Synthesis of Mixed Silylene–Carbene Chelate Ligands from N‐Heterocyclic Silylcarbenes Mediated by Nickel

The Ni II ‐mediated tautomerization of the N‐heterocyclic hydrosilylcarbene L 2 Si(H)(CH 2 )NHC 1 , where L 2 =CH(CCH 2 )(CMe)(NAr) 2 , Ar=2,6‐ i Pr 2 C 6 H 3 ; 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:(CH 2 )(NHC)NiBr 2 ] 2 (L 1 =CH(MeCNAr) 2 ). Reduction of 2 with KC 8 in the presence of PMe 3 as an auxiliary ligand afforded, depending on the reaction time, the N‐heterocyclic silyl–NHC bromo Ni II complex [L 2 Si(CH 2 )NHCNiBr(PMe 3 )] 3 and the unique Ni 0 complex [η 2 (Si‐H){L 2 Si(H)(CH 2 )NHC}Ni(PMe 3 ) 2 ] 4 featuring an agostic SiH→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:(CH 2 )NHCNi(dmpe)] 5 could be isolated. Moreover, the dicarbonyl Ni 0 complex 6 , [L 1 Si:(CH 2 )NHCNi(CO) 2 ], is easily accessible by the reduction of 2 with K(BHEt 3 ) 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.