Hindered (.eta.-cyclopentadienyl)-metal rotation caused by lateral interaction of Cp-bonded substituents at chalcogen-bridged binuclear bent metallocene complexes [(RCp)2ZrX]2

Erker, Gerhard; Nolte, R.J.M.; Tainturier, G.; Rheingold, Arnold L.

doi:10.1021/om00104a028

Cited by 31 publications

(10 citation statements)

References 6 publications

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“…1 H NMR spectroscopic investigations reveal a restricted rotation around the ( t BuC 5 H 4 )−Nb bonds at −90 °C. Although a similar conformation has been found in the related complex [( t BuC 5 H 4 ) 4 Zr 2 Te 2 ], there is no spectroscopic evidence for a restricted rotation around the ( t BuC 5 H 4 )−Zr axis 32 …”

Section: Introductionsupporting

confidence: 61%

Metal Telluride Clusters — From Small Molecules to Polyhedral Structures

Wächter

2004

Eur J Inorg Chem

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Section: Introductionsupporting

confidence: 61%

Metal Telluride Clusters — From Small Molecules to Polyhedral Structures

Wächter

2004

Eur J Inorg Chem

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“…Molecular structure of [CpЈ 4 Nb 2 Te 2 ] (5) [25] the related complex [CpЈ 4 Zr 2 Te 2 ] as well, in this complex the 1 H NMR spectra could not provide evidence for a restricted rotation around the CpЈϪZr axis. [21] In our case, examination of CD 2 Cl 2 solutions reveals two signals for the C 5 H 4 protons and one resonance for the tBu group at ambient temperature, with splitting of the aromatic resonances into four multiplets at δ ϭ 3.24, 4.79, 5.47, and 5.61 upon cooling to Ϫ90°C. As expected the tBu resonance remains unaffected.…”

Section: Preparation Characterization and Methylation Of [Cpј 4 Nb mentioning

confidence: 49%

“…Recently it has been shown that for bent group 4 metallocenes like [(tBuC 5 H 4 ) 2 ZrX 2 ] (X ϭ halogen, alkyl, aryl), chiral ground-state geometries are able to epimerize upon rotation around the CpЈϪmetal bond. [21] The activation barrier for this rotation depends on the interaction of yield. An FD mass spectrum, elemental analysis and X-ray diffraction studies confirmed the composition of 3.…”

Section: Preparation and Characterization Of Complexes 1؊4mentioning

confidence: 99%

“…A bonding interaction between opposite atoms Te(1) and Te(1Ј) [d ϭ 4.262(1) Å ] was excluded [25] in agreement with literature values given for planar M 2 Te 2 rings: Whereas in the Ni 2 Te 2 cycle of [(iPr 4 C 5 H) 2 Ni 2 (µ-Te) 2 ] the observed Te···Te distance of 3.052(5) Å has been ascribed to a bond order of nearly one, [26] a clearly nonbonding situation has been found in [CpЈ 4 Zr 2 Te 2 ] [d(Te···Te) ϭ 4.006(1) Å ]. [21] Less evident is the interpretation of the Nb(1)···Nb(1Ј) distance in 5. The found value of 3.647(1) Å is about 0.22 Å longer than that in compounds 2 and 4.…”

Section: Preparation Characterization and Methylation Of [Cpј 4 Nb mentioning

confidence: 99%

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Bis(η-tert-butylcyclopentadienyl)hydridoniobium Ditelluride, a Convenient Reagent for the Synthesis of Polynuclear Metal Telluride Complexes

Brunner¹,

Cattey²,

Evrard³

et al. 2002

Eur. J. Inorg. Chem.

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Reaction of [Cp′2NbH3] (Cp′ = tBuC5H4) with Te powder in THF gives [Cp′2Nb(Te2)H] (1) and [Cp′6Nb4Te4O] (2). The yield of 1 varies between 10 and 81% depending on the degree of oxygen contamination of the reagents. Complexes 1 and 2 react with [Cr(CO)5THF] to give [Cp′2Nb(Te2)H·Cr(CO)5] (3) and [Cp′6Nb4Te4O·2Cr(CO)5] (4), respectively. The crystal structures of 2−4 have been determined. In 3 a Te2 unit and an H ligand are coordinated to a bent niobocene moiety; the Cr(CO)5 group is attached to the lateral Te atom. The molecular cores of 2 and 4 are practically identical in that they contain two planar Nb2Te2 rings connected by a nearly linear oxygen bridge. Each of the “outer” Nb atoms bears two Cp′ ligands, whereas the “inner” Nb atom only has one such ligand. An additional structural feature in 4 is two Cr(CO)5 groups, attached to one Te bridge of each Nb2Te2 ring. Thermolysis of 3 leads to the formation of diamagnetic [Cp′4Nb2Te2] (5), which also contains a planar Nb2Te2 core. The relatively long transannular Nb−Nb distance (3.647 Å) is consistent, according to DFT calculations, with a through‐space Nb−Nb coupling. Complex 5 reacts with CH3I with successive methylation of both Te bridges to give [Cp′4Nb2Te(CH3Te)]I ([6]I) and [Cp′4Nb2(CH3Te)2]I2 ([7]I2). The crystal structure of [7]I2 may be derived from that of 5, the incoming CH3 groups being fixed at the Te bridges in a trans position. 1H NMR spectroscopic investigations reveal a restricted rotation around the Cp′−Nb bonds in 2 and 5 at −90 °C and in 4 and [7]I2 at ambient temperature. Electrochemical studies have been carried out on 5, [6]I, and [7]I2, showing that all compounds undergo two reversible one‐electron reduction steps. The reduction potential decreases by ca. 1.6 V when going from 5 to [7]I2. There is also a clear linear correlation between the reduction potentials measured for 5 to [7]I2 and the energies of the corresponding LUMO’s calculated at the DFT/B3LYP level. These LUMO’s bear some 70% contribution from both Nb atoms and, consequently, the reduction processes mainly operate at both metallic centers. (© Wiley‐VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

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“…Additionally, a hindered C 5 H 5 ligand rotation in solution at room temperature would be a novelty. All reports we found in the literature for a hindered Cp ligand rotation of bent sandwich Cp 2 ZrX 2 complexes concern such species, where both ring ligands carry bulky substituents [18].…”

Section: Resultsmentioning

confidence: 91%