Directional Fe-COS intermolecular interaction leading to chain-like crystal packing in binuclear Fe(0)-M(II) (M=Hg, Cd) complexes with 2-(diphenylphosphino)thiazole

Article abstract of DOI:10.1016/S0022-328X(98)00952-8

A new thiazole-based phosphine ligand was designed to construct heterobinuclear complexes (CO)₃Fe(μ-Ph₂PNS)₂MX₂ (M=Hg, X=SCN; M=Cd, X=I; Ph₂PNS=2-(diphenylphosphino)thiazole), in which weak Fe-COS intermolecular interaction led to chain-like molecular packing in the solid state.

Full text of DOI:10.1016/S0022-328X(98)00952-8

Journal of Organometallic Chemistry 575 (1999) 51–56
Directional Fe–CꢀO···S intermolecular interaction leading to chain-like
crystal packing in binuclear Fe(0)–M(II) (M=Hg, Cd) complexes with
2-(diphenylphosphino)thiazole
Shan-Ming Kuang a, Zheng-Zhi Zhang b, Feng Xue a, Thomas C.W. Mak a,*
a The Chinese Uni6ersity of Hong Kong, Department of Chemistry, Shatin, New Territories, Hong Kong
b Elemento-Organic Chemistry Laboratory, Nankai Uni6ersity, Tianjin, China
Received 16 July 1998
Abstract
A new thiazole-based phosphine ligand was designed to construct heterobinuclear complexes (CO)3Fe(v-Ph2PNS)2MX2
(M=Hg, X=SCN; M=Cd, X=I; Ph2PNS=2-(diphenylphosphino)thiazole), in which weak Fe–CꢀO···S intermolecular
interaction led to chain-like molecular packing in the solid state. © 1999 Elsevier Science S.A. All rights reserved.
Keywords: Intermolecular interaction; Thiazole-based phosphine ligand; Crystal packing; Heterobinuclear complex
1. Introduction
and shape, charge distribution in the molecule, and
nature of intermolecular interaction ([9]b). The con-
trolled aggregation of organometallic molecules into
directional crystal packing arrangements through weak
intermolecular interaction other than hydrogen bonding
poses an interesting problem. A feasible approach in-
volves the design of an organometallic compound
which possesses specific interaction sites, such that in-
termolecular interaction occurs in a logical fashion to
form an ordered molecular assembly in the crystalline
state.
Solid-state molecular processes and reactivity, inter-
molecular interaction, and packing modes in organic
materials have been the subject of much work and
constitute the subject matter of continuing investigation
[1–8]. The predictable self-organization of molecules
into one-, two, or three-dimensional networks is of the
utmost importance in crystal engineering. For such
rational design, hydrogen bonding has been the most
commonly used supramolecular cement, yet in its ab-
sence weaker interactions such as CH···O, CH···N, I···I,
O···I, N···Cl, or even C···H and C···C can be utilized [6].
In contrast, comparatively little has been done in the
field of organometallic crystal engineering, in spite of
increasing current interest in the solid-state behavior of
organometallic compounds [9].
With this strategy in mind, we synthesized the new
phosphine
ligand
2-(diphenylphosphino)thiazole
(Ph2PNS), which contains potential P, N and S donor
atoms (Scheme 1). It was anticipated that the rigid,
short-bite P,N-donor set would function as a bridging
ligand to form binuclear complexes consolidated by a
metal–metal bond, making the exposed S atom avail-
able for directed intermolecular interaction. Here we
report the weak Fe–CꢀO···S intermolecular interaction
which leads to aggregation of molecules into zigzag
chains in the crystal structures of new binuclear Fe(0)–
M(II) complexes (CO)3Fe(v-Ph2PNS)2MX2 (M=Hg,
X=SCN; M=Cd, X=I).
The formation of a crystalline solid is a process of
molecular aggregation that depends primarily on the
number and type of atoms, overall molecular volume
* Corresponding author. Tel.: +852-303-492-6531; fax: +852-
2603-5057; e-mail: tcwmak@cuhk.edu.hk.
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(98)00952-8

52
S.-M. Kuang et al. / Journal of Organometallic Chemistry 575 (1999) 51–56
Scheme 1.
˚
Fig. 1. Perspective view (35% thermal ellipsoids) of complex 2. Selected bond lengths (A) and angle (°): Fe(1)–Hg(1) 2.653(1), Fe(1)–P(1) 2.225(3),
Fe(1)–P(2) 2.257(3), Fe(1)–C(1) 1.821(9), Fe(1)–C(2) 1.808(10), Fe(1)–C(3) 1.811(9), Hg(1)–S(1) 2.560(4), Hg(1)–S(2) 2.535(4), Hg(1)–N(1)
2.700(8), Hg(1)–N(2) 2.647(8). P(1)–Fe(1)–P(2) 174.4(1), Hg(1)–Fe(1)–C(2) 179.0(3), C(1)–Fe(1)–C(3) 147.4(4), Fe(1)–Hg(1)–S(1) 123.0(1),
Fe(1)–Hg(1)–S(2) 130.9(1), S(1)–Hg(1)–S(2) 106.1(1), N(1)–Hg(1)–N(2) 175.3(3)°.
2. Results and discussion
Fe(CO)3(Ph2PNS)2, 1. Its IR spectrum showed an intense
carbonyl absorption at 1874 cm−1, which implies that the
local symmetry about the iron(0) atom is near D3h.
Reaction of 1 with solid MX2 gave addition products
(CO)3Fe(v-Ph2PNS)2 MX2 (M=Hg, X=SCN, 2; M=
Cd, X=I, 3), the structures of which were determined
by single crystal X-ray analysis.
Treatment of Ph2PLi (prepared by the reaction of Ph3P
with lithium metal in THF) with 2-bromothiazole yielded
thedesiredthiazole-basedphosphineligandPh2PNS,which
wasreactedwithFe(CO)5andNaOHinrefluxingn-butanol
to afford a yellow precipitate formulated as trans-

S.-M. Kuang et al. / Journal of Organometallic Chemistry 575 (1999) 51–56
53
Fig. 2. Zigzag chain structure of complex 2 connected by weak intermolecular Fe–CꢀO···S interaction.
Table 1
Selected intermolecular O···S distances and CꢀO···S angles in some sulfur-containing iron carbonyl complexes
˚
Compound
O···S (A)
CꢀO···S (°)
Reference
[Fe3(CO)9(v3-S)(v3-PPh)]
3.300
3.259
3.261
3.225
3.162
3.265
3.156
3.258
3.180
3.149
3.276
138.6
147.8
148.0
133.7
133.6
132.5
127.7
148.6
143.7
144.7
136.2
[18]
[19]
[20]
[21]
[22]
[23]
[24]
[25]
[(v-p2-SCSMe2)Fe2(CO)6]
[(v-CH3C(O)CH2SCHS)Fe2(CO)6]
[{SC(Ph)C(O)SMe}Fe2(CO)6]
[{v-CF3CC(CF3)S}Fe2(CO)6]
[(v-Sme)2(v-C2F4)Fe2(CO)6]
[Fe(CO)3{p3-CH3SC(S)PCy3}CF3SO3]
[(CO)8Fe3(ꢁCNH2)(v3-S)(v3-PiPr)]
[Fe2(CO)5{P(OMe)3}{(v-CF3CC(CF3)S}]
[(CO)3Fe(v-Ph2PNS)2Hg(SCN)2], 2
[(CO)3Fe(v-Ph2PNS)2CdI2], 3
[26]
This work
This work
As anticipated, in complex 2 a pair of Ph2PNS
ligands bridge between metal centers via coordination
by their P,N-donor sets with the S atoms uncoordi-
nated (Fig. 1). The iron(0) atom exhibits distorted
octahedral coordination geometry with P(1)–Fe(1)–
(v-Ph2Ppy)2HgI2 (2.678(2)) [11] and Fe(CO)3(v-Ph-
˚
MePpy)2Hg(v-Cl)2HgCl2 (2.592(4) A) [12], but much
˚
longer than that (avg. 2.515 A) of the Fe(0)–Hg(I)
complex (CO)4Fe(HgBr)2, [13] and those of the Fe(I)–
Hg(I) binuclear complexes (CO)3(PMe3)(Ph2MeSi)Fe-
˚
P(2)=174.4(1),
Hg(1)–Fe(1)–C(2)=179.0(3)
and
HgBr (2.515(3) A) [14] and (NCS)Fe(CO)3(v-Ph2-
˚
C(1)–Fe(1)–C(3)=147.4(4)°. The Hg(II) atom exhibits
Ppy)2Hg(SCN) (2.527(2) A) [15]. The measured Fe–P,
distorted trigonal bipyramidal coordination geometry
Fe–C, Hg–N and Hg–S distances of 2 are not signifi-
cantly different from the corresponding distances ob-
served in Fe(CO)3(v-Ph2Ppy)2Hg(SCN)2 and (NCS)Fe-
(CO)3(v-Ph2Ppy)2Hg(SCN).
with
Fe(1)–Hg(1)–S(1)=123.0(1),
Fe(1)–Hg(1)–
S(2)=130.9(1), S(1)–Hg(1)–S(2)=106.1(1) and N(1)–
Hg(1)–N(2)=175.3(3)°. The two phosphine ligands
coordinate to the mercury atom through the N rather
than the S atoms, while both thiocyanato ligands func-
tion as donors through their S terminals. The Fe(1)–
Hg(1) distance, 2.653(1), is comparable to those of the
Fe(0)“Hg(II) dative bond in related complexes:
Fe(CO)3(v-Ph2Ppy)2Hg(SCN)2 (2.648(3) [10], Fe(CO)3-
The slightly shorter Hg(1)···C(3) distance of 2.748(9)
˚
˚
A, as compared to 2.780(9) A for Hg(1)···C(1), is
suggestive of a weak interaction between the mercury
atom and the C(3)–O(3) carbonyl group, although it
cannot be construed as a semi-bridging bonding mode
[16]. Most interestingly, this weak intermolecular inter-

54
S.-M. Kuang et al. / Journal of Organometallic Chemistry 575 (1999) 51–56
˚
Fig. 3. Perspective view (35% thermal ellipsoids) of complex 3. Selected bond lengths (A) and angle (°): Fe(1)–Cd(1) 2.812(1), Fe(1)–P(1) 2.226(1),
Fe(1)–P(2) 2.224(1), Fe(1)–C(1) 1.802(4), Fe(1)–C(2) 1.789(4), Fe(1)–C(3) 1.786(4), Cd(1)–I(1) 2.789(1), Cd(1)–I(2) 2.763(1), Cd(1)–N(1)
2.488(4), Cd(1)–N(2) 2.497(4); P(1)–Fe(1)–P(2) 176.6(1), Cd(1)–Fe(1)–C(2) 177.8(2), C(1)–Fe(1)–C(3) 144.0(2), Fe(1)–Hg(1)–I(1) 121.0(1),
Fe(1)–Hg(1)–I(2) 128.2(1), I(1)–Cd(1)–I(2) 110.8(1), N(1)–Cd(1)–N(2) 168.9(1)°.
˚
A and a CꢀO···S angle of 136.2(9)°.
action in turn accounts for the selectivity of the related
carbonyl group in weak intermolecular Fe–CꢀO···S
interaction. The basicity of CO increases on going from
the terminal to the bridging mode so that the involve-
ment of the latter in intermolecular interaction is
enhanced.
In summary, we have taken advantage of the specific
donor sites of the new phosphine ligand Ph2PNS in a
rational design of crystal packing in organometallic
systems. The bridging P,N-donor set is used to form
binuclear Fe(0)–M(II) complexes with metal–metal
bonding, while the weak Fe–CꢀO···S intermolecular
interaction leads to chain structures in the solid state.
The CO basicity determines the effectiveness and direc-
tionality of this type of weak interaction, which is
consistently non-linear with CꢀO···S angles in the range
136–144° for a variety of known crystal structures.
As seen from Fig. 2, weak intermolecular Fe–CꢀO···S
interaction resulted in the formation of an infinite zigzag
chain structure, with an O···S distance of 3.149(9) A and
˚
a CꢀO···S angle of 144.7(9)°. Although the O···S distance
is only slightly shorter than the sum of the van der Waals
˚
radii of the O and S atoms (1.52+1.80=3.32 A), the
stabilizing Fe–CꢀO···S interaction is in good agreement
with the well-established soft intermolecular CꢀN···S
interaction in organic systems with an angle of about
145° [17]. The observed O···S distance and CꢀO···S angle
in 2 are consistent with those of several known sulfur-
containing iron carbonyl complexes, which were ob-
tained from a search of the Cambridge Structural
Database (Table 1), although to our knowledge the
directionality characteristics of this type of intermolecu-
lar interaction has not been discussed in the literature.
The molecular structure of binuclear compound 3
(Fig. 3) is similar to that of 2 with substitution of the
Hg(NCS)2 fragment by CdI2, yielding an Fe(0)–Cd(II)
3. Experimental section
3.1. General procedure, measurement, and materials
All reactions were carried out under a nitrogen atmo-
sphere using standard Schlenk techniques. The solvents
were purified by standard methods. The H-NMR spec-
1
tra were recorded on a Bruker-300 NMR spectrometer
using Si(Me4) as the external standard and CDCl3 as
solvent. The 31P{1H}-NMR spectra were recorded on a
Bruker-500 NMR spectrometer at 202.45 MHz using
85% H3PO4 as the external standard and CDCl3 as
solvent. The solvents were purified by standard methods.
IR spectra were measured on a Perkin Elmer 1600
spectrometer.
˚
bond distance of 2.811(1) A. The weak intermolecular
Fe–CꢀO···S interaction likewise leads to an infinite
zigzag chain structure, with an O···S distance of 3.276(9)

S.-M. Kuang et al. / Journal of Organometallic Chemistry 575 (1999) 51–56
55
Table 2
Crystal data for 2 and 3
Formula
C35H24FeHgN4O3P2S4 (2)
C33H24CdFeI2N2O3P2S2 (3)
Formula weight
Temperature (K)
Crystal system
Space group
995.2
294
Orthorhombic
P212121 (no. 19)
1044.66
294
Monoclinic
P21/c (no. 14)
Unit-cell dimensions
˚
a (A)
13.993(2)
14.036(2)
19.143(1)
90
3760(2)
4
13.758(3)
14.110(3)
19.104(4)
91.58(3)
3707.2
4
˚
b (A)
˚
c (A)
i (°)
3
˚
V (A )
Z
F (000)
1944
1.758
0.71073
4.812
2016
1.875
0.71073
2.844
Dcalc. (g cm−3
)
˚
u, A (Mo–Kh)
v (cm−1
)
Collection range
Goodness-of-fit index
2q=3–52°
1.12
2q=3–50°
0.76
Number of unique reflections
Number of observed reflection(ꢀFꢀ]4|(F))
Number of variables, p
4115
2982
452
0.034
5557
2825
415
0.085
a
Rf
b
R2wF
0.065
0. 124
a RFꢀS(ꢀFoꢀ−ꢀFcꢀ)/SꢀFoꢀ.
2
b R2wFꢀ[{Sw(ꢀFoꢀ−ꢀFcꢀ)2}/{SwꢀFoꢀ }]1/2
.
3.2. Preparation of Ph2PNS
Anal. Calc. for C33H24FeN2O3P2S2: C, 58.42; H, 3.59;
N, 4.13. Found: C, 58.23; H, 3.50; N, 4.09. 31P{H}-
Lithium strips (0.8 g, 230 mmol) was finely cut and
added to a solution of Ph3P (13.2 g, 50 mmol) in 100
ml THF. The mixture was stirred at room tempera-
ture (r.t.) for 6 h, after which the solution was trans-
NMR: l=75.4 ppm. IR w(CO): 1879 cm−1
.
3.4. Reaction of trans-Fe(Ph2PNS)2(CO)3 with
Hg(SCN)2
ferred to another flask with
a
canula. Then
2-chloro-2-methylpropane (4.6 g, 50 mmol) in 20 ml
THF was added dropwise at 0°C to remove PhLi,
after which the mixture was stirred at r.t. for 1 h.
Then the mixture was cooled to −78°C, 2-bromothi-
azole (8.2 g, 50 mmol) in 20 ml THF was added
dropwise, and the resulting solution warmed to r.t.
slowly and stirred for another 5 h. After the solvent
was nearly completely removed, 100 ml of distilled
water and 100 ml of CH2Cl2 was added to the mix-
ture. The organic layer was separated and the
aqueous layer extracted twice with CH2Cl2 (2×20
ml). The organic fraction collected was dried with
anhydrous Na2SO4 overnight and then fractionated
(128–32°C, 1 mmHg) to give a colorless liquid (6.80
g yield: 51%, 31P{H}-NMR: l= −2.7 ppm), which
was purified by column chromatography.
To a solution of complex 1 (0.34 g, 0.50 mmol) in
20 ml dichloromethane was added solid (0.19 g, 0.6
mmol) Hg(SCN)2. The mixture was stirred at r.t. for
4 h. After filtration, the filtrate was concentrated to
about 15 ml, then cooled to −30°C for 20 h to give
microcrystals of 2. Yield: orange crystals, 0.37 g,
74%. Anal. Calc. for C35H24FeHgN4O3P2S4: C, 42.24;
H, 2.43; N, 5.63. Found: C, 42.08; H, 2.46; N, 5.60.
31P{1H}-NMR: l=62.9 ppm. IR, w(CO): 2029, 1976,
1965 cm−1
.
3.5. Reaction of trans-Fe(Ph2PNS)2(CO)3 with CdI2
The above procedure was repeated, except that
CdI2 (0.22 g, 0.60 mmol) was used instead of
Hg(SCN)2. Recrystallization from dichloromethane/
methanol gave pale yellow crystals of 3. Yield: orange
microrystals, 0.32 g, 62% yield. Anal. Calc. for
C33H24CdFeI2N2O3P2S2: C, 37.94; H, 2.32; N, 2.68.
Found: C, 37.60; H, 2.34; N, 2.62. 31P{1H}-NMR:
3.3. Preparation of trans-Fe(Ph2PNS)2(CO)3, 1
This compound was synthesized by the method
used for trans-Fe(Ph2Ppy)2(CO)3 as described previ-
ously [10]. Yield: yellow microcrystals, 70% yield.
l=71.9 ppm. IR, w(CO): 2015, 1940, 1886 cm−1
.

56
S.-M. Kuang et al. / Journal of Organometallic Chemistry 575 (1999) 51–56
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methanol. The intensity data of 2 and 3 were collected
at 294 K on a Rigaku RAXIS IIC imaging-plate dif-
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˚
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