Monomeric boron and tin(II) heterocyclic derivatives of 1,8-diaminonaphthalenes: Synthesis, characterization and X-ray structures

The reaction of the diaminonaphthalene dilithium salt (THF)(2)Li(2)[(NSiMe(3))(2)C(10)H(6)] with BX(3) (X = Cl, Br) in hexane provides the monomeric compounds BX[(NSiMe(3))(2)C(10)H(6)] [3 (X = Cl), 4 (X = Br)] with a tricoordinate boron atom. Attempts to reduce 3 and 4 with lithium, sodium, potassium or sodium/potassium alloy with the intention to isolate a boranide resembling a carbene were unsuccessful. However, the diaminonaphthalene dilithium salt (THF)(2)Li(2)[(NSi-iPr(3))(2)C(10)H(6)] (2) reacts with SnCl(2) in THF to provide the carbene analog 5. Compounds 2, 3 and 5 were characterized by single-crystal X-ray structure analysis. The structures of 3 and 5 show the naphthalene backbone to be nearly planar, while the heterocycles in 3 and 5 containing boron and tin atoms, respectively, have torsion angles (3: 30.06 degrees; 5: 37.27 degrees) with respect to the naphthalene plane. The boron atom has a trigonal-planar environment, and the stannylene tin-nitrogen bonds form a very acute N-Sn-N angle of 92.2 degrees. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).