Activation of N2O, CO2, and CO at a sterically protected phosphorus center

Abstract

Functionalization of a sterically encumbered phosphorus precursor enables varied activation pathways for N₂O, CO₂, and CO. The potasssium phosphanide salt, [K(crypt)][(M^sFluInd*)PH] (crypt = 2.2.2.cryptand; M^sFluInd* = a sterically demanding hydrindacenyl substituent), was synthesized and treated with either N₂O or ¹³CO₂ to afford the potassium phosphinate, [K(crypt)][(M^sFluInd*)PHO₂], or the potassium phosphacarboxylate, [K(crypt)][(M^sFluInd*)PH(¹³CO₂)], respectively. Deprotonation of the TMS-functionalized (TMS = trimethylsilyl) phosphine, (M^sFluInd*)PTMSH, followed by treatment with either N₂O or ¹³CO₂ resulted in the formation of a phoshanorcaradiene, (M^sFluInd*)P, and an arylphosphaketene, (M^sFluInd*)P¹³CO, respectively. Reversible CO binding at phosphorus allows for the interconversion between (M^sFluInd*)P and (M^sFluInd*)PCO. The mechanism for the formation of (M^sFluInd*)PCO from (M^sFluInd*)P and CO was investigated computationally.