Discrete Triangle, Square and Hexametallic Alkynyl Cyano-Bridged Compounds Based on [cis-Pt(C≡CR)2(CN)2]2- Building Blocks

Abstract

Novel mixed bis(alkynyl)-bis(cyano)platinate(II) species [cis-Pt(C≡CR2(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)2S}2(dppa)] (dppa = diphenyl-phosphinoacetylene) gave the dianionic cyanide/dppa bridged molecular platinotriangles (NBu4)2[(C6F5) 2Pt(μ-dppa){(μ-CN)2Pt(C≡CR) 2}Pt(C6F5)2] (2). X-ray analysis of 2a confirmed that the "Pt2(C6F5) 4(μ-dppa)" binuclear moiety is connected to the dianionic "Pt(C≡CR)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, Ir) containing cyanide bridges and terminal alkynyl ligands, (NBu4)2[cyclo{[cis-Pt(C≡CR) 2(μ-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[{(C6F 5)2Pt (μ-C≡ CPh)2(μ-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(C 6F5)2(thf)2]. An X-ray diffraction study on complex 5b indicated that the derivative was formed by a simultaneous migration of one σ-alkynyl group from each "Pt(C≡ CPh) 2(μ-CN)2" corner of the square to both "Pt(C6F5)2" units, resulting in bent σ,π-double-alkynyl bridging systems. Finally, the novel supramolecular anionic assemblies (NBu4)4[cyclo{[cis-Pt(C≡CR) 2(μ-CN)2][SnPh3]}4] 7 have been obtained by self-assembly of 1 and [SnPh3(acetone)2] +.