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Imido complexes of early transition metals are key intermediates in the synthesis of many nitrogen-containing organic compounds. The metal-nitrogen double bond of the imido moiety undergoes [2+2] cycloaddition reactions with various unsaturated organic molecules to form new nitrogen-carbon and nitrogen-heteroatom bonds. This review article focuses on reactivity of the terminal imido complexes of Group 4-6 metals, summarizing their stoichiometric reactions and catalytic applications for a variety of reactions including alkyne hydroamination, alkyne carboamination, pyrrole formation, imine metathesis, and condensation reactions of carbonyl compounds with isocyanates.

Objective: Due to the high postoperative recurrence rate in eosinophilic chronic rhinosinusitis (eCRS) patients, there is a need for an index to predict the postoperative outcomes. Group 2 innate lymphoid cells (ILC2s) are important effector cells for type 2 immune responses in eosinophilic airway inflammation. The aim of this study was to investigate whether the prevalence of ILC2s in sinonasal tissues or in peripheral blood is associated with the postoperative outcome in CRS patients.Methods: Twelve patients with eCRS and ten patients with non-eCRS were recruited. We examined the ILC2 prevalence in sinonasal tissues and in peripheral blood before and after endoscopic sinus surgery (ESS). Pre- and postoperative blood eosinophil counts were also examined. Lund-Mackay computed tomography (LMK-CT) scores were used to evaluate the disease severities and the postoperative outcomes; cases with more than 50% improvement were categorized into the good outcome group, and cases with less than 50% improvement were categorized into the poor outcome group.Results: The ILC2 prevalence in sinonasal tissues was correlated with that in preoperative blood in eCRS and non-eCRS patients. The ILC2 prevalence in sinonasal tissues and in preoperative blood was not correlated with the pre- or postoperative LMK-CT scores. Postoperatively, the ILC2 prevalence in blood was decreased in eCRS and non-eCRS patients, and blood eosinophil count was also decreased in eCRS patients but not in non-eCRS patients. The ILC2 prevalence in postoperative blood was decreased in the good outcome group but not in the poor outcome group. Blood eosinophil counts were not decreased postoperatively in both good and poor outcome groups.Conclusion: The decreased ILC2 prevalence in postoperative blood may be a predictive biomarker for evaluating postoperative outcomes in eCRS and non-eCRS patients. [ABSTRACT FROM AUTHOR]

Dinuclear titanium dialkyl complexes bridged by two μ-arylimido ligands, [CpTi(CH2SiMe3)(μ-NAr)]2 (Cp=cyclopentadienyl) activated an ortho-aryl C−H bond of an μ-arylimido ligand to form a four-membered titanacycle. The subsequent insertion reaction of 1-(trimethylsilyl)propyne into a metal-carbon bond of the four-membered titanacycle yielded the corresponding six-membered titanacycle. Further ortho-C−H bond activation of the other μ-arylimido ligand and an insertion reaction proceeded to give dinuclear titanium complexes with two six-membered titanacycles. An Eyring plot in the temperature range 130-150 °C revealed activation parameters for the alkenylation reaction, and deuterium-labeling experiments showed that the C−H bond activation step is the rate determining step. Relative Gibbs free energies of the starting complexes, reaction intermediates, and transition states were calculated by using DFT calculations. [ABSTRACT FROM AUTHOR]

The development of several in situ generated catalyst systems for Ti-catalyzed oxidative nitrene transfer reactions is reported. The simplest and widely applicable catalyst system, TiCl 4 (THF) 2 /Zn 0 , can be set up on the benchtop under air. This system uses commercially available reagents and can be used as an entry point for Ti II /Ti IV multicomponent redox reactions for the synthesis of pyrroles, α,γ -unsaturated imines, α,β -unsaturated imines, cyclopropylimines, and arenes., Competing Interests: The authors declare no competing financial interest.

Dinuclear titanium dialkyl complexes bridged by two μ-arylimido ligands, [CpTi(CH 2 SiMe 3 )(μ-NAr)] 2 (Cp=cyclopentadienyl) activated an ortho-aryl C-H bond of an μ-arylimido ligand to form a four-membered titanacycle. The subsequent insertion reaction of 1-(trimethylsilyl)propyne into a metal-carbon bond of the four-membered titanacycle yielded the corresponding six-membered titanacycle. Further ortho-C-H bond activation of the other μ-arylimido ligand and an insertion reaction proceeded to give dinuclear titanium complexes with two six-membered titanacycles. An Eyring plot in the temperature range 130-150 °C revealed activation parameters for the alkenylation reaction, and deuterium-labeling experiments showed that the C-H bond activation step is the rate determining step. Relative Gibbs free energies of the starting complexes, reaction intermediates, and transition states were calculated by using DFT calculations., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)