A hydrogen-bridged bis(silylene) complex, which can be viewed as a snapshot of a transition state for 1,3-hydrogen migration, was isolated, and its unprecedented WSi2H four-membered-ring structure with a short diagonal Si-Si distance was revealed by X-ray crystallography. NMR studies including determination of the W-Si, Si-Si, and Si-H coupling constants and theoretical calculations suggest that a novel multicenter bond is formed in the WSi2H system, in which the bridging hydrogen takes on a hydridic nature.

Hydrogen-bridged bis(silylene) complexes of ruthenium and iron were synthesized as the first examples of this type containing Group 8 metals and their rare four-membered ring structures and multi-center bonding interactions at the M-Si-H-Si moiety were clarified by NMR spectroscopy, X-ray crystallography and theoretical calculations.

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