3 research outputs found
N‑Heterocyclic-Carbene Complexes Readily Prepared from Di-μ-hydroxopalladacycles Catalyze the Suzuki Arylation of 9‑Bromophenanthrene
New cyclometalated palladium complexes
of general formula [Pd(Bmim)(X)(C<sup>∧</sup>N)] have been
synthesized by a novel reaction route
involving di-μ-hydroxo-palladacycles [{Pd(μ-OH)(C<sup>∧</sup>N)}<sub>2</sub>] (C<sup>∧</sup>N = 2-benzoylpyridine
(Bzpy), <b>I</b>, previously unreported, or C<sup>∧</sup>N = 2-phenylpyridine (Phpy), <b>II</b>)] and 1,3-butylmethylimidazolium
salts [HBmim]X (X: Cl, Br, I, or saccharinate (Sacc); <b>a</b>, <b>b</b>, <b>c</b>, or <b>d</b> complexes, respectively).
This simple acid–base reaction could not be achieved under
identical conditions when corresponding di-μ-acetate complexes
were used as starting materials. An alternative pathway to NHC/imidate
complexes has also been explored by reacting <b>IIb</b> with
[Ag(Phthal)(SMe<sub>2</sub>)]<sub>2</sub> (Phthal = phthalimidate, <b>e</b>) to obtain [Pd(Bmim)(Phthal)(Phpy)], <b>IIe</b>. Structural
characterization by X-ray diffraction of complexes <b>Id</b>, <b>IIb</b>, <b>IId</b>, and <b>IIe</b> has confirmed
the proposed formulas. The mononuclear complexes have shown to catalyze
the scalable Suzuki–Miyaura cross-coupling of 9-bromophenanthrene
with a wide scope of aryl boronic acids, irrespective of their electronic
properties and at a very low catalyst concentration of 0.01%
N‑Heterocyclic-Carbene Complexes Readily Prepared from Di-μ-hydroxopalladacycles Catalyze the Suzuki Arylation of 9‑Bromophenanthrene
New cyclometalated palladium complexes
of general formula [Pd(Bmim)(X)(C<sup>∧</sup>N)] have been
synthesized by a novel reaction route
involving di-μ-hydroxo-palladacycles [{Pd(μ-OH)(C<sup>∧</sup>N)}<sub>2</sub>] (C<sup>∧</sup>N = 2-benzoylpyridine
(Bzpy), <b>I</b>, previously unreported, or C<sup>∧</sup>N = 2-phenylpyridine (Phpy), <b>II</b>)] and 1,3-butylmethylimidazolium
salts [HBmim]X (X: Cl, Br, I, or saccharinate (Sacc); <b>a</b>, <b>b</b>, <b>c</b>, or <b>d</b> complexes, respectively).
This simple acid–base reaction could not be achieved under
identical conditions when corresponding di-μ-acetate complexes
were used as starting materials. An alternative pathway to NHC/imidate
complexes has also been explored by reacting <b>IIb</b> with
[Ag(Phthal)(SMe<sub>2</sub>)]<sub>2</sub> (Phthal = phthalimidate, <b>e</b>) to obtain [Pd(Bmim)(Phthal)(Phpy)], <b>IIe</b>. Structural
characterization by X-ray diffraction of complexes <b>Id</b>, <b>IIb</b>, <b>IId</b>, and <b>IIe</b> has confirmed
the proposed formulas. The mononuclear complexes have shown to catalyze
the scalable Suzuki–Miyaura cross-coupling of 9-bromophenanthrene
with a wide scope of aryl boronic acids, irrespective of their electronic
properties and at a very low catalyst concentration of 0.01%
Structural, Magnetic, and Electronic Properties of CaBaCo<sub>4–<i>x</i></sub>M<sub><i>x</i></sub>O<sub>7</sub> (M = Fe, Zn)
The effect of substituting iron and
zinc for cobalt in CaBaCo<sub>4</sub>O<sub>7</sub> was investigated
using neutron diffraction and X-ray absorption spectroscopy techniques.
The orthorhombic distortion present in the parent compound CaBaCo<sub>4</sub>O<sub>7</sub> decreases with increasing the content of either
Fe or Zn. The samples CaBaCo<sub>3</sub>ZnO<sub>7</sub> and CaBaCo<sub>4–<i>x</i></sub>Fe<sub><i>x</i></sub>O<sub>7</sub> with <i>x</i> ≥ 1.5 are metrically hexagonal,
but much better refinements in the neutron diffraction patterns are
obtained using an orthorhombic unit cell. The two types of substitution
have opposite effects on the structural and magnetic properties. Fe
atoms preferentially occupy the sites at the triangular layer. Thus,
the replacement of Co by Fe suppresses the ferrimagnetic ordering
of the parent compound, and CaBaCo<sub>4–<i>x</i></sub>Fe<sub><i>x</i></sub>O<sub>7</sub> (0.5 ≤ <i>x</i> ≤ 2) samples are antiferromagnetically ordered
following a new propagation vector <i>k</i> = (1/3,0,0).
However, the Zn atoms prefer occupying the Kagome layer, which is
very detrimental for the long-range magnetic interactions giving rise
to a magnetic glass-like behavior in the CaBaCo<sub>3</sub>ZnO<sub>7</sub> sample. The oxidation states of iron and zinc are found to
be 3+ and 2+, respectively, independently of the content, as confirmed
by X-ray absorption spectroscopy. Therefore, the average Co oxidation
state changes accordingly with the Fe<sup>3+</sup> or Zn<sup>2+</sup> doping. Also, X-ray absorption spectroscopy data confirm the different
preferential occupation for both Fe and Zn cations. The combined information
obtained by neutron diffraction and X-ray absorption spectroscopy
indicates that cobalt atoms can be either in a fluctuating Co<sup>2+</sup>/Co<sup>3+</sup> valence state or, alternatively, Co<sup>2+</sup> and Co<sup>3+</sup> ions being randomly distributed in the
lattice. These results explain the occurrence of local disorder in
the CoO<sub>4</sub> tetrahedra obtained by EXAFS. An anomaly in the
lattice parameters and an increase in the local disorder are observed
only at the ferrimagnetic transition for CaBaCo<sub>4</sub>O<sub>7</sub>, revealing the occurrence of local magneto-elastic coupling