On the structure of tetracoordinated organocobalt complexes of the type [CoR2L2]

A series of square-planar organocobalt complexes of the type [CoR₂L₂] (R = 2,3,4,6-C₆,HCl₄ and 2,3,6-C₆H₂Cl₃, L = PEtPh₂, PEt₂Ph, and PEt₃; R = 2,3,5,6-C₆HCl₄, and 2,6-C₆H₃Cl₂, L = PEt₂Ph, PEt₃, and $\text{1}\text{2}$dpe) have been prepared in which the electronegativities of the ligand R vary progressively. The reaction of o-C₆H₄ClMgBr with [CoCl₂L₂] (L = PEtPh₂ PEt₂Ph, γ-pic or $\text{1}\text{2}$bipy) did not give air stable compounds at room temperature, but the solutions obtained at ?78°C appear to contain square-planar species for L = PEtPh₂, PEt₂Ph, and γ-pic, and tetrahedral for L₂ = bipy. The tendency towards square-planar or tetrahedral structures for the compounds [CoR₂L₂] depends on the following factors in order of importance: (i) when the neutral ligand is a phosphine a square-planar structure is adopted; (ii) when L is an aromatic amine, bulky ortho substituents on R favour a square-planar structure; and (iii) a tetrahedral geometry is favoured by bidentate amine ligands. The electronegativity of the organic group R seems to be less important.     

Intramolecular metallation of o-carboranylphosphine-palladium(II) and -platinum(II) complexes

Preparation of trans-[P^cb₂MCl₂]-type complexes (P^cb= o-HCB₁₀H₁₀CCH₂PPh₂ M = Pd, Pt), which readily undergo intramolecular metallation through the BH bonds of the carborane cage to form exocyclic compounds involving a $\text{PCCBM}$ bond system, is described. Both monomeric compounds, trans-[MCl(B-P)P^cb], and bridged complexes, such as [Pd₂Cl₂(BP)₂], are formed, where (BP) is intramolecular-metallated carborane phosphine. The bridging bond is readily cleaved under the action of various ligands (pyridine, PEt₃, etc.) to form monomeric compounds.     

Chlorinated organic derivatives containing MoHg and WHg bonds: Importance of the steric effects in their stabilization

A series of MoHg and WHg bonded complexes [RHgM(CO)₃Cp], (R = 2,4,6-C₆H₂Cl₃,2,3,5,6-C₆,HCl₄ and C₆Cl₅) have been prepared from ClHgR and the salts Na[M(CO)₃)Cp]. When R contains only one ortho chlorine atom (R = 2,5-C₆H₃Cl₂, 2,3,4-C₆H₂Cl₃ and 2,3,4,5-C₆HCl₄) a symmetrisation process occurs to give the corresponding HgR₂ and Hg[M(CO)₃Cp)₂2. These results indicate that steric effects are very important in the formation of compounds containing molybdenum- or tungsten—mercury bonds. Complexes of the type [(C₆Cl₅)HgM(CO)₂(PPh₃)Cp] (M = Mo and W) are obtained from [(C₆Cl₅)HgM(CO)₃Cp] and PPh₃ in boiling ethanol.     

X-ray photoelectron spectra of polyhydrido complexes of tungsten and molybdenum

X-Ray photoelectron spectroscopy has been applied to study MH₄L₄(M = or Mo, L = PHPh₂, PMePh₂, PEtPh₂, PBuPh₂, PEt₂Ph, P(OPr-i)₃ or $\text{1}\text{2}$ dppe). It has been shown that tungsten in these compounds has a negative charge whereas the charge of molybdenum is almost zero.     

Platinum-mercury compounds as intermediates to mono- and di-arylplatinum(II) complexes

The reaction of HgR₂ (R = 2,5-C₆H₃Cl₂; 2,3,4- and 2,4,6-C₆H₂Cl₃; 2,3,4,5-,2,3,4,6- and 2,3,5,6-C₆HCl₄ and C₆Cl₅) with Pt(PPh₃)₃ gives the new stable compounds [(PPh₃)₂RPt(HgR)] containing PtHg bonds. When R contains an ortho chlorine atom (R = 2,5-C₆H₃Cl₂; 2,3,4-C₆H₂Cl₃ and 2,3,4,5-C₆HCl₄) refluxing xylene solutions of these compounds gives the complexes [PtR₂-(PPh₃)₂], with simultaneous precipitation of mercury. In the other cases the initial compounds are recovered unaltered. All the compounds containing the PtHg bond react readily with CF₃COOH to give a new series of compounds of formula [Pt(O₂CCF₃)R(PPh₃)₂].     

Syntheses of σ-cyclobut-1-en-3-onyl complexes by cycloaddition of ketenes to some transition metal alkynyl complexes

Reactions of ketenes (R¹R²CCO) with (η⁵-C₅H₅)Ni(PPh₃)CCR (I) and (η⁵-C₅H₅)Fe(CO)(L)CCR (III, L = CO and PPh₃) give σ-cyclobut-1-en-3-onyl complexes, {(η⁵-C₅H₅)Ni(PPh₃)$\text{CC(R)COC}$}R¹R² (VI) and (η⁵-C₅H₅)Fe(CO)(L)$\text{CC(R)COC}$R¹R² (IX)}, (2 + 2) cycloaddition products, in good yields. The σ-cyclobutenonyl complexes also can be prepared by the reaction of I and III with acyl chlorides in the presence of triethylamine.     

Demercuriation reactions of the complexes [(PPh3)2RPtHgR′] containing platinum-mercury bonds

The compounds [(PPh₃)₂,RPtHgR′] (R = CH₃, R′= 2,5-C₆H₃Cl₂, 2,3,4- and 2,4,6-C₆H₂Cl₃, 2,3,4,5-, 2,3,4,6- and 2,3,5,6-C₆HCl₄, C₆Cl₅; R = Et, R′ = 2,5-C₆H₃Cl₂, 2,4,6-C₆H₂Cl₃; R = 2-C₆H₄Cl, R′=2-C₆H₄(CH₃)) have been prepared by the reactions of RHgR′ with Pt(PPh₃)₃, in order to study their possible use as intermediates in the preparation of diorganoplatinum complexes with different organic ligands. The dependence of J(³¹P-¹⁹⁵Pt) on slight differences in the electronic character of the ligand R′ in the series of compounds [(PPh₃)₂(CH₃)Pt-HgR′] has been studied.     

Substitution reactions of metal-metal quadruply-bonded tetrachlorotetrakis(phosphine)dimolybdenum compounds

Summary The substitutions of dimolybdenum compounds of the type [Mo₂Cl₄L₄] (where L=PEt₃, PEt₂Ph or PEtPh₂), together with the preparation and characterization of the metal-metal quadruply bonded [Mo₂Cl₄(triphos)₂] obtained from K₄Mo₂Cl₈] are described.     

Reactivity of polychlorophenylmercury compounds with 1,10-phenanthroline

The action of 1,10-phenanthroline (phen) on the THF solutions of RHgCl (R = 2,5-C₆H₃Cl₂; 2,3,4? and 2,4,6-C₆H₂Cl₃; 2,3,4,5?, 2,3,4,6?, and 2,3,5,6-C₄HCl₄ and C₆Cl₅) gives RHgCl (phen) when R contains two chlorine substituents in ortho (R = 2,4,6-C₆H₂Cl₃; 2,3,4,6?, and 2,3,5,6-C₆HCl₄ and C₆Cl₅), but the symmetrisation reaction occurs when R = 2,5-C₆H₃Cl₂; 2,3,4-C₆H₂Cl₃ and 2,3,4,5-C₆HCl₄. The action of phen on HgR₂ only gives HgR₂ (phen) when R = 2,3,4,5-C₆HCl₄. Compounds of the type RHgMe do not react with phen. These results indicate that steric citects are as important as the electronegativity of R in the formation of tetracoordinated mercury compounds.     

Electrochemical studies on neutral triple-bridged di-ruthenium compounds.

Voltammetric studies reveal that, like [Ru₂Cl₄(PPh₃)₄(CO)], triply-bridged complexes [Ru₂Cl₄L₅] (L = PClPh₂, PMePh₂, PEt₂Ph) are reversibly oxidized to [Ru₂Cl₄L₅]⁺. The mixed valence complexes [Ru₂Cl₅L₃Y] (L = PPh₃, P(tol)₃; Y = CO, CS) undergo a corresponding reduction to [Ru₂Cl₅L₃Y]^?; whereas [Ru₂Cl₅L₄] (L = PEt₂Ph, As(tol)₃) and [Ru₂Cl₆(AsPh₃)₃] are both reduced $\text{and}$ oxidised in reversible one-electron steps. For the bridging (RuCl₃Ru)^z+ moiety, the redox series z = 1, 2, 3, 4 is established.     

Alkoxycarbene complexes of nickel(II)

Alkynylnickel complexes trans-C₆Cl₅Ni(PPhMe₂)₂CCR (IIIa, R  H; IIIb, R  Me; IIIc, R  Et; IIId, R  CH₂OH; IIIe, R  CH₂CH₂OH; IIIf, R  Ph; IIIg, R  C₆H₄OMe-p) have been prepared from trans-[C₆Cl₅Ni-(PPhMe₂)₂L]ClO₄ and monosubstituted acetylenes in the presence of triethylamine, and their reactions with alcohols in the presence of perchloric acid were studied. Complexes IIIa and IIIe afforded alkoxycarbene complexes trans-[C₆Cl₅Ni-(PPhMe₂)₂{C(OR′)Me}]ClO₄ (IVa, R′  Me; IVb, R′  Et; IVc, R′  n-Pr) or trans-C₆Cl₅Ni(PPhMe₂)₂{$\text{C(CH}{}_2\text{)}{}_3\text{O}$}]ClO₄(IVd), respectively, but IIIb either decomposed or afforded trans-C₆Cl₅Ni(PPhMe₂)₂CHC(OMe)Me, depending on the amount of acid used. Treatment of IVaIVd with amines resulted in deprotonation to give α-alkoxyvinyl complexes, trans-C₆Cl₅Ni(PPhMe₂)₂C(OR′)CH₂ (VIaVIc) or trans-C₆Cl₅Ni(PPhMe₂)₂$\text{CCHCH}{}_2\text{CH}{}_2\text{O}$ (VId), the reaction being reversible. A ¹H NMR study indicated: (i) that the carbene methyl and the vinyl protons IV or VI are D-exchangeable by MeOD without catalyst; (ii) that the basicity of VIa is comparable to those of amines; (iii) that the carbene complexes IVaIVc have two isomers due to hindered rotation about the C(carbene)O bond in solution, IVb existing in the Z-form in the solid state; (iv) that the rotationalbarriers (°G^≠) about the C(carbene)O bond in IVb and the NiC-(carbene) bond in IVd are 20 (or more) and 11.7 kcal/mol, respectively. These results are explained in term of double bond character of the carbene carbon and its surrounding atoms.     

Polychlorophenyl-platinum(II) complexes containing triphenylphosphine

A new method to prepare compounds of the type trans-[PtCl(R)(PPh₃)₂] (R = C₆H₅; 2,5-C₆H₃Cl₂; 2,3,4-, and 2,4,6-C₆H₂Cl₃; 2,3,4,5-, 2,3,4,6- and 2,3,5,6-C₆HCl₄ and C₆Cl₅) by reaction of cis-[PtCl₂(PPh₃)₂] and HgR₂ in the molten state is described.The reactions of the complexes with HCl, Cl₂ and I₂ have been examined in order to give information about the relative ease of cleavage of the various Ptaryl bonds. The replacement of Cl by NCS suggests an associative mechanism even for the complexes in which the polychlorophenyl ligand has chlorine atoms in both ortho positions.     

Progress in NMR spectroscopy,Volume 11 : edited by J.W. Emsley,J. Feeney and J.R. Sutcliffe,Pergamon Press,Oxford, 1978, vii + 298 pages; $ 40.00 (£ 20)

Protonolysis of the complexes trans-[Pt(PEt₃)₂(R)(Me)] (R = C₆H₅ ; m-MeC₆H₄ ; o-MeC₆H₄ ; m-FC₆H₄ ; p-FC₆H₄ ; m-CF₃C₆H₄ and C₆F₅) by hydrogen chloride in methanol/water ($\text{90}\text{10}$ v/v) selectively cleaves the alkyl group yielding trans-[Pt(PEt₃)₂(R)Cl] and methane. A kinetic study of these reactions suggests that the primary step involves a proton transfer to the carbonmetal σ-bond with release of CH₄ in a three-center transition state.     

New η-allyl η-cyclopentadienylcobalt cations

[Co(R-η-C₃H₄)(η-C₅H₅)I] is a good precursor for the preparation of some new cationic complexes as the iodide can easily be replaced; thus addition of PEt₃ to the iodo-complex (R  H) gives [Co(η-C₃H₅)(η-C₅H₅)(PEt₃)]⁺. The reactions of [Co(R-η-C₃H₄)(η-C₅H₅))I] (R  H or 2-Me) with AgBF₄ give solutions containing the coordinatively unsaturated species [Co(R-η-C₃H₄)(η-C₅H₅)⁺. The presence of traces of water leads to the formation of [Co(R-ηC₃H₄)-(η-C₅H₅)(H₂O)]⁺. The addition of monodentate ligands L  PEt₃ PPh₃, AsPh₃, SbPh₃, CNCH₃ and bidentate ligands LL  Ph₂PCH₂CH₂PPh₂(dppe) and o-C₆H₄(AsMe₂)₂(diars), gives, respectively mononuclear [Co(2-Me-ηC₃H₄)-(η-C₅H₅)L]⁺ and binuclear ligand-bridged [(2-Me-ηC₃H₄)(η-C₅H₅)CoLLCo(2-Me-ηC₃H₄)(η-C₅H₅))]²⁺ complexes. Crystals of [Co(2-Me-ηC₃H₄)(η-C₅H₅)-(H₂O)]⁺[BF₄]^- are monoclinic, space group P2₁/c, with a 7.858(3), b 10.262(4), c 15.078(4) Å, β 98.36(1)°. The molecular structure contains the cobalt atom bonded to planar 2-Me-allyl and cyclopentadienyl substituents, which are almost parallel with the H₂O molecule in a staggered conformation with respect to the 2-Me group.     

Structure of trans-chloro-1,4-bis(ϱ-methoxyphenyl)-1,4-diaza-3methylbutadiene-2-yl-bis(triphenylphosphine)-palladium(II)

The structure of the compound trans-[PdCl {$\text{C(N-?-C}{}_6\text{H}{}_4\text{OMe)C}$(Me)N-?-C₆H₄OMe} (PPh₃)₂] was solved, using a conventional combination of Patterson and Fourier functions, least-squares refinements and electron density difference maps, to a reliability index R of 0.069 for the 2923 observed reflections collected by four-circle diffractometer. The palladium arom is surrounded in a roughly planar fashion by two trans phosphorus atoms, a chlorine atom, and a σ-bonded carbon atom of the diazabutadienyl group. This group assumes a trans configuration, the NCCN fragment being virtually planar and nearly normal to the mean coordination plane. The Pdligand bond lengths are: PdC 1.98(1), PdCl 2.41(1),PDP(1) 2.33(1) and PdP(2) 2.35(1) Å.     

Gold(I) and gold(III) ortho-nitrophenyl complexes. Crystal and molecular structure of ortho-nitrophenyltriphenylarsinegold(I)

The reaction between [Au(o-C₆H₄NO₂)Cl]⁻ and tetrahydrothiophene (tht) in the presence of NaClO₄ give a solution (probably containing [Au(o-C₆H₄NO₂)(tht)]) that can be used to prepare neutral [Au(o-C₆H₄NO₂)L_n] (L = AsPh₃, n = 1; L = SbPh₃, n = 2; L = 1,10-phenanthroline, n = 1) or anionic [Au(o-C₆H₄-NO₂(CN)]⁻ complexes. Treatment of [Au(o-C₆H₄NO₂)(PPh₃)] with chlorine or PhICl₂ gives trans- or cis-[Au(o-C₆H₄NO₂)Cl₂(PPh₃)]. Isomerizations occur when the cis-isomer is treated with concentrated solutions of chlorine or when the trans-isomer is heated.An X-ray diffraction study of [Au(o-C₆H₄NO₂)(AsPh₃)] has revealed an almost linear coordination around the gold atom (AsAuC mean value 177(2)°). The AuO distance is too long (mean value 2.80(3) Å) for intramolecular coordination.     

Reaction of some tertiary phosphines and phosphites with [Co(η5-C5H5)(S2C2{CN}2)]

Reaction of the 16 electron monomer [Co(η⁵-C₅H₅)(S₂C₂{CN}₂)] with various tertiary phosphines and phosphites (L) gives readily the 18 electron monomers [Co(η⁵-C₅H₅)(S₂C₂{CN}₂)L] which for L = P(OR)₃ have J($\text{P}$C₅$\text{H}$₅) ca. 6 Hz but J($\text{P}$C₅$\text{H}$₅) = 0 for L = PR₃.     

Cleavage of iron2-alkenyl and iron2-alkynyl bonds by mercury(II) chloride

Reactions of HgCl₂ with η⁵-C₅H₅Fe(CO)₂R (R  CH₂CHCH₂ and CH₂C(CH₃)CH₂) in THF at 25°C rapidly afford $\text{1}\text{1}$ adducts of the two reactants. These adducts were converted to the corresponding PF₆^? salts, [η⁵-C₅H₅Fe(CO)₂(η²-CH₂C(R)CH₂HgCl)]⁺ PF₆^? (R  H and CH₃), for characterization. Slower reactions with cleavage of the ironcarbon σ bond and elimination of the R group from η⁵-C₅H₅Fe(CO)₂R occur for R  CH₂CHC(CH₃)₂, CH₂CHCHC₆H₅, and CH₂CCC₆H₅. Both elimination and $\text{1}\text{1}$ adduct formation are observed when R  CH₂CHCHCH₃. The kinetics of the cleavage reactions are presented and possible mechanisms for both cleavage and $\text{1}\text{1}$ adduct formation are discussed.     

Insertion of isocyanides into the palladium-(2-pyridyl) bond

The reaction of the pyridyl-bridged binuclear complex [PdBr(μ-2-C₅H₄N)(PPh₃)]₂ with isocyynides CNR (R  p-C₆H₄OMe, Me, C₆H₁₁) yields the complex $\text{PdBr}${(&2.dbnd;NR)C(&2.dbnd;NR) (2-C₅H₄N)}(PPh₃)] containing a C,N-chelated 1,2-bis(imino)-2-(2-pyridyl)ethyl group, which results from successive insertions of two isocyanides molecules into the palladium2-pyridyl bond. The mononuclear compound trans-[PdBr(2-C₅H₄N)(PMePh₂)₂] readily reacts with various CNR ligands (R  p-C₆H₄OMe, Me, C₆H₁₁, CMe₃) to give the imino(2-pyridyl)methylpalladium(II) derivatives, trans-[Pdbr{C(=NR)(2-C₅H₄N)} (PMePh₂)₂].     

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.