We report the preparation and infrared spectra of the CH3I- and CH2Br2- anions formed by argon cluster-mediated electron attachment to the neutral molecular precursors. Infrared predissociation spectra were acquired for both the bare and argon-solvated species in the C-H stretching region. Partial rotational structure was recovered in the CH3I- system, consistent with the hydrogen-bonded, C-2v structure suggested in an earlier analysis of its photoelectron spectrum [J. Kim , J. Am. Soc. Mass Spectrom. 10, 810 (1999)]. The spectrum and photofragmentation pattern confirm that this species is trapped in a very weakly bound ion-methyl radical form (I-. HCH2) involving a single ionic H bond. The CH2Br2- anion displays a similar spectrum, where one CH stretch is significantly redshifted, again signaling the single H-bonding motif.