Cyclooctadiene Complexes Research Articles

Metallaantiaromaticity of 10-Platinacorrole Complexes.

The aromaticity of cyclic π-conjugated organometallic compounds is known as metallaaromaticity. π-Conjugated metallacycles, such as metallabenzenes and metallapentalenes, have been investigated in order to understand the involvement of the d electrons from the metal center in the π-conjugated systems of the organic ligands. Here, we report the synthesis of Pd(II) 10-platinacorrole complexes with cyclooctadiene (COD) and norbornadiene (NBD) ligands. While the Pd(II) 10-platinacorrole COD complex adopts a distorted structure without showing appreciable antiaromaticity, the corresponding NBD complex exhibits a distinct antiaromatic character due to its highly planar conformation. Detailed density functional theory (DFT) calculations revealed that two d orbitals are involved in macrocyclic π-conjugation. We furthermore demonstrated that Craig-Möbius antiaromaticity is not present in the studied system. The synthesis of 10-platinacorroles enables a systematic comparison of the antiaromaticity and aromaticity of closely related porphyrin analogues, providing a better understanding of π-conjugation that involves d orbitals.

Identification of Cyclohexadienyl Hydrides as Intermediates in Molybdenum‐Catalyzed Arene Hydrogenation

AbstractTreatment of phosphino(imino)pyridine (PIP) molybdenum cyclooctadiene (COD) complexes [(PIP)Mo(COD)] with dihydrogen in the presence of benzene selectively furnished the molybdenum cyclohexadienyl hydrides [(PIP)MoH(η5‐C6H7)], which are precatalysts for the hydrogenation of benzene to cyclohexane. [(PIP)MoH(η5‐C6H7)] arises from a rarely observed insertion of benzene into a molybdenum‐hydride bond, a key step in the molybdenum‐catalyzed homogeneous hydrogenation of arenes. The reaction with toluene afforded a single isomer of the corresponding molybdenum cyclohexadienyl hydride while para‐xylene predominantly formed the molybdenum η6‐arene complex with the insertion product being a minor component. Addition of carbon monoxide to a cyclohexane‐d12 solution of [(PIP)MoH(η5‐C6H7)] liberated cyclohexadiene, providing experimental support for a higher kinetic barrier for the subsequent steps en route to cycloalkanes.

Identification of Cyclohexadienyl Hydrides as Intermediates in Molybdenum-Catalyzed Arene Hydrogenation.

Treatment of phosphino(imino)pyridine (PIP) molybdenum cyclooctadiene (COD) complexes [(PIP)Mo(COD)] with dihydrogen in the presence of benzene selectively furnished the molybdenum cyclohexadienyl hydrides [(PIP)MoH(η5 -C6 H7 )], which are precatalysts for the hydrogenation of benzene to cyclohexane. [(PIP)MoH(η5 -C6 H7 )] arises from a rarely observed insertion of benzene into a molybdenum-hydride bond, a key step in the molybdenum-catalyzed homogeneous hydrogenation of arenes. The reaction with toluene afforded a single isomer of the corresponding molybdenum cyclohexadienyl hydride while para-xylene predominantly formed the molybdenum η6 -arene complex with the insertion product being a minor component. Addition of carbon monoxide to a cyclohexane-d12 solution of [(PIP)MoH(η5 -C6 H7 )] liberated cyclohexadiene, providing experimental support for a higher kinetic barrier for the subsequent steps en route to cycloalkanes.

Metal Complexes as Antifungals? From a Crowd-Sourced Compound Library to the First In Vivo Experiments.

There are currently fewer than 10 antifungal drugs in clinical development, but new fungal strains that are resistant to most current antifungals are spreading rapidly across the world. To prevent a second resistance crisis, new classes of antifungal drugs are urgently needed. Metal complexes have proven to be promising candidates for novel antibiotics, but so far, few compounds have been explored for their potential application as antifungal agents. In this work, we report the evaluation of 1039 metal-containing compounds that were screened by the Community for Open Antimicrobial Drug Discovery (CO-ADD). We show that 20.9% of all metal compounds tested have antimicrobial activity against two representative Candida and Cryptococcus strains compared with only 1.1% of the >300,000 purely organic molecules tested through CO-ADD. We identified 90 metal compounds (8.7%) that show antifungal activity while not displaying any cytotoxicity against mammalian cell lines or hemolytic properties at similar concentrations. The structures of 21 metal complexes that display high antifungal activity (MIC ≤1.25 μM) are discussed and evaluated further against a broad panel of yeasts. Most of these have not been previously tested for antifungal activity. Eleven of these metal complexes were tested for toxicity in the Galleria mellonella moth larva model, revealing that only one compound showed signs of toxicity at the highest injected concentration. Lastly, we demonstrated that the organo-Pt(II) cyclooctadiene complex Pt1 significantly reduces fungal load in an in vivo G. mellonella infection model. These findings showcase that the structural and chemical diversity of metal-based compounds can be an invaluable tool in the development of new drugs against infectious diseases.

Rhodium-Iodide Complex on a Catalytically Active SiO2 Surface for One-Pot Hydrosilylation-CO2 Cycloaddition.

In this study, a novel Rh-iodide complex was synthesized through a surface reaction between an immobilized Rh cyclooctadiene complex and alkylammonium iodide (N+ I- ) on SiO2 . In the presence of ammonium cations, the SiO2 -supported Rh-iodide complex could be effectively used for the one-pot synthesis of various silylcarbonate derivatives starting from epoxy olefins, hydrosilanes, and CO2 . The maximum turnover numbers (TONs) for the hydrosilylation reaction and the CO2 cycloaddition were 7600 (Rh) and 130 (N+ I- ), respectively. The catalyst exhibited much higher performance for hydrosilylation than solely the Rh complex on SiO2 . The mechanism of the Rh-catalyzed hydrosilylation reaction and the local structure of Rh, which is affected by the co-immobilized N+ I- , were investigated by using Rh and I K-edge XAFS and XPS. Analysis of the XAFS profiles indicated the presence of a Rh-I bond. The Rh unit was in its electron-rich state. Curve-fitting analysis of the Rh K-edge EXAFS profiles suggests dissociation of the cycloocta-1,5-diene (COD) ligand from the Rh center. Results from spectroscopic and kinetic analyses revealed that the high activity of the catalyst (during hydrosilylation) could be attributed to a decrease in steric hindrance and the electron-rich state of the Rh. The decrease in the steric hindrance could be attributed to the absence of COD, and the electron-rich state promoted the oxidative addition of Si-H. To the best of our knowledge, this is the first example of a one-pot silylcarbonate synthesis as well as a determination of a novel surface Rh-iodide complex and its catalysis.

Platinum Cyclooctadiene Complexes with Activity against Gram-positive Bacteria.

Antimicrobial resistance is a looming health crisis, and it is becoming increasingly clear that organic chemistry alone is not sufficient to continue to provide the world with novel and effective antibiotics. Recently there has been an increased number of reports describing promising antimicrobial properties of metal‐containing compounds. Platinum complexes are well known in the field of inorganic medicinal chemistry for their tremendous success as anticancer agents. Here we report on the promising antibacterial properties of platinum cyclooctadiene (COD) complexes. Amongst the 15 compounds studied, the simplest compounds Pt(COD)X2 (X=Cl, I, Pt1 and Pt2) showed excellent activity against a panel of Gram‐positive bacteria including vancomycin and methicillin resistant Staphylococcus aureus. Additionally, the lead compounds show no toxicity against mammalian cells or haemolytic properties at the highest tested concentrations, indicating that the observed activity is specific against bacteria. Finally, these compounds showed no toxicity against Galleria mellonella at the highest measured concentrations. However, preliminary efficacy studies in the same animal model found no decrease in bacterial load upon treatment with Pt1 and Pt2. Serum exchange studies suggest that these compounds exhibit high serum binding which reduces their bioavailability in vivo, mandating alternative administration routes such as e. g. topical application.

Easy Access to Versatile Catalytic Systems for C-H Activation and Reductive Amination Based on Tetrahydrofluorenyl Rhodium(III) Complexes.

On the basis of the 1,2,3,4-tetrahydrofluorenyl ligand, a simple approach was developed to new effective rhodium catalysts for the construction of C-C and C-N bonds. The halide compounds [(η5 -tetrahydrofluorenyl)RhX2 ]2 (2 a: X=Br; 2 b: X=I) were synthesized by treatment of the bis(ethylene) derivative (η5 -tetrahydrofluorenyl)Rh(C2 H4 )2 (1 a) with halogens. An analogous reaction of the cyclooctadiene complex (η5 -tetrahydrofluorenyl)Rh(cod) (1 b) with I2 is complicated by the side formation of [(cod)RhI]2 . The reaction of 2 b with 2,2'-bipyridyl leads to cation [(η5 -tetrahydrofluorenyl)Rh(2,2'-bipyridyl)I]+ (3). The halide abstraction from 2 a,b with thallium or silver salts allowed us to prepare sandwich compounds with incoming cyclopentadienyl, dicarbollide and mesityleneligands [(η5 -tetrahydrofluorenyl)RhCp]+ (4), (η5 -tetrahydrofluorenyl)Rh(η-7,8-C2 B9 H11 ) (5), and [(η5 -tetrahydrofluorenyl)Rh(η-mesitylene)]2+ (6). The structures of 1 b, 2 b ⋅ 2I2 , 3PF6 , 4TlI4 , 5, and [(cod)RhI]2 were determined by X-ray diffraction. Compounds 2 a,b efficiently catalyze the oxidative coupling of benzoic acids with alkynes to selectively give isocoumarins or naphthalenes, depending on the reaction temperature. Moreover, they showed moderate catalytic activity in other annulations of alkynes with aromatic compounds (such as benzamide, acetanilide, etc.) which proceed through CH activation. Compound 2 b also effectively catalyzes the reductive amination of aldehydes and ketones in the presence of carbon monoxide and water via water-gas shift reaction, giving amines in high yields (67-99 %).

η2-Alkene Complexes of [Rh(PONOP-iPr)(L)]+ Cations (L = COD, NBD, Ethene). Intramolecular Alkene-Assisted Hydrogenation and Dihydrogen Complex [Rh(PONOP-iPr)(η-H2)]+

Rhodium-alkene complexes of the pincer ligand κ3-C5H3N-2,6-(OPiPr2)2 (PONOP-iPr) have been prepared and structurally characterized: [Rh(PONOP-iPr)(η2-alkene)][BArF4] [alkene = cyclooctadiene (COD), norbornadiene (NBD), ethene; ArF = 3,5-(CF3)2C6H3]. Only one of these, alkene = COD, undergoes a reaction with H2 (1 bar), to form [Rh(PONOP-iPr)(η2-COE)][BArF4] (COE = cyclooctene), while the others show no significant reactivity. This COE complex does not undergo further hydrogenation. This difference in reactivity between COD and the other alkenes is proposed to be due to intramolecular alkene-assisted reductive elimination in the COD complex, in which the η2-bound diene can engage in bonding with its additional alkene unit. H/D exchange experiments on the ethene complex show that reductive elimination from a reversibly formed alkyl hydride intermediate is likely rate-limiting and with a high barrier. The proposed final product of alkene hydrogenation would be the dihydrogen complex [Rh(PONOP-iPr)(η2-H2)][BArF4], which has been independently synthesized and undergoes exchange with free H2 on the NMR time scale, as well as with D2 to form free HD. When the H2 addition to [Rh(PONOP-iPr)(η2-ethene)][BArF4] is interrogated using pH2 at higher pressure (3 bar), this produces the dihydrogen complex as a transient product, for which enhancements in the 1H NMR signal for the bound H2 ligand, as well as that for free H2, are observed. This is a unique example of the partially negative line-shape effect, with the enhanced signals that are observed for the dihydrogen complex being explained by the exchange processes already noted.

Inter-ligand delocalisations in transition metal complexes containing multiple non-innocent ligands.

Systematic bonding analysis has been carried out for transition metal complexes containing more than one redox-active/non-innocent ligand. These complexes include tetralithio spiroaromatic palladole, dicupra[10]annulene, highly reduced nickel cyclooctadiene complex and tris(dithiolene)vanadium(iv). Our detailed bonding analysis reveals a common inter-ligand delocalisation pattern in these cases.

Synthesis and crystal structure of the iridium(I) carbene complex with a pair of hydrogen wing tips

The iridium(I) cyclooctadiene complex with two (3-tert-butylimidazol-2-ylidene) ligands [(H-Im t Bu)2Ir(COD)]+PF 6 − (C22H32PF6IrN4) has been prepared, and its crystal structure is determined by X-ray diffraction. Complex exhibits slightly distorted square planar configurations around the metal atom, which is coordinated by two H-Im t Bu ligands and one cyclooctadiene group. The new iridium carbene complex has a pair of hydrogen wing tips. The Ir−Ccarbene bond lengths are 2.066(5) and 2.052(5) A, and the bond angle C−Ir−C between these bonds is 95.54(19)°. The dihedral angle between two imidazol-2-ylidene rings is 86.42°.

Synthesis and crystal structure of the rhodium(I) cyclooctadiene complex with bis(3-tert-butylimidazol-2-ylidene)borate ligand

The rhodium(I) cyclooctadiene complex with the bis(3-tert-butylimidazol-2-ylidene)borate ligand [H2B(Im t Bu)2]Rh(COD) C22H36BN4Rh, has been prepared, and its crystal structure is determined by X-ray diffraction. Complex exhibits slightly distorted square planar configurations around the metal center, which is coordinated by the bidentate H2B(Im t Bu)2 and one cyclooctadiene group. The Rh–Ccarbene bond lengths are 2.043(4) and 2.074(4) A, and the bond angle C–Rh1–C is 82.59°. The dihedral angle between two imidazol-2-ylidene rings is 67.30°.

Oxidation and β-Alkylation of Alcohols Catalysed by Iridium(I) Complexes with Functionalised N-Heterocyclic Carbene Ligands.

The borrowing hydrogen methodology allows for the use of alcohols as alkylating agents for CC bond forming processes offering significant environmental benefits over traditional approaches. Iridium(I)-cyclooctadiene complexes having a NHC ligand with a O- or N-functionalised wingtip efficiently catalysed the oxidation and β-alkylation of secondary alcohols with primary alcohols in the presence of a base. The cationic complex [Ir(NCCH3 )(cod)(MeIm(2- methoxybenzyl))][BF4 ] (cod=1,5-cyclooctadiene, MeIm=1-methylimidazolyl) having a rigid O-functionalised wingtip, shows the best catalyst performance in the dehydrogenation of benzyl alcohol in acetone, with an initial turnover frequency (TOF0 ) of 1283 h(-1) , and also in the β-alkylation of 2-propanol with butan-1-ol, which gives a conversion of 94 % in 10 h with a selectivity of 99 % for heptan-2-ol. We have investigated the full reaction mechanism including the dehydrogenation, the cross-aldol condensation and the hydrogenation step by DFT calculations. Interestingly, these studies revealed the participation of the iridium catalyst in the key step leading to the formation of the new CC bond that involves the reaction of an O-bound enolate generated in the basic medium with the electrophilic aldehyde.

Catalytic Transfer of Magnetism using a Neutral Iridium Phenoxide Complex.

A novel neutral iridium carbene complex Ir(κC,O-L1)(COD) (1) [where COD = cyclooctadiene and L1 = 3-(2-methylene-4-nitrophenolate)-1-(2,4,6-trimethylphenyl) imidazolylidene] with a pendant alkoxide ligand has been prepared and characterized. It contains a strong Ir-O bond and X-ray analysis reveals a distorted square planar structure. NMR spectroscopy reveals dynamic solution state behavior commensurate with rapid seven-membered ring flipping. In CD2Cl2 solution, under hydrogen at low temperature, this complex dominates although it exists in equilibrium with a reactive iridium dihydride cyclooctadiene complex. 1 reacts with pyridine and H2 to form neutral Ir(H)2(κC,O-L1)(py)2 which also exists in two conformers that differ according to the orientation of the seven-membered metallocycle and whilst its Ir-O bond remains intact, the complex undergoes both pyridine and H2 exchange. As a consequence, when placed under parahydrogen, efficient polarization transfer catalysis (PTC) is observed via the Signal Amplification By Reversible Exchange (SABRE) approach. Due to the neutral character of this catalyst, good hyperpolarization activity is shown in a wide range of solvents for a number of substrates. These observations reflect a dramatic improvement in solvent tolerance of SABRE over that reported for the best PTC precursor IrCl(IMes)(COD). For THF, the associated 1H NMR signal enhancement for the ortho proton signal of pyridine shows an increase of 600-fold at 298 K. The level of signal enhancement can be increased further through warming or varying the magnetic field experienced by the sample at the point of catalytic magnetization transfer.

P–H activation of secondary phosphanes on a parent amido diiridium complex

Selected secondary phosphanes (H-PR2; R = Ph, Cy, (i)Pr) smoothly react with a parent amido-bridged diiridium cyclooctadiene complex affording mixed amido/(bis)phosphido dinuclear species. A careful investigation of the reaction profile, carried out by experimental and theoretical tools, revealed that, after an initial amido/phosphido exchange, at low temperatures a second molecule of secondary phosphane adds to the dinuclear system through an oxidative addition process leading to a hydrido amido/bis(phosphido) mixed-valence complex [Ir(III)/Ir(I)]. These species rearrange above -10 °C into the most stable isomer that arises from a migration of the hydrido moiety to one of the =CH fragments of a coordinated cod molecule, a transformation facilitated by the formation of an intermetallic bond. Further heating of these species reductively eliminates ammonia affording bis(phosphido)-metal-metal bonded complexes.

Synthesis and structure of (tricarbollide)iodide iridium complex [(η-1-ButNH-1,7,9-C3B8H10)IrI2

Cyclooctadiene complex (η-1-ButNH-1,7,9-C3B8H10)Ir(cod) (1) was obtained by the reaction of [(7-ButNH-7,8,9-C3B8H10)]Tl with [(cod)IrCl]2 in the presence of TlPF6. The reaction of 1 with I2 gave diiodide [(η-1-ButNH-1,7,9-C3B8H10)IrI2]2 (2a). According to the X-ray diffraction data, complex 2a has a dimeric structure with two bridging iodine atoms.

Chiral recognition in contact ion-pairs; observation, characterization and analysis

Chiral ion-pairs are playing an increasingly important role in asymmetric catalysis. In order to understand the source of molecular recognition, a simple model system based on a BINAP-Rh(dialkene) cation and a BINOL borate anion was studied for both diastereomeric forms. It was discovered that one of these was energetically preferred and methods for quantifying the difference were devised using 31P NMR. The effect was general over a series of bis-binaphthyl borate anions, and required cycloocta-1,5-diene rather than bicyclohepta[2.2.1]diene as the dialkene component. The 1H NMR spectra of the cation in the parent ion pairs showed a range of anion-induced chemical shifts, their specificity implying selectivity in the ion-pair contact. X-ray structures of the two cyclooctadiene complexes were obtained and it proved possible to analyse the preferred contacts of individual ion-pairs. Rather than involving specific π–π, CH–π and CH–O intermolecular forces, the preference for one diastereomer in the COD case is based on dispersion forces that respond to the ability to pack the dialkene, and particularly its sp3 units, for maximum interaction with a concave naphthyl fragment. This interpretation is supported by analysis of one related NBD complex.

Iridium and Rhodium Complexes with the Hemilabile Ligand [2‐(1,3‐Dioxolane‐2‐yl)phenyl]diphenylphosphane – Behaviour in Solution and Structural Characterization

Abstract[MCl(L2)]2 (M = Ir, L2 = 1,5‐cyclooctadiene; M = Rh, L2 = norbornadiene) reacts with [2‐(1,3‐dioxolane‐2‐yl)phenyl]diphenylphosphane (1) to afford [MCl(L2)(P~O)] (M = Ir, 2; M = Rh, 3), in which the ligand is P‐monodentate. Complex 3 reacts with AgClO4 to give [Rh(Nbd)(PO)]ClO4 (4), in which the ligand is P,O‐bidentate. Complex 2 is static at room temp., whereas 3 and 4 undergo intramolecular exchanges, which are fast at room temperature and slow at 223 K. The conformational changes in 4 are still fast at 223 K. Complexes 2–4 react with CO to afford trans‐[MCl(CO)(P~O)2] (M = Ir, 5; M = Rh, 6) or trans‐[Rh(CO)2(P~O)2]ClO4 (7). Cyclooctadiene complexes react with PPh2(o‐C6H4CHO) to afford [MClH(PPh2(o‐C6H4CO))(PO] (M = Ir, 8; M = Rh, 9), in which 1 is chelating. Complex 8 contains a single diastereomer, is static in the 303–213 K range and reacts with CO to form [IrClH(PPh2(o‐C6H4CO))(P~O)(CO)] (10). Complex 9 contains two diastereomers 9a/9b in a 95:5 ratio that undergo interconversion, which is slow at low temperature, and reacts with CO to undergo reductive elimination of aldehyde, cleavage of the Rh–O bond and scrambling of phosphanes. A mixture of trans‐[RhCl(CO)(κ1‐PPh2(o‐C6H4CHO))(P~O)] (11), 6 and trans‐[RhCl(CO)(κ1‐PPh2(o‐C6H4CHO))2] is formed. Bubbling of nitrogen transforms 11 back into 9. Compound 2 reacts with hydrogen to give the fluxional [IrCl(H)2(P~O)(PO)] (12) with trans P atoms and cis H atoms, which attains coalescence at 203 K. Complex 12 reacts with mono‐ or bidentate ligands to afford static [IrCl(H)2(P~O)2L] (L = CO, 13; py, 14; nPrNH2, 15) or [Ir(H)2(P~O)2(en)]BPh4 (16, en = ethylenediamine). Abstraction of halide from 12 affords [Ir(H)2(PO)2]BPh4 (17), which is fluxional owing to interconversion between only two of the possible four diastereomers, for which ΔH‡ = 54.7 ± 0.7 kJ mol–1 and ΔS‡ = 4.7 ± 0.2 J K–1 mol–1. The X‐ray structures of 8, 15 and 16 are also reported.

Rh(I) complexes with fluorinated 2,2′-bipyridines

Rh(I) cyclooctadiene (cod) and carbonyl complexes with fluorinated 2,2′-bipyridines (N-N) have been prepared. The fluorinated tail was introduced as an alky group or through an ester function in the 4,4′- or 5,5′-positions. The X-ray structure of the cyclooctadiene complexes [Rh(cod)(4)][PF6] and [Rh(cod)(L4)][PF6] shows the square-planar coordination around the metal centre, and, in the case of complex with the ester function [Rh(cod)(4)][PF6] the fluorinated tails adopt a relative anti disposition of the ester groups. The electronic properties of the N-N ligands were studied through the stretching ν(CO) infrared frequencies of the corresponding carbonyl complexes [Rh(CO)2(N-N)][PF6].

On the isomerization of cyclooctyne into cycloocta-1,3-diene: synthesis, characterization and structure of a dinuclear platinum(ii) complex with a μ-η2:η2-1,3-COD ligand

The Zeise's salt type cyclooctyne compound [K(18C6)][PtCl(3)(COC)] (1; COC = cyclooctyne; 18C6 = 18-crown-6) was found to react in chloroform solution at room temperature within several weeks yielding the dinuclear cyclooctadiene compound [K(18C6)](2)[(PtCl(3))(2)(μ-η(2):η(2)-1,3-COD)] (2; 1,3-COD = cycloocta-1,3-diene) and non-coordinated cycloocta-1,3-diene. The identity of 2 was confirmed by microanalysis, NMR spectroscopy ((1)H, (13)C) and electrospray ionization mass spectrometry (ESI-MS). A single-crystal X-ray diffraction analysis of 2 exhibited a bridging μ-η(2):η(2)-cycloocta-1,3-diene ligand with non-conjugated double bonds each coordinated to a PtCl(3) fragment. On the basis of DFT calculations as well as energy decomposition analyses (EDA), charge decomposition analyses (CDA) and natural bond orbital (NBO) analyses the peculiarities of the nature of the Pt-C bonds in the dinuclear complex anion [(PtCl(3))(2)(μ-η(2):η(2)-1,3-COD)](2-) (2a') compared with those in mononuclear olefin complexes of Zeise's salt type [PtCl(3)L](-) (L = η(2)-1,3-COD, 3a'; cis-but-2-ene, 4a'; COE, 5a'; COE = cyclooctene) are discussed. Furthermore, the driving force for the strongly exergonic reaction with formation of the cyclooctadiene complex 2a' was found to be a significant release of ring strain of the cyclooctyne ligand in the starting compound 1.

Structure and solution behaviour of cyclooctadiene complexes of platinum(II)

The substitution behaviour of [PtCl(R)(COD)] (R − = Me and Fc) complexes, by the stepwise addition of phosphine ligands, L (L = PPh 3, PEt 3 and P(NMe 2) 3), were investigated in situ by 1H and 31P NMR spectroscopy. Addition of less than two equivalents of the phosphine ligand results in the formation of dimeric molecules with the general formula trans-[Pt(R)(μ-Cl)(L)] 2 for the sterically demanding systems where R − = Me/L = P(NMe 2) 3 and R − = Fc/L = PEt 3, PPh 3 and P(NMe 2) 3 while larger quantities resulted in cis- and trans mixtures of mononuclear complexes being formed. In the case of the relatively small steric demanding, strongly coordinating, PEt 3 ligand the trans-[PtCl(R)(PEt 3) 2] mononuclear complexes were exclusively observed in both cases. The crystal structures of the two substrates, [PtCl(R)(COD)] (R − = Me or Fc), as well as the cis-[PtCl(Fc)(PPh 3) 2] substitution product are reported.