Synthesis, structure, and reactivity of borate ester coordinated organobismuth compounds

A new class of hypervalent organobismuth compounds functionalized With coordinating pinacolborate esters of the nature ArBiCl2 (2), Ar3Bi (3), ArPh2Bi (4), Ar3BiCl2 (5), and ArPh2BiCl2 (6), where Ar = 3-fluoro-2-pinacolatoboronphenyl, have been prepared and structurally characterized. The Bi center dot center dot center dot O distance is between 2.58 and 3.47 angstrom in the solid state for all compounds, and reasonable bonding interactions are presumed to exist in compounds 2-4 and 6, where Bi center dot center dot center dot O < 3.0 angstrom. When ArPh2BiCl2 (6) is exposed to CsF in the presence of furan, the [4 + 2] cycloaddition product of 3-fluorobenzyne + furan, 8, is isolated in 58% yield. Mechanistic evidence is offered to support the claim that 6 undergoes an unprecedented fluoride-promoted fragmentation to generate 3-fluorobenzyne, pinacol, BF3, and Ph2BiF.