Conformationally rigid diamide complexes of zirconium: Electron deficient analogues of Cp2Zr

Article abstract of DOI:10.1021/om9604278

Zirconium complexes bearing a pyridine-diamide ligand [2,6-(RNCH₂)₂NC₅H₃]^2- (R = 2,6-diisopropylphenyl, 2,6-diethylphenyl (BDEP), 2,6-dimethylphenyl) have been synthesized. The mixed amide complexes [

Full text of DOI:10.1021/om9604278

5586
Organometallics 1996, 15, 5586-5590
Con for m a tion a lly Rigid Dia m id e Com p lexes of
Zir con iu m : Electr on Deficien t An a logu es of Cp 2Zr
Fre´de´ric Gue´rin,† David H. McConville,*,† and J agadese J . Vittal
Department of Chemistry, University of Western Ontario, London, Ontario, Canada N6A 5B7
Received May 31, 1996X
Zirconium complexes bearing a pyridine-diamide ligand [2,6-(RNCH2)2NC5H3]2- (R ) 2,6-
diisopropylphenyl, 2,6-diethylphenyl (BDEP), 2,6-dimethylphenyl) have been synthesized.
The mixed amide complexes [2,6-(RNCH2)2NC5H3]Zr(NMe2)2 are prepared in high yield from
[2,6-(RHNCH2)2NC5H3] and Zr(NMe2)4. The mixed amides react with excess ClSiMe3 to afford
the dichlorides [2,6-(RNCH2)2NC5H3]ZrCl2 in nearly quantitative yield. Dimethyl complexes
are prepared from [2,6-(RNCH2)2NC5H3]ZrCl2 and 2 equiv of MeMgBr. A single-crystal X-ray
diffraction study of (BDEP)ZrMe2 revealed a distorted trigonal bipyramid structure with
the amides occupying the axial positions. The frontier orbitals of a model of the fragment
(BDEP)Zr are very similar the those of Cp2Zr, suggesting that complexes bearing the
pyridine-diamide ligand may behave as sources of Cp2Zr.
In tr od u ction
gated the R-olefin polymerization chemistry of chelating
diamide ancillaries that incorporate bulky aryl substit-
uents at nitrogen.27 Complexes of the type, [RN(CH2)3-
NR]TiMe2 (R ) 2,6-iPr2C6H3, 2,6-Me2C6H3), when acti-
vated with methyl alumoxane, are highly active catalysts
for the polymerization of 1-hexene. In contrast, the
analogous zirconium complexes show little or no activity
for the polymerization of R-olefins under the same
conditions.28 Strong binding of the cocatalyst to the
electrophilic, low-coordinate zirconium metal center may
preclude formation of a cationic alkyl complex, as has
been observed for other chelating diamides of Ti and
Zr.26
The chemistry of group 4 olefin polymerization cata-
lyst precursors such as Cp2MX2,1,2 CpMX3,3-11 and
linked Cp-amide derivatives,12-18 have been studied
extensively. Much of the work in this area has been
concerned with the way in which the catalytic activity,
comonomer incorporation, and stereoregularity can be
altered with changes to the Cp ligand(s). There is,
however, a growing interest in new non-Cp ligand
environments as possible alternatives for olefin polym-
erization catalysts.19-26 Previously we have investi-
† Current address: Department of Chemistry, University of British
Columbia, 2036 Main Mall, Vancouver, BC, Canada V6T 1Z1.
X Abstract published in Advance ACS Abstracts, November 15, 1996.
(1) Mohring, P. C.; Coville, N. J . J . Organomet. Chem. 1994, 479, 1.
(2) Brintzinger, H. H.; Fischer, D.; Mu¨lhaupt, R.; Rieger, B.;
Waymouth, R. M. Angew. Chem., Int. Ed. Engl. 1995, 34, 1143.
(3) Bochmann, M.; Karger, G.; J aggar, A. J . J . Chem. Soc., Chem.
Commun. 1990, 1038.
(4) Crowther, D. J .; Baenziger, N. C.; J ordan, R. F. J . Am. Chem.
Soc. 1991, 113, 1455.
(5) Pellecchia, C.; Immirzi, A.; Grassi, A.; Zambelli, A. Organome-
tallics 1993, 12, 4473.
We have since turned our attention to a tridentate
diamide ligand system which incorporates a neutral
pyridine donor between the amides.29 This dinegative
ligand has been shown to stabilize five-coordinate
complexes of tantalum30 and titanium31 and appears to
coordinate exclusively in a meridional fashion. In this
paper, we describe the synthesis and structure of
tridentate diamide complexes of zirconium. The simi-
larities between this new ligand system and the typical
coordination geometry of metallocenes32 are presented.
(6) Go´mez, R.; Green, M. L. H.; Haggitt, J . L. J . Chem. Soc., Chem.
Commun. 1993, 1415.
(7) Flores, J . C.; Chien, J . C. W.; Rausch, M. D. Organometallics
1994, 13, 4142.
(8) Quan, R. W.; Bazan, G. C.; Kiely, A. F.; Schaefer, W. P.; Bercaw,
J . E. J . Am. Chem. Soc. 1994, 116, 4489.
(9) Quyoum, R.; Wang, Q.; Tudoret, M.-J .; Baird, M. C. J . Am. Chem.
Soc. 1994, 116, 6435.
Resu lts
The reaction of 2 equiv of LiNHR (R ) 2,6-diisopro-
pylphenyl (BDPP), 2,6-diethylphenyl (BDEP), 2,6-dim-
(10) Bazan, G. C.; Rodriguez, G.; Cleary, B. P. J . Am. Chem. Soc.
1994, 116, 2177.
(11) Fryzuk, M. D.; Mao, S. S. H.; Duval, P. D.; Rettig, S. J .
Polyhedron 1995, 14, 11.
(12) Shapiro, P. J .; Bunel, E.; Schaefer, W. P.; Bercaw, J . E.
Organometallics 1990, 9, 867.
(13) Okuda, J . Chem. Ber. 1990, 123, 1649.
(14) Stevens, J . C.; Timmers, F. J .; Wilson, D. R.; Schmidt, G. F.;
Nickias, P. N.; Rosen, R. K.; Knight, G. W.; Lai, S. Y. (Dow) Eur. Pat.
Appl. EP-416-815-A2, March 13, 1991.
(15) Canich, J . A. (Exxon) Eur. Pat. Appl. EP-420-436-A1, April 4,
1991.
(16) Hughes, A. K.; Meetsma, A.; Teuben, J . A. Organometallics
1993, 12, 1936.
(17) Devore, D. D.; Timmers, F. J .; Hasha, D. L.; Rosen, R. K.;
Marks, T. J .; Deck, P. A.; Stern, C. L. Organometallics 1995, 14, 3132.
(18) Mu, Y.; Piers, W. E.; MacGillivray, L. R.; Zaworotko, M. J .
Polyhedron 1995, 14, 1.
(21) Uhrhammer, R.; Black, D. G.; Gardner, T. G.; Olsen, J . D.;
J ordan, R. F. J . Am. Chem. Soc. 1993, 115, 8493.
(22) Brand, H.; Capriotti, J . A.; Arnold, J . Organometallics 1994,
13, 4469.
(23) van der Linden, A.; Schaverien, C. J .; Meijboom, N.; Ganter,
C.; Orpen, A. G. J . Am. Chem. Soc. 1995, 117, 3008.
(24) Cozzi, P. G.; Gallo, E.; Floriani, C.; Chiesi-Villa, A.; Rizzoli, C.
Organometallics 1995, 14, 4994.
(25) Herskovics-Korine, D.; Eisen, M. S. J . Organomet. Chem. 1995,
503, 307.
(26) Warren, T. H.; Schrock, R. R.; Davis, W. M. Organometallics
1996, 15, 562.
(27) Scollard, J . D.; McConville, D. H.; Vittal, J . J . Macromolecules
1996, 29, 5241.
(28) Scollard, J . D.; McConville, D. H. Unpublished results.
(29) Cai, S.; Schrock, R. R. Inorg. Chem. 1991, 30, 4105.
(30) Gue´rin, F.; McConville, D. H.; Vittal, J . J . Organometallics
1995, 14, 3154.
(31) Gue´rin, F.; McConville, D. H.; Payne, N. C. Organometallics,
in press.
(32) Lauher, J . W.; Hoffmann, R. J . Am. Chem. Soc. 1976, 98, 1729.
(19) Miyatake, T.; Mizunuma, K.; Seki, Y.; Kakugo, M. Makromol.
Chem., Rapid Commun. 1989, 10, 349.
(20) Canich, J . A.; Turner, H. W. (Exxon) W. PCT Int. Appl. WO
92/12162, December 26, 1991.
S0276-7333(96)00427-X CCC: $12.00 © 1996 American Chemical Society

Rigid Diamide Complexes of Zirconium
Organometallics, Vol. 15, No. 26, 1996 5587
Sch em e 1
Ta ble 1. Su m m a r y of Cr ysta llogr a p h ic Da ta ,
Collection P a r a m eter s, a n d Refin em en t
P a r a m eter s for Com p ou n d 4ba
ethylphenyl (BDMP)) with 2,6-bis(bromomethyl)pyri-
dine33 yields the diamine ligands (BDPP)H2 (1a ),
(BDEP)H2 (1b), and (BDMP)H2 (1c), as shown in
Scheme 1. (BDPP)H2 is a white crystalline solid, while
(BDEP)H2 and (BDMP)H2 are viscous oils. All three
diamines can be prepared in 50-80% yield on a scale
of 5-10 g. The aminolysis reaction between the di-
empirical formula
formula weight
crystal color, habit
crystal dimensions (mm)
crystal system
reflections used for unit cell
determination (2θ range (deg))
a (Å)
C29H39N3Zr
520.85
light orange, triclinic
0.54 × 0.26 × 0.23
monoclinic
34
amines 1a -c and Zr(NMe2)4 provides 2 equiv of
26 (24.12-25.02)
HNMe2 and the yellow crystalline mixed amide com-
plexes (BDPP)Zr(NMe2)2 (2a ), (BDEP)Zr(NMe2)2 (2b),
and (BDMP)Zr(NMe2)2 (2c) in greater than 90% yield
(Scheme 1).
12.355(2)
b (Å)
15.761(2)
c (Å)
15.701(3)
â (deg)
111.71(1)
2840.5(8)
V (Å3)
Room temperature proton NMR spectra of complexes
2a -c exhibit a single sharp resonance for the methylene
protons (CH2N) of the ligand consistent with a meridi-
onal coordination mode and local C2v symmetry of the
compounds. The isopropylmethyl groups of complex 2a
and the ethylmethylene protons of compound 2b are
diastereotopic, which we interpret as a consequence of
restricted rotation30 about the N-Cipso bond (no evidence
of N-Cipso bond rotation is observed for compound 2a
to 80 °C). We have no direct spectroscopic means of
determining whether the same restricted rotation exists
in the 2,6-dimethylphenyl substituted derivative 2c;
however, modeling studies35 and other structurally
characterized BDMP complexes31 indicate that the
barrier to rotation is high.
space group
Z
F (calc) (g/mol)
collection temp (°C)
F000
P21/c
4
1.218
25
1096
Mo KR
scan mode
graphite (monochromated)
ω (variable 2-30 deg/min)
4950
3011
total no. of unique reflections
no. of observations with
Fo g 4σ(Fo)
no. of variable parameters
R1
244
0.0592
0.1335
1.038
wR2
goodness of fit (GooF)
a
2
4 1/2
R1 ) ∑(||Fo| - |Fc||)/∑|Fo|; wR2 ) [∑w(Fo - Fc2)2/∑wFo
] ;
GooF ) [∑w(Fo - Fc2)2/(n - p)]1/2 (where n is the number of
reflections and p is the number of parameters refined).
2
Chloride derivatives were desired as precursors to
alkyl derivatives. We have previously shown that [Me2-
NH2]Cl reacts preferentially with the dimethylamido
ligands in the mixed amide complex [RN(CH2)3NR]Zr-
(NMe2)2 (R ) 2,6-iPr2C6H3).36 Presumably, the substit-
uents in the 2,6-position kinetically protect the ligand
amides from proton attack. In contrast, we observe
protonolysis of the BDPP ligand in complex 2a , as has
been noted for other chelating amide derivatives of
zirconium.18 However, a remarkably selective reaction
between compounds 2a -c and excess ClSiMe3 yields the
white crystalline dichloride derivatives in nearly quan-
titative yield (Scheme 1). The chloride complexes 3a -c
are very soluble in THF, soluble in aromatic solvents,
and insoluble in aliphatic solvents. Again, spectral data
for complexes 3a -c are consistent with meridional
coordination of the pyridine-diamide ligand and re-
stricted rotation about the N-Cipso bond.
The readily available dichlorides are excellent precur-
sors for the preparation of a number of alkyl deriva-
tives.37 In particular, reaction of the dichlorides 3a -c
with 2 equiv of MeMgBr affords the white crystalline
dimethyl complexes in 80-90% yield (Scheme 1). The
C2v symmetry of complexes 4a -c is evidenced by a
single sharp resonance (1H NMR) for the ligand meth-
ylene protons (NCH2). The 1H and 13C{1H} NMR
spectra of complex 4a display a Zr-CH3 resonance at
0.45 ppm and a Zr-CH3 signal at 44.71 ppm. These
data are comparable to the closely related complex
[RN(CH2)3NR]ZrMe2 (R ) 2,6-iPr2C6H3; Zr-CH3 δ )
0.42 ppm; Zr-CH3 δ ) 39.9 ppm)36 and other com-
plexes.26,38-41
The solid state structure of 4b was determined by
X-ray crystallography (Table 1). The molecular struc-
ture of complex 4b can be found in Figure 1, and
(33) Haeg, M. E.; Whitlock, B. J .; Whitlock, H. W., J r. J . Am. Chem.
Soc. 1989, 111, 692.
(34) Bradley, D. C.; Thomas, I. M. Proc. Chem. Soc., London 1959,
225.
(35) Calculations were performed on an appropriate model using
CAChe Scientific Inc. software.
(37) Gue´rin, F.; McConville, D. H. Unpublished results.
(38) Anderson, R. A. Inorg. Chem. 1979, 18, 2928.
(39) Anderson, R. A. Inorg. Chem. 1979, 18, 1724.
(40) J ordan, R. F.; Dasher, W. E.; Echols, S. F. J . Am. Chem. Soc.
1986, 108, 1718.
(36) Scollard, J . D.; McConville, D. H.; Vittal, J . J . Organometallics
1995, 14, 5478.
(41) Cummins, C. C.; Baxter, S. M.; Wolczanski, P. T. J . Am. Chem.
Soc. 1988, 110, 8731.

5588 Organometallics, Vol. 15, No. 26, 1996
Gue´rin et al.
F igu r e 2.
F igu r e 1. Chem 3D drawing of the molecular structure
of 4b (top). Chem 3D drawing of the core of 4b (bottom).
relevant bond distances and angles can be found in
Table 2. The structure is best described as a distorted
trigonal bipyramid with the amide nitrogens (N(2) and
N(3)) occupying the axial positions (Figure 1). The
zirconium atom lies 2.4° out of the plane of the three
nitrogens. The Zr-amide distances (2.104(5) and 2.101-
(4) Å) are comparable to other zirconium-amido
complexes.16,36,42-47 Each amide is sp2-hybridized as
evidenced by the sum of the angles about each nitrogen
(N(2) ) 359.9° and N(3) ) 359.9°). The aryl rings lie
perpendicular to the plane of the ligand with dihedral
angles of 89.8° and 89.6°. The rigid coordination of the
ligand and enforced location of the aryl ethyl groups
necessarily protects the metal above and below the N3
plane.
F igu r e 3. Frontier orbitals of 4′ and Cp2Zr.
Ta ble 2. Selected Bon d Dista n ces (Å) a n d
An gles (d eg) for 4b
Bond Distances
Zr(1)-C(1)
Zr(1)-N(1)
Zr(1)-N(3)
2.248(7)
2.325(4)
2.104(5)
Zr(1)-C(2)
Zr(1)-N(2)
2.243(6)
2.101(4)
Bond Angles
N(2)-Zr(1)-N(3)
N(2)-Zr(1)-N(1)
Zr(1)-N(3)-C(3)
C(3)-N(3)-C(20)
Zr(1)-N(2)-C(10)
139.6(2)
70.0(2)
126.4(3)
112.0(4)
122.7(4)
C(1)-Zr(1)-C(2)
N(3)-Zr(1)-N(1)
Zr(1)-N(3)-C(20)
Zr(1)-N(2)-C(9)
C(9)-N(2)-C(10)
102.4(3)
69.7(2)
121.5(3)
126.2(3)
111.0(4)
Ca lcu la tion s
The coordination sphere of compound 4b closely
48
resembles that of Cp2ZrMe2 (Figure 2). The amide-
comparable, and hence the pyridine-diamide ligand
system can be viewed as a Cp2 equivalent.
Zr-amide and Me-Zr-Me angles in 4b are about 7°
larger than the Cent-Zr-Cent (Cent ) Cp centroid) and
Me-Zr-Me angles in Cp2ZrMe2, as expected for a
distorted trigonal bipyramid versus a distorted tetra-
hedron. In addition, the associated bond lengths (amide-
Zr, Cent-Zr, and Me-Zr) of 4b and Cp2ZrMe2 are
Extended Hu¨ckel MO calculations35 were performed
on an idealized (C2v symmetry) model of compound 4b
(4′) and compared to the frontier orbitals of Cp2Zr32
(Figure 3). The b2 orbital of Cp2Zr and the 5b2 orbital
of 4′ (dxz orbital) have very similar energies as a
consequence of the limited π-donation from the pyridine
(42) Alcock, N. M.; Pierce-Butler, M.; Willey, G. R. J . Chem. Soc.,
Chem. Commun. 1974, 627.
(43) Airoldi, C.; Bradley, D. C.; Chudzynska, H.; Hursthouse, M. B.;
Malik, K. M. A.; Raithby, P. R. J . Chem. Soc., Dalton Trans. 1980,
2010.
(44) Planalp, R. P.; Andersen, R. A.; Zalkin, A. Organometallics
1983, 2, 16.
(45) Cummins, C. C.; Duyne, G. D. V.; Schaller, C. P.; Wolczanski,
P. T. Organometallics 1991, 10, 164.
(46) Bai, Y.; Roesky, H. W.; Noltemeyer, M.; Witt, M. Chem. Ber.
1992, 125, 825.
(47) Okuda, J .; Schattenmann, F. J .; Wocadlo, S.; Massa, W.
Organometallics 1995, 14, 789.
(48) Hunter, W. E.; Hrncir, D. C.; Bynum, V.; Penttila, R. A.; Atwood,
J . L. Organometallics 1983, 2, 750.
2
to the zirconium. In contrast, the 12a1 orbital (dz ) of
4′ is raised in energy relative to the 1a1 orbital of Cp2-
Zr due to the significant σ-donation from the pyridine.
This also raises the energy of the 13a1 orbital (dx -y )
of 4′, albeit to a lesser extent. Other orbitals of interest
include the 10b1 orbital (dxy) of 4′, which appears at low
energy compared to Cp2Zr, due to the absence of a
second π-bond in the amides.
2
2
It was noted that the reaction of (BDPP)Zr(NMe2)2
with [Me2NH2]Cl resulted in protonolysis of the appar-

Rigid Diamide Complexes of Zirconium
Organometallics, Vol. 15, No. 26, 1996 5589
used as received. 2,6-Dimethylaniline, 2,6-diethylaniline, and
2,6-diisopropylaniline were purchased from Aldrich and dis-
tilled under reduced pressure before use. Methylmagnesium
bromide was purchased from Aldrich and used as received.
ently more basic amides of the BDPP ligand. This is
supported by the observation of a ligand centered
nonbonding orbital on the amides (4b2, HOMO-3). The
34
Zr(NMe2)4 was synthesized as reported in the literature.
Unless otherwise specified, proton (300 MHz) and carbon
(75.46 MHz) NMR spectra were recorded in C6D6 at ap-
proximately 22 °C on a Varian Gemini-300 spectrometer. The
proton chemical shifts were referenced to internal C6D5H (δ
) 7.15 ppm) and the carbon resonances to C6D6 (δ ) 128.0
ppm). Elemental analyses were performed by Oneida Re-
search Services, Inc., Whitesboro, NY.
2,6-[RHNCH2]2NC5H3 (R ) 2,6-Diisopr opylph en yl), (BD-
P P )H2 (1a ). A THF (150 mL) solution of LiNHR (12.226 g,
66.77 mmol) was added slowly to a stirring THF (100 mL)
solution of 2,6-bis(bromomethyl)pyridine (8.842 g, 33.37 mmol)
at -78 °C. The mixture was warmed to room temperature
and stirred for 12 h. The solution was quenched with a
saturated NaHCO3 solution (100 mL) and extracted with ether.
The solvent was removed in vacuo, and the resulting solid was
dissolved in a minimum amount of hexanes and cooled to -30
°C for 12 h. A white crystalline 1a was isolated by filtration
and dried under vacuum (7.792 g, 17.02 mmol, 51%). 1H
NMR: δ 7.10-7.20 (m, 6H, Ar), 7.12 (t, 1H, py), 6.84 (d, 2H,
py), 4.24 (s, 4H, NCH2), 3.53 (sept, 4H, CHMe2), 1.24 (d, 24H,
CHMe2). 13C{1H} NMR: δ 158.21, 154.18, 143.27, 137.25,
125.12, 124.17, 121.16, 57.02, 28.24, 24.62. MS (EI): m/ z
457.346 (M+). Calcd for C31H43N3: 457.346.
2,6-[RHNCH2]2NC5H3 (R ) 2,6-Dieth ylp h en yl), (BDEP )-
H2 (1b). The preparation of compound 1b is identical to that
for 1a . LiNHR (10.40 g, 67.02 mmol) and 2,6-bis(bromometh-
yl)pyridine (8.876 g, 33.50 mmol) gave a yellow-brown liquid
1b (9.753 g, 24.29 mmol, 73%). 1H NMR: δ 6.90-7.10 (m,
6H, Ar and py), 6.80 (d, 2H, py), 4.35 (broad, 2H, NH), 4.19 (s,
4H, NCH2), 2.72 (q, 8H, CH2CH3), 1.21 (t, 12H, CH2CH3). 13C-
{1H} NMR: δ 128.93, 145.77, 136.86, 136.36, 127.17, 123.20,
120.27, 56.44, 25.10, 15.17. MS (EI): m/ z 401.284 (M+). Calcd
for C27H35N3: 401.283.
2,6-[RHNCH2]2NC5H3 (R ) 2,6-Dim eth ylp h en yl), (BD-
MP )H2 (1a ). The preparation of compound 1c is identical to
that for 1a . LiNHR (2.879 g, 22.65 mmol) and 2,6-bis-
(bromomethyl)pyridine (3.000 g, 11.32 mmol) gave a yellow-
brown liquid 1c (3.105 g, 8.987 mmol, 79%). 1H NMR: δ 6.95-
7.05 (m, 5H, Ar and py), 6.86 (m, 2H, Ar), 6.67 (d, 2H, py),
4.21 (broad, 2H, NH), 4.15 (s, 4H, NCH2), 2.25 (s, 12H, Me).
13C{1H} NMR: δ 159.04, 146.88, 136.72, 18.50, 129.24, 122.18,
120.24, 53.93, 18.87. MS (EI): m/ z 345.220 (M+). Calcd for
dimethylamido groups in (BDPP)Zr(NMe2)2 can utilize
a combination of the 5b2 and 10b1 orbitals for π-bond
formation. The 5b2 orbital mentioned above is of the
correct symmetry to interact with the symmetrical
combination of the p-orbitals on the amides; however,
the amide-Zr-amide angle of 139.6(2)° precludes ef-
ficient overlap (a small contribution from the pz (0.2%)
and the dxz (0.5%) orbitals of Zr is present). Conse-
quently, the pyridine-diamide ligand is formally an
eight-electron donor, four electrons less than the com-
bination of two cyclopentadienyl ligands. The zirconium
metal center in these new complexes is likely to be very
electrophilic which may, in part, explain the statistically
shorter Zr-Me bonds in compound 4b (2.243(6) and
2.248(7) Å) versus Cp2ZrMe2 (2.273(5) and 2.280(5) Å).
The 2a2 orbital (HOMO-5) represents the π-overlap of
the amide p-orbitals with the metal dyz orbital. The
antibonding combination of this orbital is the 4a2 orbital
(Figure 3).
Con clu sion
In summary, a high-yield route into pyridine-diamide
complexes of zirconium has been demonstrated. The
restricted rotation about the N-Cipso bond of the ligand
and the availability of substituted anilines provide an
opportunity to vary the sterics with little change to the
electronic environment about the metal. In addition,
the pyridine-diamide ligand system exhibits coordina-
tion behavior at zirconium which is very similar to a
metallocene (Cp2ZrX2). The three frontier orbitals of a
metallocene (1a1, b2, 2a1) are present in these new
fragments, albeit at slightly different energies. The
ligand-centered nonbonding orbital based on the amide
nitrogens gives rise to an unusually low electron count
at zirconium; for example, (BDEP)ZrMe2 is formally a
12-electron complex. Finally, the molecular structure
of (BDEP)ZrMe2 has revealed a coordination geometry
which is expected to direct an incoming olefin cis to the
Zr-Me bond in a putative cationic alkyl complex (e.g.,
(BDEP)ZrMe+). Work is in progress to isolate an
authentic cationic alkyl complex. Successful polymer-
ization of olefins49 and further ligand variations will be
reported shortly.
C
23H27N3: 345.220.
(BDP P )Zr (NMe2)2 (2a ). A toluene solution of Zr(NMe2)4
(1.748 g, 6.534 mmol) was added to a toluene solution (50 mL)
of 1a (2.990 g, 6.532 mmol) at room temperature. The solution
was refluxed for 12 h. The solvent was removed in vacuo, and
the resulting solid was extracted with hexanes (3 × 50 mL)
and filtered through Celite. The volume of the filtrate was
reduced to 50 mL and cooled to -30 °C for 12 h. Yellow
crystalline 2a was isolated by filtration and dried under
vacuum (1.791 g, 3.425 mmol, 92%). 1H NMR: δ 7.05-7.20
(m, 6H, Ar), 6.87 (t, 1H, py), 6.47 (d, 2H, py), 4.81 (s, 4H,
NCH2), 3.69 (sept, 4H, CHMe2), 2.53 (s, 12H, NMe2), 1.31 (d,
12H, CHMe2), 1.29 (d, 12H, CHMe2). 13C{1H} NMR: δ 163.26,
150.89, 146.28, 137.56, 124.59, 123.73, 117.18, 60.62, 41.51,
28.06, 26.44, 24.69. Anal. Calcd for C35H53N5Zr: C, 66.20;
H, 8.41; N, 11.03. Found: C, 66.69; H, 8.39; N, 10.77.
(BDEP )Zr (NMe2)2 (2b). The preparation of compound 2b
is identical to that for complex 2a . Zr(NMe2)4 (1.000 g, 3.738
mmol) and compound 1b (1.500 g, 3.735 mmol) gave yellow
crystalline 2b (1.950 g, 3.368 mmol, 90%). 1H NMR: δ 7.21
(d, 6H, Ar), 7.05 (m, 2H, Ar), 6.88 (t, 1H, py), 6.47 (d, 2H, py),
4.69 (s, 4H, NCH2), 2.86 (m, 8H, CH2CH3), 2.58 (s, 12H, NMe2),
1.29 (t, 12H, CH2CH3). 13C{1H} NMR: δ 164.07, 152.54,
141.22, 138.63, 126.03, 123.83, 117.30, 62.27, 41.44, 24.39,
15.85.
Exp er im en ta l Section
Gen er a l Deta ils. All experiments were performed under
a dry dinitrogen atmosphere using standard Schlenk tech-
niques or in an Innovative Technology, Inc., glovebox. Solvents
were distilled from sodium/benzophenone ketyl (DME, THF,
hexanes, diethyl ether, and benzene) or molten sodium (tolu-
ene) under argon and stored over activated 4 Å molecular
sieves. Zirconium(IV) chloride was purchased from Alfa and
(49) Compound 3a (10 µmol), activated with MAO (Al:Zr ) 500:1),
in 50 mL toluene under 4 atm ethylene for 5 min: activity, 6000 g of
poly(ethylene)/mmol of catalyst‚h.

5590 Organometallics, Vol. 15, No. 26, 1996
Gue´rin et al.
(BDMP )Zr (NMe2)2 (2c). The preparation of compound 2c
is identical to that for complex 2a . Zr(NMe2)4 (1.000 g, 3.738
mmol) and compound 1c (1.300 g, 3.763 mmol) gave yellow
crystalline 2c (1.950 g, 3.368 mmol, 90%). 1H NMR: δ 7.16
(d, 4H, Ar), 6.97 (m, 2H, Ar), 6.90 (t, 1H, py), 6.46 (d, 2H, py),
4.63 (s, 4H, NCH2), 2.58 (s, 12H, NMe2), 2.37 (s, 12H, Me).
13C{1H} NMR: δ 164.45, 153.25, 137.54, 135.67, 128.58,
123.34, 117.34, 63.70, 41.32, 18.86.
(BDP P )Zr Cl2 (3a ). ClSiMe3 (5.200 g, 47.86 mmol) was
added to a toluene solution (50 mL) of 2a (3.000 g, 4.724 mmol)
at room temperature. The solution was stirred for 12 hours,
and a white precipitate gradually formed. The solution was
cooled to -30 °C. White crystalline 3a was isolated by
filtration and dried under vacuum (2.862 g, 4.632 mmol, 98%).
1H NMR: δ 7.10-7.20 (m, 6H, Ar), 6.76 (t, 1H, py), 6.27 (d,
2H, py), 4.81 (s, 4H, NCH2), 3.74 (sept, 4H, CHMe2), 1.54 (d,
12H, CHMe2), 1.20 (d, 12H, CHMe 2). 13C{1H} NMR: δ 162.94,
146.03, 138.86, 127.40, 124.72, 117.74, 68.19, 28.59, 27.03,
24.78.
(BDEP )Zr Cl2 (3b). The preparation of compound 3b is
identical to that for complex 3a . ClSiMe3 (2.705 g, 24.90 mmol)
and compound 2b (1.434 g, 2.477 mmol) gave light orange
crystalline 3b (1.378 g, 2.453 mmol, 99%). 1H NMR: δ 7.10-
7.20 (m, 6H, Ar), 6.86 (t, 1H, py), 6.37 (d, 2H, py), 4.63 (s, 4H,
NCH2), 2.98 (m, 8H, CH2CH3), 1.29 (t, 12H, CH2CH3). 13C-
{1H} NMR: δ 163.93, 154.80, 141.74, 138.68, 127.12, 126.72,
117.81, 67.20, 24.60, 15.58.
(BDMP )Zr Cl2 (3c). The preparation of compound 3c is
identical to that for complex 3a . ClSiMe3 (9.430 g, 86.80 mmol)
and compound 2c (4.538 g, 8.679 mmol) gave white crystalline
3c (4.021 g, 7.953 mmol, 92%). 1H NMR: δ 7.09 (m, 4H, Ar),
7.03 (m, 2H, Ar), 6.84 (t, 1H, py), 6.36 (d, 2H, py), 4.44 (s, 4H,
NCH2), 2.46 (s, 12H, Me). 13C{1H} NMR: δ 163.01, 153.03,
138.46, 136.24, 129.31, 127.37, 117.70, 65.60, 19.30.
(BDP P )Zr Me2 (4a ). To a suspension of compound 3a
(0.250 g, 0.405 mmol) in diethyl ether (25 mL) was added 2.2
equiv of MeMgBr (0.49 mL, 1.80 M, 0.88 mmol) at room
temperature. The mixture was stirred for 12 h. The solvent
was removed in vacuo. The resulting solid was extracted with
toluene (3 × 10 mL) and filtered through Celite to give a light
yellow solution. The solvent was removed in vacuo, and the
solid was dissolved in a minimum amount of diethyl ether and
cooled to -30 °C for 12 h. White crystalline 4a was isolated
by filtration and dried under vacuum (0.207 g, 0.359 mmol,
89%). 1H NMR: δ 7.20-7.30 (m, 6H, Ar), 6.88 (t, 1H, py), 6.40
(d, 2H, py), 4.95 (s, 4H, NCH2), 3.84 (sept, 4H, CHMe2), 1.41
(d, 12H, CHMe2), 1.21 (d, 12H, CHMe2), 0.45 (s, 6H, ZrMe2).
13C{1H} NMR: d 163.94, 147.12, 137.98, 126.38, 124.44,
117.36, 67.48, 44.71 (ZrMe2), 28.32, 28.17, 24.18. Anal. Calcd
for C33H47N3Zr: C, 68.70; H, 8.21; N, 7.28. Found: C, 69.50;
H, 8.57; N, 7.49.
(BDEP )Zr Me2 (4b). The preparation of compound 4b is
identical to that for complex 4a . Compound 3b (0.400 g, 0.712
mmol) and 2.2 equiv of MeMgBr (0.87 mL, 1.80 M, 1.57 mmol)
gave white crystalline 4b (0.307 g, 0.589 mmol, 83%). 1H
NMR: δ 7.30-7.20 (m, 6H, Ar), 6.87 (t, 1H, py), 6.45 (d, 2H,
py), 4.77 (s, 4H, NCH2), 2.94 (m, 8H, CH2CH3), 1.27 (t, 12H,
CH2CH3), 0.29 (s, 6H, ZrMe2). 13C{1H} NMR: δ 164.34, 146.73,
142.63, 137.83, 126.60, 126.08, 117.60, 66.41, 42.83 (ZrMe2),
24.14, 16.17. Anal. Calcd for C29H39N3Zr: C, 66.87; H, 7.55;
N, 8.07. Found: C, 66.37; H, 7.71; N, 7.83.
gave white crystalline 4c (0.074 g, 0.159 mmol, 80%). 1H
NMR: δ 7.16 (m, 4H, Ar), 7.06 (m, 2H, Ar), 6.88 (t, 1H, py),
6.44 (d, 2H, py), 4.58 (s, 4H, NCH2), 2.40 (s, 12H, Me), 0.34 (s,
6H, ZrMe2). 13C{1H} NMR: δ 164.34, 142.83, 137.56, 136.81,
128.87, 125.47, 117.42, 64.60, 47.88 (ZrMe2), 18.54.
Molecu la r Or bita l Ca lcu la tion s. All molecular orbital
calculations were performed on a CAChe Worksystem, a
product developed by Tektronix. The parameters used for the
extended Hu¨ckel calculations of the model 4′ (restricted to C2v
symmetry) were taken from the literature50 and are listed in
the Supporting Information. The bond lengths and angles for
4′ were taken from the X-ray crystal structure analysis of
(BDEP)ZrMe2 (vide supra). The Cartesian coordinates and a
full list of the eigenvalues and symmetry labels for the model
can be found in the Supporting Information. For the model,
the following standard bond lengths were used: C-H, 1.090
Å; N-H, 1.070 Å.
X-r a y Cr ysta llogr a p h ic An a lysis. A suitable crystal of
4b was grown from a saturated ether solution at -30 °C.
Crystal data may be found in Table 1. Data were collected on
a Siemans P4 diffractometer with the XSCANS software
package.51 The Laue symmetry 2/m was determined by
merging symmetry equivalent positions. A total of 5706 data
were collected in the range of θ ) 1.77-25.0° (-1 e h e 14,
-1 e k e 18, -18 e l e 17). Three standard reflections
monitored at the end of every 297 reflections collected showed
no decay of the crystal. The data processing, solution, and
refinement were done using SHELXTL-PC programs.52 The
faces of the crystal were indexed, and the distance between
them was measured for a Gaussian absorption correction on
the data. During the least-squares cycles, the isotropic tem-
perature factor for methyl groups C(19) and C(29) were
relatively high, 0.15 and 0.13, respectively. Attempts to model
the disorder did not yield satisfactory results. Anisotropic
thermal parameters were refined for all non-hydrogen atoms
except the carbons in the two phenyl rings. The phenyl and
pyridine were restrained to have 2-fold symmetry. The C-Me
distances were restrained to be equal using the option SADI.
Some hydrogens were observed in the least-squares cycles;
however, no attempt was made to locate them. All hydrogens
were placed in calculated positions. In the final difference
Fourier synthesis, the electron density fluctuates in the range
from 0.891 to -0.421 e Å3.
Ack n ow led gm en t . Funding from the NSERC
(Canada), in the form of a Research Grant to D.H.M.,
and Union Carbide Canada is gratefully acknowledged.
Su p p or tin g In for m a tion Ava ila ble: Listings of the
extended Hu¨ckel parameters, Cartesian coordinates for 4′,
labeled model of 4′, eigenvalue and symmetry labels for 4′,
X-ray crystallographic details, crystal data and experimental
details, final crystallographic atomic coordinates and equiva-
lent isotropic thermal parameters, complete tables of bond
lengths and angles, anisotropic thermal parameters, hydrogen
atom parameters, torsional angles, least-squares planes for 4b,
and crystal structure for 4b (14 pages). Ordering information
can be found on any current masthead page.
OM9604278
(50) Hoffmann, R. J . Chem. Phys. 1963, 39, 1397.
(51) XSCANS: Siemans Analytical X-ray Instruments Inc., Madison
WI, 1990.
(52) SHELXTL, Version 5: Siemans Analytical X-ray Instruments
Inc., Madison WI, 1994.
(BDMP )Zr Me2 (4c). The preparation of compound 4c is
identical to that for complex 4a . Compound 3c (0.100 g, 0.198
mmol) and 2.2 equiv of MeMgBr (0.24 mL, 1.80 M, 0.432 mmol)