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PREPARATION OF ZIRCONIUM BOROHYDRIDE
REFERENCES
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12. Preparation and identification of [Zr(BH4)2Cl2(dabco)2] (ZrBDC): A
slurry was produced by the addition of an ethereal solution of
LiBH4 (0.344 mol) to anhydrous ZrCl4 (0.069 mol) under inert atmos-
phere and the resulting mixture[19] was stirred for 12 h. Then an ethe-
real solution of dabco (0.138 mol) was added dropwise to the slurry
and stirring was continued for 10 h to produce a dark brown solid. The
resulting solid was filtered and washed with Et2O and dried under
vacuum to afford a white powder. For further purification, the result-
ing powder was washed with dry THF and dry Et2O respectively and
was left under vacuum overnight. ZrBDC was isolated as a white,
stable, non-hygroscopic powder in 97% yield. This reducing agent
could be stored at room temperature for months without significant
change in its reducing ability. The chemical formula of the reagent
was established by IR and NMR studies.[9] IR (KBr, dabco species),
ꢀ (cmÀ1): 2974s, 296À3s, 2897s, 1623m, 1458s, 1324s, 1056s, 993s, 846s,
702b, and for BH4 species, ꢀ (cmÀ1): 2383s, 2373s, 2306s, 2268s,
1
1155s. H NMR (CDCl3, 250 MHz): ꢁ (ppm) 1.42 (broad band, 8H,
two BHÀ4 ), that its coupling constant and pattern are similar to
Zr(BH4)4,[9b] 2.9 (AA0BB0 pattern,[20] 24H of CH2 groups). 13C NMR
(CDCl3, 63 MHz): ꢁ (ppm) 51.7, 52.1 (two different CH2 groups).
Determination of BHÀ4 content was conducted by iodometric titration
method,[21] quantitative measurement of chloride content was
proceeded by potentiometric titration technique,[22] and quantitative