Molybdenum oxo and lmido complexes of β-diketiminate ligands: Synthesis and structural aspects

Article abstract of DOI:10.1021/ic701534a

Treatment of [MoO₂(η²-Pz)₂] (Pz = 3,5-di-tert-butylpyrazolate) with the diketiminate ligand NacNacH (NacNac = CH[C(Me)NAr]₂^-, Ar = 2,6-Me₂C₆H ₃) at 55°C leads under reduction of the metal to the formation of the dimeric molybdenum(V) compound [{MoO₂(NacNac)}₂] (1). The compound was characterized by spectroscopic means and by X-ray crystal structure analysis. The dimer consists of a [Mo₂O₄] ²⁺ core with a short Mo-Mo bond (2.5591-(5) A) and one coordinated diketiminate ligand on each metal atom. The reaction of [MoO ₂(η²-Pz)₂] with NacNacH in benzene at room temperature leads to a mixture of 1 and the monomeric molybdenum(VI) compound [MoO₂-(NacNac)(η²-Pz)] (2). From such solutions, yellow crystals of 2 suitable for X-ray structural analysis were obtained revealing the coordination of one bidentate NacNac and one η²- coordinate Pz ligand. This renders the two oxo groups inequivalent. Further high oxidation state molybdenum compounds containing the NacNac ligand were obtained by the reaction of [Mo(NAr)₂Cl₂(dme)] (Ar = 2,6-Me ₂C₆H₃) and [Mo(N-t-Bu)₂Cl ₂(dme)] (dme = dimethoxyethane) with 1 equiv of the potassium salt NacNacK forming [Mo(NAr)₂Cl(NacNac)] (3) and [Mo(N-t-Bu) ₂Cl(NacNac)] (4), respectively, in good yields. The X-ray structure analysis of 3 revealed a penta-coordinate compound where the geometry is best described as trigonal-bipyramidal.

Full text of DOI:10.1021/ic701534a

Inorg. Chem. 2008, 47, 113−120
Molybdenum Oxo and Imido Complexes of
Synthesis and Structural Aspects
â-Diketiminate Ligands:
Ganna Lyashenko,† Regine Herbst-Irmer,‡ Vojtech Jancik,‡,§ Aritra Pal,‡ and Nadia C. Mosch-Zanetti*,†
1
Institut fu¨r Chemie, Karl-Franzens-UniVersita¨t Graz, Schubertstrasse 1, A-8010 Graz, Austria, and
Institut fu¨r Anorganische Chemie, Georg-August-UniVersita¨t Go¨ttingen, Tammannstrasse 4,
D-37077 Go¨ttingen, Germany
Received August 1, 2007
Treatment of [MoO2(
η
)
2-Pz)2] (Pz
2,6-Me2C6H3) at 55
MoO2(NacNac)
)
3,5-di-tert-butylpyrazolate) with the diketiminate ligand NacNacH (NacNac
)
CH[C(Me)NAr]2-, Ar
°
C leads under reduction of the metal to the formation of the dimeric
molybdenum(V) compound [
{
}
2] (1). The compound was characterized by spectroscopic means
and by X-ray crystal structure analysis. The dimer consists of a [Mo2O4]2 core with a short Mo
−
Mo bond (2.5591-
2-Pz)2] with NacNacH
in benzene at room temperature leads to a mixture of 1 and the monomeric molybdenum(VI) compound [MoO2-
(NacNac)(
2-Pz)] (2). From such solutions, yellow crystals of 2 suitable for X-ray structural analysis were obtained
revealing the coordination of one bidentate NacNac and one
2-coordinate Pz ligand. This renders the two oxo
groups inequivalent. Further high oxidation state molybdenum compounds containing the NacNac ligand were
obtained by the reaction of [Mo(NAr)2Cl2(dme)] (Ar 2,6-Me2C6H3) and [Mo(N-t-Bu)2Cl2(dme)] (dme
+
(5) Å) and one coordinated diketiminate ligand on each metal atom. The reaction of [MoO2(
η
η
η
)
)
dimethoxyethane) with 1 equiv of the potassium salt NacNacK forming [Mo(NAr)2Cl(NacNac)] (3) and [Mo(N-t-
Bu)2Cl(NacNac)] (4), respectively, in good yields. The X-ray structure analysis of 3 revealed a penta-coordinate
compound where the geometry is best described as trigonal-bipyramidal.
Introduction
Ni,4 and Ti 5), bioinorganic chemistry (Cu,6 Fe 7), or coor-
dination chemistry (Al,8 Fe,9 and Zn 10). A reason for the
success of the ligand system is the easy variation of the
substitutents which allows for the adjustment of steric bulk
and electronic effects leading to unusual complexes. In
addition, the conjugated nature of the bidentate nitrogen-
The â-diketiminate ligands are being widely used for
syntheses of different kinds of metal compounds.1 First
examples were already reported in the 1960s for late-
transition metals.2 But the real development in this direction
started in the 1990s, after â-diketiminato ligands were used
as spectator ligands and metal complexes thereof were
synthesized for various applications such as catalysis (Cr,3
(3) Richeson, D. S.; Mitchell, J. F.; Theopold, K. H. Organometallics
1989, 7, 2570-2577.
(4) Feldman, J.; McLain, S. J.; Parthasarathy, A.; Marshall, W. J.;
Calabrese, C. J.; Arthur, S. D. Organometallics 1997, 16, 1514-1516.
(5) Budzelaaz, P. H. M.; van Oort, A. B.; Orpen, A. G. Eur. J. Inorg.
Chem. 1998, 1485-1494.
(6) (a) Holland, P. L.; Tolman, W. B. J. Am. Chem. Soc. 1999, 121, 7270-
7271. (b) Randall, D. W.; DeBeer, G. S.; Holland, P. L.; Heldman,
B.; Hodgson, K. O.; Tolman, W. B.; Solomon, E. I. J. Am. Chem.
Soc. 2000, 122, 11632-11648.
(7) Smith, J. M.; Sadique, A. R.; Cundari, T. R.; Rodgers, K. R.; Lukat-
Rodgers, G.; Lachicotte, R. J.; Flaschenriem, C. J.; Vela, J.; Holland,
P. L. J. Am. Chem. Soc. 2006, 128, 756-769.
(8) Cui, C.; Roesky, H. W.; Noltemeyer, M.; Schmidt, H.-G. Angew.
Chem. 2000, 112, 4705-4707; Angew. Chem., Int. Ed. 2000, 39,
4274-4276.
(9) (a) Smith, J. M.; Lachicotte, R. J.; Holland, P. L. J. Chem Soc., Chem.
Commun. 2001, 1542-1543. (b) Eckert, N. A.; Smith, J. M.;
Lachicotte, R. J.; Holland, P. L. Inorg. Chem. 2004, 43, 3306-3321.
(10) Hao, H.; Cui, C.; Roesky, H. W.; Bai, G.; Schmidt, H.-G.; Noltemeyer,
M. Chem. Commun. (Cambridge) 2001, 1118-1119.
* To whom correspondence should be addressed. E-mail:
nadia.moesch@uni-graz.at.
† Karl-Franzens-Universita¨t Graz.
‡ Georg-August-Universita¨t Go¨ttingen.
§ Currently at Instituto de Qu´ımica, Universidad Nacional Auto´noma de
Me´xico, Circuito Exterior, Ciudad Universitaria, 04510, Me´xico D.F.,
Me´xico.
(1) Bourget-Merle, L.; Lappert, M. F.; Severn, J. R. Chem. ReV. 2002,
102, 3031-3065.
(2) Holm, R. H.; Everett, G. W.; Chakravorty, A. Prog. Inorg. Chem.
1966, 7, 83-214. McGeachin, S. G. Can. J. Chem. 1968, 46, 1903-
1912. Dorman, L. C. Tetrahedron Lett. 1966, 4, 459-464. Barry, W.
J.; Finar, I.; Mooney, E. F. Spectrochim. Acta 1965, 21, 1095-1099.
Bonnett, R.; Bradley, D. C.; Fischer, K. J. J. Chem. Soc., Chem.
Commun. 1968, 886-887. Bonnett, R.; Bradley, D. C.; Fischer, K.
J.; Rendall, I. F. J. Chem. Soc. A 1971, 1622-1627. Holm, R. H.;
Parks, J. E. Inorg. Chem. 1968, 7, 1408-1416.
10.1021/ic701534a CCC: $40.75
Published on Web 12/12/2007
© 2008 American Chemical Society
Inorganic Chemistry, Vol. 47, No. 1, 2008 113

Lyashenko et al.
based ligand makes it an interesting candidate for the
development of model complexes for metalloenzymes where
the metal is coordinated by histidine of porphyrin ligands.
In recent years, our research has focused on model
chemistry for a class of enzymes that catalyze oxygen atom
transfer (OAT) from or to a substrate commonly referred as
oxotransferases.11,12 They consist of a mononuclear high
oxidation state molybdenum atom that is coordinated by at
least one oxygen atom and one or two molybdopterin ligands,
the latter being a dithiolene system.13,14 To influence steric
and redox properties of the OAT reaction, model chemistry
has focused on the [MoO2]2+ core and on the variation of
co-ligands that are S,S-, N,S-, and N,O-based.12,15,16 Far less
investigated are N,N-based molybdenum dioxo compounds
that are catalysts in OAT reactions.11,17 Recently, we reported
unusual complexes employing η2-pyrazolate ligands that lead
to trigonal prismatic molybdenum dioxo complexes capable
of catalyzing the oxygen atom transfer from dimethyl
sulfoxide to triphenylphosphine.11 The hard nitrogen atoms
contrast the soft ligation in the natural enzymes leading to
systems with unique properties.
For this reason, we got attracted by the idea of coordinating
the widely used nitrogen-based â-diketiminate ligands to the
molybdenum dioxo core. To our surprise, a literature search
did not reveal any molybdenum(VI) oxo complexes with the
â-diketiminate ligands. A few related examples are known
that contain 1,4,8,11-tetraaza(14)annulene type ligands con-
sisting of a â-diketiminate unit.18,19 In addition, the literature
search revealed not only the absence of oxo compounds but
also the scarcity of any high oxidation state molybdenum
compound with these types of ligands. Only very recently,
imido alkylidene complexes containing â-diketiminate ligands
were reported by Schrock and co-workers.20
Experimental Section
General Methods. All manipulations were carried out under dry
nitrogen or argon using standard Schlenk line or glovebox
techniques. All solvents were purified by standard methods and
distilled over sodium/benzophenone under argon atmosphere im-
mediately prior to use. NacNacH,1 NacNacK,21 KPz,22 [MoO2Cl2],23
[MoO2(η2-Pz)2],11b [Mo(NAr)2Cl2(dme)] (dme ) dimethoxy-
ethane),24 and [Mo(N-t-Bu)2Cl2(dme)]24 were prepared according
to literature procedures. All other chemicals mentioned were used
as purchased from commercial sources (Aldrich, Merck).
Samples for mass spectrometry were measured on a BIO-RAD
Digilab FTS-7 mass spectrometer with a Finnigan MAT 95 and all
NMR spectra on a Bruker Avance 200, 360, or 500 MHz. Spectra
were obtained at 25 °C unless otherwise noted. Elemental analyses
were performed by the Analytisches-Chemisches Laboratorium des
Instituts fu¨r Anorganische Chemie der Technischen Universita¨t
Graz, Austria. IR spectra were recorded on a Perkin-Elmer FT-IR
Spectrometer 1725X as Nujol mull between KBr plates.
[{MoO2(NacNac)}2] (1). Freshly sublimed [MoO2(η2-Pz)2] (0.50
g, 1.02 mmol) and NacNacH (0.61 g, 1.99 mmol) were dissolved
in toluene (30 mL) and stirred for 12 h at 55 °C. After cooling to
room temperature, a significant amount of black-green solid was
filtered off. The brown-orange filtrate was evaporated in vacuo,
and the resulting solid was thoroughly rinsed with pentane affording
the dimer 1 as a brown powder. Yield: 0.22 g (25% based on Mo).
Crystals suitable of X-ray diffraction analysis were obtained by
1
cooling a toluene solution to +5 °C. H NMR (360 MHz, C6D6):
δ 1.37 (s, 6H, N-C(CH3)), 1.47 (s, 6H, CH3-Ar), 2.30 (s, 6H, CH3-
Ar), 5.29 (s, 1H, γ-H), 6.80-6.99 (m, 6H, H-Ar). 13C{1H} NMR
(360 MHz, C6D6): δ 18.1, 18.5, 24.8, 103.3, 125.2, 129.2, 130.4,
133.1, 150.6, 167.4. MS (EI): m/z 867 (100%) ([{MoO2-
(NacNac)}2]+). IR (KBr): 959 (vs), 762 (vs) cm-1. Anal. Calcd
for C42H50N4O4Mo2: C, 58.20; H, 5.81; N, 6.46. Found: C, 57.91;
H, 5.77; N, 6.45.
[MoO2(NacNac)(η2-Pz)] (2). Crystals suitable for X-ray dif-
fraction analysis were obtained by the following procedure: a
solution of NacNacH (0.016 g, 0.052 mmol) in C6D6 (2 mL) was
added to a vigorously stirred solution of freshly sublimed [MoO2-
(η2-Pz)2] (0.025 g, 0.051 mmol) in C6D6 (2 mL) giving a clear
In this paper we describe the introduction of the NacNac
ligand to the [MoO2]2+ core by using [MoO2(η2-Pz)2] as a
precursor where the η2-Pz ligand serves as the leaving group.
In comparison, the non-oxidizing cores [Mo(NAr)2]2+ (Ar
) 2,6-Me2C6H3) and [Mo(N-t-Bu)2]2+ allowed the coordina-
tion of the NacNac ligand by conventional metal-chloride
metathesis. Syntheses, spectroscopic data, and the crystal-
lographic characterization of new oxo and imido compounds
are reported.
1
orange solution. A H NMR spectrum which was recorded after
20 min of ligand addition shows resonances for compound 2 and
[MoO2(η2-Pz)2] in the ratio 1:1, together with those for ap-
proximately 5 equiv of PzH. Storing the solution at room temper-
ature for a few days led to the formation of a dark-green precipitate
together with several yellow crystals. These crystals were picked
for the crystal structure determination. 1H NMR of the aliquot taken
after 20 min reaction time (200 MHz, C6D6) of 2: δ 1.10 (br s, 18
H, 2C(CH3)3), 1.50 (s, 6H, 2CH3), 2.20 (s, 12H, 4CH3), 5.20 (s,
1H, γ-H), 6.14 (s, 1H, γ-H), 6.90-7.20 (m, 6H, H-Ar).
[Mo(NAr)2Cl(NacNac)] (3). To [Mo(NAr)2Cl2(dme)] (0.49 g,
0.99 mmol) and NacNacK (0.34 g, 0.98 mmol) was added diethyl
ether (30 mL). The mixture was stirred under reflux for 12 h
affording a dark cherry-red suspension, which was cooled to room
temperature and filtered over a pad of Celite. The filtrate was
concentrated to half and left at -20 °C overnight. Orange crystals
were collected on a frit, thoroughly rinsed with pentane and dried
in vacuo, giving 3 as an orange powder. Yield: 0.51 g (75%).
(11) (a) Most, K.; Ko¨pke, S.; Dall’Antonia, F.; Mo¨sch-Zanetti, N. C. Chem.
Commun. (Cambridge) 2002, 1676-1677. (b) Most, K.; Hossbach,
J.; Vidovic, D.; Magull, J.; Mo¨sch-Zanetti, N. C. AdV. Synth. Catal.
2005, 347, 463-472.
(12) Lyashenko, G.; Saischek, G.; Pal, A.; Herbst-Irmer, R.; Mo¨sch-Zanetti,
N. C. Chem. Commun. (Cambridge) 2007, 701-703.
(13) Hille, R. Chem. ReV. 1996, 96, 2757-2816.
(14) Enemark, J. H.; Cooney, J. J. A.; Wang, J.-J.; Holm, R. H. Chem.
ReV. 2004, 104, 1175-1200.
(15) Enemark, J. H.; Cooney, J. J. A.; Wang, J.-J.; Holm, R. H. Chem.
ReV. 2004, 104, 1175-1200.
(16) Thapper, A.; Lorber, C.; Fryxelius, J.; Behrens, A.; Nordlander, E. J.
Inorg. Biochem. 2000, 79, 67-74.
(17) Heinze, K.; Fischer, A. Eur. J. Inorg. Chem. 2007, 1020-1026.
(18) Giraudon, J.-M.; Sala-Pala, J.; Guerchais, J.-E.; Toupet, L. Inorg.
Chem. 1991, 30, 891-899.
(21) Fekl, U.; Kaminsky, W.; Goldberg, K. I. J. Am. Chem. Soc. 2003,
125, 15286-15287.
(22) Ye´lamos, C.; Heeg, M. J.; Winter, C. H. Inorg. Chem. 1998, 37, 3892-
3894.
(23) Gibson, V. C.; Kee, T. P.; Shaw A. Polyhedron 1990, 9, 2293-2298.
(24) Fox, H.; Cai J.; Schrock, R. R. Inorg. Chem. 1992, 31, 2287-2289.
(19) Lee, S.; Floriani, C.; Chiesi-Villa, A.; Guastini, C. J. Chem. Soc.,
Dalton Trans. 1989, 145-149.
(20) Tonzetich, Z. J.; Jiang, A. J.; Schrock, R. R.; Mu¨ller, P. Organome-
tallics 2006, 25, 4725-4727. Tonzetich, Z. J.; Jiang, A. J.; Schrock,
R. R.; Mu¨ller, P. Organometallics 2007, 26, 3771-3783.
114 Inorganic Chemistry, Vol. 47, No. 1, 2008

Molybdenum Complexes of â-Diketiminate Ligands
Table 1. Selected Bond Distances (Å) and Angles (deg) for Complexes
[{MoO2(NacNac)}2] (1), [MoO2(NacNac)(η2-Pz)] (2), and
[Mo(NAr)2Cl(NacNac)] (3)a
Crystals suitable for X-ray diffraction were obtained by storing of
a concentrated THF solution at -20 °C. 1H NMR (360 MHz,
toluene-d8): δ 1.53 (s, 3H, N-C(CH3)), 1.67 (s, 3H, N-C(CH3)),
2.14 (s, 6H, CH3-Ar), 2.32 (s, 6H, CH3-Ar), 2.41 (s, 12H, CH3-
Ar), 5.43 (s, 1H, γ-H), 6.45-7.02 (m, 12H, H-Ar). 1H NMR (360
MHz, toluene-d8, -30 °C): δ 1.45 (s, 3H, N-C(CH3)), 1.62 (s,
3H, N-C(CH3)), 2.14 (s, 6H, CH3-Ar), 2.24 (s, 3H, CH3-Ar), 2.32
(s, 3H, CH3-Ar), 2.43 (s, 6H, CH3-Ar), 2.51 (s, 3H, CH3-Ar), 2.67
(s, 3H, CH3-Ar), 5.34 (s, 1H, γ-H), 6.47-7.06 (m, 12H, H-Ar).
13C{1H} NMR (500 MHz, C6D6): δ 19.9, 20.1, 20.2, 24.0, 26.1,
104.7, 125.6, 125.8, 131.6, 152.0, 157.0, 164.4, 167.7. IR (KBr):
1375 (vs), 1265 (vs), 1243 (s), 963 (m), 763 (s) cm-1. MS (EI):
m/z 676 (100%) ([Mo(NAr)2ClNacNac]+). Anal. Calcd for C37H43-
ClN4Mo‚3Et2O: C, 65.57; H, 8.20; N, 6.24. Found: C, 65.68; H,
8.26; N, 6.36.
Compound 1
Mo1-O1
1.966(1)
1.686(1)
2.151(2)
94.77(6)
82.96(6)
86.45(6)
159.95(6)
120.22(6)
Mo1-N2
2.094(2)
2.5591(5)
1.907(1)
Mo1-O2
Mo1-Mo1a
Mo1-O1a
Mo1-N1
O2-Mo1-N1
O1a-Mo1-N1
N2-Mo1-N1
O1-Mo1-N1
O2-Mo1-O1a
O2-Mo1-O1
O1a-Mo1-O1
O2-Mo1-N2
O1a-Mo1-N2
O1-Mo1-N2
104.99(6)
89.90(6)
110.65(6)
128.63(6)
83.43(6)
Compound 2
Mo1-O1
1.706(2)
1.725(2)
2.327(2)
95.32(9)
107.98(8)
102.99(9)
113.21(8)
91.60(8)
135.38(8)
142.58(8)
94.06(8)
Mo1-N2
2.094(2)
2.290(2)
2.052(2)
36.50(7)
99.12(8)
86.09(8)
169.89(8)
85.92(8)
80.59(8)
80.95(7)
Mo1-O2
Mo1-N3
Mo1-N1
Mo1-N4
O2-Mo1-N4
O1-Mo1-N4
O2-Mo1-O1
O1-Mo1-N2
N2-Mo1-O2
N4-Mo1-N2
O1-Mo1-N3
O2-Mo1-N3
N4-Mo1-N3
N2-Mo1-N3
N1-Mo1-O1
O2-Mo1-N1
N4-Mo1-N1
N2-Mo1-N1
N3-Mo1-N1
[Mo(N-t-Bu)2(NacNac)2] (4). A mixture of [Mo(N-t-Bu)2Cl2-
(dme)] (0.12 g, 0.30 mmol) and NacNacK (0.10 g, 0.30 mmol)
was dissolved in 30 mL of diethyl ether and refluxed for 4 h.
Cooling the mixture and filtration over a pad of Celite afforded a
bright yellow filtrate, which was evaporated to dryness, giving 4
as a yellow solid. Recrystallization from pentane at -30 °C
overnight yielded analytically pure yellow crystals of 4. Yield:
0.096 g (55%). 1H NMR (360 MHz, C6D6): δ 1.23 (s, 18H,
N-C(CH3)3), 1.40 (s, 3H, N-C(CH3)), 1.64 (s, 3H, N-C(CH3)),
2.23 (s, 6H, CH3-Ar), 2.32 (s, 6H, CH3-Ar), 5.23 (s, 1H, γ-H),
6.87-7.08 (m, 6H, H-Ar). 13C{1H} NMR (360 MHz, C6D6): δ
19.8, 23.2, 25.6, 29.8, 71.6, 102.5, 124.8, 125.4, 131.7, 132.1, 152.1,
158.4, 163.2, 166.6. IR (KBr): 1262 (s), 1020 (s), 856 (m), 766
(vs) cm-1. MS (EI): m/z 580 (100%) ([Mo(N-t-Bu)2ClNacNac]+).
Anal. Calcd for C29H43ClN4Mo: C, 60.15; H, 7.48; N, 9.68.
Found: C, 60.03; H, 7.63; N, 9.78.
Compound 3
Mo1-N1
2.086(2)
2.271(2)
1.759(2)
81.88(6)
165.41(16)
106.57(8)
94.73(8)
92.45(8)
Mo1-N4
1.761(2)
2.3918(8)
Mo1-N2
Mo1-Cl1
Mo1-N3
N2-Mo1-Cl1
Mo1-N4-C30
N3-Mo1-N1
N4-Mo1-N1
N2-Mo1-N3
N4-Mo1-N2
N2-Mo1-N1
N3-Mo1-Cl1
Mo1-N3-C22
159.28(8)
84.25(7)
108.90(7)
157.89(16)
a Symmetry transformations used to generate equivalent atoms: (a) -x,
1
y, -z + /2.
X-ray Crystallographic Determinations. Crystals of com-
pounds 1-3 were taken from the solution, covered with oil,
mounted on nylon loops, and placed immediately in a protective
stream of cold nitrogen (100 K). Data were collected on a Bruker
three-circle diffractometer equipped with Smart 6000 CCD area
detector using mirror-monochromated Cu KR radiation (R )
1.541 78 Å). The data for compounds 2 and 3 were collected on a
non-merohedrally twinned and on a split crystal, respectively. The
data were corrected with the program TWINABS.25a The fractional
contributions of the minor domains were determined as 0.3842 and
0.014, respectively. The structures were solved by direct methods
using SHELXS-9725b and refined against F2 on all data by full-
matrix least-squares method with SHELXL-97.25c All non-hydrogen
atoms were refined anisotropically, while all hydrogen atoms were
included in the model at geometrically calculated positions and
refined using a riding model with Uij tied to the parent atom, except
the γ-proton from the NacNac ligand, whose localization from the
electron density map led to a better model and better R values. In
structure 3 the THF group was disordered about two positions. It
was refined with distance restraints and restraints for the anisotropic
displacement parameters. Selected bond lengths and angles as well
as a summary of crystallographic and refinement details is found
in Tables 1 and 2 as well as in the Supporting Information in CIF
format.
ligands is conveniently prepared by the reaction of [MoO2-
Cl2] and KPz as we have previously reported.11b The reduced
stability of the three-membered metallacycle in [MoO2(η2-
Pz)2] in comparison to a six-membered cycle formed by a
coordinated NacNac ligand seemed to us the appropriate
driving force for product formation.
For this reason a 1:1 mixture of [MoO2(η2-Pz)2] and
NacNacH in C6D6 was heated to 55 °C and monitored by
1H NMR spectroscopy by taking aliquots every hour. Figure
1 depicts the 1H NMR spectrum of the aliquot taken after 1
h (olefinic region between 6.2 and 5.2 ppm). Next to the
resonance at 5.98 and 6.20 ppm belonging to the γ-H of the
Pz ligand in PzH and [MoO2(η2-Pz)2], respectively, new
resonances appeared that are assignable to compound [MoO2-
(NacNac)(η2-Pz)] (2) (see Scheme 1): two singlets of equal
intensity at 5.20 and 6.14 ppm for the γ-H of coordinated
NacNac and η2-Pz units. However, another singlet at 5.29
ppm for an additional compound is apparent. With progres-
1
sive reaction time (12 h), in the H NMR spectrum only
resonances for this additional compound were detectable. The
chemical shifts point to a compound containing a coordinated
NacNac ligand. The absence of an additional resonance for
a η2-Pz ligand and the unlikeliness of two coordinated
NacNac ligands to one molybdenum atom led to the
Results and Discussion
Syntheses of the Compounds. The reaction of [MoO2-
(η2-Pz)2] with 1 equiv of NacNacH in toluene was investi-
gated in order to obtain compound [MoO2(NacNac)(η2-Pz)]
by substitution of one pyrazolate with a NacNac ligand. The
unusual starting material containing η2-coordinate pyrazolate
(25) (a) Sheldrick, G. M. TWINABS; Universita¨t Go¨ttingen: Go¨ttingen,
Germany, 2007. (b) Sheldrick, G. M. SHELXS-97, Program for Crystal
Structure Solution; Universita¨t Go¨ttingen: Go¨ttingen, Germany, 1997.
(c) Sheldrick, G. M. SHELXL-97, Program for Crystal Structure
Refinement, Universita¨t Go¨ttingen: Go¨ttingen, Germany, 1997.
Inorganic Chemistry, Vol. 47, No. 1, 2008 115

Lyashenko et al.
Table 2. Summary of Crystallographic Data for Compounds 1, 2, and 3‚THF
1
2
3‚THF
M
866.74
604.60
747.25
formula
cryst syst
space group
a (Å)
b (Å)
c (Å)
C42H50Mo2N4O4
monoclinic
C2/c
19.982(3)
8.848(2)
23.761(2)
90
109.81(2)
90
3952(1)
0.15 × 0.10 × 0.10
1.457
C32H44MoN4O2
orthorhombic
Pbca
15.823(3)
14.668(3)
26.703(5)
90
C37H43ClMoN4‚THF
triclinic
P1h
8.747(2)
10.923(2)
19.725(4)
84.18(3)
79.16(3)
83.00(3)
1831(1)
R (deg)
â (deg)
γ (deg)
V (Å3)
90
90
6198(2)
0.10 × 0.05 × 0.05
1.313
cryst size (mm3)
0.30 × 0.20 × 0.10
F
calc (g‚cm-3
)
1.355
Z
4
8
2
µ (mm-1
Θ range (deg)
)
5.558
3.95-58.95
18 849
3.718
3.31-59.05
85 569
3.883
2.29-58.99
32 292
reflns collected
Rint
0.0286
0.0550
0.0382
data/restraints/params
2806/0/242
1.073
0.0191
0.0523
0.371 and -0.309
4391/0/367
1.065
0.0300
0.0798
0.468 and -0.626
5099/196/494
1.055
0.0250
0.0649
0.444 and -0.361
GOF on F2
R1 indices [I > 2σ(I)]a
wR2 (all data)a
largest peak and hole (e‚Å-3
)
2
2
2
a R1 ) ∑||Fo| - |Fc||/∑|Fo|. b wR2 ) [∑w(Fo - Fc )2/∑w(Fo )2]1/2
.
conclusion that the dimeric compound [{MoO2(NacNac)}2]
(1) formed under reduction of the metal center.
867 with the correct isotopic distribution, whereas a peak
for [MoO2(NacNac)2]+ was consistently absent, also provided
evidence for a dimeric compound. The [Mo2O4]2+ core in
general is pervasive in molybdenum chemistry, but low
coordination numbers at the metal center as in 1 are rarer.26-30
The large steric influence of the NacNac ligand is presumably
responsible, so that the usual octahedral geometry is not
obtained. A search in the Cambridge Structural Database
showed examples with anionic nitrogen ligands to be almost
absent. A vaguely related compound represents the octamo-
lybdenum oxo-pyrazolate cluster containing [Mo2O2]2+ cores
bridged by anionic pyrazolates.31 The IR spectrum of 1
revealed a vibration typical for terminal ModO groups at
959 cm-1 and one due to the Mo-O-Mo stretching vibration
at 762 cm-1, which is in a good agreement with literature
compounds.17,32
The NMR experiment provided us with a protocol for the
isolation of 1 in bulk quantity. Thus, [MoO2(η2-Pz)2] and 2
equiv of NacNacH were dissolved in 30 mL of toluene and
heated to 55 °C for 12 h. After workup compound 1 was
isolated in low yield. 1H and 13C NMR spectra show
resonances for one set of a symmetrically coordinated
1
NacNac ligand. Thus, the H NMR spectrum shows three
singulets of equal intensity at 1.37, 1.47, and 2.30 ppm for
the six methyl groups in each ligand consistent with a
symmetric coordination and a barrier to rotation along the
nitrogen aryl bond rendering the two o-methyl groups at Ar
inequivalent. The resonance for the γ-proton appears at 5.29
ppm identical to the value detected with the NMR experiment
discussed above. The 13C NMR spectrum also confirms the
coordination of a NacNac ligand: three signals for the six
methyl groups at 18.1, 18.5, and 24.8 ppm and one resonance
at 103.3 ppm for the γ-proton. The line width and the shift
of the resonances point to a diamagnetic compound consistent
with a dimeric species in which the two d electrons of the
two Mo(V) centers couple with each other. Mass spectrom-
etry (EI) revealing a peak for [{MoO2(NacNac)}2]+ at m/z
The X-ray diffraction analysis unambiguously confirmed
the dimeric structure (Figure 2, crystallographic data in
Tables 1 and 2). Suitable single crystals of [{MoO2-
(NacNac)}2] (1) were obtained by cooling a concentrated
toluene solution to +5 °C. A symmetry axis running between
the two ModO bonds converts the crystallographically
independent unit into a dimer. Thus, in the compound each
(26) Cindric, M.; Vrdoljak, V.; Kamenar, B. Inorg. Chim. Acta 2002, 328,
23-32.
(27) Ricard, L.; Martin, C.; Wiest, R.; Weiss, R. Inorg. Chem. 1975, 14,
2300-2301.
(28) Dance, I. G.; Wedd, A. G.; Boyd, I. W. Aust. J. Chem. 1978, 31,
519-526.
(29) Lim, B. S.; Willer, M. W.; Miao, M.; Holm, R. H. J. Am. Chem. Soc.
2001, 123, 8343-8249.
(30) Dahlstrohm, P. L.; Hyde, J. R.; Vella, P. A.; Zubieta, J. Inorg. Chem.
1982, 21, 927-932.
(31) Ehlert, M. K.; Rettig, S. J.; Storr, A.; Thompson, R. C.; Trotter, J.
Inorg. Chem. 1993, 32, 5176-5182.
(32) (a) Saurenz, D.; Demirhan, F.; Richard, P.; Poli, R.; Sitzmann, H.
Eur. J. Inorg. Chem. 2002, 1415-1424. (b) Bottomley, F.; Boyle, P.
D.; Chen, J. Organometallics 1994, 13, 370-373. (c) Kahrovic´, E.;
Molcˇanov, K.; Tusˇek-Bozˇic´, L.; Kojic´-Prodic´, B. Polyhedron 2006,
25, 2459-2464.
Figure 1. 1H NMR spectrum of the reaction between [MoO2(η2-Pz)2] and
NacNacH taken after 1 h reaction time showing resonances for the γ-H of
[{MoO2(NacNac)}2] (1) and [MoO2(NacNac)(η2-Pz)] (2) next to those of
unreacted [MoO2(η2-Pz)2] and formed PzH.
116 Inorganic Chemistry, Vol. 47, No. 1, 2008

Molybdenum Complexes of â-Diketiminate Ligands
Scheme 1
Mo center is pentacoordinate and the two terminal oxo
ligands are in the cis position to each other. The geometry
about the metal is between a trigonal bipyramid and a square
pyramid with a τ value of 0.52,33 where 1 would represent
the former and 0 the latter geometry. The τ value is large in
comparison to other structures of this type pointing to a high
degree of distortion.27-30 Other features, such as the metal-
metal distance (Mo1-Mo1a, 2.5591(5) Å) or the metal
oxygen single bonds (Mo1-O1, 1.966(1) Å) and double
bonds (Mo1-O2, 1.686(1) Å) are similar to those in the
literature.29 The Mo-N distances, Mo1-N1 ) 2.151(2) and
Mo1-N2 ) 2.094(2) Å, are in a good agreement with those
in the octamolybdenum oxo pyrazolate cluster mentioned
above.31
The isolation and characterization of compound 2 was
more challenging as all attempts to obtain it in pure form
led to material that was contaminated by 1 or by [MoO2-
(η2-Pz)2]. This is consistent with the data obtained by
monitoring the reaction by NMR spectroscopy showing
always additional resonances for [MoO2(η2-Pz)2] and/or 1.
The crystallizing behavior of these compounds seems to be
similar as no separation could be achieved. However, from
such mixtures, crystals of 2 could be selected that were
suitable for X-ray diffraction analysis confirming the coor-
dination of a NacNac and a η2-Pz ligand (Figure 3 and
crystallographic data in Tables 1 and 2). The molecular
structure of [MoO2(NacNac)(η2-Pz)] (2) shows several
interesting features. The coordination of a η2-Pz ligand
evidenced by the two bond lengths Mo1-N3 ) 2.290(2) Å
and Mo1-N4 ) 2.052(2) Å can still be considered unusual
although we11 and others34 have published several examples
in recent years. The small bite angle of the coordinated η2-
Pz unit (N3-Mo1-N4 ) 36.50(7)°) in comparison to that
of the NacNac ligand (N1-Mo1-N2 ) 80.59(8)°) renders
the geometry about the metal into a highly distorted
octahedron. This leads to two unsymmetric metal oxo groups
O1 and O2. In compound 2, the largest O1-Mo-N angle
is 142.52(8)°, whereas the angle O2-Mo-N is 169.89(8)°,
pointing to heavy distortion from an octahedral structure as
well as to the unsymmetrical coordination of the two oxygen
atoms. Interest in such unsymmetrical dioxo compounds is
large in view of the discussion that in dioxo complexes one
of the two oxo groups serves as a spectator oxo ligand while
the other is actually transferred.35,36 In addition, trigonal
prismatic transition states seem to play a role in biological
OAT reactions,37 but model compounds showing this ge-
ometry are limited.11 In compound 2, the pyrazolate ligand
lies approximately coplanar with the metal atom, one of the
two oxygen atoms (O1) and one of the two nitrogen atoms
of NacNac (N2). We have previously observed the preferred
coordination of the metal oxo group coplanar to the Pz-plane
in the molecular structure of the molybdenum(IV) compound
[MoO(η2-Pz)2(PEt)2].11 The ModO bond lengths in 2, Mo1-
O1 ) 1.706(2) Å and Mo1-O2 ) 1.725(2) Å, are in the
expected range for compounds containing the [MoO2]2+
core.11,12,38,39
A common way to introduce a ligand to the [MoO2]2+
core is the use of [MoO2Cl2] or [MoO2Cl2(dme)] as starting
materials and the addition of either a mixture of LH and
triethylamine or by employing deprotonated ligands such as
KL or LiL. However, all these methods were unsuccessful
(35) Rappe´, A. K.; Goddard, W. A. I. Nature 1980, 285, 311-312.
(36) Rappe´, A. K.; Goddard, W. A. I. J. Am. Chem. Soc. 1982, 104, 448-
456.
(37) (a) Kaupp, M. Angew. Chem. 2004, 116, 554-558; Angew. Chem.,
Int. Ed. 2004, 43, 546-549. (b) Thapper, S.; Deeth, R. J.; Nordlander,
E. Inorg. Chem. 2002, 41, 6695-6702. (c) Webster, C. E.; Hall, M.
B. J. Am. Chem. Soc. 2001, 123, 5820-5821.
(33) Addison, A. W.; Rao, T. N.; Reedijk, J.; van Rijn, J.; Verschoor, G.
C. J. Chem. Soc., Dalton Trans. 1984, 1349-1356.
(34) (a) Guzei, I. A.; Baboul, A. G.; Yap, G. P. A.; Rheinhold, A. L.;
Schlegel, H. B.; Winter, C. H. J. Am. Chem. Soc. 1997, 119, 3387-
3388. (b) Gust, K. R.; Knox, J. E.; Heeg, M. J.; Schlegel, H. B.; Winter,
C. H. Angew. Chem. 2002, 114, 1661-1664; Angew. Chem., Int. Ed.
2002, 41, 1591-1594. (c) Deacon, G. B.; Forsyth, C. M.; Gitlits, A.;
Harika, R.; Junk, P. C.; Skelton, B.; White, A. H. Angew. Chem. 2002,
114, 3383-3385; Angew. Chem., Int. Ed. 2002, 41, 3249-3251. (d)
Deacon, G. B.; Gitlits, A.; Skelton, B. W.; White, A. H. Chem.
Commun. (Cambridge) 1999, 1213-1214.
(38) Lyashenko, G.; Jancik, V.; Pal, A.; Herbst-Irmer, R.; Mo¨sch-Zanetti,
N. C. Dalton Trans. 2006, 1294-1301.
(39) (a) Hammes, B. S.; Chohan, B. S.; Hoffman, J. T.; Einwa¨chter, S.;
Carrano, C. J. Inorg. Chem. 2004, 43, 7800-7806. (b) Zhao, J.; Zhou,
X.; Santos, A. M.; Herdtweck, E.; Roma˜o, C. C.; Ku¨hn, F. E. Dalton
Trans. 2003, 3736-3742. (c) Go´mez, M.; Jansat, S.; Muller, G.;
Noguera, G.; Teruel, H.; Moliner, V.; Cerrada, E.; Hursthouse, M.
Eur. J. Inorg. Chem. 2001, 1071-1076.
Inorganic Chemistry, Vol. 47, No. 1, 2008 117

Lyashenko et al.
The reaction of the bisimido complexes [Mo(NAr)2Cl2-
(dme)]24 and [Mo(N-t-Bu)2Cl2(dme)]24 with the potassium
salt NacNacK21 in diethyl ether forms monosubstituted
compounds [Mo(NAr)2Cl(NacNac)] (3) and [Mo(N-t-Bu)2Cl-
(NacNac)] (4), respectively, in good yields (eq 1).
[Mo(NR)2Cl2(dme)] +
-KCl
KNacNac
[Mo(NR) Cl(NacNac)]
3, R ) 2,6-Me2C6H3
4, R ) t-Bu
8
2
(1)
It is worth noting that treatment of [Mo(NAr)2Cl2(dme)] and
[Mo(N-t-Bu)2Cl2(dme)] with 2 or more equiv of NacNacK
does not afford disubstituted complexes, but rather com-
pounds 3 and 4 are isolated in all attempts consistent with
the large steric impact of the NacNac ligand.
The 1H NMR spectra of 3 and 4 confirm the formation of
monosubstituted compounds as the integration of the reso-
nances attributable to the γ-protons of NacNac vs the
aromatic region in 3 amounts to 1:12 and vs the aliphatic
region in 4 to 1:36. In both compounds the NacNac ligand
is coordinated in an unsymmetrical fashion as the two methyl
groups in the backbone give rise to two singlets of equal
intensity, whereas the two aromatic substituents can freely
rotate along the N-C(Ar) bond evidenced by the occurrence
of only two singlets with the intensity of 6 each. 13C NMR
data confirm the structure of the two compounds. However,
the 13C NMR spectrum of compound 4 shows only one
resonance at 19.8 ppm for the two sets of two inequivalent
methyl groups attached to the aromat of the NacNac unit
which was confirmed by a HSQC spectrum (see Supporting
Information). Interestingly, only one set of resonance appears
in the spectra of both compounds for the two imido groups.
Thus, the broad signal at 2.41 ppm in the 1H NMR spectrum
of 3 can be assigned to the four methyl groups of the imido
aromats and in the spectrum of 4 the singlet at 1.23 ppm to
the two imido t-Bu groups. This points to a dymanic process
Figure 2. Molecular structure of [{MoO2(NacNac)}2] (1). Thermal
ellipsoid plot (50% probability surface). Hydrogen atoms have been omitted
for clarity.
Figure 3. Molecular structure of [MoO2(NacNac)(η2-Pz)] (2). Thermal
ellipsoid plot (50% probability surface). Hydrogen atoms have been omitted
for clarity.
and led to mixtures from which we were not able to isolate
any pure compounds, although mass spectrometry on samples
obtained from such reactions gave evidence for the formation
of 1 (a peak at m/z 867 for [{MoO2(NacNac)}2]+). Thus,
reduction of the metal center is encountered in all reactions
employing the [MoO2]2+ core and the â-diketiminate ligand.
The site of oxidation is as yet unclear, but oxidative
degradation of the NacNac backbone seems likely. Such a
degradation has recently been reported in NacNac copper
and zinc complexes where aerobic conditions result in the
formation of a ketone.40 In addition, recently reported
molybdenum imido alkylidene complexes containing a
NacNac ligand feature activation at the γ-carbon in the
backbone by the alkylidene.20 In the system reported here,
the nature of the decomposition product is unclear as the 1H
NMR spectra of the reaction solutions did not show any
resonances for organic products other than the ones described
above, suggesting insoluble oxidized products may have been
produced.
1
in solution which was investigated by low-temperature H
NMR spectroscopy by taking compound 3 as an example.
Thus, cooling a sample of 3 in toluene-d8 to -30 °C shows
splitting of the broad resonance at 2.41 ppm into four singlets
of equal intensity at 2.24, 2.32, 2.51, and 2.67 ppm. However,
the rotation along the N-C(Ar) bond of the NacNac ligand
is still not restricted at this temperature as the corresponding
resonances broaden slightly but remain at 2.14 and 2.43 ppm.
Similar behavior has been found in bisimido complexes with
bidentate phenolate ligands [Mo(NAr)2(L)X] (L ) OC6H4-
CH2NMe2), where the four ortho-substituents on the imido
aryl groups are found to be equivalent at room temperature.41
The IR spectra shows characteristic ModN stretching
vibrations at 1265 and 1262 cm-1 for 3 and 4, respectively,
which is in good agreement with the literature.42 Electron
impact mass spectrometry revealed the molecular ion for both
compounds with the correct isotopic patterns.
In contrast, no reduction or any other kind of decomposi-
tion occurs by treatment of high oxidation state molybdenum-
(VI) compounds containing two imido instead of oxo groups.
(41) Brandts, J. A. M.; Boersma, J.; Spek, A. L.; van Koten, G. Eur. J.
Inorg. Chem. 1999, 1727-1733.
(42) Radius, U.; Wahl, G.; Sundermeyer, J. Z. Anorg. Allg. Chem. 2004,
630, 848-857.
(40) Yokota, S.; Yoshimitsu, T.; Itoh, S. Inorg. Chem. 2002, 41, 1342-
1344.
118 Inorganic Chemistry, Vol. 47, No. 1, 2008

Molybdenum Complexes of â-Diketiminate Ligands
Figure 5.
) 2.271(2) Å in 3 with the longer bond being the one which
is trans to the oxo or imido substituent. The larger steric
impact of the pyrazolate vs the chloride ligand apparently
causes the bite angle of the NacNac ligand to be smaller in
comparison (N1-Mo1-N2 ) 80.59(8)° in 2 and N1-Mo1-
N2 ) 84.25(7)° in 3) even though the NAr is larger than an
oxo group.
Figure 4. Molecular structure of [Mo(NAr)2Cl(NacNac)] (3). Thermal
ellipsoid plot (50% probability surface). Hydrogen atoms have been omitted
for clarity.
Other examples of molybdenum(VI) imido compounds
that contain a NacNac ligand are the previously mentioned
imido alkylidene complexes reported by Schrock and co-
workers.20 Their method of synthesis corresponds to the one
described in this work as the imido alkylidene starting
material47 was treated with the lithium salt of a related
NacNac ligand giving [Mo(NAr)(CH-t-Bu)(NacNac)(OTf)]
(Ar ) 2,6-i-Pr2C6H3), which was crystallographically char-
acterized. The relevant bond lengths and angles of the
diketiminate ligands are similar in the two compounds (e.g.
the N-Mo-N angles are 83.91(6)° in the imido alkylidene
complex vs 84.25(7)° in 3 and the bond lengths are 2.1266-
(16) and 2.147(16) Å in Schrock’s20 and Mo1-N1 ) 2.086-
(2), Mo1-N2 ) 2.271(2) Å in 3). This leads to similar
overall geometries being trigonal-bipyramidal in both com-
plexes with one of the NacNac nitrogen atoms and the triflate
or the imido group in the apical positions, respectively.
X-ray diffraction analysis of a suitable single crystal of
3 obtained by recrystallization from a cold THF solution
(-20 °C) overnight allowed the determination of its molec-
ular structure (Figure 4 and crystallographic data in Tables
1 and 2). The molybdenum atom is pentacoordinate and the
geometry is best described as trigonal-bipyramidal33 (largest
angle, N2-Mo1-N4 ) 159.28(8)°; second largest angle,
N1-Mo1-Cl1 ) 142.29(5)°) with N4(imido) and N2-
(NacNac) in the apical positions. The two Mo-N(imido)-C
angles are 165.41(16) and 157.89(16)° consistent with the
expected sp hybridized nitrogen atom and a MtN triple
bond.43 Another imido ligand shows a much less obtuse
Mo1-N3-C22 angle of 157.89(16)°, which is at the low
end of the linear coordination. Thus, in the solid state, all
methyl groups are inequivalent, contrasting the solution data
at room temperature but being in good agreement with low-
temperature NMR spectroscopy described above. Both imido
units are cis to each other, as expected, and the ModN bond
lengths are Mo1-N3 ) 1.759(2) and Mo1-N4 ) 1.761(2)
Å, comparable to those in literature.38,41,44 The molybdenum-
chloride bond length is 2.3918(8) Å, similar to those in
literature.38,45 The bond Mo1-N1 ) 2.086(2) Å is in the
same range as the few other bisimido amido complexes
reported before.38,44-46
A comparison of the geometry of compound [MoO2-
(NacNac)(η2-Pz)] (2) to that of [Mo(NAr)2Cl(NacNac)] (3)
reveals interesting similarities (Figure 5). Considering the
middle of the N-N bond in the η2-Pz ligand as the
coordination site, both compounds adopt similar trigonal-
bipyramidal geometries with one of the NacNac N atoms in
a trans position to oxo or imido group, respectively. In
compounds 2 and 3 bond lengths of coordinated NacNac
ligands are comparable: Mo1-N1 ) 2.327(2) Å, Mo1-N2
) 2.094(2) Å in 2 and Mo1-N1 ) 2.086(2) Å, Mo1-N2
Conclusion
We demonstrate that molybdenum oxo complexes that
contain the â-diketiminate ligand NacNac can be prepared
starting from the molybdenum dioxo pyrazolate complex
[MoO2(η2-Pz)2]. This represents a novel approach to use η2-
pyrazolate ligands as leaving groups. Monitoring of its
reaction with NacNacH by NMR spectroscopy shows the
formation of a mixture of dimeric [{MoO2(NacNac)}2] (1)
and monomeric [MoO2(NacNac)(η2-Pz)] (2). The formation
of the dimeric compound 1 is clearly predominant, and it is
presumably formed by oxidative degradation of the ligand
explaining the lack of NacNac complexes in oxidizing
systems. The structures of both compounds were crystallo-
graphically determined. In contrast, the complexes [Mo-
(NAr)2Cl(NacNac)] (3) and [Mo(N-t-Bu)2Cl(NacNac)] (4)
were prepared in good yields as the bisimido cores are not
prone to reduction. We are currently working on the
development of a protocol for the formation of compounds
of the type [MoO2(NacNac)X] by employing other molyb-
denum precursors allowing the introduction of the NacNac
(43) Barrie, P.; Coffey, T. A.; Forster, G. D.; Hogarth, G. J. Chem. Soc.,
Dalton Trans. 1999, 4519-4528.
(44) (a) Chen, T.; Soraenee, K. R.; Wu, Z.; Diminie, J. B.; Xue, Z. Inorg.
Chim. Acta 2003, 345, 113-120. (b) Bryson, N.; Yoinou, M. T.;
Osborn, J. A. Organometallics 1991, 10, 3389-3382.
(45) Siewert, I.; Limberg, C.; Ziemer, B. Z. Anorg. Allg. Chem. 2006, 632,
1078-1082.
(47) Oskam, J. H.; Fox, H. H.; Yap, K. B.; McConville, D. H.; O’Dell, R.;
Lichtenstein, B. J.; Schrock, R. R. J. Organomet. Chem. 1993, 459,
185-198.
(46) Alexander, J. B.; Schrock, R. R.; Davis, W. M.; Hultzsch, K. C.;
Hoveyda, A. H.; Houser, J. H. Organometallics 2000, 19, 3700-3715.
Inorganic Chemistry, Vol. 47, No. 1, 2008 119

Lyashenko et al.
Supporting Information Available: Crystallographic data in
CIF format and gHSQC spectrum of 4. This material is available
free of charge via the Internet at http://pubs.acs.org.
ligand under milder conditions in order to investigate the
oxygen atom transfer activity of these unusual compounds.
Acknowledgment. We acknowledge the Deutsche For-
schungsgemeinschaft for generous financial support (Grant
MO 963/2).
IC701534A
120 Inorganic Chemistry, Vol. 47, No. 1, 2008