Derivate des Borols, XVI Bis(borol)nickel‐Komplexe 2)

Derivatives of Borole, XVI 1) ,—Bis(borole)nickel Complexes 2) The dilithium 1‐(dialkylamino)dihydroborolediides Li 2 [C 4 H 4 ‐BNR 2 ] 2a, b : R = Me, Et) react with NiCl 2 · DME to give bis(borole)nickel complexes Ni(C 4 H 4 BNR 2 ) 2 . Nucleophilic substitution reactions are used to produce a large variety of derivatives Ni(C 4 H 4 BR) 2 1 (e.g. R = H, t Bu, F, Cl, Br, I, OH, OMe). Treatment of Ni(C 4 H 4 BCl) 2 ( tg ) with LiO(CH 2 ) 3 OLi in THF produces a polymer and a dinuclear complex (μ‐{η 5 :η 5 ‐[(CH 2 ) 3 (OBC 4 H 4 ) 2 ]} 2 Ni 2 ( 3 ) which crystallizes from CH 2 Cl 2 as solvate 3 · CH 2 Cl 2 . The complexes 1g and 3 · CH 2 Cl 2 are characterized by X‐ray diffraction work. Barriers to internal ring‐ring rotation are measured by variable‐temperature NMR spectroscopy. The B—H bond of Ni(C 4 H 4 BH) 2 ( 1a ) is remarkably inert and does not react with H 2 O or with carboxylic acids in THF at room temperature. With PhCHO slow formation of the benzyloxy compound Ni(C 4 H 4 BOCH 2 Ph) 2 ( 1 m ) is observed at 100°C. For typical complexes such as the phenyl derivative 1e cyclic voltammetry in CH 2 Cl 2 reveals an irreversible oxidation at 1.32 and a quasi‐reversible reduction at –1.37 V vs. SCE.