Intramolecular five-membered ring compounds and their applications

Regioselective functionalization of iminophosphoranes through Pd-mediated C-H bond activation: C-C and C-X bond formation

The orthopalladation of iminophosphoranes [R(3)P=N-C(10)H(7)-1] (R(3) = Ph(3) 1, p-Tol(3) 2, PhMe(2) 3, Ph(2)Me 4, N-C(10)H(7)-1 = 1-naphthyl) has been studied. It occurs regioselectively at the aryl ring bonded to the P atom in 1 and 2, giving endo-[Pd(μ-Cl)(C(6)H(4)-(PPh(2=N-1-C(10)H(7))-2)-κ-C,N](2) (5) or endo-[Pd(μ-Cl)(C(6)H(3)-(P(p-Tol)(2)=N-C(10)H(7)-1)-2-Me-5)-κ-C,N](2) (6), while in 3 the 1-naphthyl group is metallated instead, giving exo-[Pd(μ-Cl)(C(10)H(6)-(N=PPhMe(2))-8)-κ-C,N](2) (7). In the case of 4, orthopalladation at room temperature affords the kinetic exo isomer [Pd(μ-Cl)(C(10)H(6)-(N=PPh(2)Me)-8)-κ-C,N](2) (11exo), while a mixture of 11exo and the thermodynamic endo isomer [Pd(μ-Cl)(C(6)H(4)-(PPhMe=N-C(10)H(7)-1)-2)-κ-C,N](2) (11endo) is obtained in refluxing toluene. The heating in toluene of the acetate bridge dimer [Pd(μ-OAc)(C(10)H(6)-(N=PPh(2)Me)-8)-κ-C,N](2) (13exo) promotes the facile transformation of the exo isomer into the endo isomer [Pd(μ-OAc)(C(6)H(4)-(PPhMe=N-C(10)H(7)-1)-2)-κ-C,N](2) (13endo), confirming that the exo isomers are formed under kinetic control. Reactions of the orthometallated complexes have led to functionalized molecules. The stoichiometric reactions of the orthometallated complexes [Pd(μ-Cl)(C(10)H(6)-(N=PPhMe(2))-8)-κ-C,N](2) (7), [Pd(μ-Cl)(C(6)H(4)-(PPh(2)[=NPh)-2)](2) (17) and [Pd(μ-Cl)(C(6)H(3)-(C(O)N=PPh(3))-2-OMe-4)](2) (18) with I(2) or with CO results in the synthesis of the ortho-halogenated compounds [PhMe(2)P=N-C(10)H(6)-I-8] (19), [I-C(6)H(4)-(PPh(2)=NPh)-2] (21) and [Ph(3)P=NC(O)C(6)H(3)-I-2-OMe-5] (23) or the heterocycles [C(10)H(6)-(N=PPhMe(2))-1-(C(O))-8]Cl (20), [C(6)H(5)-(N=PPh(2)-C(6)H(4)-C(O)-2]ClO(4) (22) and [C(6)H(3)-(C(O)-1,2-N-PPh(3))-OMe-4]Cl (24).

Ion-molecule reactions of "rollover" cyclometalated [Pt(bipy-H)](+) (bipy=2,2'-bipyridine) with dimethyl ether in comparison with dimethyl sulfide: an experimental/computational study

The ion-molecule reactions of dimethyl ether with cyclometalated [Pt(bipy-H)](+) were investigated in gas-phase experiments, complemented by DFT methods, and compared with the previously reported ion-molecule reactions with its sulfur analogue. The initial step corresponds in both cases to a platinum-mediated transfer of a hydrogen atom from the ether to the (bipy-H) ligand, and three-membered oxygen- and sulfur-containing metallacycles serve as key intermediates. Oxidative C--C bond coupling ("dehydrosulfurization"), which dominates the gas-phase ion chemistry of the [Pt(bipy-H)](+) ion with dimethyl sulfide, is practically absent for dimethyl ether. The competition in the formation of C(2)H(4) and CH(2)X (X=O, S) in the reactions of [Pt(bipy-H)](+) with (CH(3))(2)X (X=O, S) as well as the extensive H/D exchange observed in the [Pt(bipy-H)](+)/(CH(3))(2)O system are explained in terms of the corresponding potential-energy surfaces.

Studies on gas-phase cyclometalations of [ArNi(PPh3)n]+ (n = 1 or 2) by electrospray ionization tandem mass spectrometry

Gas-phase cyclometalation of [ArNi(PPh(3))(n)](+) (n = 1, 2) complexes have been studied by ESI-MS/MS. The electron-donating substituents of aromatic iodides in the para position were found to inhibit the cyclometalation process of losing ArH, while the electron-withdrawing substituents in the para position were found to enhance it. These results indicate that the cyclometalation process of losing ArH is favored by electron-deficient aromatic groups. In addition, the detailed dissociation pathways of the cationic nickel complexes were studied, and among these pathways, the process of aryl-aryl interchange was also found to proceed in ESI-MS/MS.

Transition-metal-catalyzed direct arylation of (hetero)arenes by C-H bond cleavage

The area of transition-metal-catalyzed direct arylation through cleavage of C-H bonds has undergone rapid development in recent years, and is becoming an increasingly viable alternative to traditional cross-coupling reactions with organometallic reagents. In particular, palladium and ruthenium catalysts have been described that enable the direct arylation of (hetero)arenes with challenging coupling partners--including electrophilic aryl chlorides and tosylates as well as simple arenes in cross-dehydrogenative arylations. Furthermore, less expensive copper, iron, and nickel complexes were recently shown to be effective for economically attractive direct arylations.

Molecular characterization of copper in soils using X-ray absorption spectroscopy

Bioavailability of Cu in the soil is a function of its speciation. In this paper we investigated Cu speciation in six soils using X-ray absorption near edge structure (XANES), extended X-ray absorption fine structure (EXAFS), and synchrotron-based micro X-ray fluorescence (mu-XRF). The XANES and EXAFS spectra in all of the soils were the same. mu-XRF results indicated that the majority of the Cu particles in the soils were not associated with calcium carbonates, Fe oxides, or Cu sulfates. Principal component analysis and target transform of the XANES and EXAFS spectra suggested that Cu adsorbed on humic acid (HA) was an acceptable match. Thus it appears that Cu in all of the soils is primarily associated with soil organic matter (SOM). Theoretical fitting of the molecular structure in the soil EXAFS spectra revealed that the Cu in the soils existed as Cu atoms bound in a bidentate complex to O or N functional groups.

Synthesis of platinum(II) cyclometallated compounds derived from imines containing pyridyl or pyrimidyl groups

The reaction of compounds [Pt2Me4(µ-SMe2)2] and cis-[PtPh2(SMe2)2] with ligands 4-(2′-C5H4N)C6H4 CHN CH2CH2NMe2 (1a) and 4-(3′,5′-C4H3N2)C6H4CHNCH2CH2NMe2 (1b) carried out in acetone at room temperature produced compounds in which the imines act as bidentate [N,N′] ligands. Analogous compounds could be obtained in refluxing methanol when cis-[PtCl2(DMSO)2] was used as starting material. The corresponding cyclometallation processes leading to platinum(II) compounds with a tridentate [C,N,N′] ligand took place under different reaction conditions, except for metallation of 1a with cis-[PtPh2(SMe2)2], which could not be achieved. All compounds were characterized by usual techniques and [PtMe{4-(3′,5′-C4H3N2)C6H3CHNCH2CH2NMe2}] (3bMe) was also characterized crystallographically.Key words: platinum, imines, pyridyl, pyrimidyl, cyclometallation, crystal structure.

Reactivity of IrCl(PPh3)3 with diphenylacetylene — A direct route to 1-iridaindene

The 1-iridaindene complex, Ir[C8H5(Ph-2)]Cl(PPh3)2 (2), has been prepared from the reaction of IrCl(PPh3)3 with PhC≡CPh by a novel direct cycloiridation reaction. A plausible mechanistic pathway has been suggested involving π-coordination assisted ortho- C–H activation and subsequent alkyne hydroiridation reaction to provide the five-member iridacycle.Key words: iridium, diphenylacetylene, C–H activation, cyclometallation, metallacycle.