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.

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 electrondeficient 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 Co II 3 complex and a homoleptic, three-coordinate Co III complex. Interestingly, the Co III 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.the filtrate under reduced pressure. The 1 H NMR (Figure S23) matches an authentic sample of 2 (11.0 mg, 28 %). ASSOCIATED CONTENTSupporting Information. Experimental procedures and characterization. This material is available free of charge via the Internet at http://pubs.acs.org.

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 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 three-coordinate CoIII complex, which 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.