Side-bonded ketone complexes of platinum(0). Alloxan and diethyl oxomalonate complexes and reactions of platinum(0) complexes with isatin and benzoyl cyanide.

Reactions of alloxan (all) with [PtL(PPh₃)₂] (L′= $\text{trans}$-stilbene, L″ diphenylacetylene) afford the side-bonded ketone complex [Pt(all)(PPh₃)₂] which may also be obtained from the hydrate of alloxan and [PtL′(Pph₃)₂]. Similarly diethyl oxomalonate (dio) and [Pt(PPh₃)₄] afford a side-bonded ketone complex [Pt(dio)(PPh₃)₂]. Reaction of isatin with [Pt(PPh₃₄] gives $\text{trans}$-[PtH{$\text{NCO(}\text{o}\text{-C}{}_6\text{H}{}_4\text{)CO}$}(PPh₃)₂] and benzoyl cyanide and [PtL′(PPh₃)₂] give $\text{cis}$-[Pt(CN)(COPh₃)₂] and $\text{trans}$-[Pt(CN)₂(PPh₂)₂].     

Synthesis of ylideplatinum(II) complexes via α-functionalised alkylplatinum(II) intermediates and some comparative data on palladium(II) complexes; X-ray structure of trans-[Pt(CH2PEt3)I(PEt3)2]I

The reaction of [Pt(PEt₃)₃] with CH₂I₂ affords trans-[Pt(CH₂PEt₃)I(PEt₃)₂]I and is believed to proceed via the α-functionalised alkyl cis-[Pt(CH₂I)I(PEt₃)₂], because similar ylides are obtained from cis- or trans-[PT(CH₂X)(PPh₃)₂X] (XCl, Br, or I) with PR₃ (PEt₃, PBu₃ⁿ, PMePh₂, PEtPh₂, or PPh₃); cis-[Pd(CH₂I)-I(PPh₃)₂] does not react with excess PPh₃, but with PEt₃ yields trans-[Pd(CH₂PEt₃)I(PPh₃)₂]I; the X-ray structure of trans-[Pt(CH₂PEt₃)I(PEt₃)₂]I (current R = 0.045) shows PtP(1) 2.332(7), PtP(2) 2.341(8), PtC 2.08(2), and PtI 2.666(2) Å, and angles (a) C(1)PtI, P(1), P(2): 176.9(8), 91.6(6), 93.4(6), (b) IPtP(1), P(2): 87.1(2), 88.5(2), and (c) P(1)P(2), 166.8(3), and (d) PtC(1)P(3), 118(1)°.     

Trifluoromethylselenato(0) and trifluoromethyltellurato(0) complexes of platinum(II)

The series of cis/trans-trifluoromethylselenato complexes [Pt(SeCF₃)_2 − xCl_x(PPh₃)₂] (x = 0, 1) was identified by NMR spectroscopic methods. While in acetonitrile solution spectra are dominated by the resonances of the cis derivatives, those of pure cis-[Pt(SeCF₃)₂(PPh₃)₂] indicate cis-trans-isomerisation in CH₂Cl₂ solution. In contrast, exchange reactions of cis-[PtCl₂(PPh₃)₂] and [NMe₄]TeCF₃ only gave evidence for cis isomers. Molecular structures of cis- and trans-[Pt(SeCF₃)₂(PPh₃)₂] and cis-[Pt(TeCF₃)₂(PPh₃)₂] are discussed in comparison with related compounds.     

Reactions of (η-allyl)dicarbonylmolybdenum(II) complexes with phosphorus and arsenic donor ligands

Reaction of [MoX(CO)₂(η-C₃H₅)(MeCN)₂] with the arsines Ph₂AsCH₂CH₂AsPh₂ (dae) and Ph₂AsCH₂AsPh₂ (dam) yields complexes of stoichiometry [MoX(CO)₂(η-C₃H₅)dae] (where X = Cl, Br or I) and [MoX(CO)₂(η-C₃H₅)]₂dam (where X = Cl or Br). The former are isomorphous with the known Ph₂PCH₂CH₂PPH₂ complexes, whereas the latter probably contain halogen and dam bridges. Under forcing conditions the corresponding ditertiary phosphines form the molybdenum(0) derivatives $\text{cis}$-Mo(CO)₂(Ph₂P(CH₂)_nPPh₂]₂ (where n = 1 or 2).     

Organoplumbio complexes of platinum(II)

The complex [Pt(C₂H₄)(PPh₃)₂] reacts with Pb₂Ph₆ to give cis-[PtPh(Pb₂Ph₅)(PPh₃)₂]; this decomposes in solution to cis-[PtPh(PbPh₃)(PPh₃)₂], which may also be obtained from the ethylene complex and PbPh₄. Lead compounds PbPhMe₃ and PbPh₃Br also give products of insertion into PbPh bonds, but PbMe₃Cl gives cis- and trans-[PtCl(PbMe₃)(PPh₃)₂]. The complex trans-[Pt(PbPh₃)₂(PEt₃)₂] reacts with 1,2-bis(diphenylphosphino)ethane (DPPE) to give [Pt(PbPh₃)₂(DPPE)] which readily decomposes in dichloromethane in presence of PEt₃ to give [Pt(PbPh₃)(PEt₃)(DPPE)]Cl and [PtPh(PEt₃)(DPPE)]Cl. The complex trans-[PtCl(PbPh₃)(PEt₃)₂] was detected in the products of reactions between trans-[PtCl₂(PEt₃)₂] and trans-[Pt(PbPh₃)₂(PEt₃)₂] or less than 2 moles of LiPbPh₃; it was not detected in the mixture after treatment of trans -[Pt(PbPh₃)₂(PEt₃)₂] with HCl. In contrast to an earlier report, we were unable to detect lead-containing complexes in the products of the reaction between trans-[PtHCl(PPh₃)₂] and Ph₃PbNO₃. The complexes and their decomposition products were identified by ^pre31P-{¹H} NMR spectroscopy.     

Carbonyl complexes of manganese(I) with chelating phosphino-alkyl or -acyl ligands. Crystal and molecular structure of [Ph2PCH2CH2(O)CMn(CO)2(dppm)l

The phosphine Ph₂PCH₂CH₂Cl reacts with fac-[XMn(CO)₃(dppm)] (X = Cl or Br) in refluxing toluene to give the complexes cis,cis-[XMn(CO)₂(dppm)(Ph₂PCH₂CH₂Cl)] (I). Treatment of those species with Na amalgam in THF leads to the alkyl complex [Ph₂$\text{PCH}{}_2\text{CH}{}_2\text{M}$n(CO)₂(dppm)] (II), which does not react with CO under normal conditions but can be converted into cis,cis-[ClMn(CO)₂(dppm)(PPh₂Et)] by reacting with HCl (g) in ether. If the reduction of I with Na/Hg is carried out in the presence of CO the compound cis-[Ph₂$\text{PCH}{}_2\text{CH}{}_2\text{(O)CM}$n(CO)₂(dppm)] (III) is obtained. The latter has also been prepared directly from fac-[BrMn(CO)3(dppm)], Ph₂PCH₂CH₂Cl, and Na/Hg in THF, and characterized by X-ray crystallography. The crystals are monoclinic, space group P2₁/n; refinement gave R = 0.053 for 2593 reflections with I ? 2.5σ(I). The reaction of the complex fac-[O₃ClOMn(CO)₃(dppm)] with Ph₂PCH₂CH₂Cl in Cl₂CH₂ gives the salt fac-[Mn(CO)₃(dppm)(Ph₂PCH₂CH₂Cl)]ClO₄ which isomerizes to mer-[Mn(CO)₃(dppm)(Ph₂PCH₂CH₂Cl)]ClO₄ in boiling butanol. Both cationic carbonyl complexes give the acyl species III upon reduction with Na amalgam.     

Four-membered chelate aminoalkenyl complexes of platinum(II). Synthesis,carbonylation and oxidation to aminoacidato complexes

Amination of Pt^II-allene complexes of the type cis[PtCl₂(Me₂CCCHR)(PPh₃)] gives the new four-membered C, N chelate aminoalkenyl complexes [$\text{PtC(CMe}{}_2\text{)CHRN}$Me₂(PPh₃)Cl]. These undergo ready insertion of carbon monoxide into the CPt σ-bond; the resulting acyl complexes are oxidized by hydrogen peroxide to aminoacidato complexes, and the free unsaturated β-aminoacids can be recovered in good yield by ligand displacement.     

Unusual rearrangement of σ-vinylpalladium complexes into η2-olefin complexes. The structure of (η2-1-triphenylphosphonium-2-carbomethoxyethylene)(triphenylphosphine)iodopalladate

β-Substituted σ-vinylpalladium complexes [Pd(σ-CHCHCOOR)(PPh₃)₂(X)] (I) (X = Cl, I; R = Me, Et) have been obtained by interaction of the E- and Z-β-halogen acrylates with tetrakis(triphenylphosphine)palladium. On heating complexes I rearrange into isomeric η²-olefin-ylidepalladium complexes [$\text{P}$$\text{dCH(COOR)-C}$HPPh₃(PPh₃)(X)] (II). The structure of these com X-ray study of the compound with X = I, R = Me.     

Formation of unsymmetrical cis-dialkyls of platinum(II) from platinum(II) hydroxo-complexes

The (hydroxo) methyl complex Pt(OH)(CH₃)(Diphos) [Diphos = Ph₂PCH₂CH₂PPh₂] reacts with compounds containing acidic CH bonds (HX) to give unsymmetrical cis-dialkyls of general formula Pt(CH₃)X(Diphos) [X = CH₂COCH₃, CH(COCH₃)₂, CH₂CN or CH₂NO₂]; both the methyl and the cyclohexenyl complexes Pt(OH)R(Diphos) (R = CH₃ or C₆H₉) insert carbon monoxide to give hydroxycarbonyl complexes PtR(CO₂H)(Diphos) which are remarkably stable to decomposition by β-elimination.     

Preparation and characterization of some mixed ligand complexes of platinum(II)

The mixed ligand complexes PtX₂(ER₃)L and PtXY(ER₃)L (where ER₃ = PR₃ or AsMe₃; L = phosphine, arsine; X = Cl; Y = Cl, H or Me) have been prepared and characterized. Reaction of PtMe₂(ER₃)L with HCl yields PtMeCl(ER₃)L, in exclusively one of three possible isomeric forms. Excess tetramethyltin reacts with Pt₂Cl₂(μ-Cl)₂(PMe₂Ph)₂ giving both cis and trans Pt₂(μ-Cl)₂(PMe₂Ph)₂, as identified from the NMR spectra. Cleavage of Pt₂(μ-Cl)₂Me₂(PMe₂Ph)₂ with donor ligands such as AsPh₃, PMe₂ or pyridine, was useful as a synthetic route to the unsymmetrical methylchloro Pt^II derivatives. The reaction of cis-[PtMe₂(PPh₃)(AsPh₃)] with excess dimethylacetylenedicarboxylate (DMA) yielded only one product, which was of the formula trans-[Pt{C(COOCH₃)C(COOCH₃)CH₃}₂(PPh₃)(AsPh₃)], with the alkenyl groups having the same geometry about the CC bond. The use of diethylacetylene-dicarboxylate (DEA) rather than DMA gave a similar product. However, when cis-[PtMe₂(PEt₃)(AsPh₃)] was allowed to react with DMA, two products of the formula trans-[Pt{C(COOCH₃)C(COOCH₃)CH₃}₂(PEt₃)(AsPh₃)] were obtained, with the stereochemistry of both alkenyl groups being either cis or trans.     

The preparation and X-ray crystal and molecular structure of (α,1,2-η-6-methylbenzyl) bis(triphenylphosphine)rhodium(I)

Reaction of [RhCl(PPh₃)₃] with [o-MeC₆H₄CH₂MgBr] affords high yields of the non-fluxional complex, [Rh(CH₂C₆H₄Me)(PPh₃)₂] which has been shown crystallographically to contain a 1-3-η-benzyl group bound through the phenyl carbon atom that is not substituted with the methyl group. Crystals of this compound are triclinic, space group P$\text{1}$, with a = 10.561(6). b = 17.705(3), c = 10.934(4) Å, α = 80.69(3), β = 116.86(4), γ = 102.30(4)° and Z = 2. The structure was solved via the heavy-atom method and refined to R = 0.032 using 5379 diffractometer data with I > 1.56(I). Attempts to prepare π-bonded xylylene complexes from this compound by reaction with base have been unsuccessful, but protonation followed by recrystallisation from acetone gives [Rh{(CH₃)₂CO}₂(PPh₃)₂]BF₄.     

Reactions of dimethyl- and diphenyl-mercury with dihalobis(isocyanide)palladium(II) complexes

The reaction of cis-[PdCl₂(CNR)₂] (R = Ph, p-MeC₆H₄, p-MeOC₆H₄) and trans-[PdI₂(CNPh)₂] with HgR′₂ (R′ = Me, Ph) followed by addition of PPh₃ (Pd/PPh₃, $\text{1}\text{2}$) gives complexes of the type trans- [PdX {C(=NR)C(R′)=NR}(PPh₃)₂] (X = Cl, I) I as main products. These bis(imino) compounds may result from double insertion of the coordinated isocyanides into a PdR′ σ-bond. NaBPh₄ was also found to act like HgPh₂ as a good phenylating agent towards coordinated isocyanide. The reactions of I with methanolic HClO₄ yield cationic compounds: trans- [PdX{C(NHR)C(R′)=NR}(PPh₃)₂]ClO₄; the protonated bis(imino) group may also be formulated as {C(=NR)C(R′)NHR} and a fast equilibrium between the two forms probably exists in solution. The factors influencing the reaction with HgR′₂ and spectroscopic data (IR and ¹H NMR) for the complexes are reported and discussed.     

Ligand behaviour of P-functionally substituted organotin halides: palladium(II) and platinum(II) complexes with Ph2PCH2CH2SnCl3

The P-functional organotin chloride Ph₂PCH₂CH₂SnCl₃ reacts with [(COD)MCl₂] and trans-[(Et₂S)₂MCl₂] (M=Pd, Pt) in molar ratio 1:1 to the zwitterionic complexes [(COD)M⁺(Cl)(PPh₂CH₂CH₂Sn⁻Cl₄)] (1: M=Pd; 2: M=Pt) and trans-[(Et₂S)₂M⁺(Cl)(PPh₂CH₂CH₂Sn⁻Cl₄)] (3: M=Pd; 4: M=Pt). The same reaction with [(COD)Pd(Cl)Me] yields under transfer of the methyl group from palladium to tin the complex [(COD)M⁺(Cl)(PPh₂CH₂CH₂Sn⁻MeCl₃)] (5) which changes in acetone into the dimeric adduct [Cl₂Pd(PPh₂CH₂CH₂SnMeCl₂·2Me₂CO)]₂ (6). In molar ratio 2:1 Ph₂PCH₂CH₂SnCl₃ reacts with [(COD)MCl₂] to the complexes [Cl₂Pd(PPh₂CH₂CH₂SnCl₃)₂] (7: M=Pd, mixture of cis/trans isomer; 8: M=Pt, cis isomer). In a subsequent reaction 8 is transformed in acetone into the 16-membered heterocyclic complex cis-[Cl₂Pt(PPh₂CH₂CH₂)₂SnCl₂]₂ (9). trans-[(Et₂S)₂PtCl₂] and Ph₂PCH₂CH₂SnCl₃ in molar ratio 1:2 yields the zwitterionic complex [(Et₂S)M⁺(Cl)(PPh₂CH₂CH₂SnCl₃)(PPh₂CH₂CH₂Sn⁻Cl₄)] (10). The results of crystal structure analyses of 1, 3, 6, 9 and of the adduct of the trans-isomer of 7 with acetone (7a) are reported. ³¹P- and ¹¹⁹Sn-NMR data of the complexes are discussed.     

Function of triazenido compound for electrocatalytic hydrogen production catalyzed by platinum complex

A new type of electrocatalyst based on a triazenido-platinum complex, Pt(PPh₃)₂(L)Cl (1), is prepared by the reaction of 1-[(2-methoxy) benzene]-3-[2-pyridine] triazene (HL) and Pt(PPh₃)₂Cl₂ in the presence of triethylamine. Electrochemical studies indicate that HL, Pt(PPh₃)₂Cl₂ and 1 can catalyze hydrogen evolution from acetic acid or a neutral buffer. To show triazenido ligand, HL, plays a role in determining the catalytic activities of the platinum complex, we systematically study the electrocatalytic activities of HL, Pt(PPh₃)₂Cl₂ and Pt(PPh₃)₂(L)Cl and provide a possible catalytic mechanism for hydrogen generation catalyzed by 1.     

Platinum(II) complexes containing the 3,3-dimethylglutarimidate ligand

Reaction of cis-[PtCl₂(PPh₃)₂] with excess 3,3-dimethylglutarimide (dmgH) and sodium chloride in refluxing methanol gives the mono-imidate complex cis-[PtCl(dmg)(PPh₃)₂], which was structurally characterized. The plane of the imidate ligand is approximately perpendicular to the platinum coordination plane which, coupled with restricted rotation about the Pt–N bond, results in inequivalent methyl groups and CH₂ protons of the dmg ligand in the room temperature ¹H NMR spectrum. These observations were corroborated by a theoretical study using density functional theory methods. The analogous bromide complex cis-[PtBr(dmg)(PPh₃)₂] can be prepared by replacing NaCl with NaBr in the reaction mixture.     

The interaction of an osmium-carbon triple bond with copper(I), silver(I) and gold(I) to give mixed dimetallocyclopropene species and the structures of Os(AgCl) (CR) Cl(CO) (PPh3)2

The osmium carbyne complex, Os(CR)Cl(CO)(PPh₃)₂, (R  p-tolyl) reacts with Group I halides to form the mixed dimetallocyclopropene species, $\text{Os(Cul)(C}$R)Cl(CO)(PPh₃)₂, $\text{Os(AgCl)(C}$R)Cl(CO)(PPh₃)₂, $\text{Os(AuCl)(C}$R)Cl(CO)(PPh₃)₂, and [$\text{Os[Ag(OClO}{}_3\text{)](C}$R)Cl(CO)(MeCN)(PPh₃)₂] ClO₄ X-ray crystal structure determination of $\text{Os(AgCl)(C}$R)Cl(CO)(PPh₃)₂ confirms the presence of a three-membered ring and the structure can be viewed as the “acetylene-like” interaction of an osmium—carbon triple bond with AgCl. In acid solution AgCl is precipitated and an alkylidene complex results from proton addition to the carbyne ligand.     

Enthalpies of reaction of bis(triphenylphosphine)(trans-stilbene)platinum(0) with diphenylcyclopropenone and benzocyclobutenedione

Enthalpies, ΔH(1) ?94.8 ± 6.0 and ΔH(6) ?57.1 ± 5.1 kJ mol^?1, of the following reactions have been measured calorimetrically [Pt(trans-stilbene)(PPh₃)₂](s) + dpcp(g) → (PPh₃)₂Pt(dpcb)(s) + trans-stilbene(g) (1) [Pt(trans-stilbene)(PPh₃)₂](s) + bcbd(g) → (PPh₃)₂Pt(bcpd)(s) + trans-stilbene (g) (6) where dpcp is diphenylcyclopropenone, (PPh₃)₂Pt(dpcb) is (1,1-bistriphenylphosphine)platinadiphenylcyclobutenone, (PPh₃)₂$\text{PtC(Ph)C(Ph)C}$O, bcbd is benzocyclobutene-1,2-dione and (PPh₃)₂Pt(bcpd) is (1,1-bistriphenylphosphine)platinabenzocyclopentanedione,

. It is concluded that the five-membered platinacyclo ring system in (PPh₃)₂Pt(dpcb) is not heavily strained.     

Reactivity of olefin an acetylene complexes of platinum(0) towards tetrachloro-o-benzoquinone

Tetracloro-o-benzoquinone reacts with (diphenylacetylene)bis(tirphenylphosphine)platinum(0) to give the novel platinum(II) diphenylacetylene complex, Pt(C₆Cl₄O₂)PhCCPh)(PPh₃), (I), which reacts with hydrogen halides to give the compelexes cis-PtX₂(PhCCPh((PPh₃), (X = Cl or Br). Hydrogen chloride also readily removes the tetrachloro-o-benzoquinoneligand from the adducts Ni(C₆Cl₄O₂)(Ph₂PCH₂CH₂PPh₂) and M(C₆Cl₄O₂)(PPh₃)₂, (M = Pd or Pt) but it has no reaction upon Ir(Cl)(C₆Cl₄O₂)(CO)(PPh₃)₂ at room temperature. The acetylene in (1) is susceptible to nucleophilic attact and reaction with diethylamine gives the vinyl adduct Pt(C₆Cl₄O₂)(CPhCPh)NHEt₂)(PPh₃). Other reactions of (I) have also been studied. Attemps to prepare other olefin or acetylene complexes of platinum(II) by the action of tetrachlor-o-benzoquinone on the complexes Pt(L)(PPh₃)₂, (L = PhCCH,(Et)(Me)(HO)CCCC(OH)(Me)(Et), HOCH₂OH, CF₃CCCF₃, CF₂CF₂, CF₂CH₂ or trans-PhCHCHPh) are also described.     

Oxidative addition - reductive elimination sequences in the photochemistry of some bis(phosphine)platinum complexes

The photolysis of [L₂Pt(C₂H₄)] (L = PPh₃, P(p-C₆H₄CH₃)₃ complexes in halocarbon solvents (CH₂Cl₂, CH₂Br₂) gives C₂H₄ and the coordinatively unsaturated species [L₂Pt]. Photolysis of platinum metallacycles [L₂Pt(CH₂)₄] (L = PPh₃, P(n-Bu)₃) generates alkanes, alkenes and [L₂Pt]. The [L₂Pt] centers are very reactive, and under prolonged photolysis undergo oxidative addition of CH₂Cl₂ forming the trans-[L₂Pt(CH₂Cl)Cl] complexes. Under appropriately controlled conditions the trans complexes isomerize to cis species before bimolecular C₂H₄ elimination occurs and [L₂PtCl₂] is formed as the final product. The oxidative addition-reductive elimination mechanism is discussed on the basis of spin-trapping experiments, quantum yield values, and the sensitivity to radical inhibitors and to solvents.     

Metal—metal bonding in dinuclear complexes of platinum(I). The crystal and molecular structure of carbonyl(chloro)-bis-μ-[bis(diphenylphosphino)methane]diplatinum hexafluorophosphate

The structure of [Pt₂Cl(CO) (μ-Ph₂PCH₂PPh₂)₂] [PF₆] was determined by $\text{X}$-ray methods and refined to $\text{R}$ = 0.082, using diffractometric intensities of 5646 independent reflections. The crystals are monoclinic, space group $\text{P}$2₁/$\text{n}$, $\text{a}$ = 12.919(3), $\text{b}$ = 15.576(6), $\text{c}$ = 25.151(5)Å, β = 94.82(3)°, $\text{Z}$ = 4. They are built of octahedral hexafluorophosphate anions and dinuclear platinum(I) cations. The latter contain PtCl and PtCO fragments linked to one another by a PtPt σ-bond and by two bridging bis(diphenylphosphino)methane ligands. The platinum atoms are in square planar environments and the dihedral angle between the two coordination planes is 40.1°. Selected bond lengths are: PtPt 2.620(1), PtCl 2.384(5), PtC 1.89(3) and PtP 2.291(5) – 2.308(5)Å.