Titanium complexes stabilized by N-(tert-hydrocarbyl)anilide ligation: A synthetic investigation

Article abstract of DOI:10.1021/om960315g

The complexes Ti(NRAr_F)2(NMe₂)₂ (4, R = C(CD₃)₂CH3, Ar_F = 2,5-C₆H₃FMe), Ti(NRAr_F)₂-(NMe₂)(I) (5), Ti(NRAr_F)₂(NMe₂)(CH₂SiMe ₃) (6), and Ti(NRAr_F)₂(I)(CH₂SiMe₃) (7) have been synthesized in 77, 71, 70, and 84percent yield, respectively, in a four step sequence of alternating salt elimination and dimethylamide deprotection steps. The complex Ti(NRAr)(I)₂(OAr′) (11, Ar = 3,5-C₆H₃Me₂, Ar′ = 2,6-C₆H₃ⁱPr₂) was prepared in 65percent yield via the complexes Ti-(NRAr)(NMe₂)₃ (9) and Ti(NRAr)(NMe₂)₂(OAr′) (10), which were generated in situ, spectroscopically characterized, and not isolated. The complexes Ti(NR′Ar)(NMe₂)₃ (12, R′ = C(CD₃)₂Ph, Ti(NR′Ar)(NMe₂)₂(OAr″) (13, Ar″ = 2,6-C₆H₃^tBu₂), and Ti(NR′Ar)(NMe₂)(OAr″)-(I) (14) were prepared in 83, 83, and 95percent isolated yield, respectively, via a salt-elimination, protonolysis, and dimethylamide deprotection sequence. Treatment of 14 with (i) neopentyllithium, (ii) thermolysis at 65°C, and (iii) excess methyl iodide at 70°C led to the isolation in 62percent yield of the cyclometallated compound Ti(NR′Ar)(O-2,6-C₆H₃[^tBu][CMe ₂CH₂](I) (17) via an intermediate neopentyl complex (15) which was not isolated. The titanium(III) "ate" complex (ArR′N)₂Ti(μ-Cl)2Li(TMEDA)_n (18, TMEDA = Me₂NCH₂CH₂NMe₂, n = ca. 3) was isolated in 80percent yield as green crystals upon treatment of TiCl₃(THF)₃ (THF = tetrahydrofuran) with 2 equiv of Li(NR′Ar)(OEt₂) in a THF/TMEDA mixture. Chloroform treatment of the ate complex 18 led to the titanium(IV) dichloride Ti(NR′Ar)₂Cl₂ (19). The titanium(III) ate complex (ArRN)₂Ti(μ-Cl)₂Li(TMEDA) (20) was isolated in 57percent yield in a manner analogous to the preparation of 18. Alkylation of 20 with LiCH(SiMe₃)₂ led to the mixed amido-alkyl titanium(III) complex Ti(NRAr)₂(CH[SiMe₃]₂) (21) in 72percent isolated yield. A single-crystal X-ray diffraction study carried out for 21 revealed an η³ bonding mode for one of the NRAr ligands and a typical η¹ bonding mode for the other. The diamagnetic dimeric complex (μ-NCPhCPhN)[Ti(NRAr)₂(CH[SiMe₃]₂)]2 (23) was obtained in 82percent yield via the blue benzonitrile adduct Ti(NRAr)₂(CH[SiMe₃]₂)(NCPh) (22), which was not isolated. A robust green pivalonitrile adduct Ti(NRAr)₂(CH[SiMe₃]₂)(NCCMe₃) (24) was observed upon treatment of 21 with pivalonitrile. Addition of azidotrimethylsilane to 24 delivered the titanium(IV) azido complex Ti(NRAr)₂(CH[SiMe₃]₂)(N₃) (25) in 37percent isolated yield. Treatment of 21 with 0.5 equiv of I₂ in benzene provided Ti(NRAr)₂(CH[SiMe₃]₂)(I) (26) in 68percent yield.

Full text of DOI:10.1021/om960315g

Organometallics 1996, 15, 3825-3835
3825
Tita n iu m Com p lexes Sta bilized by
N-(ter t-Hyd r oca r byl)a n ilid e Liga tion : A Syn th etic
In vestiga tion
Adam R. J ohnson, William M. Davis, and Christopher C. Cummins*
Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue,
Cambridge, Massachusetts 02139-4307
Received April 25, 1996X
The complexes Ti(NRArF)2(NMe2)2 (4, R ) C(CD3)2CH3, ArF ) 2,5-C6H3FMe), Ti(NRArF)2-
(NMe2)(I) (5), Ti(NRArF)2(NMe2)(CH2SiMe3) (6), and Ti(NRArF)2(I)(CH2SiMe3) (7) have been
synthesized in 77, 71, 70, and 84% yield, respectively, in a four step sequence of alternating
salt elimination and dimethylamide deprotection steps. The complex Ti(NRAr)(I)2(OAr′) (11,
i
Ar ) 3,5-C6H3Me2, Ar′ ) 2,6-C6H3 Pr2) was prepared in 65% yield via the complexes Ti-
(NRAr)(NMe2)3 (9) and Ti(NRAr)(NMe2)2(OAr′) (10), which were generated in situ, spectro-
scopically characterized, and not isolated. The complexes Ti(NR′Ar)(NMe2)3 (12, R′ )
t
C(CD3)2Ph, Ti(NR′Ar)(NMe2)2(OAr′′) (13, Ar′′ ) 2,6-C6H3 Bu2), and Ti(NR′Ar)(NMe2)(OAr′′)-
(I) (14) were prepared in 83, 83, and 95% isolated yield, respectively, via a salt-elimination,
protonolysis, and dimethylamide deprotection sequence. Treatment of 14 with (i) neopent-
yllithium, (ii) thermolysis at 65 °C, and (iii) excess methyl iodide at 70 °C led to the isolation
in 62% yield of the cyclometallated compound Ti(NR′Ar)(O-2,6-C6H3[tBu][CMe2CH2])(I) (17)
via an intermediate neopentyl complex (15) which was not isolated. The titanium(III) “ate”
complex (ArR′N)2Ti(µ-Cl)2Li(TMEDA)n (18, TMEDA ) Me2NCH2CH2NMe2, n ) ca. 3) was
isolated in 80% yield as green crystals upon treatment of TiCl3(THF)3 (THF ) tetrahydro-
furan) with 2 equiv of Li(NR′Ar)(OEt2) in a THF/TMEDA mixture. Chloroform treatment
of the ate complex 18 led to the titanium(IV) dichloride Ti(NR′Ar)2Cl2 (19). The titanium(III)
ate complex (ArRN)2Ti(µ-Cl)2Li(TMEDA) (20) was isolated in 57% yield in a manner
analogous to the preparation of 18. Alkylation of 20 with LiCH(SiMe3)2 led to the mixed
amido-alkyl titanium(III) complex Ti(NRAr)2(CH[SiMe3]2) (21) in 72% isolated yield. A
single-crystal X-ray diffraction study carried out for 21 revealed an η3 bonding mode for one
of the NRAr ligands and a typical η1 bonding mode for the other. The diamagnetic dimeric
complex (µ-NCPhCPhN)[Ti(NRAr)2(CH[SiMe3]2)]2 (23) was obtained in 82% yield via the
blue benzonitrile adduct Ti(NRAr)2(CH[SiMe3]2)(NCPh) (22), which was not isolated. A
robust green pivalonitrile adduct Ti(NRAr)2(CH[SiMe3]2)(NCCMe3) (24) was observed upon
treatment of 21 with pivalonitrile. Addition of azidotrimethylsilane to 24 delivered the
titanium(IV) azido complex Ti(NRAr)2(CH[SiMe3]2)(N3) (25) in 37% isolated yield. Treatment
of 21 with 0.5 equiv of I2 in benzene provided Ti(NRAr)2(CH[SiMe3]2)(I) (26) in 68% yield.
In tr od u ction
ization of prochiral olefins has led to a renewed interest
in such systems, the search is on for non-cyclopenta-
dienyl ligand systems that may provide catalysts with
improved properties. Thus, group 4 organometallic
molecules with N- or O-donor ancillary ligands,12-18 or
boron-based ligands,19-22 are now under inspection in
the hopes that these may provide the next generation
Group 4 organometallic molecules are under heavy
investigation as catalysts and as stoichiometric reagents
for a wide range of transformations including olefin
polymerization,1 reductive coupling,2-6 and hydrogena-
tion catalysis.7-11 While the discovery of well-behaved
metallocene-based catalysts for stereospecific polymer-
X Abstract published in Advance ACS Abstracts, August 1, 1996.
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S0276-7333(96)00315-9 CCC: $12.00 © 1996 American Chemical Society

3826 Organometallics, Vol. 15, No. 18, 1996
J ohnson et al.
Sch em e 1
of reagents or catalysts. While the focus is largely
centered on cationic organometallic complexes of group
4 transition metals,23,24 species that are d0 and highly
electrophilic, alternative ancillary ligand systems are
also under investigation for d1 and d2 group 4 com-
plexes25-27 and for group 328 and group 529-31 metal
complexes.
describing the cleavage of titanium dimethylamides
with methyl iodides,43 a deprotection protocol. Since
several of the complexes described here are halogeno
species analogous to the prototypical complexes Cp2M-
(R)(X) [M ) Ti, Zr; X ) halogen, triflate, or noncoordi-
nating anion], they are potential precursors to organo-
metallic cations of titanium(IV) or to neutral organo-
metallic titanium(III) radicals. A highlight of the
present work involves the synthesis, characterization,
and initial reactivity studies of the monomeric organo-
metallic titanium(III) complex Ti(NRAr)2(CH[SiMe3]2)
(21).
Our interest in the chemistry of group 4 complexes
has centered on inorganic reactions that utilize a d1
titanium center as a specific one-electron reductant.32,33
This aspect of group 4 chemistry has manifested itself
previously in the context of a bis(cyclopentadienyl)
ancillary ligand set,34 and also in the context of O-donor
ancillary ligands,35 but the area is essentially in its
infancy. We have discovered new implementations of
d1 titanium(III) as a specific 1e reductant for terminal
oxo complexes of vanadium(V)33 and also for terminal
oxo and nitrido complexes of molybdenum(VI).32 Uti-
lization of the latter substrates led to unprecedented
examples of radical alkoxide C-O bond cleavage.32
The present work concerns synthetic strategies lead-
ing to organometallic titanium complexes supported
either by bis(amido) ligation or by mixed amido/arylox-
ide ligation. The class of amido ligands we employ here
are sterically-demanding N-tert-hydrocarbylanilide
ligands, introduced recently for the stabilization of low-
coordinate transition metal complexes.36-42 The syn-
thetic methods described here build on our earlier note
Resu lts a n d Discu ssion
(i) Dim eth yla m id e Clea va ge by Meth yl Iod id e.
We described recently the use of methyl iodide in the
cleavage of titanium dimethylamides,43 a reaction that
results in replacement of the dimethylamide functional-
ity by iodide44 and gives tetramethylammonium iodide
as a solid byproduct insoluble in common organic
solvents. This reaction type (Scheme 1) is a nonprotic
alternative to the use of amine hydrohalides,45 most
commonly pyridine or lutidine hydrohalides, that also
lead to replacement of dimethylamide by halide, but
which give a secondary ammonium salt possessing
acidic protons as a byproduct.
The methyl iodide strategy is exemplified by the
chemistry in Scheme 1. The mixed dimethylamide
chloride complex Ti(NMe2)2Cl2 (1) is a versatile starting
material prepared by the literature method involving
conproportionation of equimolar quantities of TiCl4 and
Ti(NMe2)4.46 Addition of 2 equiv of the lithium amide
etherate Li(NRAr)(OEt2)47 to 1 leads to metathesis,
producing the mixed tetraamide Ti(NRAr)2(NMe2)2 (2)
in essentially quantitative yield. Addition of methyl
(18) Gue´rin, F.; McConville, D. H.; Vittal, J . J . Organometallics
1995, 14, 3154.
(19) Crowther, D. J .; Swenson, D. C.; J ordan, R. F. J . Am. Chem.
Soc. 1995, 117, 10403.
(20) Bowen, D. E.; J ordan, R. F.; Rogers, R. D. Organometallics 1995,
14, 3630.
(21) Kreuder, C.; J ordan, R. F.; Zhang, H. Organometallics 1995,
14, 2993.
(22) Quan, R. W.; Bazan, G. C.; Kiely, A. F.; Schaefer, W. P.; Bercaw,
J . E. J . Am. Chem. Soc. 1994, 116, 4489.
(23) Tjaden, E. B.; J ordan, R. F. Macromol. Symp. 1995, 89, 231.
(24) Wu, Z.; J ordan, R. F.; Petersen, J . L. J . Am. Chem. Soc. 1995,
117, 5867.
(25) Minhas, R. K.; Scoles, L.; Wong, S.; Gambarotta, S. Organo-
metallics 1996, 15, 1113.
(26) Beydoun, N.; Duchteau, R.; Gambarotta, S. J . Chem. Soc.,
Chem. Commun. 1992, 244.
(27) Duchateau, R.; Gambarotta, S.; Beydoun, N.; Bensimon, C. J .
Am. Chem. Soc. 1991, 113, 8986.
(36) Laplaza, C. E.; Odom, A. L.; Davis, W. M.; Cummins, C. C.;
Protasiewicz, J . D. J . Am. Chem. Soc. 1995, 117, 4999.
(37) Laplaza, C. E.; Cummins, C. C. Science 1995, 268, 861.
(38) Laplaza, C. E.; Davis, W. M.; Cummins, C. C. Angew. Chem.,
Int. Ed. Engl. 1995, 34, 2042.
(39) Laplaza, C. E.; J ohnson, A. R.; Cummins, C. C. J . Am. Chem.
Soc. 1996, 118, 709.
(40) Laplaza, C. E.; J ohnson, M. J . A.; Peters, J .; Odom, A. L.; Kim,
E.; Cummins, C. C.; George, G. N.; Pickering, I. J . J . Am. Chem. Soc.,
in press.
(28) Bazan, G. C.; Schaefer, W. P.; Bercaw, J . E. Organometallics
1993, 12, 2126.
(29) Bazan, G. C.; Rogriguez, G. Polyhedron 1995, 14, 93.
(30) Rodriguez, G.; Bazan, G. C. J . Am. Chem. Soc. 1995, 117, 10155.
(31) Bazan, G. C.; Donnelly, S. J .; Rodriguez, G. J . Am. Chem. Soc.
1995, 117, 2671.
(32) Peters, J . C.; Wanandi, P. W.; Odom, A. L.; Davis, W. M.;
Cummins, C. C. J . Am. Chem. Soc., submitted for publication.
(33) Wanandi, P. W.; Davis, W. M.; Cummins, C. C.; Russell, M. A.;
Wilcox, D. E. J . Am. Chem. Soc. 1995, 117, 2110.
(34) RajanBabu, T. V.; Nugent, W. A. J . Am. Chem. Soc. 1989, 111,
4525.
(41) Odom, A. L.; Cummins, C. C.; Protasiewicz, J . D. J . Am. Chem.
Soc. 1995, 117, 6613.
(42) Fickes, M. G.; Davis, W. M.; Cummins, C. C. J . Am. Chem. Soc.
1995, 117, 6384.
(43) J ohnson, A. R.; Wanandi, P. W.; Cummins, C. C.; Davis, W. M.
Organometallics 1994, 13, 2907.
(44) Schulz, H.; Folting, K.; Huffman, J . C.; Streib, W. E.; Chisholm,
M. H. Inorg. Chem. 1993, 32, 6056.
(45) Odom, A. L.; Cummins, C. C. Organometallics 1996, 15, 898.
(46) Benzing, E.; Kornicker, W. Chem. Ber. 1961, 94, 2263.
(47) Laplaza, C. E.; Davis, W. M.; Cummins, C. C. Organometallics
1995, 14, 577.
(35) Covert, K. J .; Wolczanski, P. T.; Hill, S. A.; Krusic, P. J . Inorg.
Chem. 1992, 31, 66.

Ti Complex Stabilization by Amido Ligation
Organometallics, Vol. 15, No. 18, 1996 3827
Sch em e 2
iodide to 2, generated in situ, gives smooth conversion
to the desired bis(amido) dihalide complex Ti(NRAr)2I2
(3), which was isolated in 60% recrystallized yield.43
line solid isolable in 77% recrystallized yield; this
property contrasts starkly with the situation for the
nonfluorinated mixed tetraamide 2 which could only be
obtained as an oil. Treatment of 4 with an excess of
methyl iodide in THF (28 °C) led to replacement of only
one of the two dimethylamide functionalities by iodide.
Monoiodide monodimethylamide 5 was isolated in 71%
recrystallized yield subsequent to such treatment. This
observation can be rationalized by assuming that the
fluorinated amido ligand renders the titanium center
in 4 more electron-deficient than that in 2, leading to
stronger dimethylamido-titanium π interactions in the
case of 4. Replacement of the first dimethylamide by
iodide, generating 5, results in an even stronger metal-
nitrogen π interaction for the remaining dimethylamide
such that it is not susceptible to further attack by
methyl iodide. The unfluorinated complex correspond-
ing to 5 in Scheme 1 (not shown) is attacked readily by
methyl iodide, leading directly to two substitutions.
The two-step procedure outlined in Scheme 1 offered
advantages over the alternative one-step process in
which 2 equiv of Li(NRAr)(OEt2) would be added to
TiCl4 in the hopes of producing Ti(NRAr)2Cl2 directly.
First, the use of exactly two dimethylamide protecting
groups as present in 1 delivers control of the stoichi-
ometry, since 1 possesses exactly two metathetically
replaceable halogens, in contrast to TiCl4. Second, the
strongly π-donating dimethylamide ligands in 1 render
the titanium(IV) center much less susceptible to reduc-
tion than is the case for TiCl4. This potential side
reaction, electron transfer, is important to consider in
the context of metathetical salt-elimination reactions
involving strongly reducing species such as lithium
amides. Finally, the fact that Scheme 1 depicts a two-
step procedure is mitigated by the fact that it is carried
out without isolation or purification of intermediate 2.
It is occasionally the case that alkyllithium or Grig-
nard alkylations of a dihalogeno species such as Cp2-
MCl2 (M ) Ti, Zr) leads to complex mixtures when the
mixed halogeno alkyl complex is the desired product.
Several strategies have been designed to circumvent
this difficulty, including initial preparation of the dialkyl
species followed by metal-carbon bond oxidation and
including conproportionation of the dialkyl species with
the corresponding dihalogeno species. In this context
it should be noted that complex 5, because of the
presence of one dimethylamide protecting group, is
poised to undergo a selective monoalkylation upon
treatment with 1 equiv of a Grignard or alkyllithium
reagent. Thus, treatment of 5 with trimethylsilylmethyl
lithium led to smooth production of the monoalkylated
species Ti(NRArF)2(NMe2)(CH2SiMe3) (6), which was
isolated as mustard yellow sheets in 70% recrystallized
yield. Removal of the dimethylamide protecting group
was effected by treatment of 6 with excess methyl iodide
in THF, delivering the iodo (trimethylsilyl)methyl com-
plex 7 in 84% crude yield as a yellow oil. The choice of
(ii) Bis(a m id o) Or ga n om eta llic Com p lex of Ti-
ta n iu m (IV). In a series of papers treating new low-
coordinate transition metal complexes and their reac-
tions with small molecules, we have introduced sterically-
demanding N-tert-butylanilide ligands (e.g. NRAr in
Scheme 1) as bulky ancillary N-donor ligands.36-42
Among the attractive features of such ligands is that
they are readily tunable in that a plethora of variously
substituted anilines may be employed in their synthesis.
Partially fluorinated anilines are especially attractive
in this respect. The chemistry displayed in Scheme 2
was carried out in order to assess the effect of a single
ortho fluorine substituent on the course of dimethyla-
mide cleavage by methyl iodide, along the lines dis-
cussed in the context of Scheme 1 above.
Treatment of bis(dimethylamide) dichloride 1 with 2
equiv of the singly fluorinated lithium amide etherate
Li(NRArF)(OEt2) in diethyl ether led to clean expulsion
of 2 equiv of LiCl with production of the mixed tetra-
amide Ti(NRArF)2(NMe2)2 (4). Complex 4 is a crystal-

3828 Organometallics, Vol. 15, No. 18, 1996
J ohnson et al.
Sch em e 3
solvent is important for the dimethylamide deprotection
step, in that the reaction (28 °C) proceeds relatively
rapidly in THF, at a moderate or slow pace in diethyl
ether, and extremely slowly in hydrocarbon solvents
such as hexane.
expect the diisopropylphenoxide ligand to be a weaker
donor than NRAr, allowing us to forward the following
electronic ordering: Ti(NRAr)2 < Ti(NRAr)(OAr′) < Ti-
(NRArF)2 for the electrophilicity at titanium. However,
we cannot discount the possibility that the unique
behavior of 4 is a consequence of the fact that this
ligand, unlike the others, has the potential to behave
as a bidentate N,F donor.
(iii) Am id o-Ar yloxid e Tita n iu m (IV) Diiod id e
Com p lex. An important class of O-donor ligands in
organometallic chemistry are the 2,6-disubstituted aryl-
oxides. The most ubiquitous members of this class are
2,6-diisopropylphenoxide, 2,6-di-tert-butylphenoxide, and
2,6-diphenylphenoxide. The latter variant has been
employed to great advantage by Rothwell and co-
workers in the development of reductive coupling chem-
istry on the Ti(O-2,6-C6H3Ph2)2 template. The chemis-
try in this section constitutes the deliberate construction
of a mixed aryloxide/amide ancillary ligand set. The
goal of this inquiry is to set the stage for production of
(i) a three-coordinate titanium species bearing C, N, and
O donors or (ii) to set the stage for the production of a
chiral-at-metal electrophilic titanium(IV) species.
Scheme 3 begins with titanium monochloride tris-
(dimethylamide) (8), a species which, like compound 1,
is available via conproportionation of TiCl4 with Ti-
(NMe2)4 employing the proper stoichiometric ratio.46 We
introduced the bulky amido ligand quantitatively upon
treatment of 8 with 1 equiv of Li(NRAr)(OEt2), giving
mixed tetraamide 9, which did not require purification.
Protonolysis of one dimethylamido substituent occurred
smoothly and selectively upon treatment of 9 with 1
equiv of 2,6-diisopropylphenol. Dimethylamine, which
was thereby liberated, was removed in vacuo. Com-
pound 10 exhibited NMR spectroscopic properties con-
sistent with its formulation as the desired bis(dimeth-
ylamido) N-tert-butylanilido aryloxide species, and it
reacted smoothly with an excess of methyl iodide in THF
to give the corresponding diiodide complex Ti(NRAr)-
(I)2(OAr′) (11) in 65% overall yield from 8. Solutions of
11 are blood-red in color, and crystals of the complex
are purple. All characterization data are consistent
with the identity of compound 11 as formulated.
Compound 11 is poised for alkylation by treatment
with a Grignard reagent or an alkyllithium reagent.
Preliminary results indicate that the compound does in
fact react smoothly with LiCH2SiMe3 to generate
Ti(NRAr)(OAr′)(CH2SiMe3)I and with LiCH2CMe2Ph to
generate Ti(NRAr)(OAr′)(CH2CMe2Ph)I. NMR charac-
terization revealed the presence of diastereotopic TiCH2
protons and CHMe2 methyls for these chiral-at-metal
four coordinate complexes.
(iv) Cyclom eta la tion In volvin g a Tita n iu m (IV)
Am id o-Ar yloxid e Com p lex. In the above sections
we utilized two variants of the N-tert-butylanilide ligand
type, the difference being the substitution pattern on
the aromatic ring. This general class of ligands is also
variable at the N-connected tertiary hydrocarbyl posi-
tion. Here we describe a variant possessing CMe2Ph
as the tertiary hydrocarbyl in conjunction with a
synthetic sequence aiming, as in the previous section,
at a titanium target bearing C, N, and O donors.
This sequence (Scheme 4) begins once again with
ClTi(NMe2)3 (8). Treatment of 8 with 1 equiv of Li-
(NR′Ar)(OEt2) led in 83% recrystallized yield to mixed
tetraamide 12, isolated as a green-brown powder.
Characterization data are consistent with the identity
of 12 as formulated. Compound 13, an orange powder,
was also isolated in 83% recrystallized yield, subsequent
to protonolysis of a single dimethylamido substituent
in 12 with 2,6-di-tert-butylphenol. Compound 13 rep-
resents the fourth bis(dimethylamido) complex newly
synthesized in this study, the others being 2, 4, and 10.
It was of obvious interest to examine the reaction of 13
with methyl iodide under conditions similar to those
utilized for the other bis(dimethylamido) complexes. The
product resulting from treatment of 13 with an excess
of methyl iodide was in fact mono(dimethylamide)
monoiodide 14, which was obtained as orange microc-
rystals in ca. 95% recrystallized yield. Evidently the
effect of aryl-for-methyl substitution at the N-connected
tertiary hydrocarbyl position leads to increased electro-
philicity at the titanium center. Neopentyllithium
alkylation of monoiodide 14 led to smooth production
of Ti(NR′Ar)(OAr′′)(CH2CMe3)(NMe2) (15) according to
NMR monitoring, but the oily yellow compound resisted
repeated attempts at crystallization. Thermolysis at 65
°C of 15 generated in situ led to expulsion of neopentane
(not quantified), giving a complex whose NMR spectra
are indicative of a cyclometalated aryloxide ligand as
depicted in Scheme 4 for 16. Compound 16 was an oily
species, difficult to purify for full characterization.
Treatment of 16 with methyl iodide at 70 °C provided
17 in 63% recrystallized yield. Compound 17 retains
the cyclometalated 2,6-di-tert-butylphenoxide substitu-
ent proposed for precursor 16. Bearing four different
groups bound to titanium, compound 17 is chiral-at-
metal, consistent with the diastereotopic nature of its
titanium-bound methylene unit. Rothwell and co-work-
Thus far we have described the reactions of the three
bis(dimethylamido) complexes 2, 4, and 10 with methyl
iodide. It is of interest to note that only the partially
fluorinated ancillary ligand set present in 4 resulted in
a titanium center sufficiently electrophilic to protect the
second dimethylamide from alkylation. One would

Ti Complex Stabilization by Amido Ligation
Organometallics, Vol. 15, No. 18, 1996 3829
Sch em e 4
Sch em e 5
ers have observed C-H activation previously in con-
junction with cyclometalation of the 2,6-di-tert-butyl-
phenoxide ligand.48-50 Such intramolecular cyclometa-
lation reactions provide a favorable six-membered ring.
Although the aryloxide ligand in 17 is cyclometalated,
the compound does nevertheless contain the desired C,
N, and O donors along with an iodide for further
elaboration. Preliminary reactivity studies indicate that
17 is readily reduced by sodium amalgam in THF to
give a persistent green color; 2H NMR spectroscopy
indicates that a single NR′Ar-containing species (δ )
ca. 4 ppm) is formed. Future efforts involving 17 will
focus on characterization of the green species which is
possibly an unique three-coordinate Ti(III) complex
supported by a C, N, and O-donor ligand set.
(v) Bis(Am id o) Tita n iu m (III) Com p lexes. In the
section above associated with Scheme 1, we described
a two-step, one-pot sequence terminating at the desired
bis(N-tert-butylanilido) diiodide complex (3), which can
be thought of as an alternative to Cp2MX2 (M ) Ti, Zr;
X ) halogen) group 4 starting materials. In this section
we show that such a compound can be accessed via an
alternative two-step sequence which begins with tita-
nium(III) rather than titanium(IV). The sequence is
analogous to that commonly utilized for the preparation
of Cp*2TiCl2 (Cp* ) η5-C5Me5).
dicyclohexylamide in the presence of TMEDA.51 This
procedure is also successful for the NR′Ar ligand, such
that treatment of TiCl3(THF)3 with 2 equiv of Li(NR′Ar)-
(OEt2) in THF/TMEDA led to the expulsion of 1 equiv
of lithium chloride and to production of ate complex
(ArR′N)2Ti(µ-Cl)2Li(TMEDA) (18) which was obtained
in 80% yield as light green crystals (Scheme 5); ca. 3
equiv of TMEDA of crystallization is present in the
crystals according to NMR integration of an oxidized
sample (see Experimental Section). The green ate
complex reacts rapidly and smoothly with excess chlo-
roform giving titanium(IV) dichloride 19 via formal
atom transfer. Production of dichloride 19 is necessarily
accompanied by elimination of one molecule of lithium
chloride; analytical and spectroscopic data are consis-
tent with the formulation of 19 as depicted in Scheme
5.
Ate complex 20 was generated similarly (Scheme 6)
via treatment of TiCl3(THF)3 with 2 equiv of Li(NRAr)-
(OEt2) in THF/TMEDA and was isolated in 57% yield.
Bright green crystalline 20 is well-behaved in the sense
that it does not retain excess TMEDA of crystallization.
Our interest in 20 was to examine the possibility of
forming a three-coordinate titanium(III) complex bear-
ing one alkyl and two bulky amido ligands. Treatment
of 20 with [(trimethylsilyl)methyl]lithium led to expul-
sion of lithium chloride and to production of green
solutions that turned orange-brown upon warming to
28 °C. NMR examination of the product mixture from
such a reaction indicated production of the titanium-
(IV) dialkyl species Ti(NRAr)2(CH2SiMe3)2, an oily spe-
cies generated independently from Ti(NRAr)2I2 (3) and
Gambarotta and co-workers have shown that the ate
complex (Cy2N)2Ti(µ-Cl)2Li(TMEDA) [Cy ) cyclohexyl]
is produced upon treatment of TiCl3(THF)3 with lithium
(48) Chamberlain, L. R.; Rothwell, I. P.; Huffman, J . C. J . Am. Chem.
Soc. 1986, 108, 1502.
(49) Chamberlain, L.; Keddington, J .; Rothwell, I. P.; Huffman, J .
C. Organometallics 1982, 1, 1538.
(50) Latesky, S. L.; McMullen, A. K.; Rothwell, I. P.; Huffman, J .
C. J . Am. Chem. Soc. 1985, 107, 5981.
(51) Scoles, L.; Minhas, R.; Duchateau, R.; J ubb, J .; Gambarotta,
S. Organometallics 1994, 13, 4978.

3830 Organometallics, Vol. 15, No. 18, 1996
J ohnson et al.
Sch em e 6
2 equiv of LiCH2SiMe3 and characterized spectroscopi-
cally. These results are in line with the findings of
Gambarotta and co-workers who suggested that (Cy2N)2-
Ti(alkyl) species disproportionate to 0.5 equiv (Cy2N)2-
Ti(alkyl)2 and 0.5 equiv “(Cy2N)2Ti”.25 The fate of the
latter titanium(II) fragment is unknown.
(vi) Mon om er ic Tita n iu m (III) Alk yl Com p lex.
Some time ago the preparation and structural charac-
terization of the three-coordinate titanium(III) homo-
leptic alkyl complex Ti(CH[SiMe3]2)3 was described by
Lappert and co-workers.52,53 The existence of this
compound indicates that, at least with the special
carbon donor CH[SiMe3]2, low-coordinate organometallic
complexes of titanium(III) can be stabilized kineti-
cally.52,53 Since we have already shown that structur-
ally characterized Ti(NRAr)3 is a thermally robust
entity, it seemed reasonable to expect that Ti(NRAr)2-
(CH[SiMe3]2) (21) would be accessible. In accord with
this expectation (Scheme 6) we found that treatment of
ate complex 20 with 1 equiv Li(CH[SiMe3]2) led to 21,
which was isolated as green blocks in 72% yield.
Solution magnetic susceptibility measurements on 21
obtained in benzene solution by the method of Evans54,55
gave µeff ) 2.21 µB, significantly higher than 1.73 µB,
the spin-only value for one unpaired electron. The
calculation of µeff employed Pascal’s constants to correct
for diamagnetic contributions to the susceptibility56 but
did not include any correction for temperature-indepen-
dent paramagnetism (TIP). Magnetic susceptibility
measurements on solid 21 were also performed from 5
to 300 K using a SQUID magnetometer.56 The data
(Figure 1) are indicative of a paramagnet, giving an
excellent fit to the Curie-Weiss law over the temper-
ature range measured. From the least-squares fit
F igu r e 1. SQUID magnetic susceptibility data for solid
Ti(NRAr)2(CH[SiMe3]2) (21) from 5 to 300 K fit to the
Curie-Weiss law (µ ) 1.66 µB; see Experimental Section
for details).
displayed in Figure 1 we obtain µeff ) 1.66 µB; this value
was obtained upon inclusion of a parameter correspond-
ing to the sum of all temperature-independent contribu-
tions to the susceptibility (see Experimental Section for
details) and is, therefore, probably more useful than the
value obtained by Evans’ method (vide supra).
Compound 21 was characterized structurally by single-
crystal X-ray diffraction; see Tables 1 and 2 and Figure
2 for selected metrical parameters and an ORTEP
diagram. Overall, the most striking aspect of the
structure is that one of the NRAr ligands adopts an η3
bonding mode involving the nitrogen atom, the aryl ipso
carbon, and one of the aryl ortho carbons. We have
observed this bonding mode previously in the case of
Ti(NRAr)3. For Ti(NRAr)3, however, two of the three
NRAr ligands engage in η3 bonding, a situation remi-
niscent of the η3 bonding mode known for certain benzyl
complexes. Given the arrangement of ligands in 21, the
complex can be regarded as an 11e complex, or as a 13e
complex if an R-agostic interaction is invoked for the
relatively planarized CH[SiMe3]2 ligand. We have no
data indicating the presence of an R-agostic interaction
for this complex. The η1-NRAr ligand can be regarded
as an anionic 4e donor (1σ + 1π), while the η3-NRAr
(52) Barker, G. K.; Lappert, M. F.; Howard, J . A. K. J . Chem. Soc.,
Dalton Trans. 1978, 734.
(53) Barker, G. K.; Lappert, M. F. J . Organomet. Chem. 1974, 76,
C45.
(54) Sur, S. K. J . Magn. Reson. 1989, 82, 169.
(55) Evans, D. F. J . Chem. Soc. 1959, 2003.
(56) Kahn, O. Molecular Magnetism; VCH: New York, 1993.

Ti Complex Stabilization by Amido Ligation
Organometallics, Vol. 15, No. 18, 1996 3831
experiments were disappointing in that, according to
NMR spectroscopy of crude reaction mixtures, multiple
products resulted. Seeking to temper the reactivity of
21 we examined its behavior in the presence of nitriles.
This led to the discovery (Scheme 6) that benzonitrile
reacts rapidly with 21 (ether, -35 °C), giving a color
change to deep blue, presumably corresponding to
formation of adduct 22. Upon warming and stirring for
17 h at 28 °C, an orange crystalline material formulated
as (µ-NCPhCPhN)[Ti(NRAr)2(CH[SiMe3]2)]2 (23) pre-
cipitated in 82% yield. Formulation of 23 as a nitrile-
coupled product is in line with previous examples of
such coupling modes mediated by titanium(III) and is
consistent with NMR spectroscopic data for the complex.
Addition of excess pivalonitrile to dark green 21
(pentane, 28 °C) induced a color change to light green,
presumably corresponding to adduct 24. Subsequent
addition of trimethylsilyl azide gave an orange-yellow
solution from which an orange powder consisting of
azide 25 was obtained in 37% yield. NMR spectroscopy
of the crude reaction mixture suggested that azide 25
had formed in good yield; the low isolated yield we
attribute to inefficient isolation. Azide 25 exhibits a
characteristic ν(N3) at 2107 cm-1 in its infrared spec-
trum.60 In its 1H NMR spectrum, diamagnetic 25
exhibits a single SiMe3 resonance, which we attribute
to the bis(trimethylsilyl)methyl ligand on the basis of
its relative integral. Azide 25 arises formally from N3
radical abstraction from trimethylsilyl azide by 21.
Abstraction of the N3 radical from hindered orga-
noazides by decamethylvanadocene has been noted
previously.61
F igu r e 2. ORTEP drawing of Ti(NRAr)2(CH[SiMe3]2) (21)
with ellipsoids at the 35% probability level.
Ta ble 1. Selected Bon d Len gth s (Å) for
Ti(NRAr )2(CH[SiMe3]2) (21)
Ti-N1
1.917(5)
2.137(7)
2.440(8)
1.493(8)
1.506(8)
1.427(9)
1.35(1)
Ti-N2
1.962(5)
2.407(7)
1.862(8)
1.363(9)
1.376(9)
1.440(9)
1.39(1)
Ti-C1
Ti-C21
Si1-C1
Ti-C26
N1-C17
N2-C27
C21-C22
C22-C23
C23-C24
N2-C21
C24-C25
C21-C26
C25-C26
Con clu d in g Rem a r k s
In this paper we have reported on the synthesis of a
variety of titanium(III) and -(IV) complexes bearing
novel N-(tert-hydrocarbyl)anilide ligands, a class of
ligands which we are developing for a myriad of ap-
plications. Herein we have shown that the reactivity
of complexes supported by N-(tert-hydrocarbyl)anilide
ligation can be altered profoundly via ortho-fluorine
substitution or via variation of the hydrocarbyl sub-
stituent; consider the contrasting reactions of 2, 6, 10,
13, and 16 with methyl iodide. The work presented
herein lays the groundwork for the preparation of new
organometallic complexes of titanium(III) and -(IV) as
exemplified by the preparation of complexes 21, 6, 7,
and 15-17. Synthetic strategies involving titanium-
(IV) can be controlled by the use of dimethylamido
ligands as protecting groups, as we have reported
previously43 and expanded upon herein. Synthetic
strategies starting with titanium(III) utilize ate com-
plexes, such as 18 and 20, as pivotal precursors.
1.41(1)
Ta ble 2. Selected Bon d An gles (d eg) for
Ti(NRAr )2(CH[SiMe3]2) (21)
N1-Ti-N2
121.7(2)
116.3(2)
107.3(2)
110.8(3)
117.0(3)
34.5(2)
135.5(2)
115.4(3)
34.5(2)
136.4(5)
71.5(4)
117.9(4)
114.4(6)
120.1(7)
Ti-N2-C27
C21-N2-C27
Ti-C1-Si1
143.8(5)
123.5(6)
118.8(4)
114.7(4)
103.4(4)
63.6(2)
138.9(4)
90.9(4)
54.6(3)
N1-Ti-C1
N1-Ti-C21
N1-Ti-C26
N2-Ti-C1
Ti-C1-Si2
Ti-N1-C11
N2-Ti-C26
Ti-N1-C17
Ti-N2-C21
Ti-C21-N2
Ti-C21-C26
Ti-C26-C25
C11-N1-C17
N2-C21-C22
C22-C21-C26
N2-Ti-C21
C1-Ti-C21
C1-Ti-C26
C21-Ti-C26
Ti-C21-C22
Ti-C26-C21
Si1-C1-Si2
N2-C21-C26
C21-C26-C25
74.0(4)
134.4(5)
116.7(5)
129.0(7)
116.0(7)
ligand is also probably best regarded as an anionic 4e
donor because its N atom is somewhat pyramidalized
and thus it probably cannot donate strongly to titanium
in the π sense. The η3-NRAr ligand can, however,
donate 2e from the CdC π system that interacts with
the Ti center, an interaction expected to disrupt the
aromaticity of the aryl substituent. CsC bond length
alternation is accordingly observed (Table 1) for the
interacting aryl ring, as was the case for the η3-NRAr
ligands in Ti(NRAr)3. The TisC bond length in 21 is
in a range typical of titanium(III) alkyl complexes.57-59
We decided initially to probe the reactivity of 21, with
organoazides. These, as we have shown recently, may
sometimes serve as nitrogen atom donors. Initial
Exp er im en ta l Section
Anhydrous diethyl ether, tetrahydrofuran, and toluene were
purchased from Mallinckrodt; 1,2-dimethoxyethane was ob-
(57) Davies, C. E.; Gardiner, I. M.; Green, J . C.; Green, M. L. H.;
Grebenik, P. D.; Mtetwa, V. S. B.; Prout, K. J . Chem. Soc., Dalton
Trans. 1985, 669.
(58) Luinstra, G. A.; Teuben, J . H. J . Organomet. Chem. 1991, 420,
337.
(59) Hagadorn, J . R.; Arnold, J . J . Am. Chem. Soc. 1996, 118, 893.
(60) Nakamoto, K. Infrared and Raman Spectra of Inorganic and
Coordination Compounds, 3rd ed.; Wiley: New York, 1978.
(61) Osborne, J . H.; Rheingold, A. L.; Trogler, W. C. J . Am. Chem.
Soc. 1985, 107, 7945.

3832 Organometallics, Vol. 15, No. 18, 1996
J ohnson et al.
tained from Fisher Scientific; benzene was purchased from J .
T. Baker; n-pentane and n-hexane were purchased from EM
Science. The ethereal solvents (diethyl ether, tetrahydrofuran,
1,2-dimethoxyethane) were distilled, under nitrogen, from
purple sodium benzophenone ketyl. The aliphatic hydrocar-
bons and benzene were distilled, under nitrogen, from very
dark blue to purple sodium benzophenone ketyl solubilized
with a small quantity of tetraglyme. Toluene was refluxed
over molten sodium for at least 2 days and then distilled under
nitrogen. Chloroform was refluxed over potassium carbonate
for at least 2 days before being distilled under nitrogen.
Distilled solvents were transferred under vacuum into bombs
before being pumped into a Vacuum Atmospheres drybox.
Benzene-d6 was degassed and dried over blue sodium ben-
zophenone ketyl and transferred under vacuum into a storage
vessel. Chloroform-d was degassed and dried over 4 Å sieves.
Tetramethylethylenediamine (TMEDA), methyl iodide, and
trimethylacetonitrile were degassed and distilled from calcium
hydride. 2,6-Diisopropylphenol was degassed and distilled.
2,6-Di-tert-butylphenol was crystallized from diethyl ether.
Sieves of 4 Å and alumina were dried in vacuo overnight at a
temperature above 150 °C. TiCl3(THF)3,62,63 TiCl(NMe2)3 (8),46
TiCl2(NMe2)2 (1),46 LiCH(SiMe3)2,64 (CD3)2CdNAr,47 HNRAr,47
HNRArF,65 Li(NRAr)(OEt2),47 and Li(NRArF)(OEt2)65 were
prepared by standard procedures. Other chemicals were used
as received. Magnetic susceptibilities were measured by the
method of Evans.54,55 1H and 13C NMR spectra were recorded
on Varian XL-300, Varian Unity-300, or Brucker AC-250
spectrometers. Chemical shifts are reported with respect to
internal solvent (7.15 and 128.0 ppm for 1H and 13C NMR
spectra, respectively, taken in benzene-d6). 2H NMR chemical
shifts are reported with respect to external C6D6 (taken as 7.15
ppm). EPR spectra were recorded on a Brucker ESP 300
spectrometer in sealed quartz tubes in toluene at either
ambient temperature or low temperature by using a liquid
nitrogen cooled nitrogen stream. Spectra were simulated
using the program EPR-SIM. CHN analyses were performed
by Oneida Research Services, Whitesboro, NY. Melting points
were obtained in sealed glass capillaries and are uncorrected.
HNR′Ar . (CD3)2CdNAr (15.4 g, 92.2 mmol) was dissolved
in Et2O (20 mL) and chilled to -35 °C. Phenyllithium (145
mL of a 1.8 M solution in cyclohexane/ether, 261 mmol) was
frozen solid and then was placed at 28 °C to thaw. J ust as it
became possible to stir, the imine solution was added to the
partially-thawed LiPh solution. The reaction mixture was
stirred for 23 h, at which time it was removed from the
glovebox and slowly poured over ∼300 mL ice contained in a
1 L Erlenmeyer flask. The organic layer was separated, and
the aqueous layer was extracted with petroleum ether (∼200
mL). The organic layer was filtered through a column of
alumina (2 × 25 cm), and the solvent was removed in vacuo
leaving a thick brown oil (16.75 g, 68.3 mmol, 74%). 1H NMR
(300 MHz, CDCl3): δ 7.50 (d, 2H), 7.32 (t, 2H), 7.20 (m, 1H),
6.25 (s, 1H, para), 5.98 (s, 2H, ortho), 3.92 (s, 1H, NH), 2.10
(s, 6H, ArMe).
Com p ou n d 4: Ti(NRAr F )2(NMe2)2. A solution of Li-
(NRArF)(OEt2) (3.00 g, 11.24 mmol) in ether (20 mL) at -30
°C was added to a stirring slurry of Ti(NMe2)2Cl2 (1.16 g, 5.61
mmol) in ether (40 mL) at -30 °C. The solution rapidly
changed from brown-red to yellow with a large amount of white
precipitate. The reaction was stirred for 14 h at 30 °C.
Lithium chloride was removed by filtration through glass
fibers to give a dark yellow filtrate, which was evaporated in
vacuo and reconstituted in pentane (15 mL). Very large
yellow-orange crystals of 4 were collected in two crops (2.20
g, 4.33 mmol, 77.2%; mp 127-129 °C). 1H NMR (300 MHz,
C6D6): δ 6.98 (d, 1H, Ar), 6.90 (dd, 1H, Ar), 6.65 (m, 1H, Ar),
3.075 (br s, 6H, NMe2), 2.220 (s, 3H, ArMe), 1.068 (s, 3H, NC-
(CD3)2CH3). 13C NMR (75 MHz, CDCl3): δ 158.252 (d, J CF
)
)
2
239 Hz, C1), 138.297 (d, J CF ) 12.9 Hz, C2), 134.16 (d, J CH
159 Hz, C6 or C4), 131.640 (s, C5), 125.343 (d, J CH ) 158.9,
C4 or C6), 114.902 (dd, J CF ) 23.4 Hz, J CH ) 160.1 Hz, C3),
60.796 (s, NC(CD3)2CH3), 45.146 (q, J ) 131 Hz, NMe2), 29.797
(q, J ) 125.1 Hz, NC(CD3)2CH3), 29.3 (m, CD3), 20.855 (q, J )
126.3, ArMe). Anal. Calcd for C26H30D12N4F2Ti: C, 61.40; H,
8.32; N, 11.02. Found C, 61.76; H, 8.73; N, 11.06.
Com p ou n d 5: Ti(NRAr F )2(NMe2)(I). To a stirring yellow
solution of Ti(NRArF)2(NMe2)2 (4, 1.91 g, 3.76 mmol) in THF
(40 mL) was added MeI (5.63 g, 39.6 mmol). The reaction
mixture slowly changed to a bright cherry red over 18 h. 1H
NMR was used to determine the extent of reaction by monitor-
ing the disappearance of the dimethylamido peak at 3.075
ppm. The THF was removed in vacuo, and the red solids
remaining were reconstituted in ether (10 mL). [NMe4]I was
removed by filtration through glass fibers, and the red solution
was concentrated to a minimum amount. Two crops of crystals
were collected and combined (5, 1.58 g, 2.67 mmol, 71%; mp
115-118 °C). 1H NMR (300 MHz, C6D6): δ 6.933 (m, 1H, Ar),
6.830 (dd, 1H, Ar), 6.637 (m, 1H, Ar), 3.057 (s, 6H, NMe2),
2.057 (s, 6H, ArMe), 1.392 (s, 6H, NC(CD3)2CH3). 13C NMR
2
(75 MHz, C6D6): δ 132.59 (s, para), 115.93 (d, J CF ) 23.2 Hz,
ipso), ortho and meta broadened into base line, 63.62 (s,
NC(CD3)2CH3), 49.00 (s, NMe2), 30.106 (s, C(CD3)2CH3), 29.589
(m, C(CD3)2CH3), 20.652 (s, ArMe). Anal. Calcd for C24H24
12F2N3ITi: C, 48.74; H, 6.14; N, 7.10. Found: C, 48.98; H,
6.44; N, 6.98.
-
D
Com pou n d 6: Ti(NRAr F)2(NMe2)(CH2SiMe3). Ti(NRArF)2-
(NMe2)(I) (5, 0.5011 g, 0.8473 mmol) was dissolved in pentane
(25 mL), and the solution was cooled to -30 °C. LiCH2SiMe3
(0.85 mL, 1 M in pentane, 0.85 mmol) was added dropwise to
the stirring solution. Precipitation of LiI with a concomitant
color change to yellow-orange was observed over 3 h. LiI was
removed by filtration through a medium frit. Volatile matter
was removed from the filtrate in vacuo, and the resulting dark
yellow oil was lyophilized with benzene (4 mL) providing a
solid which was recrystallized from pentane (2 mL). Mustard
yellow sheets were collected in two crops (6, 0.33 g, 0.60 mmol,
70%; mp 68-71 °C). 1H NMR (250 MHz, C6D6): δ 6.92 (m,
1H, Ar), 6.87 (d, 1H, Ar), 6.65 (m, 1H, Ar), 3.08 (s, 6H, NMe2),
2.12 (s, 6H, ArMe), 1.31 (s, 6H, NC(CD3)2CH3), 1.19 (s, 2H,
CH2SiMe3), 0.11 (s, 9H, Si(CH3)3). 13C NMR (75 MHz, C6D6):
δ 157.934 (d, J CF ) 242.4 Hz, C2), 135.863, 134.098, 132.502,
127.214, 115.894, 61.587 (s, NC(CD3)2CH3 or CH2SiMe3),
61.521 (s, NC(CD3)2CH3 or CH2SiMe3), 46.563 (s, NMe2), 30.262
(s, NC(CD3)2CH3), 29.75 (m, NC(CD3)2CH3), 20.769 (s, ArMe),
3.408 (s, SiMe3). Anal. Calcd for C28H35D12N3F2SiTi: C, 60.95;
H, 8.59; N, 7.62. Found: C, 61.18; H, 8.53; N, 7.37.
Li(NR′Ar )(OEt2). HNR′Ar (16.75 g, 68.25 mmol) was
dissolved in pentane (60 mL), and the solution was chilled to
-35 °C. n-Butyllithium (47 mL of a 1.6 M solution in hexanes,
75.7 mmol) was added via pipet as the solution was stirred. A
thick brown oil precipitated 20 min after the addition. Addi-
tion of Et2O (5.50 g, 74.3 mmol) elicited the formation of a
white precipitate which was collected on a frit and dried in
vacuo (9.24 g, 28.45 mmol, 42%). 1H NMR (300 MHz, C6D6):
δ 7.6 (br s, 2H), 7.15 (br s, 2H), 7.05 (s, 1H), 6.38 (br s, 2H),
5.95 (br s, 1H), 3.10 (q, 4H, O(CH2CH3)2), 2.05 (br s, 6H, ArMe),
0.94 (t, 6H, O(CH2CH3)2).
Com p ou n d 11: Ti(NRAr )(I)2(OAr ′). TiCl(NMe2)3 (1.64 g,
7.63 mmol) was dissolved in Et2O (40 mL) and chilled to -35
°C. Li(NRAr)(OEt2) (2.00 g, 7.60 mmol) was added as a solid,
causing a color change to greenish brown in about 30 s. After
3 h, LiCl was removed by filtration and the solvent was
removed from the filtrate in vacuo, yielding a thin dark brown
(62) Handlovicˇ, M.; Miklosˇ, D.; Zikmund, M. Acta Crystallogr. 1981,
B37, 811.
(63) Manzer, L. E. Inorg. Synth. 1982, 21, 135.
(64) Davidson, P. J .; Harris, D. H.; Lappert, M. F. J . Chem. Soc.,
Dalton Trans. 1976, 2268.
1
oil (9, 2.81 g) which was judged to be ∼95% pure by H NMR
(300 MHz, CDCl3): δ 6.66 (s, 1H, para), 6.58 (s, 2H, ortho),
2.91 (s, 18H, NMe2), 2.28 (s, 6H, ArMe), 1.16 (s, 3H, NC-
(CD3)2CH3). The oil was dissolved in fresh Et2O (5 mL). To
(65) Stokes, S. L.; Cummins, C. C. Manuscript in preparation.

Ti Complex Stabilization by Amido Ligation
Organometallics, Vol. 15, No. 18, 1996 3833
the solution was added a solution of 2,6-diisopropylphenol (1.35
g, 7.58 mmol) in Et2O (5 mL). The resulting solution was
stirred for 18 h, and then the solvent was removed in vacuo,
yielding a thick dark brown oil (10, 4.29 g) which was judged
to be ∼95% pure by 1H NMR (250 MHz, CDCl3): δ 7.02 (d,
2H, OAr′ meta), 6.8 (t, 1H, OAr′ para), 6.68 (s, 1H, para), 6.59
(s, 2H, ortho), 3.45 (sep, 2H, CH(CH3)2), 3.04 (s, 12H, NMe2),
2.25 (s, 6H, ArMe), 1.19 (m, 15H, NC(CD3)2CH3 and CH(CH3)2).
The crude 10 was dissolved in THF (50 mL) at 30 °C. Methyl
iodide (10.70 g, 75.4 mmol) was added, and the reaction
mixture was stirred for 9 h. The reaction mixture gradually
turned from dark brown to a blood-red color. THF was
removed in vacuo, and the resulting solids were triturated
three times with hexane. [NMe4]I was removed by filtration,
volatile matter was removed in vacuo, and the resulting solid
residue was recrystallized from ether to give bright red/purple
faceted crystals. Second and third crops were collected from
pentane as dark red crystals (11, 3.28 g, 4.96 mmol, 65%
overall; mp 130-134 °C). 1H NMR (300 MHz, CDCl3): δ 7.21
(br s, 1H, Aryl), 7.09 (br s, 2H, Aryl), 7.08 (s, 2H, Aryl), 7.07
(s, 1H, Aryl), 3.66 (m, 2H, CH(CH3)2), 2.38 (s, 6H, ArMe), 1.33
(s, 3H, C(CD3)2CH3), 1.27 (d, 12H, CH(CH3)2). 13C NMR (75
MHz, CDCl3): δ 165.33 (s), 139.19 (s), 138.37 (d), 133.33 (d),
132.00 (d), 131.94 (s), 124.04 (d), 123.19 (d), 69.88 (s, NC(CD3)2-
CH3); 29.38 (q, NC(CD3)2CH3), 28.9 (m, NC(CD3)2CH3), 27.19
(d, CH(CH3)2), 23.86 (q, CH(CH3)2), 21.21 (q, ArMe). Anal.
Calcd for C24H29D6NOI2Ti: C, 43.59; H, 5.33; N, 2.12. Found:
C, 43.98; H, 5.47; N, 1.92.
Alk yla tion of 11 w ith LiCH2SiMe3. To a stirring solution
of Ti(NRAr)(I)2(OAr′) (11, 0.3004 g, 0.4545 mmol) in hexane
(10 mL) at -35 °C was added LiCH2SiMe3 (0.0428 g, 0.4546
mmol) in hexane (5 mL). The solution rapidly turned orange
with the formation of a white precipitate. The reaction
mixture was stirred for 20 min, at which time it was filtered.
The filtrate was concentrated to a minimum volume. Micro-
crystals of Ti(NRAr)(I)(OAr′)(CH2SiMe3) were obtained in low
yield, though 1H NMR spectroscopy indicated quantitative
reaction. 1H NMR (250 MHz, CDCl3): δ 7.1 (m, 6H, aryls),
3.72 (septet, 2H, CH(CH3)2), 2.39 (s, 6H, ArMe), 2.24 (d, 1H,
CHaHbSiMe3), 1.38 (d, 6H, CH(CH3)2), 1.22 (m, 7H, CHaHb-
SiMe3 and CH(CH3)2), 1.10 (s, 3H, C(CD3)2CH3), -0.09 (s, 9H,
SiMe3).
Alk yla tion of 11 w ith LiCH2CMe2P h . Ti(NRAr)(I)2(OAr′)
(11, 1.04 g, 1.57 mmol) was dissolved in hexane (25 mL) and
chilled to -30 °C. Lithium neophyl (0.2205 g, 1.573 mmol)
was added, causing a rapid color change to a light red-brown.
After 15 min of stirring, LiI was removed as a grey solid by
filtration of the mixture through a sintered glass frit. The
filtrate was concentrated to dryness in vacuo, leaving a thick
orange-red oil. The oil was lyophilized (benzene) and subse-
quently crystallized from pentane to give red-orange waxy
crystals of Ti(NRAr)(I)(OAr′)(CH2CMe2Ph) (0.5161 g, 49.3%;
mp 75-77 °C). 1H NMR (300 MHz, CDCl3): δ 7.3 (br s, 1H,
ortho), 7.05 (m, 9H, aryls), 6.7 (br s, 1H, ortho), 3.82 (sep, 2H,
CH(CH3)2), 2.41 (br s, 6H, ArMe), 2.35 (d, 1H, CHaHbC(CH3)2-
Ph), 2.07 (d, 1H, CHaHbC(CH3)2Ph), 1.36 (d, 6H, CH(CH3)2),
1.32 (s, 3H, CHaHbC(CH3)2Ph), 1.24 (s, 3H, CHaHbC(CH3)2-
Ph), 1.09 (s, 3H, C(CD3)2CH3).
Com p ou n d 12: Ti(NR′Ar )(NMe2)3. TiCl(NMe2)3 (1.50 g,
6.97 mmol) was dissolved in THF (50 mL) and chilled to -35
°C. Li(NR′Ar)(OEt2) (2.27 g, 6.98 mmol) was added as a
powder. The solution changed color rapidly from brown to a
darker, green-brown. The reaction mixture was stirred for 12
h, and then the solvent was removed in vacuo. The mixture
was reconstituted using pentane (∼50 mL) and filtered through
a frit, giving a yellow-brown filtrate from which volatile
material was removed in vacuo, leaving a thin oil. Lyophiliza-
tion twice from benzene to remove residual THF, followed by
recrystallization from pentane (8 mL), afforded a green-brown
powder (12, 2.445 g, 5.76 mmol, 82.6%; mp 32.5-33.5 °C). 1H
NMR (300 MHz, CDCl3): δ 7.21 (d, 2H), 7.06 (t, 2H), 6.95 (t,
1H), 6.29 (s, 1H), 5.96 (s, 2H), 2.77 (s, 18H, NMe2), 1.88 (s,
6H, ArMe). 13C NMR (75 MHz, CDCl3): δ 151.056, 148.716,
136.578, 127.64, 126.44, 125.48, 124.09, 123.57. 45.09, 30.64,
21.46. MS (70 eV): m/z (%) 424 (0.9) [M+]. Anal. Calcd for
C
23H32D6N4Ti: C, 65.08; H, 9.02; N, 13.20. Found: C, 65.29;
H, 9.02; N, 13.17.
Com p ou n d 13: Ti(NR′Ar )(NMe2)2(OAr ′′). Ti(NR′Ar)-
(NMe2)3 (12, 1.4274 g, 3.3622 mmol) was dissolved in Et2O (20
mL), and the solution was cooled to -35 °C in a round bottom
flask. 2,6-Di-tert-butylphenol (0.6937 g, 3.362 mmol) was
dissolved in Et2O (10 mL), cooled to -35 °C and then added
to the solution. The green-brown reaction mixture changed
to a reddish orange color after 3 h. 1H NMR spectroscopy at
this point revealed the presence of a considerable amount of
unreacted 12. After 19.5 h reaction time, the solvent was
removed in vacuo to give a bright cherry-red foam. The foam
was redissolved in pentane (ca. 3 mL), resulting in crystal-
lization of the desired product as an orange powder at room
temperature. A second crop of powder resulted upon cooling
a concentrated solution for several days at -35 °C (13, 1.626
g, 2.776 mmol, 82.6%; mp 130-131 °C). 1H NMR (300 MHz,
CDCl3): δ 7.593 (d, 2H, J ) 7.58 Hz), 7.3450 (t, 2H, J ) 7.56
Hz), 7.25 (t, 3H, J ) 7.8 Hz), 6.799 (t, 1H, J ) 7.8 Hz), 6.5057
(s, 1H, para), 6.4372 (s, 2H, ortho), 3.0153 (s, 12H, NMe2),
1.9116 (s, 6H, ArMe), 1.4842 (s, 18H, C(CH3)3)). 13C NMR (75
MHz, CDCl3): δ 164.565 (s), 150.438 (s), 146.383 (s), 140.229
(s), 138.920 (s), 127.922 (d), 126.513 (d), 125.745 (d), 125.254
(d), 124.379 (d), 120.755 (d), 119.236 (d), 65.8920 (s, NC-
(CD3)2C6H5), 47.9519 (q, NMe2), 35.4817 (s, C(CH3)3), 31.6 (m,
CD3), 31.0918 (q, C(CH3)3), 21.5033 (q, ArMe). MS (70 eV):
m/z (%) 585 (0.5) [M+]. Anal. Calcd for C35H47D6N3OTi: C,
71.77; H, 9.12; N, 7.17. Found: C, 72.25; H, 8.94; N, 6.75.
Com p ou n d 14: Ti(NR′Ar )(NMe2)(OAr ′′)(I). Ti(NR′Ar)-
(NMe2)2(OAr′′) (13, 0.7363 g, 1.257 mmol) was dissolved in
Et2O (45 mL), and the solution was cooled to -35 °C in a round
bottom flask. Methyl iodide (1.92 g, 13.5 mmol) was added,
the flask was stoppered, and the reaction mixture was stirred
overnight. Monitoring by 1H NMR spectroscopy indicated
almost no conversion to product at that point in time. It was
thought that MeI was escaping from the stoppered flask. The
reaction mixture was transferred to a glass bomb, additional
MeI was added, and the reaction mixture was stirred (and
monitored by 1H NMR) for 48 h. A large amount of white
precipitate formed, but there was no noticeable color change.
The solvent was then removed in vacuo, the product was
extracted with pentane, and Me4NI was removed with a
medium frit. The solution was concentrated down to about 4
mL, when small microcrystals became apparent in the solu-
tion. Cooling overnight at -35 °C yielded a cake of orange
microcrystalline powder (14, 0.7952 g, 1.189 mmol, 94.6 %;
mp 57-59 °C). 1H NMR (300 MHz, CDCl3): δ 7.4 (tm, J ∼
5.4 Hz, 2H), 7.331 (d, J ) 7.8 Hz, 2H), 7.237 (dm, J ∼ 4.2 Hz,
3H), 6.912 (t, J ) 7.8 Hz, 1H), 6.850 (s, 1H, para), 6.408 (s,
2H, ortho), 2.859 (s, 6H, NMe2), 2.180 (s, 6H, ArMe), 1.620 (s,
18H, C(CH3)3). 13C NMR (75 MHz, CDCl3): δ 165.424,
144.226, 142.433, 138.998, 137.546, 129.049, 128.891, 127.820,
127.145, 126.979, 125.765, 120.894, 68.955 (NC(CD3)2C6H5),
49.836 (NMe2), 35.730 (C(CH3)3), 32.414 (C(CH3)3), 31.0 (CD3),
21.101 (ArMe). MS (70 eV): m/z (%) 667.9 (0.19) [M+]. Anal.
Calcd for C33H41D6IN2OTi: C, 59.29; H, 7.09; N, 4.19. Found:
C, 58.98; H, 7.34; N, 3.88.
Com p ou n d 17: Ti(NR′Ar )(O-2,6-C6H3[tBu ][CMe2CH2])-
(I). A solution of 14 (1.3206 g, 1.9752 mmol) in pentane (40
mL) was chilled to -40 °C. Neopentyllithium (0.1543 g, 1.9761
mmol) was added as a solution in ether. The reaction mixture
changed from red to yellow over ca. 5 min. The solution was
stirred 18 h, and the yellow-brown solution was then filtered
to remove lithium iodide. A proton NMR spectrum of the crude
product indicated a relatively clean conversion to the desired
neopentyl complex 15, but attempts to crystallize this species
proved futile. The ether was removed in vacuo, and THF (40
mL) was added. The mixture was heated at 65 °C for 2 h. A
proton NMR spectrum of an aliquot taken at this time

3834 Organometallics, Vol. 15, No. 18, 1996
J ohnson et al.
indicated ca. 50% conversion to the cyclometalated dimethyl-
amide compound 16. Further heating at 65 °C resulted in
clean production of 16. THF was removed in vacuo, and ether
(60 mL) and MeI (2.90 g, 20.4 mmol, 10.3 equiv) were added.
No reaction occurred at room temperature according to the
1H NMR spectrum of an aliquot, so the mixture was heated to
70 °C for 21 h. Precipitate was observed, but no color change
a red solution.
A
1H NMR spectrum of the solution was
consistent with clean formation of Ti(NRAr)2Cl2. 1H NMR (250
MHz, CDCl3): δ 6.877 (s, 2H, para), 6.363 (s, 4H, ortho), 2.262
(s, 12H, ArMe), 1.263 (s, 6H, C(CD3)2CH3), 2.389 (s, 4H,
TMEDA methylene), 2.20 (s, 12H, TMEDA methyl).
Com p ou n d 21: Ti(NRAr )2(CH[SiMe3]2). A solution of 20
(1.1385 g, 1.8770 mmol) in pentane (50 mL) was cooled to -35
°C prior to treatment with LiCH(SiMe3)2 (0.3123 g, 1.877
mmol), which was added as a solid. The reaction mixture
adopted a dark green color. The reaction mixture was stirred
for 15 min and then filtered to remove LiCl (0.1348 g, 3.186
mmol, 1.7 equiv). The dark green filtrate was concentrated
to ca. 20 mL and stored at -35 °C. Dark green blocklike
crystals were obtained in two crops (21, 0.7755 g, 1.356 mmol,
72.3%; mp 134-135 °C). 2H NMR (46 MHz, C6H6): δ 3.968;
∆ν1/2 17.9 Hz. µeff (300 MHz, C6D6, 25 °C) ) 2.21 µB. UV-vis
(ether): λmax (ꢀ) ) 663 nm (407 M-1 cm-1). EPR (298 K,
1
was evident. The H NMR spectrum of an aliquot showed no
resonance attributable to a dimethylamide function. The
solvent was removed from the mixture in vacuo. The solid
residue thus obtained was extracted with pentane, [Me4N]I
was removed by filtration from the extract, and the filtrate
was concentrated. Crystals were obtained after storing the
filtrate overnight at -35 °C (17, 0.7668 g, 1.230 mmol, 62.3%;
mp 102-103 °C). 1H NMR (300 MHz, CDCl3): δ 7.78 (d, J )
7.59 Hz, 2H), 7.393 (t, J ) 7.04 Hz, 2H), 7.295 (t, J ) 6.7 Hz,
1H), 7.174 (d, J ) 7.71 Hz, 1H), 7.0235 (d, J ) 7.71 Hz, 1H),
6.90 (s, 1H, para), 6.879 (t, J ∼ 10 Hz, 1H), 6.708 (s, 2H, ortho),
2.202 (s, 6H, ArMe), 1.470 (d, J ) 11.7 Hz, 1H, CH2-a), 1.320
(s, 9H, C(CH3)3), 0.9836 (s, 6H, C(CH3)2Ar), 0.833 (d, J ) 11.7
Hz, CH2-b). 13C NMR (125 MHz, CDCl3): δ 162.818, 146.038,
143.338, 139.764, 139.345, 136.051, 130.326, 129.281, 127.914,
126.766, 124.759, 124.577, 122.270, 122.070, 65.842, 46.410,
35.304, 32.578, 32.046, 30.603, 28.2, 25.455, 21.202. 15.259.
Anal. Calcd for C31H34D6INOTi: C, 59.72; H, 6.47; N, 2.25.
Found: C, 60.19; H, 6.98; N, 1.92.
toluene): g ) 1.95. EPR (95 K, toluene): g1 ) 1.997; g2
1.962; g3 ) 1.918. Anal. Calcd for C31H43D12N2Si2Ti: C, 65.10;
H, 9.69; N, 4.90. Found: C, 65.36; H, 9.76; N, 4.67.
)
SQUID Ma gn etic Mea su r em en ts on Ti(NRAr )2(CH-
[SiMe3]2) (21). Measurements were made using a Quantum
Design SQUID magnetometer. The magnetometer uses the
MPMSR2 software (Magnetic Property Measurement System
Revision 2). Data were recorded at a field strength of 5000
G. Gel caps (Gelatin Capsule No. 4 Clear), and straws were
ordered from Quantum Design, Inc. Samples of 21 for
magnetic measurements were prepared in the drybox as
described above. The solid compound was placed into a
preweighed gel cap, and a preweighed plug of Parafilm was
inserted above it to keep it in place. The mass of the 21 sample
was then ascertained by weighing the loaded gel cap. The
loaded gel cap was mounted in a straw, and the straw was
placed in an N2-filled vessel for transport to the magnetometer.
The straw was placed on the end of a rod for insertion into
the magnetometer. The field and temperature were adjusted
to 5000 G and 5 K, respectively. Once the temperature had
equilibrated and the field was stable, the sample was centered.
This was done by running a full length DC scan, adjusting
the position automatically and then recentering using a DC
centering scan. During the run, measurements were taken
over the following temperature ranges with the indicated
increments: 5-10 K (one data point every 1 K), 12-20 K (one
data point every 2 K), 23-50 (one data point every 3 K), 55-
100 (one data point every 5 K), 110-200 (one data point every
10 K), 220-300 (one data point every 20 K). The run required
approximately 5 h.
The data for 21 fit the Curie-Weiss law in the temperature
range 5-300 K (R ) 0.999 99). The calculated curve (Figure
1) is the best least-squares fit of the observed susceptiblity
data to the equation øΜ(obs) ) ((µ2)/(7.997584(T - θ))) - C.
The value of µ obtained in this manner was 1.66 µB, to be
compared with the spin-only value for one unpaired electron,
1.73 µB. In the least-squares fit, carried out using the general
curve-fitting routine included with the program Kaleidagraph,
both θ and C were treated as variable parameters. The
obtained value of θ, the Weiss constant, was -0.194 74 K. The
value of the constant C, included to represent the sum of all
temperature-independent contributions to the total observed
susceptibility, including the diamagnetic correction and TIP,
was -0.000 241 39.
Com p ou n d 19: Ti(NR′Ar )2Cl2. TiCl3(THF)3 (1.00 g, 2.70
mmol) and TMEDA (1.94 g, 16.7 mmol) were added to THF
(100 mL) to form a bright blue solution. Li(NR′Ar)(OEt2) (1.76
g, 5.41 mmol) was added, causing the solution to become olive-
green. The solvent was removed from the mixture in vacuo,
the solid residue was extracted with ether, and the extract
was filtered. Yellow green crystals consisting of ate complex
18 were collected from the concentrated filtrate at -35 °C (2.28
g). A large excess of CDCl3 (1.48 g) was added to an olive-
green ether solution of 18 (0.17 g). The solution turned blood-
red. Integration of the 1H NMR spectrum of an aliquot
indicated the presence of 3 equiv of TMEDA per titanium. The
solvent was removed in vacuo, and the crude product thus
obtained was extracted with benzene. The extract was filtered
through glass fibers and evaporated to dryness yielding a dark
red microcrystalline powder (0.10 g). The red solid was
recrystallized by vapor diffusion of pentane into toluene
1
followed by cold storage overnight; mp 155-160 °C (dec.). H
NMR (300 MHz, CDCl3): δ 7.45 (d, 2H, aryl ortho), 7.28 (m,
4H, aryl meta, para), 6.56 (s, 2H, para), 5.62 (s, 4H, ortho),
1.93 (s, 12H, ArMe). 13C NMR (75 MHz, CDCl3): δ 147.700,
143.119, 137.286, 128.699, 127.812, 126.841 (may be 2 car-
bons), 123.475, 71.2 (NC(CD3)2Ar), 28.7 (CD3), 21.094 (ArMe).
Anal. Calcd for C34H28D12Cl2N2Ti: C, 67.22; H, 6.64; N, 4.61.
Found: C, 67.00; H, 6.69; N, 4.28.
Com p ou n d 20: (Ar R N)2Ti(µ-Cl)2Li(TME DA). TiCl3-
(THF)3 (1.00 g, 2.70 mmol) was slurried in THF (100 mL).
TMEDA (1.92 g, 6.13 eq) was added, generating a blue
solution. A solution of Li(NRAr)(OEt2) (1.43 g, 5.44 mmol) in
THF (50 mL) was added to the TiCl3(THF)3/TMEDA mixture,
causing a rapid color change to bright green. After 5 min, the
shade of green changed to olive. Volatile material was
removed in vacuo, and the residual oil was triturated twice
with pentane. The residue was then extracted with pentane,
and the extract was filtered to remove LiCl. The filtrate was
stored at -30 °C overnight, giving bright green needles (20,
0.93 g, 56.9%; mp 137-138 °C). 2H NMR (46 MHz, C6H6): δ
3.809; ∆ν1/2 ) 18.5 Hz. µeff (300 MHz, C6D6, 25 °C) ) 2.22 µB.
UV-vis (hexane): λmax (ꢀ) 780 nm (188 M-1 cm-1). EPR (298
K, toluene): g ) 1.95. EPR (103 K, toluene): g1 ) 1.980; g2 )
1.964; g3 ) 1.930; this spectrum is approximately axial with
broad linewidths (∼25 G) that merge g1 and g2 into one feature.
Anal. Calcd for C30H40D12Cl2N2LiTi: C, 59.40; H, 8.64; N, 9.24.
Found: C, 58.97; H, 8.44; N, 8.46.
X-r a y Str u ctu r e of Ti(NRAr )2(CH[SiMe3]2) (21).
A
crystal of approximate dimensions 0.50 × 0.23 × 0.20 mm was
obtained from a chilled ether solution. The crystal was
mounted on a glass fiber. Data were collected at -86 °C on
an Enraf-Nonius CAD-4 difractometer with graphite-mono-
chromated Mo KR radiation. A total of 4774 reflections were
collected to a 2θ value of 44.9°, 4446 of which were unique
(Rint ) 0.098); equivalent reflections were merged. The
structure was solved by direct methods. Non-hydrogen atoms
were refined anisotropically, except C26, which was refined
isotropically. The final cycle of least-squares refinement was
Rea ction of 20 w ith Ch lor ofor m . A small amount of
(ArRN)2Ti(µ-Cl)2Li(TMEDA) (20) was added to CDCl3, giving

Ti Complex Stabilization by Amido Ligation
Organometallics, Vol. 15, No. 18, 1996 3835
based on 2735 observed reflections (I > 3.00σ(I)) and 320
13C NMR (75 MHz, CDCl3): δ 146.815 (s, ipso), 137.629 (s,
meta), 128.247 (d, J ) 157.3 Hz), 128.201 (d, J ) 157.4 Hz),
98.1749 (d, J ) 90.85 Hz, CH(SiMe3)2), 63.6716 (s, C(CD3)2-
CH3), 30.3523 (q, J ) 125.9 Hz, C(CD3)2CH3), 29.8439 (m,
C(CD3)2CH3), 21.3200 (q, J ) 126.4 Hz, ArMe), 4.2006 (q, J )
118.2 Hz, SiMe3). IR (16 scans, 2.0 cm-1, THF): ν(Ν3) 2107
variable parameters and converged (largest parameter shift
was 0.01 times its esd) with R ) 0.075 and Rw ) 0.065.
A
final difference Fourier map showed no chemically significant
features. Crystal data are a ) 10.644(2) Å, b ) 10.844(2) Å,
c ) 16.718(4) Å, V ) 1713(2) Å3, R ) 100.48(3)°, â ) 95.86(3)°,
γ ) 113.11(3)°, space group P1h (No. 2), Z ) 2, Mr ) 571.92 for
cm-1
. Anal. Calcd for C31H43D12N5Si2Ti: C, 60.64; H, 9.03;
N, 11.41. Found: C, 60.75; H, 9.07; N, 11.05.
C
31H43D12N2Si2Ti, and F(calcd) ) 1.109 g/cm3. See Tables 1
and 2 and Figure 2 for metrical parameters and an ORTEP
diagram; complete data tables have been deposited as Sup-
porting Information.
Com p ou n d 26: Ti(NRAr )2(CH[SiMe3]2)(I). Ti(NRAr)2-
(CH[SiMe3]2) (21, 0.4034 g, 0.7054 mmol) was dissolved in
benzene (5 mL). Iodine (0.0900 g, 0.3546 mmol, 0.5 equiv) was
slurried in benzene (5 mL), and the slurry was added to the
solution of 21. The reaction mixture adopted a dark orange-
red color. Volatile material was removed from the reaction
mixture in vacuo, giving a light orange powder. Crystals were
obtained from a concentrated ether solution (26, 0.3329 g,
0.4764 mmol, 67.5%; mp 175-176 °C). 1H NMR (300 MHz,
C6D6): δ 6.938 (br d, J ) 71.9 Hz, 4H, ortho), 6.710 (s, 2H,
para), 3.466 (s, 1H, CH(SiMe3)2), 2.184 (s, 12H, ArMe), 1.404
(s, 6H, C(CD3)2CH3), 0.393 (s, 18H, SiMe3). 13C NMR (125
MHz, CDCl3): δ 145.972 (s, ipso), 137.682 and 137.085 (s,
meta), 128.594 and 127.971 (d, ortho and meta), 112.023 (d,
para), 104.010 (d, J ) 90.6 Hz, CH(SiMe3)2), 65.306 (s,
NC(CD3)2CH3), 30.394 (q, NC(CD3)2CH3), 30.074 (m, NC(CD3)2-
CH3), 21.274 (q, ArMe), 5.857 (q, SiMe3). Anal. Calcd for
Com p ou n d 23:
(µ-NCP h CP h N)[Ti(NR Ar )2(CH [Si-
Me3]2)]2. Ti(NRAr)2[CH(SiMe3)2] (21, 0.4257 g, 0.7444 mmol)
was dissolved in ether (20 mL), and the solution was cooled to
-35 °C. Benzonitrile (100 mL, 0.7534 mmol) was added over
approximately 5 min, eliciting a rapid color change to deep
dark blue, a color we attribute to formation of paramagnetic
adduct 22. 2H NMR (46 MHz): δ 4.671, 1.86; ∆ν1/2 ) 20 Hz,
17 Hz. The 1.86 ppm peak, attributable to diamagnetic 23,
emerged noticeably over a 10 min period. After stirring 17 h,
an orange powder which had precipitated was collected on a
frit (23, 0.4212 g, 0.6130 mmol, 82%). The powder was
essentially insoluble in pentane and ether but could be
recrystallized from hot THF; mp 180 °C (dec.). 1H NMR (300
MHz, C6D6): δ 8.039 (br s, 2H, para), 7.28 (m, 8H, ortho/meta),
6.587 (s, 4H, paras), 6.397 (br s, 8H, orthos), 2.159 (s, 24H,
ArMe), 1.439 (s, 2H, CH[SiMe3]2), 1.210 (s, 12H, C(CD3)2CH3),
0.443 (s, 36H, SiMe3). 13C NMR (75 MHz, CDCl3): δ 173.115
(s, CdN), 148.112 (s), 143.462 (s), 135.773 (s), 129.878 (d),
129.441 (d), 128.037 (d), 127.458 (d), 127.140 (d), 77.206 (d,
CH(SiMe3)2), 62.380 (s, C(CD3)2CH3), 30.628 (q, C(CD3)2CH3),
30.065 (m, C(CD3)2CH3), 21.408 (q, ArMe), 6.181 (q, SiMe3).
Anal. Calcd for C76H96D24N6Si4Ti2: C, 67.61; H, 8.96; N, 6.22.
Found: C, 68.05; H, 9.26; N, 6.13.
Com p ou n d 25: Ti(NRAr )2(CH[SiMe3]2)(N3). Ti(NRAr)2-
(CH[SiMe3]2) (21, 0.7124 g, 1.245 mmol) was dissolved in
pentane (40 mL). tert-Butyl nitrile (575 mL, 5.20 mmol, 4
equiv) was added, causing a color change to a light green,
presumably corresponding to adduct 24. Trimethylsilyl azide
(230 mL, 1.733 mmol, 1.4 equiv) was then added, and the
solution was stirred overnight (after about 2 h the solution
had adopted an orange-yellow color). Volatile material was
removed in vacuo, and the waxy solid thus obtained was
recrystallized from pentane to give a light orange powder (25,
0.2852 g, 0.4645 mmol, 37%; mp 147-148 °C (dec. with
bubbling)). 1H NMR (300 MHz, C6D6): δ 6.839 (br s, 4H,
ortho), 6.708 (s, 2H, para), 2.50 (s, 1H, CH(SiMe3)2), 2.213 (s,
12H, ArMe), 1.251 (s, 6H, C(CD3)2CH3), 0.222 (s, 18H, SiMe3).
C
31H43D12IN2Si2Ti: C, 53.28; H, 7.93; N, 4.01. Found: C,
53.66; H, 7.90; N, 3.84.
Ack n ow led gm en t. C.C.C. thanks each of the fol-
lowing for partial support of this work: the National
Science Foundation (CAREER Award CHE-9501992),
DuPont (Young Professor Award), the Packard Founda-
tion (Packard Foundation Fellowship), Union Carbide
(Innovation Recognition Award), and 3M (Innovation
Fund Award). This work made use of MRSEC shared
facilities supported by the National Science Foundation
under Award DMR-9400334. The authors are grateful
to Esther Kim for magnetic measurements made on
compound 21.
Su p p or tin g In for m a tion Ava ila ble: Tables of positional
and thermal equivalent parameters, anisotropic thermal pa-
rameters, intramolecular distances, bond angles, and torsion
angles for Ti(NRAr)2(CH[SiMe3]2) (21) (12 pages). Ordering
information is given on any current masthead page.
OM960315G