Unexpected Rearrangement Reaction of Lewis Base Stabilized Group 13/15 Compounds with Group 13 Trialkyls

Abstract

Reactions of the monomeric, Lewis base stabilized phosphinoalane dmap−Al(Me) 2 P(SiMe 3 ) 2 with MMe 3 (M = Al, Ga, In) yielded the novel compounds dmap−Al(Me) 2 P(SiMe 3 ) 2 −MMe 3 (M = Al ( 1 ), Ga ( 2 ), In ( 3 )). 1 − 3 are stable in their pure form, whereas they easily undergo rearrangement reactions in solution with Al−P bond breakage and methyl group transfer, resulting in the formation of dmap−AlMe 3 and the corresponding heterocycle [Me 2 MP(SiMe 3 ) 2 ] x (M = Al, Ga, In), as was demonstrated by detailed temperature-dependent heteronuclear NMR studies. MMe 3 adducts of the stibinoalane dmap−Al(Me) 2 Sb(SiMe 3 ) 2 are even more susceptible to this rearrangement reaction and cannot be isolated, whereas reactions with sterically more demanding M( t -Bu) 3 (M = Al, Ga) yielded the corresponding stable adducts dmap−Al(Me) 2 Sb(SiMe 3 ) 2 −M( t -Bu) 3 (M = Al ( 4 ), Ga ( 5 )). 1 − 5 contain both regular σ-bonds and dative bonds between group 13 and group 15 elements to a single pnicogen center. 2, 4, and 5 were characterized by single-crystal X-ray diffraction.