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Compartmental pyrazolato‐bridged ligands [LPy]− and [LIm]−, each providing two {N5} binding sites but differing in the terminal N‐donors (pyridine vs. imidazole), were used to prepare a set of diferrous complexes; the ligand HLIm is new and its synthesis is reported. Complexes [LPyFe2(MeCN)2](OTf)3, (1OTf), [LPyFe2(MeCN)2](BF4)3 (1BF4), [LImFe{Fe(MeCN)}](OTf)3 (2OTf), and [LImFe{Fe(MeCN)}](BF4)3 (2BF4) were characterized by single‐crystal X‐ray diffraction, revealing a MeCN coligand at both (1OTf, 1BF4) or at only one (2OTf, 2BF4) of the two accessible Fe coordination sites that are directed into the bimetallic cleft. Magnetic measurements (SQUID) and 57Fe Mößbauer spectroscopy indicate low‐spin states for the six‐coordinate FeII ions in 1OTf and 1BF4 that are based on [LPy]−, but two high‐spin FeII ions in 2BF4 that is based on [LIm]−, in agreement with structural data. Complex 2OTf shows abrupt spin‐crossover (SCO) from a mixed high‐spin/low‐spin to an all high‐spin state at T½ = 264 K, which appears to be correlated with the Fe–N≡C(Me) bonding angle. SCO, though gradual, is observed for 2OTf also in solution (T½ = 273 K in MeCN, 248 K in EtCN), which was studied by Mössbauer spectroscopy of frozen solution samples, variable temperature UV/Vis spectroscopy and SQUID magnetometry; the latter methods consistently gave thermodynamic parameters ΔH = 24.2 kJ·mol–1, ΔS = 89 J·mol–1·K–1 for the SCO of 2OTf in MeCN, and ΔH = 19.1 kJ·mol–1, ΔS = 77 J·mol–1·K–1 in EtCN. [ABSTRACT FROM AUTHOR]

The thermal reaction of Ru3(CO)12 (1) with salicylic acid, in the presence of triphenylphosphine, pyridine, or dimethylsulfoxide, afforded the dinuclear complexes Ru2(CO)4(μ-O2CC6H4OH)2L2 (2) [L = PPh3 (2a). C5H5N (2b); (CH3)2SO (2c)]. Complex 2b was further reacted with the aromatic dimmines 2,2'-dipyridine or 1,10-phenanthroline to give the cationic diruthenium complexes [Ru2(CO)2(μ- CO)2(μ-O2CC6H4OH)(N∩N)2]+ (3) [(N ∩N) = 2,2'-dipyridine (3a); 1,10-phenanthroline (3b)], which were isolated as their tetraphenylborate salts. All five novel complexes were characterized spectroscopically and analytically. For 2a-2b and 3a-3b, single-crystal X-ray diffraction studies were also carried out. [ABSTRACT FROM AUTHOR]

Novel dinuclear silver(I) and gold(I) complexes with 4,5-disubstituted diimidazol-2,2′-diylidene ligands featuring a methylene or 1,3-propylene bridge between the two N-heterocyclic carbene moieties were prepared and characterized. The substituents in the backbone of the heterocyclic ring are electron-withdrawing groups (chlorine atoms or cyanide groups) and their effect on the spectroscopic and structural properties of the resulting complexes was analyzed and discussed. [ABSTRACT FROM AUTHOR]

The dinucleating ligand (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrayl)-tetrakis-(methylene)-tetrakis(2-methoxy-4-methylphenol), H4L, is well preorganized with an N4O2 octahedral site for a divalent transition metal ion and an O4 site (phenolates and methoxo donors, completed by added pivalates and solvent molecules) for lanthanide ions. Two 3d-4f complexes ([DyIII{NiII(μ-H2L)}piv2(OH2)]ClO4 and [DyIII{CoII(μ-H2L)}piv2(OH2)]ClO4) were prepared and fully characterized by X-ray molecular structures and electronic properties determined by ac and dc SQUID magnetometry. While the NiII based complex shows single-molecule magnetism (SMM), the CoII complex does not. With an extensive quantum-chemical analysis, this is shown to be due to a misalignment of the single ion anisotropies in the latter complex, and reasons for this are discussed. [ABSTRACT FROM AUTHOR]

Two novel chelating anion nitronyl nitroxide radical bridged dinuclear lanthanide complexes [Tb2(hfac)4(NIT2PhO)2] ( 1) and [Ho2(hfac)4(NIT2PhO)2] ( 2) [hfac = hexafluoroacetylacetonate; NIT2PhO = 2-(2′-hydroxyphenyl)-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide] were prepared and structurally characterized by single crystal X-ray diffraction, elemental analysis, and IR spectroscopy. Both complexes are dinuclear phenoxo-O anion bridged with the oxygen atom of the N-O group coordinated to a single Ln(hfac)2 unit. The central Ln atoms exhibit a heptacoordinated environment, and the shape around the metal atom is capped octahedral. This structure is first reported in the lanthanide-nitronyl nitroxide system. It provides an innovative approach to synthesize new dinuclear lanthanide-nitroxide-based complexes. Additionally, the magnetic properties of the two complexes are studied. [ABSTRACT FROM AUTHOR]

A series of imidazole-based and benzimidazole-based di-NHC dipalladium complexes with alkyl bridges of different chain lengths were prepared. All complexes were fully characterized by NMR spectroscopy and elemental analyses. The crystal structures of three complexes were determined by X-ray diffraction. X-ray studies show the length of linker effects the solid structure of these complexes and π-π stacking plays an important role for the configuration of NHC-Pd-Py subunits. The activity of NHC-palladium complexes was investigated in the mono- and double-Heck reactions, and the imidazole-based palladium complex bearing the shortest ethylene bridge shows the best activity and selectivity in both reactions. [ABSTRACT FROM AUTHOR]

The title complex, neutral {[Ni2(μ-S2O3)2(C7H9N)4H2O]C7H8} ( 1), presents a dinuclear structure with the thiosulfate group acting as a (S, O) chelate and simultaneously as a (S) bridge. The molecular structure was determined by X-ray crystallography. Complex 1 crystallizes as a hydrogen-bonded dimer with molecule of toluene solvent in the unit cell. The environment of both central nickel atoms is octahedral with NiN2O2S2 cores. This is the first metal thiosulfate complex isolated as a product of the oxidation of silanethiol. A mechanism of the reaction involving the formation of ( RO)3SiSSSi(O R)3 intermediate is proposed with the subsequent cleavage of Si-S bond. [ABSTRACT FROM AUTHOR]

The title complex, neutral {[Ni2(μ-S2O3)2(C7H9N)4H2O]C7H8} ( 1), presents a dinuclear structure with the thiosulfate group acting as a (S, O) chelate and simultaneously as a (S) bridge. The molecular structure was determined by X-ray crystallography. Complex 1 crystallizes as a hydrogen-bonded dimer with molecule of toluene solvent in the unit cell. The environment of both central nickel atoms is octahedral with NiN2O2S2 cores. This is the first metal thiosulfate complex isolated as a product of the oxidation of silanethiol. A mechanism of the reaction involving the formation of ( RO)3SiSSSi(O R)3 intermediate is proposed with the subsequent cleavage of Si-S bond. [ABSTRACT FROM AUTHOR]