Zwitterionic Ring-Borylated <i>a</i><i>nsa</i>-Chromocene Complexes

Sinnema, Piet-Jan; Shapiro, Pamela J.; Foo, David Min Jin; Twamley, Brendan

doi:10.1021/ja026633q

Cited by 27 publications

(22 citation statements)

References 12 publications

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“…Species without additional ligands such as 41 and 47 have also been reported but are very rare. [146,147] For unsubstituted 41 the a angle is about 58 less than that found in the substituted analogue 42, whereas a similar comparison of 47-49 reveals nearly invariant a angles due to intramolecular substitution. However, no examples of ring-opening reactions have been reported for these d 4 species, and the presence of strain is an intriguing and still open question.…”

Section: Metallocenophanes Of Chromium Molybdenum Tungsten and Rhementioning

confidence: 87%

Strained Metallocenophanes and Related Organometallic Rings Containing π‐Hydrocarbon Ligands and Transition‐Metal Centers

2007

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The structures, bonding, and ring-opening reactions of strained cyclic carbon-based molecules form a key component of standard textbooks. In contrast, the study of strained organometallic molecules containing transition metals is a much more recent development. A wealth of recent research has revealed fascinating nuances in terms of structure, bonding, and reactivity. Building on initial work on strained ferrocenophanes, a broad range of strained organometallic rings composed of a variety of different metals, pi-hydrocarbon ligands, and bridging elements has now been developed. Such strained species can potentially undergo ring-opening reactions to functionalize surfaces and ring-opening polymerization to form easily processed metallopolymers with properties determined by the presence of the metal and spacer. This Review summarizes the current state of knowledge on the preparation, structural characterization, electronic structure, and reactivity of strained organometallic rings with pi-hydrocarbon ligands and d-block metals.

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Section: Metallocenophanes Of Chromium Molybdenum Tungsten and Rhementioning

confidence: 87%

Strained Metallocenophanes and Related Organometallic Rings Containing π‐Hydrocarbon Ligands and Transition‐Metal Centers

2007

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“…[9] Above À20 8C, 2 decomposes cleanly to a 1:1 mixture of two Cr III species, low-spin 17 e [Cr(CO)A C H T U N G T R E N N U N G {Me 4 . Here we present the molecular structures, physical properties, and reactivity of these complexes and other 15 e and 17 e species that are derived from them.…”

Section: Complexes [Cr(co)a C H T U N G T R E N N U N G {Me 4 C 2 a Cmentioning

confidence: 99%

“…The molecular structures of complexes 2 and 3 a were described previously. [9] The molecular structure of 3 b is shown in Figure 1. Selected structural parameters for the complex are listed in the caption for Figure 1 and in Table 1.…”

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, CrH 4 remains elusive and its tetrahedral 3 A 2 ground-state structure was calculated to lie 38.5 kcal mol À1 higher in energy than that of the dihydrogen complex isomer [CrH 2 (h 2 -H 2 )] ( 5 A 1 ) at the CCSD/TZP level of theory. [3,4] À1 , B3LYP/6-311 + + G(d,p)), [5] [9] have been isolated and structurally characterized. We report herein the synthesis, characterization, and theoretical calculations of mononuclear chromium(iii) and chromium(iv) hydrides stabilized by a triamidoamine ligand.…”

Section: Dedicated To Prof E O Fischer On the Occasion Of His 85thmentioning

confidence: 99%

A Pair of Remarkably Stable Mononuclear Chromium(III) and Chromium(IV) Hydrides

2003

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Zwitterionic Ring-Borylated ansa-Chromocene Complexes

Cited by 27 publications

References 12 publications

Strained Metallocenophanes and Related Organometallic Rings Containing π‐Hydrocarbon Ligands and Transition‐Metal Centers

Strained Metallocenophanes and Related Organometallic Rings Containing π‐Hydrocarbon Ligands and Transition‐Metal Centers

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

A Pair of Remarkably Stable Mononuclear Chromium(III) and Chromium(IV) Hydrides

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