Tuning the gap: Doubly Si-bridged ansa-tungstenocene, a proposed intermediate for C-H activation

The doubly Si-bridged ansa-tungstenocene, [W(η5-C5H3)2(SiMe2)2] is calculated to have singlet and triplet states of comparable energy, therefore, on an SCF energy surface there is no barrier to formation of a sigma complex with methane, and formation of a methyl hydride is exo-energetic by −125 kJ mol−1.