Theory, synthesis and reactivity of quintuple bonded complexes

Nair, Anokh K.; Harisomayajula, N. V. Satyachand; Tsai, Yi‐Chou

doi:10.1039/c3dt53565g

Cited by 33 publications

(13 citation statements)

References 123 publications

(146 reference statements)

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“…7 The reactivities of these quintuply bonded species are currently being explored, and initial studies show promise as inorganic counterparts to the wider reactivity of unsaturated carbon–carbon bonds. 7,8 …”

Section: Introductionmentioning

confidence: 99%

Pushing the Limits of Delta Bonding in Metal–Chromium Complexes with Redox Changes and Metal Swapping

Eisenhart¹,

Rudd²,

Planas³

et al. 2015

Inorg. Chem.

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Into the metalloligand Cr[N(o-(NCH2P(iPr)2)-C6H4)3] (1, CrL) was inserted a second chromium atom to generate the dichromium complex Cr2L (2), which is a homobimetallic analogue of the known MCrL complexes, where M is manganese (3) or iron (4). The cationic and anionic counterparts, [MCrL]+ and [MCrL]−, respectively, were targeted, and each MCr pair was isolated in at least one other redox state. The solid-state structures of the [MCrL]+,0,− redox members are essentially the same, with ultrashort metal–metal bonds between 1.96 and 1.74 Å. The formal shortness ratios (r) of these interactions are between 0.84 and 0.74 and are interpreted as triple to quintuple metal–metal bonds with the aid of theory. The trio of (d–d)10 species [Cr2L]− (2red), MnCrL (3), and [FeCrL]+ (4ox) are S = 0 diamagnets. On the basis of M—Cr bond distances and theoretical calculations, the strength of the metal–metal bond across the (d–d)10 series increases in the order Fe < Mn < Cr. The methylene protons in the ligand are shifted downfield in the 1H NMR spectra, and the diamagnetic anisotropy of the metal–metal bond was calculated as −3500 × 10−36, −3900 × 10−36, and −5800 × 10−36 m3 molecule−1 for 2red, 3, and 4ox respectively. The magnitude of diamagnetic anisotropy is, thus, affected more by bond polarity than by bond order. A comparative vis–NIR study of quintuply bonded 2red and 3 revealed a large red shift in the δ4 → δ3δ* transition energy upon swapping from the (Cr2)2+ to the (MnCr)3+ core. Complex 2red was further investigated by resonance Raman spectroscopy, and a band at 434 cm−1 was assigned as the Cr—Cr bond vibration. Finally, 4ox exhibited a Mössbauer doublet with an isomer shift of 0.18 mm/s that suggests a primarily Fe-based oxidation to Fe(I).

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Section: Introductionmentioning

confidence: 99%

Pushing the Limits of Delta Bonding in Metal–Chromium Complexes with Redox Changes and Metal Swapping

Eisenhart¹,

Rudd²,

Planas³

et al. 2015

Inorg. Chem.

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“…Dichromium paddlewheels feature prominently in the history of metal-metal multiple bonds. [1][2][3][4][5] Despite the vast number of multiply bonded Cr 2 4+ paddlewheels, only one species, a dichromium tetraguanidinate complex, Cr 2 (DPPC) 4 (where DPPC is (PhN) 2 CN(CH 2 ) 4 ; Figure 1, a), was reported to exhibit reversible oxidation processes by cyclic voltammetry (CV), with two redox couples at E 1/2 of 0.02 and 1.10 V (vs. Ag/AgCl). [6] The Cr 2…”

Section: Introductionmentioning

confidence: 99%

Synthesis and redox reactivity of a phosphine-ligated dichromium paddlewheel

Eisenhart

Carlson

Boyle

et al. 2015

Inorganica Chimica Acta

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A pentadentate ligand platform, bis[2-(diispropylphosphino-methylamino)phenyl]ether (1), abbreviated as H 2 (PNONP), is introduced that enables the isolation of homodinuclear chromium complexes. In a one-step metalation using Cr(III) and Cr(II) chloride reagents, the bimetallic compounds, [Cr(μ−Cl)(PNONP)] 2 (2) and [Cr(PNONP)] 2 (3), respectively, were synthesized. These complexes have been characterized by X-ray diffraction, NMR spectroscopy, cyclic voltammetry, magnetometry, UV−vis−NIR spectroscopy, combustion analysis, and computational methods. Complex 3 has a reasonably short Cr−Cr bond length of 2.1342(5) Å. Quantum chemical calculations support a diradical singlet ground-state with a formal triple bond between the chromium centers. By cyclic voltammetry, 3 exhibits two reversible oxidations at E ½ = −472 and −753 mV versus FeCp 2 0/+. The one-and two-electron oxidized analogues, 3 + and 3 2+ , were generated in situ via chemical oxidation using ferrocenium. Based on in situ characterization of 3 + and 3 2+ , we hypothesize the oxidations are metal-based to yield Cr 2 5+ and Cr 2 6+ cores, respectively.

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“…Following Power's landmark discovery of the C donor‐supported Cr‐Cr quintuple bonds in isolable compounds Cr 2 Ar′ 2 , several groups have utilized N‐donor ligands, including diazadienide, amidopyridines, amidinates, guanidinates, diamidopyridine, and the mixed N, P‐ligand to synthesize the quintuply bonded group VI bimetallic complexes, which have been extensively reviewed recently . They all showed ultrashort Cr‐Cr bond lengths; in particular, the yet shortest Cr‐Cr bond length (1.7056 (12) å) was found with bulky guanidinate ligands .…”

Section: Introductionmentioning

confidence: 99%

Chromium to chromium quintuple bonds in a trigonal lantern configuration

Yen

Lin

Hsueh

et al. 2019

J Chinese Chemical Soc

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A new family of the quintuply bonded dichromium complexes [Cr2{μ‐κ2‐HC(N‐2,6‐R2C6H3)2}2(μ‐κ2‐HC[NAr]2)] (R = iPr, Ar = 4‐MeC6H4 (5), Ar = 3,5‐Me2C6H3 (6), and Ar = 2,6‐Me2C6H3 (7); R = Et, Ar = 4‐MeC6H4 (8), Ar = 3,5‐Me2C6H3 [9], and Ar = 2,6‐Et2C6H3 (10)) with a heteroleptic lantern configuration was obtained upon the addition of one equivalent of amidinate to the quintuply bonded dichromium amidinates [Cr{μ‐κ2‐HC(N‐2,6‐R2C6H3)2}]2 (R = iPr, Et). Additionally, the same approach was applied to the preparation of the acetate derivative [Cr2{μ‐κ2‐HC(N‐2,6‐ iPr2C6H3)2}2(μ‐κ2‐CH3CO2)] (11), which represents the first example that the quintuply bonded dinuclear complex contains an oxygen‐containing ligand. Of particular interest is that the Cr‐Cr bond lengths in these new trigonal paddlewheel quintuple Cr‐Cr bond species are comparable with those in their precursor compounds. They show ultrashort Cr‐Cr bond lengths in a narrow range of 1.740–1.755 å on the basis of single‐crystal X‐ray crystallography. The small Mayer bond orders of the long Cr‐N bonds as well as divergent, C2v and D3h, structural conformations in 5–11 suggest that the metal–ligand interactions possess minor covalent character and the electrostatic interactions play a dominant role. As a result, these extremely short Cr‐Cr quintuple bonds are caused by the overlap between five pairs of d orbitals that do not involve much in metal–ligand bonding. Additionally, anionic lantern dichromium trisamidinates 5–10 can be chemically oxidized by one electron, supported by electrochemistry, and their ease to undergo oxidation is presumably associated with their neutral lantern dichromium trisamindinate products, whose structures inherently display a Jahn‐Teller distortion, exemplified by the structure of the homoleptic dichromium complex [Cr2{μ‐κ2‐HC(N‐2,6‐Et2C6H3)2}3] [12] determined by X‐ray crystallography. These results unambiguously support the Cr‐Cr quintuple bonding in these novel anionic lantern dichromium complexes.

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Theory, synthesis and reactivity of quintuple bonded complexes

Cited by 33 publications

References 123 publications

Pushing the Limits of Delta Bonding in Metal–Chromium Complexes with Redox Changes and Metal Swapping

Pushing the Limits of Delta Bonding in Metal–Chromium Complexes with Redox Changes and Metal Swapping

Synthesis and redox reactivity of a phosphine-ligated dichromium paddlewheel

Chromium to chromium quintuple bonds in a trigonal lantern configuration

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