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(PPh2)2(n-PrSMe) (1) or N­(PPh2)2(p-(SMe)­C6H4) (2) with [Ni­(NCMe)6]­[BF4]2 in a 2:1 molar ratio afforded the bis-chelated, dicationic Ni­(II) complexes [Ni­(1)2]­[BF4]2 (3) and [Ni­(2)2]­[BF4]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((Ph2P)­N­{P­(CH2)­Ph2}­(n-PrSMe)-P,C)2]­[BF4]2 (5) and [Ni­((Ph2P)­N­{P­(CH2)­Ph2}­(p-(SMe)­C6H4)-P,C)2]­[BF4]2 (6), respectively. The formation of [Ni­((Ph2P)­N­{P­(CH2)­Ph2}­(n-PrSMe)-P,C)2]­Cl2 (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.