time 4 s, data matrix 256 ( t i ) x 512 ( I n ) , Gauss filter. 'Li('H] NOE differ- ence spectra: program NOEDIFF: irradiation time 3 s, power 35 L, delay time 7 S, 160 pulses per experiment.

[22] C. Yu, G . C. Levy, J . Am. Chem. Sbc. 106 (1984) 6533. [23] The assignment of the phenyl group signals in the 'H NMR spectrum was

achieved by 'H,'H-COSY and "C,'H-shift correlation beginning with the 'H and "C resonances of 6-H and C-6, respectively, which are shifted to high field owing to the benzyl resonance (S. Bradamante. G. A. Pagani, J . Chem. SOC. Perkin Trans. 2 1986, 1035).

1241 (1 e ' TMEDA), also has such short Li-H distances in the crystal (Li-H4 3.838, Li-HY 3.361, Li-HI I 3.437, Li-CH, 2.852, Li-CH, 3.240).

[25] H.-J. Gais, J. Vollhardt, C. Kruger, Angew. Chem. 100 (1988) 1108; AngeM. Chem. Int. Ed. Engl. 27 (1988) 1092.

Addition of Free Me,Ge: to Alkenes and Alkynes on Glass Surfaces in the Presence of Water** By Wilhelm P. Neumann,* Hideki Sakurai,* Gilbert Billeb, Hartmut Brauer, Jiirgen Kocher, and Sabine Viebahn

Dedicated to Professor Christoph Riichardt on the occasion of his 60fh birthday

Free Me,Ge: (dimethylgermanediyl or "dimethylgermyl- ene") 1 undergoes a surprising variety of additions to IT sy- stems of alkenes, 1,3-dienes, alkynes, and enones, most of them being regio- or stereospecific.['] Now we have found that reaction of 1 with conjugated substituted alkenes 2 or with alkynes 4 gives products that contain two Ge atoms and are generated by water adsorbed at the surface of glass or silica gel.

H,O/SiO,

(or D,O, Hiso) 2 Me,Ge + 2 H,C=CH-X >

1 2 (X-CH-CH,-GeMe,-fTO('sO) I

3

WD)

a, X = CN; b, X = COOMe; c , X = COMe

When we generated free 1 thermally in the presence of acrylonitrile 2 a or other conjugated substituted olefins (2 b, c) in a glass flask with the usual careful exclusion of air and moisture, we obtained a moderate yield ofcompounds 3, the hydrogen contents of which were higher than expected. The additional hydrogens are not contributed via free radical reactions between the partners or with the solvent, as suspec- ted at first. This was established by the lack of influence of cumene and triphenylmethane, as well as of tBuBr, which is a powerful scavenger of Ge radicals. Finally, after several difficulties, oxygen was found to be present in the product and structure 3 was established. Compound 3, a dimer of the adduct expected originally, contains an additional molecule of water. Saturation of the solvent benzene with water did not improve the yields of 3, and D,O gave no deuterated 3. When we added finely powdered glass or silica gel saturated with water and dried at Torr, however, we obtained

[*I Prof. Dr. W. P. Neumann, DiplLChem. G. Billeb, Dipl.-Chem. H. Brauer. Dr. J. Kocher, Dip1:Chem. S. Viebahn Lehrstuhl fur Orgdnische Chemie I der Universitat D-4600 Dortmund 50 (FRG)

Department of Chemistry, Faculty of Science Tohoku University, Sendai 980 (Japan)

[**I This work was supported by the Fonds der Chemischen Industrie. We are grateful to Dr. H. Hillgiirtner for very skilful1 mass spectrometric investi- gations.

[**I Prof. Dr. H. Sakurai

nearly quantitatively3a; in the same way, reaction with D,O and with H,180 gave [Dz]3a and [180]3a, respectively.

Indeed, water adsorbed at or in the glass[2' is involved stoichiometrically in the reaction. This is evidenced addition- ally by cross checks: Using a quartz flask after heating it for 4 h at 150 "C/10-3 Torr, we found a yield of only 45% in- stead of 70%. Silylation of its inner surface by means of F,C-CO-NMe-SiMe, (MSTFA)/Me,SiCI over 4 h at 70 "C caused the yield of 3a to decrease to 35%.

These surprising results required a reinvestigation of the reactions of 1 with alkynes. We had obtained earlier with phenylacetylene 4a a mixture of unsaturated four-, five-, and six-membered germacycles.['] Erratically, a minor byproduct with a I-alkenyl group had been observed ('H NMR), but could not be identified at first. When we now added wet silica gel before starting the reaction, high yields of the new di- germoxane 5a could be obtained instead of the: expected products. Alkynes 4 b-d behaved analogously. The struc- tures 5 have been clearly established, also by using Hi80 . It should be noted that with 4c, for example, no product could be detected earlier in the absence of H,O/SiO,.

H,O/SiO, 2 Me,Ge + 2 HCEC-R

1 4

6 5

a, R = Ph; b, R = Bu; c, R = tBu; d, R = CH,OAc

The germoxy group of 5 affords access to new organoger- manium compounds, for example to the vinylgermyl acetate 6 starting from 5a and acetic anhydride. This is additional evidence for the structure of compound 5.

The structure of the product obtained from methyl acety- lenecarboxylate 4e and 1 was, at first, puzzling. The E-olefin 7 was found exclusively instead of the expected 1-alkenyl compound corresponding to 5a-d.

H,O/SiO, ( HHGeMe)O 2 Me,Ge + 2 HCEC-COOMe -

1 4e 7

Elucidation of the mechanism of the participation of ad- sorbed water thus became a priority task. Compound 1 could react with water in a first step giving the previously unknown hydride Me,Ge(H)OH, which could yield, via hy- drogermylation, compounds 3, 5, and 7. In the absence of alkene 2 or alkyne 4, however, water/silica gel and 1 gave only the polygermane (Me,Ge),, which we futilely tried to observe.[" Thus, the intermediacy of a germoxy compound is excluded. An attempted in situ reaction of 1 with methanol led to new 'H NMR absorptions of a hydride XMe,GeH, but acrylonitrile 2 a, added consecutively, remained un- changed under the standard conditions. Further, no l-alke- nyl structure corresponding to 5 could be observed when phenylacetylene 4 a was hydrogermylated analogously by Et,Ge(H)OMe; instead, the product of an inverse orienta- tion was obtained.[31

Therefore, the first step is presumably a reaction between 1 and the alkene or alkyne. The resulting intermediate, which

102% 0 VCH Verlagsgesellschufr mhH, 0-6940 Weinheim, 1989 0570-0833/89j0808-l028 $02.50/0 Angew. Chem. lnt . Ed. Engl. 28 (1989) No. 8

has not yet been detected directly, has a lifetime sufficient for diffusion to the wall of the flask, where it is stabilized by "reactive water". This term is used in the following way: at the surface of glass, not only (monomeric) H,O has to be taken into account, but also the products of its reaction with the glass surface [Eq. (a>-(c)].[']

(a)

(-Si),O + H,O$(-SI),O-HOH or (-Si),O@-H + OHe (b)

\ \ . I

\ \ . \ . I I I

(-lS~)zO + H,O$2 -SI-OH

( 4 \ . \ . I ( - SI),O@-H G ( - l S ~ ) 2 0 + H a

Protonations of the initially formed intermediates seem to best explain the experimental results. In all cases, the most stable cation is apparently formed and is decisive for the structure of the final product (Scheme 1). Thus, also the structural differences between products obtained with 4a-c and 4e can be understood now.

ll H,C-CHCN [ YeMe, ] 1 H"/SiO,

4 a J l HC=CPh [ \deMe]

HO/SiO,, k 5 1/2 dimer 1 ' H,C-CHCN H,C-CPh

[Me;de [ i M e ]

I H,C-CH,CN [ @&Me, 1

. H" 1 H,O/SrO,

3 a

H" 1 H,O/SiO,

5 a

0 /I

HC=CCOMe [ YeMe, 1 HO/SiO, I OH

I HC-C=COMe [ "deMe, 1

H" /, H,O/SiO,

7

Scheme 1 . Proposed mechanisms for the formatiqn of 3a, 5 a and 7

When "reactive water" is Lacking, the intermediate decom- poses reversibly (4c) or dimerizes (4a, 4bL']), or, in the case of other alkynes, butadienes, or styrene, undergoes rapid insertion forming the corresponding five-membered rings."]

We have thus been able to demonstrate that, in the reac- tions of alkenes and alkynes with 1 to give the new types of compounds 3,5, and 7, molecules of water, or their products present at and in the glass even after heating)'] are capable of participating in the reaction in a surprising manner. This "reactive water" generates new products stoichiometrically and completely, when finely powdered glass or silica gel is used. This is probably done by proton donation to unstable intermediates. Our current efforts are directed at the definite identification of the intermediates and a t broadening the scope of this new reaction principle.

Experimental Procedures [41

3: SiO, (1.0 g, Celite 545, Nagel&Co.) was heated five times at 15O"C/ 0.001 Torr in a 50-mL two-necked Duran flask. At room temperature, H,O

(D,O, H,"0) (0.300 mL), 7,7-dimethyl-l,4,5,6-tetraphenyl-7-germa-2.3-ben- zonorbornadiene [I] (2.0g. 3.7 mmol), 2 (0.74mL, 11.1 mmol). and benzene (25 mL) were added. The mixture was heated at 70 "C for 4 h under dry argon. After removal ofthe solvent at 14 Torr, the residue was stirred twice with 20 mL of pentane and filtered from 1,2,3,4-tetraphenylnaphthalene and SO,. The solution was evaporated at 14 Torr. Crude yields ('H NMR) of 3: 80-85%; rest, (Me,Ge),. Equal yields were obtained with 1.5 g of powdered glass of a reaction flask. Without SO, , only 50% yields ( 3 4 were found. The products were purified by kugelrohr distillation at 0.01 -0.001 Torr. 5,7: Analogously to 3, but with 1 .O g of the norbornadiene"], 0.700 mL of H,O (D,O, H,"O), 10 mmol of4, and 10 mL ofbenzene, 3.5 h under reflux. Yields of crude products: 90-95%.

Received: March 8, 1989 123224 IE] German version: Angew. Chem. 101 (1989) 1074

CAS Registry numbers: 1,74963-95-4;2a, 107-13-1;2b,96-33-3;2~,78-94-4;3a, 121393-6S-5;(DZ)3a, 121393-73-5; ("0) 3a, 121393-74-6; 3b, 121393-66-6; 3c, 121393-67-7; 4a, 536-74-3; 4b, 693-02-7; 4c, 917-92-0; 4d, 627-09-8; 4e, 922-67-8; 5a, 121393- 68-8; ("0) Sa, 121393-75-9; 5b, 121393-69-9; SC, 121393-70-2; Sd, 121393-71- 3; 6, 121424-80-4; 7, 121393-72-4; SiO,, 7631-86-9; 7,7-dimethyI-1,4,5,6-tetra- phenyl-7-germd-2,3-benzonorbornadIene, 76054-64-3.

[l] M. Schriewer, W. P. Neumann,J. Am. Chem. Soc. /05(1983) 897; J. Kocher, W. P. Neumann, ibid. 106 (1984) 3861; Orgunometullics 4 (1985) 400; E. Michels, W. P. Neumann, Tetrahedron Lett. 27 (1986) 2455; G. Billeb, W. P. Neumann, G. Steinhoff, ibid. 29 (1988) 5245.

[2] There have been controversial discussions about the amount, kind of bond- ing, mobility, and splitting of water in glasses. H. Scholze: Glus, 3rd ed., Springer, Berlin 1988. See also references therein.

[3] M. Massol, J. Satge, P. Riviere, J. Barrau, J. Orgunomel. Chem. 22 (1970) 599.

[4] The products give correct elemental analyses and have been identified une- quivocally: 'H, I3C NMR: Bruker AM300. TMS,.,, CDCI,; MS: Varian CH7, Finnigan-MAT 8230; ["0]3a: Ma -Me by simulation and subtrac- tion of the unlabeled 3a; FT-IR: Bruker IFS 131v; Raman: Coderg T800, 1 = 514.5 nm. 3a: MS (EI): m/z 315 (Ma-Me. 27%; high resolution: found 315.0352. calcd315.0369). ' H N M R : 6 = 0 . 4 4 ( ~ , 1 2 H , G e M e ) , 1 .18(t7J=7.8Hz. 4H, CH,), 2.51 (t, J = 7.8 Hz, 4H, CH,); Raman: J (GeO) = 460cm-I. [D2]3a: MS (El): m/z 317 (@-Me, 35%). 'H NMR: 6 = 0.34 (s, 12H, GeMe), 1.08 (d, 3J(H,H) = 8.1 Hz, 4H, CH,), 2.39 (tt, 3J(H,H) = 8.1. ,J(D,H) = 2.6 Hz, 2H, CDH). ['"0]3a: MS (EI): m/r 317 (Ma-Me, 36%).3b: MS(EI):m/i381 ( M Q - M e , 7 % ) . 'HNMR:6 =0.38(s.l2H. GeMe), 1.12 (t. J = 7.8 Hz, 4H, CH,), 2.45 (t, J = 7.8 Hz. 4H. CH,), 3.68 (s.6H,C0,Me).3c:MS(EI):m/z349(Me-Me,7%). ' H NMR:6 = 0.27 (s, 12H, GeMe), 0.92 (t. J = 6.6 Hz, 4H. CH,), 2.02 (s, 6H. COMe), 2.49 (t, J = 6.6Hz,4H,CH2).5a: MS(EI):m/z428(Me,4%),413(Me-Me. 6%). 'H NMR: 6 = 0.38 ( s , 12H, GeMe), 5.10, 5.47 (each d. *J(H,H) = 2.0 Hz, each 2H, =CH,), 6.80 (m, 10H. Ph). IR (KBr): t (GeO) = 855crn-'. ["0]5a: MS (EI): m/z 430 (Ma, 4%). 5b: MS (EI): m/r 388 ( M a , 3%). 373 (Me-Me, 40%). 'H NMR: 6 = 0.34 (s, 12H. GeMe), 0.89-2.20 (18H, Bu). 5.22, 5.48 (each m, 4J(H.H) = 1.3. ,J(H.H) = 2.3 Hz, each 2H, =CH,). 5 c : MS (EI): m/z 388 ( M e , 2%), 373 (Me-Me, 54%). 'H NMR: 6 = 0.47 (s, 12H, GeMe), 1.20 (s, 18H, tBu). 5.30, 5.60 (each d, 'J(H,H) = 1.6 Hz, each 2H, =CH,). 5d: MS (El): m/r 405 (Me-Me, 33%). 'H NMR: 6 = 0.40 (s, 12H, GeMe), 2.00 (s, 6H. CH,), 4.70 (m, "J(H,H) = 1.4 Hz, 4J(H,H) = 1.6 Hz. 4H, CH,). 6: 'HNMR:6=0.66(~,6H,GeMe),1.93(~,3H,COMe),5.67,5.93(eachd, 'J(H,H) = 2.0 Hz, each 1 H, =CH,), 7.23 (s, SH. Ph). 7: MS (El): mjz 377 (Me-Me,lOO%). 'HNMR:S =0.52(s, 12H,GeMe),3.X0(s.6H.CH3), 6.25, 7.37 (each d, 3J(H,H) = 19.0 Hz, each 2H, =CH).

Visualization of Chromatographic Separations by NMR Imaging By Ernst Bayer,* Winfried Miiller, Martin Ilg, and Kluus Albert

Nuclear magnetic resonance imaging". 21 has been very successful in medical diagnosis, since it allows noninvasive observation of liquid and gel-like states as well as of dynamic

[*I Prof. Dr. E. Bayer, Dr. W. Muller, M. Ilg. Dr. K. Albert Institut fur Organische Chemie der UniversitPt Auf der Morgenstelle 18, D-7400 Tubingen (FRG)

Angeu. Chem. Int . Ed. Engl. 28 (1989) No. 8 0 VCH Verlugsgesellschufi mbH. D-6940 Weinhein?, 1989 0570-0833j89j0808-lO29 $02.50/0 1029