A five-coordinate, sixteen-electron manganese(I) complex [Mn(CO)3(S,S-C6H4)]- stabilized by S,S π-donation from chelating [S,S-C6H4]2-

Article abstract of DOI:10.1039/a903538i

The five-coordinate, sixteen-electron manganese(I) complex [N(PPh₃)₂][Mn(CO)₃(S,S-C₆H ₄)] 1 was prepared from reaction of [N(PPh₃)₂][Mn(CO)₃(NH,S-C₆H ₄

Full text of DOI:10.1039/a903538i

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A five-coordinate, sixteen-electron manganese(I) complex
[Mn(CO)3(S,S–C6H4)]؊ stabilized by S,S ð-donation from
chelating [S,S–C6H4]2؊
Chien-Ming Lee,a Ging-Yi Lin,a Chung-Hung Hsieh,a Ching-Han Hu,*a Gene-Hsiang Lee,b
Shie-Ming Pengb and Wen-Feng Liaw*a
a Department of Chemistry, National Changhua University of Education, Changhua 50058,
Taiwan. E-mail: chfeng@cc.ncue.edu.tw
b Department of Chemistry and Instrumentation Center, National Taiwan University,
Taipei 10074, Taiwan
Received 26th April 1999, Accepted 13th May 1999
The five-coordinate, sixteen-electron manganese() complex [N(PPh3)2][Mn(CO)3(S,S–C6H4)] 1 was prepared
from reaction of [N(PPh3)2][Mn(CO)3(NH,S–C6H4)] and 1,2-benzenedithiol via the hexacoordinate intermediate
fac-[Mn(CO)3(S–C6H4SH)(NH2,S–C6H4)]Ϫ. Alternatively, oxidative addition of 1,2-benzenedithiol to [Mn(CO)5]Ϫ,
followed by a Lewis acid–base reaction, with evolution of H2 gas (identified by gas chromatography), led to
formation of the coordinatively-unsaturated complex 1. In contrast, reaction of bis(2-pyridyl) disulfide and
[N(PPh3)2][Mn(CO)5] afforded hexacoordinate fac-[N(PPh3)2][Mn(CO)3(S–C5H4–N)(S–C5H4N)] 2, with one anionic
[S–C5H4N]Ϫ ligand bound to MnI in a monodentate (S-bonded) manner and the other [S–C5H4–N]Ϫ ligand bound
in a bidentate manner (S,N-bonded). Complexes 1 and 2 have been characterized in solution by infrared spectroscopy
and in the solid state by X-ray crystallography. The strong π-donating ability of the bidentate [S,S–C6H4]2Ϫ ligand
stabilizes the unsaturated complex 1 which has short MnI–S bond lengths of 2.230(1) Å (average) as a result. The
existence of one π and two σ bonds between the [Mn(CO)3]ϩ and [S,S–C6H4]2Ϫ fragments, based on qualitative
frontier molecular orbital analysis, also indicates that the lone-pair electrons are delocalized around the sulfur-
manganese-sulfur system stabilizing the five-coordinate complex 1. The IR carbonyl stretching frequencies
and the MnI–S bond distances of complexes 1 and [N(PPh3)2][Mn(CO)3(NH,S–C6H4)] suggest that the relative
π-donating ability of the bidentate ligands is [NH,S–C6H4]2Ϫ > [S,S–C6H4]2Ϫ. The Mulliken atomic charges derived
from Hartree–Fock calculations roughly quantify the charge distribution in the complex [Mn(CO)3(NH,S–C6H4)]Ϫ
(δ(N) = –1.14; δ(S) = Ϫ0.43; δ(Mn) = 1.14), and supports the premise that the reactions of [Mn(CO)3(NH,S–C6H4)]Ϫ
with electrophiles (1,2-benzenedithiol, thiophene-2-thiol, 1,2-ethanedithiol) occur at the more electron-rich amide
site, yielding charge-controlled, collision complexes.
by combining the dichalcogen synthetic methodology with the
Introduction
potential for intramolecular H-bonding, via the reaction of
Anionic metal carbonyls are known to function as nucleophiles
[Mn(CO)5]Ϫ with 1 equiv. of 2-aminophenyl disulfide [Scheme
and show a range of reactivity that depends on the metal, its
1(c)].4 By way of contrast, the six-coordinate MnI complex
oxidation state, its substituents and the ligand environment.1
fac-[Mn(CO)3(S–C5H4–N)(S–C5H4N)]Ϫ 2 was isolated and
Recently, application of the anionic metallic fragment
structurally characterized from the reaction of [Mn(CO)5]Ϫ and
[Mn(CO)5]Ϫ to the preparation of manganese chalcogenolates
bis(2-pyridyl) disulfide [Scheme 1(d)]. In an effort to examine
proved a successful approach in this direction, i.e. oxidative
addition of diorganyl dichalcogenides to the low-valent
the reaction chemistry of the coordinatively-unsaturated
complex [Mn(CO)3(NH,S–C6H4)]Ϫ, we report herein a study of
manganese carbonyl fragment [Mn(CO)5]Ϫ led to formation of
the conversion of [Mn(CO)3(NH,S–C6H4)]Ϫ to five-coordinate,
cis-[Mn(CO)4(ER)2]Ϫ (E = Te, Se, S; R = phenyl) [Scheme 1(a)].2
sixteen-electron [Mn(CO)3(S,S–C6H4)]Ϫ 1, stabilized by the
bidentate S,S π-donation of the [S,S–C6H4]2Ϫ ligand. Unsatur-
ated [Mn(CO)3(S,S–C6H4)]Ϫ was also obtained from the
reaction of 2 equiv. of 1,2-benzenedithiol with [Mn(CO)5]Ϫ. To
our knowledge, only a few examples of d6 transition metal
carbonyl complexes containing five-coordinate sixteen-electron
metal cores have been reported,5,6 e.g. [Mn(CO)3(DBCat)]Ϫ pre-
pared by oxidative substitution of two CO ligands of [Mn-
(CO)5]Ϫ by 3,5-di-tert-butyl-1,2-benzoquinone,5a and [W(CO)3-
(NHC6H4NH)]2Ϫ prepared from W(CO)5(thf) and 2 equiv. of
the monodeprotonated ligand [NHC6H4NH2]Ϫ by inter-
molecular deprotonation.6c
Scheme 1
In addition, [Mn(CO)5]Ϫ may also serve as a lone-pair-electron
Results and discussion
donor. Coordinative addition of [Mn(CO)5]Ϫ to TeCl4 led to
Synthesis
formation of a discrete chlorotellurate, [Cl4Te–Mn(CO)5]Ϫ
[Scheme 1(b)].3 Very recently, the five-coordinate, sixteen-
As illustrated in Scheme 2(a,b), treatment of 1 equiv. of
[N(PPh3)2][Mn(CO)3(NH,S–C6H4)] with 1,2-benzenedithiol in
electron MnI complex [Mn(CO)3(NH,S–C6H4)]Ϫ was prepared
J. Chem. Soc., Dalton Trans., 1999, 2393–2398
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Fig. 1 ORTEP drawing and labeling scheme for anionic [Mn(CO)3-
(S,S–C6H4)]Ϫ with thermal ellipsoids drawn at the 30% probability level.
Scheme 2
thf led to the formation of the five-coordinate sixteen-electron
manganese() complex [N(PPh3)2][Mn(CO)3(S,S–C6H4)]
1
stabilized by incorporation of the π-donating chelate [S,S–
C6H4]2Ϫ and ejection of HS-C6H4-NH2, identified by NMR.
Alternatively, complex 1 was also obtained when 2 equiv. of
1,2-benzenedithiol was added to [N(PPh3)2][Mn(CO)5] and the
solution was stirred overnight in thf at ambient temperature
[Scheme 2(c)]. The dark red-purple complex 1 is soluble in
common organic solvents, such as thf, MeCN and CH2Cl2, and
can be crystallized by vapor diffusion of diethyl ether–hexane
into a concentrated thf solution at Ϫ15 ЊC under nitrogen.
No decomposition was observed on stirring complex 1 in thf
solution at ambient temperature for 2 days. In contrast, proton-
ation of complex 1 by 2-aminothiophenol was not successful
in synthesising [Mn(CO)3(NH,S–C6H4)]Ϫ. The coordinatively-
unsaturated complex 1 is completely unreactive toward CO:
1 remains unchanged when treated with 1 atm (101 325 Pa) CO
in thf at room temperature. This is in contrast to the observ-
ation that catecholate tungsten(0) tricarbonyl and catecholate
tungsten(0) tetracarbonyl are readily interconvertible.6g The
six-coordinate MnI complex fac-[N(PPh3)2][Mn(CO)3(S–C5H4–
N)(S–C5H4N)] 2, with one anionic [S–C5H4N]Ϫ ligand bound
to MnI in a monodentate (S-bonded) manner and the second
[S–C5H4–N]Ϫ bound in a bidentate manner (S,N-bonded), was
obtained from the reaction of [Mn(CO)5]Ϫ and 1 equiv. of bis(2-
pyridyl) disulfide [Scheme 2(d)]. The air-stable complex 2 was
isolated as an orange–yellow semi-solid from thf–diethyl ether,
and is soluble in thf, MeCN and CH2Cl2.
Fig. 2 ORTEP drawing and labeling scheme for anionic fac-[Mn-
(CO)3(S–C5H4–N)(S–C5H4N)]Ϫ with thermal ellipsoids drawn at the
30% probability level.
Structures
A definitive assignment of the structure of complex 1 was
obtained by X-ray crystallography; the structure of the
[Mn(CO)3(S,S–C6H4)]Ϫ unit in the [N(PPh3)2]ϩ salt is shown in
Fig. 1. The geometry about manganese is intermediate between
square pyramidal and trigonal bipyramidal, with the bite angle
of the chelating [S–C6H4–S]2Ϫ ligand being 87.81(4)Њ. The
five-membered chelate ring MnS2C2 is almost planar, with a
deviation from planarity of 0.02 Å. The interesting feature of
complex 1 is the asymmetry in the MnI–S bond lengths
(2.211(1) and 2.248(1) Å), which shows a difference of 0.036 Å.
The significantly shorter MnI–S bonds [2.230(1) Å (average)]
in complex 1, as compared to the reported 2.398(1) Å for the
MnI–SPh bond in cis-[Mn(CO)4(SPh)2]Ϫ,8 were attributed to the
strong π-donating ability of the bidentate [S,S–C6H4]2Ϫ ligand
which stabilizes the unsaturated complex 1.6,9 The MnI–S
distances [2.230(1) Å (average)] in complex 1 are shorter than
the reported 2.268(1) Å MnI–S bond in the analogue
[Mn(CO)3(NH,S–C6H4)]Ϫ.4 The MnI–CO bonds, which aver-
age 1.767(4) Å, in compound 1 are comparable to the
MnI–CO distances [1.763(4) Å (average)] in [Mn(CO)3(NH,S–
C6H4)]Ϫ.4
The X-ray crystal structure of complex 2 is shown in Fig. 2.
The MnI–S distances of 2.380(1) and 2.445(1) Å in complex
2 are significantly longer than those in five-coordinate,
coordinatively-unsaturated complex 1 [average 2.230(1) Å].
The MnI–N(1) bond distance is 2.028(3) Å, which is also
significantly longer than that in [Mn(CO)3(NH,S–C6H4)]Ϫ
[1.889(3) Å].4 The bond angles at the MnI center are consider-
ably distorted from the idealized octahedral limits due to the
presence of the four-membered N,S-chelate ring, a character-
istic apparent in the internal chelate angle, S–Mn–N of
68.30(8)Њ.10
Characterization in solution
The IR spectrum of complex 1 shows two strong CO stretching
bands, 1986vs and 1887s cmϪ1 (thf), which suggests facial orien-
1
tation of the three CO ligands.4 The H and 13C NMR spectra
show the expected signals for the [S,S–C6H4]2Ϫ ligand in a
diamagnetic d6 MnI species. The electronic spectrum of com-
plex 1 is dominated by ligand-to-metal charge-transfer bands
at approximately 349, 400, 502 and 552 nm. Complex 2 exhibits
a three-band pattern in the ν(CO) region of its IR spectrum,
at 1994vs, 1901s and 1882s cmϪ1 (thf), which is consistent with
1
a tricarbonyl derivative of pseudo C3v symmetry.7 The H and
13C NMR spectra are consistent with the presence of low-spin
octahedrally coordinated d6 MnI.
2394
J. Chem. Soc., Dalton Trans., 1999, 2393–2398

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Table 1 Selected bond distances (Å) and angles (Њ) for (a) 1a and (b) 2
determined via X-ray diffraction
Discussion
A reasonable reaction sequence accounting for the formation
of complex 1 is shown in Scheme 2(a,b). Protonation of
[Mn(CO)3(NH,S–C6H4)]Ϫ with 1,2-benzenedithiol in thf under
N2 at ambient temperature led to formation of the unstable six-
coordinate intermediate fac-[Mn(CO)3(S–C6H4SH)(NH2,S–
C6H4)]Ϫ. Attempts to detect this extremely unstable intermedi-
ate by FTIR were unsuccessful. Presumably, the intramolecular
S–H ؒ ؒ ؒ S interaction (cis arrangement of thiolate and SH
groups in the intermediate),11 and the subsequent elimination
of 2-aminothiophenol yielded the stable five-coordinate,
sixteen-electron complex 1. Apparently, protonation of the
amide site of [Mn(CO)3(NH,S–C6H4)]Ϫ labilizes the chelating
ligand [NH,S–C6H4)]2Ϫ and results in the formation of complex
1. Alternatively, complex 1 was also obtained when 2 equiv. of
1,2-benzenedithiol were added to [N(PPh3)2][Mn(CO)5] and the
solution was stirred overnight in thf at ambient temperature
[Scheme 2(c)]. Presumably, oxidative addition of H–SC6H4SH
to [Mn(CO)5]Ϫ, leading to the intermediate [Mn(CO)4(H)-
(S–C6H4SH)]Ϫ, is followed by a Lewis acid–base reaction
(the second equiv. of 1,2-benzenedithiol reacts with [Mn-
(CO)4(H)(S–C6H4SH)]Ϫ) with evolution of H2 gas, identified by
gas chromatography. Further intermolecular deprotonation
of the [S–C6H4SH]Ϫ ligand bound to the MnI center by
free anionic [S–C6H4SH]Ϫ,6d and subsequent dissociation of
a carbonyl ligand as a result of chelation led to formation
of complex 1.6d,8 However, the presumed intermediate [Mn-
(CO)4(H)S–C6H4(SH)]Ϫ was not observed spectroscopically,
even at Ϫ20 ЊC.
(a) Complex 1
Mn–S(1)
Mn–C(1)
Mn–C(3)
C(2)–O(2)
2.211(1) [2.217]
1.750(4) [1.670]
1.770(3) [1.670]
1.154(4) [1.221]
Mn–S(2)
Mn–C(2)
C(1)–O(1)
C(3)–O(3)
2.248(1) [2.260]
1.781(3) [1.688]
1.157(4) [1.220]
1.159(4) [1.234]
S(1)–Mn–S(2)
87.81(4) [89.2]
S(1)–Mn–C(1) 117.96(11) [130.4]
S(1)–Mn–C(2) 149.67(11) [144.6] S(1)–Mn–C(3) 86.34(11) [87.9]
S(2)–Mn–C(1) 98.57(12) [92.5] S(2)–Mn–C(2) 88.76(10) [94.2]
S(2)–Mn–C(3) 170.02(12) [177.1] C(1)–Mn–C(2) 92.35 (15) [84.8]
C(1)–Mn–C(3) 91.31(16) [89.7] C(2)–Mn–C(3) 92.21(15) [88.0]
Mn–S(1)–C(4) 107.01(8) [107.5] Mn–S(2)–C(9) 106.28(11) [106.6]
(b) Complex 2
Mn–S(1)
Mn–C(1)
Mn–C(3)
C(2)–O(2)
Mn–N(1)
2.445(1)
1.790(4)
1.775(4)
1.165(4)
2.028(3)
Mn–S(2)
Mn–C(2)
C(1)–O(1)
C(3)–O(3)
2.380(1)
1.773(4)
1.152(4)
1.160(4)
S(1)–Mn–S(2)
84.84(4)
S(1)–Mn–C(1) 163.17(12)
S(1)–Mn–C(3) 103.47(13)
S(2)–Mn–C(1) 97.86(11)
S(2)–Mn–C(3) 86.07(12)
N(1)–Mn–C(1) 95.13(14)
N(1)–Mn–C(3) 170.08(14)
Mn–S(2)–C(9) 113.74(12)
S(1)–Mn–C(2) 87.06(11)
S(1)–Mn–N(1) 68.30(8)
S(2)–Mn–C(2) 170.76(12)
S(2)–Mn–N(1) 87.62(7)
N(1)–Mn–C(2) 93.51(13)
Mn–S(1)–C(4) 77.74(11)
a Numbers in brackets are geometrical parameters predicted at the
MP2/set 1 level of theory.
In contrast, protonation of [Mn(CO)3(NH,S–C6H4)]Ϫ by 1,2-
ethanedithiol in thf under N2 at ambient temperature led to the
formation of an orange–yellow solution immediately. A three-
band pattern in the ν(CO) region of the IR spectrum at 1980vs,
1899s and 1885s cmϪ1 (thf) was assigned to the formation
of six-coordinate fac-[Mn(CO)3(S–(CH2)2SH)(NH2,S–C6H4)]Ϫ,
isolated as a semi-solid. In order to add further credibility
to the formation of the six-coordinate intemediate fac-
[Mn(CO)3(S,NH2–C6H4)(S–C6H4SH)]Ϫ in the proposed mech-
anism [Scheme 2(a)] and of six-coordinate fac-[Mn(CO)3(S–
(CH2)2SH)(NH2,S–C6H4)]Ϫ in the protonation reaction, the
analogous six-coordinate MnI complex 2 was isolated and
structually characterized from the reaction of [Mn(CO)5]Ϫ and
1 equiv. of bis(2-pyridyl) disulfide [Scheme 2(d)]. The proposed
mechanism, shown in Scheme 2(d), involves oxidative addition
of bis(2-pyridyl) disulfide to [Mn(CO)5]Ϫ, possibly via the
intermediate cis-[Mn(CO)4(S–C5H4N)2]Ϫ.2,8
Table 2 Predicted reaction enthalpy for the conversion of [Mn(CO)3-
(NH,S–C6H4)]Ϫ to complex 1
Methoda
∆E
∆H(0 K)
Ϫ35.6
∆H(298 K)
Ϫ36.1
HF/set 1//
HF/set 1
MP2/set 1//
MP2/set 1
MP2/set 2//
MP2/set 1
Ϫ38.2
Ϫ14.5
Ϫ14.2
Ϫ11.9
Ϫ11.6
Ϫ12.3
Ϫ12.1
a Set 1: 6-311G on Mn, 6-31G on H, C, N, O, S; set 2: 6-311G* on Mn,
6-31G* on C, N, O, S.
while the experimental structures were determined using
crystals. Computations revealed that the energy surface is
relatively insensitive to the orientation of the S,S–C6H4 ring.
Basis set truncation and correlated level of theory applied could
also affect the prediction.
Ab initio calculations
In order to investigate the conversion of [Mn(CO)3(NH,S–
C6H4)]Ϫ to complex 1 [Scheme 2(a,b)], ab initio quantum
chemistry computations were also performed. The Gaussian 94
suite of programs were used.12 The geometries of the four
species, [Mn(CO)3(NH,S–C6H4)]Ϫ, [SH–C6H4–SH], complex 1
and [NH2–C6H4–SH] were fully optimized, firstly at the
Hartree–Fock level where a 6-311G basis set for Mn and a
6-31G basis set (set 1) for other atoms were used. The frequency
analyses on the optimized structures were performed at this
level of theory. All four molecules were identified as genuine
minima, the vibrational frequencies (scaled by 0.89) were later
used in calculating thermal corrections to the reaction ener-
getics (298 K). The structures were then further optimized at
the MP2 level of theory. Selected geometrical parameters of
complex 1 are compared with those obtained from X-ray
diffraction data (Table 1). The bond distances and bond angles
predicted at the MP2 level of theory compare reasonably well
with the experimental results. One exception is the predicted
bond angle S(1)–Mn–C(1), which differs from the experimental
value by more than 10Њ. A possible explanation for such a
deviation is that the prediction is based on gas-phase molecules,
Energetics were evaluated using the MP2 method with extra
polarization functions on each atom (6-311G* on Mn, and 6-
31G* on other atoms, named set 2). The theoretical predictions
for the energetics of reaction are summarized in Table 2. Sig-
nificant electron correlation effects have been observed for the
reaction enthalpy: the magnitude of the reaction energy and
enthalpy (∆E and ∆H) is reduced by more than 20 kcal molϪ1 at
the correlated MP2 level. Introducing zero-point vibrational
energy corrections (from the HF method) reduces the energy
difference by another 2.6 kcal molϪ1, while adding the temper-
ature correction raises this difference by about 0.5 kcal molϪ1.
The effect of adding an extra set of polarization functions to
the heavy atoms is minor. The reaction enthalpy (∆H) for the
conversion of [Mn(CO)3(NH,S–C6H4)]Ϫ to complex 1 [Scheme
2(a,b)] is Ϫ12.1 kcal molϪ1 at 298 K. This result is supportive of
the observation that the chemical conversion is not reversible
experimentally.
The calculated Mulliken charge distributions on the N, S and
Mn atoms of [Mn(CO)3(NH,S–C6H4)]Ϫ are Ϫ1.14, Ϫ0.43 and
1.14 respectively. The charge distribution on Mn of complex 1
J. Chem. Soc., Dalton Trans., 1999, 2393–2398
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charge from [S,S–C6H4]2Ϫ effectively means that there are more
than 16 electrons around MnI (the total electron count around
MnI amounts to 18 electrons instead of 16 electrons), and this
explains the unusual stability of complex 1. The hexacoordinate
metal centre as well as the long MnI–S and MnI–N bond
distances of complex 2, compared to the five-coordinate
complexes 1 and [Mn(CO)3(NH,S–C6H4)]Ϫ, reflect the fact that
bidentate [S–C5H4N]Ϫ may not serve as a strong π-donating
ligand.
Experimental
Manipulations, reactions and transfers of samples were con-
ducted under nitrogen according to standard Schlenk tech-
niques or in a glove-box (argon gas). Solvents were distilled
under nitrogen from appropriate drying agents (diethyl ether
from CaH2; acetonitrile from CaH2–P2O5; methylene chloride
from P2O5; hexane and tetrahydrofuran (thf) from sodium–
benzophenone) and stored in dried, N2-filled flasks over 4 Å
molecular sieves. A nitrogen purge was used on these solvents
before use and transfers to reaction vessels were via stainless
steel cannula under N2 at a positive pressure. The reagents
dimanganese decacarbonyl, 2-aminophenyl disulfide, 1,2-
benzenedithiol, bis(2-pyridyl) disulfide, bis(triphenylphosphor-
anylidene)ammonium chloride, 1,2-ethanedithiol (Lancaster/
Aldrich) were used as received. Infrared spectra were recorded
on a Bio-Rad FTS-185 spectrometer with sealed solution cells
(0.1 mm) and KBr windows. NMR spectra were recorded on a
Bruker AC 200 spectrometer; 1H and 13C chemical shifts being
relative to tetramethylsilane. UV/VIS spectra were taken on a
GBC 918 spectrophotometer. Gas chromatography was carried
out on a Shimadzu GC-3BT with a Shimadzu R-11 recorder.
Analyses made use of the thermal conductivity detector (TCD);
nitrogen was the carrier gas, the column was OV-17 (5%) on
Chromosorb W, 80/100 mesh, 6 ft × 1/8 in stainless steel tubing.
Analyses of carbon, hydrogen and nitrogen contents were
obtained with a Heraeus CHN analyzer.
Fig. 3 Frontier molecular orbital (MO) analysis for [N(PPh3)2][Mn-
(CO)3(S,S–C6H4)].
is 1.02. Thus both [Mn(CO)3(NH,S–C6H4)]Ϫ and complex 1 can
be accurately described as MnI complexes.
Attempts to compute the energies of the species using
density functional theory (DFT) were made. However, serious
convergence difficulties were encountered while trying to
evaluate these energies. All attempts to overcome these were
unsuccessful.
A qualitative analysis using the frontier molecular orbitals
(MOs) of complex 1 is illustrated in Fig. 3. The [Mn(CO)3]ϩ
fragment was kept within the C3v point group, while the [S,S–
C6H4]2Ϫ anionic precursor has C2v symmetry. The model com-
plex has Cs symmetry despite the optimized structure being
slightly distorted from Cs. Three unoccupied MOs (a1 and e)
of the [Mn(CO)3]ϩ fragment interact with the three highest
occupied [S,S–C6H4]2Ϫ MOs having proper symmetry (a1, b2
and a2). Two of these interactions form σ bonds, and one
interaction results in a π bond. The b1 MO in [S,S–C6H4]2Ϫ is
nonbonding. The stability of complex 1 is attributed to these
three MO interactions.
Preparations
Reaction of 1,2-benzenedithiol and [N(PPh3)2][Mn(CO)3-
(NH,S–C6H4)]. Initially, 1,2-benzenedithiol (0.2 mmol, 24 µL)
was added dropwise to a solution containing 0.16 g (0.2 mmol)
of [N(PPh3)2][Mn(CO)3(NH,S–C6H4)] in thf (5 cm3).4 After
stirring the reaction solution for 30 min at room temperature,
diethyl ether was added to precipitate the dark red-purple solid
[N(PPh3)2][Mn(CO)3(S,S–C6H4)] 1. The stable product 1 was
washed twice with thf–diethyl ether and dried under vacuum.
Crystals suitable for X-ray crystallography were grown by vapor
diffusion of diethyl ether into a concentrated thf solution of
1 at Ϫ15 ЊC. Yield 0.151 g (92%). IR (thf): ν(CO) 1986vs, 1887s
Summary
Protonation of [Mn(CO)3(NH,S–C6H4)]Ϫ by 1,2-benzenedithiol
and 1,2-ethanedithiol yielded complex 1 and fac-[Mn(CO)3-
(S–(CH2)2SH)(NH2,S–C6H4)]Ϫ respectively. The calculated
Mulliken atomic charge distribution in the complex
[Mn(CO)3(NH,S–C6H4)]Ϫ supports the hypothesis that the
reactions of [Mn(CO)3(NH,S–C6H4)]Ϫ with electrophiles (1,2-
benzenedithiol, 1,2-ethanedithiol) occur at the more electron-
rich amide site to yield charge-controlled, collision complexes.
In contrast, reaction of bis(2-pyridyl) disulfide and [N(PPh3)2]-
[Mn(CO)5] afforded the hexacoordinate complex 2. The
MnI–S bond angles, and carbonyl stretching frequencies (ν(CO)
1986vs and 1887s cmϪ1 (thf) for complex 1 vs. 1973vs and 1870s
cmϪ1 (thf) for [Mn(CO)3(NH,S–C6H4)]Ϫ) of complexes 1 and
[Mn(CO)3(NH,S–C6H4)]Ϫ unequivocally indicate that the
relative π-donating ability of the bidentate ligands investigated
here is [NH,S–C6H4]2Ϫ > [S,S–C6H4]2Ϫ.13 The existence of two
σ and one π bond between the [Mn(CO)3]ϩ and [S,S–C6H4]2Ϫ
fragments, based on qualitative frontier molecular orbital
analysis, also indicates that one lone-pair of electrons is delocal-
ized around the sulfur–manganese–sulfur chelate stabilizing
the five-coordinate complex 1, i.e. the additional donation of
1
cmϪ1. H NMR (CD3CN): δ 6.99, 7.89 (br, S,S–C6H4). 13C
NMR (CD3CN): δ 134.49, 133.27, 133.15, 133.03, 130.40,
130.23 and 130.14. UV/VIS (thf): λmax/nm (ε/MϪ1 cmϪ1)
349(2079), 400(4569), 502(2109) and 552(1556). Found: N,
1.83; C, 66.17; H, 4.27. Calc. for C45H34O3P2NS2Mn: N, 1.75; C,
66.13; H, 4.16%).
Reaction of 1,2-benzenedithiol and [N(PPh3)2][Mn(CO)5].
[N(PPh3)2][Mn(CO)5]14 (0.2 mmol, 0.147 g) dissolved in thf
(3 cm3) was stirred under N2 and 1,2-benzenedithiol (0.4 mmol,
48 µL) added dropwise at room temperature. After stirring
overnight, the volume of the solution was reduced to 2 cm3 and
the dark red-purple product precipitated by addition of diethyl
ether (15 cm3). The thermally stable product was isolated by
removing the solvent. Yield of [N(PPh3)2][Mn(CO)3(S,S–C6H4)]
(1) 0.130 g (80%). IR (thf): ν(CO) 1986vs, 1887s cmϪ1, consist-
ent with the formation of [N(PPh3)2][Mn(CO)3(S,S–C6H4)].
fac-[N(PPh3)2][Mn(CO)3(S–(CH2)2SH)(NH2,S–C6H4)]. 1,2-
Ethanedithiol (0.2 mmol, 18 µL) was added dropwise to a
2396
J. Chem. Soc., Dalton Trans., 1999, 2393–2398

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Table 3 Crystallographic data for complexes 1 and 2
solution containing 0.16
g (0.2 mmol) of [N(PPh3)2]-
[Mn(CO)3(NH,S–C6H4)] in thf (3 cm3). The reaction mixture
was stirred for 10 min at ambient temperature and hexane
added to precipitate the yellow-brown semi-solid(76% yield).
The product was washed with hexane twice and dried under
1
2
Formula
M
C45H34NO3P2S2Mn
817.77
C49H38N3O3P2S2Mn
897.82
vacuum. IR (thf): ν(CO) 1980vs, 1899s, 1885s cmϪ1. H NMR
(C4D8O): δ 4.78 (br, NH2), 3.03–2.75 (m, SCH2CH2), 2.25
(s, SH), 6.68, 6.45 (m, C6H4).
1
Crystal system
Space group
Triclinic
P1
Monoclinic
P21/c
¯
a/Å
b/Å
c/Å
α/Њ
β/Њ
10.030(3)
14.259(2)
14.396(3)
88.62(2)
80.50(2)
89.76(2)
2030.1(8)
2
14.7936(2)
10.2732(2)
29.6377(2)
fac-[N(PPh3)2][Mn(CO)3(S–C5H4–N)(S–C5H4N)] 2. Bis(2-
pyridyl) disulfide (0.4 mmol, 0.088 g) was added to a solution
containing 0.308 g (0.4 mmol) of [N(PPh3)2][Mn(CO)5] in
tetrahydrofuran (5 cm3). After stirring the reaction mixture
overnight at room temperature, diethyl ether was added to
precipitate the orange-yellow semi-solid fac-[N(PPh3)2]-
[Mn(CO)3(S–C5H4–N)(S–C5H4N)] 2. The stable product 2 was
washed twice with thf–diethyl ether and dried under vacuum.
Crystals suitable for X-ray crystallography were grown by vapor
diffusion of diethyl ether into a concentrated thf solution of 2
at Ϫ15 ЊC. Yield 0.320 g (89%). IR (thf): ν(CO) 1994vs, 1901s,
92.567(1)
γ/Њ
V/Å3
Z
4499.75(11)
4
1.325
5.02
22
dcalc/g cmϪ3
µ/cmϪ1
T/ЊC
R
1.338
5.273
25
0.036a
0.034b
0.051
Rw
RWF
GOF
0.095c
1.044
2
1.56
1
1882s cmϪ1. H NMR (CD3COCD3): δ 8.05, 7.88, 7.29, 7.11
¹
c
²
2
2
a R = Σ|(Fo Ϫ Fc)|/ΣFo; b Rw = [Σω(Fo Ϫ Fc) /ΣωFo ] ; RWF = {Σω(Fo2 Ϫ
2
(d, SC5H4N), 7.01, 6.55, 6.49 (t, SC5H4N) and 7.72–7.58
(m, Ph). 13C NMR (CD3COCD3): δ 114.68, 115.55, 127.13,
129.27, 130.25, 130.39, 130.52, 133.12, 133.23, 133.35, 133.90,
134.59, 148.22 and 151.21. UV/VIS (thf): λmax/nm (ε/MϪ1 cmϪ1)
384(4599). Found: N, 4.76; C, 65.39; H, 4.20. Calc. for
C49H38O3P2N3S2Mn: N, 4.68; C, 65.55; H, 4.27%).
¹
2
2
2 2
²
Fc ) /Σ[ω(Fo ) ]} .
CCDC reference number 186/1463.
See http://www.rsc.org/suppdata/dt/1999/2393/ for crystallo-
graphic files in .cif format.
Ab initio calculations
Acknowledgements
The support of the National Science Council (Taiwan) is
gratefully acknowledged. The authors thank Professor Donald
J. Darensbourg for helpful suggestions.
The Gaussian 94 suite of programs12 was used in the study of
several complexes. The geometries of these species were fully
optimized using analytic gradients at the Hartree–Fock (HF)
and MP2 levels of theory. At the stationary points, vibrational
frequency analysis was performed. The computed vibrational
frequencies were used to verify whether these structures are
genuine minima on the potential energy surfaces. These fre-
quencies were also used in calculating thermal corrections to
enthalpies (up to 298 K). The 6-311G basis set on Mn, and
the 6-31G basis sets on other atoms were used in geometry
optimizations (set 1). An extra set of polarization functions
were added to atoms other than hydrogen (6-311G* on Mn and
6-31G* on C, N, O, and S, named set 2) for the most elaborate
energy calculations using MP2.
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Paper 9/03538I
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J. Chem. Soc., Dalton Trans., 1999, 2393–2398