V. V. Burlakov

Novel acetylene complexes of titanocene and permethyltitanocene without additional ligands. Synthesis spectral characteristics and X-ray diffraction study

Abstract New acetylene complexes of titanocene and permethyltitanocene Cp 2 Ti(R 1 C 2 R 2 ) and Cp 2 *Ti(R 1 C 2 R 2 ) (R 1 R 2 SiMe 3 ; R 1 Ph, R 2 SiMe 3 ) without additional ligands have been prepared by the reaction of Cp 2 TiCl 2 and Cp 2 *TiCl 2 with equimolar amounts of Mg and the appropriate acetylene R 1 C 2 R 2 in THF. The complexes have been isolated from the reaction mixture in an analytically pure state and characterized by spectral methods. The structures of complexes Cp 2 Ti(PhC 2 SiMe 3 ), Cp 2 *Ti(PhC 2 SiMe 3 ) and Cp 2 *Ti(Me 3 SiC 2 SiMe 3 ) have been proved by an X-ray diffraction study. Some chemical properties of the synthesized complexes have been investigated.

Complex of titanocene with tolane. Isolation, spectral characteristics, reactivity

Abstract The interaction of Cp 2 TiCl 2 with equimolar amounts of Mg and tolane in THF results in the formation of a tolan complex of titanocene Cp 2 Ti(C 2 Ph 2 ). The complex has been isolated from the reaction mixture as a definite compound and identified by spectral and chemical means. From the data obtained the conclusion has been made that the complex has a structure close to that of titanacyclopropene.

Synthesis and x-ray structure determination of an organometallic titanoxane [Cp2TiC(Ph)CH(Ph)]2O. Evidence for the formation of a titanocene complex with tolane

Abstract The reaction of Cp2TiCl2 with magnesium in THF in the presence of tolane at a Cp2TiCl2 : Mg : Ph2C2 ratio of 1 : 1 : 1 results in formation of a dark red-brown solution which yields cis-stilbene when treated with HCl in ethanol, the titanacyclopentadiene complex Cp2 TiC(Ph)C(Ph)C(Ph)C (Ph) when treated with tolane, and the organometallic titanoxane [Cp2TiC(Ph)CH(Ph)]2O when treated with water. It is suggested that in the solution the titanocene complex with tolane [Cp2Ti(Ph2C2)], postulated previously as an intermediate in the catalytic hydrogenation of tolane to dibenzyl under the action of Cp2Ti(CO)2 is present. The structure of [Cp2TiC(Ph)CH(Ph)]2O has been established by an X-ray analysis.

13C1H NMR studies of selected transition metal alkyne complexes

Abstract 13 C 1 H NMR spectra of selected nickel alkyne complexes (Ph 3 P) 2 Ni(RC 2 R) have been recorded and the results are compared with the relevant data for other alkyne complexes of transition metals. It has been found that the complexes with two-electron alkyne ligands such as (Ph 3 P) 2 Ni(RC 2 R), (Me 3 P) 2 Ni(RC 2 R), (Ph 3 P) 2 Pt(RC 2 R) and the complexes with four-electron alkyne ligands such as Cp 2 Ti(RC 2 R), Cp 2 ★ Ti(RC 2 R) (Cp ★ = η 5 -C 5 Me 5 ), CpV(PMe 3 ) 2 (RC 2 R), W-(OCMe 3 ) 4 (RC 2 R) are characterized by the markedly different influence the electronic parameters of the substituents R have on the value of the 13 C NMR downfield shift, Δδ(CC), on going from free to complexed CC bond. The IR spectra of the two types of complexes show no specific differences in the influence of various alkyne substituents R on the relevant Δν(CC) values.

Reaction of a tolane complex of titanocene with carbonyl compounds. Synthesis of titanadihydrofuran metallacycles

Abstract The reaction of a THF solution of a tolane complex of titanocene [Cp2Ti(C2Ph2)] with benzaldehyde and acetone results in the formation of titanadihydrofuran metallacycles Cp2 TiC(Ph)C(Ph)CH(Ph)O and Cp2 TiC(Ph)C(Ph)C(CH 3 ) 2 O , respectively. The structure of the latter complex has been determined by X-ray analysis.

Interaction of carbon dioxide with acetylene complexes of titanocene Cp2Ti(RC2R) (R Ph, SiMe3). Synthesis and structure of binuclear σ-alkenylcarboxylate complexes of titanium (III) Cp2TiC(R)C(R) COOTiCp2 and unexpected transformation of these complexes into titanafuranone metallacycles under the action of air oxygen

Abstract It has been shown that carbon dioxide reacts with acetylene complexes of titanocene Cp2Ti(RC2R) (RPh, SiMe3) at room temperature and atmospheric pressure to form binuclear σ-alkenylcarboxylate complexes of trivalent titanium Cp2TiC(R)C(R)COOTiCp2 containing two fused chelate cycles and a tricoordinated oxygen atom. The interaction of these binuclear carboxylate complexes with air oxygen at 20°C results in rapid formation of titanafuranone metallacycles Cp 2 Ti(R)=C(R)C(O)O . X-ray diffraction studies of complexes Cp2TiC(SiMe3)C(SiMe3)COOTiCp2 and Cp 2 Ti(Ph)=C(Ph)C(O)O have been carried out.

Interaction of carbon dioxide with the bis(trimethylsilyl)acetylene complex of permethyltitanocene: synthesis and structure of the binuclear carbonate complex of permethyltitanocene (Cp2∗Ti)2CO3

Abstract It has been shown that in the interaction of carbon dioxide with the bis(trimethylsilyl)acetylene complex of permethyltitanocene Cp 2 ∗ Ti(Me 3 SiC 2 SiMe 3 ), full displacement of bis(trimethylsilyl)acetylene from the titanium coordination sphere takes place and carbon dioxide undergoes disproportionation to form Cp 2 ∗ Ti(CO) 2 and the binuclear carbonate complex of permethyltitanocene (Cp 2 ∗ Ti) 2 CO 3 . The structure of (Cp 2 ∗ Ti) 2 CO 3 has been established by X-ray diffraction study. Structural data on the related chlorine-containing carbonate complex Cp 2 ∗ Ti(Cl)CO 3 TiCp 2 ∗ are also reported.

Darstellung und eigenschaften des komplexes (dipy)Ni(η2-PhC2SiMe3). Zur korrelation struktureller bindungsparameter mit IR- und NMR-spektroskopischen daten in übergangsmetall-alkin-komplexen

Abstract The reaction of (dipy)Ni(cod) with PhCCSiMe3 yields, depending on the stoichiometry, first the binuclear complex (dipy)Ni(μ- PhC2SiMe3)Ni(dipy) (2) which gives, with an excess of the alkyne, the mononuclear compound (dipy)Ni(η2-PhC2SiMe3) (3). This complex was structurally characterized to study the influence of the dipy ligand on alkyne complexation in Ni(O) complexes. Furthermore, comparison of spectroscopical and structural data in a series of complexes with one alkyne: (dipy)Ni(η2-PhC2SiMe3) (3), (Ph3P)2Ni(η 2-PhC2SiMe3), Cp2Ti(η2-PhC2SiMe3) and C★2Ti(η2-PhC2SiMe3) has shown that 13C-NMR and infrared spectroscopy are better suited to characterize the complexation of an alkyne (two- or four-electron donor) at the metal atom than X-ray structure analysis.

Stability of Bridged and Unbridged η2-Alkyne−titanocene and −zirconocene Complexes − Influence of Metals, Alkyne Substituents, Cp Substitution and Additional Ligands

The influence of metals, alkyne substituents, Cp substitution and additional ligands on the stability of bridged and unbridged η2-alkyne−titanocene and −zirconocene complexes has been investigated. The reduction of the complex [(η5-C5H4)−SiMe2−(η5-C5H4)]TiCl2 with magnesium in the presence of tolan (PhC2Ph) does not give the expected alkyne−titanocene complex [(η5-C5H4)−SiMe2−(η5-C5H4)]Ti(η2-PhC2Ph) but by coupling of two tolan molecules the corresponding titanacyclopentadiene [(η5-C5H4)−SiMe2−(η5-C5H4)]TiC4Ph4 (1) was obtained. In the analogous reaction with Me3SiC2SiMe3 the stable η2-alkyne complex without additional ligands [(η5-C5H4)−SiMe2−(η5-C5H4)]Ti(η2-Me3SiC2SiMe3) (2) was formed, due to the sterical influence of the alkyne substituents. The compounds without additional ligands (thi)2Ti(η2-PhC2Ph) (3) and (thi)2Ti(η2- Me3SiC2SiMe3) (5) were isolated from the unbridged titanocene complex (thi)2TiCl2 (thi = tetrahydroindenyl). Two equivalents of complex 3 reacted with one equivalent of water to yield the dimeric alkylidene-μ-oxo complex [(thi)2Ti(CPh=CHPh)]2(μ-O) (6). The reaction of the unbridged zirconocene compound (thi)2ZrCl2 gave the alkyne complex (thi)2Zr(THF)(η2-Me3- SiC2SiMe3) (7) which is stabilized by THF. At higher temperature THF was eliminated from the orange complex 7 forming the green complex (thi)2Zr(η2-Me3SiC2SiMe3). This behaviour was investigated in detail using NMR spectroscopy and compared to similar complexes such as Cp2Zr(η2-Me3SiC2SiMe3) (not stable without THF), (ebthi)2Zr(η2-Me3SiC2SiMe3) (ebthi = ethylenebistetrahydroindenyl; stable without THF) and Cp*2Zr(η2-Me3SiC2SiMe3) (Cp* = pentamethyl-Cp, stable without THF). All complexes were characterized by spectroscopic methods. X-ray structural determinations were conducted for the complexes 1, 3 and 7. Compound 3 is the first example of a structurally characterized tolan−titanocene complex without additional ligands.

Untypical Regioselectivity of Carbon Dioxide Coupling with Titanocene Complexes of Phenyl(trimethylsilyl)acetylene by Using themeso-1,2-Ethylene-1,1′-bis(η5-tetrahydroindenyl) Ligand System

The reaction of [meso-(ebthi)TiCl2] [ebthi = 1,2-ethylene-1,1′-bis(η5-tetrahydroindenyl)] with magnesium in the presence of the alkynes Me3SiC≡CSiMe3 and PhC≡CSiMe3 resulted in the formation of the complexes [meso-(ebthi)Ti(η2-Me3SiC2SiMe3)] (1) and [meso-(ebthi)Ti(η2-PhC2SiMe3)] (2a and 2b), which were isolated and then characterized by their NMR spectra. Due to incomplete reduction the TiIII complex [meso-(ebthi)Ti(THF)Cl] (3) was also obtained as a by-product of these reactions. By insertion into the Ti–CPh bond carbon dioxide reacted with the titanacyclopropene structure of the alkyne complex [meso-(ebthi)Ti(η2-PhC2SiMe3)] (2a), with untypical regioselectivity to yield the α-silyl-substituted meso-(ebthi)titanafuranone 6a. In the analogous reactions of the complexes [(thi)2Ti(η2-PhC2SiMe3)] (thi = η5-tetrahydroindenyl), [rac-(ebthi)Ti(η2-PhC2SiMe3)], and [Cp*2Ti(η2-PhC2SiMe3)] with carbon dioxide typical regioselectivity (insertion into the M–CSi bond of the titanacyclopropene) was observed, yielding the β-silyl-substituted titanafuranones 7, 8a, and 9. These results show that insertion of carbon dioxide into the M–C bond of the titanacyclopropene structure of the alkynemetallocene complexes is governed by the substitution pattern of the alkyne and the steric enviroment around the metal center. The complexes 3, 6a, and 7 were investigated by X-ray crystal structure analysis.