Organic compounds -- part of the class 532-570 series – Organic compounds – Heavy metal containing
Reexamination Certificate
1999-03-11
2001-04-17
Shah, Mukund J. (Department: 1611)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heavy metal containing
C556S019000, C556S020000, C556S021000, C556S023000
Reexamination Certificate
active
06218559
ABSTRACT:
The present invention relates to a catalyst obtainable by the reaction of iridium salts with diphosphines and alkali metal or ammonium halides; to a preparation process for those catalysts; and to a process for the hydrogenation of imines, especially in the presence of an acid.
U.S. Pat. No. 4,994,615 describes a process for the asymmetric hydrogenation of prochiral N-arylketimines wherein iridium catalysts having chiral diphosphine ligands are used. U.S. Pat. No. 5,011,995 describes a process for the asymmetric hydrogenation of prochiral N-alkylketimines using the same catalysts. U.S. Pat. No. 5,112,999 discloses polynuclear iridium compounds and a complex salt of iridium, which contain diphosphine ligands, as catalysts for the hydrogenation of imines. The catalysts are prepared by reacting iridium olefin and iridium diolefin complexes with diphosphines.
Those homogeneous catalysis processes have proved valuable, although it is evident, especially in the case of relatively large batches or on an industrial scale, that the catalysts frequently tend to become deactivated to a greater or lesser extent depending on the catalyst precursor, the substrate and the diphosphine ligands that are used In many cases, especially at elevated temperatures—for example at temperatures >25° C., which are necessary for a short reaction time—it is not possible to achieve complete conversion. For industrial applications of the hydrogenation process, therefore, the catalyst productivity is too low from the point of view of economic viability.
A further disadvantage is the fact that as starting materials for the catalysts the iridium olefin and iridium diolefin complexes are unstable and expensive, with the result that it is not possible in practice to obtain commercial quantities.
It has now been found, surprisingly, that active homogeneous iridium catalysts can be obtained from simple iridium salts, which are considerably more economical, by reacting those salts with diphosphines in the presence of metal halides, especially alkali metal or ammonium halides.
It has also been found, surprisingly, that the catalyst activity can be increased if during the hydrogenation the reaction mixture comprises an acid in addition to the catalyst. It has also unexpectedly been found that at the same time the deactivation of the catalysts can be considerably reduced or completely eliminated.
The invention relates to iridium compounds that are obtainable by reacting iridium(III) or iridium(IV) salts or hydrates thereof and a diphosphine having secondary phosphine groups in the presence of a metal chloride, bromide or iodide or an ammonium chloride, bromide or iodide.
The iridium(IU) salts or hydrates thereof may be, for example, of formula I
[Ir
3⊕
][X
n⊖
]
3
·m
H
2
O (I)
wherein X is the n-valent anion of an acid,
n is 1, 2 or 3, and
m is 0 or a whole number or a fraction greater than 0 and up to 8.
The iridium(IV) salts or hydrates thereof may be, for example, of formula Ia
M
2
⊕
[IrX′
6
]
2⊖
·m
H
2
O (Ia)
wherein
X′ is halogen, especially F, Cl or Br,
M
2
⊕
is two H
⊕
, two alkali metal cations, for example Li
⊕
, Na
⊕
or K
⊕
, or an alkaline earth metal cation, for example Mg
2⊕
, Ca
2⊕
, Sr
2⊕
or Ba
2⊕
, and m is 0 or a whole number or a fraction greater than 0 and up to 8.
In formulae I and/or Ia, n is preferably 1 and m is preferably 0 or a whole number or a fraction greater than 0 and up to 4.
The anion X can be derived from organic or inorganic acids. Examples of organic acids are aliphatic and aromatic carboxylic acids, sulfonic acids and phosphonic acids that contain from 1 to 12, preferably from 1 to 8 and especially from 1 to 4, carbon atoms and are unsubsitituted or substituted by F or Cl. Some specific examples are formic, acetic, propionic, butyric, mono-, di- or tri-chloro- or mono-, di- or tri-fluoro-acetic acid, benzoic acid, phenylacetic acid, methyl-, phenyl- or benzyl-phosphonic acid and methyl-, phenyl-, benzyl- p-toluyl- or trifluoromethyl-sulfonic acid. Examples of inorganic acids are the hydrohalic acids, tetrafluoroboric acid, tetraphenylboric acid, hexafluoro-phosphoric, -arsenic, -antimonic and -bismuthic acid, and the oxy acids of the elements N, P, S, F, Cl, Br and I. Specific examples are HCl, HBr, HI, BF
4
, HB(phenyl)
4
, HPF
6
, HSbCl
6
, HAsF
6
, HSbF
6
, HClO
4
, HBrO
4,
HIO
4,
H
2
SO
3,
H
2
SO
4
, HNO
2,
HNO
3
, H
3
PO
3
and H
3
PO
4
.
Preferred acids from which X
n⊖
in formula I can be derived are HCI, HBr, HI, H
2
SO
4
, HClO
4
, HClO
3
, HBrO
4
, HIO
4
, HNO
3
, H
3
PO
3
, H
3
PO
4
, CF
3
SO
3
H, C
6
H
5
SO
3
H, CF
3
COOH and CCl
3
COOH. In a special form, X
n⊖
in formula I is a monovalent anion (n is preferably 1), especially a halide and more especially Cl
⊖
. The iridium(III) salt of formula I is especially IrCl
3
.mH
2
O, wherein m is a number from 1 to 4.
Virtually any of the halogen compounds of the metals of the main groups and subgroups of the Periodic Table of the Elements can be used as the metal halides, provided that they are soluble in the reaction mixture and do not act as oxidising agents towards the other reactants in the reaction mixture. The use of alkali metal halides is preferred.
The metal and alkali metal cations in the metal and alkali metal halides are preferably the Li, Na, K, Rb or Cs cations, especially Li
⊕
, Na
⊕
and K
⊕
. The ammonium cation in the ammonium halides may be NH
4
⊕
, primary ammonium having preferably from 1 to 20 carbon atoms, secondary ammonium having preferably from 2 to 24 carbon atoms, tertiary ammonium having preferably from 3 to 24 carbon atoms, and quaternary ammonium having preferably from 4 to 24 carbon atoms. Preference is given to quaternary ammonium, especially of the formula phenylN
⊕
(C
1
-C
6
alkyl)
3,
benzylN
⊕
(C
1
-C
6
alkyl)
3
or (C
1
-C
6
alkyl)
4
N
⊕
. Of the alkali metal halides and ammonium halides, the bromides and especially the iodides are preferred. In a preferred form, the alkali metal halides and ammonium halides are LiI, NaI or KI or (C
1
-C
6
alkyl)
4
NI. Tetrabutylammonium iodide is especially preferred.
The diphosphines having secondary phosphine groups are preferably those
(a) the phosphine groups of which are bonded to different carbon atoms of a carbon chain having from 2 to 4 carbon atoms, or
(b) the phosphine groups of which are either bonded directly or via a bridge group —CR
a
R
b
in the ortho positions of a cyclopentadienyl ring or are each bonded to a cyclo-pentadienyl ring of a ferrocenyl, or
(c) one phosphine group of which is bonded to a carbon chain having 2 or 3 carbon atoms and the other phosphine group of which is bonded to an oxygen atom or a nitrogen atom bonded terminally to that carbon chain, or
(d) the phosphine groups of which are bonded to the two oxygen atoms or nitrogen atoms bonded terminally to a C
2
-carbon chain; with the result that in the cases of (a), (b), (c) and (d) a 5-, 6- or 7-membered ring is formed together with the Ir atom, and R
a
and R
b
are each independently of the other hydrogen, C
1
-C
8
alkyl, C
1
-C
4
fluoroalkyl, phenyl or benzyl or are phenyl or benzyl having from 1 to 3 C
1
-C
4
alkyl or C
1
-C
4
alkoxy substituents. Rb is preferably hydrogen. R
a
is preferably C
1
-C
4
alkyl and especially methyl.
The diphosphine contains preferably at least one chiral carbon atom and is especially an optically pure stereoisomer (enantiomer or diastereoisomer), or a pair of diastereoisomers, since the use of catalysts containing those ligands leads to optical induction in asymmetric hydrogenation reactions.
The phosphine groups contain preferably two identical or different, preferably identical, unsubstituted or substituted hydrocarbon radicals having from 1 to 20, especially from 1 to 12 carbon atoms. Preference is given to diphosphines wherein the secondary phosphine groups contain two identical or different radicals from the following
Pittelkow Ulrich
Spindler Felix
Novaritis Corporation
Shah Mukund J.
Teoli, Jr. William A.
Truong Tamthom N.
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