Aluminum complexes incorporating bulky nitrogen and sulfur donor ligands

Article abstract of DOI:10.1021/om9802358

The synthesis and structures of aluminum complexes incorporating bulky thioamidate (RC(NR′)S^-), thioureido (R′HNC(NR′)S^-), and amidinate (RC(NR′)^-₂) ligands are described. The reaction of AlMe₃ with A

Full text of DOI:10.1021/om9802358

4042
Organometallics 1998, 17, 4042-4048
Alu m in u m Com p lexes In cor p or a tin g Bu lk y Nitr ogen a n d
Su lfu r Don or Liga n d s
Martyn P. Coles, Dale C. Swenson, and Richard F. J ordan*
Department of Chemistry, The University of Iowa, Iowa City, Iowa 52242
Victor G. Young, J r.
Department of Chemistry, The University of Minnesota, Minneapolis, Minnesota 55455
Received March 30, 1998
The synthesis and structures of aluminum complexes incorporating bulky thioamidate
(RC(NR′)S-), thioureido (R′HNC(NR′)S-), and amidinate (RC(NR′)2 ) ligands are described.
-
The reaction of AlMe3 with AdNdCdS (Ad ) 1-adamantyl) affords the insertion product
{MeC(NAd)S}AlMe2 (1), which binds 1 equiv of AlMe3 to generate {MeC(NAd)S}AlMe2‚AlMe3
(2). The alkane elimination reaction of AlMe3 and N,N′-disubstituted thiourea derivatives,
(R′HN)2CdS, affords thioureido complexes {R′HNC(NR′)S}AlMe2 (3a , R′ ) Ad; 3b, R′ ) Ar
) 2,6-iPr2-Ph). Carbodiimides, R′NdCdNR′, react with AlMe3 to afford acetamidinate
compounds {MeC(NR′)2}AlMe2 (4a , R′ ) Ad; 4b, R′ ) Ar). Sequential addition of tBuLi and
AlX2Cl (X ) Cl, Me) to R′NdCdNR′ affords pivamidinate compounds {tBuC(NR′)2}AlCl2 (5b,
R′ ) Ar) and {tBuC(NR′)2}AlMe2 (6a , R′ ) Ad; 6b, R′ ) Ar). Complexes 1, 3a , 6a , and 6b
have been characterized by X-ray crystallography.
In tr od u ction
thioamidate (RC(NR′)S-), thioureido (R′HNC(NR′)S-),
t
and amidinate (RC(NR′)2-) ligands (R ) Me, Bu; R′ )
1-adamantyl, 2,6-iPr2-Ph).
Cationic aluminum alkyl species of general form {L-
X}Al(R)+, which are stabilized by monoanionic, biden-
tate ancillary ligands ({L-X}-), are promising candi-
dates for catalytic applications because the enhanced
Lewis acidity of the cationic Al center and the presence
of a reactive Al-R bond may promote insertion reac-
tions.1 Dimethyl aluminum compounds that contain
bulky amidinate ligands, {RC(NR′)2}AlMe2 (R ) Me,
tBu; R′ ) iPr, cyclohexyl), are converted to {RC(NR′)2}-
Al(Me)(L′)+ cations by abstraction of one methyl group.
In these species, the {RC(NR′)2}AlMe+ cations are
stabilized by an additional donor group (L′ ) {RC-
(NR′)2}AlMe2, NMe2Ph, PMe3).1d We are investigating
the synthesis and structures of other {L-X}AlR2 com-
pounds containing more diverse ancillary {L-X}-
ligands, with the ultimate aim of developing new
{L-X}AlR+ cations with controlled structures and
reactivity.2,3 Amidinate ligands with extremely bulky
substituents (R′) at the donor nitrogen atoms, and
related ligands incorporating other donor atoms, are of
interest in this context because they may favor 3-coor-
dinate {L-X}Al(R)+ structures. Here we describe new
{L-X}AlX2 complexes (X ) Cl, Me) containing bulky
Resu lts a n d Discu ssion
Liga n d Syn th eses. The ligands used in this work
were prepared by literature methods which are sum-
marized in Scheme 1.4-6 Addition of 1-adamantylamine
to 1-adamantyl isothiocyanate yields N,N′-diadaman-
tylthiourea, and condensation of 2,6-diisopropylaniline
with CS2 yields N,N′-bis(2,6-diisopropylphenyl)thiourea.
These thioureas are oxidized to the corresponding
carbodiimides AdNdCdNAd (Ad ) 1-adamantyl) and
ArNdCdNAr (Ar ) 2,6-iPr2-Ph) by reaction with
NaOClO or NaOCl.
Syn th esis of Alu m in u m Th ioam idate Com plexes.
Insertion reactions of heteroallene compounds, including
CO2,7,8 CS2,9 isocyanates (R′NdCdO),10 and isothiocy-
anates (R′NdCdS),11 into Al-X (X ) R, OR, SR, NR2,
AlR2) bonds are well-known.12 The reaction of 1-ada-
mantyl isothiocyanate and AlMe3 yields {MeC(NAd)S}-
(4) Stetter, H.; Wulff, C. Chem. Ber. 1962, 95, 2302.
(5) Ogawa, K.; Akazawa, M. J apanese Pat. Appl. J P 91-164070
910410.
(6) Ogawa, K.; Akazawa, M. J apanese Pat. Appl. J P 91-208987
910517.
(1) Recent applications of cationic Al compounds in polymerization
catalysis: (a) Cationic polymerization of isobutylene and isobutylene/
isoprene by Cp2Al+: Bochmann, M.; Dawson, D. M. Angew. Chem.,
Int. Ed. Eng. 1996, 35, 2226. (b) Ring-opening polymerization of
propylene oxide by (salen)Al(MeOH)2+ and (acen)Al(MeOH)2+: Atwood,
D. A.; J egier, J . A.; Rutherford, D. J . Am. Chem. Soc. 1995, 117, 6779.
(7) Ziegler, K.; Krupp, F.; Weyer, K.; Larbig, W. Liebigs Ann. Chem.
1960, 629, 251.
(8) (a) Takeda, N.; Inoue, S. Bull. Chem. Soc. J pn. 1986, 51, 3564.
(b) Aida, T.; Inoue, S. J . Am. Chem. Soc. 1983, 105, 1304. (c) Kojima,
F.; Aida, T.; Inoue, S. J . Am. Chem. Soc. 1986, 108, 391.
(9) (a) Wakatsuki, K.; Takeda, Y.; Tanaka, T. Inorg. Nucl. Chem.
Lett. 1974, 10, 383. (b) Uhl, W.; Vester, A.; Hiller, W. J . Organomet.
Chem. 1993, 443, 9.
(10) (a) Hirabayashi, T.; Imaeda, H.; Sakai, S.; Ishii, Y. J . Orga-
nomet. Chem. 1969, 19, 299. (b) Hirabayashi, T.; Sakakibara, T.; Ishiii,
Y. J . Organomet. Chem. 1972, 35, 19.
(c) Ring-opening polymerization of propylene oxide by {η3-MeN-
+
(CH2CH2NMe2)2}AlMe2
: J egier, J . A.; Atwood, D. A. Inorg. Chem.
1997, 36, 2034. (d) Ethylene polymerization by {RC(NR′)2}Al(Me)(L′)+
species: Coles, M. P.; J ordan, R. F. J . Am. Chem. Soc. 1997, 119, 8125.
(2) Coles, M. P.; Swenson, D. C.; J ordan, R. F.; Young, V. G., J r.
Organometallics 1997, 16, 5183.
(11) (a) Uhl, W.; Schu¨tz, U.; Hiller, W.; Heckel, M. Chem. Ber. 1994,
127, 1587. (b) Uhl, W.; Schu¨tz, U.; Pohl, S.; Saak, W. Z. Anorg. Allg.
Chem. 1996, 622, 373.
(3) Aeilts, S. L.; Coles, M. P.; Swenson, D. C.; J ordan, R. F.; Young,
V. G., J r. Organometallics, in press.
S0276-7333(98)00235-0 CCC: $15.00 © 1998 American Chemical Society
Publication on Web 08/12/1998

Al Complexes Incorporating Bulky N and S Ligands
Organometallics, Vol. 17, No. 18, 1998 4043
Sch em e 1
Sch em e 3
Sch em e 2
made to isolate 2. Several N-phenylthioacetamidate
aluminum complexes, {MeC(NPh)S}AlR2 (R ) Me, Et,
iPr) have been reported previously.16 Analogous ami-
date complexes, {RC(NR′)O}AlR2, have been prepared
previously by alkane elimination reactions of acid
amides and AlR3 compounds.14,17
Syn th esis of Alu m in u m Th iou r eid o Com p lexes.
The methane elimination reaction of AlMe3 and the
thioureas (R′HN)2CdS (R′ ) Ad, Ar) affords thioureido
complexes {R′HNC(NR′)S}AlMe2 (3a , R′ ) Ad; 3b, R′
) Ar, Scheme 3). Complex 3a is isolated as colorless
platelike crystals by recrystallization from Et2O at 0 °C,
and 3b is isolated as colorless, hexagonal crystals by
recrystallization from hot toluene. The 1H and 13C NMR
spectra of 3a and 3b are consistent with Cs-symmetric
structures. The NMR spectra of 3b contain four iso-
propyl methyl resonances and one Al-Me resonance,
which is consistent with a structure in which the H-N-
C(ipso) plane of the amino group is parallel to the Al-
N-C-S plane, and rotation around the N-Ar bonds is
slow on the NMR time scale. It is likely that the Ar
groups are oriented perpendicular to the Al-N-C-S
plane. Analogous aluminum thioureido complexes con-
taining smaller nitrogen substituents have been pre-
pared previously by SiMe3Cl elimination reactions of
N-silylated thioureas (R′2NC(S)NR′SiMe3; R′ ) Me, Et,
AlMe2 (1, Scheme 2), which is isolated as an orange solid
by recrystallization from Et2O at -30 °C. An X-ray
crystallographic analysis (vide infra) establishes that 1
is monomeric in the solid state; that is, this compound
does not dimerize by bridging through the sulfur atom.
However, NMR studies show that 1 forms an adduct
with AlMe3. The 1H and 13C NMR spectra of {MeC-
(NAd)S}AlMe2‚AlMe3 (2, Scheme 2) contain adamantyl
resonances that are shifted from the corresponding
1
resonances of 1. The H NMR spectrum contains two
Al-Me resonances (δ -0.48, -0.64) in a 2/3 intensity
ratio that are shifted from the resonances of 1 and
AlMe3,13 and the 13C NMR spectrum also contains two
Al-Me resonances (δ -6.9, -8.5). Presumably coordi-
nation of 1 to AlMe3 occurs through the sulfur atom of
the thioamidate ligand, similar to the O-Al bonding in
{OdCPhNPhC(H)MeO}AlMe2‚AlMe3, {pyCRR′O}AlMe2‚
AlMe3 and related compounds.14,15 No attempt was
i
Ph) with AlR2Cl (R ) Me, Et, Bu) compounds.16
(16) Maringgele, W. Z. Anorg. Allg. Chem. 1981, 473, 133.
(17) (a) Kai, Y.; Yasuoka, N.; Kasai, N.; Kakudo, M. Yasuda, H.;
Tani, H. J . Chem. Soc., Chem. Commun. 1968, 1332. (b) Kai, Y.;
Yasuoka, N.; Kasai, N.; Kakudo, M. Yasuda, H.; Tani, H. J . Chem.
Soc., Chem. Commun. 1969, 575. (c) Kai, Y.; Yasuoka, N.; Kasai, N.;
Kakudo, M. J . Organomet. Chem. 1971, 32, 165. (d) Kai, Y.; Yasuoka,
N.; Kasai, N.; Kakudo, M. Bull. Chem. Soc. J pn. 1972, 45, 3388. (e)
Kai, Y.; Yasuoka, N.; Kasai, N.; Kakudo, M. Bull. Chem. Soc. J pn.
1972, 45, 3397. (f) Yasuda, H.; Araki, T.; Tani, H. J . Organomet. Chem.
1973, 49, 333. (g) Yasuda, H.; Araki, T.; Tani, H. J . Organomet. Chem.
1973, 49, 103.
(12) Weidlein, J . J . Organomet. Chem. 1973, 49, 257.
(13) 1H NMR for AlMe3 in CD2Cl2: δ -0.29.
(14) (a) Kai, Y.; Yasuoka, N.; Kasai, N.; Kakudo, M. Bull. Chem.
Soc. J pn. 1972, 45, 3403. (b) Kai, Y.; Yasouka, N.; Kasai, N.; Kakudo,
M.; Yasuda, H.; Tani, H. J . Chem. Soc., Chem. Commun. 1970, 1243.
(15) van Vliet, M. R. P., van Koten, G., de Keijser, M. S.; Vrieze, K.
Organometallics 1987, 6, 1652.

4044 Organometallics, Vol. 17, No. 18, 1998
Ta ble 1. Su m m a r y of Cr ysta l Da ta for Com p ou n d s 1, 3a , 6a , a n d 6b
Coles et al.
1
3a
6a
6b
formula
fw
C
14H24AlNS
C23H37AlN2S
400.59
C27H45AlN2
424.63
C31H49AlN2
476.70
265.38
cryst size (mm)
color/shape
d (calc) (Mg/m3)
cryst syst
space group
a (Å)
0.20 × 0.20 × 0.13
yellow/block
1.197
triclinic
P1h
6.8455(6)
9.2486(8)
13.072(1)
107.370(1)
96.595(1)
107.070(2)
736.2(1)
0.44 × 0.39 × 0.10
colorless/plate
1.164
monoclinic
P2(1)/n
16.865(6)
13.198(6)
10.285(3)
0.35 × 0.39 × 0.50
colorless/prismatic
1.142
triclinic
P1h
14.405(2)
14.835(2)
12.893(2)
112.54(1)
99.69(1)
95.35(1)
2470.5(6)
4
0.30 × 0.28 × 0.23
colorless/irreg block
1.071
triclinic
P1h
10.1845(1)
11.0117(2)
14.4123(3)
74.284(1)
77.687(1)
73.882(1)
b (Å)
c (Å)
R (deg)
â (deg)
93.42(3)
γ (deg)
V (Å3)
2285(2)
4
1477.99(4)
2
Z
2
T (K)
173(2)
213(2)
213(2)
173(2)
diffractometer
Siemens SMART
Platform CCD
Mo KR, 0.710 73
3.3 < 2θ < 50.1
(8; (10; 0,15
4136
Enraf-Nonius
CAD4
Mo KR, 0.710 73
4.0 < 2θ < 50.0
(19; -1,15; -12,2
5051
Enraf-Nonius
CAD4
Mo KR, 0.710 73
4.0 < 2θ < 50.0
(17; -17,16; -2,15
10292
Siemens SMART
Platform CCD
Mo KR, 0.710 73
3.0 < 2θ < 50.0
-11,12; -12,13; 0,17
8096
radiation, λ (Å)
2θ range (deg)
data collected: h; k; l
no. of reflns
no. of unique reflns
Rint
2485
0.0208
3912
0.0337
8534
0.0143
4944
0.0244
no. of obsd reflns
I > 2σ(I), 2045
I > 2σ(I), 2178
I > 2σ(I), 7351
I > 2σ(I), 3712
µ (mm-1
)
0.260
0.190
0.098
0.089
transmission range (%)
structure solution
no. of data/parameters
GOF on F2
76-100
83-100
96-100
72-100
direct methodsa
2485/157
1.032
direct methodsb
3912/273
1.027
direct methodsb
8534/757
1.062
direct methodsa
4943/321
1.036
R indices (I > 2σ(I))c,d
R1 ) 0.0465,
wR2 ) 0.1124
R1 ) 0.0599,
wR2 ) 0.1201
0.30
R1 ) 0.0489,
wR2 ) 0.1058
R1 ) 0.1256,
wR2 ) 0.1376
0.34
R1 ) 0.0397,
wR2 ) 0.1045
R1 ) 0.0493,
wR2 ) 0.1145
0.30
R1 ) 0.0551,
wR2 ) 0.1299
R1 ) 0.0792,
wR2 ) 0.1440
0.31
R indices (all data)c,d
max resid density (e/Å3)
a
b
SHELXTL-Plus Version 5, Siemens Industrial Automation, Inc., Madison, WI. MULTAN, Multan80, University of York, York,
England. c R1 ) ∑||Fo| - |Fc||/∑|Fo|. wR2 ) [∑[w(Fo - Fc2)2]/∑[w(Fo2)2]]1/2, where w ) [σ2(Fo2) + (aP)2 + bP]-1
.
d
2
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 1
Syn th esis of Alu m in u m Am id in a te Com p lexes.
Aluminum acetamidinate compounds, {MeC(NR′)2}-
AlMe2, have been prepared previously by the reaction
of AlMe3 and the appropriate carbodiimide.2,18 Analo-
gous compounds containing bulkier substituents at the
central carbon of the amidinate ligand can be prepared
by treating the carbodiimide with lithium alkyl reagents
to generate Li[RC(NR′)2] salts, followed by reaction with
aluminum halides.2,19 Both approaches were utilized
to prepare aluminum amidinate compounds with Ad or
2,6-iPr2-Ph substituents at nitrogen (Scheme 3). The
reaction of AlMe3 with R′NdCdNR′ in hexane affords
the acetamidinate complexes {MeC(NR′)2}AlMe2 (4a , R′
) Ad; 4b, R′ ) 2,6-iPr2-Ph). Both compounds are
isolated as white solids in good yield by simple removal
of the volatiles from the reaction mixture. Sequential
Al(1)-N(1)
Al(1)-C(1)
N(1)-C(3)
N(1)-C(5)
1.953(2)
1.960(3)
1.300(3)
1.494(3)
Al(1)-S(1)
Al(1)-C(2)
S(1)-C(3)
C(3)-C(4)
2.340(1)
1.953(3)
1.744(3)
1.502(4)
N(1)-Al(1)-C(1)
C(1)-Al(1)-C(2)
C(1)-Al(1)-S(1)
C(3)-S(1)-Al(1)
N(1)-C(3)-S(1)
C(3)-N(1)-C(5)
S(1)-C(3)-C(4)
111.1(1)
118.8(1)
113.8(1)
74.51(9)
113.4(2)
128.1(2)
117.3(2)
N(1)-Al(1)-C(2)
N(1)-Al(1)-S(1)
C(2)-Al(1)-S(1)
C(3)-N(1)-Al(1)
C(5)-N(1)-Al(1)
N(1)-C(3)-C(4)
117.7(1)
72.44(7)
114.4(1)
99.5(2)
131.8(2)
129.2(2)
metric structures and, for 4b-6b, slow rotation around
the Ar-N bonds.
Molecu la r Str u ctu r es of {MeC(NAd )S}AlMe2 (1)
a n d {Ad NHC(NAd )S}AlMe2 (3a ). Crystal data for 1
and 3a are summarized in Table 1, refinement details
are discussed in the Experimental Section, and selected
bond distances and angles are listed in Tables 2 and 3.
Molecular geometries and atom labeling schemes are
shown in Figures 1 and 2.
Complexes 1 and 3a are monomeric and exhibit
distorted tetrahedral geometry at aluminum. The
ligand bite angles (N-Al-S: 1, 72.44(7)°; 3a , 73.16(9)°)
are in the range observed for {RC(NR′)2}AlX2 (X ) Cl,
R) amidinate and {R2NC(NR′)2}AlCl2 guanidinate com-
plexes (N-Al-N ) 68-72°).2,3 The C-Al-C angles (1,
118.8(1)°; 3a , 117.9(3)°) are similar to those in {RC-
(NR′)2}AlR2 compounds.2 The N-Al-S-C metalla-
cycles are approximately planar in both 1 and 3a
t
treatment of the carbodiimides with BuLi (0 °C, Et2O)
and AlCl3 or AlMe2Cl (-78 °C, Et2O) affords the
pivamidinate compounds {tBuC(NAr)2}AlCl2 (5b) and
{tBuC(NR′)2}AlMe2 (6a , R′ ) Ad; 6b, R′ ) 2,6-iPr2-Ph),
respectively. The presumed intermediate Li[tBuC-
(NR′)2] salts were not isolated. Compounds 5b, 6a , and
6b are isolated as white or colorless crystals by recrys-
tallization from cold pentane. The relatively low iso-
lated yields (13-20%) are attributed to the high solu-
bility of these compounds in the recrystallization solvent.
The NMR data for 4-6 are consistent with C2v-sym-
(18) Lechler, R.; Hausen, H.-D.; Weidlein, J . J . Organomet. Chem.
1989, 359, 1.
(19) Kottmair-Maieron, D.; Lechler, R.; Weidlein, J . Z. Anorg. Allg.
Chem. 1991, 593, 111.

Al Complexes Incorporating Bulky N and S Ligands
Organometallics, Vol. 17, No. 18, 1998 4045
Ta ble 3. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 3a
Al(1)-N(1)
Al(1)-C(2)
N(1)-C(1)
N(1)-C(11)
N(2)-C(21)
1.910(3)
1.951(6)
1.320(4)
1.495(4)
1.479(4)
Al(1)-S(1)
Al(1)-C(3)
S(1)-C(1)
C(1)-N(2)
2.342(2)
1.943(5)
1.758(3)
1.337(4)
N(1)-Al(1)-C(2)
C(2)-Al(1)-C(3)
C(2)-Al(1)-S(1)
C(1)-S(1)-Al(1)
N(1)-C(1)-S(1)
C(1)-N(1)-C(11)
S(1)-C(1)-N(2)
113.8(3)
117.9(3)
111.0(2)
74.0(1)
111.6(2)
127.0(3)
123.0(3)
N(1)-Al(1)-C(3)
N(1)-Al(1)-S(1)
C(3)-Al(1)-S(1)
C(1)-N(1)-Al(1)
C(11)-N(1)-Al(1)
N(1)-C(1)-N(2)
C(1)-N(2)-C(21)
116.1(2)
73.16(9)
116.8(2)
100.5(2)
132.1(2)
125.4(3)
132.4(3)
(dihedral angle N-Al-S-C ) 2.5° for 1; 4.9° for 3a ),
with distorted trigonal planar coordination at the carbon
and nitrogen atoms (sum of angles ca. 360°).
The C-N distance within the metallacycle of 1 (1.300-
(3) Å) is slightly shorter than the corresponding C-N
distances in aluminum amidinate complexes (ca. 1.34
Å), and the C-S bond length (1, 1.744(3) Å) is in the
normal range for C(sp2)-S single bonds (1.75 Å; com-
pare to C(sp2)dS double-bond length of 1.68 Å in
thioureas).20,21 These results indicate that resonance
structure B in Scheme 4 dominates the bonding within
the thioamidate ligand of 1 and reflect the fact that
C-N π bonding is stronger than C-S π bonding.
The C-N and C-S distances (1.320(4) and 1.758(3)
Å) within the metallacycle of 3a are similar to those in
1. Additionally, the AdHN-C bond length (1.337(4) Å)
is intermediate between normal C(sp2)-N single- and
double-bond distances,22 and the Ad-N-H and metal-
lacycle planes are essentially coplanar (angle between
planes: Ad-N2-H/Al1-N1-C1-S1 ) 4.8°; dihedral
angle S1-C1-N2-C21 ) 5.0°). These results indicate
that the AdHN-C bond has significant double-bond
character and that resonances structures D and E in
Scheme 4 dominate the bonding in the thioureido ligand
of 3a . A similar bonding situation has been observed
in the guanidinate complex {Me2NC(NiPr)2}AlCl2.3,23
Molecu la r Str u ctu r es of {tBu C(NAd )2}AlMe2 (6a )
a n d {tBu C(NAr )2}AlMe2 (6b). Crystal data for 6a and
6b are summarized in Table 1, refinement details are
discussed in the Experimental Section, and selected
bond distances and angles are listed in Tables 4 and 5.
Molecular geometries and atom-labeling schemes are
shown in Figures 3 and 4, and selected bond angles are
given in Figure 5.
F igu r e 1. Molecular structure of {MeC(NAd)S}AlMe2 (1).
F igu r e 2. Molecular structure of {AdHNC(NAd)S}AlMe2
(3a ).
Sch em e 4
Complexes 6a and 6b are monomeric with distorted
tetrahedral geometries at aluminum. The N-Al-N-C
metallacycles are planar (dihedral angles N-Al-N-C
) 0.8, 1.9° for 6a ; -1.0° for 6b) and are structurally
very similar to those in {RC(NR′)2}AlMe2 (R ) Me,
tBu; R′ ) Cy) amidinate complexes.2 It was noted
previously that enhancement of steric interactions
between the C-R and N-R′ substituents in {RC(NR′)2}-
AlX2 complexes forces the N-R′ substituents closer to
the metal center and increases the cone angle of the
amidinate ligand. This structural effect strongly influ-
ences the amidinate bonding mode (i.e., bridging vs
chelating)24 and the chemistry that occurs at the metal
center.1,25 Key bond angles in the relatively crowded
compound {tBuC(NCy)2}AlMe2 and in 6a and 6b are
shown in Figure 5.2 The C-N-R′ and R′-N-Al angles
in 6b are similar to those in {tBuC(NCy)2}AlMe2;
(20) March, J . Advanced Organic Chemistry, 3rd ed.; J ohn Wiley:
New York, 1985; p 19.
(21) Allen, F. H.; Kennard, O.; Watson, D. G.; Brammer, L.; Orpen,
A. G.; Taylor, R. J . Chem. Soc., Perkin Trans. 2 1987, S1.
(22) Sutton, L. E. Interatomic Distances and Configuration in
Molecules and Ions, Special Publications No. 18; The Chemical
Society: London, 1965.
(23) However, the donor nitrogen atoms of {Me2NC(NiPr)2}AlCl2
exhibit some pyramidal character (sum of angles ) 348.4° average,
N-R′ substituents 26.3° (average) out of the plane of the metallacycle).
In contrast, in compound 3a there is no evidence for sp3-character at
the donor nitrogen atom (sum of angles ) 359.6°, R′ substituent in
the plane of the metallacycle).

4046 Organometallics, Vol. 17, No. 18, 1998
Coles et al.
Ta ble 4. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 6a
Molecule 1
Al(1)-N(1)
Al(1)-C(6)
N(1)-C(1)
N(2)-C(1)
C(1)-C(2)
1.920(1)
1.965(2)
1.360(2)
1.353(2)
1.553(2)
Al(1)-N(2)
Al(1)-C(7)
N(1)-C(21)
N(2)-C(11)
1.916(1)
1.963(2)
1.478(2)
1.483(2)
N(1)-Al(1)-N(2)
N(1)-Al(1)-C(6)
N(2)-Al(1)-C(6)
C(1)-N(1)-Al(1)
N(1)-C(1)-N(2)
69.02(6) C(6)-Al(1)-C(7)
116.49(9) N(1)-Al(1)-C(7)
116.79(9) N(2)-Al(1)-C(7)
114.2(1)
117.08(9)
116.06(9)
92.4(1)
92.1(1)
C(1)-N(2)-Al(1)
106.5(1)
C(21)-N(1)-Al(1) 129.5(1)
C(1)-N(1)-C(21)
N(1)-C(1)-C(2)
C(11)-N(2)-Al(1) 128.7(1)
138.2(1)
126.7(1)
C(1)-N(2)-C(11)
N(2)-C(1)-C(2)
138.8(1)
126.7(1)
Molecule 2
Al(2)-N(31)
Al(2)-C(36)
N(31)-C(31)
N(32)-C(31)
C(31)-C(32)
1.912(1)
1.963(2)
1.355(2)
1.358(2)
1.554(2)
Al(2)-N(32)
Al(2)-C(37)
N(31)-C(51)
N(32)-C(41)
1.915(1)
1.969(3)
1.479(2)
1.481(2)
F igu r e 3. Molecular structure of {tBuC(NAd)2}AlMe2 (6a ).
N(31)-Al(2)-N(32)
69.12(6) C(36)-Al(2)-C(37) 115.8(2)
N(31)-Al(2)-C(36) 117.0(1)
N(32)-Al(2)-C(36) 117.5(1)
N(31)-Al(2)-C(37) 114.5(1)
N(32)-Al(2)-C(37) 114.6(1)
C(31)-N(31)-Al(2)
92.4(9)
C(31)-N(32)-Al(2)
92.1(1)
N(31)-C(31)-N(32) 106.3(1)
C(41)-N(32)-Al(2) 129.0(1)
C(31)-N(32)-C(41) 138.6(1)
N(32)-C(31)-C(32) 126.6(1)
C(51)-N(31)-Al(2) 128.5(1)
C(31)-N(31)-C(51) 139.2(1)
N(31)-C(31)-C(32) 127.0(1)
Ta ble 5. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 6b
Al(1)-N(1)
Al(1)-C(1)
N(1)-C(3)
N(2)-C(3)
C(3)-C(4)
1.940(2)
1.952(3)
1.356(3)
1.339(3)
1.539(3)
Al(1)-N(2)
Al(1)-C(2)
N(1)-C(8)
N(2)-C(20)
1.936(2)
1.955(3)
1.440(3)
1.439(3)
N(1)-Al(1)-N(2)
N(1)-Al(1)-C(1)
N(2)-Al(1)-C(1)
C(3)-N(1)-Al(1)
N(1)-C(3)-N(2)
C(20)-N(2)-Al(1)
C(3)-N(2)-C(20)
N(2)-C(3)-C(4)
68.15(7)
C(1)-Al(1)-C(2)
N(1)-Al(1)-C(2)
N(2)-Al(1)-C(2)
C(3)-N(2)-Al(1)
C(8)-N(1)-Al(1)
C(3)-N(1)-C(8)
N(1)-C(3)-C(4)
115.8(1)
116.4(1)
114.1(1)
92.6(1)
137.1(1)
131.0(2)
125.3(2)
118.0(1)
115.9(1)
91.9(1)
107.4(2)
135.4(1)
132.0(2)
127.3(2)
F igu r e 4. Molecular structure of {tBuC(NAr)2}AlMe2 (6b;
Ar ) 2,6-iPr2-Ph)).
have been prepared and characterized. The thioamidate
and thioureido compounds {MeC(NAd)S}AlMe2 (1) and
{R′HNC(NR′)S}AlMe2 (3a , R′ ) Ad; 3b, R′ ) 2,6-iPr-
Ph) exhibit planar metallacycle structures with C-S
single bonds and sterically open Al and S centers. The
“superbulky” amidinate complexes {tBuC(NAd)2}AlMe2
(6a ) and {tBuC(NAr)2}AlMe2 (6b; Ar ) 2,6-iPr-Ph)
exhibit a greater degree of steric crowding around the
Al centers than the most crowded case described pre-
viously, i.e., {tBuC(NCy)2}AlMe2. Studies of cationic
{L-X}AlR+ complexes derived from these neutral pre-
cursors will be discussed in subsequent contributions.
however, the former compound is more crowded due to
the presence of the four isopropyl groups. The aryl rings
in 6b are oriented perpendicular to the metallacycle
(angles between aryl and metallacycle planes ) 86.7°,
85.5°), and the isopropyl groups are positioned above
and below the metallacycle plane, which minimizes
tBu/Ar steric contacts.26 In contrast, the R′-N-Al angle
in 6a is ca. 6° smaller than those in {tBuC(NCy)2}AlMe2
t
and 6b due to close H-H contacts between the Bu and
adamantyl groups.27
Con clu sion s
Exp er im en ta l Section
New {L-X}AlR2 compounds containing bulky ada-
Gen er a l P r oced u r es. All manipulations were performed
on a high-vacuum line or in a glovebox under a purified N2
atmosphere. Solvents were distilled from Na/benzophenone
ketyl, except for chlorinated solvents, which were distilled from
activated molecular sieves (3 Å) or CaH2. The compounds
(AdNH)2CdS,4 (ArNH)2CdS,5 AdNdCdNAd,4 and ArNdCd
NAr6 (Ar ) 2,6-iPr2-Ph) were prepared by literature methods.
All other chemicals were purchased from Aldrich and used as
received. NMR spectra were recorded on a Bruker AMX 360
spectrometer in sealed or Teflon-valved tubes at ambient probe
temperature unless otherwise indicated. 1H and 13C chemical
mantyl- or aryl-substituted N,S- and N,N- donor ligands
(24) (a) Hausen, H.-D.; Gerstner, F.; Schwarz, W. J . Organomet.
Chem. 1978, 145, 277. (b) Zhou, Y.; Richeson, D. S. Inorg. Chem. 1996,
35, 2448. (c) Zhou, Y.; Richeson, D. S. Inorg. Chem. 1996, 35, 1423.
(25) Zhou, Y.; Richeson, D. S. Inorg. Chem. 1997, 36, 501.
(26) Close H-H contacts: H(6B)-H(28A) ) 2.3 Å; H(6C)-H(31A)
) 2.3 Å; H(5C)-H(19A) ) 2.3 Å; H(7B)-H(16A) ) 2.4 Å. Sum of van
der Waals radii ) 2.4 Å.
(27) Close H-H contacts: H(5C)-H(12B) ) 2.2 Å; H(3C)-H(12B)
) 1.8 Å; H(3C)-H(14A) ) 2.0 Å; H(3A)-H(14A) ) 2.2 Å; H(5B)-
H(24A) ) 2.2 Å; H(4B)-H(24A) ) 1.9 Å; H(4A)-H(23B) ) 2.1 Å.

Al Complexes Incorporating Bulky N and S Ligands
Organometallics, Vol. 17, No. 18, 1998 4047
6H, Ad), 2.10 (br d, J HH ) 11, 6H, Ad), 1.90 (br d, J HH ) 2.8,
6H, Ad), 1.69 (s, 6H, Ad), 1.70 (br d, 3H, J HH ) 13, Ad), 1.64
(br d, J HH ) 13, 3H, Ad), -0.64 (s, 6H, AlMe2). 13C NMR
(CD2Cl2): δ 171.1 (s, CNHAd), 54.8 (s, Ad-CR, two signals
1
1
coincident), 42.7 (t, J CH ) 129, Ad-Câ), 42.4 (t, J CH ) 127,
1
1
Ad-Câ), 36.6 (t, J CH ) 127, Ad-Cδ), 36.5 (t, J CH ) 128, Ad-
1
1
Cδ), 30.2 (d, J CH ) 133, Ad-Cγ), 29.9 (d, J CH ) 128, Ad-Cγ),
-7.7 (br q,1J CH ) 114, AlMe2). Anal. Calcd for C23H37AlN2S:
C, 68.96; H, 9.31; N, 6.99. Found: C, 68.78; H, 9.30; N, 6.91.
MS (m/z): 385 (100, M+ - Me).
{Ar HNC(NAr )S}AlMe2 (3b). This compound was pre-
pared by the procedure described for 3a , using 1.00 g of N,N′-
bis(2,6-diisopropylphenyl)thiourea (2.52 mmol) in 80 mL of
pentane and 0.186 g of AlMe3 (2.58 mmol) in 10 mL of pentane.
After 15 h the volatiles were removed under vacuum, yielding
{ArHNC(NAr)S}AlMe2 as a white solid. Yield: 0.946 g, 83%
based on AlMe3. Analytically pure samples were obtained as
colorless hexagonal crystals by cooling a hot (70 °C) saturated
toluene solution to room temperature. 1H NMR (CD2Cl2): δ
3
7.36 (t, J HH ) 7.9, 1H, Ar-Hpara), 7.27 (m, 3H, Ar), 7.19 (d,
3J HH ) 6.8, 2H, Ar-Hmeta), 6.41 (br s, 1H, NH), 3.26 (sept, 3J HH
3
) 6.7, 2H, CHMe2), 3.06 (sept, J HH ) 6.8, 2H, CHMe2), 1.34
F igu r e 5. Key bond angles in {tBuC(NCy)2}AlMe2, 6a and
6b. The data for 6a are averaged values from the two
independent molecules.
3
3
(d, J HH ) 6.8, 6H, CHMe2), 1.33 (d, J HH ) 6.8, 6H, CHMe2),
3
3
1.21 (d, J HH ) 6.1, 6H, CHMe2), 1.08 (d, J HH ) 6.8, 6H,
CHMe2), -0.51 (s, 6H, AlMe2). 13C NMR (CD2Cl2): δ 177.9 (s,
CNHAr), 147.6 (s, Ar-Cortho), 145.8 (s, Ar-Cortho), 135.6 (s, Ar-
1
shifts are reported versus SiMe4 and were determined by
C
ipso), 131.8 (s, Ar-Cipso), 129.7 (d, J CH )162, Ar-Cpara), 128.0
1
reference to the residual H and 13C solvent peaks. Coupling
(d, 1J CH ) 160, Ar-Cpara), 124.9 (d, 1J CH ) 158, Ar-Cmeta), 124.3
(d, 1J CH ) 163, Ar-Cmeta), 28.7 (d, 1J CH ) 128, CHMe2), 28.6 (d,
1J CH ) 134, CHMe2), 26.4 (q, 1J CH ) 126, CHMe2), 24.6 (q, 1J CH
constants are reported in hertz. Elemental analyses were
performed by Desert Analytics Laboratory (Tuscon, AZ). EI-
mass spectra were obtained using the direct insertion probe
method with a VG Analytical Trio I instrument operating at
70 eV. Data for key peaks (m/z, relative % intensity vs base
peak, assignment) are listed.
1
1
) 126, CHMe2), 24.1 (q, J CH ) 126, CHMe2), 24.0 (q, J CH
)
1
126, CHMe2), -7.9 (q, J CH ) 114, AlMe2). Anal. Calcd for
C
27H41AlN2S: C, 71.63; H, 9.13; N, 6.19. Found: C, 71.60; H,
9.37; N, 5.92. MS (m/z): 437 (100, M+ - Me).
{MeC(NAd )S}AlMe2 (1). A suspension of 1-adamantyl
isothiocyanate (1.35 g, 7.00 mmol) in hexanes (50 mL) was
added to a rapidly stirred solution of AlMe3 (0.70 mL, 7.3
mmol) in hexanes (20 mL). The mixture was stirred at room
temperature for 15 h to afford a slurry of a flocculent white
precipitate in a yellow solution. The volatiles were removed
under vacuum, and {MeC(NAd)S}AlMe2 was extracted with
Et2O and isolated from the extract by crystallization at -30
°C. Yield: 1.52 g, 78%. 1H NMR (CD2Cl2): δ 2.58 (s, 3H,
CMe), 2.10 (br s, 3H, Ad-Hγ), 1.95 (br d, J HH ) 3.2, 6H, Ad-
Hâ), 1.71 (br d, J HH ) 14, 3H, Ad-Hδ), 1.67 (br d, J HH ) 14,
3H, Ad-Hδ), -0.58 (s, 6H, AlMe2). 13C NMR (CD2Cl2): δ 196.0
{MeC(NAd )2}AlMe2 (4a ). A solution of AlMe3 (0.132 g,
1.84 mmol) in hexane (10 mL) was added dropwise to a rapidly
stirred solution of 1,3-diadamantylcarbodiimide (0.500 g, 1.61
mmol) in hexane (30 mL). The reaction mixture was stirred
at room temperature for 18 h, and the volatiles were removed
under vacuum, affording pure {MeC(NAd)2}AlMe2 as a white
solid (0.62 g, 88%). Analytically pure samples were obtained
by recrystallization from Et2O at -30 °C. 1H NMR (CD2Cl2):
δ 2.22 (s, 3H, CMe), 2.03 (br s, 6H, Ad-Hγ), 1.79 (br d, J HH
)
2.9, 12H, Ad-Hâ), 1.65 (br s, 12H, Ad-Hδ), -0.82 (s, 6H, AlMe2).
13C NMR (CD2Cl2): δ 172.6 (s, CMe), 51.5 (s, Ad-CR), 44.6 (t,
1J CH ) 129, Ad-Câ), 36.8 (t, 1J CH ) 126, Ad-Cδ), 30.3 (d, 1J CH
132, Ad-Cγ), 19.7 (q, J CH) 128, CMe), -9.6 (br q, J CH ) 112,
AlMe2). Anal. Calcd for C24H39AlN2: C, 75.35; H, 10.27; N,
7.32. Found: C, 74.96; H, 10.35; N, 7.30.
)
1
1
1
(s, CMe), 58.9 (s, Ad-CR), 42.3 (t, J CH ) 127, Ad-Câ), 36.3 (t,
1
1
1J CH ) 126, Ad-Cδ), 29.9 (d, J CH ) 133, Ad-Cγ), 29.4 (q, J CH
1
) 130, CMe), -8.8 (br q, J CH ) 115, AlMe2). Anal. Calcd for
C
14H24AlNS: C, 63.36; H, 9.11; N, 5.28. Found: C, 63.32; H,
{MeC(NAr )2}AlMe2 (4b). This compound was prepared by
the procedure described for 4a , using 0.525 g of 1,3-bis(2,6-
diisopropylphenyl)carbodiimide (1.45 mmol) in 40 mL of hex-
ane and 0.111 g of AlMe3 (1.53 mmol) in 10 mL of hexane.
After 18 h the volatiles were removed under vacuum, yielding
9.10; N, 5.11. MS (m/z): 250 (99, M+ - Me).
Gen er a tion of {MeC(NAd )S}AlMe2‚AlMe3 (2). A solu-
tion of {MeC(NAd)S}AlMe2 (0.063 g, 0.24 mmol) in CD2Cl2 (400
µL) was added to a solution of AlMe3 (0.017 g, 0.24 mmol) in
CD2Cl2 (200 µL), and NMR spectra were recorded. The spectra
showed that 100% conversion to {MeC(NAd)S}AlMe2‚AlMe3
had occurred. 1H NMR (CD2Cl2): δ 2.64 (s, 3H, CMe), 2.15
(br s, 3H, Ad-Hγ), 2.01 (br s, 6H, Ad-Hâ), 1.71 (br m, 6H, Ad-
Hδ), -0.48 (s, 6H, AlMe2), -0.64 (s, 9H, AlMe3). 13C NMR
(CD2Cl2): δ 191.9 (s, CMe), 60.8 (s, Ad-CR), 42.1 (t, 1J CH ) 128,
pure {MeC(NAr)2}AlMe2 as an off-white solid (0.491 g, 74%).
3
1H NMR (CD2Cl2): δ 7.19 (m, 6H, NAr), 3.35 (sept, J HH
)
3
6.8, 4H, CHMe2), 1.49 (s, 3H, CMe), 1.23 (d, J HH ) 7.6, 12H,
3
CHMe2), 1.21 (d, J HH ) 7.2, 12H, CHMe2), -0.53 (s, 6H,
AlMe2). 13C NMR (CD2Cl2): δ 176.1 (s, CMe), 145.1 (s,
1
Ar-Cortho), 138.4 (s, Ar-Cipso), 126.3 (d, J CH ) 160, Ar-Cpara),
1
1
1
1
Ad-Câ), 36.1 (t, J CH ) 127, Ad-Cδ), 29.9 (d, J CH ) 134,
123.8 (d, J CH ) 156, Ar-Cmeta), 28.5 (d, J CH ) 126, CHMe2),
1
1
24.7 (q, 1J CH ) 126, CHMe2), 23.9 (q, 1J CH ) 126, CHMe2), 14.4
Ad-Cγ), 29.5 (q, J CH ) 131, CMe), -6.9 (br q, J CH ) 113,
1
1
1
AlMe3), -8.5 (br q, J CH ) 116, AlMe2).
(q, J CH ) 129, CMe), -9.9 (q, J CH ) 113, AlMe2).
{Ad HNC(NAd )S}AlMe2 (3a ). A solution of AlMe3 (0.210
g, 2.91 mmol) in hexanes (10 mL) was added to a suspension
of N,N′-bis(adamantyl)thiourea (1.00 g, 2.90 mmol) in hexanes
(80 mL). The solution became clear and a gas was evolved.
After 15 h the volatiles were removed under vacuum to afford
{AdHNC(NAd)S}AlMe2 as a white solid (1.08 g, 93%). Ana-
lytically pure samples were obtained by recrystallization in
Et2O at 0 °C. 1H NMR (CD2Cl2): δ 5.38 (s, 1H, NH), 2.14 (s,
{tBu C(NAr )2}AlCl2 (5b). A solution of 1,3-bis(2,6-diiso-
propylphenyl)carbodiimide (2.85 g, 7.86 mmol) in Et2O (80 mL)
was cooled to 0 °C. tBuLi (4.6 mL of a 1.7 M solution in
hexanes, 7.9 mmol) was added slowly by syringe. The result-
ing mixture was allowed to warm to room temperature and
was stirred for 2 h. The mixture was cooled to -78 °C, and a
solution of AlCl3 (1.05 g, 7.86 mmol) in Et2O (30 mL) was
added. The resulting solution was allowed to warm to room

4048 Organometallics, Vol. 17, No. 18, 1998
Coles et al.
1
1
temperature and was stirred for 18 h. The volatiles were
removed under vacuum, yielding an oily yellow solid. {tBuC-
(NAr)2}AlCl2 was extracted from LiCl with pentane and
isolated from the extract by crystallization at -30 °C. Yield:
0.687 g, 17% based on AlCl3. 1H NMR (CD2Cl2): δ 7.27 (d,
(d, J CH ) 129, CHMe2), 27.1 (q, J CH ) 128, CHMe2), 22.8 (q,
1J CH ) 127, CHMe2), -8.6 (br q, J CH ) 113.4, AlMe2). Anal.
1
Calcd for C31H49AlN2: C, 78.10; H, 10.36; N, 5.88. Found: C,
77.61; H, 10.28; N, 5.78. MS (m/z): 461 (100, M+ - Me).
X-r a y Str u ctu r e Deter m in a tion s. The structures of 1
and 6b were determined at the University of Minnesota by V.
G. Young, J r. The structures of 3a and 6a were determined
at the University of Iowa by D. C. Swenson. Crystal data, data
collection details, and solution and refinement procedures are
collected in Table 1. Additional comments specific to each
structure follow.
{MeC(NAd )S}AlMe2 (1). Crystals were obtained by crys-
tallization from Et2O at -30 °C. All non-H atoms were refined
anisotropically, and all H atoms were placed in ideal positions
and refined as riding atoms with group isotropic displacement
parameters.
{Ad N(H)C(NAd )S}AlMe2 (3a ). Crystals were obtained by
crystallization from Et2O at 0 °C. All non-H atoms were
refined anisotropically. The H2, H2A-C and H3A-C H atoms
were refined with isotropic displacement parameters. All other
H atoms were included with the riding model (C-H ) 0.98-
0.99 Å), tetrahedral angles, Uiso ) 1.2 × Uiso (equiv) C).
{tBu C(NAd )2}AlMe2 (6a ). Crystals were obtained by re-
crystallization from pentane at -30 °C. Two independent
molecules with nearly the same conformation were found in
the asymmetric unit. All non H atoms were refined with
anisotropic displacement parameters. All adamantyl H atoms
were included with a modified riding model: tetrahedral
angles, C-H refined (C-H equal for CH2 groups), Uiso refined.
Methyl H atoms were refined with no restraints or constraints,
and with independent isotropic displacement parameters.
{tBu C(NAr )2}AlMe2 (6b). Crystals were obtained by crys-
tallization from pentane at -30 °C. All non-H atoms were
refined anisotropically, and all H atoms were placed in ideal
positions and refined as riding atoms with group isotropic
displacement parameters.
3
3J HH ) 6.5, 1H, Ar), 7.24 (d, J HH ) 6.8, 1H, Ar), 7.19 (s, 3H,
3
Ar), 7.17 (d, J HH ) 6.7, 1H, Ar), 3.41 (sept, J HH ) 6.7, 4H,
3
3
CHMe2), 1.36 (d, J HH ) 6.5, 12H, CHMe2), 1.27 (d, J HH
)
6.8, 12H, CHMe2), 0.98 (s, 9H, CMe3). 13C NMR (CD2Cl2): δ
187.3 (s, CCMe3), 145.3 (s, Ar-Cortho), 136.6 (s, Ar-Cipso), 127.4
1
1
(d, J CH ) 159, Ar-Cpara), 124.2 (d, J CH ) 157, Ar-Cmeta), 42.5
1
1
(s, CMe3), 29.4 (q, J CH ) 128, CMe3), 29.1 (d, J CH ) 128,
1
1
CHMe2), 27.3 (q, J CH ) 131, CHMe2), 23.0 (q, J CH ) 126,
CHMe2). Anal. Calcd for C29H43AlN2Cl2: C, 67.30; H, 8.76;
N, 5.41. Found: C, 67.03; H, 8.39; N, 5.43. MS (m/z, 35Cl):
516 (2, M+ - Me), 473 (2, M+ - Pr).
i
{tBu C(NAd )2}AlMe2 (6a ). This compound was prepared
by the procedure described for 5b, using 2.64 g of 1,3-
diadamantylcarbodiimide (8.50 mmol) in 80 mL of Et2O, 5.0
t
mL of BuLi (1.7 M solution in pentane, 8.5 mmol), and 0.79
mL of AlMe2Cl (8.6 mmol) in 30 mL of Et2O. After 18 h the
volatiles were removed under vacuum, and the product was
extracted from the LiCl with pentane. The pentane extract
was concentrated and cooled to -30 °C to afford {tBuC(NAd)2}-
AlMe2 as white crystals, which were isolated by filtration (0.47
g, 13% based on AlMe2Cl). The low isolated yield is due to
the high solubility of the product. 1H NMR (CD2Cl2): δ 2.05
(br s, 6H, Ad-Hγ), 2.02 (s br, 12H, Ad-Hâ), 1.62 (br s, 12H,
Ad-Hδ), 1.47 (s, 9H, CMe3), -0.76 (s, 6H, AlMe2). 13C NMR
1
(CD2Cl2): δ 182.5 (s, CCMe3), 55.0 (s, Ad-CR), 46.0 (t, J CH
)
1
128, Ad-Câ), 38.5 (s, CMe3), 36.6 (t, J CH ) 126, Ad-Cδ), 32.6
1
1
(q, J CH ) 127, CMe3), 30.7 (d, J CH ) 133, Ad-Cγ), -6.8 (br q,
1J CH ) 113, AlMe2). Anal. Calcd for C27H45AlN2: C, 76.37;
H, 10.68; N, 6.60. Found: C, 76.43; H, 10.86; N, 6.65.
{tBu C(NAr )2}AlMe2 (6b). This compound was prepared by
the procedure described for 5b, using 2.71 g of 1,3-bis(2,6-
diisopropylphenyl)carbodiimide (7.48 mmol) in 80 mL of Et2O,
t
4.4 mL of BuLi (1.7 M solution in pentane, 7.5 mmol), and
Ack n ow led gm en t. This work was supported by
DOE Grant DE-FG02-88ER13935. M.P.C. was sup-
ported in part by a NATO postdoctoral research fellow-
ship.
0.7 mL of AlMe2Cl (7.48 mmol) in 30 mL of Et2O. After 15 h
the volatiles were removed under vacuum yielding an oily red-
brown solid. {tBuC(NAr)2}AlMe2 was extracted from LiCl with
pentane and isolated from the extract by crystallization at
-30 °C. Yield: 0.726 g, 20% based on AlMe2Cl. 1H NMR
(CD2Cl2): δ 7.18-7.12 (m, 6H, Ar), 3.45 (sept, 3J HH ) 6.8, 4H,
Su p p or tin g In for m a tion Ava ila ble: Tables of atomic
coordinates, isotropic displacement parameters, anisotropic
displacement parameters, bond distances and bond angles, and
hydrogen atom coordinates (31 pages). Ordering information
is given on any current masthead page.
3
3
CHMe2), 1.34 (d, J HH ) 7.2, 12H, CHMe2), 1.16 (d, J HH
)
6.8, 12H, CHMe2), 0.91 (s, 9H, CMe3), -0.6 (s, 6H, AlMe2). 13
NMR (CD2Cl2): δ 180.5 (s, CCMe3), 145.0 (s, Ar-Cortho), 139.6
(s, Ar-Cipso), 125.9 (d, J CH ) 161, Ar-Cpara), 123.7 (d, J CH
156, Ar-Cmeta), 42.3 (s, CMe3), 29.7 (q, J CH ) 127, CMe3), 28.7
C
1
1
)
1
OM9802358