We report the synthesis of a novel bidentate Nheterocyclic silylene (NHSi) ligand, N-(LSi:)-N-methyl-2-pyridinamine (1) (L = PhC(NtBu) 2 ), and the first bischelate disilylene iron hydride, [(Si,N)(Si,C)Fe(H)(PMe 3 )] (2), and monosilylene iron hydride, [(Si,C)Fe(H)(PMe 3 ) 3 ] (2′), through C sp 2 −H activation of the NHSi ligand. Compounds 1 and 2 were fully characterized by spectroscopic methods and single-crystal X-ray diffraction analysis. Density functional theory calculations indicated the multiple-bond character of the Fe−Si bonds and the π back-donation from Fe(II) to the Si(II) center. Moreover, the strong donor character of ligand 1 enables 2 to act as an efficient catalyst for the hydroboration reaction of carbonyl compounds at room temperature. Chemoselective hydroboration is attained under these conditions. This might be the first example of hydroboration of ketones and aldehydes catalyzed by a silylene hydrido iron complex. A catalytic mechanism was suggested and partially experimentally verified.

Nerve tissue engineering has been one of the promising strategies for regenerative treatment in patients suffering from neural tissue loss, but considerable challenges remain before it is able to progress toward clinical application. It has been demonstrated that transplantation of cells in combination with physically or chemically modified biomaterials provides better environments for neurite outgrowth and further promotes axonal regeneration in animal models of spinal cord injury. In this study, neurons and astrocytes were incorporated into 400-nm, 800-nm, and 1200-nm electrospun Bombyx mori silk fibroin (SF) materials to investigate the effects of scaffold-diameter in regulating and directing cell behaviors. β-III-tubulin immunofluorescence analyses reveal that SF nanofibers with smaller diameters are more favorable to the development and maturation of subventricular zone-derived neurons than 1200-nm SF scaffolds. In addition, astrocytes exhibited well-arranged glial fibrillary acidic protein (GFAP) expression on SF scaffolds, and a significant increase in cell-spreading area was observed on 400-nm but not 1200-nm SF scaffolds. Moreover, a significantly enhanced migration efficiency of astrocytes grown on SF scaffolds was verified, which highlights the guiding roles of SF nanofibers to the migratory cells. Overall, our results may provide valuable information to develop effective tissue remodeling substrates and to optimize existing biomaterials for neural tissue engineering applications.

Four different [PSiP]-pincer ligands L1–L4 ((2-Ph2PC6H4)2SiHR (R = H (L1) and Ph (L2)) and (2- i Pr2PC6H4)2SiHR′ (R′ = Ph (L3) and H (L4)) were used to investigate the effect of substituents at P and/or Si atom of the [PSiP] pincer ligands on the formation of silyl cobalt­(I) complexes by the reactions with CoMe­(PMe3)4 via Si–H cleavage. Two penta-coordinated silyl cobalt­(I) complexes, (2-Ph2PC6H4)2HSiCo­(PMe3)2 (1) and (2-Ph2PC6H4)2PhSiCo­(PMe3)2 (2), were obtained from the reactions of L1 and L2 with CoMe­(PMe3)4, respectively. Under similar reaction conditions, a tetra-coordinated cobalt­(I) complex (2- i Pr2PC6H4)2PhSiCo­(PMe3) (3) was isolated from the interaction of L3 with CoMe­(PMe3)4. It was found that, only in the case of ligand L4, silyl dinitrogen cobalt­(I) complex 4, [(2- i Pr2PC6H4)2HSiCo­(N2)­(PMe3)], was formed. Our results indicate that the increasing of electron cloud density at the Co center is beneficial for the formation of a dinitrogen cobalt complex because the large electron density at Co center leads to the enhancement of the π-backbonding from cobalt to the coordinated N2. It was found that silyl dinitrogen cobalt­(I) complex 4 is an effective catalyst for catalytic transformation of dinitrogen into silylamine. Among these four silyl cobalt­(I) complexes, complex 1 is the best catalyst for hydrosilylation of alkenes with excellent regioselectivity. For aromatic alkenes, catalyst 1 provided Markovnikov products, while for aliphatic alkenes, anti-Markovnikov products could be obtained. Both catalytic reaction mechanisms were proposed and discussed. The molecular structures of complexes 1–4 were confirmed by single-crystal X-ray diffraction.

High expression of glutaminyl cyclase (QC) contributes to the initiation of Alzheimer's disease (AD) by catalyzing the generation of neurotoxic pyroglutamate (pE)-modified β-amyloid (Aβ) peptides. Preventing the generation of pE-Aβs by QC inhibition has been suggested as a novel approach to a disease-modifying therapy for AD. In this work, a series of diphenyl conjugated imidazole derivatives (DPCIs) was rationally designed and synthesized. Analogues with this scaffold exhibited potent inhibitory activity against human QC (hQC) and good in vitro blood-brain barrier (BBB) permeability. Further assessments corroborated that the selected hQC inhibitor 28 inhibits the activity of hQC, dramatically reduces the generation of pE-Aβs in cultured cells and in vivo, and improves the behavior of AD mice.

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