Novel pathways for ligand substitution reactions of dinuclear platinum(I) complexes

Journal Article · Wed Apr 16 04:00:00 EST 1986 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00268a039· OSTI ID:5455456

Blau, R J; Espenson, J H

The terminal halide and/or triphenylphosphine ligands L in dinuclear platinum(I) complexes (Pt/sub 2/L/sub 2/(..mu..dppm)/sub 2/)/sup n /sup +// (where dppm = Ph/sub 2/PCH/sub 2/PPh/sub 2/) undergo ready substitutions. The reaction of (Pt/sub 2/Cl/sub 2/(..mu..-dppm)/sub 2/), abbreviated (Cl--Cl), with PPh/sub 3/ follows a second-order rate law, with kappa = 15.2 +/- 0.7 M/sup -1/ s/sup -1/ at 25/sup 0/C in CH/sub 2/Cl/sub 2/. The product is exclusively (Cl--PPh/sub 3/)/sup +/; (Ph/sub 3/P--PPh/sub 3/)/sup 2 +/ forms only in a more polar solvent like methanol. The complex (Ph/sub 3/P--PPh/sub 3/)/sup 2 +/ reacts in CH/sub 2/Cl/sub 2/ with halide ions (X/sup -/ = Cl/sup -/, Br/sup -/, and I/sup -/) also to yield (X--PPh/sub 3/)/sup +/. In the presence of inert salts such as perchlorates, the reaction proceeds by rate-limiting dissociation of PPh/sub 3/, unusual for square-planar, 16-electron platinum, but further evidence for the large trans influence of the metal-metal bond. In the absence of such salts, however, the reaction occurs in three distinct kinetic stages, although eventually leading to (Cl--PPh/sub 3/)/sup +/. One of the intermediates can be stabilized at low temperature; its /sup 31/P NMR spectrum identifies it (for X/sup -/ = I/sup -/ and Cl/sup -/) as a species containing both bridging and chelating dppm (Pt/sub 2/(X)(PPh/sub 3/)(..mu..-dppm)(eta-dppm))/sup +/. Substitution of PPh/sub 3/ in (Ph/sub 3/--PPh/sub 3/)/sup 2 +/, like the A-frame forming reactions of the same complex, starts with the dissociation of one arm of a bridging dppm ligand.

• Research Organization: Iowa State Univ., Ames
• DOE Contract Number: W-7405-ENG-82
• OSTI ID: 5455456
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 108:8; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400301* -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
COMPLEXES
DATA
EXPERIMENTAL DATA
INFORMATION
KINETICS
LIGANDS
MAGNETIC RESONANCE
MEDIUM TEMPERATURE
NMR SPECTRA
NUCLEAR MAGNETIC RESONANCE
NUMERICAL DATA
PHOSPHINES
PHOSPHORUS COMPOUNDS
PLATINUM COMPLEXES
REACTION INTERMEDIATES
REACTION KINETICS
RESONANCE
SPECTRA
TRANSITION ELEMENT COMPLEXES