Phoenix

A novel chiral coordination polymer, [Cu­(C₆H₅CH­(OH)­COO)­(μ-C₆H₅CH­(OH)­COO)] (<b>1</b>-L and <b>1</b>-D), was synthesized through a reaction of copper acetate with l-mandelic acid at room temperature. Although previously reported copper mandelate prepared by hydrothermal reaction was a centrosymmetric coordination polymer because of the racemization of mandelic acid, the current coordination polymer shows noncentrosymmetry and a completely different structure from that previously reported. The X-ray crystallography for <b>1</b>-L revealed that the copper center of the compound showed a highly distorted octahedral structure bridged by a chiral mandelate ligand in the unusual coordination mode to construct a one-dimensional (1D) zigzag chain structure. These 1D chains interdigitated each other to give a layered structure as a result of the formation of multiple aromatic interactions and hydrogen bonds between hydroxyl and carboxylate moieties at mandelate ligands. The coordination polymer <b>1</b>-L belongs to the noncentrosymmetric space group of C2 to show piezoelectric properties and second harmonic generation (SHG) activity

Dinuclear Iron(0) Complexes of N‑Heterocyclic Carbenes

The synthesis, structures, and reactivity of dinuclear Fe⁰ complexes of N-heterocyclic carbenes (NHCs, denoted as L) are reported. The NHC adducts of ferric chloride (L)­FeCl₃ were prepared from the reactions of FeCl₃ with L in toluene. The reduction of (L)­FeCl₃ with KC₈ resulted in the formation of the dinuclear Fe⁰ complexes Fe₂{μ-η¹(C):η⁶(arene)-L}₂ (<b>2a</b>, L = 1,3-bis­(2,4,6-trimethylphenyl)­imidazol-2-ylidene (IMes); <b>2b</b>, L = 1,3-bis­(2,6-diisopropylphenyl)­imidazol-2-ylidene (IPr)), in which NHC ligands bridge two iron atoms using one of the arene rings as an η⁶ ligand. Their magnetic properties are different: <b>2a</b> is paramagnetic and <b>2b</b> is diamagnetic. The dinuclear complexes <b>2a</b>,<b>b</b> serve as precursors for monomeric (NHC)­Fe⁰ species, and treatment of <b>2a</b>,<b>b</b> with 1 atm of CO led to the formation of (L)­Fe­(CO)₄. Complex <b>2a</b> was found to react with 1-azidoadamantane, giving rise to the dinuclear tetrazene complex (IMes)­Fe­(μ-NAd)₂Fe­(AdNNNNAd) (<b>4</b>)

A Nitrogenase Cluster Model [Fe₈S₆O] with an Oxygen Unsymmetrically Bridging Two Proto-Fe₄S₃ Cubes: Relevancy to the Substrate Binding Mode of the FeMo Cofactor

An oxygen-encapsulated iron sulfido cluster, [(DmpS)­Fe₄S₃O]­[(DmpS)­Fe₄S₃]­(μ-SDmp)₂(μ-OCPh₃) (<b>2</b>; Dmp = 2,6-(mesityl)₂C₆H₃), has been synthesized by the reaction of the preformed dinuclear iron thiolate/alkoxide [(Ph₃CO)­Fe]₂(μ-SDmp)₂ (<b>1</b>) with ¹/₈S₈ and ¹/₄H₂O in toluene. In the [Fe₈S₆O] core, the oxygen atom bridges unsymmetrically two incomplete Fe₄S₃ cubes, and two coordinatively unsaturated iron atoms are weakly bound to mesityl rings. Relevance of the cluster structure of <b>2</b> to the nitrogenase FeMo cofactor and its substrate binding mode is discussed

A Nitrogenase Cluster Model [Fe₈S₆O] with an Oxygen Unsymmetrically Bridging Two Proto-Fe₄S₃ Cubes: Relevancy to the Substrate Binding Mode of the FeMo Cofactor

An oxygen-encapsulated iron sulfido cluster, [(DmpS)­Fe₄S₃O]­[(DmpS)­Fe₄S₃]­(μ-SDmp)₂(μ-OCPh₃) (<b>2</b>; Dmp = 2,6-(mesityl)₂C₆H₃), has been synthesized by the reaction of the preformed dinuclear iron thiolate/alkoxide [(Ph₃CO)­Fe]₂(μ-SDmp)₂ (<b>1</b>) with ¹/₈S₈ and ¹/₄H₂O in toluene. In the [Fe₈S₆O] core, the oxygen atom bridges unsymmetrically two incomplete Fe₄S₃ cubes, and two coordinatively unsaturated iron atoms are weakly bound to mesityl rings. Relevance of the cluster structure of <b>2</b> to the nitrogenase FeMo cofactor and its substrate binding mode is discussed

Synthesis of Bis(N-heterocyclic carbene) Complexes of Iron(II) and Their Application in Hydrosilylation and Transfer Hydrogenation

N-heterocyclic carbene (NHC) adducts of iron dichloride, (IMes)₂FeCl₂ (<b>1a</b>; IMes = 1,3-bis­(2,4,6-trimethylphenyl)­imidazol-2-ylidene) and (IEtPh*)₂FeCl₂ (<b>1b</b>; IEtPh* = 1,3-bis­((<i>R</i>)-1′-phenylethyl)­imidazol-2-ylidene), were prepared in good yields from the reactions of Fe­{N­(SiMe₃)₂}₂ with imidazolium salts. While the iron atom of <b>1a</b> has a tetrahedral geometry, replacement of the chlorides by methyl groups via treatment of <b>1a</b> with MeLi led to the formation of the square-planar complex <i>trans</i>-(IMes)₂FeMe₂ (<b>2</b>). The molecular structures of complexes <b>1a</b>,<b>b</b> and <b>2</b> were identified by means of single-crystal X-ray diffraction analysis. Complexes <b>1a</b>,<b>b</b> and <b>2</b> are good catalyst precursors in the transfer hydrogenation of 2′-acetonaphthone, and complex <b>2</b> also efficiently catalyzes the hydrosilylation of 2′-acetonaphthone

An Iron(II) Complex of a Diamine-Bridged Bis-N-Heterocyclic Carbene

A diamine-bridged bis-N-heterocyclic carbene ligand was synthesized as imidazolium salts with chloride or triflate counteranions. Deprotonation of the chloride salt by an iron bis-amide complex or addition of the free diamine-bis-carbene ligand to FeCl₂ led to the formation of an Fe­(II) dichloride complex having a diamine-bis-carbene ligand, in which the iron atom is in a highly distorted octahedral geometry with weak Fe-N interactions. This iron complex was found to catalyze the hydrosilylation of acetophenone

An Iron(II) Complex of a Diamine-Bridged Bis-N-Heterocyclic Carbene

A diamine-bridged bis-N-heterocyclic carbene ligand was synthesized as imidazolium salts with chloride or triflate counteranions. Deprotonation of the chloride salt by an iron bis-amide complex or addition of the free diamine-bis-carbene ligand to FeCl₂ led to the formation of an Fe­(II) dichloride complex having a diamine-bis-carbene ligand, in which the iron atom is in a highly distorted octahedral geometry with weak Fe-N interactions. This iron complex was found to catalyze the hydrosilylation of acetophenone