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Nickel(II) complexes supported by a diphosphinosilyl ligand, [PhSi(2-PPrCH)] (PhSiP), reveal unusual metal-ligand cooperativity (MLC). While (PhSiP)Ni(NHMes) () was cleanly isolated at room temperature, a nickel triisopropylphenylamido species, (PhSiP)Ni(NHTrip) (), slowly transformed into a nickel(II) phenyl species, [(ArNH)SiP]Ni(Ph) (), where (ArNH)SiP = [(NHTrip)Si(2-PPrCH)]. The X-ray crystallographic data of exhibit a Si-N bond generated from Si-N coupling between the silyl moiety and amino group, along with cleavage of a Si-C bond. Because substoichiometric amounts of π-acidic ligands, such as isocyanide, enhance the conversion rate of to ( = 0.28 vs 0.44 h), this reaction may involve reductive elimination (RE) and oxidative addition (OA) operating at the silyl-nickel moiety. This is further supported by the fact that the presence of excess π-acidic ligands results in the generation of demetalated ligands (ArNH)PhSiP () having both Si-N and Si-Ph bonds and the nickel(0) species. Theoretical evaluations also agree on such a pathway. Interestingly, the reaction of a nickel phenyl species () with gaseous carbon dioxide (CO(g)) produces a nickel(II) carbamato complex, (PhSiP)Ni(OC(O)NHAr) (), which may involve a RE-OA process occurring at a nickel center. Although and might be in equilibrium, the reaction of with CO does not follow this pathway. Instead, a CO interaction induces RE at the silyl-nickel moiety, followed by amide group transfer, to give a carbamato product, , based on our experimental and theoretical evaluations. These results highly support that group transfer involving MLC can be managed via a RE-OA pathway at the silyl-nickel(II) moiety.
This article was published in the following journal.
Name: Inorganic chemistry
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