First-Row Transition Metal Complexes of a Phosphine–Silylene-Based Hybrid Ligand

We have prepared two new silylene–phosphine-based hybrid ligands Si­{N­(R)­C6H4(PPh2)}­{PhC­(N t Bu)2} [R = TMS {trimethylsilyl} (1) and TBDMS {tert-butyldimethylsilyl} (2)], which possess two donor sites. Furthermore, the treatment of the bidentate ligand 1 with base metal halides {FeBr2, CoBr2, NiCl2·dme [nickel chloride­(II) ethylene glycol dimethyl ether]} and 2 with NiBr2·dme [nickel bromide­(II) ethylene glycol dimethyl ether] afforded four-coordinate six-membered metal complexes 3–6, respectively, which feature coordination from both Si­(II) and P­(III) sites. Subsequently, complexes 3 [(FeBr2)­Si­{N­(SiMe3)­C6H4(PPh2)}­{PhC­(N t Bu)2}], 4 [(CoBr2)­Si­{N­(SiMe3)­C6H4(PPh2)}­{PhC­(N t Bu)2}], 5 [(NiCl2)­Si­{N­(SiMe3)­C6H4(PPh2)}­{PhC­(N t Bu)2}], and 6 [(NiBr2)­Si­{N­(Si t BuMe2)­C6H4(PPh2)}­{PhC­(N t Bu)2}] are studied for their redox and magnetic properties with the help of UV–vis spectroscopy, cyclic voltammetry, SQUID magnetometry, and theoretical calculations. Complexes 3–6 were found to display a paramagnetic behavior. All the compounds are well established by single-crystal X-ray diffraction studies.