Benzo-1,2,3-triselenolium Trifluoro-methanesulfonate—a C2Se3 Radical Cationic Salt with Unusual Solid-State Structure
✍ Scribed by Dr. Gotthelf Wolmershäuser; Dipl.-Chem. Gert Heckmann
- Publisher
- John Wiley and Sons
- Year
- 1992
- Tongue
- English
- Weight
- 252 KB
- Volume
- 31
- Category
- Article
- ISSN
- 0044-8249
No coin nor oath required. For personal study only.
✦ Synopsis
Compound 3 can be compared with its carbocyclic analogue 4[l61 only in solution, since 4 was not structurally characterized. The z o 7 P b 1 H and 207Pb13C coupling constants of 3 (*Jpb," = 33.6, lJpb,cz = 5.8, 1Jpb,c3 = 31.8 Hz) are smaller than those of 4, which might indicate a larger percentage of ionic bonding in 3. The significant deshielding of the carbon atoms contained in the ring in 3 (6 C2,CS =161.71, C3,C4 =105.19) in comparison with the pyrrole 2 (6 C 2,C 5 = 139.51, C 3,C 4 = 102.70) is contrary to the coordination shift in the azacyclopentadienyl compounds of the transition metals.['* 7, "I The exchange of two
CH fragments contained in the ring of 4 for nitrogen atoms leads to a significant deshielding of the Pb atom [S(207Pb) = -4142 in 3 in contrast to -4756 in 41. The mass spectrum (EI) shows, probably as a result of the low thermal capacity of 3 (decomposition above 104 "C), the molecular peak only in low intensity.
The synthesis of the diazoplumbocene 3 shows that the azacyclopentadienyl ligand is also suitable for the formation of low molecular weight main group element 7c complexes. This opens up new possibilities in the coordination chemistry of pyrrole and its derivatives.
Experimental Procedure
To a suspension of PbCI, (1.39 g, 5.2 mmol) and 2,5-C,R2H,NLi (R = ierlbutyl) (1.94 g, 10.5 mmol) in toluene (50 mL), THF (2 mL) was added, and the mixture was stirred for 2 h. After the removal of the volatiles the residue was extracted with n-pentane (40 mL). After recrystallization yellow crystals of 3 were obtained. Yield 2.50 g, (85%). M.p. 104°C (decomp). ' H N M R (60 MHz. C,F,, TMS int.): 6 = 5.51 (4H; C(3,4)-H; '1 ('07Pb, 'H) = 33.6 Hz). 1.39 (s, 36H; Me); I3CNMR (75.43 MHz, C,H,, TMS int.): 6 = 161.71 (C2.CS; 'J(Z07Pb, I3C) = 5.8 Hz), 105.19(C3,C4; 1J(207Pb, "C) = 31.4 Hz). 33.31 (qC). 32.69 (Me); '"PbNMR (62.7 MHz, C,H,, PbMe, ext.): 6 = -4142. -MS (70 eV, EI): m/z 564 (M', 1 %), 386 ( M + -pyr, 20), 164 (pyr -H' -Me, IOO), and further fragments.