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Iodophosphonium Salts with Unusual Properties and a Structural Alternative for Halophosphoranes.

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E. Shumate, J . Org Clrem. 45 (1980) 5187: 9 J. D. Oliver, D. P. Riley,
Organome/allics 2 (1983) 1032; g) E. P. Kyba. R. E. Davis, P. N. Juri, K.
R. Shirley, Inorg. Chenr. 20( 1981) 3616: h) J. M. Brown, P. A. Chaloner,
G. A. Morris, J . Chem. Soc. Chem Commun. 1983. 664; i) G. Pracejus,
H. Pracejus, J . Mul. Cat. 24 (1984) 227; j) U. Nagel, E. Kinzel, J. Andrade. G. Prescher, Chem. Ber. 119 (1986) 3326.
14) See also H. Brunner, J. Wachter, J . Schmidbauer, G. M. Sheldrick, P. G.
Jones, Angew. Chem. 98 (1986) 339; Angew. Chem. Int. Ed. Engl. 25
(1986) 37 I : Organometallics 5 (1986) 2212.
[ S ] Abbreviations: OTs = OS02-p-C,,H,CH,;
nbd = norbornadiene. Good
precedent exists that all reactions should proceed with retention of configuration at rhenium [6] and R/S assignments have been made accordingly: c = 1.0 mg/mL (THF) for all [a]values.
[61 J. H. Merrifield, J. M. Fernandez, W. E. Buhro, J. A. Gladysz, Inorg.
Chem. 23 (1984) 4022.
I71 W. E. Buhro, S. Georgiou, J. P. Hutchinson, J. A. Gladysz, J . Am. Chem.
Soc. 106 (1985) 3346.
181 New compounds were characterized by microanalysis, IR, and NMR
( ' H , "C, "P). Selected "P{'H}-NMR data (121 MHz, J values): (S)-2
(THF): 21.63 (d, Jpt.= 16.0 Hz, PPh,), -41.24 (d, Jpp= 16.0 Hz, PPh2);
(+)-(S)-3 ([DJTHF): 20.23 (d, Jpp= 14.8 Hz, PPhl), - 16.20 (s, CPPh2),
-45.15 (d, JPp=14.8 Hz, RePPh,); (+)-(R)-4 (CD,CI,): 50.38 (ddd,
J p ~ h =182.9 Hz, J p p = 18.5, 5.0 Hz, CPPh,), 9.83 (dd, J w = 14.0, 5.0 Hz,
PPh?), -49.23 (ddd, JPKh=
126.6 Hz, JI'p=18.5, 14.0 Hz, RePPh,).
[9] a) R. R. Schrock, J. A. Osborn, J. Am. Chem. Suc. 93 (1971) 2397; b) E.
W. Abel, M. A. Bennet, G . Wilkinson, J . Chem. Soc. 1959. 3178.
[lo] General hydrogenation procedure: An oven-dried 50-mL flask was
charged (under an inert atmosphere) with a stir bar, (+)-(R)-4 (0.015 g,
0.012 mmol, 0.4 mol%), a-acetamidoacrylic acid (0.616 g, 3.00 mmol),
and freshly distilled T H F (ca. 25 mL), and connected via a three-way
stopcock to a vacuum line and a gas buret. The resulting light orange
solution was subjected to a freeze-pump-thaw-degas cycle four times,
with H2 admitted on the final cycle. The reaction solution was vigorously stirred for 6 h, after which H2 uptake ceased. Work-up [3e] gave
(R)-N-acetylalanine (0.541 g, 2.61 mmol, 87%). The optical purity was
assayed both polarimetrically [3b, el and (after derivatization) chromatographically (5% SP-300 (N-lauroyl-L-valine~t-butylamide)chiral stationary phase on 100/120 Supelcoport, 130°C. 2 m x 2 - m m glass column;
see technical bulletin 7656, Supelco Inc., Bellefonte, PA).
[ I I1 Crystal data: monoclinic, P2,/C; u = 12.98014). b = 15.832(4),
c=29.1 17(7), /3=91.70(3)"; 2 = 4 ; 12009 reflections (Max,. radiation,
28,,,,=29"), R=0.074, R,, =0.083. Refinement to lower R factor was
limited by the number of parameters allowed in the programs employed
and by disorder in one solvate molecule. Details will appear in 8. D.
Zwick, Ph. D. 7'hesis. University of Utah, Salt Lake City 1987.
[I21 B. Fuchs, Top. Stereochem. I0 (1978) I.
In the case of iodophosphonium ions, the proposed structures and the suggestion of equilibria such as
(a) are based mainly on conductivity m e a s ~ r e m e n t s . [Io~.~~
dophosphonium ions are isoelectronic with the phosphane
tellurides R3P=Te, for which rapid transfer of tellurium to
tertiary phosphanes is observed. We have suggested that
the mechanism of this transfer involves nucleophilic attack
on the tellurium atom with formation of (10-Te-2) intermed i a t e ~ . ' ~In] the correspondingly rapid transfer of I @ ions
between phosphanes, (10-1-2) intermediates will be energetically favored if, despite its negative polarization, the iodine atom bonded to the phosphonium center is appreciably electr~philic.[~."~
We have now found that 3'P-NMR
spectroscopy provides a very sensitive method to detect the
significant increase in electrophilic character o f the halogen atom in going from chloro- to bromo- to iodophosphonium salts. Furthermore, the first crystal structure
analysis of a diiodophosphorane shows that, in the solid
state, a linear arrangement P-1-1 having a (10-1-2) situation
on the central iodine atom, i.e., a new structural type for
halophosphoranes (Fig. 1 C), is present."]
When the reaction of tri-tert-butylphosphane 1 with various amounts of elemental iodine in CH2C12is followed by
'H- and 3'P-NMR spectroscopy, one observes continuous
changes in the chemical shifts and the coupling constants
during the addition of the iodine; separate signals for the
reaction products are not observed (Table 1). After the
Table I. "P-NMR data for the system lliodine (31.91 MHz)
1
1 :I,
1: I ( = 2 )
1 : 1 2 = 1.1.5
1:12= 1:2(=3)
Iodophosphonium Salts with Unusual Properties and
a Structural Alternative for Halophosphoranes**
By Wolf- Walther du Mont. * Michael Batcher,
Siegfried Pohl, and Wolfgang Saak
The halogenation of tertiary phosphanes affords dihalophosphoranes, which, in the condensed phase, are present
as molecules having a trigonal-bipyramidal arrangement of
the substituents, A , or as halophosphonium halides, B (Fig.
I), depending on the substituent pattern at the phosphorus
Xe
X
R-
P-X-X
R
A
B
(I 0-P-5)
(8-P-4)
c
+
(8-P-4) (10-X-2)
[**I
Prof. Dr. W.-W. du Mont, Dipl.-Chem. M. Batcher, Prof. Dr. S . Pohl,
DipLChem. W. Saak
Fachbereich Chemie der Universitat
Carl-von-Ossietzky-Strasse 9- I I , D-2900 Oldenburg (FRG)
This work was supported by the Deutsche Forschungsgemeinschaft and
the Fonds der Chemischen Industrie.
9 12
0 VCH VerlagsgesellschaJi mbH, 0-6940 Weinheim, 1987
rBu,PIGIo 2 8
I Bu, PI @ B Php
P'P
I 'J(" P, I H ) I
IHzl
CD,CI,
CD?C12
CD2CI,
C H2CI,/C,D,
H20/D20
CD2C12
62.0
80.8
96
I12
115
I10
t 9.8
t 16.0
t 16.8
k 17.4
t 17.8
2 18.0
"equivalence point" ( 1 :I2 = 1 : 1) is attained, the 3'PNMR shift does not remain constant upon continued addition of iodine, but rather is shifted further downfield and
the 3Jz[p,1H
values increase still further. The 1 : I adduct 2
formed between 1 and iodine in water (colorless solution)
exhibits 3iP-NMR shifts and coupling constants 3J31p.1H
that are very close to those of the phosphonium salt
tBu3PI@BPh?(colorless in solution and in the solid state)
and differ clearly from the NMR data of the yellow solutions of 2 in CH2CI, or CHCI3 (Table 1). All observations
are in accord with a pronounced acceptor character of the
iodine atom bonded to the phosphonium center toward
soft nucleophiles (Ie, PR3, I:):
1. If 1 is present in excess, 2 undergoes rapid I @exchange
[Eq. (b)], so that averaged NMR shifts and coupling
constants are
Fig. I . Structural alternatives for the compounds R3PX2[I].
[*I
=
Solvent
tBu3PIo
+ P * f B u , ;=It B u , P i IP*tBuy
(b)
2. Pure 2 is characterized by a considerable iodine-iodine
interaction (2C) in aprotic dipolar solvents and in the
solid state; these interactions are the apparent cause of
0570-0833/87/0909-0912$ 02.50/0
Angew. Chem. Int. Ed. Engl. 26 (1987) No. 9
the yellow color of 2 [2 in CH3CN: /2,',,=314nm
(c=900), tailing into the visible]. Nucleophilic attack of
l o on the iodine atom in tBu3PI@leads to upfield shift
and a reduction in
Isolated, hydrated tBu3PIe
and I 0 ions are probably present in water (2B).
3. If iodine is present in excess, iodophosphonium triiodide 3 is f ~ r m e d . [ ~ - ~ .The
' " ' 1: ion is apparently less
nucleophilic than I', so that addition of iodine to 2
in CH2C12results in a downfield shift of the 3'P-NMR
signal, namely toward the value for the "free" tri-tert-butyliodophosphonium ion [Eq. (c)].
7J31p,1H.191
C
[7] A compound containing a linear As-1-1 structural fragment was recently
reported: C. A. McAuliffe. B. Beagley, G . A. Gott, A. G. Mackie, P. P.
MacRory, R. G. Pritchard, Angew. Chem. 99 (1987) 237; Angew Chem.
Int. Ed. Engl. 26 (1987) 264 and 370.
[S] A correspondingly fast bromine cation transfer is observed In the system
l/tBu3PBr": W.-W. du Mont, Z. Anorg. Allg. Chem. 458 (1979) 85.
191 The NMR data of bromo-tri-ferf-butylphosphonium salts are only
slightly dependent on the anion and the solvent [lo].
[lo] M. Batcher, Diplomarbeit. Universitat Oldenburg 1987. Correct analytical data obtained for 2 and 3.
[ I l l 2 : orthorhombic, space group Pnma, a=1543(1), b = 1229.1(1),
c=922.0(1) pm, V = 1 7 4 9 . 6 ~lo6 pm', 2 = 4 ; 1397 unique reflections,
1217 observed (1>20(1)); R,, =0.038 (measurement, Siemens-AED-2;
solution, SHELX-76). Further details of the crystal structure investigation may be obtained from the Fachinformationszentrum Energie. Physik, Mathematik GmbH, D-75 14 Eggenstein-Leopoldshafen2 (FRG), o n
quoting the depository number CSD-52635, the names of the authors,
and the journal citation.
(121 For the behavior of Ph,AsI1 in C H K N solution: A. D. Beveridge. G . S .
Harris, J. Chem. Sor. 1964. 6076.
1131 N. N. Greenwood, A. Earnshaw: Chemistry of the Elements. Pergamon,
Oxford 1984, p. 940-943.
[I41 Similarly as phosphane tellurides R,P=Te can also be regarded as Tellphosphane complexes: W.-W. du Mont, Angew. Chem. 92 (1980) 562;
Angew. Chem. Int. Ed. Engl. 19 (1980) 554.
[I51 L. Horner, H. Winkler, Tetrahedron Lett. 1964. 445.
C
Structure and Magnetic Properties of a
Gadolinium Hexafluoroacetylacetonate Adduct with
the Radical 4,4,5,5-tetramethyl-2-phenyl-4,5-dihydrolti-imidazole 3-Oxide 1-Oxyl**
I
By Cristiano Benelli, Andrea Caneschi, Dante Gatteschi,*
Jean Laugier, and Paul Rey*
Fig. 2. Crystal structure of 2 (H atoms omitted); thermal ellipsoids at 50%
probability. Selected distances [pm] and angles ["I: 11-12 332.6(1), 12-P
246.1(2), P-CI 190.5(6), P-C5 190.1(9); 11-12-P 177.6(1), 12-P-CI 106.3(2), 12P-C5 105.1(3), CI-P-C5 I12.5(2).
The X-ray structure analysis (Fig. 2)"'l carried out on a
yellow crystal of 2 confirms the existence of significant
iodine-iodine interaction in the solid state. The nearly linear P-1-1 structural fragment makes 2 comparable with
iodine charge-transfer complexes such as the recently described triphenylarsane diiodine.1'. Since the 1-1 bond in
solid 2 is considerably longer than in typical iodine
charge-transfer complexes (d(1-I) in 2 332.6, in Ph3As12
300.5 pm".'31), 2 can be regarded as an iodophosphonium
salt or as a phosphane diiodine charge-transfer comple~."~]
It remains to be shown whether, in the equilibria (a) suggested
Is] the undissociated form R3P12is indeed
present as a (10-P-5) phosphorane or instead as analogue 2
[with hypervalent (10-1-2) iodine].
Adducts of stable organic radicals with metal ions are
currently investigated"' in order to discover novel types of
magnetic interactions and also to study possible models of
biologically relevant materials.
I n principle, the interaction of radicals with lanthanoid
ions can give rise to interesting magnetic properties, because of the high spin values of the metal ions. Indeed,
although the f orbitals are relatively shielded, they can
nevertheless overlap with the orbitals of the radical in a
direct exchange mechanism, thus giving rise to appreciable
coupling.
To our knowledge, only a few solution studies of weak
interactions between nitroxides and lanthanoid ions have
been reported so far,['] but no stable adducts of a radical
ligand directly bound to a lanthanoid ion have been characterized. We wish to report here the synthesis, X-ray crystal structure, and magnetic properties of the adduct formed
by gadolinium(rr1) hexafluoroacetylacetonate, Gd(hfac),
l,I3]with the radical 4,4,5,5-tetramethyl-2-phenyl-4,5-dihydro-lH-imidazole 3-oxide I-oxyl 2.14]
Received: March 25, 1987:
supplemented: May 5, 1987 [Z 2163 I€]
German version: Angew. Chem. 99 (1987) 945
I
[I] (10-P-5) means ten valence electrons around the central atom P, to
which five ligands are bonded: C. W. Perkins, J. C. Martin, A. J. Arduengo 111, W. Lau, A. Alegria, J. K. Kochi, J. A m . Chem. Soc. 102
(1980) 7753.
[2] K. Issleib, W. Seidel, Z. Anorg. Allg. Chem. 288 (1956) 201.
[3] A. D. Beveridge, G. S. Harris, F. Inglis, J Chem. Soc. A 1966, 520.
[4] W.-W. du Mont, H. J. Kroth, J. Organomet. Chem 113 (1976) C35.
[ 5 ] H. J. Frohn, H. Maurer, J. Fluorine Chem. 34 (1986) 73.
161 The first crystallographic evidence for the acceptor behavior of an iodine atom bonded to a phosphonium center was provided by the structure
determinations of PltAlI? and PII?AIIy: S. Pohl, Z. Anorg. Allg. Chem.
498 (1983) 15, 20.
Anyew. Chem.
Inl.
Ed. Engl. 26 (1987) No. 9
00
[*I Prof. Dr. D. Gatteschi, Prof. Dr. C. Benelli, Dr. A. Caneschi
Universita degli Studi di Firenze, Dipartimento di Chimica
Via Maragliano 75, 1.50 144 Firenze (Italy)
Dr. J. Laugier, Dr. P. Rey
Laboratoires d e Chimie, UA I194 C N R S
Departement d e Recherche Fondamentale, C.E.N.G.
85 x Grenoble Cedex, F-38041 Grenoble (France)
[**I The financial support of the Italian Ministry of Public Education and of
the C N R is gratefully acknowledged.
0 VCH Verlagsgesell.ichaji mbH, 0-6940 Weinheim, 1987
0570-0833/87/0909-0913 $ 02.50/0
91 3
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salt, structure, properties, halophosphoranes, iodophosphonium, unusual, alternative
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