Two new molecular magnets, based on [M(mnt)2]- [M = Pt (1) or Ni (2)], were prepared and characterized structurally and magnetically. The [M(mnt)2]- anions form the columnar stack in 1 and 2. Both compounds are expected to be ideal quasi-1D magnets. For 1, the χm value passes a maximum at ∼150 K and increase again below 120 K, a spin transition then occurs at ∼80 K with 4 K hysteresis. For 2, the χm value decreases exponentially upon cooling and drops rapidly below ∼90 K. At this temperature a spin transition occurs, with no sizable hysteresis detected upon heating.