Abstract
The reaction of thioimidazolylborate-zinc(II)-perchlorate complex [Tt
xyly
·Zn− OClO
3
] 1 (Tt
xyly
=hydrotris[N-xylyl-thioimidazolyl]borate) with cysteine and its derivative N-acetyl cysteine and S-methyl cysteine leads to the formation of three new monomeric and dimeric thiolate complexes: [Tt
xyly
·Zn− Cys− Zn·Tt
xyly
] 2, [Tt
xyly
·Zn− Cys(NAc)− Zn·Tt
xyly
] 3, and [Tt
xyly
·Zn− Cys(SMe)] 4. The attachment of the cysteine derivatives to the Tt·Zn unit serves as structural models for the active site of methionine synthase. Methylation of the coordinated thiolate in the dinuclear zinc(II) complex 2 with methyl iodide appears to occur intramolecularly at the zinc-bound thiolates, forming methyl thioether-containing zinc(II) complex [Tt
xyly
·Zn− Cys(SMe)] 4 and iodo complex [Tt
xyly
·Zn− I] 5 with a clean second-order reaction of k=1.0×10
−5
M
−1
s
−1
.