Process for the fluorination of boron hydrides

Details Process for the fluorination of boron hydrides Process for the fluorination of boron hydrides

2003-05-01

2004-08-24

Nazario-Gonzalez, Porfirio (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Heavy metal containing

C556S008000, C568S003000, C568S004000, C568S006000

Reexamination Certificate

active

06781005

ABSTRACT:

BACKGROUND OF THE INVENTION
Halogenated boron hydride anions are weakly coordinating anions and have been used as electrolytes and as catalytic components, particularly to enhance the catalytic activity of metal cations finding use in a variety of reactions. Typically, the halogenated boron hydrides have been the fluorinated, chlorinated, and brominated borohydrides.
The following references are illustrative of processes for the production of halogenated boron hydrides, including fluorinated borohydrides:
U.S. Pat. No. 3,551,120 discloses boron compounds of the formula M
a
(B
12
H
12-y
X
y
)
b
where M is a cation having a valence of 1-4, and (B
12
H
12-y
X
y
) is a group which forms a divalent anion in an aqueous solution. The term M represents hydrogen, ammonium, and metal cations, e.g., groups I, II VIII, IIIb and so forth. X represents halogen, (F, Cl, Br, and I), carboxyl, nitro, nitroso, sulfonyl, and so forth. Example 1 shows the formation of Cs
2
B
12
H
7
F
5
by effecting fluorination of CsB
12
H
11
OH in anhydrous HF.
U.S. Pat. No. 6,180,829 discloses metal compounds of polyhalogenated heteroborane anions of the formula M[R
a
ZB
b
H
c
F
d
X
e
(OR″)
f
]
k
where M is a cation having a valence of from 1-4, e.g., an alkali or alkaline earth metal cation, R typically is a halogen or an alkyl group, Z is C, Si, Ge, Sn, Pb, N, P, As, Sb, and Bi; X is a halide and R″ is a polymer, hydrogen, alkyl and the like. The subscripts represents integers. Example 2 shows the formation of the polyfluorinated monocarborane anion from a monocarborane hydride wherein CaCB
11
H
12
is reacted with a mixture of HF and 10% F
2
in N
2
. CsCB
11
F
11
H was recovered as a white solid. Significant cluster decomposition occurred during the fluorination, and yields were 50-60% at these loadings.
U.S. Pat. No. 6,448,447, a continuation-in-part of U.S. Pat. No. 6,180,829 and others, discloses in Example 11 the formation of K
2
B
12
F
12
(1 g) by the continuous addition of a fluorine
itrogen gas phase to a suspension of K
2
B
12
H
12
in HF.
Knoth et al,
Chemistry of Boranes, IX. Fluorination of B
10
H
10
−2
and B
12
H
12
−2
Inorganic Chemistry, Vol. 2, No. 2, Feb. 1964 disclose the preparation of highly fluorinated decaborates, by (a) effecting fluorination with anhydrous HF alone to a composition up to B
12
F
6
H
6
2−
, and, (b) effecting the direct fluorination of a 5 wt. % B
12
H
12
2−
potassium salt by contacting the salt with F
2
in the presence of water (under these conditions, the HF concentration is never >10% and thus the Hammett acidity, H
o
remains >0 throughout the fluorination. (Gillespie and Liang)) The reaction when conducted in the presence of water was difficult to run to completion as evidenced by the use of a 5-fold excess of fluorine. In the end, a low yield (32%) of a hydroxy substituted fluoroborate, B
12
F
11
(OH)
2−
was obtained rather than the desired fluorine substituted dodecaborate.
Sointsev, et al,
Stereochemical Aspect of the Fluorination of the B
12
H
12
−2
Anion
, Russian Journal of Coordination of Chemistry, Vol. 23, No. 6, 1997, pp 369-376, disclose that the reaction of supercritical HF with K
2
B
12
H
12
at 600° C. generates the fully fluorinated anion. Significant decomposition was observed and yields of only 25% were obtained under these conditions.
SUMMARY OF THE INVENTION
This invention relates to an improvement in a liquid phase process for the direct fluorination of borohydride salts including the B
10
H
10
−2
and B
12
H
12
−2
salts to broadly produce compounds of the formula, M
a
[R
b
Z
c
B
d
H
e
F
y
]
k
where M is a cation having a valence of from 1-4, e.g., an alkali or alkaline earth metal cation, R typically is a halogen or an alkyl group, Z is C, Si, Ge Sn, Pb, N, P, As, Sb, or Bi; L; B is boron, H is hydrogen, a is 1 or 2; b is an integer from 0 to 7; c is an integer from 0 to 1; d is an integer from 5 to 12; e is an integer from 0 to 9; y is an integer from 3 to 12 and k is 1, 2 or 3, the respective values of a and k are determined by the valence of M, that is when the integer a is multiplied by the valence of M it is equal to the integer k or 2 times the integer wherein said borohydride salt is contacted with fluorine, under conditions for forming said fluorinated borohydride salt. The improvement in the liquid phase process resides in effecting the fluorination of said borohydride salt in the presence of a reaction medium having an acidity between that of water and neat HF. More specifically, the reaction medium should have a Hammett acidity, H
o
, such that 0>H
o
>−11. In a preferred embodiment the reaction medium, e.g., the carrier should be capable of solubilizing the borohydride salt to provide loadings of 10% and greater by weight of the borohydride salt in the carrier. Preferred fluorinated compounds are M
a
B
10
H(
10-y
)F
y
and (M
a
B
12
H(
12-y
)F
y
, where y>3 and more preferably y is at least 9 for the compound M
a
B
10
H(
10-y
)F
y
and at least 10 for the compound M
a
B
12
H(
12-y
)F
y
.
Several advantages can be achieved through the process described here. These include:
an ability to achieve high levels of fluorination of the borohydride anions, e.g., where y is 10-12;
an ability to achieve excellent yields and reaction efficiency;
an ability to achieve high loadings of reactant in the carrier; and,
an ability to minimize yield loss due to byproduct formation.


REFERENCES:
patent: 3551120 (1970-12-01), Miller et al.
patent: 6180829 (2001-01-01), Strauss et al.
patent: 6448447 (2002-09-01), Strauss et al.
Knoth et al,Chemistry of Boranes, IX, Fluorination of B10H10-2 and B12H12-2, Inorganic Chemistry, vol. 2, No. 2, Feb. 1964.
Solntsev, et al,Stereochemical Aspects of the Fluorination of the B12H12-2 Anion, Russian Journal of Coordination of Chemistry, vol. 23, No. 6, 1997, pp 369-376.

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