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The electronic structures within a series of square‐planar ruthenium(II) pincer complexes with dialkyl‐, vinyl alkyl‐, and divinyl amido pincer backbones is compared in an experimental and computational study. Although [RuCl{N(CH2CH2PtBu2)2}] exhibits a low‐spin (S=0) ground state and low‐lying triplet (S=1) excited state, [RuCl{N(CH2CH2PtBu2)(CHCHPtBu2)}] and [RuCl{N(CHCHPtBu2)2}] adopt intermediate‐spin (S=1) ground states with strong magnetic anisotropy due to large zero‐field splitting (D>+200cm–1). The change in ground‐state electronic configuration is attributed to tailored pincer ligand‐to‐metal π‐donation within the PNP ligand series. For more details, see the Full Paper by S. Schneider et al. on page 579 ff. [ABSTRACT FROM AUTHOR]

Functionalization of the PNP pincer ligand backbone allows for a comparison of the dialkyl amido, vinyl alkyl amido, and divinyl amido ruthenium(II) pincer complex series [RuCl{N(CH2CH2P tBu2)2}], [RuCl{N(CHCHP tBu2)(CH2CH2P tBu2)}], and [RuCl{N(CHCHP tBu2)2}], in which the ruthenium(II) ions are in the extremely rare square-planar coordination geometry. Whereas the dialkylamido complex adopts an electronic singlet ( S=0) ground state and energetically low-lying triplet ( S=1) state, the vinyl alkyl amido and the divinyl amido complexes exhibit unusual triplet ( S=1) ground states as confirmed by experimental and computational examination. However, essentially non-magnetic ground states arise for the two intermediate-spin complexes owing to unusually large zero-field splitting ( D>+200 cm−1). The change in ground state electronic configuration is attributed to tailored pincer ligand-to-metal π-donation within the PNP ligand series. [ABSTRACT FROM AUTHOR]

[RuCl(arene)(μ-Cl)]2 dimers were treated in a 1:2 molar ratio with sodium or thallium salts of bis- and tris(pyrazolyl)borate ligands [Na(Bp [ABSTRACT FROM AUTHOR]

A series of Ru complexes containing lutidine-derived pincer CNC ligands have been prepared by transmetalation with the corresponding silver-carbene derivatives. Characterization of these derivatives shows both mer and fac coordination of the CNC ligands depending on the wingtips of the N-heterocyclic carbene fragments. In the presence of tBuOK, the Ru-CNC complexes are active in the hydrogenation of a series of imines. In addition, these complexes catalyze the reversible hydrogenation of phenantridine. Detailed NMR spectroscopic studies have shown the capability of the CNC ligand to be deprotonated and get involved in ligand-assisted activation of dihydrogen. More interestingly, upon deprotonation, the Ru-CNC complex 5 e(BF4) is able to add aldimines to the metal-ligand framework to yield an amido complex. Finally, investigation of the mechanism of the hydrogenation of imines has been carried out by means of DFT calculations. The calculated mechanism involves outer-sphere stepwise hydrogen transfer to the CN bond assisted either by the pincer ligand or a second coordinated H2 molecule. [ABSTRACT FROM AUTHOR]

A series of tunable G0-G3 dendritic 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl (BINAP) ligands was prepared by attaching polyaryl ether dendrons onto the four phenyl rings on the P atoms. Their ruthenium complexes were employed in the asymmetric hydrogenation of β-ketoesters, α-ketoesters, and α-ketoamides to reveal the effects of dendron size on the catalytic properties. The second- and third-generation catalysts exhibited excellent enantioselectivities, which are remarkably higher than those obtained from the small molecular catalysts and the first-generation catalyst. Molecular modeling indicates that the incorporation of bulky dendritic wedges can influence the steric environments around the metal center. In addition, the ruthenium catalyst bearing a second-generation dendritic ligand could be recycled and reused seven times without any obvious decrease in enantioselectivity. [ABSTRACT FROM AUTHOR]