Homoannular disubstituted ruthenocenes containing a trifluoromethyl(tetramethyl)cyclopentadienyl ligand

The reaction of the divalent ruthenium complexes [Cp^FRuCl]_n and [Cp^FRu(MeCN)₃]PF₆ with substituted pentafulvenes 1,2-(Me₂NCH)(CO₂Et)C₅H₃ and 1,3-(Me₂NCH)(CO₂Et)- C₅H₃ followed by hydrolysis affords new homoannular disubstituted ruthenocenes {1,2- (CO₂Et)(CHO)C₅H₃}RuCp^F and {1,3-(CO₂Et)(CHO)C₅H₃}RuCp^F (Cp^F = C₅Me₄CF₃), re- spectively.     

The nature of aryloxide and arylsulfide ligand bonding in dimethyltitanium complexes containing cyclopentadienyl ligation

A series of dimethyltitanium compounds [CpTi(EAr)Me2](E = O, S) ligated by one cyclopentadienyl (Cp) and one aryloxide (OAr) or arylsulfide (SAr) have been structurally characterized in order to gain a better understanding of aryloxide and arylsulfide bonding in these systems. Experimental structures were compared to those predicted by density functional theory (DFT). Bonding in the arylsulfide systems was found to be significantly different from bonding in the aryloxide systems. The aryloxide ligands exhibited wide Ti-O-Ar angles > or = 150 degrees) with the Ar group oriented proximal to the Cp group. DFT computations revealed two conformers for the arylsulfide systems. Arylsulfides with the Ar group proximal to the Cp group had a predicted Ti-S-Ar angle of approximately 120 degrees while those with the Ar group distal to the Cp group had a measured and predicted Ti-S-Ar angle of approximately 100 degrees. Molecular and natural bond orbital (NBO) analyses were employed to explain the nature of ligand bonding in these systems.     

Sequential protonation and methylation of a hydride-osmium complex containing a cyclopentadienyl ligand with a pendant amine group

Complex OsH{eta5-C5H4(CH2)2NMe2}(P(i)Pr3)2 (1) reacts with 1 equiv of trifluoromethanesulfonic acid (HOTf) and trifluoromethanesulfonic acid-d1 (DOTf) to produce the dihydride and hydride-deuteride complexes, [OsHE{eta5-C5H4(CH2)2NMe2}(P(i)Pr3)2]OTf (E = H (2), D (2-d1), respectively. Treatment of 2 and 2-d1 with a second equivalent of HOTf gives [OsHE{eta5-C5H4(CH2)2NHMe2}(P(i)Pr3)2][OTf]2 (E = H (3), D (3-d1) as a result of the protonation of the nitrogen atom. While the hydride and deuteride ligands of 2, 2-d1, 3, and 3-d1 do not undergo any H/D exchange process with the solvent, in acetone-d6, the NH proton of 3 and 3-d1 changes places with a deuterium atom of the solvent to yield [OsHE{eta5-C5H4(CH2)2NDMe2}(P(i)Pr3)2][OTf]2 (E = H (3-Nd1), D (3-d2)). Complex 3-Nd1 can also be obtained from the treatment of complex 2 with DOTf in dichloromethane. No exchange process between the hydride and the ND positions in 3-Nd1 or between the deuteride and NH positions in 3-d1 has been observed. Treatment of 3-Nd1 and 3-d1 with sodium methoxide results in a selective reaction of the base with the ammonium group to regenerate 2 and 2-d1, respectively. Complex 1 also reacts with methyl and methyl-d3 trifluoromethanesulfonate (CH3OTf and CD3OTf, respectively) to give [OsH{eta5-C5H4(CH2)2NMe2CE3}(P(i)Pr3)2]OTf (E = H (4), D (4-d3)) as a result of the addition of the CE3 (E = H, D) group to the nitrogen atom. Complex 4 has been characterized by an X-ray diffraction analysis. It reacts with a second molecule of CH3OTf or CD3OTf to produce [OsH{eta5-C5H4(CH2)2NMe3}{CH2CH(CH3)P(i)P2}(P(i)Pr3)[OTf]2 (5). Similarly, complex 4-d3 reacts with a second molecule of CH3OTf or CD3OTf to yield [OsH{eta5-C5H4(CH2)2NMe2CD3}{CH2CH(CH3)P(i)P2}(P(i)Pr3)[OTf]2 (5-d3). In acetonitrile, complex 5 evolves to an equilibrium mixture of the acetonitrile adducts [Os{eta5-C5H4(CH2)2NMe3}(NCCH3)(P(i)Pr3)2][OTf]2 (7) and [Os{eta5-C5H4(CH2)2NMe3}(NCCH3)2(P(i)Pr3)][OTf]2 (8). In methanol or methanol-d4, complex 4 is not stable and loses trimethylamine to give the vinylcyclopentadienyl derivatives [OsHE(eta5-C5H4CH=CH2)(P(i)Pr3)2]OTf (E = H (9), D (9-d1)) as a result of the protonation or deuteration of the metallic center and a subsequent Hofmann elimination. Protonation of 4 with HOTf gives the dihydride-trimethylammonium derivative [OsH2{eta5-C5H4(CH2)2NMe3}(P(i)Pr3)2][OTf]2 (10). Treatment of 9 with sodium methoxide produces OsH(eta5-C5H4CH=CH2)(P(i)Pr3)2 (11).     

Core level ligand field splitting in photoelectron spectra: a theoretical model for covalent molecules

A simple “pseudo-atomic” model is presented to explain the ligand field splitting of the core Zn 3d and Cd 44 orbitals in the photoelectron spectra of Me₂Zn and Me₂Cd respectively. We consider the electrostatic interaction between the valence p_z electrons and the core d vacancy. Using the excess p_z population as an adjustable factor, we are able to obtain good agreement with the observed line positions. The p_z excess population determined above has also been employed to calculate the splittings of the Cd 4p, 3d and 3p vacancy levels and the ¹¹¹Cd nuclear electric field gradient in Me₂Cd.     

Ruthenium naphthalene complexes with a carboxy-substituted cyclopentadienyl ligand

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Unprecedented double C-C bond cleavage of a cyclopentadienyl ligand

Double C-C bond cleavage of a cyclopentadienyl ligand proceeded to titanacyclopentadienes when 2 equiv of nitriles were added and the resulting two-carbon unit and three-carbon unit were converted into a benzene derivative and a pyridine derivative, respectively, in one-pot.     

Partial incorporation of a cyclopentadienyl ligand into a molybdaborane to form a molybdacarbaborane

Reaction of the molybdaborane arachno-2-[Mo(η-C₅H₅)(η⁵:η¹-C₅H₄)B₄H₇] (I) with NEt₃ in toluene at 120 °C for 7 days gives a 90% yield of the molybdacarbaborane nido-1-[Mo(η-C₅H₅)(η³:η²-C₃H₃)C₂B₃H₅] (II). Two of the carbon atoms in the substituted cyclopentadienyl ring in I are incorporated into the metallacarbaborane cluster II. The carbaborane {C₂B₃H₅} fragment in II is attached to an allylic {C₃H₃} group and can be thought of as a new non-planar {C₅B₃H₈} ligand providing seven electrons to the molybdenum atom. Reaction of I with KH in thf at 20 °C gives the anion via deprotonation of a B-H-B bridging proton.     

An unprecedented intramolecular coupling of o-carboranyl and cyclopentadienyl. Synthesis and structural characterization of a ruthenium complex containing a novel doubly-bridged cyclopentadienyl-carboranyl ligand

A novel ruthenium-mediated coupling reaction of a carboranyl with a cyclopentadienyl was discovered for the first time, leading to a brand new doubly-bridged cyclopentadienyl-carboranyl ligand bearing two five-membered rings and to a new type of chiral ruthenium complex.     

Synthesis of the first metallacarborane triple-decker complexes with a central cyclopentadienyl ligand

The previously unknown metallacarboranes (η-C₅R₅)Ru(η-9-Me₂S-7,8-C₂B₉H₁₀) (R=H or Me) and (η-C₅H₅)Ni(η-9-Me₂S-7,8-C₂B₉H₁₀) were prepared and used in the synthesis of the first metallacarborane triple-decker complexes with a central cyclopentadienyl ligand, viz., [(η-C₅R₅)Ru(μ-η:η-C₅Me₅)Ru(η-9-Me₂S-7,8-C₂B₉H₁₀)]PF₆ (R=H or Me), [(η-9-Me₂S-7,8-C₂B₉H₁₀)Ni(μ-η:η-C₅H₅)Ni(η-9-Me₂S-7,8-C₂B₉H₁₀)]PF₆, and [(η-C₅H₅)Ni(μ-η:η-C₅H₅)Ni(η-9-Me₂S-7,8-C₂B₉H₁₀)]BF₄. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1368–1373, July, 1999.     

Synthesis of planar chiral ferrocenyl cyclopentadienyl chelate ligand precursors

Two families of planar chiral ferrocenyl cyclopentadienyl chelate ligands for use in ansa-half sandwich metallocene complexes of catalytically active transition metals are described. The first family was derived in 4–5 steps from an enzymatic resolution of 1-iodo-2-(methylalcohol)ferrocene and possesses a cyclopentadiene derivative [Cp(H) = 1-indenyl, 2-indenyl or Ph₄Cp(H)] directly attached to the ferrocene ring with an adjacent vicinal tether CH₂Z donor group (Z = OH, OMe, NHMe, NMe₂ or PPh₂). The second family was derived from a chiral auxiliary approach and has the donor group (Z = PPh₂ or NMe₂) attached directly to the ferrocene ring with an adjacent tether vicinal CH₂Cp(H) group [Cp(H) = Cp(H), fluorenyl, 1-indenyl, Me₄Cp(H) or Ph₄Cp(H)].     

Synthesis of an extended hexagonal molecule as a highly symmetrical ligand

An extended hexagonal molecule that has high symmetry and rigidity was designed and synthesized by a cobalt-catalyzed cyclotrimerization reaction. The ligand possesses six benzoic acids at its periphery, which were connected to a central hexakis(2,5-dodesyloxyphenyl)hexaphenylbenzene core with a maximum intramolecular carboxyl group distance of approximately 3.5 nm.     

Synthesis and reactivity of cyclopentadienyl ruthenium complexes containing ferrocenylselenolates

The heterotrimetallic complex 1,1′-[Fc(SeRuCp(PPh₃)₂)₂] is accessible by the reaction of 1,1′-[Fc(SeLi)₂·2THF] (Fc = Fe(η⁵-C₅H₄)₂, THF = Tetrahydrofuran) with two equivalents of CpRu(PPh₃)₂Cl in high yield. Complex 1,1′-[Fc(SeLi)₂·2THF] can be prepared by treatment of 1,1′-[Fc(SeSiMe₃)₂] with two equivalents of n-BuLi in THF solution. 1,1′-[Fc(SeRuCp(PPh₃)₂)₂] is converted to 1,1′-[Fc(SeRuCpCO(PPh₃))₂] under CO atmosphere in THF solution. The complexes 1,1′-[Fc(SeRuCp(PP))₂] [PP = Ph₂P(CH₂)PPh₂ (dppm), Ph₂P(CH₂)₂PPh₂ (dppe), Ph₂P(CH=CH)₂PPh₂ (dppee), Ph₂P(CH₂)₃PPh₂ (dppp)] are obtained in a one-pot reaction of CpRu(PPh₃)₂Cl and 1,1′-[Fc(SeLi)₂·2THF] with the chelating bisphosphine ligand.     

Hafnium cyclopentadienyl compounds containing various chelate ligands in the molecule

Conclusions Some previously unknown hafnium cyclopentadienyl compounds, containing various chelate ligands in the molecule, were synthesized.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2359–2361, October, 1973.     

Synthesis and characterization of chromocenes containing bulky cyclopentadienyl ligands

Two equivalents of K[Cp′] (Cp′=C₅(i-Pr)₃H₂, C₅(i-Pr)₄H, C₅(t-Bu)₂H₃) react with CrCl₂ in THF to give the corresponding chromocenes, Cp′₂Cr, in good yield. Despite the presence of bulky substituents on the rings that could affect their properties, the complexes are extremely air- and moisture-sensitive, and possess a low-spin ground state. The low-spin paramagnetic nature of each chromocene was confirmed by magnetic susceptibility measurements. The solid-state structure of [C₅(i-Pr)₃H₂]₂Cr was obtained using single crystal X-ray analysis. It displays rigorously parallel rings, with an average Cr–C(ring) distance of 2.17(1)Å; the chromium resides on a crystallographically imposed inversion center. The orientation of the isopropyl groups minimizes unfavorable steric interactions between the rings.     

Three-photon absorption cross-section enhancement in two symmetrical fluorene-based molecules

In this article, we report the pure three-photon absorption effects of two novel symmetrical fluorene-based molecules with 2D-pi-2D [9,9-diethylhexyl-2,7-bis-(N,N-diphenylamine)fluorene] and 2D-D-pi-D-2D [5,5'-(9,9-bis-(2-ethylhexyl)-9H-fluorene-2-yl)bis(N,N-diphenylthiophen-2-amine)] structural motifs. The obtained three-photon absorption cross sections, (4.74 +/- 0.01) x 10(-76) and (6.77 +/- 0.02) x 10(-76) cm(6) s(2) for the 2D-pi-2D and 2D-D-pi-D-2D archetypes, respectively, are rather high. The geometries and electronic excitations of the two molecules were systematically studied by the PM3 and ZINDO/S methods. The influence of the different molecular structures on the three-photon absorption cross section is discussed micromechanically. The experimental and theoretical results demonstrate that the transition dipole moment between the ground and final states is the most definitive factor. A new fitting method that is more accurate than those reported previously was used to obtain the 3PA coefficient.