Frustrated Lewis Pairs from Al-E{14} Bonds (E{14}=Ge, Sn, Pb)

The potassium aluminyl K[Al(NON)] ([NON](2-)=[O(SiMe(2)NDipp)(2)](2-), Dipp=2,6-iPr(2)C(6)H(3)) reacts with group 14 chloroamidinates E-{14}(Am)Cl (E-{14}=Ge, Sn, Pb. [Am](-)=[tBuC(NDipp)(2)](-)) to form (NON)Al-E-{14}(Am) Lewis pairs with unsupported Al-E-{14} bonds, including the first structurally authenticated Al-Pb bond. Analysis using spectroscopic (NMR, UV-vis and M & ouml;ssbauer for E-{14}=Sn), X-ray diffraction and computational (DFT, QTAIM, TD-DFT) methods conclude an Al-E-{14} sigma-bond derived from a Lewis basic Al and a Lewis acidic tetrylene, with back-donation from the E({14})s-orbital lone pair donor NBO to acceptor NBOs on Al that are derived from s/p-orbitals. The reaction of the Al-Ge compound with CO2 forms the dioxocarbene (NON)Al(mu-O2C)Ge(Am), whilst under the same conditions the Al-Sn compound reacts with additional CO2 to form the carbonate, (NON)Al(mu-CO3)Sn(Am). Addition of ethene to the Al-E-{14} (E-{14}=Ge, Sn) compounds introduces an ethylene bridge between the aluminium and group 14 atoms forming a frustrated Lewis pair (FLP). Reaction of the (Al/Ge) FLP with CO2 forms an activation product with new Al-O and Ge-C bonds, whilst reaction with iPrN=C=NiPr proceeds with insertion into the Al-C bond to form an aluminium amidinate.