The cyclotrimerization of aryl isocyanates and the cyclodimerization of alkyl isocyanates initiated by one praseodymium benzenethiolate complex [Pr (SPh) 3 (THF) 3] were investigated. Comparative runs with [Pr (SPh) 3 (THF) 3] and its precursor Pr [(Me3Si) 2N] 3 showed that the former has the advantages of a higher selectivity toward isocyanates, easy preparation, low catalyst loading, high conversion as well as mild reaction conditions.
