Showing papers by "Allan Zalkin published in 1990"
TL;DR: The coordinated tetrahydrofuran in (MeC 5 H 4 ) 3 Ce(THF) can be removed by Me 3 Al in a Lewis acid-base reaction or by the "toluene-reflux method" to give base-free (meC 5H 4 )3 Ce which is a monomer in the gas phase though a tetramer in the solid state: monoclinic, P2 1 /a, with a=12497 (5) A, b=26002 (8), A, c=9664 (3
99 citations
TL;DR: The trivalent cerium metallocene (Me{sub 3}CC{sub 5}H{sub 4} ) is monoclinic, P2{sub 1}/c with a = 11.962 (4)
86 citations
TL;DR: In this paper, X-ray diffraction was used to determine the structure of Na{sub 2}HPO{sub 4}{center dot}xH{sub 1}O (x = 1, 2, 7, and 12).
Abstract: Structures determined by X-ray diffraction are reported for crystals of Na{sub 2}HPO{sub 4}{center dot}xH{sub 2}O (x = 1, 2, 7, and 12). The new monohydrate phase is triclinic, space group P{bar 1}, a = 5.575 (1) {angstrom}, b = 7.949 (1) {angstrom}, c = 5.735 (1) {angstrom}, {alpha} = 103.83 (1){degree}, {beta} = 102.15 (1){degree}, {gamma} = 107.47 (1){degree}, Z = 2, R = 0.020 for 3329 independent reflections. The other structures are in agreement with independent determinations already published. For x = 1, 2, or 7 no disorder is observed, and there are unique configurations of protons in hydrogen bonds. The dodecahydrate (x = 12) has two kinds of disorder, randomness of phosphate ion orientations and of proton positions in hydrogen bonds. A model for this disorder gives 2.65 cal K{sup {minus}1} mol{sup {minus}1} as the residual entropy at low temperature, compared with 3.1 {plus minus} 0.5 and 3.5 {plus minus} 0.4 cal K{sup {minus}1} mol{sup {minus}1} derived from two thermodynamic cycles.
12 citations
TL;DR: The coordinated tetrahydrofuran in (MeC 5 H 4 ) 3 Ce(THF) can be removed by Me 3 Al in a Lewis acid-base reaction or by the "toluene-reflux method" to give base-free (meC 5 h 4 ), which is a monomer in the gas phase though a tetramer in the solid state: monoclinic, P2 1 /a, with a=12.497, b=26.002, c=9.664, β=97.32, R
Abstract: The coordinated tetrahydrofuran in (MeC 5 H 4 ) 3 Ce(THF) can be removed by Me 3 Al in a Lewis acid-base reaction or by the «toluene-reflux method» to give base-free (MeC 5 H 4 ) 3 Ce which is a monomer in the gas phase though a tetramer in the solid state: monoclinic, P2 1 /a, with a=12.497 (5) A, b=26.002 (8) A, c=9.664 (3) A, β=97.32 (3) o ; R=0.041 for 2117 data, F 2 >2σ(F 2 )
1 citations