Chelated borates: Synthesis, reactivity, and cation formation

The ligands N-salicylidene-o-aminophenol (LH2), N-(5-chlorosalicylidene)-o-aminophenol (L(CI)H-2), and N-(5-bromosalicylidene)-o-aminophenol (L(Br)H-2) were used to prepare a series of berates having the formulas LBOR (R = Me (1), Et (2), Pr-n (3), Bu-n (4)), L(Cl)BOR (R = Me (5), Et (6), Pr-n (7), Bu-n (8)), and L(Br)BOR (R = Me (9), Et (10), Pr-n (11), Bu-n (12)). Either 1-4 or 9-12 could be combined with HOSiPh3, to form unique compounds possessing a single B-O-Si linkage, LBOSiPh3 (13) and L(Br)BOSiPh3 (14), respectively. The charged species, [LB(thf)]+OTf- (15) forms when 1 is combined with HOTf It can be used as a catalyst for the oligomerization of propylene oxide. By comparison. [(Bu2B)-Bu-n]+OTf- effects the oligomerization to the same extent as 15, but the neutral species, 1-4, 13, and 14 do not, even under forcing conditions. All of the compounds were characterized by melting Feint,H-1 NMR, IR, elemental analyses, and, in the case of 13, by X-ray crystallography.