Kinetics and mechanism of the replacement of I/sup -/ by CN/sup -/ in the hexaiodoplatinate(IV) ion

Journal Article · Fri Nov 01 04:00:00 EST 1985 · Sov. J. Coordinat. Chem.; (United States)

OSTI ID:6356927

Babkov, A V; Moravskii, A P; Khramov, A V

The reaction PtI/sub 6//sup 2 -/ (I) + 5CN/sup -/ ..-->.. Pt(CN)/sub 5/I/sup 2 -/ + 5I/sup -/ has been investigated by the stopped-flow method with spectrophotometric determination of the concentrations. The rate of disappearance of complex I is characterized by the constant k = (6.7 +/- 0.3) 10/sup 4/ liter/mole sec (20/sup 0/C, ..mu.. = 0.013, pH 11.6). The reduction of Pt(IV) to Pt(II) and the particle replacement of I/sup -/ by CN/sup -/ with the formation of cis-Pt (CN)/sub 2/I/sub 2//sup 2 -/ (II) and ICN are intermediate processes. Compound II participates in the slower addition of ICN, which is induced by CN/sup -/ ions (k = (7.0 +/- 0.3) 10/sup 3/ liter/sup 2//mole/sup 2/ sec, ..delta..H/sup not equal to/ = 12.4 +/- 2 kJ/mole, ..delta..S/sup not equal to/ = -121 +/- 10 J/mole deg at 25/sup 0/C), and simultaneously in the replacement of I/sup -/ by CN/sup -/. This mechanism is confirmed by the obtaining of the same kinetic characteristics for the reaction of compound II prepared directly by replacing I/sup -/ by CN/sup -/ in the Pt(II) complex. Other intermediate complexes are not detected in the presence of an excess of CN/sup -/ in the reaction mixture. When the Pt(IV):CN/sup -/ stoichiometric ratio is equal to 1:3, a complex with an absorption spectrum similar to the spectrum of complex I forms. It has been postulated that his complex is (Pt(CN)/sub 3/I(I)/sub 2/)/sup 2 -/. The kinetics of the first alkaline hydrolysis step have been investigated for I (k = 20 liter/mole sec). The kinetics of the replacement of I/sup -/ by CN/sup -/ in trans-(Pt(NH/sub 3/)/sub 2/(CN)/sub 2/I/sub 2/) have been refined: k = 1.2 10/sup 8/ liter/mole sec (20/sup 0/C, pH 6.34). The occurrence of the direct replacement of I/sup -/ by CN/sup -/ int heinner coordination sphere of Pt(IV) has not been detected.

• OSTI ID: 6356927
• Journal Information: Sov. J. Coordinat. Chem.; (United States), Journal Name: Sov. J. Coordinat. Chem.; (United States) Vol. 11:1; ISSN SJCCD
• Country of Publication: United States
• Language: Russian

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ABSORPTION SPECTRA
ALKALINE HYDROLYSIS
CATALYTIC EFFECTS
CHEMICAL REACTION KINETICS
CHEMICAL REACTION YIELD
CHEMICAL REACTIONS
COMPLEXES
COMPLEXOMETRY
CYANIDES
CYANOGEN
DECOMPOSITION
HALIDES
HALOGEN COMPOUNDS
HYDROLYSIS
IODIDES
IODINE COMPOUNDS
ION EXCHANGE
KINETICS
LYSIS
OXIDATION
PLATINUM COMPLEXES
PLATINUM COMPOUNDS
PLATINUM IODIDES
REACTION INTERMEDIATES
REACTION KINETICS
REDOX REACTIONS
REDUCTION
SOLVOLYSIS
SPECTRA
SPECTROPHOTOMETRY
TRANSITION ELEMENT COMPLEXES
TRANSITION ELEMENT COMPOUNDS
YIELDS