Carbonylierung von Metallocenyliden Cp2M(R)(CHPPh3) des Zirconiums und Hafniums

Erker, Gerhard; Korek, Uwe; Schlund, Rüger

doi:10.1016/0022-328x(89)85338-0

Cited by 11 publications

(4 citation statements)

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“…Compounds Zr2a – c were characterized by NMR spectroscopy ( Zr2a-benzo is insoluble in common deuterated solvents); Table summarizes selected 1 H, 13 C, and 31 P NMR data. Similar to the complexes Ti2a – e , the characteristic NMR shifts of the CH exo ,, and CH ylide group can be observed. ,− Compared to the other 1 H NMR chemical shifts of the CH ylide group, the signal for Zr2b-benzo is noticeably shifted to higher fields. This phenomenon is caused by the arenes anisotropy cone.…”

Section: Resultsmentioning

confidence: 59%

“…Generally, using α- and β-C–H bond activation processes, the formation of carbene as well as olefin , complexes becomes understandable. Especially carbene and carbyne complexes of transition metals in high oxidation states are of general interest, which are used in different catalytic chemical reactions. ,− Phosphorus ylides provide an efficient access to such complexes, due to the fact that they can be described as dipolar carbenes as well as neutral molecules. This polarization of the phosphorus–carbon bond results in high Brønsted basicity of the carbon atom and exceptional donor character (Scheme ).…”

Section: Introductionmentioning

confidence: 99%

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Reaction of Pentafulvene Titanium and Zirconium Complexes with Phosphorus Ylides: Stoichiometric Reactions and Catalytic Intramolecular Proton Shuttles

et al. 2019

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The reaction of penta- and benzofulvene complexes of group 4 (M = Ti, Zr) with different phosphorus ylides is reported. Employing the bis(η5:η1-pentafulvene)titanium complexes Ti1a and Ti1b, the reactions with the corresponding phosphorus ylides Y1–5 result in a spontaneous single C–H bond activation and metallocene ylide complexes Ti2a–e can be isolated in good yields. On the basis of these results, this reactivity pattern has been extended to the mono(η5:η1-pentafulvene) and -benzofulvene complexes Ti3, Zr1a,b, and Zr1a,b-benzo. Transferring this to the titanium complex Ti3, an additional equilibrium between the reaction product (η5-C5Me5)(η5-CpAd)Ti(Cl)CHPPh3 (Ti4a) and the corresponding “tuck-in” complex (η5:η1-C5Me4CH2)(η5-CpAd)TiCl (Ti4b) can be observed. In Ti4b, a methyl group of the Cp*-ligand is activated by the coordinated phosphorus ylide. Using this intramolecular C–H activation, Ti4b can be synthesized by catalytic amounts (3 mol %) of the phosphorus ylide Y1 in quantitative yield. Subsequently, the reaction of Ti4b with different carbonyl and nitrile compounds has been investigated. In both cases, an insertion of the functional group into the newly formed Ti–CH2 bond is observed, and the insertion products Ti5–9 are isolated in good yields. Using a sterically demanding nitrile, the titanium-imine complex Ti7 is isolated. Upon heating of Ti7, a thermally induced subsequent nonreversible 1,3-H-shift can be observed, forming the titanium-enamine complex Ti7a. With reduced steric demand of the appropriate nitrile, this shift directly takes place even under mild reaction conditions with no observation of the titanium-imine species. By utilization of acetonitrile as substrate, a dimeric titanium-imine-enamine complex Ti10 is formed, due to an occurring subsequent C–C bond formation reaction.

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Section: Resultsmentioning

confidence: 59%

Section: Introductionmentioning

confidence: 99%

Reaction of Pentafulvene Titanium and Zirconium Complexes with Phosphorus Ylides: Stoichiometric Reactions and Catalytic Intramolecular Proton Shuttles

et al. 2019

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“…There are a reasonable number of hafnium ethyl complexes of the type (C 5 R 5 ) 2 HfEt(L), where L is a variety of anionic and neutral donor ligands, four of which have been crystallographically characterized: Cp 2 HfEt(CHPPh 3 ), Cp 2 HfEt(OOCMe 3 ), Cp 2 HfEt(OCCHPPh 3 ), and Cp 2 HfEt(PhCH 2 NCHCH 2 PPh 3 ) . There are a small number of non-metallocene hafnium ethyl complexes, two of which have been structurally characterized: the amide HfEt 2 [O(CH 2 CH 2 NC 6 H 3 -2,6-(i-Pr) 2 ) 2 ], and the amidinate HfEt 2 [PhC(NSiMe 3 ) 2 ] .…”

Section: Resultsmentioning

confidence: 99%

“…Consistent with this view, the 1 H and 13 C NMR chemical shifts and coupling constants for the ethyl groups of [Li(tmed)] 2 [Hf(C 2 H 4 )Et 4 ] are similar to those seen in hafnium(IV) ethyl complexes. [35][36][37][38][47][48][49][50][51][52][53][54] The principal difference is that R-proton resonance of the ethyl groups in 1 is farther upfield than those of electrically neutral hafnium(IV) compounds. This difference may reflect the presence of contacts with the lithium cations (see below).…”

Section: Resultsmentioning

confidence: 99%

Ethylene Complexes of the Early Transition Metals: Crystal Structures of [HfEt₄(C₂H₄)²⁻] and the Negative-Oxidation-State Species [TaHEt(C₂H₄)₃³⁻] and [WH(C₂H₄)₄³⁻]

et al. 2008

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Alkylation of HfCl 4 with 6 equiv of ethyllithium followed by the addition of N,N,N′,N′-tetramethylethylenediamine gives the d 2 hafnium(II) alkyl/alkene complex [Li(tmed)] 2 [HfEt 4 (C 2 H 4 )]. The X-ray crystal structure of this complex shows that the ethylene ligand has considerable metallacyclopropane character. The C-C distance of 1.49(6) Å and the 1 J CH coupling constant of 119 Hz both support this formulation. A labeling study showed that the ethylene ligand is formed by means of a -hydrogen abstraction process. Similar treatment of TaCl 2 (OMe) 3 and WCl 3 (OMe) 3 with ethyllithium affords the d 6 tantalum(-I) and d 8 tungsten(-II) complexes [Li(tmed)] 3 [TaHEt(C 2 H 4 ) 3 ] · 1 / 2 tmed and [Li(tmed)] 3 [WH(C 2 H 4 ) 4 ]. Both trianionic complexes, in which the metal centers have negative oxidation states, adopt distorted-squarepyramidal geometries with the hydride group in the axial position. The C-C bond lengths of 1.484(8), 1.502(8), and 1.515(8) Å for the ethylene groups in the tantalum complex are somewhat longer than those of 1.357(11)-1.466(10) Å in the tungsten complex. In both complexes, the Ta-H and W-H bonds are relatively long at 2.07(9) and 2.04(5) Å, due to the presence of close contacts with two lithium cations. In both the tantalum and tungsten complexes, two of the ethylene ligand(s) are involved in interactions with the lithium cations; these ethylene ligands rotate slowly about their metal-ligand axes on the NMR time scale at -80°C, whereas at this temperature the remaining ethylene ligands are rotating rapidly. At higher temperatures, the inequivalence of the ethylene environments is maintained in the tantalum complex, but they exchange in the tungsten compound. The activation parameters for the latter process are ∆H q ) 9.5(10) kcal mol -1 and ∆S q ) -5(4) cal mol -1 K -1 . Spin saturation transfer experiments show that there is no exchange of the W-H and W-C 2 H 4 environments on the NMR time scale. Qualitative molecular orbital descriptions of the bonding in all three compounds are presented.

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C‐Heterosubstituted Phosphorus Ylides

Kolodiazhnyi

1999

Phosphorus Ylides

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2004 C-Heterosubstituted Phosphorus Ylides carbon atom. Sometimes the distribution of the electron density in the ylide molecule is simultaneously affected by two or even three different factors, their relative contribution dependmg on the nature of the element and the surrounding ligands. C-substituted phosphorus ylides attract particular interest as reagents for organic synthesis, and thus find increasing application in laboratory practice and industry. For example, C-silicon phosphorus ylides have served as the basis for a series of preparative syntheses of medicinal, pheromone, and other types of phosphorus ylide. C-Phosphino phosphorus ylides are important ligands in transition-metal complexes, C-Halo phosphorus ylides are of interest for the preparation of haloalkenes. C-Nitrogen ylides are of considerable importance, especially in the synthesis of antibiotics. Numerous papers and patents on applications of C-substituted phosphorus ylides in various fields of organic synthesis have been generalized in several monograph^^^^'* and ,2,1O-I 3 . T h s present chapter summarizes data on the application in organic synthesis of phosphorus ylides substituted on the a carbon atom by atoms of elements of Groups I-VII Phosphorus Ylides Substituted on the a-Carbon by Atoms of Element Groups I-IVThe influence of the o-donor inductive and n-acceptor mesomeric effects of the elements is clearly exemplified by ylides containing metals and metalloids of the main subgroups of Groups I-IV of the periodic table on the u carbon atom. The elements with o-donor properties increase the electron density on the ylide carbon atom, thus changing the nucleophilicity and reactivity of the ylides, as for instance, in the case of C-lithiated ylides. In contrast, such elements as germanium and silicon reduce the electron density on the a carbon atom thus forming partial element-carbon double bonding by a p z d n mechanism that results in lowering of the nucleophilicity of the ylide. Often these two opposite effects act together, and their relative contribution depends on the nature of element and the surroundmg ligands. The chemistry of ylides containing lithium, boron, silicon, tin, and other elements on the u carbon atom has recently received considerable attention.

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Carbonylierung von Metallocenyliden Cp2M(R)(CHPPh3) des Zirconiums und Hafniums

Cited by 11 publications

References 56 publications

Reaction of Pentafulvene Titanium and Zirconium Complexes with Phosphorus Ylides: Stoichiometric Reactions and Catalytic Intramolecular Proton Shuttles

Reaction of Pentafulvene Titanium and Zirconium Complexes with Phosphorus Ylides: Stoichiometric Reactions and Catalytic Intramolecular Proton Shuttles

Ethylene Complexes of the Early Transition Metals: Crystal Structures of [HfEt₄(C₂H₄)²⁻] and the Negative-Oxidation-State Species [TaHEt(C₂H₄)₃³⁻] and [WH(C₂H₄)₄³⁻]

C‐Heterosubstituted Phosphorus Ylides

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Carbonylierung von Metallocenyliden Cp2M(R)(CHPPh3) des Zirconiums und Hafniums

Cited by 11 publications

References 56 publications

Reaction of Pentafulvene Titanium and Zirconium Complexes with Phosphorus Ylides: Stoichiometric Reactions and Catalytic Intramolecular Proton Shuttles

Reaction of Pentafulvene Titanium and Zirconium Complexes with Phosphorus Ylides: Stoichiometric Reactions and Catalytic Intramolecular Proton Shuttles

Ethylene Complexes of the Early Transition Metals: Crystal Structures of [HfEt4(C2H4)2−] and the Negative-Oxidation-State Species [TaHEt(C2H4)33−] and [WH(C2H4)43−]

C‐Heterosubstituted Phosphorus Ylides

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Ethylene Complexes of the Early Transition Metals: Crystal Structures of [HfEt₄(C₂H₄)²⁻] and the Negative-Oxidation-State Species [TaHEt(C₂H₄)₃³⁻] and [WH(C₂H₄)₄³⁻]