Heterobimetallic nitrido-bridged Ru(II)NOs(VIII) and Ru(II)NOs(VI) complexes containing ruthenium porphyrins

Article abstract of DOI:10.1016/S0020-1693(99)00096-1

Treatment of Ru(por)(NO)(OTf) (por=dianion of 2,3,7,8,12,13,17,18-octaethylporphyrin H₂(OEP) or 5,10,15,20-tetra(p-tolyl)porphyrin H₂(TTP), OTf=triflate) with [NⁿBu₄][OsO₃N] afforded the nitrido-bridged Ru(II)-Os(VIII) complexes [(por)(NO)RuNOsO₃] (por=OEP (3) or TTP (4)). The structure of 3 has been established by X-ray crystallography. The Ru-N(O), Ru-N(Os) and Os-N distances in 3 are 1.83(2), 2.03(1) and 1.79(1) A, respectively; the Ru-N-O and Ru-N-Os angles are 153(1) and 138.4(8)°, respectively. Reaction of Ru(por)(NO)(OTf) with [NⁿBu₄][OsNL₂] (H₂L=3,4-toluenedithiol) gave the nitrido-bridged Ru(II)-Os(VI) complexes (por)(NO)RuNOsL₂ (por=OEP (5), TTP (6)). Treatment of Ru(OEP)(NO)(OTf) with ReN(Et₂dtc)₂ (Et₂dtc=N,N-diethyldithiocarbamate) afforded the Ru(II)-Re(V) complex (OEP)(NO)RuNRe(Et₂dtc)₂(OTf) (7). Complexes 3 and 4 exhibit porphyrin-centered oxidation along with Os(VIII)-Os(VII) and Ru(II)-Ru(I) reductions. Complexes 5 and 6 exhibit Os(VII)-Os(VI) and porphyrin ring oxidation along with Ru(II)-Ru(I) reduction.

Full text of DOI:10.1016/S0020-1693(99)00096-1

Inorganica Chimica Acta 290 (1999) 28–35
Heterobimetallic nitrido-bridged Ru(II)NOs(VIII) and
Ru(II)NOs(VI) complexes containing ruthenium porphyrins
Wa-Hung Leung a,*, Joyce L.C. Chim a, Willetta Lai a, Leo Lam a, Wing-Tak Wong b,1,
Wing Hang Chan c, Chi-Hung Yeung c
a Department of Chemistry, The Hong Kong Uni6ersity of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
b Department of Chemistry, The Uni6ersity of Hong Kong, Pokfulam Road, Hong Kong
c Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic Uni6ersity, Hunghom, Kowloon, Hong Kong
Received 19 November 1998; accepted 18 February 1999
Abstract
Treatment of Ru(por)(NO)(OTf) (por=dianion of 2,3,7,8,12,13,17,18-octaethylporphyrin H2(OEP) or 5,10,15,20-tetra(p-
tolyl)porphyrin H2(TTP), OTf=triflate) with [NnBu4][OsO3N] afforded the nitrido-bridged Ru(II)–Os(VIII) complexes
[(por)(NO)RuNOsO3] (por=OEP (3) or TTP (4)). The structure of 3 has been established by X-ray crystallography. The
,
Ru–N(O), Ru–N(Os) and Os–N distances in 3 are 1.83(2), 2.03(1) and 1.79(1) A, respectively; the Ru–N–O and Ru–N–Os
angles are 153(1) and 138.4(8)°, respectively. Reaction of Ru(por)(NO)(OTf) with [NnBu4][OsNL2] (H2L=3,4-toluenedithiol) gave
the nitrido-bridged Ru(II)–Os(VI) complexes (por)(NO)RuNOsL2 (por=OEP (5), TTP (6)). Treatment of Ru(OEP)(NO)(OTf)
with ReN(Et2dtc)2 (Et2dtc=N,N-diethyldithiocarbamate) afforded the Ru(II)–Re(V) complex (OEP)(NO)RuNRe(Et2dtc)2(OTf)
(7). Complexes 3 and 4 exhibit porphyrin-centered oxidation along with Os(VIII)–Os(VII) and Ru(II)–Ru(I) reductions.
Complexes 5 and 6 exhibit Os(VII)–Os(VI) and porphyrin ring oxidation along with Ru(II)–Ru(I) reduction. © 1999 Elsevier
Science S.A. All rights reserved.
Keywords: Crystal structures; Ruthenium complexes; Osmium complexes; Nitrido-bridged complexes; Porphyrin complexes
1. Introduction
phyrins [Fe(TPP)]2(m-N) (TPP=5,10,15,20-tetraphenyl-
porphyrin dianion) [4], (por)FeNFe(pc) [5,6] and
(por)FeNRu(pc) [6] (pc=phthalocyanine dianion) have
been isolated and implicated as the intermediates for the
intermetal nitrogen atom transfer reactions of metal-
loporphyrins [7]. Previously we reported that m-nitrido-
bridged complexes Os(VIII)NM (M=Au, Pt, Ir) [8] and
Os(VI)NM (M=Au, Ir) [9] can be prepared conveniently
by reactions of cationic organometallic complexes
with [Os(VIII)O3N]− and [Os(VI)NL2]− (H2L=3,4-
toluenedithiol), respectively. This prompted us to synthe-
size the analogous complexes of metalloporphyrins using
the same methodology. Nitrosylruthenium(II) por-
phyrins were chosen to be nitride acceptors because they
are known to bind to p-donor ligands such as alkoxides
[10,11], thiolates [11,12], and hydroxide [13]. We here
describe the reactions of nitrosylruthenium(II)
porphyrins with nitrido-Os and -Re complexes
Heterobinuclear complexes containing metallopor-
phyrins are of interest because of their rich electrochem-
istry and their potential application in multi-electron
redox catalysis. While mixed-ligand v-oxo bridged heter-
obimetallic complexes of the type (por)MOM%L (M=Cr
[1], Fe [2], or Ru [3]; M%=transition metal; por=por-
phyrin dianion; L=non-porphyrin ligand) are well doc-
umented, there are relatively few examples of the
nitrido-bridged analogues. Nitrido-bridged metal por-
* Corresponding author. Tel.: +852-2358 7359; fax: +852-2358
1594.
E-mail address: chleung@ust.hk (W.-H. Leung)
1 To whom all crystallographic correspondence should be ad-
dressed.
0020-1693/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0020-1693(99)00096-1

W.-H. Leung et al. / Inorganica Chimica Acta 290 (1999) 28–35
29
and the characterization of the resulting bimetallic m-ni-
tride complexes.
was pumped off and the residue recrystallized from
CH2Cl2-hexane to give a purple solid. Yield 70–80%.
2.2.2. Spectroscopic data for 1
2. Experimental
1H NMR (CDCl3): l 2.03 (t, J=7.7 Hz, 24H, CH3),
4.24 (q, J=7.7 Hz, 16H, CH2), 10.53 (s, 4H, meso-H).
umax (CH2Cl2): 391 (Soret) nm. IR (Nujol): w(cm−1),
1854 [w(NO)], 1285 and 1277 [w(SO)]
2.1. General
1
Solvents were purified and distilled prior to use. H
NMR spectra were recorded on a Bruker ALX 300
spectrometer operating at 300 MHz, chemical shifts (l)
were reported with reference to SiMe4. Infrared spectra
(Nujol) were recorded on a Perkin-Elmer 16 PC FT-IR
spectrophotometer, UV-visible spectra on a Milton Roy
Spectronic 3000 diode-array spectrophotometer. Cyclic
voltammetry was performed with a Princeton Applied
Research (PAR) Model 273A potentiostat, the working
and reference electrodes were glassy carbon and Ag–
AgNO3 (0.1 M in acetonitrile), respectively. Potentials
were reported with reference to ferrocenium–ferrocene
(Cp2Fe+/0). Elemental analyses were performed by
Medac, Surrey, UK.
2.2.3. Spectroscopic data for 2
1H NMR (CDCl3): l 2.74 (s, 12H, p-Me), 7.58 (d,
J=7.5 Hz, 4H, Ho), 7.63 (d, J=7.5 Hz, 4H, Ho), 8.15
(d, J=7.5 Hz, 4H, Hm), 8.19 (d, J=7.5 Hz, 4H, Hm% ),
9.16 (s, 8H, Hb). umax (CH2Cl2): 411 (Soret) nm. IR
(Nujol): w(cm−1), 1870 [w(NO)], 1287 and 1250 [w(SO)].
2.2.4. (OEP)(NO)RuNOsO3 (3)
To a solution of Ru(OEP)(NO)(OTf) (100 mg, 0.143
mmol) in CH2Cl2 (20 ml) was added [NnBu4][OsO3N] (68
mg, 0.143 mmol) and the mixture was stirred at room
temperature for 30 min. The solvent was pumped off and
the residue was recrystallized from CH2Cl2-hexane to
give purple crystals. Yield: 100 mg (76%). Anal. Calc. for
C36H44N6O4OsRu: C, 47.2; H, 4.8; N, 9.2. Found: C,
The porphyrins Ru(por)(NO)Cl (por=dianion of
2,3,7,8,12,13,17,18-octaethylporphyrin H2(OEP) or
1
5,10,15,20-tetra(p-tolyl)porphyrin
H2TTP)
[14],
47.2; H, 5.1; N, 8.8%. H NMR (CDCl3): l 2.01 (t,
[NnBu4][OsO3N] [15], and ReN(Et2dtc)2 (Et2dtc=N,N%-
diethyldithiocarbamate) [16] were prepared according to
the literature methods. [NnBu4][OsNL2] was prepared
from [NnBu4][OsNCl4] [17] and H2L (3,4-toluenedithiol,
Strem) according to Sellmann’s procedure [9,18]. Hydro-
gen atomic labeling schemes for the porphyrins and L are
shown in Scheme 1.
J=7.6 Hz, 12H, CH3), 2.03 (t, J=7.6 Hz, 12H, CH3),
4.21 (q, J=7.6 Hz, 8H, CH2), 4.22 (q, J=7.6 Hz, 8H,
CH2), 10.42 and 10.44 (s, 4H, meso-H). IR (Nujol):
w(cm−1), 894 and 908 [w(OsꢀO)], 1842 [w(NꢁO)]. umax
(CH2Cl2): 396 (Soret), 487 sh, 572 sh nm.
2.2.5. (TTP)(NO)RuNOsO3 (4)
This was prepared as for 1 from Ru(TTP)(NO)(OTf)
(100 mg) and [NnBu4][OsO3N] (68 mg) in CH2Cl2 (10 ml)
and recrystallized from CH2Cl2–MeCN. Yield: 90 mg
(60%). Anal. Calc. for C48H36N6O4OsRu: C, 54.8; H, 3.4;
N, 8.0. Found: C, 54.2; H, 3.6; N, 7.7%. 1H NMR
(CDCl3): l 2.73 (s, 12H, p-Me), 7.60 (d, J=8.1 Hz, 8H,
Hm), 8.17 (d, J=8.1 Hz, 8H, Ho), 9.08 (s, 8H,
2.2. Synthesis
2.2.1. Ru(por)(NO)(OTf) (por=OEP (1), TTP(2))
To a solution of Ru(por)(NO)Cl (100 mg) in CH2Cl2
(10 ml) was added 1 equiv. of AgOTf and the mixture
was stirred at room temperature overnight. The solvent
Scheme 1.

30
W.-H. Leung et al. / Inorganica Chimica Acta 290 (1999) 28–35
1H NMR (CDCl3): l 2.29 (s br, 6H, Me of L), 2.74 (s
br, 12H, p-Me), 6.60 (dd, J=7.8 Hz, J%=3.0 Hz, 2H,
Hm of L), 6.83 (s, 1H, Ho of L), 6.85 (s, 1H, Ho of L),
6.89 (dd, J=7.8 Hz, J%=3.0 Hz, 2H, H%o of L), 7.52–
8.11 (m, 16H, Ho and Hm of ttp), 8.79–8.88 (m, 8H,
Hb). umax(CH2Cl2): 418 (Soret) nm. IR (Nujol):
w(cm−1), 1848 [w(NꢁO)].
Table 1
Crystallographic data for (OEP)(NO)RuNOsO3 (3)
Empirical formula
M
Crystal system
Colour
C36H44N6O4OsRu
916.05
triclinic
black
plate
Habit
Crystal dimension (mm)
0.16×0.26×0.28
0.71073
,
u (A)
2.2.8. (OEP)(NO)RuNRe(Et2dtc)2(OTf) (7)
(
Space group
P1 (No. 2)
,
a (A)
10.279(1)
11.010(1)
16.329(1)
99.13(2)
95.07(2)
97.33(2)
1798.5(4)
2
To a solution of 1 (70 mg, 0.09 mmol) in CH2Cl2 (10
ml) was added ReN(Et2dtc)2 (50 mg, 0.09 mmol) in
CH2Cl2 (10 ml) and the reaction mixture was stirred at
room temperature overnight. The solvent evaporated to
dryness and the residue recrystallized from CH2Cl2-hex-
ane to give a dark purple solid. Yield: 80 mg (71%).
Anal. Calc. for C47H64N8O4F3S5ReRu·CH2Cl2: C, 41.3;
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
3
,
V (A )
Z
Dc (g cm−3
Scan type
)
1.691
ꢀ–2q
39.94
4995
1
H, 4.7; N, 8.0. Found: C, 40.7, H, 4.7; N, 8.2%. H
NMR (CDCl3): l 0.99 (t, J=7.2 Hz, 12H, CH3 of
Et2dtc), 2.00 (t, J=7.5 Hz, 24H, CH3), 3.07 (m, 4H,
CH2 of Et2dtc), 3.24 (m, 4H, CH2 of Et2dtc), 4.21 (q,
J=7.5 Hz, 16H, CH2), 10.38 (s, 4H, meso-H). IR
(Nujol): w(cm−1), 1856 [w(NO)]. umax (CH2Cl2): 296,
399 (Soret) nm, 518 nm.
v (Mo Ka) (cm−1
)
No. of reflections
Observed reflections (I\3.00|(I))
793
Weighing scheme
1/|2(F)
0.057
Ra
Rw
b
0.079
908
1.94
F(000)
Goodness-of-fitc
2.3. X-ray crystallography
a R=(ꢀꢁꢁFoꢁ−ꢁFcꢁꢁ)/ꢀꢁFoꢁ.
2 1/2
b Rw=[ꢀ(wꢁFoꢁ−ꢁFcꢁ)2/ꢀwꢁFoꢁ ]
.
A summary of crystal data and experimental details
for 3 is listed in Table 1. X-ray quality crystals of 3
were grown from a CH2Cl2-hexane solution in air at
room temperature. Diffraction measurements were per-
formed with a MAR-Research Image Plate diffrac-
tometer with graphite monochromated Mo Ka
radiation at room temperature. All intensity data were
corrected for Lorentz polarization effect. An approxi-
mation to absorption correction by inter-image scaling
was also applied. The structure was solved by direct
methods and refined by full-matrix least-squares analy-
sis. All calculations were performed using the teXan
[19] crystallographic software package. The maximum
and minimum peaks on the final difference Fourier
c Goodness-of-fit=[(ꢀwꢁFoꢁ−ꢁFcꢁ)2/ꢀNobs−Nparam
] .
1/2
Hb). IR (Nujol): w(cm−1) 898 and 904 [w(OsꢀO)], 1856
[w(NꢁO)]. umax (CH2Cl2): 329, 416 (Soret) nm.
2.2.6. (OEP)(NO)RuNOsL2 (5)
To a solution of Ru(OEP)(NO)(OTf) (65 mg, 0.08
mmol) in CH2Cl2 (20 ml) was added 1 equiv. of
[NnBu4][OsNL2] (60 mg, 0.08 mmol) and the mixture
was stirred at room temperature overnight. The solvent
was pumped off and the residue extracted with ether.
Addition of hexane and slow evaporation in air af-
forded dark crystals. Yield: 30 mg (32%). Anal. Calc.
for C50H56N6OS4OsRu: C, 51.1; H, 4.8; N, 7.2. Found:
map correspond to 1.63 and −0.92 e A−3, respec-
tively. The fractional atomic coordinates for 3 are listed
,
1
C, 50.9; H, 5.1; N, 6.8%. H NMR (CDCl3): l 1.91–
1.96 (overlapping t, 24H, CH3), 2.32 (s, 6H, Me of L),
4.00–4.17 (overlapping q, 16H, CH2), 6.57 (d, J=7.8
Hz, 2H, Hm of L), 6.71 (s, 2H, Ho of L), 6.81 (d, J=7.8
Hz, 2H, Ho% of L), 10.12 (s, 4H, meso-H). umax
(CH2Cl2): 397 (Soret), 494, 529 nm. IR (Nujol):
w(cm−1), 1842 [w(NꢁO)].
in Table 2.
3. Results and discussion
3.1. Synthesis and characterization of Ru(II)NOs(VIII)
complexes
2.2.7. (TTP)(NO)RuNOsL2 (6)
Reaction of Ru(por)(NO)Cl with an equimolar
amount of AgOTf gave Ru(por)(NO)(OTf) (por=OEP
(1), TTP (2)). The observation of the splitting of w(SO)
at ca. 1260 cm−1 indicates that the triflate is bound to
metal for 1 and 2 [20]. The triflate in 1 and 2 is labile
and can be displaced easily by metal nitrides. Thus,
This was prepared as for 3 from Ru(TTP)(NO)(OTf)
(80 mg, 0.08 mmol) and [NnBu4][OsNL2] (64 mg, 0.08
mmol) and recrystallized from CH2Cl2–MeCN. Yield:
55 mg (50%). Anal. Calc. for C62H48N6OS4OsRu: C,
56.8; H, 3.7; N, 6.4. Found: C, 47.2; H, 5.1; N, 8.8%.

W.-H. Leung et al. / Inorganica Chimica Acta 290 (1999) 28–35
31
treatment of Ru(por)(NO)(OTf) with [NnBu4][OsO3N]
afforded the respective nitrido-bridged Ru(II)–Os(VIII)
complexes (por)(NO)RuNOsO3 (por=OEP (3), TTP
(4)), isolated as air-stable purple crystals (Scheme 2).
Complexes 3 and 4 are stable in both the solid state
and solutions. NMR spectroscopy reveals no signs of
osmate ligand dissociation for 3 and 4 in CDCl3. The
w(OsꢀO) for 3 (898 and 904 cm−1) are higher than
those for free [OsO3N]− (871 and 891 cm−1), indicat-
ing that upon coordination to Ru the Os–oxo bonds in
[NOsO3]− are strengthened apparently due to weaken-
ing of the Os–nitride bond (see later). The w(OsꢁN) was
not assigned due to the presence of porphyrin bands in
the 1000–1100 cm−1 region. The solid-state structure
of 3 has been established by X-ray crystallography. Fig.
1 shows a perspective view of 3; selected bond lengths
and angles are listed in Tables 3 and 4. Unlike the other
structurally characterized nitrosylruthenium(II) por-
phyrins, the Ru–N–O linkage in 3 is bent at an angle
of 153(1)°. Although the Ru–N–O angle for 3 is
comparable to that for Ru(TTP)(NO)(C6H5F-p) (152°)
[21], the w(NꢁO) for the former (1854 cm−1) is consid-
erably higher than that for the latter (1773 cm−1) [21].
Table 2
Final atomic coordinates for (OEP)(NO)RuNOsO3 3
,
The Ru–N(O) distance for 3 of 1.83(2) A is within the
range expected for nitrosylruthenium(II) porphyrins
Atom
x
y
z
,
Os(1)
Ru(1)
O(1)
O(2)
O(3)
O(4)
N(1)
N(2)
N(3)
N(4)
N(5)
N(6)
C(1)
C(2)
C(3)
C(4)
C(5)
−0.51174(10)
0.2225(2)
−0.628(2)
0.585(2)
−0.21210(9)
0.0027(1)
−0.288(2)
0.140(2)
0.320(2)
0.1966(10)
0.067(1)
0.139(1)
0.075(1)
0.143(1)
0.102(1)
0.096(2)
0.019(2)
0.097(2)
0.071(2)
0.028(2)
0.192(2)
0.296(2)
0.271(2)
0.174(2)
0.247(2)
0.229(2)
0.310(2)
0.420(2)
0.386(2)
0.264(2)
0.310(2)
−0.31088(6)
−0.22775(9)
−0.263(1)
0.384(1)
(ca. 1.72–1.79 A) [10–13]. The Ru–N(Os) bond in 3 is
,
relatively short (2.03(1) A) and is comparable to the
Ru(IV)–amide bond in Ru(TPP)(NHTs)(pz) (Ts=to-
syl, pz=pyrazolyl) (2.025(11) A) [22], suggestive of
,
0.433(2)
0.361(1)
p-bonding in Ru–N(Os). The Ru–N(Os) distance is,
0.0192(10)
−0.255(1)
0.323(1)
−0.208(1)
−0.146(1)
0.402(1)
0.059(2)
0.218(2)
0.253(2)
0.231(2)
0.336(2)
0.310(2)
0.363(2)
0.509(2)
−0.312(2)
0.359(2)
0.370(2)
0.427(2)
0.494(2)
−0.632(2)
−0.413(2)
−0.457(2)
−0.349(2)
0.346(2)
0.315(2)
0.249(2)
0.222(2)
0.250(2)
−0.147(2)
−0.165(2)
−0.133(3)
0.003(4)
−0.155(2)
−0.103(2)
−0.099(2)
0.046(2)
0.020(2)
−0.076(3)
0.064(2)
−0.034(2)
−0.156(2)
0.127(2)
−0.2061(6)
0.1077(9)
−0.2690(9)
−0.3497(9)
−0.1886(10)
−0.2352(8)
0.217(1)
0.037(1)
0.035(1)
0.124(1)
0.144(1)
0.009(1)
0.058(1)
0.061(1)
−0.081(1)
0.132(1)
0.219(1)
−0.271(1)
0.239(1)
−0.217(2)
−0.3.51(1)
−0.429(1)
−0.454(1)
−0.3.50(1)
−0.418(1)
−0.419(1)
−0.492(1)
−0.582(1)
−0.608(2)
−0.465(1)
0.518(1)
however, longer than those for symmetric m-nitrido
,
diruthenium complexes (1.718–1.744 A) [23]. The exis-
tence of p bonding in Ru–N(Os) for 3 is also evidenced
in its solution H NMR spectrum, which displays mag-
1
netically non-equivalent methyl and meso proton sig-
nals. Apparently, the low-lying vacant nitrosyl p*
molecular orbitals interact extensively with the filled Ru
dp orbitals, rendering the pp[N(Os)]–dp(Ru) interac-
tion possible, as suggested for the related trans-
[RuII(CO)X] (X=p-donor ligand) system [24]. It is
C(6)
C(7)
C(8)
C(9)
,
noteworthy that the Os–N(Ru) bond in 3 (1.79(1) A)
is significantly longer than those for [OsO3N]−
,
,
(1.67(2) A) [25], (PPh3)AuNOsO3 (1.69 (2) A) [8] and
organoimido–Os(VIII) complexes (e.g. 1.697(4) A for
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
C(17)
C(18)
C(19)
C(20)
C(21)
C(22)
C(23)
C(24)
C(25)
C(26)
C(27)
C(28)
C(29)
C(30)
C(31)
C(32)
C(33)
C(34)
C(35)
C(36)
,
OsO3(NC10H15), C10H15=1-adamantyl) [26] and, to
our knowledge, is the longest Os(VIII)–nitride bond
reported so far. This suggests a formal double bond
between Os and nitride and the bonding in 3 is best
described as Ru–NꢀOs. Apparently, the decrease in
Os–N bond order from three to two is compensated for
by the strengthening of the Ru–N(Os) and OsꢀO
bonds. In contrast to the donor–acceptor type m-ni-
trido Os(VIII) complexes, e.g. (PPh3)AuNOsO3, and
organoimido–Os(VIII) complexes (RN)OsO3, which
contain essentially linear M(R)–NꢁOs linkages, the
Ru–NꢀOs in 3 is bent at an angle of 138.4(2)°. It
might be noted that a similar bent, asymmetric m2-
bridging mode of nitride has been observed for
[NW{OC(CH3)2CF3}3]3, which contains an alterna-
tion of long and short W–N bonds within the six-mem-
bered W3N3 ring [27]. The W–NꢀW angle in
[NW{OC(CH3)2CF3}3]3 (average 152.9°) is larger than
that in 3 probably due to steric effects. Interestingly the
dihedral angle between Ru–N–Os and Ru–N–O in 3
is ca. 114.04°, indicating that different Ru dp orbitals
are used for the Ru–NO backbonding and Ru–N(Os)
0.396(2)
0.152(2)
0.075(2)
−0.031(2)
−0.111(2)
−0.090(2)
−0.004(3)
−0.205(2)
−0.320(3)
−0.309(3)
0.181(2)
−0.254(2)
0.239(2)
−0.319(2)
−0.430(2)
−0.540(3)
0.274(2)
0.529(2)
−0.377(1)
0.323(1)
0.237(1)
−0.185(1)
−0.216(1)
−0.236(2)
−0.107(1)
−0.026(1)
0.003(2)
0.321(2)
0.389(2)
−0.161(2)
−0.087(2)
−0.107(1)
0.039(1)
−0.159(2)

32
W.-H. Leung et al. / Inorganica Chimica Acta 290 (1999) 28–35
Scheme 2.
Fig. 1. Perspective view of (OEP)(NO)RuNOsO3 (3).
denced by UV–Vis spectroscopy. Intermetal nitrogen
atom transfer from Os to Cr was not observed. The IR
spectrum of this species shows the upshift of w(OsꢀO) to
910 cm−1, suggesting that the OsꢀO bonds are strength-
ened upon the complex formation. This Cr–Os species
does not react with alkenes but reacts readily with PPh3.
Attempts to crystallize this Cr(III)–Os(VIII) species led
to isolation of an intractable oil.
p-bonding. This geometry may be rationalized in terms
of maximization of the overlap between the nitrosyl p*
molecular orbital, which is perpendicular to the Ru–N–
O plane, and the ‘lone pair’ on the sp2 hybridized nitride,
which lies on the Ru–N–Os plane.
3.1.1. Synthesis and characterization of Ru(II)NOs(VI)
and Ru(II)NRe(V) complexes
Treatment of Ru(por)(NO)(OTf) with [NnBu4]-
[OsNL2] (H2L=3,4-toluenedithiol) afforded the Ru(II)–
Os(VI) complexes (por)(NO)RuNOsL2 (por=OEP (5),
TTP (6)) (Scheme 3).
NMR spectroscopy indicates that complexes 5 and 6
are stable with respect to ligand dissociation in solu-
1
tions. The observation of an unsymmetrical H NMR
The anion [OsO3N]− was found to react with other
unsaturated metalloporphyrins such as chromium(III)
porphyrins. For example, addition of [OsO3N]− to
Cr(OEP)(OTf) led to the formation a new species,
presumably nitride-bridged (OEP)CrNOsO3, as evi-
spectrum for 5 is indicative of Ru–N(Os) multiple bond
character. Although crystal structures are not available,
it seems unlikely that the Ru–N–Os in these complexes
is bent, as found in 3, in light of the steric demand of
the dithiolate ligand L. The w(NꢁO) for 3 is similar to

W.-H. Leung et al. / Inorganica Chimica Acta 290 (1999) 28–35
33
Table 3
Selected bond lengths (A) and angles (°) for (OEP)(NO)RuNOsO3
,
3
,
Bond lengths (A)
Os(1)–O(1)
Os(1)–O(3)
Ru(1)–N(1)
Ru(1)–N(3)
Ru(1)–N(5)
O(4)–N(6)
1.69(2)
1.67(2)
2.05(1)
2.06(1)
2.03(1)
1.26(2)
Os(1)–O(2)
Os(1)–N(5)
Ru(1)–N(2)
Ru(1)–N(4)
Ru(1)–N(6)
1.71(1)
1.79(1)
2.08(1)
2.08(4)
1.83(2)
Bond angles (°)
O(1)–Os(1)–O(2)
O(1)–Os(1)–N(5)
O(2)–Os(1)–N(5)
N(1)–Ru(1)–N(2)
N(1)–Ru(1)–N(4)
N(1)–Ru(1)–N(6)
N(2)–Ru(1)–N(4)
N(2)–Ru(1)–N(6)
N(3)–Ru(1)–N(5)
N(4)–Ru(1)–N(5)
N(5)–Ru(1)–N(6)
Ru(1)–N(6)–O(4)
110(1)
O(1)–Os(1)–O(3)
O(2)–Os(1)–O(3)
O(3)–Os(1)–N(5)
N(1)–Ru(1)–N(3)
N(1)–Ru(1)–N(5)
N(2)–Ru(1)–N(3)
N(2)–Ru(1)–N(5)
N(3)–Ru(1)–N(4)
N(3)–Ru(1)–N(6)
N(4)–Ru(1)–N(6)
Os(1)–N(5)–Ru(1)
106(1)
107(1)
109.8(7)
110.8(8)
89.8(5)
89.8(6)
93.6(7)
173.3(6)
94.7(6)
89.1(6)
86.5(6)
177.8(6)
153(1)
111.7(8)
174.0(6)
84.9(5)
90.2(6)
86.8(5)
89.5(6)
92.5(7)
92.0(6)
138.4(8)
Fig. 2. Cyclic voltammograms of (a) (OEP)(NO)RuNOsO3 (3) and
(b) (OEP)(NO)RuNOsL2 (5) in CH2Cl2 at a glassy carbon electrode;
scan rate=100 mV s−1
.
that for 5, suggesting that the donor strength of
[OsO3N]− and [OsNL2]− is comparable.
“[(OEP +)(NO)RuNOsO3]+
(1)
’
This potential is comparable to those found for
Ru(OEP)(NO)(OTf) (0.68 V) and [Ru(TTP)(NO)-
(OH2)]+ (1.26 V vs. standard calomel electrode) [28].
The corresponding oxidation for 4 (0.72 V) is more
anodic than that for 3, consistent with the relative ease
of oxidation for porphyrin macrocycle OEP\TTP.
Electroreduction of 3 occurs at −1.10, −1.33 and
−1.77 V. The irreversible reduction at −1.11 V is
assigned tentatively as the Ru(II)–Ru(I) reduction (Eq.
(2)) because a similar reduction potential was found for
Ru(OEP)(NO)(OTf).
Similarly reaction of Ru(OEP)(NO)(OTf) with ReN-
(Et2dtc)2 afforded the RuNRe complex (OEP)
(NO)RuNRe(Et2dtc)2(OTf) (7). Unlike 5, the H NMR
spectrum for 7 is symmetric with one singlet for
the meso protons, indicating that the ReN(Et2dtc)2
moiety is rotating freely around the Ru–N bond on the
NMR time scale. The IR spectrum for 7 shows the NO
band at 1856 cm−1, which is higher than those for 3
and 5.
1
3.2. Electrochemistry
[(OEP)(NO)Ru(II)NOs(VIII)O3]+e−
The cyclic voltammogram (CV) of complex 3 in
CH2Cl2 (Fig. 2a) exhibits a reversible oxidation couple
at 0.55 V, which is assigned as the porphyrin-centered
oxidation (Eq. (1)).
“[(OEP)(NO)Ru(I)NOs(VIII)O3]−
(2)
Consistent with this assignment, the corresponding re-
duction for the less electron-rich TTP analogue 4 was
found at a less negative potential (−0.88 V). The
irreversible reduction couple at −1.33 V for 3 is tenta-
[(OEP)(NO)Ru(II)NOs(VIII)O3]−e−
Scheme 3.

34
W.-H. Leung et al. / Inorganica Chimica Acta 290 (1999) 28–35
tively assigned as the Os-centered reduction (Eq. (3))
because a similar reduction was found for 4 (at
−1.22 V).
pears. Attempts to isolate this species by stoichiomet-
ric oxidation of 5 with Ag(OTf) in a preparative scale
were unsuccessful. The second oxidation couple for 5
at 0.75 V was assigned as the porphyrin centered oxi-
dation Eq. (5).
[(OEP)(NO)Ru(II)NOs(VIII)O3]+e−
“[(OEP)(NO)Ru(II)NOs(VII)O3]−
(3)
[(OEP)(NO)Ru(II)NOs(VII)L2]+ −e−
The Os(VIII)−Os(VII) reductions for 3 and 4 occur
at less negative potentials than that for [OsO3N]−
(−1.45 V), indicative of Ru to Os charge delocaliza-
tion in these complexes. The nature of the irreversible
reduction at −1.77 V is not clear.
The CV of 5 in CH2Cl2 (Fig. 2b) shows reversible
oxidation couples at 0.49 and 0.75 V and irreversible
reduction waves at −1.11 and −1.25 V. The oxida-
tion couple at 0.49 V is assigned as the Os-centered
oxidation (Eq. (4)) because [OsNL2]− was found to
be oxidized at 0.39 V.
“[(OEP +)(NO)Ru(II)NOs(VII)L2]2+
(5)
’
The porphyrin ring oxidation for 5 is more anodic
than that for 1 because the former involves removal
of electron from a cation rather than a neutral spe-
cies. The irreversible reduction at −1.11 V is as-
signed tentatively as the Ru(II)–Ru(I) reduction by
comparison with the electroreduction of 3. The nature
of the irreversible reduction at −1.25 V is not clear.
In summary, we have demonstrated that [Ru(por)-
(NO)]+ are capable of forming stable nitrido-bridged
complexes with [OsO3N]−, [OsNL2]− and ReN
(Et2dtc)2. X-ray crystallography indicates multiple
bond character of Ru(II)–N(Os) in 3. The structural
data are consistent with the formulation of the asym-
metric nitride bridge (Ru–NꢀOs) for these complexes,
which is in contrast to the previously reported
donor–acceptor type nitride bridges (e.g. M’NꢁOs)
[8]. Electronic communication between Ru and Os
center was observed for these nitrido-bridged Ru(II)–
Os(VIII) and Ru(II)–Os(VI) complexes.
[(OEP)(NO)Ru(II)NOs(VI)O3]−e−
“[(OEP)(NO)Ru(II)NOs(VII)O3]+
(4)
The Os(VII)–Os(VI) potential for 5 is more positive
than that for [OsNL2]−, suggesting that there is
charge delocalization from Os to Ru in 5. Fig. 3
shows the spectral trace for the reaction of 5 with
(NH4)2[Ce(NO3)6]. Upon addition of ca. 1 equiv. of
Ce(IV), a new species with the Soret band at ca. 392
nm (presumably the Ru(II)–Os(VII) complex) ap-
Fig. 3. Spectral trace for the oxidation of (OEP)(NO)RuNOsL2 (5) with Ce(IV) in CH2Cl2.

W.-H. Leung et al. / Inorganica Chimica Acta 290 (1999) 28–35
35
Table 4
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Chem. 34 (1995) 2355.
Formal potentials (E°) for the nitrido-bridged ruthenium porphyrinsa
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Wong, J. Chem. Soc., Dalton Trans. (1997) 3277.
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(1998) 6382.
[10] (a) J.W. Buchler, P.D. Smith, Chem. Ber. 109 (1976) 1465. (b) A.
Anitpas, J.W. Buchler, M. Gouterman, P.D. Smith, J. Am.
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Smith, Polyhedron 18 (1996) 3147.
Complex
E° (V vs. Cp2Fe+/0
)
Oxidation
Reduction
(OEP)(NO)RuNOsO3
(TTP)(NO)RuNOsO3
Ru(OEP)(NO)(OTf)
[OsO3N]−
0.55
0.72
0.68
−1.11b, −1.33, −1.77b
−0.88b, −1.22
−0.93b
−1.45b
(OEP)(NO)RuNOsL2
0.49, 0.75
0.39
−1.11b, −1.25b
[OsNL2]−
[11] G.-B. Yi, L. Chen, M.A. Khan, G.B. Richter-Addo, Inorg.
Chem. 36 (1997) 3876.
a Potentials measured at a glassy carbon electrode in CH2Cl2 using
[12] (a) G.-B. Yi, M.A. Khan, G.B. Richter-Addo, Chem. Commun.
(1996) 2045. (b) G.-B. Yi, M.A. Khan, G.B. Richter-Addo,
Inorg. Chem. 35 (1996) 3453. (c) G.-B. Yi, M.A. Khan, D.R.
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(1997) 4838.
0.1 M [NnBu4](PF6) as supporting electrolyte. Scan rate=100 mV
s−1
.
b Irreversible.
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4. Supplementary material
Supplementary material containing listings of atomic
coordinate and thermal parameters, final atomic coor-
dinates, and bond distances and angles is available
from the author (Wing-Tak Wong) on request.
[19] teXan: Crystal Structure Analysis Package, Molecular Structure
Corporation (1985 and 1992).
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Acknowledgements
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The support from The Hong Kong Research Grants
Council is gratefully acknowledged.
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