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

Shapiro, Pamela J.; Sinnema, Piet-Jan; Perrotin, Philippe; Budzelaar, Peter H. M.; Weihe, Høgni; Twamley, Brendan; Zehnder, Ralph A.; Nairn, Justin J.

doi:10.1002/chem.200601901

Cited by 8 publications

(5 citation statements)

References 45 publications

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“…Complex 5 shows a stretching frequency of ν CN = 2117 cm −1 in its IR spectra, practically unchanged from free isocyanide (ν CN = 2119 cm −1 ). The frequency is notably lower than in (C 6 F 5 S) 3 Cr(CNXyl) 3 (ν CN = 2183, 2330, and 2358 cm −1 ) and comparable to those observed in Shapiro’s ansa -chromocene complexes ([Me 4 C 2 (C 5 H 4 ) 2 Cr III (CNXyl)] + : ν CN = 2119 cm −1 , Me 4 C 2 (C 5 H 4 )(C 5 H 4 B(C 6 F 5 ) 3 )Cr III (CNXyl): ν CN = 2100 cm −1 ). , In contrast to these pseudotetrahedral chromocenes, for which coordination of isocyanide to a cationic, high-spin chromocene resulted in a low-spin isocyanide adduct, octahedral 5 remains, as expected, a high-spin complex (μ eff = 3.5(1) μ B ).…”

Section: Resultssupporting

confidence: 73%

Chromium(III) Bis(diketiminate) Complexes

Latreche

Schaper

2010

Organometallics

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Reaction of two equivalents of the lithium salt of N,N′-dibenzyl-2-amino-4-iminopent-2-ene, nacnac BnLi(THF), 1, with CrCl3(THF)3 or CrCl3 yielded nacnac Bn 2CrCl as a putative intermediate, which could be trapped by addition of 2,6-xylyl isocyanide to give the isocyanide-coordinated, octahedral complex nacnac Bn 2CrCl(CNC6Me2H3), 5. In the absence of isocyanide, ligand redistribution to the homoleptic tris(diketiminate) complex nacnac Bn 3Cr, 3, occurred upon concentration, standing, or workup with apolar solvents. Workup with diethyl ether afforded the bimetallic-bridged complex nacnac Bn 2Cr(μ-Cl)2Li(THF)2, 6. Reaction of CrCl3(THF)3 with one equivalent of 1 afforded the monodiketiminate complexes {nacnac BnCrCl(THF)(μ-Cl)}2 or {nacnac BnCrCl(μ-Cl)}2, depending on reaction conditions. Reaction of CrCl2(THF) x with two equivalents of 1 gave rise to nacnac Bn 2Cr, 4. Complexes 3−6 were characterized by X-ray diffraction studies. All octahedral complexes display a cis geometry with two nacnac ligands in a distorted, boat-like conformation.

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Section: Resultssupporting

confidence: 73%

Chromium(III) Bis(diketiminate) Complexes

Latreche

Schaper

2010

Organometallics

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“…While ferrocene plays a prevalent role in this field because of its ease of preparation and well-established dilithiation protocol, other sandwich compounds have also been the subject of investigations. Recently, several diamagnetic metalloarenophanes derived from [M(η 6 -C 6 H 6 ) 2 ] (M = Cr, Mo) and [M(η 5 -C 5 H 5 )(η 7 -C 7 H 7 )] (M = Ti, Cr) have been prepared and, in some instances, successfully polymerized by ROP. , Some systems, like the sandwich compounds of titanium, chromium, or rhodium, show the potential to access different oxidation states. Furthermore, cationic ansa -derivatives are known, for example, of cobaltocene , or [Ti(η 5 -C 5 H 5 )(η 8 -C 8 H 8 )] …”

Section: Introductionmentioning

confidence: 99%

A Paramagnetic Heterobimetallic Polymer: Synthesis, Reactivity, and Ring-Opening Polymerization of Tin-Bridged Homo- and Heteroleptic Vanadoarenophanes

et al. 2015

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The synthesis of the first tin-bridged bis(benzene) vanadium and trovacene sandwich compounds and the investigation of their oxidative addition and insertion behavior are reported. The vanadoarenophanes and the corresponding platinum insertion products were fully characterized including electrochemical and electron paramagnetic resonance (EPR) measurements. Controllable ring-opening polymerization of the heteroleptic tin-bridged [1]trovacenophane using Karstedt's catalyst yields a high molecular weight polymer (up to M(n) = 89 200 g·mol(-1)) composed of d(5)-vanadium metal centers in the main chain, making it a rare example of a spin-carrying macromolecule. Magnetic susceptibility measurements (SQUID) confirm the paramagnetic scaffold with repeating S = 1/2 centers in the main chain and suggest antiferromagnetic interactions between adjacent spin sites (Weiss constant Θ = -2.9 K).

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“…The negatively charged borylate group in complexes 22-25 has a dramatic influence on the redox potential of the chromium center, lowering the potential of the Cr II/III couple by as much as 500 mV [74]. We were able to capitalize on [75].…”

Section: Ring Borylation Of Ansa-chromocene Compoundsmentioning

confidence: 98%

“…Compound 22 coordinates other two-electron donating ligands such as xylyl isocyanide, trimethylphosphine, and dimethylphenylphosphine to form low spin (S = ), 17e adducts 23, 24, and 25, respectively (Eqn 10) [74]. X-ray crystal structures of 21 and 23 revealed unusual, intramolecular -stacking interactions between the CO and CNxyl ligands and a C 6 F 5 ring of the pendant borylate group.…”

Section: Ring Borylation Of Ansa-chromocene Compoundsmentioning

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

Cited by 8 publications

References 45 publications

Chromium(III) Bis(diketiminate) Complexes

Chromium(III) Bis(diketiminate) Complexes

A Paramagnetic Heterobimetallic Polymer: Synthesis, Reactivity, and Ring-Opening Polymerization of Tin-Bridged Homo- and Heteroleptic Vanadoarenophanes

The Elusive Chemistry of Bent-Sandwich Chromocene

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