Reactions of Heteroallenes with Salan-based Ti(IV) Complexes: A Joint Experimental and Computational Study

The reaction of Ti(NMe2)4 with the salan ligand precursor H2N2O2H2 led to the formation of [(L*)Ti(NHMe2)2] (L*=N2O24-) that forms [(H2N2O2)TiCl2] upon reaction with two equiv. of Me3SiCl. [(L*)Ti(py)2] was obtained from the reaction of [Ti(NtBu)Cl2(py)3] with the sodium salt H2N2O2Na2. Treatment of [(L*)Ti(NHMe2)2] with two equiv. of tBuNCO led to the insertion of the isocyanate molecules into the Ti-Nsalan bonds with the formation of [{L*(N(tBu)CO)2}Ti]. Conversely, the reaction of [(H2N2O2)Ti(OiPr)2] with two equiv. of tBuNCO led to the insertion of one isocyanate molecule into a Ti-Nsalan bond with the formation of [{(HN2O2)(N(tBu)CO)}Ti(OiPr)]. Computational studies were performed to gain insight into the reactivity of isocyanates with salan-based Ti(IV) complexes. Salan-based Ti(IV) complexes react with tBuNCO leading to the insertion of one or two isocyanate molecules into Ti-Nsalan bonds. Conversely, the reaction of [(L*)Ti(NHMe2)2] (L*=N2O24-) with CO2 reveals its insertion into Ti-NHMe2 bonds. The insertion of heteroallenes into Ti-N bonds offers the possibility to use them to functionalize salan ligands or as building blocks to prepare high-value-added compounds. image