Bridging Phosphine Ligands Research Articles

Dirhodium(II) complex catalyzed dehydrosilylation of styrenes: theoretical investigations on the mechanism, selectivity, and ligand effects.

The dirhodium(II) complexes with bridging phosphine and OAc ligands showed high reactivity and selectivities in olefin dehydrosilylation. In order to determine the structure of the actual catalyst which cannot be determined experimentally, the geometries of the dirhodium catalyst, the detailed catalytic mechanism, and the stereo- and chemo-selectivities of the title reaction were studied using DFT calculations. The results showed that one OAc group is monodentate and the other is bidentate in the dirhodium catalyst C'. The determined catalytic cycle consists of four processes: Rh-H bond activation in C', Si-H bond activation in alkoxysilane, alkylene insertion into the Rh-Si bond, followed by β-H elimination or σ-metathesis reaction. Among them, the alkylene insertion process is the rate-determining step. The stereoselectivity of the title reaction is controlled by the steric effect and orbital interactions between the alkyene and dirhodium catalysts in the β-H elimination process. The chemoselectivity is regulated by the presence of the axial ligand in the dirhodium catalyst, when there is an axial ligand coordinated to the Rh atom, E-alkene is the main product, whereas alkane would be obtained in the absence of an axial ligand. Our work determines the structure of the actual catalyst, and provides explanations and predictions for the activity, and chemo- and stereo-selectivity control of olefin dehydrosilylation.

Synthesis and Electrochemical Investigation of Phosphine Substituted Diiron Phosphadithiolate Complexes

AbstractThis work reports on ligand exchange reactions between a [FeFe] hydrogenase model containing the higher homologue (PhosDT) and phosphines selected to cover a variety of electronic properties and possible coordination modes. Additionally, the amount of the phosphines and the reaction temperature were varied to study the formation of complexes with multiple phosphines or altered binding modes. Due to steric effects caused by the position of the bridgehead, the phosphines bind preferentially at the more accessible iron centre on the phosphinate averted side. While all ligand exchanges resulted in a ligand‐specific main product at room temperature, reflux conditions induced decomposition in case of PhosDT‐(κ2‐dppe) and PhosDT‐(κ2‐dppv) and a change in the binding mode for the dppm containing complex. Moreover, we highlight two novel iron complexes obtained as side products of the reactions with dppe and dppv, while in case of dppm an additional model with two bridging phosphine ligands was generated. Finally, the six novel phosphine substituted PhosDT models were electrochemically investigated, revealing a cathodic shift compared to the starting material due to the increased electron density at the iron atoms. Moreover, the models with monodentate ligands exhibit a different CV pattern for the FeIFeI/FeIFe0 process than complexes with bidentate phosphines.

Beyond Classical Coordination Chemistry: The First Case of a Triply Bridging Phosphine Ligand

AbstractThe first example of a triply bridging (μ3‐P) phosphine ligand has been discovered in the crown‐shaped [Cu3(μ2‐Hal)3L] (Hal=Cl, Br, or I) complexes supported by tris[2‐(2‐pyridyl)ethyl]phosphine (L). Theoretical analysis completely confirms the observed μ3‐P‐bridging pattern, revealing the interaction of the same lone pair of phosphorus with three valence 4s‐orbitals of Cu atoms. The presented complexes exhibit outstanding blue phosphorescence (λem=442–465 nm) with the quantum efficiency reaching 100 %. The complex [Cu3(μ2‐I)3L] also exhibits remarkable thermo‐ and mechanochromic luminescence resulting in a sharp change in the emission colour upon external stimuli. These findings essentially contribute to coordination chemistry of the pnictine ligands.

Beyond Classical Coordination Chemistry: The First Case of a Triply Bridging Phosphine Ligand.

The first example of a triply bridging (μ3 -P) phosphine ligand has been discovered in the crown-shaped [Cu3 (μ2 -Hal)3 L] (Hal=Cl, Br, or I) complexes supported by tris[2-(2-pyridyl)ethyl]phosphine (L). Theoretical analysis completely confirms the observed μ3 -P-bridging pattern, revealing the interaction of the same lone pair of phosphorus with three valence 4s-orbitals of Cu atoms. The presented complexes exhibit outstanding blue phosphorescence (λem =442-465 nm) with the quantum efficiency reaching 100 %. The complex [Cu3 (μ2 -I)3 L] also exhibits remarkable thermo- and mechanochromic luminescence resulting in a sharp change in the emission colour upon external stimuli. These findings essentially contribute to coordination chemistry of the pnictine ligands.

Keep it tight: a crucial role of bridging phosphine ligands in the design and optical properties of multinuclear coinage metal complexes.

Copper subgroup metal ions in the +1 oxidation state are classical candidates for aggregation via non-covalent metal-metal interactions, which are supported by a number of bridging ligands. The bridging phosphines, soft donors with a relatively labile coordination to coinage metals, serve as convenient and essential components of the ligand environment that allow for efficient self-assembly of discrete polynuclear aggregates. Simultaneously, accessible and rich modification of the organic spacer of such P-donors has been used to generate many fascinating structures with attractive photoluminescent behavior. In this work we consider the development of di- and polynuclear complexes of M(i) (M = Cu, Ag, Au) and their photophysical properties, focusing on the effect of phosphine bridging ligands, their flexibility and denticity.

Discrete bimetallic Co(II) phosphinate complexes supported by 2,6-dimesitylphenylphosphinate ligand

Reactions of Co(II) sources with 2,6-dimesitylphenylphosphinate were conducted in two phase (toluene/water) solvent systems. The presence of small coordinating anions (X) and neutral ligands (L) was found to be a determining factor for the outcome of these reactions. When both were present, discrete bimetallic complexes of the type [X-Co-μ-(DmpP(H)O2)3-Co-L] were produced (X=Cl−, L=p-fluorobenzylnitrile (1a), p-cyanoaniline (1b), acetonitrile (1c), or pyridine (1d); X=Br−, L=DMF (2); X=thiocyanate, L=H2O (3)). In these complexes both Co(II) centers are in distorted tetrahedral ligand geometries that are formed by the three oxygens of the bridging phosphinate ligands and either X or L ligands. In the absence of a coordinating anion and with p-cyanoaniline as a small neutral ligand bimetallic cation [p-NH2-C6H4-CN-Co-μ-(DmpP(H)O2)3-Co(H2O)3]+ (4) was obtained. Cation 4 contains a tetrahedral and an octahedral Co(II) center; an additional phosphinate serves as a counterion and is attached to the cation via hydrogen bonding to water molecules coordinated to the octahedral cobalt center. Complexes 1a–d, 2, 3, and 4 [DmpP(H)O2] were characterized by elemental analyses, spectroscopic (UV–Vis and IR) and magnetic measurements, and by single crystal X-ray diffraction experiments. When Co(BF4)2 was reacted with two equivalents of DmpP(H)O2− with no other neutral ligands present, slow evaporation of the reaction mixtures produced blue powdery solids. In one of such reactions several large blue crystals were produced and analyzed by single crystal X-ray diffraction. The compound was characterized as trimetallic complex [((H2O)DmpP(H)O2-Co-(μ-DmpP(H)O2)2)2Co] (5). The formation of compound 5 suggests that under selected conditions formation of oligomeric/polymeric compounds with the general formula “Co(DmpP(H)O2)2” may be possible.

Palladium(II) complexes with tris(2-carboxyethyl)phosphine, structure, reactions and cytostatic activity

Water soluble and air stable P(RCOOH)3 (R=C2H4) (TCEP) is an efficient reducing agent used in biochemistry to break S–S bond in peptides, proteins and other compounds containing S–S bonds. The similarity between the coordination chemistry of Pd(II) and Pt(II) led to the investigations of antitumor activity of palladium(II) compounds however the Pd(II) complexes with TCEP were not investigated. New palladium(II) complexes with (TCEP): trans-[PdCl2(TCEP)2] (1) and trans-[Pd2(μ-Cl)2Cl2(TCEP)2] (2) were fully characterized by 1H, 13C, 31P NMR, IR and ESI-MS spectroscopic techniques. Complexes are stable in non-aqueous DMSO and DMF. In aqueous solutions Cl ligands are substituted by COO groups of phosphines. Complex 2, after crystallization from water gives polymeric compound with bridging phosphine ligand [PdCl{P(RCOO-κO-μ-O′)(RCOOH)2-κP}] (3). Structures of trans-[PdCl2{P(RCOOD)3}2] (1a), trans-[Pd2(μ-Cl)2PdCl2{P(RCOOD)3}2] (2a), and [PdCl{P(RCOO-κO-μ-O′)(RCOOD)2-κP}]n (3a) have been determined by X-ray crystallography. NMR and ESI-MS spectra reveal that [PdP2(RCOO-κO)2(RCOO)n(RCOOH)4−n]n– complexes are formed in aqueous solution of 1. Geometry optimization in the gas phase at the B3LYP/3-21G** level indicated that complex 2 with butterfly structure is more stable than that with coplanar coordination. In aqueous solution of 2, the main products [Pd2{P(RCOO-κO-μ-O′)(RCOO-κO)(RCOOH)}2] and [Pd{P(RCOO-κO)2(RCOOH)}(H2O)] exist in equilibrium which depends on temperature: content of mononuclear compound increases as the temperature is raised. Complexes 1 and 2 are active agents against melanoma and breast cancer cells.

Synthesis, Structure, and Magnetic Properties of Phosphinate‐Bridged Hexanuclear FeIII Complexes Containing Two Butterfly‐Shaped Fe3O Cores

AbstractThe reaction of FeIII salts with 1,1,2,3,3‐pentamethyltrimethylenephosphinic acid [cycPO2H] or dicyclohexylphosphinic acid [(C6H11)2PO2H] along with pivalic acid in the presence of triethylamine leads to the formation of two hexanuclear iron(III) clusters: [FeIII6(μ3‐O)2(μ‐OH)2(μ‐cycPO2)6(μ‐tBuCO2)6(η1‐tBuCO2H)2]·4CH3CN·3CH2Cl2 (1) and [FeIII6(μ3‐O)2(μ‐OH)2{μ‐(C6H11)2PO2}6(μ‐tBuCO2)6(η1‐OH2)2]·2CH3CN·CH2Cl2 (2). These complexes are made up of two butterfly‐shaped {FeIII3O} subunits that are joined to each other by two bridging phosphinate ligands. In addition, the formation of 1 and 2 is assisted by μ3‐O, μ‐OH, and pivalate ligands. Variable‐temperature magnetic susceptibility measurements of complexes 1 and 2 reveal medium to strong antiferromagnetic interactions between the FeIII ions inside the Fe3O subunits and weak inter‐trinuclear antiferromagnetic interactions through the bridging phosphinate ligands. The triangular topology of the Fe3O subunits gives rise to competing antiferromagnetic interactions and spin frustration. The different relative magnitudes of the competing interactions leads to S = 5/2 and S = 1/2 ground spin states for the Fe3O subunits in 1 and 2, respectively.

Hexanuclear Gold(I) Phosphide Complexes as Platforms for Multiple Redox-Active Ferrocenyl Units

The synthesis, X-ray crystal structures, electrochemical, and spectroscopic studies of a series of hexanuclear gold(I) μ(3)-ferrocenylmethylphosphido complexes stabilized by bridging phosphine ligands, [Au(6)(P-P)(n)(Fc-CH(2)-P)(2)][PF(6)](2) (n=3, P-P=dppm (bis(diphenylphosphino)methane) (1), dppe (1,2-bis(diphenylphosphino)ethane) (2), dppp (1,3-bis(diphenylphosphino)propane) (3), Ph(2)PN(C(3)H(7))-PPh(2) (4), Ph(2)PN(Ph-CH(3)-p)PPh(2) (5), dppf (1,1′-bis(diphenylphosphino)ferrocene) (6); n=2, P-P=dpepp (bis(2-diphenylphosphinoethyl)phenylphosphine) (7)), as platforms for multiple redox-active ferrocenyl units, are reported. The investigation of the structural changes of the clusters has been probed by introducing different bridging phosphine ligands. This class of gold(I) μ(3)-ferrocenylmethylphosphido complexes has been found to exhibit one reversible oxidation couple, suggestive of the absence of electronic communication between the ferrocene units through the Au(6)P(2) cluster core, providing an understanding of the electronic properties of the hexanuclear Au(I) cluster linkage. The present complexes also serve as an ideal system for the design of multi-electron reservoir and molecular battery systems.

Diiron Azadithiolate Complexes with Bridging Phosphine Ligand dppf: Synthesis and Characterization

Reaction of complex [(μ-SCH2)2NCH2CO2Me]Fe2(CO)6 (A) with 1,1′-bis(diphenylphosphino)ferrocene (dppf) in the presence of the decarbonylating agent Me3NO∙2H2O gave complex [(μ-SCH2)2NCH2CO2MeFe2(CO)5]2[(η 5-Ph2PC5H4)2Fe] (1) in 72 % yields, whereas complex [(μ-SCH2)2NPhFe2(CO)5]2[(η 5-Ph2PC5H4)2Fe] (2) was produced by reaction of [(μ-SCH2)2NPh]Fe2(CO)6 (B) with dppf in toluene at reflux in 41 % yield. The new complexes 1 and 2 were characterized by elemental analysis, IR, and 1H (31P, 13C) NMR spectroscopy as well as by single crystal X-ray diffraction analysis. In the crystal structures of 1 and 2, the dppf ligand resides in an apical position of the square-pyramidal geometry of the neighbouring Fe atoms and the crystal structures were stabilized by the intermolecular C–H···O hydrogen bonds.

Methanol triggered ligand flip isomerization in a binuclear copper(i) complex and the luminescence response

Methanol drives the blue emissive complex, [Cu(2)(dppy)(3)(MeCN)](BF(4))(2) (dppy = diphenylphosphino-pyridine), with a head-to-tail arrangement of the three bridging phosphine ligands to convert to its linkage isomer (head-to-head, green emissive) in the solid state, and the transformation could be reversibly realized through recrystallization in different solvents.

Synthesis, Structural Characterization, and Photophysical Study of Luminescent Face-to-Face Dinuclear Platinum(II) Alkynyl Phosphine Complexes and Their Tetranuclear Mixed-Metal Platinum(II)−Silver(I) and −Copper(I) Complexes

A series of luminescent face-to-face dinuclear platinum(II) alkynyl phosphine complexes with trimethoxyphenyl and carbazole moieties have been synthesized by phosphine exchange reaction. Two mixed-metal tetranuclear platinum(II)−silver(I) and −copper(I) complexes have also been synthesized. The complexes are well characterized by 1H, 13C, and 31P NMR spectroscopy, positive ion FAB mass spectrometry, IR spectroscopy, and elemental analysis. Most of them have been structurally characterized by X-ray crystallography. All the complexes are found to show emissive behavior. Correlations of the emissive property with the Pt···Pt distance, the nature of the alkynyl and bridging phosphine ligands, and the nature of the encapsulated metal ions on the alkynyl ligands have been made. TDDFT/CPCM calculations have been performed to provide further insight into the origin of the absorption and emission properties.

Luminescent Silver(I) and Copper(I) Systems Containing Pyridyl Phosphine Bridges

Luminescent silver(I) and copper(I) complexes containing pyridylphosphine ligands have been synthesized and structurally characterized by single crystal X-ray diffraction methods. The reaction of Ag(OTf) (OTf = trifluoromethanesulfonate) with 2-pyridyldiphenylphosphine in different molar ratios gives the species [Ag2(OTf)2(μ-PPh2py)2] (1), [Ag(PPh2py)2]OTf (2), [Ag(PPh2py)3]OTf (3), and [Ag2(PPh2py)3](OTf)2 (4) with several modes of coordination of the pyridylphosphine. The oxidation of the phosphine in compound 4 gave [Ag2(OTf)(μ-PPh2py)2(OPPh2py)]OTf (5) which has been structurally characterized. It shows two bridging phosphine ligands and one chelating OPPh2py ligand. The reactions of the silver salt with bis(2-pyridyl)phenylphosphine in different molar ratios affords the complex [Ag2(OTf)2(μ-PPhpy2)2] (6), while the corresponding reactions with [Cu(NCMe)4]PF6 lead to two different compounds, namely [Cu2(NCMe)2(μ-PPhpy2)2](PF6)2 (7) and [Cu2(PPhpy2)2(μ-PPhpy2)2](PF6)2 (8). All complexes exhibit luminescence in the solid state at room temperature and at 77 K

Gold(I) Complexes Bearing P∩N-Ligands: An Unprecedented Twelve-membered Ring Structure Stabilized by Aurophilic Interactions

The P∩N-ligands Ph2Pqn, 1, Ph2 Piqn, 2, Ph2 Ppym, 3, and the As∩N-ligands Ph2Asqn, 4, Ph2Asiqn, 5, (Ph = phenyl, qn = 8-quinoline, iqn = 1-isoquinoline, pym = 2-pyrimidine) have been synthesized, the ligands 2 and 5 for the first time. Their ligand properties were probed by the synthesis of gold(I) complexes. Reaction with (tht)AuCl (tht = tetrahydrothiophene) yielded the chlorogold complexes Ph2RP-Au-Cl (R = qn, 6; iqn, 7; pym, 8) and Ph2RAs-Au-Cl (R = qn, 9; iqn, 10) in high yields. Further treatment of 7 and 8 with one equivalent of AgBF4 provided the complexes [(Ph2Piqn)Au]BF4, 11, [(Ph2Ppym)Au]BF4, 12, and [(Ph2Piqn)Au(tht)]BF4, 14. For comparison, the previously reported complex [(Ph2Ppy)Au]BF4 (py = pyridine), 13, was re-investigated. The compounds were characterized by elemental analyses, mass spectrometry and NMR spectroscopy. In addition, the solid-state structures of 2, 3, 6, 7, 9 - 14 have been determined by X-ray crystallography. The chloro-gold compounds crystallize in the common rod-like structure known from R3EAuCl (R = aryl, E = P, As) complexes without further aggregation via aurophilic interactions. In all cases the phosphine acts as a monodentate ligand. In the solid state compounds 11 - 13 feature an unprecedented cyclic trinuclear aggregation pattern, in which the Au(I) atoms are linearly coordinated by the bridging phosphine ligands forming a cyclic (P-Au-N)3 arrangement. The resulting twelvemembered ring is further stabilized by Au · · · Au interactions. Due to the presence of these Au · · · Au contacts, 11 - 13 are emissive in the solid state but not in solution

Rational Synthesis of Molybdenum(V) Tetramers Consisting of [Mo2O4]2+ Dimers Held Together by Bridging Phosphinate Ligands and the Tungsten(VI) Dimer [(CH3O)2(O)W(μ-O)(μ-O2PPh2)2W(O)(CH3O)2]: Structural and Theoretical Considerations

Reacting MoO2(acac)2 with Ph2POOH or Me2POOH in EtOH results in the formation of the tetranuclear molybdenum (V) clusters Mo4(μ 3-O)4(μ-O2PR2)4O4, PR2 = PPh2, 1, or PMe2, 2, in functional yields (>90% and 55% respectively). The reaction of WO2(acac)2 with Ph2POOH in MeOH affords the tungsten dimer [(CH3O)2(O)W(μ-O)(μ-O2PPh2)2W(O)(CH3O)2], 3. The single crystal X-ray determined structures of complexes 1–3 are reported. In 1 and 2, the four Mo=O units are interconnected by four triply bridging oxygen atoms, resulting in a distorted cubic-like structure for the Mo4(μ 3-O)4O4 units. Each molybdenum atom forms two additional Mo–O bonds with two oxygen atoms from different adjacent phosphinato ligands. Complex 3, a tungsten dimer, contains packing disorder and consists of bridging oxo and diphenylphosphinato ligands. The bonding of 1 and 2 assessed by density-functional methods showed that bonding between the Mo(V) centers occurs through σ overlap of the d xy orbitals.

Evaluation of C4 diphosphine ligands in rhodium catalysed methanol carbonylation under a syngas atmosphere: synthesis, structure, stability and reactivity of rhodium(i) carbonyl and rhodium(iii) acetyl intermediates

The carbonylation of methanol to acetic acid is a hugely important catalytic process, and there are considerable cost and environmental advantages if a process could be designed that was tolerant of hydrogen impurities in the CO feed gas, while eliminating by-products such as propionic acid and acetaldehyde altogether. This paper reports on an investigation into the application of rhodium complexes of several C(4) bridged diphosphines, namely BINAP, 1,4-bis(diphenylphosphino)butane (dppb), bis(diphenylphosphino)xylene (dppx) and 1,4-bis(dicyclohexylphosphino)butane (dcpb) as catalysts for hydrogen tolerant methanol carbonylation. An investigation into the structure, reactivity and stability of pre-catalysts and catalyst resting states of these complexes has also been carried out in order to understand the observations in catalysis. Rh(I) carbonyl halide complexes of each of the ligands have been prepared from both [Rh(2)(CO)(4)Cl(2)] and dimeric mu-Cl-[Rh(L)Cl](2) complexes. These Rh(I) carbonyl complexes are either dimeric with bridging phosphine ligands (dppb, dcpb, dppx) or monomeric chelate complexes. The reaction of the complexes with methyl iodide at 140 degrees C has been studied, which has revealed clear differences in the stability of the corresponding Rh(III) complexes. Surprisingly, the dimeric Rh(I) carbonyls react cleanly with MeI with rearrangement of the diphosphine to a chelate co-ordination mode to give stable Rh(III) acetyl complexes. The Rh acetyls for L=dppb and dppx have been fully characterised by X-ray crystallography. During the catalytic studies, the more rigid dppx and BINAP ligands were found to be nearly 5 times more hydrogen tolerant than [Rh(CO)(2)I(2)](-), as revealed by by-product analysis. The origin of this hydrogen tolerance is explained based on the differing reactivities of the Rh acetyls with hydrogen gas, and by considering the structure of the complexes.

Gas-phase synthesis and reactivity of binuclear gold hydride cations, (R3PAu)2H+ (R = Me and Ph)

Electrospray ionization of a mixture of the two gold phosphine chlorides, R3PAuCl (R = Ph and Me), silver nitrate and the amino acid N,N-dimethylglycine (DMG) yields a range of gold containing cluster ions including: (R3P)Au(PR'3)+; (R3PAu)(R'3PAu)Cl+ and (R3PAu)(R'3PAu)(DMG-H)+ (where R = R' = Ph; R = R' = Me; R = Me and R' = Ph). Collision induced dissociation (CID) of the (R3PAu)(R'3PAu)(DMG-H)+ precursor ions yielded the hitherto unknown gold hydride dimers (R3PAu)(R'3PAu)H+. The gas-phase chemistry of these dimers was studied using ion-molecule reactions, collision induced dissociation, electronic excitation dissociation (EED) and DFT calculations on the (H3PAu)2H+ model system. A novel phosphine ligand migration was found to occur prior to fragmentation under CID conditions and this was supported by DFT calculations, which revealed a transition state with a bridging phosphine ligand.

Synthesis and optical properties of binuclear gold(I) complexes with bridging phosphine ligands: luminescence from intraligand and metal-centered excited states

The complexes Au2Cl2(P-P) with P-P=biphep (2,2′-bis(diphenylphosphino)-1,1′-biphenyl), binap (2,2′-bis(diphenylphosphino)-1,1′-binaphthyl) and xantphos (9,9′-dimethyl-4,5-bis(diphenyl-phosphino)xanthene), were prepared and characterized by elemental analysis and ESI-MS. The solid compounds show a r.t. phosphorescence. While the binap complex emits from an intraligand (IL) triplet, the luminescence of the biphep complex originates from a metal-centered (MC) triplet which is presumably lowered by gold–gold interaction. The xantphos complex displays a dual phosphorescence. In this case, the emitting triplets are of the IL and MC type.

Aurophilic attraction and excited-state properties of binuclear Au(I) complexes with bridging phosphine and/or thiolate ligands: An ab initio study

The ground- and excited-state structures were fully optimized for a series of neutral binuclear Au(I) thiolates, [Au2(dpm)(SCH2S)] (1) (dpm=bis(diphosphino)methane), trans-[Au2(PH2CH2S)2] (2), and trans-[Au2(SHCH2S)2] (3), by using the MP2 and CIS methods, respectively. The calculated AuI–AuI distances of about 3.0 Å in the ground state of the complexes are indicative of aurophilic attraction between the two Au(I) atoms, while in their excited states the separations are greatly shortened (about 2.7–2.9 Å). The promotion of Au d electron or S p electron into the bonding sσ and/or pσ lowest unoccupied molecular orbital of AuI–AuI results in such reinforcement of aurophilicity in the excited state. In the CIS calculations of the three Au(I) thiolates, we obtained the lowest-energy phosphorescent emission in the solid state for each of the complexes. The 462 nm emission of 1 was assigned as Au→S charge transfer (MLCT) transition. But for 3, the charge transfer localized on the Au centers, Au3(sσ)→1Au(dσ*) (metal-centered charge transfer, MCCT), plays a main role in the 413 nm emission. Both the MCCT and MLCT transitions are important in the 323 nm emission of 2. The results indicated that AuI–AuI aurophilicity clearly influences luminescent properties of these complexes.

The structure and dynamic behaviour of disubstituted derivatives of [Rh6(CO)16] containing heterobidentate bridging phosphine ligands

The solution structures and dynamic behaviour of [Rh6(CO)14(μ-PX)] [PX = diphenyl(2-pyridyl)phosphine, (PN); diphenyl(2-thienyl)phosphine, (PS); diphenyl(vinyl)phosphine, (PV)] have been studied by multinuclear NMR and the X-ray structure of [Rh6(CO)14(μ,κ3-PV)] is reported. In solution, the above clusters undergo a variety of localised CO-exchanges and the mechanisms of these are discussed. The PV ligand in [Rh6(CO)14(μ,κ3-PV)] is hemilabile and exhibits facile exchange/reorientation of the vinyl group.