Double
deprotonation of the salt [Ph2B(PMe3)2][OTf] (1) provides access to a bis(ylide)diphenylborate
ligand that is readily transferred in situ to iron(II).
Depending on the reaction stoichiometry, both the “ate”
complex [Ph2B(Me2PCH2)2Fe(μ-Cl)2Li(THF)2] (2) and
the homoleptic complex [Ph2B(Me2PCH2)2]2Fe(3) can be prepared from
FeCl2(THF)1.5. Further reaction of 3 with FeCl2(THF)1.5 produces the chloride-bridged
dimer [Ph2B(Me2PCH2)2Fe(μ-Cl)2Fe(CH2PMe2)2BPh2](4). Attempts to reduce or alkylate 4 provide 3 as the only isolable product, likely a consequence of the
low steric hindrance of the bis(ylide)diphenylborate ligand. On the
other hand, reaction of 4 with the strong field ligand
CN
t
Bu provides the six-coordinate, diamagnetic
complex [Ph2B(Me2PCH2)2Fe(CN
t
Bu)4][Cl](5). Electronic structure calculations for the bis(ylide)diphenylborate
ligand and homoleptic complex 3 suggest that the C(ylide)
atoms are strong σ-donors with little π-bonding character.
These initial results suggest the potential for this bis(ylide)diphenylborate
ligand in coordination chemistry.