Reactive Rigid-Rod Organometallic Polymers Involving Linear Triplatinum Units Connected by π-Conjugated Bisisocyanides

Axial ligand exchange reactions of [Pt 3 (μ-dpmp) 2 (XylNC) 2 ](PF 6 ) 2 ( 1 ) with monoisocyanide molecules afforded a series of linear triplatinum complexes, [Pt 3 (μ-dpmp) 2 (RNC) 2 ](PF 6 ) 2 (R = 2,4,6-mesityl ( 2 ), tert -butyl ( 4 ), 4-tolyl ( 5 )) and [Pt 3 (μ-dpmp) 2 (XylNC)( t- BuNC)](PF 6 ) 2 ( 3 ), which were characterized by spectroscopic, X-ray crystallographic, and absorption (EXAFS) analyses. With the increase of π-acidity of the terminal isocyanide, the Pt−Pt bond length became longer due to electron transfer from the Pt 3 core to the isocyanide group. Terminal ligand exchange reactions of 1 with bulky aromatic bisisocyanides (bisNC n ) led to successful isolation of the rigid-rod triplatinum cluster polymers formulated as {[Pt 3 (μ-dpmp) 2 (bisNC n )](PF 6 ) 2 } n (bisNC n = 2,3,5,6-tetramethylphenylene-1,4-bisisocyanide (bisNC1) ( 7a ), 3,3‘,5,5‘-tetramethylbisphenylene-4,4‘-bisisocyanide (bisNC2) ( 7b )). The structure of compound 7a, determined by X-ray crystallography, was composed of the linear, metal−metal bonded {Pt 3 (μ-dpmp) 2 } 2+ fragments (av Pt−Pt = 2.699 Å) covalently connected by the bisisocyanide molecules, resulting in an infinite rigid-rod polymeric structure. By using less bulky bisisocyanides, the ligand exchange reaction stopped at the formation of the triplatinum cluster dimers [(bisNC n )Pt 3 (μ-dpmp) 2 (bisNC n )Pt 3 (μ-dpmp) 2 (bisNC n )](PF 6 ) 4 (bisNC n = phenylene-1,4-bisisocyanide (bisNC3) ( 8a ), 2,5-dimethylphenylene-1,4-bisisocyanide (bisNC4) ( 8b )), which were characterized by EXAFS analyses to involve the weakly metal−metal bonded Pt 3 fragments (av Pt−Pt = 2.85 Å). The rigid-rod polymer 7a was demonstrated to be quite reactive even in heterogeneous systems toward H +, NO +, tetracyanoethylene (tcne), and electron-deficient alkynes, to afford the cluster polymers formulated as {[Pt 3 (μ-H)(μ-dpmp) 2 (bisNC1)](BF 4 ) 3 } n ( 13 ), {[Pt 3 (μ-NO) 2 (μ-dpmp) 2 (bisNC1)](BF 4 ) 4 } n ( 14 ), {[Pt 3 (μ-C 12 N 8 )(μ-dpmp) 2 (bisNC1)](PF 6 ) 2 } n ( 15 ), and {[Pt 3 (μ-R 1 C 2 R 2 )(μ-dpmp) 2 (bisNC1)](PF 6 ) 2 } n ( 16a, R 1 = H, R 2 = CO 2 CH 3; 16b, R 1 = R 2 = CO 2 CH 3 ). The structures of the polymers 13 − 16 were estimated on the basis of the X-ray crystallographic and spectroscopic analyses for the related reference complexes [Pt 3 (μ-H)(μ-dpmp) 2 (XylNC) 2 ] 3+ ( 9 ), [Pt 3 (μ-NO) 2 (μ-dpmp) 2 (RNC) 2 ](BF 4 ) 4 ( 10, R = Xyl, Mes), [Pt 3 (μ-C 12 N 8 )(μ-dpmp) 2 (RNC) 2 ](PF 6 ) 2 ( 11, R = Xyl, Mes), and [Pt 3 (μ-R 1 C 2 R 2 )(μ-dpmp) 2 (XylNC) 2 ](PF 6 ) 2 ( 12, R 1 = H or COOCH 3, R 2 = COOCH 3 ).