Preparation, Characterization, and Luminescence Properties of a 58-Electron Linear Pt(4) Cluster, [Pt(4)(dmb)(4)(PPh(3))(2)](2+) (dmb = 1,8-Diisocyano-p-menthane), and Its Diphosphine Polymers.

The title compounds [Pt(4)(dmb)(4)(PPh(3))(2)]Cl(2) (1) and {[Pt(4)(dmb)(4)(diphos)]Cl(2)}(n)() (diphos = dppb (2), dppp (3), dpph (4)) have been prepared in good yields from the reaction of Pt(2)(dba)(3).CHCl(3) with 2 equiv of dmb and 1 equiv of PPh(3) for 1 (dba = dibenzylideneacetone) and from the reactions of Pt(2)(dba)(3).CHCl(3) with 2 equiv of dmb and 0.5 equiv of diphos for 2-4. The structure for 1 consists of a quasi-linear Pt(4)L(2)(2+) species (L = PPh(3); d(PtPt) = 2.666(2), 2.655(2), 2.641(2) Å), where the dmb ligands bridge the Pt atoms forming a catenate. From Raman spectroscopy, the two nu(PtPt) active modes for 1 are observed at 162 and 84 cm(-)(1) (F(PtPt) = 2.36 mdyn Å(-)(1)). For 2-4, the diphos ligands induce the formation of amorphous polymeric materials (X-ray powder diffraction patterns) with MW ranging from 84 000 to 307 000 according to viscometry. EHMO calculations predict that the HOMO and LUMO are the two dsigma orbitals arising from four interacting Pt atoms via the d(x)()()2(-)(y)()()2, d(z)()()2, s, and p(x)() M atomic orbitals. These are mixed with the ddelta and CNR(pi) MO's. From the examination of the position, absorptivity, and fwhm (full width at half maximum) of the strongly allowed low-energy UV-vis band, a dsigma --> dsigma assignment is made (lambda(max) = 405 nm, epsilon = 35 800 M(-)(1) cm(-)(1); EtOH for 1). The four compounds are luminescent at 77 K in EtOH, where lambda(emi) are 750, 736, 750, and 755 nm and tau(e) are 2.71, 4.78, 5.15, and 5.17 ns for 1-4, respectively. On the basis of the Stokes shifts (10 000-12 000 cm(-)(1)) and the long emission lifetimes, a phosphorescence dsigma --> dsigma assignment is made for the observed emissions. Crystal data for 1: crystal system triclinic; space group P1; a = 12.624(4) Å; b = 14.24(2) Å; c = 27.312(3) Å; alpha = 92.35(3) degrees; beta = 91.655(15) degrees; gamma = 90.28(5) degrees; V = 4903(7) Å(3); Z = 2; D(calc) = 1.528 g cm(-)(3); R(1) = 0.0738; wR(2) = 0.2097; S = 1.018.