An alkoxide of this metal is used to catalyze the disproportionation of aldehydes through a hemiacetal intermediate in the Tishchenko reaction. (10[1])A compound containing this metal is used for the conjugate addition of cyanide to alpha, beta-unsaturated carbonyls in a reaction named for Nagata. Chelation of this metal to the methoxy group of a Weinreb amide (10[1])allows it to be reduced to an aldehyde (10[1])by a reagent containing (-5[1])this metal and two isobutyl groups. (10[1]-5[1])Titanocene (-5[1])dichloride (-5[1])is reacted with a complex (-5[1])containing this metal to generate Tebbe’s reagent. (10[2]-5[1])Either iron (10[1])chloride or (10[1])this metal’s chloride (10[1])can be used as Lewis acids (10[2])during (10[1])Friedel–Crafts (10[1])reactions. A (10[1])reducing agent stronger than sodium borohydride contains lithium, this metal, (10[2])and four hydrogen atoms. For 10 points, name this lightweight (10[1])metal (10[1])produced via the Hall–Héroult (10[1])process. (10[2])■END■ (10[3])