Facile and Room-Temperature Activation of Csp3–Cl Bonds by Cheap and Air-Stable Nickel(II) Complexes of (N-Thioether) DPPA-Type Ligands

Reaction of the diphosphine ( P, P ) ligand N(PPh 2 ) 2 ( n- PrSMe) ( 1 ) or N(PPh 2 ) 2 ( p -(SMe)C 6 H 4 ) ( 2 ) with [Ni(NCMe) 6 ][BF 4 ] 2 in a 2:1 molar ratio afforded the bis-chelated, dicationic Ni(II) complexes [Ni( 1 ) 2 ][BF 4 ] 2 ( 3 ) and [Ni( 2 ) 2 ][BF 4 ] 2 ( 4 ), respectively. Both complexes were characterized in solution by various spectroscopic techniques and in the solid state by X-ray diffraction studies. In the presence of Zn metal used as cheap reductant, complexes 3 and 4 activate the inert C–Cl bonds of dichloromethane at room temperature to afford in high yield the phosphonium ylide derivatives [Ni((Ph 2 P)N{P(CH 2 )Ph 2 }( n- PrSMe)- P, C ) 2 ][BF 4 ] 2 ( 5 ) and [Ni((Ph 2 P)N{P(CH 2 )Ph 2 }( p- (SMe)C 6 H 4 )- P, C ) 2 ][BF 4 ] 2 ( 6 ), respectively. The formation of [Ni((Ph 2 P)N{P(CH 2 )Ph 2 }( n- PrSMe)- P, C ) 2 ]Cl 2 ( 5 ′), an analogue of complex 5, from a Ni(0) precursor supports the reduction of the Ni(II) precursors by the Zn reagent prior to C–Cl bond activation. The structures of 5 and 5 ′ were unambiguously established by X-ray diffraction analysis.