Synthesis of di-, tri- and tetranuclear platinum(II) and copper(I) acetylide complexes

Heterobimetallic {cis-[Pt]( mu-sigma,pi-C CPh)(2)}[Cu(N CMe)]BF4 (3a: [Pt]=(bipy)Pt, bipy=2,2'-bipyridine; 3b: [Pt]=(bipy')Pt, bipy' = 4,4'-dimethyl-2,2'-bipyridine) is accessible by the reaction of cis-[Pt](C CPh)(2) (1a: [Pt] = (bipy)Pt, 1b: [Pt] = (bipy')Pt]) with [Cu(N CMe)(4)]BF4 (2). Substitution of N CMe by PPh3 (4) can be realized by the reaction of 3a with 4, whereby [{cis-[Pt](mu-sigma,pi-C CPh)(2})} Cu(PPh3)]BF4 (5) is formed. On prolonged stirring of 3 and 5, respectively, N CMe and PPh3 are eliminated and tetrametallic {[{cis-[Pt](eta(2)-C CPh)(2))Cu](2)}(BF4)(2) (6) is produced. Addition of an excess of N CMe to 6 gives heterobimetallic 3a. When instead of N CMe or PPh3 chelating molecules such as bipy (7) are reacted with 3a then the heterobimetallic pi-tweezer molecule [{cis-[Pt](mu-sigma,pi-C CPh)(2)) Cu(bipy)]BF4 (8) is formed. Treatment of 8 with another equivalent of 7 produced [Cu(bipy(2))]BF4 (9) along with [Pt](C CPh)(2). However, when 3b is reacted with 1b in a 1:1 molar ratio then 10 and 11 of general composition [{[Pt](C CPh)(2)}(2)Cu]BF4 are formed. These species are isomers and only differ in the binding of the PhC C units to copper(I). A possible mechanism for the formation of 10 and 11 is presented. The solid state structures of 6, 10 and 11 are reported. In 11 the [{cis-[Pt](mu-sigma,pi-C CPh)(2)}(2)Cu](+) building block is set-up by two nearly orthogonal positioned bis(alkynyl) platinum units which are connected by a Cu(I) ion, whereby the four carbon-carbon triple bonds are unsymmetrical coordinated to Cu(I). In trimetallic 10 two cis-[Pt](C CPh)(2) units are bridged by a copper(I) center, however, only one of the two PhC C ligands of individual cis-[Pt](C CPh)(2) fragments is eta(2)-coordinated to Cu(I) giving rise to the formation of a [(eta(2)-C CPh)(2)Cu](+) moiety with a linear alkyne-copper-alkyne arrangement (alkyne = midpoint of the C C triple bond). In 6 two almost parallel oriented [Pt](C CPh)(2) planes are linked by two copper(I) ions, whereby two individual PhC C units, one associated with each Pt building block, are symmetrically pi-coordinated to Cu. (c) 2007 Elsevier BN. All rights reserved.