Antiferromagnetic complexes with metalmetal bonds: XXV. Synthesis, molecular structure and magnetic properties of the triangular cluster Cp2Cr2(μ-SCMe3)(μ3-S) 2IR(CO)(PPh3) and the octanuclear cluster Cp2Cr2(μ3-S) 2(μ4-S)Rh2[Cp2Cr2(μ-SCMe3)(μ3-S)2]2 with an unusual triangular heterometalloornament f