Rigid-Rod Polymers, Oligomers, and Model Complexes with Pt−Pt Bonds in the Backbone

Reaction of [Pt 2 Cl 2 (μ-dppm) 2 ], dppm = Ph 2 PCH 2 PPh 2, with PhC⋮CH in methanol gives [Pt 2 Cl 2 (μ-dppm) 2 (μ-PhCCH)], 1, or, in the presence of base, [Pt 2 (C⋮CPh) 2 (μ-dppm) 2 ], 2, or [Pt 2 (C⋮CPh) 2 (μ-dppm) 2 (μ-PhCCH)], 4 . Complex 2 reacts with chlorinated solvents to re-form [Pt 2 Cl 2 (μ-dppm) 2 ], but in the presence of base, [Pt 2 (C⋮CPh) 2 (μ-dppm) 2 (μ-OH···Cl)], 3, may be formed. Complexes 1 and 3 have been characterized by X-ray structure determinations, and the conditions for formation of 2 have been optimized as a model reaction for polymer formation by using diacetylenes. Reaction of [Pt 2 Cl 2 (μ-dppm) 2 ] with HC⋮CArC⋮CH in methanol in the presence of base gives insoluble oligomers characterized as Cl-[Pt 2 (μ-C⋮CArC⋮C) 2 (μ-dppm) 2 ] x [Pt 2 Cl(μ-dppm) 2 ], 5, that is as a diacetylide bridged oligomer with chloride end groups; depending on the diacetylide used x varies from ca. 3−12. Cationic polymers [Pt 2 (μ-dppm) 2 (μ-L-L)] x (BF 4 ) 2 x, 6 or 7, are formed by reaction of [Pt 2 Cl 2 (μ-dppm) 2 ] with diisocyanide ligands C⋮NArN⋮C or with the diphosphine ligand Ph 2 PC 6 H 4 PPh 2, respectively. In contrast, the diphosphine ligand i -Pr 2 PC 6 H 4 C 6 H 4 P- i -Pr 2, having a longer spacer group, gives the cyclic complex [Pt 2 (μ-dppm) 2 (μ- i -Pr 2 PC 6 H 4 C 6 H 4 P- i -Pr 2 )] 2 (BF 4 ) 4 . The polymeric complexes 5 − 7 are insoluble or sparingly soluble in common organic solvents. They represent rare examples of conjugated, rigid-rod oligomers or polymers with metal−metal bonds in the backbone.