Role of Lewis bases in reactions of aluminum and gallium trialkyls with 2-mercaptobenzoxazole

• Reactions of t-Bu3Al with 2-mercaptobenzoxazole depend on a kind of Lewis bases.
• In the presence of week bases aluminum 2-mercaptobenzoxazolate is formed.
• Strong Lewis bases cause a cleavage of 2-mercaptobenzoxazolate ligand.
• Aluminum o-isotiocyanatophenolate is obtained in THF and 3-picoline.
• Gallium 2-mercaptobenzoxazolate is stable irrespective of a kind of Lewis base.

We studied reactions of tBu3M (M = Al, Ga) with 2-mercaptobenzoxazole. In the presence of strong Lewis bases, alkylaluminum o-isotiocyanatophenolates [tBu2Al(OC6H4NCS)(THF)] (1), [tBu2Al(OC6H4NCS)(3-picoline)] (2) were obtained as a result of heterocycle cleavage in the 2-mercaptobenzoxazolate ligand and Al–Ophenolate bond formation. The reaction of tBu3Al with 2-mercaptobenzoxazole in OEt2 as a weak Lewis base produced the stable tetranuclear complex [tBu2Al(C7H4NOS)]4 (3). The gallium compound [tBu2Ga(C7H4NOS)]4 (4), isostructural to compound 3, was formed as a stable complex irrespective of the kind of Lewis base. The molecular structures of 1, 3, and 4 were determined by single-crystal X-ray diffraction technique.

Alkylaluminum o-isotiocyanatophenolates [tBu2Al(OC6H4NCS)(THF)] (1), [tBu2Al(OC6H4NCS)(3-picoline] (2) and tetranuclear complexes [tBu2M(C7H4NOS)]4 [M = Al (3), M = Ga (4) were obtained in the reaction of 2-mercaptobenzoxazole with tBu3M].Figure optionsDownload as PowerPoint slide