Synthesis and crystal structure of alkali metal hydrogen fluoroacetates Rb[H(CF3COO)(2)] and M[H(CH2FCOO)(2)] (M = K, Cs)

Hydrogen mono- and trifluoroacetates were synthesized and studied by X-ray diffraction analysis. All compounds crystallize in the monoclinic system: s pace group C2/c, Z = 4, a = 11.717 (4), b = 10.558 (4), c = 8.811 (2) Angst rom, beta = 127.01 (2)degrees for Rb[H(CF3COO)(2)] (I); space group C2/c, Z = 4, a = 10.287 (5), b = 10.855 (5), c = 8.074 (3) Angstrom, B = 123.94 (4 )degrees for K[H(CH2FCOO)(2)] (II); and space group P2(1)/n, Z = 4, a = 12. 513 (3), b = 4.927 (1), c = 13.073 (3) Angstrom, beta = 105.65 (3)degrees f or Cs[H(CH2FCOO)(2)] (III). Structures I-III contain centrosymmetrical dime ric [H(RCOO)(2)](-) anions formed due to symmetrical hydrogen bonds. Two ty pes of dimeric anions are present in structure III. In the type one dimer, the hydrogen atom is located in the inversion center, while in the type two dimer, a two-minimum symmetrical hydrogen bond is formed.