Synthesis and Axial Ligand Substitution Chemistry of Ru(TTP)(NO)X. Structures of Ru(TTP)(NO)X (X = ONO, OH)

Article abstract of DOI:10.1021/ic980182m

New complexes of the family Ru(TTP)(NO)X, where TTP = tetra-p-tolylporphyrinato dianion, and X = OMe, Cl, OH, SH, S-p-tolyl O₂CH, ONO, ONO₂, NS, or NCS, have been prepared by a variety of high-yield metathesis techniques from Ru(TTP)(CO)(MeOH). New complexes have been characterized by IR, NMR, and UV spectroscopies as well as by cyclic voltammetry. elemental analysis, and, in two cases, by X-ray crystallography. The two complexes which have been characterized by single-crystal X-ray diffraction, the hydroxide and nitrite complexes 6 and 10 both crystallize in the monoclinic space group P2₁/n and have Z = 6, with two independent metalloporphyrins in the unit cell, one (ordered) lying on a general position and the other (disordered) with the ruthenium on an inversion center. Acid labilization of the methoxide results in facile substitution kinetics at room temperature and with the exception of the sulfhydryl complex, L = SH, the resulting complexes are air stable and thermally robust species. For example, the formate derivative cannot be decarboxylated thermally or photolytically to give a hydrido complex, and the azido complex does not eliminate dinitrogen under similar conditions to give a nitrido complex.

Full text of DOI:10.1021/ic980182m

5798
Inorg. Chem. 1998, 37, 5798-5806
Synthesis and Axial Ligand Substitution Chemistry of Ru(TTP)(NO)X. Structures of
Ru(TTP)(NO)X (X ) ONO, OH)
D. Scott Bohle,* Chen-Hsiung Hung, and Bryan D. Smith
Department of Chemistry, University of Wyoming, Laramie, Wyoming 82071-3838
ReceiVed February 19, 1998
New complexes of the family Ru(TTP)(NO)X, where TTP ) tetra-p-tolylporphyrinato dianion, and X ) OMe,
Cl, OH, SH, S-p-tolyl, O2CH, ONO, ONO2, N3, or NCS, have been prepared by a variety of high-yield metathesis
techniques from Ru(TTP)(CO)(MeOH). New complexes have been characterized by IR, NMR, and UV
spectroscopies as well as by cyclic voltammetry, elemental analysis, and, in two cases, by X-ray crystallography.
The two complexes which have been characterized by single-crystal X-ray diffraction, the hydroxide and nitrite
complexes 6 and 10 both crystallize in the monoclinic space group P21/n and have Z ) 6, with two independent
metalloporphyrins in the unit cell, one (ordered) lying on a general position and the other (disordered) with the
ruthenium on an inversion center. Acid labilization of the methoxide results in facile substitution kinetics at
room temperature and with the exception of the sulfhydryl complex, L ) SH, the resulting complexes are air
stable and thermally robust species. For example, the formate derivative cannot be decarboxylated thermally or
photolytically to give a hydrido complex, and the azido complex does not eliminate dinitrogen under similar
conditions to give a nitrido complex.
The family of group 8 metallonitrosyls contain species which
are biologically and heuristically important. On one hand the
nitrosyl adducts of both heme and nonheme iron enzymes have
recognized biological functions ranging from signal transduction
by soluble guanylyl cyclase, sGC,1 to the regulation of gene
transcription by the soxRS-mediated oxidative-stress response.2
On the other hand ruthenium has a renowned high affinity for
NO,3 and of these complexes, the cationic cis-dinitrosyl complex
[RuCl(NO)2(PPh3)2]+, with both bent and linear nitrosyls, is an
archetype for the relationship of MNO binding geometry to the
metal’s electronic structure and fluxionality.4-7 Because of the
critical biological roles of the NO/heme interaction, there is a
resurgence of interest in the chemistry of iron porphyrin
nitrosyls8-12 and this has in turn rekindled interest in the
corresponding ruthenium analogues.
Under these conditions the iron adducts are often paramagnetic
with bent Fe-N-O geometries,9,10 while the corresponding
ruthenium complexes are typically diamagnetic with linear
nitrosyls.13-18 Perhaps the best characterized paramagnetic
ruthenium nitrosyl is [Ru(bipy)2(NO)Cl]+ which is obtained
from the one electron reduction of [Ru(bipy)2(NO)Cl]+2 19
.
At the outset of these studies only a few reports concerning
nitrosyl adducts of ruthenium porphyrins had appeared in the
literature,20-23 and it was curious that substantially more was
known about the family of Os(OEP)(NO)X, X ) OMe-, Cl-,
NO, F-.22,24,25 Since 1995 a number of papers have reported
aspects of the chemistries of Ru(OEP)(NO)X,18,26 Ru(TPP)-
(13) Bohle, D. S.; Goodson, P. A.; Smith, B. D. Polyhedron 1996, 15,
3147-3150.
Despite the similar organometallic chemistries of iron and
ruthenium metallonitrosyls, the two metals have distinctly
different bonding trends for the complexes with metals in an
intermediary oxidation state and/or ones with weak ligand fields.
(14) Miranda, K. M.; Bu, X. H.; Lorkovic, I.; Ford, P. C. Inorg. Chem.
1997, 36, 4838-4848.
(15) Hodge, S. J.; Wang, L. S.; Khan, M. A.; Young, V. G.; Richteraddo,
G. B. Chem. Commun. 1996, 2283-2284.
(16) Kadish, K. M.; Adamian, V. A.; Caemelbeche, E. V.; Tan, Z.;
Tagliatesta, P.; Bianco, T.; Yi, G.-B.; Khan, M. A.; Richter-Addo, G.
B. Inorg. Chem. 1996, 35, 1343.
(1) Ignarro, L. J. Semin. Hematol. 1989, 26, 63-76.
(2) Nunoshiba, T.; DeRojas-Walker, T.; Wishnok, J. S.; Tannenbaum, S.
R. Proc. Natl. Acad. Sci. U.S.A. 1993, 90, 9993-9997.
(3) Griffith, W. P. The Chemistry of the Rarer Platinum Metals;
Interscience Publishers: New York, 1967.
(17) Yi, G.-B.; Khan, M. A.; Richter-Addo, G. B. Inorg. Chem. 1996, 35,
3453-3454.
(18) Yi, G. B.; Chen, L.; Khan, M. A.; Richter-Addo, G. B. Inorg. Chem.
1997, 36, 3876-3885.
(4) Pierpont, C. G.; Van Derveer, D.; Durland, W.; Eisenberg, R. J. Am.
Chem. Soc. 1970, 92, 4760-4762.
(19) Callahan, R. W.; Meyer, T. J. Inorg. Chem. 1977, 16, 574-581.
(20) Srivastava, T. S.; Hoffman, L.; Tsutsui, M. J. Am. Chem. Soc. 1972,
94, 1385-1386.
(5) Pierpont, C. G.; Eisenberg, R. Inorg. Chem. 1972, 11, 1088-1094.
(6) Mingos, D. M. P.; Sherman, D. J.; Williams, I. D. Trans. Met. Chem.
1987, 12, 493-6.
(21) Carrondo, M. A. A. F. d. C. T.; Rudolf, P. R.; Skapski, A. C.;
Thornback, J. R.; Wilkinson, G. Inorg. Chim. Acta 1977, 24, L95-
L96.
(7) Mason, J.; Mingos, D. M. P.; Sherman, D.; Wardle, R. W. M. J. Chem.
Soc., Chem. Commun. 1984, 1223-1225.
(8) Bohle, D. S.; Hung, C. H. J. Am. Chem. Soc. 1995, 117, 9584-9585.
(9) Ellison, M. K.; Scheidt, W. R. J. Am. Chem. Soc. 1997, 119, 7404-
7405.
(22) Antipas, A.; Buchler, J. W.; Gouterman, M.; Smith, P. D. J. Am. Chem.
Soc. 1978, 100, 3015-3024.
(23) Massoudipour, M.; Pandey, K. K. Inorg. Chim. Acta 1989, 160, 115-
118.
(24) Buchler, J. W.; Smith, P. D. Chem. Ber. 1976, 109, 1465-1476.
(25) Antipas, A.; Buchler, J. W.; Gouterman, M.; Smith, P. D. J. Am. Chem.
Soc. 1980, 102, 198-207.
(26) Yi, G.-B.; Khan, M. A.; Powell, D. R.; Richter-Addo, G. B. Inorg.
Chem. 1998, 37, 208-214.
(10) Nasri, H.; Ellison, M. K.; Chen, S.; Huynh, B. H.; Scheidt, W. R. J.
Am. Chem. Soc. 1997, 119, 6274-6283.
(11) Morlino, E. A.; Rodgers, M. A. J. J. Am. Chem. Soc. 1996, 118,
11798-11804.
(12) Bohle, D. S.; Debrunner, P.; Fitzgerald, J. P.; Hansert, B.; Hung, C.
H.; Thomson, A. J. Chem. Commun. 1997, 91-92.
10.1021/ic980182m CCC: $15.00 © 1998 American Chemical Society
Published on Web 10/10/1998

Structures of Ru(TTP)(NO)X (X ) ONO, OH)
Inorganic Chemistry, Vol. 37, No. 22, 1998 5799
(NO)X,14,16 and Ru(TTP)(NO)X.13,27 Herein we describe a
number of new results relating to the chemistry of Ru(TTP)-
(NO)X, in particular: (1) a high-yield synthesis of Ru(TTP)-
(NO)(OMe), 2, directly from Ru(TTP)(CO)(MeOH), 1; (2) the
derivatization of this complex to give a series of new complexes
Ru(TTP)(NO)X with X ) Cl-, OH-, ONO-, O2CH-, S(p-
tolyl)-, SH-, NCS-, and N3-; (3) the structure of two these
derivatives Ru(TTP)(NO)(OH), 6, and Ru(TTP)(NO)(ONO), 10;
and (4) spectroscopic and electrochemical characterization of
this series of compounds. Some of these results have been
described briefly before.13
dark purple-black microcrystals form. The crystals are collected by
filtration, washed with hexanes, and dried in vacuo to yield 3 (216.3
mg, 96.0%). 1H NMR (22 °C, C6D6, ppm): 9.16 (s, 8H, Hâ), 8.11 (d,
3
3JHH, 7.1 Hz, 4H, Hm), 7.91 (d, JHH, 7.7 Hz, 4H, Hm′), (Ho and Ho′
obscured by C6D5H), 2.39 (s, 12H, p-CH3). IR (KBr, cm-1): ν(NO)
1845, 1830. UV-vis (CH2Cl2) λmax nm (log ꢀ): 322 (4.34), 414 (Soret)
(5.28), 534 sh, 562 (3.94), 610 sh. Elemental anal. calcd (found) for
C48H36N5OClRu: C, 69.01 (69.00); H, 4.34 (4.48); N, 8.38 (8.34).
Formato(nitrosyl)(meso-tetra-p-tolylporphyrinato)ruthenium-
(II), Ru(TTP)(NO)(O2CH), 4. To a dichloromethane (25 mL) solution
of 2 (101.4 mg, 1.22 × 10-1 mmol) is added excess aqueous formic
acid (88%, 2.1 mL, 50 mmol), and this mixture is stirred for 5 min.
The crude reaction mixture is evaporated to dryness in vacuo and
recrystallized from dichloromethane/hexanes. The resulting dark purple
crystals were filtered, rinsed with hexanes followed by pentane, and
vacuum-dried to yield 4 (68.7 mg, 66.6%). 1H NMR (22 °C, C6D6,
ppm): 9.17 (s, 8H, Hâ), 8.09 (dd, 3JHH, 7.6 Hz, 4JHH, 1.9 Hz, 4H, Hm),
7.91 (dd, 3JHH, 7.6 Hz, 4JHH, 1.9 Hz, 4H, Hm), 7.25 (t, 3JHH, 6.0 Hz, Ho,
Ho′, partially obscured by C6D5H), 2.40 (s, 12H, p-CH3), ligand 2.87
(s, 1H, OOCH). IR (KBr, cm-1): ν(NO) 1837, νs(COO) 1661, νa(COO)
1228. IR (Nujol mull, cm-1): ν(NO) 1839, νs(COO) 1662, νa(COO)
1228. UV-vis (CH2Cl2) λmax nm (log ꢀ): 326 (4.35), 410 (Soret)
(5.31), 560 (4.13), 592 sh. Elemental anal. calcd (found) for C49H37N5O3-
Ru‚0.5CH2Cl2: C, 67.00 (67.27); H, 4.32 (4.39); N, 7.89 (8.07).
Experimental Section
General experimental techniques, methods, and instruments have
been described in detail in prior publications.28 Except where noted,
the new derivatives are air and water stable and can be handled without
precautions in solution in the open for brief periods of time. Most are
very stable in the solid state. Nitric oxide used in the following
experiments was either prepared fresh from the reduction of nitrite with
ferrous salts29 or by the solid state thermal reduction of nitrite with a
mixture of chromic and ferric oxide.30 Commercial nitric oxide used
in the preparation of 2 was scrubbed with potassium hydroxide pellets
to remove nitrogen dioxide.31
[Aquo(nitrosyl)(meso-tetra-p-tolylporphyrinato)ruthenium(II)]-
[hexafluorophosphate], [Ru(TTP)(NO)(H2O)][PF6], 5. A 50 mL
vessel is charged with a methylene chloride (20 mL) solution of 2 (200
mg, 2.41 × 10-1 mmol). To this is added aqueous HPF6 (60 wt %, 5
drops), and the reaction mixture is stirred for 5 min. The solvent is
removed in vacuo, and the remaining solid residue is placed under
vacuum at 2 × 10-5 Torr for 24 h to remove any residual H2O. The
black-purple residue is recrystallized by taking it up into dichlo-
romethane, diluting the solution with an equal quantity of hexane, and
concentrating it on a rotoevaporator. The resulting crystallites are
isolated by filtration, followed by a wash with hexanes followed by
pentane, and dried in vacuo. The reaction produced 5 (189.3 mg, 82%).
1H NMR (22 °C, C6D6, ppm): 9.22 (s, 8H, Hâ), 8.12 (d, 3JHH, 7.5 Hz,
4H, Hm), 8.07 (d, 3JHH, 7.3 Hz, 4H, Hm?), 7.27 (t, 3JHH, 8.1 Hz, Ho, Ho′,
partially obscured by C6D5H), 2.40 (s, 12H, p-CH3). The water ligand
was not detected. IR (KBr, cm-1): ν(NO) 1859, Fr(H2O) 848, Fw(H2O)
524. UV-vis (CH2Cl2) λmax nm (log ꢀ): 318 (4.36), 410 (Soret) (5.22),
562 (4.09). Elemental anal. calcd (found) for C48H38N5O2PF6Ru: C,
59.87 (60.00); H, 3.98 (4.36); N, 7.27 (6.94).
Methoxide(nitrosyl)(meso-tetra-p-tolylporphyrinato)ruthenium-
(II), Ru(TTP)(NO)(OMe), 2. This procedure is a modification of the
reductive nitrosylation reaction developed for iron porphyrins.32,33
Ru(TTP)(CO)(MeOH), prepared by the method of Rillema et al.34 (275
mg, 0.331 mmol), is added to a mixture of dichloromethane (25 mL),
methanol (5 mL), and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU, 100
µL). This solution is purged with nitrogen for 45 min, and then a stream
of nitric oxide is introduced by passing it slowly through the stirred
mixture at atmospheric pressure for 10 min. A color change from
orange-red to brick-red is noted. To ensure complete nitrosylation,
addition of nitric oxide is continued for a further 10 min. The solution
is then purged with dinitrogen to remove any excess nitric oxide.
Concentration of the solution on a rotary evaporator effected crystal-
lization of the product which was obtained as air stable red-purple
crystals. The crystals were filtered, washed with cold methanol and
vacuum-dried, to afford 2 (242 mg, 87.9%). The isolated product is
essentially pure by NMR spectroscopy, but it can be readily purified
even further by recrystallization from dichloromethane/methanol. 1H
NMR (22 °C, C6D6, ppm): 9.16 (s, 8H, Hâ), 8.10 (d, 3JHH, 6.8 Hz, 4H,
3
3
Hm), 8.00 (d, JHH, 7.7 Hz, 4H, Hm), 7.24 (t, JHH, 6.0 Hz, Ho, Ho′,
partially obscured by C6D5H), 2.39 (s, 12H, p-CH3), ligand -1.50 (s,
3H, OCH3). IR (KBr, cm-1): ν(NO) 1802. UV-vis (CH2Cl2) λmax
nm (log ꢀ): 316 (4.32), 412 (Soret) (5.11), 556 (4.15), 594 (3.84).
Elemental anal. calcd (found) for C49H39N5O2Ru: C, 70.83 (70.24);
H, 4.73 (4.99); N, 8.43 (8.38). Crystals suitable for single-crystal X-ray
diffraction are obtained by vapor phase diffusion of a hexanes/
dichloromethane solution.
Chloride(nitrosyl)(meso-tetra-p-tolylporphyrinato)ruthenium-
(II), Ru(TTP)(NO)(Cl), 3. A round-bottom flask is charged with 2
(224.1 mg, 2.697 × 10-1 mmol) and methylene chloride (50 mL) and
fitted with a septum. This solution is deoxygenated with a slow purge
of nitrogen (20 min) at which time the purge gas is switched to HCl.
A slow stream of HCl is continued for 10 min, and the reaction vessel
is then swept with nitrogen to remove excess HCl. Hexanes (10 mL)
are added, and the solution is concentrated on a rotary evaporator until
Hydroxo(nitrosyl)(meso-tetra-p-tolylporphyrinato)ruthenium-
(II), Ru(TTP)(NO)(OH), 6. To a concentrated acetonitrile solution
of 5 (52.1 mg, 5.41 × 10-2 mmol) is added tetra-n-butylammonium
hydroxide (40 wt. %, 200 µL). The product, 6, spontaneously
crystallizes as brilliant red crystallites which are isolated via filtration
and dried in vacuo. The reaction yielded 6 (37.3 mg, 84%). 1H NMR
(22 °C, C6D6, ppm): 9.16 (s, 8H, Hâ), 8.11 (d, 3JHH, 7.5 Hz, 4H, Hm),
7.94 (d, 3JHH, 7.4 Hz, 4H, Hm), 7.24 (t, 3JHH, 8.4 Hz, 8H, Ho, Ho′), 2.40
(s, 12H, p-CH3); ligand not observed. IR (KBr, cm-1): ν(NO) 1813;
ν(OH) 3597; δ(RuOH) 877; ν(RuO) 570. UV-vis (CH2Cl2) λmax nm
(log ꢀ): 316 (4.25), 412 (Soret) (5.05), 556 (4.18), 594 (3.86).
Elemental anal. calcd (found) for C48H37N5O2Ru: C, 70.48 (70.39);
H, 4.56 (4.62); N, 8.57 (8.52). Crystals suitable for single-crystal X-ray
diffraction were obtained by vapor phase diffusion of a benzene/
methanol solution. The deep brown prism selected had the dimensions
0.62 × 0.45 × 0.28 mm3.
Sulfhydro(nitrosyl)(meso-tetra-p-tolylporphyrinato)ruthenium-
(II), Ru(TTP)(NO)(SH), 7. A toluene (25 mL) solution of 2 (135.5
mg, 1.631 × 10-1 mmol) is prepared in a Schlenk flask under an inert
atmosphere of nitrogen. Gaseous H2S is flushed through the solution,
and an immediate color change from red to brick-red is observed. The
solvent and excess H2S are removed in vacuo after 10 min, and the
air-sensitive product recrystallized from dichloromethane/hexane to give
deep brick-red crystals of 7 in nearly quantitative yield. 1H NMR (22
(27) Bohle, D. S.; Hung, C.-H.; Powell, A. K.; Smith, B. D.; Wocadlo, S.
Inorg. Chem. 1997, 36, 1992-1993.
(28) Bohle, D. S.; Carron, K. T.; Christensen, A. N.; Goodson, P. A.;
Powell, A. K. Organometallics 1994, 13, 1355-1373.
(29) Blanchard, A. Inorg. Synth. 1946, 2, 126.
(30) Ray, J. D.; Ogg, R. A. J. Am. Chem. Soc. 1956, 78, 5993.
(31) Perrin, A. P.; Armarego, W. L. F. Purification of Laboratory Reagents,
3rd ed.; Pergamon Press: New York, 1990.
(32) Caulton, K. G. Coord. Chem. ReV. 1975, 14, 317.
(33) Wayland, B. B.; Olson, L. W. J. Am. Chem. Soc. 1974, 96, 6037.
(34) Rillema, D. P.; Nagle, J. K.; Barringer, L. F.; Meyer, T. J. J. Am.
Chem. Soc. 1981, 103, 3, 56.
3
°C, CDCl3, ppm): 8.99 (s, 8H, Hâ), 8.16 (d, JHH, 7.3 Hz, 8H, Hm,
H
m?), 7.60 (d, 3JHH, 6.7 Hz, 8H, Ho, Ho′), 2.74 (s, 12H, p-CH3); ligand
-6.20 (s, 1H, SH). IR (KBr, cm-1): ν(NO) 1796, ν(SH) not observed.

5800 Inorganic Chemistry, Vol. 37, No. 22, 1998
Bohle et al.
UV-vis (CH2Cl2) λmax nm (log ꢀ): 318 sh; 346 (4.44), 418 (Soret)
(5.27), 576 (3.89), 612 sh. Elemental anal. calcd (found) for C48H37N5O2-
Ru: C, 70.48 (70.39); H, 4.56 (4.62); N, 8.57 (8.52).
toluene or benzene solution of [Ru(TTP)]2,35 with excess nitric oxide
under strictly anaerobic conditions. For this transformation an efficient
inert atmosphere box was used during the reaction. The extremely
air-sensitive [Ru(TTP)]2 (40.0 mg, 2.60 × 10-2 mmol) is dissolved in
toluene (50 mL) under nitrogen, and a stream of nitric oxide, prepared
from thermal decomposition of nitrite/chromate mixtures,29 is bubbled
through the stirred solution. An instant color change from black-red
to red is noted, and the solvent is removed in vacuo. At this point the
spectroscopic characteristics of the product are identical to that prepared
by method a, and so the product can then purified in the open as
described in method a to yield 10 (38.3 mg, 87.1%).
Nitrato(nitrosyl)(meso-tetra-p-tolylyporphyrinato)ruthenium-
(II), Ru(TTP)(NO)(ONO2), 11. This preparation follows the same
procedure as the method for compound 10 except that silver nitrate is
used. In this case chromatographic purification is not required and
after filtration through diatomaceous earth, the product is recrystallized
from dichloromethane/hexane to give 11 (14.9 mg, 76%). 1H NMR
(22 °C, C6D6, ppm): 9.19 (s, 8H, Hâ), 8.09 (d, 3JHH, 7.3 Hz, 4H, Hm),
7.95 (d, 3JHH, 7.3 Hz, 4H, Hm′), 7.24 (t, 3JHH, Ho, Ho′, partially obscured
by C6D5H), 2.39 (s, 12H, p-CH3). IR (KBr, cm-1): ν(NO) 1860 s,
ν(NO) 1212 m, νa(NO2) 1273 s, νs(NO2) 964 m. UV-vis (CH2Cl2)
λmax nm (log ꢀ): 324 (4.26), 412 (Soret) (5.28), 564 (3.87), 605 sh.
Elemental anal. calcd (found) for C48H36N6O4Ru: C, 66.89 (66.24);
H, 4.21 (4.52); N, 9.75 (9.52).
Nitrosyl(p-thiocresolate)(meso-tetra-p-tolylporphyrinato)ruthe-
nium(II), Ru(TTP)(NO)(SC7H7), 8. A benzene (10 mL) solution of
2 (12.7 mg, 1.53 × 10-2 mmol) is treated with an excess of p-thiocresol
(21.2 mg, 1.71 × 10-1 mmol) for 15 min at room temperature. The
reaction progress can be monitored by withdrawing aliquots of the
reaction mixture and following the Soret shift from 412 to 420 nm in
the UV-vis spectrum. Upon completion the solvent is removed in
Vacuo, and the vessel is connected to a diffusion-assisted vacuum line
and maintained at 10-5 Torr for 24 h to ensure removal of all residual
mercaptan. Recrystallization from dichloromethane/hexane affords dark
red-purple crystals which are filtered, rinsed with hot hexanes, and
vacuum-dried. This process yields 8 (10.2 mg, 72.3%). 1H NMR (22
°C, C6D6, ppm): 9.14 (s, 8H, Hâ), 8.09 (d, 3JHH, 7.3 Hz, 4H, Hm), 8.05
(d, 3JHH, 7.3 Hz, 4H, Hm′), 7.30 (d, 3JHH, 7.3 Hz, 4H, Ho), 7.25 (d, 3JHH
,
,
3
7.3 Hz, 4H, Ho), 2.41 (s, 12H, p-CH3); S-p-tolyl ligand 3.65 (d, JHH
3
8.5 Hz, 2H, Ho), 5.92 (d, JHH, 8.5 Hz, 2H, Hp), 1.88 (s, 3H, p-CH3).
IR (KBr, cm-1): ν(NO) 1784 s. UV-vis (C6H6) λmax nm (log ꢀ): 334
(4.41), 420 (Soret) (5.08), 510 (4.13). Elemental anal. calcd (found)
for C55H43N5OSRu: C, 71.56 (71.31); H, 4.70 (4.52); N, 7.59 (7.05).
Imidazolide(nitrosyl)(meso-tetra-p-tolylporphyrinato)ruthenium-
(II), Ru(TTP)(NO)(Im), 9. A small-volume sublimation apparatus is
loaded with 2 (76.9 mg, 9.25 × 10-2 mmol), a 5-fold excess of
imidazole (6.8 mg, 4.6 × 10-1 mmol), and a small stir bar. Oxygen is
removed from the reaction chamber by repeated evacuation and back-
filling with nitrogen. Under an atmosphere of nitrogen the reaction
mixture is then heated to 90 °C, just above the melting point of
imidazole, and maintained at this temperature with stirring for 2 h.
The mixture is cooled and then evacuated, and gentle heat applied to
sublime the excess unreacted HIm. Trace HIm is completely removed
by placing the crude product mixture on a high-vacuum line and
maintaining the pressure at 10-5 Torr for 24 h. Purple microcrystals
are obtained after recrystallization from dichloromethane/hexanes. The
product is filtered, washed with hexanes, and dried in vacuo to give 9
(53.2 mg, 66.3%). 1H NMR (22 °C, C6D6, ppm): 9.13 (s, 8H, Hâ),
8.07 (d, 3JHH, 7.2 Hz, 4H, Hm), 7.87 (d, 3JHH, 7.1 Hz, 4H, Hm′), (Ho and
Azido(nitrosyl)(meso-tetra-p-tolylporphyrinato)ruthenium(II), Ru-
(TTP)(NO)(N3), 12. A 50 mL flask is charged with a dichloromethane
(20 mL) solution of 3 (19.5 mg, 2.33 × 10-2 mmol). To this is added
trimethylsilyl azide (Me3SiN3) (∼0.2 mL), and the reaction mixture is
stirred for 10 min. The solvent is removed under reduced pressure,
and the solid residue is placed under vacuum at 2 × 10-5 Torr for 24
h to remove any unreacted Me3SiN3 as well as any Me3SiCl formed
during the reaction. All recovered products are taken up in dichlo-
romethane and then recrystallized with hexanes to give black-purple
crystals which were isolated via filtration and rinsing with hexanes
followed by pentane to yield 12 (15.8 mg, 80.2%). 1H NMR (22 °C,
3
4
CD2Cl2, ppm): 9.03 (s, 8H, Hâ), 8.14 (dd, JHH, 8.2 Hz, JHH, 1.3 Hz,
8H, Hm, Hm?), 7.60 (d, 3JHH, 7.9 Hz, 8H, Ho, Ho′), 2.71 (s, 12H, p-CH3).
IR (KBr, cm-1): ν(NO) 1821, νa(NNN) 2048, νs(NNN) 1291. UV-
vis (CH2Cl2) λmax nm (log ꢀ): 332 (4.27), 414 (Soret) (5.26), 568 (3.84),
604 sh.
H
o′ are obscured by C6D5H), 2.41 (s, 12H, p-CH3); imidazolide ligand
4.93 (s, 1H), 2.55 (s, 1H), 0.54 (s, 1H). IR (KBr, cm-1): ν(NO) 1846
s. UV-vis (C6H6) λmax nm (log ꢀ): 298 (4.50), 412 (Soret) (5.20),
508 (4.25).
Isothiocyanato(nitrosyl)(meso-tetra-p-tolylporphyrinato)ruthenium-
(II), Ru(TTP)(NO)(NCS), 13. A 100 mL flask is fitted with a
Vigreaux condenser in the inert atmosphere box and loaded with toluene
(30 mL), 3 (62.1 mg, 7.43 × 10-2 mmol) and trimethylsilylisothiocy-
anate (Me3SiNCS) (1 mL, 7.09 mmol). The reaction mixture is heated
to reflux for 20 min with stirring. Cooling the solution to room
temperature and removing the solvent in vacuo resulted in a solid
residue which is recrystallized from dichloromethane/hexane to give
black-red crystals which are collected by filtration and rinsed with
pentane to yield 13 (62.6 mg, 98.1%). 1H NMR (22 °C, CD2Cl2,
ppm): 9.09 (s, 8H, Hâ), 8.16 (d, 3JHH, 8.1 Hz, 8H, Hm, Hm?), 7.63 (dd,
Nitrito(nitrosyl)(meso-tetra-p-tolylporphyrinato)ruthenium(II),
Ru(TTP)(NO)(ONO), 10. Method a. A round-bottom flask is
charged with 3 (25.1 mg, 3.00 × 10-2 mmol) dissolved in a 1:1 mixture
of benzene and acetonitrile (20 mL), and one and a half equiv of silver
nitrite (6.9 mg, 4.5 × 10-2 mmol) is then added with stirring. A silver
chloride precipitate forms immediately, but the reaction is stirred an
additional 20 min before the silver chloride is removed by passing the
mixture through diatomaceous earth and washing the residue with
dichloromethane. All solvents were removed in vacuo, and the residue
was taken up in dichloromethane and then purified by flash chroma-
tography on a silica gel column. The product elutes with dichlo-
romethane as the single mobile red-purple product from immobile
impurities. Recrystallization of this fraction from dichloromethane/
4
3JHH, 8.2 Hz, JHH, 0.6 Hz, 4H, Ho, Ho?), 2.73 (s, 12H, p-CH3). IR
(KBr, cm-1): ν(NO), 1847, ν(CN) 2026 cm-1. UV-vis (CH2Cl2) λmax
nm (log ꢀ): 322 (4.37), 414 (Soret) (5.31), 570 (3.81), 610 sh.
Elemental anal. calcd (found) for C49H36N6OSRu: C, 68.59 (69.37);
H, 4.23 (4.44); N, 9.79 (9.55).
1
hexane, filtration, and vacuum-drying affords 10 (15.2 mg, 60%). H
Single-Crystal X-ray Structure Determinations. Single-crystal
X-ray data were collected on a Siemens P3 diffractometer equipped
with a molybdenum tube [λ(KR) ) 0.710 73 Å] and a highly oriented
graphite crystal monochromator. Crystal quality was monitored
throughout the data collection by measuring the intensities of three
standard reflections after every 100 reflections were collected. The
structures were solved by a combination of Patterson synthesis and
direct methods and subsequently refined by full-matrix least-squares
techniques, using the Siemens SHELXTL IRIS36 system of programs.
3
NMR (22 °C, C6D6, ppm): 9.15 (s, 8H, Hâ), 8.10 (dd, JHH, 7.7 Hz,
3
4
4JHH, 1.8 Hz, 4H, Hm), 7.81 (dd, JHH, 7.7 Hz, JHH, 1.8 Hz, 4H, Hm′),
7.26 (d, 3JHH, 7.3 Hz, 4H, Ho), 7.20 (d, 3JHH, 7.3 Hz, 4H, Ho′), 2.38 (s,
12H, p-CH3). 15N NMR (22 °C, C6D6, 40.4 MHz, ppm): 236.6 (s,
Ru-O15NO), -26.2 (s, Ru-15NO). IR (KBr, cm-1): ν(NO) 1835 s,
νs(NO2) 1511 m, νa(NO2) 927 m, δ(NO2) 844 w, ν(15NO) 1807 s,
νs(15NO2) 1480 m, νa(15NO2) 904 m, δ(15NO2) 846 w. UV-vis (CH2-
Cl2) λmax nm (log ꢀ): 332 (4.25), 412 (Soret) (5.25), 558 (3.93), 600
(3.77). Elemental anal. calcd (found) for C48H36N6O3Ru: C, 68.15
(67.71); H, 4.29 (4.52); N, 9.93 (9.22). Crystals suitable for X-ray
diffraction were grown by slow evaporation from a 1:5 dichlo-
romethanehexanes solution. The purple-black block selected had the
dimensions 1.2 × 0.6 × 0.4 mm3.
(35) Collman, J. P.; Barnes, C. E.; Swepston, P. N.; Ibers, J. A. J. Am.
Chem. Soc. 1984, 106, 3500-3510.
(36) Sheldrick, G. M. SHELXTL Crystallographic System, Version 5.03/
Iris; Sheldrick, G. M., Ed.; Siemens Analytical X-ray Instruments:
Madison, WI, 1994.
Method b. This compound can also be obtained by treating a

Structures of Ru(TTP)(NO)X (X ) ONO, OH)
Inorganic Chemistry, Vol. 37, No. 22, 1998 5801
Table 1. Crystallographic Data and Refinement Parameters
6
10
empirical formula
C48H37N5O2Ru
816.9
brown; block
0.62 × 0.45 × 0.28
monoclinic
P21/n
11.322(2)
26.781(5)
19.355(4)
92.98(3)
C48H36N6O3Ru
845.9
black-purple; prism
1.2 × 0.6 × 0.4
monoclinic
P21/n
11.469(2)
27.465(5)
19.363(4)
93.10(3)
6090(2)
6
1.384
0.436
mass (g mol-1
color; habit
)
crystal size (mm)
crystal system
space group
a (Å)
b (Å)
c (Å)
â (deg)
volume (Å3)
Z
5860.7(23)
6
1.389
densitycalcd (Mg m-3
)
µ (mm-1
)
0.448
2θ range (deg)
index ranges h
k
4.08 to 45.00
0 e h e 12
-28 e k e 0
-20 e l e 20
4987 (F > 6.0σ(F))
w-1 ) σ2(F) + 0.0008F2
R ) 0.053, Rw ) 0.120
1.03
4.0 to 50.0
0 e h e 13
0 e k e 32
-23 e l e 22
7186 (F > 4.0σ(F))
w-1 ) σ2(F) + 0.0078F2
R ) 0.064, Rw ) 0.108
1.07
l
no. of obsd reflcns
weighting scheme
final R (obsd)
goodness-of-fit
data-to-parameter ratio
10.05:1
0.65
-0.37
9.0:1
0.81
-0.99
largest diff peak (e Å-3
)
largest diff hole (e Å-3
)
dominates the S4-ruffling of the porphyrin ring in six-coordinate low-
spin iron complexes. This distortion is also commonly observed in
the structures of five-coordinate metalloporphyrins possessing a strong
π-accepting ligand in the axial position.8 Porphyrin ring distortion in
ruthenium compounds is probably not well recognized due to the general
scarcity of structural data available for ruthenium porphyrin complexes,
and their largely low-spin diamagnetic behavior. Owing to the small
size of the axial ligands in this instance, the steric repulsion between
axial ligands and porphyrin tolyl groups is small to negligible, and
therefore electronic effects probably best rationalize the observed S4-
ruffling. Similar distortions in a pair of ruthenium octaethylporphyrin
nitrosyl complexes have recently been described.26
Figure 1.
Results and Discussion
Table 1 contains crystallographic parameters relating to the data
collection and refinement.
The synthetic pathways for all new compounds are organized
in Scheme 1. Since all compounds are ultimately prepared from
Ru(TTP)(NO)(OMe), 2, it represents a useful synthon akin to
Ru(TTP(CO)L, the initial metallation product from TTPH2 and
Ru3(CO)12. Perhaps equally useful is Ru(TTP)(NO)Cl, 3, which
can be prepared in high yield from 2, or alternatively directly
from 1 with the use of nitrosyl chloride.15 It is difficult to
decarbonylate 1 with the two most useful methods being
exhaustive UV-photolysis in the presence of excess ligand, often
as solvent, to give Ru(por)L2,22,38-40 or by oxidation with
peracids or halogens to give ruthenium(IV) complexes.41,42
In the preparation of 2 it is remarkable that NO readily
substitutes for the carbon monoxide in 1 at room temperature.
This reaction is complicated in that the final complex has an
{RuNO}6 structure, which most likely stems from one electron
oxidation of a {RuNO}7 intermediate. Thus electron transfer
from the putative Ru(TTP)(NO)L intermediate gives a [Ru-
(TTP)(NO)L]+ species which is then trapped with methoxide
Both 6 and 10 crystallized in the centrosymmetric monoclinic space
group P21/n, Z ) 6 with two independent molecules per unit cell.
Molecule A has a ruthenium located at a general position, while the
ruthenium atom of molecule B is at an inversion center. This inversion
center generates half of a molecule B from symmetry. Coordinates
for the disordered axial ligands of molecule B were calculated from
the bond lengths and bond angles found in the ordered molecule A
and were fixed during the final refinement. The ORTEP representation
of 6, Figure 1, depicts a nitrosyl that is bound to ruthenium in a nearly
linear fashion with a Ru(1)-N(5)-O(5) bond angle of 167.4(6)°. Table
2 presents important bond lengths and angles. Bond distances and
angles for the nitrosyl ligands are typical for Ru(II) complexes, but
the oxygen atom of the nitrosyl group has a larger degree of thermal
motion and as a consequence bond lengths and angles involving the
nitrosyl ligand have higher standard deviations. Overall, both systems
display a slight S4-ruffling distortion, with the ruthenium displaced
0.0536 and 0.13 Å, in 6 and 10, respectively, from the porphyrin plane
as defined by the 24 core porphyrin ring atoms. In both cases the
metal is displaced toward the nitrosyl ligand. While this distortion is
commonly observed among first row transition metal porphyrin
compounds, it has not been documented as frequently for ruthenium
porphyrin complexes. While the causal forces which induce porphyrin
ring distortion are still a matter of debate, a recent report by Munro
and Scheidt et al.37 demonstrates that nonbonding steric repulsion
between axial ligands and porphyrin meso-position aryl groups
(38) Chow, B.; Cohen, I. Bioinorg. Chem. 1971, 1, 57.
(39) Hopf, F. R.; O’Brien, T. P.; Scheidt, W. R.; Whitten, D. G. J. Am.
Chem. Soc. 1975, 97, 277.
(40) Farrell, N.; Dolphin, D. H.; James, B. R. J. Am. Chem. Soc., 1978,
100, 324.
(41) Collman, J. P.; Barnes, C. E.; Brothers, P. J.; Collins, T. J.; Ozawa,
T.; Gallucci, J. C.; Ibers, J. A. J. Am. Chem. Soc. 1984, 106, 5151-
5163.
(37) Munro, O. Q.; Marques, H. M.; Debrunner, P. G.; Mohanrao, K.;
(42) Ke, M.; Sishta, C.; James, B. R.; Dolphin, D.; Sparapany, J. W.; Ibers,
J. A. Inorg. Chem. 1991, 30, 4766-4771.
Scheidt, W. R. J. Am. Chem. Soc. 1995, 117, 935.

5802 Inorganic Chemistry, Vol. 37, No. 22, 1998
Bohle et al.
Table 2. Metrical Parameters for the Ru(TTP)(NO)X, X ) OH, 6, and X ) ONO, 10a
6
10
For the Nitrosyl Ligand
Ru(1)-N(5)
1.751(5)
1.142(8)
167.4(6)
Ru-NO (Å)
RuN-O (Å)
Ru-N-O (deg)
Ru(1)-N(1)
1.752(6)
1.152(9)
173.3(6)
N(5)-O(5)
N(1)-O(1)
Ru(1)-N(5)-O(5)
Ru(1)-N(1)-O(1)
For the Axial X Ligand
Ru-O (Å)
Ru(1)-O(1)
1.943(5)
Ru(1)-O(3)
1.998(6)
1.148(18)
1.126(25)
124.0(11)
110.9(20)
176.4(3)
RuO-N (Å)
O(3)-N(2)
RuON-O (Å)
N(2)-O(2)b
Ru-O-NO (deg)
RuO-N-O (deg)
ON-Ru-OE (deg)
Ru(1)-O(3)-N(2)b
O(3)-N(2)-O(2)b
N(1)-Ru(1)-O(3)
N(5)-Ru(1)-O(1)
Ru(1)-Npyrrole
177.0(2)
2.055(5)
For the Porphyrin
mean Ru-Npyrrole (Å)
Ru(1)-Npyrrole
2.053(6)
a Values listed for the ordered molecule, A, which lies on a general position in the unit cell. b Values for the major nitrite orientation given only.
Scheme 1
to give 2. Without the addition of base or alcohol to the reaction
mixture the product contains variable quantities of diamagnetic
complexes Ru(TTP)(NO)X with X ) -OH and -ONO being
the predominant species by 1H NMR spectroscopy. The
formation of nitrite suggests a possible metal catalyzed dispro-
portionation of NO to give NO2 and N2O, and an elegant recent
study has demonstrated that nitrous oxide is produced in the
reaction of Ru(OEP)(CO)(ROH) with nitric oxide.14 Similar
products have been characterized in the alcohol free reaction
of Ru(TPP)(CO) with NO.16 The position of the ν(NO) stretch
in the IR suggests that the nitric oxide adopts a linear
conformation in this complex,43 and this has been confirmed
by X-ray crystallography.13
In analogy to the reactivity of Ru(porphyrin)(CO)(MeOH),
which undergoes rapid ligand substitution of methanol by a wide
range of neutral two electron donor ligands,44 the methoxide
ligand in 2 is rapidly substituted by HX {HX ) HCl, HO2CH,
(43) Mingos, D. M. P.; Sherman, D. J. AdV. Inorg. Chem. 1989, 34, 293-
377.
(44) Ariel, S.; Dolphin, D.; Domazetis, G.; James, B. R.; Leung, T. W.;
Rettig, S. J.; Trotter, J.; Williams, G. M. Can. J. Chem. 1984, 62,
755-762.

Structures of Ru(TTP)(NO)X (X ) ONO, OH)
Inorganic Chemistry, Vol. 37, No. 22, 1998 5803
HPF6, H2S, HS(p-tolyl), HIm} to give derivatives 3-5 and 7-9,
respectively (Scheme 1). In general, axial ligand substitution
under basic conditions is very slow and even strongly nucleo-
philic ligands, for example, ones which might pass through an
associative transition state involving a bent nitrosyl, exhibit slow
rates of reaction. The tentative conclusion from this observation
and the acid promoted substitution noted above is that ligand
substitution pathways for Ru(TTP)(NO)X are predominately
dissociative. This conclusion must of course be considered
tentative until more definitive kinetic studies on these and related
systems have been performed.
[Ru(TTP)(NO)(H2O)][PF6]. A similar complex, with similar
spectroscopic characteristics, forms from the addition of ni-
trosonium tetrafluoroborate to Ru(TPP)(CO).16,17 In these latter
results the ν(NO) modes are at 1853 and 1872 cm-1 for the
OEP and TPP analogues, respectively, which agree with a ν(NO)
stretching frequency of 1859 cm-1 observed for complex 5.
When 5 was treated with bases such as pyridine, the water is
rapidly deprotonated rather than substituted and the neutral
hydroxide complex Ru(TTP)(NO)(OH), 6, forms in quantitative
yield. The most efficacious method to prepare 6 is by treating
a concentrated acetonitrile solution of 5 with a slight excess of
aqueous tetra-n-butylammonium hydroxide. The presence of
a hydroxide ligand was confirmed by IR, elemental analysis,
and X-ray crystallography, see below.
The formate derivative 4, prepared by treating 2 with formic
acid, is a remarkably stable dark purple crystalline product which
could not be successfully decarboxylated to give a putative
Ru(TTP)(NO)H, eq 1. Solution thermolysis of a toluene-d8
In a similar vein, when a toluene solution of 2 is exposed to
hydrogen sulfide gas, there is an immediate reaction to produce
Ru(TTP)(NO)(SH), 7, quantitatively. Because of their multiple
redox and ligation possibilities only a few well-defined mono-
nuclear compounds containing a terminal HS ligand have been
reported.50,51 Although the ν(SH) band was broad and weak in
∆ or hν
Ru(TTP)(NO){OC(O)H}
Ru(TTP)(NO)H
(1)
– CO2
4
solution of 4 at 100 °C for 42 h resulted in no observable
decomposition between 1, 3, or 6 h; however, complete
decomposition had occurred by 42 h. Another attempt em-
ployed the use of vacuum pyrolysis at 10-4 Torr on a lyophilized
solid sample of 4 at 140 °C; again, by the time any reactivity
was noted, there was concurrent decomposition. Irradiating with
a glass-filtered medium pressure mercury lamp to affect
decarboxylation photolytically also resulted in decomposition.
It is of course possible that Ru(TTP)(NO)H may be a transient
intermediate in these decomposition reactions, but the known
large high-field shifts of the hydride resonance in the proton
NMR for Ru(porphyrin)(H) species45,46 means that these types
of species are relatively easily detected if they are present in
any appreciable quantity. A key feature of metal mediated
formate decarboxylation is the availability of a vacant coordina-
tion site to promote the â-migration reaction.47,48 The IR results
for 4 are clearly consistent with monohapto coordination of the
formate, or coordinative saturation of the metal, and once again
the observed reactivity suggests that an associative seven-
coordinate intermediate, which would most likely require a linear
to bent nitrosyl interconversion, is not energetically accessible.
Treating 3 with lithium triethylborohydride in THF failed to
generate hydride-containing species as determined by 1H NMR.
A Ru(TTP)(NO)X complex where X is a weakly coordinating
anion was sought as another approach to preparing axially
substituted complexes. To this end, a methylene chloride
solution of 2 was treated with aqueous hexafluorophosphoric
acid. The expected product, Ru(TTP)(NO)(PF6), was not
realized; instead, [Ru(TTP)(NO)(OH2)]PF6, 5, was generated.
Efforts to remove the ligated water, including placement under
high vacuum at 2 × 10-5 Torr at 110 °C for 24 h, proved futile.
Ligation of the water was confirmed by IR with rocking and
wagging modes observed at 848 and 524 cm,-1 respectively.49
Although the water protons were not observed in the 1H NMR,
the elemental analysis was consistent with the formulation
1
the IR spectrum of 7, the -SH proton was observed in the H
NMR spectrum at -6.20 ppm. This shift is consistent with
both the presence of a coordinated hydrosulfide ligand, in that
these ligands often have large high-field chemical shifts, as well
as an additional contribution to the upfield shift due to the
porphyrin ring current. In solution the hydrosulfide complex 7
is extremely oxygen sensitive and rapidly gives a complex
mixture of products, including the hydroxide complex 6, upon
exposure to air. Similar IR spectroscopic and reactivity patterns
were found for the five-coordinate low-spin iron porphyrin
complex Fe(TPPOMe)(SH).50
Treatment of a benzene solution of 2 with an excess of
p-thiocresol rapidly affords 8 in 72% yield. The mercaptide
complex is a second row model for the active metal site in nitric
oxide adducts of the heme-proteins cytochrome P-450 and nitric
oxide synthase.52,53 Although Fe(porphyrin)(NO)(X) analogues
to those described herein have been reported for high-field
ligands such as methyl and phenyl,54,55 the corresponding
mercaptides have not been documented. This may be due, in
part, to the intrinsic instability of the mercaptide adducts of the
ferric porphyrins, which tend to undergo facile autoxidation and
reductive elimination of disulfide.56,57 In contrast, 8 is thermally
stable to prolonged thermolysis at 180 °C and ligand displace-
ment at reflux in neat pyridine. Finally, the pronounced thermal
stability is in contrast with the corresponding high-valent
mercaptides such as Os(IV)(TTP)(SR)2 {R ) 2,3,5,6-tetrafluo-
rophenyl, 4-methylphenyl, 2-methylphenyl, 2,6-dimethyl-
phenyl}, which readily eliminate disulfide under these condi-
tions.58 A recent series of elegant studies have described the
(50) English, E. R.; Hendrickson, D. N.; Suslick, K. S.; Eigenbrot, C. W.;
Scheidt, W. R. J. Am. Chem. Soc. 1984, 106, 7258-7259.
(51) Kuehn, C. G.; Isied, S. S. Prog. Inorg. Chem. 1980, 27, 153.
(52) Wang, J. L.; Rousseau, D. L.; Abusoud, H. M.; Stuehr, D. J. Proc.
Nat. Acad. Sci. U.S.A. 1994, 91, 10512-10516.
(53) Hu, S. Z.; Kincaid, J. R. J. Am. Chem. Soc. 1991, 113, 2843-2850.
(54) Lagrange, G.; Cocolis, P.; Guilard, R. J. Organomet. Chem. 1984,
260, C16.
(55) Guilard, R.; Lagrange, G.; Tabard, A.; Lancon, D.; Kadish, K. M.
Inorg. Chem. 1985, 24, 3649-3656.
(56) Collman, J. P.; Sorrell, T. N.; Hoffman, B. M. J. Am. Chem. Soc.
1975, 97, 913.
(45) Collman, J. P.; Wagenknecht, P. S.; Hutchison, J. E.; Lewis, N. S.;
Lopez, M. A.; Guilard, R.; Lher, M.; Bothnerby, A. A.; Mishra, P. K.
J. Am. Chem. Soc. 1992, 114, 5654-5664.
(46) Collman, J. P.; Wagenknecht, P. S.; Lewis, N. S. J. Am. Chem. Soc.
1992, 114, 5665-5673.
(47) Komiya, S.; Yamamoto, A. J. Orgametal. Chem. 1972, 46, C58-
C60.
(48) Kolomnikov, I. S.; Gusev, A. I.; Aleksandrove, G. G.; Lobeeva, T.
S.; Struchkov, T.; Vol’pin, M. E. J. Organomet. Chem. 1973, 29, 349-
351.
(57) Koch, S.; Tang, S. C.; Holm, R. H.; Frankel, R. B. J. Am. Chem. Soc.
1975, 97, 914.
(49) Nakamoto, K. Infrared and Raman Spectra of Inorganic and Coor-
dination Compounds, 4th ed.; John Wiley & Sons: New York, 1986.
(58) Collman, J. P.; Bohle, D. S.; Powell, A. K. Inorg. Chem. 1993, 32,
4004-4011.

5804 Inorganic Chemistry, Vol. 37, No. 22, 1998
Bohle et al.
eq 2 may involve a direct attack of nitric oxide on a bent nitrosyl
ligand in an intermediate such as [Ru(TTP)(NO)2]*.64 Similar
chemistry and products have been found for the nitrosylation
of a ruthenium(salen) system,65 and a related mechanism has
been proposed for the reaction between Fe(TTP)(NO) and nitric
oxide. In this later case the product, formulated as an N-bound
nitro complex, was stable only in solution in the presence of
excess nitric oxide and was not isolable.66
The nitrosyl nitrito complex, 10, crystallized in the monoclinic
space group P21/n with Z ) 6, and with two independent
molecules per unit cell. Molecule A is located at a general
position making all of its atoms unique, while molecule B has
its ruthenium located on an inversion center, thereby leading
to axial ligand disorder within the ONO-Ru-NO fragment and
thus preventing a meaningful discussion of its axial bond lengths
for molecule B. In the final refinement the disordered axial
ligand fragment in B was modeled on that in A with only the
thermal parameters for the axial atoms being refined. In the
discussion which follows the metric parameters all refer to those
refined for molecule A. An ORTEP representation of the
molecular structure of A, Figure 2, illustrates that the nitrite
has a trans O-bound geometry which is trans to a slightly bent
“linear” nitrosyl (Figure 2). The Ru is 0.13 Å out of the plane,
defined by the porphyrin ring, toward the nitrosyl ligand. The
nitrito entity is bent in the direction of a methine carbon bearing
a p-tolyl ring, which is a typical conformation found for other
axial ligands in group 8 metalloporphyrins.67 A dinitrosyl
species was ruled out during refinement, and the nitrite ligand
was slightly disordered, with N2 being partitioned 0.71/0.29,
over two orthogonal positions. For both nitrite orientations the
oxygen atoms O(2) and O(3) share common locations. Figure
S4 in the Supporting Information shows this disorder. Important
bond lengths and angles of molecule A are summarized in Table
2. The nitrosyl ligand is bound in a nearly linear fashion as
indicated by a Ru(1)-N(1)-O(1) bond angle of 173.3(6)° and
bond lengths of Ru(1)-N(1) and N(1)-O(1) being 1.752(6)
and 1.152(9) Å, respectively. The mean Ru(1)-N(pyrrole) bond
distance is 2.053(6) Å. The Ru(1)-O(3) distance is 1.998(6)
Å, and the O(3)-N(2)-O(2) bond angle is 110.9(20)°, consis-
tent with an O-bound nitrito.68 The core porphyrin ring exhibits
a slight S4-ruffling type distortion, Figure 3.
Figure 2.
chemistry of Ru(por)(NO)(SR) which are readily prepared by
addition of RSNO to Ru(por)(CO).17,18,26,59
The chloride derivative 3 is readily prepared in high purity
on large scales by treating 2 with anhydrous hydrochloric acid.
Not only does this facile access make 3 an ideal synthon, but it
is also remarkably air and thermally stable (decomposition point
480 °C by DSC), and undergoes a range of metathesis reactions
to give Ru(TTP)(NO)X (X ) NO2-, NO3-, N3-, and NCS- to
form compounds 9-13. Treatment of a benzene/acetonitrile
solution of 3 at reflux with excess AgNO2 in the presence of
ambient oxygen produces 10 in 60% yield. This compound is
formulated as containing an oxygen-bound (nitrito) ligand on
the basis of its spectroscopic and structural data. In the IR
spectrum of 10 there is a large difference, 584 cm-1, between
the νs(NO2) mode and the νa(NO2) modes, indicative of a η1-
ONO nitrito configuration.60 The 15N NMR spectrum exhibits
two resonances at 236.6 and -26.2 ppm which are assigned to
a downfield-shifted nitrite with a bent ligand geometry and a
linear nitrosyl, respectively.61 Single-crystal X-ray diffraction
confirms that the M-O-NdO unit adopts a trans configuration,
Figure 2. The nitrosyl-nitrito complex 10 also results from a
disproportionation reaction which occurs when the metal-metal
bonded dimeric complex [Ru(TTP)]2 is treated with nitric oxide
at room temperature under rigorously oxygen-free conditions,
eq 2. The formation of N2O has not been demonstrated in the
course of this research, however it has been demonstrated to
be present in the nitrosylation of Ru(TPP)(CO)L.14
NO(excess)
[Ru(TTP)]2
8 2Ru(TTP)(NO)(ONO) + 2N2O (2)
Me3SiX reagents, which are useful for double displacement
transformations, readily react with 3 to give volatile Me3SiCl
as a side-product and Ru(TTP)(NO)(X). For example, when a
dichloromethane solution of 3 is combined with Me3SiN3, the
resulting reaction rapidly affords 12 in 80% yield, eq 3.
10
A bisnitrosyl complex, which was the anticipated product, is
ruled out by the presence of two well-separated ν(NO2) stretches
in the IR and the lack of a downfield peak in the 15N NMR
between 350 and 850 ppm, which would correlate to a bent
nitrosyl ligand. Similar conclusions have been reached by other
groups working with related complexes Ru(Por)(NO)(ONO)
{Por ) TPP, OEP}.14,16 Although a variety of complexes
promote nitric oxide disproportionation,62 proposed mechanisms
usually invoke a metal-mediated coupling of two cis nitrosyl
ligands.63 The cis coordination of two nitrosyl ligands is,
however, very unlikely for ruthenium metalloporphyrin com-
plexes and the mechanism for the transformation illustrated in
Ru(TTP)(NO)Cl Me SiX8 Ru(TTP)(NO)X + Me3SiCl (3)
3
-
12, X ) N3
13, X ) SCN-
Although repeated elemental analysis of 12 indicated loss of
N2 during the combustion analysis, the spectroscopic evidence
gives compelling evidence that the product of this reaction has
a coordinated azide. For example, only one â-pyrrolic peak is
1
observed in the H NMR spectrum, so there is just a single
(59) Yi, G.-B.; Khan, M. A.; Richter-Addo, G. B. J. Chem. Soc., Chem.
Commun. 1996, 2045-2046.
(60) Hitchman, M. A.; Rowbottm, G. L. Coord. Chem. ReV. 1982, 42, 55.
(61) Bell, L. K.; Mingos, D. M. P.; Tew, D. G.; Larkworhy, L. F.; Sandell,
B.; Povey, D. C.; Mason, J. J. Chem. Soc., Chem. Commun. 1983,
125.
(62) Bottomley, F. Reactions of Coordinated Ligands; Braterman, P. S.,
Ed.; Plenum Press: New York, 1989; p 115.
(64) Meyer, C. D.; Eisenberg, R. J. Am. Chem. Soc. 1976, 98, 1364.
(65) Carrondo, M. A. A. F. C. T.; Rudolf, P. R.; Skapski, A. C.; Thornback,
J. R.; Wilkinson, G. Inorg. Chim. Acta 1977, 24, L95.
(66) Yoshimura, T. Inorg. Chim. Acta 1984, 83, 17.
(67) Scheidt, W. R.; Frisse, M. E. J. Am. Chem. Soc. 1975, 97, 17.
(68) Ooyama, D.; Nagao, N.; Nagao, H.; Miura, Y.; Hasegawa, A.; Ando,
K.; Howell, F. S.; Mukaida, M.; Tanaka, K. Inorg. Chem. 1995, 34,
6024.
(63) Bhaduri, S.; Johnson, B. F. G.; Khair, A.; Ghatak, I.; Mingos, D. M.
P. J. Chem. Soc., Dalton Trans. 1980, 1572.

Structures of Ru(TTP)(NO)X (X ) ONO, OH)
Inorganic Chemistry, Vol. 37, No. 22, 1998 5805
Table 3. Electrochemical Data for Key New Compoundsa
complex
trans X
1st oxidationb 2nd oxidationb reductionc
2
3
4
5
6
7
10
11
13
OMe-
Cl-
1221(124)
1021(126)
1150(6)
1103(68)
1229(82)
1235(119)
1150(68)
1094(80)
1051(74)
1521(116)
1489(120)
1518(82)
1531(78)
1532(87)
1542(134)
1333(86)
1530(56)
1520(98)
-889
-789
-789
-816
-876
-978
-989
-852
-857
HC(O)O-
H2O
OH-
SH-
ONO-
-
ONO2
NCS-
a Measured by cyclic voltammetry in dichloromethane with 0.1 M
N(nBu)4PF6 as backing electrolyte, with a platinum button electrode
and a silver/silver chloride reference electrode. Potentials are reported
in mV with respect to an internal ferrocene standard. Peak separation
for reversible processes reported in parentheses for scan speed of 100
mV/s. b The two reversible porphyrin observed for the oxidation
couples. c The reduction process are usually quasireversible unless
otherwise noted.
Figure 3.
OC(O)H-,ONO- > NSO- > N3- > OH- > OMe- > SH- >
SR- (R ) p-tolyl). There appears to be a direct correlation
between the energy of the ν(NO) mode and the relative donor
ability of the trans ligand for this series of compounds: as the
donor ability of the trans ligand increases there is a decrease in
the ν(NO) energy consistent with increased NO π* orbital
population. The wide 75 cm-1 range of ν(NO) stretching
frequencies for this family of derivatives has a high value of
diamagnetic metalloporphyrin present, and the IR spectrum
exhibits two absorptions consistent with νa(NNN) and νas(NNN)
modes at 2048 and 1291 cm,-1 respectively.49 Azide ligands
are known to photolytically and/or thermally release dinitrogen
to leave a coordinated nitride behind.69 Both photolytic
(irradiation with a medium-pressure mercury lamp for 20 min)
and thermal (350 °C at 3 × 10-6 Torr for 16 h) attempts were
made to produce a nitride complex but these conditions resulted
in the simultaneous release of the NO ligand and the production
of an inseparable mixture (by thin-layer chromatography) of
1H NMR silent compounds.
1860 cm-1, trans to ONO2-, to a low energy of 1784 cm-1
,
trans to S-p-tolyl-.
On the other hand the electronic absorption spectra of this
family of Ru(TTP)(NO)X have markedly little variation. Ligand
identity of X for the various Ru(TTP)(NO)(X) complexes has
a minimal effect on the positions and intensities of either the Q
or the Soret bands. Of the complexes measured the two
mercaptide ligands exhibit the largest variation in both Soret
and Q band positions. These trends are in accordance with the
series of Ru(Por)(NO)(X) {Por ) TPP, OEP; X ) ONO-,
OH-}14 and Ru(TPP)(CO)(L) {L ) vacant, EtOH, Me2SO,
pyridine, piperidine} compounds.77 Overall, the lack of varia-
tion in the electronic absorption spectra for these compounds
is attributable to the dominance of the strong π-accepting ligand,
either the nitrosyl or carbonyl, on the axial ligand-ruthenium
interaction.
There is also surprising little variation in the electrochemical
properties of this class of complexes. The cyclic voltammetry
results for 2-13 are collected in Table 3. They are uniformly
described as having one quasireversible reduction and two
reversible oxidation couples for compounds in dichloromethane
on a platinum button working electrode. Meyer et al. have used
spectroelectrochemistry to determine that in the presence of a
good π-acid ligand such as carbonyl, the first two oxidations
are porphyrin based,78 and we also assign the two oxidations
observed for Ru(TTP)(NO)X as arising from two one electron
oxidations of the porphyrin ring. Once again there is very little
variation in the two oxidation potentials as a function of the
axial ligand X. Examination of the data concurs with the results
obtained by electronic spectroscopy; the trans ligand has a
minimal effect on the electronic interactions in this series of
compounds. Just 214 mV separate the high and low potentials
for the first oxidation couple, and the second oxidation couple
has a range of only 53 mV if compound 10 is excluded. On
the other hand the quasireversible reduction potentials can
Excess trimethylsilylisothiocyanate reacts with 3 under
moderate thermal conditions to quantitatively give Ru(TTP)-
(NO)(NCS), 13. Despite the thiophilic nature of ruthenium,
the isothiocyanate complex, with a Ru-NCS bond, was formed
rather than the intuitively more stable thiocyanate, Ru-SCN,
configuration. This assignment is based on the IR spectrum
which exhibits a ν(CN) mode at 2026 cm-1. If the ligand were
bound through the sulfur atom, then the ν(CN) stretching
frequency is expected to at higher energy g2100 cm-1 70
There
.
are two features of this system which favor the ligation of NCS-
through the harder nitrogen atom instead of the softer sulfur
atom by the normally soft ruthenium metal center. First, NO
is so effective at removing electron density from the metal center
that in this environment ruthenium is more accurately described
as a hard metal center. Second, the ligation geometry may be
kinetically controlled by elimination reactions from the inter-
mediates generated from the complex and Me3SiNCS.
The spectroscopic characterization of this family of Ru(TTP)-
(NO)X compounds allows for some insight into the electronic
interaction between the axial ligand and the [Ru(TTP)(NO)]+
fragment. Although there are many review articles written about
nitrosyl complexes,71-76 and these all address the hazards of
overinterpreting the ν(NO) stretching energies, it is interesting
to note that in dichloromethane solution at room temperature
this new family of compounds has decreasing ν(NO) bands in
the following order: NO3-, H2O(cation) > NCS-, Im-, Cl- >
(69) Buchler, J. W.; Dreher, C. Z. Naturforsch. A 1984, 39A, 222.
(70) Mitchell, P. C. H.; Williams, R. J. P. J. Chem. Soc. 1960, 1912.
(71) Gans, P.; Sabatini, A.; Sacconi, L. Coord. Chem. ReV. 1966, 1, 187.
(72) Masek, J. Inorg. Chim. Acta ReV. 1969, 3, 99.
(73) Johnson, B. F. G.; McCleverty, J. A. Prog. Inorg. Chem. 1966, 7,
277.
(74) Griffith, W. P. AdV. Organomet. Chem. 1968, 7, 211.
(75) McGinnety, J. A. MTP Int. ReV. Sci.: Inorg. Chem. 1972, 5, 229.
(76) Feltham, R. D.; Enemark, J. Coord. Chem. ReV. 1974, 13, 339.
(77) Levine, L. M. A.; Holten, D. J. Phys. Chem. 1988, 92, 714.
(78) Brown, G. M.; Hopf, F. R.; Ferguson, J. A.; Meyer, T. J.; Whitten,
D. G. J. Am. Chem. Soc. 1973, 95, 5939.

5806 Inorganic Chemistry, Vol. 37, No. 22, 1998
Bohle et al.
involve a number of sites, and the lack of reversibility found
for many of these species, as well as the large range associated
for this reduction, ca. 200 mV, may be due to the variation in
X, where electron transfer is followed by a variable slow loss
of X-. Alternatively, electron transfer could lead to nitrosyl
bending and the formation of a {RuNO}7 fragment. In certain
cases other product waves and irreversible processes are
observed. Specifically, compounds 6 and 7 exhibit an irrevers-
ible oxidation process and the subsequent product waves. For
6 these are observed at 1001 and -322 mV, respectively, while
the cyclic voltammogram for 7 displays analogous processes
at 907 and -370 mV. Compound 3 has two similar features
in its voltammogram; there are two irreversible oxidation events
at 999 and 1857 mV and two irreversible reduction processes
at -375 and -1313 mV, respectively. A quasireversible
product couple is observed for 13, E1/2 ) 1210 mV with a peak
separation of 53 mV.
Interestingly, the cyclic voltammograms for 5 and 10 are less
complicated than the data for the closely related complexes [Ru-
(TPP)(NO)(H2O)][BF4] and Ru(TPP)(NO)(ONO) {TPP ) meso-
tetraphenylporphyrinato dianion}.16 In this case one reversible,
E1/2 ) -1050 mV, and two irreversible reduction, E ) -330
and -780 mV, couples were observed for the aquo complex;
we observe a single quasireversible process, E ) -816 mV,
for 5 with PF6- as counterion. In addition, the electrochemistry
of the TPP derivative also has three reduction processes for Ru-
(TPP)(NO)(ONO) compared to just one that we observe for Ru-
(TTP)(NO)(ONO). It is surprising that there are such dramatic
differences in the observed electrochemical behaviors for these
two related species, as the main experimental differences appears
to be first and foremost in the specific synthetic method
employed, and second that while the experiments reported here
were performed in a rigorously dry and oxygen free inert
atmosphere box, the results for Ru(TPP)(NO)X were performed
under a blanket of nitrogen.
Conclusion
The data described herein leads to the conclusion that the
RuNO moiety dominates the electronic interactions, in these
metalloporphyrin complexes, while the trans ligand participates
only minimally. The illusive Ru(TTP)(NO)2, bisnitrosyl com-
plex, remains largely a speculative reaction intermediate, which
most likely disproportionates nitric oxide to give the observed
product, Ru(TTP)(NO)(ONO), which is the frequently observed
thermodynamic sink for this chemistry. This work reinforces
the widely accepted hypothesis that ruthenium and nitrosyl form
a good stable marriage; for instance, the Ru(TTP)(NO)(Cl)
species is stable to thermal decomposition to 480 °C. Few other
coordination complexes with an organic ligand, the porphyrin,
remain stable under such forcing conditions. The development
of facile methods for high-yielding synthesis of the two flexible
synthons, 2 and 3, is a particularly useful development and may
lead to many additional types of complexes.
Acknowledgment. Support for this research from the NIH
(Grant GM53828), the DOE (Grant DE-FCO2-91ER), and the
American Heart Association is gratefully acknowledged.
Supporting Information Available: Tables of X-ray experimental
details, bond distances and angles, thermal parameters, and hydrogen
coordinates and fully labeled ORTEP diagrams (28 pages). Ordering
information is given on any current masthead page.
IC980182M