The First Stable 9-Silaanthracene

Abstract

The first stable 9-silaanthracene, 5, bearing an efficient steric protection group, 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl (Tbt), was successfully synthesized by the reaction of the corresponding silyl triflate, 7, with a 1.0 M amount of lithium diisopropylamide. The aromaticity of 5 is discussed on the basis of the NMR, UV/vis, and Raman spectra, X-ray structural analysis, and theoretical calculations.

Heavy Analogs of Aromatic Compounds

“…The heavy group 14 element atoms were diagnostically deshielded, indicating their sp 2 -hybridization, as was seen in their 29 Si NMR [93.6 (silabenzene 16), 61a 91.7 (1-silanaphthalene 17), 62a 87.3 (2-silanaphthalene 15), 48a 87.2 (9-silaanthracene 18), 63 86.9 (9-silaphenanthrene 19) ppm], 64 and 119 Sn NMR [264 ppm (2-stannanaphthalene 24)] 68 spectra (Scheme 6.6). The same tendency in the skeletal E-C and C-C bond lengths is also operative for other heavy arenes, including polynuclear derivatives (except for the 2-sila-and 2-germanaphthalene derivatives 15 and 21, for which a small C-C bond alternation was observed similar to that of the parent naphthalene) (Scheme 6.6).…”

Syntheses and Properties of Tin‐Containing Conjugated Heterocycles

“…In the case of the two phenyl rings in the 1a nd 4p ositions, the torsional angles are 1.28 and 478,r espectively.T he distance between SnÀC1 is 2.126 ,b etween C1ÀC2 1.352 ,a nd between C2ÀC3 it is 1.511 .T he bond lengths for SnÀC5 and SnÀC6 are both 2.125 ;this is very similar to the SnÀC1 and SnÀC4 bond distance. However, 13 CNMR shift values of 153-125 ppm (compared to (E,E)-1,2,3,4-tetraphenylbutadiene of 145-126ppm) and am aximum of the UV absorption spectrum of 355 nm suggests some s*-p*-conjugation. [32]…”

“…[12] Polycyclic aromatic rings with CÀSi replacement have also been reported;t he substituent on silicon is always sterically encumbered. [13] The substituted hexasilabenzene 1,asilicon analogue of benzene, with chair shapeg eometry has been reported to be thermally stable at 100 8C, with a "dismutational aromaticity" and three resonance forms ( Figure 1). [14] However,asimilar aromatic compound could not be observed for tin.…”

“…2 J Sn-C values for the couplingo ft he tin atom with C2 and C3 atoms are smaller with 2 J( 119/117 Sn-13 C) = 41 Hz. [32] In general, the carbon atoms of the stannole ring have 13 CNMR shifts ranging from 120 to 175 ppm. C2/C3 carbon atoms are the most deshielded inside the ring.…”

Synthesis and structure of 9,10-bis(2,4,6-triisopropylphenyl)-9,10-dihydro-9,10-disilaanthracene

“…We also reported the thermal generation and chemical trapping of the transient 9-silaanthracenes [15]. In 2002, Tokitoh and coworkers successfully isolated 9-silaanthracene, which was kinetically stabilized by a bulky substituent [16]. However, there have been no reports on the isolation or chemical trapping of the disilaaromatic 9,10-disilaanthracene.…”