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Montréal, Canada

Hao J.,Univerrsite de Montreal | Mougang-Soume B.,Univerrsite de Montreal | Vabre B.,Univerrsite de Montreal | Zargarian D.,Univerrsite de Montreal
Angewandte Chemie - International Edition | Year: 2014

We describe the results of a study on the stabilities of pincer-type nickel complexes relevant to catalytic hydroalkoxylation and hydroamination of olefins, Ci-C and Ci-X couplings, and fluorination of alkyl halides. Complexes [(POCsp3OP)NiX] are stable for X=OSiMe3, OMes (Mes=1,3,5-Me3C6H2), NPh2, and CCi-H, whereas the O(tBu) and N(SiMe3)2 derivatives decompose readily. The phenylacetylide derivative transforms gradually into the zero-valent species cis-[{κP,κC, κC′-(iPr2POCH2CHCH 2)}Ni{η2,κC,κ C′-(iPr2P(O)CCPh)}]. Likewise, attempts to prepare [(POCsp3OP)NiF] gave instead the zwitterionic trinuclear species [{(η3-allyl)Ni}2-{μ,κP, κO-(iPr2PO)4Ni}]. Characterization of these two complexes provides concrete examples of decomposition processes that can dismantle POCsp3OP-type pincer ligands by facile Ci-O bond rupture. These results serve as a cautionary tale for the inherent structural fragility of pincer systems bearing phosphinite donor moieties, and provide guidelines on how to design more robust analogues. Survival of the fittest: One or both of the Ci-O linkages in the complex [(POCsp3OP)Ni(OSiMe 3)] break under fairly mild conditions to generate unprecedented mono- and trinuclear species. These decomposition processes can serve as models for predicting the stabilities of these complexes in catalytic settings. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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