Half-sandwich ruthenium thiocarbonate complexes: Structures of CpRu(PPh3)2SCO2Bu, CpRu(dppe)SCO2Bu and CpRu(PPh3)(CO)SCO2Bu

Thiocarbonate ruthenium complexes of the form CpRu(L)(L′)SCO₂R (L = L′ = PPh₃ (1), 1/2 dppe (2), L = PPh₃, L′ = CO (3); R = Et (a), Buⁿ (b), C₆H₅ (c), 4-C₆H₄NO₂ (d)) have been synthesized by the reaction of the corresponding sulfhydryl complexes, CpRu(L)(L′)SH, with chloroformates, ROCOCl, at low temperature. The bis(triphenylphosphine) complexes 1 can be converted to 3 under CO atmosphere. The crystal structures of CpRu(PPh₃)₂SCO₂Buⁿ (1b), CpRu(dppe)SCO₂Buⁿ (2b), and CpRu(PPh₃)(CO)SCO₂Buⁿ (3b) are reported.     

The synthesis and structural characterization of the technetium nitrosyl complexes [TcCl(NO)(SC5H4N)(PPh3)2] and [Tc(NO)(SC5H4N)2(PPh3)]

The reaction of the Tc(I) complex [Tc(NO)Cl₂(HOMe)(PPh₃)₂] with stoichiometric amounts of 2-mercatopyridine and a proton scavenger yields [Tc(NO)Cl(Spy)(PPh₃)₂] or [Tc(NO)(Spy)₂(PPh₃)], depending upon quantities of ligands employed. These two complexes have been structurally characterized. The small bite angles of the bidentate mercaptopyridine ligands cause significant deviation from octahedral coordination geometry.     

Further studies on the coordination chemistry of [Pt2(μ-S)2(PPh3)4] towards indium(III) substrates

The reactivity of the metalloligand [Pt₂(μ-S)₂(PPh₃)₄] towards a variety of indium(III) substrates has been explored. Reaction with excess In(NO₃)₃ and halide (KBr or NaI) gave the four-coordinate adducts [Pt₂(μ-S)₂(PPh₃)₄InX₂]⁺[InX₄]⁻ (X = Br, I). An X-ray structure determination on the iodo complex revealed a slightly distorted tetrahedral coordination geometry at indium. In contrast, reaction of [Pt₂(μ-S)₂(PPh₃)₄] with indium(III) chloride was more complex; the ion [Pt₂(μ-S)₂(PPh₃)₄InCl₂]⁺ was initially observed in solution (using ESI mass spectrometry), and isolated as its BPh₄⁻ salt. Analysis of [Pt₂(μ-S)₂(PPh₃)₄InCl₂]⁺[BPh₄]⁻ by ESI MS showed the parent cation when analysed in MeCN solution. However in solutions containing methanol, partial solvolysis occurred to give the di-indium species [{Pt₂(μ-S)₂(PPh₃)₄InCl(OMe)}₂]²⁺ (proposed to contain an In₂(μ-OMe)₂ unit with five-coordinate indium) and its fragment ion [Pt₂(μ-S)₂(PPh₃)₄InCl(OMe)]⁺. Reaction of [Pt₂(μ-S)₂(PPh₃)₄] with InCl₃·3H₂O, 8-hydroxyquinoline (HQ) and trimethylamine in methanol gave the adduct [Pt₂(μ-S)₂(PPh₃)₄InQ₂]⁺, isolated as its PF₆⁻ salt. The same cationic complex is formed when [Pt₂(μ-S)₂(PPh₃)₄] is reacted with InQ₃ in methanol, but in this case the product is contaminated with the mononuclear complex [(Ph₃P)₂PtQ]⁺ formed by disintegration of the trinuclear complex [Pt₂(μ-S)₂(PPh₃)₄InQ₂]⁺ with byproduct Q⁻. [(Ph₃P)₂PtQ]⁺BPh₄⁻ was independently prepared from cis-[PtCl₂(PPh₃)₂] and HQ/Me₃N, and is the first example of a platinum 8-hydroxyquinolinate complex containing phosphine ligands.     

Functionalised dithiocarbamate complexes: Synthesis and molecular structures of bis(2-methoxyethyl)dithiocarbamate complexes [M{S2CN(CH2CH2OMe)2}2] (M = Ni, Cu, Zn) and [Cu{S2CN(CH2CH2OMe)2}2][ClO4]

The bis(2-methoxyethyl)dithiocarbamate complexes [M{S₂CN(CH₂CH₂OMe)₂}₂] (M = Ni, Cu, Zn, Pd) are readily prepared and the three lighter complexes have been crystallographically characterised. Disproportionation of [Cu{S₂CN(CH₂CH₂OMe)₂}₂] upon addition of Cu(ClO₄)₂ · 6H₂O affords the copper(III) complex [Cu{S₂CN(CH₂CH₂OMe)₂}₂][ClO₄] which has also been crystallographically characterised. Unlike other copper(III) dithiocarbamate salts, there are no intermolecular cation-cation or cation-anion interactions.     

Coordination chemistry of the metalloligand [Pt2(μ-S)2(PPh3)4] with nickel(II) complexes - an electrospray mass spectrometry directed synthetic study

The reactivity of [Pt₂(μ-S)₂(PPh₃)₄] towards a range of nickel(II) complexes has been probed using electrospray ionisation mass spectrometry coupled with synthesis and characterisation in selected systems. Reaction of [Pt₂(μ-S)₂(PPh₃)₄] with [Ni(NCS)₂(PPh₃)₂] gives [Pt₂(μ-S)₂(PPh₃)₄Ni(NCS)(PPh₃)]⁺, isolated as its BPh₄ ⁻ salt; the same product is obtained in the reaction of [Pt₂(μ-S)₂(PPh₃)₄] with [NiBr₂(PPh₃)₂] and KNCS. An X-ray structure determination reveals the expected sulfide-bridged structure, with an N-bonded thiocyanate ligand and a square-planar coordination geometry about nickel. A range of nickel(II) complexes NiL₂, containing β-diketonate, 8-hydroxyquinolinate, or salicylaldehyde oximate ligands react similarly, giving [Pt₂(μ-S)₂(PPh₃)₄NiL]⁺ cations.     

Comparative reactivity of triorganosilanes, HSi(OEt)3 and HSiEt3, with IrCl(CO)(PPh3)2. Formation of IrCl(H)2(CO)(PPh3)2 or Ir(H)2(SiEt3)(CO)(PPh3)2 depending on the substituents at Si

Reaction of HSi(OEt)₃ with IrCl(CO)(PPh₃)₂ (5:1 molar ratio) at room temperature for 1 h gives IrCl(H){Si(OEt)₃}(CO)(PPh₃)₂ (1), which is observed by the ¹H and ³¹P{¹H} NMR spectra of the reaction mixture. The same reaction, but in 20:1 molar ratio at 50 °C for 24 h produces IrCl(H)₂(CO)(PPh₃)₂ (2) rather than the expected product Ir(H)₂{Si(OEt)₃}(CO)(PPh₃)₂ (3) that was previously reported to be formed by this reaction. Accompanying formation of Si(OEt)₄, (EtO)₃SiOSi(OEt)₃, and (EtO)₂HSiOSi(OEt)₃ is observed. On the other hand, trialkylhydrosilane HSiEt₃ reacts with IrCl(CO)(PPh₃)₂ (10:1 molar ratio) at 80 °C for 84 h to give Ir(H)₂(SiEt₃)(CO)(PPh₃)₂ (4) in a high yield, accompanying with a release of ClSiEt₃.     

Phosphane effects on formation and reactivity of [Ru(L)(PR3)(`N2Me2S2')] complexes with L=N2, N2H4, NH3, and CO

Metal-sulfur complex fragments, to which small molecules like N₂, N₂H₂, N₂H₄, NH₃, or CO can bind, are desirable model compounds concerning enzymatic N₂ fixation.This paper reports on the effects of the phosphane co-ligand on formation and reactivity of [Ru(L)(PR₃)(`N<sub>2</sub>Me<sub>2</sub>S<sub>2</sub>')] [`N₂Me₂S₂'²⁻=1,2-ethanediamine-N,N^′-dimethyl-N,N^′-bis(2-benzenethiolate)(2−)] complexes with nitrogenase relevant ligands, especially N₂, N₂H₄, NH₃, and CO.Treatment of [Ru(NCCH₃)₄Cl₂] with Li₂`N<sub>2</sub>Me<sub>2</sub>S<sub>2</sub>', excessive LiOMe, bulky PPh<sub>3</sub> or PCy<sub>3</sub>, respectively, led to the formation of two series of [Ru(L)(PR<sub>3</sub>)(`N₂Me₂S₂')] complexes [for R=Ph: 1b, 1c (L=NCCH₃), 6b (L=N₂H₄), 7b (L=N₂), 8b_1-3 (L=CO), 9b (L=NH₃); for R=Cy: 1a (L=NCCH₃), 6a (L=N₂H₄), 7a (L=N₂), 8a (L=CO), 9a (L=NH₃)]. While the use of PPh₃ (θ=145°) yielded cis,trans and cis,cis isomers of [Ru(NCCH₃)(PPh₃)(`N<sub>2</sub>Me<sub>2</sub>S<sub>2</sub>')] (1b, 1c), no isomer formation was observed with the bulkier phosphane PCy<sub>3</sub> (θ=170°). Sterically less demanding phosphanes (θ=118-132°) afforded bisphosphane complexes [Ru(PR<sub>3</sub>)<sub>2</sub>(`N₂Me₂S₂')] [2d (R=Me), 2e (R=Et), 2f (R=nPr), and 2g (R=nBu)], which were practically inert and could only be converted in two cases and under drastic reaction conditions into the CO complexes [Ru(CO)(PR₃)(`N<sub>2</sub>Me<sub>2</sub>S<sub>2</sub>')] [4e (R=Et), 4f (R=nPr)]. The chelating bidentate phosphane dppe (bisdiphenylphosphanoethane) yielded exclusively the mononuclear complex [Ru(dppe)(`N₂Me₂S₂')] (3).     

Transition metal complexes of 2-formylpyridinethiosemicarbazone (HFpyTSC) and X-ray crystal structures of [Pd(FpyTSC)(PPh3)]PF6 and [Pd(FpyTSC)(SCN)]

The syntheses of five new complexes of the 2-formylpyridinethiosemicarbazone ligand (HFpyTSC) with Pd(II) and Rh(III) ions are described, viz., [Pd(FpyTSC)(PPh₃)]PF₆, [Pd(FpyTSC)(SCN)], [Pd(FpyTSC)Br], [Pd(HFpyTSC)₂]Br₂ and [Rh(FpyTSC)(PPh₃)₂Cl]ClO₄. The formulation of the complexes is discussed in terms of their elemental analyses and IR, Raman, NMR (¹H, ¹³C and ³¹P), mass and electronic spectra. The X-ray crystal structures of [Pd(FpyTSC)(PPh₃)]PF₆ and [Pd(FpyTSC)(SCN)] show that the HFpyTSC ligand coordinates to the central Pd(II) ion in a planar conformation through the pyridyl nitrogen, the azomethine nitrogen and the deprotonated thiol sulphur atom. Thus, HFpyTSC is a versatile ligand that usually acts as a mononegative tridentate ligand bonding through N_py, N_CN and C-S⁻ while, in the case of [Pd(HFpyTSC)₂]Br₂, it behaves as a neutral bidentate ligand via N_CN and CS.     

Dynamic properties of the fluxional Rh2H(μ-PPh2)2(PPh3)3 complex

The rhodium dimer [Rh₂H(PPh₂)₂(PPh₃)₃]⁻ was prepared from RhCl(PPh₃)₃ and K₄Sn₉ in the presence of 2,2,2-cryptand in ethylenediamine/toluene solvent mixtures. The [K(2,2,2-crypt)]⁺ salt was isolated and characterized via NMR and X-ray diffraction studies. The solid state structure reveals a binuclear, diphenylphosphido-bridged, 32 electron Rh(I)-Rh(I) complex with edge-shared tetrahedral and square planar Rh centers with overall C_s point symmetry. 1-D and 2-D ¹H, ³¹P, and ³¹P{¹H} NMR experiments were used to characterize the complex.     

‘Synthetic prospecting’ using an electrospray ionisation mass spectrometry directed survey of the alkylation and arylation chemistry of [Pt2(μ-S)2(PPh3)4]

Electrospray ionisation mass spectrometry (ESI-MS) has been used as an analytical tool in a wide-ranging scoping study of the alkylation and arylation reactions of [Pt₂(μ-S)₂(PPh₃)₄]. From these experiments, the factors that influence the formation of different product species - formed by mono- or di-alkylation - are determined. If the alkylating agent is an alkyl chloride or sulfate, monoalkylation followed by dialkylation of the two sulfido groups occurs, dependent on the alkylating power of the reagent used. For example, n-butyl chloride gives solely [Pt₂(μ-S)(μ-SBu)(PPh₃)₄]⁺ while dimethyl sulfate gives [Pt₂(μ-SMe)₂(PPh₃)₄]²⁺. This species, previously unisolated is stable in the absence of good nucleophiles, but the addition of potassium iodide results in rapid conversion to [Pt₂(μ-SMe)₂(PPh₃)₃I]⁺. This iodo complex is also observed from the reaction of [Pt₂(μ-S)₂(PPh₃)₄] with excess MeI, after the initial formation of mono- and di-methylated species. In these reactions, the iodide presumably displaces a phosphine ligand, which is then quaternised by excess alkylating agent. Changing the alkylating agent to a longer chain alkyl iodide or methyl bromide decreases the rate of alkylation of the sulfide in the initially formed [Pt₂(μ-S)(μ-SR)(PPh₃)₄]⁺. Mixed-thiolate species of the type [Pt₂(μ-SMe)(μ-SR)(PPh₃)₄]²⁺ are easily generated by reaction of [Pt₂(μ-S)(μ-SR)(PPh₃)₄]⁺ with excess Me₂SO₄ and is also dependent on the avoidance of nucleophiles. Reactions towards α,ω-dialkylating agents are surveyed; the chain length is found to have a dramatic effect on the rate of the second intramolecular cyclisation process, illustrated by a competitive reactivity study involving a mixture of Br(CH₂)₄Br and Br(CH₂)₅Br; on completion of the reaction the former gives [Pt₂{μ-S(CH₂)₄S}(PPh₃)₄]²⁺ while the latter predominantly gives monoalkylated[Pt₂(μ-S){μ-S(CH₂)₅Br}(PPh₃)₄]⁺. The reactivity of o- and p-dihaloxylenes has been explored, with the reaction with p-BrCH₂C₆H₄CH₂Br giving the bridged species [(PPh₃)₄Pt₂(μ-S)(μ-SCH₂C₆H₄CH₂S)(μ-S)Pt₂(PPh₃)₄]²⁺. Arylation reactions of [Pt₂(μ-S)₂(PPh₃)₄] with halobenzenes and 2-bromoheterocyclic compounds (pyridine, thiophene) are also described.     

Complexes of N-thiophosphorylthioureas RNHC(S)NHP(S)(OiPr)2 (HL) (R = pyridin-2-yl, pyridin-3-yl, 6-amino-pyridin-2-yl) with copper(I): Crystal structures of Cu(PPh3)nL (n = 1, 2)

Reaction of the potassium salts of N-thiophosphorylated thioureas of common formula RNHC(S)NHP(S)(OiPr)₂ [R = pyridin-2-yl (HL^a), pyridin-3-yl (HL^b), 6-amino-pyridin-2-yl (HL^c)] with Cu(PPh₃)₃I in aqueous EtOH/CH₂Cl₂ leads to mononuclear [Cu(PPh₃)₂L^a,b-S,S′] (1, 2) and [Cu(PPh₃)L^c-S,S′] (3) complexes. Using copper(I) iodide instead of Cu(PPh₃)₃I, polynuclear complexes [Cu_n(L-S,S′)_n] (4-6) were obtained. The structures of these compounds were investigated by IR, ¹H, ³¹P{¹H} NMR spectroscopy, ES-MS and elemental analyses. The crystal structures of Cu(PPh₃)₂L^b (2) and Cu(PPh₃)L^c (3) were determined by single-crystal X-ray diffraction.     

Coordination of 4-mercapto-1,2-dithiole-3-thione heterocycles to ruthenium(II) and molybdenum(VI) centres

Deprotonation of 4-mercapto-1,2-dithiole-3-thiones with NEt₃ followed by reaction with [Ru(H)(Cl)(CO)(PPh₃)₃] affords virtually quantitative yields of turquoise [Ru(H)(RC₃S₄)(CO)(PPh₃)₂] (R = Ph, Mes) in which the heterocycle is bound as a bidentate uninegative ligand through the two exocyclic sulfur atoms. The presence of both possible isomers in each case is indicated by NMR spectroscopy. Reaction of the 4-mercapto-1,2-dithiole-3-thiones with [MoO₂(acac)₂] results in displacement of the acac ligands and formation of [MoO₂(RC₃S₄)₂]. The crystal structures of [Ru(H)(MesC₃S₄)(CO)(PPh₃)₂] and [MoO₂(MesC₃S₄)₂] have been determined.     

[S2], [S3], and [N3] coordination modes of hydrotris(thioxotriazolyl)borato. Zinc, nickel, cobalt, and bismuth complexes

The ligand hydrotris(1,4-dihydro-3-methyl-4-phenyl-5-thioxo-1,2,4-triazolyl)borato (Tr^Ph,Me) was synthetized as natrium salt and the complexes [Zn(Tr^Ph,Me)₂] · 7.5H₂O · 1.5CH₃CN (2a), [Zn(Tr^Ph,Me)₂] · 8DMF (2b), [Co(Tr^Ph,Me)₂] · 8DMF (3a), [Ni(Tr^Ph,Me)₂] · H₂O · 6DMSO (4a), [Bi(Tr^Ph,Me)₂]NO₃ (5), have been isolated and structurally characterized by X-ray diffraction. In the zinc derivatives the ligand adopts different denticity and coordination modes, η² and [S₂] for 2a and η³ and [N₃] for 2b, depending on the crystallization solvent, giving rise to tetrahedral and octahedral geometry, respectively. In the octahedral cobalt and nickel complexes the ligand is η³ and [N₃] coordinated whereas in the bismuth complex the η³ and [S₃] coordination is exhibited.     

Synthesis of [SnPh2(SR)2] SR = SC6F4-4-H, SC6F5: Reactivity towards group 10 transition metal complexes

The organometallic tin(IV) complexes [SnPh₂(SR^F)₂] SR^F = ⁻SC₆F₄-4-H (1), ⁻SC₆F₅ (2), were synthesized and their reactivity with [MCl₂(PPh₃)₂] M = Ni, Pd and Pt explored. Thus, transmetallation products were obtained affording polymeric [Ni(SR^F)(μ-SR^F)]_n, monomeric cis-[Pt(PPh₃)₂(SC₆F₄-4-H)₂] (3) and cis-[Pt(PPh₃)₂(SC₆F₅)₂] (4) and dimeric species [Pd(PPh₃)(SC₆F₄-4-H)(μ-SC₆F₄-4-H)]₂ (5) and [Pd(PPh₃)(SC₆F₅)(μ-SC₆F₅)]₂ (6) for Ni, Pt and Pd, respectively. The crystal structures of complexes 1, 2, 3, 4 and 6 were determined.     

[Co{Ph2P(O)CH2P(O)Ph2}3][CoCl4] · 8CHCl3: Crystal structure and formation from [Co2(Ph2PCH2PPh2)(CO)6] in chloroform

When a solution of [Co₂(Ph₂PCH₂PPh₂)(CO)₆] in chloroform or deuterochloroform is allowed to stand in air at room temperature, it deposits dark green crystals of [Co{Ph₂P(O)CH₂P(O)Ph₂}₃][CoCl₄] · 8CHCl₃. The same product is formed more quickly and in much higher yield (80% based on Co) if the reaction is carried out in the presence of 2 equiv. of [Ph₂PCH₂PPh₂]; the Co^II appears to catalyse the air-oxidation of [Ph₂PCH₂PPh₂]. The salt was characterised by X-ray crystallography and shown to contain octahedral Co^II cations and Co^II tetrahedral anions having normal bond lengths and angles.     

Quantification of cis and trans influences in [PtX(PPh3)3] complexes. A P NMR study

In [PtX(PPh₃)₃]⁺ complexes (X = F, Cl, Br, I, AcO, NO₃, NO₂, H, Me) the mutual cis and trans influences of the PPh₃ groups can be considered constants in the first place, therefore the one bond Pt-P coupling constants of P_(cis) and P_(trans) reflect the cis and trans influences of X. The compounds [PtBr(PPh₃)₃](BF₄) (2), [PtI(PPh₃)₃](BF₄) (3), [Pt(AcO)(PPh₃)₃](BF₄) (4), [Pt(NO₃)(PPh₃)₃](BF₄) (5), and the two isomers [Pt(NO₂-O)(PPh₃)₃](BF₄) (6a) and [Pt(NO₂-N)(PPh₃)₃](BF₄) (6b) have been newly synthesised and the crystal structures of 2 and 4·CH₂Cl₂·0.25C₃H₆O have been determined. From the ¹J_PtP values of all compounds we have deduced the series: I > Br > Cl > NO₃ > ONO > F > AcO > NO₂ > H > Me (cis influence) and Me > H > NO₂ > AcO > I > ONO > Br > Cl > F > NO₃ (trans influence). These sequences are like those obtained for the (neutral) cis- and trans-[PtClX(PPh₃)₂] derivatives, showing that there is no dependence on the charge of the complexes. On the contrary, the weights of both influences, relative to those of X = Cl, were found to depend on the charge and nature of the complex.     

Synthesis of 5,6-dihydro-4H-1,3-oxazines from neutral and cationic platinum(II) nitrile complexes. X-ray structure of trans-[Pt(CF3){ H2CH2}(PPh3)2]BF4

The 1,3-oxazine complexes cis- and trans-[PtCl₂{ C(R)OCH₂CH₂C}H₂₂] (cis: R=CH₃ (1a), CH₂CH₃ (2a), (CH3)₃C (3a), C₆H₅ (4a); trans:R =CH₃ (1b), C₆H₅ (4b)) were obtained in 51-71% yield by reaction in THF at 0 °C of the corresponding nitrile complexes cis- and trans-[PtCl2(NCR)₂] with 2 equiv. of ⁻OCH₂CH₂CH₂Cl, generated by deprotonation of 3-chloro-1-propanol with n-BuLi. The cationic nitrile complexes trans-[Pt(CF₃)(NCR)(PPh₃)₂]BF₄ (R=CH3, C₆H₅) react with 1 equiv, of ⁻ OCH2CH2CH2Cl to give a mixture of products, including the corresponding oxazine derivatives trans-[Pt(CF₃){ CH₂}(PPh₃)₂]BF₄ (5 and 6), the chloro complex _trans- [Pt(CF₃)Cl(PPh₃)₂] and free oxazine H2. For short reaction times (c. 5–15 min) the oxazine complexes 5 and 6 could be isolated in modest yield (37–49%) from the reaction mixtures and they could be separated from the corresponding chloro complex (yield 40%) by taking advantage of the higher solubility of the latter derivative in benzene. For longer reaction times (> 2 h), trans-[Pt(CF₃)Cl(PPh₃)₂] was the only isolated product. Complex 6 was crystallographically characterized and it was found to contain also crystals of trans- [PtCl{ H₂}(PPh₃)₂]BF₄, which prevented a more detailed analysis of the bond lengths and angles within the metal coordination sphere. The 1,3-oxazine ring, which shows an overall planar arrangement, is characterized by high thermal values of the carbon atoms of the methylene groups indicative of disordering in this part of the molecule in agreement with fast dynamic ring processes suggested on the basis of ¹H NMR spectra. It crystallizes in the trigonal space group P , with a=22.590(4), b=15.970(3) Å, γ=120°, V=7058(1) ų and Z=6. The structure was refined to R=0.059 for 3903 unique observed (I3σ(I)) reflections. A mechanism is proposed for the conversion of nitrile ligands to oxazines in Pt(II) complexes.     

Synthesis and characterization of three group 10 complexes containing nido-carborane diphosphine: [MCl(PPh3){7,8-(PPh2)2-7,8-C2B9H10}] (M = Ni, Pd, Pt)

Three group 10 complexes containing nido-carborane diphosphine, [NiCl(PPh₃){7,8-(PPh₂)₂-7,8-C₂B₉H₁₀}] (1), [PdCl(PPh₃){7,8-(PPh₂)₂-7,8-C₂B₉H₁₀}] · 1.25CH₂Cl₂ (2) and [PtCl(PPh₃){7,8-(PPh₂)₂-7,8-C₂B₉H₁₀}] · 2.5CH₂Cl₂ (3) have been synthesized by the reactions of [M(PPh₃)₂Cl₂] (M = Ni, Pd, Pt) with closo carborane diphosphine 1,2-(PPh₂)₂-1,2-C₂B₁₀H₁₀ in ethanol. For complex 3, it could also be obtained under solvothermal condition. All three complexes were characterized by elemental analysis, FT-IR, ¹H and ¹³C NMR spectroscopy and X-ray structure determination. Single crystal structures show that their structures are similar to each other. In each complex, the nido [7,8-(PPh₂)₂-7,8-C₂B₉H₁₀]⁻, which resulted from the degradation of the initial closo ligand 1,2-(PPh₂)₂-1,2-C₂B₁₀H₁₀ during the reaction process, was coordinated bidentately through the P atoms to M(II) ion, and this resulted in a stable five-membered chelating ring between the bis-diphosphine ligand and the metal. The coordination mode of the metal can be described as a slightly distorted square-planar, in which the remaining two positions were occupied by one Cl⁻ and one PPh₃ group.     

Antisymbiosis. Preferential coordination of anionic oxygen versus neutral sulfur donor atoms of methylsulfanyl- or methylsulfinyl-acetato, 2-benzoato and 2-phenolato to the cis-Pt(PPh3)2 and Pt(dppe) residues

The interaction of an excess of the title ligands L⁻ with the cis-Pt(phos)₂ moieties gives compounds a-bcis-[Pt(L-O)₂(phos)₂] (a, phos = P(Ph)₃; b, phos = 1/2 dppe), in which O- is preferred to S-coordination. Such preference is confirmed by the fact that the same products are obtained by reaction of excess of L⁻ with the previously reported a-d complexes [Pt(L-O,S)(phos)₂]⁺, (c, phos = PPh₃, d, phos = 1/2 dppe), for which chelate ring opening occurs with rupture of Pt-S rather than Pt-O bonds. Compound a can be obtained also by oxidative addition of HL to [Pt(PPh₃)₃]. The Pt-O bonds in compounds a-d are stable towards substitution by Me₂SO, pyridine and tetramethylthiourea. Substitution of L’s occurs with N,N′-diethyldithiocarbamate, which forms a very stable chelate with Pt(II). Thiourea and N,N′-dimethylthiourea also react, because they give rise to cyclometallated products [Pt(phos)₂(NRC(S)NHR)]⁺ (R = H, CH₃), with one ionised thioamido group, as revealed by an X-ray investigation of [Pt(PPh₃)₂(NHC(S)NH₂)]⁺. The preference of O versus S coordination, as well as the stability of the Pt-O bonds, are discussed in terms of antisymbiosis.