Heterometallic Pt-Ag and Pt2Ag transition metal complexes

Complexes of type {cis-[Pt](mu-sigma,pi-C=CPh)(2)}AgX (3a, [Pt] = (bipy')Pt, X = FBF3; 36, [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](C=CPh)(2) (la, [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 sigma- and pi-bonded phenyl acetylide ligands. When the molar ratio of 1 and 2 is changed to 2:1 then trimetallic [1 cis-[Pt](mu-C=CPh)(2)](2)Ag]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](C=CPh)2 units. Within this structural arrangement the phenyl acetylides of individual [Pt](C=CPh)2 entities possess a p-bridging position between Pt(II) and Ag(I). In addition, a very weak dative Pt -> Ag interaction is found (Pt-Ag 2.8965(3) angstrom). The respective silver carbon distances Ag-C-alpha (2.548(7), 2.447(7) angstrom) and Ag-C-beta (3.042(7), 2.799(8) angstrom)(PtC alpha=C beta Ph) confirm this structural motif. Complexes 8a-8c isomerize in solution to form trimetallic [{cis-[Pt](mu-sigma,pi-C=CPh)(2)](2)Ag]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](mu-sigma,pi-C=CPh)(2)](2)Ag](+) is set-up by two nearly orthogonal positioned [Pt](C=CPh)2 entities which are hold in close proximity by the group-11 metal ion. Within this assembly all four PhC C units are eta(2)-coordinated to silver(I). A possible mechanism for the formation of 9 is presented.(c) 2007 Elsevier B.V. All rights reserved.