Heteronuclear μ-1-methylcytosinato-N3,N4 complexes containing very short Pt → Cu dative bonds

Abstract A series of mixed Pt 11 ,Cu 11 complexes derived from trans -[ a 2 Pt (1- MeC - N 3) 2 ] 2+ (a = NH 3 or CH 3 NH − ( 1,2 ), OH − ( 3 ), NH 3 ,H 2 O ( 4 ), coordinated to Pt via N3) and of general formula trans -[ a 2 Pt (1- MeC − - N 3, N 4) 2 CuL ] n + with L = μ-CO 3 2− ( 1,2 ), OH − ( 3 ), NH 3 ,NH 3 H 2 O ( 4 ) , 1-MeC-N3 ( 5 ), 9-EtGH-N7,H 2 O ( 6 ) have been isolated and characterized by X-ray analysis. In all compounds a trans - a 2 Pt II entity is bound to two cytosine nucleobases via N3 sites each, whereas a Cu II is bound to two monodeprotonated N4 sites. In all cases Pt II represents a ligand of Cu II , which either displays a distorted square-planar ( 1,2,3,5 ) or a pentacoordinate environment ( 4,6 ). Pt II Cu II distances are very short, ranging from 2.49 to 2.56 A in the six compounds. EPR spectra of frozen solutions have been examined in several cases. They appear, at least for 4a and 5 , to be consistent with PtCu hyperfine interactions rather than the presence of two different Cu-only species.