Carbonylation of four-membered ruthenium and osmium metallacycles incorporating an orthometallated phenolic function: New acylruthenium and arylosmium complexes

Article abstract of DOI:10.1016/j.jorganchem.2005.04.012

The solution reaction of Ru(QL¹)(PPh₃) ₂(CO)Cl (3) and Os(QL¹)(PPh₃)₂(CO)Br (4) with carbon monoxide at one atmosphere pressure has respectively afforded the orange acylruthenium system Ru(QL²)(PPh₃) ₂(CO)Cl (5) and the yellow arylosmium dicarbonyl system Os(QL ³)(PPh₃)₂(CO)₂Br (6) in excellent yields. (QL¹ is C₆H₂O-2-CHNHC₆H ₄Q(p)-3-Me-5, QL² is C₆H₂(CO-1)O-2- CHNHC₆H₄Q(p)-3-Me-5 and QL³ is C ₆H₂OH-2-CHNC₆H₄Q(p)-3-Me-5 and Q is Me, OMe and Cl.) It is proposed that in the case of 3 a dicarbonyl complex similar to 6 is formed as an intermediate which rapidly undergoes aryl migration with concomitant phenolato coordination furnishing 5. The stability of 6 is consistent with the greatly diminished ability of osmium in promotion of migratory reactions. In the reaction 4 → 6 the Os-O(phenolato) bond is cleaved and the Schiff base moiety undergoes iminium-phenolato → imine-phenol tautomerization. The observed cis geometry of 6 may arise by a concerted route involving edge displacement of the halide ligand. The crystal and molecular structure of 5(Q = Cl) has revealed the presence of a distorted octahedral RuC₂P₂OCl coordination sphere and a highly planar acyl chelate ring characterized by a Ru-C distance of 2.013(4) ?. In the hydrogen bonded zwitterionic iminium-phenolato ring the N ? O distance is 2.561(6) ?. The acyl complexes of type 5 display an MLCT band near 500 nm which is absent in 6. The Schiff base CN stretch in 5 (～1630 cm^-1) is significantly higher than that in 6 (～1600 cm ^-1) which displays two strong CO stretches near 2020 and 1940 cm ^-1 (cis-Os(CO)₂ configuration). A single ³¹P NMR signal occurs in both 5 and 6 near 37 and -6 ppm, respectively (trans-M(PPh₃)₂ configuration). The voltammetric reduction potentials of the M^III/M^II couple is observed near 1.0 and 0.8 V vs. SCE in 5 and 6, respectively. Both are significantly higher than those in parent complexes (3 and 4) due to stabilization of the bivalent state upon carbonylation.

Full text of DOI:10.1016/j.jorganchem.2005.04.012

Journal of Organometallic Chemistry 690 (2005) 3169–3175
www.elsevier.com/locate/jorganchem
Carbonylation of four-membered ruthenium and osmium
metallacycles incorporating an orthometallated phenolic
function: New acylruthenium and arylosmium complexes
a
Bikash Kumar Panda , Animesh Chakravorty
a,b,
*
a
Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032, India
b
Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560 064, India
Received 1 February 2005; revised 2 April 2005; accepted 4 April 2005
Available online 17 May 2005
Abstract
The solution reaction of Ru(QL1)(PPh3)2(CO)Cl (3) and Os(QL1)(PPh3)2(CO)Br (4) with carbon monoxide at one atmosphere
pressure has respectively afforded the orange acylruthenium system Ru(QL2)(PPh3)2(CO)Cl (5) and the yellow arylosmium dicar-
bonyl system Os(QL3)(PPh3)2(CO)2Br (6) in excellent yields. (QL1 is C6H2O-2-CHNHC6H4Q(p)-3-Me-5, QL2 is C6H2(CO-1)O-2-
CHNHC6H4Q(p)-3-Me-5 and QL3 is C6H2OH-2-CHNC6H4Q(p)-3-Me-5 and Q is Me, OMe and Cl.) It is proposed that in the case
of 3 a dicarbonyl complex similar to 6 is formed as an intermediate which rapidly undergoes aryl migration with concomitant phe-
nolato coordination furnishing 5. The stability of 6 is consistent with the greatly diminished ability of osmium in promotion of
migratory reactions. In the reaction 4 ! 6 the Os–O(phenolato) bond is cleaved and the Schiff base moiety undergoes iminium-phe-
nolato ! imine-phenol tautomerization. The observed cis geometry of 6 may arise by a concerted route involving edge displacement
of the halide ligand. The crystal and molecular structure of 5(Q = Cl) has revealed the presence of a distorted octahedral RuC2P2OCl
˚
coordination sphere and a highly planar acyl chelate ring characterized by a Ru–C distance of 2.013(4) A. In the hydrogen bonded
˚
zwitterionic iminium-phenolato ring the N ꢀ ꢀ ꢀ O distance is 2.561(6) A. The acyl complexes of type 5 display an MLCT band near
500 nm which is absent in 6. The Schiff base C@N stretch in 5 (ꢁ1630 cmꢂ1) is significantly higher than that in 6 (ꢁ1600 cmꢂ1
)
which displays two strong C„O stretches near 2020 and 1940 cmꢂ1 (cis-Os(CO)2 configuration). A single 31P NMR signal occurs
in both 5 and 6 near 37 and ꢂ6 ppm, respectively (trans-M(PPh3)2 configuration). The voltammetric reduction potentials of the MIII
/
MII couple is observed near 1.0 and 0.8 V vs. SCE in 5 and 6, respectively. Both are significantly higher than those in parent com-
plexes (3 and 4) due to stabilization of the bivalent state upon carbonylation.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Acylruthenium chelates; Dicarbonyl arylosmium complexes; Migratory aryl insertion
1. Introduction
ruthenium chemistry it has been observed in mononu-
clear dicarbonyl species of type
Metal mediated migratory insertion reactions of the
type stated in Eq. (1) has been of abiding interest in
transition metal organometallic chemistry [1,2]. In
R
L
L
R = alkyl / aryl
M
M
ð1Þ
C
C(=O)R
O
*
Corresponding author. Tel.: +91 33 2472 4436; fax: +91 33 2473
Ru(CO)2X(R)(D)2 (X = halide, D = tertiary phos-
phines) [3,4], hydridocarbonyls and hydridodienes [5],
2805.
E-mail address: icac@mahendra.iacs.res.in (A. Chakravorty).
0022-328X/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.04.012

3170
B.K. Panda, A. Chakravorty / Journal of Organometallic Chemistry 690 (2005) 3169–3175
Me
Me
alkyl and aryl systems [6], metallacycles [7,8], and binu-
clear species [9,10].
PPh3
H
In the present work we scrutinize the reaction of the
four-membered metallacycle 1 with carbon monoxide
via product isolation and characterization. Several con-
siderations encouraged us in this endeavour. First, 1 is
known to be reactive towards small unsaturates like
alkynes [11] and isonitriles [12] as well as towards certain
other donors [13–15]. Second, 1 is generated via decarb-
onylative metallation of formylphenols [16,17] and its
carbonylation would be an interesting case of reaction
reversal. Third, structural
CO
O
H
M
X
O
N
N
O
5
Ru
Cl
H
PPh3
CO
H
Q
3, M = Ru, X = Cl
4, M = Os, X = Br
Q
dramatically different. In Eq. (2) we observed migratory
insertion and in Eq. (3) mere CO
3 þ CO ! 5
4 þ CO ! 6
ð2Þ
ð3Þ
CO
M
X
O
1, M = Ru, X = Cl
2, M = Os, X = Br
ligation at the expense of Os–O(phenolato) bond cleav-
age. A consequence of this cleavage is the tautomeriza-
tion of the Schiff base moiety from coordinated
iminium-phenolato from (as in 3–5) to the pendant
imine-phenol form (as in 6).
characterization of a inserted product would be of inter-
est as accurate structures of very few ruthenium acyls
are known [3c,9,12]. Last, a comparative study of the
carbonylation behaviour of 1 with that of the osmium
analogue 2 would be of interest since known instances
of such comparisons are rare [4b,8].
The metallacycle 1 has indeed been found to undergo
a smooth insertion reaction affording acyl phenolato spe-
cies. The reaction of 2 did not lead to insertion and affor-
ded only an unreactive cis-dicarbonyl complex which
has, however, provided a possible model for the reaction
intermediate in the carbonylation of 1. The new organo-
metallics have been isolated in the pure state and have
been spectrally and electrochemically characterized.
The structure of an acylruthenium system is reported.
Q
14
15
16
13
12
11
H
N
H
7
6
O
5
PPh
1
9
3
CO
8
Me
4
2
Os
6
3
10
CO
Br
PPh
3
2. Results and discussion
2.2. Reaction model
2.1. Parent complexes and their carbonylation
The facile formation of the dicarbonyl complex 6 in
the case of osmium prompts us to propose that the reac-
tion of Eq. (2) proceeds via the intermediacy of a similar
ruthenium complex stylized as 7 (PPh3 ligands not
shown) which can afford the acyl complex 5 via straight-
forward nucleophilic aryl migration with concomitant
phenolato coordination, Eq. (4). The fact that under
ambient condition 7 is highly reactive and 6 is not is
qualitatively consistent with the greatly diminished abil-
ity of osmium
The substrates [16,17] incorporating the metalla-
cycles 1 and 2 are Ru(QL1)(PPh3)2(CO)Cl (3) and
Os(QL1)(PPh3)2(CO)Br (4). The Q substituents used
are Me, OMe and Cl. Specific compounds will be iden-
tified by putting the Q group in parenthesis as in
3(Me) meaning 3 having Q = Me.
Upon exposing a stirred dichloromethane solution
of 3 to carbon monoxide at one atmosphere pressure
for a few hours, the orange acylruthenium system
Ru(QL2)(PPh3)2(CO)Cl (5) is afforded in excellent
yields. A similar treatment of 4 furnished the yellow
coloured dicarbonyl family Os(QL3)(PPh3)2(CO)2Br
(6). Here no acyl complex could be isolated or identi-
fied in the reaction mixture. Both reactions, Eqs. (2)
and (3), involve the addition of one CO molecule
but the final products are
CO
CO
C
C
O
O
Ru
7
ð4Þ
Ru
5
O
Cl
Cl
CO

B.K. Panda, A. Chakravorty / Journal of Organometallic Chemistry 690 (2005) 3169–3175
3171
(compared to ruthenium) in promoting migratory acyl
formation [4b,8]. It is plausible that the observed cis
geometry of 6 (and 7, by inference) arises via a concerted
route wherein carbon monoxide attack on 4 (or 3) is
associated with edge displacement [18] of the halide li-
gand, Eq. (5) as in some other reactions of 4 and 3
[11b,13a].
H
II
Ru
O
N
H
9
CO
P
P
the dicarbonyl system 6 in which the Schiff base acts
simply as a monocoordinated aryl ligand, there is no
absorption band above ꢁ380 nm (Table 1).
Br
O
C
OC
OC
Br
C
ð5Þ
OC
In 5 a broad and strong IR band near 1630 cmꢂ1
(Table 1) is believed to incorporate both the Schiff base
C@N and C@O(acyl) stretches. The relatively high
frequency for the C@N stretch is consistent with the
protonation of the nitrogen atom in the iminium-pheno-
lato function [11,12,17,19,20]. In contrast the C@N
stretch of the imine-phenol moiety in 6 occurs at lower
frequency, ꢁ1600 cmꢂ1 (Table 1). Species of type 6 dis-
plays two strong C„O stretches near 2020 and
1940 cmꢂ1 characterizing the cis-Os(CO)2 configuration
P
P
O
Finally we note that the formation of the parent com-
plex 3 [16,17] from Ru(PPh3)3Cl2 and the Schiff mono-
base of 4-methyl-2,6-diformyl-phenol probably proceeds
via oxidative addition [17] of the aldehyde function gen-
erating the moiety 8 which then undergoes aryl migra-
tion with C–CO bond scission, Ru–C(aryl) bond
formation and reductive proton elimination leading to
the metallacycle 3. With the availability of an extra car-
bon monoxide ligand the above noted aryl migration
protocol is essentially reversed and a C–CO bond is
formed leading the transformation of Eq. (2).
[21]. The N+–H stretch in 5 occurs near 3440 cmꢂ1
.
The complexes generally show well-resolved 1H
NMR lines. The iminium N+–H signal in 5 occur near
15 ppm and is split into a doublet due to trans coupling
with the azomethine proton (ꢁ12 Hz). In 6 the O–H res-
onance is observed as a sharp feature near 13 ppm as in
related imine-phenol systems [13a,14b]. The complexes
uniformly display a single 31P NMR signal for the two
phosphine ligands implicating trans-M(PPh3)2 configu-
ration. The resonances occur near 37 and ꢂ6 ppm in 5
and 6, respectively (Table 2).
CHNHC H Q
6
4
Me
O
IV
Ru
(H)
2.4. Metal redox
O
8
The complexes exhibit a quasireversible one-electron
cyclic voltammetric response in dichloromethane
solution. The response is assigned to metal redox
(MIII/MII) and the reduction potentials are collected in
Table 2. It is instructive to compare these with those
of the parent complexes ꢂ0.7 V in 3 [17] and 0.6 V in
4 [17]. Formation of the five-membered acyl phenolato
chelate ring in going from 3 to 5 stabilizes the bivalent
state in the redox sense as reflected in the higher reduc-
tion potentials. Substitution of the Os–O(phenolato)
bond by an Os–CO bond is going from 4 to 6 stabilizes
the bivalent state via increased back-bonding resulting
in higher reduction potentials. In both families the E1/2
values follow the Hammett order of Q: OMe < Me < Cl.
2.3. Spectral features
The compositions of the complexes were confirmed
by positive ion electrospray mass spectra. Representa-
tive maximum molecular ion peaks (m/z) are: 5 (OMe),
958.05 (formula weight, 957.4) and 6 (Cl), 1096.5 (fw,
1095.43). The molecular ion mass corresponds to
[M + H]+. In every case the observed isotopic distribu-
tion pattern in the molecular ion peak fitted excellently
with the simulated pattern. All the complexes systemat-
ically displayed a peak corresponding to halide loss.
The acyl family 5 displays (Table 1) a characteristic
allowed band near 500 nm which is assigned to
t2g ! p* MLCT within the chelated zwitterionic imin-
ium-phenolato function 9 as in the precursor species 3
[16,17] and related derivatives [11,12]. In contrast
2.5. Structure
The X-ray structure of 5 (Cl) has been determined. A
molecular view is shown in Fig. 1 and selected bond

3172
B.K. Panda, A. Chakravorty / Journal of Organometallic Chemistry 690 (2005) 3169–3175
Table 1
UV–visa and IRb spectral data
Compound
k
max, nm (ec, Mꢂ1 cmꢂ1
)
mC„O
mC@N and mC@O(acyl)
mþN–H
5(Me)
5(OMe)
5(Cl)
341(9058), 497(7310)
353(11507), 501(10835)
342(11619), 503(8330)
323(28860), 378(12340)
331(25460), 374(14620)
321(21790), 375(10900)
1925
1925
1633
1631
1633
1592
1607
1607
3436
3436
3447
–
1930
6(Me)
6(OMe)
6(Cl)
2016, 1936
2016, 1930
2026, 1960
–
–
a
Solvent is dichloromethane.
In KBr disk.
Extinction coefficient.
b
c
Table 2
Cyclic voltammetric reduction potentialsa and 31P NMR data
Structurally characterized acylruthenium species are
relatively few. The Ru–C(acyl) and acyl C@O distances
E1/2b, M(III)/M(II), (DEp, mV)
d (ppm)
˚
in 5 (Cl) are 2.013(4) and 1.226(5) A, respectively. In the
Complexes
reported structurally characterized species these lengths
have been found to occur in the ranges 1.98–2.15 and
˚
1.20–1.34 A, respectively [3c,6a,6b,6c,9,12]. The two
5(Me)
5(OMe)
5(Cl)
0.99 (152)
0.96 (158)
1.11 (200)
0.82 (116)
0.79 (175)
0.87 (143)
36.8
36.6
37.1
6(Me)
6(OMe)
6(Cl)
ꢂ6.2
ꢂ6.3
ꢂ6.3
˚
Ru–P distances, 2.383(1) and 2.401(1) A lie within the
˚
expected range [11–17] 2.40 0.05 A in trans-
RuII(PPh3)2 species. The Ru–Cl length 2.558(1) A is
˚
a
Solvent is dichloromethane.
E1/2 = 1/2(Epa + Epc), DEp = Epa ꢂ Epc where Epa and Epc are
b
longer than usual presumably due to the trans influence
of the coordinated acyl function.
In the hydrogen bonded zwitterionic iminium-pheno-
anodic and cathodic peak potentials respectively.
˚
lato ring, the N ꢀ ꢀ ꢀ O distance 2.561(6) A is shorter than
parameters are listed in Table 3. In the distorted octahe-
dral RuC2P2OCl coordination sphere the RuC2OCl
fragment constitute a nearly perfect equatorial plane
˚
that in the precursor complex 3 (Me) [16b] (2.665(12) A).
The iminium hydrogen was directly observable in differ-
ence Fourier maps, the N+–H and H ꢀ ꢀ ꢀ O distances are
˚
(mean deviation, 0.007 A), the P1–Ru–P2 axis being
approximately linear with an angle of 176.42(4)ꢁ at the
metal. The acyl chelate ring Ru, C1, C2, C8 and O2 is
˚
approximately 0.9 and 1.8 A, respectively.
The type 6 complexes did not afford single crystal but
their gross structure and geometry is convincingly pro-
ven by IR (cis-Os(CO)2), 31P NMR (trans-Os(PPh3)2),
1H NMR (imine-phenol tautomeric state) UV–vis spec-
tra (lack of metal chelation) and metal reduction poten-
tial (extra Os–CO back-bonding).
˚
highly planar (mean deviation, 0.006 A) and indeed
the Ru(ClL2) fragment excluding the chlorophenyl
˚
group is a good plane (mean deviation, 0.03 A) which
makes a dihedral angle of 23.4ꢁ with the pendant chlor-
ophenyl plane.
3. Experimental
3.1. Materials
The compounds Ru(PPh3)3Cl2 [22], Os(PPh3)3Br2 [23]
and M(QL1)(PPh3)2(CO)X [16,17] were prepared by re-
ported methods. Pure carbon monoxide was delivered
from a cylinder through gauges. The purification of
dichloromethane and the preparation of tetraethylam-
monium perchlorate (TEAP) for electrochemical work
were done as described in previous work [24a]. All other
chemicals and solvents were of analytical grade and
were used as received.
3.2. Physical measurements
Fig. 1. Perspective view and atom-labelling scheme for Ru(ClL2)
(PPh3)2(CO)Cl, 5(Cl).
Electronic, IR and mass spectra were recorded
with Shimadzu UV-1601 PC spectrophotometer,

B.K. Panda, A. Chakravorty / Journal of Organometallic Chemistry 690 (2005) 3169–3175
3173
Table 3
solid mass was obtained which was dissolved in a mini-
mum volume of dichloromethane. Petroleum ether (boil-
ing point 60–80 ꢁC) was then added to precipitate the
complex, which was filtered off and washed thoroughly
by petroleum ether, affording a crystalline solid. It was
dried in vacuo. Yield: 92 mg (89%). Anal. Found: C,
67.70; H, 4.76; N, 1.43%. Calc. for C53H44NO3P2ClRu:
C, 67.62; H, 4.71; N, 1.49. MS (ES+, CH2Cl2, m/z):
941.91(M + H)+, 906.36 (M ꢂ Cl)+. 1H NMR
(CDCl3,d): 7.84 (d, 1H, H(7), JHH 12.5), 14.79 (d, 1H,
N+–H, JHH 12.0), 6.65 (s, 1H, H(3)), 7.07 (s, 1H,
H(5)), 2.10 and 2.39 (2s, 6H, 2CH3), 7.15–7.67 (m,
34H, 2PPh3, H(11), H(12), H(14) and H(15), arom).
2
˚
Selected bond distances (A) and bond angles (ꢁ) for Ru(ClL )(PPh3)2
(CO)Cl, 5(Cl)
Bond distances
Ru–P1
Ru–P2
Ru–C1
Ru–Cl6
Ru–O2
Ru–Cl1
2.383(1)
2.401(1)
2.013(4)
1.821(5)
2.121(3)
2.558(1)
C1–O1
C16–O3
C7–N1
1.226(5)
1.152(5)
1.299(6)
1.410(6)
2.561(6)
1.307(5)
N1–C10
N1 ꢀ ꢀ ꢀ O2
O2–C8
Bond angles
P1–Ru–P2
P1–Ru–C1
P1–Ru–O2
P1–Ru–Cl6
P1–Ru–Cl1
P2–Ru–C1
P2–Ru–O2
P2–Ru–Cl6
O2–C8–C2
176.42(4)
89.43(13)
88.78(8)
91.6(2)
P2–Ru–Cl1
Ru–Cl6–O3
O1–C1–Ru
O2–Ru–Cl1
O2–C8–Ru
C2–C1–Ru
O1–C1–Ru
C7–N1–C10
N1–C7–C6
86.80(4)
178.2(4)
132.2(3)
80.75(8)
112.1(3)
109.6(3)
132.2(3)
129.2(4)
121.6(4)
89.64(4)
93.88(13)
90.30(8)
89.5(2)
3.3.2. [Ru(MeOL2)(PPh3)2(CO)Cl], (5(OMe))
One hundred milligrams (0.107 mmol) Ru
(MeOL1)(PPh3)2(CO)Cl was employed. Yield: 95 mg
(92%). Anal. Found: C, 66.55; H, 4.58; N, 1.43%. Calc.
for C53H44NO4P2ClRu: C, 66.49; H, 4.63; N, 1.46. MS
(ES+, CH2Cl2, m/z): 958.05 (M + H)+, 922.07
(M ꢂ Cl)+. 1H NMR (CDCl3, d): 7.78 (d, 1H, H(7),
JHH 12.3), 15.01 (d, 1H, N+–H, JHH 12.1), 6.64 (s, 1H,
H(3)), 6.91 (s, 1H, H(5)), 2.09 (s, 3H, CH3), 3.83 (s,
3H, OCH3), 7.13–7.66 (m, 34H, 2PPh3, H(11), H(12),
H(14) and H(15), arom).
119.6(4)
Perkin–Elmer 783 IR spectrometer and Micromass
Q-TOF mass spectrometer, respectively. A Bruker
300 MHz FT NMR spectrometer was used to record
1H NMR spectra (Me4Si internal standard). The num-
1
bering scheme used for H NMR is the same as in crys-
tallography in case of 5 and as in the drawing in the
case of 6. Spin–spin structures are abbreviated as: s,
singlet; d, doublet; t, triplet; m, multiplet. 31P NMR
spectra were recorded with the help of a Varian
300 MHz spectrometer using H3PO4 as standard.
Microanalyzes (C, H, N) were done using a Perkin–El-
mer 240C elemental analyzer. All electrochemical mea-
surement were done under a nitrogen atmosphere in
dichloromethane solution using a model 620A electro-
chemical analyzer of CH Instruments. The supporting
electrolyte was tetraethylammonium perchlorate and
the reported potentials are referenced to the saturated
calomel electrode (SCE).
3.3.3. [Ru(ClL2)(PPh3)2(CO)Cl], (5(Cl))
One
hundred
milligrams
(0.107 mmol)
of
Ru(ClL1)(PPh3)2(CO)Cl was employed. Yield: 90 mg
(87%). Anal. Found: C, 64.89; H, 4.27; N, 1.52%.
Calc. for C52H41NO3P2Cl2Ru: C, 64.94; H, 4.30; N,
1.46. MS (ES+, CH2Cl2, m/z): 964.00 (M + H)+,
926.01 (M ꢂ Cl)+. 1H NMR (CDCl3, d): 7.91 (d,
1H, H(7), JHH 12.1), 14.91 (d, 1H, N+–H, JHH
12.0), 6.67 (s, 1H, H(3)), 7.09 (s, 1H, H(5)), 2.08 (s,
3H, CH3), 7.09–7.66 (m, 34H, 2PPh3, H(11), H(12),
H(14) and H(15), arom).
3.3. Synthesis of the complexes, [Ru(QL2)(PPh3)2-
(CO)Cl] (5)
3.4. Synthesis of the complexes [Os(QL3)(PPh3)2-
(CO)2Br] (6)
The [Ru(QL2)(PPh3)2(CO)Cl], (5) complexes were
synthesized in excellent yield (ꢁ90%) by reacting
Ru(QL1)(PPh3)2(CO)Cl (3) with carbon monoxide. De-
tails of a representative case are given below.
The [Os(QL3)(PPh3)2(CO)2Br] (6) complexes were
synthesized in excellent yield (ꢁ85%) by reacting
[Os(QL1)(PPh3)2(CO)Br] with carbon monoxide. Details
of a representative case are given below.
3.3.1. [Ru(MeL2)(PPh3)2(CO) Cl], (5(Me))
3.4.1. [Os(MeL3)(PPh3)2(CO)2Br] (6(Me))
One hundred milligrams (0.109 mmol) of Ru
(MeL1)(PPh3)2(CO)Cl was taken in a round bottom flask
and 20 ml of dichloromethane was added. Initially dini-
trogen gas was allowed to pass through the solution for
15 min followed by CO (1 atm, supplied from a cylinder)
for 10 min. The solution was left under CO atmosphere
for 12 h with constant stirring. The solution colour
changed from violet to orange. After that the solvent
was evaporated under reduced pressure when a orange
One hundred milligrams (0.099 mmol) of Os
(MeL1)(PPh3)2(CO)Br was treated with carbon monox-
ide in the same manner as in the case 5 (Me). Here the
solution colour changed from violet to yellow after
6 h. After that solvent was evaporated under reduced
pressure when a yellow solid was obtained which was
treated with dichloromethane and petroleum ether
(b.p. 60–80 ꢁC) in the same manner as in the case of 5

3174
B.K. Panda, A. Chakravorty / Journal of Organometallic Chemistry 690 (2005) 3169–3175
Table 4
Crystal data for Ru(ClL2)(PPh3)2(CO)Cl
(Me). The yellow solid was finally dried in vacuo. Yield:
88 mg (85%). Anal. Found: C, 59.18; H, 4.05; N, 1.25%.
Calc. for C53H44NO3P2BrOs: C, 59.22; H, 4.12; N, 1.30.
MS (ES+, CH2Cl2, m/z): 1076.08 (M + H)+, 995.12
Complex
Ru(ClL2)(PPh3)2(CO)Cl
C52H41NO3P2Cl2Ru
961.77
Empirical formula
Formula weight
Crystal system
Space group
1
(M ꢂ Br)+. H NMR (CDCl3, d): 8.04 (s, 1H, H(7)),
Monoclinic
C2/c
13.18 (s, 1H, O–H), 6.48 (s,1H, H(3)), 1.72 and 2.40
(2s, 6H, 2CH3), 7.03–7.56 (m, 35H, 2PPh3, H(5),
H(12), H(13), H(15) and H(16), arom).
˚
a (A)
34.322(7)
14.472(3)
22.554(5)
105.28(3)
10,807(4)
8
˚
b (A)
˚
c (A)
b (ꢁ)
3.4.2. [Os(MeOL3)(PPh3)2(CO)2Br] (6(OMe))
One hundred milligrams (0.098 mmol) Os-
(MeOL1)(PPh3)2(CO)Br was employed. Yield: 91 mg
(89%). Anal. Found: C, 58.28; H, 4.12; N, 1.35%. Calc.
for C53H44NO4P2BrOs: C, 58.35; H, 4.06; N, 1.28. MS
3
˚
V (A )
Z
l (Mo Ka) (mmꢂ1
)
0.485
1.182
Dcalc (g cmꢂ1
Total reflections
Independent reflections (Rint
)
8151
8151 (0.0000)
4.49, 13.53
)
(ES+,
CH2Cl2,
m/z):
1092.07
(M + H)+,
R1a, wR2 [I > 2r(I)]
b
1
1012.11(M ꢂ Br)+. H NMR (CDCl3, d): 8.04 (s, 1H,
H(7)), 13.18 (s, 1H, O–H), 6.47 (s, 1H, H(3)), 1.72 (s,
3H, CH3), 3.86 (s, 3H, OCH3), 6.94–7.56 (m, 35H,
2PPh3, H(5), H(12), H(13), H(15) and H(16), arom).
P
P
a
R1 ¼ kF o j ꢂ j F ck= j F o j.
P
P
2
2
b
wR2 ¼ ½ wðF 2o ꢂ F c2Þ = ðF 2oÞ ].
4. Conclusion
3.4.3. [Os(ClL3)(PPh3)2(CO)2Br] (6(Cl))
One hundred milligrams (0.098 mmol) Os(ClL1)
(PPh3)2(CO)Br was employed. Yield: 88 mg (86%).
Anal. Found: C, 57.10; H, 3.70; N, 1.21%. Calc. for
C52H41NO3P2ClBrOs: C, 57.02; H, 3.77; N, 1.28. MS
(ES+, CH2Cl2, m/z): 1096.05 (M + H)+, 1016.09
It is demonstrated that the metallacycle 3 undergoes
facile one-carbon expansion upon treatment with car-
bon monoxide furnishing the acyl complex 5 presumably
via aryl migration in a dicarbonyl intermediate. In 5(Cl)
we have a new structurally characterized acylruthenium
metallacycle. The reaction of 4 with carbon monoxide
affords the dicarbonyl aryl complex 6 and its stability
is consistent with the poor ability of osmium in promot-
ing aryl migration. The distinctive spectral features of 5
and 6 concern MLCT transitions, C@N and C„O
stretching frequencies and 31P NMR chemical shifts.
The MIII/MII reduction potentials follow the order
5 > 3 and 6 > 4 signifying stabilization of the MII state
upon carbonylation.
1
(M ꢂ Br)+. H NMR (CDCl3, d): 7.95 (s, 1H, H(7)),
12.81 (s, 1H, O–H), 6.42 (s, 1H, H(3)), 1.65 (s, 3H,
CH3), 7.01–7.41 (m, 35H, 2PPh3, H(5), H(12), H(13),
H(15) and H(16), arom).
3.5. X-ray structure determination
A bright orange single crystal of Ru(ClL2)(PPh3)2-
(CO)Cl, (5 (Cl)) (0.40 · 0.30 · 0.20 mm3) grown by slow
diffusion of hexane into dichloromethane solutions at
room temperature was used. Cell parameters were deter-
mined by a least squares fit of 30 machine-centered
reflections (2h range 14–28ꢁ) on a Siemens R3m/V
four-circle diffractometer with graphite-monochromated
Mo Ka radiation (k = 0.71073). Two check reflections
measured after every 198 reflections showed no signifi-
cant intensity reduction. All data were corrected for
Lorentz polarization effects and an empirical absorption
correction [25] was performed on the basis of an azi-
muthal scan of six reflections for the crystals. The metal
atom was located from Patterson maps and the rest of
the non-hydrogen atoms emerged from successive Fou-
rier syntheses. The structure was refined by full matrix
least-squares procedures. All non-hydrogen atoms were
refined anisotropically. Many of the significant hydro-
gen atoms were located in difference Fourier maps and
the others were added at calculated positions. Calcula-
tions were performed using the SHELXTL, version 5.03
[26] programme package. Significant crystal data are
listed in Table 4.
5. Supplementary material
Crystallographic data for the structure analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC no. 262182 corresponding to
Ru(ClL2)(PPh3)2(CO)Cl, (5(Cl)). Copies of this infor-
mation may be obtained free of charge from The Direc-
tor, CCDC, 12 Union Road, Cambridge CB2 1EZ, UK
(Fax: +44 1223 336033; e-mail: deposit@ccdc.cam.ac.uk
or http://www.ccdc.cam.ac.uk).
Acknowledgements
We are thankful to the Department of Science and
Technology, the Council of Scientific and Industrial Re-
search, New Delhi, India, for financial support. The help
received from Prof. Goutam Lahiri is gratefully
acknowledged.

B.K. Panda, A. Chakravorty / Journal of Organometallic Chemistry 690 (2005) 3169–3175
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