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Preparation of Dimethyl and Chloro/Methyl Complexes of Platinum(II) Supported by α ‐Diimine Ligands: Trends in the Ease of Oxidation to Platinum(IV)
Author(s) -
Scollard John D.,
Day Mike,
Labinger Jay A.,
Bercaw John E.
Publication year - 2001
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/1522-2675(20011017)84:10<3247::aid-hlca3247>3.0.co;2-w
Subject(s) - diimine , chemistry , platinum , disproportionation , medicinal chemistry , alkyl , coordination sphere , crystallography , kinetics , crystal structure , stereochemistry , catalysis , organic chemistry , physics , quantum mechanics
α ‐Diimine ligands react with the platinum(II) alkyl complexes [(Me 2 S)PtMe 2 ] 2 and (Me 2 S) 2 PtClMe to form (RDAB R′ )PtMe 2 and (RDAB R′ )PtClMe (RDAB R′ =RN=CR′−CR′=NR; R=2,6‐Me 2 Ph, 2,6‐(CHMe 2 ) 2 Ph, 3,5‐Me 2 Ph, 3,5‐(CF 3 ) 2 Ph, C 6 H 11 ; R′=Me, H). The oxidation of these complexes with Cl 2 , I 2 , N ‐chlorosuccinimide, [PtCl 6 ] 2− and (TMEDA)PtMe 2 I 2 has been investigated. Attempts to determine the oxidation potentials of the Pt II complexes electrochemically yielded only irreversible one‐electron oxidations. However, a qualitative ordering of increasing difficulty of oxidation has been determined for the series (RDAB R′ )PtMe 2 <(RDAB R′ )PtClMe<(RDAB R′ )PtCl 2 ≪(RDAB R′ )PtMe(solvent)] + . The oxidation proceeds via a two‐electron inner‐sphere electron transfer from a bridged binuclear intermediate. The oxidation of (RDAB R′ )PtMe 2 by (TMEDA)PtMe 2 I 2 exhibits characteristic third‐order kinetics, first‐order each in [Pt II ], [Pt IV ] and [I − ]. Oxidation by a one‐electron process in MeCN solution results in a rapid subsequent disproportionation to Pt II Me and Pt IV Me 3 cations with MeCN occupying the fourth or sixth coordination sites. Single‐crystal X‐ray structure determinations for [(2,6‐Me 2 PhDAB Me )PtMe 3 (MeCN)] + [PtCl 6 ] 0.5 (MeCN) and [(CyDAB H )PtMe 3 (MeCN)] + [PtCl 6 ] 0.5 (MeCN) are reported.