Ligand CH Research Articles

Kinetic studies in aqueous solutions of cobalt(II)–ethylenediamine, –malonate, and –glycinate complexes

The dynamics of equilibria in aqueous solutions of cobalt(II)–ethylenediamine (en), –malonate (mal), and –glycinate (glyO) systems have been investigated by measuring the paramagnetic relaxation rate and shift of the CH2 ligand protons over a wide range of complex formation. The formation rate constants (dm3 mol–1 s–1) of the cobalt parent complexes at 25 °C and I= 1 mol dm–3 KCl are: k2en= 3.0 × 107, k3en= 1.1 × 107, k1mal= 6.9 × 107, k2mal= 1.6 × 107, k2glyO= 2.2 × 106, and k3glyO= 6.4 × 105. Kinetic evidence is given for the formation of [Co(Hen)]3+, [Co(Hmal)]+, and [Co(mal)3]4– complexes. The ‘carboxyl-displacement’ mechanism was used to interpret the interaction between [Co(glyO)3]– and the free glyO– ligand. The complex-formation kinetics of some complexes of Co2+ and Fe2+ were compared and the similarities and differences are discussed.

Umwandlungen zwischen Vinyliden- und Alkylidin-verbrückten Dreikernclustern / Interconversions between Vinylidene and Alkylidyne Bridged Trinuclear Clusters

Based on the observation that the alkylidyne bridged cluster HFeCo2(CO)9(μ3-C—CH3) spontaneously loses H2 to form the vinylidene bridged cluster FeCo2(CO)9(μ3-C=CH2), the interconversions between these types of ligands on mixed trinuclear clusters were investigated. It was found that in all cases clusters of the type HM3μ3-C—CH2R) could be transformed into clusters of the type M3(μ3-C=CHR); for M3 = FeCo2, FeCoMo, RuCoMo, RuCoW, OsCoMo, OsCoW; for R = H and in one case CH3; for dehydrogenation by thermolysis and in one case H+/H- elimination. Conversely, hydrogenation of the vinylidene bridged clusters to the alkylidyne bridged clusters was only possible for the FeCoMo, RuCoMo, and RuCoW systems, for the unsubstituted C=CH2 ligand, and for elemental hydrogen as the reagent. Together with previous observations this leads to the conclusion that among the interconvertible alkyne, vinylidene, and alkylidyne ligands the vinylidene unit represents the most stable entity on trinuclear clusters.

Reactions of ground state Cr + with C 2H 6, C 2H 4, cyclo-C 3H 6, and cyclo-C 2H 4O: bond energies for CrCH +n ( n = 1–3)

The reaction of ground state chromium ions with ethane, ethene, cyclopropane and ethylene oxide has been studied using guided ion beam mass spectrometry. A predominant process in all these reactions is CC bond cleavage to form CrCH + n . Modeling of the translational energy dependence of endothermic reactions yields the bond energies D 0(Cr +−CH) = 75±8, D 0(Cr +−CH 2) = 53.8±1.9, and D 0(Cr +−CH 3) = 30.2±2.3 kcal mol −1. These values provide a direct comparison between experiment and theoretical calculations suggesting that Cr + forms a single, double, and triple bond with the ligands CH 3, CH 2, and CH, respectively. Bond energies for CrO, CrO +, CrC 2H + 2, CrC 2H + 4, and CrCO + are also evaluated.

On the relationship between crystallographic and spectroscopic evidence of dynamic processes in the solid state: the cases of cis- and trans-[Fe2(η-C5H5)2(CO)4

The reorientational motion of the C5H5 ligands, evidenced in solid cis-and trans-[Fe2(η-C5H5)2(CO)4] by magic angle spinning n.m.r. spectroscopy, has been examined by means of atom–atom pairwise potential-energy calculations. The results are compared with the X-ray crystallographic indications of extensive librational motion of the ligands around their five-fold axes in both species. A thermal motion analysis has been carried out showing that the mean-square displacement parameters contain relevant information on the occurrence of dynamic processes in the solid state.

Synthesis and structural characterisation of some cyclopentadienyliron–bismuth complexes

Treatment of BiCl3 with 2 equivalents of Na[Fe(CO)2(η-C5H4Me)] in tetrahydrofuran affords the green iron–bismuth complex [{[Fe(CO)2(η-C5H4Me)]2BiCl}3], identified by X-ray crystallography and containing a planar Bi3Cl3 six-membered ring derived from the cyclotrimerisation of Fe(BiCl)(CO)2(η-C5H4Me) units. Similar compounds are formed with C5H5 and C5Me5 ligands although in the latter case significant amounts of the iron chloro species [FeCl(CO)2(η-C5Me5)] are also formed, an X-ray structure of which is reported. Treatment of BiCl3 with 3 equivalents of Na[Fe(CO)2(η-C5H4Me)] affords the tri-iron–bismuth complex [Bi{Fe(CO)2(η-C5H4Me)}3], containing a trigonal-pyramidal bismuth bonded to three Fe(CO)2(η-C5H4Me) fragments. Photolysis of this compound leads to loss of three carbonyl groups and formation of the closo Fe3Bi complex [Fe3(η-C5H4Me)3(µ-CO)3(µ3-Bi)]. Both of the tri-iron–bismuth complexes were characterised by X-ray crystallography.

Chemistry of polynuclear metal complexes with bridging carbene or carbyne ligands. Part 70. Tetranuclear metal compounds with rhenium–molybdenum or –tungsten bonds. Crystal structures of [Mo2Re2(µ3-CC6H4Me-4)2(µ-CO)2(CO)7(η-C5H5)2]·1.5CH2Cl2and [W2Re2(µ-H)(µ3-σ:σ′:η2-CCH2)(µ3-CMe)(µ-CO)(CO)8(η-C5H5)2

Reactions between the compounds [M(CC6H4Me-4)(CO)2(η-C5H5)](M = Mo or W) and [Re2(µ-H)(µ-σ:η-CHCHBun)(CO)8] afford the tetranuclear metal complexes [M2Re2(µ3-CC6H4Me-4)2(µ-CO)2(CO)7(η-C5H5)2]. The corresponding reaction between [W(CMe)(CO)2(η-C5H5)] and the dirhenium compound yields a mixture of the cluster compounds [W2Re2(µ3-CMe)2(µ-CO)2(CO)7(η-C5H5)2], [W2Re2(µ-H)(µ3-σ:σ′:η2-CCH2)(µ3-CMe)(µ-CO)(CO)8(η-C5H5)2], and [WRe2(µ3CMe)(CO)10(η-C5H5)]. The molecular structures of [Mo2Re2(µ3-CC6H4Me-4)2(µ-CO)2(CO)7(η-C5H5)2]·1.5CH2Cl2 and [W2Re2(µ-H)(µ3-σ:σ′:η2-CCH2)(µ3-CMe)(µ-CO)(CO)8(η-C5H5)2] have been established by X-ray diffraction studies. Crystals of the former contain two very similar crystallographically independent molecules in the asymmetric unit and there are three molecules of CH2Cl2 of crystallisation. The structure has a tetrahedral core of metal atoms (mean metal–metal separations 2.914 A) with two of the faces of the tetrahedron capped by p-tolylmethylidyne ligands and two of the Mo–Re edges of the tetrahedron asymmetrically bridged by CO groups [Mo–C–O 155(3) and 157(3)°]. Each rhenium atom carries three orthogonal terminal CO ligands, with the remaining CO group being terminally attached to a molybdenum atom. As expected, the C5H5 moieties ligate the Mo atoms. In [W2Re2(µ-H)(µ3-σ:σ′:η2-CCH2)(µ3-CMe)(µ-CO)(CO)8(η-C5H5)2] the four metal atoms adopt a near-planar ‘butterfly’ arrangement, having a W–Re spine [2.923(1)A] and with a W and a Re atom at the wing-tip positions. The W2Re triangle is capped by a CMe group which lies perceptibly closer to the tungsten atoms than the rhenium. On the other side of the W2Re2 plane, the WRe2 triangle is triply bridged by the CCH2 group. The latter is σ bonded to the W and Re atoms which form the spine of the butterfly, and is η2-co-ordinated to the Re atom at the wing-tip position. A CO ligand asymmetrically bridges [W–C–O 159(2)°] the W–Re edge of the WRe2 triangle and, although not located by X-ray diffraction, the hydrido ligand must bridge the Re–Re edge [3.023(1)A], since the latter is perceptibly longer than the other metal–metal separations (mean 2.951 A). Each rhenium atom is ligated by three terminal CO groups, and the tungsten atom is co-ordinated by two such groups. There is a C5H5 ligand bonded to each tungsten centre. The 1H and 13C-{1H} n.m.r. spectra of the new compounds are reported and discussed.

The Mechanism of Substitution Reactions at [LRe(NO)(CO)(CH3)]⊕ in Acid Solution and the Structure of [{LRe(NO)(CO)}2(μ‐CH2OCH2)]I2 (L = 1,4,7‐Triazacyclononane)

The ligand CH in 1 can be replaced by Cl⊖ by acid catalysis. The reaction, which proceeds with retention of the configuration at Re, may be initiated by protonation of an Namine atom and cleavage of the ReNamine bond. In contrast, on attempting to replace CH by I⊖ the dinuclear complex 2 with the previously unknown 2‐oxapropane‐1,3‐diide bridge, which is stabilized by two O…HN bridges, is formed if the reaction is not carried out in the absence of light. equation image

ChemInform Abstract: The Isolobal Analogy “d6‐CpM(CO)‐ 3 ←→ Cp‐”.

AbstractThe isolobal relationship between the d6‐CpM(CO)3 groups (M: Cr, Mo, W) and the C5H5 ligand is demonstrated on the basis of qualitative considerations, MO calculations and MO diagrams, and on the basis of the known structures of complex molecules containing CpM(CO)3 or Cp groups.

C5R5–iron complexes (R = H or Me) of polyaromatic hydrocarbons: stabilization of the monoreduced state and large variation of spin distribution as a function of the ligand structures

Several new polyaromatic iron complexes have been synthesized with C5H5 or C5Me5 ligands and the synthesis of others is much improved using molten components; cyclic voltammetry shows a considerable stabilization of the FeI state by permethylation of the C5H5 ligand, and a wide range of spin distribution on the polyaromatic ligand: biphenyl ∼ triphenylene ⩽ naphthalene < phenanthrene < pyrene < perylene ⩽ corronene, is found for the C5H5 complexes only.

Chemistry of polynuclear metal complexes with bridging carbene or carbyne ligands. Part 55. Coupling of methylene and alkylidyne groups at a trimetal centre; crystal structures of [Ru2W{µ-σ:η-trans-CHC(H)R}(µ-CO)(CO)3(η-C5H5)2(η-C5Me5)]·CH2Cl2and [Ru2W(µ3-CCH2R)(µ-CO)3(CO)(η-C5H5)3](R = C6H4Me-4)

The compounds [Ru2(µ-CH2)(µ-CO)(CO)(NCMe)(η-C5H5)2] and [W(CR)(CO)2(η-C5H5)](R = C6H4Me-4 or Me) react in CH2Cl2 at room temperature to give, in low yield, mixtures of the trimetal complexes [Ru2W{µ-σ:η-trans-CHC(H)R}(µ-CO)(CO)3(η-C5H5)3](3a, R = C6H4Me-4; 3b, R = Me) and [Ru2W(µ3-CCH2R)(µ-CO)3(CO)(η-C5H5)3](4a, R = C6H4Me-4; 4b, R = Me). In a similar reaction, [W(CC6H4Me-4)(CO)2(η-C5Me5)] and [Ru2(µ-CH2)(µ-CO)(CO)(NCMe)(η-C5H5)2] afford a mixture of [Ru2W{µ-σ:η-trans-CHC(H)R}(µ-CO)(µ3-CO)2(η-C5H5)2(η-C5Me5)](5) and [Ru2W(µ3-CCH2R)(µ-CO)3(CO)(η-C5H5)2(η-C5Me5)](4c). The unsaturated complex (5) in solution reacts reversibly with CO to give [Ru2W{µ-σ:η-trans-CHC(H)R}(µ-CO)(CO)3(η-C5H5)2(η-C5Me5)](3c). The spectroscopic properties (i.r., and 1H and 13C-{1H} n.m.r.) of the new compounds are reported and discussed. Compounds (3c) and (4a) were studied by X-ray diffraction. The former, which crystallises with a molecule of CH2Cl2, has a structure based on a triangle of metal atoms [Ru–Ru 2.782(1), Ru-W 2.771(1) and 2.952(1)A] The ruthenium–ruthenium bond is symmetrically bridged by a CO ligand, and the shorter Ru–W vector is bridged by a trans-CHC(H)C6H4Me-4 group, which is σ bonded to the tungsten and η2 co-ordinated to the ruthenium. The latter carries a C5H5 ligand as does the other ruthenium atom, which is also ligated by a terminal CO. The tungsten atom is bonded by two CO groups and the η-C5Me5 moiety. The structure of (4a) proved to be disordered, but it was apparent that the Ru2W triangle was capped by the CCH2C6H4Me-4 group with the three edges of the metal triangle bridged by CO ligands.

Chemistry of di- and tri-metal complexes with bridging carbene or carbyne ligands. Part 48. Reactions of the cluster complex [Fe2W(µ3-CC6H4Me-4)(µ-CO)(CO)8(η-C5H5)] with [W(CR)(CO)2(η-C5H5)](R = Me or C6H4Me-4); crystal structures of [FeW2(µ3-σ:σ′:η2-CCH2)(CO)7(η-C5H5)2] and [FeW2(µ3-MeC2C6H4Me-4)(CO)7(η-C5H5)2

In toluene at 80 °C the compounds [Fe2W(µ3-CC6H4Me-4)(µ-CO)(CO)8(η-C5H5)] and [W(CC6H4Me-4)(CO)2(η-C5H5)] react to give the ditungsten complex [W2{µ-C2(C6H4Me-4)2}(CO)4(η-C5H5)2] as the major product. In contrast, the corresponding reaction with [W(CMe)(CO)2(η-C5H5)] yields a separable mixture of three cluster complexes: [FeW2(µ3-σ:σ′:η2CCH2)(CO)7(η-C5H5)2], [FeW2(µ3- MeC2C6H4Me-4)(CO)7(η-C5H5)2], and [FeW2(µ3-CMe)(µ3-CC6H4Me-4)(CO)6(η-C5H5)2] with the last formed in trace amounts. The structures of [FeW2(µ3σ:σ′:η2-CCH2)(CO)7(η-C5H5)2] and [FeW2(µ3-MeC2C6H4Me-4)(CO)7(η-C5H5)2] have been established by X-ray diffraction. In the vinylidene complex an ironditungsten triangle [mean Fe–W 2.854, W–W 3.030(1)A] is bridged by the CCH2 ligand in such a manner that the latter is σ-bonded to the tungsten atoms (mean µ-C–W 2.06 A) and if η2-co-ordinated to the iron [C–Fe 1.96(2) and 2.21(2)A]. The iron atom is bonded by three terminal CO ligands, while the tungsten atoms are each ligated by a C5H5 and two CO groups. Three of the latter weakly semi-bridge the metal–metal bonds. The structure of the alkyne complex [FeW2(µ3-MeC2C6H4Me-4)(CO)7(η-C5H5)2] is based on a triangle of metal atoms [W–W 2.949(1), Fe–W 2.730(1) and 2.992(1)A]. The MeC2C6H4Me-4 ligand lies on the face of the triangle with its C2 axis parallel to a Fe–W bond. The iron atom carries three CO groups and the tungsten atoms two such groups and a C5H5 ligand. Three of the tungsten-ligated CO groups semi-bridge the three edges of the metal triangle [W–C–O 1 64.5(9), 1 67.7(9), and 169.2(9)°]. The n.m.r. data for the compounds are reported, and possible pathways for formation of the three cluster complexes are discussed.

Some iridium(I) and iridium(III) complexes with the tripod-like ligand CH 3C(CH 2PPh 2) 3 (triphos) and the X-ray crystal structure of [IrCl(CO)(triphos)

The compound [IrCl(CO)(triphos)] ( 1), has been reinvestigated and its X-ray crystal structure is reported. The crystals are orthorhombic, space group Pbca, with a 18.941(6), b 22.193(8), c 17.501(7) Å, Z = 8. The structure was solved by the heavy atom method and refined by full-matrix least-squares to the conventional R factor value of 0.074 for 6462 reflections. The metal atom coordination is trigonal bipyramidal, with the three phosphorus atoms occupying one axial and two equatorial positions. The other equatorial position is occupied by CO while Cl is coordinated axially. Compound 1 readily undergoes a series of oxidative-addition reactions with H 2, HCl and Cl 2, giving [IrH 2(CO)(triphos)] + ( 4) [IrHCl(CO)(triphos)] + ( 3), and [IrCl 3(triphos)] ( 5), respectively. Compounds [IrH(CO)(triphos)] ( 2) and [IrH n Cl 3- n (triphos)] ( n = 1, 2, 3) have also been obtained from 1 and 5, respectively, by treating them with a variety of hydride sources.

Cleavage of Tris(cyclopentadienyl)lanthanide Complexes with Alkyllithium Compounds—a New Route to Alkylbis(cyclopentadienyl)lanthanides

Bis(cyclopentadieny)neodymium hydride 3 is a superb hydrogenation catalyst for alkynes. Exchange of a C5H5 ligand in 1 for sec- or tert-butyl (not for n-butyl) at −78°C affords 2a and 2b, respectively, the first alkylbis(cyclopentadienyl)neodymium complexes. 2a decomposes at −30°C to 3 and butene; 2b can be hydrogenated at room temperature to give 3 and isobutane.

Fünffach koordinierte Zirkonium(IV)-Komplexe mit der (η-C5H5)2ZrIV-Baueinheit. Die Struktur von (η-C5H5)2Zr(CF3SO3)2(THF) / Five Coordinate Zirconium(IV) Complexes with the (η-C5H5)2ZrIV Unit. The Structure of (η-C5H5)2Zr(CF3SO3)2(THF)

Bis(η-cyclopentadienyl)tetrahydrofuran-bis(trifluoromethanesulfonato)zirconium(IV), (η-C5H5)2Zr(CF3SO3)2(THF), has been prepared by reaction of (η-C5H5)2ZrCl2 with AgCF3SO3 in tetrahydrofuran. Crystal data: Orthorhombic, Pnma, a = 15.890(5), b = 13.319(4), c = 10.376(3) Å, Z = 4. An X-ray analysis shows that the complex has a five-coordinate bent metallocene structure. The geometry of the (η-C5H5)2Zr moiety (length of the vectors between Zr and the C5 ring centroids: 2.203 and 2.214 Å, angle between these vectors: 128.1°, angle between C5 ring normals: 127.8°) agrees with that of four-coordinate (η-C5H5)2ZrX2 compounds. The metal bonded O atoms of the three additional ligands lie nearly in a plane bisecting the plane of the C5H5 ligands, the THF group being symmetrically flanked by CF3SO3 ligands.

Notizen: Ungewöhnliche Umlagerung eines Phosphinliganden in der Koordinationssphäre von Palladium / Unusual Rearrangement of a Phosphine Ligand in the Coordination Sphere of Palladium

(η3-Allyl)(η5-cyclopentadienyl)palladium reacts with bis(diphenylphosphino)maleic anhydride to form a complex in which the C5H5 ligand is inserted into a P-C bond of the phosphine ligand. Reaction of this compound with iodine leads to a new type of phosphino ligand. The structure is studied by X-ray crystal structure analysis.

Effect of oxide and sulfide bridging ligands on the structure and magnetic properties of tetranuclear cyclopentadienyl chromium clusters

The indicated framework has Cr-Cr single bonds ~average 2.830(3) A) and Cr--Fe single bonds (average 2.758(3) A). Cr--S (average 2.270(5) A) and Fe--S (average 2.218(4) ~) ~3_ sulfide bridges are found above each face of the tetrahedron and each chromium atom is bound to a C5H5 ligand while the iron atom is bound to the OOCCMe~ group. The monodentate terminal coordination of this group was unexpected (Fe-~, 1.896(10) A; C-O, 1.32(1) and 1.25(1) ~) and leads to a 16-electron environment for Fe and the paramagnetism of (V) (~ef = 2.81 BM).

The synthesis and reactions of some cyclopentadienylpiatinum complexes. Crystal structure of [Pt2{µ-C(Ph)C(Ph)C(O)}(η-C5H5)2

Treatment of di-µ-chloro-dichlorobis(η-ethylene)diplatinum with Mg(C5H5)2 affords the compounds [Pt(η-C2H4)(σ-C5H5)(η-C5H5)] and [Pt2(µ-C10H10)(η-C5H5)2]. Reaction between [NBun4]2[Pt2Cl4(CO)2] and Mg(C5H5)2 affords [Pt2(CO)2(η-C5H5)2] in good yield, as well as the compound [Pt(CO)(σ-C5H5)(η-C5H5)]. Protonation of [Pt(η-C2H4)(σ-C5H55)(η-C5H5)] yields the salt [Pt(η-C2H4)(η2-C5H6)(η-C5H5)][BF4]. Reaction of [Pt(η-C2H4)(σ-C5H5)(η-C5H5)] with PhCCPh affords (η-cyclopentadienyl)(σ: 2–3-η-2,3-diphenylbicyclo[2.2.1 ] hepta-2,5-dien-7-yl) platinum. The compound [Pt2(CO)2(η-C5H5)2] on treatment with PhCCPh in the presence of Me3NO gives [Pt2{µ-C(Ph)C(Ph)C(O)}(η-C5H5)2], and on similar treatment with ButCCBut and Me3NO affords [Pt2(µ-ButC2But)(η-C5H5)2]. The complex [Pt2{µ-C(Ph)C(Ph)C(O)}(η-C5H5)2] was structurally characterised by a single crystal X-ray diffraction study. The metal–metal bond [Pt–Pt 2.590(1)A] is bridged by the C(Ph)C(Ph)–C(O) ligand, in such a manner that the terminal carbon atoms are each σ-bonded to one platinum centre, while the C(Ph)C(Ph) fragment is η2-co-ordinated to the other. Both metal atoms carry C5H5 ligands, but one is asymmetrically bound. The n.m.r. data (1H, 31C-{1H}, and 195Pt-{1H}) for the new compounds are reported and discussed, and this information used to suggest mechanisms for the dynamic behaviour of [Pt(η-C2H4)(σ-C5H5)(η-C5H5)], [Pt2(CO)2(η-C5H5)2], and [Pt(η-C2H4)(η2-C5H6)(η-C5H5)]+.

Metal promoted hydrolysis of methyl 2-( N-acetylhydrazono)propanoate and crystal structure of the derived Ni(II) complex

The new chelating ligand Ch 3C(O)NHNC(CH 3)C(O)OCH 3,L, obtained by condensation of N-acetyl-hydrazine and methyl pyruvate, undergoes quantitative hydrolysis of the −C(O)OCH 3 group by reacting, in hydro-alcoholic medium, with some first row transition metal acetates. Complexes of the type ML′ 2 have been obtained and characterized, where L′ is the derived N-acetylhydrazonopropanoate anion. An X-ray structural analysis carried out on the NiL′ 2 · 2H 2O complex has shown a terdentate behaviour of the anionic ligand, resulting in a distorted octahedral environment around the metal. Coordination occurs through the acetyl (NiO = 2.094(5) Å), the iminic (NiN = 1.995(5) Å) and the carboxylic (NiO = 2.055(5) Å) donor groups. Crystals are orthorhombic, space group Pbcn with unit cell dimensions a = 12.151(3), b = 9.677(2), c = 13.489(3) Å and Z = 4. The structure was solved by direct methods to R = 0.0495 for 694 observed reflections.

Chemistry of di- and tri-metal complexes with bridging carbene or carbyne ligands. Part 10. Synthesis of dicobalt– and dirhodium–tungsten complexes with µ3-tolylidyne groups; crystal structures of [Co2W(µ3-CC6H4Me-4)(CO)8(η-C5H5)] and [Rh2W(µ3-CC6H4Me-4)-(acac)2(µ-CO)(CO)2(η-C5H5)](acac = acetylacetonate)

The compound [WCC6H4Me-4(CO)2(η-C5H5)] reacts with [Co2(CO)8] in pentane at room temperature to give the dicobalt-tungsten complex [Co2W(µ3-CC6H4Me-4)(CO)8(η-C5H5)], the structure of which was established by a single-crystal X-ray diffraction study. The crystals are orthorhombic, space group Pcmn(non-standard setting of Pnma, no. 62), Z= 4, in a unit cell with lattice parameters a= 10.067(13), b= 11.806(26) and c= 18.203(10)A. The structure has been refined to R 0.025 (R′ 0.027) for 1 565 reflections to 2θ⩽ 40°[(Mo-Kα)X-radiation] collected at 200 K. The molecule consists of a Co2W isosceles triangle of metal atoms [Co–W 2.672(1) and Co–Co 2.488(1)A] capped by a triply-bridging tolylidyne ligand [W–C 2.103(7) and Co–C 1.953(6)A]. The carbonyl ligands are all terminal, with two on each cobalt atom approximately equatorial with respect to the metal atom plane, while the third is axial. From reactions of the compounds [Co2W(µ3-CC6H4Me-4)(CO)8(η- C5H4R)](R = H or SiMe3) with PMe2Ph, P(OMe)3, dppm (Ph2PCH2PPh2), and diars [C6H4(AsMe2)2-1,2], the complexes [Co2W(µ3-CC6H4Me-4)(CO)7(PMe2Ph)(η-C5H4R)](R = H or SiMe3) and [Co2W(µ3-CC6H4-Me- 4)(CO)6L2(η-C5H4R)][L = PMe2Ph, R = H or SiMe3; L = P(OMe)3, R = H; L2= dppm, R = H or SiMe3; L2= diars, R = H] were isolated, and characterised by i.r. and n.m.r. spectroscopy. Reaction of [Co2W-(µ3-CC6H4Me-4)(CO)8(η-C5H5)] with Me3SiC2SiMe3 affords the cluster complex [Co2W(µ3-CC6H4Me-4)-(µ-Me3SiC2SiMe3)(CO)6(η-C5H5)]. In light petroleum, at room temperature, [Rh(acac)(CO)2](acac = acetylacetonate) and [WCC6H4Me-4(CO)2(η-C5H5)] react to give [RhW(µ-CC6H4Me-4)(acac)(CO)3(η-C5H5)], and the latter with [Rh(acac)(C2H4)2] affords the dirhodiumtungsten compound [Rh2W(µ3-CC6H4Me-4)(acac)2-(µ-CO)(CO)2(η-C5H5)]. The molecular structure of this species was established by X-ray diffraction. Crystals, grown with ½C6D6 of crystallisation, are triclinic, space group P, Z= 2, in a unit cell with lattice dimensions a= 10.756(8), b= 10.805(6), c= 13.215(13)A, α= 81.32(7), β= 80.44(7), and γ= 78.60(6)°. The structure has been refined to R= 0.057 (R′ 0.061) for 5 897 reflections to 26 ⩽ 60° collected at 293 K. The molecule has a triangular array of metal atoms [Rh-W 2.809(2) and 2.764(2), Rh–Rh 2.613(2)A] with an essentially symmetrically triply-bridging tolylidyne ligand [µ3-C–Rh 2.030(8) and 1.994(9), µ3-C–W 1.991(8)A]. There is a symmetrically bridging CO ligand associated with the Rh–Rh bond, and the two CO groups on the tungsten mildly semi-bridge the two Rh–W bonds (W–C–O 171°). The acac ligands function as bidentate oxygen donors to the rhodium atoms. Although the C5H5 ligand has an η5 attachment to the tungsten atom it does not conform well with the pseudomirror symmetry of the molecule, and the distortion probably relates to the two different Rh–W bond lengths.

Komplexchemie reaktiver organischer verbindungen : XXXVII. Metallinduzierter abbau eines σ,π-koordinierten ketens in ein π-allyl/σ-aryl/π-olefin-system

Photolysis of diphenylketene in the presence of pentacarbonyliron yields the π-allyl/σ-acyl type compound [η 3:η 1-(C 6H 5) 2CCO)Fe(CO) 3 (III) the molecular structure of which has been established by means of X-ray diffraction techniques. Metal-centered carboncarbon bond breaking and bond making in III is evident from 13CO labelling and crossover experiments. The dinuclear compound IV, structurally characterized by the π-allyl/σ-aryl/π-olefin hydrocarbon ligand CH(C 6H 4)C 6H 5, is formed upon irreversible decarbonylation of the ketene precursor III.