We explore the magnetic properties of isolated a−b planes of trinuclear organometallic crystals, Mo 3 S 7 (dmit) 3 , in which an interplay of strong electronic correlations and spin molecular-orbital coupling (SMOC) occurs. The magnetic properties can be described by a XXZ+120 0 , S = 1 Heisenberg model on a honeycomb lattice with single-spin anisotropy, D, which depends strongly on SMOC. Based on ab initio estimates of SMOC in Mo 3 S 7 (dmit) 3 crystals, we predict that the honeycomb layers of Mo 3 S 7 (dmit) 3 are Néel ordered. However, in materials with a greater degree of magnetic frustration, Néel order can give way to a large-D phase. arXiv:1810.13399v1 [cond-mat.str-el]