lsolation and Reactivity of Heteroleptic Magnesium 1,3-Benzazaphospholide Complexes

Abstract

Reactions of 2,5-disubstituted-1H-1,3-benzazaphosphole (HBp) 1 [HBp1 (1a): R1 = Ph, R2 = Me; HBp2 (1b): R1 = Ph, R2 = H] with one equivalent of the - diketiminate complex [CH{C(Me)NAr}2MgnBu] (Ar = 2,6-iPr2C6H3) [(DippBDI)MgnBu], in good yields respectively, produce low-coordinate magnesium compounds (DippBDI)Mg [1(N) - Bp] 2 (Bp1(2a), Bp2(2b)), in which the ambident Bp- ligand coordinates to the magnesium centers through Mg − N bond in both solution and solid phases. Compounds 2a–b can coordinate with THF to form four-coordinate magnesium 1,3-benzazaphospholides (DippBDI)Mg(THF)[1(N) - Bp] 3 (Bp1(3a), Bp2(3b)). Interestingly, 2a–b readily reacted with elemental sulfur to give new compounds (DippBDI)Mg(3(S,S)-BpS2) 4 (Bp1(4a), Bp2(4b)). Surprisingly, compounds 2a–b treated with 2,2'-dipyridyl disulfide (PyS)2 to afford unexpected racemic axially restricted Bp(p)-(p)Bp rac-5 (Bp1(5a), Bp2(5b)). These new magnesium 1,3-benzazaphospholide complexes have been characterised by X-ray crystallography, except for 4b and rac-5b.