title: (35/37)Cl and (16/18)O isotope resolved 195Pt NMR: unique spectroscopic 'fingerprints' for unambiguous speciation of [PtCl(n)(H2O)(6-n)](4-n) (n = 2-5) complexes in an acidic aqueous solution.
abstract: At high magnetic fields the 128.8 MHz (195)Pt NMR of all the species in the series [PtCl(n)(H(2)O)(6-n)](4-n) (n = 2-6) display unique (35/37)Cl isotope effects resulting in a unique 'fine-structure' of each individual resonance, which constitutes an unambiguous spectroscopic 'fingerprint' characteristic of the structure of the octahedral platinum(IV) complex, provided (195)Pt NMR are recorded at optimum magnetic field homogeneity and carefully controlled temperature (293 ± 0.1 K). The detailed (195)Pt resonance fine-structure observed experimentally can readily be accounted for by an isotopologue and isotopomer model for each complex, showing particularly noticeable differences between stereoisomer pairs such as the cis/trans- and fac/mer-complexes. Moreover partial isotopic (18)O enrichment of the coordinated water molecules in the series [Pt(35/37)Cl(n)(H(2)(16/18)O)(6-n)](n-2) (n = 2-6) confirms this model. This technique can thus be considered a novel, direct spectroscopic method of chemical speciation of appropriate platinum(IV) complexes in solution without reference to accurate chemical shifts of authentic members of such a series. These effects are interpreted qualitatively in terms of the high sensitivity of (195)Pt NMR shielding to very small and subtle Pt-(35/37)Cl and Pt-(16/18)OH(2) bond displacements. Preliminary work shows this also applied to the corresponding bromido-complexes.
authors.affiliation: Platinum Metals Chemistry Research Group, Department of Chemistry and Polymer Science, University of Stellenbosch, P Bag X1, Matieland, 7602, South Africa.
authors.forename: Pieter
authors.initials: P
authors.lastname: Murray
authors.forename: Wilhelmus J
authors.initials: WJ
authors.lastname: Gerber
authors.forename: Klaus R
authors.initials: KR
authors.lastname: Koch