Tetra­chloro(N,N,N',N'-tetra­methyl­ethyl­enedi­amine)­zirconium(IV)

The crystal structure of the title compound, [ZrCl₄(C₆H₁₆N₂)], has a distorted octahedral coordination geometry. The chloro ligands trans to the nitro­gen donors have significantly shorter bonds than the chloro ligands which are mutually trans.

Key indicators

• Single-crystal X-ray study
• T = 203 K
• Mean [sigma](C-C) = 0.005 Å
• R factor = 0.018
• wR factor = 0.045
• Data-to-parameter ratio = 24.9

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


 Alert Level A:



SHFSU_01  Alert A The absolute value of parameter shift to su ratio > 0.20
          Absolute value of the parameter shift to su ratio given   0.362
          Additional refinement cycles may be required.


 Alert Level C:



STRVAL_01
         From the CIF: _refine_ls_abs_structure_Flack    0.440
         From the CIF: _refine_ls_abs_structure_Flack_su    0.040
           Alert C Flack test results are ambiguous.

General Notes



REFLT_03
         From the CIF: _diffrn_reflns_theta_max           28.12
         From the CIF: _reflns_number_total               3059
         Count of symmetry unique reflns         1728
         Completeness (_total/calc)            177.03%
         TEST3: Check Friedels for noncentro structure
         Estimate of Friedel pairs measured      1331
         Fraction of Friedel pairs measured     0.770
         Are heavy atom types Z>Si present          yes
          Please check that the estimate of the number of Friedel pairs is
          correct. If it is not, please give the correct count in the
          _publ_section_exptl_refinement section of the submitted CIF.


 1 Alert Level A = Potentially serious problem

 0 Alert Level B = Potential problem

 1 Alert Level C = Please check

---

S1. Comment

Simple coordination compounds of titanium and zirconium are known to be active catalysts for 1-alkene polymerizations (Pino & Mulhaupt, 1980). Titanium complexes containing the N,N,N',N'-tetramethylethylenediamine (tmeda) ligand have been found to be catalytically active when heterogeneous systems are used. For example, when [TiCl₄(tmeda)] is slurried with MgCl₂ the ethylene polymerization activity is above 5800 g mmol⁻¹ h⁻¹ at 0.5 MPa (Giannini et al., 1980) and the components [TiCl₄(tmeda)]/Et₃Al/MgCl₂ have been shown to be active in propene polymerization (Sobota et al., 1997). [TiCl₄(tmeda)] has been structurally characterized and shown to be a monomeric six-cordinate species (Sobota et al., 1997). Tmeda has been used as a solubilizing reagent for reactions involving the insoluble [ZrCl₄] (Strickler & Power, 1996, 1998, 1999) and [ZrCl₄(1.5tmeda)] has been prepared and characterized by spectroscopic methods (Gordon & Wallbridge, 1986), but little is known of the structures of these complexes.

We have found that when slightly more than one equivalent of tmeda in CH₂Cl₂ is added to [ZrCl₄] in CH₂Cl₂, the insoluble zirconium chloride compound slowly dissolves producing a colourless solution which gives rise to a highly crystalline complex which analyses as [ZrCl₄(tmeda)]. Given the propensity for zirconium to form complexes with coordination numbers greater than 6 (Fay, 1986), a crystal structure determination of [ZrCl₄(tmeda)], (I), was undertaken to establish the coordination geometry.

The complex is almost isostructural with [TiCl₄(tmeda)], except that the bite angle for the two N atoms of the tmeda ligand is slightly smaller in the zirconium complex [75.44 (7) versus 78.5 (3)°], which is surprising given its larger size. Other angles are very similar to those in the titanium complex. The Zr—Cl bond distances trans to the tmeda N atoms are significantly shorter than the two Zr—Cl bonds where the chloro ligands are mutually trans, due to the greater degree of π-donation to the metal from these ligands. In the absence of any π-donation the complex achieves an electron count of only 12, but this increases to 16 if the chloro ligands trans to the N atoms each donate two electrons into two separate metal orbitals. For the trans chloro ligands, competitive π-donation would not allow this electron count to be maximized. The chelate ring has the commonly encountered gauche conformation.

S2. Experimental

All preparations and manipulations were carried out under dry oxygen-free nitrogen using standard bench-top techniques for air-sensitive substances. ZrCl₄ and N,N,N',N'-tetramethylethylenediamine (tmeda) were used as received from commercial sources. Dichloromethane was dried over and distilled from freshly ground CaH₂ immediately prior to use. Tmeda (0.97 g, 8.35 mmol) in CH₂Cl₂ (20 ml) was added to a suspension of ZrCl₄ (1.91 g, 8.2 mol) in CH₂Cl₂ (30 ml) and the mixture was stirred for 30 min, during which time the solid completely dissolved. The colourless solution was filtered and the volume reduced to about 30 ml. On standing at 253 K, the complex was obtained as a colourless crystalline solid which was filtered off. The solution volume was reduced further to ca 15 ml and, on standing, further crystalline product was obtained. Yield: 2.7 g, 94%. Found: C 20.96, H 4.70, N 8.05%; C₆H₁₆Cl₄N₂Zr requires: C 20.64, H 4.62, N 8.02%. Once isolated, the complex is insufficiently soluble in CD₂Cl₂ to obtain NMR spectra.

S3. Refinement

The structure is a racemic twin and has been refined with the contribution from the two components as a least-squares variable. The relative contributions from the two enantiomers are 0.44 and 0.56 from the real and inverted enantiomers respectively. H atoms were placed geometrically and refined with a riding model (including free rotation about C—C bonds for methyl groups), and with U_iso values constrained to be 1.2 (1.5 for methyl groups) times U_eq of the carrier atom.

Computing details

Data collection: SMART (Siemens, 1995); cell refinement: SMART; data reduction: SAINT (Siemens, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, (1997); molecular graphics: SHELXTL (Siemens, 1994); software used to prepare material for publication: SHELXL97.

Figures

Fig. 1. The structure of (I), showing 50% probability displacement ellipsoids The H atoms have been omitted for clarity.

Tetrachloro(N,N,N',N'-tetramethylethylenediamine)zirconium(IV)

Crystal data

[ZrCl4(C6H16N2)]	Dx = 1.713 Mg m^−3
Mr = 349.23	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Pna21	Cell parameters from 5543 reflections
a = 14.6419 (3) Å	θ = 2–25°
b = 7.6642 (2) Å	µ = 1.57 mm^−1
c = 12.0660 (2) Å	T = 203 K
V = 1354.03 (5) Å^3	Irregular fragment, colourless
Z = 4	0.42 × 0.28 × 0.18 mm
F(000) = 696

Data collection

Siemens SMART diffractometer	3059 independent reflections
Radiation source: fine-focus sealed tube	2927 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.027
Area–detector ω scans	θmax = 28.1°, θmin = 2.8°
Absorption correction: multi-scan (Blessing, 1995)	h = 0→19
Tmin = 0.559, Tmax = 0.766	k = 0→10
13246 measured reflections	l = −15→15

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.018	H-atom parameters constrained
wR(F^2) = 0.045	w = 1/[σ^2(Fo^2) + (0.0236P)^2 + 0.3332P] where P = (Fo^2 + 2Fc^2)/3
S = 1.02	(Δ/σ)max = 0.362
3059 reflections	Δρmax = 0.30 e Å^−3
123 parameters	Δρmin = −0.27 e Å^−3
1 restraint	Absolute structure: Flack (1983)
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.44 (4)

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

	x	y	z	Uiso*/Ueq
Zr	0.627442 (12)	0.29424 (2)	0.00024 (2)	0.02937 (5)
Cl1	0.74056 (4)	0.06689 (7)	−0.01508 (5)	0.04599 (13)
Cl2	0.69303 (5)	0.44693 (8)	−0.15709 (5)	0.04966 (15)
Cl3	0.56170 (5)	0.16809 (8)	0.16688 (5)	0.05046 (15)
Cl4	0.50142 (5)	0.19267 (10)	−0.11037 (6)	0.06198 (19)
N1	0.54743 (13)	0.5652 (2)	0.03979 (15)	0.0374 (4)
N2	0.73028 (14)	0.4546 (3)	0.12161 (17)	0.0399 (4)
C1	0.61453 (19)	0.6866 (3)	0.0917 (3)	0.0566 (7)
H1A	0.6530	0.7378	0.0337	0.068*
H1B	0.5815	0.7816	0.1284	0.068*
C2	0.6737 (2)	0.5966 (4)	0.1743 (3)	0.0593 (7)
H2A	0.6353	0.5457	0.2324	0.071*
H2B	0.7143	0.6821	0.2091	0.071*
C3	0.5085 (2)	0.6529 (4)	−0.0606 (2)	0.0644 (8)
H3A	0.4814	0.7635	−0.0393	0.097*
H3B	0.4621	0.5787	−0.0934	0.097*
H3C	0.5567	0.6733	−0.1141	0.097*
C4	0.46831 (18)	0.5402 (4)	0.1175 (2)	0.0514 (6)
H4A	0.4386	0.6515	0.1304	0.077*
H4B	0.4903	0.4936	0.1873	0.077*
H4C	0.4250	0.4594	0.0849	0.077*
C5	0.8104 (2)	0.5300 (5)	0.0635 (3)	0.0735 (9)
H5A	0.8499	0.5872	0.1169	0.110*
H5B	0.7898	0.6143	0.0090	0.110*
H5C	0.8440	0.4376	0.0266	0.110*
C6	0.7671 (2)	0.3430 (4)	0.2132 (2)	0.0590 (7)
H6A	0.8071	0.4121	0.2598	0.088*
H6B	0.8012	0.2463	0.1818	0.088*
H6C	0.7169	0.2982	0.2572	0.088*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Zr	0.03907 (9)	0.02282 (8)	0.02621 (8)	−0.00208 (6)	0.00333 (8)	−0.00278 (8)
Cl1	0.0548 (3)	0.0321 (2)	0.0510 (3)	0.0088 (2)	0.0059 (3)	−0.0060 (3)
Cl2	0.0650 (4)	0.0463 (3)	0.0377 (3)	0.0036 (3)	0.0179 (3)	0.0096 (3)
Cl3	0.0721 (4)	0.0354 (3)	0.0439 (3)	−0.0022 (3)	0.0213 (3)	0.0074 (2)
Cl4	0.0628 (4)	0.0687 (4)	0.0545 (4)	−0.0182 (3)	−0.0137 (3)	−0.0101 (3)
N1	0.0464 (10)	0.0302 (9)	0.0355 (8)	0.0076 (8)	0.0050 (7)	0.0010 (7)
N2	0.0401 (10)	0.0339 (10)	0.0457 (10)	−0.0014 (8)	−0.0068 (8)	−0.0081 (8)
C1	0.0630 (16)	0.0272 (11)	0.080 (2)	0.0025 (11)	0.0023 (15)	−0.0130 (12)
C2	0.0719 (18)	0.0426 (13)	0.0633 (16)	0.0024 (13)	−0.0154 (14)	−0.0264 (13)
C3	0.083 (2)	0.0636 (17)	0.0465 (15)	0.0362 (17)	0.0060 (14)	0.0139 (14)
C4	0.0505 (14)	0.0508 (15)	0.0530 (14)	0.0152 (11)	0.0143 (11)	0.0045 (12)
C5	0.0538 (17)	0.077 (2)	0.090 (2)	−0.0282 (16)	−0.0043 (16)	−0.0087 (18)
C6	0.0658 (17)	0.0667 (18)	0.0444 (13)	0.0114 (15)	−0.0186 (12)	−0.0091 (13)

Geometric parameters (Å, º)

Zr—Cl4	2.4066 (7)	C2—H2A	0.9800
Zr—Cl1	2.4111 (5)	C2—H2B	0.9800
Zr—Cl2	2.4281 (6)	C3—H3A	0.9700
Zr—Cl3	2.4298 (6)	C3—H3B	0.9700
Zr—N1	2.4319 (17)	C3—H3C	0.9700
Zr—N2	2.4337 (19)	C4—H4A	0.9700
N1—C1	1.491 (3)	C4—H4B	0.9700
N1—C3	1.498 (3)	C4—H4C	0.9700
N1—C4	1.503 (3)	C5—H5A	0.9700
N2—C5	1.484 (4)	C5—H5B	0.9700
N2—C6	1.498 (4)	C5—H5C	0.9700
N2—C2	1.508 (3)	C6—H6A	0.9700
C1—C2	1.490 (4)	C6—H6B	0.9700
C1—H1A	0.9800	C6—H6C	0.9700
C1—H1B	0.9800
Cl4—Zr—Cl1	104.50 (3)	H1A—C1—H1B	107.9
Cl4—Zr—Cl2	91.46 (3)	C1—C2—N2	111.8 (2)
Cl1—Zr—Cl2	90.96 (2)	C1—C2—H2A	109.2
Cl4—Zr—Cl3	91.52 (3)	N2—C2—H2A	109.2
Cl1—Zr—Cl3	92.75 (2)	C1—C2—H2B	109.2
Cl2—Zr—Cl3	174.52 (2)	N2—C2—H2B	109.3
Cl4—Zr—N1	90.90 (5)	H2A—C2—H2B	107.9
Cl1—Zr—N1	164.40 (5)	N1—C3—H3A	109.5
Cl2—Zr—N1	86.12 (5)	N1—C3—H3B	109.5
Cl3—Zr—N1	89.23 (5)	H3A—C3—H3B	109.5
Cl4—Zr—N2	166.27 (5)	N1—C3—H3C	109.5
Cl1—Zr—N2	89.21 (5)	H3A—C3—H3C	109.5
Cl2—Zr—N2	88.99 (5)	H3B—C3—H3C	109.5
Cl3—Zr—N2	87.03 (5)	N1—C4—H4A	109.5
N1—Zr—N2	75.44 (7)	N1—C4—H4B	109.5
C1—N1—C3	108.1 (2)	H4A—C4—H4B	109.5
C1—N1—C4	109.0 (2)	N1—C4—H4C	109.5
C3—N1—C4	105.57 (19)	H4A—C4—H4C	109.5
C1—N1—Zr	107.32 (14)	H4B—C4—H4C	109.5
C3—N1—Zr	114.06 (15)	N2—C5—H5A	109.5
C4—N1—Zr	112.63 (14)	N2—C5—H5B	109.5
C5—N2—C6	106.6 (2)	H5A—C5—H5B	109.5
C5—N2—C2	110.7 (2)	N2—C5—H5C	109.5
C6—N2—C2	107.4 (2)	H5A—C5—H5C	109.5
C5—N2—Zr	113.67 (18)	H5B—C5—H5C	109.5
C6—N2—Zr	112.21 (16)	N2—C6—H6A	109.5
C2—N2—Zr	106.15 (14)	N2—C6—H6B	109.5
C2—C1—N1	112.1 (2)	H6A—C6—H6B	109.5
C2—C1—H1A	109.2	N2—C6—H6C	109.5
N1—C1—H1A	109.2	H6A—C6—H6C	109.5
C2—C1—H1B	109.2	H6B—C6—H6C	109.5
N1—C1—H1B	109.2