Synthesis and single-crystal X-ray structure of [(DMPE)2Ru(C2H4)CH3] +[(3,5-(CF3)2C6H3) 4B]-

Article abstract of DOI:10.1016/S0022-328X(98)01212-1

The reaction of cis-(DMPE)₂Ru(CH₃)₂ with [(3,5-(CF₃)₂C₆H₃)₄B] ^-[H(OEt₂)₂]⁺ afforded the ruthenium cation [(DMPE)₂

Full text of DOI:10.1016/S0022-328X(98)01212-1

Journal of Organometallic Chemistry 579 (1999) 122–125
Synthesis and single-crystal X-ray structure of
[(DMPE)2Ru(C2H4)CH3]+[(3,5-(CF3)2C6H3)4B]−
Kayo Umezawa-Vizzini, T. Randall Lee *
Department of Chemistry, Uni6ersity of Houston, Houston, TX 77204-5641, USA
Received 8 October 1998; received in revised form 8 October 1998
Abstract
The reaction of cis-(DMPE)2Ru(CH3)2 with [(3,5-(CF3)2C6H3)4B]−[H(OEt2)2]+ afforded the ruthenium cation
[(DMPE)2RuCH3]+[(3,5-(CF3)2C6H3)4B]−. This cation underwent reaction with ethylene at room temperature to give the stable
adduct trans-[(DMPE)2Ru(C2H4)CH3]+[(3,5-(CF3)2C6H3)4B]−, 1. The single crystal X-ray structure of 1 is reported. © 1999
Elsevier Science S.A. All rights reserved.
Keywords: Ruthenium; Cation; Ethylene; Olefin complex; DMPE
Although few reports of olefin polymerization via
coordinative insertion into ruthenium–alkyl bonds are
known [4], we have been exploring the development of
ruthenium-based Ziegler–Natta catalysts because
ruthenium is not only isoelectronic with iron, but is also
known to efficiently initiate the ring opening metathesis
polymerization (ROMP) of cyclic olefins that contain
polar functionalities [5]. In the present work, we
targeted the synthesis of cis-(DMPE)2Ru(CH3)2
(DMPE=dimethylphosphinoethane,
Me2PCH2CH2PMe2) as a catalyst precursor. We antici-
pated that removal of one of the methyl groups at-
tached to Ru in this complex would generate a metal
center that possessed two basic features common to
known Ziegler–Natta polymerization catalysts: (1) elec-
tron deficiency to encourage coordination of olefins and
(2) an alkyl group cis to the vacant site to permit
insertion and thus propagation [6]. This paper describes
the reaction of cis-(DMPE)2Ru(CH3)2 with the methyl
abstraction agent [(3,5-(CF3)2C6H3)4B]−[H(OEt2)2]+to
generate the resulting cationic complex [(DMPE)2Ru-
CH3]+[(3,5-(CF3)2C6H3)4B]−. Subsequent reaction of
this complex with ethylene yields a novel olefin adduct
that is fully characterized.
1. Introduction
Current efforts to develop new types of Ziegler–
Natta polymerization catalysts based on late transition
metals are motivated, at least in part, by the belief that
weakly oxophilic late transition metals will exhibit en-
hanced tolerance toward polar functional groups such
as alcohols, aldehydes and ketones [1]. The use of
catalysts based on these metals should thus permit the
direct introduction of functional groups into polymer
backbones (via the monomer) under mild reaction con-
ditions. Cationic nickel- and palladium-based metal
alkyls with bulky imine ligands have been observed to
polymerize olefins to moderately high molecular
weights and high crystallinities [2]. Furthermore, recent
studies have shown that iron dichlorides possessing
bulky ligands can polymerize ethylene to high molecu-
lar weights in the presence of methylaluminoxane co-
catalyst; the degree of activity varies with the
polymerization conditions and the ligand structure [3].
* Corresponding author. Tel.: +1-713-743-2724; fax: +1-713-743-
2726.
E-mail address: trlee@uh.edu (T. Randall Lee)
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(98)01212-1

K. Umezawa-Vizzini, T.R. Lee / Journal of Organometallic Chemistry 579 (1999) 122–125
123
Table 1
2. Results and discussion
˚
Selected bond distances (A) and angles (°) for complex 1
We synthesized the targeted catalyst precursor, cis-
(DMPE)2Ru(CH3)2, by modification of the reported
procedure [7]. We then attempted to polymerize
Bond distances
Ru–P(1)
Ru–P(2)
Ru–P(3)
2.332(3)
2.329(2)
2.343(2)
2.341(3)
Ru–C(1)
Ru–C(2)
Ru–C(3)
C(1)–C(2)
2.363(11)
2.363(9)
2.156(13)
1.404(17)
ethylene
by
exposing
the
olefin
to
cis-
Ru–P(4)
(DMPE)2Ru(CH3)2 in the presence of the borate salt
[(3,5-(CF3)2C6H3)4B]−[H(OEt2)2]+. This salt is known
to abstract methyl groups from late transition metal
complexes [2]. Indeed, exposure of 0.9 equivalents of
the salt to cis-(DMPE)2Ru(CH3)2 in either methylene
chloride or tetrahydrofuran generated the cationic
Bond angles
P(1)–Ru–P(2)
P(1)–Ru–P(3)
P(2)–Ru–P(3)
P(1)–Ru–P(4)
P(3)–Ru–P(4)
P(2)–Ru–C(2)
P(4)–Ru–C(2)
P(1)–Ru–C(3)
P(3)–Ru–C(3)
C(1)–Ru–C(3)
84.2(1)
96.0(1)
179.8(2)
174.7(1)
83.7(1)
88.3(4)
75.2(3)
87.7(4)
87.7(4)
163.2(5)
P(1)–Ru–C(1)
P(2)–Ru–C(1)
P(3)–Ru–C(1)
P(4)–Ru–C(1)
P(1)–Ru–C(2)
P(3)–Ru–C(2)
C(1)–Ru–C(2)
P(2)–Ru–C(3)
P(4)–Ru–C(3)
C(2)–Ru–C(3)
75.9(3)
89.6(4)
90.5(3)
109.4(3)
110.1(3)
91.6(4)
34.6(4)
92.3(4)
87.0(4)
162.2(5)
monoalkyl
intermediate
[(DMPE)2RuCH3]+[(3,5-
(CF3)2C6H3)4B]−, whose structure was supported by
1H- and 31P-NMR spectroscopy. The single resonance
at 37.6 ppm in the 31P-NMR spectrum suggests that all
four phosphines are equivalent in solution. The coordi-
nation site trans to the methyl group is more likely
filled by either the diethyl ether moiety derived from the
borate salt or a THF moiety when this solvent is
employed in the reaction.
˚
Ru–C(2), and Ru–C(3) are 2.36, 2.36, and 2.16 A,
respectively. The bond distance of C(1)–C(2) is slightly
elongated at 1.40 A with respect to the known 1.33 A
bond length of ethylene [8].
˚
˚
Exposure of one atmosphere of ethylene to the
cationic monoalkyl intermediate yielded the stable
ethylene complex trans-[(DMPE)2Ru(C2H4)CH3]+[(3,5-
(CF3)2C6H3)4B]−, 1. Apparently, an incoming molecule
of ethylene displaces the coordinating ether moiety to
produce the trans ethylene complex. We characterized
the structure of 1 using single crystal X-ray diffraction.
A thermal ellipsoid drawing of the cationic portion of 1
is shown in Fig. 1; the selected bond lengths and bond
angles are shown in Table 1. The ethylene group (C1
and C2) and the methyl group (C3) were refined
isotropically and found to be disordered into each other
at essentially 50:50 occupancy. All atoms involved in
this area were refined using variable distance con-
straints. The structure is pseudo-octahedral with the
ethylene moiety occupying the apical position trans to
the methyl group. The bond distances for Ru–C(1),
Although there are known examples of olefin adducts
of half-sandwich arene ruthenium alkyl or hydride
complexes [9], there are, to our knowledge, no examples
of octahedral ruthenium (II) alkyl olefin complexes that
possess either oxygen, nitrogen, sulfur, or phosphine
ligands. Only one example of an octahedral ruthenium
(II) hydride olefin complex, trans-[(DPPE)2Ru-
(C2H4)(H)]+[OC6H4-pMe · 2HOC6H4-pMe]− has been
reported [10]. It thus appears that we have synthesized
the first example of a ruthenium (II) alkyl olefin com-
plex having the type of coordinating ligands described
above.
Neither oligomerization nor polymerization of
ethylene was observed using this system despite at-
tempts to vary the reaction conditions (e.g. by increas-
ing the pressure of ethylene to 2.6 atmospheres in the
presence of weakly coordinating ligands such as ace-
tonitrile and pyridine) [11]. The lack of catalysis is
likely due to the preferred structure of the cationic
ruthenium trans olefin complex resulting from olefin
addition to the vacant site trans to the methyl group.
We are currently exploring alternative ruthenium-based
catalyst systems, in which the alkyl moiety and the
vacant site are forced to maintain a cis relationship
upon coordinative unsaturation.
3. Experimental
The syntheses were performed using standard
Schlenk and glove-box techniques. All solvents were
dried by passage through alumina and degassed by
freeze–pump–thaw methods prior to use. The com-
Fig. 1. Thermal ellipsoid drawing of trans-[(DMPE)2Ru-
(C2H4)CH3]+. Thermal ellipsoids are 40% equiprobability envelopes
with the hydrogen atoms omitted.

124
K. Umezawa-Vizzini, T.R. Lee / Journal of Organometallic Chemistry 579 (1999) 122–125
pounds dimethylmagnesium [12], dirutheniumtetra-
acetate chloride [13] and diethyloxonium tetra-
kis[tri(fluoromethyl)phenyl]borate [14] were prepared
according to literature procedures. DMPE was
purchased from Strem Chemicals and used as received.
Nuclear magnetic resonance (NMR) spectra were
recorded on a General Electric QE-300 spectrometer
Me2PCH2CH2PMe2, 1.65 (m, 8 H) Me2PCH2CH2PMe2,
1.98 (m, 4 H) Ru–C2H4, 7.57 (s, 4 H), 7.73 (s, 8 H)
C6H3(CF3)2. 31P{1H}-NMR (THF-d8; 121 MHz; 293
K):
l
41.7 (s). Anal. Calc. for C15H39P4-
Ru+ · C32H12BF2−4 : C, 43.15; H, 3.91. Found: C, 43.25;
H, 3.72.
1
operating at 300 MHz (for H) and 121 MHz (for 31P).
3.4. Experimental data for the X-ray crystal structure
determinations
Elemental analyses were performed by National
Chemical Consulting.
Collection of the X-ray data was carried out on a
crystal of dimensions 0.30 mm×0.45 mm×0.70 mm
using a Nicolet R3m/V automatic diffractometer. The
sample was placed in a stream of dry nitrogen gas at
−50°C, and the radiation used was Mo–Ka
monochromatized by a highly ordered graphite crystal.
Final cell constants, as well as other information perti-
nent to data collection and refinement, are listed in
Table 2. Intensities were measured using the omega
scan technique, with the scan rate depending on the
count obtained in rapid pre-scans of each reflection.
Two standard reflections were monitored after every 2
h or every 100 data collected, and these showed no
significant variation. During data reduction, Lorentz
and polarization corrections were applied, however, no
absorption correction was made. The structure was
solved by interpretation of the Patterson map, which
revealed the position of the Ru atom. Remaining non-
hydrogen atoms were located in subsequent difference
3.1. cis-(DMPE)2Ru(CH3)2
An aliquot of Mg(CH3)2 (4.50 ml of a 1.24 M
solution in diethyl ether; 5.58×10−3 mol) was added
to a solution of 1.04 g of Ru2(OCOCH3)4Cl (2.19×
10−3 mol) and 1.76 ml of DMPE (1.05×10−2 mol) in
70 ml of THF. The solution was stirred at room
temperature for 2 h. The orange solution was filtered,
dried, and extracted with hexane. The crude product
was purified by sublimation (160°C, 40 torr). Yield:
0.661 g; 35% of a white powder. 1H-NMR (CD2Cl2; 300
MHz; 293 K): l −0.97 (m, 6 H, JPH=3.3 Hz) Ru–
CH3, 1.02 (d, 6 H, JPH=4.5 Hz), 1.07 (d, 6 H, JPH=6
Hz), 1.08 (s, 6 H), 1.22 (t, 6 H, JPH=2.7 Hz),
Me2PCH2CH2PMe2, 1.44 (m, 4 H), 1.58 (m, 4 H),
Me2PCH2CH2PMe2. 31P{1H}-NMR (CD2Cl2; 121
MHz; 293 K): l 33.9 (t), 45.7 (t), (Jpp=19 Hz). The
1H-NMR data are consistent with those previously
reported for this compound, which was synthesized via
an alternative pathway [15].
3.2. [(DMPE)2RuCH3]+[(3,5-(CF3)2C6H3)4B]−
Table 2
Summary of crystallographic parameters for complex 1
An aliquot of [(3,5-(CF3)2C6H3)4B]-[H(OEt2)2]+(6.0
mg; 1.4×10−5 mol) was added to a solution of 12.5
mg (1.25×10−5 mol) of cis-(DMPE)2Ru(CH3)2 in
Complex
Formula
C15H39P4Ru+·C32H12BF−24
1
CD2Cl2 (0.5 ml). H-NMR (CD2Cl2; 300 MHz; 293 K):
Formula weight
Crystal system
Space group
1307.74
Orthorhombic
Pbca
19.402(6)
22.945(10)
24.571(8)
8
10938
1.59
5.07
−50°C
l −1.40 (quint, 3 H, JPH=7.5 Hz) Ru–CH3, 1.37 (s,
12 H), 1.50 (s, 12 H) Me2PCH2CH2PMe2, 1.78 (m, 8 H)
Me2PCH2CH2PMe2, 7.57 (s, 4 H), 7.73 (s, 8 H)
C6H3(CF3)2. 31P{1H}-NMR (CD2Cl2; 121 MHz; 293
K): l 37.6 (s).
˚
a (A)
˚
b (A)
˚
c (A)
Z
3
˚
V (A )
3.3. trans-[(DMPE)2Ru(C2H4)CH3]+[(3,5-(CF3)2-
C6H3)4B]−
D (g cm−3
)
Absorption coefficient (cm−1
Temperature
)
˚
Radiation
Mo–Ka (u=0.71073 A)
An aliquot of [(3,5-(CF3)2C6H3)4B]−[H(OEt2)2]+
(0.31 g; 3.1×10−4 mol) was added to a solution of
0.15 g (3.5×10−4 mol) of cis-(DMPE)2Ru(CH3)2 in
CH2Cl2 (2 ml) under 1 atm of ethylene at room temper-
ature. The solution was stirred for 5 min and cooled to
−76°C to obtain champagne-colored crystals (0.23 g;
1.8×10−4 mol; 58% yield). 1H-NMR (CD2Cl2; 300
MHz; 293 K): l −0.62 (quint, 3 H, JPH=8.1 Hz)
Ru–CH3, 1.25 (s, 12 H), 1.32 (s, 12 H)
Collection range
Scan width (°)
4°52q545°
1.25=(Ka −Ka
)
1
2
Scan speed range (° cm−1
Total data collected
)
2.0 to 15.0
7103
Independent data, I=3|(I)
Total variables
4395
646
R=ꢀꢁꢁFoꢁ−ꢁFcꢁꢁ/ꢀꢁFoꢁ
0.055
2 1/2
Rw=[ꢀw(ꢁFoꢁ−ꢁFcꢁ)2/ꢀwꢁFoꢁ ]
0.045
Weights
|(F)−2

K. Umezawa-Vizzini, T.R. Lee / Journal of Organometallic Chemistry 579 (1999) 122–125
125
[4] B.R. James, L.D. Markham, J. Catalysis 27 (1972) 442; S.
Komita, A. Yamamoto, S. Ikeda, Bull. Chem. Soc. Jpn. 48
(1975) 101.
[5] S.T. Nguyen, L.K. Johnson, R.H. Grubbs, J. Am Chem. Soc.
114 (1992) 3974; B. Mohr, D.M. Lynn, R.H. Grubbs,
Organometallics 15 (1996) 4317.
[6] R.F. Jordan, Adv. Organomet. Chem. 32 (1991) 325; H.H.
Brintzinger, D. Fischer, R. Mullhaupt, B. Rieger, R.M. Way-
mouth, Angew. Chem. Int. Ed. Engl. 24 (1995) 1143.
[7] R.A. Andersen, R.A. Jones, G. Wilkinson, J. Chem. Soc. Dalton
Trans. (1978) 446.
Fourier syntheses. The usual sequence of isotropic and
anisotropic refinement was followed, after which all
hydrogens were entered in ideal calculated positions
and constrained to riding motion with a single variable
isotropic temperature factor for all of them. The
ethylene and methyl carbon atoms were, however,
refined only isotropically.
Acknowledgements
[8] J. McMurry, Organic Chemistry, Brooks/Cole, Pacific Grove,
1988.
[9] For example, E. Lindner, S. Pautz, R. Fawzi, M. Steimann, J.
Organomet. Chem. 555 (1998) 247; J.W. Faller, K.J. Chase,
Organometallics 14 (1995) 1592.; H. Werner, H. Kletzin, A.
Hohn, W. Paul, W. Knaup, J. Organomet. Chem. 306 (1986)
227.
The National Science Foundation (CAREER Award
to TRL; CHE-9625003), the Camille and Henry Drey-
fus Foundation (New Faculty Award to TRL; NF-93-
040), the University of Houston Limited Grant-In-Aid
program, and the University of Houston Environmen-
tal Institute provided generous support for this re-
search. We thank Dr James Korp for technical
assistance with the X-ray crystallographic analysis.
Complete crystallographic data have been deposited at
the Cambridge Crystallographic Data Base Center.
[10] M.J. Burn, M.G. Fickes, F.J. Hollander, R.G. Bergman,
Organometallics 14 (1995) 137.
[11] Integral analysis of the resonances observed by 1H-NMR spec-
troscopy suggests that the treatment of cis-(DMPE)2Ru(CH3)2
with [(3,5-(CF3)2C6H3)4B]−[H(OEt2)2]+in the presence of ca. 10
equivalents of acetonitrile or pyridine in CD2Cl2 leads to the
abstraction of a single methyl group. Resonances consistent with
[(DMPE)2RuCH3]+[(3,5-(CF3)2C6H3)4B]− were, however, not
observed by either 1H or 31P-NMR spectroscopy under these
conditions. Nevertheless, complex 1 was cleanly generated (as
judged by 1H and 31P-NMR spectroscopy) upon introduction of
ethylene to this reaction mixture.
References
[1] K. Umezawa-Vizzini, T.R. Lee, Organometallics 16 (1997) 5613.
[2] L.K. Johnson, C.M. Killian, M. Brookhart, J. Am. Chem. Soc.
117 (1995) 6414; C.M. Killian, D.J. Tempel, L.K. Johnson, M.
Brookhart, J. Am. Chem. Soc. 118 (1996) 11664; L.K. Johnson,
S. Mecking, M. Brookhart, J. Am. Chem. Soc. 118 (1996) 267.
[3] G.J.P. Britovsek, V.C. Gibson, B.S. Kimberley, P.J. Maddox,
S.J. McTavish, G.A. Solan, A.J.P. White, D.J. Williams, Chem.
Commun. (1998) 849; B.L. Small, M. Brookhart, Polym.
Preprints 39 (1998) 213.
[12] R.M. Salinger, H.S. Moshier, J. Chem. Soc. 86 (1964) 1782.
[13] D.S. Martin, R.A. Newman, L.M. Vlasnik, Inorg. Chem. 19
(1980) 3404.
[14] M. Brookhart, B. Grant, A.F. Volpe Jr, Organametallics 11
(1992) 3920.
[15] J.F. Hartwig, R.G. Bergman, R.A. Andersen, Organometallics
10 (1991) 3344; J. Chatt, R.G. Hayter, J. Chem. Soc. (1963)
6017.
.