Reaction Of Cp2Ti Research Articles

An Anionic Dimer of Cyclopentadienyl- Titanium (IV) Sulfide: A Potential Precursor for Heterometallic Assemblies

Reaction of Cp2Ti(SH)2 with lithium salts in THF yields the cluster Li6[CpTi(?- S)3]2?6THF, generated by elimination of CpH. This anionic dimer is unique that during the preparation none of the sulfur atoms of the precursor has been eliminated and the Ti-S-H groups are completely converted to Ti-S-Li bonds. The crystal structure indicates the presence of all Ti-S single bonds in bridging positions of the titanium cluster.

{N,N-Bis[bis(2,2,2-trifluoroethoxy)phosphanyl]methylamine-κ2P,P′}bis(η5-cyclopentadienyl)titanium(II)

The title compound, [Ti(C5H5)2(C9H11F12NO4P2)], is a four-membered titanacycle obtained from the reaction of Cp2Ti(η2-Me3SiC2SiMe3) and CH3N[P(OCH2CF3)2]2 {N,N-bis­[bis­(tri­fluoro­eth­oxy)phosphan­yl]methyl­amine, tfepma}. The TiII atom is coordinated by two cyclo­penta­dienyl (Cp) ligands and the chelating tfepma ligand in a strongly distorted tetra­hedral geometry. The mol­ecule is located on a mirror plane.

Coordination Chemistry of Disilylated Germylenes with Group 4 Metallocenes

Reaction of the PEt3 adduct of a disilylated five-membered cyclic germylene with group 4 metallocene dichlorides in the presence of magnesium led to the formation of the respective germylene metallocene phosphine complexes of titanium, zirconium, and hafnium. Attempts to react the related NHC adduct of a disilylated four-membered cyclic germylene under the same conditions with Cp2TiCl2 did not give the expected germylene NHC titanocene complex. This complex was, however, obtained in the reaction of Cp2Ti(btmsa) with the NHC germylene adduct. A computational analysis of the structure of the group 4 metallocene germylene complexes revealed the multiple-bond character of the M–Ge(II) linkage, which can be rationalized with the classical σ-donor/π-acceptor interaction. The strength of the M–Ge(II) bond increases descending group 4.

Ambient-Temperature Carbon–Oxygen Bond Cleavage of an α-Aryloxy Ketone with Cp2Ti(BTMSA) and Selective Protonolysis of the Resulting Ti–OR Bonds

Reaction of Cp2Ti[η2-(CSiMe3)2] with an α-aryloxy ketone produces a Ti(IV) enolate aryloxide complex. Selective protonolysis of the enolate ligand or both Ti–OR bonds can be achieved with various acids. The reaction of the enolate aryloxide with 1-phenyl-2-phenoxyethanol is catalyzed by a mixture of NEt3 and [HNEt3]X (X = OTf, BPh4).

New Sandwich and Half-Sandwich Titanium Hydrazido Compounds

New mono- and bis-cyclopentadienyl terminal titanium hydrazido(2−) compounds were prepared by tert-butyl imide/N,N-disubstituted hydrazine exchange reactions. Reaction of Cp*Ti(NtBu)Cl(py) (1) with Ph2NNH2 gave the terminal hydrazide Cp*Ti(NNPh2)Cl(py) (4), whereas the corresponding reaction of CpTi(NtBu)Cl(py) gave the dimer Cp2Ti2(μ-η1:η1-NNPh2)(μ-η2:η1-NNPh2)Cl2. Reaction of 1 with Me2NNH2 (1 equiv) also gave a dimer, Cp*2Ti2(μ-η1:η1-NNMe2)(μ-η2:η1-NNMe2)Cl2 (8), while the reaction with 2 equiv of Me2NNH2 gave Cp*Ti(η2-NHNMe2)2Cl (7) containing two η2-bound hydrazide(1−) ligands. Formation of 7 and 8 proceeds via a common intermediate, Cp*Ti(NHtBu)(η2-NHNMe2)Cl, observed by NMR spectroscopy. Reaction of 4 with LiNHNPh2 gave the mixed hydrazide(2−)/hydrazide(1−) derivative Cp*Ti(NNPh2)(NHNPh2)(py) (10). The corresponding reaction of 1 formed Cp*Ti(NtBu)(NHNPh2)(py), which rearranged to Cp*Ti(NHtBu)(NNPh2)(py). The titanocene derivative Cp2Ti(NNPh2)(py) (14) was prepared by reaction of Cp2Ti(NtBu)(py) (13) with Ph2NNH2, whereas the corresponding reaction with Me2NNH2 gave mixtures including CpTi(NHtBu)(μ-η1:η1-NNMe2)(μ-η2:η1-NNMe2)TiCp(η1-Cp). The electronic structure of 14 was investigated by DFT and compared to that of the imido complex 13. Whereas the HOMO of the formally 20 valence electron compound 13 is a ligand-centered orbital based both on the Cp rings and on the imido N, in 14 this is the HOMO−1 and one of the Ti═Nα π-bonding MOs is the HOMO, destabilized by an Nα−Nβ antibonding interaction.

Titanocene-Mediated Formation of Phosphorus−Phosphorus Bonds

The reaction of Cp2Ti(btmsa) [btmsa = bis(trimethylsilyl)acetylene (Me3SiC≡CSiMe3)] with bulky dichlorophosphines leads to the formation of diphosphenes or dichlorodiphosphines depending on the stoichiometry used. (Me3Si)2NN(SiMe3)PCl2 (1) was transformed either into bis[tris(trimethylsilyl)hydrazino]dichlorodiphosphine (2) or bis[tris(trimethylsilyl)hydrazino]diphosphene (3) depending on whether an excess of 1 or Cp2Ti(btmsa) was used. Depending on the starting material ratios, Cp2TiCl2 or (Cp2TiCl)2 were obtained as byproducts besides 1 or 3. Compounds 2 and 3 were structurally characterized by X-ray diffraction. Furthermore, the known diphosphene Mes*P═PMes* (4) (Mes* = 2,4,6-tri-tert-butylphenyl) and the dichlorodiphosphine Mes*(Cl)PP(Cl)Mes* (5) were prepared by reaction of Cp2Ti(btmsa) with Mes*PCl2. The reaction of Cp2Ti(btmsa) with the sterically less demanding PhPCl2 resulted in the isolation of a triphosphinato complex. The diphosphine Ph2P−PPh2 (6) was synthesized by reaction of Ph2PCl with Cp2Ti(btmsa).

Deprotonation of Cp2Ti(SH)2 with Mononuclear Rhodium and Iridium Compounds: A New Route to Trinuclear Early−Late Heterobimetallic Complexes

The reaction of Cp2Ti(SH)2 with [M(acac)(diolefin)] (acac = acetylacetonate) yields the complexes [Cp(acac)Ti(μ3-S)2{M(diolefin)}2] (M = Rh, diolefin = 1,5-cyclooctadiene (cod) (1); diolefin = tetrafluorobenzobarrelene (tfbb) (2); M = Ir, diolefin = cod (3)). The formation of the trinuclear heterobimetallic complexes results from a complex reaction involving the deprotonation of the hydrosulfido ligands along with the addition of the late-metal fragment(s), followed by the release of cyclopentadiene and the coordination of acetylacetonate to the titanium center. Similarly, the reaction of Cp2Ti(SH)2 with [M(quinol)(diolefin)] (quinol = 8-oxyquinolinate) gives the complexes [Cp(quinol)Ti(μ3-S)2{M(diolefin)}2] (M = Rh, diolefin = cod (4); tfbb (5); M = Ir, diolefin = cod (6)), which incorporate the 8-oxyquinolinate ligand. The d0−d8 trinuclear early−late heterobimetallic complexes exhibit triangular TiRh2 and TiIr2 cores doubly capped by two μ3-sulfido ligands. Deprotonation of Cp2Ti(SH)2 with the mononuclear carbonyl complexes [M(acac)(CO)2] (M = Rh, Ir) yields the ion-pair complexes [Cp2Ti(acac)][M3(μ3-S)2(CO)6] (M = Rh (7); M = Ir (8)), which result from complete transference of the sulfido ligands to the d8 metal centers. Carbonylation of the diolefin complexes [Cp(acac)Ti(μ3-S)2{M(diolefin)}2] or [Cp(quinol)Ti(μ3-S)2{M(diolefin)}2] yields the compounds [Cp(acac)Ti(μ3-S)2{M(CO)2}2] (M = Rh (9); M = Ir (10)) and [Cp(quinol)Ti(μ3-S)2{M(CO)2}2] (M = Rh (11); M = Ir (12)), respectively. Replacement reactions on the carbonyl complexes with triphenylphosphine give the disubstituted complexes [Cp(acac)Ti(μ3-S)2{M(CO)(PPh3)}2] (M = Rh (13); M = Ir (14)) or [Cp(quinol)Ti(μ3-S)2{M(CO)(PPh3)}2] (M = Rh (15); M = Ir (16)), which are obtained as mixtures of cis and trans isomers. The molecular structures of complexes 1 and 8 have been determined by X-ray diffraction methods.

Synthesis and structure of thiolato bridged Pt–Ti heterobimetallic complexes with methyl group

Sulfur bridged Pt–Ti heterobimetallic complexes, Cp 2Ti( μ-SR) 2PtMe 2, (R=Me ( 1a), Ph ( 1b)) have been prepared by the reaction of Cp 2Ti(SR) 2 with PtMe 2(nbd). X-ray structure analysis of 1a reveals the syn conformation of the compound, while a facile equilibration between syn and anti conformers is observed in toluene solution by variable temperature 1H-NMR.

Novel Nine-Membered Titanaheterocycles – Structure, ab initio Calculations, and Preparative Use towards the Selective Synthesis of Substituted Cyclopentanols

Reactions of Cp2Ti(CO)2 (3) with two equivalents of α,β-unsaturated ketones 4 yield the novel titana-2,9-dioxacyclonona-3,7-dienes 5. Cross-coupling of 3 with two different ketones 4 and 6to give 7 can be achieved under certain reaction conditions. Hydrolysis of 5 or 7 may generate diketones 9, cyclopentanols 10/11, or cyclopentenes 12/13, depending on substituents and conditions. The X-ray crystal structure of 5a, the first nine-membered bis(η5-cyclopentadienyl)-substituted titanaheterocycle containing carbon, is presented. Ab initio calculations were performed for 5a and for titana-2-oxacyclopentene 1, a conceivable intermediate in the coupling reaction.

Reactions of the phenyl-substituted five-membered titanacyclocumulene ȁ Unusual coupling of a 1,4-disubstituted 1,3-butadiyne with two titanium atoms

The reaction of Cp2Ti(η2-Me3SiC2SiMe3) with equimolar amounts of PhCɢC-CɢCPh gives the unstable five-membered titanacyclocumulene 1, which is stabilized by dimerization to yield the dinuclear complex 2. In this reaction complex 1 shows an equilibrium and also behaves as a metallacyclocumulene and a metal alkyne complex. By the coupling of the internal double bond of the cyclocumulene with a complexed triple bond of the diyne, a complex with fused titanacyclopentadiene and titanacyclopentene is formed. With acetone and water complex 1 reacts like an alkyne complex to give the titanadihydrofuran 4 and the titanoxane 5.Complex 2 was investigated by an X-ray structural determination.

Reactions of Lactams with Titanocene‐ and Zirconocene‐Alkyne Complexes as Elemental Steps in Catalytic Anionic Ring‐Opening Polymerization of Lactams

AbstractDepending on the nature of the metal and the ring size, lactams react with titanocene and zircocene complexes of bis‐(trimethylsilyl)acetylene Cp2Ti(Me3SiC2SiMe3) and Cp2Zr‐(L)(Me3SiC2SiMe3) (L = Py, THF) to yield different products. In the reaction of Cp2Zr(Py)(Me3SiC2SiMe3) with N‐methyl‐€‐caprolactam a simple ligand exchange reaction occurs and the complex Cp2Zr(Me3SiC2SiMe3)[OH2)5] (1) was isolated. With β‐propiolactam the alkenyl‐amido complex Cp2)(SiMe3)][–NH2] (2) was obtained, which indicates that an agostic metal‐hydrogen interaction has taken place. The reaction of Cp2Ti(Me3‐SiC2SiMe3) with €‐caprolactam gives after elimination of the alkyne and molecular hydrogen the first early transition metal complex with a deprotonated coordinated €‐caprolactam in a η2‐amidate bonding fashion (3). The obtained complexes were characterized by NMR spectra (1, 2) and crystal structure analysis (1–3) and discussed as elemental steps in anionic ring‐opening polymerization of lactams catalyzed by metallocene‐alkyne complexes.

Intramolekulare Cyclisierung von terminal disubstituierten α, ω-Diinen an Titanocen “Cp 2Ti” mit einer nachfolgenden, ungewöhnlichen Cp-ringöffnung und neuen intramolekularen CC-Knüpfung

The reaction of Cp 2Ti(Me 3SiC 2SiMe 3) ( 1) with terminal disubstituted α,ω-diynes RC≡C(CH 2) n C≡CR affords, after substitution of Me 3SiC 2SiMe 3, bicyclic titanacyclopentadienes via intramolecular cyclization. The stability of the obtained products 2, 3 and 5 is determined by the spacer length ( n = 2, 4, 5, 6). The four-membered ring derivatives ( n = 2) 2a and 2b were obtained in good yield. In the case of n = 4 the bicyclic six-membered ring 3 was formed at first, which rearranges to a stable tricyclic η 4: η 3-dihydroindenyl-Ti complex 4 by Cp cleavage and intramolecular CC coupling. Complex 4 was characterized by X-ray structure analysis and NMR spectroscopy. An increase of spacer length ( n > 4) provides indefinable secondary and decomposition products.

Preparation of some cyclopentadienyl titanium complexes and crystal structure of ( η5-pentamethylcyclopentadienyl) {(1 R,2 S,3 R)- exo-3[( R)-2-phenyl-2-olato-ethyl}] sulphenyl-1,7,7-trimethylbicyclo[2.2.1]heptan-2-olato chlorotitanium(IV): [Cp ∗Ti(OC 18H 24SO)Cl]·C 6H 6

The reaction of (1 R,2 S,3 R)- exo-3[( R)-2-phenyl-2-hydroxyethyl]sulphenyl-1,7,7-trimethylbicyclo[2.2.1]heptan-2-ol ( 1) with Cp ∗TiCl 3 in the presence of Et 3N furnishes the product Cp ∗Ti(OC 18H 24SO)Cl in high yield {Cp ∗ = pentamethylcyclopentadienyl; OC 18} H 24SO = (1 R,2 S,3 R)- exo-3[(R)-2- phenyl-2-olato-ethyl]sulphyl-1,7,7-trimethylbicyclo [2.2.1]heptan-2-olato. The structure of Cp ∗Ti(OC 18H 24SO)Cl·C 6H 6 ( 2) has been determined by X-ray crystallography. The reaction of Cp 2Ti(X)Cl (X = Me, Cl) with 2-methoxybenzyl alcohol in the presence of Et 3N under refluxing benzene gave the product Cp 2Ti(X)( o-OCH 2C 6H 4OMe) (X = Cl, Me).

Electronic Structure of Planar‐Tricoordinated Phosphorus in Titanium‐Boron Complexes

The electronic structure of the recently synthesized complex 5 obtained by the reaction of Cp2Ti(PMe3)(tBu-CP) with (Et2BH)2 was analyzed by means of molecular orbital (MO) calculations. The methods applied were the extended Hückel and the ab initio Hartree-Fock procedures. The highest occupied MOs were derived from molecular fragments. The geometrical parameters calculated for a simplified model (6) are close to those obtained from an X-ray investigation of 5. The analysis of the results shows a strong donor-acceptor interaction between the P-B ó bond and the Ti center. The phosphorus lone pair is not involved in bonding.

SUBSTITUENT EFFECTS ON OXIDATIVE ADDITION TO TITANOCENE DICARBONYL COMPLEXES

Abstract The substituted titanocene dicarbonyl complexes, Cp2Ti(CO)2, CpCp∗Ti(CO)2, 1Cp∗2Ti(CO)2 and CpCpCF3Ti(CO)2, were reacted with chloroform, yielding the respective titanocene dichloride complexes. The electronic effects of the substituents on the cyclopentadienyl ligands were evaluated by infrared spectroscopy and by X-ray photoelectron spectroscopy (XPS). Pseudo first order rate constants were then determined for each of the substituted titanocene dicarbonyl complexes as they reacted with chloroform. No correlation between these electronic effects and the rate constants was possible, however, since the rate constants remained essentially identical regardless of the substituents on the cyclopentadienyl ligands. The reaction of Cp2Ti(CO)2 with chloroform was also evaluated under normal conditions and exhibited overall first order kinetics, although the rate constant was affected by the chloroform concentration. This suggests a preequilibrium dissociated and reassociation of a carbonyl ligand in the first step in the reaction. Therefore, rather than exhibiting a lack of substituent effects, the rate constants may reflect an adjustment of the preequilibrium position caused by opposing electronic and steric effects imposed by the substituted cyclopentadienyl ligands.

Studies of the Reaction Behavior of Nitryl Compounds Towards Azides: Evidence for Tetranitrogen Dioxide, N4O2

AbstractThe reaction behavior of NaN3, AgN3, and Me3SiN3 towards FNO2, CINO2, NO2SbF6, and NO2BF4 was investigated. At ‐30°C or below in a solvent‐free system sodium azide did not react with CINO2, NO2BF4, or NO2SbF6. Below ‐30°C silver azide did not react either with neat C1NO2. Treatment of Me3SiN3 with pure C1NO2 led to the formation of C1N3, N2O, and Me3SiOSiMe3. A mechanism for this reaction has been proposed. Pure chlorine azide was isolated by fractional condensation and identified by its low‐temperature Raman spectrum (liquid state). The reaction of Cp2Ti(N3)2 with C1NO2 also yielded C1N3 as the only azide‐containing reaction product. Treatment of FNO2 with NaN3 at temperatures as low as ‐78°C always ended in an explosion which was probably due to the formation of FN3 as one of the reaction products. The reaction of NO2SbF6 with NaN3 in liquid CO2 (‐55°C· T· ‐35°C) as the solvent afforded a new azide species which was stable at low temperature in solution only and was investigated by means of low‐temperature Raman spectroscopy. The obtained vibrational data give strong evidence for the presence of tetranitrogen dioxide, N4O2, which can be regarded as nitryl azide (NO2N3). The structure and vibrational frequencies of N4O2 were computed ab initio at correlated level (MP2/6‐31 + G*). In liquid xenon (‐100°C· T· ‐60°C) NaN3 did not react with NO2SbF6. A previous literature report on the preparation of N4O2 could not be established.

Telluro- and seleno-bridged TiIV-MII (M = Ni, Pd, Pt) heterobimetallic complexes

Heterobimetallic complexes of the types [Cp2Ti(μ-EAr)2-M(dppe)] (ClO4)2 [(1)–(4); M, E = Ni, Te (1); Ni, Se (2); Pt, Te (3); Pt, Se (4); Ar = Ph (a), C6H4-4-Me (b), C6H4-4-OMe (c), C6H4-4-OEt (d)] and [Cp2Ti(μ-TeAr)2-MCl 2] [M = Pd (5), Pt (6)] were obtained by the reactions of Cp2Ti(EAr)2 with M(dppe)(ClO4)2 and M(PhCN)2Cl2, respectively. While (1), (5) and (6) are stable in the solid state as well as in solution, (2)–(4) undergo dissociation to M(dppe)(EAr)2 and Cp2Ti(ClO4)2 in solution, as shown by multinuclear (31P{1H},195Pt{1H}, 125Te{1H}) n.m.r. studies. The reaction of Cp2Ti(SeAr)2 with M(PhCN)2Cl2, however, leads to the formation of Cp2TiCl2 and a polymeric material [M(SeAr)2] n .

Zum koordinationsverhalten der Lewis-Basen HCN und DCN gegenüber Cp 2Ti(AsF 6) 2

The reaction of Cp 2Ti(AsF 6) 2 ( 1) in liquid sulfur dioxide with XCN gave the cationic titanocene complexes [Cp 2Ti(XCN) 2][AsF 6] 2 (X  H, 2; D, 3). The bonding situation between the Lewis acid (CP 2Ti 2+) and the Lewis base (XCN) is discussed on the basis of IR data and qualitative MO considerations. A convenient laboratory-scale synthesis of DCN is reported.

Disulfanido ligands: preparation and reactions of Cp2Ti(SSR)X, where X = SR, phthalimido, and Cl and R = alkyl and aryl groups

The complex Cp 2 Ti(CO) 2 oxidatively adds RSSX to give the complexes Cp 2 Ti(X)(SSR), where X=SR and R=CHMe 2 , CMe 3 , CH 3 Ph, and 4-C 6 H 4 Me; X=phthalimido and R=CHMe 2 , CMe 3 , CH 2 Ph, and 4-C 6 H 4 Me; and X=Cl and R=CPh 3 . The complexes Cp 2 Ti(SR)(SSR) reacted with PhCH 2 Br to give CpTiBr 2 , PhCH 2 SR, and PhCH 2 SSR, confirming the presence of the disulfanido ligand. These complexes desulfurized slowly in solution and rapidly in the presence of PPh 3 to give Cp 2 Ti(SR) 2 and SPPh 3 . The complexes for which X=phthalimido undergo alcoholysis to give the species where X=OET

Kationische Stickstoff- und Arsen-koordinierte Titanocenbishexafluoroarsenat-Komplexe

The reaction of Cp 2Ti(AsF 6) 2 ( 1) in liquid sulfur dioxide with HCN, ICN, AsMe 3, and As 2Me 4 afforded the new cationic titanocene complexes [Cp 2TiHCN) 2][AsF 6] 2 ( 2), [Cp 2Ti(ICN) 2][AsF 6] 2 ( 3), [Cp 2Ti(AsMe 3) 2][AsF 6] 2 ( 4), and [Cp 2Ti(As 2Me 4)] 2[AsF 6] 4 ( 5) (Cp = η 5-C 5H 5, Me = CH 3). All compounds have been characterized by 1H NMR and IR spectroscopy. The dynamic 1H NMR spectrum of 5 shows a reversible temperature dependence due to the ring inversion of the six-membered TiAsAsTiAsAs heterocycle.