High Spin Cobalt Complexes Supported by a Trigonal Tris(Phosphinimide) Ligand

• Published in: Inorganic chemistry Vol. 60; no. 16; pp. 11830 - 11837
• Main Authors: Lee, Heui Beom, Ciolkowski, Nicholas, Winslow, Charles, Rittle, Jonathan
• Format: Journal Article
• Language: English
• Published: American Chemical Society 16.08.2021
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.1c01400

Terminal, π-basic moieties occupy a prominent position in the stabilization of unusual or reactive inorganic species. The electron-releasing, π-basic properties of phosphinimides (PN) have been employed to stabilize electron-deficient early transition metals and lanthanides. In principle, a ligand field comprised of terminal PN groups should enable access to high-valent states of late first row transition metals. Herein, we report a new class of multidentate phosphinimide ligands to logically explore this hypothesis. Access to such ligands is made possible by a new procedure for the electrophilic amination of rigid, sterically encumbering, multidentate phosphines. Such frameworks facilitate terminal PN coordination to cobalt as demonstrated by the synthesis of a trinuclear CoII 3 complex and a homoleptic, three-coordinate CoIII complex. Interestingly, the CoIII complex exhibits an exceedingly rare S = 2 ground state. Combined XRD, magnetic susceptibility, and DFT studies highlight that terminally bound PNs engage in strong dπ–pπ interactions that present a weak ligand field appropriate to stabilize high-spin states of late transition metals.