Improved reactivity of a cyclic 13/15 compound by increased steric demand.

Herein we present the synthesis and characterization of the new four-membered Ga/P cycle [tBuGaP(H)SitBuPh], which shows a cis/trans isomerization at ambient temperatures via a ring opening mechanism. The sterically demanding substituents on the phosphorus (-SitBuPh) and gallium (tBu) atoms lead to an unexpected reactivity towards bulky NHC ligands (IMes and IDipp). The resulting Lewis base stabilized monomeric 13/15 compounds feature an unusual binding mode of the carbene ligand.

Cyclic NHC-stabilized silylphosphinoalanes and -gallanes.

Four-membered Al/Ga-P ring systems were prepared by thermal hydrogen elimination between the primary silylphosphine H2PSitBuPh2 and the metal hydride precursors [(Me3N)MH3] (M = Al, Ga). The obtained cycles [(Me3N)HMP(SitBuPh2)]2 (M = Al: 1, Ga: 2) were functionalized by substituting the amine donor with the N-heterocyclic carbenes IPr and BImY to obtain the compounds [(NHC)HMP(SitBuPh2)]2 (IPr/Al: 3, BImY/Al: 4, IPr/Ga: 5, BImY/Ga: 6). All mentioned compounds feature an unusual external Lewis base stabilization as well as hydridic metal bound hydrogen atoms.