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

Abstract

A dinickel complex with bridging silyl ligands, [{Ni(PCy3)}2(μ-SiHPh2)2] (1), prepared from [Ni(cod)2], PCy3, and H2SiPh2, underwent exchange of the PCy3 ligands with 1,2-bis(dimethylphosphino)ethane (dmpe) to yield a complex coordinated by the two bidentate ligands, [{Ni(dmpe)}2(μ-SiHPh2)2]. Reactions of diarylacetylenes, ArCCAr (Ar = C6H5, C6H4OMe-4, C6H4Me-4, C6H4F-4, C6H4CF3-4, C6H4CN-4), with 1 in a 4/1 ratio afforded 1,2-bis{(E)-1,2-diarylethenyl}-1,1,2,2-tetraphenyldisilanes via addition of the Si–H bond of the bridging silyl ligand to the alkynes and subsequent coupling of the resulted tertiary silyl ligand. X-ray crystallography of the dialkenyldisilanes resulted in three kinds of conformation of the CC–Si–Si–CC chain depending on the aryl group at the vinyl carbon. The disilane with phenyl substituents, 4a (Ar = C6H5), contained a planar CC–Si–Si–CC alignment with small Si–Si–CC torsion angles (1.7(5) and 6.9(5)°). The other dialkenyldisilanes, 4b,c,e,f, had much larger torsion angles (30.9(3)–49.2(3)°), and the twisted conformation of the molecules was classified into two types. Compound 4a exhibited a fluorescence maximum at 488 nm in the solid state, while 4b–f showed peaks at 393–427 nm. The red shift in the emission of 4a is ascribed to orthogonal intramolecular charge transfer (OICT) from the electron-donating Si–Si to accepting CC bonds.

Reactions of Hydrosilanes with Transition Metal Complexes

“… 39 At −60 C in C 7 D 8 , the SiH resonance is observed at 6.25 ppm with 1 J SiH = 167.9 Hz). , 40 4-47 was also prepared from 4-49 and 2 equiv of dmpe 41 29 Si was not observed due to decomposition of the complex during the measurement 42 4-50 was also prepared from Ni­(COD) 2 and Ph 2 SiH 2 in the presence of ( i Pr 3 P) …”

“…The products that have been obtained from the reactions of hydrosilanes with transition metal complexes are summarized in Tables (primary silanes), − (secondary silanes), ,− ,, and (tertiary silanes)primarily for products that contain a Si–TM bond. Some researchers study reactions of primary and/or secondary and/or tertiary silanes.…”

“…This includes the simplest metal compounds, such as MCl 2 , such as reported by Peters and co-workers, and other metal chlorides that also contain replaceable olefins and phosphines (partial listing of examples): (COD)­RuCl 2 , [(COE) 2 MCl] 2 (M = Rh, 102 Ir 131 ), [(COD)­MCl] 2 (M = Rh, 196 Ir 192 ), and [(COD)­PdMeCl] . Other commercial sources contain M(0) coordinated to phosphines and/or olefins, for example: [Ni­(COD) 2 ], , Ni­(PPh 3 ) 4 , Pd­(*PEt 3 ) 4 , and Pt­(PPh 3 ) 4 . Selected examples of the use of metal halides in the preparation of complexes that were then used to react with a hydrosilane are shown in eqs and 19 and similarly from a commercial reagent in eq 18 .…”

“…For the purpose of incorporating an anionic ligand at the metal, a metal halide (particularly a chloride) is often used. This includes the simplest metal compounds, such as MCl 2 , such as reported by Peters and co-workers, 164 212 Other commercial sources contain M(0) coordinated to phosphines and/or olefins, for example: [Ni(COD) 2 ], 139,140 Ni(PPh 3 ) 4 , 210 Pd(*PEt 3 ) 4 , 110 and Pt(PPh 3 ) 4 . 212 Selected examples of the use of metal halides in the preparation of complexes that were then used to react with a hydrosilane are shown in eqs 17 and 19 and similarly from a commercial reagent in eq 18.…”

Selective Formation and SHG Intensity of Noncentrosymmetric and Centrosymmetric 1,1,2,2-Tetramethyl-1-(4-(N,N-dimethylamino)phenyl)-2-(2′-cyanophenyl)disilane Crystals under External Stimuli

“…Recently, investigation of oligosilyl derivatives represents a significant challenge to understand the photophysical properties due to the effective σ–π conjugation through Si–Si bonds. − Especially, diaryldisilanes are promising as soft crystals driven from the conformational variety and flexibility of Si–Si σ-bonds. Previously, we reported that the donor–acceptor disilane 1 (Figure ) displayed second harmonic generation (SHG) in the crystalline state, which is widely used in advanced photonic technologies. − This compound has a strong transition dipolar moment by a strong donor moiety (−NMe 2 ) and an acceptor moiety (−CN) with Si–Si σ-conjugated linker, showing no absorption in the visible light region different from a large π-extended skeleton.…”