Crystal structures and DSC investigations of trimethylphenylammonium perchlorate, trimethyl-phenylammonium tetrafluoroborate, methyltriphenyl-phosphonium perchlorate, and methyltriphenyl-phosphonium 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]: P21/c, a= 852.7(3) pm, b= 580.9(2) pm, c=2260.1(8) pm, β =96.65(3)° and Z= 4. [Me3PhN][BF4]: P212121, a= 584.82(8) pm, b= 835.04(8) pm, c=2258.5(2) pm, and Z=4. [MePh3P]·[ClO4]: P21/c, a= 1491.0(3) pm, b= 1378.6(1) pm, c= 1791.6(2)pm, β = 90.66(1)° and Z= 8. [MePh3P] ·[BF4]: P21/c, a=1487.4(2)pm, b= 1377.5(1)pm, c= 1768.7(1)pm, β = 91.00(1)° and Z= 8.Two solid-solid phase transitions were detected in DSC for both trimethylphenylammonium compounds. Modification III 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(2) pm at 373 K. No phase transitions were observed in the phosphonium compounds in the range 153-600 K.