Molecular nitrides with titanium and rare-earth metals

Article abstract of DOI:10.1021/ic2008683

A series of titanium-group 3/lanthanide metal complexes have been prepared by reaction of [{Ti(η⁵-C₅Me₅)(μ-NH)} ₃(μ₃-N)] (1) with halide, triflate, or amido derivatives of the rare-earth metals. Treatment of 1 with metal halide complexes [MCl₃(thf)_n] or metal trifluoromethanesulfonate derivatives [M(O₃SCF₃)₃] at room temperature affords the cube-type adducts [X₃M{(μ₃-NH) ₃Ti₃(η⁵-C₅Me₅) ₃(μ₃-N)}] (X = Cl, M = Sc (2), Y (3), La (4), Sm (5), Er (6), Lu (7); X = OTf, M = Y (8), Sm (9), Er (10)). Treatment of yttrium (3) and lanthanum (4) halide complexes with 3 equiv of lithium 2,6-dimethylphenoxido [LiOAr] produces the aryloxido complexes [(ArO)₃M{(μ₃- NH)₃Ti₃(η⁵-C₅Me ₅)₃(μ₃-N)}] (M = Y (11), La (12)). Complex 1 reacts with 0.5 equiv of rare-earth bis(trimethylsilyl)amido derivatives [M{N(SiMe₃)₂}₃] in toluene at 85-180 °C to afford the corner-shared double-cube nitrido compounds [M(μ₃-N) ₃(μ₃-NH)₃{Ti₃(η⁵- C₅Me₅)₃(μ₃-N)}₂] (M = Sc (13), Y (14), La (15), Sm (16), Eu (17), Er (18), Lu (19)) via NH(SiMe ₃)₂ elimination. A single-cube intermediate [{(Me ₃Si)₂N}Sc{(μ₃-N)₂(μ ₃-NH)Ti₃(η⁵-C₅Me ₅)₃(μ₃-N)}] (20) was obtained by the treatment of 1 with 1 equiv of the scandium bis(trimethylsilyl)amido derivative [Sc{N(SiMe₃)₂}₃]. The X-ray crystal structures of 2, 7, 11, 14, 15, and 19 have been determined. The thermal decomposition in the solid state of double-cube nitrido complexes 14, 15, and 18 has been investigated by thermogravimetric analysis (TGA) and differential thermal analysis (DTA) measurements, as well as by pyrolysis experiments at 1100 °C under different atmospheres (Ar, H₂/N₂, NH₃) for the yttrium complex 14.

Full text of DOI:10.1021/ic2008683

ARTICLE
pubs.acs.org/IC
Molecular Nitrides with Titanium and Rare-Earth Metals
Jorge Caballo, María García-Castro, Avelino Martín, Miguel Mena, Adri ꢀa n P ꢀe rez-Redondo, and
Carlos Y ꢀe lamos*
Departamento de Química Inorg ꢀa nica, Universidad de Alcal ꢀa , 28871 Alcal ꢀa de Henares-Madrid, Spain
S Supporting Information
b
ABSTRACT: A series of titanium-group 3/lanthanide metal complexes
5
have been prepared by reaction of [{Ti(η -C Me )(μ-NH)} (μ -N)] (1)
5
5
3
3
with halide, triflate, or amido derivatives of the rare-earth metals. Treatment
of 1 with metal halide complexes [MCl (thf) ] or metal trifluoromethane-
3
n
sulfonate derivatives [M(O SCF ) ] at room temperature affords the cube-
3
3 3
5
type adducts [X M{(μ -NH) Ti (η -C Me ) (μ -N)}] (X = Cl, M = Sc
3
3
3
3
5
5 3
3
(
(
2), Y (3), La (4), Sm (5), Er (6), Lu (7); X = OTf, M = Y (8), Sm (9), Er
10)). Treatment of yttrium (3) and lanthanum (4) halide complexes with 3
equiv of lithium 2,6-dimethylphenoxido [LiOAr] produces the aryloxido
5
complexes [(ArO) M{(μ -NH) Ti (η -C Me ) (μ -N)}] (M = Y (11),
3
3
3
3
5
5 3
3
La (12)). Complex 1 reacts with 0.5 equiv of rare-earth bis(trimethylsilyl)amido derivatives [M{N(SiMe ) } ] in toluene at
3
2 3
5
8
(
[
5ꢀ180 °C to afford the corner-shared double-cube nitrido compounds [M(μ -N) (μ -NH) {Ti (η -C Me ) (μ -N)} ] (M = Sc
3
3
3
3
3
5
5 3
3
2
13), Y (14), La (15), Sm (16), Eu (17), Er (18), Lu (19)) via NH(SiMe ) elimination. A single-cube intermediate
3 2
5
{(Me Si) N}Sc{(μ -N) (μ -NH)Ti (η -C Me ) (μ -N)}] (20) was obtained by the treatment of 1 with 1 equiv of the scandium
3
2
3
2
3
3
5
5 3
3
bis(trimethylsilyl)amido derivative [Sc{N(SiMe ) } ]. The X-ray crystal structures of 2, 7, 11, 14, 15, and 19 have been determined.
3
2 3
The thermal decomposition in the solid state of double-cube nitrido complexes 14, 15, and 18 has been investigated by
thermogravimetric analysis (TGA) and differential thermal analysis (DTA) measurements, as well as by pyrolysis experiments at
1
100 °C under different atmospheres (Ar, H /N , NH ) for the yttrium complex 14.
2
2
3
’
INTRODUCTION
Polynuclear transition-metal nitrido complexes constitute a
context, molecular heterometallic nitrido compounds with pre-
0
formed MꢀNꢀM linkages are attractive candidates to serve as
15
precursors of ternary metal nitrides, or homogeneous ceramic
composites consisting of two or more binary nitrides. Thermal
decomposition of heterobimetallic precursors with well-defined
structures can offer a unique and facile approach for the prepara-
tion of materials with optimum distribution of both metals. The
advantage of this method over the classical multicomponent
approach has recently been demonstrated for the preparation of
heterobimetallic oxide materials from organometallic cage
class of molecular cage compounds with fascinating structures
and interesting bonding properties. While nitrido complexes of
the mid transition-metals (groups 6, 7, and 8) in a high oxidation
state are usually mononuclear and feature terminal nitrido
ligands, in early transition-metal (groups 4 and 5) systems there
is a stronger tendency to form dimeric or oligomeric species with
nitrido ligands bridging two or more metal centers. Structurally
characterized examples include di-, tri-, tetra-, penta-, and
hexanuclear complexes with nitrido moieties shared between
the metal centers. In those examples, the presence of bulky
ancillary ligands (e.g., cyclopentadienyl, alkoxido) at the metal
centers is crucial to obtain discrete and soluble molecular
compounds. Species with μ -nitrido groups are proposed as
intermediates in dinitrogen fixation and activation,
new structural and electronic data on molecular systems may
provide insights into those processes.
1
2
3,4
5,6
7
8
16
9
precursors. A review of the literature shows several examples
of the use of molecular or polymeric precursors in the synthesis of
13,17
ternary metal nitrides or homogeneous nitride composites,
but
the search reveals also the lack of systematic strategies for the
rational construction of aggregates with desired metal composi-
tions.
n
1
0ꢀ12
and
As part of a project devoted to the development of polynuclear
nitrido complexes, we have been investigating the rational
synthesis of a family of heterometallic nitrido complexes by
treatment of the trinuclear titanium imido-nitrido complex
Interest in the development of polynuclear nitrido complexes
is also due to their potential role as building blocks and precu-
5
4,6
13
[{Ti(η -C Me )(μ-NH)} (μ -N)] (1) with a variety of metal
5 5 3 3
rsors of metal nitride (MN) materials. Although the literature
precedents are still scarce, Wolczanski and co-workers have
demonstrated that the geometry of the nitrido tantalum pre-
cursor [(tBuCH ) TaN] NH 2C H allows access to cubic
TaN at 820 °C, instead of the hexagonal phase, which is more
thermodynamically stable at that temperature.
derivatives. Compound 1 shows an incomplete-cube [Ti(μ-
NH) (μ -N)] core and is prone to incorporate metal fragments
3
3
2
2
5
3
3
3
7 8
Received: April 25, 2011
Published: June 16, 2011
8a,14
In this
r 2011 American Chemical Society
6798
dx.doi.org/10.1021/ic2008683
|Inorg. Chem. 2011, 50, 6798–6808

Inorganic Chemistry
ARTICLE
into the structure to give cube-type heterometallic complexes.
The sterically demanding pentamethylcyclopentadienyl groups
on the titanium atoms of 1 are crucial to confer solubility and
stability to those polynuclear nitrido complexes, enabling to
uncover a diverse spectrum of chemical structure and reactivity in
this area. Our previous work has shown that 1 is capable of acting
as a neutral chelate ligand through the basal NH groups toward
(5 mL). The reaction mixture was stirred at room temperature for 24
h to give an orange solid and a brown solution. The solid was isolated by
filtration onto a glass frit and vacuum-dried to afford 2 as an orange
ꢀ1
powder (0.26 g, 70%). IR (KBr, cm ): ν~ 3331 (s), 2912 (s), 1487 (w),
426 (m), 1380 (s), 1067 (w), 1024 (w), 730 (vs), 708 (vs), 664 (s), 643
1
1
(
1
vs), 619 (s), 535 (w), 476 (w), 436 (w). H NMR (CDCl , 20 °C): δ
2.31 (s br., 3H; NH), 2.17 (s, 45H; C
0 °C): δ 125.0 (C Me ), 12.6 (C Me
3
13 1
5
Me
5 3
). C{ H} NMR (CDCl ,
1
8
19
2
5
5
5
5
). Anal. Calcd for C30H48Cl -
3
transition and main-group metal derivatives. We have also
N ScTi (M = 759.65): C 47.43, H 6.37, N 7.38. Found: C 47.21, H
4
3
w
recently reported the preliminary results on the coordination of 1
20
6.00, N 6.97.
to yttrium and erbium halides. In those complexes, 1 acts as a
facially coordinating ligand to the rare-earth centers and resem-
bles other six-electron donors as the anionic tris(pyrazolyl)-
5
Synthesis of [Cl La{(μ -NH) Ti (η -C Me ) (μ -N)}] (4). In
3
3
3
3
5
5 3
3
a fashion similar to the preparation of 2, the treatment of 1 (0.50 g, 0.82
2
1
mmol) with [LaCl (thf)1.5] (0.28 g, 0.78 mmol) in toluene (20 mL) and
3
borates, the neutral analogous tris(pyrazolyl)methanes and
2
2,23
THF (5 mL) afforded 4 as a yellow powder (0.52 g, 78%). IR
tris(pyrazolyl)silanes,
triazacyclononanes
and cyclic triamines such as 1,4,7-
ꢀ
1
2
3,24
23b,25
(KBr, cm ): ν~ 3310 (s), 2909 (s), 2859 (m), 1489 (m), 1427 (s),
378 (s), 1066 (w), 1025 (m), 758 (s), 695 (vs), 663 (vs), 532 (w), 475
and 1,3,5-triazacyclohexanes.
Here-
1
in we report a systematic study on the coordination of the metal-
loligand 1 to group 3 and lanthanide metals, as well as prelimi-
nary experiments on the solid-state thermal decomposition of
several molecular nitrides with titanium and rare-earth metals.
1
(
(
1
4
m), 431 (w). H NMR (CDCl
s, 45H; C
3
, 20 °C): δ 13.37 (s br., 3H; NH), 2.17
). C{ H} NMR (CDCl , 20 °C): δ 123.7 (C Me ),
2.7 (C Me ). Anal. Calcd for C H Cl LaN Ti (M = 853.61): C
13
1
5
Me
5
3
5
5
5
5
30 48
3
4
3
w
2.21, H 5.67, N 6.56. Found: C 41.82, H 5.30, N 6.36.
5
Synthesis of [Cl Sm{(μ -NH) Ti (η -C Me ) (μ -N)}] (5). In
3
3
3
3
5
5 3
3
a fashion similar to the preparation of 2, the treatment of 1 (0.30 g, 0.49
mmol) with [SmCl (thf)3.5] (0.25 g, 0.49 mmol) in toluene (20 mL)
and THF (5 mL) at room temperature for 24 h gave 5 as a yellow powder
(0.35 g, 83%). IR (KBr, cm ): ν~ 3312 (s), 2909 (s), 1488 (m), 1427 (s),
1377 (s), 1066 (w), 1023 (m), 861 (w), 701 (vs), 656 (vs), 532 (w), 475
’
EXPERIMENTAL SECTION
3
General Considerations. All manipulations were carried out
ꢀ
1
under argon atmosphere using Schlenk line or glovebox techniques.
Toluene and hexane were distilled from Na/K alloy just before use.
Tetrahydrofuran (THF, thf) was distilled from purple solutions of
sodium benzophenone just prior to use. NMR solvents were dried with
1
(m), 431 (w). H NMR (CDCl
3
, 20 °C): δ 13.55 (s br., 3H; NH), 1.99
). C{ H} NMR (CDCl , 20 °C): δ 123.4 (C Me ),
). Anal. Calcd for C30 SmTi (M = 865.06): C
41.65, H 5.59, N 6.48. Found: C 41.43, H 5.69, N 6.25.
1
3
1
(s, 45H; C
12.3 (C Me
5
Me
5
3
5
5
Na/K alloy (C
6
D
6
) or calcium hydride (CDCl
3
) and vacuum-distilled.
5
5
H
48Cl
3
N
4
3
w
Oven-dried glassware was repeatedly evacuated with a pumping system
ꢀ3
5
(
ca. 1 ꢁ 10 Torr) and subsequently filled with inert gas. Thermolyses
Synthesis of [Cl
a fashion similar to the preparation of 2, the treatment of 1 (0.20 g, 0.33
mmol) with [LuCl (thf) ] (0.17 g, 0.33 mmol) in toluene (20 mL) and
Lu{(μ -NH) Ti (η -C Me ) (μ -N)}] (7). In
3 3 3 3 5 5 3 3
in solution at high temperatures were carried out by heating flame-sealed
NMR or Carius tubes in a Roth autoclave model III. Anhydrous group 3
3
3
and lanthanide metal halides [MCl
Strem and used as received. The thf adducts [MCl (thf) ] (M = Sc, Lu,
3
] were purchased from Aldrich or
THF (5 mL) at room temperature for 24 h afforded 7 as a yellow powder
(0.16 g, 55%). IR (KBr, cm ): ν~ 3329 (s), 2912 (s), 2859 (m), 1485
26
ꢀ1
3
n
27
n = 3; M = Y, Sm, Er, n = 3.5; M = La, n = 1.5) were prepared by heating
under reflux a suspension of [MCl ] in THF. Metal tris(trifluorome-
thanesulfonate) reagents [M(O SCF ) ] (M = Y, La, Sm, Er) were
(m), 1425 (s), 1380 (s), 1066 (w), 1024 (w), 775 (s), 736 (vs), 701 (vs),
1
643 (vs), 620 (vs), 535 (m), 477 (m), 436 (w), 407 (w). H NMR
3
(CDCl
3
, 20 °C): δ 12.50 (s br., 3H; NH), 2.17 (s, 45H; C
5
Me
, 20 °C): δ 124.4 (C Me ), 12.3 (C Me ). Anal.
5 5 5 5
5
).
3
3 3
1
3
1
purchased from Aldrich, and heated at 180 °C under dynamic vacuum
prior to use. Lithium 2,6-dimethylphenoxido [Li(OAr)] was prepared
by reaction of 2,6-dimethylphenol with [LinBu] (Aldrich, 1.6 M in
C{ H} NMR (CDCl
Calcd for C30 LuN
Found: C 40.52, H 5.25, N 6.31.
3
H
48Cl
3
4
Ti
3
(M
w
= 889.66): C 40.50, H 5.44, N 6.30.
5
4,6
5
hexane). [{Ti(η -C Me )(μ-NH)} (μ -N)] (1), [Y(CH SiMe ) -
Synthesis of [(CF SO O) Y{(μ -NH) Ti (η -C Me ) (μ -
5
5
3
3
2
3 3
30
3
2
3
3
3
3
5
5 3
3
28
29
(thf)
3
], and [M{N(SiMe
3
)
2
}
3
] (M = Sc, Y, La, Sm, Eu, Er, Lu)
N)}] (8). A 100 mL Schlenk flask was charged with 1 (0.30 g, 0.49
were prepared according to published procedures. The syntheses and
mmol), [Y(O SCF ] (0.24 g, 0.44 mmol), and toluene (30 mL).
3
)
3 3
2
0
characterization of complexes 3 and 6 have been reported previously.
The reaction mixture was stirred at room temperature for 2 days.
The brown suspension was filtered through a coarse glass frit, and
the resultant orange solid in the frit was vacuum-dried and char-
1
Samples for infrared spectroscopy were prepared as KBr pellets. H,
1
3
1
19
C{ H}, and F NMR spectra were recorded on a Varian Unity-300
1
ꢀ1
and/or Mercury-300 spectrometers. Chemical shifts (δ, ppm) in the H
acterized as 8 (0.36 g, 72%). IR (KBr, cm ): ν~ 3329 (w), 3294 (w),
13
1
and C{ H} NMR spectra are given relative to residual protons or to
2920 (w), 1429 (w), 1383 (m), 1338 (vs), 1240 (vs), 1196 (vs), 1036
19
1
carbon of the solvent. Chemical shifts (δ, ppm) in the F NMR spectra
are given relative to CFCl as external reference. Microanalyses (C, H,
(vs), 1014 (s), 763 (m), 635 (vs), 512 (m), 477 (w). H NMR
(CDCl
, 20 °C): δ 13.16 (s br., 3H; NH), 2.18 (s, 45H; C
C{ H} NMR (CDCl , 20 °C): δ 124.0 (C Me ), 12.1 (C Me
NMR (CDCl
, 20 °C): δ ꢀ77.9. Anal. Calcd for C33
Ti Y (M
34.85, H 4.72, N 4.85, S 7.95.
Synthesis of [(CF SO O) Sm{(μ -NH) Ti (η -C Me ) (μ -
Me ).
3
3
5 5
1
3
1
19
N, S, O) were performed in a Leco CHNSO-932 microanalyzer.
Simultaneous DTA/TG analysis were conducted on a SDT Q600 TA
Instruments coupled with quadrupole mass spectrometer system
3
5
5
5
5
).
F
3
H
48
F
9
N
4
O
9
S
3-
3
w
= 1144.45): C 34.63, H 4.23, N 4.90, S 8.41. Found: C
(THERMOSTAR GSD300 T3) at the Instituto de Ciencias de Materi-
5
ales de Madrid ICMM-CSIC. Samples were heated between 25 and
3
2
3
3
3
3
5
5 3
3
1
1
000 °C using argon as the flow gas (200 sccm) with a heating rate of
0 °C/min (sample weights ≈10 mg). SEM/EDX results were obtained
N)}] (9). In a fashion similar to the preparation of 8, the treatment of 1
(0.30 g, 0.49 mmol) with [Sm(O SCF ) ] (0.28 g, 0.47 mmol) in
3
3 3
on a Hitachi TM-1000 instrument with SwiftED-TM. Powder X-ray
diffraction (PXRD) analyses were performed on a Bruker Model D8
Advance diffractometer using Cu KR radiation (λ = 1.5418 Å).
toluene (30 mL) at 70 °C for 2 days afforded 9 as an orange solid (0.44
ꢀ
1
g, 77%). IR (KBr, cm ): ν~ 3325 (w), 3289 (w), 2920 (w), 1489 (w),
1429 (w), 1383 (w), 1337 (s), 1237 (vs), 1195 (vs), 1030 (vs), 1010
5
Synthesis of [Cl Sc{(μ -NH) Ti (η -C Me ) (μ -N)}] (2). A
(vs), 758 (s), 635 (vs), 594 (w), 536 (w), 512 (s), 476 (m), 440 (m).
3
3
3
3
5
5 3
3
1
100 mL Schlenk flask was charged with 1 (0.30 g, 0.49 mmol),
3
H NMR (CDCl , 20 °C): δ 13.87 (s br., 3H; NH), 2.01 (s, 45H;
1
3
1
[
ScCl (thf) ] (0.18 g, 0.49 mmol), toluene (20 mL) and THF
C Me ). C{ H} NMR (CDCl , 20 °C): δ 125.3 (C Me ), 12.0
3
3
5
5
3
5
5
6
799
dx.doi.org/10.1021/ic2008683 |Inorg. Chem. 2011, 50, 6798–6808

Inorganic Chemistry
ARTICLE
temperature overnight to afford dark green crystals of 14 2C (1.04
g, 85%). IR (KBr, cm ): ν~ 3336 (w), 2905 (s), 2854 (s), 2718 (w), 1604
(w), 1494 (w), 1432 (s), 1373 (s), 1156 (w), 1066 (w), 1023 (w), 803
(w), 720 (vs), 694 (s), 671 (vs), 657 (vs), 636 (vs), 621 (vs), 528 (w),
1
9
(C
5
Me
5
). F NMR (CDCl
3
, 20 °C): δ ꢀ77.5. Anal. Calcd for
7 8
H
3
ꢀ1
C H F N O S SmTi (M = 1205.90): C 32.87, H 4.01, N 4.65, S
33
48
9
4
9 3
3
w
7
.98. Found: C 31.02, H 3.93, N 4.40, S 7.52.
5
Synthesis of [(CF SO O) Er{(μ -NH) Ti (η -C Me ) (μ -
3
2
3
3
3
3
5
5 3
3
N)}] (10). In a fashion similar to the preparation of 8, the treatment
of 1 (0.30 g, 0.49 mmol) with [Er(O SCF ] (0.29 g, 0.47 mmol) in
toluene (30 mL) at room temperature for 2 days afforded 10 as an
464 (w), 418 (m), 400 (m). Anal. Calcd for C74
H N Ti Y (M =
109 8 6 w
3
3 3
)
1486.84): C 59.78, H 7.39, N 7.54. Found: C 59.39, H 7.04, N 7.41.
5
Synthesis of [La(μ -N) (μ -NH) {Ti (η -C Me ) (μ -N)} ]
3
3
3
3
3
5
5 3
3
2
ꢀ
1
orange solid (0.46 g, 81%). IR (KBr, cm ): ν~ 3329 (w), 3294 (w),
920 (w), 1489 (w), 1429 (w), 1383 (m), 1339 (vs), 1241 (vs), 1196
(15). In a fashion similar to the preparation of 14, the treatment of 1
(1.00 g, 1.64 mmol) with [La{N(SiMe ] (0.51 g, 0.82 mmol) in
toluene (20 mL) at 85 °C for 7 days afforded orange crystals of 15 (0.95
2
3 2 3
) }
(
vs), 1036 (vs), 1013 (s), 763 (m), 635 (vs), 596 (w), 537 (w), 512
ꢀ1
(m), 477 (w), 441 (w), 410 (w). Anal. Calcd for C H ErF N O S
g, 86%). IR (KBr, cm ): ν~ 3326 (w), 2905 (s), 2855 (s), 2719 (w), 1602
(w), 1492 (m), 1434 (s), 1373 (s), 1075 (m), 1024 (m), 801 (m), 717
(vs), 691 (vs), 619 (vs), 530 (m), 468 (m), 447 (w). Anal. Calcd for
3
3
48
9
4
9 3-
Ti
3 w
(M = 1222.80): C 32.41, H 3.96, N 4.58, S 7.87. Found: C 32.21,
H 4.14, N 4.34, S 8.29.
5
Synthesis of [(ArO) Y{(μ -NH) Ti (η -C Me ) (μ -N)}]
C
60
H
93LaN
53.90, H 6.99, N 7.79.
Synthesis of [Sm(μ
8
Ti
6
(M
w
= 1352.56): C 53.28, H 6.93, N 8.28. Found: C
3
3
3
3
5
5 3
3
(
11). A 100 mL Schlenk flask was charged with 3 (0.30 g, 0.37 mmol),
lithium 2,6-dimethylphenoxido (0.14 g, 1.12 mmol), and toluene
50 mL). The reaction mixture was stirred at ambient temperature for
4 h to give an orange solution and a white fine powder. After filtration,
the volatile components of the solution were removed under reduced
5
-N)
3
(μ
3
-NH)
3
{Ti
3
(η -C
Me
5
)
(μ
-N)}
]
3
5
3
3
2
(
2
(16). In a fashion similar to the preparation of 14, the treatment of 1
(0.30 g, 0.49 mmol) with [Sm{N(SiMe ] (0.16 g, 0.25 mmol) in
3 2 3
) }
toluene (20 mL) at 110 °C for 2 days afforded orange crystals of
ꢀ1
ꢀ1
pressure to afford 11 as a yellow solid (0.37 g, 95%). IR (KBr, cm ): ν~
16 C
7
H
8
(0.19 g, 53%). IR (KBr, cm ): ν~ 3331 (w), 2906 (s), 2849
3
3
1
9
5
347 (s), 2944 (s), 2911 (s), 2856 (s), 1592 (s), 1468 (vs), 1427 (vs),
377 (s), 1299 (vs), 1279 (vs), 1240 (s), 1092 (s), 1025 (w), 976 (w),
17 (w), 859 (s), 799 (m), 746 (vs), 703 (s), 676 (vs), 656 (vs), 562 (w),
(s), 1602 (w), 1494 (w), 1432 (m), 1374 (s), 1023 (w), 714 (vs), 692
(vs), 670 (vs), 620 (vs), 528 (m), 471 (m), 412 (m). Anal. Calcd for
C
H
67
N
SmTi
(M
= 1456.15): C 55.26, H 6.99, N 7.70. Found: C
101
8
6
w
1
30 (s), 477 (m), 433 (w). H NMR (CDCl
3
, 20 °C): δ 13.33 (s br., 3H;
2
55.05, H 6.77, N 7.64.
Synthesis of [Eu(μ -N) (μ -NH) {Ti (η -C Me ) (μ -N)} ]
3
3
5
NH), 6.76 (d, JHH = 7.5 Hz, 6H; OC
6
H
2
HMe
), 6.36 (t, JHH = 7.5 Hz,
HMe ).
3
3
3
3
3
5
5 3
3
2
3
H; OC
6
H
2
HMe
2
), 2.08 (s, 45H; C
5
Me
5
), 2.00 (s, 18H; OC
6
H
2
2
(17). In a fashion similar to the preparation of 14, the treatment of 1
1
3
1
2
C{ H} NMR (CDCl , 20 °C): δ 161.7 (d, J = 4.9 Hz; ipso-
(0.15 g, 0.25 mmol) with [Eu{N(SiMe ) } ] (0.078 g, 0.12 mmol) in
3
CY
3 2 3
OC
6
H
2
HMe
2
), 127.4 (m-OC
6
H
2
HMe
2
), 125.6 (o-OC
6
H
2
HMe
2
),
toluene (20 mL) at 100 °C for 4 days afforded brown crystals of 17
ꢀ
1
1
22.5 (C
5
Me
5
), 114.4 (p-OC
6
H
2
HMe
2
), 18.7 (OC
6
H
2
HMe
2
), 11.9
(0.082 g, 51%). IR (KBr, cm ): ν~ 3331 (w), 2906 (s), 2854 (s), 1494
(w), 1434 (m), 1374 (s), 1066 (w), 1023 (w), 802 (w), 721 (vs), 693
(vs), 654 (vs), 621 (vs), 584 (m), 527 (w), 471 (w), 442 (w), 417 (w).
(
C Me ). Anal. Calcd for C H N O Ti Y (M = 1060.71): C 61.15,
5 5 54 75 4 3 3 w
H 7.13, N 5.28. Found: C 61.13, H 6.81, N 5.07.
Synthesis of [(ArO) La{(μ -NH) Ti (η -C Me ) (μ -N)}]
5
Anal. Calcd for C60
H
93EuN
8
Ti
6
(M
w
= 1365.62): C 52.77, H 6.86, N
3
3
3
3
5
5 3
3
(
(
12). In a fashion similar to the preparation of 11, the treatment of 4
0.30 g, 0.35 mmol) with lithium 2,6-dimethylphenoxido (0.14 g, 1.05
mmol) in toluene (50 mL) at room temperature for 24 h afforded 12 as a
8.21. Found: C 52.75, H 6.78, N 8.44.
5
Synthesis of [Er(μ -N) (μ -NH) {Ti (η -C Me ) (μ -N)} ]
3
3
3
3
3
5
5 3
3
2
(18). In a fashion similar to the preparation of 13, the treatment of 1
(0.30 g, 0.49 mmol) with [Er{N(SiMe ) } ] (0.16 g, 0.25 mmol) in
ꢀ1
yellow solid (0.32 g, 82%). IR (KBr, cm ): ν~ 3336 (m), 2910 (s), 1591
s), 1465 (vs), 1425 (vs), 1377 (m), 1293 (vs), 1274 (vs), 1237 (vs),
090 (m), 1025 (w), 974 (w), 915 (w), 851 (m), 746 (vs), 697 (m), 667
3
2 3
(
1
(
1
(
1
toluene (20 mL) at 180 °C for 24 h afforded 18 2C H as brown crystals
3
1
7 8
ꢀ
(0.31 g, 79%). IR (KBr, cm ): ν~ 3334 (w), 2905 (s), 2855 (s), 1604
(w), 1491 (w), 1436 (m), 1373 (m), 1073 (w), 1023 (w), 941 (w), 810
(w), 722 (vs), 617 (s), 527 (m), 470 (w), 416 (s). Anal. Calcd for
C H ErN Ti (M = 1565.19): C 56.79, H 7.02, N 7.16. Found: C
1
vs), 654 (vs), 526 (m), 476 (m), 432 (w). H NMR (CDCl , 20 °C): δ
3
3
3.59 (s br., 3H; NH), 6.80 (d, JHH = 7.5 Hz, 6H; OC
6
H
2
HMe
Me ), 2.04 (s,
, 20 °C): δ 163.1 (ipso-
2
), 6.37
3
t, JHH = 7.5 Hz, 3H; OC
6
H
2
HMe
2
), 2.07 (s, 45H; C
). C{ H} NMR (CDCl
5
5
7
4
109
8
6
w
13
1
8H; OC
6
H
2
HMe
2
3
56.41, H 6.49, N 6.88.
5
OC H HMe ), 127.3 (m-C H HMe ), 125.1 (o-OC H HMe ), 122.0
(
Anal. Calcd for C54
5
Synthesis of [Lu(μ -N) (μ -NH) {Ti (η -C Me ) (μ -N)} ]
6
2
2
6
2
2
6
2
2
3
3
3
3
3
5
5 3
3
2
C
5
Me
5
), 114.3 (p-OC
6
H
2
HMe
Ti
.04. Found: C 58.16, H 6.84, N 4.75.
2
), 18.5 (OC
6
H
2
HMe
2
), 11.8 (C
5
Me
5
).
(19). In a fashion similar to the preparation of 14, the treatment of 1
(0.30 g, 0.49 mmol) with [Lu{N(SiMe ) } ] (0.16 g, 0.24 mmol) in
H
75LaN
4
O
3
3
(M
w
= 1110.71): C 58.39, H 6.81, N
3
2 3
toluene (20 mL) at 110 °C for 24 h gave 19 C H as dark green crystals
3
7 8
5
ꢀ1
Synthesis of [Sc(μ -N) (μ -NH) {Ti (η -C Me ) (μ -N)} ]
(0.27 g, 75%). IR (KBr, cm ): ν~ 3339 (w), 2905 (s), 2854 (s), 2718
(w), 1604 (w), 1493 (m), 1435 (s), 1373 (m), 1067 (m), 1023 (m), 875
(w), 804 (m), 721 (s), 694 (s), 673 (w), 636 (s), 617 (s), 588 (m), 526
3
3
3
3
3
5
5 3
3
2
(
[
13). A 100 mL Carius tube was charged with 1 (0.30 g, 0.49 mmol),
Sc{N(SiMe ] (0.13 g, 0.25 mmol), and toluene (15 mL). The
3 2 3
) }
tube was flame-sealed and heated at 180 °C for 4 days. The reaction
mixture was allowed to cool to ambient temperature overnight to
afford red crystals. The tube was opened in the glovebox, and the
67 101 8
(m), 476 (w), 419 (s). Anal. Calcd for C H LuN Ti6 (Mw =
1480.76): C 54.35, H 6.87, N 7.57. Found: C 54.91, H 7.15, N 7.10.
5
Synthesis of [{(Me Si) N}Sc{(μ -N) (μ -NH)Ti (η -C
3
2
3
2
3
3
5
crystals were collected by filtration and characterized as 13 2C
7
H
8
Me ) (μ -N)}] (20). A 100 mL ampule (Teflon stopcock) was charged
5 3 3
with 1 (0.30 g, 0.49 mmol), [Sc{N(SiMe ) } ] (0.26 g, 0.49 mmol), and
3 2 3
3
ꢀ1
(
(
0.26 g, 72%) according to analytical data. IR (KBr, cm ): ν~ 3345
m), 2905 (s), 2854 (s), 2717 (w), 1604 (w), 1494 (w), 1434 (m),
toluene (30 mL). The reaction mixture was stirred at 100 °C for 3 days
to give a dark red solution. The volatile components of the solution were
removed under reduced pressure, and the resultant deep red solid was
1
5
373 (s), 1079 (w), 1023 (w), 804 (w), 720 (vs), 640 (vs), 620 (vs),
90 (s), 531 (w), 487 (w), 464 (w), 418 (s). Anal. Calcd for
ꢀ
1
C
74
H
109
N
8
ScTi
C 61.02, H 7.60, N 7.71.
Synthesis of [Y(μ -N) (μ -NH) {Ti (η -C Me ) (μ -N)} ]
6
(M
w
= 1442.89): C 61.60, H 7.61, N 7.77. Found:
vacuum-dried and characterized as 20 (0.35 g, 88%). IR (KBr, cm ): ν~
3340 (w), 2909 (vs), 2857 (s), 2722 (w), 1493 (w), 1437 (m), 1376 (s),
1244 (s), 1179 (w), 1067 (w), 1024 (m), 986 (vs), 875 (vs), 846 (vs),
5
3
3
3
3
3
5
5 3
3
2
(
1
(
14). A 100 mL ampule (Teflon stopcock) was charged with 1 (1.00 g,
.64 mmol), [Y{N(SiMe ] (0.47 g, 0.82 mmol), and toluene
20 mL). The reaction mixture was heated at 110 °C without any
stirring for 7 days, and the solution was allowed to cool to ambient
832 (vs), 782 (m), 754 (w), 704 (vs), 664 (vs), 632 (vs), 619 (vs), 555
1
3
)
}
2 3
(s), 472 (w), 458 (w), 436 (m), 417 (m). H NMR (C
6
D
6
, 20 °C): δ
Me ), 0.28
(s, 18H; SiMe3). C{ H} NMR (C D , 20 °C): δ 118.7 (C Me ), 118.2
11.44 (s br., 1H; NH), 2.16 (s, 15H; C
5
Me
5
), 2.02 (s, 30H; C
5
5
1
3
1
6
6
5
5
6
800
dx.doi.org/10.1021/ic2008683 |Inorg. Chem. 2011, 50, 6798–6808

Inorganic Chemistry
ARTICLE
Table 1. Experimental Data for the X-ray Diffraction Studies on 2, 7, 11, 14, 15, and 19
2
7
11 0.5C
6
H
14
14 2C
7
H
8
15
7 8
19 2C H
3
3
3
formula
C
30
H
48Cl
3
C
30
H
48Cl
3
C
57
H
82
N
4
C
74
H
109
C
60
H
93
74 109
C H
N
4
ScTi
3
LuN
4
Ti
3
O
3 3
Ti Y
N
Ti
8 6
Y
LaN Ti
8 6
8 6
LuN Ti
M
r
759.73
200(2)
889.74
200(2)
1103.88
200(2)
0.71073
1487.00
200(2)
0.71073
1352.73
200(2)
0.71073
1573.06
200(2)
0.71073
T [K]
λ [Å]
0.71073
monoclinic
P2 /c
0.71073
monoclinic
P2 /c
crystal system
space group
a [Å]
monoclinic
P2 /c
orthorhombic
Pnnm
monoclinic
C2/c
orthorhombic
Pnnm
1
1
1
11.175(3)
17.723(3);
11.118(3)
17.895(3);
94.20(2)
37.373(5)
7416(3)
8
12.443(2)
21.245(2);
14.717(1)
15.433(5)
27.961(6)
11.588(1);
106.13(2)
20.911(5)
6509(2)
4
14.654(1)
15.439(4)
b [Å]; β [deg]
9
4.17(4)
110.97(2)
23.112(6)
c [Å]
37.034(11)
7315(3)
8
16.701(5)
3793(2)
2
16.711(4)
3781(1)
2
3
V [Å ]
5705(2)
4
Z
ꢀ
3
Fcalcd [g cm
]
1.380
1.594
1.285
1.456
2324
1.302
1.399
1560
1.380
1.382
1.938
1624
ꢀ
1
μMοKR [mm
]
1.053
3.503
1.381
F(000)
3152
3552
2792
3
crystal size [mm ]
θ range (deg)
index ranges
0.21 ꢁ 0.14 ꢁ 0.11 0.18 ꢁ 0.13 ꢁ 0.11 0.32 ꢁ 0.26 ꢁ 0.16 0.29 ꢁ 0.22 ꢁ 0.14 0.31 ꢁ 0.19 ꢁ 0.13 0.33 ꢁ 0.18 ꢁ 0.16
3.01 to 27.51
3.17 to 25.02
ꢀ13 to 13,
ꢀ21 to 21,
0 to 44
3.00 to 27.50
ꢀ16 to 15,
ꢀ27 to 27,
ꢀ30 to 15
121012
5.07 to 25.24
ꢀ17 to 17,
ꢀ18 to 18,
0 to 20
5.04 to 27.51
ꢀ36 to 34,
ꢀ15 to 15,
0 to 27
3.22 to 27.53
ꢀ19 to 19,
ꢀ20 to 20,
0 to 21
ꢀ14 to 14,
ꢀ
23 to 23,
0
to 48
reflections collected
123787
16798
129009
59932
67603
44357
unique data
13041
13088
3530
7396
4487
[
R(int) = 0.105]
[R(int) = 0.094]
7829
[R(int) = 0.033]
9286
[R(int) = 0.075]
2847
[R(int) = 0.059]
4911
[R(int) = 0.100]
2988
obsd data [I > 2σ(I)]
8559
2
goodness-of-fit on F
1.004
1.032
1.096
1.115
1.046
1.046
a
final R indices [I > 2σ(I)]
R1 = 0.074,
wR2 = 0.165
R1 = 0.162,
wR2 = 0.206
R1 = 0.069,
wR2 = 0.163
R1 = 0.125,
wR2 = 0.194
1.707 and ꢀ2.007
R1 = 0.041,
wR2 = 0.106
R1 = 0.070;
wR2 = 0.117
0.463 and ꢀ0.460
R1 = 0.096,
wR2 = 0.237
R1 = 0.118,
wR2 = 0.251
1.141 and ꢀ0.577
R1 = 0.056,
wR2 = 0.125
R1 = 0.100,
wR2 = 0.142
1.027 and ꢀ0.571
R1 = 0.074,
wR2 = 0.193
R1 = 0.113,
wR2 = 0.213
1.428 and ꢀ1.444
a
R indices (all data)
ꢀ
3
largest diff. peak/hole[e Å
]
1.076 and ꢀ1.042
a
2
2 2
2 2 1/2
R1 = ∑||F | ꢀ |F ||/∑|F |, wR2= {∑w(F ꢀ F ) /∑w(F ) }
.
o
c
o
o
c
o
(
C
5
C Me ), 12.2 (C Me ), 12.1 (C Me ), 5.2 (SiMe ). Anal. Calcd for
H N ScSi Ti (M = 811.67): C 53.27, H 7.95, N 8.63. Found: C
36 64 5 2 3 w
3.05, H 8.18, N 8.24.
refined. All hydrogen atoms of 2 and 7 were positioned geometrically
and refined using a riding model in the last cycles of refinement. DELU
restraints were applied for the carbon atoms C(31)ꢀC(35) and C-
(41)ꢀC(45) of two pentamethylcyclopentadienyl ligands in complex 7.
Compound 11 crystallized with a half molecule of hexane. Several
attempts to obtain chemically sensible models for the solvent failed, so
the PLATON squeeze procedure was used to remove their contribu-
tion to the structure factors. All non-hydrogen atoms were anisotropi-
cally refined. All the hydrogen atoms were positioned geometrically and
refined by using a riding model, except those of the imido groups
(H(12), H(13), H(23)), which were located in the difference Fourier
map and refined isotropically.
5
5
5
5
5
5
3
X-ray Structure Determination of 2, 7, 11, 14, 15, and 19.
Crystals of complexes 2 and 7 were obtained by slow diffusion of a THF
solution of [MCl (thf) ] in toluene solutions of 1. Crystals of com-
3
3
3
3
pound 11 0.5C
6
H
14 were grown at room temperature by diffusion of
3
7 8
hexane into a toluene solution of 11. Crystals of complexes 14 2C H ,
1
solutions of a mixture of the reagents 1 and [M{N(SiMe ] as
described above. The crystals were removed from the Schlenk flasks and
covered with a layer of a viscous perfluoropolyether (FomblinY). A
suitable crystal was selected with the aid of a microscope, attached to a
glass fiber, and immediately placed in the low temperature nitrogen
stream of the diffractometer. The intensity data sets were collected at
3
5, and 19 2C
7
H
8
were obtained by slow cooling of heated toluene
3
3 2 3
) }
Complexes 14 and 19 crystallized with two molecules of toluene in
the Pnnm space group. Attempts to model the solvent in a sensible way
3
3
also failed and similarly to 11, the PLATON squeeze procedure was
applied. Simultaneously, some of the carbon atoms of the pentamethyl-
cyclopentadienyl rings linked to Ti(2) [C(21), C(24), C(26) and C(29)
for 14, and C(21), C(24), C(25) and C(29) for 19] presented disorder,
and were refined in two sites with occupancy 50%. However, the
disorder did not affect the location of the core of the molecule. All non-
hydrogen atoms of 14 were anisotropically refined, except the C(21),
2
00 K on a Bruker-Nonius KappaCCD diffractometer equipped with an
Oxford Cryostream 700 unit. Crystallographic data for all the complexes
are presented in Table 1.
31
The structures were solved, using the WINGX package, by direct
2
methods (SHELXS-97) and refined by least-squares against F
32
(SHELXL-97). Crystals of 2 and 7 contained two independent mole-
cules in the asymmetric unit, and there were no significant differ-
C(26), C(27), C(28) and C(29) carbon atoms of the disordered C
5 5
Me
ences between them. All non-hydrogen atoms were anisotropically
group. Similarly to 14, all non-hydrogen atoms of 19 were anisotropically
6
801
dx.doi.org/10.1021/ic2008683 |Inorg. Chem. 2011, 50, 6798–6808

Inorganic Chemistry
ARTICLE
refined, except the carbon atoms (C(21), C(22), C(23), C(24), C(25),
Scheme 1. Reactions of 1 with [MCl (thf) ] or [M(OTf) ]
3
n
3
C(26), C(28) and C(29)) of the disordered C Me ring linked to Ti(2).
5
5
On the other hand, compound 15 crystallized as a solvent-free molecule
in the C2/c space group. The molecule lies on a crystallographic
inversion center situated on the lanthanum atom. All non-hydrogen
atoms were anisotropically refined. Finally, all hydrogen atoms of 14, 15
and 19 were included, positioned geometrically, and refined by using a
riding model. The imido hydrogen atoms were statistically distributed
over the six nitrogen atoms linked to the central yttrium, lanthanum, or
lutetium atom (final 50% of occupancy).
Pyrolysis of 14. In an argon-filled glovebox, an alumina boat was
charged with a pulverized sample of compound 14 C
7
H
8
(0.20 g). The
boat was placed in the middle point of a quartz tube (2.5 cm diameter
40 cm length) equipped with two 24/40 male glass joints. The tube
3
ꢁ
was fitted with 24/40 vacuum adapters (Teflon stopcock), and then
inserted into a horizontal tube furnace (Lindberg Blue M). The oven was
heated from 20 to 1100 °C with a heating rate of 5 °C/min under Ar
(UꢀN45, O e 2 ppm, and H O e 3 ppm), H /N (6ꢀ15% of H , O
2
2
2
2
2
2
<
5 ppm, and H O < 5 ppm) or NH (N50, O < 1 ppm, and H O < 1
2 3 2 2
3
ppm) flows of 100 or 1350 sccm (cm /min). The temperature was
maintained at 1100 °C for 1 h, and the tube was allowed to cool to
ambient temperature under a constant flow of the corresponding gas.
The tube was taken into the glovebox, and the residue was manipulated
toluene or toluene-THF solutions. However, the samarium
complex 9 was prepared in toluene since the presence of THF
in the reaction afforded a yellow solid which is not soluble in
common organic solvents. Similarly, the treatment of 1 with the
under argon atmosphere. In the pyrolysis experiment under H
the volatile decomposition products were subsequently trapped at
196 °C (N liquid bath) in a cooling trap, and after closing the flow
2 2
/N flow,
lanthanum triflate derivative [La(O SCF ) ] in toluene-THF
3
3 3
mixtures gave a yellow precipitate with negligible solubility.
Although the C, H, N, S microanalytical data were not fully
consistent for the solids isolated from several preparative reac-
tions, the analytical results were always close to products contain-
ing metalloligand:metal triflate ratios of 1:2. Most likely the
compounds contain triflate groups bridging the large samarium
or lanthanum atoms as those reported in the literature for
ꢀ
2
of gas, benzene-d
solution was analyzed by H NMR spectroscopy and GC-MS
measurements.
6
was injected into the cooling flask. The resultant
1
6 6
C D
’
RESULTS AND DISCUSSION
2
5,34
Reactions with Rare-Earth Metal Halide and Triflate Deri-
vatives. The synthetic chemistry is outlined in Scheme 1.
lanthanide complexes.
(1 equiv) to a suspension of the samarium precipitate in chloro-
form-d and subsequent heating at 70 °C overnight afforded an
Interestingly, the addition of 1
5
Treatment of [{Ti(η -C Me )(μ-NH)} (μ -N)] (1) with 1
1
5
5
3
3
equiv of group 3 or lanthanide trichloride adducts
orange solution of complex 9 according to NMR spectroscopy.
Complexes 2ꢀ10 were characterized by spectroscopic and
analytical methods, as well as by X-ray crystal structure determi-
nations for the scandium (2), erbium (6), and lutetium (7)
chloride derivatives. IR spectra (KBr) of the chloride derivatives
[
MCl (thf) ] (M = Sc, Lu, n = 3; M = Y, Sm, Er, n = 3.5; M =
3
n
La, n = 1.5) in a 4:1 toluene-THF mixture at room temperature
afforded the precipitation of the cube-type complexes
5
[
(
Cl M{(μ -NH) Ti (η -C Me ) (μ -N)}] (M = Sc (2), Y
3
3
3
3
5
5 3
3
ꢀ
1
3), La (4), Sm (5), Er (6), Lu (7)) as orange or yellow solids
2ꢀ7 show one νNH vibration, between 3331 and 3310 cm
,
in good yields (55ꢀ83%). Compounds 2ꢀ7 are not soluble in
benzene, toluene or THF but exhibit a good solubility in
halogenated solvents. Complexes 2, 3, and 5ꢀ7 are stable in
whereas the IR spectra of the triflate complexes 8ꢀ10 reveal two
ꢀ
ꢀ
1
ν
NH vibrations, between 3329 and 3289 cm , in a similar range
1 4
to the value determined for 1 (3352 cm ). In addition, the
infrared spectra of 8ꢀ10 show several strong absorptions
chloroform-d solutions at room temperature for several days
1
1
ꢀ1
according to H NMR spectroscopy. However, the lanthanum
between 1339 and 1010 cm for the trifluoromethanesulfonate
35
ꢀ1
derivative 4 in chloroform-d immediately undergoes partial
groups. The bands around 1338 cm , which are assignable to
1
dissociation (ca. 15%) to give complex 1 and presumably
the νas(SO
3
) vibrations, are shifted to higher wavenumbers than
ꢀ
1
ꢀ 35b
[
LaCl ]. This mixture remains unaltered for long periods of time
that near 1270 cm characteristic of the ionic CF
3
SO
3
,
and
3
35a
1
at room temperature.
are indicative of coordinated triflate ligands. The H and
1
3
1
Compounds 2ꢀ7 may also be prepared by the direct reaction
C{ H} NMR spectra in chloroform-d
of the diamagnetic complexes 2ꢀ4, 7, and 8 reveal resonance
1
at room temperature
of 1 with 1 equiv of the anhydrous metal chlorides [MCl ] in
3
5
toluene or toluene-THF mixtures, but the complexes appear
invariably accompanied by significant amounts of the [MCl3]
reagent according to microanalytical data. In contrast, the
analogous reaction of 1 with anhydrous yttrium, samarium, or
erbium trifluoromethanesulfonate derivatives [M(O SCF ) ] in
signals for equivalent NH and η -C
Me groups, and agree with a
5 5
C
3v symmetric structure in solution. The NH resonance signal in
1
the H NMR spectra (δ = 13.37ꢀ12.31) is shifted to higher field
than that found in 1 (δ = 13.40), suggesting a tridentate
18,19
1
13
1
coordination of the metalloligand.
The H and C{ H}
3
3 3
toluene afforded the precipitation of the corresponding pure
NMR spectra of the mildly paramagnetic samarium complexes 5
and 9 are very simple and analogous to those of the diamagnetic
complexes. However, the NH resonance signals (δ = 13.55 and
13.87, respectively) in the H NMR spectra of 5 and 9 are shifted
downfield with respect to that found in 1. All attempts to gain
5
triflate complexes [(CF SO O) M{(μ -NH) Ti (η -C Me ) -
3
2
3
3
3
3
5
5 3
(
μ3-N)}] (M = Y (8), Sm (9), Er (10)) (Scheme 1). Com-
pounds 8ꢀ10 were isolated as orange solids in good yields
72ꢀ81%) which are only soluble in halogenated solvents. The
preparative reactions for compounds 8 and 10 were carried out in
1
(
structural information by NMR spectroscopy of the erbium
6
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Inorganic Chemistry
ARTICLE
Scheme 2. Synthesis of Aryloxido Derivatives
coordination environment about the rare-earth atoms in com-
plexes 2, 6, and 7 is analogous to those reported for trichloride
complexes containing fac-coordinating trinitrogen ligands such
as the scandium 1,4,7-trimethyltriazacyclononane [Sc{Me [9]-
3
2
4a
aneN }Cl ] and 1,3,5-trimethyltriazacyclohexane [Sc{Me -
3
3
3
2
3b
Figure 1. Perspective view with thermal ellipsoids at the 50% prob-
ability level of one of the two crystallographically independent molecules
of 2. Hydrogen atoms are omitted for clarity.
[
6]aneN }Cl ] complexes, and the yttrium tris(pyrazolyl)-
3 3
23b
silane [Y{MeSi(3,5-Me pz) }Cl ]
and tris(pyrazolyl)meth-
2
3
3
22b
ane [Y{HC(3,5-Me pz) }Cl ] derivatives. If the differences in
ionic radii of M in six-coordinate geometries are taken into
account, the MꢀCl distances [average M = Sc, 2.414(8) Å; Er,
2.553(13) Å; Lu, 2.516(13) Å] compare well with those found in
the above-mentioned examples. However, the MꢀN bond
lengths in 2, 6 and 7 [average M = Sc, 2.427(12) Å; Er,
2
3
3
3þ
3
6
Table 2. Selected Averaged Lengths (Å) and Angles (deg) for
5
a
Complexes [Cl M{(μ -NH) Ti (η -C Me ) (μ -N)}]
3
3
3
3
5
5 3
3
M = Sc (2)
M = Er (6)
M = Lu (7)
2
.59(3) Å; Lu, 2.53(2) Å] are clearly longer than the MꢀN
distances in those complexes (cf. average ScꢀN are 2.337(8) and
.332(1) Å in [Sc{Me [9]aneN }Cl ] and [Sc{Me [6]aneN }-
MꢀNimido
MꢀCl
2.427(12)
2.414(8)
1.974(14)
1.930(7)
2.868(9)
3.219(7)
75.0(3)
2.59(3)
2.553(13)
1.98(2)
2.53(2)
2.516(13)
1.978(15)
1.939(8)
2.864(6)
3.328(8)
72.1(1)
2
3
3
3
3
3
TiꢀNimido
TiꢀNnitrido
Ti Ti
Cl ], respectively), suggesting a weaker coordination of the
3
1.931(11)
2.869(11)
3.384(11)
70.5(7)
titanium tripodal ligand. This might be caused by the steric
repulsion between the bulky pentamethylcyclopentadienyl li-
gands and the chloride groups placed in an eclipsed position.
Accordingly, the distortions in bond distances and angles within
3
3
3 3
3 3
M
Ti
NimidoꢀMꢀNimido
6
ClꢀMꢀCl
imidoꢀTiꢀNimido
nitridoꢀTiꢀNimido
99.1(8)
99.9(14)
98.4(7)
99.7(11)
97.7(5)
the tridentate ligand are small when compared to those of 1.
Despite several data collections, crystals of the triflate com-
pounds 8ꢀ10 presented severe disorder precluding an accurate
determination of their molecular structure by crystallographic
methods. However, the treatment of yttrium (3) or lanthanum
N
96.9(2)
N
85.4(4)
85.4(5)
86.0(5)
MꢀNimidoꢀTi
TiꢀNimidoꢀTi
TiꢀNnitridoꢀTi
93.4(4)
94.7(10)
93.1(7)
94.3(4)
93.2(1)
92.8(5)
(
4) chloride complexes with 3 equiv of lithium 2,6-dimethylphe-
95.9(4)
96.0(3)
95.2(5)
noxido [LiOAr] in toluene gave the analogous aryloxido deriva-
a
Averaged values for the two independent molecules in the asymmetric
unit.
5
tives [(ArO) M{(μ -NH) Ti (η -C Me ) (μ -N)}] (M = Y
3
3
3
3
5
5 3
3
(
11), La (12)) (Scheme 2), and the solid-state structure of 11
was unambiguously determined. Compounds 11 and 12 were
isolated in good yields (95 and 82%, respectively) as yellow solids
which exhibit an enhanced solubility in benzene and toluene
when compared with the triflate derivatives 8ꢀ10.
compounds 6 and 10 in solution failed because of their strong
paramagnetism.
The isomorphous chloride complexes 2, 6, and 7 crystallized
20
in the space group P2 /c with two independent molecules in the
Complexes 11 and 12 were characterized by spectroscopic and
analytical methods, as well as by an X-ray crystal structure
1
asymmetric unit. There are no substantial differences between
the two molecules, and the structure of one of them for the
scandium chloride complex 2 is shown as example in Figure 1.
Selected averaged distances and angles for the two crystallogra-
phically independent molecules of complexes 2, 6, and 7 are
compared in Table 2. The crystal structures show [MTi N ]
determination for the yttrium derivative 11 0.5C
H
14. Spectro-
3
6
scopic data of 11 and 12 are similar to those of complexes 2ꢀ10.
1
13
1
H and C{ H} NMR spectra in chloroform-d
temperature show resonances for equivalent NH and η -C
Me groups, and are consistent with a C3v symmetry in solu-
at room
1
5
-
5
3
4
5
5
cube-type cores with the neutral ligand [(μ -NH) Ti (η -
tion. In addition, the spectra reveal resonance signals for three
equivalent 2,6-dimethylphenoxido ligands coordinated to the
yttrium or lanthanum centers.
The X-ray crystal structure of 11 is presented in Figure 2, and
selected distances and angles are given in Table 3. The molecular
structure shows a distorted [YTi N ] cube-type core similar to
3 4
those of the chloride complexes 2, 6, and 7. Yttrium is bonded to
three oxygen atoms of the aryloxido ligands and three imido
3
3
3
C Me ) (μ -N)] coordinating in a tripodal fashion. In all three
5
5 3
3
complexes, each rare-earth center is six-coordinate, and its
coordination geometry is best described as distorted trigonal
antiprismatic with one tighter triangle defined by the nitrogen
atoms and with a more open one defined by the chloride ligands.
This is clearly seen by comparing the NꢀMꢀN [M = Sc,
7
9
5.0(3)°; Er, 70.5(7)°; Lu, 72.1(1)°] and ClꢀMꢀCl [M = Sc,
9.1(8)°; Er, 99.9(14)°; Lu, 99.7(11)°] averaged angles. The
groups of the [Ti
(μ-NH)
(μ
-N)] fragment. The YꢀO
3
3
3
6
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Inorganic Chemistry
ARTICLE
Scheme 3. Reactions of 1 with [M{N(SiMe ) } ]
3
2 3
angle ϕ, measured in the plane of projection, between those
38
triangular faces is 32(1)° (Figure 2). For comparison, the
analogous twist angle ϕ in the chloride complexes 2, 6, and 7
spans 34(3)ꢀ54(2)°, and therefore the coordination geometry
about the rare-earth center in those complexes is somewhat
closer to trigonal antiprismatic (ϕ = 60°).
Reactions with Rare-Earth Metal Amido Derivatives. The
synthetic chemistry is outlined in Scheme 3. Treatment of 1 with
group 3 or lanthanide bis(trimethylsilyl)amido derivatives [M-
Figure 2. (a) Perspective view of 11 with thermal ellipsoids at the 50%
probability level. Methyl groups of the pentamethylcyclopentadienyl
ligands and hydrogen atoms are omitted for clarity. (b) Schematic
representation of the six-coordinate geometry about the yttrium center
in 11.
{
N(SiMe ) } ] in toluene at 85ꢀ180 °C afforded the corner-
3
2 3
Table 3. Selected Lengths (Å) and Angles (deg) for 11
shared double-cube nitrido complexes [M(μ -N) (μ -NH) -
{
3 3 3 3
5
Ti (η -C Me ) (μ -N)} ] (M = Sc (13), Y (14), La (15),
3 5 5 3 3 2
Y(1)ꢀN(12)
Y(1)ꢀN(13)
Y(1)ꢀN(23)
TiꢀNimido (av)
Ti Ti (av)
2.629(2) Y(1)ꢀO(4)
2.618(2) Y(1)ꢀO(5)
2.662(2) Y(1)ꢀO(6)
1.943(10) TiꢀN(1) (av)
2.109(2)
2.109(2)
2.111(2)
1.912(1)
3.427(15)
Sm (16), Eu (17), Er (18), Lu (19)) in good yields (51ꢀ86%).
Compound 14 was also prepared by the reaction of 1 with 1
equiv of the yttrium alkyl derivative [Y(CH SiMe ) (thf) ].
2
3 3
3
Whereas the reaction of 1 with the triamido reagent
2.823(4) Ti Y(1) (av)
3
3 3
3 3 3
[Y{N(SiMe ) } ] is very slow at room temperature, complex 1
3
2 3
N(12)ꢀY(1)ꢀN(13) 68.1(1)
N(13)ꢀY(1)ꢀN(23) 67.8(1)
N(12)ꢀY(1)ꢀN(23) 67.9(1)
Y(1)ꢀO(4)ꢀC(41) 157.3(2)
Y(1)ꢀO(6)ꢀC(61) 165.4(2)
O(4)ꢀY(1)ꢀO(5)
O(4)ꢀY(1)ꢀO(6)
O(5)ꢀY(1)ꢀO(6)
Y(1)ꢀO(5)ꢀC(51)
102.4(1)
reacted almost immediately with the yttrium trialkyl derivative.
102.9(1)
101.2(1)
171.9(2)
The reactions in benzene-d were monitored by NMR spectros-
6
copy but no soluble intermediates were detected, and the final
spectra revealed only resonances assigned to free bis(trimeth-
ylsilyl)amine or tetramethylsilane.
N
imidoꢀTiꢀNimido (av) 98.5(3)
Complexes 13ꢀ19 are not soluble in common organic
solvents, and their lack of volatility precludes their characteriza-
tion by mass spectrometry (EI, 70 eV). Therefore, the com-
pounds were characterized by IR spectroscopy and C, H, N
microanalysis, as well as by X-ray crystal structure determinations
for 14, 15, and 19. Crystals of 13ꢀ19 contain two (13, 14, 18,
19), one (16), or zero (15, 17) toluene molecules per double-
cube unit according to crystallographic or analytical data. How-
ever, once the crystals are separated from the solution, the
toluene solvent molecules are gradually lost within hours at
room temperature. The molecular structures of 15 and 19 are
presented in Figures 3 and 4, while selected distances and angles
of complexes 14, 15, and 19 are compared in Table 4. The
structures confirm the expected corner-shared double-cube
[MTi N ] cores similar to those found in our previous studies
N
imidoꢀTiꢀN(1) (av) 85.8(3)
TiꢀNimidoꢀTi (av)
TiꢀN(1)ꢀTi (av)
93.2(1)
95.1(2)
TiꢀNimidoꢀY(1) (av) 95.7(6)
distances (average 2.110(1) Å) are in the range typical of
37
terminal yttrium 2,6-dimethylphenoxidos, and compare well
with the MꢀO bond lengths determined in the crystal structures
of complexes [M{HC(3,5-Me pz) }(OAr) ] [average M =
22b
2
3
3
23b
22b
Sc,
1.962(2) Å; M = Nd,
2.207(5) Å; M = Sm, 36
2
.180(3) Å] after correction of the difference in ionic radii.
However, the YꢀN bond lengths in 11 (2.618(2)ꢀ2.662(2) Å)
are longer than expected from the MꢀN distances found in those
complexes [M{HC(3,5-Me pz) }(OAr) ] (M = Sc, 2.354(2) Å;
2
3
3
M = Nd, 2.599(5) Å; M = Sm, 2.565(5) Å). This might be caused
by the steric repulsion between the bulky pentamethylcyclopen-
tadienyl ligands and the 2,6-dimethylphenoxido groups. The
minimization of this repulsion might also explain the coordina-
tion geometry about the yttrium atom in 11, which is best
described as intermediate between trigonal prismatic and anti-
prismatic. This is clearly seen when one looks perpendicularly
down onto the triangle defined by the nitrogen atoms and that
defined by the oxygen atoms, and finds that the average twist
6
8
18b
39
with transition or main-group metals. The six-coordinate
geometry about the yttrium, lanthanum, or lutetium centers is
best described as trigonal antiprismatic, whereby the two triden-
tate organometallic ligands adopt a mutually staggered disposi-
tion. The coordination environment about the rare-earth centers
resembles those determined for hydrotris(pyrazolyl)borate
4
0
lanthanide(II) complexes [Ln{HB(3,5-Me pz) } ] and the
2
3 2
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Inorganic Chemistry
ARTICLE
Table 4. Selected Averaged Lengths (Å) and Angles (deg) for
Complexes 14, 15, and 19
M = Y (14)
M = La (15)
M = Lu (19)
MꢀN
TiꢀN
2.439(4)
1.952(9)
3.251(5)
2.821(2)
92.5(4)
2.601(11)
1.947(9)
3.417(9)
2.806(8)
92.2(3)
2.381(15)
1.960(10)
3.200(4)
2.825(1)
92.4(7)
M
Ti
3
3 3
Ti Ti
3
3 3
TiꢀNꢀTi
N(1)ꢀTiꢀN
NꢀTiꢀN
87.4(2)
87.7(2)
87.6(2)
96.0(2)
97.2(1)
95.2(6)
a
NꢀMꢀN
73.1(1)
68.4(1)
75.1(1)
106.9(1)
111.6(1)
96.3(5)
104.9(1)
94.3(4)
TiꢀNꢀM
94.8(2)
a
Narrower values correspond to intracube and wider values to intercube
NꢀMꢀN angles.
5
scandium derivative [{(Me Si) N}Sc{(μ -N) (μ -NH)Ti (η -
3
2
3
2
3
3
C Me ) (μ -N)}] (20) (Scheme 3). Complex 20 is stable at
5
5 3
3
high temperatures in benzene-d solution according to NMR
6
spectroscopy. However, upon addition of 1 equiv of 1 to this
solution and subsequent heating at 180 °C the spectra showed
resonances assigned to NH(SiMe ) along with a red precipitate
3
2
characterized as compound 13.
Complex 20 was obtained in 88% yield as a red solid, which is
very soluble in toluene and hexane, and was characterized by
1
spectroscopic and analytical methods. The H NMR spectrum in
Figure 3. Perspective view of 15 with thermal ellipsoids at the 50%
probability level. Hydrogen atoms are omitted for clarity. Symmetry
code: (i) 1/2 ꢀ x, 1/2 ꢀ y, ꢀz.
5
benzene-d at room temperature reveals two resonances for η -
6
C Me ligands in a 1:2 ratio, a singlet for one N(SiMe ) group,
5
5
3 2
and a broad signal for the NH imido ligand. These NMR data are
consistent with a C -symmetric structure in solution as those
s
39b
19c
reported for the monoamido or monoalkyl aluminum(III)
5
derivatives [RAl{(μ -N) (μ -NH)Ti (η -C Me ) (μ -N)}] (R
3
2
3
3
5
5 3
3
=
N(SiMe ) , Me, CH SiMe ).
3 2 2 3
Thermal Decomposition of Heterometallic Double-Cube
Nitrido Complexes. The thermal stabilities in the solid-state of
5
complexes [M(μ -N) (μ -NH) {Ti (η -C Me ) (μ -N)} ]
3
3
3
3
3
5
5 3
3
2
(
M = Y (14), La (15), Er (18)) were examined as representative
examples of the large number of corner-shared double-cube
18b,39
nitrido derivatives reported by our laboratory.
This type
of compounds was chosen because they are not volatile as
determined by mass spectrometry (EI, 70 eV) and sublimation
experiments under vacuum conditions. Therefore, any mass loss
in the decomposition would be due to thermal degradation of the
complexes.
Initially, the decomposition behavior of crystalline samples of
compounds 14 C H , 15, and 18 C H under an argon flow
3
7
8
3
7 8
Figure 4. Simplified view of 19 with thermal ellipsoids at the 50%
probability level. Pentamethylcyclopentadienyl rings and hydrogen
atoms are omitted for clarity. Symmetry code: (i) x, y, ꢀz; (ii) 2 ꢀ x,
was investigated by simultaneous thermogravimetric analysis
TGA) and differential thermal analysis (DTA) experiments.
(
The volatile components generated in the degradation of the
complexes were analyzed by coupled mass spectrometry (MS).
The TGA and DTA curves for the yttrium derivative 14 C H
7 8
ꢀ
y, ꢀz; (iii) 2 ꢀ x, ꢀy, z.
3
41
lanthanide(III) compounds [Ln{HB(3,5-Me pz) } ]X. With-
are shown in Figure 5 (Figures S3 and S4 in the Supporting
Information show the TGA/DTA curves for 15 and 18 C ).
display a weight
2
3 2
in the tridentate ligands, the titaniumꢀnitrogen bond lengths
H
7 8
3
and the titaniumꢀnitrogenꢀtitanium angles in complexes 14,
The TGA curves for 14 C H and 18 C H
7 8 7 8
3
3
1
5, and 19 are very similar and compare well with those
loss of ≈7 and 6%, respectively, between 120 and 190 °C
(endothermic peaks at 159 and 140 °C in the DTA curves,
respectively), which cannot be observed during the decomposi-
tion of the lanthanum complex 15. These mass losses at the very
beginning of the decomposition are due to release of toluene
solvent molecules of crystallization, which are absent in 15. The
6
determined for 1.
Complexes 14ꢀ19 were invariably obtained by treatment of 1
with 0.5 or 1 equiv of the triamido reagents [M{N(SiMe ) } ] at
3
2 3
different temperatures, but the reaction of 1 with 1 equiv of
Sc{N(SiMe ) } ] in toluene at 100 °C afforded the monoamido
[
3
2 3
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Inorganic Chemistry
ARTICLE
Table 5. Ceramic Yields and Characteristics of the Pyrolyzed
Products of 14 C H
3
7
8
a
elemental analysis (%)
experiment
color
ceramic yield (%)
C
H
N
O
b
Ar flow
black
63
58
55
32
48.8 0.3
42.7 0.5
5.1 3.9
9.4 4.0
b
H
2
/N
2
flow black
b
NH
3
3
flow iridescent garnet
22.9 0.4 13.2 1.5
c
NH
flow iridescent garnet
0.2 0.3 18.0 0.2
a
c
b
Averaged values from at least two independent samples. 100 sccm.
1350 sccm.
the potentially reactive H /N atmosphere somewhat facilitates
2
2
the elimination of the organic groups, but the ceramic yield and
carbon content of the residue are still very high.
Figure 5. TGA (red) and DTA (blue) curves for the degradation of
Finally, pyrolyses of 14 C H from 20 to 1100 °C were
3
7 8
1
7 8
4 C H under Ar flow at a heating rate of 10 °C/min.
3
performed under different flows of anhydrous ammonia. While
the decomposition of 14 under a flow of NH of 100 sccm gave
3
an iridescent garnet solid with 55% of the initial mass, a higher
elimination of toluene was unambiguously established by MS
m/z 92) while the theoretical mass loss for one toluene
molecule from compounds 14 C H and 18 C H is 6.6 and
flow of NH (1350 sccm) afforded a residue mass of 32%, which
(
3
is closer to the calculated mass for complete degradation to
3
7
8
3
7 8
“
YTi N ” (35%) or “YTi N ” (34%). Accordingly, the residue
6
.3%, respectively. The main mass loss (20ꢀ23%) for the three
6 8 6 7
obtained in the former experiment still contains high levels of
carbon (22.9% by elemental analysis) and low levels of nitrogen
complexes starts at about 200 °C and is finished around 600 °C
(
endothermic peaks at 514ꢀ522 °C in the DTA curves).
(
13.2%), while the solid isolated under a large flow of ammonia
Analysis of the volatile components generated in this step by
has only a very small amount of carbon (0.2%) along with a
nitrogen content (18.0%) closer to the expected values for
YTi N or YTi N compositions (23.0 and 20.7%, respectively).
MS revealed fragments derived of the C Me groups (m/z 135
5
5
þ
þ
þ
þ
3
[
C Me ] , 119 [C Me CH ] , 16 [CH ] , 15 [CH ] ).
5 5 5 3 2 4
6
8
6 7
Between 600 and 1000 °C the TGA curves show additional
mass losses of about 3% to give black residues containing 67, 73,
or 70% of the initial mass of compounds 14 C H , 15, and
The garnet solid obtained under a large flow of NH was
3
studied in more detail. Elemental analyses reveal very low
hydrogen and oxygen levels (0.3 and 0.2%, respectively), whereas
compositional analysis by EDX confirms the presence of titanium
and yttrium in the solid. PXRD analysis showed that the residue
was essentially amorphous, and only weak peaks could be
assigned to TiN and Y O . Rare-earth nitrides exhibit a high
3
7 8
1
8 C H , respectively. These results suggest that a considerable
3
7 8
amount of carbon arising from the C Me groups should be
5
5
present in the residues, which were found amorphous by powder
X-ray diffraction. Elemental analysis of the black solid obtained in
the TGA of 14 demonstrated those high levels of carbon (41.9%)
along with lower levels of hydrogen and nitrogen (0.7 and 5.1%,
respectively).
2
3
42
reactivity toward air to give the metal oxides, and minor
oxidation/hydrolysis of the sample might explain the Y O
2
3
detection in the XRD experiment. Indeed, the elemental analysis
of a sample exposed to air for 20 h at room temperature gave an
increased oxygen content (1.3%) without any significant varia-
tion on the C, H, and N levels (0.4, 0.0 and 18.3%, respectively).
The ceramic yield and the negligible carbon content in this
residue agree with an efficient removal of the C Me groups in
The pyrolysis of the yttrium compound 14 C H under
3
7 8
different atmospheres was investigated (Ar, H /N , NH ) in
2
2
3
more detail. Heating under an argon flow (100 sccm) from 20 to
100 °C gave rise to a black powder (63% of the initial mass),
1
which was found to contain high levels of carbon (48.8%) by
elemental analysis (Table 5). Compositional analysis by energy
dispersive analysis of X-rays (EDX) shows the presence of
titanium and yttrium in the solid (see the Supporting Informa-
tion). The ceramic yield and large amounts of carbon derived of
the C Me groups in the resultant product are consistent with
5
5
the precursor, probably via acidꢀbase reactions with NH . We
3
are currently investigating the pyrolysis under NH at different
3
conditions (e.g., lower temperatures and slower heating rates) of
compound 14 and other cube-type heterometallic nitrido com-
plexes to optimize the preparation and characterization of metal
nitride materials.
5
5
those obtained in the TGA experiment under argon for this
compound.
The pyrolysis of 14 C H from room temperature to 1100 °C
3
7 8
’
CONCLUSION
was also carried out under a flow (100 sccm) of H /N (6ꢀ15%
2
2
H ) to give a black residue with 58% of the initial mass. Elemental
2
We have presented the systematic syntheses of a series of well-
analysis of this solid reveals about 42.7% of carbon and 9.4% of
nitrogen, whereas the EDX measurement shows the presence of
titanium and yttrium. The volatile byproduct of the decomposi-
tion were trapped at ꢀ196 °C (liquid nitrogen bath), and after
characterized titanium-group 3/lanthanide molecular nitrides by
reaction of the imido-nitrido titanium complex 1 with several
derivatives of the rare-earth metals. Complex 1 is capable of
acting as a neutral facially coordinating ligand to metal halide,
triflate or aryloxido derivatives to give single-cube complexes
closing the flow of gas, benzene-d was injected into the cooling
6
1
5
trap. The resulting C D solution was analyzed by H NMR
[X M{(μ -NH) Ti (η -C Me ) (μ -N)}]. Analogous treat-
6
6
3
3
3
3
5
5 3
3
spectroscopy and GC-MS measurements, and C Me H was
ment with metal triamido reagents produces the deprotonation
5
5
unambiguously identified in both techniques. It appears that
of 1 to yield corner-shared double-cube nitrido derivatives
6
806
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Inorganic Chemistry
M(μ -N) (μ -NH) {Ti (η -C Me ) (μ -N)} ] and the corre-
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compounds under argon atmosphere give black residues contain-
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ASSOCIATED CONTENT
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Supporting Information. Perspective views of the mo-
b
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2
002, 50, 1–10.
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AUTHOR INFORMATION
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Corresponding Author
43, 5298–5308. (b) Spencer, L. P.; MacKay, B. A.; Patrick, B. O.; Fryzuk,
M. D. Proc. Natl. Acad. Sci. U.S.A. 2006, 103, 17094–17098. (c) Fryzuk,
M. D. Acc. Chem. Res. 2009, 42, 127–133.
*Fax: (þ34) 91-8854683. E-mail: carlos.yelamos@uah.es.
(
13) Oyama, S. T., Ed.; The Chemistry of Transition Metal Carbides
and Nitrides; Blackie Academic & Professional: London, 1996.
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’
ACKNOWLEDGMENT
(
We thank Dr. Rosa Rojas of the ICMM for assistance with the
TGA/DTA experiments. We are also grateful to the Spanish
MEC (CTQ2008-00061/BQU), Comunidad de Madrid and the
Universidad de Alcal ꢀa (CCG10-UAH/PPQ-5935), and the
Factoría de Cristalizaci ꢀo n (CONSOLIDER-INGENIO 2010
CSD2006-00015) for financial support of this research. J.C.
thanks the MEC for a doctoral fellowship.
(
’
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