An in-depth investigation on the C–I bond activation by rollover cycloplatinated(ii) complexes bearing monodentate phosphane ligands: kinetic and kinetic isotope effect. (24th January 2018)

• Record Type: Journal Article
• Authors: Shahsavari, Hamid R.; Babadi Aghakhanpour, Reza; Fereidoonnezhad, Masood
• Is Part Of: New journal of chemistry. Volume 42:Number 4(2018)
• Page Start: 2564
• Page End: 2573
• Publication Date: 2018-01-24
• Subjects: Chemistry -- Periodicals; Chimie -- Périodiques; 540
• DOI: 10.1039/c7nj04159d
• Languages: English
• ISSNs: 1144-0546

Abstract

Abstract : The oxidative addition reaction of MeI reagent to some cycloplatinated(ii ) complexes was performed and kinetically investigated. Abstract : In this study, a series of platinum(ii ) complexes with the general formula of [Pt(O-bpy)(Me)(L)], 1, O-bpy = cyclometalated rollover 2, 2′-bipyridine N -oxide and L = PPh3 (1a ), PPh2 Me (1b ) and PPhMe2 (1c ) was prepared. The oxidative addition reaction of MeI reagent to the Pt(ii ) center was performed and kinetically investigated. In the Pt(ii ) → trans -Pt(iv ) reaction (kinetic product), the electronic effects of the phosphanes determine the rates of the reactions and the following trend was obtained: PPhMe2 > PPh2 Me > PPh3 . However, in the trans -Pt(iv ) → cis -Pt(iv ) isomerization (thermodynamic product), the steric effects induced by phosphane ligands controlled the conversion rates (PPh3 > PPh2 Me > PPhMe2 ). Also, a secondary α-deuterium kinetic isotope effect (KIE) study was performed for some of the reactions using the CD3 I reagent. The obtained small KIE values are indicative of a classic SN 2 mechanism with a tight transition state. Moreover, the reactions of1a with MeI and CD3 I were monitored by ( 1 H and 31 P{ 1 H}) NMR spectroscopy in order to gain an appropriate proposed mechanism. The NMR monitoring data for CD3 I exhibited the presence of scrambling twins in which the incoming CD3 ligand occupies the CH3 ligand position in the parent Pt(ii ) complex and vice versa .1a, containing PPh3 ligand, indicated the mentioned scrambling for both trans and cis products. However, the trans to cis isomerization for1b (PPh2 Me) and1c (PPhMe2 ) was very slow, so NMR data showed the scrambling only for trans geometry.