Chlorosilyl-substituted monocyclopentadienyl niobium chloro, imido chloro, and benzyl complexes. X-ray molecular structure of [{(NbCl2)2(μ-O)(μ-Cl)2}{(η 5-C5H4)2(Me2SiOSiMe 2)}]

Article abstract of DOI:10.1021/om970876n

We report the synthesis of 1-(chloromethylphenylsilyl)cyclopentadiene. The reaction of a toluene/CH₂Cl₂ suspension of NbCl₅ with 1-(SiClMeX)-1-(SiMe₃)C₅H₄ (X = Me, Ph) leads to the monocyclopentadienyl derivatives [M{η⁵-C₅H₄(SiClMeX)}Cl₄] (X = Me, Ph) in 90 and 78% yields, respectively. Reaction of 1 equiv of water with [M{η⁵-C₅H₄(SiClMe₂)}Cl ₄] in toluene takes place with elimination of HCl, resulting in formation of the dinuclear niobium oxo derivative [{(NbCl₂)₂(μ-O)(μ-Cl)₂}{(η ⁵-C₅H₄)₂(Me₂SiOSiMe ₂)}]. Reaction of the complexes [M{η⁵-C₅H₄(SiClMeX)}Cl₄] with LiNH^tBu and NEt₃ in toluene leads to the half-sandwich imido complexes [Nb{η⁵-C⁵H⁴(SiClMeX)}Cl₂(N ^tBu)] (X = Me, Ph), which react at room temperature with 1 equiv of Mg(CH₂Ph)₂(THF)₂ to give the imido dibenzyl complexes [Nb-{η⁵-C₅H₄(SiClMeX)}(CH ₂Ph)₂(N^tBu)] (X = Me, Ph). The reaction of the chloro imido complexes [Nb{η⁵-C₅H₄(SiClMeX)}Cl₂(N ^tBu)] with excess Mg(CH₂Ph)₂(THF)₂ on heating for 2-3 days to 80-90 and 50-60°C, respectively, takes place, affording the totally alkylated complexes [Nb{η⁵-C₅H₄[Si(CH ₂Ph)MeX]}(CH₂Ph)₂(N^tBu)] (X = Me, Ph). The chloro benzyl derivative [Nb{η⁵-C₅H₄(SiClMe₂)}(CH ₂Ph)Cl(N^tBu)], which could not be prepared by addition of the stoichiometric amount of the alkylating agent, was isolated in quantitative yield by heating a mixture of the dichloro and dibenzyl complexes in toluene at 120°C for 4 h. The 18-electron imido η²-iminoacyl derivatives [Nb{η⁵-C₅H₄(SiMeXY)}R(N ^tBu){η²-C(CH₂Ph)=N-(2,6-Me ₂C₆H₃)}] (R = CH₂Ph, X = Cl, Y = Me, Ph; R = CH₂Ph, X = CH₂Ph, Y = Me, Ph; R = Cl, X = Cl, Y = Me) are formed when the isocyanide CN(2,6-Me₂C₆H₃) is added to a hexane solution of the benzylimido complexes. The molecular structure of the oxo complex [{(NbCl₂)₂-(μ-O)(μ-Cl)₂}{(η ⁵-C₅H₄)₂(Me₂SiOSiMe ₂)}] has been determined by X-ray diffraction methods.

Full text of DOI:10.1021/om970876n

1144
Organometallics 1998, 17, 1144-1150
Ch lor osilyl-Su bstitu ted Mon ocyclop en ta d ien yl Niobiu m
Ch lor o, Im id o Ch lor o, a n d Ben zyl Com p lexes. X-r a y
Molecu la r Str u ctu r e of
[{(NbCl2)2(µ-O)(µ-Cl)2}{(η5-C5H4)2(Me2SiOSiMe2)}]
M. Isabel Alcalde, Pilar Go´mez-Sal,† Avelino Mart´ın,† and Pascual Royo*
Departamento de Quı´mica Inorga´nica, Facultad de Ciencias, Universidad de Alcala´ de
Henares, 28871-Alcala´ de Henares, Spain
Received October 8, 1997
We report the synthesis of 1-(chloromethylphenylsilyl)cyclopentadiene. The reaction of a
toluene/CH2Cl2 suspension of NbCl5 with 1-(SiClMeX)-1-(SiMe3)C5H4 (X ) Me, Ph) leads to
the monocyclopentadienyl derivatives [M{η5-C5H4(SiClMeX)}Cl4] (X ) Me, Ph) in 90 and
78% yields, respectively. Reaction of 1 equiv of water with [M{η5-C5H4(SiClMe2)}Cl4] in
toluene takes place with elimination of HCl, resulting in formation of the dinuclear niobium
oxo derivative [{(NbCl2)2(µ-O)(µ-Cl)2}{(η5-C5H4)2(Me2SiOSiMe2)}]. Reaction of the complexes
[M{η5-C5H4(SiClMeX)}Cl4] with LiNHtBu and NEt3 in toluene leads to the half-sandwich
imido complexes [Nb{η5-C5H4(SiClMeX)}Cl2(NtBu)] (X ) Me, Ph), which react at room
temperature with 1 equiv of Mg(CH2Ph)2(THF)2 to give the imido dibenzyl complexes [Nb-
{η5-C5H4(SiClMeX)}(CH2Ph)2(NtBu)] (X ) Me, Ph). The reaction of the chloro imido
complexes [Nb{η5-C5H4(SiClMeX)}Cl2(NtBu)] with excess Mg(CH2Ph)2(THF)2 on heating for
2-3 days to 80-90 and 50-60 °C, respectively, takes place, affording the totally alkylated
complexes [Nb{η5-C5H4[Si(CH2Ph)MeX]}(CH2Ph)2(NtBu)] (X ) Me, Ph). The chloro benzyl
derivative [Nb{η5-C5H4(SiClMe2)}(CH2Ph)Cl(NtBu)], which could not be prepared by addition
of the stoichiometric amount of the alkylating agent, was isolated in quantitative yield by
heating a mixture of the dichloro and dibenzyl complexes in toluene at 120 °C for 4 h. The
18-electron imido η2-iminoacyl derivatives [Nb{(η5-C5H4(SiMeXY)}R(NtBu){η2-C(CH2Ph)dN-
(2,6-Me2C6H3)}] (R ) CH2Ph, X ) Cl, Y ) Me, Ph; R ) CH2Ph, X ) CH2Ph, Y ) Me, Ph; R
) Cl, X ) Cl, Y ) Me) are formed when the isocyanide CN(2,6-Me2C6H3) is added to a hexane
solution of the benzylimido complexes. The molecular structure of the oxo complex [{(NbCl2)2-
(µ-O)(µ-Cl)2}{(η5-C5H4)2(Me2SiOSiMe2)}] has been determined by X-ray diffraction methods.
1. In tr od u ction
metal complexes isoelectronic with the very well-known
group 4 metal dicyclopentadienyl derivatives [M(η5-
C5R5)2X2] (M ) Ti, Zr, Hf) extensively used as Ziegler-
Natta catalysts.
The presence of different ring substituents in cyclo-
pentadienylmetal complexes has significant steric and
electronic effects on the metal center, whose behavior
can also be modeled to the required objectives in
bonding appropriate ligands in its coordination sphere.
Trimethylsilyl-substituted rings have been extensively
used1 to transfer the ring to niobium and tantalum
halides by elimination of chlorotrimethylsilane, provid-
ing one of the most convenient reactions to prepare
monocyclopentadienyl-type metal compounds.
Reactions based on carbon-carbon bond formation
have led to many important synthetic applications of
organo group 5 metal complexes by migration of alkyl
substituents to unsaturated carbonyl4 and isocyanide5
ligands through the intermediate formation of acyl- and
(iminoacyl)metal complexes. This prompted us to ex-
tend our previous studies to the chemistry of niobium.
We report herein the synthesis of the new disilyl-
substituted cyclopentadienyl ligand (SiClMePh)(SiMe3)-
C5H4 and the use of this and the already reported
(SiClMe2)(SiMe3)C5H4 compound to isolate the tetra-
The imido group is a strong π-donor ligand that very
conveniently stabilizes high-valent metal complexes,2
and acting as a four-electron donor, it is isolobal with
the cyclopentadienyl group,3 thus providing group 5
(3) Willians, D. N.; Mitchell, J . P.; Poole, A. D.; Siemeling, V.; Clegg,
W.; Hockless, D. C. R.; O’Neil, P. A.; Gibson, V. C. J . Chem. Soc., Dalton
Trans. 1992, 739.
(4) (a) Wood, C. D.; Schrock, R. R. J . Am. Chem. Soc. 1979, 101,
5421. (b) Go´mez, M.; Go´mez-Sal, P.; J ime´nez, G.; Martin, A.; Royo, P.;
Sa´nchez-Nieves, J . Organometallics 1996, 15, 3579.
(5) (a) Galakhov, M. V.; Go´mez, M.; J ime´nez, G.; Royo, P.; Pelling-
helli, M. A.; Tiripicchio, A. Organometallics 1995, 14, 1901. (b)
Galakhov, M. V.; Go´mez, M.; J ime´nez, G.; Royo, P.; Pellinghelli, M.
A.; Tiripicchio, A. Organometallics 1995, 14, 2843.
† X-ray diffraction studies.
(1) (a) Burt, R. J .; Chatt, J .; Leigh, G. J .; Teuben, J . H.; Westerchof,
A. J . Organomet. Chem. 1977, 129, C33. (b) Bunker, M. J .; de Cian,
A.; Green, M. L. H.; Moreau, J . J . E.; Singaporia, N. J . Chem. Soc.,
Dalton Trans. 1980, 2155. (c) Hidalgo, G.; Mena, M.; Palacios, F.; Royo,
P.; Serrano, R. J . Organomet. Chem. 1988, 340, 37.
(2) (a) Nugent, W. A.; Mayer, J . M. Metal Ligand Multiple Bonds;
Wiley: New York, 1988. (b) Wigley, D. E. Prog. Inorg. Chem. 1994,
42, 239.
S0276-7333(97)00876-5 CCC: $15.00 © 1998 American Chemical Society
Publication on Web 02/24/1998

ClSi-Substituted Monocyclopentadienyl Nb Complexes
Organometallics, Vol. 17, No. 6, 1998 1145
Sch em e 1
Sch em e 2
chloro(η5-cyclopentadienyl)niobium complexes [M{η5-
C5H4(SiClMeX)}Cl4] (X ) Me, Ph) and their tert-butyl-
imido chloro and benzyl derivatives [Nb{η5-C5H4-
(SiMeXY)}R2(NtBu)] (R ) Cl, CH2Ph; X ) Me, Ph; Y )
Cl, CH2Ph). We report also the insertion reactions of
isocyanides into niobium-benzyl bonds, leading to the
iminoacyl complexes [Nb{(η5-C5H4(SiMeXY)}R(NtBu)-
{η2-C(CH2Ph)dN(2,6-Me2C6H3)}], and the X-ray molec-
ular structure of the oxo derivative [{(NbCl2)2(µ-O)(µ-
Cl)2}{(η5-C5H4)2(Me2SiOSiMe2)}], which results from the
hydrolysis of the tetrachloro complex [M{η5-C5H4-
(SiClMe2)}Cl4].
The 1H NMR spectra of both complexes show the
expected resonances for the methyl groups bonded to
silicon. Two multiplets corresponding to an AA′BB′ spin
system are observed for the cyclopentadienyl ring
protons in complex 3, whereas the presence of the chiral
silicon atom is responsible for the four multiplets
observed in complex 4 for the ring protons. These
assignments were confirmed by the 13C NMR spectra.
Compounds 3 and 4 were found to be moisture- and
oxygen-sensitive compounds which can be stored for a
long time in the solid state under an inert atmosphere.
They are soluble in dichloromethane, chloroform, and
aromatic solvents but insoluble in alkanes.
2.3. Hyd r olysis of Com p lex 3. The different re-
activities of the two different types of Si-Cl and Nb-
Cl bonds were studied for complex 3 in relation to its
hydrolysis. Addition of 1 equiv of water to its toluene
solution at room temperature (see Scheme 3) led to the
formation of an insoluble crystalline orange solid, which
was identified as the oxo complex [{(NbCl2)2(µ-O)(µ-
Cl)2}{(η5-C5H4)2(Me2SiOSiMe2)}] (5) by an X-ray dif-
fraction study of its molecular structure, although its
NMR characterization was prevented by its lack of
solubility in appropriate solvents. The same compound
was also formed when the quantity of water was limited
to 0.5 equiv, leaving unreacted starting material. This
behavior reveals that both Si-Cl and Nb-Cl bonds
show similar reactivities and are simultaneously hy-
drolyzed.
2. Resu lts a n d Discu ssion
2.1. Syn th esis of Silylcyclop en ta d ien e P r ecu r -
sor s. The synthesis of 1-(chlorodimethylsilyl)-1-(tri-
methylsilyl)cyclopentadiene (1) was effected by following
the method previously reported,6 which consists of the
reaction of the lithium salt of the (trimethylsilyl)-
cyclopentadienyl anion with dichlorodimethylsilane, and
a similar method was used to synthesize 1-(chloro-
methylphenylsilyl)-1-(trimethylsilyl)cyclopentadiene (2).
The reaction of a solution of 1-(trimethylsilyl)cyclopenta-
2,4-diene in hexane with n-butyllithium at 0 °C allowed
us to obtain a suspension of a white insoluble lithium
salt, which after addition of chloromethylphenylsilane
reacted to yield a yellow liquid soluble in hexane
(Scheme 1). The excess of the starting silane was
removed by distillation (65 °C/1 × 10-2 mmHg) to give
the required product as a yellow liquid which can be
stored in the dark under an inert atmosphere for several
months (yield 70%).
1
This liquid was identified by H NMR spectroscopy
as an equilibrium mixture of the isomers shown in
Scheme 2, in which 1-(chloromethylphenylsilyl)-1-(tri-
methylsilyl)cyclopentadiene (I) is the major component
in a ratio of 80% with respect to II and III, identified
by the broad and weak signals observed at ca. δ 3.2,
corresponding to sp3-C-bonded protons, along with other
weak signals at δ -0.03 and δ 0.82 due to trimethylsilyl
and chloromethylphenylsilyl protons.
2.2. Syn th esis a n d Ch a r a cter iza tion of Niobiu m
Ch lor o Cyclop en ta d ien yl Com p lexes. Compounds
1 and 2 reacted with 1 equiv of NbCl5 in toluene/
dichloromethane at room temperature with elimination
of SiClMe3 to give the corresponding monocyclopenta-
dienyl complexes [Nb{η5-C5H4(SiClMeX)}Cl4] (X ) Me
(3), Ph (4)) (see Scheme 3). The dark orange complexes
3 and 4 were isolated in 80-90% yield by cooling their
red solutions at -20 °C.
Dinuclear complex 5 and toluene molecules of solva-
tion are present in the crystals. The structure of 5 is
shown in Figure 1 together with the atomic labeling
scheme. Selected bond angles and distances are given
in Table 1.
The structure of 5 shows two niobium atoms with
slightly distorted pseudo-octahedral coordination, each
niobium being bonded to one apical ring of the bridging
[(η5-C5H4)2(Me2SiOSiMe2)] fragment in a slightly asym-
metric η5-fashion (the Nb(1)-C distances range from
2.389(4) to 2.469(3) Å; those of Nb(2)-C are in the range
2.396(4)-2.437(4) Å), two terminal and two bridging
chlorine atoms, and one bridging oxygen. The two
octahedra share one face defined by two chlorine atoms,
each occupying one axial position trans to the cyclopen-
tadienyl ring of one octahedron (Cp(1)-Nb(1)-Cl(3) and
Cp(2)-Nb(2)-Cl(4) angles are 174.3 and 171.9°, respec-
tively) and one equatorial position of the other, and the
oxygen atom, which occupies one equatorial position of
(6) (a) Rozell, J . M.; J ones, P. R. Organometallics 1985, 4, 2206. (b)
Ciruelos, S.; Cuenca, T.; Go´mez-Sal, P.; Manzanero, A.; Royo, P.
Organometallics 1995, 14, 177.

1146 Organometallics, Vol. 17, No. 6, 1998
Alcalde et al.
Sch em e 3
Ta ble 1. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for 5
Nb(1)-O(2)
Nb(1)-Cl(2)
Nb(1)-Cl(4)
Nb(2)-O(2)
Nb(2)-Cl(4)
Nb(2)-Cl(6)
Si(2)-O(1)
1.908(2)
2.390(1)
2.554(1)
1.888(2)
2.774(1)
2.378(1)
1.611(3)
2.108
Nb(1)-Cl(1)
Nb(1)-Cl(3)
Nb(1)-Nb(2)
Nb(2)-Cl(3)
Nb(2)-Cl(5)
Si(1)-O(1)
2.378(1)
2.701(1)
3.302(1)
2.559(1)
2.382(1)
1.604(3)
2.109
Nb(1)-Cp(1)
Nb(2)-Cp(2)
O(2)-Nb(1)-Cl(1)
Cl(1)-Nb(1)-Cl(2)
Cl(1)-Nb(1)-Cl(4)
O(2)-Nb(1)-Cl(3)
Cl(2)-Nb(1)-Cl(3)
O(2)-Nb(2)-Cl(6)
Cl(6)-Nb(2)-Cl(5)
149.16(8) O(2)-Nb(1)-Cl(2)
92.31(5) O(2)-Nb(1)-Cl(4)
93.12(8)
75.51(8)
85.38(5) Cl(2)-Nb(1)-Cl(4) 151.29(4)
72.08(8) Cl(1)-Nb(1)-Cl(3)
79.47(4) Cl(4)-Nb(1)-Cl(3)
94.31(8) O(2)-Nb(2)-Cl(5)
91.53(5) O(2)-Nb(2)-Cl(3)
79.14(4)
71.99(4)
147.46(8)
75.94(8)
83.67(5)
80.50(4)
70.72(4)
111.3(2)
76.47(3)
Cl(6)-Nb(2)-Cl(3) 151.22(4) Cl(5)-Nb(2)-Cl(3)
O(2)-Nb(2)-Cl(4)
Cl(5)-Nb(2)-Cl(4)
O(1)-Si(1)-C(11)
Nb(2)-Cl(3)-Nb(1)
Si(1)-O(1)-Si(2)
Cp(1)-Nb(1)-Cl(1) 104.7
Cp(1)-Nb(1)-Cl(3) 174.3
Cp(1)-Nb(1)-O(2) 103.2
Cp(2)-Nb(2)-Cl(4) 171.9
Cp(2)-Nb(2)-Cl(6) 105.4
70.28(8) Cl(6)-Nb(2)-Cl(4)
79.22(4) Cl(3)-Nb(2)-Cl(4)
112.1(2)
77.71(3) Nb(1)-Cl(4)-Nb(2)
157.3(3)
O(1)-Si(2)-C(21)
F igu r e 1. ORTEP drawing of the molecular structure of
compound 5‚C6H5Me together with the atomic labeling
scheme.
Nb(2)-O(2)-Nb(1) 120.9(1)
Cp(1)-Nb(1)-Cl(2) 104.4
Cp(1)-Nb(1)-Cl(4) 103.9
Cp(2)-Nb(2)-Cl(3) 103.2
Cp(2)-Nb(2)-Cl(5) 105.9
Cp(2)-Nb(2)-O(2) 103.3
both octahedra with a Nb(1)-O(2)-Nb(1) angle of 120.9-
(1)° and similar Nb(1)-O(2) and Nb(2)-O(2) distances
to both niobium atoms (average 1.898(2) Å). In these
octahedra Nb(1) is located 0.580 Å above the plane Cl-
(1)-Cl(2)-Cl(4)-O(2) (maximum deviation 0.110 Å for
O(2)), which is almost parallel to the Cp(1) plane (1.13°)
while Nb(2) is 0.592 Å above the plane O(2)-Cl(3)-Cl-
(5)-Cl(6) (maximum deviation 0.088 Å for O(2)), adopt-
ing an angle of 2.73° with the Cp(2) plane. This
structural disposition is similar to that found for the
dinuclear (µ-oxo)niobium complex [{Nb(η5-C5H4SiMe3)-
Cl2}2(µ-O)(µ-Cl)2],7 containing a terminal instead of a
bridging cyclopentadienyl system, whereas (pentameth-
ylcyclopentadienyl)molybdenum ({Mo(η5-C5Me5)Cl}2(µ-
O)(µ-Cl)2)8 and -zirconium ({Zr(η5-C5Me5)Cl}3(µ3-O)(µ2-
Cl)4)9 derivatives, which also display similar face-
sharing octahedral units, always have the bridging
oxygen trans to the pentamethylcyclopentadienyl rings.
The bridging tetramethylsiloxane group shows an open
Si(1)-O(1)-Si(2) angle of 157.3(3)° with average C(11)-
(C(21))-Si(1)(Si(2))-O(1) angles of 111.7(2)° and is long
enough to allow the cyclopentadienyl ligands to behave
as almost independent rings, allowing the structure to
be similar to the dinuclear niobium complex [{Nb(η5-
C5H4SiMe3)Cl2}2(µ-O)(µ-Cl)2]7 with independent rings.
The most remarkable features are the longer Nb-Cl
distances observed for the bridging chlorine atoms trans
to the cyclopentadienyl rings (Nb(1)-Cl(3), 2.701(1) Å;
Nb(2)-Cl(4), 2.774(1) Å) in comparison with those
corresponding to the equatorial chlorines (Nb(1)-Cl(4),
2.554(1) Å; Nb(2)-Cl(3), 2.559(1) Å), indicating the
higher electron donation of the rings and providing
asymmetric bridges. All of the terminal Nb-Cl bond
distances are shorter, in the expected range between
2.377(1) and 2.390(1) Å. The same behavior was also
observed for the dinuclear niobium complex mentioned
above.
(7) Andreu, A. M.; J alo´n, F. A.; Otero, A.; Lanfredi, A. M. M.;
Tiripicchio, A. J . Chem. Soc., Dalton Trans. 1987, 953.
(8) Bottomley, F.; Chen, J . Organometallics 1992, 11, 3404.
(9) Hidalgo, G.; Pellinghelli, M. A.; Royo, P.; Serrano, R.; Tiripicchio,
A. J . Chem. Soc., Chem. Commun. 1990, 1118.

ClSi-Substituted Monocyclopentadienyl Nb Complexes
Organometallics, Vol. 17, No. 6, 1998 1147
Sch em e 4
2.4. Syn th esis a n d Ch a r a cter iza tion of Niobiu m
Im ido Cyclopen tadien yl Com plexes. A second strat-
egy to compare the reactivities of the Si-Cl and Nb-
Cl bonds was based on the study of reactions with
secondary lithium amides. Related reactions with di-
cyclopentadienyltitanium dichloride have been re-
ported10 to lead to the formation of constrained mono-
meric cyclic species containing the pendant amido group
of the cyclopentadienyl ligand coordinated to the metal
center. Therefore, in this case, simultaneous substitu-
tion of both Ti-Cl and Si-Cl bonds by a bridging NR
group takes place with elimination of LiCl and HCl.
Reactions of complexes 3 and 4 with 1 equiv of the
secondary amide LiNHtBu in the presence of NEt3 in
toluene (Scheme 3) also occur with elimination of LiCl
and the ammonium salt (NHEt3)Cl to give solutions
which after evaporation and convenient purification
afford yellow crystalline solids characterized by elemen-
tal analyses as the corresponding substitution products
containing the NtBu group, which could be formulated
either as those related to the titanium analogues with
the chelating cyclopentadienyl silylamido ligand of
constrained geometry [Nb{η5-C5H4[SiMeX(η1-NtBu)]}-
Cl3] or as imidoniobium complexes11 containing the
unreacted silyl group [Nb{η5-C5H4(SiClMeX)}Cl2(Nt-
pounds very soluble in alkanes and thermally stable in
refluxing toluene.
The related monoalkylated complexes [Nb{η5-C5H4-
(SiClMeX)}(CH2Ph)Cl(NtBu)] could not be obtained by
reaction of the dichloro derivatives with the stoichio-
metric amount (0.5 equiv) of the alkylating agent
because their further alkylation is faster than that of
the starting dichloro compounds and always led to a
mixture of the dibenzyl derivatives 8 and 9 together
with unreacted starting compounds (Scheme 4). How-
ever, a quantitative yield of [Nb{η5-C5H4(SiClMe2)}(CH2-
Ph)Cl(NtBu)] (12) was obtained when a mixture of the
dichloro complex 6 and the corresponding dibenzyl
compound 8 was heated in toluene at 120 °C for 4 h in
a sealed tube. Complex 12 was isolated after removal
of the solvent and extraction with hexane as an air-
sensitive brown solid which easily retains solvent to
become an oily solid. The benzyl complexes 8-12 were
characterized by NMR spectroscopy (see Experimental
Section). The diastereotopic methylene protons of both
equivalent benzyl groups for complexes 8 and 10 are
observed between δ 1.63 and 1.94 with coupling con-
stants J H-H ) 8.0-8.2 Hz, whereas four doublets
between δ 1.43 and 1.99 with coupling constants J H-H
) 7.5-8.2 Hz are observed for complexes 9 and 11 due
to the presence of a silicon chiral center. Moreover,
complex 10 shows one additional singlet for the meth-
ylene protons of the benzyl group bonded to silicon,
whereas they are observed as one multiplet at δ 2.48 in
CDCl3 for complex 11 due to the chiral silicon.
1
Bu)]. The H and 13C NMR spectra of these compounds
show a behavior similar to that discussed above for the
tetrachloro complexes 3 and 4, which does not provide
a definitive answer about their stuctures (see Experi-
mental Section). However, a definitive structural as-
signment as an imidoniobium complex was made for
[Nb{η5-C5H4(SiClMeX)}Cl2(NtBu)] (X ) Me (6), Ph (7))
on the basis of its 29Si NMR spectrum which shows the
silicon resonance at δ 8.34 and 6.53 ppm, respectively,
in the same range observed for the starting chloro
complex 3, in comparison with the silicon resonance
corresponding to silyl amido complexes of constrained
geometry, which is observed12 at higher field in the
range of ca. δ 20 ppm.
2.5. Syn th esis a n d Ch a r a cter iza tion of Niobiu m
Ben zyl Im id o Com p lexes. The benzyl ligand can
conveniently be introduced by reacting the chloro com-
plexes 6 and 7 with 1 equiv of Mg(CH2Ph)2(THF)2 in
hexane, affording the dibenzyl complexes [Nb{η5-
C5H4(SiClMeX)}(CH2Ph)2(NtBu)] (X ) Me (8), Ph (9))
as a brown solid and a dark yellow oil, respectively. This
behavior indicates that preferential alkylation of the
Nb-Cl bonds takes place, leaving the unmodified chlo-
rosilyl group.13 However, the Si-Cl bond can also be
reacted when a toluene solution of 6 or a hexane solution
of 7, treated with an excess of Mg(CH2Ph)2(THF)2, was
heated for 2-3 days to 80-90 or 50-60 °C, respectively.
Under these conditions slower alkylation of the Si-Cl
bond takes place, affording the totally alkylated com-
plexes [Nb{η5-C5H4[Si(CH2Ph)MeX]}(CH2Ph)2(NtBu)] (X
) Me (10), Ph (11)) as brown oils after removal of the
solvent and purification. Both are air-sensitive com-
The niobium atom in complex 12 is a chiral center
which makes both methylsilicon and ring protons non-
equivalent, the methylene protons of the benzyl ligand
being observed as two doublets between δ 2.77 and 3.20
with the coupling constant J H-H ) 7.1 Hz.
2.6. Rea ction s of Ben zyl Com p lexes w ith Iso-
cya n id e. When CN(2,6-Me2C6H3) is added to hexane
solutions of the alkylimido complexes 8-12, an instan-
taneous insertion reaction takes place to give the 18-
electron imido η2-iminoacyl derivatives [Nb{(η5-C5H4-
(SiMeXY)}R(NtBu){η2-C(CH2Ph)dN(2,6-Me2C6H3)}] (R
) CH2Ph, X ) Cl, Y ) Me (13), Ph (14); R ) CH2Ph, X
) CH2Ph, Y ) Me (15), Ph (16); R ) Cl, X ) Cl, Y ) Me
(17)) as shown in Scheme 5.
(10) Ciruelos, S.; Cuenca, T.; Go´mez, R.; Go´mez-Sal, P.; Manzanero,
A.; Royo, P. Organometallics 1996, 15, 5577.
(11) (a) Schmidt, S.; Sundermeyer, J . J . Organomet. Chem. 1994,
472, 127. (b) Baldwin, T. C.; Huber, S. R.; Bruck, M. A.; Wigley, D. E.
Inorg. Chem. 1993, 32, 5682.
(12) Herrmann, W. A.; Baratta, W. J . Organomet. Chem. 1996, 506,
357.
(13) Ciruelo, G.; Cuenca, T.; Go´mez, R.; Go´mez-Sal, P.; Mart´ın, A.;
Rodr´ıguez, G.; Royo, P. J . Organomet. Chem., in press.

1148 Organometallics, Vol. 17, No. 6, 1998
Alcalde et al.
Sch em e 5
4. Exp er im en ta l Section
All manipulations were performed under an inert atmo-
sphere (argon) using Schlenk and high-vacuum-line techniques
or a VAC Model HE 453 glovebox. Solvents were purified by
distillation from an appropiate drying/deoxygenating agent
(phosphorus pentoxide for dichloromethane, sodium for tolu-
ene, and sodium/potassium alloy for hexane). C5H5SiMe3 and
Mg(CH2Ph)2(THF)2 were prepared according to literature
t
procedures. n-BuLi, BuNH2, SiMe2Cl2, SiMePhCl2, CNR (R
) 2,6-Me2C6H3), and NbCl5 were obtained commercially. 1H
and 13C NMR spectra were recorded on Varian Unity FT-300
and Varian FT-500 Unity Plus instuments, and chemical shifts
1
were measured relative to residual H and 13C resonances in
the deuterated solvents C6D6 (δ 7.15), CDCl3 (δ 7.24) and C6D6
(δ 128), CDCl3 (δ 77), respectively. IR spectra were recorded
on a Perkin-Elmer 583 spectrophotometer (4000-200 cm-1
)
as Nujol mulls between CsI pellets. Mass spectra were
recorded on an HP 5988 A instrument. C, H, and N analyses
were carried out with a Perkin-Elmer 240C microanalyzer.
Elemental analyses for liquid compounds 9-11 and 14-16,
which partially decompose by sublimation, gave unacceptable
deviations (1.5-2.0% for C).
The migration of the second benzyl group14 does not
take place, and the presence of an excess of isocyanide,
at room temperature, does not produce a second inser-
tion reaction in the Nb-CH2Ph or Nb-C(iminoacyl)
bonds.4b,15 The presence of the η2-iminoacyl group is
confirmed by the 13C resonance δ ∼230 (η2-PhH2C-
4.1. P r ep a r a tion of 1-(SiClMeP h )-1-(SiMe3)C5H4 (2). A
1.6 M hexane solution of n-butyllithium (50.0 mL, 80.0 mmol)
was added dropwise at 0 °C to a solution of freshly distilled
C5H5SiMe3 (13.4 mL, 11.1 g, 80.0 mmol) in hexane (200 mL).
The reaction mixture was slowly warmed to room temperature
and stirred for 3 h to afford a white precipitate, which after
filtration was washed with hexane (3 × 30 mL). A suspension
of this white solid in hexane (200 mL) was inmediately treated
with SiCl2MePh (13.0 mL, 15.3 g, 80.0 mmol) at room tem-
perature, and the reaction mixture was stirred for 12 h. After
filtration the solvent was removed by evaporation under
vacuum to give a yellow oil, which was characterized as
compound 2 (16.4 g, 55.9 mmol, 70% yield). 1H NMR (300
MHz, CDCl3, 25 °C, δ): -0.17 (s, 9H, SiMe3, major component),
-0.03 (s, 9H, SiMe3, minor component), 0.36 (s, 3H, SiClMePh,
major component), 0.83 (s, 3H, SiClMePh, minor component),
6.50-6.80 (m, C5H4), 7.30-7.70 (m, SiClMePh). 13C NMR (75
MHz, CDCl3, 25 °C, δ): -2.2, -1.7, -1.1 (SiMe3, SiClMePh),
48.4, 57.8 (C5H4 ipso), 127.1, 127.5, 127.9, 129.7, 129.8, 131.2,
132.5, 133.2, 133.4, 133.6, 134.6, 140.9, 146.2 (C5H4, Ph).
4.2. P r ep a r a t ion of [Nb {η5-C5H4(SiClMeX)}Cl4] (X )
Me, 3; X ) P h , 4). 1-(SiClMeX)-1-(SiMe3)(C5H4) (X ) Me, 4.26
mL, 3.84 g, 16.66 mmol; X ) Ph, 4.87 g, 16.66 mmol) was added
to a suspension of NbCl5 (4.50 g, 16.66 mmol) in toluene (100
mL). The reaction mixture was stirred for 3 h at room
temperature. After filtration the resulting solution was
concentrated (20 mL) and cooled to -20 °C to give a dark
orange solid, which was characterized as 3 (X ) Me, 7.39 g,
18.83 mmol, 90% yield) and 4 (X ) Ph, 5.90 g, 12.98 mmol,
78% yield), respectively.
Data for 3 are as follows. Anal. Calcd for C7H10Cl5SiNb:
C, 21.41; H, 2.55. Found: C, 21.40; H, 2.60. 1H NMR (300
MHz, C6D6, 25 °C, δ): 0.54 (s, 6H, SiClMe2), 6.20 (m, 2H, C5H4),
6.24 (m, 2H, C5H4). 13C NMR (75 MHz, C6D6, 25 °C, δ): 2.7
(SiClMe2), 131.5, 131.9 (C2-C5, C5H4) (Cipso not observed). 29Si
NMR (toluene, 25 °C, δ): 8.99 (SiClMe2).
Data for 4 are as follows. Anal. Calcd for C12H12Cl5SiNb:
C, 31.70; H, 2.64. Found: C, 31.65; H,2.67. 1H NMR (300
MHz, C6D6, 25 °C, δ): 0.92 (s, 3H, SiClMePh), 6.15 (m, 1H,
C5H4), 6.21 (m, 1H, C5H4), 6.32 (m, 1H, C5H4), 6.48 (m, 1H,
C5H4), 7.07-7.51 (m, 5H, SiClMePh). 13C NMR (75 MHz, C6D6,
25 °C, δ): 0.5 (SiClMePh), 128.6, 129.2, 131.7, 134.6 (C5H4, Ph).
4.3. P r ep a r a tion of [{(NbCl2)2(µ-O)(µ-Cl)2}{(η5-C5H4)2-
(Me2SiOSiMe2)}] (5). Water (55 µL, 3.05 mmol) was added
to a solution of [Nb{η5-C5H4(SiClMe2)}Cl4] (3; 1.19 g, 3.05
mmol) in 50 mL of toluene. The reaction mixture was stirred
at room temperature for 2 h. After filtration, the resulting
orange solution was concentrated (10 mL) and cooled to -20
C)NAr) and the ν(CdN) IR band at 1624-1642 cm-1
.
Complexes 14 and 16 have two chiral centers, and their
1H NMR spectra show the signals expected for the two
pairs of diastoreomers RR/SS and RS/SR.
3. Con clu sion s
Tetrachloro silyl-substituted cyclopentadienyl com-
plexes of niobium are isolated by reaction of NbCl5 with
1-(SiClMeX)-1-(SiMe3)C5H4 (X ) Me, Ph) with elimina-
tion of SiClMe3. Unselective hydrolysis of both Si-Cl
and Nb-Cl bonds takes place simultaneously in the
presence of water to give the oxo derivative [{(NbCl2)2-
(µ-O)(µ-Cl)2}{(η5-C5H4)2(Me2SiOSiMe2)}], whose X-ray
crystal structure reveals the presence of Si-O-Si and
Nb-O-Nb bridged systems. Reaction of the tetrachloro
monocyclopentadienyl complexes with LiNHtBu and
NEt3 leads to the corresponding imido compounds,
which can be selectively alkylated by Mg(CH2Ph)2‚2THF
to give the dibenzylniobium derivatives, whereas the
monobenzyl complex results from rearrangement be-
tween the dichloro and the dibenzyl complexes. Further
alkylation of the Si-Cl bond requires heating in the
presence of an excess of the alkylating agent. All of the
benzyl-niobium compounds react rapidly with CN(2,6-
Me2C6H3) by insertion of the isocyanide into only one
of the niobium-benzyl bonds to give 18-electron η2-
iminoacyl complexes. The structural characterization
of all the new niobium compounds reported was made
1
by H and 13C NMR spectroscopy.
(14) (a) Durfee, L. D.; Hill, J . E.; Fanwick, P. E.; Rothwell, I. P.
Organometallics 1990, 9, 75. (b) Galakhov, M. V.; Go´mez, M.; J ime´nez,
G.; Royo, P.; Pellinghelli, M. A.; Tiripicchio, A. Organometallics 1994,
13, 1564.
(15) (a) Durfee, L. D.; Rothwell, I. P. Chem. Rev. 1988, 88, 1059. (b)
Filippou, A. C.; Gru¨nleitner, W.; Vo¨lk, C.; Kiprof, P. J . Organomet.
Chem. 1991, 413, 181. (c) Chamberlain, L. R.; Durfee, L. D.; Fanwick,
P. E.; Kobriger, L.; Latesky, S. L.; MacMullen, A. K.; Rothwell, I. P.;
Folting, K.; Huffman, J . C.; Streib, W. E.; Wang, R. J . Am. Chem. Soc.
1987, 109, 390. (d) Carmona, E.; Mar´ın, J . M.; Palma, P.; Poveda, P.
L. J . Organomet. Chem. 1989, 377, 157. (e) Filippou, A. C.; Vo¨lk, C.;
Kiprof, P. J . Organomet. Chem. 1991, 415, 375.

ClSi-Substituted Monocyclopentadienyl Nb Complexes
Organometallics, Vol. 17, No. 6, 1998 1149
°C to give single crystals for X-ray diffraction. Anal. Calcd
for 5, C14H20Cl6O2Si2Nb2‚C7H8: C, 32.87; H, 3.65. Found: C,
32.45; H, 3.47.
volatiles were removed under reduced pressure. The brown
oil obtained was characterized as 11.
Data for 10 are as follows. 1H NMR (300 MHz, C6D6, 25
°C, δ): 0.20 (s, 6H, Si(CH2Ph)Me2), 1.11 (s, 9H, NtBu), 1.63
(d, 2H, J H-H ) 8.06 Hz, CH2Ph), 1.89 (d, 2H, J H-H ) 8.06 Hz,
CH2Ph), 2.13 (s, 2H, Si(CH2Ph)Me2), 5.51 (m, 2H, C5H4), 5.70
(m, 2H, C5H4), 6.80-7.15 (m, Ph). 13C NMR (75 MHz, C6D6,
25 °C, δ): -2.3 (SiClMe2), 28.1 (SiMe2CH2Ph), 31.9 (C(CH3)3),
41.3 (CH2Ph), 66.5 (C(CH3)3), 107.4, 113.3 (C2-C5, C5H4) (Cipso
not observed), 124.6, 124.9, 128.5, 128.6, 128.7, 130.3, 139.6,
140.0 (Ph).
4.4. P r ep a r a tion of [Nb{η5-C5H4(SiClMeX)}Cl2(NtBu )]
(X ) Me, 6; X ) P h , 7). A mixture of [Nb{η5-C5H4(SiClMeX)}-
Cl4] (3; 1.00 g, 2.55 mmol; 4; 1.16 g, 2.55 mmol), LiNHtBu (0.20
g, 2.55 mmol), and NEt3 in 50 mL of toluene was stirred at
room temperature overnight and then filtered. After evapora-
tion under vacuum to dryness a brown solid was obtained,
which was extracted with hexane (30 mL). The resulting
extract was concentrated and cooled to -30 °C to give a yellow
solid characterized as 6 (X ) Me, 0.70 g, 1.78 mmol, 70% yield)
and 7 (X ) Ph, 0.83 g, 1.83 mmol, 72% yield).
Data for 6 are as follows. Anal. Calcd for C11H19Cl3-
NSiNb: C, 33.63; H, 4.84; N, 3.57. Found: C, 33.93; H, 4.95;
N, 3.33. 1H NMR (300 MHz, C6D6, 25 °C, δ): 0.59 (s, 6H,
SiClMe2), 1.02 (s, 9H, NtBu), 5.98 (m, 2H, C5H4), 6.34 (m, 2H,
C5H4). 13C NMR (75 MHz, C6D6, 25 °C, δ): 1.9 (SiClMe2), 29.7
(C(CH3)3), 69.8 (C(CH3)3), 110.3, 121.7 (C2-C5, C5H4) (Cipso not
observed). 29Si NMR (toluene, 25 °C, δ): 8.34 (SiClMe2).
Data for 7 are as follows. Anal. Calcd for C16H21Cl3-
NSiNb: C, 42.26; H, 4.66; N, 3.08. Found: C, 42.87; H, 4.70;
N, 2.81. 1H NMR (300 MHz, C6D6, 25 °C, δ): 0.94 (s, 3H,
SiClMePh), 0.99 (s, 9H, NtBu), 5.95 (m, 1H, C5H4), 6.00 (m,
1H, C5H4), 6.25 (m, 1H, C5H4), 6.61 (m, 1H, C5H4), 7.12-7.64
(m, SiClMePh). 13C NMR (75 MHz, C6D6, 25 °C, δ): 1.6
(SiClMePh), 30.0 (C(CH3)3), 70.5 (C(CH3)3), 111.2, 111.3, 122.9,
123.3 (C2-C5, C5H4), 120.0 (Cipso, C5H4), 128.5, 131.1, 133.6,
134.4 (SiClMePh). 29Si NMR (C6D6, 25 °C, δ): 6.53 (Si-
ClMePh).
Data for 11 are as follows. 1H NMR (300 MHz, C6D6, 25
°C, δ): 0.50 (s, 3H, Si(CH2Ph)MePh), 1.07 (s, 9H, NtBu), 1.43
(d, 1H, J H-H ) 8.06 Hz, CH2Ph), 1.56 (d, 1H, J H-H ) 7.50 Hz,
CH2Ph), 1.72 (d, 1H, J H-H ) 8.06 Hz, CH2Ph), 1.99 (d, 1H,
J H-H ) 7.50 Hz, CH2Ph), 2.40 (br s, 2H, Si(CH2Ph)MePh), 5.55
(m, 2H, C5H4), 5.80 (m, 1H, C5H4), 5.91 (m, 1H, C5H4), 6.70-
7.47 (m, Ph). 1H NMR (500 MHz, CDCl3, 25 °C, δ): 0.55 (s,
3H, Si(CH2Ph)MePh), 1.07 (s, 9H, NBut), 1.22 (d, 1H, J H-H
)
8.06 Hz, CH2Ph), 1.38 (d, 1H, J H-H ) 7.69 Hz, CH2Ph), 1.52
(d, 1H, J H-H ) 8.06 Hz, CH2Ph), 1.83 (d, 1H, J H-H ) 7.69 Hz,
CH2Ph), 2.48 (m, 2H, Si(CH2Ph)MePh), 5.53 (m, 1H, C5H4),
5.55 (m, 1H, C5H4), 5.90 (m, 1H, C5H4), 5.99 (m, 1H, C5H4),
6.65-7.45 (m, Ph). 13C NMR (75 MHz, C6D6, 25 °C, δ): -4.6
(Si(CH2Ph)MePh), 27.4 (Si(CH2Ph)MePh), 31.8 (C(CH3)3), 41.4
(CH2Ph), 69.0 (C(CH3)3), 106.2, 107.0 (C2-C5, C5H4), 111.3
(Cipso, C5H4), 113.9, 114.9 (C2-C5, C5H4), 124.6, 124.8, 125,1,
128.2, 128.6, 128.7, 129.0, 129.8, 130.2, 130.3, 130.5, 134.4,
134.9, 136.4, 138.9, 139.0, 141.1 (Ph).
4.7. P r ep a r a tion of [Nb{η5-C5H4(SiClMe2)}(CH2P h )Cl-
(NtBu )] (12). A mixture of [Nb{η5-C5H4(SiClMe2)}Cl2(NtBu)]
(6; 0.50 g, 1.27 mmol) and [Nb{η5-C5H4(SiClMe2)}(CH2Ph)2-
(NtBu)] (8; 0.64 g, 1.27 mmol) in toluene (50 mL) was warmed
to 120 °C for 4 h. After evaporation under vacuum to dryness,
an oil was obtained, which was dissolved in hexane (20 mL).
The resulting solution was concentrated and cooled to -40 °C
to give a brown solid, which was characterized as 12 (0.51 g,
1.15 mmol, 90% yield). Data for 12 are as follows. Anal.
Calcd for C18H26ClNSiNb: C, 48.21; H, 5.86; N, 3.12. Found:
C, 48.00; H, 5.98; N, 3.15. 1H NMR (300 MHz, C6D6, 25 °C,
δ): 0.57 (s, 3H, SiClMe2), 0.67 (s, 3H, SiClMe2), 1.08 (s, 9H,
NtBu), 2.77 (d, 1H, J H-H ) 7.10 Hz, CH2Ph), 3.20 (d, 1H, J H-H
) 7.10 Hz, CH2Ph), 5.65 (m, 1H, C5H4), 5.87 (m, 2H, C5H4),
6.13 (m, 1H, C5H4), 6.75-7.29 (m, Ph). 13C NMR (75 MHz,
C6D6, 25 °C, δ): 2.7 (SiClMe2), 3.6 (SiClMe2), 31.0 (C(CH3)3),
48.6 (CH2Ph), 68.3 (C(CH3)3), 105.8, 109.7, 110.9, 118.9 (C2-
C5, C5H4) (Cipso not observed), 130.1, 130.4, 132.4 (Ph).
4.8. P r ep a r a tion of [Nb{η5-C5H4(SiMeXY)}R(NtBu ){η2-
C(CH2P h )dN(2,6-Me2C6H3)}] (R ) CH2P h , X ) Cl, Y ) Me
(13), P h (14); R ) CH2P h , X ) CH2P h , Y ) Me (15), P h
(16); R ) Cl, X ) Cl, Y ) Me (17)). An equimolar mixture of
the corresponding alkyl complex and isocyanide in hexane was
stirred at room temperature for 1 h and was then evaporated
to dryness. The oily products obtained were characterized as
the corresponding iminoacyl complexes 13-17.
Data for 13 are as follows. Anal. Calcd for C34H42ClN2-
SiNb: C, 64.28; H, 6.68; N, 4.41. Found: C, 63.69; H, 6.78;
N, 4.37. 1H NMR (300 MHz, C6D6, 25 °C, δ): 0.52 (s, 3H,
SiClMe2), 0.58 (s, 3H, SiClMe2), 1.09 (s, 9H, NtBu), 1.67 (s,
6H, CdNMe2C6H3), 2.97 (m, 2H, Nb-CH2Ph), 3.62 (m, 2H,
PhCH2CdN), 5.48 (m, 1H, C5H4), 5.68 (m, 1H, C5H4), 5.98 (m,
1H, C5H4), 6.03 (m, 1H, C5H4), 6.82-7.20 (m, Ph). 13C NMR
(75 MHz, C6D6, 25 °C, δ): 3.8 (SiClMe2), 4.0 (SiClMe2), 18.5
(CdNMe2C6H3), 18.8 (CdNMe2C6H3), 32.6 (C(CH3)3), 37.0 (Nb-
CH2Ph), 43.3 (PhCH2CdN), 66.0 (C(CH3)3), 107.8, 109.2, 112.2,
115.0 (C2-C5, C5H4) (Cipso not observed), 120.7-154.7 (Ph),
230.6 (PhCH2CdN). IR (Nujol mull; ν, cm-1): 1626, 1240.
Data for 14 are as follows. 1H NMR (300 MHz, C6D6, 25
°C, δ): 0.81, 0.87 (s, 3H, SiClMePh), 1.03, 1.13 (s, 9H, NtBu),
1.62, 1.69, 1.71, 1.76 (s, 3H, CdNMe2C6H3), 3.00-3.08 (m, 2H,
Nb-CH2Ph), 3.56 (d, 1H, J H-H ) 15.4 Hz, PhCH2CdN), 3.64
4.5. P r ep a r a tion of [Nb{η5-C5H4(SiClMeX)}(CH2P h )2-
(NtBu )] (X ) Me, 8; X ) P h , 9). A mixture of [Nb{η5-
C5H4(SiClMe2)}Cl2(NtBu)] (6; 0.50 g, 1.27 mmol) and Mg(CH2-
Ph)2(THF)2 (0.45 g, 1.27 mmol) in 50 mL of hexane was stirred
at room temperature for 3 h and then filtered. The filtrate
was evaporated to dryness to give a light brown solid, which
was characterized as 8 (0.56 g, 1.11 mmol, 88% yield).
Compound
9
was
synthesized
from
[Nb{η5-C5H4-
(SiClMePh)}Cl2(NtBu)] (7; 0.58 g, 1.27 mmol), in a manner
analogous to that descrived for the preparation of 8, and
isolated as a dark yellow oil.
Data for 8 are as follows. Anal. Calcd for C25H33ClNSiNb:
C, 59.57; H, 6.61; N, 2.78. Found: C, 59.36; H, 6.59; N, 2.78.
1H NMR (300 MHz, C6D6, 25 °C, δ): 0.46 (s, 6H, SiClMe2),
1.09 (s, 9H, NtBu), 1.64 (d, 2H, J H-H ) 8.20 Hz, CH2Ph), 1.94
(d, 2H, J H-H ) 8.20 Hz, CH2Ph), 5.51 (m, 2H, C5H4), 5.93 (m,
2H, C5H4), 6.98-7.05 (m, 10H, Ph). 13C NMR (75 MHz, C6D6,
25 °C, δ): 3.6 (SiClMe2), 31.8 (C(CH3)3), 41.3 (CH2Ph), 66.1
(C(CH3)3), 106.6, 113.9 (C2-C5, C5H4) (Cipso not observed),
125.2, 128.8, 130.5, 139.6 (Ph).
Data for 9 are as follows. 1H NMR (300 MHz, C6D6, 25 °C,
δ): 0.75 (s, 3H, SiClMePh), 1.07 (s, 9H, NtBu), 1.59 (d, 1H,
J H-H ) 8.25 Hz, CH2Ph), 1.66 (d, 1H, J H-H ) 8.25 Hz, CH2-
Ph), 1.98 (m, 2H, CH2Ph), 5.51 (m, 1H, C5H4), 5.57 (m, 1H,
C5H4), 5.98 (m, 1H, C5H4), 6.15 (m, 1H, C5H4), 6.85-7.14, 7.58
(m, Ph). 13C NMR (75 MHz, C6D6, 25 °C, δ): 2.2 (SiClMePh),
31.7 (C(CH3)3), 41.6 (CH2Ph), 66.8 (C(CH3)3), 105.6, 106.3,
114.9, 115.4 (C2-C5, C5H4) (Cipso not observed), 125.0, 125.3,
128.7, 130.5, 130.7, 134.0, 138.9, 140.1 (Ph).
4.6. P r ep a r a t ion of [Nb [η5-C5H 4Si(CH2P h )MeX]-
(CH2P h )2(NtBu )] (X ) Me, 10; X ) P h , 11). A mixture of
[Nb{η5-C5H4(SiClMe2)}Cl2(NtBu)] (6; 0.50 g, 1.27 mmol) and
Mg(CH2Ph)2(THF)2 (0.67 g, 1.91 mmol) in toluene (50 mL) was
warmed to 80-90 °C for 3 days. After evaporation to dryness
the resudue was extacted with ether or hexane and the filtrate
was again evaporated to dryness to give a brown oil, which
was characterized as 10. A mixture of [Nb(η5-C5H4SiClMePh)-
Cl2(NtBu)] (7; 0.50 g, 1.10 mmol) and Mg(CH2Ph)2(THF)2 (0.58
g, 1.65 mmol) in hexane (50 mL) was heated to 50-60 °C for
2 days. The resulting suspension was filtered, and then the

1150 Organometallics, Vol. 17, No. 6, 1998
Alcalde et al.
Ta ble 2. Cr ysta l Da ta a n d Str u ctu r e Refin em en t
Deta ils for 5
(d, 1H, J H-H ) 9.7 Hz, PhCH2CdN), 3.67 (d, 1H, J H-H ) 9.7
Hz, PhCH2CdN), 3.74 (d, 1H, J H-H ) 15.4 Hz, PhCH2CdN),
5.48, 5.63, 5.67, 5.78, 5.97, 6.04, 6.17, 6.20 (m, 1H, C5H4), 6.82-
7.58 (m, Ph). 13C NMR (75 MHz, C6D6, 25 °C, δ): 2.2, 2.6
(SiClMePh), 18.4, 18.6, 18.6, 19.1 (CdNMe2C6H3), 32.5, 32.6
(C(CH3)3), 36.9 (br s, Nb-CH2Ph), 43.2, 43.3 (PhCH2CdN),
66.1 (C(CH3)3), 107.0, 108.2, 109.2, 110.0, 112.9, 114.7, 115.0,
115.3 (C2-C5, C5H4), 120.6-154.9 (Ph), 230.4 (PhCH2CdN).
IR (Nujol mull; ν, cm-1): 1625, 1240.
empirical formula
fw
C14H20Cl6Nb2O2Si2‚C7H8
767.13
temp; wavelength
cryst syst; space group
a, b, c
â
V; Z
293(2) K; 0.710 73 Å
monoclinic; P21/c
12.040(2), 12.230(2), 20.041(4) Å
93.80(3)°
2944.5(9) Å3; 4
density (calcd)
abs coeff
1.730 g/cm3
Data for 15 are as follows. 1H NMR (300 MHz, C6D6, 25
°C, δ): 0.29 (s, 3H, SiMe2CH2Ph), 0.34 (s, 3H, SiMe2CH2Ph),
1.11 (s, 9H, NtBu), 1.61 (s, 3H, CdNMe2C6H3), 1.67 (s, 3H,
1.423 mm-1
F(000)
1528
no. of rflns collected
no. of indep rflns
abs cor
5190
4963 (Rint ) 0.1185)
ψ scan
CdNMe2C6H3), 2.22 (s, 2H, SiMe2CH2Ph), 2.85 (d, 1H, J H-H
)
10.0 Hz, Nb-CH2Ph), 3.11 (d, 1H, J H-H ) 10.0 Hz, Nb-CH2-
Ph), 3.57 (m, 2H, PhCH2CdN), 5.40 (m, 1H, C5H4), 5.71 (m,
1H, C5H4), 5.79 (m, 1H, C5H4), 5.90 (m, 1H, C5H4), 6.81-7.28
(m, Ph). 13C NMR (75 MHz, C6D6, 25 °C, δ): -1.9 (SiMe2CH2-
Ph), 18.4 (CdNMe2C6H3), 18.6 (CdNMe2C6H3), 28.2 (SiMe2CH2-
Ph), 32.8 (C(CH3)3), 37.1 (Nb-CH2Ph), 43.4 (PhCH2CdN), 65.7
(C(CH3)3), 106.6, 109.4, 110.7, 116.1 (C2-C5, C5H4), 120.4-
154.8 (Ph), 231.3 (PhCH2CdN). IR (Nujol mull; ν, cm-1): 1624,
1242.
max and min transmissn
refinement method
goodness of fit on F2
final R indices (I > 2σ(I))
R indices (all data)
weighting scheme
0.276 and 0.228
full-matrix least squares on F2
1.068
R1 ) 0.0307, wR2 ) 0.0764
R1 ) 0.0458, wR2 ) 0.0908
calcd w ) 1/[σ2(Fo2) + (0.0372P)2 +
2
3.9258P]; P ) (Fo + 2Fc2)/3
largest diff peak and hole
0.656 and -0.455 e/Å3
with one molecule of toluene. The crystallographic data for
5‚C6H5Me are summarized in Table 2.
Data for 16 are as follows. 1H NMR (300 MHz, CDCl3, 25
°C, δ): 0.60, 0.64 (s, 3H, SiMePhCH2Ph), 1.00, 1.05 (s, 9H,
NtBu), 1.52, 1.53, 1.56, 1.59 (s, 3H, CdNMe2C6H3), 2.46-2.56
(m, 4H, CH2Ph), 2.77-2.82 (m, 2H, CH2Ph), 3.06-3.11 (m, 2H,
CH2Ph), 3.48-3.50 (m, 4H, PhCH2CdN), 5.38, 5.43, 5.69, 5.75
(m, 1H, C5H4), 5.83 (m, 2H, C5H4), 5.95, 6.00 (m, 1H, C5H4),
6.54-7.43 (m, Ph). 13C NMR (75 MHz, C6D6, 25 °C, δ): -3.6,
-3.8 (SiClMePh), 18.2, 18.3, 18.5 (CdNMe2C6H3), 27.1, 27.3
(SiCH2Ph), 32.6 (C(CH3)3), 37.1, 37.2 (Nb-CH2Ph), 43.3
(PhCH2CdN), 65.6 (C(CH3)3), 106.5, 107.0, 109.5, 109.9, 110.2,
110.6, 116.2 (C2-C5, C5H4), 120.4-154.8 (Ph), 230.9, 231.0
(PhCH2CdN). IR (Nujol mull; ν, cm-1): 1625, 1241.
Data for 17 are as follows. Anal. Calcd for C27H35ClN2-
SiNb: C, 55.95; H, 6.10; N, 4.83. Found: C, 56.05; H, 6.21;
N, 4.73. 1H NMR (300 MHz, C6D6, 25 °C, δ): 0.85 (s, 3H,
SiClMe2), 0.97 (s, 3H, SiClMe2), 0.97 (s, 9H, NtBu), 1.74 (s,
3H, CdNMe2C6H3), 2.07 (s, 3H, CdNMe2C6H3), 3.54 (br s, 2H,
PhCH2CdN), 5.46 (m, 1H, C5H4), 5.81 (m, 1H, C5H4), 5.87 (m,
1H, C5H4), 6.61 (m, 1H, C5H4), 7.00-7.45 (m, Ph). 1H NMR
(300 MHz, CDCl3, 25 °C, δ): 0.78 (s, 3H, SiClMe2), 0.88 (s,
3H, SiClMe2), 1.05 (s, 9H, NtBu), 1.94 (s, 3H, CdNMe2C6H3),
2.16 (s, 3H, CdNMe2C6H3), 4.04 (m, 2H, PhCH2CdN), 5.69 (m,
1H, C5H4), 5.92 (m, 1H, C5H4), 6.08 (m, 1H, C5H4), 6.66 (m,
1H, C5H4), 6.85-7.10 (m, Ph). 13C NMR (75 MHz, C6D6, 25
°C, δ): 2.91 (SiClMe2), 3.96 (SiClMe2), 18.4 (CdNMe2C6H3),
18.8 (CdNMe2C6H3), 31.5 (C(CH3)3), 43.0 (PhCH2CdN), 67.3
Data were collected at room temperature (25 °C) on an
Enraf-Nonius CAD 4 automatic four-circle diffractometer.
Intensity measurements were performed by ω scans in the
range 2° < 2θ < 50° on a crystal of dimensions 0.40 × 0.32 ×
0.28 mm. A total of 4963 of the 5190 measured reflections
were independent; the largest minimum and maximum in the
final difference Fourier synthesis were 0.455 and 0.656 e Å-3
,
respectively. R1 ) 0.031, and wR2 ) 0.076 (for 4083 reflec-
tions with F > 4σ(F)). The values of R1 and wR2 are defined
2
as R1 ) Σ||Fo| - |Fc||/[Σ|Fo|] and wR2 ) {[Σw(Fo - Fc2)2]/
[Σw(Fo2)2]}1/2. The structure was solved by direct methods and
refined by least-squares against F2 (SHELX-97).16 All non-
hydrogen atoms were anisotropically refined and the hydrogen
atoms positioned geometrically and refined by using a riding
model in the last cycles of refinement.
Ack n ow led gm en t. This work was financially sup-
ported by the DGICYT (Project PB-92/0178-C), which
is gratefully acknowledged.
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal
data and structure refinement, atomic coordinates and isotro-
pic displacement parameters, bond lengths and angles, aniso-
tropic displacement parameters, hydrogen coordinates and
isotropic displacement parameters, and least-squares planes
(7 pages). Ordering information is given on any current
masthead page.
(C(CH3)3), 103.5, 110.6, 111.9, 116.9 (C2-C5, C5H4), 115.8 (Cipso
,
C5H4), 126.6-140.3 (Ph), 226.9 (PhCH2CdN). IR (Nujol mull;
ν, cm-1): 1642, 1244.
OM970876N
4.9. Cr ysta l Str u ctu r e Deter m in a tion of 5‚C6H5Me.
Crystals suitable for X-ray study were obtained by recrystal-
lization from toluene, and the dinuclear complex 5 crystallized
(16) Sheldrick, G. M. SHELX-97 Package; University of Go¨ttingen,
Go¨ttingen, Germany, 1997.