Electronic structure factors of Ge-H bond activation by transition metals. Photoelectron spectra of [mn(η⁵-C₅H₅)(CO)₂(HGePh ₃)], [mn(η⁵-C₅H₄Me)(CO)₂(HGePh ₃)], and [mn(η⁵-C₅Me₅)(CO)₂(HGePh ₃)]

The He I photoelectron spectra of [Mn(η⁵-C₅H₅)(CO)₂(HGePh ₃)], [Mn(η⁵-C₅H₄Me)(CO)₂-(HGePh ₃)], and [Mn(η⁵-C₅Me₅)(CO)₂(HGePh ₃)] have been obtained to measure the nature and extent of Ge-H bond interaction with the transition metal centre in these complexes. The principal electronic structure factors contributing to the addition of the Ge-H bond to the transition metal involve the interaction of the Ge-H σ and σ* orbitals with the metal. The shape and splitting pattern of the metal-based ionisation band indicates the extent of Ge-H σ* interaction. The electron distribution between the Ge-H bond and the metal is indicated by the relative stabilities of the metal- and ligand-based ionisations. The electron charge-density shift from the metal to the ligand is negligible in these three complexes and the metal ionisations reflect the formal d⁶ electron count at the metal centre. The electronic structure of the Ge-H interaction with the metal is in the initial stages of Ge-H bond addition to the metal, before oxidative addition has become prevalent. The mechanism of interaction of the Ge-H bond with the manganese centre is predominantly through interaction of the filled Ge-H σ-bonding orbital with the empty metal orbitals. It is concluded that the magnitude of Ge-H σ interaction with the metal centre is similar to that of the corresponding Si-H σ interaction.