Metal Derivatives of Heterocyclic‐2‐thiones: Crystal Structures of [Bis(diphenylphosphanyl)propane][bis(pyrimidine‐2‐thiolato)]ruthenium(II) and [Bis(diphenylphosphanyl)methane][bis(pyridine‐2‐thiolato)]ruthenium(II)

Ruthenium(II) Complexes containing pyrimidine‐2‐thiolate (pymS^–) and bis(diphenylphosphanyl)alkanes [Ph₂P–(CH₂)_m–PPh₂, m = 1, dppm; m = 2, dppe; m = 3, dppp; m = 4, dppb] are described. Reactions of [RuCl₂L₂] (L = dppm, dppp) and [Ru₂Cl₄L₃] (L = dppb) with pyrimidine‐2‐thione (pymSH) in 1:2 molar ratio in dry benzene in the presence of Et₃N base yielded the [Ru(pymS)₂L] complexes (pymS^– = pyrimidine‐2‐thiolate; L = dppm ( 1 ); dppp ( 3 ); dppb ( 4 )). The complex [Ru(pymS)₂(dppe)] ( 2 ) was indirectly prepared by the reaction of [Ru(pymS)₂(PPh₃)₂] with dppe. These complexes were characterized using analytical data, IR, ¹H, ¹³C, ³¹P NMR spectroscopy, and X‐ray crystallography (complex 3 ). The crystal structure of the analogous complex [Ru(pyS)₂(dppm)] ( 5 ) with the ligand pyridine‐2‐thiolate (pyS^–) was also described. X‐ray crystallographic investigation of complex 3 has shown two four‐membered chelate rings (N, S donors) and one six‐membered ring (P, P donors) around the metal atom. Compound 5 provides the first example in which Ru^II has three four‐membered chelate rings: two made up by N, S donor ligands and one made up by P, P donor ligand. The arrangement around the metal atoms in each complex is distorted octahedral with cis:cis:trans:P, P:N, N:S, S dispositions of the donor atoms. The ³¹P NMR spectroscopic data revealed that the complexes are static in solution, except 2 , which showed the presence of more than one species.     

Chloro(η6‐p‐cymene)(phosphoramidite)ruthenium(II), a 16‐Electron Fragment Stabilized by an η2‐Aryl–Metal Interaction,and Its Use in Asymmetric Cyclopropanation

Chloride abstraction from the half‐sandwich complexes [RuCl₂(η⁶‐p‐cymene)(P*‐κP)] ( 2a : P* = (S_a,R,R)‐ 1a = (1S_a)‐[1,1′‐binaphthalene]‐2,2′‐diyl bis[(1R)‐1‐phenylethyl)]phosphoramidite; 2b : P* = (S_a,R,R)‐ 1b = (1S_a)‐[1,1′‐binaphthalene]‐2,2′‐diyl bis[(1R)‐(1‐(1‐naphthalen‐1‐yl)ethyl]phosphoramidite) with (Et₃O)[PF₆] or Tl[PF₆] gives the cationic, 18‐electron complexes dichloro(η⁶‐p‐cymene){(1S_a)‐[1,1′‐binaphthalene]‐2,2′‐diyl {(1R)‐1‐[(1,2‐η)‐phenyl]ethyl}[(1R)‐1‐phenylethyl]phosphoramidite‐κP}ruthenium(II) hexafluorophosphate ( 3a ) and [Ru(S)]‐dichloro(η⁶‐p‐cymene){(1S_a)‐[1,1′‐binaphthalene]‐2,2′‐diyl {(1R)‐1‐[(1,2‐η)‐naphthalen‐1‐yl]ethyl}[(1R)‐1‐(naphthalen‐1‐yl)ethyl]phosphoramidite‐κP)ruthenium(II) hexafluorophosphate ( 3b ), which feature the η²‐coordination of one aryl substituent of the phosphoramidite ligand, as indicated by ¹H‐, ¹³C‐, and ³¹P‐NMR spectroscopy and confirmed by an X‐ray study of 3b . Additionally, the dissociation of p‐cymene from 2a and 3a gives dichloro{(1S_a)‐[1,1′‐binaphthalene]‐2,2′‐diyl [(1R)‐(1‐(η⁶‐phenyl)ethyl][(1R)‐1‐phenylethyl]phosphoramidite‐κP)ruthenium(II) ( 4a ) and di‐μ‐chlorobis{(1S_a)‐[1,1′‐binaphthalene]‐2,2′‐diyl [(1R)‐1‐(η⁶‐phenyl)ethyl][(1R)‐1‐phenylethyl]phosphoramidite‐κP}diruthenium(II) bis(hexafluorophosphate) ( 5a ), respectively, in which one phenyl group of the N‐substituents is η⁶‐coordinated to the Ru‐center. Complexes 3a and 3b catalyze the asymmetric cyclopropanation of α‐methylstyrene with ethyl diazoacetate with up to 86 and 87% ee for the cis‐ and the trans‐isomers, respectively.     

(2,6‐Bis{1‐[4‐(dimethylamino)phenylimino]ethyl}pyridine)dichlorido(triphenylphosphine‐κP)ruthenium(II): a zigzag chain of fused centrosymmetric R22(12) rings

The title compound, [RuCl₂(C₂₅H₂₉N₅)(C₁₈H₁₅P)], a transfer hydrogenation catalyst, is supported by an N,N′,N′′‐tridentate pyridine‐bridged ligand and triphenylphosphine. The Ru^II centre is six‐coordinated in a distorted octahedral arrangement, with the two Cl atoms located in the axial positions, and the pyridine (py) N atom, the two imino N atoms and the triphenylphosphine P atom located in the equatorial plane. The two equatorial Ru—N_imino distances (mean 2.093 Å) are substantially longer than the equatorial Ru—N_py bond [1.954 (4) Å]. It is observed that the N_imino—M—N_py bond angle for the five‐membered chelate rings of 2,6‐bis(imino)pyridine‐based complexes is inversely related to the magnitude of the M—N_py bond. The title structure is stabilized by intra‐ and intermolecular C—H...Cl hydrogen bonds, as well as by intramolecular π–π stacking interactions between the aromatic rings belonging to the triphenylphosphine ligand and the dimethylaminophenyl fragment. The intermolecular hydrogen bonds form an R₂²(12) ring and a zigzag chain of fused centrosymmetric rings running parallel to the [100] direction.     

Coordination Chemistry of Organoruthenium Compounds with Benzoylthiourea Ligands and their Biological Properties

Benzoylthiourea derivatives feature several donor atoms capable of coordinating to metal centers. We report here a series of Ru(η⁶‐p‐cymene) complexes employing benzoylthiourea derivatives as ligands. Such ligands often coordinate to metal centers through their S and O donor atoms. We isolated complexes where the ligands were mono‐ or bidentately coordinated to Ru involving the S donor atom and surprisingly in bidentate coordination mode a deprotonated thiourea nitrogen resulting in a 4‐membered ring structure around the metal center. DFT calculations were used to explain the differences in coordination behavior. These were complemented by stability studies and biological investigations of the compounds as anticancer agents. Several of the synthesized derivatives exhibited significant cell growth inhibitory activity, with the complexes featuring bidentate ligands being more potent than their monodentate counterparts. This can be explained by the higher stability of the former under the conditions employed in cell culture assays.     

Investigation of the C−H Activation Potential of [Hydrotris(1H‐pyrazolato‐κN1)borato(1−)]iridium (IrTpx) Fragments Featuring Aromatic Substituents x at the 3‐Position of the Pyrazole Rings,The Choice of the Precursor

A series of pyrazole‐substituted [hydrotris(1H‐pyrazolato‐κN¹)borato(1−)]iridium complexes of the general composition [Ir(Tp^x)(olefin)₂] (Tp^x=Tp^Ph and Tp^Th) and their capability to activate C−H bonds is presented. As a test reaction, the double C−H activation of cyclic‐ether substrates leading to the corresponding Fischer carbene complexes was chosen. Under the reaction conditions employed, the parent compound [Ir(Tp^Ph)(ethene)₂] was not isolable; instead, (OC‐6‐25)‐[Ir(Tp^PhκC^Ph,κ³N,N′,N″)(ethyl)(η²‐ethene)] ( 1 ) was formed diastereoselectively. Upon further heating, 1 could be converted exclusively to (OC‐6‐24)‐[Ir(Tp^Phκ²C^Ph,C^Ph,κ³N,N′,N″)(η²‐ethene)] ( 2 ). Complex 1 , but not 2 , reacted with THF to give (OC‐6‐35)‐[Ir(Tp^Phκ³N,N′,N″)H(dihydrofuran‐2(3H)‐ylidene)] ( 3 ), a cyclic Fischer carbene formed by double C−H activation of THF. Accordingly, complexes of the general formula [Ir(Tp^x)(butadiene)] (see 4 – 6 ; butadiene=buta‐1,3‐diene, 2‐methylbuta‐1,3‐diene (isoprene), 2,3‐dimethylbuta‐1,3‐diene) reacted with THF to yield 3 or the related derivative 9 . The reaction rate was strongly dependent on the steric demand of the butadiene ligand and the nature of the substituent at the 3‐position of the pyrazole rings.     

Asymmetric Hydrogenation of Azaindoles: Chemo‐ and Enantioselective Reduction of Fused Aromatic Ring Systems Consisting of Two Heteroarenes

High enantioselectivity was achieved for the hydrogenation of azaindoles by using the chiral catalyst, which was prepared from [Ru(η³‐methallyl)₂(cod)] and a trans‐chelating bis(phosphine) ligand (PhTRAP). The dearomative reaction exclusively occurred on the five‐membered ring, thus giving the corresponding azaindolines with up to 97:3 enantiomer ratio.     

Platinum(II) Mixed Ligand Complexes with Thiourea Derivatives,Dimethyl Sulphoxide and Chloride: Syntheses,Molecular Structures,and ESCA Data

The platinum(II) mixed ligand complexes [PtCl(L^1‐6)(dmso)] with six differently substituted thiourea derivatives HL, R₂NC(S)NHC(O)R′ (R = Et, R′ = p‐O₂N‐Ph: HL¹; R = Ph, R′ = p‐O₂N‐Ph: HL²; R = R′ = Ph: HL³; R = Et, R′ = o‐Cl‐Ph: HL⁴; R₂N = EtOC(O)N(CH₂CH₂)₂N, R′ = Ph: HL⁵) and Et₂NC(S)N=CNH‐1‐Naph (HL⁶), as well as the bis(benzoylthioureato‐κO, κS)‐platinum(II) complexes [Pt(L^{1, 2})₂] have been synthesized and characterized by elemental analysis, IR, FAB(+)‐MS, ¹H‐NMR, ¹³C‐NMR, as well as X‐ray structure analysis ([PtCl(L¹)(dmso)] and [PtCl(L^{3, 4})(dmso)]) and ESCA ([PtCl(L^{1, 2})(dmso)] and [Pt(L^{1, 2})₂]). The mixed ligand complexes [PtCl(L)(dmso)] have a nearly square‐planar coordination at the platinum atoms. After deprotonation, the thiourea derivatives coordinate bidentately via O and S, DMSO bonds monodentately to the Pt^II atom via S atom in a cis arrangement with respect to the thiocarbonyl sulphur atom. The Pt—S‐bonds to the DMSO are significant shorter than those to the thiocarbonyl‐S atom. In comparison with the unsubstituted case, electron withdrawing substituents at the phenyl group of the benzoyl moiety of the thioureate (p‐NO₂, o‐Cl) cause a significant elongation of the Pt—S(dmso)‐bond trans arranged to the benzoyl‐O—Pt‐bond. The ESCA data confirm the found coordination and bonding conditions. The Pt 4f_7/2 electron binding energies of the complexes [PtCl(L^{1, 2})(dmso)] are higher than those of the bis(benzoylthioureato)‐complexes [Pt(L^{1, 2})₂]. This may indicate a withdrawal of electron density from platinum(II) caused by the DMSO ligands.     

Designing a heterotrinuclear CuII—NiII—CuII complex from a mononuclear CuII Schiff base precursor with dicyanamide as a coligand: synthesis,crystal structure,thermal and photoluminescence properties

Schiff bases are considered `versatile ligands' in coordination chemistry. The design of polynuclear complexes has become of interest due to their facile preparations and varied synthetic, structural and magnetic properties. The reaction of the `ligand complex' [CuL] {H₂L is 2,2′‐[propane‐1,3‐diylbis(nitrilomethanylylidene)]diphenol} with Ni(OAc)₂·4H₂O (OAc is acetate) in the presence of dicyanamide (dca) leads to the formation of bis(dicyanamido‐1κN¹)bis(dimethyl sulfoxide)‐2κO,3κO‐bis{μ‐2,2′‐[propane‐1,3‐diylbis(nitrilomethanylylidene)]diphenolato}‐1:2κ⁶O,O′:O,N,N′,O′;1:3κ⁶O,O′:O,N,N′,O′‐dicopper(II)nickel(II), [Cu₂Ni(C₁₇H₁₆N₂O₂)₂(C₂N₃)₂(C₂H₆OS)₂]. The complex shows strong absorption bands in the frequency region 2155–2269 cm⁻¹, which clearly proves the presence of terminal bonding dca groups. A single‐crystal X‐ray study revealed that two [CuL] units coordinate to an Ni^II atom through the phenolate O atoms, with double phenolate bridges between Cu^II and Ni^II atoms. Two terminal dca groups complete the distorted octahedral geometry around the central Ni^II atom. According to differential thermal analysis–thermogravimetric analysis (DTA–TGA), the title complex is stable up to 423 K and thermal decomposition starts with the release of two coordinated dimethyl sulfoxide molecules. Free H₂L exhibits photoluminescence properties originating from intraligand (π–π*) transitions and fluorescence quenching is observed on complexation of H₂L with Cu^II.     

Synthesis of Imines via Reactions of Benzyl Alcohol with Amines Using Half‐Sandwich (η6‐p‐cymene) Ruthenium(II) Complexes Stabilised by 2‐aminofluorene Derivatives

A new class of half‐sandwich (η⁶‐p‐cymene) ruthenium(II) complexes supported by 2‐aminofluorene derivatives [Ru(η⁶‐p‐cymene)(Cl)(L)] ( L  = 2‐(((9H‐fluoren‐2‐yl)imino)methyl)phenol ( L ¹ ), 2‐(((9H‐fluoren‐2‐yl)imino)methyl)‐3‐methoxyphenol ( L ² ), 1‐(((9H‐fluoren‐2‐yl)imino)methyl)naphthalene‐2‐ol ( L ³ ) and N‐((1H‐pyrrol‐2‐yl)methylene)‐9H‐fluorene‐2‐amine ( L ⁴ )) were synthesized. All compounds were fully characterized by analytical and spectroscopic techniques (IR, UV–Vis, NMR) and also by mass spectrometry. The solid state molecular structures of the complexes [Ru(η⁶‐p‐cymene)(Cl)(L²)], [Ru(η⁶‐p‐cymene)(Cl)(L³)] and [Ru(η⁶‐p‐cymene)(Cl)(L⁴)] revealed that the 2‐aminofluorene and p‐cymene moieties coordinate to ruthenium(II) in a three‐legged piano‐stool geometry. The synthesized complexes were used as catalysts for the dehydrogenative coupling of benzyl alcohol with a range of amines (aliphatic, aromatic and heterocyclic). The reactions were carried out under thermal heating, ultrasound and microwave assistance, using solvent or solvent free conditions, and the catalytic performance was optimized regarding the solvent, the type of base, the catalyst loading and the temperature. Moderately high to very high isolated yields were obtained using [Ru(η⁶‐p‐cymene)(Cl)(L⁴)] at 1 mol%. In general, microwave irradiation produced better yields than the other two techniques irrespective of the nature of the substituents.     

Chiral Bis(oxazoline) Ruthenium Complexes with Bipyridyl‐Type N‐Heteroaromatics: Comparative Stereochemical and Photochemical Characterization of their Λ‐ and Δ‐Diastereomeric Geminate Isomers

Diastereomeric geminate pairs of chiral bis(2‐oxazoline) ruthenium complexes with bipyridyl‐type N‐heteroaromatics, Λ‐ and Δ‐[Ru(L‐ L)₂(iPr‐biox)]²⁺ (iPr‐biox=(4S,4′S)‐4,4′‐diisopropyl‐2,2′‐bis(2‐oxazoline); L‐ L=2,2′‐bipyridyl (bpy) for 1 Λ and 1 Δ, 4,4′‐dimethyl‐2,2′‐bipyridyl (dmbpy) for 2 Λ and 2 Δ, and 1,10‐phenanthroline (phen) for 3 Λ and 3 Δ), were separated as BF₄ and PF₆ salts and were subjected to the comparative studies of their stereochemical and photochemical characterization. DFT calculations of 1 Λ and 1 Δ electronic configurations for the lowest triplet excited state revealed that their MO‐149 (HOMO) and MO‐150 (lower SOMO) characters are interchanged between them and that the phosphorescence‐emissive states are an admixture of a Ru‐to‐biox charge‐transfer state and an intraligand excited state within the iPr‐biox. Furthermore, photoluminescence properties of the two Λ,Δ‐diastereomeric series are discussed with reference to [Ru(bpy)₃]²⁺.     

Structural Studies of Bis(cyclopentadienyl)molybdenum‐Amino Acid Complexes

The crystal structures of molybdocene‐amino acid compounds of the type [Cp₂Mo^IV(κN, κO‐AA)]⁺Cl^—·xH₂O with AA = D ‐phenylalaninato (x = 1.5), DL ‐leucinato (x = 2) and DL ‐valinato (x = 1) have been determined (Cp = η⁵‐C₅H₅). The compounds feature an almost planar, five‐membered chelate ring of the aminocarboxylate moiety (deprotonated amino acid) with the molybdenum atom. In the phenylalaninato complex π‐stacking between the phenyl rings is found. The complexes were proven kinetically stable at pH < 1 for at least 24 h.     

Syntheses,Structures, and Catalytic Reactions of Palladium Adducts of Chiral Diphosphines That Contain a Rhenium Stereocenter in the Backbone

Reactions of the title diphosphines [(η⁵‐C₅H₄PPh₂)Re(NO)(PPh₃)((CH₂)_nPPh₂)] (n=0, (R)‐ 1 ; n=1, racemic or (S)‐ 2 ) with [PdCl₂(PhCN)₂] give the palladium/rhenium chelate complexes [(η⁵‐C₅H₄PPh₂)Re(NO)(PPh₃)((μ‐CH₂)_nPPh₂)PdCl₂] (n=0, (S)‐ 5 ; n=1, racemic or (S)‐ 6 ) in 75–92% yield. The crystal structure of racemic 6 shows a twisted‐boat conformation of the chelate ring, giving a chiral pocket very different from that in a related rhodium chelate. However, NOE experiments suggest a similar ensemble of conformations in solution. Catalysts are generated from various combinations of a) Pd(OAc)₂ and (R)‐ 1 or (S)‐ 2 (1 : 2), b) (S)‐ 5 or (S)‐ 6 and (R)‐ 1 or (S)‐ 2 (1 : 2), or c) (i‐Bu)₂AlH with the preceding recipes. These factors effect the Heck arylation of 2,3‐dihydrofuran with phenyl trifluoromethylsulfonate. In contrast to analogous reactions with (R)‐binap (=(R)‐2,2′‐bis(diphenylphosphanyl)‐1,1′‐binaphthalene), the major product 2‐phenyl‐2,3‐dihydrofuran is nearly racemic (≤12% ee).     

Binding H2, N2, H-, and BH3 to transition-metal sulfur sites: synthesis and properties of [RuL(PR3)(N2Me2S2)] Complexes (L=eta2-H2, H-, BH3; R=Cy, iPr)

The reactions of [Ru(N₂)(PR₃)(‘N₂Me₂S₂’)] [‘N₂Me₂S₂’=1,2‐ethanediamine‐N,N′‐dimethyl‐N,N′‐bis(2‐benzenethiolate)(2?)] [ 1 a (R=iPr), 1 b (R=Cy)] and [μ‐N₂{Ru(N₂)(PiPr₃)(‘N₂Me₂S₂’)}₂] ( 1 c ) with H₂, NaBH₄, and NBu₄BH₄, intended to reduce the N₂ ligands, led to substitution of N₂ and formation of the new complexes [Ru(H₂)(PR₃)(‘N₂Me₂S₂’)] [ 2 a (R=iPr), 2 b (R=Cy)], [Ru(BH₃)(PR₃)(‘N₂Me₂S₂’)] [ 3 a (R=iPr), 3 b (R=Cy)], and [Ru(H)(PR₃)(‘N₂Me₂S₂’)]^? [ 4 a (R=iPr), 4 b (R=Cy)]. The BH₃ and hydride complexes 3 a , 3 b , 4 a , and 4 b were obtained subsequently by rational synthesis from 1 a or 1 b and BH₃?THF or LiBEt₃H. The primary step in all reactions probably is the dissociation of N₂ from the N₂ complexes to give coordinatively unsaturated [Ru(PR₃)(‘N₂Me₂S₂’)] fragments that add H₂, BH₄^?, BH₃, or H^?. All complexes were completely characterized by elemental analysis and common spectroscopic methods. The molecular structures of [Ru(H₂)(PR₃)(‘N₂Me₂S₂’)] [ 2 a (R=iPr), 2 b (R=Cy)], [Ru(BH₃)(PiPr₃)(‘N₂Me₂S₂’)] ( 3 a ), [Li(THF)₂][Ru(H)(PiPr₃)(‘N₂Me₂S₂’)] ([Li(THF)₂]‐ 4 a ), and NBu₄[Ru(H)(PCy₃)(‘N₂Me₂S₂’)] (NBu₄‐ 4 b ) were determined by X‐ray crystal structure analysis. Measurements of the NMR relaxation time T₁ corroborated the η² bonding mode of the H₂ ligands in 2 a (T₁=35 ms) and 2 b (T₁=21 ms). The H,D coupling constants of the analogous HD complexes HD‐ 2 a (¹J(H,D)=26.0 Hz) and HD‐ 2 b (¹J(H,D)=25.9 Hz) enabled calculation of the H? D distances, which agreed with the values found by X‐ray crystal structure analysis ( 2 a : 92 pm (X‐ray) versus 98 pm (calculated), 2 b : 99 versus 98 pm). The BH₃ entities in 3 a and 3 b bind to one thiolate donor of the [Ru(PR₃)(‘N₂Me₂S₂’)] fragment and through a B‐H‐Ru bond to the Ru center. The hydride complex anions 4 a and 4 b are extremely Brønsted basic and are instantanously protonated to give the η²‐H₂ complexes 2 a and 2 b .     

Identification of the Structural Determinants for Anticancer Activity of a Ruthenium Arene Peptide Conjugate

Organometallic Ru(arene)–peptide bioconjugates with potent in vitro anticancer activity are rare. We have prepared a conjugate of a Ru(arene) complex with the neuropeptide [Leu⁵]‐enkephalin. [Chlorido(η⁶‐p‐cymene)(5‐oxo‐κO‐2‐{(4‐[(N‐tyrosinyl‐glycinyl‐glycinyl‐phenylalanyl‐leucinyl‐NH₂)propanamido]‐1H‐1,2,3‐triazol‐1‐yl)methyl}‐4H‐pyronato‐κO)ruthenium(II)] ( 8 ) shows antiproliferative activity in human ovarian carcinoma cells with an IC₅₀ value as low as 13 μM , whereas the peptide or the Ru moiety alone are hardly cytotoxic. The conjugation strategy for linking the Ru(cym) (cym=η⁶‐p‐cymene) moiety to the peptide involved N‐terminal modification of an alkyne‐[Leu⁵]‐enkephalin with a 2‐(azidomethyl)‐5‐hydroxy‐4H‐pyran‐4‐one linker, using Cu^I‐catalyzed alkyne–azide cycloaddition (CuAAC), and subsequent metallation with the Ru(cym) moiety. The ruthenium‐bioconjugate was characterized by high resolution top‐down electrospray ionization mass spectrometry (ESI‐MS) with regard to peptide sequence, linker modification and metallation site. Notably, complete sequence coverage was obtained and the Ru(cym) moiety was confirmed to be coordinated to the pyronato linker. The ruthenium‐bioconjugate was analyzed with respect to cytotoxicity‐determining constituents, and through the bioconjugate models [{2‐(azidomethyl)‐5‐oxo‐κO‐4H‐pyronato‐κO}chloride (η⁶‐p‐cymene)ruthenium(II)] ( 5 ) and [chlorido(η⁶‐p‐cymene){5‐oxo‐κO‐2‐([(4‐(phenoxymethyl)‐1H‐1,2,3‐triazol‐1‐yl]methyl)‐4H‐pyronato‐κO}ruthenium(II)] ( 6 ) the Ru(cym) fragment with a triazole‐carrying pyronato ligand was identified as the minimal unit required to achieve in vitro anticancer activity.     

The synthesis,crystal structures and antimicrobial studies of C‐methyl‐substituted hexaaza macrocycle of Cu(II) having aromatic pendant arm

Cu(II) complexes of 14‐membered hexaaza macrocyclic ligand with C‐methyl substituent of the type [CuL](X)₂ (where L = 3,10‐bisbenzyl‐6,13‐dimethyl‐1,3,5,8,10,12‐hexaazacyclotetradecane, and X = ClO₄⁻, PF₆⁻) were synthesized by tandem reaction. They were characterized by spectral and single‐crystal X‐ray diffraction techniques. The complexes show distorted octahedral geometry and the counter ions are weakly coordinated to the metal ion at the axial positions. The macrocyclic ring adopts the trans‐III configuration with six‐ and five‐membered chelate rings in chair and gauche conformation, respectively. It was observed that in the solid state the arrangement of the coordination sphere is distorted octahedral whereas, in solution, a square‐planar structure is predominant. The molar conductance of the complexes indicates that the axially bonded anions are almost dissociated in acetonitrile solution. The Electron Paramagnetic Resonance (EPR) spectrum of complex 1 is axial and consistent with a d_x² − _y² ground state. The [CuL](ClO₄)₂ was found to be active against the tested microorganism. Copyright © 2011 John Wiley & Sons, Ltd.     

New Functional Cyclic Aminomethylphosphine Ligands for the Construction of Catalysts for Electrochemical Hydrogen Transformations

Eight‐membered cyclic functional bisphosphines, namely 1,5‐di‐aryl‐3,7‐di(2‐pyridyl)‐1,5‐diaza‐3,7‐diphosphacyclooctanes (aryl=2‐pyridyl, m‐tolyl, p‐tolyl, diphenylmethyl, benzyl, (R)‐(+)‐(α‐methyl)benzyl), with 2‐pyridyl substituents on the phosphorus atoms have been synthesized by condensation of 2‐pyridylphosphine, formaldehyde, and the corresponding primary amine. The structures of some of these bisphosphines have been investigated by X‐ray crystallography. The bisphosphines readily form neutral P,P‐chelate complexes [(κ²‐P,P‐L)MCl₂], cationic bis‐P,P‐chelate complexes [(κ²‐P,P‐L)₂M]²⁺, or a five‐coordinate complex [(κ²‐P,P‐L)₂NiBr]Br. The electrochemical behavior of two of the nickel complexes, and their catalytic activities in electrochemical hydrogen evolution and hydrogen oxidation, including the fuel‐cell test, have been studied.     

Transition metal complexes with thio­semicarbazide‐based ligands. XV. A square‐pyramidal NiII complex with an asymmetric coordination of 2,6‐di­acetyl­pyridine bis(S‐methyl­iso­thio­semicarbazone)

The title compound, [di­acetyl­pyridine bis(S‐methyl­iso­thio­semicarbazonato)]­iodo­nickel(II), [Ni(C₁₃H₁₈N₇S₂)I], is the first example of a complex involving the ²N coordination of the iso­thio­semicarbazide moiety. 2,6‐Di­acetyl­pyridine bis(S‐methyl­iso­thio­semicarbazone), as a potentially pentadentate ligand (N₅), is coordinated as a tetradentate species, whereby one (deprotonated) iso­thio­semicarbazide moiety is coordinated in the usual way (¹N⁴N), but the other (neutral) is bonded via the ²N atom only, the fourth ligator being the pyridine nitro­gen. The difference in coordination mode of the iso­thio­semicarbazide moiety is reflected in the ¹N—²N bond lengths of 1.359 (4) and 1.379 (3) Å in the deprotonated and undeprotonated moieties, respectively. The structure contains three fused chelate rings in a 5:5:6 arrangement. The six‐membered ring has a non‐planar conformation.     

Synthesis and Metal Complexes of Thiourea Ligands Containing Carbohydrate‐Derived Substituents

Two glucose‐derived thiourea derivatives, 2a and 2b , were prepared by addition of the corresponding amino sugars to a solution of 4‐nitrobenzoyl isothiocyanate (Scheme 1). The thioureas were isolated as colorless solids in good yields and were fully characterized by NMR spectroscopy, optical rotation, elemental analysis, and also by single‐crystal X‐ray diffraction. Attempts to obtain Cu^II and Ni^II bis(chelate) complexes with these thioureas failed. However, the C(1)‐protected thiourea derivative 2a reacted with orthopalladated acetato‐bridged dimers to afford the corresponding monomeric Pd^II complexes 3 and 4 (Scheme 2). In these compounds, the thiourea coordinates to the metal as monoanionic O,S chelate ligand, which was confirmed by X‐ray crystallography.     

Synthesis and characterization of new complexes of the type [Ru(CO)2Cl2 (2‐phenyl‐1,8‐naphthyridine‐kN) (2‐phenyl‐1,8‐naphthyridine‐kN′)]. Preliminary applications in homogeneous catalysis

Novel ruthenium (II) complexes were prepared containing 2‐phenyl‐1,8‐naphthyridine derivatives. The coordination modes of these ligands were modified by addition of coordinating solvents such as water into the ethanolic reaction media. Under these conditions 1,8‐naphthyridine (napy) moieties act as monodentade ligands forming unusual [Ru(CO)₂Cl₂(η¹‐2‐phenyl‐1,8‐naphthyridine‐ kN )(η¹‐2‐phenyl‐1,8‐naphthyridine‐kN′)] complexes. The reaction was reproducible when different 2‐phenyl‐1,8‐naphthyridine derivatives were used. On the other hand, when dry ethanol was used as the solvent we obtained complexes with napy moieties acting as a chelating ligand. The structures proposed for these complexes were supported by NMR spectra, and the presence of two ligands in the [Ru(CO)₂Cl₂(η¹‐2‐phenyl‐1,8‐naphthyridine‐ kN )(η¹‐2‐phenyl‐1,8‐naphthyridine‐kN′)] type complexes was confirmed using elemental analysis. All complexes were tested as catalysts in the hydroformylation of styrene showing moderate activity in N,N′‐dimethylformamide. Copyright © 2008 John Wiley & Sons, Ltd.