Ligand Bond Lengths Research Articles

Resonance Raman study of oxoiron(IV) porphyrin π-cation radical complex: Porphyrin ligand effect on ν(Fe=O) frequency

Resonance Raman (rR) spectroscopy has been applied to study the nature of the iron-oxo (Fe=O) moiety of oxoiron(IV) porphyrin π-cation radical complex (CompI). While the axial ligand effect on the nature of the Fe=O moiety has been studied with rR spectroscopy, the porphyrin ligand effect has not been studied well. Here, we investigated the porphyrin ligand effect on the Fe=O moiety with rR spectroscopy. The porphyrin ligand effect was modulated by the electron-withdrawing effect of the porphyrin substituent at the meso-position. This study shows that the frequency of the Fe=O stretching band, ν(Fe=O), hardly change even when the electron-withdrawing effect of the porphyrin substituent changes. This result is further supported by theoretical calculation of CompI. The natural atomic charge analysis reveals that the oxo and axial ligands work to buffer the electron-withdrawing effect of the porphyrin substituent. The electron-withdrawing porphyrin substituent shifts an electron population from the ferryl iron to the porphyrin, but the decreased electron population on the ferryl iron is compensated by the shift of the electron population from the oxo ligand and the axial ligand. The shift of the electron population makes the Fe–axial ligand bond length short, but the Fe=O bond length unchanged, resulting in the invariable ν(Fe=O) frequency.

Investigations on the EPR parameters and local structures for the substitutional Ti3+ and W5+ centers in stishovite

Abstract Local structures and electron paramagnetic resonance (EPR) parameters (g factors g x , g y , and g z ) for the substitutional Ti3+ and W5+ centers in stishovite are theoretically investigated by using the high-order perturbation formulas of these parameters for a d1 ion in rhombically compressed octahedra. In the calculation formulas, the related molecular orbital coefficients are obtained from the cluster approach, and the relevant crystal-field (CF) parameters are determined from the superposition model, which enables to connect these CF parameters and, hence, the studied g factors with the local structures of the Ti3+ and W5+ centers in stishovite. Based on the calculations, the impurity–ligand bond lengths parallel and perpendicular to the C 2-axis are found to be R′|| (≈1.751 and 1.717 Å) and R′⊥ (≈1.788 and 1.806 Å) with the planar bond angles θ′ (≈89.0° and 88.2°) for the studied [TiO6]9− and [WO6]7− clusters, respectively. The calculated results are in good agreement with the experimental data, and the validity of the results is discussed.

Inverse design of ligands using a deep generative model semi‐supervised by a data‐driven ligand field strength metric

AbstractTransition metal (TM) complexes exhibit diverse structural and electronic properties. The properties of a TM complex can be tuned by modulating the ligand field strength (LFS) inflicted by its ligands. Current quantification of the LFS of a ligand is mainly derived from experimental measurements on a subset of highly symmetrical TM complexes and is limited in ligand scope. Herein, we report a data‐driven method to quantify the LFS of ligands assigned from experimental crystal structures of TM complexes. We first show that the experimental metal–ligand bond lengths of over 4,000 mononuclear Fe, Co, and Mn complexes form bimodal distributions. Using Gaussian fits on the bimodal distributions, each TM complex is assigned a spin state (SS) label. These SS labels can then be used to calculate the LFS of the ligands of the complexes. Using the obtained data‐driven LFS metric, we establish that a semi‐supervised deep generative model, junction tree variational autoencoder (JTVAE), can be employed to predict LFS values. Our model exhibits a mean absolute error (MAE) of 0.047 and root mean squared error of 0.072 on the training set. The model also allows the generation of novel ligands with desirable LFS values.

Photodynamics of the Molecular Ruby [Cr(ddpd)2]3.

The introduction of strong-field ligands can enable luminescence in first-row transition-metal complexes. In this way, earth-abundant near-infrared emitters can be obtained using early 3d metals. A prime example is the molecular ruby [Cr(ddpd)2]3+ (ddpd = N,N'-dimethyl-N,N'-dipyridin-2-ylpyridine-2,6-diamine) that can achieve high phosphorescence quantum yields at room temperature in aqueous solution. To understand these remarkable properties, here, we simulate its photodynamics in water using trajectory surface hopping on linear vibronic coupling potentials parametrized from multiconfigurational CASSCF/CASPT2 calculations. We find that after excitation to the second absorption band, a relaxation cascade through metal-centered states occurs. After an initial back-and-forth intersystem crossing with higher-lying doublet states, the complex relaxes through a manifold of quartet metal-centered states to the low-lying doublet metal-centered states which are responsible for the experimentally observed emission. These electronic processes are driven by an elongation of the Cr-ligand bond lengths as well as the twisting motion of the trans-coordinated pyridine units in the ddpd ligands. The low-lying doublet states are reached within 1-2 ps and are close in geometry to the doublet minima, thus explaining the high phosphorescence quantum yield of the molecular ruby [Cr(ddpd)2]3+.

Peculiar Spin-Crossover Behavior in the 2D Polymer K[FeIII(5Cl-thsa)2

A potassium salt of the N2S2O2-coordination Fe(III) anion K[Fe(5Cl-thsa)2] (1) (5Cl-thsa - 5-chlorosalicylaldehyde thiosemicarbazone) is synthesized and characterized structurally and magnetically over a wide temperature range. Two polymorphs of salt 1 characterized by the common 2D polymer nature and assigned to the same orthorhombic Pbcn space group have been identified. The molecular structure of the minor polymorph of 1 was solved and refined at 100, 250, and 300 K is shown to correspond to the LS configuration. The dominant polymorph of 1 features K+ cations disordered over a few crystallographic sites, while the minor polymorph includes fully ordered K+ cations. The major polymorph exhibits a complete three-step cooperative spin-crossover transition both in the heating and cooling modes: The first step occurs in a temperature range from 2 to 50 K; the second abrupt hysteretic step occurs from 200 to 250 K with T1/2 = 230 K and a 6 K hysteresis loop. The third gradual step occurs from 250 to 440 K. According to 57Fe Mössbauer, XRPD, and EXAFS data, the spin-crossover transition for the dominant polymorph is quite peculiar. Indeed, the increase in the HS concentration by 57% at the second step does not result in the expected significant increase in the iron(III)-ligand bond lengths. In addition, the final step of the spin conversion (ΔγHS = 26%) is associated with a structural phase transition with a symmetry lowering from the orthorhombic (Pbcn) to the monoclinic (P21/n) space group. This nontrivial phenomenon was investigated in detail by applying magnetization measurements, electron spin resonance, 57Fe Mössbauer spectroscopy, and DFT calculations. These results provide a new platform for understanding the multistep spin-crossover character in the Fe(III) thsa-complexes and related compounds.

Electrochemical Behavior of SmF3 in Alkali Chloride Melts

Electrochemical studies of the Sm(III)/Sm(II) redox couple were carried out in NaCl-KCl, KCl and CsCl melts in a temperature range of 973–1173 K by cyclic voltammetry. Diffusion coefficients (D) of Sm(III) in these melts were determined using the Randles–Sevchik equation. Diffusion coefficients decrease with a change in the composition of the second coordination sphere from sodium to cesium. It is associated with a decrease in the counter-polarizing effect during the transition from Na to Cs, which in turn causes a decrease the metal—ligand bond length in the complexes. The standard rate constants of charge transfer (k s) of the Sm(III)/Sm(II) redox couple were determined by cyclic voltammetry in all studied melts using the Nicholson’s equation, which is valid for quasi-reversible processes. The following series of the standard rate constants of charge transfer was found k s(CsCl) < k s(KCl) < k s(NaCl–KCl).

Electrochemical Behavior of the SmF3 in Alkali Chloride Melts

Electrochemical studies of the redox couple Sm(III)/Sm(II) were carried out in NaCl-KCl, KCl, and CsCl melts in a temperature range of 973-1173 K by cyclic voltammetry. Diffusion coefficients (D) of Sm(III) in these melts were determined using Randels–Shevchik equation. The diffusion coefficients decrease with a change in the composition of the second coordination sphere from sodium to cesium. It is associated with a decrease in the counter-polarizing effect during the transition from Na to Cs, which in turn causes a decrease the metal–ligand bond length in the complexes. The standard rate constants of charge transfer (k s) of the redox couple Sm(III)/Sm(II) were determined by cyclic voltammetry in the all studied melts using the Nicholson’s equation, which is valid for quasi-reversible processes. The following series of the standard charge transfer constants was found k s(CsCl)<k s(KCl)<k s(NaCl–KCl).

Complexation and bonding studies on [Ru(NO)(H2O)5]3+ with nitrate ions by using density functional theory calculation.

Complexation reactions of ruthenium–nitrosyl complexes in HNO3 solution were investigated by density functional theory (DFT) calculations in order to predict the stability of Ru species in high-level radioactive liquid waste (HLLW) solution. The equilibrium structure of [Ru(NO)(NO3)3(H2O)2] obtained by DFT calculations reproduced the experimental Ru–ligand bond lengths and IR frequencies reported previously. Comparison of the Gibbs energies among the geometrical isomers for [Ru(NO)(NO3)x(H2O)5−x](3−x)+/− revealed that the complexation reactions of the ruthenium–nitrosyl complexes with NO3− proceed via the NO3− coordination to the equatorial plane toward the Ru–NO axis. We also estimated Gibbs energy differences on the stepwise complexation reactions to succeed in reproducing the fraction of Ru–NO species in 6 M HNO3 solution, such as in HLLW, by considering the association energy between the Ru–NO species and the substituting ligands. Electron density analyses of the complexes indicated that the strength of the Ru–ligand coordination bonds depends on the stability of the Ru species and the Ru complex without NO3− at the axial position is more stable than that with NO3−, which might be attributed to the difference in the trans influence between H2O and NO3−. Finally, we demonstrated the complexation kinetics in the reactions x = 1 → x = 2. The present study is expected to enable us to model the precise complexation reactions of platinum-group metals in HNO3 solution.

Neutral and cationic phosphine and arsine complexes of tin(iv) halides: synthesis, properties, structures and anion influence.

The reaction of trans-[SnCl4(PR3)2] (R = Me or Et) with trimethylsilyltriflate (TMSOTf) in CH2Cl2 solution substitutes one chloride to form [SnCl3(PR3)2(OTf)]; addition of excess TMSOTf does not substitute further chlorides. The complexes have been fully characterised by microanalysis, IR and multinuclear NMR (1H, 13C{1H}, 19F{1H}, 31P{1H}, 119Sn) spectroscopy. The crystal structure of [SnCl3(PMe3)2(OTf)] revealed mer-chlorines and trans-phosphines. In contrast, trans-[SnBr4(PR3)2], [SnCl4{Et2P(CH2)2PEt2}], [SnCl4{o-C6H4(PMe2)2}] and [SnCl4{o-C6H4(AsMe2)2}] did not react with TMSOTf in CH2Cl2 solution even after 3 days. The arsine complexes, [SnX4(AsEt3)2] (X = Cl, Br), were confirmed as trans-isomers by similar spectroscopic and structural studies, while attempts to isolate [SnI4(AsEt3)2] were unsuccessful and reaction of SnX4 with SbR3 (R = Et, iPr) resulted in reduction to SnX2 and formation of R3SbX2. trans-[SnCl4(AsEt3)2] is converted by TMSOTf into [SnCl3(AsEt3)2(OTf)], whose X-ray structure reveals the same geometry found in the phosphine analogues, with the triflate coordinated. The salts, [SnCl3(PEt3)2][AlCl4] and [SnCl2(PEt3)2][AlCl4]2 were made by treatment of [SnCl4(PEt3)2] with one and two mol. equivalents, respectively, of AlCl3 in anhydrous CH2Cl2, whereas reaction of [SnCl4(AsEt3)2] with AlCl3 produced a mixture including Et3AsCl2 and [Et3AsCl][Sn(AsEt3)Cl5] (the latter identified crystallographically). In contrast, using Na[BArF] (BArF = [B{3,5-(CF3)2C6H3}4]-) produced [SnCl3(PEt3)2][BArF] and also allowed clean isolation of the arsine analogue, [SnCl3(AsEt3)2][BArF]. [SnCl4{o-C6H4(PMe2)2}] also reacts with AlCl3 in CH2Cl2 to form [SnCl3{o-C6H4(PMe2)2}][AlCl4] and [SnCl2{o-C6H4(PMe2)2}][AlCl4]2. Multinuclear NMR spectroscopy on the [AlCl4]- salts show that δ31P and δ119Sn move progressively to high frequency on conversion from the neutral complex to the mono- and the di-cations, whilst 1J(119Sn-31P) follow the trend: [SnCl3{o-C6H4(PMe2)2}]+ > [SnCl4{o-C6H4(PMe2)2}] > [SnCl2{o-C6H4(PMe2)2}]2+. DFT studies on selected complexes show only small changes in ligand geometries and bond lengths between the halide and triflate complexes, consistent with the X-ray crystallographic data reported and the HOMO and LUMO energies are relatively unperturbed upon the introduction of (coordinated) triflate, whereas the energies of both are ca. 4 eV lower in the cationic species and reveal significant hybridisation across the pnictine ligands.

Theoretical study on the excited state decay properties of iron(ii) polypyridine complexes substituted by bromine and chlorine.

Transition metal iron(ii) polypyridyl complexes with quintet ground states were deeply investigated by density functional theory (DFT) and time-dependent density functional theory (TDDFT). Compared with the parent complex [Fe(tpy)2]2+ (tpy = 2,2′:6′,2′′-terpyridine), the ground states of the complexes substituted by halogen atoms changed from singlet states to quintet states with rare high spin excited state lifetimes. The substituted complex [Fe(dbtpy)2]2+ (1) results in a high spin metal–ligand charge transfer lifetime of 17.4 ps, which is 1.4 ps longer than that of [Fe(dctpy)2]2+ (2) with the substitution of chlorine atoms. The reason for this is explored by a combination of electronic structures, absorption spectra, extended transition state coupled with natural orbitals for chemical valence (ETS-NOCV) studies and potential energy curves (PECs). The distortion of 1 in the angles and dihedrals of the ligands is slightly larger than that in 2, although the average metal–ligand bond lengths of the latter are larger. The twisted octahedron decreases the interactions between the d orbitals of iron(ii) and the n/π orbitals of the ligands. Compared with 2, the enlarged energy gaps among the different PECs of 1 and the increased energy crossing points caused by the larger distortion result in the increase of its excited state lifetime. The different pairwise orbital interaction contributions between the metal center and the ligands in their singlet states are qualitatively estimated by ETS-NOCV. The results show that the substitution of bromine atoms will decrease the electrostatic attraction between the metal and ligands but not significantly impact the orbital interactions.

A Bis‐Binuclear NiII Complex with Easy and Hard Axes of Magnetization: Complementary Experimental and Theoretical Insights

The preparation of a tetranuclear NiII complex, constructed of two binuclear species each containing a macrocyclic cryptand‐like ligand and bridged by a nitrate anion, is reported. The metal ions within the binuclear species are hexacoordinate with different distorted environments. One nickel site, Ni1, has as a compressed octahedral geometry, whereas the other nickel site, Ni2, has a geometry closer to a square pyramid due to the presence of a long metal–ligand bond length. A study of the magnetic properties showed that the intradimer exchange coupling is larger than the interdimer coupling due to differences in the metal–ligand intra‐ and interdimer bond lengths, as confirmed by broken‐symmetry DFT calculations. Wave‐function‐based calculations allowed analysis of both the nature and the magnitude of the magnetic anisotropy of the two Ni sites. The Ni1 and Ni2 sites have, respectively, easy and hard axes of magnetization that are almost orthogonal. Magnetostructural correlations showed that the hard axis of magnetization of Ni2 is due to its geometry, which is closer to square‐pyramidal despite the hexacoordination. On the other hand, the easy axis of magnetization of the Ni1 site is a result of the compressed octahedral geometry.

Exafs and comparative studies of copper (II) complexes

The present paper deals with the synthesis of transition metal Schiff base complexes of copper by chemical root method. The synthesized metal complexes were characterized by Extended X-ray absorption fine structure (EXAFS) is a technique that has been used for determining the metal ligand bond length using conventional X-ray source and also by EXAFS analysis using IFEFFIT programming. Bond lengths determined from these data analysis methods are compared with the bond lengths obtained from LSS, Levy's and Lytle's methods. Bond lengths of the complexes are in good agreement obtained by theoretical and experimental method.

Complexes of trimethylsilyl trifluoromethanesulfonate with nitrogen, oxygen, and phosphorus donors

The Lewis acceptor chemistry of Me3SiOTf with p-block Lewis bases has been explored and a library of complexes has been characterized by spectroscopic and, where possible, crystallographic methods. Compounds with the generic formula [Me3Si(L)][OTf] (L = 4-dmap, pyr, imz, OPMe3, OPCy3, OPPh3, OpyrMe, dmso, PMe3) were isolated from 1:1 mixtures of Me3SiOTf and the respective ligand in CH2Cl2. Characterization by NMR spectroscopy confirmed the solution stability of all but [Me3Si(PMe3)][OTf], with indications that the latter dissociates into PMe3 and Me3SiOTf. Solid-state structures of [Me3Si(4-dmap)][OTf], [Me3Si(pyr)][OTf], [Me3Si(OPCy3)][OTf], [Me3Si(OPPh3)][OTf], [Me3Si(OpyrMe)][OTf], and [Me3Si(PMe3)][OTf] were elucidated by single crystal X-ray diffraction, confirming the envisaged ionic formulations resulting from the displacement of the OTf anion from the silicon center of Me3SiOTf by the incoming ligand. Mixtures of Me3SiOTf with other related donors, including ChPPh3 (Ch = S or Se), NEt3, SMe2, PPh3, 2,2′-bipy, or Me2CO, show no evidence of reaction under ambient conditions, reflecting the lower basicity and (or) greater steric encumbrance of these ligands. Reactions of Me3SiOTf with bis-donor ligands yielded complexes of the generic formulae [Me3Si(L–L)SiMe3][OTf]2 (L–L = 4,4′-bipy, tmeda, dmpe) and [Me3Si(L–L)][OTf] (L–L = 4,4′-bipy, tmeda, dmpe). The tmeda and dmpe complexes, however, were found to dissociate in solution, with complexes only prevailing in the solid phase. X-ray diffraction studies of [Me3Si(4,4′-bipy)SiMe3][OTf]2 and [Me3Si(dmpe)SiMe3][OTf]2 confirmed the expected connectivities and ionic formulations, with Si–ligand bond lengths comparable to those observed in [Me3Si(pyr)][OTf] and [Me3Si(PMe3)][OTf], respectively.

Lanthanide Complexes with Allyl Acetoacetate in Mixed Water–Organic Media: Formation, Stability and Bonding

The equilibrium between unsaturated \(\beta \)-ketoester allyl acetoacetate and certain lanthanide ions (La3+, Pr3+, Nd3+, Sm3+, Gd3+, Ho3+, Er3+, Tm3+, Yb3+, Lu3+) was studied in mixed dioxane–water–ethyl acetate media. The formation of cationic 1:1 and 1:2 type complexes was shown and their formation constants were determined by potentiometric titration. For the 1:2 type complexes a molecular mechanics geometry optimization was performed and the bonding parameters were calculated on the basis of their electronic absorption spectra using the lanthanide aqua-ions as reference standards. The correlation between the nephelauxetic ratio and the relative metal–ligand bond length shortening due to the complexation was revealed and clarified.

Mapping the Ultrafast Changes of Continuous Shape Measures in Photoexcited Spin Crossover Complexes without Long-Range Order

Establishing a tractable yet complete reaction coordinate for the spin-state interconversion in d4–d7 transition metal complexes is an integral aspect of controlling the dynamics that govern their functionality. For spin crossover phenomena, the limitations of a single-mode approximation that solely accounts for an isotropic increase in the metal–ligand bond length have long been recognized for all but the simple octahedral monodentate FeII compounds. However, identifying the coupled deformations that also impact on the unimolecular rate constants remains experimentally and theoretically challenging, especially for samples that do not display long-range order or when crystallization profoundly alters the dynamics. Owing to the rapid progress in ultrafast X-ray absorption spectroscopy (XAS), it is now possible to obtain transient structural information in any physical phase with unprecedented details. Using picosecond XAS and DFT modeling, the structure adopted by the photoinduced high-spin state of solvated [Fe(terpy)2]2+ (terpy: 2,2′:6′,2″-terpyridine) has been recently established. Based on these results, the methodology of the continuous shape measure is applied to classify and quantify the short-lived distortion of the first coordination shell. The reaction coordinate of the spin-state interconversion is clearly identified as a double axial bending. This finding sets a benchmark for gauging the influence of first-sphere and second-sphere interactions in the family of FeII complexes that incorporate terpy derivatives. Some implications for the optimization of related photoactive FeII complexes are also outlined.

EXAFS study of copper thiosemicarbazide complexes

The present paper deals with the synthesis of transition metal Schiff base complexes of copper by chemical root method. The synthesized metal complexes have been studied by extended X-ray absorption fine structure (EXAFS) technique. The metal ligand bond length have been determined using LSS, Levy's and Lytle's methods. Bond-lengths have also been determined from the Fourier transform of the EXAFS data. Bond lengths determined from these methods are comparable to each other.

Crystal structure of bis-(1,3-bis-{[(1H-pyrrol-2-yl)methyl-idene]amino-κN}propan-2-olato-κO)manganese(III) nitrate methanol monosolvate.

The asymmetric unit of the title compound, [Mn(C13H15N4O)2]NO3·CH3OH, contains two independent complex cations, in each of which the Mn(III) ion is located on an inversion centre. The Mn(III) ion is coordinated by four N and two O atoms from two 1,3-bis-{[(1H-pyrrol-2-yl)methyl-idene]amino}-propan-2-olate ligands, resulting in a distorted octa-hedral geometry. The average Mn-ligand bond lengths in the two complex mol-ecules are 2.074 and 2.079 Å. In the crystal, inter-molecular N-H⋯O hydrogen bonds between the pyrrole group of the ligand and the non-coordinating nitrate ion give rise to a chain structure along [10-1]. The methanol solvent mol-ecule and the nitrate ion are connected by an O-H⋯O hydrogen bond.

Influence of primary and auxiliary ligand on spectroscopic properties and luminescent efficiency of organoplatinum(II) complexes bearing functionalized cyclometalated C^N^C ligands.

A theoretical investigation into eighteen recently synthesized Pt(ii) complexes [(R1(n)-C^N^C-R2(n))Pt(L)] with doubly deprotonated cyclometalated R1(n)-C^N^C-R2(n) ligands (n = 1-9, R1(n)-C^N^C-R2(n) = 2,6-diphenylpyridine derivatives) and L ligands (L = DMSO, 1-9; L = -C[triple bond, length as m-dash]N-Ar, 1a-9a), which are used as emitters in orange-red emitting diodes, is reported in this paper. Geometric and electronic structures, absorption and emission spectra, phosphorescence quantum yields, and electroluminescence (EL) efficiency were investigated by DFT and TDDFT methods. We focused on the influence of the primary ligand (R1(n)-C^N^C-R2(n)) and auxiliary ligand (L) on the optical and electronic properties of Pt(ii) complexes by introducing carbazole, fluorene, and thiophene group in the primary ligand and/or the replacement of DMSO by -C[triple bond, length as m-dash]N-Ar as an ancillary ligand. The incorporation of carbazole, fluorene, and thiophene into the primary ligand caused the red-shift of absorption and emission spectra. The metal-ligand bond length is contracted where -C[triple bond, length as m-dash]N-Ar was employed as the secondary ligand, which facilitate the metal to ligand charge transfer (MLCT). The larger involvement of MLCT character in emission process is beneficial for improving the quantum yields of 2a-9a. For EL efficiency, all the complexes have a good balance of reorganization energy as potential systems for fabricating effective OLEDs devices except for 1 and 1a. In addition, two new molecules were designed with comparable or better EL efficiency.

Analyses of cobalt-ligand and potassium-ligand bond lengths in metalloproteins: trends and patterns.

Cobalt and potassium are biologically important metal elements that are present in a large array of proteins. Cobalt is mostly found in vivo associated with a corrin ring, which represents the core of the vitamin B12 molecule. Potassium is the most abundant metal in the cytosol, and it plays a crucial role in maintaining membrane potential as well as correct protein function. Here, we report a thorough analysis of the geometric properties of cobalt and potassium coordination spheres that was performed with high resolution on a representative set of structures from the Protein Data Bank and complemented by quantum mechanical calculations realized at the DFT level of theory (B3LYP/ SDD) on mononuclear model systems. The results allowed us to draw interesting conclusions on the structural characteristics of both Co and K centers, and to evaluate the importance of effects such as their association energies and intrinsic thermodynamic stabilities. Overall, the results obtained provide useful data for enhancing the atomic models normally applied in theoretical and computational studies of Co or K proteins performed at the quantum mechanical level, and for developing molecular mechanical parameters for treating Co or K coordination spheres in molecular mechanics or molecular dynamics studies.

Azido(η5-pentamethylcyclopentadienyl)[2-(pyridin-2-yl)phenyl]iridium(III)

In the title compound, [Ir(C10H15)(C11H8N)(N3)], the IrIII ion is coordinated by three anionic ligands, namely, penta­methyl­cyclo­penta­dienyl (Cp*−), 2-(pyridin-2-yl)phenyl (ppy−) and azide (N3 −), and adopts a three-legged piano-stool geometry The coordination mode of N3 − is typical for Cp*IrIII–N3 complexes, with an Ir—N(N3) bond length of 2.125 (2) Å and an Ir—N=N bond angle of 116.5 (2)°. The N3 − ligand is almost linear [N=N=N = 176.0 (3)°], and the N=N bond length between the central and coordinating N atom and that between the central and non-coordinating terminal N atom are 1.194 (3) and 1.157 (3) Å, respectively. For the ppy− ligand, the Ir—C and Ir—N bond lengths are 2.066 (3) and 2.079 (3) Å, respectively, which are rather close to each other, compared to the related IrIII– or RhIII–ppy complexes. The Ir—C(Cp*) bond lengths vary in the range 2.163 (2)–2.232 (2) Å, indicating a strong trans influence of the cyclo­metallated C-donor atom of the ppy− ligand.