Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S010827010302376X/fr1440sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S010827010302376X/fr1440Isup2.hkl |
CCDC reference: 229085
A solution of (2-isopropyl)phenylamino-4-(2-isopropyl)phenylimino-pent-2-ene (2.617 g, 7.8 mmol) in dry hexane (5 ml), to which a solution of 'dibutylmagnesium' (8.75 ml of a 0.897M solution in heptanes, Aldrich Chemical Company) had been added under argon, was heated to boiling. Slow cooling of the solution to room temperature afforded a crop of well formed crystals, which were isolated by filtration. A yield of 1.5 g [40% based on (2-isopropyl)phenylamino-4-(2-isopropyl)phenylimino-pent-2-ene] of Mg(II)2 was obtained. Cooling of the filtrate to 245 K gave a further small crop of Mg(II)2, from which supernatant liquor was removed by syringe prior to transportation to the diffractometer.
All H atoms were placed in calculated positions and treated as riding (methyl C—H = 0.980 Å, Uiso(H) = 1.5Ueq(C); methine C—H= 1.000 Å and aryl C—H = 0.950 Å, both with Uiso(H) = 1.2Ueq(C)], with the exception of atoms H11A and H34A, the H atoms of the unsaturated pentene backbone, which were refined isotropically. Methyl-group orientations, apart from that of the C14 group, were obtained by refining a rotation about the C—Me axis. The C14 group was modeled with H atoms disordered over two sites.
Data collection: DENZO (Otwinowski & Minor, 1997) and COLLECT (Hooft, 1998); cell refinement: DENZO and COLLECT; data reduction: DENZO; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPII (Johnson, 1976); software used to prepare material for publication: SHELXL97.
[Mg(C23H29N2)2] | F(000) = 1496 |
Mr = 691.27 | Dx = 1.095 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2ybc | Cell parameters from 9856 reflections |
a = 16.6252 (10) Å | θ = 2.9–27.5° |
b = 10.6287 (5) Å | µ = 0.08 mm−1 |
c = 23.831 (2) Å | T = 173 K |
β = 95.484 (5)° | Prism, colourless |
V = 4191.8 (5) Å3 | 0.28 × 0.14 × 0.12 mm |
Z = 4 |
Nonius KappaCCD diffractometer | 5453 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.053 |
Graphite monochromator | θmax = 27.5°, θmin = 2.9° |
ω and ϕ scans | h = −21→21 |
18102 measured reflections | k = −13→12 |
9565 independent reflections | l = −30→30 |
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)] = 0.048 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.119 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.03 | w = 1/[σ2(Fo2) + (0.0545P)2] where P = (Fo2 + 2Fc2)/3 |
9565 reflections | (Δ/σ)max < 0.001 |
479 parameters | Δρmax = 0.29 e Å−3 |
0 restraints | Δρmin = −0.24 e Å−3 |
[Mg(C23H29N2)2] | V = 4191.8 (5) Å3 |
Mr = 691.27 | Z = 4 |
Monoclinic, P21/c | Mo Kα radiation |
a = 16.6252 (10) Å | µ = 0.08 mm−1 |
b = 10.6287 (5) Å | T = 173 K |
c = 23.831 (2) Å | 0.28 × 0.14 × 0.12 mm |
β = 95.484 (5)° |
Nonius KappaCCD diffractometer | 5453 reflections with I > 2σ(I) |
18102 measured reflections | Rint = 0.053 |
9565 independent reflections |
R[F2 > 2σ(F2)] = 0.048 | 0 restraints |
wR(F2) = 0.119 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.03 | Δρmax = 0.29 e Å−3 |
9565 reflections | Δρmin = −0.24 e Å−3 |
479 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. |
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 | Occ. (<1) | |
Mg1 | 0.71763 (3) | 0.37498 (4) | 0.57234 (2) | 0.02399 (14) | |
N1 | 0.66719 (8) | 0.22681 (11) | 0.61040 (6) | 0.0253 (3) | |
N2 | 0.70767 (7) | 0.28129 (11) | 0.49693 (5) | 0.0251 (3) | |
N3 | 0.65300 (7) | 0.53607 (11) | 0.58297 (6) | 0.0268 (3) | |
N4 | 0.82320 (7) | 0.47331 (11) | 0.58350 (6) | 0.0257 (3) | |
C1 | 0.68164 (9) | 0.21136 (13) | 0.67037 (7) | 0.0267 (4) | |
C2 | 0.74761 (10) | 0.13862 (14) | 0.69275 (7) | 0.0290 (4) | |
C3 | 0.76088 (11) | 0.12955 (15) | 0.75137 (8) | 0.0370 (4) | |
H3 | 0.8045 | 0.0796 | 0.7675 | 0.044* | |
C4 | 0.71253 (11) | 0.19095 (16) | 0.78670 (8) | 0.0389 (4) | |
H4 | 0.7231 | 0.1831 | 0.8264 | 0.047* | |
C5 | 0.64902 (11) | 0.26348 (15) | 0.76402 (8) | 0.0377 (4) | |
H5 | 0.6158 | 0.3065 | 0.7881 | 0.045* | |
C6 | 0.63360 (10) | 0.27355 (15) | 0.70607 (7) | 0.0337 (4) | |
H6 | 0.5896 | 0.3236 | 0.6905 | 0.040* | |
C7 | 0.80104 (10) | 0.07048 (15) | 0.65432 (8) | 0.0363 (4) | |
H7 | 0.8052 | 0.1257 | 0.6207 | 0.044* | |
C8 | 0.88643 (11) | 0.04651 (17) | 0.68025 (9) | 0.0521 (5) | |
H8A | 0.8856 | −0.0167 | 0.7101 | 0.078* | |
H8B | 0.9096 | 0.1250 | 0.6962 | 0.078* | |
H8C | 0.9194 | 0.0157 | 0.6512 | 0.078* | |
C9 | 0.76308 (13) | −0.05182 (19) | 0.63279 (12) | 0.0773 (8) | |
H9A | 0.7564 | −0.1078 | 0.6647 | 0.116* | |
H9B | 0.7981 | −0.0922 | 0.6073 | 0.116* | |
H9C | 0.7102 | −0.0347 | 0.6125 | 0.116* | |
C10 | 0.60604 (10) | 0.16748 (13) | 0.58192 (7) | 0.0272 (4) | |
C11 | 0.59149 (10) | 0.16902 (15) | 0.52290 (8) | 0.0287 (4) | |
C12 | 0.64079 (9) | 0.21455 (14) | 0.48287 (7) | 0.0273 (4) | |
C13 | 0.54658 (11) | 0.09230 (15) | 0.61323 (8) | 0.0409 (5) | |
H13A | 0.5762 | 0.0428 | 0.6431 | 0.061* | |
H13B | 0.5157 | 0.0357 | 0.5868 | 0.061* | |
H13C | 0.5095 | 0.1500 | 0.6299 | 0.061* | |
C14 | 0.61436 (10) | 0.18717 (16) | 0.42176 (7) | 0.0373 (4) | |
H14A | 0.6534 | 0.2234 | 0.3980 | 0.056* | 0.50 |
H14B | 0.5610 | 0.2243 | 0.4116 | 0.056* | 0.50 |
H14C | 0.6115 | 0.0959 | 0.4159 | 0.056* | 0.50 |
H14D | 0.5639 | 0.1390 | 0.4190 | 0.056* | 0.50 |
H14E | 0.6563 | 0.1382 | 0.4054 | 0.056* | 0.50 |
H14F | 0.6058 | 0.2665 | 0.4011 | 0.056* | 0.50 |
C15 | 0.76423 (9) | 0.30235 (14) | 0.45613 (7) | 0.0274 (4) | |
C16 | 0.81386 (10) | 0.20628 (15) | 0.43876 (7) | 0.0332 (4) | |
C17 | 0.87299 (11) | 0.23894 (19) | 0.40343 (8) | 0.0453 (5) | |
H17 | 0.9070 | 0.1749 | 0.3910 | 0.054* | |
C18 | 0.88360 (11) | 0.3611 (2) | 0.38603 (8) | 0.0485 (5) | |
H18 | 0.9244 | 0.3804 | 0.3620 | 0.058* | |
C19 | 0.83459 (11) | 0.45497 (18) | 0.40369 (8) | 0.0426 (5) | |
H19 | 0.8417 | 0.5395 | 0.3922 | 0.051* | |
C20 | 0.77503 (10) | 0.42535 (15) | 0.43830 (7) | 0.0330 (4) | |
H20 | 0.7410 | 0.4900 | 0.4501 | 0.040* | |
C21 | 0.80791 (11) | 0.07077 (15) | 0.45886 (8) | 0.0411 (5) | |
H21 | 0.7587 | 0.0640 | 0.4797 | 0.049* | |
C22 | 0.88095 (13) | 0.03628 (18) | 0.49966 (9) | 0.0596 (6) | |
H22A | 0.9304 | 0.0460 | 0.4808 | 0.089* | |
H22B | 0.8761 | −0.0512 | 0.5119 | 0.089* | |
H22C | 0.8833 | 0.0919 | 0.5326 | 0.089* | |
C23 | 0.79883 (15) | −0.02393 (18) | 0.40976 (10) | 0.0668 (7) | |
H23A | 0.7551 | 0.0033 | 0.3819 | 0.100* | |
H23B | 0.7861 | −0.1073 | 0.4242 | 0.100* | |
H23C | 0.8495 | −0.0281 | 0.3919 | 0.100* | |
C24 | 0.57608 (9) | 0.52988 (13) | 0.60533 (7) | 0.0285 (4) | |
C25 | 0.56199 (10) | 0.58422 (14) | 0.65713 (7) | 0.0308 (4) | |
C26 | 0.48868 (11) | 0.55787 (15) | 0.67876 (8) | 0.0378 (5) | |
H26 | 0.4788 | 0.5920 | 0.7143 | 0.045* | |
C27 | 0.42992 (11) | 0.48366 (16) | 0.65008 (9) | 0.0418 (5) | |
H27 | 0.3804 | 0.4678 | 0.6657 | 0.050* | |
C28 | 0.44370 (10) | 0.43293 (16) | 0.59873 (9) | 0.0409 (5) | |
H28 | 0.4035 | 0.3827 | 0.5785 | 0.049* | |
C29 | 0.51643 (10) | 0.45538 (14) | 0.57669 (8) | 0.0336 (4) | |
H29 | 0.5259 | 0.4194 | 0.5414 | 0.040* | |
C30 | 0.62401 (11) | 0.66733 (15) | 0.69083 (8) | 0.0367 (4) | |
H30 | 0.6678 | 0.6872 | 0.6662 | 0.044* | |
C31 | 0.58666 (12) | 0.79220 (16) | 0.70774 (9) | 0.0517 (5) | |
H31A | 0.5584 | 0.8319 | 0.6743 | 0.078* | |
H31B | 0.6295 | 0.8483 | 0.7240 | 0.078* | |
H31C | 0.5482 | 0.7761 | 0.7356 | 0.078* | |
C32 | 0.66269 (13) | 0.60130 (18) | 0.74348 (9) | 0.0571 (6) | |
H32A | 0.6208 | 0.5792 | 0.7680 | 0.086* | |
H32B | 0.7021 | 0.6576 | 0.7637 | 0.086* | |
H32C | 0.6900 | 0.5246 | 0.7325 | 0.086* | |
C33 | 0.67669 (10) | 0.64077 (14) | 0.55877 (7) | 0.0277 (4) | |
C34 | 0.75558 (10) | 0.65782 (15) | 0.54367 (7) | 0.0284 (4) | |
C35 | 0.82524 (10) | 0.58584 (14) | 0.55889 (7) | 0.0272 (4) | |
C36 | 0.61757 (10) | 0.74752 (14) | 0.54605 (8) | 0.0357 (4) | |
H36A | 0.5669 | 0.7142 | 0.5275 | 0.054* | |
H36B | 0.6405 | 0.8084 | 0.5211 | 0.054* | |
H36C | 0.6070 | 0.7892 | 0.5813 | 0.054* | |
C37 | 0.90481 (10) | 0.64131 (15) | 0.54561 (8) | 0.0389 (5) | |
H37A | 0.9436 | 0.6374 | 0.5792 | 0.058* | |
H37B | 0.8968 | 0.7292 | 0.5340 | 0.058* | |
H37C | 0.9257 | 0.5934 | 0.5150 | 0.058* | |
C38 | 0.89797 (9) | 0.41404 (14) | 0.60469 (7) | 0.0263 (4) | |
C39 | 0.92379 (10) | 0.42207 (14) | 0.66232 (7) | 0.0305 (4) | |
C40 | 0.99471 (11) | 0.35953 (15) | 0.68156 (8) | 0.0386 (4) | |
H40 | 1.0141 | 0.3654 | 0.7203 | 0.046* | |
C41 | 1.03776 (11) | 0.28893 (16) | 0.64578 (9) | 0.0405 (5) | |
H41 | 1.0860 | 0.2471 | 0.6599 | 0.049* | |
C42 | 1.01031 (10) | 0.27974 (15) | 0.58980 (8) | 0.0385 (5) | |
H42 | 1.0391 | 0.2303 | 0.5652 | 0.046* | |
C43 | 0.94079 (10) | 0.34244 (15) | 0.56918 (8) | 0.0336 (4) | |
H43 | 0.9222 | 0.3363 | 0.5303 | 0.040* | |
C44 | 0.87574 (11) | 0.49676 (16) | 0.70215 (8) | 0.0413 (5) | |
H44 | 0.8178 | 0.4936 | 0.6865 | 0.050* | |
C45 | 0.88042 (13) | 0.44309 (19) | 0.76177 (8) | 0.0549 (6) | |
H45A | 0.8661 | 0.3536 | 0.7601 | 0.082* | |
H45B | 0.8427 | 0.4884 | 0.7836 | 0.082* | |
H45C | 0.9355 | 0.4527 | 0.7799 | 0.082* | |
C46 | 0.90110 (16) | 0.63585 (17) | 0.70421 (9) | 0.0681 (7) | |
H46A | 0.9581 | 0.6425 | 0.7187 | 0.102* | |
H46B | 0.8678 | 0.6821 | 0.7290 | 0.102* | |
H46C | 0.8935 | 0.6716 | 0.6662 | 0.102* | |
H34A | 0.7647 (8) | 0.7342 (13) | 0.5244 (6) | 0.024 (4)* | |
H11A | 0.5436 (9) | 0.1284 (13) | 0.5082 (6) | 0.025 (4)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Mg1 | 0.0227 (3) | 0.0246 (3) | 0.0247 (3) | −0.0021 (2) | 0.0023 (2) | 0.0002 (2) |
N1 | 0.0247 (7) | 0.0273 (7) | 0.0236 (8) | −0.0006 (6) | 0.0006 (6) | 0.0030 (6) |
N2 | 0.0235 (7) | 0.0267 (7) | 0.0251 (8) | −0.0020 (6) | 0.0022 (6) | −0.0003 (6) |
N3 | 0.0244 (7) | 0.0274 (7) | 0.0288 (8) | −0.0002 (6) | 0.0033 (6) | −0.0008 (6) |
N4 | 0.0235 (7) | 0.0272 (7) | 0.0260 (8) | −0.0011 (6) | 0.0007 (6) | 0.0006 (6) |
C1 | 0.0280 (9) | 0.0251 (8) | 0.0270 (10) | −0.0050 (7) | 0.0027 (8) | 0.0054 (7) |
C2 | 0.0287 (9) | 0.0293 (9) | 0.0285 (10) | −0.0060 (7) | 0.0011 (8) | 0.0032 (8) |
C3 | 0.0358 (10) | 0.0412 (10) | 0.0333 (11) | −0.0007 (8) | −0.0010 (9) | 0.0084 (9) |
C4 | 0.0418 (11) | 0.0499 (11) | 0.0252 (10) | −0.0063 (9) | 0.0033 (9) | 0.0067 (9) |
C5 | 0.0398 (11) | 0.0433 (10) | 0.0315 (11) | 0.0002 (9) | 0.0106 (9) | 0.0022 (8) |
C6 | 0.0354 (10) | 0.0343 (9) | 0.0321 (11) | 0.0034 (8) | 0.0068 (9) | 0.0061 (8) |
C7 | 0.0347 (10) | 0.0373 (10) | 0.0363 (11) | 0.0054 (8) | 0.0004 (9) | 0.0009 (8) |
C8 | 0.0326 (11) | 0.0622 (13) | 0.0613 (15) | 0.0038 (10) | 0.0034 (10) | −0.0037 (11) |
C9 | 0.0449 (13) | 0.0696 (15) | 0.116 (2) | 0.0005 (11) | 0.0026 (14) | −0.0484 (15) |
C10 | 0.0253 (9) | 0.0225 (8) | 0.0340 (11) | −0.0006 (7) | 0.0044 (8) | 0.0034 (7) |
C11 | 0.0230 (9) | 0.0289 (9) | 0.0333 (11) | −0.0053 (7) | −0.0028 (8) | −0.0008 (8) |
C12 | 0.0269 (9) | 0.0264 (8) | 0.0281 (10) | 0.0024 (7) | −0.0001 (8) | −0.0005 (7) |
C13 | 0.0366 (11) | 0.0433 (10) | 0.0430 (12) | −0.0136 (8) | 0.0046 (9) | 0.0062 (9) |
C14 | 0.0358 (10) | 0.0434 (10) | 0.0319 (11) | −0.0078 (8) | −0.0015 (9) | −0.0025 (8) |
C15 | 0.0242 (9) | 0.0365 (10) | 0.0206 (9) | −0.0051 (7) | −0.0027 (7) | −0.0025 (7) |
C16 | 0.0287 (9) | 0.0446 (10) | 0.0260 (10) | 0.0020 (8) | 0.0004 (8) | −0.0008 (8) |
C17 | 0.0321 (11) | 0.0701 (14) | 0.0340 (12) | 0.0066 (10) | 0.0045 (9) | −0.0012 (10) |
C18 | 0.0291 (10) | 0.0821 (15) | 0.0343 (12) | −0.0119 (10) | 0.0035 (9) | 0.0093 (11) |
C19 | 0.0414 (11) | 0.0541 (12) | 0.0309 (11) | −0.0192 (10) | −0.0039 (9) | 0.0068 (9) |
C20 | 0.0354 (10) | 0.0352 (10) | 0.0274 (10) | −0.0087 (8) | −0.0017 (8) | −0.0003 (8) |
C21 | 0.0419 (11) | 0.0421 (11) | 0.0398 (12) | 0.0107 (9) | 0.0073 (10) | −0.0028 (9) |
C22 | 0.0633 (15) | 0.0546 (13) | 0.0591 (16) | 0.0172 (11) | −0.0035 (12) | 0.0059 (11) |
C23 | 0.0848 (18) | 0.0524 (13) | 0.0625 (16) | 0.0104 (12) | 0.0039 (14) | −0.0159 (12) |
C24 | 0.0270 (9) | 0.0244 (8) | 0.0344 (11) | 0.0040 (7) | 0.0047 (8) | 0.0041 (8) |
C25 | 0.0309 (10) | 0.0288 (9) | 0.0334 (11) | 0.0047 (7) | 0.0061 (8) | 0.0006 (8) |
C26 | 0.0370 (11) | 0.0372 (10) | 0.0411 (12) | 0.0064 (9) | 0.0132 (9) | −0.0001 (9) |
C27 | 0.0282 (10) | 0.0437 (11) | 0.0553 (14) | 0.0022 (9) | 0.0131 (10) | 0.0036 (10) |
C28 | 0.0283 (10) | 0.0403 (10) | 0.0534 (14) | −0.0027 (8) | 0.0005 (9) | −0.0029 (9) |
C29 | 0.0283 (10) | 0.0329 (9) | 0.0392 (11) | 0.0033 (8) | 0.0003 (9) | −0.0032 (8) |
C30 | 0.0386 (11) | 0.0387 (10) | 0.0333 (11) | −0.0023 (8) | 0.0071 (9) | −0.0066 (8) |
C31 | 0.0624 (14) | 0.0408 (11) | 0.0524 (14) | −0.0020 (10) | 0.0075 (11) | −0.0130 (10) |
C32 | 0.0559 (14) | 0.0575 (12) | 0.0549 (15) | −0.0028 (11) | −0.0098 (12) | −0.0041 (11) |
C33 | 0.0303 (9) | 0.0271 (9) | 0.0250 (10) | 0.0010 (7) | −0.0014 (8) | −0.0039 (7) |
C34 | 0.0331 (10) | 0.0235 (9) | 0.0284 (10) | −0.0029 (8) | 0.0028 (8) | 0.0039 (7) |
C35 | 0.0286 (9) | 0.0297 (9) | 0.0231 (10) | −0.0058 (7) | 0.0013 (8) | −0.0028 (7) |
C36 | 0.0350 (10) | 0.0321 (9) | 0.0392 (12) | 0.0017 (8) | −0.0006 (9) | 0.0016 (8) |
C37 | 0.0308 (10) | 0.0392 (10) | 0.0469 (12) | −0.0070 (8) | 0.0055 (9) | 0.0077 (9) |
C38 | 0.0218 (9) | 0.0260 (8) | 0.0310 (10) | −0.0069 (7) | 0.0019 (8) | 0.0015 (7) |
C39 | 0.0277 (9) | 0.0327 (9) | 0.0304 (11) | −0.0058 (8) | −0.0005 (8) | 0.0013 (8) |
C40 | 0.0334 (10) | 0.0470 (11) | 0.0336 (11) | −0.0042 (9) | −0.0061 (9) | 0.0061 (9) |
C41 | 0.0278 (10) | 0.0436 (11) | 0.0493 (13) | 0.0033 (8) | 0.0007 (10) | 0.0129 (10) |
C42 | 0.0330 (10) | 0.0400 (10) | 0.0439 (13) | 0.0046 (8) | 0.0114 (10) | 0.0041 (9) |
C43 | 0.0310 (10) | 0.0405 (10) | 0.0295 (10) | −0.0022 (8) | 0.0040 (8) | 0.0002 (8) |
C44 | 0.0370 (11) | 0.0559 (12) | 0.0297 (11) | 0.0026 (9) | −0.0030 (9) | −0.0061 (9) |
C45 | 0.0554 (14) | 0.0742 (14) | 0.0359 (12) | −0.0086 (11) | 0.0089 (11) | −0.0020 (11) |
C46 | 0.109 (2) | 0.0515 (13) | 0.0449 (14) | 0.0111 (12) | 0.0105 (14) | −0.0094 (10) |
Mg1—N1 | 2.0374 (13) | C21—H21 | 1.0000 |
Mg1—N4 | 2.0383 (13) | C22—H22A | 0.9800 |
Mg1—N2 | 2.0475 (14) | C22—H22B | 0.9800 |
Mg1—N3 | 2.0499 (13) | C22—H22C | 0.9800 |
N1—C10 | 1.327 (2) | C23—H23A | 0.9800 |
N1—C1 | 1.436 (2) | C23—H23B | 0.9800 |
N2—C12 | 1.3344 (19) | C23—H23C | 0.9800 |
N2—C15 | 1.4332 (19) | C24—C29 | 1.395 (2) |
N3—C33 | 1.3303 (19) | C24—C25 | 1.403 (2) |
N3—C24 | 1.4331 (19) | C25—C26 | 1.396 (2) |
N4—C35 | 1.3339 (19) | C25—C30 | 1.527 (2) |
N4—C38 | 1.4412 (19) | C26—C27 | 1.384 (2) |
C1—C6 | 1.389 (2) | C26—H26 | 0.9500 |
C1—C2 | 1.405 (2) | C27—C28 | 1.376 (3) |
C2—C3 | 1.396 (2) | C27—H27 | 0.9500 |
C2—C7 | 1.519 (2) | C28—C29 | 1.384 (2) |
C3—C4 | 1.382 (2) | C28—H28 | 0.9500 |
C3—H3 | 0.9500 | C29—H29 | 0.9500 |
C4—C5 | 1.376 (2) | C30—C32 | 1.525 (3) |
C4—H4 | 0.9500 | C30—C31 | 1.535 (2) |
C5—C6 | 1.384 (2) | C30—H30 | 1.0000 |
C5—H5 | 0.9500 | C31—H31A | 0.9800 |
C6—H6 | 0.9500 | C31—H31B | 0.9800 |
C7—C9 | 1.513 (2) | C31—H31C | 0.9800 |
C7—C8 | 1.515 (2) | C32—H32A | 0.9800 |
C7—H7 | 1.0000 | C32—H32B | 0.9800 |
C8—H8A | 0.9800 | C32—H32C | 0.9800 |
C8—H8B | 0.9800 | C33—C34 | 1.405 (2) |
C8—H8C | 0.9800 | C33—C36 | 1.513 (2) |
C9—H9A | 0.9800 | C34—C35 | 1.406 (2) |
C9—H9B | 0.9800 | C34—H34A | 0.952 (14) |
C9—H9C | 0.9800 | C35—C37 | 1.509 (2) |
C10—C11 | 1.404 (2) | C36—H36A | 0.9800 |
C10—C13 | 1.521 (2) | C36—H36B | 0.9800 |
C11—C12 | 1.402 (2) | C36—H36C | 0.9800 |
C11—H11A | 0.944 (15) | C37—H37A | 0.9800 |
C12—C14 | 1.509 (2) | C37—H37B | 0.9800 |
C13—H13A | 0.9800 | C37—H37C | 0.9800 |
C13—H13B | 0.9800 | C38—C43 | 1.385 (2) |
C13—H13C | 0.9800 | C38—C39 | 1.402 (2) |
C14—H14A | 0.9800 | C39—C40 | 1.392 (2) |
C14—H14B | 0.9800 | C39—C44 | 1.521 (2) |
C14—H14C | 0.9800 | C40—C41 | 1.385 (2) |
C14—H14D | 0.9800 | C40—H40 | 0.9500 |
C14—H14E | 0.9800 | C41—C42 | 1.372 (2) |
C14—H14F | 0.9800 | C41—H41 | 0.9500 |
C15—C20 | 1.392 (2) | C42—C43 | 1.383 (2) |
C15—C16 | 1.400 (2) | C42—H42 | 0.9500 |
C16—C17 | 1.398 (2) | C43—H43 | 0.9500 |
C16—C21 | 1.524 (2) | C44—C45 | 1.526 (2) |
C17—C18 | 1.379 (3) | C44—C46 | 1.537 (3) |
C17—H17 | 0.9500 | C44—H44 | 1.0000 |
C18—C19 | 1.379 (3) | C45—H45A | 0.9800 |
C18—H18 | 0.9500 | C45—H45B | 0.9800 |
C19—C20 | 1.384 (2) | C45—H45C | 0.9800 |
C19—H19 | 0.9500 | C46—H46A | 0.9800 |
C20—H20 | 0.9500 | C46—H46B | 0.9800 |
C21—C22 | 1.526 (3) | C46—H46C | 0.9800 |
C21—C23 | 1.540 (3) | ||
N1—Mg1—N4 | 136.40 (6) | C22—C21—C23 | 109.96 (16) |
N1—Mg1—N2 | 90.73 (5) | C16—C21—H21 | 107.8 |
N4—Mg1—N2 | 111.12 (5) | C22—C21—H21 | 107.8 |
N1—Mg1—N3 | 110.35 (5) | C23—C21—H21 | 107.8 |
N4—Mg1—N3 | 90.61 (5) | C21—C22—H22A | 109.5 |
N2—Mg1—N3 | 121.02 (6) | C21—C22—H22B | 109.5 |
C10—N1—C1 | 120.13 (13) | H22A—C22—H22B | 109.5 |
C10—N1—Mg1 | 117.88 (11) | C21—C22—H22C | 109.5 |
C1—N1—Mg1 | 119.65 (10) | H22A—C22—H22C | 109.5 |
C12—N2—C15 | 119.85 (13) | H22B—C22—H22C | 109.5 |
C12—N2—Mg1 | 118.32 (10) | C21—C23—H23A | 109.5 |
C15—N2—Mg1 | 121.08 (10) | C21—C23—H23B | 109.5 |
C33—N3—C24 | 120.74 (13) | H23A—C23—H23B | 109.5 |
C33—N3—Mg1 | 117.70 (10) | C21—C23—H23C | 109.5 |
C24—N3—Mg1 | 120.30 (10) | H23A—C23—H23C | 109.5 |
C35—N4—C38 | 119.25 (13) | H23B—C23—H23C | 109.5 |
C35—N4—Mg1 | 117.39 (10) | C29—C24—C25 | 119.57 (15) |
C38—N4—Mg1 | 121.65 (9) | C29—C24—N3 | 117.51 (15) |
C6—C1—C2 | 120.21 (16) | C25—C24—N3 | 122.57 (15) |
C6—C1—N1 | 120.27 (14) | C26—C25—C24 | 117.86 (16) |
C2—C1—N1 | 119.41 (14) | C26—C25—C30 | 119.43 (16) |
C3—C2—C1 | 117.44 (15) | C24—C25—C30 | 122.69 (15) |
C3—C2—C7 | 121.64 (15) | C27—C26—C25 | 122.12 (17) |
C1—C2—C7 | 120.91 (15) | C27—C26—H26 | 118.9 |
C4—C3—C2 | 122.09 (17) | C25—C26—H26 | 118.9 |
C4—C3—H3 | 119.0 | C28—C27—C26 | 119.52 (17) |
C2—C3—H3 | 119.0 | C28—C27—H27 | 120.2 |
C5—C4—C3 | 119.64 (17) | C26—C27—H27 | 120.2 |
C5—C4—H4 | 120.2 | C27—C28—C29 | 119.70 (17) |
C3—C4—H4 | 120.2 | C27—C28—H28 | 120.2 |
C4—C5—C6 | 119.82 (17) | C29—C28—H28 | 120.2 |
C4—C5—H5 | 120.1 | C28—C29—C24 | 121.20 (17) |
C6—C5—H5 | 120.1 | C28—C29—H29 | 119.4 |
C5—C6—C1 | 120.79 (16) | C24—C29—H29 | 119.4 |
C5—C6—H6 | 119.6 | C32—C30—C25 | 112.15 (14) |
C1—C6—H6 | 119.6 | C32—C30—C31 | 109.34 (15) |
C9—C7—C8 | 109.76 (15) | C25—C30—C31 | 111.62 (15) |
C9—C7—C2 | 111.42 (15) | C32—C30—H30 | 107.9 |
C8—C7—C2 | 114.42 (15) | C25—C30—H30 | 107.9 |
C9—C7—H7 | 106.9 | C31—C30—H30 | 107.9 |
C8—C7—H7 | 106.9 | C30—C31—H31A | 109.5 |
C2—C7—H7 | 106.9 | C30—C31—H31B | 109.5 |
C7—C8—H8A | 109.5 | H31A—C31—H31B | 109.5 |
C7—C8—H8B | 109.5 | C30—C31—H31C | 109.5 |
H8A—C8—H8B | 109.5 | H31A—C31—H31C | 109.5 |
C7—C8—H8C | 109.5 | H31B—C31—H31C | 109.5 |
H8A—C8—H8C | 109.5 | C30—C32—H32A | 109.5 |
H8B—C8—H8C | 109.5 | C30—C32—H32B | 109.5 |
C7—C9—H9A | 109.5 | H32A—C32—H32B | 109.5 |
C7—C9—H9B | 109.5 | C30—C32—H32C | 109.5 |
H9A—C9—H9B | 109.5 | H32A—C32—H32C | 109.5 |
C7—C9—H9C | 109.5 | H32B—C32—H32C | 109.5 |
H9A—C9—H9C | 109.5 | N3—C33—C34 | 122.78 (14) |
H9B—C9—H9C | 109.5 | N3—C33—C36 | 120.05 (14) |
N1—C10—C11 | 123.85 (15) | C34—C33—C36 | 117.17 (14) |
N1—C10—C13 | 120.07 (15) | C33—C34—C35 | 129.04 (15) |
C11—C10—C13 | 116.07 (15) | C33—C34—H34A | 115.4 (9) |
C12—C11—C10 | 129.02 (16) | C35—C34—H34A | 115.0 (9) |
C12—C11—H11A | 115.6 (9) | N4—C35—C34 | 123.11 (14) |
C10—C11—H11A | 115.2 (9) | N4—C35—C37 | 120.14 (14) |
N2—C12—C11 | 122.69 (16) | C34—C35—C37 | 116.75 (14) |
N2—C12—C14 | 120.24 (14) | C33—C36—H36A | 109.5 |
C11—C12—C14 | 117.07 (15) | C33—C36—H36B | 109.5 |
C10—C13—H13A | 109.5 | H36A—C36—H36B | 109.5 |
C10—C13—H13B | 109.5 | C33—C36—H36C | 109.5 |
H13A—C13—H13B | 109.5 | H36A—C36—H36C | 109.5 |
C10—C13—H13C | 109.5 | H36B—C36—H36C | 109.5 |
H13A—C13—H13C | 109.5 | C35—C37—H37A | 109.5 |
H13B—C13—H13C | 109.5 | C35—C37—H37B | 109.5 |
C12—C14—H14A | 109.5 | H37A—C37—H37B | 109.5 |
C12—C14—H14B | 109.5 | C35—C37—H37C | 109.5 |
H14A—C14—H14B | 109.5 | H37A—C37—H37C | 109.5 |
C12—C14—H14C | 109.5 | H37B—C37—H37C | 109.5 |
H14A—C14—H14C | 109.5 | C43—C38—C39 | 120.34 (15) |
H14B—C14—H14C | 109.5 | C43—C38—N4 | 120.18 (15) |
C12—C14—H14D | 109.5 | C39—C38—N4 | 119.33 (14) |
H14A—C14—H14D | 141.1 | C40—C39—C38 | 117.64 (16) |
H14B—C14—H14D | 56.3 | C40—C39—C44 | 121.48 (16) |
H14C—C14—H14D | 56.3 | C38—C39—C44 | 120.87 (15) |
C12—C14—H14E | 109.5 | C41—C40—C39 | 121.79 (18) |
H14A—C14—H14E | 56.3 | C41—C40—H40 | 119.1 |
H14B—C14—H14E | 141.1 | C39—C40—H40 | 119.1 |
H14C—C14—H14E | 56.3 | C42—C41—C40 | 119.60 (17) |
H14D—C14—H14E | 109.5 | C42—C41—H41 | 120.2 |
C12—C14—H14F | 109.5 | C40—C41—H41 | 120.2 |
H14A—C14—H14F | 56.3 | C41—C42—C43 | 120.02 (17) |
H14B—C14—H14F | 56.3 | C41—C42—H42 | 120.0 |
H14C—C14—H14F | 141.1 | C43—C42—H42 | 120.0 |
H14D—C14—H14F | 109.5 | C42—C43—C38 | 120.57 (17) |
H14E—C14—H14F | 109.5 | C42—C43—H43 | 119.7 |
C20—C15—C16 | 119.87 (15) | C38—C43—H43 | 119.7 |
C20—C15—N2 | 117.78 (14) | C39—C44—C45 | 113.75 (15) |
C16—C15—N2 | 122.01 (14) | C39—C44—C46 | 111.29 (16) |
C17—C16—C15 | 117.73 (16) | C45—C44—C46 | 109.90 (16) |
C17—C16—C21 | 119.64 (15) | C39—C44—H44 | 107.2 |
C15—C16—C21 | 122.58 (15) | C45—C44—H44 | 107.2 |
C18—C17—C16 | 122.16 (17) | C46—C44—H44 | 107.2 |
C18—C17—H17 | 118.9 | C44—C45—H45A | 109.5 |
C16—C17—H17 | 118.9 | C44—C45—H45B | 109.5 |
C19—C18—C17 | 119.53 (17) | H45A—C45—H45B | 109.5 |
C19—C18—H18 | 120.2 | C44—C45—H45C | 109.5 |
C17—C18—H18 | 120.2 | H45A—C45—H45C | 109.5 |
C18—C19—C20 | 119.64 (17) | H45B—C45—H45C | 109.5 |
C18—C19—H19 | 120.2 | C44—C46—H46A | 109.5 |
C20—C19—H19 | 120.2 | C44—C46—H46B | 109.5 |
C19—C20—C15 | 121.07 (17) | H46A—C46—H46B | 109.5 |
C19—C20—H20 | 119.5 | C44—C46—H46C | 109.5 |
C15—C20—H20 | 119.5 | H46A—C46—H46C | 109.5 |
C16—C21—C22 | 110.84 (15) | H46B—C46—H46C | 109.5 |
C16—C21—C23 | 112.54 (16) | ||
N4—Mg1—N1—C10 | −162.12 (11) | N2—C15—C16—C21 | 4.0 (2) |
N2—Mg1—N1—C10 | −39.72 (11) | C15—C16—C17—C18 | 0.4 (3) |
N3—Mg1—N1—C10 | 83.94 (12) | C21—C16—C17—C18 | −176.97 (17) |
N4—Mg1—N1—C1 | 35.25 (14) | C16—C17—C18—C19 | −0.1 (3) |
N2—Mg1—N1—C1 | 157.64 (11) | C17—C18—C19—C20 | −0.5 (3) |
N3—Mg1—N1—C1 | −78.69 (12) | C18—C19—C20—C15 | 0.7 (3) |
N1—Mg1—N2—C12 | 40.06 (11) | C16—C15—C20—C19 | −0.3 (2) |
N4—Mg1—N2—C12 | −178.57 (10) | N2—C15—C20—C19 | 173.05 (15) |
N3—Mg1—N2—C12 | −74.36 (12) | C17—C16—C21—C22 | 68.7 (2) |
N1—Mg1—N2—C15 | −149.87 (11) | C15—C16—C21—C22 | −108.57 (19) |
N4—Mg1—N2—C15 | −8.50 (13) | C17—C16—C21—C23 | −54.9 (2) |
N3—Mg1—N2—C15 | 95.71 (12) | C15—C16—C21—C23 | 127.82 (18) |
N1—Mg1—N3—C33 | −177.69 (11) | C33—N3—C24—C29 | 109.35 (17) |
N4—Mg1—N3—C33 | 41.39 (12) | Mg1—N3—C24—C29 | −57.53 (18) |
N2—Mg1—N3—C33 | −73.87 (13) | C33—N3—C24—C25 | −77.5 (2) |
N1—Mg1—N3—C24 | −10.42 (14) | Mg1—N3—C24—C25 | 115.62 (14) |
N4—Mg1—N3—C24 | −151.34 (12) | C29—C24—C25—C26 | 1.8 (2) |
N2—Mg1—N3—C24 | 93.40 (13) | N3—C24—C25—C26 | −171.18 (14) |
N1—Mg1—N4—C35 | −162.64 (11) | C29—C24—C25—C30 | −179.69 (15) |
N2—Mg1—N4—C35 | 82.20 (12) | N3—C24—C25—C30 | 7.3 (2) |
N3—Mg1—N4—C35 | −41.62 (12) | C24—C25—C26—C27 | −1.8 (2) |
N1—Mg1—N4—C38 | 32.36 (15) | C30—C25—C26—C27 | 179.69 (15) |
N2—Mg1—N4—C38 | −82.81 (13) | C25—C26—C27—C28 | 0.5 (3) |
N3—Mg1—N4—C38 | 153.38 (12) | C26—C27—C28—C29 | 0.8 (3) |
C10—N1—C1—C6 | −76.77 (19) | C27—C28—C29—C24 | −0.7 (3) |
Mg1—N1—C1—C6 | 85.46 (16) | C25—C24—C29—C28 | −0.6 (2) |
C10—N1—C1—C2 | 106.86 (17) | N3—C24—C29—C28 | 172.72 (15) |
Mg1—N1—C1—C2 | −90.91 (15) | C26—C25—C30—C32 | 70.7 (2) |
C6—C1—C2—C3 | 1.6 (2) | C24—C25—C30—C32 | −107.79 (19) |
N1—C1—C2—C3 | 177.96 (13) | C26—C25—C30—C31 | −52.4 (2) |
C6—C1—C2—C7 | −179.70 (14) | C24—C25—C30—C31 | 129.11 (17) |
N1—C1—C2—C7 | −3.3 (2) | C24—N3—C33—C34 | 170.50 (15) |
C1—C2—C3—C4 | −1.2 (2) | Mg1—N3—C33—C34 | −22.3 (2) |
C7—C2—C3—C4 | −179.86 (15) | C24—N3—C33—C36 | −9.9 (2) |
C2—C3—C4—C5 | 0.1 (3) | Mg1—N3—C33—C36 | 157.32 (12) |
C3—C4—C5—C6 | 0.6 (3) | N3—C33—C34—C35 | −12.6 (3) |
C4—C5—C6—C1 | −0.1 (3) | C36—C33—C34—C35 | 167.79 (16) |
C2—C1—C6—C5 | −1.0 (2) | C38—N4—C35—C34 | −171.44 (15) |
N1—C1—C6—C5 | −177.33 (14) | Mg1—N4—C35—C34 | 23.2 (2) |
C3—C2—C7—C9 | 97.9 (2) | C38—N4—C35—C37 | 9.1 (2) |
C1—C2—C7—C9 | −80.7 (2) | Mg1—N4—C35—C37 | −156.29 (12) |
C3—C2—C7—C8 | −27.3 (2) | C33—C34—C35—N4 | 12.2 (3) |
C1—C2—C7—C8 | 154.04 (15) | C33—C34—C35—C37 | −168.35 (16) |
C1—N1—C10—C11 | −174.60 (14) | C35—N4—C38—C43 | −85.61 (18) |
Mg1—N1—C10—C11 | 22.9 (2) | Mg1—N4—C38—C43 | 79.13 (17) |
C1—N1—C10—C13 | 5.5 (2) | C35—N4—C38—C39 | 98.97 (17) |
Mg1—N1—C10—C13 | −157.08 (11) | Mg1—N4—C38—C39 | −96.29 (15) |
N1—C10—C11—C12 | 9.7 (3) | C43—C38—C39—C40 | 2.2 (2) |
C13—C10—C11—C12 | −170.38 (15) | N4—C38—C39—C40 | 177.57 (13) |
C15—N2—C12—C11 | 166.84 (14) | C43—C38—C39—C44 | −177.90 (14) |
Mg1—N2—C12—C11 | −22.97 (19) | N4—C38—C39—C44 | −2.5 (2) |
C15—N2—C12—C14 | −14.4 (2) | C38—C39—C40—C41 | −1.6 (2) |
Mg1—N2—C12—C14 | 155.83 (12) | C44—C39—C40—C41 | 178.46 (15) |
C10—C11—C12—N2 | −9.5 (3) | C39—C40—C41—C42 | 0.0 (3) |
C10—C11—C12—C14 | 171.63 (16) | C40—C41—C42—C43 | 1.1 (3) |
C12—N2—C15—C20 | 114.61 (16) | C41—C42—C43—C38 | −0.5 (2) |
Mg1—N2—C15—C20 | −55.31 (18) | C39—C38—C43—C42 | −1.2 (2) |
C12—N2—C15—C16 | −72.2 (2) | N4—C38—C43—C42 | −176.54 (14) |
Mg1—N2—C15—C16 | 117.93 (14) | C40—C39—C44—C45 | −32.0 (2) |
C20—C15—C16—C17 | −0.2 (2) | C38—C39—C44—C45 | 148.01 (16) |
N2—C15—C16—C17 | −173.31 (15) | C40—C39—C44—C46 | 92.7 (2) |
C20—C15—C16—C21 | 177.10 (16) | C38—C39—C44—C46 | −87.20 (19) |
Experimental details
Crystal data | |
Chemical formula | [Mg(C23H29N2)2] |
Mr | 691.27 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 173 |
a, b, c (Å) | 16.6252 (10), 10.6287 (5), 23.831 (2) |
β (°) | 95.484 (5) |
V (Å3) | 4191.8 (5) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.08 |
Crystal size (mm) | 0.28 × 0.14 × 0.12 |
Data collection | |
Diffractometer | Nonius KappaCCD diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 18102, 9565, 5453 |
Rint | 0.053 |
(sin θ/λ)max (Å−1) | 0.650 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.048, 0.119, 1.03 |
No. of reflections | 9565 |
No. of parameters | 479 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.29, −0.24 |
Computer programs: DENZO (Otwinowski & Minor, 1997) and COLLECT (Hooft, 1998), DENZO and COLLECT, DENZO, SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), ORTEPII (Johnson, 1976), SHELXL97.
Mg1—N1 | 2.0374 (13) | Mg1—N2 | 2.0475 (14) |
Mg1—N4 | 2.0383 (13) | Mg1—N3 | 2.0499 (13) |
N1—Mg1—N4 | 136.40 (6) | N1—Mg1—N3 | 110.35 (5) |
N1—Mg1—N2 | 90.73 (5) | N4—Mg1—N3 | 90.61 (5) |
N4—Mg1—N2 | 111.12 (5) | N2—Mg1—N3 | 121.02 (6) |
The bulky 2,6-diaryl diketiminate ligand derived from deprotonation of (2,6-diisopropyl)phenylamino-4-(2,6-diisopropyl)phenylimino-pent-2-ene, (Feldman et al., 1997), the anion (I) (Clegg et al., 1998), has enjoyed extensive use in situations where a bidentate mono-anion offering extreme steric protection is required (Bourget-Merle et al., 2002). The 2,6-substituents on each aryl group are particularly effective at stabilizing two- or planar three-coordinate geometries at the ligated metal ion. In contrast, the analogous anion derived from (2-isopropyl)phenylamino-4-(2-isopropyl)phenylimino-pent-2-ene, the anion (II), is to be found in published crystal structures only twice (Cheng et al., 2001; Carey et al., 2003). The additional structural issues raised by the reduction in approximate C2v symmetry of the bulkier (I) to either a C2 or a Cs ligand symmetry, depending upon conformation, in (II) have yet to be fully investigated. A specific example is that, whereas the full series of group 2 complexes of (I) have been structurally characterized by X-ray crystallograpy (Harder, 2002), none containing (II) have been so treated. We present here the structure of Mg(II)2, the first group 2 complex containing ligand (II).
Despite the fact that the stoichiometry employed in the preparation was aimed at isolation of Mg(II)Bu, the Schlenk equilibrium (Schlenk & Schlenk, 1929) was clearly in operation here, and the least soluble component of that equilibrium proved to be Mg(II)2. This behaviour has been seen in other bidentate N,N-dianion complexes of magnesium (Hao et al., 2002). The structure at the metal centre is distorted tetrahedral. Both ligands adopt a local and approximate Cs symmetry, i.e. both isopropyl groups are disposed to the same side of the ligand. In this respect, the structure is the same as the other two known structures containing ligand (II) (Cheng et al., 2001; Carey et al., 2003). On the basis of the limited available solid-sate data, it seems that the Cs symmetric disposition, which encourages a distorted tetrahedral geometry at the ligated metal ion, is the preferred geometry of this ligand. In fact, Mg(II)2 is isomorphous, isostructural and isotypic with its zinc analogue (Cheng et al., 2001). A search of the Cambridge Crystallographic Database (Allen, 2002) revealed a small handful of other structures where identical ligand sets for both Mg and Zn generated a pseudo- tetrahedral arrangement of four N atoms around each metal (Hao et al., 2002; Gardiner et al., 1994). These pairs too were isotypic. This result underlines the similarity in both size and structural preference of the Zn2+ and Mg2+ ions. The key structural parameters for Mg(II)2 are shown in Table 2. While consideration of Shannon's ionic radii shows that the radius of the Mg2+ ion is expected to be 3 pm smaller than that of the Zn2+ ion (Shannon & Prewitt, 1969), inspection of the bond lengths shows the opposite to be true. The mean Mg—N distance [2.043 (s.u.?) Å] is comparable to the equivalent Zn—N distance [mean 2.007 9 s.u.?) Å], indicating that the radius of the Mg2+ ion is 3.6 pm larger than that of the Zn2+ ion in complexes of (II). Shannon later accounted for such discrepancies on the basis of a `covalency correction' (Shannon, 1976). An alternative in cases where covalency is thought to dominate would be to take the calculated `atomic radii', where that of Zn2+ (142 pm) differs from that of Mg2+ (145 pm) by an appropriate amount (Clementi & Raimondi, 1963). Cases such as this, where ionic radii do not predict the correct trends, could be taken as evidence for the importance of covalency in the bonding. In a previously reported case involving two-coordinate Zn and Mg atoms in isotypic molecules, the Mg atom appeared to be 8 pm larger (Armstrong et al., 2002), whilst the three-coordinate metals in isotypic inverse-crown molecules have Mg—N bonds 5–9 pm longer than corresponding their Zn—N bonds (Forbes et al., 2000). This increased discrepancy can be associated with the expected increased degree of covalency in the Zn—N bonds with reduction in coordination number. Comparison of other parameters reveals expected trends – for example, the intra-ring N—Zn—N angles are slightly more open than the N—Mg—N angles, a fact that can be directly linked to the aforementioned bond-length differences. Further informative comparisons can be drawn with the recently published structure of Mg(I)2 (Harder, 2002). In that case, the average Mg—N distance was 2.111 (2) Å, an increase of 6.8 pm. This result indicates the effect of increased steric crowding. In fact, it has been reported that Zn(I)2 could not be prepared for this reason (Cheng et al., 2001). The slightly greater radius of Mg2+ over Zn2+ in these circumstances allows for the stability of Mg(I)2. It shares the out-of-NCCCN-plane distortion found for the metal ions in Mg(II)2 and Zn(II)2 [mean 0.884 Å for Mg(II)2, 0.82 Å for Zn(II)2 and 0.91 Å for Mg(I)2]. It is to be expected that further use of ligand (II) will foster distorted-tetrahedral coordination geometries in a wide variety of circumstances, in the same way that (I) has found wide use in fostering trigonal and bent two-coordinate geometries (Bourget-Merle et al., 2002).