| 1. |
- Grachova, E V, et al.
(författare)
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The structure and dynamic behaviour of disubstituted derivatives of Rh6(CO)16 containing heterobidentate bridging phosphine ligands
- 2003
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9234 .- 1477-9226. ; :12, s. 2468-2473
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Tidskriftsartikel (refereegranskat)abstract
- The solution structures and dynamic behaviour of [Rh6(CO)14(µ-PX)][PX = diphenyl(2-pyridyl)phosphine, (PN); diphenyl(2-thienyl)phosphine, (PS); diphenyl(vinyl)phosphine, (PV)] have been studied by multinuclear NMR and the X-ray structure of [Rh6(CO)14(µ,3-PV)] is reported. In solution, the above clusters undergo a variety of localised CO-exchanges and the mechanisms of these are discussed. The PV ligand in [Rh6(CO)14(µ,3-PV)] is hemilabile and exhibits facile exchange/reorientation of the vinyl group.
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| 2. |
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| 3. |
- Legrand, S., et al.
(författare)
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Hydroxy-methoxybenzoic methyl esters : Synthesis and antifeedant activity on the pine weevil, Hylobius abietis
- 2004
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Ingår i: Zeitschrift für Naturforschung. B, A journal of chemical sciences. - : Walter de Gruyter GmbH. - 0932-0776 .- 1865-7117. ; 59:7, s. 829-835
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Tidskriftsartikel (refereegranskat)abstract
- The pine weevil Hylobius abietis (L.) (Coleoptera: Curculionidae) feeds on the bark of coniferous seedlings and is the economically most important forestry restocking pest in large parts of Europe. Substances with an antifeedant effect may offer an environmentally friendly alternative to insecticides for the protection of planted seedlings. Bioassays were performed on commercial and synthetic methyl hydroxy-methoxybenzoates in order to determine their possible antifeedant activity. Two methyl hydroxy-methoxybenzoates were synthesized by esterification and mono-O-methylation of two dihydroxybenzoic acids. A regioselective protection-deprotection strategy was used in the synthetic pathway of the other non-commercial esters, esterification and selective pivaloylation of the less-hindered hydroxyl group of other commercial dihydroxybenzoic acids gave diester intermediates, which then were O-methylated before methanolysis of the pivaloyl group which yielded the desired non-commercial methyl hydroxy-methoxybenzoates. The five synthesized methyl hydroxy-methoxybenzoic esters were complemented with commercial samples of the five other isomers of methyl hydroxy-methoxybenzoate and spectrometric data were collected for the complete set of isomers. All ten isomers were tested for their antifeedant effect on the pine weevil. The effect varied considerably among the hydroxy-methoxybenzoic esters. Methyl 2-hydroxy-3-methoxybenzoate showed the highest effect and may thus be a candidate for practical use in pine weevil pest management.
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| 4. |
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| 5. |
- Stchedroff, MJ, et al.
(författare)
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Os-187 subspectra in H-1 and P-31{H-1} spectra of triosmium carbonyl clusters
- 2002
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Ingår i: Magnetic Resonance in Chemistry. - : Wiley. - 1097-458X .- 0749-1581. ; 40:2, s. 107-113
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Tidskriftsartikel (refereegranskat)abstract
- A survey of the use of Os-187 satellite subspectra in H-1 and P-31{H-1} spectra of triosmium carbonyl clusters is reported. By varying evolution delays in HMQC spectra of [Os-3(mu-H)(2)(CO)(10)] we have selectively extracted the values for (1)J(Os,H) and (2)J(Os,H), respectively. An analysis of the principal modes of phosphine coordination in triosmium clusters demonstrates that P-31{H-1} Os-187 satellite subspectra are diagnostic for equatorial coordination [(1)J(Os, P) = 211-223 Hz] or for axial coordination (perpendicular to the plane of the cluster) [(1)J(Os, P) approximate to 147 Hz]. Chelating and bridging diphosphines yield Os-187 satellite subspectra which are the sum of A(2)X and AA'X spin systems. If significant P-P coupling is present, the AA'X component requires simulation. All observed (2)J(Os,P) trans-equatorial couplings fall in the range 38-65 Hz. Copyright (C) 2001 John Wiley Sons, Ltd.
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| 6. |
- Tunik, S P, et al.
(författare)
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Chiral hexarhodium clusters containing heterobidentate phosphine ligands, a structural and reactivity study
- 2003
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9234. ; :12, s. 2457-2467
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Tidskriftsartikel (refereegranskat)abstract
- Some intrinsically chiral [Rh6(CO)14(µ,2-PX)] clusters have been synthesized, beginning with reactions of [Rh6(CO)16–x(NCMe)x](x= 1, 2) with PX, where PX represents the bidentate bridging ligands diphenyl(benzothienyl)phosphine (1), diphenyl(2-thienyl)phosphine (2), di(2-thienyl)phenylphosphine (3), tris(2-thienyl)phosphine (4), diphenyl(2-pyridyl)phosphine (5) and diphenylvinylphosphine (6). The ligand tris(2-furyl)phosphine (7) shows no bridging capability. When x= 1 the initial products are the clusters [Rh6(CO)15(1-PX)] which undergo spontaneous CO loss to form [Rh6(CO)14(µ,2-PX)]. The structures of the [Rh6(CO)15(1-PX)] clusters have been elucidated by IR, NMR spectroscopy and FAB-MS spectrometry, and have been found to involve phosphorus atom coordination to a rhodium atom. In addition, the solid state structures of the [Rh6(CO)14(µ,2-Ph2P(2-benzothienyl))](8), [Rh6(CO)14(µ,2-Ph2P(2-thienyl))](9), [Rh6(CO)14(µ,2-PhP(2-thienyl)2)](10) and [Rh6(CO)14(µ,2-Ph2P(pyridyl))](12) clusters have been determined by X-ray crystallography. The various types of chirality exhibited by these clusters are discussed. A simple model is proposed to account for the ratios of stereochemical isomers found in the Rh6(CO)14(µ,2-PhP(2-thienyl)2 cluster. The kinetics of formation of the bridged clusters from the monosubstituted [Rh6(CO)15(1-PX)] clusters have been studied.
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| 7. |
- Tunik, S P, et al.
(författare)
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Reactions of [H2OS3(CO)(10)] with conjugated diynes (RC2C2R ') containing nucleophilic oxygen in beta position of a substituent (R = Ph, R ' = CH2OH, C(O)Ph; R = R ' = CMe2(OH))
- 2003
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Ingår i: Organometallics. - : American Chemical Society (ACS). - 1520-6041 .- 0276-7333. ; 22:17, s. 3455-3465
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Tidskriftsartikel (refereegranskat)abstract
- Reactions of [H2Os3(CO)10] with a series of diynes, RC2C2R' (1: R = Ph, R' = CH2OH; 2: R = Ph, R' = C(O)Ph; 3: R = R' = C(OH)Me2), have been studied. It was found that upon coordination to the triosmium cluster, the nucleophilic oxygens of the R' substituents of 1 and 2 take part in intramolecular cyclization reactions to give [HOs3(CO)10{-1:2-PhCH2(C=CH-C=CH-O)}] (5) and [HOs3(CO)10{-1:1-Ph(C=CH-C=C-O)CPh}] (6), respectively, both of which contain furan rings coordinated to the cluster core. On heating of the latter compound, the furan moiety remains intact, but a carbonyl group dissociates from the cluster, leading to the formation of [HOs3(CO)9(3-1:3:1-Ph(C=CH-C=C-O)CPh)] (7) with a closed "C3Os3" pentagonal pyramidal structure. Reaction of [H2Os3(CO)10] with 3 does not lead to cyclization of the diyne; instead, the clusters [Os3(CO)10{3-2-(RCH=CH-C2R)}] (8) and [Os3(CO)10{3-2-(RC2C2R)}] (9) are formed. Deuterium labeling of the starting compounds has been used in the reaction of [H2Os3(CO)10] with HOCH2C2C2CH2OH in order to investigate possible mechanisms of the cyclization reaction. The crystal and molecular structures of clusters 5, 7, and 9 are presented.
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