Ruthenium piano-stool complexes containing mono- or bidentate pyrrolidinylalkylphosphines and their reactions with small molecules

Article abstract of DOI:10.1016/j.jorganchem.2011.06.037

Ruthenium piano-stool complexes incorporating the new bidentate aminoalkylphosphine ligand 1,2-bis(dipyrrolidin-1-ylphosphino)ethane (dpyrpe, I) or its monodentate counterpart bis(pyrrolidin-1-yl)methylphosphine (pyr ₂PMe, II) have been prepared, [(C₅R₅)RuCl(PP)] (R = Me and PP = dpyrpe, 1; R = Me and PP = (pyr₂PMe)₂, 2; R = H and PP = dpyrpe, 3). Complexes 2 and 3 have been characterized by X-ray crystallography. Complexes 1 and 2 react with NaBAr₄^f in the presence of ligand L to yield [Cp*Ru(L)(dpyrpe-κ²P)] [BAr^f₄] (L = MeCN, 4a; CO, 4b; N₂, 4c) and [Cp*Ru(L)(pyr₂PMe)₂][BAr₄^f] (L = MeCN, 5a; CO, 5b; N₂, 5c). Complex 4a was crystallographically characterized. The CO complexes 4b and 5b were examined using IR spectroscopy in an attempt to establish the electron-donating capabilities of I and II. Complex 1 oxidatively adds H₂ in the presence of NaBAr₄ ^f to yield the Ru(IV) dihydride [Cp*RuH₂(dpyrpe- κ²P)][BAr₄^f], 7.

Full text of DOI:10.1016/j.jorganchem.2011.06.037

Journal of Organometallic Chemistry 696 (2011) 3198e3205
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Ruthenium piano-stool complexes containing mono- or bidentate
pyrrolidinylalkylphosphines and their reactions with small molecules
,
Michael T. Beach a, Jesse M. Walker a, Ruiyao Wang b, Gregory J. Spivak a
*
a Department of Chemistry, Lakehead University, Thunder Bay, ON, Canada P7B 5E1
b Department of Chemistry, Queen’s University, Kingston, ON, Canada K7L 3N6
a r t i c l e i n f o
a b s t r a c t
Article history:
Ruthenium piano-stool complexes incorporating the new bidentate aminoalkylphosphine ligand 1,2-
bis(dipyrrolidin-1-ylphosphino)ethane (dpyrpe, I) or its monodentate counterpart bis(pyrrolidin-1-yl)
methylphosphine (pyr2PMe, II) have been prepared, [(C5R5)RuCl(PP)] (R ¼ Me and PP ¼ dpyrpe, 1;
R ¼ Me and PP ¼ (pyr2PMe)2, 2; R ¼ H and PP ¼ dpyrpe, 3). Complexes 2 and 3 have been characterized
by X-ray crystallography. Complexes 1 and 2 react with NaBArf4 in the presence of ligand L to yield
Received 7 May 2011
Received in revised form
25 June 2011
Accepted 28 June 2011
[Cp*Ru(L)(dpyrpe-
k
2P)][BArf4] (L ¼ MeCN, 4a; CO, 4b; N2, 4c) and [Cp*Ru(L)(pyr2PMe)2][BArf4] (L ¼ MeCN,
Keywords:
Ruthenium
Piano-stool
Aminoalkylphosphine
Cyclopentadienyl ligands
5a; CO, 5b; N2, 5c). Complex 4a was crystallographically characterized. The CO complexes 4b and 5b were
examined using IR spectroscopy in an attempt to establish the electron-donating capabilities of I and II.
Complex 1 oxidatively adds H2 in the presence of NaBArf4 to yield the Ru(IV) dihydride [Cp*RuH2(dpyrpe-
k
2P)][BArf4], 7.
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
nitrogen of the pyrrolidine ring towards the phosphorus atom,
together with the inductive donor properties of the alkyl substit-
uent, lead to an overall enhancement of the donor power of the
phosphine ligand [3bee]. Thus, they deliver a unique combination
of steric and electronic effects compared to their more conventional
counterparts. Indeed, bis(pyrrolidin-1-yl)tert-butylphosphine is
proposed to be one of the most strongly-donating tertiary phos-
phines known [3c], yet it is not especially large.
We were intrigued by this rather novel class of phosphine,
which is capable of delivering the donor strength normally
reserved for the bulkiest of phosphines, yet remains moderately
sized. We were particularly interested in pairing these phosphines
with Cp* e itself a good donor auxiliary e in ruthenium chemistry
in an effort to produce an exceptionally reactive metal centre. We
report herein some of our preliminary results.
The long-standing interest in modifying the reactivity, selec-
tivity and/or stability of homogeneous metal-based catalysts has
led to the development of a multitude of unique and innovative
ligand systems displaying diverse structures and properties.
Undoubtedly, phosphorus-based ligands have likely received the
greatest attention [1] since one of the most attractive features of
the phosphine ligand within the context of rational ligand design is
the relative ease with which both the steric and electronic prop-
erties of the phosphine may be tailored simply by modifying the
substituents on the phosphorus atom(s).
In recent years, we have developed an interest in exploring the
use of novel phosphine ligands which possess exceptional electron-
donating properties [2]. In general, many of the more conventional
strongly-donating phosphines typically incorporate substituents
t
that make them rather bulky (e.g., Bu3P or Cy3P). Alternatively,
2. Experimental
bis(pyrrolidin-1-yl)alkylphosphines [3] represent a unique class of
hybrid aminoalkylphosphine ligand that possesses significantly
strong donor properties maximized through a specific combination
of hydrocarbyl and pyrrolidinyl substituents on the phosphorus
atom. They are especially attractive since the pyrrolidinyl group is
All experiments and manipulations were conducted under an
inert atmosphere of prepurified nitrogen or argon using standard
Schlenk techniques. Hexanes, toluene and CH2Cl2 were pre-dried
over activated 4A molecular sieves, passed through a column of
alumina, purged with N2 and stored over 4A molecular sieves in
bulbs with Teflon taps [4]. Diethyl ether and THF were freshly
distilled from sodium metal under argon. Acetonitrile was dried
and stored over activated 4A molecular sieves in a bulb with
not particularly large, yet
p-donation of the lone pair on the
* Corresponding author. Tel.: þ1 807 343 8297; fax: þ1 807 346 7775.
E-mail address: greg.spivak@lakeheadu.ca (G.J. Spivak).
0022-328X/$ e see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2011.06.037

M.T. Beach et al. / Journal of Organometallic Chemistry 696 (2011) 3198e3205
3199
a Teflon tap, and purged with N2 before use. NMR solvents used in
solution structure elucidations were dried with appropriate drying
agents, vacuum distilled, freeze-pump-thaw degassed three times,
and stored in bulbs with Teflon taps: CDCl3 (anhydrous CaCl2);
CD2Cl2 (CaH2); C6D6 (sodium metal); CD3CN (P2O5). NMR spectra
(1H and 31P{1H}) were obtained using a Varian Unity INOVA
500 MHz spectrometer, with chemical shifts (in ppm) referenced to
(0.055 g, 0.294 mmol) via syringe. The mixture was allowed to stir
for 1 h, at which time the volatiles were removed in vacuo yielding
a bright orange, oily solid. The solid was redissolved in diethyl ether
(4 mL) and placed into a cold bath (wꢂ60 ꢀC) to facilitate precip-
itation. After standing for several minutes, a microcrystalline bright
orange solid had deposited. The supernatant was cannulated off,
and the product was dried under reduced pressure. Yield: 0.072 g
(76%). Anal. Calcd. for C28H53N4P2ClRu: C, 52.2; H, 8.29; N, 8.70.
Found: C, 52.2; H, 8.40; N, 8.45. 1H NMR (499.9 MHz, C6D6, 22 ꢀC):
3.20, 3.07, 2.90 (3 ꢁ m,16H, eCH2NCH2e),1.67 (s, 15H, Cp*),1.60 (m,
22H, eNCH2CH2CH2CH2e and PCH3). 31P{1H} NMR (202.3 MHz,
C6D6, 22 ꢀC): 106.5 (br, pyr2PMe). 31P{1H} NMR (202.3 MHz;
residual protio solvent peaks (1H) or external 85% H3PO4 31P).
(
Infrared spectra were acquired using a Nicolet 380 FT-IR spec-
trometer. Elemental analyses were performed on a CEC 240XA
analyzer by the Lakehead University Instrumentation Laboratory.
The ligand bis(pyrrolidin-1-yl)methylphosphine was prepared
using a modification of a literature procedure [3c]. The ruthenium
precursors (Cp*RuCl2), (Cp*RuCl)4 and CpRuCl(PPh3)2 were
prepared as reported [5].
2
CD2Cl2, ꢂ50 ꢀC): 101.1, 111.0 (dd, JPP ¼ 69 Hz, pyr2PMe).
2.3.2. Method B
To a THF (10 mL) solution of (Cp*RuCl2)2 (0.050 g, 0.0814 mmol)
2.1. Synthesis of 1,2-bis(dipyrrolidin-1-ylphosphino)ethane
was added a diethyl ether solution of ligand II (0.061 g,
(dpyrpe), I
0.326 mmol) via syringe, followed by an excess of zinc powder
(0.053 g, 0.814 mmol) against a positive flow of nitrogen. The
mixture was allowed to stir for 30 min, at which time the volatiles
were removed in vacuo yielding a yellow-green oily solid. The solid
was dissolved in CH2Cl2 (7 mL) and filtered through Celite. Upon
removing the volatiles under reduced pressure, a bright orange, oily
solid was obtained. The solid was redissolved in diethyl ether
(4 mL) and placed into a cold bath (ꢂ60 ꢀC) to facilitate precipita-
tion. After standing for several minutes, a microcrystalline bright
orange solid had deposited. The supernatant was cannulated off,
and the product was dried under reduced pressure. Yield: 0.156 g
(74%). The NMR spectroscopic data of the orange solid were iden-
tical to the product isolated using Method A.
Ligand I was prepared using a modified literature procedure
[3c]. Cl2PCH2CH2PCl2 (2.00 g, 8.64 mmol) was added to a flame-
dried Schlenk tube/dropping funnel assembly, followed by dry
diethyl ether (40 mL). The solution was then cooled in an ice-water
bath. Next, pyrrolidine (7.1 mL, 86.4 mmol) in dry diethyl ether
(20 mL) was added dropwise to the cooled solution over ca. 5 min
with vigorous stirring yielding copious amounts of white solid. The
bath was removed and the mixture was allowed to stir for 4 h. The
mixture was then filtered through Celite into a flame-dried flask.
Removal of the volatiles under reduced pressure yielded a free-
flowing, extremely air-sensitive white solid. Yield: 2.72 g (85%).
1H NMR (499.9 MHz, C6D6, 22 ꢀC): 3.15 (m, 16H, eCH2NCH2e), 2.06
(m, 4H, ePCH2CH2Pe), 1.52 (m, 16H, eNCH2CH2CH2CH2e). 31P{1H}
NMR (202.3 MHz, C6D6, 22 ꢀC): 72.8 (s, ePCH2CH2Pe).
2.4. Synthesis of [CpRuCl(dpyrpe-k
2P)], 3
CpRuCl(PPh3)2 (0.095 g, 0.131 mmol) was dissolved in toluene
(5 mL). Ligand I (0.049 g, 0.131 mmol) in diethyl ether was added
via syringe, and the solution was refluxed for 2 h. The yellow-
orange solution was allowed to cool to room temperature, and
then it was cannulae transferred to a second flask in order to
separate it from a small amount of dark brown material that had
deposited. The volatiles were removed under reduced pressure,
and then the orange residue was redissolved in diethyl ether (4 mL).
The solution was cooled to ꢂ78 ꢀC for several hours, after which
time small orange microcrystals had deposited. The supernatant
was cannulated off, and the crystals were dried under reduced
pressure. Yield: 0.042 g (56%). Anal. Calcd. for C23H41ClN4P2Ru: C,
48.3; H, 7.22; N, 9.79. Found: C, 48.8; H, 6.95; N, 10.0. 1H NMR
(499.9 MHz, C6D6, 22 ꢀC): 4.85 (s, 5H, Cp), 3.51, 3.34, 2.84, 2.74
(4 ꢁ m, 16H, eCH2NCH2e), 2.28 (m, 4H, ePCH2CH2Pe), 1.79, 1.50
(2 ꢁ m, 16H, eNCH2CH2CH2CH2e). 31P{1H} NMR (202.3 MHz, C6D6,
22 ꢀC): 149.8 (s, ePCH2CH2Pe).
2.2. Synthesis of [Cp*RuCl(dpyrpe-
k
2P)], 1
2.2.1. Method A
(Cp*RuCl)4 (0.175 g, 0.161 mmol) was dissolved in hexanes
(10 mL). Next, ligand I (0.262 g, 0.708 mmol) in diethyl ether was
added via syringe to the hexanes solution, and the mixture was
allowed to stir for 1 h. Next, the mixture was evaporated to dryness
under reduced pressure, and then the orange product was washed
with a small volume of hexanes (w2e3 mL). Yield: 0.372 g (90%).
Anal. Calcd. for C28H51ClN4P2Ru: C, 52.4; H, 8.00; N, 8.72. Found: C,
52.7; H, 7.80; N, 8.61. 1H NMR (499.9 MHz, C6D6, 22 ꢀC): 3.18 (m, 8H,
eCH2NCH2e), 3.11 (m, 4H, ePCH2CH2Pe), 2.92 (m, 8H,
eCH2NCH2e), 1.77e1.71 (m, 16H, eNCH2CH2CH2CH2e), 1.66 (s, 15H,
Cp*). 31P{1H} NMR (202.3 MHz, C6D6, 22 ꢀC): 144.4 (s, ePCH2CH2Pe).
2.2.2. Method B
(Cp*RuCl2)2 (0.200 g, 0.325 mmol) was dissolved in THF (15 mL).
Next, ligand I (0.241 g, 0.650 mmol) in diethyl ether was added via
syringe, followed by excess zinc powder (0.200 g). The mixture was
stirred for 30 min, and slowly became orange. The volatiles were
then removed under reduced pressure, and the product was
extracted with CH2Cl2 (2 ꢁ 10 mL) and filtered through Celite.
Removal of the volatiles under reduced pressure yielded an orange
solid. Yield: 0.381 g (91%). The NMR spectroscopic data of the
orange solid were identical to the product isolated using Method A.
k
2.5. Synthesis of [Cp*Ru(NCMe)(dpyrpe- 2P)][BArf4], 4a
Complex
1
(0.103 g, 0.160 mmol) and NaBArf4 (0.142 g,
0.160 mmol) were combined and dissolved in a mixture of CH2Cl2
(5 mL) and MeCN (5 mL). The mixture was allowed to stir for 2 h.
After this time, the cloudy, pale yellow mixture was filtered through
Celite. Upon removing the volatiles under reduced pressure, a pale
yellow solid was produced. The solid was redissolved in CH2Cl2
(w2 mL) and excess hexanes (20 mL) were added. After standing
for several minutes, a microcrystalline yellow solid had deposited.
The supernatant was cannulated off, and the product was dried
under reduced pressure. Yield: 0.196 g (81%). Anal. Calcd. for
C62H66BF24N5P2Ru$2CH2Cl2: C, 45.7; H, 4.20; N, 4.17. Found: C, 45.5;
H, 3.92; N, 4.10. 1H NMR (499.9 MHz, CDCl3, 22 ꢀC): 7.72 (s, 8H, o-H
2.3. Synthesis of [Cp*RuCl(pyr2PMe)2], 2
2.3.1. Method A
To a hexanes (10 mL) suspension of (Cp*RuCl)4 (0.040 g,
0.037 mmol) was added a diethyl ether solution of ligand II

3200
M.T. Beach et al. / Journal of Organometallic Chemistry 696 (2011) 3198e3205
of Arf), 7.55 (s, 4H, p-H of Arf), 3.14 (br, 4H, ePCH2CH2Pe), 3.09, 3.00,
2.87 (3 ꢁ m, 16H, eCH2NCH2e), 2.11 (s, 3H, CH3CN), 1.78 (m, 16H,
eNCH2CH2CH2CH2e), 1.66 (s, 15H, Cp*). 31P{1H} NMR (202.3 MHz,
CDCl3, 22 ꢀC): 136.4 (s, ePCH2CH2Pe).
reduced pressure, an off-white solid was produced. The solid was
triturated in hexanes (15 mL) for 1 h. After standing for several
minutes, a microcrystalline solid had deposited. The supernatant
was cannulated off, and the product was dried under reduced
pressure. Yield: 0.200 g (86%). Anal. Calcd. for C61H65BF24N4OP2Ru:
C, 48.8; H, 4.37; N, 3.74. Found: C, 48.6; H, 4.38; N, 3.62. IR (Nujol,
k
2.6. Synthesis of [Cp*Ru(CO)(dpyrpe- 2P)][BArf4], 4b
NaCl):
n
(CO) ¼ 1957 cmꢂ1. 1H NMR (499.9 MHz, CDCl3, 22 ꢀC): 7.62
Complex
1
(0.154 g, 0.240 mmol) and NaBArf4 (0.213 g,
(s, 8H, o-H of Arf), 7.45 (s, 4H, p-H of Arf), 2.98e2.86 (m, 16H,
eCH2NCH2e), 1.79 (m, 16H, eNCH2CH2CH2CH2e), 1.69 (s, 15H, Cp*),
1.59 (s, 6H, PCH3). 31P{1H} NMR (202.3 MHz, C6D6, 22 ꢀC): 100.3 (s,
pyr2PMe).
0.240 mmol) were combined and dissolved in diethyl ether (10 mL)
under CO. The mixture was allowed to stir for 1 h under CO, and
then it was filtered through Celite. Removal of the volatiles under
reduced pressure yielded a pale yellow solid. Yield: 0.289 g (80%).
Analytically pure samples were prepared by recrystallizing the
solid from diethyl ether/hexanes via slow diffusion. Anal. Calcd. for
C61H63BF24N4OP2Ru: C, 48.9; H, 4.24; N, 3.74. Found: C, 48.9; H,
2.10. Synthesis of [Cp*Ru(N2)(pyr2PMe)2][BArf4], 5c
Complex 2 (0.015 g, 0.0233 mmol) and NaBArf4 (0.020 g,
0.0233 mmol) were combined in a sealable NMR tube and dissolved
in C6D6 (0.5 mL) under N2. The mixture was agitated for about
1 min, after which the contents were analyzed via 31P and 1H NMR
spectroscopy. 1H NMR (499.9 MHz, C6D6, 22 ꢀC): 7.58 (s, 8H, o-H of
Arf), 7.42 (s, 4H, p-H of Arf), 2.94, 2.76 (2 ꢁ m, 16H, eCH2NCH2e),
1.72,1.67 (2 ꢁ m, 16H, eNCH2CH2CH2CH2e), 1.50 (s, 15H, Cp*), 1.44
(m, 6H, PCH3). 31P{1H} NMR (202.3 MHz, C6D6, 22 ꢀC): 98.5 (s,
pyr2PMe).
4.31; N, 3.59. IR (Nujol, NaCl):
n
(CO) ¼ 1960 cmꢂ1
.
1H NMR
(499.9 MHz, CDCl3, 22 ꢀC): 7.63 (s, 8H, o-H of Arf), 7.45 (s, 4H, p-H of
Arf), 3.20 (br m, 4H, ePCH2CH2Pe), 3.01, 2.94, 2.82 (3 ꢁ m, 16H,
eCH2NCH2e), 1.90 (m, 8H, eNCH2CH2CH2CH2e), 1.81 (s, 15H, Cp*),
1.73 (m, 8H, eNCH2CH2CH2CH2e). 31P{1H} NMR (202.3 MHz, CDCl3,
22 ꢀC): 130.4 (s, ePCH2CH2Pe).
k
2.7. Synthesis of [Cp*Ru(N2)(dpyrpe- 2P)][BArf4], 4c
Complex
1
(0.085 g, 0.132 mmol) and NaBArf4 (0.117 g,
2.11. Synthesis of [Cp*Ru(CO)(dppe- 2P)][BArf4], 6a
k
0.132 mmol) were combined, dissolved in diethyl ether (10 mL) and
stirred under N2 for 30 min. The mixture was then filtered through
Celite, and the volatiles were removed under reduced pressure to
yield a yellow-orange solid. Yield: 0.144 g (73%). All attempts to
recrystallize the product resulted in dinitrogen loss. IR (Nujol,
Cp*RuCl(PPh3)2 (0.100 g, 0.125 mmol) and dppe (0.050 g,
0.125 mmol) were combined and stirred in C6H6 (10 mL) for 1.5 h.
After this time, the volatiles were stripped away under reduced
pressure, NaBArf4 (0.111 g, 0.125 mmol) was added, and then the
flask was evacuated/purged with CO. Next, diethyl ether (10 mL)
was added and the mixture was allowed to stir under CO for 1 h.
The murky, pale yellow mixture was then filtered through Celite
and then the volatiles were stripped from the filtrate under reduced
pressure. The product was triturated with hexanes (10 mL) for
w5 min yielding a pale yellow solid. Yield: 0.149 g (78%). An
analytically pure sample was prepared by recrystallizing the
product from diethyl ether/hexanes. Anal. Calcd. for C69H51BF24O-
P2Ru: C, 54.3; H, 3.37. Found: C, 54.5; H, 3.34. IR (Nujol, NaCl):
NaCl):
n
(N2) ¼ 2148 cmꢂ1. 1H NMR (499.9 MHz, CD2Cl2, 22 ꢀC): 7.64
(s, 8H, o-H of Arf), 7.48 (s, 4H, p-H of Arf), 3.03 (m, 8H, eCH2NCH2e),
2.90 (m, 4H, ePCH2CH2Pe), 2.79 (m, 8H, eCH2NCH2e), 1.80 (m, 8H,
eNCH2CH2CH2CH2e), 1.73 (m, 8H, eNCH2CH2CH2CH2e), 1.68 (s,
15H, Cp*). 31P{1H} NMR (202.3 MHz, CDCl3, 22 ꢀC): 131.2 (s,
ePCH2CH2Pe).
2.8. Synthesis of [Cp*Ru(NCMe)(pyr2PMe)2][BArf4], 5a
Complex
2
(0.100 g, 0.155 mmol) and NaBArf4 (0.138 g,
n
(CO) ¼ 1961 cmꢂ1. 1H NMR (499.9 MHz, CDCl3, 22 ꢀC): 7.73 (s, 8H,
0.155 mmol) were combined and dissolved in a mixture of diethyl
ether (5 mL) and MeCN (5 mL). The mixture was allowed to stir for
1 h, at which time the volatiles were removed in vacuo yielding
a pale yellow solid. The solid was redissolved in CH2Cl2 (7 mL) and
filtered through Celite. Upon removing the volatiles under reduced
pressure, a light yellow solid was produced. The solid was triturated
in hexanes (15 mL) for 1 h. After standing for several minutes,
a microcrystalline pale yellow solid had deposited. The supernatant
was cannulated off, and the product was dried under reduced
o-H of Arf), 7.56e747 (m, 20H, p-H of Arf and Ph), 7.18e7.15 (m, 4H,
Ph), 2.57 (m, 4H, ePCH2CH2Pe), 1.59 (s, 15H, Cp*). 31P{1H} NMR
(202.3 MHz, CDCl3, 22 ꢀC): 71.8 (s, ePCH2CH2Pe).
2.12. Synthesis of [Cp*Ru(CO)(Ph2PMe)2][BArf4], 6b
Cp*RuCl(PPh3)2 (0.100 g, 0.125 mmol) was dissolved in C6H6
(10 mL). To this solution, Ph2PMe (47 mL, 0.250 mmol) was added
pressure.
Yield:
0.202
g
(86%).
Anal.
Calcd.
for
via syringe. The mixture was then stirred for 1.5 h. After this time,
the volatiles were stripped away under reduced pressure, NaBAr4f
(0.111 g, 0.125 mmol) was added, and then the flask was evacuated/
purged with CO. Next, diethyl ether (10 mL) was added and the
mixture was allowed to stir under CO for 1 h. The murky, pale
yellow mixture was then filtered through Celite and then the
volatiles were stripped from the filtrate under reduced pressure.
The product was triturated with hexanes (10 mL) for w5 min
yielding a pale yellow solid. Yield: 0.132 g (69%). An analytically
pure sample was prepared by recrystallizing the product from
diethyl ether/hexanes. Anal. Calcd. for C69H53BF24OP2Ru$Et2O: C,
54.7; H, 3.96. Found: C, 54.7; H, 3.53. IR (Nujol, NaCl):
C62H68BF24N5P2Ru$CH2Cl2: C, 47.4; H, 4.42; N, 4.38. Found: C, 47.1;
H, 4.23; N, 3.94. 1H NMR (499.9 MHz, CD3CN, 22 ꢀC): 7.64 (s, 8H, o-H
of Arf), 7.48 (s, 4H, p-H of Arf), 3.08, 3.00, 2.78 (3 ꢁ m, 16H,
eCH2NCH2e), 2.35 (3H, s, CH3CN), 1.86, 1.77, 1.70 (3 ꢁ m, 16H,
eNCH2CH2CH2CH2e), 1.50 (s, 15H, Cp*), 1.42 (6H, PCH3). 31P{1H}
NMR (202.3 MHz, CD3CN, 22 ꢀC): 103.5 (s, pyr2PMe).
2.9. Synthesis of [Cp*Ru(CO)(pyr2PMe)2][BArf4], 5b
Complex
2
(0.100 g, 0.155 mmol) and NaBArf4 (0.138 g,
0.155 mmol) were combined and then suspended in hexanes
(10 mL). The mixture was allowed to stir for 1 h under CO, at which
time the volatiles were removed in vacuo yielding an off-white
solid. The solid was redissolved in CH2Cl2 (7 mL) and the solution
was filtered through Celite. Upon removing the volatiles under
n
(CO) ¼ 1951 cmꢂ1. 1H NMR (499.9 MHz, CDCl3, 22 ꢀC): 7.75 (s, 8H,
o-H of Arf), 7.61e7.25 (m, 16H, Ph), 7.54 (s, 4H, p-H of Arf), 6.81 (m,
4H, Ph), 1.50 (s, 15H, Cp*), 1.37 (m, 6H, PCH3). 31P{1H} NMR
(202.3 MHz, CDCl3, 22 ꢀC): 26.3 (s, Ph2PMe).

M.T. Beach et al. / Journal of Organometallic Chemistry 696 (2011) 3198e3205
3201
2.13. Synthesis of [Cp*RuH2(dpyrpe-
k
2P)][BArf4], 7
b
¼
103.2460(10)ꢀ,
g
¼
90ꢀ,
Z
¼
2,
V
¼
3313.20(9) Å3,
D(calc) ¼ 1.515 g/cm3,
m
(Mo Ka) ¼ 0.396 mmꢂ1, crystal dimensions
Compound 1 (0.020 g, 0.0311 mmol) and NaBArf4 (0.028 g,
0.0311 mmol) were combined in an NMR tube fitted with a rubber
septum. The contents of the tube were evacuated and purged with
H2, and then Ar-purged CD2Cl2 (0.5 mL) was added via syringe. The
mixture was allowed to mix (tumbling) for 30 min. NMR spec-
troscopy revealed clean and quantitative conversion to compound
7. 1H NMR (499.9 MHz, CD2Cl2, 22 ꢀC): 7.72 (s, 8H, o-H of Arf), 7.55 (s,
4H, p-H of Arf), 3.15 (br m, 4H, ePCH2CH2Pe), 3.02e2.93 (br m, 16H,
eCH2NCH2e), 2.03 (s, 15H, Cp*), 1.91e1.83 (br m, 16H,
0.30 ꢁ 0.25 ꢁ 0.15 mm3. The structure was refined by full matrix
least-squares on F2. Convergence to final R1 ¼ 0.0442 and
wR2 ¼ 0.1147 for 4495 (I > 2
s(I)) independent reflections, and
R1 ¼ 0.0482 and wR2 ¼ 0.1189 for all 12798 (R(int) ¼ 0.0190)
independent reflections, with 870 parameters and 22 restraints,
were achieved.
3. Results and discussion
2
eNCH2CH2CH2CH2e), ꢂ9.76 (t, JPH ¼ 29 Hz, 2H, RueH). 31P{1H}
The new ligand 1,2-bis(dipyrrolidin-1-ylphosphino)ethane
(dpyrpe, I) and its monodentate analogue bis(pyrrolidin-1-yl)
methylphosphine (pyr2PMe, II) were prepared in good yields using
a modification of an established procedure [3c] (Scheme 1). The
pyrrolidinylalkylphosphine ligands proved to be extremely air- and
moisture-sensitive, but are stable indefinitely under an inert
atmosphere. The 31P{1H} NMR spectrum of I reveals a sharp singlet
NMR (202.3 MHz, CD2Cl2, 22 ꢀC): 135.6 (s, -PCH2CH2P-).
2.14. X-ray crystallographic studies
Diffraction quality crystals were grown over a period of days at
room temperature either by slow evaporation of a concentrated
diethyl ether solution (2 and 3), or by slow diffusion of hexanes into
a concentrated CH2Cl2 solution (4a). The crystals were mounted on
a glass fibre with grease and cooled to ꢂ93 ꢀC in a stream of
nitrogen gas controlled with a Cryostream Controller 700. Data
collection was performed on a Bruker SMART APEX II X-ray
diffractometer with graphite-monochromated Mo Ka radiation
at
d
¼ 72.8 ppm, which is similar to that observed for II
(d
¼ 74.1 ppm) [3c], but slightly further downfield compared to the
corresponding pyrrolyl analogue, 1,2-bis(dipyrrol-1-ylphosphino)
ethane [8].
The synthetic approaches used to prepare the ruthenium piano-
stool complexes examined as part of this work are illustrated in
Scheme 2. Complexes 1 and 2 were isolated as orange solids from
reactions between (Cp*RuCl)4 and either ligand I or II, respectively,
in good yields upon work-up. Alternatively, they could also be
synthesized in comparable yields using a zinc reduction strategy
beginning with (Cp*RuCl2)2 [9]. The orange cyclopentadienyl
analogue 3 was prepared by thermally displacing the PPh3 ligands
in CpRuCl(PPh3)2 with ligand I. All three complexes are stable
towards the open air, at least for brief periods (hours). Thus, the
ligands I and II become remarkably stable towards atmospheric
elements upon coordination to ruthenium, and even withstand
prolonged periods of heating (i.e., in the synthesis of 3). The 31P{1H}
NMR spectra of 1 and 3 each reveal a sharp singlet at
and
¼ 149.8 ppm, respectively, at room temperature. In contrast,
complex 2 produces a very broad peak centred at
under the same conditions. When the temperature is raised to
60 ꢀC, this signal narrows into a sharp singlet. Upon lowering the
temperature, the signal first broadens significantly, and eventually
decoalesces to produce an AB spin pattern consisting of two equally
(
l
¼ 0.71073 Å), operating at 50 kV and 30 mA over 2
q ranges of
3.46 w 52.00ꢀ (2), 4.02 w 52.00ꢀ (3) or 4.28 w 52.00ꢀ (4a). No
significant decay was observed during the data collection in all
cases. Data were processed using the Bruker AXS Crystal Structure
Analysis Package [6]: Data collection: APEX2; cell refinement:
SAINT; data reduction: SAINT; structure solution: XPREP and
SHELXTL; structure refinement: SHELXTL. Neutral atom scattering
factors were taken from Cromer and Waber [7]. The structures were
solved by direct methods. Full-matrix least-square refinements
P
2
minimizing the function
w(Fo2 ꢂ Fc2
)
were applied to each
compound. All non-hydrogen atoms were refined anisotropically.
All of the H atoms were placed in geometrically calculated posi-
tions. For 4a, the phosphine ligand and the eCF3 groups of the
anion were disordered; the SHELX commands, EADP, DFIX, EXYZ
and SUMP were used to resolve the disorder.
d
¼ 144.4 ppm
d
d
¼ 106.5 ppm
2.14.1. X-ray data for 2
C28H53ClN4P2Ru,
M
¼
644.2 g/mol, monoclinic, P2(1)/c,
a ¼ 10.6418(4) Å, b ¼ 15.2543(5) Å, c ¼ 19.1045(7) Å,
a
¼ 90ꢀ,
intense sharp doublets at
d
¼ 111.0 ppm and
d
¼ 101.1 ppm
¼ 103.287(2)ꢀ,
g
¼ 90ꢀ, Z ¼ 4, V ¼ 3018.28(19) Å3, D(calc) ¼ 1.418 g/
(2JPP ¼ 69 Hz) by ꢂ50 ꢀC. These features of the variable temperature
31P{1H} NMR spectrum of 2 likely originate from hindered rotation
about the RueP bonds on the NMR time scale [10], which produce
rotational isomers at low temperatures. Indeed, the solid state
b
cm3,
m
(Mo Ka) ¼ 0.738 mmꢂ1, crystal dimensions 0.15 ꢁ 0.10
ꢁ 0.06 mm3. The structure was refined by full matrix least-squares
on F2. Convergence to final R1 ¼ 0.0228 and wR2 ¼ 0.0604 for 6315
(I> 2
s
(I))independentreflections, andR1 ¼0.0252andwR2 ¼ 0.0622
for all 5922 (R(int) ¼ 0.0225) independent reflections, with 331
parameters and 0 restraints, were achieved.
2.14.2. X-ray data for 3
C23H41ClN4P2Ru,
M
¼
572.06 g/mol, monoclinic, C2/c,
a ¼ 30.637(4) Å, b ¼ 10.7422(15) Å, c ¼ 15.205(2) Å,
a
¼ 90ꢀ,
b
¼ 93.063(2)ꢀ,
g
¼ 90ꢀ, Z ¼ 8, V ¼ 4996.9(12) Å3, D (calc) ¼ 1.521 g/
cm3,
m
(Mo Ka)
¼
0.882 mmꢂ1
,
crystal dimensions
0.25ꢁ 0.15 ꢁ 0.08mm3. Thestructurewasrefined byfullmatrix least-
squares on F2. Convergence to final R1 ¼ 0.0240 and wR2 ¼ 0.0594 for
4495 (I > 2
s
(I)) independent reflections, and R1 ¼ 0.0269 and
wR2 ¼ 0.0616 for all 4895 (R(int) ¼ 0.0178) independent reflections,
with 280 parameters and 0 restraints, were achieved.
2.14.3. X-ray data for 4a
C62H66BF24N5P2Ru,
a ¼ 12.8983(2) Å, b ¼ 13.5429(2) Å, c ¼ 19.4856(3) Å,
M
¼
1511.02 g/mol, monoclinic, P2(1),
¼ 90ꢀ,
Scheme 1. Synthesis of ligands I and II.
a

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M.T. Beach et al. / Journal of Organometallic Chemistry 696 (2011) 3198e3205
Fig. 2. Molecular structure of complex 3 (hydrogen atoms omitted for clarity).
around their respective PeN bond such that the nitrogen lone pair
is positioned away from the phosphorus lone pair (i.e., the RueP
bond). Three of the four pyrrolidinyl rings possess nitrogen atoms
that are approaching planarity (N(2), N(3) and N(4)), with the sum
of the angles around each nitrogen ranging between 353 and 357ꢀ.
A suspiciously short distance between N(3) and the methyl
substituent on the adjacent phosphine ligand, specifically the C(19)
and H(19B) atoms, might suggest a weak intramolecular hydrogen
bond. The N(3)eC(19) distance (3.263(2) Å) and the N(3)eH(19B)
distance (calculated 2.510 Å) are both shorter than the sum of the
van der Waal radii for nitrogen-carbon (3.41 Å) and nitrogen-
hydrogen (2.74 Å) [11]. Strangely, the fourth nitrogen, N(1), is
intermediate between tetrahedral and planar (347ꢀ). The shortest
N/H contact distance (2.81 Å) between this particular nitrogen
and the nearest (non-pyrrolidinyl) hydrogen atom is outside of the
sum of the van der Waal radii for nitrogen and hydrogen, thus the
observed pyramidalization in the solid state is likely not due to an
additional inter- or intramolecular NeH interaction. The roughly
planar geometries about N(2), N(3) and N(4) of the pyrrolidinyl
Scheme 2. Synthesis of complexes 1e3.
X-ray structure of 2 (vide infra) is consistent with rotamers A/A0,
both of which possess non-equivalent phosphine ligands:
Complexes 2 and 3 were crystallographically characterized, and
each structure reveals a number of interesting features. Views of
each complex are presented in Figs. 1 and 2. Selected bond lengths
and angles are provided in Tables 1 and 2.
rings might suggest
p-donation of the lone nitrogen pair into
a vacant phosphorus-based orbital, as depicted in B and C:
As expected, complex 2 adopts the typical piano-stool structure
often observed for Cp and Cp* complexes of ruthenium. The
substituents on each phosphine ligand are staggered asymmetri-
cally with respect to one another (as in A/A0, above). Also, all four
pyrrolidinyl ring substituents of the phosphine are staggered
Indeed, the four PeN distances range between 1.6833(16)e
1.7087(16) Å, with the shorter distances being observed for the
more planar nitrogen atoms. These phenomena have been noted in
a number of other systems bearing similar ligands [3]. Thus, it is
anticipated that these ligands (and hybrid aminoalkylphosphine
ligands in general) might possess enhanced Lewis basicities
compared to their hydrocarbyl counterparts. The RueP distances
Table 1
Selected bond distances (Å) and angles (ꢀ) for complex 2.
Ru(1)eP(1)
Ru(1)eP(2)
Ru(1)eCl(1)
P(1)eN(1)
P(1)eN(2)
P(2)eN(3)
2.2893(4)
2.2797(5)
2.4530(5)
1.707(2)
1.683(2)
1.709(2)
1.691(1)
3.263(2)
2.510a
P(1)eRu(1)eP(2)
P(1)eN(1)eC(11)
P(1)eN(1)eC(14)
C(11)eN(1)eC(14)
P(1)eN(2)eC(15)
P(1)eN(2)eC(18)
C(18)eN(2)eC(15)
P(2)eN(4)eC(24)
P(2)eN(4)eC(27)
C(24)eN(4)eC(27)
P(2)eN(3)eC(20)
P(2)eN(3)eC(23)
C(20)eN(3)eC(23)
89.78(2)
118.6(1)
123.1(1)
104.8(2)
126.1(1)
120.2(1)
110.3(2)
122.0(1)
122.8(1)
109.8(1)
126.5(1)
118.0(1)
108.5(2)
P(2)eN(4)
N(3)eC(19)
N(3)eH(19B)
Ru(1)ecentroid
1.899a
a
Fig. 1. Molecular structure of complex 2 (hydrogen atoms omitted for clarity).
Calculated distance.

M.T. Beach et al. / Journal of Organometallic Chemistry 696 (2011) 3198e3205
3203
Table 2
Selected bond distances (Å) and angles (ꢀ) for complex 3.
Ru(1)eP(1)
Ru(1)eP(2)
Ru(1)eCl(1)
P(1)eN(1)
P(1)eN(2)
P(2)eN(3)
2.2626(6)
2.2654(6)
2.4334(6)
1.715(2)
1.671(2)
1.682(2)
1.669(2)
1.879a
P(1)eRu(1)eP(2)
P(1)eN(1)eC(6)
P(1)eN(1)eC(9)
C(6)eN(1)eC(9)
P(1)eN(2)eC(10)
P(1)eN(2)eC(13)
C(10)eN(2)eC(13)
P(2)eN(3)eC(16)
P(2)eN(3)eC(19)
C(16)eN(3)eC(19)
P(2)eN(4)eC(20)
P(2)eN(4)eC(23)
C(20)eN(4)eC(23)
81.45(2)
118.8(1)
119.0(1)
107.5(2)
123.5(1)
124.3(1)
110.6(2)
120.6(1)
126.4(1)
110.0(2)
126.7(2)
122.7(2)
110.6(2)
P(2)eN(4)
Ru(1)ecentroid
a
Calculated distance.
(2.2893(4) Å and 2.2797(5) Å) and PeRueP bond angle in 2
(89.78(2)ꢀ) are similar to those determined for [Cp*RuCl(Ph2PH)2]
(2.282(1) Å and 2.277(1) Å), 90.68(4)ꢀ [12]. It has been suggested
that the pyrrolidinyl group exerts a steric effect similar to that of
a phenyl group [8]. Accordingly, the cone angle of II has been
estimated to be similar to that of Ph2PMe, specifically 136ꢀ [3c]. The
cone angle of Ph2PH has been estimated to be 128ꢀ [13], thus it is
likely then that the cone angle of ligand II falls within this range.
Similar structural features were also observed for complex 3.
Once again, three pyrrolidinyl ring substituents on the phosphine
ligand have nitrogen atoms (i.e., N(2), N(3) and N(4)) that are nearly
planar (the sum of the angles around each nitrogen range between
357 and 360ꢀ), while the fourth (N(1)) is more intermediate (345ꢀ)
with no reasonably short NeH contact distances observed. The PeN
distances within the phosphine ligand (1.669(2)e1.715(2) Å) again
follow a pattern where an increase in planarity about the nitrogen
atoms leads to a shortening of the PeN bond. The complex
Scheme 3. Synthesis of complexes 4aec and 5aec.
Using a similar synthetic approach, the corresponding CO
complexes [Cp*Ru(CO)(dpyrpe- 2P)][BArf4], 4b, and [Cp*Ru(CO)
k
(pyr2PMe)2][BArf4], 5b (
d
(
31P{1H}) ¼ 130.4 and 100.3 ppm, respec-
tively) were also prepared. For complex 4b,
n
(CO) ¼ 1960 cmꢂ1
,
while for 5b,
n
(CO) ¼ 1957 cmꢂ1. Infrared spectroscopy of metal-CO
derivatives has been used extensively as a method of gauging the
donor abilities of pyrrolidinylalkylphosphine ligands [3bed]. In
general, these studies have revealed that tertiary phosphines
bearing two N-bound pyrrolidinyl substituents are stronger electron
donor ligands compared to their trialkyl- or triarylphosphine
counterparts. In order to establish the relatiþve donor strengths of
ligands I and II as part of [Cp*Ru(CO)(PP)] (PP ¼ bidentate or
2 ꢁ monodentate phosphines), we also prepared the complexes
[Cp*Ru(CO)(dppe-k2P)][BAr4f ], 6a, and [Cp*Ru(CO)(Ph2PMe)2][BArf4],
6b, for the purposes of drawing comparisons with 4b and 5b,
respectively, since they contain conventional phosphine ligands
which perhaps, at least sterically, resemble the phosphine ligands
studied as part of this work. Surprisingly, our results were less
definitive when compared to what has been observed in other
studies [3bed]. The infrared absorption of the CO ligand in complex
[CpRuCl(dppe-k
2P)], a structural analogue of 3, has RueP distances
(2.275(2) Å and 2.282(2) Å) and a PeRueP bond angle (83.49(4)ꢀ)
[14] that are only slightly larger than those observed for 3
(2.2654(6) Å and 2.2626(6) Å, 81.45(2)ꢀ), suggesting the dipyrroli-
dinylphosphino group in I is perhaps close in size to the corre-
sponding diphenylphosphino group in dppe. The cone angle for
dppe has been estimated to be 125ꢀ [13], and so we might then
expect the cone angle for ligand I to be about the same.
We explored the substitution chemistry of complexes 1 and 2,
which was found to resemble in a number of ways what is typically
observed for ruthenium piano-stool complexes (Scheme 3). All of
the complexes were characterized using NMR spectroscopy and
microanalytical data. The chloride ligand in either complex is
readily removed using NaBArf4 (Arf ¼ 3,5-bis(trifluoromethyl)
phenyl) and replaced, for example, with MeCN to give [Cp*Ru(NC-
Me)(dpyrpe-k2P)][BAr4f ], 4a, and [Cp*Ru(NCMe)(pyr2PMe)2][BArf4],
5a. The 31P{1H} NMR resonance for 4a appears as a sharp singlet at
6a appears at
n
(CO) ¼ 1961 cmꢂ1, suggesting that ligand I and dppe
have very similar donor properties, despite the very different
substituents on each phosphine. For complex 6b,
which again suggests the Ph2PMe ligand is at least similar, and
n
(CO) ¼ 1951 cmꢂ1
,
perhaps is even
a slightly stronger phosphine donor ligand
compared to II. We also note that the infrared absorption of the
d
¼ 136.4 ppm, a position further upfield of the parent chloride.
Similarly, complex 5a also yields sharp upfield signal at
¼ 103.5 ppm, which contrasts the broad resonance observed for 2
a
d
at room temperature. Complex 4a was also characterized by X-ray
crystallography. A view of the cation of 4a is provided in Fig. 3;
selected bond lengths and angles are listed in Table 3. Unlike what
is observed in the solid state structures of 2 and 3, all four pyrro-
lidinyl nitrogens are essentially planar (sum of the angles around
each nitrogen ranging between 357 and 359ꢀ). The PeN distances
are short (1.672(4)e1.680(5) Å). The acetonitrile ligand is linear
(173.3(4)ꢀ). The RueP distances (2.2967(9) Å and 2.304(1) Å) are
shorter than those observed in [Cp*RuCl(dippe-
k
2P)] (2.336(2) Å
and 2.331(2) Å) [15] and [Cp*Ru(dippe- 2P)][BArf4] (2.331(1) Å and
k
2.356(1) Å) [16] (dippe ¼ 1,2-bis(diisopropylphosphino)ethane),
likely reflecting the smaller size of ligand I compared to dippe.
Fig. 3. Molecular structure of the cation of complex 4a (hydrogen atoms omitted for
clarity).

3204
M.T. Beach et al. / Journal of Organometallic Chemistry 696 (2011) 3198e3205
Table 3
reactions to include complex 2 only yielded unappealing mixtures
as evidenced by the 31P NMR spectra of the products of these
reactions.
Selected bond distances (Å) and angles (ꢀ) for complex 4a.
Ru(1)eP(1)
Ru(1)eP(2)
Ru(1)eN(5)
P(1)eN(1)
P(1)eN(2)
P(2)eN(3)
2.304(1)
2.2967(9)
2.024(4)
1.672(4)
1.680(5)
1.674(5)
1.677(4)
1.899a
P(1)eRu(1)eP(2)
N(5)eC(29)eC(30)
P(1)eN(1)eC(11)
P(1)eN(1)eC(14)
C(11)eN(1)eC(14)
P(1)eN(2)eC(15A)
P(1)eN(2)eC(18A)
C(15A)N(2)eC(18A)
P(2)eN(3)eC(19)
P(2)eN(3)eC(22)
C(19)eN(3)eC(22)
P(2)eN(4)eC(23A)
P(2)eN(4)eC(26A)
C(23A)eN(4)eC(26A)
81.34(4)
178.5(6)
124.4(3)
123.9(3)
109.4(4)
124.9(7)
126.2(7)
107.7(9)
122.8(4)
124.0(4)
111.6(5)
122.5(6)
127.0(7)
107.0(9)
4. Summary
We report here a number of new ruthenium complexes with
structures based on the common piano-stool [(C5R5)RuLn] (R ¼ H
or Me) architecture, and containing the pyrrolidinylalkylphos-
phine ligands I and II. These particular ligands appear to share the
same steric properties as the more conventional phosphines dppe
and Ph2PMe, respectively, based on solid state structural studies.
Quite unexpectedly, the IR studies involving the CO derivatives
were not as definitive in establishing the donor properties ofþthese
phosphines when bound to the Ru(II) fragment {Cp*Ru(CO)} , and
thus their effect on the metal remains unclear at the moment. We
hope to expand this investigation to include a broader range of
pyrrolidinylalkylphosphines and ruthenium complexes in our
pursuit for better insight into their impact on ruthenium
chemistry.
P(2)eN(4)
Ru(1)ecentroid
a
Calculated distance.
carbonyl ligand in the complex [Cp*Ru(CO)(PMe3)2][PF6] occurs at
n
(CO) ¼ 1935 cmꢂ1 [17], which is lower than that observed for
complex 5b, and thus indicates PMe3 is a better donor than ligand II.
Interestingly, this contrasts a separate study where ligand II was
revealed to be a better donor phosphine compared to PMe3, based
Acknowledgements
on
n
(CO) absorption data. [3c].
During the course of our efforts to explore the substitution
We are very grateful for the financial support provided by the
Natural Sciences and Engineering Research Council (NSERC) of
Canada.
chemistry of complexes 1 and 2, we also attempted to synthesize
coordinatively unsaturated, 16-electron complexes of the type
[Cp*Ru(PP)]þ (PP ¼ dpyrpe or (pyr2PMe)2). We were motivated by
the expectation that such complexes might possess exceptional
catalytic potential. Clearly, such species could at least be trapped
using a suitable ligand (i.e., complexes 4a,b and 5a,b), which
provided indirect evidence for their production. Interestingly,
when complex 1 is treated with NaBArf4 in either CH2Cl2 or diethyl
ether, rather than preparing the corresponding coordinatively
unsaturated, 16-electron complex, the 18-electron complex
Appendix A. Supplementary data
CCDC 823355, 823356 and 823357 contain the supplementary
crystallographic data for complexes 2, 3 and 4a, respectively. These
data can be obtained free of charge from The Cambridge Crystal-
lographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
[Cp*Ru(N2)(dpyrpe- 2P)][BAr4f ], 4c, was observed to form when the
k
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Coordinatively unsaturated complexes [Cp*Ru(PP)]þ generally
promote oxidative addition of dihydrogen to form the corre-
sponding Ru(IV) dihydride complexes [Cp*RuH2(PP)]þ [9c,16,18,19].
Indeed, when complex 1 is treated with NaBArf4 under an H2
atmosphere, the Ru(IV) dihydride [Cp*RuH2(dpyrpe-
forms. Complex 7 produces a sharp singlet at
¼ 135.6 ppm in its
k
2P)][BArf4], 7,
d
31P{1H} NMR spectrum. The most diagnostic feature of the 1H NMR
spectrum of 7 is a triplet centred at
d
¼ ꢂ9.76 ppm (2JPH ¼ 29 Hz),
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type [(C5R5)MH2(PP)]þ (R ¼ H or Me; M ¼ Fe or Ru) possess
a transoid arrangement of the hydride ligands [9c,18,20], and thus
this is likely the case for 7 as well. Surprisingly, extending these

M.T. Beach et al. / Journal of Organometallic Chemistry 696 (2011) 3198e3205
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