Discrete triangle, square and hexametallic alkynyl cyano-bridged compounds based on [cis-Pt(CCR)2(CN)2]2- building blocks

Novel mixed bis(alkynyl)bis(cyano)platin ate (it) species [cis-Pt(Cequivalent toCR)(2)(CN)(2)](2-) (1a: R = tBu, 1b: R = Ph) have been prepared and their potential as building blocks in the generation of self-organized systems with a variable molecular architecture has been studied. The reaction of 1 with the ditopic acceptor species [[cis-Pt(C6F5)(2)S](2)(dppa)] (dppa = diphenyl-phosphinoacetylene) gave the dianionic cyanide/dppa bridged molecular platinotriangles (NBu4)(2)[C6F5)(2)Pt(mu-dppa){(mu-CN)(2)Pt(Cequivalent toCR)(2)}Pt(C6F5)(2)] (2). X-ray analysis of 2a confirmed that the Pt-2(C6F5)(4)(mu-dppa) binuclear moiety is connected to the dianionic Pt(Cequivalent toCR)(2)(CN)(2) unit by two bridging cyanide ligands. Moreover, treatment of 1 with the solvent cationic species [M(cod)(acetone)(2)](+) afforded heterometallic molecular squares Pt2M2 (M = Rh, It) containing cyanide bridges and terminal alkynyl ligands, (NBu4)(2)[cyclo{[cis-Pt(Cequivalent toCR)(2)(mu-CN)(2)][M(cod)]}(2)] (3: M=Rh, 4: M = Ir). The solid-state structures of phenyl derivatives have been determined by X-ray crystallography. The terminal alkynyl ligands in these cyanide-bridged molecular squares 3 and 4 have been used in the assembly of higher multimetallic complexes. Thus, very unusual bis(double-alkynide)-cyanide-bridged hexametallic compounds (NBu4)(2)[{(C6F5)(2)Pt(mu-Cequivalent toCPh)(2)(mu-CN)(2)}(2){M(cod)}(2)] (5b: M=Rh, 6b: M = Ir) were easily formed by simple reactions of 3b and 4b with two equivalents Of [cis-Pt(C6F5)(2)(thf)(2)]. An X-ray diffraction study on complex 5b indicated that the derivative was formed by a simultaneous migration of one sigma-alkynyl group from each Pt(Cequivalent toCPh)(2)(mu-CN)(2) corner of the square to both Pt(C6F5)(2) units, resulting in bent sigma,pi-double-alkynyl bridging systems. Finally, the novel supramolecular anionic assemblies (NBu4)(4)[cyclo{[cis-Pt(Cequivalent toCR)(2)(mu-CN)(2)][SnPh3]}(4)] 7 have been obtained by self-assembly of 1 and [SnPh3(acetone)(2)](+).