Search

With the hope of tuning structural and electronic properties of the metal chains by changing the N‐substituent group and P‐chiral configurations, a series of PNP bridged tetraphosphines, rac‐ and meso‐Ph2PCH2P(Ph)N(Ar)P(Ph)CH2PPh2 (Ar=4‐RC6H4, R=F (rac‐dpmppanF), CH3 (rac‐dpmppanMe), H (meso‐dpmppan), OMe (meso‐dpmppanOMe); Ar=2,4‐xylyl (rac‐dpmppanMe2)), were synthesized, and utilized to prepare the Pd4 and Pt2Pd2 chains with XylNC terminal ligands, [M4(rac‐dpmppanR)2(XylNC)2](PF6)2 (M4=Pd4, R=F (1F), Me (1Me); M4=Pt2Pd2, R=F (4F), Me (4Me)) and [M4(meso‐dpmppanR)2(XylNC)2](PF6)2 (M4=Pd4, R=H (6), OMe (6OMe); M4=PdPt2Pd, R=OMe (9OMe)). While the M4 metal chains with rac‐dpmppanR (R=H, F, Me) ligands showed only marginal effects on the tetranuclear metal chains, the meso stereoisomer of meso‐dpmppanOMe afforded a new series of Pd4 (6OMe), PtPd3 (7OMe), PtPd2Pt (8OMe), PdPt2Pd (9OMe), Pt3Pd (10OMe), and Pt4 (11OMe) chains that exhibited a characteristic electronic absorption band tunable by the number and positions of incorporated Pt atoms from 628 nm to 473 nm. Especially, 11OMe is the first example of Pt4 chains supported by tetraphosphines. The coordinatively unsaturated Pd4 strings, [Pd4(rac‐dpmppan)2(CH3CN)](BF4)2 (12) and [Pd4(meso‐dpmppanOMe)2](BF4)2 (13), were also synthesized and 12 was utilized in axial ligand exchange reactions with PPh2Me, and PPh3 to disclose their successive incorporation into [Pd4(rac‐dpmppan)2(L)2](BF4)2 (L=PPh2Me (14 a), PPh3 (14 b)) and remarkable red‐shift (713–718 nm) of the HOMO‐LUMO transition of the Pd4 chains. The linear Pd4, PtnPd4‐n (n=1–3), and Pt4 complexes obtained in the present study could be useful 1D building blocks for assembling through metal−metal interaction. [ABSTRACT FROM AUTHOR]

Abstract A linear tetraphosphine meso -bis[(diphenylphosphinomethyl)phenylphosphino]methane (meso -dpmppm), was utilized to prepare a PtI dinuclear complex, [Pt 2 (μ− meso -dpmppm−κ2,κ1)(XylNC) 3 ](PF 6) 2 (2), which was derived from reaction of [PtII(meso -dpmppm−κ3)(XylNC)](PF 6) 2 (1) with 1/3 equiv. of [Pt 3 (XylNC) 6 ]. Treatment of 2 with 1/3 equiv. of [Pt 3 (XylNC) 6 ] gave an A-frame Pt 3 complex, [Pt 3 (μ− meso -dpmppm−κ2,κ1)(XylNC) 5 ](PF 6) 2 (3), demonstrating that a meso -dpmppm ligand effectively support the expansion of platinum nuclearity from Pt2+ through {Pt 2 }2+ to {Pt 3 }2+ cores in stepwise fashion. Reaction of 2 with 1 equiv. of meso -dpmppm afforded [Pt 2 (μ− meso -dpmppm−κ2,κ1) 2 ](PF 6) 2 (4), which would not react with [Pt 3 (XylNC) 6 ], and in contrast, treatment of 3 with excess of [Pt 3 (XylNC) 6 ] gave birth to a decanuclear platinum complex, [Pt 10 (μ− meso -dpmppm−κ2,κ1,κ1) 2 (XylNC) 18 ](PF 6) 6 , (5), comprised of a linear Pt 4 chain {Pt 4 (XylNC) 8 }2+ terminated by two Pt 3 A-frame units of {Pt 3 (μ− meso -dpmppm−κ2,κ1,κ1)(XylNC) 5 }2+, which is an interesting nano-ordered Pt cluster constructed with small size multinuclear building blocks, and notably contains the longest metal–metal bonded Pt chain without any bridging ligands. Graphical abstract Image 1 Highlights • An unprecedented decanuclear Pt complex was successfully synthesized. • The Pt 10 complex consists of a Pt 4 chain terminated by two A-frame Pt 3 units. • The Pt 4 chain is the longest molecular Pt chain without any bridging ligands. [ABSTRACT FROM AUTHOR]

Abstract Reaction of [PtCl 2 (cod)] with a tetraphosphine meso -bis[(diphenylphosphinomethyl)phenylphosphino]methane (meso -dpmppm), afforded mononuclear PtII complexes, [PtCl(meso -dpmppm−κ3)]X (X = Cl (1a), PF 6 (1b)); the meso -dpmppm ligand coordinates to the PtII ion tightly with two outer and one inner phosphorus atoms to form fused six- and four-membered chelate rings which is regarded as an asymmetric PPP pincer ligand bearing an uncoordinate inner phosphine unit. Complex 1 readily reacted with RNC in the presence of NH 4 PF 6 to afford [Pt(meso -dpmppm−κ3)(RNC)](PF 6) 2 (R = Xyl (2a), Cy (2b), t Bu (2c)). When 2a and 2b were reacted with excess of benzylamine (BnNH 2), N -acyclic carbene complexes, [Pt(meso -dpmppm−κ3){C(NHR)(NHBn)}](PF 6) 2 (R = Xyl (3a), Cy (3c)), were obtained, and a similar treatment of 2a with n -octylamine (C 8 H 17 NH 2) afforded [Pt(meso -dpmppm−κ3)- {C(NHXyl)(NHC 8 H 17)}](PF 6) 2 (3b). In contrast, complex 2c was transformed into a cyanide complex, [Pt(CN)(meso -dpmppm−κ3)]PF 6 (4), through N C( t Bu) bond cleavage when heated at 80 °C with BnNH 2 or PhNH 2. Complexes 1 – 4 were characterized by 1H and 31P NMR and ESI-MS spectroscopies and X-ray diffraction analyses. The uncoordinate inner phosphine of 1b is readily reacted with [Cp*MCl 2 ] 2 to give heterodimetallic complexes, [PtCl(η5-Cp*MCl 2)(μ− meso -dpmppm−κ3,κ1)]PF 6 (M = Ir (5a), Rh (5b); Cp* = 1,2,3,4,5-pentamethylcyclopentadienyl). Complex 2a also reacted with [Cp*IrCl 2 ] 2 to yield [Pt(η5-Cp*IrCl 2)(μ− meso -dpmppm−κ3,κ1)(XylNC)]PF 6 (6a) together with 5a , and however, 6a would not react with BnNH 2 , just releasing XylNC to result in 5a. Attachment of the metal fragment of {Cp*IrCl 2 } to the uncoordinated phosphine caused a crucial conformational change of the six-membered chelate ring from a stable chair conformation to a twist-boat structure, which concomitantly reduced reactivity of the isocyanide ligand toward nucleophilic attack of the amine by steric hindrance of meso -dpmppm pincer ligand. These results could be recognized as on/off switching of the asymmetric {PtII(meso -dpmppm−κ3)} pincer complex. Graphical abstract N -Acyclic carbene complexes were synthesized from Pt(II) isocyanides with meso -Ph 2 PCH 2 P(Ph)CH 2 P(Ph)CH 2 PPh 2 which acts as an asymmetric pincer ligand and shows on/off switching induced by ligation of a {Cp*IrCl 2 } unit to its uncoordinate phosphine unit. Image 1 Highlights • The tetraphosphine meso -dpmppm nests a Pt center as an asymmetric pincer ligand. • N -Acyclic carbene PtII complexes were synthesized on the PPP pincer framework. • The asymmetric pincer complex showed on/off switching via ligation of a Ir unit. [ABSTRACT FROM AUTHOR]

Linear Triplatinum Tetrahydride Complex Supported by Triphosphine Ligands, [Pt3(µ-H)2(H)2(µ-dpmp)2](BF4)2 {dpmp = bis(diphenylphosphinomethyl)phenylphosphine} By treating [Pt6(µ-H)(H)2(µ-dpmp)4]BH4 [4, dpmp = bis(diphenylphosphinomethyl)phenylphosphine] with an excess amount of HBF4 in N,N-dimethylformamide (DMF), a triplatinum tetrahydride complex, [Pt3(µ-H)2(H)2(µ-dpmp)2](BF4)2 (5), was obtained in 51 % yield and was characterized by IR, UV/Vis, ¹H NMR, and 31P{¹H} NMR spectroscopy in addition to ESI mass spectrometry, X-ray crystallography, and DFT calculations. Complex 5 is composed of linear trinuclear platinum centers supported by two dpmp ligands, {Pt3(µ-dpmp)2}6+, which accommodate two terminal and two bridging hydrides in a HPtHPtHPtH zigzag structure. The hydride positions were deter-mined by DFT optimization with B3LYP/GD3BJ functionals. Variable-temperature ¹H{31P} NMR spectroscopy in [D7]DMF revealed that the bridging hydrides exhibit fluxional behavior and migrate along the Pt3 chain by switching the bridging site, whereas the terminal hydrides are not exchanged with the bridging ones. The present results suggest that the divalent linear triplatinum unit of {Pt3(µ-dpmp)2}2+ (Pt3 II), which is a building block to construct [Pt6(µ-H)(H)2(µ-dpmp)4]+ (4, Pt3 IIPt3 II), formally acts as a four-electron source to result in [Pt3(µ-H)2(H)2(µ-dpmp)2]2+ (5, Pt3 VI) through protonation. [ABSTRACT FROM AUTHOR]

A heterobimetallic PtPd3 complex supported by three bridging diphenylsilylene ligands, [Pt{Pd(dmpe)}3(μ3-SiPh2)3] ( 1, dmpe=1,2-bis(dimethylphosphino)ethane), has been synthesized from mononuclear Pd and Pt complexes. The hexagonal core composed of Pt, Pd, and Si atoms is slightly larger than that of the tetrapalladium complex, [Pd{Pd(dmpe)}3(μ3-SiPh2)3] ( 2). Reaction of PhSiH3 with complex 1 in the presence and absence of Ph2SiH2 results in the formation of a tetranuclear complex with silyl and hydride ligands at the Pt center, [PtH(SiPh2H){Pd(dmpe)}3(μ3-SiHPh)3] ( 3), and an octanuclear complex, [{Pt{Pd(dmpe)}3(μ3-SiHPh)3}2(κ2-dmpe)] ( 5), respectively. Both M−Si (M=Pt, Pd) bond lengths and the 29Si NMR chemical shifts of 1 and 2 are located between those of mononuclear late transition-metal complexes with a silylene ligand and complexes with donor-stabilized silylene ligands. CuI and AgI adducts of 1 and 2, formulated as [M(μ-M′I){Pd(dmpe)}3(μ3-SiPh2)3] (M=Pt, Pd; M′=Cu, Ag), undergo elimination of CuI (AgI) and regenerate the tetrametallic complexes upon heating or addition of a chelating diphosphine. Elimination of AgI from 2-AgI occurs more rapidly than elimination of CuI from 2-CuI, as determined from the results of kinetics experiments. [ABSTRACT FROM AUTHOR]

From a reaction of [Pt 3 (μ-dpmp) 2 (XylNC) 2 ](PF 6 ) 2 ( 1a ) with NaBH 4 and [Pt(dba) 2 ] in N,N -dimethyl formamide (DMF), a trihydride hexaplatinum complex, [Pt 6 (μ-H)(H) 2 (μ-dpmp) 4 ]BH 4 ·DMF ( 4* ·DMF), was isolated as dark green crystals in 47% yield, and was characterized by IR, UV–vis, 1 H and 31 P{ 1 H} NMR, and ESI mass spectral analyses, X-ray crystallography, and DFT calculations. Complex 4* is stable in DMF and DMSO solutions, and contains two terminal and one bridging hydrides observed at −5.92 ppm ( 1 J PtH = 980 Hz) and −4.47 ppm ( 1 J PtH = 591 Hz) in the 1 H NMR spectrum (DMSO- d 6 ). The X-ray diffraction analysis revealed the linear hexaplatinum structure supported by four dpmp ligands, wherein two {Pt 3 (H)(μ-dpmp) 2 } + units are connected by the bridging hydride resulting in a long Pt⋯Pt separation (3.3075(6) Å) between the central two Pt atoms. Other Pt Pt distances range from 2.7243(7) to 2.7499(6) Å, indicating the presence of Pt Pt bonds within the {Pt 3 (μ-dpmp) 2 } units. On the basis of the crystal structure, the hydride positions were optimized by DFT calculations to show a bent bridging hydride (av. Pt H = 1.65 Å, Pt H Pt = 160.0°) as well as linear terminal ones (av. Pt H = 1.68 Å, av. Pt Pt H = 179.4°). The present study provides useful information in expanding molecular metallic chains by utilizing {H Pt 3 H Pt 3 H} + building blocks. [ABSTRACT FROM AUTHOR]

[Display omitted] • Linear P 3 , P 4 , and P 6 phosphines with short bite distances and their derivatives. • Finely synthesized homo- and hetero tri- and tetranuclear metal assemblies. • Linearly ordered Pt 6 , Pt 2 Pd 2 Pt 2 , Ag 6 , Au 6 , and Pd 8 chains with polyphosphines. • Strongly luminous coinage metal clusters with multidentate phosphine ligands. • Copper hydride clusters supported by multidentate phosphine ligands. Structurally constrained multinuclear metal assemblies are fascinating building blocks for atomically precise nano-structured molecular devices with a variety of functions from electronic, magnetic, photophysical, and catalytic properties arising from cooperative effects of proximate metal centers. Finely tuned structures and electronic states of metal assemblies are in debt to design of multidentate guiding and supporting ligands, and aiming to develop low valent metal assemblies as molecular miniatures of metallic materials, those with a pair of soft donors connected by a single atom, namely, bearing short bite units, are highly desired. In this regard, this review surveys the studies over a couple of decades on multinuclear metal complexes constrained by linear and branched tri-, tetra-, and polydentate phosphine ligands with short bite distances between the two donor atoms possessing P 3 , P 4 , and P 6 donor sets. Those with mixed donor phosphines having PCP, PNP, PAsP, PNNP, and N(P 3) donor sets, are also explained because the hetero soft donors of carbene, imino-nitrogen, and arsine enable fine stepwise syntheses of heterometal assemblies through metallomacrocyclic and metallocage precursors. Multinuclear complexes supported by non-phosphino multidentate ligands and by mono- and diphosphines are not included. This contribution focuses not only on 1D metal chains but on other 2D and 3D topological arrangements, and in particular, highlights the recently developed Pt and Pd based metal strings organized by linear tri- and tetraphosphine ligands, photo- and electroluminescent coinage metal assemblies in linear, ring, planar, and polyhedral metal arrangements, and copper hydride multinuclear complexes showing attractive hydride reactivity. These compounds of subnano- to nano-scaled building blocks will provide useful platforms to develop further assembled nano-molecular devices with structurally and atomically controlled synthetic strategies. [ABSTRACT FROM AUTHOR]

Abstract: Reaction of [RhCl(cod)]2 with 2,7-bis(diphenylphosphino)-1,8-naphthyridine (dpnapy) and 2,6-xylyl isocyanide (XylNC) in the presence of NH4PF6 afforded the dirhodium(I) complex, [Rh2(μ-dpnapy)2(XylNC)4](PF6)2 (5), and similar procedures using [MCl2(cod)] (M=Pt, Pd) resulted in the formation of [Pt2(μ-dpnapy)2(XylNC)4](PF6)4 (6) and [Pd2Cl2(μ-dpnapy)2(XylNC)2](PF6)2 (7). Complexes 5–7 were characterized by elemental analysis, IR, UV–Vis, 1H and 31P{1H} NMR, and ESI mass spectroscopic techniques, to involve a small and rigid d 8 {M2(μ-dpnapy)2} metallomacrocycle. Complex 5 readily incorporated a silver(I) ion into the macrocycle to afford [Rh2Ag(μ-dpnapy)2(XylNC)4](PF6)3 (8) which was characterized by X-ray crystallography. The Ag(I) ion is trapped by two trans N atoms of dpnapy ligands, resulting in an asymmetric Rh–Ag⋯Rh structure, determined as a disordered model in the crystal structure, and however, in a CH2Cl2 solution, a dynamic interconversion of the two Ag-trapped sites was observed with low-temperature NMR studies, which was further supported by DFT molecular orbital calculations. When an acetonitrile solution of complex 5 was treated over a droplet of mercury(0), the polymeric compound formulated as {[Rh(μ-dpnapy)(XylNC)2](PF6)} n (9) was isolated as yellow single crystals, which were revealed by X-ray crystallography to consist of C 6 helical rods along c axis with a pitch of 33.5Å (rise of unit=5.6Å) and a diameter of 20.64Å. [Copyright &y& Elsevier]

• Tetraphosphine rac -dpmppm supports tetranuclear Ag 4 and PtAg 2 Pt zigzag arrays. • The detailed tetranuclear structures were characterized by X-ray analyses. • PtAg 2 Pt acetylide complex emits intense photoluminescence at 534 nm. Reaction of AgOTf with a tetraphosphine, rac -bis[(diphenylphosphinomethyl) phenylphosphino]methane (rac -dpmppm), afforded [Ag 4 (rac -dpmppm) 2 (TfO) 4 (3) which consists of zigzag-arrayed tetranuclear silver(I) ions supported by syn -arrangement of two enantiomeric (RR / SS) dpmppm ligands. Complex 3 readily reacted with XylNC (Xyl = 2,6-dimethylphenyl) to give [Ag 4 (rac -dpmppm) 2 (XylNC) 2 (TfO) 4 (4), where two terminal isocyanides attach to the outer Ag sites. Complex 3 has been shown a good precursor for Pt-Ag-Ag-Pt mixed metal array as incubation of 3 with trans -[Pt(C CPh) 2 (PPh 3) 2 yielded [Ag 2 Pt 2 (C CPh) 4 (rac -dpmppm) 2 (TfO) 2 (5). Two trans -Pt(C CPh) 2 units are incorporated into the terminal positions in a site-selective fashion and the Pt-Ag-Ag-Pt tetranuclear core also adopts a zigzag array supported by syn -arrangement of two rac -dpmppm ligands. The d8 and d10 closed-shell mixed metal centers of 5 exhibited an intense photoluminescence at 534 nm, mainly from an unsymmetric triplet state generated by charge transfer transitions from ligand (acetylide π) to metal centers (Ag 2 and PtAg s/p σ), 3LMCT, and to ligands (acetylide π* and dpmppm), 3LLCT. The present results provide fundamental and useful information to construct multinuclear closed-shell metal alignments by utilizing polyphosphine ligands. [ABSTRACT FROM AUTHOR]

Abstract: A series of square planar platinum(II) salen complexes containing 4-substituted alkoxy chains of aromatic rings, [Pt((4-C n H2 n +1O)2salen)] (n =3 (1), 4 (2), 6 (3), 8 (4), 10 (5), 12 (6), 14 (7), 16 (8), and 18 (9)) has been prepared, and photophysical and mesomorphic properties have been investigated. Complexes 1–9 emitted intense phosphorescence from the mixed exited-state between the MLCT (MLCT=metal-to-ligand charge transfer) and LLCT (LLCT=ligand-to-ligand charge transfer) states both in dichloromethane solution and in solid states at room temperature. The red-shifted solid-state emission spectra from monomers in solution are caused by the supramolecular contact with one-dimensional stacking between neighboring chromophores (salen moieties) through the weak C–H⋯O type hydrogen bonding and van der Waals interactions in the solid state revealed by an X-ray crystallographic analysis for 2. Though 1–4 did not exhibit any mesophases (liquid–crystalline phases), 5–9 showed a lamello-columnar (ColL) mesophase with the high thermal stability, leading to the different phosphorescence spectra from both in solution and in solid states. This is affiliated with the appearance of the intermolecular orbital interaction in a one-dimensional stacking distance with ca. 3.0Å due to self-assemblies in the liquid crystal which gives rise to the MMLCT (MMLCT=metal–metal-to-ligand charge transfer) transition. This is supported by absorption and emission measurements in the wide range from room temperature in the solid state to the clearing points (around 280°C). The relationship between molecular assemblies and photophysical properties is discussed. [Copyright &y& Elsevier]

In the title compound, [Pt2(μ-C14H16N3O)2(NH3)4](ClO4)6·2H2O, the diplatinum(II) cation is found to be a head-to-tail isomer. The intradimer Pt—Pt distance [3.0304 (7) Å] is much shorter than the value of 3.0852 (13) Å reported for the analogous cis-diammineplatin­um(II) dimer bridged by 2-( N′-methyl-4,4′-bipyridinium-1-yl)­acetamidates [Sakai, Ikuta, Tsu­bomura, Kato, Yokoyama, Kajiwara & Ito (2003). Acta Cryst. E 59, m780–m783], showing that the electron density at the metal centers is higher in the title system than in the previously reported system. The shortest interdimer Pt⋯Pt distance is 8.4585 (8) Å. [ABSTRACT FROM AUTHOR]