28
mass spectrum appeared the peaks of [CpGd(C5H4C4H9)2]+, [Cp2Gd(C5 H 4C4 H 9)] +
and [CP3Gd] ÷ (MS data are listed in Experimental section). This indicates that the
G d - C p bond of Cp3Gd is not cleaved. It has also been shown that the neutral
hydride [Cp2YH(THF)]2 is less powerful than the corresponding system, CP3Y/NaH
(see Entry 4 in Table 1 and last paragraph of Experimental section). Therefore, the
reaction mechanism depicted in Scheme 2 is more reasonable.
Experimental
All operations were performed in an atmosphere of prepurified argon using
Schlenk techniques. Tetrahydrofuran was refluxed and distilled over either finely
divided LiAIH4 or blue sodium benzophenone under argon immediately prior to
use. The Cp3Ln complexes were prepared by the literature method [13]. Sodium
hydride (E. Merck, with 20% paraffin oil) was washed by THF or pentane and dried
in vacuum. Organic halides were dried by Call 2 and then distilled under argon.
Gas chromatography-mass spectra were determined on a Finnigan 4021 GC-MS.
Gas chromatography-lR spectra were determined on the Digilab FTS-20E capillary
GC-FTIR. Gas chromatographic analysis was carried out on a 103 gas chromato-
graphic instrument utilizing 4-m XE-60 or 2-m OV-1 column to determine the yields
of products.
Reduction of aryl and vinyl halides with Cp3Ln / NaH
The typical procedure was as follows: A 3 ml Schlenk tube equipped with a
Teflon stopcock was charged with 33.4 mg (0.0999 mmol) of Cp3La and 9.6 mg
(0.400 mmol) of N a i l , then 17.1 mg (0.0999 mmol) of p-bromotoluene was added
and 1 ml of THF was introduced by a syringe. Then the stopcock was closed and
the reaction was carried out at 65°C with stirring. The toluene generated was
verified by GC-IR and GC-MS. The amount of toluene was determined by GC after
4 and 8 h.
Reaction of alkyl halides with Cp3La / NaH
The typical procedure was as follows: A 3 ml Schlenk tube was charged with 28.6
mg (0.0856 mmol) of Cp3La, 8.3 mg (0.346 mmol) of Nail under argon, then 14.1
mg (0.0856 mmol) of 1-bromohexane and 1 ml of THF were added into the tube,
the stopcock was closed. The reaction mixture was stirred for 1 h at 65 °C and then
hydrolyzed under cooling. The product was verified by GC-MS and GC-IR. The
yield of product was determined by GC.
Reaction of Cp~Gd with n-bromobutane and Nail
439.8 mg (1.25mmol) of CP3Gd, 123.2 mg (5.13mmol) of N a i l , 171.1 mg
(1.25mmol) of n-bromobutane and 12 ml of THF were added into a Schlenk tube.
The mixture was stirred for 4 h at 50-60 ° C and the precipitate was separated. Then
THF was removed and the residue was washed with a little hexane, affording a light
yellow solid. Its mass spectrum was as follows: m/e (relative intensity and assign-
ment) 465 (0.4, [CpGd(CsH4Bu-n)2]+), 409 (0.4, [Cp2Gd(CsH4Bu-n)]+), 400 (1.2,
[Gd(CsH4Bu-n)2]+), 353 (0.4, [Cp3Gd]+), 344 (1.7, [CpGd(CsH4Bu-n)]+), 288 (1.1,
[CpEGd]+), 281 (0.4, [Gd(CsH4Bu-n)]++ 1), 223 (0.5, [CpGd]+), 122 (28.0, [n-
BuCsH4]+), 79 (100.0, [CsH4CH2]+), 66 (54.0, [C5H6]+), 65 (31.0, [C5H5]+).