Synthesis of Tris Pyrazolylborate Lab Report Example | Topics and Well Written Essays - 1000 words

Synthesis of Tris Pyrazolylborate - Lab Report Example Trispyrazolylborate (Tp) is an organic anionic tetradentate or tripodal ligand that has the chemical formula [HB (C3N2H3)3]. Trispyrazolylborate specifically refers to the derivatives substituted on the pyrazolyl rings. In the resonance structures of this compound, the nitrogen centers that are not bonded to boron are basic (Topaloglu-Sozuer et al., 2005). These centers bond to three adjacent sites of a metal such that the simple adducts have C3v symmetry. The bonding mode is similar to that of cyclopentadienyl ligands though the ligand field stabilization energy of Tp- is weaker as indicated by the fact that Fe (Tp)2 is a spin crossover complex while ferrocene is low spin (Yong Heng, Aoki, & Feng Ying, 2004). The Tp ligands are prepared in the laboratory by reacting pyrazole with potassium borohydride according to the equation:KBH4 + 3C3H3N2H → K [HB (C3N2H3)3] +3H2The intermediate compounds include the monopyrazolylborate ([H3B (C3N2H2)2]- and the bispyrazolylborate ([H2B(C3 N2H2)2]-. The potassium Trispyrazolylborate is a colorless solid that is soluble in polar solvents and has a melting point of 188-1890C (Maldonado, & Vahrenkamp, 2006).When 3-substituted pyrazoles are condensed with borohydride, the corresponding substituent Trispyrazolylborate derivatives are formed. The substituent formed pushes boron the less hindered nitrogen center and hence 3-phenylpyrazole gives [HB (C3N2H2Ph) 3]- whereas the phenyl substituents project away from the metal.