Tetraphosphine Ligand Research Articles

Allochroic cluster light-emitting diodes based on unique μ3-tetraphosphine Cu3X3 crowns with tunable excited states.

Multicomponent excited states endow copper iodide clusters with allochroic properties under diverse stimuli. However, crystal states are required, and cluster stimulus sensitivity hampers electroluminochromism. We developed PhQPCu3X3 (X = Cl, Br, and I) with the first μ3-bridging tetraphosphine ligand, whose Cu3X3 crowns were exposed to external stimulus. The increased proportion of Cu3X3 results in equal contributions of cluster- and ligand-centered components to excited states, the former of which is highly sensitive to grind, vapor, and, especially, electric stimuli, due to semi-exposed Cu3X3. Through vacuum evaporation and vapor fumigation of cluster-based emissive layers, the diodes' electroluminescence colors changed from yellow to white. Joule heat during device operation induced further color variation to orange, corresponding to Commission Internationale de l'Eclairage coordinates of PhQPCu3I3 changed from (0.44 ± 0.1, 0.34 ± 0.1) to (0.57 ± 0.1, 0.42 ± 0.1). These results demonstrate the superiority of luminescent clusters in accurate excited-state modulation, holding promise for wide applications.

Complexation of 16-membered P4N2 macrocycles with Fe(II) ion as tool for stabilization of their RPSPSPRP stereoisomers

The novel mononuclear Fe(II) complexes of 16-membered P4N2 ligands were synthesized, where octahedral Fe(II) ion is coordinated by four phosphorus atoms of the ligand in equatorial positions and nitrogen atoms of two acetonitrile co-ligands in apical positions. The tetraphosphine ligands demonstrate the RPSPSPRP-configuration regardless of the configuration of the starting stereoisomer of the macrocycles, so that the complexation with iron(II) salts drives up the fixation of this configuration of 1,9-di(R)-1,9-diaza-3,7,11,15-tetraphenyl-3,7,11,15-tetraphosphacyclohexadecanes, which in turn is favorable for the binding of octahedral metal cations.

New Silver(I)‐P4 Coordination Polymers Strongly Adsorb Congo Red to Yield Composites with Enhanced Photocurrent Responses

AbstractReaction of tetraphosphine (P4) ligand dppbpda with Ag(I) oxylates yielded new coordination polymers (CPs) of formula [(dppbpda)Ag4(Ox)4]n (Ox=Bz (1), Sal (2), LA (3), Bz=benzoate, Sal=salicylate, LA=lactate). The solid‐state structures of 1–3 consist of one dimensional (1D) chains constructed from tetranuclear μ‐η2,η2‐ connected Ag4(Ox)4 cluster cores and dppbpda bridging ligands. Compounds 1–3 absorbed Congo Red in two distinct steps, with maximum uptake quantities of 1438 (1), 1417 (2) and 1656 (3) mg/g, inversely correlating with the size of the anions in the CPs. These CPs had band gaps in the semiconducting region (Eg) 3.05–3.15 eV and all three showed enhanced two‐peak photocurrent responses during the stepwise adsorption of CR, with maximum photocurrent densities of 227 (1), 163 (2) and 386 (3) μA cm−2 for composites with optimized dye coverage.

Electrochemical hydrogen formation catalysed by a Pd8 string.

The linear Pd8 complex supported by tetraphosphines reacted with HBF4 to give an unprecedented linear tetrapalladium complex with a terminal hydride, which promoted electrocatalytic hydrogen formation from HBF4 in acetonitrile. The 1D coordination polymer of Pd8 chain confined within Nafion film was applied to the electrocatalytic H2 formation.

Terahertz time-domain absorption spectra of Cu(I) complexes bearing tetraphosphine ligands: the bridge between the C-Hπ and ππ interactions and photoluminescence properties.

The synthesis of four heteroleptic dinuclear Cu(i) complexes bearing tetraphosphine and diimine ligands was reported. Complexes 1-3 were successfully obtained through microwave synthesis while complex 4 was synthesized through traditionally stirring at room temperature. These complexes are listed as follows: [Cu2(Dpq)2(dppeda)](ClO4)2·1.5CH2Cl2 (1), [Cu2(neo)2(dppeda)](ClO4)2·1.3CH2Cl2·1.7C4H10O (2), [Cu2(batho)2(dppeda)](ClO4)2·C4H10O (3), and [Cu2(batho)2(dpppda)](ClO4)2·3CH2Cl2 (4) {(Dpq = pyrazino[2,3-f][1,10]phenanthroline, batho = 4,7-diphenyl-1,10-phenanthroline, neo = 2,9-dimethyl-1,10-phenanthroline, dppeda = N1,N1,N2,N2-tetrakis[(diphenylphosphino)methyl]-1,2-ethanediamine, and dpppda = N1,N1,N4,N4-tetrakis[(diphenylphosphino)methyl]-1,4-benzenediamine}. Their crystal structures have been elucidated by X-ray crystallography and their photophysical properties have been investigated in detail. Photophysical studies and time domain density functional theory (TD-DFT) calculations show that the luminescence performance of these four complexes is ascribed to metal-to-ligand charge transfer (MLCT) mixed with ligand-to-ligand charge transfer (LLCT), and complex 2 shows green emission at 574 nm with the highest quantum yield of up to 52.80%. In addition, the research of photoluminescence properties under the guidance of terahertz spectroscopy technology leads to the preliminary discovery of a correlation between crystal packing and luminescence. It is found that the terahertz spectrum and absorption peak are strongly interdependent on C-Hπ and ππ interactions, and the external weak interactions have negative effects on the luminescence performance. Herein, we predict that the terahertz spectroscopy analysis establishes a bridge between weak interactions (C-Hπ and ππ interactions) and the photoluminescence properties, and puts forward a problem that should be noticed in designing Cu(i) complexes.

Rearrangement of two 8-membered 1,5-diaza-3,7-diphosphacyclooctane rings into 16-membered P4N4 ligand on the gold(i) template

The reaction of gold(i) chloride with two molecules of 1,5-diaza-3,7-diphosphacyclooctane derivative causes their reorganization into 16-membered macrocyclic tetraphosphine ligand. The structure of the trinuclear gold(i) complex obtained was confirmed by X-ray analysis. The dynamic equilibrium between dinuclear gold(i) complexes with eight-membered cyclic ligands and the trinuclear gold(i) complex with 16-membered ones has been revealed.

Facially Dispersed Polyhydride Cu9 and Cu16 Clusters Comprising Apex‐Truncated Supertetrahedral and Square‐Face‐Capped Cuboctahedral Copper Frameworks

AbstractBy using a linear tetraphosphine, meso‐bis[(diphenylphosphinomethyl)phenylphosphino]methane (dpmppm), nona‐ and hexadecanuclear copper hydride clusters, [Cu9H7(μ‐dpmppm)3]X2 (X=Cl (1 a), Br (1 b), I (1 c), PF6 (1 d)) and [Cu16H14(μ‐dpmppm)4]X2 (X2=I2 (2 c), (4/3) PF6⋅(2/3) OH (2 d)) were synthesized and characterized. They form copper‐hydride cages of apex‐truncated supertetrahedral {Cu9H7}2+ and square‐face‐capped cuboctahedral {Cu16H14}2+ structures. The hydride positions were estimated by DFT calculations to be facially dispersed around the copper frameworks. A kinetically controlled synthesis gave an unsymmetrical Cu8H6 cluster, [Cu8H6(μ‐dpmppm)3]2+ (3), which readily reacted with CO2 to afford linear Cu4 complexes with formate bridges, leading to an unprecedented hydrogenation of CO2 into formate catalyzed by {Cu4(μ‐dpmppm)2} platform. The results demonstrate that new motifs of copper hydride clusters could be established by the tetraphosphine ligands, and the structures influence their reactivity.

Facially Dispersed Polyhydride Cu9 and Cu16 Clusters Comprising Apex-Truncated Supertetrahedral and Square-Face-Capped Cuboctahedral Copper Frameworks.

By using a linear tetraphosphine, meso-bis[(diphenylphosphinomethyl)phenylphosphino]methane (dpmppm), nona- and hexadecanuclear copper hydride clusters, [Cu9 H7 (μ-dpmppm)3 ]X2 (X=Cl (1 a), Br (1 b), I (1 c), PF6 (1 d)) and [Cu16 H14 (μ-dpmppm)4 ]X2 (X2 =I2 (2 c), (4/3) PF6 ⋅(2/3) OH (2 d)) were synthesized and characterized. They form copper-hydride cages of apex-truncated supertetrahedral {Cu9 H7 }2+ and square-face-capped cuboctahedral {Cu16 H14 }2+ structures. The hydride positions were estimated by DFT calculations to be facially dispersed around the copper frameworks. A kinetically controlled synthesis gave an unsymmetrical Cu8 H6 cluster, [Cu8 H6 (μ-dpmppm)3 ]2+ (3), which readily reacted with CO2 to afford linear Cu4 complexes with formate bridges, leading to an unprecedented hydrogenation of CO2 into formate catalyzed by {Cu4 (μ-dpmppm)2 } platform. The results demonstrate that new motifs of copper hydride clusters could be established by the tetraphosphine ligands, and the structures influence their reactivity.

The facile reaction of water with a bimetallic nickel tetrachloride tetraphosphine: A tale of two chelates

NMR studies demonstrate that rac- and meso-Ni2Cl4(P4), P4 = (Et2PCH2CH2)(Ph)PCH2P(Ph)(CH2CH2PEt2), bimetallic complexes readily react with water in different organic solvents (acetone, acetonitrile, DMSO) to dissociate a chloride and most likely form a hydroxide-bridged bimetallic complex, [Ni2(μ-OH)Cl2(P4)]+. The meso bimetallic complex is very susceptible to dissociation of one of the external chelated phosphines, which leads to loss of one of the nickel atoms. The tetraphosphine ligand recoordinates to the remaining nickel center to form [NiCl(κ3-meso-P4)]+, which can, in turn, react with chloride to produce NiCl2(κ2-meso-P4). The meso diastereomers of these monometallic complexes then react with one another to form a double P4-coordinated bimetallic complex, [Ni2(μ-Cl)(meso-P4)2]3+, which has been crystallographically characterized. Despite the presence of four bis-phosphino(ethane) chelates around two nickel centers, [Ni2(μ-Cl)(meso-P4)2]3+ readily fragments and can be converted back to the precursor mono- and bimetallic complexes by heating in the presence of chloride and NiCl2·6H2O. The racemic dinickel diastereomer, Ni2Cl4(rac-P4), also reacts with water to produce [Ni2(μ-OH)Cl2(rac-P4)]+, but does not fragment further at room temperature unless oxygen is present. The rac- or meso-Ni2Cl4(P4-Ph) complexes based on the much stronger chelating tetraphosphine ligand with 1,2-phenylene chelate rings also react readily with water to form a hydroxide-bridged bimetallic complex, but further reaction and fragmentation chemistry is inhibited by the much stronger chelate effect present. [Ni2(μ-OH)Cl2(meso-P4-Ph)]+ has been crystallographically and spectroscopically characterized along with some intermediate monometallic rac- and meso-P4-Ph nickel complexes from cyanolysis attempts.

A new air‐stable and reusable tetraphosphine ligand for rhodium‐catalyzed hydroformylation of terminal olefins at low temperature

Tetraphosphine and bisphosphine ligands were synthesized, characterized and employed in Rh‐catalyzed hydroformylation of 1‐octene and 1‐hexene. Conversion of over 97.7% and aldehyde yield of 94.1% were achieved at 60°C, 20 bar. This remarkable performance could also be retained at lower temperature (i.e. 40°C) by prolonging the reaction time. The tetraphosphine ligand‐modified Rh catalyst could be reused for at least seven successive runs with catalytic activity and selectivity almost unchanged; the catalyst was separated from the products and recycled directly in homogeneous hydroformylation, indicating that the catalyst might have good stability. 31P NMR and high‐resolution mass spectral characterization hinted that the reason for the reusability of the catalyst might be that the tetraphosphine ligand is relatively air‐stable and is probably slowly oxidized during the recycling runs. The tetraphosphine ligand has four phosphorus atoms to be partially oxidized and could still coordinate with the Rh center via the unoxidized phosphorus atoms to stabilize the catalyst, based on the multiple chelating modes of the tetraphosphine ligand. Hence, the catalytic activity and selectivity could be retained for a certain number of runs.

Coordination of 3‐Methylindole‐Based Tripodal Tetraphosphine Ligands to Iron(+II), Cobalt(+II), and Nickel(+II) and Investigations of their Subsequent Two‐Electron Reduction

We report the coordination chemistry of indole based tripodal tetraphosphine ligands to iron(II), cobalt(II) and nickel(II). These complexes are formed by simple synthetic protocols and were characterized by a combination of spectroscopic techniques and single‐crystal X‐ray analysis. The molecular structures as determined by X‐ray diffraction show that the geometry of the nickel and cobalt complexes are distorted trigonal bipyramidal. The monocationic iron(II) complexes also have distorted trigonal bipyramidal geometries, but the dicationic analogue has an octahedral geometry. Two‐electron reduction of the cobalt(+II) and the nickel(+II) complexes in the presence of N2 did not lead to the coordination of N2. In contrast, two‐electron reduction of the iron(+II) complexes did lead to coordination of dinitrogen to the iron center. The Fe0N2 L1H complex has a trigonal bipyramidal geometry, and the N–N bond length of the coordinated dinitrogen ligand is longer than that of free dinitrogen, indicating that coordination to this iron(0) complex results in activation of the N≡N bond.

Mechanistic Studies on NaHCO3 Hydrogenation and HCOOH Dehydrogenation Reactions Catalysed by a FeII Linear Tetraphosphine Complex.

We present a theoretical extension of the previously published bicarbonate hydrogenation to formate and formic acid dehydrogenation catalysed by FeII complexes bearing the linear tetraphosphine ligand tetraphos-1. The hydrogenation reaction was found to proceed at the singlet surface with two competing pathways: A) H2 association to the Fe-H species followed by deprotonation to give a Fe(H)2 intermediate, which then reacts with CO2 to give formate. B) CO2 insertion into the Fe-H bond, followed by H2 association and subsequent deprotonation. B was found to be slightly preferred with an activation energy of 22.8 kcal mol-1 , compared to 25.3 for A. Further we have reassigned the Fe-H complex, as a Fe(H)(H2 ), which undergoes extremely rapid hydrogen exchange.

Novel self-adaptive boat-shaped complexes with a tetraphosphine ligand.

A series of novel boat-shaped host-guest complexes were designed and synthesized by the combination of a new calixarene fragment-based tetraphosphine ligand L with group 11 metal salts Cu(MeCN)4ClO4 and AgNO3 in a self-assembly process, and by the following anion exchange reactions of complex 1 with sodium p-toluenesulfonate, AcONa, PhCO2Na and sodium 9-anthrylcarboxylate. The host with a novel boat-shaped cavity is capable of self-adaptive encapsulation of various anions of different sizes through M(i)-O coordinations and CHπ interactions between the host and guest anion. The DFT calculations confirmed that the CHπ interaction played a vital role in the self-adaptive phenomenon in complexes 4-6.

Molybdenum and nickel atrane complexes with a rigid tripodal tetraphosphine ligand incorporating imidazole rings

Abstract Tripodal, tetradentate tetraphosphine ligand tris(1H-2-diisopropylphosphinoimidazol-1-yl)phosphine (1) was synthesized in three straightforward steps from widely available starting materials. The ligand crystallized in a C3-like conformation suitable for metal coordination. Nickel(II) complex 2 was prepared from 1 and Ni(dme)Br2 and adopted a classical atrane structure with trigonal pyramidal geometry at the metal, a bromide covalently bonded in the axial position, and a bromide ion in the outer coordination sphere. Molybdenum(III) complex 3 was prepared from 1 and MoCl3(thf)3 and could be structurally characterized using a co-crystal with Cp2Co and [Cp2Co]Cl. It displayed a face-capped octahedral geometry at the seven-coordinated metal. Complexes 2 and 3 proved prone to decomposition under reductive and oxidative conditions, hindering the investigation of their chemistry. Crystallization attempts from acetonitrile led to the isolation of dinuclear hydrolysis product 4, with the Mo(III) centres bridged by two chlorides and two 2-(diisopropylphosphino)imidazole moieties in a paddlewheel arrangement.

Metalloradical Reactivity of RuI and Ru0 Stabilized by an Indole-Based Tripodal Tetraphosphine Ligand.

The tripodal, tetradentate tris(1‐(diphenylphosphanyl)‐3‐methyl‐1H‐indol‐2‐yl)phosphane PP3‐ligand 1 stabilizes Ru in the RuII, RuI, and Ru0 oxidation states. The octahedral [(PP3)RuII(Cl)2] (2), distorted trigonal bipyramidal [(PP3)RuI(Cl)] (3), and trigonal bipyramidal [(PP3)Ru0(N2)] (4) complexes were isolated and characterized by single‐crystal X‐ray diffraction, NMR, EPR, IR, and ESI‐MS. Both open‐shell metalloradical RuI complex 3 and the closed‐shell Ru0 complex 4 undergo facile (net) abstraction of a Cl atom from dichloromethane, resulting in formation of the corresponding RuII and RuI complexes 2 and 3, respectively.

Gold(I) Complexes of Ferrocenyl Polyphosphines: Aurophilic Gold Chloride Formation and Phosphine-Concerted Shuttling of a Dinuclear [ClAu···AuCl] Fragment.

A smart steric control of the metallocene backbone in bis- and poly(phosphino)ferrocene ligands favors intramolecular aurophilic interactions between [AuCl] fragments in polynuclear gold(I) complexes. We synthesized and characterized by multinuclear NMR and X-ray diffraction analysis mono-, di-, and polynuclear gold complexes of constrained ferrocenyl diphosphines, which bear either bulky tert-butyl groups or more flexible siloxane substituents at the cyclopentadienyl rings. The complexes meso-1,1'-bis(diphenylphosphino)-3,3'-di-tert-butylferrocene (4-m), rac-1,1'-bis[bis(5-methyl-2-furyl)phosphino]-3,3'-di-tert-butylferrocene (5-r), and rac-1,1'-bis(diphenylphosphino)-3,3'-bis[(tri-iso-propylsilyl)oxy]ferrocene (6-r) were used to form dinuclear gold complexes. Coordination of tert-butylated ferrocenyl phosphines generated aurophilic interactions in the corresponding dinuclear gold complexes, contrary to gold(I) complexes reported with 1,1'-bis(diphenylphosphino)ferrocene. The structurally related tetraphosphine 1,1',2,2'-tetrakis(diphenylphosphino)-4,4'-di-tert-butylferrocene (11) also gave access to mononuclear, dinuclear, and the original trinuclear gold chloride aurophilic complexes in which 14e- to 16e- gold centers coexist. In such complexes, nonbonded ("through-space") 31P-31P' nuclear spin couplings were evidenced by high-resolution NMR. In these interactions nuclear spin information is transferred between the lone-pair electron of an uncoordinated phosphorus P and a phosphorus P' that is involved in a σ covalent bond Au-P'. The dinuclear aurophilic complex displayed a concerted shuttling of its [ClAu···AuCl] fragment between the four phosphorus donors of the tetraphosphine ligand. Thus, an aurophilic Au···Au bond, which is assumed to be a weak energy interaction, can be conserved within a dynamic shuttling process at high temperature involving an intramolecular coordination-decoordination process of digold(I) at phosphorus atoms.

Diverse Tp*-Capped W-Cu-S Clusters from One-Pot Assembly Involving in Situ Thiolation of Phosphines.

In the absence/presence of S8, the one-pot assembly of [Et4N][Tp*WS3] [1; Tp* = hydridotris(3,5-dimethylpyrazol-1-yl)borate] with [Cu(MeCN)4]PF6 and bis- or tetraphosphine ligands 1,2-bis(diphenylphosphino)ethane (dppe), 1,3-bis(diphenylphosphino)propane (dppp), 1,4-bis(diphenylphosphino)butane (dppb), and N,N,N',N'-tetrakis(diphenylphosphinomethyl)ethylenediamine (dppeda) produces six W-Cu-S clusters, namely, [(Tp*WS3Cu2Cl)2(dppe)] (2), [Tp*WS3Cu4(dppp)2(μ4-Cl)(μ-Cl)]PF6·MeCN (3·MeCN), [(Tp*WS3Cu3)2(μ4-Cl)(μ-Cl)2(dpppS2)] (4), [(Tp*WS3Cu2Cl)2(dppbS2)]·2MeCN·2H2O (5·2MeCN·2H2O), [(Tp*WS3Cu3Cl2)2(dppbS2)] (6), and [(Tp*WS3Cu3)2(Ph2PS2)3(μ6-Cl)0.5](PF6)0.5·0.75CH2Cl2 (7·0.75CH2Cl2). Compounds 2-7 are characterized by elemental analysis, IR, UV-vis, (1)H and (31)P{(1)H} NMR, electrospray ionization mass spectrometry, and X-ray crystallography. For 2, the dppe ligand bridges a pair of butterfly-shaped [Tp*WS3Cu2] cores to form a double-butterfly-shaped structure. For 4, the dppp ligand is susceptible toward S association and forms an in situ generated dpppS2 ligand, supporting an octanuclear double-half-open-cubane structure and contrasting an analogous system wherein a pentanuclear motorcycle-shaped cationic cluster 3 is formed with the absence of S8. A longer dppb ligand readily converts to S-based ligands in 5 and 6, subsequently serving as bridges between a pair of a butterfly-shaped (5) and nest-shaped (6) clusters. Further use of a tetraphosphine ligand, dppeda, in the cluster formation, with the presence of S8, leads to an unexpected ligand degradation to give the [Ph2PS2](-) anions. Three [Ph2PS2](-) anions juxtapose a pair of nest-shaped cluster cores to yield an octanuclear cluster, 7, featuring a cage to encapsulate μ6-Cl(-). The third-order nonlinear-optical (NLO) properties of 2-7 in N,N-dimethylformamide, investigated using a Z-scan technique at 532 nm, show that 2-6 have a reverse saturable absorption, while 7 has a notable saturable absorption. All of 2-7 exhibit a self-focusing effect with hyperpolarizability γ values in the range of 4.71 × 10(-30)-1.02 × 10(-29) esu, which are 440-1000 times higher than that of 1. The formation of 4-7 from 1 through the in situ thiolation of phosphine ligands presents a new approach to the design and assembly of the W-Cu-S clusters with interesting structural arrays and better NLO properties.

Apology: Functionalized Tri‐ and Tetraphosphine Ligands as a General Approach for Controlled Implantation of Phosphorus Donors with a High Local Density in Immobilized Molecular Catalysts

At approximately the same time, the authors of this Full Paper independently submitted a related Communication to Chemical Communications,1 in which identical compounds were described. The overlapping timeframe resulted from delays caused by a patent application. The corresponding author did not mention this Communication to the editorial office upon submission of the Full Paper and neglected to cross-reference these articles, therefore he would like to sincerely apologize to the editorial staff and readers of ChemPlusChem for this unintentional mistake.

Synthesis, Structures, and Properties of Polynuclear Silver(I) Complexes Containing Tetra-Phosphine Ligand with Ag⋅⋅⋅C Interactions

Reaction of AgNO3 and N,N,N′,N′-tetrakis((diphenylphosphino)methyl)benzene-1,4-diamine (pbaa) with sodium N-ethyldithiocarbamate (Na(Etdtc)) in CH3CN/toluene and CH3CN/DMF solvents produced two Ag4S4-based coordination complexes [Ag4(pbaa)(µ-κ1S,κ2S-Etdtc)4] (1) and [Ag4(pbaa)(µ-κ1S,κ2S-Etdtc)2(µ-κ1S,κ1S-Etdtc)2] (2). Structural analysis shows that the Ag4S4 cores in 1 are interconnected by one pbaa ligand in a tetradentate mode and four Etdtc– anions in a µ-κ1S,κ2S mode to form a three-layer conformation, whereas the Ag4S4 cores in 2 are linked by ligands pbaa (the tetradentate mode) and Etdtc– (the µ-κ1S,κ1S and µ-κ1S,κ2S modes) to yield the other type of three-layer conformation. In addition, in different solvent systems, the Ag atoms also form different types of weak Ag···C interactions with Ag···C distances of 3.297–3.344 Å in 1 and 3.237–3.416 Å in 2. The emission spectrum of complex 1 in DMF solution displays a broad orange–red emission peak at 518 nm, which may be assigned to the ligand-to-metal charge transfer transition.

Stepwise Expansion of Pd Chains from Binuclear Palladium(I) Complexes Supported by Tetraphosphine Ligands.

Reaction of [Pd2(XylNC)6]X2 (X = PF6, BF4) with a linear tetraphosphine, meso-bis[(diphenylphosphinomethyl)phenylphosphino]methane (dpmppm), afforded binuclear Pd(I) complexes, [Pd2(μ-dpmppm)2]X2 ([2]X2), through an asymmetric dipalladium complex, [Pd2(μ-dpmppm)(XylNC)3](2+) ([1](2+)). Complex [2](2+) readily reacted with [Pd(0)(dba)2] (2 equiv) and an excess of isocyanide, RNC (R = 2,6-xylyl (Xyl), tert-butyl ((t)Bu)), to generate an equilibrium mixture of [Pd4(μ-dpmppm)2(RNC)2](2+) ([3'](2+)) + RNC ⇄ [Pd4(μ-dpmppm)2(RNC)3](2+) ([3](2+)), from which [Pd4(μ-dpmppm)2(XylNC)3](2+) ([3a](2+)) and [Pd4(μ-dpmppm)2((t)BuNC)2](2+) ([3b'](2+)) were isolated. Variable-temperature UV-vis and (31)P{(1)H} and (1)H NMR spectroscopic studies on the equilibrium mixtures demonstrated that the tetrapalladium complexes are quite fluxional in the solution state: the symmetric Pd4 complex [3b'](2+) predominantly existed at higher temperatures (>0 °C), and the equilibrium shifted to the asymmetric Pd4 complex [3b](2+) at a low temperature (∼-30 °C). The binding constants were determined by UV-vis titration at 20 °C and revealed that XylNC is of higher affinity to the Pd4 core than (t)BuNC. In addition, both isocyanides exhibited higher affinity to the electron deficient [Pd4(μ-dpmppmF2)2(RNC)2](2+) ([3F'](2+)) than to [Pd4(μ-dpmppm)2(RNC)2](2+) ([3'](2+)) (dpmppmF2 = meso-bis[{di(3,5-difluorophenyl)phosphinomethyl}phenylphosphino]methane). When [2]X2 was treated with [Pd(0)(dba)2] (2 equiv) in the absence of RNC in acetonitrile, linearly ordered octapalladium chains, [Pd8(μ-dpmppm)4(CH3CN)2]X4 ([4]X4: X = PF6, BF4), were generated through a coupling of two {Pd4(μ-dpmppm)2}(2+) fragments. Complex [2](2+) was also proven to be a good precursor for Pd2M2 mixed-metal complexes, yielding [Pd2Cl(Cp*MCl) (Cp*MCl2)(μ-dpmppm)2](2+) (M = Rh ([5](2+)), Ir ([6](2+)), and [Au2Pd2Cl2(dpmppm-H)2](2+) ([7](2+)) by treatment with [Cp*MCl2]2 and [AuCl(PPh3)], respectively. Complex [7](2+) contains an unprecedented PC(sp(3))P pincer ligand with a PCPCPCP backbone, dpmppm-H of deprotonated dpmppm. The present results demonstrated that the binuclear Pd(I) complex [2](2+) was a quite useful starting material to extend the palladium chains and to construct Pd-involved heteromultinuclear systems.