New azoniaboratacyclopropanes from (F3C)(2)BNMe2 and diazomethane derivatives - Structure of cyclo-(F3C)(2)B-CPh2-NMe2 and HOB(CF3)(2)-CHC6F5-NHMe2

l,l-Dimethyl-2,2-bis(trifluoromethyl)azoniaboratacyclo- propanes, cyclo-(F3 C)(2)B-(CRR2)-R-1-NMe2 [R-1 = R-2 = C6H5 (2a); R-1/R-2 = C12H8 (2b); R-1 = H, R-2 = C6H5 (2C), 4-FC6H4 (2d), 3FC(6)H(4) (2e), 2-FC6H4 (2f), C6F5 (2g), iPr (2h), tBu (2i); R-1 = Me, R-2 = C(=O)OMe (2j), C(=O)OEt (2k)] have bee n obtained from (F3C)(2)BNMe2 (1) and diazomethanes (RRCN2)-R-1-C-2. In con trast to compound 2a, the B-N bonds of 2b-2k hydrolyze to form the zwitteri onic species Me2NH-(CRR2)-R-1-B(CF3)(2)OH (3b-3k). The diazoacetic acid est ers HC(N-2)C(=O)OMe and HC(N-2)C(=O)OtBu react with 1 to form three-membere d rings, which hydrolyze rapidly to form Me2NH-(CRR2)-R-1 B(CF3)(2)OH [R-1 = H, R-2 = C(=O)OMe (31), C(=O) OtBu (3m)]. F3CSiF3 reacts under eliminatio n of CF2 with 1 to form the acyclic derivative (F3C)(2)BF-CF=NMe2 (4). The structures of 2a and 3g have been investigated crystallographically. A near ly eclipsed conformation is found for the central B-C bond of 3g, which is 0.097(7) Angstrom longer than the B-C bond length in the three-membered rin g of 2a.