Acta Cryst. (2007). E63, m1498 [ doi:10.1107/S1600536807019769 ]
![[mu]](/logos/entities/mu_rmgif.gif)
-bromido-bis[(![[eta]](/logos/entities/eta_rmgif.gif)
4-cycloocta-1,5-diene)iridium(I)]The title complex, [Ir2(-Br)2(C8H12)2], displays a dinuclear structure with bridging Br atoms, generated by twofold symmetry. The coordination geometry around the Ir atom is pseudo-square-planar, involving two Br atoms and two 2 C=C bonds. The Ir2(-Br)2 core shows a bent geometry with a hinge angle of 101.58 (3)°.
To a Schlenk flask were added 2.11 g of Na2IrBr6 (2.94 mmol), H2O (20 ml), isopropyl alcohol (9.0 ml) and 1,5-cyclooctadiene (2.9 ml, 24 mmol). The mixture was heated under reflux for 12 hr and then cooled to ambient temperature. The whole volume was reduced to a small volume (ca 3 ml) under reduced pressure. To the residue were added 20 ml of H2O and 30 ml of toluene. The reddish organic layer was separated and the aqueous layer was extracted three times with toluene (20 ml each). The combined organic layer and the extracts were condensed to dryness. The resulting deep red solid was washed with ethanol, H2O, and ethanol successively and dried in vacuo to yield [Ir(µ-Br)(cod)]2 as a deep red solid (1.28 g, 57%). Recrystallization from THF afforded (I) as an analytically pure product. mp.: 469 K (melt, decomp. in capillary). 1H NMR (300 MHz, CDCl3, 308 K, δ, p.p.m.): 4.35 (m, 8H, =CH), 2.20 - 2.24 (m, 8H, –CHH–), 1.40 - 1.50 (m, 8H, –CHH–). IR (Nujol, cm-1): 410(w), 330(w). Analysis calculated for C16H24Br2Ir2: C 25.27, H 3.18%; found: C 25.22; H 2.83%.
All H-atoms were geometrically placed (C—H = 0.95–0.99 Å) and refined as riding with Uiso(H) = 1.2Ueq(C) [or 1.5Ueq(C) for methyl groups].
Data collection: RAPID-AUTO (Rigaku, 1998); cell refinement: RAPID-AUTO; data reduction: PROCESS in TEXSAN PROCESS (Rigaku/MSC, 2004); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: SHELXL97 and local routines.
![[Figure 1]](./hb2369fig1thm.gif)
| Fig. 1. The molecule structure of (I), showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level. The H-atoms have been omitted. Symmetry code: (i) 1 - y, 1 - x, 3/2 - z. |
| [Ir2Br2(C8H12)2] | Dx = 2.976 Mg m−3 |
| Mr = 760.57 | Melting point: 469 K |
| Tetragonal, P41212 | Mo Kα radiation, λ = 0.71075 Å |
| Hall symbol: P 4abw 2nw | Cell parameters from 69455 reflections |
| a = 8.3839 (5) Å | θ = 3.4–31.3° |
| c = 24.1471 (19) Å | µ = 20.36 mm−1 |
| V = 1697.3 (2) Å3 | T = 100 K |
| Z = 4 | Block, red |
| F(000) = 1376 | 0.19 × 0.15 × 0.11 mm |
| Rigaku R-AXIS RAPID diffractometer | 2840 independent reflections |
| Radiation source: normal-focus sealed tube | 2591 reflections with I > 2σ(I) |
| graphite | Rint = 0.129 |
| Detector resolution: 10.00 pixels mm-1 | θmax = 31.6°, θmin = 3.4° |
| ω scans | h = −12→12 |
| Absorption correction: numerical (ABSCOR; Higashi, 1999) | k = −12→12 |
| Tmin = 0.114, Tmax = 0.431 | l = −35→35 |
| 48361 measured reflections |
| Refinement on F2 | Secondary atom site location: difference Fourier map |
| Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
| R[F2 > 2σ(F2)] = 0.034 | H-atom parameters constrained |
| wR(F2) = 0.064 | w = 1/[σ2(Fo2) + (0.0225P)2 + 4.3085P] where P = (Fo2 + 2Fc2)/3 |
| S = 1.09 | (Δ/σ)max = 0.002 |
| 2840 reflections | Δρmax = 1.33 e Å−3 |
| 91 parameters | Δρmin = −2.56 e Å−3 |
| 0 restraints | Absolute structure: Flack (1983), 1112 Friedel pairs |
| Primary atom site location: structure-invariant direct methods | Flack parameter: 0.02 (2) |
| [Ir2Br2(C8H12)2] | Z = 4 |
| Mr = 760.57 | Mo Kα radiation |
| Tetragonal, P41212 | µ = 20.36 mm−1 |
| a = 8.3839 (5) Å | T = 100 K |
| c = 24.1471 (19) Å | 0.19 × 0.15 × 0.11 mm |
| V = 1697.3 (2) Å3 |
| Rigaku R-AXIS RAPID diffractometer | 2840 independent reflections |
| Absorption correction: numerical (ABSCOR; Higashi, 1999) | 2591 reflections with I > 2σ(I) |
| Tmin = 0.114, Tmax = 0.431 | Rint = 0.129 |
| 48361 measured reflections | θmax = 31.6° |
| R[F2 > 2σ(F2)] = 0.034 | H-atom parameters constrained |
| wR(F2) = 0.064 | Δρmax = 1.33 e Å−3 |
| S = 1.09 | Δρmin = −2.56 e Å−3 |
| 2840 reflections | Absolute structure: Flack (1983), 1112 Friedel pairs |
| 91 parameters | Flack parameter: 0.02 (2) |
| 0 restraints |
Experimental. Indexing was performed from 3 oscillations which were exposed for 1.3 minutes. The camera radiuswas 127.40 mm. Readout performed in the 0.100 mm pixel mode. A total of 300 images, corresponding to 600.0 °. osillation angles, were collected with 4 different goniometer setting. Exposure time was 100 s per degree. The camera radiuswas 127.40 mm. Readout performed in the 0.100 mm pixel mode. |
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. Least-squares planes (x,y,z in crystal coordinates) and deviations from them (* indicates atom used to define plane) - 1.1015 (0.0026) x + 8.0857 (0.0009) y + 5.5390 (0.0060) z = 7.6598 (0.0050) * 0.0000 (0.0000) Ir * 0.0000 (0.0000) Br * 0.0000 (0.0000) Br_$1 Rms deviation of fitted atoms = 0.0000 8.0857 (0.0009) x - 1.1015 (0.0026) y + 5.5390 (0.0060) z = 7.6329 (0.0044) Angle to previous plane (with approximate e.s.d.) = 78.42 (0.03) * 0.0000 (0.0000) Ir_$1 * 0.0000 (0.0000) Br * 0.0000 (0.0000) Br_$1 Rms deviation of fitted atoms = 0.0000 |
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. |
| x | y | z | Uiso*/Ueq | ||
| Ir | 0.71261 (3) | 0.51576 (3) | 0.771695 (9) | 0.01892 (6) | |
| Br | 0.55064 (8) | 0.55356 (8) | 0.68431 (2) | 0.02227 (14) | |
| C1 | 0.8208 (8) | 0.5503 (8) | 0.8497 (2) | 0.0225 (14) | |
| H1 | 0.7181 | 0.5761 | 0.8637 | 0.027* | |
| C2 | 0.8474 (9) | 0.3900 (9) | 0.8320 (2) | 0.0233 (14) | |
| H2 | 0.7609 | 0.3170 | 0.8337 | 0.028* | |
| C3 | 1.0064 (9) | 0.3299 (9) | 0.8105 (3) | 0.0267 (15) | |
| H3A | 1.0216 | 0.2178 | 0.8222 | 0.032* | |
| H3B | 1.0935 | 0.3942 | 0.8269 | 0.032* | |
| C4 | 1.0161 (9) | 0.3402 (9) | 0.7468 (3) | 0.0262 (15) | |
| H4A | 1.1289 | 0.3534 | 0.7356 | 0.031* | |
| H4B | 0.9768 | 0.2390 | 0.7306 | 0.031* | |
| C5 | 0.9189 (8) | 0.4778 (9) | 0.7238 (2) | 0.0232 (13) | |
| H5 | 0.8512 | 0.4563 | 0.6931 | 0.028* | |
| C6 | 0.9213 (9) | 0.6350 (8) | 0.7443 (3) | 0.0241 (15) | |
| H6 | 0.8515 | 0.7107 | 0.7279 | 0.029* | |
| C7 | 1.0287 (9) | 0.6909 (10) | 0.7912 (3) | 0.0289 (15) | |
| H7A | 1.0621 | 0.8023 | 0.7841 | 0.035* | |
| H7B | 1.1259 | 0.6238 | 0.7921 | 0.035* | |
| C8 | 0.9438 (10) | 0.6819 (9) | 0.8479 (3) | 0.0303 (17) | |
| H8A | 1.0241 | 0.6633 | 0.8772 | 0.036* | |
| H8B | 0.8910 | 0.7852 | 0.8556 | 0.036* |
| U11 | U22 | U33 | U12 | U13 | U23 | |
| Ir | 0.02031 (13) | 0.02195 (14) | 0.01450 (9) | 0.00101 (10) | −0.00110 (9) | −0.00051 (9) |
| Br | 0.0270 (4) | 0.0221 (3) | 0.0177 (3) | 0.0016 (3) | −0.0040 (2) | 0.0020 (2) |
| C1 | 0.022 (4) | 0.026 (4) | 0.019 (3) | −0.004 (3) | −0.002 (2) | 0.004 (2) |
| C2 | 0.021 (4) | 0.033 (4) | 0.016 (3) | −0.002 (3) | −0.002 (2) | 0.003 (2) |
| C3 | 0.025 (4) | 0.033 (4) | 0.023 (3) | 0.003 (3) | 0.000 (3) | 0.009 (3) |
| C4 | 0.030 (4) | 0.027 (4) | 0.022 (3) | 0.006 (3) | 0.008 (3) | −0.001 (3) |
| C5 | 0.020 (3) | 0.033 (4) | 0.017 (3) | 0.004 (3) | 0.000 (2) | 0.005 (3) |
| C6 | 0.028 (4) | 0.021 (3) | 0.023 (3) | −0.002 (3) | 0.002 (3) | 0.005 (2) |
| C7 | 0.025 (4) | 0.034 (4) | 0.028 (3) | −0.008 (3) | 0.000 (3) | 0.000 (3) |
| C8 | 0.036 (4) | 0.032 (4) | 0.023 (3) | −0.008 (3) | −0.008 (3) | −0.005 (3) |
| Ir—C5 | 2.105 (6) | C3—H3A | 0.9900 |
| Ir—C1 | 2.111 (6) | C3—H3B | 0.9900 |
| Ir—C6 | 2.121 (7) | C4—C5 | 1.518 (9) |
| Ir—C2 | 2.123 (6) | C4—H4A | 0.9900 |
| Ir—Br | 2.5293 (7) | C4—H4B | 0.9900 |
| Ir—Bri | 2.5335 (7) | C5—C6 | 1.408 (10) |
| Ir—Iri | 2.9034 (5) | C5—H5 | 0.9500 |
| Br—Iri | 2.5335 (7) | C6—C7 | 1.519 (10) |
| C1—C2 | 1.429 (10) | C6—H6 | 0.9500 |
| C1—C8 | 1.511 (10) | C7—C8 | 1.546 (10) |
| C1—H1 | 0.9500 | C7—H7A | 0.9900 |
| C2—C3 | 1.517 (10) | C7—H7B | 0.9900 |
| C2—H2 | 0.9500 | C8—H8A | 0.9900 |
| C3—C4 | 1.542 (9) | C8—H8B | 0.9900 |
| C5—Ir—C1 | 99.1 (3) | C2—C3—H3A | 109.3 |
| C5—Ir—C6 | 38.9 (3) | C4—C3—H3A | 109.3 |
| C1—Ir—C6 | 81.9 (3) | C2—C3—H3B | 109.3 |
| C5—Ir—C2 | 82.2 (3) | C4—C3—H3B | 109.3 |
| C1—Ir—C2 | 39.4 (3) | H3A—C3—H3B | 108.0 |
| C6—Ir—C2 | 90.5 (3) | C5—C4—C3 | 112.3 (6) |
| C5—Ir—Br | 90.09 (17) | C5—C4—H4A | 109.1 |
| C1—Ir—Br | 163.4 (2) | C3—C4—H4A | 109.1 |
| C6—Ir—Br | 97.13 (19) | C5—C4—H4B | 109.1 |
| C2—Ir—Br | 156.9 (2) | C3—C4—H4B | 109.1 |
| C5—Ir—Bri | 157.1 (2) | H4A—C4—H4B | 107.9 |
| C1—Ir—Bri | 91.95 (18) | C6—C5—C4 | 125.1 (6) |
| C6—Ir—Bri | 163.9 (2) | C6—C5—Ir | 71.1 (4) |
| C2—Ir—Bri | 94.1 (2) | C4—C5—Ir | 110.8 (4) |
| Br—Ir—Bri | 84.52 (3) | C6—C5—H5 | 117.5 |
| C5—Ir—Iri | 104.1 (2) | C4—C5—H5 | 117.5 |
| C1—Ir—Iri | 134.09 (18) | Ir—C5—H5 | 88.1 |
| C6—Ir—Iri | 137.95 (19) | C5—C6—C7 | 124.0 (7) |
| C2—Ir—Iri | 105.7 (2) | C5—C6—Ir | 69.9 (4) |
| Br—Ir—Iri | 55.074 (17) | C7—C6—Ir | 113.7 (4) |
| Bri—Ir—Iri | 54.939 (16) | C5—C6—H6 | 118.0 |
| Ir—Br—Iri | 69.987 (19) | C7—C6—H6 | 118.0 |
| C2—C1—C8 | 124.8 (7) | Ir—C6—H6 | 86.4 |
| C2—C1—Ir | 70.7 (3) | C6—C7—C8 | 111.8 (6) |
| C8—C1—Ir | 111.5 (4) | C6—C7—H7A | 109.3 |
| C2—C1—H1 | 117.6 | C8—C7—H7A | 109.3 |
| C8—C1—H1 | 117.6 | C6—C7—H7B | 109.3 |
| Ir—C1—H1 | 87.7 | C8—C7—H7B | 109.3 |
| C1—C2—C3 | 123.5 (7) | H7A—C7—H7B | 107.9 |
| C1—C2—Ir | 69.8 (4) | C1—C8—C7 | 112.1 (6) |
| C3—C2—Ir | 113.5 (4) | C1—C8—H8A | 109.2 |
| C1—C2—H2 | 118.2 | C7—C8—H8A | 109.2 |
| C3—C2—H2 | 118.2 | C1—C8—H8B | 109.2 |
| Ir—C2—H2 | 86.8 | C7—C8—H8B | 109.2 |
| C2—C3—C4 | 111.6 (6) | H8A—C8—H8B | 107.9 |
| C5—Ir—Br—Iri | 107.2 (2) | C3—C4—C5—C6 | 47.0 (10) |
| C1—Ir—Br—Iri | −128.8 (6) | C3—C4—C5—Ir | −34.0 (8) |
| C6—Ir—Br—Iri | 145.6 (2) | C1—Ir—C5—C6 | −64.8 (4) |
| C2—Ir—Br—Iri | 37.3 (5) | C2—Ir—C5—C6 | −100.5 (4) |
| Bri—Ir—Br—Iri | −50.44 (3) | Br—Ir—C5—C6 | 101.3 (4) |
| C5—Ir—C1—C2 | −65.7 (4) | Bri—Ir—C5—C6 | 177.3 (4) |
| C6—Ir—C1—C2 | −100.8 (4) | Iri—Ir—C5—C6 | 155.1 (3) |
| Br—Ir—C1—C2 | 171.5 (5) | C1—Ir—C5—C4 | 56.5 (5) |
| Bri—Ir—C1—C2 | 94.1 (4) | C6—Ir—C5—C4 | 121.3 (7) |
| Iri—Ir—C1—C2 | 54.2 (5) | C2—Ir—C5—C4 | 20.8 (5) |
| C5—Ir—C1—C8 | 55.1 (6) | Br—Ir—C5—C4 | −137.4 (5) |
| C6—Ir—C1—C8 | 20.1 (5) | Bri—Ir—C5—C4 | −61.4 (7) |
| C2—Ir—C1—C8 | 120.8 (7) | Iri—Ir—C5—C4 | −83.6 (5) |
| Br—Ir—C1—C8 | −67.7 (9) | C4—C5—C6—C7 | 3.1 (11) |
| Bri—Ir—C1—C8 | −145.0 (5) | Ir—C5—C6—C7 | 105.7 (6) |
| Iri—Ir—C1—C8 | 175.1 (4) | C4—C5—C6—Ir | −102.6 (6) |
| C8—C1—C2—C3 | 2.1 (10) | C1—Ir—C6—C5 | 115.5 (4) |
| Ir—C1—C2—C3 | 105.4 (6) | C2—Ir—C6—C5 | 76.9 (4) |
| C8—C1—C2—Ir | −103.3 (6) | Br—Ir—C6—C5 | −81.2 (4) |
| C5—Ir—C2—C1 | 114.7 (4) | Bri—Ir—C6—C5 | −176.2 (5) |
| C6—Ir—C2—C1 | 76.6 (4) | Iri—Ir—C6—C5 | −37.5 (5) |
| Br—Ir—C2—C1 | −173.8 (4) | C5—Ir—C6—C7 | −119.3 (7) |
| Bri—Ir—C2—C1 | −88.0 (4) | C1—Ir—C6—C7 | −3.8 (6) |
| Iri—Ir—C2—C1 | −142.7 (4) | C2—Ir—C6—C7 | −42.4 (6) |
| C5—Ir—C2—C3 | −4.1 (6) | Br—Ir—C6—C7 | 159.4 (5) |
| C1—Ir—C2—C3 | −118.8 (8) | Bri—Ir—C6—C7 | 64.5 (10) |
| C6—Ir—C2—C3 | −42.3 (6) | Iri—Ir—C6—C7 | −156.9 (4) |
| Br—Ir—C2—C3 | 67.4 (8) | C5—C6—C7—C8 | −93.9 (8) |
| Bri—Ir—C2—C3 | 153.1 (5) | Ir—C6—C7—C8 | −12.8 (8) |
| Iri—Ir—C2—C3 | 98.4 (5) | C2—C1—C8—C7 | 48.2 (9) |
| C1—C2—C3—C4 | −93.8 (8) | Ir—C1—C8—C7 | −32.8 (8) |
| Ir—C2—C3—C4 | −13.2 (8) | C6—C7—C8—C1 | 29.7 (9) |
| C2—C3—C4—C5 | 30.8 (9) |
| Symmetry codes: (i) −y+1, −x+1, −z+3/2. |
| Ir—C5 | 2.105 (6) | Ir—Br | 2.5293 (7) |
| Ir—C1 | 2.111 (6) | Ir—Bri | 2.5335 (7) |
| Ir—C6 | 2.121 (7) | Ir—Iri | 2.9034 (5) |
| Ir—C2 | 2.123 (6) | ||
| Br—Ir—Bri | 84.52 (3) | Ir—Br—Iri | 69.987 (19) |
| Symmetry codes: (i) −y+1, −x+1, −z+3/2. |
This research was supported by a Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology, Japan.
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Crystal data for many kinds of the binuclear complexes of d8 transition metal ions of type [L2M(µ-X)]2 (M= Rh or Ir, X = halide) and their theoretical analysis have been reported (Aullón, et al., 1998; Cotton, et al., 1999). The bromide analogues are fairly rare, however. Among these complexes cyclooctadiene complexes of group 8 transition elements [M(µ-Cl)(cod)]2 (COD = cis,cis-1,5-cyclooctadiene; M = IrI or RhI) have been used as starting key complexes for various kinds of IrI or RhI complexes useful as efficient catalyst precursors. For example, we have reported the molecular structure of [Ir(µ-Cl){(R)-binap}]2 (Yamagata et al., 1997), which was prepared from the reaction of [Ir(µ-Cl)(cod)]2 with two equivalents of (R)-BINAP {(R)-(+)-2,2'-bis(diphenylphosphanyl)-1,1'-binaphthyl}, and its use as an efficient catalyst for asymmetric hydrogenation of prochiral imines (Tani, et al., 1995). The catalytic asymmetric olefin hydroamination with [Ir(µ-Cl)(diphosphine)]2 and the structure of [Ir(µ-Cl){(R)-binap}]2 have also been investigated by Togni and his co-workers (Dorta, et al., 1997). Although [Rh(µ-Cl)(cod)]2 (De Ridder, et al., 1994) has an almost square planar structure (the hinge angle 169.1 (3)°), [Ir(µ-Cl)(cod)]2 (Cotton, et al., 1986) and [Rh(µ-Br)(cod)]2 (Pettinari, et al., 2002) show bent structures; the hinge angles are 109.4 (3)° and 148.7 (3)°, respectively. Thus, it may be interest to examine the structure of [Ir(µ-Br)(cod)]2, (I), which is reported here. (I) is isostructural with [Ir(µ-Cl)(cod)]2 and [Rh(µ-Br)(cod)]2. The Ir2(µ-Br)2 core in (I) shows a bent geometry with the hinge angles of 101.58 (3)°. The M···M distances of (I), [Ir(µ-Cl)(cod)]2, and [Rh(µ-Br)(cod)]2 are 2.9034 (5), 2.910 (1), and 3.565 Å, respectively. The degree of the bending is Rh < Ir and Cl < Br. These tendencies can be explained by the differences in diffuseness of the metal d orbitals and by analyzing the <pz2/dz2> and <dz2/dz2> overlap integrals between the Slater orbitals (EH calculations) (Aullón, et al., 1998).