Trans effect and trans influence of triphenyl stibine and -phosphine in platinum(II) complexes. A comparative mechanistic and structural study
(1997) In Journal of the Chemical Society. Dalton Transactions 1997(24). p.4725-4731- Abstract
- The kinetics and mechanism of the reactions between trans-[PtI3(PPh3)]– and trans-[PtI3(SbPh3)]– with pyridine, 2- and 4-methylpyridine in acetonitrile solvent have been studied by stopped-flow spectrophotometry. The crystal and molecular structures of the tetrabutylammonium salts of the two anions have been determined. Substitution of iodide trans to stibine is reversible and takes place via parallel direct and solvolytic pathways; substitution in the phosphine complex occurs with negligible back reaction. The kinetic data indicate that triphenyl-stibine and -phosphine should be placed in a series of decreasing trans effect, C2H4 > SbPh3 > CO > P(OMe)3 > PPh3 > AsEt3, i.e. SbPh3 has a much larger trans effect than that of... (More)
- The kinetics and mechanism of the reactions between trans-[PtI3(PPh3)]– and trans-[PtI3(SbPh3)]– with pyridine, 2- and 4-methylpyridine in acetonitrile solvent have been studied by stopped-flow spectrophotometry. The crystal and molecular structures of the tetrabutylammonium salts of the two anions have been determined. Substitution of iodide trans to stibine is reversible and takes place via parallel direct and solvolytic pathways; substitution in the phosphine complex occurs with negligible back reaction. The kinetic data indicate that triphenyl-stibine and -phosphine should be placed in a series of decreasing trans effect, C2H4 > SbPh3 > CO > P(OMe)3 > PPh3 > AsEt3, i.e. SbPh3 has a much larger trans effect than that of PPh3; stibine complexes in the present study react ca. 16 times faster than their phosphine analogues. The activation parameters are typical of associatively activated processes, and in the case of the stibine complex they indicate that very little bond breaking has occurred in the transition state. In the ground states there is a clear-cut difference in the Pt–I distances trans to the pnictogen, 2.637(2) Å in the stibine complex and 2.662(3) Å in the phosphine complex, indicating that SbPh3 has a smaller ground-state trans influence and hence is a weaker σ donor than PPh3. Since the kinetic trans effect is a combination of ground-state labilisation and transition-state stabilisation, it is concluded that the large trans effect of stibine is due to a better π acceptance. Based on a comparison of Sb–C distances and C–Sb–C angles in free and co-ordinated stibine, this is proposed to be due to a higher d character of the π* orbitals on stibine as compared to phosphine, leading to a better overlap between antimony π* and platinum 5d π orbitals. (Less)
- Abstract (Swedish)
- The kinetics and mechanism of the reactions between trans-[PtI3(PPh3)]– and trans-[PtI3(SbPh3)]– with pyridine, 2- and 4-methylpyridine in acetonitrile solvent have been studied by stopped-flow spectrophotometry. The crystal and molecular structures of the tetrabutylammonium salts of the two anions have been determined. Substitution of iodide trans to stibine is reversible and takes place via parallel direct and solvolytic pathways; substitution in the phosphine complex occurs with negligible back reaction. The kinetic data indicate that triphenyl-stibine and -phosphine should be placed in a series of decreasing trans effect, C2H4 > SbPh3 > CO > P(OMe)3 > PPh3 > AsEt3, i.e. SbPh3 has a much larger trans effect than that of... (More)
- The kinetics and mechanism of the reactions between trans-[PtI3(PPh3)]– and trans-[PtI3(SbPh3)]– with pyridine, 2- and 4-methylpyridine in acetonitrile solvent have been studied by stopped-flow spectrophotometry. The crystal and molecular structures of the tetrabutylammonium salts of the two anions have been determined. Substitution of iodide trans to stibine is reversible and takes place via parallel direct and solvolytic pathways; substitution in the phosphine complex occurs with negligible back reaction. The kinetic data indicate that triphenyl-stibine and -phosphine should be placed in a series of decreasing trans effect, C2H4 > SbPh3 > CO > P(OMe)3 > PPh3 > AsEt3, i.e. SbPh3 has a much larger trans effect than that of PPh3; stibine complexes in the present study react ca. 16 times faster than their phosphine analogues. The activation parameters are typical of associatively activated processes, and in the case of the stibine complex they indicate that very little bond breaking has occurred in the transition state. In the ground states there is a clear-cut difference in the Pt–I distances trans to the pnictogen, 2.637(2) Å in the stibine complex and 2.662(3) Å in the phosphine complex, indicating that SbPh3 has a smaller ground-state trans influence and hence is a weaker σ donor than PPh3. Since the kinetic trans effect is a combination of ground-state labilisation and transition-state stabilisation, it is concluded that the large trans effect of stibine is due to a better π acceptance. Based on a comparison of Sb–C distances and C–Sb–C angles in free and co-ordinated stibine, this is proposed to be due to a higher d character of the π* orbitals on stibine as compared to phosphine, leading to a better overlap between antimony π* and platinum 5d π orbitals. (Less)
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https://lup.lub.lu.se/record/05a8ee14-4ef0-4f91-9a46-a213fc5dfe69
- author
- Wendt, Ola LU and Elding, Lars Ivar LU
- organization
- publishing date
- 1997-12-21
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- Platinum(II), Triprhenyl stibine, Triphenyl phosphine, Trans effect series, Trans influence, Stopped-flow kinetics, Reaction mechanism, Tetrabutyl ammonium salt, Crystal structure
- in
- Journal of the Chemical Society. Dalton Transactions
- volume
- 1997
- issue
- 24
- pages
- 7 pages
- publisher
- Royal Society of Chemistry
- external identifiers
-
- scopus:33748837232
- ISSN
- 1472-7773
- DOI
- 10.1039/A706617A
- language
- English
- LU publication?
- yes
- id
- 05a8ee14-4ef0-4f91-9a46-a213fc5dfe69
- date added to LUP
- 2016-12-31 22:44:01
- date last changed
- 2022-01-30 08:59:19
@article{05a8ee14-4ef0-4f91-9a46-a213fc5dfe69,
abstract = {{The kinetics and mechanism of the reactions between trans-[PtI3(PPh3)]– and trans-[PtI3(SbPh3)]– with pyridine, 2- and 4-methylpyridine in acetonitrile solvent have been studied by stopped-flow spectrophotometry. The crystal and molecular structures of the tetrabutylammonium salts of the two anions have been determined. Substitution of iodide trans to stibine is reversible and takes place via parallel direct and solvolytic pathways; substitution in the phosphine complex occurs with negligible back reaction. The kinetic data indicate that triphenyl-stibine and -phosphine should be placed in a series of decreasing trans effect, C2H4 > SbPh3 > CO > P(OMe)3 > PPh3 > AsEt3, i.e. SbPh3 has a much larger trans effect than that of PPh3; stibine complexes in the present study react ca. 16 times faster than their phosphine analogues. The activation parameters are typical of associatively activated processes, and in the case of the stibine complex they indicate that very little bond breaking has occurred in the transition state. In the ground states there is a clear-cut difference in the Pt–I distances trans to the pnictogen, 2.637(2) Å in the stibine complex and 2.662(3) Å in the phosphine complex, indicating that SbPh3 has a smaller ground-state trans influence and hence is a weaker σ donor than PPh3. Since the kinetic trans effect is a combination of ground-state labilisation and transition-state stabilisation, it is concluded that the large trans effect of stibine is due to a better π acceptance. Based on a comparison of Sb–C distances and C–Sb–C angles in free and co-ordinated stibine, this is proposed to be due to a higher d character of the π* orbitals on stibine as compared to phosphine, leading to a better overlap between antimony π* and platinum 5d π orbitals.}},
author = {{Wendt, Ola and Elding, Lars Ivar}},
issn = {{1472-7773}},
keywords = {{Platinum(II); Triprhenyl stibine; Triphenyl phosphine; Trans effect series; Trans influence; Stopped-flow kinetics; Reaction mechanism; Tetrabutyl ammonium salt; Crystal structure}},
language = {{eng}},
month = {{12}},
number = {{24}},
pages = {{4725--4731}},
publisher = {{Royal Society of Chemistry}},
series = {{Journal of the Chemical Society. Dalton Transactions}},
title = {{Trans effect and trans influence of triphenyl stibine and -phosphine in platinum(II) complexes. A comparative mechanistic and structural study}},
url = {{http://dx.doi.org/10.1039/A706617A}},
doi = {{10.1039/A706617A}},
volume = {{1997}},
year = {{1997}},
}