The crystal structures and properties of [VCL3(THF)2(H2O] and [VCl3(THF)2(H2O)]·THF

Polyhedron Vol. 15, No. 3, pp. 381 384, 1996

Pergamon 0277-5387 (95)00286-3

Copyright © 1995 Elsevier Science Ltd Printed in Great Britain. All rights reserved 027~5387/96 $9.50+0.00

THE CRYSTAL STRUCTURES AND PROPERTIES OF [VCI3(THF)2(H20)] AND [VCI3(THF)2(H20)i "THF PIOTR SOBOTA,* IGOR O. FRITSKY,t JOLANTA EJFLER, SLAWOMIR SZAFERT and TADEUSZ GLOWIAK Institute of Chemistry, University of Wroctaw, 14 F. Joliot-Curie, 50-383 Wroctaw, Poland

(Received 19 October 1994; accepted 8 June 1995) Abstract--The structure of the products formed between [mer-VC13(THF)3] and water in tetrahydrofuran (THF) or dichloromethane were investigated. Two different crystalline species were isolated: [VC13(THF)z(H20)] (1) and [VC13(THF)2(H20)]'THF (2). Their structures were determined by means of X-ray analysis. In both compounds the vanadium (III) ions are in a distorted octahedral environment surrounded by three mer-chlorine atoms, two trans-situated T H F molecules and a water molecule.

Preparing the [mer-VC13(THF)3] compound according to the standard method J we noticed that after filtration of the bulky product, the mother liquor, under cooling, produced, along with the additional quantity of trichlorotris(tetrahydrofuran)vanadium(III) complex, a small amount of orange crystals. The moisture leaked into the crystallization vessel because the solvent had washed out the grease on the stopper and a compound of formula VC13 • 2 T H F " H20 (2) was formed. Its unitcell parameters proved to be the same as of [VC13(THF)2(OH)] • T H F , which has recently been reported. 2 However, the electronic spectrum and magnetic susceptibility measurements suggest that the vanadium atom in 2 is in the 3 + oxidation state. In order to explain whether the V 3÷ atom can be oxidized by water in T H F we decided to perform this investigation. In this paper the crystal structure, magnetic and spectroscopic properties of the title compounds are described. EXPERIMENTAL All manipulations were carried out under dinitrogen by use of a Schlenk system and vacuum line. * Author to whom correspondence should be addressed. t On leave from the Department of Chemistry, Shevchenko University, 252017 Kiev, Ukraine.

The V C I 3 w a s commercial material (Aldrich). [merVCI3(THF)3] was prepared by a reported procedure, I Solvents were dried and purified by standard techniques. Magnetic susceptibilities were measured by the Faraday method within the temperature range 78-295 K. Corrections for diamagnetism were made with Pascal's constants. 3 The EPR spectra were obtained on a SE type X-band spectrometer. The following spectrometers were used: Specord Perkin-Elmer 180 for IR and Beckman UV 5240 for UV-vis spectroscopy.

Syntheses Trichloroaquabis( tetrahydrofuran) vanadium( II1) (1). To 3.7 g (10 mmol) of [mer-VC13(THF)3] dissolved in 50 cm 3 of CH2C12, 1.6 cm 3 of water was added and the solution was stirred for 1 h at room temperature. Next, the solution was layered with 5 cm 3 of n-hexane and allowed to stand at room temperature. After one week orange crystals and a small amount of light greenish solid settled down. These crystals were separated by hand. Analysis of orange compound : Found : V, 16.2 ; C1, 34.0. Calc. for C 8 H I 8 0 3 C I 3 V : V , 15.9; C1, 33.3%. IR (Nujol) : v(COC) 1040 vs, 1006 s, 852 vs; v(OH) 1622 m; other bands 3284 br, w, 688 m, 438 m, 322 vs, 272 m cm -1.

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Trichloroaquabis( tetrahydrofuran)vanadium(lll)

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P. SOBOTA et al.

tetrahydrofuran (2). 3.7 g (10 mmol) of [merVC13(THF)3] was dissolved in 50 cm 3 of T H F and then 1.6 cm 3 of water was added. The solution was stirred over 10 h at room temperature until the colour had changed from brown to orange. Next, the solution was filtered off and cooled in a refrigerator at 255 K. After 12 h, crystalline orange product was filtered offand washed with CH2C12 (3 x 5 cm3). Yield 2.8 g (90%). F o u n d : V, 13.5; C1, 26.9. Calc. for C I 2 H 2 6 0 4 C 1 3 V : V , 13.0 ; C1, 27.2%. IR (Nujol) : v(COC) 1040 vs, 1001 s, 835 vs; v(OH) 1620 m; other bands 956 m, 920 m, 640 w, 374 s, 330 vs, 306 s cm -1.

The hydrogen atoms of water molecule were found from difference syntheses. A weighting scheme of the form w = 1/a2(Fo 2)+ (0.0848p)2+0.38P and w=l/a2(Fo2)+(O.O777P)Z+l.O6P (where P is defined as (Fo2+2F~2)/3) were applied for I and 2, respectively. Final RI(F) and wR(F2) values are 0.0427 and 0.1165 for 1 and 0.0427 and 0.1141 for 2. For the last cycle of the refinement the maximum value of the ratio A/a was below 0.008 ~ for each compound. The final difference map showed a general background within - 0 . 3 9 and 0.63 for 1 and - 0 . 6 7 and 0.65 for 2. Selected bond lengths and bond angles are given in Table 1. All additional parameters are available from the authors.

X-ray crystallography R E S U L T S AND DISCUSSION

Crystal data for complex (1). Orange crystals, C8H18CI303V, M = 319.515, triclinic, space group P[, a = 8.107(6), b = 8.875(3), c = 10.075(8) ~ , = 86.30(5), / / = 83.73(7) and 7 = 78.58(5) °, Z = 2, U = 706(1) /~3, Dc = 1.504(2) g cm -3, D m = 1.507 g cm -3, F(000) = 328, T = 298(1) K, /~ = 1.26 mm -1. Crystal data for (2). Orange crystals, C12H26C1304 V , M = 391.62, triclinic, space group P1, a = 8.038(8), b = 8.984(8), c = 13.779(9) /~, = 90.24(9), /~ = 106.79(9) and 7 = 112.13(9) °, Z = 2, U = 875(2) /~3, Dc = 1.486(3) g cm -3, D m = 1.500 g c m -3, F(000) = 408, T = 100.0(1) K, = 1.03 mm 1. Data collection and processing. Intensities were collected using a Kuma K M 4 four-circle diffractometer in the o)-20 mode (with crystals of dimensions 0.5 × 0.3 × 0.3 for 1 and 0.3 × 0.3 × 0.2 for 2) and Mo-K~ radiation. The data for complex 2 were collected at low temperature by use of an Oxford System Cryostream Cooler. The crystals were cut from large crystals and in the case of 1 sealed in a glass capillary. For both crystals the intensities of three standard reflections, monitored every 100 intensity scans, showed no evidence of crystal decay. 2661 (4 ° < 20 < 56 °) and 4005 (4 ° < 20 < 56 °) reflections were measured for 1 and 2, respectively, from which 1673 and 2612 with I > 3.0a(I) were used for calculations. The structures were solved by the Patterson method and refined by full-matrix least-squares calculations using SHELXL93. 4 The number of refined parameters was 142 for 1 and 187 for 2. Neutral-atom scattering factors were taken from ref. 5; real and imaginary components of anomalous dispersion were included for all non-H atoms. The hydrogen atoms of CH2 groups in T H F rings were put in calculated positions with d ( C - - H ) = 1.08 /~ and introduced as fixed contributors in the final stage of refinement.

The reaction between [mer-VC13(THF)3] and moisture in CH2C12 at room temperature gave an air-sensitive compound of formula VC13"2THF" H20, which in dichloromethane crystallized as [VC13(THF)2(H20)] (1). The addition of one equivalent of water to the solution of [mer-VCt3(THF)3] in T H F does not change its colour and produces [VC13(THF)z(HzO)]'THF (2) in small yield. To obtain the pure aqua complex as a main product, a three-fold excess of water was added, till the colour

Table 1. Selected bond lengths (/~) and angles (°) for 1 and 2 1

V~O(1) V--O(2) V--O(3) V--CI(1) V--CI(2) V--CI(3) CI(I)--V--CI(2) CI(1)--V--CI(3) CI(I)--V--O(1) CI(1)--V--O(2) CI(1)--V--O(3) C1(2)--V--C1(3) CI(2)--V--O(1) C1(2)--V--O(2) C1(2)--V~O(3) CI(3)--V--O(1) C1(3)--V~(2) C1(3)--V--O(3) O(1)--V--O(2) O(1)--V--O(3) O(2)--V--O(3)

2.046(3) 2.043(3) 2.080(3) 2.387(1) 2.396(1) 2.307(1) 171.41(5) 94.33(5) 90.00(9) 91.08(10) 86.19(9) 94.18(5) 88.44(9) 89.77(10) 85.29(9) 92.67(9) 92.17(10) 179.41 (9) 174.95(13) 87.06(12) 88.10(12)

2

2.032(3) 2.010(3) 2.024(3) 2.385(3) 2.363(3) 2.339(3) 174.40(3) 92.22(10) 90.24(11) 89.78(11) 87.11(12) 93.37(10) 89.34(11) 90.35(11) 87.29(12) 91.59(10) 91.49(11) 179.03 (7) 176.92(8) 87.70(12) 89.22(12)

Structures of [VC13(THF)2(H20)] and [VC13(THF)2(H20)] •THF

383

(~ CI(2I

i c,.,

Fig. 1. Molecular structure and the numbering scheme for 1.

of solution changed from brown to orange. It is noteworthy that this does not afford the substitution of the second and third THF ligand in the coordination sphere of vanadium(III) ions by the water molecules. The IR spectra of 1 and 2 show bands at 1622s and 3250m, br cm -~ assigned to O--H vibrations, and characteristic modes at 322s and 438s cm -l, which are attributed to v(V--C1) and v(V--O), respectively, as well as bands due to v(COC) of the coordinated THF molecules. The [VC13(THF)z(H20)] "THF (2) complex as a solid shows bands at 13,100 and 21,100 cm- ~in its diffuse reflectance spectrum, close to the values observed for the compound in CH2C12 solution. These bands can be assigned to the 3Tlg(F) -'*3T2g(F) and 3Tlg(F)--+3TI~(P ) transitions, respectively, for coordinated d z species, cf. [VC12(H20)4]C1,6 [VC12 (ROH)4]CI 7 ( R = a l k y l ) , and [VC12(MeCN)4] [SbC16].s The electronic spectra suggest that compound 2 has a similar structure in solution and in the solid. Compound 2 is paramagnetic with a temperature-independent (80-293 K)/reef of 2.82 #B per vanadium atom (a plot of 1/Z against T gave a straight line passing through the origin). Magnetic susceptibility measurements were carried out only for 2 because it has been obtained in sufficient quantity from [mer-VC13(THF)3] and water. No EPR signal was observed in the solid state for 1 and 2, which additionally confirms the vanadium(Ill) oxidation state (S = 1). On dissolution in CH2C12, a hyperfine EPR spectrum with sets of eight lines arising from interaction of the d 1electron with a 5~V nucleus (I = 7/2) was observed. A similar spectrum was recorded for [mer-VC13(THF)3]. The comparison of the spectral parameters with those of VO 2÷ complexes suggests that vanadium(Ill) was partially oxidized in pure CH2C12 to vanadium(IV). 9 The oxidation of VCI3 by 02 to

vanadium(IV) with the intermediate formation of dioxygen adducts is already well documented.I° The tetrameric vanadyl [VOCI2{CHz(COzEt)2}]4 species is formed from [V2(#-C1)2Cla{CH2(CO2Et)2}2] under the influence of dioxygen and moisture.11 The X-ray analysis of 1 and 2 revealed that the vanadium atom in each compound is octahedrally coordinated by three mer-chlorine atoms, one oxygen from a water molecule and two oxygens from THF ligands arranged in trans-fashion (Figs 1 and 2). Selected bond lengths and angles of the compounds are given in Table 1. Comparison of the corresponding geometrical parameters with those of [VCIz(H20)4]C1,6 [VCI2(ROH)4]C1,7 [(THF)3ClzVOVCldTHF)3] '2 and [V2(/t-C1)2C14 (THF)4] ~3 indicates no noticeable differences. The structure of compound 2 differs from 1 only in the presence of the THF molecule in the lattice. All V--C1 and V--O distances in 1 and 2 are similar (see Table 1). Compound 2 is connected to solvated THF molecules through an 0(3)-HO(1)...O(4) bridge of 2.585(3) /k. The O(3)--HO(1). • .0(4) bridge angle is 169(5) °. Both tetrahydrofuran molecules coordinated to the vanadium atom in 1 have the envelope conformation, in 2 they have the twist conformation. The solvated THF molecules in 2 adopt the envelope conformation.

CONCLUSIONS The interaction of [mer-VCI3(THF)3] with water in THF or CH2C12 resulted in the substitution of one THF ligand by an H20 molecule. Three different types of crystals containing the same vanadium coordination polyhedra [mer-VC13(THF)2(H20)] were isolated. The results of EPR, magnetic susceptibility mesurements, UV-vis spectra as well as

384

P. SOBOTA et al.

Cll31

J

W

f jC(1) c~ C(31

~

clcll ~ c { 6 1 . ~ o

,o

141 C112)(~ (J~L0(3)

(~C(1 H_~ HO(2] C111~

19)

Fig. 2. Molecular structure and the numbering scheme for 2.

the crystal structure indicate that the vanadium atoms in 1 and 2 are in the V 3÷ oxidation state. Our results proved that species 2 and the well-known [VC13(THF)2(OH)]- T H F 2 are really the the same compounds. It is worth to noting that during recrystallization of [VC13(THF)2(H20)] • T H F , besides the species 2, a small amount of light greenish crystals of 3 was obtained. F o r X-ray study c o m p o u n d 3 was separated by hand. The preliminary results of the Xray analysis showed that 3* is probably a polymorphic modification o f 2. However, the V - - O and V--C1 bond distances in 3 are shorter ca 0.1 /~ than corresponding bond lengths in 1 and 2. The shrinkage in bond lengths could indicate that the oxidation state of vanadium a t o m in 3 is higher than in 1 and 2. To confirm this suggestion it is necessary to obtain species 3 in pure form for its further full characterization.

*Crystal

data

for

3.

Light

green

crystals,

CI2H26CIaOaV, M = 391.62, monoclinic, space group

P2~/c, a = 8.248(2), b = 13.632(7), c = 13.513(7) A and fl = 99.17(6) °, Z = 4, U = 1500(2) /~3, Dc = 1.734(1) g c m -3, Dm -- 1.724 g c m -3, F(000) = 816, T = 100.0(1) K, tt = 1.03 m m - 1. The V--O(water) distance is 1.971 (2)

A.

Acknowledgement--The authors thank the State Committee for the Scientific Research for financial support of this work (Grant No. 3T09A 016 08).

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