the methoxy aldehyde 3. Trapping of the radical cation 2" with water and oxygenation affords first the corre- sponding hydroxy aldehyde, which is further oxidized to the lactone 4 via the hemiacetal. Related chemistry was re- ported for the Ce( ~ v ) - c a t a l y z e d ~ ~ ~ and 1,4-dicyanonaphthal- ene-photosensitizediX1 oxidation of 1,2-diarylethanes, ex- cept that the intervening radical cation had suffered rup- ture of the ethane bond since trapping products of the re- sulting benzyl cations and radicals were observed.

Oxidation of acenaphthene (1) with ceric ammonium ni- trate in oxygen-saturated 80% aqueous methanol furnished methyl ether 5 (14%), alcohol 6 (12%), and ketone 7 (59%), all identified by comparison of TLC retention times and spectral data with those of the authentic materials. Clearly, these products are derived from the naphthalenic-type rad-

5 6 7

ical cation 1 o@,ill which deprotonates to the acenaphthyl radical. Subsequent oxygenation with molecular oxygen affords eventually ketone 7. Alternatively, further oxida- tion affords the acenaphthyl cation which is nucleophili- cally trapped by methanol or water to generate 5 and 6, respectively. Significant is that only traces of ring-cleavage products such as the methoxy aldehyde 3 and lactone 4 were observed.

This dichotomy in chemical behavior in the Ce(iv)-cata- lyzed SET-oxidation of acenaphthene (1) and the azoal- kane 2 is indicative of the structurally distinct radical cat- ions l a@ and 2O@, respectively of the naphthalenic and

benzylic type. An appreciable activation barrier (Ea 2 20 kcal/mol) must separate these two species for characteris- tic chemistry to become observable. At first sight this seems surprising since efficient carbon-carbon bond cleav- age of radical cations derived from diaryIethanes,l4] and more recently benzhydryl derivative^,^'] is well docu- mented. However, in these flexible acyclic radical cations the o-bond to be cleaved can align itself with the aromatic moiety to generate resonance-stabilized 71-type benzyl or benzhydryl radicals and cations. In the rigid naphthalenic radical cation 1 '@ the o-bond is fixed in the plane of the aromatic system, so that overlap of the orbitals of the inci- pient benzylic sites with the aromatic system to form the benzylic radical cation 2'' is only feasible after extensive o-bond rupture. We propose that such 0-71 crossing1Io1 is responsible for the slow 1 O @ * 2 '@ valence isomerization on the chemical time scale. Related cases have been exten- sively investigated concerning photochemical transforma- tions under matrix

Received: April 8, 1987; revised: May 13, 1987 [Z 2187 IE]

German version: Angew. Chem. 99 (1987) 818

[ I ] A. C. Buchanan 111, R. Livingston, A. S. Dworkin, G. P. Smith, J. Phys. Chem. 84 (1980) 423; T. Shida, S. Iwata, 3. Am. Chem. SOC. 95 (1973) 3473: L. Andrews, R. S. Friedman, B. J. Kelsall, J. Phys. Chem. 8 9 ( 1985) 4550.

121 M. Gisin, J. Win , Helu. Chim. Acta 59 (1976) 2273. 131 J. Martelli, R. Gree, J. Chem. SOC. Chem. Commun. 1980. 355; H. Abdal-

lah, R. Gree, R. Carrie, Can. J . Chem. 63 (1985) 3031; A. K. M. M. Ho- que, A. C . Kovelesky, W:K. Lee, H. J. Shine, Tetrahedron Lett. 26 (1985) 5655.

141 W. S. Trahanovsky, D. W. Brixius, J . Am Chem. SOC. 95 (1973) 6778; I . P. Beletskaya, D. 1. Makhon'kov, Rum. Chem. Rev. 50 (1981) 534.

151 3, colorless oil.--'H-NMR (CDCII; 200 MHz): 6 = 10.4 (s; 1 H), 8.10- 7.20(m; 6H), 4.73 (s; 2H), 3.37 (s; 3H).-"C-NMR (CDCI,; 50 MHz): b= 192.1 (d), 143.5 (s), 135.0 ( s ) , 134.6 (s), 131.4 (d), 130.9 (s), 128.3 (d), 128.0 (d), 123.9 (d), 121.4 (d), 121.0 (d), 70.9 (t), 55.5 (9).

161 J. Cason, D. M. Lynch, A. Weiss, J. Org. Chem. 38 (1973) 1944. 171 a) W. Adam, M. Dorr, J. Am. Chem. Soc. 109 (1987) 1570; b) S. C.

181 L. W. Reichel, G. W. Griffin, A. J. Muller, P. K. Das, S. N. Ege, Can. J.

191 A. Okamoto, M. S. Snow, D. R. Arnold, Tetrahedron 42 (1986) 6175. [lo] W. G. Dauben, L. Salem, N. J. Turro, Acc. Chem. Res. 8 (1975) 41; E. M.

Evleth, P. M. Horowitz, T. S. Lee, J. Am. Chem. Soc. 95 (1973) 7948. [ I l l T. Shida, E. Haselbach, T. Bally, Acc. Chem. Res. 17(1984) 180.

Blackstock, J. K. Kochi, ibid. 109 (1987) 2484.

Chem. 62 (1984) 424.

Stable Germaethenes** By Harald Meyer, Gerhard Baum, Werner Massa, and Armin Berndt*

The existence of short lived germaethenes has been de- monstrated by trapping reactions.11.21 We have now pre- pared stable germaethenes and characterized them spec- troscopically, in one case also by a crystal structure analy- sis. Reaction of the electrophilic cryptocarbene 1 ( 2)13] with the germanediylenes 3aI4] and 3bl5] in pentane at room temperature afforded the germaethenes 4a and 4b, respectively, as sole products. The lemon-yellow and pale yellow crystals of 4a and 4b very slowly decolorize on ex-

t B u Me3Si B'

lc<; *,, - / \ L - - J

Me3Si C=B-tBu

1

t B u

t B u I

Me3Si B

Me3Si B

\ / \

/ \ / c c:

I tBu

2

+ :GeR2

3a.b

t B u I 1

Me3Si B R Me3Si B R c o:c-ce/o

R Me3Si 6 R

\ / - \ \ / \ C C = G e \-/ \

+ / \ / \ Me,Si B

I I t B u t B u A 4a.b B

t B u t B u R R I I I /"

C C=Sn c c CI Me,Si \ / \ B / CH(SiMe3)2 Me3Si \ / \ / \ B G e

Me3Si B CH(SiMe3)2 Me3Si B H / \ / \ I \ / \

I I t B u 5

t B u 6a

a , R = N(SiMe,),; b, R, R = NtBu(Si(CH,),)NtBu

['I Prof. Dr. A. Berndt, H. Meyer, G. Baum, Priv.-Doz. Dr. W. Massa Fachbereich Chemie der Universitat Hans-Meerwein-Strasse, D-3550 Marburg (FRG)

the Fonds der Chemischen Industrie. ['*I This work was supported by the Deutsche Forschungsgemeinschaft and

198 0 VCH Verlagsgesellschafr mbH. 0-6940 Weinheim. 1987 0044-8249/87/0808-0798 $ 02.50/0 Angew. Chem. In,. Ed. Engl. 26 (1987) No. 8

posure to air (4a within 3d) and melt without decomposi- tion at 167 and I83 "C, respectively. The recently described stannaethene 513] decolorizes within 2 h under the same conditions and already decomposes at 133°C. 4a adds HCI with quantitative formation of the colorless, crystal- line 1,3-diboretane 6a.

The structures of 4a, 4b, and 6a follow from their 'H-, I3C-, and "B-NMR spectra.['] The tricoordinated C atoms of 4a and 4b, with 6(I3C)= 115 and 93 respectively, are noticeably shielded compared to the corresponding atom in 5 (6= 142), whereas the B atoms, with 6("B)=66 and 65 respectively, exhibit almost the same chemical shift as in 5 (6=64). They are more strongly shielded than the B atoms of the 1,3-diboretane 6a (6=82), thus indicating a relatively large amount of negative n charge on the B atoms and a similar ylide character (resonance formula B) of the CGe double bonds in 4a and 4b as in 5.

N19

x.

N20

Fig. 1 . Top: ORTEP drawing of the crystal structure of 4a. The vibration ellipsoids are given at the 30% probability level. Projection onto the C2,N19,N20 plane; H atoms not shown. Important bond lengths [A] and an- gles ["I: Ge-C2 1.827(4), Ge-N19 1.818(4), Ge-N20 1.835(4), B K 2 1.534(7),

1604(7), C4-Sil 1.889(4), C4-Si2 1.887(5), B I . . .B3 2.070(7), C 2 . . .C4 2.374(5): C2-Ge-N19 125.3(2), C2-Ge-N20 124.1(2), N19-Ge-N20 I10.5(2), Ge-C2-BI 138.6(4), Ge-C2-B3 135.8(4), BI-C2-B3 85.3(4), C2-BI-C4 97.4(4), BI-C4-B3 79.0(3), C4-B3-C2 97.8(4), Si ILC4-Si2 112.6(3). Torsion angle: BI- C2-Ge-N 19 29.4(6), B I-C2-Ge-N20 - 148.3(4), B3-C2-Ge-N 19 - 140.3(4), B3-C2-Ge-N20 42.0(5), Ge-C2-B I-C4 - 178.9(4), Ge-C2-B3-C4 179.3(4).- Bottom: Newman projection along the C2-Ge bond.

BI-C4 1.626(6), BI-C5 1.586(8), B3-C2 1.523(6), B3-C4 1.628(6), B3-C9

An X-ray structure analysis171 of 4a (Fig. 1 top) con- firmed the significance of the ylide resonance formula B with short distances C2-BI (1.534(7) A) and C2-B3 (1.523(6) A). The distance from the germanium atom to the tricoordinated C2-atom (1.827(4) A)-is 3% longer than that calculated for H2C=GeH2 (1.773 A).['] The GeC single bond in Ge(CH3), (1.98 A)191 is 8.4% longer than in 4a. The torsion angles BI-C2-Ge-N19 and B3-C2-Ge-N20 (Fig. 1, bottom) are 29.4(6) and 42.0(5) O , respectively, the average twist angle at the C=Ge bond is therefore 36". The angles between the line through C2-Ge and the N19,Ge,N20 and BI,C2,B3 planes are 1.7 and 4.8", respectively, i.e. the Ge atom is practically planar coordinated, the C2 atom slightly pyramidalized. The stannaethene 5 exhibits an av- erage twist angle of 61 o and dihedral angles of 5" and 16" respectively at the Sn and C2 atoms. Thus the germaethene

4a is considerably less twisted than the stannaethene 5 and markedly less puckered, especially at the C atom.

Experimental: 4a : A solution of 3a (1.42 g, 3.6 mmol) in pentane (10 mL) was treated with 1 (I. I I g, 3.6 mmol) at room temperature. After 2 d only 4a is detectable by "C-NMR spectroscopy. It precipitates in the form of lemon-yellow crystals (m.p. 167°C) on cooling the pentane solution to -25°C.

Received: March 25, 1987 [Z 2162 IE] German version: Angew. Chem. 99 (1987) 790

CAS Registry numbers: 1, 87556-27-2; 3a, 59863-12-6: 3b, 84806-15.5; 4a, 109531-23-9: 4b, 109552- 48-9; 6a, 109531-24-0.

[ I ] J . Satge, Adu. Orgunomet. Chem. 21 (1982) 241. [2] N. Wiberg, C.-K. Kim, Chem. Ber. 119 (1986) 2966, 2980. [3] H. Meyer, G. Baum, W. Massa, S. Berger, A. Berndt, Angew. Chem. 99

(1987) 559; Angew. Chem. In,. Ed. Engl. 26 (1987) 546. [4] M. J. S . Gynane, D. H. Harris, M. F. Lappert, P. P. Power, P. Riviere, M.

Riviere-Baudet, J . Chem. SOC. Dalton Trans. 1977. 2004. [5] M. Veith, M. Grosser, 2. Nuturforsch. 837 (1982) 1375. [6] Spectra recorded in CnDo, [D,<,]dimethoxyethane ("C-NMR of 4a, b at

-35°C). and CDCl, (6a). 4a (yield: "C-NMR-spectroscopically quanti- tative): 'H-NMR: 6= 1.2 ( s , l8H, fBu), 0.3 ( s , 18H, SiMe,), 0.25 (s, 36H, SiMe3): "C-NMR: 6= 115.0 (br. s, IC, C=Ge), 31.8 (q, 6C, tBu), 26.3 (br. s, 2C, CMe3), 26.1 (br. s, IC, SizC), 6.5 (q, 6C, %Me3), 5.9 (br. q, 12C, SiMez), the signal at cS=5.9 is sharp at room temperature, "B- NMR: 6= 66.-4b (yield: "C-NMR-spectroscopically quantitative): 'H- NMR: cS= 1.3, 1.2 ( s , each 18H, tBu), 0.4 (s, IXH, SiMe,), 0.2 ( s , 6H, SiMe:); "C-NMR: 6=93.2 (br. s , I C, C=Ge), 54.4 ( s , 2C, NC). 34.6 (9, 6C,NtBu),31.2(q,6C,BtBu),25.0(br.s,2C,BC),24.1(br.s, IC,B2C), 5.3 (q, 6C, SiMe,), 4.5 (4. 2C, SiMe?); "B-NMR: ii=65.-6a: colorless crystals, m.p. 195°C (decomp.). yield: 'ZC-NMR-spectroscopically quan- titative; 'H-NMR: 6 = 1.57 ( 5 , 1 H, B2CH), 1.26 (s, 18 H, tBu), 0.37. 0.30 (s. each 18H, SiMe.?); "C-NMR: 6=59.3 (br. d, J("C-H)=99 Hz, IC, B2CH), 52.5 (br. s, I C, CSi2), 31.2 (q.6C. rBu), 28.3 (br. s, 2C, CMe?), 7.8 (br. q, 12C, SiMei), 7.2, 5.8 (q, each 3C. SiMe,): "B-NMR: 6 = 8 2 .

[7] Space group P2,/c, 2 = 4 , u = 18.727(2), h=9.154(1), c=25.627(2) A, p= 105.01( I ) O , 4109 independent reflections >3o(F,,). measured at 294 K on a four-circle diffractometer (CAD4, Enrdf-Nonius) with Mokc, radia- tion. Refinement of the heavier atoms with anisotropic temperature fac- tors, H atoms riding at idealized positions (d(C-H)=0.95 A) and with iso- tropic temperature factors. R., =0.036 (weighting w = I /o'(F,,)). 426 pa- rameters, S = 1.914. Further details of the crystal structure investigation are available on request from the Fachinforrnationszentrum Energie, Phy- sik, Mathematik GmbH, D-7514 Eggenstein-Leopoldshafen 2 (FRG), on quoting the depository number CSD-52600, the names of the authors, and the journal citation.

[8] K . D. Dobbs, W. J. Hehre, Organometallics 5 (1986) 2057, and references cited therein.

191 E. G. Rochow, E. W. Abel: The Chemistrv of Germanium. Tin and Lead, Pergamon, Oxford 1975.

Preparation of F,S=CH-COF by Isomerization of F5S- CH =C=O** By Thomas Kriigerke, Jurgen Buschmann, Gert Kleemann, Peter Luger. and Konrad Seppelt*

The alkylidene sulfur tetrafluorides R,C=SF, are of spe- cial interest because of their stable, essentially nonpolar C=S double bond and their unique structure. The first compound of this type, CH2=SF4, was prepared in several steps from pentafluoro-h6-sulfanylacetic acid 1 .[I1 We have

[*I Prof. Dr. K. Seppelt, DipLChem. T. Kriigerke, Dr. J. Buschmann, Dr. G. Kleemann, Prof. Dr. P. Luger Institut fur Anorganische und Analytische Chemie und Institut fur Kristallographie der Freien Universitat Fabeckstrasse 34-36 and Takustrasse 6, respectively, D- 1000 Berlin 33

the Fonds der Chemischen Industrie. [**I This work was supported by the Deutsche Forschungsgemeinschaft and

Angew. Chem. Inl. Ed. Engl. 26 (1987) No. 8 0 V C H Verlugsgesellschaff mbH. 0-6940 Weinheim. 1987 0044-8249/87/0808-0799 $ 02.50/0 799