Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270101004954/sk1462sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270101004954/sk1462Isup2.hkl |
CCDC reference: 166973
For related literature, see: Aizenberg et al. (1996); Alvarado et al. (1997); Angermund et al. (1988); Blake et al. (1994); Butcher & Sinn (1976); Dahlenburg & Kühnlein (1997, 2000); Dean (1979); Ermer & Mason (1982); Ganis et al. (1970); Lundquist et al. (1990); McGowan et al. (1997); Raston & White (1976); Sinn (1976); Suardi et al. (1997); Toma et al. (1993); Werner et al. (1996).
[Ir2(µ-Cl)2(η2-C8H14)4] (900 mg, 1.0 mmol) was combined with sodium N,N-dimethylcarbamate (85 mg, 0.5 mmol) in acetone (40 ml) for 6 h at ambient conditions. Filtration over Celite followed by evaporation of the solvent left the product as an orange powder which was purified by crystallization from toluene/hexane at 255 K; yield: 165 mg (62%). Found: C 42.65, H 6.62, N 2.23, S 11.87%. C19H34IrNS2 (532.7) calculated: C 42.83, H 6.43, N 2.63, S 12.03%. Single crystals were selected from the recrystallized mixture.
All non-hydrogen atoms were located by direct methods and subsequent alternate cycles of difference Fourier synthesis and full matrix least-squares refinement. The resulting structural model was refined to convergence with allowance for anisotropic displacement motion of the non-H atoms. The positions of the two olefinic hydrogen atoms (H3 and H10) were refined applying a restraint of 0.95 Å to the respective C–H bonds and making equivalent 1,3 C–H distances equal. The remaining H atoms were included in geometrically idealized positions employing appropriate riding models. For all hydrogen atoms, the isotropic displacement parameters were constrained to 1.2 times the Ueq of their carrier atoms. The highest peaks and deepest holes in the final difference map were located at distances less than 1.2 Å from the heavy metal atom.
Data collection: CAD-4 EXPRESS Software (Enraf Nonius, 1994); cell refinement: CAD-4 EXPRESS Software; data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SIR97 (Altomare et al., 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX publication routines (Farrugia, 1999).
Fig. 1. View of (I) (40% probability displacement ellipsoids) [symmetry code: (i): -x, y, 1/2 - z]. |
[Ir(C3H6NS2)(C8H14)2] | F(000) = 1056 |
Mr = 532.79 | Dx = 1.698 Mg m−3 |
Monoclinic, C2/c | Mo Kα radiation, λ = 0.71073 Å |
a = 17.9277 (10) Å | Cell parameters from 25 reflections |
b = 15.2675 (8) Å | θ = 10.2–17.4° |
c = 7.662 (3) Å | µ = 6.61 mm−1 |
β = 96.39 (1)° | T = 203 K |
V = 2084.0 (7) Å3 | Block, orange |
Z = 4 | 0.4 × 0.32 × 0.19 mm |
Nonius CAD4-MACH3 diffractometer | Rint = 0.012 |
non–profiled ω scans | θmax = 27.5°, θmin = 2.7° |
Absorption correction: ψ scan (North et al., 1968) | h = −23→23 |
Tmin = 0.162, Tmax = 0.533 | k = −2→19 |
3731 measured reflections | l = −2→9 |
2377 independent reflections | 3 standard reflections every 60 min |
2080 reflections with I > 2σ(I) | intensity decay: <2% |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.019 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.053 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.23 | w = 1/[σ2(Fo2) + (0.0245P)2 + 2.0369P] where P = (Fo2 + 2Fc2)/3 |
2377 reflections | (Δ/σ)max = 0.008 |
113 parameters | Δρmax = 0.32 e Å−3 |
4 restraints | Δρmin = −1.45 e Å−3 |
[Ir(C3H6NS2)(C8H14)2] | V = 2084.0 (7) Å3 |
Mr = 532.79 | Z = 4 |
Monoclinic, C2/c | Mo Kα radiation |
a = 17.9277 (10) Å | µ = 6.61 mm−1 |
b = 15.2675 (8) Å | T = 203 K |
c = 7.662 (3) Å | 0.4 × 0.32 × 0.19 mm |
β = 96.39 (1)° |
Nonius CAD4-MACH3 diffractometer | 2080 reflections with I > 2σ(I) |
Absorption correction: ψ scan (North et al., 1968) | Rint = 0.012 |
Tmin = 0.162, Tmax = 0.533 | 3 standard reflections every 60 min |
3731 measured reflections | intensity decay: <2% |
2377 independent reflections |
R[F2 > 2σ(F2)] = 0.019 | 4 restraints |
wR(F2) = 0.053 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.23 | Δρmax = 0.32 e Å−3 |
2377 reflections | Δρmin = −1.45 e Å−3 |
113 parameters |
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. |
x | y | z | Uiso*/Ueq | ||
Ir | 0.0000 | 0.746161 (9) | 0.2500 | 0.03388 (6) | |
S | 0.07546 (4) | 0.62218 (5) | 0.21006 (13) | 0.04348 (19) | |
N | 0.0000 | 0.4722 (2) | 0.2500 | 0.0382 (8) | |
C1 | 0.0000 | 0.5581 (3) | 0.2500 | 0.0360 (8) | |
C2 | 0.06529 (19) | 0.4217 (2) | 0.2106 (5) | 0.0487 (8) | |
H2A | 0.0996 | 0.4594 | 0.1591 | 0.058* | |
H2B | 0.0494 | 0.3755 | 0.1298 | 0.058* | |
H2C | 0.0897 | 0.3968 | 0.3171 | 0.058* | |
C3 | 0.05786 (18) | 0.8420 (2) | 0.1112 (5) | 0.0459 (8) | |
H3 | 0.0268 (16) | 0.8923 (17) | 0.084 (4) | 0.055* | |
C4 | 0.0885 (3) | 0.8095 (3) | −0.0505 (5) | 0.0642 (11) | |
H4A | 0.0470 | 0.7969 | −0.1391 | 0.077* | |
H4B | 0.1151 | 0.7551 | −0.0229 | 0.077* | |
C5 | 0.1420 (3) | 0.8741 (3) | −0.1279 (6) | 0.0751 (13) | |
H5A | 0.1485 | 0.8554 | −0.2463 | 0.090* | |
H5B | 0.1184 | 0.9313 | −0.1362 | 0.090* | |
C6 | 0.2192 (3) | 0.8832 (3) | −0.0246 (6) | 0.0729 (13) | |
H6A | 0.2405 | 0.8250 | −0.0065 | 0.087* | |
H6B | 0.2511 | 0.9155 | −0.0961 | 0.087* | |
C7 | 0.2222 (2) | 0.9282 (2) | 0.1532 (6) | 0.0650 (11) | |
H7A | 0.2635 | 0.9697 | 0.1629 | 0.078* | |
H7B | 0.1763 | 0.9614 | 0.1567 | 0.078* | |
C8 | 0.2318 (2) | 0.8683 (3) | 0.3116 (7) | 0.0714 (12) | |
H8A | 0.2314 | 0.9039 | 0.4164 | 0.086* | |
H8B | 0.2808 | 0.8409 | 0.3166 | 0.086* | |
C9 | 0.17258 (19) | 0.7959 (2) | 0.3163 (6) | 0.0544 (9) | |
H9A | 0.1796 | 0.7524 | 0.2274 | 0.065* | |
H9B | 0.1789 | 0.7673 | 0.4300 | 0.065* | |
C10 | 0.09539 (18) | 0.8328 (2) | 0.2840 (5) | 0.0432 (7) | |
H10 | 0.0862 (16) | 0.8762 (18) | 0.370 (3) | 0.052* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Ir | 0.02834 (9) | 0.03388 (9) | 0.04044 (10) | 0.000 | 0.00834 (6) | 0.000 |
S | 0.0341 (4) | 0.0382 (4) | 0.0607 (5) | 0.0001 (3) | 0.0164 (3) | 0.0006 (3) |
N | 0.0366 (18) | 0.0358 (16) | 0.043 (2) | 0.000 | 0.0078 (15) | 0.000 |
C1 | 0.033 (2) | 0.040 (2) | 0.035 (2) | 0.000 | 0.0056 (17) | 0.000 |
C2 | 0.0489 (18) | 0.0412 (16) | 0.057 (2) | 0.0098 (14) | 0.0111 (16) | 0.0000 (14) |
C3 | 0.0392 (16) | 0.0425 (16) | 0.057 (2) | −0.0049 (13) | 0.0099 (15) | 0.0077 (15) |
C4 | 0.073 (3) | 0.074 (3) | 0.047 (2) | −0.028 (2) | 0.0139 (19) | 0.0008 (19) |
C5 | 0.096 (3) | 0.072 (3) | 0.062 (3) | −0.022 (2) | 0.034 (2) | 0.007 (2) |
C6 | 0.065 (2) | 0.050 (2) | 0.113 (4) | −0.003 (2) | 0.053 (2) | 0.007 (2) |
C7 | 0.0423 (19) | 0.0470 (18) | 0.108 (4) | −0.0094 (15) | 0.019 (2) | 0.000 (2) |
C8 | 0.0403 (19) | 0.070 (2) | 0.102 (4) | −0.0159 (18) | −0.001 (2) | 0.005 (2) |
C9 | 0.0387 (17) | 0.056 (2) | 0.068 (2) | −0.0075 (15) | 0.0017 (17) | 0.0084 (18) |
C10 | 0.0388 (16) | 0.0395 (15) | 0.0526 (19) | −0.0068 (13) | 0.0111 (14) | −0.0067 (14) |
Ir—C3i | 2.144 (3) | C4—H4A | 0.9700 |
Ir—C3 | 2.144 (3) | C4—H4B | 0.9700 |
Ir—C10i | 2.155 (3) | C5—C6 | 1.522 (7) |
Ir—C10 | 2.155 (3) | C5—H5A | 0.9700 |
Ir—Si | 2.3661 (8) | C5—H5B | 0.9700 |
Ir—S | 2.3661 (8) | C6—C7 | 1.521 (6) |
S—C1 | 1.724 (2) | C6—H6A | 0.9700 |
N—C1 | 1.312 (5) | C6—H6B | 0.9700 |
N—C2 | 1.461 (3) | C7—C8 | 1.514 (6) |
N—C2i | 1.461 (3) | C7—H7A | 0.9700 |
C1—Si | 1.724 (2) | C7—H7B | 0.9700 |
C2—H2A | 0.9600 | C8—C9 | 1.536 (5) |
C2—H2B | 0.9600 | C8—H8A | 0.9700 |
C2—H2C | 0.9600 | C8—H8B | 0.9700 |
C3—C10 | 1.424 (5) | C9—C10 | 1.489 (5) |
C3—C4 | 1.495 (5) | C9—H9A | 0.9700 |
C3—H3 | 0.958 (15) | C9—H9B | 0.9700 |
C4—C5 | 1.538 (5) | C10—H10 | 0.962 (15) |
C3i—Ir—C3 | 93.88 (19) | C5—C4—H4B | 108.7 |
C3i—Ir—C10i | 38.69 (13) | H4A—C4—H4B | 107.6 |
C3—Ir—C10i | 86.68 (12) | C6—C5—C4 | 115.3 (4) |
C3i—Ir—C10 | 86.68 (12) | C6—C5—H5A | 108.5 |
C3—Ir—C10 | 38.69 (13) | C4—C5—H5A | 108.5 |
C10i—Ir—C10 | 104.25 (17) | C6—C5—H5B | 108.5 |
C3i—Ir—Si | 99.60 (9) | C4—C5—H5B | 108.5 |
C3—Ir—Si | 157.76 (11) | H5A—C5—H5B | 107.5 |
C10i—Ir—Si | 92.83 (9) | C7—C6—C5 | 116.5 (3) |
C10—Ir—Si | 158.89 (10) | C7—C6—H6A | 108.2 |
C3i—Ir—S | 157.76 (11) | C5—C6—H6A | 108.2 |
C3—Ir—S | 99.60 (9) | C7—C6—H6B | 108.2 |
C10i—Ir—S | 158.89 (10) | C5—C6—H6B | 108.2 |
C10—Ir—S | 92.83 (9) | H6A—C6—H6B | 107.3 |
Si—Ir—S | 73.75 (4) | C8—C7—C6 | 115.7 (3) |
C1—S—Ir | 87.70 (12) | C8—C7—H7A | 108.3 |
C1—N—C2 | 121.86 (18) | C6—C7—H7A | 108.3 |
C1—N—C2i | 121.86 (18) | C8—C7—H7B | 108.3 |
C2—N—C2i | 116.3 (4) | C6—C7—H7B | 108.3 |
N—C1—S | 124.57 (11) | H7A—C7—H7B | 107.4 |
N—C1—Si | 124.57 (11) | C7—C8—C9 | 115.8 (3) |
S—C1—Si | 110.9 (2) | C7—C8—H8A | 108.3 |
N—C2—H2A | 109.5 | C9—C8—H8A | 108.3 |
N—C2—H2B | 109.5 | C7—C8—H8B | 108.3 |
H2A—C2—H2B | 109.5 | C9—C8—H8B | 108.3 |
N—C2—H2C | 109.5 | H8A—C8—H8B | 107.4 |
H2A—C2—H2C | 109.5 | C10—C9—C8 | 110.9 (3) |
H2B—C2—H2C | 109.5 | C10—C9—H9A | 109.5 |
C10—C3—C4 | 124.0 (3) | C8—C9—H9A | 109.5 |
C10—C3—Ir | 71.07 (18) | C10—C9—H9B | 109.5 |
C4—C3—Ir | 115.3 (2) | C8—C9—H9B | 109.5 |
C10—C3—H3 | 119.0 (17) | H9A—C9—H9B | 108.0 |
C4—C3—H3 | 110.1 (17) | C3—C10—C9 | 121.7 (3) |
Ir—C3—H3 | 111 (2) | C3—C10—Ir | 70.23 (18) |
C3—C4—C5 | 114.1 (3) | C9—C10—Ir | 119.9 (2) |
C3—C4—H4A | 108.7 | C3—C10—H10 | 118.1 (17) |
C5—C4—H4A | 108.7 | C9—C10—H10 | 111.9 (17) |
C3—C4—H4B | 108.7 | Ir—C10—H10 | 108.2 (19) |
C3i—Ir—S—C1 | 75.3 (2) | Ir—C3—C4—C5 | −169.1 (3) |
C3—Ir—S—C1 | −158.20 (11) | C3—C4—C5—C6 | 73.1 (5) |
C10i—Ir—S—C1 | −52.2 (3) | C4—C5—C6—C7 | −69.4 (5) |
C10—Ir—S—C1 | 163.45 (10) | C5—C6—C7—C8 | 103.2 (4) |
Si—Ir—S—C1 | 0.0 | C6—C7—C8—C9 | −56.3 (5) |
C2—N—C1—S | −1.62 (18) | C7—C8—C9—C10 | −50.2 (5) |
C2i—N—C1—S | 178.38 (18) | C4—C3—C10—C9 | 5.3 (5) |
C2—N—C1—Si | 178.38 (18) | Ir—C3—C10—C9 | 113.6 (3) |
C2i—N—C1—Si | −1.62 (18) | C4—C3—C10—Ir | −108.3 (3) |
Ir—S—C1—N | 180.0 | C8—C9—C10—C3 | 88.3 (4) |
Ir—S—C1—Si | 0.0 | C8—C9—C10—Ir | 172.3 (3) |
C3i—Ir—C3—C10 | 79.78 (19) | C3i—Ir—C10—C3 | −100.4 (2) |
C10i—Ir—C3—C10 | 117.8 (2) | C10i—Ir—C10—C3 | −65.63 (18) |
Si—Ir—C3—C10 | −152.8 (2) | Si—Ir—C10—C3 | 151.3 (2) |
S—Ir—C3—C10 | −82.46 (18) | S—Ir—C10—C3 | 101.86 (18) |
C3i—Ir—C3—C4 | −160.8 (3) | C3i—Ir—C10—C9 | 143.6 (3) |
C10i—Ir—C3—C4 | −122.8 (3) | C3—Ir—C10—C9 | −116.0 (4) |
C10—Ir—C3—C4 | 119.4 (4) | C10i—Ir—C10—C9 | 178.4 (3) |
Si—Ir—C3—C4 | −33.4 (4) | Si—Ir—C10—C9 | 35.3 (5) |
S—Ir—C3—C4 | 37.0 (3) | S—Ir—C10—C9 | −14.1 (3) |
C10—C3—C4—C5 | −85.7 (5) |
Symmetry code: (i) −x, y, −z+1/2. |
Experimental details
Crystal data | |
Chemical formula | [Ir(C3H6NS2)(C8H14)2] |
Mr | 532.79 |
Crystal system, space group | Monoclinic, C2/c |
Temperature (K) | 203 |
a, b, c (Å) | 17.9277 (10), 15.2675 (8), 7.662 (3) |
β (°) | 96.39 (1) |
V (Å3) | 2084.0 (7) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 6.61 |
Crystal size (mm) | 0.4 × 0.32 × 0.19 |
Data collection | |
Diffractometer | Nonius CAD-4 MACH3 diffractometer |
Absorption correction | ψ scan (North et al., 1968) |
Tmin, Tmax | 0.162, 0.533 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 3731, 2377, 2080 |
Rint | 0.012 |
(sin θ/λ)max (Å−1) | 0.649 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.019, 0.053, 1.23 |
No. of reflections | 2377 |
No. of parameters | 113 |
No. of restraints | 4 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.32, −1.45 |
Computer programs: CAD-4 EXPRESS Software (Enraf Nonius, 1994), CAD-4 EXPRESS Software, XCAD4 (Harms & Wocadlo, 1995), SIR97 (Altomare et al., 1997), SHELXL97 (Sheldrick, 1997), ORTEP-3 for Windows (Farrugia, 1997), WinGX publication routines (Farrugia, 1999).
Ir—C3 | 2.144 (3) | N—C1 | 1.312 (5) |
Ir—C10 | 2.155 (3) | N—C2 | 1.461 (3) |
Ir—S | 2.3661 (8) | C3—C10 | 1.424 (5) |
S—C1 | 1.724 (2) | ||
Si—Ir—S | 73.75 (4) | C10—C3—C4 | 124.0 (3) |
C1—S—Ir | 87.70 (12) | C3—C10—C9 | 121.7 (3) |
S—C1—Si | 110.9 (2) | ||
C4—C3—C10—C9 | 5.3 (5) |
Symmetry code: (i) −x, y, −z+1/2. |
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Due to the known lability of olefin ligands bonded to IrI or RhI, the title compound, (I), is potentially a useful precursor of coordinatively unsaturated mixed-ligand iridium(I) dithiocarbamates. The complex was therefore prepared as a part of our studies of square-planar d8 systems containing mono- and bidentate S donor ligands and derivatives resulting therefrom by oxidative addition (Dahlenburg & Kühnlein, 1997, 2000). At the outset of these investigations there existed only a limited number of well characterized dithiocarbamatoiridium(III) complexes (Butcher & Sinn, 1976; Dean, 1979; Raston & White, 1976; Sinn, 1976) but virtually no iridium(I) derivative. Only recently the synthesis of such systems having the general formula [Ir(L)(L')(S2CNEt2)] [L/L' = cyclo-C8H12, CO/CO, PPh3/PPh3, P(OPh)3/P(OPh)3, Ph2PC2H4PPh2, (C6F5)2PC2H4P(C6F5)2, CO/PPh3] has been described, of which the mixed carbonyl(phosphine) chelate complex [Ir(CO)(PPh3)S2CNEt2] was fully characterized by single-crystal diffractometry (Suardi et al., 1997). \sch
The structure determination of (I) was undertaken because a search of the data bank located at the CCDC revealed no entry referring to a tetracoordinate 16 e iridium complex containing two π-bonded monoolefin ligands. Apparently, the only bis(olefin) complexes of IrI so far investigated by X-ray structure analysis merely include some coordinatively saturated bis(ethylene) derivatives such as [IrXL2(η2-C2H4)2] [X/L = Cl/PEt3 (Aizenberg et al., 1996), Cl/SbPri3 (Werner et al., 1996); X/L2 = tris(3,5-dimethylpyrazolyl)borate (Alvarado et al., 1997)] and [IrL3(η2-C2H4)2]X, [L, X- = PMe2Ph, BF4- (Lundquist et al., 1990); L3, X- = 1,4,7-trithiacyclononane, PF6- (Blake et al., 1994)]. With respect to bis(η2-cyclooctene) complexes of the transition metals in general, there also exists only a limited number of examples structurally characterized by X-ray diffraction; viz. [W(CO)4(η2-C8H14)2] (Toma et al., 1993), [Fe(CO)3(η2-C8H14)2] (Angermund et al., 1988), [Rh{η5-C5H4[CH(C2H4)2NMe-cyclo]}(η2-C8H14)2] (McGowan et al., 1997), and [Cu(η2-C8H14)(µ-Cl)2Cu(η2-C8H14)2] (Ganis et al., 1970).
The C-centred monoclinic unit cell of structure (I) contains four molecules of [Ir(η2-C8H14)2S2CNMe2] lying on 4 e positions with site symmetry 2. Coordination about the central iridium deviates only slightly from planarity: Although the small bite of the Me2NCS2- chelate at the central metal, 73.75 (4)°, results in cis and trans angles between the sulfur atoms and the midpoints of the coordinated double bonds declining appreciably from their idealized values of 90° and 180° [cis-S—Ir–"mid" = 96.6 (1)°, trans-S–Ir–"mid" = 170.0 (1), "mid"–Ir–"mid" = 93.2 (2)°], the sum of the four inter- and intraligand cis angles, 360.2°, is as required for a planar surrounding of the central metal. Consistently, the angle bewteen the normals to the two planes defined by the IrS2 and Ir(>C═C</2)2 fragments, 3.2 (2)°, is only marginally larger than the limiting value of 0° for planar coordination.
The IrS2CNMe2 chelate system is essentially planar, the maximum deviations from the "best" l.s.q. plane through the seven non-hydrogen atoms being ±0.017 (2) Å for sulfur donors S and Si and ∓0.020 Å for the two methyl carbons C2 and C21. The Ir–S distance of 2.3661 (8) Å within the four-membered chelate ring is slightly shorter than those of 2.384 (3) and 2.372 (3) Å derived from the structure analysis of [Ir(CO)(PPh3)S2CNEt2] for the Ir–S bonds trans to CO and PPh3, respectively (Suardi et al., 1997).
The orientation of the olefin bonds with respect to the coordination plane is almost perpendicular, as anticipated, the value of the interplanar angle (C3,C10,Ir)/(Ir,S,S_1) being 79.4 (2)°. The Ir–C distances, 2.144 (3) and 2.155 (3) Å, show the olefinic carbon atoms are nearly equidistant from the iridium atom. It is difficult to make comparisons with the corresponding structural parameters of closely related complexes, because there is but one further example of a structurally characterized (η2-cyclooctene)iridium(I) derivative, [Ir(CO)L3(η2-C8H14)][BPh4] (L3 = 2,5,8-trithia(9)-o-cyclophane), the Ir–C distances of which [2.17 (5) and 2.18 (4) Å] could not be determined with sufficient accuracy (Jenkis & Loeb, 1994). The lengthening of the olefinic double bonds [d(>C═C<) = 1.424 (5) Å versus. 1.33–1.34 Å for non-complexed cycloctenes (Ermer & Mason, 1982)] is as expected for transition metal–(>C═C<) π-bonding. The –C—C═C—C– fragments remain essentially planar after coordination, as judged from the C4–C3–C10–C9 torsion angle, 5.3 (5)°. The coordinated cycloctene ligands adopt a crown-like conformation, similar to that previously observed in two cyclooctene complexes of iron (Angermund et al., 1988) and copper (Ganis et al., 1970).