A zirconium zwitterion containing a caged amine H atom

The crystallographically centrosymmetric zwitterion bis­[tris(3,5-di­methyl-2-oxidobenzyl-κO)­ammonium]­zirconium(IV) crystallizes as the chloro­form disolvate, [Zr(C₂₇H₃₁NO₃)₂]·2CHCl₃, with the two mol­ecules of chloro­form closely associated with two of the aromatic rings. The Zr atom has a distorted octahedral geometry with three phenoxy O atoms from each of the two ligands coordinated to it. Charge balance is maintained by protonation of each N atom, which then forms intramolecular hydrogen-bonding interactions to all three adjacent O atoms.

S1. Comment

When two equivalents of tris(2-hydroxy-3,5-dimethylbenzyl)amine, {N[N(YOH)₃]} (Y is?), are added to [Zr(OⁿBu)₄] in CH₂Cl₂, a colourless air-stable precipitate appears in the solution after ca 10 min. Analytical data are consistent with two tris(phenoxide) ligands and one Zr atom. The complex is insoluble in CH₂Cl₂ but readily dissolves in CHCl₃ and was crystallized from the latter solvent as the chloroform disolvate, (I). \sch

The structural arrangement in (I) is shown in Fig. 1. The Zr atom lies on a centre of symmetry surrounded by a distorted octahedral arrangement of six similar phenoxy O atoms, suggesting that this part of the complex has an overall formal charge of 2-, as might be expected for a [Zr(OAr)₆]²⁻ dianion. However, whereas [ZrCl₆]²⁻ is well known (e.g. [NMe₄]₂[ZrCl₆]; Morss et al., 1991), [Zr(OAr)₆]²⁻ is apparently not, the nearest equivalent being [Zr(SAr)₆]²⁻ (Friese et al., 2000). The alternative, whereby one of the phenoxy ligands in each ligand is protonated, is inconsistent with the observed ¹H NMR spectrum, which shows a symmetrical complex. Inspection of the difference map in the vicinity of the donor O atoms also failed to show signs of any protonation. However, a potential site for the extra H atom was detected near the N atom of each ligand, giving the N atom a positive charge and thus maintaining charge balance. A similar structure has recently been reported for the zwitterion moiety when crystallized with toluene molecules of crystallization (Davidson et al., 2003).

The Zr—O bond lengths in (I) [2.066 (2), 2.064 (2) and 2.049 (2) Å] are similar to those found in phenoxide complexes where the O → Zr π donation is also spread over several O atom donors, e.g. in [Zr(O—C₆H₄NO₂-4)(acac)₃], where the phenoxide Zr—O bond length is 2.045 (3) Å (Dinger & Scott, 2001)}, and in the toluene analogue of (I) (Davidson et al., 2003), where corresponding values of 2.058 (2), 2.064 (2) and 2.057 (2) Å are observed. The Zr—O—C bond angles of 158.0 (2), 162.6 (2) and 160.3 (2)° do not differ greatly from those observed in [Ti(OCHMe₂)(N(YO)₃)] [Ti—O—C bond angles 164.4 (6)°; Kol et al., 2001] or in the toluene solvate of (I) [Zr—O—C bond angles 157.2 (2), 154.5 (2) and 160.0 (2)°; Davidson et al., 2003]. The N-bound H atom is trapped in a cage-like arrangement, at distances of 2.27, 2.12 and 2.29 Å from atoms O1, O2 and O3, respectively, such approaches being indicative of H···O hydrogen bonding. The H atom points directly at the Zr [Zr···H—N 174 (2)°] at a distance of 2.76 (3) Å. The Zr···N separation is 3.603 (2) Å.

A further feature of the structure of (I) is the two chloroform molecules found associated with each Zr complex. In this respect the current structure differs from that of the recently reported zwitterion with toluene solvate (Davidson et al., 2003). The H atom of each chloroform points directly at one of the benzene rings of each phenoxide moiety, approaching its C atoms at 2.70, 2.74, 2.98, 3.09, 3.32 and 3.36 Å. The H···ring-centroid distance is 2.71 Å. A survey of the Cambridge Structural Database (Version?; Allen, 2002) shows that a similar feature has been previously crystallographically characterized, but only in a few phenoxide complexes (Sudbrake & Vahrenkamp, 2001, and references therein). There is NMR evidence for such an interaction in solution (Nishio et al., 1995). This weak hydrogen-bond interaction provides a possible explanation as to why the complex is soluble in CHCl₃ but is almost completely insoluble in CH₂Cl₂.

From the coeditor: AUTHOR: the datanames such as _diffrn_reflns_limit_h_min refer to the data as measured, not the unique fraction. Please supply the correct range.

S2. Experimental

A solution of tetrabutoxyzirconium (0.5 g, 1.19 mmole; 0.63 g of an 80% w/w solution in butanol) in CH₂Cl₂ (25 ml) was added dropwise to a solution of tris(2-hydroxy-3,5-dimethylbenzylamine) (0.95 g, 2.4 mmole) in CH₂Cl₂ (80 ml) and the mixture was stirred for 2 h. The colourless solid was filtered, washed with CH₂Cl₂ (30 ml) and dried in vacuo (yield 1.0 g, 98%). Analysis for C₅₄H₆₂N₂O₆Zr, found: C 69.83, H 7.05, N 3.03%; calculated: C 70.02, H 6.75, N 3.02%. Spectroscopic analysis: ¹H NMR (400.13 MHz, CDCl₃, δ, p.p.m.): 1.88 (s, 9H, 3Me), 2.10 (s, 9H, 3Me), 3.18 (b, 3H, 3CH), 4.67 (b, 3H, 3CH), 6.58 (d, ³J_H—H = 1.76 Hz, 3H, 3Me-H), 6.74 (d, ³J_H—H = 1.76 Hz, 3H, 3Me-H), 11.78, (b, 2H, 2NH); ¹³C{¹H} NMR (100.6 MHz, CDCl₃, δ, p.p.m.): 16.4 (Me), 20.3 (Me), 56.1 (CH₂), 116.7 (o-C), 124.8 (o-C), 127.9 (C), 129.5 (C), 132.6 (C), 159.0 (ipso-C). Recrystallization of this product from dry chloroform in air gave colourless crystals of the CHCl₃ solvate, (I) (yield: 1.28 g, 100%). Analysis for C₅₆H₆₄Cl₆N₂O₆Zr, found: C 57.60, H 5.52, N 2.30%; calculated: C 57.73, H 5.54, N 2.40%.

S3. Refinement

All H atoms were included in calculated positions and refined using a riding model [U_iso(H) = 1.2U_eq(C) for CH₂, with C—H = 0.99 Å, for aromatic CH, with C—H = 0.95 Å, and for chloroform atom H28, with C—H = 1.00 Å, and U_iso(H) = 1.5U_eq(C) for the Me H atom, with C—H = 0.98 Å], except for atom H1, which was located from a difference Fourier synthesis and refined with N—H = 0.845 Å.

Computing details

Data collection: SMART (Siemens 1994); cell refinement: SMART; data reduction: SAINT (Siemens 1994); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, YEAR?); software used to prepare material for publication: SHELXL97.

Figures

Fig. 1. A view of the molecular structure of (I), showing 50% probability displacement ellipsoids. H atoms have been omitted for clarity. Fig. 2. Caption required.

(I)

Crystal data

[Zr(C27H31NO3)2]·2CHCl3	F(000) = 1208
Mr = 1165.01	Dx = 1.388 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 8192 reflections
a = 11.3902 (2) Å	θ = 2–25°
b = 13.9774 (1) Å	µ = 0.54 mm^−1
c = 18.0502 (2) Å	T = 150 K
β = 104.134 (1)°	Rectangular prism, colourless
V = 2786.69 (6) Å^3	0.40 × 0.24 × 0.18 mm
Z = 2

Data collection

Siemens SMART CCD area-detector diffractometer	4880 independent reflections
Radiation source: fine-focus sealed tube	3907 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.045
ω scans	θmax = 25.1°, θmin = 1.8°
Absorption correction: multi-scan (SORTAV; Blessing, 1995)	h = −13→13
Tmin = 0.814, Tmax = 0.910	k = 0→16
14693 measured reflections	l = 0→21

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.041	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.115	H atoms treated by a mixture of independent and constrained refinement
S = 1.04	w = 1/[σ^2(Fo^2) + (0.058P)^2 + 2.019P] where P = (Fo^2 + 2Fc^2)/3
4880 reflections	(Δ/σ)max = 0.038
332 parameters	Δρmax = 0.95 e Å^−3
0 restraints	Δρmin = −0.68 e Å^−3

Special details

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Zr1	0.5000	0.5000	0.0000	0.02112 (12)
O1	0.63538 (17)	0.49429 (13)	0.09969 (11)	0.0271 (4)
O2	0.49584 (17)	0.64560 (13)	0.01822 (11)	0.0277 (4)
O3	0.37773 (17)	0.48842 (13)	0.06602 (11)	0.0279 (4)
N1	0.50973 (19)	0.62714 (15)	0.17501 (13)	0.0209 (5)
C1	0.5968 (2)	0.5714 (2)	0.23602 (15)	0.0261 (6)
H1A	0.6037	0.6030	0.2860	0.031*
H1B	0.5641	0.5063	0.2391	0.031*
C2	0.7203 (2)	0.56386 (18)	0.22100 (15)	0.0242 (6)
C3	0.7337 (2)	0.52180 (19)	0.15277 (15)	0.0253 (6)
C4	0.8516 (3)	0.5080 (2)	0.14256 (17)	0.0314 (6)
C5	0.9495 (3)	0.5437 (2)	0.19857 (18)	0.0355 (7)
H5	1.0285	0.5372	0.1905	0.043*
C6	0.9376 (3)	0.5879 (2)	0.26499 (18)	0.0338 (7)
C7	0.8216 (2)	0.59609 (19)	0.27597 (16)	0.0274 (6)
H7	0.8107	0.6242	0.3218	0.033*
C8	0.8706 (3)	0.4580 (3)	0.07308 (19)	0.0458 (8)
H8A	0.8331	0.4953	0.0275	0.069*
H8B	0.8335	0.3944	0.0693	0.069*
H8C	0.9575	0.4516	0.0769	0.069*
C9	1.0456 (3)	0.6272 (3)	0.3234 (2)	0.0488 (9)
H9A	1.0879	0.5748	0.3549	0.073*
H9B	1.0180	0.6738	0.3560	0.073*
H9C	1.1009	0.6586	0.2970	0.073*
C10	0.5523 (2)	0.72804 (19)	0.16716 (15)	0.0256 (6)
H10A	0.5472	0.7651	0.2130	0.031*
H10B	0.6383	0.7263	0.1651	0.031*
C11	0.4798 (2)	0.77852 (19)	0.09713 (15)	0.0230 (5)
C12	0.4569 (2)	0.73508 (18)	0.02470 (15)	0.0232 (6)
C13	0.3955 (2)	0.78637 (19)	−0.04029 (15)	0.0265 (6)
C14	0.3582 (3)	0.8799 (2)	−0.03070 (16)	0.0285 (6)
H14	0.3155	0.9142	−0.0745	0.034*
C15	0.3808 (3)	0.92497 (19)	0.04009 (16)	0.0285 (6)
C16	0.4416 (2)	0.87291 (19)	0.10361 (16)	0.0259 (6)
H16	0.4577	0.9020	0.1526	0.031*
C17	0.3728 (3)	0.7415 (2)	−0.11837 (16)	0.0374 (7)
H17A	0.3229	0.7846	−0.1561	0.056*
H17B	0.3304	0.6805	−0.1183	0.056*
H17C	0.4502	0.7303	−0.1315	0.056*
C18	0.3390 (3)	1.0272 (2)	0.04710 (19)	0.0426 (8)
H18A	0.2929	1.0497	−0.0030	0.064*
H18B	0.4096	1.0685	0.0655	0.064*
H18C	0.2874	1.0292	0.0833	0.064*
C19	0.3820 (2)	0.62293 (19)	0.18349 (16)	0.0255 (6)
H19A	0.3289	0.6580	0.1404	0.031*
H19B	0.3780	0.6560	0.2313	0.031*
C20	0.3342 (2)	0.52238 (19)	0.18528 (16)	0.0239 (6)
C21	0.3280 (2)	0.4613 (2)	0.12224 (15)	0.0235 (6)
C22	0.2682 (2)	0.3725 (2)	0.11978 (17)	0.0288 (6)
C23	0.2196 (2)	0.3482 (2)	0.18130 (18)	0.0329 (7)
H23	0.1770	0.2895	0.1790	0.039*
C24	0.2302 (3)	0.4051 (2)	0.24538 (17)	0.0316 (7)
C25	0.2881 (2)	0.4930 (2)	0.24632 (16)	0.0280 (6)
H25	0.2963	0.5338	0.2894	0.034*
C26	0.2572 (3)	0.3073 (2)	0.05191 (19)	0.0406 (8)
H26A	0.3369	0.2809	0.0520	0.061*
H26B	0.2263	0.3437	0.0048	0.061*
H26C	0.2013	0.2550	0.0548	0.061*
C27	0.1775 (3)	0.3743 (2)	0.3111 (2)	0.0465 (9)
H27A	0.1036	0.4109	0.3097	0.070*
H27B	0.2367	0.3861	0.3596	0.070*
H27C	0.1580	0.3059	0.3064	0.070*
C28	0.1333 (3)	0.8117 (2)	0.0938 (2)	0.0428 (8)
H28	0.2052	0.8135	0.0713	0.051*
Cl1	0.02686 (10)	0.89636 (8)	0.04580 (7)	0.0707 (3)
Cl2	0.07125 (10)	0.69675 (7)	0.08120 (9)	0.0800 (4)
Cl3	0.18107 (9)	0.83990 (8)	0.19055 (6)	0.0608 (3)
H1	0.507 (2)	0.6016 (19)	0.1322 (16)	0.016 (7)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Zr1	0.0221 (2)	0.0208 (2)	0.01944 (19)	0.00095 (14)	0.00306 (14)	−0.00211 (14)
O1	0.0256 (10)	0.0294 (10)	0.0242 (9)	−0.0001 (8)	0.0018 (8)	−0.0019 (8)
O2	0.0298 (10)	0.0244 (10)	0.0278 (10)	0.0036 (8)	0.0049 (8)	−0.0025 (8)
O3	0.0272 (10)	0.0309 (11)	0.0253 (10)	−0.0014 (8)	0.0061 (8)	−0.0017 (8)
N1	0.0202 (11)	0.0230 (12)	0.0186 (11)	0.0003 (9)	0.0030 (9)	−0.0013 (9)
C1	0.0246 (14)	0.0289 (14)	0.0239 (14)	−0.0002 (11)	0.0040 (11)	0.0047 (11)
C2	0.0219 (13)	0.0201 (13)	0.0279 (14)	0.0020 (10)	0.0008 (11)	0.0037 (11)
C3	0.0221 (14)	0.0257 (14)	0.0244 (14)	0.0016 (11)	−0.0013 (11)	0.0030 (11)
C4	0.0261 (15)	0.0383 (16)	0.0291 (15)	0.0066 (13)	0.0053 (12)	0.0051 (13)
C5	0.0203 (14)	0.0436 (18)	0.0406 (17)	0.0048 (13)	0.0037 (13)	0.0068 (15)
C6	0.0251 (15)	0.0304 (16)	0.0403 (17)	−0.0007 (12)	−0.0027 (13)	0.0042 (13)
C7	0.0282 (15)	0.0253 (14)	0.0255 (14)	0.0016 (11)	0.0001 (11)	0.0006 (11)
C8	0.0340 (18)	0.064 (2)	0.0398 (18)	0.0144 (17)	0.0101 (14)	−0.0025 (17)
C9	0.0269 (17)	0.054 (2)	0.057 (2)	−0.0029 (15)	−0.0047 (15)	−0.0072 (18)
C10	0.0240 (14)	0.0223 (13)	0.0284 (14)	−0.0042 (11)	0.0022 (11)	−0.0025 (11)
C11	0.0186 (13)	0.0249 (13)	0.0256 (13)	−0.0029 (10)	0.0054 (10)	0.0006 (11)
C12	0.0197 (13)	0.0206 (13)	0.0292 (14)	−0.0017 (10)	0.0060 (11)	−0.0005 (11)
C13	0.0269 (14)	0.0242 (14)	0.0274 (14)	0.0002 (11)	0.0044 (11)	0.0006 (12)
C14	0.0272 (15)	0.0283 (15)	0.0286 (14)	0.0043 (12)	0.0038 (12)	0.0062 (12)
C15	0.0277 (15)	0.0255 (14)	0.0328 (15)	0.0013 (11)	0.0086 (12)	−0.0003 (12)
C16	0.0248 (14)	0.0262 (14)	0.0263 (14)	−0.0012 (11)	0.0058 (11)	−0.0040 (12)
C17	0.0506 (19)	0.0327 (16)	0.0259 (15)	0.0071 (14)	0.0038 (13)	0.0018 (13)
C18	0.055 (2)	0.0324 (16)	0.0381 (18)	0.0115 (15)	0.0070 (15)	−0.0020 (14)
C19	0.0206 (13)	0.0261 (14)	0.0313 (14)	0.0027 (11)	0.0090 (11)	−0.0015 (12)
C20	0.0148 (12)	0.0277 (14)	0.0284 (14)	0.0040 (10)	0.0038 (10)	0.0006 (11)
C21	0.0154 (13)	0.0274 (13)	0.0272 (14)	0.0030 (11)	0.0040 (10)	0.0033 (11)
C22	0.0191 (13)	0.0263 (14)	0.0390 (16)	0.0011 (11)	0.0033 (12)	−0.0002 (12)
C23	0.0214 (14)	0.0264 (15)	0.0508 (19)	0.0019 (11)	0.0090 (13)	0.0092 (13)
C24	0.0226 (14)	0.0344 (16)	0.0402 (17)	0.0087 (12)	0.0120 (13)	0.0086 (14)
C25	0.0213 (14)	0.0337 (15)	0.0302 (14)	0.0065 (12)	0.0087 (11)	0.0020 (12)
C26	0.0369 (18)	0.0354 (17)	0.0483 (19)	−0.0079 (14)	0.0083 (15)	−0.0102 (15)
C27	0.045 (2)	0.0422 (19)	0.061 (2)	0.0050 (15)	0.0311 (18)	0.0118 (17)
C28	0.0363 (18)	0.0401 (18)	0.052 (2)	0.0066 (15)	0.0118 (15)	0.0047 (16)
Cl1	0.0697 (7)	0.0652 (7)	0.0746 (7)	0.0233 (5)	0.0123 (5)	0.0325 (6)
Cl2	0.0520 (6)	0.0440 (6)	0.1264 (10)	−0.0070 (4)	−0.0121 (6)	−0.0067 (6)
Cl3	0.0613 (6)	0.0692 (6)	0.0497 (5)	0.0150 (5)	0.0097 (4)	−0.0101 (5)

Geometric parameters (Å, º)

Zr1—O1	2.066 (2)	C10—C11	1.506 (4)
Zr1—O2	2.064 (2)	C11—C16	1.403 (4)
Zr1—O3	2.049 (2)	C11—C12	1.407 (4)
Zr1—H1	2.76 (3)	C12—C13	1.406 (4)
O1—C3	1.340 (3)	C13—C14	1.399 (4)
O1—H1	2.27 (3)	C13—C17	1.506 (4)
O2—C12	1.342 (3)	C14—C15	1.391 (4)
O2—H1	2.12 (3)	C15—C16	1.391 (4)
O3—C21	1.333 (3)	C15—C18	1.521 (4)
O3—H1	2.29 (3)	C19—C20	1.511 (4)
N1—C19	1.501 (3)	C20—C25	1.393 (4)
N1—C1	1.506 (3)	C20—C21	1.411 (4)
N1—C10	1.509 (3)	C21—C22	1.410 (4)
C1—C2	1.500 (4)	C22—C23	1.398 (4)
C2—C7	1.400 (4)	C22—C26	1.507 (4)
C2—C3	1.406 (4)	C23—C24	1.384 (4)
C3—C4	1.413 (4)	C24—C25	1.392 (4)
C4—C5	1.402 (4)	C24—C27	1.517 (4)
C4—C8	1.497 (4)	C28—Cl1	1.764 (3)
C5—C6	1.385 (4)	C28—Cl2	1.747 (3)
C6—C7	1.388 (4)	C28—Cl3	1.742 (4)
C6—C9	1.515 (4)
O1—Zr1—O2	86.60 (7)	C11—C10—N1	113.2 (2)
O1—Zr1—O3	87.66 (8)	C16—C11—C12	119.5 (2)
O2—Zr1—O3	86.56 (7)	C16—C11—C10	119.2 (2)
O1—Zr1—H1	53.8 (5)	C12—C11—C10	121.1 (2)
O2—Zr1—H1	49.6 (6)	O2—C12—C13	120.7 (2)
O3—Zr1—H1	54.5 (6)	O2—C12—C11	119.5 (2)
C3—O1—Zr1	158.04 (17)	C13—C12—C11	119.8 (2)
C3—O1—H1	96.0 (7)	C14—C13—C12	118.5 (2)
Zr1—O1—H1	79.0 (7)	C14—C13—C17	121.1 (2)
C12—O2—Zr1	162.56 (17)	C12—C13—C17	120.3 (2)
C12—O2—H1	97.4 (8)	C15—C14—C13	122.9 (3)
Zr1—O2—H1	82.6 (8)	C14—C15—C16	117.6 (2)
C21—O3—Zr1	160.29 (18)	C14—C15—C18	120.7 (3)
C21—O3—H1	98.0 (7)	C16—C15—C18	121.7 (3)
Zr1—O3—H1	78.8 (7)	C15—C16—C11	121.7 (3)
C19—N1—C1	112.7 (2)	N1—C19—C20	113.7 (2)
C19—N1—C10	112.8 (2)	C25—C20—C21	120.3 (2)
C1—N1—C10	112.5 (2)	C25—C20—C19	119.9 (2)
C2—C1—N1	112.5 (2)	C21—C20—C19	119.6 (2)
C7—C2—C3	120.6 (3)	O3—C21—C20	119.7 (2)
C7—C2—C1	119.7 (2)	O3—C21—C22	121.2 (2)
C3—C2—C1	119.7 (2)	C20—C21—C22	119.1 (2)
O1—C3—C2	119.7 (2)	C23—C22—C21	118.0 (3)
O1—C3—C4	121.5 (2)	C23—C22—C26	121.9 (3)
C2—C3—C4	118.8 (2)	C21—C22—C26	120.1 (3)
C5—C4—C3	118.1 (3)	C24—C23—C22	123.6 (3)
C5—C4—C8	121.2 (3)	C23—C24—C25	117.5 (3)
C3—C4—C8	120.6 (3)	C23—C24—C27	121.3 (3)
C6—C5—C4	123.6 (3)	C25—C24—C27	121.2 (3)
C5—C6—C7	117.3 (3)	C24—C25—C20	121.3 (3)
C5—C6—C9	122.0 (3)	Cl3—C28—Cl2	110.9 (2)
C7—C6—C9	120.7 (3)	Cl3—C28—Cl1	110.45 (18)
C6—C7—C2	121.4 (3)	Cl2—C28—Cl1	110.18 (19)