title: Trigonal bi- and monopyramidal cobalt(II) complexes of a novel guanidine-based tripodal ligand.
abstract: The novel ligand DIG(3)tren 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(DIG(3)tren)(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(DIG(3)tren)][BPh(4)](2) (2), yielding a rare example of a trigonal (mono)pyramidal [ML](2+) ion.
authors.affiliation: Department of Chemistry, Haverford College, 370 Lancaster Avenue, Haverford, Pennsylvania 19041, United States.
authors.forename: Cassandra E
authors.initials: CE
authors.lastname: Searls
authors.forename: Scott T
authors.initials: ST
authors.lastname: Kleespies
authors.forename: Matthew L
authors.initials: ML
authors.lastname: Eppright
authors.forename: Sarina C
authors.initials: SC
authors.lastname: Schwartz
authors.forename: Glenn P A
authors.initials: GP
authors.lastname: Yap
authors.forename: Robert C
authors.initials: RC
authors.lastname: Scarrow