Alcohol and aldehyde adducts of zinc thiolates: Structural modeling of alcoholdehydrogenase

Bis(pentafluorothiophenolato)zinc (1) and bis(2,4,6-triisopropylthiophenola to)zinc (2) can be combined with nitrogen-containing derivatives of benzyl alcohol and benzaldehyde to form (N,O-chelate) zinc thiolates. 2-Pyridylmet hanol as well as 2-quinolylmethanol (HetMeOH) yield [(HetMeO)Zn(SR)](4) (3, 4) having a cyclo-Zn-4(mu-O)(4) backbone and only terminal SR. Likewise, t hiolate 1 and 2-(dimethylamino)benzyl alcohol form zwitterionic [(dimethyla mmoniobenzylato)Zn(SR)(2)](2) (5) with bridging alkoxide and terminal thiol ate. In contrast, 6-picolylmethanol (PicMeOH) and thiolate 1 result in [(Pi cMeOH)Zn(SC6F5)(2)] (6) containing zinc in a tetrahedral ZnNS2O, environmen t. Simple aromatic aldehydes form polymeric complexes [(RCHO)Zn(SC6F5)(2)] (7: R = p-tolyl, 8: R = mesityl) with a [Zn-S](infinity) backbone. Chelatin g aldehydes (CA) yield mononuclear complexes with tetrahedral ZnNS2O coordi nation [(CA)Zn(SC6F5)(2)] (9, CA = pyridine-2-carbaldehyde; 10, CA = 6-meth ylpyridine-2-carbaldehyde: 11. CA = 6-methoxypyridine-2-carbaldehyde; 12, C A = quinoline-2-carbaldehyde; 13, CA = 2-(dimethylamino)benzaldehyde). In c ontrast, N-methylimidaznle-2-carbaldehyde (ImA) is coordinated twice in tet rahedral [(ImA)(2)Zn(SC6F5)(2)] (14) lacking any Zn-O interactions, Pyridin e-2,6-dicarbaldehyde (PDA) forms trigonal bipyramidal [(PDA)Zn(SC6F5)(2)] ( 15) with ZnNO2S2 ligation, The structures of 3. 4, 6, 8, 10, 11, 13, and 14 were determined crystallographically, and the structures of 5 and 15 were deduced from those of the corresponding ZnBr2 complexes. The ZnNS2O coordin ation pattern observed for the enzyme has been reproduced to a very good ap proximation. In complexes 6 and 10, which are almost superimposable, it is realized for both the corresponding alcohol and aldehyde.