Triply bonded transition states

We are therefore faced by the intriguing result that it is apparently easier to break a two-electron, two-center M-Cl bridge than a M-H-M bridge that contains a two-electron, three-center bond. Indeed the transition state (A) contains two large M(C5Me5)ClX entities joined only by one M-H-M bond, and clearly such bonds must be reinforced by M-M bonding. This point is also well illustrated by the very short Ir-Ir distance of 2.455 A found in the tri-ju.-hydrido complex [H3(IrC5Me5)2] (10) which has been likened to a "triply protonated Ir=Ir triple bond. ... 

Finally, it is of interest to relate the levels obtained in terms of this simple bonding unit of transition-metal d states and six oxygen hybrids to the bands we discussed earlier. Three of the d states have no a matrix elements with the hybrid. and we are dropping n matrix elements these three correspond to the triply degenerate state r 25 at the energy e. The other two d states are equally. sliiftcd... 

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