Equilibria, Kinetics and Mechanism for Rapid Substitution Reactions trans to Triphenyl Silyl in Platinum(II) Complexes
(1997) In Inorganic Chemistry 36(26). p.6028-6032- Abstract
- Fast substitution of chloride for bromide and iodide trans to triphenylsilyl in trans-PtCl(SiPh3)(PMe2Ph)2 has been studied by stopped-flow spectrophotometry in acetonitrile solution. Substitution is reversible with an observable solvent path via the solvento complex trans-[Pt(SiPh3)(MeCN)(PMe2Ph)2]+, which has also been synthesized and characterized in solution. Rate constants for the forward and reverse direct substitution pathways are 2900 ± 100 and 7500 ± 300 for bromide and 14300 ± 1100 and 81000 ± 11000 M-1 s-1 for iodide as nucleophile. The solvento complex reacts ca. 103 times faster with iodide than the parent chloride complex, and its reactivity is some 2 orders of magnitude higher than the most reactive solvento species of... (More)
- Fast substitution of chloride for bromide and iodide trans to triphenylsilyl in trans-PtCl(SiPh3)(PMe2Ph)2 has been studied by stopped-flow spectrophotometry in acetonitrile solution. Substitution is reversible with an observable solvent path via the solvento complex trans-[Pt(SiPh3)(MeCN)(PMe2Ph)2]+, which has also been synthesized and characterized in solution. Rate constants for the forward and reverse direct substitution pathways are 2900 ± 100 and 7500 ± 300 for bromide and 14300 ± 1100 and 81000 ± 11000 M-1 s-1 for iodide as nucleophile. The solvento complex reacts ca. 103 times faster with iodide than the parent chloride complex, and its reactivity is some 2 orders of magnitude higher than the most reactive solvento species of platinum(II) studied so far. Halide substitution occurs with negative volumes and entropies of activation, but the nucleophilic discrimination is low, and the leaving ligand plays the most important role in the activation process, indicating an Id mechanism. Triphenylsilyl has a very high trans effect, comparable to that of ethene and methylisocyanide, due to extensive bond-weakening in the ground state, probably enforced by π-acception in the transition state. Due to electronic and solvational effects the platinum(II) silyl moiety acts as a hard or borderline metal center in acetonitrile, the thermodynamic stability sequence of its halide complexes being Cl > Br > I, i.e. the reverse of what is usually observed for platinum(II) complexes (Less)
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- author
- Wendt, Ola LU and Elding, Lars Ivar LU
- organization
- publishing date
- 1997-12-17
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- Platinum(II), Triphenyl Silyl, Fast kinetics, trans effect, Stopped flow, Kinetics and mechanism, Id Mechanism, Reverse stability sequence, Activation parameters
- in
- Inorganic Chemistry
- volume
- 36
- issue
- 26
- pages
- 5 pages
- publisher
- The American Chemical Society (ACS)
- external identifiers
-
- scopus:0001181606
- ISSN
- 1520-510X
- DOI
- 10.1021/ic971008l
- language
- Swedish
- LU publication?
- yes
- id
- e1d231d0-f701-4e90-b698-5c80cdce6c61
- date added to LUP
- 2016-12-31 20:11:00
- date last changed
- 2022-01-30 08:59:19
@article{e1d231d0-f701-4e90-b698-5c80cdce6c61, abstract = {{Fast substitution of chloride for bromide and iodide trans to triphenylsilyl in trans-PtCl(SiPh3)(PMe2Ph)2 has been studied by stopped-flow spectrophotometry in acetonitrile solution. Substitution is reversible with an observable solvent path via the solvento complex trans-[Pt(SiPh3)(MeCN)(PMe2Ph)2]+, which has also been synthesized and characterized in solution. Rate constants for the forward and reverse direct substitution pathways are 2900 ± 100 and 7500 ± 300 for bromide and 14300 ± 1100 and 81000 ± 11000 M-1 s-1 for iodide as nucleophile. The solvento complex reacts ca. 103 times faster with iodide than the parent chloride complex, and its reactivity is some 2 orders of magnitude higher than the most reactive solvento species of platinum(II) studied so far. Halide substitution occurs with negative volumes and entropies of activation, but the nucleophilic discrimination is low, and the leaving ligand plays the most important role in the activation process, indicating an Id mechanism. Triphenylsilyl has a very high trans effect, comparable to that of ethene and methylisocyanide, due to extensive bond-weakening in the ground state, probably enforced by π-acception in the transition state. Due to electronic and solvational effects the platinum(II) silyl moiety acts as a hard or borderline metal center in acetonitrile, the thermodynamic stability sequence of its halide complexes being Cl > Br > I, i.e. the reverse of what is usually observed for platinum(II) complexes}}, author = {{Wendt, Ola and Elding, Lars Ivar}}, issn = {{1520-510X}}, keywords = {{Platinum(II); Triphenyl Silyl; Fast kinetics; trans effect; Stopped flow; Kinetics and mechanism; Id Mechanism; Reverse stability sequence; Activation parameters}}, language = {{swe}}, month = {{12}}, number = {{26}}, pages = {{6028--6032}}, publisher = {{The American Chemical Society (ACS)}}, series = {{Inorganic Chemistry}}, title = {{Equilibria, Kinetics and Mechanism for Rapid Substitution Reactions trans to Triphenyl Silyl in Platinum(II) Complexes}}, url = {{http://dx.doi.org/10.1021/ic971008l}}, doi = {{10.1021/ic971008l}}, volume = {{36}}, year = {{1997}}, }