Z. Naturforsch. 51 b, 1104Z. Naturforsch. 51 b, -1110Z. Naturforsch. 51 b, (1996; eingegangen am 22. Januar 1996The synthesis and structural properties of organo-bis-dialkylaminochlorboranes X( BNR2C1)2 X = R2NB(CHCH3)2, < 9-C6H4, 1-q-C6H4CH2, and 1.8-C10H6 are reported. The steric influ ence 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 ( C 6H4)(BNM e2C l)2 (5) only one amino-boron donor-acceptor bond is observed. The steric influence of the alkyl groups in R2NB(CHCH3BC1NR2)2 is discernible from the formation of two donor-acceptor bonds in 7a (R = Me), whereas 7b (R = /Pr) is a non-bridged species.The reaction of benzomagnesacyclobutene with chlorbis(dimethylamino)borane yields cyclic l-a (C 6H4C H 2)(BNM e2C l)2 (9). 1,8-Dilithionaphthalene reacts with C1B (NR2)