Coordination preferences of 4-dimethylaminobut-3-en-2-one in thermally and photochemically activated reactions with Ru3(CO)12

Article abstract of DOI:10.1016/j.poly.2018.04.007

The thermally and photochemically activated reactions of Ru₃(CO)₁₂ with 4-dimethylaminobut-3-en-2-one (L) were studied and several mononuclear and polynuclear products were isolated and fully characterized by a combination of spectro

Full text of DOI:10.1016/j.poly.2018.04.007

Accepted Manuscript
Coordination preferences of 4-dimethylaminobut-3-en-2-one in thermally and
photochemically activated reactions with Ru3(CO)12
Svetlana V. Osintseva, Nikolay A. Shtel'tser, Alexander S. Peregudov, Arkadii
Z. Kreindlin, Fedor M. Dolgushin
PII:
S0277-5387(18)30174-8
https://doi.org/10.1016/j.poly.2018.04.007
POLY 13108
DOI:
Reference:
Polyhedron
To appear in:
Received Date:
Accepted Date:
23 January 2018
3 April 2018
Please cite this article as: S.V. Osintseva, N.A. Shtel'tser, A.S. Peregudov, A.Z. Kreindlin, F.M. Dolgushin,
Coordination preferences of 4-dimethylaminobut-3-en-2-one in thermally and photochemically activated reactions
with Ru3(CO)12, Polyhedron (2018), doi: https://doi.org/10.1016/j.poly.2018.04.007
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1
Coordination preferences of 4-dimethylaminobut-3-en-2-one in thermally and
photochemically activated reactions with Ru3(CO)12
Svetlana V. Osintseva*, Nikolay A. Shtel’tser, Alexander S. Peregudov, Arkadii Z. Kreindlin, and
Fedor M. Dolgushin
A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilov
Street 28, 119991 Moscow, Russia
*Corresponding author. E-mail: СВЕТА@ineos.ac.ru
Abstract
The thermally and photochemically activated reactions of Ru3(CO)12 with 4-dimethylaminobut-3-
en-2-one (L) were studied and several mononuclear and polynuclear products were isolated and
fully characterized by a combination of spectroscopic IR and multinuclear NMR data as well by
single-crystal X-ray diffraction studies. Chelate five-membered oxaruthenacycles found to be
present in all the isolated organometallic products are formed via Cβ-H activation reactions. These
metallacycles can be bound to other ruthenium atoms in the different modes, namely, through π-
coordination to the olefinic bond, through σ-coordination to the Cα atom of the starting ligand, and
by coordination through the lone pair of the oxygen atom. The coordination of a metal atom to the
Cα atom caused by an isomerization of the ligand to form partially imine C=N bond and migration
of the olefinic bond has not been observed previously in reactions of Ru3(CO)12 with oxadienes.
The formation of the six-membered chelate azaoxaruthenacycles in the reaction with L is
accompanied by a migration and reduction of the olefinic bond. These chelates are significantly less
stable than the five-membered chelates and involved coordination to other metal atoms to form
polynuclear products. The structural and spectroscopic features and possible transformations
pathways of the resulting complexes are discussed.

2
Keywords: Dodecacarbonyltriruthenium; Amino vinyl ketones; Five-membered metallacycles; C-
H Activation; X-ray diffraction study.
1. Introduction
The chemistry of enamimones (or β-aminovinylketones) is attracting chemists’ interest due to
extensive applications of these compounds which have demonstrated a potential as multipurpose
synthetic intermediates in organic synthesis [1, 2], in pharmaceutical developments [3], and in
heterocyclic synthesis [4]. In coordination chemistry, enaminones, either as neutral or as anionic
species, present valuable ligands for metal-ion chelation. These metal complexes are frequently
used as reagents, intermediates, or catalysts in chemical synthesis of drugs, polymers and dyes [1,
2], for the deposition of metal coatings [5, 6], and they possess liquid-crystalline properties [7, 8].
Chelate enaminone complexes often demonstrate a good therapeutic activity and exhibit limited
neurotoxicity in contrast to uncoordinated enaminones [3]. Most common organometallic
compounds of enaminones are the six-membered N,O-metallochelates known for both transition
and non-transition metals [9, 10, 11].
Earlier we studied the reaction between Ru3(CO)12 and 1-(4-tolyl)-3-phenylaminoprop-2-en-1-
one [12]. As expected the main reaction products were the six-membered N,O-metallochelates.
However, the unexpected complex containing the five-membered C,O-chelate ring was also found
(Chart 1). The formation of the latter is occur via an activation of Сβ-Н rather than N-H bonds.
Chart 1
Ph
N
Ph
H
H
N
CO
Ru
H
OC
N
H
N
CO
H
Ph
+
OC
N
Ph
Ru3(CO)12
+
H
Ru
H
Tol
O
H
O
O
Ph
O
H
Tol
Tol
O
H
H
Tol
Tol

3
Amino vinyl ketones with secondary amino groups (for example, 1-(4-tolyl)-3-
phenylaminoprop-2-en-1-one) adopt cis-conformations [13] stabilized by an intramolecular N-
H···O hydrogen bond. In order for coordination of the β-carbon atom to occur and a five-membered
cycle to form, the breaking of the H-bond and spatial transformation of a molecule from cis- to
trans-conformation is necessary.
One possible, more selective, way of obtaining these unusual five-membered chelates and to
reduce the possibility of the formation of the six-membered chelates is to replace a secondary β-
amino group by a tertiary one. Therefore, we studied the reaction of Ru3(CO)12 with 1-phenyl-2-
metyl-3-morpholino-prop-2-en-1-one [14]. However, the reaction was accompanied by the
deamination of the ligand and the expected chelate complexes were not found.
In order to ascertain whether deamination of tertiary amino vinyl ketones is a common process
in their thermal reactions with Ru3(CO)12, we studied here the reaction with 4-dimethylaminobut-3-
en-2-one (L). In this case, a completely different reaction pathway occurs including an activation of
both Cβ-H and Cα-H olefinic bonds and a formation of the target five-membered chelate complexes.
2. Results and discussion
2.1. Reaction course and transformation of the products
The thermally activated reaction of Ru3(CO)12 with compound L was carried out first in boiling
hexane (68ºC) to afford the starting reactant and intermediate product and then in boiling heptane
(98ºC) to isolate the end products. Both reactions lead to the same products. The difference is in the
boiling point of the solvent and therefore in the temperature of the reaction. At a lower temperature
(boiling hexane), the reaction proceeds at a slower rate, which makes it possible to optimize
conditions for the formation of the intermediate products. At a higher reaction temperature (boiling
heptane), the time of obtaining the end products significantly reduces. The course of the reaction at
all stages of products separation and purification was monitored by IR spectroscopy paying a
special attention to the spectral range corresponding to metalcarbonyl stretching vibrations. After

4
slow cooling, the reaction mixture separated into a solution and a precipitate. The products of the
1
reaction were characterized by IR, H and 13C NMR spectroscopy (Table 1) and their molecular
structures were unambiguously determined by single-crystal X-ray diffraction studies.
After reflux in hexane for 4 h (the reaction time was defined by the maximum content of
complexes 1 in the reaction solution) and silica gel column chromatography, isomeric complexes 1
(31.7% yield) and complexes 2 and 3 (trace amounts) were isolated (Scheme 1). A slight amount of
unidentified precipitate was also isolated. The longer-term heating of the reaction mixture in hexane
or heating in heptane for 1 h 20 min (the reaction time was defined by the maximum content of
complexes 2 and 3 in the reaction solution) resulted in the disappearance of complexes 1 and slow
accumulation of complexes 2 (4.6% yield), 3 (14.0% yield), and 4 (traces) in solution accompanied
by abundant precipitation. The precipitate contained complex 5 (9.7% yield) and 6 (1.7% yield) as a
red-brown oily substance (Scheme 2).
Scheme 1. Thermal reaction of Ru3(CO)12 with L in boiling hexane
CH
CH
O
3
3
CH
H
3
H
N(CH )
3 2
H
N
hexane
Ru3(CO)12
O
+
CH
2 and 3 (trace amounts)
3
Ru
+
H
68oC, 4h
(CO)
COCH
3
3
(CO) Ru
N
Ru(CO)
2
3
L
CH
3
CH
3
1a-d (31.7%)

5
Scheme 2. Thermal reaction of Ru3(CO)12 with L in boiling heptane (1h20m)
CH
3
H
N
heptane
Ru3(CO)12
+
CH
3
1a-d (trace amounts)
+
H
98oC, 1h20m
COCH
3
L
H
H
H
CH
CH
H
H
3
3
CH
3
CH
CO
3
CH
CO
CH
H
N
3
3
H
O
CO
H
CO
CH
N
N(CH )
3 2
3
O
Ru
O
O
OC
CH
H
Ru
Ru
O
CH
3
O
N
N(CH )
3 2
Ru
O
O
(CH ) N
3 2
CO
H
H
O
5 (9.7%) and 6 (1.7%)
+
+
+
Ru
(CO)3
O
Ru
(CO)2
CH
CH
3
H
3
H
H
CH
3
CH
(CO)
Ru
H
3
3
3
2 (4.6%)
4 (trace amounts)
3 (14.0%)
Isomeric complexes 1 are the main products of the first stages of the thermal reaction of
Ru3(CO)12 with L, and as Ru3(CO)12 are precursors of the complexes formed in the later stages of
the reaction. In separate experiments, the reflux of complex 1 with excess L resulted in the
1
formation of complexes 2, 3, and 4 according to the IR and H NMR spectra (see Experimental
part). Complex 3 is the end product of the reaction and the only complex remaining in the reaction
solution. Complexes 2 and 4 are the minor products of the reaction and upon the long-term heating
decompose.
The heating of the reaction mixture in heptane for 3 h resulted in a significant increase in the
amount of the precipitate, and the reaction solution contains only the complex 3 (Scheme 3). Upon
long-term heating in heptane from 3 to 6 h, no changes occur in the reaction solution according to
IR spectroscopy. Also, the total amount of the precipitate remains unchanged; however, the ratio of
the complexes changes in favor of complex 6 (see Experimental part). This indirectly suggests the
transformation of 5 into 6. Unfortunately, we could not perform a separate experiment on the
transformation 5 into 6, since the complexes are insoluble in hydrocarbons. When performing the
reactions in polar chlorine-containing solvents, the complexes being a source of the oxaruthenaycles
required for the 5-to-6 transformation either decompose to unidentified precipitates or add chlorine
atoms to form complexes with strong Ru-Cl bonds [15]. The relatively low yield of complexes 5

6
and 6 is due to the decomposition of the salt compounds during column chromatography on silica
gel (see Experimental part).
Scheme 3. Thermal reaction of Ru3(CO)12 with L in boiling heptane (3h)
CH
3
H
N
heptane
98oC, 3h
Ru3(CO)12
+
CH
3
3 +
H
COCH
3
L
CH
3
H
H
H
+
+
H
N(CH )
O
3 2
N(CH )
3 2
-
]
-
[HRu (CO)
6
CH
O
18
[HRu (CO)
]
3
(CO)
6
18
(CO) Ru
2
(CO)
2
2
Ru
Ru
O
N(CH )
3 2
N(CH )
O
3 2
O
CH
CH
3
O
3
+
O
Ru
(CO)
Ru
(CO)
H
2
H
2
H
H
CH
N(CH )
3 2
3
CH
3
N(CH )
3 2
5 (17.1%)
6 (6.6%)

7
Table 1. IR and NMR spectra for 1-7
1Н NMR (C6D6), 
13C NMR (C6D6), 
Comp.
IR (hexane,
(СО)/cm–1
1678m, 1628w,
1600s
7.43 (d, 1H, CH=CH, J=12.7 Hz);
5.04 (d, 1H, CH=CH, J=12.8 Hz);
2.46, (s, 6H, CH3N); 2.09 (s, 3H,
CH3)
192.9 (C=O); 152.3 (Cβ);
99.9 (Cα); 43.7, 36.1 (N-
(CH3)2); 28.4 (C(O)-CH3)
L
L *)
1a
1b
1c
6.94 (d, 1H, CH=CH, J=12.8 Hz);
4.51 (d, 1H, CH=CH, J=12.7 Hz);
2.57, 2.33 (s, 3H, CH3N); 1.55 (s,
3H, CH3)
2072s, 2036v.s,
2008sh, 2000s,
1984s, 1968m,
1964m, 1946m
2072s, 2016v.s,
2010s, 2004sh,
1984s, 1968m,
1960m, 1936m
2072s, 2036v.s,
2008sh, 2000s,
1984s, 1968m,
1964m, 1936m
2072s, 2016v.s,
2010s, 2004sh,
1984s, 1968m,
5.28 (s, 1H, CH=C); 3.40 (s, 1H,
CH=C); 3.01, 2.89, 2.45, 2.13 (s,
3H, CH3N); 1.81, 1.66 (с, 3H, CH3)
5.42 (s, 1H, CH=C); 3.39 (s, 1H,
CH=C); 3.34, 3.24, 2.72, 2.55 (s,
3H, CH3N); 2.04, 1.58 (s, 3H, CH3)
5.24 (s, 1H, CH=C); 3.01 (s, 1H,
CH=C); 3.04, 2.50, 2.48, 2.46 (s,
3H, CH3N); 2.11, 1.84 (s, 3H, CH3)
5.48 (s, 1H, CH=C); 3.92 (s, 1H,
CH=C); 3.19, 3.05, 2.91, 2.55 (s,
3H, CH3N); 2.01, 1.55 (s, 3H, CH3)
1d

8
1960m, 1926m
2030s, 1960s
7.77 (d, 1H, CH=CH, J=4.8 Hz); 216.0 (Cβ); 200.9 (M-C=O);
5.13 (с, 1H, CH=C); 5.11 (d, 1H, 198.4 (C=O); 196.4 (C=O);
CH=CH, J=4.8 Hz); 2.79, 2.24, (s, 190.8 (M-C=O); 175.9 (Cβ);
2a
3H, CH3N); 1.96, 1.84 (s, 3H, CH3)
105.5 (Cα); 100.7 (Cα); 49.1,
40.1 (N-(CH3)2); 27.8, 23.2
(C(O)-CH3)
2030s, 1960s
2016s, 1946s
8.13 (d, 1H, CH=CH, J=4.4 Hz);
5.14 (s, 1H, CH=C); 5.10 (d, 1H,
CH=CH, J=4.3 Hz); 2.78, 2.20, (s,
3H, CH3N); 1.97, 1.73 (s, 3H, CH3)
5.53 (s, 1H, CH=C); 3.25, 2.52 (s,
3H, CH3N); 2.03 (s, 3H, CH3)
2b
3
3*)
5.48 (s, 1H, CH=C); 3.54, 3.15 (s, 226.9 (Cβ); 200.5 (M-C=O);
3H, CH3N); 2.04 (s, 3H, CH3)
199.6 (C=O); 105.3 (Cα);
51.3, 40.5 (N-(CH3)2); 23.9
(C(O)-CH3)
4*)
5.56 (s, 1H, CH=C); 4.55 (s, 1H,
CH=C); 4.38 (m, 1H, CH2-CH2);
3.78 (m, 1H, CH2-CH2); 3.65, 3.33,
3.17, 3.15, (s, 3H, CH3N); 2.06 (s,
3H, CH3); -14.02 (s, 1H, Ru-H)
5*)
2010vs, 1978w,
1962w, 1948w
(CH2Cl2)
16.48 (s, 1H, Ru-H); 5.21 (s, 1H,
CH=C); 4.69 (s, 1H, CH-C); 4.80 (t,
1H, C-H); 3.58, 3.52, 3.33, 3.17,
225.4 (Cβ); 218.8, 215.8,
207.6; 201.3
([НRu6(CO)18]‾); 200.7,

9
2.96, 2.67 (s, 3H, CH3N); 3.17 (m, 199.5, 197.8, 194.6, 163.5,
1H, C-HH); 2.11 (m, 1H, C-HH); 105.3, 103.8, 72.0 (Cα-Ru);
2.42, 1.93, 1.60 (s, 3H, CH3)
57.3, 55.4, 52.0, 51.9, 50.5,
42.4, 42.3, 29.7, 27.3, 23.2
226.7 (Cβ); 218.0, 201.6;
201.4 ([НRu6(CO)18]‾);
193.0, 71.4 (Cα-Ru); 51.5,
41.5, 27.9
6*)
2010vs, 1962w,
1948w (CH2Cl2)
16.44 (s, 1H, Ru-H); 4.41 (s, 1H,
CH-C); 3.51, 3.15 (s, 3H, CH3N);
2.25 (s, 3H, CH3)
2046 s, 1998 s,
1962 s (CH2Cl2)
5.52 (s, 1H, CH=C); 3.65, 3.24 (s, 214.0 (Cβ); 212.5 (M-C=O);
7
3H, CH3N); 1.08 (s, 3H, CH3)
202.5 (C=O); 111.0 (Cα);
51.6, 41.5 (N-(CH3)2); 21.3
(C(O)-CH3)
*) NMR spectra were detected in CDCl3
2.2. Spectral and structural characterization of isomeric complexes 1
Four isomeric complexes 1a-d were obtained during the first stages of the thermal reaction of Ru3(CO)12
with L (Scheme 1). The structures of three complexes 1a-c were established by X-ray diffraction study
(Fig. 1, Table S1). wo molecules of the ligand in complexes 1 chelate two ruthenium atoms forming
five-membered oxaruthenacycles. Each organic ligand donates three electrons with regard to the chelated
ruthenium atoms and one of the ligands which links all three ruthenium atoms donates an additional four
electrons through the π-coordination of the olefinic bond to the central Ru(2) atom and dative
coordination of the nitrogen electron lone pair. Taking into account eight carbonyl ligands, the total
number of cluster valence electrons is equal to 50, which implies two metal-metal bonds in the trimetallic
core of the complexes 1 (the average values of Ru(1)-Ru(2) and Ru(2)-Ru(3) bond lengths from the three
structures 1a-c are 2.79 Å and

10
CH
O
CH
O
3
3
H
H
N(CH )
3 2
Ru
(CO)
3
(CO) Ru
N
Ru(CO)
2
3
CH
3
CH
3
a)
b)
c)
Figure 1. Schematic presentation of complex 1 and molecular structures of the isomeric
complexes 1a (a), 1b (b), and 1c (c) with thermal ellipsoids drawn at the 50% probability level
(the hydrogen atoms are omitted).
Complexes 1a-c differ from each other by the spatial arrangement of the chelate ring and
metalcarbonyl groups around the Ru(3) atom. These differences in complexes 1 can be seen clearly
from the schematic representation of an octahedral ligand environment around the Ru(3) atom
(Scheme 4) [16]. The number of possible stereoisomers is restricted by the positions of the N(1) and
Ru(2) atoms which is specified by the structure of the unchangeable fragment of the complexes.
The cis arrangement of two metalcarbonyl ligands is fixed taking into account the destabilizing
effect of the trans arrangement of the “hardest” ligands in accordance with the theory of mutual
trans influence of ligands [17, 18, 19, 20, 21]. One of the metalcarbonyl groups (C(8)O(8)) is
always in the trans position with regard to the oxaruthenacycle O(10) atom (the “softest” ligand).

11
Thus, the difference between the complexes is defined by the arrangement of the second
metalcarbonyl group (С(7)О(7)) on the Ru(3) atom. This group can be arranged in two ways: in the
trans position to the N(1) atom (complex 1a) or the Ru(2) atom (complex 1b). The number of
stereoisomers doubles taking into account the mirror replacement of the oxaruthenacycle O(10)
atom and trans-positioned C(8)O(8) metalcarbonyl group at fixed positions of remaining ligands.
As a result, complex 1a has a stereoisomeric pair complex, 1c and complex 1b has a stereoisomeric
pair complex, 1d (whose proposed structure becomes clear from Scheme 4).
Scheme 4. Octahedral ligand environment around the Ru(3) atom in isomeric complexes 1
Ru(2)
Ru(2)
Ru(2)
Ru(2)
1936 cm-1
1936 cm-1
O
N(CH3)2
O
N(CH3)2
N(CH3)2
N(CH3)2
(CO)
(CO)
Ru(3)
Ru(3)
Ru(3)
Ru(3)
O
C
O
(CO)
1946 cm-1
(CO)
2036 cm-1
C
(CO)
1926 cm-1
(CO)
2036 cm-1
(CO)
C
2016 cm-1
C
2016 cm-1
(CO)
1b
1d
1a
1c
The IR spectra of complexes 1 contain eight bands each in the region of metalcarbonyl
stretching vibrations. Most of the bands coincide; however, there are characteristic bands
corresponding to the metalcarbonyl groups at the Ru(3) atom, which allows spectral distinguishing
of isomers or their mixtures (Scheme 4).
In the 1H NMR spectra of the isomeric complexes 1a-d (Table 1) the same sets of signals were
obtained with insignificant differences due to the different ligand environment of the Ru(3) atom.
The proton signals for the uncoordinated oxaruthenacycles in complexes 1a and 1c ( 5.28 and
5.24, respectively) are upfield shifted by 0.2 ppm compared to the analogous signals in complexes
1b and 1d ( 5.42 and 5.48, respectively). The proton signals for the π-coordinated

12
oxaruthenacycles differ more strongly (from  3.01 to 3.92). Their positions are influenced by the
ligand environment of the Ru(3) atom and this effect propagates through the Ru(2) and N(1) atoms.
The yield of the pair complexes 1b and 1d is significantly lower than that of the 1a and 1c, and
isomer 1d was obtained in trace amounts. The ratio of isomers formed in the reaction is described as
1a : 1c : 1b + 1d = 2 : 1 : 1. It follows from the ratio of the isomeric products that the trans position
of the metalcarbonyl group with regard to the nitrogen atom (as in isomers 1a and 1c) is more
preferred compared to the trans position with regard to the ruthenium atom (as in isomers 1b and
1d).
2.3. Spectral and structural characterization of complex 3
According to the X-ray diffraction data (Fig. 2), the ruthenium atom in the mononuclear complex 3
is chelated by two molecules of L and bound to two carbonyl ligands in the cis position. In the
crystal, complex 3 occupies a special position on the twofold axis passing through the ruthenium
atom. An octahedral ligand environment of the Ru atom is characterized by the transoid
arrangement of the metallacycle C atoms, whereas the carbonyl ligands are in the trans positions
with respect to the O atoms of the metallacycles. The analogous mononuclear complexes with two
five-membered oxaruthenacycles were obtained in the reactions with oxadienes [22]. In the reaction
with 1-(4-tolyl)-3-phenylaminoprop-2-en-1-one, mononuclear complexes with chelate six-
membered and five-membered metallacycles were also isolated (Chart 1) [12]. In all these
reactions, the mononuclear complexes with two chelate ligands are the main end products.
The IR spectrum of complex 3 (Table 1) contains two equal-intensity bands in the region of
metalcarbonyl stretching vibrations, which is typical for two CO ligands that are cis position to each
1
other. The Н NMR spectrum of complex 3 displays one set of signals for the coordinated ligand
(Table 1). The 13С NMR spectrum of 3 displays three downfield signals. The signal at δ 226.9 ppm
can be attributed to the -carbon atom of the five-membered rings. This can be explained by a
partial contribution of the carbene character of the Ru-C bond, which implies a partial furan

13
structure of the five-membered oxaruthenacycle [22]. The low-intensity signal at δ 200.5 ppm
can be attributed to the metalcarbonyl carbon. The slightly upfield shifted signal at δ 199.6 ppm
corresponds to the keto carbon atom.
Figure 2. Molecular structure of the mononuclear complex 3 (thermal ellipsoids at the 50%
probability level).
2.4. Characterization of complexes 5 and 6 isolated from a precipitate
The structures of two complexes isolated from a precipitate were unexpected. Complexes 5 and 6
are ionic compounds. Note that we observe for the first time the formation of salts in the reactions
of Ru3(CO)12 with substituted oxadienes.
(Fig. 3,
Table S2), two ruthenium atoms in the cation of complex 5 coordinate to three ligand molecules and
each ruthenium atom coordinates to two metalcarbonyl groups in the cis position. The distance
Ru(1)…Ru(2) of 3.647(1) Å suggests the absence of the metal-metal interaction. The Ru(1) atom is
chelated by two ligands to form the five-membered oxaruthenacycle and six-membered
azaoxaruthenacycle, and the Ru(2) atom is chelated by the third ligand to form the five-membered
oxaruthenacycle. The octahedral environment of the Ru(2) atom is supplemented by the
coordination to the O(6) atom being involved in the chelation of the Ru(1) and by the C(6) atom
forming a part of the five-membered metallacycle. The coordination to the C(6) atom (Ru(2)-C(6)
bond length equals 2.370(9) Å) adopts an η1-coordination mode; the Ru(2)-C(5) distance of

14
2.894(9) Å and the Ru(2)-C(7) distance of 3.045(9) Å suggest the absence of the interaction with
the neighbouring atoms of the metallacycle. Note that Ru(2) adopts an 18 electron configuration with
the bonding as described.
The η1-coordinated five-membered oxaruthenacycle, in contrast to the uncoordinated one, has a
nonplanar envelope conformation with the C(7) atom coming out of the Ru(1)O(5)C(5)C(6) plane
by 0.49 Å in the direction opposite to the Ru(2) atom (the angle of bending along the Ru(1)…C(6)
line is 29.3º). The Ru(2)-C(6) bond (2.370(9) Å) is significantly elongated compared to the trans-
positioned Ru(2)-C(19) bond (2.087(9) Å). Nevertheless, additional coordination results in the sp3-
1
rehybridization of the C(6) atom, which is confirmed by an upfield shift of the proton singlet in Н
NMR spectrum (see below). The interaction is weak and, therefore, the change in the neighbouring
C-C bond lengths in the metallacycle (C(5)-C(6) is 1.423(13) Å and C(6)-C(7) is 1.442(13) Å) is
not so significant as can be expected upon a change in the atom hybridization. However, they are
noticeably elongated compared to the analogous bonds in uncoordinated five-membered
oxaruthenacycle (C(17)-C(18) is 1.385(13) Å and C(18)-C(19) is 1.417(13) Å). The single character
of the C(6)-C(7) bond, and a partially multiple N(1)-C(7) bond (1.339(12) Å), and a partial
contribution of the carbene type to the Ru(1)-C(7) bond (2.042(9) Å) suggest delocalization of the
positive charge on the Ru(1), C(7), and N(1) atoms. The C(5)-O(5) bond length of 1.255(11) Å
suggests that the ketonic nature of the ligand is retained.

15
H
H
+
H
N(CH )
3 2
CH
O
3
-
(CO)
2
Ru
HRu (CO)
6
18
O
N(CH )
3 2
CH
3
O
Ru
(CO)
H
2
H
CH
N(CH )
3 2
3
Figure 3. Schematic presentation of 5 and molecular structure of the binuclear cationic complex
(thermal ellipsoids at the 50% probability level, hydrogen atoms are omitted). The cluster anion
[НRu6(CO)18]‾ is not shown.
The Ru(1) atom is chelated by the second molecule of the ligand through the nitrogen and
oxygen atoms to form a six-membered azaoxaruthenacycle. The ligand undergoes significant
restructuring. The ketonic bond of the starting amino vinyl ketone becomes single-bond (O(6)-
C(11) is 1.374(11) Å), the olefinic bond shifts to C(11)-C(12) (1.343(14) Å), the C(13) carbon atom
forming a methylene group. The six-membered ring is nonplanar and has boat conformation (the
angle of bending along the O(6)…C(13) is 51.1º). Thus, all three organic ligands in the cationic
complex 5 have a different structure.
The formal description of the complex suggests that the organic ligand in the six-membered
metallacycle is a 5е donor (coordination to the electron lone pair of the N(2) nitrogen atom and the
O(6) oxygen atom donates three electrons to both ruthenium atoms), the organic ligand in the η1-
coordinated five-membered oxaruthenacycle is a 4e donor (coordination to the electron lone pair of
the O(5) oxygen atom and two σ-bonds with the Cα and Cβ atoms), and the organic ligand in
uncoordinated five-membered oxaruthenacycle is a 3е donor. Taking into account four
metalcarbonyl ligands and the overall positive charge, such consideration results in the completed
18e shell for both ruthenium atoms.

16
According to the X-ray diffraction data, the cation of complex 6 contains three ruthenium
atoms (Fig. 4a, Table S3). Each ruthenium atom is chelated by the ligand to form the five-
membered oxaruthenacycle and bound to two CO groups in the cis position. In addition, the
ruthenium atoms are combined through the 3-oxo oxygen atom located in the plane of three
ruthenium atoms (displacement from the plane is 0.15 Å). The complex has a non-crystallographic
three-fold axis. Each ruthenium atom additionally bound to the Cα atom of one of the neighbouring
oxaruthenacycles (three independent Ru-Cα bond lengths are 2.348(5), 2.380(5), and 2.347(4) Å). The
cation of 6 has the same unusual η1-coordination of the five-membered oxaruthenacycle as in the
cation of 5. The structure of these fragments in both complexes coincides. Taking into account that
each fragment has a positive charge and the oxo ligand has a charge 2-, for the cation of 6 one
obtains the total single positive charge.
The anion in complexes 5 and 6 is the well-known octahedral hydride cluster [HRu6(CO)18]‾
containing the interstitial hydride [23] (Fig. 4b). In the crystal structures of 5 and 6, there are no
specific anion-cation interactions and all intermolecular distances correspond to usual van-der-
Waals contacts.
There are several examples of the formation of such anions in the reactions involving Ru3(CO)12
[24, 25]. In particular, the formation of salts with the [НRu6(CO)18]‾ anions was observed in the
reactions between Ru3(CO)12 and functionalized indenes in refluxing heptane, whereas no anion
formation was observed in the reactions performed in refluxing xylene [25].
Earlier, we have shown that the reaction of Ru3(CO)12 with 1-(4-tolyl)-3-phenylaminoprop-2-
en-1-one yields the hydride tetrahedral clusters H4Ru4(CO)12 and H2Ru4(CO)13 in considerable
amounts [12]. Upon formation of the oxaruthenacycle, the ligand loses a hydrogen atom, while the
Ru3(CO)12 acts as the hydrogen acceptor and is reduced to form the hydride clusters [26]. Similarly,
in the reaction with L, the Ru3(CO)12 acts as a hydrogen acceptor giving rise to the hydride cluster
[НRu6(CO)18]‾.

17
A different case was observed in the reactions between Ru3(CO)12 and oxadienes. In these
reactions, an excess amount of the ligand acts as the hydrogen acceptor and undergoes reduction to
the corresponding saturated ketone [22]. The formation of Ru6 and Ru4 hydrides in trace amounts,
presumably, from trace water which inevitable enters the reaction medium was observed [27]. Such
a difference between the behaviors of oxadienes and amino vinyl ketones is explained by the fact
that the olefinic group in the latter is deactivated by the donor effect of amino group, which gives
no way for the molecule to act as a hydrogen acceptor [28].
CH
H
3
+
N(CH )
3 2
O
-
(CO)
O
Ru
(CO)
2
2
HRu (CO)
18
Ru
6
N(CH )
3 2
O
CH
3
O
Ru
(CO)
H
2
H
CH
3
N(CH )
3 2
a)
b)
Figure 4. Schematic presentation of 6 and molecular structures of the trinuclear cationic complex
(a) and the cluster anion [НRu6(CO)18]‾ (b) forming a part of 6 (thermal ellipsoids at the 50%
probability level, hydrogen atoms excluding hydride ligand are omitted).

18
The IR spectra of complexes 5 and 6 are characterized by the presence of one high-intensity
band corresponding to the metalcarbonyl groups of the anion. In addition, these spectra display low-
intensity bands corresponding to the metalcarbonyl groups in the cations of complexes 5 (three
bands) and 6 (two bands) (Table 1).
1
The H NMR spectra of complexes 5 and 6 display a single low-intensity peak at δ 16.46 ppm
which corresponds to the interstitial hydride in the cluster anion [24, 29]. The η1-coordination to the
Cα atom of the five-membered oxaruthenacycle results in an upfield shift of the proton singlet up to
δ 4.5 ppm (the average value for complexes 5 and 6) compared to the proton singlet at δ 5.2 ppm in
the uncoordinated cycle of complex 5 (Table 1).
13
The C NMR spectra of complexes 5 and 6 (Table 1) display very high-intensity peaks at δ
201.3 ppm corresponding to the metalcarbonyl groups of the [НRu6(CO)18]‾ anion. The signals at δ
225.4 ppm (5) and 226.7 ppm (6) can be attributed to carbon atoms in the β-position of the η1-
coordinated five-membered oxaruthenacycles. The signals at δ 72.0 ppm (5) and 71.4 ppm (6) can
be attributed to carbon atoms in the α-position of the η1-coordinated five-membered
oxaruthenacycles (for comparison, the signal of the Cα atom of the uncoordinated five-membered
oxaruthenacycle in complex 3 is located at δ 105.3 ppm).
Complexes 5 and 6 were isolated in the individual state by chromatography of the reaction
precipitate (see Experimental). There have also been attempts to crystallize the precipitate without
chromatographic separation. According to the X-ray diffraction data, one of the crystalline phases
contained the cation of complex 6 and the disordered hydride cluster [НRu4(CO)13]‾ as the anion
(complex 6_Ru4 in Supplementary data, Fig. S1). The 1H NMR spectrum for the reaction precipitate
displayed two singlet signals at δ 16.5 and -15.85 ppm. According to Ref. [30], the second signal
corresponds to the hydride anion [HRu4(CO)13]‾. The integral intensities of singlets are
approximately equal, but the interstitial hydrogen atom of the [НRu6(CO)18]‾ anion appears as a
1
weaker signal in the Н NMR spectrum; therefore, the ratio of cluster anions contained in the
reaction precipitate cannot be determined.

19
Thus, the reaction precipitate contains complexes with two different anions. However, only
complexes with [HRu6(CO)18]‾ are present after chromatography (the individuality of sample
volumes was confirmed by the elemental analysis). One can assume that the [НRu4(CO)13]‾-
containing complexes decompose during chromatographic separation. Possibly, this explains a low
total yield of the complexes obtained from the precipitate.
2.5. Characterization of minor reaction products (complexes 2 and 4)
A
, complex 2 has centrosymmetrical structure and
contains t
is chelated by two molecules of the ligand and
coordinates to one metalcarbonyl group (Fig. 5, Table S4). One of the ligands forms the five-
membered oxaruthenacycle. The second ligand forms the six-membered ruthenacycle. With each
other, the ruthenium atoms are linked through the bridged oxygen atoms of the five-membered rings
to form the Ru2O2 fragment.
CH3
CH3
O
H
H
CO
Ru
H
O
O
N(CH3)2
H
O
Ru
O
(CH3)2N
CO
O
H
CH3
H
CH3
Figure 5. Schematic presentation and molecular structure of complex 2 (thermal ellipsoids at
the 30% probability level).

20
In the complex 2, one of the ligands undergoes significant changes, namely, the deamination
to form the 3-oxo-1-methyl-propenolato fragment occurs. Close transformations have been
observed in the reaction between Ru3(CO)12 and 1-phenyl-2-metyl-3-morpholino-prop-2-en-1-one
[14]. It should be noted that, due to a low quality of its crystals (small twin needles) and unsolved
disorder (see below), the accuracy of structural data for complex 2 is low. Taking into account that
the complex contains the ligand in an unusual deaminated form and the detailed discussion of its
structural features is impossible, its spectral characteristics and behavior in solution should be
considered in more detail.
To confirm complex 2 to be the reaction product rather than the chromatographic transformation
product, the reaction solution was studied by 1H NMR spectroscopy (see Fig. S2). This study shows
the reaction solution to contain a mixture of complexes, including complexes 3 and 2 in a ratio of
~10 : 1. The IR spectrum for the reaction solution also contains signals corresponding to complex 2.
To confirm that complex 2 arises from the reaction between Ru3(CO)12 and L rather than from the
transformation of complexes in the presence of trace water, a separate reaction between Ru3(CO)12
1
and L with addition of water was performed and the reaction solution was studied by H NMR
spectroscopy (see Fig. S3). According to this study, the addition of water does not result in an
increase in the yield of complex 2 compared to the conventional reaction. The reaction solution
contains a mixture of complexes, among which are complexes 3 and 2 in a ratio of ~15 : 1. In
addition, the reaction mixture contains a great amount of ruthenium hydrides, which confirms the
fact that the reaction solution undergoes dehydration due to the excess of Ru3(CO)12 [27].
The 1H NMR spectrum of complex 2, including the spectrum of the reaction mixture, displays a
double set of signals in a ratio of 1 : 2.5, which suggests that complex 2 exists as two isomers. The
isomers can be distinguished only by the 1H NMR spectra, since their IR spectra are identical.
Isomer 2a obtained in high yield was isolated in the individual state by chromatography.
Heating of the individual isomer 2a affords a mixture of isomers with the same ratio as in the

21
reaction mixture (Fig. S4). Heating of a mixture of isomers with L does not result in the
formation of new complexes (see Experimental).
To assign the signals and to establish the structure, heteronuclear 2D NMR techniques, such as
1H-13С HSQC and HMBC, were used (the NMR spectra and their discussion are given in
Supplementary data, Fig. S5 and S6). The spectral data suggest that complex 2a contains two
ligands. The singlet signal in the 1H NMR spectrum at  5.13 ppm corresponds to the proton of an
uncoordinated oxaruthenacycle. In the second ligand, the both protons of the olefinic bond are
present (doublet of doublets at  7.77 and 5.11 ppm) and dimethylamino substituent does not
detected. One can assume the formation of a five-membered oxaruthenacycle with two olefinic
protons:
Me
H
O
H
[Ru]
However, the proton signals for the complexes where the olefinic group is σ-bound to the metal
atom (Ru-Cβ(H)=C(H)) must be in the much more downfield region ( ~11 ppm [31]) as compared
13
to complex 2a. In the C NMR spectrum, the signal for the σ-bound Cβ atom would be also in the
more downfield region due to the contribution of the furan form of metallacycle (vide supra) as
compared to 2a ( 175.9 ppm). Such a behavior is typical of the Cβ atoms in the β-diketonate
complexes [9, 32, 33]. Therefore, one of the ligands in complex 2 is present in the propenedionate
form. The 13C NMR spectrum for complex 2a contains two signals for the carbonyl carbon atoms at
 175.9 and 196.4 ppm, i.e. there is no delocalization in the metallacycle and the ligand is present in
the 3-oxo-1-methyl-propenolato form:
H
Me
H
O
O
[Ru]

22
1
In the H NMR spectrum for a mixture of isomers 2a and 2b, the signals for the methyl
protons and Cβ-H in the six-membered ring differ most strongly. The signal for the methyl group
(C(O)-CH3) in 2b is more upfield shifted (δ 1.83 vs  1.94 ppm in 2a). Conversely, the signal for
3
the Cβ-H proton is more downfield shifted to be at  8.23 ppm (d, 1H, CH=CH, JHH =4.4 Hz)
versus δ 7.86 ppm in 2a. The positions of signals for the Cα-H and five-membered ring protons
change not so noticeably. Based on the structure of complex 2 (Fig. 5), one can assume that the
isomers differ by the arrangement of the six-membered ring associated with relocation of the O(3)
and O(4) atoms. Since the six-membered ring has nonsymmetric structure (due to the methyl
substituent), relocation of the oxygen atoms results in a different isomer (Scheme 5). The
superposition of these isomers is likely implemented in the crystal structure of 2; however, we
failed to solve the positions of disordered atoms (see Supplementary data for details of the crystal
structure refinement).
Scheme 5
H
H
CH
O
H
H
CH
3
H
3
CH
3
O
CO
Ru
H
CH3
CO
Ru
N(CH )
3 2
O
N(CH )
3 2
O
O
O
Ru
Ru
O
O
O
O
(CH ) N
3 2
(CH ) N
3 2
CO
CO
CH
H
3
O
O
H
H
CH
CH
3
3
CH
3
H
H
H
2a
2b
The second minor product isolated from a solution is a polynuclear complex 4. According to
the X-ray diffraction data, the metal core in complex 4 contains a triangle of ruthenium atoms and
the fourth ruthenium atom bound thereto through organic fragments (Fig. 6, Table S5). The metal-
metal bonds in the triangular cluster are inequivalent: there are two shorter bonds, viz., Ru(1)-Ru(3)
2.7383(3) Å and Ru(2)-Ru(3) 2.7267(3) Å, and one longer bond, viz., Ru(1)-Ru(2) 2.9963(3) Å.
The bridged hydride ligand is located on the longer bond. These three ruthenium atoms coordinate

23
to eight terminal metalcarbonyl groups.
H
H
H
CH
3
CH
CO
3
H
N
H
CO
Ru
H
O
O
N(CH )
3 2
H
Ru
(CO)3
Ru
(CO)2
CH
3
(CO)
Ru
3
Figure 6. Schematic presentation and molecular structure of complex 4 (thermal ellipsoids at
the 50% probability level; the methyl hydrogen atoms are omitted).
The Ru(4) atom is bonded with two metalcarbonyl groups in the cis position and chelated by
two organic ligands to form five- and six-membered metallacycles. The structure of the five-
membered ring, including the η1-coordination of the Cα atom (Ru(1)-C(18) is 2.388(2) Å) and,
correspondingly, the sp3-hybridization of this carbon atom, coincides completely with the same
fragment in complexes 5 and 6. Upon formation of the six-membered azaoxaruthenacycle on the
Ru(4) atom, the ligand undergoes transformations close to those observed upon formation of 5,
except for one important difference. The migration of the olefinic bond (formal 1,3-H shift and
metal-induced allyl rearrangement) results in a new exocyclic olefinic group (C(11)-C(14) 1.386(3)
Å), which is involved in the π-coordination to the Ru(3) atom of the ruthenium triangle (the Ru(3)-
C(11) distance is 2.411(2) Å and the Ru(3)-C(14) distance is 2.235(2) Å). The C(14) atom of the
former methyl group forms the σ-bond with the Ru(2) atom of the ruthenium triangle (Ru(2)-C(14)
2.095(2) Å) and remains only one proton. The displaced protons of the methyl group reduce the

24
olefinic bond of the chelate six-membered metallacycle (C(12)-C(13) is 1.518(4) Å), while
complex 5 has endocyclic olefinic bond. As a consequence, the conformation of the cycle changes
from boat in 5 to chair in 4. In the six-membered metallacycle of complex 4, the Ru(4), N(1), C(11),
and C(12) atoms are in one plane (the maximum deviation is less than 0.001 Å) and the O(11) and
C(13) atoms deviate from this plane to different sides by 0.748 and 0.638 Å, respectively. As in
complex 5, the ketonic bond of the starting amino vinyl ketone upon formation of the six-membered
metallacycle becomes single-bond (O(6)-C(11) 1.374(3) Å) and the O(11) oxygen atom is involved
in the coordination to Ru(1) atom of the ruthenium triangle (the distances Ru(4)-O(11) (2.087(2) Å)
and Ru(1)-O(11) (2.088(2) Å) coincide). Thus, the organic ligand being involved in chelation of the
Ru(4) atom to form the six-membered azaoxaruthenacycle combines all four atoms of the metal
cluster.
By analogy with compounds 5 and 6, the five-membered metallacycle in complex 4 has a
positive charge. Since complex 4 is neutral, it should be considered as a zwitter-ionic compound
with a negative charge being localized, presumably, on the triangular cluster. Indeed, taking into
account eight carbonyl groups, H ligand, two σ-bonds (C(8)-Ru(1) and C(14)-Ru(2)), n-donor
O(11)-Ru(1) bond, and the π-coordination of the C(11)-C(14) olefinic bond to the Ru(3) atom, for
the triangular cluster one get 47 valence electrons, which can correspond to three M-M bonds only
provided that this fragment has a negative charge. The Ru(4) atom has completed 18e shell.
2.6. Five-membered oxaruthenacycles
All isolated organometallic products of the thermal reaction of Ru3(CO)12 with L comprise chelate
five-membered oxaruthenacycles forming via Сβ-Н bond activation. The structure of the five-
membered oxaruthenacycles in complexes varies according to the type of coordination with other
metal atoms and these features are discussed below.
The uncoordinated five-membered oxaruthenacycle (in complexes 1, 3 and 5, Table 2) is planar
and the sp2-hybridized nitrogen atom (the sum of bond angles at the N atom is equal to 360º) is

25
involved in conjugation with the oxadiene fragment (the dihedral angle between the mean plane
of metallacycle and the plane of amino group in complexes does not exceed 15º). The Cβ-N bond
length of 1.33 Å (average) coincides with the value of 1.329(2)Å for the C-N bond in 3-
dimethylamino-1-(4-methylphenyl)prop-2-en-1-one (L’) [34]. However, the distribution of the C-C
bond lengths in metallacycle differs from the bond sequence in L’ where the lengths of olefinic and
single C-C bonds are 1.362(2) and 1.434(2) Å, respectively. Upon formation of the matallacycle,
the former olefinic Cα=Cβ bond elongates to 1.43 Å and the single Cα-C(O) bond shortens to 1.38 Å.
The elongation in the C=O bond upon coordination to the ruthenium atom (on the average by 1.29
Å compared to 1.239(2) Å in L’) is also observed. Thus, upon formation of the five-membered
oxaruthenacycle the contribution of the imine-enol form of L becomes more significant, although
several resonance forms of the metallacycle can be suggested (Chart 2). The imine form of the
1
fragment agrees with the Н NMR spectra of complexes 1 and 3 which display two signals
corresponding to the methyl groups at the nitrogen atom (rotation around the C-N bond is hindered)
in contrast to L (Table 1). The downfield shifted signal of the -carbon atom in the 13С NMR
spectrum of complex 3 indicates a partial contribution of the carbene character of the Ru-C bond.
Chart 2
Me
O
Me
O
H
H
Me
O
H
NMe2
NMe2
NMe2
[Ru]
[Ru]
[Ru]
The displacement of the olefinic bond in the five-membered oxaruthenacycles derived from L
distinguishes them from the analogous rings in the oxadiene complexes
Ru(CO)2(O=C(Fc)C(H)=C(Fc))2 [22] and Ru2(CO)4(μ-Cl)2(O=C(R1)C(H)=C(R2))2 [15] where the
С-С bond lengths distribution coincides with that in the starting ligands. In the mononuclear

26
complex cis-Ru(CO)2[O=C(Tol)C(H)=C(NHPh)][O=C(Tol)C(H)=C(H)-N(Ph)] (Chart 1), the C-
C bonds in the five-membered metallacycle are more equalized [12].
Table 2. Bond lengths (Å) in the uncoordinated five-membered oxaruthenacycles
Ru-O=C(R1)-C(H)=C(R2).
Compound
Ru-Cβ
Cα=Cβ
Cα-C(O)
C=O
Ru-O
N-Cβ
Ref.
2.094(4)
2.068(2)
2.113(4)
2.135(2)
2.087(9)
2.117(6)
1.425(6) 1.379(6)
1.427(3) 1.380(4)
1.421(6) 1.377(6)
1.418(4) 1.388(3)
1.281(5) 2.101(3) 1.324(5)
1.292(3) 2.101(2) 1.339(3)
1.298(5) 2.092(3) 1.324(6)
1.287(3) 2.085(2) 1.329(3)
1a
1b
1c
3
1.417(13) 1.385(13) 1.280(11) 2.079(6) 1.325(12)
1.364(8) 1.437(8) 1.260(7) 2.100(4)
5
R1 = R2 = Fc a)
R1 = R2 = Fc b)
R1 = Me, R2 = Ph
[22]
[15]
[22]
[12]
2.031(10) 1.376(12) 1.464(14) 1.259(12) 2.101(6)
2.032(2)
1.364(2) 1.434(3)
1.401(9) 1.388(9)
1.257(2) 2.123(1)
R1 = Tol, R2 = NHPh 2.067(7)
1.311(7) 2.078(5) 1.321(8)
a) in the mononuclear complex Ru(CO)2(O=C(Fc)-C(H)=C(Fc))2
b) in the binuclear complex Ru2(CO)4(μ-Cl)2(O=C(Fc)-C(H)=C(Fc))2
Thus, the structure of the five-membered oxaruthenacycles derived from L significantly differs
from the structure of previously described oxarutenacycles, and as a result, their coordination with
other metal atoms is different.
The π-coordination of the olefinic bond is usual for polynuclear complexes derived from
oxadienes [35], but it is not typical for amino vinyl ketones where the olefinic group is deactivated
due to the donor effect of the amino group. This type of coordination becomes possible in
complexes 1 since the nitrogen atom is out of conjugation with the oxadiene fragment due to
coordination of the electron lone pair of the nitrogen atom to the ruthenium atom (Figure 1, the
N(1)-C(11) bond is elongated to 1.45 Å). In contrast to the uncoordinated five-membered

27
oxaruthenacycle, the π-coordinated cycle is non-planar and has flattened envelope conformation:
the bend angle along the O(9)…C(11) line is on the average 19º. The olefinic bond being involved
in the π-coordination significantly elongates to 1.45 Å (average value, Table S1) and the formally
single C(9)-C(10) bond length of 1.42 Å coincides with that in L’ (1.434(2) Å). The geometry of
the π-coordinated metallacycles in complexes 1 is almost the same as the geometry of the analogous
fragments in the products of reactions between Ru3(CO)12 and oxadienes [35].
The above mentioned redistribution of the C-C bond lengths in the five-membered
oxaruthenacycle, resulting from a conjugation with the dimethylamino group, leads to η1-
coordination of the metallacycle through the new Ru-Cα σ-bond formation. This type of
coordination is observed in several products of the thermal reaction of Ru3(CO)12 with L including
the cationic complexes 5 and 6 isolated from a precipitate and occurs for the first time in the
transition metal complexes with amino vinyl ketones and oxadienes [36].
2.6. Concurrent transformation of amino vinyl ketone L
Besides organometallic complexes, the thermal reaction of Ru3(CO)12 with L affords an organic
molecule, 1,3,5-triacetylbenzene. The presence of 1,3,5-triacetylbenzene among the reaction
products is confirmed by 1H NMR spectroscopy of the reaction mixture (δ 8.62 ppm) (see Fig. S2).
The formation of 1,3,5-triacylbenzenes from amino vinyl ketones as a result of deamination
accompanying acid catalyzed condensation is well documented [37, 38]. It appears that 1,3,5-
triacetylbenzene can results from a concurrent transformation of amino vinyl ketone L in conditions
of the thermal reaction with Ru3(CO)12.
The yields of complex 2 and 1,3,5-triacetylbenzen arising from the deaminated form of the
organic ligand are low and comparable. Nevertheless, one can expect the presence of the amine
resulting from deamination either in the reaction products or in a free state. However, no
dimethylamine complexes were observed among the reaction products of Ru3(CO)12 and L. We also
failed to detect gaseous dimethylamine evolving from the reaction medium by passing the gas

28
fraction through the Nessler reagent.
2.7. Photochemical reactions of Ru3(CO)12 with L
The photochemical activation of the organometallic reagents differs from thermal conditions by
much higher selectivity. The photochemical reactions of Ru3(CO)12 at λ ≥ 210 nm and λ ≥ 350 nm
are known to be effective in the cleavage of Ru–CO and Ru–Ru bonds, respectively [39, 40, 41, 42,
43]. Irradiation at different wavelength allows one to obtain additional data on processes occurring
in the reaction between Ru3(CO)12 and an organic molecule. The emphasis was on the question
which reaction center of the amino vinyl ketone is guiding in the chemical transformation.
The photochemical reactions of Ru3(CO)12 with L in two wavelength ranges with λ ≥ 210 nm
and λ ≥ 350 nm were performed. Upon excitation at λ ≥ 210 nm, the final solution contained L, and
complex 7 (45 mg, 25% yield) was isolated from the precipitate. Upon excitation at λ ≥ 350 nm, no
products of the reaction between Ru3(CO)12 and L were produced and only the photodecomposition
products of Ru3(CO)12 were observed.
two molecules of L in complex 7
the Ru3 cluster moiety (Fig. 7, Table S6). In the crystal, complex 7 occupies a
special position on two-fold axis passing through the Ru(2) atom and the center of the Ru(1)-
Ru(1A) bond.
. The oxygen atom of the
second chelated ruthenium atom. The
coordinates to the
Å
(Table 2). The O(5)-
C(5) ketonic bond elongates to be 1.335(5) Å, which is explained by additional coordination to the
second ruthenium atom (Ru(1)-O(5A) is 2.167(2) Å). This is accompanied by elongation in the
Ru(1)-O(5) endocyclic bond (2.125(3) Å) compared to the analogous distances in Table 2.

29
CH
CH
CH
3
CH
3
3
3
N
N
(CO)
Ru
(CO)
Ru
2
2
O
O
CH
CH
3
3
Ru
(CO)
4
Figure 7. Schematic presentation and molecular structure of complex 7 (thermal ellipsoids at the
50% probability level; hydrogen atoms are omitted).
Considering each organic ligand as a 5e donor and taking into account eight metalcarbonyl
groups, one obtain 50 cluster electrons, which, for the trinuclear cluster implies only two metal-
metal bonds. This is confirmed by the increased Ru(1)-Ru(1A) distance 3.0866(6) Å compared to
two other bonds, Ru(1)-Ru(2) and Ru(2)-Ru(1A) with a length of 2.8437(5) Å each. In addition, for
the Ru(1) and Ru(1A) atoms, without considering the bond between them we obtain an octahedral
six-coordinated environment.
The 1H NMR spectrum of complex 7 displays one set of signals for the coordinated ligand. The
positions of signals differ slightly from those for complex 3, besides the signal for the methyl
substituent at the keto group which is upfield shifted due to additional coordination to the oxygen
atom (Table 1). The 13С NMR spectrum of 7 displays three downfield signals. The signals at δ
214.0 ppm can be attributed to the -carbon atoms of five-membered cycles. The signal at δ 212.5
ppm can be attributed to the metalcarbonyl group in the trans position with regard to the oxygen
atom of the five-membered ring. The slightly upfield signal at δ 202.5 ppm corresponds to the
carbonyl carbon atom. The signals for the -carbon atoms of the five-membered cycles in 7 (111.0