Iron(II) Complexes of an Anionic Bis(ylide)diphenylborate Ligand

Double deprotonation of the salt [Ph 2 B(PMe 3 ) 2 ][OTf] ( 1 ) provides access to a bis(ylide)diphenylborate ligand that is readily transferred in situ o iron(II). Depending on the reaction stoichiometry, both the "ate" complex [Ph 2 B(Me 2 PCH 2 ) 2 Fe(μ-Cl) 2 Li(THF) 2 ] ( 2 ) and the homoleptic complex [Ph 2 B(Me 2 PCH 2 ) 2 ] 2 Fe( 3 ) can be prepared from FeCl 2 (THF) 1.5 . Further reaction of 3 with FeCl 2 (THF) 1.5 produces the chloride-bridged dimer [Ph 2 B(Me 2 PCH 2 ) 2 Fe(μ-Cl) 2 Fe(CH 2 PMe 2 ) 2 BPh 2 ]( 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 Bu provides the six-coordinate, diamagnetic complex [Ph 2 B(Me 2 PCH 2 ) 2 Fe(CN 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.