Synthesis, structure, and reactivity of β-diketiminate complexes of manganese(II)

Article abstract of DOI:10.1021/om049857l

Reaction of the β-diketiminate lithium salt LLi(OEt₂) (1) (L = HC(CMeNAr)₂, Ar = 2,6-iPr₂C₆H₃) with MnCl₂ in diethyl ether provided the metalate complex LMn(μ-Cl)₂Li(OEt₂

Full text of DOI:10.1021/om049857l

3284
Organometallics 2004, 23, 3284-3289
Syn th esis, Str u ctu r e, a n d Rea ctivity of â-Dik etim in a te
Com p lexes of Ma n ga n ese(II)
J ianfang Chai, Hongping Zhu, Herbert W. Roesky,* Cheng He,
Hans-Georg Schmidt, and Mathias Noltemeyer
Institut fu¨r Anorganische Chemie der Universita¨t Go¨ttingen, Tammannstrasse 4,
D-37077 Go¨ttingen, Germany
Received February 26, 2004
Reaction of the â-diketiminate lithium salt LLi(OEt2) (1) (L ) HC(CMeNAr)2, Ar ) 2,6-
iPr2C6H3) with MnCl2 in diethyl ether provided the metalate complex LMn(µ-Cl)2Li(OEt2)2
(3) in high yield. The dimeric compound [LMn(µ-Cl)]2 (4) free of alkaline salt was obtained
when the â-diketiminate potassium salt LK (2) was used instead of 1. The substitution
reactions of 4 with CpNa, MeLi, and PhLi resulted in the formation of organomanganese
complexes LMnCp(THF) (7), [LMn(µ-Me)]2 (8), and LMnPh (9), respectively. The novel ionic
compound [LMnCl2][{C(Me)N(iPr)}2CH] (6) was obtained, when the N-heterocyclic carbene
{C(Me)N(iPr)}2C was used as a proton acceptor. The first doubly carboxylato-bridged complex
with four-coordinate manganese(II), [LMn(µ-O2CMe)]2 (5), was synthesized from the reaction
of 2 and Mn(O2CMe)2 in THF. Complexes 3-7 were characterized by single-crystal X-ray
structural analysis. The structures show that the â-diketiminate ligand backbone is
essentially planar and the metal centers reside in distorted tetrahedral geometry.
In tr od u ction
rides are normally the most common and inexpensive
source of manganese(II); however, manganese chlorides
containing â-diketiminate ligands remain rare prior to
this work. There are only a few reports on well-
characterized manganese complexes containing â-di-
ketiminate ligands in the literature. Power et al.
prepared manganese silylamide LMnN(SiMe3)2 using
Mn[N(SiMe3)2]2, which has a three-coordinate manga-
nese center.5 Two homoleptic manganese â-diketiminate
complexes were formed when less bulky ligands were
employed.1,6 Recently we have synthesized some man-
ganese iodides and their derivatives by taking advan-
tage of anhydrous MnI2 as starting material.7 Some
interesting results have been obtained; for example, the
first complex with three-coordinate manganese(I) [LMn]2
containing a reactive Mn-Mn bond has been success-
fully synthesized by reduction of the iodide [LMn(µ-I)]2.8
Herein, we report on easily available MnCl2 as starting
material and describe the synthesis and structural
characterization of a series of neutral and ionic man-
ganese(II) chlorides LMn(µ-Cl)2Li(OEt2)2 (3), [LMn(µ-
Cl)]2 (4), and [LMnCl2]-[{C(Me)N(iPr)}2CH]+ (6) sup-
ported by the same bulky ligand and the resulting
organomanganese derivatives LMnCp(THF) (7), [LMn-
(µ-Me)]2 (8), and LMnPh (9). In addition, we also report
on the first doubly carboxylato-bridged complex with
In the past few years there has been increasing
interest in the â-diketiminate ligands, especially those
with bulky aryl groups at the nitrogen, which have
excellent steric and electronic properties to stabilize
unusual complexes.1 A variety of main group element,
transition metal, and lanthanide complexes containing
such ligands have been synthesized and characterized,
some of which have novel structures and good catalytic
activities.1 For example, the first monomeric Al(I)
compound LAl (L ) HC(CMeNAr)2, Ar ) 2,6-iPr2C6H3)
as a stable carbene analogue was synthesized in our
group.2 Very recently, the aluminum dihydroxide with
terminal OH groups and the first terminal hydroxide
containing alumoxane were also obtained using the
same bulky â-diketiminate ligand.3
Manganese complexes are important since they are
involved in many natural processes, such as decomposi-
tion of peroxide and water oxidation of the photosystem
II.4 In view of this, it was of interest to assemble
manganese complexes and explore their reactivity.
Despite the impressive results obtained by using
â-diketiminate ligands now known, little work has
appeared on manganese â-diketiminate complexes. Chlo-
* To whom correspondence should be addressed. E-mail: hroesky@
gwdg.de.
(1) Bourget-Merle, L.; Lappert, M. F.; Severn, J . R. Chem. Rev. 2002,
102, 3031.
(2) Cui, C.; Roesky, H. W.; Schmidt, H.-G.; Noltemeyer, M.; Hao,
H.; Cimpoesu, F. Angew. Chem., Int. Ed. 2000, 39, 4274.
(3) (a) Bai, G.; Peng, Y.; Roesky, H. W.; Li, J .; Schmidt, H.-G.;
Noltemeyer, M. Angew. Chem., Int. Ed. 2003, 42, 1132. (b) Bai, G.;
Roesky, H. W.; Li, J .; Noltemeyer, M.; Schmidt, H.-G. Angew. Chem.,
Int. Ed. 2003, 42, 5502.
(4) (a) Hoganson, C. W.; Babcock, G. T. Science 1997, 277, 1953. (b)
Sakiyama, H.; Sugawara, A.; Sakamoto, M.; Unoura, K.; Inoue, K.;
Yamasaki, M. Inorg. Chim. Acta 2000, 310, 163. (c) Stubbe, J .; van
der Donk, W. A. Chem. Rev. 1998, 98, 705.
(5) Panda, A.; Stender, M.; Wright, R. J .; Olmstead, M. M.; Klavins,
P.; Power, P. P. Inorg. Chem. 2002, 41, 3909.
(6) Danopoulos, A. A.; Wilkinson, G.; Sweet, T. K. N.; Hursthouse,
M. B. J . Chem. Soc., Dalton Trans. 1995, 205.
(7) (a) Prust, J .; Most, K.; Mu¨ller, I.; Stasch, A.; Roesky, H. W.; Uso´n,
I. Eur. J . Inorg. Chem. 2001, 1613. (b) Chai, J .; Zhu, H.; Most, K.;
Roesky, H. W.; Vidovic, D.; Schmidt, H.-G.; Noltemeyer, M. Eur. J .
Inorg. Chem. 2003, 4332. (c) Chai, J .; Zhu, H.; Fan, H.; Roesky, H. W.;
Magull, J . Organometallics 2004, 23, 1177.
(8) Chai, J .; Zhu, H.; Roesky, H. W. J . Am. Chem. Soc., submitted.
10.1021/om049857l CCC: $27.50 © 2004 American Chemical Society
Publication on Web 05/20/2004

â-Diketiminate Complexes of Manganese(II)
Organometallics, Vol. 23, No. 13, 2004 3285
Sch em e 1
Sch em e 3
Sch em e 2
Sch em e 4
four-coordinate manganese(II) of composition [LMn(µ-
O2CMe)]2 (5).
Resu lts a n d Discu ssion
Syn th esis of Com p ou n d s 3-9. The â-diketiminate
lithium salt LLi(OEt2) (1) (L ) HC(CMeNAr)2, Ar ) 2,6-
iPr2C6H3) has been reported previously and widely used
as metathesis reagent.9 The reaction of 1 and anhydrous
MnCl2 in diethyl ether afforded the metalate complex
LMn(µ-Cl)2Li(OEt2)2 (3) in high yield (Scheme 1). At-
tempts to remove the coordinated lithium salt from the
manganese center were unsuccessful. According to the
experiences of preparing manganese iodides free of
lithium salt,7b we investigated the reaction of MnCl2
with the potassium salt LK (2) instead. As expected, the
dimeric compound [LMn(µ-Cl)]2 (4) free of the coordi-
nated salt was obtained in high yield (Scheme 2).
Attempts to prepare the bis(â-diketiminate) complex by
using 2 equiv of 1 or 2 were unsuccessful.
Dinuclear manganese complexes bridged by carbox-
ylate groups have attracted great attention since such
systems are known to exist at the active centers of some
manganese-containing enzymes.10 So it is of interest to
model the coordination environment of the manganese
centers in such enzymes. The doubly carboxylato-
bridged complex [LMn(µ-O2CMe)]2 (5) was prepared
from 2 and Mn(O2CMe)2 in THF in good yield. Crystals
of 5 suitable for X-ray structural analysis were obtained
by recrystallization from THF.
THF at room temperature. However, no reaction occurs
when in either case LH and {C(Me)N(iPr)}2C or LH and
MnCl2(THF)1.5 were mixed in THF at room temperature.
Therefore we suppose that the process for the formation
of 6 is a concerted one and may proceed through the
intermediate 6a (Scheme 3).
The substitution reactions of 4 with some nucleophiles
were investigated in order to prepare organomanga-
nese(II) complexes. Treatment of 4 with CpNa, MeLi,
and PhLi resulted in the formation of complexes LMnCp-
(THF) (7), [LMn(µ-Me)]2 (8), and LMnPh (9), respec-
tively. The monocyclopentadienyl manganese(II) com-
pound 7 was readily prepared as yellow crystals from
the reaction of 4 and 2 equiv of CpNa in THF in high
yield. Compound 7 is a rare example of a half-sandwich
manganese(II) complex with a metal center of 17
valence electrons.12 Complexes 8 and 9 have been
prepared from the reaction of [LMn(µ-I)]2 with MeLi and
PhLi, respectively.7c Compared with the substitution
reactions of the iodide, the reactions of 4 with MeLi and
PhLi are similar except the yields are a little lower.
Complexes of manganese with variable oxidation states
are of wide interest owing to their significance for
biological systems.4c,13 Thus, the oxidation reaction of
4 was examined in order to obtain high oxidation state
manganese complexes. However, the efforts to oxidize
4 with I2, S, or O2 all resulted in the decomposition of
4.
N-Heterocyclic carbenes have been widely used as
neutral and two-electron-donor ligands; however, the
investigation of their basicities is rare.11 We are inter-
ested in using the N-heterocyclic carbene as the acceptor
for the proton of LH. The novel ionic compound
[LMnCl2]-[{C(Me)N(iPr)}2CH]+ (6) was easily obtained
as a yellow crystalline solid in high yield from the
reaction of LH, MnCl2(THF)1.5, and {C(Me)N(iPr)}2C in
Complexes 3-7 are yellow crystalline solids and are
soluble in THF. These complexes were characterized by
(9) Ding, Y.; Roesky, H. W.; Noltemeyer, M.; Schmidt, H.-G.; Power,
P. P. Organometallics 2001, 20, 1190.
(10) Chen, X.-M.; Tong, Y.-X.; Xu, Z.-T.; Mark, T. C. W. J . Chem.
Soc., Dalton Trans. 1995, 4001, and references therein.
(11) Filipponi, S.; J ones, J . N.; J ohnson, J . A.; Cowley, A. H.;
Grepioni, F.; Braga, D. Chem. Commun. 2003, 2716.
(12) Ko¨hler, F. H.; Hebendanz, N.; Mu¨ller, G.; Thewalt, U.; Kanel-
lakopulos, B.; Klenze, R. Organometallics 1987, 6, 115.
(13) Ellison, J . J .; Power, P. P.; Shoner, S. C. J . Am. Chem. Soc.
1989, 111, 8044, and references therein.

3286 Organometallics, Vol. 23, No. 13, 2004
Ta ble 1. Cr ysta llogr a p h ic Da ta for Com p lexes 3-7
Chai et al.
3
1/24
5
6
7
formula
fw
T (K)
C
37H61Cl2LiMnN2O2
C29H41ClMnN2
508.03
200(2)
C62H88Mn2N4O4
1063.24
203(2)
C40H62Cl2MnN4
724.78
150(2)
C38H54MnN2O
609.77
133(2)
698.66
153(2)
cryst syst
space group
a (Å)
b (Å)
c (Å)
monoclinic
P21/n
12.053(2)
21.327(4)
15.706(3)
90
100.11(3)
90
3974.3(14)
4
monoclinic
C2/c
22.921(5)
14.8779(15)
16.291(2)
90
90.884(12)
90
5555.1(15)
8
monoclinic
P21/c
17.32(3)
15.210(17)
23.30(3)
90
101.94(6)
90
6010(2)
4
orthorhombic
P212121
11.218(4)
12.606(10)
28.93(2)
90
90
90
4090(1)
4
1.177
orthorhombic
P212121
10.007(2)
16.985(3)
20.081(4)
90
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
90
90
3413.3(12)
4
1.187
0.417
1316
Dcalcd (g cm-3
)
1.168
0.498
1500
1.215
0.590
2168
1.176
0.467
2280
µ (mm-1
F(000)
)
0.484
1556
cryst size (mm)
2θ range (deg)
no. of rflns collected
no. of indep rflns
0.90 × 0.60 × 0.30
7.04-50.10
10 312
6998 (R(int) )
0.0574)
6998/0/420
0.60 × 0.40 × 0.40
7.02-49.96
7144
4872 (R(int) )
0.0307)
0.70 × 0.40 × 0.30
7.06-45.00
7382
7382 (R(int) )
0.0000)
7382/0/671
0.60 × 0.50 × 0.50
7.06-44.98
3116
2999 (R(int) )
0.0745)
2999/0/449
0.30 × 0.30 × 0.30
3.14-49.44
36 246
5798 (R(int) )
0.0371)
5798/0/389
no. of data/restraints/
params
4872/0/308
goodness-of-fit, F2
R1, wR2 [I > 2σ(I)]
R1, wR2 (all data)
largest diff peak (e Å-3
1.026
1.024
1.013
1.089
1.064
0.0505, 0.1213
0.0636, 0.1322
0.562 to -0.634
0.0626, 0.1648
0.0821, 0.1817
0.400 to -1.366
0.0815, 0.1843
0.1403, 0.2315
0.579 to -0.721
0.0445, 0.1009
0.0653, 0.1136
0.533 to -0.505
0.0255, 0.0617
0.0280, 0.0626
0.305 to -0.291
)
elemental analyses, EI-MS, and IR. EI-MS of 3 shows
that the molecular ion peak is silent, and [LMnCl]+
appears as the most intense ion at m/z 507 without the
coordinated lithium salt. The molecular ion peaks of the
dimeric complexes 4 and 5 in the mass spectrum are
not observed, whereas half of the molecular mass
[1/2M]+ appeared at m/z 507 and 531 as the most
intense peak, respectively. Interestingly, the ion [M -
H]+ in the mass spectrum of 6 can be seen albeit with
low intensity (m/z 723, 2%), followed by [LMnCl]+ m/z
507 (43%) and [{C(Me)N(iPr)}2CH]+ 181 (52%). In the
EI-MS of 7, [LMnCp]+ appears at m/z 537 as the most
intense ion without the coordinated solvent, followed by
m/z 472 [M - Cp]+ (92%). The IR spectrum of 5 displays
the prominent vibrations for the O-C-O part of the
bridging acetate group νas(1602 cm-1) and νs(1437 cm-1).
X-r a y Solid -Sta te Str u ctu r a l An a lysis. Complexes
3-7 were characterized by single-crystal X-ray diffrac-
tion. Crystallographic data are given in Table 1 and
selected bond lengths and angles in Table 2.
The X-ray structural analyses reveal that LMn(µ-
Cl)2Li(OEt2)2 (3) is monomeric and [LMn(µ-Cl)]2 (4)
dimeric in the solid state (Figures 1 and 2). [LMnCl2]-
[{C(Me)N(iPr)}2CH] (6) crystallizes as separated mon-
omeric anions [LMnCl2]- and cations [{C(Me)N(iPr)}2-
CH]+. The structure of the anion is given in Figure 4.
In these three compounds each manganese center is
bound to two nitrogen atoms of the chelating ligand and
two chlorine atoms in a distorted tetrahedral geometry.
The backbone of the chelating ligand is nearly planar,
and the manganese atoms in these compounds are
always out of the C3N2 planes (0.45 Å in 3, 0.47 Å in 4,
and 0.70 Å in 6). The N-Mn-N angle in 6 (91.6°) is a
little smaller than the corresponding angles in 3 (92.2°)
and 4 (92.8°), and the Mn-N bond lengths in 6 (av 2.11
Å) are longer than those in 3 (av 2.08 Å) and 4 (av 2.08
Å), which indicates that the metal center in 6 is more
weakly bonded to the chelating ligand due to the two
terminal Mn-Cl bonds. The average value of the
terminal Mn-Cl distance (av 2.36 Å) in 6 is comparable
to those of the bridging Mn-Cl distances in 3 (av 2.38
Å) and 4 (av 2.33 Å) due to the anion character of the
[LMnCl2]- in 6. Accordingly, the Cl-Mn-Cl angle in 6
(112.0°) is significantly larger than those in 3 (96.2°)
and 4 (90.5°).
The lithium atom in 3 is connected by two bridging
chlorines and two oxygen atoms of two coordinated ether
molecules in a distorted tetrahedral geometry. The
structure is like that of the alkali metal adducts of the
â-diketiminate metal complexes of general formula
L′M(µ-X)2Li(ether)2 (L′ ) â-diketiminate ligand; X ) Cl,
I).5,7a,14 The Li-Cl and Li-O distances (av 2.38 and 1.96
Å, respectively) are similar to those found in LM(µ-
Cl)2Li(THF)2 (M ) Fe(II), Co(II)).5,14
The central core of 4 contains an ideal planar four-
membered Mn2Cl2 ring, which bisects and is perpen-
dicular (89.2°) to the two chelating ligands around them.
The distance between two manganese atoms is 3.28 Å,
which can be compared to that in [LMn(µ-I)]2 (3.62 Å)7b
and is out of the range of a Mn-Mn bond. The structure
of the cation [{C(Me)N(iPr)}2CH]+ in 6 is similar to that
in [{C(Me)N(Me)}2CH]+[Ph5C5]-.11
Compound 5 crystallizes in the monoclinic space
group P21/n with four molecules per unit cell. The
structure of 5 is shown in Figure 3. The central
manganese atoms are bonded to two nitrogen atoms
each from the chelating ligands and two oxygen atoms
from the two bridging acetates in a distorted tetrahedral
fashion. To the best of our knowledge, compound 5 is
the first example of a doubly carboxylato-bridged com-
plex with four-coordinate manganese(II). Similar to
complexes 3, 4, and 6, the manganese atoms are out of
the chelating ligand plane (av 0.64 Å). Complex 5
contains two peripheral six-membered C3N2Mn rings
and one central eight-membered C2Mn2O4 macrocycle.
(14) Smith, J . M.; Lachicotte, R. J .; Holland, P. L. Chem. Commun.
2001, 1542.

â-Diketiminate Complexes of Manganese(II)
Organometallics, Vol. 23, No. 13, 2004 3287
F igu r e 1. Molecular structure of 3 (50% probability
thermal ellipsoids). Hydrogen atoms are omitted for clarity.
F igu r e 2. Molecular structure of 4 (50% probability
thermal ellipsoids). Hydrogen atoms are omitted for clarity.
Ta ble 2. Selected Bon d Len gth s (Å) a n d Bon d
An gles (d eg) for Com p ou n d s 3-7
Compound 3
Mn(1)-N(1)
Mn(1)-N(2)
Mn(1)-Cl(1)
Mn(1)-Cl(2)
Li(1)-Cl(1)
Li(1)-Cl(2)
Li(1)-O(1)
Li(1)-O(2)
2.083(2)
2.072(2)
2.3688(11)
2.3887(10)
2.371(5)
2.383(5)
1.948(6)
1.975(6)
N(1)-Mn(1)-N(2)
N(1)-Mn(1)-Cl(1)
N(2)-Mn(1)-Cl(1)
Cl(1)-Mn(1)-Cl(2)
N(1)-Mn(1)-Cl(2)
N(2)-Mn(1)-Cl(2)
Cl(1)-Li(1)-Cl(2)
O(1)-Li(1)-O(2)
92.21(8)
118.99(7)
116.72(7)
96.10(3)
115.29(6)
119.48(6)
96.20(17)
114.7(3)
Compound 4
Mn(1)-N(1)
Mn(1)-N(2)
Mn(1)-Cl(1)
Mn(1)-Cl(1A)
Mn(1A)-Cl(1)
2.0830(9)
2.0819(10) N(1)-Mn(1)-Cl(1)
2.3422(7)
2.3093(6)
2.3093(6)
N(1)-Mn(1)-N(2)
92.80(3)
117.09(3)
118.34(3)
90.49(2)
119.74(3)
120.93(3)
N(2)-Mn(1)-Cl(1)
Cl(1)-Mn(1)-Cl(1A)
N(1)-Mn(1)-Cl(1A)
N(2)-Mn(1)-Cl(1A)
Mn(1)-Mn(1A) 3.275
Compound 5
2.075(6)
Mn(1)-N(1)
Mn(1)-N(2)
Mn(1)-O(1)
Mn(1)-O(2)
Mn(2)-N(3)
Mn(2)-N(4)
Mn(2)-O(3)
Mn(2)-O(4)
Mn(1)-Mn(2)
N(1)-Mn(1)-N(2)
N(1)-Mn(1)-O(1)
N(1)-Mn(1)-O(2)
N(2)-Mn(1)-O(1)
N(2)-Mn(1)-O(2)
O(1)-Mn(1)-O(2)
O(3)-Mn(2)-O(4)
N(3)-Mn(2)-N(4)
90.9 (2)
110.9(3)
115.6(3)
110.9(3)
112.3(3)
114.1(3)
117.8(3)
92.0 (2)
F igu r e 3. Molecular structure of 5 (50% probability
thermal ellipsoids). Hydrogen atoms are omitted for clarity.
2.077(6)
2.014(7)
1.991(7)
2.082(6)
2.086(6)
2.012(7)
2.031(7)
4.319
Compound 6
Mn(1)-N(1)
Mn(1)-N(2)
Mn(1)-Cl(1)
Mn(1)-Cl(2)
2.102(2)
2.111(2)
2.3890(11)
2.3370(10)
N(1)-Mn(1)-N(2)
N(1)-Mn(1)-Cl(1)
N(2)-Mn(1)-Cl(1)
Cl(1)-Mn(1)-Cl(2)
91.64(8)
107.84(6)
109.42(7)
112.00(4)
Compound 7
Mn(1)-N(1)
Mn(1)-N(2)
Mn(1)-O(31)
Mn(1)-C(6)
Mn(1)-C(7)
Mn(1)-C(8)
Mn(1)-C(9)
Mn(1)-C(10)
2.1242(15)
2.1306(15)
2.2787(12)
2.547(2)
2.442(2)
2.419(2)
N(1)-Mn(1)-N(2)
N(1)-Mn(1)-O(31)
N(2)-Mn(1)-O(31)
N(1)-Mn(1)-C(6)
N(2)-Mn(1)-C(6)
O(31)-Mn(1)-C(6)
N(1)-Mn(1)-C(7)
N(2)-Mn(1)-C(7)
90.26(5)
97.69(5)
97.60(6)
96.96(6)
144.79(7)
115.34(6)
120.33(7)
147.88(7)
F igu r e 4. Crystal structure of the anion of 6 (50%
probability thermal ellipsoids). Hydrogen atoms are omit-
ted for clarity.
2.5088(19)
2.5778(19)
nonbonding intramolecular Mn-Mn distance is 4.32 Å,
which is in the normal range (4.15-4.79 Å) of those
found in comparable manganese(II) complexes.10 The
Mn-N distance (av 2.08 Å) and the N-Mn-N angle
(90.9°) in 5 can be compared with those observed in 3
and 4.
The six- and eight-membered rings are nearly orthogo-
nal to each other, as shown by a dihedral angle of 85.8°.
The two acetates are in the bidentate µ1,3 syn-syn
bridging mode, which is rare in the doubly carboxylato-
bridged manganese(II) complexes.10 The Mn-O dis-
tances (av 2.01 Å) for the acetato bridges in 5 compare
well with those (2.00-2.24 Å) observed in the manga-
nese complexes adopting the same µ1,3 mode.15 The
Compound 7 is monomeric with a Cp coordinated
to the manganese center and crystallizes in the ortho-
(15) Romero, I.; Dubois, L.; Collomb, M.-N.; Deronzier, A.; Latour,
J .-M.; Pecaut, J . Inorg. Chem. 2002, 41, 1795.

3288 Organometallics, Vol. 23, No. 13, 2004
Chai et al.
in the literature.20 The syntheses of complexes 8 and 9 are
similar to those of 7c. NMR spectra of complexes 3-9 are not
available due to the paramagnetic nature of manganese(II).
LMn (µ-Cl)2Li(OEt2)2 (3). LLi(OEt2) (1.0 g, 2 mmol) in
diethyl ether (15 mL) was added to a suspension of MnCl2 (0.25
g, 2 mmol) in diethyl ether (40 mL) at -78 °C. The mixture
was warmed to room temperature and stirred for 14 h. The
resulting precipitate was removed by filtration. The solution
was concentrated to ca. 10 mL. Yellow crystals were obtained
after 2 days at -26 °C. Yield: 1.13 g (81%). Mp: > 270 °C
(dec). Anal. Calcd for C37H61Cl2LiMnN2O2 (698.66): C, 63.55;
H, 8.73; N, 4.01. Found: C, 63.13; H, 8.54; N, 4.47. EI-MS:
m/z (%) 507 (100) [M - LiCl(OEt2)2]. IR (KBr, Nujol mull,
cm-1): ν˜ 1624 (w), 1539 (w), 1523 (m), 1398 (m), 1366 (w), 1316
(m), 1262 (m), 1231 (w), 1176 (w), 1099 (m), 1056 (w), 1022
(m), 934 (w), 873 (w), 853 (w), 795 (m), 759 (w), 722 (w), 636
(w), 600 (w), 527 (w), 452 (w).
F igu r e 5. Molecular structure of 7 (50% probability
thermal ellipsoids). Hydrogen atoms are omitted for clarity.
[LMn (µ-Cl)]2 (4). LK (0.91 g, 2 mmol) in diethyl ether (15
mL) was added to a suspension of MnCl2 (0.25 g, 2 mmol) in
diethyl ether (40 mL) at -78 °C. The mixture was warmed to
room temperature and stirred for 14 h. The resulting precipi-
tate was removed by filtration. The solution was concentrated
to ca. 10 mL. Yellow crystals were obtained after 1 day at -26
rhombic space group P212121. The metal center is of
pseudotetrahedral geometry surrounded by the cyclo-
pentadienyl ring, the oxygen atom of the coordinated
THF, and two nitrogen atoms of the chelating ligand.
The Mn-C distances (2.42-2.58 Å) are consistent with
those found in [MeC5H4MnPEt3(µ-X)]2 (X ) Cl, Br, I)
(2.40-2.63 Å)12 and CpMnTMEDA(η1-Cp) (2.44-2.57
Å).16 The Mn-N distance (av 2.13 Å) in 7 is the longest
and the N-Mn-N angle (90.3)° is the smallest among
those in complexes 3-7, which is in agreement with the
higher coordination number of manganese. The Cp, the
ligand plane, and THF plane are nearly orthogonal to
each other.
°C. Yield: 0.88 g (87%). Mp: >400 °C. Anal. Calcd for C58H82
-
Cl2Mn2N4 (1016.06): C, 68.50; H, 8.07; N, 5.51. Found: C,
68.75; H, 8.23; N, 5.21. EI-MS: m/z (%) 507 (100) [1/2M]. IR
(KBr, Nujol mull, cm-1): ν˜ 1656 (w), 1623 (w), 1592 (w), 1553
(w), 1528 (w), 1326 (w), 1292 (w), 1261 (m), 1175 (m), 1098
(m), 1025 (m), 936 (w), 801 (m), 758 (w), 722 (w), 664 (w), 618
(w), 541 (w), 466 (w).
[LMn (µ-O2CMe)]2 (5). LK (0.91 g, 2 mmol) in THF (10 mL)
was added to a suspension of Mn(O2CMe)2 (0.35 g, 2 mmol) in
THF (30 mL) at -78 °C. The mixture was warmed to room
temperature and stirred for 12 h. The resulting precipitate was
removed by filtration. The solution was concentrated to ca. 5
mL. Yellow crystals were obtained after 7 days at -26 °C.
Con clu sion
Mp: >330 °C (dec). Yield: 0.80 g (75%). Anal. Calcd for C62H88
-
In summary, we have synthesized a series of neutral
and ionic manganese(II) chlorides (3, 4, and 6) by using
the bulky â-diketiminate ligand [HC(CMeNAr)2]. The
reactivity of compound 4 was investigated. The substi-
tution reactions of 4 with CpNa, MeLi, and PhLi
afforded organomanganese complexes 7-9, respectively.
In addition, we also report on the first doubly carbox-
ylato-bridged complex (5) with four-coordinate manga-
nese(II). Further studies on the chemistry of these
complexes including oxidation reactions of 4 are in
progress.
Mn2N4O4 (1063.24): C, 70.00; H, 8.28; N, 5.27. Found: C,
69.68; H, 8.19; N, 5.00. EI-MS: m/z (%) 531 (100) [1/2M]. IR
(KBr, Nujol mull, cm-1): ν˜ 1602 (s), 1544 (m), 1519 (m), 1437
(s), 1380 (m), 1317(m), 1262 (w), 1177 (w), 1099 (w), 1021 (w),
933 (w), 851 (w), 793 (w), 759 (w), 643 (w).
[LMn Cl2][{C(Me)N(iP r )}2CH] (6). THF (40 mL) was
added to a mixture of MnCl2(THF)1.5 (0.47 g, 2 mmol), LH (0.83
g, 2 mmol), and {C(Me)N(iPr)}2C (0.36 g, 2 mmol) at room
temperature. The resulting suspension was stirred for 12 h,
and a clear yellow solution was obtained. The solution was
concentrated to ca. 10 mL and kept at 4 °C. Yellow crystals
were obtained after 3 days. Yield: 1.23 g (85%). Mp: > 210
°C (dec). Anal. Calcd for C40H62Cl2MnN4 (724.78): C, 66.23;
H, 8.55; N, 7.73. Found: C, 65.85; H, 8.75; N, 7.45. EI-MS:
m/z (%) 723 (2) [M - H]+, 507 (43) [LMnCl], 181 (52) [{C(Me)-
N(iPr)}2CH]. IR (KBr, Nujol mull, cm-1): ν˜ 3126 (w), 3058 (w),
1663 (w), 1628 (w), 1551 (m), 1542 (m), 1516 (m), 1438 (s),
1400 (s), 1321 (s), 1263 (s), 1232 (m), 1193 (w), 1177 (m), 1143
(w), 1101 (s), 1056 (w), 1023 (s), 962 (w), 936 (m), 868 (w),
849 (w), 799 (s), 792 (s), 764 (m), 758 (m), 721 (w), 652 (w),
630 (w).
LMn Cp (THF ) (7). CpNa (0.6 mL, 2.0 M in THF, 1.2 mmol)
was added to a solution of 4 (0.51 g, 0.5 mmol) in THF (20
mL) at -78 °C. The mixture was allowed to warm to room
temperature and stirred for 14 h. All volatiles were removed
in vacuum, and the residue was extracted with toluene (15
mL). The yellow solution was concentrated to ca. 10 mL and
kept at room temperature for 2 days to give yellow crystals.
The crystals were collected by filtration, and the filtrate was
concentrated and kept at 4 °C for 7 days to give additional
crystals. Total yield: 0.52 g (86%). Mp: 210-212 °C. Anal.
Calcd for C38H54MnN2O (609.77): C, 74.88; H, 8.87; N, 4.60.
Exp er im en ta l Section
Gen er a l P r oced u r es. All reactions were performed using
standard Schlenk and drybox techniques. Solvents were ap-
propriately dried and distilled under dinitrogen prior to use.
Elemental analyses were performed by the Analytisches Labor
des Instituts fu¨r Anorganische Chemie der Universita¨t Go¨t-
tingen. Mass spectra were obtained on a Finnigan Mat 8230.
IR spectra were recorded on a Bio-Rad Digilab FTS-7 spec-
trometer as Nujol mulls between KBr plates. LH,17 LLi(OEt2)
(1),9 LK (2)7b (L ) HC(CMeNAr)2, Ar ) 2,6-iPr2C6H3), and {C-
(Me)N(iPr)}2C18 were prepared by literature procedures. Mn-
(O2CMe)2 was purchased from Aldrich and used without
purification. Anhydrous MnCl2 was obtained by dehydration
of MnCl2(H2O)4.19 MnCl2(THF)1.5 was synthesized as described
(16) Heck, J .; Massa, W.; Wenig, P. Angew. Chem., Int. Ed. Engl.
1984, 23, 722.
(17) Feldman, J .; McLain, S. J .; Parthasarathy, A.; Marshall, W.
J .; Calabrese, J . C.; Arthur, S. D. Organometallics 1997, 16, 1514.
(18) Kuhn, N.; Kratz, T. Synthesis 1993, 561.
(19) Horvath, B.; Moeseler, R.; Horvath, E. G. Z. Anorg. Allg. Chem.
1979, 450, 165.
(20) Kern, R. J . J . Inorg. Nucl. Chem. 1962, 24, 1105.

â-Diketiminate Complexes of Manganese(II)
Organometallics, Vol. 23, No. 13, 2004 3289
Found: C, 74.46; H, 8.76; N, 4.64. EI-MS: m/z (%) 537 (100)
[M -THF], 472 (92) [LMn]. IR (KBr, Nujol mull, cm-1): ν˜ 1653
(w), 1542 (w), 1521 (m), 1401 (m), 1315 (m), 1262 (s), 1231
(w), 1172 (w), 1098 (s), 1056 (m), 1028 (s), 933 (w), 872 (w),
846 (w), 793 (s), 765 (w), 751 (m), 721 (m), 667 (w), 601 (w),
466 (w).
X-r a y Cr ysta llogr a p h y. Crystallographic data for 3-6
were collected on a Stoe-Siemens-Huber four-circle diffracto-
meter coupled to a Siemens CCD area detector and for 7 on a
Stoe IPDS II-array detector system. In both cases graphite-
monochromated Mo KR radiation (λ ) 0.71073 Å) was used.
All structures were solved by direct methods (SHELXS-97)21
and refined against F2 using SHELXL-97.22 All non-hydrogen
atoms were refined anisotropically. The hydrogen atoms were
included at geometrically calculated positions and refined
using a riding model. For compound 6, Flack x parameter )
-0.0229 with esd 0.0382. Expected values are 0 (within 3 esd’s)
for correct and +1 for the inverted absolute structure. The
absolute structure of 7 could not be determined, and a twin
refinement was done.
Ack n ow led gm en t. We are grateful to the Deutsche
Forschungsgemeinschaft, the Fonds der Chemischen
Industrie, and the Go¨ttinger Akademie der Wissen-
schaften for support of this work.
Su p p or tin g In for m a tion Ava ila ble: X-ray structural
information for complexes 3-7. This material is available free
of charge via the Internet at http://pubs.acs.org.
(21) Sheldrick, G. M. Acta Crystallogr. Sect. A 1990, 46, 467.
(22) Sheldrick, G. M. SHELXL-97, Program for Crystal Structure
Refinement; Universita¨t Go¨ttingen, 1997.
OM049857L