σ-Borane coordinated to nickel(0) and some related nickel(II) trihydride complexes

The reactions of the complexes [(dcype)NiH](2), 1, [(dippe)NiH](2), 2, and [(dtbpe)NiH](2), 3, with a mixture of BEt3 and Super-Hydride (LiHBEt3) afforded sigma-borane nickel(O) compounds of the type [(dcype)Ni(sigma-HBEt2)], 4, [(dippe)Ni(sigma-HBEt2)], 5, [(dtbpe)Ni(sigma-HBEt2)], 6, respectively, with the concomitant formation in each case of [(dcype)(2)Ni-2(H)(3)][BEt4], 7, [(dippe)(2)Ni-2(H)(3)][BEt4], 8 and [(dtbpe)(2)Ni-2(H)(3)][BEt4], 9, respectively. X-ray crystal structures are reported for 4 and 8. The reaction of BEt3 and LiHBEt3 was also reviewed in detail.