Synthesis of New Donor-functionalized Alcohols as Organic Ligands for Metal Precursors of Metal Organic Chemical Vapor Deposition

Abstract

Recently, the development and use of single precursors for metal organic chemical vapor deposition (MOCVD) has been extensively focused on application to electronic devices. However, systematic design and synthesis of organic ligands appropriate for preparation of metal complexes with relevant chemical and physical properties, such as stability, volatility, and resistance to air and moisture have not received much attention. Generalization to prepare organic ligands for MOCVD precursors is especially important because the large scale synthesis of the metal complexes exclusively depends on the potential usefulness of the ligands. It is desirable for metal complexes to be in monomeric forms because mononuclear complexes generally show high vapor pressures and low sublimation or boiling temperatures. To do so, the coordinated atom of ligands should be crowded in its own environment with some substituents by keeping the coordinated atoms from bonding to another metal through bridging configuration. Therefore, pendant groups should be introduced into organic ligands. Some research results have been reported on the synthesis and application of organic ligands containing pendant groups. Herrmann reported his pioneering works on the synthesis of donor-functionalized alcohols and their application as bidentate ligands for the preparation of metal complexes. A variety of donor-functionalized alcohols which contain two alkyls on the α–carbon of the hydroxyl group were prepared and used to give metal complexes such as M(mmp)4 (mmp = 1-methoxy-2-methyl-2-propanolate; M = Zr, Hf), M(mmp)3 (M = Cr, Bi), 9 M(dmamp)3 (dmamp = 1-dimethylamino-2-methyl-2-propanolate; M = Y, Lu), Cu(dmamp)2. 12 The ligands in the complexes have pendant groups capable of coordinating to metals as bidentate ligands. Some of trifunctional alcohols have been used for the preparation and homoleptic complexes of alkaline-earth elements as well as transition metals. For larger cations such as Ba and Sr, it is necessary to introduce a neutral ancillary ligand possessing a sufficient number of donor sites or to incorporate a donor-functionalized feature into the anionic ligand to satisfy the multiple coordination requirement. Chi reported the successful preparation of alkalineearth metal complexes using a multi-donor site monoalcohol. Herein we disclose the synthesis and characterization of novel alcohols, which have pendant groups to stabilize the metal compounds by coordinating to the metal center in the formation of metal complexes. New alkoxyalcohols were prepared by the nucleophilic addition ring opening reaction between alkoxide anions and a highly reactive alkene oxide (epoxide).