Transition metal complexes of a sterically demanding diimine ligand

Article abstract of DOI:10.1139/v05-057

The reaction of the metal halide with the sterically demanding ligand (i-Pr₂C₆H₃N)(C(Me)(NC₆H ₃-i-Pr₂))₂ afforded the complexes (i-Pr ₂C₆H₃N)(C(M

Full text of DOI:10.1139/v05-057

477
Transition metal complexes of a sterically
demanding diimine ligand
Jason D. Masuda and Douglas W. Stephan
Abstract: The reaction of the metal halide with the sterically demanding ligand (i-Pr2C6H3N)(C(Me)(NC6H3-i-Pr2))2 af-
forded the complexes (i-Pr2C6H3N)(C(Me)(NC6H3-i-Pr2))2MX2 (X = Cl, M = Fe (2), Co (3); X = Br, M = Ni (4), M =
Cu (5), Zn (6)). The species of 2 reacts with Li(OEt2)B(C6F5)4 to form the yellow adduct [(i-Pr2C6H3N)(C(Me)(NC6H3-
i-Pr2))2Fe(µ-Cl)2Li(OEt2)2][B(C6F5)4] (7) while alkylation of 2 gave (i-Pr2C6H3N)(C(Me)(NC6H3-i-Pr2))2FeClCH2SiMe3
(8). The species [(i-Pr2C6H3N)(C(Me)(NC6H3-i-Pr2))2Ni(η3-C3H5)][B(3,5-CF3C6H3)4] (9) was obtained from reaction of
1 with [(η3-C3H5)NiBr]2 and [Na][B(3,5-(CF3)2C6H3)4] while reaction of 4 with Super-Hydride afforded (i-Pr2C6H3N)-
(C(Me)(NC6H3-i-Pr2))2NiH2BEt2 (10). X-ray data are reported for 2–10. The sterically demanding nature of the ligand
inhibits subsequent reactivity of these species.
Key words: sterically demanding ligands, chelate complexes, X-ray structure, diimine ligands.
Résumé : La réaction d’un halogénure métallique avec le ligand stériquement encombré (i-Pr2C6H3N)(C(Me)(NC6H3-i-
Pr2))2 conduit à la formation des complexes (i-Pr2C6H3N)(C(Me)(NC6H3-i-Pr2))2MX2 (X = Cl, M = Fe (2), Co (3); X =
Br, M = Ni (4), M = Cu (5), Zn (6)). L’espèce 2 réagit avec le Li(OEt2)B(C6F5)4 pour former l’adduit jaune [(i-
Pr2C6H3N)(C(Me)(NC6H3-i-Pr2))2Fe(µ-Cl)2Li(OEt2)2][B(C6F5)4] (7) alors que l’alkylation du composé 2 conduit à la
formation du complexe (i-Pr2C6H3N)(C(Me)(NC6H3-i-Pr2))2FeClCH2SiMe3 (8). On a obtenu l’espèce (i-Pr2C6H3N)-
(C(Me)(NC6H3-i-Pr2))2Ni(η3-C3H5)][B(3,5-CF3C6H3)4] (9) par réaction du composé 1 avec le [(η3-C3H5)NiBr]2 et le
[Na][B(3,5-(CF3)2C6H3)4] alors que la réaction du composé 4 avec le Super-Hydrure conduit à la formation du (i-
Pr2C6H3N)(C(Me)(NC6H3-i-Pr2))2NiH2BEt2 (10). On rapporte les données de diffraction des rayons X par les composés
2–10. L’encombrement stérique du ligand inhibe toute réactivité subséquente de ces espèces.
Mots clés : ligands stériquement encombrés, complexes de chélates, structure par diffraction des rayons X, diimine
ligands.
[Traduit par la Rédaction] Masuda and Stephan 484
Introduction
on the ligand (i-Pr2C6H3N)C6H4PPh2(NC6H3-i-Pr2). In re-
cent efforts, we have also reported the synthesis of the
sterically demanding N-aryl-imidoyl amidine ligand i-
Pr2C6H3N(C(Me)NC6H3-i-Pr2)2 and its use in the synthesis
of Al-based alkyl and hydride cations.2 Several previous re-
ports have described metal complexes involving the N-
imidoyl amidine systems (R = H) (11–19) and the related
2,2′-dipyridylamino ligand (20–34). Cotton et al. (31)
serendipitously obtained [PhNCHN(Ph)CHNPh]CoCl2 while
the related species [(4-MePh)NCHN(4-MePh)(4-MePh)-
NC]Pd(C6F5)2 was reported by Uson et al. (33). Finally,
Wilkinson and co-workers (32) characterized the species
(C5Me5)Ir[N(2,6-MeC6H3)CHNRCNC6H3(Me)CH2] (R = t-
Bu, 2,6-i-PrC6H3). In this manuscript, we report the use of
this bulky ligand i-Pr2C6H3N(C(Me)NC6H3-i-Pr2)2 in the
synthesis of a series of transition metal complexes. Struc-
tural studies of these complexes are presented and discussed.
Recently, much attention has focused on sterically de-
manding chelating ligands such as the neutral, diimine-based
ligand ((C(Me)NC6H3-i-Pr2)2) and [HC(C(Me)NC6H3-i-Pr2)2]–
(Scheme 1). Such ligands have been utilized for late transi-
tion metal olefin polymerization catalysts, as well as for the
isolation of novel low-valent Al and Ga derivatives (1–4).
Mindiola and co-workers (5) have used the latter ligand to
isolate the first Ti–phosphinidene complex. In our labs, we
have recently been probing new bulky ligands in late transi-
tion metals (6–8) and main group chemistry (9). For exam-
ple, we have recently reported the use of the bulky
phosphinimine–imine ligand (i-Pr2C6H3N)C(Me)CHPPh2-
(NC6H3-i-Pr2) to prepare neutral and cationic Al complexes
(9), while Welch et al. (10) reported related complexes based
Received 19 November 2004. Published on the NRC
Research Press Web site at http://canjchem.nrc.ca on 14 May
2005.
Experimental
J.D. Masuda and D.W. Stephan.1 Department of Chemistry
and Biochemistry, University of Windsor, Windsor, ON N9B
3P4, Canada.
General data
All preparations were done under an atmosphere of dry,
O2-free N2 employing both Schlenk line techniques and a
Vacuum Atmospheres inert atmosphere glovebox. Solvents
were purified employing a Grubbs’-type solvent purification
system manufactured by Innovative Technology. Deuterated
1Corresponding author (e-mail: stephan@uwindsor.ca).
2J.D. Masuda and D.W. Stephan. Organometallics, submitted
(2005).
Can. J. Chem. 83: 477–484 (2005)
doi: 10.1139/V05-057
© 2005 NRC Canada

478
Can. J. Chem. Vol. 83, 2005
Scheme 1. Bulking chelating ligand complexes.
R
R
R
R
R
R
R
R
R
R
Ar
M
Ar
Ar
M
Ar
Ar
M
N
Ar
N
N
P
Ar
M
Ar Ar
M
Ar
N
N
P
N
N
N
N
N
N
Ph
Ph
Ph
Ph
Ar
Ar = C6H3-i-Pr2
solvents were purified using the appropriate techniques. All
organic reagents were purified by conventional methods. H,
small amount of CH3C(i-Pr2C6H3N)2H impurity in the 1
starting material.
1
31P, 11B, 19F, and 13C NMR spectra were recorded on Bruker
Avance-300 and -500 spectrometers. All spectra were re-
corded in C6D6 at 25 °C unless otherwise noted. Trace
amounts of protonated solvents were used as references and
chemical shifts are reported relative to SiMe4. 31P, 11B, and
19F NMR spectra were referenced to external 85% H3PO4,
BF3·Et2O, and CFCl3, respectively. Combustion analyses
were done in-house employing a PerkinElmer CHN ana-
lyzer. [Na][B(3,5-CF3C6H3)4] was prepared as outlined (36).
LiCH2SiMe3 and Super-Hydride were purchased from
Aldrich Chemical Co. as solutions and crystallized. The
ligand (i-Pr2C6H3N)C(Me)(NC6H3-i-Pr2)C(Me)(NC6H3i-Pr2)
(1) was prepared by published methods.2
Synthesis of (i-Pr2C6H3N)(C(Me)(NC6H3-i-Pr2))2MBr2
(M = Cu (5), Zn (6))
These compounds were prepared in a similar fashion and
thus one preparation is detailed. To a solution of 1 (100 mg,
0.172 mmol) in 5 mL THF was added 38 mg (0.172 mmol)
CuBr2 and the mixture was left to stir overnight, after which
a copious amount of burgundy colored solids formed. The
solids were filtered from the reaction mixture to give 83 mg
of material. 5: Yield: 60%; magnetic susceptibility 1.99 µB.
X-ray quality burgundy colored crystals were grown from a
hot MeCN solution slowly cooled to –35 °C. Anal. calcd. for
C40H57N3CuBr2: C 59.81, H 7.15, N 5.23; found: C 59.43, H
7.30, N 5.15. 6: Yield: 90%. X-ray quality colorless crystals
1
were grown by cooling a CHCl3 solution to –35 °C. H
Synthesis of (i-Pr2C6H3N)(C(Me)(NC6H3-i-Pr2))2MCl2
(M = Fe (2), Co (3))
NMR (CD2Cl2): 7.24–7.57 (m, 9H, m, p-Ar), 3.42 (sept, 4H,
CH, |JH-H| = 6.9 Hz), 3.41 (sept, 2H, CH, |JH-H| = 6.9 Hz),
1.76 (s, 6H, Me), 1.37 (d, 12H, i-Pr, |JH-H| = 6.9 Hz), 1.30
(d, 12H, i-Pr, |JH-H| = 6.9 Hz), 1.13 (d, 12H, i-Pr, |JH-H| =
6.9 Hz). 13C NMR (CD2Cl2): 167.8, 146.4, 141.3, 141.1,
137.2, 132.0, 127.9, 126.8, 125.5, 29.1, 28.8, 26.0, 24.8,
24.7, 24.0. Anal. calcd. for C40H57N3ZnBr2: C 59.67, H
7.14, N 5.22; found: C 59.26, H 7.12, N 5.12.
These compounds were prepared in a similar fashion and
thus one preparation is detailed. To a solution of 1 (200 mg,
0.345 mmol) in 5 mL toluene was added FeCl2 (43 mg,
0.345 mmol). The mixture was heated to 110 °C for 3 days
after which the insoluble, off-white FeCl2 had been replaced
with a yellow solid. The toluene was then removed in vacuo
and the remaining solids dissolved in approximately 10 mL
CH2Cl2. This solution was then filtered through Celite® and
layered with 10 mL toluene. After several days, 213 mg of
bright yellow – orange crystals were isolated. 2: Yield: 79%;
magnetic susceptibility 5.79 µB. Anal. calcd. for C40H57N3FeCl2:
C 67.99, H 8.13, N 5.95; found: C 68.22, H 8.40, N 6.00. 3:
Blue crystals. Yield: 87%; magnetic susceptibility 3.35 µB.
Anal. calcd. for C40H57N3CoCl2: C 67.69, H 8.09, N 5.92;
found: C 67.55, H 7.84, N 5.87.
Synthesis of (i-Pr2C6H3N)(C(Me)(NC6H3-i-Pr2))2Fe(␮-
Cl)2Li(OEt2)2][B(C6F5)4] (7)
To
a rapidly stirring suspension of 2 (100 mg,
0.142 mmol) in 5 mL toluene was added 107 mg (0.142 mmol)
Li(OEt2)2B(C6F5)4 in 5 mL of diethyl ether. The reaction
was allowed to stir overnight after which the mixture turned
from yellow-orange to a bright yellow color. Filtration of the
mixture through Celite® and removal of the solvent gave a
yellow oil, which crystallized upon addition of pentane.
Yield: 41%; magnetic susceptibility 5.23 µB. X-ray quality
crystals were grown by diffusion of pentane vapor into a di-
ethyl ether – toluene solution of the material. Anal. calcd.
for C72H77N3FeCl2LiBF20O: C 56.12, H 5.03, N 2.73; found:
C 56.30, H 4.73, N 2.50.
Synthesis of (i-Pr2C6H3N)(C(Me)(NC6H3-i-Pr2))2NiBr2 (4)
To a solution of 1 (1.000 g, 1.72 mmol) in 15 mL xylenes
was added NiBr2 (377 mg, 1.72 mmol). The mixture was
heated to 140 °C for 3 days. This resulted in the formation
of a purple solid suspended in a bright blue solution. The
xylenes were then decanted, the solids washed with 2 ×
10 mL pentane, and dried in vacuo to give 1.186 g of pow-
der 4. X-ray quality dark purple crystals were grown from a
solution in CH2Cl2 layered with toluene. 4: Yield: 86%;
magnetic susceptibility 4.98 µB. Anal. calcd. for C40H57N3NiBr2:
C 60.17, H 7.19, N 5.26; found: C 60.38, H 7.23, N 5.25.
The decanted xylenes and pentane washings were combined
and after a few weeks, a small amount of blue crystals
formed. Crystallographic analysis proved this to be [CH3C(i-
Pr2C6H3N)2HNiBr3][CH3C(i-Pr2C6H3NH)2] resulting from a
Synthesis of (i-Pr2C6H3N)(C(Me)(NC6H3-i-
Pr2))2FeClCH2SiMe3 (8)
To a rapidly stirring suspension of 2 (100 mg, 0.142 mmol)
in 5 mL toluene cooled to –35 °C was added LiCH2SiMe3
(13 mg, 0.142 mmol) in 3 mL of cold toluene. The reaction
was allowed to warm to 25 °C over several hours. The mix-
ture became deep purple in color. Filtration of the mixture
and cooling the filtrate to –35 °C overnight gave fine purple
needles. The crystals were filtered off and washed with 2 ×
© 2005 NRC Canada

Masuda and Stephan
479
10 mL of cold pentane. Yield: 55%; magnetic susceptibility
5.61 µB. X-ray quality purple crystals were grown from a to-
luene solution layered with pentane. Anal. calcd. for
C44H68N3FeSiCl: C 69.68, H 9.03, N 5.54; found: C 70.18,
H 8.56, N 6.20.
were collected in a hemisphere of data in 1448 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° < 2θ < 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
XPREP processing packages (37). An empirical absorption
correction based on redundant data was applied to each data
set. Subsequent solution and refinement was performed us-
ing the SHELXTL solution package (37).
Synthesis of [(i-Pr2C6H3N)(C(Me)(NC6H3-i-Pr2))2Ni(␩3-
C3H5)][B(3,5-(CF3)2C6H3)4] (9)
To a solution of 1 (100 mg, 0.174 mmol) in 8 mL CH2Cl2
was added [(η3-C3H5)NiBr]2 (32 mg, 0.174 mmol) and
[Na][B(3,5-(CF3)2C6H3)4] (155 mg, 0.174 mmol). The mix-
ture was stirred overnight. The resulting brown solution was
filtered to remove NaBr and the filtrate was cooled to –35 °C
overnight to give brown crystals, which were separated from
the solution by decantation and washed with 3 × 5 mL of
Structure solution and refinement
Non-hydrogen atomic scattering factors were taken from
the literature tabulations. The heavy atom positions were de-
termined using direct methods employing the SHELXTL
direct-methods routine. The remaining non-hydrogen atoms
were located from successive difference Fourier map calcu-
lations. The refinements were carried out by using full-
matrix least-squares techniques on F. 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 were bonded. The H-
atom contributions were calculated, but not refined. The lo-
cations of the largest peaks in the final difference Fourier
map calculation as well as the magnitude of the residual
electron densities in each case were of no chemical signifi-
cance. Addition details are provided in the Supplementary
data.3 See Table 1 for the crystallographic data for 2–10.
1
cold pentane. Yield: 33%. H NMR (CD2Cl2): 7.71 (br s,
8H, o-ArF), 7.56 (br s, 4H, p-ArF), 7.00–7.58 (m, 9H, m, p-
Ar), 5.74 (dt, 1H, allyl CH, |JH-H| = 13.5 Hz, |JH-H| =
7.1 Hz), 3.69 (sept, 2H, CH, |JH-H| = 6.9 Hz), 3.01 (sept, 2H,
CH, |JH-H| = 6.9 Hz), 2.87 (sept, 1H, CH, |JH-H| = 6.9 Hz),
2.72 (sept, 1H, CH, |JH-H| = 6.9 Hz), 2.16 and 2.11 (d, 2H,
allyl-syn, |JH-H| = 13.5 Hz), 1.79 and 1.77 (d, 2H, allyl-anti,
|JH-H| = 7.1 Hz), 1.66 (s, 6H, Me), 1.55 (d, 6H, i-Pr, |JH-H| =
6.9 Hz), 1.44 (d, 6H, i-Pr, |JH-H| = 6.9 Hz), 1.33 (d, 6H, i-Pr,
|JH-H| = 6.9 Hz), 1.29 (d, 6H, i-Pr, |JH-H| = 6.9 Hz), 1.28 (d,
6H, i-Pr, |JH-H| = 6.9 Hz), 1.21 (d, 6H, i-Pr, |JH-H| = 6.9 Hz).
13C NMR (CD2Cl2): 163.7, 162.4 (q, JCF = 49 Hz), 149.4,
145.0, 149.9, 137.8, 136.9, 136.5, 135.4, 132.7, 130.6, 130.1
(br m), 129.7 (br m), 129.6, 129.3 (br m), 128.9 (br m),
128.7, 128.3, 127.3, 127.2, 127.0, 125.8, 125.5, 123.4,
119.8, 118.1 (br m), 65.6, 29.9, 29.4, 29.3, 29.1, 25.0, 24.9,
24.8, 24.2, 24.0, 23.7, 23.4, 21.7. 11B NMR (CD2Cl2): –10.9.
19F NMR (CD2Cl2): –63.2. Anal. calcd. for C75H74N3NiBF24:
C 58.38, H 4.83, N 2.72; found: C 58.07, H 4.89, N 2.66.
Synthesis of (i-Pr2C6H3N)(C(Me)(NC6H3-i-
Pr2))2NiH2BEt2 (10)
Results and discussion
To a rapidly stirring slurry of 4 (200 mg, 0.251 mmol) in
10 mL toluene was added Super-Hydride (0.551 mL,
1.0 mol/L in THF). An immediate evolution of gas was ob-
served. The purple solution was allowed to stir for 4 h after
which the solvent was removed in vacuo. The solid was dis-
solved in approx. 5 mL toluene, filtered through Celite®,
layered with 5 mL pentane, and cooled to –35 °C overnight.
The resulting brown-red crystals were separated from the so-
lution and washed with 3 × 10 mL of cold pentane. Yield:
47%; magnetic susceptibility 1.11 µB. Anal. calcd. for
C44H69N3NiB: C 74.48, H 9.80, N 5.92; found: C 74.93, H
9.81, N 5.92.
The reaction of the metal halide in toluene or xylenes with
ligand 1 at elevated temperatures afforded the complexes (i-
Pr2C6H3N)(C(Me)(NC6H3-i-Pr2))2MX2 (X = Cl, M = Fe (2),
Co (3); X = Br, M = Ni (4)) in yields of 79%, 87%, and
86%, respectively (Scheme 2). In the latter case, formation
of the Ni complex required the more forcing conditions of
4 days of heating in xylenes at 140 °C to form 4. These vig-
orous conditions stand in stark contrast to those required for
the formations of H2C(C(Me)NC6H3-i-Pr2)2NiBr2 (37) and
(C(Me)(NC6H3-i-Pr2)2)NiBr2 (38), which form readily at
room temperature. Magnetic susceptibility measurements for
2, 3, and 4 gave a magnetic moment of 4.79, 3.35, and 4.98
µB, respectively, consistent with these formulations. In a
similar fashion, the straightforward reaction of 1 with equi-
molar amounts of CuBr2 or ZnBr2 in THF at room tempera-
ture gave compounds (i-Pr2C6H3N)(C(Me)(NC6H3i-Pr2))2MBr2
X-ray data collection and reduction
Crystals were manipulated and mounted in capillaries in a
glovebox, thus maintaining a dry, O2-free environment for
each crystal. Diffraction experiments were performed on a
Siemens SMART System CCD diffractometer. The data
1
(M = Cu (5), Zn (6)). The H NMR spectrum of 5 gave se-
3 Supplementary data for this article are available on the Web site or may be purchased from the Depository of Unpublished Data, Document
Delivery, CISTI, National Research Council Canada, Ottawa, ON K1A 0S2, Canada. DUD 3657. For more information on obtaining mate-
rial refer to http://cisti-icist.nrc-cnrc.gc.ca/irm/unpub_e.shtml. CCDC 256368–256376 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).
© 2005 NRC Canada

480
Can. J. Chem. Vol. 83, 2005
Table 1. Crystallographic data.
2·2CH2Cl2
3
4
5
6
Formula
C42H61Cl6FeN3
C40H57Cl2CoN3
C40H57Br2N3Ni
C40H57Br2CuN3
C40H57Br2ZnN3
Formula weight
Crystal System
Space group
a (Å)
b (Å)
c (Å)
876.48
Monoclinic
P21/m
10.369(5)
19.199(9)
11.990(6)
709.72
Monoclinic
P21/m
10.7514(14)
17.395(3)
11.4237(18)
798.41
Monoclinic
P21/n
10.462(9)
43.18(4)
18.187(16)
803.25
Triclinic
P-1
805.08
Monoclinic
P21/c
10.512(7)
43.32(3)
18.257(11)
10.536(6)
11.758(7)
18.189(11)
81.676(11)
74.302(10)
67.424(12)
2 001(2)
2
1.333
2.572
8 599
5 676
α (°)
β (°)
101.554(10)
111.716(4)
106.392(19)
106.732(9)
γ (°)
V (Å3)
2 338.5(19)
2
1 984.9(5)
2
7 882(12)
8
7 962(9)
8
Z
d(calcd.) (g cm–1)
Abs. coeff. (µ, mm–1)
Data collected
1.245
0.696
10 074
3 469
253
0.0446
0.0996
0.827
1.187
0.597
4 578
2 596
226
0.0574
0.1477
1.043
1.346
2.550
36 954
11 284
829
0.0536
0.1241
0.937
1.343
2.654
34 217
11 329
829
0.0660
0.1528
0.770
2
2
Data Fo > 3σ(Fo )
Variables
R
Rw
415
0.0769
0.1815
0.851
GOF
Scheme 2. Synthesis of neutral and cationic complexes: (i) MX2; (ii) Li[B(C6F5)4]; (iii) LiCH2SiMe3; (iv) Super-Hydride.
Ar
X
X
+
Ar
Ar
OEt2
i
N
N
N
Cl
Cl
Ar
M
Ar
ii
N
N
Li
Fe
Ar
N
N
N
OEt2
N
Ar
Ar
Ar
[B(C6F5)4]-
iv
1
iii
7
X = Cl; M = Fe (2), Co (3), Ni (4)
X = Br; M = Cu (5), Zn (6)
Ar
Ar
Ni
N
Cl
Et
SiMe3
N
H
Fe
Ar
N
B
Ar
N
CH2
N
H
N
Et
8
Ar
10
Ar
verely broadened lines, while the spectrum of 6 was similar
to the free ligand. Magnetic susceptibility measurements of
5 gave a magnetic moment of 1.99 µB.
2.357 Å, respectively. The X-M-X angles found in 2–4 are
slightly larger than the typical tetrahedral angle ranging
from 116.79(8)° to 120.14(8)°. For 5 and 6, the Br-M-Br an-
gles were found to be 106.82(7)° and 117.80(5)°. The M—N
distances fall in a narrow range between 1.959(6) and
2.096(3) Å. Similarly, the N—C distances of the imine frag-
ments vary from 1.287(6) to 1.317(10) Å. These latter bond
lengths are slightly longer than those found in the free
ligand (1.272(3) and 1.269(3) Å). The ligand bite angles
ranged from 84.61(15)° for the Fe species to 90.1(3)° for the
Cu species. The N-M-X angles, in general, fall in the range
from 101.54(12)° to 123.67(13)°; however, the largest range
of thse angles was observed for 5 where the N-Cu-Br angles
were found to be 132.9(2)° and 105.8(2)°. These large
N-Cu-Br angles, the large bite angle, short M—N distances,
and the small X-M-X angle in 5 are illustrative of the
greater distortion from a tetrahedral geometry at Cu relative
The overall geometries of the complexes 2–6 as deter-
mined by X-ray crystallographic studies are similar and thus
only two representative ORTEP drawings are provided
(Figs. 1 and 2). In all cases, the aryl rings are approximately
orthogonal to the chelate plane and the metals adopt a
pseudo-tetrahedral geometry. In the case of compounds 2
and 3, the molecules crystallize such that they sit on a crys-
tallographically imposed mirror plane bisecting the ligand
and passing through the plane containing the metal atom –
dichloride fragment. The key metric parameters are summa-
rized in Table 2. The M—Cl distances in 2 and 3 and the
M—Br distance in 4 increases for the Fe, Co, Ni series con-
sistent with increasing atomic radius. The M—Br distances
for 5 and 6 are longer, as expected, averaging 2.367 and
© 2005 NRC Canada

Masuda and Stephan
481
Table 1 (concluded).
7
8·0.5C6H6
9·0.5C6H6·0.25CH2Cl2
10
C72H72BCl2F20FeLiN3O2
C45H69Cl3FeN3Si
C78.25H75BCl0.50F24N3Ni
C44H69BN3Ni
1535.83
Triclinic
P-1
842.32
Orthorhombic
Pnma
1600.66
Triclinic
P-1
709.54
Triclinic
P-1
15.545(3)
16.276(3)
16.461(3)
101.263(4)
92.812(4)
104.311(5)
3 937.0(13)
2
21.1151(12)
19.1255(12)
12.6066(8)
15.178(7)
16.512(7)
17.583(7)
107.375(8)
99.173(8)
97.665(9)
4 074(3)
2
11.861(4)
12.840(4)
16.590(5)
89.734(6)
75.663(7)
63.836(5)
2 181.1(11)
2
5 091.0(5)
4
1.296
0.350
19 393
11 181
883
1.099
0.507
24 184
3 782
257
1.305
0.351
17 656
11 702
929
1.080
0.475
6 910
4 018
466
0.0537
0.1267
0.837
0.0473
0.1195
1.190
0.1145
0.3241
1.211
0.0425
0.1020
0.966
Fig. 1. ORTEP of 2 or 3 (30% thermal ellipsoids are shown).
Hydrogen atoms are omitted for clarity. These compounds are
isomorphous.
Fig. 2. ORTEP of 5 (30% thermal ellipsoids are shown). Hydro-
gen atoms are omitted for clarity.
consistent with a more electron-deficient metal center as a
result of the bridging of the Cl ligands to Li. This view is
also consistent with the longer avg. Fe—Cl bond length of
2.2774(17) Å. A consequence of the bridging Cl atoms is
also a small increase in the diimine ligand bite angle to
86.18(14)°. The Li—Cl bond lengths in 7 were found to be
2.474(10) and 2.352(11) Å, which gives rise to an Fe—Li
separation of 3.163(9) Å.
Alkylation of 2 with 1 equiv. of LiCH2SiMe3 proceeds to
give (i-Pr2C6H3N)(C(Me)(NC6H3-i-Pr2))2FeClCH2SiMe3 (8)
in 55% isolated yield (Scheme 2). The magnetic susceptibil-
ity of 8 was determined to be 5.61 µB, consistent with
a high-spin Fe(II) species. X-ray structural study of 8 con-
to the other compounds (Fig. 2). In this case, it appears that
steric crowding results in the displacement of the Cu atom
out of the ligand plane, and a twisting of the CuBr2 plane to
minimize interactions with the bulky Ar groups.
The species 2 reacts with Li(OEt2)2B(C6F5)4 to form the
yellow adduct [(i-Pr2C6H3N)(C(Me)(NC6H3-i-Pr2))2Fe(µ-
Cl)2Li(OEt2)2][B(C6F5)4] (7) in 41% isolated yield (Scheme 2).
Crystallographic characterization of 7 revealed a pseudo-
tetrahedral geometry about Fe in which two chlorine atoms
bridge the Fe and Li atoms (Fig. 3). The pseudo-tetrahedral
coordination sphere of Li is completed by the coordination
of two molecules of ether. The Fe—N distances average
2.034(4) Å, which is shorter than that observed for 2. This is
© 2005 NRC Canada

482
Can. J. Chem. Vol. 83, 2005
Table 2. Metric parameters (bond distances and angles) for the complexes 2–6.
Cmpd
M—X (Å)
M—N (Å)
2.096(3)
NM—C (Å)
1.297(4)
N-M-N (°)
84.61(15)
X-M-X (°)
120.14(8)
N-M-X (°)
2
2.235(2)
110.87(9), 112.43(9)
2.252(2)
3
4
5
6
2.219(2)
2.2158(17)
2.328(2)
2.394(2)
2.3455(19)
2.389(2)
1.999(3)
1.299(4)
89.78(16)
89.84(19)
90.1(3)
116.79(8)
117.93(4)
106.82(7)
117.80(5)
108.30(10), 115.18(9)
1.996(5)
1.997(4)
1.959(6)
1.987(8)
2.050(6)
2.082(6)
1.287(6)
1.290(6)
1.317(10)
1.296(10)
1.282(8)
1.305(8)
123.67(13), 114.28(12)
101.54(12), 104.96(12)
132.9(2), 105.8(2)
102.31(19), 119.9(2)
117.08(16), 112.90(17)
106.96(15), 110.04(15)
2.3416(17)
2.3729(19)
88.1(2)
Fig. 3. ORTEP of the cation of 7 (30% thermal ellipsoids are
shown). Hydrogen atoms are omitted for clarity. Bond lengths
(Å): Fe(1)—N(3) 2.030(4), Fe(1)—N(1) 2.034(3), Fe(1)—Cl(2)
2.2706(17), Fe(1)—Cl(1) 2.2842(17), Fe(1)—Li(1) 3.163(9),
Cl(1)—Li(1) 2.474(10), Cl(2)—Li(1) 2.352(11), N(1)—C(37)
1.291(5), N(1)—C(1) 1.451(5), N(2)—C(13) 1.466(5), Li(1)—
O(2) 1.943(11), Li(1)—O(1) 1.968(10). Bond angles (°): N(3)-
Fe(1)-N(1) 86.18(14), N(3)-Fe(1)-Cl(2) 123.86(11), N(1)-Fe(1)-
Cl(2) 114.69(11), N(3)-Fe(1)-Cl(1) 113.49(10), N(1)-Fe(1)-Cl(1)
121.78(11), Cl(2)-Fe(1)-Cl(1) 98.82(7), O(2)-Li(1)-O(1) 114.8(5),
O(2)-Li(1)-Cl(2) 113.6(5), O(1)-Li(1)-Cl(2) 106.8(5), O(2)-Li(1)-
Cl(1) 111.3(5), O(1)-Li(1)-Cl(1) 116.5(5).
Fig. 4. ORTEP of 8 (30% thermal ellipsoids are shown). Hydro-
gen atoms are omitted for clarity. Bond lengths (Å): Fe(1)—
C(26) 2.038(6), Fe(1)—N(1) 2.114(3), Fe(1)—Cl(1) 2.2762(15),
N(1)—C(1) 1.281(4), N(1)—C(3) 1.454(4). Bond angles (°):
C(26)-Fe(1)-N(1) 117.67(13), N(1)-Fe(1)-N(1) 82.99(13), C(26)-
Fe(1)-Cl(1) 124.89(18), N(1)-Fe(1)-Cl(1) 102.50(7), C(1)-N(1)-
Fe(1) 127.9(2).
firmed the formulation, with the molecule residing on a
crystallographically imposed mirror plane that bisects the
ligand and passes through the pseudo-tetrahedral Fe center
and the plane containing Cl and the (CH2SiMe3) fragment
(Fig. 4). The incorporation of an electron-donating alkyl
group results in the expected lengthening of the Fe—N bond
length to 2.114(3) Å. Similarly the Fe—Cl distance of
2.2762(15) Å in 8 is longer than that found in 2. The longer
Fe—N distance also results in a slightly smaller ligand bite
angle of 82.99(13)°. Attempts to further alkylate Fe were
unsuccessful, presumably a reflection of the steric crowding
about the Fe center of 8. In addition, attempts to alkylate
with MeLi or t-BuLi were also unsuccessful leading to ap-
parent compound degradation.
Reactions of 1 with [(η3-C3H5)NiBr]2 and [Na][B(3,5-
(CF3)2C6H3)4] afforded the salt [(i-Pr2C6H3N)(C(Me)-
(NC6H3-i-Pr2))2Ni(η3-C3H5)][B(3,5-(CF3)2C6H3)4] (9) in 33%
isolated yield. The 1H NMR spectrum of 9 is consistent with
this formulation and indicative of a η3-bonding mode of the
allyl fragment. Variable-temperature studies (–90 to 35 °C)
show no change in the allyl signals, reflecting the absence of
dynamic behavior. Attempts to react 9 with CO, ethylene, or
PhPH2 failed to show any reaction, even under forcing con-
ditions (refluxing toluene), again reflecting the maintenance
of the η3-bonding mode of the allyl fragment. X-ray data
also confirmed this binding mode (Fig. 5). The Ni—N dis-
tances in 9 were found to be 1.915(6) and 1.916(6) Å. These
distances, which are shorter than those found in 4, are con-
© 2005 NRC Canada

Masuda and Stephan
483
Fig. 6. ORTEP of 10 (30% thermal ellipsoids are shown). All
hydrogen atoms except the bridging hydrogen atoms are omitted
for clarity. Bond lengths (Å): Ni(1)—N(1) 1.946(2), Ni(1)—N(3)
1.949(2), Ni(1)—B(1) 2.165(4), B(1)—C(41) 1.600(6), B(1)—C(43)
1.616(6), N(1)—C(5) 1.456(4), N(3)—C(3) 1.305(4), N(3)—C(29)
1.447(4). Bond angles (°): N(1)-Ni(1)-N(3) 89.48(10), N(1)-
Ni(1)-B(1) 138.37(13), N(3)-Ni(1)-B(1) 132.15(13), C(41)-B(1)-
C(43) 114.6(3), C(41)-B(1)-Ni(1) 119.8(3), C(43)-B(1)-Ni(1)
125.5(3), C(1)-N(1)-Ni(1) 130.1(2).
Fig. 5. ORTEP for the cation of 9 (30% thermal ellipsoids are
shown). Hydrogen atoms are omitted for clarity. Bond lengths
(Å): Ni(1)—N(1) 1.915(6), Ni(1)—N(2) 1.916(6), Ni(1)—C(42)
1.96(2), Ni(1)—C(41) 2.019(14), Ni(1)—C(43) 2.049(11),
N(1)—C(3) 1.306(8), N(2)—C(1) 1.290(8). Bond angles (°):
N(1)-Ni(1)-N(2) 92.1(2), N(1)-Ni(1)-C(42) 134.4(7), N(2)-Ni(1)-
C(42) 131.9(7), N(1)-Ni(1)-C(41) 168.9(4), N(2)-Ni(1)-C(41)
98.1(4), C(42)-Ni(1)-C(41) 37.1(7), N(1)-Ni(1)-C(43) 97.6(4),
N(2)-Ni(1)-C(43) 170.2(4), C(42)-Ni(1)-C(43) 38.5(7), C(41)-
Ni(1)-C(43) 72.2(5), C(3)-N(1)-Ni(1) 127.7(4), C(41)-C(42)-
C(43) 135(2).
Acknowledgments
sistent with the presence of the formal positive charge. The
Ni–allyl interaction results in Ni—C bond lengths of
1.96(2), 2.019(14), and 2.049(11) Å, typical of the η3-bond-
ing mode (39, 40).
Financial support from the Natural Sciences and Engi-
neering Research Council of Canada (NSERC) and the On-
tario Research and Development Challenge Fund (ORDCF)
is gratefully acknowledged. JDM is grateful for the award of
an Ontario Graduate Scholarship (OGS).
Finally, reactions of 4 with Super-Hydride afforded
brown-red crystals of the species formulated as (i-Pr2C6H3N)-
(C(Me)(NC6H3-i-Pr2))2NiH2BEt2 (10) in 45% yield (Scheme 2).
The magnetic susceptibility of 10 was determined to be
2.87 µB. X-ray data confirmed the above formulation of 10
as a formally Ni(I) species and revealed the pseudo-
tetrahedral geometry about Ni in which two hydride atoms
bridge the Ni and B centers (Fig. 6). The Ni—N distances
average 1.947(2) Å, while the Ni—B separation is 2.165(4)
Å. Location and refinement of the hydride atoms revealed an
avg. Ni—H distance of 1.70(1) Å and B—H distances of
1.20(1) Å. Attempts to remove borane from 10 via reaction
with BuLi were unsuccessful. Similarly, 10 proved to be
unreactive with primary phosphine or phenol.
References
1. G.J.P. Britovsek, V.C. Gibson, and D.F. Wass. Angew. Chem.
Int. Ed. 38, 428 (1999).
2. S.D. Ittel, L.K. Johnson, and M. Brookhart. Chem. Rev. 100,
1169 (2000).
3. C. Cui, H.W. Roesky, H.-G. Schmidt, M. Noltemeyer, H. Hao,
and F. Cimpoesu. Angew. Chem. Int. Ed. 39, 4274 (2000).
4. N.J. Hardman, R.J. Wright, A.D. Phillips, and P.P. Power. J.
Am. Chem. Soc. 125, 2667 (2003).
5. F. Basuli, B.C. Bailey, J.C. Huffman, and D.J. Mindiola.
Chem. Commun. 1554 (2003).
6. K.T.K. Chan, L.P. Spencer, J.D. Masuda, J.S.J. McCahill, P.
Wei, and D.W. Stephan. Organometallics, 23, 381 (2004).
7. J.D. Masuda, P. Wei, and D.W. Stephan. Dalton Trans. 3500
(2003).
Summary
This manuscript describes the synthesis and structure of a
series of transition metal complexes of the bulky N-aryl-
imidoyl amidine ligand (i-Pr2C6H3N)(C(Me)(NC6H3-i-Pr2))2.
While a variety of complexes are readily accessible, the re-
sulting complexes are generally robust and unreactive, prin-
cipally a result of the sterically demanding nature of the
ligand. As a result, we are continuing efforts to utilize this
ligand to stabilize and isolate reactive transition metal frag-
ments.
8. L.P. Spencer, R. Altwer, P. Wei, L. Gelmini, J. Gauld, and
D.W. Stephan. Organometallics, 22, 3841 (2003).
9. J.D. Masuda, D.M. Walsh, P. Wei, and D.W. Stephan. Organo-
metallics, 23, 1819 (2004).
10. G.C. Welch, W.E. Piers, M. Parvez, and R. McDonald.
Organometallics, 23, 1811 (2004).
11. H.C. Brown and P.D. Schuman. J. Org. Chem. 28, 1122 (1963).
12. M. Green, S.H. Taylor, J.J. Daly, and F. Sanz. J. Chem. Soc.
Chem. Commun. 361 (1974).
© 2005 NRC Canada

484
Can. J. Chem. Vol. 83, 2005
13. M. Bottrill, R. Goddard, M. Green, R.P. Hughes, M.K. Lloyd,
S.H. Taylor, and P. Woodward. J. Chem. Soc. Dalton Trans.
1150 (1975).
27. Q.-D. Liu, W.-L. Jia, G. Wu, and S. Wang. Organometallics,
22, 3781 (2003).
28. T.-B. Tsao, G.-H. Lee, C.-Y. Yeh, and S.-M. Peng. Dalton
14. V. Robinson, G.E. Taylor, P. Woodward, M.I. Bruce, and R.C.
Wallis. J. Chem. Soc. Dalton Trans. 1169 (1981).
15. M.B. Hursthouse, M.A. Mazid, S.D. Robinson, and A.
Sahajpal. J. Chem. Soc. Dalton Trans. 3615 (1994).
16. J. Barker, M. Kilner, M.M. Mahmoud, and S.C. Wallwork. J.
Chem. Soc. Dalton Trans. 837 (1989).
Trans. 1465 (2003).
29. C. Tu, J. Lin, Y. Shao, and Z. Guo. Inorg. Chem. 42, 5795
(2003).
30. T. Yajima, G. Maccarrone, M. Takani, A. Contino, G. Arena,
R. Takamido, M. Hanaki, Y. Funahashi, A. Odani, and O.
Yamauchi. Chem. Eur. J. 9, 3341 (2003).
17. D.R. Aris, J. Barker, P.R. Phillips, N.W. Alcock, and M.G.H.
Wallbridge. J. Chem. Soc. Dalton Trans. 909 (1997).
18. S.V. Kryatov, M.B. Smith, E.V. Rybak-Akimova, and A.Y.
Nazarenko. Chem. Commun. 1174 (2001).
19. M.N. Kopylovich, A.J.L. Pombeiro, A. Fischer, L. Kloo, and
V.Y. Kukushkin. Inorg. Chem. 42, 7239 (2003).
20. J.F. Berry, F.A. Cotton, L.M. Daniels, C.A. Murillo, and X.
Wang. Inorg. Chem. 42, 2418 (2003).
31. F.A. Cotton, L.M. Daniels, J.H. Matonic, X. Wang, and C.A.
Murillo. Polyhedron, 16, 1177 (1997).
32. A.A. Danopoulos, G. Wilkinson, T.K.N. Sweet, and M.B.
Hursthouse. J. Chem. Soc. Dalton Trans. 3771 (1996).
33. R. Uson, J. Fornies, P. Espinet, and E. Lalinde. J. Organomet.
Chem. 334, 399 (1987).
34. D.N. Coventry, A.S. Batsanov, A.E. Goeta, J.A.K. Howard,
and T.B. Marder. Polyhedron, 23, 2789 (2004).
35. D.L. Reger, T.D. Wright, C.A. Little, J.J.S. Lamba, and M.D.
Smith. Inorg. Chem. 40, 3810 (2001).
21. J.F. Berry, F.A. Cotton, P. Lei, T. Lu, and C.A. Murillo. Inorg.
Chem. 42, 3534 (2003).
22. J.F. Berry, F.A. Cotton, P. Lei, and C.A. Murillo. Inorg. Chem.
42, 377 (2003).
36. SAINT, XPREP, and SHELXTL [computer programs]. Bruker
AXS Inc., Madison, Wis. 2004.
23. J.F. Berry, F.A. Cotton, T. Lu, and C.A. Murillo. Inorg. Chem.
37. J. Feldman, S.J. McLain, A. Parthasarathy, W.J. Marshall, J.C.
Calabrese, and S.D. Arthur. Organometallics, 16, 1514 (1997).
38. L.K. Johnson, C.M. Killian, and M. Brookhart. J. Am. Chem.
Soc. 117, 6414 (1995).
42, 4425 (2003).
24. J.F. Berry, F.A. Cotton, T. Lu, C.A. Murillo, and X. Wang.
Inorg. Chem. 42, 3595 (2003).
25. M. Burgos, O. Crespo, M.C. Gimeno, P.G. Jones, and A.
39. K. Landolsi, M. Rzaigui, and F. Bouachir. Tetrahedron Lett.
Laguna. Eur. J. Inorg. Chem. 2170 (2003).
43, 9463 (2002).
26. Y. Kang, C. Seward, D. Song, and S. Wang. Inorg. Chem. 42,
2789 (2003).
40. A. Mechria, C. Bavoux, and F. Bouachir. J. Organomet. Chem.
677, 53 (2003).
© 2005 NRC Canada