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Kinetics of Aquation and Anation of Ruthenium( II ) Arene Anticancer Complexes, Acidity and X‐ray Structures of Aqua Adducts
Author(s) -
Wang Fuyi,
Chen Haimei,
Parsons Simon,
Oswald Iain D. H.,
Davidson James E.,
Sadler Peter J.
Publication year - 2003
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200304724
Subject(s) - aquation , chemistry , adduct , medicinal chemistry , ligand (biochemistry) , ruthenium , hydrolysis , stereochemistry , ring (chemistry) , kinetics , reaction rate constant , catalysis , organic chemistry , biochemistry , physics , receptor , quantum mechanics
The aqua adducts of the anticancer complexes [(η 6 ‐X)Ru(en)Cl][PF 6 ] (X=biphenyl (Bip) 1, X=5,8,9,10‐tetrahydroanthracene (THA) 2, X=9,10‐dihydroanthracene (DHA) 3; en=ethylenediamime) were separated by HPLC and characterised by mass spectrometry as the products of hydrolysis in water. The X‐ray structures of the aqua complexes [(η 6 ‐X)Ru(en)Y][PF 6 ] n , X=Bip, Y=0.5 H 2 O/0.5 OH, n =1.5 ( 4 ), X=THA, Y=0.5 H 2 O/0.5 OH, n =1.5 ( 5 A ), X=THA, Y=H 2 O, n =2 ( 5 B ), and X=DHA, Y=H 2 O, n =2 ( 6 ), are reported. In complex 4 there is a large propeller twist of 45° of the pendant phenyl ring with respect to the coordinated phenyl ring. Although the THA ligand in 5 A and 5 B is relatively flat, the DHA ring system in 6 is markedly bent (hinge bend ca. 35°) as in the chloro complex 3 (41°). The rates of aquation of 1 – 3 determined by UV/Vis spectroscopy at various ionic strengths and temperatures (1.23–2.59×10 −3 s −1 at 298 K, I =0.1 M ) are >20× faster than that of cisplatin. The reverse, anation reactions were very rapid on addition of 100 m M NaCl (a similar concentration to that in blood plasma). The aquation and anation reactions were about two times faster for the DHA and THA complexes compared to the biphenyl complex. The hydrolysis reactions appear to occur by an associative pathway. The p K a values of the aqua adducts were determined by 1 H NMR spectroscopy as 7.71 for 4 , 8.01 for 5 and 7.89 for 6 . At physiologically‐relevant concentrations (0.5–5 μ M ) and temperature (310 K), the complexes will exist in blood plasma as >89 % chloro complex, whereas in the cell nucleus significant amounts (45–65 %) of the more reactive aqua adducts would be formed together with smaller amounts of the hydroxo complexes (9–25 %, pH 7.4, [Cl − ]=4 m M ).