ansa-Metallocene derivatives

Raaij, Edith U. van; Mönkeberg, Sigrid; Kiesele, Herbert; Brintzinger, Hans‐Herbert

doi:10.1016/0022-328x(88)83148-6

Cited by 11 publications

(8 citation statements)

References 21 publications

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“…This explanation is confirmed by recent density functional calculations by Green and Jardine . The effect of the ansa -bridge on the redox properties of the metal center is consistent with the calculated effects of ring bending on the energies of the frontier orbitals. − , The bridge also increases the tendency of the chromocene to undergo ring slippage …”

Section: Introductionsupporting

confidence: 84%

ansa-Chromocene Complexes. 1. Synthesis and Characterization of Cr(II) Carbonyl andtert-Butyl Isocyanide Complexes

Matare¹,

Foo²,

Kane³

et al. 2000

Organometallics

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ansa-Calcocene compounds are effective reagents for the synthesis of ansa-chromocene complexes from CrCl 2 in the presence of a trapping ligand such as carbon monoxide or an isonitrile. A variety of ansa-chromocene carbonyl and tert-butyl isocyanide complexes have been prepared in this manner in high yields. The X-ray crystal structure of one of these complexes,CrCO, is described. Electrochemical studies on these complexes show that the isonitrile derivatives are more easily oxidized than the carbonyl derivatives. Preliminary examination of the reactivity of these complexes indicates that the nature of the substitution along the ethanediyl ansa-bridge influences the relative stabilities of the carbonyl complexes to oxidation in air, the ease with which the carbonyl ligands undergo substitution with tert-butyl isocyanide, and the relative sensitivities of the tert-butyl isocyanide adducts to photodecomposition. The ansa-bridge substitution also appears to influence the ability of the complexes to undergo structural changes, such as ring slippage, as revealed in their cyclic voltammograms.

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Section: Introductionsupporting

confidence: 84%

ansa-Chromocene Complexes. 1. Synthesis and Characterization of Cr(II) Carbonyl andtert-Butyl Isocyanide Complexes

Matare¹,

Foo²,

Kane³

et al. 2000

Organometallics

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“…From studies on the electrochemistry of (CH3)4C2(CsH4hCr(CO) [1] it is clear that this species is easily and reversible oxidized, at potentials of ca. co SCE, to a monocation, which is stable towards loss of CO on the CV time scale.…”

Section: Reaction Of (C5h5)2cr(co) With An Excess Of Comentioning

confidence: 99%

“…Small amounts of the dicarbonyl cation could be sufficient, however, to set up a redox-catalysed reaction cycle. instability of the unbridged monocarbonyl cation (CsHshCr(CO)+, which rapidly loses its CO ligand [1], in contrast to its tetramethylethanediyl-bridged counterpart (CH3)4C2(CsH4hCr(CO)+, which is quite stable on the CV time scale.…”

Section: Reaction Of (C5h5)2cr(co) With An Excess Of Comentioning

confidence: 99%

ansa-Metallocene derivatives

Raaij¹,

Brintzinger²

1988

Journal of Organometallic Chemistry

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“…Cyclic voltammetry measurements showed that the one and two electron oxidation products [1] + and [1] 2+ are stable against CO loss. By contrast, one electron oxidation of Cp 2 CrCO at 0ºC caused it to lose its CO ligand and a second oxidation was not observed [60].…”

Section: Ansa-chromocene Compounds Two Atom-bridged Ansa-chromocene Cmentioning

confidence: 90%

“…van Raiij et al reported in 1988 that complex 1 exhibits a quasi-reversible Cr II/III couple and an electrochemically irreversible yet chemically reversible Cr III/IV couple [60]. We too performed cyclic voltammetry measurements on complex 1 and other ansa-chromocene carbonyl and isocyanide derivatives [67,71].…”

Section: Cr(ii) Cr(iii)mentioning

confidence: 97%

The Elusive Chemistry of Bent-Sandwich Chromocene

Shapiro¹

2007

COC

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Until recently the chemistry of bent-sandwich chromocene eluded examination due to the propensity of dicyclopentadienylchromium toward cyclopentadienyl ring loss and thermodynamic barriers to coordinating two electron donating ligands such as CO. The use of modified cyclopentadienyl ligands such as acyclic pentadienyl ligands and linked dicyclopentadienyl ligands, by changing the electronic demands of the metal, have allowed access to neutral and cationic bent-sandwich chromocene derivatives with interesting structures, redox properties, and ligand coordination/substitution behavior. This review article provides an overview of the synthesis, magnetic properties, and reactivity of Cp 2 Cr (Cp = C 5 H 5 ) and related compounds, the chemistry of open chromocene compounds containing acyclic pentadienyl ligands, and a more detailed discussion of the chemistry of ansa-chromocene complexes, which has been the research focus of the author. INTRODUCTIONThe chemistry of dicyclopentadienylchromium (chromocene) [1,2] has been less illustrious than that of metallocenes of other early transition metals from groups 3-6, some of which are recognized for their catalytic activity toward alkene and alkyne polymerization and other synthetically useful reactions while others have served as model systems for fundamentally interesting transition metal mediated reactions [3]. This situation is due to chromocene's preference for a parallel-ring geometry, which allows it to maintain a high spin electronic configuration with a 3 E 2g (e 2g 3 a 1g

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ansa-Metallocene derivatives

Cited by 11 publications

References 21 publications

ansa-Chromocene Complexes. 1. Synthesis and Characterization of Cr(II) Carbonyl andtert-Butyl Isocyanide Complexes

ansa-Chromocene Complexes. 1. Synthesis and Characterization of Cr(II) Carbonyl andtert-Butyl Isocyanide Complexes

ansa-Metallocene derivatives

The Elusive Chemistry of Bent-Sandwich Chromocene

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