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The Ni(II) -mediated tautomerization of the N-heterocyclic hydrosilylcarbene L(2) Si(H)(CH2 )NHC 1, where L(2) =CH(CCH2 )(CMe)(NAr)2 , Ar=2,6-iPr2 C6 H3 ; NHC=3,4,5-trimethylimidazol-2-yliden-6-yl, leads to the first N-heterocyclic silylene (NHSi)-carbene (NHC) chelate ligand in the dibromo nickel(II) complex [L(1) Si:(CH2 )(NHC)NiBr2 ] 2 (L(1) =CH(MeCNAr)2 ). Reduction of 2 with KC8 in the presence of PMe3 as an auxiliary ligand afforded, depending on the reaction time, the N-heterocyclic silyl-NHC bromo Ni(II) complex [L(2) Si(CH2 )NHCNiBr(PMe3 )] 3 and the unique Ni(0) complex [η(2) (Si-H){L(2) Si(H)(CH2 )NHC}Ni(PMe3 )2 ] 4 featuring an agostic SiH→Ni bonding interaction. When 1,2-bis(dimethylphosphino)ethane (DMPE) was employed as an exogenous ligand, the first NHSi-NHC chelate-ligand-stabilized Ni(0) complex [L(1) Si:(CH2 )NHCNi(dmpe)] 5 could be isolated. Moreover, the dicarbonyl Ni(0) complex 6, [L(1) Si:(CH2 )NHCNi(CO)2 ], is easily accessible by the reduction of 2 with K(BHEt3 ) under a CO atmosphere. The complexes were spectroscopically and structurally characterized. Furthermore, complex 2 can serve as an efficient precatalyst for Kumada-Corriu-type cross-coupling reactions., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Polymers occupy an important role in our current society. Besides their great success, an issue is the accumulation of huge amounts of end-of-life polymers. Currently, the waste management is based primarily on landfills, thermal recycling, and downcycling. Notably, only a small portion of end-of-life materials is recycled by depolymerization, which refers to the creation of synthetic precursors that can be polymerized to new polymers to close the cycle. Widely used polymers in modern times are silicones (polysiloxanes), the intrinsic properties of which make their depolymerization demanding; only a few high-temperature or less environmentally friendly processes have been reported. In this regard, we have established an efficient low-temperature protocol for the depolymerization of silicones with benzoyl fluoride in the presence of cheap zinc salts as precatalysts to yield defined products. Notably, the products can be useful synthetic precursors for the preparation of new polymers, so that an overall recycling process is feasible., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Not copy and paste: Although β-diketiminato ligands have been employed for the stabilization of Ge(II) and Sn(II) hydrides, the corresponding Si(II) hydride is not accessible. However, coordination of silicon(II) to a {Ni(CO)(3)} fragment allowed the isolation of the first Si(II) hydride metal complex 1. This complex was used for the first silicon(II)-based and Ni(0)-mediated, stereoselective hydrosilylation of alkynes. R = phenyl, tolyl., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)