Promotion of TH₃ (T = Si and Ge) group transfer within a tetrel bond by a cation-π interaction

The possibility of the transfer of the TH₃ group across a tetrel bond is considered by ab initio calculations. The TB is constructed by pairing PhTH₃ (Ph = phenyl; T = Si and Ge) with bases NH₃, NHCH₂, and the C₃N₂H₄ carbene. The TH₃ moves toward the base but only by a small amount in these dimers. However, when a Be²⁺ or Mg²⁺ dication is placed above the phenyl ring, the tetrel bond strength is greatly magnified reaching up to nearly 100 kcal mol^-1. This dication also induces a much higher degree of transfer which can be best categorized as half-transfer for the two N-bases and a near complete transfer for the carbene.