Thiols complex hydrides

This complex has been used for the synthesis of unusual complexes containing thiol ligands,1 dihydrogen ligands,1 or ligands with short proton-hydride distances.1 1... 

The starting material is always the chalcogenol and, consequently, is more used for thiols than selenols and tellurols. There are several types of reactions depending if the starting materials are metal hydrides (hydrogen elimination), complexes with M C (alkane elimination), M-N (transamination), or M-O (hydrolysis) bonds. 

Reaction of Resin-Bound Iron Complex (54) with Alkyl Mercaptans, Thiophenols, and Phenols (Fig. 9)31. Sodium thiolates are prepared analogously to the alkoxides from thiol and sodium hydride, except that dry DMF is used as a solvent. The substitution on the polymer-bound arene (54) is performed at 70° in DMF within 16 h. The resin is filtered and washed with DMF (2 x 50 ml), MeOH (2 x 50 ml), H20 (2 x 50 ml), MeOH (2 x 50 ml), and CH2CI2 (3 x 50 ml) and then dried in vacuo at 40° to yield a red resin. 

For the Ru system the thiol hydride could not be detected, while for the Rh system and also [IrH2(HS(CH2)3SH)(PCy3)2]+(which similarly catalyzes D2/H + exchange (79)), the H2 complex could not be seen but is a transient. A related system, Ni(NHP Pr3)(S3) clearly shows that heterolysis of D2 can also occur at nickel sites, which may be relevant to H2 activation in [FeNi] hydrogenases (78). 

In search of model systems for iron hydrogenases, Sellmann et al. (67) investigated the interaction of I e(hdt)2 2 with H+, H2, and H . Formation of H2 was observed in the reaction with H+. The reaction mechanism was proposed to follow a step-wise protonation, forming a thiol-hydride complex and H2 is proposed to form via heterolytic elimination from the metal hydride species (Scheme 6). Theoretical calculations suggest that concerted H2 elimination from a dithiol species is thermally forbidden (67). 

Nucleophilic attack on ( -alkene)Fp+ cations may be effected by heteroatom nucleophiles including amines, azide ion, cyanate ion (through N), alcohols, and thiols (Scheme 39). Carbon-based nucleophiles, such as the anions of active methylene compounds (malonic esters, /3-keto esters, cyanoac-etate), enamines, cyanide, cuprates, Grignard reagents, and ( l -allyl)Fe(Cp)(CO)2 complexes react similarly. In addition, several hydride sources, most notably NaBHsCN, deliver hydride ion to Fp(jj -alkene)+ complexes. Subjecting complexes of type (79) to Nal or NaBr in acetone, however, does not give nncleophilic attack, but instead results rehably in the displacement of the alkene from the iron residue. Cyclohexanone enolates or silyl enol ethers also may be added, and the iron alkyl complexes thus produced can give Robinson annulation-type products (Scheme 40). Vinyl ether-cationic Fp complexes as the electrophiles are nseful as vinyl cation equivalents. ... 

The enzyme systems are complex two reactions are catalyzed, namely formation of a thioester and its subsequent hydrolysis to free acid. Because little or no tritium or deuterium from solution is incorporated into the rearranged product, a hydride shift was assumed. With optically pure thiols like (36) the rearrangement of (37) to (10b) can be catalyzed (equation 21). The methyl mandelate formed has a very modest enantiomeric excess. ... 

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