Syntheses and structures of 1,3,5-trihalogeno-1,3,5-triboracyclohexane derivatives

On heating bis(diiodoboryl)methane (1c) and 1,1-bis(diiodoboryl)alkanes 1i,1(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, F; 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.