N-substituted guanidinate anions as ancillary ligands in group 4 chemistry. Syntheses and characterization of M{RNC[N(SiMe3)2]NR}2Cl2, [M{CyNC[N(SiMe3)2]NCy}Cl3]- (M = Zr, Hf; R = iPr, Cy), and Zr{CyNC[N(SiMe3)2]NCy}(CH2Ph)3

Article abstract of DOI:10.1021/ic990668i

Addition of N(SiMe₃)₂ anion equivalents to carbodiimides, RN=C=NR (R = cyclohexyl, isopropyl), generated tetrasubstituted guanidinates which provided entry to a series of bis- and mono(guanidinate) complexes of Zr and Hf exhibiting the general formulas {RNC[N(SiMe₃)₂]NR}₂MCl₂ (R = isopropyl, M = Zr (1), Hf (2); R = cyclohexyl, M = Zr (3), Hf (4) and {CyNC[N(SiMe₃)₂]NCy}MCl₄]^- (M = Zr (5), Hf (6)) depending on the metal:ligand ratio used in the reaction. In addition to spectroscopic characterization, definitive evidence for the molecular structures of these products is provided through single-crystal X-ray analyses for 1, 3, 4, 5, and 6, which are presented. These results further define the ligand-bonding parameters and provide clear evidence that the planar N(SiMe₃)₂ functional groups and the MNCN planes have a nearly perpendicular orientation and therefore do not experience significant n overlap. Complex 5 provides an access to the organometallic derivative {CyNC[N(SiMe₃)₂]NCy}Zr(CH₂Ph)₃ (7) by reaction with 3 equiv of PhCH₂MgCl. Single-crystal X-ray analysis confirmed the connectivity of this species and indicated an η²-benzyl group. These results provide the first reported example of an organozirconium complex supported by a guanidinate ligand.

Full text of DOI:10.1021/ic990668i

5788
Inorg. Chem. 1999, 38, 5788-5794
N-Substituted Guanidinate Anions as Ancillary Ligands in Group 4 Chemistry. Syntheses
and Characterization of M{RNC[N(SiMe3)2]NR}2Cl2, [M{CyNC[N(SiMe3)2]NCy}Cl3]-
i
(M ) Zr, Hf; R ) Pr, Cy), and Zr{CyNC[N(SiMe3)2]NCy}(CH2Ph)3
Dayna Wood, Glenn P. A. Yap, and Darrin S. Richeson*
Department of Chemistry, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5
ReceiVed June 9, 1999
Addition of N(SiMe3)2 anion equivalents to carbodiimides, RNdCdNR (R ) cyclohexyl, isopropyl), generated
tetrasubstituted guanidinates which provided entry to a series of bis- and mono(guanidinate) complexes of Zr and
Hf exhibiting the general formulas {RNC[N(SiMe3)2]NR}2MCl2 (R ) isopropyl, M ) Zr (1), Hf (2); R )
cyclohexyl, M ) Zr (3), Hf (4) and {CyNC[N(SiMe3)2]NCy}MCl4]- (M ) Zr (5), Hf (6)) depending on the
metal:ligand ratio used in the reaction. In addition to spectroscopic characterization, definitive evidence for the
molecular structures of these products is provided through single-crystal X-ray analyses for 1, 3, 4, 5, and 6,
which are presented. These results further define the ligand-bonding parameters and provide clear evidence that
the planar N(SiMe3)2 functional groups and the MNCN planes have a nearly perpendicular orientation and therefore
do not experience significant π overlap. Complex 5 provides an access to the organometallic derivative {CyNC-
[N(SiMe3)2]NCy}Zr(CH2Ph)3 (7) by reaction with 3 equiv of PhCH2MgCl. Single-crystal X-ray analysis confirmed
the connectivity of this species and indicated an η2-benzyl group. These results provide the first reported example
of an organozirconium complex supported by a guanidinate ligand.
Introduction
Scheme 1
The search for alternatives to cyclopentadienyl-based ligands
in early transition metal chemistry has generated a great deal
of recent effort on preparing complexes with N-centered donor
ligands.1-14 In this regard we were attracted to N-substituted
guanidinate anions, [RNC(NR′2)NR′′]-, as potential bulky
supporting ligands for group 4 metals. These ligands fall into a
family of bidentate, three-atom bridging ligands with the general
formula RNXNR- (X ) CNR′2,15 CR′,16,17 or N18). Substituted
guanidinate ligands (X ) CNR′2, R′ * H) (Scheme 1) present
an interesting system for exploring the effects of making rational
modifications to both the steric bulk and electronic properties
of the supporting ligands through changes in the organic
substituents on the nitrogen atoms. A key feature of guanidinate
ligands is the presence of the NR′2 function, which allows
consideration of a zwitterionic resonance structure (I). Of course,
for this contribution to be significant the NR′2 center must be
planar, sp2 hybridized with the lone pair residing in a p orbital
which would be available for overlap with the conjugated NCN
moiety, and there must be a small dihedral angle between the
planes defined by the CNR′2 groups and that defined by NCN
in order for substantial overlap to occur. Keeping in mind these
two requirements, it is interesting to note that the attendant steric
congestion caused by the two organic substituents would
probably encourage a larger dihedral angle, thus discouraging
the appropriate orientation for π conjugation.
(1) Togni, A.; Venanzi, L. M. Angew. Chem., Int. Ed. Engl. 1994, 33,
497.
(2) Brand, H.; Arnold, J. A. Coord. Chem. ReV. 1995, 140, 137.
(3) Stephan, D. W.; Gue´rin, F.; Spence, R. E. v. H.; Koch, L.; Gao, X.;
Brown, S. J.; Swabey, J. W.; Wang, Q.; Xu, W.; Zoricak, P.; Harrison,
D. G. Organometallics 1999, 18, 2046.
(4) Baumann, R.; Davis, W. M.; Schrock, R. R. J. Am. Chem. Soc. 1997,
119, 3830.
(5) Warren, T. H.; Schrock, R. R.; Davis, W. M. Organometallics 1998,
17, 308.
(6) Gibson, V. C.; Kimberley, B. S.; White, A. J. P.; Williams, D. J.;
Howard, P. J. Chem. Soc., Chem. Commun. 1998, 313.
(7) Schaller, C. P.; Cummins, C. C.; Wolczanski, P. T. J. Am. Chem.
Soc. 1996, 118, 591.
(8) Schrock, R. R.; Cummins, C. C.; Wilhelm, T.; Lin, S.; Reid, S. M.;
Kol, M.; Davis, W. M. Organometallics 1996, 15, 1470.
(9) Scollard, J. D.; McConville, D. H. J. Am. Chem. Soc. 1996, 118, 10008.
(10) Gue´rin, F.; McConville, D. H.; Vittal, J. J.; Yap, G. P. A. Organo-
metallics 1998, 17, 5172 and references therein.
(11) Shapiro, P. J.; Cotter, W. D.; Schaefer, W. P.; Labinger, J. A.; Bercaw,
J. E. J. Am. Chem. Soc. 1994, 116, 4623.
(12) Black, D. G.; Jordan, R. F.; Rogers, R. D. Inorg. Chem. 1997, 36,
103.
We wish to report a portion of our ongoing investigation into
the incorporation of guanidinates and related ligands into metal
complexes.19-27 Included in this report are the syntheses and
(13) Uhrhammer, R.; Black, D. G.; Gardner, T. G.; Olsen, J. D.; Jordan,
R. F. J. Am. Chem. Soc. 1993, 115, 8493
(14) Jacoby, D.; Isoz, S.; Floriani, C.; Chiesi-Villa, A.; Rizzoli, C. J. Am.
Chem. Soc. 1995, 117, 5801
(17) Edelmann, F. T. Coord. Chem. ReV. 1994, 137, 403.
(18) Moore, D. S.; Robinson, S. D. AdV. Inorg. Chem. Radiochem. 1986,
30, 1.
(15) Mehrotra, R. C. In ComprehensiVe Coordination Chemistry; Wilkinson,
G., Gillard, R. D., McCleverty, J. A., Eds.; Pergamon Press: Oxford,
U.K., 1987; Chapter 13.8.
(19) Tin, M. K. T.; Yap, G. P. A.; Richeson, D. S. Inorg. Chem. 1999, 38,
998.
(20) Tin, M. K. T.; Yap, G. P. A.; Richeson, D. S. Inorg. Chem. 1998, 37,
(16) Kilner, M.; Baker, J. Coord. Chem. ReV. 1994, 133, 219.
6728.
10.1021/ic990668i CCC: $18.00 © 1999 American Chemical Society
Published on Web 11/24/1999

Guanidinate Anions as Ancillary Ligands
Inorganic Chemistry, Vol. 38, No. 25, 1999 5789
Scheme 2
Table 1. Crystallographic Data for {iPrNC[N(SiMe3)2]NiPr}2ZrCl2
(1), {CyNC[N(SiMe3)2]NCy}2ZrCl2 (3), and
{CyNC[N(SiMe3)2]NCy}2HfCl2 (4)
characterization of a novel family of bis(guanidinate) group 4
compounds of the general formula M(RNC[N(SiMe3)2]NR)2-
Cl2 (R ) isopropyl, M ) Zr (1), Hf (2); R ) cyclohexyl, M )
Zr (3), Hf (4)) and two mono(guanidinate) anionic complexes
of formula {M(CyNC[N(SiMe3)2]NCy)Cl3}- (M ) Zr (5), Hf
(6); Cy ) cyclohexyl). Complex 5 is readily converted into the
organometallic derivative Zr{CyNC[N(SiMe3)2]NCy}(CH2Ph)3
(7) by reaction with C6H5CH2MgCl.
1
3‚toluene
4‚0.5(benzene)
empirical
formula
fw
temp (K)
λ (Å)
C26H64Cl2N6Si4Zr C38H80Cl2N6Si4Zr C38H80Cl2HfN6Si4
735.31
203(2)
987.69
203(2)
0.710 73
P21/c
1018.76
213(2)
0.710 73
0.710 73
P21/c
space group Pbcn
a (Å)
b (Å)
c (Å)
â (deg)
V (Å3)
Z
12.5453(17)
17.701(2)
18.012(2)
13.818(3)
18.534(4)
21.369(4)
92.716(4)
5466(2)
4
13.7878(6)
18.5571(9)
21.4427(10)
92.8210(10)
5479.7(4)
4
Results and Discussion
Bis(guanidinate) Complexes of Zr and Hf. Guanidinate
anions were generated by the direct reaction of either 1,3-
dicyclohexylcarbodiimide or 1,3-diisopropylcarbodiimide (RNd
3999.9(9)
4
i
calcd (g/cm3) 1.221
1.200
0.421
1.235
2.119
CdNR; R ) Cy, Pr) with 1 equiv of LiN(SiMe3)2 in diethyl
d
abs coeff
(mm-1
R1a
0.552
ether. The lithium salts could be isolated in pure form by simple
removal of the solvent. However, in most cases metathesis
reactions with Zr and Hf halides can be carried out with freshly
prepared solutions of lithium guanidinate. For example, addition
of 0.5 equiv of MCl4(THF)2 (M ) Zr, Hf) to a solution of in
situ prepared guanidinate followed by recrystallization resulted
in isolation of the bis(guanidinate) complexes M{RNC-
[N(SiMe3)2]NR}2Cl2 (1-4) (Scheme 2). Spectroscopic charac-
terization provided the first confirmation of the identity of these
materials. Specifically, the four compounds exhibited similar
1H and 13C NMR spectra with the most notable features being
(1) the appearance of single isopropyl or cyclohexyl substituents
as indicated by single proton and carbon resonances for the NCH
groups and (2) the appearance of one resonance for the Si(CH3)3
moieties of the NR′2 groups. On the basis of the NMR
observations and the results of the crystallographic characteriza-
tion described below for 1 and 4, we propose the C2 symmetric
structures for these complexes shown in Scheme 2. The fact
)
0.0654
0.1686
0.0428
0.0755
0.0427
0.1284
wR2b
a R1 ) ∑||Fo| - |Fc||/∑|Fo|. b wR2 ) [∑w(|Fo| - |Fc|)2/∑w|Fo| ]1/2
.
2
that the two ends of the guanidinate ligand appear to be
equivalent on the NMR time scale is consistent with compounds
1-4 being fluxional. We have previously observed this feature
in analogous amidinate complexes of Zr, Hf, and Sn.22-27 We
have also previously noted that the incorporation of sterically
more demanding substituents on the amidinate methyne carbon
t
(e.g. Bu vs Me) can slow this fluxionality.23, 27
Single-crystal X-ray diffraction analyses of 1, 3, and 4 were
undertaken in order to establish the coordination geometry of
the metal center and the connectivity of the ligand for these
compounds (Table 1). The results of these structural studies are
displayed in Figures 1-3 and summarized in Tables 2-4. In
all three cases, the metal center is in a distorted pseudooctahedral
environment consisting of the four nitrogen atoms of two
bidentate guanidinate anions with cis chloride ligands complet-
ing the coordination sphere. Table 2 presents a summary of
selected bond distances and angles for 1. This complex possesses
a crystallographic C2 axis bisecting the Cl-Zr-ClA axis which
makes the two guanidinate ligands equivalent. The two nitrogens
(N(1), N(2)) and bridging carbon atom (C(7)) for the guanidinate
lie in a plane which includes the Zr atom. The termini of the
(21) Zhou, Y.; Yap, G. P. A.; Richeson, D. S. Organometallics 1998, 17,
4387.
(22) Foley, S. R.; Bensimon, C.; Richeson, D. S. J. Am. Chem. Soc. 1997,
119, 10359.
(23) Zhou, Y.; Richeson, D. S. Inorg. Chem. 1997, 36, 501.
(24) Zhou, Y.; Richeson, D. S. J. Am. Chem. Soc. 1996, 118, 10850.
(25) Zhou, Y.; Richeson, D. S. Inorg. Chem. 1996, 35, 2448.
(26) Zhou, Y.; Richeson, D. S. Inorg. Chem. 1996, 35, 1423.
(27) Littke, A.; Sleiman, N.; Bensimon, C.; Yap, G.; Brown, S.; Richeson,
D. Organometallics 1998, 17, 446.

5790 Inorganic Chemistry, Vol. 38, No. 25, 1999
Wood et al.
Table 2. Selected Bond Lengths (Å) and Angles (deg) for
{iPrNC[N(SiMe3)2]NiPr}2ZrCl2 (1)
Distances
Zr-N(1)
Zr-N(2)
2.219(4)
N(2)-C(7)
N(2)-C(4)
N(3)-C(7)
C(1)-C(2)
C(1)-C(3)
C(4)-C(5)
C(4)-C(6)
1.343(6)
1.480(6)
1.408(6)
1.504(7)
1.526(8)
1.494(7)
1.534(8)
2.264(4)
2.420(2)
2.700(5)
1.770(4)
1.775(4)
1.345(6)
1.462(6)
Zr-Cl
Zr-C(7)
Si(1)-N(3)
Si(2)-N(3)
N(1)-C(7)
N(1)-C(1)
Angles
ClA-Zr-C(7)
N(1)A-Zr-N(1)
N(1)A-Zr-N(2)
N(1)-Zr-N(2)
N(2)A-Zr-N(2)
N(1)A-Zr-Cl
N(1)-Zr-Cl
98.1(2)
96.13(11)
131.6(2)
123.0(4)
95.4(3)
140.5(3)
121.9(4)
93.4(3)
109.91(14) C(7)A-Zr-C(7)
Figure 1. ORTEP diagram for (iPrNC[N(SiMe3)2]NiPr)2ZrCl2 (1).
Thermal ellipsoids are drawn at 30% probability. Hydrogen atoms have
been omitted for clarity.
59.15(14) C(7)-N(1)-C(1)
164.9(2)
C(7)-N(1)-Zr
94.49(12) C(1)-N(1)-Zr
147.82(12) C(7)-N(2)-C(4)
101.99(12) C(7)-N(2)-Zr
88.73(11) C(4)-N(2)-Zr
N(2)A-Zr-Cl
N(2)-Zr-Cl
142.7(3)
Cl-Zr-ClA
90.23(12) C(7)-N(3)-Si(1) 118.8(3)
29.72(14) C(7)-N(3)-Si(2) 119.6(3)
109.37(15) Si(1)-N(3)-Si(2) 121.6(2)
N(1)A-Zr-C(7)A
N(1)-Zr-C(7)A
N(2)A-Zr-C(7)A
N(2)-Zr-C(7)A
Cl-Zr-C(7)A
ClA-Zr-C(7)A
N(1)A-Zr-C(7)
N(1)-Zr-C(7)
N(2)A-Zr-C(7)
N(2)-Zr-C(7)
Cl-Zr-C(7)
29.77(13) N(1)-C(1)-C(2)
139.49(15) N(1)-C(1)-C(3)
96.13(11) C(2)-C(1)-C(3)
118.13(12) N(2)-C(4)-C(5)
109.37(14) N(2)-C(4)-C(6)
29.72(14) C(5)-C(4)-C(6)
139.49(15) N(2)-C(7)-N(1)
29.77(13) N(2)-C(7)-N(3)
118.13(12) N(1)-C(7)-N(3)
109.4(4)
110.4(4)
110.3(5)
111.1(4)
110.6(4)
109.8(5)
110.8(4)
125.2(4)
124.0(4)
Chart 1
Figure 2. ORTEP diagram for (CyNC[N(SiMe3)2]NCy)2ZrCl2 (3).
Thermal ellipsoids are drawn at 30% probability. Hydrogen atoms and
solvent of crystallization (toluene) have been omitted for clarity.
An alternative description of the Zr coordination geometry
of 1 is as a distorted pseudotetrahedral complex with the vectors
that bisect the guanidinate ligands, Zr-C(7) and Zr-C(7)A
defining two of the vertexes and the two Zr-Cl vectors defining
the other two. This description emphasizes the relationship of
1-4 to metallocene dichloride systems and allows some
comparison of the structural features between these species. For
example the C(7)-Zr-C(7)A angle in 1 of 131.6(2)° is very
similar to the Cp(centroid)-Zr-Cp(centroid) angle of 134°
found in Cp2ZrCl2.28 However, the Zr-Cl distance (2.420(2)
Å) and Cl-Zr-Cl angle (90.23(12)°) in 1 are both smaller than
the corresponding values found for Cp2ZrCl2 (2.44 Å and 97.1°).
Monomeric complexes 3 and 4 crystallize with the molecular
geometries shown in Figures 2 and 3. These compounds
exhibited geometric and structural features similar to those of
1. In both cases, the metal centers lie on an approximate 2-fold
axis which bisects the Cl(1)-M-Cl(2) angle (M ) Zr ) 94.06-
(3)°; M ) Hf ) 93.81(7)°) with two planar bidentate guanidinate
anions. Tables 3 and 4 present a summary of selected bond
distances and angles for complexes 3 and 4, respectively. As
with 1, the termini of the planar guanidinate ligands in these
complexes can be divided into cis NCy groups and trans NCy
groups. Again, an alternative pseudotetrahedral description based
on the Zr-Cl(1), Zr-Cl(2), Zr-C(13), and Zr-C(32) vectors
in 3 and the Hf-Cl(1), Hf-Cl(2), Hf-C(7), and Hf-C(26)
vectors in 4 also provides satisfactory descriptions.
Figure 3. ORTEP diagram for (CyNC[N(SiMe3)2]NCy)2HfCl2 (4).
Thermal ellipsoids are drawn at 30% probability. The solvent of
crystallization (benzene) and hydrogen atoms have been omitted for
clarity.
guanidinate ligand can be divided into two types, the cis NiPr
groups (N(1), N(1)A) with a N-Zr-N angle of 98.1(2)° and
trans NiPr groups (N(2), N(2)A) with a N-Zr-N angle of
164.9(2)°. The structural features of 1 are quite similar to those
of the amidinate complex [CyNC(Me)NCy]2ZrCl2, which we
recently reported.27 Of particular interest in analyzing the steric
requirements of these ligands is a comparison of the angles
around the N atoms in 1 and in [CyNC(Me)NCy]2ZrCl2 (Chart
1). It is noteworthy that the C(bridge)-N-R (R ) Cy, iPr) angle
and the Zr-N-R angle for these two species are comparable,
indicating that although the substituent on the methyne carbon
is larger in 1 (N(SiMe3)2 vs Me), the effective steric effects
within the ligand framework are nearly the same.
(28) Prout, K.; Cameron, T. S.; Forder, R. A.; Critchley, S. R.; Denton,
B.; Rees, G. V. Acta Crystallogr. 1974, B30, 2290.

Guanidinate Anions as Ancillary Ligands
Inorganic Chemistry, Vol. 38, No. 25, 1999 5791
Table 3. Selected Bond Lengths (Å) and Angles (deg) for
{CyNC[N(SiMe3)2]NCy}2ZrCl2 (3)
Distances
Zr-N(4)
Zr-N(2)
Zr-N(1)
Zr-N(5)
Zr-Cl(1)
Zr-Cl(2)
Zr-C(13)
Zr-C(32)
N(1)-C(13)
2.1991(19)
2.213(2)
2.216(2)
2.232(2)
2.4229(8)
2.4259(8)
2.670(3)
2.672(3)
1.335(3)
N(1)-C(6)
N(2)-C(13)
N(2)-C(12)
N(3)-C(13)
N(4)-C(32)
N(4)-C(25)
N(5)-C(32)
N(5)-C(31)
N(6)-C(32)
1.471(3)
1.334(3)
1.462(3)
1.413(3)
1.331(3)
1.463(3)
1.348(3)
1.471(3)
1.418(3)
Angles
N(4)-Zr-N(2)
N(4)-Zr-N(1)
N(2)-Zr-N(1)
N(4)-Zr-N(5)
N(2)-Zr-N(5)
N(1)-Zr-N(5)
N(4)-Zr-Cl(1)
N(2)-Zr-Cl(1)
N(1)-Zr-Cl(1)
N(5)-Zr-Cl(1)
N(4)-Zr-Cl(2)
N(2)-Zr-Cl(2)
N(1)-Zr-Cl(2)
N(5)-Zr-Cl(2)
Cl(1)-Zr-Cl(2)
N(4)-Zr-C(13)
N(2)-Zr-C(13)
N(1)-Zr-C(13)
N(5)-Zr-C(13)
Cl(1)-Zr-C(13)
Cl(2)-Zr-C(13)
N(4)-Zr-C(32)
N(2)-Zr-C(32)
N(1)-Zr-C(32)
N(5)-Zr-C(32)
Cl(1)-Zr-C(32)
Cl(2)-Zr-C(32)
C(13)-Zr-C(32)
94.91(7) C(13)-N(1)-Zr
94.24(16)
141.16(16)
108.25(7) C(6)-N(1)-Zr
59.46(7) C(13)-N(2)-C(12) 122.5(2)
59.67(7) C(13)-N(2)-Zr
108.04(7) C(12)-N(2)-Zr
163.40(7) C(13)-N(3)-Si(2)
93.02(6) C(13)-N(3)-Si(1)
149.20(6) Si(2)-N(3)-Si(1)
94.37(15)
Figure 4. ORTEP diagram for [{CyNC[N(SiMe3)2]NCy}ZrCl4]- (5).
Thermal ellipsoids are drawn at 30% probability. The lithium cation
with coordinated solvent molecules and hydrogen atoms have been
omitted for clarity.
141.79(17)
118.60(16)
119.33(15)
121.95(12)
89.80(5) C(32)-N(4)-C(25) 122.1(2)
Table 4. Selected Bond Lengths (Å) and Angles (deg) for
{CyNC[N(SiMe3)2]NCy}2HfCl2 (4)
101.65(5) C(32)-N(4)-Zr
148.32(6) C(25)-N(4)-Zr
95.20(15)
141.71(16)
94.62(5) C(32)-N(5)-C(31) 121.5(2)
Distances
102.61(5) C(32)-N(5)-Zr
88.66(5) C(31)-N(5)-Zr
94.06(3) C(32)-N(6)-Si(4)
106.46(7) C(32)-N(6)-Si(3)
29.89(7) Si(4)-N(6)-Si(3)
93.27(15)
Hf-N(1)
Hf-N(5)
Hf-N(4)
Hf-N(2)
Hf-Cl(2)
Hf-Cl(1)
Hf-C(7)
Hf-C(26
N(1)-C(7)
2.181(4)
2.202(5)
2.211(5)
2.215(5)
2.411(2)
2.414(2)
2.656(5)
2.666(5)
1.342(7)
N(1)-C(6)
N(2)-C(7)
N(2)-C(19)
N(3)-C(7)
N(4)-C(26)
N(4)-C(25)
N(5)-C(26)
N(5)-C(38)
N(6)-C(26)
1.465(7)
1.339(7)
1.468(7)
1.418(7)
1.344(7)
1.461(7)
1.338(7)
1.461(7)
1.404(7)
141.05(16)
118.65(16)
119.72(16)
121.63(12)
29.90(7) N(2)-C(13)-N(1)) 110.8(2
137.75(8) N(2)-C(13)-N(3)
119.60(6) N(1)-C(13)-N(3)
96.65(5) N(2)-C(13)-Zr
29.75(7) N(1)-C(13)-Zr
106.22(7) N(3)-C(13)-Zr
137.77(7) N(4)-C(32)-N(5)
30.23(7) N(4)-C(32)-N(6)
95.24(5) N(5)-C(32)-N(6)
118.72(6) N(4)-C(32)-Zr
128.62(7) N(5)-C(32)-Zr
123.9(2)
125.3(2)
55.74(12)
55.86(13)
170.32(16)
110.8(2)
124.8(2)
124.4(2)
55.05(12)
56.50(12)
170.91(16)
Angles
N(1)-Hf-N(5)
N(1)-Hf-N(4)
N(5)-Hf-N(4)
N(1)-Hf-N(2)
N(5)-Hf-N(2)
N(4)-Hf-N(2)
N(1)-Hf-Cl(2)
N(5)-Hf-Cl(2)
N(4)-Hf-Cl(2)
N(2)-Hf-Cl(2)
N(1)-Hf-Cl(1)
N(5)-Hf-Cl(1)
N(4)-Hf-Cl(1)
N(2)-Hf-Cl(1)
Cl(2)-Hf-Cl(1)
N(1)-Hf-C(7)
N(5)-Hf-C(7)
N(4)-Hf-C(7)
N(2)-Hf-C(7)
Cl(2)-Hf-C(7)
Cl(1)-Hf-C(7)
95.1(2)
108.0(2)
59.9(2)
60.1(2)
107.7(2)
163.5(2)
Cl(2)-Hf-C(26)
Cl(1)-Hf-C(26)
C(7)-Hf-C(26)
C(7)-N(1)-C(6)
C(7)-N(1)-Hf
C(6)-N(1)-Hf
120.42(12)
95.80(12)
128.8(2)
121.5(5)
94.9(3)
142.7(4)
121.8(5)
93.4(3)
140.5(4)
120.1(4)
118.8(4)
121.2(3)
C(13)-N(1)-C(6) 121.4(2)
N(6)-C(32)-Zr
92.54(13) C(7)-N(2)-C(19)
150.16(13) C(7)-N(2)-Hf
90.35(13) C(19)-N(2)-Hf
101.12(13) C(7)-N(3)-Si(2)
149.51(13) C(7)-N(3)-Si(1)
94.09(13) Si(2)-N(3)-Si(1)
The dihedral angle formed by the planar N(SiMe3)2 function
and the MNCN plane offers a means of evaluating the possibility
of π overlap between these two moieties. In the case of 1, an
angle of 88.2(4)° is formed between these two planes, while
for 3 and 4, average dihedral angles of 86.3 and 85.8° were
observed for the two crystallographically unique guanidinate
ligands in each of these two complexes. This nearly perpen-
dicular disposition is likely the result of steric interactions
between the isopropyl or cyclohexyl functions and the bulky
trimethylsilyl groups and eliminates significant π conjugation
in both 1 and 4. As a result, structure I does not appear to be
a significant contributor in these cases. However, this orientation
of the bulky N(SiMe3)2 group effectively adds a third dimension
to the steric bulk of what would be an otherwise planar
guanidinate ligand. This perpendicular orientation also explains
the observation that the guanidinate ligand in 1 appears to exhibit
bonding parameters similar to those of the amidinate anion in
[CyNC(Me)NCy]2ZrCl2 (Chart 1).
101.78(14) C(26)-N(4)-C(25) 121.3(5)
89.38(12) C(26)-N(4)-Hf
94.0(3)
141.2(4)
93.81(7)
30.2(2)
106.2(2)
138.0(2)
30.2(2)
C(25)-N(4)-Hf
C(26)-N(5)-C(38) 122.1(5)
C(26)-N(5)-Hf
C(38)-N(5)-Hf
C(26)-N(6)-Si(3)
94.6(3)
142.1(4)
118.4(4)
119.9(4)
121.6(3)
110.5(5)
124.7(5)
124.8(5)
94.69(12) C(26)-N(6)-Si(4)
119.41(12) Si(3)-N(6)-Si(4)
N(1)-Hf-C(26) 106.5(2)
N(2)-C(7)-N(1)
N(2)-C(7)-N(3)
N(1)-C(7)-N(3)
N(5)-Hf-C(26)
N(4)-Hf-C(26)
N(2)-Hf-C(26) 137.5(2)
30.0(2)
30.2(2)
spectra of 5 and 6. These spectra also display the characteristic
signals for the guanidinate ligand.
Mono(guanidinate) Complexes. A single tetrasubstituted
guanidinate ligand can be introduced into the metal coordination
sphere through reaction of a 1:1 ratio of lithium salt of N,N′-
dicylohexyl-N′′-bis(trimethylsilyl)guanidinate with either Zr or
Hf chlorides. After crystallization from diethyl ether or THF,
the new “ate” complexes {CyNC[N(SiMe3)2]NCy}MCl4]Li(S)x
(Scheme 2) (S ) THF or THF/Et2O) were isolated. The first
indication that solvated Li cations remained in these materials
was the appearance of coordinated solvent peaks in the NMR
The proposed structures for 5 and 6 (Scheme 2) were
confirmed by X-ray crystallographic characterization, which
yielded the results summarized in Figures 4 and 5 and Tables
5-7. In both cases, the complexes possessed a single bidentate
guanidinate and four chloro ligands, giving a distorted octahedral
coordination geometry. The guanidinate ligands occupy two of
the octahedral sites and exhibit bonding parameters that are
similar to each other and to those of the bis(guanidinate)
complexes 1, 3, and 4. The coordination geometry of these two

5792 Inorganic Chemistry, Vol. 38, No. 25, 1999
Wood et al.
Table 6. Bond Lengths (Å) and Angles (deg) for
[{CyNC[N(SiMe3)2]NCy}ZrCl4][Li(THF)2(Et2O)] (5)
Distances
Zr-N(2)
2.179(7)
2.181(6)
2.423(2)
2.434(3)
2.441(3)
2.544(2)
2.641(9)
1.758(6)
1.855(9)
1.849(9)
1.889(9)
Si(2)-N(3)
Si(2)-C(19)
Si(2)-C(18)
Si(2)-C(17)
Cl(1)-Li
N(1)-C(13)
N(1)-C(6)
N(2)-C(13)
N(2)-C(12)
N(3)-C(13)
1.768(6)
1.852(9)
1.849(10)
1.862(9)
2.39(2)
1.312(10)
1.466(10)
1.336(10)
1.469(10)
1.426(11)
Zr-N(1)
Zr-Cl(4)
Zr-Cl(2)
Zr-Cl(3)
Zr-Cl(1)
Zr-C(13)
Si(1)-N(3)
Si(1)-C(14)
Si(1)-C(16)
Si(1)-C(15)
Angles
Si(1)-N(3)-Si(2) 124.0(4)
N(1)-C(13)-N(2) 110.7(7)
N(1)-C(13)-N(3) 125.3(7)
N(2)-C(13)-N(3) 124.0(7)
Cl(3)-Zr-C(13)
127.72(19)
89.07(15)
Cl(1)-Zr-C(13)
Figure 5. ORTEP diagram for [{CyNC[N(SiMe3)2]NCy}HfCl4]- (6).
Thermal ellipsoids are drawn at 30% probability. The lithium cation
with coordinated solvent molecules and hydrogen atoms have been
omitted for clarity.
N(3)-Si(1)-C(14) 108.4(4)
N(3)-Si(1)-C(16) 113.5(4)
N(1)-C(13)-Zr
N(2)-C(13)-Zr
N(3)-C(13)-Zr
N(2)-Zr-N(1)
N(2)-Zr-Cl(4)
N(1)-Zr-Cl(4)
N(2)-Zr-Cl(2)
N(1)-Zr-Cl(2)
Cl(4)-Zr-Cl(2)
N(2)-Zr-Cl(3)
N(1)-Zr-Cl(3)
Cl(4)-Zr-Cl(3)
Cl(2)-Zr-Cl(3)
N(2)-Zr-Cl(1)
N(1)-Zr-Cl(1)
Cl(4)-Zr-Cl(1)
Cl(2)-Zr-Cl(1)
Cl(3)-Zr-Cl(1)
N(2)-Zr-C(13)
N(1)-Zr-C(13)
Cl(4)-Zr-C(13)
Cl(2)-Zr-C(13)
55.4(4)
55.4(4)
177.7(5)
60.0(2)
C(13)-N(1)-C(6)
C(13)-N(1)-Zr
C(6)-N(1)-Zr
123.6(7)
94.9(5)
141.4(5)
C(13)-N(2)-C(12) 123.7(7)
92.77(18) C(13)-N(2)-Zr
94.3(5)
141.9(5)
93.07(17) C(12)-N(2)-Zr
155.00(19) C(13)-N(3)-Si(1) 118.0(5)
95.14(18) C(13)-N(3)-Si(2) 117.9(5)
90.70(10) C(13)-N(1)-C(6)
97.49(18) C(13)-N(1)-Zr
157.15(18) C(6)-N(1)-Zr
123.6(7)
94.9(5)
141.4(5)
91.63(9)
C(13)-N(2)-C(12) 123.7(7)
107.16(11) C(13)-N(2)-Zr
94.3(5)
141.9(5)
89.18(18) C(12)-N(2)-Zr
88.60(17) C(13)-N(3)-Si(1) 118.0(5)
177.89(9)
C(13)-N(3)-Si(2) 117.9(5)
87.87(10) C(13)-N(1)-C(6)
123.6(7)
94.9(5)
141.4(5)
87.32(9)
30.3(2)
29.7(2)
C(13)-N(1)-Zr
C(6)-N(1)-Zr
C(13)-N(2)-C(12) 123.7(7)
93.01(15) C(13)-N(2)-Zr
124.80(19)
94.3(5)
Figure 6. ORTEP diagram for {CyNC[N(SiMe3)2]NCy}Zr(CH2Ph)3
(7). Thermal ellipsoids are drawn at 30% probability. Hydrogen atoms
have been omitted for clarity.
angles formed between the two planes defined by the N(SiMe3)2
function and the MNCN cycle again indicate little π-bonding
interaction between these moieties (85.8(7)° for 5 and 86.0(9)°
for 6).
Charge compensation for these anionic complexes is provided
in both cases by a Li cation which is associated with one of the
chloro ligands (2.39(2) Å in 5 and 2.42(6) Å in 6). Tetrahy-
drofuran or a combination of diethyl ether and THF completes
the coordination spheres of the Li cations.
Table 5. Crystallographic Data for
{CyNC[N(SiMe3)2]NCy}ZrCl4]Li(THF)2(Et2O) (5),
{CyNC[N(SiMe3)2]NCy}HfCl4]Li(THF)3 (6), and
{CyNC[N(SiMe3)2]NCy}Zr(CH2Ph)3 (7)
5
6
7
empirical C31H66Cl4LiN3O3Si2Zr C31H64Cl4HfLiN3O3Si2 C40H61N3Si2Zr
formula
fw
825.01
910.26
223(2)
0.710 73
Pbcn
731.32
203(2)
0.710 73
P21/n
temp (K) 203(2)
λ (Å)
space
Preparation and Structural Characterization of {CyNC-
[N(SiMe3)2]NCy}Zr(CH2Ph)3 (7). The reaction of 5 with 3
equiv of PhCH2MgCl proceeded according to the metathesis
reaction shown in Scheme 2 to yield complex 7. Spectroscopic
characterization indicated the incorporation of three benzyl
groups and was consistent with the formulation of this species
0.710 73
Pbcn
group
a (Å)
b (Å)
c (Å)
â (deg)
V (Å3)
Z
33.284(7)
14.956(3)
17.381(4)
33.460(2)
15.0033(8)
17.3857(9)
10.483(1)
18.889(2)
20.459(3)
102.431(2)
3956.0(9)
4
1
as {CyNC[N(SiMe3)2]NCy}Zr(CH2Ph)3. Both the 13C and H
8652(3)
8
8727.8(8)
8
NMR spectra indicated a single Cy substituent and a single
benzyl group and gave no evidence of an η2-benzyl ligand.
The molecular structure of 7 was determined, and an ORTEP
diagram is provided in Figure 6 and crystallographic data are
summarized in Tables 5 and 8. The geometry of the five-
coordinate Zr center is better described as distorted tetrahedral
with vertexes defined by the three benzyl groups and the central
carbon (C(13)) of the guanidinate ligand. The corresponding
angles range from 118.2(3) to 90.7(2)° with an average value
of 107.8°.
dcalcd
1.267
1.385
1.228
(g/cm3)
abs coeff 0.588
(mm-1
R1a
wR2b
2.721
0.369
)
0.0802
0.2408
0.0937
0.2385
0.0473
0.0918
a R1 ) ∑||Fo| - |Fc||/∑|Fo|. b wR2 ) [∑w(|Fo| - |Fc|)2/∑w|Fo| ]1/2
.
2
complexes can also be reasonably described as pseudotrigonal
bipyramidal with the central C of the guanidinate ligand and
cis chloro ligands forming the equatorial plane (C(13), Cl(2),
and Cl(3) for 5 and C(13), Cl(1), and Cl(2) for 6). The dihedral
The average Zr-CH2 bond distance is 2.273(6) Å, which is
shorter than the corresponding distances in the recently reported

Guanidinate Anions as Ancillary Ligands
Inorganic Chemistry, Vol. 38, No. 25, 1999 5793
Table 7. Selected Bond Lengths (Å) and Angles (deg) for
[{CyNC[N(SiMe3)2]NCy}HfCl4][Li(THF)3] (6)
Table 8. Selected Bond Lengths (Å) and Angles (deg) for
{CyNC[N(SiMe3)2]NCy}Zr(CH2Ph)3 (7)
Distances
Distances
Hf-N(2)
Hf-N(1)
Hf-Cl(3)
Hf-Cl(1)
Hf-Cl(2)
Hf-Cl(4)
Hf-C(13)
2.17(2)
2.19(2)
2.402(6)
2.427(6)
2.424(6)
2.524(5)
2.63(2)
N(1)-C(13)
N(1)-C(6)
N(2)-C(13)
N(2)-C(12)
N(3)-C(13)
N(3)-Si(2)
N(3)-Si(4)
Cl(4)-Li
1.32(2)
1.42(2)
1.34(2)
1.46(2)
1.41(2)
1.759(14)
1.79(2)
2.42(6)
Zr-N(1)
2.241(4)
2.250(5)
2.263(7)
2.268(5)
2.288(6)
2.672(6)
2.683(6)
1.756(5)
1.775(4)
1.339(7)
N(1)-C(6)
1.465(6)
1.344(7)
1.461(6)
1.421(7)
1.466(8)
1.417(8)
1.385(8)
1.463(9)
1.491(8)
Zr-N(2)
N(2)-C(13)
N(2)-C(12)
N(3)-C(13)
C(20)-C(26)
C(21)-C(26)
C(25)-C(26)
C(27)-C(33)
C(34)-C(40)
Zr-C(27)
Zr-C(20)
Zr-C(34)
Zr-C(26)
Zr-C(13)
Si(1)-N(3)
Si(2)-N(3)
N(1)-C(13)
Angles
89.2(4)
124(2)
Cl(4)-Hf-C(13)
C(13)-N(1)-C(6)
C(13)-N(1)-Hf
C(6)-N(1)-Hf
N(1)-Hf-Cl(2)
Cl(3)-Hf-Cl(2)
97.8(5)
91.3(2)
105.8(2)
88.7(4)
89.4(4)
177.9(2)
87.7(2)
87.3(2)
30.6(6)
30.0(5)
92.9(4)
126.1(5)
127.7(5)
Angles
94.0(12) Cl(1)-Hf-Cl(2)
N(1)-Zr-N(2)
59.77(17) C(13)-N(1)-C(6)
122.7(5)
141.5(14) N(2)-Hf-Cl(4)
N(1)-Zr-C(27)
N(2)-Zr-C(27)
N(1)-Zr-C(20)
N(2)-Zr-C(20)
C(27)-Zr-C(20)
N(1)-Zr-C(34)
N(2)-Zr-C(34)
C(27)-Zr-C(34)
C(20)-Zr-C(34)
N(1)-Zr-C(26)
N(2)-Zr-C(26)
C(27)-Zr-C(26)
C(20)-Zr-C(26)
C(34)-Zr-C(26)
N(1)-Zr-C(13)
N(2)-Zr-C(13)
C(27)-Zr-C(13)
C(20)-Zr-C(13)
C(34)-Zr-C(13)
C(26)-Zr-C(13)
111.7(3)
113.8(2)
95.6(2)
126.4(2)
119.6(3)
138.9(2)
84.0(2)
99.9(3)
90.7(2)
107.20(19) C(1)-C(2)-C(3)
158.43(18) N(1)-C(13)-N(2)
86.5(2)
33.3(2)
100.2(2)
C(13)-N(1)-Zr
C(6)-N(1)-Zr
93.7(3)
143.3(4)
122.2(5)
93.1(4)
144.5(4)
117.1(3)
119.2(4)
123.7(3)
111.4(5)
111.7(5)
113.1(5)
123.6(5)
123.3(6)
56.4(3)
C(13)-N(2)-C(12) 125(2)
N(1)-Hf-Cl(4)
C(13)-N(2)-Hf
C(12)-N(2)-Hf
C(13)-N(3)-Si(2)
C(13)-N(3)-Si(4)
Si(2)-N(3)-Si(4)
N(1)-C(13)-N(2)
N(2)-Hf-N(1)
N(2)-Hf-Cl(3)
N(1)-Hf-Cl(3)
N(2)-Hf-Cl(1)
N(1)-Hf-Cl(1)
Cl(3)-Hf-Cl(1)
N(2)-Hf-Cl(2)
94.3(12) Cl(3)-Hf-Cl(4)
140.7(13) Cl(1)-Hf-Cl(4)
119.1(12) Cl(2)-Hf-Cl(4)
118.5(11) N(2)-Hf-C(13)
122.3(10) N(1)-Hf-C(13)
C(13)-N(2)-C(12)
C(13)-N(2)-Zr
C(12)-N(2)-Zr
C(13)-N(3)-Si(1)
C(13)-N(3)-Si(2)
Si(1)-N(3)-Si(2)
C(2)-C(1)-C(6)
111(2)
Cl(3)-Hf-C(13)
Cl(1)-Hf-C(13)
Cl(2)-Hf-C(13)
60.6(6)
93.2(4)
92.3(4)
95.6(4)
156.1(5)
91.2(2)
158.0(4)
N(1)-C(13)-N(3) 126(2)
N(2)-C(13)-N(3) 123(2)
N(1)-C(13)-N(3)
N(2)-C(13)-N(3)
N(1)-C(13)-Zr
N(1)-C(13)-Hf
N(2)-C(13)-Hf
N(3)-C(13)-Hf
56.0(10)
55.1(10)
177.0(13)
29.86(16) N(2)-C(13)-Zr
30.00(16) N(3)-C(13)-Zr
118.2(2)
112.0(2)
111.4(2)
56.9(3)
174.7(4)
88.7(4)
C(26)-C(20)-Zr
â-ketimino complex (TTP)Zr(CH2Ph)3 (TTP ) 2-p-tolylamino-
4-p-tolylimino-2-pentenato) which averaged 2.290(5) Å (Zr-
C-Cipso ) 99.1(2)°)29 or that in CpZr(CH2Ph)3 at 2.299(8) Å
(Zr-Cispo ) 2.818(8) Å, Zr-C-Cipso ) 94.5(5)°).30
C(25)-C(26)-C(21) 116.7(7)
C(25)-C(26)-C(20) 121.2(6)
134.14(19) C(21)-C(26)-C(20) 121.3(6)
N(3)-Si(1)-C(14) 108.7(3)
N(3)-Si(1)-C(15) 110.0(3)
N(3)-Si(1)-C(16) 113.0(3)
N(3)-Si(2)-C(19) 109.0(3)
N(3)-Si(2)-C(18) 108.9(3)
N(3)-Si(2)-C(17) 112.3(3)
C(25)-C(26)-Zr
C(21)-C(26)-Zr
C(20)-C(26)-Zr
C(33)-C(27)-Zr
C(40)-C(34)-Zr
94.2(4)
110.4(4)
58.1(3)
116.0(5)
123.2(4)
One of the benzyl groups in 7 is unique in exhibiting a
significantly more acute Zr-C-Cipso angle (Zr-C(20)-C(26)
) 88.7(4)° vs Zr-C(27)-C(33) ) 116.0(5)° and Zr-C(34)-
C(40) ) 123.2(4)°) and a short Zr-Cipso (Zr-C(26)) distance
of 2.672(6) Å. These features establish that the phenyl group
of this moiety is a weak electron donor and contrast with those
of (TTP)Zr(CH2Ph)3 (Zr-C-Cipso ) 99.1(2)°)29 and CpZr(CH2-
Ph)3 at 2.299(8) Å (Zr-Cispo ) 2.818(8) Å, Zr-C-Cipso ) 94.5-
(5)°),30 possibly indicating that the Zr center in 7 is more
electron deficient than that in these complexes. Supporting this
is the observation of similar bonding parameters observed in
related tribenzyl complexes supported by bulky aryloxides in
which the η2-benzyl exhibited a Zr-C-Cipso angle of 84.3(9)°
(Zr-CH2 ) 2.28 Å, Zr-Cispo ) 2.59 Å)31 and the structurally
characterized cationic species [Cp2Zr(CH2Ph)NCCH3]+ (Zr-
CH2 ) 2.344(8) Å, Zr-Cispo ) 2.648(6) Å, Zr-C-Cipso ) 84.9-
(4)°)32,33 For reference, Zr(CH2Ph)4 exhibits a mean Zr-C-
Cipso angle of 92(1)° (range from 85 to 101°).34 Several other
electron-deficient early transition metal complexes also exhibit
similar features.35-38
The possibility of a significant π interaction between the
planar N(SiMe3)2 function of the guanidinate and the bidentate
NCN fragment can be ruled out on the basis of the observed
dihedral angle of 85.8(3)°.
Conclusions
In summary, guanidinate ligands have proven to be useful in
the preparation of a family of bis(guanidinate) and anionic
mono(guanidinate) group 4 complexes. A combination of X-ray
crystallographic and spectroscopic studies confirm the C2
symmetric features of the bis(guanidinate) compounds and the
structures of the mono(guanidinate) species. From these results,
it is clear that little conjugation occurs between the lone pair
on the planar NR′2 group and the guanidinate NCN π system.
The nearly perpendicular orientation of the NR′2 substituents
to the MNCN plane results in a system that appears to exhibit
steric features within the plane of the ligand that are similar to
those of [RNC(Me)NR]-. The preparation of complex 7 supports
the fact that 1-6 represent a novel class of potential precursors
for soluble organometallic complexes of group 4 free of
cyclopentadienyl ligands. The use of the reported complexes
to yield catalytically active species is currently under investiga-
tion. Along with this effort, our continuing investigations are
(29) Qian, B.; Scanlon, W. J., IV; Smith, M. R., III; Motry, D. H.
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5794 Inorganic Chemistry, Vol. 38, No. 25, 1999
Wood et al.
yellow solid (0.72 g, 73% yield). Colorless crystals were obtained from
toluene at -34 °C. 1H NMR (C6D6, ppm): 3.50 (br, C6H11, 4H), 1.0-
2.2 (br, C6H11, 40H), 0.3 (s, CH3, 36H). 13C NMR (C6D6, ppm): 175.17
(s, N3C), 56.08, 35.36, 35.17, 26.34 (4s, C6H11), 3.12 (s, SiCH3).
Hf[C6H11NC(Si(CH3)3)2NC6H11]2Cl2 (4). An experimental procedure
similar to that for 1 using HfCl4(THF)2 (1.418 g, 3.1 mmol) and Li-
[C6H11NC(Si(CH3)3)2NC6H11] (2.338 g, 6.3 mmol) gave a white powder
(2.54 g, 83% yield). Colorless crystals were obtained from toluene at
-34 °C. 1H NMR (C6D6, ppm): 3.68 (br, C6H11, 4H), 1.90-1.20 (br,
C6H11, 40H), 0.32 (s, CH3, 36H). 13C NMR (C6D6, ppm): 174.61 (s,
N3C), 55.66, 35.03, 26.26, 25.61 (4s, C6H11), 3.17 (s, SiCH3). Anal.
Calcd for C38H80N6Si4HfCl2: C, 46.44; H, 8.20; N, 8.55. Found: C,
46.18; H, 8.31; N, 8.36.
oriented at further revealing the steric and electronic features
that influence the reactivity of transition metal guanidinate
compounds.
Experimental Section
General Considerations. All manipulations were carried out either
in a nitrogen-filled drybox or under nitrogen using standard Schlenk-
line techniques. LiN(Si(Me)3)2, C6H11NCNC6H11, (CH3)2CHNCNCH-
(CH3)2, ZrCl4, and HfCl4 were used as received from Aldrich Chemical
Co. Solvents were distilled under nitrogen from Na/K alloy. ZrCl4-
(THF)2 and HfCl4(THF)2 were prepared by literature procedures.
Deuterated benzene was purified by vacuum transfer from potassium
metal.
Zr{[C6H11NC(Si(CH3)3)2NC6H11]Cl4}Li(THF)2[O(CH2CH3)2] (5).
A reaction flask was charged with ZrCl4(THF)2 (1.333 g, 3.5 mmol),
50 mL of diethyl ether, and a stir bar. To this was added Li[C6H11-
NC(Si(CH3)3)2NC6H11] (1.320 g, 3.5 mmol). After 20 h of stirring, the
reaction mixture was filtered through Celite to give a clear pale lemon
yellow filtrate. The solvent was then removed under vacuum to give a
very light green powder (1.96 g, 68% yield). Pale-yellow crystals were
1H and 13C NMR spectra were run on a Gemini 200 MHz
spectrometer with deuterated benzene or pyridine as a solvent and
internal standard. All elemental analyses were run on a Perkin-Elmer
PE CHN 4000 elemental analysis system.
Li{C6H11NC[N(Si(CH3)3)2]NC6H11}. Addition of a solution of LiN-
(Si(Me)3)2 (2.239 g, 13.4 mmol) in 30 mL of diethyl ether to C6H11-
NCNC6H11 (2.761 g, 13.4 mmol) in 30 mL of diethyl ether gave a
clear pale yellow solution. The reaction mixture was allowed to stir
for 4 h. The solvent was removed under vacuum to give a white powder
(4.64 g, 93% yield). 1H NMR (C6D6, ppm): 3.38 (br, C6H11, 2H), 1.95-
1.05 (br, C6H11, 20H), 0.33 (s, CH3, 18H). 13C NMR (C6D6, ppm):
163.90 (s, N3C), 54.29, 38.70, 26.62, 26.13 (4s, C6H11), 2.63 (s, CH3)
Li{(CH3)2CHNC[N(Si(CH3)3)2]NCH(CH3)2}. Addition of a solution
of LiN(Si(CH3)3)2 (2.850 g, 17.0 mmol) in 30 mL of diethyl ether to
(CH3)2CHNCNCH(CH3)2 (2.150 g, 17.0 mmol) in 20 mL of diethyl
ether gave a clear pale yellow solution. The mixture was allowed to
stir for 4 h. The solvent was removed under vacuum to give a very
1
obtained from diethyl ether at -34 °C. H NMR (py-d5, ppm): 3.75
(br m, C6H11, 2H), 3.60 (m, THF, 8H), 3.31(q, Et2O, 4H), 2.68-1.26
(br, C6H11, 20H), 1.61 (m, THF, 8H), 1.12 (t, Et2O, 6H), 0.43 (s, CH3,
18H). 13C NMR (py-d5, ppm): 171.93 (s, N3C), 67.77, 25.41 (2s, THF),
65.72, 15.46 (2s, diethyl ether), 55.76, 34.89, 25.99, 25.77 (4s, C6H11),
2.56 (s, CH3).
Hf{[C6H11NC(N(Si(CH3)3)2)NC6H11]Cl4}{Li(THF)3} (6). An ex-
perimental procedure similar to that for 5 using HfCl4(THF)2 (0.713 g,
1.5 mmol) and Li[C6H11NC(Si(CH3)3)2NC6H11] (0.573 g, 1.5 mmol)
gave a colorless filtrate. The solvent was then removed under vacuum
to give a white powder (0.908 g, 66% yield). Colorless crystals were
1
light peach-colored solid (4.34 g, 87% yield). H NMR (C6D6, ppm):
1
obtained from diethyl ether at -34 °C. H NMR (py-d5, ppm): 3.75
3.72 (sept, CH, 2H), 1.12 (d, CH3, 12H), 0.31 (s, CH3, 18H). 13C NMR
(C6D6, ppm): 163.95 (s, N3C), 45.70, 27.71 (2s, CH(CH3)2), 2.56 (s,
CH3).
(br, C6H11, 2H), 3.62 (m, THF, 12H), 2.68-1.25 (br, C6H11, 20H), 1.59
(m, THF, 12H), 0.43 (s, CH3, 18H). 13C NMR (py-d5, ppm): 170.29
(s, N3C), 67.81, 25.79 (2s, THF), 55.43, 35.05, 26.43, 26.06 (4s, C6H11),
2.64 (s, CH3).
Zr[(CH3)2CHNC(N(Si(CH3)3)2)NCH(CH3)2]2Cl2 (1). A reaction
flask was charged with ZrCl4(THF)2 (0.568 g, 1.51 mmol), 50 mL of
diethyl ether, and a stir bar. To this was added Li[(CH3)2CHNC(Si-
(CH3)3)2NCH(CH3)2] (0.906 g, 3.09 mmol). After the reaction mixture
was allowed to stir for 16 h, the mixture was filtered and the solvent
was evaporated from the clear yellow filtrate under vacuum to give a
pale yellow powder (0.464 g, 42%). Colorless crystals were obtained
from toluene at -34 °C. 1H NMR (C6D6, ppm): 3.93 (sept, CH, 4H),
1.48 (d, CH3, 24H), 0.25 (s, CH3, 36H). 13C NMR (C6D6, ppm): 175.23
(s, N3C), 47.33 (s, CH(CH3)2), 25.47 (s, CH(CH3)2), 2.90 (s, SiCH3).
Anal. Calcd for ZrCl2Si4N6C26H64: C, 42.47; H, 8.77; N, 11.43.
Found: C, 42.94; H, 8.90; N, 10.86.
[C6H11NC(Si(CH3)3)2NC6H11]Zr(CH2C6H5)3 (7). In a reaction flask,
compound 5 (1.000 g, 1.21 mmol) was dissolved in 10 mL of toluene.
To the stirring solution was added dropwise C6H5CH2MgCl (4.5 mL,
1.0 M in diethyl ether), and the reaction mixture was allowed to stir
for 2 h. Removal of solvent followed by extraction of the resultant
solid with 10 mL of toluene, filtration, concentration, and cooling to
1
-34 °C gave orange crystals (0.64 g, 72%). H NMR(C6D6, ppm):
7.22-6.91 (mult, C6H5, 15H), 3.50 (br, CH, 2H), 2.50 (s, CH2, 6H),
1.75-0.88 (br, C6H11, 10H), 0.18 (s, CH3, 9H). 13C NMR (C6D6,
ppm): 174.19 (s, N3C), 144.75 (s, C6H5), 129.43, 128.22, 122.83 (3s,
C6H5), 77.36 (s, CH2), 56.38 (s, CH), 35.07, 26.45, 25.68 (3s, C6H11),
2.36 (s, CH3).
Hf[(CH3)2CHNC(N(Si(CH3)3)2)NCH(CH3)2]2Cl2 (2). An experi-
mental procedure similar to that for 1 using HfCl4(THF)2 (1.129 g,
2.43 mmol) and Li[(CH3)2CHNC(Si(CH3)3)2NCH(CH3)2] (1.463 g, 4.98
mmol) in diethyl ether gave an off-white powder (1.399 g, 70% yield).
Acknowledgment. This work was supported by the Natural
Sciences and Engineering Research Council of Canada.
1
Colorless crystals were obtained from toluene at -34 °C. H NMR
Supporting Information Available: Listings of crystal data and
structure refinement details, atomic coordinates, bond distances, bond
angles, and thermal parameters for 3, 4, and 6 and X-ray crystal-
lographic files in CIF format for the structure determinations of 1, 5,
and 7 and in SHELXT.TEX format for the structure determinations of
3, 4, and 6. This material is available free of charge via the Internet at
http://pubs.acs.org.
(C6D6, ppm): 4.11 (sept, CH(CH3)2, 4H), 1.48 (d, CH(CH3)2, 24H),
0.25 (s, CH3, 36H). 13C NMR (C6D6, ppm): 174.69 (s, N3C), 47.02 (s,
CH(CH3)2), 25.48 (s, CH(CH3)2), 2.93 (s, SiCH3). Anal. Calcd for HfCl2-
Si4N6C26H64: C, 37.96; H, 7.84; N, 10.22. Found: C, 37.60; H, 7.80;
N, 9.77.
Zr[C6H11NC(Si(CH3)3)2NC6H11]2Cl2 (3). An experimental procedure
similar to that for 1 using ZrCl4(THF)2 (0.421 g, 1.1 mmol) and Li-
[C6H11NC(Si(CH3)3)2NC6H11] (0.855 g, 2.3 mmol) gave a very light
IC990668I