Hydroboration of propyne and 1-butyne with HBCl2 obtained from BCl3 and Me3SiH in equimolar amounts leads to 1,1-bis(dichloroboryl)alkanes 1. When BCl3 is used in excess, no 1,1-bis(dichloroboryl)alkanes 1 but E-1-dichloroborylalkene 2 besides E-1-dichloroboryl-2- chloro-alk-1-ene 3 are formed. Other by-products are tris(2-chloro-alk-1-ene-1-yl)borane 4 and bis(2-chloro-alk-1-ene-1-yl)chloroborane 5. The reaction of 3 with catechol and the formation of pyridine adducts of 4 and 5 lead to crystalline products. The composition of the products was determined by NMR spectroscopy, MS spectrometry and X-ray structure analyses of 6a, 6b, 7a and 8b.
On heating bis(diiodoboryl)methane (1c) and 1,1-bis(diiodoboryl)alkanes 1i, l (alkane = propane, butane) under reduced pressure elimination of BI3 takes place and the corresponding 1,3,5-triiodo- 1,3,5-triboracyclohexane derivatives 2c; 2i, i’; 2l, l’ are formed. Starting with bis(dichloroboryl)- and bis(dibromoboryl)methane (1a, 1b) only small amounts of the trimerization products (H2C-BCl)3 (2a) and (H2C-BBr)3 (2b) are detectable which can not be separated from 1a,b and by-products. Reaction of 1,3,5-trichloro-2,4,6-trimethyl-1,3,5-triboracyclohexane (2d) with BBr3 provides the corresponding bromo derivative 2e in high yield. An attempt to react 2,4-bis(dichloroboryl)-3-chloro- 3-borapentane (4d) with 1,1-bis(trimethylstannyl)-2,2-diphenylethene does not lead to the expected trichloro-triboracyclohexane, but the divinylchloroborane ClB(CH=CPh2)2 6a, is formed. The compositions of the products follow from analytical data and X-ray structure analyses of 2i, 2c, 2e, and 6a.