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Acetonitrile and Propionitrile Exchange at Palladium(II) and Platinum(II)
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- Wendt, Ola (author)
- Lund University,Lunds universitet,Centrum för analys och syntes,Kemiska institutionen,Institutioner vid LTH,Lunds Tekniska Högskola,Centre for Analysis and Synthesis,Department of Chemistry,Departments at LTH,Faculty of Engineering, LTH
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- N. F., Kaiser (author)
- Lund University
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- Elding, Lars Ivar (author)
- Lund University,Lunds universitet,Centrum för analys och syntes,Kemiska institutionen,Institutioner vid LTH,Lunds Tekniska Högskola,Centre for Analysis and Synthesis,Department of Chemistry,Departments at LTH,Faculty of Engineering, LTH
- (creator_code:org_t)
- 1997
- 1997
- English 5 s.
- In: Journal of the Chemical Society. Dalton Transactions. - 1472-7773. ; 1997:24, s. 4733-4737
- Journal article (peer-reviewed)
Abstract
Subject headings
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- Ligand exchange at square-planar [Pd(MeCN)4]2+ and [Pd(EtCN)4]2+ has been studied by 1H NMR line broadening and at [Pt(MeCN)4]2+ and [Pt(EtCN)4]2+ by isotopic labelling using 1H NMR spectroscopy in deuteriated nitromethane. Exchange takes place via two-term rate laws Rex/4 = (k1 + k2[RCN])cM with well defined k1 paths. Rate constants per co-ordination site k1298/s–1, k2298/kg mol–1 s–1 are 6.9 ± 1.6, 34 ± 3; 0.59 ± 0.12, 34 ± 3; 10.7 ± 1.8, 35 ± 4; (5.1 ± 2.3) × 10–6, (2.8 ± 0.2) × 10–5 and (5.5 ± 1.0) × 10–6, (3.3 ± 0.2) × 10–5 for [Pd(MeCN)4][CF3SO3]2, [Pd(MeCN)4][BF4]2, [Pd(EtCN)4][CF3SO3]2, [Pt(MeCN)4][CF3SO3]2 and [Pt(EtCN)4][CF3SO3]2, respectively. For [Pd(MeCN)4]2+ the k1 path is much larger for triflate than for tetrafluoroborate as counter ion. Changing the tetrafluoroborate concentration has no effect on the exchange rate of acetonitrile at [Pd(MeCN)4]2+. In this case the k1 path is ascribed to an attack by solvent at the metal centre. For triflate saturation kinetics is observed. This can be rationalized in terms of ion-pair formation followed by reversible intramolecular exchange of nitrile for triflate within the ion pair, with an equilibrium constant Kip300 = 8 ± 2 kg mol–1 and a rate constant k300 = 12.5 ± 1.3 s–1. All activation entropies are negative, indicating associative activation. A new, simple one-step synthesis of the substrate complexes as their triflate salts, using [M(acac)2] (acac = acetylacetonate) as starting material, and of [Pd(MeCN)4][BF4]2 using palladium(II) acetate, is described.
- Ligand exchange at square-planar [Pd(MeCN)4]2+ and [Pd(EtCN)4]2+ has been studied by 1H NMR line broadening and at [Pt(MeCN)4]2+ and [Pt(EtCN)4]2+ by isotopic labelling using 1H NMR spectroscopy in deuteriated nitromethane. Exchange takes place via two-term rate laws Rex/4 = (k1 + k2[RCN])cM with well defined k1 paths. Rate constants per co-ordination site k1298/s–1, k2298/kg mol–1 s–1 are 6.9 ± 1.6, 34 ± 3; 0.59 ± 0.12, 34 ± 3; 10.7 ± 1.8, 35 ± 4; (5.1 ± 2.3) × 10–6, (2.8 ± 0.2) × 10–5 and (5.5 ± 1.0) × 10–6, (3.3 ± 0.2) × 10–5 for [Pd(MeCN)4][CF3SO3]2, [Pd(MeCN)4][BF4]2, [Pd(EtCN)4][CF3SO3]2, [Pt(MeCN)4][CF3SO3]2 and [Pt(EtCN)4][CF3SO3]2, respectively. For [Pd(MeCN)4]2+ the k1 path is much larger for triflate than for tetrafluoroborate as counter ion. Changing the tetrafluoroborate concentration has no effect on the exchange rate of acetonitrile at [Pd(MeCN)4]2+. In this case the k1 path is ascribed to an attack by solvent at the metal centre. For triflate saturation kinetics is observed. This can be rationalized in terms of ion-pair formation followed by reversible intramolecular exchange of nitrile for triflate within the ion pair, with an equilibrium constant Kip300 = 8 ± 2 kg mol–1 and a rate constant k300 = 12.5 ± 1.3 s–1. All activation entropies are negative, indicating associative activation. A new, simple one-step synthesis of the substrate complexes as their triflate salts, using [M(acac)2] (acac = acetylacetonate) as starting material, and of [Pd(MeCN)4][BF4]2 using palladium(II) acetate, is described.
Subject headings
- NATURVETENSKAP -- Kemi -- Oorganisk kemi (hsv//swe)
- NATURAL SCIENCES -- Chemical Sciences -- Inorganic Chemistry (hsv//eng)
Keyword
- Palladium(II)
- Platinum(II)
- Acetonitrile
- Propionitrile
- Ligand exchange
- Proton NMR line broadening
- Reaction Mechanism
- Actvation entropy
- Triflate salt
- Palladium(II)
- Platinum(II)
- Acetonitrile
- Propionitrile
- Ligand exchange
- Kinetics
- Reaction mechanism
- NMR spectroscopy
- Triflate salts
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- art (subject category)
- ref (subject category)
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