I remember writing on metathesis before. So, let's add some new things that I learned.
"..the first observation of the metathesis of propene at high temperature was reported in 1931.
Schrock, then at Du Pont, tried to synthesize [Ta(CH2CMe3)5], which would not contain b-hydrogens and thus, according to this principle, should have been stable. Good luck smiles only on good scientists, and the expected compound did not form...led to the isolation of the first stable metal-alkylidene complex, [Ta(CH2CMe3)3(=CHCMe3)]."