Synthesis and structure of zirconium(IV) complexes stabilized by the bis(amido-phosphine) macrocycle [P2N2] {[P2N2] = PhP(CH2SiMe2NSiMe2CH2) 2PPh}

Article abstract of DOI:10.1021/om9707984

The preparation and characterization of a series of zirconium(IV) complexes that incorporate the macrocyclic bis(amido - phosphine) ligand PhP(CH₂SiMe₂NSiMe₂CH₂) ₂PPh, [P₂N₂], are described. The starting material, ZrCl₂[P₂N₂], is prepared by reaction of syn-Li₂(S)[P₂N₂] (S = dioxane or THF) with ZrCl₄L₂ (L = THT, tetrahydrothiophene; L = THF, tetrahydrofuran). Subsequent replacement of the chloride ligands can be achieved to generate the dialkyl complexes ZrR₂[P₂N₂] (R = Me, CH₂Ph). Reaction with magnesium butadiene , Mg(C₄H₆)·2THF, results in the formation of π-η⁴-butadiene complex Zr(η⁴-C₄H₆)[P₂N₂]. In addition, the tert-butylimido complex Zr(NBu^t)[P₂N₂] can be prepared by addition of LiNHBu^t to ZrCl₂[P₂N₂]. A number of the above complexes have been characterized by X-ray crystallography, and all show that the Zr center sits above the plane defined by the donor atoms of the macrocyclic ligand. The distortions of the macrocyclic ring observed in the solid state are not evident in solution and suggest that these ligand backbones are considerably flexible.

Full text of DOI:10.1021/om9707984

846
Organometallics 1998, 17, 846-853
Syn th esis a n d Str u ctu r e of Zir con iu m (IV) Com p lexes
Sta bilized by th e Bis(a m id o-p h osp h in e) Ma cr ocycle
[P 2N2] {[P 2N2] ) P h P (CH2SiMe2NSiMe2CH2)2P P h }
Michael D. Fryzuk,* J ason B. Love, and Steven J . Rettig†
Department of Chemistry, University of British Columbia, 2036 Main Mall,
Vancouver, British Columbia V6T 1Z1, Canada
Received September 10, 1997
The preparation and characterization of a series of zirconium(IV) complexes that incor-
porate the macrocyclic bis(amido-phosphine) ligand PhP(CH2SiMe2NSiMe2CH2)2PPh, [P2N2],
are described. The starting material, ZrCl2[P2N2], is prepared by reaction of syn-Li2(S)-
[P2N2] (S ) dioxane or THF) with ZrCl4L2 (L ) THT, tetrahydrothiophene; L ) THF, tetra-
hydrofuran). Subsequent replacement of the chloride ligands can be achieved to generate
the dialkyl complexes ZrR2[P2N2] (R ) Me, CH2Ph). Reaction with “magnesium butadiene”,
Mg(C4H6)‚2THF, results in the formation of π-η4-butadiene complex Zr(η4-C4H6)[P2N2]. In
addition, the tert-butylimido complex Zr(NBut)[P2N2] can be prepared by addition of LiNHBut
to ZrCl2[P2N2]. A number of the above complexes have been characterized by X-ray crys-
tallography, and all show that the Zr center sits above the plane defined by the donor atoms
of the macrocyclic ligand. The distortions of the macrocyclic ring observed in the solid state
are not evident in solution and suggest that these ligand backbones are considerably flexible.
In tr od u ction
similar donor sets and prevent dissociation, we have
recently reported13 the preparation of a macrocyclic
version of ligand I that is shown as II (Chart 1). This
macrocycle can be compared to other similar cyclic
ligand arrays such as porphyrins, phthalocyanines,
tetraazannulenes (TAA), and related systems.14-18
One of the attractive features of macrocyclic type
ligands is that the cavity size can be such that larger
metal ions are forced to sit above the plane of the donors
resulting in more exposure of the metal’s coordination
sphere.19,20 Such is the case for group 3 and 4 metal
complexes incorporating porphyrins and tetraazan-
nulenes.19-28 However, in some cases it has been
The coordination chemistry of the group 4 elements
Ti, Zr, and Hf has been dominated by complexes
containing cyclopentadienyl ligands.1 The combination
of a group 4 metal and two cyclopentadienyl rings, the
so-called metallocenes, is of particular current interest
because these systems are considered to be the next
generation of polymerization catalysts.2-9 In an effort
to expand the coordination chemistry of the group 4
elements we have developed other ancillary ligand
environments using the simple strategy of combining
different donor types into chelating arrays. Our original
ancillary ligand design I involved the combination of an
amido unit flanked by two phosphine donors in a
potentially tridentate chelating array.10,11 While much
new chemistry has accrued with this ligand, the ligand
system was prone to phosphine dissociation because of
its intrinsic acyclic nature.12 In an effort to develop
(12) Fryzuk, M.; Carter, A.; Rettig, S. J . Organometallics 1992, 11,
469.
(13) Fryzuk, M. D.; Love, J . B.; Rettig, S. J . J . Chem. Soc., Chem.
Commun. 1996, 2783.
(14) Buchler, J . W. The Porphyrins; Dolphin, D., Ed.; Academic
Press, Inc.: New York, 1978; Vol. 1, p 390.
(15) Guillard, R.; Kadish, K. M. Chem. Rev. (Washington, D.C.) 1988,
88, 1121.
(16) Smith, K. M. Porpyhrins and Metalloporphyrins; Elsevier: New
York, 1975.
(17) Rogers, A. J .; Solari, E.; Floriani, C.; Chiesi-Villa, A.; Rizzoli,
C. J . Chem. Soc., Dalton Trans. 1997, 2385.
(18) Lee, L.; Berg, D. J .; Bushnell, G. W. Organometallics 1997, 16,
2556.
† Professional Officer, UBC Structural Chemistry Laboratory.
(1) Cardin, D. J .; Lappert, M. F.; Raston, C. L. Chemistry of Organo-
Zirconium and -Hafnium Compounds; Ellis Horwood: West Sussex,
U.K., 1986.
(2) Bochmann, M. J . Chem. Soc., Dalton Trans. 1996, 255.
(3) Bochmann, M.; J aggar, A. J . J . Organomet. Chem. 1992, 424,
C5.
(4) Hlatky, G. G.; Eckman, R. R.; Turner, H. W. Organomet. Synth.
1992, 11, 1413.
(5) Coughlin, E. B.; Bercaw, J . E. J . Am. Chem. Soc. 1992, 114, 7606.
(6) Chien, J . C. W.; Tsai, W. M.; Rausch, M. D. J . Am. Chem. Soc.
1991, 113, 8570.
(7) Kaminsky, W.; Sinn, H. Transition Metals and Organometallics
as Catalysts for Olefin Polymerization; Springer: New York, 1988.
(8) Hlatky, G. G.; Turner, H. W.; Eckman, R. R. J . Am. Chem. Soc.
1989, 111, 2728.
(9) Schneider, N.; Huttenloch, M. E.; Stehling, U.; Kirsten, R.;
Schaper, F.; Brintzinger, H. H. Organometallics 1997, 16, 3413.
(10) Fryzuk, M. D. Can. J . Chem. 1992, 70, 2839.
(11) Fryzuk, M. D.; Berg, D. J .; Haddad, T. S. Coord. Chem. Rev.
1990, 99, 137.
(19) Brand, H.; Arnold, J . Coord. Chem. Rev. 1995, 140, 137.
(20) Black, D. G.; Swenson, D. C.; J ordan, R. F.; Rogers, R. D.
Organometallics 1995, 14, 3539.
(21) Brand, H.; Arnold, J . Organometallics 1993, 12, 3655.
(22) Brand, H.; Capriotti, J . A.; Arnold, J . Organometallics 1994,
13, 4469.
(23) Brand, H.; Arnold, J . Angew. Chem., Int. Ed. Engl. 1994, 33,
95.
(24) Floriani, C.; Ciurli, S.; Chiesi-Villa, A.; Guastini, C. Angew.
Chem., Int. Ed. Engl. 1987, 26, 70.
(25) Giannini, L.; Solari, E.; Floriani, C.; Chiesi-Villa, A.; Rizzoli,
C. Angew. Chem., Int. Ed. Engl. 1994, 33, 2204.
(26) Giannini, L.; Solari, E.; Angelis, S. D.; Ward, T. R.; Floriani,
C.; Chiesi-Villa, A.; Rizzoli, C. J . Am. Chem. Soc. 1995, 117, 5801.
S0276-7333(97)00798-X CCC: $15.00 © 1998 American Chemical Society
Publication on Web 02/11/1998

Zirconium(IV) Complexes Stabilized by a Macrocycle
Organometallics, Vol. 17, No. 5, 1998 847
Ch a r t 1
F igu r e 1. Molecular structure and numbering scheme for
ZrCl2[P2N2] (1). The silylmethyl substituents have been
omitted for clarity as have the phenyl rings attached to
phosphorus except that the ipso carbons (C(13) and C(19))
have been retained.
Sch em e 1
observed that hydrocarbyl ligands show a propensity to
migrate from the metal to the imine carbons of such
types of macrocycles, thus complicating their usefulness
as spectator ligands. In contrast, group 4 complexes in-
corporating a tetraazamacrocyclic tropocoronand ligand
have been shown to be robust against this type of trans-
formation and have shown “metallocene-like” reactiv-
ity.29 In addition, employment of the porphyrinogen
skeleton with group 4 metals has yielded complexes that
act as carriers for polar organometallics.30,31 Recently,
macrocyclic systems that contain dialkylamido units
have been examined as ancillary ligands with Zr(IV).17,18
We have recently reported the coordination chemistry
of the macrocyclic ligand II with zirconium to generate
a reactive zirconium dinitrogen species.32 In this article
we report the full details of the syntheses and structures
of a variety of organozirconium complexes incorporating
this ligand.
Resu lts a n d Discu ssion
The high-yield synthesis of the precursor zirconium
dichloride complex 1 was accomplished by the reaction
of solvated syn-Li2(S)[P2N2] (S ) THF or dioxane)13 with
ZrCl4(THT)2 or ZrCl4(THF)2 as detailed in Scheme 1.
The route involving Li2(dioxane)[P2N2] is aided if the
dioxane is displaced in-situ, conveniently achieved by
conducting the reaction in THF; the product 1 is isolated
base free as shown by NMR spectroscopy and elemental
analyses.
Crystals of 1 suitable for X-ray diffraction were grown
from a saturated toluene solution; the solid-state mo-
lecular structure is shown in Figure 1; crystal data are
given in Table 1, and selected bond lengths and angles,
detailed in Table 2. The complex is observed to adopt
a distorted octahedral geometry, with N(1), N(2), Cl(1),
and Cl(2) occupying a square plane displaying a com-
bined equatorial angle of 360.4° and P(1) and P(2) in
axial positions but pinched back from the optimum
180° to give a P(1)-Zr-P(2) angle of 152.51(6)°, pre-
sumably due to the constraints of the macrocyclic
framework. The Zr-N, -P, and -Cl bond lengths are
not unusual and compare to other Zr-amido and
phosphine complexes.11,12,20,21,32,33
As with zirconium porphyrin and tetraazaannulene
(TAA) complexes, the zirconium ion is too large to fit in
the 12-membered macrocyclic cavity and thus sits atop
the ring skeleton, forcing the remaining chloride ligands
to be cis to each other. In porphyrins and related TAA
complexes, the distance that the metal is displaced from
the plane of the conjugated N4 plane can be determined;
however, it is not possible to easily quantify this effect
in the Zr[P2N2] complexes reported here since a plane
for the nonconjugated P and N donors cannot easily be
described. In addition, the P2N2 framework is very
distorted, adopting a C2-twist in the solid state which
is presumably caused by the trigonal planarity of the
Me2Si-N-SiMe2 links, a feature observed in many
metal complexes that incorporate the acyclic N(SiMe2-
CH2PR2)2 ligand (I).
(27) Schaverien, C. J . J . Chem. Soc., Chem. Commun. 1991, 458.
(28) Schaverien, C. J .; Orpen, A. G. Inorg. Chem. 1991, 30, 4968.
(29) Scott, M. J .; Lippard, S. J . J . Am. Chem. Soc. 1997, 119, 3411.
(30) J acoby, D.; Isoz, S.; Floriani, C.; Chiesi-Villa, A.; Rizzoli, C. J .
Am. Chem. Soc. 1995, 117, 2793.
(31) J acoby, D.; Isoz, S.; Floriani, C.; Schenk, K.; Chiesi-Villa, A.;
Rizzoli, C. Organometallics 1995, 14, 4816.
The solid-state structure of 1 (approximate C2 sym-
metry) is not reflected in solution at ambient temper-
ature by NMR spectroscopy; the solution structure is
more consistent with a C2v symmetry for the ligand
substituents. Thus, only two types of silyl methyl
(32) Fryzuk, M. D.; Love, J . B.; Rettig, S. J .; Young, V. G., J r. Science
1997, 275, 1445.

848 Organometallics, Vol. 17, No. 5, 1998
Fryzuk et al.
Ta ble 1. Cr ysta llogr a p h ic Da ta
3a
compd
formula
fw
1a
4a
6b
C24H42Cl2N2P2Si4Zr
695.02
C38H56N2P2Si4Zr
806.38
C28H48N2P2Si4Zr
678.21
C28H51N3P2Si4Zr
695.24
color, habit
cryst size, mm
cryst system
space group
a, Å
colorless, prism
0.30 × 0.45 × 0.45
orthorhombic
P212121 (No. 19)
16.791(1)
21.600(2)
9.368(3)
yellow, prism
0.35 × 0.50 × 0.50
monoclinic
C2/c (No. 15)
28.911(5)
28.921(5)
23.112(4)
108.57(1)
18318(4)
16
1.169
6784
4.40
0.87-1.00
ω-2θ
1.05 + 0.35 tan θ
16 (up to 9 scans)
+h,+k, (l
50
red, irregular
0.25 × 0.25 × 0.50
monoclinic
P21/n (No. 14)
14.378(2)
12.315(2)
20.083(3)
102.76(1)
3468.2(9)
4
1.299
1424
5.67
0.96-1.00
ω-2θ
1.21 + 0.35 tan θ
8 (up to 9 scans)
+h,+k,( l
55
yellow, prism
0.20 × 0.35 × 0.40
monoclinic
P21/n (No. 14)
11.6869(12)
21.985(2)
14.9311(3)
99.6680(10)
3781.9(4)
4
b, Å
c, Å
b, deg
90
V, Å3
3397.5(10)
4
1.359
1440
7.25
0.90-1.00
ω-2θ
0.94 + 0.35 tan θ
16 (up to 9 scans)
+h,+k,+l
60
Z
F
calc, g/cm3
1.221
1464
F(000)
µ(Mo KR), cm-1
transm factors
scan type
5.22
0.61-1.09c
ω
scan range, deg in ω
scan rate, deg/min
data collcd
0.5
full sphere
55.8
negligible
37 009
8946
2θmax, deg
cryst decay, %
tot. no. of reflcns
no. of unique reflcns
Rmerge
negligible
5511
5511
1.8
16 868
16 469
0.052
4.4
8667
8344
0.038
0.055
reflcns with I g 3σ(I)
no. of variables
R(F, I g 3σ(I))
Rw(F, I g 3σ(I))
R(F2, all data)
Rw(F2, all data)
gof
2980
317
0.039
0.033
6262
848
0.046
0.045
4010
334
0.034
0.031
4934
343
0.041
0.025
0.066
0.053
1.83
1.69
2.04
1.57
max ∆/σ (final cycle)
0.0007
-0.71 to +0.80
0.001
-0.34 to +0.49
0.001
-0.30 to +0.40
0.001
-1.19 to +1.24
residual density, e/Å3
a
Temperature 294 K, Rigaku AFC6S diffractometer, Mo KR radiation (λ ) 0.710 69 Å), graphite monochromator, takeoff angle 6.0°,
aperture 6.0 × 6.0 mm at a distance of 285 mm from the crystal, stationary background counts at each end of the scan (scan/background
time ratio 2:1, up to 8 rescans), σ2(F2) ) [S2(C + 4B)]/Lp2 (S ) scan rate, C ) scan count, B ) normalized background count), function
minimized ∑w(|Fo| - |Fc|)2, where w ) 4Fo2/σ2(Fo2), R ) ∑||Fo| - |Fc||/∑|Fo|, Rw ) (∑w(|Fo| - |Fc|)2/∑w|Fo| )1/2, and gof ) [∑w(|Fo| - |Fc|)2/
2
b
(m - n)]1/2. Values given for R, Rw, and gof are based on those reflections with I g 3σ(I). Temperature 294 K, Rigaku/ADSC CCD
diffractometer, Mo KR radiation (λ ) 0.710 69 Å), graphite monochromator, takeoff angle 6.0°, aperture 94 × 94 mm at a distance of
39.116(5) mm from the crystal, 460 frames at 60 s/image, function minimized ∑w(|Fo | - |Fc |)2, with w ) 1/[3(σ(Fo2) + 0.01(Fo2))], where
2
2
σ(Fo2) is based on counting statistics, R ) ∑||Fo | - |Fc ||/∑|Fo |, Rw ) (∑w(|Fo | - |Fc |)2/∑w|Fo | )1/2, and gof ) [∑w(|Fo | - |Fc |)2/(m -
2
2
2
2
2
2 2
2
2
n)]1/2. Values given for R, Rw, and gof are based on all reflections. c Includes corrections for decay and absorption.
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
(d eg) in Zr Cl2[P 2N2] (1)
although the choice of alkylating agent appears critical.
Thus, while the reaction between 1 and MeMgBr in
Et2O produces colorless ZrMe2[P2N2] (2) in 85% yield,
the analogous reaction using MeLi produces a dark
brown material from which only low yields of 2 (<5%)
can be isolated. The rapid reaction between 1 and
KCH2Ph in toluene is simpler, resulting in good yields
of the orange dibenzyl complex Zr(CH2Ph)2[P2N2] (3).
This latter complex appears to be sensitive to decom-
position in solution; a sample of 3 in toluene-d8 decom-
poses to a number of unidentified complexes over a
period of 48 h. Also, even in the absence of air and
moisture, the dimethyl complex undergoes decomposi-
tion to a complex number of products in the solid state
over a period of 24 h.
Zr(1)-N(1)
Zr(1)-P(1)
Zr(1)-Cl(1)
2.136(4)
2.694(2)
2.455(2)
Zr(1)-N(2)
Zr(1)-P(2)
Zr(1)-Cl(2)
2.125(4)
2.707(2)
2.448(2)
N(1)-Zr(1)-N(2)
Cl(1)-Zr(1)-Cl(2)
N(2)-Zr(1)-Cl(1)
96.8(2)
82.57(7)
91.3(1)
P(1)-Zr(1)-P(2)
N(1)-Zr(1)-Cl(2)
152.52(6)
89.5(1)
1
protons are observed in the H NMR spectrum at 0.34
and 0.30 ppm for 12H each, reflecting “top and bottom”
asymmetry of 1. The o-protons of the phosphine phenyl
rings are distinct as a multiplet at 7.84 ppm; the CH2
protons of the ring appear as AB multiplets coupled to
phosphorus centered at 1.30 ppm. The phosphorus
nuclei are equivalent, with a singlet at -14.3 ppm
observed in the 31P{1H} spectrum. It is therefore
apparent that the [P2N2] macrocyclic framework is quite
flexible in solution and undergoes dynamic processes
which can be visualized as a “rocking” motion centered
at the trigonal silylamide groups. The chemical shifts
and coupling patterns observed in the 1H NMR spec-
trum appear to be diagnostic for the [P2N2] ligand
coordinated to a large metal (see later).
In a manner similar to the dichloride 1, both dialkyls
adopt C2v-symmetric structures in solution at ambient
temperatures as evidenced by NMR spectroscopy, and
therefore a cis-orientation of the alkyl ligands is a
reasonable conclusion. In 2, the methyl protons are
observed as a triplet coupled to phosphorus at 1.07 ppm
(J PH 4.7 Hz) and overlap with the resonances due to the
ring CH2 protons. Likewise in 3, the methylene protons
of the benzyl groups are observed as a triplet at 2.16
ppm (J PH 3.0 Hz). Both complexes exhibit singlet
resonances in their respective 31P{1H} NMR spectra.
The reaction between the dichloride 1 and typical
alkylating agents was found to yield the desired dialkyl-
zirconium complexes in high yield (see Scheme 1),

Zirconium(IV) Complexes Stabilized by a Macrocycle
Organometallics, Vol. 17, No. 5, 1998 849
F igu r e 3. Molecular structure and numbering scheme for
Zr(η4-C4H6)[P2N2] (4). The silylmethyl substituents have
been omitted for clarity as have the phenyl rings attached
to phosphorus except that the ipso carbons (C(13) and
C(19)) have been retained.
F igu r e 2. Molecular structure and numbering scheme for
Zr(CH2Ph)2[P2N2] (3). The silylmethyl substituents have
been omitted for clarity as have the phenyl rings attached
to phosphorus except that the ipso carbons (C(13) and
C(19)) have been retained.
Ta ble 4. Selected Bon d Len gth s (Å) a n d An gles
(d eg) in Zr (η4-C4H6)[P 2N2] (4)
Zr(1)-N(1)
Zr(1)-P(1)
Zr(1)-C(25)
Zr(1)-C(27)
C(25)-C(26)
C(27)-C(28)
2.217(3)
2.707(1)
2.416(4)
2.445(4)
1.379(6)
1.400(6)
Zr(1)-N(2)
Zr(1)-P(2)
Zr(1)-C(26)
Zr(1)-C(28)
C(26)-C(27)
2.189(3)
2.701(1)
2.445(4)
2.380(4)
1.408(6)
Ta ble 3. Selected Bon d Len gth s (Å) a n d An gles
(d eg) in Zr (CH2P h )2[P 2N2] (3)
Zr(1)-N(1)
Zr(1)-P(1)
Zr(1)-C(25)
2.170(6)
2.730(2)
2.345(8)
Zr(1)-N(2)
Zr(1)-P(2)
Zr(1)-C(32)
2.192(6)
2.715(2)
2.335(8)
N(1)-Zr(1)-N(2)
Zr(1)-C(25)-C(26)
101.4(1) P(1)-Zr(1)-P(2)
74.7(3) Zr(1)-C(28)-C(27)
143.53(3)
75.7(2)
N(1)-Zr(1)-N(2)
C(25)-Zr(1)-C(32)
N(2)-Zr(1)-C(32)
98.0(2) P(1)-Zr(1)-P(2)
85.0(3) N(1)-Zr(1)-C(25)
159.73(8)
97.4(3)
98.7(3) Zr(1)-C(25)-C(26) 112.6(5)
Zr(1)-C(32)-C(33) 112.9(6)
The isolation of the dimeric zirconium dinitrogen
complex {[P2N2]Zr}2(µ-N2), formed by reduction of the
dichloride 1 under N2,32 suggested that diene complexes
incorporating the Zr[P2N2] fragment could be accessed.36
Cyclopentadienyl-based zirconium butadiene complexes
activated by B(C6F5)3 have also shown promise as
methylaluminoxane-free Ziegler-type catalysts.37 The
reaction between 1 and Mg(C4H6)‚2THF in THF re-
sulted in the formation of the deep red butadiene
complex Zr(η4-C4H6)[P2N2] (4) in moderate yield (Scheme
1). Crystals suitable for X-ray crystallography were
grown from hexanes; the molecular structure is shown
in Figure 3, with crystal data and selected bond lengths
and angles detailed in Tables 1 and 4, respectively.
Analysis of the butadiene C-C and Zr-C bond lengths
suggests that this interaction is best described in terms
of a π:η4-coordination mode rather than σ2:π; the
internal butadiene carbons are slightly closer to the
zirconium center than the terminal carbons [Zr(1)-
C(26)/C(27) ) 2.445 (4) Å; Zr(1)-C(25)/C(28) ) 2.416-
(4) and 2.380(4) Å] coupled with the observation that
the C-C bonds do not alternate in the long-short-long
manner expected for σ2:π bonding.38 A better gauge of
the bonding mode of the butadiene fragment is to
compare bond lengths M-C(2) and C(1)-C(2) and the
bond angle M-C(1)-C(2); higher values should be
evident for a σ2:π interaction.39,40 In the case of 4, the
values of 2.445(4) and 1.379(6) Å and 74.7(3)° for Zr-
(1)-C(26), C(25)-C(26), and Zr(1)-C(25)-C(26), re-
The dibenzyl complex 3 was crystallized as orange
prisms from a cooled mixture of toluene and hexanes;
the solid-state structure is shown in Figure 2, with
crystal data and selected bond lengths and angles
detailed in Tables 1 and 3, respectively. The substitu-
tion of the chloride ligands in 1 for the benzyl ligands
in 3 has resulted in some structural changes to the
macrocyclic framework, with increases in both the
phosphine and amide “bite angles”, P(1)-Zr-P(2) and
N(1)-Zr-N(2): 152.51(6) and 96.8(2)°, respectively, in
1 to 159.73(8) and 98.0(2)° in 3. Unlike 1, the ligand
arrangement around the zirconium center in 3 is best
described as trigonal antiprismatic with the two trigonal
planes described by N(1)P(2)C(25) and N(2)P(1)C(32);
the methylene carbons C(25) and C(32) of the benzyl
groups are not located in a square plane involving the
two amido nitrogens but are instead rotated consider-
ably out of this plane. This feature may in part be due
to steric interactions between the benzylic and macro-
cyclic phenyl groups. The benzyl groups are observed
to be coordinated in an η1-manner, with the zirconium-
carbon bond lengths of 2.335(8) and 2.345(8) Å compa-
rable to those observed in other zirconium alkyl com-
plexes incorporating amido ligands; the Zr-CH2-Cipso
angles are also relatively obtuse at 112.9(6) and 112.6-
(5)°.20,24,26 The lack of any η2-character in the benzyl
ligands34,35 suggests that the zirconium center sup-
ported by the [P2N2] ligand is not particularly electro-
philic perhaps due to the presence of the soft phosphine
donors.
(36) Fryzuk, M. D.; Haddad, T. S.; Rettig, S. J . J . Am. Chem. Soc.
1990, 112, 8185.
(37) Temme, B.; Erker, G.; Karl, J .; Luftmann, H.; Frohlich, R.;
Kotila, S. Angew. Chem., Int. Ed. Engl. 1995, 34, 1775.
(38) Diamond, G. M.; Green, M. L. H.; Walker, N. M.; Howard, J .
A. K.; Mason, S. A. J . Chem. Soc., Dalton Trans. 1992, 2641.
(39) Kruger, C.; Muller, G.; Erker, G.; Dorf, U.; Engel, K. Organo-
metallics 1985, 4, 215.
(33) Angelis, S. D.; Solari, E.; Gallo, E.; Floriani, C.; Chiesi-Villa,
A.; Rizzoli, C. Inorg. Chem. 1992, 31, 1.
(34) Latesky, S. L.; McMullen, A. K.; Niccolai, G. P.; Rothwell, I.
P.; Huffman, J . C. Organometallics 1985, 4, 902.
(35) Cloke, F. G. N.; Geldbach, T. J .; Hitchcock, P. B.; Love, J . B. J .
Organomet. Chem. 1996, 506, 343.
(40) Erker, G.; Engel, K.; Kruger, C.; Muller, G. Organometallics
1984, 3, 128.

850 Organometallics, Vol. 17, No. 5, 1998
Fryzuk et al.
spectively, compare well with those reported for π:η4-
butadiene complexes containing amido-, chloride-, or
alkoxy-based ligands.25,38,41,42 More general compari-
sons have also been made across the periodic table using
the empirical relationship that exists between the
butadiene dihedral angle φ and ∆δ, the difference
between the distances of the internal and external
carbons to the metal [average(Zr-Cter) - average(Zr-
C
int) ) 2.398 - 2.445 ) -0.047 Å].43 Again, the low
value of ∆δ (-0.047) and the φ value of 85.2 are
diagnostic of π:η4-bonding.41
In a manner similar to the dichloride 1 and the
dibenzyl 3, the backbone of the [P2N2] ligand in 4 shows
a C2-twist in the solid state. In this case, the N(1)-Zr-
(1)-N(2) and P(1)-Zr(1)-P(2) bite angles are 101.4(1)
and 143.53(3)°, respectively, which are similar to those
observed for 3 and 4; similar Zr-N and Zr-P bond
lengths are also observed.
The solution structure reflects that observed in the
solid state. Inspection of the 31P{1H} NMR spectrum
reveals a second-order AB pattern for nonequivalent
phosphorus nuclei centered at -6.1 ppm with a large
PP coupling of 78.1 Hz. This asymmetry is mirrored in
the 1H NMR spectrum, in which broad features at-
tributable to the silyl methyl protons are observed, along
with broad signals due to the o-protons of the phenyl
rings. On cooling of a sample of 4 in C7D8, these
resonances sharpen at 270 K, resulting in four silyl
methyl resonances and two o-proton signals, consistent
with a macrocyclic framework in which the phosphorus
donors are nonequivalent with a mirror plane bisecting
the N(1)-Zr(1)-N(2) angle, thus requiring that the
butadiene fragment is also bisected at the C(26)-C(27)
bond by this plane; this is shown as 4′ in Figure 4.
No change in these resonances was observed upon
further cooling to 215 K. The broad multiplets dis-
played at δ 5.78 (2H), 2.23 (2H), and 0.80 ppm (2H), for
the meso-, syn-, and anti-butadiene protons, respec-
tively, also sharpen upon cooling although the expected
low-temperature limiting spectrum of C1 symmetry
found in the solid state was not obtained. The dynamic
processes occurring in solution for 4 are commensurate
with the butadiene unit undergoing a restricted rotation
or rocking motion, as full rotation or envelope flipping
processes would equilibrate the phosphine donors and
in the latter case would also exchange the syn- and anti-
butadiene protons, neither of which are observed here.38,41
Mononuclear imido complexes of the group 4 metals
have been found to display unique reactivity, for ex-
ample undergoing a range of cycloaddition reactions and
participating in the activation of sp2 and sp3 C-H
bonds.44-47 Recently, the synthesis and reactivity of
group 4 imido complexes incorporating tetraazaannu-
lene ligands were reported.48,49
F igu r e 4. Top: Model (ball and stick) showing the solid-
state structure of Zr(η4-C4H6)[P2N2] (4) looking down the
Zr-centroid axis. Bottom: Schematic showing the average
structure in solution having Cs symmetry.
Sch em e 2
The synthesis of the imido complex Zr(NBut)[P2N2]
(6) was successfully achieved by following procedures
developed for the generation of the transient zirconocene
imido complex Cp2ZrdNBut (see Scheme 2).46
The reaction between 1 and 1 equiv of LiNHBut in
Et2O led to the formation of a compound that we
presume is the amido-chloride complex ZrCl(NHBut)-
[P2N2] (5). Satisfactory microanalytical data were not
obtained due to the high solubility of 5 in aliphatic
hydrocarbons, although 1H and 31P{1H} NMR data
indicated ca. 95% purity. The 1H NMR spectrum shows
the presence of one NHBut group per [P2N2] macrocycle,
with resonances due to the NH and But groups observed
at δ 7.33 and 1.38 ppm, respectively; curiously, the
silylmethyl protons on the ring give rise to a broad
singlet. The 31P{1H} NMR data, a singlet at δ -16.7
ppm, coupled with the above 1H NMR data suggest that
(41) Fryzuk, M. D.; Haddad, T. S.; Rettig, S. J . Organometallics
1989, 8, 1723.
(42) Giannini, L.; Solari, E.; Zanotti-Gerosa, A.; Floriani, C.; Chiesi-
Villa, A.; Rizzoli, C. Angew. Chem., Int. Ed. Engl. 1996, 35, 85.
(43) Yasuda, H.; Nakamura, A.; Kai, Y.; Kasai, N. Topics in Physical
Organometallic Chemistry; Freund Publishing House: Tel Aviv, 1987;
Vol. 2.
(44) Lee, S. Y.; Bergman, R. G. J . Am. Chem. Soc. 1995, 117, 5877.
(45) Walsh, P. J .; Baranger, A. M.; Bergman, R. G. J . Am. Chem.
Soc. 1992, 114, 1708.
(46) Walsh, P. J .; Hollander, F. J .; Bergman, R. G. Organometallics
1993, 12, 3705.
(47) Schaller, C. P.; Cummins, C. C.; Wolczanski, P. T. J . Am. Chem.
Soc. 1996, 118, 591.
(48) Nikonov, G. I.; Blake, A. J .; Mountford, P. Inorg. Chem. 1997,
36, 1107.
(49) Blake, A. J .; Mountford, P.; Nikonov, G. I.; Swallow, D. J . Chem.
Soc., Chem. Commun. 1996, 1835.

Zirconium(IV) Complexes Stabilized by a Macrocycle
Organometallics, Vol. 17, No. 5, 1998 851
bond lengths are similar to those observed in 1, 3, and
4. The But-imido unit is almost perfectly linear with a
Zr(1)-N(3)-C(25) angle of 179.50(15)°; a correspond-
ingly short Zr(1)-N(3) bond length of 1.8413(15) Å is
also observed. These values are comparable to those
reported in the limited number of structurally charac-
terized zirconium imido complexes, in which the ZrdN
bond length ranges from 1.826(4) to 1.876(4) Å and the
Zr-N-C bond angle from 164.5(3) to 175.5(8)° (not
including silyl47 or phosphaalkenyl50 substituted imides
which fall outside these ranges).46,51-54 A detailed
structural and theoretical analysis of five-coordinate
zirconium imido complexes has been reported;52 this
concluded that while complexes of the type Zr(NAr)-
(NAr2)2(py′)2 contain amido ligands that are capable of
a π-interaction with the dxy orbitals on the zirconium
center (z-direction along the ZrdN vector), such an
overlap does not interfere with the overlaps between the
zirconium dxz and dyz orbitals and the px and py sp-
hybridized orbitals of the imido nitrogen that form the
Zr-Nimido triple bond, although the former interaction
does result in a lengthening of the Zr-Namido bond. In
the case of 6, the linearity of the Zr-N-C bond angle
suggests that the interaction between the zirconium and
imido nitrogen is also best viewed as a triple bond, in
common with those previously reported, although in this
case it is difficult to discern whether significant length-
ening of the Zr-Namido bond distances of the macrocycle
has occurred, since the π-electron density could be
delocalized over the Si-N-Si unit; Zr-Namido bond
distances for the Zr[P2N2] fragment range from 2.125-
(4) to 2.254(3) Å.
F igu r e 5. Molecular structure and numbering scheme for
Zr(NBut)[P2N2] (6). The silylmethyl substituents have been
omitted for clarity as have the phenyl rings attached to
phosphorus except that the ipso carbons (C(13) and C(19))
have been retained.
Ta ble 5. Selected Bon d Len gth s (Å) a n d An gles
(d eg) in Zr (NBu t)[P 2N2] (6)
Zr(1)-N(1)
Zr(1)-P(1)
Zr(1)-N(3)
2.210(2)
2.7114(7)
1.8413(15)
Zr(1)-N(2)
Zr(1)-P(2)
N(3)-C(25)
2.203(2)
2.7360(7)
1.457(2)
N(1)-Zr(1)-N(2)
N(1)-Zr(1)-N(3)
P(1)-Zr(1)-N(3)
115.55(6)
123.59(7)
105.60(5)
P(1)-Zr(1)-P(2)
145.54(2)
N(2)-Zr(1)-N(3) 120.82(7)
P(2)-Zr(1)-N(3) 108.85(5)
Zr(1)-N(3)-C(25) 179.50(15)
this complex is fluxional; this behavior was not inves-
tigated further.
As described above, the transient, base-free, mono-
meric zirconium imido complexes Cp2ZrdNBut and
(But SiNH)2ZrdNSiBut , formed in-situ by heating the
The reaction between crude 5 and 1 equiv of MeLi in
Et2O at -78 °C led to the direct formation of the imido
complex Zr(NBut)[P2N2] (6) in high yield as evidenced
3
3
appropriate alkylamido complex, are able to activate sp2
and sp3 C-H bonds, respectively. In the formation of
6, however, there was no evidence that the putative
alkylamido intermediate Zr(NHBut)Me[P2N2] was stable
with respect to alkane elimination, with the imido com-
plex 6 being formed directly; 6 was found to be unre-
active toward aromatic C-H bonds and also toward H2.
1
by H NMR spectroscopy; however, the isolated yield
was low due to the high solubility of this complex in
aliphatic hydrocarbons.
1
The H NMR spectrum of 6 in C6D6 concurs with a
C2v-symmetric solution structure, displaying two reso-
nances for the ring silylmethyl protons and a singlet
for the imido But group. Also, the 31P{1H} NMR
spectrum is a singlet at -15.5 ppm.
Con clu sion s
In this work, we have provided full details of the
preparation and structures of a series of Zr(IV) com-
plexes that incorporate the macrocyclic bis(amido-
phosphine) ligand [P2N2]. The dichloride complex ZrCl2-
[P2N2] serves as a useful entry into bis(hydrocarbyl)
derivatives, ZrR2[P2N2], by metathesis type procedures,
although some care must be exercised as to the alky-
lating agent used. The butadiene complex Zr(η4-C4H6)-
[P2N2] has been prepared and structurally character-
ized; on the basis of the solid-state molecular structure,
the π:η4 description of the bonding seems more apt that
the σ2:π formalism. Finally, we also have included the
Complex 6 crystallized from hexanes at -40 °C as
orange blocks that were suitable for X-ray crystal-
lography. The solid-state structure of 6 is shown in
Figure 5, with crystal data and selected bond lengths
and angles detailed in Tables 1 and 5, respectively. It
is immediately evident that 6 is monomeric in the solid
state, with the geometry at the zirconium best described
as distorted trigonal bipyramidal; N(1), N(2), and N(3)
are in the trigonal plane [N(1)-Zr(1)-N(2) 115.55(6)°,
N(1)-Zr(1)-N(3) 123.59(7)°, N(2)-Zr(1)-N(3) 120.82-
(7)°], and P(1) and P(2) are apical, albeit pinched back
[P(1)-Zr(1)-P(2) ) 145.54(2)°] in a manner similar to
that described above. From this structure and those
described above, it is apparent that the [P2N2] macro-
cycle is able to adopt a range of geometries when
coordinated to a metal, from pseudo-octahedral (N-
Zr-N ) 96.8-101.4°) to distorted trigonal planar (N-
Zr-N ) 115.6°) and that this effect is largely metal
induced. The phosphine “bite-angle” also covers a large
range (143.5-159.7°). The Zr-N(amido) and Zr-P
(50) Breen, T. L.; Stephan, D. W. J . Am. Chem. Soc. 1995, 117,
11914.
(51) Profilet, R. D.; Zambrano, C. H.; Fanwick, P. E.; Nash, J . J .;
Rothwell, I. P. Inorg. Chem. 1990, 29, 4362.
(52) Zambrano, C. S.; Profilet, R. D.; Hill, J . E.; Fanwick, P. E.;
Rothwell, I. P. Polyhedron 1993, 12, 689.
(53) Bai, Y.; Roesky, H. W.; Noltemeyer, M.; Witt, M. Chem. Ber.
1992, 125, 825.
(54) Arney, D. J .; Bruck, M. A.; Huber, S. R.; Wigley, D. E. Inorg.
Chem. 1992, 31, 3749.

852 Organometallics, Vol. 17, No. 5, 1998
Fryzuk et al.
imido complex Zr(NBut)[P2N2] which shows a completely
linear Zr-N-C unit. The imide unit does not undergo
C-H activation processes.
All of the solid-state molecular structures reported
here show that the macrocyclic ligand, upon coordina-
tion to Zr(IV), distorts to generate a pseudo-C2-sym-
metric arrangement of the Zr[P2N2] unit. However, in
solution, the flexibility of the macrocycle allows confor-
mational motion that symmetrizes the Zr[P2N2] portion
of the system.
Anal. Calcd for C24H42Cl2N2P2Zr: C, 41.48; H, 6.09; N, 4.03.
Found: C, 42.05; H, 6.29; N, 4.08. 1H NMR (C6D6, 500 MHz):
δ 7.84 (m, 4H, o-H), 7.04 (m, 6H, m, p-H), 1.37 (ABX m, 4H,
CH2 ring), 1.24 (ABX m, 4H, CH2 ring), 0.34 (s, 12H, SiMe2
ring), 0.30 (s, 12H, SiMe2 ring). 31P{1H}: δ -14.3 (s).
P r ep a r a tion of Zr Me2[P 2N2] (2). To a slurry of ZrCl2-
[P2N2] (0.50 g, 0.72 mmol) in Et2O (20 mL) was added 3.0 M
MeMgBr in Et2O (0.5 mL, 1.44 mmol) at room temperature;
over a period of a few minutes, the solids dissolved and then
a colorless precipitate was formed. The slurry was stirred for
1.5 h and evaporated to dryness, the residue was extracted
into toluene (2 × 5 mL), and the extract was filtered through
Celite. The pale yellow filtrate was evaporated to dryness to
yield 0.398 g, 85%, of 2 as an off-white powder. This material
is thermally- and photochemically-sensitive; as a result nu-
merous attempts to obtain elemental analyses failed.
1H NMR (C6D6, 500 MHz): δH 7.72 (m, 4H, o-H phenyl), 7.17
(m, 6H, m/ p-H phenyl), 1.25 (m, 4H, ring CH2), 1.07 (t + m,
10H, J PH 4.7 Hz, Zr-CH3 overlapping with ring CH2), 0.26 (s,
12H, ring SiMe2), 0.25 (s, 12H, ring SiMe2). 31P{1H} NMR:
δP -18.4 (s)
P r ep a r a tion of Zr (CH2P h )2[P 2N2] (3). In the glovebox,
KCH2Ph (0.375 g, 2.88 mmol) was added as a solid to a stirred
solution of ZrCl2[P2N2] (1.00 g, 1.44 mmol) in toluene (30 mL)
at ambient temperature, the red solids slowly dissolving. The
mixture was stirred for 1.5 h and filtered through Celite, and
the yellow filtrate was evaporated to ca. 2 mL. The addition
of hexanes (10 mL) and cooling to -30 °C caused 3 to deposit
as orange prisms, yield 0.72 g, 62%.
Anal. Calcd for C38H56N2P2Si4Zr: C, 56.60; H, 7.00; N, 3.47.
Found: C, 56.83; H, 7.00; N, 3.50. 1H NMR (CD3C6D5, 200
MHz): δ 7.15-6.8 (m’s, 20 H, phenyl), 2.16 (t, 4H, J PH ) 3.0
Hz, Zr-CH2Ph), 1.20 (m, 8H, CH2 ring), 0.42 (s, 12H, SiMe2
ring), 0.35 (s, 12H, SiMe2 ring). 31P{1H} δ -7.51 (s).
P r ep a r a tion of Zr (η4-C4H6)[P 2N2] (4). THF (10 mL) was
added to an intimate mixture of ZrCl2[P2N2] (0.238 g, 0.342
mmol) and Mg(C4H6)2‚2THF (76 mg, 0.342 mmol) at -78 °C.
Upon warming of the sample to room temperature, the solids
dissolved, resulting in the formation of a deep red solution
which was stirred for 4.5 h, then evaporated to dryness; the
residue was extracted into hexanes (2 × 10 mL), and the
extract was filtered through Celite. Partial evaporation of the
filtrate and cooling to -30 °C yielded 0.135 g, 58%, of 4 as
dark red blocks.
Exp er im en ta l Section
Unless otherwise stated all manipulations were performed
under an atmosphere of dry, oxygen-free dinitrogen or argon
by means of standard Schlenk or glovebox techniques (Vacuum
Atmospheres HE-553-2 glovebox equipped with a MO-40-2H
purification system and a -40 °C freezer). Diethyl ether,
hexanes, and tetrahydrofuran (sodium benzophenone ketyl)
and toluene (sodium) were dried and distilled prior to use.
Argon was dried and deoxygenated by passing the gases
through a column containing molecular sieves and MnO.
Deuterated tetrahydrofuran and benzene were refluxed over
potassium metal under partial pressure, trap-to-trap distilled,
and freeze-pump-thaw degassed three times. Deuterated
toluene was distilled from sodium benzophenone ketyl and
freeze-pump-thaw degassed three times. Unless otherwise
stated, 1H and 31P{1H} NMR spectra were recorded on a
Bruker AC-200 instrument operating at 200 and 81.0 MHz,
respectively, and 1H{31P} NMR spectra were recorded on a
Bruker AMX-500 instrument operating at 500.1 MHz. Vari-
able-temperature NMR spectra were recorded on Varian
XL300 and Bruker AMX-500 instruments. 1H NMR spectra
were referenced to internal C6D5H (7.15 ppm), C7D7H (2.09
ppm), and C4D7HO (3.58 ppm), and 31P{1H} NMR spectra to
external P(OMe)3 (141.0 ppm with respect to 85% H3PO4 at
0.0 ppm).
The compounds Li2(THF)[P2N2], Li2(dioxane)[P2N2],13 ZrCl4-
(THT)2 (THT ) tetrahydrothiophene),21 KCH2Ph, and [Mg-
(THF)2(C4H6)]n were prepared according to literature proce-
dures. LiNHBut was prepared by treating a solution of
NH2But in Et2O with 1 molar equiv of LiBun and evaporating
to dryness. The 3.0 M MeMgBr in Et2O was purchased from
Aldrich.
Anal. Calcd for C28H48N2P2Si4 Zr: C, 49.59; H, 7.13; N, 4.13.
Found: C, 49.42; H, 7.22; N, 4.00. 1H NMR (C6D6, 500 MHz):
δH 7.63 (br s, 2H, o-H phenyl), 7.56 (br s, 2H, o-H phenyl),
7.14 (m, 6H, m/p-H phenyl), 5.84 (m, 2H, Hmeso), 2.48 (m, 2H,
Microanalyses (C, H, N) were performed by Mr. P. Borda of
this department.
P r ep a r a tion of Zr Cl2[P 2N2] (1). Meth od 1. To a stirred
mixture of Li2(THF)[P2N2] (1.35 g, 2.13 mmol) and ZrCl4(THT)2
(0.96 g, 2.34 mmol) was added Et2O (30 mL) at -20 °C. Upon
warming of the sample to room temperature, the solids began
to dissolve and a fresh, white precipitate was observed. The
mixture was then stirred at this temperature for 16 h, after
which the solvents were evaporated in vacuo, the off-white
residue was extracted into toluene (2 × 15 mL), and the
mixture was filtered through Celite. Partial evaporation of
the filtrate and cooling to -30 °C caused the deposition of 1
as pale yellow plates. Yield: 1.25 g, 85%.
H
syn), 1.37 (m, 4H, ring CH2), 1.18 (m, 4H, ring CH2), 0.67 (m,
2H, Hanti of C4H6), 0.39 (br s, 6H, ring SiMe2), 0.34 (br s, 6H,
ring SiMe2), 0.27 (br s, 6H, ring SiMe2), 0.09 (br s, 6H, ring
SiMe2). 1H NMR (C6D6, 280 K, 500 MHz): δH 7.63 (m, 2H,
o-H phenyl), 7.53 (m, 2H, o-H phenyl), 7.14 (m, 6H, m/p-H
phenyl), 5.89 (m, 2H, Hmeso), 2.51 (m, 2H, Hsyn), 1.36 (m, 4H,
ring CH2), 1.14 (m, 4H, ring CH2), 0.72 (m, 2H, Hanti of C4H6),
0.43 (s, 6H, ring SiMe2), 0.39 (s, 6H, ring SiMe2), 0.30 (s, 6H,
ring SiMe2), 0.12 (s, 6H, ring SiMe2). 31P{1H} NMR: δP -6.1
(second-order AB doublet with wings, J PP 78.1 Hz).
P r ep a r a tion of Zr Cl(NHBu t)[P 2N2] (5). A solution of
LiNHBut (30 mg, 0.38 mmol) in toluene (2 mL) was added
dropwise to a stirred solution of ZrCl2[P2N2] (0.265 g, 0.38
mmol) in toluene (10 mL) at room temperature. The resultant
mixture was stirred at this temperature for 2 h, after which
it was evaporated to dryness. The residue was extracted into
hexanes, and the extract was filtered through Celite. Evapo-
ration of the yellow filtrate yielded an oily solid, 212 mg, 76%.
The high solubility of 5 in hydrocarbon solvents precluded the
isolation of an analytically pure material, although 95% purity
was observed by NMR spectroscopy.
Meth od 2. To a stirred mixture of Li2(dioxane)[P2N2] (0.58
g, 0.91 mmol) and ZrCl4(THT)2 (0.37 g, 0.91 mmol) was added
THF (10 mL) at -78 °C. Upon warming of the sample to room
temperature, the solids dissolved; the resultant pale yellow
solution was stirred at this temperature for 30 min and then
evaporated to dryness. The residues were extracted into
toluene (2 × 5 mL), the mixture was filtered through Celite,
and the filtrate was evaporated to dryness. The filtered
residues were washed with hexanes (2 × 2 mL) and dried
under vacuum, yielding 0.532 g, 84%, of 1 as an off-white
powder. No significant change in chemical yield was observed
when ZrCl4(THF)2 was used in place of ZrCl4(THT)2.
1H NMR (C6D6, 500 MHz): δH 7.82 (m, 4H, o-H), 7.33 (s,
1H, NH), 7.18 (m, 4H, m-H), 7.09 (m, 2H, p-H phenyl), 1.38

Zirconium(IV) Complexes Stabilized by a Macrocycle
Organometallics, Vol. 17, No. 5, 1998 853
(s, 17H, C(CH3)3 + ring CH2), 0.43 (br s, 12H, ring SiMe2).
31P{1H} NMR (C6D6): δP -16.7 (s).
lying on 2-fold axes and one molecule in a general position.
There is considerable thermal motion in 3 at room tempera-
ture, peripheral atoms in general displaying high thermal
motion. All non-hydrogen atoms were refined with anisotropic
thermal parameters. Hydrogen atoms were fixed in idealized
positions (methyl groups staggered, C-H ) 0.98 Å, BH ) 1.2
P r ep a r a tion of Zr (NBu t)[P 2N2] (6). A solution of MeLi
(1.6 M, 0.18 mL, 0.29 mmol) in Et2O was added dropwise to a
stirred solution of crude ZrCl(NHBut)[P2N2] (212 mg, 0.29
mmol) in toluene (10 mL) at room temperature, causing a
colorless solid to precipitate. The mixture was stirred at this
temperature for 1 h and evaporated to dryness, the solid was
extracted into hexanes (2 × 5 mL), and the extract was filtered
through Celite. Evaporation of the filtrate yielded 0.15 g, 74%,
of a yellow residue that was extremely soluble in hydrocarbon
solvents. The slow evaporation of a solution of 6 in hexanes
resulted in a 50 mg quantity of crystals suitable for X-ray
diffraction.
B
bonded atom). A correction for secondary extinction was applied
for 1, the final value of the extinction coefficient being 5.42-
(12) × 10-7. No extinction corrections were necessary for the
three other complexes. Neutral atom scattering factors for all
atoms and anomalous dispersion corrections for the non-
hydrogen atoms were taken from ref 56. The absolute con-
figuration of 1 (for the particular crystal used) was determined
by parallel refinement of the mirror images. The R and Rw
factor ratios were 1.021 and 1.027, respectively. Selected bond
lengths and bond angles appear in Tables 2-5. Atomic
coordinates, anisotropic thermal parameters, complete bond
lengths and bond angles, torsion angles, intermolecular con-
tacts, and least-squares planes are included as Supporting
Information.
Anal. Calcd for C28H51N3P2Si4Zr: C, 48.37 H, 7.39; N, 6.04.
Found: C, 48.41; H, 7.52; N, 5.98. 1H NMR (C6D6, 500 MHz):
δH 8.03 (m, 4H, o-H), 7.09 (m, 6H, o/p-H phenyl), 1.75 (s, 9H,
C(CH3)3), 1.20 (AB m’s, 8H, ring CH2), 0.34 (s, 6H, ring SiMe2),
0.33 (s, 6H, ring SiMe2). 31P{1H} NMR (C6D6): δP -15.5 (s).
X-r a y Cr ysta llogr a p h ic An a lyses of 1, 3, 4, a n d 6.
Crystallographic data appear in Table 1. The final unit-cell
parameters were obtained by least-squares methods on the
setting angles for 25 reflections with 2θ ) 18.0-24.8° for 1,
15.0-26.3° for 3, and 17.1-22.5° for 4 and 11 949 reflections
with 2θ ) 5.0-55.8° for 6. The intensities of three standard
reflections, measured every 200 reflections throughout the data
collections for 1, 3, and 4, remained constant for 1 and decayed
linearly by 1.8% for 3 and by 4.4% for 4. The data were
processed55 and corrected for Lorentz and polarization effects
and absorption (empirical, based on azimuthal scans for 1, 3,
and 4 and symmetry analysis of redundant data using 4th
order spherical harmonics for 6).
Ack n ow led gm en t. Funding for this research was
generously provided by the NSERC of Canada.
Su p p or tin g In for m a tion Ava ila ble: Full experimental
details, tables of X-ray parameters, fractional coordinates and
thermal parameters, bond lengths, bond angles, and torsion
angles, and ORTEP diagrams for compounds 1, 3, 4, and 6
(73 pages). Ordering information is given on any current
masthead page.
OM9707984
The structures were all solved by the Patterson method.
The structure analysis of 3 was initiated in the centrosym-
metric space group C2/c on the basis of the E-statistics, this
choice being confirmed by the subsequent successful solution
and refinement of the structure. The asymmetric unit of 3
consists of two crystallographically independent half-molecules
(55) teXsan: Crystal Structure Analysis Package; Molecular Struc-
ture Corp.: The Woodlands, TX, 1995.
(56) (a) International Tables for X-Ray Crystallography; Kynoch
Press: Birmingham, U.K. (present distributor Kluwer Academic
Publishers, Boston, MA), 1974; Vol. IV, pp 99-102. (b) International
Tables for Crystallography; Kluwer Academic Publishers: Boston, MA,
1992; Vol. C, pp 200-206.