title: Li+, Cu+, and Ag+ oligonuclear structures with the sterically demanding bis(3,5-tertbutylpyrazol-1-yl)dithioacetate heteroscorpionate ligand.
abstract: The heteroscorpionate N(2)S(2) donor ligand bis(3,5-tertbutylpyrazol-1-yl)dithioacetate (L) was prepared as a Li(+) trinuclear complex, which co-crystallizes with tetrahydrofuran (THF) solvent molecules: [Li(L)](3) x (2.25)THF. When [Li(L)](3) was reacted with AgBF(4) or [Cu(CH(3)CN)(4)]BF(4), the oligonuclear species [Ag(L)](3) and [Cu(5)(L)(4)]BF(4) were isolated and structurally characterized. The Ag(+) complex presents an irregular trinuclear structure in which three AgL moieties define a central trigonal site that may potentially host a fourth metal ion. The Cu(+) complex exhibits a highly symmetric pentanuclear structure in which four equivalent CuL moieties shape an internal tetrahedral site occupied by an additional Cu(+) ion. According to electrospray-mass spectrometry (ESI-MS) and (1)H diffusion NMR spectroscopy, the Ag(+) and Cu(+) complexes maintain oligonuclear structures in solution. In particular, the Cu(+) pentanuclear complex, once dissolved, rapidly equilibrates with the tetranuclear species [Cu(4)(L)(3)](+). This is confirmed by the presence of two sets of NMR signals, which demonstrated a change in ratio at different complex concentrations effected by a NMR dilution titration. Variable temperature NMR experiments (210-303 K) defined the activation parameters associated with the fluxional behavior of [Cu(5)(L)(4)]BF(4) and [Cu(4)(L)(3)](+), and these results are consistent with intramolecular rearrangements in both species (DeltaS(double dagger) < 0).
authors.affiliation: Dipartimento di Chimica Generale ed Inorganica, Chimica Analitica, Chimica Fisica, Università degli Studi di Parma, viale G. P. Usberti 17/a, I 43100 Parma, Italy.
authors.forename: Irene
authors.initials: I
authors.lastname: Bassanetti
authors.forename: Marcello
authors.initials: M
authors.lastname: Gennari
authors.forename: Luciano
authors.initials: L
authors.lastname: Marchiò
authors.forename: Mattia
authors.initials: M
authors.lastname: Terenghi
authors.forename: Lisa
authors.initials: L
authors.lastname: Elviri
mesh_terms: D000085:Acetates / Q000737:chemistry*; D003300:Copper / Q000737:chemistry; D008024:Ligands; D008094:Lithium / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000737:chemistry*; D011720:Pyrazoles / Q000737:chemistry*; D012834:Silver / Q000737:chemistry; D012996:Solutions; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D000085:Acetates; D008024:Ligands; D009942:Organometallic Compounds; D011720:Pyrazoles; D012996:Solutions; C553447:bis(3,5-tertbutylpyrazol-1-yl)dithioacetate; D012834:Silver; D003300:Copper; D008094:Lithium