First C₂ Symmetrical Siloles:  Synthetic, Structural, and Photophysical Studies of 7-Sila-7H-dibenzo[c,g]fluorenes

Abstract

The syntheses of 7-sila-7H-dibenzo[c,g]fluorenes 1 were effected via dilithiation of 2,2‘-dibromo-1,1‘-binaphthyl (2) followed by cyclization of the resulting dianion with dihalosilanes: Me2SiCl2, Ph2SiCl2, and Ph2SiF2. The X-ray structural analysis of 7-sila-7,7-diphenyl-7H-dibenzo[c,g]fluorene (1b) provided the first geometrical parameters of the 7-sila-7H-dibenzo[c,g]fluorene derivative in which the silole skeleton was found to be twisted in the C 2 symmetrical conformation due to the significant steric repulsion of the binaphthyl group fixed within the van der Waals radii. The photophysical study and semiempirical PM3 calculation suggested the presence of significant σ*−π* conjugation in the LUMO of the 7-sila-7H-dibenzo[c,g]fluorene 1 like a silole.

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“…54 Reaction of K 2 W 2 (CO) 10 with Pb(NO 3 ) 2 gives [Pb 2 {W(CO) 5 } 4 ] 22 isoelectronic with the known [As 2 ] compound. The Pb-Pb distance is 2.806 Å, the shortest known Pb-Pb interaction, which supports the formulation Pb 2 22 . 55 Two new silyl ethers with intramolecular co-ordination of a dimethylamino group, bis [8-(dimethylamino)naphth-1-yl)dimethylsilyl] ether and bis[8-(dimethylamino)naphth-1-yl)-1-siloxacyclobut-1-yl] ether have been prepared and examined by single crystal X-ray diffraction.…”

“…Photophysical studies suggest that the s*-p* orbitals are conjugated in the LUMO of the compound. 22 Two equivalents of LiL 1 [L 1 = 9-(dimethylamino)fluorenyl] react with Me 2 M(14)Cl 2 , where M(14) = Ge or Sn, to give L 1 2 M(14)Me 2 , the first structurally characterised Scheme 1…”

“…This bimetallic material is a single-source precursor to the formation of nanoparticles with PtSn composition. 53 A heavy analogue of the carbonate ion has been reported as [Pb{Cr(CO) 5 } 3 ] 22 , which shows a trigonal planar geometry at Pb, with conjugated Pb pp -Cr dp bonding corresponding to C pp -O pp in CO 3 22 . The Pb centre is co-ordinatively unsaturated and can co-ordinate further ligands, such as PMe 3 .…”

“…60 The series of related (mes) 3 GeX, where X = CN 2 , SCN 2 or N 3 2 , have been studied crystallographically. 61 Further azide complexes of germanium have been reported, such as 18, which was shown crystallographically to comprise a planar C 7 N 2 M unit and a pyramidal M, 62 and the homoleptic anion [Ge(N 3 ) 6 ] 22 . 63 This latter compound has an idealised S 2 symmetry in its [(Ph Tin(II) imido cubanes (19) containing donor functionalised substituents have been prepared.…”

Silicon-Bridged Biaryls: Molecular Design, New Synthesis, and Luminescence Control

“…Smooth production of 2a from 6 is presumably ascribed to the less crowded surroundings of the lithiated carbons, because the disilylene-bridge forces significant distortion of the biphenyl moiety of 6. 22 With 2a in hand, we decided to prepare the bis(disilylene)-bridged biphenyl 7. We next applied the one-pot protocol to 3a and (Me 2 SiCl) 2 .…”