Nitrosylation of Octaethylporphyrin Osmium Complexes with Alkyl Nitrites and Thionitrites: Molecular Structures of Three Osmium Porphyrin Derivatives

Article abstract of DOI:10.1021/ic9708576

(OEP)Os(CQ) reacts with n-butyl nitrite to give, after workup, the (OEP)Os(NO)(O-w-Bu) trans addition product (OEP = octaethylporphyrinato dianion). Similarly, the reaction of (OEP)Os(CO) or [(OEP)Os]₂ with isoamyl nitrite gives the correspondi

Full text of DOI:10.1021/ic9708576

Inorg. Chem. 1998, 37, 533-540
533
Nitrosylation of Octaethylporphyrin Osmium Complexes with Alkyl Nitrites and
Thionitrites: Molecular Structures of Three Osmium Porphyrin Derivatives
Li Chen, Masood A. Khan, and George B. Richter-Addo*
Department of Chemistry and Biochemistry, University of Oklahoma, 620 Parrington Oval,
Norman, Oklahoma 73019
ReceiVed July 9, 1997
(OEP)Os(CO) reacts with n-butyl nitrite to give, after workup, the (OEP)Os(NO)(O-n-Bu) trans addition product
(OEP ) octaethylporphyrinato dianion). Similarly, the reaction of (OEP)Os(CO) or [(OEP)Os]2 with isoamyl
nitrite gives the corresponding nitrosyl alkoxide, (OEP)Os(NO)(O-i-C5H11). The related reactions of (OEP)Os-
(CO) or [(OEP)Os]2 with isoamyl thionitrite gives the (OEP)Os(NO)(S-i-C5H11) nitrosyl thiolate. The reaction
of the [(OEP)Os]2(PF6)2 reagent with isoamyl thionitrite gives the nitrosylation product, [(OEP)Os(NO)]PF6, which
undergoes anion hydrolysis to give the isolable difluorophosphate (OEP)Os(NO)(O2PF2) derivative. Interestingly,
the reaction of O2NC6H4NdNSPh with [(OEP)Os]2 gives the (OEP)Os(SPh)2 product with loss of the arylazo
fragments. The solid-state structures of (OEP)Os(NO)(O-n-Bu), (OEP)Os(NO)(O2PF2), and (OEP)Os(SPh)2 have
been determined by X-ray crystallography.
Introduction
in either simple adduct formation or activation of the organic
nitroso groups to give metal nitrosyls. Of particular interest
was our report that thionitrites and isoamyl nitrite add to the
group 8 metalloporphyrins via a formal trans addition process
to give nitrosyl thiolates and alkoxides, respectively.9
Although a number of ruthenium porphyrin nitrosyls are now
known,6b,9-12 only four osmium porphyrin nitrosyls were
reported prior to our studies, namely (OEP)Os(NO)X (X ) F,
NO, OMe, OClO3; OEP ) octaethylporphyrinato dianion),13
with X-ray structural data on osmium nitrosyl porphyrins being
available only for (TTP)Os(NO)(S-i-C5H11) (TTP ) tetra-
tolylporphyrinato dianion).9b In this present paper, we report
on the extension of the reaction chemistry of osmium porphyrins
with thionitrites and alkyl nitrites. We also provide new insight
on the mode of interaction of RSNO with osmium porphyrins.
The heme unit in guanylyl cyclase is a receptor for nitric
oxide (NO).1 Reactions of NO with organic fragments to result
in nitrosation reactions in vitro and in vivo are also very
important.2,3 The interaction of NO with hemes and heme
models has also commanded renewed interest.4 It is known
that various organic nitroso (and inorganic nitrite) compounds
are capable of nitrosylating metal centers, depending on the
reaction conditions.5 We have also demonstrated that organic
nitroso compounds such as nitrosamines (N-nitroso),6 Cupferron
(N-nitroso),7 nitrosoarenes (C-nitroso),8 thionitrites (S-nitroso),
and alkyl nitrites (O-nitroso)9 interact with heme models to result
(1) (a) Deinum, G.; Stone, J. R.; Babcock, G. T.; Marletta, M. A.
Biochemistry 1996, 35, 1540. (b) Stone, J. R.; Marletta, M. A.
Biochemistry 1994, 33, 5636. (c) Dierks, E. A.; Hu, S.; Vogel, K. M.;
Yu, A. E.; Spiro, T. G.; Burstyn, J. N. J. Am. Chem. Soc. 1997, 119,
7316.
(6) (a) Yi, G.-B.; Khan, M. A.; Richter-Addo, G. B. J. Am. Chem. Soc.
1995, 117, 7850. (b) Yi, G.-B.; Khan, M. A.; Richter-Addo, G. B.
Inorg. Chem. 1996, 35, 3453.
(7) Yi, G.-B.; Khan, M. A.; Richter-Addo, G. B. Inorg. Chem. 1995, 34,
5703.
(2) (a) Stamler, J. S.; Jia, L.; Eu, J. P.; McMahon, T. J.; Demchenko, I.
T.; Bonaventura, J.; Gernet, K.; Piantadosi, C. A. Science 1997, 276,
2034 and references therein. (b) Keshive, M.; Singh, S.; Wishnok, J.
S.; Tannenbaum, S. R.; Deen, W. M. Chem. Res. Toxicol. 1996, 9,
988. (c) Park, J.-W. Biochem. Biophys. Res. Commun. 1988, 152, 916.
(d) Stamler, J. S.; Simon, D. I.; Osborne, J. A.; Mullins, M. E.; Jaraki,
O.; Michel, T.; Singel, D. J.; Loscalzo, J. Proc. Natl. Acad. Sci. U.S.A.
1992, 89, 444. (e) Stamler, J. S.; Simon, D. I.; Jaraki, O.; Osborne, J.
A.; Francis, S.; Mullins, M.; Singel, D.; Loscalzo, J. Proc. Natl. Acad.
Sci. U.S.A. 1992, 89, 8087. (f) Goldstein, S.; Czapski, G. J. Am. Chem.
Soc. 1996, 118, 3419. (g) Goldstein, S.; Czapski, G. J. Am. Chem.
Soc. 1996, 118, 6806 [erratum]. (h) Jia, L.; Bonaventura, C.;
Bonaventura, J.; Stamler, J. S. Nature 1996, 380, 221. (i) Simon, D.
I.; Mullins, M. E.; Jia, L.; Gaston, B.; Singel, D. J.; Stamler, J. S.
Proc. Natl. Acad. Sci. U.S.A. 1996, 93, 4736.
(3) Williams, D. L. H. Nitrosation; Cambridge University Press: Cam-
bridge, U.K., 1988.
(4) (a) Richter-Addo, G. B.; Legzdins, P. Metal Nitrosyls; Oxford
University Press: New York, 1992; Chapter 6. (b) Hoshino, M.;
Maeda, M.; Konishi, R.; Seki, H.; Ford, P. C. J. Am. Chem. Soc. 1996,
118, 5702.
(8) (a) Wang, L.-S.; Chen, L.; Khan, M. A.; Richter-Addo, G. B. Chem.
Commun. 1996, 323. (b) We have successfully extended N-binding
of nitrosoarenes to osmium porphyrins (manuscript in preparation)
and O-binding to manganese porphyrins: Fox, S. J. S.; Chen, L.; Khan,
M. A.; Richter-Addo, G. B. Inorg. Chem. 1997, 36, 6465.
(9) (a) Yi, G.-B.; Khan, M. A.; Richter-Addo, G. B. Chem. Commun.
1996, 2045. (b) Yi, G.-B.; Chen, L.; Khan, M. A.; Richter-Addo, G.
B. Inorg. Chem. 1997, 36, 3876.
(10) (a) Miranda, K. M.; Bu, X.; Lorkovic, I.; Ford, P. C. Inorg. Chem.
1997, 36, 4838. (b) Kadish, K. M.; Adamian, V. A.; Van Caemelbecke,
E.; Tan, Z.; Tagliatesta, P.; Bianco, P.; Boschi, T.; Yi, G.-B.; Khan,
M. A.; Richter-Addo, G. B. Inorg. Chem. 1996, 35, 1343. (c) Bohle,
D. S.; Hung, C.-H.; Powell, A. K.; Smith, B. D.; Wocaldo, S. Inorg.
Chem. 1997, 36, 1992. (d) Srivastava, T. S.; Hoffman, L.; Tsutsui,
M. J. Am. Chem. Soc. 1972, 94, 1385.
(11) (a) Hodge, S. J.; Wang, L.-S.; Khan, M. A.; Young, V. G., Jr.; Richter-
Addo, G. B. Chem. Commun. 1996, 2283. (b) Massoudipour, M.;
Pandey, K. K. Inorg. Chim. Acta 1989, 160, 115.
(12) Antipas, A.; Buchler, J. W.; Gouterman, M.; Smith, P. D. J. Am. Chem.
Soc. 1978, 100, 3015.
(13) (a) Antipas, A.; Buchler, J. W.; Gouterman, M.; Smith, P. D. J. Am.
Chem. Soc. 1980, 102, 198. (b) Buchler, J. W.; Smith, P. D. Chem.
Ber. 1976, 109, 1465.
(5) (a) Richter-Addo, G. B.; Legzdins, P. Metal Nitrosyls; Oxford
University Press: New York, 1992; Chapter 2 and references therein.
(b) Bladon, P.; Dekker, M.; Knox, G. R.; Willison, D.; Jaffari, G. A.;
Doedens, R. J.; Muir, K. W. Organometallics 1993, 12, 1725. (c)
Pandey, D. S.; Khan, M. I.; Agarwala, U. C. Indian J. Chem. 1987,
26A, 570.
S0020-1669(97)00857-4 CCC: $15.00 © 1998 American Chemical Society
Published on Web 01/14/1998

534 Inorganic Chemistry, Vol. 37, No. 3, 1998
Chen et al.
Preparation of (OEP)Os(NO)(O-i-C5H11). Method I. To a
CH2Cl2 (20 mL) solution of (OEP)Os(CO) (0.080 g, 0.107 mmol) was
added excess isoamyl nitrite (0.20 mL, 1.5 mmol). The color of the
solution changed from pink red to bright red immediately. The solution
was stirred for another 30 min. The mixture was taken to dryness in
vacuo, and the product was redissolved in a CH2Cl2/hexane (1:2)
mixture and filtered through a neutral alumina column in air. The
column was washed with more of the solvent mixture until the washings
were colorless. The filtrate was taken to dryness in vacuo, and the
product obtained was dried in vacuo for 5 h to give (OEP)Os(NO)-
(O-i-C5H11)‚0.85CH2Cl2 (0.050 g, 0.055 mmol, 51% yield). Anal. Calcd
for C41H55O2N5Os1‚0.85CH2Cl2: C, 55.10; H, 6.26; N, 7.68; Cl, 6.61.
Found: C, 54.86; H, 6.23; N, 7.74; Cl, 6.98. IR (CH2Cl2, cm-1): υNO
) 1756. IR (KBr, cm-1): υNO ) 1747 s; also 2962 w, 2928 w, 2864
w, 2020 w, 1954 w, 1794 w, 1685 w, 1560 w, 1508 w, 1465 s br,
1372 m, 1316 w, 1272 m, 1230 w, 1200 w, 1153 s, 1111 s, 1077 s,
1056 s, 1020 s, 993 m, 962 m, 856 w, 842 m, 744 s, 738 s, 717 m, 704
w, 642 w, 589 m. 1H NMR (CDCl3, δ): 10.31 (s, 4H, meso-H of
OEP), 5.27 (s, CH2Cl2), 4.15 (q, J ) 8 Hz, 16H, CH3CH2 of OEP),
1.99 (t, J ) 8 Hz, 24H, CH3CH2 of OEP), -0.70 (d, J ) 7 Hz, 6H,
(CH3)2CHCH2CH2O), -1.19 (m, 1H, (CH3)2CHCH2CH2O), -2.72 (t,
J ) 8 Hz, 2H, (CH3)2CHCH2CH2O), -3.27 (dt (app q), J ) 7/8 Hz,
2H, (CH3)2CHCH2CH2O). Low-resolution mass spectrum (FAB): m/z
841 [(OEP)Os(NO)(O-i-C5H11) + H]+ (16%), 754 [(OEP)Os(NO) +
H]+ (100%), 723 [(OEP)Os]+ (20%). UV-vis spectrum (λ (ꢀ, mM-1
cm-1), 1.29 × 10-5 M in CH2Cl2): 341 (41), 418 (102), 533 (19), 567
(30) nm.
Experimental Section
All reactions were performed under an atmosphere of prepurified
nitrogen using standard Schlenk techniques and/or in an Innovative
Technology Labmaster 100 Dry Box unless stated otherwise. Solvents
were distilled from appropriate drying agents under nitrogen just prior
to use: CH2Cl2 (CaH2), benzene (Na), hexane (Na/benzophenone/
tetraglyme), and THF (Na/benzophenone).
Chemicals. (OEP)Os(CO)14 and [(OEP)Os]2 were prepared by
15a
literature methods (OEP ) octaethylporphyrinato dianion). The known
[(OEP)Os]2(PF6)215b was prepared by AgPF6 oxidation of [(OEP)Os]2.
Isoamyl nitrite (i-C5H11ONO, 97%), and isoamyl thiol (mercaptan,
i-C5H11SH, 97%), n-butyl nitrite (95%), thiophenol (97%), AgPF6
(98%), and NOPF6 (96%) were purchased from Aldrich Chemical Co.
Chloroform-d (99.8%) was obtained from Cambridge Isotope Labo-
ratories, subjected to three freeze-pump-thaw cycles, and stored over
Linde 4 Å molecular sieves. Elemental analyses were performed by
Atlantic Microlab, Norcross, GA.
Instrumentation. Infrared spectra were recorded on a Bio-Rad FT-
155 FTIR spectrometer. 1H NMR spectra were obtained on a Varian
XL-300 spectrometer and the signals referenced to the residual signal
of the solvent employed. All coupling constants are in Hz. The 31P
NMR spectrum was recorded on a Varian 400 MHz spectrometer, and
the signals were referenced to external H3PO4. The 19F NMR spectrum
was also recorded on the same 400 MHz instrument, and the signals
referenced to external trifluoroacetic acid (δ at -79.45 ppm). FAB
mass spectra were obtained on a VG-ZAB-E mass spectrometer. UV-
vis spectra were recorded on a Hewlett-Packard HP8453 Diode Array
instrument.
Method II. To a CH2Cl2 (15 mL) solution of [(OEP)Os]2 (0.030 g,
0.021 mmol) was added excess isoamyl nitrite (0.10 mL, 0.75 mmol).
The color of the solution changed from brown to bright red immediately.
The mixture was left to stir for another 3 h. The mixture was taken to
dryness, and the residue was redissolved in CH2Cl2/hexane (1:2) and
filtered over a neutral alumina column in air. The column was washed
with more of the solvent mixture until the washings were colorless.
The filtrate was taken to dryness in vacuo, and the residue was dried
in vacuo for 3 h to give (OEP)Os(NO)(O-i-C5H11) in 29% isolated yield.
Preparation of (OEP)Os(NO)(S-i-C5H11). Method I. To a CH2Cl2
(20 mL) solution of (OEP)Os(CO) (0.080 g, 0.107 mmol) was added
excess isoamyl thionitrite (ca. 1 mmol). The color of the solution
changed gradually from pink red to bright red over a period of 1 h.
The mixture was left to stir for another 4 h. The mixture was taken to
dryness, and the residue was redissolved in CH2Cl2/hexane (1:2) and
filtered over a neutral alumina column in air. The column was washed
with more of the solvent mixture until the washings were colorless.
The filtrate was taken to dryness in vacuo, and the residue was dried
in vacuo for 5 h to give (OEP)Os(NO)(S-i-C5H11)‚0.3CH2Cl2 (0.031
g, 0.035 mmol, 33% yield). Anal. Calcd for C41H55O1S1N5Os1‚
0.3CH2Cl2: C, 56.26; H, 6.36; N, 7.94; Cl, 2.41; S, 3.64. Found: C,
56.12; H, 6.39; N, 7.80; Cl, 2.58; S, 3.55. IR (CH2Cl2, cm-1): υNO
1757. IR (KBr, cm-1): υNO ) 1751 s; also 2964 w, 2932 w, 2870 w,
1467 m, 1450 m, 1373 w, 1316 w, 1271 m, 1229 w, 1154 m, 1110 w,
1057 m, 1020 m, 993 m, 962 m, 843 m, 746 m, 729 m, 717 w. 1H
NMR (CDCl3, δ): 10.29 (s, 4H, meso-H of OEP), 5.28 (s, CH2Cl2),
4.14 (q br, 16H, CH3CH2 of OEP), 1.99 (t, J ) 8 Hz, 24H, CH3CH2 of
OEP), -0.35 (d, J ) 6 Hz, 6H, (CH3)2CHCH2CH2S), -0.43 (m, 1H,
(CH3)2CHCH2CH2S), -1.92 (dt (app q), J ) 6/8 Hz, 2H, (CH3)2CHCH2-
CH2S), -3.26 (t, J ) 8 Hz, 2H, (CH3)2CHCH2CH2S). Low-resolution
mass spectrum (FAB): m/z 856 [(OEP)Os(NO)(S-i-C5H11)]+ (2%), 827
[(OEP)Os(S-i-C5H11) + H]+ (7%), 754 [(OEP)Os(NO) + H]+ (96%),
724 [(OEP)Os + H]+ (28%). UV-vis spectrum (λ (ꢀ, mM-1 cm-1),
1.18 × 10-5 M in CH2Cl2): 354 (69), 441 (38), 551 (15), 584 (11)
nm.
Preparation of Thionitrites. The preparation of thionitrites (i-
C5H11SNO and PhSNO) follows established routes from their precursor
thiols.16 The preparation of PhSNO was performed at low temperature,
since this thionitrite decomposes at room temperature in solution.
Preparation of (OEP)Os(NO)(O-n-Bu). To a CH2Cl2 (20 mL)
solution of (OEP)Os(CO) (0.075 g, 0.100 mmol) was added excess
n-butyl nitrite (0.4 mL, 3 mmol). The color of the solution changed
from pink red to bright red immediately. The mixture was left to stir
for 40 min. The mixture was taken to dryness, and the residue was
redissolved in CH2Cl2. The solvent was allowed to evaporate under
inert atmosphere to generate a crystalline solid residue. The resulting
crystals were washed with hexane to remove a green-colored compo-
nent, and the remaining solid was redissolved in CH2Cl2/hexane (1:2)
and filtered over a neutral alumina column in air. The column was
washed with more of the solvent mixture and then with CH2Cl2 until
the washings were colorless. The filtrate was taken to dryness in vacuo,
and the residue was dried in vacuo for 5 h to give (OEP)Os(NO)(O-
n-Bu)‚1.4CH2Cl2 (0.055 g, 0.058 mmol, 58% yield). Anal. Calcd for
.
C40H53O2N5Os1 1.4CH2Cl2: C, 52.62; H, 5.95; N, 7.41; Cl, 10.50.
Found: C, 52.32; H, 5.83; N, 7.56; Cl, 10.60. IR (CH2Cl2, cm-1):
υNO ) 1757. IR (KBr, cm-1): υNO ) 1743 s; also 2962 w, 2931 w,
2868 w, 1790 w, 1467 m, 1451 m, 1372 m, 1316 w, 1274 m, 1263 m,
1230 w, 1155 m, 1111 w, 1077 w, 1056 m, 1021 m, 993 m, 963 m,
860 w, 843 m, 764 w, 746 s, 718 w, 705 w, 596 m br. 1H NMR
(CDCl3, δ): 10.32 (s, 4H, meso-H of OEP), 5.27 (s, CH2Cl2), 4.16 (q,
J ) 8 Hz, 16H, CH3CH2 of OEP), 2.00 (t, J ) 8 Hz, 24H, CH3CH2 of
OEP), -0.55 (t, J ) 7 Hz, 3H, CH3CH2CH2CH2O), -1.53 (m (qt), J
) 7/8 Hz, 2H, CH3CH2CH2CH2O), -2.73 (t, J ) 7 Hz, 2H, CH3CH2-
CH2CH2O), -3.04 (m (tt), J ) 8/7 Hz, 2H, CH3CH2CH2CH2O). Low-
resolution mass spectrum (FAB): m/z 827 [(OEP)Os(NO)(OC4H9) +
H]+ (17%), 754 [(OEP)Os(NO) + H]+ (100%), 723 [(OEP)Os]+ (23%).
UV-vis spectrum (λ (ꢀ, mM-1 cm-1), 1.31 × 10-5 M in CH2Cl2): 342
(40), 418 (91), 533 (17), 567 (26) nm.
Method II. To a CH2Cl2 (15 mL) solution of [(OEP)Os]2 (0.030 g,
0.021 mmol) was added excess isoamyl thionitrite (ca. 0.7 mmol). The
color of the solution changed from brown to bright red immediately.
The mixture was left to stir for another 5 h. The mixture was taken to
dryness, and the residue was redissolved in CH2Cl2/hexane (1:2) and
filtered over a neutral alumina column in air. The column was washed
with more of the solvent mixture until the washings were colorless.
The filtrate was taken to dryness in vacuo, and the residue was dried
in vacuo for 3 h to give (OEP)Os(NO)(S-i-C5H11) in 33% isolated yield.
(14) Che, C.-M.; Poon, C.-K.; Chung, W.-C.; Gray, H. B. Inorg. Chem.
1985, 24, 1277.
(15) (a) Collman, J. P.; Barnes, C. E.; Woo, L. K. Proc. Natl. Acad. Sci.
U.S.A. 1983, 80, 7684. (b) Collman, J. P.; Prodolliet, J. W.; Leidner,
C. R. J. Am. Chem. Soc. 1986, 108, 2916.
(16) (a) Roy, B.; d’Hardemare, A. du M.; Fontecave, M. J. Org. Chem.
1994, 59, 7019. (b) Oae, S.; Shinhama, K.; Fujimori, K.; Kim, Y. H.
Bull. Chem. Soc. Jpn. 1980, 53, 775. (c) Oae, S.; Kim, Y. H.;
Fukushima, D.; Shinhama, K. J. Chem. Soc., Perkin Trans. 1, 1978,
913.

Structures of Three Osmium Porphyrin Derivatives
Inorganic Chemistry, Vol. 37, No. 3, 1998 535
Reaction of [(OEP)Os]2(PF6)2 with Isoamyl Thionitrite. To a
CH2Cl2 (20 mL) solution of [(OEP)Os]2(PF6)2 (0.040 g, 0.023 mmol)
was added excess isoamyl thionitrite (ca. 1.5 mmol). The color of the
solution changed from brown to red. A solution IR spectrum of the
reaction mixture after 10 min revealed the quantitative conversion of
[(OEP)Os]2(PF6)2 to [(OEP)Os(NO)]PF6, indicated by the presence of
a new band at 1829 cm-1 assigned to υNO and a band at 847 cm-1
discarded. A red fraction was then eluted with CH2Cl2. All the solvent
was removed from this elute, and the resulting solid was dried in vacuo
for 5 h to give (OEP)Os(NO)(SPh)‚0.65CH2Cl2 (0.035 g, 0.038 mmol,
45% yield). Anal. Calcd for C42H49N5O1S1Os1‚0.65CH2Cl2: C, 55.84;
H, 5.53; N, 7.63; Cl, 5.02; S, 3.49. Found: C, 56.49; H, 5.69; N,
7.64; Cl, 5.39; S, 3.47. IR (CH2Cl2, cm-1): υNO ) 1766. IR (KBr,
cm-1): υNO ) 1749 s; also 2966 w, 2932 w, 2870 w, 1578 w, 1470 m,
1451 m, 1375 w, 1315 w, 1265 m, 1230 vw, 1154 m, 1111 w, 1057
assigned to υPF . The reaction mixture was stirred for an additional 20
6
1
min, and the mixture was taken to dryness. An IR spectrum of the
residue (as a KBr pellet) at this stage showed the presence of noticeable
bands at 1816 and 1787 cm-1 and also at 840 cm-1. Exposure of the
solid to air for 30 h resulted in the formation of only one υNO band at
m, 1021 m, 994 m, 963 m, 867 vw, 843 m, 740 m, 702 w, 689 w. H
NMR (CDCl3, δ): 10.20 (s, 4H, meso-H of OEP), 6.25 (t, J ) 7 Hz,
1H, p-H of SPh), 5.84 (t, J ) 7 Hz, 2H, m-H of SPh), 5.28 (s, CH2Cl2),
4.12 (q, J ) 8 Hz, 16H, CH3CH2 of OEP), 2.82 (d, J ) 7 Hz, 2H, o-H
of SPh), 1.99 (t, J ) 8 Hz, 24H, CH3CH2 of OEP). Low-resolution
mass spectrum (FAB): m/z 862 [(OEP)Os(NO)(SPh)]+ (5%), 833
[(OEP)Os(SPh) + H]+ (23%), 754 [(OEP)Os(NO) + H]+ (100%), 724
[(OEP)Os + H]+ (23%). UV-vis spectrum (λ (ꢀ, mM-1 cm-1), 1.40
× 10-5 M in CH2Cl2): 363 (58), 451 (25), 555 (12), 589 (8) nm.
Structural Determinations by X-ray Crystallography. All crystal
data were collected on a Siemens P4 diffractometer with Mo KR
radiation (λ ) 0.710 73 Å). The structures were solved using the
SHELXTL (Siemens) system and refined by full-matrix least squares
on F 2 using all reflections (SHELXL-93). The data were corrected
for Lorentz and polarization effects, and empirical absorption corrections
based on ψ scans were applied. Hydrogen atoms were included in the
idealized positions. Thermal ellipsoid plots are drawn at 50% prob-
ability. Details of crystal data and refinement are given in Table 1,
and selected bond lengths and angles are collected in Tables 2 and 3.
(i) (OEP)Os(NO)(O-n-Bu). A suitable crystal was grown by slow
evaporation of a CH2Cl2 solution of the compound. Data suggested
the choice of the two space groups P2/n and Pn. The structure solution
and refinement was tried in both space groups. Best refinement was
obtained in the noncentric space group Pn using a model involving
racemic twinning. The racemic twinning which affects mainly the axial
NO, OBu, and the CH2Cl2 solvent molecule results in limiting the
accuracy of the positional and displacement parameters of these atoms.
Hence, the accuracy of the bond lengths, particularly involving the OBu
group, is of poor quality.
1808 cm-1. The peak at 840 cm-1 assigned to υPF also disappeared.
6
Crystallization by slow solvent evaporation of a CH2Cl2 solution of
the solid gives (OEP)Os(NO)(O2PF2), which was identified by X-ray
diffraction (see later).
Alternate Preparation of (OEP)Os(NO)(O2PF2). (OEP)Os(CO)
(0.060 g, 0.080 mmol) and NOPF6 (0.015 g, 96%, 0.082 mmol) were
dissolved in CH2Cl2 (20 mL). A solution IR spectrum of the reaction
mixture showed the disappearance of the starting (OEP)Os(CO) (υCO
) 1883 cm-1) and the formation of [(OEP)Os(NO)]PF6 (υNO ) 1833
cm-1; υPF ) 848 cm-1). The mixture was left to stir for 40 min and
6
then exposed to air for 3 days. The mixture was then filtered through
a neutral alumina column in air with CH2Cl2 as eluent to remove
presumably [(OEP)Os(NO)(H2O)]PF6. All the solvent was removed
from the filtrate thus obtained, and the resulting solid was dried in
vacuo overnight to give (OEP)Os(NO)(O2PF2) (0.019 g, 0.022 mmol,
28% yield). A sample for elemental analyses was obtained from
crystallization of a CH2Cl2/hexane solution by slow evaporation of the
solvent mixture at room temperature and dried in vacuo for 5 h. Anal.
Calcd for C36H44O3P1F2N5Os1‚0.2hexane: C, 51.29; H, 5.41; N, 8.04.
Found: C, 51.58; H, 5.41; N, 7.92. IR (CH2Cl2, cm-1): υNO ) 1820.
IR (KBr, cm-1): υNO ) 1808 s; also 2969 w, 2932 w, 2872 w, 1464
w, 1451 w, 1383 w, 1374 w, 1324 s, 1275 w, 1260 w, 1229 w, 1156
m, 1116 m, 1105 m, 1058 m, 1022 m, 996 m, 964 m, 887 m, 856 m,
847 m. 1H NMR (CDCl3, δ): 10.47 (s, 4H, meso-H of OEP), 4.20 (q,
J ) 8 Hz, 16H, CH3CH2 of OEP), 2.01 (t, J ) 8 Hz, 24H, CH3CH2 of
OEP), 1.25 (hexane). 31P NMR (CDCl3, 400 MHz, δ): -27.85 (t, J
P-F ) 985). 19F NMR (CDCl3, 400 MHz, δ): -89.49 (d, J P-F ) 985).
Low-resolution mass spectrum (FAB): m/z 855 [(OEP)Os(NO)(O2PF2)
+ H]+ (11%), 754 [(OEP)Os(NO) + H]+ (13%). UV-vis spectrum
(λ (ꢀ, mM-1 cm-1), 1.66 × 10-5 M in benzene): 347 (42), 374 (44),
421 (62), 539 (14), 575 (24) nm.
Preparation of (OEP)Os(SPh)2.17 To a CH2Cl2 (20 mL) solution
of [(OEP)Os]2 (0.040 g, 0.028 mmol) was added O2NC6H4NdNSPh18
(0.030 g, 0.116 mmol). Effervescence (a white smoke) was seen right
after mixing the reagents. The color of the solution changed from
brown to purple over a 1 h period. The mixture was left to stir for
another 1 h. All the solvent was then removed, the residue was
redissolved in a benzene/hexane mixture (1:5), and the product was
purified by neutral alumina column chromatography in air. Elution
with hexane and then benzene/hexane (1:5) produced a yellow band
(presumably unreacted ligand), which was discarded. Further elution
with CH2Cl2/hexane (1:3) produced a purple band, which was collected.
The solvent was removed from the purple solution, and the product
was dried in vacuo for 5 h to give the known (OEP)Os(SPh)2 (0.022 g,
0.023 mmol, 41% yield)17 which was identified by 1H NMR spectros-
copy and by X-ray crystallography. IR (KBr, cm-1): 2964 w, 2931
w, 2865 w, 1725 w, 1576 w, 1536 w, 1470 m, 1447 m, 1436 w, 1372
w, 1316 w, 1266 m, 1226 w, 1149 m, 1111 w, 1084 w, 1056 m, 1020
s, 992 m, 961 m, 924 w, 865 w, 842 m, 740 s, 719 w, 700 w, 686 m.
Preparation of (OEP)Os(NO)(SPh). To a CH2Cl2 solution of
(OEP)Os(CO) (0.064 g, 0.085 mmol) was added excess freshly prepared
PhSNO (ca. 3 mmol), and the reaction was left to stir for 90 min. The
mixture was taken to dryness in vacuo, and the residue was redissolved
in benzene and purified by chromatography using a neutral alumina
column under N2 with benzene as first eluent. The green elute was
(ii) (OEP)Os(NO)(O2PF2). A suitable crystal was grown from a
saturated solution of [(OEP)Os]2(PF6)2 and isoamyl thionitrite in CH2Cl2
left under nitrogen for 25 days, followed by slow evaporation of the
solution in the dry box for 2 days.
(iii) (OEP)Os(SPh2). A suitable crystal was obtained by slow
evaporation of CH2Cl2/toluene solution of the compound at room
temperature under inert atmosphere. Hydrogen atoms were included
in the idealized positions. The molecule is situated on a crystallographic
center of symmetry, with only half of the molecule being unique, and
the Os atom is situated at the center of symmetry.
Results and Discussion
We have previously reported that isoamyl nitrite and thio-
nitrites add to metalloporphyrins of the group 8 metals.9 The
reaction of (OEP)Os(CO) with n-butyl nitrite in CH2Cl2 at room
temperature gives, after workup, the (OEP)Os(NO)(O-n-C4H9)
trans addition product in 58% yield (eq 1).
(OEP)Os(CO) + n-C4H9ONO f
(OEP)Os(NO)(O-n-C4H9) (1)
This red nitrosyl alkoxide product is moderately air-stable,
showing no signs of decomposition for at least 8 h in solution
and several days in the solid state. The product is freely soluble
in CH2Cl2 but is only slightly soluble in hexane. The 1H NMR
spectrum of the complex in CDCl3 shows the expected peaks
for the OEP and n-butyl groups. The IR spectrum of the
complex (as a KBr pellet) shows a band at 1743 cm-1 assigned
to υNO. The value of υNO is consistent with this {Os(NO)}6
complex having a linear Os-NO linkage according to the
(17) Che, C.-M.; Leung, W.-H.; Chung, W.-C. Inorg. Chem. 1990, 29, 1841.
(18) Sakla, A. B.; Masoud, N. K.; Sawiris, Z.; Ebaid, W. S. HelV. Chim.
Acta 1974, 57, 481.

536 Inorganic Chemistry, Vol. 37, No. 3, 1998
Table 1. Crystal Data and Structure Refinement
Chen et al.
(OEP)Os(NO)(O-n-Bu)‚CH2Cl2
C41H55N5O2Cl2Os
911.00
(OEP)Os(NO)(O2PF2)
C36H44N5O3F2POs
853.93
(OEP)Os(SPh)2
C48H54N4S2Os
941.27
188(2)
empirical formula
fw
T, K
188(2)
188(2)
crystal system
space group
unit cell dimensions
monoclinic
Pn
triclinic
P1h
monoclinic
P21/c
a ) 12.572(1) Å, R ) 90°
b ) 8.497(1) Å, â ) 103.21(3)°
c ) 19.664(2) Å, γ ) 90°
2045.0(4) Å3, 2
1.529
3.259
956
a ) 8.3335(6) Å, R ) 90°
b ) 10.4951(6) Å, â ) 91.052(5)°
c ) 22.846(2) Å, γ ) 90°
1997.8(2) Å3, 2
1.514
a ) 10.232(2) Å, R ) 98.90(2)°
b ) 10.928(3) Å, â ) 95.76(2)°
c ) 15.994(4) Å, γ ) 97.71(2)°
1737.4(7) Å3, 2
1.632
V, Z
D(calcd), g/cm3
absorption coefficient, mm-1
F(000)
3.366
924
3.770
856
crystal size
θ range for data collection
index ranges
0.22 × 0.36 × 0.42 mm
0.12 × 0.22 × 0.26 mm
0.09 × 0.23 × 0.28 mm
1.78-29.73°
1.91-25.00°
2.13-25.97°
-1 e h e 9, -14 e k e 12,
-27 e l e 27
7426
3798 [R(int) ) 0.0371]
3778/303/462
0 e h e 12, -12 e k e 12,
-19 e l e 18
6466
6087 [R(int) ) 0.0349]
6073/0/442
0 e h e 14, 0 e k e 10,
-23 e l e 23
3790
3600 [R(int) ) 0.0284]
3599/0/250
no. of reflections collected
no. of independent reflections
no. of data/restraints/parameters
goodness-of-fit on F2
1.075
1.066
1.043
final R indices [I > 2σ(I)]a,b
R1 ) 0.0415, wR2 ) 0.1044
R1 ) 0.0469, wR2 ) 0.1251
2.665 and -1.392 e Å-3
R1 ) 0.0443, wR2 ) 0.1070
R1 ) 0.0596, wR2 ) 0.1223
1.583 and -1.547 e Å-3
R1 ) 0.0337, wR2 ) 0.0783
R1 ) 0.0517, wR2 ) 0.0881
1.378 and -1.590 e Å-3
R indices (all data)a,b
largest diff. peak and hole
a R1 ) ∑||Fo| - |Fc||/∑|Fo|. b wR2 ) {∑[w(Fo - Fc2)2]/∑[wFo ]}1/2
.
2
4
Table 2. Structural Parameters (in Å and deg) for Osmium Nitrosyl Complexesa
coord. no.
M-N(O)
N-O
M-N-O
ref
(OEP)Os(NO)(O-n-Bu)
(OEP)Os(NO)(O2PF2)
(TTP)Os(NO)(S-i-C5H11)
6
6
6
6
6
6
6
6
6
6
5
6
6
5
5
1.833(8)
1.711(6)
2.041(7)
1.747(11)
1.726(7)
1.741(9)
1.704(14)
1.733(6)
1.717(8)
1.706(9)
1.93(1)b
1.712(22)
1.837(10)
1.89(2)
1.173(11)
1.179(8)
1.086(10)
1.17(2)
1.209(9)
1.175(12)
1.188(19)
1.106(8)
1.16(1)
172.8(8)
174.3(6)
172.0(9)
179.8(15)
176.1(6)
180.0
176.6(10)
174.4(5)
179.2(8)
174.7
155.4(2)
174.3(29)
177.3(8)
177(2)
this work
this work
9b
22
23
24
25
26
27
28a
28b
29
29
30
[(η5-C5H5)Os(NO)(PMe3)2](PF6)2
Os(NO)(η2-O,O-ONdC(O)CF3)(O2CCF3)(PPh3)2
Os(NO)(Cl)2(CF3)(PPh3)2
trans-[Os(NO)(tpy)(Cl)2]BF4
Os(NO)(Cl)2(η1-CHdCdCPh2)(PiPr3)2
[(DMSO)2H][Os(NO)(DMSO)(Cl)4]
Os(NO){η2-C,O-CH2CH2S(O)NSO2tol}(Cl)(PPh3)2
Os(NO)(dCH2)(Cl)(PPh3)2
1.179
0.915b
Os(NO)Br3(Et2S)(Et2SO)
Os(NO)Cl2(OCH2CH2OMe)(PPhEt2)2
[MePPh3][Os(NO)(Cl)4]
1.148(31)
1.098(14)
0.90(3)
[Os(NO)2(OH)(PPh3)2]PF6
1.63(1)
1.24(2)
178(1)
134(1)
31
1.86(1)b
1.17(2)b
a All of these complexes appear to contain OsII, with the exception of [(DMSO)2H][Os(NO)(DMSO)(Cl)4] which contains OsIII. b Bent NO.
Enemark-Feltham notation.19 The related (OEP)Os(NO)-
(OMe)13b (υNO ) 1745 cm-1, KBr) was prepared previously
by a different route: via the formation of the dinitrosyl (OEP)-
Os(NO)2 intermediate obtained from the reaction of (OEP)Os-
(CO)(py) in CH2Cl2 with NO gas, in the presence of methanol.
The linearity of the Os-NO linkage was confirmed by a
single-crystal X-ray crystallographic analysis of a suitable crystal
of the compound (Figure 1) grown by slow evaporation of a
CH2Cl2 solution of the complex at room temperature under
nitrogen.
range seen for other Os alkoxides.21 The butoxide carbon C37
nearly eclipses a porphyrin nitrogen, with a N2-Os-O2-C37
torsion angle of 18.4°.
The related reaction of (OEP)Os(CO) with isoamyl nitrite
gives (OEP)Os(NO)(O-i-C5H11) in 51% isolated yield. To
determine whether the presence of the carbonyl ligand in
(OEP)Os(CO) was needed for the activation of the organic
nitrites (RONO), we employed the non-carbonyl-containing
[(OEP)Os]2 as a reagent in this reaction. Interestingly, the same
trans-addition product is also obtained from the reaction of
The Os-N(O) and N-O bond lengths are 1.833(8) and
1.173(11) Å, respectively, and the Os-N-O bond angle is
172.8(8)°. The average Os-N(porphyrin) bond length is 2.056
Å. These data are compared with those for other structurally
characterized Os nitrosyls and porphyrins in Tables 2 and 3.
The axial Os-O distance of 1.877(7) Å appears short20 relative
to the 1.909(4)-2.200(7) Å previously observed for Os alkox-
ides;21 however, it is longer than that expected for an OsdO
bond in porphyrins (Table 3, bottom). The Os-O-C alkoxide
bond angle of 130.8(9)° falls within the 123.1(2)-133.8(8)°
(20) As indicated in the Experimental Section, the OBu and NO groups
are affected by “racemic twinning” (SHELXL-93), which causes the
NO and OBu groups to be disordered. This causes a problem in
accurately determining the position of the O atom of the OBu group
because of its correlation with the N atom of the NO group. Hence,
the short Os-O contact should be treated with caution due to the
limited accuracy of this bond length.
(21) For structurally characterized Os alkoxides, see: (a) Cheng, W.-K.;
Wong, K.-Y.; Tong, W.-F.; Lai, T.-F.; Che, C.-M. J. Chem. Soc.,
Dalton Trans. 1992, 91. (b) Masuda, H.; Taga, T.; Osaki, K.; Sugimoto,
H.; Mori, M. Bull. Chem. Soc. Jpn. 1984, 57, 2345. (c) Hinckley, C.
C.; Ali, I. A.; Robinson, P. D. Acta Crystallogr. 1990, C46, 697. (d)
Reference 29. (e) Reference 36.
(19) Feltham, R. D.; Enemark, J. H. Topics Stereochem. 1981, 12, 155.

Structures of Three Osmium Porphyrin Derivatives
Inorganic Chemistry, Vol. 37, No. 3, 1998 537
Table 3. Structurally Characterized Monometallic Osmium Porphyrins with O- and S-Donor Ligands32
metal
compound
oxidation state
Os-Np (Å)
Os-X (Å) (axial)
Os-X-Y (°)
ref
nitrosyl
(OEP)Os(NO)(O-n-Bu)
(OEP)Os(NO)(O2PF2)
(TTP)Os(NO)(S-i-C5H11)
II
II
II
1.986(9), 2.078(8)
2.051(7), 2.109(8)
2.060(6), 2.053(5)
2.065(6), 2.067(6)
2.035(5), 2.074(8)
2.076(9), 2.049(6)
1.877(7)
2.046(5)
2.209(3)
130.8(9)
138.7(3)
111.8(5)
this work
this work
9b
non-nitrosyl
(OEP)Os(OPPh3)2
(OEP)Os(PMS)2
II
II
2.031(8), 2.027(8)
2.057(5), 2.044(5)
2.036(7)
2.352(2)
154.2(5)
110.3(3)
110.4(3)
109.94(20)
109.81(21)
110.9(2)
107.8(3)
33
34
a
a
[(OEP)Os(PMS)2]PF6
III
2.047(4), 2.044(4)
2.382(2)
34
(OEP)Os(SPh)2
(TTP)Os(SC6F4H)2
(TPP)Os(OR)2
R ) Et
R ) i-Pr
R ) Ph
(OEP)Os(O)2
(TTP)Os(O)2
IV
IV
IV
2.047(4), 2.050(4)
2.041(6), 2.057(6)
2.295(1)
2.294(3)
this work
35
36
2.046(5), 2.038(5)
2.042(3), 2.040(3)
2.042(3), 2.038(2)
2.052(6)
1.915(4)
1.909(4)
1.938(2)
1.745(5)
1.743(3)
128.2(5)
127.0(3)
127.5(2)
VI
VI
37
38
2.065(4), 2.067(4)
a Data from Supporting Information.
[(OEP)Os]2 with isoamyl nitrite (eq 2).
[(OEP)Os]2 + i-C5H11ONO f
2(OEP)Os(NO)(O-i-C5H11) (2)
The red (OEP)Os(NO)(O-i-C5H11) product has similar solubility
properties as the n-butyl analogue (eq 1). The υNO of 1747
cm-1 is similar to the n-butyl analogue (1743 cm-1) but is 23
cm-1 lower than the related and previously reported (TTP)Os-
(NO)(O-i-C5H11) complex (1770 cm-1).9b The UV-vis spectra
of (OEP)Os(NO)(O-n-C4H9) and (OEP)Os(NO)(O-i-C5H11) are
almost identical with that of (OEP)Os(NO)(OMe),12 which has
been described as a hypso/hyper type. Importantly, the success
of eq 2 implies that the presence of the carbonyl ligand in eq 1
is not required for the activation of the RONO group toward
formal trans addition across the metal center.
Figure 1. Molecular structure of (OEP)Os(NO)(O-n-Bu).
The red isoamyl thiolate analogue, (OEP)Os(NO)(S-i-C5H11),
is also prepared by thionitrite addition to (OEP)Os(CO) or
[(OEP)Os]2 in 33% nonoptimized yields (eqs 3 and 4).
observation (by IR spectroscopy) of the cationic [(OEP)Os(NO)]-
PF6 complex (υNO ) 1829 cm-1, υPF ) 847 cm-1), which
6
subsequently underwent anion hydrolysis by adventitious mois-
ture upon attempted crystallization to give the isolable di-
fluorophosphate (OEP)Os(NO)(O2PF2) derivative (Scheme 1).
Our attempts to isolate [(OEP)Os(NO)]PF6 have not been
successful, although the related [(OEP)Ru(NO)(H2O)]BF4 has
been prepared and structurally characterized by us previously.6b
(OEP)Os(CO) + i-C5H11SNO f
(OEP)Os(NO)(S-i-C5H11) (3)
[(OEP)Os]2 + i-C5H11SNO f
2(OEP)Os(NO)(S-i-C5H11) (4)
Scheme 1
[(OEP)Os]2(PF6)2 + i-C5H11SNO f
This nitrosyl thiolate is also freely soluble in CH2Cl2 but only
slightly soluble in hexane. It also shows no sign of decomposi-
tion in air (as judged by H NMR and IR spectroscopy) for at
2[(OEP)Os(NO)]PF6 f 2(OEP)Os(NO)(O2PF2)
1
least 5 h in solution or after several days in the solid state. The
The hydrolysis of the PF6 anion is a common feature in
coordination chemistry39,40 and is known to occur even in AgPF6
υ
NO of 1751 cm-1 is only 4 cm-1 higher than that of the alkoxide
analogue (eq 2), although their υNO’s in CH2Cl2 solution are
identical.
(22) Bruce, M. I.; Tomkins, B.; Wong, F. S.; Skelton, B. W.; White, A. H.
J. Chem. Soc., Dalton Trans. 1982, 687.
(23) Boyar, E. B.; Dobson, A.; Robinson, S. D.; Haymore, B. L.; Huffman,
J. C. J. Chem. Soc., Dalton Trans. 1985, 621.
(24) Clark, G. R.; Greene, T. R.; Roper, W. R. Aust. J. Chem. 1986, 39,
1315.
(25) Williams, D. S.; Meyer, T. J.; White, P. S. J. Am. Chem. Soc. 1995,
117, 823.
(26) Werner, H.; Flu¨gel, R.; Windmu¨ller, B.; Michenfelder, A.; Wolf, J.
Organometallics 1995, 14, 612.
We were interested in extending the thionitrite addition
chemistry to OsIII porphyrins. Interestingly, although isoamyl
thionitrite will add trans to OsII to give isolable nitrosyl thiolate
products (as shown in eqs 3 and 4), we were only able to isolate
nitrosyl adducts from the reaction with OsIII with no thiolate or
thiol ligands present. For example, the reaction of [(OEP)-
OsIII]2(PF6)2 with isoamyl thionitrite in CH2Cl2 resulted in the

538 Inorganic Chemistry, Vol. 37, No. 3, 1998
Chen et al.
(which we used to prepare the [(OEP)OsIII]2(PF6)2 reagent).41
In our case, neither the AgPF6 nor the [(OEP)Os]2(PF6)2 salts
contained the difluorophosphate group (by IR spectroscopy).
Indeed, we synthesized [(OEP)Os(NO)]PF6 independently by
reacting (OEP)Os(CO) with NOPF6.42 Exposure of this product
in solution to air also transforms it to (OEP)Os(NO)(O2PF2).
Not surprisingly, the red (OEP)Os(NO)(O2PF2) product is air-
stable. The υNO of 1808 cm-1 (KBr) is higher than those
displayed by the related osmium nitrosyl alkoxide or thiolate
complexes. The IR spectrum also contains bands attributable
to a monodentate difluorophosphate group (υPF ) 887 (υas)
2
and 856 (υs) cm-1; υPO ) 1324 cm-1).43,44 A porphyrin band
2
at 1156 cm-1 probably obscures the expected υs (PO2) A1 band
of the O2PF2 anion.43 The locations of these bands are similar
to those for other monodentate difluorophosphate groups in
structurally characterized iridium39 and palladium41 and other
η1-difluorophosphate complexes.45,46 The 31P NMR (-27.85
ppm, triplet) and 19F NMR spectra (-89.49 ppm, doublet) are
also consistent with the presence of the monodentate difluoro-
phosphate group. The JP-F coupling constant of 985 Hz is
within the range commonly found for difluorophosphoric acid
and its salts.41,50 Not surprisingly, the UV-vis spectrum of
(OEP)Os(NO)(O2PF2) is similar to that of (OEP)Os(NO)-
(OClO3).13a
Figure 2. Molecular structure of (OEP)Os(NO)(O2PF2).
plexes, with the possible exception of the (OEPMe2)Os(CO)-
(py) derivative (2.069(3) and 2.065(3) Å).32b The Os atom is
displaced by 0.16 Å from the four-nitrogen porphyrin plane
toward the NO ligand, and the Os-O(difluorophosphate) bond
length of 2.046(5) Å is longer than that of (OEP)Os(NO)(O-
n-Bu) described earlier but is similar to the Os-O bond lengths
of the only other structurally characterized OsII porphyrin
complex containing axial Os-O bonds, namely, (OEP)Os-
(OPPh3)2 (2.036(7) Å). It is also longer than the observed axial
Os-O bonds for the structurally characterized OsIV porphyrin
alkoxides (1.909-1.938 Å) or OsVI porphyrin dioxo derivatives
(1.74 Å) (Table 3). The Os-N-O bond is essentially linear
with a bond angle of 174.3(6)°. The O-P-O bond angle of
118.4(4)° is larger than the F-P-F angle of 101.1(4)°, and this
observation is not uncommon for transition metal difluorophos-
phate complexes (Table 4). The difluorophosphate P atom
essentially eclipses a porphyrin nitrogen, with the N4-Os-
O2-P1 torsion angle of 10.3°. Importantly, although the
difluorophosphate anion forms complexes with other transition
metals,39-41,49,51 main group metals,47,48,52,53 the ammonium
cation,54 and even the nitrosonium cation,55 to the best of our
knowledge this is the first reported example of a metallo-
porphyrin difluorophosphate derivative.
The molecular structure of (OEP)Os(NO)(O2PF2) is shown
in Figure 2, and selected bond lengths and angles are listed in
Tables 2-4. The Os-N(por) bond length of 2.06 Å (av)
appears longer than those observed for other (OEP)OsII com-
(27) Rudnitskaya, O. V.; Buslaeva, T. M.; Stash, A. I.; Kisin, A. V. Russ.
J. Coord. Chem. 1995, 21, 136.
(28) (a) Herberhold, M.; Hill, A. F.; Clark, G. R.; Rickard, C. E. F.; Roper,
W. R.; Wright, A. H. Organometallics 1989, 8, 2483. (b) Hill, A. F.;
Roper, W. R.; Waters, J. M.; Wright, A. H. J. Am. Chem. Soc. 1983,
105, 5939.
(29) Fergusson, J. E.; Robinson, W. T.; Coll, R. K. Inorg. Chim. Acta 1991,
181, 37.
(30) Czeska, B.; Dehnicke, K.; Fenske, D. Z. Naturforsch. B. 1983, 38,
1031.
(31) Clark, G. R.; Waters, J. M.; Whittle, K. R. J. Chem. Soc., Dalton
Trans. 1975, 463.
(32) Other structurally characterized osmium porphyrins include the
following. (a) (OEP)Os(PPh3)2: ref 33. (b) (OEPMe2)Os(CO)(py):
Buchler, J. W.; Lay, K. L.; Smith, P. D.; Scheidt, W. R.; Rupprecht,
G. A.; Kenny, J. E. J. Organomet. Chem. 1976, 110, 109. (c)
(TTP)Os(4-pic)2: Djukic, J.-P.; Young, V. G., Jr.; Woo, L. K.
Organometallics 1994, 13, 3995. (d) (TTP)Os(Cl)2: Smieja, J. A.;
Omberg, K. M.; Busuego, L. N.; Breneman, G. L. Polyhedron 1994,
13, 339. (e) (TTP)Os(CH2SiMe3)2: Leung, W.-H.; Hun, T. S. M.;
Wong, K.-Y.; Wong, W.-T. J. Chem. Soc., Dalton Trans. 1994, 2713.
(f) (TTP)Os(p-NC6H4NO2)2: Smieja, J. A.; Omberg, K. M. Inorg.
Chem. 1994, 33, 614.
(33) Che, C.-M.; Lai, T.-F.; Chung, W.-C.; Schaefer, W. P.; Gray, H. B.
Inorg. Chem. 1987, 26, 3907.
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Investigation of the Reaction Pathway for RSNO Addition.
We sought to explore further the reaction pathway for RSNO
addition to metalloporphyrins. In particular, we invoked the
well-used concept of the “element displacement principle”56 to
investigate the nature of RSNO additions to osmium porphyrins.
We sought out chemical comparisons of PhSNO with com-
pounds of the form PhSNdNAr (phenyl arylazo sulfides),18,57
(46) Bidentate (refs 47 and 48) and tridentate (ref 49) O2PF2 groups have
also been structurally characterized.
(47) Powell, J.; Horvath, M. J.; Lough, A. J. Chem. Soc., Dalton Trans.
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Pellinghelli, M. A. Inorg. Chem. 1994, 33, 2309.
(42) The reaction of (OEP)Ru(CO) with NOBF4 also generates [(OEP)-
Ru(NO)]BF4, which is converted to [(OEP)Ru(NO)(H2O)]BF4 in air
(see ref 6b).
(43) Bu¨hler, K.; Bues, W. Z. Anorg. Allg. Chem. 1961, 308, 62.
(44) Schmutzler, R. In AdVances in Fluorine Chemistry; Stacey, M., Tatlow,
J. C., Sharpe, A. G., Eds.; Butterworth: London, 1965; Vol. 5, p 252.
(45) The Cp2Rh2(µ-CO)(µ-dppm)(µ-AgO2PF2) complex contains disordered
O and F atoms in the O2PF2 group (ref 40).
(48) Granier, P. W.; Durand, J.; Cot, L.; Galigne´, J. L. Acta Crystallogr.
1975, B31, 2506.
(49) Begley, M. J.; Dove, M. F. A.; Hibbert, R. C.; Logan, N.; Nunn, M.;
Sowerby, D. B. J. Chem. Soc., Dalton Trans. 1985, 2433.
(50) Reference 44, p 262.
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J.; Rolando, C. J. Org. Chem. 1996, 61, 929.

Structures of Three Osmium Porphyrin Derivatives
Inorganic Chemistry, Vol. 37, No. 3, 1998 539
Table 4. Metric Parameters (in Å and deg) for Transition Metal η1-OP(dO)F2 Complexes
(OEP)Os(NO)(O2PF2)a
Ir(O2PF2)(PPh3)2(H)(Cl)(CO)b
Pd(O2PF2)(η3-2-MeC3H4)(PCy3)c,d
M-O
2.046(5)
1.477(5)
1.511(6), 1.531(5)
1.454(7)
138.7(3)
118.4(4)
101.1(4)
108.2(3)
111.2(4), 108.3(4)
2.201(8)
1.456(7)
1.499(10), 1.529(12)
1.421(8)
127.0(4)
122.1(6)
95.4(7)
108.3(4), 107.4(5)
112.1(5), 108.3(6)
2.314(6) [2.126(5)]
1.471(5) [1.455(5)]
O-P
P-F
PdO
1.468(8) [1.441(8)]
125.4(3) [124.7(3)]
123.3(4) [122.1(4)]
97.2(5) [96.0(4)]
M-O-P
O-PdO
F-P-F
O-P-F
OdP-F
a This work. b Reference 39. c Reference 41. d There are two independent molecules present. The data in brackets are for the second molecule.
Scheme 2
Scheme 3
where a simple replacement of the oxygen atom in PhSNO with
the valence isoelectronic NAr group will generate the “equiva-
lent” phenyl arylazo sulfide. This concept has been utilized
successfully in metal-nitrosyl (M-NO) and metal-aryldiazonium
(M-N2Ar) comparisons.58
expected to be stable,59 it would not be expected to survive the
reaction conditions to displace CO (Scheme 3, bottom) to form
the (OEP)Os(N2Ar)(SPh) addition product.60 If this is so, then
any observed band in the carbonyl region of the IR spectrum
should be due to υCO and not υNO, since there is no NO present
in the reaction mixture.
Indeed, IR monitoring of the reaction of (OEP)Os(CO) with
PhSNdNC6H4(p-NO2) reveals the formation of the band at 1957
cm-1 assigned to the intermediate carbonyl (OEP)Os(CO)(SPh)
complex (Scheme 3, bottom). We have not been able to isolate
this thermally unstable intermediate. However, reaction of this
intermediate with NO gas (2 min) gives a 1:1 mixture of (OEP)-
Os(NO)(SPh) and the known (OEP)Os(NO)2.13b This latter
compound forms from the attack of NO on unreacted (OEP)-
Os(CO)13b and (OEP)Os(NO)(SPh). A similar reaction involv-
ing (TTP)Os(NO)(S-isoamyl) has been reported.9b
To further confirm the similarity of S-binding of PhSNO and
PhSNdNAr to give the (OEP)Os(CO)(SR) thiolate initial
products, we proceeded to employ the non-carbonyl-containing
[(OEP)Os]2 dimer, with the intention of incorporating two
S-bonded ligands on opposite ends of the Os center. Remark-
ably, the reaction of [(OEP)Os]2 with 4 equiv of PhSNdNAr
(i.e., 2 equiv per Os center) gives (OEP)Os(SPh)2 in 41%
isolated yield, presumably via a bis-adduct intermediate which
undergoes homolytic cleavage of the S-N bonds to give the
known bisthiolate species17 (Scheme 4). Importantly, the
success of the reaction in Scheme 4 provides further chemical
evidence for the S-binding of RSNO to osmium porphyrins.
Not surprisingly, the reaction of (OEP)Os(CO) with PhSNO
gave, after workup, the (OEP)Os(NO)(SPh) thiophenolate
product in 45% isolated yield. In contrast to the other nitrosyl
thiolates obtained in our laboratory, this nitrosyl thiophenolate
is moderately air-sensitive. This dark-red product is soluble in
CH2Cl2 and benzene but is rather insoluble in hexane. The υNO
of 1766 cm-1 in CH2Cl2 is ca. 10 cm-1 higher than that of the
related alkanethiolate (OEP)Os(NO)(S-i-C5H11), although the
υ
NO’s of both nitrosyl thiolates as KBr pellets are virtually
identical.
IR monitoring of the reaction of PhSNO with (OEP)Os(CO)
in CH2Cl2 reveals that, in addition to the υCO band of starting
(OEP)Os(CO) (at 1883 cm-1) and the υNO band of the
thiophenolate (OEP)Os(NO)(SPh) product at 1766 cm-1, a new
higher band at 1957 cm-1 is observed. This new band is
attributed (consistent with earlier similar results)9b to an
intermediate carbonyl OsIII complex. In time, only the product
band remains.
We have proposed earlier (based on IR spectroscopy) that
thionitrites react with group 8 metalloporphyrins probably via
S-coordination of the RSNO group (Scheme 2) followed by
homolytic cleavage of the RS-NO bond.
In this pathway, rapid diffusion of the stable NO radical to
the metal site results in a substitution of CO to give the final
nitrosyl thiolate product. To test this proposed reaction pathway,
we employed the valence isoelectronic PhSNdNC6H4(p-NO2)
compound in place of PhSNO. We rationalized that the success
of proposed Scheme 2 depends on the known stability of the
NO radical, enabling it to displace the bound carbonyl from
.
(59) Suehiro, T.; Masuda, S.; Nakausa, R.; Taguchi, M.; Mori, A.; Koike,
A.; Date, M. Bull. Chem. Soc. Jpn. 1987, 60, 3321.
the osmium center. Since the N2Ar radical is generally not
(60) Aryldiazonium adducts of metalloporphyrins are known: Farrell, N.;
Neves, A. A. Inorg. Chim. Acta 1981, 54, L53.
(58) Sutton, D. Chem. Soc. ReV. 1975, 4, 443.

540 Inorganic Chemistry, Vol. 37, No. 3, 1998
Chen et al.
Scheme 4
Figure 3. Molecular structure of (OEP)Os(SPh)2.
We were able to obtain suitable crystals of the moderately
air-stable bisthiolate OsIV porphyrin complex by slow evapora-
tion of a CH2Cl2/toluene solution of the compound. The
molecular structure of the complex is shown in Figure 3. The
Os-N(por) bond lengths are 2.047(4) and 2.050(4) Å. The
Os-S and S-C bond lengths are 2.295(1) and 1.782(5) Å,
respectively. The Os-S-C thiolate angle is 110.9(2)° and is
within the range found for other osmium aryl thiolates (107.0-
123.9°)35,61 or alkanethiolates (102.5-111.8°).9b,62 The thiolate
ligands nearly eclipse diagonal porphyrin nitrogens, with the
N1-Os-S1-C19 torsion angle of 14.2°. The structure is
essentially similar to that of the related (TTP)Os(SC6F4H)2
reported by Collman and synthesized by the reaction of (TTP)-
Os(O)2 with thiol.35
produced in the reactions of thionitrites and alkyl nitrites with
OsII porphyrins, only the osmium nitrosyl difluorophosphate
complex is isolated in the case of OsIII. This work also adds to
the sparse structural data currently available for osmium nitrosyl
porphyrins: prior to this work, only one other osmium nitrosyl
porphyrin had been structurally characterized.9b By using the
valence isoelectronic phenyl arylazo sulfide in place of PhSNO,
we have been able to isolate and characterize the bisthiolate
adduct, thereby giving more spectroscopic and chemical evi-
dence that RSNO binds through the sulfur atom to the osmium
porphyrin center. These results may have mechanistic implica-
tions for the further study of thionitrite and alkyl nitrite
vasodilators with heme and other heme models.
Acknowledgment. We are grateful to the National Institutes
of Health (FIRST Award 1R29 GM53586-01A1) and the
National Science Foundation (CAREER Award CHE-9625065)
for funding for this research. We also thank Dr. P. C. Ford for
providing us with his results on ruthenium porphyrins (ref 10a)
prior to publication.
Conclusion. In summary, we have provided new insight into
the reactions of thionitrites and alkyl nitrites with osmium
porphyrins. Whereas nitrosyl thiolates and alkoxides are
(61) (a) Che, C.-M.; Cheng, W.-K.; Mak, T. C. W. Inorg. Chem. 1986,
25, 703. (b) Cruz-Garritz, D.; Gelover, S.; Torrens, H.; Leal, J.;
Richards, R. L. J. Chem. Soc., Dalton Trans. 1988, 2393. (c) Cruz-
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A.; Hughes, D. L.; Richards, R. L.; Roman, P.; Sosa, P.; Torrens, H.
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Supporting Information Available: Drawings and listings of
crystal data, atomic coordinates, anisotropic displacement parameters,
bond lengths and angles, hydrogen coordinates and isotropic displace-
ment parameters, torsion angles, and least-squares planes (47 pages).
Ordering information is given on any current masthead page.
(62) Lynch, W. E.; Lintvedt, R. L.; Shui, X. Q. Inorg. Chem. 1991, 30,
1014.
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