Al/P‐ and Ga/P‐based frustrated Lewis pairs (FLPs) reacted with an azirine under mild conditions under cleavage of the heterocycle on two different positions. Opening of the C−C bond yielded an unusual nitrile–ylide adduct in which a C−N moiety coordinated to the FLP backbone. Cleavage of a C−N bond afforded the thermodynamically favored enamine adduct with the N atom bound to P and Al or Ga atoms. Ring closure was observed upon treatment of an Al/P FLP with electronically unsaturated substrates (4‐(1‐cyclohexenyl)‐1‐aza‐but‐1‐en‐3‐ynes) and yielded by C−N bond formation hexahydroquinoline derivatives, which coordinated to the FLP through P−C and Al−C bonds. Diphenylcyclopropenone showed a diverse reactivity, which depending on steric shielding and the polarizing effect of Al or Ga atoms afforded different products. An AltBu2/P FLP yielded an adduct with the C=O group coordinated to P and Al. The dineopentyl derivative gave an equilibrium mixture consisting of a similar product and a simple adduct with O bound to Al and a three‐coordinate P atom. Both compounds co‐crystallize. The Ga/P FLP only formed the simple adduct with the same substrate. Rearrangement resulted in all cases in C3‐ring cleavage and migration of a mesityl group from P to a former ring C atom by C−C bond formation. Diphenylthiocyclopropenone (evidence for the presence of P=C bonds) and an imine derivative afforded similar products.
Two equivalents of
the phosphinylvinyl Grignard reagent Mes2PC[MgCl(THF)2]CHPh (2) reacted
with MeGaCl2, EtGaCl2, or MeInCl2 by salt elimination and formation of the frustrated Lewis pairs 4–6, which have two Lewis basic P atoms
in their molecular backbones. These FLPs coordinated and solubilized
MCl2 compounds (M = Zn, Cd, Hg) by the chelating coordination
of the Zn, Cd, or Hg atoms with phosphorus. The interaction of one
Cl atom with the Lewis acidic Ga or In atoms resulted in the formation
of norbornane type molecular structures with M–Cl–E
bridges (E = Ga, In) and relatively weak M–Cl bonds. The products
showed a fascinating dynamic behavior in solution, which gave rise
to highly complex NMR spectra. The reaction of 4 with
AuCl resulted in cleavage of the Au–Cl bond and the transfer
of the Cl atom to the Lewis acidic Ga atom.
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