摘要:
Tridentate PSiP pincer ligands featuring two phosphine donors and an anionic Si donor have attracted considerable attention in recent years. Here, we report the synthesis of the eta(3)-cyclooctenyl complex, ((PSiP)-P-Ph)Ni(eta(3)-cyclooctenyl) (1; (PSiP)-P-Ph = Si(Me)(2-PPh2-(CH4)-H-6)(2)) through the reaction of Ni(COD)(2) with (Ph)psi(H)p ((Ph)psi(H)p = HSi(Me)(2-PPh2-C6H4)(2)). We propose, that as a result of beta-hydride elimination of 1,3-COD, 1 can act as a synthetic equivalent for ((PSiP)-P-Ph)NiH. The reaction of 1 with a variety of different reagents including another equivalent of (Ph)PSi(H)p to form ((PSiP)-P-Ph)Ni-2 (2), 1,3-COD and H-2, PPh3 to form the Ni(0) species ((PSiP)-P-Ph-P-H)Ni(PPh3) (3) and 1,3-COD and 2,6-lutidine HCI to generate (PhPSiP)NiCI (4), 1,3-COD and H2 are in agreement with this hypothesis. In addition, in the reaction of 1 with BH3"THF, (PhPSiP)Ni(K2-BH4) (5) was observed but could not be isolated. This reaction presumably proceeds via (PhPSiP)NiH. This is supported by the observation that the reaction of (cYPSiP)NiH (cYPSiP = Si(Me)(2-PCY2-C6F14)2) with BH3.THF formed (cYPSiP)Ni(K2-BH4) (6). Catalytic reactions such as alkene isomerization and CO2 reduction using 1 as precatalyst are also consistent with a nickel hydride being accessible. Compounds 1, 2 and 6 were characterized by X-ray crystallography. (C) 2014 Elsevier Ltd. All rights reserved.