Crystal structures and DSC investigations of trimethylphenylammonium perchlorate, trimethylphenylammonium tetrafluoroborate, methyltriphenylphosphonium perchlorate, and methyltriphenylphosphonium tetrafluoroborate, [Me3PhN][ClO4], [Me3PhN][BF4], [MePh3P][ClO4], and [MePh3P][BF4]

Abstract

[Me3PhN][ClO4], [Me3PhN][BF4], [MePh3P] [ClO4], and [MePh3P][BF4] were synthesized and their structures and thermodynamic data of transitions were determined. [Me3PhN][ClO4]: P2(1)/c, a = 852.7(3) pm, b = 580.9(2) pm, c = 2260.1(8) pm, beta = 96.65(3)degrees and Z = 4. [Me3PhN][BF4]: P2(1)2(1)2(1), a = 584.82(8) pm, b = 835.04(8) pm, c = 2258.5(2)pm, and Z = 4. [MePh3P] . [ClO4]: P2(1)/c, a = 1491.0(3)pm, b = 1378.6(1) pm, c = 1791.6(2) pm, beta = 90.66(1)degrees and Z = 8. [MePh3P] . [BF4]: P2(1)/c, a = 1487.4(2) pm, b = 1377.5(1)pm, c = 1768.7(1) pm, beta = 91.00(1)degrees and Z = 8. Two solid-solid phase transitions were detected in DSC for both trimethylphenylammonium compounds. Modification II of [Me3PhN][BF4] and the modification II of [Me3PhN][ClO4] are isotypic. The latter phase has lattice parameters of a = 2260.6(7) pm, b = 852.7(3) pm, and c = 586.3(21 pm at 373 K. No phase transitions were observed in the phosphonium compounds in the range 153-600 K.