Structural and Electronic Properties of Old and New A₂[M(pin^F)₂] Complexes

Abstract

Seven new homoleptic complexes of the form A2[M(pin(F))2] have been synthesized with the dodecafluoropinacolate (pin(F))(2-) ligand, namely (Me4N)2[Fe(pin(F))2], 1; (Me4N)2[Co(pin(F))2], 2; ((n)Bu4N)2[Co(pin(F))2], 3; {K(DME)2}2[Ni(pin(F))2], 4; (Me4N)2[Ni(pin(F))2], 5; {K(DME)2}2[Cu(pin(F))2], 7; and (Me4N)2[Cu(pin(F))2], 8. In addition, the previously reported complexes K2[Cu(pin(F))2], 6, and K2[Zn(pin(F))2], 9, are characterized in much greater detail in this work. These nine compounds have been characterized by UV-vis spectroscopy, cyclic voltammetry, elemental analysis, and for paramagnetic compounds, Evans method magnetic susceptibility. Single-crystal X-ray crystallographic data were obtained for all complexes except 5. The crystallographic data show a square-planar geometry about the metal center in all Fe (1), Ni (4), and Cu (6, 7, 8) complexes independent of countercation. The Co species exhibit square-planar (3) or distorted square-planar geometries (2), and the Zn species (9) is tetrahedral. No evidence for solvent binding to any Cu or Zn complex was observed. Solvent binding in Ni can be tuned by the countercation, whereas in Co only strongly donating Lewis solvents bind independent of the countercation. Indirect evidence (diffuse reflectance spectra and conductivity data) suggest that 5 is not a square-planar compound, unlike 4 or the literature K2[Ni(pin(F))2]. Cyclic voltammetry studies reveal reversible redox couples for Ni(III)/Ni(II) in 5 and for Cu(III)/Cu(II) in 8 but quasi-reversible couples for the Fe(III)/Fe(II) couple in 1 and the Co(III)/Co(II) couple in 2. Perfluorination of the pinacolate ligand results in an increase in the central C-C bond length due to steric clashes between CF3 groups, relative to perhydropinacolate complexes. Both types of pinacolate complexes exhibit O-C-C-O torsion angles around 40°. Together, these data demonstrate that perfluorination of the pinacolate ligand makes possible highly unusual and coordinatively unsaturated high-spin metal centers with ready thermodynamic access to rare oxidation states such as Ni(III) and Cu(III).

Homoleptic Transition Metal Complexes of the 7-Azaindolide Ligand Featuring κ1-N1 Coordination

“…Similar behavior has been observed previously with homoleptic naphthalide and alkoxide complexes of the mid 3 d metals. 43-50 In the case of the benzene adduct of 2 ( 2·benz ), the complex crystallizes as a coordination polymer featuring sodium coordination to the C2-C3 π-bond of an adjacent azaindolide ligand in place of one Na-benzene interaction (see Supporting Information). In all cases, the bond metrics about the metal centers are consistent with high-spin ions corroborating solution magnetic susceptibility measurements.…”

On the Way to a Trisanionic {Cu3O2} Core for Oxidase Catalysis: Evidence of an Asymmetric Trinuclear Precursor Stabilized by Perfluoropinacolate Ligands

“…Elongated CÀCb onds in chelating pinacolate and perfluoropinacolate ligands have been discussed previously. [26] The Cu1ÀP1 bond length is 2.128(6) ,a nd the {PCuO 2 }c orei s nearly planar,w ith the Cu1 atom displaced by only 0.002 from the best {PO 2 }p lane. The O1-Cu1-P1 and O2-Cu1-P1 angles are nearly equivalent (136.…”

“…The anionic Cu I complexes K[(Ph 3 P)Cu(pin F )] (4)a nd K[(Cy 3 P)Cu(pin F )] (5)w ere synthesized by the reaction of {Cu(mes)} n (mes = mesityl) with KHpin F ,i mmediately followed by the addition of the PR 3 L-donor ligand. If an L-donor ligand was not presenti ns olution disproportionation was observed within minutes, presumably to Cu 0 and the known complex [26] K 2 [Cu(pin F ) 2 ]. The more-soluble [18]crown-6 complexes [K( [18]crown-6)][(Ph 3 P)Cu(pin F )] (6)a nd [K( [18]crown-6)][(Cy 3 P)Cu(pin F )] (7)w ere prepared by addition of [18]crown-6 to the reaction mixture after 4 and 5 had formed.…”

“…[24] Severalh eteroleptic Cu I -phosphine complexesw ith bridging fluorinated alkoxide compounds have also been reported. [25] More recently complexes with ab identate perfluoropinacolate [(pin F ) 2À ]l igand were prepared for reactivity studies of [M II (pin F ) 2 ] 2À (M = Fe II , [23,26] Co II , [23,26] Ni II , [26] Cu II , [26] and Zn II ). [23,26] Herein, we reportt he synthesis and characterization of as eries of anionic Cu I complexes of the form A[(R 3 P)Cu(pin F )] (A = cation).…”

“…[25] More recently complexes with ab identate perfluoropinacolate [(pin F ) 2À ]l igand were prepared for reactivity studies of [M II (pin F ) 2 ] 2À (M = Fe II , [23,26] Co II , [23,26] Ni II , [26] Cu II , [26] and Zn II ). [23,26] Herein, we reportt he synthesis and characterization of as eries of anionic Cu I complexes of the form A[(R 3 P)Cu(pin F )] (A = cation). These Cu I -(pin F ) 2À complexes react with O 2 regardless of the cation (A) or Ld onor (PR 3 )t of orm the symmetric bis(m 3oxo) trinuclear copper(II,II,III) complex Sy T pinF via an asymmetric trimericc ore As T pinF .T he reactive species Sy T pinF joins the few reported {Cu 3 (m 3 -O) 2 }s pecies described above, and is the first anionic trimerw ith O-donorl igands that has been characterized by multiple techniques, including stopped-flow spectroscopy,a nd therefore can be directlyc ompared to cationic or neutral{ Cu 3 O 2 }s pecies with N-donorl igandsi nt erms of spectroscopy, kinetics of formation, and reactivity.…”