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.     

Synthesis and characterization of bis-isonitrile complexes Cp2M(CNR)2 (M = Ti,Zr; R = 2,6-dimethylphenyl)

Bis-isonitrile complexes Cp₂M(CNR)₂ (M  Ti, Zr), where RNC is the sterically hindered 2,6-dimethylphenyl isonitrile, can be prepared in high yield by reduction of Cp₂MCl₂ with magnesium in THF solution in the presence of the isonitrile. ¹H NMR spectroscopy reveals that with the titanium complex dissociation of the isonitrile ligands takes place in solution.     

Elimination of bis(trimethylsilyl)stannylene from tris(trimethylsilyl)stannylated zirconocene and hafnocene chlorides

Reactions of (Me₃Si)₃SnK with Cp₂MCl₂ (M = Zr, Hf) give the respective stannylated metallocene chlorides. These complexes display a tendency to eliminate bis(trimethylsilyl)-stannylene under Cp₂M(Cl)SiMe₃ formation.     

Allyl complexes of dicyclopentadienyl-niobium(III) and -tantalum(III)

The synthesis and the properties of the complexes Cp₂TaCl₂, Cp₂M(allyl), Cp₂M(1-methylallyl) and Cp₂M(2-methylallyl) with M  Nb, Ta are described. The complex Cp₂TaCl₂ has one unpaired electron per tantalum atom, while the allyl complexes are diamagnetic. The IR and PMR spectra indicate that the allyl group is π-bonded to the metal. The mass spectra of the complexes are discussed; the thermal stability of the Cp₂Nb- and Cp₂Ta-(allyl) complexes was investigated by differential thermal analysis. The properties of the niobium and tantalum complexes are compared with those of the corresponding titanium complexes.     

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.     

Half-sandwich Ru(II), Ir(III) and Rh(III) complexes with bridging or chelating N-heterocyclic bis-carbene ligand: Synthesis and characterization

N-heterocyclic bis-carbene ligand (bis-NHC) which was derived from 1,1′-diisopropyl-3,3′-ethylenediimidazolium dibromide (L·2HBr) via silver carbene transfer method, reacted with [(η⁶-p-cymene)RuCl₂]₂ and [Cp^∗MCl₂]₂ (Cp^∗ = η⁵-C₅Me_5, M = Ir, Rh) respectively, afforded complexes [(η⁶-p-cymene)RuCl₂]₂(L) (1), [Cp^∗IrCl₂]₂(L) (2) and [Cp^∗RhCl(L)][Cp^∗RhCl₃] (3). When [Cp^∗IrCl₂]₂ was treated with 2 equiv AgOTf at first, and then reacted with bis-NHC ligand, [Cp^∗IrCl(L)]OTf (4) was obtained. The molecular structures of complexes 1-4 were determined by X-ray single crystal analysis, showing that 1 and 2 adopted bridging coordination mode, 3 and 4 adopted chelating coordination mode. All of these complexes were characterized by ¹H, ¹³C NMR spectroscopy and element analysis.     

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).     

Vinylierung und 91Zr-NMR-Spektren von Substituierten Zirconocendichloriden

Vinylation and ⁹¹Zr N.M.R. Spectra of substituted Zirconocene Dichlorides Substituted zirconocene dichlorides react with vinyl lithium with formation of zirconacyclopent-2-enes, Cp₂ZrCH = CHCH₂CH₂, or zirconocene butadiene complexes, Cp₂Zr(C₄H₆). The compounds obtained were characterized by their ¹H and ¹³C n.m.r. spectra. The ⁹¹Zr n.m.r. chemical shifts of substituted zirconocene dichlorides correlate with the bond angles Cp′? Zr? Cp′ and Cl? Zr? Cl respectively. They can be used to estimate the reaction behaviour of zirconocene dichlorides.     

General route for the synthesis of terminal phosphanylphosphido complexes of Zr(IV) and Hf(IV): Structural investigations of the first zirconium complex with a phosphanylphosphido ligand

Reactions of R₂P-P(SiMe₃)Li with [Cp₂MCl₂] (M = Zr, Hf) in hydrocarbons yield the related terminal phosphanylphosphido complexes [Cp₂M(Cl){(Me₃Si)P-PR₂-κP¹}] (R = ⁱPr and ^tBu). The solid state structures of [Cp₂M(Cl){P(SiMe₃)-PⁱPr₂-κP¹}] (M = Zr, Hf) were established by single crystal X-ray diffraction studies. The phosphido-P atoms adopt almost planar geometries and the phosphanyl P atoms adopt pyramidal geometries. The reaction of a mixture of (Me₃Si)₂PLi and Ph₂P-P(SiMe₃)Li with [CpZrCl₃] in toluene yields the dinuclear complex [Cp₂Zr₂Cl₅(Ph₂PPPSiMe₃)(Li THF DME)].     

Synthesis,characterization and soft transformation of some bis(cyclopentadienyl) Ti(IV) and Zr(IV) complexes of Schiff's base ligands to nano‐sized titania or zirconia materials

Some bis(cyclopentadienyl) complexes of Ti(IV)and Zr(IV) have been synthesized by the metathetical reactions of Cp₂MCl₂ with the sodium salt of monofunctional bidentate Schiff's base ligands in 1:1 and 1:2 stoichiometry in anhydrous THF. All the derivatives of the types Cp₂MCl_2?n{O(C₆H₄)CH₆H₅}_n and Cp₂MCl_2?n{OC(CH₃)(R)₆H₅}_n (where R = CH₃ or C₆H₅ and n = 1 or 2) have been characterized by elemental analyses, molecular weight measurements, FT‐IR and ‐NMR [¹H and ¹³C{¹H}] studies. The FAB mass spectra of a few representative complexes and the molecular weight measurements in freezing benzene indicate their monomeric nature in solution. Spectral studies appear to indicate mono‐ and bi‐dentate mode of attachment of the ligand in solution and in the solid state, respectively. Thermogravimetric analyses (TGA) of Cp₂TiCl{O(C₆H₄)CH} ( 1 ) and Cp₂ZrCl{O(C₆H₄)CH} ( 7 ) indicate their low thermal stability. Transformations of some of these complexes to pure titania (TiO₂)/zirconia (ZrO₂) have been observed at relatively low sintering temperatures. Powder X‐ray diffraction (XRD) and scanning electron micrograph (SEM) studies suggest the nanocrystalline nature of these materials. Copyright © 2007 John Wiley & Sons, Ltd.     

Metal-catalysed organic transformations in water: From bromination to polymerisation

Reaction ofα,Β-unsaturated aromatic carboxylic acids with KBr and H₂O₂ in the presence of Na₂MoO₄·2H₂O in aqueous medium affordsΒ-bromo alkenes in high yields. Metallocene dichlorides, Cp₂MCl₂ (M = Ti, Zr, or V) catalyse polymerisation of olefins in aqueous medium to afford high molecular weight polymers with low molecular weight distribution.     

Titanocene(IV) and vanadocene(IV) complexes of dicyanomethanidobenzoate

The new titanocene and vanadocene complexes of the non-linear pseudohalides Cp₂Ti(dcmb)₂, Cp₂VCl(dcmb), (η⁵-C₅H₄Me)₂VCl(dcmb) and Cp₂V(dcmb)₂ were prepared by reaction of titanocene dichloride (Cp₂TiCl₂) and vanadocene dichlorides (Cp₂VCl₂, (η⁵-C₅H₄Me)₂VCl₂) with dicyanomethanidobenzoic acid (dcmbH, PhC(OH)C(CN)₂). These reactions have proven that the dcmb ligand could be coordinated to the central metal by oxygen or nitrogen donor atoms. The bonding mode of the dcmb ligand reflects properties of the central metal. The strongly oxophilic titanium(IV) shows the bonding through oxygen atom while bonding through nitrogen atom was observed for less oxophilic vanadium(IV). The bonding fashion of the dcmb ligands was determined by spectroscopic methods. X-ray diffraction analysis was used for the structure determination of the compounds dcmbH·H₂O, Cp₂Ti(dcmb)₂·CH₂Cl₂, (η⁵-C₅H₄Me)₂VCl(dcmb) and [Cp₂V(OC(Ph)C(CN)C(OMe)NH)][dcmb].     

Reactions of half-sandwich rhodium(III) and iridium(III) compounds with pyridinethiolate ligands: Mono-, di-, and tri-nuclear complexes

Neutral trinuclear metallomacrocycles, [Cp^*RhCl(μ-4-PyS)]₃ (3) and [Cp^*IrCl(μ-4-PyS)]₃ (4) [Cp^* = pentamethylcyclopentadienyl, 4-PyS = 4-pyridinethiolate], have been synthesized by self-assembly reactions of [Cp^*RhCl₂]₂ (1) and [Cp^*IrCl₂]₂ (2) with lithium 4-pyridinethiolate, respectively. In situ reaction of complex 3 with three equivalent of lithium 4-pyridinethiolate resulted in [Cp^*Rh(μ-4-PyS)(4-PyS)]₃ (5) containing both skeleton and pendent 4-PyS groups. Chelating coordination of 2-pyridinethiolate broke down the triangular skeleton to give mononuclear metalloligands Cp^*Rh(2-PyS)(4-PyS) (6) and Cp^*Ir(2-PyS)(4-PyS) (7) [2-PyS = 2-pyridinethiolate], which could also be synthesized from Cp^*RhCl(2-PyS) (10) and Cp^*IrCl(2-PyS) (11) with lithium 4-pyridinethiolate. The coordination reactions of 6 with complexes 1 and 2 gave dinuclear complexes [Cp^*Rh(2-PyS)(μ-4-PyS)][Cp^*RhCl₂] (8) and [Cp^*Rh(2-PyS)(μ-4-PyS)][Cp^*IrCl₂] (9), respectively. Molecular structures of 3, 4, 6 and 11 were determined by X-ray crystallographic analysis. All the complexes have been well characterized by elemental analysis, NMR and IR spectra.     

Synthesis of Functionalized (η5‐Indenyl)rhodium(III) Complexes and Their Application to C−H Bond Functionalization

It has been established that reductive complexation of functionalized benzofulvenes, which are readily prepared from commercially available indene and 2‐methylindene, with RhCl₃ in ethanol affords the corresponding indenyl–rhodium(III) dichlorides bearing substituents at the 1‐ (H or CO₂Et), 2‐ (H or Me), and 3‐ [CH₂Ph or CH₂(2‐MeOC₆H₄)] positions. The indenyl–rhodium(III) complexes bearing one ethoxycarbonyl group showed higher thermal stability and regioselectivity than our previously reported Cp^ERh^III complex toward the oxidative [3+2] annulation of acetanilides with internal alkynes.     

Preparation,characterization and reactivity of Cp2M(PMe3)2 complexes (M = Ti,Zr): the molecular structure of Cp2Zr(PMe3)2

The reduction of Cp₂MCl₂ (M = Ti, Zr) with magnesium in THF in the presence of PMe₃ affords the complexes Cp₂M(PMe₃)₂ in high yields. These compounds lose one or both PMe₃ ligands under very mild conditions. Cp₂Ti(PMe₃)₂ reacts readily with CH₃I, CH₃C(O)Cl, PhSSPh, Me₂PCH₂CH₂PMe₂, CO, RCN (R = Me, t-Bu) or (RN)₂S (R = t-Bu, Me₃Si) to give the corresponding titanocene products. The structure of Cp₂Zr(PMe₃)₂ has been determined by X-ray diffraction; the structural parameters are similar to those of the titanium analog Cp₂Ti(PMe₃)₂ except that the Zr-P and Zr-C distances are longer.     

Synthesis and spectral properties of new complexes between glycine and titanium(III), vanadium(III), chromium(III), iron(III), cobalt(II), nickel(II) and copper(II)

Summary Complexes of formula [MCl₃(glyH)₃] (M=Ti, V and Fe) [CrCl₃(glyH)₂H₂O], [MCl₂(glyH)₂(H₂O)₂] (M=Co and Cu) and [NiCl₂(glyH)₃H₂O] have been prepared and characterized by potentiometric curves, chemical analysis, magnetic properties, i.r. and electronic spectral data.     

Synthesis,characterization and toxicity of new heterobimetallic complexes of platinum(II) and palladium(II)

Heterobimetallic complexes of the type [M(C₆H₆N₂)₂(M′)₂(R)₄]Cl₂ have been synthesized by the direct reaction of [M(C₆H₈N₂)₂]Cl₂ with Group 4 or 14 organometallic dichlorides Ph₂M′Cl₂,Me₂M′Cl₂ or Cp₂M″Cl₂ in 1:2 molar ratio in MeOH (M = Pd or Pt, M′ = Si or Sn and M″ = Ti or Zr). The compounds were characterized by elemental analysis, molecular weight determination, electronic, ¹H NMR and IR spectra, magnetic susceptibilities and conductivity measurements. These studies showed that the compounds are monomers and dimagnetic in nature, with a square‐planar geometry around palladium and platinum metals. Both the free ligands and their metal complexes were screened for antimicrobial activity on different species of pathogenic fungi and bacteria and were found active in this respect.Copyright © 2001 John Wiley & Sons, Ltd.     

Highly Strained Heterometallacycles of Group 4 Metallocenes with Bis(diphenylphosphino)amide Ligands

A study regarding coordination chemistry of the bis(diphenylphosphino)amide ligand Ph₂P‐N‐PPh₂ at Group 4 metallocenes is presented herein. Coordination of N,N‐bis(diphenylphosphino)amine ( 1 ) to [(Cp₂TiCl)₂] (Cp=η⁵‐cyclopentadienyl) generated [Cp₂Ti(Cl)P(Ph₂)N(H)PPh₂] ( 2 ). The heterometallacyclic complex [Cp₂Ti(κ²‐P,P‐Ph₂P‐N‐PPh₂)] ( 3 Ti ) can be prepared by reaction of 2 with n‐butyllithium as well as from the reaction of the known titanocene–alkyne complex [Cp₂Ti(η²‐Me₃SiC₂SiMe₃)] with the amine 1 . Reactions of the lithium amide [(thf)₃Li{N(PPh₂)₂}] with [Cp₂MCl₂] (M=Zr, Hf) yielded the corresponding zirconocene and hafnocene complexes [Cp₂M(Cl){κ²‐N,P‐N(PPh₂)₂}] ( 4 Zr and 4 Hf ). Reduction of 4 Zr with magnesium gave the highly strained heterometallacycle [Cp₂Zr(κ²‐P,P‐Ph₂P‐N‐PPh₂)] ( 3 Zr ). Complexes 2 , 3 Ti , 4 Hf , and 3 Zr were characterized by X‐ray crystallography. The structures and bondings of all complexes were investigated by DFT calculations.     

3,3′-Dicarbomethoxy-2,2′-bipyridyl complexes of palladium(II), platinum(II) and rhodium(III)

3,3′-Dicarbomethoxy-2,2′-bipyridyl(DCMB)reacts with K₂MCl₄(M = Pd,Pt) to give M(DCMB)Cl₂ and with RhCl₃ to give the cis-[Rh(DCMB)₂Cl₂]⁺ ion. Attempts to prepare the tris (DCMB) complex with Rh(III) and analogous Co(III) complexes were unsuccessful.     

Paradigm Shift from Alkaline (Earth) Metals to Early Transition Metals in Fluoroorganometal Chemistry: Perfluoroalkyl Titanocene(III) Reagents Prepared via Not Titanocene(II) but Titanocene(III) Species

Perfluoroalkyl (R_F) titanocene reagents [Cp₂Ti^IIIR_F] synthesized via [Cp₂Ti^IIICl] rather than [Cp₂Ti^II] show new types of perfluoroalkylation reactions. The [Cp₂Ti^IIIR_F] reagents exhibit a wide variety of reactivity with carbonyl compounds including esters and nitriles, and selectivities far higher than those reported for conventional R_FLi and R_FMgX reagents.