Inorganic Chemistry, Vol.33, No.9, 1940-1947, 1994
Rational Construction of Metallointercalators - Syntheses, Structures, and Characterizations of Isomers of ((2S,9S)-Diamino-4,7-Diazadecane)(9,10-Phenanthrenequinone Diimine)Rhodium(III)
In an effort to design metallointercalators which bind DNA with predictable sequence specificity, a series of isomers of the complex [Rh(Me2trien)phi]3+ (Me2trien = (2S,9S)- or (2R,9R)-2,9-diamino-4,7-diazadecane; phi = 9,10-phenanthrenequinone diimine) have been constructed. Here we report the synthesis and characterization of all six diastereomers (2alpha and 4beta) of [Rh[(SS)-Me2trien]phi]3+ (1a-f) and their enantiomers. The isomer distribution of products formed is found to depend on the reaction sequence used. Reaction of RhCl3 with 9,10-diaminophenanthrene and then with (S,S)-Me2trien followed by air oxidation results in no substantial formation of a-isomers. However reaction of [Rh[(S,S)-Me2trien]Cl2]Cl with 9,10-diaminophenanthrene followed by air-oxidation yields about 30% alpha-isomers 1a and 1d (ratio 6:1). No asymmetric induction at the rhodium center is observed (ratio of LAMBDA-isomers (1a-c) to A-isomers (1d-f) is 1:1). The diastereomers are separated by reversed-phase C18 HPL-chromatography. X-ray crystallography and base-catalyzed epimerization have been used to identify and characterize the isomers in detail. Crystal structures are reported for LAMBDA,alpha-[Rh[(2S,9S)-Me2trien]phi](PF6)2Cl.H2O (monoclinic crystal system, space group P2(1), Z = 2, a = 7.450(7) angstrom, b = 21.347(6) angstrom, c = 10.285(3) angstrom, beta = 95.92(5)degrees, V = 1627(2) angstrom3), LAMBDA,anti-beta-[Rh[(2S,9S)-Me2trien]phi]Cl3.3.9H2O (monoclinic crystal system, space group C2,Z = 4, a = 28.366-(9) angstrom, b = 10.317(4) angstrom, c = 10.014(2) angstrom, beta = 90.71(2)degrees, V = 2930(4) angstrom3), LAMBDA,alpha-[Rh[(2R,9R)-Me2trien]phi](ClO4)3 (monoclinic crystal system, space group P2(1), Z = 4, a = 8.323(5) angstrom, b = 18.432(16) A, c = 19.913(8) angstrom, beta = 90.46(4)degrees, V = 3055(3) angstrom3), and LAMBDA,syn-beta-[Rh[(2R,9R)-Me2trien]phi] [(+)-Sb-tartrate]2ClO4.8H2O (triclinic crystal system, space group P1 (No. 1), Z = 1, a = 11.303(3) angstrom, b = 11.409(4) angstrom, c = 11.875(4) angstrom, alpha = 92.69(3)degrees, beta = 114.66(3)degrees, gamma = 117.42(3)degrees, V = 1179.8(7) angstrom3). Characteristic features of the H-1 NMR, UV/visible, and CD spectroscopic data provide a basis for the rapid assignment of absolute and relative configurations of complexes with the structure [Rh(R2trien)phi]3+.