Primary selectivity in the activation of the carbon-hydrogen bonds of propane by silica supported zirconium hydride

The stoichiometric reaction between propane and (≡ SiO)₃ZrH leads to the formation of a mixture of (≡ SiO)₃ZrCH(CH₃)₂ and (= SiO)₃ZrCH₂CH₂CH₃. The relative amounts of each complex resultant from the reaction was determined by (a) reaction of (≡ SiO)₃ZrC₃H₇ with D₂O to produce quantitatively a mixture of CH₃CH₃CH₂D and CH₃CHDCH₃ which in turn were discriminated by mass spectroscopy, and (b) reaction of (≡ SiO)₃ZrC₃H₇ with O₂ followed by HCl yielding 1-propanol and 2-propanol in low yield. Each of these methods indicated that (≡ SiO)₃ZrCH₂CH₂CH₃ was the major product of propane activation. The catalytic deuteration of propane by deuterium at room temperature catalysed by (= SiO)₃ZrH showed that the primary C-H bonds of propane reacted seven times faster than the secondary C-H bonds. A mechanism of degenerate carbon-hydrogen bond activation is invoked for the latter reaction.