Reaction of [Pt3(μ-CO)3(PBu3)3] with activated olefins and alkynes: the X-ray-structure of [Pt(CO)(PBu3)(CF3CCCF3)]

The reactions of the triangulo-cluster [Pt₃(μ-CO)₃(P^tBu₃)₃] with activated olefins and alkynes have been examined under various conditions. At low temperature, cluster fragmentation occurs yielding the Pt(0) complexes [Pt(CO)(P^tBu₃)(olefin)] (olefin = maleic anhydride and maleimide), while di(tert-butyl)acetylenedicarboxilate reacts quantitatively giving the dinuclear Pt(0) complex [Pt₂(CO)₂(P^tBu₃)₂(μ-η²:η²-^tBuO₂CCCCO₂^tBu)]. At higher temperature and in the presence of alkyne in large excess, the latter dimer converts quantitatively to the monomers [Pt(CO)(P^tBu₃)(alkyne)] (alkyne = CF₃CCCF₃ and ^tBuO₂CCCCO₂^tBu). The stereochemistry of these complexes has been established by NMR and IR measurements. The structure of [Pt(CO)(P^tBu₃)(CF₃CCCF₃)] was confirmed by X-ray diffraction analysis.     

Thallium(III) complexes of the metalloligands [Pt2(μ-S)2(PPh3)4] and [Pt2(μ-Se)2(PPh3)4]

Reactions of [Pt₂(μ-S)₂(PPh₃)₄] with the diarylthallium(III) bromides Ar₂TlBr [Ar = Ph and p-ClC₆H₄] in methanol gave good yields of the thallium(III) adducts [Pt₂(μ-S)₂(PPh₃)₄TlAr₂]⁺, isolated as their salts. The corresponding selenide complex [Pt₂(μ-Se)₂(PPh₃)₄TlPh₂]BPh₄ was similarly synthesised from [Pt₂(μ-Se)₂(PPh₃)₄], Ph₂TlBr and NaBPh₄. The reaction of [Pt₂(μ-S)₂(PPh₃)₄] with PhTlBr₂ gave [Pt₂(μ-S)₂(PPh₃)₄TlBrPh]⁺, while reaction with TlBr₃ gave the dibromothallium(III) adduct [Pt₂(μ-S)₂(PPh₃)₄TlBr₂]⁺[TlBr₄]⁻. The latter complex is a rare example of a thallium(III) dihalide complex stabilised solely by sulfur donor ligands. X-ray crystal structure determinations on the complexes [Pt₂(μ-S)₂(PPh₃)₄TlPh₂]BPh₄, [Pt₂(μ-S)₂(PPh₃)₄TlBrPh]BPh₄ and [Pt₂(μ-S)₂(PPh₃)₄TlBr₂][TlBr₄] reveal a greater interaction between the thallium(III) centre and the two sulfide ligands on stepwise replacement of Ph by Br, as indicated by shorter Tl-S and Pt?Tl distances, and an increasing S-Tl-S bond angle. Investigations of the ESI MS fragmentation behaviour of the thallium(III) complexes are reported.     

The arylation of [Pt2(μ-S)2(PPh3)4]

Routes to the synthesis of the mixed sulfide-phenylthiolate complex [Pt₂(μ-S)(μ-SPh)(PPh₃)₄]⁺ have been explored; reaction of [Pt₂(μ-S)₂(PPh₃)₄] with excess Ph₂IBr proceeds readily to selectively produce this complex, which was structurally characterised as its PF₆⁻ salt. Reactions of [Pt₂(μ-S)₂(PPh₃)₄] with other potent arylating reagents (1-chloro-2,4-dinitrobenzene and 1,5-difluoro-2,4-dinitrobenzene) also produce the corresponding nitroaryl-thiolate complexes [Pt₂(μ-S){μ-SC₆H₂(NO₂)₂X}(PPh₃)₄]⁺ (X = H, F). The complex [Pt₂(μ-S)(μ-SPh)(PPh₃)₄]⁺ reacts with Me₂SO₄ to produce the mixed alkyl/aryl bis-thiolate complex [Pt₂(μ-SMe)(μ-SPh)(PPh₃)₄]²⁺, but corresponding reactions with the nitroaryl-thiolate complexes are plagued by elimination of the nitroaryl group and formation of [Pt₂(μ-SMe)₂(PPh₃)₄]²⁺. [Pt₂(μ-S)(μ-SPh)(PPh₃)₄]⁺ also reacts with Ph₃PAuCl to give [Pt₂(μ-SAuPPh₃)(μ-SPh)(PPh₃)₄]²⁺.     

Metal-sulfur dπ-pπ buffering of the oxidations of metal-thiolate complexes: Photoelectron spectroscopy of (η-C5H5)Fe(CO)2SR (SR = SCH3, SBu) and (η-C5H5)Re(NO)(PR3)SCH3 (PR3 = PPr3, PPh3)

The metal-sulfur bonding present in the transition metal-thiolate complexes CpFe(CO)₂SCH₃, CpFe(CO)₂S^tBu, CpRe(NO)(PⁱPr₃)SCH₃, and CpRe(NO)(PPh₃)SCH₃ (Cp = η⁵-C₅H₅) is investigated via gas-phase valence photoelectron spectroscopy. For all four complexes a strong dπ-pπ interaction exists between a filled predominantly metal d orbital of the [CpML₂]⁺ fragment and the purely sulfur 3pπ lone pair of the thiolate. This interaction results in the highest occupied molecular orbital having substantial M-S π^∗ antibonding character. In the case of CpFe(CO)₂SCH₃, the first (lowest energy) ionization is from the Fe-S π^∗ orbital, the next two ionizations are from predominantly metal d orbitals, and the fourth ionization is from the Fe-S π orbital. The pure sulfur pπ lone pair of the thiolate fragment is less stable than the filled metal d orbitals of the [CpFe(CO)₂]⁺ fragment, resulting in a Fe-S π^∗ combination that is higher in sulfur character than the Fe-S π combination. Interestingly, substitution of a tert-butyl group for the methyl group on the thiolate causes little shift in the first ionization, in contrast to the shift observed for related thiols. This is a consequence of the delocalization and electronic buffering provided by the Fe-S dπ-pπ interaction. For CpRe(NO)(PⁱPr₃)SCH₃ and CpRe(NO)(PPh₃)SCH₃, the strong acceptor ability of the nitrosyl ligand rotates the metal orbitals for optimum backbonding to the nitrosyl, and the thiolate rotates along with these orbitals to a different preferred orientation from that of the Fe complexes. The initial ionization is again the M-S π^∗ combination with mostly sulfur character, but now has considerable mixing among several of the valence orbitals. Because of the high sulfur character in the HOMO, ligand substitution on the metal also has a small effect on the ionization energy in comparison to the shifts observed for similar substitutions in other molecules. These experiments show that, contrary to the traditional interpretation of oxidation of metal complexes, removal of an electron from these metal-thiolate complexes is not well represented by an increase in the formal oxidation state of the metal, nor by simple oxidation of the sulfur, but instead is a variable mix of metal and sulfur content in the highest occupied orbital.     

Reaction of cyanamide and their derivatives with (η-C5H5)Mn(CO)3 and (η-C5H4CH3)Mn(CO)3

The reaction of cyanamide and its derivatives with the (η⁵-C₅H₅)Mn(CO)₂(THF) and (η⁵-C₅H₄CH₃)Mn(CO)₂(THF) complexes affords the cyanamide substituted complexes of types (η⁵-C₅H₅)Mn(CO)₂(NCN(R′)(R″)) (2a-d) and (η⁵-C₅H₄CH₃)Mn(CO)₂(NCN(R′)(R″)) (3a-e). All complexes were characterized by spectroscopy (¹H, ¹³C NMR, IR), elemental and mass spectroscopy analysis. Complex 2b (η⁵-C₅H₅)Mn(CO)₂(NCN(CH₃)₂) was additionally examined by single crystal X-ray structure determination.     

Synthesis of some pentanuclear platinum clusters [Pt5(CO)6(L)4]. The X-ray structure of [Pt5(μ-CO)5(CO)(PCy3)4]

[Pt₅(μ-CO)₅(CO)L₄] (L = PPh₃1, PPh₂Bz 2, AsPh₃3, PEt₃4, PCy₃5) have been synthesized by reacting [Pt₃(μ-CO)₃(PR₃)₃] with H₂O₂ (1 and 2), by reduction of cis-[PtCl₂(CO)(PEt₃)] with Zn dust (4), and by the Zn reduction of [Pt₃(μ-CO)₃(PCy₃)₃] in the presence of [PtCl₂(CH₃CN)₂] (5). Complex 5 has not been observed previously and has been characterized by X-ray crystallography. Oxidation of the phosphine ligands with H₂O₂ is a new way to synthesize 1 and 2. The first complete NMR characterization of these complexes has also been achieved, and showed that these pentanuclear cluster complexes exhibit similar stereochemistries in solution and in the solid state. The observed ¹J_Pt-Pt values do not have any correlation with the corresponding bond lengths, again pointing out the irregular behaviour of such parameter in Pt complexes.     

N-Heterocyclic carbene gold(I) and silver(I) adducts of [Pt2(μ-S)2(PPh3)4]

Reaction of the metalloligand [Pt₂(μ-S)₂(PPh₃)₄] with the N-heterocyclic carbene (NHC) complexes IPrAuCl, IMesAuCl and IMesAgCl in methanol gave the first examples of metal adducts of [Pt₂(μ-S)₂(PPh₃)₄] that contain NHC ligands, namely [Pt₂(μ-S)₂(PPh₃)₄AuL]⁺ (L = IPr, IMes) and [Pt₂(μ-S)₂(PPh₃)₄AgIMes]⁺. The complexes were isolated as hexafluorophosphate salts. Reaction of [Pt₂(μ-S)₂(PPh₃)₄] with excess IPrAuCl in refluxing methanol yielded only the mono-adduct, in contrast to the behaviour with the gold(I) phosphine complex Ph₃PAuCl, which undergoes double addition giving [Pt₂(μ-SAuPPh₃)₂(PPh₃)₄]²⁺. The X-ray structure of [Pt₂(μ-S)₂(PPh₃)₄AuIPr]PF₆ was determined and reveals that the ‘free’ sulfide is substantially sterically protected by the IPr ligand, accounting for the low reactivity towards addition of a second AgIPr⁺ moiety.     

Synthesis and structure of the cyclic amido bismuth imide, {[(Me3Si)2N]Bi[μ-N(SiMe3)]}2, via loss of SiMe3 from a [N(SiMe3)2] ligand

The synthesis of Bi[N(SiMe₃)₂]₃ from BiCl₃ and KN(SiMe₃)₂ generates an unusual amido bismuth imide by-product, {[(Me₃Si)₂N]Bi[μ-N(SiMe₃)]}₂, evidently formed via SiN bond cleavage. X-ray diffraction shows that the complex contains a planar Bi₂N₂ ring with tetrahedral bismuth and trigonal planar imido nitrogen atoms.     

Hydrido-derivatives of [Ir4(CO)10(diphosphine)]: X-ray analyses of [Ir4H(CO)9(μ-Ph2PH(CH3)PPh2)] and [Ir4 H(CO)9(μ-Ph2P(CH2)nPPh2)] (n = 2, 3)

Some novel hydrido-anions of general formula [Ir₄H(CO)₉(μ-L-L)]⁻ (L-L = Ph₂PCH(CH₃)PPh₂, Ph₂P(CH₂)₂PPh₂, Ph₂P(CH₂)₃PPh₂ and Ph₂AsCH₂AsPh₂) have been obtained by the reaction of [Ir₄(CO)₁₀(μ-L-L)] with the base 1,8-diazabicyclo[5.4.0]undec-7-ene in wet dichloromethane. According to IR and ¹H, ³¹P and ¹³C NMR data at low temperature, these anionic derivatives display a single conformation in solution: three edge-bridging COs around the triangular basal face and both the hydride and the bidentate ligands located in axial positions relative to this face. The structures of four compounds were established by X-ray diffraction studies, which confirmed the configuration proposed on the basis of spectroscopic data.     

Synthesis and characterisation of [Pt2(μ-S)(μ-I)(PPh3)4] - A cationic iodo analogue of the metalloligand [Pt2(μ-S)2(PPh3)4]

Reaction of [Pt₂(μ-S)₂(PPh₃)₄] with a number of transition metal-iodo complexes leads to the formation of the cationic iodo analogue [Pt₂(μ-S)(μ-I)(PPh₃)₄]⁺, identified using electrospray ionisation mass spectrometry (ESI MS). Synthetic routes to this complex were developed, using the reaction of [Pt₂(μ-S)₂(PPh₃)₄] with either [PtI₂(PPh₃)₂] or elemental iodine. The complex was characterised by NMR spectroscopy, ESI MS and an X-ray structure determination, which reveals the presence of a planar, disordered {Pt₂SI}⁺ core. Monitoring the iodine reaction by ESI MS allows the identification of various iodine species, including the short-lived intermediate [Pt₂(μ-S)₂(PPh₃)₄I]⁺, which allows a mechanism for the reaction to be proposed.     

D and D Nuclear magnetic resonance of new silver(I) complexes with achiral and chiral bases as ligands: Crystal structure of [Ag{(S)-(6-CH3)C5H3N-CHN-C*H(α-CH3)C6H5}(PPh3)2](O3SCF3)

Treatment of equimolar amounts of substituted aniline or amine with substituted benzaldehyde leads to the corresponding achiral or chiral Schiff bases (L). The reaction of the bases with [Ag(O₃SCF₃)(PPh₃)] leads to the preparation of three or four coordinated cationic complexes, [Ag(k¹-L)(PPh₃)_n]⁺ (n = 1 or 2) which have been characterized by IR, ¹D and ²D NMR spectroscopy. The crystal structure of [Ag{(S)-(6-CH₃)C₅H₃N-CHN-C*H(α-CH₃)C₆H₅}(PPh₃)₂](O₃SCF₃) is reported.     

Chalcogenide-capped triruthenium clusters: X-ray structures of [Ru3(CO)6(μ3-CO){P(C4H3S)3}(μ-dppm)(μ3-O)] and [(μ-H)2Ru3(CO)6{P(C4H3S)3}(μ-dppm)(μ3-S)]

Treatment of [Ru₃(CO)₉{P(C₄H₃S)₃}(μ-dppm)] (1) [dppm = bis(diphenylphosphino)methane] with molecular oxygen in benzene at 60 °C affords oxo-capped [Ru₃(CO)₆(μ₃-CO){P(C₄H₃S)₃}(μ-dppm)(μ₃-O)] (2), while with elemental sulfur and selenium related chalcogenide-capped clusters [Ru₃(CO)₆(μ₃-CO){P(C₄H₃S)₃}(μ-dppm)(μ₃-E)] (3, E = S; 5, E = Se) and bis(chalcogenide) clusters [Ru₃(CO)₆{P(C₄H₃S)₃}(μ-dppm)(μ₃-E)₂] (4, E = S; 6, E = Se) result. Reaction of 1 with H₂S in refluxing THF affords the previously reported [(μ-H)₂Ru₃(CO)₇(μ-dppm)(μ₃-S)] (7) together with the new sulfido-capped dihydride [(μ-H)₂Ru₃(CO)₆{P(C₄H₃S)₃}(μ-dppm)(μ₃-S)] (8). All new compounds have been characterized by spectroscopic data, and 2 and 8 by single-crystal X-ray diffraction analyses. Oxo-capped 2 consists of a triangular ruthenium framework capped on opposite sides by oxo and carbonyl groups, while 8 consists of a ruthenium triangle by a capping sulfido ligand and two inequivalent bridging hydride ligands.     

Synthesis and characterisation of adducts of [Pt2(μ-S)2(PPh3)4] with organo-palladium and platinum-hydride substrates

The reactions of [Pt₂(μ-S)₂(PPh₃)₄] towards a range of palladium(II) complexes containing organometallic ligands (cyclopalladated N-donor ligands, η³-allyl, phenyl) have been explored, leading to the formation of a series of cationic, trinuclear sulfido-bridged aggregates containing {Pt₂PdS₂} cores. [Pt₂(μ-S)₂(PPh₃)₄] also reacts with the platinum(II) hydride complex trans-[PtHCl(PPh₃)₂] giving the adduct [Pt₂(μ-S)₂(PPh₃)₄PtH(PPh₃)]⁺. X-ray crystal structure determinations on the complexes [Pt₂(μ-S)₂(PPh₃)₄PdPh(PPh₃)]PF₆ and [Pt₂(μ-S)₂(PPh₃)₄PtH(PPh₃)]PF₆ are reported, and show the expected bis μ₃-sulfido aggregates with three square-planar metal centres.     

Ligand induced PH bond formation and a comparison of the reactivity of two isomers of the carbonyl hydride [Pt2(μ-PBu2)2(H)(CO)(PBu2H)]CF3SO3

The Pt₂ ^(II) isomeric terminal hydrides [(CO)(H)Pt(μ-PBu^t ₂)₂Pt(PBu^t ₂H)]CF₃SO₃ (1a), and [(CO)Pt(μ-PBu^t ₂)₂Pt(PBu^t ₂H)(H)]CF₃SO₃ (1b), react rapidly with 1 atm of carbon monoxide to give the same mixture of two isomers of the Pt₂ ^(I) dicarbonyl [Pt₂(μ-PBu^t ₂)(CO)₂(PBu^t ₂H)₂]CF₃SO₃ (3-Pt); the solid state structure of the isomer bearing the carbonyl ligands pseudo-trans to the bridging phosphide was solved by X-ray diffraction. A remarkable difference was instead found between the reactivity of 1a and 1b towards carbon disulfide or isoprene. In both cases 1b reacts slowly to afford [Pt₂(μ-PBu^t ₂)(μ,η²,η²-CS₂)(PBu^t ₂H)₂]CF₃SO₃ (4-Pt), and [Pt₂(μ-PBu^t ₂)(μ,η²,η²-isoprene) (PBu^t ₂H)₂]CF₃SO₃ (6-Pt), respectively. In the same experimental conditions, 1a is totally inert. A common mechanism, proceeding through the preassociation of the incoming ligand followed by the PH bond formation between one of the bridging P atoms and the hydride ligand, has been suggested for these reactions.     

A one-dimensional copper (II) coordination polymer [Cu3(ampym)2(μ1,1-N3)4(μ1,3-N3)2(dmf)2]n (ampym = 2-aminopyrimidine) containing both end-on and end-to-end azido bridges

A new polynuclear copper (II) complex, derived from the azido-bridging ligand and 2-aminopyrimidine, has been synthesized and its 3-D structure has been determined by X-ray diffraction methods at two different temperatures. The compound crystallizes in the triclinic system space group, with the central copper atom lying on an inversion centre. The crystal structure is built up by trinuclear units (each of them contains two double end-on azido bridges) linked through two azide ions in an end-to-end (EE) fashion, to yield the polymer chain [Cu₃(ampym)₂(μ_1,1-N₃)₄(μ_1,3-N₃)₂(dmf)₂]_n. Magnetic susceptibility measurement shows a ferromagnetic interaction above 30 K, whereas a weak anti-ferromagnetic interaction prevails in the range of 30-2 K.     

Influence of CH3 group of μ-N-C-S ligand on the properties of [Fe2(C4H5N2S)2(NO)4] complex

Bi-nuclear neutral sulfur-nitrosyl iron complex [Fe₂(SR)₂(NO)₄] (I) has been obtained by replacement of thiosulfate ligands in dianion [Fe₂(S₂O₃)₂(NO)₄]²⁻ by 1-methyl-imidazole-2-yl. From X-ray analysis data, the complex has centrosymmetrical dimeric structure, with the iron atoms being linked via μ-N-C-S bridge. From Mossbauer spectroscopy, isomeric shift δ_Fe is 0.180(1) mm/s and quadrupole splitting ΔE_Q is 0.928(2) mm/s at T = 290 K. By comparative studying the mass-spectra in the gaseous phase of solid samples decomposition and kinetics of NO release in 1% aqueous solutions of dimethylsulfoxide, using of the ligand with CH₃ substituent in position 1 of imidazole-2-thiol was shown to yield a more stable donor of nitrogen monoxide than earlier obtained analog with imidazole-2-thiol, [Fe₂(C₃H₃N₂S)₂(NO)₄].     

Synthesis, characterization and molecular structures of the trichloro-η-benzoyldiazenido [ReCl3{η-NNC(O)Ph}(PPh3)2] and oxorhenium [ReOCl2(OMe)(PPh3)2] complexes derived from reactions of [ReCl2{η-NNC(O)Ph}(PPh3)2] with a peroxide or dioxygen

The reactions of [ReCl₂{η²-NNC(O)Ph}(PPh₃)₂] (1) with t-BuOOH, in C₆H₆ or chlorinated solvents, at room temperature or with MeOH upon reflux in air lead to the trichloro-η¹-benzoyldiazenido [ReCl₃{η¹-NNC(O)Ph}(PPh₃)₂] (2) or the methoxy-oxo [ReOCl₂(OMe)(PPh₃)₂] (3) compound, respectively, which have been characterized by spectroscopic and FAB⁺-MS methods, elemental and single crystal X-ray diffraction analyses. They show distorted octahedral coordinaiton geometries with trans triphenylphosphine ligands, an essentially linear η¹-diazenido moiety in 2 and the methoxy group in 3 in trans position to the oxo ligand.     

A convenient preparation of [(Ph3P)3Pt2(μ-H)(μ-PPh2)Ph]BF4 by rearrangement of trans-aquahydridobis(triphenylphosphine) platinum(II) tetrafluoroborate

The cation [(PPh₃)₂Pt(H)OH₂]⁺ previously suggested as an intermediate in the synthesis of [(Ph₃P)₃Pt₂(μ-H)(μ-PPh₂)Ph]⁺ has been isolated as the tetrafluoroborate salt and characterised by X-ray crystallography. The structure shows a large unit cell with three independent cations and extensive hydrogen bonding between the water molecules and the tetrafluoroborate anions. The rearrangement of [(PPh₃)₂Pt(H)OH₂]⁺ in aqueous THF provides a convenient high yield route to [(Ph₃P)₃Pt₂(μ-H)(μ-PPh₂)Ph]⁺.     

A facile reaction of bibenzyl trisulfide with [(η-C5H5)Cr(CO)3]2: formation of a thiolato-bridged dichromium complex of [CpCr(CO)2(SBz)]2 (Bz = PhCH2-)

The reaction of [CpCr(CO)₃]₂ (Cp = η⁵-C₅H₅) (1) with an equivalent of Bz₂S₃ at ambient temperature gave [CpCr(CO)₂]₂S (3) [L.Y. Goh, T.W. Hambley, G.B. Robertson, Organometallics 6 (1987) 1051], novel complexes of [CpCr(CO)₂(SBz)]₂ (4) and together with [CpCr(SBz)]₂S (5) as main products. Thermolytic studies showed that 4 underwent complete decarbonylation to give [CpCr(SBz)]₂S (5). Final thermal decomposition of 3 and 5 eventually yielded Cp₄Cr₄S₄ (6) (Goh et al., 1987) after prolonged reaction at 100 °C. However, the reaction of [CpCr(CO)₂]₂ (CrCr) (2) with Bz₂S₃ was much slower at ambient temperature which required 72 h to complete eventually yielding 3 and 5. All the products have been characterized by elemental and spectral analyses. 4 has been structurally determined.