Fundamental study of (ferrocenylethynyl)phosphines: Correlation of steric and electronic effects in C,C cross-coupling reactions

Article abstract of DOI:10.1016/j.jorganchem.2012.01.017

Complexes [Pd(Cl)(μ-Cl)(P(CCFc)R₂)]₂ (Fc = (η⁵-C₅H₄)(η⁵-C ₅H₅); 6e, R = ^tBu; 6f, R = ^cC ₆H₁₁) and [PdCl₂(P(CCFc)R₂) ₂] (7a, R = C₆H₅; 7b, R = 2-MeC ₆H₄; 7c, R = 2,4,6-Me₃C₆H ₂; 7d, R = ^cC₄H₃O; 7e, R = ^tBu; 7f, R = ^cC₆H₁₁) are accessible by the reaction of P(CCFc)R₂ (3a-f) with either [PdCl ₂(cod)] (5) (cod = cyclo-1,5-octadiene) or [PdCl₂(SEt ₂)₂] (8). The spectroscopic, mass-spectrometric and cyclovoltammetric data of 6 and 7 were investigated and the structures of four complexes (6e, 6f, 7b, 7c) in the solid state determined. Complexes 7a-f are mononuclear with palladium in a square-planar environment and show a cis- (7b) or trans-configuration (7c) with linear FcCCP moieties in the solid state. In contrast, 6e and 6f are forming dimers with a planar Pd₂P ₂Cl₂(μ-Cl)₂ core with the ferrocenylethynyl ligands positioned above and below this plane. Electrochemical studies of phosphines 3a-3f and the appropriate seleno phosphines 4a-4f show after oxidation follow-up reactions, while a reversible behavior is found for the corresponding palladium complexes 6 and 7. UV-Vis/NIR and IR spectro-electrochemical measurements of 7f indicate moderate electronic interactions between the ferrocenyl units. All complexes are catalytically active in Heck (reaction of iodo benzene with tert-butyl acrylate) and Suzuki (2-bromo toluene or 4′-chloro acetophenone with phenyl boronic acid) C,C cross-couplings. The influence of the electronic (¹J( ³¹P-⁷⁷Se)) and the steric (Tolman cone angle) properties of the phosphine ligands on the activity of the respective palladium catalysts will be discussed.

Full text of DOI:10.1016/j.jorganchem.2012.01.017

Journal of Organometallic Chemistry 706-707 (2012) 52e65
Contents lists available at SciVerse ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Fundamental study of (ferrocenylethynyl)phosphines: Correlation of steric and
electronic effects in C,C cross-coupling reactions
*
Bianca Milde, Dieter Schaarschmidt, Petra Ecorchard, Heinrich Lang
Chemnitz University of Technology, Faculty of Science, Institute of Chemistry, Department of Inorganic Chemistry, Straße der Nationen 62, 09111 Chemnitz, Germany
a r t i c l e i n f o
a b s t r a c t
5-C5H4)(
h
5-C5H5); 6e, R ¼ tBu; 6f, R ¼ cC6H11) and
Article history:
Complexes [Pd(Cl)(
m
-Cl)(P(C^CFc)R2)]2 (Fc ¼ (
h
[PdCl2(P(C^CFc)R2)2] (7a, R ¼ C6H5; 7b, R ¼ 2-MeC6H4; 7c, R ¼ 2,4,6-Me3C6H2; 7d, R ¼ cC4H3O; 7e,
R ¼ tBu; 7f, R ¼ cC6H11) are accessible by the reaction of P(C^CFc)R2 (3aef) with either [PdCl2(cod)] (5)
(cod ¼ cyclo-1,5-octadiene) or [PdCl2(SEt2)2] (8). The spectroscopic, mass-spectrometric and cyclo-
voltammetric data of 6 and 7 were investigated and the structures of four complexes (6e, 6f, 7b, 7c) in
the solid state determined. Complexes 7aef are mononuclear with palladium in a square-planar envi-
ronment and show a cis- (7b) or trans-configuration (7c) with linear FcC^CP moieties in the solid state.
Received 22 September 2011
Received in revised form
16 January 2012
Accepted 23 January 2012
Keywords:
(Ferrocenylethynyl)phosphine
Palladium
In contrast, 6e and 6f are forming dimers with a planar Pd2P2Cl2(m-Cl)2 core with the ferrocenylethynyl
ligands positioned above and below this plane. Electrochemical studies of phosphines 3ae3f and the
appropriate seleno phosphines 4ae4f show after oxidation follow-up reactions, while a reversible
behavior is found for the corresponding palladium complexes 6 and 7. UVeVis/NIR and IR spectroe
electrochemical measurements of 7f indicate moderate electronic interactions between the ferrocenyl
units. All complexes are catalytically active in Heck (reaction of iodo benzene with tert-butyl acrylate)
and Suzuki (2-bromo toluene or 40-chloro acetophenone with phenyl boronic acid) C,C cross-couplings.
The influence of the electronic (1J(31Pe77Se)) and the steric (Tolman cone angle) properties of the
phosphine ligands on the activity of the respective palladium catalysts will be discussed.
Ó 2012 Elsevier B.V. All rights reserved.
Seleno phosphine
(Spectro-) electrochemistry
Tolman cone angle
C,C cross-coupling
1. Introduction
and chemical properties [5b,6]. Just as the alkynyl phosphines,
(ferrocenylethynyl)phosphines found use as ligands in homoge-
Recently, alkynyl phosphines of general type P(C^CR0)nR3-n
(n ¼ 1, 2, 3; R, R0 ¼ organic or organometallic single-bonded group;
R ¼ R0; R s R0) have come into focus because they are of interest due
to their versatile reaction chemistry toward different organome-
tallic and metaleorganic compounds leading into the area of, for
example, clusters [1], coordination polymers [2], polynuclear
complexes [2b,c,3], or metallacycles [4]. The properties of alkynyl
phosphines are unique including their structure, chemical behavior,
reactivity, and catalytic activity. The reaction chemistry of these
molecules is driven either by the fact that they act as P and/or C^C
donors toward metal species or by the cleavage of the PeCalkynyl
bond induced by thermolysis, photolysis or chemical activation
resulting in the formation of phosphido and acetylide fragments,
respectively [2a,4b,5]. In addition, (ferrocenylethynyl)phosphines
have gained attraction in supra- and macro-molecular chemistry
allowing the development of new materials with peculiar physical
neous C,C cross-coupling reactions (Heck and Suzuki) [2c,7], and as
redox-active compounds to study multinuclear redox processes
[5c,6,8]. Palladium-promoted Suzuki and Heck carbonecarbon
cross-couplings represent one of the most effective trans-
formations in organometallic and organic synthesis. The Heck
reaction allows to convert (un)saturated halides or triflates into
substituted alkenes in a very efficient, convenient and inexpensive
way in the presence of a base and a palladium source [9]. In this
respect, most active catalysts are bulky, electron-rich phosphine-
[10], NHC- [11], and biphenyl phosphine-based palladium
complexes [12], as well as phosphapalladacycles [12b,13]. The
Suzuki reaction is the conversion of aryl- or vinyl-boronic acids
with an aryl- or vinyl-halide to polyolefins, styrenes, and
substituted biphenyls, and has been extended to incorporate alkyl
bromides in the presence of palladium [9].
In this work we present the synthesis of a series of (ferrocenyl-
ethynyl)phosphines and their reaction behavior toward selenium
and palladium dichloride. The utilization of the appropriate phos-
phine palladium dichlorides in Heck and Suzuki C,C couplings is
reported as well.
* Corresponding author. Tel.: þ49 0 371 531 21210; fax: þ49 0 371 531 21219.
E-mail address: heinrich.lang@chemie.tu-chemnitz.de (H. Lang).
0022-328X/$ e see front matter Ó 2012 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2012.01.017

B. Milde et al. / Journal of Organometallic Chemistry 706-707 (2012) 52e65
53
2. Results and discussion
7c) were additionally carried out. The electrochemical behavior of
the newly prepared compounds (cyclic voltammetry (CV) (3, 4, 6
and 7), square wave voltammetry (SWV) (6, 7), linear sweep vol-
tammetry (LSV) (7), UVeVis/NIR spectroscopy (280e3000 nm) and
in situ IR spectroscopy (7f)) is discussed as well.
Single crystals of 6e, 6f, cis-7b, and trans-7c suitable for X-ray
diffraction studies could be obtained by diffusion of nhexane or
diethyl ether into chloroform solutions containing the appropriate
complexes at ambient temperature. The molecular structures of 6e
and 6f in the solid state are shown in Fig. 1, the ones of cis-7b and
trans-7c in Fig. 2. Important bond distances (Å), bond angles (ꢀ) and
torsion angels (ꢀ) are summarized in Table 1. For crystal and
structure refinement data see Experimental Section.
2.1. Synthesis, reaction chemistry and characterization
(Ferrocenylethynyl)phosphines P(C^CFc)R2 (Fc ¼ (
h
5-C5H4)(h5
-
C5H5); 3a, R ¼ C6H5 [6b]; 3b, R ¼ 2-MeC6H4; 3c, R ¼ 2,4,6-Me3C6H2;
3d, R ¼ cC4H3O; 3e, R ¼ tBu; 3f, R ¼ cC6H11) were synthesized by
reacting FcC^CH (1) with one equivalent of nbutyllithium and
subsequent treatment with ClPR2 (2aef) (Reaction 1).
Complexes 6e and 6f crystallize in the triclinic space group P1 as
red needles. Both species are iso-structural possessing Pd2P2Cl2(m-
Cl)2 moieties featuring a crystallographically imposed inversion
symmetry with the inversion center in the middle between the
palladium atoms Pd1 and Pd1A (symmetry transformations used to
generate equivalent atoms: ꢁxþ1, ꢁyþ1, ꢁzþ1) (Fig. 1). The (fer-
rocenylethynyl) groups are oppositely oriented with the ferrocenyl
units above or below the slightly distorted square-planar
To obtain 1st information on the Lewis-basicity of phosphines
3aef we prepared the respective seleno phosphines (Se)P(C^CFc)
R2 (4aef) by treatment of 3aef with elemental selenium in toluene
at 100 ꢀC (Experimental Section). Seleno phosphines 4aef could be
isolated in virtually quantitative yield as yellow to orange solids.
Addition of [PdCl2(cod)] (5) (cod ¼ cyclo-1,5-octadiene) to
dichloromethane solutions containing 3aef in a molar ratio of 1:2
Pd2P2Cl2(m-Cl)2 core (6e: r. m. s. deviation 0.0120 Å, highest devi-
ation from planarity observed for Pd1 with ꢁ0.0240 Å; 6f: r.m.s.
deviation 0.0049 Å, highest deviation from planarity observed
for Pd1 with ꢁ0.0098 Å) with characteristic parameters for this
type of compounds [14]. The Pd1eCl2 and Pd1eCl2A bond
distances in 6e and 6f are asymmetric with the somewhat longer
bonds situated opposite the more strongly trans influencing
(ferrocenylethynyl)phosphine substituents (Table 1). Obviously, the
gave complexes [Pd(Cl)(
m
-Cl)(P(C^CFc)R2)]2 (6e, R ¼ tBu; 6f,
R ¼ cC6H11) and cis/trans-[PdCl2(P(C^CFc)R2)2] (7a, R ¼ C6H5; 7b,
R ¼ 2-MeC6H4; 7c, R ¼ 2,4,6-Me3C6H2; 7d, R ¼ cC4H3O), respectively
(Scheme 1). While the formation of 7aed is expected, the building
of 6e and 6f surprises at first. The latter complexes are also
generated, when repeating the reactions in a 1:1 M ratio. From
these reactions it is obvious that the alkyl groups R at phosphorus
palladiumechloride distances within the Pd2(m-Cl)2 cycle
(Pd1eCl2: 6e, 2.3176(6) Å; 6f, 2.4479(6) Å) are longer as the
terminal Pd1eCl1 bonds (Pd1eCl1: 6e, 2.2755(6) Å; 6f, 2.2729(6) Å)
allegeable due to their different environment (Fig. 1, Table 1). The
bond lengths and angles of the PeC units are comparable to those
favor the formation of a palladium dimer with a planar Pd2(m-Cl)2
four-membered cycle, while aryl substituents solely gave mono-
nuclear 7aed as it could be proven by single X-ray structure
determination (see below). For bulky substituents at phosphorus
this reaction behavior is a known phenomenon [14]. It can be
explained by the different solubility of the palladium sources and
the formed complexes in dichloromethane [14a] as well as the size
of their coordinated ligands (e.g., NCMe, cod) [14f]. Another
straightforward synthesis methodology to prepare 7aef is given by
treatment of 3aef with the palladium source [PdCl2(SEt2)2] (8)
(Scheme 1). However, by this reaction exclusively 7aef are formed.
Seleno phosphines 4aef as well as complexes 6e, f and 7aef are
stable in air and moisture both in the solid state and in solution,
whereas 3aef slowly oxidize in solution. All compounds have been
observed in similar species, i.e. [PdCl(
[PdCl(
-Cl)(P(cC4H3O)3)]2 [14b], respectively. The (ethynyl)phos-
phine units are essentially linear (Table 1) which is in contrast to
other (ferrocenylethynyl) palladium complexes, e.g.
m
-Cl)(PPhn2Pr)]2 [14d] and
m
[PdCl2(P(C^CFc)Ph2)2] in which a significant deviation from line-
arity was found (PeC^C: 171, 157ꢀ) [6b]. The cyclopentadienyl
ligands at the iron centers show an almost staggered conformation
(6e: 4.6ꢀ, 6f: ꢁ2.7ꢀ).
In crystals of 7b the molecules are packed in the monoclinic
space group C2/c, in 7c the crystals are packed in the triclinic space
group P1. Complex 7b exhibits a mirror plane through the palla-
dium center Pd1, while 7c possesses an inversion center at the
central palladium atom Pd1 (Fig. 2). The crystal structure analysis
identified by elemental analysis as well as by IR and NMR (1H, 13
C
{1H}, 31P{1H}) spectroscopy. High resolution-ESI-TOF mass-spec-
trometry and single crystal X-ray structure analysis (6e, 6f, 7b and
Fe
1/2
R2
Cl
Cl
C
C
P
Cl
P
Pd
Pd
Cl
C
C
3e, 3f
R2
- cod
C
C PR2
Fe
Fe
[PdCl2(cod)] (5)
6e, 6f
3a - 3d
- cod
3a - 3f
Fe
C
C PR2
Cl
Pd
R2
[PdCl2(SEt2)2] (8)
- 2 SEt2
C
C
P
P
C
C
Fe
R2
Fe
Cl
7a - 7f
Scheme 1. Synthesis of 6e, 6f and 7ae7f from 3, 5, and 8.
3a - 3f

54
B. Milde et al. / Journal of Organometallic Chemistry 706-707 (2012) 52e65
Fig. 1. ORTEP diagrams (50% probability level) of the molecular structures of 6e (left) and 6f (right) with the atom-numbering scheme. All hydrogen atoms and two CHCl3 solvent
molecules (6f) have been omitted for clarity. For selected bond distances (Å), angles (ꢀ) and torsion angels (B) see Table 1. (Symmetry generated atoms are indicated by the suffix A;
symmetry code: ꢁxþ1, ꢁyþ1, ꢁzþ1.)
showed that 7b is cis-configurated, whereas 7c owns a trans
arrangement in the solid state (Fig. 2). cis-configuration is generally
observed for (alkynyl)phosphine palladium chloride complexes,
although corresponding palladium iodide species are trans oriented
[6b]. However, in solution only one isomer exists, most likely
showing the thermodynamically more stable trans-configuration as
indicated by IR and NMR studies (vide infra). For both species, the
complex geometries around palladium are square-planar as
expected for a d8 transition metal ion (7b: r.m.s. deviation 0.0728 Å,
highest deviation from planarity observed for P1 with ꢁ0.0914 Å).
Typical for 7b is that the PeC^CeCFc ligands are not coplanar to the
PdP2Cl2 core, similar to [M(P(C^CFc)Ph2)2Cl2] (M ¼ Pd, Pt), with
a PeC^C angle of 175.1(4)ꢀ (Table 1) [5c,6b,8]. In 7c a coplanar s-
trans-like structure for the (ferrocenylethynyl)phosphines is found
(Fig. 2). The trans orientation in 7c, compared to cis-7b, is most
probably attributed to the larger substituents at phosphorus, which
also has an influence on the linearity of the (alkynyl)phosphine
units. The PeC^C and C^CeCFc angles in 7c deviate more from
linearity then the ones in 7b (Table 1). All other structural param-
eters are similar to other (ferrocenyl) [6b] and (phenylethynyl) [2c]
phosphine palladium complexes.
The completeness of the reaction of 1 with nBuLi/2 to give 3
(Reaction 1) can be confirmed by IR spectroscopy, since the C^C
and ^CeH vibrations of the HC^C unit in 1 [30] at 2102 and
3279 cmꢁ1, respectively, disappear during the course of the reaction
and new absorptions between 2140 and 2155 cmꢁ1 appear which
can be assigned to the nC^C frequencies of the (ferrocenylethynyl)
phosphines 3aef (Experimental Section). Oxidation of 3aef with
Fig. 2. ORTEP diagrams (30% (7b), 50% (7c) probability level) of the molecular structures of cis-7b (left) and trans-7c (right) with the atom-numbering scheme. All hydrogen atoms
and two molecules of the solvent CHCl3 (7b) have been omitted for clarity. For selected bond distances (Å), angles (ꢀ) and torsion angels (B) see Table 1. (Symmetry generated atoms
are indicated by the suffix A; symmetry code: 7b: ꢁx, y, ꢁzþ1/2; 7c: ꢁx, ꢁy, ꢁzþ2.)

B. Milde et al. / Journal of Organometallic Chemistry 706-707 (2012) 52e65
55
Table 1
Table 2
Selected bond lengths (Å), bond angles and torsion angles (ꢀ) for complexes 6e, 6f,
7b, and 7c.a
Chemical shifts (ppm) of 4aef, 6e, 6f, 7aec, 1J(31Pe77Se) coupling constants (Hz) of
4aef and calculated Tolman cone angles
Q
(ꢀ) of 6e, 6f and 7aec; Ph3P(]Se) and
[(Ph3P)2PdCl2] for comparison.
6e
2.2504(6)
6f
2.2297(6)
7b
2.2644(13)
7c
2.3227(7)
Compd.
d
[ppm]
1J(31Pe77Se) [Hz] Compd.
d
[ppm]
Q
[ꢀ] a
Pd1eP1
Pd1eCl1
2.2755(6)
2.3176(6)
2.4081(5)
1.748(2)
1.874(2)
1.882(2)
2.2729(6)
2.4479(6)
2.3341(6)
1.747(3)
1.834(2)
2.3422(13)
2.3075(7)
4a
4b
4c
4d
4e
4f
Ph3P]Se
4.3
0.9
ꢁ17.5
ꢁ37.9
56.3
746
729
710
784
715
713
6e
6f
49.7
31.0
183
177
Pd1eCl2
Pd1eCl2Ac
P1eC12
1.732(5)
1.814(5)
1.760(3)
1.843(3)
7a [6b]
7b
7c
5.0
168
168
213
145 [16a]
P1eC13
P1eC17
P1eC19
ꢁ6.8
31.0
ꢁ24.0
1.839(2)
35.9 [7] 732 [7]
[(PPh3)2PdCl2]
24.5
P1eC20
P1eC22
C1eC11
1.829(5)
a
Q
¼ Tolman cone angle calculated by STERIC [17].
1.833(3)
1.434(4)
1.201(4)
1.6482(3)
1.6548(3)
88.49(3)
1.421(3)
1.199(3)
1.6377(3)
1.6468(3)
91.89(2)
1.426(4)
1.203(4)
1.6429(5)
1.6503(5)
88.71(2)
178.81(2)
94.37(2)
1.416(7)
1.205(6)
1.6465(7)
1.6513(7)
88.09(4)
C11eC12
D1eFe1b
and steric effects are intimately related [16], Table 2 also contains
the Tolman cone angles of 6e, 6f, and 7aec. The Tolman cone angle
Q
D2eFe2b
P1ePd1eCl1
P1ePd1eCl2
P1ePd1eCl2Ac
P1ePd1eP1Ac
P1ePd1eCl1Ac
Pd1eCl2ePd1Ac
Cl1ePd1eCl2
Cl1ePd1eCl1Ac
P1eC12eC11
C1eC11eC12
D1eFe1eD2b
P1eC12eC11eC1
Pd1eP1eC12eC11
is the apex angle of a cylindrical cone centered 2.28 Å from the
94.20(2)
178.857(19)
center of the phosphorus atom which touches the van-der-Waals
radii of the outermost atoms [16]. Increasing the MePeR angle
between P and R decreases the percentage of the s character in the
phosphorus lone-pair. Within our studies we replaced one
substituent R of PR3 by a (ferrocenylethynyl) ligand to obtain
R2(FcC^C)P (3aef). Out of this reason, we calculated the Tolman
cone angle from the structural data obtained from the single X-ray
determination of 6e, 6f, 7a [6b], 7b and 7c using the program
STERIC [17] (Table 2).
From Table 2 it can be seen that substitution of R by a ferroce-
nylethynyl unit causes a shielding of the phosphorus atom with an
increase of 1J(31Pe77Se) confirming that the (ferrocenylethynyl)
building block is electron-withdrawing. Furthermore, the replace-
93.57(7)
175.24(5)
180.0
91.51(2)
94.992(19)
173.64(2)
95.33(2)
92.23(2)
90.61(6)
175.1(4)
176.5(5)
179.46(5)
129(7)
180.0
175.46(19)
176.9(2)
178.43(2)
ꢁ66(5)
177.1(2)
176.2(3)
176.86(4)
86(6)
171.1(3)
173.6(3)
178.94(3)
ꢁ106(3)
ꢁ8.4(18)
4.4(3)
18(2)
75(5)
90(5)
161.0(3)
Pd1eP1eC13eC14 ꢁ62.81(15) ꢁ177.15(14)
Pd1eP1eC17eC18
Pd1eP1eC19eC20
Pd1eP1eC20eC21
Pd1eP1eC22eC27
Cl1ePd1eP1eC12
Cl1eP1ePd1eC13
Cl1eP1ePd1eC17
Cl1eP1ePd1eC19
Cl1ePd1eP1eC20
Cl1ePd1eP1eC22
156.65(13)
ꢁ66.84(18)3
ꢁ58.9(5)
85.7(2)
ꢁ48.97(10)
64.74(11)
ment of R by FcC^C directly influences the Tolman cone angle
(for example, P(C6H5)3 (145ꢀ) [16a]/3a (168ꢀ)) showing that the
introduction of a FcC^C unit increases . However, for larger
Q
170.44(7)
ꢁ77.47(8)
56.83(8)
ꢁ155.11(9)
ꢁ36.74(9)
ꢁ148.92(18)
90.94(17)
Q
87.92(9)
substituents, i.e. mesityl, the increase in the Tolman cone angle is
less significant (P(2,4,6-Me3C6H2)3 (212ꢀ) [16a]/3c (213ꢀ)). The
electronic and steric parameters can be used for the specific design
of catalytic active palladium transition metal complexes, for
example, for C,C coupling reactions (vide supra) which should have
direct influence on the catalytic activity of the appropriate catalyst.
The redox properties of (ferrocenylethynyl)phosphines 3, 4, and
their corresponding palladium complexes 6 and 7 were studied by
cyclic voltammetry (CV), square wave voltammetry (SWV,
complexes 6 and 7), linear sweep voltammetry (LSV, 7), and
spectroeelectrochemistry (in situ UVeVis/NIR and IR spectroscopy,
7f) in dry dichloromethane utilizing 0.1 mol Lꢁ1 solutions con-
taining [NnBu4][B(C6F5)4] as supporting electrolyte. Tetra-nbutyl
ammonium tetrakis(perfluorophenyl)borate was chosen because it
provides close-to-optimal conditions for electrochemical experi-
ments by minimizing nucleophilic attack by the electrolyte anion
and improvement of the product solubility [18]. The cyclo-
voltammetric studies were carried out at scan rates of 100 mV sꢁ1
and the results are summarized in Table 3. All potentials are
ꢁ32.4(2)
ꢁ165.81(11)
a
Standard uncertainties of the last significant digit(s) are shown in parenthesis.
D1 denotes the centroid of C5H4 at Fe1; D2 denotes the centroid of C5H5 at Fe1.
Symmetry generated atoms (for symmetry code see Figs. 1 and 2).
b
c
selenium in its elemental form to afford the seleno phosphines
4aef as well as the coordination of the phosphorus atoms of 3ae3f
to palladium(II) to produce the corresponding phosphine palla-
dium complexes 6 and 7 resulted in a shift of the nC^C bands to
higher wavenumbers, which is typical for these reactions (Experi-
mental Section) [6b]. Next to IR also 13C{1H} and 31P{1H} NMR
spectroscopy allows to monitor the reaction progress owing to the
C^C units and the phosphorus atoms present in 1, 3, 4, 6, and 7
(Experimental Section). In this respect, most indicative is 31P{1H}
NMR spectroscopy. It was found that upon coordination of the
phosphorus atom to palladium a shift to lower field is observed, i. e.
3b: ꢁ47.7 ppm, 7b: ꢁ6.8 ppm (Experimental Section). Changing the
phosphorus oxidation state of III in 3 to V in 4 also induces, as
expected, a significant down-field shift (i. e., 3b: ꢁ47.7 ppm; 4b:
0.9 ppm). In general, the donor capacity of phosphines PRR’R00
(R ¼ R0 ¼ R00; R s R0 s R00; R, R0, R00 ¼ alkyl, aryl, alkoxyl) toward
selenium acceptors can be quantified by the coupling constant
1J(31Pe77Se) [7,15]. It was found that electron-withdrawing groups
at phosphorus increase 1J(31Pe77Se), due to the increased s char-
acter of the phosphorus orbital involved in the PeSe bonding.
Furthermore, the steric demand around phosphorus causes marked
changes in the behavior of the respective transition metal
complexes. These features are essential parameters for the specific
design of transition metal complexes. The 1J(31Pe77Se) values for
seleno phosphines 4aef are summarized in Table 2. Since electronic
referenced to the FcH/FcHþ redox couple (Fc ¼ Fe(
h -
5-C5H4)(h5
C5H5)) as recommended by IUPAC [19].
The electrochemically most studied member of the series of
(ferrocenylethynyl)phosphines 3aef is 3a [6b], which undergoes
a reversible one-electron oxidation at E0 ¼ 0.161 V (Table 3). As
already described in literature for various phosphines, including
1,10-bis(diphenylphosphine)ferrocene, the resulting ferrocenium
ion participates in intra-molecular electron transfer from the PPh2
group to iron. The formed phosphorus(IV) radical then reacts in
different follow-up reactions, e.g. dimerization or reaction with
traces of oxygen [20,21a]. Nevertheless, in consecutive cycles
depending on the groups R reversible as well as irreversible
oxidations occur as it is typical of ferrocenyl phosphines (Fig. 3)

56
B. Milde et al. / Journal of Organometallic Chemistry 706-707 (2012) 52e65
Table 3
Cyclovoltammetric data (potentials vs. FcH/FcHþ), scan rate 100 mV sꢁ1 at a glassy carbon electrode of 1.0 mmol Lꢁ1 solutions of 3, 4, 6, and 7 in dry dichloromethane
containing 0.1 mol Lꢁ1 of [NnBu4][B(C6F5)4] as supporting electrolyte at 25 ꢀC.
Compd.
E0
(
DEp)/V (V)
Eox-irrev/V
Ered-irrev/V
Compd.
E10
(D
Ep)/V (V)
E20
(
DEp)/V (V)
Eirrev/V
D
E0/V
a
a
3a
3b
3c
0.161 (0.068)
0.149 (0.094)
6e
6f
0.204 (0.144)
0.204 (0.120)
Ered ¼ ꢁ0.976
Ered ¼ ꢁ0.916
0.153
0.271
0.483
0.807
1.161
0.152
0.528
1.182
0.144
0.380
0.496
0.085
0.287
0.407
b
a
3d
3e
0.165 (0.072)
0.497
0.078
0.262
0.450
0.314
0.444
7a
7b
0.630 (0.080)
0.280 (0.100)
0.374 (0.100)
0.094
3f
7c
0.162 (0.184)
a
a
7d
7e
0.301 (0.142)
0.152 (0.140)
4b
4c
0.293
0.629
0.745
ꢁ0.799
ꢁ0.413
0.249
0.495
0.234
0.578
0.808
0.529
ꢁ0.616
7f
0.273 (78)
0.438 (0.080)
0.165
0.270
0.476
4d
4e
0.292 (0.082)
ꢁ0.627
0.491
0.289
0.753
ꢁ0.355
0.161
0.603
4f
0.286
0.716
ꢁ0.400
0.192
0.592
a
Two non-resolved Fe(II)/Fe(III) processes.
b
Redox potential E0 and
D
Ep from reference 6b. E0 ¼ redox potential, E10 ¼ potential of 1st redox process, E20 ¼ potential of 2nd redox process, Eox-irrev ¼ irreversible oxidation
potential, Ered-irrev ¼ irreversible reduction potential,
D
Ep ¼ difference between oxidation and reduction potential,
D
E0 ¼ potential difference between two redox processes.
[20,21a]. Obviously, the phosphines featuring electron-rich organic
groups, for example, 3c, 3e and 3f show without exception irre-
versible behavior and more follow-up processes (Fig. 3).
spacer unit. As recently described for ferrocenyl phosphines [15g],
we did synthesize the seleno phosphines 4aef (vide supra) which
show a similar behavior with irreversible oxidation events and
follow-up reactions as ferrocenyl-substituted seleno phosphines
(Table 3) [15g,18,21a]. Compared to 3aef with phosphorus III, the
seleno phosphines 4aef with phosphorus in the oxidation state þ V
are, as expected, more difficult to oxidize (Table 3).
Coordination of the phosphorus lone-pair in 3aef to palladium
(complexes 6 and 7) inhibits intra-molecular oxidation of the
phosphorus (Fig. 4).
From Table 3 it further can be seen that more electron-rich
species can more easily be oxidized. The potential E0 and Eox-irrev
,
respectively,
decreases,
for
example,
in
the
series:
furyl > phenyl > o-tolyl z mesityl. The appropriate alkyl-
functionalized ferrocenylethynyl phosphines show the trend E(t-
butyl) > E(cyclohexyl) (Table 3). Compared with the corresponding
ferrocenyl phosphines PFcR2 [15g], the ferrocenylethynyl-
functionalized derivatives are more difficult to oxidize which
complies with the electron-withdrawing character of the ethynyl
Typical for both dimeric palladium complexes 6e and 6f is that
in the cyclic voltammograms beside two non-resolved redox events
50
40
30
20
10
0
25
20
15
10
5
0
-5
1st cycle
2nd cycle
-10
-15
1st cycle
2nd cycle
-10
-20
-1,5
-20
-1,5
-1,0
-0,5
0,0
0,5
1,0
1,5
-1,0
-0,5
0,0
0,5
1,0
1,5
Potential / V vs. FcH/FcH+
Potential / V vs. FcH/FcH+
Fig. 3. Electrochemical data of dichloromethane solutions containing 1.0 mmol Lꢁ1 of 3a (left) and 3c (right) at 25 ꢀC, supporting electrolyte [NnBu4][B(C6F5)4] with a scan rate of
100 mV sꢁ1
.

B. Milde et al. / Journal of Organometallic Chemistry 706-707 (2012) 52e65
57
Fig. 4. Electrochemical data of dichloromethane solutions containing 1.0 mmol Lꢁ1 of 7c (left) and 7f (right) at 25 ꢀC, supporting electrolyte [NnBu4][B(C6F5)4] with a scan rate of
100 mV sꢁ1 (CV ¼ Cyclic Voltammetry, SWV ¼ Square Wave Voltammetry, LSV ¼ Linear Sweep Voltammetry).
at 0.204 V (
D
Ep ¼ 0.144 V (6e) and
D
Ep ¼ 0.120 V (6f), respectively)
studies were conducted by stepwise increase of the potential
from 0.0 to 1.2 V vs. Ag/AgCl in an OTTLE cell (OTTLE ¼ Optically
Transparent Thin-Layer Electrochemical) containing dichloro-
methane solutions of 7f (1.0 mmol Lꢁ1) and [NnBu4][B(C6F5)4]
(0.1 mol Lꢁ1) as supporting electrolyte allowing the generation of
mono-cationic [7f]D and di-cationic [7f]2þ species. Complex 7f
does not display, as expected, any absorption in the NIR range.
Surprisingly, the spectrum of the mono-oxidized species 7f
[B(C6F5)4] shows an absorption with relatively high intensity
(Fig. 5), which is in contrast to other ferrocenyl phosphine palla-
dium complexes, i. e. [PdCl2(P(2-CH3C6H4)2Fc)2] [15g]. Neverthe-
less, it must be noted that during the UVeVis/NIR measurements
decomposition of the oxidized species occurred, which resulted in
incomplete disappearance of the IVCT band. However, when
increasing the speed of the measurement and reducing the amount
of data, the IVCT band completely disappeared (Figure S2,
Supplementary Information). To investigate this behavior we tried
to synthesize the mono-cationic species by treatment of 7f with
one equivalent of [Ag][B(C6F5)4] in tetrahydrofuran at ꢁ60 ꢀC. After
filtration and precipitation with nhexane a dark purple solid could
be obtained. Nevertheless, characterization of this material indi-
cated that solely di-cationic [7f]2þ was formed. UVeVis/NIR
measurements showed no absorption in the NIR range (Supple-
mentary Information, Figure S3).
for the oxidation of the ferrocenyl groups an irreversible reduction
peak at ꢁ0.9 V associated with the reduction of Pd(II) to Pd(0)
[21b,c] is observed (Supplementary Information, Figure S1;
Table 3). However, mononuclear palladium complexes 7bef show
two reversible redox events between 0.2 and 0.5 V, i.e. 7f:
E10 ¼ 0.27 V (
D
Ep ¼ 0.078 V), E20 ¼ 0.44 V (
Ep ¼ 0.080 V) (Table 3,
D
Fig. 4). The same behavior is found for all other species, even
though they are partially not separable. Conspicuous is the obser-
vation that aliphatic 7f shows a larger peak separation of the 1st
and 2nd oxidation than the aromatic systems 7aed (Fig. 4). Square
wave (SWV) and linear sweep (LSV) voltammetric studies indi-
cated, as exemplary shown for 7f (Fig. 4, right), two reversible one-
electron processes with a peak separation of 0.165 V. This divergent
behavior shows that the two ferrocenyl moieties in 7f can sepa-
rately be oxidized rather than 7aee. As already described for 3aef
and 4aef, respectively, complexes 7 show the same trend, in that
the ferrocenyl groups of the more electron-rich aromatic phos-
phines are, as expected, easier to oxidize. Compared to the non-
coordinated (ferrocenylethynyl)phosphines, the respective palla-
dium complexes are also more difficult to oxidize which can be
explained by electron donation of the phosphines to palladium
upon coordination (Table 3). In addition, for 6 and 7 no further
redox events indicating follow-up reactions have been observed.
To probe, if the redox splitting in 7f is due to electronic
communication we investigated the electronic absorptions in the
visible and near infrared region of the electrochemically generated
oxidized species (7fþ, 7f2þ) (Fig. 5). In general, the absence of any
NIR charge transfer bands points to electron-localized mixed-val-
ent species, whereas the presence of such absorptions would argue
in favor of electron delocalization. The spectroeelectrochemical
Deconvolution of the NIR absorption of in situ generated [7f]þ
was achieved by using three separate overlapping transitions
with Gaussian shapes (Fig. 6). The fits provide an almost
exact overlay of the sum of the Gaussian curves with the experi-
mental spectra. Two bands were found at 6303 and 4444 cmꢁ1
,
respectively. The absorption possessing the highest intensity
(åmax ¼ 1410 L molꢁ1 cmꢁ1) at 6303 cmꢁ1 showed a characteristic
Fig. 5. NIR-Spectra of 7f at rising potentials (left: 0.0e0.775 V; right: 0.8e1.2 V vs. Ag/AgCl) at 25 ꢀC, in dichloromethane, supporting electrolyte [NnBu4][B(C6F5)4].

58
B. Milde et al. / Journal of Organometallic Chemistry 706-707 (2012) 52e65
2000
1500
1000
500
0
to þ1.2 V in an OTTLE cell containing a dichloromethane solution of
7f (2.5 mmol Lꢁ1) and [NnBu4][B(C6F5)4] (0.1 mol Lꢁ1) as supporting
electrolyte. The IR spectrum of 7f displays one strong nC^C band at
2159 cmꢁ1 and one very weak band at 2180 cmꢁ1 which most
probably can be assigned to the trans-complex (Fig. 7). Oxidation of
7f to [7f]þ results in a shift to lower wavenumbers (2154 cmꢁ1) and
the disappearance of the 2nd weak band. Further oxidation to
[7f]2þ causes an additional shift (2151 cmꢁ1) and a broadening of
the respective absorption. Besides, for [7f]þ only one absorption is
observed which seems like the average of the neutral and di-
cationic species. However, these differences are small [26].
IVCT
baseline
correction
ε
LMCT
4000
6000
8000
10000
2.1.1. C,C cross-coupling reactions
Suzuki and Heck reactions are of great interest because they
allow C,C coupling of alkyl and aryl halides with aryl boronic acids,
Wavenumber / cm-1
Fig. 6. Deconvolution of NIR absorptions of electro generated [7f]þ using three
Gaussian-shaped bands. Solid line: experimental data; dashed/dotted lines: Gaussian-
shaped absorptions.
or aryl and alkenyl halides with a-olefines under mild conditions,
providing a convenient access to biaryls and diverse alkenes [9].
These couplings are one of the most powerful C2speCs2p bond form-
ing reactions in organic and organometallic synthesis. Next to N-
heterocyclic carbenes [11] and phosphapalladacycles [13] etc.,
phosphines remain among the best studied ligands in such reac-
tions [10].
peak width-at-half-height for inter-valence charge transfer bands
(2089 cmꢁ1) [22]. The band at 4444 cmꢁ1 can be assigned to
a ligand-to-metal charge transfer absorption [23]. A 3rd Gaussian
curve represents the baseline correction.
In addition, band shape analysis was performed according to the
Hush model for symmetric mixed-valent species (equations (1) and
(2)) [23b,24] and the classification criteria of Brunschwig, Creutz
and Sutin [25].
2.1.2. Suzuki reaction
In recent years, manifold and efficient synthetic methodologies
were developed to synthesize specifically designed phosphine
ligands for the homogeneous palladium-catalyzed Suzuki cross-
coupling reaction [9]. Contrary, transition metal-containing phos-
phines are only little described of which dppf (¼1,10-bis(diphenyl-
phosphino)ferrocene) and derivatives thereof have been best
investigated [10f]. With this study we enrich the family of ferro-
cenyl phosphine palladium dichloride complexes and describe
their use as catalysts in the Suzuki reaction. The reactants 2-bromo
toluene and 40-chloro acetophenone, respectively, of the catalytic
process were treated with phenyl boronic acid in presence of
potassium carbonate in a 2:1 (v/v) mixture of dioxane/water
(Reaction 2). The reaction mixture was stirred at 100 ꢀC for 1 h,
samples were taken after defined periods of time (Experimental
Section). Acetyl ferrocene was added as internal standard for 1H
NMR analysis to determine the conversions of the catalytic reac-
tions. Palladium complexes 6 and 7 were applied in the catalytic
reaction of 2-bromo toluene with phenyl boronic acid (Fig. 8, left).
From these studies the most promising candidates were addition-
ally used in the coupling of 40-chloro acetophenone with phenyl
boronic acid (Fig. 8, right).
0
1
pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
B
@
C
A
Dn
¼
2310$nmax
(1)
1
2
theo
0
1
B
@
C
Dn
A
1
2
0
1
G
¼ 1 ꢁ
(2)
B
C
Dn
@
A
1
2
theo
Theoretical band width-at-half-height could be calculated as
3816 cmꢁ1 for [7f]þ and a
s value of 0.45 indicates that this radical
cation is rather close to a Class II/III borderline system. According to
this classification, complex 7f can be assigned as moderately
coupled class II system.
Additionally, spectroeelectrochemical IR measurements of 7f
were performed to confirm electronic interactions. These studies
were performed by stepwise increase of the potential from ꢁ1.0
K2CO3, [Pd]
dioxane/H2O
100 °C
B(OH)2
(2)
X
+
R
R
R = 2-CH3
R = 4-COCH
, X = Br
3 , X = Cl
100
95
In the Suzuki reaction electron-rich phosphine ligands are best
suited [10a,b], which correlates with our results (Fig. 8). From Fig. 8
it further can be seen that quantitative conversions are obtained for
the reaction of 2-bromo toluene with phenyl boronic acid using 6
and 7 as catalyst, except 7c (54% conversion) and 7d (87% conver-
sion), respectively. At first glance this is surprising but considering
the Tolman cone angles (7c, 212ꢀ; vide supra) in a certain manner it
is comprehensible. Complex 7d features with its furyl groups
electron-withdrawing substituents and hence shows the lowest
catalytic activity and needs an induction period of ca. 10 min. From
these studies we chose complexes 6e, 6f, 7e and 7f as catalysts for
the activation of 40-chloro acetophenone. These results are depicted
in Fig. 8 (right). The highest catalytic activity is observed for 6e and
7f, whereas complete conversion is only observed for 6e. A clear
-1.0 V
0.8 V
1.2 V
90
2250
2200
2150
2100
2050
Wavenumbers / cm-1
Fig. 7. IR spectra of 7f at rising potentials (ꢁ1.0 to þ1.2 V vs. Ag/AgCl) at 25 ꢀC in
dichloromethane, supporting electrolyte [NnBu4][B(C6F5)4].

B. Milde et al. / Journal of Organometallic Chemistry 706-707 (2012) 52e65
59
Fig. 8. Reaction profiles for the coupling of 2-bromo toluene (left) and 40-chloro acetophenone (right) (2.92 or 3.0 mmol) with phenyl boronic acid (3.85 mmol) using 6e, b and 7aef
as catalysts (catalyst loading 0.25 (2-bromo toluene) and 0.5 mol% (40-chloro acetophenone), 100 ꢀC, 1 h, K2CO3 (8.76 mmol) in a mixture of dioxane/water (ratio 2:1, v/v) (10 mL)).
trend between dimeric 6 and monomeric 7 cannot be seen.
since smaller conversions and longer reaction times are expected.
In contrast to now-a-days used catalysts [11f,12d,28] our systems
are less active and productive. Compared to ferrocenyl phosphine
palladium catalysts the appropriate (ferrocenylethynyl) complexes
possess lower activity attributed to the electron-withdrawing effect
of the ethynyl linker unit.
Compared to ferrocenyl phosphine palladium dichloride complexes
of type [PdCl2(PR2Fc)2] (Fc ¼ Fe(
h h
5-C5H4)( 5-C5H5)) [15g] and up-
to-date used catalyic systems [9e13] they show, however, a lower
activity and productivity.
2.1.3. Heck reaction
The palladium-promoted Heck C,C cross-coupling between aryl-
or vinyl halides and triflates and alkenes in the presence of a base
allows the straightforward synthesis of Csp2eCsp2 single bonds for
fine chemical synthesis [9]. One advantage of the Heck reaction is
its trans selectivity. As catalysts, for example, phosphapalladacycles
[13], various palladium(II)eacetate/phosphine systems [9], palla-
dium nanoparticles [27], and N-heterocyclic carbene palladium
complexes [11] have been applied. Within this work, complexes 6e,
6f, and 7aef were used in the coupling of iodo benzene with tert-
butyl acrylate (Reaction 3) in a mixture of tolueneeacetonitrile
(ratio 1:1, v:v) in presence of NEtiPr2 at 80 ꢀC with a catalyst
loading of 0.5 mol% (Experimental Section, Table 4).
3. Conclusions
Within this study the synthesis of a series of (ferrocenylethynyl)
phosphine palladium dichloride complexes of type [Pd(Cl)(m-
Cl)(P(C^CFc)R2)]2 (Fc ¼ Fe(
h
5-C5H4)(
h
5-C5H5); R ¼ tBu, cC6H11) and
[PdCl2(P(C^CFc)R2)2] (R ¼ C6H5, 2-MeC6H4, 2,4,6-Me3C6H2, cC4H3O,
tBu, cC6H11) by the reaction of P(C^CFc)R2 with [PdCl2(cod)]
(cod ¼ cyclo-1,5-octadiene) or [PdCl2(SEt2)2] is discussed. The
structures of four complexes could be determined by single crystal
X-ray diffraction analysis. [PdCl2(P(C^CFc)(2-MeC6H4)2)2] shows
in the solid state
(C^CFc)(2,4,6-Me3C6H2)2)2] prefers the trans-form with linear
FcC^CP moieties. In contrast, [Pd(Cl)(
-Cl)(P(C^CFc)(tBu)2)]2 and
[Pd(Cl)( planar
-Cl)(P(C^CFc)(cC6H11)2)]2 form dimers with
Pd2P2Cl2( -Cl)2 core with the (ferrocenylethynyl) ligands oriented
above and below the square-planar unit. For classification of the
a
cis-configuration, whereas [PdCl2(P
O
m
t
m
a
i
O Bu
EtNPr2, [Pd]
t
(3)
I
O Bu
+
m
MeCN, toluene
O
80 °C
s
-
donor ability of the (ferrocenylethynyl)phosphines the respective
seleno derivatives (Se)P(C^CFc)R2 have been synthesized upon
addition of selenium in its elemental form to the (ferrocenyle-
thynyl)phosphines. High 1J(31Pe77Se) values indicate electron-poor
phosphines and hence less donor capability [7,15]. Cyclo-
voltammetric measurements showed that depending on the groups
R reversible as well as irreversible oxidations occur. The oxidation
at the iron center leads to an intra-molecular electron transfer
process from the phosphino group to iron resulting in irreversible
oxidations which lead to various follow-up processes [20,21a]. We
also investigated the electrochemistry of the newly synthesized
seleno phosphines and (ferrocenylethynyl)phosphine palladium(II)
complexes in which the lone-pair of electrons at phosphorus is part
From Table 4 it can be seen that the catalyst featuring sterically
demanding tolyl (7b) and mesityl phosphines (7c), or weekly
s
-
donating furyl ligands (7d) are best suited for C,C couplings under
the above mentioned conditions. However, with these species
quantitative conversion could not be reached. Complexes 6e, 6f,
and 7a with aliphatic (6e, b) or less bulky and electron-poor
phosphines show lesser activity and productivity as compared
with 7b, 7c, and 7d. It is obvious that dimeric 6e and 6f are only
active at the beginning of the reaction but significantly slowed
down in activity due to their lower stability, when compared to
7aef (Supplementary Information, Figure S4). Based on these
results, we did not consider the reactions of bromo or chloro
benzene with tert-butyl acrylate supported by catalysts 6 and 7
of
a phosphoruseselenium or phosphorusepalladium bond.
Nevertheless, the seleno phosphines also show follow-up
processes, presumably resulting from an intra-molecular electron
transfer from the selenium-centered radical [15g,18,21]. Such
oxidations are, however, inhibited, when the phosphorus atom is
datively-bonded to Pd as implemented in the respective transition
metal complexes. As expected, the phosphino palladium species are
more difficult to oxidize because of electron donation to Pd(II).
Table 4
Heck reaction of iodo benzene with tert-butyl acrylate with a catalyst loading of
0.5 mol% of 6 and 7, 10 h reaction time.
Entry
Compd.
Yield/%
Entry
Compd.
Yield/%
1
2
3
4
6e
6f
7a
7b
27.1
41.2
41.9
61.9
5
6
7
8
7c
7d
7e
7f
41.9
52.9
3.8
Complex [PdCl2(P(C^CFc)(cC6H11 2 2
electron processes with a peak separation of
) ) ] revealed two reversible one-
21.4
D
E0 ¼ 0.165 V in

60
B. Milde et al. / Journal of Organometallic Chemistry 706-707 (2012) 52e65
dichloromethane and in the presence of [NnBu4][B(C6F5)4] as sup-
porting electrolyte. In situ UVeVis/NIR spectroscopy confirmed
moderate electronic coupling between the (ferrocenylethynyl)
units and the complex can be classified as class II system according
to Robin and Day [29] by band shape analysis of the IVCT absorp-
tion. Due to the long “through bond” electron transfer distance
between the end-grafted ferrocenyl moieties we suppose that
communication occurs rather “through space” than “through
bond”. Additional in situ IR measurements showed a small shift in
the nC^C band which underlines the supposition of “through space”
electronic coupling.
4.3. Electrochemistry
Measurements on 1.0 mmol Lꢁ1 solutions of 3, 4, 6 and 7 in dry
degassed dichloromethane containing 0.1 mol Lꢁ1 of [NnBu4]
[B(C6F5)4] as supporting electrolyte were conducted under
a blanket of purified argon at 25 ꢀC utilizing a Radiometer Voltalab
PGZ 100 electrochemical workstation interfaced with a personal
computer. A three electrode cell, which utilized a Pt auxiliary
electrode,
a glassy carbon working electrode (surface area
0.031 cm2) and an Ag/Agþ (0.01 mol Lꢁ1 [AgNO3]) reference elec-
trode mounted on a luggin capillary was used. The working elec-
trode was pre-treated by polishing on a Buehler microcloth first
with 1 micron and then ¼ micron diamond paste. The reference
electrode was constructed from a silver wire inserted into a solu-
tion of 0.01 mol Lꢁ1 [AgNO3] and 0.1 mol Lꢁ1 [NnBu4][B(C6F5)4] in
acetonitrile, in a luggin capillary with a vycor tip. This luggin
capillary was inserted into a second luggin capillary with vycor tip
filled with a 0.1 mol Lꢁ1 [NnBu4][B(C6F5)4] solution in dichloro-
methane. Successive experiments under the same experimental
conditions showed that all formal reduction and oxidation poten-
tials were reproducible within 10 mV. Experimentally potentials
were referenced against an Ag/Agþ reference electrode but results
are presented referenced against ferrocene as an internal standard
as required by IUPAC [19]. Data were manipulated on a Microsoft
Excel worksheet to set the formal reduction potentials of the FcH/
FcHþ couple to 0.0 V. Under our conditions the FcH/FcHþ couple
was at 230 mV vs. Ag/Agþ.
All (ferrocenylethynyl)phosphine palladium(II) complexes were
tested as catalysts in C,C coupling reactions. In the palladium-
promoted Heck reaction, iodo benzene was treated with tert-
butyl acrylate. All complexes are active, although the most efficient
catalysts were the ones featuring furyl, mesityl or o-tolyl
substituted phosphines explainable either by the bulkiness (Tol-
man cone angle) or the weak s
-donor ability (1J(31Pe77Se)) of these
ligands. Furthermore, it could be shown that all Pd species are
active in Suzuki couplings of aryl-bromide and activated
arylechloride with phenyl boronic acid. A relation between the
basicity of the phosphines and the activity of the corresponding
complexes exists. The lower the 1J(31Pe77Se) coupling constant and
hence the higher the basicity of the phosphine, the higher the
catalyst activity. However, the catalysts reported within this work
are compared with up-to-date catalytic systems [9e13,15g,28] less
active.
4. Experimental section
4.4. Spectroeelectrochemistry
4.1. General data and materials
Spectroeelectrochemical
UV/Vis-NIR
measurements
of
a 1.0 mmol Lꢁ1 solution of 7f in dry degassed dichloromethane
containing 0.1 mol Lꢁ1 of [NnBu4][B(C6F5)4] as supporting electro-
lyte were carried in an OTTLE cell [34] using a Varian Cary 5000
spectrometer. In situ spectroeelectrochemical IR measurements of
7f (2.5 mmol Lꢁ1) in dichloromethane (0.1 mol Lꢁ1 [NnBu4]
[B(C6F5)4]) were also carried in an OTTLE cell [34] using a Thermo IR
100 spectrometer.
All reactions were carried out under an atmosphere of nitrogen
or argon using standard Schlenk techniques. Toluene and diethyl
ether were purified by distillation from sodium/benzophenone,
dichloromethane was purified by distillation from calcium hydride.
Celite (purified and annealed, Erg. B.6, Riedel de Haen) was used for
filtrations. For column chromatography alumina with a particle size
of 90
mm (standard, Merck KGaA) or silica with a particle size of
40e60
mm (230e400 mesh (ASTM), Becker) was used. All starting
4.5. General procedure for the synthesis of phosphines 3bef
materials were obtained from commercial suppliers and were used
without further purification. Ethynylferrocene [30] (1), (ethy-
nylferrocenyl)diphenyl phosphine [6b] (3a), (ethynylferrocenyl)
diphenyl seleno phosphine [7] (4a) and bis((ethynylferrocenyl)
diphenylphosphino)palladiumdichloride [6b] (7a) were prepared
according to published procedures. Chlorophosphines 2bef [31],
[PdCl2(cod)] [32] (5) and [PdCl2(SEt2)2] [33] (8) were synthesized as
described in literature.
To a solution of 1 dissolved in 50 mL of dry diethyl ether one
equivalent of a 2.5 M solution of nBuLi was added dropwise
at ꢁ30 ꢀC. After stirring the solution for 30 min at ambient
temperature it was again cooled to ꢁ30 ꢀC and one equivalent of
the appropriate chlorophosphine 2 was added dropwise. The
reaction mixture was stirred for 1 h at ambient temperature and
then concentrated in vacuum. The resulting residue was purified by
column chromatography (column size: 15 ꢂ 3.0 cm) and dried in
vacuum.
4.2. Instruments
NMR spectra were recorded on a Bruker Avance III 500 spec-
trometer (500.3 MHz for 1H, 125.7 MHz for 13C{1H}, and 202.5 MHz
4.5.1. Synthesis of P(C^CFc)(2-MeC6H4)2 (3b)
Using the general procedure described above, 1.0 g (4.76 mmol)
of 1 was reacted with 1.90 mL (4.75 mmol) of nBuLi and then 1.18 g
(4.75 mmol) of chlorodi-o-tolylphosphine (2b) was added in
a single portion. The resulting residue was purified by column
chromatography on alox using a mixture of nhexane/diethyl ether
(ratio 20:1, v:v) as eluent. Phosphine 3b was obtained as a yellow
solid. Yield: 1.33 g (3.15 mmol, 66% based on 2b). Anal. Calcd. for
C26H23FeP (422.28 g/mol): C, 73.95; H, 5.49. Found: C, 73.71; H,
for 31P{1H} NMR spectra). Chemical shifts are reported in
d
units
(parts per million) downfield from tetramethylsilane with the
solvent as reference signal (1H NMR: standard internal CDCl3,
7.26
or CD2Cl2, 77.16 or
5.30; 13C{1H} NMR: standard internal CDCl3,
CD2Cl2,
53.52; 31P{1H} NMR: standard external rel. 85% H3PO4,
0.0 or P(OMe)3, 139.0, respectively). HRMS were recorded on
d
d
d
d
d
d
a Bruker Daltonik micrOTOF-QII spectrometer (ESI-TOF). Elemental
analyses were measured with a Thermo FlashAE 1112 series
instrument. Melting points of analytical pure samples were deter-
mined by a Gallenkamp MFB 595 010 M melting point apparatus. FT
IR spectra were recorded on a Thermo Nicolet IR 200 spectrometer
using either KBr pellets or NaCl plates.
5.23. Mp.: 118 ꢀC. IR (KBr,
benzene), 1449 (m, PeC), 2150 (m, C^C), 2913/2937/2966 (w,
n
/cmꢁ1): 745 (s, ]CeH, ortho-disubst.
CeH), 3059/3083 (w, ]CeH). 1H NMR (500.30 MHz, CDCl3,
d): 2.52
(s, 6 H, 2-CH3C6H4), 4.22 (s, 5 H, C5H5), 4.24 (pt, 3JHH ¼ 1.9 Hz, 2 H,
3
C5H4), 4.52 (pt, JHH ¼ 1.9 Hz, 2 H, C5H4), 7.20e7.26 (m, 4 H, 2-

B. Milde et al. / Journal of Organometallic Chemistry 706-707 (2012) 52e65
61
CH3C6H4), 7.28e7.34 (m, 2 H, 2-CH3C6H4), 7.56e7.62 (m, 2 H, 2-
H, 7.68. Found: C, 67.92; H, 7.85. Mp.: 121 ꢀC. IR (KBr,
n
/cmꢁ1):
CH3C6H4). 13C{1H} NMR (125.81 MHz, CDCl3,
d): 21.3 (d,
1467 (m, PeC), 1653 (w, C]C), 2364 (s, C^C), 2859/2954 (s, CeH),
3JCP ¼ 20.6 Hz, 2-CH3C6H4), 69.2 (m, Cb/C5H4), 70.1 (s, C5H5), 72.0 (d,
3099 (w, ]CeH). 1H NMR (500.30 MHz, CDCl3,
d): 1.29 (d,
2
2JCP ¼ 1.6 Hz, Ca/C5H4), 81.1 (d, JCP ¼ 3.9 Hz, eC^CeP), 107.7 (d,
3JHP ¼ 12.5 Hz, 18 H, C(CH3)3), 4.20 (pt, 3JHH ¼ 1.9 Hz, C5H4), 4.23 (s,
1JCP ¼ 5.5 Hz, eC^CeP), 126.3 (d, JCP ¼ 2.2 Hz, 2-CH3C6H4), 129.3 (s,
2-CH3C6H4),130.3 (d, JCP ¼ 5.1 Hz, 2-CH3C6H4),133.0 (d, JCP ¼ 3.4 Hz,
5
H, C5H5), 4.46 (pt, JHH
¼
1.9 Hz, C5H4). 13C{1H} NMR
3
2
(125.81 MHz, CDCl3,
d
): 29.8 (d, JCP ¼ 14.4 Hz. C(CH3)3), 32.7 (d,
2-CH3C6H4), 133.7 (d, JCP
¼
6.4 Hz, 2-CH3C6H4), 142.0 (d,
1JCP ¼ 16.3 Hz, C(CH3)3), 69.9 (s, C5H5), 70.2 (m, Ca/C5H4), 71.8 (d,
3JCP ¼ 0.9 Hz, Cb/C5H5), 83.9 (d, 1JCP ¼ 18.0 Hz, -C^CeP), 104.8 (d,
JCP ¼ 26.6 Hz, 2-CH3C6H4). 31P{1H} NMR (202.53 MHz, CDCl3,
d
): ꢁ47.7. HRMS (ESI-TOF) C26H23FeP [M þ nH]þ m/z: calcd.:
2JCP ¼ 2.2 Hz, -C^CeP). 31P{1H} NMR (202.53 MHz, CDCl3,
d): 10.9.
423.0960, found: 423.0963.
HRMS (ESI-TOF) C20H27FeP [M þ nH]þ m/z: calcd.: 354.1194,
found: 355.1152.
4.5.2. Synthesis of P(C^CFc)(2,4,6-Me3C6H4)2 (3c)
Using the general procedure described above, 1.0 g (4.76 mmol)
of 1 was reacted with 1.90 mL (4.75 mmol) of nBuLi and then with
1.45 g (4.75 mmol) of chlorodimesitylphosphine (2c). The resulting
residue was purified by column chromatography on silica gel using
nhexane/diethyl ether (ratio 15:1, v:v) as eluent. Compound 3c was
obtained as a yellow solid. Yield: 1.82 g (3.80 mmol, 80% based on
2c). Anal. Calcd. for C30H31FeP (478.39 g/mol): C, 75.32; H, 6.53.
4.5.5. Synthesis of P(C^CFc)(cC6H11 2
) (3f)
1.0 g (4.76 mmol) of 1 was reacted (general synthesis procedure
see earlier) with 1.90 mL (4.75 mmol) of nBuLi followed by addition
of 1.10 g (4.73 mmol) of chlorodicyclohexylphosphine (2f). The
resulting residue was purified by column chromatography on silica
gel using nhexane as eluent. Phosphine 3f was obtained as a yellow
solid. Yield: 1.71 g (4.21 mmol, 89% based on 2f). Anal. Calcd. for
C24H31FeP (406.32 g/mol): C, 70.94; H, 7.69. Found: C, 70.48; H, 7.77.
Found: C, 75.27; H, 6.63. Mp.: 113 ꢀC. IR (KBr, /cmꢁ1): 820 (s, ]
n
CeH, para-subst. benzene), 1449/1467 (m, PeC), 1598 (m, C]C),
Mp.: 77 ꢀC. IR (KBr,
(m, C^C), 2847/2923 (s, CeH). 3095 (w, ]CeH). 1H NMR
(500.30 MHz, CDCl3, ): 1.25e1.44 (m, 10 H, C6H11), 1.71e1.84 (m,
n
/cmꢁ1): 1444 (m, PeC), 1657 (w, C]C), 2146
2140 (m, C^C), 2919/2954 (m, CeH), 3096 (w, ]CeH). 1H NMR
(500.30 MHz, CDCl3,
d
): 2.28 (s, 6 H, 2,4,6-(CH3)33C6H2), 2.47 (s, 12 H,
d
3
2,4,6-(CH3)3C6H2), 4.16 (s, 5 H, C5H5), 4.20 (pt, JHH ¼ 1.8 Hz, 2 H,
10 H, C6H11), 1.97e2.02 (m, 2 H, H1/C6H11), 4.21 (pt, JHH ¼ 1.8 Hz,
C5H4), 4.41 (pt, 3JHH ¼ 1.8 Hz, 2 H, C5H4), 6.84 (d, 4JHP ¼ 3.1 Hz, 4 H,
2 H, C5H4), 4.22 (s, 5 H, C5H5), 4.47 (pt, 3JHH ¼ 1.8 Hz, 2 H, C5H4). 13
C
2,4,6-(CH3)3C6H2). 13C{1H} NMR (125.81 MHz, CDCl3,
d): 21.0 (s,
{1H} NMR (125.81 MHz, CDCl3,
d): 26.4 (s, C6H11), 26.8 (d,
3
2,4,6-(CH3)3C6H2), 23.2 (d, JCP ¼ 14.3 Hz, 2,4,6-(CH3)3C6H2), 65.8
JCP ¼ 18.2 Hz, C6H11), 26.9 (d, JCP ¼ 1.9 Hz, C6H11), 29.2 (d,
JCP ¼ 4.5 Hz, C6H11), 30.0 (d, JCP ¼ 18.1 Hz, C6H11), 32.9 (d,
1JCP ¼ 8.2 Hz, C1/C6H11), 65.2 (s, Ci/C5H4), 68.6 (s, C5H4), 69.9 (s,
(m, Ci/C5H4), 68.9 (s, Cb/C5H4), 69.7 (s, C5H5), 71.4 (d, JCP ¼ 1.6 Hz,
4
2
1
Ca/C5H4), 83.4 (d, JCP ¼ 2.9 Hz, C^CeP), 106.2 (d, JCP ¼ 9.4 Hz,
3
1
C^CeP), 130.0 (d, JCP ¼ 3.6 Hz, Cm/2,4,6-(CH3)3C6H2), 130.4 (d,
C5H5), 71.6 (s, C5H4), 82.5 (d, JCP ¼ 20.1 Hz, -C^CeP), 104.4 (d,
1JCP ¼ 12.6 Hz, Ci/2,4,6-(CH3)3C6H2), 138.2 (s, Cp/2,4,6-(CH3)3C6H2),
2JCP ¼ 2.3 Hz, eC^CeP). 31P{1H} NMR (202.53 MHz, CDCl3,
2
142.0 (d, JCP ¼ 15.8 Hz, Co/2,4,6-(CH3)3C6H2). 31P{1H} NMR
d
): ꢁ22.1. HRMS (ESI-TOF) C24H31FeP [M þ nH]þ m/z: calcd.:
(202.53 MHz, CDCl3,
d
): ꢁ55.7. HRMS (ESI-TOF) C30H31PFe [M]þ m/
407.1586, found: 407.1571.
z: calcd.: 478.1508, found: 478.1507.
4.5.3. Synthesis of P(C^CFc)(cC4H3O)2 (3d)
4.6. General procedure for the synthesis of seleno phosphines 4bef
Using the general procedure described above, 1.0 g (4.76 mmol)
of 1 was reacted with 1.90 mL (4.75 mmol) of nBuLi and then with
0.95 g (4.74 mmol) of chlorodi-2-furylphosphine (2d). The resulting
residue was purified by column chromatography on alox using
nhexane as eluent giving 3c as a yellow solid. Yield: 1.37 g
(3.66 mmol, 77% based on 2d). Anal. Calcd. for C20H15FeO2P
(374.15 g/mol): C, 64.20; H, 4.04. Found: C, 64.33; H, 4.04. Mp.:
To a toluene solution (20 mL) containing 100 mg of the
respective phosphine 3bef, 1.2 equivalents of elemental selenium
were added in a single portion and the reaction mixture was stirred
for 1 h at 100 ꢀC. After cooling the reaction mixture to ambient
temperature, it was filtered through a pad of Celite. All volatiles
were removed in vacuum giving the appropriate compounds.
110 ꢀC. IR (KBr, /cmꢁ1): 1010 (s, CeO), 1458 (m, PeC), 1655 (w, C]
n
C), 2153 (m, C^C), 3114/3142 (w, ]CeH). 1H NMR (500.30 MHz,
4.6.1. Synthesis of (Se)P(C^CFc)(2-MeC6H4)2 (4b)
CDCl3,
d
): 4.19 (s, 5 H, C5H5), 4.22 (pt, 3JHH ¼ 1.9 Hz, C5H4), 4.50 (pt,
100 mg (0.24 mmol) of 3b were reacted with 22 mg (0.28 mmol)
of elemental selenium. After appropriate work-up, 4b was obtained
as a yellow solid. Yield: 120 mg (0.24 mmol, 100% based on 3b).
Anal. Calcd. for C26H23FePSe (501.24 g/mol): C, 62.30; H, 4.63.
4
3
3JHH ¼ 1.9 Hz, C5H4), 6.44 (dt, JHP ¼ 1.8 Hz, JHH ¼ 3.3 Hz,
3JHH ¼ 1.8 Hz, 2 H, H4/C4H3O), 6.90 (m, 2 H, H3/C4H3O), 7.67 (m, 2 H,
H5/C4H3O). 13C{1H} NMR (125.81 MHz, CDCl3,
d): 70.4 (m, C5H4),
70.6 (s, C5H5), 72.6 (m, C5H4), 111.9 (pt, JCP ¼ 4.9 Hz, C4/C4H3O),
Found: C, 62.12; H, 4.83. Mp.: 64 ꢀC. IR (KBr, /cmꢁ1): 556 (m, PeSe),
n
3
125.2 (d, JCP ¼ 24.8 Hz, C3/C4H3O), 140.9 (d, JCP ¼ 99.3 Hz, C2/
1450 (m, PeC), 2155 (s, C^C), 2922/2961 (w, CeH), 3055 (w, ]
2
1
4
C4H3O), 148.8 (d, JCP
¼
2.9 Hz, C5/C4H3O). 31P{1H} NMR
CeH). 1H NMR (500.30 MHz, CDCl3,
d
): 2.29 (s, 6 H, 2-CH3C6H4),
3
(202.53 MHz, CDCl3,
d
): ꢁ83.4. HRMS (ESI-TOF) C20H15FeO2P [M]þ
4.23 (s, 5 H, C5H5), 4.32 (pt, JHH ¼ 1.8 Hz, 2 H, C5H4), 4.58 (pt,
m/z: calcd.: 374.0154, found: 374.0053; [M þ nK]þ m/z: calcd.:
412.9791, found: 412.9884. The 13C signals for the ethynyl func-
tionality could not be observed.
3JHH ¼ 1.8 Hz, 2 H, C5H4), 7.17e7.20 (m, 2 H, Hp/2-CH3C6H4),
7.38e7.45 (m, 4 H, Hm/2-CH3C6H4), 8.38e8.43 (m, 4 H, Ho/2-
3
CH3C6H4). c21.3 (d, JCP
¼
5.7 Hz, 2-CH3C6H4), 61.1 (d,
3JCP ¼ 4.1 Hz, Ci/C5H4), 70.2 (s, C5H5), 70.3 (s, C5H4), 72.4 (s, C5H4),
4.5.4. Synthesis of P(C^CFc)(tBu)2 (3e)
76.7 (d, JCP ¼ 148.9 Hz, eC^CeP), 108.8 (d, JCP ¼ 26.3 Hz,
1
2
1.0 g (4.76 mmol) of 1 was reacted according to the general
synthesis methodology described earlier with 1.90 mL
(4.75 mmol) of nBuLi and 0.86 g (4.75 mmol) of chlorodi-t-butyl-
phosphine (2e). The resulting residue was purified by column
chromatography on silica gel using nhexane as eluent. Compound
3e was obtained as a yellow solid. Yield: 1.03 g (2.90 mmol, 61%
based on 2e). Anal. Calcd. for C20H27FeP (354.25 g/mol): C, 67.81;
eC^CeP), 126.4 (d, JCP
¼
14.7 Hz, 2-CH3C6H4), 129.4 (d,
JCP ¼ 85.5 Hz, 2-CH3C6H4), 132.1 (d, JCP ¼ 11.1 Hz, 2-CH3C6H4), 132.2
(d, JCP ¼ 3.0 Hz, 2-CH3C6H4), 133.8 (d, JCP ¼ 15.2 Hz, 2-CH3C6H4),
140.5 (d, JCP ¼ 9.7 Hz, 2-CH3C6H4). 31P{1H} NMR (202.53 MHz,
CDCl3,
d
): 0.9 (1JPSe ¼ 728.7 Hz). HRMS (ESI-TOF) C26H23FePSe
[M þ nNa]þ m/z: calcd.: 524.9946, found: 524.9946; [M þ nK]þ m/z:
calcd.: 540.9686, found: 540.9665.

62
B. Milde et al. / Journal of Organometallic Chemistry 706-707 (2012) 52e65
4.6.2. Synthesis of (Se)P(C^CFc)(2,4,6-Me3C6H4)2 (4c)
1448 (m, PeC), 2158 (s, C^C), 2852/2928 (s, CeH), 3095 (w, ]
100 mg (0.21 mmol) of 3c were reacted with 20 mg (0.25 mmol)
of elemental selenium. After appropriate work-up, 4c was obtained
as an orange solid. Yield: 117 mg (0.21 mmol, 100% based on 3c).
Anal. Calcd. for C30H31FePSe (557.35 g/mol): C, 64.65; H, 5.61.
CeH). 1H NMR (500.30 MHz, CDCl3,
d): 1.24e1.78 (m, 11 H, C6H11),
1.91e2.09 (m, 11 H, C6H11), 4.26 (s, 5 H, C5H5), 4.30 (pt, 3JHH ¼ 1.9 Hz,
3
2 H, C5H4), 4.55 (pt, JHH ¼ 1.9 Hz, 2 H, C5H4). 13C{1H} NMR
(125.81 MHz, CDCl3,
d
): 25.9 (d, JCP ¼ 8.0 Hz, C6H11), 25.9 (d,
Found: C, 64.91; H, 5.22. Mp.: 165 ꢀC. IR (KBr,
n
/cmꢁ1): 563 (m,
JCP ¼ 6.5 Hz, C6H11), 26.2 (d, JCP ¼ 15.5 Hz, C6H11), 26.4 (d,
JCP ¼ 13.8 Hz, C6H11), 27.1 (d, JCP ¼ 4.4 Hz, C6H11), 38.3 (d,
1JCP ¼ 50.9 Hz, C1/C6H11), 61.3 (d, 3JCP ¼ 3.6 Hz, Ci/C5H4), 70.0 (s, Cb/
PeSe), 821 (m, ]CeH, para-subst. benzene),1448 (m, PeC), 2157 (s,
C^C), 2924/2963 (m, CeH), 3021/3098 (w, ]CeH). 1H NMR
1
(500.30 MHz, CDCl3,
d
): 2.28 (s, 6 H, 2,4,6-(CH3)3C6H2), 2.61 (s, 12 H,
C5H4), 70.3 (s, C5H5), 72.5 (m, Ca/C5H4), 74.5 (d, JCP ¼ 118.4 Hz,
2,4,6-(CH3)3C6H2), 4.18 (s, 5 H, C5H5), 4.27 (pt, 3JHH ¼ 1.9 Hz, 2 H, Hb/
eC^CeP), 106.6 (d, JCP ¼ 17.6 Hz, eC^CeP). 31P{1H} NMR
2
C5H4), 4.49 (pt, 3JHH ¼ 1.9 Hz, 2 H, Ha/C5H4), 6.85 (dd, 4JHP ¼ 5.2 Hz,
(202.53 MHz, CDCl3,
d
): 31.0 (1JPSe ¼ 712.5 Hz). HRMS (ESI-TOF)
4JHH ¼ 0.4 Hz, 4 H, 2,4,6e(CH3)3C6H2); 13C{1H} NMR (125.81 MHz,
C24H31FePSe [M]þ m/z: calcd.: 486.0675, found: 486.0679.
5
CDCl3,
d
): 21.9 (d, JCP ¼ 1.5 Hz, 2,4,6-(CH3)3C6H2), 23.2 (d,
3JCP ¼ 6.9 Hz, 2,4,6-(CH3)3C6H2), 62.2 (d, 3JCP ¼ 4.5 Hz, Ci/C5H4), 69.9
4.7. General procedure for the synthesis of palladium complexes 6e,
6f and 7aef
(s, Cb/C5H4), 69.9 (s, C5H5), 71.9 (d, JCP ¼ 1.4 Hz, Ca/C5H4), 81.0 (d,
4
1JCP ¼ 143.7 Hz, eC^CeP), 107.3 (d, 2JCP ¼ 26.8 Hz, eC^CeP), 128.4
1
(d, JCP ¼ 86.1 Hz, C/2,4,6-(CH3)3C6H2), 131.8 (d, JCP ¼ 11.6 Hz, C/
Phosphines 3ae3f were reacted with 0.5 equivalents of
[PdCl2(cod)] (5) or [PdCl2(SEt2)2] (8) in 40 mL of dry dichloro-
methane. The appropriate reaction solution was stirred for 2 h at
ambient temperature. Afterward, the solvent was removed in
vacuum and the residue was washed 5e6 times with 5 mL portions
of diethyl ether. After drying in vacuum the appropriate complexes
were obtained as red or brown solids.
2,4,6-(CH3)3C6H2),140.5 (d, JCP ¼ 10.9 Hz, C/2,4,6-(CH3)3C6H2),140.6
(d, JCP ¼ 2.4 Hz, C/2,4,6-(CH3)3C6H2); 31P{1H} NMR (202.53 MHz,
CDCl3,
d
): ꢁ17.5 (1JPSe ¼ 709.5 Hz). HRMS (ESI-TOF) C30H31FePSe
[M]þ m/z: calcd.: 558.0675, found: 558.0627.
4.6.3. Synthesis of (Se)P(C^CFc)(cC4H3O)2 (4d)
100 mg (0.27 mmol) of 3d were reacted with 25 mg (0.32 mmol)
of elemental selenium. After appropriate work-up, 4d was obtained
as an orange solid. Yield: 122 mg (0.27 mmol, 100% based on 3d).
Anal. Calcd. for C20H15FeO2PSe (453.11 g/mol): C, 53.01; H, 3.34.
4.7.1. Synthesis of [Pd(Cl)(m
-Cl)(P(C^CFc)tBu2)]2 (6e)
0.5 g (1.41 mmol) of 3f were reacted with 0.20 g (0.70 mmol) of
5. After appropriate work-up, 6e was isolated as a brown solid.
Yield: 700 mg (0.66 mmol, 94% based on 5). Anal. Calcd. for
C40H54Cl4Fe2P2Pd2 (1063.15 g/mol): C, 45.19; H, 5.12. Found: C,
Found: C, 53.40; H, 3.37. Mp.: 162 ꢀC. IR (NaCl, /cmꢁ1): 575 (m,
n
PeSe), 1005 (m, CeO), 1456 (w, PeC), 1549 (w, C]C), 2156 (vs,
C^C), 3108 (w, ]CeH). 1H NMR (500.30 MHz, CDCl3,
5 H, C5H5), 4.34 (pt, JHH ¼ 1.9 Hz, C5H4), 4.60 (pt, JHH ¼ 1.9 Hz,
C5H4), 6.51 (dpt, 4JHP ¼ 1.8 Hz, 3JHH ¼ 3.5 Hz, 3JHH ¼ 1.7 Hz, 2 H, H4/
C4H3O), 7.31 (m, 2 H, H3/C4H3O), 7.74 (m, 2 H, H5/C4H3O). 13C{1H}
d
): 4.26 (s,
44.91; H, 5.16. Mp.: 156 ꢀC. IR (KBr, /cmꢁ1): 1468 (w, PeC), 2155
n
3
3
(vs, C^C), 2867/2890/2922/2966 (w, CeH), 3097 (w, ]CeH). 1H
NMR (500.30 MHz, CDCl3,
d
): 1.62 (d, 3JHP ¼ 16.9 Hz, 36 H, C(CH3)3),
3
4.28 (pt, JHH ¼ 1.9 Hz, 4 H, C5H4), 4.32 (s, 10 H, C5H5), 4.58 (pt,
NMR (125.81 MHz, CDCl3,
d
): 60.1 (d, 3JCP ¼ 5.1 Hz, Ci/C5H4), 70.6 (s,
3JHH ¼ 1.9 Hz, 4 H, C5H4). 13C{1H} NMR (125.81 MHz, CDCl3,
d): 30.2
4
Cb/C5H4), 70.6 (s, C5H5), 72.8 (d, JCP ¼ 1.5 Hz, Ca/C5H4), 74.0 (d,
(d, 2JCP ¼ 3.4 Hz, C(CH3)3), 40.2 (d, 1JCP ¼ 24.5 Hz, C(CH3)3), 62.0 (m,
1JCP ¼ 169.3 Hz, eC^CeP), 108.6 (d, 2JCP ¼ 32.7 Hz, eC^CeP), 111.6
Ci/C5H4), 70.0 (s, C5H4), 70.7 (s, C5H5), 72.7 (s, C5H4), 77.3 (C^CeP*),
3
2
(d, JCP ¼ 10.2 Hz, C4/C4H3O), 122.8 (d, JCP ¼ 25.3 Hz, C3/C4H3O),
116.8 (s, eC^CeP). 31P{1H} NMR (202.53 MHz, CDCl3,
d
): 49.7.
Cl]þ m/z: calcd.:
1026.9536, found: 1026.9515* signal concealed by CDCl3.
1
4
145.4 (d, JCP ¼ 132.1 Hz, C2/C4H3O), 149.0 (d, JCP ¼ 8.1 Hz, C5/
HRMS (ESI-TOF) C40H54Cl4Fe2P2Pd2 [M
ꢁ
C4H3O). 31P{1H} NMR (202.53 MHz, CDCl3,
d): ꢁ37.9
(1JPSe ¼ 783.9 Hz). HRMS (ESI-TOF) C20H15FeO2PSe [M]þ m/z: calcd.:
453.9320, found: 453.9275.
4.7.2. Synthesis of [Pd(Cl)(m
-Cl)(P(C^CFc)(cC6H11)2)]2 (6f)
0.5 g (1.23 mmol) of 3g were reacted with 0.17 g (0.61 mmol) of
5. After appropriate work-up, 6f was obtained as a brown solid.
Yield: 642 mg (0.55 mmol, 90% based on 5). Anal. Calcd. for
C48H62Cl4Fe2P2Pd2 (1167.30 g/mol): C, 52.58; H, 5.70. Found: C,
4.6.4. Synthesis of (Se)P(C^CFc)(tBu)2 (4e)
100 mg (0.28 mmol) of 3e were reacted with 27 mg (0.34 mmol)
of selenium in its elemental form. After appropriate work-up, 4e was
obtained as an orange solid. Yield: 113 mg (0.28 mmol, 100% based
on 3e). Anal. Calcd. for C20H27FePSe (433.21 g/mol): C, 55.45; H, 6.28.
52.71; H, 5.65. Mp.: 200 ꢀC (dec). IR (KBr, /cmꢁ1): 1446 (w, PeC),
n
1653 (w, C]C), 2151 (s, C^C), 2851/2928 (vs, CeH), 3098 (w, ]
Found: C, 55.50; H, 6.19. Mp.: 165 ꢀC. IR (NaCl,
n
/cmꢁ1): 533 (m,
CeH). 1H NMR (500.30 MHz, CDCl3,
d
): 1.26e1.37 (m, 8 H, C6H11),
PeSe),1470 (m, PeC), 2158 (s, C^C), 2868/2922/2962 (s, CeH), 3092
1.75e2.01 (m, 20 H, C6H11), 2.21e2.38 (m, 8 H, C6H11), 2.52e2.58
(m, 4 H, C6H11), 2.88e2.92 (m, 4 H, C6H11), 4.28 (m, 4 H, C5H4),
4.29 (s, 10 H, C5H5), 4.56 (pt, 3JHH ¼ 1.7 Hz, 4 H, C5H4). 13C{1H} NMR
(w, ]CeH). 1H NMR (500.30 MHz, CDCl3,
d
): 1.46 (d, 3JHP ¼ 17.3 Hz,
18 H, C(CH3)3), 4.24 (s, 5 H, C5H5), 4.27 (pt, 3JHH ¼ 1.8 Hz, 2 H, C5H4),
4.52 (pt, 3JHH ¼ 1.8 Hz, 2 H, C5H4). 13C{1H} NMR (125.81 MHz, CDCl3,
(125.81 MHz, CDCl3, d
): 25.9 (, C6/C6H11), 26.6 (m, C2/3/C6H11), 26.8
d
): 27.7 (d, 2JCP ¼ 2.8 Hz, C(CH3)3), 38.4 (d, 1JCP ¼ 41.9 Hz, C(CH3)3),
(m, C2/3/C6H11), 29.0 (m, C4/5/C6H11), 31.2 (s, C4/5/C6H11), 36.4 (d,
1JCP ¼ 35.5 Hz, C1/C6H11), 62.6 (s, Ci/C5H4), 70.2 (s, C5H4), 70.8 (s,
61.5 (d, 3JCP ¼ 3.8 Hz, Ci/C5H4), 69.9 (s, Cb/C5H4), 70.1 (s, C5H5), 72.2 (d,
4JCP ¼ 1.3 Hz, Ca/C5H4), 75.0 (d, 1JCP ¼ 114.2 Hz, -C^C-P), 106.7 (d,
1
C5H5), 72.8 (s, C5H4), 75.7 (d, JCP ¼ 91.5 Hz, C^CeP), 110.2 (pt,
2JCP ¼ 15.8 Hz, eC^CeP). 31P{1H} NMR (202.53 MHz, CDCl3,
d): 56.3
J
CP
¼ 5.3 Hz, C^CeP). 31P{1H} NMR (202.53 MHz, CDCl3,
d): 31.0.
2,3
(1JPSe ¼ 715.3 Hz). HRMS (ESI-TOF) C20H27FePSe [M þ nNa]þ m/z:
HRMS (ESI-TOF) C48H62Cl4Fe2P2Pd2 [M]þ m/z: calcd.: 1167.9843,
calcd.: 457.0259, found: 457.0256.
found: 1167.9851.
4.6.5. Synthesis of (Se)P(C^CFc)(cC6H11 2
)
(4f)
4.7.3. Synthesis of [PdCl2(P(C^CFc)(2-MeC6H4)2)2] (7b)
100 mg (0.25 mmol) of 3f were reacted with 24 mg (0.30 mmol)
of selenium. After appropriate work-up, 4f was obtained as an
orange solid. Yield: 121 mg (0.25 mmol, 100% based on 3f). Anal.
Calcd. for C24H31FePSe (485.28 g/mol): C, 59.40; H, 6.44. Found: C,
0.5 g (1.18 mmol) of 3b were reacted with 0.17 g (0.59 mmol) of
5. After appropriate work-up, 7b was obtained as a red solid. Yield:
560 mg (0.55 mmol, 95% based on 5). Anal. Calcd. for
C52H46Cl2Fe2P2Pd $ 1/3 CH2Cl2 (1050.20 g/mol): C, 59.85; H, 4.48.
60.12; H, 6.60. Mp.: 135 ꢀC. IR (NaCl,
n
/cmꢁ1): 526/536 (m, PeSe),
Found: C, 60.14; H, 4.44. Mp.: 214 ꢀC. IR (KBr, /cmꢁ1): 756 (s, ]
n

B. Milde et al. / Journal of Organometallic Chemistry 706-707 (2012) 52e65
63
CeH, o-disubst. benzene), 1448 (w, PeC), 1627 (C]C), 2159 (vs,
C^C), 2922/2963 (w, CeH), 3056/3081 (w, ]CeH). 1H NMR
C40H54Cl2Fe2P2Pd (885.82 g/mol): C, 54.24; H, 6.14. Found: C, 53.75;
H, 6.17. Mp.: 250 ꢀC. IR (KBr, /cmꢁ1): 1459 (w, PeC), 1655 (w, C]C),
n
(500.30 MHz, CDCl3,
d
): 2.86 (s, 12 H, 2-CH3C6H4), 4.24 (pt,
2162 (s, C^C), 2863/2917/2955 (m, CeH), 3097 (w, ]CeH). 1H
3JHH ¼ 1.9 Hz, 4 H, C5H4), 4.25 (s, 10 H, C5H5), 4.55 (pt, 3JHH ¼ 1.9 Hz,
4 H, C5H4), 5.30 (s, CH2Cl2), 7.18e7.41 (m, 12 H, Hm,p/2-CH3C6H4),
7.77e7.86 (m, 4 H, Ho/2-CH3C6H4). 13C{1H} NMR (125.81 MHz,
NMR (500.30 MHz, CD2Cl2,
d
): 1.59 (t, JHP ¼ 7.7 Hz Hz, 36 H,
3
C(CH3)3), 4.25 (pt, 3JHH ¼ 1.8 Hz, 4 H, C5H4), 4.28 (s, 10 H, C5H5), 4.54
(pt, 3JHH ¼ 1.8 Hz, 4 H, C5H4). 13C{1H} NMR (125.81 MHz, CDCl3,
d):
2
CDCl3,
d
): 23.5 (pt, 3JCP ¼ 4.0 Hz, 2-CH3C6H4), 53.52 (s, CH2Cl2), 62.9
30.2 (pt, JCP ¼ 3.4 Hz, C(CH3)3), 40.1 (pt, 1JCP ¼ 24.5 Hz, C(CH3)3),
(m, Ci/C5H4), 69.7 (s, Cb/C5H4), 70.4 (s, C5H5), 72.3 (s, Ca/C5H4), 74.9
(pt, 1JCP ¼ 51.9 Hz, eC^CeP),111.4 (d, 2JCP ¼ 9.2 Hz, eC^CeP),125.9
62.0 (m, Ci/C5H4), 70.0 (s, C5H4), 70.7 (s, C5H5), 72.7 (s, C5H4), 77.4
(C^CeP*), 116.8 (m, C^CeP). 31P{1H} NMR (202.53 MHz, CDCl3,
d):
(pt, JCP ¼ 6.0 Hz, 2-CH3C6H4), 126.8 (pt, JCP ¼ 28.7. Hz, Ci/2-
49.7. HRMS (ESI-TOF) C40H54Cl2Fe2P2Pd [M]þ m/z: calcd.: 886.0808,
found: 886.0780; [M ꢁ Cl]þ m/z: calcd.: 849.1134, found: 849.1083;
[MþnH-2Cl]þ m/z: calcd.: 815.1526, found: 815.1471; [M]2þ m/z:
calcd.: 443.0401, found: 443.0332* signal concealed by CDCl3.
1
CH3C6H4), 131.3 (s, Cp/2-CH3C6H4), 131.5 (pt, JCP ¼ 4.2 Hz, 2-
CH3C6H4), 135.1 (pt, JCP
¼
8.0 Hz, 2-CH3C6H4), 142.6 (pt,
JCP ¼ 5.5 Hz, 2-CH3C6H4). 31P{1H} NMR (202.53 MHz, CDCl3,
d
): ꢁ6.8. HRMS (ESI-TOF) C52H46Cl2Fe2P2Pd [M]þ m/z: calcd.:
1022.0186, found: 1022.0145; [M ꢁ Cl]þ m/z: calcd.: 985.0511,
found: 985.0487; [M]2þ m/z: calcd.: 511.0090, found: 511.0083;
[M ꢁ Cl]2þ m/z: calcd.: 492.5253, found: 492.5236.
4.7.7. Synthesis of [PdCl2(P(C^CFc)(cC6H11 2 2
) ) ] (7f)
0.5 g (1.23 mmol) of 3f were reacted with 0.22 g (0.61 mmol) of 8.
Afterappropriatework-up, 7f was obtained as an orange solid. Yield:
481 mg (0.58 mmol, 95% based on 8). Anal. Calcd. for
C48H62Cl2Fe2P2Pd (829.71 g/mol): C, 58.24; H, 6.31. Found: C, 58.34;
4.7.4. Synthesis of [PdCl2(P(C^CFc)(2,4,6-Me3C6H4)2)2] (7c)
0.5 g (1.05 mmol) of 3c were reacted with 0.15 g (0.52 mmol) of
5. After appropriate work-up, 7c could be isolated as a brown solid.
Yield: 556 mg (0.49 mmol, 94% based on 5). Anal. Calcd. for
C60H62Cl2Fe2P2Pd (1134.10 g/mol): C, 63.54; H, 5.51. Found: C,
H, 6.80. Mp.: 210 ꢀC. IR (KBr, /cmꢁ1): 1447 (w, PeC), 1655 (w, C]C),
n
2158 (s, C^C), 2849/2925 (s, CeH), 3075 (w, ]CeH). 1H NMR
(500.30 MHz, CD2Cl2, d
): 1.28 (m, 4 H, H6/C6H11), 1.39 (m, 8 H, H2/3/
C6H11),1.63 (m, 8 H, H4/5/C6H11),1.74 (m, 4 H, H6/C6H11),1.86 (m, 8 H,
H2/3/C6H11), 2.13 (m, 4 H, H4/5/C6H11), 2.45 (m, 4 H, H4/5/C6H11), 2.76
(m, 4 H, H1/C6H11), 4.21 (s, 10 H, C5H5), 4.26 (pt, 3JHH ¼ 1.5 Hz, 4 H,
C5H4), 4.36 (pt, 3JHH ¼ 1.5 Hz, 4 H, C5H4). 13C{1H} NMR (125.81 MHz,
63.67; H, 5.69. Mp.: 172 ꢀC. IR (KBr, /cmꢁ1): 818 (m, ]CeH, para-
n
subst. benzene), 1459 (m, PeC), 1603 (m, C]C), 2152 (s, C^C),
2923/2963 (w, CeH), 3072 (w, ]CeH). 1H NMR (500.30 MHz,
CDCl3,
d
): 2.24 (s, 6 H, 2,4,6-(CH3)3C6H2), 2.70 (s, 12 H, 2,4,6-
CDCl3,
d
): 25.2 (s, C6/C6H11), 25.8 (pt, 2JCP ¼ 5.7 Hz, C2/3/C6H11), 26.0
3
2
(CH3)3C6H2), 4.19 (s, 5 H, C5H5), 4.20 (pt, JHH ¼ 1.8 Hz, 2 H, C5H4),
(pt, JCP ¼ 8.0 Hz, C2/3/C6H11), 28.7 (m, C4/5/C6H11), 29.3 (s, C4/5/
C6H11), 37.5 (dpt, 1JCP ¼ 32.3 Hz, C1/C6H11), 61.4 (m, Ci/C5H4), 68.9 (s,
C5H4), 69.0 (s, C5H5), 71.0 (s, C5H4), 74.4 (d, 1JCP ¼ 92.7 Hz, C^CeP),
109.4 (pt, 2JCP ¼ 5.1 Hz, C^CeP). 31P{1H} NMR (202.53 MHz, CDCl3,
3
4.49 (pt, JHH ¼ 1.8 Hz, 2 H, C5H4), 6.84 (m, 4 H, 2,4,6-(CH3)3C6H2).
13C{1H} NMR (125.81 MHz, CDCl3,
d): 21.1 (s, 2,4,6-(CH3)3C6H2), 25.6
(pt, 3JCP ¼ 4.1 Hz, 2,4,6-(CH3)3C6H2), 64.2 (pt, 3JCP ¼ 1.2 Hz, Ci/C5H4),
69.3 (s, Cb/C5H4), 70.1 (s, C5H5), 72.0 (s, Ca/C5H4), 77.4 (pt,
1JCP ¼ 66.7 Hz, C^CeP), 109.1 (pt, 2JCP ¼ 8.9 Hz, C^CeP), 126.0 (pt,
d
): 28.4. HRMS (ESI-TOF) C48H62Cl2Fe2P2Pd [M]þ m/z: calcd.:
990.1437, found: 990.1377; [M ꢁ Cl]þ m/z: calcd.: 953.1762, found:
953.1705; [M]2þ m/z: calcd.: 495.0716, found: 495.0667; [M ꢁ Cl]2þ
m/z: calcd.: 477.5872, found: 477.5838.
1JCP ¼ 27.6 Hz, Ci/2,4,6-(CH3)3C6H2), 130.7 (pt, JCP ¼ 4.5 Hz, Cm/
3
2,4,6-(CH3)3C6H2), 140.1 (s, Cp/2,4,6-(CH3)3C6H2), 142.5 (pt,
2JCP ¼ 5.8 Hz, Co/2,4,6-(CH3)3C6H2). 31P{1H} NMR (202.53 MHz,
CDCl3,
d
): ꢁ24.0. HRMS (ESI-TOF) C60H62Cl2Fe2P2Pd [M]þ m/z:
4.8. Synthesis of [PdCl2(P(C^CFc)(cC6H11 2 2
) ) ][B(C6F5)4]2 ([7f]
[(B(C6F5)4)]2)
calcd.: 1134.1441, found: 1134.1351; [M
ꢁ
Cl]þ m/z: calcd.:
1097.1765, found: 1097.1688; [M-nH-2Cl]þ m/z: calcd.: 1061.2001,
found: 1061.1929; [M-(C30H31FeP)PdCl2]þ m/z: calcd.: 478.1508,
found: 478.1480.
80 mg (0.096 mmol) of 7f were dissolved in 20 mL of dry
tetrahydrofuran, cooled to ꢁ60 ꢀC and 83 mg (0.096 mmol) of
[AgB(C6F5)4]∙Et2O dissolved in 20 mL of dry tetrahydrofuran were
added dropwise. The resulting yellow solution was slowly warmed
to ambient temperature and stirred overnight. After concentration
in vacuum to 5 mL, 20 mL of nhexane were added forming a dark
precipitate. The supernatant layer was decanted and the precipitate
was washed 3 times with 10 mL portions of nhexane. The product
was obtained as a dark purple solid after drying it in vacuum. Yield:
95 mg (0.040 mmol, 42% based on 7f). Anal. Calcd. for
C96H62B2Cl2F40Fe2P2Pd (2348.04 g/mol): C, 49.11; H, 2.66. Found: C,
4.7.5. Synthesis of [PdCl2(P(C^CFc)(cC4H3O)2)2] (7d)
0.5 g (1.34 mmol) of 3d were reacted with 0.19 g (0.67 mmol) of
5. After appropriate work-up, 7d was obtained as a dark red solid.
Yield: 596 mg (0.64 mmol, 96% based on 5). Anal. Calcd. for
C40H30Cl2Fe2O4P2Pd/1/4 CH2Cl2 (946.86 g/mol): C, 51.06; H, 3.25.
Found: C, 51.05; H, 3.32. Mp.: >250 ꢀC. IR (KBr, /cmꢁ1): 1010 (m,
n
CeO), 1454 (w, PeC), 1573 (w, C]C), 2155 (s, C^C), 3107 (w, ]
CeH). 1H NMR (500.30 MHz, CDCl3,
d): 4.12 (s, 5 H, C5H5), 4.26
(pt, 3JHH ¼ 1.6 Hz, 2 H, C5H4), 4.32 (pt, 3JHH ¼ 1.6 Hz, 2 H, C5H4), 5.30
50.66; H, 3.89. Mp: 196 ꢀC (dec.). IR (KBr,
1642 (w, C]C), 2146 (s, C^C), 2856/2934 (s, CeH). HRMS (ESI-
n
/cmꢁ1): 1465 (s, PeC),
(s, CH2Cl2), 6.53 (m, 2 H, H4/C4H3O), 7.33 (m, 2 H, H3/C4H3O), 7.70
(m, 2 H, H2/C4H3O). 13C{1H} NMR (125.81 MHz, CDCl3,
d
): 53.52 (s,
TOF) C96H62B2Cl2F40Fe2P2Pd [M-
953.1762, found: 953.1568.
2
B(C6F5)4]2þ m/z: calcd.:
CH2Cl2), m60.8 (m, Ci/C5H4), 70.4 (s, C5H4), 70.6 (s, C5H5), 72.6 (s,
1
2
C5H4), 73.7 (d, JCP ¼ 60.0 Hz, C^CeP), 94.6 (pt, JCP ¼ 8.1 Hz,
C^CeP), 111.9 (pt, 3JCP ¼ 4.4 Hz, C4/C4H3O), 125.2 (d, 2JCP ¼ 24.8 Hz,
4.9. General procedure for the Suzuki reaction
C3/C4H3O), 148.8 (d, JCP
¼
99.1 Hz, C2/C4H3O), 148.8 (pt,
1
4JCP ¼ 3.3 Hz, C5/C4H3O). 31P{1H} NMR (202.53 MHz, CDCl3,
2-Bromo toluene (500 mg, 2.92 mmol) or 40-chloro acetophe-
none (464 mg, 3.00 mmol), phenyl boronic acid (470 mg,
3.85 mmol), potassium carbonate (1.21 g, 8.76 mmol) and acetyl
ferrocene (114 mg, 0.50 mmol) were dissolved in a dioxane-water
mixture (12 mL, ratio 2:1, v/v). After addition of 0.1 mol% (reac-
tion of 2-bromo toluene) or 0.5 mol% (reaction of 40-chloro aceto-
phenone) of the appropriate catalyst (6e, 6f, 7aef), the reaction
mixture was stirred for 1 h at 100 ꢀC. Samples of 1 mL were taken
d
): ꢁ32.4. HRMS (ESI-TOF) C40H30Cl2Fe2O4P2Pd [M]þ m/z: calcd.:
925.8727, found: 925.8656.
4.7.6. Synthesis of [PdCl2(P(C^CFc)tBu2)2] (7e)
0.5 g (1.41 mmol) of 3e were reacted with 0.25 g (0.70 mmol) of
8. After appropriate work-up, 7e was obtained as an orange solid.
Yield: 584 mg (0.66 mmol, 94% based on 8). Anal. Calcd. for

64
B. Milde et al. / Journal of Organometallic Chemistry 706-707 (2012) 52e65
Table 5
Crystal and intensity collection data for 6e, 6f, 7b, and 7c.
6e
6f
7b
7c
Formula weight
Chemical formula
Crystal system
Space group
a (Å)
1063.07
C40H54Cl4Fe2P2Pd2
Triclinic
P ꢁ1
1405.95
C50H64Cl10Fe2P2Pd2
Triclinic
1260.56
1134.04
C60H62Cl2Fe2P2Pd
Triclinic
C54H48Cl8Fe2P2Pd
Monoclinic
C2/c
16.5847(4)
15.3081(18)
21.4121(14)
90.02
95.826(7)
90.0010(10)
5408.0(7)
1.548
P-1
P-1
7.8922(3)
11.3363(6)
12.7408(6)
107.024(4)
92.317(3)
101.085(3)
1063.92(9)
1.659
11.1687(5)
12.0851(5)
12.3642(5)
108.658
104.146
110.544
1355.68(10)
1.722
708
10.7065(3)
11.1859(3)
11.7479(3)
70.779(2)
78.395(2)
74.904(2)
1272.35(6)
1.480
b (Å)
c (Å)
a
b
g
(ꢀ)
(ꢀ)
(ꢀ)
V (Å3)
rcalc (g cmꢁ3
F(000)
)
536
2544
584
Crystal dimensions (mm)
Z
0.2 ꢂ 0.2 ꢂ 0.1
0.1 ꢂ 0.1 ꢂ 0.05
0.05 ꢂ 0.05 ꢂ 0.05
0.2 ꢂ 0.1 ꢂ 0.08
1
1
4
1
Max. and min. transmission
Absorption coefficient (
Scan range (ꢀ)
1.00000, 0.92315
1.854
1.00000, 0.30942
14.834
1.00000, 0.74777
1.349
1.00000, 0.95654
1.120
l )
, mmꢁ1
2.92e26.06
ꢁ9 ꢃ h ꢃ 9,
ꢁ14 ꢃ k ꢃ 14,
ꢁ15 ꢃ l ꢃ 15
9450
4.37e61.99
ꢁ12 ꢃ h ꢃ 12,
ꢁ11 ꢃ k ꢃ 13,
ꢁ14 ꢃ l ꢃ 14
10,537
2.97e26.07
ꢁ20 ꢃ h ꢃ 20,
ꢁ18 ꢃ k ꢃ 18,
ꢁ26 ꢃ l ꢃ 26
15,697
2.88e26.00
ꢁ13 ꢃ h ꢃ 13,
ꢁ11 ꢃ k ꢃ 13,
ꢁ14 ꢃ l ꢃ 13
12,216
Index ranges
Total reflections
Unique reflections
Rint
4174
0.0205
4247
0.0199
5113
0.0844
4963
0.0242
Data/restraints/para-meters
4174/0/226
0.971
0.0212, 0.0451
0.0306, 0.0467
0.550, ꢁ0.431
4247/0/298
1.073
0.0233, 0.0636
0.0262, 0.0653
0.542, ꢁ0.575
5113/0/303
0.951
0.0439, 0.0843
0.0955, 0.1024
0.766, ꢁ0.692
4963/0/304
1.117
0.0315, 0.0877
0.0432, 0.0939
0.708, ꢁ0.670
Goodness-of-fit on F2
a
R1a, wR2 [I 2
r
(I)]
a
R1a, wR2 (all data)
Largest differences in peak and hole peak in final Fourier map (e Åꢁ3
)
R1 ¼ ½SðjjFoj ꢁ jFcjÞ=SjFojꢄ; wR2 ¼ ½SðwðFo2 ꢁ Fc2Þ2Þ=SðwFo4Þꢄ1=2; S ¼ ½SwðFo2 ꢁ Fc2Þ2ꢄ=ðn ꢁ pÞ1=2. n ¼ number of reflections, p ¼ parameters used.
a
after 2.5, 5, 10, 20, 30, and 60 min and chromatographed on silica
gel with diethyl ether as eluent. All volatiles were evaporated under
reduced pressure and the conversions were determined by 1H NMR
spectroscopy.
Appendix A. Supplementary material
CCDC 838741; 838740; 838738; 838739 contain the supple-
mentary crystallographic data for the compounds 6e, 6f, 7b and 7c
respectively. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
4.10. General procedure for the Heck reaction
Iodo benzene (612 mg, 3.0 mmol), t-butylacrylate (397 mg,
3.1 mmol), EtNiPr2 (452 mg, 3.5 mmol) and acetyl ferrocene
(114 mg, 0.5 mmol) were dissolved in a tolueneeacetonitrile
mixture (15 mL, 1:1, v/v) and loaded with 0.5 mol% of the respec-
tive catalyst (6e, 6f, 7ae7f). The reaction mixture was stirred at
80 ꢀC and samples (1 mL) were taken in periods of 1 h. The samples
were chomatographed on silica gel with diethyl ether as eluent. All
volatiles were evaporated and the conversions were determined by
1H NMR spectroscopy.
Appendix. Supplementary material
Supplementary material associated with this article can be
found, in the online version, at doi:10.1016/j.jorganchem.2012.01.
017.
References
[1] For example: P.J. Low, T.M. Hayes, K.A. Udachin, A.E. Goeta, J.A.K. Howard,
G.D. Enright, A.J. Carty J. Chem. Soc. Dalton Trans. (2002) 1455e1464 (and
references cited therein).
4.11. Crystal structure determination
[2] For example: (a) J. Fornies, E. Lalinde, A. Martin, M.T. Moreno, A.J. Welch,
J. Chem. Soc. Dalton Trans. 1 (1995) 1333e1340;
The crystal and intensity collection data for 6e, 6f, 7b, and 7c are
summarized in Table 5. All data were collected on an Oxford Gemini
S diffractometer with graphite monochromatized Mo Ka radiation
(b) M. Bardaji, A. Laguna, Organometallics 20 (2001) 3906e3912;
(c) T. Baumgartner, K. Huynth, S. Schleidt, A.J. Lough, I. Manners, Chem. Eur. J.
8 (2002) 4622e4632;
(d) T. De Simone, R.S. Dickson, B.W. Skelton, A.W. White, Inorg. Chim. Acta 240
(1995) 323e333;
(e) I. Moldes, J. Ros, Inorg. Chim. Acta 232 (1995) 75e81.
[3] For example: (a) H. Lang, L. Zsolnai, Chem. Ber. (1991) 259e264;
(b) J. Fornies, M.A. Gomez-Saso, E. Lalinde, F. Martinez, M.T. Moreno, Organ-
ometallics 11 (1992) 2873e2883;
(
l
¼ 0.71073 Å) at 100 K (6e, 7b, 7c) and graphite monochromatized
Cu Ka radiation (
l
¼ 1.54 Å) at 110 K (6f). The structures were solved
by direct methods using SHELXS-97 [35] (6e, 6f) or SIR-92 [36] (7b,
7c) and refined by full-matrix least-square procedures on F2 using
SHELXL-97 [37]. All non-hydrogen atoms were refined anisotropi-
cally and a riding model was employed in the refinement of the
hydrogen atom positions.
(c) J.R. Berenguer, L.R. Falvello, J. Fornies, E. Lalinde, M. Tomas, Organome-
tallics 12 (1993) 6e7;
(d) J. Diez, M.P. Gamasa, J. Gimeno, E. Lastra, A. Villar, Eur. J. Inorg. Chem. 1
(2006) 78e87;
(e) F. Hong, Y. Ho, Y. Chang, Y. Lai, Tetrahedron 60 (2004) 2639e2645;
(f) H. Lang, M. Leise, A. Schmitzer, J. Organomet. Chem. 489 (1995) 77e81.
[4] For example: (a) E. Louattini, I. Moldes, J. Suades, J.F.M. Piniella, A. Alvarez-
Larena, Organometallics 17 (1998) 3394e3397;
Acknowledgment
We are grateful to the Deutsche Forschungsgemeinschaft and
the Fonds der Chemischen Industrie for financial support.
(b) J.P.H. Charmant, J. Fornies, J. Gomez, E. Lalinde, M.T. Moreno, A.G. Orpen,
S. Solano, Angew. Chem. Int. Ed. 38 (1999) 3058e3061;

B. Milde et al. / Journal of Organometallic Chemistry 706-707 (2012) 52e65
65
(c) Y. Miquel, A. Igau, B. Donnadieu, J.P. Mayoral, N. Pirio, P. Meunier, J. Am.
Chem. Soc. 120 (1998) 3504e3505.
[15] (a) R.P. Pinnell, C.A. Megerle, S.L. Manatt, P.A. Kroon, J. Am. Chem. Soc. 95
(1973) 977e978;
[5] For example: (a) B. Li, S. Xu, H. Song, B. Wang, Eur. J. Inorg. Chem. (2008)
5494e5504;
(b) D.W. Allen, B.F. Taylor, J. Chem. Soc. Dalton Trans. 37 (1982) 51e54;
(c) D.W. Allen, I.W. Nowell, J. Chem. Soc. Dalton Trans. (1985) 2505e2508;
(d) A. Suarez, M.A. Mendez-Rojas, A. Pizzano, Organometallics 21 (2002)
4611e4621;
(b) C. Ledesma, A. Alvarez-Larena, J. Suades, J. Organomet. Chem. 693 (2008)
2775e2783;
(c) A. Diez, E. Lalinde, M.T. Moreno, S. Sanchez, Dalton Trans. (2009)
3434e3446.
[6] (a) B. Di Credico, F. Fabrizi de Biani, L. Gonsalvi, A. Guerri, A. Ienco, F. Laschi,
M. Peruzzini, G. Reginato, A. Rossin, P. Zanello, Chem. Eur. J. 15 (2009)
11985e11998;
(b) T. Baumgartner, M. Fiege, F. Pontzen, R. Arteaga-Müller, Organometallics
25 (2006) 5657e5664 (and references cited therein).
[7] A. Jakob, B. Milde, P. Ecorchard, C. Schreiner, H. Lang, J. Organomet. Chem. 693
(2008) 3821e3830.
[8] A. Jakob, P. Ecorchard, M. Linseis, R.F. Winter, H. Lang, J. Organomet. Chem.
694 (2009) 655e666.
(e) D.J.M. Snelders, C. van der Burg, M. Lutz, A.L. Spek, G. van Koten,
R.J.M. Klein Gebbink, Chem. Cat. Chem. 2 (2010) 1425e1437;
(f) S. Jeulin, S. Duprat de Paule, V. Ratovelomanana-Vidal, J.-P. Genet,
N. Champion, P. Dellis, Angew. Chem. Int. Ed. 43 (2004) 320e325;
(g) B. Milde, M. Lohan, C. Schreiner, T. Rüffer, H. Lang, Eur. J. Inorg. Chem.
(2011) 5437e5449.
[16] (a) C.A. Tolman, Chem. Rev. 77 (1977) 313e348;
(b) C.A. Tolman, W.C. Seidel, L.W. Gosser, J. Am. Chem. Soc. 96 (1974) 53e60.
[17] (a) J.M. Smith, B.C. Taverner, N.J. Coville, J. Organomet. Chem. 530 (1997)
131e140;
(b) B.C. Taverner, STERIC, Program for Calculation of Cone Angles, University
of the Witwatersrand/South Africa, 1996.
[9] For example: (a) D. Astruc, Anal. Bioanal. Chem. 399 (2011) 1811e1814;
(b) X.-F. Wu, P. Anbarasan, H. Neumann, M. Beller, Angew. Chem. Int. Ed. 49
(2010) 9047e9050;
[18] F. Barriere, R.U. Kirss, W.E. Geiger, Organometallics 24 (2005) 48e52.
[19] G. Gritzner, J. Kuta, Pure Appl. Chem. 56 (1984) 461e466.
[20] (a) J.C. Kotz, C.L. Nivert, J. Organomet. Chem. 52 (1973) 387e406;
(b) J.C. Kotz, C.L. Nivert, J.M. Lieber, J. Organomet. Chem. 91 (1975) 87e95;
(c) J. Podlaha, P. Stepnicka, J. Ludvik, I. Cisarova, Organometallics 15 (1996)
543e550;
(c) R. Jana, T.P. Pathak, M.S. Sigman, Chem. Rev. 111 (2011) 1417e1492;
(d) D. Steinborn, Grundlagen der metallorganischen Komplexkatalyse, Teub-
ner, Wiesbaden, 2007;
(e) M. Beller, C. Bolm, Transition Metals for Organic Synthesis 2nd Edition,
Wiley-VCH, Weinheim, 2004;
(d) M.A. Bennett, S.K. Bhargava, A.M. Bond, I.M. Burgar, S.-X. Guo, G. Kar,
S.H. Priver, J. Wagler, A.C. Willis, A.A.J. Torriero, Dalton Trans. 39 (2010)
9079e9090.
(f) B. Cornils, W.A. Herrmann, Applied Homogeneous Catalysis with Organo-
metallic Compounds, VCH, Weinheim, 1996;
(g) F. Diederich, P.J. Stang, Metal-Catalyzed Cross Coupling Reactions 2nd
Edition, Wiley-VCH, Weinheim, 2004.
[21] (a) B.D. Swartz, C. Nataro, Organometallics 24 (2005) 2447e2451;
(b) C. Amatore, M. Azzabi, A. Jutand, J. Am. Chem. Soc. 113 (1991) 8375e8384;
(c) C. Amatore, M. Azzabi, A. Jutand, J. Am. Chem. Soc. 113 (1991) 1670e1677.
[22] (a) F. Paul, C. Lapinte, Coord. Chem. Rev. 178-180 (1998) 431e509;
(b) D.M. D’Alessandro, F.R. Keene, Chem. Soc. Rev. 35 (2006) 424e440;
(c) W. Kaim, B. Sarkar, Coord. Chem. Rev. 251 (2007) 584e594.
[23] (a) M. Lohan, P. Ecorchard, T. Rüffer, F. Justaud, C. Lapinte, H. Lang, Organo-
metallics 28 (2009) 1878e1890;
[10] (a) S.-Y. Liu, M. J Choi, G.C. Fu, Chem. Comm. (2001) 2408e2409;
(b) T.E. Pickett, C.J. Richards, Tetrahedron 42 (2001) 3767e3769;
(c) D. Schaarschmidt, H. Lang, Cat. Commun. 11 (2010) 581e583;
(d) D. Schaarschmidt, H. Lang, Eur. J. Inorg. Chem. 30 (2010) 4811e4821;
(e) A.L. Boyes, I.R. Butler, S.C. Quayle, Tetrahedron Lett. 39 (1998)
7763e7766;
(f) O.V. Gusev, T.A. Peganova, A.M. Kalsin, N.V. Vologdin, P.V. Petrovskii,
K.A. Layssenko, A.V. Tsvetkov, I.P. Beletskaya, Organometallics 25 (2006)
2750e2760;
(g) J.-C. Hierso, M. Beauperin, P. Meunier, Eur. J. Inorg. Chem. (2007)
3767e3780;
(b) A. Hildebrandt, D. Schaarschmidt, H. Lang, Organometallics 30 (2011)
556e563.
[24] (a) N.S. Hush, Electrochim. Acta 13 (1968) 1005e1023;
(b) C. Lapinte, J. Organomet. Chem. 693 (2008) 793e801;
(c) D. Astruc, Electron Transfer and Radical Processes in Transition-Metal
Chemistry, VCH, New York, 1995.
[25] B.S. Brunschwig, C. Creutz, N. Sutin, Chem. Soc. Rev. 31 (2002) 168e184.
[26] (a) M. Sato, Y. Hayashi, Organometallics 15 (1996) 721e728;
(b) M.I. Bruce, P.J. Low, F. Hartl, P.A. Humphrey, F. de Montigny, M. Jevric,
C. Lapinte, G.J. Perkins, R.L. Roberts, B.W. Skelton, A.H. White, Organometallics
24 (2005) 5241e5255.
(h) T.J. Colacot, H.A. Shea, Org. Lett. 6 (2004) 3731e3734.
[11] For example: (a) A.T. Normand, K.J. Cavell, Eur. J. Inorg. Chem. (2008)
2781e2800;
(b) J.A. Loch, M. Albrecht, E. Peris, J. Mata, J.W. Faller, R.H. Crabtree, Organo-
metallics 21 (2002) 700e706;
(c) X. Xu, B. Xu, Y. Li, S.H. Hong, Organometallics 29 (2010) 6343e6349;
(d) N. Debono, A. Labande, E. Manoury, J.-C. Daran, R. Poli, Organometallics 29
(2010) 1879e1882;
[27] For example: (a) S. Dietrich, A. Nicolai, H. Lang, J. Organomet. Chem. 696
(2011) 739e747;
(e) J.-Y. Lee, P.-Y. Cheng, Y.-H. Tsai, G.-R. Lin, S.-P. Liu, M.-H. Sie, H.M. Lee,
Organometallics 29 (2010) 3901e3911;
(f) C. Zhang, M.L. Trudell, Tetrahedron Lett. 41 (2000) 595e598.
[12] For example: (a) C. Baillie, L. Zhang, J. Xiao, J. Org. Chem. 69 (2004)
7779e7782;
(b) I.P. Beletskaya, A.V. Cheprakov, Chem. Rev. 100 (2000) 3009e3066.
[28] For example: (a) W.A. Herrmann, C. Brossmer, C.-P. Reisinger, T.H. Riermeier,
K. Öfele, M. Beller, Chem. Eur. J. 3 (1997) 1357e1364;
(b) A.F. Littke, G.C. Fu, J. Org. Chem. 64 (1999) 10e11;
(c) J.P. Wolfe, R.A. Singer, B.H. Yang, S.L. Buchwald, J. Am. Chem. Soc. 121
(1999) 9550e9561;
(d) H. Weissman, D. Milstein, Chem. Commun. (1999) 1901e1902;
(e) N. Kataoka, Q. Shelby, J.P. Stambuli, J.F. Hartwig, J. Org. Chem. 67 (2002)
5553e5566.
(b) S. Nadri, M. Joshaghani, E. Rafiee, Organometallics 28 (2009) 6281e6287;
(c) W.A. Herrmann, M. Elison, J. Fischer, C. Köcher, G.R.J. Artus, Angew. Chem.
Int. Ed. Engl. 34 (1995) 2371e2374;
(d) J.P. Wolfe, S.L. Buchwald, Angew. Chem. Int. Ed. Engl. 38 (1999)
2413e2416.
[29] M.B. Robin, P. Day, Adv. Inorg. Chem. Radiochem 10 (1967) 247e360.
[30] J. Polin, H. Schottenberger, Org. Synth. 73 (1996) 262e267.
[31] (a) P.W. Clark, B.W. Mulraney, J. Organomet. Chem. 217 (1981) 51e59;
(b) P.W. Dyer, J. Fawcett, M.J. Hanton, Organometallics 27 (2008) 5082e5087;
(c) N.G. Andersen, R. McDonald, B.A. Keaya, Tetrahedron: Asymmetry 12
(2001) 263e269;
[13] For example: (a) W.A. Herrmann, V.P.W. Böhm, J. Organomet. Chem. 572
(1999) 141e145;
(b) A. Zapf, M. Beller, Chem. Eur. J. 7 (2001) 2908e2915.
[14] (a) S. Vuoti, M. Haukka, J. Pursiainen, J. Organomet. Chem. 692 (2007)
5044e5052;
(b) P. Zoufala, R. Gyepes, P. Stepnicka, J. Organomet. Chem. 689 (2004)
3556e3566;
(c) S. Vuoti, J. Autio, M. Laitila, M. Haukka, J. Pursiainen, Eur. J. Inorg. Chem.
(2008) 397e407;
(d) S.J. Coles, P. Faulds, M.B. Hursthouse, D.G. Kelly, G.C. Ranger, A.J. Toner,
N.M. Walker, J. Organomet. Chem. 586 (1999) 234e240;
(e) J.O. Yu, E. Lam, J.L. Sereda, N.C. Rampersad, A.J. Lough, C.S. Browning,
D.H. Farrar, Organometallics 24 (2005) 37e47.(f) J.J. Stone, R.A. Stockland Jr.,
N.P. Rath, Inorg. Chim. Acta 342 (2003) 236e240;
(d) H. Tomori, J.M. Fox, S.L. Buchwald, J. Org. Chem. 65 (2000) 5334e5341.
[32] D. Drew, J.R. Doyle, Inorg. Synth. 28 (1990) 348e349.
[33] D. Zim, A.L. Monteiro, J. Dupont, Tetrahedron Lett. 41 (2000) 8199e8202.
[34] (a) M. Krejcik, M. Danek, F. Hartl, J. Electroanal. Chem. 317 (1991) 179e187;
(b) A. Hildebrandt, T. Rüffer, E. Erasmus, J.C. Swarts, H. Lang, Organometallics
29 (2010) 4900e4905.
[35] G.M. Sheldrick, Acta Cryst., Sect. A 46 (1990) 467e473.
[36] A. Altomare, G. Cascarano, C. Giacovazzo, A. Gualardi, J. Appl. Cryst 26 (1993)
343e350.
(g) R.A. Baber, A.G. Orpen, P.G. Pringle, M.J. Wilkinson, R.L. Wingad, Dalton Trans.
(2005) 659e667.
[37] G.M. Sheldrick, SHELXL-97, Program for Crystal Structure Refinement,
University of Göttingen, 1997.