Synthesis, characterization, and reactivity of a novel thallium arylspiroboronate ester

Addition of 3,5-di-tert-butylcatechol (butcat) to solutions of H3B center dot SMe2 gave the novel diboron species B-2(butcat)(3) (2) in moderate to high yields. Compound 2 reacts with Tl(acac) to give butcatB(acac) (4) and Tl(Bbutcat(2)) (5). Attempts to abstract the chlorides from [(dppb)Rh(mu-Cl)](2) (where dppb = 1,4-bis(diphenylphosphino)buthane) using 5 led to the unusual dimer [(dppb)Rh(mu-Cl)(2)(mu-Tl)Rh(dppb)][Bbutcat(2)] (6), which contains an unsymmetrical Rh-Tl-Rh bridge.