Formation of an unsymmetrical Pt-Ir tetraalkynyl complex and investigationinto subsequent construction of multimetallic systems

The reactions between [Pt(C drop CR)(4)](2-) (R = Ph, t-Bu, SiMe3) and [Ir( mu -Cl)(COD)](2) have been studied, but the formation of an unsymmetrical h eterobinuclear complex (NBu4)[(COD)Ir(mu -1 kappaC(alpha):eta (2)-C drop CS iMe3)(mu -2 kappaC(alpha):eta (2)-C drop CS (NBu4)[{Ir-Pt}(C drop CSiMe3)(2 )], 1 was only observed with the homoleptic species [Pt(C drop CSiMe3)(4)]( 2-). Complex 1 exhibits in the solid state a bent sigma,pi double-alkynyl b ridging system, which is formed through a migration of one a-alkynyl group from platinum to iridium. The stability of the remaining Pt-acetylide sigma -bonds in 1 and its possible application in the assembly of multimetallic compounds containing the {Ir-Pt} "pincer" unit has been investigated. Treat ment of (NBu4)[{Ir-Pt}(C drop CSiMe3)(2)] (1) with neutral [cis-M(C6F5)(2)( THF)(2)] (THF = tetrahydrofuran, M = Pt, Pd) or cationic [Rh(COD)(acetone)( x)](+) or [Pd(eta (3)-C3H5)S-x](+) solvento species (the latter generated " in situ") leads to very unusual anionic (NBu4) [{Ir-Pt}(mu -2 kappaC(alpha) :eta (2)-C drop CSiMe3)(2)M(C6F5)(2)] (M = Pt, 2; Pd, 3) or neutral heterot rimetallic complexes [{Ir-Pt}(mu -2 kappaC(alpha):eta C-2 drop CSiMe3)(2)Rh + (COD)] (4) and [{Ir-Pt-}(mu -2 kappaC(alpha):eta (2)-C drop CSiMe3)(2)Pd(eta (3)-C3H5)] (5), respectively. The molecular structure of 4 confirms th e presence of a formally heterotrimetallic zwitterion [(COD)Ir(mu -1 kappaC (alpha):eta (2)-C drop CSiMe3)(mu -2 kappaC(alpha):eta (2)-CSiMe3)(2)Rh+(CO D)], formed by the binuclear anionic fragment [(COD)Ir(mu -1 kappaC(alpha): eta (2)-C drop CSiMe3)(mu -2 kappaC(alpha):eta (2)-C drop CSiMe3)Pt(C drop CSiMe3)(2)](-), which in its turn acts as a chelating dimetallo bidentate l igand toward the cationic [Rh(COD)](+) unit. However, a similar neutralizat ion reaction of 1 with 1 equiv of AgClO4 produces an unusual hexanuclear tr imetallic complex [(eta (2)-(Ir-Pt)(C drop CSiMe3)(2))(2)Ag-2] (B), in whic h the heterobimetallic diyne anionic substrate [{Ir-Pt}(C drop CSiMe3)(2)]( -) acts as a mu-eta (2):eta (2) bridging ligand of two different silver(I) centers.