A new arene-bridged diamidophosphine ligand and its coordination chemistry with zirconium(IV)

Article abstract of DOI:10.1021/om049165x

The arene-bridged dilithium diamidophosphine ligand, [(2,4,6-Me ₃C₆H₂)NLi-2-(5-MeC₆H ₃)]₂-PPh, [NPN]*Li₂, was prepared from (2,4,6-Me₃C₆H₂)(2-Br-4-MeC₆H ₃)NH, ⁿBuLi, and PhPCl₂ in Et₂O and isolated as a dioxane adduct in ～85% yield. The solid-state structure of [NPN]-*Li₂(THF)₂ as determined by X-ray diffraction shows both lithiums bridged by the amido nitrogens with one Li ion coordinated to the phosphine donor. The reaction of [NPN]*H₂ and Zr(NMe₂)₄ in toluene produced (NPN]*Zr(NMe ₂)₂ in 90% isolated yield. Addition of excess Me ₃SiCl to [NPN]*Zr(NMe₂)₂ converts it to [NPN]*ZrCl₂ in high yield. The solid-state structure of [NPN]*ZrCl₂ as determined by X-ray diffraction shows the Zr center is a distorted trigonal bipyramid with the phosphine and the chloride apical. The ortho-Me's on the N-mesityl moiety are inequivalent in both the Li and Zr complexes of [NPN]* by NMR spectroscopy, while in [NPN]*H₂ MesN ortho-Me's appear as broad singlets. VT-NMR of [NPN]*H₂ indicated that ΔG_rot ^? of MesC_ipso-N is approximately 15.5 ± 0.3 kcal mol^-1. The thermally labile and light-sensitive zirconium dimethyl complex [NPN]*ZrMe₂ was prepared from [NPN]*ZrCl₂ and MeMgCl in Et₂O in 80% yield.

Full text of DOI:10.1021/om049165x

1112
Organometallics 2005, 24, 1112-1118
A New Arene-Bridged Diamidophosphine Ligand and Its
Coordination Chemistry with Zirconium(IV)
Erin A. MacLachlan and Michael D. Fryzuk*
Department of Chemistry, University of British Columbia, 2036 Main Mall,
Vancouver, BC, Canada V6T 1Z1
Received October 26, 2004
The arene-bridged dilithium diamidophosphine ligand, [(2,4,6-Me3C6H2)NLi-2-(5-MeC6H3)]2-
PPh, [NPN]*Li2, was prepared from (2,4,6-Me3C6H2)(2-Br-4-MeC6H3)NH, nBuLi, and PhPCl2
in Et2O and isolated as a dioxane adduct in ∼85% yield. The solid-state structure of [NPN]-
*Li2(THF)2 as determined by X-ray diffraction shows both lithiums bridged by the amido
nitrogens with one Li ion coordinated to the phosphine donor. The reaction of [NPN]*H2
and Zr(NMe2)4 in toluene produced [NPN]*Zr(NMe2)2 in 90% isolated yield. Addition of excess
Me3SiCl to [NPN]*Zr(NMe2)2 converts it to [NPN]*ZrCl2 in high yield. The solid-state
structure of [NPN]*ZrCl2 as determined by X-ray diffraction shows the Zr center is a distorted
trigonal bipyramid with the phosphine and the chloride apical. The ortho-Me’s on the
N-mesityl moiety are inequivalent in both the Li and Zr complexes of [NPN]* by NMR
spectroscopy, while in [NPN]*H2 MesN ortho-Me’s appear as broad singlets. VT-NMR of
q
[NPN]*H2 indicated that ∆Grot of MesCipso-N is approximately 15.5 ( 0.3 kcal mol-1. The
thermally labile and light-sensitive zirconium dimethyl complex [NPN]*ZrMe2 was prepared
from [NPN]*ZrCl2 and MeMgCl in Et2O in 80% yield.
Introduction
arrays. This design strategy takes into account that
amido donors generally stabilize high oxidation state,
electron-poor metal complexes, while phosphine donors
are known to stabilize more electron-rich metal systems.
In the activation of molecular nitrogen, such ancillary
ligands have enjoyed considerable success due to the fact
that highly reducing conditions are generally required
for coordination of N2 to the early transition metals.6
While we have reported7 dinitrogen activation using
complexes stabilized with [PNP], [P2N2], and [NPN]
ligand sets, in each of these cases the linkages have
involved N-Si bonds, typically to facilitate ligand
synthesis and also to provide reduced basicity of the
amido nitrogen donor.8 Recently, we have discovered
that this N-Si linkage is not robust.9 The hydroboration
of the ditantalum dinitrogen complex ([NPN]Ta)2(η1:η2-
µ-N2)(µ-H)2 results in cleavage of N2 and [NPN] decom-
position via loss of a phenyl substituent from one
amido.10 The resulting imide-, nitride-bridged ditanta-
lum complex features a newly formed N-Si bond
between the [NP] ligand and the bridging imide formed
from N2.
The ability to control the reactivity patterns of a metal
complex by appropriate choice of the ancillary ligands
is at the core of inorganic chemistry. Examples abound
of ligand sets that can facilitate oxidation state changes,1
allow unusual electronic states,2 generate chiral envi-
ronments for asymmetric synthesis,3 and modulate light
absorption for energy transfer.4 Even though it is not
yet possible to predict reaction outcomes on the basis
of a particular choice of a ligand set, research into ligand
design continues guided by ideas of geometry control,
donor atom types, and substituent effects. The recent
report of the effect of one methyl group on the ability to
completely change the reactivity of a zirconium complex
with N2 and H2 exemplifies the inability to predict
reaction outcomes.5
Research in the Fryzuk group has focused on multi-
dentate ligand designs that incorporate different com-
binations of amido and phosphine donors into chelating
* To whom correspondence should be addressed. E-mail:
fryzuk@chem.ubc.ca.
(1) Matyjaszewski, K.; Xia, J. Chem. Rev. 2001, 101, 2921-2990.
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J. C.; Betley, T. A.; Peters, J. C. Inorg. Chem. 2004, 43, 4645-4662.
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Since ancillary ligand decomposition is a major bar-
rier to the development of a catalytic cycle based on N2
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(7) (a) Shaver, M. P.; Fryzuk, M. D. Adv. Synth. Catal. 2003, 345,
1061-1076. (b) MacKay, B. A.; Fryzuk, M. D. Chem. Rev. 2004, 104,
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(4) (a) Chang, C. J.; Loh, Z.-H.; Deng, Y.; Nocera, D. G. Inorg. Chem.
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Res. 1989, 22, 163-170. (d) Campagna, S.; Di Pietro, C.; Loiseau, F.;
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530.
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2003, 350, 293-298.
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Angew. Chem., Int. Ed. 2002, 41, 3709-3712.
10.1021/om049165x CCC: $30.25 © 2005 American Chemical Society
Publication on Web 02/12/2005

New Arene-Bridged Diamidophosphine Ligand
Organometallics, Vol. 24, No. 6, 2005 1113
Scheme 1
functionalization, we sought to develop a more robust
diamidophosphine ligand with similar basicity to the
N-Si linked [NPN]. For comparison, the pKa of diphe-
nylamine is 24.95,11 very similar to that of bis(trimeth-
ylsilyl)amine at 25.8.12 An arene-bridged diamidophos-
phine with aryl substituents on N and P is therefore
likely to provide a similar electronic environment to
[NPN], while the aromatic backbone should inhibit the
kind of ligand decomposition described above.
In this work, two main approaches to prepare an
arene-bridged diamidophosphine are reported. First,
Cu-catalyzed arylation of 2,2′-diaminotriphenylphos-
phine oxide, (2-NH2C6H4)2PhPdO, followed by phos-
phine oxide reduction and deprotonation to form [(4-
MeC6H4)NLi-(2-C6H4)]2PPh, [NPN]′Li2, was investigated,
and second, lithiation of (2,4,6-Me3C6H2)(2-Br-4-MeC6H3)-
NH, (Mes)(BrTol)NH, followed by metathesis with Ph-
PCl2 to produce [(2,4,6-Me3C6H2)NLi-2-(5-MeC6H3)]2-
PPh, [NPN]*Li2, was examined. In addition, the coordina-
tion chemistry of this new ligand set with Zr(IV) is
included.
Scheme 2
Results and Discussion
Our first approach to the synthesis of an arene-
bridged diamidophosphine was to prepare the phenyl-
bridged [NPN]′ ligands (where [NPN]′ ) [(4-MeC6H4)N-
(2-C6H4)]2PPh) by Cu-catalyzed arylation of (2-NH2-
C6H4)2PhPdO, A, which is readily prepared from phe-
nylphosphine (PhPH2) and 2-iodoaniline, in the presence
of catalytic Pd(PPh3)4 and the water-soluble triarylphos-
phine GUAP-3.13 Attempts to directly couple 2,2′-
diaminotriphenylphosphine to aryliodides were unsuc-
cessful, likely due to binding of the chelating diamino-
phosphine substrates and products to the copper cata-
lyst. Thus, phosphine oxide A was reacted with 2.2 equiv
of 4-iodotoluene (Tolyl-I) and catalytic CuI(Phen)(PPh3)
to produce [(4-MeC6H4)NH-(2-C6H4)]2PhPdO, B, in 85%
yield by a modification of a literature procedure.14
Compound B was reduced to [NPN]′H2, C, using stan-
There are several drawbacks to the synthesis of D
shown in Scheme 1. First, the reaction requires four
steps from phenylphosphine, which is malodorous to
prepare and extremely pyrophoric. Second, the Cu-
catalyzed arylation reaction must be refluxed over
several days. These conditions promote the formation
of the side product [(4-MeC6H4)2N(2-C6H4)][(4-MeC6H4)-
NH(2-C6H4)]PhPdO, E, the product of three Tolyl-I
1
additions to A. This product was identified by H and
31P{1H} NMR spectroscopy and electron impact mass
spectrometry (EI-MS), and it must be removed from B
by extensive chromatography (Scheme 2). Thus, the
yield of B decreases when the Cu-catalyzed reaction is
performed on a multigram scale. It was clear that a new
route to arene-bridged diamidophosphines was needed.
As an alternative, we explored diamidophosphine
synthesis from (Mes)(BrTol)NH, readily prepared in
high yield from (4-MeC6H4)(2,4,6-Me3C6H2)NH, (Mes)-
(Tol)NH,17 and N-bromosuccinimide (NBS). This follows
recent reports for the synthesis of related [PNP] ligand
sets.18 (Mes)(BrTol)NH reacts with 2 equiv of nBuLi over
3 h to form (2-Li-4-MeC6H3)(2,4,6-Me3C6H2)NLi, F, the
product of Li/Br exchange. PhPCl2 (0.5 equiv) was added
to a solution of intermediate F to produce [(2,4,6-
Me3C6H2)NLi-2-(5-MeC6H3)]2PPh, 1, by a metathesis
reaction. The dioxane adduct of 1 was isolated in up to
85% yield (Scheme 3). The tmeda adduct of F, (2-Li-4-
MeC6H3)(2,4,6-Me3C6H2)NLi‚(Me2NCH2CH2NMe2)2, was
n
dard conditions.15 Finally, addition of 2 equiv of BuLi
to C provided [NPN]′Li2(THF)2, D, in 53% yield (Scheme
1).
[NPN]′Li2(THF)2 (D) displays a 31P{1H} NMR spec-
trum similar to [NPN]Li2(THF)2 (where NPN ) PhP-
(CH2SiMe2NPh)2), previously reported;16 a quartet is
7
observed at -33.0 ppm due to coupling with Li (I )
3/2, JPLi ) 41 Hz). As expected, a doublet and a singlet
7
are apparent in the Li NMR spectrum of [NPN]′Li2-
(THF)2, indicating that one Li ion is bound to P (-0.35
ppm), while the other Li ion is not closely associated
with the phosphine donor (-1.72 ppm). By 1H NMR
spectroscopy, two THF molecules are present.
(11) Bordwell, F. G. Acc. Chem. Res. 1988, 21, 456-463.
(12) Fraser, R. R.; Mansour, T. S.; Savard, S. J. Org. Chem. 1985,
50, 3232-3234.
(13) (a) Hessler, A.; Kottsieper, K. W.; Schenk, S.; Tepper, M.;
Stelzer, O. Z. Naturforsch. 2001, 56b, 347-353. (b) Herd, O.; Hessler,
A.; Hingst, M.; Machnitzki, P.; Tepper, M.; Stelzer, O. Catal. Today
1998, 42, 413-420. (c) Hessler, A.; Stelzer, O.; Dibowski, H.; Worm,
K.; Schmidtchen, F. P. J. Org. Chem. 1997, 62, 2362-2369. (d) Herd,
O.; Hessler, A.; Hingst, M.; Tepper, M.; Stelzer, O. J. Organomet. Chem.
1996, 522, 69-76.
1
also isolated and was characterized by H NMR spec-
troscopy. The isolation of intermediate F and subse-
quent reaction with PhPCl2 (0.5 equiv) were not found
(14) Gujadhur, R. K.; Bates, C. G.; Venkataraman, D. Org. Lett.
2001, 3, 4315-4317.
(17) Antilla, J. C.; Buchwald, S. L. Org. Lett. 2001, 3, 2077-2079.
(18) (a) Liang, L.-C.; Lin, J.-M.; Hung, C.-H. Organometallics 2003,
22, 3007-3009. (b) Huang, M.-H.; Liang, L.-C. Organometallics 2004,
23, 2813-2816. (c) Fan, L.; Foxman, B. M.; Ozerov, O. V. Organome-
tallics 2004, 23, 326-328. (d) Fan, L.; Yang, L.; Guo, C.; Foxman, B.
M.; Ozerov, O. V. Organometallics 2004, 23, 4778-4787.
(15) Quin, L. D. A Guide to Organophosphorus Chemistry; Wiley:
New York, 2000.
(16) Fryzuk, M. D.; Johnson, S. A.; Rettig, S. J. J. Am. Chem. Soc.
1998, 120, 11024-11025.

1114 Organometallics, Vol. 24, No. 6, 2005
MacLachlan and Fryzuk
Scheme 3
to increase the yield of [NPN]*Li2, in comparison to the
one-pot reaction described above.
Figure 1. ORTEP drawing of the solid-state structure of
1‚2THF (ellipsoids drawn at the 50% probability level). All
hydrogen atoms and carbon atoms of THF and phenyl
(except ipso C) have been omitted for clarity. Selected bond
lengths (Å) and angles (deg): P1-Li1 2.510(3), N1-Li1
2.078(3), N1-Li2 2.046(4), Li1...Li2 2.518(4), O1-Li1
1.908(3), O2-Li2 1.932(3), N2-Li2 2.051(3), N2-Li1 2.076-
(3), P1-Li1-Li2 77.01(11), N1-Li2-N2 105.76(15), O1-
Li1-Li2 144.07(18), C06-N1-C08 116.60(14), C01-P1-
C23 105.40(8), C23-P1-C17 103.18(8), C01-P1-C17
105.62(8).
Like other NPN lithium salts,16,19 the 31P{1H} NMR
spectrum of 1‚dioxane shows a quartet at -35.2 ppm
(JPLi ) 40 Hz), and the 7Li NMR spectrum shows a
doublet at -0.07 ppm and a singlet at -1.97 ppm. The
1H NMR spectrum of 1‚dioxane is notable in that ortho-
Me and meta-CH protons of the N-mesityl unit are
inequivalent, due to restricted rotation about the N-C
bond of these groups on the NMR time scale at room
temperature.
Crystals of 1‚2THF suitable for X-ray analysis were
grown by slow evaporation of a solution of 1‚dioxane in
C6D6 and THF. The solid-state molecular structure of
1‚2THF (Figure 1) determined by single-crystal X-ray
diffraction shows two distinct Li environments: Li1 is
coordinated to N1, N2, and P1, and O1 of one coordi-
nated THF, while Li2 is coordinated to N1 and N2, and
O2 of the second coordinated THF. Although spectro-
scopic and X-ray diffraction techniques confirmed the
identity of 1‚2THF, microanalysis of this compound has
repeatedly shown it to be low in carbon, likely due to
the extreme air- and moisture-sensitivity of this mate-
rial.
Scheme 4
The reaction of the dilithium salt 1‚dioxane with
ZrCl4(THF)2 under various conditions led to the forma-
tion of multiple products by 31P{1H} NMR spectroscopy.
Thus, the preparation of zirconium complexes of [NPN]*
from the protonated ligand precursor was investigated.
To prepare [NPN]*H2 (2), Me3NHCl was stirred with
[NPN]*Li2(dioxane) in THF. The 31P{1H} NMR spec-
trum of 2 in C6D6 solution has a singlet at -31.4 ppm,
and the 1H NMR spectrum at room temperature consists
of broad singlets for the ortho-Me’s and meta-CH’s on
the N-mesityl substituents, indicating hindered rotation
about the N-C bond of the bulky mesityl group. In the
variable-temperature 1H NMR experiment, coalescence
of the broad Me singlets was observed at 320 K; thus,
C6D6 has a singlet at -11.5 ppm, and the 1H NMR
spectrum has four singlets for the [NPN]* Me’s, indicat-
ing that two ortho-Me’s of the N-mesityl substituents
are not exchanging on the NMR time scale. There are
two NMe2 resonances at 3.06 and 2.31 ppm, correspond-
ing to two different NMe environments. We propose that
Zr is a five-coordinate trigonal bipyramid, with one
NMe2 apical and the other equatorial, with free rotation
about each of the Zr-NMe2 bonds. The 1H NMR
spectrum shows the complex has a mirror plane of
symmetry in solution. Addition of THF, pyridine, or
PMe3 to [NPN]*Zr(NMe2)2 in benzene produces no color
change or shift in the resonance in the 31P{1H} NMR
∆Gq was calculated to be 15.5 ( 0.3 kcal mol-1 20
.
rot
Zirconium complexes of [NPN]* were synthesized
from [NPN]*H2 and Zr(NMe2)4 in toluene. The reaction
was complete in 2 h at room temperature, and [NPN]-
*Zr(NMe2)2 (3) was formed as a yellow powder in high
yield (Scheme 3). The 31P{1H} NMR spectrum of 3 in
1
spectrum. The H and 31P{1H} NMR spectra of 3 are
similar to those of [PhP(CH2SiMe2NAr)2]Zr(NMe2)2.21
[NPN]*ZrCl2 (4) was readily synthesized by reaction
of excess Me3SiCl with 3 in toluene and isolated in 89%
yield as a bright yellow powder (Scheme 4). A singlet
at -2.8 ppm was observed in the 31P{1H} NMR spec-
(19) Shaver, M. P.; Thomson, R. K.; Patrick, B. O.; Fryzuk, M. D.
Can. J. Chem. 2003, 81, 1431-1437.
(20) Friebolin, H. Basic One-and Two-Dimensional NMR Spectros-
copy, 2nd ed.; VCH: Weinheim, 1993.
(21) Schrock, R. R.; Seidel, S. W.; Schrodi, Y.; Davis, W. M.
Organometallics 1999, 18, 428-437.

New Arene-Bridged Diamidophosphine Ligand
Organometallics, Vol. 24, No. 6, 2005 1115
the 13C{1H} NMR spectrum. Similarly, the doublet at
1
0.93 ppm in the H NMR spectrum is correlated to the
doublet at 45.1 ppm (JCP ) 6 Hz) in the 13C{1H} NMR
spectrum. Crystals suitable for X-ray diffraction have
not yet been obtained, due in part to the instability of
the complex.
Conclusions
A synthetic pathway to arene-bridged diamidophos-
phine ligands has been developed from a readily pre-
pared diarylamine and commercially available dichlo-
rophenylphosphine. This route provides [NPN]*Li2 as
the dioxane adduct in three steps in high yield in
multigram quantities and avoids the use of PhPH2,
which is both expensive and malodorous. Zirconium
complexes of [NPN]* were prepared via a protonolysis
route from Zr(NMe2)4. Single-crystal X-ray diffraction
indicates that [NPN]*ZrCl2 is a monomeric, distorted
trigonal bipyramidal complex in solution and the solid
state. We are currently investigating the ability of these
organometallic compounds of [NPN]*Zr to undergo
migratory insertion processes as well as act as polym-
erization catalysts; in addition, reduction of [NPN]-
*ZrCl2 under N2 is a current priority in our laboratory.
Figure 2. ORTEP drawing of the solid-state structure of
4 (ellipsoids at 50% probability). Selected bond lengths (Å)
and angles (deg): Zr1-N1 2.060(2), Zr1-N2 2.072(2), Zr1-
P1 2.7229(8), Zr1-Cl1 2.4279(8), Zr1-Cl2 2.4099(8), N1-
Zr1-N2 113.96(9), N1-Zr1-P1 72.73(7), N1-Zr1-Cl1
106.25(7), Cl1-Zr1-Cl2 96.23(3), P1-Zr1-Cl1 178.63(3),
P1-Zr1-Cl2 85.02(3).
trum in C6D6. 1H NMR spectroscopy shows that the
ortho-Me and meta C-H groups of MesN are inequiva-
lent, as with 1 and 3.
Crystals of 4 were grown from a concentrated benzene
solution and analyzed by single-crystal X-ray diffraction.
The ORTEP drawing is shown in Figure 2. In the solid
state, the stereochemistry around Zr is distorted trigo-
nal bipyramidal with Cl1 and P1 apical, and N1, N2,
and Cl2 bent below the 90° plane (by 16°, 6°, and 19°,
respectively). The [NPN]* ligand coordinates to Zr
facially, and the two chlorides are cis to each other. The
Zr-N (average 2.066(5) Å), Zr-Cl (2.419(2) Å), and
Zr-P (2.7229(8) Å) bond lengths are not atypical.
The THF adduct of [NPN]*ZrCl2 (4) was readily
prepared by addition of THF to solutions of 4 in benzene
or toluene to generate bright red-orange [NPN]*ZrCl2-
(THF), 5; diagnostic of its formation was the downfield
shift in the 31P{1H} NMR resonance from -2.8 found
for 4 to 2.7 ppm for 5.
By addition of methylmagnesium chloride to an
ethereal suspension of 4 at -35 °C, [NPN]*ZrMe2 (6)
was prepared in high yield as a highly photo- and
thermosensitive yellow powder (eq 1). It is characterized
by a singlet at -14.1 ppm in the 31P{1H} NMR spec-
trum. In the 1H NMR spectrum two distinct zirconium-
methyl resonances are observed: a doublet at 0.93 ppm
(JPH ) 5 Hz) and a singlet at -0.11 ppm. There are four
singlets for the [NPN]* methyl substituents. The aryl
region is consistent with 6 having Cs symmetry. The
structural assignment of 6 is supported by 13C{1H}
NMR spectroscopy, which shows the expected peaks for
[NPN]* and two resonances for the zirconium methyls:
Experimental Section
General Considerations. 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 glove-
box equipped with a MO-40-2H purification system and a -40
°C freezer). Argon and nitrogen were dried and deoxygenated
by passing the gases through a column containing molecular
sieves and MnO. Hexanes, toluene, tetrahydrofuran, pentane,
and diethyl ether were purchased anhydrous from Aldrich,
sparged with nitrogen, and passed through columns containing
activated alumina and Ridox catalyst. Dioxane was dried by
refluxing over sodium-benzophenone ketyl and distilled. Deu-
terated toluene and benzene were dried by refluxing over
sodium/potassium alloy under partial pressure, trap-to-trap
1
distilled, and freeze-pump-thaw degassed three times. H,
31P{1H}, and 13C{1H} NMR spectra were recorded on a Bruker
AV-300, a Bruker AV-400, or a Bruker AMX-500, operating
1
at 300.1, 400.0, and 500.1 MHz for H spectra, respectively.
7Li NMR spectra were recorded on the AV-400 or AMX-500.
1H NMR spectra were referenced to residual protons in the
deuterated solvent: C6D6 (7.16 ppm), CDCl3 (7.24 ppm), C7D8
(2.09 ppm), or d8-THF (3.58 ppm). 31P{1H} NMR spectra were
referenced to external P(OMe)3 (141.0 ppm with respect to 85%
H3PO4 at 0.0 ppm). 13C{1H} spectra are referenced to residual
solvent: C6D6 (128.0 ppm), CDCl3 (77.23 ppm), or d8-THF (67.4
ppm). 7Li NMR spectra were referenced to external LiCl in
D2O/H2O at 0.0 ppm. Chemical shifts (δ) are listed as ppm,
and coupling constants are in Hz. Me3SiCl and PhPCl2
(Aldrich) were distilled prior to use. (2-NH2C6H4)2PPh,13 Zr-
(NMe2)4,22 CuI(Phen)(PPh3),14 and (Mes)(Tol)NH17 were pre-
two doublets at 45.1 ppm (JCP ) 6 Hz) and 41.8 (JCP
)
29 Hz) correspond to Me’s trans and cis disposed to P,
respectively, in analogy with that described elsewhere.21
Efforts to confirm this using NOEDIFF experiments
were inconclusive. However, HMQC showed that the
1
singlet at -0.11 ppm in the H NMR spectrum of 6 is
(22) Diamond, G. M.; Jordan, R. F.; Petersen, J. L. J. Am. Chem.
Soc. 1996, 118, 8024.
correlated to the doublet at 41.8 ppm (JCP ) 29 Hz) in

1116 Organometallics, Vol. 24, No. 6, 2005
MacLachlan and Fryzuk
Table 1. X-ray Diffraction Crystal Data and Structure Refinement for Li2[NPN]*(THF)2 (1‚2THF) and
[NPN]*ZrCl2 (4)
1‚2THF
4
empirical formula
cryst description
cryst size (mm3)
fw
C
46H55Li2O2P
C53H54Cl2N2PZr
yellow needle
0.35 × 0.35 × 0.20
912
monoclinic
C2/c
colorless tablet
0.30 × 0.25 × 0.10
712.77
cryst syst
space group
a, b, c (Å)
â (deg)
monoclinic
P2(1)/n
12.0195(11), 24.292(2), 14.2557(11)
44.638(2), 10.8958(5), 19.4505(9)
102.308(4)
94.334(2)
V (Å3)
4066.7(6)
9433.0(8)
Z
4
8
Dcalcd (g cm-3
)
1.164
1.166
µ(Mo KR) (mm-1
F(000)
)
0.106
0.411
1528
3416
θ range (deg)
limiting indices
1.68-27.88
1.83-27.98
-15 e h e 15, -31 e k e 31, -18 e l e 17
-58 e h e 58, -12 e k e 14, -25 e l e 25
no. of reflns collected
no. of indep reflns
no. of params
54955
95473
9577
11331
486
541
F
max, Fmin, e Å-3
0.720, -0.472
0.0510
0.1411
1.044
0.920, -0.661
0.0505
0.1379
1.163
R1a
wR2a
GOOF on F2
2
2
a R1 ) ∑||Fo| - |Fc||/∑|Fo|, 2σ data; wR2 ) [∑(w(Fo - Fc )2)/∑w(Fo2)2]1/2 all data.
pared by literature methods. All other compounds were
purchased from commercial suppliers and used as received.
Mass spectrometry (EI-MS) and microanalyses (C, H, N) were
performed at the Department of Chemistry at the University
of British Columbia.
(d, 12 Hz), 124.7 (d, 13 Hz), 123.8, 120.4, 117.4 (d, 7 Hz), 116.4
and 115.0 (ArC), 20.9 and 20.8 (CH3). EI-MS (m/z): 578 (100,
M+). Anal. Calcd for C39H35N2OP: C, 80.95; H, 6.10; N, 4.84.
Found: C, 80.63; H, 6.22; N, 5.24.
[(4-MeC6H4)NH(2-C6H4)]2PhP (C). Toluene (30 mL), trichlo-
rosilane (1.2 g, 8.9 mmol), and triethylamine (0.62 g, 6.1 mmol)
were added to B (1.0 g, 2.1 mmol) under N2 in a long Schlenk
tube. The solution was refluxed overnight. The white suspen-
sion was cooled, degassed H2O (3 mL) was added, and the
volatiles were removed. The solids were triturated with toluene
(25 mL), and the suspension was filtered through Celite. The
solution was concentrated, and a white solid was obtained (1.07
g, 2.3 mmol, 92%).
Preparation of Compounds. [(4-MeC6H4)NH(2-C6H4)]2-
PhPdO (B). In air, (2-NH2C6H4)2PPh (1.0 g, 3.4 mmol) was
dissolved in hexanes (30 mL) and acetone (5 mL). H2O2 (30%
w/v, 0.5 mL) was added dropwise to the stirring solution.
Solvent was removed, and the pale brown residue was ex-
tracted from CH2Cl2/water (3 × 50 mL). The organic layer was
dried over Na2SO4, filtered, and concentrated in vacuo. Com-
pound A was recrystallized from acetone/EtOAc. In air, the
beige solids were dissolved in xylenes (30 mL) and THF (10
mL), and K2CO3 (2.0 g, 14.5 mmol), 4-iodotoluene (1.64 g, 7.5
mmol), and CuI(Phen)(PPh3) (0.220 g, 0.35 mmol) were added.
The solution was refluxed for 4 days at about 120 °C. The
solvents were removed, and B was isolated by silica gel
chromatography (9:1 petroleum ether/EtOAc) as a beige
powder (1.42 g, 85%).
1H NMR (CDCl3, 300 MHz): δ 8.52 (bs, 2H, NH), 7.67 (dd,
2H, JHH ) 8 Hz, JHP ) 7 Hz), 7.51 (t, 1H, 7 Hz), 7.44 (m, 2H),
7.29 (m, 4H), 7.03 (d, 4H, 8 Hz), 6.97 (d, 4H, 8 Hz), 6.86 (dd,
2H, JHH ) 8 Hz, JHP ) 7 Hz) and 6.68 (t, 2H, 7 Hz) (ArH),
2.26 (s, 6H, CH3). 31P{1H} NMR (CDCl3, 121 MHz): δ 42.4 (s).
13C{1H} NMR (CDCl3, 75 MHz): δ 150.9 (d, JCP ) 5 Hz), 139.0,
133.8, 133.7, 133.6 (d, JCP ) 2 Hz), 132.4, 132.3, 132.2, 129.9,
128.7 (d, JCP ) 23 Hz), 121.7, 118.0 (d, JCP ) 13 Hz), 115.2 (d,
JCP ) 8 Hz), and 113.6 (ArC), 20.9 (CH3). EI-MS (m/z): 488
(100, M+), 305 (50, M+ - TolNHPh), 183 (40, [TolNHPh]+).
[(4-MeC6H4)2N(2-C6H4)][(4-MeC6H4)NH(2-C6H4)]PhPd
O (E). Compound E was obtained as an impurity when the
above reaction was repeated with >5 g of (2-NH2C6H4)2PPh.
The off-white product was purified by silica gel chromatogra-
phy (4:1 petroleum ether/EtOAc) and recrystallized from
EtOH/H2O.
1H NMR (CDCl3, 300 MHz): δ 7.41 (m, 4H), 7.31-7.07 (m,
8H), 7.03 (d, 2H, 8 Hz), 6.94 (d, 2H, 8 Hz), 6.71 (bd, 8H), and
6.54 (t, 1H, 7 Hz) (ArH), 2.27 (s, 3H) and 2.12 (s, 6H) (CH3).
31P{1H} NMR (CDCl3, 121 MHz): δ 34.1 (s). 13C{1H} NMR
(CDCl3, 75 MHz): δ 152.2 (d, JCP ) 3 Hz), 149.8 (d, 4 Hz),
145.8, 139.3, 135.4 (d, 11 Hz), 133.5 (d, 2 Hz), 133.2 (d, 11
Hz), 132.6 (d, 3 Hz), 132.5, 132.4 (d, 2 Hz), 132.0 (d, 10 Hz),
131.4, 131.2 (d, 6 Hz), 131.1 (d, 3 Hz), 130.9, 129.7, 129.2, 128.1
1H NMR (C6D6, 300 MHz): δ 7.48 (bd, 2H), 7.29 (m, 4H),
7.04 (m, 5H), 6.82 (d, 4H, 8 Hz), 6.76 (d, 4H, 8 Hz), and 6.72
(m, 2H) (ArH), 6.36 (bs, 2H, NH), 2.06 (s, 6H, CH3). 31P{1H}
NMR (C6D6, 121 MHz): δ -30.9 (bs). 13C{1H} NMR (C6D6, 75
MHz): δ 148.5 (bs), 140.4, 135.2 (bs), 134.6, 134.3 (bs), 131.5,
130.8, 130.1, 129.2, 129.1, 122.5, 121.2, 120.5, and 116.6 (ArC),
20.7 (CH3).
[(4-MeC6H4)NLi(2-C6H4)]2PhP‚2THF (D). nBuLi (1.6 M
in hexanes, 1.1 mL, 1.75 mmol) was added dropwise to a
solution of C (0.37 g, 0.78 mmol) in hexanes (10 mL) and THF
(1 mL) at -35 °C. A yellow precipitate formed overnight and
was isolated on a frit, washed with pentane (3 × 1 mL), and
dried. Compound D was recrystallized from THF/toluene
layered with pentane (0.26 g, 53%).
1H NMR (C6D6, 500 MHz): δ 7.81 (bt, 2H, 6 Hz, ArH), 7.74
(t, 2H, 7 Hz, ArH), 7.66 (t, 2H, 7 Hz, ArH), 7.38 (d, 4H, 8 Hz,
ArH), 7.13 (m, 8H, ArH), 7.02 (t, 1H, 7 Hz, ArH), 6.67 (t, 2H,
7 Hz, ArH), 2.96 (bs, 8H, THF), 2.27 (s, 6H, Me), 0.87 (bs, 8H,
THF). 31P{1H} NMR (C6D6, 202 MHz): δ -33.0 (q, JPLi ) 41
Hz). 7Li NMR (C6D6, 194 MHz): δ -0.35 (d, 1Li, JLiP ) 41 Hz),
-1.72 (s, 1Li).
(2,4,6-Me3C6H2)(2-Br-4-MeC6H3)NH, (Mes)(BrTol)NH.
In air, N-bromosuccinimide (3.0 g, 16.9 mmol) was added
portionwise to a stirring solution of (Mes)(Tol)NH (3.8 g, 16.9
mmol) in CH3CN (100 mL) at 0 °C over 30 min. The solution
was warmed to room temperature, and a saturated solution
of NaHSO3 (5 mL) was added. The solution was evaporated
to dryness. The beige solids were purified by flash column
chromatography on silica gel (9:1 petroleum ether/ethyl
acetate). The first fraction was collected and concentrated to
yield beige crystals, which were isolated by filtration, washed
with petroleum ether (2 × 10 mL), and dried (4.9 g, 96%).

New Arene-Bridged Diamidophosphine Ligand
Organometallics, Vol. 24, No. 6, 2005 1117
1H NMR (CDCl3, 300 MHz): δ 7.33 (s, 1H, m-TolH), 6.96
(s, 2H, m-MesH), 6.83 and 6.07 (d, 1H, 8 Hz, o-, m-TolH), 5.51
(bs, 1H, NH), 2.33 (s, 3H, CH3), 2.23 (s, 3H, CH3), 2.17 (s, 6H,
o-CH3). 13C{1H} NMR (C6D6, 75 MHz): δ 141.5, 136.5, 136.0,
135.5, 132.9, 129.4, 129.1, 128.1, 112.6, and 109.4 (ArC), 21.1,
20.2, and 18.3 (CH3). EI-MS (m/z): 303 [100, M+]. Anal. Calcd
for C16H18N: C, 63.17; H, 5.96; N, 4.60. Found: C, 62.81; H,
5.99; N, 4.72.
(2,4,6-Me3C6H2)(2-Li-4-Me-C6H3)NLi‚2(tmeda)(F‚2tmeda).
A solution of (Mes)(BrTol)NH (0.79 g, 2.59 mmol) and tmeda
(0.80 mL, 5.30 mmol) in Et2O (5 mL) was cooled to -35 °C,
and 2.1 equiv of nBuLi (3.4 mL, 1.6 M in hexanes, 5.44 mmol)
was added dropwise with stirring. A light yellow precipitate
formed immediately and was isolated and dried (0.68 g, 1.44
mmol, 56%).
NH), 2.12 (s, 6H, CH3), 2.04 (bs, 6H, o-CH3), 1.98 (s, 6H, CH3),
1.90 (bs, 6H, o-CH3). 1H NMR (C6D5CD3, 500 MHz, 273 K): δ
7.63 (t, 2H, 7 Hz), 7.26 (d, 2H, 7 Hz), 7.10 (m, 3H), 6.84 (d,
2H, 7 Hz), 6.75 (s, 2H), 6.69 (s, 2H), 6.35 (dd, 2H, JPH ) 5 Hz,
JHH ) 9 Hz), 5.91 (d, 2H, 5 Hz, NH), 2.16 (s, 6H), 2.08 (s, 6H),
1
2.01 (s, 6H), 1.93 (s, 6H). H NMR (C6D5CD3, 300 MHz, 370
K): δ 7.59 (t, 2H, 8 Hz), 7.12 (m, 4H), 6.95 (m, 1H), 6.82 (d,
2H, 8 Hz), 6.73 (s, 4H), 6.23 (dd, 2H, JPH ) 5 Hz, JHH ) 9 Hz),
5.88 (bd, 2H, JPH ) 5 Hz), 2.12 (s, 6H), 2.01 (s, 6H), 1.98 (s,
12H, o-CH3). 31P{1H} NMR (C6D6, 121 MHz, 300K): δ -31.4
(s). 13C{1H} NMR (C6D6, 75 MHz, 300 K): δ 147.4 (JCP ) 16
Hz, ArC), 136.2 (ArC), 135.4 and 135.2 (bs, o-, m-MesC), 134.8,
134.7, 134.4, 134.2, 131.5, 129.3, 128.8, 128.7 (JCP ) 4 Hz),
117.9 (d, JCP ) 7 Hz), and 112.5 (JCP ) 3 Hz) (ArC), 20.6 (CH3),
20.1 (CH3), 18.0 (bs, o-CH3), 17.7 (bs, o-CH3). EI-MS (m/z): 556
(20, M+), 541 (100, M+ - Me). Anal. Calcd for C38H41N2P: C,
81.98; H, 7.42; N, 5.03. Found: C, 82.04; H, 7.46; N, 4.87.
[NPN]*Zr(NMe2)2 (3). Zr(NMe2)4 (0.58 g, 2.2 mmol) and 2
(1.20 g, 2.2 mmol) were mixed together, and toluene (15 mL)
was added. The lemon yellow solution was stirred for 2 h and
the solvent removed to yield a yellow residue. Upon addition
of pentanes (5 mL), a light yellow precipitate formed, which
was isolated on a frit and dried (1.4 g, 90%).
1H NMR (THF-d8, 300 MHz): δ 6.93 (d, 1H, 2 Hz, ArH),
6.74 (s, 2H, ArH), 6.38 (dd, 1H, 8 Hz, 2 Hz, ArH), 5.54 (d, 1H,
8 Hz, ArH), 2.31 (s, 4H, tmeda), 2.17 (s, 3H, CH3), 2.15 (s, 12H,
tmeda), 2.02 (s, 3H, CH3), 2.00 (s, 6H, CH3). 13C{1H} NMR
(THF-d8, 75 MHz): δ 153.8, 152.1, 133.5, 132.2, 129.4, 129.3,
128.4, 116.4, 113.3, and 111.5 (ArC), 58.8 and 46.2 (tmeda),
21.0, 20.0, and 18.9 (CH3).
[NPN]*Li2(dioxane) (1‚dioxane). To a solution of (Mes)-
(BrTol)NH (4.84 g, 15.9 mmol) in Et2O (100 mL) at -35 °C
was added nBuLi (1.55 M in hexanes, 20.5 mL, 31.8 mmol)
dropwise over 1 h. The clear yellow solution was warmed to
room temperature and stirred for 3 h. The solution was chilled
(-35 °C), and PhPCl2 (1.40 g, 7.8 mmol) in Et2O (10 mL) was
added dropwise over 2 h. The orange solution was warmed
slowly to room temperature and stirred for 24 h. The solvent
was removed, and hexanes (30 mL) and 1,4-dioxane (5 mL)
were added to the orange foam. A yellow precipitate formed,
which was collected on a frit and washed with hexanes. The
dark orange filtrate was concentrated and chilled to yield
additional yellow precipitate. The combined isolated solids
were dissolved in toluene (50 mL) and THF (0.5 mL), filtered
through Celite, and taken to dryness. The yellow powder was
recrystallized from toluene/hexanes and dried in vacuo (4.4 g,
85% isolated yield based on PhPCl2). NMR spectroscopy was
facilitated by the addition of a drop of THF to the suspension
of 1‚dioxane in C6D6. Although crystals and powders of
1‚dioxane decompose at room temperature over a period of a
few days, 1‚dioxane can be stored in crystalline form at -35
°C for months. Elemental analyses of 1‚dioxane were ham-
pered by its sensitivity to moist air; despite many attempts,
results that were low in carbon were found.
1H NMR (C6D6, 300 MHz): δ 7.60 (t, 2H, 8 Hz, o-PPh), 7.52
(d, 2H, 7 Hz, p-PTol), 7.11 (m, 3H, 7 Hz, m-, p-PPh), 7.02 (s,
2H, m-Mes), 6.97 (s, 2H, m-Mes), 6.93 (d, 2H, 9 Hz, m-PTol),
6.19 (dd, 2H, 8 Hz, o-PTol), 3.06 (s, 6H, N(CH3)2), 2.42 (s, 6H),
2.32 (s, 6H), 2.31 (s, 6H), 2.25 (s, 6H), and 2.08 (s, 6H) (ArCH3
and N(CH3)2). 31P{1H} NMR (C6D6, 121 MHz): δ -11.5. 13C-
{1H} NMR (C6D6, 75 MHz): δ 161.5 (JCP ) 31 Hz), 145.2, 144.6,
137.2, 136.4, 135.0, 134.7, 134.3, 133.3, 133.1, 130.3, 130.2,
118.0, 117.6, 115.1, and 115.0 (ArC), 43.6 and 43.5 (N(CH3)2),
21.0, 20.4, 19.3, and 19.2 (CH3). EI-MS (m/z): 732 (<1, M+),
688 (30, M+ - NMe2), 556 (30, M+ - Zr(NMe2)2), 541 (100, M+
- Zr(NMe2)2, - Me). Anal. Calcd for C42H45N4PZr: C, 68.72;
H, 7.00; N, 7.63. Found: C, 68.42; H, 6.99; N, 7.38.
[NPN]*ZrCl2 (4). To a toluene solution (40 mL) of 3 (1.20
g, 1.6 mmol) was added chlorotrimethylsilane (1.77 g, 16.3
mmol). The clear yellow solution was stirred overnight and a
yellow precipitate formed. The reaction was followed by 31P-
{1H} NMR spectroscopy to ensure completion. Solvent was
removed, and the resulting yellow powder was washed with
pentanes (3 × 5 mL) and dried (1.04 g, 89%).
1H NMR (C6D6, 400 MHz): δ 7.60 (dd, 2H, 7 Hz), 7.45 (d,
2H, 8 Hz), 7.05 (m, 3H), 6.91 (s, 2H), 6.84 (d, 2H, 8 Hz), 6.80
(s, 2H), and 6.05 (dd, 2H, 7 Hz) (ArH), 2.46 (s, 6H), 2.34 (s,
6H), 2.09 (s, 6H), and 1.94 (s, 6H) (CH3). 31P{1H} NMR (C6D6,
121 MHz): δ -2.8. 13C{1H} NMR (C6D6, 75 MHz): δ 159.9 (JCP
) 32 Hz), 138.5, 138.3, 137.0, 135.3, 134.6, 132.3, 132.2, 131.1,
130.8, 129.6, 125.6, 121.1, 120.6, 114.9, and 114.8 (ArC), 21.1,
20.3, and 19.1 (CH3). EI-MS (m/z): 714 (3, M+), 541 (100, M+
- ZrCl2 - Me). Anal. Calcd for C38H39N2Cl2PZr: C, 63.67; H,
5.48; N, 3.91. Found: C, 63.65; H, 5.80; N, 3.98.
1H NMR (C6D6, 300 MHz): δ 7.81 (t, 2H, JHP ) JHH ) 7
Hz), 7.72 (bd, 2H, 3 Hz), 7.19 (t, 2H, 7 Hz), 7.02 (t, 1H, 8 Hz),
6.97 (s, 2H), 6.87 (s, 2H), 6.85 (d, 2H, 8 Hz), and 6.52 (dd, 2H,
8 Hz) (ArH), 3.36 (s, 8H, C4H8O2) 2.35 (s, 6H), 2.33 (s, 6H),
2.28 (s, 6H), and 2.16 (s, 6H) (CH3). 31P{1H} NMR (C6D6, 121
7
MHz): δ -35.2 (q, JPLi ) 40 Hz). Li NMR (C6D6, 155 MHz):
δ -0.07 (d, 1Li, JPLi ) 40 Hz), -1.97 (s, 1Li). 13C{1H} NMR
(C6D6, 75 MHz): δ 162.1 (JCP ) 28 Hz), 152.0, 140.2, 134.9
(JCP ) 3 Hz), 133.8, 132.3 (JCP ) 14 Hz), 132.2, 132.1, 131.8,
130.8, 129.0, 128.8, 126.8, 122.9, 120.9 (JCP ) 12 Hz), and 117.9
(JCP ) 5 Hz) (ArC), 67.1 (C4H8O), 20.9, 20.7, 20.4, and 20.2
(CH3). Anal. Calcd for C46H55N2Li2O2P: C, 77.51; H, 7.78; N,
3.93. Found: C, 74.75; H, 7.59; N, 4.02.
[NPN]*ZrCl2(THF) (5). THF (1-2 drops) was added to an
NMR tube with 4 (20 mg, 28 µmol) in C6D6 to produce a bright
red-orange solution. This species was characterized by NMR
spectroscopy only; coordinated THF was obscured by the excess
THF present.
1H NMR (C6D6, 300 MHz): δ 7.75 (t, 2H, 8 Hz), 7.38 (d, 2H,
8 Hz), 7.07 (m, 3H), 6.91 (s, 2H), 6.83 (s, 2H), 6.82 (d, 2H, 8
Hz), and 6.04 (dd, 2H, JHH ) 7 Hz, JPH ) 6 Hz) (ArH), 2.46 (s,
6H), 2.30 (s, 6H), 2.12 (s, 6H), and 1.95 (s, 6H) (CH3). 31P{1H}
NMR (C6D6, 121 MHz): δ 2.7.
[NPN]*H2 (2). Trimethylammonium chloride (0.319 g, 3.3
mmol) was added all at once to a stirring solution of 1‚dioxane
(1.06 g, 1.6 mmol) in THF (15 mL). After 1 h, solvent was
removed from the beige suspension and toluene was added (20
mL). The toluene suspension was filtered through Celite and
the filtrate taken to dryness. The solids were washed with
pentane and dried to yield a white powder (0.87 g, 97%).
1H NMR (C6D6, 300 MHz, 300 K): δ 7.68 (dd, 2H, JPH ) 7
Hz, JHH ) 7 Hz, ArH), 7.29 (d, 2H, JPH ) 7 Hz, ArH), 7.12 (d,
6 Hz, 4H, ArH), 7.02 (t, 1H, 8 Hz, p-PhP), 6.88 (d, 2H, 7 Hz,
ArH), 6.78 (bs, 2H, m-MesH), 6.74 (bs, 2H, m-MesH), 6.38 (dd,
2H, JPH ) 5 Hz, JHH ) 9 Hz, ArH), 5.98 (d, 2H, JPH ) 5 Hz,
[NPN]*ZrMe2 (6). To a solution of 4 (0.300 g, 0.42 mmol)
in Et2O (10 mL) at -35 °C in the dark was added methylmag-
nesium chloride (3.0 M in THF, 0.31 mL, 0.92 mmol) dropwise
with stirring. The yellow solution was warmed to room
temperature, and 1,4-dioxane (0.1 mL) was added. The solution
was filtered through Celite, and the solvent was removed.
Addition of pentane (5 mL) precipitated a yellow solid, which
was isolated and dried under vacuum (0.225 g, 80%).

1118 Organometallics, Vol. 24, No. 6, 2005
MacLachlan and Fryzuk
1H NMR (C6D6, 500 MHz): δ 7.54 (m, 4H), 7.07 (m, 2H),
7.02 (m, 1H), 6.93 (s, 2H), 6.90 (d, 2H, 2 Hz), 6.88 (s, 2H), and
6.12 (t, 2H, JPH ) JHH ) 7 Hz) (ArH), 2.51 (s, 6H), 2.14 (s,
6H), 2.09 (s, 6H), and 2.00 (s, 6H) (ArCH3), 0.93 (d, JPH ) 5
Hz, 3H, ZrCH3), -0.11 (s, 3H, ZrCH3). 31P{1H} NMR (C6D6,
202.5 MHz): δ -14.1. 13C{1H} NMR (C6D6, 125.8 MHz): δ
159.4 (JCP ) 33 Hz), 139.4, 138.6, 137.5, 135.3 (JCP ) 5 Hz),
135.1 (JCP ) 3 Hz), 134.4, 132.1 (JCP ) 13 Hz), 130.9, 130.4,
129.2 (JCP ) 4 Hz), 129.1, 129.0, 128.3, 121.1 (JCP ) 25 Hz),
and 114.3 (JCP ) 9 Hz) (ArC), 45.1 (JCP ) 6 Hz, ZrCH3), 41.8
(JCP ) 29 Hz, ZrCH3), 21.1, 20.3, 19.1, and 18.9 (ArCH3). Anal.
Calcd for C40H45N2PZr: C, 71.07; H, 6.71; N, 4.14. Found: C,
71.35; H, 7.06; N, 4.08.
were performed using the SHELXTL29 crystallographic soft-
ware package of Bruker-AXS. The structure was solved by
direct methods.30 All non-hydrogen atoms were refined aniso-
tropically using SHELXL-97.31 Compound 4 crystallized with
two and a half molecules of benzene in the asymmetric unit.
Hydrogen atoms were included in fixed positions. Structures
were solved and refined using the WinGX software package
version 1.64.05.32
Acknowledgment. We thank NSERC of Canada
and the Izaak Walton Killam Foundation for funding
(Discovery Grant to M.D.F., Postgraduate Scholarships
to E.M.). We also thank Ms. Nelly Ousatiouk for help
with compound preparation.
X-ray Crystal Structure Analysis. Selected crystals were
coated in oil, mounted on a glass fiber, and placed under an
N2 stream. Measurements for compounds 1‚2THF and 4 were
made on a Bruker X8 Apex diffractometer with graphite-
monochromated Mo KR radiation (λ ) 0.71073 Å). The data
were collected at a temperature of -100 ( 1 °C. Data were
collected and integrated using the Bruker SAINT23 software
package. Data were corrected for absorption effects using the
multiscan technique (SADABS24) and for Lorentz and polar-
ization effects. Neutral atom scattering factors were taken
Supporting Information Available: Variable-tempera-
ture NMR spectrum of [NPN]*H2; X-ray data for 1‚2THF and
4 are given as CIF files. This material is available free of
charge via the Internet at http://pubs.acs.org.
OM049165X
from Cromer and Waber.25 Anomalous dispersion effects were
(27) Creagh, D. C., McAuley, W. J. In International Tables for
Crystallography; Wilson, A. J. C., Ed.; Kluwer Academic Publishers:
Boston, 1992; Vol. C, Table 4.2.6.8, pp 219-222.
26
included in Fcalc
;
the values for ∆f ′′ and ∆f ′′′ were those of
Creagh and McAuley.27 The values for the mass attenuation
coefficients are those of Creagh and Hubbell.28 All refinements
(28) Creagh, D. C., Hubbell, J. H. In International Tables for
Crystallography; Wilson, A. J. C., Ed.; Kluwer Academic Publishers:
Boston, 1992; Vol C, Table 4.2.4.3, pp 200-206.
(23) SAINT, Version 6.02; Bruker AXS Inc.: Madison, WI, 1999.
(24) SADABS, Bruker Nonius area detector scaling and absorption
correction-V2.05; Bruker AXS Inc.: Madison, WI.
(29) SHELXTL Version 5.1; Bruker AXS Inc.: Madision, WI,
1997.
(30) SIR92: Altomare, A.; Cascarano, M.; Giacovazzo, C.; Gua-
gliardi, A. J. Appl. Crystallogr. 1994, 26, 343.
(25) Cromer, D. T., Waber, J. T. International Tables for X-ray
Crystallography; The Kynoch Press: Birmingham, England, 1974; Vol.
IV, Table 2.2 A.
(31) Sheldrick, G. M. Shelx97. Programs for Crystal Structure
Analysis; University of Gottingen: Germany, 1997.
(32) Farrugia, L. J. J. Appl. Crystallogr. 1999, 32, 837.
(26) Ibers, J. A.; Hamilton, W. C. Acta Crystallogr. 1964, 17, 781.