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Oxidation of Half-Lantern Pt2(II,II) Compounds by Halocarbons. Evidence of Dioxygen Insertion into a Pt(III)–CH3 Bond

V. Sicilia *†, M. Baya ‡, P. Borja ‡, and A. Martín ‡

† Departamento de Química Inorgánica, Escuela de Ingeniería y Arquitectura de Zaragoza, Instituto de Síntesis Química y Catálisis Homogénea (ISQCH), CSIC - Universidad de Zaragoza, Campus Río Ebro, Edificio Torres Quevedo, 50018 Zaragoza, Spain

‡ Departamento de Química Inorgánica, Facultad de Ciencias, Instituto de Síntesis Química y Catálisis Homogénea (ISQCH), CSIC - Universidad de Zaragoza, Pedro Cerbuna 12, 50009 Zaragoza, Spain

Inorg. Chem., Article ASAP

DOI: 10.1021/acs.inorgchem.5b00846

Publication Date (Web): July 21, 2015

Copyright © 2015 American Chemical Society

*Phone: (+34)976-762559. E-mail: sicilia@unizar.es.

Synopsis

New Pt2(III,III)X2 half-lantern compounds resulted in the C−X bond activation in haloalkanes (CHCl3,CHBr3, CHI3, or CH3I) by the corresponding Pt2(II,II) derivative. Mechanistic studies using 13CH3I revealed that this reaction initiates with the thermal oxidative addition to render [I(bzq)Pt(μ-N^S)2Pt(bzq)(13CH3)], which photochemically transforms into [Pt2(bzq)2(μ-N^S)2I2]. In the presence of O2, the methylperoxo intermediate [I(bzq)Pt(μ-N^S)2Pt(bzq)(O−O13CH3)}] was detected, which, in the presence of 13CH3I, renders the final product together with 13CH3OH.

http://pubs.acs.org/doi/pdf/10.1021/acs.inorgchem.5b00846

Abstract

The half-lantern compound [{Pt(bzq)(μ-N^S)}2] (1) [bzq = benzo[h]quinoline, HN^S = 2-mercaptopyrimidine (C4H3N2HS)] reacts with CH3I and haloforms CHX3 (X = Cl, Br, I) to give the corresponding oxidized diplatinum(III) derivatives [{Pt(bzq)(μ-N^S)X}2] (X = Cl 2a, Br 2b, I2c). These compounds exhibit half-lantern structures with short intermetallic distances (∼2.6 Å) due to Pt–Pt bond formation. The halogen abstraction mechanisms from the halocarbon molecules by the Pt2(II,II) compound 1 were investigated. NMR spectroscopic evidence using labeled reagents support that in the case of 13CH3I the reaction initiates with an oxidative addition through an SN2 mechanism giving rise to the intermediate species [I(bzq)Pt(μ-N^S)2Pt(bzq)(13CH3)}]. However, with haloforms the reactions proceed through a radical-like mechanism, thermally (CHBr3, CHI3) or photochemically (CHCl3) activated, giving rise to mixtures of species [X(bzq)Pt(μ-N^S)2Pt(bzq)R] (3a–c) and [X(bzq)Pt(μ-N^S)2Pt(bzq)X] (2a–c). In these cases the presence of O2 favors the formation of species 2 over 3. Transformation of 3into 2 was possible upon irradiation with UV light. In the case of [I(bzq)Pt(μ-N^S)2Pt(bzq)(13CH3)}] (3d), in the presence of O2 the formation of the unusual methylperoxo derivative [I(bzq)Pt(μ-N^S)2Pt(bzq)(O–O13CH3)}] (4d) was detected, which in the presence of 13CH3I rendered the final product [{Pt(bzq)(μ-N^S)I}2] (2c) and 13CH3OH.