A Kinetic Study of the Competition between Carbon Monoxide and Alkenes in Chloro Complexes of Platinum(II)

Abstract

Alkenes (cyclohexene; 1-octene) react with cis-PtCl 2 -(CO) 2 , leading to cis-PtCl 2 (CO)(alkene) (1a, alkene ) cyclohexene; 1b, alkene ) 1-octene). The substitution kinetics to 1a and 1b in 1,2-dichloroethane in the temperature range 273-308 K haVe the following second-order rate constants at 298 K, respectiVely: cyclohexene, (0.94 ( 0.07) × 10 -3 M -1 s -1 ; 1-octene, (2.33 ( 0.05) × 10 -2 M -1 s -1 . The actiVation parameters are ∆H* ) 37 ( 4 kJ mol -1 , ∆S* ) -180 ( 10 J K -1 mol -1 for the reaction affording 1a and ∆H* ) 36.5 ( 0.7 kJ mol -1 , ∆S* ) -154 ( 2 J K -1 mol -1 for the reaction to 1b. The large negatiVe Values of the actiVation entropies are consistent with an associatiVe mechanism. The reVerse reactions proceed with a similar rate constant.

A convenient route to dinuclear chloro-bridged platinum(ii) derivatives vianitrile complexes

“…The outcome of the reaction was followed by 195 Pt NMR. The analysis of the residue, dissolved in CDCl 3 , showed a signal due to trans-( 6), 5 and two more signals due to trans- (7). 29 The presence of two 195 Pt resonances for this dinuclear complex has been already observed and discussed.…”

“…With the aim of obtaining [Pt(m-Cl)Cl(CO)] 2 (7), a sample of cis-6 was dissolved in dry mesitylene and the solution was heated (75 • C) and slowly evaporated under vacuum. The outcome of the reaction was followed by 195 Pt NMR.…”

Katalytische carbophile Aktivierung: Platin‐ und Gold‐π‐Säuren als Katalysatoren

“…Da mit der Verwendung von CO kein nennenswerter präparativer Aufwand verbunden ist und nach Aufarbeitung der Reaktionsgemische keine Rückstände aus dem Liganden zurückbleiben, büßt die Durchführung der Reaktion nichts an Anwenderfreundlichkeit ein. [147,151,166,167] Auf [175] Allerdings soll betont werden, dass der Verlauf sowohl substrat-als auch katalysatorabhängig sein könnte. [176] Unabhängig davon, wie die späten Stufen des Mechanismus im Detail aussehen mögen, bleibt unbestritten, dass derartige Reaktionen durch den nukleophilen Angriff auf ein aktiviertes Alkin ausgelöst werden (Schema 26).…”

Reaction mechanisms in solution

“…123 Kinetic studies of the addition of cyclohexene and 1-octene to cis-[PtCl 2 (CO) 2 ] to produce cis-[PtCl 2 (CO)(alkene)] showed behaviour typical of substitution at square-planar centres. 124 Large negative activation entropies for the reactions were consistent with an associative mechanism.…”