(~s-Cyclopentadienyl)hydridozirconiwn Complexes 257

21. R. E. Rieke and S. E. Bales, J . Am. Chem. Soc.. %, 1775 (1974). 22. D. F. Shriver, The Manipulation of Air-Sensitiw Compounds, McGraw-Hill, New York, 1978. 23. J. M. Manriquez, D. R. McAlister, E. Rosenberg, A. M. Shiller, K. L. Williamson, S. I. Chan,

24. .L. F. Fieser and M. Fieser, Reagentsfor Organic Synthesis, Wiley, New York, 1967, p. 950. and J. E. Bercaw. J . Am. Chem. Sw., 100,3078 (1978).

65. ( ~s-CYCLOPENTADIENYL)HYDRIDOZIRCONIUM COMPLEXES

Submitted by P. C. WAILES* and H. WIGOLD* Checked by JEFFREY SCHWARTZt and CHU JUNGt

The dihydridozirconium complex, ZrH,(qS-C,Hs),, was prepared origin- ally’ by the action of trialkylamines on the bis(tetrahydroborate), Zr(BH4),(qS-CsH,),. Below are described more convenient methods for the preparation of the dihydride and of the chlorohydrido derivative, ZrHCl(q’- C,H,),, from readily available starting materials. These compounds are useful intermediates in the preparation of alkyl- and alkenylzirconium com- pound~,”~ and under hydrogen pressure they are active catalysts for hydro- genation of olefins and acetylenes.2 The “hydrozirconation” reactions require ZrHCl(qs-CsHs)2 as starting material.4

A. BIs($-CYCL0PENTADINYL)DIHYDRIDOZIRCONIUM

2ZrCl2(q5-CSHs), + H,O -, [ZrCl(q5-CsHs),],0 + 2HC1

[ZrCl(qs-CsHs),],O + Li[AlH4] + 2ZrH2(q5-CSHS), + LiCl

+ -IC~OClI,

1. p-Oxo-bis~chlorobis(bcyclope~~tadienyl)zirco~um]

The method of preparation described here is an adaption of the original,s.6 which gives consistently high yields.

Procedure

To a solution of ZrCl~(qs-CsHs)2 (29 g, 0.1 mol) in dichloromethane (250 mL) in a conical flask is added aniline (10 mL) and water (1.3 mL) with

*Division of Chemicals and Polymers CSIRO, Private Bag 10, Clayton, Victoria, Australia

tDepartment of Chemistry, Princeton University, Princeton, NJ, 08540. 3168.

Inorganic Syntheses, Volume 28 Edited by Robert J. Angelici

Copyright © 1990 by Inorganic Syntheses, Inc.

258 Cyclopentadienyl Complexes

shaking. A white precipitate of aniline hydrochloride forms immediately. After it is chilled for several hours in a refrigerator, the suspension is filtered. Occasionally large crystals of the product are present at this stage and these are dissolved by addition of more CH,C12. The filtrate is evaporated to a small volume, and light petroleum ether (100 mL, bp 30-40") is added to precipitate the product. After filtration and washing with petroleum ether, white crystals of the oxo-bridged compound are obtained (25.5 g, 97% yield); these slowly turn pink on storage. The melting point varies with the rate of heating, but if the sample in an evacuated capillary is placed in a melting point apparatus preheated to 2W, a melting point around 305" should be obtained.

2. Bis(q5eyclopentadienyl)diiydridozirconium

In this reaction purified tetrahydrofuran (THF) is required, as well as a standardized solution of LiCAlH,] in tetrahydrofuran. The THF from freshly opened bottles is distilled from LiCAlH,].

(m Caution. LiCAlH,] is a hazardous material and must be handled in dry conditions and in small quantities. Serious explosions can occur when impure THF is purijied if it contains peroxides (see Ref: 7).

Standardized solutions of LiCAlH,] are prepared by stirring LiCAlH,] in purified THF for several hours under nitrogen or argon and filtering through Celite (previously baked out at 140" and degassed under vacuum) using the apparatus shown in Fig. 1, followed by hydrolysis of an aliquot of this solution with dilute acid and accurate measurement of the hydrogen evolved. This is best done on a vacuum line using a Topler pump, but simpler methods should also suffice.

Ni troqcn or

Argon -.I ,in

Hypodermic needle -

I /

I

I * Fri t React ion flask

Fig. 1. Simple apparatus for filtering under inert atmosphere. The flow of N, or Ar is controlled by a finger over the base of the needle.

(t~~-CyclopentadienyI)hydridozirconim Complexes 259

Procedure

To a solution of [ZrCl(qS-CsHs),],O (17.7 g, 33.4 mmol) in purified THF (200 mL) in a 500-mL flask of the type shown in Fig. 1, a clear solution of LiIAlH,] in THF (20 mL of 1.7 M, 34 mmol) is added dropwise from a hypodermic syringe with stirring. An atmosphere of nitrogen or argon is maintained at all times. A white precipitate slowly appears, but precipitation is not complete for several hours. The mixture is set aside overnight and then filtered anaerobically as in Fig. 1, giving the dihydrido complex as an almost colorless microcrystalline solid (yield 10.1 g, 66%).

Anal. Calcd. for C,,H,,Zr: ash (ZrO,), 55.14%; hydrolyzable H, 2.00 g- atoms mol-'. Found: ash, 55.5%; hydrolyzable H, 1.89 g-atom mol-'. The yield of dihydride never exceeds 66%; the remainder of the zirconium is believed to be a complex with an aluminum compound (see Properties section).

B. CHLOROBIS($-CYCLOPENTADIENYL)HYDRIDOZIRCONIUM

ZrCl,(q5-CsHs)z + Li[AlH(t-BuO),] + ZrHCl(qS-C,H,), + LiCl

+ Al(t-BuO),

Procedure*

The apparatus and procedures are similar to those in the preparation above, and a I-L flask is used. A solution of lithium tri-tert-butoxyhydridoalu- minatetg (28.6 g, 113 mmol) in purified THF (100 mL) is added slowly to a solution of ZrC12(~s-CsHs)2 (32.9 g, 113 mmol) in THF (500 mL) with stirring. After complete addition, stirring is continued for 1 h, after which the mono-hydrido complex is collected- by anaerobic filtration (Fig. 1) and washed with THF (yield 26.3 g, 90%).

Anal. Calcd. for C,,H,,ClZr: ash (ZrO,), 47.77%; hydrolyzable H, 1.00 g-atom mol-'; C1, 13.75. Found ash, 47.0%; hydrolyzable H, 1.02 g- atoms mol-'; C1,13.4.0ne-quarter mol of LiCAlH,] may be used instead of the tri-tert-butoxy hydrido complex, but the essential control of stoichiome- try is more difficult (see Properties section).

*An interesting alternative procedure is to stir ZrCI2(q5-C,H,), in tetrahydrofuran with 0.5 g- atom of magnesium turnings. A red color develops and after 3-5 days a 30% yield of ZrHCl($-C,H,), can be recovered by filtration.

?Available from Aldrich Chemical Co.

260 Cydopentadienyl Complexes

Other hydridozirconium derivatives that have been prepared from aluminum hydrides are ZTH(CH~)(~~-C,H,)~, ZrH(AIH,)(qs-C,H,),, the complex ZrH,(q5-C,H,)2-[ZrH(q-CSH,),],0, and deuterido derivatives corresponding to all of these hydrido complexes.'

Properties

The bis(~s-cyclopentadienyl)zirconium hydrides are colorless solids that hydrolyze in water. Accurate measurement of the hydrogen thus evolved is a sensitive method of analysis. Alternatively, reaction with CH,Cl, in a stoppered NMR tube and quantitative estimation of the CH3CI so formed can be used. The compounds are associated through bridging hydrido ligands, which explains their insolubility and the low infrared frequencies of the metal-hydrogen bands [1520 and 1300 cm-' for ZrH,(qS-C,H,), and 1390 cm-' for ZrHCl(qs-C,H,),]. All dissolve readily in excess Li[AlH4] solution, probably forming zirconium-aluminum complexes with bridging hydrido ligands. All but the dihydrido complex slowly develop a pink color when exposed to light and therefore appear to be photosensitive.

References

1. R. K. Nanda and M. G. H. Wallbridge, Inorg. Chem., 3, 1798 (1964). 2. P. C. Wailes, H. Weigold, and A. P. Bell, J . Orgonomet. Chem., 43, C32 (1972). 3. P. C. Wailes, H. Weigold, and A. P. Bell, J . Orgonomet. Chem., 27, 373 (1971). 4. J. Schwartz and J. A. Labinger, Angew. Chem. Int. Ed. Engl., 15, 333 (1976). 5. E. Samuel and R. Setton, C. R., 256,443 (1963). 6. A. F. Reid, J. S. Shannon, J. M. Swan, and P. C. Wailes, Aust. J . Chem., 18, 173 (1965). 7. Inorg. Synth., 12, 317 (1970). 8. P. C. Wailes and H. Weigold, J . Organomet. Chem., 24,405 (1970). 9. H. C. Brown and R. F. McFarlin, J . Am. Chem. Soc., SO, 5372 (1958).

66. CYCLOPENTADIENYL COMPLEXES OF TITANIUM(I1I) AND VANADIUM(I1I)

Submitted by L E. MANZER* Cbecked by E. A. MINTZt aod T. J. MARKST

The chlorodicyclopentadienyl complexes of Ti(II1) and V(II1) are useful synthetic reagents for the synthesis of a variety of paramagnetic organo-

*Central Research and Development Dept., E. I. du Pont de Nemours & Co., Experimental Station, Wilmington, DE 19898. Dept. of Chemistry, Northwestern University, Evanston, IL 60201.