Group IV phosphinimide amide complexes

Article abstract of DOI:10.1139/v04-141

Complexes of formula TiCp(NPR₃)(NMe₂)₂ (R = t-Bu 1, Ph 2) were prepared via salt metathesis of TiCp(NPR ₃)Cl₂ with a slight excess of LiNMe₂. The species Ti(NP-t-Bu₃)(NMe₂)₃ (3) was obtained as a by-product. The related derivative ZrCp(NP-t-Bu₃)(NMe ₂)₂ (4) was also prepared. Reaction of TiCp(NP-t-Bu ₃)Cl₂ with LiNHC₆H₃(2,6-i-Pr ₂) afforded TiCp(NP-t-Bu₃)(NHC₆H ₃(2,6-i-Pr₂))Cl (5) and Ti(NP-t- Bu₃)(NHC ₆H₃(2,6-i-Pr₂))₃ (6). In a similar manner, the Zr analogs ZrCp(NP-t-Bu₃)(NHC₆H ₃(2,6-i-Pr₂))Me (7) and ZrCp(NP-t-Bu₃)(NHC ₆H₃(2,6-i-Pr₂))₂ (8) were also prepared. X-ray structural data for compounds 5, 6, and 8 are reported. Reactivity of these phosphinimideamide derivatives was explored. While these species do not yield imide derivatives upon thermolysis, reaction of 5 with excess AlMe₃ afforded TiCp(NP-t-Bu₃)Me₂ while reaction with 1 equiv. of A1Me₃ gave TiCp(NP-t-Bu₃)MeCl (9) and A1₂(m-NHC₆H₃(2,6-i-Pr ₂))2Me₄ (10).

Full text of DOI:10.1139/v04-141

1634
Group IV phosphinimide amide complexes
Emily Hollink, Pingrong Wei, and Douglas W. Stephan
Abstract: Complexes of formula TiCp(NPR3)(NMe2)2 (R = t-Bu 1, Ph 2) were prepared via salt metathesis of
TiCp(NPR3)Cl2 with a slight excess of LiNMe2. The species Ti(NP-t-Bu3)(NMe2)3 (3) was obtained as a by-product.
The related derivative ZrCp(NP-t-Bu3)(NMe2)2 (4) was also prepared. Reaction of TiCp(NP-t-Bu3)Cl2 with
LiNHC6H3(2,6-i-Pr2) afforded TiCp(NP-t-Bu3)(NHC6H3(2,6-i-Pr2))Cl (5) and Ti(NP-t-Bu3)(NHC6H3(2,6-i-Pr2))3 (6). In a
similar manner, the Zr analogs ZrCp(NP-t-Bu3)(NHC6H3(2,6-i-Pr2))Me (7) and ZrCp(NP-t-Bu3)(NHC6H3(2,6-i-Pr2))2 (8)
were also prepared. X-ray structural data for compounds 5, 6, and 8 are reported. Reactivity of these phosphinimide–
amide derivatives was explored. While these species do not yield imide derivatives upon thermolysis, reaction of 5 with
excess AlMe3 afforded TiCp(NP-t-Bu3)Me2 while reaction with 1 equiv. of AlMe3 gave TiCp(NP-t-Bu3)MeCl (9) and
Al2(m-NHC6H3(2,6-i-Pr2))2Me4 (10).
Key words: titanium, zirconium, phosphinimide, amide, ligand metathesis.
Résumé : On a préparé des complexes de formule TiCp(NPR3)(NMe2)2 (R = t-Bu 1, Ph 2) par la métathèse du sel de
TiCp(NPR3)Cl2 avec un léger excès de LiNMe2. On a obtenu l’espèce Ti(NP-t-Bu3)(NMe2)3 (3) comme sous-produit.
On a aussi préparé le dérivé apparenté ZrCp(NP-t-Bu3)(NMe2)2 (4). La réaction du TiCp(NP-t-Bu3)Cl2 avec du
LiNHC6H3(2,6-i-Pr2) conduit à la formation de TiCp(NP-t-Bu3)(NHC6H3(2,6-i-Pr2))Cl (5), et de Ti(NP-t-Bu3)(NHC6H3(2,6-
i-Pr2))3 (6). Opérant de la même façon, on a aussi préparé les analogues ZrCp(NP-t-Bu3)(NHC6H3(2,6-i-Pr2))Me (7) et
ZrCp(NP-t-Bu3)(NHC6H3(2,6-i-Pr2))2 (8). On a déterminé les structures des composés 5, 6 et 8 par diffraction des
rayons X. On a examiné la réactivité de ces dérivés phosphinimide–amides. Alors que la thermolyse de ces espèces ne
conduit pas à des dérivés imides, la réaction de 5 avec un excès de AlMe3 conduit à la formation de TiCp(Np-t-
Bu3)Me2 alors que la réaction avec un équivalent de AlMe3 fournit les composés TiCp(Np-t-Bu3)MeCl (9) et Al2(µ-
NHC6H3(2,6-i-Pr2))2Me4 (10).
Mots clés : titane, zirconium, phosphinimide, amide, métathèse de ligand.
[Traduit par la Rédaction] Hollink et al. 1639
Introduction
the syntheses of phosphinimide–amide complexes. In this
manuscript we describe the syntheses, characterization, and
our initial studies of the reactivity of the group IV
phosphinimide–amide complexes. These systems are com-
pared with the metallocene analogs.
Group IV amide complexes have received enormous atten-
tion because of their remarkable diversity, serving as precur-
sors for imido derivatives (1–5), olefin polymerization
catalysts (6–11), precursors in chemical vapour deposition
processes (12–18), and as hydroamination (pre)catalysts
(19–22). In addition, the propensities of Ti- (23–25) or Zr-
(2, 3, 26, 27) imide complexes to effect C-H activation and
hydroamination (21) are the subject of theoretical (28, 29)
and experimental interest. In our own work, we have demon-
strated that phosphinimide ligands can replace cyclopenta-
dienyl ligand derivatives to give highly active olefin
polymerization catalysts (30–32). Studies of the structure–
reactivity relationship have shown that a range of sterically
demanding phosphinimide ligands provide effective catalysts
(33–38), whereas sterically less-demanding ligands prompt
novel reactivity with Lewis acids including C-H activation
processes (39–41). In an effort to broaden the range of reac-
tivity of group IV phosphinimide complexes, we undertook
Experimental
All syntheses were performed employing an atmosphere
of dry, oxygen-free nitrogen in a Vacuum Atmospheres inert
atmosphere glove box or standard Schlenk techniques using
1
oven-dried (140 °C) glassware unless otherwise stated. H
NMR data were acquired on a Bruker Avance 500 MHz
spectrometer, while 13C and 31P NMR data were obtained
1
from a Bruker Avance 300 MHz spectrometer. H and 13C
chemical shifts are listed relative to SiMe4 in ppm and were
referenced to the residual proton or carbon peak of the sol-
vent. 31P NMR data were referenced using 85% H3PO4 as an
external standard. All NMR spectra were recorded in C6D6
unless otherwise noted. University of Windsor Analytical
Services, using a Perkin Elmer 2400 Series II instrument,
performed the combustion analyses. Despite repeated at-
tempts, carbon analyses for Zr complexes consistently gave
systematically low values as a result of the formation of ZrC
(i.e., incomplete combustion). Reagent grade solvents were
purchased from Aldrich Chemical Co. and were predried us-
ing Grubbs’ column systems, manufactured by Innovative
Received 1 April 2004. Published on the NRC Research Press
Web site at http://canjchem.nrc.ca on 21 December 2004.
E. Hollink, P. Wei, and D.W. Stephan.1 Department of
Chemistry and Biochemistry, University of Windsor, Windsor,
ON N9B 3P4, Canada.
1Corresponding author (e-mail: stephan@uwindsor.ca).
Can. J. Chem. 82: 1634–1639 (2004)
doi: 10.1139/V04-141
© 2004 NRC Canada

Hollink et al.
1635
Technologies, Inc. (42). Deuterated benzene, toluene, and
methylene chloride were purchased from Canadian Isotopes
Laboratories and degassed by at least four freeze–pump–
thaw cycles before storing over 4 Å molecular sieves. The
reagents n-BuLi (2.0 mol L–1 in hexanes), Al2Me6,
TiCp2Cl2, LiNMe2, and NH2C6H3(2,6-i-Pr2) were purchased
from Aldrich Chemical Co. NH2C6H3(2,6-i-Pr2) was vacuum
distilled from KOH, and all other reagents were used with-
out further purification. The compounds Ti(NP-t-Bu3)Cl3
(37) and TiCp(NP-t-Bu3)Cl2 (32) were prepared according to
literature methods, and LiNHC6H3(2,6-i-Pr2) was prepared
via a modification of a literature procedure (43).
δ: 31.4. Anal. calcd. for C21H44N3PZr (%): C 54.74, H 9.62,
N 9.12; found: C 53.73, H 9.64, N 8.49.
Synthesis of TiCp(NP-t-Bu3)(NHC6H3(2,6-i-Pr2))Cl (5)
Solid LiNHC6H3(2,6-i-Pr2) (1.51 g, 12.2 mmol) was
added in small portions at 25 °C over a 1 h period to a clear
solution of TiCp(NP-t-Bu3)Cl2 (4.91 g, 12.2 mmol) in ben-
zene (150 mL). The slurry was stirred for 20 h, after which
time the mixture was filtered through Celite. The solution
was concentrated in vacuo to ca. 20 mL, during which time
a bright yellow solid precipitated. The solid was filtered,
washed with pentanes (3 × 20 mL), and dried to afford a
1
fine, yellow powder (5.94 g, 89%). H NMR δ: 9.65 (br, 1H,
3
NH), 7.23 (br, 2H, C6H3 (m-H)), 7.05 (t, 1H, JH-H = 7 Hz,
Synthesis of TiCp(NP-t-Bu3)(NMe2)2 (1) and
TiCp(NPPh3)(NMe2)2 (2)
3
C6H3 (p-H)), 6.21 (s, 5H, Cp), 3.26 (sep, 2H, JH-H = 7 Hz,
3
3
i-Pr), 1.39 (d, 12H, JH-H = 7 Hz, i-Pr), 1.19 (d, 27H, JP-H
=
These compounds were prepared in a similar fashion and
thus one preparation is detailed. Solid LiNMe2 (46 mg,
0.90 mmol) was added in several portions to a clear solution
of TiCp(NP-t-Bu3)Cl2 (179 mg, 0.45 mmol) in benzene
(20 mL). The slurry was stirred for 20 h, after which time
the mixture was filtered through Celite. The solvent was re-
moved in vacuo affording a bright orange solid. The residue
was washed with pentanes (3 × 5 mL) and dried to afford a
fine, orange powder (126 mg, 67%). Small quantities (typi-
cal yields ca. 10%–15%) of the by-product Ti(NP-t-
Bu3)(NMe2)31 (3) were isolated from the pentane washings
(1). For 1: H NMR δ: 6.18 (s, 5H, Cp), 3.28 (s, 12H,
13 Hz, t-Bu). 13C NMR δ: 153.9, 128.3, 123.3, 123.1, 112.8,
41.5 (d, JP-C = 27 Hz), 29.5, 28.1, 22.6. 31P NMR δ: 39.0.
1
Anal. calcd. for C29H50ClN2PTi (%): C 64.38, H 9.32, N
5.18; found: C 63.95, H 9.06, N 4.74. Bright yellow crystals
suitable for X-ray diffraction were grown by slow evapora-
tion from benzene.
Synthesis of Ti(NP-t-Bu3)(NHC6H3(2,6-i-Pr2))3 (6)
A slurry of LiNHC6H3(2,6-i-Pr2) (591 mg, 4.8 mmol) in
benzene (20 mL) was added over a 0.5 h period at 25 °C to a
clear solution of TiCp(NP-t-Bu3)Cl2 (380 mg, 0.96 mmol) in
the same solvent (25 mL). The slurry was stirred for an addi-
tional 10 h, then filtered through Celite. The solvent was re-
moved in vacuo, and the residue was washed with hexanes
3
NMe2), 1.24 (d, 27H, JP-H = 13 Hz, t-Bu). 13C NMR δ:
1
109.7, 50.5, 40.6 (d, JP-C = 28 Hz), 29.7. 31P NMR δ: 28.9.
Anal. calcd. for C21H44N3PTi (%): C 60.42, H 10.62, N
1
10.07; found: C 60.34, H 10.52, N 9.67. For 2: yellow solid
(3 × 10 mL) to afford a yellow solid (586 mg, 77%). H
1
3
(312 mg, 77%). H NMR δ: 7.75 (m, 6H, Ph), 7.06 (m, 9H,
NMR δ: 7.80 (br, 3H, NH), 7.11 (d, 6H, JH-H = 8 Hz, C6H3
Ph), 5.99 (s, 5H, Cp), 3.34 (s, 12H, NMe2). 13C NMR δ:
3
(m-H)), 6.96 (t, 3H, JH-H = 8 Hz, C6H3 (p-H)), 3.70 (sep,
1
2
3
3
135.9 (d, JP-C = 58 Hz), 132.4 (d, JP-C = 6 Hz), 128.3,
6H, JH-H = 7 Hz, i-Pr), 1.28 (d, 36H, JH-H = 7 Hz, i-Pr),
3
128.6 (d, JP-C = 7 Hz), 109.8, 50.1. 31P NMR δ: –9.3. Anal.
1.06 (d, 27H, JP-H = 13 Hz, t-Bu). 13C NMR δ: 150.9,
3
137.6, 123.0, 120.8, 40.6 (d, 1JP-C = 46 Hz), 29.4, 29.2, 24.1.
31P NMR δ: 37.4. Anal. calcd. for C48H81N4PTi (%): C
72.70, H 10.30, N 7.06; found: C 72.49, H 10.60, N 7.28.
Deep red crystals suitable for X-ray diffraction were grown
by slow evaporation from benzene.
calcd. for C27H32N3PTi (%): C 67.93, H 6.76, N 8.80; found:
C 67.67, H 6.54, N 8.52.
Synthesis of Ti(NP-t-Bu3)(NMe2)3 (3)
A slurry of LiNMe2 (44 mg, 0.87 mmol) in benzene
(1 mL) was added to a suspension of Ti(NP-t-Bu3)Cl3
(105 mg, 0.28 mmol) in the same solvent (10 mL). After
stirring for 12 h at 25 °C, the mixture was filtered through
Celite. Removal of the solvent in vacuo afforded an orange
Synthesis of ZrCp(NP-t-Bu3)(NHC6H3(2,6-i-Pr2))Me (7)
NH2C6H3(2,6-i-Pr2) (58 mL, 0.31 mmol) was added
dropwise to
a clear solution of ZrCp(NP-t-Bu3)Me2
1
crystalline solid (83 mg, 75%). H NMR δ: 3.40 (s, 18H,
(125 mg, 0.31 mmol) in benzene (20 mL) at 25 °C. After
stirring for 12 h, the volatile products were removed in
NMe2), 1.27 (s, 27H, 3JP-H = 13 Hz, t-Bu). 13C NMR δ: 46.3,
1
39.9 (d, JP-C = 48 Hz), 29.5. 31P NMR δ: 29.8. Anal. calcd.
1
vacuo to afford a beige solid (162 mg, 92%). H NMR δ:
3
3
for C18H45N4PTi (%): C 54.54, H 11.44, N 14.13; found: C
54.74, H 11.63, N 13.78. Deep orange-red crystals suitable
for X-ray diffraction were grown by slow evaporation from
hexanes–pentanes.
7.21 (d, 2H, JH-H = 8 Hz, C6H3 (m-H)), 7.04 (t, 1H, JH-H
=
8 Hz, C6H3 (p-H)), 6.51 (br, 1H, NH), 6.20 (s, 5H, Cp), 3.45
3
3
(sep, 2H, JH-H = 7 Hz, i-Pr), 1.36 (d, 6H, JH-H = 7 Hz, i-
3
Pr), 1.35 (d, 6H, JH-H = 7 Hz, CMe2H), 1.13 (d, 27H,
3JP-H = 13 Hz, t-Bu), 0.47 (s, 3H, ZrMe). 13C NMR δ: 150.9,
1
137.7, 122.7, 120.1, 110.0, 40.0 (d, JP-C = 47 Hz), 29.0,
Synthesis of ZrCp(NP-t-Bu3)(NMe2)2 (4)
27.9, 27.9, 23.8, 22.8. 31P NMR δ: 34.3. Anal. calcd. for
C30H53N2PZr (%): C 63.89, H 9.47, N 4.97; found: C 62.84,
H 9.43, N 4.90.
Solid LiNMe2 (193 mg, 3.6 mmol) was added in several
portions at 25 °C to a clear solution of ZrCp(NP-t-Bu3)Cl2
(411 mg, 0.90 mmol) in benzene (50 mL). The slurry was
stirred for 18 h and was subsequently filtered through Celite.
The solvent was removed in vacuo affording 4 as a fine,
Synthesis of ZrCp(NP-t-Bu3)(NHC6H3(2,6-i-Pr2))2 (8)
A slurry of LiNHC6H3(2,6-i-Pr2) (527 mg, 2.9 mmol) in
benzene (20 mL) was added over a 15 min period at 25 °C
to a solution of ZrCp(NP-t-Bu3)Cl2 (320 mg, 0.72 mmol) in
1
white powder (340 mg, 82%). H NMR δ: 6.32 (s, 5H, Cp),
3
3.14 (s, 12H, NMe2), 1.21 (s, 27H, JP-H = 12 Hz, t-Bu). 13C
1
NMR δ: 109.6, 46.3, 39.9 (d, JP-C = 48 Hz), 29.6. 31P NMR
© 2004 NRC Canada

1636
Can. J. Chem. Vol. 82, 2004
Scheme 1. Synthesis of 5–8: (i) 1 equiv. of LiNHC6H3(2,6-i-
Pr2); (ii) 2 equiv. of LiNHC6H3(2,6-i-Pr2).
the same solvent (25 mL). The slurry was stirred for an ad-
ditional 10 h, after which time it was filtered through Celite.
The solvent was removed in vacuo, and the residue was
washed with hexanes (3 × 5 mL) to afford a beige solid
1
3
(486 mg, 93%). H NMR δ: 7.18 (d, 4H, JH-H = 8 Hz, C6H3
3
(m-H)), 7.02 (t, 2H, JH-H = 8 Hz, C6H33(p-H)), 6.34 (s, 5H,
Cp), 5.75 (s, 2H, NH), 3.73 (sep, 4H, JH-H = 7 Hz, i-Pr),
3
3
1.34 (d, 24H, JH-H = 7 Hz, i-Pr), 1.04 (d, 27H, JP-H
=
13 Hz, t-Bu). 13C NMR δ: 151.9, 138.7, 122.9, 120.2, 111.4,
39.9 (d, JP-C = 47 Hz), 29.5, 28.7, 24.3. 31P NMR δ: 35.8.
1
Anal. calcd. for C41H68N3PZr (%): C 67.90, H 9.45, N 5.79;
found: C 66.62, H 9.84, N 5.86. Colourless crystals suitable
for X-ray diffraction were grown by slow evaporation from
benzene (Scheme 1).
Generation of TiCp(NP-t-Bu3)MeCl (9) and Al2(m-
NHC6H3(2,6-i-Pr2))2Me4 (10)
Neat Al2Me6 (0.14 mL, 0.14 mmol) was added dropwise
at 25 °C to a clear orange solution of 5 (153 mg, 0.28 mmol)
in benzene (15 mL). The solution became deeper yellow in
colour and was stirred for an additional 2 h, after which time
the solvent was removed in vacuo. The residue was
recrystallized from pentanes to afford yellow and colourless
crystals (combined yield: 162 mg, 94%). X-ray analysis of
the crystals isolated from the mixture confirmed the pres-
ence of 9 and 10, although because of their similar solubility
properties, they could not be adequately separated. Thus,
microanalysis was performed on the mixture, confirming a
1:1 ratio of the two products. Anal. calcd. for
C32H59AlClN2PTi (%): C 64.50, H 9.83, N 4.85; found: C
65.19, H 10.25, N 5.01. Both, however, were identified spec-
XPREP processing packages. An empirical absorption cor-
rection based on redundant data was applied to each data set.
Subsequent solution and refinement was performed using
the SHELXTL solution package operating on a Pentium-3
computer (Table 1).
Structure solution and refinement
Non-hydrogen atomic scattering factors were taken from
the literature tabulations (44). The heavy atom positions
were determined using direct methods employing the
SHELXTL direct methods routine. The remaining non-
hydrogen atoms were located from successive difference
Fourier map calculations. The refinements were carried out
by using full-matrix least-squares techniques on F, minimiz-
ing the function ω(|Fo| – |Fc|)2 where the weight ω is defined
1
troscopically. 9: H NMR δ: 6.27 (s, 5H, Cp), 1.20 (s, 3H,
3
TiMe), 1.04 (d, 27H, JP-H = 20 Hz, t-Bu). 13C NMR δ:
2
2
as 4Fo /2s (Fo ) and Fo and Fc are the observed and calcu-
lated structure factor amplitudes. In the final cycles of each
refinement, all non-hydrogen atoms were assigned
anisotropic temperature factors in the absence of disorder or
insufficient data. In the latter cases atoms were treated
isotropically. C-H atom positions were calculated and al-
lowed to ride on the carbon to which they are bonded assum-
ing a C—H bond length of 0.95 Å. H-atom temperature
factors were fixed at 1.10 times the isotropic temperature
factor of the C atom to which they are bonded. The H-atom
contributions were calculated, but not refined. The locations
of the largest peaks in the final difference Fourier map cal-
culation as well as the magnitude of the residual electron
densities in each case were of no chemical significance. Ad-
ditional details are provided in the supplementary data.2
1
113.3, 41.4 (d, JP-C = 45 Hz), 29.4, 25.2. 31P NMR δ: 42.0.
1
3
10: H NMR: 7.06 (d, 2H, JH-H = 8 Hz, C6H3 (m-H)), 6.98
3
(t, 1H, JH-H = 8 Hz, C6H3 (p-H)), 4.58 (br, 1H, NH), 3.40
3
3
(sep, 2H, JH-H = 7 Hz, i-Pr), 1.26 (d, 12H, JH-H = 7 Hz, i-
Pr), –0.32 (s, 6H, AlMe). 13C NMR δ: 139.2, 137.7, 124.6,
123.8, 29.0, 25.0, –7.2. The spectroscopic and crystallo-
graphic data for Al2(m-NH(2,6-i-Pr2)C6H3)2Me4 were con-
sistent with literature data.
X-ray data collection and reduction
Crystals were manipulated and mounted in capillaries in a
glove box, thus maintaining a dry, O2-free environment for
each crystal. Diffraction experiments were performed on a
Siemens SMART System CCD diffractometer. The data
were collected in a hemisphere of data in 1329 frames with
10 s exposure times. The observed extinctions were consis-
tent with the space groups in each case. The data sets were
collected (4.5° < 2q < 45°–50.0°). A measure of decay was
obtained by recollecting the first 50 frames of each data set.
The intensities of reflections within these frames showed no
statistically significant change over the duration of the data
collections. The data were processed using the SAINT and
Results and discussion
Complexes of formula TiCp(NPR3)(NMe2)2 (R = t-Bu 1,
Ph 2) were prepared via salt metathesis of TiCp(NPR3)Cl2
with a slight excess of LiNMe2 affording the desired prod-
ucts in 67% and 77% yields, respectively. In the case where
R = t-Bu, the by-product Ti(NP-t-Bu3)(NMe2)3 (3) was also
2 Supplementary data may be purchased from the Directory of Unpublished Data, Document Delivery, CISTI, National Research Council
Canada, Ottawa, ON K1A 0S2, Canada (http://www.nrc.ca/cisti/irm/unpub_e.shtml for information on ordering electronically). CCDC
235292–235294 contain the crystallographic data for this manuscript. These data can be obtained, free of charge, via
www.ccdc.cam.ac.uk/conts/retrieving.html (or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ,
UK; fax +44 1223 336033; or deposit@ccdc.cam.ac.uk).
© 2004 NRC Canada

Hollink et al.
1637
Table 1. Crystallographic data.a
5·0.5C6H6
6
8
Formula
C32H53ClN2PTi
C48H81N4PTi
C41H68N3PZr
Formula wt.
Crystal syst.
Space group
a (Å)
b (Å)
c (Å)
580.08
Triclinic
P-1
793.04
Monoclinic
P21/c
11.476(2)
42.136(8)
20.590(4)
725.17
Orthorhombic
Pbca
19.38(2)
19.77(2)
21.92(2)
11.334(6)
11.891(6)
13.769(7)
100.315(9)
101.464(9)
107.256(9)
1680(1)
1.147
α (°)
β (°)
92.248(5)
γ (°)
V (Å3)
9 949(3)
1.059
8
0.233
47 974
14 448
973
0.090 7
0.224 8
1.040
8 400(2)
1.147
8
0.329
34 645
3 049
415
0.041 6
0.062 9
1.022
D(calcd.) (g cm–1)
Z
2
Abs coeff (µ, cm–1)
Data collected
0.403
7162
4078
343
0.036 5
0.101 8
1.028
2
2
Data Fo > 3σ(Fo )
Variables
R
Rw
GOF
aAll data collected at 24 °C with Mo Kα radiation (λ = 0.710 69 Å), R = Σ||Fo| – |Fc|| / Σ|Fo|, Rw = [Σ[ω(Fo2
2
– Fc2)2] / ωFo )2]]0.5
.
generated in low yields (ca. 10%–15%). While the formation
of 3 was unexpected as it requires Cp–M cleavage, such re-
actions are not unprecedented (45–48). This by-product 3
was prepared in a more conventional manner by a metathesis
route in 75% yield from Ti(NP-t-Bu3)Cl3 and an excess of
the lithium amide reagent. The related Zr derivative
ZrCp(NP-t-Bu3)(NMe2)2 (4) was also prepared in 82% yield
from the dichloride precursor using an excess of the Li am-
ide. Similarly the preparation of the related complexes
TiCp′(NMe2)3 (Cp′ = Cp, C5Me5, indenyl) have been previ-
Fig. 1. PLUTO drawing of 3 (30% thermal ellipsoids are
shown). Hydrogen atoms are omitted for clarity.
1
ously reported (9, 49). The H NMR chemical shift of the
amido-methyl groups for 3 and TiCp*(NMe2)3 were
observed at 3.40 and 3.09 ppm, respectively. Preliminary
X-ray data3 for 3 was obtained from rather poor quality
crystals. While these data confirmed the connectivity and in-
ferred that 3 exhibits threefold symmetry in the solid state
(Fig. 1), the poor quality of the crystals precludes a discus-
sion of the metric parameters.
Similarly, reaction of TiCp(NP-t-Bu3)Cl2 with Li-
NHC6H3(2,6-i-Pr2) afforded TiCp(NP-t-Bu3)(NHC6H3(2,6-i-
Pr2))Cl (5) and Ti(NP-t-Bu3)(NHC6H3(2,6-i-Pr2))3 (6). How-
ever, unlike the dialkyl amide reaction, preparation of
TiCp(NP-t-Bu3)(NHC6H3(2,6-i-Pr2))2 could not be achieved
cleanly, presumably a result of excessive steric crowding
about the metal centre. The room-temperature 1H NMR
spectrum of 5 exhibited broad resonances attributed to the
methine protons on the isopropyl groups and a doublet sig-
nal originating from the methyl groups. Variable-temperature
studies confirmed restricted rotation about the Ti—N amide
bond with coalescence of the methine protons of the
isopropyl groups at 308 K. The free energy of activation
(∆G‡) for rotation of the N—Cipso bond was determined to
be 58.1(5) kJ mol–1 at 298 K. This value is greater than
those reported for Ti(NR2)3Cl (R = Me, Et) (<42 kJ mol–1),
but compares well with an estimation of 55.6 kJ mol–1 ob-
tained for rotation of the N—Cipso bond in the related com-
plex Zr((NC6H3(2,6-i-Pr2)CH2]2CH2)Me2 (50). The higher
activation energies reflect the greater steric crowding around
the metal center (51, 52). Compounds 5 and 6 were also
characterized crystallographically (Figs. 2 and 3, Table 2).
In both cases, the Ti—N bond for the phosphinimide ligands
were significantly shorter than the Ti—N amide bonds, con-
3 Preliminary X-ray data for 3: C18H45N4PTi, trigonal, R3, a = 14.066(6), c = 11.023(7), V = 1888.9(7). 9: C18H35ClNPTi, orthorhombic,
Pbca, a = 10.294(5), b = 14.828(8), c = 28.49(1), V = 4348(5). 10: C28H46N2Al2, orthorhombic, Pna21, a = 18.810(8), b = 10.160(4), c =
15.902(7), V = 3039(2).
© 2004 NRC Canada

1638
Can. J. Chem. Vol. 82, 2004
Table 2. Metric parameters.a
Cmpd
M—N (NR2)
M—N (NPR3)
N—P
M-N-P
5
6
1.946(2)
1.790(2)
1.782(6)
1.796(6)
1.604(7)
1.592(6)
1.576(6)
167.1(3)
170.3(3)
167.0(4)
1.931(5), 1.934(5)
1.933(5), 1.914(6)
1.927(5), 1.937(5)
2.107(4), 2.110(3)
8
1.939(3)
1.592(3)
176.5(2)
aBond distance in Å, angles in °.
Fig. 2. ORTEP drawing of 5 (30% thermal ellipsoids are shown).
Hydrogen atoms are omitted for clarity.
Fig. 4. ORTEP drawing of 8 (30% thermal ellipsoids are shown).
Hydrogen atoms are omitted for clarity.
Fig. 3. ORTEP drawing of 6 (30% thermal ellipsoids are shown).
Hydrogen atoms are omitted for clarity.
revealed that the Zr—N bond distances were slightly longer
than those in the Ti complexes as expected (Fig. 4, Table 2).
Reactivity of these phosphinimide–amide derivatives was
explored. Attempts to effect the thermolytic formation of
group IV phosphinimide imide complexes (1–3, 5, 53–56)
were unsuccessful, affording instead the elimination of both
free amine and phosphinimine. Similarly, attempts to pre-
pare imido derivatives directly employing Mountford’s pre-
cursor Ti(N-t-Bu)Cl2(t-BuPy)2 (57) were also unsuccessful.
In other chemistry, reaction of 5 with excess AlMe3 re-
sulted in the clean, near-quantitative isolation of TiCp(NP-t-
Bu3)Me2. However, when 1 equiv. of AlMe3 was used,
TiCp(NP-t-Bu3)MeCl (9) and the dimer Al2(m-
NH(C6H3(2,6-i-Pr2))2Me4 (10) were obtained. The formation
of 9 and 10 were confirmed via preliminary crystallographic
data.3 Similar methylations using AlMe3 have been previ-
ously reported to replace alkoxide (58) or amide (59) lig-
ands.
We noted the work of Doye and co-workers (60) who re-
ported moderate conversion of 3-hexyne and 4-methylaniline
to the secondary amine using TiCp(NPPh3)Me2 as a catalyst.
Efforts to effect similar transformations using 6–8 as catalyst
precursors were unsuccessful resulting again in liberation of
amine and phosphinimine ligands. It is interesting to note
that while the phosphinimide ligand is an effective replace-
ment for Cp in olefin polymerization catalysts, the present
data imply that this is not the case for hydroamination cata-
lysts. Intuitively, this may be related to the Lewis basicity of
the phosphinimide N and its affinity for small Lewis acids
such as protons. Nonetheless, efforts are continuing to ex-
sistent with the strength of the Ti—phosphinimide bond.
The related compound ZrCp(NP-t-Bu3)(NHC6H3(2,6-i-
Pr2))Me (7) was prepared in 92% yield via a stoichiometric
protonolysis reaction of ZrCp(NP-t-Bu3)Me2 with NH2(2,6-
i-Pr2)C6H3. In contrast, the bis-amido analog ZrCp(NP-t-
Bu3)(NHC6H3(2,6-i-Pr2))2 (8) was prepared in 93% yield via
metatheses of the chloride ligands of ZrCp(NP-t-Bu3)Cl2
with LiNHC6H3(2,6-i-Pr2). The crystallographic data for 8
© 2004 NRC Canada

Hollink et al.
1639
Wei, R.E.v.H. Spence, W. Xu, L. Koch, X. Gao, and D.G.
Harrison. Organometallics, 22, 1937 (2003).
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ancillary ligands.
31. D.W. Stephan, F. Guerin, R.E.v.H. Spence, L. Koch, X. Gao,
S.J. Brown, J.W. Swabey, Q. Wang, W. Xu, P. Zoricak, and
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32. D.W. Stephan, J.C. Stewart, F. Guerin, R.E.v.H. Spence, W.
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33. N. Yue, E. Hollink, F. Guerin, and D.W. Stephan. Organo-
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