<i>a</i><i>nsa</i>-Chromocene Complexes. 2. Isocyanide Derivatives of Cr(II) and Cr(III), Their Syntheses, X-ray Crystal Structures, and Physical Properties

Shapiro, Pamela J.; Zehnder, Ralph A.; Foo, David Min Jin; Perrotin, Philippe; Budzelaar, Peter H. M.; Leitch, Sharon; Twamley, Brendan

doi:10.1021/om050710j

Cited by 25 publications

(12 citation statements)

References 55 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%

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%

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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“…In 1983, Brintzinger and co-workers reported the first bent-sandwich ansa -chromocene complex, Me 4 C 2 (C 5 H 4 ) 2 CrCO, which is stable to CO loss, unlike its unbridged counterpart, (C 5 H 5 ) 2 CrCO . Our group discovered a more facile route to Me 4 C 2 (C 5 H 4 ) 2 CrCO and other ethanediyl-bridged chromocene carbonyl and isocyanide complexes that employs ansa -calcocene compounds as a ligand source (Scheme ) . We have used these ansa -metallocene complexes of Cr(II) as an entry point to novel bent-metallocene complexes of Cr(III) and Cr(IV) .…”

Section: Introductionmentioning

confidence: 99%

In Search of a Versatile Pathway toansa-Chromocene Complexes. Synthesis and Characterization of the Highly Unstableansa-Chromocene Carbonyl Complex Me₂C(C₅H₄)₂CrCO

et al. 2007

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In an effort to develop a general synthetic route to ansa-chromocene complexes with diverse ligand frameworks, we investigated ansa-magnesocene compounds as an alternative, potentially more versatile ligand source than ansa-calcocene compounds. The first single-carbon-bridged ansa-chromocene compound, Me2C(C5H4)2CrCO, was isolated from the reaction between Me2C(C5H4)2Mg and CrCl2 in THF under an atmosphere of carbon monoxide. This new ansa-chromocene compound is considerably more air-sensitive and less chemically stable than its ethanediyl-bridged counterparts.

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“…[Li(12-crown-4) 2 ] 2 [Zr(C 6 F 5 ) 4 Cl 2 ] (tilt angles: 30.8-66.9 • ), 13 5) pm). 16 It is interesting to note, however, that the low magnetic moments obtained for these ansametallocenium complexes (m eff ~1.8 m B ), indicate an electronic configuration that is substantially different from that found in our Cp-free compounds (see below). The coordination of the CNXy ligand to the "Cr(C 6 F 5 ) 4 " fragment in 3 produces no significant change in the structural features associated with the C N-R unit.…”

Section: Synthesis and Structural Characterisationmentioning

confidence: 56%

Synthesis, characterisation and magnetic properties of octahedral chromium(iii) compounds with six C-donor ligands

et al. 2011

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The homoleptic, square pyramidal organochromium(III) compound [NBu(4)](2)[Cr(C(6)F(5))(5)] (1) reacts with excess organic isocyanides, CNR [R = (t)Bu, 2,6-dimethylphenyl (Xy)], under dissociation of the apical C(6)F(5) ligand to give the more saturated, singly charged complexes [NBu(4)][trans-Cr(C(6)F(5))(4)(CNR)(2)] [R = (t)Bu (2), Xy (3)], containing six monodentate C-donor ligands. These compounds exhibit an axially distorted octahedral structure (single-crystal X-ray diffraction) with the four C(6)F(5) groups defining the equatorial positions and the CNR ligands occupying the axial ones. Compounds 2 and 3 both behave as spin quartet species (S = 3/2) at microscopic level (EPR spectroscopy), their macroscopic magnetic properties depending upon the nature of the terminal R group, as established by magnetisation measurements. When the R substituent is the saturated alkyl group (t)Bu, the compound (2) behaves as a simple paramagnet, with no magnetic interaction between individual Cr(III) centres along the whole temperature range measured (1.8-265 K). By contrast, a weak antiferromagnetic interaction is detected for compound 3 at low temperature with T(N) = 0.19(1) K. Since the closest intermetallic distances are similar in the crystals of 2·CH(2)Cl(2) and 3·1.75CH(2)Cl(2) (ca. 1.1 nm), we conclude that the insaturation of the aromatic Xy group together with the extended intermolecular π-π stacking interactions between Xy rings observed in the crystal lattice of 3·1.75CH(2)Cl(2) (centroid-to-centroid distance: 0.35 nm) favour magnetic interaction between the individual magnetic centres.

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ansa-Chromocene Complexes. 2. Isocyanide Derivatives of Cr(II) and Cr(III), Their Syntheses, X-ray Crystal Structures, and Physical Properties

Cited by 25 publications

References 55 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

In Search of a Versatile Pathway toansa-Chromocene Complexes. Synthesis and Characterization of the Highly Unstableansa-Chromocene Carbonyl Complex Me₂C(C₅H₄)₂CrCO

Synthesis, characterisation and magnetic properties of octahedral chromium(iii) compounds with six C-donor ligands

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ansa-Chromocene Complexes. 2. Isocyanide Derivatives of Cr(II) and Cr(III), Their Syntheses, X-ray Crystal Structures, and Physical Properties

Cited by 25 publications

References 55 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

In Search of a Versatile Pathway toansa-Chromocene Complexes. Synthesis and Characterization of the Highly Unstableansa-Chromocene Carbonyl Complex Me2C(C5H4)2CrCO

Synthesis, characterisation and magnetic properties of octahedral chromium(iii) compounds with six C-donor ligands

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In Search of a Versatile Pathway toansa-Chromocene Complexes. Synthesis and Characterization of the Highly Unstableansa-Chromocene Carbonyl Complex Me₂C(C₅H₄)₂CrCO