Yttrium complexes of the chelating, C2-symmetric, bis(silylamido)biphenyl ligand [DADMB]2- (={[6,6′-Me2-(C6H3) 2](2,2′-NSiMe2tBu)2}2-)

Article abstract of DOI:10.1021/om9901170

The yttrium bis(silylamido)biphenyl complex [DADMB]YCl(THF)₂ (2; DADMB = 2,2′-bis-((tert-butyldimethylsilyl)amido)-6,6′-dimethylbiphenyl) was prepared from Li₂[DADMB]· 2THF and YCl₃(THF)₃, and its structure was determined by X-ray crystallography. Compound 2 reacts with MeLi and (Me₃Si)₂CHLi to give the corresponding alkyl derivatives [DADMB]-YMe(THF)₂ (3) and [DADMB]Y[CH(SiMe₃)₂](THF)(OEt₂) (5), respectively. In the presence of silicone grease, the reaction of 2 with MeLi produces the yttrium trimethylsiloxide complex [DADMB]Y(OSiMe₃)(THF)₂ (4), which was also crystallographically characterized. Both 3 and 5 react with phenylsilane or H₂ to give the insoluble, dimeric yttrium hydride {[DADMB]Y(μ-H)(THF)}₂·C₆H₆ (6). The alkyl derivatives 3 and 5 exhibit only limited olefin polymerization activity; however, the hydride 6 reacts rapidly with ethylene or 1-hexene to give a single insertion product. The resulting yttrium ethyl complex 7 was structurally characterized. Compound 6 reacts with pyridine to produce a mixture of the isomeric 1,2-and 1,4-insertion products 9 and 10, [DADMB]Y(NC₅H₆)(pyr)₂. Compound 9 converts quantitatively to 10 upon heating.

Full text of DOI:10.1021/om9901170

2896
Organometallics 1999, 18, 2896-2905
Yttr iu m Com p lexes of th e Ch ela tin g, C2-Sym m etr ic,
Bis(silyla m id o)bip h en yl Liga n d [DADMB]2-
t
(){[6,6′-Me2-(C6H3)2](2,2′-NSiMe2 Bu )2}2-)
Tomislav I. Gountchev and T. Don Tilley*
Department of Chemistry, University of California, Berkeley, Berkeley, California 94720-1460
Received February 22, 1999
The yttrium bis(silylamido)biphenyl complex [DADMB]YCl(THF)2 (2; DADMB ) 2,2′-bis-
((tert-butyldimethylsilyl)amido)-6,6′-dimethylbiphenyl) was prepared from Li2[DADMB]‚
2THF and YCl3(THF)3, and its structure was determined by X-ray crystallography. Compound
2 reacts with MeLi and (Me3Si)2CHLi to give the corresponding alkyl derivatives [DADMB]-
YMe(THF)2 (3) and [DADMB]Y[CH(SiMe3)2](THF)(OEt2) (5), respectively. In the presence
of silicone grease, the reaction of 2 with MeLi produces the yttrium trimethylsiloxide complex
[DADMB]Y(OSiMe3)(THF)2 (4), which was also crystallographically characterized. Both 3
and 5 react with phenylsilane or H2 to give the insoluble, dimeric yttrium hydride
{[DADMB]Y(µ-H)(THF)}2‚C6H6 (6). The alkyl derivatives 3 and 5 exhibit only limited olefin
polymerization activity; however, the hydride 6 reacts rapidly with ethylene or 1-hexene to
give a single insertion product. The resulting yttrium ethyl complex 7 was structurally
characterized. Compound 6 reacts with pyridine to produce a mixture of the isomeric 1,2-
and 1,4-insertion products 9 and 10, [DADMB]Y(NC5H6)(pyr)2. Compound 9 converts
quantitatively to 10 upon heating.
In tr od u ction
particular, the use of multidentate amido ligands has
become an area of intensive study.15,16,18-29
The chemistry of d0 early-transition-metal complexes
has recently attracted considerable attention, as these
species have been developed as catalysts for various
transformations, including olefin polymerization, dehy-
dropolymerization, hydrosilylation, and hydrogenation.1-9
In much of this chemistry, it is widely appreciated that
reaction pathways are readily controlled via changes in
electronic and steric environments, and that much of
the observed reactivity for these complexes derives from
electrophilicity and coordinative unsaturation at the
metal center.2,3 Much of the work with d0 metal com-
plexes has featured cyclopentadienyl ligand sets. In an
attempt to extend the possibility for modifying and
controlling the reactivity of early-transition-metal com-
plexes, recent research efforts have been directed toward
development of alternative ligand sets that may increase
the electrophilicity of the metal center and create a
different steric environment at the reactive site.10-17 In
Our previous work in this area led to the synthesis
and investigation of a number of complexes of the bis-
(triisopropylsilyl)-o-phenylenediamido ligand [o-C6H4(NSii-
Pr3)2]2- 30,31
A common structural feature for these
.
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van Duijnen, P. T.; Teuben, J . H. Organometallics 1997, 16, 3511-
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1997, 119, 3830-3831.
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Macromolecules 1996, 29, 5241.
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1996, 15, 5085-5089.
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1995, 14, 5478.
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H. Organometallics 1996, 15, 2672-2674.
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J . Am. Chem. Soc. 1996, 118, 6784.
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C.; Orpen, A. G. J . Am. Chem. Soc. 1995, 117, 3008.
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T.; Teuben, J . H. Organometallics 1996, 15, 2279-2290.
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1995, 34, 5477.
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McPartlin, M. J . Chem. Soc., Dalton Trans. 1996, 125.
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M.; Kol, M.; Davis, W. M. Organometallics 1996, 15, 1470-1476.
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tallics 1996, 15, 923.
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4299.
10.1021/om9901170 CCC: $18.00 © 1999 American Chemical Society
Publication on Web 07/01/1999

Y Complexes of a Bis(silylamido)biphenyl Ligand
Organometallics, Vol. 18, No. 15, 1999 2897
complexes is the presence of a secondary bonding
interaction between the aromatic ring and the metal
center. While confirming the electron-poor character of
the metal center in complexes of this ligand, this
donation of electron density from the ligand has the
potentially undesirable effect of reducing electrophilicity
at the metal. To reduce the possibility of such an
interaction, and also to create a chiral environment at
the reactive site, we began to explore alternative bis-
(silylamido) ligands based on C2-symmetric biphenyl
backbones.32 Asymmetric early-transition-metal com-
plexes, usually based on substituted cyclopentadienyl
ligands, have found application as olefin polymerization
catalysts for control of stereoregularity of the resulting
polymer.2,3,7,10,33,34 Group 3 and lanthanide metallocene
complexes have also been used as regio- and stereose-
lective hydrosilylation catalysts, and the effect of vary-
ing the ancillary Cp-based ligands on the reactivity and
selectivity of the catalyst has been studied exten-
sively.35-37 Even though many alternatives to cyclopen-
tadienyl ligands in early-transition-metal chemistry
have been explored,10-29 the study of chelating diamides
as ligands has been mostly restricted to symmetric
systems.
We recently reported studies on a tantalum mixed
amido-imido ligand system derived from a bis((tri-
methylsilyl)amino)biphenyl ligand.32 Here we describe
studies on a series of yttrium complexes with a related
bis(silylamido)biphenyl ligand, using more sterically
demanding tert-butyldimethylsilyl substituents. Unlike
the tantalum system, where reactivity was dominated
by reactions of the nitrogen-silicon bond, the yttrium
complexes described here appear to possess more robust
bis(silylamido) spectator ligands.
Yttrium complex 2 (Figure 1) adopts a distorted-
trigonal-bipyramidal coordination geometry, with the
chelating diamide and chloride ligands in the equatorial
plane and the two coordinated THF molecules in the
axial positions. Selected bond distances and angles are
given in Table 1. The molecule has an approximate
(noncrystallographic) C2 axis coincident with the Y-Cl
bond. The ligand bite angle is 123.3(2)°, and the average
Y-N distance is 2.25 Å. The dihedral angle between the
phenyl planes is 84.8°. The short Y-Cipso (average 2.75
Å) and Y-Cortho (average 2.87 Å) distances, and the
small Y-N-Cipso angles (average 94.6°), suggest the
presence of Y-aromatic carbon bonding interactions,
which are often observed in complexes of this type.30,31
The methyl derivative 3, an off-white crystalline solid,
was synthesized in 60% yield by reaction of 2 with MeLi
in Et2O/THF (eq 2). The methyl group of 3 gives rise to
1
a doublet in the H NMR spectrum at -0.42 ppm, and
2
the coupling constant J YH ) 1.8 Hz is slightly smaller
than those reported for Cp*2YMe(THF) (2J YH ) 2.3 Hz)
Resu lts a n d Discu ssion
1
and related complexes.13,39 The J CH ) 101 Hz coupling
The starting material 2,2′-diamino-6,6′-dimethylbi-
phenyl was prepared according to the literature proce-
dure.38 Silylation of this diamine was achieved via
(cf. 108.2 Hz in Cp*2YMe(THF)39 and 108 Hz in Cp*Y-
t
(OC6H3 Bu2)Me(THF)213) is lower than the typical 120-
n
130 Hz for an sp3 CH bond.40-42
deprotonation with BuLi in THF, followed by reaction
t
The synthesis of 3 was found to be very sensitive to
the presence of adventitious amounts of silicone grease,
such that high yields require exclusive use of hydrocar-
bon grease in the Schlenkware used for the synthesis.
In the presence of Dow Corning silicone grease, the
reaction of 2 with MeLi resulted in formation of the
yttrium trimethylsiloxide derivative 4 in 50% yield (as
the only isolable product). Complex 4 was characterized
by X-ray crystallography (Figure 2), and selected bond
distances and angles are listed in Table 2. The structure
is very similar to that of the chloride complex 2, with
an Y-N distance of 2.26 Å (average), a ligand bite angle
of 118.8(1)°, and an almost linear Y-O-Si linkage of
of the resulting dianion with BuMe2SiCl (eq 1). Lithia-
tion of the silylamine in situ with nBuLi produced the
lithium salt (1), isolated as a THF adduct in 84% yield
from pentane.
(35) Fu, P.-F.; Brard, L.; Li, Y.; Marks, T. J . J . Am. Chem. Soc. 1995,
117, 7157.
(36) Molander, G. A.; J ulius, M. J . Org. Chem. 1992, 57, 6347.
(37) Molander, G. A.; Nichols, P. J . J . Am. Chem. Soc. 1995, 117,
4415-4416.
(38) Kanoh, S.; Goka, S.; Murose, N.; Kubo, H.; Kondo, M.; Sugino,
T.; Motoi, M.; Suda, H. Polym. J . 1987, 19, 1047.
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J . Organomet. Chem. 1987, 323, 181.
(40) Brookhart, M.; Green, M. L. H.; Wong, L.-L. Prog. Inorg. Chem.
1988, 36, 1.
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395-408.
(42) Crabtree, R. H. Angew. Chem., Int. Ed. Engl. 1993, 32, 789-
805.
Reaction of 1 with YCl3(THF)3 in refluxing THF
yielded the yttrium complex 2 as a white crystalline
solid, in 92% yield (eq 2).
(32) Gountchev, T. I.; Tilley, T. D. J . Am. Chem. Soc. 1997, 119,
12831-12841.
(33) Mitchell, J . P.; Hajela, S.; Brookhart, S. K.; Hardcastle, K. I.;
Henling, L. M.; Bercaw, J . E. J . Am. Chem. Soc. 1996, 118, 1045.
(34) Schaverien, C. J . Adv. Organomet. Chem. 1994, 36, 283.

2898 Organometallics, Vol. 18, No. 15, 1999
Gountchev and Tilley
F igu r e 1. ORTEP diagram of [DADMB]YCl(THF)2 (2).
F igu r e 2. ORTEP diagram of [DADMB]Y(OSiMe3)(THF)2
(4).
Ta ble 1. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for Com p ou n d 2
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for Com p ou n d 4
Y(1)-Cl(1)
Y(1)-N(1)
Y(1)-N(2)
Y(1)-O(1)
Y(1)-O(2)
2.574(2)
2.247(7)
2.252(7)
2.365(6)
2.388(5)
Y(1)-C(1)
Y(1)-C(6)
Y(1)-C(7)
Y(1)-C(8)
2.745(8)
2.847(8)
2.884(9)
2.749(7)
Y(1)-O(1)
Y(1)-N(1)
Y(1)-N(2)
Y(1)-O(2)
Y(1)-O(3)
2.111(3)
2.262(3)
2.254(3)
2.358(3)
2.365(3)
Y(1)-C(1)
Y(1)-C(6)
Y(1)-C(7)
Y(1)-C(8)
O(1)-Si(3)
2.827(4)
3.010(4)
2.993(4)
2.816(4)
1.601(3)
N(1)-Y(1)-N(2)
O(1)-Y(1)-O(2)
O(1)-Y(1)-Cl(1)
O(2)-Y(1)-Cl(1)
123.3(2)
167.9(2)
83.5(2)
84.3(2)
N(1)-Y(1)-Cl(1)
N(2)-Y(1)-Cl(1)
Y(1)-N(1)-C(1)
Y(1)-N(2)-C(8)
116.9(2)
119.8(2)
94.5(5)
94.6(5)
Y(1)-O(1)-Si(3)
N(1)-Y(1)-N(2)
O(1)-Y(1)-O(2)
O(1)-Y(1)-O(3)
175.5(2)
118.8(1)
84.9(1)
84.9(1)
N(1)-Y(1)-O(1)
N(2)-Y(1)-O(1)
Y(1)-N(1)-C(1)
Y(1)-N(2)-C(8)
120.4(1)
120.8(1)
98.3(2)
98.1(2)
175.5(2)°. The dihedral angle between the phenyl planes
is 92.0°. The Y-Cipso and Y-Cortho bonding interactions
are again present, but the corresponding distances are
longer (averages of 2.82 and 3.00 Å, respectively), and
the Y-N-Cipso angles are larger (average 98.2°) than
those observed for 2. The mechanism of formation of 4
is unclear, but the methyl complex 3 was found to be
unreactive toward silicone grease (benzene-d6, 24 h,
room temperature), suggesting that formation of 4
proceeds via trapping by silicone grease of an interme-
diate in the reaction of 2 with MeLi. Analogous reactiv-
ity was reported for the samarium hydride complex
[(C5Me5)2Sm(µ-H)]2, which reacts with hexamethylcy-
clotrisiloxane to afford the dimeric siloxide [(C5Me5)2-
Sm(THF)]2(µ-OSiMe2OSiMe2O).43
Exposure of 2 to C2H4 (80 psi) in the presence of MAO
cocatalyst (500 equiv) in toluene produced only 0.06 g
of polyethylene. The methyl derivative 3 was also found
to be inert toward olefins, since no reaction was ob-
served between 3 and 1-hexene in benzene-d6 (24 h,
room temperature). A benzene-d6 solution of 3 under 5
psi of C2H4 appears to react very slowly, as indicated
by formation of a cloudy precipitate, presumed to be
polyethylene, over the course of a few days. During this
time, only a small decrease in the amount of C2H4 was
observed (by 1H NMR spectroscopy), 3 remained un-
changed after 3 days, and no new organoyttrium species
1
were detected by H NMR spectroscopy.
Reasoning that the coordinated THF ligands may act
to greatly diminish the reactivity of 3 toward alkenes,
we sought to introduce a bulkier alkyl group which
might facilitate dissociation of THF with production of
a more coordinatively unsaturated complex. The bis-
(trimethylsilyl)methyl derivative [DADMB]Y[CH(SiMe3)2]-
(THF)(OEt2) (5) was obtained by reaction of 2 with
(Me3Si)2CHLi in diethyl ether. The incorporation of Et2O
into 5 suggests that the more crowded steric environ-
ment in 5 can indeed favor dissociation of coordinated
solvent. A similar tendency toward THF dissociation in
the presence of a bulky alkyl substituent has been
observed for [NON]Y[CH(SiMe3)2](THF) ([NON]2-
)
[tBu-d6-N-o-C6H4)2O]2-).44 The YCH resonance in the 1H
NMR spectrum appears as a doublet at δ -0.94 (2J YH
) 2.1 Hz), and the corresponding resonance in the 13C
NMR spectrum appears at δ 39.4 (1J YC ) 35.6 Hz). The
downfield chemical shift for the R-carbon is much closer
(43) Evans, W. J .; Ulibarri, T. A.; Ziller, J . W. Organometallics 1991,
10, 134.
(44) Graf, D. D.; Davis, W. M.; Schrock, R. R. Organometallics 1998,
17, 5820.

Y Complexes of a Bis(silylamido)biphenyl Ligand
Organometallics, Vol. 18, No. 15, 1999 2899
to those reported for [NON]Y[CH(SiMe3)2](THF)44 (37.9
11
ppm) and [PhC(NSiMe3)2]2YCH(SiMe3)2 (43.5 ppm)
than to the one for Cp*2YCH(SiMe3)245 (25.19 ppm) and
can therefore be viewed as an indication of the high
electrophilicity of the metal center in 5. The small C-H
coupling for the R-C-H bond (1J CH ) 80 Hz, cf. 88 Hz
in [PhC(NSiMe3)2]2YCH(SiMe3)211 and 84.2 Hz in Cp*2-
YCH(SiMe3)245) is consistent with the presence of an
R-agostic interaction, as observed for many group 3 and
lanthanide bis(trimethylsilyl)methyl complexes.40,41
Reaction of 5 with C2H4 (5 psi, benzene-d6) also
resulted in the very slow formation of insignificant
amounts of polyethylene, with no new organoyttrium
1
species observed in the H NMR spectrum after 5 days.
This low olefin polymerization activity for 3 and 5
should be compared to the behavior of other group 3 and
lanthanide alkyl derivatives, some of which are reported
to be active polymerization catalysts. Thus, Cp*2YMe-
(THF),39 Cp*2ScMe,46 [TpMeYR2(THF)] (TpMe ) tris(3,5-
dimethyl-1-pyrazolyl)borohydride),17 and R2Si(η5-C5H4)(η5-
F igu r e 3. ORTEP diagram of {[DADMB]YH(THF)}2‚C6H6
(6).
exposure of 3 or 5 to H2 gas in benzene-d6 (5 psi, room
temperature). The other products of these reactions
(methane and (Me3Si)2CH2,50 respectively) were ob-
served to form quantitatively (by NMR spectroscopy).
47
C5Me4)LuCH(SiMe3)2 are reported to be active as
olefin polymerization catalysts, whereas [PhC(NSiMe3)2]2-
YCH2Ph(THF)48 is moderately active and [Me2Si-
(NCMe3)(OCMe3)]2YCH(SiMe3)2,12 Cp*2MCH(SiMe3)2 (M
) La, Nd, Lu),49 and [NON]Y[CH(SiMe3)2](THF)44 are
inactive. The lack of olefin polymerization activity in
such systems is usually attributed to steric hindrance
(in the case of CH(SiMe3)2 derivatives), coordinated THF
(which blocks coordination sites), or high ionicity in the
bonding (which leads to more contracted vacant metal
orbitals).11,12,48
To evaluate the activities of 3 and 5 toward σ-bond
metathesis processes involving hydrosilanes, their in-
teractions with PhSiH3 were investigated. Both com-
pounds 3 and 5 were found to react with PhSiH3 in
benzene at room temperature via Si-C bond formation,
to give PhMeSiH2 and PhSiH2CH(SiMe3)2,35 respec-
tively. These reactions also produced a white crystalline
precipitate, insoluble in pentane and benzene but
soluble in THF, characterized as an yttrium hydride (eq
3). Hydride 6 was also produced by hydrogenolysis, upon
1
The hydride resonance for 6 was observed in the H
NMR spectrum as a triplet at δ 5.88 (1J YH ) 28 Hz) in
THF-d8. The Y-H coupling constant is similar to that
observed for other yttrium hydride dimers,11,12,51,52 and
the chemical shift is rather downfield compared to most
yttrium hydrides with bis(cyclopentadienyl) ligands (δ
2.02-5.45).47,51,53,54 However, the shift for 6 is not as
low as those reported for bis(benzamidinato)yttrium
hydrides (δ 8.28-8.31)11 and {[Me2Si(NCMe3)(OCMe3)]2Y-
12
(µ-H)}2 (δ 6.80). This hydride signal was observed to
decay slowly in intensity and completely disappear
within 4 days at room temperature, indicating exchange
with deuterium from the THF-d8 solvent. In the IR
spectrum of 6, the Y-H absorption at 1240 cm-1 was
obscured by strong ligand absorptions in the same
region and could be assigned only by comparison with
the spectrum of the deuterated analogue 6-d2 (obtained
by hydride exchange with THF-d8), which exhibits a
Y-D absorption at 870 cm-1. This frequency is, how-
ever, in good agreement with those reported for other
dimeric yttrium hydride species.50,51
X-ray-quality crystals of 6 were grown by slow diffu-
sion of PhSiH3 (in benzene solution) layered above a
benzene solution of 5, and the molecular structure
(Figure 3) may be described as a centrosymmetric dimer.
The hydride atom, located in the Fourier difference map,
was refined isotropically. Selected bond distances and
angles are given in Table 3. The Y-H distance is 2.25-
(4) Å (average), and the Y-H-Y angle is 109(2)°. The
(47) Stern, D.; Sabat, M.; Marks, T. J . J . Am. Chem. Soc. 1990, 112,
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1996, 15, 2291-2302.
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Am. Chem. Soc. 1982, 104, 2008-2014.
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Organometallics 1987, 6, 2279-2285.
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Meetsma, A.; Teuben, J . H. Organometallics 1993, 12, 3531.
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Am. Chem. Soc. 1984, 106, 1291-1300.
(45) 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.
(46) Burger, B. J .; Thompson, M. E.; Cotter, W. D.; Bercaw, J . E. J .
Am. Chem. Soc. 1990, 112, 1566.

2900 Organometallics, Vol. 18, No. 15, 1999
Gountchev and Tilley
Ta ble 3. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for Com p ou n d 6
Y(1)-Y(1)*
Y(1)-H(1)
Y(1)-H(1)*
Y(1)-N(1)
3.6652(8)
2.27(4)
2.22(4)
Y(1)-N(2)
Y(1)-O(1)
Y(1)-C(1)
Y(1)-C(8)
2.228(4)
2.329(3)
2.702(4)
3.098(5)
2.213(4)
Y(1)-H(1)-Y(1)*
H(1)-Y(1)-H(1)*
N(1)-Y(1)-N(2)
N(1)-Y(1)-O(1)
109(2)
71(2)
103.9(1)
100.3(1)
N(2)-Y(1)-O(1)
Y(1)-N(1)-C(1)
Y(1)-N(2)-C(8)
91.0(1)
93.4(2)
114.6(3)
geometry of the four-membered ring is very similar to
that found in other structurally characterized dimeric
yttrium hydrides, [(1,3-Me2C5H3)2Y(µ-H)(THF)]252 (aver-
51
age 2.15(7) Å and 118(3)°), [(MeC5H4)2Y(µ-H)(THF)]2
(2.18(8) Å and 114(3)°), and {[PhC(NSiMe3)2]2Y(µ-H)}2
11
(2.14(3) Å and 111.5(15)°). The N-Y-N ligand bite
angle in 6 (103.9(1)°) is significantly lower than those
of ca. 120° in the 5-coordinate complexes 2 and 4, and
only one of the ligand ipso carbons is in a close contact
with the yttrium center (Y-C(1) ) 2.702(4) Å, Y-C(6)
) 3.069(5) Å, and Y-N(1)-C(1) ) 93.4(2)°, whereas
Y-C(8) ) 3.098(5) Å, Y-C(7) ) 3.409(4) Å, and Y-N(2)-
C(8) ) 114.6(3)°). The dihedral angle between the
phenyl planes is 81.9°. These differences may be
attributed to steric crowding in the hydride dimer
relative to the monomeric complexes 2 and 4.
related value (3J YH ) 1.4 Hz) reported for (η5-
1
CH3C5H4)2Y(CH2CH3)(THF),54 and the J CH coupling
constant of 120 Hz is typical for an sp3 C-H bond.
Although â-agostic interactions are often observed in
early-transition-metal ethyl complexes,40-42,46,55-57 their
existence cannot be determined on the basis of the
(averaged) 1J CH coupling constant only. The IR spectrum
of 7 does not contain evidence for agostic C-H bonds
(no low-energy C-H bands were detected). The rela-
Compound 6 represents a rare example of an yttrium
hydride that contains no cyclopentadienyl ligands. We
are aware of only one other structurally characterized
non-Cp yttrium hydride, the bis(benzamidinato) com-
plex {[PhC(NSiMe3)2]2Y(µ-H)}2.11 Other examples of
such hydrides are the unstable species {[Me2Si(NCMe3)-
1
tively small J CH coupling constant of 70-80 Hz (mul-
tiplet broadness prevents accurate measurement) for the
R-protons, however, is consistent with the presence of
an R-agostic interaction with the metal center,40,41,58-60
analogous to that reported for some bis(trimethylsilyl)-
methyl yttrium complexes (vide supra). In the 13C NMR
spectrum of 6, the R-carbon appeared as a doublet at
35.5 ppm, with a coupling of 50 Hz to yttrium.
12
(OCMe3)]2Y(µ-H)}2 and the (tris(pyrazolyl)borato)-
yttrium hydride TpMeYH2(THF)4,17 for which a trimeric
solution structure was suggested. All of the structurally
characterized yttrium hydrides are dimers11,33,47,51,52 or
trimers52 in the solid state, although more complicated
aggregates have also been observed in anionic or het-
erometallic species.54
The solid-state structure of 7 was determined by
X-ray crystallography (Figure 4 and Table 4). The
molecule lies on a crystallographic C2 symmetry axis,
and the ethyl group is disordered between two sym-
metry-related positions. Unfortunately, this disorder
does not allow us to positively determine the presence
or absence of agostic interactions, although the rather
large Y-C(1)-C(2) angle of 148(1)° may be consistent
with R-CH coordination. The ligand geometry is very
similar to that in compounds 2 and 4, with a ligand bite
angle of 119.8(3)°, and close Y-Cipso contacts (Y(1)-C(3)
) 2.809(7) Å, Y(1)-N(1)-C(3) ) 97.4(4)°). The dihedral
angle between the phenyl planes is 88.2°.
The reactivity of 6 appears to be restricted by its
dimeric nature (preserved even in THF solution, as
1
suggested by the H NMR spectrum) and its very low
solubility in nonpolar organic solvents. No polymeriza-
tion activity was observed toward 1-hexene or C2H4 (5
psi) in benzene-d6 at room temperature, and heating
these mixtures at 80 °C for 2 h resulted in decomposition
of the hydride with precipitation of only a small amount
of polyethylene. However, when dissolved in THF,
compound 6 was found to rapidly insert ethylene at
room temperature, to give the yttrium ethyl complex 7
(eq 4).
In THF-d8 solution, the slower insertion of 1-hexene
into the Y-H bond of 6 was observed (eq 4) to give the
1-hexyl derivative 8 (by 1H NMR spectroscopy). No
reaction occurred between 6 and cyclohexene, however.
Single insertion of terminal olefins to give yttrium alkyl
At longer reaction times (6-7 h), compound 7 seems
to undergo a slow insertion of a second molecule of C2H4,
but positive identification of multiple insertion products
was hindered by their decomposition, and no formation
of polyethylene was observed even at elevated pressure
(80 psi, THF, 48 h at room temperature). Decomposition
of 7 to unidentified products was also found to occur in
the solid state, under N2, over the period of a few
months. The ethyl group of 7 gives rise to a broad
multiplet at 0.0 ppm (YCH2CH3, 2 H) and a triplet of
(55) Dawoodi, Z.; Green, M. L. H.; Mtetwa, V. S. B.; Prout, K.;
Schultz, A. J .; Williams, J . M.; Koetzle, T. F. J . Chem. Soc., Dalton
Trans. 1986, 1629.
(56) Crackness, R. B.; Orpen, A. G.; Spencer, J . L. J . Chem. Soc.,
Chem. Commun. 1984, 326.
(57) Haaland, A.; Scherer, W.; Ruud, K.; McGrady, G. S.; Downs,
A. J .; Swang, O. J . Am. Chem. Soc. 1998, 120, 3762.
(58) Bruno, J . W.; Smith, G. M.; Marks, T. J .; Fair, C. K.; Schultz,
A. J .; Williams, J . M. J . Am. Chem. Soc. 1986, 108, 40.
(59) Mena, M.; Pellinghelli, M. A.; Royo, P.; Serrano, R.; Tiripicchio,
A. J . Chem. Soc., Chem. Commun. 1986, 108, 1118.
(60) Cayias, J . Z.; Babaian, E. A.; Hrncir, D. C.; Bott, S. G.; Atwood,
J . L. J . Chem. Soc., Dalton Trans. 1986, 2743.
1
doublets at 1.67 ppm (YCH2CH3, 3 H) in the H NMR
3
spectrum. The J YH coupling constant of 1.9 Hz for the
CH3 protons of the ethyl ligand is very similar to the

Y Complexes of a Bis(silylamido)biphenyl Ligand
Organometallics, Vol. 18, No. 15, 1999 2901
Ta ble 5. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for Com p ou n d 9
Y(1)-N(1)
Y(1)-N(2)
Y(1)-N(3)
Y(1)-N(4)
Y(1)-N(5)
Y(1)-C(6)
Y(1)-C(13)
2.281(5)
2.255(4)
2.253(4)
2.482(4)
2.486(4)
2.717(5)
2.822(5)
N(1)-C(1)
C(1)-C(2)
C(2)-C(3)
C(3)-C(4)
C(4)-C(5)
C(5)-N(1)
1.424(8)
1.46(1)
1.36(1)
1.372(9)
1.369(8)
1.397(7)
N(1)-Y(1)-N(2)
N(1)-Y(1)-N(3)
N(2)-Y(1)-N(3)
N(4)-Y(1)-N(5)
N(1)-C(1)-C(2)
119.5(2)
121.4(2)
118.9(1)
170.8(2)
115.2(6)
C(1)-C(2)-C(3)
C(2)-C(3)-C(4)
C(3)-C(4)-C(5)
C(4)-C(5)-N(1)
C(1)-N(1)-C(5)
115.8(6)
119.8(6)
119.6(6)
122.3(6)
109.6(5)
F igu r e 4. ORTEP diagram of [DADMB]YEt(THF)2 (7).
Ta ble 4. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for Com p ou n d 7
Y(1)-N(1)
Y(1)-O(1)
Y(1)-C(1)
2.251(5)
2.371(5)
2.464(9)
Y(1)-C(3)
Y(1)-C(4)
2.809(7)
2.996(7)
Figu r e 5. ORTEP diagram of [DADMB]Y(NC5H6)(NC5H5)2‚
C5H12 (9).
C(1)-C(2)
N(1)-Y(1)-N(1)*
O(1)-Y(1)-O(1)*
1.13(2)
119.8(3)
169.1(3)
Y(1)-N(1)-C(3)
Y(1)-C(1)-C(2)
97.4(4)
148(1)
complexes has been reported for [(η5-RC5H4)2YH(THF)]2
(R ) H, Me).54 The lack of olefin polymerization activity
for compound 6 can be contrasted with the high catalytic
activity of certain dimeric group 3 and lanthanide
hydrides of the type [Cp*2MH]2 (M ) La, Nd, Sm, Lu)49
but is similar to the reported low activity for {[PhC-
(NSiMe3)2]2Y(µ-H)}211 and {[Me2Si(NCMe3)(OCMe3)]2Y-
(µ-H)}2.12 Other dimeric hydrides have been reported
to undergo single, reversible olefin insertion to give
mixed hydrido-alkyl complexes (e.g., [Cp*Y(OC6H3-
tBu2)]2(µ-H)(µ-alkyl)13 and [Et2Si(η5-C5H4)(η5-C5Me4)M]2-
(µ-H)(µ-CH2CH3) for M ) Lu, Y45), but we have not been
able to observe such species in reactions of 6 with
olefins.
As shown in eq 5, yttrium hydride 6 was found to
react with pyridine to give a mixture of pyridine
insertion products, 9 (major) and 10 (minor), in variable
ratios. The structure of 9, confirmed by X-ray crystal-
lography (Figure 5), is again based on a distorted-
trigonal-bipyramidal geometry, with neutral donors
(pyridine) occupying the axial positions. The ligand bite
angle is 118.9°, and the two ipso carbons are in close
contact with yttrium (average distance 2.77 Å). The
dihedral angle between the phenyl planes is 92.8°. The
third pyridine unit attached to the metal center has
been reduced via 1,2-insertion, as can be deduced from
the changes in the C-C bond lengths (Table 5) and a
puckering of the pyridine ring.
The identities of the 1,2- and 1,4-insertion products
9 and 10 were further confirmed by 2D NMR studies
(TOCSY and HMQC), which revealed a characteristic
coupling pattern for the partially hydrogenated pyridine
ring54,61,62 and allowed assignment of the ring protons
and carbons (see Experimental Section). Heating a
solution containing both 9 and 10 to 80 °C in benzene-
d6 resulted in complete conversion of the mixture within
1
2 h to compound 10, as observed by H NMR spectros-
copy. This indicates that 10 is the thermodynamically
(61) Duchateau, R.; Brussee, E. A. C.; Meetsma, A.; Teuben, J . H.
Organometallics 1997, 16, 5506-5516.
(62) Woo, H.-G.; Tilley, T. D. J . Organomet. Chem. 1990, 393, C6.

2902 Organometallics, Vol. 18, No. 15, 1999
Gountchev and Tilley
more stable isomer, while 9 is kinetically generated.
This reactivity toward pyridine has precedent in a
number of previously reported reactions for yttrium
hydride and alkyl complexes. Metalation of pyridine via
CH activation has been reported for [Cp*2YH]2,63 Cp*2-
YCH(SiMe3)2,50 and Cp*2YMe(THF),50 while 1,2-inser-
tion of pyridine followed by rearrangement to the 1,4-
insertion product has been reported for [(η5-
C5H4R)2YH(THF)]2 (R ) H, CH3).54 Also, an analogous
1,2- to 1,4-isomer rearrangement has been observed for
the bis(alkoxysilylamido)yttrium derivative [Me2Si-
(NCMe3)(OCMe3)]2YNC5H6.61 The bis(trimethylsilyl)-
benzamidinate complexes {[PhC(NSiMe3)2]2YH}2 and
[PhC(NSiMe3)2]2YCH2Ph(THF) have also been reported
to undergo the 1,2-insertion of pyridine,48 but no further
isomerization was noted in these cases. The reactivity
of 6 toward pyridine is thus different from that of
similar (pentamethylcyclopentadienyl)yttrium com-
plexes and is more similar to that of other known
yttrium hydrides and alkyls with monosubstituted Cp,
or noncyclopentadienyl, ligands.
of dimer formation, which is particularly important in
the case of hydride derivatives. Although apparently not
promising in terms of olefin polymerization activity,
these (silylamido)yttrium species exhibit reactivity pat-
terns which are distinct from those known for more
traditional cyclopentadienyl derivatives. The possible
use of these yttrium complexes as catalysts for other
transformations, such as catalytic hydrosilylation, is
currently under investigation.
Exp er im en ta l Section
Gen er a l Con sid er a tion s. All reactions with air-sensitive
compounds were performed under dry nitrogen, using standard
Schlenk and glovebox techniques. Reagents were obtained
from commercial suppliers and used without further purifica-
tion, unless otherwise noted. Olefin-free pentane, benzene, and
toluene were prepared by pretreating with concentrated H2-
SO4, 0.5 N KMnO4 in 3 M H2SO4, NaHCO3, and finally
anhydrous MgSO4. Solvents (pentane, diethyl ether, benzene,
toluene, tetrahydrofuran) were distilled under nitrogen from
sodium benzophenone ketyl. Benzene-d6 was distilled from
Na/K alloy. Commercial silanes were distilled and dried over
molecular sieves before use. nBuLi was used as a 1.6 M solution
in hexanes, as supplied by Aldrich, and MeLi as a 1.6 M
solution in Et2O, as supplied by Alfa Aesar. 2,2′-Diamino-6,6′-
Con clu sion s
We have synthesized and characterized a series of
novel yttrium complexes with bis(silylamido)biphenyl
ligands. The structures and reactivities of the chloride,
alkyl, and hydrido derivatives have been investigated.
In their reactivity, these complexes resemble more
closely some benzamidinate11 and alkoxysilylamido12
yttrium species, rather than the more fully investigated
cyclopentadienylyttrium derivatives.45,47,52,54,64 The high
degree of ionicity in the yttrium-nitrogen bonding
appears to result in a highly electrophilic metal center,
which leads to lower reactivity toward olefin polymer-
ization and σ-bond metathesis, perhaps resulting from
more contracted vacant metal orbitals which are less
effective in substrate binding.11,12,48 The reactivity of the
hydride is also inhibited by the high stability of the
bridged yttrium hydride unit and the insolubility of the
dimer in noncoordinating solvents. Very low olefin
polymerization activity is exhibited by the MAO-
activated chloride and the alkyl and the hydride com-
plexes. A single insertion of olefins into the Y-H bond,
reminiscent of the reactivity of some monosubstituted-
Cp yttrium hydrides,54 results in formation of yttrium
alkyl species, and the ethyl complex is sufficiently stable
to be isolated and characterized. The reactivity of the
yttrium hydride 6 toward pyridine also resembles that
observed for related hydride derivatives containing
benzamidinate and alkoxysilylamido ancillary ligands.
The yttrium derivatives studied represent another
example of noncyclopentadienyl early-transition-metal
complexes. This study further contributes to an under-
standing of the factors behind the reactivity of such d0
complexes. As has been already suggested, in addition
to the electrophilicity of the metal center, other possibly
important factors include the degree of ionicity in the
metal-ligand bonds, and the steric environment created
by the ligand. The latter affects not only the accessibility
of the metal center by the substrate but also the ease
65
dimethylbiphenyl,38 YCl3(THF)3,45 and LiCH(SiMe3)2 were
prepared according to published literature procedures. NMR
spectra were recorded at 300 or 500 MHz (1H) with Bruker
AMX-300 and DRX-500 spectrometers, or at 100 MHz (13C-
{1H}) with an AMX-400 spectrometer, at ambient temperature
and in benzene-d6, unless otherwise noted. CH coupling
constants were obtained from nondecoupled HMQC experi-
ments. Signal multiplicities are reported as follows: s, singlet;
d, doublet; t, triplet; q, quartet; qn, quintet; m, multiplet.
Elemental analyses were performed by the Microanalytical
Laboratory at UC Berkeley, E+R Microanalytical Laboratory,
or Desert Analytics. Infrared spectra were recorded with a
Mattson Infinity 60 MI FTIR spectrometer, as KBr pellets.
Li2[DADMB]‚2THF (1). To a cold (0 °C) solution of 2,2′-
diamino-6,6′-dimethylbiphenyl (4.00 g, 18.8 mmol) in THF (100
mL) was added dropwise 25.0 mL (40 mmol) of 1.6 M nBuLi.
A white precipitate formed initially but dissolved completely
after all of the nBuLi had been added. The solution was allowed
to warm to room temperature and was then stirred for 3 h. A
t
solution of BuMe2SiCl (6.22 g, 41.2 mmol) in 20 mL of THF
was then added dropwise. The mixture was heated at reflux
for 5 h, which resulted in the formation of a white precipitate.
After the mixture was cooled to room temperature, a second
portion of nBuLi (25.0 mL, 40 mmol) was added and this
mixture was stirred overnight at room temperature. The THF
was removed under vacuum to give an oily white solid.
Extraction with pentane (2 × 100 mL) gave a light yellow
solution, which was concentrated in vacuo until crystals
appeared and then cooled to -78 °C. The resulting crystalline
product was recrystallized from pentane and dried to afford
1
9.45 g (15.8 mmol, 84% yield) of colorless crystals. H NMR:
δ 7.06 (d, 2 H, J ) 7.7 Hz), 6.95 (t, 2 H, J ) 7.7 Hz), 6.48 (d,
2 H, J ) 7.1 Hz biphenyl H’s), 3.14 (m, 8 H, THF), 1.99 (s, 6
t
H, Me), 1.25 (m, 8 H, THF), 1.16 (s, 18 H, BuMe2Si), 0.49 (s,
6 H, tBuMe2Si), 0.09 (s, 6 H, tBuMe2Si). 13C{1H} NMR: δ 157.5,
140.1, 133.2, 128.0, 121.8, 116.6, 68.6 (THF), 28.7 (CMe3), 25.4
(THF), 21.8, 21.7 (Me; CMe3), 1.0, -0.5 (tBuMe2Si). IR (cm-1):
3039 (w), 2951 (s), 2923 (s), 2879 (s), 2848 (s), 1575 (s), 1559
(s), 1460 (s), 1440 (s), 1288 (s), 1250 (s), 1049 (s), 968 (m), 899
(m), 842 (s), 824 (s), 769 (s), 668 (m), 605 (m), 457 (m), 419
(m). Anal. Calcd for C34H58N2Li2O2Si2: C, 68.42; H, 9.79; N,
4.69. Found: C, 68.18; H, 9.85; N, 4.56.
(63) Deelman, B.-J .; Stevels, W. M.; Lakin, M. T.; Spek, A. L.;
Teuben, J . H. Organometallics 1994, 13, 3881.
(64) den Haan, K. H.; Teuben, J . H. J . Organomet. Chem. 1987, 322,
321.
(65) Davidson, P. J .; Harris, D. H.; Lappert, M. F. J . Chem. Soc.,
Dalton Trans. 1976, 2268.

Y Complexes of a Bis(silylamido)biphenyl Ligand
Organometallics, Vol. 18, No. 15, 1999 2903
[DADMB]YCl(THF )2 (2). A solution of 1 (3.00 g, 5.03
mmol) and YCl3(THF)3 (2.10 g, 5.10 mmol) in 100 mL of THF
was heated at reflux for 4 h, resulting in formation of a white
precipitate. The solvent was removed in vacuo, and the
resulting white powder was extracted with a mixture of 60
mL of pentane and 25 mL of THF. The filtrate was concen-
trated to about 15 mL, and more pentane (20 mL) was added
to initiate crystallization of the product as a white precipitate.
After it was cooled to -78 °C, the solution was filtered and
the product was then dried in vacuo to obtain 3.28 g (92% yield)
solution was filtered, the clear filtrate was concentrated to
about 15 mL, and 20 mL of pentane was then added. Further
concentration and cooling to -78 °C resulted in the formation
of a white crystalline precipitate, which was isolated by
filtration and dried in vacuo to give 0.59 g of product (43%
yield). The product can be purified by recrystallization from
1
pentane. H NMR: δ 7.23 (m, 1 H), 6.85 (m, 3 H), 6.70 (m, 1
H), 6.59 (m, 1 H, aromatic H’s), 3.52 (m, broad, 4 H, THF),
3.24 (q, 6 H, Et2O), 1.88 (s, 3 H, MeAr), 1.84 (s, 3 H, MeAr),
1.38 (m, 4 H, THF), 1.11 (t, 4 H, Et2O), 1.10 (s, 9 H, Me3C,
overlaps with Et2O), 1.08 (s, 9 H, Me3C), 0.60 (s, 3 H, Me2Si),
0.32 (s, 3 H, Me2Si), 0.31 (s, 3 H, Me2Si), 0.29 (s, 9 H, Me3Si,
overlaps Me2Si), 0.26 (s, 3 H, Me2Si), 0.25 (s, 9 H, Me3Si), -0.94
(d, 1 H, 2J YH ) 2.1 Hz, 1J CH ) 80 Hz, YCH). 13C NMR: δ 150.3,
141.7, 138.6, 129.3, 120.1, 113.4, (biphenyl), 71.7, 68.5, 66.2
(THF, Et2O), 39.4 (YCH, 1J YC ) 35.6 Hz), 28.7, 27.9, 26.0, 25.3
(Me3C), 26.5 (THF), 22.4 (MeAr), 21.2, 20.6 (Me3C), 15.9 (Et2O),
5.7, 4.8 (Me3Si), 1.28, -0.51 (Me2Si). IR (cm-1): 3043 (w), 2952
(s), 2887 (s), 2851 (s), 1577 (m), 1559 (m), 1462 (s), 1443 (s),
1387 (w), 1247 (s), 1091 (w), 1044 (s), 1006 (m), 963 (m), 836
(s), 793 (m), 768 (m), 711 (w), 661 (m), 594 (w), 427 (w). Anal.
Calcd for C41H79N2O2Si2Y: C, 63.36; H, 10.25; N, 3.60. Found:
C, 63.07; H, 10.45; N, 3.76.
1
of white crystalline powder. H NMR: δ 7.07 (d, 2 H), 6.95 (t,
2 H), 6.55 d, 2 H, aromatic H), 3.70-3.46 (br m, 8 H, THF),
t
1.88 (s, 6 H, Me), 1.24 (m, 8 H, THF), 1.11 (s, 18 H, BuMe2-
Si), 0.52, 0.50 (s, 6 H each, tBuMe2Si). 13C{1H} NMR: δ 152.4,
142.4, 130.5, 129.9, 123.5, 120.1 (aromatic C), 68 (THF), 28.3
(Me3C), 25.5 (THF), 22.3 (MeAr), 21.5 (Me3C), 1.8, -1.6 (Me2-
Si). IR (cm-1): 3040 (w), 2949 (s), 2925 (s), 2882 (s), 2851 (s),
1578 (m), 1558 (m), 1471 (m), 1461 (m), 1441 (s), 1387 (w),
1356 (w), 1272 (s), 1248 (s), 1085 (w), 1048 (s), 1021 (m), 963
(m), 872 (m), 830 (s), 777 (s), 708 (m), 668 (m), 568 (m), 440
(m). Anal. Calcd for C34H58N2O2Si2YCl: C, 57.73; H, 8.26; N,
3.96. Found: C, 57.61; H, 8.44; N, 3.85.
[DADMB]YMe(THF )2 (3). Compound 2 (1.16 g, 1.64 mmol)
was dissolved in 100 mL of Et2O, and MeLi (1.10 mL, 1.76
mmol) was added at room temperature. To the reaction
mixture was added a small amount of THF, to bring the
remaining undissolved 2 into solution. The resulting pale
yellow solution was stirred overnight, the solvents were
removed in vacuo, and the oily residue was extracted with 2
× 50 mL of pentane. The product was isolated by crystalliza-
tion at -78 °C in two crops (0.67 g, 60% yield) as a white
{[DADMB]YH(THF )}2‚C6H6 (6). To a solution of 5 (1.05
g, 1.35 mmol) in 50 mL of benzene was added 0.6 mL (5.5
mmol) of PhSiH3. The mixture was left undisturbed at room
temperature for 5 days, resulting in formation of a highly
crystalline, colorless precipitate. The product was then isolated
by filtration, washed with benzene (30 mL) and pentane (30
1
mL), and briefly dried in vacuo (0.53 g, 61% yield). H NMR
(THF-d8): δ 6.99 (m, 4 H, aromatic H), 6.54 (m, 2 H, aromatic
H), 5.88 (t, 1 H, J ) 28 Hz, YH), 3.61 (m, THF), 1.77 (m, THF),
1.69 (s, 6 H, MeAr), 0.90 (s, 18 H, Me3C), 0.35 (s, 6 H, Me2Si),
0.21 (s, 6 H, Me2Si). 13C{1H} NMR (THF-d8): δ 152.7, 142.6,
130.8, 130.3, 124.0, 120.3 (aromatic C), 129.2 (C6H6), 68.4
(THF), 28.3 (Me3C), 26.5 (THF), 22.2 (MeAr), 21.7 (Me3C), 1.5
(Me2Si), -1.7 (Me2Si). IR (cm-1): 3038 (m), 2949 (s), 2926 (s),
2881 (s), 2850 (s), 2703 (w), 1564 (m), 1462 (s), 1441 (s), 1388
(m), 1359 (m), 1251 (s, broad), 1087 (m), 1047 (s), 1014 (s),
966 (s), 865 (s), 834 (s, broad), 791 (s), 767 (s), 707 (m), 682
(s), 662 (s), 617 (m), 595 (m), 567 (m), 464 (m), 431 (m). A
sample of the deuterated analogue (6-d2) was obtained by
allowing a THF-d8 solution of 6 to stand at room temperature
for 4 days, followed by removal of the solvent in vacuo, which
resulted in complete exchange of the Y-hydride with deute-
rium. Subtraction of the IR spectrum of 6-d2 showed the
presence of a strong Y-H absorption at 1240 cm-1, overlapping
with a strong ligand absorption. Anal. Calcd for C66H108N4O2-
Si4Y2: C, 61.94; H, 8.51; N, 4.38. Found: C, 61.95; H, 8.55; N,
4.19.
1
crystalline powder. H NMR: δ 7.07 (m, 2 H), 6.96 (m, 2 H),
6.56 (m, 2 H, aromatic H), 3.43 (m, 8 H, THF), 1.89 (s, 6 H,
t
Me), 1.24 (m, 8 H, THF), 1.14 (s, 18 H, BuMe2Si), 0.52, 0.40
t
2
1
(s, 6 H each, BuMe2Si), -0.42 (d, 3 H, J YH ) 1.8 Hz, J CH
)
101 Hz, YMe). 13C{1H} NMR: δ 153.2, 142.1, 131.1, 129.4,
123.4, 119.5, 70.9 (THF), 28.4 (Me3C), 25.5 (THF), 22.4 (MeAr),
21.7 (YMe), 21.7 (Me3C), 2.0, -1.9 (Me2Si). IR (cm-1): 3038
(w), 3043 (m), 2951 (s), 2890 (s), 2851 (s), 1906 (w), 1577 (s),
1555 (s), 1460 (s), 1440 (s), 1398 (m), 1358 (m), 1271 (s), 1243
(s), 1085 (m), 1048 (s), 1031 (s), 981 (s), 880 (m), 830 (s), 784
(s), 769 (s), 708 (m), 673 (m), 661 (m), 607 (w), 567 (w), 454
(m), 436 (w). Anal. Calcd for C35H61N2Si2O2Y: C, 61.20; H, 8.95;
N, 4.08. Found: C, 59.74; H, 9.48; N, 3.87.
[DADMB]Y(OSiMe3)(THF )2 (4). Compound 2 (0.54 g, 0.76
mmol) and 0.3 g of Dow Corning silicone grease were dissolved
in 100 mL of Et2O, and MeLi (0.5 mL, 0.8 mmol) was added
at room temperature. To the reaction mixture was added a
small amount of THF, to bring the remaining undissolved 2
into solution. The resulting pale yellow solution was stirred
overnight, the solvents were removed in vacuo, and the oily
residue was extracted with 2 × 40 mL of pentane. The product
was isolated by crystallization from pentane at -78 °C (0.29
[DADMB]YEt(THF )2 (7). A sample of the yttrium hydride
6 (0.184 g, 0.144 mmol) was dissolved in 15 mL of THF. The
reaction flask was filled with C2H4 at 5-10 psi, and the
solution was stirred for 30 min. The solvent was removed
under vacuum, and the solid residue was extracted into 20
mL of hexane. The extract was filtered, and the filtrate was
then concentrated to 5 mL and cooled to -35 °C overnight, to
give 7 as a white crystalline solid (0.121 g, 60% yield). 1H
NMR: δ 7.07, 6.95, 6.56 (m, 2 H each, aromatic H), 3.49 (m,
1
g, 50% yield) as a white crystalline powder. H NMR: δ 7.04
(m, 2 H), 6.96 (m, 2 H), 6.57 (m, 2 H, aromatic H), 3.46 (m, 8
H, THF), 1.91 (s, 6 H, Me), 1.28 (m, 8 H, THF), 1.14 (s, 18 H,
tBuMe2Si), 0.50, 0.29 (s, 6 H each, tBuMe2Si), 0.26 (s, 9 H, Me3-
SiO). 13C{1H} NMR: δ 153.6, 142.2, 131.2, 129.4, 123.2, 119.4,
70.7 (THF), 28.5 (Me3C), 25.4 (THF), 22.4 (MeAr), 21.6 (Me3C),
4.0 (Me3SiO), 1.7, -1.3 (Me2Si). IR (cm-1): 3078 (w), 3043 (m),
2951 (s), 2890 (s), 2851 (s), 1906 (w), 1577 (s), 1555 (s), 1460
(s), 1440 (s), 1398 (m), 1358 (m), 1271 (s), 1243 (s), 1085 (m),
1048 (s), 1031 (s), 981 (s), 880 (m), 830 (s), 784 (s), 769 (s), 708
(m), 673 (m), 661 (m), 607 (w), 567 (w), 454 (m), 436 (w). Anal.
Calcd for C37H67N2Si3O3Y: C, 58.39; H, 8.87; N, 3.68. Found:
C, 58.66; H, 9.25; N, 3.58.
[DADMB]YCH(SiMe3)2(THF )(Et2O) (5). A mixture of 2
(1.24 g, 1.75 mmol) and LiCH(SiMe3)2(Et2O)0.1 (0.30 g, 1.76
mmol) was dissolved in 80 mL of Et2O. The reaction mixture
was kept in an ice bath for 30 min then allowed to warm to
room temperature and stirred for 8 h. The cloudy yellow
3
3
8 H, THF), 1.88 (s, 6 H, MeAr), 1.67 (dt, J HH ) 7.4 Hz, J YH
1
) 1.9 Hz, J CH ) 70-80 Hz, 3 H, YCH2CH3), 1.25 (m, 8 H,
THF), 1.13 (s, 18 H, tBuMe2Si), 0.53, 0.37 (s, 6 H each, tBuMe2-
Si), 0.0 (br m, J CH ) 120 Hz, 2 H, YCH2CH3). 13C NMR: δ
1
153.1, 141.9, 131.4, 129.3, 123.5, 119.7 (biphenyl C), 72 (THF),
35.5, (d, J ) 50 Hz, YCH2CH3), 28.4 (Me3C), 25.5 (THF), 22.4
(MeAr), 21.6 (Me3C), 15.7 (YCH2CH3), 1.7, -1.9 (Me2Si). IR
(cm-1): 3043 (w), 3034 (w), 2953 (s), 2851 (s), 1578 (m), 1555
(m), 1461 (m), 1440 (m), 1268 (s), 1048 (s), 964 (m), 829 (s),
785 (m), 768 (m), 662 (w). Anal. Calcd for C36H63N2Si2O2Y: C,
61.68; H, 9.06; N, 4.00. Found: C, 61.08; H, 8.96; N, 4.05. Slow
decomposition of 7 at room temperature, even in the solid

2904 Organometallics, Vol. 18, No. 15, 1999
Ta ble 6. Cr ysta llogr a p h ic Da ta for Com p ou n d s 2, 4, 6, 7, a n d 9
Gountchev and Tilley
2
4
6
7
9
(a) Crystal Parameters
formula
fw
C
34H58N2ClO2Si2Y
C37H67N2O3Si3Y
761.11
C33H54N2Si2OY
639.88
C36H63N2Si2O2Y
700.98
C46H70N5Si2Y
838.17
707.37
size (mm)
cryst syst
space group
a (Å)
b (Å)
c (Å)
0.1 × 0.07 × 0.06
orthorhombic
Pca21 (No. 29)
17.1765(5)
10.5593(3)
20.7010(7)
90, 90, 90
3754.6(2)
4
0.2 × 0.1 × 0.08
monoclinic
P21/n (No. 14)
11.3639(2)
17.3411(2)
21.7183(3)
90, 102.836(1), 90
4172.9(1)
4
0.1 × 0.1 × 0.1
monoclinic
P21/c (No. 14)
10.7444(5)
19.0747(8)
17.7776(8)
90, 106.838(1), 90
3487.2(2)
4
0.2 × 0.12 × 0.08
monoclinic
C2/c (No. 15)
17.516(4)
13.777(3)
15.927(3)
90, 99.19(3), 90
3794(1)
0.2 × 0.15 × 0.25
monoclinic
C2/c (No. 15)
23.8332(1)
11.8922(1)
33.2391(3)
90, 91.062(1), 90
9419.3(1)
8
R, â, γ (deg)
V (Å3)
Z
4
Dcalcd (g cm-3
F000
)
1.251
1504.00
17.20
1.211
1632.00
15.19
1.219
1364.00
17.69
1.227
1504
16.34
1.182
3584.00
13.26
µ(Mo KR) (cm-1
)
(b) Data Collection
temp (°C)
unique/total no. of rflns
Rint
-120
5472/12 491
0.067
-110
7636/19 613
0.047
-155
5153/14 444
0.049
-141
3525/9055
0.070
-110
7098/19 732
0.052
empirical abs cor
µR, Tmin-Tmax
0.05
0.828-0.886
0.07
0.786-0.879
0.3
0.05
0.824-0.919
0.5
0.473-0.547
0.216-0.270
(c) Refinement
no. of observns (I > 3σ(I))
no. of variables
rflen/param ratio
Ra
3431
379
9.05
0.047
0.052
1.63
4655
416
11.19
0.042
0.047
1.66
3213
357
9.00
0.038
0.044
1.51
1627
192
8.47
0.055
0.058
1.60
4366
488
8.95
0.045
0.055
1.79
b
Rw
goodness of fitc
max and min peaks in
0.41/-0.54
0.41/-0.47
0.51/-0.37
0.79/-0.75
0.48/-0.41
final diff map (e/Å3)
R ) ∑(|Fo| - |Fc|)2/∑|Fo|. Rw ) [(∑w(|Fo| - |Fc|)2/∑wFo2)]1/2
.
c Goodness of fit ) [∑w(|Fo| - |Fc|)2/(No - Nv)]1/2
.
a
b
state, is probably responsible for the slight deviation in the
percentage of observed carbon.
(tBuMe2Si). Assignment of the NMR signals is based on 2D
NMR studies (TOCSY and HMQC). Heating the NMR sample
(product mixture of 9 and 10) to 80 °C resulted in complete
conversion of the mixture within 2 h to compound 10. IR
(cm-1): 3040 (m), 2952 (s), 2926 (s), 2888 (s), 2852 (s), 2795
(m), 1645 (m), 1603 (s), 1579 (s), 1557 (m), 1506 (w), 1489 (w),
1471 (m), 1461 (m), 1443 (s), 1387 (w), 1359 (w), 1304 (w), 1268
(s), 1248 (s), 1231 (m), 1152 (w), 1100 (m), 1067 (m), 1046 (s),
1038 (s), 1007 (m), 998 (m), 965 (s), 932 (w), 867 (w), 829 (s),
786 (m), 769 (m), 752 (m), 702 (s), 661 (w), 627 (m), 567 (w),
536 (w), 432 (w). Anal. Calcd for C46H70N5Si2Y: C, 65.92; H,
8.42; N, 8.36. Found: C, 65.21; H, 8.03; N, 8.31. The inclusion
of pentane in the crystal lattice of these compounds suggests
that desolvation is probably responsible for the slight deviation
in the percentage of observed carbon.
[DADMB]Y(n -C6H13)(THF )2 (8). A sample of 6 (ca. 10 mg)
was dissolved in THF-d8 (0.5 mL), and ca. 0.05 mL of 1-hexene
was added. After 30 min, the YH signals had nearly disap-
peared, and after 5 h a complete conversion to product was
observed. 1H NMR: δ 6.9-7.0 (m, 4 H), 6.54 (m, 1 H), 6.47
(m, 1 H, biphenyl H), 1.65 (s, 6 H, MeAr), 1.46 (m, 2 H,
YCH2CH2), 1.33-1.38 (m, overlaps with 1-hexene, YCH2CH2-
(CH2)3CH3), 0.89 (s, 18 H, Me3C), 0.85 (m, overlaps, Y(CH2)5-
CH3), 0.38 (s, 6 H, Me2Si), 0.16 (s, 6 H, Me2Si), -0.32 (m, 2 H,
YCH2).
[DADMB]Y(NC5H6)(p yr )2‚C5H12 (Mixtu r e of 9 a n d 10).
A sample of 6 (0.36 g, 2.8 mmol) was dissolved in 20 mL of
pyridine at room temperature. The dark yellow solution was
stirred for 2 days, and the volatile material was then removed
by vacuum transfer. The remaining solid was extracted with
2 × 75 mL of pentane, and then the combined yellow extracts
were concentrated to 20 mL. Cooling the solution to -35 °C
X-r a y Str u ctu r e Deter m in a tion s. X-ray diffraction mea-
surements were made on a Siemens SMART diffractometer
with a CCD area detector, using graphite-monochromated Mo
KR radiation. The crystal was mounted on a glass fiber using
Paratone N hydrocarbon oil. A hemisphere of data was
collected using ω scans of 0.3°. Cell constants and an orienta-
tion matrix for data collection were obtained from a least-
squares refinement using the measured positions of reflections
in the range 4 < 2θ < 45°. The frame data were integrated
using the program SAINT (SAX Area-Detector Integration
Program; V4.024; Siemens Industrial Automation, Inc.: Madi-
son, WI, 1995). An empirical absorption correction based on
measurements of multiply redundant data was performed
using the programs XPREP (part of the SHELXTL Crystal
Structure Determination Package; Siemens Industrial Auto-
mation, Inc.: Madison, WI, 1995) or SADABS. Equivalent
reflections were merged. The data were corrected for Lorentz
and polarization effects. A secondary extinction correction was
applied if appropriate. The structures were solved using the
teXsan crystallographic software package of the Molecular
Structure Corp., using direct methods, and expanded with
Fourier techniques. All non-hydrogen atoms were refined
anisotropically, and the hydrogen atoms were included in
1
produced bright yellow crystals (0.14 g, 30% yield). H NMR:
compound 9, δ 8.23 (m, 4 H, pyr), 7.27 (d, 1 H, NC5H6 vinylic),
6.83-6.54 (m, pyr and aromatic H), 6.47 (t, 1 H, NC5H6
vinylic), 5.40 (m, 1 H, NC5H6 vinylic), 5.04 (m, 1 H, NC5H6
vinylic), 4.30 (dd, 1 H, NC5H6 methylene), 4.04 (dd, 1 H, NC5H6
t
methylene), 2.03 (s, 6 H, Me), 1.05 (s, 18 H, BuMe2Si), 0.23
t
t
(s, 6 H, BuMe2Si), 0.18 (s, 6 H, BuMe2Si); compound 10, δ
8.32 (m, 4 H, pyr), 6.92 (m, 2 H, aromatic H), 6.71 (d, 2 H,
NC5H6 vinylic), 6.63-6.58 (m, pyr and aromatic H), 4.55 (m,
2 H, NC5H6 vinylic), 3.69 (m, 2 H, NC5H6 methylene), 2.02 (s,
t
t
6 H, Me), 1.04 (s, 18 H, BuMe2Si), 0.20 (s, 6 H, BuMe2Si),
0.13 (s, 6 H, BuMe2Si). 13C{1H} NMR: compound 9, δ 152.3,
t
150.4, 146.4, 141.0, 132.9, 129.3 (aromatic C), 125.8 (NC5H6),
124.0, 120.4 (aromatic C), 113.4 (NC5H6), 102.2 (NC5H6), 96.8
(NC5H6), 47.9 (NC5H6 methylene), 28.6 (Me3C), 22.3 (MeAr),
21.4 (Me3C), 0.9 (tBuMe2Si), -0.8 (tBuMe2Si); compound 10,
152.3, 150.5, 141.0 (aromatic C), 137.0 (NC5H6), 133.0, 129.7,
129.6, 125.8, 124.1, 120.5 (aromatic C), 95.2 (NC5H6), 28.6
(Me3C), 25.5 (NC5H6), 21.4 (Me3C), 0.8 (tBuMe2Si), -0.9

Y Complexes of a Bis(silylamido)biphenyl Ligand
Organometallics, Vol. 18, No. 15, 1999 2905
calculated positions but not refined unless otherwise noted.
The function minimized in the full-matrix least-squares refine-
ment was ∑w(|Fo| - |Fc|)2. The weighting scheme was based
on counting statistics and included a p-factor to downweight
the intense reflections. Crystallographic data are summarized
in Table 6.
F or 2. Crystals were grown from a 10:1 pentane/THF
solution of 2 at -35 °C. The Flack parameter of the structure
was 0.009(2), suggesting that the correct enantiomorph was
chosen. The other enantiomorph was also tested, but this
structure resulted in R ) 9.64% with a Flack parameter of
0.88.
F or 7. Crystals were grown from a dilute hexane solution
of 7 at -35 °C. The non-hydrogen atoms were refined aniso-
tropically, except for those of the disordered ethyl group, which
were refined isotropically.
F or 9. Crystals were grown from a pentane solution of a
mixture of 9 and 10 at -15 °C. The single crystal selected was
found to be compound 9. The non-hydrogen atoms were refined
anisotropically, except for those of the solvating pentane, which
were disordered and refined isotropically.
Ack n ow led gm en t is made to the National Science
Foundation for their generous support of this work. We
thank Dr. Fred Hollander for assistance with the X-ray
structure determinations.
F or 4. Crystals were grown from a pentane solution of 4 at
-35 °C.
F or 6. Crystals were grown by slow diffusion of PhSiH3 (0.3
mL dissolved in 20 mL of benzene) into a solution of 5 (0.16 g
in 20 mL of benzene), the two solutions being separated with
a layer of neat benzene, at room temperature for 4 days. The
non-hydrogen atoms were refined anisotropically. The hydride
H was located on the Fourier difference map and refined
isotropically; the rest of the hydrogen atoms were included in
calculated positions.
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal,
data collection, and refinement parameters, bond distances
and angles, and anisotropic displacement parameters for 2,
4, 6, 7, and 9. This material is available free of charge via the
Internet at http://pubs.acs.org.
OM9901170