CCL: Explanation on specific metal reactivity

Sent to CCL by: Sebastian Kozuch [seb.kozuch^]
For all the computational organometallists out there:
Why Ir and not other metals catalyses hydrogenation?
Why Pd for cross-coupling?
Why Ru for metathesis?
I cannot find any specific explanation that connects a metal to its reaction. Tons of mechanistic studies and reviews, without explanations on why this metal and only this metal for this reactions.
Is this info hidden or unknown? Any good paper or book?