Reactivity of lanthanide and yttrium hydrides and hydrocarbyls toward organosilicon hydrides and related compounds

Organometallics 1997, 16, 4041-4055

4041

Rea ctivity of La n th a n id e a n d Yttr iu m Hyd r id es a n d

Hyd r oca r byls tow a r d Or ga n osilicon Hyd r id es a n d

Rela ted Com p ou n d s

Alexander Z. Voskoboynikov,*^,1aInna N. Parshina,^1aAlla K. Shestakova,^1a

Kim P. Butin,^1bIrina P. Beletskaya,^1bLyudmila G. Kuz’mina,^1cand

J udith A. K. Howard^1d

State Research Institute of Chemistry and Technology of Organoelement Compounds, sh.

Entuziastov 38, Moscow 111123, Russia, Department of Chemistry, Moscow State University,

V-234, Moscow, GSP 119899, Russia, N. S. Kurnakov Institute of General and Inorganic

Chemistry of Russian Academy of Sciences, 31 Leninsky ave., Moscow 117907, Russia, and

Department of Chemistry, Durham University, South Road, Durham DH1 3LE, U.K.

Received April 29, 1997^X

t

The reaction of lanthanide and yttrium hydrocarbyls {Cp*₂Ln(µ-Me)}₂(Cp* ) BuC₅H₄

(Cp′), Ln ) Y (1), Tb (2), Yb (3), Lu (4); Cp* ) Me₃SiC₅H₄(Cp′′), Ln ) Lu (5)), one of which,

2, has been characterized by X-ray crystal analysis, with various organosilicon, -germanium,

and -tin hydrides (as well as some organoaluminum and -gallium hydrides) in hydrocarbon

solution was found to yield the corresponding unsolvated dimeric lanthanide and yttrium

hydrides {Cp*₂Ln(µ-H)}₂rather than compounds with lanthanide-element (Si, Ge, Sn)

bonding. Thus, the reaction involves hydride transfer to Ln rather than the silyl transfer

studied earlier for pentamethylcyclopentadienyllanthanide hydrocarbyls. Dimeric compounds

Cp*₂Ln(µ-H)(µ-Me)LnCp*₂with different bridging ligands were isolated; they are intermedi-

ates in this reaction. Dimeric lanthanide and yttrium hydrides catalyze the H/D exchange

in silanes. This catalytic reaction is most correctly described by a mechanism involving

nucleophilic substitution at the silicon atom. Yttrium and lutetium hydrocarbyls 1 and 4

react with various alkoxysilanes to produce the dimeric alkoxides {Cp′₂Ln(µ-OR)}₂or the

hydrocarbyl alkoxides Cp′₂Ln(µ-Me)(µ-OR)LnCp′₂(R ) Me, Et), depending on the reaction

conditions. The reaction of 4 with (MeO)₄Si provided Cp′₂Lu(µ-Me)(µ-OMe)LuCp′₂, which

has been characterized by X-ray crystal analysis. This compound contains one methyl bridge

(Lu-C 2.57(2) and 2.58(2) Å) and nonsymmetrically bonded µ-OMe ligand (Lu-O 2.20(2)

and 2.12(2) Å). The reaction of 1 and 4 with Me₃SiCl leads to the corresponding dimeric

chlorides {Cp′₂Ln(µ-Cl)}₂only. Thus, the reaction of lanthanide and yttrium hydrocarbyls

with various heterosubstituted organosilanes R₃SiX, where X ) H, OR, or Cl, is a selective

and convenient synthetic method in the chemistry of the group 3 elements. Complexes with

Ln(µ-H)(µ-Me)Ln and Ln(µ-H)(µ-Cl)Ln bridging were prepared in high yield by the exchange

reactions between the corresponding dimeric compounds {Cp*₂Ln(µ-X)}₂(X ) H, Me, Cl) in

a hydrocarbon solution. The capacities of various bridging fragments to undergo reversible

cleavage (dissociation) in the hydrocarbon solution increase in the sequence Ln-O(Me)-Ln

, Ln-Cl-Ln < Ln-H-Ln < Ln-Me-Ln.

In tr od u ction

further studies can bring about the development of both

new synthetic methods and novel reactivity of the

compounds. In this work, we found a convenient and

effective method for the synthesis of bis(cyclopentadi-

enyl)lanthanide hydrides. This method involves reac-

tion of the corresponding lanthanide hydrocarbyls with

silanes (eq 1, Cp ) C₅H₅, Cp′, Cp′′) or with organohy-

drides of some nontransition metals. This reaction was

Bis(cyclopentadienyl)lanthanide hydrides and hydro-

carbyls, Cp₂LnH and Cp₂LnR, play a significant role in

the chemistry of organolanthanides,²particularly due

to their peculiar catalytic properties.³Therefore, these

complexes were investigated in detail. Nevertheless,

^XAbstract published in Advance ACS Abstracts, August 1, 1997.

(1) (a) State Research Institute of Chemistry and Technology of

Organoelement Compounds. (b) Moscow State University. (c) N. S.

Kurnakov Institute of General and Inorganic Chemistry of Russian

Academy of Sciences. (d) Durham University.

Cp₂Ln-R + R′₃SiH f Cp₂Ln-H + 2R′₃SiR (1)

(2) To simplify the discussion the term lanthanide means both

lanthanides and yttrium because of similar properties of their com-

pounds.³

suggested by this group^4,5and Marks⁶to be a key stage

(3) (a) Marks, T. D.; Ernst, R. D. In Comprehensive Organometallic

Chemistry; Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon

Press: Oxford, 1982; Vol. 3, p 173. Edelmann, F. T. In Comprehensive

Organometallic Chemistry II: A review of the literature 1982-1994;

Abel, E. W., Stone, F. G. A., Wilkinson, G., Eds.; Pergamon Press:

Exeter, 1995; Vol. 4, p 11. (b) Bochkarev, M. E.; Zacharov, L. N.;

Kalinina, G. S. Organoderivatives of Rare Earth Elements; Kluwer

Academic Publishers: Dordrecht, The Netherlands, 1995.

(4) Beletskaya, I. P.; Voskoboynikov, A. Z.; Parshina, I. N.; Mago-

medov, G. K.-I. Bull. Acad. Sci. USSR, Div. Chem. Sci. 1990, 39, 613-

614.

(5) Beletskaya, I. P.; Magomedov, G. K.-I.; Voskoboynikov, A. Z.;

Parshina, I. N. Abstracts of Posters; XXVIII International Conference

on Coordination Chemistry, Gera, GDR, August 13-18, 1990, Vol. 2,

pp 3-67.

4042 Organometallics, Vol. 16, No. 19, 1997

Voskoboynikov et al.

of the catalytic cycle of olefin hydrosilylation catalyzed

by organolanthanides.

The interaction between molecules of alkyl (aryl)

lanthanide complexes with silane can be described as

proceeding via either a four-centered transition state

A or the alternative B state. Transition state A implies

formation of methane and the corresponding compound

with Ln-Si bonding, is preferred over the hydride

transfer (like eq 1) found in the reaction of (C₅H₅)₂YMe

with SiH₄in the gas phase.

On the other hand, the reaction of silanes with less

sterically hindered lanthanide hydrides Cp₂LnH was

recently shown by Marks^15band Tilly⁸for complexes

containing C₅Me₅ligands to proceed via a four-centered

transition state B′ and form H₂and compounds with

Ln-Si bonding. This fact correlates well with our

hydride transfer to the lanthanide atom and alkylation

of the silane. On the contrary, structure B corresponds

to the transfer of the silyl group to the metal atom,

leading to the formation of a compound with Ln-Si

bonding⁷and the corresponding hydrocarbon (pathway

b). This structure corresponds to the transition state

of σ-bond metathesis, which was studied earlier for early

transition metal complexes and silanes (as well as H₂

or hydrocarbons).^10-13As this duality evoked some

discussion,^4-6,8we have performed MO calculations for

the alternative reaction pathways involving transforma-

tions of several simple molecules. The calculations

indicate a silyl group transfer to the metal atom, i.e.,

calculation results (see below). Apparently, the dehy-

drogenative coupling of silanes catalyzed by organolan-

thanides,¹⁵a mechanism studied by Marks^15b(see also

the results of Ziegler’s MO calculation¹⁴), includes a

similar Ln-Si bond formation stage. In this paper, we

have shown that the reaction of lanthanide hydrides

with silanes can proceed in a different manner. This

reaction between R′₃SiD and lanthanide hydrides that

involves monosubstituted cyclopentadienyl ligands can

be used for the preparation of the corresponding lan-

thanide deuterides. In a catalytic manner, this reaction

causes an isotope exchange between various silanes (R′₃-

SiH and R′′₃SiD) (see below). Certainly, this isotope

exchange could include the stage of silane metalation.

However, we obtained some data which favors a direct

participation of the lanthanide hydride intermediates

in the degenerative exchange between Cp₂LnH and R′₃-

SiH(D) proceeding via a four-centered transition state

type A′.

In the absence of suitable salts (e.g., LiCl) or donating

molecules (e.g., THF, Et₂O), organolanthanides are

known to form stable associated complexes, particularly

dimers that contain various bridging ligands.³We

found that various dimeric complexes can take part in

exchange reactions to form new dimers either with

different bridging ligands (eq 2) or with different metals

(eq 3). These stable dimers could be good models for

(6) Fu, P.-F.; Brard, L.; Li, Y.; Marks, T. J . J . Am. Chem. Soc. 1995,

117, 7157-7168.

(7) A number of compounds both with lanthanide-silicon^8,9a,band

with lanthanide-germanium, lanthanide-tin bonding^9b-ehave been

synthesized and characterized.

(8) (a) Radu, N. S.; Tilley, T. D.; Rheingold, A. L. J . Am. Chem. Soc.

1992, 114, 8293-8295. (b) Radu, N. S.; Tilley, T. D. J . Am. Chem. Soc.

1995, 117, 5863-5864.

(9) (a) Schumann, H.; Nickel, S.; Hahn, E. Organometallics 1985,

4, 800-801. Schumann, H.; Nickei, S.; Loebel, J .; Pickardt, J . Orga-

nometallics 1988, 7, 2004-2009. Schumann, H.; Meese-Marktscheffel,

J . A.; Hahn, E. J . Organomet. Chem. 1990, 390, 301-308. Campion,

B. K.; Heyn, R. H.; Tilley, T. D. Organometallics 1993, 12, 2584-2590.

(b) Bochkarev, L. N.; Makarov, V. N.; Hrzhanovskaya, Y. N.; Zakharov,

L. N.; Fukin, G. K.; Yanovsky, A. I.; Struchkov, Y.-T. J . Organomet.

Chem. 1994, 467, C3-C5. (c) Schumann, H.; Cygon, M. J . Organomet.

Chem. 1978, 144, C43-C45. (d) Razuvaev, G. A.; Kalinina, G. S.;

Fedorova, E. A. J . Organomet. Chem. 1980, 190, 157-165. Fedorova,

E. A.; Kalinina, G. S.; Bochkarev, M. N.; Razuvaev, G. A. Zh. Obshch.

Khim. (USSR) 1982, 52, 1187-1190. (e) Bochkarev, L. N.; Cholodilova,

M. N.; Zhil’tsov, S. F.; Guseva, T. V.; Bochkarev, M. N.; Razuvaev, G.

A. Zh. Obshch. Khim. (USSR) 1986, 56, 723-724. Bochkarev, L. N.;

Fedyushkin, I. L.; Cholodilova, M. N.; Zhil’tsov, S. F.; Bochkarev, M.

N.; Razuvaev, G. A. Izv. Akad. Nauk SSSR, Ser. Khim. 1987, 658-

659. Bochkarev, M. N.; Khramenkov, V. V.; Rad’kov, Y.-F.; Zakharov,

L. N.; Struchkov, Y.-T. J . Organomet. Chem. 1991, 408, 329-334.

Bochkarev, M. N.; Khramenkov, V. V.; Rad’kov, Y.-F.; Zakharov, L.

N.; Struchkov, Y.-T. J . Organomet. Chem. 1991, 421, 29-38. Cloke,

F. G. N.; Dalby, C. I.; Hitchcock, P. B.; Karamallakis, H.; Lawless, G.

A. J . Chem. Soc., Chem. Commun. 1991, 779-781. Bochkarev, L. N.;

Grachev, O. V.; Molosnova, N. E.; Zhiltsov, S. F.; Zakharov, L. N.;

Fukin, G. K.; Yanovsky, A. I.; Struchkov, Y.-T. J . Organomet. Chem.

1993, 443, C26-C28. Bochkarev, L. N.; Makarov, V. M.; Zakharov, L.

N.; Fukin, G. K.; Yanovsky, A. I.; Struchkov, Y.-T. J . Organomet. Chem.

1995, 490, C29-C31.

C₆H₆

{Cp₂Ln(µ-L)}₂+ {Cp₂Ln(µ-L′)}₂

8

Cp₂Ln(µ-L)(µ-L′)LnCp₂(2)

C₆H₆

{Cp₂Lu(µ-L)}₂+ {Cp₂Y(µ-L)}₂

8

Cp₂Lu(µ-L)₂YCp₂(3)

the transition state of type A or A′. Reaction 2 was

found to proceed readily for those compounds that

include alkyl, hydride, and chloride bridging ligands.

However, this reaction does not take place for alkoxy

derivatives of lanthanides. Dimeric complexes with Ln-

(µ-Me)(µ-OR)Ln bridging can be synthesized by an

alternative reaction between the corresponding alkox-

ysilanes and complexes with Ln(µ-Me)₂Ln bridging (a

reaction like eq 1). The study of various equilibrium

processes makes it possible to obtain the relative

(10) (a) Woo, H. G.; Tilley, T. D. J . Am. Chem. Soc. 1989, 111, 3757-

3758 and references therein. (b) Woo, H. G.; Tilley, T. D. J . Am. Chem.

Soc. 1989, 111, 8043-8044. (c) Tilley, T. D.; Woo, H. G. Polym. Prepr.

1990, 31, 228-229. (d) Tilley, T. D. Comm. Inorg. Chem. 1990, 10,

37-51. (e) Woo, H. G.; Tilley, T. D. in Inorganic and Organometallic

Oligomers and Polymers; Laine, R. M., Harrod, J . F., Eds.; Kluwer

Publishers: Amsterdam, 1991; p 3. Tilley, T. D.; Radu, N. S.; Walzer,

J . F.; Woo, H.-G. Polym. Prepr. 1992, 33, 1237. (f) Woo, H. G.; Waltzer,

J . F.; Tilley, T. D. J . Am. Chem. Soc. 1992, 114, 7047-7055. (g) Tilley,

T. D. Acc. Chem. Res. 1993, 26, 22-29.

(11) Woo, H. G.; Heyn, R. H.; Tilley, T. D. J . Am. Chem. Soc. 1992,

114, 5698-5707.

(12) (a) Walzer, J . F.; Woo, H. G.; Tilley, T. D. Polym. Prepr. 1991,

32, 441-442. Ziegler, T.; Folga, E.; Berces, A. J . Am. Chem. Soc. 1993,

115, 636-646 and references therein. (b) Nolan, S. P.; Porchia, M.;

Marks, T. J . Organometallics 1991, 10, 1450-1457.

(15) (a) Watson, P. L.; Tebbe, F. N. U.S. Patent 4,965,386, Oct. 23,

1990 (March 26, 1990). (b) Forsyth, C. M.; Nolan, S. P.; Marks, T. J .

Organometallics 1991, 10, 2543-2545. (c) Sakakura, T.; Lauten-

schlager, H. J .; Nakajima, M.; Tanaka, M. Chem. Lett. 1991, 913-

916.

(13) Crabtree, R. H. Angew. Chem., Int. Ed. Engl. 1993, 32, 789-

805.

(14) Ziegler, T.; Folga, E. J . Organomet. Chem. 1994, 478, 57-65.

Lanthanide and Yttrium Hydrides and Hydrocarbyls

Organometallics, Vol. 16, No. 19, 1997 4043

Ta ble 1. Selected Bon d Dista n ces (Å) a n d An gles

(d eg) for {(^tBu C₅H₄)₂Tb(µ-Me)}₂(2)

Bond Distances

Tb‚‚‚Tb′

3.629(3)

2.573(6)

2.771(9)

2.63(1)

0.570(8)

1.42(2)

1.41(1)

1.42(2)

Tb-C(2)

2.716(7)

2.678(7)

2.654(8)

1.068(5)

1.40(2)

Tb-C(1)

Tb-C(3)

Tb-C(5)

C(1)-H(1)

C(2)-C(3)

C(3)-C(4)

C(4)-C(5)

Tb-C(4)

Tb-C(6)

C(1)-H(2)

C(2)-C(6)

C(3)-C(7)

C(5)-C(6)

1.53(1)

1.38(2)

Angles

C(1)-Tb-C(1′)

H(1)-C(1)-H(2)

C(3)-C(2)-C(6)

C(2)-C(3)-C(7)

C(3)-C(4)-C(5)

C(2)-C(6)-C(5)

90.3(2)

71.1

Tb-C(1)-Tb′

89.7(2)

100.2

104.9(8)

125.1(8)

107.5(9)

H(2)-C(1)-H(2′)

C(2)-C(3)-C(4)

C(4)-C(3)-C(7)

C(4)-C(5)-C(6)

109.6(9)

129.3(8)

109.7(9)

108.2(9)

turned out to have a dimeric structure (C_2hsymmetry)

with two Me bridges. The terbium atoms symmetrically

coordinate both methyl bridges.¹⁸

Dimeric hydrocarbyls 1-5 completely dissociate into

monomeric solvates 6-10 in THF solution (eq 5) (see

also ref 20). The Y-Me resonance of 6 occurs at δ -0.99

F igu r e 1. ORTEP view of {(^tBuC₅H₄)₂Tb(µ-Me)}₂(2).

Me

THF, 20 °C

Cp*₂Ln

LnCp*₂

2Cp*₂LnMe(THF)

capacity of various bridgings Ln(µ-X)Ln, where X ) Me,

H, Cl, OMe, to cleave in hydrocarbon solution. Alter-

natively, this investigation brings about a development

of several convenient synthetic methods for none-

symmetrical dimeric lanthanide complexes.

Me

6–10

(5)

Cp* = Cp′; Ln = Y(6), Tb(7), Yb(8), Lu(9)

Cp* = Cp′′; Ln = Lu(10)

2

ppm, and the ⁸⁹Y-¹H coupling pattern (doublet, J _Y-H

) 2.1 Hz) is consistent with a monomeric structure.

Even under vacuum at ambient temperature solids

6-10 were found to lose coordinated THF to form the

corresponding dimeric hydrocarbyls.

Resu lts

Syn th esis a n d Str u ctu r a l Ch a r a cter iza tion of

Dim er ic (µ-Met h yl)b is(cyclop en t a d ien yl)la n t h a -

n id es. Dimeric methyl complexes of lanthanides 1-5

were prepared as shown in eq 4. The compounds were

Rea ctivity of La n th a n id e a n d Yttr iu m Hyd r o-

ca r byls tow a r d Or ga n osilicon a n d Or ga n oelem en t

Hyd r id es. Recently, we described the synthesis of

lutetium hydride {(C₅H₅)₂Lu(µ-H)(THF)}₂upon treat-

ment of (C₅H₅)₂LuC₆H₄Me-4(THF) with PhMeSiH₂in

benzene at ambient temperature.⁴Here, we have found

that a similar reaction readily proceeds with various

unsolvated dimeric hydrocarbyls 1-5. In an excess

amount of organosilicon hydride, compounds 1-5 form

the corresponding dimeric hydrides 11-15 in quantita-

tive yield (eq 6).²¹Deuterium-labeled yttrium hydride

1. 2Cp*Na, THF, 20 °C

2.MeLi, Et₂O, –78 °C

Me

3. toluene, 70–80 °C

0.5 Cp*₂Ln

LnCp*₂

LnCl₃

–2NaCl, LiCl

(4)

1–5

Cp* = Cp′; Ln = Y(1), Tb(2), Yb(3), Lu(Me) = CH(4);Me = CD₃(4-d)

Cp* = Cp′′; Ln = Lu(5)

isolated as extremely air- and moisture-sensitive solids

in high yield after decomposition of the intermediate ate

complexes Cp*₂Ln(µ-Cl)(µ-Me)M(THF)_n, where M ) Li

or Na, by treatment with hot toluene. Complexes 1-5

were characterized by standard analytical and spectro-

C₆H₆, 20 °C

{Cp*₂Ln(µ-Me)}₂+ 2PhMeSiH₂

1

scopic techniques (see Experimental Section). The H

{Cp*₂Ln(µ-H)}₂+ 2PhMe₂SiH

NMR spectra of 1, 4, and 5 in C₆D₆are consistent with

C_2vdimeric structures characterized by two Cp*-H

signals, the appropriate AA′BB′ patterns being ob-

served. The Ln-CH₃resonances occur at a relatively

high field (e.g., δ -0.47 ppm for 1, -0.01 ppm for 4),

which is typical for lanthanide hydrocarbyls.^16,17The

(6)

11–15

Cp* = Cp′; Ln = Y(11), Tb(12), Yb(13), Lu(14)

Cp* = Cp′′; Ln = Lu(15)

(18) A number of unsolvated dimeric (methyl)bis(cyclopentadienyl)-

lanthanides have been characterized by structural analysis. Some of

them, as well as 2, contain symmetrically coordinated methyl

fragments;^16,19a,bthe other compounds possess two nonequivalent

hydrocarbyl ligands.^19c,d

(19) (a) Evans, W. J .; Drummond, D. K.; Hanusa, T. P.; Doedens,

R. J . Organometallics 1987, 6, 2279-2285. (b) Stults, S. D.; Andersen,

R. A.; Zalkin, A. J . Organomet. Chem. 1993, 462, 175-182. (c) Watson,

P. L.; Parshall, G. W. Acc. Chem. Res. 1985, 18, 51-56. (d) Shen, Q.;

Cheng, Y.; Lin, Y. J . Organomet. Chem. 1991, 419, 293-298.

(20) Evans, W. J .; Dominguez, R.; Hanusa, T. P. Organometallics

1986, 5, 263-270.

⁸⁹Y-¹H coupling pattern in 1 (triplet, J _Y-H) 3.1 Hz)

2

is consistent with the symmetrical Y(µ-Me)₂Y bridging

(cf., {(C₅H₅)₂Y(µ-Me)}₂where J _Y-H) 3.6 Hz¹⁶).

2

t

The structure of the terbium complex 2 with the -

BuC₅H₄ligands was determined by X-ray diffraction

analysis (Figure 1). The bond lengths and selected bond

angles are given in Table 1. The compound under study

(16) Holton, J .; Lappert, M. F.; Ballard, D. G. H.; Rearce, R.; Atwood,

J . L.; Hunter, W. E. J . Chem. Soc., Dalton Trans. 1979, 54-61.

(17) Schumann, H.; Genthe, W.; Bruncks, N.; Pickardt, J . Organo-

metallics 1982, 1, 1194-1200.

(21) Lutetium hydrocarbyl {(C₅H₅)₂Lu(µ-Me)}₂also forms the cor-

responding hydride {(C₅H₅)₂Lu}₃(µ-H)₂(µ³-H) in quantitative yield

under treatment with PhMeSiH₂or PhSiH₃in benzene or toluene

solution.

4044 Organometallics, Vol. 16, No. 19, 1997

Voskoboynikov et al.

F igu r e 3. ¹H NMR spectrum of the reaction mixture of 1

and PhMeSiH₂in benzene-d₆at 20 °C: (a) 1.3 h; (b) 4.5 h;

(c) 13 h; (d) 120 h.

F igu r e 2. ¹H NMR spectrum of the reaction mixture of 4

and PhMeSiH₂in benzene-d₆at 20 °C: (a) 0.5 h; (b) 6 h;

(c) 21 h; (d) 48 h; (e) 2 weeks.

17 forms lutetium hydride 14 (eq 7). The formation of

fast

{Cp′₂Y(µ-D)}₂(11-d ) was prepared in quantitative yield

in a similar manner starting from 1 and PhMeSiD₂. The

¹H NMR spectra of the diamagnetic compounds 11, 11-

d , 14, and 15 are consistent with C_2vdimeric structures,

characterized by two Cp*-H resonances (AA′BB′). The

Ln-H resonances occur at a relatively low field (e.g., δ

3.09 ppm for 11 and δ 5.91 ppm for 14), which is typical

for unsolvated organolanthanide hydrides.^22,23In com-

Me

PhMeSiH₂

Cp*₂Ln

LnCp*₂

–PhMe₂SiH

Me

1, 4, 5

slow

H

PhMeSiH₂

Cp*₂Ln

LnCp*₂

(7)

Cp*₂Ln

LnCp*₂

–PhMe₂SiH

Me

16-18

11, 14, 15

Cp* = Cp′; Ln = Y(16), Lu(17)

Cp* = Cp′′; Ln = Lu(18)

1

pound 11, the ⁸⁹Y-¹H coupling pattern (triplet, J _Y-H

) 32.8 Hz) is consistent with symmetrical Y(µ-H)₂Y

bridging (cf. ¹J _Y-H) 35.3 Hz for {Et₂Si(C₅H₄)(C₅Me₄)Y-

(µ-H)}₂²³).

intermediates 16 and 18 was also observed for dimeric

hydrocarbyls 1 and 5.

Monitoring the reaction of 4 with PhMeSiH₂(eq 6)

The ¹H NMR spectra for the reaction mixture of

yttrium hydrocarbyl 1 and PhMeSiH₂are presented in

Figure 3. Only dimeric organoyttrium compounds were

observed during the reaction. All the proton resonances

of 16 assigned to methyl and hydride ligands (δ -0.73

1

with the use of H NMR reveals the formation of an

intermediate. This intermediate has one µ-methyl (δ

-0.26 ppm) and one µ-hydride (δ 5.82 ppm) ligand

(Figure 2). The quantitative conversion of 4 into the

intermediate complex requires only an equivalent of the

organosilicon hydride and takes several hours at ambi-

2

1

ppm and J _Y-H) 3.3 Hz for µ-Me; δ 3.00 ppm and J _Y-H

) 36.0 Hz for µ-H) are triplets, which means that such

ligands bridge two yttrium atoms. The proton reso-

nances of the cyclopentadienyl rings in 16 are broad

compared to those of 17.

1

ent temperature. The H NMR data for the intermedi-

ate are consistent with the C_sdimeric structure 17 with

two different ligands (H and Me) and four equivalent

^tBuC₅H₄ligands in the vicinity of two lanthanide atoms.

In particular, the occurrence of four Cp′-H signals was

attributed to the nonequivalent protons of the Cp′ ring,

which constitute an ABCD spin system, with the tert-

butyl substituent behaving as an anchor. In the pres-

ence of an excess amount of PhMeSiH₂, intermediate

The rates of both of the steps of reaction 7 increase

with an increase in the lanthanide radius and when the

t

Me₃SiC₅H₄ligand is changed to a BuC₅H₄ligand. Since

the second step of this reaction is slow, we have isolated

dimeric organolanthanides 16-18 and characterized

them using standard analytical and spectroscopic tech-

niques (see Experimental Section). The compounds do

not disproportionate in benzene, toluene, or pentane

solutions and can be purified by recrystallization.

Stepwise reactions of lanthanide hydrocarbyls 1-5,

analogous to eq 7, proceed for various organoelement

(22) J eske, G.; Lauke, H.; Mauermann, H.; Swepston, P. N.; Schu-

mann, H.; Marks, T. J . J . Am. Chem. Soc. 1985, 107, 8091-8103. J eske,

G.; Schock, L. E.; Swepston, P. N.; Schumann, H.; Marks, T. J . J . Am.

Chem. Soc. 1985, 107, 8103-8110.

(23) Stern, D.; Sabat, M.; Marks, T. J . J . Am. Chem. Soc. 1990, 112,

9558-9575.

Lanthanide and Yttrium Hydrides and Hydrocarbyls

Organometallics, Vol. 16, No. 19, 1997 4045

hydrides, i.e., hydrides of silicon, germanium, and tin

and complex hydrides of aluminium and gallium.²⁴The

rates of both steps of the transformation decrease in the

following sequence (C₆D₆, 20 °C):

a complete statistical redistribution of hydrogen iso-

topes. Neither the formation of products with deute-

rium in their Ph, Et, and Me fragments nor that of

compounds with Si-Si bonding was observed even when

the reaction was carried out at elevated temperatures

for a week.

In the presence of an excess amount of PhMeSiD₂,

yttrium hydride 11 forms the corresponding yttrium

deuteride 11-d , which has a high content of deuterium

in the bridging fragments, after several hours at ambi-

ent temperature (eq 10). No formation of products

PhMeSiD₂

{Cp′ Y(µ-D)}

{Cp′₂Y(µ-H)}₂

8

(10)

2

C₆H₆

11-d

In THF solution, the reactions with silanes are

complicated by several side reactions. Thus, the total

yield of the corresponding lanthanide hydrides was ca.

20-30% (with the quantitative conversion of the start-

ing hydrocarbyls 6 and 9). In addition to Cp′₃Y, yttrium

hydrocarbyl 7 forms the corresponding dimeric solvate

19 after several weeks at ambient temperature (eq 8).

with lanthanide-silicon bonding was observed in ben-

zene solution either at ambient or at elevated temper-

atures.

Deh yd r ogen a tive Cou p lin g of Or ga n otin Hy-

d r id es Ca ta lyzed by La n th a n id e a n d Yttr iu m Hy-

d r id es. Lanthanide hydrides 11-14 were found to

catalyze the dehydrogenative coupling of tin hydrides

at elevated temperature. For instance, both Et₃SnH

and ⁿBu₃SnH give the corresponding distannanes X₃-

SnSnX₃, where X ) Et or ⁿBu, in quantitative yield

and molecular hydrogen in the presence of 1-3 mol %

of 11-14 at 70 °C for several minutes. This reaction

does not take place at room temperature. In the

absence of the lanthanide compounds, these organotin

hydrides give the corresponding distannanes (probably

via a free radical pathway²⁹) in 5-10% yield after 0.5 h

at 70 °C.

E xch a n ge R ea ct ion s of Dim er ic La n t h a n id e

a n d Yttr iu m Com p ou n d s w ith Va r iou s Br id gin g

Liga n d s. We observed an equilibrium between yttrium

and lutetium hydrocarbyl complexes 1 and 4 (eq 11), in

which, according to the NMR data, up to 70% of

heterometallic compound 20 is present after several

minutes at ambient temperature. The upfield region

PhMeSiH₂

{Cp′ Y(µ-H)(THF)}

2Cp′₂YMe(THF) _{THF, 20 °C}8

(8)

2

19

In this compound, the Y-H resonance occurs at δ 2.64

1

ppm, with the ⁸⁹Y-¹H coupling constant J _Y-H) 29.3

1

Hz (cf. δ 2.18 ppm, J _Y-H) 20 Hz for {(C₅H₅)₂Y(µ-H)-

(THF)}₂²⁰). It was found that lutetium hydrocarbyl 9

does not react with PhMeSiH₂in THF at ambient

temperature. However, it forms ca. 30% of the dimeric

unsolvated hydride 14 (eq 9), along with Cp′₃Lu, CH₄,

and other unidentified products, after 30 h at 80 °C.

PhMeSiH₂

{Cp′ Lu(µ-H)}

2Cp′₂LuMe(THF) _{THF, 80 °C}8

(9)

2

14

This result is rather unusual (cf., for instance, ref 28).

We performed an additional study and showed that

yttrium hydride 11 forms solvate 19 on dissolving in

THF. In contrast, lutetium hydride 14 does not react

with THF.

Me

C₆D₆, 20 °C

2Cp′₂Y LuCp′₂

(11)

1 + 4

Me

Deu ter iu m -P r otiu m Exch a n ge in Sila n es Ca ta -

lyzed by La n th a n id e a n d Yttr iu m Hyd r id es. Yt-

trium and lanthanide hydrides 11-15 are efficient

catalysts of the Si-H/Si-D exchange between various

silanes. Treatment of a PhMeSiD₂and PhEtSiH₂

mixture with 11 (2 mol %) at 70 °C for 1.5 h results in

20

of the NMR spectrum of the reaction mixture is shown

in Figure 4. Since the yttrium-89 nucleus has a spin

equal to ^1/₂, the central doublet resonance (δ -0.26 ppm;

²J _Y-H) 3.8 Hz) corresponds to the heterometallic

compound 20, which contains both yttrium and lutetium

atoms. The ¹³C{¹H} NMR spectrum exhibits a reso-

nance at δ 27.56 ppm (d, ¹J _Y-C) 22.9 Hz) corresponding

to the Y-Me-Lu bridging.³⁰No monomeric particles

were detected by NMR spectroscopy.

(24) When uncomplexed organoaluminium and organogallium com-

pounds are used, heterometallic lanthanide-aluminum complexes are

formed.^25,26For instance, we found that yttrium hydrocarbyl 1 reacts

with {Et₂Al(µ-H)}₂in benzene at ambient temperature to form the

Cp′₂Y(µ-H)(µ-alkyl)Al(alkyl)₂heterometallic complex, in which the Y-H

1

resonance occurs at δ 2.64 ppm with ⁸⁹Y-¹H coupling constant J _Y-H

) 30.2 Hz (doublet) (cf. δ 2.88 ppm for µ-H in {Et₂Al(µ-H)}₂in C₆D₆).

Such heterobimetallic compounds decompose in the presence of various

bases to form homometallic lanthanide complexes.^16,27

In contrast, dimeric hydrides 11 and 14 require 2

weeks to equilibrate in benzene at ambient temperature

(25) Rabaaˆ, H.; Saillard, J .-Y.; Hoffmann, R. J . Am. Chem. Soc. 1986,

108, 4327-4333.

(29) Kocheshkov, K. A.; Zemlyanski, N. N.; Shverdina, N. I.; Panov,

E. M. Metody elementoorganicheskoy khimii. Germani, olovo, svinets

(Methods of Organo-Element Chemistry. Germanium, Tin, Lead);

Nauka: Moscow, 1968; and references therein.

(26) (a) Ballard, D. G. H.; Pearse, R. J . Chem. Soc., Chem. Commun.

1975, 621. (b) Holton, J .; Lappert, M. F.; Scollary, G. R.; Ballard, D.

G. H.; Pearce, R.; Atwood, J . L.; Hunter, W. E. J . Chem. Soc., Chem.

Commun. 1976, 425-426. Holton, J .; Lappert, M. F.; Ballard, D. G.

H.; Pearce, R.; Atwood, J . L.; Hunter, W. E. J . Chem. Soc., Dalton

Trans. 1979, 54-61. (c) Watson, P. L. J . Am. Chem. Soc. 1982, 104,

337-339. (d) Evans, W. J .; Chamberlain, L. R.; Ziller, J . W. J . Am.

Chem. Soc. 1987, 109, 7209-7211.

(30) (^tBu C₅H₄)₂Y(µ-Me)₂Lu (C₅H₄^tBu )₂(20). ¹H NMR (benzene-

2

t

d₆): δ -0.26 (d, 6H, J _Y-H) 3.8 Hz, µ-Me), 1.35 (s, 18H, BuC₅H₄Y),

t

1.38 (s, 18H, BuC₅H₄Lu), 6.08 (t, 4H, J ) 2.7 Hz, H2,5 in C₅H₄Lu),

6.15 (t, 4H, J ) 2.8 Hz, H2,5 in C₅H₄Y), 6.46 (t, 4H, J ) 2.7 Hz, H3,4

in C₅H₄Lu), 6.54 (t, 4H, J ) 2.7 Hz, H3,4 in C₅H₄Y). ¹³C NMR (benzene-

1

(27) Gun’ko, Y.-K.; Bulychev, B. M.; Soloveichik, G. L.; Belsky, V.

K. J . Organomet. Chem. 1992, 424, 289-300.

(28) Evans, W. J .; Meadows, J . H.; Wayda, A. L.; Hunter, W. E.;

Atwood, J . L. J . Am. Chem. Soc. 1982, 104, 2008-2014.

d₆): δ 27.56 (d, J _Y-C) 22.9 Hz, µ-Me), 29.02 (CMe₃), 32.44 (CMe₃),

108.76 (C2,5 in C₅H₄Lu), 108.76 (C3,4 in C₅H₄Lu), 110.39 (C2,5 in

C₅H₄Y), 111.18 (C3,4 in C₅H₄Y), 135.35 (C1 in C₅H₄Lu), 137.37 (C1 in

C₅H₄Y).

4046 Organometallics, Vol. 16, No. 19, 1997

Voskoboynikov et al.

yields complexes 16-18. A similar reaction between

dimeric complexes 22 and 23 with the µ-Cl ligands³²and

the corresponding dimeric hydrides 11 and 14 proceeds

very slowly at ambient temperature and gives rise to

the dimeric hydridochloro complexes 24 and 25 in

quantitative yield after ca. 1 h at 70 °C (eq 14) (see also

ref 33).

H

Cl

H

C₆H₆

2Cp′₂Ln

LnCp′₂

Cp′₂Ln

LnCp′₂

Cp′₂Ln

LnCp′₂

+

(14)

Cl

22, 23

24, 25

Ln = Y(22, 24), Lu(23, 25)

The ¹H NMR spectra of 24 and 25 are consistent with

C_sdimeric structures, characterized by four Cp′-H

resonances (ABCD). The Y-H resonance for 24 occurs

at δ 2.95 ppm, with the ⁸⁹Y-¹H coupling pattern (triplet,

¹J _Y-H) 33.5 Hz) consistent with symmetrical Y(µ-H)Y

bridging.

Our attempts to synthesize compounds with both Ln-

(µ-H)(µ-OMe)Ln and Ln(µ-Me)(µ-OMe)Ln bridging using

the same strategy failed. Binary lutetium alkoxide

{Cp′₂Lu(µ-OMe)}₂(26), which is prepared by alcoholysis

of 4 (see also ref 34), turned out to react with neither

hydrocarbyl 4 nor hydride 14 either at ambient or

elevated temperatures.

F igu r e 4. The upfield region of ¹H NMR spectrum of the

equimolar mixture of 1 and 4 in benzene-d₆.

Rea ction s of La n th a n id e Hyd r oca r byls w ith

Alk oxy- a n d Ch lor osila n es. Not much is known

about the reactivity of organolanthanides toward chloro-

and alkoxysilanes.^35,36We have found that the reaction

of these or similar heterosubstituted silanes with lan-

thanide complexes is a convenient route for the prepa-

ration of various compounds with both Ln(µ-R)(µ-X)Ln

and Ln(µ-X)₂Ln bridging (R ) H, Me; X ) OR, SR, NR₂,

PR₂, etc.).

Lanthanide hydrocarbyls 1 and 4 react readily with

various alkoxysilanes to yield the corresponding dimeric

compounds with different bridging fragments ((µ-Me)-

(µ-OMe) (27 and 28), (µ-Me)(µ-OEt) (29)) and with an

excess amount of the organosilicon compound to yield

the respective dimeric alkoxides 26, 30, and 31 (eq 15).³⁷

Compounds 26-28 and 30 have been isolated in high

F igu r e 5. The region of the µ-H resonances of the ¹H NMR

spectrum of an equimolar mixture of 11 and 14 in benzene-

d₆.

(eq 12). According to the NMR spectra, the equilibrium

C₆D₆

H

(12)

2Cp′₂Y LuCp′₂

fast

11 + 14

Me

R₃SiX

H

Cp′₂Ln

LnCp′₂

–R₃SiMe

21

slow

X

R₃SiX

mixture contains ca. 50% of heterometallic compound

21. The region of the µ-H resonances in the NMR

spectrum of this mixture is shown in Figure 5. The

Cp′₂Ln

LnCp′₂

Cp′₂Ln

LnCp′₂

(15)

–R₃SiMe

Me

27–29

26, 30, 31

1

central doublet (δ 4.64 ppm, J _Y-H) 30.5 Hz) corre-

X = OMe; Ln = Y(27, 30), Lu(26, 28)

X = OEt; Ln = Lu(29, 31)

sponds to heterometallic compound 21.³¹

The exchange between dimeric hydrides and hydro-

carbyls of the same metal (eq 13) proceeds rather slowly

in benzene at ambient temperature. This reaction

yield and characterized by standard analytical and

(32) Shen, Q.; Qi, M.; Guan, J .; Lin, Y. J . Organomet. Chem. 1991,

406, 353-361.

H

Me

H

C₆H₆

2Cp*₂Ln

LnCp*₂

(13)

Cp*₂Ln

LnCp*₂

Cp*₂Ln

LnCp*₂

+

(33) Qiao, K.; Fischer, R. D.; Paolueci, G. J . Organomet. Chem. 1993,

456, 185-194.

Me

(34) Stults, S. D.; Andersen, R. A.; Zalkin, A. Organometallics 1990,

9, 1623-1629.

(35) Evans, W. J .; Ulibarri, T. A.; Ziller, J . W. Organometallics 1991,

10, 134-132.

(36) Yasuda, H.; Yamamoto, H.; Yokota, K.; Nakamura, A. Chem.

Lett. 1989, 1309-1312. Magomedov, G. K.-I.; Voskoboynikov, A. Z.;

Kirillova, N. I.; Gusev, A.I.; Parshina, I. N.; Beletskaya, I. P. Metal-

loorgan. Khim. (USSR) 1992, 5, 679-683.

(37) Evans, W. J .; Sollberger, M. S.; Khan, S. I.; Bau, R. J . Am.

Chem. Soc. 1988, 110, 439-446.

16-18

(31) (^tBu C₅H₄)₂Y(µ-H)₂Lu (C₅H₄^tBu )₂(21). ¹H NMR (benzene-d₆):

t

1

δ 1.22 (s, 36H, Bu), 4.64 (d, 2H, J _Y-H) 30.5 Hz, µ-H), 6.17 (t, 4H, J

) 2.3 Hz, H2,5 in C₅H₄Lu), 6.21 (t, 4H, J ) 2.6 Hz, H2,5 in C₅H₄Y),

6.78 (t, 8H, J ) 2.8 Hz, H3,4 in C₅H₄). ¹³C NMR (benzene-d₆): δ 30.16

(CMe₃), 31.35 (CMe₃), 107.69 (C2,5 in C₅H₄Lu), 108.65 (C2,5 in C₅H₄Y),

109.24 (C3,4 in C₅H₄Lu), 109.46 (C3,4 in C₅H₄Y), 136.98 (C1 in C₅H₄-

Lu), 138.54 (C1 in C₅H₄Y).

Lanthanide and Yttrium Hydrides and Hydrocarbyls

Organometallics, Vol. 16, No. 19, 1997 4047

Ta ble 2. Selected Bon d Dista n ces (Å) a n d An gles

(d eg) for (^tBu C₅H₄)₂Lu (µ-Me)(µ-OMe)Lu (C₅H₄^tBu )₂

(28)

Bond Distances

Lu(1)‚‚‚Lu(2)

Lu(1)-O(1)

Lu(1)-C(1)

Lu(1)-C(3)

Lu(1)-C(20)

Lu(1)-C(4)

Lu(1)-C(2)

Lu(1)-C(5)

Lu(2)-O(1)

Lu(2)-C(20)

Lu(2)-C(10)

Lu(2)-C(12)

Lu(2)-C(11)

3.498(1)

2.201(14)

2.709(10)

2.557(11)

2.57(2)

2.610(11)

2.638(10)

2.678(10)

2.12(2)

Lu(2)-C(13)

Lu(2)-C(14)

O(1)-C(19)

C(1)-C(5)

2.618(11)

2.687(10)

1.42(2)

1.39(2)

1.425(14)

1.42(2)

1.41(2)

1.46(2)

1.40(2)

1.45(2)

1.36(2)

1.44(2)

1.41(2)

C(1)-C(2)

C(2)-C(3)

C(3)-C(4)

C(4)-C(5)

C(10)-C(11)

C(10)-C(14)

C(11)-C(12)

C(12)-C(13)

C(13)-C(14)

2.58(2)

2.708(11)

2.583(11)

2.615(11)

Angles

Lu(1)-C(20)-Lu(2)

Lu(2)-O(1)-Lu(1)

C(19)-O(1)-Lu(1)

C(19)-O(1)-Lu(2)

O(1)-Lu(1)-C(20)

O(1)-Lu(2)-C(20)

C(5)-C(1)-C(2)

85.6(8)

108.3(7)

C(4)-C(3)-C(2)

109.7(10)

106.1(11)

108.1(10)

C(3)-C(4)-C(5)

121.1(11) C(1)-C(5)-C(4)

129.3(11) C(11)-C(10)-C(14) 105.3(10)

82.3(8)

83.8(7)

C(12)-C(11)-C(10) 111.1(11)

C(11)-C(12)-C(13) 108.7(10)

F igu r e 6. ORTEP view of (^tBuC₅H₄)₂Lu(µ-Me)(µ-OMe)-

109.1(10) C(14)-C(13)-C(12) 105.9(10)

106.9(10) C(13)-C(14)-C(10) 108.9(11)

t

Lu(C₅H₄Bu)₂(28).

C(3)-C(2)-C(1)

spectroscopic techniques (see Experimental Section).

Sch em e 1

Compounds 29 and 31 were detected by NMR spectros-

1

copy. The H NMR spectra of 27-29 correspond to C_s

dimeric structures, which are characterized by four

Cp′-H resonances (ABCD). The Y-Me resonance for

27 occurs at δ -0.42 ppm, and the ⁸⁹Y-¹H coupling

2

pattern (triplet, J _Y-H) 3.4 Hz) is consistent with

symmetrical Y(µ-Me)Y bridging. Reaction 15 proceeds

easily for tri- and tetrasubstituted alkoxysilanes, such

as (RO)₄Si and (RO)₃SiMe (R ) Me, Et). Mono- and

disubstituted alkoxysilanes are rather inactive, and only

traces of the products were observed in the reaction with

MeOSiMe₃, (MeO)₂SiMe₂, and EtOSiMe₃. However, the

rate of this reaction increases considerably at elevated

temperature. No cleavage of the Cp′-Ln bonds was

observed at ambient temperature in excess amounts of

alkoxysilanes.

by the exchange reaction between the corresponding

dimeric hydrocarbyls 1 and 4 and chlorides 22 and 23.

The structure of the lutetium complex 28 was deter-

mined by X-ray diffraction analysis (Figure 6). The

bond lengths and selected bond angles are given in

Table 2. The molecule represents a binuclear complex.

Two (η⁵-Cp′)₂Lu fragments are linked through a couple

of bridges, Me and OMe. Some differences in the similar

geometrical parameters of the OMe bridge (the Lu-O

distances are 2.20(2) and 2.12(2) Å and the Lu-O-C

angles are 122(1) and 129(1)°) are observed.

The reactivity of lanthanide hydrocarbyls toward

chlorosilanes turned out to be quite different. Com-

plexes 1 and 4 react with various chlorosilanes to form

halogenide complexes 22 and 23, respectively (eq 16),

but do not form compounds with Ln(µ-Me)(µ-Cl)Ln

bridging. The latter compounds also cannot be prepared

Discu ssion

Rea ction s of La n th a n id e Hyd r oca r byls w ith

Sila n es or Or ga n oelem en t Hyd r id es: Hyd r id e vs

Silyl Tr a n sfer . The reactions of hydrocarbyl (and

hydride) complexes of various early transition metals

with silanes can involve the formation of different

intermediates and products, depending on the reaction

mechanism. Possible reaction pathways are presented

in Scheme 1.³⁹Pathway a is preferable for complexes

of the early transition metals that can exist in several

stable oxidation states. Silyl complexes of niobium and

tantalum,^41-43as well as titanium⁴⁴and zirconium,^45-48

(39) Interpretation of synthetic experiments in the context of such

reaction mechanisms should be made with great care because of the

possibility that the reaction may occur by a multistep mechanism,^8b

even involving redox processes different from the oxidative addition^15b

and free-radical pathways.⁴⁰

(40) (a) Harrod, J . F.; Yun, S. S. Organometallics 1987, 6, 1381-

1387. (b) Aitken, C.; Barry, J .-P.; Gauvin, F.; Harrod, J . F.; Malek, A.;

Rousseau, D. Organometallics 1989, 8, 1732-1736.

(41) Curtis, M. D.; Bell, L. G.; Butler, W. M. Organometallics 1985,

4, 701-707.

(42) Berry, D. H.; J iang, Q. J . Am. Chem. Soc. 1989, 111, 8049-

8051.

(43) Berry, D. H.; Koloski, T. S.; Carroll, P. J . Organometallics 1990,

9, 2952-2962.

Me

Cl

Me₃SiCl

(16)

Cp′₂Ln

LnCp′₂

Cp′₂Ln

LnCp′₂

C₆H₆, –78 °C

22, 23

(38) The reaction of lutetium hydride 14 with (MeO)₄Si was moni-

tored by NMR. This reaction produced Cp′₂Lu(µ-H)(µ-OMe)LuCp′₂and

then compound 26 (see also ref 38). It is of interest that the compound

with the Lu(µ-H)(µ-OMe)Lu bridging cannot be prepared upon

treatment of hydrocarbyl complex 28 with PhMeSiH₂both at ambient

a

and at elevated temperatures.

4048 Organometallics, Vol. 16, No. 19, 1997

Voskoboynikov et al.

are probably formed through the oxidative addition of

organosilicon hydrides to organometallic intermediates

with the metal in a low oxidation state.

Transition metal hydrides (and probably hydrocar-

byls) can react with silane as a base with a “Si-H acid”.

Thus, silanes and d⁰metal complexes,^10a,b,d,f,11including

some lanthanide hydrides with C₅Me₅ligands,^8,15bhave

recently been shown to undergo σ-bond metathesis to

form compounds with direct silicon-transition-metal

bonding (pathway b).

computation of transition metal complexes (see Sup-

porting Information for more details).⁵⁴Analysis of

Cp₂Y-R + SiH₄h Cp₂Y-H + RSiH₃

Cp₂Y-R + SiH₄h Cp₂Y-SiH₃+ RH

(17)

(18)

molecular orbital plots for the encounter complexes and

transition states enabled us to construct a correlation

diagram for the five upper occupied molecular orbitals

for the alternative reactions of hydride transfer and silyl

group transfer to the yttrium atom (Figure 7).

The most significant result of these studies can be

drawn: along with the additional agostic interaction,

the transition states revealed are characterized by the

effective interaction of yttrium with all three atoms

involved in the bond transposition processes. In other

words, the interaction in the transition states may be

considered as occurring between the Cp₂Y⁺cation and

the respective allyl-like anion.

On the other hand, in this paper we have shown that

bis(cyclopentadienyl)lanthanide hydrocarbyls containing

t

C₅H₅, BuC₅H₄, Me₃SiC₅H₄, and even C₅Me₅ligands

react readily with silanes to form the products of

nucleophilic substitution at silicon and the correspond-

ing lanthanide hydrides (pathway c and eq 1).^4,5,49,50

This reaction is a very convenient route for the synthesis

of the corresponding lanthanide hydrides,³which are

difficult to prepare. In regard to reaction conditions,

both {Cp₂Ln(µ-H)}₂and {Cp₂LnH(THF)}, where Cp )

The calculation indicates the silyl group transfer to

the metal atom to be more preferable to the hydride

transfer in the reaction of (C₅H₅)₂YMe with SiH₄in the

gas phase. Thermodynamic parameters ∆H and ∆E^q

(kcal/mol) were 1.4 and 24.0 for hydride transfer (eq 17),

-99.5 and 2.9 for silyl transfer (eq 18). This result

correlates poorly with our chemical experiments (see

above). Thermochemical data obtained for bis(pentam-

ethylcyclopentadienyl) derivatives of Sm(III) showed

both of these alternative reactions to be exothermic,

with ∆H equal to ca. -11 and -9 kcal mol^-1for the silyl

and hydride transfer, respectively.⁶The comparative

analysis of the geometry of the corresponding alterna-

tive intermediates, as well as the chemical experiments,

demonstrated that the steric factor plays a crucial role.

Evidence for this is the fact that trisubstituted silanes

R₃SiH do not react with the yttrium and lanthanide

hydrocarbyls studied. However, silanes R₂SiH₂and

RSiH₃react readily in this manner (see above). The

steric factor must affect the reaction of the silyl group

transfer to the lanthanide atom to a greater extent than

the alternative hydride transfer (see Supporting Infor-

mation for more details). However, a single-step meta-

lation of silane with lanthanide hydrocarbyl should not

be excluded. The results of our investigation of olefin

hydrosilylation catalyzed by organolanthanides suggest

an occurrence of a slow single-step reaction of silyl group

transfer for sterically unhindered monomeric lanthanide

complexes Cp₂LnR that include an alkyl group R with

a high basicity.⁵²

R ea ct ion s of La n t h a n id e H yd r id es w it h Si-

la n es: H/D Exch a n ge vs Meta la tion . The reaction

of {Cp′₂Ln(µ-H)}₂with deuterosilanes can be used for

preparation of {Cp′₂Ln(µ-D)}₂(eq 10) and, in a catalytic

manner, for H/D scrambling between R₃SiH (or R₃SnH)

and R′₃SiD. The observed H/D exchange in silanes can

proceed by one of two alternative routes. The first one

involves two sequential hydrogen exchanges with the

participation of Cp′₂Ln-H(D) intermediates (Scheme 2,

pathway i). Pathway ii suggests the formation of

intermediates with Ln-Si bonding, Cp′₂Ln-SiR₃. This

situation is similar to the possibility of two alternative

mechanisms for the olefin hydrosilylation catalyzed by

t

C₅H₅, BuC₅H₄, or Me₃SiC₅H₄, were prepared in a high

yield. A similar reaction is suggested to be a key stage

of the catalytic cycle of olefin hydrosilylation catalyzed

by organolanthanides.^{4-6,15a,51-53}In contrast, complexes

with permethylcyclopentadienyl ligands (C₅Me₅)₂LnCH-

(SiMe₃)₂react with silanes in a different manner to form

the corresponding compounds with Ln-Si bonds.^8a,15b

However, Tilley et al. recently showed that this reaction

is not a single-step process. ^8bThe compound with Ln-

Si bonding is formed by the reaction of silane with the

hydride (C₅Me₅)₂LnH, which is generated by the hydro-

genolysis of the former lanthanide hydrocarbyl with

traces of H₂.

Thus, a single-step reaction of alkyl (aryl) lanthanide

complexes with silanes can proceed via two alternative

pathways, i.e., it can include either hydride transfer to

the lanthanide atom (pathway c) or transfer of a silyl

group to the metal atom (pathway b). We have per-

formed geometrical and energy calculations for the

encounter complexes and transition states in the alter-

native model reactions of hydride and silyl transfer (eqs

17 and 18, Cp ) C₅H₅and R ) Me) using the semiem-

pirical ZINDO/1 method proposed by Zerner et al. for

(44) Aitken, C. T.; Harrod, J . F.; Samuel, E. J . Am. Chem. Soc. 1986,

108, 4059-4066.

(45) Aitken, C. T.; Harrod, J . F.; Samuel, E. Can. J . Chem. 1986,

64, 1677-1679.

(46) Mu, Y.; Aitken, C.; Cote, B.; Harrod, J . F.; Samuel, E. Can. J .

Chem. 1991, 69, 264-276.

(47) Takahashi, T.; Hasegawa, M.; Suzuki, N.; Saburi, M.; Rousset,

C. J .; Fanwick, P. E.; Negishi, E.-I. J . Am. Chem. Soc. 1991, 113, 8564-

8566.

(48) Corey, J . Y.; Huhmann, J . L.; Zhu, X.-H. Organometallics 1993,

12, 1121-1130.

(49) Beletskaya, I. P.; Voskoboynikov, A. Z.; Parshina, I. N.; Mago-

medov, G. K.-I. USSR Patent 1,745,727, March 8, 1992 (J une 27, 1990).

(50) Beletskaya, I. P. Proceedings of the 206th Meeting of the ACS;

Chicago, August 1993; American Chemical Society: Washington, DC,

1993; INOR 333.

(51) Beletskaya, I. P.; Voskoboynikov, A. Z.; Parshina, I. N.; Mago-

medov, G. K.-I. USSR Patent 1,663,832, March 15, 1991 (Nov. 17,

1989).

(52) Voskoboynikov, A. Z.; Shestakova, A. K.; Beletskaya, I. P.

Unpublished results.

(53) Sakakura, T.; Lautenschlager, H. J .; Tanaka, M. J . Chem. Soc.,

Chem. Commun. 1991, 40-41. Takahashi, T.; Hasegawa, M.; Suzuki,

N.; Saburi, M.; Rousset, C. J .; Fanwick, P. E.; Negishi, E. J . Am. Chem.

Soc. 1991, 113, 8564-8566. Molander, G. A.; J ulius, M. J . Org. Chem.

1992, 57, 6347-6351. Kesti, M. R.; Waymouth, R. M. Organometallics

1992, 11, 1095-1103. Onozawa, S.-Y.; Sakakura, T.; Tanaka, M.

Tetrahedron Lett. 1994, 8177-8180. Molander, G. A.; Retsch, W. H.

Organometallics 1995, 14, 4570-4575.

(54) Bacon, A. D.; Zerner, M. C. Theor. Chim. Acta 1979, 53, 21-

54. Anderson, W. P.; Edwards, W. D.; Zerner, M. C. Inorg. Chem. 1986,

25, 2728-2732.

Lanthanide and Yttrium Hydrides and Hydrocarbyls

Organometallics, Vol. 16, No. 19, 1997 4049

F igu r e 7. Schematic correlation diagram for σ-bond metathesis reactions of eqs 17 and 18 (Cp ) C₅H₅and R ) Me).

organolanthanides.⁶Pathway ii seems to be more

Sch em e 2

probable. The complexes (C₅Me₅)₂LnH are known to

react readily with silanes to form compounds with Ln-

Si bonding.^8b,15bMoreover, a similar H/D exchange in

hydrocarbons catalyzed by lanthanide d⁰complexes

proceeds via transmetalation, i.e., analogously to mech-

anism ii.⁵⁵However, in this paper we have shown that

the reaction between silanes and lanthanide hydrides

with unsubstituted and monosubstituted cyclopentadi-

enyl ligands does not give the corresponding complexes

with Ln-Si bonding under different conditions. More

evidence for this reactivity is the results of our recent

detailed study of olefin hydrosilylation catalyzed by

{Cp′₂Ln(µ-H)}₂.⁵²All of these data favor mechanism i

for H/D exchange in silanes and tin hydrides.

Geometrical and energy calculations for the encounter

complexes and transition state in the model reaction of

silyl transfer (eq 18, Cp ) C₅H₅and R ) H) using the

semiempirical ZINDO/1 method show that the strongly

exothermic (∆H ) -85.4 kcal/mol) metalation reaction

must proceed rapidly (∆E^q) 3.8 kcal/mol) (see Sup-

porting Information for more details). This fact cor-

relates poorly with the recent theoretical study results

on the σ-bond metathesis reaction between Cl₂ScH and

SiH₄,¹⁴but it is in a good agreement with the experi-

mental results on the reactivity of (C₅Me₅)₂LnH. These

(55) Deelman, B.-J .; Teuben, J . H.; Macgregor, S. A.; Eisenstein, O.

New J . Chem. 1995, 19, 691-698.

4050 Organometallics, Vol. 16, No. 19, 1997

Voskoboynikov et al.

Sch em e 3

Syn th esis a n d Dissocia tive Sta bility of Dim er ic

Or ga n ola n th a n id es. Highly associated complexes

with various bridging ligands are known to have a great

significance in organolanthanide chemistry.³In this

paper, we propose two new methods for the synthesis

of dimeric lanthanide compounds. The first one implies

selective reaction of silane or alkoxysilane with lan-

thanide hydrocarbyl {Cp′₂Ln(µ-Me)}₂. Depending on

the ratio of the reagents, this reaction gives either {Cp′₂-

Ln(µ-X)}₂or Cp′₂Ln(µ-Me)(µ-X)LnCp′₂(X ) H, OR). The

formation of the complexes with different bridging

ligands starting from {Cp′₂Ln(µ-Me)}₂should involve

preliminary dissociation of the dimeric methyl com-

plexes (eq 19).⁵²In unsolvated media, the following

unsolvated monomeric hydride complexes react rapidly

with silanes (k_obs> 5.4(5) × 10^-2M^-1s^-1at 25 °C, Ln

) La). This reaction has a ∆H of ca. -4 kcal mol^{-1 15b}

.

^fast8

However, the computational data indicate that the silyl

transfer should be strongly exothermic. This discrep-

ancy may be explained by the influence of two donating

C₅Me₅ligands, whose introduction into the molecule

brings about a large change in the electron density

formally matching the decrease in the oxidation state

of the metal by unit.⁵⁶

{Cp′₂Ln(µ-Me)}₂7

2Cp′₂LnMe

(19)

nucleophilic substitution at silicon must proceed via the

four-centered transition state C, and therefore, the

corresponding dimeric complexes with the Ln(µ-Me)(µ-

X)Ln metallocycle (D) could be a model for the transition

state of this reaction. The following reaction, i.e., the

The calculations performed indicate the evolution of

hydrogen to be preferable in the interaction of (C₅H₅)₂-

YH with SiH₄in the gas phase (eq 18, Cp ) C₅H₅and

R ) H). The calculated parameters for the alternative

hydrogen exchange reaction (eq 17, R ) H) are ∆H ) 0

kcal/mol and ∆E^q> 12 kcal/mol. Even small steric

problems give rise to an essentially different result. The

rates of these alternative reactions become practically

equal (see Supporting Information for more details).

Even greater changes in the reactivity can occur in the

case of substantial steric hindrances to putting the

silicon atom in the coordination sphere of yttrium in the

transition state. Obviously, that hydride transfer (com-

pared to the alternative transfer of silyl group) to the

lanthanide atom could include no considerable Ln‚‚‚Si

interaction in transition state A′. In this case, the

structure of the transition state is likely to be similar

to the structure of dimeric lanthanide hydrides that

involve a silicon atom instead of one lanthanide atom

in the Ln(µ-H)₂Ln metallocycle.

Lanthanide hydrides {Cp′₂Ln(µ-H)}₂catalyze a rapid

isotope exchange in organotin hydrides at ambient

temperature. Alternatively, organolanthanides catalyze

dehydrogenative coupling of stannanes at elevated

temperatures. Most likely, the latter reaction proceeds

via a free radical pathway,²⁹which is initiated by either

a redox reaction between Cp′₂LnH and R₃SnH or by

thermal decomposition of some intermediates with

Ln-Sn bonding. It is well-known that tin hydrides

are metalated more easily than the corresponding

silanes.^3b,9d,57Therefore, the formation of Ln-Sn in-

termediates is probable. On the other hand, if the inter-

mediates are formed (although they were not detected

by NMR spectroscopy), then the dehydrogenative

coupling of stannanes could proceed via the nonho-

molytic mechanism (Scheme 3). This pathway is similar

to the mechanism of the dehydrogenative coupling of

silanes.^15b

formation of {Cp′₂Ln(µ-X)}₂from Cp′₂Ln(µ-Me)(µ-X)-

LnCp′₂, seems to imply a cleavage of only one bridging

bond Ln-Me-Ln and, probably, proceed via a bimetallic

transition state,^50,52e.g.

This selective method of bridging ligand substitution

seems to be the general synthetic procedure and can be

used for the preparation of various lanthanide com-

plexes starting from various substituted silanes. In

preliminary experiments, we showed that {Cp′₂Lu(µ-

H)}₂reacts readily with (MeO)₄Si to form {Cp′₂Lu(µ-

OMe)}₂and Cp′₂Lu(µ-H)(µ-OMe)LuCp′₂. Yttrium com-

plex {Cp′₂Y(µ-Me)}₂reacts with (Me₂N)₄Si in a similar

manner to form {Cp′₂Y(µ-NMe₂)}₂and Cp′₂Y(µ-Me)(µ-

NMe₂)YCp′₂.

Another general approach studied for the synthesis

of new dimeric lanthanide complexes either with dif-

ferent bridging ligands or with different metals is an

exchange between two different starting dimeric com-

plexes in hydrocarbon solution. Both of the above-

mentioned methods are used for the synthesis of dif-

ferent objects and, therefore, they complete with one

another. Not much is known about the dissociative

stability of dimeric organolanthanides with various

bridging ligands, particularly comparative data.^16,58-60

(58) Schaverien, C. J . Organometallics 1994, 13, 69-82.

(56) Kaupp, M.; Schleyer, P. v. R.; Dolg, M.; Stoll, H. J . Am. Chem.

Soc. 1992, 114, 8202-8208.

(57) Comprehensive Organic Chemistry; Barton, D., Ollis, W. D.,

Eds.; Pergamon Press: Oxford, 1979; Vol. 3. Comprehensive Organo-

metallic Chemistry; Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.;

Pergamon Press: Oxford, 1982; Vol. 1.

(59) Watson, P. L. J . Am. Chem. Soc. 1983, 105, 6491-6493.

(60) Watson, P. L. J . Chem. Soc., Chem. Commun. 1980, 652-653.

Watson, P. L.; Whitney, J . F.; Harlow, R. D. Inorg. Chem. 1981, 20,

3271-3278. Evans, W. J .; Meadows, J . H.; Hanusa, T. P. J . Am. Chem.

Soc. 1984, 106, 4454-4460. J eske, G.; Lauke, H.; Mauermann, H.;

Schumann, H.; Marks, T. J . J . Am. Chem. Soc. 1985, 107, 8111-8118.

Lanthanide and Yttrium Hydrides and Hydrocarbyls

Organometallics, Vol. 16, No. 19, 1997 4051

The above-mentioned experimental data on the relative

rates of ligand exchange for the complexes Cp′₂Ln(µ-

X)(µ-Y)LnCp′₂confirm that the capacities of various

bridging fragments in the vicinity of yttrium and

lutetium atoms to undergo reversible cleavage in hy-

drocarbon solution increase in the sequence Ln-O(Me)-

Ln , Ln-Cl-Ln < Ln-H-Ln < Ln-Me-Ln. It is very

important that this series does not correlate with the

sequence of the corresponding D(Cp*₂Sm-X) values,

where Cp* ) C₅Me₅, which is as follows (kcal/mol) [X]:

47.0 (1.5) [CH(SiMe₃)₂], 54.2 (3.0) [H], 82.4 (3.5) [O^tBu],

97.1 (3.0) [Cl].⁶⁰Interestingly, the Ln-SR-Ln frag-

ments dissociate relatively rapidly in hydrocarbon solu-

tion and the corresponding compounds take part in the

exchange processes,³⁴although the respective thermo-

dynamic parameters D(Cp*₂Sm-X), where X ) OR and

SR, are rather close.⁶¹Moreover, the preceding se-

quence is rather imprecise because of a strong depen-

dence of the dissociative ability of separate bridges on

the structure of the second bridge in the dimeric

organolanthanide compound. The discussed exchange

in the series of dimeric lanthanide complexes with

bridging ligands can presumably proceed without com-

plete dissociation of these compounds in solution, as well

as by the associative mechanism involving cleavage or

loosening of only one bridging bond. Only in the case

of the dimeric methyl complexes which enter into the

rapid exchange in eq 19 does the dissociative mechanism

appear to be well-grounded, although the equilibrium

in this reaction is shifted toward the starting associates.

Another point of interest is the mobility of various

ligands in the coordination sphere of the metal of

lanthanide complexes in solution (see also ref 62). The

study of various equilibrium processes makes it possible

to obtain the relative capacity of various bridgings Ln-

(µ-X)Ln, where X ) Me, H, Cl, OMe, to cleave in

hydrocarbon solution. These results are of significance

for synthetic chemistry. They enable carrying out the

synthesis of well-designed dimeric lanthanide complexes

either with different bridging ligands Ln(µ-L′)(µ-L′′)Ln

or with different metals Ln′(µ-L)₂Ln”. On the other

hand, the information about the mobility of various

bridging ligands in the vicinity of lanthanide atoms is

of importance for further insight into the mechanism

of some commercial-scale catalytic reactions, such as

stereospecific diene polymerization catalyzed by Zie-

gler-Natta systems, including lanthanide compounds.⁶³

Exp er im en ta l Section

Gen er a l P r oced u r e. All manipulations were performed

either on

a high-vacuum line in an all-glass apparatus

equipped with PTFE stopcocks or in an atmosphere of thor-

oughly purified argon using standard Schlenk techniques or

in a Vacuum Atmospheres drybox. The tetrahydrofuran and

ether used for synthesis (and THF-d₈for NMR measurements)

were purified by distillation over LiAlH₄and kept over sodium

benzophenone ketyl. Hydrocarbon solvents (including benzene-

d₆and toluene-d₈for NMR measurements) were distilled and

stored over CaH₂or Na/K alloy. Anhydrous YCl₃, TbCl₃, YbCl₃,

and LuCl₃were obtained from commercially available hydrates

(Reachim).⁶⁴The organosilicon hydrides PhSiH₃, ⁿC₆H₁₃SiH₃,

Ph₂SiH₂, PhMeSiH₂, ⁿBu₂SiH₂, Ph₃SiH, and Et₃SiH were

prepared from commercially available organochlorosilanes by

standard literature procedures.^{65 t}BuC₅H₅,⁶⁶Me₃SiC₅H₅,⁶⁷Ph₃-

Con clu sion s

68

SnH, Et₃SnH, Bu₃SnH, ⁿBu₂GeH₂, Et₃GeH,²⁹and PhMeSiD₂

In this paper, we have shown that the reaction of

lanthanide and yttrium hydrocarbyls with organosilicon

hydrides and alkoxy- and chlorosilanes, as well as with

other substituted silanes, is a very convenient and

selective route for the preparation of the corresponding

heterosubstituted organolanthanide and -yttrium com-

pounds, particularly those complexes that include vari-

ous bridging ligands, Cp′₂Ln(µ-L′)(µ-L”)LnCp′₂. This

method is important for the preparation of lanthanide

hydrides, which are known to be very active catalysts

for various transformations of organic and organoele-

ment substrates. Here, we have shown that the reac-

tion between lanthanide hydrocarbyls and silanes giving

the corresponding lanthanide hydrides must be a key

stage of the catalytic cycle of olefin hydrosilylation

catalyzed by organolanthanides. Marks⁶and our group^4,5

suggested this previously.

were prepared by the published methods. ^tBuC₅H₄Na and Me₃-

SiC₅H₄Na were prepared by the treatment of the corresponding

cyclopentadienes with NaH in THF. ¹H and ¹³C NMR spectra

were recorded with a Bruker AM 360 for 3-10% solutions in

deuterated solvents. The chemical shifts for the ¹H and ¹³C

NMR spectra were measured relative to TMS. MS measure-

ments were carried out on a MX-1321 spectrometer (E_i) 70

eV). C,H microanalyses were done using commercial equip-

ment for CHN microanalysis (Khimlaborpribor, Klin, Russia)

or a CHN-O-Rapid analyzer (Heracus). Lanthanide contents

were assayed by titration (EDTA, Xylenol Orange). Electron-

probe X-ray analysis were performed with a scanning electron

microscope SEM-505 (Phillips) equipped with a unit for X-ray

energy dispersive analysis (Edax).

{(^tBu C₅H₄)₂Y(µ-Me)}₂(1). A mixture of 5.89 g (30 mmol)

of YCl₃with 8.68 g (60 mmol) of Cp′Na in 150 mL of THF was

(62) Beletskaya, I. P.; Voskoboynikov, A. Z.; Chuklanova, E. B.;

Kirillova, N. I.; Shestakova, A. K.; Parshina, I. N.; Gusev, A. I.;

Magomedov, G. K.-I. J . Am. Chem. Soc. 1993, 115, 3156-3166.

(63) Mazzei, A. In Organometallics of the f-Elements; Marks, T. J .,

Fischer, R. D., Eds.; Reidel Publishing: Dordrecht, The Netherlands,

1979; pp 379-393. Bruzzone, M.; Carbonaro, A. In Fundamental and

Technological Aspects of Organo-f-Element Chemistry; Marks, T. J .,

Fragala, I. L., Eds.; Reidel Publishing: Dordrecht, The Netherlands,

1985; pp 387-400. Monakov, Y.-B.; Tolstikov, G. A. Kataliticheskaya

polimerizatsiya 1,3-dienov (Catalytic Polymerization of 1,3-dienes);

Nauka: Moscow, 1990.

(64) Handbuch der Praparativen Anorganischen Chemie; Brauer,

G., Ed.; Verlag: Stuttgart, 1981.

(65) Andrianov, K. A. Metody elementoorganicheskoy khimii. Krem-

nij (Methods of Organo-Element Chemistry. Silicon); Nauka: Moscow,

1968.

We have also shown that the reaction of lanthanide

hydrides with silanes that gives compounds with Ln-

Si bonding has an alternative pathway, i.e., hydride

exchange. Therefore, the corresponding dimeric lan-

thanide deuterides were prepared in the presence of

deuterosilanes. In a catalytic manner, this reactivity

enables carrying out H/D scrambling in silanes R₃SiH

and R′₃SiD. The dual behavior of lanthanide and

yttrium hydrides and hydrocarbyls toward organosilicon

hydrides is a dramatic example of how a relatively small

modification in the immediate metal environment can

influence the reactivity of early transition metal com-

plexes.

(66) Reimschneider, R.; Nehring, R. Monatsh. Chem. 1959, 90, 568-

570.

(67) Abel, E. W.; Dunster, M. O.; Waters, A. J . Organomet. Chem.

1973, 49, 287-321.

(68) Watanabe, H.; Ohsawa, N.; Sudo, T.; Hirakata, K.; Nagai, Y. J

Organomet. Chem. 1977, 128, 27-35.

(61) Nolan, S. P.; Stern, D.; Marks, T. J . J . Am. Chem. Soc. 1989,

111, 7844-7853.

4052 Organometallics, Vol. 16, No. 19, 1997

Voskoboynikov et al.

stirred for 24 h at ambient temperature. The solution formed

was cooled to -78 °C and treated with 17.9 mL of a 1.68 M

solution of MeLi in Et₂O. The reaction mixture was stirred

for 1 h at -78 °C. After slowly warming the mixture to

ambient temperature, it was evaporated to dryness. The

organolanthanide was extracted by hot toluene (150 mL) using

a special pressure filter (10-20 µ) funnel equipped with a

thermostated (70 °C) water jacket. The extract was evapo-

rated to dryness, and treatment with hot toluene (100 mL)

was repeated until complete decomposition of the ate com-

plexes. Then the solution was evaporated to ca. 30 mL. The

crystals that precipitated at -30 °C were separated, washed

with a minimal amount of cold toluene, and dried in vacuo.

Yield: 6.95 g (67%) of colorless crystals of 1, mp 199-202 °C

(dec). The complex can be purified by recrystallization from

Si), 28.69 (µ-Me), 113.67 (C2,5 in C₅H₄), 116.94 (C1 in C₅H₄),

121.02 (C3,4 in C₅H₄). MS: m/ z 928 (M⁺, 1.5), 449 ([0.5M -

CH₃]⁺, 100). Anal. Calcd for C₃₄H₅₈Lu₂Si₄: C, 45.95; H, 6.53;

Lu, 39.41. Found: C, 46.13; H, 6.67; Lu, 39.45. Electron probe

microanalysis: Lu:Si ) 1:2.

(^tBu C₅H₄)₂YMe(THF ) (6). A sample of 235 mg (0.34 mmol)

of 1 was dissolved in ca. 5 mL of THF. This mixture was

stirred for 15 min at ambient temperature and evaporated to

dryness. The residue was dried in vacuum for 2 h at ambient

temperature. Yield: 241 mg (95%) of the colorless solid of 6,

mp 80-82 °C (dec). ¹H NMR (THF-d₈): δ -0.99 (d, 3H, ²J _Y-H

t

) 2.1 Hz, YMe), 1.21 (s, 18H, Bu), 5.83 (t, 4H, J ) 2.7 Hz,

H2,5 in C₅H₄), 6.01 (t, 4H, J ) 2.9 Hz, H3,4 in C₅H₄). ¹³C NMR

1

(THF-d₈): δ 14.22 (d, J _Y-C) 53.3 Hz, YMe), 30.63 (CMe₃),

32.49 (CMe₃), 108.34 (C2,5 in C₅H₄), 108.59 (C3,4 in C₅H₄),

138.73 (C1 in C₅H₄). Anal. Calcd for C₂₃H₃₇YO: C, 66.03; H,

8.85; Y, 21.29. Found: C, 66.17; H, 8.92; Lu, 21.15.

(^tBu C₅H₄)₂TbMe(THF ) (7). The synthesis was carried out

similar to the preparation of compound 6, starting from 211

mg (0.25 mmol) of 2. Yield: 238 mg (96%) of a colorless solid

of 7, mp 76-78 °C (dec). Anal. Calcd for C₂₃H₃₇TbO: C, 56.55;

H, 7.58; Tb, 32.58. Found: C, 56.70; H, 7.69; Tb, 32.33.

(^tBu C₅H₄)₂YbMe(THF ) (8). The synthesis was carried out

similar to the preparation of compound 6, starting from 268

mg (0.31 mmol) of 3. Yield: 291 mg (93%) of a yellow-orange

solid of 8, mp 69-70 °C (dec). Anal. Calcd for C₂₃H₃₇YbO:

C, 54.98; H, 7.37; Yb, 34.46. Found: C, 55.14; H, 7.46; Yb,

34.20.

2

toluene. ¹H NMR (benzene-d₆): δ -0.47 (t, 6H, J _Y-H) 3.1

t

Hz, µ-Me), 1.36 (s, 36H, Bu), 6.15 (t, 8H, J ) 2.7 Hz, H2,5 in

C₅H₄), 6.50 (t, 8H, J ) 2.7 Hz, H3,4 in C₅H₄). ¹³C NMR

(benzene-d₆): δ 25.03 (t, ¹J _Y-C) 24.9 Hz, µ-Me), 30.17 (CMe₃),

32.52 (CMe₃), 110.04 (C2,5 in C₅H₄), 110.43 (C3,4 in C₅H₄),

137.32 (C1 in C₅H₄). MS: m/ z 692 (M⁺, 0.3), 331 ([0.5M -

CH₃]⁺, 100). Anal. Calcd for C₃₈H₅₈Y₂: C, 65.90; H, 8.38; Y,

25.72. Found: C, 66.07; H, 8.45; Y, 25.57.

{(^tBu C₅H₄)₂Tb(µ-Me)}₂(2). The reaction was carried out

similar to the preparation of compound 1, starting from 7.20

g (27 mmol) of TbCl₃, 7.80 g (54 mmol) of Cp′Na in 150 mL of

THF, and 16.1 mL of a 1.68 M solution of MeLi in Et₂O.

Yield: 6.70 g (59%) of colorless crystals of 2, mp 193-197 °C

(dec). MS: m/ z 832 (M⁺, 0.7), 401 ([0.5M - CH₃]⁺, 100). Anal.

Calcd for C₃₈H₅₈Tb₂: C, 54.81; H, 6.97; Tb, 38.22. Found: C,

54.97; H, 7.08; Tb, 38.01.

{(^tBu C₅H₄)₂Yb(µ-Me)}₂(3). The reaction was carried out

similar to the preparation of compound 1, starting from 5.40

g (19 mmol) of YbCl₃, 5.60 g (38 mmol) of Cp′Na in 150 mL of

THF, and 11.3 mL of a 1.68 M solution of MeLi in Et₂O.

Yield: 6.05 g (74%) of orange crystals of 3, mp 179-182 °C

(dec). MS: m/ z 860 (M⁺, 0.6), 415 ([0.5M - CH₃]⁺, 100). Anal.

Calcd for C₃₈H₅₈Yb₂: C, 53.02; H, 6.74; Yb, 40.23. Found: C,

53.21; H, 6.85; Yb, 40.05.

(^tBu C₅H₄)₂Lu Me(THF ) (9). The synthesis was carried out

similar to the preparation of compound 6, starting from 205

mg (0.24 mmol) of 4. Yield: 227 mg (95%) of a colorless solid

of 9, mp 69-71 °C (dec). ¹H NMR (THF-d₈): δ -0.87 (s, 3H,

t

LuMe), 1.27 (s, 18H, Bu), 5.81 (t, 4H, J ) 2.6 Hz, H2,5 in

C₅H₄), 5.99 (t, 4H, J ) 2.7 Hz, H3,4 in C₅H₄). ¹³C NMR (THF-

d₈): δ 19.20 (LuMe), 30.72 (CMe₃), 32.46 (CMe₃), 107.70 (C2,5

in C₅H₄), 108.29 (C3,4 in C₅H₄), 137.35 (C1 in C₅H₄). Anal.

Calcd for C₂₃H₃₇LuO: C, 54.76; H, 7.34; Lu, 34.72. Found:

C, 54.92; H, 7.40; Lu, 34.56.

(Me₃SiC₅H₄)₂Lu Me(THF ) (10). The synthesis was carried

out similar to the preparation of compound 6, starting from

241 mg (0.26 mmol) of 5. Yield: 267 mg (96%) of a colorless

solid of 10, mp 68-71 °C (dec). ¹H NMR (THF-d₈): δ -0.94

(s, 3H, LuMe), 0.21 (s, 18H, Me₃Si), 6.11 (t, 4H, J ) 2.5 Hz,

H2,5 in C₅H₄), 6.24 (t, 4H, J ) 2.5 Hz, H3,4 in C₅H₄). ¹³C NMR

(THF-d₈): δ 0.65 (SiMe₃), 18.67 (LuMe), 112.52 (C2,5 in C₅H₄),

118.34 (C1,3,4 in C₅H₄). Anal. Calcd for C₂₁H₃₇LuSi₂O: C,

47.01; H, 6.90; Lu, 32.65. Found: C, 47.20; H, 7.02; Lu, 32.53.

Electron probe microanalysis: Lu:Si ) 1:2.

{(^tBu C₅H₄)₂Lu (µ-Me)}₂(4). The reaction was carried out

similar to the preparation of compound 1, starting from 8.12

g (28 mmol) of LuCl₃, 8.31 g (58 mmol) of Cp′Na in 150 mL of

THF, and 16.7 mL of a 1.68 M solution of MeLi in Et₂O.

Yield: 9.07 g (59%) of colorless crystals of 4, mp 188-190 °C

(dec). ¹H NMR (benzene-d₆): δ -0.01 (s, 6H, µ-Me), 1.37 (s,

t

36H, Bu), 6.08 (t, 8H, J ) 2.7 Hz, H2,5 in C₅H₄), 6.50 (t, 8H,

J ) 2.8 Hz, H3,4 in C₅H₄). ¹³C NMR (benzene-d₆): δ 29.02

(µ-Me), 31.18 (CMe₃), 32.48 (CMe₃), 109.08 (C2,5 in C₅H₄),

110.88 (C3,4 in C₅H₄), 135.14 (C1 in C₅H₄). MS: m/ z 864 (M⁺,

0.4), 417 ([0.5M - CH₃]⁺, 100). Anal. Calcd for C₃₈H₅₈Lu₂:

C, 52.78; H, 6.71; Lu, 40.51. Found: C, 52.96; H, 6.89; Lu,

40.43.

{(^tBu C₅H₄)₂Y(µ-H)}₂(11). A mixture of 7.83 g (11.3 mmol)

of 1 with 4.51 g (37 mmol) of PhMeSiH₂in 150 mL of toluene

was stirred for 6 days at ambient temperature (or for 1 day at

ca. 40 °C). Then the mixture was evaporated to dryness. The

product was purified by recrystallization from hot hexane and

dried in vacuum. Yield: 3.82 g (88%) of colorless crystals of

11, mp 174-175 °C. ¹H NMR (benzene-d₆): δ 1.23 (s, 36H,

{(^tBu C₅H₄)₂Lu (µ-CD₃)}₂(4-d ). The reaction was carried

out similar to the preparation of compound 1, starting from

3.19 g (11 mmol) of LuCl₃, 3.15 g (22 mmol) of Cp′Na in 80

mL of THF, and 10.8 mL of a 1.02 M solution of CD₃Li in Et₂O.

Yield: 3.14 g (66%) of colorless crystals of 4-d , mp 187-190

°C (dec). The ¹H and ¹³C NMR spectra were the same as those

of 4, excluding the resonance attributed to the protons of the

µ-Me ligands. MS: m/ z 870 (M⁺, 0.5), 417 ([0.5M - CH₃]⁺,

100). Anal. Calcd for C₃₈H₅₂D₆Lu₂: C, 52.41; H/D, 7.36; Lu,

40.23. Found: C, 52.53; H/D, 7.29; Lu, 40.37.

{(Me₃SiC₅H₄)₂Lu (µ-Me)}₂(5). The reaction was carried

out similar to the preparation of compound 1, starting from

3.70 g (13 mmol) of LuCl₃, 4.20 g (27 mmol) of Cp′′Na in 70

mL of THF, and 7.7 mL of a 1.68 M solution of MeLi in Et₂O.

Recrystallization of the compound was performed using hot

hexane because of the high solubility of 5 in toluene. Yield:

3.64 g (63%) of colorless crystals of 5, mp 176-178 °C (dec).

¹H NMR (benzene-d₆): δ -0.19 (s, 6H, µ-Me), 0.38 (s, 36H,

Me₃Si), 6.33 (t, 8H, J ) 2.3 Hz, H2,5 in C₅H₄), 6.80 (t, 8H, J

) 2.3 Hz, H3,4 in C₅H₄). ¹³C NMR (benzene-d₆): δ 0.66 (Me₃-

1

^tBu), 3.09 (t, 2H, J _Y-H) 32.8 Hz, µ-H), 6.24 (t, 8H, J ) 2.7

Hz, H2,5 in C₅H₄), 6.78 (t, 8H, J ) 2.7 Hz, H3,4 in C₅H₄). ¹³C

NMR (benzene-d₆): δ 30.05 (CMe₃), 31.31 (CMe₃), 108.87 (C2,5

in C₅H₄), 108.96 (C3,4 in C₅H₄), 138.64 (C1 in C₅H₄). Anal.

Calcd for C₃₆H₅₄Y₂: C, 65.06; H, 8.13; Y, 26.81. Found: C,

65.21; H, 8.18; Y, 26.69.

{(^tBu C₅H₄)₂Y(µ-D)}₂(11-d ). The reaction was carried out

similar to the preparation of compound 11, starting from 1.31

g (1.9 mmol) of 1 and 0.94 g (7.6 mmol) of PhMeSiH₂in 30

mL of toluene. The reaction mixture was stirred for 6 h at 60

°C. Yield: 0.69 g (55%) of colorless crystals of 11-d , mp 172-

175 °C. ¹H and ¹³C NMR spectra were the same as those of

11, excluding the resonance attributed to the protons of the

µ-H ligands. Anal. Calcd for C₃₆H₅₂D₂Y₂: C, 64.86; H/D, 8.41;

Y, 26.73. Found: C, 65.02; H/D, 8.50; Y, 26.61.

{(^tBu C₅H₄)₂Tb(µ-H)}₂(12). The reaction was carried out

similar to the preparation of compound 11, starting from 3.16

Lanthanide and Yttrium Hydrides and Hydrocarbyls

Organometallics, Vol. 16, No. 19, 1997 4053

g (3.9 mmol) of 2 and 1.55 g (12.7 mmol) of PhMeSiH₂in 50

mL of toluene. The mixture was stirred for 12 days at ambient

temperature. Yield: 2.52 g (83%) of colorless crystals of 12,

mp 194-197 °C. Anal. Calcd for C₃₆H₅₄Tb₂: C, 53.73; H, 6.72;

Tb, 39.55. Found: C, 53.86; H, 6.80; Tb, 39.41.

{(^tBu C₅H₄)₂Yb(µ-H)}₂(13). The reaction was carried out

similar to the preparation of compound 11, starting from 4.07

g (4.7 mmol) of 3 and 2.05 g (19 mmol) of PhSiH₃in 70 mL of

toluene. The mixture was stirred for 5 days at ambient

temperature. Yield: 3.07 g (78%) of orange crystals of 13, mp

214-216 °C. Anal. Calcd for C₃₆H₅₄Yb₂: C, 51.92; H, 6.49;

Yb, 41.59. Found: C, 52.14; H, 6.56; Yb, 41.50.

(^tBu C₅H₄)₂Lu (µ-H)(µ-Me)Lu (C₅H₄^tBu )₂(17): Meth od A.

The reaction was carried out similar to the preparation of

compound 16 (method A), starting from 3.62 g (4.2 mmol) of 4

and 0.51 g (4.2 mmol) of PhMeSiH₂in 100 mL of toluene. The

reaction mixture was stirred for 3 days at ambient tempera-

ture. Yield: 2.88 g (81%) of colorless crystals of 17, mp 189-

190 °C (dec). ¹H NMR (benzene-d₆):⁶⁹δ -0.25 (t, 3H, µ-Me),

t

1.31 (s, 36H, Bu), 5.82 (s, 1H, µ-H), 6.03 (q, 4H, J ) 3.0 Hz,

J ) 5.6 Hz, H5 in C₅H₄), 6.29 (q, 4H, J ) 2.8 Hz, J ) 5.5 Hz,

H2 in C₅H₄), 6.50 (q, 4H, J ) 2.4 Hz, J ) 5.1 Hz, H3 in C₅H₄),

6.76 (q, 4H, J ) 2.4 Hz, J ) 5.1 Hz, H4 in C₅H₄). ¹³C NMR

(benzene-d₆):⁶⁹δ 30.03 (µ-Me), 31.92 (CMe₃), 32.26 (CMe₃),

107.16 (C5 in C₅H₄), 109.00 (C2 in C₅H₄), 109.97 (C3 in C₅H₄),

110.21 (C4 in C₅H₄), 136.92 (C1 in C₅H₄). Anal. Calcd for

{(^tBu C₅H₄)₂Lu (µ-H)}₂(14). The reaction was carried out

similar to the preparation of compound 11, starting from 6.78

g (7.8 mmol) of 4 and 3.35 g (31 mmol) of PhSiH₃in 150 mL

of toluene. The mixture was stirred for 5 days at ambient

temperature. Yield: 4.88 g (74%) of colorless crystals of 14,

C

₃₇H₅₆Lu₂: C, 52.24; H, 6.59; Lu, 41.18. Found: C, 52.30; H,

6.52; Lu, 41.29.

Meth od B. The synthesis was carried out similar to the

preparation of compound 16 (method B), starting from 1.12 g

(1.30 mmol) of 4 and 1.08 g (1.30 mmol) of 14 in 50 mL of

toluene. The reaction mixture was stirred for 7 days at

ambient temperature. Yield: 0.97 g (44%). Anal. Found: C,

52.39; H, 6.65; Lu, 41.02.

t

mp 227-229 °C. ¹H NMR (benzene-d₆): δ 1.21 (s, 36H, Bu),

5.91 (s, 2H, µ-H), 6.17 (t, 8H, J ) 2.6 Hz, H2,5 in C₅H₄), 6.79

(t, 8H, J ) 2.6 Hz, H3,4 in C₅H₄). ¹³C NMR (benzene-d₆): δ

30.03 (CMe₃), 31.33 (CMe₃), 108.04 (C2,5 in C₅H₄), 109.34 (C3,4

in C₅H₄), 136.91 (C1 in C₅H₄). Anal. Calcd for C₃₆H₅₄Lu₂: C,

51.67; H, 6.46; Lu, 41.87. Found: C, 51.71; H, 6.44; Lu, 41.95.

{(Me₃SiC₅H₄)₂Lu (µ-H)}₂(15). The reaction was carried

out similar to the preparation of compound 11, starting from

2.32 g (2.6 mmol) of 5 and 1.14 g (10.6 mmol) of PhSiH₃in 50

mL of toluene. The mixture was stirred for 5 days at ambient

temperature. The product was recrystallized from pentane.

Yield: 1.00 g (44%) of colorless crystals of 15, mp 219-222

°C. ¹H NMR (benzene-d₆): δ 0.25 (s, 36H, Me₃Si), 5.80 (s, 2H,

µ-H), 6.47 (t, 8H, J ) 2.3 Hz, H2,5 in C₅H₄), 7.19 (t, 8H, J )

2.4 Hz, H3,4 in C₅H₄). ¹³C NMR (benzene-d₆): δ -0.31 (Me₃-

Si), 112.52 (C2,5 in C₅H₄), 119.57 (C3,4 in C₅H₄), 121.04 (C1

in C₅H₄). Anal. Calcd for C₃₂H₅₄Lu₂Si₄: C, 42.67; H, 6.00; Lu,

38.89. Found: C, 42.91; H, 6.14; Lu, 38.77. Electron probe

microanalysis: Lu:Si ) 1:2.

(Me₃SiC₅H₄)₂Lu (µ-H)(µ-Me)Lu (C₅H₄SiMe₃)₂(18): Meth od

A. The reaction was carried out similar to the preparation of

compound 16 (method A), starting from 2.85 g (3.1 mmol) of 5

and 0.37 g (3.1 mmol) of PhMeSiH₂in 50 mL of toluene. The

reaction mixture was stirred for 6 days at ambient tempera-

ture. Yield: 1.71 g (61%) of colorless crystals of 18, mp 174-

175 °C (dec). ¹H NMR (benzene-d₆):⁶⁹δ -0.38 (s, 3H, µ-Me),

0.34 (s, 36H, Me₃Si), 5.65 (s, 1H, µ-H), 6.28 (q, 4H, H5 in C₅H₄),

6.58 (q, 4H, H2 in C₅H₄), 6.86 (q, 4H, H3 in C₅H₄), 7.10 (q, 4H,

H4 in C₅H₄). ¹³C NMR (benzene-d₆):⁶⁹δ 0.42 (Me₃Si), 32.60

(µ-Me), 112.22 (C5 in C₅H₄), 113.96 (C2 in C₅H₄), 119.15 (C3

in C₅H₄), 120.31 (C4 in C₅H₄), 120.59 (C1 in C₅H₄). Anal. Calcd

for C₃₁H₅₂Lu₂Si₄: C, 40.70; H, 5.69; Lu, 38.29. Found: C,

40.91; H, 5.80; Lu, 38.15. Electron probe microanalysis: Lu:

Si ) 1:2.

(^tBu C₅H₄)₂Y(µ-H)(µ-Me)Y(C₅H₄^tBu )₂(16): Meth od A. A

mixture of 5.20 g (7.5 mmol) of 1 with 0.92 g (7.5 mmol) of

PhMeSiH₂in 70 mL of toluene was stirred for 1 day at ambient

temperature. Then the mixture was evaporated to dryness.

The crude product was treated with 250 mL of pentane. The

solution was evaporated to ca. 100 mL. The crystals that

precipitated at -30 °C were separated, washed with a minimal

amount of cold pentane, and dried in vacuo. Yield: 2.85 g

(56%) of colorless crystals of 16, mp 198-200 °C (dec). ¹H

Meth od B. The synthesis was carried out similar to the

preparation of compound 16 (method B), starting from 1.36 g

(1.47 mmol) of 5 and 1.32 g (1.47 mmol) of 15 in 50 mL of

toluene. The reaction mixture was stirred for 5 days at

ambient temperature. Yield: 0.75 g (28%). Anal. Found: C,

40.84; H, 5.60; Lu, 38.09.

{(^tBu C₅H₄)₂Y(µ-H)(THF )}₂(19). A sample of 314 mg (0.47

mmol) of 11 was dissolved in 5 mL of THF and stirred for 0.5

h at ambient temperature. Then the mixture was evaporated,

and the solid was dried in vacuo for 2 h. Yield: 337 mg (97%)

of colorless crystals of 19, mp 151-152 °C. ¹H NMR (THF-

2

NMR (benzene-d₆):⁶⁹δ -0.73 (t, 3H, J _Y-H) 3.3 Hz, µ-Me),

t

1

1.32 (s, 36H, Bu), 3.00 (t, 1H, J _Y-H) 36.0 Hz, µ-H), 6.11 (s,

4H, line width (lw) ) 25 Hz, H5 in C₅H₄), 6.39 (s, 4H, lw ) 25

Hz, H2 in C₅H₄), 6.54 (s, 4H, lw ) 25 Hz, H3 in C₅H₄), 6.76 (s,

4H, lw ) 25 Hz, H4 in C₅H₄). ¹³C NMR (benzene-d₆):⁶⁹δ 26.34

(t, ¹J _Y-C) 25.8 Hz, µ-Me), 30.18 (CMe₃), 32.26 (CMe₃), 108.66

(lw ) 35 Hz, C5 in C₅H₄), 109.54 (lw ) 35 Hz, C2 in C₅H₄),

110.27 (lw ) 35 Hz, C3 in C₅H₄), 111.84 (lw ) 35 Hz, C4 in

C₅H₄), 134.40 (lw ) 35 Hz, C1 in C₅H₄). Anal. Calcd for

t

1

d₈): δ 1.25 (s, 36H, Bu), 2.64 (t, 2H, J _Y-H) 29.3 Hz, µ-H),

6.02 (t, 8H, J ) 2.6 Hz, H2,5 in C₅H₄), 6.34 (t, 8H, J ) 2.6 Hz,

H3,4 in C₅H₄). ¹³C NMR (THF-d₈): δ 30.61 (CMe₃), 32.35

(CMe₃), 107.13 (C2,5 in C₅H₄), 108.93 (C3,4 in C₅H₄), 134.09

(C1 in C₅H₄). Anal. Calcd for C₄₀H₆₂Y₂O: C, 65.22; H, 8.42;

Y, 24.18. Found: C, 65.11; H, 8.37; Y, 24.26.

{(^tBu C₅H₄)₂Y(µ-Cl)}₂(22): Meth od A. A mixture of 3.14

g (16 mmol) of YCl₃with 4.63 g (32 mmol) of Cp′Na in 100 mL

of THF was stirred for 24 h at ambient temperature. Then

the mixture was evaporated to dryness. The crude product

was extracted by hot toluene (100 mL) using a special pressure

filter (10-20 µ) funnel equipped with a thermostated (70 °C)

water jacket. The extract was evaporated to ca. 30 mL. The

crystals that precipitated at -30 °C were separated, washed

with a minimal amount of cold toluene, and dried in vacuo.

Yield: 4.84 g (82%) of colorless crystals of 22, mp 201-203

°C. The complex can be purified by the recrystallization from

C

₃₇H₅₆Y₂: C, 65.49; H, 8.26; Y, 26.25. Found: C, 65.57; H,

8.34; Y, 26.07.

Meth od B. A mixture of 1.31 g (1.89 mmol) of 1 with 1.64

g (1.90 mmol) of 11 in 50 mL of toluene was stirred for 5 days

at ambient temperature. The treatment of the solution

obtained was carried out similar to the procedure described

in method A. Yield: 0.95 g (37%) of 16. Anal. Found: C,

65.61; H, 8.31; Y, 26.11.

(69) The assignment of the ¹H and ¹³C resonances of the ring nucleus

t

of the RC₅H₄-η⁵ligands, where R ) Bu, and Me₃Si in the complexes

with Ln(µ-X)(µ-Y)Ln bridging is according to the following scheme

t

toluene. ¹H NMR (toluene-d₈): δ 1.38 (s, 36H, Bu), 6.30 (t,

8H, J ) 2.5 Hz, H2,5 in C₅H₄), 6.52 (t, 8H, J ) 2.5 Hz, H3,4

in C₅H₄). ¹³C NMR (toluene-d₈): δ 30.09 (CMe₃), 32.94 (CMe₃),

111.15 (C2,5 in C₅H₄), 113.70 (C3,4 in C₅H₄), 138.36 (C1 in

C₅H₄). Anal. Calcd for C₃₆H₅₂Cl₂Y₂: C, 58.94; H, 7.09; Y,

24.28. Found: C, 59.07; H, 7.14; Y, 24.20. Electron probe

microanalysis: Y:Cl ) 1:1.

4054 Organometallics, Vol. 16, No. 19, 1997

Voskoboynikov et al.

Meth od B. A solution of 0.76 g (7.0 mmol) of Me₃SiCl in

10 mL of toluene was added dropwise to a solution of 2.41 g

(3.5 mmol) of 1 in 50 mL of toluene at -20 °C. The reaction

mixture was stirred at this temperature for 1 h. After slow

warming the mixture to ambient temperature, it was stirred

for 2 h and then evaporated to dryness. The product was

crystallized from hot toluene. Yield: 2.31 g (90%). Anal.

Found: C, 59.00; H, 7.13; Y, 24.17.

{(^tBu C₅H₄)₂Lu (µ-Cl)}₂(23): Meth od A. The reaction was

carried out similar to the preparation of compound 22 (method

A), starting from 2.35 g (8.3 mmol) of LuCl₃and 2.40 g (16.7

mmol) of Cp′Na in 50 mL of THF. Yield: 2.93 g (78%) of

colorless crystals of 23, mp 237-238 °C. ¹H NMR (benzene-

d₆): δ 1.38 (s, 36H, ^tBu), 6.25 (t, 8H, J ) 2.7 Hz, H2,5 in C₅H₄),

6.54 (t, 8H, J ) 2.7 Hz, H3,4 in C₅H₄). ¹³C NMR (benzene-

d₆): δ 29.85 (CMe₃), 32.05 (CMe₃), 110.34 (C2,5 in C₅H₄),

111.82 (C3,4 in C₅H₄), 138.81 (C1 in C₅H₄). Anal. Calcd for

mixture was stirred at this temperature for 0.5 h. After slowly

warming the mixture to ambient temperature, it was evapo-

rated to dryness. Purification of the product was carried out

as described in method A. Yield: 2.08 g (59%). Anal.

Found: C, 51.03; H, 6.58; Lu, 38.89.

(^tBu C₅H₄)₂Y(µ-Me)(µ-OMe)Y(C₅H₄^tBu )₂(27). A mixture

of 2.24 g (3.2 mmol) of 1 and 0.49 g (3.2 mmol) of (MeO)₄Si in

50 mL of toluene was stirred for 30 min at ambient temper-

ature. The solution was immediately evaporated to dryness.

The residue was recrystallized with hot toluene. The crystals

that precipitated at -30 °C were separated, washed with cold

toluene, and then dried in vacuo. Yield: 1.63 g (71%) of

colorless crystals of 27, mp 181-183 °C (dec). ¹H NMR

2

(benzene-d₆):⁶⁹δ -0.42 (t, 3H, J _Y-H) 3.4 Hz, µ-Me), 1.39 (s,

t

36H, Bu), 3.12 (s, 3H, OMe), 6.05 (q, 4H, J ) 3.0 Hz, J ) 5.5

Hz, H5 in C₅H₄), 6.25 (q, 4H, J ) 2.8 Hz, J ) 5.6 Hz, H2 in

C₅H₄), 6.39 (q, 4H, J ) 2.5 Hz, J ) 5.1 Hz, H3 in C₅H₄), 6.53

(q, 4H, J ) 2.4 Hz, J ) 5.3 Hz, H4 in C₅H₄). ¹³C NMR

(benzene-d₆):⁶⁹δ 20.23 (t, ¹J _Y-C) 26.1 Hz, µ-Me), 30.37 (CMe₃),

32.53 (CMe₃), 53.84 (OMe), 109.47 (C5 in C₅H₄), 109.62 (C2 in

C₅H₄), 110.17 (C3 in C₅H₄), 111.23 (C4 in C₅H₄), 138.10 (C1 in

C₅H₄). Anal. Calcd for C₃₈H₅₈Y₂O: C, 64.41; H, 8.19; Y, 25.14.

Found: C, 64.60; H, 8.28; Y, 24.98.

C

₃₆H₅₂Cl₂Lu₂: C, 47.73; H, 5.75; Lu, 38.67. Found: C, 47.81;

H, 5.79; Lu, 38.60. Electron probe microanalysis: Lu:Cl ) 1:1.

Meth od B. The synthesis was carried out similar to the

preparation of compound 22 (method B), starting from 0.33 g

(3.0 mmol) of Me₃SiCl and 1.30 g (1.5 mmol) of 4 in 50 mL of

toluene. Yield: 1.15 g (84%). Anal. Found: C, 47.90; H, 5.87;

Lu, 38.52.

(^tBu C₅H₄)₂Lu (µ-Me)(µ-OMe)Lu (C₅H₄^tBu )₂(28). The re-

action was carried out similar to the preparation of compound

27, starting from 3.43 g (4.0 mmol) of 4 and 0.60 g (8.0 mmol)

of (MeO)₄Si in 100 mL of toluene. The solution was stirred

for 6 h at ambient temperature. Yield: 2.86 g (82%) of

colorless crystals of 28, mp 228-230 °C (dec). ¹H NMR

(^tBu C₅H₄)₂Y(µ-H)(µ-Cl)Y(C₅H₄^tBu )₂(24). A mixture of

2.07 g (3.1 mmol) of 11 with 2.28 g (3.1 mmol) of 22 in 100 mL

of toluene was stirred for 2 h at 70 °C. Then the mixture was

evaporated to ca. 30 mL. The crystals that precipitated at -30

°C were separated and recrystallized from a minimal amount

of hot toluene. The product was dried in vacuo. Yield: 2.78

t

(benzene-d₆):⁶⁹δ -0.02 (s, 3H, µ-Me), 1.41 (s, 36H, Bu), 3.08

g (64%) of colorless crystals of 24, mp 157-158 °C(dec). ¹H

(s, 3H, OMe), 6.01 (q, 4H, J ) 3.0 Hz, J ) 5.6 Hz, H5 in C₅H₄),

6.22 (q, 4H, J ) 2.9 Hz, J ) 5.5 Hz, H2 in C₅H₄), 6.41 (q, 4H,

J ) 2.4 Hz, J ) 5.2 Hz, H3 in C₅H₄), 6.54 (q, 4H, J ) 2.5 Hz,

J ) 5.3 Hz, H4 in C₅H₄). ¹³C NMR (benzene-d₆):⁶⁹δ 23.00 (µ-

Me), 31.00 (CMe₃), 32.52 (CMe₃), 54.06 (OMe), 108.54 (C5 in

C₅H₄), 109.78 (C2 in C₅H₄), 110.39 (C3 in C₅H₄), 110.64 (C4 in

C₅H₄), 136.38 (C1 in C₅H₄). Anal. Calcd for C₃₈H₅₈Lu₂O: C,

51.82; H, 6.59; Lu, 39.77. Found: C, 51.87; H, 6.48; Lu, 39.65.

{(^tBu C₅H₄)₂Y(µ-OMe)}₂(30). The synthesis was carried

out similar to the preparation of compound 26 (method A),

starting from 1.66 g (2.3 mmol) of 1 and 0.70 g (4.6 mmol) of

(MeO)₄Si in 50 mL toluene. Yield: 1.44 g (83%) of colorless

crystals of 30, mp 186-187 °C. ¹H NMR (benzene-d₆): δ 1.43

t

NMR (benzene-d₆):⁶⁹δ 1.31 (s, 36H, Bu), 2.95 (t, 1H,¹J _Y-H

)

33.5 Hz, µ-H), 6.17 (q, 4H, J ) 3.0 Hz, J ) 5.6 Hz, H5 in C₅H₄),

6.37 (q, 4H, J ) 2.9 Hz, J ) 5.5 Hz, H2 in C₅H₄), 6.57 (q, 4H,

J ) 2.4 Hz, J ) 5.0 Hz, H3 in C₅H₄), 6.76 (q, 4H, J ) 2.4 Hz,

J ) 5.1 Hz, H4 in C₅H₄). ¹³C NMR (benzene-d₆):⁶⁹δ 30.02

(CMe₃), 31.87 (CMe₃), 108.63 (C5 in C₅H₄), 109.50 (C2 in C₅H₄),

110.28 (C3 in C₅H₄), 111.81 (C4 in C₅H₄), 140.00 (C1 in C₅H₄).

Anal. Calcd for C₃₆H₅₃ClY₂: C, 61.85; H, 7.59; Y, 25.48.

Found: C, 61.90; H, 7.63; Y, 25.39. Electron probe mi-

croanalysis: Y:Cl ) 2:1.

(^tBu C₅H₄)₂Lu (µ-H)(µ-Cl)Lu (C₅H₄^tBu )₂(25). The reaction

was carried out similar to the preparation of compound 24,

starting from 1.89 g (2.3 mmol) of 14 and 2.05 g (2.3 mmol) of

23 in 70 mL of toluene. Yield: 2.92 g (74%) of colorless crystals

of 25, mp 210-212 °C (dec). ¹H NMR (benzene-d₆):⁶⁹δ 1.30

t

(s, 36H, Bu), 3.32 (s, 6H, OMe), 6.17 (t, 8H, J ) 2.9 Hz, H2,5

in C₅H₄), 6.47 (t, 8H, J ) 2.8 Hz, H3,4 in C₅H₄). ¹³C NMR

(benzene-d₆): δ 30.16 (CMe₃), 32.61 (CMe₃), 54.28 (OMe),

109.76 (C2,5 in C₅H₄), 110.69 (C3,4 in C₅H₄), 138.26 (C1 in

C₅H₄). Anal. Calcd for C₃₈H₅₈Y₂O₂: C, 62.90; H, 8.01; Y, 24.59.

Found: C, 63.07; H, 8.10; Y, 24.51.

t

(s, 36H, Bu), 5.56 (s, 1H, µ-H), 6.14 (q, 4H, J ) 2.9 Hz, J )

5.5 Hz, H5 in C₅H₄), 6.28 (q, 4H, J ) 2.9 Hz, J ) 5.5 Hz, H2

in C₅H₄), 6.56 (q, 4H, J ) 2.4 Hz, J ) 5.1 Hz, H3 in C₅H₄),

6.81 (q, 4H, J ) 2.4 Hz, J ) 5.0 Hz, H4 in C₅H₄). ¹³C NMR

(benzene-d₆):⁶⁹δ 30.16 (CMe₃), 31.94 (CMe₃), 108.17 (C5 in

C₅H₄), 108.89 (C2 in C₅H₄), 110.70 (C3 in C₅H₄), 111.32 (C4 in

C₅H₄), 138.07 (C1 in C₅H₄). Anal. Calcd for C₃₆H₅₃ClLu₂: C,

49.63; H, 6.09; Lu, 40.21. Found: C, 49.78; H, 6.01; Lu, 40.18.

Electron probe microanalysis: Lu:Cl ) 2:1.

Deh yd r ogen a tive Cou p lin g of ⁿBu ₃Sn H. A mixture of

2.80 mL (3.03 g, 10.4 mmol) of ⁿBu₃SnH and 70 mg (0.11 mmol)

of 1 in 5 mL of benzene was stirred for 0.5 h at 70 °C. Vigorous

gas evolution was observed. The reaction mixture was frac-

tionated. This procedure yielded 2.75 g (91%) of hexabu-

tylditin, bp 136-139 °C/0.5 mmHg, n²⁰) 1.5133. ¹³C NMR

D

{(^tBu C₅H₄)₂Lu (µ-OMe)}₂(26): Meth od A. A mixture of

1.17 g (1.31 mmol) of 4 and 0.40 g (2.62 mmol) of (MeO)₄Si in

50 mL of toluene was stirred for 5 days at ambient tempera-

ture. The solution was evaporated to dryness. The crude

product was recrystallized from hot toluene. The crystals that

precipitated at 30 °C were separated, washed with cold

toluene, and then dried in vacuo. Yield: 1.04 g (86%) of

colorless crystals of 26, mp 230-232 °C. ¹H NMR (benzene-

(CDCl₃): δ 10.04 (C1), 27.57 (C3), 29.42 (C2), 30.74 (C4).

Dehydrogenative coupling of Et₃SnH was carried out in a

similar manner.

X-r a y Cr yst a l An a lysis of Com p lex 2. X-ray data

acquisition was accomplished with a single crystal of 2 packed

in thin-walled glass capillary under argon. Crystallographic

data are given in Table 3. An empirical absorption correction

based on three Ψ scans was used to fit the data. The structure

was solved using the heavy-atom technique and refined by the

anisotropic least-squares procedure. Hydrogen atoms were

located from the difference Fourier synthesis. All computa-

tions were run with the SHELXS-86 software package⁷⁰on

an IBM PC AT.

t

d₆): δ 1.45 (s, 36H, Bu), 3.28 (s, 6H, OMe), 6.15 (t, 8H, J )

2.8 Hz, H2,5 in C₅H₄), 6.51 (t, 8H, J ) 2.7 Hz, H3,4 in C₅H₄).

¹³C NMR (benzene-d₆): δ 29.83 (CMe₃), 32.50 (CMe₃), 54.43

(OMe), 109.78 (C2,5 in C₅H₄), 110.31 (C3,4 in C₅H₄), 136.64

(C1 in C₅H₄). Anal. Calcd for C₃₈H₅₈Lu₂O₂: C, 50.89; H, 6.47;

Lu, 39.06. Found: C, 50.94; H, 6.51; Lu, 39.01.

Meth od B. A solution of 0.25 g (7.8 mmol) of MeOH in 5

mL of toluene was added dropwise to a solution of 3.40 g (3.9

mmol) of 4 in 70 mL of toluene at -78 °C. The reaction

X-r a y Cr ysta l An a lysis of Com p lex 28. Details of the

X-ray experiment and crystallographic parameters are given

(70) Sheldrick, G. M. Acta Crystallogr. 1990, A46, 467-473.

Lanthanide and Yttrium Hydrides and Hydrocarbyls

Organometallics, Vol. 16, No. 19, 1997 4055

Ta ble 3. Cr ysta llogr a p h ic Da ta for Com p lexes 2

a n d 28

Com p u ta tion a l Deta ils. All quantum-chemical calcula-

tions were carried out with the use of the semiempirical

ZINDO/1 method⁵⁴implemented in the program package

HyperChem release 4.0.⁷³Assumptions were made in all cases

that the forward and reverse reactions in eqs 17 and 18

proceed via the same four-centered transition states (the

microreversability principle). Every transition state was

supposed to be preceded and followed along the reaction

coordinate by bimolecular encounter complexes, the energies

of which in the gas phase were considered to be lower than

those of the free reagents for both the forward and back

reactions. Geometry optimization (RHF) for the lowest states

of all complexes studied in vacuum was performed using either

the Polak-Ribiere algorithm down to a gradient value of 0.01

kcal Å^-1mol^-1for the encounter complexes or the steepest

descent algorithm down to the 0.1 kcal Å^-1mol^-1gradient

value for the transition states. The transition states were

identified following the procedures described in the Supporting

Information. No restrictions were imposed on the geometry

of the metallocene fragment. A separate study showed that

the optimization down to the gradient 0.1 kcal Å^-1mol^-1is

insufficient for finding out the true conformation of the

metallocene fragment, the appropriate value being 0.02-0.03

kcal Å^-1mol^-1. However, the bond lengths and angles of the

moiety involved in the bond transposition process as well as

the total energy of the system turned out to be affected little

by the further improvement of the geometry that is machine-

time consuming. The orbital sketches for molecules and their

fragments were drawn employing the possibilities provided by

the software package HyperChem release 4.0.⁷³The computa-

tions were performed with an IBM PC AT.

2

28

formula

fw

F(000)

space group

a, Å

b, Å

c, Å

â, deg

C₃₈H₅₈Tb₂

C₃₈H₅₅Lu₂O

877.76

1732

832.73

1664

a

B_bam

C2/c

9.414(2)

16.456(2)

23.009(3)

90

16

3564(1)

1.55

18.621(3)

23.774(2)

9.140(1)

118.032(1)

4

Z

V, Å³

3571.5(6)

1.632

d (calcd), g‚cm^-3

diffractometer

radiation

Enraf-Nonius CAD-4 Siemens SMART

Mo KR (λ ) 0.710 73 Å)

µ, cm^-1(Mo KR)

T, K

40.0

55.22

150

296

scan method

θ limits (deg)

no. of unique reflns;

total with I₀> 2σ(I)

no. of params refined

R^b

ω-2θ

ω

2 e θ e 25

1191, 825

1.51 e θ e 25.50

3304, 3060

93

0.0211

186

0.0574

a

C_mcaspace group in the standard classification.

in Table 3. The experimental reflections were collected on a

Siemens three-circle diffractometer with a CCD area detector.

Experimental frames were integrated using a three-dimen-

sional Lehman-Larsen algorithm. The structure was solved

by the heavy-atom method. Both Lu atoms of the molecule

are situated at the 2-fold axis. In the space group found (C2/

c), the positions of metals resulted in disorder of the CH₃and

OMe bridges between the positions occupied. As a result, in

the difference Fourier synthesis, three partly overlapping

peaks of electron density were found in the area of the bridging

groups. These peaks were included in further calculations as

corresponding to oxygen and carbon atoms of the bridging

groups with site occupation factors equal to 0.5. This struc-

tural model was refined in the anisotropic approximation for

all non-hydrogen atoms except for those of the bridging groups.

The bridging group atoms were refined isotropically. Hydro-

gen atoms of non-bridging groups were calculated in their ideal

positions and included in the refinement as riding on the

corresponding carbon atoms with B(iso) equal to 1.5B(eq) for

the corresponding carbon atoms. An alternative possibility

noncentrocymmetric space group (C_c) was also checked. How-

ever, disordered positions of the two bridging groups were

found in this group as well. Moreover, least-squares refine-

ment of the structure in the C_cspace group resulted in

nonpositive definition for many carbon atoms. These observa-

tions show that the first model is the correct one. In the

difference Fourier synthesis, the highest electron density peaks

are located in the vicinity of the heavy atoms. Their rather

high value (Table 3) is probably due to the poor quality of the

single crystal and the disorder, which results in partial

superposition of three electron density peaks corresponding

to the bridge group atoms. All the calculations were performed

using the SHELXS-86⁷⁰and SHELXL-93⁷¹software. The

SHELXTL-Plus molecular graphics program⁷²was used for

drawing the molecule (a thermal ellipsoid probability equal

to 0.5 was taken).

Ack n ow led gm en t. This work was generously sup-

ported by the Russian Foundation for Basic Research

(Grant No. 95-03-09658). The authors thank the Inter-

national Science Foundation (Grant No. MRR000) and

this Foundation and Russian Government (Grant No.

MRR300) for their support. We thank Dr. O. J ust and

Prof. Dr. H. Schumann from Technische Universita¨t

Berlin who performed the synthesis and kindly supplied

us with a sample of HGa(CH₂CH₂CH₂)₂NMe. We are

also grateful to Dr. E. B. Chuklanova and Dr. A. I.

Gusev who carried out the X-ray diffraction study

of 2.

Su p p or tin g In for m a tion Ava ila ble: Tables of positional

and thermal parameters, bond lengths, bond angles, aniso-

tropic displacement parameters, and hydrogen coordinates for

2 and 28, text giving computational analysis data, calculation

parameters, energies and gradient, atomic orbital electron

populations, and net charges and coordinates for the corre-

sponding encounter complexes and transition states as well

as for H₂, CH₄, SiH₄, H₃CSiH₃, and Si₂H₆, and energy profile

diagrams (75 pages). Ordering information is given on any

current masthead page.

OM970363G

(72) Sheldrick, G. M. SHELXTL-Plus, Release 4.1; Siemens Analyti-

cal X-ray Instruments Inc.: Madison, WI, 1991.

(73) HyperChem Release 4 for Windows, Molecular Modeling System;

Hypercube, Inc., 1994.

(71) Sheldrick, G. M. SHELX93, Program for Refinement of Crystal

Structure; University of Go¨ttingen: Go¨ttingen, Germany, 1993.

Article Doi

Reactivity of lanthanide and yttrium hydrides and hydrocarbyls toward organosilicon hydrides and related compounds

DOI: 10.1021/om970363g

Source and publish data:

Authors:

Article abstract of DOI:10.1021/om970363g

Full text of DOI:10.1021/om970363g

Products guided by the article

R&D Labs maybe for 813-19-4

Relevant to this article

Hot Product