Silylmethyl and related complexes II. Preparation,spectra, and thermolysis of the tetraneopentyls of titanium,zirconium, and hafnium

The preparation and characterisation of the Group IVA neopentyls (Me₃CCH₂)₄M (M = Ti, Zr, or Hf) is described. Spectroscopic data (IR, Raman, mass, ¹H NMR, and PE) are provided; IR and Raman bands have been assigned by comparison with results on Group IVB analogues (M = Ge or Sn). MC₄ stretching vibrations fall in the range 540–485 cm^?1, and bending modes at 240–283 cm^?1. Thermal decomposition gives neopentane as the sole detectable product; qualitatively, stability increases in the order M = Ti < Zr < Hf and for R₄M : R = Me ? Me₃CCH₂ ≈ Me₃SiCH₂. (Me₃CCH₂)₄Ti is aerobically oxidised in benzene to give (Me₃CCH₂O)₄Ti     

Synthesis, characterization, and materials chemistry of Group 4 silylimides

This paper focuses on the development of potential single source precursors for M-N-Si (M = Ti, Zr or Hf) thin films. The titanium, zirconium, and hafnium silylimides (Me(2)N)(2)MNSiR(1)R(2)R(3) [R(1) = R(2) = R(3) = Ph, M = Ti(1), Zr (2), Hf (3); R(1) = R(2) = R(3) = Et, M = Ti (4), Zr (5), Hf (6); R(1) = R(2) = Me, R(3) = (t)Bu, M = Ti (7), Zr (8), Hf (9); R(1) = R(2) = R(3) = NMe(2), M = Ti (10), Zr (11), Hf (12)] have been synthesized by the reaction of M(NMe(2))(4) and R(3)R(2)R(1)SiNH(2). All compounds are notably sensitive to air and moisture. Compounds 1, 2, 4, and 7-10 have been structurally characterized, and all are dimeric, with the general formula [M(NMe(2))(2)(μ-NSiR(3))](2), in which the μ(2)-NSiR(3) groups bridges two four-coordinate metal centers. The hafnium compound 3 possesses the same basic dimeric structure but shows additional incorporation of liberated HNMe(2) bonded to one metal. Compounds 11 and 12 are also both dimeric but also incorporate additional μ(2)-NMe(2) groups, which bridge Si and either Zr or Hf metal centers in the solid state. The Zr and Hf metal centers are both five-coordinated in these species. Aerosol-assisted CVD (AA-CVD) using 4-7 and 9-12 as precursors generates amorphous films containing M, N, Si, C, and O; the films are dominated by MO(2) with smaller contributions from MN, MC and MSiON based on XPS binding energies.     

Catenated polysulfur ligands: the pentasulfides of di-η5-cyclopentadienyl-zirconium(IV) and -hafnium(IV)

The thiols Cp₂M(SH)₂, where M = Ti and Zr, react to form the complexes Cp₂MS₅ when treated with mono- and di-sulfur transfer reagents. Treatment of Cp₂MCl₂ with Li₂S₂ and sulfur gave Cp₂MS₅, M = Ti, Zr and Hf, in better yield. The new Zr and Hf complexes have a six-membered MS₅ ring in a chair conformation similar to the previously observed for M = Ti. Variable temperature NMR studies show that the barriers to MS₅ ring inversion decrease in the order Ti > Hf > Zr.     

Tetramethyldisilan-1,2-diyl-verbrückte Dicyclopentadienyl-und Diindenylmetalldichloride der 4. Gruppe – Kristallstruktur von

Tetramethyldisilane-1,2-diyl bridged Dicyclopentadienyl and Diindenyl Metal Dichlorides of the Group 4 Metals – Crystal Structure of Dicyclopentadienyl and diindenyl metal dichlorides of the type Cp′? SiMe₂SiMe₂? Cp′MCl₂ (Cp′ = C₅H₄, M = Ti ( 1 ), Zr ( 2 ), Hf ( 3 ); Cp′ = C₉H₇, M = Zr ( 4 ), Hf ( 5 )) were synthesized and characterized by means of their ¹H, ¹³C, ²⁹Si-n.m.r., MS, and IR spectra. The crystal structure of 2 was determined.     

立体化学刚性的七配位环戊二烯基三(二苄基二硫代氨基甲酸)钛、锆、铪配合物的合成和性质

二烷基二硫代氨基甲酸基作为良好的双齿配体较易与过渡金属生成高配位的配合物,含有环戊二烯基的高配位钛、锆、铪配合物的研究相继出现^[1-5],这类七配位、18-电子构型的配合物是立体化学刚性,具有独特的光谱性质和结构行为。选择钛、锆和铪二茂二氯化物与三当量的二苄基二硫代氨基甲酸钠反应合成了五种未见报道的七配位配合物,讨论了产物的光谱性质和配位结构。     

Fluoride mit zweiwertigem Silber. Zur Kenntnis der Verbindungen AgII[MF6] mit M = Ge,Sn, Pb,Ti, Zr,Hf, Rh,Pd, Pt.

Fluorides with divalent Silver. On the compounds Ag^II[MF₆] with M = Ge, Sn, Pb, Ti, Zr, Hf, Rh, Pd, Pt. For the first time AgTiF₆, AgGeF₆, AgSnF₆ AgPbF₆ (all light-blue), AgRhF₆ (black), AgPdF₆ (d.brown), AgPtF₆ (brownviolet) as well as AgZrF₆ and AgHfF₆ (both deeply blueviolet) are prepared. AgSnF₆, AgPbF₆ and AgPdF₆ obey the Curie-Weiss Law (m? = 2,0 m?_B, small θ-value). In the case of AgZrF₆ and AgHfF₆ there is a strong magnetic exchange between Ag²⁺ ions; this may be the cause for the unexpected deep colour.     

Chemical bonding in “early–late” transition metal complexes [(H2N)3M–M′(CO)4] (M = Ti, Zr, Hf; M′ = Co, Rh, Ir)

Quantum chemical DFT calculations at the BP86/TZ2P level have been carried out for the complex [HSi(SiH₂NH)₃Ti–Co(CO)₄], which is a model for the experimentally observed compound [MeSi{SiMe₂N(4-MeC₆H₄)}₃Ti–Co(CO)₄] and for the series of model systems [(H₂N)₃M–M′(CO)₄] (M = Ti, Zr, Hf; M′ = Co, Rh, Ir). The Ti–Co bond in [HSi(SiH₂NH)₃Ti–Co(CO)₄] has a theoretically predicted BDE of D _e = 59.3 kcal/mol. The bonding analysis suggests that the titanium atom carries a large positive charge, while the cobalt atom is nearly neutral. The covalent and electrostatic contributions to the Ti–Co attraction have similar strength. The Ti–Co bond can be classified as a polar single bond, which has only little π contribution. Calculations of the model compound (H₂N)₃Ti–Co(CO)₄ show that the rotation of the amino groups has a very large influence on the length and on the strength of the Ti–Co bond. The M–M′ bond in the series [(H₂N)₃M–M′(CO)₄] becomes clearly stronger with Ti < Zr < Hf, while the differences between the bond strengths due to change of the atoms M′ are much smaller. The strongest M–M′ bond is predicted for [(H₂N)₃Hf–Ir(CO)₄].     

Die Reaktion von SeCl4 mit Übergangsmetalltetrachloriden. Synthese und Kristallstrukturen von (SeCl3)2MCl6 mit M = Zr,Hf, Mo,Re

The Reaction of SeCl₄ with Transition Metal Tetrachlorides. Synthesis and Crystal Structures of (SeCl₃)₂MCl₆ with M = Zr, Hf, Mo, Re The transition metal tetrachlorides ZrCl₄, HfCl₄ and MoCl₄ react with SeCl₄ in closed ampoules at temperatures of 140°C to (SeCl₃)₂MCl₆ (M = Zr, Hf, Mo) which are all isotypic and crystallize in the (SeCl₃)₂ReCl₆ structure type (orthorhombic, Fdd2, Z = 8, lattice constants for M = Zr: a = 1165.7(1)pm, b = 1287.2(2)pm, c = 2180.2(2)pm; for M = Hf: a = 1162.9(2)pm, b = 1285.0(2)pm, c = 2178.2(3)pm; for M = Mo: a = 1153.8(1)pm, b = 1267.7(1)pm, c = 2147.4(2)pm). The Cl^? ions form a hexagonal closest packing with one fourth of the octahedral holes filled by Se⁴⁺ and M⁴⁺ in an ordered way. The MCl₆ octahedra are regular, the SeCl₆ octahedra are distorted with 3 short and 3 long Se? Cl bonds (mean 215 pm and 287 pm). The structures can thus be regarded as built of SeCl₃⁺ and MCl₆^2? ions. Magnetic susceptibility measurements show for M = Zr the expected diamagnetic behavior, for M = Mo and Re paramagnetic behavior according to the Curie-Weiss law with magnetic moments of 2.5 B. M. for M = Mo and 3.7 B. M. for M = Re corresponding to 2 and 3 unpaired electrons respectivly.     

A cyclopentadienyl ring exchange method for the attachment of early transition metal metallocene dichlorides to a polymer support

PMR and mass spectral analysis have been used to study the interchange of π-bonded cyclopentadienyl rings with σ-bonded cyclopentadienyl rings in the compounds (C₅H₅)₄M (M = Ti, Zr, Hf, Nb, Ta, Mo and W) and (C₅H₅)₃V or a-bonded benzylcyclopentadienyl rings in the compounds (C₆H₅CH₂C₅H₄) (C₅H₅)₂MC1 (M = Ti, Zr, Hf, Nb, Ta, Mo and W). As soon as the Cp₄M species are generated (indicated by a color change), the interchange occurs and the equilibrium is established. As reported, no such interchange was observed in (C₅H₅) ₄Mo in the PMR time scale; however, it does occur after a longer time. By using this interchange behavior of the cyclopentadienyl ring, metallocene dichlorides of Ti, Zr, Hf, V, Nb, Ta, Mo and W have been attached to polystyrene-divinylbenzene beads.     

Hydridoorganostannylene Coordination: Group 4 Metallocene Dichloride Reduction in Reaction with Organodihydridostannate Anions

Organodihydridoelement anions of germanium and tin were reacted with metallocene dichlorides of Group 4 metals Ti, Zr and Hf. The germate anion [Ar*GeH₂]⁻ reacts with hafnocene dichloride under formation of the substitution product [Cp₂Hf(GeH₂Ar*)₂]. Reaction of the organodihydridostannate with metallocene dichlorides affords the reduction products [Cp₂M(SnHAr*)₂] (M=Ti, Zr, Hf). Abstraction of a hydride substituent from the titanium bis(hydridoorganostannylene) complex results in formation of cation [Cp₂M(SnAr*)(SnHAr*)]⁺ exhibiting a short Ti–Sn interaction. (Ar*=2,6-Trip₂C₆H₃, Trip=2,4,6-triisopropylphenyl).     

Homoleptic alkenyls of the early transition metals and related compounds

The first stable homoleptic alkenyls of the early transition metals, MR_n, (R = C(Ph)=CMe₂; M = Ti, Zr, Hf, n = 4; and M = Cr, n = 3) and the related species (C₅H₅)₂MR₂ (M = Ti, Zr) and (C₅H₅)₂Zr(Cl)R have been prepared using appropriate organolithium reagents. Cleavage and insertion reactions are reported for the new compounds.     

New substituted titanocene, zirconocene and hafnocene dichlorides

Summary Twentytwo new substituted metallocene Cp¹Cp²MCl₂ (M = Ti, Zr or Hf) dichlorides have been prepared and the catalytic activity of some of them in alkene polymerization has been primarily evaluated.     

Cycloaddition of tertiary amines to fullerene C<Subscript>60</Subscript>, catalyzed by Ti,Zr, and Hf complexes

Cycloaddition of various tertiary amines to fullerene C₆₀ in the presence of Cp₂MCl₂ complexes (M = Ti, Zr, Hf) in toluene at 20–150°C in 3–48 h leads to the formation of pyrrolofullerenes in high yields.     

Are cyclopentadienyl complexes more stable than their pyrrolyl analogues?

Metal-η⁵-cyclopentadienyl (M-Cp) and metal-η⁵-pyrrolyl (M-pyr) bond dissociation enthalpies in group 4 complexes were determined from DFT/B3LYP calculations with a VTZP basis set. Thermochemical cycles involving calculated enthalpies of ligand exchange reactions and experimental values of ligand electron affinities and M-Cl bond dissociation enthalpies were applied to [M(η⁵-X)Cl₃] piano stool complexes (M = Ti, Zr, Hf; X = pyr, Cp), allowing a comparative study of those metal-ligand bond strengths. The results indicate that both ligands establish weaker bonds with Ti than with the heavier elements, Zr and Hf. Very similar bond dissociation enthalpies were obtained for pyrrolyl and cyclopentadienyl (within 1 kcal mol⁻¹), suggesting that the well known difference in reactivity between those families of complexes should derive from kinetic rather than thermodynamic causes.     

A theoretical and experimental study of the electronic transport properties of the compounds Cu2MTe3 (M =Ti,Zr, Hf)

A theoretical model that involves metal nonstoichiometry is proposed to explain the unexpected electronic conductivities in the close-packed ternary tellurides Cu₂MTe₃ (M =Ti, Zr, Hf). Conductivity, thermoelectric power, and Hall effect measurements indicate that these compounds are hole carriers with a concentration of the order of 5 × 10¹⁹ cm⁻³ for M =Zr at 300 K. Such a concentration corresponds to roughly 0.4% Cu vacancies or 0.2% Zr vacancies, levels below the detection limit by X-ray diffraction methods of the corresponding elements in theM =Hf compound.     

Syntheses and Molecular Structures of [(thf)4Li] [{(thf)Li}M(C4H8)3] (M = Zr,Hf) and Their Solution Behavior

The reaction of MCl₄(thf)₂ (M = Zr, Hf) with 1,4-dilitiobutane in diethyl ether at –25 °C or at 0 °C with a molar ratio of 1 : 3 yields the homoleptic “ate” complexes [(thf)₄Li] [{(thf)Li}M(C₄H₈)₃] 1 - Zr (M = Zr) and 1 - Hf (M = Hf). The crystalline compounds form ion lattices with solvent-separated [(thf)₄Li]⁺ cations and [{(thf)Li}M(C₄H₈)₃]^– anions. The NMR spectra at –20 °C show magnetic equivalence of the M–CH₂ and of the β-CH₂ groups of the butane-1,4-diide ligands on the NMR time scale. Analogous reactions of MCl₄(thf)₂ with 1,4-dilithiobutane with a molar ratio of 1 : 2 proceed unclear. However, single crystals of [Li(thf)₄] [HfCl₅(thf)] ( 2 ) can be isolated with the hafnium atom in a distorted octahedral coordination sphere of five chloro and one thf ligand. NMR spectra allow to elucidate the time-dependent degradation of 1-Hf and 1-Zr in THF and toluene at 25 °C via THF cleavage. Addition of tmeda to a solution of 1-Zr allows the isolation of intermediately formed [{(tmeda)Li}₂Zr(nBu)₂(C₄H₈)₂] ( 3 ).     

Access a divers dichalcogenophenylenes metallocenes (M = Ti, Zr, Hf). Premier exemple d'un ditellurophenylene-zirconocene

Elementary sulfur and selenium combine (in boiling heptane) with [(tBuCp)₂-Zr(C₆H₄R)₂] (Cp = η⁵-C₅H₄; R = OCH₃) to give the corresponding dichalcogenophenylenezirconocene. With tellurium, the reaction proceeds only at lower temperature (in boiling hexane), affording the first ditellurophenylenezirconocene. As no metallacycle was obtained with the Cp ligand or when the metal is Hf, complexes of the general type [(RCp)₂MSe₂C₆H₄-o] (M = Ti, Zr, Hf; R = H, t-Bu, (CH₃)₅) have been synthesized by allowing metallocene dichlorides to react with potassium benzenediselenolate, prepared by cleaving [(t-BuCp)₂ZrSe₂C₆H₄-o] with t-BuOK.     

EXAFS Study of Amorphous Precursors for Pb(Zr,Ti)O3 Ceramics

In as-hydrolyzed amorphous precursors of Pb(Zr,Ti)O₃ (PZT) ceramics with various Zr/Ti ratios prepared from lead acetate and transition metal n-butoxides in parent alcohol medium the local environment of constituent metal atoms has been determined by EXAFS. The local zirconium atom environment in high-Zr precursors consists of distorted octahedra of oxygen atoms with all the bonds made up of Zr–O–Zr links. For low-Zr precursors a smaller distortion of the oxygen octahedra is observed, and two Ti atoms are found in the second shell. The titanium local environment is almost independent of the Zr/Ti ratio, with five oxygen atoms in the first and two titanium atoms in the second shell of neighbors. Lead atoms contain two oxygen atoms in the first coordination shell. Pb–O–M (M = Zr, Ti) links are identified in all precursors: the former at Zr/Ti 75/25 and the latter at lower Zr/Ti ratios. Although a pronounced tendency for the homocondensation of zirconium species is found down to a Zr/Ti 50/50 ratio, heterometallic links (Pb–O–M) are determined in PZT precursors.     

Anion photoelectron spectroscopy of germanium and tin clusters containing a transition- or lanthanide-metal atom; MGe(n)- (n = 8-20) and MSn(n)- (n = 15-17) (M = Sc-V, Y-Nb, and Lu-Ta)

The electronic properties of germanium and tin clusters containing a transition- or lanthanide-metal atom from group 3, 4, or 5, MGe(n) (M = Sc, Ti, V, Y, Zr, Nb, Lu, Hf, and Ta) and MSn(n) (M = Sc, Ti, Y. Zr, and Hf), were investigated by anion photoelectron spectroscopy at 213 nm. In the case of the group 3 elements Sc, Y, and Lu, the threshold energy of electron detachment of MGe(n)(-) exhibits local maxima at n = 10 and 16, while in the case of the group 4 elements Ti, Zr, and Hf, it exhibits a local minimum only at n = 16, associated with the presence of a small bump in the spectrum. A similar behavior is observed for MSn(n)(-) around n = 16, and these electronic characteristics of MGe(n) and MSn(n) are closely related to those of MSi(n). Compared to MSi(n), however, the larger cavity size of a Ge(n) cage allows metal atom encapsulation at a smaller size n. A cooperative effect between the electronic and geometric structures of clusters with a large cavity of Ge(16) or Sn(16) is discussed together with the results of experiments that probe their geometric stability via their reactivity to H(2)O adsorption.     

Synthesis and structure of (Ph4P)2MCl6 (M = Ti, Zr, Hf, Th, U, Np, Pu)

High-purity syntheses are reported for a series of first, second, and third row transition metal and actinide hexahalide compounds with equivalent, noncoordinating countercations: (Ph(4)P)(2)TiF(6) (1) and (Ph(4)P)(2)MCl(6) (M = Ti, Zr, Hf, Th, U, Np, Pu; 2-8). While a reaction between MCl(4) (M = Zr, Hf, U) and 2 equiv of Ph(4)PCl provided 3, 4, and 6, syntheses for 1, 2, 5, 7, and 8 required multistep procedures. For example, a cation exchange reaction with Ph(4)PCl and (NH(4))(2)TiF(6) produced 1, which was used in a subsequent anion exchange reaction with Me(3)SiCl to synthesize 2. For 5, 7, and 8, synthetic routes starting with aqueous actinide precursors were developed that circumvented any need for anhydrous Th, Np, or Pu starting materials. The solid-state geometries, bond distances and angles for isolated ThCl(6)(2-), NpCl(6)(2-), and PuCl(6)(2-) anions with noncoordinating counter cations were determined for the first time in the X-ray crystal structures of 5, 7, and 8. Solution phase and solid-state diffuse reflectance spectra were also used to characterize 7 and 8. Transition metal MCl(6)(2-) anions showed the anticipated increase in M-Cl bond distances when changing from M = Ti to Zr, and then a decrease from Zr to Hf. The M-Cl bond distances also decreased from M = Th to U, Np, and Pu. Ionic radii can be used to predict average M-Cl bond distances with reasonable accuracy, which supports a principally ionic model of bonding for each of the (Ph(4)P)(2)MCl(6) complexes.