Dissymmetrical <i>trans-</i>Ethynyl-Butadiynyl Adducts on a Diruthenium Core: Synthesis, Characterization, and Selective Deprotection

Reactions between the ethynyl complexes (4,0)-[Ru2(ap)4](C2SiR3) (ap is 2-anilinopyridinate, R = iPr (1a) and CH3 (1b)) and LiC4SiMe3 result in the formation of dissymmetrical ethynyl-butadiynyl adducts trans-(4,0)-(Me3SiC4)[Ru2(ap)4](C2SiR3) (R = iPr (2a) and CH3 (2b)). Treating 2b with K2CO3 in MeOH/THF leads to trans-(HC4)[Ru2(ap)4](C2SiMe3) (3b) and trans-(HC4)[Ru2(ap)4](C2H) (4) in 86% and ca. 10% yields, respectively, and the former can be quantitatively converted to 4 using NaOH. Treating 2a with NaOH in MeOH/THF yields trans-(HC4)[Ru2(ap)4](C2SiiPr3) (3a) only. Single-crystal structural analysis of 2a and 3b revealed that the Ru−Ru unit and the axial alkynyl ligands are approximately collinear in both molecules. Rich redox chemistry was revealed for all the compounds through voltammetric study:  compound 1 exhibits reversible one-electron oxidation and reduction, and compounds 2−4 exhibit one one-electron oxidation and two one-electron reductions. All the ethynyl-butadiynyl adducts (2−4) exhibit an intense charge-transfer absorption of λmax around 1035 nm, revealing a HOMO−LUMO gap of 1.20 eV

Dissymmetrical <i>trans-</i>Ethynyl-Butadiynyl Adducts on a Diruthenium Core: Synthesis, Characterization, and Selective Deprotection

Reactions between the ethynyl complexes (4,0)-[Ru2(ap)4](C2SiR3) (ap is 2-anilinopyridinate, R = iPr (1a) and CH3 (1b)) and LiC4SiMe3 result in the formation of dissymmetrical ethynyl-butadiynyl adducts trans-(4,0)-(Me3SiC4)[Ru2(ap)4](C2SiR3) (R = iPr (2a) and CH3 (2b)). Treating 2b with K2CO3 in MeOH/THF leads to trans-(HC4)[Ru2(ap)4](C2SiMe3) (3b) and trans-(HC4)[Ru2(ap)4](C2H) (4) in 86% and ca. 10% yields, respectively, and the former can be quantitatively converted to 4 using NaOH. Treating 2a with NaOH in MeOH/THF yields trans-(HC4)[Ru2(ap)4](C2SiiPr3) (3a) only. Single-crystal structural analysis of 2a and 3b revealed that the Ru−Ru unit and the axial alkynyl ligands are approximately collinear in both molecules. Rich redox chemistry was revealed for all the compounds through voltammetric study:  compound 1 exhibits reversible one-electron oxidation and reduction, and compounds 2−4 exhibit one one-electron oxidation and two one-electron reductions. All the ethynyl-butadiynyl adducts (2−4) exhibit an intense charge-transfer absorption of λmax around 1035 nm, revealing a HOMO−LUMO gap of 1.20 eV

DFT Study of Electronic Properties of 3d Metal Complexes of σ-Geminal Diethynylethenes (<i>gem</i>-DEEs)

A density functional theory (DFT) analysis has been carried out to evaluate the structural and electronic properties of bimetallic compounds bridged by geminal diethynylethene (gem-DEE). Five stable equilibrium structures of the [M]−gem-DEE−[M] type ([M] = −M(H2PCH2CH2PH2)2Me) were obtained for the first-row transition metals, namely Ti, V, Cr, Fe, and Ni, using DFT at the B3LYP/LanL2DZ level. While the d orbitals in the Ti and Ni compounds exhibited minimal interactions with the gem-DEE-based orbitals, extensive interactions between the dπ orbitals and π(DEE) orbitals were found for the V, Cr, and Fe compounds. A detailed natural bond orbital (NBO) analysis revealed that the electronic delocalization in [M]−gem-DEE−[M] is attributed to both the σ orbitals along the DEE backbone and π orbitals perpendicular to the DEE plane

Ru-σ-butadiynyl Complexes of the Tetraanilinopyridinatodiruthenium Core: Formation of a Bis-adduct

The stoichiometric reaction between Ru2(ap)4Cl (ap = 2-anilinopyridinate) and LiC⋮CC⋮CSiMe3 yielded Ru2(ap)4(C⋮CC⋮CSiMe3) (1) as the only product. A similar reaction utilizing a 5-fold excess of LiC⋮CC⋮CSiMe3 resulted in a mixture of 1 and the bis-alkynyl adduct trans-Ru2(ap)4(C⋮CC⋮CSiMe3)2 (2), and the ratio of two products depends on workup procedures. X-ray diffraction studies of 1 and 2 revealed that the bridging ap ligands are in the (4,0) polar arrangement and the Ru−Ru vector and butadiynyl backbone are approximately collinear. Both compounds 1 and 2 are rich in redox chemistry:  two reversible one-electron couples were observed for the former and three for the latter from the cyclic voltammetry study

Bisaryl Diruthenium(III) Paddlewheel Complexes: Synthesis and Characterization

Aryls represent a class of both σ- and π-donating electron-rich axial ligands that is underexplored in the field of metal–metal multiply bonded paddlewheel species. By a decrease in the steric bulk around the diruthenium axial sites and an increase in the basicity of the bridging ligands, the first examples of bisaryl diruthenium­(III) paddlewheel complexes have been isolated. Compounds of the form Ru2(DMBA)4Ar2 (DMBA = N,N′-dimethylbenzamidinate, Ar = C6H4-4-tBu (1), C6H5 (2), C6H3-3,5-(OCH3)2 (3)) were synthesized via a lithium–halogen exchange reaction between Ru2(DMBA)4Cl2 and excess LiAr and characterized using mass spectrometry, electronic absorption spectroscopy, cyclic and differential pulse voltammetry, and 1H NMR spectroscopy. The molecular structures of compounds 1–3 were established using single-crystal X-ray diffraction analysis and their electronic structures (both ground and excited state) analyzed using density functional theory calculations

Axial Butadiynyl Adducts on a Tetrakis- (di(<i>m</i>-methoxyphenyl)formamidinato)diruthenium Core: First Examples of M−M Bonded Complexes Containing σ-Poly-ynyl Ligand

Axial Butadiynyl Adducts on a Tetrakis- (di(m-methoxyphenyl)formamidinato)diruthenium Core:  First Examples of M−M Bonded Complexes Containing σ-Poly-ynyl Ligan

Bisaryl Diruthenium(III) Paddlewheel Complexes: Synthesis and Characterization

Aryls represent a class of both σ- and π-donating electron-rich axial ligands that is underexplored in the field of metal–metal multiply bonded paddlewheel species. By a decrease in the steric bulk around the diruthenium axial sites and an increase in the basicity of the bridging ligands, the first examples of bisaryl diruthenium­(III) paddlewheel complexes have been isolated. Compounds of the form Ru2(DMBA)4Ar2 (DMBA = N,N′-dimethylbenzamidinate, Ar = C6H4-4-tBu (1), C6H5 (2), C6H3-3,5-(OCH3)2 (3)) were synthesized via a lithium–halogen exchange reaction between Ru2(DMBA)4Cl2 and excess LiAr and characterized using mass spectrometry, electronic absorption spectroscopy, cyclic and differential pulse voltammetry, and 1H NMR spectroscopy. The molecular structures of compounds 1–3 were established using single-crystal X-ray diffraction analysis and their electronic structures (both ground and excited state) analyzed using density functional theory calculations

Diruthenium(II,III) Bis(tetramethyl-1,3-benzenedipropionate) as a Novel Catalyst for <i>tert</i>-Butyl Hydroperoxide Oxygenation

The reaction of Ru2(OAc)4Cl with 2.2 equiv of H2esp (esp = α,α,α′,α′-tetramethyl-1,3-benzenedipropionate) resulted in a new compound, Ru2(esp)2Cl (1), that is soluble in organic media. 1 is an active catalyst for the oxygenation of organic sulfides by tert-butyl hydroperoxide (TBHP) in both an acetonitrile solution or neat (solvent-free) conditions. Solvent-free reactions display the quantitative utility of TBHP and hence excellent chemical selectivity for sulfoxide formation

Selective Ligand Modification on the Periphery of Diruthenium Compounds: Toward New Metal-Alkynyl Scaffolds

Diruthenium compounds Ru2(DmAniF)3(OAc)Cl (1, DmAniF is N,N‘-di(m-methoxyphenyl)formamidinate) and cis-Ru2(DmAniF)2(OAc)2Cl (6) reacted with N,N‘-dimethyl-4-iodobenzamidine (HDMBA-I) to furnish new compounds Ru2(DmAniF)3(DMBA-I)Cl (2) and cis-Ru2(DmAniF)2(DMBA-I)2Cl (7), respectively. Both compounds 2 and 7 were modified with a terminal alkyne under Sonogashira conditions. Examples reported include 2 cross-coupled with HC⋮CSiiPr3 or HC⋮CFc to yield Ru2(DmAniF)3(DMBA-4-C2SiiPr3)Cl (3a) or Ru2(DmAniF)3(DMBA-4-C2Fc)Cl (3b), respectively, and 7 cross-coupled with HC⋮CFc to yield cis-Ru2(DmAniF)2(DMBA-4-C2Fc)2Cl (8). The peripherally modified compounds (2, 3a/3b, 7, and 8) were further alkynylated at the axial positions of the Ru2 core to yield a series of bis-alkynyl adducts:  Ru2(DmAniF)3(DMBA-4-C2SiiPr3)(C4SiMe3)2 (4a), Ru2(DmAniF)3(DMBA-4-C2Fc)(C4SiMe3)2 (4b), Ru2(DmAniF)3(DMBA-I)(C4SiMe3)2 (5), cis-Ru2(DmAniF)2(DMBA-4-C2Fc)2(C2Ph)2 (9), and cis-Ru2(DmAniF)2(DMBA-I)2(C2Ph)2 (10). All compounds reported were characterized with voltammetric, vis−NIR, and NMR (whenever applicable) techniques. Molecular structures of compounds 1, 4a, 5, 6, 9, and 10 were established through X-ray diffraction studies

Ru-σ-butadiynyl Complexes of the Tetraanilinopyridinatodiruthenium Core: Formation of a Bis-adduct

The stoichiometric reaction between Ru2(ap)4Cl (ap = 2-anilinopyridinate) and LiC⋮CC⋮CSiMe3 yielded Ru2(ap)4(C⋮CC⋮CSiMe3) (1) as the only product. A similar reaction utilizing a 5-fold excess of LiC⋮CC⋮CSiMe3 resulted in a mixture of 1 and the bis-alkynyl adduct trans-Ru2(ap)4(C⋮CC⋮CSiMe3)2 (2), and the ratio of two products depends on workup procedures. X-ray diffraction studies of 1 and 2 revealed that the bridging ap ligands are in the (4,0) polar arrangement and the Ru−Ru vector and butadiynyl backbone are approximately collinear. Both compounds 1 and 2 are rich in redox chemistry:  two reversible one-electron couples were observed for the former and three for the latter from the cyclic voltammetry study