Oligomerization of ethylene using new tridentate iron catalysts bearing α-diimine ligands with pendant S and P donors

Article abstract of DOI:10.1021/om1007743

Stoichiometric Schiff base condensations of sterically bulky primary amines with acenaphthenequinone yield isolable monoimines. In the presence of iron(II) chloride, the remaining ketone reacts with a second primary amine bearing a pendant donor atom to g

Full text of DOI:10.1021/om1007743

Organometallics 2010, 29, 6723–6731 6723
DOI: 10.1021/om1007743
Oligomerization of Ethylene Using New Tridentate Iron Catalysts
Bearing r-Diimine Ligands with Pendant S and P Donors
Brooke L. Small,*,† Ray Rios,† Eric R. Fernandez,† Deidra L. Gerlach,‡ Jason A. Halfen,‡
and Michael J. Carney‡
†Chevron Phillips Chemical Company, 1862 Kingwood Drive, Kingwood, Texas 77339, United States, and
‡Department of Chemistry, University of Wisconsin-Eau Claire, 105 Garfield Avenue, Eau Claire,
Wisconsin 54702, United States
Received August 9, 2010
Stoichiometric Schiff base condensations of sterically bulky primary amines with acenaphthene-
quinone yield isolable monoimines. In the presence of iron(II) chloride, the remaining ketone reacts
with a second primary amine bearing a pendant donor atom to give asymmetric, tridentate, R-diimine
complexes that possess remarkable structural variability. A series of NNP and NNS tridentate
iron(II) complexes are prepared; these coordination compounds become active catalysts for ethylene
oligomerization when activated with methylalumoxanes. X-ray crystallographic studies of the
precatalyst complexes confirm that the ligand binds in a tridentate fashion. Correlations between
the precatalyst solid-state structures and catalyst activity and R-olefin product distribution are
explored.
Introduction
for dimerizing ethylene to 1-butene.5,6 Typically, because
1-butene has had a historically low market value relative to
ethylene, these dimerization facilities have been used to
produce 1-butene for captive plant requirements in remote
locations where butene is not readily available. A very
interesting and more recent trend is the emergence of multiple
catalyst systems for ethylene trimerization,7-11 and even more
recently, tetramerization, to selectively prepare 1-hexene and
1-octene.12-17 Chevron Phillips was the first commercial
Current commercial processes for the production of linear
R-olefins reflect both past and future market conditions.
These conditions include relative growth rates of various R-
olefin end uses, captive requirements of R-olefin producers,
development of new end uses, feedstock cost considerations,
product quality requirements, and catalyst limitations.1-4
Because of these various concerns, full-range R-olefin pro-
duction (e.g., production of C4-C20þ R-olefins) has raised a
somewhat elevated barrier to entry, requiring major produ-
cers to balance the supply and demand of multiple products,
each one having different end uses and values. For example,
Chevron Phillips sells 13 different R-olefin fractions, as well
as several derivatives! The advantage to full-range produc-
tion is the ability to leverage temporarily undervalued pro-
ducts against those that are economically advantaged,
thereby insulating the business from some of the vagaries
of the petrochemical cycle.
(7) Dixon, J. T.; Green, M. J.; Hess, F. M.; Morgan, D. H. J.
Organomet. Chem. 2004, 689, 3641.
(8) McGuinness, D. S.; Brown, D. B.; Tooze, R. P.; Hess, F. M.;
Dixon, J. T.; Slawin, A. M. Z. Organometallics 2006, 3605.
(9) Wu, F.-J. (BP Amoco) U.S. Patent 5968866,1999.
(10) Carter, A.; Cohen, S. A.; Cooley, N. A.; Murphy, A.; Scutt, J.;
Wass, D. F. Chem. Commun. 2002, 858.
(11) McConville, D. H.; Ackerman, L.; Li, R. T.; Bei, X.; Kuchta,
M. C.; Boussie, T.; Walzer, J. F.; Diamond, G.; Rix, F. C.; Hall, K. A.;
LaPointe, A.; Longmire, J.; Murphy, V.; Sun, P.; Verdugo, D.; Schofer,
S.; Dias, E. (ExxonMobil) U.S. Patent 7414006 2008.
(12) Bollmann, A.; Blann, K.; Dixon, J. T.; Hess, F. M.; Killian, E.;
Maumela, H.; McGuinness, D. S.; Morgan, D. H.; Neveling, A.; Otto,
S.; Overett, M.; Slawin, A. M. Z.; Wasserscheid, P.; Kuhlmann, S. J. Am.
Chem. Soc. 2004, 14712.
An emerging alternative to full-range R-olefin production
is the selective production of R-olefins. This has been done
for many years commercially using IFP’s Alphabutol process
(13) Overett, M. J.; Blann, K.; Bollmann, A.; Dixon, J. T.; Haas-
broek, D.; Killian, E.; Maumela, H.; McGuinness, D. S.; Morgan, D. H.
J. Am. Chem. Soc. 2005, 10723.
(14) Overett, M. J.; Blann, K.; Bollmann, A.; Dixon, J. T.; Hess, F.;
Killian, E.; Maumela, H.; Morgan, D. H.; Neveling, A.; Otto, S. Chem.
Commun. 2005, 622.
*To whom correspondence should be addressed. E-mail:
smallbl@cpchem.com. Phone: 281-359-0281.
(1) Lappin, G. R.; Sauer, J. D., Eds. Alpha Olefins Applications
Handbook; Marcel Dekker, Inc.: New York, 1989.
(2) Vogt, D. In Applied Homogeneous Catalysis with Organometallic
Compounds, 2nd ed.; Cornils, B.; Herrmann, W. H., Eds.; Wiley-VCH:
Weinheim, 2002; p 240.
(3) Reuben, B.; Wittcoff, H. J. Chem. Educ. 1988, 65 (7), 605.
(4) Kirschner, M. ICIS Chem. Bus. 2008, April 21-27, 42.
(5) Olivier-Bourbigou, H.; Saussine, L. In Applied Homogeneous
Catalysis with Organometallic Compounds, 2nd ed.; Cornils, B.; Herrmann,
W. H., Eds.; Wiley-VCH: Weinheim, 2002; p 259.
(15) Wass, D. F. Dalton Trans. 2007, 816.
(16) Blann, K.; Bollmann, A.; Dixon, J. T.; Neveling, A.; Morgan,
D. H.; Maumela, H.; Killian, E.; Hess, F. M.; Otto, S.; Pepler, L.;
Mahomed, H. A.; Overett, M. J.; Green, M. J. (Sasol) U.S. Patent
7297832, 2007.
(17) Blann, K.; Bollmann, A.; Dixon, J. T.; Neveling, A.; Morgan,
D. H.; Maumela, H.; Killian, E.; Hess, F. M.; Otto, S.; Pepler, L.;
Mahomed, H. A.; Overett, M. J.; Green, M. J. (Sasol) WO 2004/056479
A1, 2007.
(6) Al-Jarallah, A. M.; Anabtawi, J. A.; Siddiqui, M. A. B.; Aitani,
A. M. Catal. Today 1992, 14, 1.
r
2010 American Chemical Society
Published on Web 11/19/2010
pubs.acs.org/Organometallics

6724 Organometallics, Vol. 29, No. 24, 2010
Small et al.
Scheme 1
producer of selective 1-hexene,18 and other companies have
since followed.19 While selective R-olefin production can
meet the growing needs of polyethylene comonomer end
users, the attractiveness of making a single R-olefin fraction
must be balanced with the risk of “commoditization” or
downturns in demand. In addition to the commercial and
emerging ethylene oligomerization technologies, the R-olefin
industry is also affected by non-ethylene-based processes,
such as the availability of refinery 1-butene,20 Fischer-Tropsch
R-olefins,21 and butadiene-based 1-octene.22,23
Figure 1. Schematic diagrams of iron(II) NNS complexes
1-11.
Scheme 2
Clearly, maintaining a portfolio of full-range and selective
R-olefin options provides needed flexibility for large-scale
producers. Recently, in addition to our selective oligomer-
ization studies, we reported a new family of pendant donor
modified R-diimine complexes for the oligomerization of
ethylene.24-27 The complexes were readily prepared via a
selective 1:1 reaction of various anilines with acenaphthene-
quinone, followed by a template-mediated condensation of a
primary aliphatic amine with the remaining ketone group
(Scheme 1). Many of these complexes, following activation
with MMAO, were highly active for the preparation of linear
R-olefins. In particular, the NNS- and NNP-ligated systems
made useful product distributions and exhibited high catalyst
activities. In this report, further structural variations on the
imino-aryl rings and the phosphine and thioether substituents
have been introduced. These complexes have been screened
for ethylene oligomerization activity; X-ray crystallographic
Scheme 3
studies have been used to supplement the discussion of
catalyst behavior.
(18) CPChem’s proprietary 1-hexene process is based on Cr-pyrrole
complexes. Reagan, W. K.; Conroy, B. K. (Phillips) U.S. Patent
5198563, 1993. Bridges, S. D.; Abbott, R. G.; Baralt, E. J.; Knudsen,
R. D.; Kreischer, B. E.; Small, B. L. (CPChem) U.S. Patent 7384886,
2008. Kreischer, B. E. (CPChem) U.S. Patent 7476775, 2009. Battiste,
D. R. (CPChem) U.S. Patent 7396970, 2008. Freeman, J. W.; Ewert,
W. M.; Kreischer, B. E.; Knudsen, R. D.; Cowan, G. D. (CPChem) U.S.
Patent 6455648, 2002. Kreischer, B. E.; Ewert, W. M.; Knudsen, R. D.
(CPChem) U.S. Patent 6380451, 2002. Conroy, B. K.; Pettijohn, T. M.;
Reagan, W. K.; Freeman, J. W. (Phillips) U.S. Patent 5376612, 1994. Conroy,
B. K.; Pettijohn, T. M.; Reagan, W. K.; Freeman, J. W. (Phillips) U.S. Patent
5523507, 1996.
(19) Recent press releases have indicated that other companies are
intent on producing 1-hexene via selective ethylene trimerization.
(20) ExxonMobil and Texas Petrochemicals can produce 1-butene by
distillation from raffinate streams.
(21) Sasol extracts R-olefins in the comonomer range by distilling
them from Fischer-Tropsch hydrocarbon streams. Sasol has also
employed successive hydroformylation, hydrogenation, and alcohol
dehydration to convert the odd-carbon-number olefins to even-num-
bered comonomer olefins, i.e., 1-heptene into 1-octene.
Results and Discussion
Oligomerization Using NNS-Ligated Iron Complexes. Several
new thioetheramines were prepared by the halide displacement
method disclosed in the literature (Scheme 2).24,28 These
thioetheramines were used to prepare NNS-ligated iron com-
plexes 1-11, via addition to the appropriate acenaphthene-
monoimines in the presence of FeCl2 4H2O or FeCl2. The
3
acenaphthene-monoimines were made according to Scheme 3.
Complexes 1 and 11 were reported in our prior publication;24
the thioether and imine substituents on complexes 2-10 were
chosen to allow a systematic study of the steric and electronic
effects of modifications to the NNS catalysts, especially with
respect to the Schulz-Flory K values (K = mol Cnþ2/mol Cn)
and the catalyst activities. The schematic structures of com-
plexes 1-11 are shown in Figure 1.
(22) Dow has recently constructed a plant in Spain to prepare
1-octene from butadiene: Schaart, B. J.; Pelt, H. L.; Jacobsen, G. B.
(Dow) U.S. Patent 5254782, 1993.
(23) Clement, N. D.; Routaboul, L.; Grotevendt, A.; Jackstell, R.;
Beller, M. Chem.;Eur. J. 2008, 14, 7408.
(24) Schmiege, B. M.; Carney, M. J.; Small, B. L.; Gerlach, D. L.;
Halfen, J. A. Dalton Trans. 2007, 2547.
(25) Small, B. L.; Rios, R.; Fernandez, E. R.; Carney, M. J. Organo-
Oligomerization of ethylene was carried out for each of the
complexes. The conditions and results of the experiments are
reported in Table 1. More details are described in the
Experimental Section. The first modification to the NNS
systems was the replacement of the Cl in 1 with a tert-butyl
group in complex 2. Given the solid-state structure of
metallics 2007, 26, 1744.
(26) Small, B. L.; Carney, M. J. (CPChem) U.S. Patent 7268096,
2007.
(27) Small, B. L.; Carney, M. J. (CPChem) U.S. Patent 7129304,
(28) Katritzky, A. R.; Hu, Y.-J.; He, H.-Y.; Mehta, S. J. Org. Chem.
2001, 66, 5590.
2006. Small, B. L.; Carney, M. J. (CPChem) U.S. Patent 7271121, 2007.

Article
Organometallics, Vol. 29, No. 24, 2010 6725
Table 1. Ethylene Oligomerization Data for NNS-Ligated Fe Catalystsa
amt MMAO Pethylene
(psig)
length
(min)
T
Tmax
yield
C4-C20 (g)
prod (g prod/
mmol cat)
C6%
purity
C8%
purity
C10%
purity
entry cat. (mg)
Al:Fe
(°C) (°C)
K (C12/C10
)
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
8
3.0
1.0
1.0
1.2
1.2
1.2
1.5
1.2
3.0
3.0
3.2
500
300
300
300
300
300
300
300
500
300
500
1000
1000
1000
1000
1000
1000
1000
1000
1000
1000
1000
60
60
60
60
60
60
30
60
30
30
60
50
50
50
50
50
50
50
50
50
35
50
68
55
58
62
53
53
65
52
50
37
50
110
91.0
149
21 400
54 900
91 600
15 300
32 900
26 900
39 400
48 600
∼20 100
2700
0.65
99.5
99.7
99.8
99.6
99.4
99.3
99.7
99.5
99.3
99.6
99.7
99.4
99.3
99.3
99.7
99.5
99.0
99.6
99.5
99.2
99.2
99.3
99.6
99.4
0.73
0.72
0.68
0.72
0.72
0.72
0.78
27.9
57.9
54.8
98.1
98.7
∼40
14.0
116
9
10
11
9
10
11
0.24 - 0.61 C8 - 18
0.74
0.85
35 500
98.9
a All reactions were run in cyclohexane solvent.
unactivated 1 with an unbound thioether,24 it was reasoned
that an electron -donating alkyl group (in this case tert-butyl)
might stabilize the active species. When tested under similar
conditions to those for 1, complex 2 showed higher produc-
tivity (entry 2). Replacing the 2,6-dimethylphenyl ring of 2
with a mesityl (2,4,6-trimethyl) group gave an even more
active catalyst system, 3 (entry 3), but further pushing this
trend with a tert-butyl group on the N-aryl para position gave
the significantly less active 4 (entry 4). Using an electron-
withdrawing group (Br) on the N-aryl ring increased the
activity, placing complex 5 between 2 and 4 on the activity
scale (entry 5). These significant activity differences between
similar systems would tempt one to make sweeping argu-
ments regarding ligand electronics and catalyst activity. In
fact, computational studies have been performed on related
pyridine bisimine (PBI) Fe catalysts,29 with the contention
that subtle changes in ligand electronics may dramatically
affect catalyst activity. While this may be the case for these
NNS (and NNP) catalysts, it is noted that only one set of
conditions is being used. A batch activity, while somewhat
useful, often does not give a good picture of catalyst lifetime,
thermal stability, or productivity.
Further electronic modifications were tested in complexes
6-8. Use of meta-methyl groups on the thioether aryl ring in
6 gave a system with lower activity than the p-tert-butyl
catalysts 2 and 3. Interestingly, it was also much easier to
isolate 2-5 in higher yield (>73%) than 6 (<50%). Com-
plexes 7 and 8, with a p-methoxy group on the S-aryl rings,
also produced highly active catalysts.
The productivities for complexes 2-8 were all reasonably
high, with 3 giving the highest productivity of >90 000 g
product/mmol Fe. The second area of interest was the
Schulz-Flory K value and whether it could be modulated by
these subtle electronic changes. From the data for 1-8, with
the possible exception of 8,theKvalues were relatively constant,
ranging between 0.65 (entry 4) and 0.73 (entry 5). While these K
value changes would be considered significant in a commercial
setting, they do not appear to represent any trend from these
batch data. The only exception is complex 8, with a K value
of 0.78. Certainly the interaction of aluminum with the
methoxy group could be proposed as a significant difference
in this system; regardless of explanation, this high K value is
moving to the high end of the typically relevant distributions.1
Further modifications to the NNS ligands were introduced in
complexes 9 and 10. In 9, the steric bulk of the N-aryl group
was reduced, resulting in a lighter distribution, in agreement
Figure 2. Schematic diagrams of iron(II) NNP complexes
12-20.
with literature precedent.25,30,31 Due to the loss of butene
from the reactor prior to analysis, and a nonconstant K value,
the productivity of this system could only be estimated. Even
the mol C10/mol C8 ratio for this system was a remarkably
low 0.24, indicating that the actual ratio of C6/C4 produced
was much lower, essentially meaning that 9 is an ethylene
dimerization catalyst. The higher olefins are likely produced
by reincorporation, i.e., co-dimerization of higher olefins
with ethylene. Thus, the broadening of the K value is con-
version dependent, as was discussed for another system in
our prior publication.25 In complex 10, the steric bulk was
added to the S-aryl ring by placing methyl groups at the ortho
positions. The K value did in fact increase, but with the effect
of dramatically reducing catalyst activity. It is an interesting
observation that ortho substituents on the pendant donor
aryl rings tend to suppress catalyst activity much more than
ortho groups on the N-aryl rings. This observation is further
supported by the results for the previously reported complex
11, with bulky 2,6-isopropyl substituents on the N-aryl ring.
Despite this steric bulk, 11 is an order of magnitude more
active than 10. This trend holds true for the NNP catalysts as
well (see following discussion).
Oligomerization Using NNP-Ligated Iron Complexes. Seven
new NNP Fe complexes (Figure 2) were prepared using new
2-phosphinoethylamines. The complexes were made according
to our previously reported method24 by reaction of the phos-
phinoamine with the appropriate acenaphthene-based mono-
imine in n-butanol in the presence of FeCl2. NNP-ligated
iron(II) complexes 12 and 13 were disclosed earlier24 and are
included here for comparison purposes.
Oligomerization experiments for catalysts 12-20 are re-
ported in Table 2. Similar to the NNS systems and for many
other ethylene oligomerization systems, the product distributions
(30) Small, B. L.; Brookhart, M. J. Am. Chem. Soc. 1998, 120, 7143.
(31) Britovsek, G. J. P.; Mastroianni, S.; Solan, G. A.; Baugh,
S. P. D.; Redshaw, C.; Gibson, V. C.; White, A. J. P.; Williams, D. J.;
Elsegood, M. R. J. Chem.;Eur. J. 2000, 6 (12), 2221.
(29) Zhang, T.; Sun, W.-H.; Li, T.; Yang, X. J. Mol. Catal. A: Chem.
2004, 218, 119.

6726 Organometallics, Vol. 29, No. 24, 2010
Table 2. Ethylene Oligomerization Data for NNP-Ligated Fe Catalystsa
Small et al.
amt MMAO
entry cat. (mg) Al:Fe ratio
Pethylene
(psig)
length
(min)
T
(°C)
Tmax
(°C)
yield
(g)
prod (g prod/
mmol cat)
C6%
purity
C8%
purity
C10%
K (C12/C10
)
purity
99.4
12
13
14
15
16
17
18
19
20
12 3.1
13 1.8
14 3.0
15 1.9
16 3.0
17 3.0
18 2.0
19 2.0
20 2.0
500
300
250
350
300
500
500
500
500
1000
1000
1000
1000
1000
1000
1000
1000
1000
60
90
60
60
30
30
30
30
30
50
50
50
50
42
34
45
50
50
63
52
54
53
42
34
45
55
65
108
124
48.7
149
35 200
70 600
11 900
55 600
1970
0.49-0.61
0.60
0.72
0.60
0.82
mostly C4
0.88
0.86
99.4
99.4
99.1
99.3
99.6
99.8
99.5
99.3
8.9
∼10, n.d.
4.4
1520
7300
15 900
22.5
∼50
mostly C4
98.9
a All reactions were run in cyclohexane solvent.
are clearly tied to the ligand steric environment. Complexes
12 and 13 illustrate this trend, as moving from a CH3 group to
an i-Pr group at the 6-position of the N-aryl ring causes a
significant increase in the K value (entries 12 and 13). Com-
plex 14 introduces an additional steric consideration, with
methyl groups at meta positions on the P-aryl rings. This
change led to a significant increase in the K value from about
0.60 to 0.72 (entries 13 and 14), indicative of a meta steric
influence. This 3,5-dimethyl effect has been cited in the
literature for other phosphine systems32,33 and is likely due
to a more rigidly enforced ring conformation induced by the
meta methyl groups. The ligand bulkiness was decreased in
complex 15 (entry 15) by changing one of the i-Pr groups on
the imine aryl ring to a CH3 group, and a corresponding
decrease in K value to 0.60 was observed (entry 15). A
similar steric trend is observed for 12 and 13. It is also
interesting to note that catalysts 13 and 15 behave similarly,
both with respect to catalyst activity and product distribu-
tion, indicating that the 3,5-dimethyl effect can be almost
directly offset by steric tuning on the imine aryl ring.
Thus, steric tuning of the P-aryl meta positions provided a
means for modulating the product distribution without
significantly affecting the catalyst activity. However, addi-
tion of an ortho-methyl group on the P-aryl ring caused a
dramatic reduction in activity. For example, the o-tolyl
phosphines of complexes 16 and 17 (entries 16 and 17)
produced only modestly active catalysts, similar to NNS
system 10. Similarly, complexes containing bulky cyclohexyl
phosphine substituents (complexes 18 and 19) displayed low
catalyst productivity as well as the expected shift of product
distribution toward higher K values (K = 0.86-0.88).
Furthermore, complexes 17 and 20 demonstrate that while
removal of steric bulk at the imine nitrogen can improve
catalyst productivity, it also causes a dramatic shift in catalyst
performance from oligomerization to ethylene dimerization.
Product distribution data for catalysts 12-20 demonstrates
the ability to adjust the K value by changing the steric environ-
ment surrounding either the phosphine or the imine nitrogen.
Catalyst activity data for these same complexes suggests
that activity is more severely impacted by modifications
made to the phosphine substituents. Crystallographic studies
on selected iron(II) complexes supported by NNS and
NNP ligands were carried out to better understand the
details of metal-ligand binding and to examine possible
connections between solid-state structure and catalyst
performance.
Crystallographic Studies. Iron(II) Complexes Supported by
Tridentate NNS Ligands. Crystals of NNS-ligated complexes 2
and 4 were grown by pentane diffusion into a concentrated
dichloromethane solution of each complex, which resulted in
dichloromethane incorporation into each unit cell. Noncoor-
dinating dichloromethane was chosen as the crystallization
solvent to avoid solvent coordination to the iron center and,
instead, to promote ligation of the thioether sulfur atom. X-ray
data collection parameters for 2 and 4 are contained in Table 3,
while the molecular structures of 2and 4are shown in Figures 3
and 4, respectively. Selected distances and angles are provided
in Table 4. The crystal structure of a thioether ligated complex
11 was reported by us previously;24 distance and angle data for
11 are listed in Table 4 for comparison purposes. In our
previous study, we found that sulfur ligation to Fe was
dependent on the thioether aryl substituents. For example,
the thioether sulfur atom in para-Cl complex 1 did not
coordinate to the iron center (a chloride-bridged dimer was
formed instead),24 whereas the sulfur did bind in 3,5-dimethyl
derivative 11, albeit with a relatively long Fe-S distance
24
˚
(2.7126 A). In the present study, the structures of 2 and 4
clearly show sulfur ligation to form monomeric, five-coordi-
nate complexes. Similar to 11, the Fe-S bond distances in 2
˚
and 4are long, with the Fe-Sdistancein4(2.8170 A) beingthe
longest distance among our family of iron(II) complexes and
one of the longest Fe-S distances yet observed.24 Further
inspection of Table 4 shows that, in contrast to 11, complexes 2
(both independent molecules) and 4 display relatively dissim-
ilar Fe-N(1) and Fe-N(2) distances, with the Fe-N(1)
(imine) bond being significantly shorter than the Fe-N(2)
(imine) bond. These dissimilar Fe-N bond lengths are observed
for both independent molecules of complex 2 (Fe-N(3) <
Fe-N(4) for molecule 2 of 2). These Fe-N distances are much
more similar in 11. Furthermore, complexes 2 and 4 exhibit
larger (more linear) N(2)-Fe-S angles (ranging from 152.70°
to 156.24°) and larger Cl(1)-Fe-Cl(2) angles than 11. Due to
these large angles, 2 and 4 are perhaps best characterized as
distorted trigonal-bipyramidal structures, with the sulfur and
imino-aryl nitrogen atoms occupying apical positions.
It is also notable that for 2 the Fe-S bond lengths and the
N-Fe-S angles are slightly different in the two independent
molecules. Close inspection of the packing diagram for 2
indicates that the differences are not due to obvious inter-
molecular interactions. However, we note that the Fe-S
bonding is quite long (weak), and weak solid-state effects
˚
could alter the Fe-S bond length by (0.05 A, with a
corresponding small impact on the N-Fe-S angles.
Unfortunately, catalyst activity (Table 1) does not clearly
correlate with the Fe-S bond length or with other structural
parameters in Table 4. Complex 4 displays relatively low
(32) Trabesinger, G.; Albinati, A.; Feiken, N.; Kunz, R.; Pregosin,
P. S.; Tschoerner, M. J. Am. Chem. Soc. 1997, 119, 6315.
(33) Dotta, P.; Kumar, P. G. A.; Pregosin, P. S. Organometallics
2004, 23, 2295.

Article
Organometallics, Vol. 29, No. 24, 2010 6727
Table 3. Summary of X-ray Crystallographic Data for Iron(II) Complexes 2, 4, 14, and 18a
2 1.25CH2Cl2
3
4 CH2Cl2
3
14 C2H3N
3
2 18 C2H3N
3
empirical formula
fw
C33.25H34.50Cl4.50FeN2S
709.56
173(2)
triclinic
P1
14.780(3)
14.781(3)
16.780(4)
87.90(2)
66.23(2)
85.14(1)
3342.8(12)
4
C37H42Cl4FeN2S
744.44
173(2)
monoclinic
C2/c
30.520(6)
14.238(2)
18.924(4)
90
116.20(3)
90
C44H48Cl2FeN3P
776.57
173(2)
monoclinic
I2/a
22.288(2)
12.3291(13)
29.903(3)
90
93.632(1)
90
C78H101Cl4Fe2 N5P2
1424.08
173(2)
triclinic
P21/n
15.583(2)
14.318(2)
33.016(5)
90
91.984(2)
90
temperature (K)
cryst syst
space group
˚
a (A)
˚
b (A)
˚
c (A)
R (deg)
β (deg)
γ (deg)
3
˚
V (A )
Z
7378(2)
8
1.340
8200.5(15)
8
1.258
7361.9(19)
4
1.285
dcalcd (Mg m-3
cryst size (mm)
)
1.410
0.44 ꢀ 0.20 ꢀ 0.12
3
0.45 ꢀ 0.32 ꢀ 0.06
0.35 ꢀ 0.25 ꢀ 0.15
0.40 ꢀ 0.40 ꢀ 0.30
abs coeff (mm-1
2θmax (deg)
transmn range
)
0.90
50.02
0.78
52.06
0.571
54.98
0.629
50.06
0.6930-0.8997
10 205
9704
6557
757
0.0681 (0.1642)
1.021
1.07, -1.05
0.8258-1.0
7388
7249
4406
420
0.0718 (0.1693)
1.011
1.06, -0.71
0.8252-0.9193
39 853
9318
7255
497
0.0380 (0.0914)
1.054
0.746, -0.306
0.7871-0.8338
79 366
12 995
9990
829
no. of reflns collected
no. of indep reflns
no. of obsd reflns
no. of variables
R1 (wR2)b [I > 2σ(I)]
goodness-of-fit (F2)
0.0554 (0.1308)
1.107
-3
˚
A
diff peaks (e-
)
0.979, -0.549
P
3
P
a See Experimental Section for additional data collection, reduction, and structure solution and refinement details. b R1 =
Fo| - |Fc
/
|Fo|; wR2
P
= [ [w(Fo2 - Fc2)2]]1/2 where w = 1/σ2(Fo2) þ (aP)2 þ bP.
Figure 4. Thermal ellipsoid representation (35% probability
boundaries) of the X-ray crystal structure of 4 with hydrogen
atoms omitted for clarity.
Figure 3. Thermal ellipsoid representation (35% probability
boundaries) of the X-ray crystal structure of 2 (molecule 2) with
hydrogen atoms omitted for clarity.
acetonitrile for coordination to the iron center. The struc-
tures of 14 and 18 are shown in Figures 5 and 6, respectively;
selected distances and angles can be found in Table 5. The
crystal structure for 13 was reported previously;24 distance
and angle data for 13 are included in Table 3 for comparison.
As with 13, and in contrast to the NNS-ligated complexes 2
and 4, the five-coordinate geometries of 14 and 18 are best
described as distorted square pyramidal; the tridentate
ligand and one chloride ligand form the pyramidal base
and the remaining chloride resides in the apical position.
As shown in Table 5, the Fe-N and Fe-Cl distances, as well
as N-Fe-N, N-Fe-P, and Cl-Fe-Cl angles, are similar
among the three NNP complexes. The Fe-P distances
productivity and possesses a long Fe-S bond. Furthermore,
10 has low productivity and, although not structurally
characterized, should display (at best) weak Fe-S binding
due to the 2,6-dimethyl substituents on the S-aryl ring.
However, complex 1, in which the sulfur is not coordinated
to iron (at least not in the solid state), displays higher activity
than complex 4. Thus clear and convincing correlations
between the structure and catalyst performance are not
readily apparent.
Iron(II) Complexes Supported by Tridentate NNP Ligands.
Crystals of NNP-ligated complexes 14 and 18 were grown by
slow cooling of saturated acetonitrile solutions of each
compound, which resulted in acetonitrile incorporation into
each unit cell. In contrast to sulfur-containing complexes,
phosphorus effectively competes with donor solvents such as
˚
˚
(2.5455 A for 14 and 2.5377 and 2.5414 A for 18) are 0.041
˚
to 0.048 A longer than that previously found for 13, but
remain in the range of Fe-P bond lengths typical of five-
coordinate, high-spin Fe(II) centers.24 The longer Fe-P

6728 Organometallics, Vol. 29, No. 24, 2010
Small et al.
˚
Table 4. Selected Distances (A) and Angles (deg) for NNS-Ligated Metal Complexes
2
molecule 1
molecule 2
4
11
Fe(1)-N(1)
Fe(1)-N(2)
Fe(1)-S(1)
2.102(5)
2.245(5)
2.6980(19)
2.241(2)
2.2822(18)
77.2(2)
75.88(17)
152.70(13)
129.26(8)
Fe(2)-N(3)
Fe(2)-N(4)
Fe(2)-S(2)
2.094(5)
2.244(4)
2.7483(18)
2.252(2)
2.277(2)
77.79(18)
78.78(13)
156.24(13)
131.32(8)
Fe(1)-N(1)
Fe(1)-N(2)
Fe(1)-S(1)
Fe(1)-Cl(1)
Fe(1)-Cl(2)
N(1)-Fe(1)-N(2)
N(1)-Fe(1)-S(1)
N(2)-Fe(1)-S(1)
Cl(1)-Fe(1)-Cl(2)
2.112(4)
2.227(4)
Fe(1)-N(1)
Fe(1)-N(2)
Fe(1)-S(1)
Fe(1)-Cl(1)
Fe(1)-Cl(2)
N(1)-Fe(1)-N(2)
N(1)-Fe(1)-S(1)
N(2)-Fe(1)-S(1)
Cl(1)-Fe(1)-Cl(2)
2.136(2)
2.165(3)
2.7126(10)
2.2665(10)
2.3089(10)
77.81(9)
75.24(7)
144.24(7)
116.96(4)
2.8170(17)
2.2560(16)
2.2676(16)
78.03(14)
76.65(11)
154.66(11)
126.45(6)
Fe(1)-Cl(1)
Fe(2)-Cl(3)
Fe(1)-Cl(2)
Fe(2)-Cl(4)
N(1)-Fe(1)-N(2)
N(1)-Fe(1)-S(1)
N(2)-Fe(1)-S(1)
Cl(1)-Fe(1)-Cl(2)
N(3)-Fe(2)-N(4)
N(3)-Fe(2)-S(2)
N(4)-Fe(2)-S(2)
Cl(3)-Fe(2)-Cl(4)
Figure 5. Thermal ellipsoid representation (35% probability
boundaries) of the X-ray crystal structure of 14 with hydrogen
atoms omitted for clarity.
Figure 6. Thermal ellipsoid representation (35% probability
boundaries) of the X-ray crystal structure of 18 with hydrogen
atoms omitted for clarity.
length in 18 (relative to 13) may be ascribed to the greater
steric bulk of dicyclohexylphosphine relative to diphenyl-
phosphine. The longer Fe-P bond in 14 (relative to 13) is
perhaps a manifestation of the steric influence of the meta
methyl groups on P-aryl conformations, as mentioned pre-
viously. In both cases, the slight elongation of the Fe-P
distance is consistent with a modest increase in steric bulk at
phosphorus, and, as noted previously, increased steric bulk
at phosphorus correlates with the higher K values found for
14 (K = 0.72) and 18 (K = 0.88) relative to the less sterically
congested 13 (K = 0.60).
Product Analysis. A Hewlett-Packard 6890 Series GC system
with an HP-5 50 m column with a 0.2 mm inner diameter was
used for R-olefin characterization. An initial temperature of 35 °C
and a rate of 2.4 °C/min were used to raise the temperature to 52 °C,
followed by a rate of 15.0 °C/min to raise the temperature to 157 °C.
A final ramp rate of 22.5 °C/min was used to reach the final
temperature of 250 °C. ChemStation from Hewlett-Packard was
used to analyze the collected data. Odd-carbon-numbered,
nonvolatile internal standards were used to estimate catalyst
productivity. Volatile R-olefin (i.e., 1-hexene and 1-butene) amounts
were estimated by extrapolation using the Schulz-Flory K values.
Ethylene Oligomerization/Polymerization. A 500 mL Zipperclave
reactor from Autoclave Engineers was used for the oligomerization
and polymerization reactions. The catalyst was dissolved in a small
amount of dichloromethane in an NMR tube, which was then sealed
and bound to the stirrer shaft of the clean, dry reactor. The reactor
was evacuated, then charged with cyclohexane (typically 200 mL)
and the aluminum cocatalyst/scavenger. The desired pressure
of ethylene was introduced, and the reactor stirrer was started,
resulting in breakage of the NMR tube and catalyst activation.
Ethylene was fed “on demand” using a TESCOM regulator, and the
reactor temperature was maintained by internal cooling. Reactions
were terminated by slowly venting the reactor over a few minutes.
Preparation of Thioetheramines A -D. 2-(4-tert-Butylphe-
nylthio)ethylamine (A). To a stirring mixture of 4.36 g (38.0 mmol)
of 2-chloroethylamine hydrochloride and 12.00 g (87.0 mmol) of
K2CO3 in 30 mL of CHCl3 was added 4.82 g (29.0 mmol) of 4-tert-
butylbenzenethiol. The mixture was stirred at 50 °C in a sealed vial
overnight. The mixture was washed three times with distilled water,
dried with MgSO4, and filtered. Volatiles were removed in vacuo,
Conclusion
A variety of phosphinoamines, thioetheramines, and ani-
lines have been used to illustrate the structural diversity
available in pendant donor modified R-diimine complexes.
Steric and electronic modifications have been used to show
how this diversity can affect catalyst activity and ethylene
oligomer distributions. It is likely that continued study of
this new family of ligands will open the door to other
catalytic transformations as the coordination and synthetic
chemistries are better understood and applied.
Experimental Section
Materials and Methods. Heptane and cyclohexane were pur-
chased from Aldrich or acquired from internal company re-
sources, degassed, and pumped repeatedly in a circular loop
over a molecular sieve bed. Monoimines I and J were reported in
our prior publication.24 MMAO-3A (Al 7% by wt) was pur-
chased from Akzo Nobel. All of the 2-phosphinoethylamines
were purchased from Digital Specialty Chemicals. All other
starting materials were purchased from Aldrich and used as received.
1
leaving 4.50 g (74%) of clear oil. H NMR (300 MHz, CDCl3):
δ 7.32, m, 4H; 2.93, m, 4H; 1.42, br s, 2H; 1.30, s, 9H.
2-(3,5-Dimethylphenylthio)ethylamine (B). To a stirring mix-
ture of 1.93 g (9.4 mmol) of 2-bromoethylamine hydrobromide
and 3.00 g (21.7 mmol) of K2CO3 in 30 mL of CH2Cl2 was added

Article
Organometallics, Vol. 29, No. 24, 2010 6729
˚
Table 5. Selected Distances (A) and Angles (deg) for NNP-Ligated Metal Complexes
18
13
14
molecule 1
2.1834(16) Fe(1a)-N(1a)
molecule 2
Fe(1)-N(1)
Fe(1)-N(2)
Fe(1)-P(1)
Fe(1)-Cl(1)
Fe(1)-Cl(2)
2.181(6)
2.166(6)
2.497(2)
2.287(2)
2.3131(18) Fe(1)-Cl(2)
75.9(2)
74.01(16)
Fe(1)-N(1)
Fe(1)-N(2)
Fe(1)-P(1)
Fe(1)-Cl(1)
2.196(3)
2.168(3)
Fe(1b)-N(1b)
Fe(1b)-N(2b)
2.162(3)
2.190(3)
2.1750(16) Fe(1a)-N(2a)
2.5455(6)
2.2958(6)
2.2846(6)
74.98(6)
73.09(4)
132.67(4)
Fe(1a)-P(1a)
2.5377(13) Fe(1b)-P(1b)
2.3192(12) Fe(1b)-Cl(1b)
2.2799(12) Fe(1b)-Cl(2b)
2.5414(11)
2.3112(12)
2.2847(11)
75.20(11)
76.67(8)
Fe(1a)-Cl(1a)
Fe(1a)-Cl(2a)
N(1)-Fe(1)-N(2)
N(1)-Fe(1)-N(2)
N(1)-Fe(1)-P(1)
135.20(16) N(2)-Fe(1)-P(1)
N(1a)-Fe(1a)-N(2a)
N(1a)-Fe(1a)-P(1a)
N(2a)-Fe(1a)-P(1a)
75.39(11)
75.46(9)
138.57(9)
N(1b)-Fe(1b)-N(2b)
N(1)-Fe(1)-P(1)
N(1b)-Fe(1b)-P(1b)
N(2b)-Fe(1b)-P(1b)
N(2)-Fe(1)-P(1)
138.23(8)
Cl(1)-Fe(1)-Cl(2) 111.98(8)
Cl(1)-Fe(1)-Cl(2) 106.28(2)
Cl(1a)-Fe(1a)-Cl(2a) 112.15(5)
Cl(1b)-Fe(1b)-Cl(2b) 112.30(5)
1.00 g (7.2 mmol) of 3,5-dimethylbenzenethiol. The mixture was
stirred at room temperature under argon for two days. The
mixture was washed twice with distilled water, dried with
MgSO4, and filtered. Volatiles were removed in vacuo, leaving
a slightly cloudy yellow oil. Distillation of the oil under reduced
pressure (0.10 Torr) at 80-95 °C produced 0.547 g (41.7%) of a
clear liquid, which was identified as the desired product by its 1H
and 13C NMR spectra. 1H NMR (400 MHz, CDCl3): δ 6.98, s,
2H; 6.82, s, 1H; 2.98, t, 2H; 2.89, t, 2H; 2.27, s, 6H; 1.55, br s, 2H.
13C{1H} NMR (100 MHz, CDCl3): δ 138.58, 135.10, 128.21,
127.50, 41.00, 38.07, 21.29. EI mass spectrum: m/z 181 [Mþ].
2-(4-Methoxyphenylthio)ethylamine (C). To a stirring mixture
of 4.36 g (38.0 mmol) of 2-chloroethylamine hydrochloride and
12.00 g (87.0 mmol) of K2CO3 in 30 mL of CHCl3 was added
4.07 g (29.0 mmol) of 4-methoxythiophenol. The mixture was
stirred at 50 °C in a sealed vial overnight. The mixture was
washed three times with distilled water, dried with MgSO4, and
filtered. Volatiles were removed in vacuo, leaving 4.97 g (89%)
of yellow oil. 1H NMR (300 MHz, CDCl3): δ 7.36, d, 2H; 6.82, d,
2H; 3.80, s, OMe; 2.93, m, 4H; 1.42, br s, 2H.
Monoimine G. An ethanol (150 mL) suspension of acenaphthe-
nequinone (3.82 g, 21.0 mmol) was treated with 0.6 mL of formic
acid and heated to 68 °C, followed by slow, dropwise addition
(over approximately 24 h) of a solution of 2,6-dimethyl-4-tert-
butylaniline (3.54 g, 20.0 mmol) in 160 mL of ethanol. The
resulting mixture was stirred at 68 °C overnight, cooled, and
filtered. Orange crystals were collected from the filtrate, upon
cooling to 0 °C, for a yield of 1.64 g (24%). 1H NMR (300 MHz,
CDCl3): δ 8.18, d, 2H (chemical shift equivalence); 7.99, d, 1H;
7.81, t, 1H; 7.43, t, 1H; 7.14, s, 2H; 6.70, d, 1H, 2.03, s, 6H; 1.38, s, 9H.
Monoimine H. An ethanol (200 mL) suspension of acenaphthe-
nequinone (10.0 g, 54.9 mmol) was treated with 1 mL of formic
acid and heated to 60 °C, followed by slow, dropwise addition
(over approximately 12 h) of a solution of 2,4-dimethylaniline
(5.40 mL, 44.0 mmol) in 100 mL of ethanol. The resulting mixture
was stirred at 60 °C overnight, cooled, and filtered. Two crops of
orange crystals were collected from the filtrate, upon cooling to 0 °C,
for a total yield of 7.83 g (62%). 1H NMR (300 MHz, CDCl3): δ
8.18, m, 2H; 7.99, d, 1H; 7.80, t, 1H; 7.43, t, 1H; 7.13, s, 1H; 7.06, d,
1H, 6.92, d, 1H; 6.78, d, 1H; 2.39, d, 3H; 2.12, d, 3H.
2-(2,6-Dimethylphenylthio)ethylamine (D). To a stirring mix-
ture of 2.73 g (23.6 mmol) of 2-chloroethylamine hydrochloride
and 7.50 g (54.0 mmol) of K2CO3 in 20 mL of CHCl3 was added
2.50 g (18.0 mmol) of 2,6-dimethylthiophenol. The mixture was
stirred at 50 °C in a sealed vial overnight. The mixture was
washed three times with distilled water, dried with Na2SO4, and
filtered. Volatiles were removed in vacuo, leaving 2.83 g (86%)
of a brown, oily solid. 1H NMR (300 MHz, CDCl3): δ 7.10, m,
3H; 2.80, d, 2H; 2.55, s, 6H; 1.42, br s, NH2. Residual thiophenol
appeared to also be present in about 10% by mass.
Preparation of Acenaphthene-monoimines E-H. Monoimine E.
An ethanol (200 mL) suspension of acenaphthenequinone (10.0 g,
54.9 mmol) was treated with 1 mL of formic acid and heated to 70 °C,
followed by slow, dropwise addition (over approximately 12 h) of a
solution of 2,4,6-trimethylaniline (6.68 g, 49.5 mmol) in 100 mL of
ethanol. The resulting mixture was stirred at 70 °C overnight,
cooled, and filtered. Two crops of orange crystals were collected
from the filtrate, upon cooling to 0 °C, for a total yield of 9.64 g
(65%). 1H NMR (300 MHz, CDCl3): δ 8.18, d, 2H (chemical shift
equivalence); 7.99, d, 1H; 7.81, t, 1H; 7.43, t, 1H; 6.95, s, 2H; 6.78, d,
1H, 2.37, s, 3H; 2.01, s, 6H.
Monoimine F. An ethanol (200 mL) suspension of ace-
naphthenequinone (5.00 g, 27.5 mmol) was treated with 2 mL
of formic acid and heated to 75 °C, followed by slow, dropwise
addition (over approximately 16 h) of a solution of 2,6-dimeth-
yl-4-bromoaniline (5.49 g, 27.5 mmol) in 100 mL of ethanol. The
resulting mixture was stirred and cooled to 25 °C and filtered to
give about 100 mg of a brown powder. Cooling the filtrate
to -30 °C for 1 h, followed by filtration, gave 153 mg of orange
crystals, which were identified as the product with significant
acenaphthenequinone present. A second crop collected after
overnight crystallization at -30 °C gave 3.01 g (30%) of the
desired product in 92% purity by mass. The remainder was
identified as acenaphthenequinone. 1H NMR (300 MHz,
CDCl3): δ 8.20, d, 1H; 8.18, d, 1H; 8.04, d, 1H; 7.83, t, 1H;
7.48, t, 1H; 7.30, s, 2H; 6.83, d, 1H; 2.02, s, 6H.
Preparation of 2,6-Dimethyl-4-tert-butylaniline. 1-Nitro-4-tert-
butyl-2,6-dimethylbenzene. 1-tert-Butyl-3,5-dimethylbenzene (40.0 g,
250 mmol) was dissolved in 60 mL of acetic acid. To this stirring
mixture was added dropwise over 20 min 45 mL of a 50:50 v/v
mixture of concentrated nitric and sulfuric acid, resulting in a
temperature increase from 25 to 45 °C. Once the reaction had
cooled to 30 °C, it was poured into water, ether was added, and the
aqueous layer was extracted three times with ether. The ether layer
was then extracted three times with a 1.0 M KOH solution.
Removal of the ether left an oil that solidified upon standing.
Pentane was added, and multiple crops of the desired product were
collected as white needles from the resultant solution, for a total
isolated yield of 18.5 g (36%). 1H NMR (300 MHz, CDCl3): δ 7.08,
s, 2H; 2.30, s, 6H; 1.28, s, 9H.
2,6-Dimethyl-4-tert-butylaniline. 1-Nitro-4-tert-butyl-2,6-di-
methylbenzene (12.0 g, 58.0 mmol) was dissolved in 160 mL of
ethanol, followed by the addition of 20 mL of water. Then 4.8 g
(43.2 mmol) of CaCl2 dissolved in 20 mL of water was added to
the stirring solution, followed by the addition of 50.0 g (76.5 mmol)
of zinc powder.34 The reaction was stirred overnight at 65 °C,
then cooled to ambient temperature and filtered. The filtrate was
extracted three times with ether, and the organic layer was dried
over MgSO4. Removal of the solvent gave 9.58 g (93%) of a
brown oil. 1H NMR (300 MHz, CDCl3): δ 6.90, s, 2H; 3.40, br s,
2H; 2.11, s, 6H, 1.21, s, 9H.
Selected Syntheses for NNS-Ligated Iron Complexes. Complex
3. A solution of 0.250 g (1.20 mmol) of 2-(4-tert-butylphenylthio)-
ethylamine A in 10 mL of cyclohexane was added to a mixture of
0.289 g (1.00 mmol) of monoimine E and 0.190 g (0.95 mmol) of
FeCl2 4H2O in a 20 mL vial. The vial was sealed, and the contents
3
were stirred overnight under nitrogen at 55 °C. The green product was
isolated by filtration, washed with pentane, and dried to give 0.508 g
(86%) of product. The compound analyzed as the monohydrate.
(34) Kuhn, W. E. Organic Syntheses; Wiley: New York, 1943; Coll. Vol.
2, p 447.

6730 Organometallics, Vol. 29, No. 24, 2010
Small et al.
Complex 4. A solution of 0.184 g (0.88 mmol) of 2-(4-tert-
butylphenylthio)ethylamine A in 7 mL of cyclohexane was
added to a mixture of 0.273 g (0.80 mmol) of monoimine G
Table 6. Yield and Analytical Data for NNS- and NNP-Ligated
Iron Complexes
elemental analyses of complexes
and 0.151 g (0.76 mmol) of FeCl2 4H2O in a 20 mL vial. The vial
3
was sealed, and the contents were stirred overnight under
nitrogen at 55 °C. The green product was isolated by filtration,
washed with pentane, and dried to give 0.399 g (80%) of
product. The compound analyzed as the monohydrate.
Complex 5. A solution of 0.214 g (1.02 mmol) of 2-(4-tert-
butylphenylthio)ethylamine A in 3.5 mL of anhydrous n-buta-
nol was added to a mixture of 0.400 g (1.10 mmol) of monoimine
F and 0.127 g (1.00 mmol) of FeCl2 in a 10 mL vial. The vial was
sealed, and the contents were stirred overnight under nitrogen at
55 °C. The green product was isolated by filtration, washed with
ether and pentane, and dried to give 0.378 g (55%) of product.
The compound analyzed as the butanol adduct.
calculated
found
complex % yield %C %H %N %O %C %H %N %O
2 H2O
3
98
86
73
55
48
62
60
37
48
81
75
72
40
74
72
41
61.85 5.51 4.51
62.37 5.71 4.41
61.56 5.21 4.52
62.97 6.18 3.97
3 H2O
3
4 H2O
3
63.82 6.25 4.13 2.36 63.92 6.35 3.98 2.32
57.16 5.46 3.70 2.12 56.94 5.17 3.77 1.28
5 BuOH
6 H2O
3
61.30 5.31 4.61
58.50 4.74 4.71
59.13 4.96 4.60
60.43 5.37 4.65
59.12 4.63 4.86
59.64 4.86 4.75
3
7 H2O
8 H2O
3
3
9 H2O
10 H2O
61.85 5.51 4.51 2.57 62.80 5.82 4.22 2.55
3
60.72 5.10 4.72
68.58 6.17 3.81
67.91 5.84 3.96
66.79 5.30 4.21
60.53 5.00 4.31
3
14
15
16
0
0
0
67.66 6.14 3.81 0.75
67.37 5.86 4.01 0.64
66.64 5.33 4.18 0.21
Complex 10. A solution of 0.200 g (1.10 mmol) of 2-(2,6-
dimethylphenylthio)ethylamine D in 10 mL of cyclohexane was
added to a mixture of 0.285 g (1.00 mmol) of monoimine H and
17 H2O
64.59 5.27 4.18 2.39 63.71 5.05 3.93 2.39
3
0.190 g (0.95 mmol) of FeCl2 4H2O in a 20 mL vial. The vial was
3
18
19
20
66.00 7.14 4.05
64.73 6.67 4.31
64.27 6.50 4.41
0
0
0
65.04 7.34 3.97 1.04
64.53 6.76 4.20 0.54
63.83 6.50 4.31 0.72
sealed, and the contents were stirred overnight under nitrogen at
55 °C. The green product was isolated by filtration, and the
green solid was redissolved in 5 mL of methylene chloride and
refiltered to remove unreacted iron species. This redissolution
was typically performed for complexes having lower yields, so as
to remove insoluble materials. Removal of the CH2Cl2 from the
filtrate gave 0.261 g (48%) of product. The compound analyzed
as the monohydrate.
2θ value of 50.02° (2) or 52.06° (4). Absorption corrections
based on azimuthal scans were applied to the data, resulting in
transmission factors ranging from 0.8997 to 0.6930 (2) or from
1.0 to 0.8258 (4). Corrections for crystal decay were not
required. The intensity data were corrected for Lorentz and
polarization effects and converted to structure factors using the
CrystalStructure program.35
The other NNS precatalyst complexes were prepared simi-
larly. Yields and additional characterization data are provided
in Table 6.
Space groups were determined on the basis of systematic
absences and intensity statistics. Successful direct-methods so-
lutions were calculated, which provided the positions of most of
the non-hydrogen atoms directly from the E-map. The remain-
ing non-hydrogen atoms were located after several cycles of
structure expansion and full matrix least-squares refinement.
Hydrogen atoms were added geometrically. All non-hydrogen
atoms were refined with anisotropic displacement parameters
except as noted below. Carbon-bound hydrogen atoms were
refined as riding atoms with group isotropic displacement
parameters fixed at 1.2U(eq) of the host carbon atom (for
methylene and methine hydrogens) or 1.5U(eq) of the host
carbon atom (for methyl hydrogens). The final difference maps
Selected Syntheses for NNP-Ligated Iron Complexes. Com-
plex 14. (2E)-2-[(2,6-Diisopropylphenyl)imino]acenaphthylen-
1(2H)-one (1.24 g, 3.64 mmol), 1.00 g (3.50 mmol) of 2-(bis-(3,5-
dimethyldiphenylphosphino))ethylamine, and 443 mg (3.49
mmol) of FeCl2 powder were added to a scintillation vial with
a stirbar. Then 17 mL of anhydrous n-butanol was added, the
vial was sealed, and the reaction was stirred at 60 °C for 16 h.
After cooling to ambient temperature, a green solid (2.07 g,
81%) was isolated by filtration and washed thoroughly with
ether and pentane.
Complex 16. Monoimine E (299 mg, 1.00 mmol), 257 mg (1.00
mmol) of 2-(bis(2-methyldiphenylphosphino))ethylamine, and
121 mg (0.95 mmol) of FeCl2 powder were added to a scintilla-
tion vial with a stirbar. Then 9 mL of anhydrous n-butanol was
added, the vial was sealed, and the reaction was stirred at 55 °C
for 6 h. After cooling to ambient temperature, a green solid (453
mg, 72%) was isolated by filtration and washed thoroughly with
ether and pentane.
Complex 19. Monoimine E (598 mg, 2.00 mmol) and 242 mg
(1.90 mmol) of FeCl2 powder were added to a scintillation vial
with a stirbar. In a separate vial, 482 mg (2.00 mmol) of
2-(dicyclohexylphosphino)ethylamine was dissolved in 13 mL
of anhydrous n-butanol. The solution of the phosphinoamine
was added to the first vial, the vial was sealed, and the reaction
was stirred at 55 °C for 6 h. After cooling to ambient tempera-
ture, a green solid (887 mg, 72%) was isolated by filtration and
washed thoroughly with ether and pentane.
were featureless, with the largest residual peak for 2 (1.065 e-
-3
˚
˚
A
) located 1.11 A from Cl92, while the largest residual peak
˚
for 4 (1.055 e-
A
-3
˚
) was located 0.99 A from Fe1. Structure
solution and refinement calculations were performed using the
SHELXTL suite of programs36 running on a Pentium PC.
The asymmetric unit of 2 contains two crystallographically
independent complexes, two fully occupied molecules of
CH2Cl2, and one-half-occupied molecule of CH2Cl2, which
straddles an inversion center. The asymmetric unit of 4 contains
a single molecule of CH2Cl2. One of the two tert-butyl groups of
the ligand is disordered over two positions with refined occu-
pancies of 0.703(11) and 0.297(11); a split atom model was
applied to account for the rotational disorder. The low occu-
pancy carbon atoms of this disordered tert-butyl group were
modeled with isotropic displacement parameters.
Complex 14. A crystal (approximate dimensions 0.35 ꢀ 0.25 ꢀ
0.15 mm3) of 14 was placed onto the tip of a 0.1 mm diameter
glass capillary and mounted on a CCD area detector diffract-
ometer for data collection at 173(2) K.37 A preliminary set of cell
constants was calculated from reflections harvested from four
sets of 30 frames. These initial sets of frames were oriented such
The other NNP precatalyst complexes were prepared simi-
larly. Yields and additional characterization data are provided
in Table 6.
X-ray Crystallography. Complexes 2 and 4. Single crystals of
2 and 4 were mounted in thin-walled glass capillaries and
transferred to a Bruker/Nonius MACH3S diffractometer
equipped with graphite-monochromated Mo KR radiation (λ =
˚
0.71073 A) for data collection at -100 °C. Relevant crystal-
(35) CrystalStructure V. 3.60; Rigaku Corporation and Rigaku/MSC,
2004.
(36) SHELXTL V. 6.10; Bruker AXS: Madison, WI, 2000.
(37) SMART V5.054; Bruker Analytical X-ray Systems: Madison, WI,
2001.
lographic information is given in Table 3. Unit cell constants
were determined from a least-squares refinement of the setting
angles of 25 intense, machine-centered reflections. Intensity
data were collected using the ω/2θ scan technique to a maximum

Article
Organometallics, Vol. 29, No. 24, 2010 6731
that orthogonal wedges of reciprocal space were surveyed. This
produced initial orientation matrices determined from 165
reflections. The data collection was carried out using Mo KR
radiation (graphite monochromator) with a frame time of 30 s
and a detector distance of 4.8 cm. A randomly oriented region of
reciprocal space was surveyed to the extent of one sphere and to
constants was calculated from reflections harvested from three
sets of 20 frames. These initial sets of frames were oriented such
that orthogonal wedges of reciprocal space were surveyed. This
produced initial orientation matrices determined from 151
reflections. The data collection was carried out using Mo KR
radiation (graphite monochromator) with a frame time of 40 s
and a detector distance of 4.9 cm. A randomly oriented region of
reciprocal space was surveyed to the extent of one sphere and to
˚
a resolution of 0.77 A. Four major sections of frames were
collected with 0.30° steps in ω at four different φ settings and a
detector position of -28° in 2θ. The intensity data were cor-
rected for absorption and decay (SADABS).38 Final cell con-
stants were calculated from 2912 strong reflections from the
actual data collection after integration (SAINT).39 Please refer
to Table 3 for additional crystal and refinement information.
The structure was solved and refined using Bruker SHELXTL.40
The space group I2/a was determined on the basis of systematic
absences and intensity statistics. A direct-methods solution was
calculated that provided most non-hydrogen atoms from the
E-map. Full-matrix least-squares/difference Fourier cycles were
performed, which located the remaining non-hydrogen atoms.
All non-hydrogen atoms were refined with anisotropic displace-
ment parameters. All hydrogen atoms were placed in ideal
positions and refined as riding atoms with relative isotropic
displacement parameters. The final full matrix least-squares
refinement converged to R1 = 0.0380 and wR2 = 0.1037 (F2,
obsd data). The structure is the one suggested. One acetonitrile
solvent molecule is found disordered in nearly 50:50 ratio,
swinging between two positions roughly with the methyl carbon
as fulcrum, where the angle between the two disordered positions
is ∼58°. The occupancies of these were fixed at 50% once it was
noticed that two of the disordered positions had a close nonbonded
contact of the nitrile nitrogen atoms, respectively. The bond
distances and ADPs for this pair were restrained for reasonable
values. The I2/a setting was chosen over the equivalent C2/c setting
since the β angle was nearer to normal for the I-centered setting.
Complex 18. A crystal (approximate dimensions 0.40 ꢀ 0.40 ꢀ
0.30 mm3) of 18 was placed onto the tip of a 0.1 mm diameter
glass capillary and mounted on a CCD area detector diffract-
ometer for data collection at 173(2) K.37 A preliminary set of cell
˚
a resolution of 0.84 A. Four major sections of frames were
collected with 0.30° steps in ω at four different φ settings and a
detector position of -28° in 2θ. The intensity data were cor-
rected for absorption and decay (SADABS).38 Final cell con-
stants were calculated from 2843 strong reflections from the
actual data collection after integration (SAINT).39 Please refer
to Table 3 for additional crystal and refinement information.
The structure was solved and refined using Bruker
SHELXTL.40 The space group P21/n was determined on the
basis of systematic absences and intensity statistics. A direct-
methods solution was calculated that provided most non-hydro-
gen atoms from the E-map. Full-matrix least-squares/difference
Fourier cycles were performed, which located the remaining
non-hydrogen atoms. All non-hydrogen atoms were refined
with anisotropic displacement parameters. All hydrogen atoms
were placed in ideal positions and refined as riding atoms with
relative isotropic displacement parameters. The final full-matrix
least-squares refinement converged to R1 = 0.0554 and wR2 =
0.1422 (F2, all data). The structure is the one suggested. There
are two molecules of interest in the asymmetric unit along with
one acetonitrile solvent molecule of crystallization. It appears
there is some minor disorder of the cyclohexyl group C7A-
C12A that cannot be modeled. Most warnings of merit in the
CHECKCIF output are related to the minor disorder of this group.
Acknowledgment. The authors thank Chevron Phillips
Chemical Company for permission to publish these re-
sults and for their generous support of this work at the
University of Wisconsin-Eau Claire. M.J.C. also ac-
knowledges the University of Wisconsin-Eau Claire
Office of Research and Sponsored Programs for financial
support. In addition, we thank Dr. Victor G. Young, Jr.
and the X-ray Crystallographic Laboratory at the Uni-
versity of Minnesota for determining the X-ray crystal
structures of 14 and 18.
(38) An empirical correction for absorption anisotropy: Blessing, R.
Acta Crystallogr. 1995, A51, 33–38.
(39) SAINTþ V6.45; Bruker Analytical X-Ray Systems: Madison, WI,
2003.
(40) SHELXTL V6.14; Bruker Analytical X-Ray Systems: Madison,
WI, 2000.