Selective Hydrogen Generation from Formic Acid with Well-Defined Complexes of Ruthenium and Phosphorus-Nitrogen PN(3) -Pincer Ligand.

An unsymmetrically protonated PN(3) -pincer complex in which ruthenium is coordinated by one nitrogen and two phosphorus atoms was employed for the selective generation of hydrogen from formic acid. Mechanistic studies suggest that the imine arm participates in the formic acid activation/deprotonation step. A long life time of 150 h with a turnover number over 1 million was achieved.

Ir(III)-catalyzed C-H alkynylation of arenes under chelation assistance.

An efficient and mild Ir(III)-catalyzed, chelation assisted C-H alkynylation of arenes has been developed using hypervalent iodine alkynes as alkynylating reagents. A broad scope of N-phenyl-2-aminopyridines and 2-phenoxypyridines has been established as effective substrates for this C-H functionalization and the desired alkynylated products were isolated in moderate to high yields.

Rhodium(iii)-catalyzed annulation of arenes with alkynes assisted by an internal oxidizing N-O bond.

Rh(iii)-catalyzed C-H activation of 3-aryl-dihydroisoxazoles in the coupling with diarylacetylenes has been developed under redox-neutral conditions. This reaction occurred under mild conditions with no by-product, and the N-O bond functions as an oxidizing directing group, leading to efficient synthesis of isoquinolines functionalized with a proximal secondary alcohol.

Cubic and doubly-fused cubic samarium clusters from Sm(II)-mediated reduction of organic azides and azobenzenes.

A polynuclear samarium imido complex [(L)Sm(4)(µ(3)-NSiMe(3))(4)] (2) featuring a cubane-like cluster has been synthesized from the reaction of an organic azide and a samarium(II) complex [(L)SmI(2)Li(2)(THF)(Et(2)O)(2)] (1). In addition, this divalent samarium starting material (1) reacts with azobenzene to give the first example of a well-defined doubly-fused cubic imido-cluster [(L)Sm(6)(µ(3)-NPh)(4)(µ(4)-NPh)(2)I(2)(THF)(2)] (4) in addition to a major cubic complex [(L)Sm(4)(µ(3)-NPh)(4)] (3).

A heterometallic sandwich complex of europium(II) for luminescent studies.

A divalent europium complex [(L(Ph))(2)Eu{K(THF)(2)}(2)] (L(Ph) = Ph(2)Si(NAr)(2), Ar = 2,6-(i)Pr(2)C(6)H(3)) (THF = Tetrahydrofuran) (2), which has a sandwich structure with potassium-arene π interactions, was synthesized in high yield via a one-pot process. This complex has been fully characterized, and luminescent studies showed that the 528 nm emission peak can be attributed to the 4f-5d transition of Eu(2+).

Rh(III)-catalyzed oxidative coupling of N-aryl-2-aminopyridine with alkynes and alkenes.

[RhCp*Cl(2)](2) (1-2 mol %) can catalyze the oxidative coupling of N-aryl-2-aminopyridines with alkynes and arylates to give N-(2-pyridyl)indoles and N-(2-pyridyl)quinolones, respectively, using Cu(OAc)(2) as an oxidant. Coupling with styrenes gave mono- and/or disubstituted olefination products.

Rh-catalyzed oxidative coupling between primary and secondary benzamides and alkynes: synthesis of polycyclic amides.

A methodology for the high yield and facile synthesis of isoquinolones from benzamides and alkynes via the oxidative ortho C-H activation of benzamides has been developed. Ag(2)CO(3) proved to be an optimal oxidant when MeCN was used as a solvent, and [RhCp*Cl(2)](2) was utilized as an efficient catalyst. Both N-alkyl and N-aryl secondary benzamides can be applied as effective substrates. Furthermore, primary benzamides react with two alkyne units, leading to tricyclic products via double C-H activation and oxidative coupling. The reactivity of the structurally related 1-hydroxyisoquinoline was also demonstrated, where both N- and O-containing rhodacyclic intermediates can be generated, leading to the construction of different O- or N-containing heterocycles.

Lanthanide-alkali metal sandwich complexes: synthesis, structure, and solvent-mediated redox transformations, and one-dimensional frameworks assembled through cation-arene pi interactions.

Reaction of the potassium salt of amido ligand [Ph(2)Si(NAr)(2)](2-) (L, Ar = 2,6-iPr(2)C(6)H(3)) and LnI(2)(thf)(2) (Ln = Sm, Yb) gives sandwich complexes [(L)(2)Ln{K(Et(2)O)}(2)] (Ln = Sm (2), Yb (3)) with potassium-arene pi interactions. Reaction of 2 with azobenzene gave the dimeric samarium cluster [(L)(2)Sm(2)(mu-eta(2):eta(2)-N(2)Ph(2))(2){K(thf)(2)}(2)] (4) and the tetrameric [(L)Sm(4) (mu-eta(2):eta(2)-N(2)Ph(2))(3) (mu(3)-NPh)(2)(thf)(3)] (5). On the other hand, the reaction of 2 with alpha-diimines ligands ArN=CRCR=NAr (DAD, R = H, Me) gives two Sm(III) complexes: polymeric [(L)Sm{(ArN)RC=CR(NAr)}K](n) (R = H (6), Me (7)) assembled through cation-pi interactions and byproduct [{(L)(2)Sm}{K(thf)(6)}] (8). Complexes 2-8 have been fully characterized by elemental analyses and X-ray crystallography. In particular, crystallographic analyses of 6 and 7 revealed that in both complexes samarium(III) is stabilized by dianionic DAD units.

Stabilization of imidosamarium(III) cubane by amidinates.

An imidosamarium(III) cubane has been prepared from the reductive cleavage of azobenzene by a divalent samarium bis(amidinate) complex, indicating that the "spectrator" bis(amidinate) and the resulting imido ligands help to stabilize the cubane framework. The cubane-type imido cluster is a novel unit in lanthanide chemistry.