Heterometallic Pt–Ag and Pt2Ag transition metal complexes

Complexes of type {cis-[Pt](μ-σ,π-Ctriple bond; length of mdashCPh)2}AgX (3a, [Pt] = (bipy′)Pt, X = FBF3; 3b, [Pt] = (bipy′)Pt, X = FPF5; 3c, [Pt] = (bipy)Pt, X = OClO3; 3d, [Pt] = (bipy′)Pt, X = BPh4; bipy′ = 4,4′-dimethyl-2,2′-bipyridine; bipy = 2,2′-bipyridine) are accessible by combining cis-[Pt](Ctriple bond; length of mdashCPh)2 (1a, [Pt] = (bipy′)Pt; 1b, [Pt] = (bipy)Pt) with equimolar amounts of [AgX] (2a, X = BF4; 2b, X = PF6; 2c, X = ClO4; 2d, X = BPh4). In 3a–3d the platinum(II) and silver(I) ions are connected by σ- and π-bonded phenyl acetylide ligands. When the molar ratio of 1 and 2 is changed to 2:1 then trimetallic [{cis-[Pt](μ-Ctriple bond; length of mdashCPh)2}2Ag]X (8a, [Pt] = (bipy)Pt, X = BF4; 8b, [Pt] = (bipy′)Pt, X = PF6; 8c, [Pt] = (bipy)Pt, X = BF4) is produced. The solid state structure of 8a was determined by single X-ray crystal structure analysis. In 8a the silver(I) ion is embedded between two parallel oriented cis-[Pt](Ctriple bond; length of mdashCPh)2 units. Within this structural arrangement the phenyl acetylides of individual [Pt](Ctriple bond; length of mdashCPh)2 entities possess a μ-bridging position between Pt(II) and Ag(I). In addition, a very weak dative Pt → Ag interaction is found (Pt–Ag 2.8965(3) Å). The respective silver carbon distances Ag–Cα (2.548(7), 2.447(7) Å) and Ag–Cβ (3.042(7), 2.799(8) Å)(PtCαtriple bond; length of mdashCβPh) confirm this structural motif. Complexes 8a–8c isomerize in solution to form trimetallic [{cis-[Pt](μ-σ,π-Ctriple bond; length of mdashCPh)2}2Ag]X (9a, [Pt] = (bipy)Pt, X = BF4; 9b, [Pt] = (bipy′)Pt, X = PF6; 9c, [Pt] = (bipy)Pt, X = ClO4). In the latter molecules the organometallic cation [{cis-[Pt](μ-σ,π- Ctriple bond; length of mdashCPh)2}2Ag]+ is set-up by two nearly orthogonal positioned [Pt](Ctriple bond; length of mdashCPh)2 entities which are hold in close proximity by the group-11 metal ion. Within this assembly all four PhCtriple bond; length of mdashC units are η2-coordinated to silver(I). A possible mechanism for the formation of 9 is presented.