Why thiolates are better nucleophiles, weaker bases than alkoxides?

Answer 1

Thiolates (RS[-]) (that are the conjugate bases of thiols (R-SH)),are better nucleophilic groups because of the presence of atom sulphur which is in turn a very nucleophilic species.

They are weaker bases than alkoxides (R-O[-]) which are the conjugate bases of an alcohol (R-OH) because sulphur atom is less electronegative (and more "willing" to donate its electrons) than oxygen in alkoxides and in turn, less "willing" to form the thiolate from the origin thiol than alcoxide from alcohol.

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