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 = P h: 1; 3,5-Xy (= 3,5-xyl-yl): 2; 2,6-Xy: 3; Bz (= benzyl): 4; Me: 5), tBuLi and thereafter with oxygen affords various lithium zincate species, the sol id-state structures of which reveal a diversity of oxo-capture modes. Amine 1 reacts to give both dimeric THF . [Li(Me)OZn{N(2-C5H4N)Ph}(2)] (6), wher ein oxygen has inserted into the Zn-C bond of a {MeZn[N(2-C5H4N)-Ph](2)}(-) ion, and the trigonal Li2Zn complex, bis(OtBu)-capped (THF . Li)(2)-[{( mu (3)-O)tBu}(2)Zn{N(2-C5H4N)Ph}(2)] (7). The structural analogue of 6 (8) re sults from the employment of 2, while the use of more sterically congested 3 yields a pseudo-cubane dimer [{THF . [Li(tBu)OZn(OtBu)Me]}(2)] (9) notabl e for the retention of labile Zn-C(Me). Amines 4 and 5 afford the oxo-encap sulation products [(mu (4)-O)Zn-4{(2-C5H4N)-NBz}(6)] (10b), and [tBu(mu (3) -O)-Li-3( mu (6)-O)Zn-3{(2-C5H4N)NMe}(6)] (11), respectively, with concomit ant oxo-insertion into a Li-C interaction resulting in capping of the fac-i someric (mu (6)-O)M3M'(3) distorted octahedral core of the latter complex b y a tert-butoxide group.