Structures of cationic metallacarborane complexes [(η-9-Me2S-7,8-C2B9H10)Ni(μ-Cp)Ni(η-9-Me2S-7,8-C2B9H10)]+ and [Cp*Ru(Me2S-C2B9H10)RuCp*]+

The structures of the metallacarborane cations [(-9-Me₂S-7,8-C₂B₉H₁₀)Ni(-Cp)Ni(-9-Me₂S-7,8-C₂B₉H₁₀)]⁺ (2) and [Cp*Ru(Me₂S-C₂B₉H₁₀)RuCp*]⁺ (4b) were established by X-ray diffraction analysis. These results confirmed the triple-decker structure proposed for complex 2 earlier, whereas complex 4b proved to be 13-vertex dimetallacarborane rather than the triple-decker complex, as has been suggested earlier.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1879–1883, September, 2004.     

Synthesis of the cyclooctadiene and cyclooctenediyl cobalt complexes. Structures of [(η2,η2-cyclooctadiene)Co(η-1,2,4,5-C6H2Me4)]BF4 and [(η1,η3-cyclooctenediyl)Co(η-9-SMe2-7,8-C2B9H10)

Cobaltacarboranes (η¹, η³-cyclooctenediyl)Co(Carb) (Carb = η-9-SMe₂-7,8-C₂B₉H₁₀, η-1-tBuHN-1,7,9-C₃B₈H₁₀) were synthesized by the reaction of the carborane anions [Carb]⁻ with the acetonitrile complex [(η¹, η³-cyclooctenediyl)Co(MeCN)₃]⁺ generated in situ upon the dissolution of [(η¹, η³-cyclooctenediyl)Co(η-1,4-C₆H₄Me₂)]⁺ in MeCN. The structures of (η¹,η³-cyclooctenediyl)Co(η-9-SMe₂-7,8-C₂B₉H₁₀ and [(η²,η²-cyclooctadiene)Co((η-1,2,4,5-C₆H₂Me₄)]BF₄ were determined by X-ray diffraction analysis.     

Low-temperature X-ray diffraction study of [CuII(1,10-C12H8N2)3]2+{CoIII[η5-(3)-1,2-C2B9H11]2} 2? ·CH3CN

Single crystal XRD is used to study the crystal structure of a new compound containing the dicarbollyl cluster anion Co(III) with the composition [CuPhen₃][Co(C₂B₉H₁₁)₂]₂·CH₃CN, where Phen is 1,10-phenanthroline. The crystallographic data: C₄₆H₇₁B₃₆N₇Co₂Cu, M = 1292.66, monoclinic system, P2₁/c space group, unit cell parameters a = 14.7178(2) ?, b = 19.5640(4) ?, c = 22.8663(5) ?, β = 106.6601(7)°, V = 6307.75(33) ?³, Z = 4, d _x = 1.361 g/cm³, T = 100 K, μ = 0.90 mm⁻¹. The structure is solved by the direct method and refined by the full-matrix LSM in an anisotropic-isotropic (for H atoms) approximation up to the final agreement factors R ₁ = 0.0370, wR ₂ = 0.0869 for 13,807 I _hkl ≥ 2 σ _I out of 18,295 measured I _hkl . The structure consists of [CuPhen₃] cations, Co(C₂B₉H₁₁)₂ anions, and acetonitrile molecules MeCN. The central Cu atom in the cation in the general position, and its coordination geometry is a distorted extended octahedron formed by six nitrogen atoms of the three bidentate Phen ligands. The coordination of Cu(II) in the cation is (2+2+2) with two long axial and four shorter equatorial Cu-N bonds, whose average lengths are 2.239(2) ? and 2.077(1) ? respectively. Each anion has its own position of the -C₂-groups; for Co(1), it is a quasi-gauche-configuration; for Co(2), a quasi-trans-configuration.     

Nonsymmetrical iron bis(carborane) complexes (η-1-ButNH-1,7,9-C3B8H10)Fe(η-9-L-7,8-C2B9H10) (L = SMe2, NMe3)

Visible light irradiation of the benzene complex [(η-1-Bu^tNH-1,7,9-C₃B₈H₁₀)Fe(η-C₆H₆)]⁺ in the presence of the charge-compensated carborane anions [9-L-7,8-C₂B₉H₁₀]⁻ (L = SMe₂, NMe₃) affords ferracarboranes (η-1-Bu^tNH-1,7,9-C₃B₈H₁₀)Fe(η-9-L-7,8-C₂B₉H₁₀). Their structures were established by X-ray diffraction analysis.     

1,2,3,4,7-Pentamethylindenyl complex [(η5-C9H2Me5)RhI2]2 as a synthon for the [(η5-C9H2Me5)Rh]2+ fragment

The reaction of the iodide complex [(η⁵-C₉H₂Me₅)RhI₂]₂ (1) or the acetonitrile complex [(η⁵-C₉H₂Me₅)Rh(MeCN)₃]²⁺ with Tl[Tl(η-7,8-C₂B₉H₁₁)] afforded rhodacarborane (η⁵-C₉H₂Me₅)Rh(7,8-C₂B₉H₁₁) (2). The cationic triple-decker complex with the bridging boratabenzene ligand [Cp*Fe(μ-η:η-C₅H₃Me₂BMe)Rh(η⁵-C₉H₂Me₅)]²⁺ (3) was synthesized by the reaction of the nitromethane solvate [(η⁵-C₉H₂Me₅)Rh(MeNO₂)₃]²⁺ with the sandwich compound Cp*Fe(η-C₅H₃Me₂BMe). The structure of 2 was established by X-ray diffraction. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1623–1625, August, 2008.     

Alternative syntheses and X-ray diffraction analyses of the parent tricarbaborane compounds [nido-7,8,9-C3B8H11], [nido-7,8,10-C3B8H11] and [1-(η-C5H5)-closo-1,2,4,10-FeC3B8H11]

Reaction of the neutral tricarbaborane nido-7,8,9-C₃B₈H₁₂ (1) with triethylamine in CH₂Cl₂ led to quantitative deprotonation and isolation of the corresponding Et₃NH⁺ salt of the [nido-7,8,9-C₃B₈H₁₁]⁻ anion (2). This was converted into PSH⁺ and Me₄N⁺ salts via metathetic cation exchange. Heating of the solid Me₄N⁺[7,8,9-C₃B₈H₁₁]⁻ in mineral oil at 350 °C for 2 h resulted in thermal rearrangement and isolation of the cage isomeric compound Me₄N⁺[7,8,10-C₃B₈H₁₁]⁻. Finally, compound 1 was directly complexed via reaction with [CpFe(CO)₂]₂ (Cp = η⁵-C₅H₅) to generate the ferratricarbollide sandwich [1-Cp-closo-1,2,4,10-FeC₃B₈H₁₁] (4) in 60% yield. The structures of all the generic compounds of tricarbollide chemistry, 1 (PSH⁺ salt), 2 (MePPh₃⁺salt), and 4, were established unambiguously by an X-ray diffraction analysis.     

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}].     

Synthesis and reactivity of η-tetramethylcyclopentadienyl-propenyl rhenium complexes: Molecular structure of [(η:η-C5Me4CH2CHCH2)Re(CO)2]

The fulvene complexes [(η⁶-C₅Me₄CH₂)Re(CO)₂(R)] (1a, RI; 1b, RC₆F₅) react at the exocyclic methylene carbon with a vinylmagnesium bromide solution to produce the anionic species [(η⁵-C₅Me₄CH₂CHCH₂)Re(CO)₂(R)]⁻. Protonation with HCl at 0 °C produces the hydride complexes [trans-(η⁵-C₅Me₄CH₂CHCH₂)Re(CO)₂(R)(H)] (2a, RI; 2b, RC₆F₅). Thermolysis of an hexane solution of the iodo-hydride (2a) under a CO atmosphere yields the complex [(η⁵-C₅Me₄CH₂CHCH₂)Re(CO)₃] (3) and [Re(CO)₅I] as by-product. Thermolysis of 2b produced three new products, mainly the chelated complex [(η⁵:η²-C₅Me₄CH₂CHCH₂)Re(CO)₂] (4) and complex 3, with a non-coordinated olefin group, in moderated yield, and traces of [Re(CO)₅(C₆F₅)]. Thermolysis of an hexane solution of 2 in presence of an excess of PMe₃, afforded the phosphine derivative [(η⁵-C₅Me₄CH₂CHCH₂)Re(CO)₂(PMe₃)] (5). All the complexes were characterized by IR, ¹H, ¹³C and ³¹P NMR spectroscopies and mass spectrometry. The molecular structure of 4 has also been determined. The molecule exhibits a formal three-legged piano-stool structure, with two CO groups, and the third position corresponding to the η²-coordination of the propenyl side arm of the η⁵-C₅Me₄ ring.     

An unexpected cluster opening upon the formation of electronically unsaturated η-(cyclooctenyl)metallacarboranes of rhodium(III) and iridium(III) with sterically reduced [(PhCH2)2C2B9H9] ligand

The room-temperature metallation reactions of the K⁺ salt of the [7,8-(PhCH₂)₂-7,8-nido-C₂B₉H₁₀]⁻ anion (1) with the COD-metal μ-chloride dimers [(η⁴-C₈H₁₂)₂Rh₂(μ-Cl)₂] (2) and [(η⁴-C₈H₁₂)₂Ir₂(μ-Cl)₂] (3) in benzene/ethanol solution gave formally 16-electron pseudocloso-type complexes with the η³-cyclooctenyl ligand at the metal vertices, [3-{(1-3-η³)-C₈H₁₃}-1,2-(PhCH₂)₂-pseudocloso-3,1,2-MC₂B₉H₉] [4, M = Rh(III); 5, M = Ir(III)]. No evidence supporting the existence of an agostic C-H?M bonding interaction in these compounds was obtained either from the crystallographic or the phase-sensitive 2-D [¹H-¹H] NOESY/EXSY studies of 4. The extraordinary stability of complexes 4 and 5 can therefore be associated with their cage-deformed cluster structures, where electronically-deficient (16-electron) metal centers are believed to be stabilized by additional electron density released from the polyhedral C-C bond cleavage. DFT solid-state calculations performed for closo (18-electron) and pseudocloso (16-electron) Rh(III) complexes, [3-(η⁵-C₅Me₅)-1,2-(PhCH₂)₂-closo-3,1,2-RhC₂B₉H₉] (6, C-C, 1.7397 Å) and [3-{(1-3-η³)-C₈H₁₃}-1,2-(4′-MeC₆H₄)₂-pseudocloso-3,1,2-RhC₂B₉H₉] (9, C?C, 2.420(2) Å), showed that the electron density transfer from the carborane moiety to the rhodium center is marginally greater for complex 9, in accordance with the idea that electronics rather than sterics play a crucial role in the stabilization of 16-electron pseudocloso-metallacarborane species.     

New ferrocenylmethylphosphines - Preparation, characterisation and coordination chemistry of PH(CH2Fc)2, P(CH2Fc)3 [Fc = Fe(η-C5H5)(η-C5H4)] and their derivatives

The new ferrocenylmethylphosphines PH(CH₂Fc)₂ (1) [Fc = Fe(η⁵-C₅H₅)(η⁵-C₅H₄)] and P(CH₂Fc)₃ (2) and the phosphonium salt [P(CH₂Fc)₃(CH₂OH)]I (3) were synthesised from P(CH₂OH)₃ and [FcCH₂NMe₃]I. [P(CH₂Fc)(CH₂OH)₃]Cl (4) was obtained from P(CH₂Fc)(CH₂OH)₂, CH₂O and HCl. The new phosphines and phosphonium salts were fully characterised by NMR and IR spectroscopy and MS. [Mo(CO)₆] reacts with 1 to give [Mo(CO)₅{PH(CH₂Fc)₂}] (5) in high yield, but attempts to employ 2 as a ligand failed. The reaction of [P(CH₂Fc)₃(CH₂OH)]I (3) and [PH(CH₂Fc)₃]I (obtained in situ from 3 and Na₂S₂O₅) with [WI₂(CO)₃(NCMe)₂] gave the complex salts [P(CH₂Fc)₃(CH₂OH)][WI₃(CO)₄] (6) and [PH(CH₂Fc)₃][WI₃(CO)₄] (7), respectively. [P(CH₂Fc)₄]I (8) was synthesized from PH₂CH₂Fc and [FcCH₂NMe₃]I. Crystal structures were obtained for 1, 3-8.     

Syntheses and characterization of η-cyclopentadienyl and η-indenyl ruthenium(II) complexes of arylazoimidazoles: The molecular structure of the complex [(η-C5H5)Ru(PPh3)(C6H5-NN-C3H3N2)]

The complex [(η⁵-C₅H₅)Ru(PPh₃)₂Cl] (1) reacts with several arylazoimidazole (RaaiR′) ligands, viz., 2-(phenylazo)imidazole (Phai-H), 1-methyl-2-(phenylazo)imidazole (Phai-Me), 1-ethyl-2-(phenylazo)imidazole (Phai-Et), 2-(tolylazo)imidazole (Tai-H), 1-methyl-2-(tolylazo)imidazole (Tai-Me) and 1-ethyl-2-(tolylazo)imidazole (Tai-Et), gave complexes of the type [(η⁵-C₅H₅)Ru(PPh₃)(RaaiR′)]⁺ {where R, R′ = H (2), R = H, R′ = CH₃ (3), R = H, R′ = C₂H₅ (4), R = CH₃, R′ = H (5), R, R′ = CH₃ (6), R = CH₃, R′ = C₂H₅ (7)}. The complex [(η⁵-C₉H₇)Ru(PPh₃)₂(CH₃CN)]⁺ (8) undergoes reactions with a series of N,N-donor azo ligands in methanol yielding complexes of the type [(η⁵-C₉H₇) Ru(PPh₃)(RaaiR′)]⁺ {where R, R′ = H (9), R = H, R′ = CH₃ (10), R = CH₃, R′ = H (11), R = CH₃, R′ = C₂H₅ (12)}, respectively. These complexes were characterized by FT IR and FT NMR spectroscopy as well as by analytical data. The molecular structure of the complex [(η⁵-C₅H₅)Ru(PPh₃)(C₆H₅-NN-C₃H₃N₂)]⁺ (2) was established by single crystal X-ray diffraction study.     

Effect of high external pressures on the vibrational spectra of Zeise’s complexes, K[Pt(η-C2H4)Cl3] and [Pt(η-C2H4)Cl2]2

The pressure dependences (dν/dP) of the main IR and Raman bands of Zeise’s complexes, K[Pt(η²-C₂H₄)Cl₃] and [Pt(η²-C₂H₄)Cl₂]₂, have been determined for the first time for selected pressures up to ∼33 kbar with the aid of diamond-anvil cells. Neither complex undergoes a pressure-induced structural change throughout the pressure range investigated. The dν/dP values range from −0.13 to 0.79 cm⁻¹ kbar⁻¹. The negative values have proved particularly informative in identifying the location of the CC stretching modes of the Pt-ethylene groups, a topic of considerable disagreement in the literature.     

Ring expansion of a Cp moiety upon CO insertion: Synthesis and characterization of [(η-C6H5OCo)Co3(CO)9]

Reaction of [(CpV)₂(B₂H₆)₂], 1 (Cp = η⁵-C₅H₅) with four equivalents of [Co₂(CO)₈] or [Co₄(CO)₁₂] in hexane at 70 °C leads to the isolation of the tetranuclear carbonyl cluster, [(η⁶-C₆H₅OCo)Co₃(CO)₉], 2 in modest yield. The geometry of 2 is similar to that of [Co₄(CO)₁₂] where all the four Co atoms are arranged in a tetrahedral geometry. The apical cobalt atom in 2 is coordinated to C₆H₅O ring in a η⁶-fashion and the other three cobalt atoms are each coordinated to three carbonyl ligands. Compound 2 has been characterized in solution by IR, ¹H, ¹³C NMR and mass spectrometry and the structural types were unequivocally established by crystallographic analysis.     

Photochemical arene exchange in the ferracarborane complex [1-(η-C6H6)-12-ButNH-1,2,4,12-FeC3B8H10]+

The benzene complex [1-(η-C₆H₆)-12-Bu^tNH-1,2,4,12-FeC₃B₈H₁₀]⁺ (3a) was synthesized by the photochemical reaction of [(η⁵-C₆H₇)Fe(η-C₆H₆)]⁺ (1) with the anion [7-Bu^tNH-7,8,9-C₃B₈H₁₀]⁻ followed by the treatment of ferracarborane 1-(η⁵-C₆H₇)-12-Bu^tNH-1,2,4,12-FeC₃B₈H₁₀ (2) with hydrochloric acid. The benzene ligand in cation 3a is replaced by alkyl-substituted benzenes under visible light irradiation in CH₂Cl₂ to form [1-(η-C₆R₆)-12-Bu^tNH-1,2,4,12-FeC₃B₈H₁₀]⁺ (3b–e; C₆R₆ is toluene (b), mesitylene (c), hexamethylbenzene (d), or anisole (e)). The structure of [3c]PF₆ was established by X-ray diffraction.     

Synthesis and reactivity of asymmetrically substituted ansa-bridged zirconocene complexes: X-ray crystal structures of [Zr{R(H)C(η-C5Me4)(η-C5H4)}Cl2] (R = Bu, Bu) and [Zr{Bu(H)C(η-C5Me4)(η-C5H4)}(CH2Ph)2]

The dialkyl complexes, (R = Prⁱ, R′ = Me (2a), CH₂Ph (3a); R = Buⁿ, R′ = Me (2b), CH₂Ph (3b); R = Bu^t, R′ = Me (2c), CH₂Ph (3c); R = Ph, R′ = Me (2d), CH₂Ph (3d)), have been synthesized by the reaction of the ansa-metallocene dichloride complex, [Zr{R(H)C(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂] (R = Prⁱ (1a), Buⁿ (1b), Bu^t (1c), Ph (1d)), and two molar equivalents of the alkyl Gringard reagent. The insertion reaction of the isocyanide reagent, CNC₆H₃Me₂-2,6, into the zirconium-carbon σ-bond of 2 gave the corresponding η²-iminoacyl derivatives, [Zr{R(H)C(η⁵-C₅Me₄)(η⁵-C₅H₄)}{η²-MeCNC₆H₃Me₂-2,6}Me] (R = Prⁱ (4a), Buⁿ (4b), Bu^t (4c), Ph (4d)). The molecular structures of 1b, 1c and 3b have been determined by single-crystal X-ray diffraction studies.     

Cyclopentadienyl chromium and tungsten complexes with halide, methyl and σ-phenylethynyl ligands: Structures of (η-C5H5)Cr(NO)2(-CC-C6H5), (η-C5H5)Cr(NO)2I and [(η-C5H4)-COOCH3]W(CO)3Cl

With copper(I) iodide as catalyst, σ-alkynyls, compounds (η⁵-C₅H₅)Cr(NO)₂(CC-C₆H₅) (5), [(η⁵-C₅H₄)-COOCH₃]Cr(NO)₂(CC-C₆H₅) (10), and [(η⁵-C₅H₄)-COOCH₃]W(CO)₃(CC-C₆H₅) (13), were prepared from their corresponding metal chloride 1, 6 and 12. Structures of compound 3, 5 and 12 have been solved by X-ray diffraction studies. In the case of 5, there is an internal mirror plane passing through the phenylethynyl ligand and bisecting the Cp ring. The phenyl group is oriented perpendicularly to the Cp with an eclipsed conformation. The twist angle is 0° and 118.4° for -CC-Ph and two NO ligands, respectively. The orientation is rationalized in terms of orbital overlap between ψ₃ of Cp, dπ of Cr atom, and π^∗ of alkynyl ligand, and complemented by molecular orbital calculation. The opposite correlation was observed on the chemical shift assignments of C(2)-C(5) on Cp ring in compounds 6 and 12, using HetCOR NMR spectroscopy. The electron density distribution in the cyclopentadienyl ring is discussed on the basis of ¹³C NMR data and compared with the calculations via density functional B3LYP correlation-exchange method.     

(Cyclopentadienyl){(N,N-dimethylaminoethyl)cyclopentadienyl} complexes of zirconium: Crystal structure of [(η-C5H5)(η-C5H4CH2CH2NHMe2)ZrCl2]2[ZrCl6]

[(η⁵-C₅H₅)ZrCl₃] reacts with [C₅H₄CH₂CH₂NMe₂]Li yielding the coordination polymer [(C₅H₅)(C₅H₄CH₂CH₂NMe₂)ZrCl₂]_n (1) as a brown solid which is very sensitive to moisture. The reaction of 1 with 1.35 equivalent of HCl (methanolic solution) yields pale yellow green crystals of [(η⁵-C₅H₅)(η⁵-C₅H₄CH₂CH₂NHMe₂)ZrCl₂]₂[ZrCl₆] (2). Compound 2 was fully characterized on the basis of NMR data and X-ray crystal structure analysis. The formation of this product indicates the elimination of C₅H₄CH₂CH₂NMe₂ as well as C₅H₅ ligands from the Zr(IV) metal centre.     

Dynamic behavior of [(η-C5H4CH3)Cr(CO)2(μ-SBu)Pt(PPh3)2] in solution

The structure and dynamic behavior of complex [(η⁵-C₅H₄CH₃)Cr(CO)₂(μ-SBu)Pt(PPh₃)₂] in solution was studied by multinuclear (¹H, ¹³C, ³¹P) NMR spectroscopy including a phase-sensitive NOESY experiment. Increasing temperature causes rupture of the Cr-Pt bond in the three-membered ring of the complex and rotation of the S-Pt(PPh₃)₂ unit around the Cr-S bond line, followed by formation of a new Cr-Pt bond to close the ring. All activation parameters for this dynamic process have been determined.