Fluoride-Bridged {Gd-III M-3(III) (2)} ( M= Cr, Fe, Ga) Molecular Magnetic Refrigerants**.

The reaction of fac-[(MF3)-F-III(Me(3)tacn)]xH(2)O with Gd(NO3)(3)5H(2)O affords a series of fluoride-bridged, trigonal bipyramidal {(Gd3M2III)-M-III} (M=Cr (1), Fe (2), Ga (3)) complexes without signs of concomitant GdF3 formation, thereby demonstrating the applicability even of labile fluoride-complexes as precursors for 3d-4f systems. Molecular geometry enforces weak exchange interactions, which is rationalized computationally. This, in conjunction with a lightweight ligand sphere, gives rise to large magnetic entropy changes of 38.3Jkg(-1)K(-1) (1) and 33.1Jkg(-1)K(-1) (2) for the field change 7T0T. Interestingly, the entropy change, and the magnetocaloric effect, are smaller in 2 than in 1 despite the larger spin ground state of the former secured by intramolecular Fe-Gd ferromagnetic interactions. This observation underlines the necessity of controlling not only the ground state but also close-lying excited states for successful design of molecular refrigerants.