NITRIDOOSMIUM(VI) AND NITRIDORUTHENIUM(VI) COMPLEXES OF CYSTEINE(2-) AND RELATED LIGANDS

Anionic complexes of nitridoruthenium(VI) and nitridoosmium(VI) containing covalently bound N-acetyl-L-cysteinato, 3-sulfidopropionato, and 3-sulfidopropionamidato ligands have been synthesized to model the binding of delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine to the iron center in the metalloenzyme isopenicillin N synthetase. The complexes are prepared by the reaction of N-acetyl-L-cysteine, 3-mercaptopropionic acid, and 3-mercaptopropionamide with [NBu(n)4][Os(N)(OSiMe3)4], [NBu(n)4][Os(N)Cl4], [NBu(n)4][Ru(N)(CH2SiMe3)4], or [NBu(n)4][Ru(N)(OSiMe3)4]. They have been characterized by elemental analysis and IR and NMR spectroscopy. Spectroscopic data show that the N-acetyl-L-cysteinato and 3-sulfidopropionato ligands are bound to the metal center through sulfur and oxygen, while the 3-sulfidopropionamidato ligands are bound through sulfur and nitrogen. The molecular structures of cis-[NBu(n)4][Os(N)(O2CCH2CH2S)2], [NBu(n)4][Os(N){O2CCH(NHCOCH3)CH2S}2], and [PPh4][Ru(N)(NHCOCH2CH2S)2)] were determined by single-crystal X-ray diffraction. These complexes were found to have distorted square-pyramidal geometry around the metal center. cis-[NBu(n)4][Os(N)(O2CCH2CH2S)2] crystallizes in monoclinic space group P2(1)/c with a = 13.718 (6) angstrom, b = 10.080 (3) angstrom, c = 19.890 (5) angstrom, beta = 92.16 (3) angstrom, and Z = 4. [NBu(n)4][Os(N){L-O2CCH(NHCOCH3)CH2S}2] crystallizes in monoclinic space group C2 with a = 18.371 (6) angstrom, b = 9.261 (1) angstrom, c = 21.125 (7) angstrom, beta = 102.92 (3) angstrom, and Z = 4. [PPh4][Ru(N)(NHCOCH2CH2S)2)] crystallizes in orthorhombic space group Pbca with a = 23.022 (1) angstrom, b = 16.120 (1) angstrom, c = 15.728 (1) angstrom, and Z = 8.