A paramagnetic cobalt-SiH intermediate possessing the Co-(η(1)-H-Si) moiety was studied using various spectroscopic techniques. Frozen solution ENDOR experiments show a Co-H distance of ∼1.53 Å and a Si-Co-H angle of ∼15°, whereas XRD data suggest a TBP geometry about a Co(ii) centre. Its stepwise deprotonation with base followed by dehalogenation was identified experimentally and theoretically.

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Nickel(II) complexes supported by a diphosphinosilyl ligand, [PhSi(2-P i Pr 2 C 6 H 4 ) 2 ] − (PhSiP 2 ), reveal unusual metal−ligand cooperativity (MLC). While (PhSiP 2 )-Ni(NHMes) (2a) was cleanly isolated at room temperature, a nickel triisopropylphenylamido species, (PhSiP 2 )Ni(NHTrip) (2b), slowly transformed into a nickel(II) phenyl species, [(ArNH)SiP 2 ]Ni(Ph) (3b), where (ArNH)SiP 2 − = [(NHTrip)Si(2-P i Pr 2 C 6 H 4 ) 2 ] − . The X-ray crystallographic data of 3b 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 2 to 3 (k obs = 0.28 vs 0.44 h −1 ), 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 2 (4) 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 (3) with gaseous carbon dioxide (CO 2 (g)) produces a nickel(II) carbamato complex, (PhSiP 2 )Ni(OC(O)NHAr) (6), which may involve a RE−OA process occurring at a nickel center. Although 2 and 3 might be in equilibrium, the reaction of 3 with CO 2 does not follow this pathway. Instead, a CO 2 interaction induces RE at the silyl-nickel moiety, followed by amide group transfer, to give a carbamato product, 6, 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.