Unexpected structural and electronic effects of internal rotation in diruthenium paddlewheel complexes containing bulky carboxylate ligands

Gracia, Raquel; Adams, Harry; Patmore, Nathan J.

doi:10.1016/j.ica.2010.07.024

Cited by 13 publications

(9 citation statements)

References 59 publications

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“…The optimized N–Ru–Ru–O eq angles are higher in Categories 1 (18.5° to 20.1°) and 2 (18.6° to 21.0°) than in Category 3 (16.2° to 17.5°; Figure S10). As observed in the crystal structures, the computed torsion angles generally show the same inverse correlation with Ru–Ru distance observed by Patmore and co-workers . The PPh 3 adduct 4 is the sole outlier, which may come from a steric effect between the PPh 3 aryl rings and the chp oxygen atoms.…”

Section: Results and Discussionsupporting

confidence: 75%

“…The Ru−L eq bond distance that shows the most variability is the Ru−O eq bond length (range: 2.029 [6] Ru−O eq torsion angle, in agreement with the observations made by Patmore and co-workers, except in 4 and 5, which have higher torsion angles than would be expected based on their long Ru−Ru distances (Figure 6). 75 The formal shortness ratio (FSR) of the Ru−L ax bond, calculated as the ratio between the measured bond length and the sum of the single-bond covalent radii of the constituent atoms, 76 is an indicator of bond multiplicity. 1,77 Since the donor atoms of the axial ligands differ in 2−6 and 8, the multiplicity of the Ru−L ax bond is inadequate for evaluating the strength of those interactions, but may give some insight into the extent of back-donation from the metal orbitals into the axial ligands.…”

Section: Methodsmentioning

confidence: 99%

“…As observed in the crystal structures, the computed torsion angles generally show the same inverse correlation with Ru−Ru distance observed by Patmore and co-workers. 75 The PPh 3 adduct 4 is the sole outlier, which may come from a steric effect between the PPh 3 aryl rings and the chp oxygen atoms. Though many of these measures vary between categories, as does the Ru−Ru distance, none of the distances or angles to the equatorial ligands aside from torsion angle reliably vary with the Ru−Ru distance within each category.…”

Section: Inorganic Chemistrymentioning

confidence: 99%

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Electronic Structure of Ru₂(II,II) Oxypyridinates: Synthetic, Structural, and Theoretical Insights into Axial Ligand Binding

Brown

Dolinar

Hillard³

et al. 2015

Inorg. Chem.

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Reduction of (4,0)-Ru2(chp)4Cl (1) (chp = 6-chloro-2-oxypyridinate) with Zn or FeCl2 yields a series of axial ligand adducts of the Ru2(II,II) species Ru2(chp)4(L), with L = tetrahydrofuran (2), dimethyl sulfoxide (DMSO; 3), PPh3 (4), pyridine (5), or MeCN (6). Zn reduction in noncoordinating solvents such as toluene or CH2Cl2 leads to the dimeric species [Ru2(chp)4]2 (7) or [Ru2(chp)4]2(ZnCl2) (8), whereas addition of strongly σ-donating ligands such as CO causes cleavage of the Ru-Ru bond. Density functional theory (DFT) models of these complexes, the axially free species, and the axial adducts of several other potential ligands (H2O, NH3, CH2Cl2, S-bound DMSO, N2, and CO) indicate that these compounds can be divided into three distinct categories, based on their Ru-Ru bond length and electronic structure. Compounds 2, 3, 5, 6, 7, and 8, the hypothetical axially free species, and adducts of H2O and NH3 fit in Category 1 with a (δ*)(2)(π*)(2) ground state, as indicated by their electronic spectra, magnetic properties, and Ru-Ru bond distances. However, compound 4 and the CH2Cl2 adduct (Category 2) show a pseudo-Jahn-Teller distortion and spectroscopic signs of δ*/π* orbital mixing suggestive of a new electronic ground state intermediate between the (δ*)(2)(π*)(2) and (δ*)(1)(π*)(3) configurations. Category 3 consists of the hypothetical adducts of N2, S-bound DMSO, and CO, all of which are predicted to have a (δ*)(1)(π*)(3) configuration. Electronic spectra were recorded and assigned using time-dependent DFT, allowing assignment of a band in the 10,000-13,000 cm(-1) range as the δ → π* transition. The axial ligand's π-acid character heavily influences the δ*-π* gap, and thereby the ground-state electronic configuration, but not the axial ligand binding strength, which is dictated more by the σ-donor character of the ligands. Thus, this work greatly expands the number of axial ligand adducts known for Ru2(II,II) complexes supported by N,O-donor ligands and provides a predictive theoretical framework for their stability and electronic structures.

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Section: Results and Discussionsupporting

confidence: 75%

Section: Methodsmentioning

confidence: 99%

Section: Inorganic Chemistrymentioning

confidence: 99%

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Electronic Structure of Ru₂(II,II) Oxypyridinates: Synthetic, Structural, and Theoretical Insights into Axial Ligand Binding

Brown

Dolinar

Hillard³

et al. 2015

Inorg. Chem.

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“…The electronic absorption spectrum of 4-N 3 contains features similar to those seen in the spectrum of 4-Cl , but with a significant blue-shift. The Ru–Ru distances for the two complexes are effectively identical, precluding an explanation based on the character of the metal–metal bond . Instead, this effect can be explained in terms of the significantly decreased torsion angle observed in the equatorial ligands of 4-N 3 .…”

Section: Resultsmentioning

confidence: 75%

“…The Ru−Ru distances for the two complexes are effectively identical, precluding an explanation based on the character of the metal−metal bond. 33 Instead, this effect can be explained in terms of the significantly decreased torsion angle observed in the equatorial ligands of 4-N 3 . This would allow greater mixing between the π(O eq ) orbital and the metal-based δsymmetry orbitals, such that both the π(O eq )/π* and δ xy /δ xy * gaps are increased.…”

Section: Inorganic Chemistrymentioning

confidence: 99%

New Oxypyridinate Paddlewheel Ligands for Alkane-Soluble, Sterically-Protected Ru₂(II,III) and Ru₂(II,II) Complexes

et al. 2018

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The paddlewheel complex Ru(chp)Cl (1-Cl, chp = 6-chloro-2-oxypyridinate), upon reduction with Zn, has been previously shown to dimerize to [Ru(chp)] (2), blocking further chemistry at the Ru(II,II) axial site [ Inorg. Chem. 2015 , 54 , 8571 - 8589 ]. Functionalization of the chp ligand at the 3 and 5 positions with either bromine (dbchpH = 3,5-dibromo-6-chloro-2-pyridone) or trimethylsilyl (TMS) groups (dsichpH = 6-chloro-3,5-bis(trimethylsilyl)-2-pyridone) allows for the preparation of the Ru(II,II) paddlewheel complexes Ru(dbchp) (3) and Ru(dsichp) (6), respectively, neither of which shows evidence of dimerization. Though the utilization of 3 is limited due to insolubility, complex 6 is soluble even in typically non-coordinating solvents, forming a stable κ-axial adduct in CHCl (6-CHCl) and showing evidence of an axial interaction with n-decane. The first example of an axially free Ru(II,II) complex with a A ground state is observed upon crystallization of 6 from benzene (6-CD). Complex 6 is accessed via Zn reduction of Ru(dsichp)Cl (4-Cl), which along with Ru(dsichp)N (4-N), show similar structural and electronic properties to their non-TMS-substituted analogues, 1-Cl and 1-N. Photolysis of 4-N in frozen solution generates Ru(dsichp)N (5); no N atom transfer to PPh is observed upon room temperature photolysis in fluid solution.

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Torsion Effects Beyond the δ Bond and the Role of π Metal‐Ligand Interactions

Inchausti,

Mollfulleda,

Swart

et al. 2024

Advanced Science

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Previous studies on bimetallic paddlewheel compounds have established a direct correlation between metal–metal distance and ligand torsion angles, leading to the rule that higher torsion results in longer metal‐metal bond distances. Here, the new discovery based on diarylformamidinate Ru₂⁵⁺ paddlewheel compounds [Ru2Cl(DArF)4] that show an opposite behavior is reported: higher torsions lead to shorter metal–metal distances. This discovery challenges the assumption that internal rotation solely impacts the δ bond. By combining experimental and theoretical techniques, it is demostrated that this trend is associated with previously overlooked π metal‐ligand interactions. These π metal‐ligand interactions are a direct consequence of the paddlewheel structure and the conjugated nature of the bidentate ligands. This findings offer far‐reaching insights into the influence of equatorial ligands and their π‐conjugation characteristics on the electronic properties of paddlewheel complexes. That this effect is not exclusive of diruthenium compounds but also occurs in other bimetallic cores such as ditungsten or dirhodium is demonstrated, and with other ligands showing allyl type conjugation. These results provide a novel approach for fine‐tuning the properties of these compounds with significant implications for materials design.

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Unexpected structural and electronic effects of internal rotation in diruthenium paddlewheel complexes containing bulky carboxylate ligands

Cited by 13 publications

References 59 publications

Electronic Structure of Ru₂(II,II) Oxypyridinates: Synthetic, Structural, and Theoretical Insights into Axial Ligand Binding

Electronic Structure of Ru₂(II,II) Oxypyridinates: Synthetic, Structural, and Theoretical Insights into Axial Ligand Binding

New Oxypyridinate Paddlewheel Ligands for Alkane-Soluble, Sterically-Protected Ru₂(II,III) and Ru₂(II,II) Complexes

Torsion Effects Beyond the δ Bond and the Role of π Metal‐Ligand Interactions

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Unexpected structural and electronic effects of internal rotation in diruthenium paddlewheel complexes containing bulky carboxylate ligands

Cited by 13 publications

References 59 publications

Electronic Structure of Ru2(II,II) Oxypyridinates: Synthetic, Structural, and Theoretical Insights into Axial Ligand Binding

Electronic Structure of Ru2(II,II) Oxypyridinates: Synthetic, Structural, and Theoretical Insights into Axial Ligand Binding

New Oxypyridinate Paddlewheel Ligands for Alkane-Soluble, Sterically-Protected Ru2(II,III) and Ru2(II,II) Complexes

Torsion Effects Beyond the δ Bond and the Role of π Metal‐Ligand Interactions

Contact Info

Product

Resources

About

Electronic Structure of Ru₂(II,II) Oxypyridinates: Synthetic, Structural, and Theoretical Insights into Axial Ligand Binding

Electronic Structure of Ru₂(II,II) Oxypyridinates: Synthetic, Structural, and Theoretical Insights into Axial Ligand Binding

New Oxypyridinate Paddlewheel Ligands for Alkane-Soluble, Sterically-Protected Ru₂(II,III) and Ru₂(II,II) Complexes