Abstract
Two new functionalized S
3Zn-bound pyridinethiol complexes [TtiZn–SpyH]
2·HClO
4
1 and [TtiZn–Spy]
2 [Tti
=
tris(2-mercapto-1-xylyl-imidazolyl)hydroborate, SpyH
=
pyridine-2-thiol, and Spy
=
pyridine-4-thiol] were synthesized and characterized. Structural determination of complex
1 showed that the coordination geometry around zinc atom is ideally regular tetrahedral with three thione donors from the ligand Tti and one thiolate donor from the coligand pyridine-2-thiol. The average Zn(1)–S(thione) bond length is 2.349
Å and the Zn(1)–S(thiolate) bond length is 2.289
Å. The reactivity studies of both complexes
1 and
2 as models for the active sites of
thiolate-alkylating enzymes toward methylation reactions showed that
1 is much less susceptible to methylation than that of complex
2. This decrease in the nucleophilicity of complex
1 could be explained by electronic effects of the pyridinum salts as well as the steric hindrance, which is provided by the perchlorate anion.