title: PGSE and NOE NMR evidence for higher order aggregation in some cationic ruthenium complexes in both protic and aprotic solvents.
abstract: PGSE and NOE NMR measurements were carried out for complexes [Ru(eta(6)-cymene)((2-R-C(6)H(4))N=C(Me)-C(Me)=N(2-R-C(6)H(4)))Cl]X (X = BF(4) or BPh(4)) in both protic and aprotic solvents with a relative permettivity (epsilon(r)) ranging from 2.27 (benzene-d(6)) to 46.45 (dimethyl sulfoxide-d(6)). PGSE and NOE results indicate that complexes have a tendency to aggregate even in medium-polarity solvents such as ethanol (epsilon(r) = 24.55) and methanol (epsilon(r) = 32.66). In addition, the aggregation process is favored by a decrease of epsilon(r) and, unexpectedly, by protic solvents. NOE measurement investigations, interpreted with the help of theoretical calculations and confirmed by X-ray single crystal studies, suggest different aggregation processes for the two counteranions: two cationic moieties approach each other when X = BF(4) while the anion bridges two cationic moieties when X = BPh(4).
authors.affiliation: Dipartimento di Chimica, Università degli Studi di Perugia, Via Elce di Sotto 8, 06123 Perugia, Italy.
authors.forename: Daniele
authors.initials: D
authors.lastname: Zuccaccia
authors.forename: Stefano
authors.initials: S
authors.lastname: Sabatini
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Bellachioma
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Cardaci
authors.forename: Eric
authors.initials: E
authors.lastname: Clot
authors.forename: Alceo
authors.initials: A
authors.lastname: Macchioni