Synthesis and Characterization of Calcium N,N-Dimethylaminodiboranates as Possible Chemical Vapor Deposition Precursors

Abstract

The reaction of CaBr2 with 2 equiv of sodium N,N-dimethylaminodiboranate, Na(H3BNMe2BH3) in Et2O at 0 °C followed by crystallization and drying in vacuum yields the unsolvated calcium compound Ca(H3BNMe2BH3)2, 1. Before the vacuum drying step, the colorless crystals obtained by crystallization consist of the diethyl ether adduct Ca(H3BNMe2BH3)2(Et2O)2, 2. If the reaction of CaBr2 with 2 equiv of Na(H3BNMe2BH3) is carried out in the more strongly coordinating solvent tetrahydrofuran (thf), the solvate Ca(H3BNMe2BH3)2(thf)2, 3, is obtained. This compound does not desolvate as easily in vacuum as the diethyl ether compound 2. Treating the thf adduct 3 with 1,2-dimethoxyethane (dme), bis(2-methoxyethyl) ether (diglyme), or N,N,N',N'-tetramethylethylenediamine (tmeda) in thf affords the new compounds Ca(H3BNMe2BH3)2(dme), 4, Ca(H3BNMe2BH3)2(diglyme), 5, and Ca(H3BNMe2BH3)2(tmeda), 6, respectively, in greater than 60% yields. Treatment of 3 with 2 equiv of the crown ether 12-crown-4 in thf affords the charge-separated salt [Ca(12-crown-4)2][H3BNMe2BH3]2, 7. Crystal structures of all the Lewis base adducts are described. Compounds 2-6 all possess chelating κ(2)-BH3NMe2BH3-κ(2) groups, in which two hydrogen atoms on each boron center are bound to calcium. Compound 7 is the only ionic compound in the series; the Ca atom is completely encapsulated by two 12-crown-4 rings, and the anions are charge-separated counterions within the unit cell. When heated, the dme, diglyme, and tmeda compounds 4, 5, and 6 melt without decomposition, and can be sublimed readily under reduced pressure (1 Torr) at 90 °C (4) and 120 °C (5, 6). The dme adduct is one of the most volatile calcium compounds known, and is a promising CVD precursor for the growth of calcium-containing thin films.

PC‐Activated Bimetallic Rhodium Xantphos Complexes: Formation and Catalytic Dehydrocoupling of Amine–Boranes

“…Each xantphos′ ligand is bound in a κ 2 -P,P configuration and the central Rh 2 P 2 unit adopts a butterfly geometry. [ 10 ] A [H 3 BNMe 2 BH 3 ] − ion[ 11 , 12 ] bridges the two metal centers. The B–H hydrogen atoms were located, and each BH 3 group is bound η 2 to the metal center (Rh–B 2.234(5), 2.229(5) Å).…”

Synthesis and Characterization of Strontium N,N-Dimethylaminodiboranates as Possible Chemical Vapor Deposition Precursors

“…gous calcium complex, in which the outer oxygen atoms of the diglyme ligand occupy the two axial sites. 39 The average Sr−O distance to the central oxygen atom in 5 is 2.579(2) Å, whereas those to the outer oxygen atoms are slightly longer at 2.626( 2 The two 12-crown-4 ligands in 7 almost completely encapsulate the strontium atom and leave very little room in the coordination sphere for additional ligands (Figure 7). S1).…”

Synthesis of Calcium(II) Amidinate Precursors for Atomic Layer Deposition through a Redox Reaction between Calcium and Amidines

“…Several other types of volatile Ca II complexes (fluoroalkoxides, fluorinated β‐diketonates, β‐diketiminates, and aminodiboranates) have been reported, but not employed in ALD reactions. To complement the currently known Ca ALD precursors, we chose to explore the amidinate ligand system.…”