The control of the spin of the ground state in molecular clusters behaving like single molecule magnets (SMM) has been an important challenge in coordination chemistry. The spin value is a critical parameter because the barrier for the orientation of the magnetization depends on the square of it. [1,2] The most common strategies exploit antiferromagnetic interactions both in hetero-spin clusters, such as the archetypal SMM, [Mn 12 O 12 (CH 3 COO) 16 (H 2 O) 4 ], [3][4][5] and in particular spin topologies, such as the propeller structure of Fe 4 clusters. [6,7] Ferromagnetic interactions are relatively rare in molecular clusters, and often encountered in very symmetric structures, where the orthogonality of the magnetic orbitals is more easily controlled. [8 ,9] In low-symmetry environments the sign of the magnetic interaction is, in general, easily predictable for paramagnetic centers with one unpaired electron. [10] Magneto-structural correlations are well established, for instance, for oxo-bridged {VO 2+ } fragments [11] and ferromagnetic interactions have been observed when the d xy magnetic orbitals are orthogonal to each other, where a local reference system with the x and y axis pointing towards the oxobridging ligands is considered. The J values usually do not exceed À10 cm À1 , [12] the Hamiltonian being defined as h =