Heterometallic Pt–Ag and Pt2Ag transition metal complexes

Complexes of type {cis-[Pt](μ-σ,π-CCPh)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](CCPh)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-CCPh)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](CCPh)2 units. Within this structural arrangement the phenyl acetylides of individual [Pt](CCPh)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)(PtCαCβPh) confirm this structural motif.Complexes 8a–8c isomerize in solution to form trimetallic [{cis-[Pt](μ-σ,π-CCPh)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- CCPh)2}2Ag]+ is set-up by two nearly orthogonal positioned [Pt](CCPh)2 entities which are hold in close proximity by the group-11 metal ion. Within this assembly all four PhCC units are η2-coordinated to silver(I). A possible mechanism for the formation of 9 is presented.

Depending on the stoichiometry of cis-[Pt](CCPh)2 ([Pt] = (bipy′)Pt, (bipy)Pt) and [AgX] (X = BF4, PF6, ClO4) these species react to give heterobi- and -trimetallic complexes of type {cis-[Pt](μ-σ,π-CCPh)2}AgX, [{cis-[Pt](μ-CCPh)2}2Ag]X and [{cis-[Pt](μ-σ,π-CCPh)2}2Ag]X. The molecular solid state structure of one molecule, [{cis-[Pt](μ-CCPh)2}Ag]BF4, is reported.Figure optionsDownload as PowerPoint slide