On the Reactions of Bisdiolatotungsten(VI) Phenoxides. Syntheses, Characterizations, and Molecular Structures of trans-[WCl 2 (Diol)(OAr) 2 ] Ari Lehtonen* and Reijo Sillanpa1 a1 Department of Chemistry, University of Turku, FIN-20014, Turku, Finland ReceiVed June 4, 2001 Coordinated phenoxide groups in [W(eg) 2 (mephe) 2 ](2a) and [W(eg) 2 (prphe) 2 ](2c) (eg ) ethanediolate dianion; mephe ) OC 6 H 3 Me 2 -2,6; prphe ) OC 6 H 3 i Pr 2 -2,6) undergo reaction with Br 2 , leading to substitution at the para position of the phenyl rings and formation of the complexes [W(eg) 2 (OC 6 H 2 R 2 -2,6-Br-4) 2 ](2b,R ) Me; 2d,R ) i Pr). The reaction of complexes 2a-2d and [W(eg) 2 (buphe) 2 ](2e) (buphe ) OC 6 H 3 tBu 2 -2,4) with HCl leads to the displacement of one bidentate diolato ligand from the complex unit and formation of the corresponding trans dichloro diolato bis(phenoxide) tungsten(VI) complex [WCl 2 (eg)(OAr) 2 ](3). The X-ray crystal structure determinations of these compounds confirmed that all complexes 3 have a similar gross structure in which the chloro ligands are arranged at trans positions. Introduction Early transition metal alkoxides have been widely studied due to their applications in organometallic and catalytic chemistry, and a number of these studies have been stimulated by the demonstrated ability of various tungsten compounds containing alkoxide and aryloxide ligands to catalyze metathesis reactions of cyclic and acyclic alkenes. 1-5 For example, tungsten phenoxides of the type [WCl 6-x (OAr) x ] and [WOCl 4-y (OAr) y ] are used as precursors for two-component catalyst systems, typically in the presence of an organometallic activator. 2 A standard procedure for the preparation of these complexes is the reaction of WCl 6 or WOCl 4 with a phenolic compound, which often results in a mixture of species with varying numbers of phenoxide substituents, some of which may also carry positional isomers with respect to the tungsten center. 6,7 Previ- ously, we reacted [W(eg) 3 ](1) (eg ) 1,2-ethanediolate dianion) with substituted phenyl acetates to prepare heteroleptic W(VI) phenoxides of the type [W(eg) 2 (OAr) 2 ](2) and have used these complexes as catalyst precursors in a two-component system for the ring opening metathesis polymerization of dicyclopen- tadiene and norbornene. 8,9 To attain a greater degree of un- derstanding of the chemistry of these complexes, we have now examined chloride-for-alkoxide substitution and prepared com- plexes of the type [WCl 2 (eg)(OAr) 2 ](3) by treating 2 with HCl. Complexes 3 are the first examples of tungsten(VI) alkoxide phenoxides which carry a trans-dichloro moiety. Furthermore, bromination of the coordinated phenoxide group in the com- plexes 2 was also studied as an example of aromatic substitution in a ligand. Our long-term goal is to employ these functionalities in the preparation of polymer- or silica-supported tungsten catalysts. Experimental Section General Information. Solvents were dried over CaH2 and distilled prior to use. Other chemicals were of reagent grade and used as purchased. Complexes 1, 2a, 2c, and 2e were prepared according to the literature procedures. 8,9 1 H NMR spectra were recorded using a Bruker AM 200 spectrometer in CDCl3 solutions and were referenced internally to SiMe4. IR spectra were recorded as KBr disks, using a Mattson Galaxy FTIR spectrometer. Elemental analyses were obtained using a Perkin-Elmer CHNS-Analyzer 2400. Analytical samples were dried in vacuo at 40 °C for 2 h prior to elemental and spectral analyses. Bromination of 2a and 2c. To a solution of 2a or 2c (0.20 mmol, 110 mg or 130 mg, respectively) in CCl4 (10 mL) was added Et3N (1.0 mmol, 0.14 mL) and Br2 (0.50 mmol, 25 μl) at room temperature. The reaction mixture was stirred for 2 h, filtered, and dried under reduced pressure. The yellow, solid crude product was purified by column chromatography using CH2Cl2 as eluent. 2b and 2d were also prepared from 1 and the appropriate phenyl acetates using literature methods. 9 [W(eg)2(OC6H2Me2-2,6-Br-4)2] (2b). Yield, 120 mg (85%). 1 H NMR (CDCl3): δ 7.15 (4H, s, aromatics), 5.50 (2H, m, CH2), 5.30 (6H, m, CH2), 2.45 (12H, s, CH3). IR (KBr): 1469 vs, 1380 vs, 1360 w, 1320 w, 1269 s, 1200 vs (br), 1070 vs (br), 1005 w, 930 s, 905 s, 900 s, 860 s, 850 m, 794 vs, 725 m, 652 s, 625 vs, 580 m, 568 s, 560 m, 525 s, 444 m, 415 w cm -1 . Anal. Calcd for C20H24Br2O6W: C, 34.1; H, 3.4. Found: C, 34.3; H, 3.4. [W(eg)2(OC6H2 i Pr2-2,6-Br-4)2] (2d). Yield, 145 mg (89%). 1 H NMR (CDCl3): δ: 7.16 (4H, s, aromatics), 5.55 (2H, m, CH2), 5.30 (6H, m, CH2), 3.60 (4H, m, CHMe2), 1.18 (24H, s, CH3). IR (KBr): 1470 vs, 1385 vs, 1360 w, 1340 w, 1320 w, 1270 w, 1200 vs (br), 1070 vs (br), 1005 w, 990 w, 930 s, 905 s, 900 s, 860 s, 850 m, 795 vs, 725 m, 650 s, 625 vs, 580 m, 568 s, 560 m, 525 s, 442 m, 415 w cm -1 . Anal. Calcd for C28H40Br2O6W: C, 41.2; H, 4.9. Found: C, 41.0; H, 4.8. General Procedure for the Syntheses of 3a-3e. To a solution of 2 (0.250 mmol) in CH2Cl2 (20 mL) was introduced a slow stream of * To whom correspondence should be addressed. Telefax:+358-2- 3336700. E-mail: ari.lehtonen@utu.fi. (1) Mayer, J. M. Polyhedron 1995, 14, 3273-3292. (2) Ivin, K. J.; Mol, J. C. Olefin Metathesis and Metathesis Polymerization; Academic Press: London, 1997. (3) Lefebvre, F.; Leconte, M.; Pagano, S.; Mutch, A.; Basset, J.-M. Polyhedron 1995, 14, 3209-3226. (4) Go´ mez, F. J.; Abboud, K. A.; Wagener, K. B. J. Mol. Catal. A: Chem. 1998, 133, 159-166. (b) Go´mez, F. J.; Manak, M. S.; Abboud, K. A.; Wagener, K. B. J. Mol. Catal. A: Chem. 2000, 160, 145-156. (5) Kelsey, D. R.; Handlin, D. L.; Narayana, M.; Scardino, B. M. J. Polym. Sci. A: Polym. Chem. 1997, 35, 3027-3047. (6) Quignard, F.; Leconte, M.; Basset, J.-M.; Hsu, L.-Y.; Alexander, J. J.; Shore, S. G. Inorg. Chem. 1987, 26, 4272-4277. (7) Nugent, W. A.; Feldman, J.; Calabrese, J. C. J. Am. Chem. Soc. 1995, 117, 8992-8998. (8) Lehtonen, A.; Sillanpa¨a¨, R. Polyhedron 1999, 18, 175-179. (9) Lehtonen, A.; Sillanpa¨a¨, R. Inorg. Chem. Commun. 2001, 4, 108- 110. 6047 Inorg. Chem. 2001, 40, 6047-6051 10.1021/ic010583t CCC: $20.00 © 2001 American Chemical Society Published on Web 10/03/2001