ν-alkoxy-β-ketoiminate complexes of groups 4 and 5: Synthesis and characterization of the complexes [(η-C5H4R)M{CH3C(O)CHC(NCH 2CHR'O)CH3}Cln] (M = Ti, n = 1; M = Nb, n = 2; R = H, Me; R′ = H, Me), [Ti{CH3C(O)CHC(NCH2CHR'O)CH3}Cl 2(thf)]

Article abstract of DOI:10.1021/om980510q

The synthesis and characterization of a range of ν-alkoxo β-ketoiminate complexes of groups 4 and 5 are reported. Reactions between the acylic ν-hydroxyalkyl β-ketoimines CH₃C(O)CII₂C(NCH₂CHR'OH)CH₃ (R′ = H, Me) and [(η²-C₅H₄R)TiCl₃] (R = H, Me) in the presence of triethylamine afford the monocyclopentadienyl derivatives [(η-C₅H₄R)Ti-{CH₃C(O)CHC(NCH ₂CHR'O)CH₃}C1] (R = H, R′ = H, 2a; R = Me, R′ = H, 2b; R = H, R′ = Me, 2c; R = Me, R′ = Me, 2d). Complex 2a adopts a square pyramidal coordination geometry with the Cp occupying the apical site and the terdentate ketoiminate and chloride occupying basal positions. Upon standing in thf, solutions of 2a-d containing NEt₃HCl deposit deep orange crystals of [Ti{CH₃C(O)CHC(NCH₂CHR'O)CH₃}Cl2(thf)] (R′ = H, 3a; R′ = Me, 3b) via protonolysis of the Ti-Cp bond. Alternatively, compounds 3a and 3b can be prepared in near quantitative yield either from the reaction between [TiCl₄(thf)₂] and the corresponding acylic ν-hydroxyalkyl β-ketoimine, in the presence of NEt₃, or via a ligand exchange reaction between [Ti(OPrⁱ)2Cl₂] and the ν-hydroxyalkyl β-ketoimine. Variable-temperature ²H NMR studies of 3a and 3b have shown that stereoisomers of these complexes interchange via a dissociative dynamic process, involving the trigonal bypyramidal intermediate [Ti-{CH₃C(O)CHC(NCH₂CHR′O)CH₃}Cl ₂]. The free energy of activation associated with this exchange has been determined (ΔG = 45.5 kJ mol^-1, 3a; ΔG = 47.0 kJ mol^-1, 3b). Surprisingly, treatment of [TiCOPrⁱ₄] with ν-hydroxyalkyl β-ketoimine (1:1) results in complete alcoholysis to afford [Ti{CH₃C(O)CHC(NCH₂CHR'O)CH₃}₂] (R′ = H, 4a; R′ = Me, 4b), which contain two meridianally coordinated terdentate ketoiminate ligands. The reactions between ν-hydroxyalkyl β-ketoimine derivatives and [(η²-C₅H₄R)NbCl₄] afford [(η²C₅H₄R)Nb{CH₃C(O)CHC(NCH ₂CHR'O)CH₃}Cl₂] (R = H, R′ = H, 5a; R = Me, R′ = H, 5b; R = H, R′ = Me, 5c; R = Me, R′ = Me, 5d). A single-crystal X-ray study of 5a revealed a structure based on an octahedral geometry, such that the nitrogen of the mer-terdentate ligand is trans to the Cp and the two chloro ligands mutually trans. The single-crystal X-ray structures of 2a, 3a, 3b, 4a-CH₃Cl₃, and 5a are reported.

Full text of DOI:10.1021/om980510q

1
018
Organometallics 1999, 18, 1018-1029
N-Alk oxy-â-k etoim in a te Com p lexes of Gr ou p s 4 a n d 5:
Syn th esis a n d Ch a r a cter iza tion of th e Com p lexes
5
[
(η -C H R)M{CH C(O)CHC(NCH CHR′O)CH }Cl ] (M )
5
4
3
2
3
n
Ti, n ) 1; M ) Nb, n ) 2; R ) H, Me; R′ ) H, Me),
[
Ti{CH C(O)CHC(NCH CHR′O)CH }Cl (th f)], a n d
3
2
3
2
[
Ti{CH C(O)CHC(NCH CHR′O)CH } ]
3
2
3 2
,
†
,‡
Simon Doherty,* R. J ohn Errington,* Neil Housley, J ohn Ridland,
William Clegg, and Mark R. J . Elsegood
Department of Chemistry, Bedson Building, The University of Newcastle upon Tyne,
Newcastle upon Tyne, NE1 7RU, U.K.
Received J une 19, 1998
The synthesis and characterization of a range of N-alkoxo â-ketoiminate complexes of
groups 4 and 5 are reported. Reactions between the acylic N-hydroxyalkyl â-ketoimines
5
CH
3
C(O)CH
2
C(NCH
2
CHR′OH)CH
3
(R′ ) H, Me) and [(η -C
5
H
4
R)TiCl
3
] (R ) H, Me) in the
5
presence of triethylamine afford the monocyclopentadienyl derivatives [(η -C
5
H
4
R)Ti-
{
CH C(O)CHC(NCH CHR′O)CH
3
2
3
}Cl] (R ) H, R′ ) H, 2a ; R ) Me, R′ ) H, 2b; R ) H, R′ )
Me, 2c; R ) Me, R′ ) Me, 2d ). Complex 2a adopts a square pyramidal coordination geometry
with the Cp occupying the apical site and the terdentate ketoiminate and chloride occupying
basal positions. Upon standing in thf, solutions of 2a -d containing NEt
orange crystals of [Ti{CH C(O)CHC(NCH CHR′O)CH }Cl (thf)] (R′ ) H, 3a ; R′ ) Me, 3b)
via protonolysis of the Ti-Cp bond. Alternatively, compounds 3a and 3b can be prepared in
near quantitative yield either from the reaction between [TiCl (thf) ] and the corresponding
acylic N-hydroxyalkyl â-ketoimine, in the presence of NEt , or via a ligand exchange reaction
3
HCl deposit deep
3
2
3
2
4
2
3
i
1
2 2
between [Ti(OPr ) Cl ] and the N-hydroxyalkyl â-ketoimine. Variable-temperature H NMR
studies of 3a and 3b have shown that stereoisomers of these complexes interchange via a
dissociative dynamic process, involving the trigonal bypyramidal intermediate [Ti-
{
3 2 3 2
CH C(O)CHC(NCH CHR′O)CH }Cl ]. The free energy of activation associated with this
q
-1
q
-1
exchange has been determined (∆G ) 45.5 kJ mol , 3a ; ∆G ) 47.0 kJ mol , 3b).
Surprisingly, treatment of [Ti(OPr )
complete alcoholysis to afford [Ti{CH
4
i
4
] with N-hydroxyalkyl â-ketoimine (1:1) results in
3
C(O)CHC(NCH
2
CHR′O)CH
3
}
2
] (R′ ) H, 4a ; R′ ) Me,
b), which contain two meridianally coordinated terdentate ketoiminate ligands. The
5
5
reactions between N-hydroxyalkyl â-ketoimine derivatives and [(η -C
R)Nb{CH C(O)CHC(NCH CHR′O)CH }Cl
5
H
4
R)NbCl
4
] afford [(η -
C
)
5
H
4
3
2
3
2
] (R ) H, R′ ) H, 5a ; R ) Me, R′ ) H, 5b; R
H, R′ ) Me, 5c; R ) Me, R′ ) Me, 5d ). A single-crystal X-ray study of 5a revealed a
structure based on an octahedral geometry, such that the nitrogen of the mer-terdentate
ligand is trans to the Cp and the two chloro ligands mutually trans. The single-crystal X-ray
structures of 2a , 3a , 3b, 4a ‚CH
2
Cl
2
, and 5a are reported.
In tr od u ction
tain nitrogen- and/or oxygen-donor ligands such as di-
2
3
4
amides, amidinates, azamacrocycles, tetradentate
Cyclic and acyclic multidentate ligands with varying
5
6
7
Schiff bases, porphyrins, alkoxides, or donor-func-
combinations of donor atoms and charges have become
an increasingly popular class of ligands for transition
metals, lanthanides, and main group elements. In par-
ticular, group 4 transition metal complexes of such
ligands have attracted considerable interest as possible
alternatives to catalysts containing the bent metallocene
8
tionalized cyclopentadienyl ligands, and the focus of
attention has been their use as catalysts for R-olefin
(2) (a) Aizenberg, M.; Turculet, L.; Davis, W. M.; Schattenmann, F.
Schrock, R. R. Organometallics 1998, 17, 4795. (b) Schrock, R. R.;
Schattenmann, F.; Aizenberg, M.; Davis, W. M. Chem. Commun. 1998,
1
99. (c) Gibson, V. C.; Kimberly, B. S.; White, A. J . P.; Williams, D. J .;
1
fragment Cp2M. The majority of these complexes con-
Howard, P. Chem. Commun. 1998, 313. (d) Scollard, J . D.; McConville,
D. H. J . Am. Chem. Soc. 1996, 118, 10008. (e) Scollard, J . D.;
McConville, D. H.; Vittal, J . J . Organometallics 1995, 14, 5478. (f)
Scollard, J . D.; McConville, D. H.; Rettig, S. J . Organometallics 1997,
16, 1810. (g) Tinkler, S.; Deeth, R. J .; Duncalf, D. J .; McCamley, A.
Chem. Commun. 1996, 2623. (h) Scott, M. J .; Lippard, S. J . Organo-
metallics 1998, 17, 1769. (i) Warren, T. H.; Schrock, R. R.; Davis, W.
N. Organometallics 1998, 17, 308. (j) J oen, Y.-M.; Park, S. J .; Heo, J .;
Kim, K. Organometallics 1998, 17, 3161.
*
To whom correspondence should be addressed.
E-mail: simon.doherty@newcastle.ac.uk.
E-mail: john.errington@newcastle.ac.uk.
†
‡
(
1) (a) Brintzinger, H. H.; Fischer, D.; Mulhaupt, R.; Rieger, B.;
Waymouth, R. M. Angew. Chem., Int. Ed. Engl. 1995, 34, 1143. (b)
Bochmann, M. J . Chem. Soc., Dalton Trans. 1996, 255. (c) Mohring,
P. C.; Coville, N. J . J . Organomet. Chem. 1994, 479, 1.
1
0.1021/om980510q CCC: $18.00 © 1999 American Chemical Society
Publication on Web 02/25/1999

N-Alkoxy-â-ketoiminate Complexes of Groups 4 and 5
Organometallics, Vol. 18, No. 6, 1999 1019
polymerization,9 for the addition of nucleophiles to
carbonyl groups,10 and for various other carbon-carbon
bond-forming processes.11 Although nitrogen-donor
ligands have dominated the development of non-
metallocene chemistry, there have been relatively few
reports that describe the coordination chemistry of bis-
Ch a r t 1a
imines1 and ketoimine complexes of the early transi-
2
13
a
R) H, 1a ; R ) Me, 1b.
tion metals and lanthanides. This is somewhat surpris-
ing given that bis(iminates), [CH3C(NR)CHC(NR)CH3] ,
-
transformations, we are investigating the coordination
are potentially pseudo-isoelectronic with the cyclopen-
tadienyl anion and that they are easily prepared from
inexpensive and readily available starting materials.
Moreover, through a judicious choice of primary amine
and â-diketone used in their synthesis, the steric and
electronic properties of this ligand type can be tuned
and chirality and further functionalization readily in-
troduced.14 In an effort to develop novel reagents for
Lewis-acid-promoted or -catalyzed asymmetric organic
chemistry of N-hydroxyalkyl-functionalized ketoimines
1
5
such as 1a ,b containing a pendant alcohol functional-
ity, tautomeric forms of which are shown in Chart 1.
These compounds are capable of coordinating to a metal
center in a terdentate(-2) manner or as bidentate(-1)
ketoiminates and as such offer a broad scope for the
preparation of complexes with potential as catalysts for
polymerization chemistry and/or for use in Lewis-acid-
1
6
mediated asymmetric organic synthesis, especially as
chiral derivatives can be prepared and the number and
type of donor atoms varied. Herein, we report the results
of our preliminary studies in this area, including details
of the synthesis and structural characterization of the
mono(cyclopentadienyl) derivatives [CpM(L)Cln] (M )
Ti, n ) 1; Nb, n ) 2), which contain a terdentate
N-alkoxy â-ketoiminate, with one (M ) Ti) or two (M )
Nb) M-Cl bonds available for further development of
their reaction chemistry, and the noncyclopentadienyl
derivatives [Ti{CH3C(O)CHC(NCH2CHR′O)CH3}Cl2-
(
3) (a) Hagadorn, J . R.; Arnold, J . Organometallics 1998, 17, 1355.
(
b) Sita, L. R.; Babcock, J . R. Organometallics 1998, 17, 5228. (c) Volkis,
V.; Shmulinson, M.; Averbuj, C.; Lisovskii, A.; Edelmann, F. T.; Eisen,
M. S. Organometallics 1998, 17, 3155. (d) Dawson, D. Y.; Arnold, J .
Organometallics 1997, 11, 11111. (e) Brand, H.; Capriotti, J . A.; Arnold,
J . Organometallics 1994, 13, 4469. (f) Hagadorn, J . R.; Arnold, J . J .
Chem. Soc., Dalton Trans. 1997, 3087. (g) Maidanto Gomez, R.; Green,
M. L. H.; Haggitt, J . L. J . Chem. Soc., Chem. Commun. 1994, 2607.
(
h) Duchateau, R.; Cornelis, T. W.; Meetsma, A.; van Duijnen, P. T.;
Teuben, J . H. Organometallics 1996, 15, 2279. (i) Herskovics-Korine,
D.; Eisen, M. S. J . Organomet. Chem. 1995, 503, 307.
(4) (a) Martin, A.; Uhrhammer, R.; Gardner, T. G.; J ordan, R. F.;
Rogers, R. D. Organometallics 1998, 17, 382. (b) Lee, L.; Berg, D. J .;
Bushnell, G. W. Organometallics 1997, 16, 2556. (c) Mountford, P. J .
Chem. Soc. Rev. 1998, 27, 105, and references therein.
(
thf)], which contain two Ti-Cl bonds and a labile thf
ligand.
(5) (a) Tjaden, E. B.; Swenson, D. C.; J ordan, R. F. Organometallics
1
1
995, 14, 371. (b) Lee, L.; Berg, D. J .; Bushnell, G. W. Organometallics
997, 16, 2556. (c) Lee, L.; Berg, D. J .; Einstein, F. W.; Batchelor, R.
Resu lts a n d Discu ssion
J . Organometallics 1997, 16, 1819. (d) Coles, S. J .; Hursthouse, M. B.;
Kelly, D. G.; Toner, A. J .; Walker, N. M. J . Chem. Soc., Dalton Trans.
5
Syn th esis a n d Ch a r a cter iza tion of [(η -C5H4R)-
Ti{CH3C(O)CHC(NCH2CHR′O)CH3}Cl2] (2a-d). The
addition of 1 equiv of H2NCH2CH(R′)OH (R′ ) H, Me)
to a dichloromethane solution of 2,4-pentanedione at
room temperature results in the formation of the desired
N-hydroxyalkyl â-ketoimine CH3C(O)CH2C(NCH2CH-
R′OH)CH3 (R′ ) H, 1a ; Me, 1b) in high yield as colorless
crystals, after workup and crystallization (eq 1).
1
998, 3489.
6) (a) Brand, H.; Arnold, J . Organometallics 1993, 12, 3655. (b)
Brand, H.; Arnold, J . J . Am. Chem. Soc. 1992, 114, 2266.
7) (a) Fokken, S.; Spaniol, T. P.; Okuda, J .; Serentz, F. G.;
(
(
Mullhaupt, R. Organometallics 1997, 16, 4240. (b) Mack, H.; Eisen,
M. S. J . Chem. Soc., Dalton Trans. 1998, 7. (c) Bei, X.; Swenson, D.
C.; J ordan, R. F. Organometallics 1997, 16, 3282. (d) Kim, I.; Nishihara,
Y.; J ordan, R. F.; Rogers, R. D.; Rheingold, A. L.; Yap, G. P. A.
Organometallics 1997, 16, 3314. (e) Tsukahara T.; Swenson, D. C.;
J ordan, R. F. Organometallics 1997, 16, 3303.
(8) (a) Gielens, E. E. C. G., Tiesnitsch, J . Y.; Hessen, B.; Teuben, J .
H. Organometallics 1998, 17, 1652. (b) Flores, J . C.; Chien, J . C. W.;
Rausch, M. D. Organometallics 1994, 13, 4140. (c) Chen, Y. X.; Fu, P.
F.; Stern, L. L.; Marks, T. J . Organometallics 1997, 16, 5958. (d) Blais,
M. S.; Chien, J . C. W.; Rausch, M. D. Organometallics 1998, 17, 3775.
(
e) Chen, Y.-X.; Marks, T. J . Organometallics 1997, 16, 3649. (f) Van
der Zeikden, A. A. H.; Mattheis, C.; Frohlich, R.; Zippel, F. Inorg. Chem.
997, 36, 4444.
9) (a) Scollard, J . D.; McConville, D. H.; Payne, N. C.; Vittal, J . J .
1
(
Macromolecules 1996, 29, 5241. (b) Baumann, R.; Davis, W. M.;
Schrock, R. R. J . Am. Chem. Soc. 1997, 119, 3820. (c) Scollard, J . D.;
McConville, D. H.; Vittal, J . J .; Yap, G. A. P. Organometallics 1997,
1
6, 4415.
(10) Duthaler, R. O.; Hafner, A. Chem. Rev. 1992, 92, 807.
11) (a) Guerin, F.; McConville, D. H.; Vittal, J . J .; Yap, G. A. P.
(
Organometallics 1998, 17, 1290. (b) Guerin, F.; McConville, D. H.;
Vittal, J . J . Organometallics 1997, 16, 1491. (c) Guerin, F.; McConville,
D. H.; Vittal, J . J .; Yap, G. A. P. Organometallics 1996, 15, 5586.
Dropwise addition of a thf solution of 1a and triethy-
lamine into a thf solution of [(η -C5H5)TiCl3] results in
a gradual color change from yellow to orange with the
(
12) (a) Rahim, M.; Taylor, N. J .; Xin, S.; Collins, S. Organometallics
5
1
998, 17, 1315. (b) Kim, W. W.; Fevola, M. J .; Liable-Sands, L. M.;
Rheingold, A. L. Theopold, K. H. Organometallics 1998, 17, 4541. (c)
Hitchcock, P. B.; Lappert, M. F.; Liu, D.-S. J . Chem. Soc., Chem.
Commun. 1994, 1699. (d) Deelman, B.-J .; Lappert, M. F.; Lee, H.-K.;
Mak, T. C. W.; Leung, W.-P.; Wei, P.-R. Organometallics 1997, 16,
(15) Bertrand, J . A.; Kelley, J . A.; Breece, J . L. Inorg. Chim. Acta
1969, 4, 247.
1
247. (e) Hitchcock, P. B.; Lappert, M. F.; Liu, D.-S. J . Chem. Soc.,
(16) For review articles see: (a) Kagan, H. B.; Riant, O. Chem. Rev.
1992, 92, 1007. (b) Halterman, R. L. Chem. Rev. 1992, 92, 965. For
relevant articles see: (c) Armistead, L. T.; White, P. S.; Gagne, M. R.
Organometallics 1998, 17, 4232. (d) Shao, M. Y.; Gao, H. M.; Organo-
metallics 1998, 17, 4822. (e) Boyle, T. J .; Barnes, D. L.; Heppert, J . A.;
Morales, L.; Takusagawa, F.; Connolly, J . W. Organometallics 1992,
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5
13, 281. (g) Vega, P.; Floriani, C.; Chiesi-Villa, A.; Rizzoli, C.
Organometallics 1993, 12, 4892.
13) (a) J ones, D.; Roberts, A.; Cavell, K.; Keim, W.; Englert, U.;
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14) McGeachin, S. G. Can J . Chem. 1968, 46, 1903.
(
(
(

1
020 Organometallics, Vol. 18, No. 6, 1999
Doherty et al.
Sch em e 1
Figu r e 1. Molecular structureof[CpTi{CH
3 2
C(O)CHC(NCH -
CH O)CH }Cl] (2a ) illustrating the square pyramidal
2
3
coordination geometry of the metal center. Ellipsoids are
at 50% probability. H-atoms omitted for clarity.
5
formation of [(η -C5H5)Ti{CH3C(O)CHC(NCH2CH2O)-
CH3}Cl] (2a ) in yields of up to 85% (Scheme 1). In a
typical preparation, the reaction solution was filtered
after stirring for 12 h, the remaining solid extracted
exhaustively with thf, and the solvent removed to yield
the product as a spectroscopically pure orange solid,
which can be further purified by crystallization from thf/
Ch a r t 2
1
hexane or toluene/hexane mixtures. The H NMR
spectroscopic data for 2a -d are readily interpreted, and
1
13
a full spectroscopic assignment of the H and C NMR
resonances has been obtained by using a combination
1
1
1
1
13
of H, H- H COSY, and H- C heteronuclear single-
bond correlation studies. In the case of 2a the methine
proton appears as a sharp singlet at δ 5.30, while the
methylene protons associated with the OCH2CH2N
backbone appear as four distinct complex multiplets
between δ 4.83 and 3.91, fully consistent with the
structure shown in Scheme 1. In contrast, there are
1
several noteworthy features in the H NMR spectrum
of 2c, the first of which is the presence of two high-field
3
doublets of equal intensity at δ 1.20 and 1.17 ( J HH )
5
.8 Hz), which belong to the OCHMe-methyl group.
tallization proved unsuccessful and in each case 1
H
Second, six distinct multiplets ranging from δ 5.28 to
.57 have been assigned to the methylene protons of the
3
NMR spectroscopy revealed the presence of a 50:50
mixture of isomers.
five-membered chelate ring. The complexity of this
spectrum is not surprising since the generation of a
chiral-at-metal complex from [(η -C5H4R)TiCl3] (R ) H,
Me) and N-hydroxyalkyl â-ketoimine racemate, derived
from the condensation of (()-1-amino-2-propanol with
2
meric mixture of products. The stereoisomeric relation-
ship between the two possible diastereoisomers and
their corresponding enantiomers (I-IV) is shown in
Chart 2. The H NMR spectrum of the product isolated
from the reaction between [(η -C5H4Me)TiCl3] and the
5
X-r a y Str u ctu r e of [(η -C5H5)Ti{CH3C(O)CHC-
5
(NCH2CH2O)CH3}Cl] (2a ). As no examples of early
transition metal complexes of N-alkoxy-functionalized
â-ketoiminates have previously been reported, a single-
crystal X-ray study was undertaken to confirm the mode
of binding and to provide precise structural details of
the metal’s coordination environment. A perspective
view of the molecular structure together with the atomic
numbering scheme is shown in Figure 1 and a selection
of relevant bond lengths and angles listed in Table 1.
The structure reveals 2a to be monomeric with a
coordination geometry best described as square-based
pyramidal, with the centroid of the C5H5 ring occupying
the apical site and the terdentate ketoiminate and a
single chloride occupying the basal positions. The Ti-
Cl(1) bond length of 2.3741(9) Å is substantially longer
than those in CpTiCl3 [2.201(5)-2.248(5) Å]17 and is
similar to the Ti-Cl bond length of 2.3785(4) Å trans
,4-pentanedione, is expected to afford a diastereoiso-
1
5
â-ketoimine, derived from enantiomerically pure (R)-
(+)-1-amino-2-propanol and 2,4-pentanedione, also con-
tains two sets of equal intensity resonances associated
with the OCHMe-methyl group of the five-membered
chelate, indicating that there is no diastereoselectivity
5
in the reaction between [(η -C5H4R)TiCl3] and (R)-(+)-
CH3C(O)CH2C(NCH2CHMeOH)CH3. Attempts to sepa-
rate diastereoisomers of 2c and 2d by fractional crys-

N-Alkoxy-â-ketoiminate Complexes of Groups 4 and 5
Organometallics, Vol. 18, No. 6, 1999 1021
Ta ble 1. Selected Bon d Dista n ces (Å) a n d An gles
isolated in yields of up to 70% from the reaction between
(
d eg) for Com p ou n d 2a
[TiCl4(thf)2] and the corresponding N-hydroxyalkyl â-ke-
Ti(1)-C(1)
Ti(1)-C(3)
Ti(1)-C(5)
Ti(1)-O(2)
Ti(1)-O(1)
C(9)-C(10)
N(1)-C(8)
2.383(1)
2.35(2)
Ti(1)-C(2)
Ti(1)-C(4)
Ti(1)-Cl(1)
Ti(1)-N(1)
O(2)-C(10)
C(8)-C(9)
2.364(16)
2.390(8)
2.3741(9)
2.161(3)
1.318(4)
1.445(5)
toimine in the presence of excess NEt3. However,
samples of 3a and 3b prepared in this manner are
consistently contaminated with NEt3HCl byproduct,
which cannot be removed even after repeated crystal-
lization. A more convenient route to analytically pure
3a and 3b involves the ligand exchange reaction be-
2.409(7)
1.924(2)
1.844(2)
1.355(5)
1.296(4)
i
tween [Ti(OPr )2Cl2] and the corresponding N-hydroxy-
alkyl â-ketoimine, generating propan-2-ol as the only
O(2)-Ti(1)-Cl(1)
O(1)-Ti(1)-Cl(1)
O(2)-Ti(1)-N(1)
C(8)-N(1)-Ti(1)
C(8)-N(1)-C(7)
85.78(7)
87.89(8)
80.63(10) O(1)-Ti(1)-N(1)
128.0(2)
119.2(3)
N(1)-Ti(1)-Cl(1) 142.03(8)
O(1)-Ti(1)-O(2)
132.14(11)
75.86(10)
112.7(2)
byproduct. Dropwise addition of a thf solution of the
C(7)-N(1)-Ti(1)
C(6)-O(1)-Ti(1)
i
ketoimine into a rapidly stirred solution of [Ti(OPr )2-
128.1(2)
Cl2] results in the immediate formation of an intense
orange-red color followed by precipitation of the desired
N-alkoxy â-ketoiminate complex as a microcrystalline
solid. Spectroscopically pure 3a and 3b are obtained in
near quantitative yield upon filtration, while analyti-
cally pure samples can be obtained by crystallization
from a dichloromethane solution layered with hexane
or from concentrated thf solutions. In the 1H NMR
spectrum of 3a two broad triplets at δ 4.71 and 4.07
C(10)-O(2)-Ti(1) 130.6(2)
i
to the pyridyl group in [CpTi{NC5H4(CPr 2O)-2}Cl2].18
A comparison of the Ti-O bond lengths reveals the
titanium-alkoxide bond [Ti(1)-O(1) ) 1.844(2) Å] to be
considerably shorter than the titanium-ketoiminate
bond [Ti(1)-O(2) ) 1.924(2) Å]. The Ti(1)-O(1) bond
length is comparable to those reported for other Ti(IV)
and Ti(III) alkoxide complexes such as Cp2Ti(OC2H5)-
3
t
( J HH ) 5.6 Hz) for the methylene protons of the
Cl] (1.855(2) Å) [CpTi(OC6H2Bu 2-2,4-Ph-2)Me2] (1.815-
t
OCH2CH2N backbone, a sharp singlet at δ 5.47 for the
methine proton of the six-membered chelate ring, two
sharp singlets of intensity 3H (δ 2.04 and 1.96) for the
methyl groups, and two multiplets at δ 3.80 and 1.83
belonging to the coordinated thf are consistent with a
C2 symmetric complex containing a trans arrangement
of chloro ligands (V, R ) H) or a rapidly interconverting
mixture of enantiomers with C1 symmetry and cis
(
2) Å), and [CpTi(OC6HNp2-2,6-Bu 2-3,5)Cl]2 (1.817(2)
1
9
Å). The bond length pattern within the six-membered
ring system suggests significant localization of bonding
electron density. For instance, the N(1)-C(8) bond
length of 1.296(2) Å is close to that expected for a C-N
double bond (∼1.30 Å), and the planar nature of N(1)
[sum of angles at N(1) 359.9°] and the Ti(1)-N(1) length
of 2.161(3) Å suggest that N-Ti pπ-dπ bonding is not
significant and that Ti(1)-N(1) is a σ-dative bond in-
volving a nitrogen atom with imine character. Addition-
al noteworthy structural features include significantly
different carbon-carbon bond lengths of 1.445(5) and
1
chlorides (VI, R ) H). The H NMR spectrum of 3b
2
contains two doublets of doublets at δ 4.18 ( J HH ) 13.1
3
2
3
Hz; J HH ) 5.1 Hz) and 3.78 ( J HH ) 13.1 Hz; J HH )
8
.2 Hz) for the two methylene protons attached to the
carbon atom adjacent to the imine nitrogen, a complex
second-order multiplet at δ 5.23 associated with the
methine proton on the carbon atom adjacent to the
oxygen, CHMe, and two complex multiplets at δ 3.97
and 1.87 for the coordinated THF. The presence of only
a single set of ligand resonances indicates that 3b exists
either as a mixture of enantiomers with a trans ar-
rangement of chlorides (V, R ) Me) or as two rapidly
interconverting diastereoisomers with cis chloro ligands
1
.355(5) Å for C(8)-C(9) and C(9)-C(10), respectively
(∆ ) 0.09 Å), both of which are shorter than a normal
C-C single bond (∼1.54 Å), and a C(10)-O(2) bond
length of 1.318(4) Å, which is somewhat longer than
expected for a C-O double bond (ca. ∼1.19 Å). This bond
length pattern is consistent with the terdentate ligand
binding to Ti(1) as an enolate, with N(1) coordinated
2
through the sp lone pair of the imine and through O(2)
as a conventional alkoxide with O(pπ)-Ti(dπ) donation.
Syn th esis a n d Ch a r a cter iza tion of [Ti{CH3C(O)-
CHC(NCH2CHR′O)CH3}Cl2(th f)] (3a ,b). Upon stand-
ing, thf/hexane solutions of the reaction mixture con-
taining [(η -C5H4R)TiCl3] and CH3C(O)CH2C(NCH2-
CHR′OH)CH3 (R ) Me, racemic mixture) deposit deep
(VI, R ) Me).
5
1
orange-red crystals of [Ti{CH3C(O)CHC(NCH2CHR′O)-
CH3}Cl2(thf)] (R′ ) H, 3a ; R′ ) Me, 3b), identified in
1
13
the first instance by H and C NMR spectroscopy and
later structurally characterized by single-crystal X-ray
crystallography (vide infra). At this stage we tentatively
suggest that 3a ,b arise from inter- or intramolecular
protonolysis of the Ti-Cp bond of an intermediate
containing a bidentate or terdentate N-alkoxy â-ketomi-
nate (Scheme 1). Alternatively, compounds 3a ,b can be
X-r a y St r u ct u r es of [Ti{CH 3C(O)CH C(NCH 2-
CH 2O)CH 3}Cl2(t h f)] (3a ) a n d [Ti{CH 3C(O)CH C-
NCH2CHMeO)CH3}Cl2(th f)] (3b). In view of the
(
(
17) Englehardt, L. M.; Papasergio, R. I.; Raston, C. L.; White, A.
H. Organometallics 1983, 3, 18.
18) Doherty, S.; Errington, R. J .; J arvis, A.; Collins, S.; Clegg, W.;
Elsegood, M. R. J . Organometallics 1998, 17, 3408.
19) (a) Huffman, J . C.; Moloy, K. G.; Marsella, J . A.; Calulton, K.
1
ambiguous H NMR data for 3a and 3b, single-crystal
X-ray analyses of both compounds were undertaken to
unequivocally establish the stereochemistry at the metal
center and the precise nature of the metal-ligand
bonding. Perspective views of the molecular structures
of 3a and 3b together with their numbering schemes
(
(
G. J . Am. Chem. Soc. 1980, 102, 3009. (b) Thorn, M. G.; Vilardo, J . S.;
Fanwick, P. E.; Rothwell, I. P. Chem. Commun. 1998, 2427. (c) Thorn,
M. G.; Vilardo, J . S.; Fanwick, P. E.; Rothwell, I. P. Chem. Commun.
1
998, 2425.

1
022 Organometallics, Vol. 18, No. 6, 1999
Doherty et al.
Ta ble 2. Selected Bon d Dista n ces (Å) a n d An gles
(
d eg) for Com p ou n d s 3a a n d 3b
compound 3a compound 3b
Ti(1)-Cl(1) 2.3161(6)
Ti(1)-Cl(1)
2.3251(8)
1.9010(17)
2.139(2)
1.8066(18)
2.1376(19)
2.3256(8)
1.312(3)
1.357(4)
1.435(4)
1.303(3)
Ti(1)-O(1)
Ti(1)-N(1)
Ti(1)-O(2)
Ti(1)-O(3)
Ti(1)-Cl(2)
O(1)-C(1)
C(1)-C(2)
C(2)-C(3)
C(3)-N(1)
1.9060(14) Ti(1)-O(1)
2.1421(17) Ti(1)-N(1)
1.8150(15) Ti(1)-O(2)
2.1585(14) Ti(1)-O(3)
2.3276(6)
1.313(2)
1.358(3)
1.429(3)
1.310(3)
Ti(1)-Cl(2)
O(1)-C(1)
C(1)-C(2)
C(2)-C(3)
C(3)-N(1)
O(1)-Ti(1)-Cl(1) 100.50(5)
N(1)-Ti(1)-Cl(1) 171.95(5)
O(2)-Ti(1)-Cl(1) 97.78(5)
O(3)-Ti(1)-Cl(1) 87.04(4)
Cl(1)-Ti(1)-Cl(2) 95.79(2)
O(1)-Ti(1)-Cl(1) 103.89(6)
Cl(1)-Ti(1)-N(1) 170.26(6)
Cl(1)-Ti(1)-O(2) 94.98(6)
Cl(1)-Ti(1)-O(3) 86.07(6)
Cl(1)-Ti(1)-Cl(2) 95.79(2)
O(1)-Ti(1)-N(1)
O(2)-Ti(1)-O(1)
82.41(6)
O(1)-Ti(1)-N(1)
O(2)-Ti(1)-O(1)
82.65(8)
158.08(7)
O(1)-Ti(1)-Cl(2) 91.86(5)
159.15(8)
O(1)-Ti(1)-Cl(2) 90.05(6)
F igu r e 2. Molecular structure of [Ti{CH
3 2
C(O)CHC(NCH -
O(1)-Ti(1)-O(3)
N(1)-Ti(1)-O(3)
O(2)-Ti(1)-N(1)
82.93(6)
85.87(6)
77.93(7)
O(1)-Ti(1)-O(3)
N(1)-Ti(1)-O(3)
O(2)-Ti(1)-N(1)
82.48(8)
87.68(8)
77.56(8)
CH O)CH }Cl (thf)] (3a ). Ellipsoids are at 50% probability.
2
3
2
H-atoms omitted for clarity.
N(1)-Ti(1)-Cl(2) 91.59(5)
O(2)-Ti(1)-O(3) 86.06(6)
N(1)-Ti(1)-Cl(2) 92.38(6)
O(2)-Ti(1)-O(3) 90.16(8)
O(2)-Ti(1)-Cl(2) 98.24(5)
O(3)-Ti(1)-Cl(2) 174.46(4)
C(1)-O(1)-Ti(1)
C(5)-O(2)-Ti(1)
C(3)-N(1)-Ti(1)
C(4)-N(1)-Ti(1)
C(3)-N(1)-C(4)
O(2)-Ti(1)-Cl(2) 97.21(7)
O(3)-Ti(1)-Cl(2) 172.47(6)
138.40(14) C(1)-O(1)-Ti(1) 136.95(17)
123.13(13) C(5)-O(2)-Ti(1)
125.10(18)
129.09(18)
112.21(16)
118.6(2)
129.04(14) C(3)-N(1)-Ti(1)
112.07(13) C(4)-N(1)-Ti(1)
118.51(18) C(3)-N(1)-C(4)
imposed on 3a or 3b and no significant steric interac-
tions within the metal’s coordination sphere. Floriani
has noted that dichloride derivatives of the type TiL2-
Cl2, where L is a bidentate Schiff base, can adopt either
a cis or trans arrangement of chloride ligands.20 In 3a ,
the N(1)‚‚‚O(1) six-membered chelate ring is nearly
planar, Ti(1) being displaced by 0.241 Å from the plane
containing the remaining five atoms toward Cl(2). The
ethylene bridge adopts the usual gauche conformation
with a O(2)-C(5)-C(4)-N(1) torsion angle of 37.0°. The
ketoiminate nitrogen atom N(1) is close to planar (sum
of the angles ) 360(2)°), and the N(1)-C(3) bond
distance of 1.310(3) Å is comparable to the C-N bond
distance of 1.321(5) Å in the ketoiminate complex [Zr-
3 2
F igu r e 3. Molecular structure of [Ti{CH C(O)CHC(NCH -
CHMeO)CH }Cl (thf)] (3b). Ellipsoids are at 50% prob-
3 2
ability. H-atoms omitted for clarity.
are shown in Figures 2 and 3, respectively, and selected
bond lengths and angles for both molecules are given
in Table 2. For clarity, as the structures of 3a and 3b
are essentially identical, the following discussion is
based on the structure of 3a , with the corresponding
parameters for 3b listed in Table 2. The structures show
a cis arrangement of chloride ligands in 3a and 3b,
which is clearly inconsistent with the 1H NMR data
reported in the previous section, unless a dynamic
exchange process is occurring in solution. Complex 3a
is monomeric, based on a distorted octahedral geometry
with the ketoiminate ligand occupying a meridianal
coordination environment, two mutually cis chloro
ligands, and a molecule of thf. While the Ti(1)-Cl(2)
bond trans to O(3) [2.3276(6) Å (Å)] is markedly longer
than that trans to N(1) [2.3161(6) Å], both are substan-
tially shorter than the Ti-Cl bond length in 2a [2.3741-
12a
{CH3C(NPh)CH(O)CH3}2Cl2]. The bonding within the
terdentate ligand is highly localized, as evidenced by
the difference in the C(1)-C(2) and C(2)-C(3) bond
lengths of 0.071 Å, which is substantially larger than
the comparable differences in the bis(iminate) and
â-diketonate complexes [Zr{CH3C(NPh)CH(NPh)CH3}2-
12a
i
Cl2] (0.005 Å) and [Ti{CH3C(O)CH(O)CH3}(OPr 2)3]2
(
21
0.003 Å), respectively. In addition, the titanium
ketoiminate bond length Ti(1)-O(1) of 1.9060(14) Å is
considerably longer than its alkoxide counterpart of
1
.8150(15) Å for Ti(1)-O(2). Similar bond length pat-
terns in â-diketonate derivatives of titanium alkoxide
complexes have been noted, although the absolute
differences in 3a and 3b are not as marked as those in
i
[
Ti{CH3C(O)CH(O)CH3}(OPr 2)3]2 (2.073(4) Å versus
(
9) Å] and are close to previously reported values of Ti-
(20) (a) Corazza, F.; Solari, E.; Floriani, C.; Chiesi-Villa, A.; Guastini,
C. J . Chem. Soc., Dalton Trans. 1990, 1335. (b) Mazzanti, M.; Rosset,
J . M.; Floriani, C.; Chiesi-Villa, A.; Guastini, C. J . Chem. Soc., Dalton
Trans. 1989, 953. (c) Cozzi, P. G.; Floriani, C. Chiese-Villa, A.; Rizzoli,
C. Inorg. Chem. 1995, 34, 2921. (d) Cozzi, P. G.; Gallo, E.; Floriani,
C.; Chiese-Villa, A.; Rizzoli, C. Organometallics 1995, 14, 4994.
Cl bond lengths in noncyclopentadienyl complexes such
as cis-[TiL2Cl2], where L is a (hydroxyphenyl)oxazoline
2
0a,c
ligand.
The preference for a cis arrangement of
chloride ligands is likely to be electronic in origin,
especially since there are no geometrical constraints
(21) Errington, R. J . E.; Ridland, J .; Clegg, W.; Coxall, R. A.;
Sherwood, J . M. Polyhedron 1998, 17, 659.

N-Alkoxy-â-ketoiminate Complexes of Groups 4 and 5
Organometallics, Vol. 18, No. 6, 1999 1023
1
F igu r e 5. Variable-temperature H NMR spectra of [Ti-
1
F igu r e 4. Variable-temperature H NMR spectra of [Ti-
{
CH
3
C(O)CHC(NCH
Cl
2
3 2
CHMeO)CH }Cl (thf)] (3b) recorded
{
CH
3 2 2 3 2
C(O)CHC(NCH CH O)CH }Cl (thf)] (3a ) recorded in
in CD
2
2
.
CD Cl .
2
2
Sch em e 2
1
.782(4) Å), presumably because localized bonding in the
six-membered chelate of 3a ,b enables O(1) to compete
for O(pπ) to Ti(dπ) bonding more effectively than in
delocalized chelate rings in â-diketonate complexes.
Va r ia ble-Tem p er a tu r e NMR Stu d ies. As noted
1
above, the room-temperature H NMR spectrum of 3a
contains two broad triplets for the OCH2CH2N meth-
ylene protons, while that of 3b contains a single complex
AB multiplet for the diastereotopic protons of NCHaHb,
spectroscopic characteristics that are inconsistent with
their solid-state structures. To resolve this ambiguity,
variable-temperature 1H NMR spectra of 3a and 3b
were obtained, the results of which are shown in Figures
to uncoordinated thf in slow exchange with coordinated
thf. While the low-temperature limiting spectrum of 3a
is consistent with the solid state structure, the temper-
ature dependence of these resonances clearly shows that
enantiomers VIa and VIb rapidly interconvert on the
NMR time scale, most likely via dissociation of thf to
generate the trigonal bipyramidal intermediate [Ti-
{CH3C(O)CHC(NCH2CH2O)CH3}Cl2] (Scheme 2). These
spectroscopic characteristics and the free energy of
4
and 5, respectively. Qualitatively both compounds
exhibit similar line-broadening characteristics. For 3a ,
a cis-arrangement of chlorides should render the me-
thylene protons diastereotopic, yet at room temperature
these protons appear as two broad triplets at δ 4.71 and
q
-1
activation (∆G ) 46.0 kJ mol ), determined from an
analysis of the coalescence behavior in the temperature
range 228-238 K, are consistent with the generation
of time-averaged Cs symmetry by the dynamic process
shown in Scheme 2. To demonstrate that 3a exists in
dissociative equilibrium with thf, a sample of 3a in
CDCl3 was treated with 1 equiv of thf and as expected
4
.07, which suggests a structure with Cs symmetry. As
the temperature was lowered (Figure 4), these two
resonances start to broaden and at 193 K appear as a
complex AB multiplet at δ 4.19 and 3.91, corresponding
to diastereotopic NCHaHb protons, and a triplet at δ
4
.65 for the protons attached to the carbon atom
1
adjacent to the alkoxide oxygen, OCHaHb. Within the
same temperature range the resonances associated with
the coordinated thf broaden and eventually give rise to
two sets of complex multiplets, one at δ 3.89 and 1.87,
the other, a minor set of exchange-broadened signals
at δ 3.63 and 1.76, those at higher field corresponding
a shift of the H NMR resonances was observed (∆δ )
0.16 ppm).
The room-temperature 1H NMR spectrum of 3b
contains a single set of sharp well-resolved resonances,
which, as the temperature is lowered, begin to broaden
and decoalesce, eventually giving rise to two indepen-

1
024 Organometallics, Vol. 18, No. 6, 1999
Doherty et al.
dent sets of signals (Figure 5). The most distinctive
features of the low-temperature limiting spectrum (203
K) of 3b include two singlets at δ 5.63 and 5.60,
associated with the ketoiminate methine proton, four
doublets of doublets at δ 4.18, 4.01, 3.85, 3.49 (J HH )
Ch a r t 3
1
4.0, 4.60, 9.15, 13.7 Hz) for the diastereotopic meth-
ylene protons on the carbon atom adjacent to the imine
3
nitrogen, and two doublets at δ 1.16 and 1.12 ( J HH )
6
.1 Hz) for the methyl group attached to the alkoxide
carbon atom, CHMe. The signals associated with the
ketoiminate methyl groups appear as three separate
resonances in a 1:1:2 ratio, presumably as a result of
accidental equivalence of two separate signals of equal
intensity, while the methine proton, OCHMe, appears
as two complex overlapping multiplets at δ 5.20. These
two sets of resonances correspond to the two possible
diastereoisomers of 3b, VII-VIII and IX-X (Chart 3),
their near equal abundance indicating that both are of
q
similar energy. The free energy of activation, ∆G ) 44.1
-
1
kJ mol , calculated from the coalescence behavior of
the diastereotopic methylene signals at 233 K, is similar
to that found for 3a , which suggests that the same
dynamic process is responsible for the line broadening
associated with both compounds. In the case of 3a the
dynamic process shown in Scheme 2 interconverts
enantiomers VIa and VIb, while the same process for
This is perhaps not surprising since 4b was prepared
from the exchange reaction between [Ti(OPr )4] and a
i
racemic mixture of N-hydroxyalkyl â-ketoimine. We
would expect several diastereoisomers on the basis of
an octahedral coordination geometry comprised of two
meridianally coordinated N-alkoxy ketoiminate ligands.
Since these ligands are geometrically constrained to
coordinate in a meridianal manner, the total number
of possible diastereoisomers is restricted to three, two
of which have C2 symmetry, the RR/SS, XI/XII, and SS/
RR, XIII/XIV diastereoisomeric pairs, while the third,
3
b interconverts VII and VIII with their diastereoiso-
meric counterparts IX and X (Chart 3).
Syn th esis a n d Ch a r a cter iza tion of [Ti{CH3C(O)-
CHC(NCH2CHR′O)CH3}2] (4a ,b). While 3a ,b can
most conveniently be prepared from the reaction be-
i
tween stoichiometric quantities of [Ti(OPr )2Cl2] and the
N-hydroxyalkyl â-ketoimine, the corresponding reaction
i
1
with [Ti(OPr )4] results in complete alcoholysis to give
RS/SR, XV/XVI, has C1 symmetry. A complete H NMR
[
)
Ti{CH3C(O)CHC(NCH2CHR′O)CH3}2] (R′ ) H, 4a ; R′
spectroscopic assignment of 4b has been achieved using
1
1
1
13
1
Me, 4b) (eq 2), as evidenced by the absence of signals
a combination of H, H- H COSY, and C- H het-
1
eronuclear single-bond correlation studies and a H-
H TOSCY experiment (Figure 6), the latter clearly
1
showing two- and three-bond correlations that were not
1
1
evident in the H- H COSY spectrum. The three
possible diastereoisomers and their corresponding enan-
tiomers are shown in Chart 4.
Considering each enantiomeric pair in turn, C2-
symmetrical XI and XII are expected to give rise to a
single set of resonances comprising an AB multiplet for
the diastereotopic NCHaHb protons, a complex multip-
let for the CHMe methine proton, two singlets of
intensity three and one of intensity one for the methyl
groups and methine protons, respectively, of the six-
membered chelate ring, and a doublet for the methyl
in the 1H NMR spectrum associated with isopropyl
groups. In the H NMR spectrum of 4a , an “apparent”
1
1
group, OCHMe. While an analogous H NMR spectrum
triplet at δ 4.4 for the OCH2 protons, a complex AB
multiplet at δ 4.0 and 3.9 for the diastereotopic NCHaHb
protons, and two singlets for the methyl groups (δ 1.90
and 2.05) are consistent with a C2-symmetric complex
containing two meridianally coordinated N-alkoxo â-ke-
toiminate ligands.
is expected for the other enantiomeric pair with C2
symmetry, XIII/XIV, the remaining diastereoisomeic
pair with C1 symmetry, XV/XVI, gives rise to two sets
of signals. As both RS/SR and SR/RS pairs are equiva-
lent, the C1 pair is twice as abundant as the RR/SS and
SS/RR pairs. Thus, we suggest that two of the four sets
1
1
The H NMR spectrum of 4b is considerably more
of resonances in the H NMR spectrum of 4b correspond
complex and clearly shows the presence of several
species in solution, as evidenced by four equal intensity
methine C-H resonances in the region δ 5.21-5.12, four
sets of complex AB multiplets between 4.12 and 3.54,
eight methyl resonances associated with the six-
membered chelate ring (δ 1.98-1.81), and four doublets
belonging to the OCHMe methyl groups (δ 1.13-1.11).
to diastereoisomers XI-XII and XIII-XIV, while the
remaining two belong to XV-XVI, with a ratio consis-
tent with the expected statistical distribution of 1:1:2
respectively, that is, there is no apparent diastereose-
lectivity in the reaction.
X-r ay Str u ctu r e of [Ti{CH3C(O)CHC(NCH2CH2O)-
CH3}2] (4a ‚CH 2Cl2). The solid-state structure of 4a ‚

N-Alkoxy-â-ketoiminate Complexes of Groups 4 and 5
Organometallics, Vol. 18, No. 6, 1999 1025
F igu r e 7. Molecular structure of [Ti{CH
3 2
C(O)CHC(NCH -
CH O)CH ] (4a ‚CH Cl ) illustrating the octahedral ge-
2
3
}
2
2
2
ometry of the metal center. Ellipsoids are at 50% probabil-
ity. H-atoms and solvent molecules omitted for clarity.
1
1
Ta ble 3. Selected Bon d Dista n ces (Å) a n d An gles
Figure 6. H- H TOSCYspectrum of[Ti{CH
CHMeO)CH ] (4b).
3 2
C(O)CHC(NCH -
(
2 2
d eg) for Com p ou n d 4a ‚CH Cl
3 2
}
Ti(1)-O(1)
Ti(1)-O(3)
Ti(1)-N(1)
O(1)-C(1)
C(2)-C(3)
O(3)-C(8)
C(9)-C(10)
1.956(2)
1.940(2)
2.175(2)
1.301(3)
1.416(4)
1.299(3)
1.424(4)
Ti(1)-O(2)
Ti(1)-O(4)
Ti(1)-N(2)
C(1)-C(2)
C(3)-N(1)
C(8)-C(9)
C(10)-N(2)
1.857(2)
1.858(2)
2.160(2)
1.361(4)
1.309(4)
1.358(4)
1.303(4)
Ch a r t 4
O(1)-Ti(1)-N(2)
O(1)-Ti(1)-N(1)
O(4)-Ti(1)-O(1)
N(2)-Ti(1)-N(1)
O(3)-Ti(1)-N(2)
O(2)-Ti(1)-O(3)
O(4)-Ti(1)-O(3)
N(1)-Ti(1)-O(4)
C(8)-O(3)-Ti(1)
C(3)-N(1)-Ti(1)
101.65(9)
82.04(9)
94.13(9)
168.55(9)
81.59(9)
90.34(9)
158.53(9)
91.69(9)
O(2)-Ti(1)-O(1)
O(3)-Ti(1)-O(1)
O(2)-Ti(1)-N(2)
O(4)-Ti(1)-N(2)
O(2)-Ti(1)-N(1)
O(2)-Ti(1)-O(4)
O(3)-Ti(1)-N(1)
C(7)-O(2)-Ti(1)
156.86(9)
86.32(9)
100.49(9)
77.30(9)
77.54(9)
97.22(9)
109.59(9)
118.87(16)
136.24(19) C(14)-O(4)-Ti(1) 125.2(2)
129.3(2)
C(10)-N(2)-Ti(1) 129.24(19)
C(10)-N(2)-C(13) 119.4(2)
C(13)-N(2)-Ti(1) 111.41(7)
N(1) and O(2)‚‚‚N(2) are nearly planar, the titanium
atom being displaced by 0.276 and 0.363 Å, respectively,
from the plane containing the remaining five atoms. The
ethylene bridges C(6)-C(7) and C(13)-C(14) adopt the
usual gauche conformation, with torsion angles of 40.7°
and 34.1° for N(1)-C(6)-C(7)-O(2) and N(2)-C(13)-
C(14)-O(4), respectively. As for 2a , 3a , and 3b, the
bonding in the six-membered chelate rings is localized
and can most aptly be described as a N-hydroxyalkyl
imine-enolate. The two six-membered rings are close to
perpendicular with a dihedral angle of 82.6°.
5
Syn th esis a n d Ch a r a cter iza tion of [(η -C5H4R)-
Nb{CH3C(O)CHC(NCH2CHR′O)CH3}Cl2] (5a-d). Fol-
lowing a procedure similar to that used to prepare 2a -
5
CH2Cl2 has been confirmed by single-crystal X-ray
crystallography. The molecular structure together with
the atomic numbering scheme is shown in Figure 7, and
a selection of bond lengths and angles is given in Table
d , the reaction between [(η -C5H4R)NbCl4] and 1a gave
5
high yields of [(η -C5H4R)Nb{CH3C(O)CHC(NCH2CH2O)-
CH3}Cl2] (5a ) as an orange crystalline material. In the
1
H NMR spectrum the methine proton of the six-
3
. The structure is based on a distorted octahedron in
membered chelate ring appears as a singlet at δ 5.31,
while that associated with the Cp ring is high-field
shifted (δ 6.70). Surprisingly, in contrast to the complex
multiplets associated with the methylene protons of the
terdentate ligand in 2a , those in 5a appear as two
which the O-Ti(1)-N angles involving the N-alkoxy
â-ketoiminate ligand are distorted significantly from 90°
(
(
7
O(1)-Ti(1)-N(1) ) 82.04(9); O(2)-Ti(1)-N(1) ) 77.54-
9); O(3)-Ti(1)-N(2) ) 81.59(9); O(4)-Ti(1)-N(2) )
3
7.30(9)°). The two six-membered chelate rings O(1)‚‚‚
triplets at δ 4.61 and 4.08 ( J HH ) 5.5 Hz). If the

1
026 Organometallics, Vol. 18, No. 6, 1999
Doherty et al.
Ta ble 4. Selected Bon d Dista n ces (Å) a n d An gles
(
d eg) for Com p ou n d 5a
molecule a molecule b
Nb(1)-C(1) 2.429(12) Nb(2)-C(13)
2.446(14)
2.433(10)
2.458(10)
2.45(2)
Nb(1)-C(2)
Nb(1)-C(3)
Nb(1)-C(4)
Nb(1)-C(5)
Nb(1)-Cl(1)
Nb(1)-Cl(2)
Nb(1)-O(1)
Nb(1)-O(2)
Nb(1)-N(1)
O(1)-C(6)
C(6)-C(7)
C(7)-N(1)
N(1)-C(8)
C(1)-C(2)
C(2)-C(3)
C(3)-C(4)
C(4)-C(5)
C(1)-C(5)
2.479(10) Nb(2)-C(14)
2.479(11) Nb(2)-C(15)
2.457(15) Nb(2)-C(16)
2.394(15) Nb(2)-C(17)
2.4999(6) Nb(2)-Cl(3)
2.4689(6) Nb(2)-Cl(4)
1.9142(15) Nb(2)-O(3)
1.9884(14) Nb(2)-O(4)
2.2395(18) Nb(2)-N(2)
2.43(2)
2.4974(6)
2.4825(6)
1.9164(15)
1.9918(15)
2.2351(18)
1.416(3)
1.512(3)
1.432(3)
1.303(3)
1.382(9)
1.411(3)
1.492(3)
1.479(3)
1.303(3)
O(3)-C(18)
C(18)-C(19)
C(20)-C(21)
N(2)-C(20)
1.380(11) C(13)-C(14)
1.385(11) C(14)-C(15)
1.385(11) C(15)-C(16)
1.396(11) C(16)-C(17)
1.392(11) C(13)-C(17)
1.405(11)
1.380(11)
1.388(11)
1.417(10)
Figu r e 8. Molecular structureof[CpNb{CH
3 2
C(O)CHC(NCH -
CH O)CH }Cl ] (5a ) illustrating the trans arrangement of
2
3
2
O(2)-Nb(1)-Cl(1) 85.97(5)
O(4)-Nb(2)-Cl(3) 85.02(5)
chloride ligands and the octahedral coordination geometry
of the metal center. Ellipsoids are at 50% probability.
H-atoms omitted for clarity.
O(1)-Nb(1)-O(2) 156.07(6) O(3)-Nb(2)-O(4) 155.64(7)
O(2)-Nb(1)-Cl(2) 85.81(5)
O(2)-Nb(1)-N(1) 80.39(6)
Cl(2)-Nb(1)-Cl(1) 153.96(2) Cl(3)-Nb(2)-Cl(4) 154.84(2)
O(4)-Nb(2)-Cl(4) 87.16(5)
O(4)-Nb(2)-N(2) 80.01(7)
ketoimine is assumed to bind in a terdentate manner,
N(1)-Nb(1)-Cl(1) 77.51(5)
O(1)-Nb(1)-N(1) 75.83(7)
Cl(2)-Nb(1)-N(1) 76.77(5)
O(1)-Nb(1)-Cl(1) 86.39(5)
O(1)-Nb(1)-Cl(2) 91.25(5)
Cl(3)-Nb(2)-N(2) 77.66(5)
O(3)-Nb(2)-N(2) 75.81(7)
Cl(4)-Nb(2)-N(2) 77.45(5)
O(3)-Nb(2)-Cl(3) 86.89(5)
O(3)-Nb(2)-Cl(4) 90.52(5)
we would expect two possible isomers, XVII and XVIII,
1
which should be readily distinguishable by H NMR
spectroscopy, since the former contains trans chlorides
and the latter a cis arrangement of chloride ligands. We
Nb(1)-O(2)-C(10) 138.45(14) C(22)-O(4)-Nb(2) 137.46(15)
1
Nb(1)-O(1)-C(6)
123.27(13) C(18)-O(3)-Nb(2) 123.72(14)
are confident that the H NMR spectrum of 5a corre-
Nb(1)-N(1)-C(7) 110.83(14) C(20)-N(2)-Nb(2) 129.65(15)
Nb(1)-N(1)-C(8) 129.67(15) C(19)-N(2)-Nb(2) 110.70(14)
sponds to XVII, since XVIII has C1 symmetry, for which
resonances corresponding to four nonequivalent meth-
ylene protons would be expected, the presence of only
two triplet resonances being consistent with the Cs
symmetry of XVII.
C(8)-N(1)-C(7)
119.29(19) C(20)-N(2)-C(19) 119.64(19)
are slightly longer (∼1.33 Å), presumably due to delo-
calization within the π-system of these ligands. The sum
of the angles at N(1) (359.8°) is consistent with sp2
hybridization, which, together with the short N(1)-C(8)
bond, is suggestive of imine coordination. The Nb(1)-
Cl(1) and Nb(1)-Cl(2) bond lengths, 2.4999(6) and
2
.4689(6) Å, respectively, are similar to that in the 18-
5
t
23
electron complex [(η -C5H5)2NbCl(NBu )PMe3]. As 5a
is a 16-electron compound, the unexpectedly long Nb-
Cl bond length is most likely the result of competitive
ligand(pπ)-M(dπ) bonding between the Cp-Nb, alkox-
ide-Nb, and chloride-Nb bonds. As is common in
2
4
cyclopentadienyl compounds of niobium, the Cp ring
5
The structure of 5a has been confirmed by a single-
crystal X-ray study, the result of which is shown in
Figure 8, with selected bond lengths and angles listed
in Table 4. The molecular structure reveals 5a to be
monomeric and based on a distorted octahedral geom-
etry. The cyclopentadienyl ligand occupies one site,
while the terdentate ligand adopts a meridianal ar-
rangement with the nitrogen atom trans to the Cp
ligand and chlorides occupying the two remaining trans
sites. There are two essentially identical molecules in
the unit cell, both with 2-fold disorder in the Cp rings.
There are a number of noteworthy similarities between
the structures of 2a and 5a . In the first instance, the
bond length pattern within the six-membered ketoimi-
nate chelate ring is similar to that in 2a , the short N(1)-
C(8) and C(6)-C(7) bond lengths of 1.303(3) and 1.355(3)
Å, respectively, indicating a significant contribution
from the enolate tautomer. By comparison, reported
C-N bond lengths in bisiminate complexes of group 4
is distorted away from a symmetrical η -geometry with
bond lengths that range from 2.394(15) to 2.479(11) Å.
Although approximated to octahedral coordination, Nb-
(1) lies 0.476 Å out of the mean plane defined by C1(1),
O(1), Cl(2), and O(2) toward the Cp ring.
Con clu sion
0
A range of d chiral-at-metal complexes of groups 4
and 5 containing N-alkoxy â-ketoiminates have been
prepared in high yield and characterized by X-ray
crystallography and a range of NMR techniques. In each
case the â-ketoiminate appears to coordinate as a
â-imino enolate, rather than as its â-ketoamide tau-
(
22) Williams, D. N.; Mitchell, J . P.; Poole, A. D.; Siemeling, U.;
Clegg, W.; Hockless, D. C. R.; O’Neil, P. A.; Gibson, V. C. J . Chem.
Soc., Dalton Trans. 1992, 739.
(
23) Green, M. L. H.; J ames, J . T.; Sanders, J . F. Chem. Commun.
1
996, 1343.
(24) Gibson, V. C. J . Chem. Soc., Dalton Trans. 1994, 1607.

N-Alkoxy-â-ketoiminate Complexes of Groups 4 and 5
Organometallics, Vol. 18, No. 6, 1999 1027
tomer (Chart 1), possibly reflecting the differing π-donor
ability of OR compared with NR2.24 The terdentate
ligand in these compounds might therefore be described
as an asymmetric imine-bisalkoxide. As enantiomeric
derivatives of these and related terdentate ligands with
variable charge and number/type of donor atoms are
readily synthesized, complexes of this type offer inter-
esting possibilities for use in stoichiometric and catalytic
organic transformations. In this regard, we are cur-
rently investigating the coordination chemistry and the
synthesis of alkyl, alkoxide, and amide derivatives of
these compounds, including their cationic derivatives.
61.8 (s, NCH
2 3 3 5 4
), 23.9 (s, CH ), 22.8 (s, CH ), 15.7 (s, C H Me).
Anal. Calcd for C H ClO NTi: C, 51.55: H, 5.95; N, 4.65.
13 18
2
Found: C, 51.02; H, 5.65; N, 4.47.
5
[
(η -C
5
H
5
)Ti{CH
3
C(O)CHC(NCH
2
CHMeO)CH
3
}Cl] (2c).
2
c was obtained as orange crystals in 72% yield from thf/
1
hexane at room temperature. H NMR (500.1 MHz, CDCl
δ): 6.35 (s, 5H, C ), 6.33 (s, 5H, C ), 5.30 (s, 1H, C-H
methine), 5.25 (s, 1H, C-H methine), 5.28 (m, J HH ) 5.2, J HH
3
,
5
H
5
5 5
H
3
3
3
3
3
)
)
5.8, J HH ) 6.4 Hz, 1H, CHCH ), 4.89 (ddq, J HH ) 6.4, J HH
2
3
3
6.4 Hz, J HH ) 4.5 Hz, 1H, CHMe), 4.30 (dd, J HH ) 13.4
3
2
Hz, J
HH
) 6.4 Hz, 1H, NCHaHb), 3.90 (ABd, J
HH
) 12.5 Hz,
3
2
3
J
HH ) 5.2 Hz, 1H, NCHcHd), 3.86 (ABd, J HH ) 12.5 Hz, J HH
) 11.0 Hz, 1H, NCHcHd), 3.57 (dd, J HH ) 13.4 Hz, J HH
2
3
)
4
1
3
.5 Hz, 1H, NCHaHb), 1.99 (s, 3H, CH
.97 (s, 3H, CH ), 1.95 (s, 3H, CH ), 1.20 (d, J HH ) 6.4 Hz,
H, OCHMe), 1.17 (d, J HH ) 5.8 Hz, OCHMe). C{ H} NMR
, δ): 177.7 (s, OCCH ), 177.4 (s, OCCH ),
), 167.4 (s, NCCH ), 117.8 (s, C ), 117.7 (s,
), 104.5 (s, C-H methine), 104.1 (s, C-H methine), 85.4
s, OCH ), 83.0 (s, OCH ), 68.9 (s, NCH ), 67.4 (s, NCH ), 25.6
s, CH ), 23.8 (s, CH ), 22.9 (s, CH ), 22.8 (s, CH ), 22.7 (s,
), 21.4 (s, CH ). Anal. Calcd for C13 NTi: C, 51.55:
3 3
), 1.98 (s, 3H, CH ),
3
3
3
Exp er im en ta l Section
3
13
1
(125.7 MHz, CDCl
3
3
3
Gen er a l P r oced u r es. Unless otherwise stated all manipu-
lations were carried out in an inert atmosphere glovebox or
by using standard Schlenk line techniques. Diethyl ether and
hexane were distilled from Na/K alloy, toluene from Na,
tetrahydrofuran from potassium, and dichloromethane from
CaH . CDCl was predried over freshly ground calcium hydride
2 3
and vacuum transferred and stored over 4 Å molecular sieves.
NMR samples were prepared in the drybox in 5 mm Wilmad
1
68.2 (s, NCCH
3
3
5 5
H
5 5
C H
(
(
2
2
2
2
3
3
3
3
CH
3
3
H18ClO
2
H, 5.95; N, 4.65. Found: C, 51.43; H, 5.87, N, 4.44.
5
[
(η -C
5
H
4
Me)Ti{CH
3
C(O)CH C(NCH
2
CH MeO)CH
3
}Cl]
(
2d ). 2d was obtained as orange crystals in 78% yield from
tubes equipped with a Young’s Teflon valve. TiCl
4
was
1
3
thf/hexane at room temperature. H NMR (500.1 MHz, CDCl ,
δ): 6.3-7.30 (m, 10H, C H ), 5.3 (s, 1H, C-H, methine), 5.26
(s, 1H, C-H methine), 5.24 (m, J
purchased from Aldrich and used with out further purification,
5
25
26
[(η -C
5
H
4
R)TiCl
3
]
and [TiCl
4
(thf)
2
]
were prepared according
5
5
3
3
i
) 6.1 Hz, J
) 5.1 Hz,
to published procedures, and [Ti(OPr )
mixing equimolar amounts of [Ti(OPr )
2
Cl
2
] was prepared by
HH
HH
3
3
3
i
J HH ) 11.3 Hz, 1H, CHCH ), 4.90 (ddq, J
) 4.6 Hz, J
2
] with [TiCl
4
] in
3
HH
HH
4
3
)
6.8 Hz, J HH ) 6.1 Hz, 1H, CHCH ), 4.32 (dd, J HH ) 13.4
3
toluene.
3
2
5
Hz, J HH ) 6.8 Hz, 1H, CHaHb), 3.94 (ABd, J HH ) 12.5 Hz,
2 3
[
(η -C
5
H
5
)Ti{CH
3
C(O)CHC(NCH
C(NCH CH
2
CH
OH)CH
2
O)CH
3
}Cl] (2a ). A
3
J
HH ) 5.1 Hz, 1H, CHaHb), 3.87 (ABd, J HH ) 12.5 Hz, J HH
3 3
solution of [CH
3
C(O)CH
2
2
2
3
] (0.36 g, 2.52
)
12.0 Hz, 1H, CHaHb), 3.56 (dd, J HH ) 13.4 Hz, J HH ) 4.6
Hz, 1H, CHaHb), 2.30 (s, 3H, C Me), 1.99 (s, 3H, CH ), 1.98
s, 3H, CH ), 1.96 (s, 3H, CH ), 1.95 (s, 3H, CH
mmol) and triethylamine (0.52 mL, 3.8 mmol) in thf (20 mL)
5
5
H
4
3
5 5 3
was added over 1 h to a stirred solution of [(η -C H )TiCl ] (0.55
3
(
3
3
3
), 1.17 (d, J HH
, δ):
), 167.3
g, 2.52 mmol) in thf (40 mL). During the addition the reaction
mixture changed color from yellow and an orange precipitate
appeared. The resulting deep orange suspension was stirred
for 5 h and then filtered. The remaining solid was extracted
with thf (3 × 10 mL) and the solvent removed to yield the
desired product as a spectroscopically pure orange solid.
Crystallization from thf/hexane at room temperature yielded
6.1 Hz, 6H, CHMe). 13C{ H} NMR (125.7 MHz, CDCl
1
)
1
(
C
3
77.0 (s, OCCH
s, NCCH ), 132.7 (s, C
Me), 118.4 (s, C Me), 117.6 (S, C
Me), 116.7 (s, C Me), 116.0 (s, C
04.1 (s, C-H methine), 103.7 (s, C-H methine), 84.6 (s,
3
), 176.7 (s, OCCH
3
), 168.0 (s, NCCH
3
3
5
H
4
Me), 131.9 (s, C
Me), 117.4 (s, C
Me),
5 4
H Me), 119.2 (s,
5
H
4
5
H
4
5
H
4
5 4
H -
Me), 116.8 (s, C
1
5
H
4
5
H
4
5 4
H
1
OCH
CH ), 23.5 (s, CH
15.4 (s, CH
N, 4.42. Found: C, 52.97; C, 6.21; N, 4.51.
[Ti{CH C(O)CHC(NCH CH O)CH }Cl (th f)] (3a ). A so-
2
), 82.2 (s, OCH
2
), 68.8 (s, NCH
2
), 67.1 (NCH
), 21.3 (s, CH ), 15.6 (s, CH
NTi: C, 53.08; H, 6.36;
2
), 23.6 (s,
orange crystals of 2a in 73% yield (0.53 g). H NMR (500.1
3
3
), 22.6 (s, CH
3
3
3
),
MHz, CDCl
3
, δ): 6.37 (s, 5H, C H ), 5.30 (s, 1H, C-H methine),
5 5
2
3
3
3
). Anal. Calcd for C14
H
20ClO
2
4
.83 (ddd, J HH ) 10.1 Hz, J HH ) 6.4 Hz, J HH ) 8.2 Hz, 1H,
2 3 3
OCHaHb), 4,59 (ddd, J HH ) 10.1 Hz, J HH ) 4.9 Hz, J HH
7
)
2
.0 Hz, 1H, OHaHb), 4.22 (br m, 1H, NHcHd), 3.91 (ddd, J HH
3
2
2
3
2
3
3
3 2 2 2 3
lution of [CH C(O)CH C(NCH CH OH)CH ] (0.36 g, 2.5 mmol)
)
11.3 Hz, J HH ) 4.6 Hz, J HH ) 6.4 Hz, 1H, NHcHd), 2.00
1
3
1
in thf (20 mL) was added dropwise to a stirred solution of
(s, 3H, CH
3
), 1.97 (s, 3H, CH
, δ): 177.4 (s, OCCH ), 168.1 (s, NCCH
), 61.8 (s, NCH
). Anal. Calcd for C12 NTi: C,
9.91: H, 5.55; N, 4.87. Found: C, 49.53; H, 5.57; N, 4.80.
3
). C{ H} NMR (125.7 MHz,
), 117.9 (s, C ),
), 23.7
i
[
2 2
TiCl (OPr ) ] (0.60 g, 2.5 mmol) in thf (40 mL) over 1 h, during
CDCl
3
3
3
5 5
H
which time a deep red microcyrstalline solid was deposited.
The resulting suspension was stirred for an additional 3 h,
the volume reduced to approximately 15 mL, and the solid
isolated by filtration. After washing with hexane the solid was
dried in vacuo to give analytically pure 3a in 86% yield (0.57
1
(
4
04.6 (s, C-H methine), 76.7 (s, OCH
2
2
s, CH ), 22.8 (s, CH
3
3
H16ClO
2
Compounds 2b-d were prepared using a procedure similar
to that described above for 2a .
5
g). X-ray quality crystals were grown from a concentrated thf
solution at room temperature. H NMR (500.1 MHz, CDCl
[
(η -C
5
H
4
Me)Ti{CH
3
C(O)CHC(NCH
2
CH
2
O)CH
3
}Cl] (2b).
1
3
,
2
b was obtained as orange crystals in 80% yield from thf/
1
298 K δ): 5.47 (s, methine C-H), 4.71 (br, 2H, OCH
2
), 4.52
H ), 2.04 (s,
H ). C{ H} NMR
4 8
hexane at room temperature. H NMR (500.1 MHz, CDCl
δ): 6.29 (br m, 1H, C Me), 6.10 (br m, 3H, C Me), 5.29
s, 1H, C-H methine), 4.80 (ddd, J HH ) 6.7 Hz, J HH ) 9.2
3
,
3
(
br, 2H, NCH
3H, CH ), 1.96 (s, 3H, CH
(125.7 MHz, CDCl , δ): 178.8 (s, OCCH
109.0 (s br, methine C-H), 78.1 (s, OCHMe), 73.9 (s, OC
62.1 (s, s, NCH ), 27.3 (s, OC ), 25.0 (s, CH ), 24.5 (s, CH
Anal. Calcd for C11 NO
Found: C, 39.96; C, 6.11; N, 4.51.
Ti{CH C(O)CHC(NCH CHMeO)CH
2
), 3.80 (t, J HH ) 6.4 Hz, 4H, OC
4 8
5
H
4
5 4
H
1
3
1
3
3
3
3
), 1.83 (m, 4H, OC
(
3
2
3
3
), 170.6 (s, NCCH
3
8
3
),
),
).
Hz, J HH ) 6.6 Hz, 1H, OCHaHb), 4.60 (ddd, J HH ) 10.9 Hz,
3
3
2
4
H
J
HH ) 4.4 Hz, J HH ) 6.7 Hz, 1H, OCHaHb), 4.19 (br m, J HH
3 3
2
4
H
8
3
)
13.1 Hz, J HH ) 7.9 Hz, 1H, NCHcHd), 3.90 (dd, J HH ) 13.1
3
H
19Cl
2
3
Ti: C, 39.88; H, 5.78; N, 4.23.
Hz, J HH ) 4.4 Hz, 1H NCHcHd), 2.28 (s, 3H, C
5
H
4
Me), 2.0 (s,
). C{ H} NMR (125.7 MHz,
), 168.1 (s, NCCH ), 133.2 (C
Me), 118.5 (s, C Me), 117.0 (s, C Me),
Me), 104.3 (s, C-H methine), 76.7 (s, OCH ),
1
3
1
3
H, CCH
CDCl , δ): 177.2 (s, OCCH
Me), 119.3 (s, C
17.3 (s, C
3 3
), 1.98 (s, 3H, CCH
[
3
2
3
}Cl
2
(th f)] (3b). 3b
3
3
3
5 4
H -
was prepared using a procedure similar to that described above
for 3a . X-ray quality crystals were grown from a dichlo-
romethane solution layered with hexane. H NMR (500.1 MHz,
5
H
4
5
H
4
5 4
H
1
5
H
4
2
1
3
CDCl
3
, 298 K, δ): 5.60 (s, 1H, methine C-H), 5.23 (ddt, J HH
(
25) Cardoso, A. M.; Clark, R. J . H.; Moorhouse, S. J . Chem. Soc.,
Dalton Trans. 1980, 1156.
26) Inorg. Synth. 1987, 21, 137.
3
3
)
6.1 Hz, J HH ) 5.2 Hz, J HH ) 8.2 Hz, 1H, OCHMe), 4.18
3 2
(
(dd, J HH ) 5.2 Hz, J HH ) 13.1 Hz, 1H, NCHaHb), 3.97 (br, t,

1
028 Organometallics, Vol. 18, No. 6, 1999
Doherty et al.
Ta ble 5. Su m m a r y of Cr ysta l Da ta a n d Str u ctu r e Deter m in a tion for Com p ou n d s 2a , 3a , 3b, 4a , a n d 5a
2
a
3a
3b
4a
5a
mol form
fw
C12H16ClNO2Ti
289.61
C11H19Cl2NO3Ti
332.07
C12H21Cl2NO3Ti
346.10
C14H22N2O4Ti‚CH2Cl2 C12H16Cl2NO2Nb
415.16
370.07
radiation and wavelength, Å
Mo KR, 0.71073
Mo KR, 0.71073
Mo KR, 0.71073
Cu KR, 1.54184
Mo KR, 0.71073
temp, K
cryst size, mm
cryst color
cryst syst
space group
a, Å
173
160
160
160
190
0.35 × 0.30 × 0.22 0.26 × 0.19 × 0.14 0r e. 4d 2 × 0.21 × 0.10 0.29 × 0.27 × 0.23
0.65 × 0.50 × 0.24
orange
triclinic
P1h
7.8414(5)
13.0378(8)
14.4708(9)
104.134(2)
94.292(2)
98.097(2)
1411.10(15)
4
orange
monoclinic
P21/c
orange
monoclinic
P21/c
8.7435(5)
11.6855(8)
14.3168(9)
90
91.346(2)
90
1462.37(16)
4
yellow
triclinic
P1h
orthorhombic
Pbca
14.4022(9)
14.6208(9)
14.8973(9)
90
12.5279(9)
6.7169(5)
15.4844(12)
90
96.677(2)
90
1294.15(17)
4
1.486
7.995(3)
11.264(5)
11.580(5)
79.44(3)
72.290(19)
74.96(2)
953.2(7)
2
b, Å
c, Å
R, deg
â, deg
90
90
γ, deg
3
V, Å
3136.9(3)
8
1.466
0.889
1440
Z
-
3
Dcalcd, g cm
µ, mm
F(000)
1.508
0.950
688
1.446
6.569
432
1.742
1.224
744
-
1
0.856
600
reflns for cell refinement; θ
range, deg
6211; 2.6-28.8
6340; 2.2-28.8
11095; 2.4-28.6
36; 24.6-27.4
9044; 2.4-28.7
θ range for data collection, deg 2.6-28.8
2.2-28.8
11, 15, 19
9084
2.4-28.8
18, 18, 20
18642
4.0-55.0
8, 11, 12
4297
1.5-28.7
10, 17, 19
10419
max indices: h, k, l
reflns measd
16, 8, 20
8043
no. of unique reflns
3063
2718
0.862 to 0.750
0.0213
0.0709, 3.2732
3479
2837
0.928 to 0.751
0.0316
0.0460, 0.5759
3764
3024
0.862 to 0.690
0.0424
0.0354, 4.6646
2392
2334
0.313 to 0.252
0.0591
0.0418, 1.0776
0.0038(4)
0.0390
0.0972
232
1.039
0.736, -0.481
6299
5761
0.564 to 0.403
0.0175
0.0360, 0.7602
0.0070(4)
0.0267
0.0714
422
1.073
0.594, -0.730
no. of reflns with F > 2σ(F2)
2
transmission coeff range
2
Rint (on F )
a
weighting parameters a, b
b
extinction coefficient x
2
2
c
R [F > 2σ(F )]
0.0585
0.1546
202
1.062
2.320, -0.784
0.0383
0.0954
165
1.055
0.605, -0.418
0.0457
0.1037
184
1.070
0.831, -0.680
d
wR2 [ all data]
no. of refined params
e
GOF
-
3
max, min in diff map, e Å
a
-1
) σ (Fo ) + (aP) + bP, where P ) (Fo + 2Fc )/3. b Fc′ ) Fc (1 + 0.001xFc λ /sin 2θ)-1/4. c R ) ∑||Fo| - |Fc||/∑|Fo|. wR2 ) {∑w(Fo2
2
2
2
2
2
2
3
d
w
2
2
2
2
1/2
e
2
2
2
1/2
-
Fc ) /∑w(Fo ) }
.
GOF ) [∑w(Fo - Fc ) /(no. of unique reflections - no. of parameters)] .
3
2
4
H, OC
4
H
8
), 3.78 (dd, 3
J
HH ) 8.2 Hz, 3
), 1.99 (s, 3H, CH
J
HH ) 13.1 Hz, 1H,
13.4 Hz, J HH ) 4.9 Hz, 1H, CHaHb), 3.77 (dd, J HH ) 13.1
3
3
2
NCHaHb), 2.03 (s, 3H, CH
3
3
), 1.23 (d, J HH
6.1 Hz, 3H, OCHMe). C{ H} NMR (125.7 MHz, CDCl , δ):
76.9 (s, OCCH ), 168.1 (s, NCCH ), 107.3 (s, methine C-H),
3.0 (s, OCHMe), 72.6 (s, OC ), 67.3 (s, NCH ), 25.5 (s,
), 23.6 (s, CH ), 22.8 (s, CH ), 20.4 (s, CH ). Anal. Calcd
for C12 NO Ti: C, 41.62; H, 6.11; N, 4.04. Found: C,
1.96; C, 6.23; N, 4.31.
Ti{CH C(O)CHC(NCH
CH C(O)CH C(NCH CH OH)CH
toluene was added to a solution of [Ti(OPr )
Hz, J HH ) 8.6 Hz, 1H, CHaHb), 3.70 (dd, J HH ) 13.1 Hz,
2 3
1
3
1
3
)
1
8
3
J HH ) 7.6 Hz, 1H, CHaHb), 3.56 (dd, J HH ) 13.1 Hz, J HH )
2 3
3
3
6.4 Hz, 1H, CHaHb), 3.54 (dd, J HH ) 13.4 Hz, J HH ) 7.3 Hz,
1H, CHaHb), 1.98 (s, 3H, CH ), 1.97 (s, 3H, CH ), 1.96 (s, 3H,
CH ), 1.94 (s, 3H, CH ),
1.81 (s, 3H, CH
4
H
8
2
3
3
OC
4
H
8
3
3
3
3
3 3 3
), 1.85 (s, 3H, CH ), 1.84 (s, 3H, CH
H
21Cl
2
3
3
), 1.13 (d, 3J HH ) 6.1 Hz, 3H, OCHMe), 1.12
3
3
4
(d, J HH ) 6.1 Hz, 3H, OCHMe), 1.11 (d, J HH ) 6.1 Hz, 6H,
OCHMe). 13C{ H} NMR (125.65 MHz, CD
1
Cl , δ): 176.0 (s,
[
3
2
CH
2
O)CH
3
}
2
] (4a ). A solution of
2 2
[
3
2
2
2
3
] (1.01 g, 7.70 mmol) in
OCCH
NCCH
NCCH
3
3
3
), 175.9 (s, OCCH
), 169.0 (s, NCCH
), 102.6 (s, methine C-H), 102.2 (s, methine C-H),
3
3
), 175.7 (s, OCCH
), 169.0 (s, NCCH
3
3
), 169.1 (s,
), 168.8 (s,
i
4
] (1.0 g, 3.53 mmol)
in toluene, with rapid stirring. The addition of N-hydroxyalkyl
â-ketoimine was accompanied by the appearance of a pale
yellow coloration. After stirring overnight the solvent was
removed to leave a yellow solid reside, which was recrystallized
102.0 (s, methine C-H), 101.8 (s, methine C-H), 77.9 (s,
OCH
NCH
2
), 77.4 (s, OCH
), 67.0 (s, NCH
2
), 77.0 (s, OCH
), 66.8 (s, NCH
2
), 76.9 (s, OCH
), 66.6 (s, NCH
2
), 67.7 (s,
), 24.6 (s,
2
2
2
2
1
from n-hexane to give 4a in 96% yield (1.13 g). H NMR (200.0
CH
22.7 (s, CH
(s, CH ), 21.1 (s, CH
3
), 24.5 (s, CH
), 22.6 (s, CH
), 20.7 (s, CH
3
), 24.2 (s, CH
), 22.5 (s, CH
26 2 4
). Anal. Calcd for C16H N O -
3
), 24.1 (s, CH
3
), 22.8 (s, CH
3
),
MHz, CDCl
3
, 298 K, δ): 5.20 (s, 1H, methine C-H), 4.4 (t,
3
3
3
), 21.4 (s, CH
3
), 21.2
3
3
3
J
HH ) 5.2 Hz, 2H, OCH
2
), 4.0 (ABt, J HH ) 5.2 Hz, J HH ) 5.2
3
3
3
2
3
Hz,
J
HH ) 5.2 Hz 1H, NCHaHb), 3.9 (ABt,
J
HH ) 5.2 Hz,
),
, δ): 176.0
), 103.0 (s, methine C-H), 71.6
), 22.8 (s, CH ). Anal.
: C, 47.93; H, 6.36; N, 7.79.
Ti: C, 53.62; H, 7.31; N, 7.81. Found: C, 53.46; C, 7.41; N,
7.79.
3
2
J
HH ) 5.2 Hz, J HH ) 5.2 Hz 1H, NCHaHb), 2.05 (s, 3H, CH
.90 (s, 3H, CH
3
1
5
1
3
). 13C{ H} NMR (50.3 MHz, CDCl
3
[(η -C H )Nb{CH C(O)CHC(NCH CH O)CH }Cl ] (5a ).
A solution of [CH C(O)CH C(NCH CH OH)CH ] (0.286 g, 2.0
3 2 2 2 3
mmol) and triethylamine (0.41 mL, 3.0 mmol) in THF (20 mL)
was added over 2 h to a stirred suspension of [(η -C H )NbCl ]
(0.60 g, 2.0 mmol) in THF (40 mL). The reaction mixture was
allowed to stir overnight, during which time the color changed
from red to golden-yellow orange. The reaction mixture was
filtered, the remaining solid extracted with thf (3 × 10 mL),
and the solvent removed in vacuo to yield a golden yellow solid.
Crystallization of the crude product from thf/hexane at room
5
5
3
2
2
3
2
(
s, OCCH
s, OCH
3
), 169.4 (s, NCCH
3
(
2
), 60.3 (s, NCH
Ti.0.35CH
Found: C, 47.98; C, 6.42; N, 7.80.
Ti{CH C(O)CHC(NCH CHMeO)CH
2
), 24.6 (s, CH
3
3
5
Calcd for C14
H
22
N
2
O
4
2
Cl
2
5
5
4
[
3
2
3
}
2
] (4b). Prepared
using a procedure similar to that described above for 4a and
crystallized from dichloromethane/hexane at room tempera-
ture. H NMR (500.1 MHz, CDCl
C-H), 5.19 (s, 1H, methine C-H), 5.16 (s, 1H, methine C-H),
5
4
1
3
, δ): 5.21 (s, 1H, methine
.12 (s, 1H, methine C-H), 4.74-4.90 (multiplet, 4H, OCHMe),
temperature gave 5a as yellow crystals in 57% yield (0.42 g).
H NMR (500.1 MHz, CDCl
2
3
1
.12 (dd, J HH ) 13.1 Hz, J HH ) 5.2 Hz, 1H, CHaHb), 3.99
3
, δ): 6.70 (s, 5H, C
5
H
5
), 5.31 (s,
), 4.08 (t,
), 1.82 (s, 3H, CH ).
2
3
3
(
dd, J HH ) 13.4 Hz, J HH ) 5.2 Hz, 1H, CHaHb), 3.90 (dd,
1H, C-H methine), 4.61 (t, J HH ) 5.5 Hz, 2H, OCH
3
2
2
3
2
J
HH ) 13.4 Hz, J HH ) 5.2 Hz, 1H, CHaHb), 3.87 (dd, J HH
)
J
HH ) 5.5 Hz, 2H, NCH
2
), 2.06 (s, 3H, CH
3
3

N-Alkoxy-â-ketoiminate Complexes of Groups 4 and 5
Organometallics, Vol. 18, No. 6, 1999 1029
1
3
1
C{ H} NMR (125.7 MHz, CDCl
64.7 (s, NCHCH ), 122.4 (s, C
6.1 (s, OCH ), 57.4 (s, NCH ), 24.7 (s, CH
l2NONb: C, 39.03: H, 4.37; N, 3.79.
3
, δ): 169.2 (s, OCHCH
), 105.4 (s, C-H methine),
), 23.5 (s, CH ).
3
),
made on a Bruker AXS SMART CCD area-detector diffracto-
meter using narrow frame exposures (0.3° in ω). Cell param-
eters were refined from the observed ω angles of all strong
reflections in each data set. Intensities were corrected semiem-
pirically for absorption, based on symmetry-equivalent and
repeated reflections. No significant intensity decay was ob-
2
1
7
3
5 5
H
2
2
3
3
Anal. Calcd for C12
Found: C, 39.05; H, 4.17; N, 3.71.
16
H C
Compounds 5b-d were prepared using a procedure similar
to that described above for 5a .
served. Measurements for 4a ‚CH Cl2 were made on a Stoe-
5
27
[
(η -C
5
H
4
Me)Nb{CH
3
C(O)CHC(NCH
2
CH
2
O)CH
3
}Cl
2
] (5b).
Siemens 4-circle diffractometer using on-line profile fitting.
5
b was obtained as yellow-orange crystals in 54% yield from
Accurate cell parameters were determined from the setting
angles of reflections measured on both sides of the direct beam
to avoid zero-point errors. A semiempirical absorption correc-
tion was made using ψ scan data. Intensity decay of 2.5% was
monitored by five check reflections remeasured each hour, and
a correction was made using a least-squares fit. Structure
1
3
thf/hexane at room temperature. H NMR (500.1 MHz, CDCl ,
3
3
δ): 6.53 (t, J HH ) 2.7 Hz, 2H, C
5 4
H Me), 6.47 (t, J HH ) 2.7
3
Hz, 2H, C Me), 5.31 (s, 1H, C-H, methine), 4.64 (t, J HH )
5
H
4
3
5
.5 Hz, 2H, OCH
H, CH ), 2.06 (s, 3H, CH
, δ): 168.8 (s, OCHCH
Me), 123.9 (s, C Me), 120. 7 (s,
Me), 106.9 (s, C-H methine), 75.7 (s, OCH ), 67.7 (s,
), 24.2 (s, CH ), 23.9 (s, CH ), 14.8 (s, C Me). Anal.
Calcd for C13 l2NONb: C, 40.74; H, 4.73; N, 3.65. Found:
C, 40.51; H, 4.34; N, 3.31.
2
), 4.07 (t, J HH ) 5.5 Hz, 2H, NCH
), 1.85 (s, 3H, C
Me). 13C{ H}
), 164.2 (s,
2
), 2.26 (s,
1
3
3
3
5 4
H
NMR (125.7 MHz, CDCl
NCHCH ), 133.3 (s, C
3
3
2 2
solution was by direct methods for 3a , 4a ‚CH Cl , and 5a and
3
5
H
5
5
H
5
by Patterson synthesis for 2a and 3b. Refinement was on F
2
C
NCH
5
H
5
2
values for all unique data by full-matrix least-squares. Table
2
3
3
5 5
H
5
gives further details. All non-H atoms were refined aniso-
18
H C
tropically. H atoms were constrained with a riding model; U(H)
was set to 1.2 (1.5 for methyl groups) times Ueq for the parent
atom. Twofold disorder was modeled with restraints for atoms
5
[
(η -C
5 5 3 2 3 2
H )Nb{CH C(O)CHC(NCH CHMeO)CH }Cl ] (5c).
5
c was obtained as orange crystals in 63% yield from thf/
2 2
C(5) in 3b and C(14) in 4a ‚CH Cl , and for the Cp rings in 2a
1
hexane at room temperature. H NMR (500.1 MHz, CDCl
3
,
28
and 5a . Programs used were SHELXTL for structure solu-
δ): 6.45 (s, 5H, C ), 5.06 (s, 1H, C-H methine), 4.48 (ddq,
5
H
5
tion, refinement, and molecular graphics, Bruker AXS SMART
3
3
3
J
HH ) 6.5 Hz, J HH ) 4.6 Hz, J HH ) 8.8 Hz, 1H, CHaHb),
29
(
control) and SAINT (integration), Stoe DIF4 (control), and
2
3
3
(
CH
.82 (dd, J HH ) 13.4 Hz, J HH ) 4.6 Hz, 1H, CHaHb), 3.61
2 3
local programs.
dd, J HH ) 13.4 Hz, J HH ) 8.8 Hz, 1H, CHaHb), 1.80 (s, 3H,
3 13 1
3
), 1.57 (s, 3H, CH
3
), 0.93 (d, J HH ) 6.5 Hz, CH
3
). C{ H}
), 164.5 (s,
), 105.9 (s, C-H methine), 83.2 (s,
), 24.0 (s, CH ). Anal. Calcd
l2NONb: C, 40.74; H, 4.73; N, 3.65. Found: C,
1.03; H, 4.84; N, 3.79.
NMR (125.7 MHz, CDCl
NCHCH ), 122.7 (s, C
OCH ), 71.2 (s, NCH
for C13
3
, δ): 169.9, (s, OCHCH
3
Ack n ow led gm en t. We gratefully acknowledge the
University of Newcastle upon Tyne, the Nuffield Foun-
dation, and the Royal Society for support (S.D.), Tioxide
Specialities for funding (R.J .E. and J .R.), and the
EPSRC for funding for a diffractometer (W.C.).
3
5
H
4
3
2
), 25.0 (s, CH
3
3
18
H C
4
5
[
(η -C
5 4 3 2 3
H Me )Nb {CH C(O)CH C(NCH CH Me O)CH }-
Cl
2
] (5d ). 5d was obtained as orange crystals in 71% yield
1
Su p p or tin g In for m a tion Ava ila ble: For 2a , 3a , 3b, 4a ‚
CH Cl , and 5a details of the structure determination (Tables
2 2
from thf/hexane at room temperature. H NMR (500.1 MHz,
CDCl , δ): 6.5 (m, 2H, C Me), 6.48 (m, 1H, C Me), 6.45
m, 1H, C Me), 5.29 (s, 1H, C-H methine), 4.74 (ddq, J HH
3
5
H
4
5 4
H
3
S1, S6, S11, S16, and S21), non-hydrogen atomic positional
parameters (Tables S2, S7, S12, S17, and S22), full listings of
bond lengths and angles (Tables S3, S8, S13, S18, and S23),
anisotropic displacement parameters (Tables S4, S9, S14, S19,
and S24), hydrogen atomic coordinates (Tables S5, S10, S15,
S20, and S25). This material is available free of charge via
the Internet at http://pubs.acs.org.
(
5 4
H
3
3
)
6.1 Hz, J HH ) 4.6 Hz, J HH ) 8.9 Hz 1H, CHMe), 4.07 (dd,
3 2
2
J
HH ) 13.5 Hz, J HH ) 4.6 Hz, 1H, CHaHb), 3.85 (dd, J HH )
3
1
3
3.5 Hz, J HH ) 9.2 Hz, 1H, CHaHb), 2.24 (s, 3H, CH ), 2.03
3
(s, 3H, CH
3
3
), 1.83 (s, 3H, CH
3
), 1.12 (d,
OCHMe). C{ H} NMR (125.7 MHz, CDCl
OCHCH ), 163.4 (s, NCHCH ), 131.8 (s, C
Me), 123.9 (s, C Me), 120.4 (s, C Me), 120. 3 (s, C
Me), 104.7 (s, C-H methine), 82.0 (s, OCHMe), 63.2 (s, NCH
5.3 (s, CH ), 23.9 (s, CH ), 19.4 (s, OCHMe), 14.7 (s, C Me).
Anal. Calcd for C14 l2NONb: C, 42.32; H, 5.07; N, 3.52.
J
3
HH ) 6. 1 Hz,
, δ): 168.8, (s,
1
1
3
3
5 4
H Me), 124.2 (s,
C
5
H
4
5
H
4
5
H
4
5 4
H -
OM980510Q
2
),
2
3
3
5 4
H
(
27) Clegg, W. Acta Crystallogr., Sect. A. 1981, 37, 22.
20
H C
(28) Sheldrick, G. M. SHELXTL user manual, version 5; Bruker AXS
Found: C, 42.33; H, 4.84; N, 3.39.
Inc.: Madison, WI, 1994.
29) SMART and SAINT software for CCD diffractometers; Bruker
AXS Inc.: Madison, WI, 1994.
Cr ysta l Str u ctu r e Deter m in a tion of 2a , 3a , 3b, 4a ‚
(
2 2
CH Cl , a n d 5a . Measurements for 2a , 3a , 3b, and 5a were