Molecular routes to materials in New York

A symposium entitled “Molecular Routes to Materials” was held in New York City at the 4th Chemical Congress of the North American Continent in August, 1991. The talks focused on synthetic and mechanistic studies of the formation of metals, borides, nitrides, carbides, oxides, and compound semiconductors from molecular precursors. Dr. Joel Miller (DuPont) outlined recent success in obtaining magnetic materials from molecular organometallic precursors. The crystalline product obtained from the reaction between decamethylferrocene and TCNE consisted of stacks of alternating cation and anion radicals. The material becomes magnetically ordered at low temperature (c = 4.8 K) to give a molecular ferromagnet that has a higher saturation magnetization than metallic iron. During the investigation of related complexes, the reaction of bisbenzenevanadium with TCNE yielded an air-sensitive, amorphous black powder. Although the structure of this material is unknown, both benzene ligands were replaced with interactions between TCNE and vanadium. This solid was found to exhibit ferromagnetic behavior well above room temperature and more studies are underway to establish the structure of the compound. Mossbauer spectroscopy was utilized to probe the magnetic behavior of thin films of iron boride glasses prepared using molecular metal carbonyl clusters containing boron. In this work, Thomas Fehlner (Notre Dame) established a relationship between the Fe/B ratio in the thin film and the Fe/B ratio of the precursor. For example, Fe,(CO),(B,H,) led to FeB. The small amount of oxygen present in these films was shown to be present as B,O, . New synthetic routes to nanocrystalline phosphides of zinc, cadmium, gallium, and indium were described by William Buhro (Washington Univ.). Molecular metal silylphosphido complexes (e.g. Cd[P(SiPh,),],) were typically used as precursors. These compounds react with alcohols to form the soluble silyl ether and unsubstituted phosphido (PH,) complexes which further react to give nanocrystalline materials such as Cd,P, . An alternative route to Cd,P, involving the reaction of P(SiMe,), with metal alkoxides such as Cd[OCH(Me)CH,NMe,], was described. Transmission electron microscopy was used to establish that the Cd,P,