Transient Dipnictyl Analogues of Acrylamides, R-E=E′-CONR2, and a Related Diphosphadigalletane from Na[OCP] and (R2N)2ECl (E, E′=P, As, Ga)

The reaction of Na[OCP] with (R2N)(2)ECl (E=P or As; R=alkyl) granted direct access to transient amine-substituted diphospha- and arsaphospha-acrylamide analogues, (R2N)E=P(CONR2) 1. Their facile formation allowed for a comprehensive reactivity study. Dimerization yielded the four-membered rings (R2N)(2)E2P2(CONR2)(2), whereas in the presence of excess Na[OCP], a stepwise [2+2] cycloaddition occured, leading to the sodium salts of carboxotripnictides [(R2N)EP2CO(CONR2)](-). These salts served as a reservoir of 1, either by extrusion of Na[OCP] or by reaction with the appropriate (R2N)(2)ECl, giving the [4+2]-cycloaddition products (R2N)EP(C6H10)(CONR2) in the presence of 2,3-dimethylbutadiene. The formal conjugate addition product K[(tBuO)(R2N)PP(CONR2)] was obtained by reaction of Na[(R2N)PP2CO(CONR2)] with tBuOK. In addition, a rare diphosphadigalletane with a ladder-type (R2N)(2)Ga2P2(CONR2)(2) core was isolated from the reaction of Na[OCP] with (R2N)(2)GaCl (R=alkyl). The unprecedented pnictogenyl carboxamide compounds were thoroughly characterized, including single-crystal X-ray structure determinations, and mechanisms for their formation were investigated by DFT calculations.