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

The 1 : 1 reactions of [ClP(µ-NtBu)]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-NtBu)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-NtBu)]2 [Y = O (3), S (4)] with nBuLi followed by cyclisation with [ClP(µ-NtBu)]2. The solid-state structures of 1·cis/trans (50 : 50), 2·cis, 3 and 4 are reported.