Synthesis, Structure, and Magnetic Properties of a Family of Complexes Containing a {CoII 2 DyIII } Pivalate Core and a Pentanuclear CoII 4 DyIII Derivative: Synthesis, Structure, and Magnetic Properties of a Family of Complexes Containing a {CoII2DyIII} Pivalate Core and a Pentanuclear CoII4DyIII Derivativ