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Transition Metal Complexes with Bidentate Ligands Spanning trans-Positions. Part XII. Steric Effects in the Kinetics and Mechanism of Substitutions at Hydride and Methyl Bisphosphine Platinum(II)) Complexes.

Elding, Lars Ivar LU ; Kellenberger, Bruno and Venanzi, Luigi M. (1983) In Helvetica Chimica Acta 66(6). p.1676-1690
Abstract (Swedish)
Ligand substitution reactions on square-planar platinum (II) complexes of the types trans-[PtRXL2], trans-[PtR(4-PADA)L2][BF4], trans-[PtRX(LL)] and trans-[PtR(4-PADA)(LL)][BF4], R=H, Me; X=Cl−, I−; L=PEt3, bis(3-trifluoromethyl-phenyl)benzylphosphine (4). LL=the trans-spanning 2,11-bis[bis(3-trifluoro-methylphenyl)phosphinomethyl]benzo [c]phenanthrene (3); 4-PADA (=pyridine-4-azo-4′-(N, N-dimethyl)aniline have been studied at 30° using stopped-flow and conventional spectrophotometry, methanol as solvent, and 2.5 × 10−2 M ionic strength (LiClO4 as supporting electrolyte). 4-PADA was used as indicator ligand, as its absorption spectrum differs from those spectra where it is complexed.
The expected steric effects of the bulky ligands,... (More)
Ligand substitution reactions on square-planar platinum (II) complexes of the types trans-[PtRXL2], trans-[PtR(4-PADA)L2][BF4], trans-[PtRX(LL)] and trans-[PtR(4-PADA)(LL)][BF4], R=H, Me; X=Cl−, I−; L=PEt3, bis(3-trifluoromethyl-phenyl)benzylphosphine (4). LL=the trans-spanning 2,11-bis[bis(3-trifluoro-methylphenyl)phosphinomethyl]benzo [c]phenanthrene (3); 4-PADA (=pyridine-4-azo-4′-(N, N-dimethyl)aniline have been studied at 30° using stopped-flow and conventional spectrophotometry, methanol as solvent, and 2.5 × 10−2 M ionic strength (LiClO4 as supporting electrolyte). 4-PADA was used as indicator ligand, as its absorption spectrum differs from those spectra where it is complexed.
The expected steric effects of the bulky ligands, especially of 3, on the rates and mechanisms of all the reactions studied are small. All reactions take place by the usual two-term rate law. Noteworthy, for the complexes with the bulky ligands 3 and 4, the direct reaction path with the entering nucleophile is predominant. There is no preference for a solvent or dissociative path. The reactivity order for the hydride complexes is trans-[PtHX (PEt3)2]<trans-[PtHX(4)2]<trans-[PtHX (3)]. However, for the corresponding methyl complexes, there is some retardation by ligand 3, probably due to an interaction between the methyl group and the hydrocarbon moiety of 3, which inhibits the fluxional behavior of this ligand. The results have some relevance for the understanding of olefin insertion reactions of hydride complexes containing these phosphine ligands. (Less)
Abstract
Ligand substitution reactions on square-planar platinum (II) complexes of the types trans-[PtRXL2], trans-[PtR(4-PADA)L2][BF4], trans-[PtRX(LL)] and trans-[PtR(4-PADA)(LL)][BF4] R=H, Me; X=Cl−, I−; L=PEt3, bis(3-trifluoromethyl-phenyl)benzylphosphine (4), LL=the trans-spanning 2,11-bis[bis(3-trifluoro-methylphenyl)phosphinomethyl]benzo [c]phenanthrene (3); 4-PADA (=pyridine-4-azo-4′-(N, N-dimethyl)aniline) have been studied at 30° using stopped-flow and conventional spectrophotometry, methanol as solvent, and 2.5 × 10−2 M ionic strength (LiClO4 as supporting electrolyte). 4-PADA was used as indicator ligand, as its absorption spectrum differs from those spectra where it is complexed.
The expected steric effects of the bulky ligands,... (More)
Ligand substitution reactions on square-planar platinum (II) complexes of the types trans-[PtRXL2], trans-[PtR(4-PADA)L2][BF4], trans-[PtRX(LL)] and trans-[PtR(4-PADA)(LL)][BF4] R=H, Me; X=Cl−, I−; L=PEt3, bis(3-trifluoromethyl-phenyl)benzylphosphine (4), LL=the trans-spanning 2,11-bis[bis(3-trifluoro-methylphenyl)phosphinomethyl]benzo [c]phenanthrene (3); 4-PADA (=pyridine-4-azo-4′-(N, N-dimethyl)aniline) have been studied at 30° using stopped-flow and conventional spectrophotometry, methanol as solvent, and 2.5 × 10−2 M ionic strength (LiClO4 as supporting electrolyte). 4-PADA was used as indicator ligand, as its absorption spectrum differs from those spectra where it is complexed.
The expected steric effects of the bulky ligands, especially of 3, on the rates and mechanisms of all the reactions studied are small. All reactions take place by the usual two-term rate law. Noteworthy, for the complexes with the bulky ligands 3 and 4, the direct reaction path with the entering nucleophile is predominant. There is no preference for a solvent or dissociative path. The reactivity order for the hydride complexes is trans-[PtHX (PEt3)2]<trans-[PtHX(4)2]<trans-[PtHX (3)]. However, for the corresponding methyl complexes, there is some retardation by ligand 3, probably due to an interaction between the methyl group and the hydrocarbon moiety of 3, which inhibits the fluxional behavior of this ligand. The results have some relevance for the understanding of olefin-insertion reactions of hydride complexes containing these phosphine ligands. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Platinum(II), trans-spanning ligand, Steric effects, Stopped-flow kinetics, Reaction mechanism, Steric blocking, 4-PADA
in
Helvetica Chimica Acta
volume
66
issue
6
pages
15 pages
publisher
John Wiley & Sons
external identifiers
  • scopus:0000433826
ISSN
0018-019X
DOI
10.1002/hlca.19830660607
language
English
LU publication?
yes
id
8fb312fd-73da-4865-82ae-fdecdb9d3e2d
date added to LUP
2017-02-07 22:21:37
date last changed
2017-07-30 05:21:17
@article{8fb312fd-73da-4865-82ae-fdecdb9d3e2d,
  abstract     = {Ligand substitution reactions on square-planar platinum (II) complexes of the types trans-[PtRXL2], trans-[PtR(4-PADA)L2][BF4], trans-[PtRX(LL)] and trans-[PtR(4-PADA)(LL)][BF4] R=H, Me; X=Cl−, I−; L=PEt3, bis(3-trifluoromethyl-phenyl)benzylphosphine (4), LL=the trans-spanning 2,11-bis[bis(3-trifluoro-methylphenyl)phosphinomethyl]benzo [c]phenanthrene (3); 4-PADA (=pyridine-4-azo-4′-(N, N-dimethyl)aniline) have been studied at 30° using stopped-flow and conventional spectrophotometry, methanol as solvent, and 2.5 × 10−2 M ionic strength (LiClO4 as supporting electrolyte). 4-PADA was used as indicator ligand, as its absorption spectrum differs from those spectra where it is complexed.<br>
The expected steric effects of the bulky ligands, especially of 3, on the rates and mechanisms of all the reactions studied are small. All reactions take place by the usual two-term rate law. Noteworthy, for the complexes with the bulky ligands 3 and 4, the direct reaction path with the entering nucleophile is predominant. There is no preference for a solvent or dissociative path. The reactivity order for the hydride complexes is trans-[PtHX (PEt3)2]&lt;trans-[PtHX(4)2]&lt;trans-[PtHX (3)]. However, for the corresponding methyl complexes, there is some retardation by ligand 3, probably due to an interaction between the methyl group and the hydrocarbon moiety of 3, which inhibits the fluxional behavior of this ligand. The results have some relevance for the understanding of olefin-insertion reactions of hydride complexes containing these phosphine ligands.},
  author       = {Elding, Lars Ivar and Kellenberger, Bruno and Venanzi, Luigi M.},
  issn         = {0018-019X},
  keyword      = {Platinum(II),trans-spanning ligand,Steric effects,Stopped-flow kinetics,Reaction mechanism,Steric blocking,4-PADA},
  language     = {eng},
  number       = {6},
  pages        = {1676--1690},
  publisher    = {John Wiley & Sons},
  series       = {Helvetica Chimica Acta},
  title        = {Transition Metal Complexes with Bidentate Ligands Spanning trans-Positions. Part  XII. Steric Effects in the Kinetics and Mechanism of Substitutions at Hydride and Methyl Bisphosphine Platinum(II)) Complexes.},
  url          = {http://dx.doi.org/10.1002/hlca.19830660607},
  volume       = {66},
  year         = {1983},
}