Carbon-oxygen bond cleavage promoted by a scandium borohydride complex

Article abstract of DOI:10.1021/om030374b

Treatment of (Nacnac)ScCl₂(THF) (Nacnac^- = ArNC(CH₃)CHC(CH₃)NAr, Ar = 2,6- (CH-(CH₃)₂)₂C₆H₃) with KNHAr in THF affords in 83% yield the chloro-anilide complex (Nacnac)- ScCl(NHAr)(THF) (1-Cl(THF)). 1-Cl(THF) was fully characterized, and a single-crystal X-ray diffraction study reveals the complex to be a five-coordinate scandium complex containing a bound THF ligand. The complex 1-Cl(THF) reacts cleanly with NaBHEt₃ in toluene to yield the triethylborohydride adduct (Nacnac)Sc(NHAr)(HBEt₃) (1-HBEt₃) in 78% yield. The molecular structure of 1-HBEt₃ indicated a bridged hydride ligand confined between the scandium and boron atoms. The coordination environment of scandium was that of an octahedron, with the two remaining coordination sites being occupied by one hydrogen from each methylene group on the borane interacting with the scandium center through agostic interactions. Variable-temperature ¹¹B NMR spectroscopy indicated a doublet with J_BH = 53 Hz (70°C). Borane extrusion in the complex 1-HBEt₃ in Et₂O affords the ethoxide (Nacnac)Sc(NHAr)(OEt) (1-OEt), which was structurally characterized. Tetrahydrofuran also reacts cleanly with 1-HBEt₃ to yield the enolate complex (Nacnac)Sc(NHAr)- (OCH=CH₂) (1-OCH=CH₂) in 70% yield. The molecular structure of 1-OCH=CH₂ was also determined by single-crystal X-ray diffraction methods. In the absence of Lewis bases such as Et₂O or THF, 1-HBEt₃ was found to thermally decompose to a mixture of products. When 1 equiv of benzophenone was added to 1-HBEt₃, the putative hydride 1-H was trapped to yield the diphenylmethoxide complex (Nacnac)Sc(NHAr)(OCHPh₂) (1-OCHPh₂) in 80% yield. As an alternative to 1-HBEt₃ cleaving C-O bonds, the stable tert-butyl complex (Nacnac)- Sc(NHAr)(^tBu) (1-¹Bu), prepared in 94% yield from 1-Cl(THF) and solid Li^tBu, was also found to react with Et₂O to yield 1-OEt. The complex 1-^tBu was fully characterized, and the molecular structure was established by single-crystal X-ray diffraction methods. 1-^tBu was thermally stable in the absence of Et₂O and THF.

Full text of DOI:10.1021/om030374b

Organometallics 2003, 22, 4705-4714
4705
Ca r bon -Oxygen Bon d Clea va ge P r om oted by a
Sca n d iu m Bor oh yd r id e Com p lex
Falguni Basuli, J ohn Tomaszewski, J ohn C. Huffman, and Daniel J . Mindiola*
Department of Chemistry and Molecular Structure Center, Indiana University,
Bloomington, Indiana 47405
Received May 20, 2003
Treatment of (Nacnac)ScCl2(THF) (Nacnac- ) ArNC(CH3)CHC(CH3)NAr, Ar ) 2,6-(CH-
(CH3)2)2C6H3) with KNHAr in THF affords in 83% yield the chloro-anilide complex (Nacnac)-
ScCl(NHAr)(THF) (1-Cl(THF )). 1-Cl(THF ) was fully characterized, and a single-crystal
X-ray diffraction study reveals the complex to be a five-coordinate scandium complex
containing a bound THF ligand. The complex 1-Cl(THF ) reacts cleanly with NaBHEt3 in
toluene to yield the triethylborohydride adduct (Nacnac)Sc(NHAr)(HBEt3) (1-HBEt3) in 78%
yield. The molecular structure of 1-HBEt3 indicated a bridged hydride ligand confined
between the scandium and boron atoms. The coordination environment of scandium was
that of an octahedron, with the two remaining coordination sites being occupied by one
hydrogen from each methylene group on the borane interacting with the scandium center
through agostic interactions. Variable-temperature 11B NMR spectroscopy indicated a doublet
with J BH ) 53 Hz (70 °C). Borane extrusion in the complex 1-HBEt3 in Et2O affords the
ethoxide (Nacnac)Sc(NHAr)(OEt) (1-OEt), which was structurally characterized. Tetrahy-
drofuran also reacts cleanly with 1-HBEt3 to yield the enolate complex (Nacnac)Sc(NHAr)-
(OCHdCH2) (1-OCHdCH2) in 70% yield. The molecular structure of 1-OCHdCH2 was also
determined by single-crystal X-ray diffraction methods. In the absence of Lewis bases such
as Et2O or THF, 1-HBEt3 was found to thermally decompose to a mixture of products. When
1 equiv of benzophenone was added to 1-HBEt3, the putative hydride “1-H” was trapped to
yield the diphenylmethoxide complex (Nacnac)Sc(NHAr)(OCHPh2) (1-OCHP h 2) in 80% yield.
As an alternative to 1-HBEt3 cleaving C-O bonds, the stable tert-butyl complex (Nacnac)-
Sc(NHAr)(tBu) (1-tBu ), prepared in 94% yield from 1-Cl(THF ) and solid LitBu, was also
found to react with Et2O to yield 1-OEt. The complex 1-tBu was fully characterized, and
the molecular structure was established by single-crystal X-ray diffraction methods. 1-tBu
was thermally stable in the absence of Et2O and THF.
In tr od u ction
has been known for a long time.8 â-Diketiminate ligands
are particularly attractive ligands, since the aryl deriva-
tives are easy to prepare in large scale starting from
commercially available reagents.1,2,5 These ligands also
lack â-hydrogens and are easy to modify at both the
â-carbon and the nitrogen positions.1,2,5 Modification of
the â-carbon backbone and aryl flanking groups allows
for control of both electronic and steric factors governing
the system of interest. In addition, Tolman and coau-
thors reported recently a new class of â-diketiminates
in which the γ-position of the backbone could be easily
modified to alter the electronic properties of the ligand.9
Budzelaar,5 Piers,10-14 Theopold,15 and others1b have
The use of â-diketiminates as supporting ligands for
reactive organometallic complexes has undergone a
revival of interest.1-7 Such a renaissance in the usage
of this ligand is remarkable, since this class of molecules
* To whom correspondence should be addressed. Phone: 812-855-
2399. Fax: 812-855-8300. E-mail: mindiola@indiana.edu.
(1) For a recent review on early-transition-metal non-metallocene
and â-diketiminate complexes see: (a) Piers, W. E.; Emslie, D. J . H.
Coord. Chem. Rev. 2002, 233, 131. (b) Bourget-Merle, L.; Lappert, M.
F.; Severn, J . R. Chem. Rev. 2002, 102, 3031.
(2) Stender, M.; Wright, R. J .; Eichler, B. E.; Prust, J .; Olmstead,
M. M.; Roesky, H. W.; Power, P. P. J . Chem. Soc., Dalton Trans. 2001,
3465 and references therein.
(3) (a) Kakaliou, L.; Scanlon, W. J ., IV; Qian, B.; Baek, S. W.; Smith,
M. R., III; Motry, D. H. Inorg. Chem. 1999, 38, 5964. (b) Qian, B.;
Scanlon, W. J .; Smith, M. R., III; Motry, D. H. Organometallics 1999,
18, 1693.
(4) Andres, H.; Bominaar, E. L.; Smith, J . M.; Eckert, N. A.; Holland,
P. L.; Munck, E. J . Am. Chem. Soc. 2002, 124, 3012 and references
therein.
(8) (a) Parks, J . E.; Holm, R. H. Inorg. Chem. 1968, 7, 1408. (b)
McGeachin, S. G. Can. J . Chem. 1968, 46, 1903. (c) Holm, R. H.;
O’Connor, M. J . Prog. Inorg. Chem. 1971, 14, 241.
(9) Spencer, D. J . E.; Reynolds, A. M.; Holland, P. L.; J azdzewski,
B. A.; Duboc-Toia, C.; LePape, L.; Yokota, S.; Tachi, Y.; Itoh, S.;
Tolman, W. B. Inorg. Chem. 2002, 41, 6307 and references therein.
(10) Hayes, P. G.; Piers, W. E.; Lee, L. W. M.; Knight, L. K.; Parvez,
M.; Elsegood, M. R. J .; Clegg, W. Organometallics 2001, 20, 2533.
(11) Zhang, S.; Piers, W. E.; Gao, X.; Parvez, M. J . Am. Chem. Soc.
2000, 122, 5499.
(12) Lee, L. W. M.; Piers, W. E.; Elsegood, M. R. J .; Clegg, W.;
Parvez, M. Organometallics 1999, 18, 2947.
(13) Hayes, P. G.; Welch, G. C.; Emslie, D. J . H.; Noack, C. L.; Piers,
W. E.; Parvez, M. Organometallics 2003, 22, 1577.
(5) Budzelaar, P. H. M.; van Oort, A. B.; Orpen, A. G. Eur. J . Inorg.
Chem. 1998, 1485.
(6) Kim, W.-K.; Fevola, M. J .; Liable-Sands, L. M.; Rheingold, A.
L.; Theopold, K. H. Organometallics 1998, 17, 4541.
(7) (a) Neculai, A. M.; Neculai, D.; Roesky, H. W.; Magull, J .; Baldus,
M.; Andronesi, O.; J ansen, M. Organometallics 2002, 21, 2590. (b)
Nikiforov, G. B.; Roesky, H. W.; Magull, J .; Labahn, T.; Vidovic, D.;
Noltemeyer, M.; Schmidt, H.-G.; Hosmane, N. S. Polyhedron 2003, 22,
2669 and references therein.
10.1021/om030374b CCC: $25.00 © 2003 American Chemical Society
Publication on Web 10/07/2003

4706 Organometallics, Vol. 22, No. 23, 2003
Basuli et al.
Sch em e 1
F igu r e 1. Perspective view of 1-Cl(THF ) with thermal
ellipsoids at the 50% probability level. Hydrogens, with the
exception of the R-hydrogen have been omitted for clarity.
Aryl groups on the â-diketiminate nitrogens, with the
exception of ipso carbons have also been omitted for the
purpose of clarity. Selected bond lengths (Å): Sc(1)-N(3),
2.0453(13); Sc(1)-N(20), 2.1763(11); Sc(1)-N(16), 2.2281-
(11); Sc(1)-O(47), 2.2844(10); Sc(1)-Cl(2), 2.3778(5); N(3)-
C(4), 1.3935(19); N(16)-C(17), 1.3318(17); C(17)-C(18),
1.4073(19); C(18)-C(19), 1.3952(19); C(19)-N(20), 1.3472-
(17). Selected angles (deg): N(20)-Sc(1)-N(16), 85.12(4);
N(3)-Sc(1)-N(20), 122.88(5); N(3)-Sc(1)-N(16), 104.66-
(5); N(3)-Sc(1)-O(47), 88.60(4); N(20)-Sc(1)-O(47), 90.24-
(4); N(16)-Sc(1)-O(47), 166.40(4); N(3)-Sc(1)-Cl(2), 109.91-
(4); N(20)-Sc(1)-Cl(2), 126.43(3); N(16)-Sc(1)-Cl(2),
90.37(3); O(47)-Sc(1)-Cl(2), 82.10(3); Sc(1)-N(3)-C(4),
155.70(11); Sc(1)-N(16)-C(17), 122.94(9); Sc(1)-N(20)-
C(19), 123.43(9); N(20)-C(19)-C(18), 124.46(12); C(19)-
C(18)-C(17), 128.18(13); C(18)-C(17)-N(16), 124.25(12).
demonstrated that bulky and chelating ligands such as
â-diketiminates (referred to as Nacnac-) can stabilize
neutral as well as cationic group 3 and 4 alkyl com-
plexes. These systems have been shown to be active
olefin polymerization catalysts,5,10-15 as well as excellent
ligand scaffolds for the stabilization of metal hydrides.16
â-Diketiminates have also been incorporated into the
heavier lanthanides.1b,17 Whereas metallocene-based
hydride systems of scandium have been studied,18,19
reports of nonmetallocene scandium hydrides are sur-
prisingly scarce and have received far less attention.20,21
In view of the ability of the â-diketiminate ligand to
support reactive metal complexes, we turned our atten-
tion to the precursor complex prepared by Piers and co-
workers10 in pursuit of a reactive scandium hydride. Our
goal was to assemble a useful scandium template
composed of both a robust Nacnac- and a π-donor
monoanionic amide ligand lacking â-hydrogens. Herein
we report a series of reactions containing the (Nacnac)-
Sc(NHAr) (Nacnac- ) ArNC(CH3)CHC(CH3)NAr, Ar )
2,6-CH(CH3)2C6H3) skeleton (defined as 1). Such a
framework has allowed us to prepare a reactive scan-
dium triethylborohydride complex and observe facile
C-O bond cleavage of Et2O and THF. The putative
scandium hydride intermediate was trapped with ben-
zophenone to afford the corresponding alkoxide, the
consequence of ketone insertion into the Sc-hydride
bond. In addition, a stable and rare tert-butyl complex
of scandium has been prepared and has been shown to
also engage in C-O bond cleavage. The present work
describes the synthesis and characterization of the
products generated from C-O bond rupture of ethers
as well as reduction of benzophenone by a scandium
triethylborohydride complex.
Resu lts a n d Discu ssion
When a cold THF solution of Piers’ complex (Nacnac)-
ScCl2(THF)10 is treated with 1 equiv of KNHAr, the
monoanilide complex (Nacnac)ScCl(NHAr)(THF) (1-Cl-
(THF )) is formed in good yield (83%) as pale yellow
crystals (Scheme 1). The use of the potassium anilide
salt leads to formation of 1-Cl(THF ) without any
contamination of “ate” complexes.1a,17 1-Cl(THF ) was
fully characterized, and 1H and 13C solution NMR
spectroscopy in addition to solid-state characterization
(elemental analysis and X-ray) are consistent with the
molecule coordinating one THF per metal center. NMR
spectra are in accordance with the molecule retaining
Cs symmetry in solution (equivalent methyl groups on
the â-diketiminate â-carbons), thus suggesting that THF
is dissociating from the metal center. In fact, mild
heating of 1-Cl(THF ) under dynamic vacuum generates
the desolvated complex 1-Cl, thus indicating that the
THF is labile. This characteristic has been observed for
the corresponding bis(alkyl) complexes studied by Piers
and co-workers.14 Single crystals of 1-Cl(THF ) were
grown from Et2O, and the molecular structure is de-
picted in Figure 1. The structure of 1-Cl(THF ) reveals
(14) Hayes, P. G.; Piers, W. E.; Parvez, M. J . Am. Chem. Soc. 2003,
125, 5622.
(15) (a) Richeson, D. S.; Mitchell, J . F.; Theopold, K. H. Organome-
tallics 1989, 8, 2570. (b) Kim, W.-K.; Fevola, M. J .; Liable-Sands, L.
M.; Rheingold, A. L.; Theopold, K. H. Organometallics 1998, 17, 4541.
(c) MacAdams, L. A.; Kim, W.-K.; Liable-Sands, L. M.; Guzei, I. A.;
Rheingold, A. L.; Theopold, K. H. Organometallics 2002, 21, 952.
(16) For a recent paper on a metal hydride complex supported by
bulky â-diketiminates see: MacAdams, L. A.; Buffone, G. P.; Incarvito,
C. D.; Golen, J . A.; Rheingold, A. L.; Theopold, K. H. Chem. Commun.
2003, 1164 and references therein.
(17) For recent publications regarding lanthanides supported by
â-diketiminate ligands see: (a) Yao, Y.; Zhang, Y.; Shen, Q.; Yu, K.
Organometallics 2002, 21, 819. (b) Avent, A. G.; Hitchcock, P. B.;
Khvostov, A. V.; Lappert, M. F.; Protchenko, A. V. J . Chem. Soc., Dalton
Trans. 2003, 1070 and references therein.
(18) Thompson, M. E.; Baxter, S. M.; Bulls, A. R.; Burger, B. J .;
Nolan, M. C.; Santarsiero, B. D.; Schaefer, W. P.; Bercaw, J . E. J . Am.
Chem. Soc. 1987, 109, 203.
(19) (a) Sadow, A. D.; Tilley, T. D. Angew. Chem., Int. Ed. 2003, 42,
803. (b) Sadow, A. D.; Tilley, T. D. J . Am. Chem. Soc. 2003, 125, 7971.
(20) For a recent review on early-transition-metal hydrides see:
Hoskin, A. J .; Stephan, D. W. Coord. Chem. Rev. 2002, 233, 107.
(21) Some examples of nonmetallocene scandium hydrides include:
(a) Hagadorn, J . R.; Arnold, J . Organometallics 1996, 15, 984. (b)
Bazan, G. C.; Shaefer, W. P.; Bercaw, J . E. Organometallics 1993, 12,
2126.

Scandium Borohydride Promoted C-O Bond Cleavage
Organometallics, Vol. 22, No. 23, 2003 4707
Ta ble 1. Su m m a r y of Cr ysta llogr a p h ic Da ta a n d Str u ctu r e Refin em en t Deta ils for 1-Cl(THF ), 1-HBEt3, a n d
1-OEt
1-Cl(THF )
1-HBEt3
1-OEt
formula
fw
C45H67ClN3OSc
746.43
C47H75BN3Sc
737.87
C43H64N3OSc
683.93
space group
a (Å)
b (Å)
P21/n
P21/c
P1h
12.1239(5)
17.0782(7)
20.3922(8)
11.3666(6)
17.6914(9)
22.4483(12)
10.0234(11)
11.1852(12)
19.658(2)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
84.590(3)
83.677(3)
70.261(3)
2058.0(4)
93.4750(10)
91.6940(10)
4214.3
4
4512.2(4)
4
2
Dcalcd
1.176
2.740
1616
1.086
1.960
1616
1.104
2.120
744
µ (mm-1
F(000)
)
cryst color
pale yellow
yellow
pale yellow
cryst form
plate
block
diamondlike
230 × 180 × 50
2.09-27.61
-12 e h e 12, -14 e k e 14,
-25 e l e 25
22 418
9440
5791
0.1394
cryst size (µm)
θ range (lattice, deg)
index ranges
300 × 100 × 100
350 × 350 × 250
2.06-30.02
2.13-30.03
-17 e h e 12, -24 e k e 24,
-15 e h e 16, -24 e k e 24,
-28 e l e 28
-30 e l e 31
no. of rflns collected
no. of indep rflns
no. of obsd rflns
Rint
50 854
12 298
8002
0.0626
73 003
13 163
8496
0.0840
final R indices (I > 2σ(I))
R indices (all data)
GOF on F2
R1 ) 0.0715, wR2 ) 0.0797
R1 ) 0.0390, wR2 ) 0.0902
0.913
R1 ) 0.0932, wR2 ) 0.0956
R1 ) 0.0454, wR2 ) 0.1232
1.020
R1 ) 0.1185, wR2 ) 0.1722
R1 ) 0.0744, wR2 ) 0.1899
0.978
a scandium center in a pseudo-trigonal-bipyramidal
geometry, with the Nacnac- ligand occupying both the
axial and equatorial positions. The geometrical param-
eters are nearly identical with those of the precursor
complex (Nacnac)ScCl2(THF).10,14 Selected metrical pa-
rameters are displayed with Figure 1, and structural
parameters for 1-Cl(THF ) are shown in Table 1. The
anilido nitrogen N(3) is nearly planar, and the Sc-
Nanilido bond length of 2.0453(13) Å is considerably
shorter than the Sc-NNacnac bonds (N(16)-Sc(1), 2.2281-
(11) Å; N(20)-Sc(1), 2.1763(11) Å). The molecular
structure of 1-Cl(THF ) displays no other exceptional
features.
F igu r e 2. Perspective view of 1-HBEt3 with thermal
ellipsoids at the 50% probability level. The hydrogen atoms
on the borane ethyl groups were located in the Fourier map
and refined isotropically. Hydrogen atoms, with the excep-
tion of the hydride and the methylene groups on the borane,
have been omitted for clarity. Aryl groups on nitrogens,
with the exception of ipso carbons, have also been omitted
for clarity. Selected bond lengths (Å): Sc(1)-N(2), 2.0280-
(15); Sc(1)-N(19), 2.1509(14); Sc(1)-N(15), 2.1538(14);
N(19)-C(18), 1.337(2); C(18)-C(17), 1.401(2); C(17)-C(16),
1.408(2); C(16)-N(15), 1.327(2); B(46)-C(47), 1.672(3);
B(46)-C(49), 1.659(3); B(46)-C(51), 1.617(3); N(2)-C(3),
1.407(2); N(19)-C(34), 1.452(2); N(15)-C(20), 1.448(2).
Selected angles (deg): N(2)-Sc(1)-N(19), 98.59(6); N(2)-
Sc(1)-N(15), 98.05(6); N(19)-Sc(1)-N(15), 87.57(5); Sc(1)-
N(3)-C(3), 153.73(12); Sc(1)-N(15)-C(16), 119.14(11); Sc-
(1)-N(15)-C(20), 121.33(10); N(15)-C(16)-C(17), 123.48-
(15); C(16)-C(17)-C(18), 129.80(15); C(17)-C(18)-N(19),
123.83(16); Sc(1)-N(19)-C(18), 117.63(11).
Having the “(Nacnac)Sc(NHAr)” framework assembled,
we reasoned that metathesis of 1-Cl(THF ) with a
hydride source would generate a reactive scandium
hydride complex. Accordingly, treatment of 1-Cl(THF )
with NaHBEt3, in toluene, generates in 78% yield the
triethylborohydride complex (Nacnac)Sc(NHAr)(HBEt3)
(1-HBEt3) (Scheme 1). 1-HBEt3 is thermally stable both
in solution and in the solid state, but in the presence of
Lewis bases it transforms into a new product (depending
on the Lewis base, vide infra). Indicative of a hydride
being present was the variable-temperature 11B NMR
spectrum of 1-HBEt3, displaying a resonance at -8.70
ppm with J B-H ) 53 Hz (70 °C, C6D6). We have not been
able to locate the hydride resonance in the 1H NMR
spectrum, presumably due to broadening of the signal
7
by coupling of the hydride to both 45Sc (I ) /2, 100%)
and 11B (I ) 3/2, 80%) quadrupolar nuclei.22 This
phenomenon has been inferred with related hydrido
complexes of scandium.18 Varying the temperature of
NMR samples containing 1-HBEt3 did not alleviate the
quadrupolar broadening.22b Attempts to make the cor-
responding deuterium analogue were hampered by the
formation of side products generated from the reaction
of 1-Cl(THF ) with LiDBEt3. Single crystals of 1-HBEt3
were grown from hexane at -35 °C, and the molecular
structure is displayed in Figure 2. Geometrical and
crystal structure parameters are shown in Figure 2 and
Table 1, respectively. The structure of 1-HBEt3 reveals
a scandium center confined in a pseudo-octahedral
(22) (a) Harris, R. K., Mann, B. E., Eds. NMR and the Periodic Table;
Academic Press: London, 1978. (b) Akitt, J . W. NMR and Chemistry,
An Introduction to the Fourier Transform-Multinuclear Era; Chapman
and Hall: New York, 1983; Chapter 4.

4708 Organometallics, Vol. 22, No. 23, 2003
Basuli et al.
Sch em e 2
Sch em e 3
environment and represents the first structurally char-
acterized triethylborohydride complex of scandium. In
fact, structurally characterized examples of scandium
borohydride complexes are scarce.23 In addition to the
Nacnac- and anilide occupying three coordination posi-
tions, the hydride and two methylene hydrogens from
the ethyl groups of the borane complete the additional
three coordination sites in the pseudo-octahedron. Al-
though there is a systematic error in detection of
hydrogens by X-ray diffraction,24 the location of the
hydrogens in the Fourier map leaves little uncertainty
about their presence. Unfortunately, the room-temper-
ature 1H NMR spectrum of 1-HBEt3 did not suggest any
evidence for such an agostic interaction. Variable-
temperature 1H NMR (-65 °C, CD2Cl2) only led to
broadening of the ethyl groups on the borane. However,
high-temperature 11B NMR was consistent with flux-
ionality of the HBEt3 unit in solution (vide supra).
the pendant olefin fragment might be taking place
during the reaction (Scheme 3). Goldberg and co-
workers have reported reversible â-hydride elimination
and reinsertion reactions in platinum complexes sup-
ported by the Nacnac- ligand derivative used in the
present study.25 One possible explanation for scrambling
of deuterium into these positions is depicted in Scheme
3. Scheme 3 suggests that a reactive scandium imide26,27
and scandium hydride could be formed during the
course of the reaction. Examination of the volatiles from
1
Although stable as a solid, 1-HBEt3 extrudes BEt3 in
solution and in the presence of a Lewis base, transform-
ing into a new product. Hence, mild heating of 1-HBEt3
with Et2O leads to C-O bond cleavage and subsequent
formation of the ethoxide complex (Nacnac)Sc(NHAr)-
(OEt) (1-OEt) in 64% isolated yield (Scheme 2). The
ethoxide resonances were located at 3.86 and 0.84 ppm
in the 1H NMR spectrum of 1-OEt. This transformation
led us to speculate that the putative hydride (Nacnac)-
Sc(NHAr)(H) (1-H) is generated upon extrusion of the
borane. Lewis bases such as Et2O can promote elimina-
tion of the borane (Et2OfBEt3 elimination), which
would accompany production of the reactive hydride
species. Preparation of the corresponding d5 isotopomer
of 1-OEt (using Et2O-d10) led to washing of deuterium
into the isopropyl methyls and methine hydrogens, as
suggested by 2H NMR spectra. We observed deuteration
of the γ-CH backbone of the Nacnac as well as the NH
proton for the supporting anilide ligand. This suggests
that formation of 1-OEt likely occurs by C-H and N-H
hydrogen abstraction reactions. Piers and co-workers
observed C-H bond cleavage of the isopropyl methyl
on the aryl in Nacnac- via thermolysis of the bis(alkyl)
species to make the corresponding scandium metalla-
cycle.10 In our case, deuterium scrambling into the
methine positions suggests that â-hydride elimination
of a putative scandium metallacycle and reinsertion of
the reaction mixture by H NMR spectroscopy did not
indicate formation of CH2dCH2 or H2 but, rather, a
complex mixture of products with multiple resonances
in the aliphatic region. We are not certain which of these
likely intermediates is involved in the C-O cleavage
process, and at this point our mechanism is merely
speculative. Scrambling of deuterium into the γ-C of the
Nacnac- backbone is intriguing, and this result could
suggest that electrophilic activation of this site1b by
another scandium center could be responsible for this
occurrence.
Single crystals of 1-OEt were grown from hexane, and
the molecular structure is shown in Figure 3. Relevant
crystal parameters are displayed in Table 1. Salient
features in the structure of 1-OEt include the Sc-
Oalkoxide bond length of 1.882(3) Å. The Sc(1)-O(46)-
C(47) angle of 156.2(3)° is indicative of substantial
π-donation from the alkoxide oxygen. In fact, structur-
ally characterized terminal or bridging ethoxide com-
(25) Fekl, U.; Goldberg, K. I. J . Am. Chem. Soc. 2002, 124, 6804.
(26) C-H activation by three-coordinate titanium and zirconium
imido species have been reported: (a) Cummins, C. C.; Baxter, S. M.;
Wolczanski, P. T. J . Am. Chem. Soc. 1988, 110, 8731. (b) Cummins,
C. C.; Schaller, C. P.; Van Duyne, G. D.; Wolczanski, P. T.; Chan, A.
W.; Hoffmann, R. J . Am. Chem. Soc. 1991, 113, 2985. (c) Schaller, C.
P.; Wolczanski, P. T. Inorg. Chem. 1993, 32, 131. (d) Bennett, J . L.;
Wolczanski, P. T. J . Am. Chem. Soc. 1994, 116, 2179. (e) Schaller, C.
P.; Cummins, C. C.; Wolczanski, P. T. J . Am. Chem. Soc. 1996, 118,
591. (f) Bennett, J . L.; Wolczanski, P. T. J . Am. Chem. Soc. 1997, 119,
10696. (g) Schafer, D. F.; Wolczanski, P. T. J . Am. Chem. Soc. 1998,
120, 4881.
(23) Few structurally characterized scandium borohydride examples
have been described in the literature: (a) Lappert, M. F.; Singh, A.;
Atwood, J . L.; Hunter, W. E. Chem. Commun. 1983, 206. (b) Mancini,
M.; Bougeard, P.; Burns, R. C.; Mlekuz, M.; Sayer, B. G.; Thompson,
J . I. A.; McGlinchey, M. J . Inorg. Chem. 1984, 23, 1072.
(27) Intramolecular C-H activation by a reactive cobalt imido
species has been reported: Thyagarajan, S.; Shay, D. T.; Incarvito, C.
D.; Rheingold, A. L.; Theopold, K. H. J . Am. Chem. Soc. 2003, 125,
4440.
(24) Bau, R.; Drabnis, M. H. Inorg. Chim. Acta 1997, 259, 27.

Scandium Borohydride Promoted C-O Bond Cleavage
Organometallics, Vol. 22, No. 23, 2003 4709
however, observe incorporation of deuterium into the
γ-CH backbone of the Nacnac- ligand, thus hinting as
to whether formation of 1-OEt and 1-OCHdCH2 might
involve different mechanistic pathways. In the absence
of Lewis bases (e.g. Et2O or THF), prolonged thermolysis
of 1-HBEt3 in C6D6 leads to decomposition and forma-
tion of a myriad of products.
Single crystals of the enolate 1-OCHdCH2 were
grown from a saturated hexane solution cooled to -35
°C. Crystal structure parameters are listed in Table 2,
and a molecular structure representation of one of the
two crystallographically independent molecules present
in the asymmetric unit is displayed in Figure 4. Salient
features for the structure of 1-OCHdCH2 include a
short C-C bond for the enolate ligand (1.298(5) Å), in
comparison to the ethoxide derivative (vide supra, 1.495-
(7) Å). The molecular structure of 1-OCHdCH2 repre-
sents a rare example of a terminal and parent enolate
complex of scandium.29
F igu r e 3. Perspective view of 1-OEt with thermal el-
lipsoids at the 50% probability level. Hydrogens, with the
exception of the anilido N(2) and the ethoxide ligands, have
been omitted for clarity. Hydrogen atoms were located in
the Fourier map and refined isotropically. Aryl groups on
the â-diketiminate nitrogens, with the exception of ipso
carbons, have been also omitted for clarity. Selected bond
lengths (Å): Sc(1)-O(46), 1.882(3); Sc(1)-N(2), 2.059(2);
Sc(1)-N(19), 2.122(2); Sc(1)-N(15), 2.148(2), N(15)-C(16),
1.334(4); C(16)-C(17), 1.418(4); C(17)-C(18), 1.397(4);
C(18)-N(19), 1.342(3); N(19)-C(34), 1.440(4); N(15)-C(20),
1.436(4); O(46)-C(47), 1.411(5); C(47)-C(48), 1.495(7).
Selected angles (deg): N(19)-Sc(1)-N(2), 100.2(2); N(15)-
Sc(1)-N(2), 121.2(1); N(19)-Sc(1)-N(15), 88.12(9); N(19)-
Sc(1)-O(46), 108.2(2); N(2)-Sc(1)-O(46), 125.5(1); Sc(1)-
N(2)-C(3), 144.4(2); Sc(1)-O(46)-C(47), 156.2(3); O(46)-
C(47)-C(48), 112.3(4); Sc(1)-N(19)-C(18), 119.7(9); Sc(1)-
N(15)-C(16), 120.6(2); N(19)-C(18)-C(17), 123.6(3); C(18)-
C(17)-C(16), 129.9(3); C(17)-C(16)-N(15), 123.4(3); Sc(1)-
N(19)-C(34), 119.3(7); Sc(1)-N(15)-C(20), 117.8(7).
Precedent in the literature suggests substrates such
as benzophenone to be ideal reagents for trapping
transient and reactive hydride complexes generated
from their corresponding borohydride precursors.30,31
Accordingly, treatment of 1-HBEt3 with an equimolar
amount of OCPh2 in toluene afforded the diphenyl-
methoxide complex 1-OCHP h 2 in 80% isolated yield
(Scheme 2). Formation of 1-OCHP h 2 entails insertion
of the carbonyl functionality into the Sc-H bond. Our
data, however, cannot indicate whether reduction of
benzophenone occurs before or after borane extrusion.
Exhibited features of 1-OCHP h 2 include the â-hydrogen
of the alkoxide ligand, which was located at 5.96 ppm
1
in the H NMR spectrum using HMQC methods.32 The
plexes of group 3 metals are rare, and to our knowledge
the structure of 1-OEt is a unique example.28
downfield shift for the proton in the OCHPh2 ligand is
similar to that for previously reported benzophenone
insertion reactions into Nb-H30 and Mo-H31 bonds. 1H
NMR resonances for the anilido nitrogen (4.46 ppm, NH)
and γ-carbon of the Nacnac- ligand (5.15 ppm, CH) were
also assigned unambiguously. Crystals of 1-OCHP h 2
suitable for X-ray analysis were obtained from a satu-
rated Et2O solution cooled to -35 °C. The molecular
structure of 1-OCHP h 2 is shown in Figure 5, and
crystal structure parameters are displayed in Table 2.
The structure of 1-OCHP h 2 reveals an intact “(Nacnac)-
Sc(NHAr)” frame containing the diphenylmethoxide
ligand. Relevant bond lengths and angles are listed in
Figure 5. The â-hydrogen of the alkoxide (C(47)) was
located and refined isotropically. J udging from the
angles, the â-carbon of the diphenylmethoxide ligand
is clearly sp3 hybridized, and the elongation of the O-C
bond (1.405(5) Å) is substantial relative to free ben-
zophenone (1.224-1.238 Å).33
THF also reacts with 1-HBEt3 to afford the corre-
sponding enolate complex (Nacnac)Sc(NHAr)(OCHd
CH2) (1-OCHdCH2) in 70% isolated yield (Scheme 2).
Diagnostic features for 1-OCHdCH2 include the pres-
1
ence of three inequivalent H NMR resonances for the
enolate hydrogens centered at 6.65 (dd, J H-Htrans ) 14
and J H-Hcis ) 6 Hz), 4.16 (d, J H-Htrans ) 14 Hz), and
3.92 ppm (d, J H-Hcis ) 6 Hz). In general, lanthanide
complexes containing a terminal enolate ligand with
only hydrogens in both the â- and γ-positions are
exceedingly rare, and such complexes are typically
prepared from analogous metalation or reduction of
THF,29a,b or by direct salt metathesis of the metal halide
with LiOCHdCH2.29c,d Examination of the volatiles
revealed CH2dCH2 to be one of the main products
formed in the reaction. Preparation of the deuterio
complex 1-OCHdCH2-d3 from THF-d8 revealed scram-
bling of deuterium into the methine and methyl posi-
tions of the isopropyl groups as well as into the NH
position. As suggested for the formation of 1-OEt (vide
supra), 1-OCHdCH2 appears to also form via C-H and
N-H hydrogen atom abstraction processes. We do not,
tert-Butyl alkyl groups attached directly to early-
transition-metal complexes are rare.34-36 The instability
(30) Mindiola, D. J .; Cummins, C. C. Organometallics 2001, 20,
3626.
(31) Liang, F. P.; J acobsen, H.; Schmalle, H. W.; Fox, T.; Berke, H.
Organometallics 2000, 19, 1950.
(32) Summers, M. F.; Marzilli, L. G.; Bax, A. J . J . Am. Chem. Soc.
1986, 108, 4285.
(33) A search in the Cambridge Structural Database shows crystal-
lized benzophenone to have a CdO bond length between 1.224 and
1.238 Å.
(34) Lu, Z.; Yap, G. P. A.; Richeson, D. S. Organometallics 2001,
20, 706.
(28) (a) Miele, P.; Foulon, J . D.; Hovnanian, N.; Cot, L. Chem.
Commun. 1993, 29. (b) Miele, P.; Foulon, G.; Hovnanian, N. Inorg.
Chim. Acta 1997, 255, 289. (c) J ubb, J .; Gambarotta, S.; Duchateau,
R.; Teuben, J . H. Chem. Commun. 1994, 2641.
(29) (a) Marks, T. J .; Ernst, R. D. In Comprehensive Organometallic
Chemistry; Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Perga-
mon: Oxford, U.K., 1982; Chapter 21. (b) Evans, W. J . Adv. Organomet.
Chem. 1985, 24, 131. (c) Aspinall, H. C.; Tillotson, M. R. Inorg. Chem.
1996, 35, 2163. (d) Evans, W. J .; Dominguez, R.; Hanusa, T. P.
Organometallics 1986, 5, 1291.
(35) Firth, A. V.; Stewart, J . C.; Hoskin, A. J .; Stephan, D. W. J .
Organomet. Chem. 1999, 591, 185.

4710 Organometallics, Vol. 22, No. 23, 2003
Basuli et al.
Ta ble 2. Su m m a r y of Cr ysta llogr a p h ic Da ta a n d Str u ctu r e Refin em en t Deta ils for 1-OCHdCH2,
1-OCHP h 2‚0.5Et2O, a n d 1-tBu ‚0.5Et2O
1-OCHdCH2
1-OCHP h 2
1-tBu
formula
fw
C43H62N3OSc
681.92
C56H75N3O1.5Sc
859.15
C47H73N3O0.5Sc
733.04
space group
a (Å)
b (Å)
P21/c
P1h
P21/c
40.771(5)
9.7758(15)
20.661(4)
10.2169(3)
20.2074(19)
10.7832(10)
20.592(2)
11.5960(4)
22.0076(7)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
97.9060(10)
95.6130(10)
105.8220(10)
2459.55(14)
101.259(8)
91.364(2)
8077(2)
8
4485.7(7)
4
2
Dcalcd
1.122
2.160
2960
1.160
1.920
930
1.085
1.920
1604
µ (mm-1
F(000)
)
cryst color
pale yellow
pale yellow
pale yellow
cryst form
plate
plate
block
cryst size (µm)
θ range (lattice, deg)
index ranges
120 × 80 × 60
250 × 250 × 130
200 × 180 × 180
2.01-27.57
2.17-30.02
2.13-30.02
-52 e h e 53, -12 e k e 12,
-26 e l e 26
87 693
18 584
7302
0.2009
-14 e h e 14, -16 e k e 16,
-30 e l e 30
78 828
14 367
10 091
-28 e h e 28, -15 e k e 15,
-28 e l e 28
138 820
13 092
9129
no. of rflns collected
no. of indep rflns
no. of obsd rflns
Rint
0.0719
0.0834
final R indices (I > 2σ(I))
R indices (all data)
GOF on F2
R1 ) 0.655, wR2 ) 0.1714
R1 ) 0.0561, wR2 ) 0.0825
0.780
R1 ) 0.0692, wR2 ) 0.1027
R1 ) 0.0423, wR2 ) 0.1164
0.997
R1 ) 0.0739, wR2 ) 0.0943
R1 ) 0.0383, wR2 ) 0.1141
1.011
F igu r e 4. Perspective view of 1-OCHdCH2 with thermal
ellipsoids at the 50% probability level. Hydrogens, with the
exception of the anilido N33B and the enolate, have been
omitted for clarity. Hydrogen atoms were located in the
Fourier map and refined isotropically. Aryl groups on the
â-diketiminate nitrogens, with the exception of ipso car-
bons, have been also omitted for clarity. Selected bond
lengths (Å): Sc(1B)-N(33B), 2.045(3); Sc(1B)-N(6B), 2.110-
(2); Sc(1B)-N(2B), 2.159(2); Sc(1B)-O(46B), 1.904(2);
O(46B)-C(47B), 1.339(4); C(47B)-C(48B), 1.298(5); N(33B)-
C(34B), 1.393(4); N(6B)-C(5B), 1.341(3); C(5B)-C(4B),
1.390(4); C(4B)-C(3B), 1.412(4); C(3B)-N(2B), 1.340(3).
Selected angles (deg): N(6B)-Sc(1B)-N(33B), 98.44(10);
N(6B)-Sc(1B)-O(46B), 111.5(1); N(6B)-Sc(1B)-N(2B),
87.27(9); N(33B)-Sc(1B)-O(46B), 122.9(2); N(2B)-Sc(1B)-
O(46B), 106.1(1); O(46B)-C(47B)-C(48B), 126.1(4); Sc-
(1B)-N(33B)-C(34B), 146.5(2); Sc(1B)-O(46B)-C(47B),
178.0(2); Sc(1B)-N(6B)-C(5B), 120.7(9); Sc(1B)-N(2B)-
C(3B), 120.8(9); N(6B)-C(5B)-C(4B), 123.5(3); C(5B)-
C(4B)-C(3B), 129.6(3); C(4B)-C(3B)-N(2B), 123.6(3).
F igu r e 5. Perspective view of 1-OCHP h 2 with thermal
ellipsoids at the 50% probability level. Hydrogens, with the
exception of the anilido nitrogen N(33) and carbon C(47),
have been omitted for clarity. Hydrogen atoms were located
in the Fourier map and refined isotropically. Aryl groups
on the â-diketiminate nitrogens, with the exception of ipso
carbons, and a solvent molecule have been also omitted for
clarity. Selected bond lengths (Å): Sc(1)-O(46), 1.8941-
(9); Sc(1)-N(33), 2.048(2); Sc(1)-N(6), 2.122(1); Sc(1)-N(2),
2.162(1); O(46)-C(47), 1.405(5); N(33)-C(34), 1.389(7);
C(47)-C(48), 1.531(8); C(47)-C(54), 1.532(9); N(6)-C(5),
1.342(7); C(5)-C(4), 1.395(8); C(4)-C(3), 1.418(9); C(3)-
N(2), 1.331(7). Selected angles (deg): N(6)-Sc(1)-N(33),
97.81(5); N(6)-Sc(1)-O(46), 113.05(4); N(6)-Sc(1)-N(2),
87.93(4); N(2)-Sc(1)-O(46), 107.91(4); N(2)-Sc(1)-N(33),
120.36(5); Sc(1)-O(46)-C(47), 170.42(8); Sc(1)-N(33)-
C(34), 143.6(1); Sc(1)-N(6)-C(5), 118.45(9); Sc(1)-N(2)-
C(3), 118.09(9); N(6)-C(5)-C(4), 112.8(2); C(5)-C(4)-C(3),
130.1(2); C(4)-C(3)-N(2), 124.0(2); C(54)-C(47)-O(46),
111.5(1); C(48)-C(47)-O(46), 111.1(1); C(54)-C(47)-C(48),
111.9(1).
of these systems arises from the presence of nine
â-hydrogens, often leading to â-hydride elimination
concomitant with formation of the metal hydride spe-
cies.37 Isobutene, the olefin generated from â-hydride
elimination, can engage in further reactions such as
reinsertion into the metal-hydride bond to form the
corresponding isobutyl isomer.37 In fact, early-transi-
tion-metal complexes bearing any alkyl groups with
(36) No¨th, H.; Schmidt, M. Organometallics 1995, 14, 4601.

Scandium Borohydride Promoted C-O Bond Cleavage
Organometallics, Vol. 22, No. 23, 2003 4711
Sch em e 4
â-hydrogens are relatively rare.5,10,38 Hence, we thought
that preparation of the scandium tert-butyl derivative
would serve as a precursor to a scandium hydride
complex via â-hydride elimination. Accordingly, treat-
ment of cold ethereal solutions of 1-Cl(THF ) with LitBu
afforded in good yield (94% isolated yield) the tert-butyl
complex (Nacnac)Sc(NHAr)(tBu) (1-t Bu ) (Scheme 4).
1-tBu is stable both in solution and in the solid state
and represents a rare case of a tBu complex in the
context of group 3 metal alkyls.34 The room-temperature
1H NMR spectrum of 1-tBu reveals one singlet for the
tBu group at an unexceptional chemical shift, thus
suggesting no evidence of the scandium engaging in
â-hydrogen agostic interactions. When ethereal solu-
tions of 1-tBu are refluxed, the ethoxide 1-OEt is formed
in good yield (g88% isolated yield, Scheme 4). Isobutene
is not observed in the reaction mixture, inasmuch as
â-hydride elimination does not occur upon formation of
1-OEt. In fact, examination of the volatiles reveals only
F igu r e 6. Perspective view of 1-tBu with thermal el-
lipsoids at the 50% probability level. Hydrogens, with the
exception of the R-anilido nitrogen N(33), have been omit-
ted for clarity. The hydrogen atom was located in the
Fourier map and refined isotropically. Aryl groups on the
â-diketiminate nitrogens, with the exception of ipso car-
bons, and a solvent molecule have been also omitted for
clarity. Selected bond lengths (Å): Sc(1)-N(33), 2.024(1);
Sc(1)-N(6), 2.160(1); Sc(1)-N(2), 2.155(1); Sc(1)-C(46),
2.228(3); N(33)-C(34), 1.406(6); N(6)-C(5), 1.338(7); C(5)-
C(4), 1.408(8); C(4)-C(3), 1.402(8); C(3)-N(2), 1.337(6).
Selected angles (deg): N(6)-Sc(1)-N(2), 88.19(4); N(6)-
Sc(1)-N(33), 115.42(4); N(6)-Sc(1)-C(46), 118.39(5); N(2)-
Sc(1)-N(33), 119.87(5); N(2)-Sc(1)-C(46), 112.74(5); N(33)-
Sc(1)-C(46), 102.91(5); Sc(1)-N(6)-C(5), 117.36(8); Sc(1)-
N(2)-C(3), 117.46(8); Sc(1)-N(33)-C(34), 150.78(9); N(6)-
C(5)-C(4), 124.3(2); C(5)-C(4)-C(3), 130.4(2); C(4)-C(3)-
N(2), 123.9(2).
formation of Bu-H. This result is consistent with Bu•
radical loss and subsequent C-H abstraction reactions
in the formation of 1-OEt from 1-tBu . Surprisingly,
heating 1-tBu in C6D6 (60 °C, 16 h) leads to no
decomposition, thus suggesting that binding of the
Lewis base might be the promoter in the C-O bond
cleavage reaction. The highly congested structure of
1-tBu was confirmed by single-crystal X-ray diffraction
(Figure 6 and Table 2), and from direct inspection the
scandium metal lies in a pseudo-tetrahedral environ-
ment, where one of the positions is occupied by the bulky
t
t
lishes that a scandium borohydride in combination with
the supporting Nacnac- and anilide ligand N[2,6-(CH-
(CH3)2)2C6H3] is capable of performing both C-O bond
cleavage and reduction reactions. Hence, the scandium
triethylborohydride or scandium tert-butyl complexes
described in this paper are close analogues of LiH or
LitBu in the context of C-O bond cleavage reactions.40
Terminal and stable scandium hydrides systems remain
attractive as synthetic targets.
t
t
Exp er im en ta l P r oced u r es
Bu alkyl ligand. The Sc-C Bu bond distance (Sc(1)-
C(46), 2.228(3) Å) is in accordance with typical scandium
alkyl complexes supported by the Nacnac- ligand (with
or without â-hydrogens).10
Gen er a l Con sid er a tion s. Unless otherwise stated, all
operations were performed in a M. Braun LabMaster drybox
under an atmosphere of purified nitrogen or using high-
vacuum standard Schlenk techniques under an argon atmos-
phere.41 Hexane, pentane, toluene, and benzene were dried by
passage through activated alumina and Q-5 columns.42 Diethyl
ether and CH2Cl2 were dried by passage through two activated
alumina columns. THF was distilled, under nitrogen, from
purple sodium benzophenone ketyl and stored under sodium
metal. Distilled THF was transferred under vacuum into
bombs before being pumped into a drybox. C6D6, THF-d8, Et2O-
In summary, we have shown that the skeleton “(Nac-
nac)Sc(NHAr)” is compatible with halide, triethylboro-
hydride, alkoxides, enolate, and a bulky alkyl having
â-hydrogens. Synthesis and characterization of an amaz-
ingly stable scandium tert-butyl complex is surprising
(even at elevated temperatures), despite the presence
of nine â-hydrogens. Most notably, we do not observe
dehydrohalogenation of the scandium chloro-anilide
precursor with LitBu to generate the corresponding
scandium imide complex. Such a result is remarkable,
since lanthanide complexes possessing the imido func-
tionality have been reported.39 The present work estab-
d
10, and CD2Cl2 were purchased from Cambridge Isotope
Laboratory (CIL). C6D6 was degassed and dried over activated
4 Å molecular sieves, and CD2Cl2 was dried over CaH2 and
vacuum-transferred into 4 Å molecular sieves. THF-d8 and
(40) (a) Bates, R. B.; Kroposki, L. M.; Potter, D. E. J . Org. Chem.
1972, 37, 560. (b) Tomboulian, P.; Amick, D.; Beare, S.; Dumke, K.;
Hart, D.; Hites, R.; Metzger, A.; Nowack, R. J . Org. Chem. 1973, 38,
322. (c) J ung, M. E.; Blum, R. B. Tetrahedron Lett. 1977, 43, 3791.
(41) For a general description of the equipment and techniques used
in carrying out this chemistry see: Burger, B. J .; Bercaw, J . E. In
Experimental Organometallic Chemistry; Wayda, A. L., Darensbourg,
M. Y., Eds.; ACS Symposium Series 357; American Chemical Society;
Washington, DC, 1987; pp 79-98.
(37) For references describing the use of tert-butyl as a hydrido
source in early-transition-metal chemistry see: (a) Pool, J . A.; Bradley,
C. A.; Chirik, P. J . Organometallics 2002, 21, 1271. (b) Pool, J . A.;
Lobkovsky, E.; Chirik, P. J . J . Am. Chem. Soc. 2003, 125, 2241.
(38) For a recent article see: Wendt, O. F.; Bercaw, J . E. Organo-
metallics 2001, 20, 3891.
(39) Synthesis of lanthanide complexes containing metal-ligand
multiple bonds are exceedingly rare: (a) Chan, H.-S.; Li, H.-W.; Xie,
Z. Chem. Commun. 2002, 652. (b) Asparna, K.; Ferguson, M.; Cavell,
R. G. J . Am. Chem. Soc. 2000, 122, 726.
(42) Pangborn, A. B.; Giardello, M. A.; Grubbs, R. H.; Rosen, R. K.;
Timmers, F. J . Organometallics 1996, 15, 1518.

4712 Organometallics, Vol. 22, No. 23, 2003
Basuli et al.
Et2O-d10 were degassed and stored over sodium metal. Celite,
alumina, and 4 Å molecular sieves were activated under
vacuum overnight at 200 °C. Li(Nacnac)2 (Nacnac- ) [Ar]NC-
(Me)CHC(Me)N[Ar], Ar ) 2,6-(CHMe2)2C6H3) and (Nacnac)-
ScCl2(THF)10 were prepared according to the literature. 2,6-
Diisopropylaniline was distilled prior to usage and deprotonated
in Et2O at -35 °C with KCH2Ph43 to give the potassium salt
KNHAr. Solid LitBu was collected by cooling a saturated
pentane solution to -78 °C, followed by rapid filtration. All
other chemical were used as received. In all reported reactions
percentage yields are based on the scandium precursor.
Infrared data (CaF2 plates) were measured by using a Nicolet
510P FTIR spectrometer. CHN elemental analyses were
(CH3)2, 18H), 0.63 (t, BCH2CH3, 9H), 0.51 (br, BCH2CH3, 6H).
The hydride was not located in the 1H NMR spectrum of
1-HBEt3. 13C NMR (25 °C, 100.6 MHz, C6D6): δ 168.6
(ArNC(CH3)CHC(CH3)NAr), 150.1 (aryl), 143.9 (aryl), 143.2
(aryl), 142.5 (aryl), 137.3 (aryl), 133.4 (aryl), 125.2 (aryl), 127.2
(aryl), 125.2 (aryl), 124.6 (aryl), 123.7 (aryl), 122.3 (aryl), 118.8
(aryl), 98.64 (ArNC(CH3)CHC(CH3)NAr), 29.00 (CH(CH3)2),
28.91 (CH(CH3)2), 28.39 (CH(CH3)2), 28.16 (CH(CH3)2), 25.58
(CH3), 25.04 (CH3), 24.85 (CH3), 24.67 (CH3), 24.52 (CH3), 24.25
(CH3), 24.16 (CH3), 17.67 (br, BCH2CH3), 10.80 (BCH2CH3).
11B NMR (70 °C, 128.37 MHz, C6D6): δ -8.70 (d, BH, J B-H
)
53 Hz). IR (C6H6, CaF2): 3097 (w), 3076 (m), 2963 (s), 2869
(m), 1957 (m), 1813 (m), 1590 (w), 1523 (s), 1487 (s), 1463 (s),
1
performed by Desert Analytics (Tucson, AZ). H, 13C, and 11B
1386 (s), 1315 (s), 1256 (s), 1170 (w), 1117 (w), 1042 (w) cm-1
.
NMR spectra were recorded on Varian 400 and 300 MHz NMR
Anal. Calcd for C47H75N3BSc: C, 76.50; H, 10.24; N, 5.696.
Found: C, 76.16; H, 10.16; N, 5.84.
1
spectrometers. H and 13C NMR are reported with reference
to solvent resonances (for 1H and 13C, respectively: residual
C6D5H in C6D6, 7.16 ppm and 128.0 ppm; residual CHDCl2 in
CD2Cl2, 5.32 ppm and 53.8 ppm; residual protio THF in THF-
d8, 1.73 and 3.58 ppm and 65.6 and 23.5 ppm). 11B NMR
spectra were reported with respect to external BF3‚OEt2 (δ 0.0
ppm). X-ray diffraction data were collected on a SMART6000
(Bruker) system under a stream of N2(g) at low temperatures.
Syn th esis of 1-OEt. In a vial was dissolved 1-HBEt3 (300
mg, 0.41 mmol) in 20 mL of Et2O. The solution was transferred
to a reaction vessel and the mixture heated for 28 h, the color
changing to pale yellow. The solution was dried under reduced
pressure, the yellow powder was extracted with hexane, and
the extracts were filtered. The filtrate was concentrated, and
cooled for 2 days at -35 °C to afford in two crops pale yellow
crystals of 1-OEt (178 mg, 0.26 mmol, 64% yield). 1H NMR
(20 °C, 399.8 MHz, C6D6): δ 7.16-7.02 (m, aryl, 8H), 6.77 (t,
aryl, 1H), 5.22 (s, NH, 1H), 4.96 (s, ArNC(CH3)CHC(CH3)NAr,
1H), 3.86 (q, OCH2CH3, 2H), 3.42 (septet, CH(CH3)2, 2H), 3.23
(septet, CH(CH3)2, 2H), 2.46 (br, CH(CH3)2, 2H), 1.54 (s, ArNC-
(CH3)CHC(CH3)NAr, 6H), 1.34 (d, CH(CH3)2, 12H), 1.17 (d,
CH(CH3)2, 6H), 1.06 (d, CH(CH3)2, 12H), 1.04 (d, CH(CH3)2,
12H), 0.84 (t, OCH2CH3, 3H). 13C NMR (25 °C, 100.6 MHz,
C6D6): δ 168.6 (ArNC(CH3)CHC(CH3)NAr), 149.9 (aryl), 143.3
(aryl), 142.7 (aryl), 142.0 (aryl), 133.4 (aryl), 126.9 (aryl), 124.6
(aryl), 122.7 (aryl), 116.7 (aryl), 97.24 (ArNC(CH3)CHC(CH3)-
NAr), 65.40 (OCH2CH3), 30.08, 28.71, 28.37, 25.23 (CH3), 24.63
(CH3), 24.56 (CH3), 23.87 (CH3), 23.76 (CH3), 21.16 (OCH2CH3).
IR (C6H6, CaF2): 3098 (w), 3088 (s), 2962 (s), 2926 (m), 2868
(m), 1958 (m), 1814 (m), 1590 (w), 1512 (s), 1462 (s), 1430 (s),
1386 (s), 1319 (s), 1262 (s), 1153 (s), 1104 (w), 1074 (w), 1041
(w) cm-1. Anal. Calcd for C43H64N3OSc: C, 75.51; H, 9.43; N,
6.17. Found: C, 75.13; H, 9.82; N, 5.98.
Syn th esis of 1-Cl(THF ). In a vial was dissolved (Nacnac)-
ScCl2(THF) (300 mg, 0.49 mmol) in 10 mL of THF and the
solution cooled to -35 °C. To the pale yellow solution was
added a cold THF solution (5 mL) of KNHAr (104 mg, 0.48
mmol), causing a color change to yellow. After the reaction
was stirred, for 24 h, the solution was filtered, and the filtrate
dried under reduced pressure. The yellow powder was ex-
tracted with Et2O, and the extracts were filtered, concentrated,
and cooled for 2 days at -35 °C to afford in two crops yellow
crystals of 1-Cl(THF ) (306 mg, 0.41 mmol, 83% yield). 1H
NMR (20 °C, 399.8 MHz, C6D6): δ 7.06 (m, aryl, 4H), 7.00 (m,
aryl, 2H), 6.93 (d, aryl, 2H), 6.77 (t, aryl, 1H), 6.20 (bs, NH,
1H), 5.06 (s, ArNC(CH3)CHC(CH3)NAr, 1H), 3.52 (m, THF,
4H), 3.50 (septet, CH(CH3)2, 2H), 3.18 (septet, CH(CH3)2, 2H),
2.36 (septet, CH(CH3)2, 2H), 1.53 (s, ArNC(CH3)CHC(CH3)-
NAr, 6H), 1.42 (d, CH(CH3)2, 6H), 1.33 (m, THF, 4H), 1.12 (d,
CH(CH3)2, 6H), 1.08 (d, CH(CH3)2, 6H), 1.02 (d, CH(CH3)2,
12H), 0.97 (d, CH(CH3)2, 6H). 13C NMR (25 °C, 100.6 MHz,
C6D6): δ 168.8 (ArNC(CH3)CHC(CH3)NAr), 148.9 (aryl), 143.8
(aryl), 142.3 (aryl), 141.7 (aryl), 133.9 (aryl), 127.4 (aryl), 125.2
(aryl), 124.6 (aryl), 122.9 (aryl), 118.4 (aryl), 98.25 (ArNC(CH3)-
CHC(CH3)NAr), 68.18 (THF), 31.15 (CH(CH3)2), 28.86 (CH-
(CH3)2), 28.67 (CH(CH3)2), 26.19 (CH(CH3)2), 25.62 (THF),
24.79 (CH(CH3)2), 24.59 (CH(CH3)2), 23.99 (CH(CH3)2), 23.87
(ArNC(CH3)CHC(CH3)NAr). IR (C6H6, CaF2): 3300 (w), 3071
(s), 3044 (s), 3028 (s), 2964 (s), 2868 (m), 1959 (w), 1815 (w),
1528 (w), 1483 (s), 1433 (m), 1378 (s), 1319 (m), 1259 (m), 1171
(w) cm-1. Anal. Calcd for C45H67N3OClSc: C, 72.40; H, 9.05;
N, 5.63. Found: C, 72.02; H, 8.86; N, 5.62.
Syn t h esis of 1-OCH dCH 2. In
a vial was dissolved
1-HBEt3 (300 mg, 0.41 mmol) in 20 mL of THF. The solution
was transferred to a reaction vessel and the mixture heated
for 28 h, the color changing to pale yellow. The solution was
dried under reduced pressure and the vessel taken into the
glovebox. The yellow powder was extracted with hexane, and
the extracts were filtered. The filtrate was concentrated, and
cooled for 2 days at -35 °C to afford in two crops pale yellow
1
crystals of 1-OCHdCH2 (195 mg, 0.28 mmol, 70% yield). H
NMR (20 °C, 399.8 MHz, C6D6): δ 7.08-6.99 (m, aryl, 6H),
6.96 (d, aryl, 2H), 6.76 (t, aryl, 1H), 6.67-6.63 (dd, OCHdCH2,
J H-Htrans ) 14 Hz, J H-Hcis ) 6 Hz, 1H), 5.49 (s, NH, 1H), 4.99
(s, ArNC(CH3)CHC(CH3)NAr, 1H), 4.16 (broad d, OCHdCH2,
J H-Htrans ) 14 Hz, 1H), 3.92 (d, OCHdCH2, J H-Hcis ) 6 Hz, 1H),
3.32 (septet, CH(CH3)2, 2H), 3.23 (septet, CH(CH3)2, 2H), 2.36
(br, CH(CH3)2, 2H), 1.54 (s, ArNC(CH3)CHC(CH3)NAr, 6H),
1.36 (d, CH(CH3)2, 6H), 1.34 (d, CH(CH3)2, 6H), 1.17 (d, CH-
(CH3)2, 6H), 1.12 (d, CH(CH3)2, 6H), 1.04 (d, CH(CH3)2, 12H).
13C NMR (25 °C, 100.6 MHz, C6D6): δ 168.4 (ArNC(CH3)-
CHC(CH3)NAr), 154.7 (aryl), 149.4 (aryl), 143.6 (aryl), 142.6
(aryl), 142.0 (aryl), 133.6 (aryl), 127.0 (aryl), 124.8 (aryl), 124.7
(aryl), 122.7 (aryl), 117.4 (aryl), 97.75 (ArNC(CH3)CHC(CH3)-
NAr), 90.48 (OCHdCH2), 68.06 (OCHdCH2), 30.45 (CH(CH3)2),
28.80 (CH(CH3)2), 28.41 (CH(CH3)2), 25.67 (CH3), 25.20 (CH3),
24.68 (CH3), 24.27 (CH3), 23.90 (CH3), 23.78 (CH3), 22.53. IR
(C6H6, CaF2): 3097 (w), 3088 (s), 3061 (m), 3029 (s), 2963 (s),
2926 (m), 2868 (m), 1957 (m), 1814 (m), 1591 (m), 1524 (s),
1476 (s), 1462 (s), 1431 (s), 1386 (s), 1317 (s), 1261 (s), 1214
Syn th esis of 1-HBEt3. In a vial was dissolved 1-Cl(THF )
(300 mg, 0.40 mmol) in 15 mL of toluene and the solution
cooled to -35 °C. To the cold solution was added a cold
NaHBEt3 solution (0.43 mmol, 1 M solution in toluene),
causing a rapid color change to a darker yellow. After the
reaction was stirred for 6 h, the solution was filtered, and the
filtrate dried under reduced pressure. The yellow powder was
extracted with hexane, and the extracts were filtered, concen-
trated, and cooled for 3 days at -35 °C to afford in three crops
large yellow blocks of 1-HBEt3 (232 mg, 0.31 mmol, 78% yield).
1H NMR (20 °C, 399.8 MHz, C6D6): δ 7.10 (m, aryl, 8H), 6.88
(t, aryl, 1H), 5.94 (s, NH, 1H), 5.18 (s, ArNC(CH3)CHC(CH3)-
NAr, 1H), 3.51 (septet, CH(CH3)2, 1H), 3.37 (septet, CH(CH3)2,
2H), 3.29 (septet, CH(CH3)2, 1H), 3.14 (septet, CH(CH3)2, 2H),
1.60 (s, ArNC(CH3)CHC(CH3)NAr, 6H), 1.36 (d, CH(CH3)2, 6H),
1.29 (d, CH(CH3)2, 6H), 1.26 (d, CH(CH3)2, 6H), 1.01 (d, CH-
(43) Schlosser, M.; Hartmann, J . Angew. Chem., Int. Ed., Engl. 1973,
12, 508.

Scandium Borohydride Promoted C-O Bond Cleavage
Organometallics, Vol. 22, No. 23, 2003 4713
(s), 1173 (w), 1152 (w), 1103 (w) cm-1. Anal. Calcd for C43H62N3-
OSc: C, 75.73; H, 9.16; N, 6.16. Found: C, 75.62; H, 8.55; N,
5.77.
extracts were filtered, the filtrate concentrated, and cooled
overnight at -35 °C to afford yellow crystals of 1-OEt (40.9
mg, 0.59 mmol, 88% yield). Examination by 1H NMR spectrum
of the volatiles revealed the major product to be 2-methylpro-
Syn th esis of 1-OCHP h 2. In a vial was dissolved 1-HBEt3
(100 mg, 0.13 mmol) in 10 mL of toluene and the solution
cooled to -35 °C. To the solution was added solid Ph2CO (25
mg, 0.14 mmol), causing a rapid color change to light yellow.
After it was stirred for 2 h, the solution was filtered and the
filtrate dried under reduced pressure. The light yellow powder
was extracted with Et2O, and the extracts were filtered, the
filtrate concentrated, and cooled for 2 days at -35 °C to afford
in three crops light yellow crystals of 1-OCHP h 2 (89 mg, 0.11
mmol, 80% yield). HMQC experiments was performed on
1-OCHP h 2 in order to assign some of the 1H and 13C NMR
resonances.32 1H NMR (20 °C, 399.8 MHz, C6D6): δ 7.38 (br,
aryl, 1H), 7.19-6.80 (m, aryl, 18H), 5.96 (s, OCHPh2, 1H), 5.46
(s, NH, 1H), 5.15 (s, ArNC(CH3)CHC(CH3)NAr, 1H), 3.31 (br,
CH(CH3)2, 2H), 3.07 (br, CH(CH3)2, 2H), 2.70 (br, CH(CH3)2,
1H), 2.24 (br, CH(CH3)2, 1H), 1.64 (s, ArNC(CH3)CHC(CH3)-
NAr, 6H), 1.38 (br, CH(CH3)2, 6H), 1.06 (br, CH(CH3)2, 24H),
0.92 (br, CH(CH3)2, 6H). 13C NMR (25 °C, 100.6 MHz, C6D6):
δ 168.8 (ArNC(CH3)CHC(CH3)NAr), 149.9 (aryl), 146.7 (aryl),
143.8 (aryl), 142.5 (aryl), 141.7 (aryl), 134.2 (aryl), 133.5 (aryl),
127.0 (aryl), 126.8 (aryl), 126.7 (aryl), 126.5 (aryl), 124.7 (aryl),
124.5 (aryl), 122.9 (aryl), 122.8 (aryl), 116.9 (aryl), 97.56
(ArNC(CH3)CHC(CH3)NAr), 83.23 (OCHPh2), 31.24 (CH-
(CH3)2), 28.65 (CH(CH3)2), 28.39 (CH(CH3)2), 28.19 (CH(CH3)2),
25.24 (CH3), 25.04 (CH3), 24.64 (CH3), 24.50 (CH3), 24.21 (CH3),
23.56 (CH3), 22.67, 14.24. IR (C6H6, CaF2): 3097 (m), 3071 (s),
3029 (s), 3023 (m), 2962 (s), 2926 (m), 2868 (m), 1960 (m), 1815
(m), 1575 (m), 1558 (m), 1539 (m), 1506 (s), 1476 (s), 1457 (s),
1430 (s), 1386 (s), 1318 (s), 1261 (s), 1173 (m), 1122 (m), 1070
(w) cm-1. Anal. Calcd for C43H64N3OSc‚0.5Et2O: C, 78.28; H,
8.80; N, 4.89. Found: C, 78.52; H, 8.95; N, 5.03.
1
pane (tBu-H), as evidenced by H NMR spectroscopy.
Th er m olysis of 1-HBEt3 in th e Absen ce of Lew is Ba ses.
In a vial was dissolved 1-HBEt3 (50 mg, 0.068 mmol) in 10
mL of benzene. The solution was transferred to a reaction
vessel and heated at 80 °C for 12 h, causing a color change to
pale yellow. The solution was then dried under reduced
pressure, and the vessel was taken into the glovebox. Exami-
nation of the crude mixture by 1H NMR spectroscopy revealed
formation of a myriad of products.
Th er m olysis of 1-tBu in th e Absen ce of Lew is Ba ses.
In a vial was dissolved 1-tBu (72.4 mg, 0.104 mmol) in 15 mL
of benzene. The solution was transferred to a reaction vessel
and was heated at 60 °C for 16 h. The solution was dried under
reduced pressure, and the vessel was taken into the glovebox.
The yellow powder was extracted with hexane, and the
extracts were filtered, concentrated, and cooled overnight at
-35 °C to afford yellow crystals. The 1H NMR spectrum
revealed that no reaction had occurred.
Str u ctu r e Solu tion a n d Refin em en t. A summary of
crystal data and refinement details for all structures are given
in Tables 1 and 2.
Gen er a l P a r a m eter s for Da ta Collection a n d Refin e-
m en t. Single crystals of 1-Cl(THF ), 1-OCHP h 2‚0.5Et2O, and
1-tBu ‚0.5Et2O were grown from Et2O at -35 °C. Single
crystals of 1-HBEt3, 1-OEt, and 1-OCHdCH2 were grown
from hexane at -35 °C. Inert-atmosphere techniques were
used to place the crystal onto the tip of a diameter glass
capillary (0.06-0.20 mm), which was mounted on a SMART-
6000 instrument (Bruker) at 127-140(2) K. A preliminary set
of cell constants was calculated from reflections obtained from
three nearly orthogonal sets of 20-30 frames. The data
collection was carried out using graphite-monochromated Mo
KR radiation with a frame time of 3 s and a detector distance
of 5.0 cm. A randomly oriented region of a sphere in reciprocal
space was surveyed. Three sections of 606 frames were
collected with 0.30° steps in ω at different φ settings with the
detector set at -43° in 2θ. Final cell constants were calculated
from the xyz centroids of strong reflections from the actual data
collection after integration (SAINT).44 The structure was solved
by using SHELXS-97 and refined with SHELXL-97.45 A direct-
methods solution was calculated which provided most non-
hydrogen atoms from the E map. Full-matrix least-squares/
difference Fourier cycles were performed, which located the
remaining non-hydrogen atoms. All non-hydrogen atoms were
refined with anisotropic displacement parameters. All hydro-
gen atoms were refined with isotropic displacement param-
eters.
For 1-HBEt3, the structure is unique in that the HBEt3
anion is bound to the Sc atom through three hydrogen atoms.
The bonds are weak (d[Sc-H] ) 1.98-2.18 Å) but are located
such that the coordination about the Sc atom is pseudo-
octrahedral. These values are longer than estimated values
calculated with the Pauling and Schomaker-Stevenson cova-
lent radii, with corrections for electronegativity differences
(d[Sc-H] ) 1.68 Å).46
For 1-OCHP h 2‚0.5Et2O, in addition to the molecule of
interest a disordered Et2O solvent was located. All non-
hydrogen atoms were refined with anisotropic displacement
parameters, with the exception of that particular solvent. All
hydrogen atoms were placed in ideal positions and refined as
riding atoms with relative isotropic displacement parameters.
One of the solvent hydrogen atoms was not located.
Syn th esis of 1-tBu . In a vial was dissolved 1-Cl(THF ) (100
mg, 0.13 mmol) in 10 mL of Et2O and the solution cooled to
-35 °C. To the solution was added a cold Et2O (5 mL) solution
containing LitBu (9.01 mg, 0.14 mmol), causing a color change
to darker yellow. After it was stirred for 2 h, the solution was
filtered and the filtrate dried under reduced pressure. The
yellow powder was extracted with hexane, and the extracts
were filtered. The filtrate was concentrated, and cooled for 2
days at -35 °C to afford in three crops yellow crystals of 1-tBu
1
(87.6 mg, 0.12 mmol, 94% yield). H NMR (20 °C, 399.8 MHz,
C6D6): δ 7.20-7.10 (m, aryl, 8H), 6.94 (t, aryl, 1H), 5.87 (s,
NH, 1H), 5.16 (s, ArNC(CH3)CHC(CH3)NAr, 1H), 3.49 (septet,
CH(CH3)2, 2H), 3.41 (septet, CH(CH3)2, 1H), 3.16 (septet,
CH(CH3)2, 2H), 2.86 (septet, CH(CH3)2, 1H), 1.69 (s, ArNC-
(CH3)CHC(CH3)NAr, 6H), 1.36 (d, CH(CH3)2, 6H), 1.33 (d, CH-
(CH3)2, 6H), 1.31 (d, CH(CH3)2, 6H), 1.22 (d, CH(CH3)2, 6H),
1.10 (d, CH(CH3)2, 6H), 1.06 (d, CH(CH3)2, 6H), 0.92 (s,
C(CH3)3, 9H). 13C NMR (25 °C, 100.6 MHz, C6D6): δ 168.6
(ArNC(CH3)CHC(CH3)NAr), 150.6 (aryl), 143.7 (aryl), 142.7
(aryl), 142.3 (aryl), 135.5 (aryl), 132.9 (aryl), 127.0 (aryl), 124.9
(aryl), 124.5 (aryl), 122.9 (aryl), 122.8 (aryl), 117.4 (aryl), 97.97
(ArNC(CH3)CHC(CH3)NAr), 31.91 (CH(CH3)2), 31.08 (CH-
(CH3)2), 30.18 (ArNC(CH3)CHC(CH3)NAr), 28.87 (CH(CH3)2),
28.52 (CH(CH3)2), 28.41 (CH(CH3)2), 25.67 (CH(CH3)2), 25.10
(C(CH3)3), 24.73 (CH(CH3)2), 24.42 (CH(CH3)2), 23.52 (CH-
(CH3)2), 23.00, 14.30 (C(CH3)3). IR (C6H6, CaF2): 3200 (w), 3097
(w), 3077 (s), 3044 (s), 2962 (s), 2927 (m), 2869 (m), 2798 (m),
1957 (m), 1812 (w), 1591 (w), 1517 (s), 1461 (s), 1430 (s), 1386
(s), 1315 (s), 1260 (s), 1171 (w), 1107 (w), 1041 (w), 1019 (w)
cm-1. Anal. Calcd for C45H68N3Sc: C, 77.65; H, 9.85; N, 6.04.
Found: C, 77.60; H, 9.88; N, 6.18.
Th er m olysis of 1-tBu in Et2O To P r ep a r e 1-OEt. In an
NMR tube was dissolved 1-tBu (47 mg, 0.067 mmol) in 0.6
mL of C6D6, and ∼3 drops of Et2O were added. The solution
was heated at 60 °C for 44 h. The volatile materials were
vacuum-transferred into another NMR tube, leaving behind
a yellow residue, which was extracted with hexane; the
(44) SAINT 6.1; Bruker Analytical X-ray Systems, Madison, WI.
(45) SHELXTL-Plus V5.10; Bruker Analytical X-ray Systems, Madi-
son, WI.
(46) Pauling, L. The Nature of the Chemical Bond, 3rd ed.; Cornell
University Press: Ithaca, NY, 1960.

4714 Organometallics, Vol. 22, No. 23, 2003
Basuli et al.
For 1-tBu ‚0.5Et2O, in addition to the molecule of interest a
disordered Et2O solvent was located and modeled. All non-
hydrogen atoms were refined with anisotropic displacement
parameters. All hydrogen atoms were located and refined with
isotropic displacement parameters. The only exception is the
absence of two of the hydrogen atoms associated with one of
the terminal methyl groups of the solvent.
Foundation. D.J .M. thanks Professor K. G. Caulton for
insightful discussions and Ms. J . Chandler.
Su p p or tin g In for m a tion Ava ila ble: Complete details for
data sets including tables of atomic coordinates, bond lengths
and angles, anisotropic displacement parameters, hydrogen
coordinates, and structural diagrams for 1-Cl(THF ), 1-HBEt3,
1-OEt, 1-OCHdCH2, 1-OCHP h 2‚0.5Et2O, and 1-tBu ‚0.5Et2O.
This material is available free of charge via the Internet at
http://pubs.acs.org.
Ack n ow led gm en t. For financial support of this
work we thank Indiana University-Bloomington, the
Ford Foundation, and the Camille and Henry Dreyfus
OM030374B