The rare-earth metal(III) complexes [M2(piv)6(Hpiv)6] (monoclinic, P21/c, 1), [M2(piv)6(Hpiv)6]·Hpiv (monoclinic, C2/c, 2), [M(piv)3]n (trigonal, P63/m, 3), and [(Hpiv)2(iPrOH)2Sm2(piv)6]·2Hpiv (triclinic, P-1, 4), where piv is (CH3)3CCO2−, were synthesized, and their structures were determined by single-crystal X-ray diffraction (SC-XRD). The crystallization was shown to be controllable by varying the nature of the salting-out agent – the non-coordinating organic solvent in the M(OAc)3·4H2O–Hpiv system. The following bulky single-phase samples were obtained: dimers 1 or 2 with M = Pr, Nd, Sm, Eu, and Gd using hexane C6H14; dimer 1 or 1D polymer 3 with M = Y, Er, and Yb using EtOH; dimers 2 or 4 with M = Sm using iPrOH. A reversible phase transition to a commensurate modulated modification (P21/c) was observed for crystals of 1 (Pn). The magnetic properties of complexes 1a (Pr), 1b (Nd), 4 (Sm), 1d (Eu), 1f (Dy), 1 g (Ho), and 1 h (Er) were investigated.