dppe ligand complexes

Polyhedron 101 (2015) 251–256

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Synthesis, crystal structures and conducting properties of heteroleptic nickel(II) 1,1-dithiolate-bpy/dppe ligand complexes Ajit N. Gupta a, Vinod Kumar a, Vikram Singh a, Krishna K. Manar a, Avadhesh K. Singh a, Michael G.B. Drew b, Nanhai Singh a,⇑ a b

Department of Chemistry, Faculty of Science, Banaras Hindu University, Varanasi 221005, India Department of Chemistry, University of Reading, Whiteknights, Reading RG6 6AD, UK

a r t i c l e

i n f o

Article history: Received 22 May 2015 Accepted 5 September 2015 Available online 14 September 2015 Keywords: Nickel(II) 1,1-dithiolate Anagostic Theoretical calculations Semiconducting

a b s t r a c t New heteroleptic complexes, [Ni(LL0 )] (L = 2-(methylene-1,10 -dithiolato)-5,50 -dimethylcyclohexane-1,3dione (L1), L0 = 2,20 -bipyridyl (bpy) 1; L = 2-(methylene-1,10 -dithiolato)-1,3-indandione (L2), L0 = 1,2-bis (diphenylphosphino)ethane (dppe) 2) have been synthesized and characterized by elemental analysis, IR, NMR and UV–Vis spectroscopy, and their structures have been determined crystallographically. In the two structures, the Ni atom lies at the centre of a distorted square plane. In 1, the ligand L1 is uniquely bonded to the Ni atom in an adjacent molecule in a l2, j2 S,S-chelating–bridging manner, forming a weak dimer with a Ni. . .S distance of 2.96 Å, which is shorter than the sum of the van der Waal’s radii of the Ni and S atoms. In 2 the steric restrictions of the bulky dppe ligand hindered any dimerization, but result in the formation of a rare intramolecular C–H. . .Ni anagostic interaction between the ortho hydrogen atom of the phenyl ring and the nickel centre, which has been assessed by theoretical calculations. The supramolecular structures of 1 and 2 are sustained by p(chelate). . .p(bpy), C–H. . .O, C–H. . .p(chelate) and C–H. . .p(Ar) interactions. The two compounds are weakly conducting (rrt = 107–105 S cm1), but show semiconducting behavior in the 303–363 K temperature range. Ó 2015 Elsevier Ltd. All rights reserved.

1. Introduction There has been phenomenal growth of the interest in metal dithiolate complexes due to their structural diversity, intriguing conducting, magnetic and optical properties, as single source MOCVD precursors for the preparation of metal sulfides, as photocatalysts in solar energy schemes and for a wide range of applications in industries as rubber vulcanization accelerators, flotation agents in metallurgy, heavy metal scavengers from waste, in agriculture, medicine and importance in biological systems [1–12]. A growing interest in dithiolate chemistry is due to the functionalization of the dithio backbone which may give rise to more intriguing architectures and modified physical properties. The sulfur rich planar complexes of Ni, Pd, Pt and Cu continue to attract interest due to their molecular electrical conductivities, including superconducting to metallic to semiconducting, due to varying degrees of intermolecular S. . .S contacts in the solid state; TTF[Ni(dmit)2]2 behaves as superconductor at low temperature and high pressures [13].

⇑ Corresponding author. Fax: +91 542 2386127. E-mail addresses: [email protected], [email protected] (N. Singh). http://dx.doi.org/10.1016/j.poly.2015.09.024 0277-5387/Ó 2015 Elsevier Ltd. All rights reserved.

Amongst the 1,1-dithiolates, a great deal of attention has been paid to the monoanionic xanthate, dithiocarbamate and dithiophosphate, and dianionic 1,1-ethylenedithiolate type (XYC = CS2 2 ), such as isomaleonitrile dithiolate (i-mnt2) and 1-ethoxycarbonyl1-cyanoethylene-2,2-dithiolate (ecda2), chemistry [14–18]. By comparison, despite synthetic versatility and practical utility, metal complexes of dianionic 1,1-dithiolates with an active methylene group on the cyclic skeleton are extremely limited [19,20]. It was therefore considered worthwhile to undertake the synthesis, crystal structures and pressed pellet conducting behavior of the first examples of heteroleptic Ni(II) complexes formed with the dianionic 2-(methylene-1,10 -dithiolato)-5,50 -dimethylcyclohexane-1,3-dione and 2-(methylene-1,10 -dithiolato)-1,3-indandione ligands; 2,20 -bipyridyl (bpy) and 1,2-bis(diphenylphosphino) ethane (dppe) have been used as co-ligands. In spite of some obvious similarities with the 1,1-ethylenedithiolate type ligands, as mentioned above, the ligands used here (Fig. 1) present some interesting features: (i) the cyclic substituents on the C@CS2 backbone may enhance conjugation with some degree of delocalization of negative charge over the cyclic skeleton; (ii) they can provide greater electron delocalisation through the C–S, C–C and beyond the MS2 bond; (iii) the presence of additional donor atoms on the

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O

CDCl3 whereas, because of insufficient solubility, the 13C NMR spectrum of 1 could not be obtained in this solvent. The rare C–H. . .Ni intramolecular anagostic interaction observed in 2 has been assessed by DFT calculations. Pressed pellets electrical conducting behavior of the complexes have been studied. In addition to the coordinated dppe and bpy ligands and dithiolate ligand backbone bands [21] in the IR spectra, complexes 1/2 show bands at 1652/1644, 1472/1469 and 1059/997 cm1, diagnostic of the mC@O, mC@CS2 and mCS2 frequencies of the coordinated dithiolate ligand [19–21], respectively. The purity of the complexes was checked by NMR spectra. In the 1H NMR spectrum, complex 1 shows signals at d 1.047 ppm for the protons of methyl groups and at d 2.38 ppm for the methylene protons of the ligand L1; the signals in the d 7.34–8.13 ppm range correspond to the bpy ligand. The 13C{1H} NMR spectrum of this complex could not be obtained due to low solubility. The 1 H NMR spectrum of complex 2 displays resonances at d 2.72 ppm due to the ethylene groups of the dppe ligand and between d 7.81 and 7.26 ppm due to the aromatic protons of the L2 and dppe ligands. The 13C{1H} NMR spectrum of 2 displays resonances at d 211.39, 179.77, 132.70–121.33 and 25.44 ppm due to the CS2, CO, aromatic and ethylene carbon atoms respectively, characteristic of both ligands. In the 31P{1H} NMR spectrum, the occurrence of a single resonance at d 58.69 ppm is indicative of symmetrical bidentate bonding behavior of the dppe ligand. The UV–Vis spectra of complexes 1 and 2 were recorded in a dichloromethane solution at room temperature (Fig. 2). The features and positions of the absorptions of the two complexes are significantly different; 1 shows absorptions near 500

O S

S

S

S

O

O

(a)

L1

(b)

O

O S

S

S

S

O

O (d)

(c) L2

Fig. 1. Resonance forms of the dithiolate ligands used in this work.

substituents may induce intra- and intermolecular non-covalent interactions, organizing the supramolecular architectures. Metal complexes containing phosphine ligands have played an important role in catalytic reactions, while those with diimine ligands are important from the view point of their optical properties. Furthermore, the steric and electronic properties of dithiolate ligands in conjunction with bpy and dppe ligands may markedly influence their structural features and properties. The interesting p(chelate). . .p(bpy) intermolecular interactions in 1 and rare intramolecular C–H. . .Ni anagostic interaction observed in 2 have been supported by theoretical calculations. The results of these investigations are described herein.

1.2

1 2

ε (105 M -1cm-1)

2. Results and discussion The in situ formation of the potassium/sodium salt of the ligands K2L1/Na2L2 was achieved by reaction of 5,50 -dimethylcyclohexane-1,3-dione, KOH and CS2/1,3-indandione, NaH and CS2 in THF under a nitrogen atmosphere with ice cold conditions. The heteroleptic complexes 1 [Ni(L1)(bpy)] and 2 [Ni(L2)(dppe)] were obtained in good yields (Scheme 1) by the reaction of equivalent amounts of a mixture containing K2L1/Na2L2 and bpy/ dppe and NiCl2 in methanol. Despite our best efforts, the analogous complexes [Ni(L2)(bpy)] and [Ni(L1)(dppe)] could not be isolated. The complexes (1 and 2) have been characterized by elemental analysis, IR, UV–Vis and 1H NMR spectroscopies, and their structures have been elucidated by X-ray crystallography. Complex 2 was also characterized by 13C{1H} and 31P{1H} NMR spectra in

O

0.8

0.4

0.0

O

400

450

500

O

N

S

bpy, NiCl2

Ni

S K MeOH, -KCl O

S

N

O 1

O

O

550

Fig. 2. UV–Vis spectra of 1 and 2 in CH2Cl2 solution.

SK

THF, 0-5 C

350

λ (nm)

O KOH, CS2

300

O

O S Na dppe, NiCl2

S

THF, 0-5 C

S Na MeOH, -KCl

S

O

O 2

Scheme 1. Synthetic methodology for the ligands and complexes.

Ph

Ph

NaH, CS2

P Ni Ph

P Ph

600

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(e = 2.94  104 M1 cm1) and 300 nm (e = 1.26  105 M1 cm1), whereas in 2 bands are observed at 405 (e = 3.0  104 M1 cm1) and 340 nm (e = 2.16  104 M1 cm1); in both complexes these bands can be assigned to the metal to ligand charge transfer (MLCT) and intraligand charge transfer (ILCT) transitions [19,22] respectively.

3. Crystal structures Single crystals of 1 and 2 were grown upon slow evaporation of a dichloromethane/methanol solution. The crystallographic details and data collection parameters for both structures are given in Table S1. The molecular structures of 1 and 2 are presented in Fig. 3, while important bond distances and angles are given in Table 1. In the two structures, the Ni atom is at the centre of a distorted square plane defined by N,N-/P,P- and S,S-chelating bpy/dppe and dithiolate ligands. The average Ni–N and Ni–P bond distances in 1 and 2 are 1.926(3) and 2.172(2) Å. The Ni–S(11) and Ni–S(13) distances of 2.174(1) and 2.172(1) Å in 1 are virtually equivalent, but are significantly less than the values of 2.195(1) and 2.200(1) Å observed in 2. The N(21)–Ni(1)–N(32) and P(1)–Ni(1)–P(4) angles of 83.24(9)° and 87.45(5)°, resulting from the bpy and dppe coordination, and the S(11)–Ni–S(13) bite angles of 77.04(3)° and 78.92(5)° in 1 and 2 respectively are significantly smaller than the ideal value of 90° for a square planar geometry. These metric parameters are well within the range for analogous mixed-ligand complexes [12c,23]. The root mean square (r.m.s.) deviations of the four donor atoms in the equatorial plane from the least square planes are 0.041 and 0.035 Å with the metal atoms 0.108(2) and 0.031(2) Å from the plane for 1 and 2 respectively. A noteworthy feature of complex 1 is the head to tail dimeric aggregation of the molecule through coordinated sulfur atoms of the dithiolate ligands to the nickel centres on adjacent molecules, with a Ni1. . .S13 (1/2  x, 1/2  y, z) distance of 2.964(2) Å, which is significantly less than the sum of the Van der Waals’ radii of nickel and sulfur atoms (3.43 Å) (Fig. 4a). There are also close contacts between the two adjacent molecules in the dimer, the closest being C12. . .N32 (1/2  x, 1/2  y, z) of 3.30(1) Å. The Ni. . .Ni distance of 3.729(2) Å in the dimer indicates no intermetallic interaction in this complex. The implications of this dimer formation were investigated by DFT methods. The energy of the monomer and dimer were calculated by single point methods. The resulting energy difference of E(dimer)-2  E(monomer) was favourable, but only by a small amount, being 1.17 kcal mol1.

Table 1 Selected bond lengths (Å) and angles (o) for 1 and 2.

Ni(1)–S(11) Ni(1)–S(13) Ni(1)–X Ni(1)–Y C(12)–S(11) C(12)–S(13) C(14)–C(12) S(11)–Ni–S(13) X–Ni–Y X–Ni–S(11) X–Ni–S(13) Y–Ni–S(11) Y–Ni–S(13)

1 (X = N(21), Y = N(32)

2 (X = P(4), Y = P(1)

2.1741(8) 2.1717(8) 1.925(2) 1.928(2) 1.724(3) 1.717(3) 1.394(4) 77.04(3) 83.24(9) 99.83(7) 175.28(7) 171.02(7) 99.33(7)

2.1952(13) 2.2001(13) 2.1599(13) 2.1836(13) 1.737(5) 1.744(5) 1.361(6) 78.92(5) 87.45(5) 93.81(5) 171.94(5) 178.73(5) 99.83(5)

In 1, the p(chelate). . .p(bpy) (1  x, y, 1  z) interactions, at 3.643 Å between the dimers, extend the dimers into a 1-D supramolecular array with a head to tail arrangement (Fig. 4b). In 2, the molecule is stabilized through weak intermolecular C–H. . .p(Ar), C–H. . .O and C–H. . .p(chelate) interactions. In this molecule, the H55 atom of one molecule interacts with the centroid of one phenyl ring of the dppe ligand of an adjacent molecule, with a short distance of 2.66 Å (Fig. 5). To investigate the importance of this interaction, single point DFT calculations were carried out to calculate E(tetramer)-2  E(dimer), which turned out to be significantly unfavourable at 15.02 kcal mol1. It can be concluded that this C–H. . .p interaction is of negligible importance in this structure. In 1 and 2, the intraligand S(11). . .S(13) distances of 2.707(2) and 2.793(2) Å are considerably shorter than the sum of the Van der Waals’ radii of two sulfur atoms, i.e. 3.60 Å, indicating significant non-bonding S. . .S interactions. The shortest intermolecular S. . .S distance of 3.848(4) Å within the dimer in 1 indicates a lack of significant S. . .S intermolecular interactions. In 2, these distances are far greater due to the greater steric hindrance of the phosphine ligands. The C(12)–C(14) bond distances of 1.394(4) and 1.361(6) Å in 1 and 2 are well within the range for C(sp2)@C (sp2) [19]. The orientations of the phenyl rings on the dppe ligand in 2 are worthy of note. They can be measured by the Ni–P–C–C torsion angles, which are 13.1(1)°, 70.6(1)°, 29.7(1)° and 68.6(1)°, and as these values approach zero, an ortho phenyl hydrogen atom will approach the axial position of the nickel atom. For the two smaller angles, the Ni–H52 and Ni–H32 distances are 2.90 and 3.08 Å respectively. These two hydrogen atoms lie on the same side of the equatorial plane. The C–H. . .Ni angles are 117.6° and

Fig. 3. The molecular structure and atom numbering scheme for 1 and 2.

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Fig. 4. (a) Head to tail dimeric structure through Ni. . .S and (b) p(chelate). . .p(bpy) stacking interactions between the dimers in 1.

Fig. 5. C–H. . .p intermolecular interaction in 2.

115.0° respectively and both fall within the range of anagostic or preagostic interactions which are less commonly observed in metal dithio complexes [24]. These interactions are important because of their possible implication in C–H bond activation in organic synthesis [24]. There was no obvious way to calculate the energy of these interactions, so we created a model in which the two smaller torsion angles of 13.1° and 29.7°, which facilitate the Ni. . .H interactions, were increased to 45.0°. The energy difference of E(2)–E(model) was then calculated as 3.07 kcal mol1, showing that the experimental conformation was favourable. A second calculation involved setting the two angles to 0° and geometry optimisation led to angles of 13.5° and 23.3°, suggesting that the angles in the crystal structure were close to the energy minimum for the individual molecule (Fig. 6).

Fig. 7. Temperature dependant conducting behavior of 1 and 2.

4. Electrical conductivity The pressed pellet electrical conducting behavior of complexes 1 and 2 has been measured using complex impedance spectroscopy with powdered samples as pressed pellets sandwiched by silver electrodes (diameter: 13 mm for 1 and 2; pellet thickness of 1.1 (1) and 1.3 mm (2)). The room temperature conductivity rrt values are 4.49  107 and 8.84  105 S cm1 for 1 and 2 respectively, indicating their weakly conducting nature, which may be ascribed to the lack of an effective S. . .S intermolecular association [13] in the solid state (vide supra in the crystal structures). However, they show semiconducting behavior in the 303–363 K temperature range (Fig. 7).

5. Experimental 5.1. Material and methods

Fig. 6. Intramolecular Ni  H–C anagostic interaction in 2.

All experiments and manipulations were carried out in the open, at ambient temperature and pressure unless otherwise quoted. The chemicals 5,50 -dimethylcyclohexane-1,3-dione (HIMEDIA) and 1,3-indanedione (Sigma–Aldrich) were used as received. Solvents were distilled prior to use. The experimental details pertaining to elemental (C, H, N) analyses, IR (KBr disc), 1 H, 13C{1H} and 31P{1H} NMR (CDCl3), UV–Vis. absorption spectra (CH2Cl2) and electrical conductivity measurements are the same as described elsewhere [12d].

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5.2. Synthesis of the dithiolate ligands K2L1 and Na2L2

5.6. Theoretical calculations

(L1 = 2-(methylene-1,10 -dithiolato)-5,50 -dimethylcyclohexane1,3-dione); L2 = 2-(methylene-1,10 -dithiolato)-1,3-indandione)) The potassium/sodium salts of the ligands L1/L2 were synthesized in situ by the reaction of 5,50 -dimethylcyclohexane-1,3-dione (0.140 g, 1 mmol), pulverized KOH (0.168 g, 3 mmol) and CS2 (0.076 g, 1 mmol)/1,3-indanedione (0.146 g, 1 mmol), NaH (0.072 g, 3 mmol) and CS2 (0.076 g, 1 mmol) in 15 ml dry THF under a nitrogen atmosphere in ice cold conditions. The reaction mixture was stirred overnight yielding a yellow sticky product. The solvent was removed and the sticky product was extracted with 10 ml methanol for further reactions.

Single point calculations were carried out using the Gaussian 03 program [28]. Structures were optimized using the B3LYP density functional together with basis sets LANL2DZ for Ni, 6-31+G⁄ for S and 6-31G for the remaining atoms. Starting models were taken from the crystal structures, but with hydrogen atoms given theoretical positions.

5.3. Synthesis of complexes 1 and 2 5.3.1. [Ni(L1)(bpy)] 1 and [Ni(L2)(dppe)] 2 To a 10 ml methanol solution of K2L1(0.291 g, 1 mmol)/Na2L2/ (0.265 g, 1 mmol), prepared as described above, was added gradually a 10 ml solution of bpy (0.156 g, 1 mmol)/dppe (0.398 g, 1 mmol) in the same solvent and the resulting solution was stirred for 15 min. To this stirred solution was added a 5 ml methanolic solution of NiCl2.6H2O (0.237 g, 1 mmol), followed by stirring for 6 h at room temperature. In each case, the solid product formed was filtered off and washed with the methanol. Reddish brown needle shaped crystals of complexes 1 and 2 were obtained from a dichloromethane/methanol solution within 10–15 days.

5.4. Characterization data (1) Yield: (0.342 g, 80%); m.p.: 167–169 °C. Anal. Calc. for C19H18N2NiO2S2 (429.18): C, 53.17; H, 4.23; N, 6.53. Found: C, 52.92; H, 4.35; N, 6.33%. IR (KBr, cm1) m: 1644 (mC@O), 1445 (mC@CS2), 1059 (mC–S). 1H NMR (300.40 MHz, CDCl3) d, ppm: 8.13, 8.06, 7.51, 7.34 (4s, 8H, bpy-H), 2.38 (broad s, 4H, –(CH2)2–), 1.04 (s, 6H, (CH3)2). UV–Vis. (CH2Cl2, kmax/nm, e/M1 cm1): 300 (1.26  105), 480 (2.94  104). rrt, S cm1: 4.49  107. (2) Yield: (0.528 g, 78%), m.p.: 178–180 °C. Anal. Calc. for C36H30NiO2P2S2 (677.35): C, 63.64; H, 4.45. Found: C, 63.45; H, 4.50%. IR (KBr, cm1) m: 1652 (mC@O), 1469 (mC@CS2), 997 (mC–S). 1H NMR (300.40 MHz, CDCl3) d, ppm: 7.81–7.79 (m, 10H, –PPh2, Ar–H), 7.46–7.43 (m, 14H, –PPh2–), 2.71 (s, 4H, (CH2)2). 13C{1H} (75.45 MHz, CDCl3) d, ppm: 211.3 (CS2), 179.7 (C@O), 131.9,130.7, 129.7, 128.5, 121.3 (Ar–C, PPh2–C) 25.44 (–(CH2)2–). 31 1 P{ H} NMR (121.50 MHz, CDCl3) d, ppm: 58.69. UV–Vis. (CH2Cl2, kmax/nm, e/M1 cm1): 340 (2.16  104), 404 (3.0  104). rrt, S cm1: 8.84  105.

5.5. X-ray crystal structure determinations The X-ray diffraction data were collected by mounting single crystals of the samples on glass fibers. Single crystal X-ray data for 1 and 2 were collected on an Oxford Diffraction X-calibur CCD diffractometer at 293 K using Mo Ka radiation. The CRYSALIS program was used for data reduction [25]. The crystal structures were solved by direct method using the SHELXS-97 program [26] and refined on F2 by the full matrix least-squares technique using SHELXL-97 [27]. All non-hydrogen atoms were refined anisotropically and hydrogen atoms were geometrically fixed. Molecular structures and their weak interactions were drawn using Diamond 3.0 and Mercury 2.2.

6. Conclusions Heteroleptic Ni(II) complexes formed with the novel dianionic dithiolates 2-(methylene-1,10 -dithiolato)-5,50 -dimethylcyclohexane-1,3-dione)-bpy (1) and 2-(methylene-1,10 -dithiolato)-1,3-indandione-dppe (2) have been synthesized and fully characterized. The crystal structure of 1 revealed an intriguing dimeric structure where the ligand L1 is uniquely bonded to the metal atom on an adjacent molecule in a l2, j2 S,S-chelating– bridging fashion through weak intermolecular Ni. . .S interactions, whereas the larger steric bulk of the dppe ligand prevented dimerization in 2. In 1, the supramolecular structure is sustained via interesting p(chelate). . .p(bpy) interactions between the dimers. Remarkably in 2 the crystal packing effect and steric bulk of the dppe ligand resulted in the formation of a rare intramolecular C–H. . .Ni anagostic interaction which has been assessed by theoretical calculations. Such type of anagostic interactions are important because of their involvement in C–H bond activation. The crystal structure of 2 is stabilized by C–H. . .O, C–H. . .p(chelate) and C–H. . .p(Ar) interactions. Both the complexes are weakly conducting at room temperature due to the lack of significant S. . .S intermolecular interactions in the solid state, but show semiconducting behavior in the 303–363 K temperature range. This study demonstrates the scope of such a type of dianionic dithiolate ligand metal complex for further investigations as functional materials. Acknowledgements The Science and Engineering Research Board (SERB, SB/SI/ IC-15/2014) (NS) and University Grants Commission (ANG; SRF) New Delhi for financial assistance and the Department of Chemistry (CAS-I) Banaras Hindu University, Varanasi INDIA for the Oxford diffraction X-calibur CCD diffractometer facility are gratefully acknowledged. Appendix A. Supplementary data CCDC 1058688 and 1058689 contains the supplementary crystallographic data for 1 and 2. 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 associated with this article can be found, in the online version, at http://dx.doi.org/10. 1016/j.poly.2015.09.024. References [1] (a) D. Coucouvanis, Prog. Inorg. Chem. 11 (1970) 233; (b) D. Coucouvanis, Prog. Inorg. Chem. 26 (1979) 301. [2] G. Hogarth, Prog. Inorg. Chem. 53 (2005) 71. [3] P.J. Heard, Prog. Inorg. Chem. 53 (2005) 1. [4] J. Cookson, P.D. Beer, Dalton Trans. 15 (2007) 1459. [5] (a) E.R.T. Tiekink, I. Haiduc, Prog. Inorg. Chem. 54 (2005) 127; (b) C.S. Lai, E.R.T. Tiekink, CrystEngComm 5 (2003) 253. [6] (a) S. Naeem, S.A. Serapian, A. Toscani, A.J.P. White, G. Hogarth, J.D.E.T. WiltonEly, Inorg. Chem. 53 (2014) 2404;

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[7] [8]

[9] [10]

[11]

[12]

[13]

[14]

[15]

[16]

[17] [18]

A.N. Gupta et al. / Polyhedron 101 (2015) 251–256 (b) O.D. Fox, M.G.B. Drew, P.D. Beer, Angew. Chem., Int. Ed. Engl. 39 (2000) 135; (c) M.E. Padilla-Tosta, O.D. Fox, M.G.B. Drew, P.D. Beer, Angew. Chem., Int. Ed. Engl. 40 (2001) 4235. E.J. Mensforth, M.R. Hill, S.R. Batten, Inorg. Chim. Acta 403 (2013) 9. (a) P. O’ Brien, J.H. Park, J. Waters, Thin. Solid. Films 431 (2003) 502; (b) N. Alam, M.S. Hill, G. Kociok-Kohn, M. Zeller, M. Mazhar, K.C. Molloy, Chem. Mater. 20 (2008) 6157; (c) Y.S. Tan, A.L. Sudlow, K.C. Molloy, Y. Morishima, K. Fujisawa, W.J. Jackson, W. Henderson, S.N.B.A. Halim, S.W. Ng, E.R.T. Tiekink, Cryst. Growth Des. 13 (2013) 3046. A.A. Abramov, K.S.E. Forssberg, Miner. Process. Extr. Metall. Rev. 26 (2005) 77. (a) T. Okubo, N. Tanaka, K.H. Kim, H. Yone, M. Maekawa, T. Kuroda-Sowa, Inorg. Chem. 49 (2010) 3700; (b) T. Okubo, H. Anma, N. Tanaka, K. Himoto, S. Seki, A. Saeki, M. Maekawa, T. Kuroda-Sowa, Chem. Commun. 49 (2013) 4316; (c) D. Zhu, X.C. Xing, P.J. Wu, D.M. Zhang, D.L. Yang, Synth. Met. 42 (1991) 2541; (d) N. Singh, S. Gupta, R.K. Sinha, Inorg. Chem. Commun. 6 (2003) 46; (e) N. Singh, S. Gupta, Polyhedron 18 (1999) 1265. (a) R.F. Semeniuc, T.J. Reamer, J.P. Blitz, K.A. Wheeler, M.D. Smith, Inorg. Chem. 49 (2010) 2624; (b) Y. Yan, S. Krishnakumar, H. Yu, S. Ramishetti, L.-W. Deng, S. Wang, L. Huang, D. Huang, J. Am. Chem. Soc. 135 (2013) 5312. (a) A. Kumar, R. Chauhan, K.C. Molloy, G. Kociok-Kohn, L. Bahadur, N. Singh, Chem. Eur. J. 16 (2010) 4307; (b) V. Singh, R. Chauhan, A.N. Gupta, V. Kumar, M.G.B. Drew, L. Bahadur, N. Singh, Dalton Trans. 43 (2014) 4752; (c) S.K. Singh, R. Chauhan, K. Diwan, M.G.B. Drew, L. Bahadur, N. Singh, J. Organomet. Chem. 745–746 (2013) 190; (d) A.N. Gupta, V. Singh, V. Kumar, A. Rajput, L. Singh, M.G.B. Drew, N. Singh, Inorg. Chim. Acta 408 (2013) 145. (a) M. Bousseau, L. Valade, J.P. Legros, P. Cassoux, M. Garboukas, L.V. Interrante, J. Am. Chem. Soc. 108 (1986) 1908; (b) P. Cassoux, L. Valade, Inorganic Materials, John Wiley and Sons, Chichester, 1996. p 1. (a) C.W. Liu, B.J. Liaw, J.C. Wang, L.S. Liou, T.C. Keng, J. Chem. Soc., Dalton Trans. (2002) 1058; (b) C.W. Liu, R.J. Staples, J.P. Fackler, Coord. Chem. Rev. 174 (1998) 147; (c) B. Sarkar, B.-J. Liaw, C.-S. Fang, C.W. Liu, Inorg. Chem. 47 (2008) 2777; (d) F. Yang, P.E. Fanwick, C.P. Kubiak, Inorg. Chem. 41 (2002) 4805; (e) B.-S. Kang, Z.-N. Chew, C.-Y. Su, Z. Lin, T.-B. Wen, Polyhedron 17 (1998) 2497; (f) J. Vicente, M.T. Chicote, P. Gonzaliz-Herreo, P.G. Jones, Chem. Commun. (1997) 2047. (a) D. Coucouvanis, D. Swenson, N.C. Baenziger, R. Pedelty, M.L. Caffery, S. Kanodia, Inorg. Chem. 28 (1989) 2829; (b) D. Coucouvanis, N.C. Baenziger, S.N. Johnson, Inorg. Chem. 13 (1974) 1191. (a) E.I. Stiefel, Prog. Inorg. Chem. 52 (2004) 1; (b) S. Huertas, M. Hissler, J.E. McGarrah, R.J. Lachicotte, R. Eisenberg, Inorg. Chem. 40 (2001) 1183. J.P. Fackler, R.J. Staples, C.W. Liu, R.T. Stubbs, C. Lopez, J.T. Pitts, Pure Appl. Chem. 70 (1998) 839. (a) L. Bolundut, I. Haiduc, E. Ilyes, G.K. Köhn, K.C. Molloy, S.G. Ruiz, Inorg. Chim. Acta 363 (2010) 4319;

[19]

[20]

[21]

[22]

[23] [24]

[25] [26] [27] [28]

(b) L.F. Sánchez-Barba, A. Garcés, J. Fernández-Baeza, A. Otero, M. Honrado, A. Lara-Sánchez, A.M. Rodríguez, I. López-Solera, Eur. J. Inorg. Chem. (2014) 1922. (a) J. Vicente, P. González-Herrero, Y. García-Sánchez, P.G. Jones, M. Bardajı, Inorg. Chem. 43 (2004) 7516; (b) J. Vicente, P. González-Herrero, María Pérez-Cadenas, P.G. Jones, D. Bautista, Inorg. Chem. 46 (2007) 4718; (c) J. Vicente, P. González-Herrero, Y. García-Sánchez, P.G. Jones, Inorg. Chem. 48 (2009) 2060; (d) J. Vicente, P. González-Herrero, Y. García-Sánchez, P.G. Jones, D. Bautista, Eur. J. Inorg. Chem. (2006) 115. (a) P.C. Savino, R.D. Beremen, Inorg. Chem. 12 (1973) 173; (b) R.D. Bereman, D. Nalewajek, Inorg. Chem. 15 (1976) 2981; (c) R.D. Bereman, M.L. Good, B.J. Kalbacher, J. Buttone, Inorg. Chem. 15 (1976) 618; (d) B.J. Kalbacher, R.D. Bereman, J. Inorg. Nucl. Chem. 38 (1976) 471. (a) K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination Compounds, 4th ed., Wiley Interscience, New York, 1986; (b) K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination Compounds, Part B, 6th ed., Wiley Interscience, New York, 2009. (a) A.B.P. Lever, Inorganic Electronic Spectroscopy, Elsevier, Amsterdam, 1984; (b) S.P. Kaiwar, J.K. Hsu, L.M. Liable-Sands, A.L. Rheingold, R.S. Pilato, Inorg. Chem. 36 (1997) 4234. K. Diwan, R. Chauhan, S.K. Singh, B. Singh, M.G.B. Drew, L. Bahadur, N. Singh, New J. Chem. 38 (2014) 97. (a) M. Brookhart, M.L.H. Green, G. Parkin, Proc. Natl. Acad. Sci. U.S.A. 104 (2007) 6908; (b) H.V. Huynh, L.R. Wong, P.S. Ng, Organometallics 27 (2008) 2231; (c) R. Angamuthu, L.L. Gelauff, M.A. Siegler, A.L. Spek, E. Bouwman, Chem. Commun. (2009) 2700; (d) B. Singh, M.G.B. Drew, G.K. Kohn, K.C. Molloy, N. Singh, Dalton Trans. 40 (2011) 623; (e) A.N. Gupta, V. Kumar, V. Singh, K.K. Manar, M.G.B. Drew, N. Singh, CrystEngComm 16 (2014) 9299. Oxford Diffraction, CRYSALIS CCD, RED, Version 1.711.13, copyright 1995– 2003, Oxford Diffraction Poland Sp. G.M. Sheldrick, SHELXS 97, Program for Crystal Structure Solution, University of Gottingen, Gottingen, 1997. G.M. Sheldrick, SHELXS 97, Program for Crystal Structure Refinement, University of Gottingen, Gottingen, 1997. M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman, J.A. Montgomery, T. Vreven, K.N. Kudin, J.C. Burant, J.M. Millam, S.S. Iyengar, J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega, G.A. Petersson, H. Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J.E. Knox, H.P. Hratchian, J.B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R.E. Stratmann, O. Yazyev, A.J. Austin, R. Cammi, C. Pomelli, J.W. Ochterski, P.Y. Ayala, K. Morokuma, G.A. Voth, P. Salvador, J.J. Dannenberg, V.G. Zakrzewski, S. Dapprich, A.D. Daniels, M.C. Strain, O. Farkas, D.K. Malick, A.D. Rabuck, K. Raghavachari, J.B. Foresman, J.V. Ortiz, Q. Cui, A.G. Baboul, S. Clifford, J. Cioslowski, B.B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R.L. Martin, D.J. Fox, T. Keith, M.A. Al-Laham, C.Y. Peng, A. Nanayakkara, M. Challacombe, P.M.W. Gill, B. Johnson, W. Chen, M.W. Wong, C. Gonzalez, J.A. Pople, Gaussian 03, revision C.02; Gaussian Inc., Wallingford, CT, 2004.