Oxygen Capture by Lithiated Organozinc Reagents Containing Aromatic 2-Pyridylamide Ligands

Abstract

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)OZn[N(2-C5H4N)Ph]2] (6), wherein 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 x Li)2-[[(mu3-O)tBu]2Zn[N(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.

Oxygenation of a Me2Zn/α‐Diimine System: A Unique Zinc Methylperoxide Cluster and Evidence for Its Sequential Decomposition Pathways

“…Nevertheless, the observed transformation of the ZnOOMe species to the zincoxane is fully consistent with our recent studies on the oxygenation of an alkylzinc carboxylate complex, which leads to the oxo‐encapsulated aggregate 6. It is also worth noting that oxide entrapment in the oxygenation reactions of alkylzinc compounds has also occasionally been observed,16 although homolytic OO bond cleavage to give metal–oxo species has not generally been considered to be an efficient mode of decomposition for main‐group metal alkylperoxides 17. 18 Furthermore, this transformation of zinc alkylperoxides into oxo species could also be relevant to the recently developed methodologies for the preparation of ZnO nanoparticles from alkylzinc precursors, especially the high‐temperature method based on the R 2 Zn/O 2 /amine system19 or the low‐temperature procedure involving the R 2 Zn/O 2 /H 2 O/amine system,20 and thermolysis of [RZnOR′] 4 precursors in the presence of O 2 (the presence of oxyzinc radicals has been demonstrated for the latter procedure in the resulting ZnO samples) 21…”

Ligand and Metal Effects on the Formation of Main‐Group Polyhedral Clusters

“…It is only very recently that categorical evidence has been obtained in this respect, with the solution of a single crystal neutron diffraction structure of 2 8. To date, attempts to significantly alter the composition of such hydride‐yielding systems have met with little success; the employment of, for example, N,N ′‐diphenylbenzamidine gives the hydride‐free superlithiate [Li 4 {PhNC(Ph)NPh} 3 ] + [Li(Me 2 AlMe t Bu) 2 ] − ( 8 ) 9. In seeking to probe the generality of cage–cluster formation and hydride entrapment, two variations on the methodology that yields 2 and 3 (and also 4 – 7 ) have been deployed; 1) N ‐2‐pridylaniline has been replaced by a non‐aromatic guanidine ligand, and 2) while the use of MeLi and HMDSLi (HMDS=hexamethyldisilazide) has circumstantially established the importance of β‐hydrogen‐containing t BuLi in hydride encapsulation chemistry10 the Group 13 organometallic substrate is now replaced by a Group 12 analogue.…”

Zinc: Organometallic ChemistryBased in part on the article Zinc: Organometallic Chemistry by Gerard Parkin which appeared in theEncyclopedia of Inorganic Chemistry, First Edition.

“…258 The nature of the products was found to be dependent on R and suggested a competition between the oxophilicity of lithium and zinc (Scheme 18). When N ,N -diphenylbenzamidine (HAm) is used instead of 2-pyridylamine, and depending on the solvent conditions, the sequential reaction leads to various triorganozincate species.…”