Nickel and palladium phosphinimine-imine ligand complexes

Article abstract of DOI:10.1039/b306110h

The imine (C₆H₃i-Pr₂)NCMe₂ 1 was prepared and used to make the phosphine (C₆H₃i-Pr ₂)NC(Me)CH₂PPh₂ 2. Oxidation with the substituted arylazide resulted in t

Full text of DOI:10.1039/b306110h

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Nickel and palladium phosphinimine-imine ligand complexes
Jason D. Masuda, Pingrong Wei and Douglas W. Stephan*
Department of Chemistry & Biochemistry, University of Windsor, Windsor, Ontario, Canada
N9B3P4. E-mail: stephan@uwindsor.ca; Fax: 591-973-7098; Tel: 519-253-3000 x3537
Received 30th May 2003, Accepted 25th July 2003
First published as an Advance Article on the web 6th August 2003
The imine (C6H3i-Pr2)NCMe2 1 was prepared and used to make the phosphine (C6H3i-Pr2)NC(Me)CH2PPh2
2. Oxidation with the substituted arylazide resulted in the isolation of the phosphinimine-imine species
(C6H3i-Pr2)NC(Me)CH2PPh2(NC6H3i-Pr2) 3. The ligand 3 forms the neutral Ni-complex NiBr2((C6H3i-Pr2)-
NC(Me)CH2PPh2(NC6H3i-Pr2)) 4 while attempts to prepare the analogous Pd species were unsuccessful. Reaction
of 3 with n-BuLi produced the Li-salt Li(thf )((C6H3i-Pr2)NC(Me)CHPPh2(NC6H3i-Pr2)) 5. Subsequent reaction
with NiBr2(dme) afforded [Ni((C6H3i-Pr2)NC(Me)CHPPh2(NC6H3i-Pr2))(µ-Br)2Li(thf )2] 6. In related syntheses 5
reacted with NiBr2(dme) or (PhCN)2PdCl2 and PPh3 to give the complexes of formulation MX((C6H3i-Pr2)-
NC(Me)CHPPh2(NC6H3i-Pr2))(PPh3) (X = Br, M = Ni 7; X = Cl, M = Pd 8). The latter complexes 7 and 8 are
phosphinimine-N–C bound. Structural studies of 2 and 4–8 are reported. The implications of these studies for
the utility of this phosphinimine-imine ligand in olefin polymerization catalysts are considered.
purified employing a Grubb’s type solvent purification system
Introduction
manufactured by Innovative Technology. All organic reagents
were purified by conventional methods. 1H, 31P{1H} and
13C{1H} NMR spectra were recorded on Bruker Avance-300
and 500 spectrometers. All spectra were recorded in C6D6 at
25 ЊC unless otherwise noted. Trace amounts of protonated
solvents were used as references and chemical shifts are
reported relative to SiMe4. 31P{1H} NMR spectra were refer-
enced to external 85% H3PO4. Combustion analyses were done
in-house employing a Perkin Elmer CHN Analyzer. Magnetic
susceptibility measurements were performed using the Evans
method.
A variety of late transition metal complexes containing chelat-
ing ligands have been shown to act as catalysts for the poly-
merization and oligomerization of olefins. Early work on the
Shell Higher Olefin Process (SHOP)1 utilized neutral Ni
catalysts containing P–O chelates. Subsequent work by Keim
et al. resulted in the development of a Ni–iminophosphorane
amidato ligand complex which effected the polymerization of
olefins.2 More recently, Ni– and Pd–diimine complexes3–7 and
bis(imino)pyridine complexes of Fe and Co8,6 have been shown
be effective polymerization catalysts upon activation with
methylalumoxane (MAO). Very recent Ni() complexes of
N–O salicylaldiminates, a Ni complex of 2-(2,6-diisopropyl-
anilino)tropone9 and a cationic Ni()–allyl complex of a P–O
chelate10 act as very active single-component catalysts
producing highly linear polyethylene.
In seeking alternative systems, we and others have focused
attention on the phosphinimine-based ligand complexes. While
a number of bis-phosphinimine complexes11–14 have been pre-
pared, few have been examined for the potential in catalysis.
Bochmann and coworkers have shown that Fe complexes of
bis(aryliminophosphoranyl)pyridine ligands, which are struc-
turally reminiscent to the bis(imino)pyridine ligand complexes,
exhibited only modest activity.15 The complex (C6H4(NPPh3)2)-
NiCl2 has been recently reported to effect ethylene oligo-
merisation.16 In our own work we have shown that Ni and Fe
complexes of pyridinephosphinimine chelates act as ethylene
dimerization catalysts. Pd–β-diketiniminate complexes have
been shown to afford dimetallic derivatives upon metallation of
the central C atom,17 whereas Ni–β-diketiminates have been
recently shown to stabilize the rather unusual three-coordinate
Ni() and Ni() complexes.18,19 In this paper, we consider a
hybrid phosphinimine-imine ligand, which is structurally simi-
lar to β-diketiniminate ligands, with the replacement of one of
the imine-groups by a phosphinimine fragment. Ni and Pd
complexes of this ligand are prepared and the implications of
the structural information with respect to suitability for use in
olefin-polymerization catalysts are considered.
Synthesis of (C6H3i-Pr2)NCMe2 1
100 mL toluene, 20.0 g (112.8 mmol) (C6H3i-Pr2)NH2, 65.5 mL
acetone and 100 mL molecular sieves were added to a flask. The
mixture was brought to reflux for 6 days, after which heating
was stopped and the solution was allowed to cool. The molecu-
lar sieves were filtered off and washed with 2 × 50 mL hexanes.
A brown oil remained after removal of the solvent in vacuo.
Distillation (98–103 ЊC, 0.5 mm) gave 21.48 g (98.8 mmol) of a
pale yellow oil. Yield: 88%. 1H NMR (CDCl3): δ 7.02–7.13 (m,
3H, m,p-Ar), 2.77 (sept, 2H, |3JH–H| = 7 Hz, CH), 2.26 (3H, s,
cis-CH3), 1.69 (3H, s, trans-CH3), 1.16 (6H, d, |3JH–H| = 7 Hz,
Me), 1.15 (6H, d, |3JH–H| = 7 Hz, Me). 13C NMR (CDCl3):
δ 168.9 (s, NC), 146.3 (s, ipso-Ph), 136.8 (s, o-Ph), 123.5 (s,
p-Ph), 123.1 (s, m-Ph), 28.1 (s, CH), 27.9 (s, Me), 23.6 (s, Me),
23.3 (s, Me), 21.7 (s, Me).
Synthesis of (C6H3i-Pr2)NC(Me)CH2PPh2 2
To a solution of 250 mL n-pentane, 1 (10.00 g, 46.0 mmol) and
tmen (7.6 mL 5.85 g, 50.4 mmol), cooled to Ϫ78 ЊC, was added
n-BuLi (20.25 mL of 2.5 M solution (hexanes), 50.6 mmol). The
solution immediately turned yellow and a white precipitate
formed. The mixture was allowed to warm to 25 ЊC and stirred
for 2 h, whereupon the flask was cooled again to Ϫ78 ЊC and
ClPPh2 (10.10 g, 46.0 mmol) of was added dropwise. After
refluxing overnight, the solution containing an off-white pre-
cipitate (LiCl) was filtered through Celite, and the solids
washed with 2 × 20 mL n-pentane. Upon removal of n-pentane
in vacuo, an off-white solid remained. Dissolving the solid in a
minimum of boiling EtOH and cooling to 25 ЊC gave 7.60 g of
colorless crystals. Multiple crops offered an additional 6.35 g of
material. Yield: 76%. X-Ray quality crystals were obtained by a
Experimental
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 glove box. Solvents were
1
second recrystallization from EtOH. H NMR (CDCl3, major
D a l t o n T r a n s . , 2 0 0 3 , 3 5 0 0 – 3 5 0 5
T h i s j o u r n a l i s © T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 3
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isomer): δ 7.55–7.61 (m, 4H, o-PPh2), 7.35–7.41 (m, 6H, m,p-
PPh2), 7.01–7.07 (m, 3H, m,p-Ar), 3.43 (d, 2H, CH2, |2JP–H| =
2 Hz), 2.49 (sept, 2H, CH, |JH–H| = 7 Hz), 1.77 (s, 3H, Me), 1.00
(d, 6H, Me, |JH–H| = 7 Hz), 0.99 (d, 6H, Me, |JH–H| = 7 Hz).
31P{1H} NMR (CDCl3): δ Ϫ18.0 (95%, major isomer), Ϫ17.5
(5%, minor isomer). 13C{1H} NMR (CDCl3, major isomer):
δ 168.5 (s, NC), 146.2 (s, ipso-Ar), 138.4 (d, ipso-PPh2, |JP–C| =
14 Hz), 136.7 (s, m-Ar), 133.1 (d, o-PPh2, |2JP–C| = 19 Hz), 129.1
(s, p-PPh2), 128.7 (d, m-PPh2, |3JP–C| = 7 Hz), 123.5 (s, p-Ar),
123.0 (s, m-Ar), 42.8 (d, CH2P, |JP–C| = 16 Hz), 28.0 (s, CH), 23.6
(s, Me), 23.4 (s, Me), 21.6 (d, |JP–C| = 7 Hz, Me). Anal. Calc. for
C27H32NP: C, 80.76; H, 8.03; N, 3.49. Found: C, 80.43; H, 8.27;
N, 3.16%.
6H, |JH–H| = 7 Hz, Me), 1.01–1.06 (m, 2H, thf ). 13C{1H} NMR:
δ 169.5 (NC), 150.2, 146.8 (d, 9 Hz), 145.0 (d, 7 Hz), 142.9,
136.8 (d, |JP–C| = 94 Hz, ipso-PPh2), 132.6 (d, 7 Hz), 130.1,
127.7–128.3 (m, obscured by C6D6), 123.3, 123.1, 122.8, 121.3
(d, 4 Hz), 68.1, 65.8 (d, |JP–C| = 29 Hz, PCH), 28.8, 27.7, 25.0,
24.9, 24.4, 23.9 (d, |3JP–C| = 18 Hz, Me). 31P{1H} NMR: δ 11.5.
Anal. Calc. for C43H56N2OPLi: C, 78.87; H, 8.62; N, 4.28.
Found: C, 78.63; H, 8.69; N, 4.30%.
Synthesis of [Ni((C6H3i-Pr2)NC(Me)CHPPh2(NC6H3i-Pr2))-
(ꢀ-Br)2Li(thf)2]6
To a solution of 3 (159 mg, 0.276 mmol) in thf (4 mL) was
added n-BuLi in hexanes (0.181 mL, 1.6 M). The resulting yel-
low solution was allowed to stir for 1 h and NiBr2(dme) (85 mg,
0.276 mmol) in thf (4 mL) was added. After stirring overnight,
the solvent was removed and the dark solids dissolved in hot
n-pentane. After filtration through Celite, the solution was
stored at Ϫ35 ЊC overnight yielding black/red crystals of
6. Yield: 37%, magnetic susceptibility: 3.93 µB. Anal. Calc. for
C47H64N2O2PNiBr2Li: C, 59.71; H, 6.82; N, 2.96. Found: C,
59.80; H, 6.68; N, 2.92%.
Synthesis of (C6H3i-Pr2)NC(Me)CH2PPh2(NC6H3i-Pr2)3
To a solution of 2 (6.83 g, 17.5 mmol) in 125 mL CH2Cl2 was
added (C6H3i-Pr2)N3 (5.10 g, 25 mmol). N2 evolution com-
menced immediately and the mixture was refluxed for 3 h.
Removal of CH2Cl2 under vacuum left a thick brown oil. The
oil was dissolved in 300 mL boiling MeOH, filtered through
Celite and cooled overnight. Filtration of solids and washing
with 2 × 50 mL cold n-pentane gave 6.60 g of a white powder.
Additional crops gave an extra 0.54 g of material. Yield of
3ؒMeOH: 70%. Analytical crystals were grown from a hot
Synthesis of MX((C6H3i-Pr2)NC(Me)CHPPh2(NC6H3i-Pr2))-
(PPh3) (X ؍ Br, M ؍ Ni 7; X ؍ Cl, M ؍ Pd8)
1
MeOH solution slowly cooled to 25 ЊC. H NMR (major iso-
These compounds were prepared in a similar fashion and thus
only one preparation is detailed. To a solution of 3 (116 mg,
0.201 mmol) in 4 mL thf was added n-BuLi in hexanes (0.087
mL, 2.5 M). The yellow solution was allowed to stir for 1 h,
after which (PhCN)2PdCl2 (76 mg) in 3 mL thf was added,
forming a dark brown solution. Then PPh3 (52 mg) was added
and the mixture was stirred overnight. Removal of solvent, addi-
tion of toluene and filtration through Celite gave a green–
brown solution. After 2 days, 123 mg of light brown crystals of
8 were isolated after washing with n-pentane. 7: Yield: 57%: 1H
mer): δ 7.71–7.75 (m, 10H, PPh2), 6.99–7.18 (m, 6H, m,p-Ar),
3.73 (d, |2JP–H| = 14 Hz, 2H, PCH2), 3.67 (sept, |JH–H| = 7 Hz, 2H,
CH), 2.57 (sept, |JH–H| = 7 Hz, 2H, CH), 1.62 (s, 3H, Me), 1.17
(d, |JH–H| = 7 Hz, 12H, Me), 1.06 (d, |JH–H| = 7 Hz, 6H, Me), 1.05
(d, |JH–H| = 7 Hz, 6H, Me). 13C{1H} NMR (CD2Cl2, major iso-
mer): δ 165.3 (d, |2JP–C| = 6 Hz, NC), 146.1 (imine ipso-Ar),
144.2 (ipso-Ar), 142.5 (d, |3JP–C| = 8 Hz, o-Ar), 136.4 (o-Ar),
133.8 (d, |JP–C| = 98 Hz, ipso-PPh2), 131.8 (p-PPh2), 131.6
(o-PPh2), 128.9 (d, |3JP–C| = 12 Hz, m-PPh2), 124.1 (p-Ar), 123.2
(m-Ar), 123.0 (m-Ar), 119.2 (p-Ar), 45.7 (d, |JP–C| = 65 Hz, CH2)
29.0 (PCH), 28.0 (CH), 24.0 (Me), 23.8 (Me), 23.3 (Me), 22.6
(Me); 31P{1H} NMR: δ Ϫ13.2 (73%, major isomer), 3.6 (27%,
minor isomer). Anal. Calc. for C40H53N2PO: C, 78.91; H, 8.77;
N, 4.60. Found: C, 78.76; H, 9.12; N, 4.59%.
NMR (CD2Cl2): δ 6.85–7.14 (m, Ph), 4.50 (sept, 1H, CH, |JH–H
|
= 7 Hz), 3.87 (sept, 1H, CH, |JH–H| = 7 Hz), 1.81 (sept, 1H, CH,
|JH–H| = 7 Hz), 1.51 (d, 3H, Me, |JH–H| = 7 Hz), 1.27 (d, 3H, Me,
|JH–H| = 7 Hz), 1.24 (d, 3H, Me, |JH–H| = 7 Hz), 1.12 (d, 3H, Me,
|JH–H| = 7 Hz), ca. 1.11 (m, obscured by adjacent Me peak, 1H,
CH), 1.03 (s, 3H, Me), 0.88 (d, 3H, Me, |JH–H| = 7 Hz), 0.86 (d,
3H, Me, |JH–H| = 7 Hz), 0.74 (d, 3H, Me, |JH–H| = 7 Hz), 0.50 (d,
3H, Me, |JH–H| = 7 Hz), 0.21 (d, 3H, Me, |JH–H| = 7 Hz). 13C{1H}
NMR (CH2Cl2): δ 171.61 (d, NC, |2JP–C| = 6 Hz), 149.2 (d, 5 Hz),
147.6, 146.2, 144.5, 144.0, 138.8, 138.7, 138.3, 137.8, 137.8,
137.0, 136.8, 136.7, 135.4, 135.2, 134.6, 133.0, 132.9, 132.5,
132.0, 130.6, 130.2, 130.1, 128.5, 128.4, 128.4, 128.3, 124.1,
123.4, 123.3, 123.2, 123.0, 122.8, 29.5, 28.2, 27.2, 25.8, 24.4,
24.4, 24.8, 23.7, 23.5, 23.5, 23.3, 6.1 (d of d, 1JP–C = 76 Hz, 2JP–C
= 17 Hz, CH). 31P{1H} NMR: δ 24.4 (d, |3JP–P| = 39 Hz), 18.0 (d,
|3JP–P| = 39 Hz). Anal. Calc. for C58H65N2P2NiCl2Br: C, 65.62;
H, 6.17; N, 2.64. Found: C, 65.43; H, 6.45; N, 2.49%. 8: Yield
Synthesis of NiBr2((C6H3i-Pr2)NC(Me)CH2PPh2-
(NC6H3i-Pr2))4
In toluene (8 mL) 3 (132 mg, 0.229 mmol) was combined with
NiBr2(dme) (71 mg, 0.229 mmol) and the mixture was allowed
to stir overnight. A blue precipitate formed. The solvent was
removed in vacuo to give a light blue powder 4. The solid was
dissolved in CH2Cl2 (6 mL), filtered through Celite and the blue
solution layered with toluene (12 mL). After two days, blue
crystals were separated from the solution by decantation. The
crystals were washed with n-pentane. Yield: 30%, magnetic
susceptibility: 4.34 µB. Anal. Calc. for C46H57N2PNiBr2: C,
62.26; H, 6.47; N, 3.16. Found: C, 61.99; H, 6.42; N, 3.03%.
1
57%: H NMR: δ 7.80–8.05 (m, 10H, o-PPh2), 6.87–7.56 (m,
26H, m,p-PPh2, m,p-Ar), 4.43 (sept, 1H, CH, |JH–H| = 7 Hz),
3.30 (sept, 1H, CH, |JH–H| = 7 Hz), 3.29 (sept, 1H, CH, |JH–H| =
7 Hz), 2.35 (s, 3H, Me), 1.91 (d of d, 2H, CH, |1JP–H| = 7 Hz,
|2JP–H| = 6 Hz), 1.70 (sept, 1H, CH, |JH–H| = 7 Hz), 1.35 (d, 3H, Me,
|JH–H| = 7 Hz), 1.21 (d, 6H, Me, |JH–H| = 7 Hz), 0.96 (d, 3H, Me,
|JH–H|=7Hz),0.95(d,3H,Me,|JH–H|=7Hz),0.93(s,3H,Me),0.69
(d, 3H, Me, |JH–H| = 7 Hz), 0.47 (d, 3H, Me, |JH–H| = 7 Hz), 0.19 (d,
3H, Me, |JH–H| = 7 Hz). 13C{1H} NMR: δ 171.3 (d, NC, |2JP–C| =
6 Hz), 149.0 (d, 7 Hz), 148.2, 146.5, 139.3 (d, 8 Hz), 138.6,
137.7, 137.2, 137.1, 135.4–136.0 (m), 133.4, 133.3, 132.7, 132.5,
132.4, 131.4, 130.7, 130.6, 129.6, 128.8–129.1 (m), 125.8,
124.5, 123.7, 123.6, 123.4, 123.2, 122.7, 29.9, 28.8, 28.4,
27.6, 25.8, 25.0, 24.9, 24.8, 24.2, 24.1, 24.0, 23.7, 23.6, 23.3,
Synthesis of [Li(thf)][(C6H3i-Pr2)NC(Me)CHPPh2-
(NC6H3i-Pr2)]5
To a solution of 302 mg (0.524 mmol) 3 in 5 mL of thf was
added 0.231 mL of 2.5 M n-BuLi in hexanes (10% excess). The
solution immediately turned orange–yellow and was allowed to
stir for 2 h, after which the solvent was removed under vacuum.
The yellow solids were then dissolved in ca. 15 mL hot n-penta-
ne and filtered through a pad of Celite to remove any insoluble
material. The clear yellow solution was then stored at 25 ЊC,
1
giving 261 mg of large yellow blocks. Yield: 77%, H NMR:
δ 7.92–8.00 (m, 4H, o-PPh2, o-Ar), 7.01–7.23 (m, 11H, m,p-
PPh2, m,p-Ar), 3.96 (sept, 2H, |JH–H| = 7 Hz, CH), 3.96 (d, 1H,
|2JP–H| = 27 Hz, CHP), 3.29 (sept, 2H, |JH–H| = 7 Hz, CH), 2.94–
2.98 (m, 2H, thf ), 1.89 (d, 3H, |4JP–H| = 2 Hz, Me) 1.33 (d, 6H,
|JH–H| = 7 Hz, Me), 1.28 (br d, 12H, |JH–H| = 7 Hz, Me), 1.13 (d,
21.7, 15.9 (d, |1JP–C| = 79 Hz, CH). 31P{1H} NMR: 29.2 (d, |3JP–P
|
= 15 Hz), 25.5 (d, |3JP–P| = 15 Hz). Anal. Calc. for C64H71N2P2-
PdCl: C, 71.70; H, 6.68; N, 2.61. Found: C, 71.39; H, 6.59; N,
2.82%.
D a l t o n T r a n s . , 2 0 0 3 , 3 5 0 0 – 3 5 0 5
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Table 1 Crystallographic data
2
4
5
6
7
8
Formula
Formula wght
C54H64N2P2
803.01
C46H57Br2N2NiP
887.44
C43H55LiN2OP
653.80
C47H64Br2LiN2NiO2P
945.44
C59H70BrCl4N2NiP2
1149.53
C64H71ClN2P2Pd
1072.02
Crystal system
Space group
Monoclinic
P21/c
Monoclinic
P21/c
Monoclinic
P21/n
Triclinic
P1
Monoclinic
P21/c
Monoclinic
P21/n
¯
a/Å
b/Å
c/Å
α/Њ
21.355(12)
17.586(10)
13.052(7)
13.932(7)
13.976(7)
23.942(12)
10.687(7)
19.406(12)
19.757(12)
11.284(6)
13.404(7)
18.234(10)
81.631(10)
74.457(12)
67.997(9)
2460(2)
1.276
23.05(3)
10.399(15)
24.60(3)
10.367(7)
26.477(17)
23.410(15)
β/Њ
98.315(12)
105.303(9)
98.359(13)
104.11(3)
96.274(13)
γ/Њ
V/Å3
4850(5)
1.100
4
0.125
20418
4287
4497(4)
1.311
4
2.276
18638
6404
4054(4)
1.071
4
0.100
17063
5785
5719(14)
1.335
4
1.319
19576
8239
6387(7)
1.115
4
0.418
27188
9140
Dc/g cmϪ3
Z
2
µ/cmϪ1
2.086
10205
6993
Data collected
Data Fo2 > 3σ(Fo )
2
Variables
R
Rw
523
457
433
501
622
631
0.0390
0.0925
0.905
0.0369
0.0747
1.000
0.0498
0.1085
1.012
0.0675
0.1491
0.908
0.0684
0.1749
0.862
0.0541
0.1416
1.099
GOF
X-Ray data collection and reduction
Results and discussion
Crystals were manipulated and mounted in capillaries in a glove
box, thus maintaining a dry, O2-free environment for each crys-
tal. 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 consistent with the space groups
in each case. The data sets were collected (4.5 < 2θ < 45–50.0Њ).
A measure of decay was obtained by re-collecting 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.20a An empirical
absorption correction based on redundant data was applied to
each data set. Subsequent solution and refinement was per-
formed using the SHELXTL20b solution package operating on
a Pentium computer.
The imine (C6H3i-Pr2)NCMe2 1 was prepared from the conden-
sation of the arylamine and acetone over 6 days. This product
was reacted with n-BuLi in the presence of tmen and sub-
sequently reacted with ClPPh2 to give the phosphine (C6H3i-
Pr2)NC(Me)CH2PPh2 2. A similar strategy has been reported
for related phosphineimines.22 NMR data for this product
revealed the presence of two isomers which gave rise to 31P{1H}
NMR signals at δ Ϫ18.0 and Ϫ17.5 in a 95 : 5 ratio. These were
attributed to the enolization of the imine (Scheme 1). The major
1
isomer was attributed to the imine form based on the H and
13C NMR data. X-Ray data (Fig. 1) also supported this form-
ulation of 2 and were consistent with the major isomer as the
imine as the observed N–C bond length was 1.276(3) Å.
Structure solution and refinement
Non-hydrogen atomic scattering factors were taken from the
literature tabulations.21 The heavy atom positions were deter-
mined 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, minimizing the function w(|Fo| Ϫ |Fc|)2
2
2
where the weight w is defined as 4Fo /2σ(Fo ) and Fo and Fc
are the observed and calculated 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 allowed to ride on the carbon to which
they are bonded assuming a C–H bond length of 0.95 Å.
H-Atom temperature factors were fixed at 1.10 times the iso-
tropic 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 calculation as well as the magnitude of
the residual electron densities in each case were of no
chemical significance. Crystallographic data are provided in
Table 1.
Scheme 1
Oxidation of the 2 with the substituted arylazide resulted in
the evolution of N2 and the isolation of the phosphinimine-
imine species (C6H3i-Pr2)NC(Me)CH2PPh2(NC6H3i-Pr2) 3 in a
yield of 70%. As expected, this species also existed in two forms
as indicated by the 31P{1H} NMR signals at δ Ϫ13.2 and 3.6
observed in a 73 : 27 intensity ratio. Again the major isomer is
assigned to the imine species (Scheme 1). The higher proportion
of the amine isomer in the case of 3 compared to 2 may result
from some degree of hydrogen bonding of the amine NH to the
phosphinimine nitrogen.
The ligand 3 reacts with NiBr2(dme) to give the blue complex
NiBr2((C6H3i-Pr2)NC(Me)CH2PPh2(NC6H3i-Pr2)) 4 in good
yield. This species was paramagnetic with a magnetic moment
of 4.34 µB. X-Ray quality crystals of 4 were obtained upon
CCDC reference numbers 211491–291496.
See http://www.rsc.org/suppdata/dt/b3/b306110h/ for crystal-
lographic data in CIF or other electronic format.
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In a similar synthetic procedure, attempts to react ligand 3
with (PhCN)2PdCl2 did not give the square-planar species
PdCl2((C6H3i-Pr2)NC(Me)CH2PPh2(NC6H3i-Pr2)). The nature
of the product(s) remains unclear. In contrast to the related
diimine ligands,17 the presence of the diphenylphosphino-
fragments in the backbone of 3 may impact on the in-plane
steric congestion and prevent this seemingly straightforward
complexation.
Reaction of 3 with n-BuLi proceeds rapidly to give a yellow
solution and subsequently yellow crystals of Li(thf )((C6H3i-
Pr2)NC(Me)CHPPh2(NC6H3i-Pr2)) 5 in 77% yield (Scheme 2).
Both NMR and an X-ray structure determination confirmed
the formulation of 5 (Fig. 3). The geometry about Li is distorted
trigonal planar as the sum of the angles about Li exceeds 359Њ.
The N–Li–N angle or the ligand bite angle is 108.5(3)Њ. The
Li–N distances are similar with the phosphinimine N–Li dis-
tance of 1.925(6) Å and the imine-N–Li distance of 1.914(6) Å.
The imine N–C distance is 1.321(3) Å, slightly longer than that
Fig. 1 ORTEP23 drawing of 2; 30% thermal ellipsoids are shown.
Hydrogen atoms are omitted for clarity. Selected bond distances (Å):
P(1)–C(1) 1.834(2), P(1)–C(7) 1.837(2), P(1)–C(13) 1.869(2), N(1)–
C(14) 1.276(3), N(1)–C(16) 1.443(2).
Scheme 2
Fig. 2 ORTEP23 drawing of 4; 30% thermal ellipsoids are shown.
Hydrogen atoms are omitted for clarity. Selected bond distances (Å)
and angles (Њ): Ni(1)–N(1) 2.019(3), Ni(1)–N(2) 2.036(3), Ni(1)–Br(1)
2.3309(10), Ni(1)–Br(2) 2.4193(11), P(1)–N(1) 1.605(3), P(1)–C(7)
1.803(4), P(1)–C(25) 1.803(4), P(1)–C(1) 1.816(4), N(1)–C(13) 1.473(4),
N(2)–C(26) 1.286(4), N(2)–C(28) 1.469(4); N(1)–Ni(1)–N(2) 98.26(12),
N(1)–Ni(1)–Br(1) 112.29(9), N(2)–Ni(1)–Br(1) 119.33(9), N(1)–Ni(1)–
Br(2) 110.53(8), N(2)–Ni(1)–Br(2) 96.71(9), Br(1)–Ni(1)–Br(2)
117.35(4), C(13)–N(1)–P(1) 119.1(2), C(13)–N(1)–Ni(1) 120.7(2), P(1)–
N(1)–Ni(1) 118.39(16), C(26)–N(2)–C(28) 118.2(3), C(26)–N(2)–Ni(1)
120.1(2), C(28)–N(2)–Ni(1) 121.7(2).
recrystalization from CH2Cl2 layered with toluene (Fig. 2). The
geometry about the Ni center is approximately tetrahedral as
expected with the coordination sphere comprised of the two N
and two Br atoms. The Ni–N distances were found to be
2.019(3) and 2.036(3) Å for the phosphinimine and imine N
atoms, respectively. This is consistent with previous observ-
ations that suggest that phosphinimines are in fact stronger
σ-donors than imines. The N–Ni–N ligand bite angle is
98.26(12)Њ. This is larger than the bite-angle of 93.7(2)Њ seen for
the related diketinimine complex NiBr2(((C6H3i-Pr2)NCMe)2-
CH2).17 The Ni–Br distances were found to be 2.3309(10) and
2.4193(11) Å while the Br–Ni–Br angle is 117.35(4)Њ. The longer
Ni–Br distance is associated with the Br atom that affords the
relative small N–Ni–Br angle of 96.71(9)Њ. Thus it may be that
the closer approach of the imine substituent to this Br results
in steric congestion and thus the longer Ni–Br distance. The
P–N distances along with the remainder of the ligand metric
parameters are unexceptional.
Fig. 3 ORTEP23 drawing of 5; 30% thermal ellipsoids are shown.
Hydrogen atoms are omitted for clarity. Selected bond distances (Å)
and angles (Њ): Li(1)–O(1) 1.894(6), Li(1)–N(2) 1.914(6), Li(1)–N(1)
1.925(6), P(1)–N(1) 1.597(2), P(1)–C(37) 1.727(3), P(1)–C(13) 1.813(3),
P(1)–C(19) 1.831(3), C(37)–C(38) 1.399(4), N(2)–C(38) 1.321(3); O(1)–
Li(1)–N(2) 126.1(3), O(1)–Li(1)–N(1) 125.2(3), N(2)–Li(1)–N(1)
108.5(3), C(1)–N(1)–Li(1) 114.6(2), P(1)–N(1)–Li(1) 116.2(2), C(38)–
N(2)–Li(1) 122.7(3), C(25)–N(2)–Li(1) 116.7(2).
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seen in 2, consistent with some delocalization of the anionic
charge over the NC2PN linkage.
Reaction of 5 with NiBr2(dme) proceeds smoothly to give the
complex formulated on the basis of NMR and analytical data
as red/black [Ni((C6H3i-Pr2)NC(Me)CHPPh2(NC6H3i-Pr2))-
(µ-Br)2Li(thf )2] 6. An X-ray structure determination confirmed
this formulation (Fig. 4). The structure of 6 is similar to
that reported very recently for diketimine analog [Ni((C6H3i-
Pr2)NCMe)2CH)(µ-Cl)2Li(thf )(Et2O)].19 The geometry about
Ni is pseudo-tetrahedral, with two N and two Br atoms making
up the coordination sphere. The Ni–N distances in 6 of 2.000(7)
and 1.988(6) Å are shorter than those seen in 3 consistent with
the anionic nature of the ligand in 6. This is also reflected in the
shortening of the central-C–imine-C distance, which was found
to be 1.385(14) compared to the distance of 1.513(5) Å found in
4. In a similar fashion, the P–C bond involving the central
carbon is also shortened to 1.727(10) Å, compared to that of
1.803(4) Å found in 4. Interestingly, the P–N distance in 6 is
slightly longer at 1.628(7) vs. 1.605(3) Å found in 4. These
features of the anionic ligand also gives rise to a larger bite-
angle (N–Ni–N) of the chelate (101.0(3)Њ) ligand. Similarly the
Ni–Br bond lengths (2.4585(18), 2.4428(19) Å) are longer com-
pared to those in 3 as well, presumably a result of the bridging
to Li. The longer Ni–Br distances also accommodate a smaller
Br–Ni–Br angle of 96.12(5)Њ. The Li–Br distances were found
to be 2.550(19) and 2.517(18) Å while the Li–O distances were
typical.
Fig. 5 (a) ORTEP23 drawing of 7 and (b) 8; 30% thermal ellipsoids are
shown. Hydrogen atoms are omitted for clarity. Selected bond distances
(Å) and angles (Њ): 7: Ni(1)–N(1) 1.946(5), Ni(1)–C(27) 2.023(6), Ni(1)–
P(2) 2.201(3), Ni(1)–Br(1) 2.341(3), Ni(1)–P(1) 2.570(3), P(1)–N(1)
1.589(6), P(1)–C(27) 1.778(7), P(1)–C(1) 1.807(6), P(1)–C(7) 1.822(7),
P(2)–C(44) 1.829(7), P(2)–C(52) 1.830(7), P(2)–C(46) 1.839(7), N(1)–
C(28) 1.425(8), N(2)–C(25) 1.268(8), N(2)–C(13) 1.421(9), C(25)–C(27)
1.485(9); N(1)–Ni(1)–C(27) 78.8(2), N(1)–Ni(1)–P(2) 165.37(18),
C(27)–Ni(1)–P(2) 98.44(17), N(1)–Ni(1)–Br(1) 93.58(16), C(27)–Ni(1)–
Br(1) 170.00(16), P(2)–Ni(1)–Br(1) 90.53(7), N(1)–Ni(1)–P(1)
38.12(15), C(27)–Ni(1)–P(1) 43.54(19), P(2)–Ni(1)–P(1) 133.37(7),
Br(1)–Ni(1)–P(1) 130.59(9), C(28)–N(1)–Ni(1) 131.0(4), P(1)–N(1)–
Ni(1) 92.7(2), C(25)–N(2)–C(13) 124.3(6). 8: Pd(1)–N(1) 2.115(4),
Pd(1)–C(25) 2.141(5), Pd(1)–P(2) 2.2720(18), Pd(1)–Cl(1) 2.3347(18),
Pd(1)–P(1) 2.698(2), P(1)–N(1) 1.592(4), P(1)–C(25) 1.791(5), P(1)–
C(7) 1.808(6), P(1)–C(1) 1.848(6), P(2)–C(52) 1.815(6), P(2)–C(40)
1.828(6), P(2)–C(46) 1.839(6), N(1)–C(13) 1.439(6), N(2)–C(26)
1.279(6), N(2)–C(28) 1.440(7), C(25)–C(26) 1.484(7); N(1)–Pd(1)–
C(25) 74.39(17), N(1)–Pd(1)–P(2) 165.15(12), C(25)–Pd(1)–P(2)
101.15(14), N(1)–Pd(1)–Cl(1) 95.89(12), C(25)–Pd(1)–Cl(1) 168.63(13),
P(2)–Pd(1)–Cl(1) 89.71(7), N(1)–Pd(1)–P(1) 36.12(11), C(25)–Pd(1)–
P(1) 41.49(13), P(2)–Pd(1)–P(1) 133.76(6), Cl(1)–Pd(1)–P(1) 130.58(5),
C(13)–N(1)–P(1) 134.7(4), C(13)–N(1)–Pd(1) 131.2(3), P(1)–N(1)–
Pd(1) 92.31(18), C(26)–N(2)–C(28) 121.4(4).
Fig. 4 ORTEP23 drawing of 6; 30% thermal ellipsoids are shown.
Hydrogen atoms are omitted for clarity. Selected bond distances (Å)
and angles (Њ): Ni(1)–N(2) 1.988(6), Ni(1)–N(1) 2.000(7), Ni(1)–Br(2)
2.4428(19), Ni(1)–Br(1) 2.4585(18), Br(1)–Li(1) 2.550(19), Br(2)–Li(1)
2.517(18), P(1)–N(1) 1.628(7), P(1)–C(38) 1.727(10), P(1)–C(1)
1.825(11), P(1)–C(7) 1.826(9), N(1)–C(18) 1.431(10), N(2)–C(37)
1.337(11), N(2)–C(25) 1.432(11), O(1)–Li(1) 1.98(2), O(2)–Li(1)
1.925(19); N(2)–Ni(1)–N(1) 101.0(3), N(2)–Ni(1)–Br(2) 129.6(2), N(1)–
Ni(1)–Br(2) 108.71(19), N(2)–Ni(1)–Br(1) 105.5(2), N(1)–Ni(1)–Br(1)
117.1(2), Br(2)–Ni(1)–Br(1) 96.12(5), Ni(1)–Br(1)–Li(1) 83.8(4), Ni(1)–
Br(2)–Li(1) 84.8(4), C(18)–N(1)–P(1) 121.6(5), C(18)–N(1)–Ni(1)
120.2(5), P(1)–N(1)–Ni(1) 118.2(4), C(37)–N(2)–Ni(1) 124.0(7), C(25)–
N(2)–Ni(1) 115.2(5).
In related syntheses 5 was generated in situ and reacted with
NiBr2(dme) and an equivalent of PPh3. This yielded deep red
crystals of 7 in 57% yield. This species was diamagnetic. The
31P{1H} NMR spectrum of 7 showed resonances at δ 24.6 and
18.0 with a P–P coupling of 39 Hz. 13C{1H} NMR data
revealed a resonance at δ 6.12 which suggested metallation of
the central carbon of the ligand. X-Ray data confirmed the
formulation as NiBr((C6H3i-Pr2)NC(Me)CHPPh2(NC6H3i-
Pr2))(PPh3) 7. The structure of 7 is pseudo-square planar at Ni
with coordination of the phosphinimine-imine ligand via the
phosphinimine-N and the central C atoms (Fig. 5(a)). Similar
four-membered MCPN rings have been observed for Rh–24 and
Ir–bis(phosphinimino)methane25 complexes. The imine frag-
ment of 7 does not bind to the metal but rather dangles free,
adopting a position which is pseudo-trans to the axial phenyl
ring on the P adjacent the central carbon. The Ni–N distance is
1.946(5) Å while the Ni–C distance is 2.023(6) Å. This tight
four-membered chelate ring gives rise to the small bite angle of
78.8(2)Њ as well as the relatively short transannular Ni–P dis-
tance of 2.570(3) Å. Approximately trans to the C is a Br atom
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(C–Ni–Br 170.00(16)Њ), while the ligand PPh3 is pseudo-trans to
the N (N–Ni–P 165.37(18)Њ). The Ni–P distance in this case is
2.201(3) Å while the Ni–Br distance is 2.341(3) Å, similar to
that seen in 4. The central-C of the ligand to imine-C bond is
lengthened to 1.485(9) Å compared to that seen in 6 consistent
with localization of the ligand anionic charge on the central
carbon. In contrast, the P–N distance in 7 is 1.589(6) Å, slightly
shorter than that seen in 4 and 6. This may result from a
decrease in the Lewis acidity of the Ni as a result of effective
electron donation from the coordinated C atom.
J. D. M. is grateful for the award of an OGS scholarship.
D. W. S. is grateful for the award of Forschungpreis from the
Alexander von Humboldt Stiftung.
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In a similar fashion the analogous Pd species, brown crystals
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8
were prepared in 57% isolated yield. The 31P{1H} NMR spec-
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Acknowledgements
Financial support from NSERC of Canada, NOVA Chemicals
Corporation and the ORDCF is gratefully acknowledged.
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