http://www.cnr.it/ontology/cnr/individuo/prodotto/ID53918

Dynamic NMR study of ethene exchange in cationic CNN-type platinum (II) complexes (Articolo in rivista)

Type

Prodotto della ricerca (Classe)
Articolo in rivista (Classe)

Label

Dynamic NMR study of ethene exchange in cationic CNN-type platinum (II) complexes (Articolo in rivista) (literal)

Anno

2010-01-01T00:00:00+01:00 (literal)

Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#doi

10.1021/ic901078u (literal)

Alternative label

M.R. Plutino; L. Fenech; S. Stoccoro; S. Rizzato; A. Albinati; C. Castellano (2010)
Dynamic NMR study of ethene exchange in cationic CNN-type platinum (II) complexes
in Inorganic chemistry; American Chemical Society, Washington (Stati Uniti d'America)
(literal)

Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori

M.R. Plutino; L. Fenech; S. Stoccoro; S. Rizzato; A. Albinati; C. Castellano (literal)

Pagina inizio

407 (literal)

Pagina fine

418 (literal)

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49 (literal)

Rivista

Inorganic chemistry (Rivista)

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12 (literal)

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2 (literal)

Note

SCImago (literal)
ISI Web of Science (WOS) (literal)

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Istituto per lo Studio dei Materiali Nanostrutturati, ISMN-CNR, Unità di Messina-Sezione di Palermo, Messina, Italy. Dipartimento di Chimica Inorganica, Chimica Analitica e Chimica Fisica, Università di Messina, Salita Sperone 31, 98166 Vill. S. Agata, Messina, Italy. Dipartimento di Chimica, Università di Sassari, via Vienna 2, 07100, Sassari, Italy. Dipartimento di Chimica Strutturale e Facoltà di Farmacia, via Venezian 21, Università di Milano, 20133, Milano, Italy. (literal)

Titolo

Dynamic NMR study of ethene exchange in cationic CNN-type platinum (II) complexes (literal)

Abstract

Cationic ethylene platinum(II) complexes of the type [Pt(CNN)(C(2)H(4))](+), containing a methyl fragment and different diimines (NN), or terdentate (kappa C-kappa(2)NN') anionic ligands, were synthesized and fully characterized both as solids and in solution [NN = 2,2'-dipyddylamine, 1; 2,2'-dipyridylsulfide, 2; 1,10-phenanthroline, 3; 4,7-diphenyl-1,10-phenanthroline, 4; 3,4,7,8-tetramethyl-1,10-phenanthroline, 5; 2,2'-bipyridine, 6; HC-NN = 6-tert-butyl-2,2'-bipyridine, 7; 6-neo-pentyl-2,2'-bipyridine, 8; 6-phenyl-2,2'-bipyridine, 9; 6-(alpha-methyl)benzyl-2,2'-bipyridine, 10; 6-((x-ethyl)benzyl-2,2'-bipy dine, 11; 6-(alpha,alpha-dimethyl)benzyl-2,2'-bipyhdine, 12]. Crystals suitable for X-ray analysis of complexes 5 and 7 were obtained. Ethene exchange at the cyclometalated platinum(II) complexes 7, 8, and 10-12 was studied by (1)H NMR line-broadening experiments in chloroform-d, as a function of both temperature and olefin concentrations. For the other prepared complexes the process was too fast to be monitored on the NM R time scale even at the lowest temperature. The ethylene exchange rates show a linear dependence on the concentration of the free ligand, with a negligible k(1) term indicating that either a solvolytic or a dissociative pathway to the products is absent or negligible. The values of the second-order rate constants kexc, as obtained by linear regression analysis of the experimental data at 298 K, are in a range of ca. 10(4) - 10(5) s(-1) m(-1). The activation entropies are negative, ranging between - 129 and - 112 J K(-1) mol(-1), as expected for associative processes. The activation process is largely entropy controlled: the TAS* contribution to the free energy of activation is extremely large, amounting to more than 80% for all complexes, with a smaller enthalpy contribution. All the experimental findings evidence that the mechanism takes place via an associative attack by the entering olefin, through a well-ordered, stable pentacoordinated transition state with the two ethene molecules on the trigonal plane. The reactivity of [Pt(CNN)(C(2)H(4))](+) complexes is strongly dependent on the choice of coordinated 6-substituted-2,2'-bipyridines, especially when the terdentate anionic fragment is capable of generating steric crowding and congestion on the coordination plane. (literal)

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