Tuning Reactivity of Platinum(II) Complexes

In order to extend our understanding on the role of the π-backbonding beyond the first
pyridine ring surrounding the Pt(II) centre, we have investigated substitution reactions
of complexes of the type [Pt(N-N-N)Cl] + , (N-N-N = terpy; 4’-(2’’’-CH3-phenyl)terpy; 4’-
(2’’’-CH3-phenyl)-6-(3’’-isoquinoyl)-2,2’-bipyridine and 2-(2’-pyridyl)-1,10-
phenanthroline), with three neutral sulphur nucleophiles (TU, DMTU, and TMTU) and
three anionic nucleophiles (I ¯, Br ¯, and SCN ¯). The structures of the investigated
complexes are shown in Scheme 3.1.
+
CH 3
+ +
N
N
N
N
N Pt N N Pt N N Pt N
N Pt N
Cl
Cl
Cl
Cl
PtCl CH3PhPtCl CH3PhisoqPtCl pyPhenPtCl
Scheme 3.1: Stuctures of the investigated Pt(II) polypyridyl complexes
3.2 Experimental
3.2.1 Materials and Procedures
Methanol (Saarchem) was purchased from Merck and used after purification and drying
over magnesium. Lithium trifluoromethanesulfonate (96%) and the nucleophiles:
§ thiourea (TU, 99%), N,N-dimethyl-2-thiourea (DMTU, 99%), N,N,N,N-tetramethyl-2-
thiourea (TMTU, 98%), sodium bromide (99%) and sodium thiocyanide (98%) were
obtained from Aldrich and was used as supplied. Sodium iodide (NaI, 99%, Saarchem)
was obtained from Merck and used as supplied. The platinum complexes, [Pt{4’-(2’’’-
CH3-phenyl)-2,2’:6’,2’’-terpyridine}Cl]CF3SO3 CH3PhPtCl and [Pt{4’-(2’’’-CH3-phenyl)-6-
(3’’-isoquinoyl)-2,2’-bipyridine}Cl]SbF6 CH3PhisoqPtCl were synthesised and
characterised using literature methods. 18,19 Details of the synthesis and characterisation
of CH3PhPtCl and CH3PhisoqPtCl have been reported previously by Field 19 and our
group. 20 The complex, [Pt{2-(2’-pyridyl)-1,10-phenanthroline}Cl]Cl, pyPhenPtCl, was a
donation from McMillin and co-workers 21 (University of Purdue, West Lafayette,
Indiana, USA). Solutions of the nucleophiles were prepared shortly before use by
dissolution in a 0.1 M LiCF3SO3 solution in methanol whose ionic strength had been
3
CH 3
+