Novel Germoles and Stannoles With Unexpected Properties

Abstract

Stannoles were prepared by 1,1-organoboration of bis(amino)di(l-alkynyl)tin compounds or di(l-alkynyl)tin dichlorides or -dibromides. Bulky amino groups are required in order to obtain bis(amino)tin dichlorides which do not exchange their ligands. These bis(amino)tin dichlorides were converted into bis(amino)di(lalkynyl)tin compounds, the precursors of the stannoles bearing amino groups at the tin atom. The stannoles bearing chloro or bromo ligands at the tin atom could also be obtained by exchange reactions of other stannoles with tin tetrachloride or -bromide, and, bearing Me 3 Si groups in the 2,5-positions, they were found to be surprisingly unstable with respect to elimination of tin dichloride or -dibromide, respectively. Di(methoxyethynyl)dimethyltin, Me 2 Sn(CsCOMe)2, and -germanium, Me2Ge(C»COMe) 2 , were treated with trialkylboranes. In the case of germanium, new germoles with methoxy groups in 2,5-positions were obtained. In the case of tin, the formation of an unstable intermediate was detected by NMR followed by extensive decomposition at room temperature, and a stannole was not observed. Vol. 24, Nr. 9, 2001New germoles with methoxy groups in 2,5-positions Germoles can be obtained in the same way as stannoles by 1,1-organoboration of di(l-alkynyl)-germanium compounds (Scheme 2) [9]. In general, the 1-alkynylgermanium compounds are less reactive towards EtjB when compared with their tin analogues. However, most of the 1-alkynylgermanium derivatives react with Et3B at room temperature or after gentle heating at 50 to 70°C. We have prepared di(lmethoxyethynyl)dimethylgermanium, Me 2 Ge(C*C-OMe) 2 which proved fairly stable towards thermally induced decomposition. These properties enabled us to carry out 1,1-organoboration reactions, leading straightforwardly to new germoles 14 and 15 (Scheme 7) [18]. This particular pattern of substituents, with methoxy groups in 2,5 and a boryl group in 3-position is now available for the first time. According to "B NMR spectra, coordinative 0-»B interactions are negligible. The new germoles undergo [4+2] cycloadditions with dimethyl acetylene dicarboxylate in the usual way [19]: the 7-germa-noibornadiene derivatives 16 and 17 were detected by NMR in solution before they rearrange into the respective benzenes 18 and 19 by ejection of dimethylgermylene which forms a polymer. In contrast, the analogous stannoles were not accessible from the reaction of Me 2 Sn(C"C-OMe)2 [20] with Et3B. Although a zwitterionic intermediate as shown in Scheme 2 could be detected by NMR spectroscopy at -40 °C, decomposition into numerous products occurred when the mixtures were allowed to reach ambient temperature.

Metallacyclopentadienes and related heterocycles via 1,1‐organoboration of alkyn‐1‐ylmetal compounds

“…This has led to the germoles 33 [7,55] and spirogermanium compounds (1,1 -spirobigermoles) 34 [51] (Scheme 17). In the case of Me 2 Ge(C C R 1 ) 2 the germole 33 was also obtained for R 1 = OMe [56]. This is noteworthy, since the 1,1-ethylboration of the analogous tin compound Me 2 Sn(C C-OMe) 2 was accompanied by extensive decomposition [56].…”

Tuning the Optoelectronic Properties of Stannoles by the Judicious Choice of the Organic Substituents

“…However, using σ*-π*-conjugation as a means for lowering the HOMO-LUMO gap is much less common; this phenomenon can be observed by formally substituting the sp 3 Since then, investigations of different synthetic routes [19][20][21] and studies of the (opto-) electronic properties, [22][23] aromaticity 24 and reactivity were conducted for the related siloles, [25][26][27] but germoles, [28][29] stannoles 30 and plumboles [31][32] are much less well investigated. 33 However, the study of such heterocycles is of great interest, since they themselves or their ring fused analogs [34][35][36][37][38][39][40] show great potential in organic electronic devices.…”

“…Tin-containing metalloles (Figure 1) are part of heavy group 14 (Si, Ge, Sn, and Pb) cyclopentadiene analogues and were first synthesized in 1959. 18 Since then, investigations of different synthetic routes 19−21 and studies of the (opto)electronic properties, 22,23 aromaticity, 24 and reactivity were conducted for the related siloles, 25−27 but germoles, 28,29 stannoles, 30 and plumboles 31,32 are much less well investigated. 33 However, the study of such heterocycles is of great interest because they themselves or their ringfused analogues 34−40 show great potential in organic electronic devices.…”

“…Since then, investigations of different synthetic routes − and studies of the (opto)­electronic properties, , aromaticity, and reactivity were conducted for the related siloles, − but germoles, , stannoles, and plumboles , are much less well investigated . However, the study of such heterocycles is of great interest because they themselves or their ring-fused analogues − show great potential in organic electronic devices. − The formal replacement of the methylene C atom by Si, Ge, Sn, or Pb in cyclopentadiene and its derivatives leads to unique optoelectronic properties in comparison to their carbon analogues.…”

Synthetic Route to Benzostannoles via Al−Li‐dimetal Intermediate and Their Application to Dibenzofulvene Synthesis

“…Stannoles are a family of heteroles that contain a tin atom in a five-membered electron-rich diene ring and exhibit specific chemical and physical properties. [1][2][3] They are also known as starting materials for other heteroles, [4,5] metalloles, [6] and polycyclic aromatic hydrocarbons (PAHs). [7] Therefore, several methods utilizing dilithium compounds as a key intermediate have been reported for preparing stannoles (Scheme 1a, eq.…”