Thomas Deforth

Unsaturated polymers containing boron and thiophene units in the backbone

2,5-Dialkynylthiophenes (RCC)2C4H2S (R = Ph, Me3Si or But) treated successively with HBCl2 and Et3SiH in CH2Cl2 undergo hydroboration polymerization to give intensely-coloured polymers of general structure –[CHCR–BCl–CRCH–C4H2S]n– for which the 11B NMR resonances occur ca. 50 ppm upfield of those for analogous monomers.

Darstellung und Eigenschaften von Derivaten des 4,5-Benzo-2,3-dihydro- \ ,3-diborols/ Synthesis and Properties of Derivatives of the 4,5-Benzo-2,3-dihydro-1,3-diborole

Reactions of 1,2-bis(trimethyIstannyl)benzene (4) with bis(dichIoroboryl)methane derivatives (Cl2B)2CHR1 (R1 = H ,Me) lead to the formation of the 4,5-benzo-1,3-dichloro-2,3-dihydro-1,3-diboroles 2a,b.Substitution of chlorine in 2a,b by a methyl group using A1Me3 yields the 4,5-benzo-1,3-dimethyl-2,3-dihydro-1,3-diboroles 2c,d, of which 2c is thermally labile. Complexation of 2c,d with [(C5H5)Co(C2H4)2] did not give the expected sandwich complexes 6c,d, but the formation of the triple-decker 7d was observed. The paramagnetic 7d and the diamagnetic 7d+, obtained by oxidation with Ag+BF4-, were studied by 1H NMR .

Synthesis of C2B3 X-Heterocycles (X = C, N, P, O, S) from 1,3,5-Triborapentanes

Abstract The hydroboration of acetylene with HBCl2 yields the products (Cl2B)2CHMe (1a), (Cl2BCHMe)2BCl (2a), (Cl2BCHMeBCl)2CHMe (3a), and (ClBCHMe)3 (4a). The crystal structure of 4a as well as of the pentaiodo derivative 2b were determined. A mechanism for the formation of the different hydroboration products is proposed. The 1,3,5-triborapentane 2a serves as precursor for the synthesis of derivatives of 1,3,5-triboracyclohexanes, 1,3,5-tribora-2-aza-cyclohexanes, 1,3,5-tribora-2-phospha-cyclo-hexanes, and 1,3,5-tribora-2-thia-cyclohexanes. Their constitutions have been derived from spectroscopic studies. The crystal structure of the 1,3,5-tribora-2-oxa-cyclohexane derivative was also determined.

Intramolekular verbrückte Organo-bis[dialkylaminochlorborane] / Intramolecularly Bridged Organo-bis[dialkylaminochloroboranes]

The synthesis and structural properties of organo-bis-dialkylaminochlorboranes X(BNR2Cl)2, X = R2NB(CHCH3)2, o-C6H4, 1-α-C6H4CH2, and 1.8-C10H6 are reported. The steric influence of the alkylamino group and the geometrical situation caused by a chain of sp2 or sp3 hybridized carbon atoms control the formation of intramolecular donor-acceptor bonds. In o-(C6H4)(BNMe2Cl)2 (5) only one amino-boron donor-acceptor bond is observed. The steric influence of the alkyl groups in R2NB(CHCH3BClNR2)2 is discernible from the formation of two donor-acceptor bonds in 7a (R = Me), whereas 7b (R = iPr) is a non-bridged species. The reaction of benzomagnesacyclobutene with chlorbis(dimethylamino)borane yields cyclic 1-α(C6H4CH2)(BNMe2Cl)2 (9). 1,8-Dilithionaphthalene reacts with ClB(NR2)2 (R = Me, Et, iPr) to yield 1,8-(C10H6)[B(NR2)2]2 (10a-c), its reaction with BCl3 gives 1,8-(C10H6)(BClNR2)2 (11a: R = Me; 11b: R = Et; 11c: R = iPr). In 11a,b two tetracoordinate boron atoms are observed, in 11c the steric hinderance of the isopropyl substituents prevents donor-acceptor bonding.