Cobalt(II) tri‐<i>tert</i>‐butoxysilanethiolates: in search of models for catalytic metal site of liver alcohol dehydrogenase

Abstract

Abstract The reaction of dimeric [Co{SSi(O t Bu) 3 } 2 (NH 3 )] 2 ( 1 ) with 2‐picoline at 0 °C leads to the formation of a thiolate complex [Co{SSi(O t Bu) 3 } 2 (NH 3 )(2‐Pic)] ( 3 ), with two different nitrogen ligands in the cobalt(II) coordination sphere. Dissolution of 1 in acetonitrile gives one cobalt(II) thiolate complex with two ammine ligands bonded to metal: [Co{SSi(O t Bu) 3 } 2 (NH 3 ) 2 ]·MeCN ( 4 ). A second, unique, aqua‐ligated cobalt(II) thiolate — [Co{SSi(O t Bu) 3 } 3 (H 2 O)] − + HNEt 3 ( 5 ) — forms when CoCl 2 reacts with an excess of ( t BuO) 3 SiSH in the presence of triethylamine in water. The structures of 3 , 4 and 5 were determined by X‐ray structure methods, revealing a distorted tetrahedral arrangement of ligands around cobalt. Under normal conditions, all three complexes are unstable. 3 loses ammonia to give stable [Co{SSi(O t Bu) 3 } 2 (2‐Pic)] ( 2 ). A reverse reaction is also possible. Moreover, 2 is able to capture water, and there is spectral evidence that a complex [Co{SSi(O t Bu) 3 } 3 (H 2 O)(2‐Pic)] with a CoNOS 2 core, mimicking the cobalt‐substituted liver alcohol dehyrogenase active site, is formed in solution. Copyright © 2002 John Wiley &amp; Sons, Ltd.