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An In-Depth Investigation on the C-I Bond Activation by Rollover Cycloplatinated(II) Complexes Bearing Monodentate Phosphane Ligands: Kinetic and Kinetic Isotope Effect

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), PPh2Me (1b) and PPhMe2 (1c) was prepared. The oxidative addition reaction of MeI reagent to Pt(II) center was performed and kinetically investigated. In Pt(II) → trans-Pt(IV) reaction (kinetic product), the electronic effects of the phosphanes determine the rates of the reactions and this trend was obtained: PPhMe2 > PPh2Me > PPh3. However, in trans-Pt(IV) → cis-Pt(IV) isomerization (thermodynamic product), the steric effects induced by phosphane ligands controlled the conversion rates (PPh3 > PPh2Me > PPhMe2). Also, secondary α-deuterium kinetic isotope effect (KIE) study was performed for some of the reactions using the CD3I reagent. The obtained small KIE values are indicative of a classic SN2 mechanism with a tight transition state. Moreover, the reactions of 1a with MeI and CD3I were monitored by (1H and 31P{1H}) NMR spectroscopy in order to gain an appropriate proposed mechanism. The NMR monitoring data for CD3I exhibited the presence of scrambling twins in which the incoming CD3 ligand occupies the CH3 ligand disposition in parent the 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 for 1b (PPh2Me) and 1c (PPhMe2) was very slow, so NMR data showed the scrambling only for trans geometry.

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Publication details

The article was received on 26 Oct 2017, accepted on 09 Jan 2018 and first published on 10 Jan 2018


Article type: Paper
DOI: 10.1039/C7NJ04159D
Citation: New J. Chem., 2018, Accepted Manuscript
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    An In-Depth Investigation on the C-I Bond Activation by Rollover Cycloplatinated(II) Complexes Bearing Monodentate Phosphane Ligands: Kinetic and Kinetic Isotope Effect

    H. R. Shahsavari, R. Babadi Aghakhanpour and M. fereidoonnezhad, New J. Chem., 2018, Accepted Manuscript , DOI: 10.1039/C7NJ04159D

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