The coordination behaviour of ferrocene-based pyridylphosphine ligands towards ZnII, CdII and HgII

Article abstract of DOI:10.1039/c0dt01810d

The reaction of Group 12 metal dihalides MX₂ with the P,N-ligands [Fe(C₅H₄-PPh₂)(C₅H ₄-2-py)] (1) (2-py = pyrid-2-yl), [Fe(C₅H ₄-PPh₂)(C₅H_4<

Full text of DOI:10.1039/c0dt01810d

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PAPER
The coordination behaviour of ferrocene-based pyridylphosphine ligands
towards ZnII, CdII and HgII†‡
a
a
a
b
b
ˇ
Ulrich Siemeling,* Thorsten Klemann, Clemens Bruhn, Jirˇ´ı Schulz and Petr Steˇpnicˇka
Received 22nd December 2010, Accepted 17th February 2011
DOI: 10.1039/c0dt01810d
The reaction of Group 12 metal dihalides MX2 with the P,N-ligands [Fe(C5H4-PPh2)(C5H4-2-py)] (1)
(2-py = pyrid-2-yl), [Fe(C5H4-PPh2)(C5H4-CH2-2-py)] (2) and [Fe(C5H4-PPh2)(C5H4-3-py)] (3) (3-py =
pyrid-3-yl) was investigated. For a 1 : 1 molar ratio of MX2 and the respective ligand, three structure
types were found in the solid state, viz. chelate, cyclic dimer and chain-like coordination polymer. The
MII coordination environment is distorted pseudo-tetrahedral in each case. The P–M–N angle is much
larger in the chelates (≥119◦) than in the ligand-bridged structures (£109◦). 1 prefers the formation of
2
chelates [MX2(1-k N,P)]. 3 forms coordination polymers [MX2(m-3)]n. With the more flexible 2 all three
structure types can occur. Dynamic coordination equilibria were observed in solution for the molecular
complexes obtained with 1 and 2. NMR data indicate that the N- and P-donor sites interact most
strongly with ZnII and HgII, respectively. While the formation of bis(phosphine)mercury complexes
(soft–soft) was easily achieved, no bis(pyridine)zinc complex (borderline–borderline) could be
obtained, which is surprising in view of the HSAB principle.
1. Introduction
Pyridylphosphines are highly versatile P,N-ligands which are
widely used in coordination chemistry. The combination of a
soft P-donor site with a hard N-donor site has been utilised
for applications in catalysis and supramolecular chemistry.1 We
have a long-standing interest in ferrocene-based bidentate ligands
Fig. 1 Heterobidentate ligands investigated in this work.
with a focus on symmetric N,N-ligands which contain a 1,1¢-
ferrocenediyl backbone.2 We recently expanded our work to
related heteroditopic P,N-systems, since to date the majority of
ferrocene-based P,N-ligands do not contain the 1,1¢-ferrocenediyl
(fc) backbone but rather have the P- and N-donor groups attached
to the same cyclopentadienyl ring.3 We have reported already on
complexes of the fc-containing pyridyl-amidophosphine ligands
[Fe(C5H4-PPh2){C5H4-C(O)NH-(CH2)n-2-py}] (n = 1, 2; 2-py =
pyrid-2-yl) and [Fe(C5H4-PPh2){C5H4-C(O)NH-CH2-4-py}] (4-
py = pyrid-4-yl),4 and the homologous pyridylphosphine ligands
[Fe(C5H4-PPh2)(C5H4-2-py)] (1) and [Fe(C5H4-PPh2)(C5H4-CH2-
2-py)] (2) (Fig. 1).5 We have extended our study of 1 and 2
systematically from the square-planar tetracoordinate PdII to the
divalent Group 12 metal centres ZnII, CdII and HgII, which prefer
an approximately tetrahedral environment in their tetracoordinate
state. We have included the pyrid-3-yl (3-py) analogue of 1 in our
investigation, viz. [Fe(C5H4-PPh2)(C5H4-3-py)] (3) (Fig. 1). The
main focus of the present study is the coordination mode of the
bidentate ligands 1–3. In previous work, 1 was found to act as a cis-
chelating ligand towards tetracoordinate square-planar RhI, IrI,6
and PdII.5 The homologous ligand 2, which is more flexible due
to the presence of the methylene linker between the pyridyl group
and the ferrocene moiety, behaves similarly, forming complexes
2
such as, for example, cis-[PdCl2(2-k N,P)].5 Both ligands exhibit
bite angles close to 90◦ in these square-planar complexes, with
2
the exception of [Pd(LNC)(1-k N,P)] (LNC = [(2-dimethylamino-
aInstitute of Chemistry, University of Kassel, Heinrich-Plett-Str. 40, 34132,
Kassel, Germany. E-mail: siemeling@uni-kassel.de
kN)methyl]phenyl-kC1), which has a bite angle value of 99.13(8)◦.
The chelate ring sizes are comparatively large, viz. seven atoms in
the case of 1 and even eight atoms in the case of 2, so that a non-
chelating binding mode is increasingly likely for these ligands.7
Note that for the bis(phosphine) ligands Ph2P-(CH2)n-PPh2 the
tendency for chelation is largest for n = 2.8 For example, the
bDepartment of Inorganic Chemistry, Faculty of Science, Charles University
in Prague, Hlavova 2030, 12840, Prague 2, Czech Republic
† Dedicated to Prof. Dr Hansgeorg Schno¨ckel on the occasion of his 70th
birthday.
‡ Electronic supplementary information (ESI) available: Figures showing
the structures of the crystallographically characterised compounds. CCDC
reference numbers 805316–805336. For ESI and crystallographic data in
CIF or other electronic format see DOI: 10.1039/c0dt01810d
2
square-planar complexes [RhCl(CO){Ph2P-(CH2)n-PPh2-k P,P¢}]
are trans-configurated bis(phosphine)-bridged dimers when n = 1,
4722 | Dalton Trans., 2011, 40, 4722–4740
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3 or 4; a mononuclear cis-chelate is observed only in the case of n =
2.9 A recent comprehensive study of P,P- and P,N-ligands, which
utilised the ZnCl2 and PdCl2 fragment, respectively, for analysing
the chelating interaction for pseudo-tetrahedral and square-planar
structures revealed that a fairly limited bite angle range is possible
in the case of the latter (mean value 93.5◦), whereas with ZnCl2
the ligands are free to adopt a wide range of bite angles, with no
clustering around the ideal tetrahedral angle of 109.5◦.10
Hg < Cd. The smaller than expected radius of Hg and higher
than expected electronegativity (absolute values: cZn 4.45 eV, cCd
4.33 eV, cHg 4.91 eV)33 may be rationalised by a combination of
lanthanide contraction and relativistic effects.34 While the covalent
bond lengths of the linear molecules MX2 (M = Zn, Cd, Hg; X =
Cl, Br, I) nicely follow the trend expected from the covalent radii
(Table 2),35 this is not quite the case for the M–X bond lengths in
the complexes under consideration here, since the Hg–X bonds are
not shorter on average than the corresponding Cd–X bonds. This
trend is much more pronounced for the M–N bond lengths, where
Hg–N is always considerably longer than Cd–N. An inspection
of the interhalide angles X–M–X reveals that this angle is by far
largest for the mercury complexes [HgBr2(Py)2] and [HgI2(Py)2]
(>140◦), which exhibit particularly long M–N bonds. The smallest
interhalide angles (<111◦) are observed for the corresponding
mercury phosphine complexes, which have short Hg–P bond
lengths, slightly shorter even than the average Zn–P bond length
of [ZnCl2(PPh3)2]. We note in this context that the coordination
angles of [HgI2(PPh3)2] are very close to the tetrahedral value
of 109.5◦, since triphenylphosphine and iodide bind equally
strongly to HgII.36 Considering Haaland’s NBP > ABP rule (vide
supra), these structural features indicate a comparatively weak
dative Hg←N interaction and a comparatively strong Hg←P
interaction of a more covalent nature, in line with Pearson’s
HSAB principle.37 The fact that dative M←L bonds are very
sensitive to the environment of the acceptor atom is reflected by
the rather different bond angles observed for the monoclinic and
orthorhombic form of [HgCl2(PPh3)2] (Table 1), caused by weak
secondary interactions commonly summarised as crystal packing
forces.38 It is instructive to inspect the values of different bond
type radii in this context (Table 3).39–42 Not surprisingly, the use
of effective ionic radii does not lead to a satisfactory agreement
with experimentally determined bond lengths. The best agreement,
in particular for the M–L bond lengths, is achieved when using
Pauling’s tetrahedral covalent radii, which reflect a convolution of
covalent and dative bonding.32
2. Results and discussion
Before addressing the coordination behaviour of ligands 1–3, it
is useful to provide a survey of closely related complexes for
comparison and reference purposes. Only very few examples of
structurally characterised Group 12 metal complexes are available
which simultaneously contain a phosphine-type P-donor and
an amine- or pyridine-type N-donor coordinated to the metal
centre. All of them are chelates with ring sizes of five or six
atoms. P,N-Coordinated Group 12 metal complexes of the type
[MX2(PPh3)Py] (Py = pyridine) are unknown. Table 1 contains
pertinent bond lengths and angles of structurally characterised
complexes of the type [MX2(Py)2], [MX2(PPh3)2] and [MX2(dppf)]
(dppf = 1,1¢-bis(diphenylphosphino)ferrocene, M = Zn, Cd, Hg;
X = Cl, Br, I), together with data of the few known relevant P,N-
chelates.11–31 Most of these complexes are four-coordinate and
exhibit a distorted pseudo-tetrahedral structure. There are just
five exceptions, viz. the chlorido-bridged dimeric P,N-chelates
[CdCl(m-Cl){2-py-CH(PPh2)2}]2 and [CdCl(m-Cl){Et2N-(CH2)2-
PPh2}]2, whose metal atoms are in a pentacoordinate distorted
trigonal-bipyramidal environment and the polymeric chlorido-
bridged bis(pyridine) complexes trans-[Cd(m-Cl)2(Py)2]n and trans-
[Hg(m-Cl)2(Py)2]n as well as their bromido-bridged analogue trans-
[Cd(m-Br)2(Py)2]n, whose metal atoms are in a hexacoordinate
pseudo-octahedral environment. In the dominant tetracoordinate
case, the metal atom is surrounded by two ‘normal’ (i.e. covalent)
electron bond pairs (NBPs) and two accepted bond pairs (ABPs)
due to the dative M←L interactions according to the bond
description provided by Haaland,32 who pointed out that (i) dative
M←L bonds are very sensitive to the environment of the acceptor
atom and (ii) the spatial requirements for the bond pairs are in the
order NBP > ABP. This explains why interhalide angles X–M–
X larger than the ideal tetrahedral angle of 109.5◦ are commonly
observed. Coordination angles in chelate complexes are influenced
by the size and flexibility of the chelate ring. A comparison
of the unchelated bis(phosphine) complexes [MX2(PPh3)2] with
their dppf analogues reveals no substantial coordination angle
differences. This indicates only small effects of the formally
six-membered chelate ring present in these dppf complexes. By
far the smallest coordination angles among the tetracoordinate
complexes collected in Table 1 are the P,N-chelate bite angles,
which lie in the range of only ca. 77◦–83◦. The average bond lengths
Complexes with [Fe(C5H4-PPh2)(C5H4-2-py)] (1)
We previously reported an improved synthesis of ligand 15 and
have now also determined its crystal structure, which exhibits
no unexpected features and will therefore not be described
here any further (see ESI‡). The reaction of ligand 1 with one
equivalent of metal halide MX2 (M = Zn, Cd, Hg; X = Cl, Br, I)
afforded products of the expected general composition [MX2(1)].
In order to elucidate their solid state structures, single-crystal
X-ray diffraction studies were performed for these compounds,
with the exception of [ZnI2(1)], [CdCl2(1)] and [HgCl2(1)], for
which suitable single crystals could not be obtained, despite many
attempts. Instead, single-crystals of the bis(phosphine) complexes
[CdCl2(1-kP)2] and [HgCl2(1-kP)2] were serendipitously isolated
in such crystallisation experiments, when utilising a diffusion
method (layering a solution of 1 with a solution of the respective
metal dichloride). [HgBr2(1-kP)2] was intentionally prepared in
this context for reference purposes by reacting HgBr2 with 2
equivalents of ligand 1. Analogous reactions of the other Group
12 metal dibromides with 2 equivalents of ligand 1 did not afford
similar bis(phosphine) complexes. Instead, [MBr2(1)] (M = Zn,
Cd) and unreacted 1 were isolated. The results of the structural
˚
for the tetracoordinate cases are the following: Zn–N 2.06 A, Cd–
˚
˚
˚
˚
N 2.27 A, Hg–N 2.46; Zn–P 2.47 A, Cd–P 2.64 A, Hg–P 2.52 A;
˚
˚
˚
˚
Zn–Cl 2.22 A, Cd–Cl 2.47 A, Hg–Cl 2.50 A; Zn–Br 2.35 A, Cd–Br
˚
˚
˚
˚
˚
2.56 A, Hg–Br 2.56 A; Zn–I 2.55 A, Cd–I 2.72 A, Hg–I 2.73 A.
The following bond length trends are apparent: M–N Zn < Cd
< Hg, M–P Zn £ Hg < Cd, M–X Zn < Cd £ Hg. Only the M–
P bond length trend is compatible with na¨ıve expectations based
solely on the covalent radii of the group 12 metals, viz. Zn <
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◦
˚
Table 1 Pertinent bond lengths (A) and angles ( ) for [MX2(Py)2], [MX2(PPh3)2], [MX2(dppf)] and relevant P,N-chelates (M = Zn, Cd, Hg; X = Cl, Br,
I). Mean bond lengths are given in italics for the structures with metal coordination number (CN) 4
M–La
M–X
L–M–La
106.3(2)
X–M–X
120.9(1)
Ref.
11
[ZnCl2(Py)2]
[ZnBr2(Py)2]
[ZnI2(Py)2]
2.046(5)
2.215(2)
2.052(6)
Zn–N 2.05
2.036(6)
2.043(6)
Zn–N 2.04
2.05(1)
2.06(1)
Zn–N 2.06
2.498(3)
2.228(2)
Zn–Cl 2.22
2.354(1)
2.366(1)
Zn–Br 2.36
2.551(2)
2.553(2)
Zn–I 2.55
2.214(3)
2.216(3)
Zn–Cl 2.22
2.218(2)
12
13
14
15
15
107.2(2)
109.2(4)
114.88(9)
82.0(1)
120.90(5)
120.32(8)
115.1(1)
[ZnCl2(PPh3)2]
2.611(3)
Zn–P 2.55
P: 2.395(2)
N: 2.104(5)
[ZnCl2(NP1)]
NP1: 8-Ph2P-quinoline
116.53(6)
115.17(3)
119.92(2)
2.201(2)
Zn–Cl 2.21
2.3601(8)
2.3377(6)
Zn–Br 2.35
2.5388(6)
2.5509(6)
2.6487(6)
2.6520(6)
2.7657(7)
[ZnBr2(NP1)]
NP1: 8-Ph2P-quinoline
P: 2.395(1)
N: 2.096(5)
82.4(1)
15
16
16
16
[ZnI2(NP1)]
NP1: 8-Ph2P-quinoline
[CdCl2(Py)2]n
P: 2.390(1)
N: 2.094(3)
2.346(2)
83.30(9)
180
87.68(2)c
92.32(2)c
89.80(3)c
90.20(3)c
129.37(3)
b
b
[CdBr2(Py)2]n
2.321(5)
180
[CdI2(Py)2]
2.267(6)
2.281(6)
Cd–N 2.27
2.632(6)
2.635(5)
Cd–P 2.63
2.631(2)
2.653(2)
Cd–P 2.64
2.618(2)
2.655(2)
Cd–P 2.64
2.633(1)
2.6833(10)
2.6901(11)
Cd–I 2.69
2.440(6)
2.504(6)
Cd–Cl 2.47
2.724(2)
95.0(2)
17
18
19
20
21
22
[CdCl2(PPh3)2]
[CdI2(PPh3)2]
[CdBr2(dppf)]
[CdI2(dppf)]
107.6(2)
105.1(1)
104.01(5)
103.67(3)
73.30(7)
77.56(9)
113.9(2)
116.2(1)
110.95(3)
113.61(1)
2.731(2)
Cd–I 2.73
2.5553(9)
2.5578(9)
Cd–Br 2.56
2.7325(4)
2.7458(4)
Cd–I 2.74
2.4099(10)
2.5372(11)
2.6515(11)
2.4277(12)
2.4835(11)
2.7788(12)
2.754(2)
2.654(1)
Cd–P 2.64
P: 2.5925(11)
N: 2.442(3)
[CdCl2(NP2)]f
NP2: 2-py-CH(PPh2)2
112.02(4)
99.43(4)
84.73(4)
112.46(4)
94.91(4)
85.31(4)
90.21(6)
89.79(6)
141.2(1)
[CdCl2(NP3)]f
NP3: Et2N-(CH2)2-PPh2
P: 2.5634(12)
N: 2.503(4)
b
23
23
[HgCl2(Py)2]n
2.266(6)
180
2.765(2)
2.478(3)
2.483(3)
[HgBr2(Py)2]
2.38(2)
2.39(2)
90.7(7)
Hg–N 2.39
2.424(9)
Hg–N 2.42
Hg–Br 2.48
24
[HgI2(Py)2]
2.668(1)
93.8(4)
142.7(1)
106.6(2)
110.7(1)
107.12(8)
110.43(4)
105.78(6)
2.664(1)
Hg–I 2.67
2.491(7)
2.504(4)
Hg–Cl 2.50
2.545(3)
2.559(2)
Hg–Cl 2.55
2.627(2)
2.6368(14)
Hg–Br 2.63
2.733(1)
2.763(1)
Hg–I 2.75
2.510(2)
2.528(2)
Hg–Cl 2.52
25d
26e
27
[HgCl2(PPh3)2]
2.503(6)
2.532(4)
Hg–P 2.52
2.462(2)
2.478(2)
Hg–P 2.47
2.491(5)
2.550(4)
Hg–P 2.52
2.557(3)
2.574(3)
Hg–P 2.57
2.510(2)
113.5(1)
134.1(1)
113.01(14)
108.95(9)
114.04(5)
[HgBr2(PPh3)2]
[HgI2(PPh3)2]
[HgCl2(dppf)]
28
29
2.5162(16)
Hg–P 2.51
4724 | Dalton Trans., 2011, 40, 4722–4740
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Table 1 (Contd.)
[HgI2(dppf)]
M–La
M–X
L–M–La
106.50(5)
X–M–X
Ref.
30
2.5585(15)
2.5718(14)
Hg–P 2.57
P: 2.417(3)
N: 2.641(11)
2.7723(5)
2.7801(5)
Hg–I 2.78
2.443(3)
107.119(16)
31
[HgCl2(NP3)]
NP3: Et2N-(CH2)2-PPh2
77.7(3)
109.0(1)
2.445(3)
Hg–Cl 2.44
a L = ligating atom (N or P). b CN 6. c cis Cl–M–Cl angle. d monoclinic (P21/c). e orthorhombic (Pna21). f CN 5.
˚
Table 2 Comparison of bond lengths (A) for linear MX2 molecules in the
gas phase
Cl
DdCl/Br Br
DdBr/I
I
Mean Dd
Zn
DdZn/Cd
Cd
DdCd/Hg
Hg
Mean Dd
2.064(5) 0.130 2.194(9)
0.202 0.192
2.266(6) 0.120 2.386(5)
-0.026 -0.012
0.195 2.389(6)
0.181
0.192
0.184 2.570(6)
-0.012
-0.017
2.240(7) 0.134 2.374(12) 0.184 2.558(7)
0.128
0.188
Table 3 Survey of relevant covalent and ionic radii
Covalent
radiusa/b
Tetrahedral
Effective ionic
radiusd
covalent radiusc
Zn
Cd
Hg
Cl
Br
I
1.22/1.18
1.44/1.36
1.32/1.33
1.02/0.99
1.20/1.14
1.39/1.33
0.71/0.71
1.07/1.11
1.31
1.48
1.48
0.99
1.11
1.28
0.70
1.10
0.60e
0.78e
0.96e
1.81
1.96
2.20
N
P
a Ref. 39 b Ref. 40. c Ref. 41. d Ref. 42. e CN 4.
investigations revealed the P,N-chelate nature of [MX2(1)] in all
but one case. The molecular structure of [CdBr2(1)] is shown in
Fig. 2 as a representative example for the chelates obtained. The
structural exception is [HgI2(1)], which turned out to be the iodido-
bridged dimer [HgI(m-I)(1-kP)]2, which contains ligand 1 in a
P-coordinated form (Fig. 3). Pertinent bond lengths and angles
are collected for the chelates in Table 4; data for the structurally
characterised bis(phosphine) complexes are also included. The
bond length trends are essentially identical to those observed for
the tetracoordinate complexes collected in Table 1 (M–N Zn < Cd
< Hg, M–P Zn £ Hg < Cd, M–X Zn < Cd £ Hg; vide supra). The
chelate ring of [MX2(1)] contains seven atoms. The bite angle of
ligand 1 in these compounds lies in the range of ca. 119◦–125◦,
which is much larger than the bite angle range of only ca. 77◦–83◦
observed for the P,N-chelates with ‘standard’ ring sizes of five
and six atoms (Table 1). It is also considerably larger than the
bite angles exhibited by ligand 1 in the distorted square-planar d8-
configurated complexes described above, where bite angles close
to 90◦ were observed.
Fig. 2 Molecular structure of [CdBr2(1)] in the crystal.
angles (D◦ ca. 10◦–15◦) and smaller X–M–X angles (D◦ ca. 10◦).
It is not clear whether this can be ascribed to the larger steric
bulk of ligand 1 vs. PPh3 and dppf. In view of the quite different
bond angles observed for the monoclinic and orthorhombic forms
of [HgCl2(PPh3)2] (vide supra), it seems likely that crystal packing
forces are more important in this context.
All products obtained showed fairly good solubilities in polar
organic solvents. Their structure in solution was probed by
NMR spectroscopy in CDCl3. Metal N-coordination leads to a
diagnostic shift of the 1H NMR signal due to the a-pyridyl proton
H6. Likewise, metal P-coordination is reflected by a shift of the
31P NMR signal due to the PPh2 substituent of 1. Pertinent NMR
spectroscopic data are collected in Table 5. A substantial low-
field shift ≥0.4 ppm of the pyridyl H6 NMR signal with respect
to the corresponding signal of uncoordinated 1 is observed in
all cases except [HgBr2(1-kP)2], which indeed contains a non-
coordinated pyridyl group. This shift is most pronounced in the
case of the zinc complexes (Dd ca. 1.1 ppm), which agrees well
The molecular structures of the bis(phosphine) complexes
[CdCl2(1-kP)2], [HgCl2(1-kP)2] and [HgBr2(1-kP)2] are very sim-
ilar to one another. The latter one is exemplarily shown in Fig.
4. In comparison with their bis(triphenylphosphine) and dppf
analogues (Table 1), our complexes tend to exhibit larger P–M–P
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˚
Table 4 Pertinent bond lengths (A) and angles ( ) for chelate and bis(phosphine) complexes of 1
M–N
M–P
M–X
L1–M–L2
X–M–X
[ZnCl2(1-j2N,P)]
2.142(4)
2.135(4)
2.120(3)
2.139(4)
2.341(4)
2.375(3)
2.573(3)
2.4442(14)
2.4623(14)
2.4278(10)
2.4277(10)
2.6188(12)
2.5932(11)
2.4462(9)
2.2609(15)
2.2324(16)
2.2369(14)
2.2627(15)
2.3704(6)
2.4001(6)
2.3757(6)
2.3981(6)
2.5596(6)
2.5800(6)
2.7326(4)
2.7520(5)
2.6291(5)
2.5574(5)
2.448(2)
120.42(11)a
124.78(11)a
120.22(9)a
124.90(10)a
118.70(10)a
121.60(9)a
118.87(7)a
113.05(6)
117.60(6)
109.66(2)
115.48(2)
112.58(2)
116.990(15)
111.667(16)
2 independent molecules
[ZnBr2(1-j2N,P)]
2 independent molecules
[CdBr2(1-j2N,P)]
[CdI2(1-j2N,P)]
[HgBr2(1-j2N,P)]
[CdCl2(1-jP)2]
[HgCl2(1-jP)2]
2.580(2)
122.04(8)b
123.99(2)b
103.63(9)
100.04(3)
2.4946(6)
2.4949(6)
2.5029(11)
2.4971(12)
2.5554(7)
2.5546(7)
2.6818(6)
2.6775(6)
[HgBr2(1-jP)2]
124.28(4)b
100.26(2)
a L1 = N, L2 = P. b L1 = L2 = P.
Fig. 3 Molecular structure of [HgI(m-I)(1-kP)]2 in the crystal.
with the notion based on the HSAB principle that among the
divalent Group 12 metals the strongest interaction with pyridine
type donors is exhibited by ZnII, both partners being borderline
between hard and soft.37a The shift observed for the 31P NMR
signal with respect to non-coordinated 1 is very small in the case
of the zinc complexes (Dd £ 3.7 ppm). It is moderately larger
for the cadmium complexes (Dd ≥ 9.7 ppm) and substantially
larger for the mercury complexes, where low-field shifts of up
to ca. 50 ppm are observed, indicative of a comparatively robust
metal-phosphorus bond, which is also reflected by the observation
of 199Hg satellite signals at room temperature. We have observed
111,113Cd satellite signals only in the case of the bromido complex
[CdBr2(1)], which shows the largest low-field shift of the 31P NMR
signal among the cadmium chelates of 1 and consequently has the
strongest Cd–P interaction in this series. The lability of Cd←P
bonds, indicated by the absence of 111,113Cd satellite signals in the
other two cases, is compatible with results reported for a range of
complexes of the type [CdX2(PR3)2], which are known to undergo
facile phosphine dissociation.18 Bu¨rgi et al. have demonstrated
1
for [HgX2(PPh3)2] that J(199Hg,31P) coupling constants can be
expressed as a function of X–Hg–X and P–Hg–P angles.43 Large
coupling constants are accompanied by small X–Hg–X and large
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Fig. 4 Molecular structure of [HgBr2(1-kP)2] in the crystal.
respectively (Table 5). No such 199Hg satellites were detected in
the case of the bis(phosphine) complex [HgBr2(1-kP)2]. Among
the mercury complexes of 1, this compound exhibits the smallest
low-field shift of the 31P NMR signal. These spectral features
indicate phosphine ligand exchange processes which are fast
on the NMR time scale.46 In the case of [HgI2(1)], which is
not a chelate in the solid state, but exhibits the iodido-bridged
dimeric structure [HgI(m-I)(1-kP)]2 (see ESI‡), a broad 31P NMR
signal was observed, compatible with dynamic processes close
to the coalescence regime. This compound exhibits the smallest
coordination-induced low-field shift of the pyridyl H6 NMR signal
of only ca. 0.4 ppm, which indicates a highly dynamic equilibrium
in solution, containing similar concentrations of P,N-coordinated
chelate and isomers without N-coordination. It is likely that
these exclusively P-coordinated isomers are [HgI2(1-kP)] and
[HgI(m-I)(1-kP)]2, in accord with findings previously reported for
the system HgI2/PR3.47 The broadness of the 31P NMR signal
suggests that the monomer–dimer equilibrium of these isomers
is comparatively slow on the NMR time scale. Concentration-
and temperature-dependent NMR studies would be useful for
testing this hypothesis, but were not within the scope of our
investigation.
Table 5 NMR spectroscopic data indicative of the coordination of 1
1H NMR signal
pyridyl H6/Dd
31P NMR signal/Dd
1
8.47
-17.7
[ZnCl2(1)]
[ZnBr2(1)]
[ZnI2(1)]
[CdCl2(1)]
[CdBr2(1)]
[CdI2(1)]
[HgCl2(1)]
[HgBr2(1)]
[HgI2(1)]
[HgBr2(1-jP)2]
9.57/1.10
9.57/1.10
9.60/1.13
8.99/0.52
9.35/0.88
9.27/0.80
9.36/0.89
9.15/0.68
8.89/0.42
8.48
-14.0/3.7
-14.4/3.3
-19.2/-1.5
-8.0a/9.7
-3.6/14.1 (1708, 1782)b
-8.0a/9.7
32.2/49.9 (7470)c
28.5/46.2 (6359)c
19.7a/37.4
14.5/32.2
a broad. b 1J(111Cd,31P) and 1J(113Cd,31P), respectively, in Hz. c 1J(199Hg,31P)
in Hz.
P–Hg–P angles and also by short Hg–P bond lengths.44 They
reported 1J(199Hg,31P) values of 4675 Hz, 4156 Hz and 3074 Hz for
[HgCl2(PPh3)2], [HgBr2(PPh3)2] and [HgI2(PPh3)2], respectively,45
which are considerably smaller than the values of 7470 Hz and
6359 Hz obtained for the chelates [HgCl2(1)] and [HgBr2(1)],
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Complexes with [Fe(C5H4-PPh2)(C5H4-CH2-2-py)] (2)
The reaction of ligand 2 with CdBr2 in ethanolic solution
afforded a precipitate of the composition [CdBr2(2)] according
to elemental analysis. Unfortunately, single crystals could not
be obtained either by simple recrystallisation from chloroform
or dichloromethane or by liquid-phase diffusion of non-polar
solvents into chlorocarbon solutions of the precipitate. After many
unsuccessful attempts, single crystals were finally afforded by a
reactive diffusion method using two different solvents. A solution
of ligand 2 in dichloromethane was layered first with a small
amount of pure ethanol and then with an ethanolic solution of
CdBr2. The crystals turned out to be composed of the coordination
polymer [CdBr2(m-2)]n (Fig. 7), instead of the expected chelate or
cyclic dimer. The analogous reaction of 2 with CdI2 in ethanol
gave a precipitate, which could be recrystallised from chloroform
by liquid-phase diffusion of hexane, affording the chelate [CdI2(2-
We previously reported the synthesis of ligand 25 and have now
also determined its crystal structure, which exhibits no unexpected
features and will therefore not be described here any further (see
ESI‡). According to our experience gathered in the chemistry
of ligand 1, the Group 12 metal dibromides worked best in
terms of crystallinity. They were therefore chosen as primary
targets for the study of the coordination behaviour of ligand
2, which is more flexible than 1 due to the presence of the
methylene spacer. The reaction of ligand 2 with one equivalent
of ZnBr2 in ethanol and subsequent evaporation of the solvent
in vacuo afforded a product whose composition was [ZnBr2(2)]
according to elemental analysis. Single-crystals were obtained by
recrystallisation from chloroform. They were subjected to an X-ray
diffraction study, which revealed the anticipated chelate structure
(Fig. 5). In contrast, storage of the combined ethanolic solutions
of 2 and ZnBr2 at room temperature afforded single crystals of the
centrosymmetric P,N-bridged cyclic dimer [ZnBr2(m-2)]2 (Fig. 6).
Interestingly, a reactive diffusion experiment utilising a 2 : 1 molar
ratio of 2 and ZnBr2 also afforded this cyclic dimer instead of the
expected [ZnBr2(2)2]. Pertinent bond parameters are collected in
Table 6 for both isomers. There are no significant bond length
differences between the two isomers. While the interhalide angles
differ only marginally, we note a pronounced difference in the P–
Zn–N angle, which is wider by almost 20◦ in the chelate compound,
the value of 122.64(8)◦ being almost identical to the average
bite angle value observed for the two independent molecules of
2
k N,P)]. Selected bond lengths and angles of these two cadmium
complexes are also collected in Table 6. The main difference in
2
bond parameters between the chelate [CdI2(2-k N,P)] and the
polymeric [CdBr2(m-2)]n is the P–Cd–N angle, which is wider by
ca. 11◦ in the chelate.
The reaction of ligand 2 with HgBr2 in ethanolic solution
yielded a precipitate of the composition [HgBr2(2)] according
to elemental analysis. Single-crystals were again obtained by a
reactive diffusion method, using ethanol as the solvent. The result
of the X-ray diffraction analysis proves the chelate structure of
the product obtained. Crystals of a completely different product
were isolated when the experiment was performed under mixed-
solvent conditions, i.e. by layering a dichloromethane solution
of 2 with a small amount of pure ethanol and then with an
ethanolic solution of HgBr2. Despite the 1 : 1 molar ratio of the two
starting materials and identical concentrations of their solutions,
this procedure afforded the polymeric complex [{HgBr(m-Br)}2(m-
2)]n (Fig. 8), which has a 1 : 2 ligand-to-metal stoichiometry. The
stoichiometrically “inverse” bis(phosphine) complex [HgBr2(2)2]
was prepared by reacting HgBr2 and 2 in a 1 : 2 ratio in ethanol.
The precipitate was recrystallised from chloroform by liquid-phase
diffusion of hexane, which afforded single crystals of the solvate
[HgBr2(2)2]·CHCl3. Table 6 contains pertinent structural data
for these three mercury complexes. A comparison of [HgBr2(1-
2
[ZnBr2(1-k N,P)] (Table 4).
2
2
k N,P)] and [HgBr2(2-k N,P)] reveals essentially identical Hg–P
˚
distances of ca. 2.44 A, but rather different Hg–N distances of
2.573(3) A and 2.372(7) A, respectively. The same M–N bond
length trend, although less pronounced, is also observed for the
˚
˚
2
2
˚
pairs [ZnBr2(1-k N,P)]/[ZnBr2(2-k N,P)] (average value 2.13 A vs.
2
2
˚
˚
˚
2.09 A) and [CdI2(1-k N,P)]/[CdI2(2-k N,P)] (2.38 A vs. 2.31 A).
Again, the M–P bond lengths differ only marginally in these pairs.
A factor contributing to comparatively shorter M–N bond lengths
observed with ligand 2 may be that, owing to the presence of
an alkyl substituent on the pyridyl unit, its N-donor strength is
higher than that of 1, whose corresponding substituent has an
sp2 hybridised, and thus more electronegative, pivotal atom. The
Pauling electronegativities of C(sp3) and C(sp2) are 2.48 and 2.66,
respectively.48 The bite angles of 1 and 2 in their chelates lie in
the narrow range between ca. 119◦ and 125◦, with no systematic
differences between the two ligands. Ligand 2 is coordinatively
more flexible and less predictable than 1. It gives us the opportunity
to compare P,N-chelates with unchelated analogues, viz. chain-
like polymeric and cyclic dimeric complexes, whose P–M–N angles
turned out to be much more acute than the chelate bite angles.
2
Fig. 5 Molecular structure of the chelate [ZnBr2(2-k N,P)] in the crystal.
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◦
˚
Table 6 Pertinent bond lengths (A) and angles ( ) for complexes of 2
M–N
M–P
M–X
L1–M–L2
122.64(8)a
100.5(2)a
109.13(19)a
120.0(9)a
123.8(2)a
X–M–X
114.19(2)
112.31(5)
115.36(4)
116.74(3)
110.31(4)
[ZnBr2(2-j2N,P)]
[ZnBr2(l-2)]2
2.087(3)
2.097(6)
2.323(7)
2.309(6)
2.372(7)
2.365(8)
2.4389(9)
2.455(2)
2.637(2)
2.607(2)
2.443(2)
2.419(3)
2.4040(5)
2.3904(5)
2.4003(12)
2.3790(12)
2.5578(10)
2.5734(10)
2.7675(9)
2.7605(8)
2.6120(13)
2.6278(10)
2.4710(11)
3.1498(14)
2.8647(12)
2.5319(13)
2.6514(12)
2.5999(12)
2.6615(8)
2.6640(8)
[CdBr2(l-2)]n
[CdI2(2-j2N,P)]
[HgBr2(2-j2N,P)]
[{HgBr(l-Br)}2(l-2)]n
[HgBr2(2-jP)2]
2.510(2)
2.512(2)
124.01(5)b
a L1 = N, L2 = P. b L1 = L2 = P.
Fig. 6 Molecular structure of the cyclic dimer [ZnBr2(m-2)]2 in the crystal.
The complexes obtained with ligand 2 were studied by NMR
spectroscopy in CDCl3 solution in order to gain insight into their
structures in solution. Pertinent data are collected in Table 7.
Although the data set here is not as large as in the case of ligand
1, we can identify salient features which indicate coordination
equilibria in solution similar to those discussed in detail for the
complexes of 1. In analogy to the results obtained with 1, the
signal due to the a-pyridyl H6 is low-field shifted with respect to
uncoordinated 2 in all cases except the bis(phosphine) complex
[HgBr2(2-kP)2]. Again, this shift is largest for ZnII and smallest
for HgII. The general trend concerning the coordination-induced
shift of the 31P NMR signal is also similar to that found for 1.
The 31P NMR signal remains essentially unshifted in the case of
ZnII, indicating no substantial Zn–P bonding in solution. While
broad 31P NMR signals were observed for cadmium complexes of
1, indicative of dynamic processes close to the coalescence point,
no 31P NMR signal was detected for [CdBr2(2)], which is therefore
in the coalescence regime. The strongest M–P interaction occurs in
the case of [HgBr2(2)], as is reflected by the largest Dd value and the
observation of metal–phosphorus coupling for this compound.
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Fig. 7 Section of the polymeric chain of [CdBr2(m-2)]n in the crystal.
Fig. 8 Section of the polymeric chain of [{HgBr(m-Br)}2(m-2)]n in the crystal.
Complexes with [Fe(C5H4-PPh2)(C5H4-3-py)] (3)
crystal X-ray diffraction analysis, which revealed no unusual
features. The structure of 3 is therefore not described here any
further (see ESI‡). Due to the relative orientation of the P- and
N-donor sites in 3, this ligand was expected to be unsuitable for
chelation and consequently prone to the formation of coordination
polymers. Indeed, the reactions of 3 with the Group 12 metal
dibromides in a 1 : 1 molar ratio afforded insoluble, and therefore
probably polymeric, materials whose composition was [MBr2(3)]
according to elemental analysis. In order to obtain crystals of
Attempts to prepare ligand 3 by a Negishi cross-coupling
reaction49 in analogy to 1 failed. The synthesis was achieved
by utilising standard Suzuki–Miyaura cross-coupling methodol-
ogy instead.50 3-Pyridylboroxin51 was reacted with 1-bromo-1¢-
(diphenylphosphino)ferrocene52 in a 1,4-dioxane–water mixture in
the presence of [Pd(PPh3)4] (2.5 mol%) and an excess of potassium
carbonate. The product was structurally characterised by a single-
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˚
˚
Table 7 NMR spectroscopic data indicative of the coordination of 2
for mercury (Hg–N: 2.44 A vs. 2.57 A for [HgBr2(1)]). The M–
P bond lengths, on the other hand, are almost identical. The
P–Zn–N angle is wider by ca. 15◦ in the case of the chelates.
These data suggest the presence of significant chelate ring strain
in the complexes of ligand 1, affecting particularly the M–N
bond.
1H NMR signal
pyridyl H6/Dd
31P NMR signal/Dd
2
8.48
-16.2
[ZnBr2(2)]
[CdBr2(2)]
[CdI2(2)]
[HgBr2(2)]
[HgBr2(2-jP)2]
9.66/1.18
9.45/0.97
9.23/0.75
9.09/0.61
8.44
-18.1/-1.9
n. d.a
24.3/40.5
24.4/40.6 (6321)b
15.4/31.6
The polymeric nature of the complexes obtained from 3 and
MBr2 prevented their NMR spectroscopic characterisation in
solution. The donor solvent DMSO turned out to dissolve the
products by depolymerisation. In the 1H NMR spectrum the
signals due to the pyridyl protons H2 and H6 were observed
essentially unshifted in comparison to those of uncoordinated 3
in each case. The 31P NMR spectrum of the solution of the zinc
complex in DMSO exhibited two sharp signals, one at -18.9 ppm
(free ligand) and a second one of much lower intensity at 25.3 ppm.
The cadmium complex showed essentially identical behaviour.
A large excess of DMSO certainly leads to the formation of
solvento complexes of the type [MBr2(DMSO)n] (M = Zn, Cd),53
thus liberating ligand 3. The minor species responsible for the
31P NMR signal at 25.3 ppm in both cases might be [MBr2(3-
kP)(DMSO)n-1]. However, this is extremely unlikely, since in the
case of the mercury complex, a single, broad 31P NMR signal
at 19.3 ppm is observed, clearly indicating P-coordination. An
analogous, hypothetical, P-coordination should be weaker in the
case of Zn and Cd and should therefore lead to a low-field shift
of the 31P NMR signal much smaller than that observed in the
case of Hg, as was noted above in the chemistry of ligand 1 (Table
5). Furthermore, only a single, averaged, signal would be expected
for the fast exchange cases ZnII and CdII. We therefore believe
that the signal at 25.3 ppm is rather due to the corresponding
P-oxide of 3, which may be formed slowly in solution by oxygen
transfer from DMSO. This type of reaction has been thoroughly
investigated for Ph3P and was shown to be catalysed by Lewis
acids.54 As a final test of our P-oxide hypothesis, 3 was reacted
with hydrogen peroxide. This afforded the oxidation product 3O,
which indeed exhibited a 31P NMR signal at 25.3 ppm in DMSO.
We note that phosphine oxides are interesting ligands in their own
a not detected. b 1J(199Hg,31P) in Hz.
◦
˚
Table 8 Pertinent bond lengths (A) and angles ( ) for complexes of 3
M–N
M–P
M–X
L1–M–L2 X–M–X
104.22(12) 119.20(3)
107.63(9) 112.81(2)
[ZnBr2(m-3)]n 2.077(4) 2.4628(14) 2.3771(7)
2.3823(7)
[HgBr2(m-3)]n 2.439(3) 2.4423(10) 2.5727(4)
2.5847(4)d
these products suitable for a single-crystal X-ray diffraction study,
reactive diffusion experiments were carried out by layering a
solution of 3 in dichloromethane with a small amount of pure
dichloromethane and then with an ethanolic solution of MBr2.
This procedure was successful in the case of M = Zn and Hg. Both
compounds exhibit the anticipated polymeric chain structure. We
surmise an analogous structure for the cadmium compound. A
section of the polymeric chain of [ZnBr2(m-3)]n is displayed in Fig.
9. Pertinent bond parameters for both structurally characterised
complexes are collected in Table 8.
A comparison of these data with those of the corresponding
chelate complexes of the pyrid-2-yl analogue 1 shows the following
trends. The M–N bond lengths are shorter in the coordination
˚
polymers of 3. This effect is relatively small for zinc (Zn–N: 2.08 A
˚
vs. 2.13 A (average value) for [ZnBr2(1)]), but quite substantial
Fig. 9 Section of the polymeric chain of [ZnBr2(m-3)]n in the crystal.
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right, which can bind both hard55 and borderline-type56 metal
centres.57
than the HgII–Npyridine interaction, both being borderline–soft
combinations.
3. Conclusions
4. Experimental
A main aspect of our study is the preferred coordination mode of
the heterobidentate ligands 1–3 in complexes formed with Group
12 metal dihalides MX2 in a 1 : 1 molar ratio. Three structure types
were found in the solid state, viz. chelate (A), cyclic dimer (B)
and chain-like coordination polymer (C) (Fig. 10). Irrespective
of the structure type, the MII coordination environment is best
described as distorted pseudo-tetrahedral in each case. The P–
M–N angle is considerably larger in the chelates (type A, ≥119◦)
than in the ligand-bridged structures (types B and C, £109◦). The
pyrid-2-yl substituted ligand 1 prefers the formation of chelates
General considerations
All preparations involving air-sensitive compounds were carried
out under an atmosphere of dry nitrogen by using standard
Schlenk techniques or in a conventional argon-filled glove box.
Solvents and reagents were appropriately dried and purified by
conventional methods and stored under inert gas atmosphere. 3-
Pyridylboroxin51 and 1-bromo-1¢-(diphenylphosphino)ferrocene52
were prepared according to published procedures. Elemental
analyses were carried out by the microanalytical laboratories of
the Institute of Thermal Energy Management at the University
of Kassel and the Department of Chemistry, Charles University,
Prague. NMR spectra were recorded with the following Varian
spectrometers: Unity INOVA (500 MHz), VNMR 500 (500 MHz)
and Varian 400-MR (400 MHz). 13C and 31P NMR data were
collected by proton-decoupled methods. Chemical shifts (d) are
given in ppm and are referenced to the signals due to the residual
protio impurities of the solvents used relative to tetramethylsilane
for 1H and to the respective solvent signal for 13C.58,59 In the case
of 31P NMR spectra obtained from samples in CDCl3, chemical
shifts were indirectly referenced to PPh3 (d -6.0 ppm, relative
to 85% phosphoric acid in D2O), spectra obtained from samples
in DMSO-d6 were referenced to external 85% phosphoric acid
in DMSO-d6 (d 0.0 ppm).60 Coupling constants are given as
absolute values in Hz. Mass spectra were obtained with a Bruker
Esquire 3000 spectrometer (ESI) and a quadrupole ion-trap
spectrometer (ESI and APCI) Finnigan LCQDECA (ThermoQuest,
San Jose´, USA). MALDI mass spectra were obtained with a
BiFlex IV spectrometer (Bruker Daltonics, Bremen, Germany)
equipped with an N2 laser (wavelength 337 nm, 3 ns pulse
duration). DCTB (2-[(2E)-3-(4-tert-butylphenyl)-2-methylprop-2-
enylidene]malononitrile) was used as matrix.
2
[MX2(1-k N,P)], in which the chelate ring comprises seven atoms.
The size of an analogous, hypothetical, chelate ring formed by
the pyrid-3-yl analogue 3 is eight atoms. However, due to the
relative orientation of its P- and N-donor sites, 3 is unsuitable
for chelation. It acts as a bridging ligand, forming coordination
polymers [MX2(m-3)]n. Ligand 2 is more flexible than 1 and 3,
because its pyridyl group is separated from the ferrocene moiety
by a methylene group. Consequently, its coordination behaviour
is more temperamental. We have observed all three structure
types A–C with 2. On top of that, it is possible that different
structure types occur with the same MX2 fragment, depending
on the crystallisation conditions. This was demonstrated for the
ZnBr2 fragment (types A and B). With only a handful of examples
reported to date, Group 12 metal complexes which contain a
phosphine-type P-donor and an amine- or pyridine-type N-donor
are surprisingly rare. Our compounds which belong to structure
types B and C are the first examples of this class which are
not chelates. In the case of the chelates formed by 1 and 2, the
experimentally observed bite angles range from ca. 90◦5 to 125◦ for
both ligands, which shows that they can adapt to the requirements
of rather diverse metal centres.
Preparative work
[Fe(C5H4-PPh2)(C5H4-3-py)]
(3).
A
solution
of
3-
pyridylboroxin (0.63 g, 2.0 mmol) and K2CO3 (2.80 g, 20.0 mmol)
in water (10 mL) and solid [Pd(PPh3)4] (115 mg, 0.1 mmol, 2.5
mol%) were added sequentially to a solution of 1-bromo-1¢-
(diphenylphosphino)ferrocene (1.80 g, 4.0 mmol) in 1,4-dioxane
(25 mL). The reaction mixture was stirred at 120 ◦C (bath
temperature) for 14 h and was subsequently allowed to cool to
room temperature. The organic layer was separated off. Volatile
components were evaporated by using a rotary evaporator.
The residue was dissolved in dichloromethane (20 mL). The
solution was washed with water (2 ¥ 20 mL) and the combined
washings extracted with dichloromethane (2 ¥ 10 mL). The
combined organic layers were dried with Na2SO4 and filtered.
Neutral alumina (5.0 g) was added and volatile compounds
were removed in vacuo. The adsorbed material was subjected to
column chromatography on neutral alumina, el◦uting first with
Fig. 10 Structure types encountered for 1 : 1 complexes of 1–3 with Group
12 metal dihalides.
NMR spectroscopic data reveal the presence of dynamic coordi-
nation equilibria in CDCl3 solution for the molecular compounds
obtained with ligands 1 and 2. Coordination-induced signal shifts
indicate that the N- and P-donor sites interact most strongly with
ZnII and HgII, respectively, in accordance with Pearson’s HSAB
principle. Not surprisingly, therefore, it proved possible to obtain
the HgII bis(phosphine) complexes such as [HgBr2(1-kP)2], which
was prepared straightforwardly from 1 and HgBr2 in a 2 : 1 molar
ratio. Interestingly, the reaction of ZnBr2 with two equivalents of 1
did not afford the respective ZnII bis(pyridine) complex, although
this, too, should be a perfect match in terms of the HSAB principle.
2
Instead, the P,N-chelate [ZnBr2(1-k N,P)] was obtained, and
◦
one equivalent of 1 remained unreacted, which is entropically
more favourable than the formation of [ZnBr2(1-kN)2]. These
observations suggest that the ZnII–Pphosphine interaction is stronger
a 5 : 1 mixture of petroleum ether (bp 40 C–60 C) and diethyl
ether to remove non-polar components and subsequently with
chloroform, which afforded 3 as an orange oil, which solidified
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1
7.76 (m, 5H, Ph + Py), 9.57 (m, 1H, Py). 13C{ H} NMR (CDCl3):
upon standing. Yield: 0.76 g (43%). Crystals suitable for a
single-crystal X-ray diffraction analysis were obtained by slow
evaporation of a concentrated dichloromethane solution. 1H
NMR (CDCl3): d 3.96 (m, 2H, fc), 4.22 (m, 2H, fc), 4.26 (m, 2H,
fc), 4.56 (m, 2H, fc), 7.15 (m, 1H, Py), 7.30–7.36 (m, 10H, Ph),
7.58 (m, 1H, Py), 8.40 (m, 1H, Py), 8.61 (m, 1H, Py). H NMR
(DMSO-d6): d 3.88 (s, 2H, fc), 4.22 (s, 2H, fc), 4.27 (s, 2H, fc),
d 71.41, 71.59, 73.39 (d, JPC = 6 Hz), 75.63 (d, JPC = 10 Hz), 84.34,
123.10, 125.22, 128.98 (d, JPC = 10 Hz), 131.22, 133.79 (d, JPC
=
13 Hz), 139.32, 152.78, 158.46. 31P{ H} NMR (CDCl3): d -14.0.
MS/ESI(+): m/z (%) 605 (10) [M + Na]+, 546 (20) [M - Cl]+,
510 (35) [C27H22FeNPZn]+, 464 (30) [C27H22FeNPO]+, 448 (100)
[C27H22FeNP]+. Calc. for C27H22NCl2FePZn (583.6): C, 55.57; H,
3.80; N, 2.40. Found: C, 56.27; H, 3.84; N 2.57%.
1
1
4.78 (s, 2H, fc), 7.27 (m, 1H, Py), 7.30–7.37 (m, 10H, Ph), 7.59
1
(m, 1H, Py), 8.40 (m, 1H, Py), 8.61 (m, 1H, Py). 13C{ H} NMR
[ZnBr2(1)]. Reactants: 1 (44.7 mg, 0.1 mmol), ZnBr2 (22.5 mg,
0.1 mmol). Work-up: The solvent was evaporated in vacuo and
the residue dissolved in dichloromethane (2 mL). Hexane (15 mL)
was added. The solid precipitate was isolated by filtration, washed
with hexane (5 mL) and dried in vacuo. This procedure afforded
(CDCl3): d 67.67 (d, JPC = 1 Hz), 70.94 (d, JPC = 1 Hz), 73.08 (d,
JPC = 4 Hz), 74.52 (d, JPC = 15 Hz), 82.56, 123.38, 128.33 (d, JPC
=
7 Hz), 128.73, 133.37, 133.59 (d, JPC = 20 Hz), 134.82, 138.96 (d,
1
JPC = 10 Hz), 147.33, 147.56. 31P{ H} NMR (CDCl3): d -17.8.
1
31P{ H} NMR (DMSO-d6): d -18.8. MS/APCI(+): m/z (%) 464
1
4
[ZnBr2(1)]· C6H14. Yield: 41 mg (61%). Single-crystals suitable
(45) [MO + H]+, 448 (100) [M + H]+, 370 (21) [C21H17FeNP]+, 263
(15) [C15H12FeN]+. Calc. for C27H22NFeP (477.3): C, 72.50; H,
4.96; N, 3.13. Found: C, 73.34; H, 4.94; N, 3.23%.
for an X-ray diffraction analysis were obtained in analogy to the
procedure described for [ZnCl2(1)]. 1H NMR (CDCl3): d 4.23 (m,
2H, fc), 4.54 (m, 2H, fc), 4.60 (m, 2H, fc), 5.02 (m, 2H, fc), 7.43 (m,
8H, Ph + Py), 7.78 (m, 5H, Ph + Py), 9.57 (m, 1H, Py). 13C{ H}
1
[Fe(C5H4–P(O)Ph2)(C5H4-3-py)] (3O). Hydrogen peroxide
(0.01 mL of a 30% aqueous solution, 0.1 mmol) was added
to solution of 3 (22.3 mg, 0.05 mmol) in acetone (5 mL). The
mixture was stirred for 1 h. Volatile components were removed
in vacuo. Water (5 mL) was added and the mixture extracted with
dichloromethane (3 ¥ 2 mL). The combined extracts were dried
with Na2SO4 and filtered. The solution was reduced to dryness
in vacuo, affording 3O as an orange solid in essentially quantitative
yield. 1H NMR (DMSO-d6): d 4.17 (s, 2H, fc), 4.22 (s, 2H, fc), 4.40
(s, 2H, fc), 4.86 (s, 2H, fc), 7.32 (m, 1H, Py), 7.51 (m, 4H, Ph), 7.58
(m, 2H, Ph), 7.65 (m, 4H, Ph), 7.85 (m, 1H, Py), 8.52 (m, 1H, Py),
NMR (CDCl3): d 71.32, 71.40, 73.7 (br d, JPC ª 5 Hz), 75.97
(d, JPC = 12 Hz), 84.75, 123.12, 125.10, 128.96 (d, JPC = 10 Hz),
131.22, 133.82 (d, JPC = 12 Hz), 139.29, 153.46, 157.93 (s). 31P{ H}
1
NMR (CDCl3): d -14.4. MS/ESI(+) m/z (%) 592 (15) [M - Br]+,
510 (15) [C27H22FeNPZn]+, 464 (22) [C27H22FeNPO]+, 448 (100)
1
4
[C27H22FeNP]+. Calc. for C27H22NBr2FePZn· C6H14 (694.0): C,
49.32; H, 3.70; N, 2.02. Found: C, 49.73; H, 3.73; N 2.16%.
[ZnI2(1)]. Reactants: 1 (44.7 mg, 0.1 mmol), ZnI2 (31.9 mg,
0.1 mmol). Work-up: The solvent volume was reduced to slightly
more than half and the product precipitated by addition of hexane
(10 mL). Yield: 49 mg (65%). 1H NMR (CDCl3): d 4.18 (m, 2H,
fc), 4.60 (m, 2H, fc), 4.69 (m, 2H, fc), 4.94 (m, 2H, fc), 7.38 (m, 1H,
1
8.81 (m, 1H, Py). 31P{ H} NMR (DMSO-d6): d 25.3. MS/ESI(+):
m/z (%) 463 (100) [C27H22FeNOP]+.
Py), 7.41–7.52 (m, 7H, Ph + Py), 7.74–7.83 (m, 5H, Ph + Py), 9.60
(m, 1H, Py). 13C{ H} NMR (CDCl3): d 70.95, 71.34, 73.79 (d, JPC
=
General procedure for the preparation of metal complexes
1
10 Hz), 76.14 (d, JPC = 12 Hz), 77.36, 84.88, 122.87, 124.67, 128.91
Solid metal halide MX2 (M = Zn, Cd, Hg and X = Cl, Br,
I) (0.1 mmol) was added to a solution of one (0.1 mmol) or
two equivalents (0.2 mmol) of the respective ligand in ethanol
(10 mL). The mixture was stirred at room temperature for 14 h. If
precipitation of the product occurred, the solvent volume was
reduced in vacuo to slightly less than half. If no precipitation
occurred, the solvent was completely removed in vacuo, the
residue was dissolved in dichloromethane and hexane was added
carefully to precipitate the product. In either case a suspension
of the respective product was obtained. The solid was isolated
by filtration, washed with diethyl ether (2 mL) and subsequently
with hexane (5 mL) and was finally dried in vacuo. Reactive
diffusion experiments to obtain crystalline material directly from
the reaction were carried out in a 5 mm NMR tube. Typically,
equal volumes (ca. 0.5 mL) of 0.1 M solutions of the respective
starting materials were used for the layering experiments. Possible
variations are given in the detailed descriptions.
(d, JPC = 10 Hz), 130.60 (d, JPC = 39 Hz), 131.18, 134.01 (d, JPC
=
1
11 Hz), 139.26, 153.95, 157.45. 31P{ H} NMR (CDCl3): d -19.2.
MS/ESI(+): m/z (%) 767 (7) [M]+, 510 (33) [C27H22FeNPZn]+, 447
(100) [C27H22FeNP]+. Calc. for C27H22NFeI2PZn (766.5): C, 42.31;
H, 2.89; N 1.83. Found: C, 42.29; H, 3.12; N 1.80%.
[CdCl2(1)]. Reactants: 1 (44.7 mg, 0.1 mmol), CdCl2 (18.3 mg,
0.1 mmol). Work-up: The product was isolated by filtration directly
from the reaction mixture. Yield: 14 mg (22%). 1H NMR (CDCl3):
d 4.12 (s, 2H, fc), 4.27 (s, 2H, fc), 4.43 (s, 2H, fc), 5.04 (s, 2H, fc),
7.25 (m, 1H, Py), 7.37 (m, 1H, Py), 7.41 (m, 6H, Ph), 7.59 (m, 4H,
1
Ph), 7.65 (m, 1H, Py), 8.99 (br s, 1H, Py). 13C{ H} NMR (CDCl3):
d 68.28, 71.56, 73.23 (d, JPC = 6 Hz), 75.15 (d, JPC = 13 Hz), 77.36,
84.73, 122.82, 128.93, 129.18 (d, JPC = 10 Hz), 130.03, 131.22,
1
133.77 (d, JPC = 14 Hz), 138.69, 152.03, 158.26, 167.90. 31P{ H}
NMR (CDCl3): d -8.0 (br). Calc. for C27H22NCdCl2FeP (630.6):
C, 51.43; H, 3.52; N, 2.22. Found: C, 52.44; H, 3.52; N, 2.33%.
[ZnCl2(1)]. Reactants: 1 (44.7 mg, 0.1 mmol), ZnCl2 (13.6 mg,
0.1 mmol). Work-up: The solvent was evaporated in vacuo and
the residue dissolved in dichloromethane (2 mL). [ZnCl2(1)]
was precipitated with hexane (25 mL). Yield: 55 mg (95%).
Crystals suitable for a single-crystal X-ray diffraction analysis
were obtained by layering a dichloromethane solution of 1 with a
solution of ZnCl2 in diethyl ether. 1H NMR (CDCl3): d 4.30 (m,
4H, fc), 4.58 (m, 2H, fc), 5.19 (m, 2H, fc), 7.42 (m, 8H, Ph + Py),
[CdBr2(1)]. Reactants: 1 (44.7 mg, 0.1 mmol), CdBr2·4H2O
(34.4 mg, 0.1 mmol). Work-up: The product was isolated by
filtration directly from the reaction mixture. Yield: 43 mg (60%).
Single-crystals suitable for an X-ray diffraction analysis were
obtained by slow evaporation of a dichloromethane solution of
the product. 1H NMR (CDCl3): d 4.21 (m, 2H, fc), 4.27 (m, 2H,
fc), 4.60 (m, 2H, fc), 5.19 (m, 2H, fc), 7.38 (m, 1H, Py), 7.44–7.52
(m, 7H, Ph + Py), 7.72 (m, 1H, Py), 7.75 (m, 4H, Ph), 9.35 (m, 1H,
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 4722–4740 | 4733
©

View Article Online
1
Py). 13C{ H} NMR (CDCl3): d 71.05, 71.44, 73.44 (d, JPC = 7 Hz),
[HgI2(1)]. Reactants: 1 (44.7 mg, 0.1 mmol), HgI2 (45.4 mg,
0.1 mmol). Work-up: Hexane (10 mL) was added to the reaction
mixture. The precipitate was isolated by filtration, washed with
hexane (5 mL) and dried in vacuo. This procedure afforded
75.62 (d, JPC = 13 Hz), 77.36, 85.06, 123.19, 124.48, 129.22 (d, JPC
10 Hz), 129.42, 131.58 (d, JPC = 2 Hz), 133.80 (d, JPC = 13 Hz),
=
31
1
111
139.12, 152.87, 157.88. P{ H} NMR (CDCl3): d -3.6 (J
=
CdP
1
113
[HgI2(1)]· C6H14. Yield: 72 mg (80%). Single-crystals suitable for
1708 Hz, J
= 1782 Hz). MS/MALDI(+): m/z (%) 639 (21)
CdP
4
[M - Br]+, 446 (100) [C27H22FeNP]+. Calc. for C27H22NBr2CdFeP
(719.5): C, 45.07; H, 3.08; N, 1.95. Found: C, 45.32; H, 3.00; N,
2.07%.
an X-ray diffraction analysis were obtained by recrystallisation
from chloroform. 1H NMR (CDCl3): d 4.23 (m, 2H, fc), 4.37 (m,
2H, fc), 4.44 (m, 2H, fc), 4.98 (m, 2H, fc), 7.18 (m, 1H, Py), 7.24
(m, 1H, Py), 7.45–7.55 (m, 6H, Ph), 7.57 (m, 1H, Py), 7.66 (m, 4H,
1
Ph), 8.89 (m, 1H, Py). 13C{ H} NMR (CDCl3): d 70.03, 70.30,
[CdI2(1)]. Reactants: 1 (44.7 mg, 0.1 mmol), CdI2 (36.6 mg,
0.1 mmol). Work-up: The solvent volume was reduced to slightly
more than half in vacuo and hexane (10 mL) was added. The pre-
cipitate was isolated by filtration, washed with hexane (5 mL) and
71.71, 74.44 (d, JPC = 8 Hz), 75.43 (d, JPC = 13 Hz), 86.39, 121.57,
122.12, 129.5 (d, JPC = 12 Hz), 131.95, 133.68 (d, JPC = 12 Hz),
1
136.93, 151.72, 156.85. 31P{ H} NMR (CDCl3): d 19.74 (br).
1
2
MS/ESI(+): m/z (%) 776 (33) [M - I]+, 448 (100) [C27H22FeNP]+.
dried in vacuo. This procedure afforded [CdI2(1)]· C6H14. Yield:
1
4
Calc. for C27H22NFeHgI2P· C6H14 (923.2): C, 37.08; H, 2.78; N,
25 mg (34%). Single-crystals suitable for an X-ray diffraction
analysis were obtained by layering a chloroform solution of the
product with hexane. 1H NMR (CDCl3): d 4.21 (m, 2H, fc), 4.34
(m, 2H, fc), 4.57 (m, 2H, fc), 5.06 (m, 2H, fc), 7.34–7.40 (m, 2H,
1.52. Found: C, 37.65; H, 2.61; N, 1.62%.
[CdCl2(1)2]. The product was obtained by serendipity in a
reactive diffusion experiment aimed at producing single-crystals
of [CdCl2(1)] by layering a 0.1 M solution of 1 in dichloromethane
with an equal volume (0.5 mL) of a 0.1 M solution of CdCl2 in
diethyl ether.
Py), 7.43–7.52 (m, 6H, Ph), 7.67–7.74 (m, 5H, Ph + Py), 9.27 (m,
1H, Py). 13C{ H} NMR (CDCl3): d 70.66, 71.31, 73.55 (d, JPC
=
1
6 Hz), 75.76 (d, JPC = 12 Hz), 77.40, 85.42, 122.88, 123.94, 129.07
(d, JPC = 10 Hz), 131.21 (d, JPC = 44 Hz), 131.23, 133.90 (d, JPC
=
13 Hz), 134.18, 138.67, 153.08, 157.56. 31P{ H} NMR (CDCl3): d
-8.9 (br). MS/ESI(+): m/z (%) 838 (3) [M + Na]+, 688 (15) [M
- I]+, 464 (34) [C27H22FeNPO]+, 448 (100) [C27H22FeNP]+. Calc.
1
[HgCl2(1)2]. The product was obtained by serendipity in a
reactive diffusion experiment aimed at producing single-crystals
of [HgCl2(1)] by layering a 0.1 M solution of 1 in dichloromethane
with an equal volume (0.5 mL) of a 0.1 M solution of HgCl2 in
diethyl ether.
1
2
for C27H22NCdFeI2P· C6H14 (856.6): C, 42.07; H, 3.41; N, 1.64.
Found: C, 42.63; H, 2.98; N, 1.73%.
[HgBr2(1)2]. Reactants:
1 (89.4 mg, 0.2 mmol), HgBr2
[HgCl2(1)]. Reactants: 1 (44.7 mg, 0.1 mmol), HgCl2 (27.1 mg,
0.1 mmol). Work-up: The solvent volume was reduced to ca. one
third in vacuo. The precipitate was filtered off, washed and dried
in vacuo. Yield: 61 mg (84%). H NMR (CDCl3): d 4.25 (s, 2H,
fc), 4.32 (s, 2H, fc), 4.60 (s, 2H, fc), 5.19 (s, 2H, fc), 7.30 (m, 1H,
(36.0 mg, 0.1 mmol). Work-up: The product was isolated by
filtration directly from the reaction mixture. The solid was washed
with ethanol (5 mL) and dried in vacuo. Yield: 107 mg (85%).
Single-crystals suitable for an X-ray diffraction analysis were
obtained by layering a dichloromethane solution of the product
with a small amount of pure dichloromethane and then with
1
Py), 7.36 (m, 1H, Py), 7.56 (m, 6H, Ph), 7.64 (m, 1H, Py), 7.80 (m,
1
4H, Ph), 9.36 (m, 1H, Py). 13C{ H} NMR (CDCl3): d 71.44, 71.47,
1
diethyl ether. H NMR (CDCl3): d 4.12 (m, 4H, fc), 4.19 (m,
74.08 (d, JPC = 9 Hz), 75.53 (d, JPC = 14 Hz), 77.36, 86.36, 122.91,
123.25, 127.75 (d, JPC = 52 Hz), 129.70 (d, JPC = 11 Hz), 132.69
(d, JPC = 3 Hz), 133.61 (d, JPC = 13 Hz), 137.72, 152.21, 156.97.
4H, fc), 4.36 (m, 4H, fc), 4.86 (m, 4H, fc), 7.05 (m, 2H, Py),
7.15 (m, 2H, Py), 7.36 (m, 8H, Ph + Py), 7.43–7.51 (m, 8H, Ph),
7.35–7.45 (m, 6H, Ph + Py), 7.61 (m, 8H, Ph), 8.48 (m, 2H, Py).
31
1
199
P{ H} NMR (CDCl3): d 32.2 (J
= 7470 Hz). MS/ESI(+):
HgP
1
13C{ H} NMR (CDCl3): d 69.19, 70.42, 72.94, 74.76, 77.39, 85.41,
m/z (%) 684 (100) [M - Cl]+, 447 (35) [C27H22FeNP]+. Calc. for
C27H22NCl2FeHgP (718.8): C, 45.12; H, 3.08; N 1.95. Found: C,
45.28; H, 3.15; N, 1.94%.
120.85, 121.13, 128.99, 131.27, 133.71, 136.29, 149.55, 157.74.
1
31P{ H} NMR (CDCl3): d 14.5. MS/ESI(+): m/z (%) 1254 (3)
[M]+, 1175 (4) [M - Br]+, 728 (19) [C27H22FeNPHgBr]+, 448 (100)
[C27H22FeNP]+. Calc. for C54H44N2Br2Fe2HgP2 (1254.9): C, 51.68;
H, 3.53; N, 2.23. Found: C, 51.32; H, 3.49; N, 2.05%.
[HgBr2(1)]. Reactants: 1 (44.7 mg, 0.1 mmol), HgBr2 (36.0 mg,
0.1 mmol). Work-up: The product was isolated by filtration directly
from the reaction mixture. Yield: 67 mg (83%). Single-crystals
suitable for an X-ray diffraction analysis were obtained by layering
a dichloromethane solution of the product with a small amount
[ZnBr2(2)]. Reactants:
2 (23.1 mg, 0.05 mmol), ZnBr2
(11.3 mg, 0.05 mmol). Procedure: The starting materials were
each dissolved in ethanol (5 mL) and the solutions combined. The
mixture was stirred for 30 min. Volatile components were removed
in vacuo. The residue was dissolved in dichloromethane (1 mL) and
the solution added dropwise to hexane (10 mL). The precipitate
was filtered off, washed with hexane (5 mL) and dried in vacuo.
1
of pure dichloromethane and then with diethyl ether. H NMR
(CDCl3): d 4.33 (m, 2H, fc), 4.38 (m, 2H, fc), 4.57 (m, 2H, fc),
5.11 (m, 2H, fc), 7.24 (m, 1H, Py), 7.30 (m, 1H, Py), 7.52–7.62 (m,
1
7H, Ph + Py), 7.77 (m, 4H, Ph), 9.15 (m, 1H, Py). 13C{ H} NMR
1
4
(CDCl3): d 70.75, 71.62, 74.47 (d, JPC = 9 Hz), 75.52 (d, JPC
=
This procedure afforded [ZnBr2(2)]· CH2Cl2. Yield: 30 mg (90%).
13 Hz), 86.46, 122.46, 122.54, 129.58 (d, JPC = 9 Hz), 132.49 (d,
Single-crystals suitable for an X-ray diffraction analysis were
obtained by liquid-phase diffusion of hexane into a chloroform
solution of the product. 1H NMR (CDCl3): d 3.85 (br s, 2H), 4.01
(s, 2H), 4.37–4.59 (br m, 6H), (Fc + CH2Py); 7.39 (m, 5H, Ph +
Py), 7.45 (m, 2H, Ph), 7.52 (m, 1H, Py), 7.55–7.82 (br m, 4H,
1
JPC = 2 Hz), 133.64 (d, JPC = 13 Hz), 137.35, 152.04, 156.84. 31P{ H}
199
NMR (CDCl3): d 28.5 (J
= 6359 Hz). MS/MALDI(+):
HgP
m/z (%) 728 (80) [M - Br]+, 447 (100) [C27H22FeNP]+. Calc. for
C27H22NBr2FeHgP (807.7): C, 40.15; H, 2.75; N, 1.73. Found: C,
40.21; H, 2.58; N, 1.84%.
Ph), 7.96 (m, 1H, Py), 9.66 (m, 1H, Py). 13C{ H} NMR (CDCl3):
1
4734 | Dalton Trans., 2011, 40, 4722–4740
This journal is
The Royal Society of Chemistry 2011
©

View Article Online
d 37.45, 68.96, 69.83, 72.92, 74.24, 77.36, 87.01, 123.58, 127.19,
128.85 (d, JPC = 10 Hz), 130.16 (d, JPC = 40 Hz), 131.06, 133.91
(CDCl3): d 4.04, 4.07, 4.17, 4.39, 4.55 (5 s, 5 ¥ 2H, fc + CH2),
7.22 (m, 1H, Py), 7.35 (m, 1H, Py), 7.50 (m, 6H, Ph), 7.73 (m,
1
1
(d, JPC = 12 Hz), 140.56, 150.96, 159.96. 31P{ H} NMR (CDCl3):
5H, Ph + Py), 9.23 (m, 1H, Py). 13C{ H} NMR (CDCl3): d 37.63,
d -18.1. MS/ESI(+): m/z (%) 524 (100) [C28H24FeNPZn]+. Calc.
69.25, 70.64, 73.69 (d, JPC = 8 Hz), 74.65 (d, JPC = 12 Hz), 77.39,
88.49, 122.90, 125.11, 129.48 (d, JPC = 12 Hz), 132.27, 133.56 (d,
1
4
for C28H24NBr2FeZnP· CH2Cl2 (707.7): C, 47.94; H, 3.49; N, 1.98.
1
Found: C, 47.59; H, 3.58; N 1.92%.
JPC = 13 Hz), 138.45, 150.16, 159.88. 31P{ H} NMR (CDCl3): d
24.3. Calc. for C28H24NCdFeI2P (827.5): C, 40.64; H, 2.92; N, 1.69.
Found: C, 40.40; H, 2.93; N 1.68%.
[ZnBr2(l-2)]2]. Reactants: 2 (46.1 mg, 0.1 mmol), ZnBr2
(22.5 mg, 0.1 mmol). Work-up: The volume of the solution was
reduced to ca. one half in vacuo. The solution was stored for 3 d
at room temperature, which afforded crystals suitable for a single-
crystal X-ray diffraction analysis. Yield: 42 mg (61%).
[HgBr2(2)]. Reactants: 2 (23.1 mg, 0.05 mmol), HgBr2
(18.0 mg, 0.05 mmol). Procedure: The starting materials were
each dissolved in ethanol (10 mL) and the solutions combined.
The mixture was stirred for 1 h. The precipitate was isolated by
filtration, washed and dried in vacuo. Yield: 37 mg (91%). Single-
crystals suitable for an X-ray diffraction analysis were obtained by
layering a 0.1 M solution of HgBr2 in ethanol (0.1 mL) with a 0.1
M solution of the 2 in ethanol (0.1 mL). 1H NMR (CDCl3): d 4.07,
4.10, 4.12, 4.55 (4 s, 4H + 3 ¥ 2H, fc + CH2), 7.19 (m, 1H, Py),
7.30 (m, 1H, Py), 7.51 (m, 6H, Ph), 7.69–7.72 (m, 5H, Ph + Py),
[CdBr2(2)]. Reactants: 2 (23.1 mg, 0.05 mmol), CdBr2·4H2O
(17.2 mg, 0.05 mmol). Procedure: The starting materials were
each dissolved in ethanol (10 mL) and the solutions combined.
The mixture was stirred for 1 h. The precipitate was isolated by
filtration, washed and dried in vacuo. Yield: 34 mg (94%). 1H NMR
(CDCl3): d 3.96, 4.00, 4.29, 4.48, 4.52 (5 s, 5 ¥ 2H, fc + CH2), 7.35
(m, 1H, Py), 7.39–7.53 (m, 7H, Ph + Py), 7.62 (m, 4H, Ph), 7.92
1
1
9.09 (m, 1H, Py). 13C{ H} NMR (CDCl3): d 37.65, 69.84, 70.69,
(m, 1H, Py), 9.45 (m, 1H, Py). 13C{ H} NMR (CDCl3): d 38.35,
73.84 (d, JPC = 9 Hz), 74.61 (d, JPC = 13 Hz), 77.39, 88.38, 122.73,
124.82, 128.83 (d, JPC = 51 Hz), 129.50 (d, JPC = 12 Hz), 132.31
(d, JPC = 3 Hz), 133.55 (d, JPC = 13 Hz), 138.29, 149.93, 159.92.
68.64, 70.31, 72.93 (d, JPC = 7 Hz), 74.51 (d, JPC = 12 Hz), 77.39,
87.12, 123.61, 126.38, 129.16 (d, JPC = 10 Hz), 131.33, 133.71 (d,
1
JPC = 14 Hz), 140.26, 150.77, 160.50. 31P{ H} NMR (CDCl3): No
31
1
199
P{ H} NMR (CDCl3): d 24.4 (J
= 6321 Hz). MS/ESI(+):
HgP
signal could be detected. Calc. for C28H24NBr2CdFeP (733.5): C,
45.85; H, 3.30; N, 1.91. Found: C, 45.68; H, 3.27; N, 1.85%.
m/z (%) 742 (76) [C28H24BrFeHgNP]+, 462 (100) [C28H24FeNP]+.
Calc. for C28H24Br2FeHgNP (821.7): C, 40.93; H, 2.94; N, 1.71.
Found: C, 40.93; H, 2.94; N, 1.69%.
[CdBr2(l-2)]n. Single-crystals were obtained by layering a 0.1
M solution of 2 in dichloromethane (0.5 mL) with a small amount
of pure ethanol and then with a 0.1 M solution (0.5 mL) of
CdBr2·4H2O in ethanol.
[{HgBr(l-Br)}2(l-2)]n. Single-crystals were obtained from
HgBr2 and 2 in analogy to the procedure described for [CdBr2(m-
2)]n.
[CdI2(2)]. Reactants: 2 (46.1 mg, 0.1 mmol), CdI2 (0.1 mmol,
36.6 mg). The procedure was analogous to that described for
[CdBr2(2)]. Yield: 37.3 mg (90%). Single-crystals suitable for an
X-ray diffraction analysis were obtained by liquid-phase diffusion
[HgBr2(2)2]. Reactants: 2 (92.3 mg, 0.2 mmol), HgBr2 (36.0 mg
0.1 mmol). Work-up: Immediately after the addition of the metal
salt a yellow solid precipitated. The reaction mixture was stirred
for 14 h, the precipitate was filtered off, washed with ethanol
1
of hexane into a chloroform solution of the product. H NMR
Table 9 Crystal data and structure refinement details for ligands 1–3
1
2
3
Empirical formula
Molecular weight
Crystal size/mm
C27H22FeNP
447.28
0.49 ¥ 0.39 ¥ 0.24
0.72/0.82
173(2)
C28H24FeNP
461.30
0.57 ¥ 0.40 ¥ 0.15
0.72/0.88
100(2)
C27H22FeNP
447.28
0.25 ¥ 0.21 ¥ 0.02
0.55/0.56
173(2)
T
min/Tmax
T/K
Crystal system
Triclinic
Triclinic
Triclinic
¯
¯
¯
Space group
P1
P1
P1
˚
a/A
10.1437(9)
11.0401(9)
10.9432(9)
72.013(6)
85.964(7)
66.324(6)
1065.47(16)
2
8.4956(11)
10.9419(13)
13.4071(15)
67.813(9)
75.752(9)
84.294(10)
1118.5(2)
2
10.1847(12)
11.0585(12)
10.9491(13)
72.890(9)
85.100(10)
65.974(8)
1075.6(2)
2
˚
b/A
˚
c/A
a (◦)
b (◦)
g (◦)
3
˚
V/A
Z
Dc/g cm-1
1.394
0.797
9178
3636
0.0340
3430
1.370
0.761
8622
3867
0.0501
3663
1.381
0.789
7001
3555
0.0534
2598
m/mm-1
Refl. measured
Unique refl.
Rint
Refl. obsd
R1, wR2 (I > 2s(I))
0.0264, 0.0732
0.0278, 0.0739
-0.357/0.311
0.0323, 0.0892
0.0336, 0.0900
-0.445/0.383
0.0483, 0.1119
0.0677, 0.1182
-0.584/0.550
R1, wR2 (all data)
-3
˚
Drmin
/
max//e A
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4736 | Dalton Trans., 2011, 40, 4722–4740
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©

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This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 4722–4740 | 4737
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Table 12 Crystal data and structure refinement details for complexes of
ligand 3
(10 mL) and diethyl ether (20 mL) and dried in vacuo. Yield:
71.1 mg (55%). Single-crystals suitable for an X-ray diffraction
analysis were obtained by layering a chloroform solution of the
product with hexane. 1H NMR (CDCl3): d 3.48 (s, 4H, CH2), 3.92
(s, 4H, fc), 4.06 (s, 4H, fc), 4.19 (s, 4H, fc), 4.30 (s, 4H, fc), 7.04 (m,
4H, Py), 7.36(m, 8H, Ph), 7.44 (m, 4H, Ph), 7.51 (m, 2H, Py), 7.66
[ZnBr2(m-3)]n
[HgBr2(m-3)]n
Empirical formula
Molecular weight
Crystal size/mm
C27H22Br2FeNPZn
672.47
0.13 ¥ 0.12 ¥ 0.09
0.55/0.67
100(2)
C27H22Br2FeHgNP
807.69
0.60 ¥ 0.45 ¥ 0.09
0.05/0.39
173(2)
1
(m, 8H, Ph), 8.44 (s, 2H, Py). 13C{ H} NMR (CDCl3): d 37.98,
T
min/Tmax
70.53, 70.99, 73.31, 74.44, 77.36, 88.12, 121.34, 122.99, 128.93,
T/K
1
131.23, 133.75, 136.67, 148.92, 160.79. 31P{ H} NMR (CDCl3): d
Crystal system
Space group
Monoclinic
P 21/c
15.3284(10)
9.0578(6)
18.4976(10)
90
96.220(5)
90
2553.1(3)
4
1.749
4.716
16069
4461
Monoclinic
P 21/c
16.0531(9)
8.9781(4)
19.1000(11)
90
105.934(4)
90
2647.0(2)
4
2.027
9.436
16588
4720
15.4. MS/APCI(+): m/z (%) 1283 (3) [M]+, 1202 (5) [M - Br]+,
741 (46) [C28H24BrFeHgNP]+, 462 (100) [C28H24FeNP]+. Calc. for
C56H48N2Br2Fe2HgP2 (1283.0): C, 52.42; H, 3.77; N, 2.18. Found:
C, 52.68; H, 3.25; N 2.19%.
˚
a/A
˚
b/A
˚
c/A
a (◦)
b (◦)
g (◦)
[ZnBr2(l-3)]n. Reactants: 3 (44.7 mg, 0.1 mmol), ZnBr2
(22.5 mg, 0.1 mmol). Work-up: Immediately after the addition
of the metal salt a yellow solid precipitated. The reaction mixture
was stirred for 6 h. The solvent volume was reduced to ca. one
half in vacuo. The solid was filtered off, washed with ethanol
(5 mL) and dried in vacuo. Yield: 42 mg (53%). Crystals suitable
for an X-ray diffraction analysis were obtained by layering a 0.1 M
dichloromethane solution of 3 (0.5 mL) with a small amount pure
3
˚
V/A
Z
Dc/g cm-1
m/mm-1
Refl. measured
Unique refl.
Rint
0.0776
3378
0.0518
4423
Refl. obsd
R1, wR2 (I > 2s(I))
0.0408, 0.0861
0.0595, 0.0915
-0.747/2.014
0.0261, 0.0723
0.0285, 0.0734
-0.731/0.933
R1, wR2 (all data)
1
ethanol and then with a 0.1 M solution of ZnBr2 (0.5 mL). H
-3
˚
Drmin
/
max//e A
NMR (DMSO-d6): d 3.88 (s, 2H, fc), 4.22 (s, 2H, fc), 4.28 (s, 2H,
fc), 4.77 (s, 2H, fc), 7.31 (m, 5H, Ph + Py), 7.34 (m, 6H, Ph), 7.79
1
(m, 1H, Py), 8.38 (m, 1H, Py), 8.67 (m, 1H, Py). 13C{ H} NMR
10 Hz), 132.28, 133.01 (d, JPC = 13 Hz), 133.15, 146.85, 147.37.
1
(DMSO-d6): d 67.52, 70.55, 72.83 (d, JPC = 4 Hz), 74.02 (d, JPC
15 Hz), 76.42 (d, JPC = 8 Hz), 81.98, 123.62, 128.34 (d, JPC = 7 Hz),
=
31P{ H} NMR (DMSO-d6): d 19.3 (br). MS/MALDI(+): m/z
(%) 808 (8) [C27H22Br2FeHgNP]+, 728 (29) [C27H22BrFeHgNP]+,
447 (100) [C27H22FeNP]+. Calc. for C27H22NBr2FeHgP (807.7): C,
40.15; H, 2.75; N, 1.73. Found: C, 40.15; H, 2.72; N 1.79%.
128.68, 133.04 (d, JPC = 20 Hz), 133.41, 134.40, 138.53 (d, JPC
=
10 Hz), 146.78, 146.87. 31P{ H} NMR (DMSO-d6): d -18.9, 25.3.
1
MS/MALDI(+): m/z (%) 447 (100) [C27H22FeNP]+.
Crystal structure analyses
[CdBr2(l-3)]n. Reactants: 3 (44.7 mg, 0.1 mmol), CdBr2·4H2O
(34.4 mg, 0.1 mmol). Work-up: Immediately after the addition of
the metal salt a yellow solid precipitated. The reaction mixture was
stirred for 14 h. The solid was filtered off, washed with ethanol
(5 mL) and dried in vacuo. Yield: 30 mg (38%). 1H NMR (DMSO-
d6): d 3.89 (s, 2H, fc), 4.22 (s, 2H, fc), 4.28 (s, 2H, fc), 4.77 (s, 2H,
fc), 7.29 (m, 5H, Ph + Py), 7.34 (m, 6H, Ph), 7.78 (m, 1H, Py), 8.38
For each data collection a single-crystal was mounted on a glass
fibre and all geometric and intensity data were taken from this
sample. Data collection using Mo-Ka radiation (l = 0.71073 A)
˚
was made on a Stoe IPDS2 diffractometer equipped with a 2-
circle goniometer and an area detector. Absorption correction was
done by integration using X-red.61 The data sets were corrected
for Lorentz and polarisation effects. The structures were solved
by direct methods (SHELXS97) and refined using alternating
cycles of least squares refinements against F2 (SHELXL97).62
All non-H atoms were found in difference Fourier maps and
were refined with anisotropic displacement parameters. A solvent
molecule (probably ethanol) in [{HgBr(m-Br)}2(m-2)]n was not
included to the model using the SQUEEZE routine in PLATON.63
H atoms were placed in constrained positions according to the
riding model with the 1.2 fold isotropic displacement parameters.
Crystallographic details are collected in Tables 9–12. Graphical
representations were made using ORTEP-3 win.64 All figures
represent the displacement ellipsoids at the 30% probability level,
except for the H atoms, which are drawn as circles of arbitrary
radius.
1
(m, 1H, Py), 8.67 (s, 1H, Py). 13C{ H} NMR (DMSO-d6): d 67.46,
70.51, 72.80 (d, JPC = 4 Hz), 73.98 (d, JPC = 15 Hz), 76.38 (d, JPC
=
8 Hz), 82.03, 123.49, 128.31 (d, JPC = 7 Hz), 128.65, 132.92, 133.18
1
(d, JPC = 20 Hz), 134.25, 138.49, 146.89, 146.94. 31P{ H} NMR
(DMSO-d6): d -18.8, 25.3. MS/MALDI(+): m/z (%) 447 (100)
[C27H22FeNP]+. Calc. for C27H22NBr2CdFeP (719.5): C, 45.07; H,
3.08; N, 1.95. Found: C, 44.77; H, 3.02; N 1.88%.
[HgBr2(l-3)]n. Reactants: 3 (44.7 mg, 0.1 mmol) and HgBr2
(36.0 mg, 0.1 mmol). Work-up: Immediately after the addition
of the metal salt a light orange solid precipitated. The reaction
mixture was stirred for 14 h. The solid was filtered off, washed with
ethanol (5 mL) and dried in vacuo. Yield: 55 mg (68%). Single-
crystals suitable for an X-ray diffraction analysis were obtained
by layering a 0.1 M dichloromethane solution of 3 (0.5 mL) with
a small amount pure dichloromethane and then with a 0.1 M
1
solution of HgBr2 in ethanol (0.5 mL). H NMR (DMSO-d6): d
Acknowledgements
4.41–4.46 (m, 6H, fc), 4.85 (s, 2H, fc), 7.53 (m, 5H, Ph + Py), 7.61
1
(m, 7H, Ph + Py), 8.36 (m, 1H, Py), 8.57 (m, 1H, Py). 13C{ H}
This work was supported by the Czech Science Foundation
(project no. P207/10/0176) and a bilateral KONTAKT program
by the Ministry of Education of the Czech Republic (project
NMR (DMSO-d6): d 68.11, 71.56, 73.55 (d, JPC = 13 Hz), 74.65 (d,
JPC = 7 Hz), 83.48, 123.53, 129.35 (d, JPC = 11 Hz), 130.76 (d, JPC
=
4738 | Dalton Trans., 2011, 40, 4722–4740
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