Jan Pecak, Wolfgang Eder, Berthold Stöger, Sara Realista, Paulo N. Martinho, Maria José Calhorda, Wolfgang Linert, and Karl Kirchner

The reaction of coordinatively unsaturated Co(II) PCP pincer complexes with nitric oxide leads to the formation of new, air-stable, diamagnetic mono nitrosyl compounds. The synthesis and characterization of five- and four-coordinate Co(III) and Co(I) nitrosyl pincer complexes based on three different ligand scaffolds is described. Passing NO through a solution of [Co(PCPNMe-iPr)Cl], [Co(PCPO-iPr)Cl] or [Co(PCPCH2-iPr)Br] led to the formation of the low-spin complex [Co(PCP-iPr)(NO)X] with a strongly bent NO ligand. Treatment of the latter species with (X = Cl, Br) AgBF4 led to chloride abstraction and formation of cationic square-planar Co(I) complexes of the type [Co(PCP-iPr)(NO)]+ featuring a linear NO group. This reaction could be viewed as a formal two electron reduction of the metal center by the NO radical from Co(III) to Co(I), if NO is counted as NO+. Hence, these systems can be described as {CoNO}8 according to the Enemark–Feltham convention. X-ray structures, spectroscopic and electrochemical data of all nitrosyl complexes are presented. Preliminary studies show that [Co(PCPNMe-iPr)(NO)]+ catalyzes efficiently the reductive hydroboration of nitriles with pinacolborane (HBpin) forming an intermediate {CoNO}8 hydride species.
Doi: 10.1021/acs.organomet.0c00167

Cited as: Pecak J, Eder W, Stöger B, Realista S, Martinho PN, Calhorda MJ, Linert W, Kirchner K (2020) Synthesis, Characterization, and Catalytic Reactivity of {CoNO}8 PCP Pincer Complexes. Organometallics 39, 14, 2594–2601; https://doi.org/10.1021/acs.organomet.0c00167.