Chemistry of chromium bis-acetylide complexes

López‐Hernández, Alberto; Venkatesan, Koushik; Schmalle, Helmut W.; Berke, Heinz

doi:10.1007/s00706-008-0094-2

Cited by 10 publications

(4 citation statements)

References 42 publications

(23 reference statements)

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“…It has been shown that [(dmpe) 2 Cr II (C 2 R) 2 ] complexes can be prepared by addition of 2 equiv of LiC 2 R to [(dmpe) 2 CrCl 2 ]. , However, Berben demonstrated that a dinuclear Cr I dinitrogen-bridged acetylide complex could be synthesized by mixing [(dmpe) 2 CrCl 2 ] with stoichiometric LiC 2 SiMe 3 and excess n -butyllithium; the latter acts as a reducing agent. Nitrogen dissolved in the solvents cap and bridge the reduced Cr(dmpe) 2 (C 2 R) moieties.…”

Section: Resultsmentioning

confidence: 99%

Unusual Electronic Effects Imparted by Bridging Dinitrogen: an Experimental and Theoretical Investigation

2010

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We describe the preparation, structural and magnetic characterizations, and electronic structure calculations for a redox-related family of dinitrogen-bridged chromium acetylide complexes containing the [RC(2)Cr(μ-N(2))CrC(2)R](n+) (R = Ph-, (i)Pr(3)Si-; n = 0, 1, 2) backbone: [(dmpe)(4)Cr(2)(C(2)Ph)(2)(μ-N(2))] (1), [(dmpe)(4)Cr(2)(C(2)Si(i)Pr(3))(2)(μ-N(2))] (2), [(dmpe)(4)Cr(2)(C(2)Si(i)Pr(3))(2)(μ-N(2))]BAr(F)(4) (3), and [(dmpe)(4)Cr(2)(C(2)Si(i)Pr(3))(2)(μ-N(2))](BAr(F)(4))(2) (4). Compounds 3 and 4 are synthesized via chemical oxidation of 2 with [Cp(2)Co](+) and [Cp*(2)Fe](+), respectively. X-ray structural analyses show that the alteration of the formal Cr oxidation states does not appreciably change the Cr-N-N-Cr skeletal structures. Magnetic data collected for 2 and 4 are consistent with high-spin triplet and quintet ground states, respectively. The mixed-valent complex 3 exhibits temperature dependent magnetic behavior consistent with a quartet ⇌ doublet two-center spin equilibrium. Electronic structure calculations (B3LYP) performed on the full complexes in 2 and 4 suggest that the high-spin states arise from singly occupied orthogonal π* orbitals coupled with a variable occupation of dδ orbitals. Significant N-N and Cr-N π-bonding pins the occupation of the π manifold, leading to variable occupation of the dδ space. In contrast, mixed-valent 3 is not well described by a B3LYP hybrid density functional model. A [9,11] CAS-SORCI study on a simplified model of 3 reproduces the observed Hund's rule violation for the S = 1/2 ground state and places the lowest quartet 1.45 kcal/mol above the doublet ground state.

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Section: Resultsmentioning

confidence: 99%

Unusual Electronic Effects Imparted by Bridging Dinitrogen: an Experimental and Theoretical Investigation

2010

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“…In light of these applications we were curious as to the ability of 1 to serve as a synthon to form a new σ‐bond via a salt metathesis reaction with LiC 2 Ph. We reasoned this substrate a good choice to evaluate the electrophilic reactivity of 1 as lithium phenylacetylide is readily prepared, [57] phenlacetylide complexes of Cr are known to the crystallographic record, [58–69] and the steric demands of the square‐capping pentadentate NHC ought not prohibit access by the phenylacetylide anion. We observed no change to the paramagnetic 1 H NMR spectrum over the course of 24 hr upon charging a J‐young NMR tube with 1 and 1.2 equivalents of lithium phenylacetylide using THF‐d8 solvent.…”

Section: Resultsmentioning

confidence: 99%

A S=3/2 Cr(III) Complex In A Square‐Capping NHC Framework

Gau,

Scepaniak

2024

ChemistrySelect

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Deprotonation of our pentadentate N‐Heterocyclic Carbene (NHC) ligand with lithium diisopropylamine in tetrahydrofuran and subsequent salt metathesis with CrCl3THF3 readily forms the complex PhCC4MeCrCl (1), a S=3/2 species in moderate yield. DFT calculations reveal three singly occupied molecular orbitals with π‐backbonding character to the square‐capping framework, UV‐Vis spectroscopy reveals 3 bands ascribed to d‐to‐d transitions, and cyclic voltammetry reveals an irreversible and quazi‐reversible reduction events as well as an irreversible oxidation event. We attempted to exchange the chloride ligand of 1 through salt‐metathesis with lithium phenylacetylide without success, the absence of reactivity is rationalized considering our XRD and DFT results.

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“…Substitution reactions of the Cl 2 Cr(dmpe) 2 complex with lithium acetylides to form bis(acetylide) complexes were investigated earlier in our group, [38] however similar conditions could not be adopted for the synthesis of the monosubstituted alkyne complexes and the dinuclear butadiyne complexes. Hence, a different synthetic strategy was sought that involved the use of trimethylstannyl alkynyl reagents with the starting Cl 2 Cr(dmpe) 2 complex.…”

Section: Resultsmentioning

confidence: 99%

“…[38] X-ray Diffraction Studies: Single-crystal X-ray diffraction data were collected at 183(2) K with an Xcalibur diffractometer (Agilent Technologies, Ruby CCD detector) for compounds 2, 2[SnMe 3 -Cl 2 ] 2 , 8, and 10, and with a SuperNova Dual diffractometer (Agilent Technologies, Atlas CCD detector) for compound 9 using a single wavelength Enhance X-ray source with Mo-K α radiation (λ = 0.71073 Å). The cell was equipped with a Au working and Pt counter electrode, and a nonaqueous reference electrode.…”

Section: H Nmr and Varianmentioning

confidence: 99%

Dinuclear and Mononuclear Chromium Acetylide Complexes

et al. 2011

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2 ), which could be transformed to the 2[PF 6 ] 2 and 3[BPh 4 ] 2 salts. Substitutions of the chloride groups in 2 were carried out to achieve the corresponding iodo (4) and (trimethylsilyl)alkynyl (5) complexes. Utilizing similar reactions and treatment with only 1 equiv. of the corresponding alkynyl ligand [Me 3 Sn-CϵC-R (R = -SnMe 3 , -C 6 H 5 ), Me 3 Sn-CϵC-CϵC-R (R = -SiMe 3 , -SnMe 3 ), and Me 3 Sn-CϵC-C 6 H 4 -CϵC-SnMe 3 ] allowed us to prepare a series of mononuclear monoacetylide Eur. J. Inorg. Chem. 2012, 1536-1545

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Chemistry of chromium bis-acetylide complexes

Abstract: (R = Ph, SiMe 3 , SiEt 3 , C:C-SiMe 3 n = 0, 1) were prepared and characterised by NMR, cyclic voltammetry, EPR, magnetic measurements, and X-ray single-crystal diffraction studies.

Cited by 10 publications

References 42 publications

Unusual Electronic Effects Imparted by Bridging Dinitrogen: an Experimental and Theoretical Investigation

Unusual Electronic Effects Imparted by Bridging Dinitrogen: an Experimental and Theoretical Investigation

A S=3/2 Cr(III) Complex In A Square‐Capping NHC Framework

Dinuclear and Mononuclear Chromium Acetylide Complexes

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