Selection of the cis and trans phosph(iii)azane macrocycles [{P(µ-NtBu)}2(1-Y-2-NH-C6H4)]2 (Y = O, S)

Abstract

The 1 : 1 reactions of [ClP(µ-N^tBu)]₂ with the difunctional aromatic amines 1,2-1-YH-2-NH₂-C₆H₄ in the presence of Et₃N give the dimeric phosph(III)azane macrocycles [{P(µ-N^tBu)₂(1-Y-2-HN-C₆H₄)]₂, predominantly as the cis isomer in the case of Y = O (1·cis) and as the trans isomer for Y = S (2·trans). Model M.O. calculations suggest that the selection of the cis and trans isomers is not thermodynamically controlled. The alternative isomers 1·trans and 2·cis are generated exclusively by the deprotonation of the model intermediates [(1-Y-2-NH₂-C₆H₄)P(µ-N^tBu)]₂ [Y = O (3), S (4)] with ⁿBuLi followed by cyclisation with [ClP(µ-N^tBu)]₂. The solid-state structures of 1·cis/trans (50 : 50), 2·cis, 3 and 4 are reported.