Eric W. Stern

Catalytic asymmetric hydrogenation of β-ketoesters using new BINAP complexes of ruthenium

Abstract Two new, air-stable BINAP complexes of ruthenium(II), (RCp)Ru(S-(−)-BINAP)Cl (R=1cr; H, CH3) have been prepared in good yield from the reaction of (RCp)Ru(PPh3)2Cl with S-(−)-BINAP in refluxing toluene. The structure of the methylcyclopentadienyl analog has been determined by X-ray crystallography. Both complexes have been found to be effective homogeneous catalysts for the enantioselective hydrogenation of β-ketoesters.

Low-temperature vapour deposition of high-purity iridium coatings from cyclooctadiene complexes of iridium. Synthesis of a novel liquid iridium chemical vapour deposition precursor

High-purity, crystalline iridium coatings have been prepared by low-temperature chemical vapour deposition (CVD) from three volatile cyclooctadiene (COD) iridium precursors. One of these, (MeCp)Ir(COD)(MeCp = methylcyclopentadienyl), is a novel complex which melts at low temperature (40 °C) and therefore can be used as a liquid iridium source for CVD. When hydrogen is used as a carrier gas, iridium coatings containing < 1 atm % carbon are generated at ca. 120 °C using (MeCp)Ir(COD) and CpIr(COD)(Cp = cyclopentadienyl). Likewise, deposition under low oxygen pressure in partial vacuum also generates coatings free of carbon and oxygen. However, when the deposition is carried out in vacuo(no carrier gas), ca. 80% carbon is incorporated into the films. When [(COD)Ir(µ-OAc)]2(OAc = acetate) is used as the metal-organic CVD (MOCVD) precursor, films containing < 1% carbon and oxygen are obtained at ca. 250 °C in vacuo without the need for a carrier gas.

Synthesis of new bis(trimethylsilylcyclopentadienyl) complexes of hafnium

The new trimethylsilylcyclopentadienyl hafnocene complexes, (Me3SiCp)2Hf(Cl)(BH4), (Me3SiCp)2Hf(H)(BH4), (Me3SiCp)2HfMe2, (Me3SiCp)2Hf(OR)2 (R = Me and Et), and (Me3SiCp)2Hf(Cl)(OMe), have been prepared in good yield from the reactions of (Me3SiCp)2HfCl2 with LiBH4, MeLi, Et3N/ROH (R = Me and Et), or NaOMe. All were isolated as volatile, low melting solids or oils. In the reaction of (Me3SiCp)2HfCl2 with LiBH4 in hexane, either the borohydride-chloride complex, (Me3SiCp)2Hf(Cl)(BH4) or the borohydride-hydride complex, (Me3SiCp)2Hf(H)(BH4), was isolated depending on the reaction temperature. Although the expected bis(borohydride) complex, (Me3SiCp)2Hf(BH4)2, was not obtained, 11B NMR spectroscopy suggests that it may be formed as an intermediate which subsequently loses BH3 to form (Me3SiCp)2Hf(H)(BH4).

Low-temperature vapour deposition of high-purity copper coatings from bis[N-(fluoroalkyl)salicylaldiminato]copper chelates

High-purity copper coatings have been prepared by chemical vapour deposition at low temperature from two nove bis[N-(fluoroalkyl)salicylaldiminato] chelates of copper(II). When hydrogen is used as the carrier gas at ambient pressure, copper coatings containing < 1 atom.% carbon, oxygen, nitrogen, and fluorine are generated at 290 and 330 °C using Cu(NCH2CF2CF3-SAL)2 and Cu(NCH2CF2CF2CF3-SAL)2, respectively (SAL = salicylaldiminato). When the deposition is carried out in vacuo, ca. 6% carbon, 2% oxygen, and 3% fluorine are incorporated into the films using Cu(NCH2CF2CF3-SAL)2 as the copper source.