Oxidative Additions to Ti(IV) in [(dadi)4–]TiIV(THF) Involve Carbon–Carbon Bond Formation and Redox-Noninnocent Behavior

Abstract

An attempt at transferring the imide of (dadi)Ti═NAd (2═NAd, dadi2–, dadin = [{−CH═N(1,2-C6H4)N(2,6-iPr2-C6H3)}2]n)to C2H4 led instead to low yields of trans-C6H4-{1,2-(N,2-N(2,6-iPr2-C6H3)-C6H4)2Ti-NHAd}2 (3), a product that features four new C–C bonds to two new carbons. Mechanistic evaluation of its formation led to oxidative addition studies of SnX4 (X = Cl, Br, I) and RX to (dadi)Ti(THF) (1-THF, dadi4–), in which the oxidation occurs at the dadi ligand. Products include (dadi)TiX2 (2-X2, X = Cl, Br, I) and the imine-triamide (R-ita)TiX (5-RX, R = Me, Bn; X = Cl, Br; R-ita = [{−CH2N(1,2-C6H4)N(2,6-iPr2-C6H3)}{CR═N(1,2-C6H4)N(2,6-iPr2-C6H3)}]). Studies of the RX additions, including implementation of radical clocks, pointed toward concerted process(es). Rearrangements of 2-X2 and 2═NAd revealed a new tridentate benzimidazole diamide chelate (bida) structurally characterized in (bida)TiCl2 (4-Cl2) and (bida)Ti═NAd (OPMe2Ph) (6). The nature of various products suggests that the (dadin)Ti core can act as a nucleophile (n = 4), electrophile (n = 2), or as a radical center (n = 3) under certain conditions.