The enthalpies of formation of CH3Mn(CO)5 and of CH3Re(CO)5, and the strengths of the CH3Mn and CH3Re bonds

From measurements of the heats of iodination of CH₃Mn(CO)₅ and CH₃Re(CO)₅ at elevated temperatures using the ‘drop’ microcalorimeter method, values were determined for the standard enthalpies of formation at 25° of the crystalline compounds: ΔH^o_f[CH₃Mn(CO)₅, c] = ?189.0 ± 2 kcal mol^?1 (?790.8 ± 8 kJ mol^?1), ΔH^o_f[Ch₃Re(CO)₅,c] = ?198.0 ± kcal mol^?1 (?828.4 ± 8 kJ mo^?1). In conjunction with available enthalpies of sublimation, and with literature values for the dissociation energies of MnMn and ReRe bonds in Mn₂(CO)₁₀ and Re₂(CO)₁₀, values are derived for the dissociation energies: D(CH₃Mn(CO)₅) = 27.9 ± 2.3 or 30.9 ± 2.3 kcal mol^?1 and D(CH₃Re(CO)₅) = 53.2 ± 2.5 kcal mol^?1. In general, irrespective of the value accepted for D(MM) in M₂(CO)₁₀, the present results require that, D(CH₃Mn) = $\text{1}\text{2}$D(MnMn) + 18.5 kcal mol^?1 and D(CH₃Re) = $\text{1}\text{2}$D(ReRe) + 30.8 kcal mol^?1.     

Darstellung und eigenschaften von und reaktionen mit metallhaltigen heterocyclen: XXV. Synthese und eigenschaften neuer platina- und rhodacycloalkane durch substitution und oxidative addition einer CCl-bindung

The platinacyclopentane derivative [Cl(CH₂)₃R₂P](Cl)$\text{PtPR}{}_2\text{CH}{}_2\text{CH}{}_2\text{CH}{}_2$ is formed by action of Cl(CH₂)₃PR₂ on Pt(COD)₂ in n-hexane via the not isolable Pt[PR₂(CH₂)₃Cl]₂ (R  C₆H₁₁) by oxidative addition of a CCl bond to platinum. [μ-CIRh(CO)₂]₂ reacts in benzene with Cl(CH₂)₃PR₂ under partially CO substitution to give the stable intermediate Cl(OC)Rh[PR₂(CH₂)₃Cl]₂. In boiling toluene oxidative addition of a CCl bond to rhodium occurs under formation of the phospharhodacyclopentane [CI(CH₂)₃R₂P] Cl₂(OC)-$\text{RhPR}{}_2\text{CH}{}_2\text{CH}{}_2\text{CH}{}_2$ (R  C₆H₅). The ³¹P{¹H}-NMR spectra of the rhodium compound is characterized by an ABX system, that of the platinum by superposition of an ABX pattern with an AB spectrum.     

Synthesis and structural characterization of acetatobis(triphenylphosphine)dicarbonylmanganese(I), (CH3CO2)Mn(CO)2[P(C6H5)3]2: An organometallic complex containing a chelating acetate ligand

The accidental but intriguing synthesis of acetatobis(triphenylphosphine)dicarbonylmanganese(I), (CH₃CO₂)Mn(CO)₂[P(C₆H₅)₃]₂, has been accomplished by the reaction of NaMn(CO)₅ with (CH₃)₃SiCl followed by the addition of triphenylphosphine and acetic acid. A three-dimensional single-crystal X-ray diffraction analysis has shown an octahedral-like molecule containing a symmetrically oxygen-chelating acetate group, the first such group to be reported in a metal carbonyl complex. The two triphenylphosphine ligands occupy mutually trans positions with the two carbonyl ligands possessing the remaining cis sites in the octahedral complex. The compound crystallizes with four molecules in a monoclinic unit cell of space group symmetry $\text{P}\text{2}{}_1\text{c}$ and of dimensions a = 17.744(2) Å, b = 9.692(1) Å, c = 20.004(2) Å, and β = 106.195(4)°. The relatively long MnO(acetate) bond lengths [2.066(6) and 2.069(7) Å] and the relatively short MnCO bond lengths [1.701(12) and 1.760(13) Å] and the relatively short MnP(C₆H₅)₃ bond lengths [2.260(3) and 2.275(3) Å], compared to the corresponding MnCO and MnP(C₆H₅)₃ bond lengths in other manganese carbonyl triphenylphosphine complexes, are rationalized on the basis that the acetate ligand in this molecule functions primarily as a σ-donor.     

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.     

Formation of an iridium σ-cyclopropane complex by the intramolecular activation of a cyclopropylphosphine: Rearrangement to a chelating σ-vinyl complex

When (t-Bu)₂PCH₂CHCH₂CH₂ is combined with [IrCl(C₈H₁₄)₂]₂ in toluene, the σ-bound cyclopropane complexes

(P(t-Bu)₂CH₂$\text{CHCH}{}_2\text{C}$H₂) (1a, 1b) are formed. Complexes 1a,1b react readily with H₂ to form IrClH₂P(t-Bu)₂CH₂$\text{CHCH}{}_2\text{C}$H₂)₂ (2). In polar solvents 1a,1b isomerize to the σ-vinyl chelated complex $\text{IrClH(P(t-Bu)}{}_2\text{CH}{}_2\text{C(CH}{}_3\text{)C}$H)(P(t-Bu)₂CH₂$\text{CHCH}{}_2\text{C}$H₂) (3). The structure of this 5-coordinate, 16-electron Ir^III complex was deduced from spectroscopic data, reaction chemistry, and from the crystal structure of its CO adduct (4). Compound 4 crystallizes in the monoclinic space group C_2h⁵-P2₁/n (a 15.610(14), b 15.763(16), c 11.973(13) Å, and β 104.74(5)°) with 4 molecules per unit cell. The final agreement indices for 2326 reflections having F_o² > 3σ(F_o²) are R(F) = 0.089 and R_w(F) = 0.095 (271 variables) while R(F²) is 0.148 for the 3423 unique data. Bond lengths in the 5-atom chelate ring $\text{IrPCCC}$ are IrP 2.341(4), PC 1.857(26), CC 1.520(30), CC 1.341(25), and CIr 1.994(21) Å. The IrCl distance is 2.479(5) Å.     

The chemical oxidation and electronic spectra of the complexes trans-[M(CNR)2(Ph2PCH2CH2PPh2)2] (M = Mo or W)

Oxidation of the complexes $\text{trans}$-[M(CNR)₂(dppe)₂] (A) (M = Mo or W; R = Me, Bu^t or CH₃C₆H₄-$\text{4}$; dppe = Ph₂PCH₂CH₂PPh₂) with diiodine or silver (I) salts gives the paramagnetic cations $\text{trans}$-[M(CNR)₂(dppe)₂]⁺, (M = Mo, R = CH₃C₆H₄-$\text{4}$; M = W, R = Bu^t) and $\text{trans}$-[M(CNR)₂(dppe)₂]²⁺ (M = Mo, R = Me or CH₃C₆H₄-$\text{4}$; M = W, R = Me or Bu^t). Mixtures of products are generally produced when dichlorine or dibromine are the oxidising agents, however pure salts, the seven-coordinate complex cations [MX(CNC₆H₄CH₃-$\text{4}$)₂(dppe)₂]⁺ (B, X = Cl or Br) have been isolated. A simple molecular orbital scheme is proposed for complexes (A) and used to discuss their electronic spectra and their oxidation.     

Synthesis and structural elucidation of some new heterocyclic β-diketone derivatives of boron

Some new β-diketone derivatives of boron having the general formula B₂O(OAc)_4?n[OC(R)$\text{C:CON(Ph)N:C}$ CH₃]_n (where n = 1 or 2; R = CH₃, C₂H₅, C₆H₅ and p-ClC₆H₄) have been synthesised by the reactions of oxy-bis(diacetatoborane) and substituted pyrazolones, such as 4-acyl-3-methyl-1-phenyl-2-pyrazolin-5-ones (acyl = acetyl, propionyl, benzoyl and p-chlorobenzoyl) in dry toluene solution in 1:1 and 1:2 molar ratios. These derivatives have been characterised by elemental analysis, molecular weight measurements. Structures have been proposed on the basis of chemical reactions, IR, ¹H and ¹¹B NMR spectral studies.In the derivatives B₂O(OAc)₃[OC(R)$\text{C:CON(Ph)N:C}$ CH₃] two of the three acetate groups are unidentate and the third is bridged between two boron atoms along with BOB linkage. Whereas the derivatives B₂O(OAc)₂[OC(R)$\text{C:CON(Ph)N:C}$ CH₃]₂ are the mixture of geometrical isomers.     

Studies on metal carboxylates: XI. Reactions of rhenium carbonyl with picolinic acid and of the tungsten(I) complex [W(CO)3(pic)]n with monodentate tertiary phosphines

The reactions of the tungsten(I) complex of picolinic acid [W(CO)₃(pic)]_n with certain monodentate tertiary phosphines affords a convenient route to complexes of the types W(CO)₃(PR₃)₃ and HW(CO)₂(PR₃)₂(pic). The latter hydrido complexes of tungsten(II) have been characterized by infrared and NMR spectroscopy. The reactions of Re₂(CO)₁₀ with picolinic acid have also been investigated and the new series of rhenium(I) derivatives of the types Re(CO)₃(L)(pic), where L = py, 4-Ph-py, PPh₃ or dppe, and Re(CO)₂(L')₂(pic), where L' = PPh₃ or $\text{1}\text{2}$dppe, have been isolated and characterized.     

The interaction of vinyl acetate and allyl acetate with chloro-bridged platinum(II) complexes [Pt2Cl4(PR3)2]: Crystal structure of cis-[PtCl2(PMe2Ph2)(CH2=CHOCOCH3)]

Five complexes of type cis-[PtCl₂(PR₃)Q] (PR₃ =PMe₃, PMe₂Ph, PEt₃; Q = CH₂ CHOCOCH₃ or CH₂=CHCH₂OCOCH₃) have been prepared. The crystal structure of cis-[PtCl₂[PME₂Ph)(CH₂=CHOCOCH₃)] is described. Crystals of cis-[PtCl₂(PME₂Ph)(CH₂-CHOCOCH₃)] are triclinic, with a 8.441(4), b 13.660(5), c 7.697(3) Å, a 101.61(3)°, β 111.85(3)° γ 95.22(3)°, pP1, Z = 2. The structure was determined from 2011 reflections I σ 3σ (I) and refined to R = 0.037. The CH₃COO grouping is syn to the cis-PMe₂Ph ligand, with bond lengths of PtCl (trans to P) 2.367(3), PtCl (trans to olefin) 2.314(3), PtP 2.264(2), and PtC of 2.147(12) and 2.168(11) Å. The complexes cis-[PtCl₂- (PR₃)Q] were studied by variable temperature ¹H and ³¹P NMR spectroscopy. Spectra of the vinyl acetate complexes were temperature dependent as a result of rotation about the platinum—olefin bond. The rotation was “frozen out” at ca. 240 K; for cis-[PtCl₂(PME₂Ph)(CH₂=CHOCOCH₃] ΔG≠ (rotation) 15.0 ± 0.2 kcal mol^-1. NMR parameters for the rotamers are reported. NMR studies of the interaction between chloro-bridged complexes of type [Pt₂Cl₂(PR₃)₂] (PR₃ = P-N-Pr₃ or PMe₂Ph) and vinyl acetate shows that even at low temperatures (213 K) equilibrium favours the bridged complex and the proportion of trans-[PtCl₂(PR₃)CH₂=CHOCOCH₃)] is very small e.g. 2%. The allyl acetate complexes cis-[PtCl₂(PR₃)(CH₂₌CHCH₂OCOCH₃)] showed only one rotamer over the range 333–213 K. Reversible dissociation of cis-[PtCl₂(PMe₂Ph)- (CH₂=CHCH₂OCOCH₃)] to [Pt₂Cl₄(PMe₂Ph)₂] + allyl acetate was studied at ambient temperature. At low temperatures e.g. 213–190 K addition of allyl acetate to a CDCl₃ solution of [Pt₂Cl₂(P-n-Pr₃)₂] reversibly gave some olefin complex trans-[PtCl₂(P-n-Pr₃)(CH₂=CHCH₂OCOCH₃)] and some O-bonded complex trans-[PtCl₂(P-n-Pr₃)(CH₂=CHCH₂OCOCH₃)].     

Reactions of the carbonyl complexes M(CO)3(L)3 (L = py,M = Mo,W; L = NH3, M = Mo) and M(CO)4(2-Mepy)2 (M = Mo,W) with HgX2 (X = Cl,CN, SCN)

The reactions of the substituted Group VI metal carbonyls of the type M(CO)₄(2-Mepy)₂ (M = Mo, w) and M(CO)₃(L)₃ (L = py, M = Mo, W; L = NH₃, M = Mo) with mercuric derivatives HgX₂ (X = Cl, CN, SCN) have given rise to three series of tricarbonyl complexes: M(CO)₃(py)HgCl₂ · 1/2HgCl₂ (M = Mo, W); 2[M(CO)₃(L)]Hg(CN)·nHg(CN)_x (L = py, M = Mo, W, n = $\text{1}\text{2}$, × = 2; L = 2- Mepy, × = 1; M = Mo, n = 3; M = W, n = 1); and [M(CO)₃(L)Hg(SCN)₂ · nHg(SCN)₂] (L = py, M = Mo,W, n = 0; L = 2-Mepy, M = Mo, W, n = $\text{1}\text{2}$; L = NH₃, M = Mo, n = 0) depending on which mercuric compound is employed. All the reactions with Hg(SCN)₂ give isolable products whereas those with Hg(CN)₂ and HgCl₂ did so far only the reactions with [M(CO)₄(2-Mepy)₂] and M(CO)₃(py)₃. The greater reactivity of Hg(SCN)₂ than of Hg(CN)₂ and HgCl₂ is consistent with the various acceptor capacities of the groups bonded to the mercury atom.The reactions studied always involve displacement of the N-donor ligand of the original complex and partial or total displacement of the halide or pseudohalide groups of the mercury compound to give in all cases compounds containing MHg bonds. In addition, elimination of a CO group in the tetracarbonyl complexes M(CO)₄(2-Mepy)₂occurs.     

Transition metal complexes of hexaphenylcarbodiphosphorane

The displacement of tetrahydrofuran (THF) from W(CO)₅(THF) with hexaphenylcarbodiphosphorane yields a compound with a carbon-metal bond (CO)₅W C[P(C₆H₅)₃]₂. The in situ photolysis of tungsten hexacarbonyl and hexaphenylcarbodiphosphorane, however, yields a product (CO)₅W^?CC ⁺P(C₆H₅)₃. Ethylenebis(triphenylphosphine)platinum and hexaphenylcarbodiphosphorane in benzene yield a platinum containing heterocycle [(C₆H₅)₃P]₂$\text{PtC[ P(C}{}_6\text{H}{}_5\text{)}{}_3\text{]P}$-(C₆H₅)₃.     

Darstellung und eigenschaften von und Reaktionen mit metallhaltigen Heterocyclen: X. Untersuchungen über den Ablauf der heterolytischen Spaltung der ReRe-Bindung bei der Darstellung von Rhenacycloalkanen; Grenzen ihrer Stabilität und SO2-Insertion in die ReC-σ-Bindung

The six- and seven-membered rhenacycloalkanes (OC)₄R$\text{ePR}{}_2\text{OCH}{}_2\text{XC}$H₂ (R = CH₃, C_oH₅; X = CH₂, CH₂CH₂) are obtained by reaction of the binuclear anions [(OC)₄RePR₂O]₂^2? with the alkanediylbis(triflouromethanesulfonates) X(CH₂Y)₂ (Y = CF₃SO₂O) in dimethoxyethane. In the Reσ bond of (OC)₄R$\text{ePPh}{}_2\text{OCH}{}_2\text{CH}{}_2\text{C}$H₂SO₂ can be inserted under ring expansion. The rhenacycloheptanes (OC)₄R$\text{PR}{}_2\text{OCH}{}_2\text{CH}{}_2\text{CH}{}_2\text{C}$H₂ (R = CH₃, C_oH₅) are thermally unstable and decompose by cleavage of the α-CC bond. The heterolytic cleavage of the ReRe bond in [(OC)₄RePR₂O]₂^2? results in the open chain, ionic intermediate products [R₂(O)PRe(CO)₄CH₂XCH₂Y]^?, which in competition with the cyclisation, are liable to a β-hydrogen transfer. The mechanisms which are responsible for the formation of the hdrido complexes [HRe(CO)₄PR₂O]^? and HRe(CO)₄PR₂OCH₂XCH₃, are discussed.     

A series of hydridoplatinum(II) complexes stabilized with tribenzylphosphines: their preparation,and an empirical approach to the mutual influence of ligands

The preparation, IR and NMR spectra of 123 platinum hydrides of the general formula, trans-PtHX(PBz₃)₂ or trans-PtHL(PBz₃)₂BPh₄ (X = a uninegative anionic ligand, L = a neutral donor molecule, Bz = benzyl), are described. Neutral platinum hydrides have been synthesized by the reduction of trans-PtCl₂-(PBz₃)₂ with NaBH₄, by the Michaelis—Arbuzov rearrangement, or by metathesis. Cationic hydridoplatinum(II) complexes are obtained from the reaction of trans-PtHX(PBz₃)₂ (X = Cl or NO₃) with a donor molecule (L) in the presence of NaBPh₄, or by coordinating a donor molecule through use of PtH(PBz₃)₂BPh₄ · $\text{1}\text{2}$CH₂Cl₂. The observed trends in ν(PtH), τ(H), ¹J(PtH) and ¹J(PtP) in a series of the hydridobenzylphosphineplatinum(II) complexes are discussed in terms of “trans- or cis-influences”, defined as the ability of a ligand to weaken the bond trans or cis to itself. The data support the view that a donor atom trans to the hydridic ligand is important in determining the strength of the PtH bond in this series. Some remarks on the distinctive characteristics of some complexes, e.g., dissociation of coordinated cycloalkanone from platinum(II) or stereochemical non-rigidity of the sym-dimethylurea ligand, are included. Tricyclohexylphosphine analogs also have been prepared for comparison.     

Synthese und reaktivität von dienylmetall-verbindungen XXVIII. Über kationen des typs [C5H5Fe(CO)L(EME2)]+ (E = S,Se, Te)

The chiral cations, [CpFe(CO)(EMe₂)L]⁺, are obtained both by reaction of [CpFe(CO)(EMe₂)₂]⁺ with the ligands (L) by heating, and by irradiation of the cations [C₅H₅Fe(CO)₂EMe₂]⁺ in the presence of L (E = S, Se, Te; L = PR₃, AsR₃, SbR₃). The inversion about the chalcogen atom is investigated by DNMR spectrocopy. Compounds of the type [C₅H₅Fe(TeMe₂)L₂]⁺] are formed by irradiation of [C₅H₅Fe(CO)₂(TeMe₂)]⁺ and the ligands (L₂ = 2 PR₃, R = CH₃, OCH₃, OC₆H₅; L₂ = R₂P(CH₂)_nPR₂, R = C₆H₅, n = 1,2,3). ⁷⁷Se and ¹²⁵Te NMR data vary according to the donor properties of the ligand L in the complexes.     

Electrochemical studies on monomeric ruthenium complexes.

Voltammetric studies on monomeric Ru(II) and Ru(III) complexes establish $\text{inter}$$\text{alia}$ reversible one-electron reduction and irreversible oxidation of [RuCl₃L₃] in contrast to [RuCl₄L₂]^?, and reversible one-electron oxidation of [RuCl₂(CO)_xL_4?x] (X = 1,2) for L = a variety of neutral ligands.     

The preparation and catalytic hydroformylation activity of some halocarbonylrhodium(I) complexes containing phosphinoalkylorganosilicon ligands

The synthesis and properties of a series of trans-halocarbonylrhodium(I) complexes containing the phosphinoalkylorganosilicon ligands Me₃SiCH₂PPh₂, Me₃Si(CH₂)₃PPh₂, and PPh₂CH₂(Me)$\text{Si(OSiMe}{}_2\text{)}{}_3\text{O}$ have been investigated. The complexes could be prepared by an exchange reaction involving RhCl(CO)(PPh₃)₂ and the organosilicon ligands or in better yields by the reaction of Rh₂Cl₂(CO)₄ with the ligands. Iodorhodium derivatives were obtained as the exclusive products in the latter reaction if a small amount of LiI was present. The catalytic activity of RhCl(CO)(PPh₂CH₂SiMe₃)₂ was similar to that of RhCl(CO)(PPh₃)₂ in the hydroformylation of hex-1-ene at 100°C and 1000 psi pressure of H₂/CO. The catalytic properties of the iodo derivatives RhI(CO)L₂ [L = Me₃SiCH₂PPh₂, Me₃Si(CH₂)₃PPh₂, and PPh₂CH₂(Me)$\text{Si(OSiMe}{}_2\text{)}{}_3\text{O}$] varied considerably, with RhI(CO)(PPh₂CH₂SiMe₃)₂ producing an unexpectedly low linear/branched aldehyde product ratio.     

The effect of the solvent upon the rates and machanisms of organometallic reactions: VII. A 19F NMR study of complexation of CF3 HgX (X = Cl,I, OCOCF3)

The concentration and temperature dependence of J(¹⁹⁹HgC¹⁹F) for solutions of CF₃HgX (X = Cl, I, OCOCF₃) in various solvents shows that in inert solvents these molecules exist mainly as non-solvent dimers (X = I or OCOCF₃) or as monomers (X = Cl). In strongly coordinated solvents $\text{1}\text{2}$ complexes are largely formed from CF₃HgX and the electron-donating solvent molecules. In pyridine solution an equilibrium exists between the $\text{1}\text{1}$ and $\text{1}\text{2}$ complexes. Complexes of the type CF₃HgX·D are T-shaped and have a higher relative content of s-electrons in the HgCF group compared with tetrahedral CF₃HgX·2D complexes.     

Synthesis and molecular structure of niobocene(tricarbonyl)(π-cyclopentadienyl)molybdenum with metalmetal bond and unusual coordination of carbonyl groups

(C₅H₅)₂NbBH₄ reacts with C₅H₅M(CO)₃Me in toluene solution in the presence of Et₃N to give binuclear complexes (C₅H₅)₂NbM(CO)₃C₅H₅ where M is Mo or W (IV and V, respectively). The structure of IV has been studied by X-ray diffraction (the crystals are orthorhombic, a 12.748(5), b 16.745(6), c 14.314 $\text{A/ac>}\text{?}$;; Z = 8, space group of Pbca, automatic difractometer Syntex P2_I, λ(Mo-K_α, 1382 reflections, R = 0.056, R_w = 0.058). Molecule IV contains a wedge-like sandwich (π-C₅H₅)₂Nb (NbC 2.37–2.48, CC (av) 1.42 $\text{A/ac>}\text{?}$;, angle between ring planes 49°) linked with the (π-C₅H₅)Mo(CO) fragment by a direct NbMo bond (3.073 $\text{A/ac>}\text{?}$;) and two bridging CO groups, one nonsymmetrically bonded through the carbon atom only (CO 1.17, NbC 2.53, MoC 2.02 $\text{A/ac>}\text{?}$;) and the other σ-bonded to Mo (MoC 1.944 $\text{A/ac>}\text{?}$;) and π-bonded to Nb (CO 1.22, NbC 2.22, NbO 2.26 $\text{A/ac>}\text{?}$;). Three types of carbonyl groups present in IV give rise to strong IR bands at 1870, 1700 and 1560 cm^?1 assigned to the terminal, μ-bridging and σ, π-bridging CO groups respectively. Complex IV has a similar structure. The electronic structure of IV and its dissociation across the NbMo bond are discussed.     

Addition and migration of ligands on a metal atom pair: The oxidative addition of hexafluoro-2-butyne to dinuclear dihydridoiridium(II) complexes [Ir(H)(μ-SBu-t)(CO)(PR3)]2(IrIr) (R = OMe or Me), and its dehydrogenation reaction when R = OMe

Dissymmetric dinuclear complexes (PR₃)(CO)(H)₂Ir(μ-SBu-t)₂Ir(C₄F₆(CO)-(PR₃) (III, R = OMe or Me), which can be described as the juxtaposition of dihydrido and alkyne adducts of Vaska's complex associated through thiolato bridges, were obtained by the reaction of hexafluoro-2-butyne with symmetric dinuclear dihydridoiridium(II) complexes, [Ir(H)(μ-SBu-t)(CO)(PR₃)]₂(]IrIr) (II). When R = OMe, after the loss of H₂, a molecular rearrangement leads to the symmetric dinuclear iridium(II) complex [Ir(μ-SBu-t)(CO)(P(OMe)₃)]₂(C₄F₆) (IV). A correlation between the presence of an intense absorption near 230 nm in the UV-visible spectra and the existence of a metal—metal bond is established. A sequence of formation, splitting and re-formation of the metal—metal bond is observed along the series of derivatives obtained from [Ir(μ-SBu-t)(CO)P(OMe)₃]₂ (I) to IV, via II and III.