First Isolation and Full Characterization of 2,2‘-Bishalosilyl-Substituted 1,1‘-Binaphthyls:  Synthesis of 2,2‘-Bis(fluorodimethylsilyl)-1,1‘-binaphthyl and X-ray Structural Analysis of Highly Strained Disilanylene-Bridged Precursors

Abstract

Brominative Si-Si cleavage of 3,4-disila-3,3,4,4-tetramethyl-3,4-dihydrodibenzo[c,g]phenanthrene (3a), LiAlH 4 reduction of the resulting dibromide, and fluorination of the dihydride 14a thus gave 2,2′-bis(fluorodimethylsilyl)-1,1′-binaphthyl (7a) in high yield as the first isolated and fully characterized 2,2′-bis(halosilyl)-1,1′-binaphthyl. Similar conversion of the more sterically hindered 3,4-disila-3,3-dimethyl-4,4-diphenyl-3,4-dihydrodibenzo[c,g]phenanthrene (3b) also gave the corresponding bishydrosilane 14b. However, subsequent fluorination did not give the desired bisfluorosilane 7b but rather the hydrolyzed siloxane 6b. The syntheses of the disilanylene-bridged precursors 3 were effected via bis-silylation reactions of 2,2′-dibromo-1,1′-binaphthyl (DBBN, 2) with dihalodisilanes ClMe 2 SiSiMe 2 Cl, ClMe 2 SiSiPh 2 Cl, FMe 2 SiSiPh 2 F, and FPh 2 SiSiPh 2 F. Although ClMe 2 SiSiMe 2 Cl predominately gave the disilanylene-bridged product 3a, XMe 2 SiSiPh 2 X (X ) F, Cl) produced not only the disilanylene-bridged product 3b but also the dimethylsilylene-bridged product 8a. FMe 2 -SiSiPh 2 F served better in preparation of the desired 3b than ClMe 2 SiSiPh 2 Cl. The sterically hindered FPh 2 SiSiPh 2 F did not give silylation products. The X-ray structural analyses of 3a and 3b provided the first geometrical parameters of the 2,2′-disilanylene-bridged 1,1′binaphthyl derivatives. In comparison with the acyclic analogues and less sterically hindered disilanylene-bridged biaryls such as 2,2′-bis(trimethylsilyl)-1,1′-binaphthyl ((()-1a), (R)-(-)-2,2′-bis(dimethylphenylsilyl)-1,1′-binaphthyl ((R)-(-)-1b), dibenzo-1,1,2,2-tetramethyl-1,2-disilacyclohexa-3,5-diene (12), and dithienodisilacyclohexadiene 13 the disilanylenebridged binaphthyls 3 were found to be highly strained due to the steric repulsion of the binaphthyl groups fixed in a narrow angle.

Disilane-bridged architectures: an emerging class of molecular materials

“…In 2000, highly strained rings 71 and 72 consisting of a disilane linker and binaphthyl were synthesized. 115 The crystal structure revealed that the silicon atom is substantially deformed from the tetrahedral geometry. Take 71 as an example, the Si–Si–C(methyl) bond angle is enlarged to 119.0°.…”

Preparation and Properties of Perarylated 3,4-Disila-1,5-hexadienes. A Fluorescent Disilane Accommodated in the Crystal Lattice

“…In the solid state, perarylated siloles exhibit high luminescent properties owing to restricted rotation of the aromatic rings . The luminescent properties of the siloles were attributed to their low LUMO level caused by conjugation of σ*(Si) and π*(diene) orbitals. , 1,2-Disilacyclohexadienes with a six-membered ring composed of two CC bonds and an Si–Si bond were reported to possess nonplanar ring structures. , Marder et al compared the electronic state and luminescent behavior of the siloles and 1,1,2,2-tetramethyl-3,4,5,6-tetraphenyl-1,2-disila-3,5-cyclohexadiene . Acyclic disilanes with π-conjugated substituents also show unique luminescent properties based on the intramolecular charge-transfer mechanism between the Si–Si σ bonds and π orbitals of CC bonds or aromatic rings. − Similar intramolecular charge transfer from the disilanylene unit was also proposed for disilanylene-bridged silafluorene with a rigid planar structure, which emitted at a longer wavelength in the solid state .…”