Synthesis and coordination chemistry of an integrated binucleating ligand based on bidentate NacNac and NCN pincer frameworks

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A new binucleating “Janus” ligand based on the β-diketiminato (“NacNac”) donor combined with an NCN pincer ligand framework has been designed and synthesized. By incorporating pyridyl donors on the imino carbons of the NacNac ligand, two binding sites for metals are introduced. The ligand's binucleating capabilities are demonstrated by ligating BF 2 in the NacNac pocket and NiBr into the NCN pincer bay. The resulting binuclear boron–nickel complexes chemistry was explored by substitution of the bromide ligand on nickel and one fluoride ion on boron with the weakly coordinating triflimide anion [N(SO 2 CF 3 ) 2 ] − (NTf 2 ). The bromide is replaced preferentially with AgNTf 2 and further treatment with Me 3 SiNTf 2 produces a borenium ion by abstracting F − from the BF 2 unit. Semiquantitative assessment of the Lewis acidity at the nickel center using the Gutmann–Beckett method shows a substantial increase in Lewis acidity upon conversion of the BF 2 to the [BF] + borenium moiety.