Mixed-Ligand Organometallic Polymers Containing the “Pd₂(dmb)₂²⁺” Fragment:  Properties of the {Pd₂(dmb)₂(diphos)²⁺}_n Polymers/Oligomers in Solution and in the Solid State

Abstract

The 1:1 reaction between the d(9)-d(9) Pd(2)(dmb)(2)Cl(2) complex (dmb = 1,8-diisocyano-p-menthane) and the diphosphine ligands (diphos) bis(diphenylphosphino)butane (5, dppb), bis(diphenylphosphino)pentane (6, dpppen), bis(diphenylphosphino)hexane (7, dpph), and bis(diphenylphosphino)acetylene (8, dpa) in the presence of LiClO(4) leads to the [[Pd(2)(dmb)(2)(diphos)](ClO(4))(2)](n) polymers. These new materials are characterized by NMR ((1)H, (13)C, (31)P), IR, Raman, and UV-vis spectroscopies (466 < lambda(max)(dsigma-dsigma*) < 480 nm), by ATG, XRD, and DSC methods, and by the capacity to make stand-alone films. From the measurements of the intrinsic viscosity in acetonitrile, the M(n) ranges from 16000 to 18400 (12 to 16 units). The dinuclear model complex [Pd(2)(dmb)(2)(PPh(3))(2)](ClO(4))(2) (4) is prepared and investigated as well. The molecular dynamic of the title polymers in acetonitrile solution is investigated by means of (13)C spin-lattice relaxation time (T(1)) and nuclear Overhauser enhancement methods (NOE). The number of units determined by T(1)/NOE methods is 3 to 4 times less than that found from the measurements of intrinsic viscosity, and is due to flexibility in the polymer backbone, even for bridging ligands containing only one (dmb) or two C-C single bonds (dpa). During the course of this study, the starting material Pd(2)(dmb)(2)Cl(2) was reinvestigated after evidence for oligomers in the MALDI-TOF spectrum was noticed. In solution, this d(9)-d(9) species is a binuclear complex (T(1)/NOE). This result suggests that the structure of the title polymers in solution and in the solid state may not be the same either. Finally, these polymers are strongly luminescent in PrCN glasses at 77 K, and the photophysical data (emission lifetimes, 1.50 < tau(e) < 2.75 ns; quantum yields, 0.026 < Phi(e) < 0.17) are presented. X-ray data for [Pd(2)(dppe)(2)(dmb)(2)](PF(6))(4): monoclinic, space group C2/c, a = 24.3735 A, b = 21.8576(13) A, c = 18.0034(9) A, b = 119.775(1) degrees, V = 8325.0(8) A(3), Z = 4.

Small Metal‐Containing Oligomers Using M2(dmpm)x and M2(dmb)y Luminescent Building Blocks (M = Cu, Ag; x = 2, 3; y = 1, 2)

“…There are also some differences in the photophysical data, in particular the emission lifetimes, between the polymers and the corresponding building blocks [here M 4 (dmb) 4 2ϩ (M ϭ Pd, Pt)]. More recently, a new series of amorphous polymeric materials of the type {M(diphos)(dmb) ϩ } n (M ϭ Cu, Ag), [22] {Pd 2 (diphos) 2 (dmb) 2ϩ } n (diphos ϭ dppe, dppp), [22] {Pd 2 (dmb) 2 Cl 2 } n , [23] and {Pd 2 (dmb) 2 (diphosЈ) 2ϩ } n (diphosЈ ϭ dppb, dpppen, dpph) [23] (Scheme 3) were prepared and characterized. It was clearly demonstrated that polymers in the solid state dissociated to give oligomers in solution (8Ϫ16 units).…”

The Spectroscopy and Photophysical Behavior of Diphosphine- and Diisocyanide-Containing Coordination and Organometallic Oligomers and Polymers: Focus on Palladium and Platinum, Copper, Silver, and Gold

“…Other examples of d 9 -d 9 Pd-Pd-bond containing polymers were reported (19). These polymers, 16-18, are structurally related to 12-15 but differ in the relative position of the phosphine and isocyanide ligands (equatorial versus axial, where axial is along the M-M bond).…”

“…But it was only recently that it was unambiguously demonstrated that these simple complexes exist as polymers in the solid state and a stressed Pd-Pd-bonded complex in solution (Figure 4.1). In the solid state, the Pd 2 (dmb) 2 Cl 2 (7) is amorphous and exhibits a glass transition at about 5 °C (from differential scanning calorimetry [DSC]) and can make stand alone films [19]. In solution, the polymer becomes a binuclear complex as is demonstrated by the estimation of the molecular dimension from the measurements of spin-lattice relaxation time (T 1 ) and nuclear Overhauser enhancement (NOE) constants using closely related binuclear palladium complexes.…”

“…The replacement of the halides by triphenylphosphine and diphosphines such as Ph 2 P(CH 2 ) m PPh 2 (m = 4; bis(diphenylphosphino)butane; m = 5, bis(diphenylphosp hino)pentane; m = 6, bis(diphenylphosphino)hexane) and Ph 2 P-C≡C-PPh 2 (bis(dip henylphosphino)acetylene) new model complex (11), and polymers (12)(13)(14)(15) are obtained, respectively [19]. These species are moderately luminescent at 77 K in butyronitrile, but are not luminescent at room temperature, both in the solid state and in solution.…”

An Original Calix[4]arene‐Containing Oligomer/Polymer Catalyst for Homogeneous Hydroformylation

“…[13] The equilibrium between the polymer (solid state) and the 'stressed' dimer (solution) is not unprecedented ({Pd 2 (dmb) 2 Cl 2 } n (solid) versus Pd 2 (dmb) 2 Cl 2 (solution); dmb ¼ 1,8-diisocyano-p-menthane). [14] Consequently, the catalytic properties should be a function of the ring opening polymerization (ROP) process prior to efficient catalysis. Kubas and collaborators investigated 1,3-difunctionalized compound 9 (Scheme 1) which shows no ring stress and minimal steric hindrance about the metal atoms, and exhibits 'comparable' results in catalytic activity and properties with other systems such as 1-8.…”