Complexation of 1,1′-bis(diphenylphosphino)ferrocene dioxide (dppfO2) with 3d metals and revisit of its coordination to Pd(ii)

Article abstract of DOI:10.1039/c1dt10920k

Complexation of dppfO₂ with 3d metals has been examined and its coordination towards Pd(ii) re-visited. Adduct formation is complicated by ligand exchanges followed by formation of coordination metal salts, and oxidation.

Full text of DOI:10.1039/c1dt10920k

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PAPER
Complexation of 1,1¢-bis(diphenylphosphino)ferrocene dioxide (dppfO2) with
3d metals and revisit of its coordination to Pd(II)†
Wenhua Zhang and T. S. Andy Hor*
Received 16th May 2011, Accepted 26th August 2011
DOI: 10.1039/c1dt10920k
Complexation of dppfO2 with 3d metals has been examined and its coordination towards Pd(II)
re-visited. Adduct formation is complicated by ligand exchanges followed by formation of coordination
metal salts, and oxidation.
and Zn(II) could also give similar or even better R factors with
reasonable bond data (ESI). In principle, dppfO2 should complex
with a range of 3d metals and give tetrahedral complexes such as
MX2(dppfO2) (X = halides or pseudohalides; M = Fe(II), Co(II),
Introduction
Pd(II) complexes are almost invariably square planar, al-
though there are exceptions, such as the trigonal pyrami-
dal tris(phosphino)silyl Pd(II) cation.1
A
decade ago one
Ni(II), Cu(II), Zn(II), etc), but surprisingly very few of these are
known in the literature.10–13 This adds to the mystery of the identity
of 1 and precludes a comprehensive structural comparison with
related complexes. Accepting that the nature of the metal in 1 is
questionable and as there is no concrete data in our laboratory or
the literature to pinpoint an alternative, we have re-investigated
and expanded the coordination chemistry of dppfO2 with PdCl2
and PdCl2(MeCN)2 as well as a range of 3d metals from Cr(III)
to Zn(II). Reported herein is a series of single-crystal X-ray
crystallographic diffraction and supplementary characterisation
analyses of the products. It also highlights some unexpected
structural features thus unveiled.
of us reported the formation of [PdCl2(dppfO2)] (dppfO2
=
bis(diphenylphosphino)ferrocene dioxide-O,O¢) (1) with an un-
usual tetrahedral Pd(II) structure from the reaction of dppfO2 with
PdCl2(MeCN)2 in CH2Cl2.2 Fey and Orpen et al. subsequently
performed DFT calculation which suggested that the energy
content of the paramagnetic triplet configuration is probably too
high, and that the metal is more likely to be Ni(II).3 Personal
correspondence with Orpen, Koch and a few others4 suggested
that this work required substantiation and that the substance in
question is probably a Ni(II) species.
The nature of the metal remains a mystery today. Confusion
with NiCl2(dppfO2) obtained in poor yield from NiCl2·6H2O and
2
dppfO2 is suspected but could not be verified. We have since
repeated this Ni(II) reaction but no crystals suitable for X-ray
analysis could be obtained (see below). Repeated refinement of
the crystal structure using the original experimental diffraction
data but with the metal fitted as Ni (instead of Pd) indeed gave
improved results in terms of significantly lower R factor (R =
0.0388 (Ni) vs. 0.0713 (Pd) based on 4010 unique reflections), and
more reasonable thermal motion of the metal ion compared to
its four bonded atoms. The latter also leads to the absence of
two Hirshfeld rigid-bond test alert for the M–O bonds in the
CheckCIF/Platon5 report which in many cases are caused by
mis-assigned atom types (ESI).6–9 However, structural refinement
without other experimental or supporting characterisation data
would not be sufficient as several 3d metals such as Co(II), Cu(II)
Results and discussion
Stoichiometric reaction of PdCl2(MeCN)2 with dppfO2 (1 : 1) in
CH2Cl2 at r.t. for 8 h leads to a deep-red solution accompanied
by a small amount of brown precipitate which was filtered off.
Saturated slowly by Et2O vapour, the solution gave rise to a deep
red solid (A). Upon isolation, it (A) is stable in air and partly
soluble in CH2Cl2, but quickly decomposes in DMF and DMSO
to give free dppfO2. Solid A was extracted into CH2Cl2 to give
a suspension, which led to the isolation of B (from the filtrate),
and brown residue C in a roughly 2 : 1 mass ratio. Subsequent
elemental analysis and infrared analysis suggested that B and C
are chemically indistinguishable. Comparison of the carbon and
hydrogen content of B and C with those of A suggests that in
the isolation process, A has transformed to B and C that have
significantly lower carbon and hydrogen content. B and C may
also be obtained in a similar mass ratio from the filtrate of
the reaction mixture through direct precipitation upon addition
of Et2O followed by phase separation using CH2Cl2. Recrys-
tallizations of both B and C in different solvents have insofar
failed to yield any crystals suitable for X-ray crystallographic
analysis.
Department of Chemistry, National University of Singapore, 3 Science Drive
3, 117543, Singapore. E-mail: andyhor@nus.edu.sg
† Bond distances and angles for 2–12. Ortep diagrams of 3–5, 8, 10–12.
Field dependence of the magnetization for B and C at 100 K and 193 K.
1H V.T. NMR for the in situ mixture of PdCl2(MeCN)2 and dppfO2 in
CD2Cl2. XRD spectra. CheckCIF/Platon report for 1 and the metal fitted
as Co, Ni, Cu and Zn using the same diffraction data. CCDC reference
numbers 823889–823899. For ESI and crystallographic data in CIF or
other electronic format see DOI: 10.1039/c1dt10920k
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 10725–10730 | 10725
©

The powder X-ray diffraction (XRD) patterns shows that
B is amorphous in nature. C exhibits some crystallinity but
its diffraction pattern is inconsistent with that simulated from
the crystallographic data set of 1 (ESI†). Vibrating Sample
Magnetometric (VSM) measurements of B and C at both 100 K
and 193 K suggested that they are diamagnetic (ESI†), thus ruling
out tetrahedral Pd(II).
1
V. T. 31P{ H} NMR analysis have been carried out on the in situ
reaction mixture of PdCl2(MeCN)2 and dppfO2 in CD2Cl2. The r.t.
spectrum shows a broad peak at d 34.0 and a minor resonance at d
47.2 ppm (Fig. 1), which is in agreement with that reported.2 The
major peak (d 34.0 ppm) gradually sharpens as the temperature
is lowered to 233 K, but broadens at 193 K with the formation
1
of a shoulder peak. The V.T. H NMR spectra do not give any
additional information (ESI†). These are indicative of a dynamic
system of interchanging species with similar ligand environment
but statistically varied dispositions.14–17
1
Fig. 1 V. T. 31P{ H} NMR spectra (193 K to 298 K) of the in situ reaction
mixture of [PdCl2(MeCN)2] and dppfO2 in CD2Cl2.
Mixing of PdCl2 and dppfO2 (1 : 1) in CH2Cl2, CHCl3,
CH2Cl2/CHCl3, MeOH/CH2Cl2, MeOH/CHCl3 and many other
solvent systems led to incomplete reactions. Attempts to isolate
the products therein through Et2O vapour diffusion invariably
yielded single crystals of dppfO2. Oxidation of [PdCl2(dppf)]18,19
with excess t-BuOOH (5–6 M in decane) or H2O2 (30%) in CH2Cl2
for one day at r.t. also failed to give any product apart from near-
quantitative recovery of [PdCl2(dppf)].
Similar reactions of PtCl2(MeCN)2 or PtCl2 with dppfO2 under
various solvent conditions were carried out for comparisons. There
is no evidence of addition reaction between PtCl2(MeCN)2 and
dppfO2 in CH2Cl2 or CHCl3 but formation of uncharacterisable
white inorganic salt. There is no apparent reaction between PtCl2
and dppfO2 in CH2Cl2 and CHCl3 upon mixing for 2 days.
These results suggest that the reported reaction leading to 1 is
irreproducible and that the exact identity of the product remains
elusive. Since the tetrahedral metal is suspected to be Ni, we
proceeded to investigate similar preparations using Ni(II) sub-
strates. Treatment of NiCl2·6H2O and dppfO2 in CHCl3/MeOH
(2 : 1, v/v) followed by slow diffusion with Et2O did not yield the
anticipated tetrahedral complex NiCl2(dppfO2). Instead, it gave
rise to a poor yield (ca 5%) of a mix-valent Ni complex salt
[NiIVCl2(dppfO2)2][NiIICl4] (2) (Fig. 2a). The identity of the bulk of
the product remains unknown whilst all optimisation experiments
aiming to improve the yield of 2 have been futile. During the crystal
Fig. 2 Ortep diagrams of 2 (a), 6 (b), 7 (c) and 9 (d) with 50% thermal
ellipsoids. All solvent molecules, hydrogen atoms and one disordered
component of [NiCl4]2- in 2 are omitted for clarity purpose. Symmetry
code for 6: A: 1 - x, y, 0.5 - z; 7: A: 1 - x, y, 1.5 - z.
growing process, the solution turned from orange-red to deep
red, possibly due to aerial oxidation. When the freshly prepared
reaction mixture was treated with Et2O and the orange crystalline
precipitate was subjected to XRD analysis, it gives a diffraction
pattern that partly resembles that simulated from the original X-
ray data set of 1 (ESI†). This suggests that if Ni is indeed the metal
10726 | Dalton Trans., 2011, 40, 10725–10730
This journal is
The Royal Society of Chemistry 2011
©

in 1, the tetrahedral complex is just one of the products in this
deceptively simple addition reaction.
or alternative products such as in Ni(II)Ni(IV) (2), Cr(III) (3) and
Fe(III) (4). Other cationic complexes such as [FeX2(dppfO2)2]X¢ or
[FeX(dppfO2)2]X¢X¢¢ (5 & 6) are accordingly formed. Those that
give neutral adducts tend to be divalent metals with predominantly
tetrahedral structures MX2(dppfO2), such as Mn (8), Co (9–11)
and Zn (12), but octahedral MX2(dppfO2)2 (Cu(II) in 7) is also
possible. These adduct formation reactions are complicated by
oxidation, as witnessed in the formation of Ni(IV) from Ni(II)
(in 2) and Fe(III) from Fe(II) (in 5 & 6). The d8 complexes
of interest NiCl2(dppfO2) and PdCl2(dppfO2) are unstable with
respect to ligand exchanges (and oxidation, in Ni(II)) under the
formation conditions and hence their exact identity remains elu-
sive. Reproduction of the Pd(II) preparation yielded a diamagnetic
product that could give exchange products which can be tentatively
assigned as [Pd2(m-Cl)2(dppfO2)2][PdCl4] in solution. Although
Mn(II), Co(II) and Zn(II) form MX2(dppfO2) easily, they are
unlikely to be the metal in the questionable “MCl2(dppfO2)” (1)
based on the differences in the space groups and XRD patterns.
Ni(II) remains the more likely option but further study is needed
since NiCl2(dppfO2) appears to be susceptible to oxidation and we
are still unable to obtain suitable stable single-crystals for X-ray
crystallographic analysis. Worthy of mention is that dppfO2 can
support octahedral complexes in a mutually trans bis-chelating
fashion. It therefore poses an intriguing question on why the sq.
planar [M(dppfO2)2] core remains elusive. Current activities in
our laboratories are targeting at such structural motif apart from
addressing the mysterious puzzle on tetrahedral Pd(II).
To examine the possibility that the metal in question could
be other 3d metals, we have carried out additional experiments.
Reactions of dppfO2 with CrCl3·6H2O in 1 : 1 stoichiometric ratio
gives [Cr(dppfO2)2Cl2][CrCl4]·MeOH (3) (22%), as revealed by X-
ray single-crystal diffraction. Similar reaction with FeCl3·6H2O
gives [Fe(dppfO2)2Cl2][FeCl4]·3CH2Cl2 (4) (77%). Both 3 and 4
are isostructural to 2 except that their lattice solvent are different.
Together with 2, formation of these products suggested that for
metals that are amenable to tetrahedral and octahedral geometries,
there is a tendency for halide migratory reaction leading to cationic
octahedral dppfO2 complexes with anionic tetrachlorometallates.
The steric bulk of dppfO2 possibly forces the two dppfO2 chelates
to be mutually trans on the same coordination plane thus fixing
the chloride above and below the plane. Other reactions on the
Fe(ClO4)2/2Et4NX/dppfO2 (X = Cl; I) mixtures failed to give the
complex FeX2(dppfO2). Instead, these preparations led to the iso-
lation of oxidised octahedral [FeCl2(dppfO2)2][ClO4]·0.5CH2Cl2
(5) (8%) and square pyramidal [FeI(dppfO2)2][I3][Cl]·Et2O·H2O (6)
(trace) (Fig. 2b). The absence of FeX2(dppfO2) in these reactions is
noteworthy, suggesting also that the metal in 1 is unlikelytobe iron.
The experimental conditions used favored facile aerial oxidation
of Fe(II). Similar reaction of dppfO2 with CuCl2·2H2O gives
[CuCl2(dppfO2)2]·2CH2Cl2·3H2O (7), which is the only primary
neutral and octahedral adduct isolated in this series (Fig. 2c).
Reactions of MnCl2·4H2O, CoCl2·6H2O, Co(BF4)2/2NaBr,
CoI2 and ZnCl2·4H2O with dppfO2 successfully result in the
1 : 1 adduct of neutral tetrahedral complexes in [MnCl2(dppfO2)]
(8), [CoX2(dppfO2)] (X = Cl (9); Br (10); I (11)) (Fig. 2d) and
[ZnCl2(dppfO2)]·0.25H2O (12) respectively, which are isostructural
to 1. Their facile formation and ease of crystallisation is a sharp
contrast to those of Ni(II) and Pd(II), adding further mystery to the
nature of the metal in 1. Their space groups and M–X (X = Cl, Br, I)
bond lengths are listed in Table 1. Only 10 and 11 crystallize in the
same space group as “PdCl2(dppfO2)” (1). But they are unlikely to
Experimental
General remarks
1,1¢-Bis(diphenylphosphino)ferrocene dioxide (dppfO2) was syn-
thesized following the literature method.20 All synthetic proce-
dures were carried out at ambient conditions in air. Elemental
analyses were performed on a Perkin–Elmer PE 2400 CHNS
Elemental Analyzer. The 1H and 31P NMR spectra were recorded
on Bruker AMX 500-MHz spectrometer and their chemical shifts
were referenced to Me4Si (TMS). IR spectra were recorded on
a Bruker IFS 48 FTIR spectrometer using KBr as pellets. MS-
FAB spectra were obtained with a Finnigan MAT95XL mass
spectrometer. Peaks were assigned from the m/z values and the
isotope distribution patterns. Powder X-ray diffraction spectra
were recorded on a Siemens D5005 X-ray diffractometer. Magnetic
measurement was carried out on a Lakeshove 7400 vibrating
sample magnetometer.
˚
be the same materials as their respective Co–Br (av. 2.373 A) and
˚
Co–I (av. 2.567 A) lengths are significantly longer than those of 1
˚
(av. 2.213 A). A CSD search of the M–Cl bond distances for the
˚
tetrahedral MCl2(R3PO)2 complexes gives Mn–Cl (2.29–2.34 A),
˚
˚
˚
Fe–Cl (2.19–2.29 A), Co–Cl (2.20–2.26 A), Ni–Cl (2.20–2.22 A),
˚
˚
Cu–Cl (2.13–2.20 A) and Zn–Cl (2.20–2.27 A), suggesting that the
M–Cl lengths in 1 are much closer to that of a 3d metal although
its exact identity remains uncertain.
This study suggested that formation of the deceptively straight-
forward MX2(dppfO2) is complicated by facile ligand (halide
and dppfO2) dissociation, migration and interchanges, and hence
generating coordination salts [MX2(dppfO2)2][MX4] as secondary
Reaction of PdCl2(MeCN)2 with dppfO2. PdCl2(MeCN)2
(0.26 g, 1.0 mmol) was dissolved in CH2Cl2 (40 mL) and dppfO2
(0.58 g, 1.0 mmol) added. The mixture was stirred at r.t. for 8
h. A small amount of brown powder formed which was filtered
off. The deep red filtrate was slowly saturated using Et2O vapor
to yield a small amount of deep red solid (A). This solid was re-
dissolved in CH2Cl2 and stirred for 24 h to yield the red solution
and a brown powder (C). Solid C was separated from the mother
liquor which was then concentrated and Et2O added to precipitate
the red solid B. Solid B and C may be prepared alternatively
by dropwise addition of Et2O to the original reaction mixture
to precipitate a brown solid (0.57 g) which was then separated
using CH2Cl2 similar to that describe for A. Yield: B (0.30 g), C
Table 1 A list of tetrahedral MX2(dppfO2) complexes prepared in this
study for comparison with “PdCl2(dppfO2)” (1)
˚
˚
Complex
Space Group
M–X(1) (A)
M–X(2) (A)
“PdCl2(dppfO2)” (1)
MnCl2(dppfO2) (8)
CoCl2(dppfO2) (9)
CoBr2(dppfO2) (10)
CoI2(dppfO2) (11)
ZnCl2(dppfO2) (12)
Cc
2.204(3)
2.222(4)
P21/c
P21/n
Cc
2.3341(9)
2.2370(8)
2.3695(8)
2.5624(8)
2.2122(14)
2.3052(11)
2.2489(8)
2.3770(8)
2.5722(8)
2.2005(16)
Cc
Pbca
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 10725–10730 | 10727
©

(0.15 g). Characterization data of A: 1H NMR (500 MHz, CD2Cl2):
d 7.43–7.58 (m, 20H), 4.55 (s, 4H), 4.29 (s, 4H), 1.96 (s, 3H) ppm.
31P NMR (202 MHz, CDCl3): 33.8 ppm. Anal. calcd. (%) for
C34H28Cl12FeO2P2Pd: C 53.47, H 3.70; found: C 47.53, H 3.28
corresponding to [Pd2(m-Cl)2(dppfO2)2][PdCl4]. IR (KBr pellet):
3054 (w), 1971 (w), 1902 (w), 1821 (w), 1588 (w), 1483 (m), 1435 (s),
1388 (w), 1310 (w), 1253 (w), 1186 (s), 1121 (s), 1066 (w), 1033 (m),
997 (w), 931 (w), 912 (m), 832 (m), 752 (s), 727 (s), 692 (s), 629 (m),
569 (s), 529 (s), 492 (s) cm-1. Characterization data of B: FAB-MS
(-): 212.6 m/z, [PdCl3]-. Anal. calcd. (%) for C34H28Cl12FeO2P2Pd:
C 53.47, H 3.70; found: C 45.57, H 3.40 corresponding to [Pd2(m-
Cl)2(dppfO2)2][PdCl4][PdCl2]0.5. IR (KBr pellet): 3079 (w), 3055
(w), 1970 (w), 1899 (w), 1822 (w), 1618 (w), 1589 (m), 1483 (m),
1435 (s), 1388 (w), 1311 (m), 1252 (w), 1186 (s), 1121 (s), 1068 (w),
1032 (w), 997 (w), 930 (w), 911 (w), 832 (m), 752 (s), 727 (s), 693 (s),
629 (m), 569 (s), 530 (s), 494 (s), 448 (w) cm-1. Characterization
data of C: FAB-MS (-): 212.6 m/z, [PdCl3]-. Anal. calcd. (%)
for C34H28Cl12FeO2P2Pd: C 53.47, H 3.70; found: C 45.39, H 3.37
corresponding to [Pd2(m-Cl)2(dppfO2)2][PdCl4][PdCl2]0.5. IR (KBr
pellet): 3108 (w), 3054 (w), 1987 (w), 1901 (w), 1822 (w), 1588 (m),
1484 (w), 1436 (s), 1389 (w), 1311 (m), 1251 (w), 1208 (m), 1186
(s), 1122 (s), 1069 (w), 1035 (m), 998 (w), 931 (m), 912 (m), 887
(w), 833 (m), 752 (m), 729 (s), 692 (s), 631 (m), 568 (s), 525 (s), 493
(s), 447 (m) cm-1.
(w), 1313 (m), 1192 (s), 1170 (s), 1122 (s), 1104 (m), 1037 (m), 998
(w), 856 (w), 829 (w), 749 (m), 728 (s), 706 (s), 691 (s), 641 (w), 571
(s), 528 (s), 501 (s), 485 (w), 408 (w) cm-1.
Synthesis of [FeCl2(dppfO2)2][FeCl4]·3CH2Cl2 (4). Compound
4 was prepared as black platelet crystals similarly as 2 using
FeCl3·6H2O (0.27 g, 1.0 mmol) and dppfO2 (0.58 g, 1.0 mmol)
as starting materials and CH2Cl2 (15 mL) as solvent. Yield 0.67
g, 77%. FAB-MS (+): 1300.0 m/z [FeCl2(dppfO2)2]+. Anal. calcd.
(%) for C71H62Cl12Fe4O4P4: C 48.67, H 3.57; found: C 53.83, H 3.72
corresponding to [FeCl2(dppf)2][FeCl4]. IR (KBr pellet): 3145 (w),
3101 (w), 3056 (w), 1589 (w), 1484 (w), 1436 (s), 1389 (w), 1361
(w), 1310 (w), 1191 (s), 1151 (s), 1120 (s), 1098 (s), 1032 (m), 997
(w), 845 (w), 829 (m), 751 (s), 726 (s), 702 (s), 636 (w), 618 (w), 570
(s), 528 (s), 498 (s), 449 (w) cm-1.
Synthesis of [FeCl2(dppfO2)2][ClO4]·0.5CH2Cl2 (5). Com-
pound 5 was prepared as black block crystals using the method as
described for 2 using Fe(ClO4)2·xH2O (0.26 g, 1.0 mmol), dppfO2
(0.58 g, 1.0 mmol) and Et4NCl (0.33 g, 2.0 mmol) as starting
materials and CH2Cl2 (20 mL) as solvent. Yield 0.057 g, 8%.
FAB-MS (+): 1300.0 m/z [FeCl2(dppfO2)2]+. Anal. calcd. (%) for
C68.5H57Cl4Fe3O8P4: C 57.08, H 3.99; found: C 57.17, H 3.62. IR
(KBr pellet): 3101 (w), 3055 (w), 1628 (w), 1589 (m), 1484 (m),
1437 (s), 1389 (m), 1362 (w), 1312 (m), 1190 (s), 1147 (br, s), 1094
(br, s), 1032 (s), 998 (m), 929 (w), 900 (w), 880 (w), 841 (m), 827
(m), 754 (s), 727 (s), 704 (s), 636 (m), 622 (m), 570 (s), 529 (s), 498
(s), 448 (w) cm-1.
Synthesis of [NiIVCl2(dppfO2)2][NiIICl4] (2). NiCl2·6H2O
(0.24 g, 1.0 mmol) and dppfO2 (0.58 g, 1.0 mmol) were mixed in
a CH2Cl2/MeOH solvent mixture (15 mL, 2 : 1 v/v). The solution
was stirred at r.t. for 24 h and then filtered. Diffusion with an atmo-
sphere of Et2O vapor yielded a few red block crystals of 2 deposited
on the outside surface of the inner glass tube and the surface of
the host tube (see the figure below). The crystals were collected,
washed with Et2O and dried under vacuum. Yield 0.04 g, 5% based
on dppfO2. FAB-MS (+): 711.8 m/z [NiCl(dppfO2)(CH3OH)]+;
1298.1 m/z [NiCl(dppfO2)2(CH3OH)]+. FAB-MS (-): 197.5 m/z
[NiCl3(CH3OH)]-. Anal. calcd. (%) for C68H56Cl6Fe2Ni2O4P4: C
54.34, H 3.76; found: C 54.23, H 3.98. IR (KBr pellet): 2861 (w),
1632 (br, m), 1590 (w), 1484 (w), 1436 (s), 1388 (w), 1363 (w), 1311
(w), 1191 (s), 1153 (s), 1120 (s), 1099 (s), 1070 (w), 1032 (m), 997
(w), 830 (m), 751 (m), 726 (s), 701 (s), 636 (w), 570 (s), 529 (s), 497
(s), 447 (m) cm-1.
Synthesis of [FeI(dppfO2)2][I3][Cl]·Et2O·H2O (6). Compound
6 was prepared as black block crystals using the method as
described for 2 using Fe(ClO4)2·xH2O (0.25 g, 1.0 mmol) and
dppfO2 (0.58 g, 1.0 mmol) and Et4NI (0.51 g, 2.0 mmol) as starting
materials and CH2Cl2 (20 mL) as solvent. Yield: trace amount.
FAB-MS (+): 676.8 m/z [FeI(dppfO2)2]2+. Anal. calcd. (%) for
C72H68ClFe3I4O6P4: C 46.40, H 3.68; found: C 45.96, H 3.26. IR
(KBr pellet): 3083 (w), 3052 (w), 2970 (w), 2865 (w), 2477 (w),
1588 (m), 1574 (w), 1483 (m), 1435 (s), 1388 (w), 1366 (w), 1311
(w), 1224 (m), 1188 (s), 1151 (s), 1120 (s), 1098 (s), 1071 (m), 1036
(s), 997 (m), 924 (w), 902 (w), 874 (w), 843 (m), 823 (m), 749 (s),
726 (s), 700 (s), 638 (m), 568 (s), 529 (s), 496 (s), 444 (m) cm-1.
Synthesis of [CuCl2(dppfO2)2]·2CH2Cl2·3H2O (7). Compound
7 was prepared as orange block crystals using the method as
described for 2 using CuCl2·2H2O (0.17 g, 1.0 mmol) and dppfO2
(0.58 g, 1.0 mmol) as substrates in a mixture of CH2Cl2/MeOH
(16 mL, 1 : 1 v/v) solvent. Yield 0.13 g, 17%. Anal. calcd. (%)
for C70H66Cl6CuFe2O7P4: C 54.91, H 4.34; found: C 50.41, H
3.46 corresponding to [CuCl2(dppfO2)2]·3CH2Cl2·H2O. IR (KBr
pellet): 3098 (w), 3054 (w), 2986 (w), 1589 (w), 1484 (w), 1437 (s),
1388 (w), 1362 (w), 1312 (w), 1190 (s), 1147 (s), 1121 (s), 1095 (s),
1072 (w), 1032 (m), 997 (w), 899 (w), 851 (w), 821 (m), 753 (s), 726
(s), 702 (s), 695 (s), 640 (w), 619 (w), 569 (s), 530 (s), 498 (s), 484
(m), 449 (m) cm-1.
Synthesis of [CrCl2(dppfO2)2][CrCl4]·MeOH (3). Compound
3 was prepared as brown-red block crystals similarly as 2 using
CrCl3·6H2O (0.27 g, 1.0 mmol) and dppfO2 (0.58 g, 1.0 mmol) as
starting material and CH2Cl2/MeOH (24 mL, 2 : 1 v/v) as solvent.
Yield 0.17 g, 22%. FAB-MS (+): 1294.0 m/z [CrCl2(dppfO2)2]+.
Anal. calcd. (%) for C69H60Cl6Cr2Fe2O5P4: C 54.47, H 3.97; found:
C 54.46, H 3.82. IR (KBr pellet): 3096 (w), 3053 (w), 2022(w),
1915 (w), 1897 (w), 1617 (w), 1591 (w), 1485 (w), 1438 (s), 1389
Synthesis of [MnCl2(dppfO2)2] (8). Compound 8 was prepared
as orange block crystals using the method as described for 2 using
MnCl2·4H2O (0.20 g, 1.0 mmol) and dppfO2 (0.58 g, 1.0 mmol) as
starting material and CH2Cl2/MeOH (24 mL, 1 : 1 v/v) as solvent.
Yield 0.11 g, 15%. FAB-MS (+): 675.8 m/z [MnCl(dppfO2)]+.
Anal. calcd. (%) for C34H28Cl2FeMnO2P2: C 57.34, H 3.96; found:
10728 | Dalton Trans., 2011, 40, 10725–10730
This journal is
The Royal Society of Chemistry 2011
©

This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 10725–10730 | 10729
©

˚
C 57.75, H 4.08. IR (KBr pellet): 3097 (w), 3054 (w), 1633 (w),
1589 (w), 1483 (w), 1436 (s), 1389 (m), 1363 (w), 1311 (m), 1198
(br, s), 1119 (s), 1101 (s), 1071 (m), 1037 (s), 997 (m), 845 (s), 829
(m), 753 (s), 726 (s), 700 (s), 635 (m), 570 (s), 535 (s), 497 (s), 448
(m) cm-1.
Mo-Ka (l = 0.71073 A). The data were corrected for Lorentz
and polarization effects with the SMART suite of programs and
for absorption effects with SADABS.21 All crystal structures were
solved by direct methods and refined on F2 by full-matrix least-
squares techniques with SHELXTL-97 program.22 A summary of
the key crystallographic data for 2–12 are listed in Table 2.
Synthesis of [CoCl2(dppfO2)] (9). Compound 9 was prepared
as green platelet crystals using the method as described for 2 using
CoCl2·6H2O (0.24 g, 1.0 mmol) and dppfO2 (0.58 g, 1.0 mmol) as
starting materials and CH2Cl2 (20 mL) as solvent. Yield 0.52 g,
73%. FAB-MS (+): 679.8.9 m/z [CoCl(dppfO2)]+. Anal. calcd. (%)
for C34H28Cl2CoFeO2P2: C 57.02, H 3.94; found: C 56.94, H 3.99.
IR (KBr pellet): 3092 (w), 3055 (w), 1589 (w), 1483 (w), 1437 (s),
1389 (w), 1368 (w), 1312 (w), 1203 (s), 1159 (s), 1119 (s), 1100 (m),
1072 (w), 1038 (m), 997 (m), 828 (m), 755 (m), 725 (s), 700 (s), 630
(m), 568 (s), 536 (m), 528 (m), 497 (s), 447 (m) cm-1.
Acknowledgements
We acknowledge those (whose names are given in Ref. 3 and 4) who
highlighted this problem to us and subsequent helpful discussions.
We thank Prof. Zhao Bei (Soochow University), Dr Liu Xun-Gao
(Hangzhou Normal University), Dr Koh Lip Lin (NUS), and Dr
Martin Schreyer (ICES, A*Star) for helpful discussion of the VT-
NMR, magnetic and XRD data respectively. We are also indebted
to additional experimental assistance from and discussion with Dr
Bai Shiqiang (NUS).
Synthesis of [CoBr2(dppfO2)] (10). Compound 10 was pre-
pared as green platelet crystals using the method as described
for 2 using Co(BF4)2·xH2O (0.32 g, 1.0 mmol), dppfO2 (0.58 g,
1.0 mmol) and NaBr (0.21 g, 2.0 mmol) as starting materials and
CH2Cl2 (20 mL) as solvent. Yield 0.72 g, 90%. FAB-MS (+): 723.8
m/z [CoBr(dppfO2)]+. Anal. calcd. (%) for C34H28Br2CoFeO2P2: C
50.72, H 3.51; found: C 50.68, H 3.53. IR (KBr pellet): 3089 (w),
3053 (w), 1590 (w), 1483 (w), 1437 (s), 1389 (w), 1363 (w), 1311
(w), 1193 (s), 1161 (m), 1142 (s), 1121 (s), 1096 (m), 1069 (w), 1036
(s), 996 (w), 835 (m), 753 (m), 728 (s), 704 (s), 693 (s), 635 (m), 572
(s), 531 (s), 493 (s), 449 (m) cm-1.
References
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CoI2 (0.31 g, 1.0 mmol), dppfO2 (0.58 g, 1.0 mmol) as starting
materials and CH2Cl2 (20 mL) as solvent. Yield 0.55 g, 61%.
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C34H28CoFeI2O2P2: C 45.42, H 3.14; found: C 45.14, H 3.22. IR
(KBr pellet): 3088 (w), 3052 (w), 1590 (w), 1483 (w), 1436 (s), 1389
(w), 1363 (w), 1310 (w), 1191 (s), 1161 (s), 1139 (s), 1121 (s), 1093
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692 (s), 635 (w), 617 (w), 571 (s), 531 (s), 493 (s), 448 (m) cm-1.
ˆ
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dppfO2 (0.58 g, 1.0 mmol) in a mixture of CH2Cl2/MeOH (15
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1
mL, 2 : 1 v/v) solvent. Yield 0.39 g, 54%. H NMR (400 MHz,
CD2Cl2): d 7.28–7.80 (m, 20H), 4.84 (s, 4H), 4.27 (s, 4H) ppm.
31P NMR (162 MHz, CDCl3): 48.4 ppm. FAB-MS (+): 684.9
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C 56.16, H 3.95; found: C 56.21, H 3.81 corresponding to
ZnCl2(dppfO2). IR (KBr pellet): 3099 (w), 3055 (w), 1624 (w),
1589 (w), 1484 (m), 1436 (s), 1390 (w), 1361 (w), 1311 (w), 1205
(s), 1166 (s), 1153 (s), 1121 (s), 1100 (m), 1072 (w), 1037 (s), 997
(w), 875 (w), 841 (m), 825 (w), 753 (s), 726 (s), 700 (s), 695 (s), 631
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X-ray Crystallography
Crystallographic measurements were made on
a Bruker
AXS APEX diffractometer by using graphite-monochromated
10730 | Dalton Trans., 2011, 40, 10725–10730
This journal is
The Royal Society of Chemistry 2011
©