Bis(tetramethylcyclopentadienyl)zirconium dichloride, Zirconium,Dichlorobis[(1,2,3,4,5-H)-1,2,3,4-Tetramethyl-2,4-Cyclopentadien-1-Yl]-, [(CH3)4C5H]2ZrCl2, C18H26ZrCl2