A new organometallic rhodium(I) complex with dpp-bian ligand: Synthesis, structure and redox behaviour

Polyhedron 173 (2019) 114110

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A new organometallic rhodium(I) complex with dpp-bian ligand: Synthesis, structure and redox behaviour Nikolai F. Romashev a,b, Artem L. Gushchin a,b,⇑, Iakov S. Fomenko a, Pavel A. Abramov a, Irina V. Mirzaeva a, Nikolay B. Kompan’kov a, Danila B. Kal’nyi a,b, Maxim N. Sokolov a,b a b

Nikolaev Institute of Inorganic Chemistry, Siberian Branch of the Russian Academy of Sciences, 3 Lavrentiev Avenue, 630090 Novosibirsk, Russia Novosibirsk State University, 2 Pirogov Street, 630090 Novosibirsk, Russia

a r t i c l e

i n f o

Article history: Received 4 June 2019 Accepted 11 August 2019 Available online 16 August 2019 Keywords: Rhodium Acenaphthene-1,2-diimines Synthesis Cyclic voltammetry DFT calculations

a b s t r a c t Reaction of [{Rh(COD)}2(l-Cl)2] with 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (dpp-bian) has afforded a new organometallic complex [Rh(COD)(dpp-bian)Cl] (1). The crystal structure of 1
0.25H2O was determined by X-ray single crystal analysis. The rhodium(I) ion has a distorted square-pyramidal coordination. The RhACl distance (2.5908 (12) Å) is rather long, indicating weak coordination of the chloride. Dissociation of chloride in solution to produce cationic [Rh(COD)(bian)]+ ([1-Cl]+) was confirmed by ESI-MS, 1H NMR, CV and DFT calculations. Cyclic voltammetry of 1 in acetonitrile (CH3CN) showed two reversible one-electron redox waves at E1/2 = 0.36 V and 1.18 V (versus Ag/AgCl) attributable to successive reduction of the dpp-bian ligand in [1-Cl]+. DFT calculations were performed to explain the anomalously long RhACl distance and interpret the reduction sequence of 1. Ó 2019 Elsevier Ltd. All rights reserved.

1. Introduction Bis(imino)acenaphthenes (BIANs) are well known redox active

a-diimines that have been exploited widely as N,N-bidentate

ligands in coordination chemistry and catalysis [1–14]. The key characteristic of BIANs as strong p-acceptor molecules is their ability to reversibly accept up to four electrons, and reversibly exchange electrons with the coordinated metal, which can trigger redox based chemical processes. The BIANs have been extensively studied in olefin polymerization reactions [15–24] and have been shown to be catalytically active in many other organic transformations [25–36]. In addition, a reversible metal-to-ligand electron transfer (redox isomerism or valence tautomerism) has been established in such metal complexes [3,7,8,10]. An important feature of the interaction between BIANs as redox active ligands with late transition metal ions is the energetic proximity of the metal d orbitals and the frontier ligand orbitals, which can lead to complicated, non-additive electronic properties of the resulting complexes. Indeterminacy in the assignment of metal and ligand oxidation states often originates here, prompting the description of BIANs as noninnocent ligands [37,38]. ⇑ Corresponding author at: Nikolaev Institute of Inorganic Chemistry, Siberian Branch of the Russian Academy of Sciences, 3 Lavrentiev Avenue, 630090 Novosibirsk, Russia. E-mail address: [email protected] (A.L. Gushchin). https://doi.org/10.1016/j.poly.2019.114110 0277-5387/Ó 2019 Elsevier Ltd. All rights reserved.

A number of late transition metal complexes (especially, those of the group 11 and 12 metals) with BIANs have been prepared and thoroughly studied [39–48]. However, the group 9 metal complexes with BIANs, especially of rhodium [49–51] and iridium [50– 54] have been scarcely explored. In fact, there are only three reports on Rh–BIAN complexes [49–51]. Their first mention is found in the report by Mahabiersing and co-workers. They reported [RhI(CO)(dpp-bian)Cl] (dpp-bian = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) and its spectroscopic data [49]. Later, Singh and co-workers reported synthesis of [RhIII(Cp*) (Ph-bian)(Cl)]BF4 and its catalytic activity in reduction of terephthaldehyde under aqueous aerobic conditions [50]. Optoelectronic properties of some iridium complexes with BIAN ligands have been reported by Hasan et al. [52,53]. Coordination compounds based on Rh(I) metal ion occupy a special position in chemistry due to their versatile reactivity in stoichiometric and catalytic bond activation reactions [55]. The coordination of a redox active BIAN ligand to a Rh(I) ion offers a unique opportunity to complement the nucleophilicity of the Rh(I) center with a ligand capable of taking up to four-electron load. In this paper we report on the synthesis, structure and characterization of a new organometallic complex of rhodium(I) which contains a redox-active dpp-bian ligand, [Rh(COD)(dpp-bian)Cl] (COD = 1,5-cyclooctadiene). This is the second example of a structurally characterized rhodium(I) complex with acenaphthene-1,2diimine ligand.

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2. Experimental part

Table 1 Summary of crystal data for 1
0.25H2O.

2.1. General procedures All the experiments were performed under Ar atmosphere using standard Schlenk techniques. All commercially available reagents (RhCl3
3H2O (Krastsvetmet, metal content – 37.0–40.0%), Na2CO3 (Sigma Aldrich, 99.5%), 1,5-cyclooctadiene (Sigma Aldrich, 99%)) were used as purchased. [{Rh(COD)}2(l-Cl)2] was prepared as reported [56]. 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (dpp-bian) was prepared according to the published procedure [57]. Organic solvents (acetonitrile (CH3CN), dichloromethane (CH2Cl2), ethanol (EtOH), diethyl ether ((C2H5)2O) and n-hexane (C6H14)) were dried by standard methods before use.

2.2. Physical measurements Elemental C, H, N analysis was performed with a EuroEA3000 Eurovector analyzer. IR spectrum was recorded in the 4000– 300 cm1 range with a Perkin-Elmer System 2000 FTIR spectrometer (KBr pellets). 1H NMR spectra (500 MHz) were acquired on a Bruker Avance-500 spectrometer with a 5 mm PABBO-PLUS probe at room temperature. The chemical shifts were given in parts per million (ppm) from tetramethylsilane. X-ray powder diffraction analysis was conducted on a Shimadzu XRD-7000 diffractometer (Cu Ka irradiation, Ni filter). ESI mass-spectrum was obtained on a 6130 Quadrupole massspectrometer (Agilent). Nitrogen was used as a drying gas at flow rate of 300 Lh1. The sample solution (approximately 5
105 M) in acetonitrile was infused through a syringe pump directly into the interface at a flow rate of 0.4 mL min1. The temperature of the source block was set to 120 °C and the interface to 150 °C. A capillary voltage of 2.0 kV was used in the positive scan mode, and low values of the cone voltage (Uc = 5–10 V) were used to control the extent of fragmentation. The observed isotopic pattern of each compound perfectly matched the theoretical isotope pattern calculated from their elemental composition by using the MassLynx 5.1 program. Cyclic voltammograms were recorded with a 797 VA Computrace system (Metrohm, Switzerland). All measurements were carried out with a conventional three-electrode configuration consisting of glassy carbon working electrode, platinum auxiliary electrode and Ag/AgCl/KCl reference electrode. The solvent (CH3CN) was deoxygenated before use. The solution of tetra-n-butylammonium hexafluorophosphate, Bu4NPF6 (0.1 M) was used as a supporting electrolyte. The concentration of the complex was 1
103 M. Redox potential values (E1/2) were determined as (Ea + Ec)/2, where Ea and Ec are anodic and cathodic peak potentials, respectively. Thermogravimetric measurements were carried out on a thermobalance TG 209 F1 (Iris). Mass spectra of the evolved gases were measured using a STA 409 PC Luxx device (NETZSCH) combined with a QMS 200 quadrupole mass spectrometer. The mass spectrometer was equipped with a capillary 1.5 m long at ambient temperature with m/z range of 1–200.

1
0.25H2O Chemical formula Mr Crystal system, space group T (K) a, b, c (Å)

C44H52.50ClN2O0.25Rh 751.74 orthorhombic, Pnma 150 18.7018 (5), 19.5383 (4), 10.3665 (3) 3787.93 (17) 4 Mo Ka 0.56 0.27  0.26  0.20 Bruker Apex Duo Multi-scan SADABS (BrukerAXS, 2004) 0.649, 0.746 19888, 4959, 3353

V (Å3) Z Radiation type m (mm1) Crystal size (mm) Diffractometer Absorption correction Tmin, Tmax No. of measured, independent and observed [I > 2r(I)] reflections Rint h values (°) (sin h/k)max (Å1) Range of h, k, l

0.047 hmax = 30.5, hmin = 2.1 0.714 25  h  22, 27  k  17, 9  l  14 0.044, 0.114, 1.03 4959, 226, 0 H-atom parameters constrained w = 1/[r2(Fo2) + (0.057P)2], where P = (F2o + 2F2c )/3 0.62, 0.36

R[F2 > 2r(F2)], wR(F2), S No. of reflections, parameters, restraints H-atom treatment Weighting scheme

Dqmax, Dqmin (e Å3)

Table 2 Selected geometric parameters (Å) for 1
0.25H2O. C1AC1i C1AC2 C1AH1A C1AH1B C2AC3 C2ARh1 C2AH2A C3AC4 C3ARh1 C3AH3A C4AC4i C4AH4A C4AH4B C5AC7 C5AH5A C5AH5B C5AH5C C6AC7 C6AH6A C6AH6B C6AH6C C7AC8 C7AH7A C8AC13 C8AC9 C9AC10 C9AH9A C10AC11 C10AH10A

1.482 (5) 1.503 (4) 0.9900 0.9900 1.401 (5) 2.115 (3) 1.0000 1.489 (5) 2.142 (3) 1.0000 1.441 (7) 0.9900 0.9900 1.520 (5) 0.9800 0.9800 0.9800 1.534 (4) 0.9800 0.9800 0.9800 1.505 (5) 1.0000 1.393 (4) 1.400 (4) 1.363 (6) 0.9500 1.368 (5) 0.9500

C11AC12 C11AH11A C12AC13 C12AC16 C13AN1 C14AC16 C14AH14A C14AH14B C14AH14C C15AC16 C15AH15A C15AH15B C15AH15C C16AH16A C17AN1 C17AC18 C17AC17i C18AC19 C18AC23 C19AC20 C19AH19A C20AC21 C20AH20A C21AC22 C21AH21A C22AC23 N1ARh1 Cl1ARh1

1.406 (4) 0.9500 1.394 (4) 1.514 (4) 1.455 (3) 1.521 (5) 0.9800 0.9800 0.9800 1.531 (5) 0.9800 0.9800 0.9800 1.0000 1.294 (3) 1.470 (4) 1.486 (5) 1.382 (4) 1.422 (3) 1.409 (4) 0.9500 1.367 (4) 0.9500 1.422 (3) 0.9500 1.396 (5) 2.127 (2) 2.5908 (12)

Symmetry code(s): (i) x, y + 1/2, z.

2.3. X-ray data collection and structure refinement Diffraction data for compound 1
0.25H2O were collected at 150 K on a Bruker Apex Duo diffractometer. Mo Ka radiation (k = 0.71073 Å) was employed. Absorption correction was done empirically using SADABS. The crystallographic data collection and refinement parameters are given in Table 1. The main geometrical parameters are summarized in Table 2.

The structure of 1
0.25H2O was solved by direct method and refined by full-matrix least-squares treatment against |F|2 in anisotropic approximation with SHELX 2017/1 [58] in SHELXLE program [59]. Hydrogen atoms were refined in geometrically calculated positions. Since X-ray single crystal analysis could not provide an information regarding the nature of solvate molecules, thermogravimetry

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combined with coupled with mass spectrometry analysis of the evolved gases (TGA-MS) was additionally employed to clarify this situation. It was shown that residual electron density refers to water. The crystallographic data have been deposited in the Cambridge Crystallographic Data Centre under the deposition code CCDC 1885194. 2.4. Synthesis of [Rh(COD)(dpp-bian)Cl]
0.25H2O (1
0.25H2O) A mixture of [{Rh(COD)}2(l-Cl)2] (100 mg, 0.203 mmol) and dpp-bian (203 mg, 0.406 mmol) was dissolved in 30 mL of acetonitrile. The mixture was refluxed for 12 h. The resulting brown solution was evaporated in vacuo. The solid residue was dissolved in CH2Cl2. An excess of n-hexane was layered onto the resulting solution. The brown solid produced by diffusion was washed with nhexane, diethyl ether, and dried in vacuum. Yield: 168 mg (52%). Cubic-shaped crystals of 1
0.25H2O suitable for X-ray structure analysis were obtained by repeated layering n-hexane onto a solution of 1 in dichloromethane. Anal. Calc. for C44H52N2ClRh
0.25H2O: C, 70.3; H, 7.0; N, 3.7%. Found: C, 70.3; H, 7.1; N, 3.8%. IR (KBr, cm1): 3672(w), 3378(w); 3058(w); 3018(w); 2960(vs); 2939(w), 2925(w), 2867(vs); 2827(s); 1615(w), 1595(m); 1581(m); 1530 (m); 1463(s); 1434(s); 1417(vs); 1385(m); 1361(m); 1326(m); 1294(vs); 1249(w); 1216(vw), 1190(m); 1180(w), 1160(m); 1141 (m); 1109(w); 1087(w); 1073(w), 1060(w), 1043(m); 1005(w); 972(w), 955(m); 935(w); 876(m); 846(m), 831(s); 803(m); 779 (vs); 760(s); 735(w), 716(w), 694(w); 634(m); 592(w), 573(w), 546(m); 507(w); 478(w); 455(m), 384(w). 1H NMR (500 MHz, 298 K, CD3CN): d 0.91 (d, 12H, CH3 (ipr, coordinated dpp-bian)) 0.99 (d, 12H, CH3 (ipr, free dpp-bian)), 1.18 (d, 12H, CH3 (ipr, free dpp-bian)), 1.51 (d, 12H, CH3 (ipr, coordinated dpp-bian)), 1.79– 1.95 (m, 8H, CH2 (COD)), 2.35–2.50 (m, 8H, CH2 (COD)) 2.94 (sept, 4H, CH (ipr, free dpp-bian)), 3.57 (sept, 4H, CH (ipr, coordinated dpp-bian)), 3.95 (s, 4H, CH (COD)) 4.22 (s, 4H, CH (COD)), 6.49 (d, 2H, H3, (coordinated dpp-bian)), 6.68 (d, 2H, H3, (free dpp-bian)), 7.25–7.60 (m, 12H, H4,10,11, H4,10,11 (free and coordinated dppbian)), 7.98 (d, 2H, H5 (free dpp-bian)), 8.21 (d, 2H, H5 (coordinated dpp-bian)) ppm. 1H NMR (500 MHz, 298 K, CDCl3): d 0.89 (d, 12H, CH3 (ipr, coordinated dpp-bian)) 0.99 (d, 12H, CH3 (ipr, free dppbian)), 1.26 (d, 12H, CH3 (ipr, free dpp-bian)), 1.45 (d, 12H, CH3 (ipr, coordinated dpp-bian)), 1.74–1.88 (m, 8H, CH2 (COD)), 2.52 (m, 8H, CH2 (COD)) 3.05 (sept, 4H, CH (ipr, free dpp-bian)), 3.82 (s, 4H, CH, (COD)), 3.93 (sept, 4H, CH (ipr, coordinated dpp-bian)), 4.26 (s, 4H, CH (COD)), 6.46 (d, 2H, H3, (coordinated dpp-bian)), 6.66 (d, 2H, H3, (free dpp-bian)), 7.20–7.50 (m, 12H, H4,10,11, H4,10,11 (free and coordinated dpp-bian)), 7.90 (d, 2H, H5 (free dpp-bian)), 8.04 (d, 2H, H5 (coordinated dpp-bian)) ppm. K = 5.7
104. CV (CH3CN, versus Ag/AgCl): E1/2 = 0.36 V (reversible process), E1/2 = 1.18 V (reversible process), Ec = 1.49 V (irreversible process) at a potential sweep rate of 0.1 V/s. ESI-MS (CH3CN): m/z: = 711.3 ([Rh(bian)(COD)]+). 2.5. Computational details All calculations were carried out using the Amsterdam Density Functional (ADF2017) program. The crystal structure data for

3

1
0.25H2O were used as the initial input for the geometry optimization (with enforced ’no symmetry’ option) of free molecule of 1 in gas phase and solvated molecule in acetonitrile. Conductor-like screening model (COSMO) [60] approach was used to model solvent effects. The S12g [61] functional which includes Stefan Grimme’s dispersion correction [62,63] was applied along with all-electron triple-f basis set of Slater-type functions augmented with a set of polarization functions (TZP/ADF). To account for scalar relativistic effects, zero order regular approximation (ZORA) approach was employed [64,65]. Vibrational frequencies were calculated for all optimized structures to confirm that obtained stationary points refer to minima on the corresponding potential energy surfaces. The neutral [Rh(COD)(dpp-bian)] radical was treated within the spin-unrestricted approach; the spin-restricted approach was used in all other cases.

3. Results and discussion 3.1. Synthesis and characterization Reaction of [{Rh(COD)}2(l-Cl)2] with 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (dpp-bian) in 1:1 stoichiometry gives rise to a mono-chelated complex, [Rh(COD)(dpp-bian)Cl] (1), in 52% yield, according to Scheme 1. The complex 1 was characterized by 1H NMR and IR spectroscopies, ESI-MS, CV, elemental and X-ray structural analysis. IR spectrum of 1
0.25H2O shows typical OAH stretching bands of crystallization water molecules (3378–3672 cm1), as well as typical CAH bands in the region of 2827–2960 cm1, and of C@N and C@C groups at 1581–1595 cm1 and 1530 cm1, respectively, of the dpp-bian ligand (Fig. S1, ESI). The position of these absorption bands indicates that the dpp-bian ligand in 1 is coordinated in the neutral state, as dpp-bian0. The m(CAN) stretching mode appears as a strong band at 1326 cm1. ESI(+) mass spectrum of 1 in CH3CN reveals a pseudomolecular peak at m/z = 711.3 which associates with the [Rh(COD)(dppbian)]+ cation ([1-Cl]+) on the basis of the m/z value and characteristic isotope pattern. Easy release of Cl from 1 agrees with weak coordination of the chloride to the rhodium, as implied by a rather long RhACl distance (2.59 Å). The complex 1 (or [1-Cl]+) is unstable in solution towards the dpp-bian dissociation. 1H NMR spectrum of 1 in CD3CN shows two sets of signals that refer to dpp-bian (see full spectrum in Fig. S2a, ESI). The positions and widths of the broader set (halfwidth 5 Hz) agree with the spectrum of free dpp-bian in CD3CN (Fig. S2b, ESI). From this we conclude that the broader set of signals correspond to the uncoordinated dpp-bian, while the narrower set (2 Hz at half-height) correspond to the dpp-bian coordinated to the rhodium atom. There are also two sets of the signals that refer to the COD coordinated to Rh(I) cation. Based on their integral intensities, they may be attributed either to the Rh(I) complex with coordinated dpp-bian ligand or to the complex without the dppbian ligand. The 1H NMR spectra indirectly confirm that, upon dissolving of 1 in CD3CN, it dissociates into Cl and [1-Cl]+ because no additional splitting in COD and Ar 1H NMR signals of the complex is observed. While, if Cl had stayed coordinated to Rh(I), it would

Scheme 1.

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lead to inequivalency of the hydrogen atoms of COD and Ar groups that are located on the opposite sides from the equatorial plane. To describe quantatively the dissociation process of dpp-bian, we studied the time evolution of 1H NMR spectra of 1 dissolved in CD3CN. The signals from free dpp-bian appear immediately after the dissolution of complex 1, and their intensity increases with time. In particular, two doublet signals at 6.53 and 6.69 ppm were observed, which correspond to the H3 protons of the acenaphthene moiety of the coordinated and uncoordinated dpp-bian, respectively (Fig. 1). The integral ratio between these signals was 4.3:1 in eight minutes after dissolution. After 90 min this ratio reached 1.3:1, and remained constant for the next 24 h. We assume that an equilibrium between [1-Cl]+ and free dpp-bian is reached in 90 min after dissolving 1. Similar behavior was found in weakly coordinating CDCl3 (Fig. S3 and S4, ESI)

3.2. Crystal structure Single crystals of 1
0.25H2O suitable for X-ray structure analysis were grown by layering n-hexane onto a solution of 1 in methylene chloride. The molecular structure of 1 is represented in Fig. 2. Main bond distances and angles are listed in Table 2. Rhodium(I) cation has a distorted square-pyramidyl coordination environment. The equatorial plane is defined by the nitrogen atoms from the dppbian ligand and two olefin bonds of the cyclooctadiene, the remaining axial coordination site being occupied by chloride. The rhodium (I) cation is located 0.34 Å above the equatorial plane. The RhAN bond length of 2.127 (2) Å is not significantly different from those of [Rh(CO)(dpp-bian)Cl] (2.00–2.12 Å) [49], [Rh(COD)(bpy)]+ or [Rh (COD)(Me2bpy)]+ (2.09–2.10 Å) [66,67], [Rh(COD)(Ph2bpy)]+ (2.08– 2.16 Å) (R = Ph) [68], [Rh(COD)((CO2Me)2bpy)]+ (2.08–2.09 Å) [69], [Rh(COD)(phen)]+ (2.08–2.11 Å) [70]. The RhAC bond lengths are 2.115 (3) and 2.142 (3) Å which are typical for the {RhI(COD)} moiety in related complexes [71,72]. The bond lengths in the N@CAC@N moiety are indicative of a CAC single bond and two C@N double bonds, which is in full agreement with the formulation of a neutral 1,2-diimine ligand [8,43,73]. The crystal packing of of 1
0.25H2O is represented in Fig. S5. Remarkably, the RhACl bond length of 2.5908 (12) Å lies at the upper limit of the range of known RhAterminal Cl bond length, of which the average value is around 2.4 Å [74]. There are only a few known rhodium complexes with elongated RhACl bond. Those are [Rh(Cp*H)(bpy)Cl] (Cp*H = pentamethylcyclopentadiene) (2.5440 (6) Å) [75], [Rh(COD)(PP)Cl] (PP = diphosphine) (2.60 Å) [76] and [Rh(nbd)(bpy)Cl] (nbd = norbornadiene) (2.59 Å) [77]. A common feature of these complexes is that the chloride is in apical position to the equatorial plane defined by the P- or N-donor bidentate ligand and the diene molecule. 3.3. Redox properties Cyclic voltammetry (CV) of a solution of [Rh(COD)(dpp-bian)Cl] (1) in acetonitrile shows two reversible waves in the cathodic region at E1/2 = 0.36 V and 1.18 V (versus Ag/AgCl), followed by an irreversible process at 1.49 V (versus Ag/AgCl) (Fig. 3). The separations between the potentials of the anodic (Ea) and cathodic (Ec) peaks, DE, for both reduction processes (70 and

Fig. 1. 1H NMR spectra of 1 in CD3CN in the region of H3 protons of dpp-bian. H3 protons are indicated on the structure of dpp-bian.

Fig. 2. Molecular structure of [Rh(COD)(dpp-bian)Cl] (1).

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Fig. 3. Cyclic voltammogram of 1 mM solution of 1 in CH3CN (from 0 to 1.8 V; scan rate – 0.1 V/s).

Scheme 2.

60 mV, respectively, scan rate is 100 mV/s) are not significantly different from 59 mV, and change only slightly with the scan rate (50–250 mV/s), which is characteristic for electrochemically reversible electron exchange. Moreover, the ratio between the peak-current and the square root of the scan rate (Ip
m1/2) was constant relative to the scan rate, which is characteristic for diffusion-controlled electron transfer processes. These redox events may be attributed to successive reduction of the dpp-bian ligand, in accordance with the mainly ligand-centered nature of the LUMO in 1 or [1-Cl]+ (see below). This is not surprising, taking into account strongly electron-withdrawing character of the dpp-bian ligand and the ability of the acenaphthene diimines to be reduced into acenaphthylene diamines [78–82]. This conclusion is in full agreement with the previous spectroelectrochemical studies of similar Rh(I) complex with dpp-bian, [Rh(CO)(dpp-bian)Cl], where it has been shown that the electrons added during the electrochemical reduction reside predominantly in the aromatic p*(dpp-bian) system and give rise to one- and two-electron-reduced products; both the radical anion [Rh(CO) (dpp-bian)Cl] and the dianion [Rh(CO)(dpp-bian)Cl]2 were detected in tetrahydrofuran (THF) solution by EPR, IR and UV–Vis spectroscopies. Differently from THF, where the RhACl bond in [Rh(CO)(dpp-bian)Cl] remains preserved, in strongly coordinating butyronitrile (PrCN) the chloride ligand is substituted by a solvent molecule to afford the neutral radical complex [Rh(CO) (dpp-bian)(PrCN)]. This leads to a completely chemically irreversible first cathodic step in CV of [Rh(CO)(dpp-bian)Cl] in PrCN as testified by the absence of anodic counter-peak on the reverse scan. This is the opposite of the situation with complex 1 in strongly coordinating CH3CN: both reduction processes observed in CV are chemically reversible. This could mean that the RhACl bond is preserved during the reduction. However, given the weak coordination of chlorine to rhodium in 1 and its possible dissociation in solution based on ESI and 1H NMR spectra, we assume that all the electrochemical activity found in CV belongs to [Rh(COD)(dpp-bian)]+ ([1-Cl]+). This hypothesis was also confirmed by DFT calculations (see below). They showed that the optimized RhACl distance for 1 in CH3CN (2.75 Å) is much longer than that in gas phase (2.57 Å) and solid state (X-ray structure of 1
0.25H2O, 2.59 Å). Additionally, the system with separate [Rh (COD)(dpp-bian)]+ and Cl species is energetically more preferable

than [Rh(COD)(dpp-bian)Cl]. Interpretation of the observed redox processes is represented in Scheme 2. The formation of free chloride in solution was also proven by the appearance of an irreversible peak at 1.1 V in the anodic region of CV which is associated with Cl oxidation (see full CV on Fig. S6, ESI). The position of this peak matches well with that in CV of tetrabutylammonium chloride in acetonitrile. An appearance of irreversible cathodic wave at more negative potentials (1.49 V) is assumed to associate with the formation of a free dpp-bian. This assumption is consistent with observations in the 1H NMR spectra of 1 (Fig. 1). In addition, the CV recorded for the free dpp-bian under the same experimental conditions shows the presence of an irreversible wave at 1.51 V. Similarly to NMR observations the corresponding peak in CV appears immediately after the dissolution of the complex and its intensity increases with the time. A second irreversible anodic wave at 0.67 V was also observed (Fig. S5, ESI). This irreversible process is most likely related to the Rh(I)/Rh(II) oxidation. This assignment is in accordance with the predominantly metallic character of the HOMO in [1-Cl]+ (see below). The irreversibility can be explained by the insufficient stabilization of the Rh(II) state by the donor ligands. A similar irreversible oxidation at 0.48 V was detected for [Rh(CO)(dpp-bian) Cl] [49]. 3.4. DFT calculations DFT calculations were performed to explain the anomalously long RhACl distance and interpret redox behavior of 1 in solution. The optimized RhACl distance in the gas phase was calculated to be 2.57 Å (Table 3), which is very close to the value obtained by X-ray structure analysis of 1
0.25H2O (2.5908 (12) Å). Such a long distance may be explained with the fact that a number of highest occupied molecular orbitals, as well as LUMO, contain only antibonding contributions for the RhACl interaction (Fig. 4). For interpretation of redox processes found in CV, we performed geometry optimization of [Rh(COD)(dpp-bian)Cl] (1) in acetonitrile. In this case the optimized RhACl distance increased up to 2.75 Å (Table 3), which suggests that the complex dissociates in solution. To corroborate this hypothesis, we calculated the binding

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Table 3 Selected optimized interatomic distances (d, Å) for [Rh(COD)(dpp-bian)Cl] (1), [Rh(COD)(dpp-bian)]+ ([1-Cl]+) and its reduced species in gas phase and acetonitrile.

[Rh(COD)(dpp-bian)Cl] in gas phase [Rh(COD)(dpp-bian)Cl] in acetonitrile [Rh(COD)(dpp-bian)]+ in acetonitrile [Rh(COD)(dpp-bian)] in acetonitrile [Rh(COD)(dpp-bian)] in acetonitrile

d(Rh-Cl), Å

d(Rh-C), Å

2.57 2.75 – – –

2.14; 2.12; 2.14; 2.12; 2.11;

Fig. 4. HOMO and LUMO for [Rh(COD)(dpp-bian)Cl] (1) in gas phase.

energy between [Rh(COD)(dpp-bian)]+ ([1-Cl]+) and Cl fragments as the difference between the formation energy of the [Rh(COD) (dpp-bian)Cl] complex in acetonitrile and the sum of the formation

2.14; 2.13; 2.14; 2.13; 2.12;

d(Rh-N), Å 2.14; 2.15; 2.17; 2.15; 2.14;

2.17 2.18 2.17 2.15 2.15

2.13; 2.15; 2.14; 2.11; 2.08;

2.14 2.17 2.14 2.12 2.08

energies of the fragments in the same solvent (see Table S2, ESI). The resulting value is +1.3 kJ/mol, and it rises up to +5.19 kJ/mol if vibrational zero-point corrections are taken into account. The positive sign suggests that the system of separate [Rh(COD)(dppbian)]+ and Cl fragments is more energetically preferable than [Rh(COD)(dpp-bian)Cl], although both values are rather small. While the parent [Rh(COD)(dpp-bian)Cl] complex had a significant contribution of both Cl and dpp-bian orbitals to the HOMO, the HOMO of [Rh(COD)(dpp-bian)]+ cation consists predominantly of Rh orbitals (Table 4). At the same time, the LUMO of [Rh(COD) (dpp-bian)]+ cation consists mostly of dpp-bian orbitals. Reduction of [Rh(COD)(dpp-bian)]+ cation leads to population of vacant orbitals on dpp-bian (Table 4, Fig. 5) and shortening of RhAN distances (Table 3).

Table 4 Energies and percentage composition of selected molecular orbitals (leading contributions >1% from atomic orbitals) summed over chemically meaningful fragments (Cl, Rh, dppbian, and COD) for [Rh(COD)(dpp-bian)Cl] (1) in gas phase and [Rh(COD)(dpp-bian)]+ ([1-Cl]+) and its reduced forms solvated in acetonitrile. E, eV

Cl

Rh

dpp-bian

COD

[Rh(COD)(dpp-bian)Cl]

LUMO HOMO HOMO-1

3.649 4.845 5.426

7.58 19.11 55.82

17.69 38.94 16.31

67.69 19.34 2.61

0 6.94 4.92

[Rh(COD)(dpp-bian)]+

LUMO HOMO HOMO-1

4.351 5.242 6.008

– – –

2.84 83.81 68.19

82.74 0 11.85

0 0 4.22

[Rh(COD)(dpp-bian)]

LUMO HOMO HOMO-1

2.799 3.700 4.463

– – –

0 1.56 84.57

97.15 79.9 1.29

0 2.15 0

[Rh(COD)(dpp-bian)]

LUMO HOMO HOMO-1

2.115 2.774 3.759

– – –

0 2.10 84.13

101.65 75.13 4.12

0 6.39 0

Fig. 5. Selected molecular orbitals of [Rh(COD)(dpp-bian)]+ ([1-Cl]+) and its reduced species solvated in acetonitrile.

N.F. Romashev et al. / Polyhedron 173 (2019) 114110

4. Conclusion Reaction of [{Rh(COD)}2(l-Cl)2] with 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) (dpp-bian) in CH3CN lead to an organometallic complex [Rh(COD)(dpp-bian)Cl] (1). This is the second structurally characterized rhodium complex with the BIAN ligand. The rhodium has a rare square-pyramidal coordination geometry. The anomalously elongated RhACl bond prompts readily elimination of Cl to produce a square planar cationic species [Rh(COD)(bian)]+ ([1-Cl]+), as proven by 1H NMR, ESI-MS, CV and DFT calculations. The complex [1-Cl]+ in acetonitrile is capable of two reversible one-electron redox steps attributed to successive reduction of the dpp-bian ligand. The presence of labile chloride ligand in compound 1 can be used to produce different derivatives by ligand-exchange reactions. Taking into account the relevance of organometallic rhodium(I) complexes in homogenous catalysis, compound 1 and/or its derivatives may hold interest for future investigations of their catalytic properties. This work is under way. Acknowledgement The work was supported by the Russian Foundation for Basic Research (grant № 19-43-543022). Appendix A. Supplementary data CCDC 1885194 contains the supplementary crystallographic data. These data can be obtained free of charge via http://www. ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: [email protected]. Supplementary data to this article can be found online at https://doi. org/10.1016/j.poly.2019.114110. References [1] W. Kaim, B. Schwederski, Non-innocent ligands in bioinorganic chemistry-an overview, Coord. Chem. Rev. 254 (2010) 1580, https://doi.org/10.1016/j. ccr.2010.01.009. [2] T. Tezgerevska, K.G. Alley, C. Boskovic, Valence tautomerism in metal complexes: stimulated and reversible intramolecular electron transfer between metal centers and organic ligands, Coord. Chem. Rev. 268 (2014) 23, https://doi.org/10.1016/J.CCR.2014.01.014. [3] I.L. Fedushkin, O.V. Maslova, E.V. Baranov, A.S. Shavyrin, Redox isomerism in the lanthanide complex [(dpp-Bian)Yb(DME)(l-Br)]2 (dpp-Bian = 1,2-Bis[(2,6diisopropylphenyl)imino]acenaphthene), Inorg. Chem. 48 (2009) 2355, https:// doi.org/10.1021/ic900022s. [4] X. Tang, Y.-T. Huang, H. Liu, R.-Z. Liu, D.-S. Shen, N. Liu, F.-S. Liu, aHydroxyimine palladium complexes: synthesis, molecular structure, and their activities towards the Suzuki-Miyaura cross-coupling reaction, J. Organomet. Chem. 729 (2013) 95, https://doi.org/10.1016/J. JORGANCHEM.2013.01.018. [5] D.A. Razborov, A.N. Lukoyanov, V.M. Makarov, M.A. Samsonov, I.L. Fedushkin, Complexes of gallium(III), antimony(III), titanium(IV), and cobalt(II) with acenaphthenequinonimine, Russ. Chem. Bull. 64 (2015) 2377, https://doi.org/ 10.1007/s11172-015-1166-1. [6] D.A. Razborov, A.N. Lukoyanov, E.V. Baranov, I.L. Fedushkin, Addition of phenylacetylene to a magnesium complex of monoiminoacenaphtheneone (dpp-mian), Dalton Trans. 44 (2015) 20532, https://doi.org/10.1039/ C5DT03174E. [7] I.L. Fedushkin, O.V. Maslova, A.G. Morozov, S. Dechert, S. Demeshko, F. Meyer, Genuine redox isomerism in a rare-earth-metal complex, Angew. Chem., Int. Ed. 51 (2012) 10584, https://doi.org/10.1002/anie.201204452. [8] I.L. Fedushkin, D.S. Yambulatov, A.A. Skatova, E.V. Baranov, S. Demeshko, A.S. Bogomyakov, V.I. Ovcharenko, E.M. Zueva, Ytterbium and europium complexes of redox-active ligands: searching for redox isomerism, Inorg. Chem. 56 (2017) 9825, https://doi.org/10.1021/acs.inorgchem.7b01344. [9] K.M. Clark, J. Bendix, A.F. Heyduk, J.W. Ziller, Synthesis and characterization of a neutral titanium tris(iminosemiquinone) complex featuring redox-active ligands, Inorg. Chem. 51 (2012) 7457, https://doi.org/10.1021/ic301059p. [10] J. Bendix, K.M. Clark, Delocalization and valence tautomerism in vanadium tris (iminosemiquinone) complexes, Angew. Chem., Int. Ed. 55 (2016) 2748, https://doi.org/10.1002/anie.201510403.

7

[11] I.S. Fomenko, A.L. Gushchin, L.S. Shul’pina, N.S. Ikonnikov, P.A. Abramov, N.F. Romashev, A.S. Poryvaev, A.M. Sheveleva, A.S. Bogomyakov, N.Y. Shmelev, M.V. Fedin, G.B. Shul’pin, M.N. Sokolov, New oxidovanadium(IV) complex with a BIAN ligand: synthesis, structure, redox properties and catalytic activity, New J. Chem. 42 (2018) 16200–16210, https://doi.org/10.1039/C8NJ03358G. [12] I.L. Fedushkin, A.A. Skatova, V.A. Chudakova, G.K. Fukin, Four-step reduction of dpp-bian with sodium metal: crystal structures of the sodium salts of the mono-, di-, tri- and tetraanions of dpp-bian, Angew. Chem. 115 (2003) 3416, https://doi.org/10.1002/ange.200351408. [13] I.L. Fedushkin, A.N. Lukoyanov, E.V. Baranov, Lanthanum complexes with a diimine ligand in three different redox states, Inorg. Chem. 57 (2018) 4301, https://doi.org/10.1021/acs.inorgchem.7b03112. [14] P.A. Abramov, A.A. Dmitriev, K.V. Kholin, N.P. Gritsan, M.K. Kadirov, A.L. Gushchin, M.N. Sokolov, Mechanistic study of the [(dpp-bian)Re(CO)3Br] electrochemical reduction using in situ EPR spectroscopy and computational chemistry, Electrochim. Acta 270 (2018) 526, https://doi.org/10.1016/J. ELECTACTA.2018.03.111. [15] D.H. Leung, J.W. Ziller, Z. Guan, Axial donating ligands: a new strategy for late transition metal olefin polymerization catalysis, J. Am. Chem. Soc. 130 (2008) 7538, https://doi.org/10.1021/ja8017847. [16] J.M. Rose, A.E. Cherian, G.W. Coates, Living polymerization of a-olefins with an a-diimine Ni(II) catalyst: formation of well-defined ethylenepropylene copolymers through controlled chain-walking, J. Am. Chem. Soc. 128 (2006) 4186, https://doi.org/10.1021/JA058183I. [17] D.J. Tempel, L.K. Johnson, R. Leigh Huff, P.S. White, M. Brookhart, Mechanistic studies of Pd(II)a-diimine-catalyzed olefin polymerizations, J. Am. Chem. Soc. 122 (2000) 6686, https://doi.org/10.1021/JA000893V. [18] L. Li, C.S.B. Gomes, P.T. Gomes, M.T. Duarte, Z. Fan, New tetradentate N, N, N, Nchelating a-diimine ligands and their corresponding zinc and nickel complexes: synthesis, characterisation and testing as olefin polymerisation catalysts, Dalton Trans. 40 (2011) 3365, https://doi.org/10.1039/c0dt01308k. [19] J. Flapper, J.N.H. Reek, Templated encapsulation of pyridyl-bian palladium complexes: tunable catalysts for CO/4-tert-butylstyrene copolymerization, Angew. Chem. 119 (2007) 8744, https://doi.org/10.1002/ange.200703294. [20] A.E. Cherian, J.M. Rose, E.B. Lobkovsky, G.W. Coates, A C2-symmetric, living adiimine Ni(II) catalyst: regioblock copolymers from propylene, J. Am. Chem. Soc. 127 (2005) 13770, https://doi.org/10.1021/JA0540021. [21] F. Amoroso, E. Zangrando, C. Carfagna, C. Müller, D. Vogt, M. Hagar, F. Ragaini, B. Milani, Catalyst activity or stability: the dilemma in Pd-catalyzed polyketone synthesis, Dalton Trans. 42 (2013) 14583, https://doi.org/ 10.1039/c3dt51425k. [22] C. Romain, V. Rosa, C. Fliedel, F. Bier, F. Hild, R. Welter, S. Dagorne, T. Avilés, Highly active zinc alkyl cations for the controlled and immortal ring-opening polymerization of e-caprolactone, Dalton Trans. 41 (2012) 3377, https://doi. org/10.1039/c2dt12336c. [23] B. Scott Williams, M.D. Leatherman, P.S. White, M. Brookhart, Reactions of vinyl acetate and vinyl trifluoroacetate with cationic diimine Pd(II) and Ni(II) alkyl complexes: identification of problems connected with copolymerizations of these monomers with ethylene, J. Am. Chem. Soc. 127 (2005) 5132, https:// doi.org/10.1021/JA045969S. [24] L.K. Johnson, C.M. Killian, M. Brookhart, New Pd(II)- and Ni(II)-based catalysts for polymerization of ethylene and alpha-olefins, J. Am. Chem. Soc. 117 (1995) 6414, https://doi.org/10.1021/ja00128a054. [25] M. Villa, D. Miesel, A. Hildebrandt, F. Ragaini, D. Schaarschmidt, A. Jacobi von Wangelin, Synthesis and catalysis of redox-active bis(imino)acenaphthene (BIAN) iron complexes, ChemCatChem 9 (2017) 3203, https://doi.org/10.1002/ cctc.201700144. [26] A. Scarel, M.R. Axet, F. Amoroso, F. Ragaini, C.J. Elsevier, A. Holuigue, C. Carfagna, L. Mosca, B. Milani, Subtle balance of steric and electronic effects for the synthesis of atactic polyketones catalyzed by Pd complexes with metasubstituted aryl-bian ligands, Organometallics 27 (2008) 1486, https://doi.org/ 10.1021/om7011858. [27] A.L. Gottumukkala, J.F. Teichert, D. Heijnen, N. Eisink, S. van Dijk, C. Ferrer, A. van den Hoogenband, A.J. Minnaard, Pd-diimine: a highly selective catalyst system for the base-free oxidative heck reaction, J. Org. Chem. 76 (2011) 3498, https://doi.org/10.1021/jo101942f. [28] L. Li, P.S. Lopes, V. Rosa, C.A. Figueira, M.A.N.D.A. Lemos, M.T. Duarte, T. Avilés, P.T. Gomes, Synthesis and structural characterisation of (aryl-BIAN)copper(I) complexes and their application as catalysts for the cycloaddition of azides and alkynes, Dalton Trans. 41 (2012) 5144, https://doi.org/10.1039/ c2dt11854h. [29] M. Viganò, F. Ragaini, M.G. Buonomenna, R. Lariccia, A. Caselli, E. Gallo, S. Cenini, J.C. Jansen, E. Drioli, Catalytic polymer membranes under forcing conditions: reduction of nitrobenzene by CO/H2O catalyzed by ruthenium bis (arylimino)acenaphthene complexes, ChemCatChem 2 (2010) 1150, https:// doi.org/10.1002/cctc.201000044. [30] M. Gholinejad, V. Karimkhani, I. Kim, Active palladium catalyst supported by bulky diimine ligand catalyzed Suzuki-Miyaura coupling reaction in water under phosphane-free and low catalyst loading conditions, Appl. Organomet. Chem. 28 (2014) 221, https://doi.org/10.1002/aoc.3110. [31] C.D. Nunes, P.D. Vaz, V. Félix, L.F. Veiros, T. Moniz, M. Rangel, S. Realista, A.C. Mourato, M.J. Calhorda, Vanadyl cationic complexes as catalysts in olefin oxidation, Dalton Trans. 44 (2015) 5125, https://doi.org/10.1039/ C4DT03174A. [32] L. Li, P.S. Lopes, C.A. Figueira, C.S.B. Gomes, M.T. Duarte, V. Rosa, C. Fliedel, T. Avilés, P.T. Gomes, Cationic and neutral (Ar-BIAN)Copper(I) complexes

8

[33]

[34]

[35]

[36]

[37]

[38]

[39]

[40]

[41]

[42]

[43]

[44]

[45]

[46]

[47]

[48]

[49]

[50]

[51]

[52] [53]

[54]

[55]

N.F. Romashev et al. / Polyhedron 173 (2019) 114110 containing phosphane and arsane ancillary ligands: synthesis, molecular structure and catalytic behaviour in cycloaddition reactions of azides and alkynes, Eur. J. Inorg. Chem. 2013 (2013) 1404, https://doi.org/10.1002/ ejic.201201211. M.W. van Laren, C.J. Elsevier, Selective homogeneous palladium(0)-catalyzed hydrogenation of alkynes to (Z)-alkenes, Angew. Chem., Int. Ed. 38 (1999) 3715, https://doi.org/10.1002/(SICI)1521-3773(19991216)38:24<3715::AIDANIE3715>3.0.CO;2-O. F. Ragaini, S. Cenini, M. Gasperini, Reduction of nitrobenzene to aniline by CO/ H2O, catalysed by Ru3(CO)12/chelating diimines, J. Mol. Catal. A Chem. 174 (2001) 51, https://doi.org/10.1016/S1381-1169(01)00175-3. David B. Llewellyn, D. Adamson, B.A. Arndtsen, A novel example of chiral counteranion induced enantioselective metal catalysis: the importance of ionpairing in copper-catalyzed olefin aziridination and cyclopropanation, Org. Lett. 2 (2000) 4165, https://doi.org/10.1021/OL000303Y. I.L. Fedushkin, M.V. Moskalev, A.N. Lukoyanov, A.N. Tishkina, E.V. Baranov, G.A. Abakumov, Dialane with a redox-active bis-amido ligand: unique reactivity towards alkynes, Chem. Eur. J. 18 (2012) 11264, https://doi.org/10.1002/ chem.201201364. C.K. Jørgensen, Differences between the four halide ligands, and discussion remarks on trigonal-bipyramidal complexes, on oxidation states, and on diagonal elements of one-electron energy, Coord. Chem. Rev. 1 (1966) 164, https://doi.org/10.1016/S0010-8545(00)80170-8. W. Kaim, B. Schwederski, Cooperation of metals with electroactive ligands of biochemical relevance: beyond metalloporphyrins, Pure Appl. Chem. 76 (2004) 351, https://doi.org/10.1351/pac200476020351. M.M. Khusniyarov, K. Harms, O. Burghaus, J. Sundermeyer, Molecular and electronic structures of homoleptic nickel and cobalt complexes with noninnocent bulky diimine ligands derived from fluorinated 1,4-diaza-1,3butadiene (DAD) and bis(arylimino)acenaphthene (BIAN), Eur. J. Inorg. Chem. 2006 (2006) 2985, https://doi.org/10.1002/ejic.200600236. P. de Frémont, H. Clavier, V. Rosa, T. Avilés, P. Braunstein, Synthesis, characterization, and reactivity of cationic gold(I) a-diimine complexes, Organometallics 30 (2011) 2241, https://doi.org/10.1021/om2000426. T.L. Lohr, W.E. Piers, M. Parvez, Monomeric platinum(II) hydroxides supported by sterically dominant a-diimine ligands, Inorg. Chem. 51 (2012) 4900, https://doi.org/10.1021/ic300337a. V. Rosa, C.I.M. Santos, R. Welter, G. Aullón, C. Lodeiro, T. Avilés, Comparison of the structure and stability of new a-diimine complexes of copper(I) and silver (I): density functional theory versus experimental, Inorg. Chem. 49 (2010) 8699, https://doi.org/10.1021/ic100450y. C.J. Adams, N. Fey, Z.A. Harrison, I.V. Sazanovich, M. Towrie, J.A. Weinstein, Photophysical properties of platinum(II)acetylide complexes: the effect of a strongly electron-accepting diimine ligand on excited-state structure, Inorg. Chem. 47 (2008) 8242, https://doi.org/10.1021/ic800850h. C.J. Adams, N. Fey, J.A. Weinstein, Near-infrared luminescence from platinum (II) diimine compounds, Inorg. Chem. 45 (2006) 6105, https://doi.org/10.1021/ IC060399D. T. Kern, U. Monkowius, M. Zabel, G. Knör, Mononuclear copper(I) complexes containing redox-active 1,2-bis(aryl-imino)acenaphthene acceptor ligands: synthesis, crystal structures and tuneable electronic properties, Eur. J. Inorg. Chem. 2010 (2010) 4148, https://doi.org/10.1002/ejic.201000061. J. Parmene, A. Krivokapic, M. Tilset, Synthesis, characterization, and protonation reactions of Ar-BIAN and Ar-BICAT diimine platinum diphenyl complexes, Eur. J. Inorg. Chem. 2010 (2010) 1381, https://doi.org/10.1002/ ejic.200900975. M.J. Sgro, D.W. Stephan, Synthesis and exchange reactions of Ni-dimine-COD, acetylene and olefin complexes, Dalton Trans. 39 (2010) 5786, https://doi.org/ 10.1039/c001312a. A.A. Rachford, F. Hua, C.J. Adams, F.N. Castellano, [Pt(mesBIAN)(tda)]: a nearinfrared emitter and singlet oxygen sensitizer, Dalton Trans. 20 (2009) 3950, https://doi.org/10.1039/b818177b. T. Mahabiersing, H. Luyten, R.C. Nieuwendam, F. Hartl, Synthesis, spectroscopy and spectroelectrochemistry of chlorocarbonyl {1,2-bis[(2,6-diisopropylphenyl) imino]acenaphthene-j2-N, N’}rhodium(I), Collect. Czechoslov. Chem. Commun. 68 (2003) 1687, https://doi.org/10.1135/cccc20031687. S.K. Singh, S.K. Dubey, R. Pandey, L. Mishra, R.-Q. Zou, Q. Xu, D.S. Pandey, Ruthenium(II), rhodium(III) and iridium(III) based effective catalysts for hydrogenation under aerobic conditions, Polyhedron 27 (2008) 2877, https://doi.org/10.1016/J.POLY.2008.06.015. K. Gray, M.J. Page, J. Wagler, B.A. Messerle, Iridium(III) Cp* complexes for the efficient hydroamination of internal alkynes, Organometallics 31 (2012) 6270, https://doi.org/10.1021/om300550k. K. Hasan, E. Zysman-Colman, Panchromic cationic iridium(III) complexes, Inorg. Chem. 51 (2012) 12560, https://doi.org/10.1021/ic301998t. K. Hasan, E. Zysman-Colman, The effect of aryl substitution on the properties of a series of highly absorptive cationic iridium(III) complexes bearing ancillary bis(arylimino)acenaphthene ligands, Eur. J. Inorg. Chem. 6 (2013) 4421, https://doi.org/10.1002/ejic.201300583. D.F. Kennedy, B.A. Messerle, M.K. Smith, Synthesis of Cp* iridium and rhodium complexes containing bidentate sp2-N-donor ligands and counter-anions [Cp*MCl3], Eur. J. Inorg. Chem. (2007) 80, https://doi.org/10.1002/ejic.200600735. D.A. Colby, R.G. Bergman, J.A. Ellman, Rhodium-catalyzed CC bond formation via heteroatom-directed CH bond activation, Chem. Rev. 110 (2010) 624, https://doi.org/10.1021/cr900005n.

[56] G. Giordano, R.H. Crabtree, R.M. Heintz, D. Forster, D.E. Morris, Di-l-Chloro-Bis (g 4-1,5-Cyclooctadlene) Dirhodium(I), John Wiley & Sons, Ltd, 2007, pp. 218– 220, doi:10.1002/9780470132500.ch50. [57] A. Paulovicova, U. El-Ayaan, K. Shibayama, T. Morita, Y. Fukuda, Mixed-ligand copper(II) complexes with the rigid bidentate bis(N-arylimino)acenaphthene ligand: synthesis, spectroscopic-, and X-ray structural characterization, Eur. J. Inorg. Chem. 2001 (2001) 2641, https://doi.org/10.1002/1099-0682(200109) 2001:10<2641::AID-EJIC2641>3.0.CO;2-C. [58] G.M. Sheldrick, IUCr, crystal structure refinement with SHELXL, Acta Crystallogr. Sect. C Struct. Chem. 71 (2015) 3, https://doi.org/10.1107/ S2053229614024218. [59] C.B. Hübschle, G.M. Sheldrick, B. Dittrich, IUCr, ShelXle: a Qt graphical user interface for SHELXL, J. Appl. Crystallogr. 44 (2011) 1281, https://doi.org/ 10.1107/S0021889811043202. [60] A. Klamt, Conductor-like screening model for real solvents: a new approach to the quantitative calculation of solvation phenomena, J. Phys. Chem. 99 (1995) 2224, https://doi.org/10.1021/j100007a062. [61] M. Swart, A new family of hybrid density functionals, Chem. Phys. Lett. 580 (2013) 166, https://doi.org/10.1016/J.CPLETT.2013.06.045. [62] S. Grimme, S. Ehrlich, L. Goerigk, Effect of the damping function in dispersion corrected density functional theory, J. Comput. Chem. 32 (2011) 1456, https:// doi.org/10.1002/jcc.21759. [63] S. Grimme, J. Antony, S. Ehrlich, H. Krieg, A consistent and accurate ab initio parametrization of density functional dispersion correction (DFT-D) for the 94 elements H-Pu, J. Chem. Phys. 132 (2010), https://doi.org/10.1063/1.3382344 154104. [64] E. van Lenthe, A. Ehlers, E.-J. Baerends, Geometry optimizations in the zero order regular approximation for relativistic effects, J. Chem. Phys. 110 (1999) 8943, https://doi.org/10.1063/1.478813. [65] E. van Lenthe, E.J. Baerends, J.G. Snijders, Relativistic total energy using regular approximations, J. Chem. Phys. 101 (1994) 9783, https://doi.org/10.1063/ 1.467943. [66] Y. Peng, M.V. Ramos-Garcés, D. Lionetti, J.D. Blakemore, Structural and electrochemical consequences of [Cp*] ligand protonation, Inorg. Chem. 56 (2017) 10824, https://doi.org/10.1021/acs.inorgchem.7b01895. [67] Á. Álvarez, R. Macías, M.J. Fabra, M.L. Martín, F.J. Lahoz, L.A. Oro, Square-planar rhodium(I) complexes partnered with [arachno-6-SB9H12]-: a route toward the synthesis of new rhodathiaboranes and organometallic/thiaborane salts, Inorg. Chem. 46 (2007) 6811, https://doi.org/10.1021/IC700648Z. [68] A.C. Carrasco, E.A. Pidko, A.M. Masdeu-Bultó, M. Lutz, A.L. Spek, D. Vogt, C. Müller, 2-(20 -Pyridyl)-4,6-diphenylphosphinine versus 2-(20 -pyridyl)-4,6diphenylpyridine: an evaluation of their coordination chemistry towards Rh (I), New J. Chem. 34 (2010) 1547, https://doi.org/10.1039/c0nj00030b. [69] A. Campos-Carrasco, C. Tortosa-Estorach, A.M. Masdeu-Bultó, Rh(I) complexes with fluorinated 2,20 -bipyridines, Inorg. Chem. Commun. 18 (2012) 61, https:// doi.org/10.1016/J.INOCHE.2012.01.010. [70] C. Pettinari, F. Marchetti, A. Cingolani, G. Bianchini, A. Drozdov, V. Vertlib, S. Troyanov, The reactivity of new (1,5-cyclooctadiene)rhodium acylpyrazolonates towards N- and P-donor ligands: X-ray structures of [Rh (1,5-COD)Qs], [Rh(1,5-COD)(phen)]Qs
0.5H2O (HQs=1-phenyl-3-methyl-4-(2thenoyl)-pyrazol-5-one) and [Rh(1,5-COD)Br]2, J. Organomet. Chem. 651 (2002) 5, https://doi.org/10.1016/S0022-328X(02)01122-1. [71] M.V. Jiménez, M.I. Bartolomé, J.J. Pérez-Torrente, F.J. Lahoz, L.A. Oro, Rhodium (I) complexes with hemilabile phosphines: rational design for efficient oxidative amination catalysts, ChemCatChem 4 (2012) 1298, https://doi.org/ 10.1002/cctc.201200101. [72] S. Burling, L.D. Field, H.L. Li, B.A. Messerle, P. Turner, Mononuclear rhodium(I) complexes with chelating N-heterocyclic carbene ligands  catalytic activity for intramolecular hydroamination, Eur. J. Inorg. Chem. 2003 (2003) 3179, https://doi.org/10.1002/ejic.200300172. [73] W.-J. Tao, J.-F. Li, A.-Q. Peng, X.-L. Sun, X.-H. Yang, Y. Tang, Water as an activator for palladium(II)-catalyzed olefin polymerization, Chem. Eur. J. 19 (2013) 13956, https://doi.org/10.1002/chem.201300890. [74] A.G. Orpen, L. Brammer, F.H. Allen, O. Kennard, D.G. Watson, R. Taylor, Supplement. Tables of bond lengths determined by X-ray and neutron diffraction. Part 2. Organometallic compounds and co-ordination complexes of the d- and f-block metals, J. Chem. Soc. Dalton Trans (1989) S1, https://doi. org/10.1039/dt98900000s1. [75] C.L. Pitman, O.N.L. Finster, A.J.M. Miller, Cyclopentadiene-mediated hydride transfer from rhodium complexes, Chem. Commun. 52 (2016) 9105, https:// doi.org/10.1039/C6CC00575F. [76] A. Meißner, A. König, H.-J. Drexler, R. Thede, W. Baumann, D. Heller, New pentacoordinated rhodium species as unexpected products during the in situ generation of dimeric diphosphine-rhodium neutral catalysts, Chem. Eur. J. 20 (2014) 14721, https://doi.org/10.1002/chem.201402816. [77] J.J. Robertson, A. Kadziola, R.A. Krause, S. Larsen, Preparation and characterization of four- and five-coordinate rhodium(I) complexes. Crystal structures of chloro(2-phenylazo)pyridine)(norbornadiene)rhodium (I), (2,2’-bipyridyl)(norbornadiene)rhodium(I) chloride hydrate, and chloro (2,2’-bipyridyl)(norbornadiene)rhodium(I), Inorg. Chem. 28 (1989) 2097, https://doi.org/10.1021/ic00310a017. [78] M. Viganò, F. Ferretti, A. Caselli, F. Ragaini, M. Rossi, P. Mussini, P. Macchi, Easy entry into reduced Ar-BIANH2 compounds: a new class of quinone/ hydroquinone-type redox-active couples with an easily tunable potential, Chem. Eur. J. 20 (2014) 14451, https://doi.org/10.1002/chem.201403594.

N.F. Romashev et al. / Polyhedron 173 (2019) 114110 [79] V.V. Khrizanforova, V.I. Morozov, M.N. Khrizanforov, A.N. Lukoyanov, O.N. Kataeva, I.L. Fedushkin, Y.H. Budnikova, Iron complexes of BIANs: redox trends and electrocatalysis of hydrogen evolution, Polyhedron 154 (2018) 77, https:// doi.org/10.1016/J.POLY.2018.07.041. [80] K. Hasan, E. Zysman-Colman, Synthesis, UV-Vis and CV properties of a structurally related series of bis(Arylimino)acenaphthenes (Ar-BIANs), J. Phys. Org. Chem. 26 (2013) 274, https://doi.org/10.1002/poc.3081.

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[81] I.L. Fedushkin, V.A. Dodonov, A.A. Skatova, V.G. Sokolov, A.V. Piskunov, G.K. Fukin, Redox-active ligand-assisted two-electron oxidative addition to gallium (II), Chem. Eur. J. 24 (2018) 1877, https://doi.org/10.1002/chem.201704128. [82] I.L. Fedushkin, A.A. Skatova, V.A. Chudakova, G.K. Fukin, Four-Step reduction of dpp-bian with sodium metal: crystal structures of the sodium salts of the mono-, di-, tri- and tetraanions of dpp-bian, Angew. Chem., Int. Ed. 42 (2003) 3294, https://doi.org/10.1002/anie.200351408.