Dppe Complexes Research Articles

Carboxylation of a Palladacycle Formed via C(sp3 )-H Activation: Theory-Driven Reaction Design.

Theory-driven organic synthesis is a powerful tool for developing new organic transformations. A palladacycle(II), generated from 8-methylquinoline via C(sp3 )-H activation, is frequently featured in the scientific literature, albeit that the reactivity toward CO2 , an abundant, inexpensive, and non-toxic chemical, remains elusive. We have theoretically discovered potential carboxylation pathways using the artificial force induced reaction (AFIR) method, a density-functional-theory (DFT)-based automated reaction path search method. The thus obtained results suggest that the reduction of Pd(II) to Pd(I) is key to promote the insertion of CO2 . Based on these computational findings, we employed various one-electron reductants, such as Cp*2 Co, a photoredox catalyst under blue LED irradiation, and reductive electrolysis ((+)Mg/(-)Pt), which afforded the desired carboxylated products in high yields. After screening phosphine ligands under photoredox conditions, we discovered that bidentate ligands such as dppe promoted this carboxylation efficiently, which was rationally interpreted in terms of the redox potential of the Pd(II)-dppe complex as well as on the grounds of DFT calculations. We are convinced that these results could serve as future guidelines for the development of Pd(II)-catalyzed C(sp3 )-H carboxylation reactions with CO2 .

Kinetics of the SN1 Dissociation of Ligands L (Nitriles, Phosphines) in the Complexes [CpFe(P-P)L]PF6 with Variable Chelate Ring Size. A Surprising Bimolecular Substitution in the Nonchelate Complex [CpFe(PPh2Me)2L]PF6

The complexes [CpFe{Ph2P(CH2)nPPh2}NCMe]PF6, [CpFe(PPh2Me)2NCMe]PF6, and [CpFe{Ph2P(CH2)nPPh2}PPh2(OR)]PF6, R = Me, Et, and iPr, with chelate ring sizes between 4 and 7 were synthesized and characterized by spectroscopy and X-ray analysis. In these complexes, the monodentate ligands acetonitrile and PPh2(OR) tend to dissociate. The kinetics of the ligand exchanges MeCN/P(OMe)3 and PPh2(OR)/P(OMe)3 was measured. In the acetonitrile series, the first-order reaction of the five-membered chelate complex [CpFe(dppe)NCMe]PF6 had a half-life of 549 min in CDCl3 at 293 K. The other chelate complexes [CpFe(P-P)NCMe]PF6 and the nonchelate analogue [CpFe(PPh2Me)2NCMe]PF6 reacted faster by factors of 20–50. The PPh2(OR) series revealed a dramatic difference between the complexes [CpFe(P-P)PPh2(OR)]PF6 with five- and six-membered chelate rings. The PPh2(OR)/P(OMe)3 exchange in the dppp complex (six-membered chelate ring) was 500 times faster than in the dppe complex (five-membered chelate ring). This is due to the inc...

Oxidative Addition of the N–H Bond of Ammonia to Iridium Bis(phosphane) Complexes: A Combined Experimental and Theoretical Study

The chloro complex [IrCl(cod)(dppe)] (dppe = bis(diphenylphosphane)ethane; cod = 1,5-cyclooctadiene) was found to react with gaseous ammonia, affording the amido-bridged diiridium complex [{Ir(μ-NH2)H(dppe)(NH3)}2][Cl]2 (1), whose molecular structure has been solved by X-ray methods. The related cationic complexes [{Ir(μ-NH2)H(dppp)(NH3)}2][BF4]2 (3) and [{Ir(μ-NH2)H(dppb)(NH3)}2][BF4]2 (4) (dppp = bis(diphenylphosphane)propane; dppb = bis(diphenylphosphane)butane) are only accessible from the reactions of NH3(g) with the cationic starting materials [Ir(cod)(dppp)][BF4] and [Ir(cod)(dppb)][BF4], respectively. The formation of these species comes from an oxidative addition of an N–H bond of ammonia to the metals. The main structural difference between complex 2 and 3/4 relies on the relative stereochemistry of both ammonia and hydrido ligands; their cisoidal disposition in dppe complex [{Ir(μ-NH2)H(dppe)(NH3)}2][BF4]2 (2) directed the reactivity toward dppm (dppm = bis(diphenylphosphane)methane), generatin...

NC Palladacycles and C,C-chelating phosphorus ylide complexes: synthesis, X-ray characterization, and comparison of the catalytic activity in the Suzuki-Miyaura reaction

Six secondary amine palladacycles bearing monodentate ligands (1a, 2a), 1,2-bis(diphenylphosphino)ethane (dppe) and 1,3-bis(diphenylphosphino)propane (dppp) containing bridging and bidentate ligands (1b, 2b–d), and four C,C-type phosphorus ylide complexes containing thiourea (tu) (3a), phenyl isothiocyanate (4a), and bridging and terminal azide groups (5 and 5a) have been synthesized. Resulting complexes have been characterized by elemental analyses, IR, 1H-, 13C{1H}-, and 31P{1H}-NMR spectroscopy with single crystal X-ray structure determination of 1a and 2a. The Pd in 1a and 2a occupies the center of a slightly distorted square planar environment formed by Caryl, Namine, Npyridine, and Cl. The catalytic efficiency of complexes showed that in most cases, amine palladacycles display better catalytic activities than the phosphorus ylide Pd(II) complexes. Comparison between bidentate and bridging dppe complexes showed that dppe-bridged dimer 2d has higher catalytic activity than dppe bidentate complex.

Nickel‐Molybdenum and Nickel‐Tungsten Dithiolates: Hybrid Models for Hydrogenases and Hydrodesulfurization

AbstractThe heterobimetallic complexes [(dppe)Ni(pdt)Mo(CO)4], [(dcpe)Ni(pdt)Mo(CO)4], [(dppe)Ni(pdt)W(CO)4] and [(dcpe)Ni(pdt)W(CO)4] {dppe = Ph2P(CH2)2PPh2; dcpe = Cy2P(CH2)2PCy2; pdt2– = –S(CH2)3S–} have been prepared and structurally characterized. The internuclear separation in these NiIIM0 species is highly sensitive to diphosphine basicity and is smallest in the dppe complexes wherein the planar Ni centres are electron‐poor and require interaction with the group 6 metal. The NiIIW0 species [(dppe)Ni(pdt)W(CO)4] was converted into its stable conjugate acid [(dppe)Ni(pdt)HW(CO)4]+, a rare example of a nickel–tungsten hydride. This NiIIHWII complex is an electrocatalyst for H+ reduction and is relevant to both biological and synthetic H2‐processing catalysts.

Cobalt Catalysis in the Gas Phase: Experimental Characterization of Cobalt(I) Complexes as Intermediates in Regioselective Diels–Alder Reactions

In situ-formed cobalt(I) complexes are proposed to act as efficient catalysts in regioselective Diels-Alder reactions of unactivated substrates such as 1,3-dienes and alkynes. We report the first experimental evidence for the in situ reduction of CoBr2(dppe) [dppe = 1,2-bis(diphenylphosphino)ethane] by Zn/ZnI2 to [Co(I)(dppe)](+) by means of electrospray MS(n) experiments. Additionally, the reactivities of Co(II) and Co(I) dppe complexes toward the Diels-Alder substrates isoprene and phenylacetylene were probed in gas-phase ion/molecule reactions (IMRs). Isoprene and phenylacetylene were introduced into the mass spectrometer via the buffer gas flow of a linear ion trap. The IMR experiments revealed a significantly higher substrate affinity of [Co(I)(dppe)](+) compared with [Co(II)Br(dppe)](+). Furthermore, the central intermediate of the solution-phase cobalt-catalyzed Diels-Alder reaction, [Co(I)(dppe)(isoprene)(phenylacetylene)](+), could be generated via IMR and examined in the gas phase. Collision activation of this complex ion delivered evidence for the gas-phase reaction of isoprene with phenylacetylene in the coordination sphere of the cobalt ion. The experimental findings are consistent with the results of quantum-chemical calculations on all of the observed Co(I) dppe complex ions. The results constitute strong analytical evidence for the formation and importance of different cobalt(I) species in regioselective Diels-Alder reactions of unactivated substrates and identify [Co(I)(dppe)](+) as the active Diels-Alder catalyst.

Bite Angle Effects of κ2P-dppm vs κ2P-dppe in Seven-Coordinate Complexes: A DFT Case Study

This paper predicts the effects of replacing dppm (bis(diphenylphosphino)methane) with dppe (1,2-bis(diphenylphosphino)ethane) in seven-coordinate organometallic complexes by employing density functional theory (DFT) computations for a case example: WI2(CO)(κ2P-dppm)(η2:η2-nbd) (nbd = norbornadiene), an intermediate in the W(II)-catalyzed ring-opening metathesis polymerization (ROMP) of nbd. Effects on both structure and ligand binding energy (i.e., reactivity) were investigated. For the known W–dppm complex (crystal structure provided here), of 37 energy-distinct stereoisomers found, only one low-energy stereoisomer is predicted, and it agrees with the known X-ray crystal structure, lending faith to the conformer search procedure. For the as yet unknown W–dppe complex, of 31 energy-distinct stereoisomers found, two low-energy stereoisomers are predicted. The computed DFT ligand binding energies {W–P, W–ene, W–CO, W+–I–} are {9, 17, 44, 102} kcal mol–1 for the W–dppm complex and {3, 15, 37, 95} for the W–dppe complex. The conclusion is that the increased PWP bite angle of dppe vs dppm will reduce all ligand binding energies due to increased interligand steric repulsion.

Structural comparison of [PdX2(P–P)] complexes (X− = Cl, Br and I; P–P = α,ω-bis(diphenylphosphino)alkanes) and their trends of redox potentials

X-ray crystallographic analyses revealed that the Pd–P and Pd–X bond lengths of [PdX2(P–P)] complexes (X−=Cl, Br and I and P–P=Ph2P(CH2)nPPh2; n=1: dppm, 2: dppe, 3: dppp, 4: dppb) are: Pd–P (dppm, dppe)<Pd–P (dppp, dppb) and Pd–X (dppm, dppe)>Pd–X (dppp, dppb). The oxidation potentials values, E½(ox), of the shorter Pd–P and longer Pd–X bond lengths in the dppm and dppe complexes are high and reflect strong dxy (dπ (Pd)) interaction with dx2-y2 (dσ∗ (Pd)) and that this interaction is less dependent on X−. The longer Pd–P and shorter Pd–X bonds for the dppp and dppb complexes reflect that the dx2-y2 (dσ∗ (Pd)) interaction is largely dependent on X−. The reduction potential, E½(red), which reflects the dx2-y2 (dσ∗ (Pd) LUMO energy, and the oxidation potential, E½(ox), which reflects the (dxy (dπ (Pd) HOMO energy were, determined. The E½(red) and E½(ox) values indicate the σ-bonding properties and π-interaction in the system, respectively. Good linear relationships were observed between the potentials difference [E½(ox)−E½(red)] and the ligand-field transition energy (dπ (dxy)→dσ∗ (dx2-y2)) in the series of dihalogenopalladium(II) complexes. The linear relationship shows that the energies of the d–d transitions and ΔE(Redox) of the dppm and dppe complexes are less dependent on X− whilst those of the dppp and dppb are largely X− dependent.

Synthesis and Structural Studies of Tetrahedral [M(Ph2P(CH=CH)PPh2)2]BPh4 and [M(Ph2P(CH2)nPPh2)2]BPh4 (n = 2, 3) Complexes for M = Copper(I), Silver(I), and Gold(I)

Tetraphenylborate salts of the 1 : 2 tetrahedral bis(bidentate) complexes of copper(i), silver(i), and gold(i) with cis-bis(diphenylphosphino)ethene (dppey), [M(Ph2PCH=CHPPh2)2]BPh4, cis-bis(diphenylphosphino)ethane (dppe), and cis-bis(diphenylphosphino)propane (dppp), [M(Ph2P–R–PPh2)2]BPh4 (R = (CH2)2, (CH2)3), have been prepared and characterized by NMR spectroscopy, electrospray mass spectrometry, and single crystal X-ray structural analysis at 200 K. Structures of the dppey complexes as acetone solvates show the Cu and Ag complexes to be isostructural with the previously reported Au complex, crystallizing in space group P 21/n with a ~ 25.5, b ~ 15.6, and c ~ 34.2 Å, and β ~ 103°. Structures of the dppe complexes show the copper complex to crystallize in the chiral space group P21 with a 11.8954(5), b 20.1904(5), and c 14.8999(5) Å, and β 111.366(5)°. The Ag and Au complexes are isostructural, crystallizing in space group P21/c with a ~ 17.8, b ~ 17.6, and c ~ 20.9 Å, and β ~ 107°. Structures of the dppp complexes show the copper complex to crystallize in space group P21/c with a 17.8399(4), b 19.8803(4), and c 18.7165(3) Å, and β 102.197(2)°. The Ag and Au complexes are isostructural, crystallizing in space group P21/n with a ~ 17.7, b ~ 18.6, and c ~ 19.6 Å, and β ~ 100°. Across the three series of complexes, the M–P bond lengths increase in the order Cu &lt; Au &lt; Ag with Cu–P = 2.281(3)–2.314(1) Å, average 2.30(1) Å; Au–P = 2.363(1)–2.4322(8) Å, average 2.40(2) Å, and Ag–P = 2.445(1)–2.5303(5) Å average 2.49(2) Å.

Aza-Claisen Rearrangement in the Cyclization Reactions of Nitrogen-Containing Enynes via Ruthenium Vinylidene Complexes

The cyclization reaction of several diallyl aromatic amine molecules, each containing an ethynyl group at the ortho position of the aromatic ring, is accompanied by an aza-Claisen rearrangement, causing an allyl group migration to give substituted indole compounds. This cyclization is catalyzed by ruthenium triphenylphosphine and diphenylphosphinoethane (dppe) complexes as well as gold complexes with silver reagent. The less sterically crowded dppe complex is a more efficient catalyst. The mechanism involving a vinylidene intermediate is proposed on the basis of isolation of several intermediates in the ruthenium-catalyzed system. Single crystals of a metal complex with the cyclized ligand were obtained, and the structure was determined by an X-ray diffraction analysis.

3+2] Cycloadditions of Molybdenum(II) Azide Complexes with Nitriles and an Alkyne

A series of products of [3+2] cycloaddition reactions of molybdenum azide complexes with nitriles and an alkyne were prepared and characterized. These include the tetrazolate complexes Mo(η3-C3H5)(CO)2(en)(N4CR) (R = CH3 (1), C6H5 (2), C(CH3)3 (3), CH═CHCN (4)) and the triazolate complexes Mo(η3-C3H5)(CO)2(L2){N3C2(CO2CH3)2} (L2 = en (6), dppe (7)). They are the first examples of a complex with a heterocyclic ligand prepared via a reaction of a group VIB metal azide with an unsaturated dipolarophile. All these complexes are fluxional in solution, with those containing en ligands displaying broad unresolved proton NMR signals at room temperature. With the exception of 1, their solution behavior was studied by low-temperature NMR spectroscopy. In contrast, the dppe complexes display average NMR signals at room temperature due to a fast exchange. The solid-state structures of these cycloaddition products were also determined by single-crystal X-ray diffraction analysis. The tetrazolate complexes 1, 2, and 4 ...

Sterically‐Directed Consecutive and Size‐Selective Self‐Assembly of Palladium Diphosphane Complexes with an Ar‐BIAN Ligand: Unexpected Formation of Pentameric and Hexameric Aggregates

The coordination properties of N,N'-bis[4-(4-pyridyl)phenyl]acenaphthenequinonediimine (L(1)) and N,N'-bis[4-(2-pyridyl)phenyl]acenaphthenequinonediimine (L(2)) were investigated in self-assembly with palladium diphosphane complexes [Pd(P;P)(H(2)O)(2)](OTf)(2) (OTf = triflate) by using various analytical techniques, including multinuclear ((1)H, (15)N, and (31)P) NMR spectroscopy and mass spectrometry (P;P = dppp, dppf, dppe; dppp = bis(diphenylphosphanyl)propane, dppf = bis(diphenylphosphanyl)ferrocene, and dppe = bis(diphenylphosphanyl)ethane). Beside the expected trimeric and tetrameric species, the interaction of an equimolar mixture of [Pd(dppp)](2+) ions and L(1) also generates pentameric aggregates. Due to the E/Z isomerism of L(1), a dimeric product was also observed. In all of these species, which correspond to the general formula [Pd(dppp)L(1)](n)(OTf)(2n) (n = 2-5), the L(1) ligand is coordinated to the Pd center only through the terminal pyridyl groups. Introduction of a second equivalent of the [Pd(dppp)](2+) tecton results in coordination to the internal, sterically more encumbered chelating site and induces enhancement of the higher nuclearity components. The presence of higher-order aggregates (n = 5, 6), which were unexpected for the interaction of cis-protected palladium corners with linear ditopic bridging ligands, has been demonstrated both by mass-spectrometric and DOSY NMR spectroscopic analysis. The sequential coordination of the [Pd(dppp)](2+) ion is attributed to the dissimilar steric properties of the two coordination sites. In the self-assembled species formed in a 1:1:1 mixture of [Pd(dppp)](2+)/[Pd(dppe)](2+)/L(1), the sterically more demanding [Pd(dppp)](2+) tectons are attached selectively to the pyridyl groups, whereas the more hindered imino nitrogen atoms coordinate the less bulky dppe complexes, thus resulting in a sterically directed, size-selective sorting of the metal tectons. The propensity of the new ligands to incorporate hydrogen-bonded solvent molecules at the chelating site was confirmed by X-ray diffraction studies.

A novel series of nickel(II)-dppe-arylazoimidazole complexes. Synthesis and spectroscopic characterization

Reaction of [Ni(dppe)Cl2/Br2] with AgOTf in CH2Cl2 medium following ligand addition leads to [Ni(dppe)(OSO2CF3)2] and then [Ni(dppe)(RaaiR)](OSO2CF3)2 [RaaiR′ = p–R–C6H4–N=N–C3H2–NN-1–R′,(1–3), abbreviated as N,N′-chelator, where N(imidazole) and N(azo) represent N and N′, respectively; R = H (a), Me (b), Cl (c) and R′ = Me (1), CH2CH3 (2), CH2Ph (3), OSO2CF3 is the triflate anion]. 31P{1H}-NMR confirm that stable bis-chelated square planar Ni(II) azoimine–dppe complex formation with one sharp peaks. The 1H NMR spectral measurements suggest azoimine link is present with lot of phenyl protons in the aromatic region. Considering all the moities there are a lot of different carbon atoms in the molecule which gives many different peaks in the 13C(1H)-NMR spectrum. In the 1H-1H COSY spectrum in the present complexes and contour peaks in the 1H-13C-HMQC spectrum in the present complexes, assign the solution structure and stereoretentive conformation in each complexes.

Intramolecular Metathesis of a Vinyl Group with Vinylidene CC Double Bond in Ru Complexes

The cationic complex {[Ru]=C=CHCPh2CH2CH=CH2}BF4 (3a, [Ru] = (eta5-C5H5)(PPh3)2Ru) in solution transforms to {[Ru]=C=CHCH2CPh2CH=CH2}BF4 (4a) via a new metathesis process of the terminal vinyl group with the C=C of the vinylidene group which is confirmed by 13C labeling studies. This transformation is irreversible as revealed by deuteration and decomplexation studies. The cationic complex {[Ru]=C=CHCPh2CH2CMe=CH2}BF4 (3b) undergoes a cyclization process yielding 6b containing a eta2-cyclic allene ligand which is fully characterized by single-crystal X-ray diffraction analysis. Analogous complexes 4a' and 6b' ([Ru] = (eta5-C5H5)(dppe)Ru) containing dppe ligands were similarly obtained from protonation of the corresponding acetylide complexes via formation of vinylidene intermediate. Protonation of the acetylide complex containing a terminal alkynyl group [Ru]-CCCPh2CH2CCH (2c) generates the vinylidene complex {[Ru]=C=CHCPh2CH2CCH}BF4 (3c) which again undergoes an irreversible transformation to give {[Ru]=C=CHCH2CPh2CCH}BF4 (4c) possibly via a pi-coordinated alkynyl complex followed by hydrogen and metal migration. No similar transformation is observed for the analogous dppe complex 3c'. With an extra methylene group, complex {[Ru]=C=CHCPh2CH2CH2CH=CH2}BF4 (3d) and complex {[Ru]=C=CHCPh2CH2Ph}BF4 (3e) are stable. The presence of a gem-diphenylmethylene moiety at the vinylidene ligand with the appropriate terminal vinyl or alkynyl group along with the correct steric environment implements such a novel reactivity in the ruthenium vinylidene complexes.

Dismutation of a Molybdenum(IV) Acetonitrile−NNH2Complex to a Molybdenum(IV) Ethylimido Complex + N2: Mechanistic Implications on the Protonation of Coordinated Nitriles at the β-Carbon Atom

Reaction of the Mo(0) depe complex [Mo(N2H2)(depe)2(CH3CN)](OTf)2 (3) (depe = 1,2-bis(diethylphosphino)ethane) with base gives the ethylimido complex [Mo(depe)2(CH3CH2N)(CH3CN)](OTf)2 (10), whereas base treatment of the corresponding dppe complex [Mo(N2H2)(dppe)2(OTf)](OTf) (12; dppe = 1,2-bis(diphenylphosphino)ethane) leads to formation of [Mo(N2)(dppe)2(CH3CN)] (14). Reaction of dinitrogen complex 14 with HBF4 gives the ethylimido complex [Mo(dppe)2(CH3CH2N)(F)](BF4) (17). The protonation of coordinated acetonitrile in complexes 3 and 14 giving the corresponding ethylimido complexes is investigated. Experimental and theoretical evidence is presented for the hypothesis that acetonitrile is only activated toward protonation at the β-carbon if it is bound along with a Lewis base like triflate or fluoride to a Mo(0) center. The activation is further influenced by the phosphine coligands (depe > dppe). DFT geometry optimizations show that the acetonitrile ligand is bent in the activated complexes, exhibiting a lone pair at Cβ. Protonation at this position first leads to Mo(II) methyl-azavinylidene intermediates (which cannot be isolated) and then to Mo(IV) ethylimido complexes.

Synthesis, structures and some reactions of Ru(C [tbnd]CC [tbnd]CFc)(PP)Cp (PP = dppm, dppe) and related compounds

The compounds Ru(C CC CFc)(PP)Cp [PP = dppe ( 1), dppm ( 2)], have been obtained from reactions between RuCl(PP)Cp and FcC CC CSiMe 3 in the presence of KF ( 1) or HC CC CFc and K[PF 6] ( 2), both with added dbu. The dppe complex reacts with Co 2(CO) 6(L 2) [L 2 = (CO) 2, dppm] to give 3, 4 in which the Co 2(CO) 4(L 2) group is attached to the outer C C triple bond. The PPh 3 analogue of 3 ( 5) has also been characterised. In contrast, tetracyanoethene reacts to give two isomeric complexes 6 and 7, in which the cyano-olefin has added to either C C triple bond. The reaction of RuCl(dppe)Cp with HC CC CFc, carried out in a thf/NEt 3 mixture in the presence of Na[BPh 4], gave [Ru{C CC(NEt 3) CHFc}(dppe)Cp]BPh 4 ( 8), probably formed by addition of the amine to an (unobserved) intermediate butatrienylidene [Ru( C C C CHFc)(dppe)Cp] +. The reaction of I 2 with 8 proceeds via an unusual migration of the alkynyl group to the Cp ring to give [RuI(dppe){η-C 5H 4C CC(NEt 3) CHFc}]I 3 ( 9). Single-crystal X-ray structural determinations of 1, 2 and 4– 9 are reported.

Synthesis of the first polymeric Cu(I) dppe (dppe=1,2-bis(diphenylphosphino)ethane) complexes

The first polymeric Cu(I) dppe complexes have been synthesized and their structures in solution and solid state have been studied.

Infrared and laser Raman studies of [Ni(II)(dppe)Cl 2] and [Co(III)(dppe) 2Cl 2]PF 6 (dppe=1,2-bis(diphenylphosphino)ethane)

Infrared and laser Raman spectral investigations of [Ni(II)(dppe)Cl 2] and [Co(III)(dppe) 2Cl 2]PF 6 have been made to determine the conformation and nature of bonding in Ni(II) and Co(III) dppe complexes. The stereochemistry of the two forms of these complexes has been confirmed. The role of steric interferences in cis-Planar [Ni(II)(dppe)Cl 2] complex is interpreted in terms of reduction in symmetry upon coordination. The strong trans influence of the chelating dppe ligand is observed in the [Co(III)(dppe) 2Cl 2]PF 6 complex. Both complexes exhibit the effect of crystalline field on molecular vibrations. The Fermi resonance overtone is also observed in these complexes.

Heptacoordinate dithiophosphate W(II) and Mo(II) complexes of diphosphines and iodide

New complexes [MI(CO) 2(dppe){S 2P(OEt) 2}] (M=W, 1a; M=Mo, 1b), [MI(CO) 2(dppm){S 2P(OEt) 2}] (M=W, 2a; M=Mo, 2b) and [W(CO)(dppe){S 2P(OEt) 2} 2][O 2dppe] ( 3a), were synthesised from [MI 2(CO) 3(NCMe) 2] (M=Mo, W), after treatment with ammonium diethyldithiophosphate and phosphine under different conditions. The structure of the tungsten complexes was determined by single crystal X-ray diffraction. During the synthesis of 3a, oxidation of the phosphine took place and a molecule of oxidised phosphine occupies channels in the crystal. DFT/B3LYP calculations on models of 1a and 2a showed the capped octahedron structure, observed in most dicarbonyl complexes of this family, to be preferred by 1.4 and 2.6 kcal mol −1 for the dppm and the dppe complexes, respectively. Strong steric repulsions can reverse this trend, as happens with the rigid dppm ligand. Complex 1a adopts a pentagonal bipyramidal geometry, which is often found in related monocarbonyl complexes.

Studies on PtS bonds. Methylsulfanyl-acetato, -benzoato and -phenolato complexes of the Pt (II)(PPh 3) 2 and Pt (II)(dppe) moieties and the crystal structure of bis-triphenylphosphine(methylsulfanylacetato)platinum(II) nitrate

Bis-triphenylphosphine and bis(diphenylphosphine)ethane platinum(II) complexes with the chelating anionic ligands methylsulfanyl-acetato (sa), -benzoato (sb) and -phenolato (sph) have been synthesised and characterised. Infrared and multinuclear NMR spectra are in accordance with chelation of these ligands through the sulfur and the anionic oxygen atoms. The structure of [Pt(PPh 3) 2(sa)]NO 3 has been determined through X-ray diffraction and confirms chelation of sa. 1H NMR spectra suggest that the chelate ring in this compound is rigid, with the same conformation found in the solid state, while in the analogous dppe complex both chelate rings undergo inversion of conformation at room temperature.