Phosphine Coordination Research Articles

Mononuclear palladacycles versus acyclic analogues: a structure and reactivity comparison

The metallocyclic ring in mononuclear iminoisoindoline-based palladacycle [(κ2-iminoisoidoline)PdCl(PCy3)] (3) can be ring opened by coordination of phosphine to form the trans bis(phosphine) iminoisoindoline-based palladium(II) complex [(η1-iminoisoidoline)PdCl(PCy3)2] (4) where the η1-iminoisoindoline is coordinated only by an Ar-Pd bond. The ring-opened analogue showed significantly higher coupling activity in Suzuki-Miyaura reactions with aryl chlorides than any iminoisoindoline-based palladacycle studied to date. These results are compared to existing mononuclear palladacycles and reported acyclic analogues.

Ferrocene‐Based Phosphenium Ion with Intramolecular Phosphine Coordination

AbstractA bis(ferrocenyl)phosphenium ion with intramolecular phosphine‐coordination, incorporated within [2]ferrocenophane framework, was synthesized as an air‐stable compound. Although it can be thought as a phosphino‐phosphonium derivative, considering the potential rotation of the cyclopentadienyl group of the ferrocene moiety, the isolated compound should be a masked phosphenium ion with intramolecular phosphine coordination. The redox behavior of the isolated phosphine‐coordinated phosphenium ion has been revealed by CV measurements and the theoretical calculations, suggesting its oxidation at the ferrocenyl moieties and reduction at the phosphorus center consecutively giving the corresponding phosphinyl radical and phosphide ion.

Triggering Electron Transfer in Co(I) Dimers: Computational Evidences for a Reversible Disproportionation Mechanism.

An inner-sphere disproportionation mechanism of the Co(I) precursor CoCl(PPh3 )3 is described through a Density Functional Theory study. The essential role of oleylamine in this process is unravelled. A detailed analysis of the electronic structure of Cobalt dimers of the general formula Co2 Cl2 Ln (L=NH3 and PH3 ) demonstrates that electron transfer is triggered by asymetric coordination of amine and phosphine to stabilize a mixed-valence Co(II)-Co(0) dimer. This is consistent with the HSAB statement that both amine and phosphine ligands are required to stabilize the reaction products, respectively Co(II) and Co(0) centers. We propose a quasi-athermic multi-step disproportionation mechanism with low activation barriers where the electron transfer goes through simple ligand exchanges between Co.

Multifunctionality in Polymer Networks by Dynamic of Coordination Bonds

AbstractThe need for multifunctional materials is driven by emerging technologies and innovations, such as in the field of soft robotics and tactile or haptic systems, where minimizing the number of operational components is not only desirable, but can also be essential for realizing such devices. This study report on designing a multifunctional soft polymer material that can address a number of operating requirements such as solvent resistance, reshaping ability, self‐healing capability, fluorescence stimuli‐responsivity, and anisotropic structural functions. The numerous functional abilities are associated to rhodium(I)–phosphine coordination bonds, which in a polymer network act with their dynamic and non‐covalently bonded nature as multifunctional crosslinks. Reversible aggregation of coordination bonds leads to changes in fluorescence emission intensity that responds to chemical or mechanical stimuli. The fast dynamics and diffusion of rhodium–phosphine ions across and through contacting areas of the material provide for reshaping and self‐healing abilities that can be further exploited for assembly of multiple pieces into complex forms, all without any loss to material‐sensing capabilities.

Neutral and cationic germanium(IV) fluoride complexes with phosphine coordination - synthesis, spectroscopy and structures.

The neutral complexes trans-[GeF4(PiPr3)2] and [GeF4(κ2-L)] (L = CH3C(CH2PPh2)3 or P(CH2CH2PPh2)3) are obtained from [GeF4(MeCN)2] and the ligand in CH2Cl2. Treatment of [GeF4(PMe3)2] with n equivalents of TMSOTf (Me3SiO3SCF3) leads to formation of the series [GeF4-n(PMe3)2(OTf)n] (n = 1, 2, 3), each of which contains six-coordinate Ge(IV) with trans PMe3 ligands and X-ray structural data confirm that the OTf groups interact with Ge(IV) to varying degrees. Unexpectedly, [GeF3(PMe3)2(OTf)] undergoes reductive defluorination in solution, forming the Ge(II) complex, [Ge(PMe3)3][OTf]2 (and [FPMe3]+). The bulkier PiPr3 leads to formation of the ionic [GeF3(iPr3P)2][OTf], containing a [GeF3(iPr3P)2]+ cation. [GeF4{o-C6H4(PMe2)2}], containing the cis-chelating diphosphine, also reacts with n equivalents of TMSOTf to generate [GeF4-n{o-C6H4(PMe2)2}(OTf)n] (n = 1, 2, 3). As for the PMe3 system, the trifluoride, [GeF3{o-C6H4(PMe2)2}(OTf)], is unstable to reductive defluorination in solution, producing the pyramidal Ge(II) complex [Ge{(o-C6H4(PMe2)2}(OTf)][OTf], whose crystal structure has been determined. The [GeF3{Ph2P(CH2)2PPh2}(OTf)] and [GeF2{Ph2P(CH2)2PPh2}(OTf)2], obtained similarly from the parent tetrafluoride complex, are poorly soluble, however their structures were confirmed crystallographically. The complexes in this work have been characterised via variable temperature 1H, 19F{1H} and 31P{1H} NMR studies in solution, IR spectroscopy and microanalysis and through single crystal X-ray analysis of representative examples across each series. Trends in the NMR and structural parameters are also discussed.

Tin(IV) fluoride complexes with neutral phosphine coordination and comparisons with hard N- and O-donor ligands.

The reactions of trans-[SnF4(PMe3)2] with one, two or three equivalents of Me3SiO3SCF3 (TMSOTF), respectively, in anhydrous CH2Cl2 form six-coordinate [SnF4-n(PMe3)2(OTf)n] (n = 1-3), which have been characterised by microanalysis, IR and multinuclear NMR (1H, 19F{1H}, 31P{1H} and 119Sn) spectroscopy. The crystal structure of [SnF3(PMe3)2(OTf)] reveals the three fluorines are in a mer-arrangement with mutually trans PMe3 ligands. The multinuclear NMR spectra confirm this structure is retained in solution, and show that [SnF2(PMe3)2(OTf)2] has trans-phosphines, while [SnF(PMe3)2(OTf)3] has trans PMe3 groups and hence mer-triflate ligands. The [SnF4-n(PMe3)2(OTf)n] are unstable in solution and the decomposition products include [Me3PF]+ and the tin(II) complexes [Sn(PMe3)2(OTf)2] and [Sn3F5(OTf)], both of the latter identified by their crystal structures. The reaction of trans-[SnF4(PiPr3)2] containing the bulkier phosphine, with one and two equivalents of TMSOTf produced unstable mono- and bis-triflates, which the NMR data also suggest contain weakly coordinated triflate, [SnF3(PiPr3)2(OTf)] and [SnF2(PiPr3)2(OTf)2], again with axial phosphines, although some OTf dissociation from the former to give [SnF3(PiPr3)2]+ may occur in solution at room temperature. The new phosphine complexes of SnF4, trans-[SnF4(PiPr3)2] and (cis) [SnF4(κ2-triphos)] (triphos = CH3C(CH2PPh2)3) have also been fully characterised, including the crystal structure of [SnF4(κ2-triphos)]. Attempts to promote P3-coordination by further treatment of this complex with TMSOTf were unsuccessful. The [SnF4(L)2] (L = dmso, py, pyNO, DMF, OPPh3) complexes, which exist as mixtures of cis and trans isomers, react with one equivalent of TMSOTf, followed by addition of one equivalent of L, to form the ionic [SnF3(L)3][OTf] complexes, which were characterised by microanalysis, IR and multinuclear NMR spectroscopy. In nitromethane solution they are a mixture of mer and fac isomers based upon multinuclear NMR data (1H, 19F{1H}, 119Sn). Reaction of [SnF4(OPPh3)2] with two equivalents of TMSOTf and further OPPh3 produced [SnF2(OPPh3)4][OTf]2, which is a mixture of cis and trans isomers in solution. The crystal structure of [SnF2(OPPh3)4][OTf]2 confirms the trans isomer in the solid state, with the triflate ionic. These complexes are rare examples of fluorotin(IV) cations with neutral monodentate ligands.

Phosphine-substituted diiron complexes Fe2(μ-Rodt)(CO)6−n(PPh3)n(R = Ph, Me, H andn= 1, 2) featuring desymmetrized oxadithiolate bridges: structures, protonation, and electrocatalysis

The influence of desymmetrized dithiolates (Rodt) and phosphine coordination modes (PPh3) on the structural, protophilic, and electrocatalytic features of diiron complexes 4–6 and 7–9 is described.

A green synthesis of CISe nanocrystal ink and preparation of quantum dot sensitized solar cells

I–III–VI chalcopyrite copper indium selenium is one of therepresentatives of the light absorbing layer material, and is often used for a thin-film solar cell. With the development of nano-technology, CuInSe2 quantum dots (CISe QDs) which have intermediate belt and excitation effect characteristics are applied to the solar cells as an alternative of Cd- or S-based QDs. Most conventional methods for the synthesis of CISe QDs using solution involve the dangerous and environmentally unfriendly Oleylamine or phosphine coordination compounds. In this work, CISe QDs were synthesized by a green, safe and low-temperature method in triethylene glycol. Through controlling the growth temperature and time, the diameter can be adjusted from 3[Formula: see text]nm to 10[Formula: see text]nm. The samples exhibit quantum confinement effect, and have a controllable optical band gap. QDs were deposited on the surface of ZnO nanorods to obtain a photoanode, which were fabricated into quantum dot-sensitized solar cells. The device exhibits size-dependent performance. And the open circuit voltage shows a fluctuation up to 0.26[Formula: see text]V. When the size is 4[Formula: see text]nm, the short circuit current density is the largest (15[Formula: see text]mA/cm2).

A Smart Phosphine–Diyne Polymer Displays “Turn-On” Emission with a High Selectivity for Gold(I/III) Ions

A polymeric phosphine sensor is reported that exhibits bright blue fluorescence in the presence of gold(I/III) ions but is nonemissive with other metal ions. Specifically, solutions of a poly(p-arylenediethynylene phosphine) copolymer are 35 or 94 times more emissive when treated with solutions of (tht)AuCl or HAuCl4·3H2O, respectively. Model compound studies confirm phosphine coordination to metals, including gold(I/III) and rhodium(I), and the selective "turn-on" fluorescence was investigated using time-dependent density functional theory calculations.

Experimental and Computational Study of the Structure, Steric Properties, and Binding Equilibria of Neopentylphosphine Palladium Complexes.

Steric properties of crystallographically and computationally determined structures of linear palladium(0) and square planar palladium(II) complexes of di(tert-butyl)neopentylphosphine (P(t-Bu)2Np), tert-butyldineopentylphosphine (P(t-Bu)Np2), and trineopentylphosphine (PNp3) have been determined. Structures of linear palladium(0) complexes show that steric demand increases as tert-butyl groups are replaced with neopentyl groups (P(t-Bu)2Np < P(t-Bu)Np2 < PNp3). In square planar palladium(II) complexes, PNp3 gives the smallest steric parameters, whereas P(t-Bu)Np2 has the largest steric demand. The change in the steric demand of PNp3 compared to P(t-Bu)2Np and P(t-Bu)Np2 results from a significant conformational change in PNp3 depending on the coordination number of the metal. The steric properties of these ligands were also probed by measuring the equilibrium constant for coordination of free phosphine to dimeric [(R3P)Pd(μ-Cl)Cl]2 complexes. Binding equilibria follow the same trend as the steric parameters for square planar complexes with PNp3 having the highest binding constant. In contrast to the normal trend, the neopentylphosphines show increased pyramidalization at phosphorus with increasing steric demand. We hypothesize that this unusual dependence reflects the low back side strain of the neopentyl group, which allows the ligand to be more pyramidalized while still exerting a significant front side steric demand.

Phosphine-Based Covalent Organic Framework for the Controlled Synthesis of Broad-Scope Ultrafine Nanoparticles.

In this work, a phosphine-based covalent organic framework (Phos-COF-1) is successfully synthesized and employed as a template for the confined growth of broad-scope nanoparticles (NPs). Ascribed to the ordered distribution of phosphine coordination sites in the well-defined pores, various stable and well-dispersed ultrafine metal NPs including Pd, Pt, Au, and bimetallic PdAuNPs with narrow size distributions are successfully prepared as determined by transmission electron microscopy, X-ray photoelectron spectroscopy, inductively coupled plasma, and powder X-ray diffraction analyses. It is also demonstrated that the as-prepared Phos-COF-1-supported ultrafine NPs exhibit excellent catalytic activities and recyclability toward the Suzuki-Miyaura coupling reaction, reduction of nitro-phenol and 1-bromo-4-nitrobenzene, and even tandem coupling and reduction of p-nitroiodobenzene. This work will open many new possibilities for preparing COF-supported ultrafine NPs with good dispersity and stability for a broad range of applications.

The ambiguous behaviour of diphosphines towards the quasilinear iron(i) complex [Fe(N(SiMe3)2)2]- - between inertness, P-C bond cleavage and C-C double bond isomerisation.

Chelating phosphines are widely used as robust and reliable ligands in catalysis. We show that the anionic iron(i) complex [FeI(N(SiMe3)2)2]- is able to selectively cleave a P-aryl bond of 1,2-bis(diphenylphosphino)benzene. Furthermore, the related cis-1,2-bis(diphenylphosphino)-ethylene (dppee) binds not to the P donors but to the ethylene unit, and is (catalytically) transformed to the trans-isomer.

Direct, One-Pot Syntheses of MOFs Decorated with Low-Valent Metal-Phosphine Complexes

We demonstrate a simple and generalizable method for the one pot, in situ formation of bimetallic metal–organic framework (MOF) materials decorated with crystallographically defined, low-valent metal sites. Solvothermal reactions between poly(carboxylated) aryl(phosphine) ligands and mixtures of higher- and lower-valent metal precursors achieves concomitant P–M complexation and MOF formation via metal–carboxylate network bonding. This method is demonstrated in the preparation of two new phosphine coordination materials, PCM-107 and PCM-74, which feature Ar3P–AuX (X = Cl, Br) and chelated PN–Cu2I2–PN units as the MOF building blocks, respectively. PCM-107 is an active catalyst for alkyne hydroaddition, while PCM-74 shows promise for the crystallization of MOFs bearing kinetically favored isomers.

Group 9 and 10 Metal Complexes of an Ylide-Substituted Phosphine: Coordination versus Cyclometalation and Oxidative Addition.

Ylide-substituted phosphines (YPhos) have been shown to be excellent ligands for several transition metal catalyzed reactions. Investigations of the coordination behavior of the YPhos ligand YSPPh2 (1) [with YS = (Ph3P)(SO2Tol)C] toward group 9 and 10 metals revealed a surprisingly diverse coordination chemistry of the ligand. With Ni(CO)4, the formation of a di- as well as tricarbonyl complex is observed depending on the reaction conditions. In [(κP,η2-benzene-1)Ni(CO)2] the phosphine ligand also coordinates via a phosphonium bound phenyl group to the metal leading to a unique nickel η2-arene interaction, which can be viewed as an intermediate state toward P–C bond activation. Full cleavage of the P–C bond takes place with [Rh(COD)Cl]2 leading to a complex salt with [(κP,κO-1)Rh(COD)]+ as cation and a dirhodium trichloride complex anion. Here, YSPPh2 underwent P–C bond cleavage to thus act as an anionic diphosphine ligand. In contrast, in [(κP,κO-1)Rh(COD)]+ as well as [(κP,κO-1)Rh(CO)Cl], formed from the reaction of 1 with [Rh(CO)2Cl]2, the YPhos ligand acts as bidentate ligand complexing the metal via the phosphine and sulfonyl moiety with an intact PPh3 unit. A further type of coordination is observed with [Ir(COD)Cl]2. Here, phosphine coordination is accompanied by C–H activation at one of the phosphonium bound phenyl groups leading to a cyclometalated complex.

Novel silver-phosphine coordination polymers incorporating a Wurster's blue - like radical cation with enhanced photoelectric properties.

Tetraphosphine ligand dpppda reacts with AgNO3 to generate two 1D coordination polymers containing cubic and chair-like [Ag4(NO3)4] clusters. ESR spectroscopy supported by DFT calculations indicated the presence of dpppda˙+, a Wurster's blue - like radical cation formed by intramolecular ligand-to-metal charge transfer (LMCT). This LMCT results in higher AgI → Ag0 potentials and good photocurrent responses.

A Metal–Organic Framework with Cooperative Phosphines That Permit Post‐Synthetic Installation of Open Metal Sites

AbstractPCM‐101 is a phosphine coordination material comprised of tris(p‐carboxylato)triphenylphosphine and secondary pillaring groups coordinated to [M3(OH)]5+ nodes (M=Co, Ni). PCM‐101 has a unique topology in which R3P: sites are arranged directly trans to one another, with a P⋅⋅⋅P separation distance dictated by the pillars. Post‐synthetic coordination of soft metals to the P: sites proceeds at room temperature to provide X‐ray quality crystals that permit full structural resolution. Addition of AuCl groups forces a large distortion of the parent framework. In contrast, CuBr undergoes insertion directly between the trans‐P sites to form dimers that mimic solution‐phase complexes, but that are geometrically strained due to steric pressure exerted by the MOF scaffold. The metalated materials are active in heterogeneous hydroaddition catalysis under mild conditions, yielding different major products compared to their molecular counterparts.

A Metal-Organic Framework with Cooperative Phosphines That Permit Post-Synthetic Installation of Open Metal Sites.

PCM-101 is a phosphine coordination material comprised of tris(p-carboxylato)triphenylphosphine and secondary pillaring groups coordinated to [M3 (OH)]5+ nodes (M=Co, Ni). PCM-101 has a unique topology in which R3 P: sites are arranged directly trans to one another, with a P⋅⋅⋅P separation distance dictated by the pillars. Post-synthetic coordination of soft metals to the P: sites proceeds at room temperature to provide X-ray quality crystals that permit full structural resolution. Addition of AuCl groups forces a large distortion of the parent framework. In contrast, CuBr undergoes insertion directly between the trans-P sites to form dimers that mimic solution-phase complexes, but that are geometrically strained due to steric pressure exerted by the MOF scaffold. The metalated materials are active in heterogeneous hydroaddition catalysis under mild conditions, yielding different major products compared to their molecular counterparts.

Highly selective room temperature acetylene sorption by an unusual triacetylenic phosphine MOF.

The new ligand tris(p-carboxyphenylethynyl)phosphine (P{C[triple bond, length as m-dash]CC6H4-4-CO2H}3) was used to synthesize a permanently porous Mn(ii)-based acetylenic phosphine coordination material, PCM-48. This triply-interpenetrated MOF contains 1-D microchannels that are decorated with electron-rich and adsorbate-accessible acetylenic moieties and phosphine lone pairs. PCM-48 has a moderate room-temperature C2H2 adsorption capacity (25.54 cm3 g-1) and displays high separation selectivities for C2H2 over CH4 (C2H2/CH4 = 23.3), CO2 (C2H2/CO2 = 4.3), and N2 (C2H2/N2 = 76.9) at 296 K.

1-D and 2-D phosphine coordination materials based on a palladium(II) PCP pincer metalloligand

Ancillary functionalization of a PCP pincer ligand with para-carboxylic acids provides a simple route to the subsequent preparation of crystalline coordination polymers using pre-cyclometallated complexes as polymer building blocks. This synthetic strategy is demonstrated here using air- and moisture-stable PCP-PdCl metalloligands to prepare new coordination polymers with both 1-D (chain) and 2-D (sheet) networks, named PCM-29 and PCM-30, respectively. The single crystal X-ray structures and solid-state gas sorption properties of both materials are presented. The Brunauer-Emmett-Teller (BET) surface area of PCM-30 was found to be 302m2g−1 using CO2 as the probe gas, indicating permanent porosity and reversible small molecule diffusion between the 2-D sheets.

Pyrrolyl-based pincer complexes of iron – Synthesis and electronic structure

Four- and five-coordinate high-spin (S=2) Fe(II) complexes bearing the pyrrolyl-derived tBuPNP pincer ligand [tBuPNP=2,5-(tBu2PCH2)2(C4H2N)] have been prepared. All three complexes were characterized by X-ray diffraction, zero-field 57Fe Mössbauer spectroscopy and solid-state magnetic susceptibility studies. Furthermore, the experimentally determined Mössbauer parameters of compounds 4–6 can be modeled satisfactorily by density functional theory (DFT) computations at the B97D level of theory. Introduction of the sterically demanding bis(trimethylsilyl)amido moiety induces significant distortions from ideal tetrahedral geometry in [(tBuPNP)FeN(SiMe3)2] (4), featuring an Fe(II) high-spin state with large negative axial zero-field splitting and slow paramagnetic relaxation at low temperature, as evidenced by measurements of the solid-state magnetic susceptibility and zero-field 57Fe Mössbauer spectroscopy. Replacing the chlorido ligand in [(tBuPNP)FeCl] (3) by the bidentate acetylacetonato (acac) ligand enforces a trigonal–bipyramidal structure in [(tBuPNP)Fe(acac)] (5), in which the Fe(II) atom also adopts a high-spin configuration. Reaction of 3 with adamantyl azide allowed us to confirm the inherent lability of the phosphine coordination, since the azide inserts into the FeP bond to form [(tBuPNPN3Adamantyl)FeCl] (6), in which the tBuPNP ligand is transformed to a phosphino-pyrrolyl-phosphazide ligand framework (tBuPNPN3Adamantyl). This motif can be considered as a trapped Staudinger intermediate along the reaction pathway of free phosphines with organic azides to form phosphinimines. Bidentate binding of the phosphazide sidearm in κN:κN-fashion to the Fe(II) atom enforces an s-anti coordination of the P1–N2–N3–N4 moiety, which raises the barrier for the thermodynamically favorable N2 elimination and allows this intermediate to be trapped. Complex 6 contains a high-spin Fe(II) atom with a square-pyramidal structure.