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Methylene Phosphonium Ions.

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uncommon complexes with unique features. The overall reactivity pattern observed here is substantially different from
that of electron-rich Ir' phosphane complexes with ammonia,r4"]perhaps because of the better ability of phosphanes to
stabilize the soft Ir' metal center and the steric constraints
imposed by these ligands. Indeed, the reaction described
here, which occurs even at -50°C, is to our knowledge the
fastest reported ammonia oxidative addition to a transitionmetal center in s o l ~ t i o n . ~ ~ ~
We are currently studying the mechanism and scope of this
unusual N-H cleavage process and the chain of events leading to the final products. The advantages of using ammonia
as both a substrate and ligand for potential catalysis is also
being explored.
which is isostructural with these compounds, could only
recently be completely characterized.I3I Although for steric
reasons the halves of the molecule are twisted through 60"
relative to one another, the P-C distance of 1.62 8, is very
short, which can be attributed to strong electrostatic interact i o n ~ . ' Variation
~'
of the substituents at the P or C atom, or
both, should change the character of the P-C bond. Thus the
synthesis of P-alkylated methylene phosphonium ions,
which we now report, is interesting.
2
1
3a
3b
Received: December 28, 1990 [24363 IE]
German version: Angew. Chem. 103 (1991) 724
[1] F, T. Campbell, R. Pfefferkorn, J. F. Rounsaville (Eds.): Ullmanns Encyclopedia of' Industrial Chemisfry, Vol. A2, 5th ed., VCH, Weinheim 1985;
pp. 228-230.
[2] Reviews: a) J. J. Brunet, D. Neibecker, F. Niedercorn, J. Mol. Caral. 49
(1989) 235-259; b) D. Steinborn, R. Taube, 2. Chem. 26 (1986) 349-359.
[3] A. L. Casalnuovo, J. C. Calabrese, D. Milstein, J. Am. Chem. Soc. 110
(1988) 6738-6744.
[4] a) M. M. Banaszak Holl, P. T. Wolczanski, G. D. Van Duyne, J. Am.
Chem. Soc. 112 (1990) 7989-7994; b) H. W. Roesky, Y Bai, M. Noltemeyer. Angew. Chem. 101 (1989) 788-789; Angew. Chem. Int. Ed. Engl. 28
(1989) 754-755; c) A. L. Casalnuovo, J. C. Calabrese, D. Milstein, Inorg.
Chem. 26 (1987)971 -973; d) J. E. Bercaw, D. L. Davies, P. T. Wolczanski,
Organomefallics5 (1986) 443-450; e) G. L. Hillhouse, J. E. Bercaw, J. Am.
Chem. SOC.106 (1984) 5472-5478; f) G. Suss-Fink, 2. Narurforsch. B 35
(1980)454-457: g) J. N. Armor, Inorg. Chem. 17(1978) 203-213; h) E. G.
Bryan, B. F. G. Johnson, J. Lewis, J. Chem. Soc. Dalfon Trans. 1977,13281330.
(51 We also observe a small amount of the monomeric, square-planar complex
cis-[(C,H,,),Ir(NH,)CI], which exhibits sharp vinylic "C NMR signals,
as opposed to the broad I3C NMR signals of 2. The broadness is probably
a result of fluxional behavior expected in a trigonal-bipyramidalcomplex.
Free cyclooctene is not observed ('H NMR), thus excluding dissociative
equilibria.
[6] The maximum theoretical yield is 50%.
[7] A. L. Casalnuovo, private communication.
[8] D. A. House in R. D. Gillard, J. A. McCleverty (Eds.): Comprehensive
Coordination Chemistry, Vol. 2, Pergamon, Oxford 1987, pp. 26-28.
[9] A mechanism based on deprotonation of an ammine ligand by ammonia
is highly unlikely since (1) deprotonation of Ir"'-NH, would be preferred
over that of 1r'-NH, and formation of at least some Ir"'-NH, would be
expected, but none is observed, (2) the Ir"'-NH, complexes 3 and 4 do not
undergo deprotonation even in the presence of a large excess of ammonia,
(3) reaction of 4s with KN(SiMe,), leads to deprotonation of Ir-H (and
not of Ir-NH3), and (4) equivalent amounts of Ir"' and Ir' complexes are
formed, regardless of the ammonia concentration employed.
[lo] Complexes 4a, 5, and 6 were obtained as pure solids. Complex 2 was
isolated together with minor amounts of its monomer. Complex 3a was
obtained in a mixture with 4a. The structures of 3a and 4a were further
confirmed by substitution reactions with PEt,.
The reaction of lithiobis(trimethylsi1yl)methane 41'' with
di-tert-butylchlorophosphane5 in THF afforded quantitatively phosphane 6.r61Oxidation of this compound with
CCI,"l in hexane led to loss of CHCl, and the concomitant
formation of the chloro-substituted phosphorus ylide 7,
whereas the reaction at -78 "C in CH,CI, yielded ylide 8
exclusively, with loss of Me,SiCCI,. The abstraction of chloride from (iPr,N),CIPe -C@(SiMe,), by aluminum trichlobut the corresponding
ride to form 3 was not successf~l,[~l
reactions with 7 and 8 yielded the desired methylene phosphonium ions 9 and 10, respectively.['Ol
LiCH(SiMe&
4
+
tBu2PCI
-
tBuZP-CH(SiMe&
6
5
9
7
Rapid workup of the reaction mixtures at temperatures
below - 30 "C allowed the isolation of 9 and 10 as colorless,
crystalline solids. They may be stored in the solid state at
- 30 "C, but decompose in dichloromethane solution.
The NMR spectra of 9 and 10 differ greatly from those of
3 (Table 1). The resonance signal of both the phosphorus
Methylene Phosphonium Ions**
By Hunsjorg Grutzmucher* and Hans Pritzkow
Table 1. Selected NMR data of 3, 9, 10, 11, 12, and 13 [a]
Stable silaethenes 1 ['I and phosphinoboranes 2 ['I are wellknown. In contrast, the methylenephosphonium ion 3,
[*I Dr. H. Grutzmacher, Dr. H. Pritzkow
Anorganisch-chemisches Institut der Universitat
Im Neuenheimer Feld 270, W-6900 Heidelberg
[**I This work was supported by the Dr. Otto Rohm Gedachtnisstiftung, the
Deutsche Forschungsgemeinschaft, the Fonds der Chemischen Industrie
and by Prof. W. Sundenneyer and Prof. G. Huttner. We thank Prof. R.
Ahlrichs sincerely for helpful discussions.
Angew. Chem. Int. Ed. Engl. 30 (199t) No. 6
0 VCH
~~~~~~~
Cmpd.
fpP)
a(%)
'J(CP) (Hz]
Ref
3
130.8
258.7
245.4
330.2
438.7
328.2
76.5
178.8
149.6
128.6
194.4
87.6
8.6
45.2
76.8
94.3
[31
-
-
9
10
11
12
13
~~~~~~~~~
[111
[I21
1131
~
[a] For a complete list of the NMR data for 9 and 10, see ref [lo].
Verlagsgesellschafl mbH, W-6940 Weinheim. 1991
8 3.50-k,2810
0570-0833/91~0606-0709
709
atom and the carbon atom of the double bond are strongly
shifted to lower field relative to 3. Comparison with ll,'"]
12,[l21and 13[l3'shows that the chemical shifts of the sp2
carbon atoms in 9 and 10 lie among the typical values for
phosphaalkenes. Predictably, the 31PNMR signals of 9 and
10 are strongly shifted to higher field with respect to the
corresponding signals in 12 and 13, as a result of the increase
in the coordination number of the phosphorus atom. On the
grounds of these NMR data, 9 and 10 may be considered
analogues of olefins, while in 3 interaction with the lone pairs
of the amino groups compensates for the electron deficiency
at the phosphorus atom. The "double bond" between the
phosphorus and carbon atoms in 3 has a pronounced ylide
character.
Because of the facile decomposition of 9 and 10 in solution, only crystals of 10 have been obtained, though in poor
quality, by rapid crystallization from n-hexane/CH,CI,. The
X-ray structure analysis['41could give only qualitative information about the molecular geometry, but indicates that the
phosphorus atom is in an almost planar environment (sum
of the bond angles: 359°C) and the halves of the molecule
are twisted 11 relative to one another. The length of the
P-C double bond is 1.69(4) A, which lies in the range typical
of phosphaalkenes. The cations and anions are separated in
the crystal (shortest P-CI distance: 3.9 A).
Remarkably, in both the 'H and 13CNMR solution spectra of 10, even at temperatures as low as -90 "C, the signals
of the tert-butyl groups are equivalent, from which we conclude that the rotational barrier for the P-C multiple bond
is unusually low compared with phosphaalkenes.
The reactivities of 3,9, and 10 also differ widely. Whereas
only nucleophilic attack on the phosphorus atom is available
to 3,1319 and 10 react rapidly with 2,3-dimethylbutadiene at
room temperature, in spite of steric hindrance of the P-C
bond. (The reaction of 10 is exothermic!) The product from
9 in this reaction is predominantly 14, formed by an ene
reaction, while the sterically less hindered 10 undergoes exclusively a [2+ 41 cycloaddition to yield 15.r'51The ene reac-
=f
14
131 A. Igau, A. Bacereido, H. Grulzmacher. H. Pritzkow, G. Bertrand, J. Am.
Chem. Soc. 111 (1989) 6853.
[41 M. Ehrig. H. Horn, C. Kolmel, R. Ahlrichs, J. Am. Chem. Soc., in press.
I51 N. Wiberg, G. Wagner, G . Muller, J. Riede, J. Organomel. Chem. 271
(1984) 381.
[61 B.-L. Li, R. H. Neilson, lnorg. Chem. 23 (1984) 3665. Pure 6 has a melting
point of 44°C.
171 0.1. Kolodiazhnyi. 2. Chem. 29 (1989) 396, and references cited therein.
Product distributions that are solvent dependent are well known for the
reaction of phosphanes with CCI,: R. Appel, F. Knoll, W. Michel, W.
Morbach, H. D. Wihler, H. Veltmann, Chem. Ber. 109 (1976) 58.
I81 0 . 1 . Kolodiazhnyi, Zh. Obshch. Khim. 5 1 (1981) 2466.
191 H. Grutzmacher. unpublished results; see also. R. Appel, R. Schmitz,
Chem. Ber. 116 (1983) 3521.
(101 Preparative details: 7: Compound 6(3.04 g, 10 mmol) wasdissolved indry,
degassed n-hexane (20 mL), and CCI, (4.62 g, 30 mmol) was added at
- 78 "C. The reaction vessel was then warmed to room temperature and
stirred for 3 h. Thereafter all volatile components were removed under
vacuum, CH,CN (10 mL) was added to the bright yellow, oily residue, and
the mixture was solidified at - 30 "C. Further purification of 7 can be
achieved by sublimationat 100"C/lO-'Torr. M.p. 127'C; ,'P(l H} NMR
(C6D6): 6 = 105.9; ',CNMR (C,D6): 6 = 8.5 (d, ,J(PC) = 3.7 Hz,
'J(SiC) = 52.9 Hz, SiCH,), 27.65 (d, 'J(PC) = 130.1 Hz, P@-Ce), 28.68
(d, ,J(PC) = 3.5 Hz, CCH,). 44.3 (d. 'J(PC) = 39.3 Hz, CMe,); 'H NMR
(C6D6): 6 = 0.46 (s, 18H. SiCH,), 1.12 (d, ,J(PH) = 16.4Hz, 18H.
CCH,); "Si NMR (CDCI,. T = 230 K): 6 = - 2.43 (d, ,J(PSi) =
1.8 Hz), - 11.33 (d, 'J(PSi) = 23.3 Hz). MS (EI, 70 eV): mjz 338 ( M e ,
5%). 323 (Me-CH,, 7.5). 267 (5). 226 (7), 211 (9). 147 (11). 120 (13), 73
(Me,Si, 461, 57 (Me,C, 100). 9: Compound 7 (1 g, 3 mmol) was dissolved
in CH,CI, (10 mL) and added dropwise by syringe to a suspension of
freshly sublimed AICI, (0.45 g, 3.4 mmol) at -78 "C. The resulting pale
yellow solution was stirred for 10 min and then rapidly separated from
unreacted AICI, by filtration without warming. The solvent was thereafter
removed in vacuum at - 30--10 "C. The crystalline residue was washed
with n-hexane and dried in vacuum; yield 80-90%. I3C NMR (CD,CI,):
6 = 5.1 (d. 'J(PC) = 6 Hz, 'J(SiC) = 54.5 Hz, SiCH,), 31.4 (5, CCH,),
54.6 (d, 'J(PC) = 8.7 Hz, CMe,), 178.8 (d, 'J(PC) = 8.6 Hz, P = C);
'HNMR (CD,CI,): 6 = 0.48 (s, 18H, SiCH,) 1.75 (d, ,J(PH) = 18.5 Hz,
18H, CCH,); 27AINMR (CD,CI,): 6 = 103.6. 10: Analogous to 9, from
8 (1 g, 3.7mmol) and AICI, (0.56g. 4.2 mmol). ',CNMR (CD,CI,):
6 = 1.2 (d, "(PC) = 6.3 Hz, SiCH,), 30.3 (d, 'J(PC) = 1.4 Hz, CCH,).
47.5 (d, 'J(PC) = 10.6 Hz, CMe,), 149.6 (d, 'J(PC) = 45.2 Hz, P = C);
'H N MR (CD,CI,): 6 = 0.11 (d, 4J(PH) = 1 Hz, 9H, SiCH,), 1.43 (d,
'J(PH) = 18.8 Hz, 18H, CCH,), 7.75 (d, ,J(PH) = 36.7 Hz, 1 H, CH);
27A1NMR (CD,CI,): 6 = 103.6. The chloride abstraction from 7 or 8
failed with GaCI, or SbCI,.
[ I l l R. J. Thoma, C. A. Prieto, R. H. Neilson, Inorg. Chem. 27 (1988) 784.
[12] K. Issleib, H. Schmidt, C. Wirkner, 2. Anorg. Allg. Chem. 473 (1981)
85.
(131 I. F. Lutsenko, A. A. Prishchenko, A. A. Borisenko, Z. S . Novikova,
Dokl. Akad. Nauk. SSSR 256 (1981) 1401.
[14] Thin colorless flakes, poorcrystal quality, space group Pbcb, a = 12.90(1),
b = 16.51(1), c=21.17(2).&, V=451OA3, Z = 8 ; 550 observed reflections with I > 20(0 (/er/-butyl and trimethylsilyl groups and AlClF as
rigid groups, Al, C1, P, and Si refined anisotropically, C isotropically; 85
parameters, R = 0.15).
[15] 14: m.p. = 144°C. "P('H}NMR (CDCI,): 6 = 61.4. Another signal of
low intensity (S0/o) at 6 = 53.4 can be assigned to the corresponding I2 41
cycloadduct. Cf. ,'P NMR signal of 15. "CNMR (CDCI,): 6 = 6.0 (d,
'J(PC) = 2.3 Hz, SiCH,), 6.5 (d, 'J(PC) = 9.1 Hz, CHSi,), 21.2 (s, CH,),
25.1 (d, 'J(PC) = 42.8Hz, PCH,), 29.1 (s, CCH,), 37.7 (d, 'J(PC) =
35.1 Hz, CMe,), 115.5 (s, H,C= CMe-), 118.1 (d, ,J(PC) = 4.5 Hz,
H,C = CMe-), 138.6 (d, 'J(PC) =7.0 Hz, H,C = CCH,), 142.3 (d,
*J(PC) = 8.9 Hz, H,C = CCH,); 'HNMR (CDCI,): 6 = 0.52 ( s , 18H,
SiCH,), 1.28 (d, ,J(PH) = 22.8 Hz, 1 H, CHSi,), 1.56 (d, ,J(PH) =
15.4Hz,18H,CCH3),2.00(~,3H,CH3),3.20(d,'J(PH)=
12.3Hz,2H,
CH,), 5.21 (s, 1 H, HHC =), 5.23 ( s , 1 H, HHC =), 5.27 (s, 1 H, HHC=),
5.72 (s, l H , HHC =); "AINMR (CDCI,): 6 = 102.3 15: m.p. = 169°C.
"P('H}NMR (CD,CI,): 6 = 55.8; l3CNMR (CD,CI,): 6 = 1.2 (d,
'J(PC) = 1.6 Hz, SiCH,), 16.1 (d, 'J(PC) = 34.9 Hz, CHSi), 19.8 (d,
4J(PC) = 1.9Hz, CH,), 20.3 (d, 'J(PC) =7.0Hz, CH,), 21.6 (d,
'J(PC) = 40.1 Hz, PCH,), 27.4 ( s , CCH,), 27.6 (s, CCH,), 32.6 (d,
'J(PC) =7.3 Hz, CH,), 34.5 (d, 'J(PC) = 36.1 Hz, CMe,), 35.6 (d,
'J(PC) = 35.4 Hz, CMe,), 120.3 (d, "(PC) = 8.4 Hz, = C), 133.7 (d,
'J(PC) = 8.2Hz, =C);'HNMR(CD,CI,):6 =0.31(s,9H,SiCH3),1.11
(ddd. 'J(PH) = 31.4 Hz. 'J(HH) = 12.5 Hz, 'J(HH) = 3.4 Hz, 1 H,
CHSi), 1.26(d, 'J(PH) = 15.0Hz, 9H, CCH,), 1.39(d, 'J(PH) = 15.2 Hz,
9H, CCH,), 1.70 (s, 3H, CH,). 1.79 (s, 3H, CH,), 2.10-2.44 (m. 2H,
CH,), 2.55 (d, 'J(PH) = 11.0 Hz, 2H, CH,); 29Si (CD,CI,): 6 = 8.0 (d,
*J(PSi) = 15.15 Hz); 27AINMR(CDCI,): 6 = 102.3.
[16] With silaethenes the [2+4] cycloaddition product is often observed in a
mixture with products of theene reaction; see, forexample, N. Wiberg, M.
Link, G. Fischer, Chem. Ber. 122 (1989) 409
+
15
tion is, to our knowledge, not yet described for phosphaalkenes, but is often observed in the chemistry of the
silaethenes 1 and underlines their close relationship to 9 and
10."6'
Received: January 11. 1991 (24379 IE]
German version: Angew. Chem. 103 (1991) 721
CAS Registry numbers:
6,89982-67-2; 7,133474-11-0; 8,81176-02-5;9, 133474-13-2;10,133474-15-4;
14, 133474-17-6; 15, 133474-19-8;CCI,, 56-23-5; 2,3-dimethylbutadiene, 51381-5.
[l] A. G. Brook in E. Block (Eds.): Heteroatom Chemistry, VCH Publishers,
New York 1990, p. 105; G. Raabe, J. Michl in S. Patai, Z. Rappoport
(Eds.): The Chemistry of Organic Silicon Compounds, Wiley, Chichester
1989, p. 1015; N. Wiberg, J. Urgunomet. Chem. 272 (1984) 141.
[2] P. P. Power, Angew. Chem. 102(1990) 527; Angew. Chem. Int. Ed. Engl. 29
(1990) 449.
710
0 VCH
VerlagsgeseUschaft mbH. W-6940 Weinheim, 1991
0S70-0833l9l/0606-0710S 3SO+ .25/0
Angew. Chem. Int. Ed. Engl. 30 (1991) No. 6
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