A 1,2,4-diazaphospholane complex of rhodium.

The crystal structure of a prospective olefin catalyst, namely [2-[1-acetyl-5-(2-hydroxyphenyl)-4-phenyl-1,2,4-diazaphospholan-3-yl]phenyl acetate-kappaP]chloro(eta(4)-cycloocta-1,5-diene)rhodium(I) dichloromethane solvate, [RhCl(C(8)H(12))(C(24)H(23)N(2)O(4)P)].CH(2)Cl(2), has been determined at 173 K. The five-membered heterocycle of the phosphine ligand is in a slightly distorted twist conformation.

Syntheses and oxidation of methyloxorhenium(V) complexes with tridentate ligands.

Four new methyloxorhenium(V) compounds were synthesized with these tridentate chelating ligands: 2-mercaptoethyl sulfide (abbreviated HSSSH), 2-mercaptoethyl ether (HSOSH), thioldiglycolic acid (HOSOH), and 2-(salicylideneamino)benzoic acid (HONOH). Their reactions with MeReO(3) under suitable conditions led to these products: MeReO(SSS), 1, MeReO(SOS), 2, MeReO(OSO)(PAr(3)), 3, and MeReO(ONO)(PPh(3)), 4. These compounds were characterized spectroscopically and crystallographically.

Hydrogenation and carbon-sulfur bond hydrogenolysis of benzothiophene promoted by Re2(CO)10 and H4Re4(CO)12.

In the search for metal complexes that promote the cleavage of C-S bonds in thiophenes, we observe that the reaction of Re(2)(CO)(10) and benzothiophene (BT) under a hydrogen atmosphere gives the trinuclear cluster Re(3)(mu-H)(2)(mu(3)-S-2-EtC(6)H(4))(mu-2,3-DHBT)(CO)(9) (1), which contains a hydrogenated BT ligand and a thiolate ligand resulting from the hydrogenation and cleavage of a C-S bond in BT. A detailed study of the reaction shows that Re(2)(CO)(10) initially reacts with H(2) to give H(3)Re(3)(CO)(12), which subsequently converts to H(4)Re(4)(CO)(12), which finally reacts with BT to give 1.

"Inverse-electron-demand" ligand substitution in palladium(0)-olefin complexes.

Ligand substitution reactions are ubiquitous in transition-metal chemistry and catalysis. Investigation of ligand substitution reactions for a series of electron-rich palladium(0)-olefin complexes, (bathocuproine)Pd(nitrostyrene) reveals an unprecedented mechanism in which the metal serves as the nucleophilic partner in an "associative" substitution pathway.

Structural isomers of aryl-substituted eta(3)-propargyl complexes: eta(2)-1-Metalla(methylene)cyclopropene and eta(3)-benzyl complexes.

Hydride abstraction from C(5)Me(5)(CO)(2)Re(eta(2)-PhC triple bond CCH(2)Ph) (1) gave a 3:1 mixture of eta(3)-propargyl complex [C(5)Me(5)(CO)(2)Re(eta(3)-PhCH-C triple bond CPh)][BF(4)] (5) and eta(2)-1-metalla(methylene)cyclopropene complex [C(5)Me(5)(CO)(2)Re(eta(2)-PhC-C=CHPh)][BF(4)] (6). Observation of the eta(2)-isomer requires 1,3-diaryl substitution and is favored by electron-donating substituents on the C(3)-aryl ring. Interconversion of eta(3)-propargyl and eta(2)-1-metalla(methylene)cyclopropene complexes is very rapid and results in coalescence of Cp (1)H NMR resonances at about -50 degrees C.

Chemistry of the aromatic 9-germafluorenyl dianion and some related silicon and carbon species.

Dipotassio-9-germafluorenyl dianion (3b) was synthesized by reduction of 9,9-dichloro-9-germafluorene (4b) with sodium/potassium alloy in tetrahydrofuran. The X-ray crystal structure of 3b, like that for the analogous silicon compound 3a, shows C-C bond length equalization in the five-membered metallole rings and C-C bond length alternation in the six-membered benzenoid rings, indicating aromatic delocalization of electrons into the germole ring of 3b. Calculated nucleus independent chemical shift (NICS) values indicate that the five-membered ring is more aromatic than the six-membered rings in 3a and 3b.

Kinetic and mechanistic studies of sulfur transfer from imidomethylrhenium sulfides.

The bis(2,6-diisopropylphenylimido)methylrhenium(VII) sulfide dimer, [CH(3)Re(NAr)(2)](2)(mu-S)(2) (1), reacts with a 1:1 amount of a phosphine or an alkyl isocyanide to yield a dimeric rhenium(VI) species, [CH(3)Re(NAr)(2)](2)(mu-S) (2), which has been structurally characterized. The two rhenium atoms in 2 are within bonding distance, 280 pm, more than 90 pm shorter than in 1. With excess L, 1 reacts to give a monomeric rhenium(V) complex, CH(3)Re(NAr)(2)L(2) (3A, L = PZ(3), Z = alkyl, aryl; 3B, L = isocyanide).

Novel reactivity of SeO2 with 1,3-dienes: selenophene formation.

A novel and efficient method for the synthesis of selenophenes is disclosed. Selenophenes were synthesized in high yields in a single operation from 1,3-dienes containing a carbonyl group at the C-1 position and selenium dioxide. The bidirectional synthesis of selenophenes can also be demonstrated using this method.

Synthesis and characterization of dimetallic oxorhenium(V) and dioxorhenium(VII) compounds, and a study of stoichiometric and catalytic reactions.

Chelating dithiolate ligands--e.g., mtp from 2-(mercaptomethyl)thiophenol, edt from 1,2-ethanedithiol, and pdt from 1,3-propanedithiol--stabilize high-valent oxorhenium(V) against hydrolytic and oxidative decomposition.

Halophilic reactions of a stable silylene with chloro and bromocarbons.

A number of disilanes have been synthesized from a stable silylene, 1 (N,N'-di-tert-butyl-1,3-diaza-2-silacyclopent-4-en-2-ylidene), and a variety of halocarbons. It is proposed that disilane formation is a result of an initial halophilic interaction between the silylene and halocarbon. Formation of disilanes from 1 and CCl4, 2a, CHCl3, 2b, CH2Cl2, 2c, benzyl chloride, 2d, and bromobenzene, 5, are described here.

Pseudosymmetry in pyridinium tetrachloro(oxo)pyridineniobate(V) pyridine solvate.

The title compound, (C(5)H(6)N)[NbCl(4)O(C(5)H(5)N)]center dotC(5)H(5)N, crystallizes as discrete ions, with a very strong linear N-H...

Re(2)(CO)(10)-promoted S-binding, C-S bond cleavage, and hydrogenation of benzothiophenes: organometallic models for the hydrodesulfurization of thiophenes.

In hydrodesulfurization model reactions of dinuclear metal complexes with thiophenes, we observe that ultraviolet photolysis of Re(2)(CO)(10) and benzothiophenes (BT) in hexanes solution produces the ring-opened BT complexes Re(2)(CO)(7)(mu-BT) (1a-d) (BT = benzothiophene (BT) 1a, 2-methylbenzothiophene (2-MeBT) 1b, 3-methylbenzothiophene (3-MeBT) 1c, and 3,5-dimethylbenzothiophene (3,5-Me(2)BT) 1d). The eta(1)(S)-bound BT complexes Re(2)(CO)(9)(eta(1)(S)-BT) (2a-d), prepared from Re(2)(CO)(9)(THF) and BT, are readily converted into 1a-d in good yields (40-60%) during UV photolysis in hexanes solution, which suggests that the eta(1)(S)-bound complexes 2a-d are precursors to 1a-d in the reactions of Re(2)(CO)(10) with BT. Irradiation of Re(2)(CO)(10) and 3,5-Me(2)BT with UV light in decane solution under an atmosphere of H(2) produces complex 1d and the partially hydrogenated BT complex Re(2)(CO)(7)(mu-3,5-Me(2)BT-H)(eta-H) (3d).

Syntheses and solid state structures of tris(pyrazolyl)methane complexes of sodium, potassium, calcium, and strontium: comparison of structures with analogous complexes of lead(II).

The reaction of NaI with 2 equiv of HC(pz)(3) or HC(3,5-Me(2)pz)(3) (pz = pyrazolyl ring) leads to the formation of [[HC(pz)(3)](2)Na](I) (1) and [[HC(3,5-Me(2)pz)(3)](2)Na](I) (2), respectively. Both compounds have trigonally distorted octahedral arrangements about the sodium. A similar reaction of KPF(6) with HC(3,5-Me(2)pz)(3) results in the formation of [[HC(3,5-Me(2)pz)(3)](2)K](PF(6)) (3), a complex also shown crystallographically to have a trigonally distorted octahedral arrangement about the potassium, which is an unusually low coordination number for this large metal ion.

Structure and chemistry of 1-silafluorenyl dianion, its derivatives, and an organosilicon diradical dianion.

1-Silafluorene dianion was synthesized by potassium reduction of 1,1-dichloro-1-silafluorene in refluxing THF. The X-ray structure of 1,1-dipotassio-1-silafluorene (3b) shows C-C bond length equalization in the five-membered silole ring and C-C bond length alternation in the six-membered benzene rings, indicating aromatic delocalization of electrons in the silole ring. The downfield (29)Si chemical shift at 29.

Molecular Structures of the Heavier Alkali Metal Salts of Supermesitylphosphane: A Systematic Investigation.

The molecular structures of the rubidium and cesium derivatives of supermesitylphosphane [i.e., (2,4,6-(t)Bu(3)C(6)H(2))PH(2) = (t)Bu(3)MesPH(2)] as well as several base adducts of these are reported.

Structural Diversity in the Reaction of Mono- and Disubstituted Pyrazoles with Titanium Tetrachloride. Importance of Hydrogen Bonding and Trends in cis/trans Geometry of Binary Adducts with Unidentate Ligands.

Treatment of titanium tetrachloride with 3,5-di-tert-butylpyrazole affords the complexes [3,5-(C(CH(3))(3))(2)C(3)H(3)N(2)](2)[TiCl(6)] and (3,5-(C(CH(3))(3))(2)C(3)HN(2))(2)TiCl(2) in 37 and 42% yields, respectively. An analogous reaction with 3,5-dimethylpyrazole, 3-methylpyrazole, 4-bromopyrazole, and 4-iodopyrazole leads to the formation of corresponding TiCl(4)L(2) binary adducts in 30-86% yields. Crystal structures of [3,5-(C(CH(3))(3))(2)C(3)H(3)N(2)](2)[TiCl(6)], (3,5-(C(CH(3))(3))(2)C(3)HN(2))(2)TiCl(2), TiCl(4)(3,5-(CH(3))(2)C(3)H(2)N(2))(2), and TiCl(4)(4-IC(3)H(3)N(2))(2) were determined.

Structural Diversity in the Solid-State Structures of the Rubidium and Cesium Salts of 2,6-Dimesitylphenylphosphane.

A coordination environment reminiscent of a paddle-wheel is exhibited by aryl groups about one of the two cesium ions in CsP(H)Dmp (Dmp=2,6-dimesitylphenyl; structure depicted on the right), which has now been synthesized and is found to exhibit Cs {Cs [P(H)Dmp] } contact ion pairs in the solid state. In contrast, the analogous rubidium compound displays a Rb P cube as the central structural motif.

The Weak-Link Approach to the Synthesis of Inorganic Macrocycles.

Homobimetallic macrocycles are prepared from flexible ligands in high yield by means of a new and general synthetic strategy called the "weak-link approach" [Eq. (a)]. Small aromatic molecules can be aligned inside the cage based on their interactions with the two Rh centers of the macrocycle.