8.3 C−H Bond Activation
125
A
B
Fig. 8.3 A Relative product branching ratios for metal oxides with n-butane: (a) V 2 O 5
+ , oxygen
transfer dominates, negligible cracking; (b) Nb 2 O 5
+ , small oxygen transfer and cracking channel;
(c) Ta 2 O 5
+ , negligible oxygen transfer, cracking reaction dominates. B Relative product branching
ratios for metal oxides with 1, 3-butadiene. Note various cracking channels which differ with the
metal type and organic composition. Reproduced with permission from Ref. [2]. Copyright 2002
American Chemical Society
on active electron transfer and proton transfer, they participate in radical substitution or allow C–H bond activation by well-designed reactants/catalysts. The homoand heterolytic C–H bond cleavage (as well as functionalization) is well known for
its significance in chemistry and is regarded as a longstanding central challenge
[28, 73–85].
Metal cluster reactivity shows its own novelty in this topic. For example, considerable investigations have been conducted upon the activation of methane by gas-phase
palladium model systems [86–92]. Experimental observations showed that neutral
clusters Pd x (x ≤ 24) tend to adsorb methane with a few exceptions (e.g., Pd 3 and Pd 4 ).
While in contrast, the reactivity of small palladium oxides toward methane finds size
125
A
B
Fig. 8.3 A Relative product branching ratios for metal oxides with n-butane: (a) V 2 O 5
+ , oxygen
transfer dominates, negligible cracking; (b) Nb 2 O 5
+ , small oxygen transfer and cracking channel;
(c) Ta 2 O 5
+ , negligible oxygen transfer, cracking reaction dominates. B Relative product branching
ratios for metal oxides with 1, 3-butadiene. Note various cracking channels which differ with the
metal type and organic composition. Reproduced with permission from Ref. [2]. Copyright 2002
American Chemical Society
on active electron transfer and proton transfer, they participate in radical substitution or allow C–H bond activation by well-designed reactants/catalysts. The homoand heterolytic C–H bond cleavage (as well as functionalization) is well known for
its significance in chemistry and is regarded as a longstanding central challenge
[28, 73–85].
Metal cluster reactivity shows its own novelty in this topic. For example, considerable investigations have been conducted upon the activation of methane by gas-phase
palladium model systems [86–92]. Experimental observations showed that neutral
clusters Pd x (x ≤ 24) tend to adsorb methane with a few exceptions (e.g., Pd 3 and Pd 4 ).
While in contrast, the reactivity of small palladium oxides toward methane finds size