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Structural characterization of an oxotungsten(IV) complex, [WOBr(Me2PCH2CH2PMe2)2]Br.5H2O

1989; Wiley; Volume: 45; Issue: 8 Linguagem: Inglês

10.1107/s0108270189000545

1600-5759

F. Albert Cotton, Piotr A. Kibala, Charla S. McCaleb, R. B. W. SANDOR,

Polyoxometalates: Synthesis and Applications

(1) Bromobis[ethylenebis (dimethylphosphine-P,P')]oxotungsten(IV) bromide pentahydrate, [WBrO(C6H~6P2)2]Br.5H20, Mr = 75003, orthorhombic, Pbcm, a = 9 . 5 9 5 (2), b = 12.278 (3), c = 23.488 (6) A, V = 2767 (2) A 3, z = 4, D x = 1.800 g cm -3, 2(Mo Ka) = 0.7107 A, ~ = 73.75 cm -~, F(000)-1464, T = 294 K, R = 0.040 for 1673 observed reflections. The coordination of W is distorted octahedral with Br trans to O and the two phosphine ligands forming five-membered chelate rings. The W=O distance is 1-736 (9)A. The mean O W P angle is 96.9(4) ° . Introduction. During the course of a synthetic program directed towards the preparation of sulfur-capped tritungsten cluster compounds we inadvertently prepared and structurally characterized [WOBr(Me2PCH2CH2PMe2)2]Br.5H20. This compound was synthesized from two sets of starting materials. Due to the paucity of structural data on oxotungsten complexes, we report this work here. Experimental. The syntheses of (1) follow. Method A. WBra(THF)3 (420 mg, 0.66 mmol) and NariS (37 mg, 0-66 mmol) were suspended in 15 mL of THF and cooled to 195 K. Methanol (3 mL) was added to dissolve the sulfide. Dmpe O10p.L, 0.66mmol) was introduced and the mixture was slowly warmed to room temperature and stirred for 16 h. A blue precipitate formed which was separated from the brown solution by filtration under argon. The solution was then absorbed on a silia-gel column. After the column had been washed with a dichloromethane/acetone mixture (1:1), a brown band remained on top of the column which was eluted with an acetone/methanol mixture (1:1). Slow evaporation of the brown solution in air afforded red crystals of (1). Method B. A suspension of WaSTBr4(250 mg, 0.228 mmol) in 20 mL of THF and dmpe (5701aL, 3.42mmol) was stirred for 72h. The mixture was filtered under argon leaving a black residue. The residue was suspended in 10mL of * To whom correspondence should be addressed. 0108-2701/89/081126-03 $03.00 methanol and stirred for 5 h. This mixture was then filtered under argon and the pale brown filtrate was allowed to evaporate in air affording red crystals of (1). A small red needle-like crystal was selected from the product and was shown to be of good quality by polarized-light microscopy. The crystal was sealed with epoxy cement to the end of a glass fiber and mounted on the goniometer head of a Syntex P3 diffractometer. The crystal parameters and basic information relating to data collection and structure refinement are summarized in Table 1. Periodically monitored check reflections displayed no significant change in intensity throughout the data collection. The W atom was located by direct methods (SHELXS86; Sheldrick, 1986) and the remainder of the molecule was located and refined by alternating difference Fourier maps and least-squares cycles employing the Enraf-Nonius (1979) Structure Determination Package. The H atoms were not included in the model. All atoms were refined anisotropically. N o disorder or other non-routine problems arose. Atomic scattering factors were those of SDP. Discussion. The positional parameters and equivalent isotropic displacement parameters are given in Table 2.t The structure of the oxotungsten cation is depicted in Fig. 1 where the atom-numbering scheme is also defined. A unit-cell diagram is shown in Fig. 2. Table 3 presents selected important interatomic distances and angles. There are very few oxotungsten(IV) complexes known. The first report describing preparation in moderate yields of WOC1E(PR3)3, PRa=PMePh2, PMe2Ph and PEtEPh, appeared in 1972 (Butcher, Chatt, Leigh & Richards, 1972). In 1983 more efficient preparative methods for the PMe 3, PMe2Ph and PMePh2 derivatives were reported. These compounds t Lists of structure factors and anisotropic thermal parameters, and fuller lists of bond distances and angles have been deposited with the British Library Document Supply Centre as Supplementary Publication No. SUP 51755 (14 pp.). Copies may be obtained through The Executive Secretary, International Union of Crystallography, 5 Abbey Square, Chester CH 1 2HU, England. © 1989 International Union of Crystallography F. A. COTTON, P. A. KIBALA, C. S. McCALEB AND R. B. W. SANDOR 1127 Table 1. Crystallographic data for [WOBr(Me2PCH2CH2PMe2)2]Br.5H20 Systematic absences Okl: k = 2n + 1 hOl: l = 2n + 1 Crystal size (mm) 0.55 x 0.45 x 0.35 Data collection instrument Syntex P3 Orientation reflections: 25; 20 3a(Fo 2) No. of parameters refined 119 Transmission factors: max., min. 1.000, 0.896 R* 0-0399 w R 0.0600 Quality-of-fit indicators 1.283 Largest shift/e.s.d, final cycle 0.01 Largest peak (e/~,-3) 2.27§ -0 .88 * R = X l l F o l IF~l l /__. iFoi . f wR = [V_w(I Fo I IF<I )71~.WlFoi 21'/2; w = l / a2 ( I Fo I). $ Quality-of-fit = [ 5-w( I F o I IFcl )2/(Nob s -N o . . . . . t~,s)l ,/z. § The second highest positive peak is 1.39 e/~-3. Both peaks are within 0 . 9 / ~ of the W atom. All other peaks are random and below 0.8 e A-3. Table 2. Positional and equivalent isotropic displacement parameters and their estimated standard deviations for [WOBr(dmpe)2]Br.5H20 The equivalent isotropic displacement parameter is: ~[a2a*2Bll + bEb*2B22 + ¢2¢'2B33 + 2 a b ( c o s y ) a * b * B l 2 + 2 a c ( c o s l ) a * c * B l 3 + 2 b c ( c o s a ) b * c* B23]. x y z Beq(A 2) W 0.22446 (6) 0.00611 (4) 0.250 2.34 (1) Br(-) 0.0273 (2) 0.250 0.500 6.34 (5) Br(l) 0.3882 (2) -0.1705 (1) 0.250 4.29 (4) P(I) 0.3788 (3) 0.0557 (2) 0.3310 (1) 3.15 (6) P(2) 0.1009 (3) -0 .0858 (2) 0.3304 (1) 3.43 (6) O 0.124 (1) 0-1238 (8) 0.250 3.0 (2) C(II) 0.349 (1) 0.1961 (9) 0.3544(6) 5.0(3) C(12) 0.572 (1) 0.046 (1) 0.3276 (6) 5.0 (3) C(13) 0.338 (2) -0.031 (1) 0.3925 (5) 5.8 (3) C(21) 0.100 (1) -0.2337 (9) 0.3357 (6) 4.5 (3) C(22) -0 .089 (1) -0 .052 (1) 0.3363 (7) 6.5 (4) C(23) 0.172 (2) -0 .040 (I) 0.3980 (6) 6.4 (4) Ol 0.269 (1) 0.6214 (9) 0.4534 (5) 7.6 (3) 02 0.310 (1) 0.3977 (8) 9.4653 (5) 6.8 (3) 03 0.520 (1) 0.250 0.500 7.2 (4) Table 3. Selected bond distances (,I~) and angles (°)for [WOBr(dmpe)2]Br.5H20 Numbers in parentheses are estimated standard deviations in the least significant digits. W-Br ( l ) 2-678 (2) W P ( l ) 2.487 (3) W O 1.736 (9) W-P(2) 2.500 (3) Br( l ) -W-P(l ) 81.31 (7) P(2)--W-P(2)' 98.2 (l) Br(1)-W-P(2) 84.98 (7) P(1) -W-P(1) ' 99.9 (1) a r ( l ) W O 177.8 (3) P ( I ) W O 97.3 (2) P ( I ) -W-P(2 ) 79.3 (l) P (E ) -W-O 96.5 (2) P ( I ) -W-P(2 ) ' 166.2 (l) were characterized spectroscopically and utilized in some exchange reactions to give WOX2(Me3) 3 with X = NCO and NCS and with X 2 = Me2NCS 2 (Carmona, Sanchez, Poveda, Jones & Hefner, 1983). The preparation of three diphosphine compounds of the type [WOCI(L-L)2]BPh 4, where L-L = dppe, o-CrHa(PPh2) 2 and cis-Ph2PCH=CHPPh2, were also reported (Levason, McAuliffe & McCullough, 1977). The first crystallographically characterized oxotungsten(IV) compound, WOC12(PMePh2) 2(CH2=CH2), (2), was reported in 1986 (Su, Cooper, Geib, Rheingold & Mayer, 1986). More recently, Cotton & Llusar (1988) reported a structural study of [WOCI(Me2PCH2CH2PMe2)2]CIO4, (3) and [WOC1{Me2PCH2P(S)Me2}2]PF 6, (4). The compound we report here is closely related to (3) and shares several key characteristics with (2). The W=O bond lengths are the same to within +3a, viz W=O 1.736 (9), 1.714 (6), 1.68(1) and 1 .711(5)A for (1), (2), (3) and (4), respectively. The W = O unit appears to demand a large solid angle in the coordination sphere as all O W P angles are greater than 90 °. We also note that (1) crystallizes with five interstitial water molecules which results in a layered structure with extensive hydrogen bonding (see Fig. 2).