Dmitry S. Perekalin

Observation of superconductivity in hydrogen sulfide from nuclear resonant scattering

Peeking into a diamond pressure cell A defining characteristic of a superconductor is that it expels an external magnetic field. Demonstrating this effect can be tricky when the sample is under enormous pressures in a diamond anvil cell. Troyan et al. placed a tinfoil sensor inside a sample of H2S under pressure. They then bombarded it with synchrotron radiation and watched how the scattering of photons of tin nuclei changed over time. When H2S was in the normal state, an external magnetic field reached the sensor through the sample, causing the nuclear levels of tin to split. In the superconducting state, however, no splitting was observed because H2S expelled the field before it could reach the sensor. Science, this issue p. 1303 A tin foil sensor inside a pressurized superconducting sample of hydrogen sulfide is used to demonstrate the expulsion of magnetic field. [Also see Perspective by Struzhkin] High-temperature superconductivity remains a focus of experimental and theoretical research. Hydrogen sulfide (H2S) has been reported to be superconducting at high pressures and with a high transition temperature. We report on the direct observation of the expulsion of the magnetic field in H2S compressed to 153 gigapascals. A thin 119Sn film placed inside the H2S sample was used as a sensor of the magnetic field. The magnetic field on the 119Sn sensor was monitored by nuclear resonance scattering of synchrotron radiation. Our results demonstrate that an external static magnetic field of about 0.7 tesla is expelled from the volume of 119Sn foil as a result of the shielding by the H2S sample at temperatures between 4.7 K and approximately 140 K, revealing a superconducting state of H2S.

Synthesis and structure of rhodium complexes with monoanionic carborane ligand [9-SMe2-7,8-C2B9H10]−

Abstract (Rhodacarborane)halide complexes [(η-9-SMe 2 -7,8-C 2 B 9 H 10 )RhX 2 ] 2 ( 4a : X=Cl; 4b : X=Br; 4c : X=I), which are analogous to [Cp*RhX 2 ] 2 , were synthesized by reaction of (η-9-SMe 2 -7,8-C 2 B 9 H 10 )Rh(cod) (cod=1,5-cyclooctadiene) with HX. Compounds 4 were used to prepare several sandwich and half-sandwich complexes containing (η-9-SMe 2 -7,8-C 2 B 9 H 10 )Rh fragment. 2e-Ligands destroy the dimeric structure of 4 to give the adducts (η-9-SMe 2 -7,8-C 2 B 9 H 10 )RhLX 2 , exemplified by preparation of (η-9-SMe 2 -7,8-C 2 B 9 H 10 )Rh(CO)I 2 and (η-9-SMe 2 -7,8-C 2 B 9 H 10 )Rh(PPh 3 )Cl 2 . The reaction of 4a with dppe in the presence of TlBF 4 affords the cationic complex [(η-9-SMe 2 -7,8-C 2 B 9 H 10 )Rh(dppe)Cl]BF 4 ( 7 BF 4 ). Sandwich complexes [(η-9-SMe 2 -7,8-C 2 B 9 H 10 )Rh(η-C 5 R 5 )]CF 3 SO 3 ( 11a CF 3 SO 3 : R=H; 11b CF 3 SO 3 : R=Me) were obtained by abstracting chloride from 4a by CF 3 SO 3 Ag with subsequent treatment with C 5 R 5 H. Complex 11b PF 6 was prepared by reaction of [Cp*RhCl 2 ] 2 with Na[9-SMe 2 -7,8-C 2 B 9 H 10 ]. Complex (η-9-SMe 2 -7,8-C 2 B 9 H 10 )Rh(η-7,8-C 2 B 9 H 11 ), containing two carborane ligands, was obtained by reaction of 4a with Tl[Tl(η-7,8-C 2 B 9 H 11 )]. Structures of 7 BF 4 and 11b PF 6 were confirmed by X-ray diffraction study.

Simple Synthesis of Ruthenium π Complexes of Aromatic Amino Acids and Small Peptides

The interaction of [Ru(eta(6)-C(10)H(8))(Cp)](+) (Cp=C(5)H(5)) with aromatic amino acids (L-phenylalanine, L-tyrosine, L-tryptophane, D-phenylglycine, and L-threo-3-phenylserine) under visible-light irradiation gives the corresponding [Ru(eta(6)-amino acid)(Cp)](+) complexes in near-quantitative yield. The reaction proceeds in air at room temperature in water and tolerates the presence of non-aromatic amino acids (except those which are sulfur containing), monosaccharides, and nucleotides. The complex [Ru(eta(6)-C(10)H(8))(Cp)](+) was also used for selective labeling of Tyr and Phe residues of small peptides, namely, angiotensin I and II derivatives.

Unprecedented steric deformation of ortho-carborane

The reduction and subsequent oxidation of meta-carboranes containing bulky groups attached to the cage C atoms affords sterically-crowded ortho-carboranes with unprecedentedly long C-C connectivities.

Heterogeneous bromination of alkenes using Bi(III) polybromide complexes as {Br2} source

A new polybromide Bi(III) complex (PyH)3{[Bi2Br9](Br2)} was synthesized and characterized by XRD and other methods. This compound is able to act as a selective bromination agent towards various types of substituted alkenes.

Synthesis of the iridacarborane halide complexes [(η-9-SMe2-7,8-C2B9H10)IrX2]2 (X = Cl, Br, or I)

The reaction of Na[9-SMe2-7,8-C2B9H10] with [(Cod)IrCl]2 (Cod is cycloocta-1,5-diene) gave rise to the iridium complex (η-9-SMe2-7,8-C2B9H10)Ir(Cod). Treatment of the latter with anhydrous acids HX (X = Cl, Br, or I) afforded the corresponding iridacarborane halide complexes [(η-9-SMe2-7,8-C2B9H10)IrX2]2 analogous to the cyclopentadienyl complexes [(C5Me5)IrX2]2.

Selective Ruthenium Labeling of the Tryptophan Residue in the Bee Venom Peptide Melittin

Melittin is a membrane-active peptide from bee venom with promising antimicrobial and anticancer activity. Herein we report on a simple and selective method for labeling of the tryptophan residue in melittin by the organometallic fragment [(C5 H5 )Ru](+) in aqueous solution and in air. Ruthenium coordination does not disturb the secondary structure of the peptide (as verified by 2D NMR spectroscopy), but changes the pattern of its intermolecular interactions resulting in an 11-fold decrease of hemolytic activity. The high stability of the organometallic conjugate allowed the establishment of the biodistribution of the labeled melittin in mice by inductively coupled plasma MS analysis of ruthenium.

(Arene)ruthenium complexes with the monoanionic carborane ligand [9-SMe2-7,8-C2B9H10]–

The ruthenium arene complexes [(η-arene)Ru(η-9-SMe2-7,8-C2B9H10)]+ (arene = C6H6 (3a); arene = 1,3,5-C6H3Me3 (3b)) with the monoanionic carborane ligand were synthesized by the reactions of the [9-SMe2-7,8-C2B9H10]– anion with [(η-arene)RuCl2]2. The structure of the compound [3a]BPh4 was established by single-crystal X-ray diffraction analysis.

A Planar‐Chiral Rhodium(III) Catalyst with a Sterically Demanding Cyclopentadienyl Ligand and Its Application in the Enantioselective Synthesis of Dihydroisoquinolones

The rapid development of enantioselective C-H activation reactions has created a demand for new types of catalysts. Herein, we report the synthesis of a novel planar-chiral rhodium catalyst [(C5 H2t Bu2 CH2t Bu)RhI2 ]2 in two steps from commercially available [(cod)RhCl]2 and tert-butylacetylene. Pure enantiomers of the catalyst were obtained through separation of its diastereomeric adducts with natural (S)-proline. The catalyst promoted enantioselective reactions of aryl hydroxamic acids with strained alkenes to give dihydroisoquinolones in high yields (up to 97 %) and with good stereoselectivity (up to 95 % ee).

General Route to Cyclobutadiene Rhodium Complexes.

Cyclobutadiene rhodium complexes bear high potential for applications in organometallic synthesis and catalysis. We have found that the cyclobutadiene complexes with substitutionally labile p-xylene ligands [(C4 R4 )Rh(p-xylene)](+) can be synthesized in one step from the commercially available bis(ethylene) complex [{(C2 H4 )2 RhCl}2 ], p-xylene, and internal alkynes. The replacement of p-xylene by various ligands provides a general access to other [(C4 R4 )Rh] compounds, such as [(C4 R4 )RhCl]x , [(C4 R4 )RhL3 ](+) , [(C4 R4 )Rh(C5 H5 )], and [(C4 R4 )Rh(arene)](+) . Complex [(C4 Et4 )Rh(p-xylene)](+) also catalyzes an unusual cycloisomerization of a 1,11-dien-6-yne into a bicyclic diene.