Reactions of Unsaturated Quinoline Triosmium Clusters [Os3(CO)9(μ3-η2-C9H5(4-R)N)(μ-H)] (R=Me or H) with Tetramethylthiourea: X-ray Structures of [Os3(CO)8(μ-η2-C9H5(4-Me)N)(η2-SC(NMe2NCH2Me)(μ-H)2] and [Os3(CO)9(μ-η2-C9H6N)(η1-SC(NMe2)2)(μ-H)]

Treatment of the electronically unsaturated 4-methylquinoline triosmium cluster $[\hbox{Os}_{3}\hbox{(CO)}_{9}(\upmu_3\hbox{-}\upeta^{2}\hbox{-}\hbox{C}_{9}\hbox{H}_{5} \hbox{(4-Me)N})(\upmu\hbox{-H})]$ (1) with tetramethylthiourea in refluxing cyclohexane at 81°C gave $[\hbox{Os}_{3}\hbox{(CO)}_{8}(\upmu\hbox{-}\upeta^{2}\hbox{-C}_{9}\hbox{H}_{5} \hbox{(4-Me)N})(\upeta^2\hbox{-SC}(\hbox{NMe}_2\hbox{NCH}_2\hbox{Me})(\upmu \hbox{-H})_2]$ (2) and $[\hbox{Os}_{3}\hbox{(CO)}_{9}(\upmu\hbox{-}\upeta^{2}\hbox{-C}_{9}\hbox{H}_{5}\hbox{(4-Me)N})(\upeta^1\hbox{-SC}(\hbox{NMe}_2)_2)(\upmu\hbox{-H})]$ (3). In contrast, a similar reaction of the corresponding quinoline compound $[\hbox{Os}_{3}\hbox{(CO)}_{9}(\upmu_{3}\hbox{-}\upeta^{2}\hbox{-C}_{9}\hbox{H}_{6}\hbox{N})(\upmu\hbox{-H})]$ (4) with tetramethylthiourea afforded $[\hbox{Os}_{3}\hbox{(CO)}_{9}(\upmu\hbox{-}\upeta^{2}\hbox{-C}_{9}\hbox{H}_{6}\hbox{N})(\upeta^{1}\hbox{-SC(NMe}_{2})_{2})(\upmu\hbox{-H)}]$ (5) as the only product. Compound 2 contains a cyclometallated tetramethylthiourea ligand which is chelating at the rear osmium atom and a quinolyl ligand coordinated to the Os₃ triangle via the nitrogen lone pair and the C(8) atom of the carbocyclic ring. In 3 and 5, the tetramethylthiourea ligand is coordinated at an equatorial site of the osmium atom, which is also bound to the carbon atom of the quinolyl ligand. Compounds 3 and 5 react with PPh₃ at room temperature to give the previously reported phosphine substituted products $[\hbox{Os}_{3}\hbox{(CO)}_{9}(\upmu \hbox{-}\upeta^{2}\hbox{-C}_{9}\hbox{H}_{5}\hbox{(4-Me)N)(PPh}_{3})(\upmu\hbox{-H)}]$ (6) and $[\hbox{Os}_{3}\hbox{(CO}_{9}(\upmu \hbox{-}\upeta^{2}\hbox{-C}_{9}\hbox{H}_{6}\hbox{N)(PPh}_{3})(\upmu\hbox{-H)}]$ (7) by the displacement of the tetramethylthiourea ligand.     

Synthesis and structures of the η5-C5H5Cl(CO)2W-η1,η5-(PPh2)C5H4(CO)2Fe-η1,η5-C5H4Mn(CO)3 and MeSi[C5H4(CO)2Fe-η1,η5-C5H4Mn(CO)2PPh3]3 complexes

The metallation of the η⁵-C₅H₅(CO)₂Fe-η¹,η⁵-C₅H₄Mn(CO)₃ complex with BuⁿLi (THF, ?78 °C) followed by the treatment of the lithium derivative with Ph₂PCl afforded the η⁵-Ph₂PC₅H₄(CO)₂Fe-η¹,η⁵-C₅H₄Mn(CO)₃ complex. The reaction of the latter with η⁵-C₅H₅(CO)₃WCl in the presence of Me₃NO produced the trinuclear complex η⁵-C₅H₅Cl(CO)₂W-η¹,η⁵-(Ph₂P)C₅H₄(CO)₂Fe-η¹,η⁵-C₅H₄Mn(CO)₃. The structure of the latter complex was established by IR, UV, and 1H and ³¹P NMR spectroscopy and X-ray diffraction. The reaction of MeSiCl₃ with three equivalents of LiC₅H₄(CO)₂Fe-η¹,η⁵-C₅H₄Mn(CO)₂PPh₃ gave the hexanuclear complex MeSi[C₅H₄(CO)₂Fe-η¹,η⁵-C₅H₄Mn(CO)₂PPh₃]₃.     

Preparation and crystal structures of [μ-SbPh2]2[Mo(CO)2(η5-C5H5)]2·CHCl3 and SbPh[Fe(CO)2(η5-C5H5)]2

Antimony is reduced when [SbPh₂BrO]₂ is treated with Na[Mo(CO)₃(η⁵-C₅H₅)] to produce [μ-SbPh₂]₂[Mo(CO)₂(η⁵-C₅H₅)]₂. A structure determination shows diphenylstibido groups bridging between two Mo(CO)₂(η⁵-C₅H₅) moieties giving a central ‘butterfly’ shaped Sb₂Mo₂ ring. The cyclopentadiene rings are trans to each other and Mo–Sb and Sb–Sb separations are both short. An iron analogue could not be obtained from [SbPh₂BrO]₂ and Na[Fe(CO)₂(η⁵-C₅H₅)] but a mixture of SbPh[Fe(CO)₂(η⁵-C₅H₅)]₂ and SbPh₂[Fe(CO)₂(η⁵-C₅H₅)] was obtained using SbPh₂Cl. An X-ray structure for SbPh[Fe(CO)₂(η⁵-C₅H₅)]₂ shows an open stibinidine structure.     

[C5H4C(CH3)(C3H7)CH2CH=CH2]NdMg2(μ3-OH)(μ3-Cl)(μ2-Cl)3(THF)4Cl的合成和晶体结构分析

用Ｘ－射线衍射法测定了［Ｃ５Ｈ４Ｃ（ＣＨ３）（Ｃ３Ｈ７）ＣＨ２ＣＨ＝ ＣＨ２］ＮｄＭｇ２（μ３－ＯＨ）（μ３－Ｃｌ）（μ２－Ｃｌ）３（ＴＨＦ）４Ｃｌ的晶体结构。它属三斜晶系,空间群为Ｐ１－ ,ａ＝ １２．６９８（３）, ｂ＝ １３．６１６（３）, ｃ＝ １３．７１２（３）, α＝ ６８．９１（３）, β＝ ８４．３４（３）, γ＝ ６３．０７（３）°, Ｖ＝ １９６６（１）３, Ｍｒ＝ ８４９．７４, Ｄｘ＝ １．４１２ ｇ·ｃｍ － ３, μ＝ １．７２９７ ｍ ｍ － １, Ｆ（０００）＝ ８４０, Ｚ＝ ２, Ｒ＝ ０．０７３, ｗ Ｒ＝ ０．０８６（Ｉ≥３σ（Ｉ））。分子中Ｎｄ（Ⅲ）原子的配位数为八,形成一个严重扭曲的八面体结构。两个Ｍｇ 原子的配位情况相似,它们的配位数都是六,构成两个扭曲的八面体。这三个八面体通过三个共用平面联接     

Synthesis and crystal structure of [(η3-C3H5)(CO)2Mo(μ-S2CPCy3)-Mo(η3-CH2CMeCH2)(CO)2]

A novel dimolybdenum complex [(³-C₃H₅)(CO)₂Mo(-S₂CPCy₃)Mo(³-CH₂CMeCH₂)(CO)₂], obtained by reacting the [(CO)₂(³-C₃H₅)Mo(-S₂CPCy₃)Mo(CO)₃]^– anion with an excess of ClCH₂CMe=CH₂, has been characterized by i.r., ³¹P{¹H}, ¹H- and ¹³C-n.m.r. spectroscopy and by elemental analysis. The crystal structure of the complex, determined by X-ray diffraction, shows a definite preference for the central carbon of the S₂CPCy₃ bridge to bind to the Mo(2) atom coordinated by ³-2-methylallyl, rather than the Mo(1) atom attached to unsubstituted ³-allyl ligand.     

Triphospha-Ferrocenes as Ligands. Crystal Structures of [Fe(η5-C5Me5)(η5-C2 TBu2P3)M(CO)5)], (M= Cr,MO, W) and the Novel ruthenium and Nickel Complexes [Fe(η5-C5Me5) (η5-C2 TBu2P3)Ru3(CO)9] and [Fe(η5-C5Me5)(η5-C2 tBu2P3)Ni(Co)2]2

Abstract

Syntheses and structures of penta- and hexaphosphorus analogues of ferrocene have been described recently¹. Unlike their simple ferrocene analogues, these complexes have further ligating potential towards other transition metal centres by virtue of the availability of the ring phosphorus lone-pair electrons that are not involved in the η⁵-coordination. We now describe the first examples of coordination compounds of the triphospha-ferrocene [Fe(η⁵-C₅Me₅) (η⁵-C₂ ^tBu₂P₃]. In the ruthenium complex [Fe(η⁵-C₅Me₅)(η⁵-C₂ ^tBu₂P₃) Ru₃(CO)₉] ² two adjacent phosphorus atoms of the η⁵-C₂ ^tBu₂P₃ ring are interlinked by a ruthenium carbonyl cluster in which all three ruthenium atoms interact with the phosphorus atoms. The tetrametallic nickel complex [Fe(η⁵-C₅Me₅)(η⁵-C₂ ^tBu₂P₃)Ni(CO)₂]₂ ³ represents the first example of intermolecular interlinkage of two phospha-ferrocene systems by two metal centres.     

The Thermolysis of [Ru3(CO)12] in Cyclohexene: Synthesis and Charaterisation of the New Clusters [Ru3H2(CO)9(μ3-η1:η2:η1-C6H8)] and [Ru5(CO)12(μ4-η2-C6H8)(η4-C6H8)]

Thermolysis of [Ru₃(CO)₁₂] in cyclohexene for 24 h affords the complexes [Ru(CO)₃(η⁴-C₆H₈)] (1), [Ru₃H₂(CO)₉(μ₂-η¹:η²:η¹-C₆H₈)] (2), [Ru₄(CO)₁₂(μ₄-C₆H₈)] (3) [Ru₄(CO)₉(μ₄-C₆H₈)(η⁶-C₆H₆)] (4a and 4b, two isomers) and [Ru₅(CO)₁₂(μ₄-η²-C₆H₈)(η⁴-C₆H₈)] (5), where 1, 3, 4a and 4b have been previously characterised as products of the thermolysis of [Ru₃(CO)₁₂] with cyclohexa-1,3-diene. The molecular structures of the new clusters 2 and 5 were determined by single-crystal X-ray crystallography, showing that two conformational polymorphs of 5 exist in the solid state, differing in the orientation of the cyclohexa-1,3-diene ligand on a ruthenium vertex.     

New electron-deficient alkene and alkyne derivatives of Ru5(μ5-C)(CO)15: The syntheses and crystal structure analyses of Ru5(μ5-C)(CO)13 [C2H2(CO2Me)2] and Ru5(μ5-C)(CO)15 [C2(CO2Me)2]

Treatment of carbido cluster Ru₅(μ ₅-C)(CO)₁₅ with Me₃NO in acetonitrile solution followed by addition of dimethyl maleate or dimethyl acetylene dicarboxylate affords new clusters Ru₅(μ ₅-C)(CO)₁₃[C₂H₂(CO₂Me)₂] (1) and Ru₅(μ ₅-C)(CO)₁₅[C₂(CO₂Me)₂] (2), respectively. Single crystal X-ray structural studies reveal that both complexes contain a wingtip-bridged butterfly pentametallic skeleton. In complex1 the maleate fragment is coordinated to one wingtip Ru atom through its carbon-carbon double bond and to the adjacent Ru atom by the formation of two O → Ru dative bonding interactions, while the acetylene dicarboxylate fragment in2 is best considered as acis-dimetallated alkene, linking one hinge Ru atom and the nearby Ru atom at the bridged position. Crystal data for1: space group P 4₂/n;a=20.199(6),c=13.941(3) Å,Z=8; finalR _F=0.025,R _w=0.026 for 3963 reflections withI>2σ(I). Crystal data for2: space group P2₁/n;a=9.634(3),b=20.062(6),c=17.372(5) Å,β=90.62(2)°,Z=4; finalR _F=0 033,R _w=0.036 for 4683 reflections withI>3σ(I).     

Reactivity of triosmium clusters with 3,4-dimethyl-1-phenylphosphole and cyanoethyldi-tert-butylphosphine ligands: X-ray crystal structures of [Os3(CO)9(μ-OH)(μ-H)(η1-PhPC4H2Me2)] and [Os3(CO)11(η1- t Bu2PC2H4CN)]

Reaction of [Os₃(μ-H)₂(CO)₁₀] with 3,4-dimethyl-1-phenylphosphole in refluxing cyclohexane affords two substituted triosmium clusters: [Os₃(CO)₉(μ-H)(μ³:η¹:η¹:η²-PhPC₄H₃Me₂)] (1) and [Os₃(CO)₉(H)(μ²-η¹:η²-PhPC₄H₄Me₂)] (2), of which cluster 2 exhibits two chromatographically non-separable isomeric forms attributed to terminal and bridging coordination of the hydride ligand, respectively. When this reaction is performed in refluxing THF, the only product is the cluster [Os₃(CO)₉(μ-OH)(μ-H)(η¹-PhPC₄H₂Me₂)] (3). Crystallographic information obtained for cluster 3 shows the phosphole ligand occupying an equatorial position, as expected, while the OH group is asymmetrically bridging unlike previously reported similar compounds. Additionally, interaction of the labile cluster [Os₃(CO)₁₁(CH₃CN)] with cyanoethyldi-tert-butylphosphine in dichloromethane at room temperature was found to give [Os₃(CO)₁₁(η¹- ^t Bu₂PC₂H₄CN)] (4) as the only product; its crystallographic characterization shows that the phosphine ligand coordinates by means of the phosphorus atom in an equatorial fashion, analogous to compound 3.     

Coordination-unsaturated complexes of tris(cyclopentadienyl)samarium: Solvate (η5-C5H5)3Sm·OC4H8 and ionic salt [Li(Et2O)2][η5-C5H5)3Sm(μ-Cl)Sm(η5-C5H5)3]

X-ray structural analysis of a samarium triscyclopentadienyl complex, Cp₃Sm·OC₄H₈ (1), and a samarium ionic salt, [Li(Et₂O)₂][Cp₃Sm(-Cl)SmCp₃] (2), was carried out. In both compounds coordination saturation is achieved by coordination of the THF molecule (in1) or the Cl^– anion (in2) to the monomeric fragment Cp₃Sm. An unusual coordination of the Li⁺ cation was observed in complex2: it is bound to one of the ⁵-type cyclopentadienyl rings in addition to two ether molecules.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1129–1132, June, 1993.     

Reactions of Triruthenium Clusters with Quinolines: X-Ray Structures of [Ru3(μ-CO)(CO)7{μ3-η2-P(C6H5)CH2P(C6H5)2)}{μ-η2-C9H5(CH3)N}] and [Ru3(CO)10(μ-H){μ-η2-C9H6N}]

The reactions of [Ru₃(CO)₁₀(μ-dppm)] 4 with quinolines afforded [Ru₃ (μ-CO)(CO)₇{μ₃-η²-P(C₆H₅)CH₂P(C₆H₅)₂)}{μ-η²-C₉H₅(R)N}] (8, R = 4-Me; 9, R = H) as the major products along with small amounts of known compound [Ru₃(CO)₉{μ₃-η³-P(C₆H₅)CH₂P(C₆H₅)(C₆H₄)}] 5. The molecular structure of 8 has been determined by single crystal X-ray studies. The reaction of 5 with 4-methylquinoline in refluxing cyclohexane afforded 8 and two known dinuclear compounds, [Ru₂(CO)₆{μ-CH₂P(C₆H₅)(C₆H₄)P(C₆H₅}] 10 and [Ru₂(CO)₆ {μ-(C₆H₄)P(C₆H₅)(CH₂)P(C₆H₅}] 11, in 40, 12, and 10% yields, respectively. The compounds 10 and 11 are also formed from the thermolysis of 4 in addition to the major compound 5. The solid state structure of the previously reported [Ru₃(CO)₁₀(η-H){μ-η²-C₉H₆N}] 2a is also reported for comparison.     

Synthesis, Characterization and Crystal Structure of [Co2Mo2(μ4-C2HPh)(μ-CO)4(CO)4(η5-C5H4C(O)Me)2]

The reaction of μ-alkyne-bridged dimolybdenum compound [Mo2(μ-C2HPh)(CO)4(η5-C5H4C(O)Me)2] 1 with Co2(CO)8 in refluxing toluene gave a new butterfly compound [Co2Mo2(μ4-C2HPh)(μ-CO)4(CO)4(η5-C5H4C(O)Me)2] 2 which was fully characterized by elemental analysis, IR, 1H NMR and X-ray single crystal diffraction techniques. 2 crystallized in monoclinic system, C30H20Co2Mo2O10, Mr=850.23, space group P21/a(#14), a=14.165(5), b=12.498(2), c=16.204(2)(A), β = 96.50(2)°, V = 2850(1)(A)3, Z = 4, Dc = 1.981 g cm-3, F(000)=1672, μ(MoKα)=20.41 cm-1, final R=0.030, Rw=0.039 for 4831 observable reflections with I>2σ(I). The structure contains a Co2Mo2 butterfly core, and each Mo-Co bond is spanned by an asymmetric semi-bridging carbonyl ligand.     

Reaction of alkyne cluster Os3(μ-CO)(CO)9(μ3-η1:η1:η2-Me3SiC2Me) with HC≡CCOOMe. Molecular and crystal structures of Os3(CO)9{μ3-η1:η1:η2:η2-C(SiMe3)C(Me)C(COOMe)CH× and Os3(CO)8{μ3-η1:η1:η4:η1-C(SiMe3)C(Me)C(H)C(COOMe)CH× complexes

Reaction of the cluster Os₃(μ-CO)(CO)₉(μ₃-η¹:η¹:η²-Me₃SiC₂Me) with HC≡CCOOMe in benzene at 70 °C results in Os₃(CO)₉{μ₃-η¹:η¹:η²:η²-C(SiMe₃)C(Me)C(COOMe)CH× (5), Os₃(CO)₉{μ₃-η¹:η¹:η²:η²-C(SiMe₃)C(Me)C(H)C(COOMe)CH× (6), Os₃(CO)₉{μ-η¹:η¹:η⁴-C(SiMe₃)C(Me)C(H)C(COOMe)CH× (7), and Os₃(CO)_δ{μ₃-η¹:η¹:η⁴:η¹-C(SiMe₃)C(Me)C(H)C(COOMe)× complexes (8), containing an osmacyclopentadiene moiety. Complexes5–8 were characterized by¹H NMR and IR spectroscopy. The structure of clusters5 and8 was confirmed by X-ray analysis. Complex7 is formed from cluster5 as a result of a new intramolecular rearrangement and complex8 is obtained by decarbonylation of compound6. Complex8 adds PPh₃ to give Os₃(CO)_δ(PPh₃){μ-η¹:η¹:η⁴-C(SiMe₃)C(Me)C(H)C(COOMe)×.     

Nature of M-Ga bonds in dihalogallyl complexes (η5-C5H5)(Me3P)2M(GaX2) (M = Fe, Ru, Os) and (η5-C5H5)(OC)2Fe(GaX2) (X = Cl, Br, I): a DFT study

Density functional theory (DFT) calculations have been performed on the terminal dihalogallyl complexes of iron, ruthenium, and osmium (η(5)-C(5)H(5))(Me(3)P)(2)M(GaX(2)) (M = Fe, Ru, Os; X = Cl, Br, I) and (η(5)-C(5)H(5))(OC)(2)Fe(GaX(2)) (X = Cl, Br, I) at the BP86/TZ2P/ZORA level of theory. On the basis of analyses suggested by Pauling, the M-Ga bonds in all of the dihalogallyl complexes are shorter than M-Ga single bonds; moreover, on going from X = Cl to X = I, the optimized M-Ga bond distances are found to increase. From the perspective of covalent bonding, however, π-symmetry contributions are, in all complexes, significantly smaller than the corresponding σ-bonding contribution, representing only 4-10% of the total orbital interaction. Thus, in these GaX(2) complexes, the gallyl ligand behaves predominantly as a σ donor, and the short M-Ga bond lengths can be attributed to high gallium s-orbital character in the M-Ga σ-bonding orbitals. The natural population analysis (NPA) charge distributions indicate that the group 8 metal atom carries a negative charge (from -1.38 to -1.62) and the gallium atom carries a significant positive charge in all cases (from +0.76 to +1.18). Moreover, the contributions of the electrostatic interaction terms (ΔE(elstat)) are significantly larger in all gallyl complexes than the covalent bonding term (ΔE(orb)); thus, the M-Ga bonds have predominantly ionic character (60-72%). The magnitude of the charge separation is greatest for dichlorogallyl complexes (compared to the corresponding GaBr(2) and GaI(2) systems), leading to a larger attractive ΔE(elstat) term and to M-Ga bonds that are stronger and marginally shorter than in the dibromo and diiodo analogues.     

The preparation of a series of ring-linked derivatives of [Fe2(η-C5H5)2(CO)2(μ-CO)2] starting from [Fe2η5,η5-C5H4CH(NMe3)CH(NMe2)C5H4}(CO)2(μ-CO)2]+ salts

The salts [Fe₂η⁵,η⁵-C₅H₄CH{NMe₃)CH(NMe₂)C₅H₄}(CO)₂(μ-CO)₂][X] (X = I or SO₃CF₃) are the synthetic precursors to a wide range of [Fe₂(η-C₅H₅)₂(CO)₂(μ-CO)₂] derivatives in which the two cyclopentadienyl ligands are joined by a two-carbon bridge.     

Crystal structure of [Pd3(μ-OH)(μ-CH3COO)5]

The crystals of the [Pd₃(μ-OH)(μ-CH₃COO)₅] complex are obtained and characterized using powder and single crystal X-ray diffraction and IR spectroscopy. The crystal structure (a = 15.6942(6) Å, b = 11.7190(3) Å, c = 9.7871(3) Å, V = 1800.05(10) ų, space group Pna2₁, Z = 4) is formed from neutral trinuclear cyclic molecules of [Pd₃(μ-OH)(μ-CH₃COO)₅], in which the OH^? group, together with five CH₃COO^? anions, is a bridge ligand.     

Self-recognition by the iron chiral auxiliary [(η5-C5H5)Fe(CO)(PPh3] in the formation of (RR,SS)-[(η5-C5H5)FE(CO)(PPh3)COCH2]2CH2

Complete self-recognition of chirality is observed in the Michael addition of the enolate derived from R,S-[η⁵-C₅H₅Fe(CO)(PPh₃-COCH₃] to the acryloyl complex R,S-[(η⁵-C₅H₅Fe(CO)(PPh₃)-COCHCH₂)] to generate exclusively the single diastereoisomer of the glutaroyl complex RR,SS-[(η⁵-C₅H₅)Fe(CO)(PPh₃)COCH₂]₂CH₂.     

Preparation of organozirconium aromatic compounds in mixed aqueous-organic solvents: X-ray structures of [Cp2ZrCl(μ2-O′,O′′C-C6H5)], [(CpZr)3(μ2-O′,O′′C-C6H3Cl2)3(μ3-OH)(μ2-OH)3](Cl2C6H3COO)2, and [(CpZr)3(μ2-O′,O′′C-C6H4Cl)3(μ3-OH)(μ2-OH)3]Cl2·CH2Cl2

A new and facile method is presented for the synthesis of zirconocene carboxylate compounds, in which zirconocene dichloride (Cp₂ZrCl₂) is dissolved in 1 M aqueous HCl solution and the requisite ligand is dissolved in an organic solvent. Five such compounds [Cp₂ZrCl(μ₂-O′,O′′C-C₆H₅)] (1), [Cp₂ZrCl(μ₂-O′,O′′C-C₆H₃Cl₂)] (2), [Cp₂Zr(μ₂-O′,O′′C-C₆H₃(OH)Cl)₂] (3), [Cp₂Zr(μ₂-O′,O′′C-C₆H₃(OH)(NO₂))₂] (4), and [Cp₂Zr(μ₂-O′,O′′C-C₆H(OH)Cl₃)₂] (5) have been obtained by this method. The effect of pH on the stability of Cp₂ZrCl₂ in 1 M HCl solution has been investigated by UV/vis spectrophotometry and ¹H NMR spectrometry. The results showed that the aqueous Cp₂ZrCl₂ solutions became less stable with increasing pH, liberating cyclopentadiene. Accordingly, at higher pH (～7), two trinuclear zirconium monocyclopentadienyl compounds, [(CpZr)₃(μ₂-O′,O′′C-C₆H₃Cl₂)₃(μ₃-OH)(μ₂-OH)₃](Cl₂C₆H₃COO)₂ (6) and [(CpZr)₃(μ₂-O′,O′′C-C₆H₄Cl)₃(μ₃-OH)(μ₂-OH)₃]Cl₂·CH₂Cl₂ (7), were obtained. All compounds 1–7 have been characterized by FT-IR, ¹H NMR spectra and elemental analysis. In all of the compounds, the aromatic acid acts as a bidentate ligand in coordinating to the zirconium; both chelating and bridging modes are observed. X-ray crystallographic studies on 1, 6, and 7 have revealed that the geometries at zirconium are distorted octahedral in 6 and 7, and distorted trigonal-bipyramidal in 1.     

Comparison of the Bonding of Benzene and C60 to a Metal Cluster: Ru3(CO)9(μ3-η2,η 2,η2-C6H6) and Ru3(CO)9(μ3-η2,η2,η2-C60)

The electron distributions and bonding in Ru₃(CO)₉( ³- ², ², ²-C₆H₆) and Ru₃(CO)₉( ³- ², ², ²-C₆₀) are examined via electronic structure calculations in order to compare the nature of ligation of benzene and buckminsterfullerene to the common Ru₃(CO)₉ inorganic cluster. A fragment orbital approach, which is aided by the relatively high symmetry that these molecules possess, reveals important features of the electronic structures of these two systems. Reported crystal structures show that both benzene and C₆₀ are geometrically distorted when bound to the metal cluster fragment, and our ab initio calculations indicate that the energies of these distortions are similar. The experimental Ru–C_fullerene bond lengths are shorter than the corresponding Ru–C_benzene distances and the Ru–Ru bond lengths are longer in the fullerene-bound cluster than for the benzene-ligated cluster. Also, the carbonyl stretching frequencies are slightly higher for Ru₃(CO)₉( ³- ², ², ²-C₆₀) than for Ru₃(CO)₉( ³- ², ², ²-C₆H₆). As a whole, these observations suggest that electron density is being pulled away from the metal centers and CO ligands to form stronger Ru–C_fullerene than Ru–C_benzene bonds. Fenske-Hall molecular orbital calculations show that an important interaction is donation of electron density in the metal–metal bonds to empty orbitals of C₆₀ and C₆H₆. Bonds to the metal cluster that result from this interaction are the second highest occupied orbitals of both systems. A larger amount of density is donated to C₆₀ than to C₆H₆, thus accounting for the longer metal–metal bonds in the fullerene-bound cluster. The principal metal–arene bonding modes are the same in both systems, but the more band-like electronic structure of the fullerene (i.e., the greater number density of donor and acceptor orbitals in a given energy region) as compared to C₆H₆ permits a greater degree of electron flow and stronger bonding between the Ru₃(CO)₉ and C₆₀ fragments. Of significance to the reduction chemistry of M₃(CO)₉( ³- ², ², ²-C₆₀) molecules, the HOMO is largely localized on the metal–carbonyl fragment and the LUMO is largely localized on the C₆₀ portion of the molecule. The localized C₆₀ character of the LUMO is consistent with the similarity of the first two reductions of this class of molecules to the first two reductions of free C₆₀. The set of orbitals above the LUMO shows partial delocalization (in an antibonding sense) to the metal fragment, thus accounting for the relative ease of the third reduction of this class of molecules compared to the third reduction of free C₆₀.