The reaction of Ru-3(CO)(12) with Pt(IMes)(2) in benzene solvent at room temperature afforded the monoplatinum-triruthenium cluster complex Ru3Pt(IMes)(2)(CO)(11), 1, in 21% yield and the trigonal bipyramidal cluster complex Ru3Pt2(IMes)(2)(CO)(12), 2, in 26% yield. The reaction of Ru(CO)(5) with Pt(IMes)(2) in benzene solvent at 0 degrees C yielded two trinuclear cluster complexes, the monoplatinum-diruthenium Ru2Pt(IMes)(CO)(9), 3, and the monoruthenium-diplatinum cluster complex RuPt2(IMes)(2)(CO)(6), 4. The reaction of 2 with hydrogen at 80 degrees C afforded the tetrahydrido-tetraruthenium complex Ru-4(IMes)(CO)(11)(mu-H)(4), 5, and the dihydrido-diruthenium-diplatinum complex Ru2Pt2(IMes)(2)(CO)(8)(mu-H)(2), 6. All six compounds were structurally characterized by single-crystal X-ray diffraction analyses.