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Intramolecular Base Stabilization of Silicenium Ions A New Route to Siliconium Ions.

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DAB-(/[,ii//,.-(NH,),: To a hydrogenation vessel. filled with Raney Cobalt catalyst ( C r promoted. Grace 2724. pretreated with hydroxide. YO0 g) and wafer
(22.5 L) was iidded DAB-r/mdr-(CN), (450 g) dissolved in methanol. Subsequentl! the mixture was hydrogenated at 40 atm hydrogen pressure at 70 C for
1 h. The cooled reaction mixture was then filtered and the solvents were evaporated at reduced pressure. The residue contained 450 g (95%) N M R spectroscopically pure DAB-r/wx/r-(NH,), as a colorless oil.
l3C N M R (50 MH7, D,O). 6 = 53.4 (NCH,CH,CH,CH,N),
39.5 (CH,NH,).
28.8 (CH2CH2NHL). 23.9
(NCH,C'H,CH,CH,N); 'H N M R (200 MHz. CDCI,): 6 = 2.70 (t. 8 H .
2.40 (m. 4H.
2.44 (I. 8 H . NCH,CHJH,NH,).
1.58 (quin. 8 H . CHLCH,NHL), 1.42 (m. 12H.
NCH,C'/I,CH,CH,N. NH,): IR (film): i. = 3284. 3355 c m - ' (NH?).
Received: April 28, 1993 [ Z 6041 IEJ
German version: Angeii. C/im. 1993. 105, 1370
[I] D. A . Tomalia, A. M. Naylor. W. A. Goddard 111, Angru,. Chwi. 1990.
102. 119. .4ngeu Chem. Inr. €d. €ng/. 1990, 29, 138-175.
[2] D. A. Tomalia. H. Baker, J. Dewald. M. Hall, G. Kallos, S. Martin. J.
Roeck. J. Ryder. P. Smith. Poh.777. J. Tokjo 1985. 17, 117-132.
[3] c'. J. Hawker, J. M. J. Frechet. J. Am. Chem. Sw. 1990. f12, 7638.
[4] G R. Neukome. X. Lin, Mucromulecules 1991.24.1443; G. R. Newkome,
A Nayak. R. K. Behera, C. N. Moorefieid. G. R. Baker. J. Org. Chun.
1992. 57. 358.
[5] C. J. Hawker. J. M. J. F r k h e t , Poljino. 1992. 33. 1507.
[h] H -B. Mekelburger. W. Jaworek, F. Vogtle. A n g ~ i vChem.
1992. 104. 1609:
.4iig<w.<'/lcv71.I n l . Ed. Ei7gl. 1992, 31, 1571.
[7] T. M. Miller, E. W. Kwock. T. X. Neenan. Mucroi77olecrrles 1992.25, 3143:
A W van der Made. P. W. N. M. van Leeuwen. J. Cliern. Soc. CIiem. Comi m m 1992. 1400: A. Morikawa. M. Kakimato, Y. Imai. Mucromo/wu/e.\
1991. 24. 3469.
[XI E. Buhleier. W. Wehner, F. Vogtle. S?nlhrc.i.c 1978. 155- 158.
[Y] Independently C. Worner and R. Mulhaupt (Angew. Cliem. 1993. 105.
1367 1370; Angen.. Chew. Inl. Ed. Engl. 1993, 32. 1306 1308) have disclosed a similar reaction scheme.
[lo] DAB-hir/r-(CN), means a dendrimer with DAB (DiAminoButane) as
core and s nitrile end groups: DAB-dendr-(NH,), one with .r primary
iimine end groups. A proposal for the systematic naming of dendrimers is
given by G. R. Newkome, G. R. Baker. J. K. Young, 3. G. Traynhdm. J.
Sci. Purl .4 1993. 31. 641 - 651.
[l 1 I Retro-Michael addition during the hydrogenations is strongly base-catalyrcd by dendrimers with NH, end groups.
[12] T. H. Mourey. S . R. Turner, M. Rubinstein. 3. M. J. Trechet. C. J. Hawker.
K.L. Wooley. Mucron7o/rcu/e.s 1992. 26. 2401
However, these examples d o not constitute a general route to
cationic silicon species with a functional group at silicon that
enables reactivity studies.
Some years ago, we showed that pentacoordinate neutral
and anionic silicon species have unusual, often unexpected
reactivity.[161That led us to prepare cations containing pentacoordinate silicon centers (siliconium ions) in order to
study their reactivity.
Since intramolecular coordination of the amino group stabilizes silanethione,[' 71 silaphosphene.[lS1silanimine,[' 'I and
transition metal silanediyl complexes very efficiently,['8,
we decided to extend this intramolecular stabilization to the
silylium ions. We report here a novel and general route to
functional and nonfunctional siliconium ions using the potentially bischelating iigdnd A,["]
The reaction of the silane 1 with half an equivalent of
iodine in ether at room temperature results in the formation
of a precipitate and loss of half an equivalent of H, in a redox
reaction. The precipitate was identified as the ionic species
2a (Scheme 1).
0.5 I?
@y h
F /-\
Intramolecular Base Stabilization of Silicenium
Ions: A New Route to Siliconium Ions
Scheme 1.
Ph&? BFC
2 a : X=I(loO%)
b : X=Br(90%)
C : X=C1(92%)
d : X = BF4 (86%)
e : X = CF3S03(91%)
By Ckiude Chuii, Robert J. P. Corriu,* Ahmad Mehdi,
and Curherine ReyG
The possible existence of trisubstituted silylium "silicenium" ions (R,Si') has intrigued chemists for a long time.[',21
Nevertheless claims to have generated such species in solutionI3' have been disputedJ4' and the question whether triorganylsilyl perchlorates undergo ionization in solvents has
been reviewed by EabornrS1and Lickiss.16] Recently silyl
cations have been prepared in nonnucleophilic solvents with
weakly coordinating anion^.[^-*^ However, the structural
analysis of one of these derivatives showed a strong interaction between anion and cation.[']
Some silyl cations that can be prepared are spabilked by
the rr-pentamethylcyclopentadienyl ligand,"] intermolecular
coordination,[', l o - 31 o r intramolecular coordination.[14- '1
[*J Prof: Dr. R J P. Corriu. Dr. C. Chuit, A. Mehdi, Dr. C. Reye
Universite d e Montpellier I1
Sciences et Techniques du Languedoc, U R A 1097
Place Eugene Batdillon, case 007. F-34095 Montpellier Ckdex 5 (France)
Telehx: In[. code + (67)1438-88
The 'H N M R spectrum of 2 a shows a singlet at 6 = 5.3,
shifted to low field with respect to the resonance signal of the
SiH, protons of 1 and assigned to the SiH proton. The signal
of the methylene protons in 2a has an A B pattern. The two
NMe, groups are magnetically equivalent as a result of the
coordination of both nitrogen atoms to the silicon center and
give rise to two singlets of equal intensity. In the coupled ' H
29Si N M R spectrum of 2a, a doublet is observed at 6 =
- 29.7 ('JS,,"= 280 Hz), whereas the 29Si resonance of the
pentacoordinate silane 1["1 appears as a triplet at 6 =
- 51.5 ('&, = 200 Hz). Interestingly, the 29Si N M R spectrum of 2a in the solid state shows a sharp signal with the
same chemical shift (6 = - 28.8) as in solution. which indicates that 2a remains ionic even in the solid state.
The IR spectrum of 2 a in CHCI, shows a Si-H stretch at
i, = 2202 cmsubstantially higher than for 1 (21 11 cm- I ) .
Moreover this frequency is very close to that observed by
Jutzi et aLr91for the silyl cation [(rr-Me,C,),SiH]+.
The positive-ion FAB mass spectrum (FAB = fast atom
bombardement) of 2 a shows an ion at m/z 297 corresponding to the mass of the siliconium ion.
The same cation can also be generated by treating 1 with
one equivalent of various electrophiles such as N-chlorosuccinimide, PhCOX (X = C1, Br; reduced to PhCH0[221).
AgBF,, Ph,C'BF,,
o r CF,SO,SiMe, (Scheme 1). Species
2b-2e have all the same IR spectra, 'H and 29Si N M R
spectra, and the same positive-ion FAB mass spectra as 2 a .
These salts are air- and moisture-sensitive but they are stable
in solution under argon, as well as in the solid state.
As a confirmation of the ionic nature of the salts2 we
carried out conductivity titrations: aliquots of reagents in
CH,C1, (PhCOCI, PhCOBr, I,, CF,SO,SiMe,) were added
to a solution of the silane 1 in CH,CI,; the conductivity was
measured after each addition. Figure 1 depicts a plot of conductivity as a function of the added reagent. The conductivity increases until one molar equivalent of reagent has been
added, and thereafter it is constant.
The reaction of the lithium derivative 9IZ5]and dichlorophenylsilane or trichlorosilane also affords the corresponding siliconium ions (Scheme 2).
[rnScrn '1 o.6.
x [rnmol]
Scheme 2
Fig. 1. The conductivity ( K ) a s a function of the amount of electrophilic reagent
added (s)to a solution of 0.146 moles of silane 1 in CH,CI,.
In contrast, the chlorosilane 4 resulting from the reaction
of N-chlorosuccinimide with the silane 3 [Eq. (a), NClS =
N-chlorosuccinimide] shows no conductance in dichloromethane, as expected for a covalent c h l ~ r o s i l a n e . [ ~ ~ -
The formation of these siliconium ions should result either
from the abstraction of a hydride ion (when Ph,C+BF, o r
CF,SO,SiMe, is the reagent) o r from the substitution of an
hydrogen atom by a halogen atom that is displaced by the
nucleophilic coordination of the second NMe, group at silicon.
It is interesting to note that the dichlorosilane 11, the Xray structure of which has been determined,["] is covalent.
The preparation of siliconium ions by reaction of a electrophile on a silane bearing the ligand A and at least one
hydrogen atom is quite general. As indicated in Equations (b)
and (c), difunctional and nonfunctional siliconium ions have
also been obtained with a good yield by this process.
mbH, 0-69451 Weinheim, I993
This indicates the importance of the geometry of the ligand A in the formation of siliconium ions.
0570-0833/93/0909-1312$ l0.00+ .25/0
Angew. Chem. In[. Ed. Engl. 1993. 32, No. 9
Exprrimental procedure
[14] E. L. Muetterties, H. Roesky, C. M. Wright. J. Am. Chem. Sue. 1966. 88.
1 : A solution of 9 [25] (22 mmol) in Et,O (40 mL) was added slowly over 15 min
[15] G. Schott, K. Golz, 2. Anorg. Atig. Chrm. 1971, 383, 314; ibid. 1973,
at 0 -C to a solution of phenylsilane (2.4 g, 22 mmol) in Et,O (40 mL). The
399, 7.
mixture was stirred at room temperature for 2 h and then hydrolyzed at 0°C
[16] R. 1.P. Corriu, J. C. Young in The Chemrsrry of Orgunre Silicon Comwith 0.4 mL ofH,O. After filtration on celite. distillation gave 5.4 g (83%) of
pounds (Eds.: S . Patai, Z. Rappoport), Wiley, Chichester 1989, S. 1241;
1 as a colorless oil. B.p. 115-117 'C/0.02Torr; ' HNMR (250 MHz, CDCI,,
R.J. P. Corriu, J. Orgunornet. Chem., 1990, 400, 81; C. Chuit. R. J. P.
~ ~ S ~C.NReye,
M R J. C. Young, Chem. Rev. 1993, 93, 1371.
TMS):6 = 2.0(s. 12H.CH3),3.51( S , ~ H , C H ~ ) , ~ . ~ ~ ( S , ~ H , S ~ H , ) ;Corriu,
(200 MHz. CDCI,, TMS): 6 = - 51.5 (t. 'J(SiH), 200 Hz): IR(CC1,):
[17] P. Aryd, J. Boyer, F. Carre, R. Corriu, G . Lanneau, J. Lappasset, M.
i.[cm- '1 = 21 11 (SiH,). Correct elemental analyses (C.H.N,Si).
Perrot. C. Priou, Angeu. Chem. 1989, 101, 1069; Angnt,. Chem. h l . Ed.
Engl. 1989,28, 1016.
2 a : A solution ofiodine (0 43 g. 1.67 mmol) i n ether (10 mL) was added dropwise to a solution of silane 1 (1 g, 3.35 mmol) in Et,O (10 mL) at room temper[18] R. Corriu, G. Lanneau, C. Priou, Angen. Chem. 1991, 103, 1153; Angew.
Chem. Inr. Ed. Engl. 1991, 30, 1130.
ature under argon. The resulting mixture was stirred until evolution of H, had
ceased It became progressively colorlessas a precipitate appeared. The mixture
[19] R. Prohst. C. Leis. S. Gamper, E.Herdtweck, C. Zybill, N. Auner, Angebv.
Chem. 1991, 103, 1155; Angew.. Chem. Int. Ed. Engl. 1991. 30. 1132.
was then filtered, and the residue washed twice with ether to give 1.4 g (100%
yield) of a white microcrystalline powder. M.p. 135°C (decomp); ' H N MR
[20] G. van Koten. J. T. B. H. Jastrzehski, J. G. Noltes, A. L. Spek, J. C.
Schoone, J. Orgunomel. Chem. 1978, 148, 233.
(250 MHz, CD,CI,, TMS). 6 = 2.2 ( s , 6 H , CH,),2.85 ( s , 6 H , CH,). 4.0 (d,
[211 J. Boyer, C. Breliere, F. Carre, R. J. P. Corriu, A. Kpoton. M. Poirier. G.
SiH): "C NMR (200 MHz, CDCI,. TMS): 6 = 63.1 (CH,N), 47.1, 47.6
Royo, J. C. Young, J. Cliem. Sor. Dulton Truns. 1989, 43.
1221 R. Corriu, G. Lanneau, M. Perrot, Tetrohedron Letr. 1988, 29. 1271.
(N(CH,),). 11-3.2. 124.2, 127.3, 128.8, 131.2, 134.0, 143.0; 29Si NMR
(200 MHz. CDCI,, TMS): 6 = - 29.7 (d, 'J(Si,H) = 280 Hz); IR(KBr):
1231 A suspension of N-chlorosuccinimide (0.56 g, 4.15 mmol) in CCI, (1 5 mL)
i. [cm I] = 2202.
was added slowly at 0 "C to a solution of the silane 3 (b.p. 104- 110 'CjO.06
Torr) (1 g. 4.15 mmol) in CCI, (15 mL). The mixture was then stirred for
2c: A solution of 9 [25] (7.38 mmol) in Et,O (50 mL) was added slowly to a
5 h at room temperature. After the succinimide had been filtered off and
solution of dichlorophenylsilane (1.1 mL. 7.38 mmol) in Et,O (50mL). The
the solvent removed, 4 was obtained in 85 % yield; 'H NMR (80 MHz,
mixture was stirred at room temperature for 2 h. After filtration. the solid
obtained was dissolved in CH,CI, to precipitate LiCl which was removed by
5.5 (s. 1 H, SiH); 29Si NMR (250 MHz, CDCI,. TMS): 6 = - 53.6 (d,
filtration. After concentration. Et,O was added to precipitate crude 2 c as a
'J(Si,H) = 279 Hz).
whlte \olid (1.9 g. 90%) whose characterlstics are the same as those of 2a.
[241 R.J. P. Corriu, A. Kpoton, M. Poirier, G. Royo, A. de Saxce, J. C. Young,
6: A solution of I, (0.4 g. 1.56 mmol) in Et,O (15 mL) was added dropwise at
J. Orgunomel. Chem. 1990.3Y5. 1.
- 5 C to asolution ofsilane 5(b.p. = 45-50'C/0.1 Torr)(0.7 g, 3.15 mmol)in
[251 J. T. 9. H. Jastrzebski, G . van Koten, M. Konijn, C. H. Stam. J. Am. Chem.
Et,O (15 inL). The mixture was stirred at room temperature for 4 h, filtered.
Sor. 1982, f04.5490.
and the solid obtained washed twice with Et,O to give 1.1 g (100%) ofcrude 6.
M.p. 145 C (decomp); ' H NMR (80 MHz, CDCI,. TMS): 6 = 2.9 (s, 12H.
CH,). 4.4 (s. 4 H , CH,), 4.9 (s, 2 H , SiH,); "Si NMR (250 MHz, CDCI,.
TMS): d = - 46.4 (t, 'J(S1.H) = 265 Hz); IR (KBr): i.[crn-'] = 2191 and
8 : CF,SO,SiMe, (0.57 mL, 2.95 mmol) was added dropwise at 0°C to a solution of7 (b.p. = 120'C/0.2 Torr) (0.7 g. 2.8 mmol) in Et,O (15 mL). After stirring (30 min). the solvent was removed, and the solid obtained washed twice
Photochemical 1,2 Shift of the Phosphane
with Et,O to give 1.1 g (100%) of crude8. M.p. =118-121'C; ' H N M R
Ligands in the Silanediyl Complex
(250 MHz. CDCI,. TMS): 6 = 0.4 (5. 6H. Si(CH,),). 2.4 (s. 12H. N(CH,),).
3.8 (s. 4H. CH,): "F NMR (80MHz. CDCI,. C,F,,). 6 = 85 (s); '9Si NMR
[ (2-Ph,PCH,C6H4),Si=Cr(CO),1""
(250 MHr. CDCI,. TMS): 6 = 4.1 (s); positive-ion FAB-MS: m/; 249 ( M + ,
10001" )
By Hermann Handwerker, Martin Paul, Janet Bliimel,
10: A solution of 9 1251 ( I 1 .I mmol) in Et,O (30 mL) were added slowly to a
and Christian Zybill"
solution of HSiCI, (1.2g. 11.1 mmol) in Et,O (30mL). After 1 h at room
Dedicated to Professor Robert West
temperature. the solvent was removed under vacuum. and CH,CI, (50 mL)was
added. After filtration and evaporation of the solvent the oil obtained was
on the occasion of his 65th birthday
solidified by addition of Et,O. After washing twice with Et,O, 2.5 g (78%) of
crude LO was obtained as a light yellow-green solid. M.p. 140°C (decomp);
The successive 1,2 shifts of two intramolecular donor
'H NMR (250 MHz, CDCI,, TMS): 6 = 2.9 (s, 12H. CH,). 4.4 ( s , 4H, CH,),
groups from an atom A to an atom B in a molecule can be
5.2 (s. 1 H, SiH); ,'Si-NMR (250 MHz, CDCI,, TMS): 6 = - 40.3 (d,
considered as a tandem reaction;"] in the case discussed here
'J(S1.H) = 334 Hz). IR(KBr): i.[cin-'] = 2204.
Received: April 11, 1993 [ Z 5977 IE]
German version: Angrii . Chrn7. 1993, 105. 1372
A=Si and B=M=Cr.
Tandem reactions of this kind permit the abstraction of
weakly bonded donor groups from silicon atoms in
silanediyl complexes, by migration to the metal (Scheme 1).
[I] R J. P. Corriu, M. Henner, J. Orgummet. Chem. 1974, 74, I. and refer-
ences therein.
[2] J. B. Lambert, W. J. Schulz, Jr., in The fhemisiry oforgunit. Sificon COn7puunds (Eds.: S. Patai, 2. Rappoport), Wiley, Chichester. 1989, S. 1007,
and references therein.
[3] a) J. B. Lambert. W. J. Schuiz, Jr., J. A. A. McConnell, W. Schilf, J. Am.
Cheni. Suc. 1988, 110. 2201 ; J. B. Lamhert. W. Schilf, ibid. 1988, 110,6364;
b) J. B. Lamhert, L. Kania, W. Schilf, J. A. A. McConnell. OrgunomeruNirs
1991, 10. 2578.
[4] G. K. S. Prakash. S. Keyaniyan, R. Aniszfeld, L. Heiliger, G. A. Olah,
R. C. Stevens, H. K. Choi, R. Bau, J. Am. Chem. SOC.1987. 105. 5123,
G. A. Olah. L. Heiliger, X.-Y Li, G. K. S. Prakash, ihid. 1990. f12,5991.
151 C . Eaborn. J Orgunornet. Chrm. 1991,405, 173.
1992, 1333, and references
[6] P. D. Lickiss, J Chrm. So<. D U / I U T,-uns.
[71 J. 9. Lamhert, S. Zhang. 1 Chem. Sue. Chem. Commun. 1993, 383.
[XI 2. Xie. D.J. Liston, T. Jelinek. V. Mitro, R. Bau, C. A. Reed. J. Chem. Sot..
~ h l V 1 7 .CWlU7lUn. 1993. 384.
[9] P Jutzi, E. A. Bunte, Angeir. Chem. 1992. 104, 1636; Angew. Chem. Inf.
El/ Engl. 1992. 31, 1605.
[lo] J. Y. Corey. R. West, J. Am. Chem. Sor. 1963, 85, 4034.
[I 11 H.J. Campbell-Ferguson, E. A. V. Ehsworth, J. Chem. Sue. A 1967, 705.
[I21 A . R. Bassindale. T. Stout, J. Chem. Soc. Chrm. Commun. 1984. 1387.
[13] M. Kira, T. Hino. H. Sakurai, J. Am. Chem. Soc. 1992, 114. 6697.
Angmi. <'hem. I n t . Ed. Engl. 1993. 32, No 9
Scheme 1.
Thus, the 1,2 shift of phosphane or amine donor groups
opens up a thermodynamically favored route to silanediyl
complexes containing a three-coordinate silicon
[*] Dr. C. Zybill, Dr. H. Handwerker, Dip].-Chem. M. Paul. Dr. J. Blumel
Anorganisch-chemisches Institut der Technischen Universitit Miinchen
Lichtenbergstrasse 4, D-85747 Garching (FRG)
Telefax: Int. code + (89)3209-3125
[**I We thank Professor H. Schmidbaur for generous support. as well as J.
Riede for creating a crystallographic data base.
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base, silicenium, intramolecular, ions, stabilization, new, siliconium, route
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