Isolation and chemistry of tantalum(v) compounds containing two resolved 3,3′-disubstituted-1,1′-bi-2,2′-naphthoxide ligands

Article abstract of DOI:10.1021/om0108200

Reaction of dimeric [(Et₂N)₂Cl₂Ta(μ-Cl)₂TaCl₂ (NEt₂)₂] with (R)-[H₂O₂C₂₀H₁₀(R)₂-3,3 ′] (R = SiMe₃, SiMe₂Ph, SiMePh₂, or SiPh₃) produces the 3,3′-dialkyl-1,1′-bi-2,2′-naphthoxido complexes (R,R)-[H₂NEt₂][Ta(O₂C₂₀H₁₀ {R}₂-3,3′)₂Cl₂] (R = SiMe₃, (R,R)-1; SiMe₂Ph, (R,R)2; SiMePh₂, (R,R)-3; SiPh₃, (R,R)-4). Structural studies of the SiMe₃ derivative (R,R)-1 showa pseudo-octahedral anion with mutually cis chloride ligands. Although NMR studies indicate that the anion of (R,R)-1 is stable in DMSO-d₆, an equilibrium mixture is observed in C₆D₆ solution with the neutral complex (R,R)-[Ta{O₂C₂₀H₁₀(SiMe₃)₂ -3,3′}₂Cl], (R,R)-1a, and [H₂NEt₂]Cl. The temperature dependence of the equilibrium has been studied. Addition of [ⁿBu₄N]Cl to a mixture of (R,R)-l/(R,R)-1a in C₆D₆ is shown (¹H NMR) to shift the equilibrium toward (R,R)-1. Alkylation of (R,R)-1 with Grignard reagents RMgCl results in formation of the five-coordinate (R,R)-[Ta(O₂C₂₀H₁₀{SiMe₃}₂ -3,3′}₂R′] (R′ = CH₂SiMe₃, (R,R)-5; CH₂Ph, (R,R)-6; c-C₅H₉, (R,R)-7).

Full text of DOI:10.1021/om0108200

484
Organometallics 2002, 21, 484-490
Isola tion a n d Ch em istr y of Ta n ta lu m (V) Com p ou n d s
Con ta in in g Tw o Resolved
3,3′-Disu bstitu ted -1,1′-bi-2,2′-Na p h th oxid e Liga n d s
Charles S. Weinert,* Phillip E. Fanwick, and Ian P. Rothwell*
Department of Chemistry, 1393 Brown Building, Purdue University,
West Lafayette, Indiana 47907-1393
Received September 11, 2001
Reaction of dimeric [(Et2N)2Cl2Ta(µ-Cl)2TaCl2(NEt2)2] with (R)-[H2O2C20H10(R)2-3,3′]
(R ) SiMe3, SiMe2Ph, SiMePh2, or SiPh3) produces the 3,3′-dialkyl-1,1′-bi-2,2′-naphthoxido
complexes (R,R)-[H2NEt2][Ta(O2C20H10{R}2-3,3′)2Cl2] (R ) SiMe3, (R,R)-1; SiMe2Ph, (R,R)-
2; SiMePh2, (R,R)-3; SiPh3, (R,R)-4). Structural studies of the SiMe3 derivative (R,R)-1 show
a pseudo-octahedral anion with mutually cis chloride ligands. Although NMR studies indicate
that the anion of (R,R)-1 is stable in DMSO-d6, an equilibrium mixture is observed in C6D6
solution with the neutral complex (R,R)-[Ta{O2C20H10(SiMe3)2-3,3′}2Cl], (R,R)-1a , and
[H2NEt2]Cl. The temperature dependence of the equilibrium has been studied. Addition of
[nBu4N]Cl to a mixture of (R,R)-1/(R,R)-1a in C6D6 is shown (1H NMR) to shift the equilibrium
toward (R,R)-1. Alkylation of (R,R)-1 with Grignard reagents RMgCl results in formation of
the five-coordinate (R,R)-[Ta(O2C20H10{SiMe3}2-3,3′}2R′] (R′ ) CH2SiMe3, (R,R)-5; CH2Ph,
(R,R)-6; c-C5H9, (R,R)-7).
In tr od u ction
niobium and tantalum aryloxide compounds with the
goal of carrying out asymmetric transformations. Yama-
moto et al. have achieved the isolation and resolution
of C2-symmetric, chiral monodentate aryloxide ligands.4
We have also synthesized and studied potentially chiral
2,6-di(1-naphthyl)phenoxide ligands and explored some
of their reaction chemistry.2m-o However, low yields and
the difficulty of resolution of these materials have
hampered this effort.
The readily resolved 2,2′-dihydroxy-1,1′-binaphthyl
(BINOL) ligand is one of the most important chiral
auxiliaries in chemistry.5 The unsubstituted BINOL has
been used in a vast number of asymmetric catalytic
applications, although in some of these applications the
exact nature (molecularity) of the active species is
uncertain. To help control solubility and increase the
chiral impact and steric size of the ligand, various
strategies have been devised to introduce substituents
at the 3,3′-positions. These bulkier ligands have also
been applied to asymmetric syntheses and have been
instrumental in allowing the isolation and characteriza-
tion of discrete molecular species. In particular, Mikami
et al. have applied a compound formulated as [(binaph-
thoxide)TiCl2] to numerous organic transformations.6
Heppert and co-workers have managed to structurally
characterize and better understand the molecularity,
dynamics, and bonding modes of Ti(IV) derivatives of
The use of bulky aryloxide ligands for supporting
stoichiometric and catalytic chemistry at early transi-
tion metal centers continues to be an important area in
inorganic/organometallic chemistry.1 In the case of the
group 5 metals niobium and tantalum, the mixed chloro/
aryloxide species [M(OAr)xCl5-x] (OAr ) 2,6-disubsti-
tuted phenoxides) are important starting materials for
exploring the chemistry of these elements. In particular,
the stoichiometric and catalytic reactivity of d0-alkyl-
and hydridoaryloxides2,3 has been well developed, par-
ticularly involving their use as precursors/catalysts for
arene hydrogenation. These developments have led us
to attempt the synthesis of chiral analogues of known
* Corresponding author. E-mail: rothwell@purdue.edu.
(1) Bradley, D. C.; Mehrotra, R. C.; Singh, A.; Rothwell, I. P. Alkoxo
and Aryloxo Derivatives of Metals; Academic Press: London, 2001.
(2) (a) Chamberlain, L. R.; Keddington, J . L.; Rothwell, I. P.
Organometallics 1992, 1, 1098. (b) Chamberlain, L. R.; Rothwell, I.
P.; Huffman, J . C. Inorg. Chem. 1984, 23, 2575. (c) Chamberlain, L.
R.; Rothwell, I. P.; Huffman, J . C. J . Am. Chem. Soc. 1986, 108, 1502.
(d) Chesnut, R. W.; Durfee, L. D.; Fanwick, P. E.; Rothwell, I. P.
Polyhedron 1987, 6, 2019. (e) Chamberlain, L. R.; Kerscher, J . L.;
Rothwell, A. P.; Rothwell, I. P.; Huffman, J . C. J . Am. Chem. Soc. 1987,
109, 6471. (f) Chamberlain, L. R.; Steffey, B. D.; Rothwell, I. P.
Polyhedron 1989, 8, 341. (g) Steffey, B. D.; Chesnut, R. W.; Kerschner,
J . L.; Pellechia, P. J .; Fanwick, P. E.; Rothwell, I. P. J . Am. Chem.
Soc. 1989, 111, 378. (h) Steffey, B. D.; Chamberlain, L. R.; Chesnut,
R. W.; Chebi, D. E.; Fanwick, P. E.; Rothwell, I. P. Organometallics
1989, 8, 1419. (i) Chesnut, R. W.; Yu, J . S.; Fanwick, P. E.; Rothwell,
I. P. Polyhedron 1990, 8, 1051. (j) Steffey, B. D.; Fanwick, P. E.;
Rothwell, I. P. Polyhedron 1990, 9, 963. (k) Yu, J . S.; Fanwick, P. E.;
Rothwell, I. P. J . Am. Chem. Soc. 1990, 112, 8171. (l) Chesnut, R. W.;
J acob, G. G.; Yu, J . S.; Fanwick, P. E.; Rothwell, I. P. Organometallics
1991, 10, 321. (m) Vilardo, J . S.; Thorn, M. G.; Fanwick, P. E.; Rothwell,
I. P. J . Chem. Soc., Chem. Commun. 1998, 2425. (n) Thorn, M. G.;
Vilardo, J . S.; Fanwick, P. E.; Rothwell, I. P. J . Chem. Soc., Chem.
Commun. 1998, 2427. (o) Riley, P. N.; Thorn, M. G.; Vilardo, J . S.;
Lockwood, M. A.; Fanwick, P. E.; Rothwell, I. P. Organometallics 1999,
18, 3016. (p) Thorn, M. G.; Fanwick, P. E.; Rothwell, I. P. Organome-
tallics 1999, 18, 4442. (q) Thorn, M. G.; Fanwick, P. E.; Chesnut, R.
W.; Rothwell, I. P. J . Chem. Soc., Chem. Commun. 1999, 2543.
(3) (a) Rothwell, I. P. J . Chem. Soc., Chem. Commun. (Feature
Article) 1997, 1331. (b) Clark, J . R.; Fanwick, P. E.; Rothwell, I. P. J .
Chem. Soc., Chem. Commun. 1995, 553. (c) Parkin, B. C.; Clark, J . C.;
Visciglio, V. M.; Fanwick, P. E.; Rothwell, I. P. Organometallics 1995,
14, 3002.
(4) (a) Saito, S.; Kano, T.; Muto, H.; Nakadai, M.; Yamamoto, H. J .
Am. Chem. Soc. 1999, 121, 8943. (b) Saito, S.; Kano, T.; Nakadai, M.;
Yamamoto, H. J . Org. Chem. 1997, 62, 5651.
(5) Noyori, R. Asymmetric Catalysis in Organic Synthesis; Wiley-
Interscience: New York, 1994.
(6) Mikami, K. Pure Appl. Chem. 1996, 68, 639.
10.1021/om0108200 CCC: $22.00 © 2002 American Chemical Society
Publication on Web 01/03/2002

Isolation and Chemistry of Tantalum(V) Compounds
Organometallics, Vol. 21, No. 3, 2002 485
Sch em e 1
substituted binaphthoxide ligands.7 Schaverien has
shown that binaphthoxide derivatives of Ti and Zr will
produce isotactic poly(R-olefins) when activated with
MAO.8 Heppert has also studied a number of molybde-
num and tungsten complexes containing these ligands.9
Schrock has reported the application of binaphthoxide
ligands containing bulky 3,3′-substituents to give well-
defined, asymmetric metathesis catalysts.10
However, there appears to be little reported on the
chemistry of Nb and Ta binaphthoxide complexes, and
hence we decided to investigate potential routes to
complexes of these metals containing this bis(aryloxide)
chiral auxiliary. We have used the synthetic methodol-
ogy of Snieckus11 to obtain gram quantities of the
resolved ligands [H2O2C20H10(R)2-3,3′] (R ) SiMe3,
SiMe2Ph, SiMePh2, SiPh3). Preliminary studies of the
reaction of simple metal halides with either these parent
BINOLs or their dilithio derivatives have proven disap-
pointing. However, the use of dialkylamido precursors
has proven to be a convenient approach to introducing
the chiral ligands into the metal coordination sphere.
In this paper we report on the reactivity of the dimeric
compound [(Et2N)2Cl2Ta(µ-Cl)2TaCl2(NEt2)2] shown by
Wigley et al. to contain an edge-shared bis(octahedral)
structure with terminal diethylamido groups located
trans to the bridging chloride ligands.12
Resu lts a n d Discu ssion
Syn th esis a n d Str u ctu r a l Stu d ies. Reaction of the
dimer [(Et2N)2Cl2Ta(µ-Cl)2TaCl2(NEt2)2] with (R)-3,3′-
bis(trimethylsilyl)-1,1′-bi-2,2′-naphthol proceeds rapidly
in hydrocarbon solvents. However, the reaction is not
straightforward. Addition of 1 equiv. of (R)-3,3′-bis(tri-
methylsilyl)-1,1′-bi-2,2′-naphthol per Ta results in a
product mixture that did not contain expected mono-
(binaphthoxide) products such as [Ta(O2C20H10{SiMe3}2-
3,3′)Cl3]. Spectroscopic (1H NMR in C6D6) characteriza-
tion of the product mixture obtained indicated the
presence of unreacted reagent [(Et2N)2Cl2Ta(µ-Cl)2-
TaCl2(NEt2)2] and an equilibrium mixture (vide infra)
of two new tantalum compounds (R,R)-1 and (R,R)-1a .
The reaction of 2 equiv. of (R)-3,3′-bis(trimethylsilyl)-
2,2′-bi-1,1′-naphthol per Ta results in the clean (NMR)
formation of (R,R)-1/(R,R)-1a . Hence it appears that any
mono(binaphthoxide) intermediates that are formed
react more rapidly with (R)-3,3′-bis(trimethylsilyl)-1,1′-
bi-2,2′-naphthol than does [(Et2N)2Cl2Ta(µ-Cl)2TaCl2-
(NEt2)2].
Slow cooling of a hot, concentrated benzene solution
of the clean product mixture resulted in X-ray quality
crystals of a single morphology. Analysis by X-ray
diffraction showed them to contain the salt (R,R)-
[H2NEt2][Ta(O2C20H10{SiMe3}2-3,3′)Cl2], (R,R)-1 (Scheme
1). An ORTEP diagram of the anion of (R,R)-1 is shown
in Figure 1, and selected bond distances and angles are
listed in Table 1. The anion is a six-coordinate pseudo-
octahedral complex of Ta(V), with two binaphthoxide
ligands bound to the metal center in a bidentate fashion.
The two chlorine atoms are in a mutually cis-arrange-
ment. The average Ta-O bond distance is 1.92 Å, while
the average Ta-Cl distance is 2.46 Å. The average acute
O-Ta-O bond angle is 92.7°, and the Cl-Ta-Cl angle
(7) (a) Eilerts, N. W.; Heppert, J . A. Polyhedron 1995, 14, 3255. (b)
Eilerts, N. W.; Heppert, J . A.; Kennedy, M. L.; Takusagawa, F. Inorg.
Chem. 1994, 33, 4813. (c) Boyle, T. J .; Eilerts, N. W.; Heppert, J . A.;
Takusagawa, F. Organometallics 1994, 13, 2218. (d) Boyle, T. J .;
Barnes, D. L.; Heppert, J . A.; Morales, L.; Takusagawa, F.; Connolly,
J . C. Organometallics 1992, 11, 1112.
(8) van der Linden, A.; Schaverien, C. J .; Meijboom, N.; Grant, C.;
Orpen, A. G. J . Am. Chem. Soc. 1995, 117, 3008.
(9) (a) Heppert, J . A.; Dietz, S. D.; Eilerts, N. W.; Henning, R. W.;
Morton, M. D.; Takusagawa, F.; Kaul, F. A. Organometallics 1993, 12,
2565. (b) Morton, M. D.; Heppert, J . A.; Dietz, S. D.; Huang, W. H.;
Ellis, D. A.; Grant, T. A.; Eilerts, N. W.; Barnes, D. L.; Takusagawa,
F.; VanderVelde, D. J . Am. Chem. Soc. 1993, 115, 7916. (c) Barnes, D.
L.; Eilerts, N. W.; Heppert, J . A.; Huang, W. H.; Morton, M. D.
Polyhedron 1994, 13, 1267.
(10) (a) Zhu, S. S.; Cefalo, D. R.; La, D. S.; J amieson, J . Y.; Davis,
W. M.; Hoveyda, A. H.; Schrock, R. R. J . Am. Chem. Soc. 1999, 121,
8251. (b) La, D. S.; Ford, J . G.; Sattely, E. S.; Bonitatebus, P. J .;
Schrock, R. R.; Hoveyda, A. H. J . Am. Chem. Soc. 1999, 121, 11603.
(c) La, D. S.; Alexander, J . B.; Cefalo, D. R.; Graf, D. D.; Hoveyda, A.
H.; Schrock, R. R. J . Am. Chem. Soc. 1998, 120, 9720. (d) Totland, K.
M.; Boyd, T. J .; Lavoie, G. G.; Davis, W. M.; Schrock, R. R. Macromol-
ecules 1996, 29, 6114.
(11) Cox, P. J .; Wang, W.; Snieckus, V. Tetrahedron Lett. 1992, 33,
2253.
(12) Chao, Y. W.; Wexler, P. A.; Wigley, D. E. Inorg. Chem. 1989,
28, 3860.

486 Organometallics, Vol. 21, No. 3, 2002
Weinert et al.
relative to (R,R)-1, and complexes (R,R)-3 and (R,R)-4
are increasingly less soluble.
Solu tion Stu d ies. The 1H NMR spectrum of the
crystals of (R,R)-1 in DMSO-d6 exhibits two resonances
in the aromatic region at δ 7.98 and 7.53 ppm, which
can be assigned to the 4,4′-hydrogens of a coordinated
binaphthoxide ligand, and two sharp peaks at δ 0.49
and -0.29 ppm attributable to two distinct sets of
trimethylsilyl groups (Table 2). The solid state structure
of (R,R)-1 can be used to rationalize the 1H NMR
spectrum in DMSO-d6. There are two groups of mag-
netically and chemically inequivalent 4,4′-hydrogen
atoms, one group pointing in toward the chiral pocket
and one group pointing away. Similarly, two trimeth-
ylsilyl groups point into the chiral pocket and two lie
away from the metal center. The SiMe3 resonance at δ
0.49 ppm corresponds to the groups pointing away from
the metal, which are slightly deshielded by the magnetic
anisotropy of the naphthyl rings. Similarly, the reso-
nance at δ 7.53 ppm is assigned to the 4,4′-hydrogens
that point toward the chiral pocket.
The 13C NMR of (R,R)-1 in DMSO-d6 exhibits 20
distinct resonances for the carbon atoms of the binaph-
thyl rings. Two peaks at δ 163.0 and 160.4 ppm are
assigned to the carbons bound to oxygen, while the
upfield features at δ 21.7 and 13.8 ppm are assigned to
the carbon atoms bound to silicon. The 1H and 13C NMR
data indicate that the two binaphthoxide ligands are
equivalent on the NMR time scale.
The 1H NMR spectrum of (R,R)-1 in C6D6 is more
complex than that in DMSO-d6. There are three distinct
resonances for the 4,4′-hydrogens, as well as three peaks
for the SiMe3 groups. This indicates the presence of
another binaphthoxide-containing complex in solution.
We believe complex (R,R)-1 undergoes an equilibrium
between the six-coordinate salt complex that exists in
the solid state and a neutral, five-coordinate species
[Ta(O2C20H10{SiMe3}2-3,3′)2Cl], (R,R)-1a , as shown in
Scheme 2.
F igu r e 1. ORTEP diagram for the anion of [H2NEt2][Ta-
(O2C20H10{SiMe3}2-3,3′)2Cl2], (R,R)-1. Thermal ellipsoids
are drawn at 50% probability.
Ta ble 1. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for [H2NEt2][Ta (O2C20H10{SiMe3}2-3,3′)2Cl2],
(R,R)-1‚C6H6
Ta-O(1)
Ta-O(3)
Ta-Cl(1)
1.945(4)
1.945(4)
2.456(2)
Ta-O(2)
Ta-O(4)
Ta-Cl(2)
1.880(4)
1.896(4)
2.454(2)
O(1)-Ta-O(2)
O(1)-Ta-O(4)
O(2)-Ta-O(4)
O(1)-Ta-Cl(1)
O(2)-Ta-Cl(1)
O(3)-Ta-Cl(1)
O(4)-Ta-Cl(1)
Cl(1)-Ta-Cl(2)
90.0(2)
91.6(2)
100.8(2)
89.2(2)
170.6(2)
88.4(2)
88.6(2)
84.65(7)
O(1)-Ta-O(3)
O(2)-Ta-O(3)
O(3)-Ta-O(4)
O(1)-Ta-Cl(2)
O(2)-Ta-Cl(2)
O(3)-Ta-Cl(2)
O(4)-Ta-Cl(2)
177.6(2)
92.3(2)
88.8(2)
89.6(2)
86.0(2)
89.8(2)
173.2(2)
is 84.6°. The O(2)-Ta-O(4) angle is significantly larger
than the others, likely resulting from the steric repul-
sion of the two bulky binaphthoxide ligands. The Ta-O
bond length in (R,R)-1 is slightly longer than that of
the neutral complex (S)-[Ta(O2C20H10{SiMe3}2-3,3′)-
(NMe2)3(HNMe2)].13 This is likely due to the anionic
charge of (R,R)-1, which reduces π-bonding between the
binaphthoxide ligands and the metal center, resulting
in a longer Ta-O bond. An average bond length of 1.89
Å was found for the Ta-O bond of [H2NMe2](S)-
[Ta(O2C20H10{SiMe3}2-3,3′)Cl4], which also contains an
anionic tantalum binaphthoxide complex.13 Complex
(R,R)-1 is the only structurally characterized bis(bi-
naphthoxide) complex of tantalum. A complex, H[Ta-
(O2C20H12)3], has been reported which was not struc-
turally characterized.14
Upon addition of [nBu4N]Cl to an NMR sample of
(R,R)-1/(R,R)-1a in C6D6, the partially soluble material
completely dissolves and the resonances due to neutral
(R,R)-1a at δ 8.19 and 0.66 ppm disappear, while those
due to (R,R)-1 at δ 8.22, 7.83, 0.91, and 0.09 ppm
remain. Surprisingly, addition of [nBu4N]Br results in
the mixed-halide complex [H2NEt2][Ta(O2C20H10-3,3′-
{SiMe3}2)2ClBr], which exhibits resonances identical to
those using [Bu4N]Cl despite the presence of a less
electronegative halide ligand. Although we are unable
to provide a definite explanation for this effect, it
appears the incoming bromide anion drives the equi-
librium to the left as well. Furthermore, complex (R,R)-
1a is expected to exhibit two resonances for both the
4,4′-hydrogens and the trimethylsilyl groups. However,
the presence of one feature for each group indicates that
(R,R)-1a is fluxional on the NMR time scale, while
conformational rigidity seems to be enforced in the salt
(R,R)-1 by the presence of a second chloride ligand.
Related compounds (R,R)-2-4 were prepared from
[(Et2N)2Cl2Ta(µ-Cl)2TaCl2(NEt2)2] and (R)-3,3′-dimeth-
ylphenylsilyl-1,1′-bi-2,2′-naphthol, (R)-3,3′-methyldiphen-
ylsilyl-1,1′-bi-2,2′-naphthol, and (R)-3,3′-triphenylsilyl-
1,1′-bi-2,2′-naphthol, respectively, as shown in Scheme
1. Complex 2 exhibits diminished solubility in C6D6
Variable-temperature NMR experiments over the
temperature range -90 to +90 °C on (R,R)-1 in toluene-
d8 also confirm the existence of the equilibrium process.
At very low temperatures (-90 °C), the spectrum lacks
distinct features due to the low solubility of 1 in toluene,
but at -70 °C, an approximate 1:1 mixture of (R,R)-1
(13) Thorn, M. G.; Moses, J . E.; Fanwick, P. E.; Rothwell, I. P. J .
Chem. Soc., Dalton Trans. 2000, 2659.
(14) Andrae, K. J . Less-Common Met. 1969, 17, 297.

Isolation and Chemistry of Tantalum(V) Compounds
Organometallics, Vol. 21, No. 3, 2002 487
Ta ble 2. 1H NMR Da ta for Com p lexes (R,R)-1-(R,R)-7
species
solvent
C6D6
DMSO-d6
C6D6
DMSO-d6
DMSO-d6
DMSO-d6
C6D6
δ (4,4′-hydrogens)
δ (alkylsilyl groups)
0.91, 0.66, 0.09
0.49, -0.29
0.89, 0.88, 0.87, 0.85, 0.71, -0.15
0.90, 0.84, 0.36, -0.53
0.90, 0.42
[H2NEt2][Ta(O2C20H10{SiMe3}2-3,3′)2Cl2] (R,R)-1
8.22, 8.19, 7.83
7.98, 7.53
8.07, 7.98, 7.91, 7.89
7.80, 7.78, 7.73, 7.71
8.45, 7.70
8.75, 7.83
8.24, 8.00
8.02, 7.89
8.23, 8.21, 8.03, 8.00
[H2NEt2][Ta(O2C20H10{SiMe2Ph}2-3,3′)2Cl2] (R,R)-2
[H2NEt2][Ta(O2C20H10{SiMePh2}2-3,3′)2Cl2] (R,R)-3
[H2NEt2][Ta(O2C20H10{SiPh3}2-3,3′)2Cl2] (R,R)-4
[Ta(O2C20H10{SiMe3}2-3,3′)2(CH2SiMe3)] (R,R)-5
[Ta(O2C20H10{SiMe3}2-3,3′)2(CH2C6H5)] (R,R)-6
[Ta(O2C20H10{SiMe3}2-3,3′)2(CH2C5H9)] (R,R)-7
0.56, 0.16, -0.18
0.37, 0.14
0.53, 0.49, 0.15, 0.14
C6D6
C6D6
Sch em e 2
and (R,R)-1a becomes evident. At -50 °C, the reso-
nances become sharp and distinctive, and they increase
in intensity across the range between -40 and +30 °C
with little change in the relative intensities for (R,R)-1
and (R,R)-1a . Above +30 °C, the peaks at δ 8.10 and
0.60 ppm begin to decrease in intensity, indicating the
predominance of the salt (R,R)-1, and by +90 °C, the
resonances of (R,R)-1a are very low in intensity. This
is likely the result of the increased solubility of
[H2NEt2][Cl] at higher temperatures, which drives the
equilibrium to the left.
vacuo) and MgCl2. Two resonances at δ 8.24 and 8.00
ppm in the H NMR spectrum of (R,R)-5 correspond to
1
the 4,4′-hydrogens, and three peaks in the alkylsilyl
region at δ 0.56, 0.16, and -0.18 ppm (intensity ratio
2:2:1) arise from the two nonequivalent trimethylsilyl
groups on the binaphthoxide ligands and the CH2SiMe3
group, respectively. The diastereotopic hydrogens of the
CH2SiMe3 group result in an AX pattern, with reso-
nances at δ 2.09 and 1.47 ppm and a coupling constant
of 12.3 Hz.
Two additional alkyl species, [Ta(O2C20H10{SiMe3}2-
3,3′)2(CH2C6H5)], (R,R)-6, and [Ta(O2C20H10{SiMe3}2-
3,3′)2(c-C5H9)], (R,R)-7, were prepared from (R,R)-1 and
ClMgCH2C6H5 or ClMgC5H9, respectively, as shown in
Compound (R,R)-2 is a salt with the formula [H2N-
Et2][Ta(O2C20H10{Me2PhSi}2-3,3′)2Cl2], which exhibits
resonances for the diethylammonium cation identical
to (R,R)-1. Similar to (R,R)-1, the NMR spectrum of
(R,R)-2 contains two features for the 4,4′-hydrogens of
the binaphthoxide ligands, as well as four distinct
signals for the magnetically nonequivalent Me2PhSi
groups (Table 2). Compound (R,R)-2 also appears to
undergo an equilibrium process similar to (R,R)-1. The
1H NMR spectrum in C6D6 exhibits three 4,4′-hydrogen
resonances and six features for the Me2PhSi groups
1
Scheme 3. The H NMR of the benzyl derivative (R,R)-6
contains two peaks for the 4,4′ aromatic hydrogens at
δ 8.02 and 7.89 ppm and peaks for the trimethylsilyl
groups at δ 0.37 and 0.14 ppm (Table 2). The diaste-
reotopic CH2 hydrogens again result in an AX pattern,
with doublets at 3.57 and 3.19 ppm and a coupling
constant of 14.7 Hz.
The 1H NMR spectrum of (R,R)-7 contains four
resonances for the 4,4′ aromatic protons and four
features for the trimethylsilyl groups (Table 2). Incor-
poration of the cyclopentyl ligand removes C2 symmetry
from the molecule, which is present in both (R,R)-5 and
(R,R)-6, resulting in all four -SiMe3 groups and all four
4,4′-hydrogens being nonequivalent. Nine distinct fea-
tures are observed for the protons attached to the
cyclopentyl ring. A signal for the proton bound to the
R-carbon appears at δ 2.90 ppm and appears as a
multiplet, close to the predicted triplet of triplets.
Additionally, four SiMe3 peaks are observed in the 13C
NMR of (R,R)-7, further indicating the absence of C2
symmetry in this complex.
1
(Table 2). The H and 13C NMR spectra of (R,R)-3 and
(R,R)-4 in DMSO-d6 indicate that these materials are
also salts with the formulas [H2NEt2][Ta(O2C20H10{Me-
Ph2Si}2-3,3′)2Cl2] and [H2NEt2][Ta(O2C20H10{Ph3Si}2-
3,3′)2Cl2], respectively. The limited solubility of both
(R,R)-3 and (R,R)-4 in C6D6 precluded NMR studies in
this solvent.
Alk yla tion Stu d ies. Reaction of (R,R)-1 with 2.2
equiv. of ClMgCH2SiMe3 cleanly produces the neutral
complex [Ta(O2C20H10{SiMe3}2-3,3′)2CH2SiMe3], (R,R)-
5, as shown in Scheme 3. The excess Grignard reagent
deprotonates the [H2NEt2]+ cation, resulting in the
formation of HNEt2 and SiMe4 (which are removed in

488 Organometallics, Vol. 21, No. 3, 2002
Weinert et al.
Sch em e 3
Sch em e 4
The preparation of (R,R)-5 was attempted by an
alternate strategy, as illustrated in Scheme 4. The dimer
[(Et2N)2Cl2Ta(µ-Cl)2TaCl2(NEt2)2] was reacted with 3
equiv. of ClMgCH2SiMe3 in an attempt to prepare the
mixed amide alkyl complex [Ta(NEt2)2(CH2SiMe3)3]. The
1H NMR of the product suggested the desired complex
was present, but that it was one component of a mixture
of species. Treatment of the crude reaction mixture with
2 equiv. of (R)-3,3′-bis(trimethylsilyl)-1,1′-bi-2,2′-naph-
thol also yielded (R,R)-5, but again as a component of a
mixture of products.
Attempts to isolate (R,R)-5 in pure form from the
reaction mixture by successive recrystallization were
unsuccessful. However, colorless crystals were isolated
which were determined to be [H2NEt2]2[Mg(O2C20H10
-
{SiMe3}2-3,3′)Cl2], (R,R)-8. An ORTEP plot of the anion
is shown in Figure 2, and selected bond distances and
angles are listed in Table 3. Binaphthoxide complexes
of magnesium are rare, and only one series of Mg-
bintahphthoxide complexes has been reported, (S)-
Li2[Mg(O2C20H12)R2] (R ) CH3, C2H5, n-C4H9, t-C4H9,
CH2dCHCH2, C6H5, CH2dCH, or Me3SiCC).15 To our
F igu r e 2. ORTEP diagram for the anion of [H2NEt2]2[Mg-
(O2C20H10{SiMe3}2-3,3′)Cl2], (R)-8. Thermal ellipsoids are
drawn at 50% probability.
knowledge, complex (R,R)-8 represents the only struc-
turally characterized example of a material of this type.
The environment about the magnesium atom ap-
(15) Noyori, R.; Suga, S.; Kawai, K.; Okada, S.; Kitamura, M. Pure
Appl. Chem. 1988, 60, 1597.

Isolation and Chemistry of Tantalum(V) Compounds
Organometallics, Vol. 21, No. 3, 2002 489
Ta ble 3. Selected Bon d Dista n ces (Å) a n d
An gles (d eg) for
122.0, 117.8, 116.0, 41.2, 21.7, 13.8, 10.9, 0.7, -0.7. Anal. Calcd
for C66H74Cl2NO4Si4Ta [1‚C6H6]: C, 59.03; H, 5.91; N, 1.11;
Cl, 5.62. Found: C, 58.79; H, 5.97; N, 1.17; Cl, 5.84.
[H2NEt2]2[Mg(O2C20H10{SiMe3}2-3,3′)Cl2]‚C6H6,
(R)-8‚C6H6
Syn th esis of [H2NEt2][Ta(O2C20H10{SiMe2P h }2-3,3′)2Cl2],
(R,R)-2. In a manner analogous to the synthesis of (R,R)-1,
[(Et2N)2Cl2Ta(µ-Cl)2TaCl2(NEt2)2] (0.561 g, 0.649 mmol) was
reacted with (R)-3,3′-(dimethylphenylsilyl)-1,1′-bi-2,2′-naphthol
Mg-O(1)
Mg-Cl(1)
1.979(2)
2.348(1)
Mg-O(2)
Mg-Cl(2)
1.912(2)
2.3906(9)
O(1)-Mg-O(2)
O(1)-Mg-Cl(2)
O(2)-Mg-Cl(2)
99.44(7)
116.06(6)
108.10(6)
O(1)-Mg-Cl(1)
O(2)-Mg-Cl(1)
Cl(1)-Mg-Cl(2)
109.15(5)
118.29(6)
106.21(4)
1
(1.52 g, 2.73 mmol) to yield 0.74 g (79%) of (R,R)-2. H NMR
(C6D6, 25 °C, 300 MHz): δ 8.42 (s), 8.31 (s), 7.98 (s), 7.92 (s),
7.84 (s), 7.68 (m), 7.53 (s), 7.34-6.66 (m, aromatics); 2.12 (s)
1.72 (br s), 1.44(s), 1.29 (s, Si(CH3)3), 0.89 (s, Si(CH3)3), 0.88
(s, Si(CH3)3), 0.87 (s, Si(CH3)3), 0.85(s, Si(CH3)3), 0.52 (br s),
-0.15 (s, Si(CH3)3). 1H NMR (DMSO-d6, 25 °C, 500 MHz): 8.52
(br, 2 H, H2NEt2); 7.80 (s, 2 H); 7.78 (s, 2 H); 7.72 (br, 4H);
7.51-6.85 (m, 28 H, aromatics); 6.71 (d, 2 H J ) 8.5 Hz); 6.25
(d, 2 H, J ) 8.5 Hz); 2.89 (pseudosept, 4 H, H2N(CH2CH3)2);
1.17 (t, 6 H, J ) 7.0 Hz, H2N(CH2CH3)2); 0.92 (s, SiPh(CH3)2);
0.85 (s, SiPh(CH3)2); 0.37 (s, SiPh(CH3)2); -0.52 (s, SiPh(CH3)2).
13C NMR (DMSO-d6, 25 °C, 125.7 MHz): δ 163.0, 160.2, 140.1,
139.8, 136.9, 135.5, 135.2, 134.7, 134.5, 133.2, 130.1, 129.3,
128.2, 128.0, 127.9, 127.7, 127.5, 127.2, 126.5, 126.0, 125.4,
125.0, 123.0, 122.4, 117.2, 116.7, 41.2, 11.0, -1.1, -1.5, -1.6,
-3.5. Anal. Calcd for C76H76Cl2NO4Si4Ta: C, 63.76; H, 5.35.
Found: C, 62.31; H, 5.75.
proaches tetrahedral, and the average Mg-O and Mg-
Cl bond lengths are 1.95 and 2.37 Å, respectively.
Exp er im en ta l Section
Gen er a l Rem a r k s. All manipulations were carried out
using standard syringe, Schlenk line, and glovebox tech-
niques.16 Benzene, toluene, ether, THF, and hexane were dried
over sodium benzophenone ketyl and were freshly distilled
before use. Pentane was dried over sodium ribbon. The rea-
gents [(Et2N)2Cl2Ta(µ-Cl)2TaCl2(NEt2)2],4 (R)-3,3′-trimethylsi-
lyl-1,1′-bi-2,2′-naphthol, (R)-3,3′-dimethylphenylsilyl-1,1′-bi-
2,2′-naphthol, (R)-3,3′-methyldiphenylsilyl-1,1′-bi-2,2′-naphthol,
and (R)-3,3′-triphenylsilyl-1,1′-bi-2,2′-naphthol11,17 were pre-
pared according to literature procedures or slight variations
thereof. (Trimethylsilylmethyl)magnesium chloride (1.0 M
solution in Et2O), benzylmagnesium chloride (2.0 M solution
in THF), and cyclopentylmagnesium chloride (2.0 M solution
in Et2O) were purchased from Aldrich and used as received.
1H NMR spectra were recorded on a Varian INOVA-300 NMR
spectrometer or a Bruker DRX-500 NMR spectrometer and
were referenced to residual protio solvent. 13C NMR spectra
were recorded on a Bruker DRX-500 NMR spectrometer at
125.7 MHz and were internally referenced to the solvent
signal. Elemental analyses were carried out in house at Purdue
University. The low percentage of carbon found in some of
these analyses (typically by 2-3%) is due to the formation of
carbide species, which is typical for early transition metal
organometallic compounds.
Syn th esis of [H2NEt2][Ta(O2C20H10{SiMeP h 2}2-3,3′)2Cl2],
(R,R)-3. In a manner analogous to the synthesis of (R,R)-1,
[(Et2N)2Cl2Ta(µ-Cl)2TaCl2(NEt2)2] (0.208 g, 0.242 mmol) was
reacted with (R)-3,3′-(methyldiphenylsilyl)-1,1′-bi-2,2′-naphthol
1
(0.690 g, 1.01 mmol) to yield 0.65 g (79%) of (R,R)-3. H NMR
(DMSO-d6, 25 °C, 500 MHz): 8.65 (br, H2NEt2); 8.46 (s); 7.70-
6.64 (m, aromatics); 2.88 (pseudosept, H2N(CH2CH3)2); 1.17 (t,
J ) 7.2 Hz, H2N(CH2CH3)2); 0.90 (s, SiPh2(CH3)); 0.42 (s,
SiPh2(CH3)). 13C NMR (DMSO-d6, 25 °C, 125.7 MHz): δ 163.4,
158.2, 138.8, 138.6, 136.9, 136.8, 135.3, 135.2, 135.2, 135.0,
134.9, 134.8, 134.7, 134.4, 126.1, 129.0, 128.9, 128.3, 127.9,
127.7, 127.6, 127.5, 127.3, 127.1, 126.7, 125.6, 123.7, 122.4,
112.2, 39.8, 11.0, -2.1, -2.4, -2.8, -3.2. Anal. Calcd for
C
96H84Cl2NO4Si4Ta: C, 68.64; H, 5.04. Found: C, 66.59; H,
5.64.
Syn t h esis of [H2NE t 2][Ta (O2C20H 10{SiP h 3}2-3,3′)2Cl2],
Syn t h esis of [H2NE t 2][Ta (O2C20H 10{SiMe3}2-3,3′)2Cl2],
(R,R)-1. The complex [(Et2N)2Cl2Ta(µ-Cl)2TaCl2(NEt2)2] (1.87
g, 2.17 mmol) was dissolved in 25 mL of benzene. To this was
added (R)-3,3′-trimethylsilyl-1,1′-bi-2,2′-naphthol (3.92 g, 9.10
mmol) in 15 mL of benzene dropwise over 10 min. The
resulting solution was stirred for 18 h, resulting in the
formation of an orange-red precipitate. The volume of the
solution was reduced to approximately 10 mL in vacuo and
was then heated to reflux and allowed to cool slowly. After 3
h, orange crystals had formed. These were isolated by filtra-
tion, washed with 4 × 10 mL of pentane, and dried in vacuo
to yield 3.87 g (75%) of (R,R)-1. 1H NMR (C6D6, 25 °C, 300
MHz): δ 8.21 (s), 8.19 (s), 7.82 (s) (4,4′-aromatic H); 7.68 (d,
J ) 8.1 Hz), 7.60 (d, J ) 3.9 Hz), 7.57 (d, J ) 3.9 Hz) (7,7′-
aromatic H); 7.11-6.62 (m, aromatics), 1.51 (pseudosept,
H2NCH2CH3); 0.91 (s, Si(CH3)3); 0.88 (t, J ) 7.3 Hz, H2NCH2-
CH3); 0.65 (s, Si(CH3)3); 0.09 (s, Si(CH3)3). 1H NMR (DMSO-
d6, 25 °C, 500 MHz): δ 8.50 (br s, 2H H2NCH2CH3); 7.98 (s,
2H); 7.80 (d, 2H, J ) 8.1 Hz); 7.74 (d, 2H, J ) 8.1 Hz); 7.53 (s,
2H); 7.35 (s, 2H); 7.13 (t, 2H, J ) 7.5 Hz); 7.10 (t, 2H, J ) 7.5
Hz); 6.95 (t, 2H, J ) 7.2 Hz); 6.88 (t, 2H, J ) 7.2 Hz); 6.53 (d,
2H, J ) 8.4 Hz); 6.29 (d, 2H, J ) 8.4 Hz); 2.89 (pseudosept,
4H, H2N(CH2CH3)2); 1.16 (t, 6H, J ) 7.2 Hz); 0.49 (s, 18H,
Si(CH3)3); -0.29 (s, 18H, Si(CH3)3). 13C NMR (DMSO-d6, 25
°C, 125.7 MHz): δ 163.0, 160.4, 136.2, 135.6, 134.2, 131.2,
130.5, 129.2, 128.6, 127.5, 127.3, 126.7, 126.1, 125.0, 122.6,
(R,R)-4. In a manner analogous to the synthesis of (R,R)-1,
[(Et2N)2Cl2Ta(µ-Cl)2TaCl2(NEt2)2] (0.200 g, 0.231) mmol) was
reacted with (R)-3,3′-(triphenylsilyl)-1,1′-bi-2,2′-naphthol (0.778
g, 0.969 mmol) to yield 0.56 g (73%) of (R,R)-4. 1H NMR
(DMSO-d6, 25 °C, 300 MHz): δ 8.75 (s); 8.70 (br s); 7.83-7.52
(m, aromatics); 7.42-7.03 (m, aromatics); 2.88 (pseudosept,
H2N(CH2CH3)2); 0.86 (t, J ) 7.2 Hz, H2N(CH2CH3)2).
Syn t h esis of [Ta (O2C20H 10{SiMe3}2-3,3′)2(CH2SiMe3)],
(R,R)-5. Compound (R,R)-1 (0.552 g, 0.466 mmol) was sus-
pended in 10 mL of benzene. A 1.0 M ethereal solution of
ClMgCH2SiMe3 (1.1 mL) was added via syringe. All materials
dissolved, and the reaction mixture changed from orange to
yellow over a period of 2 h with stirring. The solution was
filtered through Celite, and the solvent was removed in vacuo
1
to yield 0.43 g (83%) of (R,R)-5 as a yellow powder. H NMR
(C6D6, 25 °C, 300 MHz): 8.24 (s, 2 H); 8.00 (s, 2 H); 7.71 (d, 2
H J ) 8.1 Hz); 7.63 (d, 2 H, J ) 8.1 Hz); 7.19-6.80 (m, 12 H,
aromatics); 2.09 (d, 1 H, J ) 12.3 Hz, CH2SiMe3); 1.47 (d, 1 H,
J ) 12.3 Hz, CH2SiMe3); 0.56 (s, 18 H, BINOL-SiMe3); 0.16
(s, 18 H, BINOL-SiMe3); -0.18 (s, 9 H, CH2Si(CH3)3). 13C NMR
(C6D6, 25 °C, 125.7 MHz): 160.9, 160.5, 137.8, 137.6, 136.5,
136.0, 131.6, 131.4, 131.0, 130.3, 128.9, 127.7, 127.6, 127.5,
127.3, 124.9, 124.6, 119.1, 117.4, 71.8, 4.1, 1.7, -0.1. Anal.
Calcd for C56H67O4Si5Ta: C, 59.76; H, 6.00. Found: C, 57.80;
H, 6.30.
Syn t h esis of [Ta (O2C20H 10{SiMe3}2-3,3′)2(CH2C6H 5)],
(R,R)-6. To a suspension of (R,R)-1 (0.310 g, 0.262 mmol) in
benzene was added 0.6 mL of ClMgCH2C6H5 (2.0 M in THF).
After stirring for 2 h, the reaction mixture had become yellow.
The solution was filtered through Celite, and the solvent was
removed in vacuo to yield 0.20 g (69%) of (R,R)-6 as a dark
(16) Shriver, D. F.; Drezdzon, M. A. The Manipulation of Air-
Sensitive Compounds, 2nd ed.; J ohn Wiley & Sons: New York, 1986.
(17) Buisman, G. J . H.; van der Veen, L. A.; Klootwijk, A.; de Lange,
W. G. J .; Kamer, P. C. J .; van Leeuwen, P. W. N. M.; Vogt, D.
Organometallics 1997, 16, 2929.

490 Organometallics, Vol. 21, No. 3, 2002
Weinert et al.
Ta ble 4. Cr ysta llogr a p h ic Da ta for
[H2NEt2][Ta (O2C20H10{SiMe3}2-3,3′)2Cl2], (R,R)-1, a n d
[H2NEt2]2[Mg(O2C20H10{SiMe3}2-3,3′)Cl2], (R)-8
yellow solid. 1H NMR (C6D6, 25 °C, 300 MHz): δ 8.02 (s, 2 H);
7.89 (s, 2H); 7.63 (d, 4 H, J ) 8.1 Hz); 7.19-6.36 (m, 17 H,
aromatics); 3.57 (d, 1 H, J ) 14.7, CH2C6H5); 3.19 (d, 1 H, J )
14.7, CH2C6H5); 0.37 (s, 18 H, Si(CH3)3); 0.14 (s, 18 H,
Si(CH3)3). 13C NMR (C6D6, 25 °C, 125.7 MHz): δ 160.6, 159.8,
140.3, 139.5, 137.3, 137.1, 131.3, 129.5, 129.0, 128.8, 128.7,
127.8, 127.5, 127.1, 127.0, 126.8, 126.6, 124.7, 124.1, 119.0,
116.2, 79.3, 67.8, 33.5, 0.9, -0.7. Anal. Calcd for C59H63O4Si4-
Ta: C, 62.74; H, 5.62. Found: C, 59.32; H, 6.10.
(R,R)-1‚C6H6
(R)-8‚C6H6
formula
space group
a, Å
C66H74Cl2NO4Si4Ta
P212121 (#19)
15.8407(2)
C40H58Cl2MgN2O2Si2
P212121 (#19)
11.5471(2)
b, Å
c, Å
16.1199(2)
14.8484(3)
31.0956(6)
24.8848(6)
Syn th esis of [Ta (O2C20H10{SiMe3}23,3′)2(C5H9)], (R,R)-
7. To a suspension of (R,R)-1 in 10 mL of benzene was added
0.4 mL of ClMgC5H9 (2.0 M in Et2O). The reaction mixture
became yellow after 2 h of stirring. The solution was filtered
through Celite, and the solvent was removed in vacuo to yield
0.32 g (80%) of (R,R)-7 as a yellow-brown solid. 1H NMR (C6D6,
25 °C, 300 MHz): δ 8.23 (s, 1 H); 8.21 (s, 1 H); 8.03 (s, 1 H);
8.00 (s, 1 H); 7.73-7.61 (m, 4 H, aromatics); 7.15-7.00 (m, 8
H, aromatics); 6.86-6.76 (m, 4 H, aromatics); 2.89 (m, 1 H,
H-CR); 2.30 (m, 1 H); 2.02 (m, 1 H); 1.70 (m, 1 H); 1.52 (m, 1
H); 1.41 (m, 1 H); 0.92 (m, 1 H); 0.73 (m, 1 H); 0.29 (m, 1 H);
0.53 (s, Si(CH3)3); 0.47 (s, Si(CH3)3); 0.16 (s, Si(CH3)3); 0.15 (s,
Si(CH3)3). 13C NMR (C6D6, 25 °C, 125.7 MHz): δ 160.2, 159.9,
138.6, 137.4, 136.9, 136.8, 135.8, 135.6, 130.7, 130.3, 129.9,
129.2, 128.9, 128.5, 128.8, 127.4, 127.2, 127.1, 126.8, 124.9,
124.4, 124.2, 119.0, 117.0, 33.9, 32.9, 28.4, 27.7, 1.4, 1.3, -0.5,
R, deg
â, deg
γ, deg
V, Å3
Z
90
90
90
90
90
90
7940.3(4)
4
1.055
220
4266.6(3)
4
1.168
150
F
calc, g cm-3
temperature, K
radiation
(wavelength)
R
Rw
Mo KR (0.71073 Å)
Mo KR (0.71073 Å)
0.048
0.095
0.045
0.085
cal absorption correction using SCALEPACK was applied.19
Intensities of equivalent reflections were averaged. The struc-
ture was solved using the structure solution program PATTY
in DIRDIF92.20 The remaining atoms were located in succeed-
ing difference Fourier syntheses. Hydrogen atoms were in-
cluded in the refinement but restrained to ride on the atom to
which they are bonded. The structure was refined in full-
matrix least-squares where the function minimized was
-0.9. Anal. Calcd for
C57H65O4Si4Ta: C, 61.82; H, 5.92.
Found: C, 59.10; H, 5.86.
2
2
2
∑w(|Fo| - |Fc| )2 and the weight w is defined as w ) 1/[σ2(Fo
)
Alter n a te Syn th esis of [Ta (O2C20H10{SiP h 3}2-3,3′)2(CH2-
SiMe3)], (R,R)-5. A flask was charged with [Ta(NEt2)2Cl3]2
(1.32 g, 1.53 mmol). The solid was dissolved in 15 mL of
benzene and 10.5 mL of ClMgCH2SiMe3 (1.0 M in Et2O) was
added dropwise at 0 °C. The reaction mixture was stirred at
room temperature for 18 h. The solvent was removed in vacuo
to yield a thick red-brown oil. This was redissolved in 20 mL
of benzene, and (R)-3,3′-trimethylsilyl-1,1′-bi-2,2′-naphthol
(2.76 g, 6.41 mmol) in 10 mL of benzene was added dropwise.
The solution was stirred for 12 h, filtered through Celite, and
dried in vacuo. The product was recrystallized from hot
benzene (10 mL) to yield a yellow powder. Further recrystal-
lization from benzene yielded colorless blocklike crystals,
which were determined to be [H2NEt2]2[Mg(O2C20H10{SiMe3}2-
+ (0.0585P)2 + 1.4064P], where P ) (Fo + 2Fc2)/3. Scattering
factors were taken from the International Tables for Crystal-
lography.21 Refinement was performed on a AlphaServer 2100
using SHELX-97.22 Crystallographic drawings were done using
the programs ORTEP.23
2
Ack n ow led gm en t. This work was supported by the
Department of Energy, Office of Basic Energy Sciences.
Su p p or tin g In for m a tion Ava ila ble: X-ray crystallo-
graphic files in CIF format for (R,R)-1 and (R,R)-8, and NMR
spectra for complexes 2-7 are availible. This material is
available free of charge via the Internet at http://pubs.acs.org.
1
3,3′)Cl2], (R)-8. H NMR (C6D6, 300 MHz): δ 8.19 (s), 7.74 (d,
J
) 7.8 Hz); 7.11-6.82 (m, aromatics); 1.87 (pseudosept,
OM0108200
H2N(CH2CH3)2); 0.89 (t, J ) 6.3 Hz, H2N(CH2CH3)2), 0.74 (s,
Si(CH3)3).
(19) Otwinowski, Z.; Minor, W. Methods Enzymol. 1996, 276.
(20) Beurskens, P. T.; Admirall, G.; Beurskens, G.; Bosman, W. P.;
Garcia-Granda, S.; Gould, R. O.; Smits, J . M. M.; Smykalla, C. The
DIRDIF92 Program System, Technical Report; Crystallography Labo-
ratory, University of Nijmegen: The Netherlands, 1992.
(21) International Tables for Crystallography; Kluwer Academic
Publishers: Dordrecht, The Netherlands, 1992; Vol. C, Tables 4.2.6.8
and 6.1.1.4.
(22) Sheldrick, G. M. SHELXS97. A Program for Crystal Structure
Refinement; University of Gottingen: Germany, 1997.
(23) J ohnson, C. K. ORTEPII, Report ORNL-5138; Oak Ridge
National Laboratory: Oak Ridge, TN, 1976.
X-r a y Da ta Collection a n d Red u ction . Crystal data and
data collection parameters are contained in Table 4. A suitable
crystal was mounted on a glass fiber in a random orientation
under a cold stream of dry nitrogen. Preliminary examination
and final data collection were performed with Mo KR radiation
(λ ) 0.71073 Å) on
a Nonius KappaCCD. Lorentz and
polarization corrections were applied to the data.18 An empiri-
(18) McArdle, P. C. J . Appl. Crystallogr. 1996, 239, 306.