Palladium-yttrium catalysts

Alkenes and alkynes can also add to each other to give cyclic products in other ways (see 15-61 and 15-63). The first exclusive exo-dig carbocyclization was reported using HfCU as a catalyst. Alkynes also add to alkenes for form rings in the presence of a palladium catalyst or a zirconium catalyst. " Carbocyclization of an alkene unit to another alkene unit was reported using an yttrium catalyst and alkenes add to alkynes to give cyclic compounds with titanium catalysts. ... 

A number of transition metal complexes will catalyze the dehydrogenative coupling of organotin tin hydrides, R SnI I, to give the distannanes, RjSnSnRj.443 These metals include palladium,449 gold,450, hafnium,451 yttrium, and ruthenium.452 The catalyst that is most commonly used is palladium, often as Pd(PPh3>4, and the most active catalysts appear to be the heterobimetallic Fe/Pd complexes, in which both metals are believed to be involved in the catalysis.443... 

In the 1990 s research on the replacement of the noble metals (platinum, rhodium, palladium) in the catalyst has centered on oxides of cobalt with smaller amounts of co-catalysts such as lanthanum metal and oxides of scandium, yttrium and lanthanum. It is believed that new catalyst designs will provide more-efficient, lighter-weight gauzes that will reduce (but not eliminate) the amount of platinum required91. 

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