[Pt-2(PPh3)(4)(mu-S)(2)] (1) reacts with AgCl(PPh3) and CuCl under a mild pressure of CO (60 psi) to give [Pt-2(Co)(PPh3)(3)(mu(3)-S)MCl] [M = Ag (4) and Cu (6)] via the intermediates [Pt-2(PPh3)(4)(mu(3)-S)(2)Ag(PPh3)]Cl (2a), [Pt-2(PPh3)(5)(mu(3)-S)(2)AgCl] (3), and [Pt-2(PPh3)(5)(mu(3)-S)(2)CuCl] (5), respectively. These transformations demonstrate an unprecedented concomitant process which involve heterometalation, carbonylation, reductive desulfurization, and metal-metal bond formation. The Ru-Pt aggregate of [Pt-2(PPh3)(4)(mu(3)-S)(2)RuCl(PPh3)(2)]Cl (7), prepared from 1 and RuCl2(PPh3)(3), similarly converts to a [Pt-2(CO)(2)(PPh3)(2)(mu(3)-S)RuCl(CO)(PPh3)]Cl (8) cluster under a CO atmosphere. Such transformation establishes a synthetic relationship between the {Pt2MS2} trigonal bipyramidal aggregates and {Pt2MS} tetrahedral clusters and provides a general entry to triangular heterometallic sulfide clusters of platinum. All complexes are characterized by IR, P-31{H-1}, and C-13 NMR spectroscopy and conductivity measurements. The structures of 4, 6, and the PF6- derivative of 2a (viz. 2b) have also been determined by single-crystal X-ray diffraction analyses. The structure of 2b shows a sulfide-bicapped Ag-Pt mixed-metal triangle without significant Pt Pt [3.351(2) and 3.375(2) Angstrom] or Ag ... Pt [av 3.064(1) and 3.101(1) Angstrom] interactions. Complex 2b crystallizes in two polymorphic modifications with different degrees of disposition of the Ag moieties with respect to the {Pt2S2} core. As a result, the Ag-S bonds [2.479(1) vs 2.585(1) Angstrom and 2.502(2) vs 2.607(2) Angstrom] are significantly different between the polymorphs in which the Ag ... Pt distances are near-equivalent [3.061(1) vs 3.066(1) Angstrom] in one form but significantly different [2.962(1) vs 3.240(1) Angstrom] in the other. Complex 4 shows a triangular {AgPt2} cluster mono-capped by sulfide. Removal of a capping sulfur atom from 2a effectively reduces both Pt-II centers and favors Pt-Pt bond formation [Pt-Pt 2.658(2) Angstrom] and heterometallic Ag-Pt interactions [av Ag-Pt 2.965(1) Angstrom] in 4. Both the Pt-S and Ag-S bonds also strengthen significantly from 2b to 4. Cluster 6 is isostructural to 4 with similar homo-[Pt-Pt 2.657(1) Angstrom] and heterometal [av Cu-Pt 2.832(1) Angstrom interactions. Both 4 and 6 thus constitute a {MPt2S} distorted tetrahedral cluster frame. A facile and general aggregates-to-clusters conversion through the elimination of COS gas is thus established.