<i>ansa</i>-Chromocene Complexes. 1. Synthesis and Characterization of Cr(II) Carbonyl and <i>tert</i>-Butyl Isocyanide Complexes

Matare, Gilbert J.; Foo, David Min Jin; Kane, Kevin M.; Zehnder, Ralph A.; Wagener, Marion; Shapiro, Pamela J.; Concolino, Tom; Rheingold, Arnold L.

doi:10.1021/om9909993

Cited by 33 publications

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References 34 publications

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“…In fact, the CO ligand is required to stabilize the 16 e ansa-chromocene fragment. Improved synthetic routes to 1 and related isocyanide derivatives [6][7][8] …”

Section: }]mentioning

confidence: 99%

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Ring‐Borylated 15‐Electron and 17‐Electron ansa‐Chromocene Complexes, their Physical Properties and Molecular Structures

Shapiro

Sinnema

Perrotin

et al. 2007

Chemistry A European J

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A detailed study of the thermal decomposition of the zwitterionic, ring-borylated ansa-chromocene hydrido carbonyl complex [Cr(CO)H{Me(4)C(2)(C(5)H(4))[C(5)H(3)B(C(6)F(5))(3)]}] (2) is described. This complex is formed in the reaction between [Cr(CO){Me(4)C(2)(C(5)H(4))(2)}] (1) and B(C(6)F(5))(3) in toluene at -78 degrees C. Above -25 degrees C, 2 decomposes to a 50:50 mixture of the low-spin, 17e Cr(III) complexes [Cr(CO){Me(4)C(2)(C(5)H(4))[C(5)H(3)B(C(6)F(5))(3)]}] (3b) and [Cr(CO){Me(4)C(2)(C(5)H(4))(2)}][HB(C(6)F(5))(3)] (4). Carbon monoxide elimination from 3 b generates high-spin, 15 e [Cr{Me(4)C(2)(C(5)H(4))[C(5)H(3)B(C(6)F(5))(3)]}] (3a), which coordinates two other electron-donating ligands, such as xylyl isocyanide, PMe3, and PPh(2)Me to form the low-spin, 17 e electron complexes 3c, 3d, and 3e, respectively. High-spin, 15 e [Cr{Me(4)C(2)(C(5)H(4))(2)}][HB(C(6)F(5))(3)] (5) is generated by heating 3 b in toluene at 100 degrees C and periodically removing the evolved CO. Efforts to isolate more than a few X-ray quality crystals of 5 were thwarted by its tendency to form an insoluble precipitate (6) with the same molecular formula. Heating the solution of 5 at 120 degrees C results in its partial conversion (ca. 28 %) to 3a, thereby allowing the formation of 3a in yields as high as 74 % from the reaction between 1 and B(C(6)F(5))(3). The X-ray crystal structures of 3 b-e and 5 are described. Cyclic voltammetry measurements on 3 a-e reveal a dramatic reduction in the redox potentials of the complexes relative to their non-borylated analogues. DFT calculations show that this is due primarily to electrostatic stabilization of the oxidized species by the negatively charged borylate group. EPR and 19F NMR spectroscopy allow 3a to be distinguished from its Lewis base adducts 3 b-e and reveal the relative affinities of different Lewis bases for the chromium.

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“…In fact, the CO ligand is required to stabilize the 16 e ansa-chromocene fragment. Improved synthetic routes to 1 and related isocyanide derivatives [6][7][8] …”

Section: }]mentioning

confidence: 99%

“…Improved single-point energies were obtained at the b3-lyp/TZVPP level and solvent corrections were calculated using the cosmo solvation model (e = 7.5, THF). Frequency calculations were not feasible for the larger systems, so all energies discussed below are elec- [7].…”

mentioning

confidence: 99%

Ring‐Borylated 15‐Electron and 17‐Electron ansa‐Chromocene Complexes, their Physical Properties and Molecular Structures

Shapiro

Sinnema

Perrotin

et al. 2007

Chemistry A European J

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“…They do, however produce a mixture of rac and meso stereoisomers that can be readily separated by crystallization (Eqn 4). Ansa-chromocene carbonyl and t-butylisocyanide complexes 3-6 were isolated in 60-80% yields [67] as compared with 30-50% yields for 1 and 2 (Eqn 5).…”

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

confidence: 99%

“…We too performed cyclic voltammetry measurements on complex 1 and other ansa-chromocene carbonyl and isocyanide derivatives [67,71]. Some interesting trends are worth noting from the data in Table 1.…”

Section: Cr(ii) Cr(iii)mentioning

confidence: 99%

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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“…Whereas the carbonyl complex Cp 2 CrCO cannot be isolated due to the reversible binding of CO by chromocene [8], various ansa-chromocenes were prepared and crystallographically characterized [9,10]. DFT calculations indicated that the stabilization of the CO complex of ansa-chromocene is the consequence of the stability of the triplet metallocene product.…”

Section: Introductionmentioning

confidence: 99%

Electronic Structure of Ferrocene-Substituted Cavitands: A QTAIM and NBO Study

Kégl

Kollár

Kégl

2014

Journal of Quantum Chemistry

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Ferrocene-substituted tetrakis(methyl)resorcin [4]arenes have been investigated by means of DFT calculations employing the gradient-corrected PBEPBE functional. In comparison with ferrocene and simple ansa-ferrocenes containing 2-4 bridging methylene groups, it was found that the tilt angle of the functionalized cyclopentadienyl (Cp) rings strongly influences the electron density distribution of the ferrocenyl moieties. According to NBO analyses, the iron atoms in the cavitands are more positive in comparison to those in ferrocene, whereas they are less positive in ansa-ferrocenes. The partial charges of carbon atoms belonging to Cp rings show some correlation with the tilt angle.

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

Cited by 33 publications

References 34 publications

Ring‐Borylated 15‐Electron and 17‐Electron ansa‐Chromocene Complexes, their Physical Properties and Molecular Structures

Ring‐Borylated 15‐Electron and 17‐Electron ansa‐Chromocene Complexes, their Physical Properties and Molecular Structures

The Elusive Chemistry of Bent-Sandwich Chromocene

Electronic Structure of Ferrocene-Substituted Cavitands: A QTAIM and NBO Study

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