Structures and CO2 Reactivity of Zinc Complexes of Bis(diisopropyl-) and Bis(diphenylphosphino)amines

The bis(phosphino)amines (R2P)NH(PR'(2)) (R = R' = isopropyl; R = R' = phenyl; R = isopropyl, R' = phenyl) react with ZnEt2 to form complexes with two different structural motifs, either the homoleptic monomeric P,P-chelates Zn[N(i-Pr2P)(2)](2) and Zn[N(i-Pr2P)(Ph2P)](2) or the heteroleptic dimeric Zn2N2P2 heterocycles {EtZn[N(PPh2)(2)]}(2) and {EtZn[N(PPh2)(i-Pr2P)]}(2). In two cases, CO2 reacts with these complexes to give adducts Zn[O2CP(i-Pr-2)NP(i-Pr-2)](2) and Zn[O2CP(i-Pr-2)NPPh2][Ph2PN(i-Pr2P)]ZnEt2, similar to adducts formed from the reaction of CO2 with frustrated Lewis pairs (FLPs). In the other two cases, reaction with CO2 results in cleavage and rearrangement of the NP bonds to give either N(PPh2)(3) or Ph2P(iPr(2)P)NPPh2. The zinc complexes and their CO2 products were characterized with a combination of single crystal X-ray diffraction and multinuclear NMR spectroscopy.