Becker, Sabine

Huch, Volker

Veith, Michael

Acronym

both the 3‘-5‘-coupled pyrophosphate 3f and the 5’-5‘-cou- pled 4 are rapidly formed in the template-independent reac- tion with 1 f (cf. 6). The results described here offer evidence that chemical self-replication is possible even in model systems in which oligonucleotides with 3’-5’ pyrophosphate bonds are synthe- sized. Oligonucleotides with pyrophosphate backbones are increasingly being discussed as possible prebiotic “informa- tion molecules”; their template properties in nonenzymatic oligomerizations have been described recently.“’] Further investigations into sequence dependence will presumably show to what extent the selection values of self-replicating molecules can be understood in terms of thermodynamically and kinetically controlled selectivities in the synthesis of al- ternative sequences. Such studies might afford insight into the question whether a self-constitution[’ of sequential in- formation must be considered in the later phases of chemical evolution. Received: April 7, 1989 [Z 3280 IE] German version: Angew. Chem. 101 (1989) 1259 CAS Registry numbers: l b ,  122238-09-9; lc, 122238-10-2; Id,  122238-11-3; le, 122238-12-4; If .  122238-13-5; l g ,  122238-14-6; lh ,  122238-15-7; Zb, 122238-16-8; 3a, 122238- 25-9; 3b, 122238-17-9; 3c, 122238-18-0; 3d, 122238-19-1 ; 3e, 122238-20-4; 3f. 122238-21-5; 3g, 122238-22-6; 3h, 122238-23-7; 4, 122238-24-8. [I] G. F. Joyce, Cold Spring Harbor Symp. Quant. Biol. 7 (1987) 41 -51. [2] G. von Kiedrowski, Angew. Chem. 98 (1986) 932-934; Angew. Chem. lnt. [3] W S. Zielinski, L. E. Orgel, Nature (London) 327 (1987) 346-347. [4] The use of an MTM protecting group instead of the previously used methyl group has, in addition to logistical advantages in the synthesis of trimers. the effect that the kinetic measurements can be carried out more exactly by HPLC. Thus, 1 f reacts with the 5‘-hydroxy trimer 2a to give a hexamer. which differs from the template used, 3a, only in the protecting group at the 5’ end, but which can be separated chromatographically from 3a. This obviates the necessity of following the reaction by calculating differences between HPLC integrals. [5] Equation (1) should be referred to as the “square root law”, where c‘ is the concentration of the hexamer formed (here, 30, c the concentration of the added template (here, 3a), a an empirical constant for the template-depen- dent synthesis of 3f, and h the rate of the template-independent synthesis of 3f .  The constants a and h correspond to k ,  and k ,  in [2], K,  and K,, in [I] .  and 1 and /3 in [3]. [6] N .  G. Dolinnaya. N. I. Sokolova, 0. I.  Gryamova, Z.  A. Shabarovd, Nu- d e r ~  Acids Res. 16 (1988) 3721-3738. [7] C. R. Cantor, P. R. Schimmel: Biophysical Chemistry, Freeman, San Francisco 1980, pp. 325, 11 83 ff. [XI S. M. Freier, D. D. Albergo, D. H. Turner, Biopolymers 22 (1983) 1107- 1131. 191 K.  J. Breslauer in H. J. Hinz (Ed.): Thermodynamic Data for Biochemi.str.p und Biolechnology, Springer, Berlin 1986; S. M. Freier, A. Sinclair, T. Neilson, D. H. Turner, J Mot.  Biol. 185 (1985) 645-647. [lo] J. Visscher, C. G. Bakker, R. van der Woerd, A. W. Schwartz, Science (Wushinglon) 244 (1989) 329-331. [11] A.  Eschenmoser, Angew. Chem. 100 (1988) 5-40; Angew. Chem. Int. Ed. Engl. 27 (1988) 5-39. Ed. Engl. 2S (1986) 932-935. A Base-Stabilized Ge-S Double Bond By Michael Veith,* Subine Becker, and Volker Huch Elements of higher periods (principle quantum number n 2 3 )  apparently undergo multiple bonding with oxygen or sulfur when the d-orbitals can participate in the stabilization of the system or when resonance structures can be invoked in which the element in question carries a positive charge and [*I Prof. Dr. M. Veith, Dipl.-Chem. S. Becker, Dr. V. Huch Institut fur Anorganische Chemie der Universitdt D-6600 Sdarbrucken 11 (FRG) the chalcogen atom a negative charge. This type of bonding is particularly common in the case of phosphorus where it is generally described in terms of the resonance structures la and Ib.”] Recently, silicon-containing intermediates have al- so been characterized to which a structure analogous to that of the phosphorus compounds can be ascribed (Scheme I a  I h  BGEI=X - s&Xe I1 a I1 b B Scheme 1. X = 0,s ;  El = Si, Ge; B = base. We posed ourselves the question ofjust how far the “base- stabilization concept” can be extended to the homologous element germanium. All attempts to isolate compounds with “unprotected” Ge-0 and Ge-S double bonds have previ- ously failed, even with sterically demanding ligands on the germanium.f3 - ’1 We wanted to achieve intramolecular addi- tion of a base at germanium and therefore used polycyclic lithium silylamide 1 (Li bridges),[61 which apart from con- taining two amide nitrogen atoms also contains two amine nitrogen atoms capable of coordination. tBu Li Li tBu \ / tBu \ / N I N  I , N \ I Si Me’ Me + GeCI;C,H,O, + si\ / , IBU tBu 2 1 reacts with the dioxane adduct of germanium(I1) chloride to give the bis(amin0)germanediyl 2 in high yields [Eq. (a)], which has been characterized by elemental analysis, molecu- lar weight determination and ‘H NMR spectro~copy.[’~ 2 can be easily converted with oxygen or sulfur into the oxida- tion products 3 and 4, respectively [Eq. (b)]. r 1 3, X = 0, n = 2 4, x = s, n = 1 The ‘H NMR spectra of 3 and 4 are identical at room temperature (in each case three resonance signals are ob- served for the tert-butyl groups,[’’ indicating intramolecular chelation by one of the N-atoms of the N,Si, group in solu- tion, whereas the spectrum of 4, in contrast to that of 3, becomes simpler on increasing the temperature (coalescence of two tert-butyl signals). Apparently, in the case of 4 the Angew. Chrm. Int. Ed. Engl. 28 (1989)  Nr. 9 0 VCH Vertugsgeset1schafi mbH, D-6940 Weinheim, 1989 OS70-0833/89/0909-1237 $02.SOjO 1231 N-Ge donor bond then rapidly opens and closes on the NMR time scale (competition between the N-atoms in the N,Si, ring). The compounds also differ greatly in their solu- bility: 3 precipitates as main product from the solution of 2 upon the introduction of oxygen, whereas 4 is readily solu- ble. X-Ray crystal structure analyses of 3 and 4 confirm that 3 is present as a dimer, whereas 4 is surprisingly, monomeric, i.e. contains a singly coordinated sulfur atom (in the crys- talline state 4 still contains 1/2 molecule of benzene per for- mula unit). The structures of the oxidation products 3 and 4 are shown alongside each other in Figure 1. The germanium S Fig. 1. The molecular structures of 3 (top) and 4 (bottom) (the carbon atoms are not labelled) [S]. Some important bond lengths [A] and bond angles I"]: 3: Gee0 1.809(4), G e e 0  1.825(4), Ge-N1 2.370(5), Ge-N2 1.880(5), GeeN3 1.887(5), Si-N 1.744(9) (mean); NI-Gee0 90.5(2), Nl-Ge-0 175.312). N2- Ge-O' 108.1(2), N3-Ge-O' 109.9(2), N2G-0  119.9(2), N3Ge-0  119.3(2), N24e-N3 110.7(2), 0-Ge-0 84.8(2), Ge-0-Ge' 95.1(2). - 4: Ge-S 2.063(3), Ge-N3 2.050(6), Ge-N2 1.882(6), Ge-N4 1.886(6), Si-N(1,2,4) 1.721(8) (mean), Si(1,2)-N3 1.831(5) (mean); N2-Ge-S 121.4(2), N4-Ge-S 123.0(2), N 2 G e N 4  110.6(3), S-Ge-N3 128.9(2), N2-Ge-N3 79.8(2), N4Ge-N3 79.5(2). atoms in 3 are coordinated almost trigonal-bipyramidally by two oxygen atoms and three nitrogen atoms, whereby the longer bonds are, as expected, the axial bonds in each case (to N1 and 0 and N1' and 0, respectively). The polycycle, with crystallographic point group T(C,), contains two sec- onorcubane units (N,Si,Ge), which are coupled to each oth- er via a Ge,O, four-membered ring. In 4 the germanium atom is only four coordinate. The coordination can be described as distorted tetrahedral, or better still as trigonal-planar (N2, S, N4) with an additional bond (Ge-N3), since the sum of the angles at the germanium atom for the bonds to N2,S and N4 deviates only 5" from the ideal value of 360". Especially striking is the difference in length (0.17 A) between the G e N 3  bond and the other, shorter Ge-N bonds. The Ge-S distance of 2.063(3) 8, is so far the shortest germanium-sulfur distance and is about 0.2 8, shorter than the value for a Ge-S single bond.['] In the thiogermanate ion Ge,StF, which has an adamantane-like structure, the terminal Ge-S distances are 2.12(1) and are thus 0.06 8, longer than in 4. According to calculations on H,Ge = S the p ~ p x  Ge-S double bond should be 2.02 8, in length. Accordingly, all structural data suggest that the bonding model I1 can also be applied to 4. Compound 4 is therefore the first isolable compound with a base-stabilized double bond between sulfur and a tetravalent element of a higher period. Molecules with intramolecular base-stabilized Si-S and Ge-S bond, respectively, have recently been obtained via an entirely different route."21 Of interest in the impor- tance of the resonance structures IIa and IIb for the descrip- tion of 4 is that a molecule isoelectronic to 4 with Ga and C1 instead of Ge and S exists[131 (see also the corresponding methylgallium Experimental 2: A solution of the dilithium compound 1 (385 mg, 1 mmol) in benzene was added dropwise within 30 min to a slurry of the dioxane adduct of german- ium(u) chloride (232 mg, 1 mmol) in benzene (5 mL)'6'. After 12 hours the precipitate was filtered off, the solvent removed from the filtrate by distilla- tion, and the resulting residue sublimed at 80"C/10-3 torr; this furnished 363.3 mg (82%) of colorless, crystalline 2. 3,4:Asolutionof181.1 mg(0.41 mmol)of2in2 mLoftoluenewas treatedwith a stream of oxygen diluted with nitrogen, or with 13.1 mg(0.41 mmol) ofsulfur. 3 precipitated as a colorless powder, which was recrystallized from benzene; 4 could first he isolated after evaporation of the solution to dryness. Yields 112.9 mg (60%) 3; 190.6mg (98%) 4. Received: April 14, 1989 [Z 3295 IE] German version: Angew. Chem. 101 (1989) 1287 CAS Registry numbers: 1,122093-34-9; 2,122093-35-0; 3, [Gei'")], 122093-36-1 ; 3, (chelate), 1221 14-35- 6; 4, [Ge"V'], 122093-37-2; 4, (chelate), 122093-39-4; 4 (Ge('")]-1/2 benzene, 122093-38-3; 4 (chelate).1/2 benzene, 122093-40-7; GeCI,.D, 28595-67-7. [I] M. W. Schmidt. M. S. Gordon, J.  Am. Chem. Soc. 107 (1985) 1922. 121 N. Wiberg, G. Preiner, K. Schurz, Chem. Ber. 12f (1988) 1407. (31 L. Lange, B. Meyer, W. W. du Mont, J.  Organomet. Chem. 329 (1987) [4] J. Barreau, G. Rima, M. El-Amme, J. Satge, J.  Organomet. Chem. 345 [5] M. Andrianarison, C. Couret, L P .  Declercq, A. Dubourg, J. Escudie, H. [6] M. Veith, E Goffng, Chem. Ber. 121 (1988) 943. [7] 'H-NMR (toluene): 2 (290 K): 6 = 0.55 (s, 6H, SiCH,), 1.26 (s, 18H, NC(CH,),), 1.41 ( s ,  18H,NC(CH3),);3(290K):6 = 0.71 (s,6H,SiCH3), 1.28 ( s ,  9H, NC(CH,),), 1.57 (s, 9H, NC(CH,),), 1.73 (s, 18H, NC(CH,),);4(370 K):6 = 0.65(s,6H,SiCH,), 1.34(s, 18H,NC(CH,),), 1.51 (s, 18H, NC(CH,),); coalescence temperature: 307 K;  4 (290 K): C17-C20. (1988) 39. Ranaivonjatovo, J. Satge, OrganometaNics 7 (1988) 1545. 6 = 0 58(s,6H,S1CH3), 1.28(s,9H,NC(CH3),), 1.39(s,9H,NC(CH3),), 1.52 (s ,  18H, NC(CH,),). [8] Crystallographic data: 3: triclinic, Pi, a = 10.794(8), b = 10.816(8), c = ll.l21(8)A, a =97.5(1), j3= 102.9(1), y =  97.8(1)", V =  1236A3; Z = 1 ; 2064 ,,observed" reflections (2 c r F ) ,  278 parameters, R = 0.049. - 4 .  '12 C,H,: orthorhombic, Pbca, u = 10.619(6), b = 15.834(9), c = 33.84(2) A, V = 5687 A'; Z = 8; 2128 ,,observed" reflections (3 uF), 305 parameters, R = 0,051. - Further details of the crystal structure investiga- tion are available on request from the Fachinformationszentrum Karls- ruhe, Gesellschaft fur wissenschaftlich-technische Information mbH, D-7514 Eggenstein-Leopoldshafen 2 (FRG), on quoting the depository number CSD-53903, the names of the authors, and the journal citation. [9] P. Jutzi, W Steiner, E. Konig, Chem. Ber. 111 (1978) 606; R. J. Chadha, J. E. Drake, A. B. Sarkar, Inorg. Chem. 26 (1987) 2885. [lo] B. Krebs, S. Pohl, Z. Naturforsch. 826 (1971) 853. I l l]  G. Trinquier, M. Pelissier, B. Saint-Roch, H. Lavayssiere, J.  Organomet. Chrm. 2/4(1981) 169. [12] (Me,N--C,,H,)(Ph)SiS and the analogous germanium compound: P. Arya, J. Boyer, R. Corriu, G. Lanneau, M. Perrot, C. Priou, Euchem Con5 PSIBLOCS (ParisiPalaiseau 1988). 1131 F. Goffing, Dissermrion, Universitat Saarbriicken 1988; M. Veith, F. Gof- fing, unpublished. [14] M. Veith, F. Goffing, V. Huch, Z.  Naturforsch. 8 4 3  (1988) 846. 1238 0 VCH Verlagsgeseftschaf! mbH, 0-6940 Weinheim. 1989 0570-0833i89l0909-1238 $O2.S0/0 Angew. Chem. In{. Ed. Engl. 28 (1989) Nr. 9 

A base-stabilized Ge-S double-bond

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A base-stabilized Ge-S double-bond

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