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The homodinuclear [CIM(μ-dppm)2MCI] complexes 1 (M = Pd) and 2 (M = Pt) react with RNC ligands (R = Ph, xylyl, p-tolyl, p-C6H4iPr) to provide the A-frame [CIPd(μ-dppm)2(μ-C=N-R)PdCI] (R = Ph (5a), xylyl (5b)), [CIPt(μ-dppm)2(μ-C=N-R)PtCI] (R = p-tolyl (4a); p-C6H4iPr (4b)), and the d9-d9 M2-bonded [CIPt(μ-dppm)2Pt(CN-R)]Cl (R = xylyl (3a); p-C6H4iPr (3b)) complexes. The heterodinuclear [XPd(μ-dppm)2PtX] complexes 6a (X = Cl) and 6b (X = I) react with RNC (R = o-anisyl) to form the A-frame [XPd(μ-dppm)2(μ-C=N-R)PtX] (X = Cl (9); I (10a)) and M2-bonded [CIPt(μ-dppm)2Pt(CN-R)]Cl (10b) complexes. The dangling ligand-containing complex [CIPd(u- dppm)2Pt(η1-dppm=O)](BF4) (7) reacts with xylyl-NC stoichiometrically to produce the dicationic salt [(xylyl-NC)Pd(μ-dppm)2Pt(η1-dppm=O)](BF4)2 (8). Parameters ruling the coordination site terminal versus bridging are discussed. The precursor 10a reacts with RNC (R = o-anisyl, tBu) to form the heterobimetallic bis(isonitrile) [lPd(μ-dppm)2(μ-C=N-o-anisyl)Pt(CN-R)]l complexes 11b and 12, respectively, demonstrating the site selectivity of the second CNR ligand coordination, Pd versus Pt. The X-ray structures of 11b and 12 were obtained. Complex 12 is the first example of an A-frame system of the Ni-triad bearing two different isocyanide ligands. Several d9-d9 terminal and d8-d8 A-frame homo- and heterodinuclear complexes in 2-MeTHF at 77 K were studied by UV-vis and luminescence spectroscopy. Assignments for the lowest energy absorption and emission bands are made on the basis of density functional theory and time-dependent density functional theory computations. [ABSTRACT FROM AUTHOR]

The new conjugated organometallic polymer (spacerC≡CPt(PBu3)2C≡C)n (3; spacer = para-bis(diphenyl(tetramethyl)quinone diimine) and the cyclic mononuclear model complex, spacer′C≡CPt(PEt3)2C≡C·CuCl (4; spacer′ = ortho-diphenyl-2,3,5,6-tetramethyl-1,4-benzoquinone diimine) were synthesized from the 1:1 condensation of the corresponding diethynyl ligands (2-para and 2-ortho (para- and ortho-diethynyl-diphenyl-2,3,5,6-tetramethylquinone diimine), respectively), with the trans-Pt(PBu3)2Cl2 for polymer 3 and cis-Pt(PEt3)2Cl2 for 4. The materials were characterized by GPC, DSC, ATG, and electrochemistry for polymer 3, and by X-ray diffraction for 4. Polymer 3 exhibits a Mn of 18500, Mw of 25000 with a PD of 1.37. The trans-geometry about Pt in polymer 3 was confirmed by31 P NMR and IR/Raman spectroscopy. The cyclic voltammogram study on the model complex trans-Pt(PBu3)2(C≡CPh)2, spacer 1-para (Me3SiC≡CRC≡CSiMe3; R = para-diphenyl-2,3,5,6-tetramethyl-1,4-benzoquinone diimine) and polymer 3 demonstrated that polymer 3 in the presence of trifluoroacetic acid (TFA) exhibits a quasi reversible 2-electron reduction process centered at 0.48 V versus SCE corresponding to the reduction of the protonated quinone diimine unit into the corresponding diamine. The UV-vis spectra of the spacer 2-para (440 nm) and polymer 3 (502 nm) are characterized by red-shifted charge transfer (CT) absorptions (C6H4C≡C → quinone diimine for 2-para; and (C6H4C≡C)2Pt → quinone diimine for polymer 3). These assignments are corroborated by density-functional theory (DFT) and time-dependent density-functional theory (TDDFT) computations. Polymer 3 is not luminescent in the solid state or in solution at 77 K and 298 K. [ABSTRACT FROM AUTHOR]

The homodinuclear d9-d9 CIM(μ-dppm)2MCl2 complexes, 1 (M = Pt) and 2 (M = Pd) react with the conjugated and luminescent PCP-NC ligand (3, PCP = [2.2]paracyclophane) to provide the corresponding d9-d9 terminal [ClPt(μ-dppm)2Pt(CN-PCP)]Cl (4) and d8-d8 A-frame [CIPd(μ-dppm)2(μ-C=N-PCP)PdCl] (5) isocyanide complexes, respectively. These two bimetallic complexes were characterized by IR, 1H, and 31P{1H} NMR and by chemical analysis. IR data (υ(CN) bridging vs terminal) reveal a terminal isocyanide bonding mode for 4 (2147 cm-1) and an A-frame structure for 5 (1616 cm-1). The optical and emission properties of the free isocyanide 3 as well as those of the homodinuclear complexes 4 and 5 were studied by UV-visible and luminescence spectroscopy and by photophysical measurements. The unexpected presence of simultaneous intraligand μμ* fluorescence and phosphorescence attributable to the organic PCP-NC ligand, as well as luminescence from the inorganic M2- bonded Pt2(μ-dppm)2 center arising from a lower energy excited LMCT state (ligand-to-metal-charge-transfer) for 4 at 77 K, indicates a weak conjugation between the two chromophores and an absence of efficient singlet and triplet energy transfers. For 5, only the fluorescence and phosphorescence bands of the PCP-NC ligand are observed [since the A-frame XPd(μ-dppm)2(μ-L)PdX (L = isocyanide, X halide) is not luminescent], stressing that the N≡C bridge exhibits modest electronic communication properties. [ABSTRACT FROM AUTHOR]

The heterodinuclear d9-d9 title compound 1, whose crystal structure has been solved, reacts with dppm [bis(diphenylphosphino)methane] in the presence of NaBF4 to generate the salt [ClPd(μ-dppm)2Pt(Β¹-dppm)][BF4] (2a), which contains a Pt-bound dangling dppm ligand. 2a has been characterized by ¹H and 31P NMR, Fourier transform Raman [ν(Pd-Pt) = 138 cm-1], and UV-vis spectroscopy [λmax(dσ-dσ∗) = 366 nm]. In a similar manner, [ClPd(μ-dppm)2Pt(Β¹-dppm=O)][BF4] (2b), ligated with a dangling phosphine oxide, has been prepared by the addition of dppm=O. The molecular structure of 2b has been established by an X-ray diffraction study. 2a reacts with 1 equiv of NaBH4 to form the platinum hydride complex [(Β¹-dppm)Pd(μ-dppm)2Pt(H)][BF4] (3). Both 2a and 3 react with an excess of NaBH4 to provide the mixed-metal d10-d10 compound [Pd(μ-dppm)3Pt] (4). The photophysical properties of 4 were studied by UV-vis spectroscopy [λmax(dσ-dσ∗) = 460 nm] and luminescence spectroscopy (λemi = 724 nm; τe = 12 ± 1 μs, 77 K). The protonation of 1 and 4 leads to [ClPd(μ-dppm)2(μ-H)PtCl]+ (5) and 3, respectively. Stoichiometric treatment of 1 with cyclohexyl or xylyl isocyanide yields [ClPd(μ-dppm)2Pt(CNC6H11)]Cl (6a) and [ClPd(μ-dppm)2Pt(CN-xylyl)]Cl (6b) ligated by terminal-bound CNR ligands. In contrast, treatment of 1 with the phosphonium salt [C≡NCH2PPh3]Cl affords the structurally characterized A-frame compound [ClPd(μ-dppm)2(μ-C=NCH2PPh3)PtCl]Cl (6c), spanned by a bridging isocyanide ligand. The electrochemical reduction of 2a at -1.2 V vs SCE, as well as the reduction of 5 in the presence of dppm, leads to a mixture of products 3 and 4. Further reduction of 3 at -1.7 V vs SCE generates 4 quantitatively. The reoxidation at 0 V of 4 in the presence of Cl- ions produces back complex 2a. The whole mechanism of the reduction of 1 has been established. [ABSTRACT FROM AUTHOR]

The homodinuclear d9-d9 ClM(mu-dppm)2MCl2 complexes, 1 (M ) Pt) and 2 (M ) Pd) react with the conjugated and luminescent PCP-NC ligand (3, PCP ) [2.2]paracyclophane) to provide the corresponding d9-d9 terminal[ClPt(mu-dppm)2Pt(CNsPCP)]Cl (4) and d8-d8 A-frame [ClPd(mu-dppm)2(mu-CdNsPCP)PdCl] (5) isocyanide complexes, respectively. These two bimetallic complexes were characterized by IR, 1H, and 31P{1H} NMR and bychemical analysis. IR data (nu(CN) bridging vs terminal) reveal a terminal isocyanide bonding mode for 4 (2147cm(-1)) and an A-frame structure for 5 (1616 cm(-1)). The optical and emission properties of the free isocyanide 3as well as those of the homodinuclear complexes 4 and 5 were studied by UV-visible and luminescence spectroscopy and by photophysical measurements. The unexpected presence of simultaneous intraligand pipi* fluorescence and phosphorescence attributable to the organic PCP-NC ligand, as well as luminescence from the inorganic M2-bonded Pt2(mu-dppm)2 center arising from a lower energy excited LMCT state (ligand-to-metal-charge-transfer) for4 at 77 K, indicates a weak conjugation between the two chromophores and an absence of efficient singlet andtriplet energy transfers. For 5, only the fluorescence and phosphorescence bands of the PCP-NC ligand are observed [since the A-frame XPd(mu-dppm)2(mu-L)PdX (L ) isocyanide, X ) halide) is not luminescent], stressing that the NtC bridge exhibits modest electronic communication properties.

The heterodinuclear d(9)-d(9) title compound 1, whose crystal structure has been solved, reacts with dppm [bis(diphenylphosphino)methane] in the presence of NaBF4 to generate the salt [ClPd(mu-dppm)2Pt(eta(1)-dppm)][BF4] (2a), which contains a Pt-bound dangling dppm ligand. 2a has been characterized by 1H and 31P NMR, Fourier transform Raman [nu(Pd-Pt) = 138 cm(-1)], and UV-vis spectroscopy [lambda(max)(dsigma-dsigma*) = 366 nm]. In a similar manner, [ClPd(mu-dppm)2Pt(eta(1)-dppm=O)][BF4] (2b), ligated with a dangling phosphine oxide, has been prepared by the addition of dppm=O. The molecular structure of 2b has been established by an X-ray diffraction study. 2a reacts with 1 equiv of NaBH4 to form the platinum hydride complex [(eta(1)-dppm)Pd(mu-dppm)2Pt(H)][BF4] (3). Both 2a and 3 react with an excess of NaBH4 to provide the mixed-metal d(10)-d(10) compound [Pd(mu-dppm)3Pt] (4). The photophysical properties of 4 were studied by UV-vis spectroscopy [lambda(max)(dsigma-dsigma*) = 460 nm] and luminescence spectroscopy (lambda(emi) = 724 nm; tau(e) = 12 +/- 1 micros, 77 K). The protonation of 1 and 4 leads to [ClPd(mu-dppm)2(mu-H)PtCl]+ (5) and 3, respectively. Stoichiometric treatment of 1 with cyclohexyl or xylyl isocyanide yields [ClPd(mu-dppm)2Pt(CNC6H11)]Cl (6a) and [ClPd(mu-dppm)2Pt(CN-xylyl)]Cl (6b) ligated by terminal-bound CNR ligands. In contrast, treatment of 1 with the phosphonium salt [C[triple bond]NCH2PPh3]Cl affords the structurally characterized A-frame compound [ClPd(mu-dppm)2(mu-C=NCH2PPh3)PtCl]Cl (6c), spanned by a bridging isocyanide ligand. The electrochemical reduction of 2a at -1.2 V vs SCE, as well as the reduction of 5 in the presence of dppm, leads to a mixture of products 3 and 4. Further reduction of 3 at -1.7 V vs SCE generates 4 quantitatively. The reoxidation at 0 V of 4 in the presence of Cl- ions produces back complex 2a. The whole mechanism of the reduction of 1 has been established.