Immobilization of Pyrene-Tagged Palladium and Ruthenium Complexes onto Reduced Graphene Oxide: An Efficient and Highly Recyclable Catalyst for Hydrodefluorination

The co-immobilization of palladium and ruthenium complexes with pyrene-tagged N-heterocyclic carbene ligands onto reduced graphene oxide allows the formation of a highly efficient catalyst for the hydrodefluorination of a series of fluoroarenes. This procedure constitutes an easy one-pot preparation of materials with homogeneously distributed polymetallic catalysts. The catalytic system can be recycled up to 12 times without measurable loss of activity. The activity of the catalyst is attributed to the synergistic action of the two metals

Y-Shaped Tris-N-Heterocyclic-Carbene Ligand for the Preparation of Multifunctional Catalysts of Iridium, Rhodium, and Palladium

A series of homo- and hetero-dimetallic complexes of Ir, Rh, and Pd have been obtained using our previously reported Y-shaped tris-NHC ligand. The new complexes can be obtained through the isolation of the corresponding monometallic intermediates (in which the ligand always coordinates in a chelating form) or by a one-pot stepwise synthetic protocol that avoids the isolation of the intermediate. The catalytic properties of the Ir–Pd complexes have been explored in two tandem processes: dehalogenation/transfer hydrogenation of haloacetophenones and Suzuki-coupling/transfer hydrogenation of <i>p</i>-bromoacetophenone. These two complexes have been also tested in two model reactions typically catalyzed by iridium (cyclization of 2-aminophenyl ethyl alcohol to yield indole) and palladium (acylation of bromobenzene with <i>n</i>-hexanal)

Rhodium and Iridium Complexes with Chelating <i>C–C′</i>-Imidazolylidene–Pyridylidene Ligands: Systematic Approach to Normal, Abnormal, and Remote Coordination Modes

A series of linked imidazolium–pyridinium salts ([Him-pyH]­(X)₂) have been used as imidazolylidene–pyridylidene ligand precursors for the preparation of rhodium­(III) and iridium­(III) complexes. The relative configuration of the [Him-pyH]­(X)₂ salts determines whether the coordination of the pyridylidene occurs through the normal, abnormal, or remote form. In order to obtain complexes with the imidazolylidene part of the ligand coordinated through the abnormal form, salts with the C2 position of the imidazolium blocked with a methyl group were used, although the products resulting from the C–H aliphatic activation of the methyl group or the C–C cleavage of the C2–Me bond were obtained instead. The crystallographic study of three molecules allowed us to evaluate the relative <i>trans</i> influence of the normal, abnormal, and remote coordination forms of the pyridylidene and also to compare it to the trans influence provided by the imidazolylidene

Rhodium and Iridium Complexes with Chelating <i>C–C′</i>-Imidazolylidene–Pyridylidene Ligands: Systematic Approach to Normal, Abnormal, and Remote Coordination Modes

A series of linked imidazolium–pyridinium salts ([Him-pyH]­(X)₂) have been used as imidazolylidene–pyridylidene ligand precursors for the preparation of rhodium­(III) and iridium­(III) complexes. The relative configuration of the [Him-pyH]­(X)₂ salts determines whether the coordination of the pyridylidene occurs through the normal, abnormal, or remote form. In order to obtain complexes with the imidazolylidene part of the ligand coordinated through the abnormal form, salts with the C2 position of the imidazolium blocked with a methyl group were used, although the products resulting from the C–H aliphatic activation of the methyl group or the C–C cleavage of the C2–Me bond were obtained instead. The crystallographic study of three molecules allowed us to evaluate the relative <i>trans</i> influence of the normal, abnormal, and remote coordination forms of the pyridylidene and also to compare it to the trans influence provided by the imidazolylidene

Rhodium and Iridium Complexes with Chelating <i>C–C′</i>-Imidazolylidene–Pyridylidene Ligands: Systematic Approach to Normal, Abnormal, and Remote Coordination Modes

A series of linked imidazolium–pyridinium salts ([Him-pyH]­(X)₂) have been used as imidazolylidene–pyridylidene ligand precursors for the preparation of rhodium­(III) and iridium­(III) complexes. The relative configuration of the [Him-pyH]­(X)₂ salts determines whether the coordination of the pyridylidene occurs through the normal, abnormal, or remote form. In order to obtain complexes with the imidazolylidene part of the ligand coordinated through the abnormal form, salts with the C2 position of the imidazolium blocked with a methyl group were used, although the products resulting from the C–H aliphatic activation of the methyl group or the C–C cleavage of the C2–Me bond were obtained instead. The crystallographic study of three molecules allowed us to evaluate the relative <i>trans</i> influence of the normal, abnormal, and remote coordination forms of the pyridylidene and also to compare it to the trans influence provided by the imidazolylidene

Rhodium and Iridium Complexes with Chelating <i>C–C′</i>-Imidazolylidene–Pyridylidene Ligands: Systematic Approach to Normal, Abnormal, and Remote Coordination Modes

A series of linked imidazolium–pyridinium salts ([Him-pyH]­(X)₂) have been used as imidazolylidene–pyridylidene ligand precursors for the preparation of rhodium­(III) and iridium­(III) complexes. The relative configuration of the [Him-pyH]­(X)₂ salts determines whether the coordination of the pyridylidene occurs through the normal, abnormal, or remote form. In order to obtain complexes with the imidazolylidene part of the ligand coordinated through the abnormal form, salts with the C2 position of the imidazolium blocked with a methyl group were used, although the products resulting from the C–H aliphatic activation of the methyl group or the C–C cleavage of the C2–Me bond were obtained instead. The crystallographic study of three molecules allowed us to evaluate the relative <i>trans</i> influence of the normal, abnormal, and remote coordination forms of the pyridylidene and also to compare it to the trans influence provided by the imidazolylidene

Rhodium and Iridium Complexes with Chelating <i>C–C′</i>-Imidazolylidene–Pyridylidene Ligands: Systematic Approach to Normal, Abnormal, and Remote Coordination Modes

A series of linked imidazolium–pyridinium salts ([Him-pyH]­(X)₂) have been used as imidazolylidene–pyridylidene ligand precursors for the preparation of rhodium­(III) and iridium­(III) complexes. The relative configuration of the [Him-pyH]­(X)₂ salts determines whether the coordination of the pyridylidene occurs through the normal, abnormal, or remote form. In order to obtain complexes with the imidazolylidene part of the ligand coordinated through the abnormal form, salts with the C2 position of the imidazolium blocked with a methyl group were used, although the products resulting from the C–H aliphatic activation of the methyl group or the C–C cleavage of the C2–Me bond were obtained instead. The crystallographic study of three molecules allowed us to evaluate the relative <i>trans</i> influence of the normal, abnormal, and remote coordination forms of the pyridylidene and also to compare it to the trans influence provided by the imidazolylidene

Coordination Singularities of a Bis(<i>p</i>‑xylyl)bis(benzimidazolylidene) Ligand and the Bis-iridium and -rhodium-Related Complexes

The reaction of bis­(α,α′-<i>p</i>-xylyl)­bis­(benzimidazolium) dichloride with [IrCp*Cl₂]₂ or [RhCl­(COD)]₂ affords the corresponding dimetallic bis-N-heterocyclic carbene complexes of Ir and Rh. The reaction with the iridium complex occurs by the transmetalation method, in the presence of Ag₂O, while the reaction with the rhodium complex is carried out in the presence of NaO<i>t</i>Bu. The two complexes display an <i>anti</i> configuration of the bis-NHC ligand, with the two metal atoms pointing at different faces of the bis-carbene ligand. In both complexes, the two metal fragments disclose different coordination environments (in–out, with respect to the inner and outer part of the cyclophane-bis-NHC), as a consequence of noncovalent interactions. DFT calculations have been used to rationalize this “less intuitive” coordination singularity. The reaction of the bis­(α,α′-<i>p</i>-xylyl)­bis­(benzimidazolium) dichloride with [RhCl­(CO)₂]₂ in the presence of Ag₂O affords a dirhodium complex in which the two metals are on the same side of the ligand, which adopts a <i>syn</i> conformation. In the latter case, the two metals are bridged by a chloride and hydroxyl ligands, therefore facilitating the <i>syn</i> disposition of the ligand

Coordination Singularities of a Bis(<i>p</i>‑xylyl)bis(benzimidazolylidene) Ligand and the Bis-iridium and -rhodium-Related Complexes

The reaction of bis­(α,α′-<i>p</i>-xylyl)­bis­(benzimidazolium) dichloride with [IrCp*Cl₂]₂ or [RhCl­(COD)]₂ affords the corresponding dimetallic bis-N-heterocyclic carbene complexes of Ir and Rh. The reaction with the iridium complex occurs by the transmetalation method, in the presence of Ag₂O, while the reaction with the rhodium complex is carried out in the presence of NaO<i>t</i>Bu. The two complexes display an <i>anti</i> configuration of the bis-NHC ligand, with the two metal atoms pointing at different faces of the bis-carbene ligand. In both complexes, the two metal fragments disclose different coordination environments (in–out, with respect to the inner and outer part of the cyclophane-bis-NHC), as a consequence of noncovalent interactions. DFT calculations have been used to rationalize this “less intuitive” coordination singularity. The reaction of the bis­(α,α′-<i>p</i>-xylyl)­bis­(benzimidazolium) dichloride with [RhCl­(CO)₂]₂ in the presence of Ag₂O affords a dirhodium complex in which the two metals are on the same side of the ligand, which adopts a <i>syn</i> conformation. In the latter case, the two metals are bridged by a chloride and hydroxyl ligands, therefore facilitating the <i>syn</i> disposition of the ligand