Rigid-rod polymers, oligomers, and model complexes with Pt-Pt bonds in the backbone

Reaction of [Pt2Cl2(mu-dppm)(2)], dppm = Ph(2)PCH(2)PPh(2), with PhC=CH in methanol gives [Pt2Cl2(mu-dppm)(2)(mu-PhCCH)], 1, or, in the presence of base, [Pt-2(C=CPh)(2)(mu-dppm)(2)], 2, or [Pt-2(C=CPh)(2)(mu-dppm)(2)(mu-PhCCH)], 4. Complex 2 reacts with chlorinated solvents to reform [Pt2Cl2(mu-dppm)(2)], but in the presence of base, [Pt-2(C=CPh)(2)(mu-dppm)(2)(mu-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 [Pt2Cl2(mu-dppm)(2)] with HC=CArC=CH in methanol in the presence of base gives insoluble oligomers characterized as Cl-[Pt-2(mu-C=CArC=C)(2)(mu-dppm)(2)](x)[Pt2Cl(mu-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(mu-dppm)(2)(mu-L-L)](x)(BF4)(2x), 6 or 7, are formed by reaction of [Pt2Cl3(mu-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-Pr2PC6H4C6H4P-i-Pr-2, having a longer spacer group, gives the cyclic complex [Pt-2(mu-dppm)(2)(mu-i-Pr2PC6H4C6H4P-i-Pr-2)](2)(BF4)(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.