Synthesis and reactivity of bis(alkoxysilylamido)yttrium η2-pyridyl and η2-α-picolyl compounds

Article abstract of DOI:10.1021/om970540d

The synthesis and reactivity of bis(alkoxysilylamido)yttrium pyridyl and α-picolyl complexes [Me₂Si(NCMe₃)(OCMe₃)]₂YR (R = η²-(C,N)-2-NC₅H₄ (1); R = η²-(C,N)-CH₂-2-NC₅H₄ (2); R = η²-(C,N)-C(H)Me-2-NC₅H₄ (3); R = η²-(C,N)-C(H)Me-2-NC₅H₃-6-Me (4)) is reported. 1-4 have been prepared by C-H activation of pyridine and the corresponding methyl (ethyl) and dimethyl-substituted pyridines from [Me₂Si(NCMe₃)(OCMe₃)]₂YCH(SiMe ₃)₂ and by salt metathesis with the appropriate lithium salts from [Me₂Si(NCMe₃)(OCMe₃)] ₂YCl·THF. The molecular structure of 2 shows that the picolyl group is bonded to yttrium in an η³-aza-allylic fashion. With dihydrogen, stepwise hydrogenation of the pyridyl fragment of 1 has been observed, finally yielding the 2,3-dihydropyridyl complex [Me₂Si(NCMe₃)(OCMe₃)]₂Y-NC ₅H₈ (7). Compound 1 inserts ethene to form the α-methylpicolyl derivative 4. Polymerization of ethene was not observed. The pyridyl compound 1 reacts with PhC≡CH to yield the corresponding acetylide pyridine complex [Me₂Si(NCMe₃)(OCMe₃)] ₂YC≡CPh·Py (8). The complexed pyridine can be substituted by THF to give [Me₂Si(NCMe₃)(OCMe₃)] ₂YC≡CPh·THF (9), which easily loses THF and forms the base-free acetylide [Me₂Si(NCMe₃)(OCMe₃)]₂-YC≡CPh (10). Compounds 1 and 2 readily insert nitriles yielding imido-pyridine complexes. The imido-pyridine complexes that contain α-hydrogen readily undergo a 1,3-H shift affording the corresponding enamido-pyridine compounds. With CO, the pyridyl compound 1 gives a dipyridylketone complex {[Me₂Si(NCMe₃)(OCMe₃)] ₂Y}{μ,η²,η²-(N,N',O)-OC(2-NC ₅H₄)₂} (15).

Full text of DOI:10.1021/om970540d

5506
Organometallics 1997, 16, 5506-5516
Syn th esis a n d Rea ctivity of Bis(a lk oxysilyla m id o)yttr iu m
η2-P yr id yl a n d η2-r-P icolyl Com p ou n d s
Robbert Duchateau, Edward A. C. Brussee, Auke Meetsma, and J an H. Teuben*
Groningen Center for Catalysis and Synthesis, Department of Chemistry, University of
Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
Received J une 26, 1997X
The synthesis and reactivity of bis(alkoxysilylamido)yttrium pyridyl and R-picolyl
complexes [Me2Si(NCMe3)(OCMe3)]2YR (R ) η2-(C,N)-2-NC5H4 (1); R ) η2-(C,N)-CH2-2-NC5H4
(2); R ) η2-(C,N)-C(H)Me-2-NC5H4 (3); R ) η2-(C,N)-C(H)Me-2-NC5H3-6-Me (4)) is reported.
1-4 have been prepared by C-H activation of pyridine and the corresponding methyl (ethyl)
and dimethyl-substituted pyridines from [Me2Si(NCMe3)(OCMe3)]2YCH(SiMe3)2 and by salt
metathesis with the appropriate lithium salts from [Me2Si(NCMe3)(OCMe3)]2YCl‚THF. The
molecular structure of 2 shows that the picolyl group is bonded to yttrium in an η3-aza-
allylic fashion. With dihydrogen, stepwise hydrogenation of the pyridyl fragment of 1 has
been observed, finally yielding the 2,3-dihydropyridyl complex [Me2Si(NCMe3)(OCMe3)]2Y-
NC5H8 (7). Compound 1 inserts ethene to form the R-methylpicolyl derivative 4. Polym-
erization of ethene was not observed. The pyridyl compound 1 reacts with PhCtCH to yield
the corresponding acetylide pyridine complex [Me2Si(NCMe3)(OCMe3)]2YCtCPh‚Py (8). The
complexed pyridine can be substituted by THF to give [Me2Si(NCMe3)(OCMe3)]2YCtCPh‚THF
(9), which easily loses THF and forms the base-free acetylide [Me2Si(NCMe3)(OCMe3)]2-
YCtCPh (10). Compounds 1 and 2 readily insert nitriles yielding imido-pyridine complexes.
The imido-pyridine complexes that contain R-hydrogen readily undergo a 1,3-H shift
affording the corresponding enamido-pyridine compounds. With CO, the pyridyl compound
1 gives a dipyridylketone complex {[Me2Si(NCMe3)(OCMe3)]2Y}{µ,η2,η2-(N,N′,O)-OC(2-
NC5H4)2} (15).
In tr od u ction
the ligand environment has a pronounced influence on
the stability and reactivity of the complexes. Whereas
benzamidinates form a robust ancillary ligand system,
the alkoxysilylamidos are not inert but reactive ligands.
For instance, active hydrogen on substrate molecules
leads to spectator ligand protonation and loss of alkoxy-
silylamine Me2Si(N(H)CMe3)(OCMe3). Other typical
reactivity features are facile exchange of alkoxysilyla-
mido ligands between metal centers (leading to dispro-
portionation) and limited thermal stability (leading to
degradation of the alkoxysilylamido ligands).
In the alkyl compound [Me2Si(NCMe3)(OCMe3)]2Y-
CH(SiMe3)2, the reactions of the Y-C bond and of the
Y-N and N-C bonds of the alkoxysilylamido ligand
have about the same activation barrier and it is difficult
to study them independently. The possibility of sepa-
rating these two reactivities is much better for bis-
(alkoxysilylamido)yttrium pyridyl and picolyl complexes.
The reduced steric hindrance (relative to the bis-
(trimethylsilyl)methyl ligand) and the Y-C-N ring
strain of the pyridyl (picolyl) group is expected to
increase the reactivity of the Y-C bond, while the
bidentate bonding of the pyridyl/picolyl fragment is
expected to increase the thermal stability of the com-
plexes.5
Although metallocene derivatives are still the most
extensively studied compounds of group 3 metals and
lanthanides,1 there is rapidly growing interest in orga-
nometallic compounds of these elements stabilized by
other ligands.2 As part of a study to assess the effect
of the ancillary ligand system on the reactivity of
yttrium alkyl and hydrido bonds, we recently reported
bis(N,N′-bis(trimethylsilyl)benzamidinato)yttrium, [PhC-
(NSiMe3)2]2YR,3 and bis(N,O-bis(tert-butyl)alkoxy(di-
methylsilyl)amido)yttrium complexes, [Me2Si(NCMe3)-
(OCMe3)]2YR4 (R ) alkyl, hydrido). It was found that
X Abstract published in Advance ACS Abstracts, December 1, 1997.
(1) For an overview, see: (a) Schumann, H. Angew. Chem., Int. Ed.
Engl. 1984, 23, 474. (b) Evans, W. J . Adv. Organomet. Chem. 1985,
24, 131. (c) Evans, W. J .; Foster, S. E. J . Organomet. Chem. 1992, 433,
79. (d) Schaverien, C. J . Adv. Organomet. Chem. 1994, 36, 283.
(2) For example, see: (a) Edelmann, F. T. Angew. Chem., Int. Ed.
Engl. 1995, 34, 2466. (b) Evans, W. J . New J . Chem. 1995, 19, 525. (c)
Reger, D. L.; Lindeman, J . A.; Lebioda, L. Inorg. Chem. 1988, 27, 1890.
(d) Oki, A. R.; Zhang, H.; Hosmane, N. S. Organometallics 1991, 10,
2964. (e) Recknagel, A.; Steiner, A.; Noltemeyer, M.; Brooker, S.; Stalke,
D.; Edelmann, F. T. J . Organomet. Chem. 1991, 414, 327. (f) Schav-
erien, C. J .; Orpen, A. G. Inorg. Chem. 1991, 30, 4968. (g) Schaverien,
C. J .; Meijboom, N.; Orpen, A. G. J . Chem. Soc., Chem. Commun. 1992,
124. (h) Bazan, G. C.; Schaefer, W. P.; Bercaw, J . E. Organometallics
1993, 12, 2126. (i) Karsch, H. H.; Ferazin, G.; Kooijman, H.; Steigel-
mann, O.; Schier, A.; Bissinger, P.; Hiller, W. J . Organomet. Chem.
1994, 482, 151. (j) Shapiro, P. J .; Cotter, W. D.; Schaefer, W. P.;
Labinger, J . A.; Bercaw, J . E. J . Am. Chem. Soc. 1994, 116, 4623. (k)
Schaverien, C. J .; Orpen, A. G. Organometallics 1994, 13, 69.
(3) (a) Duchateau, R.; van Wee, C. T.; Meetsma, A.; Teuben, J . H.
J . Am. Chem. Soc. 1993, 115, 4931. (b) Duchateau, R.; van Wee, C. T.;
Meetsma, A.; van Duijnen, P. Th.; Teuben, J . H. Organometallics 1996,
15, 2279. (c) Duchateau, R.; van Wee, C. T.; Teuben, J . H. Organome-
tallics 1996, 15, 2291.
This paper reports the synthesis and characterization
of bis(N,O-bis(tert-butyl)alkoxy(dimethylsilyl)amido)-
yttrium pyridyl and (substituted) R-picolyl complexes.
(4) Duchateau, R.; Tuinstra, T.; Brussee, E. A. C.; Meetsma, A.; van
Duijnen, P. Th.; Teuben, J . H. Organometallics 1997, 16, 3511.
(5) (a) Deelman, B.-J .; Stevels, W. M.; Lakin, M. T.; Spek, A. L.;
Teuben, J . H. Organometallics 1994, 13, 3881. (b) Deelman, B.-J . Ph.D.
Thesis, University of Groningen, Groningen, The Netherlands, 1994.
S0276-7333(97)00540-2 CCC: $14.00 © 1997 American Chemical Society

Synthesis and Reactivity of Yttrium Compounds
Organometallics, Vol. 16, No. 25, 1997 5507
Sch em e 1. Syn th esis of Bis(a lk oxysilyla m id o)yttr iu m P yr id yl a n d r-P icolyl Com p lexes
Their reactivity has been investigated and compared
with the chemistry of Cp*2Ln(η2-(C,N)-2-NC5H4) (Ln )
Sc, Y, Lu),5,6 [Cp2Zr(η2-(C,N)-2-NC5H4)]+,7,8 and [Cp2-
Zr(η2-(C,N)-CH2-2-NC5H3-6-Me)]+.7,9
pounds Cp*2Y(η2-(C,N)-2-NC5H3-6-Me) and [Cp2Zr(η2-
(C,N)-2-NC5H3-6-Me)‚(THF)]+, respectively.
(b ) Ch lor id e Met a t h esis of [Me2Si(NCMe3)-
(OCMe3)]2YCl‚THF . Chloride metathesis of [Me2Si-
(NCMe3)(OCMe3)]2YCl‚THF with pyridyl and (substi-
tuted) R-picolyl lithium reagents10 appears to be a much
better synthetic method (Scheme 1). Exploratory NMR-
tube experiments showed that the reactions are es-
sentially quantitative within hours at room tempera-
ture. On a preparative scale, the compounds [Me2Si-
(NCMe3)(OCMe3)]2YR (R ) η2-(C,N)-2-NC5H4 (1), η2-
(C,N)-CH2-2-NC5H4 (2), η2-(C,N)-CH2-2-NC5H3-6-Me (3),
η2-(C,N)-C(H)Me-2-NC5H4 (4)) could be isolated in mod-
erate to high yields as red-brown or yellow crystals. The
success of this method is surprising since earlier at-
tempts to synthesize bis(alkoxysilylamido)yttrium alkyl
complexes with alkyl ligands less bulky than the bis-
(trimethylsilyl)methyl ligand by chloride metathesis
invariably failed.4 Probably, the bidentate bonding of
the pyridyl and picolyl groups efficiently blocks coordi-
nation of the salt (LiCl) or solvent molecules which often
hampers purification.
(c) Ch a r a cter iza tion of 1-4. All compounds are
very air sensitive and are extremely soluble in common
organic solvents (pentane, toluene, THF). They are
stable at room temperature, but like [Me2Si(NCMe3)-
(OCMe3)]2YCH(SiMe3)2,4 they thermolyze rapidly above
about 60 °C with degradation of the ancillary ligands
to give isobutene, the alkoxysilyamine (Me2Si(N(H)-
CMe3)(OCMe3)), the corresponding (substituted) pyri-
dine, and other, so far not identified products. The
NMR data of the pyridine-derived parts of 1-4 cor-
respond well with those of Cp*2Ln(η2-(C,N)-2-NC5H4)
(Ln ) Sc,6b,d Y,5,6c Lu6a), [Cp2Zr(η2-(C,N)-2-NC5H4-6-R)]+
(R ) H, Me),7 [PhC(NSiMe3)2]2Y(η2-(C,N)-CH2-2-NC5H4),3c
and [Cp2Zr(η2-(C,N)-CH2-2-NC5H3-6-Me)]+,7 respec-
tively. Due to coupling to Y, the resonance of the ipso-
carbon of the pyridyl group in 1 appears as a doublet (δ
) 226.0 ppm, 1J Y-C ) 26 Hz) in the 13C NMR spectrum.
For the picolyl complex 2, the R-CH2 group also emerges
Resu lts a n d Discu ssion
Syn th esis of Bis(Alk oxysilyla m id o) Yttr iu m P yr -
id yl a n d r-P icolyl Com p lexes. (a ) Th r ou gh C-H
Bon d Activa tion . Group 3 metal and lanthanide alkyl
and hydride complexes easily activate aromatic C-H
bonds by σ-bond metathesis.5-6 This reaction forms an
attractive route to new M-C bond containing complexes
and appears to be useful for the synthesis of the pyridyl
and picolyl complexes reported in this paper. Treatment
of [Me2Si(NCMe3)(OCMe3)]2YCH(SiMe3)2 with (ortho-
substituted) pyridines (NC5H5, 2-Me-NC5H4, 2,6-Me2-
NC5H3, 2-Et-NC5H4) gave the corresponding metalation
products 1-4 (Scheme 1). However, the reactions had
to be carried out at elevated temperatures, and competi-
tive thermal decomposition of the starting compound
and the products kept yields (as determined by 1H
NMR) low to moderate (1, 9%; 2, 72%; 3, 65%, 4, 65%).
Interestingly, with R-picoline and 2-ethylpyridine, the
R-alkyl group and not the aryl is metalated exclusively
to give 2 and 4, respectively. This is similar to the
reaction of [PhC(NSiMe3)2]2YR (R ) CH2Ph‚THF, CH-
(SiMe3)2) and {[PhC(NSiMe3)2]2Y(µ-H)}2 with R-picoline3c
but is in marked contrast with bis(pentamethylcyclo-
pentadienyl) derivatives like Cp*2YMe‚THF6c or [Cp2-
ZrMe‚THF]+,7 which selectively afford the pyridyl com-
(6) (a) Watson, P. L. J . Chem. Soc., Chem. Commun. 1983, 276. (b)
Tompson, M. E.; Bercaw, J . E. Pure Appl. Chem. 1984, 56, 1. (c) Den
Haan, K. H.; Wielstra, Y.; Teuben, J . H. Organometallics 1987, 6, 2053.
(d) Thompson, M. E.; Baxter, S. M.; Bulls, A. R.; Burger, B. J .; Nolan,
M. C.; Santarsiero, B. D.; Schaefer, W. P.; Bercaw, J . E. J . Am. Chem.
Soc. 1987, 109, 203. (e) Booij, M.; Deelman, B.-J .; Duchateau, R.;
Postma, D. S.; Meetsma, A.; Teuben, J . H. Organometallics 1993, 12,
3531.
(7) For example, see: J ordan, R. F.; Guram, A. S. Organometallics
1990, 9, 2116 and references cited therein.
(8) For example, see: (a) J ordan, R. F.; Taylor, D. F. J . Am. Chem.
Soc. 1989, 111, 778. (b) J ordan, R. F.; Taylor, D. F.; Baenziger, N. C.
Organometallics 1990, 9, 1546. (c) Guram, A. S.; J ordan, R. F.
Organometallics 1991, 10, 3470.
(10) Lithiation of pyridine, R-picoline, lutidine, and 2-ethylpyridine
were carried out in either pentane, ether, or THF at -80 °C using
n-BuLi. See also: Colgan, D.; Papasergio, R. I.; Raston, C. L.; White,
A. H. J . Chem. Soc., Chem. Commun. 1984, 1708.
(9) (a) Guram, A. S.; J ordan, R. F.; Taylor, D. F. J . Am. Chem. Soc.
1991, 113, 1833. (b) Guram, A. S.; Swenson, D. C.; J ordan, R. F. J .
Am. Chem. Soc. 1992, 114, 8991.

5508 Organometallics, Vol. 16, No. 25, 1997
Duchateau et al.
of the alkoxysilylamido ligands in axial positions. The
bonding of the alkoxysilylamido ligands in 2 is similar
to that found in other crystallographically characterized
bis(N,O-bis(tert-butyl)alkoxysilylamido) yttrium4 and
-lanthanide11 derivatives: The alkoxysilylamido ligands
form almost planar four-membered rings with yttrium.
The short Y-N and long Y-O bonds indicate that the
ligands are mainly bonded through the Y-N bonds.4 Of
particular interest is the bonding of the (planar) R-pi-
colyl fragment to yttrium. The Y(1)-C(6) bond (2.632(5)
Å) is notably longer than other nonbridging Y-C bonds
(ranging from 2.38(2) to 2.558(19) Å),4,12 whereas Y(1)-
N(1) (2.389(3) Å) is very short for a Yr:N(sp2) dative
bond.13 The weak Y(1)-C(6) interaction is confirmed
by the small coupling constant (1J Y-C ) 6 Hz) as
compared with other yttrium carbyl species (vide supra).
The four-membered (Y(1)-N(1)-C(5)-C(6)) ring is folded
over an angle of 32.2(5)° along the N(1)-C(6) vector. As
a result, the yttrium atom is located 1.55 Å out of the
pyridine plane. The exo C(5)-C(6) bond length (1.420(7)
Å) is intermediate to that of a regular C-C and CdC
F igu r e 1. ORTEP drawing of [Me2Si(NCMe3)(OCMe3)]2Y-
(η2-(C,N)-CH2-2-NC5H4) (2) at the 50% probability level.
Hydrogen atoms are omitted for clarity. Relevant carbon
atoms are labeled only.
1
bonds. The high value of J C-H (143 Hz) found for the
Ta ble 1. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for [Me2Si(NCMe3)(OCMe3)]2-
Y(η2-(C,N)-CH2-2-NC5H4) (2)
methylene group of the picolyl fragment indicates a
considerable sp2 hybridization of this carbon atom.
Hence, the bonding of the R-picolyl fragment can be
described as a distorted η3-(C,C,N)-aza-allylic interac-
tion. This type of bonding is common in alkali metal
and early transition metal R-picolyl complexes and is
intermediate between an η2-alkyl-amine and an η1-
amido-olefin.10,14
distances
angles
Y(1)-O(1)
2.427(4)
2.498(4)
2.269(4)
2.243(3)
2.389(3)
2.632(5)
1.349(6)
1.386(6)
1.361(7)
1.402(8)
1.359(7)
1.406(7)
1.420(7)
Si(1)-Y(1)-Si(2)
138.46(4)
64.83(12)
63.53(12)
174.21(11)
108.63(13)
89.62(12)
95.77(12)
84.4(3)
122.59(13)
128.79(13)
56.30(14)
115.9(4)
Y(1)-O(2)
Y(1)-N(2)
Y(1)-N(3)
Y(1)-N(1)
Y(1)-C(6)
N(1)-C(1)
N(1)-C(5)
C(1)-C(2)
C(2)-C(3)
C(3)-C(4)
C(4)-C(5)
C(5)-C(6)
O(1)-Y(1)-N(2)
O(2)-Y(1)-N(3)
O(1)-Y(1)-O(2)
N(2)-Y(1)-N(3)
O(1)-Y(1)-C(5)
O(2)-Y(1)-C(5)
Y(1)-C(6)-C(5)
N(2)-Y(1)-C(5)
N(3)-Y(1)-C(5)
N(1)-Y(1)-C(6)
N(1)-C(5)-C(6)
Reactivity of [Me2Si(NCMe3)(OCMe3)]2Y(η2-(C,N)-
2-NC5H 4) (1) a n d [Me2Si(NCMe3)(OCMe3)]2Y(η2-
(C,N)-CH2-2-NC5H4) (2). Yttrocene and cationic zir-
conocene pyridyl and picolyl complexes, Cp*2Y(η2-(C,N)-
2-NC5H4),5 [Cp2Zr(η2-(C,N)-2-NC5H3-6-R]+ (R ) H, Me),7,8
and [Cp2Zr(η2-(C,N)-C(H)Me-2-NC5H3-6-Et)]+,7,9 have a
diverse chemistry which ranges from simple complex-
ation of Lewis bases to catalytic alkylation of pyridine.
With 1 and 2 available, we decided to explore their
reactivity toward dihydrogen and unsaturated sub-
strates. In order to make a realistic comparison, the
reactions selected to be investigated were those reported
for the yttrocene and zirconocene pyridyl and R-picolyl
derivatives.7-9
2
1
as a doublet (δ ) 2.73 ppm, J Y-H ) 0.9 Hz) in the H
1
NMR and as a double-triplet (δ ) 52.3 ppm, J C-H
)
143 Hz, J Y-C ) 6 Hz) in the 13C NMR spectrum. The
1
1
observed J Y-C in 2 is very small compared with other
1
yttrium carbyl species (bridging carbyls, J Y-C ) 18-
21 Hz; terminal carbyls, J Y-C ) 23-74 Hz)3,4,5 and
1
suggests a relatively weak interaction between the
methylene fragment and yttrium (vide infra). Since the
NMR spectra of 1-4 are so closely analogous with those
of the corresponding Cp*2Ln(η2-(C,N)-NC5H4) (Ln ) Sc,
Y, Lu),6a,d [Cp2Zr(η2-(C,N)-2-NC5H3-6-Me)‚(PMe3)]+,8c
and [Cp2Zr(η2-(C,N)-C(H)Me-2-NC5H3-6-Et)]+ 9b sys-
tems, we assume that the pyridyl and picolyl fragments
are also η2-bonded in complexes 1-4. The data of 3 and
4 show no remarkable features, and with chemical shifts
Dih yd r ogen . Under dihydrogen (NMR tube experi-
ment, 4 atm, 65 °C), compound 1 was rapidly hydroge-
nated (96%, 85 min) to yield [Me2Si(NCMe3)(OCMe3)]2Y-
NC5H6 (5).15 This reaction is comparable to the Ziegler
alkylation of pyridines by alkyllithium reagents, for
(11) Recknagel, A.; Steiner, A.; Brooker, S.; Stalke, D.; Edelmann,
F. T. J . Organomet. Chem. 1991, 415, 315.
(12) For example, see: (a) Giardello, M. A.; Conticello, V. P.; Brard,
L.; Sabat, M.; Reingold, A. L.; Stern, C. L.; Marks, T. J . J . Am. Chem.
Soc. 1994, 116, 10212. (b) Booij, M.; Kiers, N. H.; Meetsma, A.; Teuben,
J . H.; Smeets, W. J . J .; Spek, A. L.; Organometallics 1989, 8, 2454. (c)
Evans, W. J .; Drummond, D. K.; Hanusa, T. P.; Olofson, J . M. J .
Organomet. Chem. 1989, 376, 311.
(13) (a) Evans, W. J .; Meadows, J . H.; Hunter, W. E.; Atwood, J . L.
Organometallics 1983, 2, 1252. (b) Evans, W. J .; Meadows, J . H.;
Hunter, W. E.; Atwood, J . L. J . Am. Chem. Soc. 1984, 106, 1291. (c)
Reger, D. L.; Lindeman, J . A.; Lebioda, L. Inorg. Chem. 1988, 27, 3923.
(14) (a) Bailey, S. I.; Colgan, D.; Engelhardt, L. M.; Leung, W.-P;
Papasergio, R. I.; Raston, C. L.; White, A. H. J . Chem. Soc., Dalton
Trans. 1986, 603. (b) Beshouri, S. M.; Chebi, D. E.; Fanwick, P. E.;
Rothwell, I. P. Organometallics 1990, 9, 2375. (c) Chisholm, M. H.;
Folting, K.; Huffman, J . C.; Rothwell, I. P. Inorg. Chem. 1981, 20, 1496.
(15) The reaction of 2 and 3 with hydrogen is similar to that
observed for 1, although the reaction rate decreases dramatically with
increasing steric bulk. Hence, thermolysis of the complexes becomes
substantial. Duchateau, R.; Brussee, E. A. C.; Teuben, J . H. Unpub-
lished results.
1
and J Y-C values strictly comparable to 2, they are
assumed to be structurally very similar to 2.
To verify the assigned bonding of the R-picolyl frag-
ment, an X-ray structure determination of 2 was carried
out. An ORTEP drawing of the molecular structure is
shown in Figure 1, and selected bond distances and
angles are listed in Table 1. Details concerning the data
collection and refinement are given in Table 3. The
R-picolyl fragment can be assumed to occupy one
coordination vertex and the yttrium regarded in dis-
torted trigonal-pyramidal coordination, with the alkoxy-
silylamido nitrogens (N(2), N(3)) and the picolyl carbon
C(5) in a tilted equatorial plane and the oxygen atoms

Synthesis and Reactivity of Yttrium Compounds
Organometallics, Vol. 16, No. 25, 1997 5509
which 1,2-addition products of pyridine have been
observed as intermediates.16 Similar 1,2-addition prod-
ucts were obtained when hydrides {[PhC(NSiMe3)2]2Y-
3c
(µ-H)}2 and {[C5H4R]2Y(µ-H)‚THF}2 (R ) H, Me)13b
were treated with pyridine, which strongly suggests that
1 is first hydrogenolyzed to the corresponding hydride
which subsequently inserts the pyridine (eq 1).17
(3)
(1)
Although feasible within the proposed mechanism,
hydrogenation of the final double bond in 7 was not
observed. Heating of mixtures containing 7 under
dihydrogen (4 atm) for prolonged periods of time (days,
65 °C) resulted exclusively in the thermolysis of 7 (1H
NMR). A vanadium-mediated, partial reduction of
pyridine, similar to the reaction described here, has been
reported by Gambarotta et al.21 Reaction of [(Me3-
Si)2N]V[η2-(C,N)-N(SiMe3)Si(Me2)CH2] with pyridine
under dihydrogen, resulted in partial hydrogenation,
giving the vanadium analog of 7, [(Me3Si)2N]2V-NC5H8.
Eth en e. When 1 reacted with excess ethene, the
insertion product [Me2Si(NCMe3)(OCMe3)]2Y(η2-(C,N)-
2-C(H)Me-2-NC5H4) (4) formed in 36% yield (65 h, 50
°C).
The reaction is not clean, and the formation of
substantial amounts of Me2Si(N(H)CMe3)(OCMe3), 2-eth-
ylpyridine, and isobutene illustrates concurrent degra-
dation of the ancillary ligand system. Nevertheless, 4
could unequivocally be identified by NMR spectroscopy.
The expected 1,2-insertion product [Me2Si(NCMe3)-
(OCMe3)]2Y(η2-(C,N)-CH2CH2-2-NC5H4) (eq 4) was not
observed. Probably, it had been formed as an interme-
Upon heating (hours, 65 °C), 5 rearranged, presum-
ably by a 1,3-H-shift, to the 1,4-isomer (6, eq 2).
(2)
Similarly, the hydrides {[C5H4Me]2Y(µ-H)‚THF}213b and
5 18
{Cp*2Y(µ-H)}2 , reacted with pyridine to form the
corresponding 1,4-insertion products. Direct formation
of the 1,4-insertion product has not been observed, and
this seems to exclude nucleophilic attack at the para-
position of pyridine (vide infra). When 1 was treated
with deuterium, incorporation of deuterium was mainly
observed at the ortho and para positions of the pyridyl
ligand, indicating that hydrogenolysis of 1 and isomer-
ization of 5 to 6 are reversible (eqs 1 and 2). With excess
dihydrogen, 6 was not the final product. Subsequent
hydrogenation of one of the double bonds in 6 was
observed, affording the 2,3-dihydropyridyl complex 7 (24
h at 65 °C, 50% yield, eq 3). Most likely, formation of 7
follows hydrogenolysis of 6 (eq 3). Although hydro-
genolysis of a Ln-N bond (Ln ) Sc, Y, lanthanide) is
not expected to be facile, it has been proposed as one of
the key steps in the scandium-catalyzed hydrogenation
of nitriles.19 Hydrogenolysis of 6 will give an intermedi-
ate hydride enamine adduct (eq 3). Subsequent enam-
ine-imine tautomerism affords the NdC double bond,
necessary for 1,2-insertion of the intermediate hydride
to yield 7 (eq 3).20
(4)
(16) (a) March, J . Advanced Organic Chemistry, Reactions, Mechan-
sims and Structure, 3rd ed.; J ohn Wiley and Sons: New York, 1985; p
598. (b) J oule, J . A.; Smith, G. F. Heterocyclic Chemistry; Van Nostrand
Reinhold Company: London, 1972; Chapter 4 and references cited
therein.
(17) The existence of the hydride {[Me2Si(NCMe3)(OCMe3)]2Y(µ-H)}2,
formed during hydrogenolysis of [Me2Si(NCMe3)(OCMe3)]2YCH(SiMe3)2
was proven with NMR, see ref 4.
(18) The 1,4-insertion product Cp*2Y-NC5H6 was formed only in
the presence of additional hydrogen. In the absence of hydrogen, the
pyridyl compound, Cp*2Y(η2-(C,N)-2-NC5H4), was obtained.
(19) Bercaw, J . E.; Davies, D. L.; Wolczanski, P. T. Organometallics
1986, 5, 443.
(20) If 7 is formed by hydrogenolysis of the Y-N bond in 6,
competitive hydrogenolysis of the alkoxysilylamido ligands should be
taken into account. It is not clear whether the Me2Si(N(H)CMe3)-
(OCMe3) present (15%) after 21 h at 65 °C is formed by thermolysis or
by hydrogenolysis.
diate which rapidly rearranged into 4 under the condi-
tions applied. A comparable isomerization has been
observed for the reaction of Cp*2Y(η2-(C,N)-2-NC5H4)
with ethene.5 Initially, the 1,2-insertion product
Cp*2Y(η2-(C,N)-CH2CH2-2-NC5H4) was formed, which
upon heating, rearranged into a mixture of Cp*2Y(η2-
(C,N)-2-NC5H3-6-Et) and Cp*2Y(η2-(C,N)-(C(H)Me-2-
NC5H4).
In analogy with the catalytic conversion of pyridine
into 2-ethylpyridine by Cp*2Y(η2-(C,N)-2-NC5H4)5 re-
(21) Berno, P.; Gambarotta, S. J . Chem. Soc., Chem. Commun. 1994,
2419.

5510 Organometallics, Vol. 16, No. 25, 1997
Duchateau et al.
ported earlier, 1 was treated with excess ethene and
pyridine (65 °C). However, catalytic pyridine alkylation
was not observed, and the reaction stops after the
formation of 4, leaving the excess of ethene and pyridine
unreacted. Heating (70 °C) the reaction mixture for
prolonged periods of time resulted exclusively in the
thermal decomposition of 4.
As expected on the basis of these results, the picolyl
complex 2 did not react with ethene. Heating (days, 65
°C) a benzene-d6 solution of 2 under ethene (4 atm) only
gave thermal decomposition of 2; no ethene consumption
could be observed.
P h en yla cetylen e. Whereas the yttrium alkyl [Me2-
Si(NCMe3)(OCMe3)]2YCH(SiMe3)2 reacts completely in
a nonselective fashion with HCtCR (R ) Ph, SiMe3,
CMe3), liberating H2C(SiMe3)2 and Me2Si(N(H)CMe3)-
(OCMe3) (1:2 ratio),4 reaction of 1 with PhCtCH (1
equiv) selectively gave the alkynyl complex [Me2Si-
(NCMe3)(OCMe3)]2Y-CtCPh‚Py (8, eq 5) in 51% yield
(1H NMR).22
R-carbons appear as triplets (1J Y-C ≈ 20 Hz),3 due to
the coupling of two (time-averaged) identical yttrium
atoms. Probably, the alkoxysilylamido ligands (larger
than two Cp* ligands4) hamper coordination of THF and
even block dimerization of unsolvated 10. Similarly, the
steric congestion in {Cp*2Sm-CtCCMe3}2 precluded
bridging of the alkynyl fragments, and the monomeric
units are stabilized by a peculiar agostic interaction of
a Cp*-methyl group of an adjacent molecule.24c Unfor-
tunately, compound 10 crystallizes as thin needles
unsuitable for X-ray analysis so that verification of the
assigned structure was not possible.
Compared to other bis(alkoxysilylamido)yttrium car-
byl complexes (vide supra), the acetylides 8-10 are
thermally remarkably stable and show no decomposition
in benzene after several days at 100 °C. For 10, no C-C
coupling to µ-trienediyl species was observed, in contrast
to the reaction found upon heating of {Cp*2Ln-CtCR}n
(Ln ) La, R ) Ph, CMe3; Ln ) Ce, R ) Me, CMe3; Ln
) Sm, R ) Ph, CH2CH2Ph, CH2CH2CHMe2).24 Prob-
ably, the steric bulk of the alkoxysilylamido ligands in
10, which prevents dimerization, also blocks C-C
coupling of the acetylide fragments.
(5)
The reaction of 1 with PhCtCH resembles that of
Cp*2Y(η2-(C,N)-2-NC5H4), which affords Cp*2Y-
CtCR‚Py.5 In contrast, [Cp2Zr(η2-(C,N)-2-NC5H3-6-
Me)]+ and [Cp2Zr(η2-(C,N)-CH2-2-NC5H3-6-Me)]+ insert
terminal alkynes,8c which clearly indicates the differ-
ence in the character of the Y-C and Zr-C bonds.
The extreme solubility of [Me2Si(NCMe3)(OCMe3)]2-
YCtCPh‚Py (8) hampered its purification and isolation.
While attempts to remove the coordinated pyridine
(stripping with toluene, sublimation) failed, the pyridine
could be replaced by THF yielding the adduct [Me2Si-
(NCMe3)(OCMe3)]2YCtCPh‚THF (9, eq 6).23 Complex
The molecular structure of 9 is shown in Figure 2.
Selected bond distances and angles listed in Table 2
(details of the data collection and refinement are listed
in Table 3). The n-pentane in the crystal lattice is not
shown. The center of the monomeric molecule is a
distorted octahedral yttrium atom coordinated by two
alkoxysilylamido ligands, one acetylide fragment, and
one THF molecule.
In pseudo-trigonal-pyramidal-coordinated complexes
4
[Me2Si(NCMe3)(OCMe3)]2Y-CH(SiMe3)2 and 2, the
alkoxysilylamido nitrogens are in the equatorial plane.
In 9, one of the nitrogen atoms is equatorial, trans to
the acetylide group, whereas the other is axial. Since
the same orientation of the alkoxysilylamido ligands
(6)
was observed in {[Me2Si(NCMe3)(OCMe3)]2Y(µ-(N,N′)-
4
N(H)-C(Me)dC(H)sCtN)}2
and [Me2Si(NCMe3)-
9 could also be synthesized directly by chloride meta-
thesis of [Me2Si(NCMe3)(OCMe3)]2YCl‚THF with
NaCtCPh. Surprisingly, stripping 9 with toluene
resulted in the loss of the coordinated THF (eq 7) and
produced the base-free alkynyl [Me2Si(NCMe3)(OCMe3)]2-
YCtCPh, 10. Interestingly, the 13C NMR spectrum of
10 is identical to that of 9, with the only exception being
that the resonances are slightly shifted. The doublet
(OCMe3)]2Yb(µ-Cl)2Li‚THF2,11 this seems to be the most
favorable conformation in octahedral bis(alkoxysilyla-
mido) complexes. With torsion angles of -3.63(10)°
(N(1)-Y(1)-O(1)-Si(1)) and -5.67(11)° (N(2)-Y(1)-
O(2)-Si(2)), respectively, both alkoxysilylamido ligands
form almost planar rings with yttrium. The Y(1)-N(1)
(2.279(3) Å) and Y(1)-N(2) (2.266(3) Å) bonds are within
the normal range for Y-N σ-bonds in bis(N,O-bis(tert-
butyl)alkoxy(dimethylsilyl)amido)yttrium derivatives.4
Whereas the Y(1)-O(2) (2.375(2) Å) and Y(1)-O(3)
(2.378(2) Å) bond distances are normal Yr:O dative
bonds,4 O(1) seems only weakly bonded to yttrium with
Y(1)-O(1) ) 2.571(2) Å. The Y(1)-C(1) (2.448(4) Å)
distance is very similar to the yttrium-carbon bonds
in [p-MeO-C6H4C(NSiMe3)2]2YCH(SiMe3)2 (2.431(5) Å),3b
1
resonance for the R-C of 10 (δ ) 144.2 ppm, J Y-C ) 60
1
Hz; cf. 9(R-C) δ ) 145.3 ppm, J Y-C ) 53 Hz) excludes
a dimeric structure with bridging alkynyl fragments,
as normally found in organoyttrium and lanthanide
chemistry. For such complexes, the resonances of the
(22) Partial protolysis of the alkoxysilylamido was also observed and
indicates that this reaction still competes with the protolysis of the
pyridyl fragment. With 3 equiv of PhCtCH, complete protolysis of both
the pyridyl and alkoxysilylamido ligands was observed.
(23) The solubility of 9 was sufficiently low to allow recrystallization
and isolation from n-pentane. Unfortunately, crystals of 9 readily lost
n-pentane from the crystal lattice. While stable enough to obtain a
low-temperature X-ray structure determination (vide infra), the n-
pentane had to be removed to obtain a satisfactory elemental analysis.
(24) (a) Evans, W. J .; Keyer, R. A.; Ziller, J . W. Organometallics
1990, 9, 2628. (b) Heeres, H. J .; Nijhof, J .; Teuben, J . H. Organome-
tallics 1993, 12, 2609. (c) Evans, W. J .; Keyer, R. A.; Ziller, J . W.
Organometallics 1994, 12, 2618. (d) Forsyth, C. M.; Nolan, S. P.; Stern,
C. L.; Marks, T. J . Organometallics 1993, 12, 3618.

Synthesis and Reactivity of Yttrium Compounds
Organometallics, Vol. 16, No. 25, 1997 5511
The reactions of 1 and 2 with benzonitrile and
acetonitrile are summarized in Scheme 2. The reactiv-
ity of both complexes is dominated by insertion and,
when possible, subsequent 1,3-H shift. Generally, the
reactions are fast at room temperature and the products
are formed in high yield. The extremely high solubility
of the complexes hampered their purification. Only 13b
and 14b could be isolated as analytically pure crystals.
However, all compounds could unequivocally be identi-
1
fied by H and 13C NMR spectroscopy.
With benzonitrile, 1 gave insertion affording [Me2Si-
(NCMe3)(OCMe3)]2Y(η2-(N,N′)-NdC(Ph)-2-NC5H4) (11).
Similarly, 2 inserted benzonitrile, but the initially
formed [Me2Si(NCMe3)(OCMe3)]2Y(η2-(N,N′)-NdC(Ph)-
CH2-2-NC5H4) (12a ) rearranged by a 1,3-H shift to the
corresponding enamide-pyridine complex, [Me2Si-
(NCMe3)(OCMe3)]2Y(η2-(N,N′)-N(H)-C(Ph))C(H)-2-
NC5H4) (12b). With acetonitrile, either C-H bond
activation or insertion may occur. Which reaction will
take place depends strongly on the character of the
M-C bond. Compound 1 reacted instantaneously with
MeCtN, initially yielding [Me2Si(NCMe3)(OCMe3)]2Y-
(η2-(N,N′)-NdC(Me)-2-NC5H4) (13a ). This complex is
not stable and rearranged (room temperature) by a
1,3-H shift into [Me2Si(NCMe3)(OCMe3)]2Y(η2-(N,N′)-
N(H)-C(dCH2)-2-NC5H4) (13b). Similar to the reaction
with benzonitrile, 2 reacted with acetonitrile to form
[Me2Si(NCMe3)(OCMe3)]2Y(η2-(N,N′)-N(H)-C(Me)dC-
(H)-2-NC5H4) (14b). The reaction is fast at room tem-
perature. Although [Me2Si(NCMe3)(OCMe3)]2Y(η2-(N,N′)-
NdC(Me)CH2-2-NC5H4) (14a ) was not observed in the
1H NMR spectra recorded during the reaction, it is likely
that it was formed as an intermediate that rearranges
rapidly into 14b (Scheme 2). With the CH3 resonance
located at δ 1.94 ppm, the vinylic proton as a doublet
at δ 5.02 ppm (4J HH ) 2.1 Hz), and the NH as a broad
singlet at δ 6.23 ppm, the 1H NMR spectrum of 14b
corresponds well with that of [Cp2Zr(η2-(N,N′)-N(H)-
C(Me)dC(H)-2-NC5H3-6-Me)]+, formed by reaction of
[Cp2Zr(η2-(C,N)-CH2-2-NC5H3-6-Me)]+ with acetoni-
trile.9
F igu r e 2. ORTEP drawing of [Me2Si(NCMe3)(OCMe3)]2-
YCtCPh‚THF (9) at the 50% probability level. Hydrogen
atoms are omitted for clarity. Relevant carbon atoms are
labeled only.
Ta ble 2. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for [Me2Si(NCMe3)(OCMe3)]2YCtCP h ‚THF (9)
distances
angles
Y(1)-N(1)
2.279(3)
2.266(3)
2.571(2)
2.375(2)
2.378(2)
2.448(4)
1.217(5)
1.444(5)
N(1)-Y(1)-O(1)
62.22(9)
65.36(9)
173.47(9)
97.25(9)
87.67(10)
87.78(10)
85.15(11)
80.85(8)
98.37(10)
147.69(11)
98.28(9)
Y(1)-N(2)
Y(1)-O(1)
Y(1)-O(2)
Y(1)-O(3)
Y(1)-C(1)
C(1)-C(2)
C(2)-C(3)
N(2)-Y(2)-O(2)
N(2)-Y(1)-O(1)
N(1)-Y(1)-O(2)
C(1)-Y(1)-O(3)
O(1)-Y(1)-C(1)
O(2)-Y(1)-C(1)
O(1)-Y(1)-O(3)
N(2)-Y(1)-O(3)
N(1)-Y(1)-C(1)
N(1)-Y(1)-O(3)
O(2)-Y(1)-O(3)
Si(1)-Y(1)-Si(2)
N(1)-Y(1)-N(2)
160.87(8)
133.00(3)
111.66(10)
Cp*2YMe‚THF (2.44(2) Å),25a and Cp*2YCH(SiMe3)2
(2.446(7) Å),25b respectively. This is unusual since
metal-alkynyl bonds are generally shorter than the
corresponding metal-alkyl bonds.12c Interestingly, a
comparable long metal-alkynyl bond has been observed
in the closely related Cp*2Sm-CtCPh‚THF complex.26
Whereas the long Sm-C bond is accompanied by a short
CtC bond (CtCav, 1.12(2) Å), the CtC bond (1.217(5)
Å) in 9 is normal for nonbridging alkynyl groups.27
The observation that both 1 and 2 insert acetonitrile
demonstrates that the pyridyl and picolyl groups are
not as strong a Brønsted base as the bulky CH(SiMe3)2
group in Cp*2LnCH(SiMe3)2 (Ln ) La, Ce),28b [PhC-
(NSiMe3)2]2YCH(SiMe3)2,3
and
[Me2Si(NCMe3)-
(OCMe3)]2YCH(SiMe3)24 for which C-H bond activation
is observed.
Nitr iles. Group 3 metal and lanthanide alkyl and
hydrido complexes ({[C5H4R]2Y(µ-H)‚THF}2 (R ) H,
Me),28 Cp*2LnR (Ln ) Sc, R ) C6H4-4-Me, H; Ln ) Y,
La, Ce, R ) CH(SiMe3)2),19,28b [PhC(NSiMe3)2]2YR (R )
CH2Ph,THF, CH(SiMe3)2), {[PhC(NSiMe3)2]2Y(µ-H)}2)3c
react smoothly with nitriles, either giving insertion or
C-H bond activation.
Ca r bon Mon oxid e. Group 3 and lanthanide carbyl
complexes are known to react with CO with the forma-
tion of unstable η2-acyl compounds which either rear-
range to enolates or form dinuclear enedione diolate
derivatives.2e,29 Deelman et al.5 reported the formation
of a novel µ,η2,η2-dipyridylketone derivative upon treat-
ment of Cp*2Y(η2-(C,N)-2-NC5H4) with CO. This reac-
tion clearly demonstrates the ability of pyridyl frag-
ments to stabilize otherwise unstable functionalities. In
order to compare the pyridyl group in 1 with that in
Cp*2Y(η2-(C,N)-2-NC5H4), reaction with CO was carried
out.
(25) (a) Den Haan, K. H.; Wielstra, Y.; Eshuis, J . J . W.; Teuben, J .
H. J . Organomet. Chem. 1987, 323, 181. (b) Den Haan, K. H.; de Boer,
J . L.; Teuben, J . H.; Spek, A. L.; Kojic-Prodic, B.; Hays, G. R.; Huis, R.
Organometallics 1986, 5, 1726.
(26) Evans, W. J .; Ulibarry, T. A.; Chamberlain, L. R.; Ziller, J . W.;
Alvarez, D., J r. Organometallics 1990, 9, 2124.
(27) (a) Atwood, J . L.; Hains, C. F., J r.; Tsutsui, M.; Gebala, A. E.
J . Chem. Soc., Chem. Commun. 1973, 452. (b) Atwood, J . L.; Tsutsui,
M.; Ely, N.; Gebala, A. E. J . Coord. Chem. 1976, 5, 209. (c) Evans, W.
J .; Bloom, I.; Doedens, R. J . J . Organomet. Chem. 1984, 265, 249.
(28) (a) Evans, W. J .; Meadows, J . H.; Wayda, A. L.; Hunter, W. E.;
Atwood, J . L. J . Am. Chem. Soc. 1982, 104, 2008. (b) Heeres, H. J .
Ph.D. Thesis, University of Groningen, Groningen, The Netherlands,
1990.
Treatment of 1 with excess CO resulted in the
intensely blue compound {[Me2Si(NCMe3)(OCMe3)]2Y}-
(29) (a) Evans, W. J .; Wayda, A. D.; Hunter, W. E.; Atwood, J . L. J .
Chem. Soc., Chem. Commun. 1981, 706. (b) J eske, G.; Schock, L. E.;
Swepton, P. N.; Schumann, H.; Marks, T. J . J . Am. Chem. Soc. 1985,
107, 8091.

5512 Organometallics, Vol. 16, No. 25, 1997
Duchateau et al.
Ta ble 3. Deta ils of th e X-r a y Str u ctu r e Deter m in a tion of [Me2Si(NCMe3)(OCMe3)]2Y(η2-(C,N)-CH2-2-NC5H4)
(2) a n d {Me2Si(NCMe3)(OCMe3]2YCtCP h ‚THF (9)
2
9
formula
mol wt
cryst syst
space group
a, Å
C26H54N3O2Si2Y
585.81
monoclinic
P21/n
16.757(1)
12.170(1)
17.454(1)
112.401(8)
3290.8(4)
1.182
C32H61N2O3Si2Y‚(C5H12)
0.5
703.00
monoclinic
C2/c
21.041(1)
19.321(1)
21.437(1)
107.946(6)
8290.9(8)
1.126
b, Å
c, Å
â, deg
V, Å3
D
Z
calc, g mol-3
4
8
F(000)
1256
18.77
3032
15.0
µ (Mo KR), cm-1
cryst size, mm
0.30 × 0.35 × 0.40
0.20 × 0.27 × 0.37
T, K
130
130
θ range; min, max, deg.
1.26, 27.0
∆ω ) 0.85 + 0.34 tan q
h, -21 to 19; k, -1 to 15, l, 0 to 22
1.00, 27.0
∆ω ) 0.80 + 0.34 tan θ
h, -26 to 25; k, 0 to 24; l, 0 to 27
ω/2θ scan, deg
data set
total no. of data
no. of unique data
no. of obsd data (l g 2.5 σ(I))
no. of refined params
final agreement factors:
RF ) ∑(||Fo| - |Fc||)/∑|Fo|
8933
7166
4741
497
9603
8998
5735
628
0.060
0.056
0.045
2
wR ) [∑(w(|Fo| - |Fc)2)/∑w|Fo| ]1/2
0.041
weighting scheme
1/σ2(F)
2.30(2)
-0.86, 1.25
1/σ2(F)
S ) [∑w(|Fo| - |Fc|)2/(m - n)]1/2 a
residual electron density in final diff Fourier map, e/Å3
1.549(15)
-0.48, 0.51
a
m ) No. of observations; n ) No. of variables.
Sch em e 2. Rea ction of
[Me2Si(NCMe3)(OCMe3)]2Y(η2-(C,N)-2-NC5H4) (1)
a n d [Me2Si(NCMe3)(OCMe3)]2Y(η2-(C,N)-
CH2-2-NC5H4) (2) w ith Ben zon itr ile a n d
Aceton itr ile
reduction of the carbonyl functionality.29b,30 As proposed
by Deelman et al., the formation of 15 is thought to
proceed by CO insertion followed by nucleophilic attack
of an other equivalent of 1 and is schematically pre-
sented in eq 8. A more detailed discussion concerning
the bonding of the µ,η2,η2-dipyridylketone fragment is
given elsewhere.5
Con clu d in g Rem a r k s. Even though the intrinsic
reactivity of the alkoxysilylamido ligands of the bis-
(alkoxysilylamido)yttrium complexes may make this
system unsuitable for catalytic applications, the bis-
(alkoxysilylamido)yttrium pyridyl (1) and picolyl (2)
derivatives show interesting stoichiometric reactions.
Whereas the bulky bis(trimethylsilyl)methyl ligand in
[Me2Si(NCMe3)(OCMe3)]2YCH(SiMe3)2 reacts as a clas-
sical Brønsted base, the pyridyl and picolyl ligands in
1 and 2 are much better nucleophiles, as illustrated by
their diverse insertion chemistry. Reduction of the
{µ,η2,η2-(N,N′,O)-OC(2-NC5H4)2} (15, eq 8). This reac-
tion proceeds analogously to that of the permethylated
yttrocene derivative which gives {Cp*2Y}2{µ,η2,η2-
(N,N′,O)-OC(2-NC5H4)2}.5 The spectral data (13C NMR,
δ ) 147.3 ppm (C(dO)-ipso); IR, νCdO ) 1404 cm-1) of
15 are nearly identical to those of {Cp*2Y}2{µ,η2,η2-
(N,N′,O)-OC(2-NC5H4)2}5 and indicate a considerable
(30) Fachinetti, G.; Floriani, C.; Marchetti, F.; Merlino, S. J . Chem.
Soc., Chem. Commun. 1976, 522.

Synthesis and Reactivity of Yttrium Compounds
Organometallics, Vol. 16, No. 25, 1997 5513
hexanes, 7.0 mmol) at -40 °C. The red solution obtained was
allowed to warm to room temperature and then stirred for 90
min. The volatiles were removed in vacuo, and the residue
was dissolved in toluene (80 mL). After the mixture was cooled
to -80 °C, [Me2Si(NCMe3)(OCMe3)]2YCl‚THF (4.2 g, 7.0 mmol)
was added and the reaction mixture was allowed to warm to
room temperature. After the mixture was stirred for 20 min,
the solvent was evaporated and the crude product stripped
with n-pentane (3 × 15 mL). Then the product was redissolved
in n-pentane (30 mL). Filtration, concentration, and slow
cooling to -30 °C yielded 2 (2.05 g, 3.5 mmol, 50%) as rod-
shaped orange crystals. 1H NMR (benzene-d6, δ): 7.75 (d, 1H,
steric saturation at yttrium and introduction of reactiv-
ity promoting ring strain by replacing the bulky CH-
(SiMe3)2 by a pyridyl group clearly leads to an increased
reactivity of the Y-C bond, e.g., with dihydrogen and
phenylacetylene. When substrates containing acidic
protons and high reaction temperatures are avoided, the
bis(alkoxysilylamido)yttrium pyridyl and picolyl com-
plexes 1 and 2 react comparably to the corresponding
permethylated yttrocene and cationic zirconocene py-
ridyl and R-picolyl complexes.
The fact that the bis(N,O-bis(tert-butyl)alkoxy(di-
methylsilyl)amido) ligand environment is sterically
more demanding than the bis(N,N′-bis(trimethylsilyl)-
benzamidinato) and bis(pentamethylcyclopentadienyl)
ligand systems is clearly illustrated by the isolation of
a monomeric, unsolvated acetylide complex [Me2Si-
(NCMe3)(OCMe3)]2YCtCPh (10). This is in strong
contrast with the bis(N,N′-bis(trimethylsilyl)benzamidi-
nato)yttrium analogs [{PhC(NSiMe3)2}2YCtCR]2 that
exclusively form stable dimers. The electronic differ-
ences induced by the auxiliary ligand systems that have
been compared are illustrated by the difference in
reactivity between [Me2Si(NCMe3)(OCMe3)]2YCtCPh
and the unsolvated compounds Cp*2YCtCR. The latter
undergo further insertion and catalytically dimerize
terminal alkynes to enynes, while [Me2Si-
(NCMe3)(OCMe3)]2YCtCPh does not react.
3
3
NC5H4, J H-H ) 5.6 Hz), 6.73 (ddd, 1H, NC5H4, J H-H ) 8.6
Hz, 3J H-H ) 6.8 Hz, 4J H-H ) 1.7 Hz), 6.52 (d, 1H, NC5H4, 3J H-H
3
3
) 8.6 Hz), 5.90 (ddd, 1H, NC5H4, J H-H ) 6.8 Hz, J H-H ) 5.6
4
2
Hz, J H-H ) 1.3 Hz), 2.73 (d, 2H, Y-CH2, J Y-H ) 0.9 Hz),
1.51 (s, 9H, C(CH3)3), 1.49 (s, 9H, C(CH3)3), 1.31 (s, 18H,
C(CH3)3), 0.43 (s, 6H, Si(CH3)2), 0.36 (s, 3H, Si(CH3)2), 0.32 (s,
3H, Si(CH3)2). 13C NMR (benzene-d6, δ): 166.9 (s, NC5H4(ipso-
1
1
C)), 146.2 (d, NC5H4, J C-H ) 169 Hz), 135.5 (d, NC5H4, J C-H
) 158 Hz), 120.8 (d, NC5H4, 1J C-H ) 163 Hz), 106.7 (d, NC5H4,
1J C-H ) 164 Hz), 77.1 (s, C(CH3)3), 52.3 (td, Y-CH2, J C-H
)
1
143 Hz, 1J Y-C ) 6 Hz), 52.1 (s, C(CH3)3), 37.0 (q, C(CH3)3, 1J C-H
) 125 Hz), 32.0 (q, C(CH3)3, 1J C-H ) 128 Hz), 8.2 (q, Si(CH3)2,
1J C-H ) 118 Hz). Anal. Calcd for C26H54N3O2Si2Y: C, 53.31;
H, 9.29; Y, 15.18. Found: C, 53.35; H, 9.24; Y, 15.21.
P r ep a r a t ion of [Me2Si(NCMe3)(OCMe3)]2Y(η2-(C,N)-
CH2-2-NC5H3-6-CH3) (3). To a n-pentane solution (20 mL)
of 2,6-dimethylpyridine (0.39 mL, 3.3 mmol), n-BuLi (1.3 mL,
2.5 M in hexanes, 3.3 mmol) was added at -30 °C. The
resulting yellow suspension was allowed to warm to room
temperature and then stirred for 20 min. Subsequently, [Me2-
Si(NCMe3)(OCMe3)]2YCl‚THF (2.0 g, 3.3 mmol) was added at
-80 °C. After the mixture was warmed to room temperature,
it was stirred for 2 h. The volatiles were removed in vacuo,
and the residue was stripped with n-pentane (3 × 10 mL).
Subsequently, the crude product was extracted with n-pentane
(25 mL). Concentration and cooling to -80 °C afforded 3 (0.61
g, 1.0 mmol, 31%) as yellow crystals. 1H NMR (benzene-d6,
δ): 6.74 (dd, 1H, NC5H3, 3J H-H ) 8.1 Hz, 3J H-H ) 6.8 Hz), 6.44
Exp er im en ta l Section
Gen er a l Com m en ts. For general aspects and methods
and techniques used, see ref 3b. Hydrogen (Hoekloos 99.9995%),
deuterium (Matheson, C.P.), and ethylene (DSM Research
B.V.) were used as purchased. PhCtCH, MeCtN, PhCtN,
pyridine, R-picoline, and 2,6-dimethylpyridine (J anssen) were
dried over 4 Å molecular sieves and distilled prior to use. [Me2-
Si(NCMe3)(OCMe3)]2YCl‚THF and [Me2Si(NCMe3)(OCMe3)]2Y-
CH(SiMe3)2 were prepared following literature procedures.4
P r ep a r a t ion of [Me2Si(NCMe3)(OCMe3)]2Y(η2-(C,N)-
NC5H4) (1). 2-bromopyridine (0.63 mL, 6.61 mmol) was
dissolved in ether (40 mL) and cooled to -80 °C. Then n-BuLi
(2.67 mL, 2.5 M solution in hexanes, 6.67 mmol) was added.
After the mixture was stirred for 30 min, [Me2Si-
(NCMe3)(OCMe3)]2YCl‚THF (3.97 g, 6.60 mmol) was added to
the resulting red solution. The reaction mixture was allowed
to warm slowly to room temperature and stirred for 20 h. The
volatiles were removed in vacuo, and the resulting sticky
residue was stripped with n-pentane (3 × 7 mL). Extraction
with n-pentane (15 mL), concentration, and cooling to -80 °C
yielded 1 (1.10 g, 1.92 mmol, 29%) as red-brown crystals.
Further concentration of the mother liquor yielded a second
crop of 1 (0.65 g, 1.13 mmol, 17%) as a microcrystalline powder
after cooling to -80 °C. 1H NMR (benzene-d6, δ): 8.41 (dd,
3
3
(d, 1H, NC5H3, J H-H ) 8.6 Hz), 5.81 (d, 1H, NC5H3, J H-H
)
6.8 Hz), 2.75 (d, 2H, Y-CH2, 2J Y-H ) 1.3 Hz), 2.43 (s, 3H, CH3),
1.50 (s, 18H, C(CH3)3), 1.28 (s, 18H, C(CH3)3), 0.45 (s, 3H, Si-
(CH3)2), 0.40 (s, 3H, Si(CH3)2), 0.36 (s, 6H, Si(CH3)2). 13C NMR
(benzene-d6, δ): 168.2 (s, NC5H3(ipso-C)), 154.5 (s, NC5H3(ipso-
1
1
C)), 136.4 (d, NC5H3, J C-H ) 156 Hz), 118.1 (d, NC5H3, J C-H
) 163 Hz), 106.6 (d, NC5H3, 1J C-H ) 163 Hz), 76.9 (s, C(CH3)3),
1
1
52.3 (s, C(CH3)3), 50.6 (td, Y-CH2, J C-H ) 142 Hz, J Y-C ) 8
Hz), 37.2 (q, C(CH3)3, 1J C-H ) 123 Hz), 36.7 (q, C(CH3)3, 1J C-H
1
) 128 Hz), 32.0 (q, C(CH3)3, J C-H ) 124 Hz), 24.9 (q, CH3,
1J C-H ) 126 Hz), 8.0 (q, Si(CH3)2, J C-H ) 118 Hz). Anal.
1
Calcd for C27H56N3O2Si2Y: C, 54.06; H, 9.41; N, 7.01; Y, 14.82.
Found: C, 54.28; H, 9.48; N, 6.73; Y, 14.72.
P r ep a r a t ion of [Me2Si(NCMe3)(OCMe3)]2Y(η2-(C,N)-
CH(CH3)-2-NC5H4) (4). To a THF solution (40 mL) of
2-ethylpyridine (0.38 mL, 3.5 mmol), n-BuLi (1.4 mL, 2.5 M
in hexanes, 3.5 mmol) was added at -80 °C to give an orange
suspension. The reaction mixture was allowed to warm to
room temperature and stirred for 1 h. After the THF was
evaporated, the remaining sticky solid was stripped with
n-pentane (3 × 5 mL) and subsequently dissolved in toluene
(40 mL). The orange-red solution was cooled to -80 °C, and
[Me2Si(NCMe3)(OCMe3)]2YCl‚THF (2.0 g, 3.5 mmol) was added.
After the mixture was warmed to room temperature, the dark-
orange solution formed was stirred for 20 h. After filtration,
the volatiles were removed in vacuo. The oily residue was
stripped with n-pentane (3 × 15 mL), leaving an oily residue
which did not solidify (1.3 g, 2.1 mmol, 60%). The extreme
solubility of 4 precluded further purification. 1H NMR (benzene-
3
4
1H, NC5H4, J H-H ) 5.1 Hz, J H-H ) 0.9 Hz), 7.96 (dd, 1H,
3
4
NC5H4, J H-H ) 7.3 Hz, J H-H ) 1.3 Hz), 7.07 (td, 1H, NC5H4,
3J H-H ) 7.5 Hz, J H-H ) 1.3 Hz), 6.70 (ddd, 1H, NC5H4, J H-H
4
3
3
4
) 7.3 Hz, J H-H ) 5.1 Hz, J H-H ) 1.3 Hz), 1.53 (s, 18H,
C(CH3)3), 1.08 (s, 18H, C(CH3)3), 0.39 (s, 12H, Si(CH3)2). 13C
NMR (benzene-d6, δ): 226.0 (d, NC5H4(ipso-C), 1J Y-C ) 26 Hz),
1
1
145.8 (d, NC5H4, J C-H ) 174 Hz), 132.9 (d, NC5H4, J C-H
)
1
162 Hz), 132.3 (d, NC5H4, J C-H ) 157 Hz), 121.0 (d, NC5H4,
1J C-H ) 158 Hz), 76.3 (s, C(CH3)3), 51.9 (s, C(CH3)3), 37.2 (q,
1
1
C(CH3)3, J C-H ) 124 Hz), 31.4 (q, C(CH3)3, J C-H ) 126 Hz),
8.0 (q, Si(CH3)2, 1J C-H ) 118 Hz). Anal. Calcd for C25H52N3O2-
Si2Y: C, 52.52; H, 9.17; N, 7.35; Y, 15.55. Found: C, 52.19;
H, 9.04; N, 6.97; Y, 15.43.
3
4
P r ep a r a t ion of [Me2Si(NCMe3)(OCMe3)]2Y(η2-(C,N)-
CH2-2-NC5H4) (2). A THF (40 mL) solution of R-picoline (0.7
mL, 7.0 mmol) was treated with n-BuLi (2.8 mL, 2.5 M in
d6, δ): 7.64 (dd, 1H, NC5H4, J H-H ) 5.6 Hz, J H-H ) 1.3 Hz),
3 3 4
6.78 (ddd, 1H, NC5H4, J H-H ) 7.7 Hz, J H-H ) 5.6 Hz, J H-H
) 0.9 Hz), 6.36 (d, 1H, NC5H4, J H-H ) 9.0 Hz), 5.74 (t, 1H,
3

5514 Organometallics, Vol. 16, No. 25, 1997
Duchateau et al.
3
3
NC5H4, J H-H ) 6.0 Hz), 3.00 (qd, 1H, Y-C(H)CH3, J H-H
)
CMe3)(OCMe3) (37%). Subsequent addition of 16 µL (0.15
mmol) of PhCtCH resulted in fast protolysis of the alkoxysi-
lylamido ligands (1H NMR). 1H NMR (benzene-d6, δ): 9.62 (s
2
3
5.6 Hz, J Y-H ) 2.1 Hz), 1.78 (d, 3H, YC(H)CH3, J H-H ) 5.6
Hz), 1.52 (s, 9H, C(CH3)3), 1.42 (s, 9H, C(CH3)3), 1.32 (s, 9H,
C(CH3)3), 1.22 (s, 9H, C(CH3)3), 0.43 (s, 6H, Si(CH3)2), 0.39 (s,
3H, Si(CH3)2), 0.34 (s, 3H, Si(CH3)2). 13C NMR (benzene-d6,
δ): 162.2 (s, NC5H4(ipso-C)), 146.2 (d, NC5H4, 1J C-H ) 175 Hz),
3
4
(br), 2H, NC5H5), 7.68 (dd, 2H, o-C6H5, J H-H ) 8.1 Hz, J H-H
3
) 1.3 Hz), 7.13 (t, 2H, m-C6H5, J H-H ) 7.7 Hz), 6.99 (t, 1H,
3
3
p-C6H5, J H-H ) 7.3 Hz), 6.85 (t (br), 1H, NC5H5, J H-H ) 6.8
1
1
3
135.5 (d, NC5H4, J C-H ) 155 Hz), 114.3 (d, NC5H4, J C-H
)
Hz), 6.59 (t (br), 2H, NC5H5, J H-H ) 6.4 Hz), 1.53 (s, 18H,
1
163 Hz), 103.4 (d, NC5H4, J C-H ) 165 Hz), 77.4 (s, C(CH3)3),
C(CH3)3), 1.48 (s, 18H, C(CH3)3), 0.59 (s, 6H, Si(CH3)2), 0.45
(s, 6H, Si(CH3)2).
1
1
60.9 (td, Y-C(H)CH3, J C-H ) 162 Hz, J Y-C ) 5 Hz), 52.1 (s,
1
C(CH3)3), 37.7 (q, C(CH3)3, J C-H ) 124 Hz), 37.2 (q, C(CH3)3,
P r epar ation of [Me2Si(NCMe3)(OCMe3)]2YCtCP h ‚THF‚
(p en ta n e)0.5 (9). To a toluene solution (20 mL) of [Me2Si-
(NCMe3)(OCMe3)]2YCl‚THF (1.50 g, 2.5 mmol), NaCtCPh
(0.31 g, 2.5 mmol) was added at -80 °C. The initially white
suspension turned light orange within 10 min. After the
mixture was stirred for 30 min at room temperature, the
solvent was removed in vacuo and the resulting brown oil was
stripped with n-pentane (3 × 7 mL). Extraction with n-
pentane (10 mL), concentration of the extracts, and cooling to
-30 °C gave 9 (0.77 g, 1.1 mmol, 44%) as a white microcrys-
talline powder. Repeated recrystallization from n-pentane
yielded colorless bar-shaped crystals of 9 suitable for an X-ray
structure analysis. Since the crystals rapidly lost solvent (n-
pentane) from the crystal lattice, satisfactory elemental analy-
ses could not be obtained. 1H NMR (benzene-d6, δ): 7.59 (d,
1J C-H ) 124 Hz), 36.9 (q, C(CH3)3, J C-H ) 124 Hz), 33.0 (q,
1
1
1
C(CH3)3, J C-H ) 126 Hz), 31.8 (q, C(CH3)3, J C-H ) 126 Hz),
1
1
12.8 (q, Y-C(H)CH3, J C-H ) 124 Hz), 8.2 (q, Si(CH3)2, J C-H
1
) 118 Hz), 7.9 (q, Si(CH3)2, J C-H ) 118 Hz).
Hyd r ogen a tion of [Me2Si(NCMe3)(OCMe3)]2Y(η2-(C,N)-
NC5H4) (1). An NMR tube containing a solution of 1 (17 mg,
0.030 mmol) in benzene-d6 (0.5 mL) was charged with hydro-
1
gen (ca. 4.0 atm). For 21 h, the reaction was followed by H
NMR spectroscopy at 65 °C. 1H NMR spectra, recorded at
fixed time intervals, showed the gradual conversion of 1 into
the 1,2-inserted product [Me2Si(NCMe3)(OCMe3)]2Y-NC5H6 (5,
96% after 85 min). While the intensity of resonances attribut-
able to the 1,4-inserted product [Me2Si(NCMe3)(OCMe3)]2Y-
NC5H6 (6, 10% after 20 h) and the hydrogenated product
[Me2Si(NCMe3)(OCMe3)]2Y-NC5H8 (7, 46% after 20 h) in-
creased, the resonances of 1 and 5 subsided. Some Me2Si-
(N(H)CMe3)(OCMe3) (15% after 21 h) was also formed during
the reaction.20 Separation and purification of the various
reaction products proved to be impossible due to their high
solubility. 5: 1H NMR (benzene-d6, δ) 7.01 (d, 1H, NC5H6,
3
3
2H, o-C6H5, J H-H ) 8.3 Hz), 7.09 (t, 2H, m-C6H5, J H-H ) 7.7
3
Hz), 6.96 (t, 1H, p-C6H5, J H-H ) 6.8 Hz), 4.05 (m, 4H, THF-
R-CH2), 1.61 (s, 18H, C(CH3)3), 1.47 (s, 18H, C(CH3)3), 1.38 (m,
4H, THF-â-CH2), 1.23 (m, 3H, n-pentane-CH2), 0.88 (t, 3H,
3
n-pentane-CH3, J H-H ) 6.7 Hz), 0.49 (s, 6H, Si(CH3)2), 0.39
(s, 6H, Si(CH3)2). 13C NMR (benzene-d6, δ): 145.3 (d, Y-CtC-
3J H-H ) 6.4 Hz), 6.24 (ddd, 1H, NC5H6, J H-H ) 5.6 Hz, J H-H
Ph, J Y-C ) 53 Hz), 131.3 (d, Ar, J C-H ) 159 Hz), 128.1 (d,
1 1
3
3
1
1
4
3
) 5.1 Hz, J H-H ) 0.9 Hz), 5.20 (td, 1H, NC5H6, J H-H ) 6.4
Hz, 4J H-H ) 0.9 Hz), 4.87 (m, 1H, NC5H6), 4.29 (m, 2H, NC5H6),
1.39 (s, 18H, C(CH3)3), 1.36 (s, 18H, C(CH3)3), 0.37 (s, 12H,
Si(CH3)2). 13C{1H} NMR (benzene-d6, δ): 144.3 (s, NC5H6),
127.5 (s, NC5H6), 101.9 (s, NC5H6), 94.8 (s, NC5H6), 78.8 (s,
C(CH3)3), 52.0 (s, C(CH3)3), 47.5 (s, NC5H6(C2)), 37.1 (s,
C(CH3)3), 31.6 (s, C(CH3)3), 7.8 (s, Si(CH3)2). 6: 1H NMR
Ar, J C-H ) 159 Hz), 125.5 (d, Ar, J C-H ) 161 Hz), 108.1 (dt,
2 3
Y-CtC-Ph, J Y-C ) 5 Hz, J C-H ) 11 Hz), 77.6 (s, C(CH3)3),
1
70.5 (t, THF-R-CH2, J C-H ) 149 Hz), 52.0 (s, C(CH3)3), 37.1
1
1
(q, C(CH3)3, J C-H ) 123 Hz), 31.8 (q, C(CH3)3, J C-H ) 125
1
Hz), 25.1 (t, THF-â-CH2, J C-H ) 133 Hz), 22.9 (t, n-pentane-
1
1
CH2, J C-H ) 126 Hz), 14.2 (q, n-pentane-CH3, J C-H ) 124
1
1
Hz), 8.1 (q, Si(CH3)2, J C-H ) 118 Hz), 7.8 (q, Si(CH3)2, J C-H
) 117 Hz).
3
4
(benzene-d6, δ) 6.45 (dd, 2H, NC5H6, J H-H ) 8.1 Hz, J H-H
)
1.3 Hz), 4.48 (dt, 2H, NC5H6, 3J H-H ) 8.1 Hz, 3J H-H ) 3.0 Hz),
P r ep a r a tion of [Me2Si(NCMe3)(OCMe3)]2YCtCP h (10).
Compound 9 (0.50 g, 0.7 mmol) was stripped with toluene (3
× 5 mL) and subsequently dried in vacuo until all the THF
resonances in the 1H NMR spectrum of the product had
disappeared. Then the product was dissolved in n-pentane (7
mL). Crystallization at -80 °C yielded 10 (0.39 g, 0.64 mmol,
91%) as white needles. 1H NMR (benzene-d6, δ): 7.57 (d, 2H,
o-C6H5, 3J H-H ) 8.2 Hz), 7.09 (t, 2H, m-C6H5, 3J H-H ) 7.3 Hz),
3
4
3.54 (td, 2H, NC5H6, J H-H ) 3.0 Hz, J H-H ) 1.7 Hz), 1.47 (s,
18H, C(CH3)3), 1.34 (s, 18H, C(CH3)3), 0.35 (s, 12H, Si(CH3)2).
13C NMR (benzene-d6, δ): 135.8 (d, NC5H6(C2, C6), J C-H
)
1
1
162 Hz), 94.7 (d, NC5H6(C3, C5), J C-H ) 158 Hz), 79.1 (s,
1
C(CH3)3), 52.0 (s, C(CH3)3), 37.1 (q, C(CH3)3, J C-H ) 129 Hz),
31.5 (q, C(CH3)3, 1J C-H ) 126 Hz), 23.7 (t, NC5H6(C4), 1J C-H
)
126 Hz), 7.7 (q, Si(CH3)2, J C-H ) 118 Hz). 7: 1H NMR
1
3
3
(benzene-d6, δ) 6.87 (d, 1H, NC5H8, J H-H ) 7.3 Hz), 4.51 (m,
6.98 (t, 1H, p-C6H5, J H-H ) 7.3 Hz), 1.62 (s, 18H, C(CH3)3),
1H, NC5H8), 3.61 (m, 2H, NC5H8), 2.42 (m, 2H, NC5H8), 1.94
(m, 2H, NC5H8), 1.40 (s, 18H, C(CH3)3), 1.37 (s, 18H, C(CH3)3),
0.38 (s, 12H, Si(CH3)2). 13C NMR (benzene-d6, δ): 139.2 (d,
NC5H8, 1J C-H ) 153 Hz), 87.8 (d, NC5H8(C5), 1J C-H ) 159 Hz),
1.40 (s, 18H, C(CH3)3), 0.42 (s, 6H, Si(CH3)2), 0.38 (s, 6H, Si-
(CH3)2). 13C NMR (benzene-d6, δ): 144.2 (d, Y-CtC-Ph, 1J Y-C
1
1
) 60 Hz), 131.5 (d, Ar, J C-H ) 160 Hz), 128.3 (d, Ar, J C-H
)
1
159 Hz), 126.0 (d, Ar, J C-H ) 157 Hz), 108.9 (dt, Y-CtC-
1
2
2
78.5 (s, C(CH3)3), 51.9 (s, C(CH3)3), 47.0 (t, NC5H8(C2), J C-H
Ph, J Y-C ) 5 Hz, J C-H ) 12 Hz), 79.1 (s, C(CH3)3), 52.2 (s,
) 133 Hz), 37.1 (q, C(CH3)3, 1J C-H ) 128 Hz), 31.5 (q, C(CH3)3,
1
C(CH3)3), 37.1 (q, C(CH3)3, J C-H ) 121 Hz), 31.5 (q, C(CH3)3,
1J C-H ) 126 Hz), 25.0 (t, NC5H6(C3), J C-H ) 126 Hz), 23.8 (t,
1
1J C-H ) 126 Hz), 8.0 (q, Si(CH3)2, J C-H ) 118 Hz), 7.6 (q, Si-
1
NC5H8(C4), 1J C-H ) 126 Hz), 7.8 (q, Si(CH3)2, 1J C-H ) 118 Hz).
(CH3)2, 1J C-H ) 117 Hz). Anal. Calcd for C28H53N2O2Si2Y: C,
NMR Tu be Rea ction of 1 w ith Eth en e. An NMR tube
containing a solution of 1 (56 mg, 0.10 mmol) in benzene-d6
(0.5 mL) was charged with ethene (4.7 atm, 0.27 mmol) and
heated to 50 °C. The 1H NMR spectra collected at fixed
intervals during the reaction showed the slow formation of 4.
The reaction was not clean and considerable amounts of
thermolysis products were formed. After 65 h at 50 °C, 95%
of 1 had been consumed to give a mixture (1H NMR) of 4 (36%),
Me2Si(N(H)CMe3)(OCMe3) (15%), 2-ethylpyridine (15%), and
isobutene (19%).
NMR Tu be P r ep a r a tion of [Me2Si(NCMe3)(OCMe3)]2-
YCtCP h ‚P y (8). PhCtCH (7.8 µL, 0.071 mmol) was added
to an NMR tube charged with a solution of 1 (40 mg, 0.070
mmol) in benzene-d6 (0.5 mL). After 1 h at room temperature,
nearly all of 1 had reacted, yielding a mixture of [Me2Si-
(NCMe3)(OCMe3)]2Y-CtCPh‚Py (8, 51%) and Me2Si(N(H)-
56.54; H, 8.98; Y, 14.95. Found: C, 56.67; H, 8.96; Y, 15.03.
NMR Tu be P r ep a r a tion of [Me2Si(NCMe3)(OCMe3)]2Y-
(η2-(N,N′)-NdC(P h )-2-NC5H4) (11). PhCtN (11.0 µL, 0.108
mmol) was added to an NMR tube containing a benzene-d6
(0.4 mL) solution of 1 (59 mg, 0.103 mmol). Upon addition,
the red solution turned intense purple. The 1H NMR spectrum
recorded after 10 min at room temperature showed full
conversion of 1 to 11. 1H NMR (benzene-d6, δ): 9.04 (d, 1H,
3
3
NC5H4, J H-H ) 4.6 Hz), 7.74 (d, 2H, o-C6H5, J H-H ) 6.8 Hz),
3
7.25 (t, 2H, m-C6H5, J H-H ) 7.3 Hz), 7.17 (m, 2H, NC5H4,
p-C6H5), 7.05 (td, 1H, NC5H4, 3J H-H ) 7.6 Hz, 4J H-H ) 1.7 Hz),
3
3
4
6.61 (ddd, 1H, NC5H4, J H-H ) 6.4 Hz, J H-H ) 5.1 Hz, J H-H
) 1.2 Hz), 1.41 (s br, 36H, C(CH3)3), 0.44 (s, 6H, Si(CH3)2),
0.39 (s, 6H, Si(CH3)2). 13C NMR (benzene-d6): 161.3 (s, NC5H4-
1
(ipso-C)), 156.7 (s, NdC), 151.1 (d, Ar, J C-H ) 179 Hz), 144.0
(s, Ar(ipso-C)), 140.0 (d, Ar, 1J C-H ) 164 Hz), 128.1 (d, Ar, 1J C-H

Synthesis and Reactivity of Yttrium Compounds
Organometallics, Vol. 16, No. 25, 1997 5515
1
1
1
) 158 Hz), 128.0 (d, Ar, J C-H ) 158 Hz), 127.4 (d, Ar, J C-H
164 Hz), 78.5 (t, dCH2, J C-H ) 155 Hz), 77.1 (s, C(CH3)3),
1
1
1
) 159 Hz), 122.2 (d, Ar, J C-H ) 166 Hz), 121.9 (d, Ar, J C-H
) 166 Hz), 76.4 (s, C(CH3)3), 51.8 (s, C(CH3)3), 37.4 (q, C(CH3)3,
76.6 (s, C(CH3)3), 51.9 (s, C(CH3)3), 37.1 (q, C(CH3)3, J C-H
)
1
124 Hz), 31.9 (q, C(CH3)3, J C-H ) 126 Hz), 29.3 (q, C(CH3)3,
1J C-H ) 121 Hz), 37.1 (q, C(CH3)3, J C-H ) 122 Hz), 31.8 (q,
1J C-H ) 125 Hz), 7.9 (q, Si(CH3)2, J C-H ) 118 Hz). Anal.
1
1
1
1
C(CH3)3, J C-H ) 127 Hz), 8.1 (q, Si(CH3)2, J C-H ) 117 Hz),
7.7 (q, Si(CH3)2, J C-H ) 118 Hz).
Calcd for C27H55N4O2Si2Y: C, 52.92; H, 9.05; N, 9.14; Y, 14.51.
Found: C, 52.14; H, 8.75; N, 9.05; Y, 14.35.
1
NMR Tu be P r ep a r a tion of [Me2Si(NCMe3)(OCMe3)]2Y-
(η2-(N,N′)-N(H)-C(P h )dC(H)-2-NC5H4) (12b). To an NMR
tube charged with a solution of 2 (39 mg, 0.067 mmol) in
benzene-d6 (0.5 mL), PhCtN (6.9 µL, 0.068 mmol) was added.
Upon addition of the benzonitrile, the solution changed from
yellow to orange-red. The 1H NMR spectrum recorded directly
after the NMR tube was filled showed resonances character-
istic of [Me2Si(NCMe3)(OCMe3)]2Y(η2-(N,N′)-NdC(Ph)-CH2-2-
NC5H4) (12a ) and [Me2Si(NCMe3)(OCMe3)]2Y(η2-(N,N′)-N(H)-
C(Ph)dC(H)-2-NC5H4) (12b). After 2 h at room temperature,
all 12a had been converted into 12b. 12a : 1H NMR (benzene-
P r ep a r a tion of [Me2Si(NCMe3)(OCMe3)]2Y(η2-(N,N′)-N-
(H)-C(Me)dC(H)-2-NC5H4) (14b). To a toluene solution (20
mL) of 2 (0.52 g, 0.89 mmol), acetonitrile (48 µL, 0.92 mmol)
was added at -80 °C. The solution was allowed to warm to
room temperature and stirred for 4 h, after which the solvent
was evaporated. Extraction of the yellow residue with pentane
(10 mL), followed by concentration and cooling to -80 °C,
afforded 14b (0.43 g, 0.69 mmol, 77%) as yellow crystals. 1H
NMR (benzene-d6, δ): 9.10 (s (br), 1H, NC5H4), 6.84 (ddd, 1H,
3
3
4
NC5H4, J H-H ) 8.6 Hz, J H-H ) 6.8 Hz, J H-H ) 1.7 Hz), 6.61
3
(d, 1H, NC5H4, J H-H ) 8.6 Hz), 6.22 (s (br), 1H, NH), 6.20
3
4
3
4
d6, δ) 9.41 (dd, 1H, NC5H4, J H-H ) 6.4 Hz, J H-H ) 2.1 Hz),
(td, 1H, NC5H4, J H-H ) 6.8 Hz, J H-H ) 1.3 Hz), 5.02 (d (br),
4
8.00 (d, 2H, o-C6H5, 3J H-H ) 6.8 Hz), 7.35 (t, 2H, m-C6H5, 3J H-H
1H, dCH, J H-H ) 2.1 Hz), 1.93 (s, 3H, CH3), 1.55 (s, 18H,
3
) 6.8 Hz), 7.20 (t, 1H, p-C6H5, J H-H ) 6.8 Hz), 6.93 (td, 1H,
C(CH3)3), 1.23 (s, 18H, C(CH3)3), 0.50 (s, 6H, Si(CH3)2), 0.44
(s, 3H, Si(CH3)2), 0.41 (s, 3H, Si(CH3)2). 13C NMR (benzene-
d6, δ): 162.0 (s, NC5H4(ipso-C)), 159.5 (s, C(Ph)dCH), 147.3
(d (br), NC5H4, 1J C-H ) 173 Hz), 135.5 (d, NC5H4, 1J C-H ) 160
Hz), 123.2 (d, NC5H4, 1J C-H ) 162 Hz), 110.5 (d, NC5H4, 1J C-H
NC5H4, 3J H-H ) 7.7 Hz, 4J H-H ) 1.7 Hz), 6.63 (m, 2H, NC5H4),
2
2
4.59 (d, 1H, CH2, J H-H ) 14.3 Hz), 4.18 (d, 1H, CH2, J H-H
)
14.3 Hz), 1.54 (s, 18H, C(CH3)3), 1.28 (s, 18H, C(CH3)3), 0.50
(s, 6H, Si(CH3)2), 0.41 (s, 6H, Si(CH3)2). 12b: 1H NMR
(benzene-d6, δ) 9.18 (s (br), 1H, NC5H4), 7.75 (d, 2H, o-C6H5,
3J H-H ) 7.3 Hz), 7.17 (m, 3H, m,p-C6H5), 6.87 (t, 1H, NC5H4,
3J H-H ) 7.3 Hz), 6.80 (s (br), 1H, NH), 6.72 (d, 1H, NC5H4,
3J H-H ) 8.1 Hz), 6.27 (t, 1H, NC5H4(C5), 3J H-H ) 6.4 Hz), 5.47
(s (br), 1H, dCH), 1.62 (s, 9H, C(CH3)3), 1.50 (s, 9H, C(CH3)3),
1.31 (s, 9H, C(CH3)3), 1.20 (s, 9H, C(CH3)3), 0.50 (s, 3H, Si-
(CH3)2), 0.47 (s, 3H, Si(CH3)2), 0.41 (s, 6H, Si(CH3)2). 13C NMR
(benzene-d6): 163.6 (s, NC5H4(ipso-C)), 159.9 (s, C(Ph)dCH),
1
) 166 Hz), 92.7 (d, C(Ph)dCH, J C-H ) 154 Hz), 76.6 (s,
1
C(CH3)3), 52.0 (s, C(CH3)3), 37.1 (q, C(CH3)3, J C-H ) 125 Hz),
1
1
31.9 (q, C(CH3)3, J C-H ) 126 Hz), 29.3 (q, CH3, J C-H ) 124
1
Hz), 7.9 (q, Si(CH3)2, J C-H ) 118 Hz). Anal. Calcd (found)
for C28H57N4O2Si2Y: C, 53.65; H, 9.17; N, 8.94; Y, 14.18.
Found: C, 53.44; H, 8.97; N, 9.00; Y, 14.08.
P r ep a r a tion of {[Me2Si(NCMe3)(OCMe3)]2Y}2{µ,η2,η2-
(N,N′,O)-OC-(2-NC5H4)2} (15). A Schlenk flask (200 mL)
containing a red-brown solution of 1 (0.50 g, 0.87 mmol) in
n-pentane (20 mL) was degassed and charged with CO (1 atm).
The color of the solution instantaneously turned purple. After
20 h at room temperature, the color of the solution had
changed to deep blue. Evaporation of the volatiles gave 15
(0.72 g, 0.61 mmol, 70%) as a microcrystalline powder. 1H
NMR (benzene-d6, δ): 9.04 (s (br), 1H, NC5H4), 7.65 (d, NC5H4,
3J H-H ) 8.8 Hz), 7.04 (t, 1H, NC5H4, 3J H-H ) 6.5 Hz), 5.93 (m,
1H, NC5H4), 1.52 (s, 9H, C(CH3)3), 1.48 (s, 9H, C(CH3)3), 1.34
(s, 9H, C(CH3)3), 1.30 (s, 9H, C(CH3)3), 0.54 (s, 3H, Si(CH3)2),
0.52 (s, 3H, Si(CH3)2), 0.47 (s, 3H, Si(CH3)2), 0.45 (s, 3H, Si-
(CH3)2). 13C NMR (benzene-d6, δ): 149.2 (s, ipso-C), 147.3 (s,
1
1
147.2 (d, Ar, J C-H ) 170 Hz), 135.7 (d, Ar, J C-H ) 163 Hz),
1
1
128.7 (d, Ar, J C-H ) 162 Hz), 128.2 (d, Ar, J C-H ) 160 Hz),
1
1
126.1 (d, Ar, J C-H ) 157 Hz), 124.3 (d, Ar, J C-H ) 162 Hz),
1
1
111.4 (d, Ar, J C-H ) 165 Hz), 93.4 (d, C(Ph)dCH, J C-H
)
151 Hz), 76.8 (s, C(CH3)3), 52.1 (s, C(CH3)3), 37.2 (q, C(CH3)3,
1J C-H ) 123 Hz), 32.0 (q, C(CH3)3, J C-H ) 125 Hz), 8.0 (q,
1
1
Si(CH3)2, J C-H ) 117 Hz).
NMR Tu be Rea ction of [Me2Si(NCMe3)(OCMe3)]2Y(η2-
(C,N)-2-NC5H4) (1) w ith MeCtN. Acetonitrile (5.0 µL, 0.096
mmol) was added to a solution of 52 mg (0.091 mmol) of 1 in
benzene-d6 (0.5 mL). An instantaneous color change from red-
brown to brown-yellow occurred. The 1H NMR spectrum taken
after 10 min at room temperature showed resonances of [Me2-
Si(NCMe3)(OCMe3)]2Y(η2-N,N′)-NdC(Me)-2-NC5H4) (13a ).
Within hours at room temperature, 13a had been rearranged
into [Me2Si(NCMe3)(OCMe3)]2Y(η2-N,N′)-N(H)-C(dCH2)-2-
NC5H4) (13b). 13a : 1H NMR (benzene-d6, δ) 9.00 (d, 1H,
NC5H4, 3J H-H ) 4.7 Hz), 7.10 (dd, 1H, NC5H4, 3J H-H ) 7.3 Hz,
1
ipso-C), 146.9 (d, NC5H4, J C-H ) 166 Hz), 133.5 (d, NC5H4,
1
1J C-H ) 158 Hz), 120.1 (d, NC5H4, J C-H ) 159 Hz), 104.7 (d,
1
NC5H4, J C-H ) 164 Hz), 78.0 (s, C(CH3)3), 77.1 (s, C(CH3)3),
1
52.5 (s, C(CH3)3), 51.9 (s, C(CH3)3), 37.4 (q, C(CH3)3, J C-H
)
1
124 Hz), 37.0 (q, C(CH3)3, J C-H ) 124 Hz), 32.4 (q, C(CH3)3,
1J C-H ) 126 Hz), 31.7 (q, C(CH3)3, J C-H ) 126 Hz), 8.2 (q,
1
1
1
4J H-H ) 1.7 Hz), 6.96 (td, 1H, NC5H4, 3J H-H ) 7.7 Hz, 4J H-H
1.7 Hz), 6.58 (ddd, 1H, NC5H4, J H-H ) 7.3 Hz, J H-H ) 4.7
Hz, 4J H-H ) 1.3 Hz), 2.45 (s, 3H, CH3), 1.47 (s, 18H, C(CH3)3),
1.32 (s, 18H, C(CH3)3), 0.49 (s, 12H, Si(CH3)2).
)
Si(CH3)2, J C-H ) 118 Hz), 7.9 (q, Si(CH3)2, J C-H ) 118 Hz).
Anal. Calcd for C51H104N6O5Si4Y2: C, 52.28; H, 8.95; N, 7.17;
Y, 15.18. Found: C, 52.04; H: 9.01; N, 7.07; Y, 15.08.
3
3
X-r a y Str u ctu r e Deter m in a tion of [Me2Si(NCMe3)-
(OCMe3)]2Y(η2-(C,N)-CH2-2-NC5H4) (2) an d [Me2Si(NCMe3)-
(OCMe3)]2YCtCP h ‚THF ‚(p en ta n e)0.5 (9). Suitable crystals
were measured at 130 K with graphite-monochromated Mo
KR radiation on an Enraf-Nonius CAD-4F diffractometer
equipped with a low-temperature unit.31 Precise lattice pa-
rameters and their standard deviation and orientation matrix
were derived from the angular settings of 22 reflections (2,
14.93° < θ < 19.90°; 9, 16.55 < θ < 20.33°) in four alternative
settings.32 The unit cell was identified as monoclinic, space
group P21/n for 2 and space group C2/c for 9.33 Intensity data
were corrected for Lorentz and polarization effects and scale
P r ep a r a tion of [Me2Si(NCMe3)(OCMe3)]2Y(η2-(N,N′)-N-
(H)-C(dCH2)-2-NC5H4) (13b). Acetonitrile (120 µL, 2.3
mmol) was added to a solution of 1 (1.3 g, 2.2 mmol) in hexanes
(15 mL). After 24 h at room temperature, the volatiles were
removed in vacuo, leaving a brown sticky solid. After the
mixture was stripped (3 × 5 mL) with hexanes, the solid was
redissolved in hexanes (5 mL) and cooled to -80 °C for
crystallization. Repeated recrystallization from hexanes yielded
13b (0.9 g, 1.4 mmol, 65%) as a red-brown crystalline material.
1H NMR (benzene-d6, δ): 9.17 (d, 1H, NC5H4, 3J H-H ) 4.3 Hz),
7.66 (d, 1H, NC5H4, 3J H-H ) 8.1 Hz), 6.99 (t, 1H, NC5H4, 3J H-H
3
) 7.3 Hz), 6.65 (t, 1H, NC5H4, J H-H ) 6.0 Hz), 4.99 (s (br),
1H, NH), 4.50 (s, 1H, dC(H)H), 4.20 (s, 1H, dC(H)H), 1.56 (s,
9H, C(CH3)3), 1.54 (s, 9H, C(CH3)3), 1.17 (s, 9H, C(CH3)3), 1.11
(s, 9H, C(CH3)3), 0.48 (s, 12H, Si(CH3)2). 13C NMR (benzene-
d6): 162.3 (s, NC5H4(ipso-C)), 156.9 (s, C(dCH2)), 149.8 (d,
(31) van Bolhuis, F. J . Appl. Crystallogr. 1971, 4, 263.
(32) de Boer, J . L.; Duisenberg, A. J . M. Acta Crystallogr. 1984, A40,
C410.
(33) No higher metric lattice symmetry or extra metric symmetry
elements were found: (a) Spek, A. L. J . Appl. Crystallogr. 1988, 21,
578. (b) Le Page, Y. J . Appl. Crystallogr. 1987, 20, 264. (c) Le Page, Y.
J . Appl. Crystallogr. 1988, 21, 983.
1
1
NC5H4, J C-H ) 181 Hz), 137.1 (d, NC5H4, J C-H ) 162 Hz),
1
1
121.3 (d, NC5H4, J C-H ) 164 Hz), 121.1 (d, NC5H4, J C-H
)

5516 Organometallics, Vol. 16, No. 25, 1997
Duchateau et al.
variation and reduced to Fo.34 The structures were solved by
Patterson methods, and extension of the model was ac-
complished by direct methods applied to difference structure
factors using the program DIRDIF.35 The positional and
anisotropic thermal displacement parameters for the non-
hydrogen atoms refined with block-diagonal least-squares
procedures (CRYLSQ)36 minimizing the function Q ) ∑h [w(|Fo|
- k|Fc|)2]. After completion of the isotropic refinement of 2,
empirical absorption corrections based on (Fo - Fc) difference
were applied with the program DIFABS.37 Final refinement
on Fo was by full-matrix least-squares techniques with aniso-
tropic thermal displacement parameters for the non-hydrogen
atoms and isotropic thermal displacement parameters for the
hydrogen atoms. The crystals of 2 exhibited some secondary
extinction for which the Fc values were corrected by refinement
of an empirical isotropic extinction parameter (g ) 0.27(4) ×
10-4).38 Scattering factors were taken from Cromer and
Mann.39 Anomalous dispersion factors were taken from
Cromer and Liberman.40 All calculations were carried out on
a HP9000/735 computer at the University of Groningen with
the program packages Xtal,41 PLATON42 and ORTEP.43
Ack n ow led gm en t. This work was financially sup-
ported by Shell Research B. V. Amsterdam, which is
gratefully acknowledged.
Su p p or tin g In for m a tion Ava ila ble: Text giving the IR
spectral data for complexes 1-4, 9, 10, 13b, 14b, and 15 and
tables of anisotropic thermal displacement parameters, atomic
coordinates, bond lengths, bond angles, and torsion angles for
[Me2Si(NCMe3)(OCMe3)]2Y(η2-(C,N)-CH2-2-NC5H4) (2) and [Me2-
Si(NCMe3)(OCMe3)]2YCtCPh‚THF‚(pentane)0.5 (9) (30 pages).
Ordering information is given on any current masthead page.
OM970540D
(34) Spek, A. L. HELENA Program for Data Reduction; University
of Utrecht: Utrecht, The Netherlands, 1993.
(35) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.;
Garc´ıa-Granda, S.; Gould, R. O.; Smits, J . M. M.; Smykalla, C. The
DIRDIF program system. Technical Report of the Crystallography
Laboratory. University of Nijmegen: Nijmegen, The Netherlands,
1992.
(36) Olthof-Hazekamp, R. QRYLSQ, Xtal3.0 Reference Manual; Hall,
S. R.; Stewart, J . M., Eds.; University of Western Australia and
Maryland. Lamb: Perth, 1992.
(38) Zachariasen, W. H. Acta Crystallogr. 1967, 23, 558.
(39) Cromer, D. T.; Mann, J . B. Acta Crystallogr. 1968, A24, 321.
(40) Cromer, D. T.; Libermann, D. J . Chem. Phys. 1970, 53, 1891.
(41) Hall, S. R.; Flack, H. D.; Stewart, J . M. Xtal3.2 Reference
Manual; Universities of Western Australia, and Maryland. Lamb:
Perth, 1992.
(42) Spek, A. L. Acta Crystallogr. 1990, A46, C34.
(43) J ohnson, C. K. ORTEP. Report ORNL-3794; Oak Ridge Na-
tional Laboratory; Oak Ridge, TN, 1965.
(37) Walker, N.; Stuart, J . M. Acta Crystallogr. 1983, A39, 158.