Search

Asymmetric one‐carbon homologation or ring expansion of ketones with formal insertion of carbene intermediate, is a challenging but useful strategy to construct a complex skeleton. Sc(III) and chiral ligands have been employed in this regard. However, due to flexible conformations and a variety of stereo models, the origin of stereochemistry remains ambiguous. Density functional theory (DFT) calculations were carried out to explore the interactions that control the stereoselectivity of a Sc(III)‐catalyzed asymmetric homologation. The trans influence of counterions was found to affect the coordination mode of ketone to Sc(III), and consequently affect the stereoselectivity. [ABSTRACT FROM AUTHOR]

[Fe(TPA)(N3)2](ClO4) and [Fe(TPA)Br2](ClO4), where TPA is tris-(2-pyridylmethyl)amine, crystallize in the monoclinic space group P21/c with a = 8.7029(5) Å, b = 19.168(1) Å, c = 13.5728(7) Å, β = 101.472(3)°, and a = 8.944(3) Å, b = 16.578(6) Å, c = 15.108(6) Å, β = 103.18(2)°, respectively. The structures were determined at 150 K from 3397 reflections (1426 observed) with R = 0.063 (Rw = 0.097), and at 115 K from 5617 reflections (2261 observed) with R = 0.057 (Rw = 0.065), respectively. In both cases, the iron is pseudo-octahedral with the two halide/pseudohalide ions cis. The Fe–X bond trans to the tertiary amine is shorter. The structures of [{Fe(TPA)X}2O](ClO4)2 where X = N3, Br, NCO, and two polymorphic forms of NCS, are also reported. The azide derivative [CH3CN solvate, monoclinic P21/n, a = 11.8038(11) Å, b = 22.547(2) Å, c = 17.344(2) Å, β = 106.972(4)°, determined at 100 K from 8972 reflections (4404 observed) with R = 0.087 (Rw = 0.145)] has two distinct Fe environments—the tertiary amine is cis to the oxido bridge at one site and is trans to the oxido bridge at the other site; the trans Fe–N3° distance is longer. Both the Br and NCO derivatives are monoclinic, C2/c [with a = 16.1480(17), b = 17.2036(13), c = 16.8521(12), β = 111.204(10), data collected at 293 K, 3753 reflections (2404 observed), R = 0.069 (Rw = 0.151), and a = 15.7470(9), b = 18.2270(11), c = 16.8950(8), β = 110.666(3), data collected at 90 K, 5392 reflections (3028 observed), R = 0.064 (Rw = 0.091), respectively]. Both polymorphs of the NCS derivative are monoclinic—one is P21/c and the other P21/n [a = 11.075(2), b = 15.436(2), c = 12.351(2), β = 95.528(7), data collected at 90 K, 5378 reflections (4345 observed), R = 0.068 (Rw = 0.198), and a = 12.396(2), b = 15.428(3), c = 44.505(8), β = 95.211(7), data collected at 110 K, 16,527 reflections (6540 observed), R = 0.069 (Rw = 0.105), respectively]. For the Br, NCO and NCS dimers, each iron of the [{Fe(TPA)X}2O]2+ unit is pseudo-octahedral with the halide/pseudohalide and oxide ions cis. The oxide bridge is linear, and the two halides/pseudohalides are anti. The ranking of trans influence of the ligands is O2− ≫ Br− > Cl− > N3− > NCO− ≥ NCS− > pyridyl > tertiary amine and the ranking of cis influence of the ligands is O2− ≫ N3− > NCO− > Cl− ≥ Br− > NCS−. The X-ray structures of two monomeric [Fe(TPA)(X)2](ClO4), where TPA is tris-(2-pyridylmethyl)amine and X = N3, and Br, and four dimeric [{Fe(TPA)Y}2O](ClO4)2, where Y =N3, Br, NCO, and NCS are presented and discussed. [ABSTRACT FROM AUTHOR]

The reaction of complexes [Pt(μ‐Cl)(arylolefin)]2 with various either weak σ‐donor LN,S,O ligands or strong σ‐donor NHCs ligands results in [PtCl(arylolefin)(LN,S,O)] with LN,S,O in a cis position to the C=C group (series A) or [PtCl(arylolefin)(NHC)] with NHC in a trans position to the C=C group (series B), respectively. The reaction directions are decided by the nature of the reactants, and not by the reaction conditions. Analyses of NMR spectra, XRD and DFT results indicate that the formation of series B is strongly dominated by electronic properties, while steric factors direct the reaction to form series A. The chemical shifts of ethylenic protons and carbons as well as the values of 2JPtH, 3JPtH for the allyl protons and the 3JPtH value for H6 in the aryl group are unambiguously different for series A and series B. In addition, one complex [Pt(μ‐Cl)(EtEug)]2 and five complexes [PtCl(arylolefin)(NHC)] have been characterized by single crystal XRD. [ABSTRACT FROM AUTHOR]

[Fe(TPA)Cl2](ClO4), where TPA is tris-(2-pyridylmethyl)amine, crystallizes in the orthorhombic space group P212121 with Z = 4, a = 8.6264(10) Å, b = 15.459(3) Å, and c = 16.008(3) Å. The structure was determined at 110 K from 4333 reflections (3520 observed) with R = 0.041 (Rw = 0.082). The iron is pseudo-octahedral with the two chloride ions cis. The Fe-Cl bond trans to the tertiary amine is shorter. [{Fe(TPA)Cl}2O](ClO4)2 exhibits two polymorphic monoclinic forms, and the monohydrate also crystallizes in a monoclinic form. For the P21/c polymorph, Z = 2, a = 10.839(2) Å, b = 15.956(3) Å, c = 12.416(2) Å, β = 107.024(10)°, and the structure was determined at 95 K from 6514 reflections (3974 observed) with R = 0.052 (Rw = 0.099). For the C2/c polymorph, Z = 4, a = 20.5023(17) Å, b = 15.2711(13) Å, c = 16.1069(11) Å, β = 124.465(4)°, and the structure was determined at 161 K from 6250 reflections (3130 observed) with R = 0.0632 (Rw = 0.1229). For the hydrate, P21/n, Z = 4, a = 16.201(2) Å, b = 16.980(3), c = 16.451(3), β = 112.234(5)°, and the structure was determined at 100 K from 12,745 reflections (6600 observed) with R = 0.097 (Rw = 0.190). In each of the [{Fe(TPA)Cl}2O]2+ units, each iron is pseudo-octahedral with the chloride and oxide ions cis. The oxide bridge is linear, and the two chlorides are anti. The Fe-N distance for the pyridyl ring trans to the oxide bridge is quite long due to the trans influence of the oxide. The X-ray structures of [Fe(TPA)Cl2](ClO4), where TPA is tris-(2-pyridylmethyl)amine, and three polymorphs of dimeric [{Fe(TPA)Cl}2O](ClO4)2 are presented and discussed. [ABSTRACT FROM AUTHOR]

The title compound, an (N^C)-cyclometalated gold(III) diazide, namely, diazido[5-ethoxycarbonyl-2-(5-ethoxycarbonylpyridin-2-yl)phenyl-κ2C1,N]gold(III), [Au(C17H16NO4)(N3)2] or Au(ppyEt)(N3)2, was synthesized by reacting Au(ppyEt)Cl2 with NaN3 in water for 24 h. The complex has been structurally characterized and features a gold center with a square-planar environment. The Au—N(azide) bond lengths are significantly different depending on the influence of the atom trans to the azide group [Au—N(trans to C) of 2.067 (2) Å versus Au—N(trans to N) of 2.042 (2) Å]. The azide groups are twisted in-and-out of plane by 56.2 (2)°.

The crystal structures of the complexes (SP-4-2)-cis-bis­[8-(di­methyl­phosphan­yl)quinoline-κ²N,P]nickel(II) bis­(perchlorate) nitro­methane monosolvate, [Ni(C11H12NP)2](ClO4)2·CH3NO2 (1), and (SP-4-2)-cis-bis­[8-(di­methyl­phos­phan­yl)quinoline-κ²N,P]platinum(II) bis­(tetra­fluoro­borate) aceto­nitrile monosolvate, [Pt(C11H12NP)2](BF4)2·C2H3N (2), are reported. In both complex cations, two phosphanyl­quinolines act as bidentate P,N-donating chelate ligands and form the mutually cis configuration in the square-planar coordination geometry. The strong trans influence of the di­methyl­phosphanyl donor group is confirmed by the Ni—N bond lengths in 1, 1.970 (2) and 1.982 (2) Å and, the Pt—N bond lengths of 2, 2.123 (4) and 2.132 (4) Å, which are relatively long as compared to those in the analogous 8-(di­phenyl­phosphan­yl)quinoline complexes. Mutually cis-positioned quinoline donor groups would give a severe steric hindrance between their ortho-H atoms. In order to reduce such a steric congestion, the NiII complex in 1 shows a tetra­hedral distortion of the coordination geometry, as parameterized by τ4 = 0.199 (1)°, while the PtII complex in 2 exhibits a typical square-planar coordination geometry [τ4 = 0.014 (1)°] with a large bending deformation of the ideally planar Me2Pqn chelate planes. In the crystal structure of 2, three F atoms of one of the BF4− anions are disordered over two sets of positions with refined occupancies of 0.573 (10) and 0.427 (10). [ABSTRACT FROM AUTHOR]

The title compound, an (N^C)-cyclo­metalated gold(III) diazide, namely, di­azido­[5-eth­oxy­carbonyl-2-(5-eth­oxy­carbonyl­pyridin-2-yl)phenyl-κ²C¹,N]gold(III), [Au(C17H16NO4)(N3)2] or Au(ppyEt)(N3)2, was synthesized by reacting Au(ppyEt)Cl2 with NaN3 in water for 24 h. The complex has been structurally characterized and features a gold center with a square-planar environment. The Au—N(azide) bond lengths are significantly different depending on the influence of the atom trans to the azide group [Au—N(trans to C) of 2.067 (2) Å versus Au—N(trans to N) of 2.042 (2) Å]. The azide groups are twisted in-and-out of plane by 56.2 (2)°. [ABSTRACT FROM AUTHOR]

The reaction of 1,1′‐Li2[(2,2′‐C2B10H10)2] with the cyclometallated gold(III) complex (C^N)AuCl2 afforded the first examples of gold(III) dicarboranyl complexes. The reactivity of these complexes is subject to the trans‐influence exerted by the dicarboranyl ligand, which is substantially weaker than that of non‐carboranyl anionic C‐ligands. In line with this, displacement of coordinated pyridine by chloride is only possible under forcing conditions. While treatment of (C^N)Au{(2,2′‐C2B10H10)2} (2) with triflic acid leads to Au−C rather than Au−N bond protonolysis, aqueous HBr cleaves the Au−N bond to give the pyridinium bromo complex 7. The trans‐influence of a series of ligands including dicarboranyl and bis(dicarboranyl) was assessed by means of DFT calculations. The analysis demonstrated that it was not sufficient to rely exclusively on geometric descriptors (calculated or experimental) when attempting to rank ligands for their trans influence. Complex (C^N)Au(C2B10H11)2 containing two non‐chelating dicarboranyl ligands was prepared similar to 2. Its reaction with trifluoroacetic acid also leads to Au−N cleavage to give trans‐(Hpy^C)Au(OAcF)(C2B10H11)2 (8). In crystals of 8 the pyridinium N−H bond points towards the metal centre, while in 7 it is bent away. The possible contribution of gold(III)⋅⋅⋅H−N hydrogen bonding in these complexes was investigated by DFT calculations. The results show that, unlike the situation for platinum(II), there is no evidence for an energetically significant contribution by hydrogen bonding in the case of gold(III). [ABSTRACT FROM AUTHOR]

In this work, we study the trans influence of boryl ligands and other commonly used non-boryl ligands in order to search for a more active catalyst than the ruthenium dihydride complex Ru(PNP)(CO)H2 for the hydrogenation of CO2. The theoretical calculation results show that only the B ligands exhibit a stronger trans influence than the hydride ligand and are along increasing order of trans influence as follows: –H < –BBr2 < –BCl2 ≈ –B(OCH)2 < –Bcat < –B(OCH2)2 ≈ –B(OH)2 < –Bpin < –B(NHCH2)2 < –B(OCH3)2 < –B(CH3)2 < –BH2. The computed activation free energy for the direct hydride addition to CO2 and the NBO analysis of the property of the Ru–H bond indicate that the activity of the hydride can be enhanced by the strong trans influence of the B ligands through the change in the Ru–H bond property. The function of the strong trans influence of B ligands is to decrease the d orbital component of Ru in the Ru–H bond. The design of a more active catalyst than the Ru(PNP)(CO)H2 complex is possible.

The ground (S 0) and excited triplet (T 1) electronic states and corresponding optical spectra of a series of cationic complexes [RuH(CO)L(PPh 3) 2 ]+ (L = 2,2′-bipyridyl) (Rubpy), 4,4′-dicarboxylic-2,2′-bipyridyl(Rudcbpy),bis-4,4′-(N-methylamide)-2,2′-bipyridyl(Rudamidebpy),bis-4,4′-(methyl)-2,2′-bipyridyl(RudMebpy),[Ru(CO) 2 dcbpy(PPh 3) 2 ]2+(Ru(2CO)dcbpy),and [Ru(H) 2 dcbpy(PPh 3) 2 ] (Ru(2H)dcbpy) have been studied by combined Density Functional/Time-Dependent Density Functional (DFT/TDDFT) techniques using different combinations of DFT exchange-correlation functionals and basis sets. PBE0/LANL2DZ provided more accurate geometries to describe S 0 whereas B3LYP/LANL2DZ predicted spectral energies that correlated better with the available experiment data. The Ru (II) complexes with different substituents emit photons ranging from 560 to 610 nm in the series RudMebpy, Rubpy, Rudamidebpy, Rudcbpy. The calculations predicted a maximum emission at about 540 nm for the complex constructed from two carbonyl π-acceptors ligands trans to the dcbpy, while an emission in the far infrared region is calculated when two H σ-donor ligands trans to the dcbpy. Our calculation results show correlations between HOMO-LUMO energy gap, Stokes shift, and T 1 distortion, which reflect the different effects of electron-withdrawing and donating groups. We proposed that these correlations can be used to predict the photophysical properties for new complexes. The correlation between HOMO-LUMO energy gap, absorption and emission energies, Stokes shift, and the geometric distortion in the triplet excited state (T 1) as a result of introducing electron-withdrawing substituent (-COOH) (Rudcbpy) in [RuH(CO)bpy(PPh 3) 2 ]+ (Rubpy). Image 1 • Combined DFT/TDDFT calculations reproduced the spectroscopic data of Ru(bpy)(PPh 3) 2 derivatives. • Evidence of the trans influence and the substituents effects to control the HOMO-LUMO energy gap and Stokes shift. • Small HOMO-LUMO energy gap is associated with large geometric distortion in the triplet excited state and large Stokes shift. [ABSTRACT FROM AUTHOR]

A series of picolinato chelated acylrhodium(III) organometallics have been prepared and characterized by different spectroscopic techniques and by X-ray crystallography. Picolinato chelation is attended with the cleavage of the Rh Cl bonds and concomitant hydrolysis of the aldiminium function. Density function theory (DFT) and time-dependent DFT calculations are also reported. The heterogeneous phase reaction of Rh(MeL sb)(PPh 3) 2 Cl 2 (1) with the sodium salt of three differently substituted picolinate ligands [Na(R-pic), R = H, Me, Cl] in dichloromethane–acetone–water medium afforded the complexes of the type Rh(L al)(PPh 3) 2 (R-pic) (2 (R)) in excellent yield. These are the first examples of acylrhodium(III) complexes with the picolinate ligand. The chelation of the picolinate ligand is attended with the cleavage of the two Rh Cl bonds and concomitant hydrolysis of the aldiminium function in 1. The picolinate ligand is coordinated to the rhodium center as bidentate N,O-donor forming five-membered chelate ring. The spectral (UV–Vis, IR, NMR) and electrochemical data of the complexes are reported. The identity of 2 (H) has been established by single-crystal X-ray structure determination which revealed distorted octahedral RhCNO 2 P 2 coordination sphere. The pairs (P,P), (C,O) and (O,N) define the three trans directions. The electronic structures and the absorption spectra of the complexes are also scrutinized by the density functional theory (DFT) and time-dependent DFT analysis. [ABSTRACT FROM AUTHOR]

The molecular structure of the benzimidazol‐2‐ylidene–PdCl2–pyridine‐type PEPPSI (pyridine‐enhanced precatalyst, preparation, stabilization and initiation) complex {1,3‐bis[2‐(diisopropylamino)ethyl]benzimidazol‐2‐ylidene‐κC2}dichlorido(pyridine‐κN)palladium(II), [PdCl2(C5H5N)(C23H40N4)], has been characterized by elemental analysis, IR and NMR spectroscopy, and natural bond orbital (NBO) and charge decomposition analysis (CDA). Cambridge Structural Database (CSD) searches were used to understand the structural characteristics of the PEPPSI complexes in comparison with the usual N‐heterocyclic carbene (NHC) complexes. The presence of weak C—H...Cl‐type hydrogen‐bond and π–π stacking interactions between benzene rings were verified using NCI plots and Hirshfeld surface analysis. The preferred method in the CDA of PEPPSI complexes is to separate their geometries into only two fragments, i.e. the bulky NHC ligand and the remaining fragment. In this study, the geometry of the PEPPSI complex is separated into five fragments, namely benzimidazol‐2‐ylidene (Bimy), two chlorides, pyridine (Py) and the PdII ion. Thus, the individual roles of the Pd atom and the Py ligand in the donation and back‐donation mechanisms have been clearly revealed. The NHC ligand in the PEPPSI complex in this study acts as a strong σ‐donor with a considerable amount of π‐back‐donation from Pd to Ccarbene. The electron‐poor character of PdII is supported by π‐back‐donation from the Pd centre and the weakness of the Pd—N(Py) bond. According to CSD searches, Bimy ligands in PEPPSI complexes have a stronger σ‐donating ability than imidazol‐2‐ylidene ligands in PEPPSI complexes. [ABSTRACT FROM AUTHOR]

The crystal structures of dichloridopalladium(II), -platinum(II) and -rhodium(III) complexes containing 8-(diphenylphosphanyl)quinoline, (SP-4)-[PdCl2(C21H16NP)], (1) [systematic name: dichlorido(8-diphenylphosphanylquinoline)palladium(II)], (SP-4)-[PtCl2(C21H16NP)]·CH2Cl2, (2) [systematic name: dichlorido(8-diphenylphosphanylquinoline)platinum(II) dichloromethane monosolvate], and (OC-6–32)-[RhCl2(C21H16NP)2]PF6·0.5CH2Cl2·0.5CH3OH, (3) [systematic name: cis-dichloridobis(8-diphenylphosphanylquinoline)rhodium(III) hexafluoridophosphate dichloromethane/methanol hemisolvate] are reported. In these complexes, the phosphanylquinoline acts as a bidentate ligand, forming a planar asymmetrical five-membered chelate ring. The palladium(II) and platinum(II) complex molecules in (1) and (2), respectively, show a typical square-planar coordination geometry and form a dimeric structure through an intermolecular π–π stacking interaction between the quinolyl rings. The centroid–centroid distances between the stacked six-membered rings in (1) and (2) are 3.633 (2) and 3.644 (2) Å, respectively. The cationic rhodium(III) complex in (3) has a cis(Cl),cis(P),cis(N) (OC-6–32) configuration of the ligands, in which two kinds of intramolecular π–π stacking interactions are observed: between the quinolyl and phenyl rings and between two phenyl rings, the centroid–centroid distances being 3.458 (2) and 3.717 (2) Å, respectively. The PF6− anion in (3) is rotationally disordered, the site occupancies of each F atom being 0.613 (14) and 0.387 (14). The CH2Cl2 and CH3OH solvent molecules are also disordered and equal site occupancies of 0.5 are assumed.

Copyright of Kobunshi Ronbunshu is the property of Society of Polymer Science and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the title compound, [Re(C10H6NO2)(CO)3{As(C6H5)3}], the coordination environment of ReI is that of a distorted octahedron. Three coordination sites are occupied by three carbonyl groups in a facial arrangement and the remaining three sites by triphenylarsane and deprotonated quinaldic acid in As-mono- and N,O-bidentate fashions, respectively. In the crystal, the complexes are linked through weak C—H...O hydrogen bonds, forming a three-dimensional network. It worth noting that, as far as we know, this complex is the first ReI triphenylarsane tricarbonyl compound to be reported.

Acetonitrile suspensions of the dichlorido complexes [MCl2(κ4 C,N, N′,P− L)] [M=Rh ( 1), Ir ( 2)] react with AgSbF6 in a 1:2 molar ratio affording the bis-acetonitrile complexes [M(κ4 C,N, N′,P− L)(NCMe)2][SbF6]2 ( 3 and 4). The reaction takes place in a sequential manner and the intermediates can be isolated varying the M:Ag molar ratio. In a 2:1 molar ratio, it affords the dimetallic monochlorido-bridged compounds [{MCl(κ4 C,N, N′,P− L)}2( μ-Cl)][SbF6] ( 5 and 6). In a 1:1 molar ratio, the monosubstituted solvato-complexes [MCl(κ4 C,N, N′,P− L)(Solv)][SbF6] (Solv=H2O, MeCN, 7- 10) were obtained. Finally, in a 2:3 molar ratio, it gives complexes 11 and 12 of formula [{M(κ4 C,N, N′,P− L)(NCMe)( μ-Cl)}2Ag][SbF6]3 in which a silver cation joints two cationic monosubstituted acetonitrile-complexes [MCl(κ4 C,N, N′,P− L)(NCMe)]+ through the remaining chlorido ligands and two Ag⋅⋅⋅C interactions with one of the phenyl rings of each PPh2 group. In all the complexes, the aminic nitrogen and the central metal atom are stereogenic centers. In the trimetallic complexes 11 and 12, the silver atom is also a stereogenic center. The formation of the cation of the dimetallic complexes 5 and 6, as well as that of the trimetallic complexes 11 and 12, takes place with chiral molecular self-recognition. Experimental data and DFT calculations provide plausible explanations for the observed molecular recognition. The new complexes have been characterized by analytical, spectroscopic means and by X-ray diffraction methods. [ABSTRACT FROM AUTHOR]

This review includes more than 100 monomeric derivatives in which the Pt(II) atom is in a distorted square planar environment with inner coordination spheres of PtP2X2 (X=Br, I, Se, Si or Te). The P-donor ligands are organomonophosphanes. These complexes crystallize in three crystal systems: orthorhombic (5.7%), triclinic (37.5%) and monoclinic (56.8%). The X-donor ligands are mono-Br, Se, Si, I or Te or bi- Se, Si, Te, dentate. The chelating ligands form a wide variety of three-, four-, five-, six-, and even seven-membered metallocycles. There are at least two types of isomerism: cis-trans and distortion. Several relationships were found and are discussed. [ABSTRACT FROM AUTHOR]

Surprisingly general effects of trans ligands L on the ligand NMR shifts in third-row transition-metal complexes have been found by quasi-relativistic computations, encompassing 5d10, 5d8, and to some extent even 5d6 situations. Closer analysis, with emphasis on 1H shieldings in a series of linear HAuILq complexes, reveals a dominance of spin-orbit (SO) effects, which can change sign from appreciably shielding for weak trans ligands to appreciably deshielding for ligands with strong trans influence. This may be traced back to increasing destabilization of a σ-type MO at scalar relativistic level, which translates into very different σ-/π-mixing if SO coupling is included. For the strongest trans ligands, the σ-MO may move above the highest occupied π-type MOs, thereby dramatically reducing strongly shielding contributions from predominantly π-type spinors. The effects of SO-mixing are in turn related to angular momentum admixture from atomic spinors at the metal center. These SO-induced trends hold for other nuclei and may also be used to qualitatively predict shifts in unknown complexes. [ABSTRACT FROM AUTHOR]

The influence of the axial ligand on the Co–pyridine bond distance and on the extent of the pyridine dissociation was investigated in a series of cobaloximes featuring different inorganic ligands (X = Cl, N 3 , NO 2 ) together with the corresponding metallorganic derivatives: ClCo( dmg H) 2 Py ( 1 ), N 3 Co( dmg H) 2 Py ( 2 ), NO 2 Co( dmg H) 2 Py ( 3 ), EtCo( dmg H) 2 Py ( 4 ), ClCo( dpg H) 2 Py ( 5 ) and EtCo( dpg H) 2 Py ( 6 ). The molecular structures of NO 2 Co( dmg H) 2 Py ( 3 ), EtCo( dmg H) 2 Py ( 4 ) and EtCo( dpg H) 2 Py ( 6 ) were determined by X-ray crystallography. The analysis of the bond distances in the X–Co–Py fragment showed an increment of about 0.1 Å in the Co–Py bond distance when passing from the chloride derivatives 1 or 5 to the ethyl derivatives 4 or 6 . In the dmg H series, the Co–Py bond distance increases in the order 1 < 2 < 3 < 4 . The dissociation reactions in which the pyridine ligand is displaced by the solvent was also explored via NMR. At 303 K, the lowest equilibrium constant was observed for 1 ( K diss = 5.55 × 10 −5 M) while the highest one ( K diss = 1.37 × 10 −3 M) was determined for 4 . The corresponding standard free energy variations span over the range 3.97–5.90 kcal/mol. The topological properties of the electronic density at bond critical points in the X–Co–Py fragment revealed that the bonds between the cobalt atom and the axial ligands are predominantly ionic with slight covalent contribution. [ABSTRACT FROM AUTHOR]

In the title compound, [Re(C10H6NO2)(CO)3{As(C6H5)3}], the coordination environment of ReI is that of a distorted octahedron. Three coordination sites are occupied by three carbonyl groups in a facial arrangement and the remaining three sites by triphenylarsane and deprotonated quinaldic acid in As-mono- and N,O-bidentate fashions, respectively. In the crystal, the complexes are linked through weak C--H···O hydrogen bonds, forming a three-dimensional network. It worth noting that, as far as we know, this complex is the first ReI triphenylarsane tricarbonyl compound to be reported. [ABSTRACT FROM AUTHOR]

In the title compound, [Rh(C2H11B9)(NO3)(C18H15P)2]·2.2CH2Cl2, studied as a 2.2-solvate of what was assumed to be dichloromethane, the nitrate ligand lies cis with respect to both cage C atoms. Accordingly, the compound displays a pronounced preferred exopolyhedral ligand orientation (ELO) which is traced to both the greater trans influence of the cage B over the cage C atoms and the greater trans influence of the triphenylphosphane ligands over the nitrate ligand. The overall molecular architecture therefore agrees with that of a number of similar 3- L-3,3- L′2-3,1,2- closo- MC2B9H11 species in the literature. [ABSTRACT FROM AUTHOR]

A new class of chiral Pd(II) complexes bearing a rigid, bidentate C,N-ligand are synthesized and characterized. The ligands are obtained in good yield via a simple five-step synthetic route beginning with cheap and commercially available amino alcohols. The structure of one of these new complexes is determined by X-ray crystallography. This data shows the expected large trans effect difference between the N and C donors (0.07 Å Pd Cl bond length difference) as well as a boat conformation of the 6-membered chelate ring. [ABSTRACT FROM AUTHOR]

A library of unsymmetrical SCN pincer palladacycles, [ClPd{2-pyr-6-(RSCH2)C6H3}], R = Et, Pr, Ph, p-MePh, and p-MeOPh, pyr = pyridine, has been synthesized via C–H bond activation, and used, along with PCN and N’CN unsymmetrical pincer palladacycles previously synthesized by the authors, to determine the extent to which the trans influence is exhibited in unsymmetrical pincer palladacycles. The trans influence is quantified by analysis of structural changes in the X-ray crystal and density functional theory (DFT) optimized structures and a topological analysis of the electron density using quantum theory of atoms in molecules (QTAIM) to determine the strength of the Pd-donor atom interaction. It is found that the trans influence is controlled by the nature of the donor atom and although the substituents on the donor-ligand affect the Pd-donor atom interaction through the varied electronic and steric constraints, they do not influence the bonding of the ligand trans to it. The data indicate that the strength of the trans influence is P > S > N. Furthermore, the synthetic route to the family of SCN pincer palladacycles presented demonstrates the potential of late stage derivitization for the effective synthesis of ligands towards unsymmetrical pincer palladacycles.

Highlights: [•] Products of the reaction of rhenates(VII) with hydrogen chloride in methanol were isolated. [•] No trans influence of the short Re–O bond in trans-tetrachloridomethoxidooxidorhenate(VI) anion is observed. [•] EPR and magnetic properties studies confirm the Re(VI) oxidation state. [•] DFT studies are presented for trans-tetrachloridoalkoxidooxidorhenate(VI) anions. [ABSTRACT FROM AUTHOR]

Highlights: [•] Pd–C bonds have dual covalent/electrostatic nature. [•] EDA findings explain changes in BDEs. [•] Trans influence of X is identified. [•] Localization regions of Pd’s outer core electrons are revealed. [ABSTRACT FROM AUTHOR]

Electronegativity and chemical hardness are important conceptual tools in organic and organometallic chemistry. Computational chemistry can aid understanding of these concepts by simulating fictitious substituents with smoothly varying electronegativity and chemical hardness. This work shows that Gaussian smearing of an atom’s nuclear charge distribution enables variation of its electronegativity and chemical hardness, without changing the total molecule charge. Tunable covalent, Lewis acid, and Lewis base substituents give chemically reasonable results in several canonical chemical reactions. These include hard–soft acid–base effects on thiocyanate and enolate isomerization, ligand trans influences on the stability of organometallic complexes and the thermodynamics of reductive elimination, and substituent effects on the proton affinities of benzene derivatives. The results illustrate the utility of these fictitious substituents and motivate their use as interpretive tools. [ABSTRACT FROM AUTHOR]

Abstract: The naphthalene ruthenacarboranes 3-(η-C10H8)-3,1,2-closo-RuC2B9H11 (1), 4-(η-C10H8)-4,1,6-closo-RuC2B10H12 (2) and 4-(η-C10H8)-4,1,10-closo-RuC2B10H12 (4) have been synthesised by the general method of reaction of a carborane dianion with [RuCl2(COD)] x in the presence of excess naphthalene under THF reflux. Compounds 4-(η-C10H8)-4,1,8-closo-RuC2B10H12 (3) and 4-(η-C10H8)-4,1,12-closo-RuC2B10H12 (5) were prepared from 2 and 4, respectively, by thermolysis in refluxing toluene. Compounds 1–5 were characterised spectroscopically and crystallographically. For the supraicosahedral ruthenacarboranes 2–5 the main structural point of interest was the conformation of the naphthalene ligand with respect to the ruthenacarborane cage, in comparison with conformations of the analogous ferracarboranes 4-(η-C10H8)-4,1,x-closo-FeC2B10H12 previously studied computationally. Good agreement is found between experimental and computational conformations for compounds 2, 3 and 4. Crystallographic disorder in 5 renders comparison between theoretical and experimental conformations difficult in this case. [Copyright &y& Elsevier]

Trans influence of triphenylphosphines and pseudohalogens on Ni-S bonds of NiSPN and NiSPC chromophores has been investigated by synthesizing and characterizing them. The complexes show the characteristic thioureide IR band at ∼ 1530 cm. Electronic spectrum of the cyanide analogue shows a strong blue shift relative to others. X-ray structures of [Ni(pipdtc)(4-MP)(NCS)] ( 1), [Ni(pipdtc)(PPh)(NCS)] ( 2) and [Ni(pipdtc)(PPh)(CN)] ( 3) (pipdtc = piperidinecarbodithioate anion, 4-MP = tri(4-methylphenyl)phopshine) are reported. Ni-S bond distance trans to 4-MP( 1) is longer than the distances in ( 2) and ( 3) and Ni-S bond distances trans to Ni-NCS/CN decrease as follows: ( 3) > ( 2) > ( 1). Particularly, 4-MP shows a highly significant trans influence than triphenylphosphine on Ni-S bond. Similarly, CN exerts a marginally significant trans influence compared to NCS-. Thioureide C-N distances are relatively very short due to the drift of electron density towards the metal. The Ni-N-C angle (163.5(2)°) observed in ( 2) indicates deviation from linearity to a larger extent compared to that in ( 1) (176.3(3)°) due to the steric effect of the 4-methyl group. The reduction potentials (CV) for the mixed ligand complexes are much less compared to that of the parent NiS chromophore due to the π-acidic phosphines. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The ligand (C6H5)2P(O)NC4H8O (L) was synthesized and used to prepare new octahedral complex mer-[(C6H5)2(NC4H8O)PO]3LaCl3 (LaL3Cl3). In the solid state structure of LaL3Cl3, the chloride anion trans to neutral ligand L3 (Cl2) has an inverse trans influence, while the La–O3 (trans to Cl2) distance is slightly shorter than the La–O1 and La–O2 distances (La–O1 trans to La–O2). On the contrary, the La–O3 distance is considerably longer than the La–O1 and La–O2 distances in the gas phase structure of LaL3Cl3, as a result of the normal trans influence of Cl2. The La–Cl2 (trans to La–O3) binding energy is larger in magnitude than the calculated values for the La–Cl1 and La–Cl3 bonds. The directional dependence of La–ligand bonding is in agreement with the trends in calculated electron density (ρ) values at bond critical points (bcp’s) and wiberg bond indices. Based on the results of atoms in molecules (AIM) analysis, the positive values for the electronic energy density, H(r), at the bcp of La–O bond paths suggest an ionic character for the La–O bonds, and the small negative values for H(r), at the bcp of La–Cl bonds, indicate a partial covalent character of the La–Cl interaction. The NBO analysis reveals a partial occupancy of La 5d and 6s orbitals which is originated from the ligand to metal charge transfer (LMCT) in complex LaL3Cl3, agreeing with the loss of electron density from the coordinated ligands L and chloride counterions. [ABSTRACT FROM AUTHOR]

Abstract: DFT calculations using MPWB1K method with COSMO continuum solvation model have been carried out to quantify the trans influence of various X ligands (E X) in [PtIICl3X]n− complexes as well as the mutual trans influence of two X and Y ligands (E XY) in [PtIICl2XY]n− complexes. A quantitative structure energy relationship (QSER) is derived for predicting the E XY using E X and E Y and this relationship showed a strong similarity to a QSER derived for predicting E XY of [PdIICl2XY]n− complexes. Quantification of the contributions of E X and E XY to the bond dissociation energy of the ligand X (BDE X) in complexes of the type [MIIX(Y)X′(Y′)] (M = Pd, Pt) is also achieved. The BDE X of any ligand X in these complexes can be predicted using the equations, viz. BDE X(Pd) = 1.196E X − 0.603E XY − 0.118E X’Y’ + 0.442D X + 15.169 for Pd(II) complexes and BDE X(Pt) = 1.420E X − 0.741E XY − 0.125E X’Y’ + 0.498D X + 13.852 for Pt(II) complexes, where D X corresponds to the bond dissociation energy of X in [MIICl3X]n− complexes. These expressions suggest that the mutual trans influence from X and Y is more dominant than the mutual trans influence from X′ and Y′ and both factors contribute significantly to the weakening of M–X bond. We also obtained a strong linear relationship between E X and the electron density ρ(r) at the bond critical point of M–Cl bond trans to the X in [MIICl3X]n− and this allows us to express the BDE X(Pd) and BDE X(Pt) in terms of only the ρ(r) and D X. We have demonstrated that using a database comprising of D X and the ρ(r), the bond dissociation energy of X in complexes of the type [MIIX(Y)X′(Y′)] can be predicted. [Copyright &y& Elsevier]

Abstract: In [PtX(PPh3)3]+ complexes (X=F, Cl, Br, I, AcO, NO3, NO2, H, Me) the mutual cis and trans influences of the PPh3 groups can be considered constants in the first place, therefore the one bond Pt–P coupling constants of P( cis ) and P( trans ) reflect the cis and trans influences of X. The compounds [PtBr(PPh3)3](BF4) (2), [PtI(PPh3)3](BF4) (3), [Pt(AcO)(PPh3)3](BF4) (4), [Pt(NO3)(PPh3)3](BF4) (5), and the two isomers [Pt(NO2-O)(PPh3)3](BF4) (6a) and [Pt(NO2-N)(PPh3)3](BF4) (6b) have been newly synthesised and the crystal structures of 2 and 4·CH2Cl2·0.25C3H6O have been determined. From the 1 J PtP values of all compounds we have deduced the series: I>Br>Cl>NO3 >ONO>F>AcO>NO2 >H>Me (cis influence) and Me>H>NO2 >AcO>I>ONO>Br>Cl>F>NO3 (trans influence). These sequences are like those obtained for the (neutral) cis- and trans-[PtClX(PPh3)2] derivatives, showing that there is no dependence on the charge of the complexes. On the contrary, the weights of both influences, relative to those of X=Cl, were found to depend on the charge and nature of the complex. [ABSTRACT FROM AUTHOR]

The trans influence of ligands T in trans-[Ni(Cl)2NH3T]n complexes with T-&dbond;B(Me)2-, H-, CP-, CH2CH3-, CN-, HC&tbond;C-, Cl-, F- for n = -1 and T&dbond;PF3, PH3, P(CH3)3, CO for n = 0 has been analyzed with the help of the extended transition state (ETS) energy decomposition scheme as well as the natural orbitals for chemical valence (NOCV) method. The TCl2Ni&bond;NH3 bond is made up of the bonding interaction between the empty σNi acceptor orbital on the [TCl2Ni]n fragment and the σNH3 donor orbital. The σNi orbital is in turn an out-of-phase combination between dz2 on the metal and an occupied σT orbital: σNi = dz2 - C1 × σT. It is shown that the trans influence is related to the contribution (C1) to σNi from σT. Thus, the smaller the contribution C1 to σNi the larger the <σNi|σNH3> overlap and the stronger the TCl2Ni&bond;NH3 bond. The contribution C1 is in turn related to the orbital energy ℇ(σT) of T. Thus the lower ℇ(σT) is, the smaller is C1. There is thus an inverse relation between the trans influence of a ligand T and its electronegativity. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009 [ABSTRACT FROM AUTHOR]

Abstract: The synthesis and characterization of ruthenium(II) complexes, [RuCl2(dmso)2(bfmh)] (1; dmso=dimethyl sulfoxide, bfmh=benzoic acid furan-2-ylmethylene-hydrazide), [RuCl2(dmso)2(btmh)](2; btmh=benzoic acid thiophen-2-ylmethylene-hydrazide), [RuCl2(dmso)2(bfeh)](3; bfeh=benzoic acid (1-furan-2-yl-ethylidene)-hydrazide) and [RuCl2(dmso)2(bpeh)](4; bpeh=benzoic acid (1-pyridin-2-yl-ethylidene)-hydrazide) are described. The ligands, when treated with either cis-[RuCl2(dmso)4] or trans(Cl)–[RuCl2(dmso)2(bpy)], resulted in the same products. This has been confirmed by IR spectra and single crystal X-ray diffraction studies. The redox behaviors of the complexes have been found to be strongly dependent on the electronic nature of the moieties present in the hydrazone ligands. The binding of the complexes to Herring sperm DNA has been studied by absorption titration and cyclic voltammetry. But, due to the random change in the absorption on the addition of DNA, only a qualitative result rather than a quantitative result has been obtained. All the complexes have been found to bind DNA through different modes to different extents. The antibacterial properties of the ligands and the complexes have been studied against five pathogenic bacteria and also the minimum inhibitory concentrations (MIC) of all the ligands and complexes 2 and 4 have been evaluated. [Copyright &y& Elsevier]

The use of COSzY and NOESY 1H NMR techniques allows for the assignment of 1H NMR chemical shifts for the bis(2,2'-bipyridine)carbonatocobalt(III) ion. These assignments are further confirmed by DFT GIAO-NMR calculations using the model chemistry B3LYP/6-31G(d,p) and invoking the IEF-PCM representing acetone. These computations also allow for initial quantification of a cis influence on the chemical shift due to anisotropic ring currents and a much less pronounced trans influence on the chemical shift due to inductive effects. The computational model employed is also compared to previously accepted models for anisotropic effects. [ABSTRACT FROM AUTHOR]

Octahedral, six-coordinate Co2+ can exist in two spin states: S = 3/2 and S = 1/2. The difference in energy between high spin (S = 3/2) and low spin (S = 1/2) is dependent on both the ligand mix and coordination stereochemistry. B3LYP calculations on combinations of neutral imidazole, NH3, and H2O ligands show that low-spin isomers are stabilized by axial H2O ligands and in structures that also include trans pairs of equatorial NH3 and protonated imidazole ligands, spin crossover structures are predicted from spin state energy differences. Occupied Co d orbitals from the DFT calculations provide a means of estimating effective ligand strength for homoleptic and mixed ligand combinations. These calculations suggest that in a labile biological system, a spin crossover environment can be created. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 [ABSTRACT FROM AUTHOR]

The complex [Rh(O2Cisoq)(H)(SnPh3)(PPh3)2] (O2Cisoq = isoquinoline-1-carboxylate), characterized by x-ray crystallography, was used as a precursor to three-center bonded complexes [Rh(O2Cisoq)(η²-HSnPh3) (PPh3)(4-Rpy)] (R = carbomethoxy, acyl, bromo, aldehyde, hydrogen, methoxy, dimethylamino), which were prepared in situ from the bis(phosphine) complex in dichloromethane by addition of the pyridine. Of two isomeric forms of [Rh(O2Cisoq)(η²-HSnPh3) (PPh3)(4-Rpy)], one, with 4-Rpy positioned trans to tin, is formed at 0°C; the other, with isoquinoline positioned trans to tin, is formed by partial (25-50%) conversion of the first isomer (in solution) upon warming to 30-35°C for a few minutes. The relative coordination geometries of the two isomers were established by using a 15N-enriched pyridine. NMR parameters (¹H, 31P, 103Rh, and 119Sn) for the pyridine-containing complexes show trends consistent with a significantly greater SnH interaction in complexes having isoquinoline lying trans to tin and a threshold of σ donor strength for the pyridine below which the influence on Rh(SnH) bonding is minimal and above which the influence is to enhance the SnH interaction. Possible reasons for these effects are discussed. [ABSTRACT FROM AUTHOR]

Abstract: Fifteen cis-dichloroplatinum complexes (5a–5o) were synthesized by treatment of 1-(2-aminophenyl)-1,2,3,4-THIQs (4a–4o) with K2PtCl4. The antitumor activity of these compounds was examined against four different human tumor cell lines. Their structure–activity relationships for antitumor activity are reported. All of these compounds exhibited activity against MCF-7 cell line and showed good activity against WiDr cell line except 5c and 5f. On the other hand, compounds 5j and 5o are more active than the other compounds against Hepa59T/VGH cell line. The electron-donating group at the 6-position of isoquinoline ring seems to decrease the antitumor activity and the chloro substituent at the C-4 position of the aniline ring shown the highest potency. The “trans influence” dominates the control of the stability of [1-(2-aminophenyl)-1,2,3,4-THIQ]dichloroplatinums(II). [Copyright &y& Elsevier]

Substitution reactions of propyl cobaloxime with imidazole, substituted imidazoles, histidine, histamine, glycine and ethyl glycine ester are carried out as a function of pH. Trends in the formation constants are explained based on the steric hindrance, extent of π-bonding and Σ-donor capacity of the incoming ligand. Molecular mechanics is used to theoretically determine the bond length and bond strain values by MM2 parametrization and these are correlated with the experimental data. [ABSTRACT FROM AUTHOR]

Abstract: Cobalt(III) and rhodium(III) complexes of the series of [MIIICl3−n(P)3+n]n+ (M=Co or Rh; n=0, 1, 2 or 3) have been prepared with the use of 1,1,1-tris(dimethylphosphinomethyl)ethane (tdmme) and mono- or didentate phosphines. The single-crystal X-ray analyses of both series of complexes revealed that the M–P and M–Cl bond lengths were dependent primarily on the strong trans influence of the phosphines, and secondarily on the steric congestion around the metal center resulting from the coordination of several phosphine groups. In fact, the M–P(tdmme) bonds became longer in the order of [MCl3(tdmme)]<[MCl2(tdmme)(PMe3)]+<[MCl(tdmme)(dmpe)]2+ (dmpe=1,2-bis(dimethylphosphino)ethane)<[M(tdmme)2]3+ for both CoIII and RhIII series of complexes, while the M–Cl bond lengths were shortened in this order (except for [M(tdmme)2]3+). Such a steric congestion around the metal center can also account for the structural and spectroscopic characteristics of the series of complexes, [MCl(tdmme)(dmpm, dmpe or dmpp)]2+ (dmpm=bis(dimethylphosphino)methane, dmpp=1,3-bis(dimethylphosphino)propane). The X-ray analysis for [CoCl(tdmme)(dmpm or dmpe)](BF4)2 showed that all Co–P bonds in the dmpm complex were shorter by 0.03–0.04 Å than those in the dmpe complex. Furthermore, the first d–d transition energy of the CoIII complexes and the 1JRh–P(tdmme) coupling constants observed for the RhIII complexes indicated an unusual order in the coordination bond strengths of the didentate diphosphines, i.e., dmpm>dmpe>dmpp. [Copyright &y& Elsevier]