ISSN:0749-1581    

DOI:10.1002/mrc.1260291302

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

ISSN:0749-1581    

DOI:10.1002/mrc.1260291303

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractDerivatives of 2,5‐dihydro‐1,2,5‐oxoniastannaboratoles were studied by multinuclear magnetic resonance both in the liquid (11B,13C,29Si,119Sn NMR) and solid state (13C,29Si,119Sn CP/MAS NMR). Together with the results of the x‐ray analysis of the 4,5,5‐triethyl‐2,5‐dihydro‐1,2,2‐trimethyl‐3‐phenyl‐1,2,5‐oxoniastannaboratole‐tetrahydrofuran adduct (1‐THF) (space groupP21/c) the NMR data [chemical shifts and coupling constantsJ(119SnE) (E =13C,29Si,119Sn)] allowed the assessment of structural features in solution and in the solid state (e.g. the weakened coordinative Sn‐O interactions in 1‐THF in solution). The1J(13C13C) values in 4,5,5‐triethyl‐2,5‐dihydro‐1,2,2‐trimethyl‐3‐trimethylsilyl‐ and ‐3‐trimethylstannyl‐1,2,5‐oxoniastannaboratole and in some non‐cyclic alkenes bearing organometallic substituents were measured using INEPT experiments based on3J(13C1H) long‐range coupling constants. In the presence of one boryl‐ and two stannyl groups the magnitude of1J(13C13C) values is reduced toca.30 Hz. A positive sign for2J(119Sn117Sn) in 2‐diethylboryl‐1,1‐bis(trimethylstannyl)but‐1‐ene was determined by 2D13C1H and 2D119Sn‐H heteronuclear shift correlations. Scalar13C11B an

ISSN:0749-1581    

DOI:10.1002/mrc.1260291304

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractPlatinum‐phosphorus heteronuclear multiple‐quantum coherence spectroscopy has been employed for the characterization of platinum‐phosphine cluster compounds. Rules are developed for the interpretation of these spectra, whose appearance depends on the chosen pulse‐sequence, phase‐cycling and whether direct or remote platinum‐phosphorus coupling constants have been selected. Spectral editing according to the different isotopomers (with respect to195Pt) is possible when complete evolution of multiple‐quantum coherence is allowed. This method offers a substantial advantage in the characterization of larger clus

ISSN:0749-1581    

DOI:10.1002/mrc.1260291305

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe second sphere coordination of protonated, branched polyethleneimine (PEI) with [Cr(CN)5(NO)]3−(CPN) was studied by EPR spectroscopy. The interaction between the CPN complex ion and protonated PEI is reported as a function of pH. Simulation of the spectra indicated thatca.98% of the CPN is bound to the polymer at pH ≈︁ 7. The tumbling rate of this species was determined by simulation as 1/τc= 1 × 10−8s−1. The binding of CPN by PEI was influenced by the addition of other salts. Exchange interaction between Cu2+and CPN was observed on the simultaneous binding of these two paramagnetic species to PEI. The pH dependence of the exchange was measured. At an intermediate pH range (7–9), CPN binds in the second and Cu2+in the first sphere. The exchange interaction increases with the ‘loading’ of the polymer with the two paramagnetic species. Based on these results, a model is proposed for the sp

ISSN:0749-1581    

DOI:10.1002/mrc.1260291306

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractBy the use of the INEPT pulse sequence it has been possible to obtain15N and103Rh NMR data on [RhH2(PPh3)2(bipy)]Cl (bipy = 2,2′‐bipyridyl) containing natural abundance15N and prove the stereochemistry;1H and31P NMR data are also reported for [RhH2(PPh3)2(bipy)]Cl which can be easily prepared in the pure state by the reaction of [RhCl(PPh3)3] or [Rh2Cl2(PPh3)4] with bipy ([Rh]: [bipy] = 1:1) under an H2atmosph

ISSN:0749-1581    

DOI:10.1002/mrc.1260291307

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

Abstract119Sn NMR data are reported for organotin compounds containing potentially C,N‐chelating ligands capable of forming five‐ or six‐membered chelate rings. The119Sn chemical shifts of divalent organotin compounds containing such a ligand are found at relatively high frequency. Intramolecular coordination in tetraorganotin compounds has little influence on their119Sn chemical shifts. However, additional coordination in tri‐ and di‐organotin halides causes a large shift to lower frequency of about 100 ppm. Finally, for organotin compounds which exist as a diastereoisomeric mixture in solution, two well resolved119Sn resonances are

ISSN:0749-1581    

DOI:10.1002/mrc.1260291308

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractA series of mixed‐metal carbonyl clusters containing Co and Ru atoms was investigated by59Co NMR and, for the first time in cluster chemistry, by99Ru NMR. These techniques were successfully used to follow the reactivity of these complexes towards nitrosylation by NO+. Whereas [NEt4] [RuCo3(CO)12] reacts with [NO]BF4with the formation of RuCo3(CO)11(NO), which subsequently fragments into RuCo2(CO)11and Co(CO)3(NO), [NEt4] [FeCo3(CO)12] leadsinter aliato FeCo2(μ3‐NH)(CO)9, in which the coordinated NO ligand has been red

ISSN:0749-1581    

DOI:10.1002/mrc.1260291309

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

Abstract(1H,103Rh) and (1H,103Rh){2H} inverse correlation techniques, which profit from the presence of a magnetically active central metal nucleus, were applied to the complex [RhY2(Y2){HB(3,5‐Me2pz)3}] (Y = H or D; pz = pyrazolyl) containing both ‘classical’ and ‘non‐classical’ hydrogen ligands. The sample examined was a mixture of all species ranging from the perprotio to the perdeuterio compound. It is shown that the large isotope chemical shifts of the Rh nucleus can be used to separate the 1D1H and1H{2H} NMR spectra of the different H/D isotopomers. The observed isotope effects ar

ISSN:0749-1581    

DOI:10.1002/mrc.1260291310

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractRate constants and activation parameters for water exchange on hexaaqua‐ and monohydroxypentaaquarhodium(III) were determined by17O NMR as a function of temperature (323–364 K) and pressure (up to 210 MPa, at 323 K) at several acidities (1.0–5.0 molal HClO4). The observed rate constant was of the formkex=k1+k2/[H+], where the subscripts 1 and 2 refer to the exchange pathways on Rh(H2O)63+and Rh(H2O)5(OH)2+, respectively. The kinetic parameters are as follows:k1298= 2.2 × 10−9s−1, ΔH1‡ = 131 ± 23 kJ mol−1, ΔS1‡ = + 29 ± 69 J K−1mol−1, ΔV1‡ = −4.2 ± 0.6 cm3mol−1;k2298= 1.5 × 10−8m s−1, ΔH2‡ = 136 ± 7 kJ mol−1, ΔS2‡ = + 61 ± 21 J K−1mol−1, ΔV2‡ = + 1.3 ± 0.3 cm3mol−1. The thermodynamic parameters for the acid dissociation reaction of Rh(H2O)63+were determined potentiometrically and spectrophotometrically: pKa298= 3.45 and ΔVa0= −0.2 ± 0.5 cm3mol−1. Values were estimated for the first‐order rate constant (using the relationshipk2=kOHKa) and the corresponding activation volume for Rh(H2O)5(OH)2+:kOH298= 4.2 × 10−5s−1and ΔVOH‡ = + 1.5 cm3mol−1. The kinetic results imply an associative interchange mechanism Iafor Rh(H2O)63+and an interchange mechanism I with a slight

ISSN:0749-1581    

DOI:10.1002/mrc.1260291311

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY