Bis-ortho-chelated diaminoaryl platinum compounds with σ-acetylene substituents.: Investigations into their stability and subsequent construction of multimetallic systems.: The crystal structure of [(μ2-[(η2-NCN)Pt(η1-CO)CCSiMe3])Co2(CO)6] (NCN=2,6-bis[(dimethylamino)methyl]phenyl)

A series of related platinum sigma-acetylide complexes {Pt}C drop CR ({Pt} = [Pt(C6H3{Me2NCH2}(2)-2,6)](+)) were prepared by reacting lithium acetylides with (Pt)C1 (I) in order to investigate the stability of the Pt-acetylide sigma-bond and their possible application in the assembly of multimetallic compounds containing the {Pt} "pincer" unit. This may be achieved by eta(2)-coordination of the acetylide or by incorporating a second ligating site in the acetylide anion. Both of these approaches are demonstrated herein. {Pt}C drop CSiMe3 (2) was reacted with [M][BF4] ([M] = [Cu(NCMe)(4)], Ag) and different forms of Cu(I) halides. Only with the former was the formation of stable pi-coordinated M(I) compounds observed. [(eta(2)-[{Pt}C drop CSiMe3](2))-Cu][BF4] exhibits eta(2)-coordination of both acetylenic units to a formal Cu(I) metal center, thus forming a heterotrimetallic compound. In the presence of halide ions, 2 undergoes cleavage of the Pt-C=C sigma-bond with concomitant formation of {Pt}X (X = C; or I). The reaction of 2 with Co-2(CO)(8) leads via pi-coordination to the formation of a trimetallic dicobaltatetrahedrane. The structure of [mu(2)-[eta(2)-NCN)Pt(eta(1)-CO)C drop CSiMe3])Co-2(CO)(6)] in the solid state shows that one ortho-CH2NMe2 substituent of the NCN ligand is no longer coordinated to the Pt metal center. Instead, a CO ligand coordinates trans to the Pt-N bond, yielding a metal center with four different ligand donor atoms. Attempts to obtain related Pt(TV) acetylides by reaction of 2 with CuCl2 resulted in the formation of {Pt}Cl-3, [CuX](n), and [CuC drop CSiMe3](n). The reaction with I-2 gave neither a Pt(IV) diiodide nor a Pt(II) eta(1)-I-2 complex, but instead led to Pt-C(acetylide) bond cleavage and formation of (Pt)I and IC drop CSiMe3. The reaction of {Pt}C drop CC6H4CN-4 with [{Pt}H2O][BF4] and {Ru}N drop N{Ru} ({Ru} = [RuCl2(C5H3N{CH2NMe2}(2)-2,6)]) gives air-stable well-defined bimetallic compounds. In contrast, the reaction of {Pt}C drop CC6H4CN-4 with [AuCl3](2) Or Au(CO)Cl leads to the formation of a gold mirror, NCC6H4(C drop C)(2)C6H4CN, and {Pt}Cl-3 or {Pt}Cl, respectively. Cyclic voltammetry studies with representative Pt-acetylides show irreversible oxidative processes which are shifted to a more negative potential upon substitution of C1 by acetylide.