C₅H₅) in boiling methanol, bis(cyclopentadienyl)-methoxytitanium(IV) cyanide, Cp₂Ti(OCH₃)CN, is formed which in air is converted into the dinuclear oxygen-bridged derivative (Cp₂TiCN)₂O. By the same procedure, the bis(methylcyclopentadienyl) analogue [MeCp₂TiCN]₂O has been obtained. An X-ray diffraction study of (Cp₂TiCN)₂O has shown that the CN group acts as a unidentate ligand with a Ti? C bond length of 2.158 Å and a Ti? C? N bond angle of 177.7°, very close to linearity. The Ti? O bond distance, 1.836 Å, and the bond angle at the bridging O atom, 174.1°, are normal. The ligands are arranged in a nearly tetrahedral way around the Ti atoms. The structural results are compared to those for similar dinuclear titanium complexes.     

Structure of Methanol Solvated Iodozinc(II) Complexes in Solution

The structures of the solvated zinc ion and the solvated zinc–iodide complexes in methanol solution have been determined by EXAFS. The zinc ion is six-coordinated in an octahedral fashion with a mean Zn–O bond distance of 2.071(4) Å. According to the stability constants of the zinc–iodide system in methanol solution the first complex, ZnI⁺, is suppressed, which may indicate that a coordination change takes place at this step. On the other hand, the second complex, ZnI₂, predominates at excess of iodide. The methanol solvated ZnI₂ complex has a tetrahedral structure with mean Zn–I and Zn–O bond distances of 2.55(1) and 1.99(1) Å, respectively. The mean Zn–I bond distance in a solution containing a maximal content of ZnI⁺, ca. 12%, strongly indicates that the first complex also has a tetrahedral structure.     

Darstellung und Struktur neuer Calix[4]aren-Titan(IV)-Imidokomplexe

Synthesis and Structure of New Calix[4]arene Titanium(IV) Imido Complexes The syntheses of the novel calix[4]arene titanium imido compounds [Cax(OMe)₂O₂Ti(NR)] ( 2 ) (R = tBu) and ( 3 ) (R = Mes = 2,4,6-trimethylphenyl) (Cax = C₄₄H₅₂) starting from [Cax(OMe)₂O₂TiCl₂] ( 1 ) and lithium amides LiNHR are described. Complexes 2 and 3 are mononuclear compounds in solution. An X-ray crystal structure analysis of the toluene adduct of 3 (Space group: P 1, lattice dimensions: a = 12.979(2) Å, b = 13.707(2) Å, c = 16.573(3) Å, α = 81.751(11)°, β = 80.555(13)°, γ = 73.541(12)°) reveals that this compound is mononuclear in the solid state. The central atom in 3 is distorted trigonal bipyramidal ligated by two ether oxygen atoms in axial positions, two phenoxide oxygen atoms in the equatorial plane, and an imido nitrogen atom in an equatorial position. The titanium nitrogen bond distance in 3 is 171.8(3) pm.     

Synthesis and Characterizations of Ti(O‐i‐Pr)Cl3(THF)(PhCOR) (R = H,Me, Ph) and Ti(O‐i‐Pr)Cl3(PhCOR)2 (R = Me,Ph). The Molecular Structure of Ti(O‐i‐Pr)Cl3(PhCOPh)2

A series of titanium(IV) complexes Ti(O‐i‐Pr)Cl₃(THF)(PhCOR) (R = H ( 1 ), CH₃ ( 2 ), or Ph ( 3 )) is prepared quantitatively from reactions of [Ti(O‐i‐Pr)Cl₂(THF)(μ‐Cl)]₂ with 2 molar equiv. PhCOR. Treatment of Ti(O‐i‐Pr)Cl₃ with 2 molar equiv. of PhCOR affords the disubstituted complexes Ti(O‐i‐Pr)Cl₃(PhCOR)₂ (R = CH₃ ( 4 ) or Ph ( 5 )). The ¹³C NMR study of these complexes shows that the relative bonding abilities are in the order of PhCOCH₃ > PhCHO > PhCOPh. The molecular structure of 5 reveals that one of the benzophenone ligands is trans to the strongest 2‐propoxide ligand with a long Ti‐O(carbonyl) distance of 2.193(5) Å which is much longer than the other Ti‐O(carbonyl) distance of 2.097(4) Å by ?0.1 Å. All ligands cis to the alkoxide ligand are bending away from the alkoxide ligand with the RO‐Ti‐L angles ranging from 93.6(2) to 99.0(2)°.     

Ein Titan(IV)-Komplex mit zwei koordinativ gebundenen Wassermolekülen: [(π-C5H5)2 Ti(H2O)2](NO3)2

A Titanium (IV) Complex with Two Coordinatively Bonded Water Molecules: [(π-C₅H₅)₂Ti(H₂O)₂](NO₃)₂ (π-C₅H₅)₂Ti(NO₃)₂ and H₂O react in acetone to form the diaquo complex [(π-C₅H₅)₂-Ti(H₂O)₂](NO₃)₂ ( A ). An X-ray analysis shows the titanium atom to be nearly tetrahedrally coordinated. Mean values of distances: Ti? O 2.01 Å, Ti? Z 2.03 Å (Z = center of ring); angles: O? Ti? O 92.7°, Z? Ti? Z 133.6°. Anions and cations are joined by hydrogen bonds to form strands that run in the direction of the crystallographic a axis. A crystallizes in the orthorhombic space group Pnma with Z = 4 and lattice parameters at ? 100°C a = 7.601(2), b = 13.458(4) and c = 13.139(4) Å.     

Die Kristallstruktur eines dinuklearen Peroxotitan(IV)-nitrilotriacetatkomplexes

Crystal Structure of a Dinuclear Peroxotitanium(IV)-Nitrilotriacetate Complex The structures of four peroxotitanium(IV) dipicolinates, with colours ranging from deep red to yellow orange, have been reported earlier, and a correlation between their colours and the variations of certain bond lengths has been proposed. This paper describes the pale yellow dinuclear peroxotitanium nitrilotriacetate complex Na₄[Ti₂O₅(C₆H₆O₆N)₂]11 H₂O. The monoclinic structure, space group B2/b, contains 25 independent non-hydrogen atoms and 17 hydrogen atoms. It has been determined from diffractometer data and refined to R = 3.2%. Titanium is again coordinated approximately pentagonal-bipyramidally. The μ-oxygen bridge occupies an axial position. The short (1.819 Å), nearly linear Ti–O–Ti bonds show double bond character. The titaniumperoxide bonds, however, are relatively long, thus confirming the rule proposed before: the more basic the axial ligands, the higher is the frequency of the absorption band, the longer are the Ti-peroxide bonds and the shorter are the axial distances. This is confirmed by electron density maps, which are to be discussed elsewhere in detail, showing bent Ti-peroxide bonds enclosing an angle of about 70° and a strong electron bridge on the μ-oxygen bond. Hydrogen bonding and the packing of the complexes is discussed.     

Synthesis and Crystal Structure of Bis(methyltriphenylphosphonium) Hexabromotellurate(IV)‐bis{dibromoselenate(II)}, [PMePh3]2[TeBr6(SeBr2)2], the Salt of a Mixed‐valence Bromotellurate(IV)‐Selenate(II) Anion

Brown crystals of [PMePh₃]₂[TeBr₆(SeBr₂)₂] ( 1 ) were obtained when selenium and bromine (1:1) react in acetonitrile solution in the presence of tellurium(IV) bromide and methyltriphenylphosphonium bromide. The salt 1 crystallizes in the triclinic space group P1¯ with the cell dimensions a = 10.3630(14)Å, b = 11.5140(12)Å, c = 11.7605(17)Å, α = 108.643(9)°, β = 106.171(10)° and γ = 99.077(9)° (296 K). In the solid state the [TeBr₆(SeBr₂)₂]^2— anion contains a nearly regular [TeBr₆] octahedron where the four equatorial bromo ligands each have developed a bond to the Se^II atom of a SeBr₂ molecule. The contacts between the bridging bromo and the Se^II atoms of the SeBr₂ molecules are observed in the range 3.11—3.21Å, and can be interpreted as bonds of the donor‐acceptor type with the bridging bromo ligands as donors and the SeBr₂ molecules as acceptors. The Te^IV—Br distances are in the range 2.67—2.72Å, and the Se^II—Br bond lengths in coordinated SeBr₂ molecules in the range 2.33—2.34Å.     

A new dinuclear Ti(IV)-peroxo-citrate complex from aqueous solutions. Synthetic,structural, and spectroscopic studies in relevance to aqueous titanium(IV)-peroxo-citrate speciation

The wide use of titanium in applied materials has prompted pertinent studies targeting the requisite chemistry of that metal's biological interactions. In order to understand such interactions as well as the requisite titanium aqueous speciation, we launched investigations on the synthesis and spectroscopic and structural characterization of Ti(IV) species with the physiological citric acid. Aqueous reactions of TiCl(4) with citric acid in the presence of H(2)O(2) and neutralizing ammonia afforded expediently the red crystalline material (NH(4))(4)[Ti(2)(O(2))(2)(C(6)H(4)O(7))(2)].2H(2)O (1). Complex 1 was further characterized by UV-vis, FT-IR, FT- and laser-Raman, NMR, and finally by X-ray crystallography. Compound 1 crystallizes in the monoclinic space group P2(1)/n, with a = 10.360(4) A, b = 10.226(4) A, c = 11.478(6) A, beta = 107.99(2) degrees, V = 1156.6(9) A(3), and Z = 2. The X-ray structure of 1 reveals a dinuclear anionic complex containing a Ti(IV)(2)O(2) core. In that central unit, two fully deprotonated citrate ligands are coordinated to the metal ions through their carboxylate moieties in a monodentate fashion. The central alkoxides serve as bridges to the two titanium ions. Also attached to the Ti(IV)(2)O(2) core are two peroxo ligands each bound in a side-on fashion to the respective metal ions. NH(4)(+) ions neutralize the 4- charge of the anion in 1, further contributing to the stability of the derived lattice through H-bond formation. The structural similarities and differences with congener vanadium(V)-peroxo-citrate complexes may point out potential implications in the chemistry of titanium with physiological ligands, when the former is present in a biologically relevant medium.     

Cobalt(II) complex with 4,4,4-trifluoro-1-thienylbutane-1,3-dione and dimethyl sulfoxide: Molecular and crystal structures

The crystal structure of a cobalt(II) complex with 4,4,4-trifluoro-1-thienylbutane-1,3-dione (Tfa) and dimethyl sulfoxide (DMSO) was determined using X-ray diffraction. The crystals are monoclinic: a = 7.590(3) Å, b = 17.996(8) Å, c = 10.440(4) Å, β = 106.263(8)°, V = 1368.9(10) ų, space group P2 ₁, Z = 2, ρ_calcd = 1.595 g/cm³, R = 0.0364. The coordination polyhedron of the cobalt atom is an octahedron made up of four O atoms of two Tfa ligands and two O atoms of two DMSO molecules. The deviation of the cobalt atom from the plane of 4O(Tfa) is 0.037 Å. The average Co-O(DMSO) and Co-O(Tfa) bond lengths are 2.122 and 2.052 Å, respectively.     

Chloroheptakis(dimethyl sulfoxide)­uranium(IV) trichloride

In the title complex, [UCl(C₂H₆OS)₇]Cl₃, the uranium metal center is coordinated in a distorted bicapped trigonal prism geometry by seven O atoms from di­methyl sulfoxide ligands and by a terminal chloride ligand. Charge balance is maintained by three outer‐sphere chloride ions per uranium(IV) metal center. Principle bond lengths include U—O 2.391 (2)–2.315 (2) Å, U—Cl 2.7207 (9) Å, and average S—O 1.540 (5) Å.     

Structure of the hydrated, hydrolysed and solvated zirconium(IV) and hafnium(IV) ions in water and aprotic oxygen donor solvents. A crystallographic, EXAFS spectroscopic and large angle X-ray scattering study

The tetrameric hydrolysis products of zirconium(IV) and hafnium(IV), the zirconyl(IV) and hafnyl(IV) ions, [M(4)(OH)(8)(OH(2))(16)(8+)], often labelled MO(2+).5H(2)O, are in principle the only zirconium(IV) and hafnium(IV) species present in aqueous solution without stabilising ligands and pH larger than zero. These complexes are furthermore kinetically very stable and do not become protonated even after refluxing in concentrated acid for at least a week. The structures of these complexes have been determined in both solid state and aqueous solution by means of crystallography, EXAFS and large angle X-ray scattering (LAXS). Each metal ion in the [M(4)(OH)(8)(OH(2))(16)](8+) complex binds four hydroxide ions in double hydroxo bridges, and four water molecules terminally. The M-O bond distance to the hydroxide ions are markedly shorter, ca. 0.12 A, than to the water molecules. The hydrated zirconium(IV) and hafnium(IV) ions only exist in extremely acidic aqueous solution due to their very strong tendency to hydrolyse. The structure of the hydrated zirconium(IV) and hafnium(IV) ions has been determined in concentrated aqueous perchloric acid by means of EXAFS, with both ions being eight-coordinated, most probably in square antiprismatic fashion, with mean Zr-O and Hf-O bond distances of 2.187(3) and 2.160(12) A, respectively. The dimethyl sulfoxide solvated zirconium(IV) and hafnium(IV) ions are square antiprismatic in both solid state and solution, with mean Zr-O and Hf-O bond distances of 2.193(1) and 2.181(6) A, respectively, in the solid state. Hafnium(IV) chloride does not dissociate in N,N'-dimethylpropyleneurea, dmpu, a solvent with good solvating properties but with a somewhat lower permittivity (epsilon= 36.1) than dimethyl sulfoxide (epsilon= 46.4), and an octahedral HfCl(4)(dmpu)(2) complex is formed.     

The crystal and molecular structure of hexadecaphenyloctasiloxyspiro(9,9)titanate(IV)

The crystal and molecular structures of the title compound have been determined by single crystal X-ray diffraction methods. In the spiro molecule, the metal atom has a geometry very close to tetrahedral, with OTiO angles of 107.9–111.0(2)° and very short TiO bonds of length 1.777–1.791(5)Å. The two TiO₅Si₄ rings have different, ill-defined conformations; the SiO bond lengths and SiOSi angles are similar to those in (SiO)_n rings.     

Mononuclear titanium(IV)-citrate complexes from aqueous solutions: pH-specific synthesis and structural and spectroscopic studies in relevance to aqueous titanium(IV)-citrate speciation

Titanium is a metal frequently employed in a plethora of materials supporting medical applications. In an effort to comprehend the involvement of titanium in requisite biological interactions with physiological ligands, synthetic efforts were launched targeting aqueous soluble species of Ti(IV). To this end, aqueous reactions of TiCl(4) with citric acid afforded expediently, under pH-specific conditions, the colorless crystalline materials Na(6)[Ti(C(6)H(4.5)O(7))(2)(C(6)H(5)O(7))].16H(2)O (1) and Na(3)(NH(4))(3)[Ti(C(6)H(4.5)O(7))(2)(C(6)H(5)O(7))].9H(2)O (2). Complexes 1 and 2 were characterized by elemental analysis, FT-IR, (13)C-MAS solid state and solution NMR, cyclic voltammetry, and X-ray crystallography. 1 crystallizes in the triclinic space group P, with a = 15.511(9) A, b = 15.58(1) A, c = 9.848(5) A, alpha = 85.35(2) degrees, beta = 76.53(2) degrees, gamma = 61.97(2) degrees, V = 2042(2) A(3), and Z = 2. 2 crystallizes in the triclinic space group P, with a = 12.437(5) A, b = 12.440(5) A, c = 12.041(5) A, alpha = 83.08(2) degrees, beta = 81.43(2) degrees, gamma = 67.45(2) degrees, V = 1697(2) A(3), and Z = 2. The X-ray structures of 1 and 2 reveal the presence of a mononuclear complex, with Ti(IV) coordinated to three citrate ligands in a distorted octahedral geometry around Ti(IV). The citrates employ their central alkoxide and carboxylate groups to bind Ti(V), while the terminal carboxylates stay away from the Ti(IV)O(6) core. Worth noting in 1 and 2 is the similar mode of coordination but variable degree of protonation of the bound citrates, with the locus of (de)protonation being the noncoordinating terminal carboxylates. As a result, this work suggests the presence of a number of different Ti(IV)-citrate species of the same nuclearity and coordination geometry as a function of pH. This is consistent with the so far existing pool of mononuclear Ti(IV)-citrate species and provides a logical account of the aqueous speciation in the requisite binary system. Such information is vital in trying to delineate the interactions of soluble and bioavailable Ti(IV) forms promoting biological interactions in humans. To this end, chemical properties, structural attributes, and speciation links to potential ensuing biological effects are dwelled on.     

X-ray diffraction structural investigation of two hafnium(IV) complexes with dipivaloylmethane

Synthesis and single crystal X-ray diffraction study of hafnium(IV) dipivaloylmethanate Hf(dpm)₄ and chloro-tris-(dipivaloylmethanato)hafnium(IV) Hf(dpm)₃Cl have been carried out. Crystal data: a = 22.6606(5) Å, b = 11.3990(4) Å, c = 19.8513(7) Å, β = 106.458(1)°, Pc, Z = 4, d _calc = 1.231 g/cm³, R = 0.075 for C₄₄H₇₆HfO₈; a = 10.6376(13) Å, b = 10.6701(10) Å, c = 19.4400(22) Å, α = 74.970(3)°, β = 75.672(3)°, γ = 61.725(2)°, P-1, Z = 2, d _calc = 1.366 g/cm³, R = 0.031 for C₃₃H₅₇ClHfO₆. The structures are molecular and are built from discrete mononuclear complexes joined by van der Waals interactions. Disordering of carbon atoms preserving at low temperature is observed for the compound Hf(dpm)₄. It has been found out that the structure contains two crystallographically unique complexes of hafnium(IV) with central atoms coordinated with eight oxygen atoms of four dipivaloylmethane ligands, bond lengths Hf-O fall within 2.084–2.222 Å, the distances Hf...Hf between the molecules are 10.07–13.87 Å. In Hf(dpm)₃Cl the hafnium atom is seven-coordinated with six oxygen atoms of three β-diketonate ligands and one chlorine atom, the distances Hf-O fall within 2.087–2.179 Å, the lengths of the bond Hf-Cl for two crystallographically independent molecules Hf(1) and Hf(2) are 2.466 Å and 2.442 Å, respectively.     

Crystal structure of oxotitanium(IV) 2,2,6,6-tetramethyl-3,5-heptanedionate

The structure of titanyl dipivalylmethanate TiO(dpm)₂ has been studied by X-ray diffraction analysis. The compound has a molecular structure formed by isolated centrosymmetrical dimers [TiO(dpm)₂]₂; the unit cell contains two structurally related, crystallographically unique binuclear molecules. The Ti...Ti distance in the dimer is 2.73 Å. Crystal data for Ti₂C₃₆H₇₆O₁₀: a = 32.477(6) Å, b = 14.409(3) Å, c = 25.630(5) Å; β = 107.82(3)°, space group C2/c, Z = 8, d _calc = 1.002 g/cm³.     

Synthesis, structural elucidation and X-ray analysis of triphenyltin(IV) [2-(2,3-dimethylanilino)nicotinate]

Triphenyltin(IV) [2-(2,3-dimethylanilino)nicotinate] was prepared by the interaction of triphenyltin(IV) hydroxide and 2-(2,3-dimethylanilino)nicotinic acid in 1:1 ratio. This compound was characterized by elemental analyses, IR, multinuclear NMR spectroscopy (¹H and ¹³C) and mass spectrometry. The structure of title compound was confirmed by single crystal X-ray crystallography. The coordination around the tin atom was studied both in solution and solid state. The geometry around tin is trigonal bipyramidal in solid state while it is tetrahedral in solution. The compound belongs to Monoclinic system, having space group P 21/c with unit cell dimensions a = 17.002(8) Å, b = 9.0793(3) Å, c = 18.2616(9) Å, α = 90 (°) β = 107.381(4) (°), γ = 90 (°).     

Tris(dimethylamido)bis(dimethylamine)titanium(IV) chloridobis(dimethylamine)[tris(pentafluorophenyl)boron–amido][tris(pentafluorophenyl)boron–nitrido]titanate(IV) toluene solvate

The title ionic solid, [Ti(C₂H₆N)₃(C₂H₇N)₂][Ti(C₁₈BF₁₅N)(C₁₈H₂BF₁₅N)Cl(C₂H₇N)₂]·C₇H₈, (I), comprises a cation with three dimethylamide ligands in the equatorial plane and two dimethylamine ligands positioned axially in a trigonal–bipyramidal geometry about the central Ti^IV atom. The anion has a highly distorted octahedral structure. The two dimethylamine ligands are coordinated mutually trans. The chloride is trans to the tris(pentafluorophenyl)boron–amide, while the sixth coordination site is occupied by an ortho‐F atom of the tris(pentafluorophenyl)boron–amide group in a trans disposition with respect to the tris(pentafluorophenyl)boron–nitride ligand. The most significant feature of the anion is the presence of an unprecedented terminal Ti[triple‐bond]N moiety [1.665 (2) Å], stabilized by coordination to B(C₆F₅)₃, with a Ti[triple‐bond]N—B angle of 169.50 (19)°.     

Imido Derivatives of Titanium (IV)

Reactions of titanium(IV) isopropoxide with acetamide, benzamide, and nicotinamide in different stoichiometric ratios in anhydrous benzene yielded imido derivatives of type (PrⁱO)_4-nTi(NHOCR)_n where n = 1, 2, 3, and 4; R = CH₃, C₆H₅, and C₅H₄N. All these complexes are insoluble in common organic solvents suggesting their polymeric nature. All these derivatives, with the exception of three which have characteristic melting points, did not sublime at 250°C in vacuo nor did they appear to decompose appreciably below 300°C. I.R. spectra of these derivatives are discussed.     

Cerium(III/IV) and Cerium(IV)–Titanium(IV) Citric Complexes Prepared in Ethylene Glycol Medium

Summary. Cerium(III/IV) and Ce(IV)–Ti(IV) citric complexes were synthesized in ethylene glycol medium under conditions similar to those of the polymerized complex method (PCM). Solution phase ¹H, ¹³C NMR, solid state ¹³C CP MAS NMR and IR spectroscopy, and X-ray powder diffractometry were used to characterize the composition and structure of the synthesized products. Thermal decomposition of the isolated complexes was studied and a scheme of the processes taking place is proposed. Complexes of Ce(III) can be prepared at low temperature (40°C), only. In the presence of Ti(IV) ions, the oxidation takes place even at this temperature. A mixed-metal nature of the Ce(IV)–Ti(IV) complexes is established. The comparison between their composition and the one of analogous lanthanide(III)–Ti(IV) citrates contributes to the elucidation of the complexation process mechanism in the case of the PCM application. The increased charge of the complexation agent in the Ce⁴⁺–Ti⁴⁺ complex (in comparison with Ln ³⁺–Ti⁴⁺ citrates) is “compensated” by the increase of the relative number of the ligands with deprotonated OH group.     

Synthesis and molecular structures of some new titanium(IV) aryloxides.

The coordination chemistry of model phenolic ligands (pyrocatechol, salicylic acid, and 2,2'-biphenol) that are able to form respectively five-, six-, or seven-membered rings with titanium(IV) alkoxides is investigated. With pyrocatechol, a polynuclear complex containing 10 Ti atoms was characterized with a not very common doubly bridging mu3-(O,O,O',O') coordination mode. With salicylic acid, a monomeric tris(chelate) complex was obtained. With 2,2'-biphenol, a polynuclear complex containing six Ti atoms was obtained showing both mu2-(O,O') and mu2-(O,O,O') coordination modes for the ligands. Intermolecular interactions in the solid state for these three new compounds are also quantitatively discussed using the partial charge model.