The synthesis of PNP-supported low-spin nitro manganese(I) carbonyl complexes

Article abstract of DOI:10.1016/j.poly.2016.04.007

The coordination chemistry of Mn(CO)₅Br was investigated with a series of PNP-pincer ligands. The ligands^iPrPONOP (^iPrPONOP?=?2,6-bis(diisopropylphosphinito)pyridine) and^iPrPN^HP (^iPrPN^HP?=?HN{CH₂CH₂(PiPr₂)}₂) gave the desired organometallic manganese complexes (^iPrPONOP)Mn(CO)₂Br and (^iPrPN^HP)Mn(CO)₂Br, respectively, upon chelation to Mn(CO)₅Br. The reactivity of^iPrPNNNP (^iPrPNNNP?=?N,N′-bis(diisopropylphosphino)-2,6-diaminopyridine) with Mn(CO)₅Br yielded a pair of products, [(^iPrPNNNP)Mn(CO)₃][Br] and (^iPrPNNNCO)Mn(CO)₃. The formation of the asymmetric chelate arises from a formal loss of iPr₂PBr and C–N bond formation from a carbonyl ligand and NH, yielding a Mn(I) amide core. The nitration reactions of (^iPrPONOP)Mn(CO)₂Br and (^iPrPN^HP)Mn(CO)₂Br were carried out using silver nitrite, yielding the nitro compounds (^iPrPONOP)Mn(CO)₂(NO₂) and (^iPrPN^HP)Mn(CO)₂(NO₂), respectively. The analogous iron complex (^iPrPONOP)Fe(CO)Cl₂was nitrated under the same conditions to yield the salt pair [(^iPrPONOP)Fe(CO)₂][FeCl₃NO]. This reactivity underlines the difference between iso-valent iron and manganese centers. The manganese complexes (^iPrPONOP)Mn(CO)₂(NO₂) and (^iPrPN^HP)Mn(CO)₂(NO₂) were ineffective as oxygen atom transfer reagents for a variety of substrates.

Full text of DOI:10.1016/j.poly.2016.04.007

Accepted Manuscript
The synthesis of PNP-supported low-spin nitro manganese(I) carbonyl com-
plexes
Aaron M. Tondreau, James M. Boncella
PII:
S0277-5387(16)30079-1
DOI:
http://dx.doi.org/10.1016/j.poly.2016.04.007
POLY 11933
Reference:
To appear in:
Polyhedron
Received Date:
Accepted Date:
26 January 2016
6 April 2016
Please cite this article as: A.M. Tondreau, J.M. Boncella, The synthesis of PNP-supported low-spin nitro
manganese(I) carbonyl complexes, Polyhedron (2016), doi: http://dx.doi.org/10.1016/j.poly.2016.04.007
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The synthesis of PNP-supported low-spin nitro manganese(I) carbonyl complexes.
a
Aaron M. Tondreau, James M. Boncella
a
a.
LANL
boncella@lanl.gov
Abstract.
The coordination chemistry of Mn(CO) Br was investigated with a series of
PNP-pincer
bis(diisopropylphosphinito)pyridine) and PN P ( PN P = HN{CH2CH2(PiPr
5
iPr
iPr
ligands.
The
ligands
PONOP
( PONOP
=
2,6-
)}
Br and
Br. The reactivity of
iPr
H
iPr
H
2
2
)
iPr
gave the desired organometallic manganese complexes ( PONOP)Mn(CO)
2
iPr
H
(
PN P)Mn(CO)
2
Br, respectively, upon chelation to Mn(CO)
5
iPr
iPr
PNNNP ( PNNNP = N,Nꢀ-bis(diisopropylphosphino)-2,6-diaminopyridine) with
iPr
Mn(CO)
(
5
Br yielded
PNNNCO)Mn(CO)
loss of iPr PBr and C-N bond formation from a carbonyl ligand and NH, yielding a
a
pair of products, [( PNNNP)Mn(CO)
. The formation of the asymmetric chelate arises from a formal
3
][Br] and
iPr
3
2
iPr
Mn(I) amide core. The nitration reactions of ( PONOP)Mn(CO)
2
Br and
iPr
iPr
H
(
(
PN P)Mn(CO)
PONOP)Mn(CO)
2
Br were carried out using silver nitrite, yielding the nitro compounds
iPr
H
2
(NO
2
) and ( PN P)Mn(CO)
was nitrated under the same conditions to yield the
][FeCl NO]. This reactivity underlines the difference
between iso-valent iron and manganese centers. The manganese complexes
2
(NO
2
), respectively. The analogous
iPr
iron complex ( PONOP)Fe(CO)Cl
salt pair [( PONOP)Fe(CO)
2
iPr
2
3
iPr
iPr
H
(
PONOP)Mn(CO)
2
(NO
2
) and ( PN P)Mn(CO)
2
(NO
2
) were ineffective as oxygen
atom transfer reagents for a variety of substrates.
1
. Introduction.
1
Manganese is a bioactive metal present in a variety of metalloenzymes. Often
the manganese center catalyzes oxidative transformations, and specifically we are
interested in the reactivity of oxalate decarboxylase, wherein oxalate is converted to
2
carbon dioxide and formate. As a transition metal catalyst in the laboratory,
3
manganese is also well known for its oxidative transformations. Metal nitrites have
found use as oxidants in both organic synthesis as well as transition metal coordination
4
chemistry. We have been investigating the synthesis of a PNP supported manganese
nitro compound for the express purpose of oxygen atom transfer from the nitro group to
relevant substrates.
Figure 1. The three ligands explored in this study and their shorthand names are shown above.

Successful catalysis and reaction chemistry has been observed with a variety of
tridentate PNP ligand supported iron complexes. We have chosen three related PNP
ligands (Figure 1) with which to investigate the coordination of Mn(CO) Br. The
5
iPr
oxygen-linked PONOP ligand has been used as a support for iron complexes by
different groups and catalytically competent coordination complexes for the transfer
5
hydrogenation of aldehydes have been developed. Kirchner has investigated the
iPr
coordination and reactivity of PNNNP supported iron complexes and has found
6
iPr
H
certain complexes catalytically competent for ketone hydrogenation. Recently, PN P
complexes of iron have been successfully used for the dehydrogenation of formic acid
7
8
and methanol, the hydrogenation of esters to alcohols, the hydrogenation and
9
10
dehydrogenation of N-heterocycles, alcohols and ketones,
hydrogenation of aromatic and aliphatic nitriles. Ozerov has investigated diarylamido-
as well as the
1
1
based PNP ligands on manganese carbonyl complexes along with subsequent ligand
1
2
centered reactivity. Certain pentadentate bis(imino)pyridine derived PNP ligands have
also been used to synthesize manganese complexes that show high catalytic activity for
1
3
the hydrosilylation of aldehydes and ketones. Although the PNP ligand class has
found wide-ranging use with iron, tridentate PNP-supported manganese complexes
remain rare in the literature.
During our initial efforts to effect the conversion of oxalic acid into its
component parts, carbon dioxide and dihydrogen, one course of experiments led to the
investigation of PNP supported manganese carbonyl compounds. Within this line of
investigation we found a rational route to an uncommon class of nitro-manganese
complexes. The paucity of such complexes coupled with the lure of ligand-mediated
reactivity, specifically oxygen atom transfer reactions from a coordinated nitro group,
prompted us to investigate these nitro-manganese coordination complexes. Reported
herein are the reactions of ligation, nitration, and attempts at deoxygenation of a series
of PNP supported manganese carbonyl bromide complexes derived from Mn(CO) Br.
5
Silver nitrite was used as the nitro-source due to the facile removal of AgBr and fast
reaction times. Multiple attempts were made to deoxygenate the nitro ligands, but they
proved resilient to the reducing agents that were employed.
2
. Experimental
General Considerations.
All air- and moisture-sensitive manipulations were carried out using standard
Schlenk techniques or in an MBraun dry box containing a purified nitrogen atmosphere.
THF, diethyl ether, toluene, and N-hexane were dried on molecular sieves and shaved
sodium before use. N,N,-dimethyl formamide (DMF) and DMSO were purchased as
anhydrous solvents from Fisher Scientific and stored over 4 Å molecular sieves. THF-
d
8
, DMSO-d
dried over 4 Å molecular sieves. The chemicals: Mn(CO)
PMe , Phenylsilane, 1,2-dihydroanthracene, and N-butyllithium were ordered from
Fisher Scientific and were used as received. The compounds: PONOPFe(CO)Cl
6
, and C
6
D
6
were purchased from Cambridge Isotope Laboratories and
iPr
5
Br, AgNO
2
, PNHP, FeCl ,
2
3
iPr
5b
2
,
iPr
14 iPr
6d
PONOP,
PNNNP, were synthesized according to published procedures.
1
13
31
H NMR, C NMR, and P NMR spectra were recorded on a Bruker Avance
00 MHz spectrometer operating at 400.132 MHz, 100.627 MHz, and 161.978 MHz,
4

1
13
respectively. All H and C NMR chemical shifts are reported relative to SiMe using
4
1
13
the H (residual in the deuterated solvents) and C chemical shifts of the solvent as a
secondary standard. Paramagnetically shifted peaks are listed with the peak width at
half height (Hz). Infrared spectra were collected on a Thermo Scientific Nicolet iS10
spectrometer equipped with a Smart Omni transmission tool for the collection.
Elemental analysis was performed by Atlantic Microlab, inc. Several EA’s have values
outside of the accepted values; therefore NMR spectra are provided (SI) that label
impurities.
Single crystals suitable for X-ray diffraction were coated with n-paratone (dried
under reduced pressure overnight at 100 °C) oil in a drybox, placed on a nylon loop and
then transferred to the goniometer head of a Bruker AXS APEX II diffractometer
equipped with a graphite-monochromatized molybdenum Kꢁ X-ray tube ( = 0.71073
Å) and an APEX II CCD detector (complexes ) or to a Bruker D8 Quest equipped with
a graphite-monochromatized molybdenum Kꢁ X-ray tube ( = 0.71073 Å) and a
1
5
CMOS detector (complexes ). A hemisphere routine was used for data collection and
determination of lattice constants. The space group was identified and the data were
processed using the Bruker SAINT+ program and corrected for absorption using
1
6
SADABS. The structures were solved using direct methods (SHELXS) completed by
1
7
subsequent Fourier synthesis and refined by full-matrix least-squares procedures.
Complexe 7 was solved using Olex2 software with solvent suppression due to the
1
8
presence of a highly disordered diethyl ether solvent molecule.
iPr
Synthesis of ( PONOP)Mn(CO) Br (1).
2
To a 100 mL Schlenk flask was added 25 mL of fluorobenzene, 2.00 g (7.275 mmol) of
MnBr(CO) , and a stir bar. A syringe containing 5 mL of fluorobenzene and 2.620 g
7.640 mmol) of PONOP was used to add the ligand to the stirring manganese
solution. Upon addition of the ligand, the solution evolved gas. The reaction was stirred
at room temperature until gas generation ceased and the MnBr(CO) completely
5
iPr
(
5
dissolved, at which point the solution was brought to reflux for approximately ten
minutes. The solution was cooled to room temperature and volatiles were removed
under reduced pressure. The product was isolated by adding hexane to the residue and
mobilizing the solid, followed by isolation of the orange powder on a glass frit. This
iPr
yielded 3.66 g (94%) of ( PONOP)Mn(CO)
2
Br. Analysis for C19
H
31BrMnNO
4
2
P :
Calculated: C = 42.72%, H = 5.85%, N = 2.62%. Found: C = 43.04%, H = 5.93%, N =
1
2
.51%. H NMR (C
6
6
D ): 6.61 (t, 1H, J= 7.9 Hz, p-Py), 6.10 (d, 2H, J= 7.9 Hz, m-Py),
4
.05 (ddt, 2H, J= 14.5, 11.9, 7.2 Hz, iPr-CH), 2.72 (ddt, 2H, J= 14.3, 12.3, 7.9 Hz, iPr-
1
CH), 1.52-1.36 (m, 6H, iPr-CH
3
), 1.36-1.15 (m, 18H, iPr-CH
.72 (t, 1H, J= 7.9 Hz, p-Py), 6.76 (d, 2H, J= 7.9 Hz, m-Py), 3.86 (ddt, 2H, J= 14.5,
1.9, 7.2 Hz, iPr-CH), 3.05 (ddt, 2H, J= 14.3, 12.3, 7.9 Hz, iPr-CH), 1.56-1.40 (m,
3
). H NMR (THF-d
8
):
7
1
1
d
1
31
31
8H, iPr-CH
3
1
), 1.39-1.27 (m, 6H, iPr-CH
3
). P NMR (C
): 228.09, 225.74, 163.59 (t, J= 5.4 Hz), 142.15,
02.43 (t, J= 2.3Hz), 29.39 (t, 5.9 Hz), 28.69 (t, 9.4 Hz), 16.91 (t, 4.0 Hz), 16.82 (t, 4.4
6
D
6
): 231.57. P NMR (THF-
3
1
8
): 230.38. C{ H} NMR (THF-d
8
-1
Hz), 16.42, 15.65 (t, J= 1.4 Hz). IR (KBr, ꢂ CO): 1866, 1946 cm .
iPr
H
Synthesis of PN PMn(CO) Br (2).
2

To a 100 mL Schlenk flask was added 25 mL of fluorobenzene, 2.25 g (8.185 mmol) of
MnBr(CO) , and a stir bar. A syringe containing 5 mL of fluorobenzene and 2.50 g
8.185 mmol) of bis[(2-diisopropylphosphino)ethyl]amine was used to add the ligand to
5
(
the stirring manganese solution. Upon addition of the ligand, the solution evolved gas,
presumably CO. The reaction was stirred at room temperature until gas generation
ceased, at which point the solution was brought to reflux for approximately ten minutes.
The solution was cooled to room temperature and volatiles were removed under
reduced pressure. The product was isolated by adding hexane to the residue and
mobilizing the solid, followed by isolation of the orange powder on a glass frit. This
iPr
H
yielded 3.49g (86%) of PN PMn(CO) Br. A second batch of product could be
2
isolated by removing the volatiles of the mother liquor and re-mobilizing with hexane,
followed by isolation of the orange powder on a glass frit to yield an additional 0.330 g
for an overall 94% yield. Analysis for C18
H
37BrMnNO
2
P : Calculated: C = 43.56%, H
2
1
=
7.51%, N = 2.82%. Found: C = 43.71%, H = 7.40%, N = 2.75%. H NMR (C
6
D ):
6
3
1
2
1
.24 (ddt, 2H, J= 13.6, 9.7, 4.9 Hz), 2.96 (t, 1H, N-H, J= 12.8 Hz), 2.59 (q, 2H, J=
3.6, 12.7 Hz), 2.23 (dtt, 2H, J= 16, 8.7, 4.3 Hz), 1.97 (q, 2H, J= 12.6 Hz), 1.68 (dq,
H, J= 14.4, 3.9 Hz), 1.55-1.47 (m, 6H, iPr-CH
.15 (m, 6H, iPr-CH ), 1.14-1.04 (m, 6H, iPr-CH
): 232.72, 229.62, 52.77 (t, J= 5.2 Hz), 27.23 (t, 5.9 Hz), 26.17 (t, 9.4 Hz),
4.49 (t, 9.42 Hz), 20.38, 20.20, 18.93, 18.49 (t, J= 2.3 Hz). IR (KBr, ꢂ CO): 1824,
3
), 1.37-1.27 (m, 6H, iPr-CH ), 1.27-
3
13
31
1
3
3
). P NMR (C
6
6
D ): 81.22. C{ H}
NMR (C
2
1
6
D
6
-1
916 cm .
iPr
iPr
Synthesis of ( PNNNCO)Mn(CO)
A 100 mL Schlenk flask was charged with 25 mL of fluorobenzene, 1.00 g (3.638
mmol) of MnBr(CO) , and a stir bar. Under nitrogen flow, 1.245 g (3.640 mmol) of
PNNNP was added as a solid. The reaction mixture immediately began to evolve gas
3
(3) and [( PNNNP)Mn(CO)
3
][Br] (4).
5
iPr
iPr
and PNNNP dissolved quickly, while MnBr(CO) dissolved after roughly one hour.
5
The reaction was stirred at room temperature overnight and the formed off-white solid
was collected on a glass frit and washed with 2x10 mL of fluorobenzene followed by
2
x10 mL of N-hexane. This yielded a roughly 50:50 mixture of 3 and 4.
Isolation of 3.
Small quantities of ( PNNNCO)Mn(CO)
iPr
3
could be isolated in pure form by stirring
the mixture of 3 and 4 in 50 mL of THF warmed to 60 °C followed by a hot filtration of
the mixture. Concentration of the THF down to 10 mL, followed by cooling to -30 °C
iPr
gave an off white powder of ( PNNNCO)Mn(CO)
3
in a yield of 0.025 g.
Alternatively, the mixture of 3 and 4 was extracted with warm DMF (7 mL) and filtered
on a glass frit. The solid was washed with 3 mL of DMF, followed by 2 x 5 mL of
benzene then 2 x 5 mL of diethyl ether. The mother liquor was concentrated under
reduced pressure to remove benzene and ether. The yellow mother liquor (~10 mL) was
then mixed with 3 mL of benzene and 3 mL of N-hexane and cooled to -30 °C. The
white solid that formed was filtered off and washed with benzene. The remaining
mother liquor was removed to a Schlenk line in a Schlenk flask and the DMF was
removed with heating. The residue was mobilized with THF and filtered, yielding 0.463
iPr
g (64% of ½ of the starting manganese) of analytically pure ( PNNNCO)Mn(CO) .
3
Analysis for C15
H
19MnN
3
O P: Calculated: C = 46.05%, H = 4.90%, N = 10.75%.
4

1
Found: C = 46.56%, H = 5.92%, N = 8.09%. H NMR (C
H, CO-NH-Py), 8.48 (d, 1H, P-NH-Py, J= 4.5 Hz), 7.41 (t, 1H, p-Py, J= 8.0 Hz), 6.27
d, 1H, m-Py, J= 7.9 Hz), 6.17 6.27 (d, 1H, m-Py, J= 7.8 Hz), 2.39 (dp, 2H, iPr-CH, J=
6
D
6
): (DMSO-d
6
): 10.10 (s,
1
(
3
1
13
1
1
0.8, 7.0 Hz), 1.28-1.08 (m, 12H, iPr-CH
): 225.75 (d, J= 11.0 Hz), 223.74, 217.53 (d, J= 12.0 Hz), 161.13 (d,
J= 12.6 Hz), 157.16 (d, J= 3.7 Hz), 140.19, 98.20 (d, J= 6.5 Hz), 96.51, 31.16 (d, J=
3.5 Hz), 18.58 (d, J= 6.0 Hz), 18.42 (d, J= 2.5 Hz). IR (KBr, ꢂ CO): br. 1977-1821
3
). P NMR (DMSO-d
6
): 144.49. C{ H}
NMR (DMSO-d
6
2
-
1
cm .
Isolation of 4.
The solid that formed from the DMF solution was washed successively with THF (2
x10 mL), diethyl ether (2 x 30 mL), and finally N-hexane (2 x 10 mL). The solid was
kept under reduced pressure to remove volatiles. This left an off-white powder (0.890
g, 87% from ½ of the starting manganese) that was identified as
iPr
[
4
(
( PNNNP)Mn(CO)
3
][Br]. Analysis for C20
H
33BrMnN
3
O
3
P : Calculated: C =
2
1
2.87%, H = 5.94%, N = 7.50%. Found: C = 47.29%, H = 6.12%, N = 7.11%. H NMR
DMSO-d ): 9.09 (s, 2H, N-H), 7.48 (t, 1H, p-Py, J= 8.0 Hz), 6.45 (d, 2H, m-Py, J= 8.0
Hz), 2.81-2.70 (m, 4H, iPr-CH), 1.41 (dd, 12H, iPr-CH
6
3
, J= 15.7, 6.4 Hz), 1.28 (dd,
3
1
13
1
1
2H, iPr-CH
3
, J= 16.6, 7.3 Hz).
P NMR (DMSO-d ): 133.79. C{ H} NMR
6
(
DMSO-d ): 221.01, 215.18, 160.75 (t, J= 7 Hz), 140.85, 99.16 (t, J= 3.1 Hz), 30.43 (t,
6
-1
J= 13.2 Hz), 17.98, 17.80. IR (KBr, ꢂ CO): br. 1996-1826 cm . Rinsing 4 with copious
amounts of ether and removing the volatiles under reduced pressure for extended
periods of time was not sufficient to remove DMF and THF from the compound, as
seen in the H and C NMR spectra. We attribute the high carbon and hydrogen
numbers observed in the elemental analysis to the presence of these solvents in the
solid samples.
1
13
iPr
iPr
Synthesis of ( PNNNCO)Mn(CO)
3
(3) and [( PNNNP)Mn(CO) ][Br] (4) in a
3
closed vessel.
A 50 mL stainless steel vessel was charged with 0.110 g (0.400 mmol) of MnBr(CO)
5
and a stir bar in an inert atmoshere glovebox. This vessel was transferred to a
manometer apparatus outside of the glovebox while maintaining inert atmosphere in the
iPr
vessel. Under a flow of N , 0.140 g (0.410 mmol) of PNNNP, dissolved in 12 mL of
2
fluorobenzene, was syringed into the stainless steel vessel and the reaction was
immediately sealed. The pressure began to rise slowly, at which point heating was
turned on and the reaction was allowed to proceed with stirring for 72 hours at 60 °C.
The pressure rose to roughly 7.5 psi over this period of time. After the reaction was
brought to room temperature, the pressure was vented, the volatiles were removed
1
under reduced pressure, and the product distribution was assayed via H NMR
spectroscopy. The ration of 3:4 skewed to favor the formation of 4 by roughly 10 %
(
40:60).
iPr
Observation of ( PNNNP)Mn(CO)
2
(Br) (5).
In a 25 mL Schlenk flask, 0.100 g of 4 was dissolved in 5 mL of DMSO-d
6
. The
Schlenk flask was moved to a Schlenk line and heated to 105 °C while slightly open to
vacuum. The reaction was stirred for four hours, over the course of which the color

1
went from near colorless to yellow. A H NMR spectrum of the reaction mixture was
1
obtained, showing a clean partial conversion to the desired complex 5. H NMR
(
DMSO-d
Hz), 3.28 (m, 2H, iPr-CH), 3.28 (m, 2H, iPr-CH), 1.40-1.30 (m, 18H, iPr-CH
m, 6H, iPr-CH ), (the isopropylmethyl groups of 4 and 5 overlap significantly). P
NMR (DMSO-d
6.52, 18.82, 18.57, 18.05, 17.13.
6
): 8.34 (s, 2H, N-H), 7.23 (t, 1H, p-Py, J= 8.0 Hz), 6.25 (d, 2H, m-Py, J= 8.0
3
), 1.13
3
1
(
3
1
3
1
6
): 133.57. C{ H} NMR (DMSO-d ): 161.18, 138.30, 97.23, 27.96,
6
2
iPr
Synthesis of ( PNNNP)Mn(Cl)
A 100 mL round bottom flask was charged with 2.0 g (5.858 mmol) of
PNNNP, 0.735 g of MnCl (5.850 mmol) and roughly 30 mL of THF. The reaction
was allowed to stir overnight. Over that time original pink spheres of MnCl were
2
(6).
iPr
2
2
replaced with a flocculent white precipitate. White product was further precipitated
upon the addition of 40 mL of N-hexane. The precipitate was collected on a glass frit,
rinsed with 2 x 30 mL of hexane, and dried under reduced pressure. This yielded 2.35 g
iPr
(
87 %) grams of ( PNNNP)Mn(Cl) (6) as an off-white powder. Single crystals
2
suitable for X-ray diffraction were grown from the mother liquor of 6 by slow
evaporation under reduced pressure. Analysis for C17 MnN : Calculated: C =
3.70%, H = 7.12%, N = 8.99%. Found: C = 45.54%, H = 6.97%, N = 8.48%. H NMR
THF-d ): 12.2 (1140 Hz). µeff (Evans, DMSO-d , 23 °C, ꢃ ): 5.77. THF was
H
33Cl
2
P
3 2
1
4
(
8
6
B
1
consistently present in the H NMR spectrum of the complex, indicating strong non-
covalent interactions between the solvent and the complex. We attribute the
unsuccessful elemental analysis results to the presence of THF in the samples.
iPr
Observation of ( PNNNP)
3
Mn (7).
2
A 100 mL round bottom flask was charged with 0.500 g (1.070 mmol) of 6 and
3
5 mL of fluorobenzene. NaHMDS (0.400g, 2.181 mmol) was added portion-wise over
the course of five minutes. The white slurry turned yellow and the solution became
clear as the starting material reacted. After the addition was complete, the reaction was
allowed to stir for an hour, at which time the solution was filtered over Celite and the
volatiles were removed. The residue was taken into fluorobenzene and layered with
hexane. This yielded 0.135 g (12 % based on the amount of ligand present) of a yellow
iPr
powder identified as ( PNNNP)
3
Mn (7). More product could be gathered by
2
resubmitting the residue to the same crystallization method. Crystals were grown from
a concentrated ether solution of 7 allowed to slowly evaporate over the course of a
weekend. Complex 7 is NMR silent in either THF-d
8
or benzene-d . The limited
6
solubility and lack of spectroscopic handles of the material hindered attempts to acquire
adequate characterization of complex 7.
iPr
Synthesis of ( PONOP)Mn(CO)
2
(NO ) (8).
2
A fluorobenzene (5 mL) solution of 0.150 g (0.281 mmol) of
PONOP)Mn(CO) Br (1) was stirred overnight with 0.044 g (0.282 mmol) of silver
iPr
(
2
nitrite. The light yellow solution was filtered through Celite and cooled to -30 °C
before being layered with 5 mL of N-hexane. After several days pale yellow crystals
had formed that were isolated by decantation and washing with N-hexane before being
placed under reduced pressure to remove volatiles. This gave 0.115 g (81 %) of an off-

iPr
white solid identified as ( PONOP)Mn(CO)
2
(NO
2
). Analysis for C19
H
31MnN
2
O
6
P
2
:
Calculated: C = 45.61%, H = 6.25%, N = 5.60%. Found: C = 46.78%, H = 6.37%, N =
1
5
.42%. H NMR (C
6
6
D ): 6.75 (t, 1H, J= 8 Hz), 6.19 (d, 2H, J= 8 Hz), 2.75 (tdd, 2H, J=
1
CH
3.6, 9.1, 6.4 Hz, iPr-CH), 2.57 (dh, 2H, J= 14.2, 7.2 Hz, iPr-CH), 1.26 (m, 12H, iPr-
3
1
3
), 1.18 (q, 6H, J= 7.4 Hz, iPr-CH
3
), 1.08 (q, 6H, J= 6.8 Hz, iPr-CH
): 224.86, 163.58 (t, J= 5.3), 141.67, 102.39,
0.88 (t, J= 6.8 Hz), 28.40 (t, J= 10 Hz), 17.65 (t, J= 4.1 Hz), 17.30 (t, J= 3.5 Hz),
6.97, 15.66. Only one carbonyl resonance was located. IR (KBr, ꢂ CO): 1878 and
3
); P NMR
1
3
1
(
C
6
D
6
): 232.92; C{ H} NMR (C
6
D
6
3
1
1
-1
955 cm .
iPr
H
Synthesis of ( PN PMn)(CO)
2
(NO
2
) (9).
A fluorobenzene (5 mL) solution of 0.150 g (0.302 mmol) of
iPr
H
(
PN P)Mn(CO) Br (2) was stirred overnight with 0.047 g (0.303 mmol) of silver
2
nitrite. The light yellow solution was filtered through Celite and cooled to -30 °C
before being layered with 5 mL of N-hexane. After several days pale yellow crystals
had formed that were isolated by decantation and washing with N-hexane before being
placed under reduced pressure to remove volatiles. This gave 0.095 g (69 %) of an off-
iPr
H
white solid identified as ( PN PMn)(CO)
diffraction studies were grown in the same manner. Analysis for C18
Calculated: C = 46.76%, H = 8.07%, N = 6.06%. Found: C = 44.80%, H = 7.18%, N =
2
(NO ). Single crystals suitable for X-ray
2
H
37MnN
2
O
4
2
P :
1
5
.68%. H NMR (C
br s, 2H), 1.49 (m, 6H, iPr-CH
br s, 2H), 0.92 (m, 6H, iPr-CH
29.15, 52.12 (t, J= 5.1 Hz), 27.82 (t, J= 8.8 Hz), 26.05 (t, J= 6.6 Hz), 23.89 (t, J= 9.3
Hz), 20.11, 19.84, 18.66, 17.55. Only one carbonyl resonance was located. IR (KBr, ꢂ
6
D
6
): 5.55 (br s, 1H, N-H), 2.67 (br s, 2H), 2.22-1.95 (m, 6H), 1.66
), 1.34 (m, 6H, iPr-CH ), 1.20 (m, 6H, iPr-CH ), 1.06
): 86.40. C{ H} NMR (C ):
(
(
3
3
3
3
1
13
1
3
). P NMR (C
6
D
6
6
D
6
2
-1
CO): 1844 and 1928 cm .
iPr
Synthesis of [( PNNN)PMn(CO)
3
][(NO )] (10).
2
iPr
A slurry of 0.200 g (0.357 mmol) of [( PNNNP)Mn(CO) ][Br] (4) in 3 mL
3
DMF was stirred with 0.056 g (0.360 mmol) of silver nitrite overnight. The solution
was filtered through Celite, which was then rinsed with 2 mL of THF. The solution was
layered with 3 mL diethyl ether at room temperature. After the solutions had mixed, a
white powder had formed. The mother liquor was decanted and placed at -30 °C. The
remaining powder was washed with 2 mL of THF and 10 mL of diethyl ether and
volatiles were removed under reduced pressure, leaving 0.140 g (75 %) of a white
iPr
powder identified as [ PNNNPMn(CO)
3
][(NO
2
)]. Analysis for C20
H
33MnN
4
O
5
2
P :
Calculated: C = 45.64%, H = 6.32%, N = 10.64%. Found: C = 44.60%, H = 6.03%, N =
1
9
(
.51%. H NMR (DMSO-d
6
): 9.22 (br. s, 2H, N-H), 7.47 (t, 1H, p-Py, J= 8.0 Hz), 6.37
, J= 15.7,
): 133.51.
): 221.01, 215.12, 160.86 (t, J= 7 Hz), 140.88, 99.11 (t, J=
d, 2H, m-Py, J= 8.0 Hz), 2.83-2.68 (m, 4H, iPr-CH), 1.40 (dd, 12H, iPr-CH
.4 Hz), 1.27 (dd, 12H, iPr-CH
C{ H} NMR (DMSO-d
.1 Hz), 30.48 (t, J= 13.2 Hz), 17.92, 17.80. IR (KBr, ꢂ CO, NO
3
3
1
6
3
, J= 16.6, 7.3 Hz).
P NMR (DMSO-d
6
1
3
1
6
-1
3
1
2
): br. 1996-1826 cm ,
-1
13
689 cm . THF was consistently present in the C NMR spectrum of the complex,
even after prolonged exposure to reduced pressure.
iPr
Synthesis of [( PONOP)Fe(NO)(CO)][FeCl NO] (12).
3

A 20 mL scintillation vial was loaded with 0.100 g (0.201 mmol) of
PONOPFe(CO)Cl (11) and 5 mL of THF. To this stirring slurry was added AgNO
0.031 g, 0.202 mmol) as a solid. The reaction immediately turned dark red/brown in
iPr
2
2
(
color. The reaction was allowed to stir for one hour, at which time the solution was
filtered over Celite and placed at -30 °C. When the solution was cool, hexane (~ 7 mL)
was carefully layered on top of the THF solution. The layered solution was allowed to
sit undisturbed for one week, after which time dark clumps of crystals had formed on
the bottom of the vial. After decanting the mother liquor and removing volatiles under
iPr
reduced pressure, 0.045 g (70 %) of [( PONOP)Fe(NO)(CO)][FeCl NO] were
3
recovered. Cutting and separating a fragment from a cluster of the recovered crystalline
solid resulted in a single crystal suitable for X-ray diffraction. Analysis for
C
3
19
H
31Cl
2
Fe
3.88%, H = 4.93%, N = 4.05%. H NMR (THF-d
s, 2H, 42 Hz), 2.50 (br. s, 4H, 65 Hz), 1.31 (br. s, 24H, 67 Hz). µeff (Evans, THF-d
2
N
2
O
5
P : Calculated: C = 33.29%, H = 4.81%, N = 6.33%. Found: C =
2
1
8
): 7.75 (br. s, 1H, 29 Hz), 6.69 (br.
, 23
): 3.80. IR (KBr, ꢂ NO, CO): 1732, 1780, 1948 cm . The low nitrogen content
8
-1
°C, ꢃ
B
for the EA was consistent over several attempts. The IR and X-ray confirm one nitrosyl
per iron and only one carbonyl present.
3
. Results and Discussion
3
.1 Synthesis of PNP-manganese dicarbonyl bromide complexes
Few low-spin synthons for manganese are readily available except for
Mn(CO) Br. Rather than perform alkali metal reductions of the PNP-supported
5
manganese dihalides in the presence of CO, these initial studies utilized the
commercially available Mn(I) precursor. Ligation of a meridional PNP chelate will
likely yield a species that maintains the low-spin ground state of the starting manganese
iPr
iPr
H
complex. The two initial ligands used in this study, PONOP and PN P, were both
successfully chelated onto the manganese center with concurrent loss of three
iPr
equivalents of CO to yield the complexes ( PONOP)Mn(CO) Br and
2
iPr
H
(
PN P)Mn(CO)
2
Br, complexes 1 and 2, respectively (Scheme 1, a and b).
a)
b)
Figure 2. The solid-state structures of 1 (a) and 2 (b) are shown at 30 % probability ellipsoids. Hydrogen
atoms, except for N-H, have been removed for clarity.
iPr
1
(
PONOP)Mn(CO) Br, 1, was isolated as an orange powder that exhibits a H-
2
NMR spectrum consistent with a diamagnetic complex. The resonances of the proton
NMR spectrum are also indicative of a top-bottom inequivalent complex, with two sets

of isopropyl resonances. The carbonyl resonances appeared at 228.09 and 225.74 ppm
1
3
-1
in the C NMR spectrum, and the two intense bands at 1866 and 1946 cm are
assigned to the asymmetric and symmetric CO stretches, respectively. A solid-state
structure was obtained (Figure 2) in order to verify the structure of the complex, as
well as to build a library of ligand metrics with which to compare similar metal
complexes.
iPr
iPr
H
iPr
Scheme 1. The reactivity of PONOP (a) PN P (b) and PNNNP (c) with Mn(CO)
Number notation and isolated yields are given in bold under the compound.
5
Br is summarized.
iPr
H
(
PN P)Mn(CO)
2
Br (2) was isolated as the syn complex, where the N-H is syn
1
to the bromide ligand. The H NMR spectrum indicated that complex 2 is a diamagnetic
molecule that contains four isopropyl methyl resonances as well as the N-H resonance
at 2.96 ppm. The C NMR spectrum of 2 has carbonyl resonances at 232.72 and
29.62 ppm. Infrared spectroscopy in KBr displays two strong bands assigned to the
carbonyl stretches at 1916 and 1824 cm . These stretches are lower in energy than
those found in 1 as is expected for the more electron donating ( PN P) ligand.
1
3
2
-
1
iPr
H
a)
b)

Figure 3. The solid-state structures of 3 (a) and 4 (b) are shown at 30 % probability ellipsoids. Hydrogen
atoms, except for N-H, have been removed for clarity.
iPr
6d
Upon reaction of Mn(CO) Br with the Kirschner-reported chelate PNNNP
in fluorobenzene, two manganese complexes are formed in a roughly 50:50 ratio. H
NMR investigations of the reaction mixture show resonances that are consistent with a
5
1
left/right inequivalent C molecule 3, and a C2v symmetric molecule 4 (Scheme 2). The
s
similar solubility properties of these complexes in ethers and hydrocarbon solvents
initially complicated the separation of the two compounds. However, extraction of the
mixture of 3 and 4 into DMF completely dissolved 3, leaving 4 as a spectroscopically
pure, off-white powder. The DMF could be removed with mild heating (~ 50 °C) under
vacuum, and the residue washed with THF to afford the purified 3. Carbonyl stretching
1
3
frequencies, C NMR shifts and selected metrical parameters of 3 and 4 are
summarized for direct comparison (Table 1). Single-crystals suitable for X-ray
diffraction were grown and solid-state structures were obtained to unambiguously
verify the identity of 3 and 4 (Figure 3).
5
Table 1. Selected properties of the two products, 3 and 4, that result from the reaction of Mn(CO) Br and
iPr
PNNNP.
Distance (Å), Angles(°)
Mn(1)-P(1)
Mn(1)-C(6)
Mn(1)-N(2)
P(1)-N(1)
3
4*
2.263 (1)
-
2.059 (4)
1.689 (3)
2.266 (1)
2.003 (1)
2.019 (1)
-
P(1)-N(3)
C(6)-N(1)
1.708 (1)
1.407 (2)
160.71 (4)
-
-
-
-
P(1)-Mn(1)-C(6)
P(1)-Mn(1)-P(1)
N(2)-Mn(1)-C(11)
N(2)-Mn(1)-C(15)
C(13)-Mn(1)-C(14)
C(10)-Mn(1)-C(12)
163.76
177.7
-
-
177.46 (6)
167.55 (6)
-
10.10, 8.48
225.75, 223.74, 217.53 221.01, 215.18,
-
176.4
9.09
1
δ (N-H) H NMR (ppm)
1
3
δ (CO) C NMR (ppm)
*
The solid-state structure of 4 contains a mirror plane through the center of the molecule, and thus only
has one manganese-phosphorus distance.
15
Scheme 2. A previously reported formation of an amide bond from a manganese carbonyl complex.

i
Complex 3 arises from the formal loss of Pr
2
PBr and amide formation from the
i
31
remaining pyridine “NH” fragment and CO. However, Pr Br is not observed in the P
NMR spectrum of the reaction mixture, but several unidentified phosphorus signals
were detected, ranging from approximately -50 ppm to 220 ppm in the P NMR
spectrum. Similar transformations, a carbonyl insertion into amides to form the metal-
formamide moiety, have been observed previously in the reaction of dimanganese
2
1
9
3
1
2
0
nonacarbonyl acetonitrile (Mn
2
(CO) MeCN) with thioamides (Scheme 2). This
9
reaction proceeds in low yields (10% isolated yield with thioacetamide and 7% with
1
thiobenzamide). Both N-H’s remain in the complex, observed both by H NMR
spectroscopy and in the solid-state structure (Table 1). Three separate carbonyl carbon
1
3
resonances were observed by C NMR spectroscopy for 3, one each for the two CO
ligands and a third for the formed formate moiety. The bond length of P(1)-N(1) of
1
.708(1) Å is consistent with other N-P bonds that have the N-H bond intact.
Scheme 3. The product distribution from the attempted decarbonylation of compound 4 is shown.
iPr
The other 50% of the yield from the complexation of PNNNP with
iPr
Mn(CO)
5
Br is preserved as the expected [ PNNNPMn(CO) ][Br] 4. Unlike the
3
iPr
iPr
H
PONOP and PN P supported compounds, 4 is isolated as the salt pair and the
manganese retains three carbonyl ligands. The limited solubility can be attributed to the
extended salt lattice that is observed in the solid-state structure that was obtained from a
DMSO solution of 4. Performing the reaction in a closed, stainless steel manifold
altered the product ratio of 3:4 to 40:60, indicating that select alteration of the reaction
conditions may yield either 3 or 4 preferentially. In this case, retaining the released CO
in the reaction mixture increased the formation of 4. Heating complex 4 in a DMSO
solution under vacuum at 100 °C for 5 hours resulted in the loss of one carbonyl group
and the formation of the bromine-coordinated manganese complex 5 in roughly 60%
yield, with the remaining material persisting as the starting complex (Scheme 3).
Further heating under reduced pressure generated only slightly more pure 5, but always
contaminated with appreciable quantities of 4. This reactivity is reminiscent of a
previously reported inability to fully remove a carbonyl ligand from a PNP manganese
1
2
complex.
iPr
The bifurcated product mixture arising from PNNNP and Mn(CO)
5
Br led us
with PNNNP to form a single manganese starting
material. Not surprisingly, the coordination proceeded smoothly and in high yield to
iPr
to explore the chelation of MnCl
2
iPr
form the off-white flocculent powder of PNNNPMnCl (6; Scheme 4). Complex 6
possesses an uninformative H NMR spectrum, with a single broad (1140 Hz peak-
width at half-height) resonance located at 12.2 ppm. An Evans method measurement of
2
1

6
confirmed the high-spin Mn(II) oxidation state of the metal with a ꢃeff of 5.77 ꢃ
close to the expected spin only value of 5 unpaired electrons (5.92 ꢃ ). Other tridentate,
meridional-chelating ligands coordinated to MnCl have also been reported to maintain
ꢄ
,
ꢄ
2
2
1
the high-spin state. Single-crystal X-ray diffraction confirmed the structure of 6.
Pr
Scheme 4. The reactivity of MnCl
2
with PNNNP and subsequent dehydrohalogenation reactivity are
summarized.
a)
b)
Figure 4. The solid-state structures of 6 (a) and 7 (b) are shown at 30 % probability ellipsoids. Hydrogen
atoms, except for N-H, have been removed for clarity. A THF molecule (for 6) and a diethyl ether
molecule and isopropyl methyl groups (for 7) have also been removed for clarity.
The dehydrohalogenation of 6 was performed to free the manganese
coordination sites of chloride (Scheme 4). In THF or the non-coordinating solvents
toluene or fluorobenzene, the dehydrohalogenation resulted in the formation of a
bimetallic, three ligand compound 7 (Figure 4b). Even when the reaction was
performed in the presence of 10 equivalents of trimethylphosphite, the formation of the
bimetallic complex dominates the reactivity. Both manganese centers adopt a pseudo-
tetrahedral geometry and coordinate to three nitrogen atoms, one nitrogen from the
central ligand and two nitrogen atoms from a second ligand, and a phosphorus atom
from the third ligand. The manganese centers are not within bonding distance at 3.433
Å (the covalent radius of manganese is 1.37 Å). The amine hydrogen (N-H) atoms of
the ligand were found and refined in the solid state structure on N(6) and N(9). The
bond distances are consistent with this assignment as N(6)-C(22) and N(9)-C(39) are
roughly 0.02 Å longer than the amide nitrogen atoms. Further evidence for protonation
of N(6) and N(9) is found in the nitrogen phosphorus bond lengths, with N(6)-P(4) and
N(9)-P(6) being longer than N(1)-P(1) and N(3)-P(3) by an average of 0.025 Å and
N(4)-P(3) and N(7)-P(5) by 0.05 Å. This leaves a total of four anionic charges for the
+
three ligands, which is consistent with two manganese 2 centers as can be expected
given the starting material’s spin-state and the tetrahedral environment of each of the
1
two manganese centers. This also explains the lack of NMR signals in the H NMR
spectrum.
Table 2. Select metrical parameters of the solid-state structure of 7 are presented.

Distance (Å), Angles(°)
Mn(1)-N(1)
Mn(1)-N(4)
Mn(1)-N(5)
Mn(1)-P(5)
7
2.016 (2)
2.122 (2)
2.198 (2)
2.538 (1)
3.433
Mn(1)-Mn(2)
Mn(2)-N(3)
2.024 (2)
2.134 (2)
2.241 (2)
2.538 (1)
1.679 (3)
1.681 (3)
1.656 (3)
1.699 (3)
1.655 (3)
1.714 (3)
1.383 (4)
1.372 (4)
1.362 (4)
1.387 (4)
1.361 (4)
1.381 (4)
118.19 (9)
126.25 (9)
114.70 (7)
61.93 (9)
135.80 (9)
115.65 (9)
114.78 (7)
61.21 (8)
Mn(2)-N(7)
Mn(2)-N(8)
Mn(2)-P(3)
P(1)-N(1)
P(2)-N(3)
P(3)-N(4)
P(4)-N(6)
P(5)-N(7)
P(6)-N(9)
N(1)-C(1)
N(3)-C(5)
N(4)-C(18)
N(6)-C(22)
N(7)-C(35)
N(9)-C(39)
N(1)-Mn(1)-N(5)
N(1)-Mn(1)-N(4)
N(1)-Mn(1)-P(5)
N(4)-Mn(1)-N(5)
N(3)-Mn(2)-N(7)
N(3)-Mn(2)-N(8)
N(3)-Mn(2)-P(3)
N(7)-Mn(2)-N(8)
3
.2 Reactivity with silver nitrite
The synthesis of manganese nitro compounds was performed with the use of
stoichiometric quantities of silver nitrite in either THF or fluorobenzene (Scheme 5).
The reaction of 1 with silver nitrite proceeded smoothly with concomitant formation of
iPr
a grey precipitate, AgBr, to yield ( PONOP)Mn(CO)
2
(NO ), (8). Compound 8 was
2
isolated as an off-white solid. Upon prolonged sitting at room temperature in an inert
1
atmosphere, a purple discoloration concurrent with a broadening of the signals in the H
NMR spectrum. This decomposition occurred to only a small extent in the solid state
and 8 was easily purified by recrystallization. Spectroscopic characterization of the
purified 8 revealed the coordination geometry as similar to that of 1, with two distinct
1
13
isopropyl resonances identified in both H and C NMR spectra. The carbonyl

-1
stretching frequencies of 1878 and 1955 cm are also similar to the values observed for
1
. A solid-state structure confirmed the identity of 8 (Figure 5a).
The same reaction was performed using complex 2. The nitration occurred in a
similar manner and yielded the pale yellow nitro manganese complex
iPr
H
(
PN P)Mn(CO)
2
(NO ), (9). NMR investigations led to the assignment of 9 as the
2
nitro-complex analogous to the bromide 2. Complex 9 exhibited four isopropyl methyl
1
resonances in the H NMR spectrum, and the N-H resonance was located at 5.55 ppm,
far downfield compared to the N-H shift of 2 that appears at 2.35 ppm. This shift most
likely arises from the hydrogen bonding of the N-H proton to the nitro group of the
manganese. This is consistent with previously described hydrogen bonding properties
of the N-H of the chelate to a second ligand on the metal; a stronger hydrogen bond
1
7b
results in a further downfield resonance in the H NMR spectrum. In this case, the
nitro-group of 9 is forming a stronger hydrogen bond than the bromide of 2 to the N-H
1
3
of the chelate, hence the more downfield shift of 5.55 ppm. Obtaining a C NMR
spectrum of 9 revealed a single carbonyl resonance at 229.15 ppm and a pattern
associated with the ligand similar to that observed with 2. A solid-state structure of 9
(
Figure 5b) reveals a close-contact hydrogen bond between the proton of the chelate
nitrogen and the nitro group on the manganese.
Scheme 5. A summary of the nitration of 1 (a), 2 (b), 4 (c), and 11 (d) to yield 8, 9, 10, and 12,
respectively, is shown.

The addition of silver nitrite to the salt pair 4 yielded the salt pair 10 (Scheme
c). When the reaction was performed in THF, a grey precipitate formed, but filtration
5
through Celite yielded negligible quantities of product. When the reaction was carried
out in DMF, 10 could be isolated in good yield. There was no evidence for the
displacement or oxidation of carbonyl by the nitrite moiety. Complex 10 was nearly
identical to 4 by NMR and IR spectroscopies and is most likely the salt pair
iPr
[
PNNNPMn(CO)
3
][NO ]. Attempts to grow single crystals were met with mild
2
success; thin plates were isolated, but the single-crystals were weakly diffracting and
only connectivity was obtained from the experiment (SI), confirming the assignment of
the structure of 10.
a)
b)
c)
d)
iPr
Figure 5. a) The solid-state structure of the nitration product 8, ( PONOP)Mn(CO)
2 2
(NO ), is shown at
3
0 % probability ellipsoids. Hydrogen atoms have been omitted for clarity; b) The solid-state structure of
iPr
H
the nitration product 9, ( PN P)Mn(CO)
2 2
(NO ), is shown at 30 % probability ellipsoids. Hydrogen
atoms except for the N-H have been omitted for clarity; c) The cationic portion of solid-state structure of
iPr
+
1
2, [( PONOP)Fe(CO)(NO)] , is shown at 30 % probability ellipsoids. Hydrogen atoms have been
-
3
omitted for clarity; d) The anionic portion of solid-state structure of 12, [FeCl (NO)] , is shown at 30 %
probability ellipsoids. Disorder has been omitted for clarity.
Previously reported iron complexes that are iso-electronic with these manganese
complexes have been known for some time. The reactivity of the iron complexes with
silver nitrite would give a direct comparison to the results obtained with the manganese,
iPr
5b
and ( PONOP)Fe(CO)Cl
2
, 11, was chosen as the iron analogue for nitration. The
reaction of 11 with silver nitrite produced a dark red/brown crystalline solid identified
iPr
+
as [( PONOP)Fe(CO)(NO)] using NMR and IR spectroscopies, and single crystal X-
1
ray diffraction (Figure 5c). The H NMR spectrum of 12 showed four broad resonances
attributed to the PONOP ligand. A solid-state structure was collected to provide more
iPr
information on the connectivity of the complex. The anion of 12 was revealed to be a

-
trichloro-iron nitrosyl, [FeCl
3
(NO)] (Figure 5d), a moiety first observed by Connelly
2
2
23
in 1976, which has been sparsely reported up until the most recent report by Lippard
whereby bis(imidazole) iron is used in nitrosyl detection. The carbonyl stretch of
( PONOP)Fe(CO)(NO)] was assigned to the strong band at 1948 cm , blue-shifted
2
4
iPr
+
-1
[
compared to the previously reported carbonyl stretches of the neutral complex
iPr
-1 5b
(
PONOP)Fe(CO) reported at 1824 and 1876 cm . This expected strengthening of
2
the CO bonds arises from the cationic iron center of 12 having less electron density to
*
back-donate into the ꢅ orbitals of the carbonyl ligands compared the neutral
iPr
-
-1
(
PONOP)Fe(CO)
similar to other “FeX
reported in the literature. The nitrosyl stretch attributed to [( PONOP)Fe(CO)(NO)]
2
. The nitrosyl stretch attributed to the [FeCl
3
(NO)] of 1790 cm is
-1
3
NO” (X= Cl, Br; ꢆ NO = 1802 cm for both in CH Cl ) anions
2
2
1
5
iPr
+
-1
of 1732 cm is comparable to another TBP iron compound containing both a CO and
an NO ligand. The groups of Roustan and Berke have reported complexes of the type
2
5
L (NO)(CO)FeX, where L = monodentate phosphines and X = hydride or chloride.
2
+
26
Cationic [L
between 1780 cm and 1697 cm and CO stretches between 1975 cm and 1915 cm .
These values are consistent with the values obtained for 12. The ꢃeff of 3.8 ꢃ is also
3
(NO)(CO)Fe] compounds, reported by Johnson, have NO stretches
-1
-1
-1
-1
B
-
22
consistent with reported values for the [FeCl (NO)] moiety.
3
The oxidation of a variety of organic substrates was attempted with 8 and 9 with
no success. A stoichiometric quantity of the olefins 1-hexene or 1,3-cyclooctadiene was
added to THF solutions containing either 8 or 9, which were subsequently heated to 70
1
°
C. There was no change in the H NMR spectrum of either starting material after
heating overnight. Both 9,10-dihydroanthracene and 5 equivalents of phenylsilane with
either 8 or 9 produced no change in the starting nitro-manganese complexes. This series
of experiments confirms the stability of the nitro-moiety in these compounds and their
lack of reactivity under various conditions.
4
. Summary/Conclusions
A series of PNP chelates were added to Mn(CO) Br in an attempt to gain access
5
iPr
iPr
H
to low spin manganese(I) starting materials. Both PONOP and PN P ligands were
successfully chelated to the manganese center with the concurrent loss of three
equivalents of CO to yield the (PNP)Mn(CO)
2
Br complexes. Upon reaction of
iPr
PNNNP with Mn(CO)
form. A carbonyl ligand from [( PNNNP)Mn(CO)
5
Br, two complexes were formed that could be isolated in pure
iPr
3
][Br] could be removed to give the
iPr
iPr
neutral complex ( PNNNP)Mn(CO)
2
Br, although not in pure form. PNNNP was
capable of yielding three different manganese complexes for further study.
iPr
Coordination of MnCl with PNNNP gave the high-spin manganese (II) chloride
2
complex. The product resulting from dehydrohalogenation of 6 is dimanganese,
trisligand complex. Structural varieties similar to 6 remain of interest to us and we
continue to pursue the synthesis reactivity of such systems.
The nitration of the manganese complexes was achieved with the use of silver
nitrite to furnish the nitro-manganese complexes in high yields. Unfortunately, no
reactivity with the coordinated nitro group was observed with a variety of organic
substrates. Although these compounds do not display the desired reactivity, several of
the manganese materials presented here show promise in other chemistry. We continue

to research the reactivity of PNP-supported manganese complexes and will present our
findings in due course.
Acknowledgements
We wish to acknowledge a LANL director’s funded post-doctoral fellowship for AMT
and also acknowledge LANL science campaign 5 for partial support.
Appendix A. Supplementary data
CCDC: 1449437 (Compound 1), 1449435 (Compound 2), 1449436 (Compound
3
), 1449430 (Compound 4), 1449432 (Compound 6), 1449429 (Compound 7), 1449434
(
Compound 8), 1449431 (Compound 9), and 1449433 (Compound 12) are available
free of charge from http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the
Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK;
fax: (+44) 1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk. Supplementary
1
3
1
information including C NMR data for all diamagnetic compounds, H NMR spectra
for select compounds, and tabulated crystal data can be found at

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