Fluoride as a Terminal and Bridging Ligand for Copper: Isolation and X-ray Crystallographic Characterization of Monomeric and Dimeric Complexes [Cu¹¹ (TMPA)F]_nⁿ⁺ (n = 1 or 2; TMPA = Tris[(2-pyridyl)methyl]amine)

The copper(1) complex with tripodal tetradentate amine ligand TMPA, [Cu^I(TMPA)CH₃CN]PF₆ (I; TMPA = tris[(2-pyridyl)methyl]amine), reacts with dioxygen, resulting in breakdown of the hexafluorophosphate anion and providing two distinct fluoride Cu(II) complexes that have been crystallographically characterized. [Cu^II(TMPA)F]₂(PF₆)₂ (2) is a fluoride doubly bridged dimer (axial-equatorial), where each copper ion is pseudooctahedrally coordinated [C₃₆H₃₆Cu₂F₁₄N₈P₂, monoclinic P2₁/n; a = 11.649 (4), b = 12.942 (4), c = 14.654 (4) Å; β = 110.67 (2)°; Z = 4, V = 2067 (1) ų]. However, [Cu^II(TMPA)F]•PF₆•CH₂Cl₂ (3a) contains a trigonal-bipyramidal (TBP) coordination environment, with axial fluoride and tertiary amine ligation [C₁₉H₂₀CI₂CuF, N₄P, orthorhombic Pcab; a = 11.869 (2), b = 15.891 (3), c = 26.116 (6) Å; Z = 8, V = 4926 (2) ų]. Complex 3a readily loses its dichloromethane to give [Cu^II(TMPA)PF₆•1/₂H₂O (3b), which has solution properties (i.e. UV-vis, EPR) characteristic of TBP coordination. Compound 2 breaks down in solution to give the same monomeric structure as 3b, and solution UV-vis and EPR studies indicate the 3b structure can also be directly generated by addition of fluoride ion to [Cu^II-(TMPA)H₂O](ClO₄) (4).