Oxygen capture by lithiated organozinc reagents containing aromatic 2-pyridylamide ligands

The sequential reaction of ZnMe2 with a 2-pyridylamine (HN(2-C5H4N)R, R = Ph: 1; 3,5-Xy (=3,5-xylyl): 2; 2,6-Xy: 3; Bz (=benzyl): 4; Me: 5), tBuLi and thereafter with oxygen affords various lithium zincate species, the solid-state structures of which reveal a diversity of oxo-capture modes. Amine 1 reacts to give both dimeric THF Li(Me)OZnN(2-C5H4N)Ph]2] (6), wherein oxygen has inserted into the Zn-C bond of a MeZnN(2-C5H4N)-Ph]2] ion, and the trigonal Li2Zn complex, bis(OtBu)-capped (THF x Li)2-(mu3-O)tBu]2ZnN(2-C5H4N)Ph]2] (7). The structural analogue of 6 (8) results from the employment of 2, while the use of more sterically congested 3 yields a pseudo-cubane dimer (THF x Li(tBu)OZn(OtBu)Me]]2] (9) notable for the retention of labile Zn-C(Me). Amines 4 and 5 afford the oxo-encapsulation products mu4-O)Zn4(2-C5H4N)-NBz]6] (10b), and tBu(mu3-O)-Li3(mu6-O)Zn3(2-C5H4N)NMe]6] (11), respectively, with concomitant oxo-insertion into a Li-C interaction resulting in capping of the fac-isomeric (mu6-O)M3M'3 distorted octahedral core of the latter complex by a tert-butoxide group.