A Remarkable Switch from a Diamination to a Hydrohydrazination Catalyst and Observation of an Unprecedented Catalyst Resting State

A small change with a big effect: Reaction of the titanium complex 1 with terminal alkynes gave the unusual acetylide–vinylhydrazide(1−) compounds 2 (R=4‐C6H4X (X=Me, CF3, OMe), C6F5, SiMe3) as hydrohydrazination intermediates. In contrast, a complex similar to 1 with bulkier trimethylsilyl substituents in place of the isopropyl groups is known to catalyze the 1,2‐diamination of alkynes with hydrazines.