95Mo NMR spectral studies on seven-coordinate molybdenum(II) isocyanide complexes

The ⁹⁵Mo NMR spectra of a series of seven-coordinate molybdenum(II) isocyanide complexes of the types [Mo(CNR)_7-nL_n](PF₆)₂ (R = CH₃, CHMe₂, CMe₃, C₆H₁₁, CH₂Ph; L = py, bpy, Me₂bpy, phen, dppe, P-n-Bu₃; n = 0,1,2) [Mo(CNC-Me₃)₆X]PF₆ (X = Cl, Br, I) and [{Mo(CNCMe₃)₄(NN)}₂(μ-CN)](PF₆)₃ (NN = bpy, Me₂bpy, phen) have been studied. The ⁹⁵Mo chemical shift range for this group of complexes is about 1100 ppm. An increase in the size of the R group attached to the isocyanide ligand generally tends to shield the ⁹⁵Mo nucleus. Replacement of the isocyanide ligand with a phosphorus ligand also increases the shielding, whereas the replacement of isocyanide with a heterocyclic nitrogen donor leads to deshielding by 800–900 ppm. This group of complexes shows a normal halogen dependence, i.e. replacement of Cl^? by Br^? and I^? increases the shielding of the ⁹⁵Mo nucleus. The cyano-bridged cations [{Mo(CNCMe₃)₄(NN)}₂(μ-CN)]³⁺ (NN = bpy, Me₂bpy, or phen) show two ⁹⁵Mo NMR signals, one for the molybdenum coordinated to the carbon of the bridging CN and one for the N-coordinated molybdenum. Comparison of the chemical shifts and linewidths of the cyano-bridged species with those of the corresponding mononuclear molybdenum(II) complexes [Mo(CNCMe₃)₅(NN)](PF₆)₂ leads to the assignment of the more deshielded signal to the N-coordinated molybdenum. The ¹⁴N and ³¹P NMR spectra for these complexes have also been measured, as have the ¹³C NMR spectra of the pairs of complexes [Mo(CNCMe₃)₅(NN)](PF₆)₂ and [{Mo(CNCMe₃)₄(NN)}₂(μ-CN)](PF₆)₃ (NN = bpy or phen). The ¹⁸³W NMR spectra for [W(CNR)₅(bpy)](PF₆)₂ (R = CMe₃ and CH₂Ph), show that the δ(¹⁸³W)/δ(⁹⁵Mo) chemical shift ratios for isocyanide complexes are different from the ratio found for M⁰ and M^VI.     

Magnetic Exchange Interactions in Dinuclear Copper(II) and Nickel(II) Complexes with μ‐Oxalato Bridges. The Structure of μ‐Oxalato(O,O′, O″, O‴)‐bis{[1, 8‐di(2‐pyridyl)‐3, 6‐dithiaoctane‐N,N′, S,S′]nickel(II)} Dinitrate Dihydrate

A copper(II) and two nickel(II) dinuclear oxalato‐bridged compounds of formulae [{Cu(bpdto)}₂(μ‐ox)](ClO₄)₂ ( 1 ), [{Ni(bpdto)]₂(μ‐ox)](ClO₄)₂( 2 ), and [{Ni(bpdto)}₂(μ‐ox)](NO₃)₂·2H₂O ( 3 ), where bpdto = 1, 8‐bis(2‐pyridyl)‐3, 6‐dithiaoctane and ox = oxalate = C₂O₄^2— anion, have been synthesized and characterized. The crystal structure of 3 was determined by single‐crystal X‐ray analysis. It is a dinuclear complex with i symmetry in which the oxalate ligand is coordinated in bis(didentate) fashion to the inversion centre‐related nickel atoms. The distorted octahedral environment of each nickel atom is completed by two sulphur atoms in the equatorial plane and by two pyridyl nitrogen atoms in axial positions. Magnetic susceptibility measurements over the range 5 — 299K, show antiferromagnetic interactions that are weak in 1 (J = —12.8 cm^—1) and strong in 2 and 3 (J = —37.8 and —40.9 cm^—1, respectively), which in the case of 3 is in keeping with the observed structural parameters.     

Reaction of [CpRu(CH3CN)3]PF6 with bidentate ligands: structural characterization of [{CpRu(CH3CN)2}2(μ-η-dppe)](PF6)2 [dppe=1,2-bis(diphenylphosphino)ethane]

The reaction of [CpRu(CH₃CN)₃]PF₆ with the bidentate ligands L-L=1,2-bis(diphenylphosphino)ethane, dppe, and (1-diphenylarsino-2-diphenylphosphino)ethane, dpadppe, affords mononuclear or dinuclear complexes of formula [CpRu(η²-L-L)(CH₃CN)]PF₆, [{CpRu(CH₃CN)₂}₂(μ-η^1:1-L-L)](PF₆)₂ and [{CpRu(CH₃CN)}₂(μ-η^1:1-L-L)₂](PF₆)₂ (L-L=dppe, dpadppe). All of the compounds are characterized by microanalysis and NMR [¹H and ³¹P{¹H}] spectroscopy. The crystal structure of [{CpRu(CH₃CN)₂}₂(μ-η^1:1-dppe)](PF₆)₂ has been determined by X-ray diffraction analysis. The complex exhibits a dppe ligand bridging two CpRu(CH₃CN)₂ fragments.     

Dinuclear copper complexes with cyanamide derivatives as bridging ligands

Three mixed-valence copper complexes [{Cu(phen)₂}₂(μ-L)](PF₆)₂ (where phen = 1,10-phenanthroline, L = 1,4-dicyanamidobenzene (dicyd)), 1,4-dicyanamido-2,5-dimethylbenzene (Me₂dicyd) and 1,4-dicyanamido-2,5-dichlorobenzene (Cl₂dicyd), and one dinuclear Cu(II) complex [{Cu(phen)₂}₂(μ-apc)](PF₆)₃ (where apc = monoanion of 4-azo(phenylcyanamido)benzene) have been prepared and characterized by elemental analysis, IR and electronic absorption spectroscopies and cyclic voltammetry. [{Cu(phen)₂}₂(μ-apc)](PF₆)₃ · 2CH₃COCH₃ crystallized in the triclinic system and both five-coordinate Cu(II) ions in the dinuclear unit are linked through a bridging 4-azo(phenylcyanamido)benzene (apc) ligand. The cyanamide group (NCN) of the bridging ligand is coordinated to Cu(II) ions through the cyano-nitrogen and amido-nitrogen. The bond length between Cu(1) and cyano-nitrogen is slightly larger than that formed by Cu(2) and amido-nitrogen. The angular structural index parameters, τ, for Cu(1) and Cu(2) are 0.9 and 0.5, respectively. The copper(II) atoms display a different geometry with a N₅ chromophore group. The intra Cu?Cu separation is 5.156(1) Å. All of the dicyd dinuclear copper complexes show radical anion absorption.     

Solid-state anion interactions in the diastereoisomers of dinuclear ruthenium complexes based on 2,2′-bipyrimidine

The cations in the solid-state structures of meso-(ΛΔ)-[{Ru(bpy)₂}₂(μ-bpm)](PF₆)₄, meso-(ΛΔ)-[{Ru(Me₂bpy)₂}₂(μ-bpm)](tos)₄ · 2CH₃OH · 4H₂O and meso-(ΛΔ)-[{Ru(Me₄bpy)₂}₂(μ-bpm)](tos)₄ · 26H₂O (bpm = 2,2′-bipyrimidine; bpy = 2,2′-bipyridine; Me₂bpy = 4,4′-dimethyl-2,2′-bipyridine; Me₄bpy = 4,4′,5,5′-tetramethyl-2,2′-bipyridine; tos⁻ = toluene-4-sulfonate anion) exhibit similar features including comparable bond lengths and angles, and metal–metal separations of 5.56–5.59 Å. The counter-ions present in the structures reside in the clefts above and below the plane of the bridging ligand, but show considerable variation in location compared with their known occupancy in solution.     

Ligand‐Controlled Formation of a Low‐Valent Pincer Rhodium(I)–Dioxygen Adduct Bearing a Very Short O?O Bond

Treatment of [{Me₂C₆H(CH₂P^tBu₂)₂}Rh(η¹‐N₂)] ( 1a ) with molecular oxygen (O₂) resulted in almost quantitative formation of the dioxygen adduct [{Me₂C₆H(CH₂P^tBu₂)₂}Rh(η²‐O₂)] ( 2a ). An X‐ray diffraction study of 2a revealed the shortest O? O bond reported for Rh? O₂ complexes, indicating the formation of a Rh^I? O₂ adduct, rather than a cyclic Rh^III η²‐peroxo complex. The coordination of the O₂ ligand in 2a was shown to be reversible. Treatment of 2a with CO gas yielded almost quantitatively the corresponding carbonyl complex [{Me₂C₆H(CH₂P^tBu₂)₂}Rh(CO)] ( 3a ). Surprisingly, treatment of the structurally very similar pincer complex [{C₆H₃(CH₂PⁱPr₂)₂)}Rh(η¹‐N₂)] ( 1b ) with O₂ led to partial decomposition, with no dioxygen adduct being observed.     

Discovering the chemical reactivity of the molecular oxonitride [{Ti(η-C5Me5)(μ-O)}3(μ3-N)]

The ability of the oxonitride [{Ti(η⁵-C₅Me₅)(μ-O)}₃(μ₃-N)] (1) to act as an organometallic ligand has been studied from both theoretical and experimental points of view. DFT calculations have allowed understanding the electronic structure of 1, and rationalizing its chemical behavior by comparison with the electronic structures of isoelectronic species [{Ti(η⁵-C₅Me₅)(μ-O)}₃(μ₃-CH)] and [{Ti(η⁵-C₅Me₅)(μ-NH)}₃(μ₃-N)]. Reactions of 1 with different inorganic molecules such as [Mo(CO)₃(1,3,5-Me₃C₆H₃)] or AlEt₃ have confirmed the possibility of 1 to act as a tridentate or monodentate ligand to give the [{(CO)₃Mo}(μ₃-O)₃{Ti₃(η⁵-C₅Me₅)₃(μ₃-N)}] (2) and [{Et₃Al}(μ₃-O){(μ-O)₂Ti₃(η⁵-C₅Me₅)₃(μ₃-N)}] (3) complexes, respectively. Surprisingly, reactions of 1 with [M(CO)₆] (M = Cr, Mo, W) complexes led to activate the μ₃-N unit in 1 to afford the new compounds [Ti₃(η⁵-C₅Me₅)₃(μ-O)₄{(NC)M(CO)₅}]₂ [M = Cr (4), Mo (5), W (6)]. Molecular structures of complexes 2-6 have been established by single crystal X-ray analysis.     

Asymmetric 1,3-dipolar cycloaddition reaction of α,β-unsaturated nitriles with nitrones catalyzed by chiral-at-metal rhodium or iridium complexes

The aqua complexes (S_M,R_C)-[(η⁵-C₅Me₅)M{(R)-Prophos}(H₂O)](SbF₆)₂ (M = Rh, Ir; (R)-Prophos = 1,2-bisdiphenylphosphino propane) catalyze the 1,3-dipolar cycloaddition reaction (DCR) of nitrones with α,β-unsaturated nitriles with low-to-moderate enantioselectivity. The involved catalysts [(η⁵-C₅Me₅)M{(R)-Prophos}(α,β-unsaturated nitrile)](SbF₆)₂, isolated as mixtures of the (S_M,R_C)- and (R_M,R_C)-diastereomers, have been fully characterized, and the molecular structure of the complexes (S_Rh,R_C)-[(η⁵-C₅Me₅)Rh{(R)-Prophos}(cis-2-pentenenitrile)](SbF₆)₂ and (S_Ir,R_C)-[(η⁵-C₅Me₅)Ir{(R)-Prophos}(acrylonitrile)](SbF₆)₂ has been determined by X-ray diffraction. The (R)-at-metal epimers isomerize to the (S)-at-metal counterparts. Diastereopure (S_M,R_C)-[(η⁵-C₅Me₅)M{(R)-Prophos}(α,β-unsaturated nitrile)](SbF₆)₂ complexes catalyze the above-mentioned DCR in a stoichiometric manner with up to 97% ee. The results make clear the influence of the metal configuration on the catalytic stereochemical outcome. The catalysts can be recycled without significant loss of either activity or selectivity.     

Ammonia-Borane Derived BN Fragments Trapped on Bi- and Trimetallic Titanium(III) Systems

Titanium(III) complexes containing unprecedented (NH₂BH₂NHBH₃)²⁻ and {N(BH₃)₃}³⁻ ligands have been isolated, and their structures elucidated by a combination of experimental and theoretical methods. The treatment of the trimethyl derivative [TiCp*Me₃] (Cp*=η⁵-C₅Me₅) with NH₃BH₃ (3 equiv) at room temperature gives the paramagnetic dinuclear complex [{TiCp*(NH₂BH₃)}₂(μ-NH₂BH₂NHBH₃)], which at 80 °C leads to the trinuclear hydride derivative [{TiCp*(μ-H)}₃{μ₃-N(BH₃)₃}]. The bonding modes of the anionic BN fragments in those complexes, as well as the dimethylaminoborane group trapped on the analogous trinuclear [{TiCp*(μ-H)}₃(μ₃-H)(μ₃-NMe₂BH₂)], have been studied by X-ray crystallography and density functional theory (DFT) calculations.     

Synthesis and characterization of complexes imparting N-pyridyl bonded meso-pyridyl substituted dipyrromethanes

The meso-pyridyl substituted dipyrromethane ligands 5-(4-pyridyl)dipyrromethane (4-dpmane) and 5-(3-pyridyl)dipyrromethane (3-dpmane) have been employed in the synthesis of a series of complexes with the general formulations [(η⁶-arene)RuCl₂(L)] (η⁶-arene = C₆H₆, C₁₀H₁₄) and [(η⁵-C₅Me₅)MCl₂(L)] (M = Rh, Ir). The reaction products have been characterized by microanalyses and spectral studies and molecular structures of the complexes [(η⁶-C₁₀H₁₄)RuCl₂(4-dpmane)] and [(η⁵-C₅Me₅)IrCl₂(3-dpmane)] have been determined crystallographically. For comparative studies, geometrical optimization have been performed on the complex [(η⁵-C₅Me₅)IrCl₂(4-dpmane)] using exchange correlation functional B3LYP. Optimized bond length and angles are in good agreement with the structural data of the complex [(η⁵-C₅Me₅)IrCl₂(3-dpmane)]. The complexes [(η⁶-C₁₀H₁₄)RuCl₂(3-dpmane)], [(η⁵-C₅Me₅)RhCl₂(3-dpmane)] and [(η⁵-C₅Me₅)IrCl₂(3-dpmane)] have been employed as a transfer hydrogenation catalyst in the reduction of aldehydes. It was observed that the rhodium and iridium complexes mentioned above are more effective in this regard in comparison to the ruthenium complex.     

Preparation,crystal structures and NMR characterization of substituted-benzoate complexes Nickel(II)-N3-macrocycles

Substituted-benzoate complexes of nickel(II) of the types bidentate [Ni(mcN₃)(Bz)](PF₆) and monodentate [Ni(mcN₃)(Bz)(H₂O)](PF₆) have been prepared by acid-base reaction between the hydroxo complexes [Ni(mcN₃)(μ-OH)]₂(PF₆)₂ (mcN₃ = 2,4,4-trimethyl-1,5,9-triazacyclododec-1-ene (Me₃-mcN₃) or its 9-methyl derivative (Me₄-mcN₃)) and the corresponding benzoic acid. The paramagnetic nickel(II) complexes have been characterized in solution by NMR spectroscopy. The influence of the substituents on the hyperfine shift patterns for substituted-benzoate complexes of nickel(II) has been studied. The substituent effects upon the coordination mode of substituted benzoates have been established by X-ray diffraction.     

Dinuclear formamidino and triazenido compounds [{2,6-(Me2NCH2)2C6H3} (p-tolylNYNR)PtHgBrCl] (Y  CH,N) containing a platinum-to-mercury donor bond

Complexes [{2,6-(Me₂NCH₂)₂C₆H₃} (p-tolylNYNR)PtHgBrCl] (Y  CH, N; R  Me, Et, i-Pr) have been prepared by the reaction of [{2,6-(Me₂NCH₂)₂C₆H₃}-PtBr] with [Hg(p-tolylNYNR)Cl]. Similar complexes were obtained, although in lower yields, from exchange reactions of [{2,6-(Me₂NCH₂)₂C₆H₃} (RCO₂)-PtHg(O₂CR)Br] with p-tolylNNN(H)-p-tolyl and p-tolylNC(H)N(H)Et.The proposed structure for these heterodinuclear compounds involves a Pt-to-Hg donor bond which is bridged by a triazenido (Y  N) or a formamidino (Y  CH) group, the five-membered ring thus formed acting as a stabilizing factor. The absence of a subsequent electron transfer reaction is ascribed to the constraints of the terdentate 2,6-(Me₂NCH₂)₂C₆H₃ ligand, which fixes the N-donor atoms in mutual trans-positions.The use of p-tolylNYNR, where R is an alkyl group, results in the formation of two isomers of [{2,6-(Me₂NCH₂)₂C₆H₃} (p-tolylNYNR)PtHgBrCl] with p-tolyl-N and alkyl-N sites bonded either to Pt or Hg. The relative abundance of these isomers varies systematically with the nature of the group R. It is suggested that the ratio is determined during the formation of the complexes and that both steric and electronic factors are important.     

Group 1 and 13 complexes of aryl-substituted bis(phosphinimino)methyls

The organolithium reagent [{HC(Ph₂PNC₆H₂Me₃-2,4,6)₂}Li(OEt₂)] was easily obtained by deprotonation of H₂C(Ph₂PNC₆H₂Me₃-2,4,6)₂ with nBuLi in diethyl ether solution. The crystal structure of [{HC(Ph₂PNC₆H₂Me₃-2,4,6)₂}Li(OEt₂)] has been determined and shown to consist a monomeric chelate structure that contains a distorted, trigonal planar lithium centre. The ligand precursor has also been deprotonated with both Me₃Al and Me₂AlCl to yield the tetrahedral organoaluminium complexes, [{HC(Ph₂PNC₆H₂Me₃-2,4,6)₂}AlMe₂] and [{HC(Ph₂PNC₆H₂Me₃-2,4,6)₂}Al(Cl)Me]. Reaction of [{HC(Ph₂PNC₆H₂Me₃-2,4,6)₂}Li(OEt₂)] with either AlX₃ (X=Cl, Br, I) or GaCl₃ yielded a series of dihalo derivatives [{HC(Ph₂PNC₆H₂Me₃-2,4,6)₂}MX₂] all of which have been shown to exist as similar monomeric species containing four-coordinate group 13 centres.     

Electrophilic Organobismuth Dication Catalyzes Carbonyl Hydrosilylation

Bismuth compounds are gaining importance as potential alternatives to transition-metal complexes and electron deficient lighter p-block compounds in homogeneous catalysis. Computational analysis on the two-coordinate [(Me₂NC₆H₄)Bi]²⁺ possessing three electrophilic sites is experimentally evidenced by the isolation of [{Me₂NC₆H₄}Bi{OP(NMe₂)₃}₃][B(3,5-C₆H₃Cl₂)₄]₂. These observations led us to generate dicationic organobismuth catalyst, [(Me₂NC₆H₄)Bi(L)₃]²⁺ (L=aldehyde/ketone), evidenced by NMR spectroscopy in solution and by single-crystal X-ray diffraction in the solid state. It efficiently catalyzes hydrosilylation of aldehydes and ketones resulting in silyl ethers as the only products in high yields. Our investigations support a carbonyl activation mechanism at the bismuth center followed by Si−H addition.     

Synthesis and magnetism of 6-nitrobenzimidazolate and imidazolate-bridged copper(II) complexes

Summary Four new trinuclear copper(II) complexes, [Cu(phen)-(NBzIm)] (ClO₄) (1), [Cu(bpy)(NBzIm)](ClO₄) (2), [Cu-(Me₂-bpy)(NBzIm)](Ac)·1/2H₂O (3) and [Cu(Me₂-bpy)-(Im)](ClO₄)·1/2H₂O (4) (phen = 1, 10-phenanthroline, bpy = 2,2-bipyridine, NBzIm = 6-nitrobenzimidazolate ion, Im=imidazolate ion) have been prepared and characterized by variable temperature magnetic susceptibility measurements. A weak antiferromagnetic spin exchange interaction operates between copper(II) ions, exchange integrals evaluated as J =-23.82 cm^-1 for (1); and J=-21.91 cm^-1 for (2).     

Rare‐Earth‐Metal Alkylaluminates Supported by N‐Donor‐Functionalized Cyclopentadienyl Ligands: C?H Bond Activation and Performance in Isoprene Polymerization

Homoleptic tetramethylaluminate complexes [Ln(AlMe₄)₃] (Ln=La, Nd, Y) reacted with HCp^NMe2 (Cp^NMe2=1‐[2‐(N,N‐dimethylamino)‐ethyl]‐2,3,4,5‐tetramethyl‐cyclopentadienyl) in pentane at ?35 °C to yield half‐sandwich rare‐earth‐metal complexes, [{C₅Me₄CH₂CH₂NMe₂(AlMe₃)}Ln(AlMe₄)₂]. Removal of the N‐donor‐coordinated trimethylaluminum group through donor displacement by using an equimolar amount of Et₂O at ambient temperature only generated the methylene‐bridged complexes [{C₅Me₄CH₂CH₂NMe(μ‐CH₂)AlMe₃}Ln(AlMe₄)] with the larger rare‐earth‐metal ions lanthanum and neodymium. X‐ray diffraction analysis revealed the formation of isostructural complexes and the C? H bond activation of one aminomethyl group. The formation of Ln(μ‐CH₂)Al moieties was further corroborated by ¹³C and ¹H‐¹³C HSQC NMR spectroscopy. In the case of the largest metal center, lanthanum, this C? H bond activation could be suppressed at ?35 °C, thereby leading to the isolation of [(Cp^NMe2)La(AlMe₄)₂], which contains an intramolecularly coordinated amino group. The protonolysis reaction of [Ln(AlMe₄)₃] (Ln=La, Nd) with the anilinyl‐substituted cyclopentadiene HCp^AMe2 (Cp^AMe2=1‐[1‐(N,N‐dimethylanilinyl)]‐2,3,4,5‐tetramethylcyclopentadienyl) at ?35 °C generated the half‐sandwich complexes [(Cp^AMe2)Ln(AlMe₄)₂]. Heating these complexes at 75 °C resulted in the C? H bond activation of one of the anilinium methyl groups and the formation of [{C₅Me₄C₆H₄NMe(μ‐CH₂)AlMe₃}Ln(AlMe₄)] through the elimination of methane. In contrast, the smaller yttrium metal center already gave the aminomethyl‐activated complex at ?35 °C, which is isostructural to those of lanthanum and neodymium. The performance of complexes [{C₅Me₄CH₂CH₂NMe(μ‐CH₂)AlMe₃}‐ Ln(AlMe₄)], [(Cp^AMe2)Ln(AlMe₄)₂], and [{C₅Me₄C₆H₄NMe(μ‐CH₂)AlMe₃}Ln(AlMe₄)] in the polymerization of isoprene was investigated upon activation with [Ph₃C][B(C₆F₅)₄], [PhNMe₂H][B(C₆F₅)₄], and B(C₆F₅)₃. The highest stereoselectivities were observed with the lanthanum‐based pre‐catalysts, thereby producing polyisoprene with trans‐1,4 contents of up to 95.6 %. Narrow molecular‐weight distributions (M_w/M_n<1.1) and complete consumption of the monomer suggested a living‐polymerization mechanism.     

Arene ruthenium complexes incorporating immine/azine hybrid-chelating N-N donor ligands: synthetic, spectral, structural aspects and DFT studies

New series of mono and binuclear arene ruthenium complexes [{(η⁶-arene)RuCl(L)}]⁺ and [{(η⁶-arene)RuCl}₂(μ-L)₂]²⁺ (arene=benzene, p-cymene or hexamethylbenzene), {L=pyridine-2-carbaldehyde azine (paa), p-phenylene-bis(picoline)-aldimine (pbp) and p-bi-phenylene-bis(picoline)-aldimine (bbp)} are reported. The complexes have been fully characterized and molecular structure of the representative mononuclear complex [(η⁶-C₆Me₆)RuCl(paa)]BF₄ (1), binuclear complexes [{(η⁶-C₁₀H₁₄)RuCl}₂(μ-paa)](BF₄)₂ (3) and [{(η⁶-C₁₀H₁₄)RuCl}₂(μ-pbp)](BF₄)₂ (6) have been determined by single crystal X-ray diffraction analyses. Single crystal X-ray structure determination revealed that in the binuclear complexes the [(η⁶-C₁₀H₁₄)RuCl]⁺ units are trans disposed. Further, the crystal packing in the complexes 1, 3 and 6 is stabilized by C-H?X type (X=Cl, F) inter, intramolecular hydrogen bonding and π-π stacking (3). To explore the ambiguous nature of the bonding between pyridine-2-carbaldehyde azine (paa) with ruthenium containing units [(η⁶-arene)RuCl]⁺, DFT/B3LYP calculations have been performed on the complexes [(η⁶-arene)RuCl(paa)]⁺ (arene=C₆H₆, I; C₆Me₆, II; C₁₀H₁₄, III).     

Modeling [FeFe] hydrogenase: Synthesis and protonation of a diiron dithiolate complex containing a phosphine-N-heterocyclic-carbene ligand

The ligand exchange reaction of I_Me-(CH₂)₂-PPh₂ (I_Me = 1-methyimidazol-2-ylidene) and the hexacarbonyl complex [{Fe₂{μ-S(CH₂)₃S}(CO)₆] (1) resulted in the formation of the chelated complex [{Fe₂{μ-S(CH₂)₃S}(CO)₄(I_Me-(CH₂)₂-PPh₂)] (2). The molecular structure of 2 was confirmed by spectroscopic and X-ray analyses. This complex catalyzes proton reduction. Low temperature NMR studies on the protonation of 2 revealed the formation of a terminal hydride intermediate.     

Stack by Stack: From the Free Cyclopentadienylgermanium Cation Via Heterobimetallic Main-Group Sandwiches to Main-Group Sandwich Coordination Polymers

Heterobimetallic cationic sandwich complexes [M(μ-Cp)M′Cp]⁺ of group 13 (M=Ga, In) and group 14 (M′=Ge, Sn) elements have been prepared as [WCA]⁻ salts (WCA=Al(OR^F)₄; OR^F=OC(CF₃)₃). Their molecular structures include free apical gallium or indium atoms. The sandwich complexes were formed in the reactions of [M(HMB)]⁺[WCA]⁻ (HMB=C₆Me₆) with the free metallocenes [M′Cp₂]. Their structures are related to known stannocene and stannocenium salts; the unprecedented germanium analogues, namely the free germanocenium cation [GeCp]⁺ and the corresponding triple-decker complex cation [CpGe(μ-Cp)GeCp]⁺, are described herein. By variation of the reaction conditions, these sandwich complexes can be transformed into the group 13/14 mixed cationic coordination polymer [{In(HMB)(μ-SnCp₂)}_n][WCA]_n. This polymeric chain motif was also successfully replicated by the synthesis of complexes [{Ga/In(HMB)(μ-FeCp₂)}_n][WCA]_n containing FeCp₂ as a bridging ligand.     

Experimental and Computational Studies on the Reactivity of a Terminal Thorium Imidometallocene towards Organic Azides and Diazoalkanes

The reaction of the base‐free terminal thorium imido complex [{η⁵‐1,2,4‐(Me₃C)₃C₅H₂}₂Th?N(p‐tolyl)] ( 1 ) with p‐azidotoluene yielded irreversibly the tetraazametallacyclopentene [{η⁵‐1,2,4‐(Me₃C)₃C₅H₂}₂Th{N(p‐tolyl)N?N? N(p‐tolyl)}] ( 2 ), whereas the bridging imido complex [{[η⁵‐1,2,4‐(Me₃C)₃C₅H₂]Th(N₃)₂}₂{μ‐N(p‐tolyl)}₂][(n‐C₄H₉)₄N]₂ ( 3 ) was isolated from the reaction of 1 with [(n‐C₄H₉)₄N]N₃. Unexpectedly, upon the treatment of 1 with 9‐diazofluorene, the NN bond was cleaved, an N atom was transferred, and the η²‐diazenido iminato complex [{η⁵‐1,2,4‐(Me₃C)₃C₅H₂}₂Th{η²‐[N?N(p‐tolyl)]}{N?(9‐C₁₃H₈)}] ( 4 ) was formed. In contrast, the reaction of 1 with Me₃SiCHN₂ gave the nitrilimido complex [{η⁵‐1,2,4‐(Me₃C)₃C₅H₂}₂Th{NH(p‐tolyl)}{N₂CSiMe₃}] ( 5 ), which slowly converted into [{η⁵‐1,2,4‐(Me₃C)₃C₅H₂}{η⁵:κ‐N‐1,2‐(Me₃C)₂‐4‐CMe₂(CH₂NN?CHSiMe₃)C₅H₂}Th{NH(p‐tolyl)}] ( 6 ) by intramolecular C? H bond activation. The experimental results are complemented by density functional theory (DFT) studies.