Trigonal Bi- and Monopyramidal Cobalt(II) Complexes of a Novel Guanidine-Based Tripodal Ligand

The novel ligand DIG3tren has three N′,N′′-diisopropylguanidinyl (DIG) moieties. We report on the structures of two cobalt complexes that show how an isopropylamino group from each DIG acts as a flap that can either close over the metal or rotate away from the metal to open up a site for auxiliary ligand binding. Two of the −NH(iPr) flaps are open in pink [Co(DIG3tren)(OAc)]OAc (1), and each of these flaps provides a hydrogen bond to stabilize acetate binding to trigonal bipyrimidal cobalt. The flaps are closed in blue [Co(DIG3tren)][BPh4]2 (2), yielding a rare example of a trigonal (mono)pyramidal [ML]2+ ion.