Titanium ferrocenyl-phosphinimide complexes

Article abstract of DOI:10.1039/b918919j

Oxidation of [CpFe(η⁵-C₅H₄PtBu ₂)] with Me₃SiN₃ gave the phosphinimine [CpFe(η⁵-C₅H₄PtBu₂NSiMe ₃)] (1) which was used to prepare [Cp′TiCl ₂(NPtBu₂C₅H₄)FeCp] (Cp′ = Cp 2, Cp* 4) and subsequently [Cp′TiMe₂(NPtBu ₂C₅H₄)FeCp] (Cp′ = Cp 3, Cp* 5). Similarly, [(η⁵-C₅Ph₅)Fe(η⁵- C₅H₄PtBu₂NSiMe₃)] 6 was converted to [CpTiX₂(NPtBu₂C₅H₄) Fe(η⁵-C₅Ph₅)] (X = Cl 7, Me 8). The bis-phosphinimine [Fe{η⁵-C₅H₄PtBu ₂(NSiMe₃)}₂] (9) was prepared and used to obtain [{Fe(η⁵-C₅H₄PtBu₂N) ₂}TiCl₂] (10) and [{Fe(η⁵-C ₅H₄PtBu₂N)₂}TiMe₂] (11). These species exhibited a temperature dependent conformational change in the chelate geometry on the NMR time scale. Cyclic voltammetry studies showed pseudo reversible redox waves assigned to the Fe²⁺/Fe³⁺ couple for 2 and 4, while 10 exhibited only irreversible oxidations. Compound 9 was also used to prepare [Fe(η⁵-C₅H₄PtBu ₂NTiXCl₂)₂] (X = Cl 12, Cp 13, Cp* 15). Compounds 3 and 5 react with B(C₆F₅)₃ or [CPh₃][B(C₆F₅)₃] to generate salts of the formula [Cp′TiMe{(NPtBu₂C₅H ₄)FeCp}]X (Cp′ = Cp, X = [MeB(C₆F₅) ₃] 17a, [B(C₆F₅)₄] 17b; Cp′ = Cp*, X = [MeB(C₆F₅)₃] 18a, [B(C ₆F₅)₄] 18b). Compounds 18 further generated [Cp*TiMe{HNPtBu₂(C₅H₄) Fe(η⁵,η¹-C₅H₄)}]X (X = [MeB(C₆F₅)₃] 19a, [B(C₆F ₅)₄] 19b), respectively. The cationic species 17a and 18a are very active polymerization catalysts, giving polyethylene with activities of 2400 and 5000 g mmol^-1 h^-1 atm^-1, respectively at 25 °C. The Royal Society of Chemistry 2010.

Full text of DOI:10.1039/b918919j

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PAPER
www.rsc.org/dalton | Dalton Transactions
Titanium ferrocenyl-phosphinimide complexes†
Alberto Ramos and Douglas W. Stephan*
Received 11th September 2009, Accepted 15th October 2009
First published as an Advance Article on the web 23rd November 2009
DOI: 10.1039/b918919j
5
5
Oxidation of [CpFe(h -C5H4PtBu2)] with Me3SiN3 gave the phosphinimine [CpFe(h -C5H4PtBu2-
NSiMe3)] (1) which was used to prepare [Cp¢TiCl2(NPtBu2C5H4)FeCp] (Cp¢ = Cp 2, Cp* 4) and
5
5
subsequently [Cp¢TiMe2(NPtBu2C5H4)FeCp] (Cp¢ = Cp 3, Cp* 5). Similarly, [(h -C5Ph5)Fe(h -
5
C5H4PtBu2NSiMe3)] 6 was converted to [CpTiX2(NPtBu2C5H4)Fe(h -C5Ph5)] (X = Cl 7, Me 8). The
5
bis-phosphinimine [Fe{h -C5H4PtBu2(NSiMe3)}2] (9) was prepared and used to obtain
5
5
[{Fe(h -C5H4PtBu2N)2}TiCl2] (10) and [{Fe(h -C5H4PtBu2N)2}TiMe2] (11). These species exhibited a
temperature dependent conformational change in the chelate geometry on the NMR time scale. Cyclic
voltammetry studies showed pseudo reversible redox waves assigned to the Fe2+/Fe3+ couple for 2 and
4, while 10 exhibited only irreversible oxidations. Compound 9 was also used to prepare
5
[Fe(h -C5H4PtBu2NTiXCl2)2] (X = Cl 12, Cp 13, Cp* 15). Compounds 3 and 5 react with B(C6F5)3 or
[CPh3][B(C6F5)3] to generate salts of the formula [Cp¢TiMe{(NPtBu2C5H4)FeCp}]X (Cp¢ = Cp, X =
[MeB(C6F5)3] 17a, [B(C6F5)4] 17b; Cp¢ = Cp*, X = [MeB(C6F5)3] 18a, [B(C6F5)4] 18b). Compounds 18
5
1
further generated [Cp*TiMe{HNPtBu2(C5H4)Fe(h ,h -C5H4)}]X (X = [MeB(C6F5)3] 19a, [B(C6F5)4]
19b), respectively. The cationic species 17a and 18a are very active polymerization c◦atalysts, giving
polyethylene with activities of 2400 and 5000 g mmol-1 h-1 atm-1, respectively at 25 C.
a labile yet proximal donor group is incorporated to stabilize the
Introduction
cationic catalysts and yet be readily displaced in the presence of
substrate. For such a system to ultimately be commercially viable
the ligand precursors should be readily accessible. In considering
these strategic issues, we have recently reported phosphinimide
ligands that show good activity and high temperature stability as
a result of the inclusion of pendant hemilabile donors.50 In a related
approach, we now focus on phosphinimide ligand complexes that
incorporate pendant ferrocenyl fragments. This target is based
on the demonstration by Arnold and co-workers51-55 that the
Lewis basicity of the Fe center in ferrocene can act to stabilize
cationic Ti-amido-ferrocenyl polymerization catalysts via a direct
Fe–Ti interaction (Scheme 1). It is also noteworthy that other
authors have developed early metal polymerization catalysts with
pendant ferrocenyl fragments. For instance, ferrocenyldithiolate
has been employed to prepare olefin polymerization catalysts
of formula [{(C5H4S)2Fe}M(NMe2)2] (M = Ti or Zr).56 Metal-
locenes with pendant silyl-ferrocenyl groups,57-59 or ferrocenyl-
indenyl ligands60 as well as constrain-geometry catalysts with
pendant ferrocenyl units61 (Scheme 1) have also been investigated.
These observations augur well for systems involving ferrocenyl-
phosphinimide ligands. Thus, in this paper we describe the use of
readily accessible ferrocenyl-phosphines to access phosphinimines
and subsequently a series of Ti-complexes. The utility and
reactivity of resulting cationic derivatives in olefin polymerization
is examined and the potential of these systems is assessed.
The development of homogeneous catalysts for olefin polymeriza-
tion has spurred numerous reports over the past three decades.1-7
In the early years, the development of metallocene- based catalyst
systems was particularly successful. Subsequently, clever ligand
modifications afforded the production of stereo-regular polyolefin
polymers.8-11 The next generation of catalysts to arise were
based on half-sandwich complexes. Among these systems is the
renowned “constrained geometry catalysts”12-15 based on linked
amide-cyclopentadienyl ligands introduced by Bercaw et al.16 In
the 1990s, “non-metallocene” complexes were shown to be highly
effective catalysts. Such systems have continued to evolve from the
initial reports of McConville et al. who described bulky bis-amido-
Ti-chelate complexes,17-20 to the more recent work on “FI” catalysts
from Matsui et al.21-25 Our approach to developing new catalysts
has been based on our 1999 report of the exceptional activity
for olefin polymerization catalysis demonstrated by Ti-complexes
incorporating phosphinimide ligands. Indeed, these systems have
proved to be highly active olefin polymerization catalysts under
commercial conditions.26-28 Our progress over the issuing years
target an understanding of the structure–activity relationship,29-43
and the mechanisms of deactivation44-49 of phosphinimide-catalyst
systems has been recently reviewed.
In targeting the development of new phosphinimide com-
plexes that exhibit high activity even at higher temperatures, we
planned to advance two strategies. Firstly, sterically demanding
substituents are employed to protect the active site and secondly
Experimental
Department of Chemistry, University of Toronto, 80 St. George St., Toronto,
Ontario, Canada M5S 3H6. E-mail: dstephan@chem.utoronto.ca; Tel: 416-
946-3294
† CCDC reference numbers 747506–747514. For crystallographic data in
CIF or other electronic format see DOI: 10.1039/b918919j
All preparations were done under an atmosphere of dry, O2-
free N2 employing both Schlenk line techniques and Innovative
Technology or Vacuum Atmospheres inert atmosphere glove
boxes. Solvents were purified employing a Grubbs’ type column
1328 | Dalton Trans., 2010, 39, 1328–1338
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The Royal Society of Chemistry 2010
©

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1
14, CH3-tBu, 18H), 0.49 (s, SiMe3, 9H). 13C{ H} NMR (C6D6):
77.3 (d, JPC = 90, C1-C5H4), 73.3 (d, JPC = 10, C2/3-C5H4), 70.5 (s,
Cp), 70.1 (d, JPC = 8, C3/2-C5H4), 36.4 (d, JPC = 67, C-tBu), 28.3
(d, JPC = 1.4, CH3-tBu), 5.5 (d, JPC = 1.4, SiMe3). 6 Yield 0.680 g
(80%). X-Ray quality crystals were grown by vapour diffusion of
pentane into a saturated solution of 6 in dichloromethane. Anal.
Calcd. for C51H56FeNPSi. C, 76.77; H, 7.07; N, 1.76. Found: C,
1
1
76.52; H, 6.99; N, 1.82%. 31P{ H} NMR (C6D6): 30.7. H NMR
(C6D6): 7.36 (m, o-C6H5, 10H), 6.98 (m, m,p-C6H5, 15H), 4.79
(br, C5H4, 2H), 4.37 (br, C5H4, 2H), 0.99 (d, JPH = 14, CH3-tBu,
18H), 0.44 (s, SiMe3, 9H). 13C{ H} NMR (C6D6): 135.9 (s, C1-
1
Ph), 133.1, 127.7 (2 ¥ s, C2,3-Ph), 126.9 (s, C4-Ph), 88.2 (s, C5Ph5),
81.6 (d, JPC = 87, C1-C5H4), 79.3 (d, JPC = 9, C2/3-C5H4), 78.0 (d,
JPC = 8, C3/2-C5H4), 38.1 (d, JPC = 68, CMe3), 28.2 (s, CH3), 5.5
(s, SiMe3).
Scheme 1 Examples of olefin polymerization catalyst precursors. incor-
porating ferrocenyl fragments.
Synthesis of [Cp¢TiCl2(NPtBu2C5H4)FeCp] (Cp¢ = Cp (2), Cp*
(4)) and [CpTiCl2(NPtBu2C5H4)Fe(g5-C5Ph5)] (7)
1
system manufactured by Innovative Technology. H, 13C, 31P, 11B
and 19F NMR spectroscopy spectra were recorded on Varian 200,
300, 400 MHz and Bruker 400 MHz spectrometers. H and 13C
These compounds were prepared in an analogous fashion and thus
only one preparation is detailed. CpTiCl3 (0.180 g, 0.819 mmol)
was added to a solution of compound 1 (0.342 g, 0.819 mmol)
in 10 mL of benzene and stirred at room temperature for 15 h.
After this time, the orange solution was concentrated to 3-4 mL
of solvent under vacuum and an orange precipitate of compound
2 appeared. Hexane (10 mL) was added to help precipitate the
product. The mother liquor was then decanted; the solid was
washed with more hexane (5 mL) and dried under vacuum to
afford compound 2 as an orange solid. 2: Yield 0.370 g (85%).
Anal. Calcd. for C23H32Cl2FeNPTi. C, 52.31; H, 6.10; N, 2.65.
1
NMR spectra are referenced to SiMe4 using the residual solvent
peak impurity of the given solvent. 31P, 11B and 19F NMR spectra
were referenced to 85% H3PO4, Et2O·BF3, and CFCl3 respectively.
Chemical shifts are reported in ppm and coupling constants in
Hz. C6D6, C6D5CD3, CDCl3, CD2Cl2 and BrC6D5 were used
as the NMR solvents after being dried over Na/benzophenone
(C6D6, C6D5CD3) or CaH2 (the others), vacuum-transferred into
Young bombs and freeze–pump–thaw degassed (three cycles).
Combustion analyses were performed in house employing a Perkin
Elmer 2400 Series II CHNS Analyzer.
Cyclic voltammetry experiments were performed in a BASi
RDE-2 cell stand for rotating disk electrochemical experiments,
using a glassy carbon working electrode with a disk diameter
of 3.0 mm, an aqueous Ag/AgCl reference electrode and a Pt
wire auxiliary electrode. The working electrode was polished
with alumina (0.05 mm) and rinsed with deionized water prior
to use. [NBu4][PF6] was used as the supporting electrolytes
(0.1 M solutions). All the potentials were referenced versus
Cp2Fe+/0. All electrochemical data were acquired with a computer
controlled BASi Epsilon EC potentiostat, using the Epsilon EC
software.
1
Found: C, 51.91; H, 5.72; N, 2.59%. 31P{ H} NMR (CD2Cl2):
1
42.9. H NMR (CD2Cl2): 6.55 (s, Ti-Cp, 5H), 4.61, 4.60 (2 ¥ m,
C5H4, 2 ¥ 2H), 4.44 (s, Fe-Cp, 5H), 1.37 (d, JPH = 15, CH3-tBu,
1
18H). 13C{ H} NMR (CD2Cl2): 115.6 (s, Ti-Cp), 73.7 (d, JPC
=
10, C2/3-C5H4), 71.7 (d, JPC = 10, C3/2-C5H4), 71.3 (s, Fe-Cp),
70.6 (d, JPC = 92, C1-C5H4), 39.4 (d, JPC = 55, C-tBu), 28.1 (d,
JPC = 1, CH3-tBu). 4: Yield 440 mg (88%). Crystals suitable for
X-ray analysis were grown from a concentrated solution of 4 in
hexane at -35 ◦C. Anal. Calcd. for C28H42Cl2FeNPTi. C, 56.22; H,
1
7.08; N, 2.34. Found: C, 56.11; H, 6.91; N, 2.47%. 31P{ H} NMR
1
(CD2Cl2): 40.7. H NMR (CD2Cl2): 4.66, 4.56 (2 ¥ m, C5H4, 2 ¥
2H), 4.37 (s, Fe-Cp, 5H), 2.18 (s, C5Me5, 15H), 1.33 (d, JPH = 15,
1
CH3-tBu, 18H). 13C{ H} NMR (CD2Cl2): 126.1 (s, C5Me5), 74.6
(d, JPC = 10, C2/3-C5H4), 72.4 (d, JPC = 89, C1-C5H4), 71.4 (d,
JPC = 9, C3/2-C5H4), 39.4 (d, JPC = 56, C-t-Bu), 28.1 (d, JPC = 1,
CH3-tBu), 13.4 (s, C5Me5). 7: Compound 7 is extremely air and
moisture sensitive in solution, decomposing progressively in any
solvent. Yield 0.160 g (70%). Crystals suitable for X-ray analysis
were grown at room temperature from a saturated toluene solution
of the compound. Anal. Calcd. for C53H52Cl2FeNPTi. C, 70.06; H,
Synthesis of [CpFe(g5-C5H4PtBu2NSiMe3)] (1) and
[(g5-C5Ph5)Fe(g5-C5H4PtBu2NSiMe3)] (6)
These compounds were prepared in an analogous fashion and thus
only one preparation is detailed. An excess of N3SiMe3 (2.8 mL,
5
20.2 mmol) was added to a solution of CpFe(h -C5H4PtBu2)62
(1.25 g, 3.79 mmol) in 15 mL of toluene. The solution was
stirred for 15 h at 90 ◦C, filtered through Celite and washed
with toluene (2 ¥ 5 mL). After evaporating the solvent under
vacuum, compound 1 was afforded as an orange powder. 1: Yield
1.40 g (89%). Crystals suitable for X-ray analysis were grown from
a concentrated solution in pentane at -35 ◦C. Anal. Calcd. for
C21H36FeNPSi: C, 60.42; H, 8.69; N, 3.36. Found: C, 60.37; H,
1
5.77; N, 1.54. Found: C, 69.89; H, 5.89; N, 1.62%. 31P{ H} NMR
1
(C6D6): 44.6. H NMR (C6D6): 7.30 (m, o-C6H5, 10H), 7.01 (m,
m,p-C6H5, 15H), 6.51 (s, Cp, 5H), 4.95, 4.33 (2 ¥ br, C5H4, 2 ¥ 2H),
1
1.06 (d, JPH = 15, CH3-tBu, 18H). 13C{ H} NMR (C6D6): 135.4 (s,
C1-Ph), 133.3, 128.3 (2 ¥ s, C2,3-Ph), 127.6 (s, C4-Ph), 115.9 (s, Cp),
90.8 (s, C5Ph5), 79.4 (d, JPC = 9, C2/3-C5H4), 79.4 (br, C3/2-C5H4),
75.8 (d, JPC = 82, C1-C5H4), 40.9 (d, JPC = 56, CMe3), 28.4 (d,
JPC = 1, CH3).
8.37; N, 3.39%. 31P{ H} NMR (C6D6): 24.3. H NMR (C6D6):
1
1
4.23, 4.05 (2 ¥ m, C5H4, 2 ¥ 2H), 4.13 (s, Cp, 5H), 1.13 (d, JPH
=
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1
36H), 0.11 (s, SiMe3, 18H). 13C{ H} NMR (CD2Cl2) 78.5 (d, JPC
=
=
Synthesis of [Cp¢TiMe2(NPtBu2C5H4)FeCp] (Cp¢ = Cp (3),
90 Hz, C1-C5H4), 74.2 (d, JPC = 10 Hz, C2/3-C5H4), 72.0 (d, JPC
Cp* (5))
8 Hz, C3/2-C5H4), 37.6 (d, JPC = 66 Hz, CMe3), 28.3 (s, C(CH3)3),
4.90 (s, JSi–C = 56 Hz, SiMe3).
These compounds were prepared in an analogous fashion and
thus only one preparation is detailed. 0.4 mL of MeMgBr (3.0 M
in Et2O) were added to a solution of compound 2 (0.287 g,
0.543 mmol) in 10 mL of benzene. After stirring for 30 min at room
temperature, solvents were evaporated under vacuum. The orange
precipitate was extracted with benzene (4 ¥ 15 mL) and filtered
through Celite. Solvent was again evaporated under vacuum to
obtain compound 3 as an orange solid. 3: Yield 0.205 g (77%).
Anal. Calcd. for C25H38FeNPTi. C, 61.62; H, 7.86; N, 2.87. Found:
Synthesis of [{Fe(g5-C5H4PtBu2N)2}TiCl2] (10)
Method A. A solution of 9 (0.983 g, 1.515 mmol) in 10 mL
was added to a solution of TiCl4 (0.288 g, 1.518 mmol) in
10 mL of toluene. The dark orange mixture thus obtained was
transferred to a 100 mL bomb, which was frozen in liquid N2
(-196 ◦C) to evacuate the headspace, allowed to reach room
temperature and then heated to 115 ◦C for 15 h. After this
time, the color had changed from dark to light orange, and an
orange precipitate appeared upon cooling down to reach room
temperature. This orange precipitate was collected on a frit and
washed with hexanes (3 ¥ 15 mL). For further purification of
the product, the solid on the frit was fractionally dissolved in
dichloromethane (5 ¥ 15 mL), the fractions were collected in
a flask and the solvent was evaporated, yielding compound 10
as an orange microcrystalline solid (0.600 g). A second fraction
of 10 was obtained from the mother liquor after adding more
hexane to precipitate compound 10 (0.140 g). Yield: 0.740 g (79%).
Crystals of 10 suitable for X-ray analysis were grown by layering
a saturated solution of the compound in dichloromethane with
pentane at -35 ◦C. Compound 10 is insoluble in aliphatic solvents,
scarcely soluble in toluene, slightly soluble in dichloromethane and
moderately soluble in bromobenzene.
1
C, 61.38; H, 7.61; N, 2.92%. 31P{ H} NMR (C6D6): 23.9. 1H NMR
(C6D6): 6.31 (s, Ti-Cp, 5H), 4.36, 4.06 (2 ¥ m, C5H4, 2 ¥ 2H), 4.15
(s, Fe-Cp, 5H), 1.19 (d, JPH = 14, CH3-tBu, 18H), 0.77 (s, Ti-Me,
1
6H). 13C{ H} NMR (C6D6): 111.2 (s, Ti-Cp), 74.6 (d, JPC = 87,
C1-C5H4), 73.6 (d, JPC = 9, C2/3-C5H4), 70.8 (s, Fe-Cp), 70.8 (d,
JPC = 9, C3/2-C5H4), 40.7 (s, Ti-Me), 38.7 (d, JPC = 59, C-tBu), 28.2
(d, JPC = 1, CH3-tBu). 5: Yield 0.235 g (63%). Crystals suitable
for X-ray analysis were grown from a concentrated solution of 5
in hexane at -35 ◦C. Anal. Calcd. for C30H48FeNPTi. C, 64.64;
H, 8.68; N, 2.51. Found: C, 64.33; H, 8.77; N, 2.82%. 31P{ H}
1
1
NMR (C6D6): 22.8. H NMR (C6D6): 4.56, 4.12 (2 ¥ m, C5H4,
2 ¥ 2H), 4.17 (s, Fe-Cp, 5H), 2.12 (s, C5Me5, 15H), 1.25 (d, JPH
=
1
14, CH3-tBu, 18H), 0.50 (s, Ti-Me, 6H). 13C{ H} NMR (C6D6):
118.6 (s, C5Me5), 75.7 (d, d, JPC = 84, C1-C5H4), 74.6 (d, JPC = 9,
C2/3-C5H4), 70.8 (s, Fe-Cp), 70.8 (d, JPC = 8, C3/2-C5H4), 43.7 (s,
Ti-Me), 38.9 (d, JPC = 59, C-tBu), 28.3 (d, JPC = 1, CH3-tBu), 12.8
(s, C5Me5).
Method B. A solution of 6 (0.649 g, 1.000 mmol) in 10 mL
of toluene was added to a solution of [TiCl4(THF)2] (0.340 g,
1.018 mmol) in 10 mL of toluene. The mixture was heated at 70 ◦C
for 15 h. After this time, an orange solid starts to precipitate upon
cooling down to reach room temperature. The mother liquor was
decanted; the solid was collected on a frit, washed with toluene
(2 ¥ 5 mL) and extracted with dichloromethane (4 ¥ 10 mL). The
dichloromethane solution of 10 was concentrated under vacuum
until only 5 mL of solvent was left and the product was precipitated
with hexane (30 mL). Solvents were decanted again and the solid
dried under vacuum for 24 h. Yield 0.435 g (70%). Anal. Calcd. for
C26H44Cl2FeN2P2Ti. C, 50.27; H, 7.14; N, 4.51. Found: C, 50.19;
Synthesis of [CpTiMe2(NPtBu2C5H4)Fe(g5-C5Ph5)] (8)
0.1 mL of MeMgBr (3.0 M in diethyl ether) was added to a solution
of compound 7 (0.100 g, 0.110 mmol) in 10 mL of toluene. After
stirring for 30 min at room temperature, solvents were evaporated
under vacuum. The dark pink precipitate was extracted with
pentane (3 ¥ 10 mL) and filtered through a Celite plug to yield
a solid which contains 8 as the major product (90%). Attempts
to further purify the product led to progressive decomposition. It
also decomposes progressively in solution in any solvent. 31P{ H}
1
NMR (C6D6): 29.2. 1H NMR (C6D6): 7.32 (m, o-C6H5, 10H), 6.97
(m, m,p-C6H5, 15H), 6.26 (s, Cp, 5H), 4.97, 4.36 (2 ¥ s, 2 ¥ br,
C5H4, 2 ¥ 2H), 1.09 (d, JPH = 16, CH3-tBu, 18H), 0.71 (s, Ti-Me2,
1
1
H, 6.85; N, 4.36%. 31P{ H} NMR (BrC6D5, 278 K): 29.4. 31P{ H}
1
NMR (BrC6D5, 298 K): 29.4. 31P{ H} NMR (BrC6D5, 371 K):
1
1
6H). 13C{ H} NMR (C6D6): 135.9 (s, C1-Ph), 133.4, 128.1 (2 ¥ s,
29.4. H NMR (BrC6D5, 253 K): 5.03, 4.28, 4.24, 3.96 (4 ¥ s,
C2,3-Ph), 127.4 (s, C4-Ph), 111.6 (s, Cp), 88.7 (s, C5Ph5), 79.7 (d,
JPC = 78, C1-C5H4), 78.8 (d, JPC = 8, C2/3-C5H4), 43.3 (s, TiMe2),
40.1 (d, JPC = 57, CMe3), 28.4 (s, CH3-tBu). Signal for C3/2-C5H4
not observed.
C5H4, 4 ¥ 2H), 1.35 (d, JPH = 15, CH3-tBu, 18H), 0.90 (d, JPH
=
1
15, tBu, 18H). H NMR (BrC6D5, 298 K): 5.03 (br, C5H4, 2H),
4.30 (m, C5H4, 4H), 4.09 (br, C5H4, 2H), 1.25 (br, tBu, 18H), 0.99
(br, CH3-tBu, 18H). 1H NMR (BrC6D5, 371 K): 4.61 (s, br, C5H4,
4H), 4.33 (s, br, C5H4, 4H), 1.19 (d, JPH = 15, CH3-tBu, 36H).
1
13C{ H} NMR (BrC6D5, 298 K): 74.7 (br, C5H4), 76.0 (d, JPC
=
Synthesis of [Fe{g5-C5H4PtBu2(NSiMe3)}2] (9)
78, C1-C5H4), 73.0-70.0 (br, C5H4), 38.0 (d, br, JPC = 61, C(CH3)3),
An excess of N3SiMe3 (6 mL, 45.22 mmol) was added to a solution
of [Fe(C5H4PtBu2)2] (2.02 g, 4.26 mmol) in 20 mL of toluene. The
solution was stirred for 15 h at 80 ◦C, filtered through Celite and
washed with toluene (3 ¥ 20 mL). After evaporating the solvent
under vacuum compound 9 was afforded as an orange powder.
Yield 2.55 g (92%). Anal. Calcd. for C32H62FeN2P2Si2. C, 59.24;
1
27.6 (s, br, CH3). 13C{ H} NMR (BrC6D5, 245 K): 78.8 (d, JPC
=
8, C5H4), 75.7 (d, JPC = 81, C1-C5H4), 72.5 (d, JPC = 8, C5H4), 71.4
(d, JPC = 10, C5H4), 70.7 (d, JPC = 8, C5H4), 38.6 (d, JPC = 60,
CMe3), 37.5 (d, JPC = 59, C(CH3)3), 28.1, 27.0 (2 ¥ s, 2 ¥ CH3).
Synthesis of [{Fe(g5-C5H4PtBu2N)2}TiMe2] (11)
H, 9.63; N, 4.32. Found: C, 59.30; H, 9.53; N, 4.25%. 31P{ H}
1
1
NMR (CD2Cl2): 24.2. H NMR (CD2Cl2, 300.23 MHz): 4.59,
0.45 mL of a 3 M solution of MeMgBr (1.35 mmol) was added to
4.36 (2 ¥ m, 2 ¥ C5H4, 2 ¥ 4H), 1.19 (d, JPH = 13 Hz, CH3-tBu,
a suspension of 10 (0.380 g, 0.612 mmol) in 10 mL of toluene. The
1330 | Dalton Trans., 2010, 39, 1328–1338
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mixture was stirred at room temperature for 1 h. After this time, the
solvents were evaporated, and the remaining brownish precipitate
was extracted with toluene (4 ¥ 10 mL), filtered through Celite, and
the solvents evaporated yielding compound 11 as a yellow-orange
solid. Yield 0.175 g (49%). Anal. Calcd. for C28H50FeN2P2Ti. C,
57.95; H, 8.68; N, 4.83. Found: C, 58.19; H, 8.85; N, 4.76%.
9, C2/3-C5H4), 74.9 (d, JPC = 10, C3/2-C5H4), 73.9 (d, JPC = 91,
C1-C5H4), 38.6 (d, JPC = 55, C(CH3)3), 27.8 (s, CH3).
Synthesis of [Fe(g5-C5H4PtBu2NTiCpMe2)2] (14)
0.15 mL of a 3 M solution of MeMgBr (0.45 mmol) were added
to a solution of 13 (0.087 g, 0.100 mmol) in 10 mL of toluene.
The mixture was stirred for 30 min and then the solvents were
evaporated. The product was extracted with toluene (5 ¥ 5 mL)
and filtered through Celite to yield, after evaporation of solvent,
compound 14 as an orange solid. Yield: 0.055 g (70%). Anal.
Calcd. for C40H66FeN2P2Ti2. C, 60.93; H, 8.44; N, 3.55. Found:
1
1
31P{ H} NMR (tol-d8, 295 K): 17.4. H NMR (tol-d8, 183 K):
4.90, 3.91, 3.85, 3.60 (4 ¥ s, C5H4, 4 ¥ 2H), 1.42 (br, CH3-tBu,
1
18H), 1.27 (s, Ti-Me, 6H), 1.10 (br, CH3-tBu, 18H). H NMR
(tol-d8, 223 K): 4.88, 3.95, 3.93, 3.69 (4 ¥ s, C5H4, 4 ¥ 2H), 1.41
(d, JPH = 14, CH3-tBu, 18H), 1.12 (s, Ti-Me, 6H), 1.08 (d, JPH
=
14, CH3-tBu, 18H). 1H NMR (tol-d8, 298 K): 4.89 (br, C5H4, 2H),
4.05 (s, C5H4, 4H), 3.85 (br, C5H4, 2H), 3.69, 1.42, 1.08 (2 ¥ br,
CH3-tBu, 2 ¥ 18H), 0.89 (s, Ti-Me, 6H). 1H NMR (tol-d8, 373 K):
4.44 (br, C5H4, 4H), 4.11 (s, C5H4, 4H), 1.27 (d, JPH = 14, CH3-tBu,
1
1
60.83; H, 8.29; N, 3.49. 31P{ H} NMR (C6D6): 23.6 (s, 2P). H
NMR (C6D6): 6.30 (s, Cp, 10H), 4.75, 4.46 (2 ¥ m, 2 ¥ C5H4, 2 ¥
4H), 1.18 (d, JPH = 14, CH3-tBu, 36 H), 0.76 (s, Ti-Me, 12H).
13C{ H} NMR (C6D6): 111.4 (s, Ti-Cp), 76.5 (d, JPC = 85, C1-
1
1
36H), 0.74 (s, Ti-Me, 6H). 13C{ H} NMR (BrC6D5, 233 K): 79.7
C5H4), 74.8 (d, JPC = 9, C2/3-C5H4), 74.1 (d, JPC = 8, C3/2-C5H4),
41.2 (s, Ti-Me), 38.8 (d, JPC = 58, C(CH3)3), 28.2 (s, CH3-tBu).
(d, JPC = 76, C1-C5H4), 79.3 (d, JPC = 9, C5H4), 72.0 (d, JPC = 7,
C5H4), 71.6 (d, JPC = 9, C5H4), 70.7 (d, JPC = 9, C5H4), 38.6 (d,
JPC = 60, CMe3), 37.5 (d, JPC = 59, C(CH3)3), 28.1, 27.0 (2 ¥ s,
2 ¥ CH3).
Synthesis of [Fe(g5-C5H4PtBu2NTiCp*Cl2)2] (15)
A solution of 9 (0.324 g, 0.499 mmol) and Cp*TiCl3 (0.308 g,
1.064 mmol) in 15 mL of toluene was heated at 90 C for 72 h.
Synthesis of [Fe(g5-C5H4PtBu2NTiCl3)2] (12)
◦
Then the solvent was evaporated, the orange residue washed with
pentane (3 ¥ 10 mL), extracted with dichloromethane and filtered
through Celite. The solvent was then evaporated, affording com-
pound 15 as an orange solid. Yield: 0.490 g (97%). Crystals suitable
for X-ray analysis were grown from a concentrated solution of 15
in CDCl3 at room temperature. Calcd. for C46H74Cl4FeN2P2Ti2. C,
A solution of 9 (0.325 g, 0.501 mmol) in 10 mL of toluene was
added to a solution of TiCl4 (0.220 g, 1.003 mmol) in 10 mL
of toluene. The mixture was refluxed for 15 h. After this time, the
color changed from dark to light orange, and an orange precipitate
appears upon leaving the mixture to reach room temperature. This
mixture is filtered and washed with hexanes (3 ¥ 15 mL) to collect
a first fraction containing 12, and the remaining solid in the frit
was washed with dichloromethane (4 ¥ 5 mL) to collect a second
fraction of the product. Solvents were evaporated under vacuum
in both fractions. The dichloromethane fraction yielded pure 12
as an orange microcrystalline solid (0.140 g). The other fraction
was further purified by washing it with toluene (2 ¥ 15 mL)
and pentane (2 ¥ 15 mL), yielding 0.150 g more of 12. Overall
yield: 0.290 g (71%). Crystals suitable for X-ray analysis were
grown by vapour diffusion of pentane into a saturated solution
of 12 in dichloromethane at room temperature. Anal. Calcd. for
C26H44Cl6FeN2P2Ti2. C, 38.51; H, 5.47; N, 3.45. Found: C, 38.29;
1
54.68; H, 7.38; N, 2.77 Found: 54.76; H, 7.25; N, 2.69. 31P{ H}
NMR (CDCl3): 40.3 (s, 2P). 1H NMR (CDCl3): 5.15, 4.78 (2 ¥ s,
2 ¥ C5H4, 2 ¥ 4H), 2.19 (s, C5Me5, 30 H), 1.32 (d, JPH = 15, CH3-
1
tBu, 36 H). 13C{ H} NMR (CDCl3): 126.0 (s, C5Me5), 75.2 (d,
JPC = 10, C2/3-C5H4), 75.1 (d, JPC = 10, C3/2-C5H4), 74.9 (d, JPC
=
88, C1-C5H4), 38.7 (d, JPC = 56, C(CH3)3), 28.1 (s, CH3-tBu), 13.2
(s, CH3).
Synthesis of [Fe(g5-C5H4PtBu2NTiCp*Me2)2] (16)
0.2 mL of a 3 M solution of MeMgBr (0.60 mmol) were added to
a solution of 15 (0.110 g, 0.109 mmol) in 10 mL of toluene. The
mixture was stirred for 15 h at room temperature. Solvents were
then evaporated and the product was extracted with toluene (5 ¥
5 mL) and filtered through Celite to yield, after evaporation of
solvent, compound 16 as an orange solid. Yield: 0.055 g (54%).
Anal. Calcd. for C50H86FeN2P2Ti2. C, 64.66; H, 9.33; N, 3.02.
1
H, 5.65; N, 3.63%. 31P{ H} NMR (CD2Cl2): 51.9 (s, 2P). 1H NMR
(CD2Cl2): 5.25, 4.86 (2 ¥ s, 2 ¥ br, 2 ¥ C5H4, 2 ¥ 4H), 1.49 (d,
1
JPH = 16, CH3-tBu, 36 H). 13C{ H} NMR (CDCl3): 76.2 (d, JPC
=
9, C2/3-C5H4), 75.1 (d, JPC = 10, C3/2-C5H4), 71.2 (d, JPC = 88,
C1-C5H4), 40.2 (d, JPC = 52, C(CH3)3), 28.2 (s, CH3).
1
Found: 64.45; H, 9.22; N, 2.89. 31P{ H} NMR (CDCl3): 23.5 (s,
2P). 1H NMR (CDCl3): 4.78, 4.69 (2 ¥ s, 2 ¥ C5H4, 2 ¥ 4H), 2.00
(s, C5Me5, 30 H), 1.33 (d, JPH = 14, CH3-tBu, 36 H), -0.03 (s,
Synthesis of [Fe(g5-C5H4PtBu2NTiCpCl2)2] (13)
1
Ti-Me, 12H). 13C{ H} NMR (CDCl3): 118.5 (s, C5Me5), 76.8 (d,
A solution of 9 (0.400 g, 0.617 mmol) and CpTiCl3 (0.270 g,
1.231 mmol) in 15 mL of toluene was heated at 70 ◦C for 4 h.
Then the solution was filtered through Celite and the solvent
evaporated, affording compound 13 as an orange solid. Yield:
0.500 g (93%). Crystals suitable for X-ray analysis were grown
by layering a saturated solution of 13 in toluene with pentane at
JPC = 82, C1-C5H4), 75.0 (d, JPC = 9, C2/3-C5H4), 73.5 (d, JPC = 8,
C3/2-C5H4), 42.8 (s, Ti-Me), 38.5 (d, JPC = 58, C(CH3)3), 28.2 (s,
CH3-tBu), 12.2 (s, CH3).
Generation of [Cp¢TiMe(NPtBu2C5H4FeCp)]X (Cp¢ = Cp, X =
[MeB(C6F5)3] (17a), [B(C6F5)4] (17b); (Cp¢ = Cp*, X =
[MeB(C6F5)3] (18a), [B(C6F5)4] (18b))
◦
-35 C. Anal. Calcd. for C36H54Cl4FeN2P2Ti2. C, 49.69; H, 6.25;
1
N, 3.22. Found: 49.53; H, 6.17; N, 3.38. 31P{ H} NMR (C6D6):
1
39.8. H NMR (C6D6, 500.13 MHz): 6.49 (s, Cp, 5H), 5.40, 4.72
(2 ¥ s, 2 ¥ C5H4, 2 ¥ 4H), 1.07 (d, JPH = 15, CH3-tBu, 36 H).
These compounds were generated in a similar fashion and thus
only one preparation is detailed. A solution of B(C6F5)3 (0.026 g,
1
13C{ H} NMR (C6D6, 125.77 MHz): 115.4 (s, Cp), 75.6 (d, JPC
=
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0.051 mmol) in 0.7 mL of BrC6D5 was added to 0.025 g of
compound 3 (0.051 mmol) to immediately give an orange solution
of 17a which decomposes progressively in solution at room
temperature yielding a dark green-brownish solution containing
multiple products after 24 h. Formation of CH4 was detected by 1H
NMR (singlet at 0.13 ppm). Any attempts to isolate 17a or 17b as
NMR (C6D5Br): 5.09 (m, C5H4, 1H), 4.41 (3 ¥ m, C5H4, 3 ¥ 1H),
4.19, 4.07, 3.50, 3.44 (4 ¥ m, C5H4, 4 ¥ 1H), 3.16 (d, JPH = 3, N-H,
1H), 1.70 (s, C5Me5, 15H), 1.13 (s, Ti-Me, 3H), 1.10 (d, JPH = 15,
CH3-tBu, 9H), 0.90 (d, JPH = 15, CH3-tBu, 9H). The signal for the
Me-B could not be unambiguously assigned. 19F NMR (C6D5Br):
-131.6 (d, JFF = 22, o-C6F5, 6F), -163.8 (br, p-C6F5, 3F), -166.3
1
1
a solid led to decomposition. 17a: 31P{ H} NMR (C6D5Br): 45.5.
(br, m-C6F5, 6F). 11B NMR (C6D5Br): -14.1. 19b: (~70%) 31P{ H}
1H NMR (C6D5Br): d 6.21 (s, Ti-Cp, 5H), 4.28 (m, C5H4, 2H),
4.06 (s, Fe-Cp, 5H), 3.99 (br, C5H4, 2H), 1.22 (br, Ti-Me, 3H),
0.98 (d, JPH = 15, CH3-tBu, 18H), 0.80 (br, B-Me, 3H). 19F NMR
(C6D5Br): -132.6 (br, o-C6F5, 6F), -160.3 (br, p-C6F5, 3F), -164.4
NMR (C6D5Br): 94.0. 1H NMR (C6D5Br): 5.11, 4.42 (2 ¥ m, C5H4,
2 ¥ 1H), 4.40 (2 ¥ m, C5H4, 2 ¥ 1H), 4.19, 4.07, 3.52, 3.44 (4 ¥ m,
C5H4, 4 ¥ 1H), 3.17 (d, JPH = 3, N–H, 1H), 1.70 (s, C5Me5, 15H),
1.14 (s, Ti-Me, 3H), 1.11 (d, JPH = 15, CH3-tBu, 9H), 0.91 (d,
JPH = 15, CH3-tBu, 9H). 19F NMR (C6D5Br): -132.1 (d, JFF = 10,
o-C6F5, 6F), -162.6 (d, JFF = 21, p-C6F5, 3F), -166.3 (m, m-C6F5,
6F). 11B NMR (C6D5Br): -16.2.
1
(br, m-C6F5, 6F). 11B NMR (C6D5Br): -13.7. 17b: 31P{ H} NMR
(C6D5Br, 253 K): 49.8. 1H NMR (C6D5Br, 253 K): d 6.11 (s, Ti-Cp,
5H), 4.35 (m, C5H4, 2H), 4.12 (br, C5H4, 2H), 4.11 (s, Fe-Cp, 5H),
1.25 (br, Ti-Me, 3H), 1.03 (d, JPH = 15, CH3-tBu, 18H). 1H NMR
(C6D5Br, 295 K): d 6.15 (s, Ti-Cp, 5H), 4.38 (m, C5H4, 2H), 4.16
(br, C5H4, 2H), 4.12 (s, Fe-Cp, 5H), 1.21 (br, Ti-Me, 3H), 1.07 (d,
JPH = 15, CH3-tBu, 18H). 19F NMR (C6D5Br, 253 K): -131.5 (d,
JFF = 10, o-C6F5, 6F), -162.0 (t, JFF = 21, p-C6F5, 3F), -165.7
(m, m-C6F5, 6F). 19F NMR (C6D5Br, 295 K): -131.6 (d, JFF = 10,
o-C6F5, 6F), -161.8 (t, JFF = 21, p-C6F5, 3F), -165.6 (m, m-C6F5,
6F). 11B NMR (C6D5Br, 253 K): -16.1 (s, 1B). 11B NMR (C6D5Br,
Polymerization protocol using B(C6F5)3 as cocatalyst
A typical procedure for ethylene polymerization using B(C6F5)3 is
as follows. Stocksolutions ofpre- andco-catalyst, as well as solvent
scrubber (i-Bu3Al), in toluene were prepared in the glovebox and
stored in the freezer at -35 ◦C prior to use. Dry toluene (50 mL) was
charged into a 250 mL Schlenk flask in the glovebox. The flask and
syringes containing solutions with the right volume of pre-catalyst,
co-catalyst and solvent scrubber were taken out of the box. The
flask was connected to a Schlenk line and placed under ethylene (1
atm) through five evacuate-refill cycles. Then, i-Bu3Al (10% w. in
toluene) was added (0.1 mL, 50 mmol approx.), and the solution
stirred for 5 min. After that time, a solution containing B(C6F5)3
(0.25 mL, 2.5 mmol) was injected followed by a solution containing
the pre-catalyst (0.25 mL, 2.5 mmol). This mixture was stirred for
10 min, before quenching it with an HCl solution in MeOH (1 M),
and poured into a beaker containing more of the latter solution
(100 mL approx.). The resultant polymer was filtered, washed with
MeOH and toluene and dried in vacuo for, at least, 15 h.
1
295 K): -16.1 (s, 1B). 13C{ H} NMR (C6D5Br, 253 K): 148.4 (dm,
JCF ~ 241, o-C6F5), 138.3 (dm, JCF ~ 246, p-C6F5), 136.4 (dm, JCF
~
248, m-C6F5), 115.9 (s, Ti-Cp), 72.6 (d, JPC = 10, C2/3-C5H4), 71.3
(d, JPC = 9, C3/2-C5H4), 70.5 (s, Fe-Cp), 67.5 (d, JPC = 91, C1-C5H4),
60.6 (s, Ti-Me), 37.7 (d, JPC = 53, C(CH3)3), 26.7 (s, CH3-tBu).
1
1
18a: 31P{ H} NMR (C6D5Br): 44.2. H NMR (C6D5Br): d 4.32
(m, C5H4, 2H), 4.12 (br, C5H4, 2H), 4.08 (s, Fe-Cp, 5H), 1.85 (s,
C5Me5, 15H), 1.06 (s, Ti-Me, 3H), 1.01 (d, br, JPH = 15, CH3-tBu,
18H), 0.65 (br, B-Me, 3H). 19F NMR (C6D5Br): -131.9 (d, JFF
=
20, o-C6F5, 6F), -160.5 (br, p-C6F5, 3F), -164.9 (br, m-C6F5, 6F).
1
11B NMR (C6D5Br): -13.8. 18b: 31P{ H} NMR (C6D5Br, 295 K):
1
48.7. H NMR (C6D5Br, 295 K): d 4.37 (m, C5H4, 2H), 4.17 (m,
C5H4, 2H), 4.10 (s, Fe-Cp, 5H), 1.79 (s, C5Me5, 15H), 1.11 (s, Ti-
X-Ray data collection and reduction
1
Me, 3H), 1.08 (d, JPH = 15, CH3-tBu, 18H). H NMR (C6D5Br,
253 K): d 4.35 (m, C5H4, 2H), 4.14 (br, C5H4, 2H), 4.11 (s, Fe-Cp,
5H), 1.75 (s, C5Me5, 15H), 1.10 (s, Ti-Me, 3H), 1.05 (d, JPH = 15,
CH3-tBu, 18H). 19F NMR (C6D5Br, 295 K): -131.5 (d, JFF = 10,
o-C6F5, 6F), -160.5 (t, JFF = 21 p-C6F5, 3F), -165.7 (m, m-C6F5,
6F). 19F NMR (C6D5Br, 253 K): -131.5 (d, JFF = 10, o-C6F5, 6F),
-160.5 (t, JFF = 10 p-C6F5, 3F), -165.7 (m, m-C6F5, 6F). 11B NMR
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 (4.5◦ < 2q < 45-
50.0◦) 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. 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 SHELXTL processing packages.
An empirical absorption correction based on redundant data was
applied to each data set. Subsequent solution and refinement was
performed using the SHELXTL solution package.
1
(C6D5Br, 295 K, 253 K): -16.0. 13C{ H}NMR (C6D5Br, 253 K):
148.4 (dm, JCF ~ 241, o-C6F5), 138.3 (dm, JCF ~ 245, p-C6F5),
136.4 (dm, JCF ~ 247, m-C6F5), 127.0 (s, C5Me5), 73.2 (d, JPC = 10,
C2/3-C5H4), 71.7 (d, JPC = 8, C3/2-C5H4), 70.6 (s, Fe-Cp), 68.9 (d,
JPC = 89, C1-C5H4), 63.1 (s, Ti-Me), 38.0 (d, JPC = 54, C(CH3)3),
26.7 (s, CH3-tBu).
Observation of [Cp*Ti(HNPtBu2C5H4)Fe(g5:g1-C5H4))]X (X =
[MeB(C6F5)3] 19a, [B(C6F5)4] 19b)
Structure solution and refinement
Compounds 18a,b evolve in solution to give, after 48 h (18a) or
15 h (18b), a mixture containing compounds 19a,b as the major
species (70-80%), and 20-30% of other uncharacterized products
derived most likely from the loss of CH4 (detected by 1H NMR).
A mixture containing the same ratio of products was isolated as
a solid after addition of hexane, letting it to settle at -35 ◦C and
Non-hydrogen atomic scattering factors were taken from the
literature tabulations.63 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,
1
decanting mother liquor. 19a: 31P{ H} NMR (C6D5Br): 94.4. 1H
1332 | Dalton Trans., 2010, 39, 1328–1338
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©

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Table 1 Crystallographic data
1
4
5
6
7(0.5C6H5Me)
9
10(CH2Cl2) 12
15(2CHCl3)
Formula
C21H36-
FeNPSi
417.42
C28H42Cl2-
FeNPTi
598.25
C30H42-
FeNPTi
557.41
C51H56-
FeNPSi
797.88
C56.5H56Cl2-
FeNPTi
954.64
C32H72-
FeN2P2Si2
658.89
Monoclinic
C2/c
26.915(3)
9.7197(11)
15.1251(18)
C27H46Cl4-
FeN2P2Ti
706.15
Monoclinic Monoclinic Monoclinic
C2/c
19.361(4)
10.900(2)
17.105(3)
C26H44Cl6-
FeN2P2Ti2
810.92
C48H76Cl10-
FeN2P2Ti2
1249.20
Formula wt
Cryst. syst.
Space grp
Monoclinic Orthorhombic Monoclinic Monoclinic Triclinic
P21/n
10.083(2)
10.733(2)
41.135(8)
¯
P1
P212121
P21/n
P21/c
C2/c
P21/n
˚
a/A
9.1534(4)
15.9165(7)
19.9410(10)
8.4917(17)
15.639(3)
22.514(5)
18.467(4)
12.868(3)
20.237(4)
14.3943(14)
16.9970(17)
21.197(2)
72.4480(10)
89.9460(10)
89.9460(10)
4883.6(8)
4
298
1.298
0.1262
0.641
26.615(5)
9.6625(19)
14.696(3)
8.6321(17)
18.488(4)
18.445(4)
˚
b/A
˚
c/A
a/◦
b/◦
g /◦
95.94(3)
95.91(3)
115.06(3)
104.8850(10) 98.55(3)
105.29(3)
102.45(3)
3
˚
V/A
Z
4427.7(15)
2
150
2905.2(2)
4
150
1.368
0.0478
1.030
26 143
6667
2974.0(10)
4
150
1.245
0.0411
0.828
18 221
6727
4356.3(15)
4
150
1.217
0.1036
0.445
40 834
9951
3824.1(8)
4
298
1.144
0.0299
0.563
17 871
3370
3569.8(12)
4
150
1.314
0.0331
1.038
12 144
4060
3645.6(12)
4
150
1.477
0.0522
1.368
11 621
4156
2874.3(10)
2
298
1.443
0.0705
1.075
17 636
5045
T/K
d(calc)/gcm-1 1.409
R(int)
0.0575
0.913
20 154
9194
m/cm-1
Total data
47 239
17 148
Data
>3s(Fo
2
)
Variables
R (>3s)
Rw
451
307
307
496
1126
178
182
177
295
0.0545
0.1150
1.032
0.0363
0.0778
1.021
0.0489
0.1373
1.042
0.0578
0.1555
1.013
0.0600
0.1590
0.891
0.0338
0.0995
1.034
0.0322
0.0864
1.064
0.0456
0.1124
1.062
0.0500
0.1320
1.034
GOF
ꢀ
ꢀ
ꢀ
ꢀ
1
a
2
2
2
2
Data collected with Mo Ka radiation (l = 0.71069 A). R = (Fo - Fc)/ Fo; bRw={ [w(Fo - Fc 2]/ [w(Fo) ]} .
˚
)
minimizing the function w(Fo - Fc)2 where the weight w is defined
as 4Fo2/2s(Fo2) and Fo and Fc are the observed and calculated
structure factor amplitudes, respectively. 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
yield (Scheme 2). The presence of the methyl groups was evidenced
by the appearance of the 1H resonance at 0.77 ppm.
˚
which they are bonded assuming a C–H bond length of 0.95 A. 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
calculation as well as the magnitude of the residual electron
densities in each case were of no chemical significance. Additional
details are provided in Table 1 and the supplementary data.†
Results and discussion
Mono-ferrocenylphosphinimide complexes
Scheme 2 Synthesis of compounds 1-8.
Oxidation of CpFe(h -C5H4PtBu2)62 with Me3SiN3 proceeds
smoothly to give the phosphinimine derivative [CpFe(h -
C5H4PtBu2NSiMe3)] 1 in 89% isolated yield. The NMR data as
well as X-ray diffraction data were consistent with the formu-
lation (Fig. 1(a)). The metric parameters of 1 are as expected
5
5
In an analogous manner the species [Cp*TiX2(NPtBu2C5H4)-
FeCp] (X = Cl 4, Me 5) were prepared employing Cp*TiCl3
(Scheme 2). In these cases the yields were 88% and 63%, respec-
5
tively. In a similar oxidation of the ferrocenyl phosphinimine [(h -
˚
with a typical P–N and N–Si bond lengths of 1.534(3) A and
C5Ph5)Fe(C5H4PtBu2NSiMe3)] (6) was obtained in 80% yield and
38,64
5
˚
1.660(3) A, respectively.
In a conventional synthesis, this
the derivatives [CpTiX2(NPtBu2C5H4)Fe(h -C5Ph5)] (X = Cl 7,
ligand reacts with CpTiCl3 to give the phosphinimide complex
Me 8) were prepared in 70 and 90% yields respectively (Scheme 1).
The latter species 8 proved to be difficult to isolate in an analytically
pure form as it undergoes progressive decomposition in solution.
Nonetheless, the spectroscopic data for 4-8 were as expected and
unexceptional.
[CpTiCl2(NPtBu2C5H4)FeCp] (2) which was isolated in 85% yield
1
as an orange solid. The downfield shift of the 31P{ H} signal
to 42.9 ppm is consistent with substitution on Ti. Subsequent
methylation of 2 gave [CpTiMe2(NPtBu2C5H4)FeCp] (3) in 77%
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Fig. 2 ORTEP drawings of (a) 6, (b) 7, 50% thermal ellipsoids are
shown. Hydroge◦n atoms are omitted for clarity. Selected bond distances
˚
(A) and angles ( ): 6: P–N 1.532(2), Si–N 1.669(2), P–N-Si1 168.3(2), 7:
Ti–N 1.755(4), Ti–Cl(2) 2.286(2), T–Cl(1) 2.317(2), P–N 1.606(4), P–N–Ti
170.0(3), Cl(2)–Ti–Cl(1) 101.12(8).
supporting electrolyte and a scan speed of 250 mV s-1. Both
compounds 2 and 4 exhibited quasi-reversible waves at 0.23 and
0.17 V versus the Cp2Fe0/+ standard. These waves exhibited peak-
to-peak separation of 161 mV and 185 mV, respectively and were
attributable to the Fe(II)/Fe(III) redox couple for these compounds
(Fig. 3), both being in the range of the first oxidation potential
Fig. 1 ORTEP drawings of (a) 1, (b) 4, (c) 5, 50% thermal ellipsoids
5
previously reported for [Cp2Ti{(h -C5H4)FeCp}2].65 The presence
are shown. Hydrogen atoms are omitted for clarity. Selected bond
◦
˚
distances (A) and angles ( ): 1: P–N 1.534(3), N–Si 1.660(3), P–N–SiAVG
170.50(19). 4: Ti–N 1.777(2), Ti–Cl 2.3151(9), 2.3169(9), P–N 1.603(2),
Cl(1)–Ti–Cl(2) 102.33(4), P–N–Ti 163.81(15). 5: Ti–N 1.816(2), Ti–C(20)
2.138(3), Ti–C(19) 2.152(3), P–N 1.583(2), C(20)–Ti–C(19) 98.65(14),
P–N–Ti 167.58(15).
of the phosphinimide substituent on one of the cyclopentadienyl
ligands of the ferrocenyl fragment is consistent with the higher
oxidation potential of the Fe centers in compounds 2 and 4 versus
that in Cp2Fe. The lower oxidation potential of 4 is consistent with
Structural studies of 4, 5 (Fig. 1(b), (c)) and 6 and 7 (Fig. 2)
confirmed these formulations. In the case of 4, 5 and 7, the metric
parameters about Ti were typical of titanium phosphinimine
complexes38 with Ti–N distances of 1.777(2) A, 1.816(2) A
˚
˚
˚
and 1.755(4) A, respectively. Similarly, the corresponding P–N
˚
˚
˚
distances of 1.603(2) A, 1.583(2) A and 1.606(4) A, as well as the P–
N–Tiangles of 163.81(15)◦, 167.58(15)◦ and 170.0(3)◦, respectively
were similar to those reported in a series of phosphinimide com-
plexes of the form [Cp¢Ti(NPR3)X2]. Perhaps the most interesting
feature of these molecules is the variability of the orientation of
the ferrocenyl fragments. The Ti center in 4 is generating a Ti–
˚
Fe separation of 5.891 A whereas in 5 the ferrocenyl fragment is
oriented towards the Ti center with a Fe–Ti distance of 5.368 A.
˚
˚
The Fe–Ti distance in 7 is similar to the one found in 4 at 5.843 A.
The electrochemical properties of compounds 2 and 4 were
studied by cyclic voltammetry in THF using [NBu4][PF6] as the
Fig. 3 Cyclic voltammetry on compound 2 (THF/NBu4PF6, 0.1 M), v =
250 mV s-1 at r.t.; potentials were calibrated against the Cp2Fe0/+ internal
standard. E0 (20/+) = 0.23 V, DEp = 161 mV; Ep = -2.07 V; -2.75 V.
1334 | Dalton Trans., 2010, 39, 1328–1338
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the greater electron donating ability of Cp* versus Cp. In addition,
to this quasi-reversible waves, both compounds also exhibited two
irreversible features (Fig. 3) at -2.07 V and -2.75 V for 2 and
-2.27 V and -2.87 V for 4. These are irreversible reductions
attributable to Ti(IV)/Ti(III) and Ti(III)/Ti(II) redox couples.
Similar irreversible waves have been previously described for
[Cp¢2TiCl2] species.66 Despite the quasi-reversible behavior, efforts
to access the Fe(III)/Ti(IV) species chemically were unsuccessful.
Treatment of 2 or 4 with [NO][BF4] gave only green solutions
containing mixtures of products that yielded inseparable oils.
Bis-ferrocenylphosphinimide complexes
In very similar chemistry the bis-phosphinimine [Fe(C5H4PtBu2-
(NSiMe3)2] (9) was readily prepared via oxidation of
[Fe(C5H4PtBu2)2] with N3SiMe3. This procedure afforded 9 in
92% yield. This species proved to be quite versatile as a ligand.
Reaction with TiCl4 in a 1 : 1 stoichiometry affords the chelate
Scheme 3 Fluxional process involving chelating ferrocenyl bis-phosphin-
imide ring proposed for 10 and 11.
5
bis-phosphinimide complex [{Fe(h -C5H4PtBu2N)2}TiCl2] (10) in
presumable accounted for the only moderate isolated yield of
this yellow-orange solid (49%). The same fluxional behaviour
with a similar activation energy was also observed for 11. Such
conformational fluxionality has also been observed for other
[5]ferrocenophanes.68
The electrochemical behavior of 10 was also examined under
the same conditions to those described above. Interestingly, in
contrast to 2 and 4, compound 10 exhibits irreversible oxidation
waves at 0.64 V and 0.89 V, as well as an irreversible reduction wave
at -0.65 V. These data suggest that in the chelating geometry the
oxidation of Fe results in an unstable situation, perhaps because
of the closer proximity of the metal centres.
79% isolated yield. Alternatively, this compound was also isolable
from reaction of the phosphinimine with [TiCl4(THF)2], albeit
1
in 70% yield. The 31P{ H} NMR data for 10 shows a singlet at
29.4 ppm which is invariant with temperature. In contrast, the
1H NMR spectra show marked temperature dependence. At room
temperature the resonances attributable to the cyclopentadienyl
protons gave broad singlets at 5.03 and 4.09 and a signal at
4.30 ppm. The corresponding signals arising from the t-butyl
methyl groups were very broad too, coming out at 1.25 and
0.99 ppm (Fig. 4). Upon cooling to 253 K, the cyclopentadienyl
protons gave rise to slightly broadened singlets at 5.03, 4.28, 4.24
and 3.96 ppm while the t-butyl methyl protons gave rise to two dou-
blets at 1.35 and 0.90 ppm, with P–H coupling constants of 15 Hz.
Upon warming to 371 K, the cyclopentadienyl signals coalesce
to two resonances at 4.61 and 4.33 ppm and the t-butyl methyl
resonance is reduced to a single doublet at 1.19 ppm (Fig. 4).
Analysis of the temperature dependence employing a modified
Eyring equation67 infers the temperature dependent process has
an activation barrier measured at the coalescence temperature
(Tc) for the cyclopentadienyl signals (DG#306 K) of approximately
62 KJ/mol. These data are consistent with the formation of a
bis-phosphinimide chelate complex that undergoes a temperature-
dependent conformational change involving torsion about the
Fe–Cp-centroid axes (Scheme 3). Treatment of 10 with MeMgBr
A crystallographic study of 10 confirmed the proposed chelating
nature of the ferrocenyl bis-phosphinimide ligand (Fig. 5). The
˚
˚
Ti–N and Ti–Cl distances of 1.7888(16) A and 2.3038(7) A are
comparable to those seen in [(tBu3PN)2TiCl2], as is the P–N bond
˚
length of 1.5881(17) A. The bite angle for the eight-membered
chelate ring is 112.66(11)◦, almost identical to the seen for
[(tBu3PN)2TiCl2] (112.9(2)◦).28 The P–N–Ti vectors approaches
linearity in 10 at 170.0(3)◦ and 164.1(3)◦ for the two molecules
in the asymmetric unit. These values are in the r◦ange of those
observed for [(tBu3PN)2TiX2] (X = Cl, Me; 175.5(2) , 167.8(3)◦).28
As such deviation must arise from packing forces, this observation
suggests that there is flexibility in the P–N–Ti vector. The Ti–Fe
˚
separation is 4.647 A, denoting negligible interaction between the
5
readily afforded the corresponding dimethyl derivative, [{Fe(h -
two metal centres.
C5H4PtBu2N)2}TiMe2] (11), although the enhanced solubility
In an alternative strategy, reaction of 9 with two equivalents
5
of TiCl4 afforded a trimetallic species. The product, [Fe(h -
1
C5H4PtBu2NTiCl3)2] (12) was isolated in 71% yield. The 31P{ H}
NMR spectrum of 12 is a single resonance at 51.9 ppm,
markedly downfield of that one for 10. Similarly, reaction of
5
6 with two equivalents of CpTiCl3 affords the species [Fe(h -
C5H4PtBu2NTiCpCl2)2] (13) in 93% yield. A subsequent methy-
5
lation affords [Fe(h -C5H4PtBu2NTiCpMe2)2] (14). Analogously,
5
the species [Fe(h -C5H4PtBu2NTiCp*X2)2] (X = Cl (15), Me (16))
were also prepared and fully characterized (Scheme 4). Crystal
structures of 12 and 15 were determined (Fig. 5(c), (d)). In both
cases, the bis-ferrocenylphosphinimide ligand is oriented so as to
maximize the Ti–Fe separations. The Ti–Fe distances in 12 and
15 were found to be 4.938 A and 5.217 A, respectively. The metric
parameters in 15 are similar to those seen in 5 as expected.
Fig. 4 The portion of the variable temperature 1H NMR spectra of (10)
showing the resonances attributable to the t-butyl methyl protons.
˚
˚
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Scheme 4 Synthesis of compounds 9-16.
Fig. 5 ORTEP drawings of (a) 9, (b) 10, (c) 12, (d) 15, 50% thermal
ellipsoids are shown. Hydrogen◦atoms are omitted for clarity. Selected
˚
bond distances (A) and angles ( ): 9: N–Si 1.6469(19), P–N 1.5234(19),
P–N–Si 171.59(15). 10: Ti–N 1.7888(16), Ti–Cl 2.3038(7), P–N 1.5881(17),
N–Ti–N 112.66(11), Cl–Ti–Cl¢ 109.33(4), P–N–Ti 170.0(3). 12: Ti–N
1.715(3), Ti–Cl(1) 2.2332(13), Ti–Cl(3) 2.2335(11), Ti–Cl(2) 2.2492(13),
P–N 1.625(3), P–N–Ti 172.76(18). 15: Ti–Cl(1) 2.3189(12), Ti–Cl(2)
2.3210(14), P–N 1.604(3), Ti–N 1.782(3), P–N–Ti 166.2(2).
Scheme 5 Generation of compounds 17-19.
species 17b appeared to be even more sensitive, decomposing to
multiple uncharacterized products before 24 h, with the generation
of methane as well.
Zwitterionic and cationic complexes
Compound 3 reacts with B(C6F5)3 in bromobenzene to gen-
erate the [CpTiMe{(NPtBu2C5H4)FeCp}][MeB(C6F5)3] (17a)
(Scheme 5). This species is extremely sensitive and decomposes
progressively in solution at room temperature over 24 h to give a
dark green-brownish mixture of multiple products with the gener-
The analogous salts derived from compound 5,
[TiCp*Me(NPtBu2(C5H4)FeCp)]X (X
=
[MeB(C6F5)3] 18a,
[B(C6F5)4] 18b) were prepared in a similar manner (Scheme 5).
Similarly, attempts to isolate these species also were problematic
as compound 18 evolves in solution over 48 h (using B(C6F5)3)
or 15 h (employing [CPh3][B(C6F5)3]) at room temperature
to generate mixtures containing [Cp*TiMe(HNPtBu2(C5H4)
1
ation of methane. Nonetheless, 17a was characterized by 31P{ H}
and 11B resonances at 45.5 and -13.7 ppm respectively. 1H NMR
signals attributable to the Ti-bound Cp and ferrocenyl protons
were observed at 6.21 and 4.28, 4.06 and 3.99 ppm, respectively.
The Ti- and B-bound methyl resonances were observed at 1.22
and 0.80 ppm, respectively. 19F NMR data were consistent with
the presence of the MeB(C6F5)3 anion. Any attempts to isolate
17a as a solid were unsuccessful leading to decomposition. In
a similar fashion reactions of 3 with [CPh3][B(C6F5)3] gave [Cp-
TiMe(NPtBu2(C5H4)FeCp)] [B(C6F5)4] (17b). The spectroscopic
data were similar, albeit a little bit shifted from those of 17a. The
5
1
Fe(h :h -C5H4))]X (X = [MeB(C6F5)3] 19a, [B(C6F5)4] 19b) as
the major products respectively in about 80% and 70% yields
(Scheme 5). The formation of other uncharacterized minor
products and methane was also detected by NMR spectroscopy,
as these experiments were carried out in NMR tubes sealed with
J-Young valves. Compounds 19a,b were found to degrade slowly
in solution, giving rise to higher amounts of the by-products
mentioned before. The most notable spectroscopic features
1
of 19a,b are the downfield 31P{ H} NMR signals at 94.4 and
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1
94.0 ppm, as well as the H resonance consistent with formation
are highly effective olefin polymerization catalysts. Interestingly,
these cations in the absence of olefin are quite sensitive and prone
to intramolecular ferrocenyl C–H activation. Studies designed to
further assess the broader application of these catalysts are under
way and will be reported in due course.
of a Ti–C bond to the previously unsubstituted cyclopentadienyl
ring on Fe. The proton bound to the N atom, ca. 3.2 ppm,
shows a small coupling with phosphorus (3 Hz) and could
be unambiguously assigned after performing 2D homonuclear
1H-1H NMR experiments (COSY and NOESY). This proved that
19a,b are genuine products of an intramolecular C–H activation
of the ferrocenyl moiety prompted by the enhanced Lewis acidity
of the cationic Ti centres of 18a,b which occurs without methane
elimination, as the proton acceptor is the N atom. The anions in
both cases give rise to 19F and 11B NMR spectra consistent with
the free ions. It is noteworthy that metallated ferrocenes such as
[(C5H4R)2Zr(C5H4)2Fe],69 [Cp2M(C5H4)2Fe] (M = Ti, Zr, Hf)70
and [Cp2TiCl(C5H4)FeCp]71 have been previously characterized.
Moreover the apparent addition of the cyclopentadienyl C–H
bond of the ferrocenyl fragment across the Ti–N bond is
Notes and references
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and 360 000 and polydispersities of 5.5 and 6.6 respectively. The
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some of the resulting species give rise to cationic species that
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1338 | Dalton Trans., 2010, 39, 1328–1338
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