One-Pot Synthesis of Dihalo(porphyrinato)osmium(IV) Complexes. Evidence for Monohalo(carbonyl)osmium(III) Intermediates 1

Article abstract of DOI:10.1021/ic960363t

trans-Dichloro-, trans-dibromo-, and trans-diiodoosmium(IV) tetraarylporphyrins were obtained by extremely facile synthetic routes directly from the reactions of the corresponding (carbonyl)osmium(II) complexes with CCl₄, CBr₄, and C

Full text of DOI:10.1021/ic960363t

7260
Inorg. Chem. 1996, 35, 7260-7263
One-Pot Synthesis of Dihalo(porphyrinato)osmium(IV) Complexes. Evidence for
Monohalo(carbonyl)osmium(III) Intermediates†
Zeev Gross* and Atif Mahammed
Department of Chemistry, TechnionsIsrael Institute of Technology, Haifa 32000, Israel
ReceiVed April 3, 1996X
trans-Dichloro-, trans-dibromo-, and trans-diiodoosmium(IV) tetraarylporphyrins were obtained by extremely
facile synthetic routes directly from the reactions of the corresponding (carbonyl)osmium(II) complexes with
CCl4, CBr4, and CI4, respectively. At short reaction times, appreciable amounts of intermediatessone for each
reactionswere observed by spectroscopic investigations. These intermediates were shown to be (carbonyl)-
(halo)(porphyrinato)osmium(III) complexes by independent preparation of an authentic (carbonyl)(bromo)-
(porphyrinato)osmium(III) complex, which was identical to the reaction intermediate in the reaction of CBr4 and
very similar to those of the other reactions. This provided strong evidence for the reaction mechanism, two
stepwise one-electron oxidations of the metal ion. The relatively strong binding of carbon monoxide to osmium(III)
is proposed to be an important factor in avoiding dimerization of the reaction intermediates.
Introduction
and experimentally demanding procedures were avoided in the
recently reported two-step syntheses of the first two dihalo-
(porphyrinato)osmium(IV) complexes by three independent
groups. In all three cases, the carbonyl complexes [Os(por)-
(CO)] were first oxidized to the corresponding trans-dioxo-
osmium(VI) porphyrins. Subsequent reduction of [OsVI(oep)-
(O)2] with Br2 afforded [OsIV(oep)Br2] in 40% yield,2c and
[OsIV(ttp)Cl2] was obtained in yields of 80% and 51% from
the reaction of [OsVI(ttp)(O)2] with SOCl2 or SnCl2, respec-
tively.4
In line with the desire for simple methods for the preparation
of [MIV(por)X2] derivatives, we have very recently discovered
an extremely simple alternative one-pot synthetic route to
[RuIV(por)X2] complexes. Thus, [RuIV(tdmpp)Cl2] and [RuIV-
(tdmpp)Br2] were prepared directly from [Ru(tdmpp)(CO)] in
> 80% yields by simply heating it with CCl4 or CBr4.5 For
non sterically hindered porphyrins, such as [Ru(ttp)(CO)],
dimeric derivatives were however formed. We now report our
investigation of that reaction for osmium porphyrins, which
shows that it has even a larger scope for Os than for Ru. Thus,
the dichloro-, dibromo-, and diiodoosmium(IV) complexes of
both ttp and tmp were prepared in very simple one-pot
procedures directly from the corresponding (carbonyl)os-
mium(II) porphyrins (Scheme 1). The in situ observation of
[OsIII(por)(CO)(X)] intermediates during these reactionssidentified
by comparison to the independently prepared and fully char-
acterized [OsIII(por)(CO)(Br)] complexsclearly suggest that the
transformations of [OsII(por)(CO)] to [OsIV(por)X2] proceed by
two distinct one-electron oxidation steps. In addition, the
characterization of the intermediates as (carbonyl)osmium(III)
complexes also provided a clue about the different reaction
pathways of [Os(por)(CO)] and [Ru(por)(CO)].
Ongoing interest in the chemistry of ruthenium(IV) and
osmium(IV) porphyrins derives from their rich coordination
chemistry,1-5 including very interesting organometallic
complexes.3,4a The most important precursors of organoruthe-
nium and organoosmium porphyrins are trans-dihalometal(IV)
complexes, [MIV(por)X2], with M ) Ru, Os, and X ) halide
anion. It was also recently proposed that [RuIV(por)X2]
complexes are important intermediates in the highly efficient
oxygenation of hydrocarbons by aromatic N-oxides under
catalysis of ruthenium porphyrins in the presence of mineral
acids.6 Practically all ruthenium and osmium porphyrin com-
plexes are prepared from the corresponding metal carbonyls,
[MII(por)(CO)]. The carbonyl group in these complexes is
considered chemically inert, and most existing synthetic routes
for preparation of more reactive derivatives rely on its removal
by either oxidative or photochemical methods. The full series
of dihalo(porphyrinato)ruthenium complexess[RuIV(por)X2],
with X ) F, Cl, Br, Iscan be prepared from [Ru(por)(CO)] in
three distinct steps. The first two steps, leading to the dinuclear
complexes [Ru(por)]2, require however photochemical, high
temperatures, and ultrahigh-vacuum procedures.3 Such lengthy
† Abbreviations used: por ) unspecified porphyrin dianion; oep )
2,3,7,8,12,13,17,18-octaethylporphyrin dianion; tpp ) 5,10,15,20-tetra-
phenylporphyrin dianion; ttp )5,10,15,20-tetra-p-tolylporphyrin dianion;
tmp ) 5,10,15,20-tetrakis(2,4,6-trimethylphenyl)porphyrin dianion; tdmpp
) 5,10,15,20-tetrakis(2,6-dimethylphenyl)porphyrin dianion.
X Abstract published in AdVance ACS Abstracts, November 1, 1996.
(1) Groves, J. T.; Scott, J. S. J. Am. Chem. Soc. 1995, 117, 5594. Cheng,
S. Y. S.; Rajapakse, N.; Rettig, S. J.; James, B. R. J. Chem. Soc.,
Chem. Commun. 1994, 2669. Huang, J.-S.; Che, C.-M.; Li, Z.-Y.;
Poon, C.-K. Inorg. Chem. 1992, 31, 1313.
(2) (a) Collman, J. P.; Bohle, D. S.; Powell, A. K. Inorg. Chem. 1993,
32, 4004. (b) Che, C. M.; Huang, J. S.; Li, Z. Y.; Poon, C. K.; Tong,
W. F.; Lai, T. F.; Cheng, M. C.; Wang, C. C.; Wang, Y. Inorg. Chem.
1992, 31, 5220. (c) Che, C. M.; Leung, W. H.; Chung, W. C. Inorg.
Chem. 1990, 29, 1841. (d) Masuda, H.; Taga, T.; Osaki, K.; Sugimoto,
H.; Mori, M. Bull. Chem. Soc. Jpn. 1984, 57, 2345.
(3) (a) Collman,J. P. ; Rose, E.; Venburg, G. D. J. Chem. Soc., Chem.
Commun. 1994, 11. (b) Ke, M.; Sishta, C.; James, B. R.; Dolphin, D.;
Sparapany, J. W.; Ibers, J. A. Inorg. Chem. 1991, 30, 4766.
(4) (a) Leung, W. H.; Hun, T. S. M.; Wong, K. Y.; Wong, W. T. J. Chem.
Soc., Dalton Trans. 1994, 2713. (b) Smieja, J. A.; Ormberg, K. M.;
Busuego, L. N.; Breneman, G. L. Polyhedron 1994, 13, 339.
(5) Gross, Z.; Barzilay, C. M. J. Chem. Soc., Chem. Commun. 1995, 1287.
(6) Ohtake, H.; Higuchi, T.; Hirobe, M. Heterocycles 1995, 40, 867.
Results and Discussion
The reactions were investigated for two porphyrin derivatives,
one which can form dimeric productss[Os(ttp)(CO)]sand one
which cannots[Os(tmp)(CO)]. In the reactions with CCl4 the
reagent served as solvent as well and the reactions with CBr4
and CI4 were performed in benzene at reflux. Since CI4 releases
I2 very easily, the last reactions were also studied with I2. The
yields were very high for both CI4 and I2, and accordingly the
syntheses were much more conveniently performed with I2. The
S0020-1669(96)00363-1 CCC: $12.00 © 1996 American Chemical Society

Dihalo(porphyrinato)osmium(IV) Complexes
Inorganic Chemistry, Vol. 35, No. 25, 1996 7261
1
Table 1. 200 MHz H NMR Data for the [OsIV(tmp)X2] Complexes at Various Temperatures in CDCl3
chem shift (δ)
[OsIV(tmp)Cl2]
[OsIV(tmp)Br2]
[OsIV(tmp)I2]
T (K)
m-H
p-CH3
o-CH3
pyr-H
m-H
p-CH3
o-CH3
pyr-H
m-H
p-CH3
o-CH3
pyr-H
215
235
250
295
8.21
8.22
8.21
8.20
3.32
3.32
3.31
3.31
2.67
2.67
2.67
2.68
-5.68
-5.59
-5.41
-5.10
8.22
8.21
8.21
8.20
3.29
3.28
3.28
3.28
2.67
2.68
2.69
2.70
-5.05
-4.93
-4.75
-4.42
8.27
8.26
8.25
8.25
3.25
3.25
3.25
3.24
2.75
2.76
2.78
2.80
-4.17
-3.91
-3.57
-3.16
Scheme 1a
a Reagents and conditions: i, reflux of 10-30 mg of [M(por)(CO)]
in 20 mL of CCl4 or with 10 equiv of either CBr4, CI4, or I2 in 20 mL
of benzene for 2-24 h. Key: (a) M ) Ru, Ar ) 2,6-dimethylphenyl;
(b) M ) Os, Ar ) 2,4,6-trimethylphenyl; (c) M ) Os, Ar )
4-methylphenyl.
1
mixtures by H NMR at given times, which also led to a very
meaningful observation. In all investigations we noticed that
at early stages up to 65% of a complex was formed that is
neither the starting material nor the product. The position of
its proton resonances (i.e., pyrrole H at 4.13 ppm for the reaction
of [Os(tmp)(CO)] with CBr4) pointed toward a paramagnetic
complex, while the observation of two sets of resonances for
each of the phenyl’s meta H and ortho H (ttp) or ortho CH3
(tmp) indicated a complex of low symmetry. Furthermore, at
longer reaction times these complexes disappeared in favor of
the final products, strongly indicating that the reactions proceed
in two discrete steps. Attempts to isolate intermediates by
column chromatography disclosed curious behavior. Reaction
mixtures, which according to NMR contained only traces of
[Os(por)(CO)] and about equimolar amounts of [OsIV(por)X2]
and the intermediate, were eluted on silica with CHCl3. First
[OsIV(por)X2] came out, followed by unreacted [Os(por)(CO)].
The rest of the material remained at the top of the column and
could only be liberated with acetone. But, to our surprise, what
came out was [Os(por)(CO)]. We thus concluded that the
intermediates were decomposed on the column back to the
starting material, which also implies that they still carry a metal-
bound carbonyl. A reasonable structure to account with all of
these observations is [OsIII(por)(X)(CO)], since it is also in
accord with the earlier mentioned paramagnetism and low
symmetry.
Figure 1. 200 MHz 1H NMR spectra of [(OsIV(tmp)(X)2] in CDCl3 at
room temperature: (a) X ) Cl; (b) X ) Br; (c) X ) I.
dibromo derivatives could also be prepared by reaction with
Br2/benzene at reflux, but the yields were lower than with CBr4
and many byproducts were formed. In all cases the trans-
dihaloosmium(IV) derivatives were obtained free of dimeric
products. The yields for the various products were as follows:
[OsIV(ttp)Cl2], 48%; [OsIV(ttp)Br2], 56%; [OsIV(ttp)I2], 94%;
[OsIV(tmp)Cl2], 45%; [OsIV(tmp)Br2], 71%; [OsIV(tmp)I2], 96%.
These moderate to excellent yields are not only higher than the
existing methods for the only previously reported complex of
this types[OsIV(ttp)Cl2], obtained in 30-64% from [Os(ttp)-
(CO)]sbut the synthetic procedure is much simpler and is of
broader scope.
All five new complexes were identified by routine methods
and by comparison of their 1H NMR data to that of previously
characterized [OsIV(ttp)Cl2].4 In particular, the high symmetry
of the complexes is apparent by the observation of only one
signal for each of the meta H and the ortho H (ttp) or ortho
CH3 (tmp) of the phenyl groups (Figure 1). The chemical shifts
of the pyrrole H of the six complexes were located at high
fieldsbetween -5.23 and -3.16 ppmsin accord with their
paramagnetism. Only the pyrrole H chemical shifts were
temperature-dependent, as can be seen from the data collected
in Table 1 for the [OsIV(tmp)X2] complexes.
Supporting evidence for the above mentioned structural
proposal was provided by the reaction of [Os(tmp)(CO)] with
0.5 equiv of Br2 in benzene at room temperature. Fortunately,
this reaction was very clean and required no chromatographic
treatment, which when attempted gave results similar to the
earlier mentioned observationssreduction to the starting mate-
rial. The reaction product was identified as [OsIII(tmp)(Br)-
(CO)] by elemental analysis and a combination of spectroscopic
methods. In particular, a CO stretch at 1933 cm-1 was observed
in its IR spectrum, which is shifted in the expected position
relative to the value of 1920 cm-1 in the lower valent [OsII(tmp)-
We have also examined the effect of light, O2, and MeOH
on the reactions with CCl4 and CBr4. Ambient laboratory light
had no effect, MeOH (17% v/v) inhibited the reactions
completely, and reactions performed aerobically were much
slower (24 h for full consumption of starting material) than those
under N2 or Ar (2 h), although the final yields were not affected.
The last result was found by examining small aliquots of reaction
1
(CO)] complex. Most important, the H NMR spectrum of
[OsIII(tmp)(Br)(CO)], which is shown in Figure 2, was identical
to that of the in situ observed intermediate in the reaction of
[Os(tmp)(CO)] with CBr4. Furthermore, heating of the inde-
pendently prepared [OsIII(tmp)(Br)(CO)] with CBr4 in benzene

7262 Inorganic Chemistry, Vol. 35, No. 25, 1996
Gross and Mahammed
CO spontaneously, providing the required empty coordination
site for dimerization.
In conclusion, in this paper we introduce an extremely easy
one-pot synthetic procedure for superior preparation of dihalo-
(porphyrinato)osmium(IV) derivatives, utilized for one recently
reported complex and five new complexes. In addition, we have
characterized an intermediate reaction product which shines
some light on the mechanism of this reaction and on the
difference between Os and Ru porphyrins. Crystallographic
characterization of the Os(IV) derivatives, as well as their
utilizations as precursors for new organoosmium complexes are
currently under investigation.
Experimental Section
Figure 2. 200 MHz 1H NMR spectrum of [(Os(tmp)(CO)(Br)] in
CDCl3 at room temperature.
Solvents and Reagents. Dichloromethane (Lab-Scan, HPLC grade)
was dried by distillation over CaH2. Thiophene-free benzene (Biolab
Ltd.) was repeatedly washed with concentrated H2SO4 until colorless,
followed by washing with water, drying with CaCl2 and final distillation
over CaH2. Analytical grade CCl4 (Frutarom), CBr4 (Merck, >98%),
CDCl3 (Aldrich), and Os3(CO)12 (Strem Chemicals, 99%) were used
as received. 5,10,15,20-tetra-p-tolylporphyrin and 5,10,15,20-tetrakis-
(2,4,6-trimethylphenyl)porphyrin were prepared by literature methods.10
[Os(ttp)(CO)] and [Os(tmp)(CO)] were synthesized from the corre-
sponding porphyrins in 70% and 63% yields, respectively, by metalation
with Os3(CO)12 in diethylene glycol monomethyl ether, as previously
described.11
Scheme 2
Spectroscopic Measurements. The 1H NMR spectra were recorded
on a Brucker AM 200 instrument, operating at 200 MHz. Chemical
shifts are reported relative to residual hydrogens in the deuterated
solvent, 7.24 ppm for CHCl3. Electronic spectra were recorded on a
HP 8452A diode array spectrophotometer, and infrared spectra on a
FT-IR Nicolet Impact 400 spectrometer. Elemental analyses were
performed by the microanalysis service at the Hebrew University,
Jerusalem.
Preparation of the Dihalo(porphyrinato)osmium(IV) Complexes
[Os(por)X2], X ) Cl, Br. The appropriate [Os(por)(CO)] (22-25 mg,
25 µmol) was dissolved in 20 mL of CCl4 or in 20 mL of benzene
containing 8.3 mg (250 µmol) of CBr4 and heated under Ar at reflux
temperatures for 2-3 h. After evaporation of the solvents, column
chromatography (silica/CHCl3), solvent evaporation, and recrystalli-
zation from CH2Cl2/hexane, [Os(ttp)(Cl)2], [Os(ttp)(Br)2], [Os(tmp)-
(Cl)2], and [Os(tmp)(Br)2], were obtained as dark violet crystals in 48,
56, 45, and 71% yields, respectively.
[Os(ttp)(Cl)2]. MS (DCI, isobutane, negative ion): cluster around
m/z 930.3 (M-, 100%, correct isotopic pattern for C48H36Cl2N4Os). 1H
NMR (δ, CDCl3, room temperature): 10.89 (8H, d, J ) 7.2 Hz, Ho),
8.68 (8H, d, J ) 7.2 Hz, Hm), 3.41 (12H, s, p-CH3), -5.23 (8H, s,
pyrrole H). UV-vis (CH2Cl2), λmax/nm (log ꢀ, M-1 cm-1): 394 (5.29),
504 (3.88), 530 (3.81), 612 (3.62).
[Os(ttp)(Br)2]. MS (FAB-, Magic Bullet): cluster around m/z
1018.2 (M-, 100%, correct isotopic pattern for C48H36Br2N4Os). 1H
NMR (δ, CDCl3, room temperature): 10.65 ((8H, d, J ) 7.4 Hz, Ho)
8.64 (8H, d, J ) 7.4 Hz, Hm), 3.39 (12 H, s, p-CH3), -4.42 (8H, s,
pyrrole H). UV-vis (CH2Cl2): λmax/nm (log ꢀ, M-1 cm-1) 398 (5.34),
508 (4.13), 534 (4.06), 618 (3.80).
resulted in its transformation to [OsIV(tmp)Br2]. Thus, we may
safely conclude that the reactions of [Os(por)(CO)] with CX4
proceed according to Scheme 2, one-electron oxidation to
[OsIII(por)(X)(CO)], followed by a second one-electron oxidation
to [OsIV(por)(X)2].
The presence of the carbonyl group in [OsIII(por)(X)(CO)]
constitutes a quite rare case of a high-valent metal carbonyl.7
The strong binding of CO to Os is actually already reflected in
the +2 oxidation state, as the comparison of a series of [M(ttp)-
(CO)(pyr)] complexes clearly shows, i.e., νCO ) 1977, 1943,
and 1920 cm-1 for M ) Fe, Ru, and Os, respectively.8
Furthermore, assuming a similar mechanism for the reactions
of [Os(por)(CO)] and [Ru(por)(CO)] with CX4, the stronger
binding of CO to the former can account for the different
reaction products in the two cases. Monomeric [M(por)(X)2]
are obtained for both [Os(tmp)(CO)] and [Os(ttp)(CO)], regard-
less of porphyrin structure, and also for [Ru(tdmpp)CO]. For
[Ru(ttp)(CO)] however, in which no steric protection against
dimerization is provided by the porphyrin, dimeric products are
formed.5 We propose that dimerization is avoided in the
reactions of (carbonyl)(porphyrinato)osmium(II) with CX4,
because the intermediate [OsIII(por)(X)(CO)] complexes are
hexacoordinated. The νCO of a putative [RuIII(por)(X)(CO)]
complex is however expected at 1955 cm-1 (1942 cm-1 of
[RuII(ttp)(CO)] + 13 cm-1 for the increased positive charge), a
value well above 1935 ( 5 cm-1, which is considered the upper
limit for irreversible binding of CO to metalloporphyrins.9 Thus,
[RuIII(por)(X)(CO)] intermediates can be expected to lose their
[Os(tmp)(Cl)2]. MS (DCI, isobutane, negative ion): cluster around
m/z 1042.4 (M-, 100%, correct isotopic pattern for C56H52Cl2N4Os);
1H NMR (δ, CDCl3, room temperature): 8.21 (8H, s, Hm), 3.31 (12H,
s, p-CH3), 2.68 (24H, s, o-CH3), -5.13 (8H, s, pyrrole H). UV-vis
(CH2Cl2), λmax/nm (log ꢀ, M-1 cm-1): 394 (5.14), 508 (3.82), 612 (3.55).
[Os(tmp)(Br)2]. Anal. Calcd. for C56H52Br2N4Os.CH2Cl2: C, 56.30;
H, 4.48; N, 4.61. Found: C, 56.32; H, 4.73; N, 4.25; MS (FAB-):
cluster around m/z 1132.5 (M-, 100%, correct isotopic pattern for
C56H52Br2N4Os). 1H NMR (δ, CDCl3, room temperature): 8.21 (8H,
(7) Hill, A. F. in ComprehensiVe Organometallic Chemistry II; Abel, E.
W., Stone, F. G. A., Wilkinson, G., Eds.; Elsevier: Oxford, England,
1995; Vol. 7 (Shriver, D. F., Bruce, M. I., Eds.), p 319.
(8) Buchler, J. W.; Kokish, W.; Smith, P. D. Struct. Bonding (Berlin)
1978, 34, 121.
(9) Buchler, J. W. In The Porphyrins; Dolphin, D., Ed.; Academic: New
York, 1978; Vol. I, p 463.
(10) Adler, A. D.; Longo, F. R.; Finarelli, J. D.; Goldmacher, J.; Assour,
J.; Korsakoff, L. J. Org. Chem. 1967, 32, 476. Lindsey, J. S.; Wagner,
R. J. J. Org. Chem. 1989, 54, 828.
(11) Che, C. M.; Chung, W. C.; Lai, T. F. Inorg. Chem. 1988, 27, 2801.
Che, C. M.; Poon, C. K.; Chung, W. C.; Gray, H. B. Inorg. Chem.
1985, 24, 1277.

Dihalo(porphyrinato)osmium(IV) Complexes
Inorganic Chemistry, Vol. 35, No. 25, 1996 7263
s, Hm), 3.28 (12H, s, p-CH3), 2.70 (24H, s, o-CH3), -4.44 (8H, s, pyrrole
H). UV-vis (CH2Cl2), λmax/nm (log ꢀ, M-1 cm-1): 398 (5.28), 508
(3.95), 534 (3.81), 616 (3.57).
o-CH3), -3.16 (8H, s, pyrrole H). UV-vis (CH2Cl2), λmax/nm (log ꢀ,
M-1 cm-1): 366 (4.48), 410 (4.81), 526 (3.20), 630 (3.32).
Preparation of [Os(tmp)(CO)(Br)]. A solution of [Os(tmp)CO]
(10 mg, 10 µmol) in 20 mL benzene was treated with 0.5 equiv Br2
(0.8 mg, 5 µmol). Evaporation of the solvent and recrystallization from
CH2Cl2/hexane afforded [Os(tmp)(CO)(Br)] as a dark violet solid (9.4
mg, 87%). Anal. Calcd. for C57H52BrON4Os.2H2O: C, 61.39; H, 5.06;
N, 5.02. Found: C, 61.84; H, 5.05; N, 4.79. MS (FAB+): clusters
around m/z 1079 (M+, 24%), 1050 (M+ - CO, 32%), 1000 (M+ - Br,
80%), 971 (M+ - Br - CO, 100%). 1H NMR (δ, CDCl3, room
temperature): 11.74 (4H, s, Hm), 11.64 (4H, s, Hm), 4.11 (8H, br s,
pyrrole H), 3.32 (12H, s, p-CH3), 2.80 (12H, s, o-CH3), 2.41 (12H, s,
o-CH3). UV-vis (CH2Cl2), λmax/nm (log ꢀ, M-1 cm-1): 410 (5.06),
518 (4.20). IR (KBr): 1933 cm-1 (CO).
Preparation of the Diiodo(porphyrinato)osmium(IV) complexes,
[Os(por)I2]. A 10 mg sample of [Os(ttp)CO] or [Os(tmp)CO] (11.3
and 10.0 µmol, respectively) and 25 mg (98.5 µmol) of I2 were dissolved
in 20 mL of benzene and heated for 30 min. After evaporation of the
solvent at reduced pressure and recrystallization from CH2Cl2/hexane,
dark violet crystals were obtained in quantitative yields: isolated yields
of 94% and 96% for [Os(ttp)I2] and [Os(tmp)I2], respectively.
[Os(ttp)I2]. MS (DCI, isobutane, negative ion): cluster around m/z
1113.7 (M-, 100%, correct isotopic pattern for C48H36I2N4Os); 1H NMR
(δ, CDCl3, room temperature): 10.30 (8H, d, J ) 7.4 Hz, Ho), 8.58
(8H, d, J ) 7.4 Hz, Hm), 3.37 (12H, s, p-CH3), -2.88 (8H, s, pyrrole
H). UV-vis (CH2Cl2), λmax/nm (log ꢀ, M-1 cm-1): 358 (4.43), 408
(4.76), 520 (3.75), 630 (3.81).
[Os(tmp)I2]: Anal. Calcd. for C56H52I2N4Os.4CH2Cl2: C, 46.05;
H, 3.86; N, 3.58. Found: C, 46.40; H, 4.10; N, 3.60. MS (DCI,
isobutane, negative ion): cluster around m/z 1225.8 (M-, 100%, correct
isotopic pattern for C56H52I2N4Os). 1H NMR (δ, CDCl3, room
temperature): 8.25 (8H, s, Hm), 3.24 (12H, s, p-CH3), 2.80 (24H, s,
Acknowledgment. We acknowledge “The Israel Science
Foundation”, administered by “The Israel Academy of Sciences
and Humanities” for financial support of this research.
IC960363T