Three nicotine molecules or three picolinic acid molecules are coordinated 
Three nicotine molecules or three picolinic acid molecules are coordinated to this element in a series of compounds that enhance glucose tolerance. The first Fischer carbene was a complex containing this element bonded to four carbonyl groups, and that complex participates in the Dotz reaction. Six equivalents of a reagent in which this element is bonded to chloride are used in the Takai olefination. It's not sulfur or oxygen, but reagents containing this element often have one of its (*) "esters" as an intermediate. A gentler alternative to one reagent containing this metal was developed by Corey and Suggs and consists of this element bonded to two oxygen and two chlorine atoms, with a pyridinium counterion. Another reagent containing this element is used to transform primary alcohols to carboxylic acids. For 10 points, name this transition metal, whose trioxide is dissolved in sulfuric acid and acetone to create Jones' reagent.
Three nicotine molecules or three picolinic acid molecules are coordinated to this element in a series of compounds that enhance glucose tolerance.
chromium [or Cr]