Exo-H- andendo-H-η4-pentamethylcyclopentadiene complexes of platinum

A mixture ofendo-H andexo-H isomers (1a and1b) of the (⁴-C₅Me₅H)PtCl₂ complex was prepared by the reaction of K₂PtCl₄ with C₅Me₅H in MeOH. The mixture of isomers reacts with CpTl in the presence of TiBF₄ to give a novel complex, [(⁴-C₅Me₅H)Pt(⁵-C₅H₅)]⁺BF₄ ^–, as a mixture ofendo-H- andexo-H-isomers (2a and2b). The data of¹H and¹³C NMR spectroscopy of the resulting complexes are discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 514–517, March, 1994.     

Stilbene analogues incorporating the Co(η-C4Ph4)(η-C5H4-) end group

A number of organometallic stilbenes of the general type [Co(η⁴-C₄Ph₄)(η⁵-C₅H₄CHCHR] are reported where R is C₆H₄X-4 (X = H, OMe, Br, NO₂), 1-naphthyl, 9-anthryl, 1-pyrenyl, (η⁵-C₅H₄)Co(η⁴-C₄Ph₄), and (η⁵-C₅H₄)Fe(η⁵-C₅H₄Y) {Y = CHO, CHC(CN)₂ and CHCHC₅H₄-η⁵)Co(η⁴-C₄Ph₄)}. They were prepared by Wittig or Horner-Wadsworth-Emmons reactions which yield both E and Z or only E products respectively. The isomers were separated and all compounds characterised by standard spectroscopic techniques as well as by X-ray diffraction methods in many cases. The electrochemistry of the stilbene analogues in dichloromethane solution is also reported. In most, the (η⁵-C₅H₄)Co(η⁴-C₄Ph₄) functional group undergoes a reversible one-electron oxidation. For those molecules that also include (η⁵-C₅H₄)Fe(η⁵-C₅H₄Y), this is preceded by the reversible oxidation of the ferrocenyl group. Spectroscopic and structural data suggests that for most compounds there is little electronic interaction between Co(η⁴-C₄Ph₄)(η⁵-C₅H₄) and the R end groups which are effectively independent of one another. The only exceptions to this are Z and E-[Co(η⁴-C₄Ph₄)(η⁵-C₅H₄CHCHC₆H₄NO₂-4], and [Co(η⁴-C₄Ph₄)(η⁵-C₅H₄CHCHC₅H₄-η⁵)Fe{η⁵-C₅H₄CHC(CN)₂}] where the electronic spectra are respectively consistent with a significant Co(η⁴-C₄Ph₄)(η⁵-C₅H₄)/NO₂ donor/acceptor interaction and a less significant Co(η⁴-C₄Ph₄)(η⁵-C₅H₄)/C(CN)₂ one. However, OTTLE studies show that in the electronic spectra of [Co(η⁴-C₄Ph₄)(η⁵-C₅H₄CHCHR]⁺ there are low energy absorption bands (950-1800 nm) which are attributed to R → Co(η⁴-C₄Ph₄)(η⁵-C₅H₄)⁺ or, when R is a ferrocenyl-base group, Co(η⁴-C₄Ph₄)(η⁵-C₅H₄) → (η⁵-C₅H₄)Fe(η⁵-C₅H₄Y)⁺ charge transfer transitions. The ferrocenyl compounds undergo cis/trans isomerisation on the OTTLE experiment timescale.     

Dimeric uranium complexes with bridging phospholyl ligands. Crystal structure of [{U(η5-C4Me4P)(μ-η5-C4Me4P)(BH4)}2]

In the symmetrical crystal structure of [{U(η⁵-C₄Me₄P)(μ-η⁵,η¹-C₄Me₄P)(BH₄)}₂], the U-P bond distances for the terminal and bridging η⁵-phospholyl ligands are 2.945(3) and 2.995(3) Å respectively, and the U-P (η¹-phospholyl) bond length is equal to 2.996(3) Å; the tridentate borohydride ligands are cis to the (UP)₂ ring. The cis and trans isomers of [{U(Cp¹)(μ-η⁵,η¹C₄ Me₄P)(BH₄)}₂] (Cp¹ = η⁵-C₅Me₅) are in equilibrium in toluene.     

Regioselective, stereoselective, and conformationally controlled synthesis of (η4-tetraarylcyclobutadiene)(η5-carbomethoxycyclopentadienyl)cobalt metallocenes

The Friedel-Crafts reaction of (η(4)-tetraphenylcyclobutadiene)(η(5)-carbomethoxycyclopentadienyl)cobalt with acid chlorides/aluminum chloride resulted exclusively in para-phenyl acylation. Both monoacylated (1.1 equiv of RCOCl/AlCl(3)) and tetraacylated products (>4 equiv of RCOCl/AlCl(3)) were synthesized. Reaction of PhCC(o-RC(6)H(4)) (R = Me, i-Pr) with Na(C(5)H(4)CO(2)Me) and CoCl(PPh(3))(3) gave predominantly (η(4)-1,3-diaryl-2,4-diphenylcyclobutadiene)(η(5)-carbomethoxycyclopentadienyl)cobalt metallocenes (1,3-[trans] vs 1,2-[cis] selectivity up to 6:1). Conformational control of Friedel-Crafts reactions on the major isomers gave exclusively para-acylation of the unsubstituted phenyl groups.     

Synthese von Tricarbonyl-η5-cyclohexadienyl-wolframat und Tricarbonyl-η5-cyclohexadienyl-methyl-wolfram

η⁶-Arene-tricarbonyl-tungsten (arene = benzene (1a), toluene (1b), m-xylene (1C), P-xylene (1D), o-xylene (1E), mesitylene (1F)) yield with potassium-tri-sec-butylboranate correspondingly methyl-substituted tricarbonyl-η⁵-cyclohexadienyl-tungstates (2A–2F). Similarly 1A reacts with methyllithium to tricarbonyl-η⁵-anti-6-methylcyclohexadienyl-tungstate (4A). In THF 2A–2F and 4A are converted by methyliodide to tricarbonyl-μ⁵-cyclohexadienyl-tungsten (3A–3F) and tricarbonyl-η⁵-anti-6-methylcyclophexadienyl-methyl-tungsten (5A). The complexes were characterized by C, H elemental analyses and by IR and ¹H-NMR spectroscopy.     

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.     

The Superbulky Pn Ligand Complexes [CpBIGFe(η5−P5)] and [(CpBIGFe)2(μ,η4:4-P4)]—Synthesis and Characterization

Abstract

A new synthesis of [Cp^BIGFe(CO)₂]₂ 3 (Cp^BIG = C₅(4-ⁿBuC₆H₄)₅) was developed starting from Cp^BIGNa and FeCl₂ in the presence of CO. Reaction of this product with P₄ leads to the two new P_n ligand complexes [Cp^BIGFe(η⁵-P₅)] 1b and [(Cp^BIGFe)₂(μ,η^4:4-P₄)] (4) containing the highly sterically demanding Cp^BIG ligand. Depending on the solvent, different ratios of 1b:4 are obtained. The products 1b, 3, and 4 were characterized by spectroscopic methods as well as by X-ray diffraction.     

Tetramers Cu4(μ4-O)(η-X)6(L4): Analysis of structural data

This review summarizes structural parameters for forty five Cu₄(μ₄-O)(η-X)₆(L₄) tetramers. There are four types of structurally equal core units, CuCl₃ON, CuCl₃OO, CuCl₃OCl and CuBr₃ON. There are also tetramers which contain structurally unequal core units: CuCl₃ON (x2) and CuCl₂BrON (x2); CuCl₃ON (x1), CuCl₂BrON (x2) and CuCl₃OCl (x1). There is a tendency for an elongated Cu?Cu separation as well as Cu–L bond distances with increase of the covalent radius of the coordinating atom(s). Tetrahedral distortion around oxygen atom (OCu₄) increases in the order: 1.67° (CuCl₃OCl) < 2.10° (CuCl₃ON) < 2.11° (CuCl₃OO′) < 2.27° (CuBr₃ON). The mean Cu–Cl–Cu bridge angle of 80.5° is about 4.0° more open than that of a Cu–Br–Cu (76.5°). The cluster Cu₁₆O₄Br₇Cl₁₇(4-Mepy)₁₆ (4-Mepy = 4-methylpyridine) contains four crystallographically independent tetramers: Cu₄OBrCl₅(4-Mepy)₄ (1), Cu₄OBrCl₅(4-Mepy)₄ (2) Cu₄OBr₂Cl₄(4-Mepy)₄ (3) and Cu₄OBr₃Cl₃(4-Mepy)₄ (4), which is a unique example of stereoisomerism. There are other examples which exist in two isomeric forms. Another contains two or even four crystallographically independent tetramers within the same crystal, differing mostly by degree of distortion and is an examples of distortion isomerism. Pairs of Cu₄OCl₆(n-Meim)₄ (n-Meim = n-methylimidazole) (n = 1 or 2) are examples of ligand isomerism.     

Kinetics of η6→η5 isomerization of (η6-fluorenyl)(η5-cyclopentadienyl)iron

The kinetics of the reversible isomerization of the zwitterionic complex [(⁶-C₁₃H₉)Fe(⁵-C₅H₅)] (1) into dibenzoferrocene (2) was studied by electronic spectroscopy in the temperature range from 70 to 103 °C. The activation parameters of the reaction 1 2 were determined, E _a = 22.5 kcal mol^–1.     

The Chloromethylation Reaction of Substituted Titanocenes(η~5-C_5H_5)(η~5-C_5H_4CRR'C_6H_4X)TiCl_2

Thereactionsof6,6-dialkylfulveneswithactiveorganometal(Li,Na,Mg)reagentshavebeensystematicallystudiedin0urlab0ratory.Thesereactionsprovideapracticalpathwayforthepreparationofcyclopentadienylanions,inparticularthosewithbulkysubstituents,whichcanbereadilycoordinatedwithtransitionmetalhalidestopr0ducesubstitutedmetall0cenes(Ti,Zr,Fe)1.6,6-Dimethylfulvene0r6,6-pentamethylenefulvenecaneasilyundergoexocyclicdoublebondadditionreactionsbythetreatmentof(substituted)phenyllithiumt0givearylsubstitutedc…     

Hydro- and chloro-substituted silyl- and silyl-η-amido-η-tetramethylcyclopentadienyl titanium complexes

Chlorosilyl-cyclopentadienyl titanium precursors [Ti(η⁵-C₅Me₄SiMeXCl)Cl₃] (X=H 2, Cl 3) were prepared by reaction of TiCl₄ with the trimethylsilyl derivatives of the corresponding cyclopentadienes. Methylation of these compounds with MgClMe under appropriate conditions afforded the methyl complexes [Ti(η⁵-C₅Me₄SiMe₂R)XMe₂] (R=H, X=Cl 5, Me 6; R=X=Me 7). Reactions of 2 and 3 with two equivalents of LiNH^tBu afforded the ansa-silyl-η-amido compounds [Ti{η⁵-C₅Me₄SiMeX(η¹-N^tBu)}Cl₂] (X=H 8, Cl 9). Methylation of 8 gave [Ti{η⁵-C₅Me₄SiMeH(η¹-N^tBu)}Me₂] 10. Complex 9 was also obtained by reaction of 8 with BCl₃, whereas the same reaction using alternative chlorinating agents (TiCl₄, HCl) resulted in deamidation to give 2, which was also converted into 3 by reaction with BCl₃. All of the new compounds were characterized by NMR spectroscopy and the molecular structures of 2 and 4 were determined by X-ray diffraction methods.     

Molecular structure of ansa-compound (η5-C5H4)CMe2(η5-C9H6)TiCl2

The structure of a new ansa compound, (⁵-C₅H₄)CMe₂(⁵-C₉H₆)TiCl₂ (1), was studied by X-ray analysis:a = 15.00(1),b =15.500(5),c = 13.032(4) Å, = 92.66°(4),V = 3025.1(1) ų, space groupP2₁/.,R = 0.038. The distorted tetrahedral coordination sphere of the Ti atom is formed by two Cl atoms and two -ligands. It was proposed that the angle () between theC-M direction and the line normal to M-Cp can be considered as one of the geometric parameters characteristic of the structure-properties correlation.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 305–308, February, 1995.     

The crystal structure of tetracarbonyl[η4-(1,1,3,4-tetramethylsilole)]chromium

An X-ray diffraction study has shown that tetracarbonyl[η⁴-(1,1,3,4-tetramethyl- silole)]chromium has a conjugated 1,3-diene bonded to a distorted piano stool Cr(CO)₄ fragment. The intra-ring CC bond lengths (139.2, 145.8 and 139.0 pm) indicate predominant diene-to-metal donor bonding. The bending angle of the silole ligand is 37.7°, and the Cr(CO)₂ trans angles are 105.87 and 149.12°.     

Phosphine-centred resolution of (η4-diene)Fe(CO)3 complexes: (η4-tropone)Fe(CO)2L and (η4-isoprene)Fe(CO)2L [L = (+)-(neomenthyl)PPh2]

(η⁴-Tropone)Fe(CO)₃ and (η⁴-isoprene)Fe(CO)₃ form separable diastereoisomers on substitution of CO by (+)-(neomenthyl)PPh₂. In the tropone complex, diastereoisomer interconversion occurs by a 1,3-metal shift. The absolute configuration of the isoprene complex has been determined crystallographically.     

First cobalt (borole)arene complexes [(η-C4H4BOH)Co(arene)]+

Heating of (η-C₄H₄BCy)Co(CO)₂I (Cy is cyclohexyl) with arene ligands in the presence of AlCl₃ at 80 °C followed by hydrolysis afforded the [(η-C₄H₄BOH)Co(arene)]⁺ complexes (arene = C₆H₆ (2a), C₆H₅Me (2b), and 1,3-C₆H₄Me₂ (2c)). The starting iodide complex was synthesized by the reaction of [(η-C₄H₄BCy)Co(CO)₂]₂ with I₂. The structure of [2a]BPh₄ was established by X-ray diffraction. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1620–1622, August, 2008.     

Aldol condensation reactions of [Co(η-C4Ph4){η-C5H4C(O)CH3}]

The aldol condensation reaction between [Co(η⁴-C₄Ph₄){η⁵-C₅H₄C(O)CH₃}] and a range of aromatic aldehydes [RCHO] and [RCHCH-CHO] gives a series of α,β-unsaturated ketones [Co(η⁴-C₄Ph₄){η⁵-C₅H₄C(O)CHCH-R}] and [Co(η⁴-C₄Ph₄){η⁵-C₅H₄C(O)CHCH-CHCH-R}] (3). The reaction is promoted by various bases: NaH proved to be the most effective whilst ⁿBuLi gave [Co(η⁴-C₄Ph₄){η⁵-C₅H₄C(OH)(ⁿBu)CH₃}] as the major product. NaOH was ineffective, perhaps indicating that that the methyl protons in [Co(η⁴-C₄Ph₄){η⁵-C₅H₄C(O)CH₃}] are less acidic than those in [Fe(η⁵-C₅H₅){η⁵-C₅H₄C(O)CH₃}]. Compounds 3 were characterised spectroscopically. Their ¹H NMR spectra are consistent with a trans configuration about their CC bond, and this was confirmed by X-ray crystallography in five cases, which showed that all have the same basic structure with parallel cyclobutadiene and cyclopentadienyl ligands, but they are not identical. The C₅H₄C(O)(CHCH)_n-R (n = 1 or 2) moieties show little evidence for delocalisation and often deviate from planarity. The UV/Vis spectra of those 3 with smaller aromatic rings (R = C₆H₅, 4-C₆H₄NMe₂, 2-C₄H₃S and 1-C₁₀H₇) suggest that these are donor-π-acceptor systems, but as the annellation of R increases (R = 9-C₁₄H₉, 1-C₁₆H₉ and 1-C₂₀H₁₁) the spectra increasingly resemble those of the parent polycyclic aromatic hydrocarbon, RH. Reduction of [Co(η⁴-C₄Ph₄){η⁵-C₅H₄C(O)CHCH-C₁₀H₇-1}] with DIBAL gives a mixture of [Co(η⁴-C₄Ph₄){η⁵-C₅H₄C(O)CH₂CH₂-C₁₀H₇-1}] and [Co(η⁴-C₄Ph₄){η⁵-C₅H₄CH(OH)CHCH-C₁₀H₇-1}]. A minor product from the preparation of [Co(η⁴-C₄Ph₄){η⁵-C₅H₄C(O)CH₃}] was shown by X-ray crystallography to be the η⁴-butadiene complex [Co{η⁴-Ph(H)CC(Ph)-C(Ph)C(H)Ph}{η⁵-C₅H₄C(O)CH₃}].     

(Tetragermacyclobutadiene)ruthenium tricarbonyl [η4-(But 2MeSi)4Ge4]Ru(CO)3

Tetrakis(di-tert-butylmethylsilyl)tetragermacyclobutadiene]ruthenium tricarbonyl [η⁴-(Bu^t ₂MeSi)₄Ge₄]Ru(CO)₃ is synthesized. This analogue of well-known cyclobutadiene transition metal complexes bears a tetragermacyclobutadiene derivative as ligand. The structure and spectroscopic parameters of the complex are compared with those of its iron-containing analogue [η⁴-(Bu^t ₂MeSi)₄Ge₄]Fe(CO)₃. Based on experimental data and results of quantum chemical calculations, it is shown that the π-donating ability of ligands increases upon replacement of carbon atoms in the cyclobutadiene moiety by silicon or germanium atoms, tetrasilacyclobutadiene and tetragermacyclobutadiene being comparable in π-donating activity.