Neutral and Cationic Organoaluminum Complexes Utilizing a Novel Anilido-Phosphinimine Ancillary Ligand

Article abstract of DOI:10.1021/om034302w

A new chelating N,N ligand family incorporating an anilido-phosphinimine donor set has been designed and an example prepared in multigram quantities in three steps using a convenient, modular synthetic approach. The ligand 1-(NHAr)-2-(PPh₂=NAr′

Full text of DOI:10.1021/om034302w

Organometallics 2004, 23, 1811-1818
1811
Neu tr a l a n d Ca tion ic Or ga n oa lu m in u m Com p lexes
Utilizin g a Novel An ilid o-P h osp h in im in e An cilla r y
Liga n d
Gregory C. Welch,† Warren E. Piers,*,† Masood Parvez,† and Robert McDonald‡
Department of Chemistry, University of Calgary, 2500 University Drive, NW,
Calgary, Alberta, Canada T2N 1N4, and X-ray Structure Laboratory, Department of
Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2G2
Received November 17, 2003
A new chelating N,N ligand family incorporating an anilido-phosphinimine donor set has
been designed and an example prepared in multigram quantities in three steps using a
convenient, modular synthetic approach. The ligand 1-(NHAr)-2-(PPh2dNAr′)C6H4 (1‚H; Ar
) 2,6-iPr2-C6H3; Ar′ ) 2,4,5-Me3C6H2) was prepared in three steps in a 30-35% overall yield
and was fully characterized in its protio form as well as in the form of its lithium salt, 1‚Li.
In both compounds, the donor array assumes a conformation in which the PdN moiety dips
out of the plane formed by the four atoms in the rigid ortho-disubstituted aryl ring of the
ligand backbone. The coordinating properties of the new ligand were demonstrated by the
synthesis of some organoaluminum derivatives. The monomeric compounds LAlMe2 (2) and
LAlH2 (3) were prepared by the reaction of 1‚H with AlMe3 and AlH3‚NMe3, respectively,
and were fully characterized by NMR spectroscopy and X-ray crystallography. Cationic
derivatives were formed by activation of 2 and 3 with either B(C6F5)3 or [Ph3C]+[B(C6F5)4]-.
All of the neutral and cationic compounds qualitatively exhibited high levels of stability in
comparison to related organoaluminum compounds, illustrating the exemplary steric and
electronic properties of the new ligand system.
In tr od u ction
Rearrangements involving cleavage of the nacnac ligand
structure similar to what Mindiola et al. have observed
in (nacnac)TiIIIR2 compounds5 appear to be initiated by
hydride transfer from the metal to the ligand backbone,
indicating a susceptibility to nucleophilic attack.
To mitigate against the tendency toward this type of
process, we developed the anilido imine donor II,6
presuming that the aromatic ring in the ligand backbone
would discourage nucleophilic transfer to the ligand.
While this ligand has allowed for access of highly
reactive yttrium cations, the isolated imine function is
still subject to attack by nucleophiles (aldimines) or to
deprotonation (ketimines) in ligands of this type. Similar
problems were encountered in organo-group 3 com-
pounds of the related salicylaldiminato ligands.7
The need for noncyclopentadienyl ligand frameworks
to support reactive electrophilic organotransition-metal
complexes has resulted in a wide range of new ancillary
ligands.1 Our focus has been on development of ligands
able to provide a foundation for new organogroup 3
metal chemistry.2 To this end, we have established the
emerging â-diketiminato ligand3 (“nacnac”) framework
I as a suitable platform for the development of the
The recent surge of activity in the use of the phos-
phinimine donor in organotransition-metal chemistry8
pointed the way to the next step in the evolution of our
ligand system. Incorporation of a phosphinimine instead
of the imine function as in III should make the ligand
chemistry of organoscandium cations.4 This ligand
system has many strengths as an ancillary ligand for
electrophilic metals; however, in recent work directed
toward the synthesis of hydrido complexes, some draw-
backs to the nacnac ligand family have come to light.
(5) Basuli, F.; Bailey, B. C.; Tomaszewski, J .; Huffman, J . C.;
Mindiola, D. J . J . Am. Chem. Soc. 2003, 125, 6052.
(6) (a) Welch, G. C.; Hayes, P. G.; Emslie, D. J . H.; Noack, C. L.;
Piers, W. E.; Parvez, M. Organometallics 2003, 22, 1577. (b) A similar
ligand was first reported here: Porter, R. M.; Winston, S.; Danopoulos,
A. A.; Hursthouse, M. B. Dalton 2002, 3290.
* To whom correspondence should be addressed. Phone: 403-220-
5746. Fax: 403-289-9488. E-mail: wpiers@ucalgary.ca. S. Robert Blair
Professor of Chemistry (2000-2005).
† University of Calgary.
‡ University of Alberta.
(1) Gibson, V. C.; Spitzmesser, S. K. Chem. Rev. 2003, 103, 283.
(2) Emslie, D. J . H.; Piers, W. E. Coord. Chem. Rev. 2002, 233-
234, 129.
(3) Bourget-Merle, L.; Lappert, M. F.; Severn, J . R. Chem. Rev. 2002,
102, 3031.
(4) (a) Hayes, P. G.; Piers, W. E.; McDonald, R. J . Am. Chem. Soc.
2002, 124, 2132. (b) Hayes, P. G.; Piers, W. E.; Parvez, M. J . Am. Chem.
Soc. 2003, 125, 5622.
(7) (a) Emslie, D. J . H.; Piers, W. E.; McDonald, R. Dalton 2002,
293. (b) Emslie, D. J . H.; Piers, W. E.; Parvez, M.; McDonald, R.
Organometallics 2002, 21, 4226. (c) Emslie, D. J . H.; Piers, W. E.;
Parvez, M. Dalton 2003, 2615.
(8) (a) Stephan, D. W.; Stewart, J . C.; Guerin, F.; Spence, R. E. v.
H.; Xu, W.; Harrison, D. G. Organometallics 1999, 18, 1116. (b) Cavell,
R. G.; Babu, K.; Aparna, K. J . J . Organomet. Chem. 2001, 617-618,
158.
10.1021/om034302w CCC: $27.50 © 2004 American Chemical Society
Publication on Web 02/03/2004

1812 Organometallics, Vol. 23, No. 8, 2004
Welch et al.
Sch em e 1
resistant to nucleophilic attack while improving its
abilities as donor in comparison to the imine-based
ligands II. In this paper, we describe the synthesis of a
ligand of type III, where NAr is the 2,6-diisopropyl group
and the PNAr aryl substituent is the mesityl group.
Stephan et al. have recently reported a ligand with an
amido/phosphinimine donor array based on the nacnac
structure I;9 the ligand family III offers a more rigid
backbone without any tautomerization pathways to
complicate the chemistry involved. Here we demonstrate
the efficacy of the new ligand for stabilizing electrophilic
metal centers by the synthesis and characterization of
some neutral and cationic organoaluminum compounds.
Although ultimately designed for implementation in
group 3, organoaluminum chemistry has served as a
proving ground for new monoanionic ligands and several
recent studies on LAlR2 derivatives are available for
comparison.10-17
with chlorodiphenylphosphine leads to the fluorinated
triphenylphosphine derivative shown.18 The presence of
the fluorine is clearly indicated in both the 19F and 31P
NMR spectra (3J FP ) 53.4 Hz). Attempts at this stage
to institute the anilido portion of the ligand via nucleo-
philic aromatic substitution (NAS)19 failed, due to the
electron-donating nature of the -PPh2 group. Therefore,
the phosphinimine function was introduced by a
Staudinger reaction20 with mesityl azide21 as shown; the
NAS reaction then proceeded smoothly in refluxing THF
with the 2,6-iPr-C6H3NHLi reagent to give the protio
ligand 1 in three steps with an overall yield of 30-35%.
The procedure can be conveniently performed on a
multigram scale using commercially available or easily
prepared reagents. Furthermore, the synthesis is highly
amenable to variation, potentially allowing for extensive
steric and electronic tuning of this ligand system. For
example, substitution on the aromatic backbone should
be possible with tolerant functional groups. Use of
different phosphine chloride reagents ClPRR′ will allow
for variation at phosphorus, and both of the N-aryl
groups can be readily changed. Examples of ligands with
several different combinations of N-aryl groups have
been prepared using various azide or anilidolithium
reagents;22 this contribution will focus on ligand 1
specifically.
Resu lts a n d Discu ssion
Liga n d Syn th esis. The synthesis of the ligand 1 is
outlined in Scheme 1. Low-temperature, selective lithia-
tion of bromo-2-fluorobenzene followed by quenching
(9) (a) Masuda, J . D.; Wei, P.; Stephan, D. W. Dalton 2003, 3500.
(b) See also the following paper: Masuda, J . D.; Walsh, D. M.; Wei,
P.; Stephan, D. W. Organometallics 2004, 23, 1819.
(10) L ) phosphinimine: (a) Schultz, S.; Raab, M.; Nieger, M.;
Niecke, E. Organometallics 2000, 19, 2616. (b) Ong, C. M.; McKarns,
P.; Stephan, D. W. Organometallics 1999, 18, 4197. (c) Aparna, K.;
McDonald, R.; Ferguson, M.; Cavell, R. G. Organometallics 1999, 18,
4241.
(11) L ) â-diketiminato: (a) Radzewich, C. E.; Guzei, I. A.; J ordan,
R. F. J . Am. Chem. Soc. 1999, 121, 8673. (b) Radzewich, C. E.; Coles,
M. P.; J ordan, R. F. J . Am. Chem. Soc. 1998, 120, 9384. (c) Qian, B.;
Ward, D. L.; Smith, M. R., III. Organometallics 1998, 17, 3070. (d)
Cui, C.; Roesky, H. W.; Hao, H.; Schmidt, H. G.; Noltemeyer, M. Angew.
Chem., Int. Ed. 2000, 39, 1815. (e) Cosledan, F.; Hitchcock, P. B.;
Lappert, M. F. Chem. Commun. 1999, 705.
(12) L ) amidinato: (a) Coles, M. P.; J ordan, R. F. J . Am. Chem.
Soc. 1997, 119, 8125. (b) Dagorne, S.; Guzei, I. A.; Coles, M. P.; J ordan,
R. F. J . Am. Chem. Soc. 2000, 122, 274. (c) Abeysekera, D.; Robertson,
K. N.; Cameron, T. S.; Clyburne, J . A. C. Organometallics 2001, 20,
5532. (d) J enkins, H. A.; Abeysekera, D.; Dickie, D. A.; Clyburne, J . A.
C. Dalton 2002, 3919. (e) Schmidt, J . A. R.; Arnold, J . Organometallics
2002, 21, 2306. (f) Aeilts, S. L.; Coles, M. P.; Swenson, D. C.; J ordan,
R. F.; Young, V. G., J r. Organometallics 1998, 17, 3265.
(13) L ) aminotroponiminato: (a) Korolev, A. V.; Ihara, E.; Guzei,
I. A.; Young, V. G., J r.; J ordan, R. F. J . Am. Chem. Soc. 2001, 123,
8291. (b) Korolev, A. V.; Delpech, F.; Dagorne, S.; Guzei, I. A.; J ordan,
R. F. Organometallics 2001, 20, 3367. (c) Dias, H. V. R.; J in, W.;
Ratcliff, R. E. Inorg. Chem. 1995, 34, 6100.
(14) L ) amido/imino or pyridyl: (a) Bruce, M.; Gibson, V. C.;
Redshaw, C.; Solan, G. A.; White, A. J . P.; Williams, D. J . Chem.
Commun. 1998, 2523. (b) Gibson, V. C.; Redshaw, C.; White, A. J . P.;
Williams, D. J . J . Organomet. Chem. 1998, 550, 453. (c) Pappalardo,
D.; Tedesco, C.; Pellechchia, C. Eur. J . Inorg. Chem. 2002, 621. (d)
Emig, M.; Nguyen, H.; Krautscheid, H.; Reau, R.; Casaux, J .-B.;
Bertrand, G. Organometallics 1998, 17, 3599. (e) Emig, M.; Reau, R.;
Krautscheid, H.; Fenske, D.; Bertrand, G. J . Am. Chem. Soc. 1996,
118, 5822. (f) Trepanier, S.; Wang, S. Organometallics 1994, 13, 2213.
(g) Trepanier, S.; Wang, S. Can. J . Chem. 1996, 74, 2032. (h)
Ashenhurst, J .; Brancaleon, L.; Gao, S.; Liu, W.; Schmider, H.; Wang,
S.; Wu, G.; Wu, Q. G. Organometallics 1998, 17, 5334.
(15) L ) pendant arm Schiff base: Cameron, P. A.; Gibson, V. C.;
Redshaw, C.; Segal, J . A.; Bruce, M. D.; White, A. J . P.; Williams, D.
J . Chem. Commun. 1999, 1883.
(16) L ) pendant arm triazacyclononane: (a) Robson, D. A.; Rees,
L. H.; Mountford, P.; Schro¨der, M. Chem. Commun. 2000, 1269. (b)
Cui, C.; Giesbrecht, G. R.; Schmidt, J . A. R.; Arnold, J . Inorg. Chim.
Acta 2003, 351, 404.
The protio ligand 1‚H has been fully characterized by
multinuclear NMR spectroscopy and X-ray crystal-
lography (Figure 1). Characteristic NMR resonances
1
include a signal at 9.1 ppm in the H NMR spectrum
for the chelated NH‚‚‚N proton and a peak at -0.8 ppm
in the 31P{1H} NMR spectrum. In the solid state, the
ligand structure is confirmed and an anilido/phosphin-
imine ligand array is apparent. However, the five atoms
in the chelating network are not coplanar, with the
phophinimine nitrogen N(2) dipping below the plane
defined by N(1)-C(14)-C(13)-P(1) by 0.922(3) Å; the
C(14)-C(13)-P(1)-N(2) dihedral angle is 44.1(2)°. As
a result, the N-aryl groups are arranged in a funda-
mentally different, and less symmetrical, spatial array
(18) McEwen, E. W.; J anes, A. B.; Knapczyk, J . W.; Kyllingstad, V.
L.; Shiau, W.; Shore, S.; Smith, J . J . Am. Chem. Soc. 1978, 100, 7304.
(19) Miller, J . Aromatic Nucleophilic Substitution; Elsevier: New
York, 1968.
(20) (a) Meyer, J .; Staudinger, H. Helv. Chim. Acta 1919, 2, 635.
(b) Alajarin, M.; Leonardo, C. L.; Lorente, P. L.; Bautista, D. Synthesis
2000, 14, 2085.
(21) Abe, S.; Murata, S.; Tomioka, H. J . Org. Chem. 1997, 62, 3055.
(22) Conroy, K. D.; Welch, G. C.; Piers, W. E.; Parvez, M. Unpub-
lished results.
(17) L ) miscellaneous: (a) Walfort, B.; Leedham, A. P.; Russell,
C. A.; Stalke, D. Inorg. Chem. 2001, 40, 5668. (b) Hasselbring, R.;
Roesky, H. W.; Heine, A.; Stalke, D.; Sheldric, G. M. Z. Naturforsch.,
B 1993, 48, 43. (c) Parkin, G.; Dowling, C. M. Polyhedron 1999, 18,
3567. (d) Zheng, W.; Hohmeister, H.; Mo¨sch-Zanetti, N. C.; Roesky,
H. W.; Noltemeyer, M.; Schmidt, H.-G. Inorg. Chem. 2001, 40, 2363.
(e) Ong, C. M.; Stephan, D. W. Inorg. Chem. 1999, 38, 5189. (f) Wang,
Z.-X.; Li, Y.-X. Organometallics 2003, 22, ASAP.

Al Complexes with an Anilido-Phosphinimine Ligand
Organometallics, Vol. 23, No. 8, 2004 1813
F igu r e 1. Crystalmaker diagram of the molecular struc-
ture of 1‚H . Selected bond distances (Å): P(1)-N(2),
1.563(2); P(1)-C(13), 1.817(2); N(1)-C(14), 1.382(3); N(1)-
C(1), 1.436(3); N(2)-C(31), 1.413(3). Selected bond angles
(deg): C(13)-P(1)-N(2), 116.45(10); N(1)-C(14)-C(13),
120.1(2). Selected torsion angles (deg): N(1)-C(14)-C(13)-
P(1), -3.7(3); N(2)-P(1)-C(13)-C(14), 44.06(19).
F igu r e 2. Crystalmaker diagram of the molecular struc-
ture of 1‚Li. Selected bond distances (Å): P(1)-N(2),
1.5932(14); P(1)-C(14), 1.7881(18); N(1)-C(13), 1.360(2);
N(1)-C(1), 1.429(2); N(2)-C(31), 1.417(2); N(1)-Li(1),
1.941(3); N(2)-Li(1), 1.946(3); Li(1)-C(34), 2.643(3); Li(1)-
C(35), 2.410(3). Selected bond angles (deg): C(14)-P(1)-
N(2), 117.38(8); N(1)-C(13)-C(14), 120.57(15); N(1)-
Li(1)-N(2), 106.31(14); Selected torsion angles (deg): N(1)-
C(13)-C(14)-P(1), 11.5(2); N(2)-P(1)-C(14)-C(13),
-53.57(16).
in comparison to that found for the nacnac ligands, with
the phosphinimine N-aryl group angling below the
coordination plane of the ligand. The P-aryl groups
occupy axial and equatorial orientations, with the axial
phenyl group in particular showing potential for provid-
ing steric protection to a coordinated metal. The P(1)-
N(2) length of 1.563(2) Å is typical of PdN double bonds.
The ligand is readily lithiated by treatment with
n-BuLi in toluene/hexanes at -78 °C. Lithiation is
indicated by a loss of the N-H proton resonance in the
1H NMR spectrum, with the rest of the spectrum
remaining topologically similar to that of 1‚H. In the
31P{1H} NMR spectrum, the signal appears downfield
of that in 1‚H at 13.3 ppm, indicating strong electron
donation to the Li cation relative to the proton. The
material is soluble in C6D6, and crystals grown from this
medium were examined by X-ray crystallography; the
structure is shown in Figure 2. The Li cation is unsol-
vated, and the compound forms a dimer in which the
Li is satiated by π donation from the N-mesityl ring of
the opposing molecule; the Li(1)-C(34) and Li(1)-C(35)
distances are 2.643(3) and 2.410(3) Å, respectively. Such
interactions are not uncommon in unsolvated lithium
salts.23 Within the monomer, the Li(1)-N(1) and Li(1)-
N(2) separations are 1.941(3) and 1.946(3) Å, surpris-
ingly close for a ligand expected to coordinate in a more
localized mode; the dimeric structure of this particular
complex may play a role in equalizing these M-N
lengths, since these distances are generally more dis-
parate in other complexes.22 The P(1)-N(2) length has
increased slightly over that in the protio ligand to
1.5932(14) Å, and the ligand maintains its nonplanar
coordinating style.
Sch em e 2
ligand’s coordinating ability, some organoaluminum
complexes have been prepared and compared with
related compounds supported by other ligand systems.
While the salt 1‚Li is an effective reagent for introduc-
ing the ligand to early-transition-metal complexes,22 1‚
H itself is all that is required to generate organo-
aluminum complexes (Scheme 2). Reaction between 1‚
H and AlMe3 below 0 °C in toluene results in rapid
adduct formation, as indicated by a downfield shift in
the 31P{1H} resonance to 22.9 ppm and an upfield shift
to 5.32 ppm for the anilido proton in the 1H NMR
spectrum, which is no longer chelated by the two
nitrogen donors. A singlet at -0.45 ppm integrated to
nine protons is assigned to the AlMe3 protons. As the
reaction mixture is warmed to room temperature, slow
evolution of CH4 is observed with the concomitant
Or ga n oa lu m in u m Ch em ist r y: Neu t r a l Com -
p lexes. To demonstrate the new anilido phosphinimido
(23) See for example: Said, M.; Thornton-Pett, M.; Bochmann, M.
Organometallics 2001, 20, 5629 and references therein.

1814 Organometallics, Vol. 23, No. 8, 2004
Welch et al.
F igu r e 3. Crystalmaker diagram of the molecular struc-
ture of 2. Selected bond distances (Å): P(1)-N(2),
1.6139(3); N(1)-Al(1), 1.891(3); N(2)-Al(1), 1.926(3);
Al(1)-C(1), 1.972(4); Al(1)-C(2), 1.974(4); P(1)-C(4),
1.782(2). Selected bond angles (deg): N(1)-Al(1)-N(2),
99.07(12); N(1)-Al(1)-C(2), 112.99(18); N(2)-Al(1)-C(2),
107.65(15); C(1)-Al(1)-C(2), 113.7(2); C(4)-P(1)-N(2),
110.40(15).
F igu r e 4. Crystalmaker diagram of the molecular struc-
ture of 3. Selected bond distances (Å): P(1)-N(1),
1.6181(17); N(1)-Al(1), 1.904(2); N(2)-Al(1), 1.8921(19);
Al(1)-H(1), 1.53(2); Al(1)-H(2), 1.53(2); P(1)-C(1),
1.779(2). Selected bond angle (deg): N(1)-Al(1)-N(2),
100.02(8).
appearance of a new signal in the 31P{1H} NMR
spectrum at 30.0 ppm, as the dimethyl aluminum
complex 2 is formed. It can be isolated as a white solid
from pentane in >70% yield. Solid or solution samples
of 2 that were exposed to atmosphere for time periods
of 1 day or more showed no signs of decomposition, as
judged by 31P and 1H NMR spectroscopy, attesting to
this ligand’s ability to stabilize electrophilic metal
centers both sterically and electronically. While other
LAlMe2 compounds have been reported to exhibit mod-
erate stability upon brief exposure to the atmosphere,12c
2 shows remarkable tolerance to the dry air of the
western foothills.
when larger groups (Me vs H) are on Al. In any case, it
is likely that the energy surface connecting various
coordination geometries is quite soft. In variable-tem-
perature NMR studies, the methyl groups on the Al
remain equivalent down to -90 °C, indicating a highly
fluxional system in comparison to, for example, (nac-
nac)ScR2 compounds.25
In both 2 and 3, the Al-N lengths are again quite
similar, differing by only 0.03 and 0.01 Å, respectively.
In a localized bonding picture, the amido N bond to
aluminum might be expected to be shorter than the
dative interaction between the phosphinimine N donor
and aluminum. The similarity in these distances again
illustrates the ability of the phosphinimine function to
act as a strong donor, a notion supported by concomitant
lengthening in the P-N bond and contraction in the
P-C bonds observed in the Li and Al complexes of 1
relative to the corresponding parameters in 1‚H. The
chelate bite angle of this ligand is quite wide relative
to other N,N donors that have been applied to organo-
aluminum chemistry. In 2, the N(1)-Al(1)-N(2) angle
is 99.07(12)°, while in 3 this value is 100.02(8)°. For
comparison, the N-Al-N bite angle in other complexes
LAlMe2 are 96.17(7)° for L ) â-diketiminato,11a,b
83.3(1)° for L ) aminotroponiminate,13a and ∼69° for
amidinate complexes.12 The angle for 1 is smaller than
that for a bis(iminophosphorane)AlMe2 (108.96(8)°)
compound.10c
24
Reaction of 1‚H with freshly prepared AlH3‚NMe3
rapidly generates a dihydride species 3 (Scheme 2) with
loss of H2. The NMR spectra for 3 are similar to those
obtained for 2, except that the AlMe resonances are
replaced by a broad singlet integrated to two hydrogens
at 4.67 ppm for the AlH2 moieties. The IR spectrum for
3 exhibits absorptions at 1828 and 1780 cm-1, typi-
cal values for asymmetric and symmetric Al-H
stretches.11d,13c
Both the dimethyl compound 2 and the dihydride 3
were characterized by X-ray crystallography, and the
molecular structures are shown as Crystalmaker dia-
grams in Figures 3 and 4, respectively. Although the
aluminum center is of distorted-tetrahedral geometry
in each case, the two structures illustrate the flexibility
with which the ligand coordinates the Al center. In the
dimethyl derivative, of the six atoms in the chelate
array, it is the Al atom that protrudes from an idealized
plane; in dihydride 3, the P atom deviates from this
putative plane. As a result, the P-phenyl rings are
“axial” and “equatorial” in a much more pronounced way
in 3 than in the dimethyl derivative 2, with the axial
phenyl group leaning toward the Al coordination envi-
ronment. Perhaps this arrangement is discouraged
Or ga n oa lu m in u m Ch em istr y: Ca tion ic Com -
p lexes. Low-coordination-number cationic organo-
aluminum compounds are an extraordinarily electro-
philic class of molecules that have been implicated as
catalysts for ethylene polymerization11a,14a,b and initia-
tors for polyisobutylene synthesis26 and ring-opening
(25) Hayes, P. G.; Lee, L. W. M.; Knight, L. K.; Piers, W. E.; Parvez,
M.; Elsegood, M. R. J .; Clegg, W.; MacDonald, R. Organometallics 2001,
20, 2533.
(26) Bochmann, M.; Dawson, D. M. Angew. Chem., Int. Ed. Engl.
1996, 35, 2226.
(24) Ruff, J . K.; Hawthorne, M. F. J . Am. Chem. Soc. 1960, 82, 2141.

Al Complexes with an Anilido-Phosphinimine Ligand
Organometallics, Vol. 23, No. 8, 2004 1815
Sch em e 3
Sch em e 4
polymerization of propylene oxide.13a,27 While the active
species in the former process has not been firmly
established,14a,28 the role of the cationic organoalumi-
num species is less ambiguous in the last two reactions,
where a cationic polymerization mechanism is unques-
tioned.
Compound 2 serves as a precursor to cationic methyl-
aluminum derivatives 4 upon treatment with Lewis acid
activators such as B(C6F5)3 (4a ) and [Ph3C]+-
[B(C6F5)4]- (4b ) in toluene or bromobenzene solution
(Scheme 3). Cation formation is signaled by a downfield
shift in the 31P{1H} NMR spectrum of about 10 ppm
relative to the neutral precursor 2. The ion pair 4a
formed from B(C6F5)3 can be isolated as an analytically
pure solid, while that obtained from [Ph3C]+[B(C6F5)4]-
was generated cleanly in situ and characterized in
solution. As for other [LAlMe]+[MeB(C6F5)3]- ion pairs,
the two methyl groups in 4a were distinct in the 1H
NMR spectrum at room temperature, but EXSY spec-
troscopy showed that they are exchanging on the time
scale of this experiment, indicating that the methide
abstraction by B(C6F5)3 is reversible. Both of these ion
pairs exhibit high stability in solution, with no measur-
able change in the NMR spectrum after several days at
room temperature. Thus, there is a low tendency toward
-C6F5 back-transfer in ion pairs 4,13a,29 underscoring
the ligand’s ability to quench the positive charge at
aluminum. Use of 1/2 equiv of activator led to µ-methyl
dimers;12 to suppress formation of these species in the
preparations of ion pairs 4, inverse addition of the
aluminum reagent to the activator was employed.
This is further illustrated by the stability of the
cationic hydride compound 5 formed from 3 and
[Ph3C]+[B(C6F5)4]- (Scheme 4). Cationic aluminum hy-
drides tend to be even more reactive than the alkyl
derivatives, often succumbing to -C6F5 back-transfer.13
Rapid hydride abstraction yields a compound with an
intact [B(C6F5)4]- anion, a new set of ligand resonances,
and a slightly upfield shifted signal at 4.18 ppm for the
Al-H moiety, now integrating to one proton. Compound
5 is stable for long periods at room temperature and
reacts slowly with diphenylacetylene to yield the hy-
droalumination product 6, which was characterized in
situ; methyl cations 4 exhibit no reaction with PhCt
CPh even under heating for prolonged periods.
nacnac and anilido-imine ligands we have studied
previously in our group. The new anilido-phosphin-
imine donor array is more resistant to nucleophilic
attack or tautomerization processes and additionally
offers a different steric and electronic presence about
the metal center. The phosphinimine moiety is more
electron donating than the imine donor, and substitu-
tion of the four-coordinate, tetrahedral phosphorus
nucleus for the three-coordinate, planar imine carbon
orients the N-aryl groups in a fundamentally different
spatial arrangement compared to nacnac and nacnac-
like ligands. Combined, these features make this an
exciting ligand family to exploit as supports for elec-
trophilic metal centers in a variety of applications. We
have demonstrated the attributes of this ligand family
by deploying a bulky example in cationic organoalumi-
num chemistry and found it to stabilize these highly
reactive compounds, including a three-coordinate alu-
minum hydride complex.
Exp er im en ta l Section
Gen er a l P r oced u r es. All operations were performed under
a purified argon atmosphere using glovebox or vacuum line
techniques. Toluene, hexanes, and THF solvents were dried
and purified by passing through activated alumina and Q5
columns. Acetonitrile was dried over CaH2 and distilled under
reduced pressure. Diethyl ether was dried over Na and distilled
under reduced pressure. Chlorobenzene was dried over CaH2
and distilled under reduced pressure. NMR spectra were
recorded at room temperature in dry, oxygen-free C6D6, unless
1
1
otherwise noted. H, H{31P}, 11B, 13C, 19F, 31P, COSY, EXSY,
and HMQC NMR experiments were performed on Bruker AC-
200, AMX-300, and DRV-400 and Varian 200 MHz spectrom-
eters. Data are given in units of ppm relative to residual
1
solvent signals for H and 13C spectra. 11B, 19F, and 31P spectra
were referenced to external BF3‚Et2O, CFCl3, and 85% H3PO4
respectively. Elemental analyses were performed by Ms.
Roxanna Simank (University of Calgary). IR spectra were
recorded on a Nicolet NEXUS 470 FT-IR spectrometer using
KBr plates, and data are given in units of reciprocal centime-
ters (cm-1). X-ray crystallographic analyses were performed
on suitable crystals coated in Paratone oil and mounted on
either a Bruker P4/RA/SMART 1000 CCD diffractometer
(University of Alberta) or a Rigaku AFC6S diffractometer
(University of Calgary). Details of the crystallographic data
and data analysis are given in Table 1; full details can be found
Con clu sion s
We have developed a new ligand system that we
believe addresses some of the shortcomings of the
(27) (a) Atwood, D. A.; J egier, J . A.; Rutherford, D. J . Am. Chem.
Soc. 1995, 117, 6779. (b) J egier, J . A.; Munoz-Hernandez, M.-A.;
Atwood, D. A. J . Chem. Soc., Dalton Trans. 1999, 2583.
(28) Talarico, G.; Budzelaar, P. H. M.; Gal, A. W. J . Comput. Chem.
2000, 21, 398.
in the Supporting Information. o-C6H4FP(C6H5)2 (19F NMR,
18
(29) Bochmann, M.; Sarsfield, M. J . Organometallics 1998, 17, 5908.

1816 Organometallics, Vol. 23, No. 8, 2004
Ta ble 1. Su m m a r y of Da ta Collection a n d Str u ctu r e Refin em en t Deta ils
Welch et al.
1‚H
1‚Li
2
3
formula
fw
C
39H43N2P
C45H42D6LiN2P
665.80
C41H48AlN2P‚1.5C7D8
764.96
C39H44AlN2P
598.71
570.72
cryst syst
a, Å
b, Å
orthorhombic
15.362(2)
21.174(3)
10.048(5)
triclinic
11.924(2)
12.300(2)
13.216(3)
75.700(8)
79.250(8)
81.178(13)
1833.6(6)
P1h
monoclinic
10.388(2)
18.790(4)
monoclinic
12.0811(7)
14.7741(9)
19.7917(12)
c, Å
24.636(7)
R, deg
â, deg
γ, deg
V, Å3
91.982(8)
101.6354(11)
3268.4(17)
Pna21
4
1.160
0.113
0.038
0.080
0.088
1.035
4805.8(19)
P21/n
4
1.057
0.109
0.075
0.218
0.252
1.14
3460.0(4)
P21/c
4
1.149
0.133
0.0584
0.1658
space group
Z
2
d
calcd, Mg m-3
1.197
0.109
0.049
0.109
0.127
1.01
µ, mm-1
R1
wR2
wR2 (all data)
GOF
1.030
3
3
-103.25 (d, J F-P ) 53.36 Hz); 31P NMR, -19.46 (d, J P-F
)
(m, 6H, o,p-P(C6H5)2, C6H4PN), 6.88 (s, 2H, NC6H2), 6.39 (m,
24
3
53.34 Hz)), mesityl azide,21 and AlH3‚NMe3 were prepared
using literature procedures. B(C6F5)3 was purchased from
Boulder Scientific Co. and dried and sublimed prior to use.
[Ph3C]+[B(C6F5)4]- was supplied as a generous gift by Nova
Chemicals Corp. All other materials were obtained from
Sigma-Aldrich and purified according to standard procedures.
o-C6H4F {(C6H5)2P dN(2,4,6-Me3C6H2)}. The following is
based on a published procedure.20b A solution of mesityl azide
(4.25 g, 26.40 mmol) in MeCN (25 mL) was transferred by
cannula onto a mixture of o-C6H4F{P(C6H5)2) (7.40 g, 26.43
mmol) in MeCN (50 mL) at 23 °C. Dinitrogen was given off
exothermically, and after 30 min of vigorous stirring a white
precipitate crashed out of solution. After it was stirred for an
additional 6 h, the reaction mixture was filtered and the
isolated white precipitate dried in vacuo. Yield: 9.33 g (85%).
IR (KBr plate): 3103 (w, aromatic C-H), 2945, 2932, 2901
(m, C-H), 1600, 1560, 1469 (s, CdC), 1340 (s, C-P), 1280,
1258, 1207, 1157 (s, PdN), 1105, 994, 859, 819 (C-C). 1H
2H, C6H4PN), 3.20 (sp, J H-H ) 6.8 Hz, 2H, CHMe2), 2.35 (d,
4
4J H-H ) 1.3 Hz, 6H, NC6H2Me-2,6), 2.23 (d, J H-H ) 2.3 Hz,
3H, NC6H2Me-4), 1.10 (d, 3J H-H ) 6.87 Hz, 6H, CH(CH3)2), 0.93
3
(d, J H-H ) 6.87 Hz, 6H, CH(CH3)2). 13C{1H} NMR: 153.8,
147.7, 144.8, 135.4, 134.4 (5 quaternary aromatic), 133.4,
133.3, 132.9, 132.6, 132.4 (5 Ph), 131.2 (quaternary aromatic),
129.5, 128.5, 127.6 (3 Ph), 124.2 (quaternary aromatic), 115.7,
113.9 (2 Ph), 112.4 (quaternary aromatic), 28.6 (CHMe2), 24.8
(CHMe2), 23.5 (CHMe2), 21.7 (NC6H2Me-2,6), 20.8 (NC6H2Me-
4). 31P NMR: -0.8. Anal. Calcd for C39H43N2P: C, 82.07; H,
7.59; N, 4.91. Found: C, 82.01; H, 7.45; N, 4.91.
Syn th esis of 1‚Li. A 1.6 M n-hexane solution of nBuLi (2.2
mL, 3.52 mmol) was added dropwise via syringe to a toluene
(30 mL) solution of 1‚H (1.35 g, 2.37 mmol) at -78 °C. The
reaction mixture was slowly warmed to 23 °C and stirred for
a further 24 h. The reaction mixture was then evaporated to
dryness in vacuo, and n-hexane (10 mL) was added. The
mixture was cooled to -78 °C and filtered to give a yellow
powder, which was dried in vacuo. Yield: 1.1 g (80%). IR (KBr
plate): 3124, 3050 (s, aromatic C-H), 2962, 2863 (s, C-H),
1579, 1476, 1454 (s, CdC), 1339 (s, C-P), 1246, 1160, 1145
(s, PdN), 1110, 1078, 1045, 998 (C-C). 1H NMR: 7.53 (dt,
3J H-H ) 7.11 Hz, 4J H-P ) 1.19 Hz, 4H, m-P(C6H5)2), 7.28-6.94
(m, 10H, o,p-P(C6H5)2, NC6H3, C6H4PN), 6.84 (dd, 3J H-H ) 7.69
3
4
3
NMR: 7.99 (m, J H-H ) 6.32 Hz, J H-P ) 1.78 Hz, J H-F
)
6.28 Hz, 1H, C6H4PN), 7.79 (dt, 3J H-H ) 7.64 Hz, 4J H-P ) 1.70
Hz, 4H, m-P(C6H5)2), 7.00 (m, 6H, o,p-P(C6H5)2), 6.92 (s, 2H,
NC6H2), 6.83 (m, 3J H-H ) 7.23 Hz, 1H, C6H4PN), 6.73 (m, 3J H-H
3
4
) 7.47 Hz, 1H, C6H4PN), 6.53 (ddd, J H-H ) 7.23 Hz, J H-P
)
1.78 Hz, 1H, C6H4PN), 2.24 (s, 9H, NC6H2Me-2,4,6). 13C{1H}
NMR (C7D8): 162.3 (quaternary aromatic, CF) 144.8, 135.0 (2
quaternary aromatic), 134.6, 133.9, 133.5, 132.2, 132.1, 131.1,
128.4 (7 Ph), 127.3, 124.4, 116.3, (3 quaternary aromatic),
116.0 (Ph) 21.5 (NC6H2Me-2,6), 20.9 (NC6H2Me-4). 19F NMR:
4
Hz, J H-P ) 1.55 Hz, 1H, C6H4PN), 6.79 (s, 2H, NC6H2) 6.18
(dd, 3J H-H ) 6.45 Hz, 5J H-P ) 2.36 Hz, 1H, C6H4PN), 6.04 (dd,
3J H-H ) 7.16 Hz, 3J H-P ) 3.29 Hz, 1H, C6H4PN), 2.73 (sp, J H-H
) 6.92 Hz, 2H, CHMe2), 2.21 (m, 9H, NC6H2Me-2,4,6), 1.09
(d, J H-H ) 6.92 Hz, 6H, CH(CH3)2), 1.04 (d, J H-H ) 6.92 Hz,
6H, CH(CH3)2). 13C{1H} NMR: 163.4, 149.9, 144.9, 134.6, 134.3
-99.4 (d, J F-H ) 6 Hz). 31P NMR: -16.5. Anal. Calcd for
27H25FNP: C, 78.43; H, 6.09; N, 3.39. Found: C, 78.64; H,
6.07; N, 3.42.
3
C
3
(4 quaternary aromatic), 133.5 (d, J C-P ) 8.70 Hz), 132.7,
131.5 (Ph), 130.1 (quaternary aromatic), 129.6 (d, 5J C-P ) 3.30
Syn th esis of 1‚H. A 1.6 M n-hexane solution of nBuLi
(11.25 mL, 18.00 mmol) was added to a solution of 2,6-
diisopropylaniline (3.25 mL, 17.25 mmol) in THF (40 mL) at
-78 °C, and the mixture was warmed to room temperature
over 60 min. The resulting solution of LiNHAr was transferred
by cannula onto a solution of o-C6H4{(C6H5)2PdN(2,4,6-
Me3C6H2)} (5.70 g, 13.8 mmol) in THF (50 mL) at 23 °C. The
reaction mixture was stirred for 72 h at 70 °C. The mixture
was then quenched with distilled H2O (50 mL), extracted with
diethyl ether (2 × 50 mL), dried over MgSO4, and evaporated
to dryness in vacuo. The resulting orange oil was dissolved in
hot methanol (200 mL) and slowly cooled to -10 °C to give
cream-colored crystals, which were dried in vacuo. Yield: 4.20
g (53%). IR (KBr plate): 3246 (m, N-H), 2962, 2902, 2852 (m,
C-H), 1592, 1567, 1507, 1477, 1431 (s, CdC), 1361 (s, C-P),
1294, 1266, 1149 (s, PdN), 1109, 1134, 1023, 954 (m, C-C).
3
Hz), 128.6, 126.1, 124.1, 123.2 (Ph), 116.3 (d, J C-P ) 10.02
2
Hz), 110.1, 109.8 (2 quaternary aromatic), 107.8 (d, J C-P
)
13.88 Hz), 28.0 (CHMe2), 26.5 (CHMe2), 24.8 (CHMe2), 21.3
(NC6H2Me-4), 20.8 (NC6H2Me-2,6). 31P NMR: 13.3. Anal. Calcd
for C39H42N2PLi: C, 81.23; H, 7.34; N, 4.86. Found: C, 80.12;
H, 7.18; N, 4.36.
Gen er a tion of th e Ad d u ct Betw een 1‚H a n d AlMe3. To
an NMR tube charged with 1‚H (0.030 g, 0.053 mmol) and
toluene-d8 (200 µL) at -78 °C was added neat AlMe3 (5.0 µL,
0.052 mmol) in toluene-d8 (300 µL), and the resulting solution
was warmed to 0 °C. The adduct was characterized in situ
1
(methane elimination begins above 0 °C). H NMR (C7D8, 270
K): 8.59 (br s, 1H, C6H4PN), 7.65 (br m, 4H, m-P(C6H5)2), 7.80
3
(dd, J H-H ) 7.55 Hz, 1H, C6H4PN), 6.99-6.94 (m, 9H, o,p-
3
P(C6H5)2, NC6H3), 6.72 (dd, J H-H ) 7.51 Hz, 1H, C6H4PN),
1H NMR: 9.68 (s, 1H, NH), 7.79 (dt, 3J H-H ) 7.68 Hz, 4J H-P
)
6.61 (s, 2H, NC6H2), 6.12 (dd, J H-H ) 7.55 Hz, 1H, C6H4PN),
3
1.33 Hz, 4H, m-P(C6H5)2), 7.21-7.13 (m, 3H, NC6H3), 7.09 (dd,
5.36 (br s, 1H, NH), 2.65 (br sp, 3J H-H ) 6.54 Hz, 2H, CHMe2),
3J H-H ) 7.69 Hz, J H-P ) 1.54 Hz, 1H, C6H4PN), 7.00-6.97
2.22 (m, 6H, NC6H4Me-2,6), 2.08 (d, J H-H ) 2.38 Hz, 3H,
4
4

Al Complexes with an Anilido-Phosphinimine Ligand
Organometallics, Vol. 23, No. 8, 2004 1817
3
NC6H4Me-4), 0.99 (d, J H-H ) 6.88 Hz, 6H, CHMe2), 0.74 (d,
1.40 Hz, 4H, m-(C6H5)2), 7.16-7.04 (m, 9H, o,p-P(C6H5)2,
3J H-H ) 6.80 Hz, 6H, CHMe2), -0.45 (s, 9H, Al(CH3)3). 13C-
{1H} NMR (C7D8, 270 K): 152.2, 147.3, 140.0, 138.2 (4
quaternary aromatic), 135.0 (Ph), 134.2 (1 quaternary aro-
matic), 134.0 (Ph), 133.6 (quaternary aromatic), 133.1 (Ph),
130.2, 129.1, 128.8, 128.4, 124.4, 117.7, 113.7 (7 Ph), 108.5,
107.5 (2 quaternary aromatic), 28.0 (CHMe2), 24.4 (CHMe2),
23.6 (CHMe2), 21.8 (NC6H2Me-2,6), 20.7 (NC6H2Me-4), -3.2
(AlMe3). 31P NMR (C7D8, 270 K): δ 22.9.
N(C6H3)), 6.88 (m, 1H, C6H4PN), 6.79 (dd, J H-H ) 7.44 Hz,
3
4J H-P ) 1.48 Hz, 1H, C6H4PN), 6.48 (m, 3H, NC6H2, C6H4PN),
6.27 (dd, 3J H-H ) 7.44 Hz, 4J H-P ) 1.48 Hz, 1H, C6H4PN), 2.62
3
(sp, J H-H ) 6.84 Hz, 2H, CHMe2), 2.09 (m, 3H, NC6H4Me-4),
1.83 (m, 6H, NC6H4Me-2,6), 1.28 (br s, 3H, BMe), 0.91 (d, 3J H-H
) 6.92 Hz, 6H, CHMe2), 0.85 (d, 3J H-H ) 6.92 Hz, 6H, CHMe2),
0.77 (br s, 3H, AlCH3). 11B NMR (C7D8): -15.2. 13C{1H} NMR
(C6D5Br): 155.8 (quaternary aromatic, C-N, C6H4NP), 148.3
(d, 1J C-F ) 246 Hz, MeB(C6F5)3-), 137.6 (quaternary aromatic,
N-C, C6H3), 137.5 (d, 1J C-F ) 240 Hz, MeB(C6F5)3-), 136.3 (d,
1J C-F ) 240 Hz, MeB(C6F5)3-), 135.7 (C6H4), 134.9 (p-(C6H5)2),
134.6 (quaternary aromatic, N-C, C6H2), 133.5 (C6H4), 133.3
Syn th esis of LAlMe2 (2). A 2 M toluene solution of AlMe3
(377 µL, 0.754 mmol) was added via syringe to a solution of
1‚H (430 mg, 0.753 mmol) in toluene (30 mL) at 23 °C. After
it was stirred for 4 h at 50 °C, the yellow solution was
evaporated to dryness in vacuo. The residue was then slurried
in isopentane (15 mL) and filtered at 23 °C to collect a white
solid, which was dried in vacuo. Yield: 0.35 g (75%). IR (KBr
plate): 3131, 3082, 3022 (m, C-H), 2962, 2918, 2858 (s,
aromatic C-H), 1594, 1540, 1466, 1430 (s, CdC), 1325, 1271
(s, C-P), 1206, 1183, 1161, 1123 (s, PdN), 1107, 1033, 995 (s,
C-C). 1H NMR (C7D8): 7.47 (dt, 3J H-H ) 7.11 Hz, 4J H-P ) 1.36
Hz, 4H, m-(C6H5)2), 7.28-6.92 (m, 9H, o,p-P(C6H5)2, N(C6H3)),
6.86 (m, 1H, C6H4PN), 6.63 (dd, 3J H-H ) 8.05 Hz, 4J H-P ) 1.62
3
(d, J C-P ) 10 Hz, m-(C6H5)2), 132.9 (quaternary aromatic, d,
2
4J C-P ) 8 Hz, C6H3), 130.7 (C6H2), 129.5 (d, J C-P ) 13 Hz,
o-(C6H5)2), 128.7 (p-C6H3), 125.3 (m-C6H3), 122.5, 122.0 (2
quaternary aromatic, C6H2), 121.4 (quaternary aromatic, d,
4
1
J C-P ) 85 Hz, (C6H5)2), 119.4 (d, J C-P ) 8 Hz, C6H4), 119.3
(d, 2J C-P ) 13 Hz, C6H4), 106.9 (quaternary aromatic, d, 1J C-P
) 100 Hz, C-P, C6H4PN), 28.3 (CHMe2), 24.8 (CHMe2), 24.1
(CHMe2), 20.4 (NC6H2Me-4), 20.0 (NC6H2Me-2,6), -13.9 (AlMe),
MeB not identified. 19F NMR (C7D8): -131.3 (o-F), -163.7 (p-
F), -166.3 (m-F). 31P NMR (C7D8): 38.1. Anal. Calcd for C59H48
-
3
Hz, 1H, C6H4PN), 6.59 (s, 2H, NC6H2), 6.53 (d, J H-H ) 7.53
Hz 1H, C6H4PN), 6.15 (m, 1H, C6H4PN) 3.79 (sp, 3J H-H ) 6.84
AlBF15N2P: C, 62.23; H, 4.25; N, 2.46. Found: C, 62.89; H,
4.15; N, 2.38.
4
Hz, 2H, CHMe2), 2.07 (d, J H-H ) 2.22 Hz, 3H, NC6H4Me-4),
1.82 (d, J H-H ) 1.27 Hz, 6H, NC6H4Me-2,6), 1.30 (d, J H-H
4
3
)
Syn th esis of [LAlMe]+[B(C6F 5)4]- (4b). An NMR tube
charged with [CPh3]+[B(C6F5)4]- (0.028 g, 0.030 mmol) and
C6D5Br (0.1 mL) was cooled to -35 °C. A solution of LAlMe2
(0.019 g, 0.030 mmol) in C6D5Br (0.4 mL) was then added
dropwise to the NMR tube. The orange mixture was warmed
3
6.84 Hz, 6H, CHMe2), 1.23 (d, J H-H ) 6.84 Hz, 6H, CHMe2),
-0.47 (s, 6H, Al(Me)2). 13C{1H} NMR (C7D8): 163.2, 146.9,
143.4, 137.7, 137.6, 137.2 (6 quaternary aromatic), 136.1 (d,
4J C-P ) 14.63 Hz, C6H4PN), 134.3 (d, J C-P ) 10.12 Hz, m-P-
3
(C6H5)2), 132.2 (Ph), 130.2 (NC6H2), 129.2 (Ph), 128.4 (d, 3J C-P
to -30 °C before being monitored via NMR experiments. H
1
3
) 12.32 Hz, C6H4PN), 126.2, 124.9 (2 Ph), 120.8 (d, J C-P
)
NMR (C6D5Br): 7.69 (m, 1H, C6H4PN), 7.41-6.90 (m, 28H,
P(C6H5)2, NC6H3, C(C6H5)3), 6.59 (m, 4H, NC6H2, C6H4PN), 6.35
9.24 Hz, C6H4PN), 113.6 (d, 2J C-P ) 15.31 Hz, C6H4PN), 101.1,
99.9 (2 quaternary aromatic), 28.1 (CHMe2), 26.1 (CHMe2),
24.8 (CHMe2), 20.7 (NC6H2Me-4), 20.5 (NC6H2Me-2,6), -7.1
(AlMe2). 31P NMR (C7D8): 30.0. Anal. Calcd for C41H48AlN2P:
C, 78.57; H, 7.72; N, 4.47. Found: C, 78.17; H, 7.63; N, 4.49.
Syn th esis of LAlH2 (3). To a dried round-bottom flask was
added freshly prepared AlH3‚NMe3 (0.420 g, 4.71 mmol) and
solid 1‚H (2.7 g, 4.74 mmol). The flask was attached to a
swivelfrit apparatus and cooled to -78 °C. Toluene (50 mL)
was condensed into the vessel, and the mixture was warmed
to room temperature. After it was stirred for 7 h at 23 °C, the
yellow-green solution was evaporated to dryness in vacuo. The
residue was then slurried in isopentane (20 mL) and filtered
at 23 °C to collect a white solid, which was dried in vacuo.
3
(m, 1H, C6H4PN), 2.60 (sp, J H-H ) 5.58 Hz, 2H, CH(Me)2),
2.10 (s, 3H, NC6H3Me-4), 2.04 (s, 3H, MeC(Ph)3), 1.98 (s, 6H,
3
NC6H3Me-2,6), 0.91 (d, J H-H ) 6.60 Hz, 6H, CHMe2), 0.86 (d,
3J H-H ) 6.54 Hz, 6H, CHMe2), 0.77 (s, 3H, AlMe). 11B NMR
(C6D5Br): -16.10. 19F NMR (C6D5Br): -132.9 (o-F), -163.3 (p-
F), - 167.1 (m-F). 31P NMR (C6D5Br): 36.8.
Syn th esis of [LAlH]+[B(C6F 5)4]- (5). A round-bottomed
flask (25 mL) was charged with [Ph3C]+[B(C6F5)4]- (0.308 g,
0.33 mmol) and C6H5Cl (10 mL). A solution of LAlH2 (0.200 g,
0.33 mmol) in C6H5Cl (5 mL) was then added dropwise to the
vessel, causing a color change from orange to yellow. The vessel
was attached to a swivelfrit apparatus, and the yellow solution
was stirred under argon at 23 °C for 15 min. The reaction
mixture was dried in vacuo and left under full vacuum for 6
h. Hexanes (15 mL) was added and the solid isolated by
filtration to obtain a orange powder, which was dried in vacuo.
Yield: 300 mg (70%). The ion pair is stable in solution for at
least 12 h. 1H NMR (C6D5Br): 7.46-6.94 (m, 15H), 6.65 (m,
1H, C6H4PN), 6.55 (s, 2H, NC6H2), 6.34 (m, 1H, C6H4PN), 4.18
Yield: 2.51 g (88%). IR (KBr plate): 1828, 1780 cm-1 (asym-
metric, symmetric absorptions). 1H NMR: 7.67 (dt, J H-H
)
3
4
7.11 Hz, J H-P ) 1.36 Hz, 4H, m-(C6H5)2), 7.30 (s, 3H, NC6H3)
6.95 (m, 2H, C6H4PN), 6.88 (m, 6H, o,p-P(C6H5)2), 6.55 (s, 2H,
3
NC6H2), 6.45 (t, J H-H ) 7.10 Hz, 1H, C6H4PN), 6.23 (m, 1H,
3
C6H4PN), 4.67 (bs, 2H, AlH2), 3.50 (sp, J H-H ) 6.84 Hz, 2H,
3
CHMe2), 2.31 (s, 6H, NC6H4Me-2,6), 1.99 (s, 3H, NC6H4Me-4),
(bs, 1H, AlH), 2.38 (sp, J H-H ) 6.58 Hz, 2H, CHMe2), 2.20 (s,
3
3
3
1.41 (d, J H-H ) 6.84 Hz, 6H, CHMe2), 1.10 (d, J H-H ) 6.84
Hz, 6H, CHMe2). 13C{1H} NMR: 160.4 (quaternary aromatic),
148.1 (C-H), 140.5, 139.0, 136.9 (3 quaternary aromatic),
134.3, 134.1, 134.0, 132.9, 131.3, 128.4 (C-H), 126.9 (quater-
nary aromatic), 125.1 (C-H), 118.5, 113.3, 105.4 (3 quaternary
aromatic), 28.2 (CHMe2), 25.7 (CHMe2), 25.0 (CHMe2), 21.0
(NC6H2Me-4), 20.6 (NC6H2Me-2,6). 31P NMR: 31.9. Anal. Calcd
for C39H44AlN2P: C, 78.23; H, 7.41; N, 4.68. Found: C, 77.64;
H, 7.41; N, 4.64.
Syn th esis of [LAlMe]+[MeB(C6F 5)3]- (4a ). A 25 mL vial
was charged with 2 (0.022 g, 0.035 mmol) and hexanes (10
mL). In a separate vial, B(C6F5)3 (0.018 g, 0.035 mmol) was
dissolved in hexanes (10 mL). The aluminum species was
added dropwise to the clear borane solution, causing immedi-
ate formation of a white precipitate. The mixture was cooled
to -35 °C for 48 h, upon which the supernatant was removed
and the remaining white solid was dried in vacuo. Yield: 0.027
6H, NC6H4Me-2,6), 1.93 (s, 3H, NC6H4Me-4), 0.78 (d, J H-H
)
6.34 Hz, 12H, CHMe2). 11B NMR (C6D5Br): δ -19.4. 13C{1H}
NMR (C6D6): 155.8 (d, 5.4 Hz), 148.4 (d, 242.5 Hz, C6F5), 147.2,
143.8, 138.3 (d, 245 Hz, C6F5), 136.3 (d, 242.5 Hz, C6F5), 137.2
(d, 3.8 Hz), 135.6, 135.0 (d, 3.1 Hz), 135.0 (d, 4.6 Hz), 134.3 (d,
8.4 Hz), 133.4 (d, 10.7 Hz), 132.2 (10.7 Hz), 130.5 (d, 2.3 Hz),
129.6, 128.5, 128.2, 125.6, 121.0 (d, 102 Hz), 119.7 (d, 8.4 Hz),
118.8 (d, 14.6 Hz), 109.2 (d, 99.7 Hz), 56.8, 27.9, 25.7, 23.2,
20.5, 20.3. 19F NMR (C6D5Br): δ-132.9 (o-F), -163.2 (p-F),
-167.0 (m-F). 31P NMR (C6D5Br): δ 38.7. Repeated attempts
at elemental analysis of 5 failed to give satisfactory numbers;
the results were consistently low in carbon by 3-5%.
Syn th esis of [LAl(P h CCHP h )]+[B(C6F 5)4]- (6). A solu-
tion of LAlH2 (0.015 g, 0.025 mmol) in C6D5Br (0.4 mL) was
added dropwise to an NMR tube charged with [CPh3]+-
[B(C6F5)4]- (0.023 g, 0.025 mmol) and C6D5Br (0.1 mL) at 23
°C. The NMR tube was cooled to -78 °C, and PhCCPh (0.005
g, 0.025 mmol) in C6D5Br (0.1 mL) was added via syringe. The
1
3
4
g (67%). H NMR (C7H8): 7.29 (dt, J H-H ) 6.91 Hz, J H-P
)

1818 Organometallics, Vol. 23, No. 8, 2004
Welch et al.
mixture was warmed to 23 °C, shaken, and allowed to react
for 90 min. 1H NMR (C6D5Br): 7.38-6.89 (m, 20H), 6.78-6.41
(m, 9H) 5.69 (s, 1H, AlPhCCHPh), 5.44 (s, 1H, Ph3CH), 2.51
Ack n ow led gm en t. Funding for this work came
from the Natural Sciences and Engineering Research
Council of Canada in the form of a Discovery Grant (to
W.E.P.).
3
(sp, J H-H ) 6.82 Hz, 2H, CHMe2), 2.01 (s, 3H, NC6H4Me-4),
3
1.92 (s, 6H, NC6H4Me-2,6), 1.01 (d, J H-H ) 6.85 Hz, 12H,
3
CHMe2), 0.81 (d, J H-H ) 6.85 Hz, 12H, CHMe2). 11B NMR
(C6D5Br): -19.3. 13C{1H} NMR: 154.1 (d, 6 Hz), 150.7, 148.4
(d, 325 Hz, C6F5), 146.7, 143.8, 142.8, 141.9, 140.8, 138.2 (d,
325 Hz, C6F5), 136.2 (d, 325 Hz, C6F5), 137.3 (d, 3 Hz), 135.4,
135.1, 133.7 (d, 6 Hz), 133.2 (d, 14 Hz), 132.6 (14 Hz), 130.0,
129.5, 129.2, 128.1, 126.3, 125.6 (d, 20 Hz), 122.1 (d, 84 Hz),
120.0 (d, 133 Hz), 119.9 (d, 18 Hz), 118.3 (d, 10 Hz), 109.7 (d,
131 Hz), 56.8, 28.2, 24.6, 24.4, 20.2, 19.9. 19F NMR (C6D5Br):
-132.9 (o-F), -163.4 (p-F), 167.1 (m-F). 31P NMR (C6D5Br):
38.4.
Su p p or tin g In for m a tion Ava ila ble: ORTEP diagrams
and tables of atomic coordinates, anisotropic displacement
parameters, and all bond distances, bond angles, and torsion
angles for the structurally characterized molecules presented
here; crystallographic data are also available as CIF files. This
material is available free of charge via the Internet at
http://pubs.acs.org.
OM034302W