ABSTRACT
A number of novel alkynyl-functionalized diarylbis(dimethylamino)diboranes(4) are prepared by salt metathesis, and the appended alkynyl groups are subjected to hydroboration. Their reactions with monohydroboranes lead to discrete boryl-appended diborane(4) species, while dihydroboranes induce their catenation to oligomeric species, the first known examples of well-characterized macromolecular species with B-B bonds. The oligomeric species were found to comprise up to ten repeat units and are soluble in common organic solvents. Some of the oligomeric species have good air stability and all were characterized by NMR and vibrational spectroscopy and size-exclusion chromatography techniques.
ABSTRACT
Direct functionalization and Pd-catalyzed cross-coupling of difuryl(supermesityl)borane (1) led to highly emissive organoborane compounds 3 and 4. Photophysical and TD-DFT studies reveal an increase of the HOMO levels with higher hetarene content and stabilization of the HOMO and LUMO levels through B-doping, leading to very robust, air-stable electron-accepting materials.
ABSTRACT
The reaction of n-C8 H17 B[N(Me)SiMe3 ]2 (1) with n-C8 H17 BCl2 (2 a) yielded, instead of a linear poly(iminoborane), the aminoborane n-C8 H17 B(Cl)N(Me)SiMe3 (4) and after cyclotrimerization the borazine cyclo-(n-C8 H17 BNMe)3 (6). Side reactions that result in borazine formation were effectively suppressed if 1,3-bis(trimethylsilyl)-1,3,2-diazaborolidines 7 were employed as co-monomers in combination with dichloro- or dibromoboranes 2 or 8, respectively. Silicon/boron exchange polycondensation led to oligo(iminoborane)s 11 a,b,ac,d. Alternative synthetic routes to such species involve Sn/B exchange of 1,3-bis(trimethylstannyl)-2-n-octyl-1,3,2-diazaborolidine (16) and n-C8 H17 BBr2 (8 a), and the initiated polycondensation of the dormant monomer 14 in the presence of a Brønsted acid (HCl, HOTf, or HNTf2 ; Tf=trifluoromethylsulfonyl). Although an attempt to obtain an oligo-/poly(iminoborane) with phenyl side groups yielded only insoluble material, the incorporation of aryl groups was proven for a derivative with both phenyl and n-octyl boron substituents (11 ac), as well as for a derivative with 4-n-butylphenyl side groups (11 d). The highest-molecular-weight sample obtained was 11 ac. Featuring about 18 catenated BN units, on average, this is the closest approach to a poly(iminoborane) known.
