Showing papers by "Richard D. Adams published in 1999"
TL;DR: W(CO){sub 5}(NCMe) has been found to transform vinylthiirane and a series of methyl-substituted vinylthsiiranes into 3,6-dihydro-1,2-dithiin compounds as discussed by the authors.
Abstract: W(CO){sub 5}(NCMe) has been found to transform vinylthiirane and a series of methyl-substituted vinylthiiranes into a series of 3,6-dihydro-1,2-dithiin compounds. Two equivalents of the vinylthiirane are required, and 1 equiv of a butadiene is formed by the transfer of its sulfur atom to the second vinylthiirane, which is then transformed into the dihydrodithiin. The formation of 3,6-dihydro-1,2-dithiin proceeds at 15 turnovers/h at 25 C using vinylthiirane as the catalyst. The catalyst is long-lived (up to 2,000 turnovers have been obtained without loss of activity) and relatively insensitive to air. Methyl substituents on the vinyl group increase the rate of reaction while methyl substituents on the thiirane ring slow it considerably. The introduction of phosphine ligands to the catalyst also leads to significant increases in the rate of reaction. The dithiin complex W(CO){sub 5}({ovr SSCH{sub 2}CH{double_bond}CHC}H{sub 2}) was isolated from the catalytic reactions and was structurally characterized. The dihydrodithiin is coordinated to the tungsten atom through one of its two sulfur atoms. This product was shown to be a species in the catalytic cycle. A mechanism involving a vinylthiirane intermediate that undergoes spontaneous ring opening, followed by addition of a second vinylthiirane to the terminal carbon of the chain, elimination ofmore » 1 equiv of butadiene, and formation of a sulfur-sulfur bond leading to the compound above is proposed. The vinylthiirane intermediate is regenerated by ligand substitution which releases the dihydrodithiin product. 3,6-dihydro1,2-dithiin readily polymerizes when its pure form is exposed to visible light. If the polymerization is interrupted at an early stage, 1,2,7,8-tetrathiacyclododeca-4,10-diene, a dimer, can be isolated. The dimer was obtained in 5.6% yield and was structurally characterized crystallographically.« less
28 citations
TL;DR: In this article, new halide-substituted cluster anions of the [Cd10S4X4(SR)12]4-family have been prepared and characterized; investigations of their luminescence show that the introduction of the halide groups produces red shifts and significant enhancements in their emission intensities.
27 citations
TL;DR: Two ruthenium carbonyl cluster complexes: Ru3(CO)10[μ3-η2-C2(CCSiMe3)2], 2 (6% yield) and Ru4(CO), 12[μ4−2−C2 (CCSIMe3), 3 (36% yield), were obtained from the reaction of the 1,6-bis-(trimethylsilyl)-1,3,5-hexatriyne, 1 with Ru( CO)5 at 25
18 citations
TL;DR: In this paper, a coupling of bistrimethylsilylpropargylic alcohol over CpCo(CO)2 to give the respective ortho and para bishydroxymethyl substituted cyclobutadiene complexes is reported.
17 citations
TL;DR: In this paper, the reaction of the cyclic tetrayne 2 with Co2(CO)8 at 25°C has yielded the double addition product, C20H8[Co2(Co)6]2, 3 in a 39% yield.
14 citations
TL;DR: A series of 1,3-dioxolanes have been prepared by the addition of ketones to epoxides in the presence of the catalyst [Cp*Ir(NCMe)3]2+, Cp*C5Me5.
12 citations
TL;DR: The reaction of Os3(CO)10(NCMe)2 with 2-vinyltetrahydrothiophene (VTHT) at 25°C yielded two products: Os3CO10[μ-SCH2CH2C(H)C(SCH 2C)C (H)CH2](μ-H), 1 (38% yield) and Os2CO)6[μη4-S(CH2)3CHCHCH2]-2(H), 2 (27%
11 citations
TL;DR: In this paper, a combination of IR, 1H-NMR and single-crystal X-ray diffraction analyses was used to characterize the disulfido complexes of 3,6-dihydro-1,2-dithiin, SCH 2 CHCHCH 2 S, 1 at 0°C yielded two isomeric products Os3(CO)10(μ3-SCH2CH CHCH2S), 2, and Os3
7 citations
TL;DR: In this article, the cyclic sulfone, 1,3-dithietane-1,1-dioxide, 1 with Os 3 (CO) 10 (μ -CH 2 SCH 2 SO 2 ), 3 in 73% yield.
6 citations
TL;DR: The reaction of o-bis(phenylethynyl)benzene with the reaction of Pt2Ru4(CO)18 (1) has yielded the product Pt2RRu4CO)14[μ5-C6H4(C2Ph2)2] (3) which exhibits an unexpected "raft" structure for the six metal atoms as mentioned in this paper.
6 citations
TL;DR: In this article, a series of thiolate-capped CdS quantum dots having reasonably narrow size distributions was synthesized and optical properties were compared to the crystallographically defined Cd S molecular clusters having essentially zero size distribution.
Abstract: In the last several years, great advances have been made in the ability to synthesize semiconductor quantum dots with very narrow size distributions. Here, we report the synthesis of a series of thiolate-capped CdS quantum dots having reasonably narrow size distributions and make optical property comparisons to the crystallographically defined CdS molecular clusters having essentially “zero” size distribution. These clusters contain a “Cd 10 S 4 ” core and thiolate/halide capping ligands. The luminescence of the molecular clusters, like the nanoparticles, is greatly influenced by the nature of the capping ligands. Additionally, the luminescence of the molecular clusters can be quite similar to that observed for their larger quantum dot counterparts.
TL;DR: W(CO){sub 5}(NCMe) has been found to transform vinylthiirane and a series of methyl-substituted vinylthsiiranes into 3,6-dihydro-1,2-dithiin compounds.
Abstract: W(CO){sub 5}(NCMe) has been found to transform vinylthiirane and a series of methyl-substituted vinylthiiranes into a series of 3,6-dihydro-1,2-dithiin compounds. Two equivalents of the vinylthiirane are required, and 1 equiv of a butadiene is formed by the transfer of its sulfur atom to the second vinylthiirane, which is then transformed into the dihydrodithiin. The formation of 3,6-dihydro-1,2-dithiin proceeds at 15 turnovers/h at 25 C using vinylthiirane as the catalyst. The catalyst is long-lived (up to 2,000 turnovers have been obtained without loss of activity) and relatively insensitive to air. Methyl substituents on the vinyl group increase the rate of reaction while methyl substituents on the thiirane ring slow it considerably. The introduction of phosphine ligands to the catalyst also leads to significant increases in the rate of reaction. The dithiin complex W(CO){sub 5}({ovr SSCH{sub 2}CH{double_bond}CHC}H{sub 2}) was isolated from the catalytic reactions and was structurally characterized. The dihydrodithiin is coordinated to the tungsten atom through one of its two sulfur atoms. This product was shown to be a species in the catalytic cycle. A mechanism involving a vinylthiirane intermediate that undergoes spontaneous ring opening, followed by addition of a second vinylthiirane to the terminal carbon of the chain, elimination ofmore » 1 equiv of butadiene, and formation of a sulfur-sulfur bond leading to the compound above is proposed. The vinylthiirane intermediate is regenerated by ligand substitution which releases the dihydrodithiin product. 3,6-dihydro1,2-dithiin readily polymerizes when its pure form is exposed to visible light. If the polymerization is interrupted at an early stage, 1,2,7,8-tetrathiacyclododeca-4,10-diene, a dimer, can be isolated. The dimer was obtained in 5.6% yield and was structurally characterized crystallographically.« less