Shiuh-Tzung Liu

Biscarbene palladium(II) complexes. reactivity of saturated versus unsaturated N-heterocyclic carbenes.

A series of designed palladium biscarbene complexes including saturated and unsaturated N-heterocyclic carbene (NHC) moieties have been prepared by the carbene transfer methods. All of these complexes have been characterized by (1)H and (13)C NMR spectroscopy as well as X-ray diffraction analysis. The reactivity of Pd-C((saturated NHC)) is distinct from that of Pd-C((unsaturated NHC)). The Pd-C((saturated NHC)) bonds are fairly stable toward reagents such as CF(3)COOH, AgBF(4) and I(2), whereas Pd-C((unsaturated NHC)) bonds are readily cleaved under the similar conditions. Notably, the catalytically activity of these palladium complexes on Suzuki-Miyaura coupling follows the order: (sat-NHC)(2)PdCl(2) > (sat-NHC)(unsat-NHC)PdCl(2 )> (unsat-NHC)(2)PdCl(2).

Metal–metal interaction in polynuclear silver(I) complexes: spectroscopy, luminescent properties and X-ray crystal structure of [Ag3(dppp)2(MeCN)2(ClO4)2]+[dppp = bis(diphenylphosphinophenylphosphine)]

The [Ag3(dppp)2(MeCN)2(ClO4)2]+ complex displays 1(dσ*→ pσ) transition at 288 nm and solid state photoluminescence at 467 nm; the Ag–Ag distances are 2.943–-3. 014 (2)A.

Carbene transfer reactions between transition-metal ions

Carbene transfer processes are often involved in catalytic or metal-mediated reactions, however, a limited number of works concerning such transfer between transition metal complexes appear in the literature. This article presents an overview of the progress of this chemistry with an emphasis on examples with well-defined structures. A few studies, which are discussed in some detail, provide an insight of what has been achieved as well as an indication of the future work.

Diamination of Phenylene Dihalides Catalyzed by a Dicopper Complex

Diamination of phenylene dihalides with aqueous ammonia to give the corresponding phenylenediamines can be achieved by using a dicopper complex [Cu(2)(bpnp)(OH)(CF(3)COO)(3)] (1) (bpnp = 2,7-bis(pyridine-2-yl)-l,8-naphthyridine) as the catalyst in the presence of Bu(4)NBr and Cs(2)CO(3) in high yields. In addition, 1,3,5-tribromobenzene was converted into benzenetriamine quantitatively under the same conditions. This method offers a new opportunity, particularly simplifying steps and increasing yields, for the preparation of aryl diamines.

Unusual tripodal ligands. Synthesis of 2,2-bis(diphenylphosphinomethyl)-1-phenylthiopropane and its group VI complexes

Abstract A hybrid tripodal ligand containing phosphorus and sulfur atoms, 2,2-bis(diphenylphosphinomethyl)-1-phenylthiopropane ( P 2 S ), was synthesized and its metal carbonyl complexes ( P 2 S )M(CO) 4 (M = Cr, Mo and W) were prepared. All synthetic intermediates and complexes have been characterized by spectroscopic methods and elemental analysis. The spectroscopic identification of complexes shows that the P 2 S ligand behaves as a bidentate ligand with two phosphorus atoms coordinating to the metal center. The structure was confirmed by a crystal structure study of ( P 2 S )Mo(CO) 4 , which revealed an octahedral coordination around the molybdenum atom, and two cis -coordinated phosphorus donors. The conformation of the six-membered chelate ring is a twisted-boat and the possible reasons for this conformational arrangement are discussed.

Synthesis and characterization of PdII-methyl complexes with N-heterocyclic carbene-amine ligands

A number of palladium(ii) complexes with a heteroditopic NHC-amine ligand and their precursor silver(i) carbene complexes have been efficiently prepared and their structural features have been investigated. The heteroditopic coordination of this ligand class was unequivocally shown by NMR-spectroscopy and X-ray crystallographic analysis. The neutral and cationic cis-methyl-palladium(NHC) complexes are not prone to reductive elimination, which is normally a major degenerative pathway for this type of complex. In contrast, under carbon monoxide atmosphere rapid reductive elimination of the acyl-imidazolium salt was observed.

Tripodal ligands with mixed donors. Synthesis of 2-diphenylphosphinomethyl-2-phenylthiometryl-1-methoxypropane (PSO) and its transition metal complexes

Abstract A tripodal ligand containing phosphorus, sulphur and oxygen donors has been synthesized and its coordination in chromium(0), molybdenum(0), tungsten(0)

Photoredox properties of luminescent trinuclear copper(I) complexes with a bridging phosphine ligand and crystal structure of [Cu3(dpmp)2(MeCN)2(µ-Cl)2]ClO4[dpmp = bis(diphenylphosphinomethyl)phenylphosphine]

The complexes [Cu3(dpmp)2(MeCN)2(µ-X)2]ClO4 were prepared by the reaction of CuX (X = Cl or I) with bis(diphenylphosphinomethyl)phenylphosphine (dpmp) in methanol followed by recrystallisation from acetonitrile. The complex cation [Cu3(dpmp)2(MeCN)2(µ-Cl)2]+[triclinic, space group P(no. 2), a= 12.839(1), b= 13.582(3), c= 21.510(3)A, α= 84.06(1), β= 72.71(1), γ= 78.00(1)°, Z= 2, R= 0.083 for 11 520 unique Mo-Kα data] consists of three copper(I) ions bridged by two chloride ions on the same side and by two dpmp ligands. The intramolecular, Cu ⋯ Cu separations are 3.26 and 3.30 A indicating no metal–metal interaction. Both [Cu3(dpmp)2(MeCN)2(µ-Cl)2]ClO4 and [Cu3(dpmp)2(MeCN)2(µ-I)2]ClO4 display room-temperature photoluminescence at 530 and 560 nm respectively. The photoredox properties of [Cu3(dpmp)2(MeCN)2(µ-Cl)2]+ have been investigated by flash photolysis and Stern–Volmer quenching experiments.

Copper-catalyzed activation of α-amino peroxy and hydroxy intermediates to iminium ion precursor: an access to C4-substituted 3,4-dihydroquinazolines via oxidative cross coupling strategy.

A simple and straightforward approach to access C4-substituted-3,4-dihydroquinazolines has been achieved, where copper-catalyzed activation of α-amino peroxide and hydroxide intermediates to iminium ion precursors has been realized as an important step. Reactions of these intermediates with alkynes, indoles, pyrrole, and silylenol ether afforded the structurally diverse C4-substituted-3,4-dihydroquinazoline derivatives in good yields.

Structural characterization of tripodal phosphine complexes of transition metals. Examples of chair and twisted-boat conformations in six-membered chelate rings

Abstract Complexation of a “hybrid” tripodal ligand 2,2-bis(diphenylphosphinomethyl)-1-methoxypropane ( P 2 O ) with group VI carbonyls, nickel(II) and palladium(II) compounds has been studied. Thus P 2 O reacts with M(CO) 6 , NiCl 2 and PdCl 2 to give ( P 2 O )M(CO) 4 (M = Cr, Mo, W), ( P 2 O )NiCl 2 and ( P 2 O )PdCl 2 , respectively. All the complexes have been characterized by spectroscopy and elemental analysis, and the crystal structures of the complexes of ( P 2 O )Mo(CO) 4 ( 4b ), ( P 2 O )W(CO) 4 ( 4c ) and ( P 2 O )NiCl 2 ( 6 ) have been determined by X-ray diffraction. In all cases, the tripodal ligand behaves solely as a bidentate with two phosphorus donors coordinating to the metal centers. In the examination of the conformations of the six-membered chelate rings, it was found that both 4b and 4c were in the twisted-boat form; whereas 6 was in the chair form. The possible reasons for this conformational difference are discussed.