Transition-metal complexes with sulfur ligands. 132.1 electron-rich Fe and Ru complexes with [MN2S3] cores containing the new pentadentate ligand 'N2H2S3'2- (= 2,2′-Bis(2-mercaptophenylamino)diethyl sulfide(2-))

Article abstract of DOI:10.1021/ic980383q

The new pentadentate amine thioether thiolate ligand 'N₂H₂S₃'-H₂ (= 2,2′-bis(2-mercaptophenylamino)diethyl sulfide) (3) was synthesized in order to obtain iron and ruthenium complexes with high electron densities at the metal centers. The reaction of 'N₂H₂S₃'^2- with Fe²⁺ yielded the dinuclear high-spin complex [Fe('N₂H₂S₃')]₂ (5). Complex 5 added CO to give the low-spin complex [Fe(CO)('N₂H₂S₃')] (6) whose low frequency v(CO) (1932 cm^-1) indicates a high electron density at the iron center and a strong Fe-CO bond. However, 6 is labile and readily dissociates CO in solution. Treatment of suitable ruthenium precursor complexes with 'N₂H₂S₃'^2- yielded [Ru(CO)(PCy₃)('N₂H₂S₃')] (7), [Ru(PPr₃)₂('N₂H₂S₃')] (8), [Ru(PR₃)('N₂H₂S₃')] (R = Pr (9), Ph (10)), and [Ru-(NO)('N₂HS₃')] (13). In complexes 7 and 8, 'N₂H₂S₃'^2- acts as a tetradentate ligand. When heated in solution, complex 8 dissociates one PPr₃ ligand to give 9. Complex 13 contains the trisanionic 'N₂HS₃'^3- resulting from deprotonation of one amine NH function. All [Ru(L)('N₂H₂S₃')] complexes proved inert toward dissociation of the Ru-L bonds. The NH functions of [M(L)('N₂H₂S₃')] complexes are acidic and show H⁺/D⁺ exchange reactions with D₂O. Methylation of the thiolate donors in 10 yielded the thioether derivative [Ru(PPh₃)('N₂H₂S₃'-Me ₂)]I₂ (11) whose PPh₃ ligand is as inert to substitution as that of 10. Complex 11 can reversibly be deprotonated to give [Ru(PPh₃)('N₂HS₃'-Me₂)]I (12). NMR spectroscopic investigations showed that the deprotonation/protonation reactions of 11 and 12 are stereoselective. In contrast, protonation of 13 with HBF₄ gives two diastereomers of the corresponding [Ru(NO)('N₂H₂S₃')]BF₄ salt (14). X-ray structure analyses of 5, 6, 9, and 11 and NMR spectra showed that the 'N₂H₂S₃'^2- ligand and its derivatives bind to the metal centers in the same fashion which combines fac and mer coordination of the donor atoms. The [MN₂S₃] cores of all complexes have an analogous C₁ symmetrical structure in which both the two N and the two terminal S donors assume cis positions.

Full text of DOI:10.1021/ic980383q

Inorg. Chem. 1999, 38, 459-466
459
Transition-Metal Complexes with Sulfur Ligands. 132.1 Electron-Rich Fe and Ru
Complexes with [MN2S3] Cores Containing the New Pentadentate Ligand ′N2H2S3′2-
() 2,2′-Bis(2-mercaptophenylamino)diethyl Sulfide(2-))
Dieter Sellmann,* Ju1rgen Utz, and Frank W. Heinemann
Institut fu¨r Anorganische Chemie, Universita¨t Erlangen-Nu¨rnberg, Egerlandstrasse 1,
D-91058 Erlangen, Germany
ReceiVed April 3, 1998
The new pentadentate amine thioether thiolate ligand ′N2H2S3′-H2 () 2,2′-bis(2-mercaptophenylamino)diethyl
sulfide) (3) was synthesized in order to obtain iron and ruthenium complexes with high electron densities at the
metal centers. The reaction of ′N2H2S3′2- with Fe2+ yielded the dinuclear high-spin complex [Fe(′N2H2S3′)]2 (5).
Complex 5 added CO to give the low-spin complex [Fe(CO)(′N2H2S3′)] (6) whose low frequency ν(CO) (1932
cm-1) indicates a high electron density at the iron center and a strong Fe-CO bond. However, 6 is labile and
readily dissociates CO in solution. Treatment of suitable ruthenium precursor complexes with ′N2H2S3′2- yielded
[Ru(CO)(PCy3)(′N2H2S3′)] (7), [Ru(PPr3)2(′N2H2S3′)] (8), [Ru(PR3)(′N2H2S3′)] (R ) Pr (9), Ph (10)), and [Ru-
(NO)(′N2HS3′)] (13). In complexes 7 and 8, ′N2H2S3′2- acts as a tetradentate ligand. When heated in solution,
complex 8 dissociates one PPr3 ligand to give 9. Complex 13 contains the trisanionic ′N2HS3′3- resulting from
deprotonation of one amine NH function. All [Ru(L)(′N2H2S3′)] complexes proved inert toward dissociation of
the Ru-L bonds. The NH functions of [M(L)(′N2H2S3′)] complexes are acidic and show H+/D+ exchange reactions
with D2O. Methylation of the thiolate donors in 10 yielded the thioether derivative [Ru(PPh3)(′N2H2S3′-Me2)]I2
(11) whose PPh3 ligand is as inert to substitution as that of 10. Complex 11 can reversibly be deprotonated to
give [Ru(PPh3)(′N2HS3′-Me2)]I (12). NMR spectroscopic investigations showed that the deprotonation/protonation
reactions of 11 and 12 are stereoselective. In contrast, protonation of 13 with HBF4 gives two diastereomers of
the corresponding [Ru(NO)(′N2H2S3′)]BF4 salt (14). X-ray structure analyses of 5, 6, 9, and 11 and NMR spectra
showed that the ′N2H2S3′2- ligand and its derivatives bind to the metal centers in the same fashion which combines
fac and mer coordination of the donor atoms. The [MN2S3] cores of all complexes have an analogous C1 symmetrical
structure in which both the two N and the two terminal S donors assume cis positions.
Introduction
In our search for nitrogenase-related complexes, the [Fe-
(′NHS4′)] fragment (′NHS4′2- ) 2,2′-bis(2-mercaptophenylthio)-
The metal oxidation state, the type and number of donor
atoms, and the core structure are major factors determining
structure-function relationships of metal complexes.2 In the
quest for complexes that model structural and functional features
of the transition metal sulfur centers in enzymes such as
nitrogenases, hydrogenases, and CO dehydrogenases, our interest
focuses on transition-metal complexes with multidentate ligands
containing thiolate, thioether, and amine donors. When these
complexes bind biologically relevant molecules and catalyze
enzyme-related reactions, they model structural (metal sulfur
sites) and functional (reactivity) features of the active centers
in the enzymes.3 One ultimate goal in this area of research are
complexes with enzymelike activity, which can be termed
“competitive” catalysts.4
diethylamine(2-)) was found to bind the key molecules of N2
fixation, N2H2, N2H4, and NH3,5 but not N2.
The [Fe(′NHS4′)] fragment demonstrated the importance of
the core structures for binding and/or stabilization of the
coligands. The [Fe(′NHS4′)] fragment exists in the two diaster-
eomeric forms A and B. While A binds only σ ligands such as
NH3, N2H4, or MeOH, B binds only σ-π ligands such as CO,
PMe3, or diazene, N2H2.5,6 In the diazene complex, the trans
coordination of the thiolate donors in B proved pivotal for the
stabilization of N2H2, because it renders possible strong
bifurcated N-H...(S)2 bridges in the [FeN2H2Fe] unit of the
binuclear [µ-N2H2{Fe(′NHS4′)}2] according to C.
Because almost all stable N2 complexes exhibit electron-rich
metal centers,7 a major factor for the binding of N2 can be
considered a high electron density at the metal center. Whereas
the ν(CO) frequency of [Fe(CO)(′NHS4′)] (1960 cm-1) indicates
* To whom correspondence should be addressed.
(1) Part 131: Sellmann, D.; Hennige, A. C.; Heinemann, F. W. Eur. J.
Inorg. Chem. 1998, 819.
(2) (a) Mellor, D. P. In Chelating Agents and Metal Chelates; Dwyer, F.
P., Mellor, D. P., Eds.; Academic Press: New York, London, 1964;
p 44. (b) Burger, K. In Biocoordination Chemistry; Burger, K., Ed.;
Ellis Horwood: New York, 1990; p 11.
(3) Wieghardt, K. Nachr. Chem., Tech. Lab. 1985, 33, 961.
(4) (a) Sellmann, D.; Sutter, J. In Sulfur Coordinated Transition Metal
Complexes: Biological and Industrial Significance; Stiefel, E. I.,
Matsumoto, K., Eds.; ACS Symposium Series 653; American Chemi-
cal Society: Washington, DC, 1996; p 101. (b) Sellmann, D. New J.
Chem. 1997, 21, 681.
(5) (a) Sellmann, D.; Soglowek, W.; Knoch, F.; Ritter, G.; Dengler, J.
Inorg. Chem. 1992, 31, 3711. (b) Sellmann, D.; Soglowek, W.; Knoch,
F.; Moll, M. Angew. Chem. 1989, 101, 1244; Angew. Chem., Int. Ed.
Engl. 1989, 28, 1271.
(6) (a) Sellmann, D.; Kunstmann, H.; Knoch, F.; Moll, M. Inorg. Chem.
1988, 27, 4183. (b) Sellmann, D.; Hofmann, T.; Knoch, F. Inorg. Chim.
Acta 1994, 224, 61.
(7) Henderson, R. A.; Leigh, G. J.; Picket, C. J. AdV. Inorg. Chem.
Radiochem. 1983, 27, 245.
10.1021/ic980383q CCC: $18.00 © 1999 American Chemical Society
Published on Web 01/22/1999

460 Inorganic Chemistry, Vol. 38, No. 3, 1999
Sellmann et al.
(80 mL), and dried in vacuo to yield 15.2 g (60%) of 2: IR (KBr,
cm-1) 1678 vs ν(CO); 1H NMR (CDCl3, ppm, 269.6 MHz) δ 7.42 (d,
2 H, C6H4), 7.32 (t, 2 H, C6H4), 7.15 (t, 2 H, C6H4), 7.09 (d, 2 H,
C6H4), 4.14 (t, 4 H, NCH2), 2.92 (t, 4 H, SCH2); 13C{1H} NMR (CDCl3,
ppm, 67.7 MHz) δ 169.9 (CO), 136.4, 126.5, 123.3, 122.7, 122.6, 110.4
(C6H4), 41.9 (NCH2), 28.9 (SCH2); MS (FD, DMSO) m/z 388
[′N2S3O2′]+. Anal. Calcd for C18H16N2O2S3 (388.54): C, 55.64; H, 4.15;
N, 7.21; S, 24.76. Found: C, 55.49; H, 4.22; N, 7.24; S, 24.74.
′N2H2S3′-H2 (3). A solution of NaOH (14.4 g, 360 mmol) in H2O
(150 mL) was added to a suspension of 2 (14.0 g, 36.0 mmol) in EtOH
(150 mL). The mixture was refluxed for 14 h and cooled to room
temperature and concentrated hydrochloric acid was added (ca. 25 mL)
until pH 3 was reached. The resulting solution was evaporated in vacuo
to one-half of its original volume, diluted with H2O (100 mL) and
extracted with CH2Cl2 (150 mL). The combined CH2Cl2 phases were
dried with anhydrous Na2SO4 and evaporated to dryness, yielding 12.0
g (99%) of 3 as a yellow, highly viscous oil: 1H NMR (CDCl3, ppm,
269.6 MHz): δ 7.41 (d, 2 H, C6H4), 7.19 (t, 2 H, C6H4), 6.64 (m, 4 H,
C6H4), 5.00 (s, br, 2 H, NH), 3.41 (t, 4 H, NCH2), 2.88 (t, 6 H, SCH2
and SH superimposed); 13C{1H} NMR (CDCl3, ppm, 67.7 MHz) δ
136.8, 135.3, 128.7, 128.1, 123.1 (C6H4), 48.3 (NCH2), 27.6 (SCH2);
MS (FD, CDCl3) m/z 336 [′N2H2S3′-H2]+. Anal. Calcd for C16H20N2S3
(336.55): C, 57.10; H, 5.99; N, 8.32; S, 28.58. Found: C, 55.89; H,
6.26; N, 8.67; S, 27.79.
a relatively high electron density of the Fe(II) center, it is
possibly not high enough to enable the coordination of N2. For
this reason, we have started a systematic study aiming at the
stepwise substitution of the potentially π-accepting thioether
sulfur donors in the ′NHS4′2- ligand by amine functions which
act as σ donors only. Our first target ligand in this context was
′N2H2S3′-H2 () 2,2′-bis(2-mercaptophenylamino)diethyl sul-
fide).
′N2H2S3′-H2‚2HCl (3‚2HCl). Concentrated hydrochloric acid (0.75
mL, 9.0 mmol) was added to a solution of ′N2H2S3′-H2 (3) (0.50 g,
1.50 mmol) in MeOH (20 mL). Removal of the solvents gave a white
residue, which was digested three times with CH2Cl2 (15 mL) and dried
in vacuo, yielding 0.56 g (91%) of 3‚2HCl: 1H NMR (CD3OD, ppm,
269.6 MHz): δ 7.61 (d, 2 H, C6H4), 7.45-7.25 (m, 6 H, C6H4), 3.68
(t, 4 H, NCH2), 3.03 (t, 4 H, SCH2); 13C{1H} NMR (CD3OD, ppm,
67.7 MHz) δ 137.7, 136.5, 129.9, 129.8, 124.7, 123.7 (C6H4), 50.0
(NCH2), 28.5 (SCH2); MS (FD, MeOH) m/z 338 [′N2H4S3′-H2]+. Anal.
Calcd for C16H22Cl2N2S3 (409.47): C, 46.93; H, 5.42; N, 6.84; S, 23.49.
Found: C, 47.16; H, 5.53; N, 6.86; S 23.63.
′N2H2S3′-H2 relates to ′NHS4′-H2 by having one more amine
donor and one less thioether donor. ′N2H2S3′-H2 further
maintains terminal thiol functions which are necessary for the
trans coordination of thiolate donors as found in the form B of
[Fe(′NHS4′)].
The notation ′N2H2S3′-H2 has been chosen in order to allow
a facile designation of the varying sets of donor atoms and of
deprotonation states of the ′N2H2S3′-H2 or related ligands. The
synthesis of the ′N2H2S3′-H2 ligand and a couple of characteristic
Fe and Ru complexes will be described here.
′N2H2S3′-Me2 (4). MeI (0.75 mL, 11.7 mmol) was added to a solution
of ′N2H2S3′-H2 (3) (0.99 g, 2.9 mmol) and LiOMe (6.2 mmol, 6.2 mL
of a 1 M solution in MeOH) in THF (20 mL). The reaction mixture
was stirred for 16 h and then evaporated to dryness. The residue was
redissolved in 80 mL of a 1:1 mixture of H2O and CH2Cl2, the CH2Cl2
phase was separated, dried with anhydrous Na2SO4, and evaporated to
dryness yielding 1.00 g (95%) of 4 as a yellow oil: 1H NMR (CDCl3,
ppm, 269.6 MHz) δ 7.35 (d, 2 H, C6H4), 7.13 (t, 2 H, C6H4), 6.63 (t,
2 H, C6H4), 6.54 (d, 2 H, C6H4), 5.24 (t, 2 H, NH), 3.33 (dt, 4 H,
NCH2), 2.78 (t, 4 H, SCH2), 2.27 (s, 6 H, SCH3); 13C{1H} NMR (CDCl3,
ppm, 67.7 MHz) δ 147.3, 133.7, 129.1, 120.0, 117.1, 109.8 (C6H4),
42.6 (NCH2), 31.1 (SCH2), 17.9 (SCH3); MS (FD, CH2Cl2) m/z 364
[′N2H2S3′-Me2]+.
Experimental Section
General Methods. Unless noted otherwise, all procedures were
carried out under an atmosphere of dinitrogen at room temperature by
using standard Schlenk techniques. Solvents were dried and distilled
before use. As far as possible the reactions were monitored by IR
spectroscopy. Spectra were recorded on the following instruments: IR,
Perkin-Elmer 16 PC FT-IR; NMR, JEOL JNM-GX 270 and JNM-EX
270; mass spectra, Varian MAT 212 and JEOL JMS-700. Bis(2-
bromoethyl)sulfide,8 [RuCl3(NO)(PPh3)2],9 [RuCl2(PPh3)3],10 [Ru(H)-
(Cl)(CO)(PCy3)2]11, and 2(3H)-benzothiazolone12 were prepared by
literature methods. Hydrazine was obtained by 2-fold distillation of
N2H4‚H2O over solid potassium hydroxide under reduced pressure.
Alkylation of 2(3H)-Benzothiazolone (1) to give 2. n-BuLi (130.8
mmol, 52.3 mL of a 2.5 M solution in n-hexane) was added dropwise
to a solution of 2(3H)-benzothiazolone (1) (19.74 g, 130.6 mmol) in
THF (100 mL) at -78 °C. The reaction mixture was warmed to room
temperature, and bis(2-bromoethyl)sulfide (16.19 g, 65.3 mmol) was
added. The resulting yellow solution was refluxed for 14 h and then
evaporated to dryness, yielding a foamy residue which was redissolved
in boiling EtOH (80 mL). Addition of H2O (120 mL) led to precipitation
of a white powder, which was separated, digested two times with EtOH
′N2H2S3′-Me2‚2HCl (4‚2HCl). Concentrated hydrochloric acid (0.20
mL, 2.40 mmol) was added to a solution of ′N2H2S3′-Me2 (4) (0.20 g,
0.55 mmol) in MeOH (20 mL). Removal of the solvents gave a bright
yellow residue, which was digested with CH2Cl2 (15 mL) and dried in
vacuo yielding 0.22 g (91%) of 4‚2HCl: 1H NMR (CD3OD, ppm, 269.6
MHz) δ 7.70-7.38 (m, 8 H, C6H4), 5.11 (s, br, 4 H, NH), 3.68 (t, 4 H,
NCH2), 3.08 (t, 4 H, SCH2), 2.58 (s, 8 H, SCH3); 13C{1H} NMR (CD3-
OD, ppm, 67.7 MHz) δ 136.2, 133.5, 133.1, 131.0, 129.4, 124.2 (C6H4),
51.1 (NCH2), 28.2 (SCH2), 18.5 (SCH3); MS (FD, MeOH) m/z 364
[(′N2H2S3′-Me2)]+. Anal. Calcd for C18H26Cl2N2S3 (437.52): C, 49.41;
H, 5.99; N, 6.40; S, 21.99. Found: C, 49.79; H, 6.19; N, 6.45; S, 22.18.
[Fe(′N2H2S3′)]2 (5). A light green solution of FeCl2‚4H2O (0.19 g,
0.95 mmol) in MeOH (10 mL) was added to a yellow solution of
′N2H2S3′-H2 (3) (0.32 g, 0.95 mmol) and LiOMe (1.9 mmol, 1.9 mL
of a 1 M solution in MeOH) in MeOH (20 mL). The color of the
solution changed to orange, and an orange solid precipitated. The solid
was separated, washed with MeOH (20 mL), and dried in vacuo. During
drying, the color of the solid changed from orange to green, yield 0.30
g (81%) of 5: IR (KBr, cm-1) 3240 w, br ν(NH); MS (FD, DMSO)
m/z 334 [(′N2H2S3′)]+, 390 [Fe(′N2H2S3′)]+; µeff(293 K) 4.14 µB. Anal.
Calcd for C32H36Fe2N4S6 (780.76): C, 49.23; H, 4.65; N, 7.18; S, 24.64.
Found: C, 49.05; H, 4.60; N, 7.13; S, 24.53.
(8) Steinkopf, W.; Herold, J.; Sto¨hr, J. Ber. Dtsch. Chem. Ges. 1920, 53,
1007.
(9) Levison, J. J.; Robinson, S. D. J. Chem. Soc. A 1970, 2947.
(10) Stephenson, T. A.; Wilkinson, G. J. Inorg. Nucl. Chem. 1966, 28,
945.
(11) Sellmann, D.; Ruf, R.; Knoch, F.; Moll, M. Inorg. Chem. 1995, 34,
4745.
(12) Hunter, R. F. J. Chem. Soc. 1930, 125.

Transition-Metal Complexes with Sulfur Ligands
Inorganic Chemistry, Vol. 38, No. 3, 1999 461
[Fe(CO)(′N2H2S3′)] (6). CO was bubbled through a suspension of
[Fe(′N2H2S3′)]2 (5) (0.38 g, 0.49 mmol) in THF (30 mL) for 2 h. A
green solid resulted which was separated, washed with THF (20 mL),
and dried in vacuo yielding 0.42 g (97%) of 6‚0.33THF (6 was obtained
in equally high yields when the reaction mixture resulting in the
at 20 °C, washed with THF and MeOH (20 mL each), and dried in
vacuo yielding 0.25 g (50%) of 10‚0.5THF. IR (KBr, cm-1) 3202 m,
3178 m ν(NH); 1H NMR (CD2Cl2, ppm, 269.6 MHz) δ 7.84-6.57 (m,
23 H, C6H4 and P(C6H5) superimposed), 5.36 (s, br, 1 H, NH), 4.46
(dd, 1 H, NH), 3.30-2.08 (m, 8 H, C2H4); 13C{1H} NMR (CD2Cl2,
ppm, 67.7 MHz) δ 155.1, 148.3, 144.0, 136.9, 136.3 (C6H4), 134.0 (d,
P(C6H5)), 133.9, 132.5, 130.6 (C6H4), 129.5 (s, br, P(C6H5)), 128.4 (d,
P(C6H5)), 126.5, 126.4, 125.6, 121.6 (C6H4), 120.6 (d, P(C6H5)), 59.0,
51.1 (NCH2), 42.5, 40.7 (SCH2); 31P{1H} NMR (CD2Cl2, ppm, 109.38
MHz) δ 63.8 (s, P(C6H5)); MS (FD, CH2Cl2, 102Ru) m/z 697 [Ru-
(PPh3)(′N2HS3′)]+. Anal. Calcd for C34H33N2PRuS3‚0.5C4H8O (733.95):
C, 58.91; H, 5.08; N, 3.82; S, 13.11. Found: C, 58.92; H, 5.22; N,
3.81; S, 12.94.
[Ru(PPh3)(′N2D2S3′)] (10a). (a) A suspension of [Ru(PPh3)(′N2H2S3′)]‚
0.5THF (10‚0.5THF) (0.09 g, 0.12 mmol) and D2O (2.0 mL) in THF
(20 mL) was refluxed for 5 h. After removal of the solvents, the yellow
residue was characterized by IR spectroscopy (KBr) to be a mixture of
10 and [Ru(PPh3)(′N2D2S3′)] (10a).
(b) LiOMe (0.24 mmol, 0.24 mL of a 1 M solution in MeOH) and
D2O (1.0 mL) were added to a suspension of [Ru(PPh3)(′N2H2S3′)]‚
0.5THF (10‚0.5THF) (0.09 g, 0.12 mmol) in THF (20 mL). The reaction
mixture was refluxed for 1 h and then evaporated to dryness. The
residue was redissolved in CH2Cl2 and the resulting green solution was
filtered over filter pulp and evaporated to dryness to give 0.09 g (100%)
of 10a‚0.5THF as a yellow powder: IR (KBr, cm-1) 2385 m, br ν(ND);
1H NMR (CD2Cl2, ppm, 269.6 MHz) δ 7.84-6.57 (m, 23 H, C6H4 and
P(C6H5) superimposed), 3.25-2.08 (m, 8 H, C2H4).
[Ru(PPh3)(′N2H2S3′-Me2)]I2 (11). Under stirring, MeI (1.0 mL, 16
mmol) was added to a suspension of [Ru(PPh3)(′N2H2S3′)]‚0.5THF (10‚
0.5THF) (0.27 g, 0.37 mmol) in THF (30 mL). The color of the
suspension slowly changed from yellow to beige. The resulting beige
solid was separated after 3 d, washed with THF (10 mL), and dried in
vacuo to yield 0.32 g (82%) of 11‚THF: IR (KBr, cm-1) 3180 w ν(NH);
1H NMR (CD2Cl2, ppm, 269.6 MHz) δ 8.95 (m, 2 H, NH), 7.88-7.13
(m, 23 H, C6H4 and P(C6H5) superimposed), 4.41 (m, 1 H, C2H4), 3.74-
2.86 (m, 6 H, C2H4), 2.33 (s, 3 H, SCH3), 1.92 (s, 3 H, SCH3), 1.40
(m, 1 H, C2H4); 13C{1H} NMR (CD2Cl2, ppm, 67.7 MHz) δ 149.6,
149.2, 135.2, 134.1 (d), 133.6 (d), 133.0, 132.6, 131.4, 130.8, 130.2,
129.4, 129.1 (d), 126.9, 124.7 (C(aryl)), 54.1, 47.5 (NCH2), 39.4 (d),
36.2 (SCH2), 27.2, 26.4 (SCH3); 31P{1H} NMR (CD2Cl2, ppm, 109.38
MHz) δ 33.8 (s, P(C6H5)); MS (FD, CH2Cl2, 102Ru) m/z 727 [Ru-
(PPh3)(′N2HS3′-Me2)]+, 712 [Ru(PPh3)(′N2HS3′-Me)]+, 697 [Ru-
(PPh3)(′N2HS3′)]+. Anal. Calcd for C36H39I2N2PRuS3‚C4H8O (1053.88):
C, 45.59; H, 4.50; N, 2.66; S, 9.13. Found: C, 45.74; H, 4.41; N, 2.64;
S, 9.01.
synthesis of 5 is directly treated with CO for 2 h): IR (KBr, cm-1
)
1
3229 w, 3166 w ν(NH), 1932 vs ν(CO); H NMR (DMSO-d6, ppm,
269.6 MHz) ν 8.06 (s, br, 1 H, NH), 7.50-6.34 (m, 8 H, C6H4), 5.10
(d, 1 H, NH), 4.25-1.90 (m, 8 H, C2H4); 13C{1H} NMR (DMSO-d6,
ppm, 67.7 MHz) ν 221.0 (CO), 152.9, 151.3, 148.0, 146.4, 129.1, 128.3,
125.3, 125.2, 120.8, 120.6, 119.5 (C6H4), 52.8, 52.1 (NCH2), 35.2, 33.0
(SCH2); MS (FD, DMSO) m/z 334 [(′N2H2S3′)]+, 390 [Fe(′N2H2S3′)]+,
780 {[Fe(′N2H2S3′)]2}+. Anal. Calcd for C17H18FeN2OS3‚0.33C4H8O
(442.43): C, 49.77; H, 4.71; N, 6.33; S, 21.74. Found: C, 49.86; H,
4.74; N, 6.32; S, 21.60.
[Ru(CO)(PCy3)(′N2H2S3′)] (7). [Ru(H)(Cl)(CO)(PCy3)2] (1.08 g,
1.49 mmol) was added to a solution of ′N2H2S3′-H2 (3) (0.50 g, 1.49
mmol) and LiOMe (1.5 mmol, 1.5 mL of a 1 M solution in MeOH) in
THF (40 mL). The reaction mixture was stirred for 3 d and yielded a
green suspension. The gray-green solid was separated, washed with
THF (10 mL), and dried in vacuo yielding 0.75 g (65%) of 7‚MeOH.
IR (KBr, cm-1) 3213, 3203 w ν(NH), 1935 s ν(CO); 1H NMR (DMF-
d7, ppm, 269.6 MHz) δ 9.12 (s, 1 H, NH), 7.67-6.54 (m, 8 H, C6H4),
5.41 (s, 1 H, NH), 4.30-0.97 (m, 41 H, C2H4 and P(C6H11)3
superimposed); 13C{1H} NMR (DMSO-d6, ppm, 67.7 MHz) δ 160.3,
160.0, 146.7, 131.6, 129.6, 126.2, 125.9, 125.3, 118.9, 118.7, 117.3
(C6H4), 51.8, 48.9 (NCH2), 38.0, 37.7 (SCH2), 29.3, 28.9, 27.3, 26.3
(br, P(C6H11)); 31P{1H} NMR (DMF-d7, ppm, 109.38 MHz) δ 47.8 (s,
P(C6H11)); MS (FD, DMSO, 102Ru) m/z 716 [Ru(PCy3)(′N2H2S3′)]+.
Anal. Calcd for C35H51N2PORuS3‚CH3OH (776.09): C, 55.72; H, 7.14;
N, 3.61; S, 12.40. Found: C, 55.45; H, 7.18; N, 3.62; S, 12.27.
[Ru(PPr3)2(′N2H2S3′)] (8). [RuCl2(PPr3)3] was synthesized in situ
by treating a suspension of [RuCl2(PPh3)3] (3.18 g, 3.32 mmol) in
n-hexane (50 mL) with PPr3 (4.0 mL, 20.0 mmol) for 20 h. The resulting
green solution was filtered and evaporated to dryness. The green residue
was suspended in MeOH (30 mL), combined with a solution of
′N2H2S3′-H2 (3) (1.12 g, 3.32 mmol) and LiOMe (6.65 mmol, 6.65 mL
of a 1 M solution in MeOH) in MeOH (30 mL), and stirred for 3 d to
yield a red suspension. The orange solid was separated, washed with
MeOH and n-hexane (30 mL each), and dried in vacuo to yield 1.46 g
1
(58%) of 8: IR (KBr, cm-1) 3289 w, 3227 w ν(NH); H NMR (CD2-
Cl2, ppm, 269.6 MHz): δ 7.60-6.50 (m, 8 H, C6H4), 5.88 (dd, 1 H,
NH), 5.09 (s, br, 1 H, NH), 3.68-2.20 (m, 7 H, C2H4), 1.94-1.37 (m,
25 H, P(C3H7) and C2H4 superimposed), 0.95 (dt, 18 H, P(C3H7)); 13C-
{1H} NMR (CD2Cl2, ppm, 67.7 MHz) δ 155.3, 151.9, 148.6, 135.8,
135.7, 130.3, 126.5, 124.8, 124.7, 121.3, 118.9, 114.7 (C6H4), 59.6,
44.8 (NCH2), 38.6, 31.8 (SCH2), 32.3, 28.3 (d, P(CH2CH2CH3)), 19.2,
18.0 (d, P(CH2CH2CH3)), 16.4, 16.3 (d, P(CH2CH2CH3)); 31P{1H} NMR
(CD2Cl2, ppm, 109.38 MHz) δ 22.0 (d, 1 P, P(C3H7)), 17.3 (d, 1 P,
P(C3H7)); MS (FD, DMSO, 102Ru) m/z 756 [Ru(PPr3)2(′N2H2S3′)]+, 596
[Ru(PPr3)(′N2H2S3′)]+. Anal. Calcd for C34H60N2P2RuS3 (756.08): C,
54.01; H, 8.00; N, 3.71. Found: C, 54.20; H, 7.86; N, 3.50.
[Ru(PPh3)(′N2HS3′-Me2)]I (12). [Ru(PPh3)(′N2H2S3′-Me2)]I2‚THF
(11‚THF) (0.62 g, 0.59 mmol) was dissolved in N2H4 (5.0 mL). The
yellow reaction mixture was stirred for 4 h and evaporated to dryness.
The yellow residue was redissolved in CH2Cl2 (50 mL) and the CH2-
Cl2 solution was filtered over filter pulp and evaporated to dryness.
The resulting yellow powder was digested with MeOH (10 mL) and
dried in vacuo to yield 0.47 g (90%) of 12‚MeOH: IR (KBr, cm-1
)
[Ru(PPr3)(′N2H2S3′)] (9). A red solution of [Ru(PPr3)2(′N2H2S3′)]
(8) (1.30 g, 1.72 mmol) in THF (40 mL) was refluxed for 4 h in the
course of which the color changed to green-brown. The solution was
cooled to room temperature and layered with n-hexane (40 mL). Green-
brown crystals precipitated which were separated after 5 d, washed
with THF (5 mL, 0 °C), and dried in vacuo to yield 0.46 g (42%) of
3124 w, br ν(NH); 1H NMR (DMSO-d6, ppm, 269.6 MHz) δ 7.80 (dd,
1 H, CH(aryl)), 7.71 (d, 1 H, CH(aryl)), 7.58 (s, 1 H, NH), 7.50-7.08
(m, 17 H, CH(aryl)), 6.94 (dt, 1 H, CH(aryl)), 6.85 (dd, 1 H, CH(aryl)),
6.23 (d, 1 H, CH(aryl)), 6.09 (t, 1 H, CH(aryl)), 3.41-2.76 (m, 6 H,
C2H4), 2.37-2.20 (m, 1 H, C2H4), 2.16, 1.97 (s, 3 H each, CH3), 1.94-
1.79 (m, 1 H, C2H4); 13C{1H} NMR (DMSO-d6, ppm, 67.7 MHz) δ
158.9, 146.9, 136.1 (d) (C6H4), 133.1, 132.3 (d, P(C6H5)), 131.5, 131.2,
130.6 (C6H4), 130.2 (s, br, P(C6H5)), 129.3, 128.7 (C6H4), 128.2 (d,
P(C6H5)), 127.2, 119.6, 111.4, 110.3 (C6H4), 57.5, 48.4 (NCH2), 40.5,
34.2 (SCH2), 27.4, 21.9 (d) (SCH3); 31P{1H} NMR (DMSO-d6, ppm,
109.38 MHz) δ 43.7 (s, P(C6H5)); MS (FD, DMSO, 102Ru) m/z 727
[Ru(PPh3)(′N2HS3′-Me2)]+, 712 [Ru(PPh3)(′N2HS3′-Me)]+, 698 [Ru-
(PPh3)(′N2H2S3′)]+. Anal. Calcd for C36H38IN2PRuS3‚CH3OH (885.91):
C, 50.16; H, 4.78; N, 3.16; S, 10.86. Found: C, 50.42; H, 4.94; N,
3.18; S, 10.52.
1
9‚0.5THF: IR (KBr, cm-1) 3251 w ν(NH); H NMR (CD2Cl2, ppm,
269.6 MHz) δ 7.38-6.64 (m, 8 H, C6H4), 5.55 (s, 1 H, NH), 4.44 (s,
1 H, NH), 3.85-2.37 (m, 8 H, C2H4), 1.88-1.26 (m, 12 H, P(CH2CH2-
CH3)3), 0.94 (t, 9 H, P(CH2CH2CH3)3); 31P{1H} NMR (THF-d8, ppm,
109.38 MHz) δ 31.6 ppm (s, P(C3H7)); MS (FD, CH2Cl2, 102Ru) m/z
596 [Ru(PPr3)(′N2H2S3′)]+. Anal. Calcd for C25H39N2PRuS3‚0.5C4H8O
(631.90): C, 51.32; H, 6.86; N, 4.43. Found: C, 51.12; H, 7.09; N,
4.13.
[Ru(PPh3)(′N2H2S3′)] (10). [RuCl2(PPh3)3] (0.65 g, 0.68 mmol) was
added to a solution of ′N2H2S3′-H2 (3) (0.23 g, 0.68 mmol) and LiOMe
(1.3 mmol, 1.3 mL of a 1 M solution in MeOH) in THF (20 mL). The
reaction mixture was refluxed for 4 h to yield a green suspension, from
which a yellow solid precipitated. The yellow precipitate was separated
[Ru(PPh3)(′N2H2S3′-Me2)](I)(Cl) from 12 and HCl. Hydrochloric
acid (0.50 mmol, 5 mL of a 0.1 M solution of HCl in H2O) was added
to a solution of [Ru(PPh3)(′N2HS3′-Me2)]I‚MeOH (12‚MeOH) (0.048
g, 0.054 mmol) in CH2Cl2 (15 mL). The reaction mixture was stirred

462 Inorganic Chemistry, Vol. 38, No. 3, 1999
Sellmann et al.
Table 1. Selected Crystallographic Data for [Fe(′N2H2S3′)]2‚4MeOH (5‚4MeOH), [Fe(CO)(′N2H2S3′)] (6), [Ru(PPr3)(′N2H2S3′)]‚2THF
(9‚2THF), and [Ru(PPh3)(′N2H2S3′-Me2)]I2‚2CH2Cl2 (11‚2CH2Cl2)
compd
5‚4MeOH
6
9‚2THF
11‚2CH2Cl2
formula
fw
C36H52Fe2N4O4S6
908.88
0.5 × 0.5 × 0.5
triclinic
P1h
976.3(3)
1025.5(4)
1160.7(6)
114.01(4)
95.03(3)
95.23(3)
1.0471(8)
1
C17H18FeN2OS3
418.36
0.8 × 0.4 × 0.2
monoclinic
P21/n
813.6(8)
1141(2)
1987(2)
90
95.36(7)
90
1.836(3)
4
C33H55N2O2PRuS3
740.01
0.4 × 0.4 × 0.2
monoclinic
P21/c
1053.7(3)
2443.7(7)
1453.1(7)
90
102.35(3)
90
C38H43Cl4I2N2PRuS3
1151.56
0.5 × 0.4 × 0.4
monoclinic
C2/c
3313(1)
1625.2(5)
1718.5(7)
90
109.24(5)
90
8.736(6)
8
crystal size, mm3
crystal system
space group
a, pm
b, pm
c, pm
R, deg
â, deg
γ, deg
V, nm3
Z
3.655(2)
4
λ, pm
71.073
1.441
1.034
4 e 2θ e 48
4287
3291
2677
339
3.60 (10.52)
0.0693
71.073
1.514
1.169
4 < 2θ < 54
5010
4030
2741
217
71.073
1.345
0.675
4 e 2θ e 54
12031
8036
3914
535
4.29 (8.89)
0.0246
71.073
1.751
2.227
4 < 2θ < 48
18249
6895
5063
460
3.61 (9.04)
0.0515
d
calc, g/cm-3
µ, mm-1
2 θ range, deg
meas reflections
indep reflections
obsd reflections
refined parameters
R1 (wR2),a,b
%
4.15 (14.24)
0.0639
1.0635
qb
rb
a R1 ) [∑||Fo| - |Fc||/∑|Fo| ] for F > 4σ(F). b wR2 ) [∑[w(Fo - Fc2)2]/∑[w(Fo )2]]1/2, where w ) 1/[σ2(Fo ) + (qP)2+ rP] and P ) (Fo
+
2
2
2
2
2Fc2)/3.
for 5 min. Removal of the solvents yielded a yellow powder, which
of FeCl2‚4H2O (0.95 g, 0.48 mmol) in MeOH (80 mL). Brown columns
was identified by 1H NMR spectroscopy as [Ru(PPh3)(′N2H2S3′-Me2)]-
of [Fe(CO)(′N2H2S3′)] (6) formed when a saturated solution of 6 in a
1:1 mixture of MeOH and THF was layered with Et2O under an
atmosphere of CO. Brown plates of [Ru(PPr3)(′N2H2S3′)]‚2THF (9‚
2THF) crystallized from a saturated THF solution of 9 which was
layered with n-hexane. Yellow plates of [Ru(PPh3)(′N2H2S3′-Me2)]I2‚
2CH2Cl2 (11‚2CH2Cl2) were grown from a saturated solution of 11 in
CH2Cl2 by slowly evaporating the solvent. Suitable single crystals were
sealed under N2 in glass capillaries and data were collected with a
Siemens P4 diffractometer at 200 K. The structures were solved by
direct methods (SHELXTL-PLUS).13 Full-matrix least-squares refine-
ment was carried out on F2 values (SHELXL-93).14 The hydrogen atoms
were located in a difference Fourier synthesis and either restricted during
refinement (6, 11) or isotropically refined (5, 9). Complex 5 crystallizes
with four molecules of MeOH, 11 with two molecules of CH2Cl2, and
9 with two molecules of THF per unit. The hydrogen atoms of the
THF molecules in 9‚2THF and of the CH2Cl2 molecules of 11‚2CH2-
Cl2 were calculated for ideal geometries. Their isotropic temperature
factors were fixed at 1.5 times the Ueq value of the preceding carbon
atom. Table 1 contains selected crystallographic data of [Fe(′N2H2S3′)]2‚
4MeOH (5‚4MeOH), [Fe(CO)(′N2H2S3′)] (6), [Ru(PPr3)(′N2H2S3′)]‚
2THF (9‚2THF), and [Ru(PPh3)(′N2H2S3′-Me2)]I2‚2CH2Cl2 (11‚2CH2-
Cl2).
(I)(Cl).
[Ru(NO)(′N2HS3′)] (13). [RuCl3(NO)(PPh3)2] (0.648 g, 0.85 mmol)
was added to a solution of ′N2H2S3′-H2 (3) (0.285 g, 0.85 mmol) and
LiOMe (2.55 mmol, 2.55 mL of a 1 M solution in MeOH) in THF (25
mL). The reaction mixture was stirred for 14 h to yield a green
suspension. The deep green opalescent precipitate was separated,
washed with MeOH and THF (20 mL each), and dried in vacuo to
yield 0.287 g (67%) of 13‚0.5THF: IR (KBr, cm-1) 3228 m ν(NH),
1
1799 vs ν(NO); H NMR (DMSO-d6, ppm, 269.6 MHz) δ 7.20 (d, 1
H, C6H4), 7.00-6.73 (m, 6 H, C6H4 and NH), 6.49 (d, 1 H, C6H4),
6.39 (t, 1 H, C6H4), 4.15-2.64 (m, 8 H, C2H4); 13C{1H} NMR (DMSO-
d6, ppm, 67.7 MHz) δ 159.2, 145.6, 145.4, 137.7, 128.9, 127.1, 126.5,
125.0, 122.8, 122.0, 115.7, 110.0 (C6H4), 58.5, 54.8 (NCH2), 39.2, 34.7
(SCH2); MS (FD, DMSO, 102Ru) m/z 465 [Ru(NO)(′N2HS3′)]+. Anal.
Calcd for C16H17N3ORuS3‚0.5C4H8O (500.65): C, 43.18; H, 4.23; N,
8.39; S, 19.21. Found: C, 43.22; H, 4.27; N, 8.26; S, 18.94.
[Ru(NO)(′N2H2S3′)]BF4 (14). HBF4 (1.63 mmol, 0.225 mL of a 54%
solution in Et2O) was added to a green suspension of [Ru(NO)(′N2-
HS3′)]‚0.5THF (13‚0.5THF) (0.816 g, 1.63 mmol) in Et2O (40 mL)
and stirred for 14 h. A red solid precipitated, which was separated,
washed with Et2O (40 mL), and dried in vacuo to yield 0.890 g (99%)
of 14. 13C{1H} and 1H NMR spectra showed that the red solid contained
a 1:1 mixture of two diastereomers of 14. IR (KBr, cm-1) 3202 w, br,
Results and Discussion
1
3169 w ν(NH), 1856 vs ν(NO), 1084 s ν(BF4); H NMR (DMSO-d6,
Syntheses of Ligands. The requirement of having terminal
thiolate functions in the target ligand ′N2H2S3′2- necessitated
the development of the synthesis route shown in Scheme 1.
Deprotonation of 2(3H)-benzothiazolone (1) by n-BuLi and
subsequent treatment with bis(2-bromoethyl)sulfide yielded 2
ppm, 269.6 MHz) δ 9.97 (d, 0.5 H, NH), 8.64 (s, 0.5 H, NH), 7.99 (d,
0.5 H, NH), 7.39 (s, 0.5 H, NH), 7.70-6.90 (m, 8 H, C6H4), 4.80-
2.70 (m, 8 H, C2H4); 13C{1H} NMR (DMSO-d6, ppm, 67.7 MHz) δ
150.0, 147.2, 146.7, 145.2, 145.1, 142.6, 141.5, 141.1, 129.5, 129.3,
128.8, 128.7, 128.4, 128.3, 128.0, 127.7, 127.0, 125.4, 124.0, 123.9,
123.7, 122.7 (C6H4), 63.6, 59.3, 57.1, 51.5 (NCH2), 39.3, 37.0, 36.2,
36.0 (SCH2); MS (FD, DMSO, 102Ru) m/z 465 [Ru(NO)(′N2HS3′)]+.
Anal. Calcd for C16H18BF4N3ORuS3 (552.41): C, 34.79; H, 3.28; N,
7.61; S, 17.41. Found: C, 34.75; H, 3.31; N, 7.38; S, 17.34.
1
as the major product. The H NMR spectrum of the crude
product indicated that byproducts resulting from O-alkylation
of 1 had also formed.15 These byproducts could readily be
removed by extraction with EtOH. The remaining 2 proved
X-ray Structure Analyses of [Fe(′N2H2S3′)]2‚4MeOH (5‚4MeOH),
[Fe(CO)(′N2H2S3′)] (6), [Ru(PPr3)(′N2H2S3′)]‚2THF (9‚2THF), and
[Ru(PPh3)(′N2H2S3′-Me2)]I2‚2CH2Cl2 (11‚2CH2Cl2). Black columns
of [Fe(′N2H2S3′)]2‚4MeOH (5‚4MeOH) were obtained by layering a
solution of ′N2H2S3′-H2 (3) (0.16 g, 0.48 mmol) and LiOMe (0.95 mmol,
0.95 mL of a 1 M solution in MeOH) in MeOH (80 mL) with a solution
(13) SHELXTL-PLUS for Siemens Crystallographic Research Systems,
Release 4 21/V, Siemens Analytical X-ray Instruments Inc., Madison,
WI, 1990.
(14) Sheldrick, G. M. SHELXL-93, Program for crystal structure refine-
ment, Universita¨t Go¨ttingen, 1993.
(15) Klein, G.; Prijs, B. HelV. Chim. Acta 1954, 37, 2057.

Transition-Metal Complexes with Sulfur Ligands
Inorganic Chemistry, Vol. 38, No. 3, 1999 463
Scheme 1. Synthesis of ′N2H2S3′-H2 and Its Derivativesa
a Key: (a) +2n-BuLi, + S(C2H4Br)2, THF, reflux, 14 h; (b) (1) + NaOH, EtOH/H2O, reflux, 14 h, (2) + HCl; (c) + HCl, MeOH; (d) +
2LiOMe, + exc. MeI, 16 h.
soluble in CH2Cl2 and THF and was characterized by spectro-
scopic methods and elemental analysis. The CO group 13C NMR
signal (δ ) 169.9 ppm) and the ν(CO) IR band (1678 cm-1
)
proved particularly suitable to confirm the N-alkylation of 1.
Alkaline hydrolysis of 2 and subsequent acidification yielded
3 as a highly viscous yellow oil which could be purified via
the white dihydrochloride [′N2H4S3′-H2]Cl2 (3‚2HCl). For the
syntheses of complexes, 3 could be used without further
purification. Successive treatment of 3 with LiOMe and MeI
yielded the dimethyl derivative ′N2H2S3′-Me2 (4).
The facile alkylation of the thiol functions of 3 illustrates
the necessity to provide an efficient protective group for the
sulfur functions, which are to become thiol groups in the
synthesis of 3. Accordingly, numerous attempts to obtain the
target ligand 3 via other routes remained unsuccessful. For
example, template alkylations of doubly deprotonated 2-ami-
nothiophenol bound to [Fe(CO)2]2+ fragments yielded un-
tractable materials. Benzylation of the thiol function in 2-ami-
nothiophenol and subsequent treatment of the resulting
2-benzylthioaniline with S(C2H4Br)2 led to 2-fold alkylation of
the NH2 group and formation of 4-(2-benzylthiophenyl)-
thiomorpholine.16
The unexpected lability of 6 prompted us to search for less
labile ruthenium complexes of 3 (Scheme 2). All efforts to
obtain the ruthenium analogue of 6, [Ru(CO)(′N2H2S3′)], from
ruthenium carbonyl precursor complexes and ′N2H2S3′2- re-
mained as yet unsuccessful. Precursor complexes such as [Ru-
(H)(Cl)(CO)(PCy3)2] or [RuCl2(CO)3(THF)]17,18 proved too inert
to exchange all ligands except one CO for the ′N2H2S3′2- donors.
For example, the reaction of [Ru(H)(Cl)(CO)(PCy3)2] with
′N2H2S3′2- yielded green [Ru(CO)(PCy3)(′N2H2S3′)] (7), whose
composition suggests that ′N2H2S3′2- acts as tetradentate ligand
only. Complex 7 proved so stable that it did not loose PCy3 or
CO even when heated for 14 h in refluxing THF.
Phosphine complexes such as [RuCl2(PR3)3] (R ) Pr, Ph)
proved more reactive toward ′N2H2S3′2-. At room temperature,
the reaction of [RuCl2(PPr3)3] with ′N2H2S3′2- yielded orange
[Ru(PPr3)2(′N2H2S3′)] (8), in which the ′N2H2S3′2- ligand again
probably utilizes only four of its five donors. However, 8 is
readily converted into green-brown [Ru(PPr3)(′N2H2S3′)] (9) in
boiling THF. The C1 symmetrical structure of 9 and 10 indicated
in Scheme 2 was concluded from NMR spectra and could be
confirmed for 9 by X-ray structure analysis. Complexes 9 and
10 proved inert toward substitution of the remaining PR3 ligands
with CO, N2H4, N2, or other PR3 ligands. In an attempt to
labilize the Ru-PR3 bonds via alkylation of the thiolate donors,
10 was treated with MeI and yielded beige [Ru(PPh3)(′N2H2S3′-
Me2)]I2 (11). The molecular structure of 11 could be elucidated
by X-ray structure determination, but the PPh3 ligand in 11
proved as inert to substitution as that in 10. In the respective
experiments, however, it was observed that Brønsted bases such
as N2H4 caused deprotonation of one amine function of the
′N2H2S3′-Me2 ligand of 11. The monoiodide [Ru(PPh3)(′N2HS3′-
Me2)]I (12) resulted which contains one amide donor (Scheme
2, reaction e). A similar deprotonation of amine functions was
Syntheses of Complexes. The reaction between Fe(II) salts
and the ′N2H2S3′2- anion obtained by deprotonation of 3 with
LiOMe yielded green [Fe(′N2H2S3′)]2 (5) (eq 1). In solid state,
5 is dinuclear (X-ray diffraction) and paramagnetic (µeff (293
K) ) 4.14 µB). The paramagnetism of 5 is compatible with four
unpaired electrons at the Fe centers, whose spins partially couple
via Fe-S-Fe bridges. In solution (THF or MeOH), 5 proved
unreactive toward N2H4, NEt4N3, PMe3, and also N2, but readily
added CO to give diamagnetic green [Fe(CO)(′N2H2S3′)] (6).
The molecular structure of 6 was determined by X-ray diffrac-
tion.
The low frequency ν(CO) IR band of 6 (1932 cm-1 in KBr)
indicates strong Fe-CO π-back bonding, and solid 6 is indeed
stable at room temperature for unlimited periods of time.
Therefore, it was surprising to observe that 6 is labile in solution
and slowly loses CO to regenerate 5.
(17) Bruce, M. I.; Stone, F. G. A. J. Chem. Soc. A 1967, 1238.
(18) Chatt, J.; Shaw, B. L.; Field, A. E. J. Chem. Soc. 1964, 3466.
(16) Cf.: Helfrich, O. B.; Reid, E. E. J. Am. Chem. Soc. 1920, 42, 1226.

464 Inorganic Chemistry, Vol. 38, No. 3, 1999
Sellmann et al.
Scheme 2. Synthesis of [Ru(′N2H2S3′)] Complexesa
a Key: (a) + [Ru(H)(Cl)(CO)(PCy3)2], THF, 3 d; (b) + [RuCl2(PPr3)3], MeOH, 3 d; (c) + [RuCl2(PR3)3] (R ) Pr, Ph), THF, reflux, 4 h; (d) +
exc. MeI, THF, 3 d; (e) + N2H4; (f) + [RuCl3(NO)(PPh3)2], + LiOMe, MeOH/THF, 14 h; (g) + HBF4, Et2O.
observed when the nitrosyl complex [RuCl3(NO)(PPh3)2] was
(′N2H2S3′-Me2)]I2 (11) and [Ru(NO)(′N2H2S3′)]BF4 (14) spon-
taneously exchanged with D+ from D2O. In these two cases,
the corresponding amide complexes could also be isolated.
Addition of Brønsted bases such as N2H4 and NEt4N3 to
solutions of 11 and 14 gave [Ru(PPh3)(′N2HS3′-Me2)]I (12) and
[Ru(NO)(′N2HS3′)] (13), respectively.
treated with ′N2H2S3′-H2 in the presence of 3 equiv of LiOMe.
Deep green [Ru(NO)(′N2HS3′)] (13) (ν(NO) ) 1799 cm-1
)
formed, which is neutral and diamagnetic and contains the tris-
anionic ′N2HS3′3- ligand. Subsequent treatment of 13 with HBF4
yielded red [Ru(NO)(′N2H2S3′)]BF4 (14) (ν(NO) ) 1856 cm-1
)
and showed that the amine deprotonation is reversible. In
accordance with expectations, the protonation of 13 to yield 14
shifts the ν(NO) band to higher frequencies.
These results show that the amine NH donors of [M(L)-
(′N2H2S3′)] complexes can be reversibly deprotonated to give
amide donors according to the equilibrium of eq 3.
Substitution and Acid-Base Reactions. The lability of [Fe-
(CO)(′N2H2S3′)] (6) toward CO dissociation and the resulting
formation of the dinuclear [Fe(′N2H2S3′)]2 (5) can be regarded
as substitution of CO by thiolate ligands. This reaction is
plausibly explained by the equilibrium according to eq 2. The
formation of the sparingly soluble dinuclear 5 most likely serves
as driving force. It precipitates from solution and shifts the
equilibrium to the right side. The favored formation of the
dinuclear 5 could also explain why the attempts to obtain [Fe-
(L)(′N2H2S3′)] derivatives with L ) N2H4, NH3, N3- remained
unsuccessful.
[M(L)(′N2H2S3′)] h [M(L)(′N2HS3′)]- + H+
(3)
The formation of the amide species [M(L)(′N2HS3′)]- can
have two opposite consequences with respect to the M-L
bond: (1) The M-L bond can be labilized because the amide
donor stabilizes a coordinatively unsaturated species via π
donation, resulting from M-L bond dissociation according to
eq 4.19 (2) In the opposite case, and this could be favored when
L is a π acceptor, the M-L bond is stabilized by exactly the
same effect of π donation from the amide donor.6b
[M(L)(′N2HS3′)]- h [M(′N2HS3′)]- + L
(4)
2[Fe(CO)(′N2H2S3′)] h [Fe(′N2H2S3′)]2 + 2 CO (2)
In contrast to the labile [Fe(CO)(′N2H2S3′)], the ruthenium
complexes [Ru(PR3)(′N2H2S3′)] (R ) Pr (9), Ph (10)) and [Ru-
(NO)(′N2HS3′)] (13) proved extremely inert to substitution. The
PPh3 ligand in 10 could be substituted by CO neither under
elevated pressure (50 bar, 20 °C, 2 d) nor by treatment with
hydrazine as solvent (40 °C, 1 d). Attempts to nucleophilically
attack the NO ligand in [Ru(NO)(′N2HS3′)] (13) with N2H4 or
NEt4N3 in boiling THF or MeOH also remained unsuccessful.
A possible reason for this inertness to substitution is, in addition
to the inherent kinetic stability of ruthenium complexes, the
Brønsted acidity of the ′N2H2S3′2- amine functions. The NH
Brønsted acidity was indicated by the deprotonation of the
′N2H2S3′-Me2 ligand, when 11 was treated with N2H4, and it
could subsequently be observed for ′N2H2S3′2- in the formation
of the NO complex 13.
The Brønsted acid-base reactions could further be established
by H+/D+ exchange reactions. Addition of D2O to THF
solutions of [Fe(CO)(′N2H2S3′)] (6) spontaneously yielded [Fe-
(CO)(′N2D2S3′)] (6a). The H+/D+ exchange of the ruthenium
complex [Ru(PPh3)(′N2H2S3′)] (10) was rather slow with neutral
D2O (in THF), but highly accelerated by addition of base
(LiOMe) and yielded [Ru(PPh3)(′N2D2S3′)] (10a). [Ru(PPh3)-
For the complexes described here, apparently the second
alternative prevails. It also explains why the NO ligand in [Ru-
(NO)(′N2H2S3′)]BF4 (14), which shows a high-frequency ν(NO)
at 1856 cm-1, is insusceptible to nucleophilic attack by N2H4
or azide ions. The primary reaction is a deprotonation of 14 to
give 13, whose ν(NO) of 1799 cm-1 indicates a relatively high
electron density at the NO ligand.
The investigation of the protonation/deprotonation reactions
of [Ru(PPh3)(′N2HS3′-Me2)]I (12) and [Ru(NO)(′N2HS3′)] (13)
further revealed that the attack of the amide donors by H+ can
be influenced by the ligands L so that it occurs in a stereocon-
trolled manner. 13C{1H} and 1H NMR spectra (see below)
showed that protonation of 12 by HCl yielded only one
stereoisomer of [Ru(PPh3)(′N2H2S3′-Me2)](I)(Cl). However, the
protonation of [Ru(NO)(′N2HS3′)] (13) (with HBF4) resulted
in a 1:1 mixture of two diastereomers of [Ru(NO)(′N2H2S3′)]-
BF4. These findings are explained by the chirality of the
complexes, which allows the protons to approach the amide
donors from two distinguishable (“front” or “back”) sides. In
12, which exhibits the sterically demanding PPh3 ligand and
(19) Tobe, M. L. AdV. Inorg. Bioinorg. Mech. 1983, 2, 1.

Transition-Metal Complexes with Sulfur Ligands
Inorganic Chemistry, Vol. 38, No. 3, 1999 465
two methyl groups at the terminal sulfur atoms, one of these
two sides is evidently blocked. In 13, which carries the small
NO ligand, both sides are accessible so that protons can attack
the amide function from the front as well as from the back side
as indicated in eq 5.
Figure 1. ORTEP diagrams of (a) [Fe(′N2H2S3′)]2‚4MeOH (5‚4MeOH)
and (b) [Fe(CO)(′N2H2S3′)] (6) (50% probability ellipsoids; H atoms
and solvate molecules omitted).
Characterization of Complexes. All complexes but [Fe-
(′N2H2S3′)]2 (5) proved to be diamagnetic and exhibit similar
solubilities. The neutral CO, NO, and phosphine complexes are
soluble in DMF, DMSO, CH2Cl2, THF, and acetone but virtually
insoluble in all other common organic solvents. The salt 14 is
soluble only in DMF and DMSO and is sparingly soluble in
MeOH. All complexes have been characterized by elemental
analyses, IR, NMR, and mass spectra. The FD mass spectra
showed the molecular ions or ions resulting from loss of CO
(6, 7). Characteristic IR bands of the complexes containing
[M(′N2H2S3′)] cores are either one, unresolved, broad or two,
weak-to-medium ν(NH) absorptions in the region of 3290 to
3160 cm-1 (in KBr). The complexes containing [Ru(′N2HS3′)]
cores display one medium ν(NH) IR band at 3124 cm-1 (12)
or 3228 cm-1 (13). The strong ν(CO) or ν(NO) IR bands of 6
(1932 cm-1), 7 (1935 cm-1), 13 (1799 cm-1), and 14 (1856
cm-1) are suited to monitor reactions by IR spectroscopy. All
mononuclear complexes possess only C1 symmetry. This is
clearly displayed by the 13C{1H} NMR spectra. The [M(′N2HnS3′)]
cores (n ) 1 or 2) of the respective complexes give rise to 12
aromatic 13C signals in the range of 160-110 ppm and two
signals each for the N-bonded (63-44 ppm) and S-bonded (42-
31 ppm) aliphatic C atoms. The 13C{1H} NMR spectrum of
[Ru(NO)(′N2H2S3′)]BF4 (14) displays two sets of this signal
pattern, which indicates that 14 exists in two diastereomeric
forms.
Figure 2. ORTEP diagrams of (a) [Ru(PPr3)(′N2H2S3′)]‚2THF (9‚
2THF) and (b) the cation of [Ru(PPh3)(′N2H2S3′-Me2)]I2‚2CH2Cl2
(11‚2CH2Cl2) (50% probability ellipsoids; H atoms and solvate
molecules omitted).
Table 2. Selected Distances (pm) and Angles (deg) of
[Fe(′N2H2S3′)]2‚4MeOH (5‚4MeOH) and [Fe(CO)(′N2H2S3′)] (6)
5‚
5‚
4MeOH
complex 4MeOH
6
complex
6
Fe1-S1 242.7(1) 229.9(2) N1-Fe1-S1
Fe1-S2 244.7(1) 227.9(2) N1-Fe1-N2
79.79(9) 86.8(1)
94.9(1) 89.8(1)
Fe1-S3 257.2(1) 231.5(2) S2-Fe1-S3 158.70(3) 92.21(8)
Fe1-N1 225.4(3) 207.5(3) N1-Fe1-S3
Fe1-N2 232.1(3) 210.2(3) N2-Fe1-S3
79.41(8) 175.76(9)
80.37(7) 85.9(1)
Fe1-S2a 251.7(2)
Fe1-C1
N2-Fe1-S2a 88.84(8)
175.6(4) C1-Fe1-N1
93.8(2)
Table 3. Selected Distances (pm) and Angles (deg) of
[Ru(PPr3)(′N2H2S3′)]‚2THF (9‚2THF) and
[Ru(PPh3)(′N2H2S3′-Me2)]I2‚2CH2Cl2 (11‚2CH2Cl2)
9‚
11‚
9‚
2THF
11‚
2CH2Cl2
X-ray Structure Analyses of [Fe(′N2H2S3′)]2‚4MeOH (5‚
4MeOH), [Fe(CO)(′N2H2S3′)] (6), [Ru(PPr3)(′N2H2S3′)]‚2THF
(9‚2THF), and [Ru(PPh3)(′N2H2S3′-Me2)]I2‚2CH2Cl2 (11‚
2CH2Cl2). The molecular structures of four complexes could
be elucidated by X-ray structure determination. Figures 1 and
2 show views of the molecular structures, and Tables 2 and 3
list selected distances and angles.
complex 2THF 2CH2Cl2
complex
Ru1-S1 236.9(2) 233.2(2) N1-Ru1-S1 83.0(1)
Ru1-S2 236.2(2) 233.6(2) N1-Ru1-N2 90.8(2)
Ru1-S3 229.1(2) 234.3(2) N2-Ru1-P1 95.0(2)
Ru1-N1 223.2(4) 220.5(4) N1-Ru1-S3 84.4(1)
Ru1-N2 214.2(5) 213.9(5) N2-Ru1-S3 86.9(1)
83.0(1)
86.3(2)
98.4(1)
94.2(1)
83.4(1)
Ru1-P1 225.7(2) 235.6(2) S2-Ru1-S3 167.35(5) 168.12(5)
In all four complexes, the metal centers exhibit pseudo-
octahedral coordination. The ′N2H2S3′2- ligand and its ′N2H2S3′-
Me2 derivative bind to the metals in the same characteristic
fashion which combines mer and fac coordination of the donor
atoms. For the ′N2H2S3′2- ligand, cis positions of both the two
amine and the two thiolate donors result. A further result of
this coordination is that all [M(′N2S3′)] cores exhibit C1
symmetry only. Bond distances and angles show no anomalies.
The distances of 5 and 6 are typical for high-spin and low-spin
Fe(II) complexes, respectively, which contain thiolate-thio-
ether-amine ligands.5,6 They correspond with distances found
in high-spin/low-spin [Fe(L)(′NHS4′)] complexes. The low-spin
complexes always show markedly shorter distances than the
high-spin complexes. Worth being noted are the very similar
Fe-S(thiolate) and Fe-S(thioether) distances of 6, which are
found in the narrow range of 227.9(2)-231.5(2) pm. In the high-
spin Fe(II) complex 5 which possesses crystallographically
imposed inversion symmetry, Fe-S(thiolate) and Fe-S(thio-
ether) distances differ more from each other (∼15 pm). It is
also noted that the Fe1-S2a and Fe1a-S2 distances (251.7(2)
pm) in the Fe-S(thiolate)-Fe bridges are distinctly longer than
the Fe-S(thiolate) distances (242.71(12), 244.66(13) pm) within
the two [Fe(′N2H2S3′)] halves. This certainly reflects the ability
of 5 to dissociate into [Fe(′N2H2S3′)] monomers in solution.

466 Inorganic Chemistry, Vol. 38, No. 3, 1999
Sellmann et al.
The Ru-N and Ru-S distances of 9 and 11 are in the range
expected for Ru(II) complexes. The comparison of 9 with 11,
which contains only thioether S donors, shows that the Ru-S
distances do not allow an unambiguous differentiation between
Ru-S(thiolate) and Ru-S(thioether) distances. This certainly
reflects the electronic flexibility of thiolate and thioether S
donors which can exhibit σ-donor, σ-donor-π-acceptor as well
as σ-donor-π-donor properties.20 Therefore, the Ru-P distance
in 11 (235.6(2) pm), which is markedly longer than that in 9
(225.7(2) pm), may be due not only to a higher steric demand
of PPh3 vs PPr3 but also to the decreased electron density at
the ruthenium center of 11 which carries three potentially
π-accepting thioether donors.
readily loses its CO ligand though its low frequency ν(CO)
indicates strong Fe-CO π-back bonding, whereas [Fe(CO)-
(′NHS4′)] is practically inert toward loss of CO. With regard to
the labile CO binding, it was not unexpected to be found that
N2 could not be coordinated. Another important difference
between the [M(L)(′N2H2S3′)] and [M(L)(′NHS4′)] complexes
is the relatively high acidity of the (aromatic) NH functions in
the [M(L)(′N2H2S3′)] complexes. The NH acidity was proved
by H+/D+ exchange reactions and isolation of conjugate acid-
base complex couples. The NH acidity also influences the
substitution properties of the M-L bonds via intermediate
formation of amide complexes. For example, when L is a strong
electron withdrawing ligand such as NO in [Ru(NO)(′N2H2S3′)]-
BF4, one NH function is easily deprotonated by bases such as
N2H4 or by azide ions. As a consequence, the NO ligand in the
resulting [Ru(NO)(′N2HS3′)] becomes insusceptible for attack
by nucleophiles. Similar effects have been observed with Fe,
Ni, and Ru complexes which contain [M(′N2H2S2′)] fragments
(′N2H2S2′2- ) 1,2-ethanediamino-N,N′-bis(2-benzenethiolato)-
(2-)).21 The resulting coordination geometry and, in addition,
acid-base reactions of the amine functions drastically reduce
the versatility of the [Fe(′N2H2S3′)] or [Ru(′N2H2S3′)] fragments
with respect to coordination and/or substitution of small coligand
molecules. In particular, the cis coordination of the thiolate
donors in [M(′N2H2S3′)] fragments is unsuited to effect a
stabilization of the unstable diazene molecule via [M-NH-
NH-M] four-center/six-electron π bonds and tricentric N-H...
(S)2 bridges. This stabilization has been observed in complexes
such as [µ-N2H2{Fe(′NHS4′)}2]5 or [µ-N2H2{Ru(PPh3)(′S4′)}2],22
and it imperatively requires trans-thiolate donors at the metal
centers.
Conclusion
The new pentadentate ′N2H2S3′-H2 ligand has been synthe-
sized, aiming at transition metal complexes which exhibit
electron rich-metal centers, possess core configurations with
thiolate, thioether, and amine donors relating to the structures
of [Fe(′NHS4′)] fragments, and bind biologically relevant small
molecules.
The goal of increasing the electron density at the metal centers
by replacing thioether S by amine N donors in pentadentate
thiolate thioether amine ligands could be reached. This is
evidenced by the ν(CO) frequencies of [Fe(CO)(′N2H2S3′)]
(1932 cm-1) vs [Fe(CO)(′NHS4′)] (1960 cm-1). However, the
metal donor core configurations of [M(′NHS4′)] and [M(′N2H2S3′)]
complexes strongly differ. While [M(′NHS4′)] complexes exhibit
either structure A or B (cf. introduction), all [M(′N2H2S3′)]
complexes characterized so far invariably show the structure
D. A major geometric difference between these structures is
Acknowledgment. Support of this work by the Fonds der
chemischen Industrie is gratefully acknowledged.
Supporting Information Available: X-ray crystallographic data,
in CIF format, for compounds 5‚4MeOH, 6, 9‚2THF, and 11‚2CH2Cl2
are available on the Internet. Access information is given on any current
masthead page. Crystallographic data (excluding structure factors) for
the structures reported in this paper have been deposited with the
Cambridge Crystallographic Data Centre as depository nos. 104537
(5‚4MeOH), 104538 (6), 104539 (9‚2THF), and 104540 (11‚2CH2Cl2).
Copies of the data can be obtained free of charge upon application to:
The Director, CCDC, 12 Union Road, Cambridge CB2 1EZ, UK [fax:
int.code +44(1223)336-033, e-mail: deposit@chemcrys.cam.ac.uk].
IC980383Q
(21) (a) Sellmann, D.; Ka¨ppler, O. Angew. Chem. 1988, 100, 706; Angew.
Chem., Int. Ed. Engl. 1988, 27, 689. (b) Spence, J. T.; Minelli, M.;
Kroneck, P. J. Am. Chem. Soc. 1980, 102, 4538. (c) Sellmann, D.;
Ruf, R. Z. Naturforsch., B: Chem. Sci. 1993, 48B, 723. (d) Gardner,
J. K.; Pariyadath, N.; Corbin, J. L.; Stiefel, E. I. Inorg. Chem. 1978,
17, 897. (e) Sellmann, D.; Reinecke, U. J. Organomet. Chem. 1986,
314, 91. (f) Sellmann, D.; Ka¨ppler, O.; Knoch, F.; Moll, M. Z.
Naturforsch., B: Chem. Sci. 1990, 45B, 803.
the fac-fac coordination of the ′NHS4′2- ligand versus the fac-
mer coordination of the ′N2H2S3′2- ligand. This structural
difference complicates direct comparison between [M(L)-
(′NHS4′)] and [M(L)(′N2H2S3′)] complexes and may explain
some unexpected results. For example, [Fe(CO)(′N2H2S3′)]
(20) Sellmann, D.; Geck, M.; Knoch, F.; Ritter, G.; Dengler, J. J. Am. Chem.
Soc. 1991, 113, 3819.
(22) Sellmann, D.; Bo¨hlen, E.; Waeber, M.; Huttner, G.; Zsolnai, L. Angew.
Chem. 1985, 97, 984; Angew. Chem., Int. Ed. Engl. 1985, 24, 981.