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The combination of different donor moieties often results in unconventional coordination behavior. This contribution describes the synthesis of a new hybrid ligand, phosphanylferrocene amidine Ph2PfcN=CHNMe2 (1; fc=ferrocene‐1,1′‐diyl), and its coordination behavior toward the light platinum metals. Reacting compound 1 with [PdCl2(MeCN)2] produced the chelate complex [PdCl2(1‐κ2P,N)] and the bis (phosphane) complex trans‐[PdCl2(1‐κP)2], depending on the ligand‐to‐metal stoichiometry. Halide removal from [PdCl2(1‐κ2P,N)] with Na[BARF] afforded the chloride‐bridged dimer [Pd2(μ‐Cl)2(1‐κ2P,N)2][BARF]2, which was presumably in equilibrium with the mononuclear κ3‐complex [PdCl(1‐κ3Fe,P,N)][BARF] in solution (BARF=tetrakis [3,5‐bis(trifluoromethyl)phenyl]borate). The reactions of 1 with the isoelectronic precursors [(arene)MCl(μ‐Cl)]2 (M/arene=Ru(II)/p‐cymene, and Rh(III)/C5Me5) generated the respective bridge‐cleavage products [(arene)MCl2(1‐κP)], which transformed into the P,N‐chelate complexes [(arene)MCl(1‐κ2P,N)][BARF] when treated with Na[BARF] as a chloride scavenger. All this suggests preferential coordination the phosphane moiety to soft metal ions, while the coordination of the amidine moiety can be induced through changing the reaction stoichiometry or by generating a vacant coordination site at the metal ion. The compounds were characterized using a combination of standard spectroscopic methods (multinuclear NMR, IR, and ESI MS) and single‐crystal X‐ray crystallography, and compounds 1 and 3 were further studied by cyclic voltammetry. [ABSTRACT FROM AUTHOR]

A class of 2‐hydroxypyridine based ligands are explored to achieve enhanced catalytic activity for ortho‐C−H bond activation/arylation reaction over [(η6‐p‐cymene)RuCl2]2 catalyst in water. Extensive studies using a series of substituted 2‐hydroxypyridine based ligands (L1–L6) inferred that 5‐trifluoromethyl‐2‐hydroxypyridine (L6) exhibited favorable effects to enhance the catalytic activity of Ru(II) catalyst for ortho C−H bond arylation of 2‐phenylpyridine by 8 folds compared to those performed without ligands. The (η6‐p‐cymene)Ru – L6 system also exhibited enhanced catalytic activity for ortho C−H bond arylation of 2‐phenylpyridine using a variety of aryl halides. NMR and mass investigations inferred the presence of several ligand coordinated Ru(II) species, suggesting the involvement of these species in C−H bond activation reaction. Further in concurrence with the experimental findings, the density functional theory (DFT) calculations also evidenced the prominent role of 2‐hydroxypyridine based ligands in Ru(II) catalyzed C−H bond arylation of 2‐phenylpyridine with lower energy barrier for the C−H activation step. [ABSTRACT FROM AUTHOR]

Water‐soluble ruthenium(II)–arene complexes [(η6‐arene)Ru(κ2‐L)]n+ (n = 0, 1) ([Ru]‐1–[Ru]‐10) containing pyridine‐based bischelating N,O/N,N donor ligands (L1–L5) are synthesized and employed for the catalytic C–H bond activation/arylation of a wide range of 2‐phenylpyridines and aryl halides in water, affording the corresponding mono‐ and biarylated products. Exploring the reactivity of the synthesized complexes, our investigations, including time‐dependent 1H NMR spectroscopic studies with ruthenium–arene catalysts, demonstrate a remarkable structure–activity relationship for the ligand‐tuned C–H activation/arylation of 2‐phenylpyridine, where the complexes with bischelating N,O donor‐based ligands (acteylpyridine and picolinate) outperform those with N,N donor ligands (iminopyridine). Moreover, among the N,O donor ligands, a distinct effect of the nature of the coordinating oxygen donor on the catalytic activity is also observed, where ruthenium–arene complexes having N,O donor ligands (acetylpyridine) with neutral oxygen‐donor atoms exhibit enhanced catalytic activity over those with anionic oxygen‐donor atoms (picolinate). The observed trend in the catalytic activity is attributed to the ligand‐promoted facile deprotonation and coordination–decoordination interconversion behavior. In addition, molecular structures for a few of the representative complexes ([Ru]‐2, [Ru]‐4, and [Ru]‐5) are authenticated by single‐crystal X‐ray diffraction studies. [ABSTRACT FROM AUTHOR]

Water-soluble arene-ruthenium complexes coordinated with readily available aniline-based ligands were successfully employed as highly active catalysts in the C−H bond activation and arylation of 2-phenylpyridine with aryl halides in water. A variety of (hetero)aryl halides were also used for the ortho-C−H bond arylation of 2-phenylpyridine to afford the corresponding ortho- monoarylated products as major products in moderate to good yields. Our investigations, including time-scaled NMR spectroscopy and mass spectrometry studies, evidenced that the coordinating aniline-based ligands, having varying electronic and steric properties, had a significant influence on the catalytic activity of the resulting arene-ruthenium-aniline-based complexes. Moreover, mass spectrometry identification of the cycloruthenated species, {(η6-arene)Ru(κ2- C, N-phenylpyridine)}+, and several ligand-coordinated cycloruthenated species, such as [(η6-arene)Ru(4-methylaniline)(κ2- C, N-phenylpyridine)]+, found during the reaction of 2-phenylpyridine with the arene-ruthenium-aniline complexes further authenticated the crucial roles of these species in the observed highly active and tuned catalyst. At last, the structures of a few of the active catalysts were also confirmed by single-crystal X-ray diffraction studies. [ABSTRACT FROM AUTHOR]