Taming Neutral Silylidenebismuthanes (Si═Bi) with a Low-Coordinate Bismuth Atom

Area of Science:

• Organometallic Chemistry
• Main-Group Chemistry
• Silicon-Bismuth Chemistry

Background:

• Heteroleptic double bonds of bismuth are rare due to weak pπ-pπ bonding.
• Isolating unsaturated main-group compounds presents significant synthetic challenges.

Purpose of the Study:

• To synthesize and characterize novel, isolable silylidenebismuthane complexes.
• To investigate the nature of the silicon-bismuth double bond and its reactivity.

Main Methods:

• Synthesis via salt metathesis reaction of LSi^IICl with potassium bis(silyl)bismuthanide complexes.
• Characterization of the resulting silylidenebismuthane complexes.
• Density Functional Theory (DFT) calculations to corroborate bonding and reactivity.

Main Results:

• First isolable silylidenebismuthane complexes, (E)-L(Me₃Si)Si═Bi(SiR₃) (R = Me, ⁱPr), were synthesized in good yields.
• These complexes feature a neutral, strongly polarized silicon-bismuth double bond.
• Reactions with [W(CO)₅(thf)] induced isomerization and formation of terminal Bi→W(CO)₅ complexes, indicating weakened Si═Bi π bonding.

Conclusions:

• The successful synthesis of these silylidenebismuthanes overcomes the limitations of pπ-pπ bond weakness in bismuth compounds.
• The study provides fundamental insights into the electronic structure and reactivity of silicon-bismuth π systems.
• The observed reactivity highlights the potential for further exploration of unsaturated main-group element compounds.