HYDROTRIS(3-MESITYLPYRAZOL-1-YL)BORATE AND HYDROBIS(3-MESITYLPYRAZOL-1-YL)(5-MESITYLPYRAZOL-1-YL)BORATE - SYMMETRICAL AND ASYMMETRIC LIGANDS WITH ROTATIONALLY RESTRICTED ARYL SUBSTITUENTS

Two novel ligands, hydrotris(3-mesitylpyrazol-1-yl)borate [HB(3Mspz)3]- (= Tp(Ms)) and its isomer hydrobis(3-mesitylpyrazol-1-yl)(5-mesitylpyrazol-1-yl)borate (= Tp(Ms*)), were synthesized; the latter is the first example of an asymmetric tris(pyrazolyl)borate ligand. They were used to form the complexes Tp(Ms)ZnX, Tp(Ms*)MX (M = Zn, Cd; X = Cl, I, NCS), Tp(Ms)Pd(eta3-methallyl), Tp(Ms*)Pd(eta3-methallyl), Tp(Ms)Rh(COD), Tp(Ms*)Rh(COD), Tp(Ms)Rh-(CO)2, Tp(Ms*)Rh(CO)2, Tp(Ms)Mo(CO)2(eta3-methallyl), and Tp(Ms*)Mo(CO)2(eta3-methallyl). Above 220-degrees-C some of the Tp(Ms*) complexes rearrange into their Tp(Ms) analogs. Structures of Tp(Ms)Mo(CO)2(eta3-CH2CMeCH2) and of Tp(Ms*)ZnI were established by X-ray crystallography. The complex Tp(Ms)Mo(CO)2(eta3-CH2CMeCH2) crystallizes in the space group P2(1)/m (No. 11) with parameters a = 12.709(3) angstrom, b = 21.085(4) angstrom, c = 17.856(4) angstrom, beta = 108.66(3)degrees, V = 4533(2) angstrom3 for Z = 4. It contains octahedrally coordinated Mo, with the mesityl groups deviating by 0-17.2-degrees from orthogonality to the pyrazolyl plane. The complex Tp(Ms*)ZnI crystallizes in the space group P1BAR (No. 2) with parameters a = 12.188(3) angstrom, b = 12.905(4) angstrom, c = 14.1104(6) angstrom, alpha = 97.21(3)degrees, beta = 113.61(3)degrees, gamma = 109.45(2)degrees, and V = 1828.6(6) angstrom3 for Z = 2. It contains tetrahedral Zn(II), and the mesityl groups deviate from orthogonality to the pyrazolyl plane by 10.2-31.8-degrees.