SYNTHESIS AND CHARACTERIZATION OF NOVEL QUASIAROMATIC ZINC SULFUR AGGREGATES AND RELATED ZINC OXYGEN COMPLEXES

The synthesis and structural characterization of several alkylzinc alkoxides, aryloxides, and thiolates, many of which have unusual structures, are described. The compounds were synthesized by the simple reaction of the zinc dialkyl, ZnR2 (R = CH2SiMe3), with 1 equiv of an alcohol or thiol to afford the products [RZnOR']n (n = 2, R' = 2,6-i-Pr2C6H3 (1) or 2,4,6-t-Bu3C6H2 (2); n = 4, R' = 1-adamantyl (1-Ad) (3) or t-Bu (4)), or [RZnSR'']n (n = 2, R'' = -CPh3(5); n = 3, R'' = 2,4,6-i-Pr3C6H2 (6) or 2,4,6-t-Bu3C6H2 (7)). The aggregate [Zn3{O(2,6-i-Pr2C6H3)}4R2] (8) was also obtained. All compounds were characterized by C and H elemental analysis, by H-1 NMR spectroscopy, and, with the exception of 4 (which was only partially structurally characterized), by X-ray crystallography. The main feature of interest in these compounds derives from their structures. For example, the [RZnSR'']3 trimers 6 and 7 possess flattened, almost planar, Zn3S3C6 arrays and may be considered to be isoelectronic to the recently synthesized quasiaromatic Al3N3C6, Ge3N3C3, or B3P3C6 ring systems. In contrast, the ''antiaromatic'' dimer, [RZnSCPh3]2 (5), possesses very pyramidal coordination at the sulfur centers and little apparent delocalization. Attempts to crystallize a compound having a planar Zn3O3C6 array analogous to 6 and 7 have not been successful to date. The reaction between ZnR2 and HOR' gave either dimers or tetramers that feature Zn2O2 or Zn4O4 cores as exemplified by compounds 1-4. An alkylzinc alkoxide product, 8, featuring three zinc centers was obtained when the stoichiometry of the reactants was changed slightly. However, the product did not possess a six-membered-ring structure. Instead, an almost linear Zn3 array, in which the zinc centers are linked by bridging -OR' groups and each terminal zinc is also bound to one alkyl group, was obtained.