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A series of benzoylacetone‐imine ligands, PhCOCHCMeNHR (L1H, R = CH2Ph; L2H, R = CH2Ph‐4‐Me; and L3H, R = CH2Ph‐4‐OMe), are first synthesized following the condensation of benzoylacetone and 4‐substituted benzylamine. Later, reacting L1H–L3H with one equivalent of AlMe3 in toluene, the monomeric Al derivatives are generated, (PhCOCHCMeNR)AlMe2 (1, R = CH2Ph; 2, R = CH2Ph‐4‐Me; 3, R = CH2Ph‐4‐OMe). All the ligands and metal derivatives are characterized by 1H and 13C NMR spectroscopy. Single crystal X‐ray diffraction analysis reveals the geometry of all ligands and complex 2. As supporting catalysts, the Al derivatives, 1–3, are effective to initiate the coupling of CO2 and styrene oxide to form cyclic carbonates. Although employing TBAI (tetra‐n‐butylammonium iodide), TBAC, tetrabutylammonium chloride, and TBAB (tetra butyl ammonium bromide) as cocatalyst, the optimized catalytic system exhibits the best conversion of epoxide in presence of TBAI under the reaction temperature and time, respectively, 90°C and 6 hr, respectively. The ring opening polymerization of ε‐caprolactone is also appraised subjecting the Al derivatives, 1–3, as catalysts in presence of benzyl alcohol and all the conversions of ε‐caprolactone reach over 95% at the reaction condition of 100°C and 1 hr. [ABSTRACT FROM AUTHOR]

A rare in situ-generated mononuclear rhenium complex [Re(bpt)(CO)3(NH3)] (1, bpt = 3,5-bis(2-pyridyl)-1,2,4-triazolate) can be used as a "turn-on" luminescent probe for selectively sensing L -histidine against other amino acids. Compound 1 was prepared by reacting Re2(CO)10, 2-cyanopyridine and hydrazine with an in situ formed bpt ligand through cyclization via C–N and N–N couplings with its single-side chelating mode arrayed with respect to the Re center. Compound 1 was highly stable and showed a green light MLCT emission in DMF solution at 507 nm upon excitation at 360 nm. Interestingly, the emission from 1 could be quenched by the addition of metal ions such as Ni2+ and Cu2+ but the emission efficiently recovered with the introduction of histidine. However, histidine could only be selectively detected when a combination of compound 1 and Ni2+ was used. Therefore, the luminescence response of the Ni2+-modified compound 1 could be utilized as a "turn-on" probe for the selective detection of histidine. This work provides a simple method for developing new sensing platforms of a discrete metal complex based on rare in situ generation. [ABSTRACT FROM AUTHOR]

The use of the diolate ligand derived from the deprotonation of 2,2'-methylenebis(6-tert-butyl-4-methylphenol) abbreviated as HO-CH2-OH was discussed. The nature of interconversion of bridged and chelate isomers in the presence of Lewis bases was established. The reaction of MO2(NMe2)6 and HO-CH2-OH yielded MO2(NMe2)2(O-CH2-O)2, which exists in both bridged and chelate isomers. The first example of reversible C-H oxidative addition to M-M multiple bond was observed and monitored.

A series of mononuclear tantalum derivatives containing substituted pyrrole‐amine ligands are synthesized. Reacting TaCl5 with one equivalent of Li[C4H2N‐2,5‐(CH2NMe2)2] in toluene affords TaCl4[C4H2N‐2,5‐(CH2NMe2)2] (1), whereas TaCl4[C4H3N‐2‐(CH2NEt2)] (2) is generated between the combination of TaCl5 and Li[C4H3N‐2‐(CH2NEt2)] in moderate yield. Similarly, while subjecting Li[C4H2N‐2‐(CH2NMe2)‐5‐(CH2NHtBu)] with TaCl5 in diethyl ether, it affords TaCl3[C4H2N‐2‐(CH2NMe2)‐5‐(CH2NtBu)] (3) at moderate yield. Interestingly, the mixing of TaCl4[C4H2N‐2,5‐(CH2NMe2)2] (1) with excess Li[O‐Ph‐2,6‐iPr2] in tetrahydrofuran generates the tantalum aryloxide compound, Ta(O‐Ph‐2,6‐iPr2)Cl3[C4H2N‐2,5‐(CH2NMe2)2] (4). Single crystal X‐ray diffraction analysis reveals that compound 4 is hepta‐coordinated possessing a distorted pentagonal bipyramidal geometry. All the compounds are characterized by proton nuclear magnetic resonance and carbon‐13 nuclear magnetic resonance spectroscopy, and we highlight the structural variation of tantalum derivatives with bi‐ or tridentate (symmetric and asymmetric) pyrrole precursors. [ABSTRACT FROM AUTHOR]

A series of ruthenium hydride compounds containing substituted bidentate pyrrole‐imine ligands were synthesized and characterized. Reacting RuHCl(CO)(PPh3)3 with one equivalent of [C4H3NH(2‐CH=NR)] in ethanol in the presence of KOH gave compounds {RuH(CO)(PPh3)2[C4H3N(2‐CH=NR)]} where trans‐Py‐Ru‐H 1, R = CH2CH2C6H9; cis‐Py‐Ru‐H 2, R = Ph‐2‐Me; and cis‐Py‐Ru‐H 3, R = C6H11. Heating trans‐Py‐Ru‐H 1 in toluene at 70°C for 12 hr resulted a thermal conversion of the trans‐Py‐Ru‐H 1 into its cis form, {RuH(CO)(PPh3)2[C4H3N(2‐CH=NCH2CH2C6H9)]} (cis‐Py‐Ru‐H 1) in very high yield. The 1H NMR spectra of trans‐Py‐Ru‐H 1, cis‐Py‐Ru‐H 2, cis‐Py‐Ru‐H 3, and cis‐Py‐Ru‐H 1 all show a typical triplet at ca. δ–11 for the hydride. The trans and cis form indicate the relative positions of pyrrole ring and hydride. The geometries of trans‐Py‐Ru‐H 1, cis‐Py‐Ru‐H 1, and cis‐Py‐Ru‐H 3 are relatively similar showing typical octahedral geometries with two PPh3 fragments arranged in trans positions. [ABSTRACT FROM AUTHOR]

Propynylidene 1 (HCCCH) is the simplest alkynylcarbene that, along with abundant interstellar cyclopropenylidene 2 and propadienylidene 3 has attracted substantial interest. The propynylidene can be generated as an organodimetallic ligand in solution by double C-H activation of allene and it can adopt a curved structure.

A series of ruthenium compounds containing a pyrrole-ketone bidentate ligand, 2-(2'- methoxybenzoyl)pyrrole (1), have been synthesized and characterized. Reacting 1 with [(η6- cymene)RuCl2]2 and RuHCl(CO)(PPh3)3 generated Ru(η6-cymene)[C4H3N-2-(CO-C6H4-2-OMe)]Cl (2) and {RuCl(CO)(PPh3)2[C4H3N-2-(COC6H4-2-OMe)]} (3), respectively, in moderate yields. Successively reacting 2 with sodium cyanate and sodium azide gave {Ru(η6-cymene)[C4H3N-2-(CO- C6H4-2-OMe)]X} (4, X=OCN; 5, X=N3) with the elimination of sodium chloride. Compounds 2-5 were all characterized by ¹H and 13C-NMR spectra and their structures were also determined by X-ray single crystallography. [ABSTRACT FROM AUTHOR]