Synthesis and characterization of iron and ruthenium complexes bearing P-N ligands based on 8-hydroxyquinoline

Article abstract of DOI:10.1016/j.ica.2010.05.019

The synthesis of bidentate aminophosphine ligands (PN^quin) based on 8-hydroxyquinoline is described. These ligands react with cis-Fe(CO) ₄Br₂ to give selectively octahedral complexes of the type cis,cis-Fe(PN^quin)(CO)₂Br₂. There is only one isomer formed where the two CO and the two bromide ligands adopt a cis configuration. The reaction of [RuCp(CH₃CN)₃]PF ₆ with PN^quin ligands affords the halfsandwich complexes [RuCp(PN^quin)(CH₃CN)]PF₆ in high isolated yields. Likewise, treatment of [Ru(η⁶-p-cymene)(μ-Cl)Cl] ₂ with PN^quin in the presence of AgCF₃SO ₃ affords halfsandwich complexes of the type [Ru(η⁶-p- cymene)(PN^quin)Cl]CF₃SO₃. All ligands and complexes are characterized by NMR and IR spectroscopy. The X-ray structure of representative compounds is reported. In addition, the relative stability of isomeric structures and conformers of Fe(PN^quin-Ph)(CO) ₂Br₂ is studied by means of DFT calculations.

Full text of DOI:10.1016/j.ica.2010.05.019

Inorganica Chimica Acta 363 (2010) 3674–3679
Contents lists available at ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Synthesis and characterization of iron and ruthenium complexes bearing
P–N ligands based on 8-hydroxyquinoline
David Benito-Garagorri a, Wolfgang Lackner-Warton a, Christina M. Standfest-Hauser a, Kurt Mereiter b,
Karl Kirchner a,
*
a Institute of Applied Synthetic Chemistry, Vienna University of Technology, Getreidemarkt 9, A-1060 Vienna, Austria
b Institute of Chemical Technologies and Analytics, Vienna University of Technology, Getreidemarkt 9, A-1060 Vienna, Austria
a r t i c l e i n f o
a b s t r a c t
The synthesis of bidentate aminophosphine ligands (PNquin) based on 8-hydroxyquinoline is described.
These ligands react with cis-Fe(CO)4Br2 to give selectively octahedral complexes of the type cis,cis-Fe(PN-
quin)(CO)2Br2. There is only one isomer formed where the two CO and the two bromide ligands adopt a cis
configuration. The reaction of [RuCp(CH3CN)3]PF6 with PNquin ligands affords the halfsandwich com-
Article history:
Received 12 November 2009
Received in revised form 28 April 2010
Accepted 11 May 2010
Available online 19 May 2010
plexes [RuCp(PNquin)(CH3CN)]PF6 in high isolated yields. Likewise, treatment of [Ru(
g
6-p-cymene)(
6-p-
l-
Cl)Cl]2 with PNquin in the presence of AgCF3SO3 affords halfsandwich complexes of the type [Ru(
g
Keywords:
Phosphinito quinoline ligands
Iron complexes
Ruthenium complexes/carbonyl complexes
DFT calculations
cymene)(PNquin)Cl]CF3SO3. All ligands and complexes are characterized by NMR and IR spectroscopy.
The X-ray structure of representative compounds is reported. In addition, the relative stability of isomeric
structures and conformers of Fe(PNquin-Ph)(CO)2Br2 is studied by means of DFT calculations.
Ó 2010 Elsevier B.V. All rights reserved.
1. Introduction
dral molybdenum complexes of the type Mo(PNpy)(CO)4 [5] have
been reported. Woollins and co-workers described the synthesis
The construction of phosphorus–nitrogen and phosphorous–
oxygen bonds, in contrast to phosphorus–carbon bonds, is gener-
ally achieved by rather simple synthetic procedures, i.e., primary
or secondary amines or primary alcohols are reacted with R2PCl
in the presence of base. R2PCl may contain both bulky and/or elec-
tron-rich dialkyl phosphines as well as P–O and P–N bond contain-
ing achiral and chiral phosphite units derived from diols,
aminoalcohols, and diamines [1]. It is thus not surprising that in re-
cent years such compounds have attracted increasing attention as
ligands because of their bonding versatility with metal centers
allowing them to form a large number of complexes with interest-
ing and unique properties [2].
of several Pd, Pt, and Au complexes featring the PNpy ligand
PPh2NHpy [7].
N
N
NH
N
NH
HN
PR2
O
PR2
PR2
R2P
III (PNquin
)
II (PNpy
)
I (PNP)
In the present work we extend our ongoing studies on PN com-
plexes and describe the synthesis of several iron(II) and ruthe-
nium(II) complexes of the types cis,cis-Fe(PNquin)(CO)2Br2,
In this context, we have recently focused on the synthesis of a
series of tridentate (pincer) PNP ligands (I) [3] and bidentate PNpy
ligands (II) [4,5] in which an amine acts as spacer between the aro-
matic pyridine ring and the phosphines. With PNP ligands we have
thus far studied their reactivity towards different transition metal
fragments which has resulted in the preparation of a range of new
pincer complexes, including the first heptacoordinated molybde-
num pincer complexes [3a], various iron complexes capable of act-
ing as CO sensors [3d], and several pentacoordinated nickel
complexes [6]. As PNpy ligands are concerned, the synthesis of a
series of square planar Ni(II) and Pd(II) complexes [4] and octahe-
[RuCp(PNquin)(CH3CN)]PF6, and [Ru( 6-p-cymene)(PNquin)Cl]CF3SO3
g
featuring phosphinito quinoline ligands PNquin (III). Some ligands
of the type III and Ru(II), Ni(II), and Pd(II) complexes thereof have
been already described in the recent literature [8–12].
2. Experimental
2.1. General procedure
All manipulations were performed under an inert atmosphere
of argon by using Schlenk techniques. The solvents were purified
* Corresponding author. Tel.: +43 1 58801 15340; fax: +43 1 58801 16399.
E-mail address: kkirch@mail.zserv.tuwien.ac.at (K. Kirchner).
0020-1693/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2010.05.019

D. Benito-Garagorri et al. / Inorganica Chimica Acta 363 (2010) 3674–3679
3675
according to standard procedures [13]. cis-Fe(CO)4Br2 [14]
[RuCp(CH3CN)3]PF6 [15], and [Ru( -Cl)Cl]2 [16]
6-p-cymene)(
20 °C): 10.57 (s, 1H, quin), 8.80 (s, 1H, quin), 7.88–7.73 (m, 10H,
Ph), 7.35–7.18 (m, 4H, quin). 13C NMR (d, acetone-d6, 20 °C):
212.0 (d, J = 24.2 Hz, CO), 211.2 (d, J = 25.0 Hz, CO). All other reso-
nances are not informative and have not been assigned. 31P NMR
(d, acetone-d6, 20 °C): 172.3. IR (attenuated total reflection (ATR),
g
l
were prepared according to the literature. The deuterated solvents
were purchased from Aldrich and dried over 4 Å molecular sieves.
1H, 13C, and 31P NMR spectra were recorded on a Bruker AVANCE-
250 spectrometer and were referenced to SiMe4 and H3PO4 (85%),
respectively.
cmꢀ1): 2003 (
mCO), 2061 (mCO).
2.2.5. cis,cis-Fe(PNquin-iPr)(CO)2Br2 (2b)
2.2. Syntheses
This complex was prepared analogously to 2a with 1b (225 mg,
0.86 mmol) and cis-Fe(CO)4Br2 (282 mg, 0.86 mmol) as the starting
materials. Yield: 408 mg (89%). Anal. Calc. for C17H20Br2FeNO3P: C,
38.31; H, 3.78; N, 2.63. Found: C, 38.29; H, 3.70; N, 2.69%. 1H NMR
(d, acetone-d6, 20 °C): 10.51 (s, 1H, quin), 8.78 (d, J = 5.5 Hz, 1H,
quin), 8.00 (s, 1H, quin), 7.83–7.79 (m, 3H, quin), 3.07 (s, 1H,
CH(CH3)2), 2.86 (s, 1H, CH(CH3)2), 1.59 (dd, J = 3.1 Hz, J = 15.5 Hz,
CH(CH3)2), 1.44 (dd, J = 4.1 Hz, J = 18.4 Hz, CH(CH3)2), 1.25 (dd,
J = 5.0 Hz, J = 13.4 Hz, CH(CH3)2), 0.68 (dd, J = 5.9 Hz, J = 16.0 Hz,
CH(CH3)2). 13C NMR (d, acetone-d6, 20 °C): 213.8 (d, J = 21.8 Hz,
CO), 211.6 (d, J = 23.5 Hz, CO), 164.1 (quin), 147.8 (d, J = 5.2 Hz,
quin), 141.5 (quin), 138.6 (quin), 130.1 (quin), 128.9 (quin), 125.5
(quin), 122.8 (quin), 122.1 (quin), 34.0 (d, J = 16.1 Hz, CH(CH3)2),
31.8 (d, J = 29.9 Hz, CH(CH3)2), 17.5 (CH(CH3)2), 17.2 (CH(CH3)2),
16.9 (CH(CH3)2), 15.0(CH(CH3)2). 31P NMR (d, acetone-d6, 20 °C):
2.2.1. PNquin-Ph (1a)
To a solution of 8-hydroxyquinoline (1.6 g, 11.1 mmol) and tri-
ethylamine (1.5 mL, 11.1 mmol) in toluene (50 mL) PPh2Cl (2.0 mL,
11.1 mmol) was added dropwise at 0 °C and the mixture was then
stirred for additional 3 h at 80 °C. After that the solution was fil-
tered and the solvent was removed under vacuum to give 1a as a
pale yellow oil. Yield: 2.7 g (74%). Anal. Calc. for C21H16NOP: C,
76.59; H, 4.90; N, 4.25. Found: C, 76.70; H, 4.81; N, 4.29%. 1H
NMR (d, CDCl3, 20 °C): 8.96 (dd, J = 1.5 Hz, J = 4.3 Hz, 1H, quin),
8.13 (dd, J = 1.8 Hz, J = 8.2 Hz, 1H, quin), 7.87–7.81 (m, 4H, quin),
7.52–7.26 (m, 10H, Ph). 13C NMR (d, CDCl3, 20 °C): 149.4 (quin),
147.9 (quin), 141.8 (d, J = 18.4 Hz, Ph), 135.8 (quin), 130.8 (d,
J = 22.4 Hz, Ph), 129.6 (Ph), 128.4 (d, J = 6.9 Hz, Ph), 126.5 (quin),
122.1 (quin), 121.5 (quin), 117.9 (quin), 117.3 (d, J = 13.4 Hz, quin),
110.0 (quin). 31P NMR (d, CDCl3, 20 °C): 118.4.
214.9. IR (ATR, cmꢀ1): 1998 (
mCO), 2050 (mCO).
2.2.6. cis,cis-Fe(PNquin-BIPOL)(CO)2Br2 (2c)
2.2.2. PNquin-iPr (1b)
This complex was prepared analogously to 2a with 1c (325 mg,
0.90 mmol) and cis-Fe(CO)4Br2 (296 mg, 0.90 mmol) as the starting
materials. Yield: 431 mg (76%). Anal. Calc. for C23H14Br2FeNO5P: C,
43.78; H, 2.24; N, 2.22. Found: C, 43.89; H, 2.30; N, 2.18%. 1H NMR
(d, acetone-d6, 20 °C): 10.47 (s, 1H, quin), 8.80 (s, 1H, quin), 7.78–
7.18 (m, 12H, quin and Ph). 13C NMR (d, acetone-d6, 20 °C): 209.6
(d, J = 19.5 Hz, CO), 209.0 (d, J = 13.2 Hz, CO). All other resonances
are not informative and have not been assigned. 31P NMR (d, ace-
This ligand has been prepared analogously to 1a with 8-
hydroxyquinoline (1.1 g, 7.6 mmol), iPr2PCl (1.2 mL, 7.6 mmol)
and triethylamine (1.1 mL, 7.6 mmol) as the starting materials.
Yield: 1.4 g (69%). Anal. Calc. for C15H20NOP: C, 68.95; H, 7.71; N,
5.36. Found: C, 69.04; H, 7.80; N, 5.25%. 1H NMR (d, CDCl3,
20 °C): 8.92 (dd, J = 1.5 Hz, J = 4.0 Hz, 1H, quin), 8.07 (dd,
J = 1.5 Hz, J = 8.2 Hz, 1H, quin), 7.55–7.41 (m, 1H, quin), 7.39–7.32
(m, 3H, quin), 2.17 (m, J = 7.2 Hz, 2H, CH(CH3)2), 1.30 (dd,
J = 7.0 Hz, J = 11.3 Hz, 6H, CH(CH3)2), 1.14 (dd, J = 7.0 Hz,
J = 15.9 Hz, 6H, CH(CH3)2). 13C NMR (d, CDCl3, 20 °C): 149.3 (quin),
147.8 (quin), 141.5 (quin), 135.7 (quin), 126.5 (quin), 121.3 (quin),
120.8 (quin), 116.3 (d, J = 18.8 Hz, quin), 109.9 (quin), 28.9
(CH(CH3)2), 28.6 (CH(CH3)2), 17.8 (d, J = 23.4 Hz, CH(CH3)2), 17.5
(d, J = 11.1 Hz, CH(CH3)2). 31P NMR (d, CDCl3, 20 °C): 158.2.
tone-d6, 20 °C): 191.3. IR (ATR, cmꢀ1): 2018 (
mCO), 2065 (mCO).
2.2.7. [RuCp(PNquin-Ph)(CH3CN)]PF6 (3a)
A solution of [RuCp(CH3CN)3]PF6 (0.382 g, 0.881 mmol) und 1a
(0.290 g, 0.881 mmol) in CH2Cl2 (5 mL) was stirred at room tem-
perature for 2 h. After that time the solution was filtered and the
solvent was removed under vacuum. After redissolving the residue
in CH2Cl2, the yellow product was precipitated by addition of Et2O,
collected on a glass frit, washed twice with Et2O and dried under
vacuum. Yield: 0.482 g (80%). Anal. Calc. for C28H24F6N2OP2Ru: C,
49.35; H, 3.55; N, 4.11. Found: C, 49.21; H, 3.61; N, 4.22%. 1H
2.2.3. PNquin-BIPOL (1c)
This ligand has been prepared analogously to 1a with 8-
hydroxyquinoline (1.0 g, 6.9 mmol), 2-chlorodibenzo[d,f][1,3,2]
dioxaphosphepine (1.7 g, 6.9 mmol) and triethylamine (1.0 mL,
6.9 mmol) as the starting materials. Yield: 2.0 g (82%). Anal. Calc.
for C21H14NO3P: C, 70.20; H, 3.92; N, 3.90. Found: C, 70.11; H,
3.80; N, 3.89%. 1H NMR (d, CDCl3, 20 °C): 9.05 (dd, J = 1.2 Hz,
J = 4.3 Hz, 1H, quin), 8.17 (dt, J = 1.2 Hz, J = 7.3 Hz, 1H, quin),
7.57–7.28 (m, 12H, quin and Ph). 13C NMR (d, CDCl3, 20 °C):
149.6 (d, J = 4.6 Hz, quin), 149.3 (Ph), 149.1 (quin), 147.9 (quin),
135.9 (quin), 131.5 (d, J = 3.4 Hz, Ph), 129.9 (d, J = 1.2 Hz, Ph),
129.1 (Ph), 128.3 (quin), 126.8(quin), 125.2 (Ph), 122.5 (d,
J = 1.2 Hz, Ph), 121.8 (quin), 118.7 (d, J = 4.0 Hz, quin), 110.0 (quin).
31P NMR (d, CDCl3, 20 °C): 142.1.
1
NMR (d, CD2Cl2, 20 °C): 9.67 (d, JHH = 4.34 Hz, 1H, quin), 8.39
1
4
(dd, JHH = 8.34 Hz, JPH = 1.26 Hz, 1H, quin), 7.80–7.40 (m, 14H,
Ph, quin), 4.49 (s, 5H, Cp), 2.08 (s, 3C, CH3CN). 13C NMR (d, CD2Cl2,
20 °C): 161.9 (s, quin), 148.7 (s, quin), 146.5 (s, Ph), 139.4 (s, quin),
134.4 (s, quin), 131.0–128.2 (m, Ph + quin), 124.7 (s, quin), 122.4 (s,
quin), 121.1 (s, quin), 79.7 (d, JCP = 2.87 Hz, Cp), 3.3 (s, CH3CN). 31
NMR (d, CD2Cl2, 20 °C): 160.0, ꢀ142.8 (m, PF6ꢀ).
P
2.2.8. [RuCp(PNquin-iPr)(CH3CN)]PF6 (3b)
This complex was prepared analogously to 3a with
[RuCp(CH3CN)3]PF6 (0.245 g, 0.565 mmol) and 1b (0.147 g,
0.565 mmol) as starting materials. Yield: 0.324 g (94%). Anal. Calc.
for C22H28F6N2OP2Ru: C, 43.78; H, 2.24; N, 2.22. Found: C, 43.67; H,
2.2.4. cis,cis-Fe(PNquin-Ph)(CO)2Br2 (2a)
1
To a solution of cis-Fe(CO)4Br2 (318 mg, 0.97 mmol) in toluene
(15 mL) 1a (318 mg, 0.97 mmol) was added whereupon an imme-
diate evolution of CO was observed. Once the CO evolution sub-
sided the reaction mixture was stirred at room temperature for
1 h and the solvent was decanted from the resulting brown solid,
which was washed twice with Et2O and dried under vacuum. Yield:
478 mg (82%). Anal. Calc. for C23H16Br2FeNO3P: C, 45.96; H, 2.68; N,
2.33. Found: C, 45.09; H, 2.70; N, 2.41%. 1H NMR (d, acetone-d6,
2.30; N, 2.16%. 1H NMR (d, CD2Cl2, 20 °C): 9.75 (d, JHH = 4.11 Hz,
1
1H, quin), 8.33 (d, JHH = 7.99 Hz, 1H, quin), 7.65–7.40 (m, 4H,
1
quin), 4.69 (s, 5H, Cp), 2.72 (m, JHH = 7.42 Hz, 2H, CH(CH3)2),
2.31 (s, 3C, CH3CN), 1.45–1.10 (m, 12H, CH3). 13C NMR (d, CD2Cl2,
2
20 °C): 161.8 (d, JCP = 1.15 Hz, quin), 149.9 (d, JCP = 4.02 Hz, quin),
139.1 (s, quin), 139.0 (d, 3JCP = 5.17 Hz, quin), 131.0 (s, quin), 128.6
(s, CH3CN), 128.1 (s, quin), 123.7 (s, quin), 121.2 (d, JCP = 4.60 Hz,
quin), 120.9 (s, quin), 78.0 (d, JCP = 2.30 Hz, Cp), 34.4 (d,

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D. Benito-Garagorri et al. / Inorganica Chimica Acta 363 (2010) 3674–3679
1
1JCP = 25.86 Hz, CH(CH3)2), 32.2 (d, JCP = 23.56 Hz, CH(CH3)2), 17.5
2.2.12. [Ru(
This complex was prepared analogously to 4a with [RuCl2(g
6-p-
g
6-p-cymene)(PNquin-BIPOL)Cl]CF3SO3 (4c)
2
2
(d, JCP = 3.45 Hz, CH3), 17.0 (d, JCP = 8.62 Hz, CH3), 16.2 (d,
2JCP = 4.60 Hz, CH3), 3.9 (s, CH3CN). 31P NMR (d, CD2Cl2, 20 °C):
194.3, ꢀ142.8 (m, PF6ꢀ).
cymene)]2 (0.152 g, 0.248 mmol), 1c (0.178 g, 0.495 mmol), and
AgCF3SO3 (0.127 g, 0.495 mmol) as starting materials. Yield:
0.328 g (0.421 mmol; 85%). Anal. Calc. for C32H28ClF3NO6PRuS: C,
49.33; H, 3.62; N, 1.80. Found: C, 49.21; H, 3.72; N, 1.91%. 1H
2.2.9. [RuCp(PNquin-BIPOL)(CH3CN)]PF6 (3c)
1
NMR (d, CD2Cl2, 20 °C): 9.90 (d, JHH = 5.03 Hz, 1H, quin), 8.57 (d,
This complex was prepared analogously to 3a with
[RuCp(CH3CN)3]PF6 (0.387 g, 0.891 mmol) and 1c (0.320 g,
0.891 mmol) as starting materials. Yield: 0.590 g (93%). Anal. Calc.
for C28H22F6N2O3P2Ru: C, 47.27; H, 3.12; N, 3.94. Found: C, 47.09;
H, 3.08; N, 4.07%. 1H NMR (d, CD2Cl2, 20 °C): 9.79 (d, 1JHH = 4.80 Hz,
1H, Quin1), 8.44 (dd, 1JHH = 8.22 Hz, 4JPH = 1.14 Hz, 1H, quin3), 7.90–
7.10 (m, 14H, Ph, quin), 4.74 (d, JPH = 0.69 Hz, 5H, Cp), 2.53 (s, 3C,
CH3CN). 13C NMR (d, CD2Cl2, 20 °C): 162.7 (s, 1C, quin1), 149.6 (d,
1JHH = 7.99 Hz, 1H, quin), 7.92–7.48 (m, 12H, Ph, quin), 6.40 (d,
1
1JHH = 6.17 Hz, 1H, cym), 6.18 (d, JHH = 6.40 Hz, 1H, cym), 5.94 (d,
1
1JHH = 6.40 Hz, 1H, cym), 5.37 (d, JHH = 6.17 Hz, 1H, cym), 1.93
1
(m, JHH = 6.85 Hz, 1H, CH(CH3)2), 1.79 (s, 3H, CH3), 0.78 (d,
1JHH = 6.94 Hz, 3H, CH(CH3)2), 0.76 (d, 1JHH = 6.17 Hz, 3H, CH(CH3)2).
13C NMR (d, CD2Cl2, 20 °C): 163.9 (s, quin), 149.3 (s, Ph), 146.7 (s,
Ph), 144.3 (s, quin), 141.1 (s, quin), 137.8 (s, quin), 131.1 (s, quin),
4
4
2
10
130.9 (d, JCP = 1.72 Hz, Ph), 130.4 (d, JCP = 1.72 Hz, Ph), 130.1 (s,
2JCP = 12.64 Hz, 1C, Ph1), 147.6 (d, JCP = 6.90 Hz, 1C, Ph ), 146.2
(d, JCP = 1.72 Hz, 1C, quin8), 139.7 (s, 1C, quin3), 139.5 (s, 1C,
2
Ph), 129.5 (s, Ph), 129.1 (s, Ph), 128.6 (s, quin), 126.5 (s, quin),
4
quin9), 131.0 (s, 1C, quin4), 130.5–121.7 (m, 13C, Ph + quin),
121.5 (s, 1C, quin7), 79.9 (d, JCP = 3.45 Hz, 5C, Cp), 4.3 (s, 1C, CH3CN).
31P NMR (d, CD2Cl2, 20 °C): 175.6, ꢀ142.8 (m, PF6ꢀ).
127.4 (s, Ph), 123.7 (d, JCP = 4.60 Hz, Ph), 123.1 (s, quin), 122.5
4
(d, JCP = 5.75 Hz, Ph), 121.5 (s, quin), 111.3 (s, cym), 108.4 (s,
2
2
cym), 99.4 (d, JCP = 9.20 Hz, cym), 98.3 (d, JCP = 5.75 Hz, cym),
2
2
94.4 (d, JCP = 4.60 Hz, cym), 90.0 (d, JCP = 4.60 Hz, cym), 30.5 (s,
CH(CH3)2), 21.7 (s, CH(CH3)2), 20.7 (s, CH(CH3)2), 18.3 (s, H3). 31P
NMR (d, CD2Cl2, 20 °C): 153.8.
2.2.10. [Ru(
g
6-p-cymene)(PNquin-Ph)Cl]CF3SO3 (4a)
6-p-cymene)(
-Cl)Cl]2 (0.237 g, 0.387 mmol)
A solution of [Ru(
g
l
and 1a (0.255 g, 0.775 mmol) in CH2Cl2 (2 mL) was treated with
AgCF3SO3 (0.199 g, 0.775 mmol) and was stirred at room tempera-
ture for 2 h. After that time the solution was filtered and the sol-
vent was removed under vacuum. After redissolving the residue
in CH2Cl2, the yellow product was precipitated by addition of
Et2O, collected on a glass frit, washed twice with Et2O and dried
under vacuum. Yield: 0.500 g (0.667 mmol; 86%). Anal. Calc. for
2.3. X-ray structure determination for 2a and 3cꢁ½(C2H5)2O
X-ray data were collected on a Bruker Smart APEX CCD area
detector diffractometer using graphite-monochromated Mo K
a
radiation (k = 0.71073 Å) and 0.3° -scan frames. Corrections for
x
absorption, k/2 effects, and crystal decay were applied [17]. After
structure solution with program SHELXLS97 refinement on F2 was
carried out with the program SHELXL97 [18]. Non-hydrogen atoms
were refined anisotropically. All H atoms were placed in calculated
positions and thereafter treated as riding.
C
32H30ClF3NO4PRuS: C, 51.31; H, 4.04; N, 1.87. Found: C, 50.89;
H, 4.12; N, 1.81%. 1H NMR (d, CD2Cl2, 20 °C): 10.07 (d,
1JHH = 5.25 Hz, 1H, quin), 8.57(d, JHH = 7.54 Hz, 1H, quin), 8.14
1
(m, 2H, Ph), 7.90–7.90 (m, 8H, Ph), 7.30–7.10 (m, 4H, quin), 5.90
Important crystallographic data are: 2a:
C23H16Br2FeNO3P,
1
1
(d, JHH = 6.62 Hz, 1H, cym), 5.55 (d, JHH = 6.17 Hz, 1H, cym), 5.47
Mr = 601.01, orange prism, 0.36 ꢂ 0.23 ꢂ 0.20 mm, monoclinic,
1
1
(d, JHH = 6.40 Hz, 1H, cym), 5.13 (d, JHH = 6.17 Hz, 1H, cym), 2.39
space group P21/c (No. 14), a = 10.2554(5) Å, b = 10.9390(5) Å,
1
c = 19.7572(10) Å, b = 93.306(1)°, V = 2212.8(2) Å3, Z = 4,
l =
(m, JHH = 6.80 Hz, 1H, CH(CH3)2), 1.53 (s, 3H, CH3), 1.12 (d,
1JHH = 7.08 Hz, 3H, CH(CH3)2), 0.96 (d, 1JHH = 6.85 Hz, 3H, CH(CH3)2).
13C NMR (d, CD2Cl2, 20 °C): 162.8 (s, quin), 145.1 (s, quin), 141.3 (s,
quin), 137.1–128.0 (m, Ph + quin), 126.0 (s, quin), 123.2 (d,
JCP = 6.32 Hz, quin), 122.8 (s, quin), 114.1 (s, Cym), 101.6 (s, cym),
4.391 mmꢀ1, dx = 1.804 g cmꢀ3, T = 173(2) K. Of 28777 reflections
were collected up to hmax = 30.0° and, after applying absorption
corrections, merged to 6221 independent data (Rint = 0.028); final
R
indices: R1 = 0.0422 (5595 reflections with I > 2r(I)),
2
2
96.8 (d, JCP = 5.17 Hz, cym), 96.5 (d, JCP = 6.90 Hz, cym), 92.8 (d,
2JCP = 3.45 Hz, cym), 89.2 (d, 2JCP = 2.30 Hz, cym), 30.7 (s, CH(CH3)2),
22.3 (s, CH(CH3)2), 20.7 (s, CH(CH3)2), 17.7 (s, CH3). 31P NMR (d,
CD2Cl2, 20 °C): 126.2.
wR2 = 0.0803 (all data), 296 parameters. One bromide (Br2) and
one carbonyl group (C23–O3) in trans-disposition to each other
and cis to P and N were partly disordered with a 73/27% comple-
mentary occupation by CO and Br, respectively. Distance restraints
were used to stabilize the refinement of these two CO groups.
3cꢁ½(C2H5)2O: C30H27F6N2O3.5P2Ru, Mr = 784.55, orange plates,
0.42 ꢂ 0.30 ꢂ 0.20 mm, monoclinic, space group P21/c (No. 14),
a = 7.4420(6) Å, b = 13.5287(11) Å, c = 29.226(2) Å, b = 95.399(1)°,
2.2.11. [Ru(
This complex was prepared analogously to 4a with [RuCl2(
g
6-p-cymene)(PNquin-iPr)Cl]CF3SO3 (4b)
g
6-p-
cymene)]2 (0.251 g, 0.409 mmol), 1b (0.213 g, 0.818 mmol) and
AgCF3SO3 (0.210 g, 0.818 mmol) as starting materials. Yield:
0.494 g (89%). Anal. Calc. for C26H34ClF3NO4PRuS: C, 45.85; H,
5.03; N, 2.06. Found: C, 45.74; H, 5.11; N, 2.09%. 1H NMR (d, CD2Cl2,
20 °C): 9.97 (d, 1JHH = 4.80 Hz, 1H, quin), 8.55 (d, 1JHH = 8.22 Hz, 1H,
V = 2929.5(4) Å3,
Z = 4,
l
= 0.721 mmꢀ1
,
dx = 1.697 g cmꢀ3
,
T = 100(2) K. Of 31247 reflections were collected up to hmax = 30.0°
and, after applying absorption corrections, merged to 8496 inde-
pendent data (Rint = 0.020); final R indices: R1 = 0.0297 (7997
1
quin), 7.90–7.60 (m, 4H, quin), 3.45 (m, JHH = 7.22 Hz, 1H,
reflections with I > 2r(I)), wR2 = 0.0770 (all data), 416 parameters.
1
CH(CH3)2), 2.28 (m, JHH = 7.42 Hz, 1H, CH(CH3)2), 2.16 (m,
1JHH = 6.91 Hz, 1H, CH(CH3)2), 1.85–1.60 (m, 6H, CH3), 1.62 (s, 3H,
2.4. Computational details
1
CH3), 1.20–1.00 (m, 6H, CH3), 0.92 (d, JHH = 7.08 Hz, 1H, CH3),
0.80–0.65 (m, 3H, CH3).13C NMR (d, CD2Cl2, 20 °C): 162.2 (s, quin),
Calculations were performed using the GAUSSIAN 03 software
package on the Phoenix Linux Cluster of the Vienna University of
Technology [19]. The geometries and relative energies of 2a–c,
and isomers thereof were optimized at the B3LYP level [20] with
the Stuttgart/Dresden ECP (SDD) basis set [21] to describe the elec-
2
146.8 (d, JCP = 5.17 Hz, quin), 140.9 (s, quin), 137.2 (d,
3JCP = 6.32 Hz, quin), 131.1 (s, quin), 129.0 (s, quin), 124.9 (s, quin),
122.2 (s, quin), 122.1 (d, JCP = 5.17 Hz, quin), 113.5 (s, cym), 99.1 (s,
cym), 94.8 (d, 2JCP = 4.02 Hz, cym), 93.6 (d, 2JCP = 3.45 Hz, cym), 92.1
2
2
**
(d, JCP = 6.32 Hz, cym), 87.5 (d, JCP = 2.87 Hz, cym), 34.5 (d,
trons of the iron atom. For all other atoms the 6-31g basis set was
1JCP = 28.74 Hz, CH(CH3)2), 32.6 (d, JCP = 16.67 Hz, CH(CH3)2), 30.8
employed [22]. Frequency calculations were performed to confirm
the nature of the stationary points yielding no imaginary frequency
for the minima. A scaling factor of 0.9614 was applied for the CO
1
(s, CH(CH3)2), 21.7 (s, CH(CH3)2), 21.2 (s, CH(CH3)2), 17.8 (s, CH3),
17.8–17.1 (m, CH3). 31P NMR (d, CD2Cl2, 20 °C): 160.2.

D. Benito-Garagorri et al. / Inorganica Chimica Acta 363 (2010) 3674–3679
3677
frequencies [23]. Solvent effects (toluene) were considered
through single point energy calculations with the optimized geom-
etries using the Polarizable Continuum Model (PCM) initially de-
vised by Tomasi and co-workers [24] as implemented in GAUSSIAN
03 [25] and, thus, the energy values can be taken as free energy
[26]. The molecular cavity was based on the united atom topolog-
ical model applied on UAHF radii, optimized for the HF/6-31G(d)
level.
N
O
CO
Fe
CO
Fe
R2P
CO
CO
N
1a-c
Br
Br
O
P
toluene, r.t., 1h
OC
OC
R2
Br
Br
2a-c
Scheme 2.
3. Results and discussion
3.1. Ligands
mentally observed values are given in Table 1 and show a reason-
ably good agreement.
The PNquin ligands 1a–c were prepared in 69–82% yield by
reacting 8-hydroxyquinoline with 1 equiv. of the respective chloro-
phosphine or chlorophosphite in the presence of the base NEt3
(Scheme 1). The reactions were carried out in toluene at 80 °C for
3 h. It has to be noted that the synthesis of PNquin-Ph (1a) and
PNquin-iPr (1b) has been reported elsewhere by a slightly different
methodology [8]. The ligands 1a–c were isolated as moderately air
stable solids or oils and were characterized by 1H, 13C and 31P NMR
spectroscopy. Most diagnostic is the 31P NMR spectrum, which
The molecular structure of 2a as determined by X-ray crystal-
lography confirms that the two CO and the two bromide ligands
are cis to one another with one CO ligand trans to the quinoline
nitrogen atom and one trans to a bromide ligand. A structural view
is shown in Fig. 1 with selected bond lengths and angles given in
the caption This Figure and the subsequent discussion concern
the predominant conformer of the solid state structure; by disor-
der, a second conformer with Br2 and C23–O3 in interchanged
positions is present in the solid for about quarter of all complexes.
The coordination geometry around the iron center corresponds to a
slightly distorted octahedron. All cis-bond angles about Fe are close
to 90° varying between 84° and 95°. The bite angle N–Fe–P is 85.8°.
The Fe–P, Fe–N1, Fe–C22, Fe–C23, Fe–Br1, and Fe–Br2 bond dis-
tances are 2.167(1), 2.076(2), 1.786(3), 1.786(4), 2.510(1),
2.446(1) Å, respectively. The complex exhibits significant strain
with the result that the quinoline moiety is notably twisted
(r.m.s. non-planarity 0.05 Å; interplanar angle between its two 6-
membered rings is 5.2(1)°) and that the iron and the phosphorus
deviate much from the mean plane of the quinoline, namely by
+0.37 Å for Fe and ꢀ0.73 Å for P. The angle between the mean
exhibits
a single resonance at 118.4 (1a), 158.2 (1b), and
142.1 ppm (1c), respectively (cf. 120.7 and 160.5 ppm for 1a and
1b in Ref. [8]). All other resonances are unremarkable and are
not discussed here.
3.2. Iron complexes
Treatment of cis-Fe(CO)4Br2 with 1 equiv of the respective
PNquin ligands in toluene at room temperature for 1 h afforded
the dicarbonyl dibromo complexes cis,cis-Fe(PNquin)(CO)2Br2 (2a–
c) in good isolated yields (76–82%) (Scheme 2). All complexes are
dark brown solids that are air stable in the solid state for several
days but decompose in solution within a few hours to intractable
materials. Their identity was unequivocally established by 1H, 13C
and 31P NMR, IR spectroscopy, and elemental analysis.
Table 1
Comparison of the calculated and experimental mCO absorptions.
Complex
calcd. msym
calcd. masym
exptl. msym
exptl. masym
In the 31P NMR spectra, 2a–c exhibit singlets which show the
expected low-field shifts relative to the free uncoordinated ligands
2a
2b
2c
2068
2051
2072
2023
2014
2048
2061
2050
2065
2003
1998
2018
[2a: 172.3 ppm (
2c: 191.3 ppm (
D
D
d = 53.9 ppm), 2b: 214.9 ppm (
Dd = 56.7 ppm),
d = 49.2 ppm)]. In the 13C NMR spectra of 2a–c
the carbon atoms of the two CO ligands give rise to two character-
istic low-field doublets. For instance, 2a exhibits signals at 213.8
(JPC = 21.8 Hz) and 211.6 (JPC = 23.5 Hz) ppm. The small coupling
constants are diagnostic for the phosphorus atom being in cis posi-
tion with respect to the two CO ligands. The IR spectrum of 2a–c
displays the two expected peaks for a cis dicarbonyl structure.
The scaled calculated frequencies mCO together with the experi-
ClPR2, NEt3
N
toluene, 80oC, 3h
N
O
OH
R2P
1a-c
O
O
P
P
PR2
=
P
PNquin
-iPr (1b)
Fig. 1. Molecular structure of Fe(PNquin-Ph)(CO)2Br2 (2a) showing 40% displace-
ment ellipsoids. Selected distances and angles (Å, deg): Fe–P 2.167(1), Fe–N1
2.076(2), Fe–C22 1.786(3), Fe–C23 1.786(4), Fe–Br1 2.510(1), Fe–Br2 2.446(1), N1–
Fe–P 85.83(7), N1–Fe–C22 176.1(1), Br1–Fe–P 178.09(3), Br2–Fe–C23 172.5(2).
PNquin-Ph (1a)
PNquin-BIPOL (1c)
Scheme 1.

3678
D. Benito-Garagorri et al. / Inorganica Chimica Acta 363 (2010) 3674–3679
planes of the quinoline and O1–P–Fe–Br1 is 50.8(1)°. In the six-
membered chelate ring N1–C9–C8–O1–P–Fe the angles C8–C9–
O1 = 124.0(2)° and C9–N1–Fe = 128.3(2)° are notably bigger than
the corresponding exo-angles, C7–C8–O1 = 114.3(2)° and C1–N1–
Fe = 114.3(2)°.
3.3. Ruthenium complexes
The reaction of [RuCp(CH3CN)3]PF6 with 1 equiv. of PNquin li-
gands in CH2Cl2 at room temperature for 2 h yields, on workup,
the halfsandwich complexes [RuCp(PN)(CH3CN)]PF6 (3a–c) in 80–
94% isolated yields (Scheme 4). Complexes 3 are orange solids
which are air-stable both in the solid state and in solution for sev-
eral days. They have been characterized by 1H, 13C and 31P NMR
spectroscopy, and elemental analysis. The 1H NMR spectra of 3a–
c bear no unusual features.
Thus, the Cp ligand exhibits a singlet at about 4.6 ppm and the
proton resonance of the CH3CN ligand gives a doublet in the range
of 2.1–2.5 ppm. In the 31P NMR spectra of 3a–c the PNquin ligand
exhibits, respectively, a singlet at 160.0, 194.3, and 175.6 ppm.
Both NMR and IR spectroscopy and X-ray crystallography
clearly reveal that the reaction of cis-Fe(CO)4Br2 with PNquin li-
gands 1a–c resulted in all cases in the selective formation of cis,-
cis-Fe(PNquin)(CO)2Br2. In principle, however, several isomers are
conceivable. We therefore determined the geometries and relative
free energies (in kcal/mol) of 2a and possible isomers and conform-
ers thereof by means of DFT/B3LYP calculations. These results are
shown in Scheme 3. The reliability of the computational method
(details in Section 2) can be checked by comparing the X-ray struc-
ture of 2a (Fig. 1) with its calculated geometry (Fig. 2). In addition,
the geometries of cis,cis-Fe(PNquin-iPr)(CO)2Br2 (2b) and cis,cis-
Fe(PNquin-BIPOL)(CO)2Br2 (2c) have also been determined (Fig. 2).
Relevant data are given in the caption. According to our calcula-
tions, 2a0 (a conformer of 2a) and A are thermodynamically more
stable than 2a by 4.0 and 4.2 kcal/mol, respectively (numbers in
parenthesis refer to toluene as solvent), while B, B0 (a conformer
of B), and C are less stable by 5.5, 3.5, and 3.8 kcal/mol, respec-
tively. However, since in the starting material cis-Fe(CO)4Br2 as
well as in 2a and 2a0, respectively, the two bromide ligands adopt
a cis geometry, isomerization processes apparently do not take
place in the course of the substitution reactions. Thus, the forma-
tion of A – having a trans-bromide arrangement – is presumably
kinetically disfavored, while the formation of B, B0, and C is ther-
modynamically unfavorable.
N
O
+
+
R2P
1a-c
Ru
Ru
NCCH3
CH2Cl2, r.t., 2h
N
PR2
NCCH3
H3CCN
O
NCCH3
3a-c
Scheme 4.
Br
Fe
Br
Br
CO
Fe
N
N
N
OC
OC
Br
Br
Fe
O
O
P
O
P
P
Ph2
Ph2
Ph2
OC
OC
CO
Br
2a'
-4.0 (-2.8)
A
2a
0.0
-4.2 (-1.6)
Br
N
CO
Fe
CO
N
N
OC
Br
OC
Br
Br
Br
Fe
Fe
O
O
O
P
P
P
Ph2
Ph2
Ph2
CO
Br
CO
Fig. 3. Molecular structure of [RuCp(PNquin-BIPOL)(CH3CN)]PF6ꢁ½(C2H5)2O
B'
3.5 (5.0)
ꢀ
B
C
(3cꢁ½(C2H5)2O) showing 50% displacement ellipsoids (PF6 and solvent omitted
5.5 (5.1)
3.8 (4.4)
for clarity). Selected distances and angles (Å, deg): Ru–C(1–5)av 2.206(2), Ru–N1
2.149(2), Ru–N2 2.059(1), Ru–P1 2.1681(4), P1–Ru–N1 89.02(4), P1–Ru–N2
95.63(4), N1–Ru–N2 84.34(6).
Scheme 3.
Br1
C1
Br2
Br1
Br1
C1
Fe
P
C2
N
Fe
C1
Fe
P
P
N
N
Br2
Br2
C2
C2
2a
2b
2c
**
Fig. 2. Optimized geometries of 2a–c calculated at the B3LYP level of theory (Fe sdd; C, N, P, O, Br, H 6-31g ). Selected distances and angles (Å, deg): 2a: Fe–P 2.223, Fe–N
2.142, Fe–C1 1.816, Fe–C2 1.801, Fe–Br1 2.491, Fe–Br2 2.532, N–Fe–P 86.7, N–Fe–C1 170.3, Br2–Fe–P 178.2, Br1–Fe–C2 173.6. 2b: Fe–P 2.248, Fe–N 2.146, Fe–C1 1.812, Fe–C2
1.796, Fe–Br1 2.492, Fe–Br2 2.537, N–Fe–P 88.8, N–Fe–C1 170.0, Br2–Fe–P 177.5, Br1–Fe–C2 175.4. 2c: Fe–P 2.175, Fe–N 2.188, Fe–C1 1.816, Fe–C2 1.815, Fe–Br1 2.475, Fe–
Br2 2.546, N–Fe–P 90.3, N–Fe–C1 171.1, Br2–Fe–P 172.5, Br1–Fe–C2 176.1.

D. Benito-Garagorri et al. / Inorganica Chimica Acta 363 (2010) 3674–3679
3679
N
O
+
R2P
1a-c
[Ru(η6-
p-cymene)(μ-Cl)Cl]2
Ru
Cl
PR2
AgCF3SO3
CH2Cl2, r.t., 2h
N
O
4a-c
Scheme 5.
The solid state structure of 3cꢁ½(C2H5)2O was determined by
single-crystal X-ray diffraction. An ORTEP diagram is depicted in
Fig. 3 with selected bond distances and angles reported in the
caption.
These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_re-
quest/cif.
Complex 3cꢁ½(C2H5)2O adopts a typical three legged piano stool
conformation with CH3CN and the N and P atoms of the PNquin li-
gand as the legs. The Ru–N(1), Ru–N(2), and Ru–P(1) distances
are 2.149(2), 2.059(2), and 2.1681(4) Å, respectively, with P(1)–
Ru–N(1), P(1)–Ru–N(2), and N(1)–Ru–N(2) angles of 89.02(4)°,
95.63(4)°, and 84.34(6)°. The Ru–C distances range from 2.163(2)
to 2.257(2) Å (mean 2.206 Å). Similar like in 2a, the chelate ring
Ru1–P1–O1–C13–C14–N1 is notably non-planar and the quinoline
moiety remarkably twisted (r.m.s. non-planarity 0.065 Å, interpla-
nar angle between its two 6-membered rings 7.0(1)°). Ru1, P1, and
O1 deviate by 0.77, 0.37, and ꢀ0.42 Å from the mean plane through
quinoline.
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Acknowledgements
D. B.-G. thanks the Basque Government (Eusko Jaurlaritza/Gobi-
erno Vasco) for a doctoral fellowship.
Appendix A. Supplementary material
CCDC 735393 and 753281contain the supplementary crystallo-
graphic data for the crystal structure of 2a and 3cꢁ½(C2H5)2O.