Nitrosyl derivatives of the unsaturated dihydrides [Mn2(μ-H) 2(CO)6(μ-L2)] (L2 = Ph 2PCH2PPh2, (EtO)2POP(OEt) 2)

Article abstract of DOI:10.1016/j.jorganchem.2010.09.079

The title dimanganese complexes react with NO (5% in N₂) at room temperature to give as major products the corresponding hexanitrosyl derivatives [Mn₂(NO)₆(μ-L₂)] in moderate yields, and they react rapidly with NO₂ to give the corresponding hydride derivatives [Mn₂(μ-H)(μ-NO₂)(CO) ₆(μ-L₂)], these having a nitrite ligand bridging the dimetal centre through the N and O atoms. The dppm-bridged dihydride also reacts selectively at 273 K with (PPN)NO₂ to give first the nitro derivative (PPN)[Mn₂(μ-H)(H)(NO₂)(CO) ₆(μ-dppm)], which then transforms into the nitrosyl complex (PPN)[Mn₂(μ-CO)(CO)₅(NO)(μ-dppm)] at room temperature or above (dppm = Ph₂PCH₂PPh₂; PPN⁺ = [N(PPh₃)₂]⁺). The latter anion reacts with (NH₄)PF₆ to give the hydride-bridged nitrosyl complex [Mn₂(μ-H)(μ-NO)(CO)₆(μ-dppm)] and with [AuCl(PPh₃)] to give the trinuclear cluster [AuMn ₂(μ-NO)(CO)₆(μ-dppm)(PPh₃)] (Mn-Au = ca. 2.68 ; Mn-Mn = 2.879(2) ). Both products are derived from the addition of the added electrophile at the intermetallic bond and rearrangement of the nitrosyl ligand into a bridging position. In contrast, methylation of the anion with CF₃SO₃Me takes place at the nitrosyl ligand to yield the unstable methoxylimide derivative [Mn₂(μ-NOMe)(CO) ₆(μ-dppm)]. Analogous reactions at the nitrosyl ligand take place upon the addition of HBF₄·OEt₂ to the nitrosyl-bridged hydrides [Mn₂(μ-H)(μ-NO)(CO) _n(μ-dppm)_m] (n = 6, m = 1; n = 4, m = 2) to give the corresponding hydroxylimide derivatives [Mn₂(μ-H)(μ-NOH)(CO) _n(μ-dppm)_m]BF₄, which were also thermally unstable and could not be isolated nor fully characterized.

Full text of DOI:10.1016/j.jorganchem.2010.09.079

Journal of Organometallic Chemistry 696 (2011) 559e567
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Nitrosyl derivatives of the unsaturated dihydrides [Mn2(
m
-H)2(CO)6(
m
-L2)]
(L2 ¼ Ph2PCH2PPh2, (EtO)2POP(OEt)2)
,
b
b
M. Esther García a, Sonia Melón a, Miguel A. Ruiz a , Luciano Marchiò , Antonio Tiripicchio
*
a Departamento de Química Orgánica e Inorgánica/IUQOEM, Universidad de Oviedo, Julian Clavería, E-33071 Oviedo, Spain
b Dipartimento di Chimica Generale ed Inorganica, Chimica Analitica, Chimica Fisica, Università di Parma, Viale G. P. Usberti 17/A, I-43100 Parma, Italy
a r t i c l e i n f o
a b s t r a c t
Article history:
The title dimanganese complexes react with NO (5% in N2) at room temperature to give as major products
Received 2 August 2010
Received in revised form
9 September 2010
Accepted 9 September 2010
Available online 21 October 2010
the corresponding hexanitrosyl derivatives [Mn2(NO)6(
with NO2 to give the corresponding hydride derivatives [Mn2(
a nitrite ligand bridging the dimetal centre through the N and O atoms. The dppm-bridged dihydride also
reacts selectively at 273 K with (PPN)NO2 to give first the nitro derivative (PPN)[Mn2( -H)(H)(NO2)
-CO)(CO)5(NO)( -dppm)]
m
-L2)] in moderate yields, and they react rapidly
m
-H)( -NO2)(CO)6( -L2)], these having
m
m
m
(CO)6(
m
-dppm)], which then transforms into the nitrosyl complex (PPN)[Mn2(
m
m
at room temperature or above (dppm ¼ Ph2PCH2PPh2; PPNþ ¼ [N(PPh3)2]þ). The latter anion reacts with
Keywords:
Manganese
(NH4)PF6 to give the hydride-bridged nitrosyl complex [Mn2(m-H)(m-NO)(CO)6(m-dppm)] and with [AuCl
(PPh3)] to give the trinuclear cluster [AuMn2(
m
-NO)(CO)6(
m
-dppm)(PPh3)] (MneAu ¼ ca. 2.68 Å; Mn
Metalemetal interactions
Hydride ligands
Nitrosyl ligands
Carbonyl ligands
Diphosphine ligands
eMn ¼ 2.879(2) Å). Both products are derived from the addition of the added electrophile at the
intermetallic bond and rearrangement of the nitrosyl ligand into a bridging position. In contrast,
methylation of the anion with CF3SO3Me takes place at the nitrosyl ligand to yield the unstable
methoxylimide derivative [Mn2(
place upon the addition of HBF4$OEt2 to the nitrosyl-bridged hydrides [Mn2(
dppm)m] (n ¼ 6, m ¼ 1; n ¼ 4, m ¼ 2) to give the corresponding hydroxylimide derivatives [Mn2(
NOH)(CO)n(
characterized.
m-NOMe)(CO)6(m-dppm)]. Analogous reactions at the nitrosyl ligand take
m
-H)(
m
-NO)(CO)n(
-H)(
m
m
-
-
m
m
-dppm)m]BF4, which were also thermally unstable and could not be isolated nor fully
Ó 2010 Elsevier B.V. All rights reserved.
1. Introduction
Recently we have shown that full cleavage of the NeO bond in
a
coordinated nitrosyl ligand can take place at quite low
Nitrogen monoxide is a remarkable molecule able to strongly
bind to transition metal atoms both in high and low oxidation
states, thus giving rise to a wide variety of coordination and
organometallic complexes exhibiting a rich chemistry [1,2]. Further
interest in this molecule stems from its biological activity [1,3], and
also because nitrogen monoxide is one of the important air
pollutants requiring catalytic abatement [1,4,5]. Therefore the
activation and cleavage of the strong NeO bond of nitrogen
monoxide when bound to a metal atom is a process not only of
academic interest, but of particular relevance too for the under-
standing of the biological role of this molecule and also to devel-
oping better catalysts for its abatement in diverse gas effluents. In
this context we have carried out a prospective study on this
important reaction using different binuclear carbonyl complexes as
potential activators of the NeO bond of the nitrosyl ligand.
temperatures on heterometallic complexes combining group 6 and
group 7 metal atoms. Thus, the anionic complexes [MCp(CO)2L]ꢀ
(M ¼ Mo, W; Cp ¼
h
5-C5H5; L ¼ CO, P(OMe)3, PPh3) reacted with
the nitrosyl cations [M0Cp0(CO)2(NO)]þ (M0 ¼ Mn, Re; Cp0 ¼ h5
-
C5H4Me) to give the nitride-bridged derivatives [MM0CpCp0(
m-N)
(CO)3L] [6] and, in a different type of reaction, the dimolybdenum
anion [Mo2Cp2( -PPh2)(
-CO)2]ꢀ reacted with the mentioned
nitrosyl cations to give the corresponding oxonitride derivatives
[Mo2MCp2Cp0(
-N)( -O)( -PPh2)(CO)3] [7]. It was thus of interest
m
m
m
m
m
to explore in this context the potential of homometallic complexes
having either group 6 or group 7 metal atoms. In this paper we
report the synthesis and some reactions of several new
dimanganese nitrosyl complexes derived from the unsaturated
dihydrides [Mn2(
m
-H)2(CO)6(
m
-L2)] (L2 ¼ Ph2PCH2PPh2 or dppm
(1a), (EtO)2POP(OEt)2 or tedip (1b)). At this point we should note
that only a handful of dimanganese nitrosyl complexes have
been reported so far, perhaps due to synthetic difficulties, these
being limited to the neutral dinitrosyls [Mn2(CO)7(NO)2] [8],
* Corresponding author. Fax: þ34 985103446.
E-mail address: mara@uniovi.es (M.A. Ruiz).
0022-328X/$ e see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2010.09.079

560
M.E. García et al. / Journal of Organometallic Chemistry 696 (2011) 559e567
[Mn2L*2(CO)2(NO)2] [L* ¼ Cp [9a], Cp0 [9b]], [Mn2Cp2(
m
-SR)2(NO)2]
substitution of six CO molecules for an equal number of nitrosyl
ligands. In addition, the variable yields in which the hydride 3a was
formed suggested that trace amounts of oxygen might be behind its
formation, a matter to be dealt with in the next section. As
expected, compound 2a can be alternatively prepared through the
thermal reaction of [Mn(CO)3(NO)] with substoichiometric
amounts of the dppm ligand (see the experimental section).
The tedip-bridged complex 1b reacts somewhat faster with NO,
and the reaction can be completed in ca. 3 h at room temperature to
[10], [Mn2Cp2(CS)2(NO)2] [11] and [Mn2Cp2(m-S2)2(NO)2] [12], the
trinitrosyls [Mn2L*2X(NO)3] (X ¼ halogen, NO2, alkyl, aryl) [13],
the cation [Mn2L* -CO)(NO)2]þ [14] and the anion
(m-NH2)(m
2
[Mn2(CO)6(NO)2]2ꢀ [15]. Moreover, except for the dicarbonyl
complexes [Mn2L*2(CO)2(NO)2], the chemical behaviour of this
reduced group of compounds has not been examined.
Because of the unsaturated nature of their central Mn2(m-H)2
core, the dihydride complexes 1a,b are highly reactive towards
a great variety of molecules under mild conditions [16e18], and
thus were ideal candidates as starting substrates for the synthesis
of novel dimanganese nitrosyl complexes via their reactions with
different sources of NO under mild conditions. As it will be seen
below, the direct reaction of compounds 1a,b with NO caused full
substitution of CO ligands, but a more controlled nitrosylation
could be achieved through their reaction with the nitrite ion, this
giving with good yield the anionic nitrosyl complex [Mn2(CO)6(NO)
give [Mn2(NO)6(m-tedip)] (2b) in moderate yield (ca. 40%). In this
case, no nitriteehydride side product analogous to compound 3a
was detected, although such a species can be prepared selectively in
an independent way (Scheme 1). On the other hand, an IR moni-
toring of this reaction allowed the detection of small amounts of
intermediate species having possibly partial degrees of CO substi-
tution (ie. of the type [Mn2(NO)x(CO)y(m-tedip)]) but unfortunately
we could not find conditions to obtain them in significant amounts.
The structural characterization of compounds 2 is straightfor-
ward after considering that each of them exhibit a single resonance
in the corresponding 31P NMR spectrum and two NeO stretching
bands in the IR spectrum with frequencies and relative intensities
comparable to those reported previously for the isoelectronic
(m
-dppm)]ꢀ, which in turn proved to have a multisite reactivity,
then being an useful synthetic precursor to several derivatives
having nitrosyl as well as hydroxyl- and methoxylimide bridges.
2. Results and discussion
complexes [Mn(NO)3(PPh3)] and [Mn2(NO)6(m-Ph2PCH2CH2PPh2)]
[19], consistent with tetrahedral environment around the
a
2.1. Reactions of the hydride complexes 1a,b with NO
manganese centres (Table 1). As expected from the better donor
properties of the dppm ligand (compared to those of the diphos-
phite tedip), the NeO stretching frequencies of 1a are lower (by
some 15 cmꢀ1) than those of 1b.
The dppm-bridged complex 1a reacts with NO (5% in N2) slowly
at room temperature, but does it more rapidly at ca. 318 K to give as
major product the hexanitrosyl derivative [Mn2(NO)6(
(2a) in moderate yield (ca. 40%), along with variable amounts
(0e25%) of the nitriteehydride complex [Mn2( -H)( -NO2)(CO)6(
m-dppm)]
2.2. Reactions of the hydride complexes 1a,b with NO2
m
m
m-
dppm)] (3a), the reaction being completed in ca. 90 min at this
temperature (Scheme 1). In spite of this, no intermediates could be
spectroscopically detected in significant amounts in this obviously
multistep reaction implying the elimination of hydrogen and the
As noted above, it was suspected that the formation of 3a might
require the concurrence of oxygen, but a separated experiment
revealed that 1a would not react with oxygen alone to give 3a. By
considering, however, that oxygen reacts readily with NO at room
temperature to give NO2, it was therefore likely that the latter species
mightbe the actual reagentleading tothenitrite side product. Indeed
an independent experiment revealed that compound 3a was rapidly
formed as the major product when a mixture of NO and NO2
(generated in situ from nitric oxide an oxygen, see the experimental
section) was allowed to react with a toluene solution of 1a at room
temperature. Moreover, the hydride 1b reacted analogously to give
the tedip-bridged complex [Mn2(m-H)(m-NO2)(CO)6(m-tedip)] (3b) as
major product (Scheme 1).
The spectroscopic data for compounds 3a,b (Table 1) are strongly
reminiscent of those of the hydrideealkenyl complexes [Mn2( -H)
h1 2-CRCH2)(CO)6(
-dppm)] previously reported by us [17b]
m
(m-
:h
m
and they are clearly indicative of the presence of a bridging
hydride and an asymmetrically-bound NO2 ligand in these mole-
cules. The coordination of the hydride is revealed by the presence of
strongly shielded 1H NMR resonances at ca. ꢀ17 ppm, exhibiting
essentially identical coupling to both phosphorus atom. The latter
atoms are inequivalent, as indicated by the presence of two doublets
in the low temperature 31P NMR spectra of both complexes, but
there is a slow dynamic process rendering the phosphorus atoms
equivalent, since the room temperature spectra display two broad
(3a) or just one averaged and broad (3b) resonances. All of this
suggests that coordination of the NO2 ligand to the dimetal centre
must occur through both the N and one of the O atoms, and these
would exchange their positions easily. Interestingly, the vinyl
complex mentioned above also exhibited dynamic behaviour in
solution [17b]. The asymmetric coordination of the NO2 ligand in
compounds 3 is further supported by the observation in both cases
of two quite separated NeO stretching bands at ca. 1430 and
1160 cmꢀ1, as usually found for N,O-bound NO2 ligands [20].
Scheme 1. Reactions of the dihydride compounds 1a,ba. a A ¼ Ph, OEt; X ¼ CH2, O; .the
PPNþ cation of compounds 4 and 5 is omitted for clarity.

M.E. García et al. / Journal of Organometallic Chemistry 696 (2011) 559e567
561
Table 1
Selected IRa and 31P{1H} NMRb data for new compounds.
Compound
n(CO)
n(NO)
d(P)
JPP
[Mn2(NO)6(
[Mn2(NO)6(
m
m
-dppm)] (2a)
-tedip)] (2b)
1783 (w), 1685 (vs)
1795 (w), 1703 (vs)c
1421, 1161e
1437, 1164e
1326, 1302e
1609 (m)h
37.2
161.0d
[Mn2(
[Mn2(
m
m
-H)(
m
-NO2)(CO)6(
-NO2)(CO)6(
m
m
-dppm)] (3a)
-tedip)] (3b)
2046 (vs), 2019 (s), 1969 (m), 1947 (s), 1924 (m)
2059 (vs), 2029 (s), 1985 (m), 1958 (s), 1939 (m)
2018 (vs), 1977 (m), 1937(m), 1912 (s), 1901 (m, sh), 1877(m)h
1982 (s), 1898 (vs), 1872 (m, sh), 1817 (m)h
2038 (s), 1999 (vs), 1969 (m), 1925 (s), 1917 (m, sh)
2007 (s), 1965 (vs), 1937 (w), 1918 (m, sh), 1902 (s)
2035 (s), 2004 (vs), 1965 (s), 1947 (m), 1922 (s)
1956 (w), 1925 (vs), 1862 (s)
49.6, 43.8f
160.0, 159.0g
76.7, 64.8i
69.4, 67.3j
52.2
66
57
72
-H)(m
(PPN)[Mn2(
(PPN)[Mn2(
m
m
-H)(H)(NO2)(CO)6(
-CO)(CO)5(NO)( -dppm)] (5)
-dppm)] (6)
-dppm)(PPh3)] (7)
-dppm)] (8)
m-dppm)] (4a)
m
[Mn2(
[AuMn2(
m
-H)(
-NO)(CO)6(
-NOMe)(CO)6(m
m
-NO)(CO)6(
m
1471e
m
m
1446e
64.5 (t), 53.1 (d)
37.7, 33.6
61.7
13
35
[Mn2(
[Mn2(
[Mn2(
[Mn2(
[Mn2(
m
m
m
m
m
-H)(
-H)(
-H)(
-H)(
m
m
m
m
-NO)(CO)4(
-NO)(CO)4(
-NOH)(CO)6(
-NOH)(CO)4(
m
m
-dppm)2] (9a)
-dmpm)( -dppm)] (9c)
-dppm)]BF4 (10)
-dppm)2]BF4 (11)
1408e
m
1949(w), 1916 (vs), 1857 (s)
61.7, 48.6k
55.6, 55.2l
63.0m
m
m
129
in cmꢀ1
Recorded in CD2Cl2 solutions at 290 K and 121.50 MHz, unless otherwise stated,
.
a
Recorded in dichloromethane solution, unless otherwise stated,
n
b
d
in ppm relative to external 85% aqueous H3PO4, JPP in Hertz; all low temperature spectra
recorded at 161.99 MHz.
c
Petroleum ether solution.
C6D6 solution.
Recorded in a KBr disk.
228 K.
d
e
f
g
200 K.
h
Tetrahydrofuran solution.
Recorded at 213 K in tetrahydrofuraneC6D6 solution.
i
j
Broad resonances recorded at166 K.
k
AA0XX0multiplets, JPP þ JPP ¼ 91.
0
l
185 K.
m
Broad resonance recorded at 248 K.
2.3. Reactions of the hydride complexes 1a,b with (PPN)NO2
Compound 1a reacts readily with (PPN)NO2 at 273 K (PPNþ ¼ [N
further broaden and eventually disappear into the baseline of the
spectrum at room temperature, this suggesting the operation of
some exchange process between the terminal and bridging hydrides
in solution, as previously observed for the related trihydride anions
(PPh3)2]þ) to give the anionic nitro complex (PPN)[Mn2(
m-H)(H)
(NO2)(CO)6(m-dppm)] (4a) as the single product. This compound,
[Mn2(
m
-H)(H)2(
m
-L2)]ꢀ (L2 ¼ tedip [16b], dppm [23]) and also for the
however, could not be isolated as a pure solid, because it progres-
sively transforms (even at low temperature) into the nitrosyl
derivative (PPN)[Mn2(m-CO)(CO)5(NO)(m-dppm)] (5), the reaction
being completed in a few hours at room temperature or just in about
1 h at 318 K (Scheme 1). The tedip-bridged compound 1b reacts
initially with (PPN)NO2 at 273 K in a similar way to give a related
compound 4b, as deduced from the IR spectrum of the reaction
mixture after a few minutes, but this species rapidly decomposes at
that temperature to give a complex mixture of compounds, and thus
no further attempts were made to characterize it.
neutral dihydride [Re2(m-H)(H)(CO)6{P(OMe)3}] [24].
The IR spectrum of 5 displays four strong to medium bands in the
2000e1800 cmꢀ1 region that can be assigned to CeO bond stretches
of terminal carbonyls, and a fifth band whose low frequency
(1609 cmꢀ1) might be indicative of the presence of either a terminal
nitrosyl (cf. 1646 and 1609 cmꢀ1 for the mononuclear anion [Mn
(CO)2(NO)2]ꢀ [25])ora bridgingcarbonyl(cf.1660e1550 cmꢀ1 forthe
binuclear anions [Mo2Cp2(m-PR2)(m
-CO)2]ꢀ [26]), or to both of them.
The pattern of the terminal stretches, however, is substantially
different from that shown by the mentioned halide-bridged anions
Compound 4a displays six CeO stretching bands of strong to
medium intensity in the IR spectrum (Table 1), which is indicative of
a lowsymmetry for the anion (Cs or below), while the intensity of the
two more energetic bands is suggestive of the retention of a local
facial arrangement in both Mn(CO)3 oscillators [21], as also found for
[M2(m-X)(CO)6(m
-L2)]ꢀ; in particular, the anion in 5 exhibits just one
(instead of two) strong band above 1900 cmꢀ1, this indicating the
presence of just a single facial Mn(CO)3 oscillator in the anion. We
thus can safely exclude for 5 a structure with a bridging nitrosyl and
six terminalcarbonyls. Instead, theIRspectrumof5 isconsistentwith
the presence of a bridging carbonyl and facial Mn(CO)3 and Mn(NO)
(CO)2 oscillators (Scheme 1). In apparent disagreement with this,
however, the room temperature NMR spectra of 5 display single
resonancesforbothphosphorusatomsandforallsixcarbonylligands
of the anion, obviously revealing the presence of dynamic effects.
Indeed, on lowering the temperature, the 31P resonance broadens
and eventually splits below ca. 173 K into two separated resonances,
as expected. In the same way, the single 13C carbonyl resonance
observed at room temperature (at 235 ppm) eventually splits into
three ones of roughly the same intensity at 241.9, 234.7 and
230.6 ppm at 213 K. Although the latter are still averaged resonances,
the expected limiting spectrum with six different carbonyl reso-
nances was not reached on further cooling of the solution. To explain
the partial averaging of carbonyl resonances observed at 213 K we
propose the dynamic process depicted in the Scheme 2, inspired in
the halide-bridged anions [M2(
m
-X)(CO)6(
m
-L2)]ꢀ (M ¼ Mn, Re;
L2 ¼ dppm, tedip; X ¼ Br, Cl) [22]. The average CeO stretching
frequency for 4a, however, is substantially higher than those of the
mentioned halide complexes and only some 20 cmꢀ1 lower than
the average value for the neutral hydride 1a, thus indicating that the
negative charge in the anion of 4a is largelylocated at the NO2 ligand.
The latter is proposed to be coordinated exclusively through the N
atom (nitro coordination), with this being supported by the obser-
vation of two NeO stretches of similar frequency at ca. 1300 cmꢀ1
,
corresponding to the respective asymmetric and symmetric
stretches [20].
The presence of two inequivalent hydride ligands in 4a is clearly
indicated by the appearance, in the 1H NMR spectrum recorded at
223 K, of twoverydifferentlyshielded resonances at ca. ꢀ7 (terminal
H) and ꢀ19 ppm (bridging H). In agreement with this, the 31P NMR
spectrum displays two doublet resonances at that temperature.
However, upon warming of the solution, the hydride resonances
that observed for the carbonyl-bridged complexes [Mn2(
m
-
h1
-dppm)]
:h
2-CO)
(CO)4( -dppm)2] [27] and [Mn2( m
m
m-
h1 2-CO)(CO)5(PPh3)(
:h

562
M.E. García et al. / Journal of Organometallic Chemistry 696 (2011) 559e567
Scheme 2. Fluxional process proposed for the anion of compound 5 in solutiona.
a
PeCeP ¼ dppm; O atoms of nitrosyl and carbonyl ligands omitted for clarity.
[28], and involving a limited rearrangement of the ligands placed in
the plane perpendicular to the average place defined by the
diphosphine and the metal atoms. As a result, the carbonyl ligands
are averaged pairwise (1/2, 3/6 and 4/5 in Scheme 2), as they are the
phosphorus atoms of the molecule. The full averaging of all CO
resonances observed at room temperature obviously requires the
concurrenceofadditional rearrangements, possiblyalocalrotationof
the pyramidal moieties Mn(CO)3 and Mn(CO)2(NO) through their
false local C3 axis, this being a common dynamic process found in
transition metal carbonyl clusters [29].
Scheme 3. Reactions of compound 5a. a The PPNþ cation of compound 5 is omitted for
clarity.
shorter than the one measured in the electron-precise bromide-
bridged cluster (3.090(3) Å), and it actually approaches the MneMn
separation measured in the electron-deficient (with a 32-electron
The formation of 5 from 4a formally implies the conversion of
NO2 into NO via the hydride ligands present in the anion of 4a,
presumably with formation of water. This is an unusual evolution of
a nitroecarbonyl complex, more likely to evolve to the corre-
sponding nitrosyl derivative via elimination of CO2 [2c,d, 30].
However, from a mechanistic point of view, this might not be
considered as an unusual evolution in the chemistry of the hydrides
1, because these compounds have been shown to be able to transfer
their hydride ligands to the incoming reagent in a number of
reactions. In particular, the hydride 1a has been shown to react with
several 1-alkynes HC^CR to give a molecule of the corresponding
dimanganese centre) cluster [Au2Mn2(CO)6(m-dppm)(PPh3)2]
(2.865(4) Å [23]). We attribute this shortening effect not to an
electronic deficiency of the dimanganese centre in 7, but to the
small covalent radius of the N atom (compared to Br). For instance,
a comparable shortening effect has been measured previously for
the azavinylidene complex [Mn2(m-H)(m-N]CHPh)(CO)6(m-dppm)]
(2.818(4) Å, [18f]), which also is an electron-precise complex.
Spectroscopic data in solution for 7 (Table 1) are fully consistent
with the structure found in the crystal. In particular, its IR spectrum
exhibits a five CeO stretching band pattern common to many
alkenylidene complex [Mn2(m- :h m-dppm)] and
h1 2-CCHR)(CO)6(
a molecule of the free alkene CH2]CHR, this implying the full
transfer of two hydride atoms to a molecule of alkyne [17b].
binuclear manganese complexes of the type [Mn2(
m-X)(m-Y)
(CO)6(
m
-L2)] (X, Y ¼ 1 or 3-electron donor ligand, [18]) having two
facial Mn(CO)3 oscillators. We only note the large separation
2.4. Reactions of 5 with Hþ and Au(PPh3)þ cations
Compound 5 reacts readily with weak protic acids such as the
ammonium ion to give the corresponding hydride derivative
[Mn2(m-H)(m-NO)(CO)6(m-dppm)] (6), this being derived from the
expected addition of the proton to the intermetallic bond and a less
anticipated rearrangement of the nitrosyl ligand, from a terminal
into a bridging coordination position. A similar reaction takes place
between
[AuMn2(
5 and [AuCl(PPh3)] to give the trinuclear cluster
m
-NO)(CO)6(m-dppm)(PPh3)] (7), this resulting from the
addition at the intermetallic bond of a Au(PPh3)þ cation, isolobal
with a proton [30], and a comparable rearrangement of the nitrosyl
ligand (Scheme 3).
The structure of 7 in the crystal is shown in the Fig. 1, while the
Table 2 collects some relevant bond lengths and angles. This
molecule can be described as two facial Mn(CO)3 fragments bridged
by nitrosyl and Au(PPh3) fragments, with the diphosphine ligand
acting as a third bridge and positioned perpendicularly to the
average Mn2AuN plane. This bioctahedral structure is thus very
similar to that previously determined by us for the isoelectronic
cluster [AuMn2(m-Br)(CO)6(m-tedip)(PPh3)] [22]. The MneAu
lengths is these two compounds are comparable to each other (ca.
Fig. 1. ORTEP diagram (25% probability) of compound 7, with H atoms and phenyl
2.68 Å) but the MneMn length in 7 (2.879(2) Å) is some 0.2 Å
groups (except their ipso carbons) omitted for clarity.

M.E. García et al. / Journal of Organometallic Chemistry 696 (2011) 559e567
563
Table 2
possibility of the methyl group being attached at the nitrogen atom
of the former nitrosyl ligand cannot be ruled out completely.
The formation of 8 implies the binding of the Me group at the
oxygen atom of the nitrosyl anion, as opposed to the formation of
compounds 6 and 7, these implying the binding of the electrophile
at the intermetallic bond in the anion of 5. This is an unusual result
for a terminal nitrosyl ligand, that at most would have been
expected to react with a small and hard electrophile such as Hþ or
Meþ at its nitrogen atom [33]. In contrast, trinuclear complexes
having m2- or m3-bridging nitrosyl ligands actually have been shown
to react with Hþ or Meþ at their O(nitrosyl) atoms to give the
corresponding hydroxylimide (m3-NOH) [34e36] and methoxyl-
imide (m3-NOMe) derivatives [34,36]. In this context we should
note that the dimanganese complexes [Mn2L*2(CO)2(NO)2], dis-
playing in solution different isomers with both bridging and
terminal nitrosyls, were reported to react with HBF4$OEt2 to give no
NOH derivatives, but a mixture of compounds, one of the being the
Selected bond lengths (Å) and angles (deg) for compound 7.
Mn(1)eMn(2)
Mn(1)eAu
2.879(2)
2.694(2)
2.329(3)
1.876(8)
1.76(1)
1.78(1)
1.84(1)
1.81(1)
AueP(3)
2.321(2)
2.668(2)
2.336(3)
1.940(8)
1.77(1)
1.83(1)
1.81(1)
1.80(1)
Mn(2)eAu
Mn(2)eP(2)
Mn(2)eN(1)
Mn(2)ꢀC(6)
Mn(2)eC(4)
Mn(2)eC(5)
P(2)eC(8)
Mn(1)eP(1)
Mn(1)eN(1)
Mn(1)eC(1)
Mn(1)eC(2)
Mn(1)eC(3)
P(1)eC(8)
P(1)eMn(1)eMn(2)
P(1)eMn(1)eN(1)
P(1)eMn(1)eAu
N(1)eMn(1)eC(2)
N(1)eMn(1)eAu
91.4(1)
92.7(2)
92.4(1)
169.4(5)
98.9(3)
P(2)eMn(2)eMn(1)
P(2)eMn(2)eN(1)
P(2)eMn(2)eAu
N(1)eMn(2)eC(5)
N(1)eMn(2)eAu
91.6(1)
94.6(2)
90.1(1)
168.7(5)
98.1(2)
between the two more energetic bands (42 cmꢀ1), to be compared
with the values of ca. 30 cmꢀ1 usually found for this short of
metalemetal bonded compounds, an observation that must be
taken as indicative of a strong MneMn interaction for 7 also in
solution, in agreement with the short intermetallic length found in
the crystal. On the other hand, the NMR data (Table 1 and Experi-
mental Section) reveal the chemical equivalence in solution of the P
atoms of the diphosphine and the inequivalence of the methylenic
protons, and deserve no further comments. As for the nitrosyl
already mentioned amide complex [Mn2L* -CO)(NO)2]þ
(m-NH2)(m
2
[14]. Since compound 8 therefore represents a rare example of
a binuclear species having a m2-NOX ligand, we decided to pursue
these transformations of the nitrosyl ligands by examining the
protonation reactions of the neutral hydride 6 as well as some
electron-richer diphosphine-substituted derivatives (see below).
Related reactions with the methylating agents [Me3O]BF4 or
CF3SO3Me led to mixtures of unstable products that could not be
characterized.
ligand, it gives rise to a medium intensity band at 1450 cmꢀ1
,
a position only slightly lower than those reported for the m2-NO
ligands in the manganese complexes [Mn2Cp2(CO)2(NO)2] and
[Mn3Cp3(m3-NO)(m2-NO)3] (1480e1520 cmꢀ1 [9a]).
2.6. Tetracarbonyl derivatives of the hydride 6
Spectroscopic data for the hydride 6 are similar to those of 7 (IR
pattern, 31P chemical shifts) and therefore support a structure
comparable to that of the gold cluster just discussed. The CeO and
NeO stretching frequencies in 6 are higher than those in 7, as
expected from the higher electronegativity of the H atom compared
to that of the gold fragment, but the chemical shift for the bridging
hydride (ꢀ8.31 ppm) is significantly higher than usually found for
our dimanganese complexes (ꢀ12 to ꢀ17 ppm). We can attribute
this relative deshielding effect to the presence of the bridging
nitrosyl in the molecule, placed almost in the Mn2H plane, an effect
previously described for mononuclear complexes having hydride
and nitrosyl ligands arranged trans to each other [31]. Binuclear
species having H and NO bridging ligands are exceedingly rare.
Actually, the only other binuclear species we can use for compar-
Two carbonyls trans to the dppm ligand are easily replaced in
the hydride 6 with a second molecule of dppm under photo-
chemical conditions, or under moderate heating (333 K) if using the
more basic Me2PCH2PMe2 (dmpm) diphosphine, to give respec-
tively the corresponding tetracarbonyl derivatives [Mn2(
m
-H)
-dppm)
-dmpm)] (9c), that can be isolated as dark blue solids with good
(m-NO)(CO)4(m-dppm)2] (9a) and [Mn2(m-H)(m-NO)(CO)4(m
(m
yields (Chart 1).
The spectroscopic data for compounds 9 are comparable to
those reported previously for the related diphosphine-bridged
complexes [Mn2(
the diphosphite-bridged [Mn2(
m
-H)(
m
-X)(CO)4(
m
-dppm)2] (X ¼ OEt, Br, [37]) or
m-H)( -Br)(CO)4( -tedip)2] [22], and
m
m
ative purposes is the dirhodium complex [Rh2(
molecule displaying also poorly shielded resonance at
ꢀ7.14 ppm [32].
m-H)(m
-NO)(PiPr3)4]
a
a
2.5. Methylation reactions of compound 5
Compound 5 failed to react below 273 K with MeI or (Me3O)BF4,
while a generalized decomposition was observed when carrying
out these reactions at room temperature. In contrast, a fast and
selective reaction took place at 243 K when using CF3SO3Me as the
methylating agent, to give the methoxylimide derivative [Mn2(
m-
NOMe)(CO)6( -dppm)] (8). Unfortunately, compound 8 decom-
m
poses in solution at room temperature and could be not isolated as
a pure solid in the usual way.
The IR spectrum of 8 in solution exhibits five medium to strong
CeO stretching bands with a pattern not very different from that of
the hydride 6, but its 31P NMR spectrum denotes the chemical
inequivalence of the P atoms, indicative of the presence of an
asymmetric bridging group. The latter is identified as a bridging
methoxylimide group on the basis of the appearance of the corre-
sponding proton resonance at 3.41 ppm, although the alternative
a
Chart 1. The BFꢀ4 anion of compounds 10 and 11 is omitted for clarity.

564
M.E. García et al. / Journal of Organometallic Chemistry 696 (2011) 559e567
therefore deserve no detailed comments. We just note the signifi-
cant reduction by some 60 cmꢀ1 in the NeO stretching frequency
for 9a compared to its hexacarbonyl precursor, this reflecting
a considerable increase of electron density at the dimetal centre as
a result of the substitution of two CO ligands with a diphosphine
molecule. We also notice the appearance of poorly shielded hydride
resonances in both cases (ca. ꢀ9 ppm), also observed for 6 and
3. Experimental
All manipulations and reactions were carried out under
a nitrogen (99.995%) atmosphere using standard Schlenk tech-
niques. Solvents were purified according to literature procedures,
and distilled prior to use [39]. Compounds 1a [17b], 1b [16b], [Mn
(CO)(NO)3] [40], and [AuCl(PPh3)] [41] were prepared as described
previously, and all other reagents were obtained from the usual
commercial suppliers and used as received, unless otherwise
stated. Petroleum ether refers to that fraction distilling in the range
338e243 K. Photochemical experiments were performed using
jacketed Schlenk tubes, cooled by tap water (ca. 288 K). A 400 W
mercury lamp placed ca. 1 cm away from the Schlenk tube was
typically used in these the experiments. Filtrations were carried out
using diatomaceous earth. Chromatographic separations were
carried out using jacketed columns cooled by tap water at ca. 285 K
or by a closed 2-propanol circuit, kept at the desired temperature
attributed to influence of the bridging nitrosyl in the flat Mn2(
-NO) central core of all these molecules.
m-H)
(m
2.7. Protonation reactions of the hydrides 6 and 9a
The title hydride complexes react with HBF4$OEt2 in dichloro-
methane solution at 243 K to give a single species in each case (as
determined by low temperature NMR spectroscopy), which we
propose to be the corresponding hydroxylimide derivatives
[Mn2(m-H)(
m-NOH)(CO)6(
m
-dppm)]BF4 (10) and [Mn2(
m-H)(
m-NOH)
with a cryostat. Commercial Florisil (100e200 mesh) and
(CO)4(
m
-dppm)2]BF4 (11) respectively (Chart 1). Unfortunately,
aluminium oxide (activity I, 150 mesh) were degassed under
vacuum prior to use. The latter was mixed under nitrogen with the
appropriate amount of water to reach the activity desired. IR
stretching frequencies of CO and NO ligands were measured in
solution using CaF2 windows or in the solid state, in KBr discs.
Nuclear Magnetic Resonance (NMR) spectra were routinely recor-
ded at 300.13 (1H),121.50 (31P{1H}) or 75.47 MHz (13C{1H}), at 290 K
these products were thermally unstable and decomposed rapidly
above 273 K, and therefore could not be isolated as pure solids nor
fully characterized in the desired way (even an IR spectrum in
solution could not be obtained). We note, however, that these
products were easily deprotonated by Et2O or solid Na2CO3 to give
the corresponding neutral precursors, this therefore excluding any
irreversible transformation of the nitrosyl ligand upon protonation
of these hydride complexes.
The spectroscopic data and dynamic behaviour of compounds
10 and 11 (Table 1 and Experimental Section) are comparable to
each other, although the low solubility of the tetracarbonyl product
at low temperature precluded a more detailed spectroscopic anal-
ysis in that case. In both complexes, the averaged 31P NMR reso-
nance is close to that of the corresponding starting substrate, thus
suggesting little modification on the electron density at the dimetal
centre upon protonation, and being therefore consistent with
a protonation located at the nitrosyl ligand. Both compounds
display a hydride resonance at ca. ꢀ14 ppm and a strongly
deshielded resonance at 19.2 (10) or 16.6 ppm (11) which we
attribute to the presence of a hydroxylimide ligand on the basis of
their very high chemical shift, while the more “normal” shielding of
the hydride resonances is also consistent with the transformation
of the bridging nitrosyl.
In a static structure, the angular NeOeH ligand in compounds
10 and 11 is expected to be placed in the Mn2N plane, due to the
likely persistence of some residual multiplicity in the NeO bond, as
found for the related hydroxy- and alkoxycarbyne ligands (m2-COH,
m2-COR) in binuclear complexes [38]. This renders inequivalent
environments for the metal fragments of these complexes. Indeed,
the 31P NMR spectrum of 10 at 185 K displays an AB multiplet
consistent with the above proposal. Upon warming of the solution,
these resonances broaden and eventually collapse into a single
resonance, thus revealing the concurrence of a dynamic process
averaging the chemical environments of both metal fragments. At
the same time, the 1H NMR resonance at ca. 19 ppm also broadens
and eventually disappears in the baseline of the spectrum, so that
above 203 K only a broad resonance due to the excess HBF4$OEt2
present in the solution is detected in the spectrum, while other
resonances (hydride, diphosphine ligands) remained little per-
in CD2Cl2 solutions unless otherwise stated. Chemical shifts (d) are
given in ppm, relative to internal tetramethylsilane (1H, 13C) or
external 85% aqueous H3PO4 solutions (31P). Coupling constants (J)
are given in Hertz.
3.1. Preparation of [Mn2(NO)6(
m-dppm)] (2a)
3.1.1. Method A
A
toluene solution (12 mL) of compound 1a (0.030 g,
0.045 mmol) was stirred at 318 K for 1.5 h while gently bubbling
nitric oxide (5% in N2) through the mixture, to give a dark green
solution. After removal of most of the solvent under vacuum, the
concentrated solution was chromatographed through Florisil at
285 K. Elution with petroleum ether gave first a dark green fraction
and then a red-purple one containing some residual starting
material. Removal of the solvent from the first fraction gave
compound 2a (0.011 g, 36%) as a dark green powder. A yellow
fraction was afterwards eluted with dichloromethaneepetroleum
ether (1:1), which gave analogously variable amounts of compound
3a as a yellow solid (0e25%).
3.1.2. Method B
Solid dppm (0.050 g, 0.130 mmol) was added to a toluene
solution (25 mL) of [Mn(CO)(NO)3] (0.100 g, 0.580 mmol), and the
mixture was stirred at room temperature for 90 min to give a dark
green solution that was filtered through a Florisil pad at 285 K.
Removal of the solvent from the filtrate and washing of the residue
with petroleum ether at 273 K gave compound 2a as a dark green
powder (0.081 g, 42%). Anal. Calc. for C25H22Mn2N6O6P2: C, 44.53;
H, 3.28; N, 12.46. Found: C, 44.39; H, 3.21; N, 12.31. 1H NMR
(200.13 MHz)
d
7.56e7.19 (m, Ph, 20H), 3.89 (t, JHP ¼ 9, CH2, 2H).
3.2. Preparation of [Mn2(NO)6( -tedip)] (2b)
m
turbed. This strongly suggests
a protonation/deprotonation
sequence as the most probable mechanism for the averaging of the
chemical environments of the metal atoms in the complexes 10 and
11. At this point we should note that, due to the lower solubility of
11, it was not possible to record a 31P NMR spectrum of this complex
below 248 K, and therefore the limiting spectrum with separate 31P
resonances could not be obtained in that case.
A toluene solution (15 mL) of compound 1b (0.050 g,
0.093 mmol) was stirred at room temperature for 3 h while gently
bubbling nitric oxide (5% in N2) through the mixture, to give a dark
green solution. After removal of the solvent under vacuum, the
residue was extracted with petroleum ether and the extracts were
chromatographed on an alumina column (activity III) at 285 K.

M.E. García et al. / Journal of Organometallic Chemistry 696 (2011) 559e567
565
Elution with petroleum ether gave a dark green fraction which
gave, upon removal of the solvent, compound 2b as a spectro-
scopically pure, but oily residue (0.015 g, 35%). All attempts to
further purify this product resulted in the progressive decomposi-
dichloromethaneediethyl ether at room temperature to give
compound 5 (0.167 g, 90%) as a pale brown solid. Anal. Calc. for
C67H52Mn2N2O7P4: C, 65.37; H, 4.26; N, 2.27. Found: C, 65.45; H,
4.39; N, 2.34. 1H NMR (200.13 MHz)
d 7.49e7.21 (m, Ph, 50H), 3.83
tion of the complex. 1H NMR (C6D6)
d
3.78 (m, OCH2, 8H), 0.93 (t,
(t, JHP ¼ 9, CH2, 2H). 31P NMR (161.99 MHz, 293 K)
d
68.5 (s,
68.7 (s, vbr,
-dppm), 21.8 (s, PPN). 31P{1H} NMR (161.99 MHz, 166 K)
d 69.4,
m-
JHH ¼ 7, CH3, 6H).
dppm), 21.5 (s, PPN). 31P{1H} NMR (161.99 MHz,173 K)
d
m
3.3. Preparation of [Mn2(
m-H)(
m-NO2)(CO)6(
m-dppm)] (3a)
67.3 (2s, vbr,
m
-dppm), 21.7 (s, PPN). 13C{1H} NMR (50.33 MHz,
293 K)
d
235 (br, s, CO),140.1e126.4 (m, Ph), 49 (t, JPC ¼ 15, CH2). 13
C
Nitrogen dioxide was generated in situ by introducing a gentle
stream of nitric oxide (5% in N2) into a 100 mL Schlenk tube
previously filled with dry oxygen, until the gaseous phase adopted
an intense red-brown colour. Then a toluene solution (12 mL) of
compound 1a (0.030 g, 0.045 mmol) was transferred to this tube,
and the mixture was stirred for 15 min to yield a lemon yellow
solution. After removal of most of the solvent under vacuum, the
concentrated solution was chromatographed through alumina
(activity III) at 253 K. Elution with dichloromethaneepetroleum
ether (1:1) gave a yellow fraction yielding, after removal of
solvents, compound 3a as a yellow, quite air-sensitive powder
{1H} NMR (100.63 MHz, 213 K)
d 241.9, 234.7, 230.6 (3s, br, CO),
139.0e125.6 (m, Ph), 47.2 (s, br, CH2).
3.7. Preparation of [Mn2( -H)( -NO)(CO)6(m-dppm)] (6)
m
m
Solid (NH4)PF6 (0.025 g, 0.153 mmol) was added to a dichloro-
methane solution (15 mL) of compound 5 (0.050 g, 0.040 mmol)
and the mixture was vigorously stirred at room temperature for
45 min to give a cherry-red suspension. After removal of the solvent
under vacuum, the residue was extracted with dichloro-
methaneepetroleum ether (1:1) and the extracts were filtered
through an alumina pad (activity III) at 285 K. Removal of the
solvents from the filtrate and washing of the residue with petro-
leum ether (3 ꢁ 5 mL) gave compound 6 as a red-purple solid
(0.018 g, 62%). Anal. Calc. for C31H23Mn2NO7P2: C, 53.70; H, 3.34; N,
(0.013 g, 41%). 1H NMR (200.13 MHz)
(dt, JHH ¼ 13, JHP ¼ 14, CH2, 1H), 2.91 (dt, JHH ¼ 13, JHP ¼ 10, CH2, 1H),
-H, 1H). 31P{1H} NMR (161.99 Hz, 293 K)
49.0,
49.6, 43.8
d 7.33e7.27 (m, Ph, 20H), 3.40
ꢀ16.57 (t, JHP ¼ 25,
m
d
45.0 (2s, vbr,
m
-dppm). 31P{1H} NMR (161.99 Hz, 228 K)
-dppm).
d
(2d, JPP ¼ 66,
m
2.02. Found: C, 53.61; H, 3.91; N, 1.99. 1H NMR
20H), 3.05 (dt, JHH w JHP ¼ 11, CH2, 1H), 2.83 (dtd, JHH ¼ 11, 4,
JHP ¼ 11, CH2, 1H), ꢀ8.31 (td, JHP ¼ 12, JHH ¼ 4, -H, 1H).
d 7.45e6.85 (m, Ph,
3.4. Preparation of [Mn2(
m-H)(
m-NO2)(CO)6(
m-tedip)] (3b)
m
The procedure is analogous to that described for 3a, but using
compound 1b (0.030 g, 0.056 mmol). The crude reaction product
was extracted with dichloromethaneepetroleum ether (1:2) and
the extracts were chromatographed through alumina (activity IV)
at 285 K. Elution with the same solvent mixture gave a fraction
yielding, after removal of solvents, compound 3b as a yellow solid
(0.012 g, 37%). This solid was crystallized from a petroleum ether
solution at 253 K. Anal. Calc. for C14H21Mn2NO13P2: C, 28.83; H,
3.8. Preparation of [AuMn2( -NO)(CO)6( -dppm)(PPh3)] (7)
m
m
Solid [AuCl(PPh3)] (0.017 g, 0.037 mmol) was added to
a dichloromethane solution (15 mL) of compound 5 (0.050 g,
0.040 mmol) and the mixture was stirred at room temperature for
45 min to give an orange solution. After removal of the solvent
under vacuum, the residue was extracted with toluene and the
extracts were filtered through an alumina pad (activity III) at 285 K.
Removal of the solvents from the filtrate and washing of the residue
with petroleum ether (5 mL) gave compound 7 as an orange solid
(0.037 g, 79%). The crystals used in the X-ray study were grown by
the slow diffusion at room temperature of a layer of petroleum
ether into a concentrated benzene solution of the complex. Anal.
Calc. for C49H37AuMn2NO7P3: C, 50.97; H, 4.02; N, 1.01. Found: C,
3.26; N, 2.40. Found: C, 28.65; H, 3.21; N, 2.55. 1H NMR (C6D6)
(m, OCH2, 8H), 0.94 (m, CH3, 12H), ꢀ17.61 (t, JHP ¼ 32,
-H, 1H). 1H
NMR (400.13 MHz, CD2Cl2, 253 K) 4.33e3.92 (m, OCH2, 8H), 1.43
(t, JHH ¼ 6, CH3, 6H), 1.32, 1.31 (2t, JHH ¼ 6, CH3, 2 ꢁ 3H), ꢀ18.09 (t,
JHP ¼ 32, 161.0 (br,
-H, 1H). 31P{1H} NMR (121.49 Hz, C6D6, 293 K)
-tedip). 31P{1H} NMR (161.99 Hz, CD2Cl2, 200 K)
160.0, 159.0 (AB
mult, JPP ¼ 57, -tedip).
d 3.81
m
d
m
d
m
d
m
51.11; H, 3.24; N, 1.22. 1H NMR (400.13 MHz)
35H), 2.78, 2.73 (ABM2X mult, JHH ¼ 11, CH2, 2H).
d 7.60e6.86 (m, Ph,
3.5. Preparation of (PPN)[Mn2(m-H)(H)(NO2)(CO)6(m-dppm)] (4a)
3.9. Preparation of [Mn2( -NOMe)(CO)6( -dppm)] (8)
m
m
Solid (PPN)NO2 (0.089 g, 0.152 mmol; PPNþ ¼ [N(PPh3)2]þ) was
added to a tetrahydrofuran solution (25 mL) of compound 1a
(0.100 g, 0.151 mmol) cooled at 273 K, and the mixture was stirred
at that temperature for 30 min to give a yellow solution which was
filtered. Removal of the solvent from the filtrate gave an oily residue
which was crystallized from dichloromethaneepetroleum ether at
253 K to give compound 4a (0.181 g, 96%) as a dark yellow solid.
This crude product was found to be unstable at room temperature,
and it quantitatively gave back the starting material 1a upon
addition of diethyl ether. 1H NMR (400.13 MHz, thf-C6D6, 213 K)
Neat CF3SO3Me (5 mL, 0.044 mmol) was added to a dichloro-
methane solution (15 mL) of compound 5 (0.050 g, 0.040 mmol) at
243 K, and the mixture was stirred at that temperature for 15 min to
give an orange solution. After removal of the solvent under vacuum,
the residue was extracted with toluene and the extracts were
filtered through an alumina pad (activity III) at 243 K. Removal of
the solvents from the filtrate and washing of the residue with
petroleum ether (5 mL) at 273 K or below gave compound 8 as an
orange solid (0.015 g, 52%). This product decomposed at room
temperature either as a solid or (more rapidly) in solution. 1H NMR
d
ꢀ7.0 (br, MneH, 1H), ꢀ19.0 (br,
m-H, 1H).
(400.13 MHz, 243 K)
d 7.65e7.13 (m, Ph, 20H), 3.41 (s, OMe, 3H),
3.6. Preparation of (PPN)[Mn2( -CO)(CO)5(NO)(m-dppm)] (5)
m
2.92 (dt, JHH w JHP ¼ 13, CH2, 1H), 2.27 (dt, JHH w JHP ¼ 13, CH2, 1H).
A tetrahydrofuran solution of compound 4a, prepared in situ as
described above from compound 1a (0.100 g, 0.151 mmol) was
stirred at 318 K for 90 min to give a brown solution which was
filtered at room temperature. Removal of the solvent from the
filtrate gave an oily residue which was crystallized from
3.10. Preparation of [Mn2( -H)( -NO)(CO)4( -dppm)2] (9a)
m
m
m
Solid dppm (0.056 g, 0.146 mmol) was added to a tetrahydro-
furan solution (25 mL) of compound 6 (0.100 g, 0.144 mmol) and
the mixture was irradiated with visibleeUV light for 90 min at

566
M.E. García et al. / Journal of Organometallic Chemistry 696 (2011) 559e567
Table 3
285 K with a gentle N2 purge, to give a dark greenish solution. After
removal of the solvent under vacuum, the residue was dissolved in
a minimum dichloromethane and chromatographed on alumina
(activity III) at 285 K. Elution with dichloromethaneepetroleum
ether (1:1) gave a pale yellow fraction containing some residual
dppm and the mononuclear complex [Mn(H)(CO)3(dppm)]. Elution
with dichloromethane gave a dark blue fraction yielding, after
removal of solvent, compound 9a as a deep blue solid (0.109 g, 74%).
Anal. Calc. for C54H45Mn2NO5P4: C, 63.48; H, 4.43; N, 1.37. Found: C,
Crystal data for compound 7$3/2C6H6.
Mol formula
Mol wt
Crystal syst
Space group
Radiation (
a, Å
b, Å
C58H46AuMn2NO7P3
1268.71
Monoclinic
P21/a
0.71073
19.598(1)
14.710(1)
20.613(2)
90.00
98.98(2)
90.00
5869.6(8)
l, Å)
c, Å
a
, deg
, deg
63.09; H, 4.60; N,1.30. 1H NMR (200.12 MHz)
2.96, 2.83 (2m, CH2, 2 ꢁ 2H), ꢀ8.90 (qn, JHP ¼ 14,
d
7.4e6.9 (m, Ph, 40H),
-H, 1H).
b
m
g
, deg
V, Å3
Z
4
Calcd density, gcmꢀ3
Absorpt. coeff., mmꢀ1
Temperature, K
1.436
3.047
293(2)
3.07e26.00
3.11. Preparation of [Mn2(m-H)(m-NO)(CO)4(m-dppm)
(m-dmpm)] (9c)
q
range (ꢂ)
Neat dmpm (23
m
L, 0.147 mmol; dmpm ¼ Me2PCH2PMe2) was
Index ranges (h, k, l)
Reflections collected
Independent refln.
ꢀ24, 23; 0, 18; 0, 25
11769
added to a tetrahydrofuran solution (25 mL) of compound 6
(0.100 g, 0.144 mmol) and the mixture was stirred for 30 min at
333 K to give a dark blue solution. After removal of the solvent
under vacuum, the residue was extracted with dichloro-
methaneepetroleum ether (1:1) and the extracts were chromato-
graphed on an alumina column (activity III) at 285 K. Elution with
dichloromethaneepetroleum ether (2:1) gave an orange fraction
containing small amounts of several unidentified species. Elution
with dichloromethaneepetroleum ether (3:1) gave a dark blue
fraction yielding, after removal of solvents, compound 9c as a lead-
gray solid (0.092 g, 83%). Anal. Calc. for C34H37Mn2NO5P4: C, 52.79;
H, 4.82; N, 1.81. Found: C, 52.55; H, 4.71; N, 1.97. 1H NMR
11454 [Rint ¼ 0.0747]
3656
Refln. with I > 2
s
(I)
R indexes (I > 2
s
(I))a
R1 ¼ 0.0509, wR2 ¼ 0.0903b
R1 ¼ 0.2337, wR2 ¼ 0.1237b
1.037
R indexes (all data)a
GOF
Restraints/parameters
12/593
1.334, ꢀ1.499
Dr(max, min), e Åꢀ3
a
R
¼
S||Fo|
ꢀ
|Fc||/S|Fo|. wR
¼
[Sw(|Fo|2
ꢀ
|Fc|2)2/Sw|Fo|2]1/2
.
w
¼
1/
[
s
2(F2o) þ (aP)2 þ bP] where P ¼ (Fo2 þ 2F2c)/3.
b
a ¼ 0.0300, b ¼ 0.0000.
3.14. X-ray structure determination of compound 7
(200.12 MHz)
d
7.49e6.85 (m, Ph, 20H), 2.95 (m, CH2-dppm, 2H),
1.42 (AA0X3X03 mult, JHP þ JHP ¼ 7, CH3, 6H), 1.35 (m, CH2-dmpm,
0
Single crystal data were collected with a Philips PW 1100
diffractometer (Mo-Ka radiation,
¼ 0.71073 Å). Cell constants
1H), 1.29 (AA0X3X03 mult, JHP þ JHP ¼ 7, CH3, 6H), 1.03 (dt, JHH ¼ 13,
0
l
JHP ¼ 10, CH2-dmpm, 1H), ꢀ9.59 (qn, JHP ¼ 15,
m-H, 1H).
were obtained by a least square refinement of the setting angles of
24 randomly distributed and carefully centered reflections. The
absorption correction was applied using the program NEWABS92
(min. and max. transmission factors: 0.850e1.000) [42]. The
structures were solved by direct methods (SIR97) [43] and refined
on F2 with full-matrix least squares (SHELXL-97) [44], using the
WINGX software package [45]. The solvent of crystallization
(benzene) was refined with isotropic thermal parameters. One of
the benzene molecules was found disordered in two positions,
which were refined with site occupancy factors of 0.6/0.4. Another
benzene molecule was refined with a site occupancy factor of 0.5.
The remaining non-hydrogen atoms were refined anisotropically,
and the hydrogen atoms were placed at their calculated positions.
Graphical material was prepared with the ORTEP3 program for
Windows [46] (Table 3).
3.12. Preparation of solutions of [Mn2(m-H)(m-NOH)(CO)6
-dppm)]BF4 (10)
(m
Neat HBF4$OEt2 (13 mL of a 54% solution in Et2O, 0.050 mmol)
was added to a dichloromethane solution (5 mL) of compound 6
(0.035 g, 0.050 mmol) cooled at 243 K, and the mixture was stirred
for 1 min at that temperature to give a blue-green solution shown
(by 31P NMR) to contain compound 10 as the major species. All
attempts to isolate this product as a solid led to its complete
decomposition. 1H NMR (200.12 MHz, 243 K)
20H), 3.27, 2.96 (2m, CH2, 2 ꢁ 1H), ꢀ12.77 (br,
(200.12 MHz, 185 K) 19.20 (br, NOH, 1H), 7.52e6.83 (m, Ph, 20H),
3.30, 2.90 (2m, CH2, 2 ꢁ 1H), ꢀ13.54 (br,
-H, 1H). 31P{1H} NMR
(161.99 MHz, 243 K) 55.5 (br,
-dppm). 31P{1H} NMR (161.99 MHz,
185 K) -dppm).
55.6, 55.2 (AB mult, JPP ¼ 129,
d
7.58e7.92 (m, Ph,
m
-H, 1H). 1H NMR
d
m
d
m
Acknowledgments
d
m
We thank the Consejería de Educación de Asturias for financial
support (PA-MAS94-05).
3.13. Preparation of solutions of [Mn2(m-H)(m-NOH)(CO)4(m-
dppm)2]BF4 (11)
Appendix A. Supplementary material
Neat HBF4$OEt2 (13 mL of a 54% solution in Et2O, 0.050 mmol)
was added to a dichloromethane solution (5 mL) of compound 9a
(0.051 g, 0.050 mmol) cooled at 243 K, and the mixture was stirred
for 1 min at that temperature to give a greenish solution shown (by
31P NMR) to contain compound 11 as the major species. All
attempts to isolate this product as a solid led to its complete
CCDC 787009 contains the supplementary crystallographic data
for compound 7. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
decomposition. 1H NMR (400.13 MHz, 248 K)
d
16.62 (br, NOH, 1H),
References
7.5e6.7 (m, Ph, 40H), ꢀ14.62 (m, br,
m-H,1H). The resonances for the
methylenic protons of the complex were obscured by those of Et2O
arising from the added protonation reagent.
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