Highly reduced organometallics 52. Synthesis and chemistry of tricarbonylnitrosylmanganate(2-), [Mn(CO)3(NO)]2-

Article abstract of DOI:10.1016/S0020-1693(99)00546-0

Treatment of Mn(CO)₃(NO)(PPh₃) in THF at 20°C with excess sodium amalgam, followed by treatment with cryptand 2.2.2, or with two equiv. of potassium tri-sec-butylborohydride afforded high isolated yields (≥ 80%) of air sensitive yellow solids identified as [Na(crypt.2.2.2)]₂[Mn(CO)₃(NO)] and K₂[Mn(CO)₃(NO)], respectively. These products contain the only known mixed carbonylnitrosylmetallate dianion, isoelectronic with [Fe(CO)₄]^2- and [Mn(CO)₄]^3-. Reactions of [Mn(CO)₃(NO)]^2- with Ph₃SnCl, Mn(CO)₄(NO) and Fe(CO)₅, followed by metathesis, provided the new derivatives [Et₄N][Mn(CO)₃(NO)(SnPh₃)], [PPN]₂[Mn₂(CO)₆(NO)₂], and [PPN]₂[MnFe(CO)₇(NO)]. On the basis of IR spectral data the latter two have been formulated to contain non-bridged structures analogous to that previously established for the isoelectronic salt [PPN]₂[Fe₂(CO)₈]. (C) 2000 Elsevier Science S.A.

Full text of DOI:10.1016/S0020-1693(99)00546-0

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Inorganica Chimica Acta 300–302 (2000) 675–682
Highly reduced organometallics 52. Synthesis and chemistry of
tricarbonylnitrosylmanganate(2−), [Mn(CO)3(NO)]2−ꢀ
Yu-Sen Chen, John E. Ellis *
Department of Chemistry, Uni6ersity of Minnesota, Minneapolis, MN 55455, USA
Received 30 September 1999; accepted 16 November 1999
Dedicated to Professor Marcetta Y. Darensbourg for her friendship, support, inspiration and in recognition of her many wonderful
contributions to inorganic and organometallic chemistry over the past 30+ years.
Abstract
Treatment of Mn(CO)3(NO)(PPh3) in THF at 20°C with excess sodium amalgam, followed by treatment with cryptand 2.2.2,
or with two equiv. of potassium tri-sec-butylborohydride afforded high isolated yields (]80%) of air sensitive yellow solids
identified as [Na(crypt.2.2.2)]2[Mn(CO)3(NO)] and K2[Mn(CO)3(NO)], respectively. These products contain the only known mixed
carbonylnitrosylmetallate dianion, isoelectronic with [Fe(CO)4]2− and [Mn(CO)4]3−. Reactions of [Mn(CO)3(NO)]2− with
Ph3SnCl, Mn(CO)4(NO) and Fe(CO)5, followed by metathesis, provided the new derivatives [Et4N][Mn(CO)3(NO)(SnPh3)],
[PPN]2[Mn2(CO)6(NO)2], and [PPN]2[MnFe(CO)7(NO)]. On the basis of IR spectral data the latter two have been formulated to
contain non-bridged structures analogous to that previously established for the isoelectronic salt [PPN]2[Fe2(CO)8]. © 2000
Elsevier Science S.A. All rights reserved.
Keywords: Manganese complexes; Carbonyl complexes; Nitrosyl complexes; Organotin; Organophosphane complexes
metalate di-, tri- and tetra-anions [6] no corresponding
highly reduced carbonylnitosylmetalates were previ-
ously known. The objective of this present study was to
prepare the first dianion of this type. In view of the
remarkable thermal stabilities of alkali metal salts of
[Fe(CO)4]2− [7] and [Mn(CO)4]3− [8], an appropriate
initial target was the isoelectronic [Mn(CO)3(NO)]2−, a
dianionic analog of Hieber’s [Fe(CO)3(NO)]1− [2].
Herein is presented the first full account of this re-
search, a portion of which has previously appeared as a
communication [9].
1. Introduction
For several years we have been interested in the
synthesis of new mixed carbonylnitrosylmetalates of the
general formula [M(CO)x(NO)y]z− since these sub-
stances could be useful as reagents in the chemical
synthesis of new materials as are the closely related
carbonylmetalates [1]. Mononuclear metalates contain-
ing only CO and NO are quite rare substances. Indeed,
when this study was initiated, only two compounds of
this type were known, i.e. [Fe(CO)3(NO)]− [2] and
[Mn(CO)2(NO)2]− [3]. More recently, Gladfelter and
co-workers also prepared [Cr(CO)4(NO)]− [4] and
[Ru(CO)3(NO)]− [5], the only carbonylnitrosylmetalate
of a second or third row transition metal reported to
date. Despite the existence of homoleptic carbonyl
2. Experimental
2.1. General procedures and starting materials
All operations were carried out under an atmosphere
of purified dinitrogen or argon further purified by
passage through columns of activated BTS catalyst and
molecular sieves. Solutions were transferred by stainless
steel cannulas and syringes. Otherwise reactions were
ꢀ Part 51: P.J. Fischer, V.G. Young Jr., J.E. Ellis, Angew. Chem.,
Int. Ed. Engl. 39 (2000) 189.
* Corresponding author. Tel.: +1-612-625 6391; fax: +1-612-626
7541.
E-mail address: ellis@chem.umn.edu (J.E. Ellis)
0020-1693/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0020-1693(99)00546-0

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Y.-S. Chen, J.E. Ellis / Inorganica Chimica Acta 300–302 (2000) 675–682
performed using standard Schlenk techniques [10]. Sol-
vents were freed of impurities by standard procedures
and stored under dinitrogen or argon. The following
reactants were prepared according to literature proce-
dures: [Mn(CO)5(CH3CN)][BF4] [11] and [PPN][NO2]
[12]. An improved modification of the prior synthesis of
Mn(CO)3(NO)(PPh3) [13] was developed and is in-
cluded herein. All other reagents were obtained from
commercial sources, made anaerobic when necessary,
and used without additional purification. Infrared spec-
tra were recorded on a Perkin–Elmer 283 grating with
samples in 0.1 mm sealed NaCl liquid cells or as Nujol
mulls between NaCl plates. Melting points are uncor-
rected and were obtained in sealed capillaries on a
Thomas–Hoover Unimelt apparatus. Elemental analy-
ses were obtained by Analytischen Laboratorien, Engel-
skirchen, Germany.
vacuo to provide 0.652 g (83%) of (2), which gave
satisfactory analysis without further purification, m.p.
185°C (w. dec.) IR (silicone fluid mull); w(CO, NO)
1840 m, 1720 s, 1480 m cm−1. Anal. Calc. for
C39H72MnN5Na2O16: C, 48.39; H, 7.50; N, 7.23. Found:
C, 48.05; H, 7.61; N, 7.41%.
2.1.3. [PPN][Mn(CO)5] (3) 6ia reduction of
Mn(CO)4NO by NaꢀHg
To a solid mixture of [PPN][NO2] (0.904 g, 1.55
mmol) and [Mn(CO)5(CH3CN)][BF4] (0.500 g, 1.55
mmol), 50 ml of THF was added with vigorous stirring
to provide a red solution of Mn(CO)4NO (see the above
preparation of 1). This solution was vacuum distilled
into a flask containing excess approximately 0.72%
NaꢀHg (Na, 0.36 g; Hg, 50 g) at −195°C. After
warming to r.t. and stirring for 19 h, the mercury was
separated by filtration giving a pale yellow solution.
Inspection of its IR spectrum in the w(CO, NO) region
showed the following bands: 1890 s, 1860 s, 1825 w
cm−1. This spectrum was superimposable with that of
an authentic THF solution of Na[Mn(CO)5] prepared
from Na–Hg reduction of Mn2(CO)10 [16]. Metathesis
with [PPN]Cl in THF, filtration and recrystallization
from THF–petroleum ether (30–60°C) afforded shiny
yellow crystals of [PPN][Mn(CO)5]. Yield: 0.15 g (13%,
based on [Mn(CO)5(CH3CN)][BF4]). IR(THF): w(CO)
1890 s, 1855 vs cm−1. Literature value [17] w(CO) in
2.1.1. Mn(CO)3(NO)(PPh3) (1)
A solution of [PPN][NO2] (1.808 g, 3.10 mmol) in 20
ml of ethanol was added dropwise into solution of
[Mn(CO)5(CH3CN)][BF4] (1.00 g, 3.10 mmol) in 10 ml
of ethanol. Gas evolution and formation of a red
reaction mixture occurred immediately. An IR spec-
trum of this red solution showed the following bands:
w(CO) 2090 m, 2010 vs. 1970 vs. w(NO) 1755 cm−1
,
indicating the formation of Mn(CO)4(NO) (literature
value [14] (cm−1), w(CO) 2095 m, 2019 vs. 1972 vs;
w(NO) 1759 s). This red solution was then vacuum
distilled and condensed into another flask containing
PPh3 (0.810 g, 2.10 mmol) at −196°C. Upon warming
to room temperature (r.t.), a solution of Me3NO·2H2O
(0.35 g, 3.10 mmol) in 20 ml of ethanol was added
dropwise with vigorous stirring. Instantaneous gas evo-
lution occurred, accompanied by precipitation of bril-
liant red crystals of Mn(CO)3(NO)(PPh3). The crystals
were collected by filtration, washed with 20 ml of cold
ethanol and vacuum dried. Yield: 0.68 g (51% based on
[Mn(CO)5(CH3CN)][BF4]). IR data in THF: w(CO)
2030 s, 1965 m, 1920 s; w(NO) 1705 cm−1. Literature
value [15] in THF: w(CO) 2034 s, 1972 m, 1925 s;
THF: 1893, 1860 cm−1
.
2.1.4. K2[Mn(CO)3(NO) (4)
2.1.4.1. Reduction of Mn(CO)4NO by K[sec-Bu3BH]. To
solid [PPN][NO2] (1.808 g, 3.10 mmol) and
[Mn(CO)5(CH3CN)][BF4] (1.00 g, 3.10 mmol) 40 ml of
THF was added with vigorous stirring. A red solution
of Mn(CO)4NO was immediately formed as described
above. One hour later, the resulting solution was vac-
uum distilled and condensed into another flask cooled
with liquid nitrogen. Upon warming to r.t., this red
THF solution of Mn(CO)4(NO) was treated with 31 ml
of 1.0 M THF solution of K[sec-Bu3BH] (31 mmol).
The reaction mixture was first stirred at ambient tem-
perature for 30 min while some yellow product precipi-
tated. Then it was heated to reflux for 1.5 h, during
which time considerably more yellow precipitate
formed. An almost colorless solution remained. The
product was collected by filtration, washed with THF
(2×30 ml) and hexanes (30 ml), and dried in vacuo, to
provide 0.48 g (62% yield, based on [Mn(CO)5-
(CH3CN)][BF4]) of a yellow crystalline solid that gave
satisfactory analyses for the composition K2[Mn(CO)3-
(NO)]. M.p. 176°C (decomp). Fluorolube mull IR
spectrum: w(CO) 1900 m, 1775 sh, 1755 vs; n(NO)
1
w(NO) 1712 cm−1. H NMR (300 MHz, d6-acetone,
20°C) 7.75–7.26 (m, P(C6H5)3) ppm.
2.1.2. [Na(cryptand 2.2.2)]2[Mn(CO)3(NO)] (2)
A solution of 1 (0.350 g, 0.812 mmol) in 35 ml of
THF was added to sodium amalgam (Na, 0.374 g; Hg,
38 g) and the reaction mixture was stirred for 16 h at
r.t. During this time, the red color of 1 changed to a
golden yellow. The IR spectrum of this solution in the
w(CO, NO) region showed bands at: 1918 s, 1860 w,
1815 vs br, 1380 m br, 1345 m br cm−1). Filtration of
this solution and treatment of the resulting filtrate with
cryptand 2.2.2 (1.23 g, 3.25 mmol) resulted in precipita-
tion of 2 as a pale yellow solid. The latter was separated
by filtration, washed with THF (20 ml) and dried in
1440 sh, 1420 s, cm−1
MnNO4: C, 14.58; H, 0.00; K, 31.64; Mn, 22.23;
. Anal. Calc. for C3K2-

Y.-S. Chen, J.E. Ellis / Inorganica Chimica Acta 300–302 (2000) 675–682
677
N, 5.66. Found: C, 13.80; H, 0.24; K, 31.97; Mn, 22.00;
N, 5.50%.
filtration. Addition of Et2O to the filtrate produced
brilliant orange crystals, characterized as [PPN]2-
[Mn(CO)6(NO)2]. Yield: 0.77 g (40%), m.p. 125°C
(decomp), air-stable as a solid for hours. IR spectrum
(THF): w(CO) 1970 m, 1890 s, 1860 s; w(NO) 1650
2.1.4.2. Reduction of Mn(CO)3(NO)(PPh3) by K[sec-
Bu3BH]. 27 ml of 1.0 M THF solution of K[sec-Bu3BH]
(27.0 mmol) was added to 40 ml of a THF solution of
Mn(CO)3(NO)(PPh3) (1.16 g, 2.70 mmol). The red
color was discharged and yellow insoluble 4 began to
form within 15 min of stirring. Three hours later the
yellow precipitate was collected by filtration, washed
with THF (2×30 ml) and hexanes (30 ml), and dried in
vacuo. Brilliant yellow crystalline 4 (0.56 g) was ob-
tained in 84% yield. Spectroscopic properties of this
compound were identical to those obtained from route
a shown above. Anal. Calc. for C3K2MnNO4: C, 14.58;
H, 0.00; N, 5.66. Found: C, 13.18; H, 0.12; N, 5.87%.
Almost invariably low carbon analyses were obtained
(inexplicably) for 4 obtained by either route a or b.
1
w-m, 1610 m cm−1. H NMR (300 MHz, d6-acetone,
20°C): l 7.77–7.30 (m, PPN+). Anal. Calc. for
C78H60Mn2N4O8P4: C, 66.20; H, 4.27; N, 3.96; P, 8.75.
Found: C, 66.07; H, 4.15; N, 3.80; P, 8.79%.
2.3.2. From reaction of K2[Mn(CO)3(NO)] with
C7H7BF4
To a solid mixture of 4 (0.25 g, 1.10 mmol) and
tropylium tetrafluoroborate (0.18 g, 1.10 mmol) in a
flask was added 25 ml of THF. It was allowed to stir
for 5 days. A mixture of yellow solids and orange
solution was obtained. A silicone fluid mull IR spec-
trum of the yellow solids showed bands at 1900 m, 1750
s, and 1420 s cm−1, indicating the presence of 4. There
were also mysterious bands at 2170 m and 1590 s, br
cm−1. After filtration, the orange solution was treated
with [PPN]Cl (1.45 g, 2.53 mmol). After overnight
stirring and filtration, about 20 ml of the THF was
removed in vacuo from the orange filtrate. Initial addi-
tion of Et2O caused formation of a white precipitate
that was removed by filtration. Further addition of
Et2O afforded a brilliant orange crystalline product,
identified as [PPN]2[Mn2(CO)6(NO)2] by its IR spec-
trum. (THF): w(CO) 1970 m, 1980 s, 1860 s; w(NO)
1650 w-m, 1610 m cm−1, which was superimposable on
an IR spectrum of bona fide [PPN]2[Mn2(CO)6(NO)2]
prepared by route a. Yield: 0.10 g (14%).
2.2. [Et4N][Mn(CO)3(NO)SnPh3] (5)
A solution of Ph3SnCl (0.31 g, 0.81 mmol) in 20 ml
of THF was added dropwise into a slurry of 4 (0.20 g,
0.81 mmol), in 15 ml of THF. After 24 h of stirring, an
orange solution had formed, which showed the follow-
ing bands in the w(CO, NO) region: 1970s, 1900m,
1865s, 1835w, 1645m cm−1. Solvent was then removed
by evaporation in vacuo and [Et4N]Br (0.17g, 0.81
mmol) dissolved in 25 ml of CH3CN was added. After
removing the precipitated KCl and KBr by filtration,
Et2O was added to afford beautiful orange crystals.
Further recrystallization from THF–Et2O gave analyti-
cally pure 5, which was air-stable for an indefinite
period of time. Yield: 0.22 g (41%) m.p. 141°C (de-
comp). Anal. Calc. for C29H35MnN2O4Sn: C, 53.65; H,
5.40; N, 4.32. Found: C, 53.62; H, 5.53; N, 4.25%, IR
(CH3CN): w(CO) 1975 s, 1895 m, 1860 s; w(NO):
2.4. [PPN]2[MnFe(CO)7(NO)] (7)
2.4.1. From reaction of K2[Mn(CO3(NO)] with Fe(CO)5
Iron pentacarbonyl (1.6 ml, 12 mmol) was dissolved
in 100 ml of THF. 10 ml of this THF solution (1.2
mmol of Fe(CO)5) was then added dropwise into a
slurry of 4 (0.300 g, 1.21 mmol) in 50 ml of THF. All
solid 4 was consumed after 17 h of stirring, resulting in
a dark brownish-red solution that showed w(CO,NO)
bands at 1965 m, 1955 sh, 1890 s, 1870 s, 1830 m, 1645
m, 1615 m cm−1. After filtration through a medium
frit, all solvent and unreacted Fe(CO)5 were removed in
vacuo. The resulting oily brownish red solids were
redissolved in 50 ml of THF and filtered into a flask
containing solid [PPN]Cl (2.08 g, 3.64 mmol).
Overnight stirring and filtration, followed by crystal-
lization from THF–Et2O gave yellow-gold crystals of
[PPN]2[MnFe(CO)7(NO)], contaminated with a small
amount of [PPN]Cl. Further recrystallization from
THF–Et2O gave the pure sample. Yield, 0.46 g (30%)
m.p. 155°C (decomp). IR (THF): w(CO) 1985 m, 1940
w, 1870 vs; w(NO) 1645 m cm−1; (Nujol) mull): w(CO)
1985 m, 1970 w, 1910 s, 1875 vs br; w(NO) 1645 m
1
1640 m cm−1. H NMR (300 MHz, CD3CN, 20°C): l
1.20 (t of t, 12H, CH3 of Et4N), 3.14 (q, 8H, CH2 of
Et4N), 7.24–7.74 (m, 15H, SnPh3), ppm.
2.3. [PPN]2[Mn2(CO)6(NO)2] (6)
2.3.1. From reaction of K2[Mn(CO)3(NO)] with
Mn(CO)4(NO)
A solution of Mn(CO)4(NO) in 40 ml of THF was
freshly prepared from the reaction of [Mn(CO)5-
(CH3CN)][BF4] (0.80 g, 2.48 mmol) with [PPN][NO2]
(1.45 g, 2.48 mmol) as described previously. This solu-
tion was then added dropwise into a slurry of 4
(0.61g, 2.48 mmol) in 20 ml of THF over a period of 2
h. No apparent change of the reaction mixture was
observed during an overnight stirring. The resulting red
solution was then filtered into a suspension of [PPN]Cl
(5.68 g, 9.89 mmol) in 20 ml of THF. It was allowed to
stir for 16 h. Potassium chloride was removed by

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Y.-S. Chen, J.E. Ellis / Inorganica Chimica Acta 300–302 (2000) 675–682
cm−1 (there are also very weak bands at 1610 and 1585
3. Results and discussion
1
cm−1 due to PPN+ ion). H NMR (300 MHz, d6-ace-
tone, 20°C) l 7.80–7.30 (m, phenyl of PPN+); no MꢀH
signals were present. Anal. Calc. for C79H60FeMnN3-
O8P4: C, 67.10; H, 4.29; N, 2.97. Found: C, 67.03; H,
4.41; N, 2.79%.
3.1. Synthesis of [Mn(CO)3(NO)]2− 6ia reductions of
Mn(CO)3(NO)PPh3 and Mn(CO)4(NO)
3.1.1. Sodium-amalgam reductions
Although alkali metal or alkali metal–amalgam re-
ductions of homoleptic mono- or di-nuclear metal car-
bonyls are often good routes to pure carbonylmetalates
[18], corresponding reductions of mixed carbonylnitro-
sylmetal complexes almost invariably result in loss of a
nitrosyl group via irreversible and poorly understood
processes. For example, Co(CO)3(NO) and Fe(CO)2-
(NO)2 undergo such reductions to provide [Co(CO)4]−
[19] and [Fe(CO)3(NO)]− [20], respectively, as the only
isolable products. The fates of the lost NO groups in
these reductions remain unknown. Similarly, we found
that reduction of Mn(CO)4(NO) by sodium amalgam
gave only a low isolated yield (13%) of microcrystalline
[PPN][Mn(CO)5] after metathesis of the initially formed
Na[Mn(CO)5] with PPN+Cl− (Eq. (1)). Due to the
2.4.2. From reaction of K2[Mn(CO)3(NO)] with
Fe2(CO)9
A dark purple solution of Fe2(CO)9 (0.442 g, 1.21
mmol) in 25 ml of THF was added dropwise to a slurry
of 4 (0.300 g, 1.21 mmol) in 15 ml of THF with
vigorous stirring. Six hours later the original purple
solution changed to a dark brownish red reaction mix-
ture. Inspection of the infrared spectrum showed the
following bands in the w(CO, NO) region: 2020 s, 1995
vs, 1965 s, 1955 vs, 1890 vs, 1870 vs, 1830 m, 1645 m,
1615 w cm−1 (the first two bands are due to liberated
and unreacted Fe(CO)5). THF and Fe(CO)5 were re-
moved under vacuum. The reaction mixture was
then redissolved in 50 ml of THF and filtered into a
flask containing solid [PPN]Cl (2.50 g, 4.36 mmol).
After stirring overnight, the solution was filtered
and the compound was precipitated by addition
of diethyl ether. Further recrystallization from
CH3CN–Et2O and THF–Et2O gave yellowish brown
crystals of [PPN]2[MnFe(CO)7(NO)]. Yield: 0.38 g
(25%). The IR spectrum of 5 prepared by this route
was superimposable with that of the sample made by
route a.
Mn(CO)4(NO)+
THF
[PPN]Cl
excess NaꢀHg ꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢁ ꢀꢀꢀꢀꢁ [PPN][Mn(CO)5]+…
−196°C to 20°C
(1)
failure to obtain the desired Na2[Mn(CO)3(NO)] from
this route via Mn(CO)4(NO), we decided to examine
the corresponding reduction of Mn(CO)3(NO)(PPh3)
(1). The presence of the relatively good donor
triphenylphosphane group in complex 1 was expected
to make the nitrosyl group in the latter complex more
difficult to reduce than that in Mn(CO)4(NO). How-
ever, and perhaps more importantly, it seemed likely
that the PPh3 group would be lost from complex 1,
rather than CO or NO, during reduction. Thus, it has
been found that reduction of mononuclear transition
metal complexes containing a mixture of good and
poor- or non-acceptor ligands usually causes preferen-
tial loss of one or more of the weakest acceptor/
strongest donor ligands, provided reduction of
coordinated ligands does not occur. This synthetic
strategy, which has been called ‘the reductive labiliza-
tion method’ [6], represents an often unique and rather
poorly explored route to unusual highly reduced
organometallics/inorganics. It was first introduced sev-
eral years ago for the syntheses of the ‘superreduced’
species Na4[M(CO)4], M=Cr, Mo, W. The latter could
only be accessed in good yield and pure form by
reduction of the respective M(CO)4(h2-TMEDA),
TMEDA=N,N,N%,N%-tetramethylethylenediamine with
sodium metal in liquid ammonia [21].
2.4.3. From reaction of Na2[Fe(CO)4] with
Mn(CO)4(NO)
A solution of Mn(CO)4(NO) in 40 ml of THF was
freshly prepared from the reaction of [PPN][NO2] (1.70
g, 2.84 mmol) and [Mn(CO)5(CH3CN)][BF4] (0.94 g,
2.84 mmol) as described previously. This solution was
then added dropwise with vigorous stirring into a solu-
tion of Na2[Fe(CO)4] (1.5 dioxane) (1.01 g, 2.84 mmol)
in 50 ml of THF. Inspection of the solution spectrum at
the end of addition showed the following bands in the
w(CO, NO) region: 1995 m, 1985 m, 1965 m, 1895 s,
1880 s, 1645 m, 1605 w cm−1. The absence of bands
due to Mn(CO)4(NO) indicated that the reaction was
complete. The resulting dark brownish red solution was
then filtered into a flask containing solid [PPN]Cl (7.37
g, 11.36 mmol). After overnight stirring, filtration and
removal of about 60 ml of THF from the dark brown-
ish red filtrate, Et2O was added to precipitate the
compound. Further recrystallization from THF–Et2O
gave brilliant gold crystals of [PPN]2[MnFe(CO)7(NO)].
Yield 1.63 g (40%). Compound 5 obtained by route c
had an identical IR spectrum to those accessed by
routes a and b.
Reduction of complex 1 by excess NaꢀHg in THF at
r.t. was a remarkably clean reaction compared to that
of Mn(CO)4NO and provided, after complexation with

Y.-S. Chen, J.E. Ellis / Inorganica Chimica Acta 300–302 (2000) 675–682
679
a
THF
cryptand 2.2.2, a high isolated yield (83%) of a pale
yellow powdery solid, for which satisfactory analyses
were obtained as the unsolvated [Na(crypt
2.2.2)]2[Mn(CO)3(NO)] (2) (Eq. (2)). Interestingly, 2 is
isoelectronic with
Mn(CO)3(NO)L+2K[R3BH] ꢀꢀꢀꢀꢀꢀꢀꢁ
-H ,-2BR
2 3
K2[Mn(CO)3(NO)]¡+L
(3)
L=CO, PPh3, R=sec-Bu, aL=CO, reflux, 1.5 h,
yield=62%; L=PPh3, 20°C, 3 h, yield=84%.
Interestingly, the reaction of Mn(CO)4(NO) with
K[R3BH] required substantially more forcing condi-
tions (reflux in THF) to go to completion than the
corresponding one of Mn(CO)3(NO)(PPh3), which pro-
ceded efficiently at r.t. Since carbonyls are far more
susceptible towards nucleophilic attack than nitrosyl
ligands, for a given mixed carbonylnitrosylmetal com-
plex [25], it is believed that Mn(CO)3(NO)L, L=CO,
PPh3, initially reacted with [R3BH]− to generate formyl
anions, [Mn(CO)2(NO)L(CHO)]−. Loss of L from the
putative formyl intermediates would provide the
presently unknown hydride, [Mn(CO)3(NO)H]−, vide
infra. The latter would be expected to react with addi-
tional [R3BH]− to afford the observed product
[Mn(CO)3(NO)]2−, along with hydrogen gas and tri-
sec-butylborane.
Mn(CO)3(NO)(PPh3)+
excess NaꢀHg ꢀꢀTꢀHꢀFꢀꢀꢁ ꢀꢀꢀꢀꢀꢀꢀꢁ [Na(crypt 2.2.2)]2-
crypt 2.2.2
20°C-PPh
3
[Mn(CO)3(NO)]¡ 83%
(2)
[Na(crypt 2.2.2)]2[Fe(CO)4], which was established by
single-crystal X-ray crystallography to contain an es-
sentially undistorted tetrahedral [Fe(CO)4]2− unit [22].
On the basis of IR spectral and derivative data complex
2
is formulated to contain similarly discrete
[Mn(CO)3(NO)]2− units of C3V symmetry. This infor-
mation will be discussed in detail below.
3.2. Potassium tri-sec-butylborohydride reductions
The proposed reaction sequence above is well prece-
dented in the corresponding reactions of Fe(CO)5
[23,26] and Fe(CO)4PPh3 [26] with K[R3%BH], R%=sec-
Bu [23], O-i-Pr [26], which initially provide the formyl
anions, [Fe(CO)3L(CHO)]−, L=CO, PPh3. The latter
lose L to provide [Fe(CO)4H]−, which undergoes facile
deprotonation by [R3BH]− to give [Fe(CO)4]2−. Loss
of L from the formyl iron anions is more facile for
L=PPh3 than CO, undoubtedly because the electron
rich iron center leads to preferential labilization of the
phosphane, which is a better donor and weaker accep-
tor than CO. We believe the same situation obtains for
the proposed manganese analogs and it is this facile
Since Fe(CO)5 [23] and Fe(CO)4PPh3 [24] both un-
dergo reduction by potassium tri-sec-butylborohydride,
K[R3BH], to give high isolated yields of unsolvated
K2[Fe(CO)4], the corresponding reductions of
Mn(CO)3(NO)L, L=CO, PPh3 were also examined.
These reactions provided identical yellow microcrys-
talline solids of the formulation K2[Mn(CO)3(NO)] (4)
in 62% (L=CO), and 84% (L=PPh3) isolated yields,
respectively (Eq. (3)). IR spectral and chemical reactiv-
ity data for complex 4 are completely in accord with the
presence of [Mn(CO)3(NO)]2− units in this potassium
salt. These data will be discussed in later sections.
Table 1
Infrared data for carbonylnitrosylmanganese complexes
Compound
Solvent/medium
ethanol
IR w(CO)
w(NO) (cm−1
)
Mn(CO)4NO
2090 s,
1755 m
2010 vs, 1970 vs
2030 s,
1965 m, 1920s
1918 s, 1860 w,
1815 vs br
1840 m,
1720 vs
1900 m
1775 sh, 1755 vs br
1975 s
1895 m, 1860 s
1970 m,
Mn(CO)3(NO)PPh3
Na2[Mn(CO)3(NO)]
[Na(crypt2.2.2)]2[Mn(CO)3(NO)]
K2[Mn(CO)3(NO)]
THF
1705 m
THF
1380 m br,
1345 m br
1480 m
silicone
fluid mull
fluorolube
mull
1440 sh
1420 m
1640 m
[Et4N][Mn(CO)3(NO)SnPh3]
[PPN]2[Mn2(CO)6(NO)2]
[PPN]2[MnFe(CO)7(NO)]
CH3CN
THF
THF
1650 w-m
1610 m
1645 m
1890 s, 1860 s
1985 m,
1940 w, 1870 vs br

680
Y.-S. Chen, J.E. Ellis / Inorganica Chimica Acta 300–302 (2000) 675–682
3.4. Reactions of [Mn(CO)3(NO)]2−
Further confirmation of the natures of (2) and (4)
has been obtained by the preparation of appropriate
derivatives thereof from the reactions of these species
with Ph3SnCl, Mn(CO)4NO, and Fe(CO)5, all of which
also combine with the isoelectronic [Fe(CO)4]2− to give
reasonably robust products, vide infra. The results of
these various reactions are shown in Scheme 1.
Scheme 1.
3.5. [Mn(CO)3(NO)(SnPh3)]−
loss of PPh3 that accounts for the mild conditions
required for the reaction of Mn(CO)3(NO)(PPh3) with
K[R3BH], as depicted above in Eq. (3).
Treatment of slurry of complex 4 with 1 equiv. of
Ph3SnCl in THF at r.t. gave rise to an orange solution.
After metathesis with [Et4N]Br and recrystallizations
from CH3CN–Et2O and THF–Et2O a pure orange
microcrystalline and thermally robust product (mp:
141°C w dec.). was identified as [Et4N][Mn(CO)3-
(NO)SnPh3] (5), by elemental analyses, IR (Table 1)
3.3. Infrared spectral properties of [Mn(CO)3(NO)]2−
Infrared data for salts of [Mn(CO)3(NO)]2− are
shown in Table 1. Fluorolube mull spectra of
K2[Mn(CO)3(NO)] in the w(CO,NO) region show three
1
and H NMR spectra. Crystalline 5 is stable in air for
main peaks at 1900 (m), 1755 (vs) and 1420 (m) cm−1
.
hours at r.t. and forms thermally stable solutions in
THF, acetonitrile and acetone. The w(CO,NO) band
shapes and relative intensities are virtually identical to
those found for Mn(CO)3(NO)(PPh3) (1), 2030 (s),
1965 (m), 1920 (s), 1705 (s) cm−1, except the latter are
all shifted about 60 cm−1 to higher energies. On this
basis, it seems likely that [Mn(CO)3(NO)SnPh3]− and
[Mn(CO)3(NO)PPh3] are also isostructural. The latter
species has been shown to have a trigonal bipyramidal
structure, where the PPh3 and NO groups occupy axial
and equatorial positions, respectively [30]. The isoelec-
tronic neutral Fe(CO)3(NO)SnPh3 also has a very simi-
lar spectral signature, 2065 (s), 2010 (m), 1980 (s), 1773
(s) cm−1 [31], except all corresponding bands have
shifted from about 90 to 130 cm−1 to higher energy.
In the same region, THF solution spectra of
Na2[Mn(CO)3(NO)] exhibit principal bands at 1918 (s),
1815 (vs, br), 1380 (m, br), 1345 (m, br) cm−1. The
two very low-energy bands for the disodium salt at
1380 and 1345 cm−1 are undoubtedly caused by strong
interactions between sodium cations and nitrosyl oxy-
gens. To the best of our knowledge, these are the
lowest w(NO) bands previously observed for mononu-
clear metal nitrosyls. The related K3[Mn(CN)2(NO)2],
which likely also contains linear nitrosyls, exhibited
w(NO) values of 1455, 1425 cm−1, the previous lowest
energies for metal nitrosyls of this type [27]. The ꢀ-NO
binding is significantly weaker in K2[Mn(CO3(NO)]
than for Na2[Mn(CO)3(NO)]. This feature also ac-
counts for the lower w(CO) values observed for the
potassium salt compared to those for Na2[Mn(CO)3-
(NO)] [28]. Addition of cryptand 2.2.2 to THF solutions
of the latter species caused the two broad w(NO)
peaks to coalesce into a dramatically sharper one at
considerably higher energy, 1480 cm−1. The correspond-
ing w(CO) peaks also sharpened and moved to lower
energies of 1840 m, 1720 vs cm−1. These spectral
changes indicate that the complexation of Na+ by cryp-
tand 2.2.2 substantially (or completely) disrupted the
nitrosyl oxygen ꢀNa+ ion pairing interactions and
perturbation of the pseudotetrahedral [Mn(CO)3(NO)]2−
unit. Similar trends have been previously reported
for the isoelectronic [Fe(CO)3(NO)]−. For example,
infrared spectra of Na[Fe(CO)3(NO)] in Et2O, where
the nitrosyl oxygen is ion-paired with Na+, show
peaks in the w(CO,NO) region at 2001, 1900 and
1599 cm−1, while corresponding spectra of [PPN][Fe-
(CO3(NO)] in THF, where no such interaction is possible,
show peaks at 1978, 1876 and 1645 cm−1 [29].
3.6. [Mn2(CO)6(NO)2]2− and [MnFe(CO)7(NO)]2−
Since [Fe(CO)4]2− readily interacts with Fe(CO)5 to
provide the dinuclear dianion, [Fe2(CO)8]2− [32], corre-
sponding reactions of [Mn(CO)3(NO)]2− with
Mn(CO)4(NO) and Fe(CO)5 were examined. As shown
in the above Scheme, both combinations provide new
dinuclear anions, which were isolated as PPN+, i.e.
[N(Ph3P)2]+, salts. On the basis of elemental analyses,
1
IR and H NMR spectra, these products were formu-
lated as [PPN]2[Mn2(CO)6(NO)2] (6) and [PPN]2[MnFe-
(CO)7(NO)] (7), respectively. Compounds 6 and 7 were
isolated in 40 and 30% yields as brilliant orange and
golden microcrystals, respectively. Their 1H NMR
spectra confirmed that no metal hydrides were present
in significant amounts. Further confirmation of the
natures of complexes 6 and 7 were obtained by their
independent syntheses as shown below in Eqs. (4) and
(5), respectively, where

Y.-S. Chen, J.E. Ellis / Inorganica Chimica Acta 300–302 (2000) 675–682
681
2K2[Mn(CO)3(NO)]+2[C7H7][BF4]
1. 20°C, THF
To the best of our knowledge, the only other known
reaction of K2[Mn(CO)3(NO)] was that recently re-
ported with the chlorogallane, ClGaRR%, R=
(CH2)3NMe2, R%=t-Bu. After metathesis, high (88%)
yields of the respective [PPN][Mn(CO)3(NO)(GaRR%)]
were obtained [36]. This latter report, as well as our
ꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢁ [PPN]2[Mn2(CO)6(NO)2]
2. [PPN]Cl-KBF ,-KCl,-C
4
H
14 14
14%
(4)
(5)
Mn(CO)4(NO)+Na2[Fe(CO)4]
1. 20°C, THF
ꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢁ [PPN]2[MnFe(CO)7(NO)]
2. [PPN]Cl-NaCl
40%
studies
described
herein,
demonstrate
that
[C7H7][BF4] is tropylium tetrafluoroborate, a conve-
nient one electron oxidant [34]. Compound 7 was also
obtained in 25% isolated yield via the reaction of
K2[Mn(CO)3(NO)] and Fe2(CO)9 in THF, followed by
metathesis with [PPN]Cl and recrystallizations. IR spec-
tra of complexes 6 and 7 in the w(CO,NO) region
indicate that no bridging ligands are present, as is the
case for [Fe2(CO)8]2− [33]. Further, the very simple IR
patterns observed for compounds 6 and 7 suggest that
only one structural isomer of each is present. The
remarkable similarity of the w(CO,NO) spectral signa-
ture of compounds 5 and 6 indicate that the local
geometry about the manganese atoms in both species
are closely related. Indeed, as noted previously, com-
[Mn(CO)3(NO)]2− is an effective nucleophile and a
potentially useful reagent for the syntheses of new
classes of mixed metal complexes, some of which may
find applications in the production of novel alloy-films
[36].
4. Conclusions
Our success in obtaining [Mn(CO)3(NO)]2− by the
alkali metal reduction of [Mn(CO)3(NO)(Ph3P)] repre-
sents another demonstration of the value of the ‘reduc-
tive labilization method,’ vide supra, in the synthesis
of unusual organometallic complexes of the transi-
tion metals. The same strategy has been employed in
the preparation of the previously unknown
[V(CO)4(NO)]2−, which cannot be obtained by a direct
reduction of V(CO)5(NO) [37]. Similarly, it is pos-
sible that a wide variety of highly reduced carbonyl-
nitrosylmetallates may be available by related re-
ductions, including unusual electronically saturated
plex
5
and
the
structurally
characterized
Mn(CO)3(NO)(Ph3P) [30] almost certainly have identi-
cal structures. Thus, on the basis of available data,
complex 6 is likely to have a structure essentially identi-
cal to that of [Fe2(CO)8]2−, except two of the equato-
rial carbonyl groups in the latter are replaced by
nitrosyl groups. It is well established that nitrosyls have
a great preference to occupy equatorial positions in
trigonal bipyramidal mixed carbonylnitrosyl complexes,
due to their much stronger acceptor abilities compared
to carbonyls [35]. Similar arguments suggest that com-
plex 7 and [Fe2(CO)8]2− are also isostructural. How-
ever, single crystal X-ray structural characterizations of
6 and 7 will be required to corroborate these claims.
Unfortunately, attempts to obtain suitable single crys-
tals of these species have so far failed.
three coordinate dianions such as [Mn(NO)3]2−
,
[Fe(CO)(NO)2]2−, and [Co(CO)2(NO)]2−. These are all
unknown presently but are isoelectronic with the
known species [Co(CO)3]3− [38]. Since free or coordi-
nated [NO]+ and NO can undergo facile reductive
coupling to form the hyponitrite ion, [N2O2]2− [39], the
existence of highly reduced di- or poly-nitrosyl meta-
lates may be problematic. Indeed, presently the only
known mononuclear polynitrosylmetallate anion is
[Mn(CO)2(NO)2]− [3]. However, at least in this case,
there is no indication from its crystal structure [3,40]
that the NO units are involved in a form of ‘incipient
reductive coupling,’ which is well established in certain
dicarbonyl metal complexes, such as Nb(CO)2(dmpe)2-
Cl2 [41].
3.7. Other reactions of [Mn(CO)3(NO)]2−
Earlier in this article it was suggested that the hy-
dride route to K2[Mn(CO)3(NO)] likely involved the
intermediate formation of the presently unknown hy-
dride [Mn(CO)3(NO)H]−. The latter species would be
entirely analogous to the neutral Fe(CO)3(NO)H, which
decomposes at −45°C and was obtained by protona-
tion of [Fe(CO)3(NO)]− [2]. Unfortunately, all attempts
to protonate salts of [Mn(CO)3(NO)]2−, even by weak
Brønsted acids such as methanol at −78°C, led only to
intractable products, which decomposed well below am-
bient temperature. Also, treatment of Mn(CO)4(NO)
with methanolic Et4N+ OH− gave quite unstable spe-
cies, which showed no NMR resonances due to metal
hydrides. In contrast, corresponding methanolysis of
[Fe(CO)4]2− or hydroxide attack of [Fe(CO)5] provide
high yields of the thermally robust [Fe(CO)4H]− [1].
Acknowledgements
We sincerely thank the US National Science Founda-
tion and the donors of the Petroleum Research Fund,
administered by the American Chemical Society for
financial support and Christine Lundby for her expert
assistance with the manuscript. We also are indebted to
Robert E. Stevens and Professor Wayne L. Gladfelter
for advice on how to best prepare [Mn(CO)4(NO)] from
readily available precursors.

682
Y.-S. Chen, J.E. Ellis / Inorganica Chimica Acta 300–302 (2000) 675–682
[20] (a) W. Hieber, H. Beutner, Z. Naturforsch., Teil B 15 (1960) 323.
References
(b) H. Beutner, J. Ellerman, W. Hieber, Chem. Ber. 96 (1963)
1659.
[21] (a) J.E. Ellis, C.P. Parnell, G.P. Hagen, J. Am. Chem. Soc. 100
(1978) 3605. (b) J.T. Lin, G.P. Hagen, J.E. Ellis, J. Am. Chem.
Soc. 105 (1983) 2296.
[22] R.G. Teller, R.G. Finke, J.P. Collman, H.B. Chin, R. Bau, J.
Am. Chem. Soc. 99 (1977) 1104.
[23] J.A. Gladysz, W. Tam, J. Org. Chem. 43 (1978) 2279.
[24] J.E. Ellis, Y.-S. Chen, Organometallics 8 (1989) 1350.
[25] G.B. Richter-Addo, P. Legzdins, Metal Nitrosyls, Oxford Uni-
versity Press, New York, 1992.
[26] C.P. Casey, S.M. Neumann, J. Am. Chem. Soc. 98 (1976) 5395.
[27] H. Behrens, E. Lindner, H. Schindler, Z. Anorg. Allg. Chem. 365
(1969) 119.
[28] (a) C.P. Horwitz, D.F. Shriver, Adv. Organomet. Chem. 23
(1984) 219. (b) M.Y. Darensbourg, Prog. Inorg. Chem. 33 (1986)
221. Both of these reviews contain valuable background infor-
mation on the influence of oxophilic electrophiles on carbonyl
and nitrosyl stretching frequencies.
[29] K.H. Pannell, Y.-S. Chen, K.L. Belknap, Chem. Commun.
(1977) 362.
[30] J.H. Enemark, J.A. Ibers, Inorg. Chem. 7 (1968) 2339.
[31] M. Casey, A.R. Manning, J. Chem. Soc. A (1971) 256.
[32] J.P. Collman, R.L. Finke, P.L. Matlock, R. Wahren, J.I. Ko-
moto, J. Am. Chem. Soc. 100 (1978) 1119.
[1] F. Calderazzo, in: R.B. King (Ed.), Carbonyl Complexes of the
Transition Metals in Encyclopedia of Inorganic Chemistry, vol.
2, Wiley, Chichester, 1994.
[2] W. Hieber, H. Beutner, Z. Anorg. Allg. Chem. 320 (1963) 101.
[3] R.E. Stevens, T.J. Yanta, W.L. Gladfelter, J. Am. Chem. Soc.
103 (1981) 4981.
[4] D.R. Mantell, W.L. Gladfelter, J. Organomet. Chem. 347 (1988)
333.
[5] R.E. Stevens, D.E. Fjare, W.L. Gladfelter, J. Organomet. Chem.
347 (1988) 373.
[6] J.E. Ellis, Adv. Organomet. Chem. 31 (1990) 1.
[7] W. Hieber, W. Beck, G. Braun, Angew. Chem. 72 (1960) 795.
[8] (a) J.E. Ellis, R.A. Faltynek, J. Chem. Soc. Chem. Commun.
(1975) 966. (b) G.F. Warnock, L.C. Moodie, J.E. Ellis, J. Am.
Chem. Soc. 111 (1989) 2131.
[9] Y.-S. Chen, J.E. Ellis, J. Am. Chem. Soc. 105 (1983) 1689.
[10] A.L. Wayda, M.Y. Darensbourg (Eds.), Experimental
Organometallic Chemistry, ACS Symposium Series 357, Ameri-
can Chemical Society, New York, NY, 1987.
[11] D. Drew, D.J. Darensbourg, M.Y Darensbourg, Inorg. Chem.
14 (1975) 1579.
[12] A. Martinsen, J. Songstad, Acta Chem. Scand., Ser. A. 31 (1977)
645.
[13] (a) R.F. Lambert, J.D. Johnson, Chem. Ind. (London) (1960)
1267. (b) W. Hieber, H. Tengler, Z. Anorg. Allg. Chem. 318
(1962) 136.
[14] P.M. Treichel, E. Pitcher, R.B. King, F.G.A. Stone, J. Am.
Chem. Soc. 83 (1961) 2593.
[33] H.B. Chin, M.B. Smith, R.D. Wilson, R. Bau, J. Am. Chem.
Soc. 96 (1974) 5258.
[34] N.G. Connelly, W.E. Geiger, Chem. Rev. 96 (1996) 877.
[35] R. Hoffman, M.M.L. Chen, M. Elian, A.R. Rossi, D.M.P.
Mingos, Inorg. Chem. 13 (1974) 2666.
[15] H. Wawarsik, F. Basolo, J. Am. Chem. Soc. 89 (1967) 4626.
[16] M.Y. Darensbourg, D.J. Darensbourg, D. Burns, D.A. Drew, J.
Am. Chem. Soc. 98 (1976) 3127.
[17] R.A. Faltynek, M.S. Wrighton, J. Am. Chem. Soc. 100 (1978)
2701.
[18] (a) R.B. King, Adv. Organomet. Chem. 2 (1964) 157. (b) H.
Behrens, Adv. Organomet. Chem. 18 (1980) 1.
[19] (a) W. Hieber, J. Ellermann, Chem. Ber. 96 (1963) 1667. (b) G.
Piazza, A. Foffani, G. Paliani, Z. Phys. Chem. Neue Folge 60
(1968) 167.
[36] R.A. Fischer, M.M. Schulte, E. Herdtweck, M.R. Mattner,
Inorg. Chem. 36 (1997) 2010.
[37] (a) K.L. Fjare, J.E. Ellis, J. Am. Chem. Soc. 105 (1983) 2303. (b)
K.L. Fjare, J.E. Ellis, manuscript in preparation.
[38] J.E. Ellis, P.T. Barger, M.L. Winzenburg, G.F. Warnock, J.
Organomet. Chem. 383 (1990) 521.
[39] J. Laane, J.R. Ohlsen, Prog. Inorg. Chem. 27 (1980) 465.
[40] R.E. Stevens, W.L. Gladfelter, Inorg. Chem. 22 (1983) 2034.
[41] P.A. Bianconi, R.N. Vrtis, C.P. Rao, I.D. Williams, M.P. En-
geler, S.J. Lippard, Organometallics 6 (1987) 1968.
.