Rhodium(III)-cyclometalated-imine complexes: Solution behavior and reactivity with molecular hydrogen

Article abstract of DOI:10.1021/om049121o

Acetone solutions of cis,trans,cis-[Rh(H)₂(PPh₃) ₂(acetone)₂]PF₆ and cis-[Rh(PPh ₃)₂(acetone)₂]-PF₆ react with the imines RN=CR′(R″), where R = PhCH₂, Ph, or C ₆H₁₁; R′ = H or Me; and R″ = Ph or p-OMe-C₆H₄, to form orthometalated complexes exemplified by [Rh(H){RN= CR′(o-C₆H₄)}(PPh₃) ₂(acetone)]PF₆ that are generally characterized spectroscopically, and in one case (where R = PhCH₂, R′ = Me, and R″ = p-OMe-C₆H₄) by X-ray crystallography. These complexes maintain their integrity in acetone solution and show no reaction toward 1 atm H₂ at ambient conditions. In MeOH, the complexes in which R′ = Me simply change to the corresponding MeOH derivative, but when R′ = H they are partially converted to the non-orthometalated, η¹-N-imine species [Rh(PPh₃)₂(RN= CHR″)(MeOH)]PF₆ (I), and in MeOH, stoichiometric hydrogenation of the imine to the corresponding amine occurs via I. We have shown recently (Inorg. Chem. 2004, 43, 4820) that the catalyzed hydrogenation of PhCH ₂N=C(H)Ph to dibenzylamine using cis,trans,cis-[Rh(H) ₂(PPh₃)₂(MeOH)₂]PF₆ as catalyst precursor in MeOH proceeds via a cationic Rh-(η¹-N- imine)(amine) intermediate (II), analogous to I but with the MeOH replaced by the amine that is formed via hydrolysis of the imine by the presence of adventitious water. Intermediate I (R = PhCH₂, R″ = Ph) is shown to be somewhat less active than II toward H₂, but both intermediates provide viable pathways for hydrogenation of the imine. The orthometalated imine-amine complex [Rh(H){PhCH₂N=C(Me)(o-C ₆H₄)}(PPh₃)₂(NH₂CH ₂Ph)]PF₆, where the benzylamine comes from imine hydrolysis, is also isolated and characterized crystallographically.

Full text of DOI:10.1021/om049121o

Organometallics 2005, 24, 1445-1451
1445
Rhodium(III)-Cyclometalated-Imine Complexes: Solution
Behavior and Reactivity with Molecular Hydrogen
Paolo Marcazzan, Brian O. Patrick, and Brian R. James*
Department of Chemistry, The University of British Columbia, 2036 Main Mall,
Vancouver, B.C. V6T 1Z1, Canada
Received November 12, 2004
Acetone solutions of cis,trans,cis-[Rh(H)2(PPh3)2(acetone)2]PF6 and cis-[Rh(PPh3)2(acetone)2]-
PF6 react with the imines RNdCR′(R′′), where R ) PhCH2, Ph, or C6H11; R′ ) H or Me; and
R′′ ) Ph or p-OMe-C6H4, to form orthometalated complexes exemplified by [Rh(H){RNd
CR′(o-C6H4)}(PPh3)2(acetone)]PF6 that are generally characterized spectroscopically, and in
one case (where R ) PhCH2, R′ ) Me, and R′′ ) p-OMe-C6H4) by X-ray crystallography.
These complexes maintain their integrity in acetone solution and show no reaction toward
1 atm H2 at ambient conditions. In MeOH, the complexes in which R′ ) Me simply change
to the corresponding MeOH derivative, but when R′ ) H they are partially converted to the
non-orthometalated, η1-N-imine species [Rh(PPh3)2(RNdCHR′′)(MeOH)]PF6 (I), and in
MeOH, stoichiometric hydrogenation of the imine to the corresponding amine occurs via I.
We have shown recently (Inorg. Chem. 2004, 43, 4820) that the catalyzed hydrogenation of
PhCH2NdC(H)Ph to dibenzylamine using cis,trans,cis-[Rh(H)2(PPh3)2(MeOH)2]PF6 as cata-
lyst precursor in MeOH proceeds via a cationic Rh-(η1-N-imine)(amine) intermediate (II),
analogous to I but with the MeOH replaced by the amine that is formed via hydrolysis of
the imine by the presence of adventitious water. Intermediate I (R ) PhCH2, R′′ ) Ph) is
shown to be somewhat less active than II toward H2, but both intermediates provide viable
pathways for hydrogenation of the imine. The orthometalated imine-amine complex
[Rh(H){PhCH2NdC(Me)(o-C6H4)}(PPh3)2(NH2CH2Ph)]PF6, where the benzylamine comes
from imine hydrolysis, is also isolated and characterized crystallographically.
Introduction
early examples in Rh and Ir chemistry.5,6 Our group has
recently reported on orthometalation within semicar-
bazone complexes of Rh (semicarbazone being a substi-
tuted imine)7 and within Ir species containing simple
imines such as PhCH2NdC(H)Ph,8 but to our knowledge
this work is the first report of orthometalation of simple
imines at Rh (specifically imines of the type RNdCR′-
(R′′), where R ) PhCH2, Ph, or C6H11; R′ ) H or Me;
and R′′ ) Ph or p-OMe-C6H4, containing solely alkyl or
aryl substituents). Of more interest and relevance,
however, are the solution chemistry of these new
orthometalated species, their reaction with H2, and the
implications of the findings to catalyzed hydrogenation
of the imines, a topic that continues to attract much
interest.9
Our recent studies on the homogeneous H2-hydroge-
nation of the imine PhCH2NdC(H)Ph catalyzed by the
[Rh(COD)(PPh3)2]PF6 (1) precursor (when, for example,
imine:Rh ) 100) have revealed that the active catalyst
(the species that reacts with H2) is a mixed Rh(I)-imine-
amine species, the amine benzylamine being formed via
an accompanying Rh-catalyzed hydrolysis of the imine
by adventitious water.1 Under stoichiometric conditions
(imine:Rh ) 1), we now observe quite different chem-
istry, which is reported here: the imine coordinates with
orthometalation in an η2 fashion via the imine-N and
the ortho-C atom of a phenyl group, giving rise to a five-
membered metallacycle within a hydrido-Rh(III)-o-
metalated complex. Such intramolecular activation of
a C-H bond of an aryl group of a donor ligand has long
been known for platinum metal complexes of a variety
of ligands, including N-donors,2-4 and there are many
(5) Hughes, R. P. In Comprehensive Organometallic Chemistry;
Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon Press:
Oxford, 1982; Vol. 5, Chapter 34, p 392.
(6) Leigh, G. J.; Richards, R. L. In Comprehensive Organometallic
Chemistry; Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon
Press: Oxford, 1982; Vol. 5, Chapter 35, p 578.
(7) (a) Ezhova, M. B.; Patrick, B. O.; James, B. R.; Ford, M. E.;
Waller, F. J. Russ. Chem. Bull. Int. Ed. 2003, 52, 2707 (M. Vol’pin
Memorial Volume). (b) Ezhova, M. B.; Patrick, B. O.; Sereviratne, K.
N.; James, B. R.; Waller, F. J.; Ford, M. E. Inorg. Chem., in press.
(8) Marcazzan, P.; Patrick, B. O.; James, B. R. Russ. Chem. Bull.
Int. Ed. 2003, 52, 2715 (M. Vol’pin Memorial Volume).
(9) (a) Kobayashi, S.; Ishitani, H. Chem. Rev. 1999, 99, 1069. (b)
Tang, W.; Zhang, X. Chem. Rev. 2003, 103, 3029. (c) Blaser, H.-U.;
Malan, C.; Pugin, B.; Spindler, F.; Steiner, H.; Studer, M. Adv. Synth.
Catal. 2003, 345, 103. (d) Dorta, R.; Broggini, D.; Kissner, R.; Togni,
A. Chem. Eur. J. 2004, 10, 4546.
* To whom correspondence should be addressed. Tel: +1-(604)-822-
6645. Fax: +1-(604)-822-2847. E-mail: brj@chem.ubc.ca.
(1) (1) (a) Marcazzan, P.; Patrick, B. O.; James, B. R. Organome-
tallics 2003, 22, 1177. (b) Marcazzan, P.; Abu-Gnim, C.; Seneviratne,
K. N.; James, B. R. Inorg. Chem. 2004, 43, 4820. (c) Marcazzan, P.;
Patrick, B. O.; James, B. R. Inorg. Chem. 2004, 43, 6838.
(2) (a) Parshall, G. W. Acc. Chem. Res. 1970, 3, 179. (b) Parshall,
G. W. Acc. Chem. Res. 1975, 8, 113.
(3) (a) van Baar, J. F.; Vrieze, K.; Stufkens, D. J. J. Organomet.
Chem. 1975, 97, 461. (b) van Baar, J. F.; Vrieze, K.; Stufkens, D. J. J.
Organomet. Chem. 1975, 85, 249.
(4) Omae, I. Chem. Rev. 1979, 79 (4), 287.
10.1021/om049121o CCC: $30.25 © 2005 American Chemical Society
Publication on Web 02/23/2005

1446 Organometallics, Vol. 24, No. 7, 2005
Marcazzan et al.
maintains the solid state structure shown in Figure 1
and confirmed crystallographically for a closely related
imine complex (5, see below).
In CD3OD, 4 shows different and more complex
behavior (Figure 2) that was studied by variable-
temperature NMR experiments (Figure S1 in the Sup-
porting Information). The room-temperature 31P{1H}
NMR spectrum of 4 now indicates the presence of three
species: [Rh(H){PhCH2NdCH(o-C6H4)}(PPh3)2(CD3-
OD)]PF6 (4′)13 (δ 40.52 d, JRhP ) 116), cis-[Rh(PPh3)2(CD3-
OD)2]PF6 (3′) (δ 57.02 d, JRhP ) 207),11 and a fluxional
species that gives rise to two broad, unresolved reso-
nances centered at δ ∼46 and ∼55. These resonances
resolve at 253 K into an AMX, 8-line pattern (δ 44.55
Figure 1. Scheme showing reactions for formation of 4.
dd, JRhP ) 164, 2JPP ) 54; 54.74 dd, JRhP ) 214, 2JPP
)
Results and Discussion
54), indicative of a species containing two inequivalent
cis-phosphines, each trans to a different ligand, and this
is identified as the imino-solvento complex cis-[Rh-
(PPh3)2(PhCH2NdCHPh)(CD3OD)]PF6 (I), shown in
Figure 2. Free acetone (δ 2.10) is detected in the room-
temperature 1H NMR spectrum of 4 in CD3OD (Figure
S1), indicating its displacement by CD3OD to give 4′,
while detection of free imine indicates that 4′ has
undergone “reductive elimination” of this ligand, a
premise confirmed by the presence of [Rh(PPh3)2(CD3-
OD)2]PF6 (3′) in the 31P{1H} NMR spectrum (Figure S1)
in an amount that corresponds to the amount of free
Reaction of either cis,trans,cis-[Rh(H)2(PPh3)2(acetone)2]-
PF6 (2) or cis-[Rh(PPh3)2(acetone)2]PF6 (3)10,11 with
PhCH2NdC(H)Ph (Rh:imine ) 1:1) in acetone at room
temperature (∼20 °C) under Ar affords the Rh(III)-
orthometalated complex [Rh(H){PhCH2NdCH(o-C6H4)}-
(PPh3)2(acetone)]PF6 (4) (Figure 1), isolated as an off-
white solid. Formation of orthometalated complexes via
reaction of a simple imine with a Rh(I) species has not
been reported in detail, although we have noted the
existence of such species1 and have reported on the Ir
analogue of 4 that was isolated from reaction of the
imine with the Ir analogue of 2.8 The mechanism3,8
presumably involves displacement of an acetone ligand
by imine when the ortho-CH group becomes close to the
metal, this being accompanied, when 2 is the reactant,
by reductive elimination of the hydride ligands as H2
(detected in the 1H NMR spectrum at δH 4.40 in acetone-
d6); oxidative addition of C-H then generates 4. Detec-
tion of hydride (see below) versus deuteride in the
product isolated from reaction of PhCH2NdCHPh with
the precursor [Rh(D)2(PPh3)2(acetone-d6)2]PF6 in acetone-
d6 is consistent with the hydrido ligand emanating from
the orthometalation process. Of note, reaction of [RhCl-
(CO)2]2 with MeNdC(H)Ph forms the η1-N-imine com-
plex cis-RhCl(CO)2(MeNdCHPh), presumably because
the presence of the electron-withdrawing CO ligands
diminishes the tendency for oxidative addition.3
1
imine. The room-temperature H NMR spectrum also
shows sharp singlets at δ 4.80 and 4.99 for the benzylic
protons of free imine and the orthometalated imine (of
4′), respectively, as well as a broad signal in the δ 4.7-
5.3 region; at 253 K (Figure S1), this broad signal
2
sharpens into a pair of doublets (δ 4.50 d, 5.35 d, JHH
) 6), showing diastereotopic inequivalence of the ben-
zylic protons within I, presumably because of some
restricted rotation of the imine moiety at lower tem-
peratures. The CHdN resonances of 4′ and I are not
seen, presumably being masked by the aromatic proton
signals. The room-temperature 1H NMR spectrum also
shows a downfield doublet (δ 9.65 d, 2H, 3JHH ≈ 7) that
is not attributable to 3′ or to free imine; the correspond-
ing 1H-13C HETCOR NMR experiment reveals correla-
tion of this signal with resonances corresponding to
aromatic C atoms (δ 132), and so the signal is attributed
to the o-protons of the imine-Ph moiety of I being
involved in a π-arene interaction with Ph groups of the
PPh3 ligands that causes a shielding of this resonance.
A similar shielding was observed for a Rh(I)-imine-
amine complex recently reported by our group.1c Neither
4′ nor I could be isolated pure from a solution mixture
of 4′, 3′, and I, formed either from a solution of 4 in
MeOH or from a MeOH solution of 4′ formed directly
from reaction of cis-[Rh(PPh3)2(MeOH)2]PF6 with 1
equiv of PhCH2NdC(H)Ph.
The IR data for 4 reveal bands for νRhH, νCdN, and νCO
for the coordinated acetone. The room-temperature 31P-
{1H} NMR spectrum in acetone-d6 shows a doublet (δ
40.40, JRhP ) 116), the J value being indicative of
mutually trans phosphines.1c The high-field hydride 1H
2
NMR resonance (δ -12.85, JHP ≈ JRhH ) 13) appears
as a pseudo-quartet (ps q) instead of the expected
doublet of triplets; such overlapping of triplets has been
reported for other trans-Rh(PPh3)2-hydrido moieties.12
Upfield-shifted δH resonances for the orthometalated
ring protons and for the NdCH signal (δH 7.81 versus
8.50 for the free imine) are similar to those reported
for the Ir analogue.8 Thus, in acetone solution, 4
Thus in MeOH, the orthometalation process evident
in 4 (and 4′) is effectively reversed and affords 3′ and I,
square planar species that can both undergo oxidative
addition of H2 (see below). Such behavior is relevant in
that [Rh(COD)(PPh3)2]PF6 (1) is an effective precursor
catalyst for hydrogenation of imines in MeOH solution
but not in acetone. In the latter solvent, the integrity
of the coordinatively saturated Rh(III) species 4 is
(10) (a) Schrock, R. R.; Osborn, J. A. J. Am. Chem. Soc. 1971, 93,
2397. (b) Haines, L. M.; Singleton, E. J. Chem. Soc., Dalton 1972, 1891.
(11) Marcazzan, P.; Ezhova, M. B.; Patrick, B. O.; James, B. R. C.
R. Chim. 2002, 5, 373 (J. A. Osborn Memorial Volume).
(12) (a) Al-Najjar, I. M.; El-Baih, F. E. M.; Abu-Loha, F. M.; Gomaa,
Z. Trans. Met. Chem. 1994, 19, 325. (b) Ghedini, M.; Neve, F.; Lanfredi,
A. M. M.; Uguzzoli, F. Inorg. Chim. Acta 1988, 147, 243. (c) Bhayat, I.
I.; McWhinnie, W. R. J. Organomet. Chem. 1972, 46, 159. (d) Di Vaira,
M.; Peruzzini, M.; Zanobini, F.; Stoppioni, P. Inorg. Chim. Acta 1983,
69, 37.
(13) A prime superscript (e.g., as in 4′) refers to the CD3OD/CH3-
OH analogue of the corresponding acetone/acetone-d6 species (e.g., 4).

Rh(III)-Cyclometalated-Imine Complexes
Organometallics, Vol. 24, No. 7, 2005 1447
Figure 2. Scheme showing the species generated in a CD3OD solution of 4 (or 4′).
Figure 3. Structural and ORTEP diagram of [Rh(H){PhCH2NdC(Me)(o-C6H3-p-OMe}(PPh3)2(acetone)]PF6‚Me2CO (5) with
50% probability thermal ellipsoids.
Table 1. Crystallographic Data for 5 and 9*
maintained, and there is no reactivity toward H2.
5
9*
However, exposure of a MeOH solution of 4′ to 1 atm
H2 results in quantitative hydrogenation of the coordi-
nated imine within 5 min to afford dibenzylamine and
cis,trans,cis-[Rh(H)2(PPh3)2(CD3OD)2]PF6 (2′), as de-
tected by 31P{1H} and 1H NMR spectroscopies.10,11
Monitoring the H2-hydrogenation of 4 in MeOH (i.e. 4′)
by variable-temperature NMR spectroscopy showed no
evidence for hydrido-imine intermediates. At 243 K, the
spectra revealed the presence of 4′, 2′ (formed from 3′),
I, free acetone, and a smaller amount of free imine; as
the solution was warmed to 300 K, I and 4′ gradually
disappeared with concomitant formation of dibenzy-
lamine (δCH2 4.80) and increased amounts of 2′ and 3′.
The dibenzylamine is, in fact, involved in a labile
equilibrium with 3′, and we have reported earlier on
the NMR investigation of this equilibrium.1a The only
Rh species seen in the final solution at 300 K is 2′, when
all the imine has been converted to free amine.
formula
fw
C58H59NO3F6P3Rh C59.50H60N2O1.50F6P3Rh
1127.88
1136.92
cryst color, habit colorless, needle
red, irregular
cryst size (mm)
space group
a (Å)
0.30 × 0.07 × 0.07 0.40 × 0.30 × 0.20
P21/c
P21/n
10.060(1)
19.129(2)
27.912(3)
91.600(5)
5369(1)
4
16.5613(5)
17.8073(4)
18.7853(5)
107.822(2)
5274.2(2)
4
b (Å)
c (Å)
â (deg)
V (Å3)
Z
Dcalcd (g cm-3
)
1.395
0.473
1.432
µ (mm-1
)
0.481
total no. of reflns 157 997
48 378
no. of unique
reflns
Rint
no. of variables
R1
30 620
12 155
0.071
697
0.047
660
0.044 (I > 2σ(I),
16 036 obs reflns)
0.104 (all data)
0.94 (all data)
0.032 (I > 3σ(I),
8601 obs reflns)
0.090 (all data)
1.12 (all data)
wR2
GOF
Attempts to obtain a crystal of 4 suitable for X-ray
analysis were unsuccessful, but the ketimine PhCH2Nd
C(Me)(p-MeOC6H4) similarly underwent the orthometa-
lation reaction with 2 in acetone to give [Rh(H)-
{PhCH2NdC(Me)(o-C6H3-p-OMe}(PPh3)2(acetone)]PF6
(5), which was characterized crystallographically (Fig-
ure 3); selected structural parameters are given in Table
2. The complex crystallizes as a two-component twin
with one acetone molecule in the asymmetric unit. The
geometry at the Rh is essentially octahedral with trans-
phosphines, the acetone being trans to the metalated
o-carbon and the refined, located Rh-H hydrogen atom
being trans to the imine-N atom. As for the related Ir
complex [Ir(H){PhCH2NdCH(o-C6H4)}(PPh3)2(acetone)]-
PF6, the large C(53)-O-Rh angle of 137.9° and the
P(1)-Rh-P(2) angle of 166.8° indicate that the acetone-
Me groups are subject to steric repulsions by the Rh-
(PPh3)2 moiety. The structure of 5 is generally very
similar to that of the Ir complex noted above, with the
five-membered cyclometalated rings being essentially
planar. The N(1)-C(8) imine bond is 0.18 Å shorter than
the N(1)-C(10) single bond, while the Rh-O bond
length of 2.19 Å likely reflects a trans-influence of the
ortho-C ligand, although we have been unable to find
any structural data on a Rh-acetone moiety (the Rh-O
distances within related orthometalated Rh-semicarba-
zone complexes7 are in the range 2.207-2.310 Å). The
solid state IR of 5 reveals the νRh-H, νCdN, and νCdO
bands. The room-temperature 31P{1H} and 1H NMR
spectra of 5 in acetone-d6 correspond closely to those of
4, with the former showing also the “extra” resonances
for the imine Me and OMe protons. Interestingly, and
in contrast with 4, complex 5 upon dissolution in MeOH
simply forms the MeOH-solvated analogue 5′ (δP 40.33
2
d, JRhP ) 117.8; δH -12.70 ps q, JRhH ≈ JHP ) 13) and
displays none of the behavior associated with the

1448 Organometallics, Vol. 24, No. 7, 2005
Marcazzan et al.
imine-C atom show the same complex behavior in
MeOH as 4′ and 6′ (cf. Figure 2). Thus, the labile
chemistry noted in MeOH is seen only for the imine
systems that contain the NdCH moiety, but it is unclear
why this governs the “reverse orthometalation”. There
is no evidence for incorporation of deuterium into 4′, 3′,
or I in the observed chemistry of Figure 2, and thus
cleavage of the Rh-C bond by protons/deuterons is ruled
out, implying that direct reductive elimination from the
cis-Rh(H)-C moiety occurs (or alternatively the oxidative
addition of the imine is less complete in MeOH).
Possibly some H-bonding interaction between the MeOH
and the H atom of the imine NdCH increases the acidity
of the H atom, decreases the basicity of the imine, and
thus decreases the propensity for oxidative addition to
the Rh(I). A contributing factor is also likely to be the
somewhat higher donor number of MeOH versus that
of acetone (20 versus 17),14 a feature that has been
demonstrated within the related cis,trans,cis-[Ir(H)2-
(PPh3)2(solvent)2]BF4 species.15
The labile chemistry noted in MeOH is also reflected
in the catalytic hydrogenation of the different imines
in this solvent. As noted above, hydrogenation of 4′ in
MeOH gives dibenzylamine and cis,trans,cis-[Rh(H)2-
(PPh3)2(MeOH)2]PF6 (2′); this solution can then be
treated with a further equivalent of PhCH2NdCHPh,
and under H2 the imine is again reduced to the amine
via the partial formation of 4′ and the chemistry of
Figure 2. Thus, via a series of stoichiometric hydrogena-
tions, the net process is a catalyzed imine hydrogenation
via [Rh(PPh3)2(PhCH2NdCHPh)(MeOH)]PF6 (I). Of note,
if excess imine is used under the same conditions in
MeOH, catalytic hydrogenation occurs via [Rh(PPh3)2-
(PhCH2NdCHPh)(NH2CH2Ph)]PF6 (II), the amine be-
ing formed via a Rh-catalyzed hydrolysis of the imine
by adventitious water.1 The rate (turnover)-determining
step of the catalytic process is oxidative addition of H2
to II with a rate constant that we will define as kII,
whose value at 30 °C has been determined1b as ∼45 M-1
s-1. An estimate of the corresponding kI value for
oxidative addition of H2 to I at ∼20 °C can be made as
follows. Integration of the 31P{1H} resonances of the
species present in a solution of 4′ at this temperature
([Rh]total ) 0.022 M) shows a 4:1 ratio of I:4′ and much
smaller amounts of 3′ (see Figures 2 and S1), and thus
the [I] is ∼0.017 M; when the solution is shaken under
1 atm H2 (which is effectively maintained at a constant
solution concentration of ∼1.5 × 10-3 M1b), the imine
is converted to amine with t1/2 ≈ 90 s, corresponding to
a kI value of ∼8 M-1 s-1 at room temperature. Although
the kinetic activation parameters have not been mea-
sured for these systems, it is almost certain that
reactivity to give amine via II is more favorable than
via I (probably by a factor of ∼3, as rate constants for
oxidative addition of H2 to such systems typically double
with a 10 °C increase in temperature).16 The difference
in oxidative addition reactivity (see Figure 5) seems
reasonable considering the higher basicity of benzyl-
amine versus that of CD3OD/MeOH. An important
Figure 4. Complexes 7-10.
Table 2. Selected Bond Distances and Angles for
[Rh(H){PhCH2NdC(Me)(o-C6H3-p-OMe}(PPh3)2-
(acetone)]PF6‚Me2CO (5) (estimated standard
deviations in parentheses)
bond
length (Å)
bond
angle (deg)
Rh(1)-P(1)
Rh(1)-P(2)
Rh(1)-N(1)
Rh(1)-O(2)
Rh(1)-C(2)
Rh(1)-H(1)
N(1)-C(8)
N(1)-C(10)
O(2)-C(53)
C(53)-C(54)
C(53)-C(55)
C(8)-C(1)
2.3313(8)
2.3529(7)
2.1597(19) P(2)-Rh(1)-O(2)
2.1937(18) P(2)-Rh(1)-H(1)
P(1)-Rh(1)-C(2)
P(2)-Rh(1)-N(1)
88.92(7)
99.56(6)
92.15(5)
85.0(6)
171.4(7)
79.86(9)
92.11(8)
115.8(2)
117.0(2)
88.18(7)
2.001(2)
1.564(17)
1.296(3)
1.479(3)
1.223(3)
1.496(4)
1.498(4)
1.465(3)
1.521(3)
1.414(3)
1.527(3)
N(1)-Rh(1)-H(1)
N(1)-Rh(1)-C(2)
N(1)-Rh(1)-O(2)
N(1)-C(8)-C(1)
C(2)-C(1)-C(8)
P(2)-Rh(1)-C(2)
O(2)-C(53)-C(54) 122.6(3)
O(2)-C(53)-C(55) 120.1(3)
C(53)-O(2)-Rh(1) 137.93(19)
C(8)-C(9)
C(1)-C(2)
C(10)-C(11)
Rh(1)-C(2)-C(1)
Rh(1)-C(2)-C(3)
Rh(1)-N(1)-C(8)
113.62(19)
128.52(19)
113.53(17)
bond
angle (deg) Rh(1)-N(1)-C(10) 124.54(16)
P(1)-Rh(1)-P(2) 166.86(3)
O(2)-Rh(1)-C(2) 171.90(9)
P(1)-Rh(1)-N(1) 92.54(6)
P(1)-Rh(1)-O(2) 92.52(5)
P(1)-Rh(1)-H(1) 82.4(7)
C(53)-O(2)-Rh(1) 137.93(19)
Rh(1)-C(2)-C(1)
Rh(1)-C(2)-C(3)
Rh(1)-N(1)-C(8)
113.62(19)
128.52(19)
113.53(17)
Rh(1)-N(1)-C(10) 124.54(16)
chemistry of 4′ shown in Figure 2. Consistent with this,
no reaction is observed when exposing a MeOH solution
of 5 (or 5′) to 1 atm H2.
The orthometalated complex [Rh(H){CH3NdCH(o-
C6H4)}(PPh3)2(acetone)]PF6 (6), formed from the imine
MeNdC(H)Ph, was also isolated and characterized
spectroscopically as for 4, and its solution behavior is
similar to that of 4: in acetone, the solid state structure
is maintained, while in CD3OD, chemistry correspond-
ing to that of Figure 2 is seen (i.e., formation of 6′, the
“reverse” of orthometalation, and reactivity toward H2).
Analogous orthometalated species [Rh(H){RNdCR′(o-
C6H4)}(PPh3)2(acetone-d6)]PF6, 7-10, were synthesized
in situ in acetone-d6 from the precursor imines PhNd
C(H)Ph, C6H11NdC(H)Ph, PhCH2NdC(Me)Ph, and
PhCH2NdCPh2, respectively (Figure 4); their NMR
spectra were assigned as for complexes 4-6, and in the
1
case of 7, the high-field hydride H resonance is seen
as the expected doublet of triplets because of a sufficient
2
difference in the JRhH and JHP values (16 and 13 Hz,
respectively). Of key interest, species 9′ and 10′ (the
MeOH derivatives of 9 and 10 that can be made in situ
in MeOH from cis-[Rh(PPh3)2(MeOH)2]+ and 1 equiv of
the imine), like 5′ with the Me substituent at the
imine-C atom, are essentially stable as such in MeOH
(but see below for 9′), while 7′ and 8′ (the MeOH
analogues of 7 and 8) that have the H atom at the
(14) Huheey, J. E. Inorganic Chemistry, 3rd ed.; Harper Collins:
New York, 1983; p 340.
(15) Crabtree, R. H.; Mellea, M. F.; Mihelcic, J. M.; Quirk, J. M. J.
Am. Chem. Soc. 1982, 104, 107.
(16) James, B. R. Homogeneous Hydrogenation; Wiley: New York,
1973; Chapter XII.

Rh(III)-Cyclometalated-Imine Complexes
Organometallics, Vol. 24, No. 7, 2005 1449
Figure 5. Oxidative addition of H2 to species I and II.
The supposed dihydrido products have not been detected
(see ref 1b).
Figure 6. ORTEP diagram of the cation [Rh(H){PhCH2Nd
C(Me)(o-C6H4)}(PPh3)2(NH2CH2Ph)]+ of complex 9* with
50% probability thermal ellipsoids.
result from this study is the demonstration that Rh-
catalyzed imine hydrogenation can, in principle, occur
without the need for hydrolysis of imine to amine. Under
catalytic conditions in MeOH,1 the ketimine PhCH2Nd
C(Me)Ph was hydrogenated much more slowly than the
aldimine PhCH2NdC(H)Ph, with conversions of only ∼4
and ∼40% after 1 and 40 h, respectively. Ketimines are
invariably hydrogenated more slowly than a corre-
sponding aldimine because of increased steric bulk
around the NdC moiety,17 but whether the hydrogena-
tion of PhCH2NdC(Me)Ph occurs via a solvent-η1-imine
intermediate such as I or an η1- amine-η1-imine species
such as II is unclear, particularly as an orthometalated
species (9*) containing also η1-benzylamine has been
isolated (see below). With the more heavily substituted
imine PhCH2NdCPh2, no catalytic hydrogenation is
observed under ambient conditions in MeOH, while we
have reported earlier1a that the corresponding hydro-
genation of PhNdC(H)Ph is inhibited by catalyst poi-
soning, the amine product PhNHCH2Ph coordinating to
the Rh via the N-phenyl group (η4 in the solid state and
η6 in solution).
When the MeOH solution of [Rh(H){PhCH2NdCMe-
(o-C6H4)}(PPh3)2(acetone)]PF6 (9′) was left at room
temperature for about a week “under vacuo”, a small
crystal formed, and this proved by X-ray analysis
(Figure 6) to be [Rh(H){PhCH2NdC(Me)(o-C6H4)}-
(PPh3)2(NH2CH2Ph)]PF6 (9*), where the MeOH ligand
of 9′ has been replaced by benzylamine, the amine
hydrolysis product of the imine. We have reported
elsewhere on this metal-catalyzed hydrolysis reaction,1,8
and indeed in the Rh-catalyzed hydrogenation of
PhCH2NdCHPh the active catalyst is II, as noted above.
Whether 9* is a catalyst precursor for hydrogenation
of PhCH2NdC(Me)Ph will remain unknown until a
reliable synthetic method is realized for this complex.
The structure of 9* (Table 3) is similar to that of complex
5 but where the acetone has been replaced by the amine;
the key bond lengths and angles are close to those in 5,
and even the Rh-N(2)amine distance is the same as the
Rh-O distance in 5. We have noted recently the close
correspondence in the structures of the Ir complexes [Ir-
(H){PhCH2NdCH(o-C6H4)}(PPh3)2(L)]PF6, where L )
acetone or benzylamine.8
Table 3. Selected Bond Distances and Angles for
[Rh(H){PhCH2NdC(Me)(o-C6H4)}(PPh3)2-
(NH2CH2Ph)]PF6 (9*) (estimated standard
deviations in parentheses)
bond
length (Å)
bond
angle (deg)
Rh(1)-P(1)
Rh(1)-P(2)
Rh(1)-N(1)
Rh(1)-N(2)
Rh(1)-C(18)
Rh(1)-H(54)
N(2)-C(15)
N(2)-C(8)
2.3499(6)
2.3344(6)
2.224(2)
2.162(2)
1.999(2)
1.43(2)
1.288(3)
1.478(3)
1.509(4)
1.509(4)
1.511(3)
1.467(3)
1.512(3)
1.411(3)
P(2)-Rh(1)-N(1)
P(2)-Rh(1)-N(2)
P(1)-Rh(1)-C(18)
P(2)-Rh(1)-C(18)
N(2)-Rh(1)-H(54)
N(2)-Rh(1)-N(1)
N(2)-Rh(1)-C(18)
N(2)-C(15)-C(16)
N(2)-C(15)-C(17)
C(15)-C(17)-C(18)
C(8)-N(2)-C(15)
N(2)-C(8)-C(9)
92.29(7)
91.49(5)
88.50(6)
86.79(6)
175(1)
101.70(8)
79.45(8)
124.9(2)
116.0(2)
116.4(2)
121.0(2)
115.1(2)
114.3(2)
114.3(2)
128.0(2)
113.8(1)
121.0(2)
115.1(2)
114.3(2)
114.3(2)
128.0(2)
113.8(1)
N(1)-C(1)
C(1)-C(2)
C(15)-C(16)
C(15)-C(17)
C(8)-C(9)
N(1)-C(1)-C(2)
C(17)-C(18)
Rh(1)-C(18)-C(17)
Rh(1)-C(18)-C(19)
bond
P(1)-Rh(1)-P(2)
N(1)-Rh(1)-C(18) 178.55(9)
P(1)-Rh(1)-N(1)
P(1)-Rh(1)-N(2)
P(1)-Rh(1)-H(54) 85(1)
P(2)-Rh(1)-H(54) 86(1)
angle (deg) Rh(1)-N(2)-C(15)
169.30(2)
C(8)-N(2)-C(15)
N(2)-C(8)-C(9)
N(1)-C(1)-C(2)
Rh(1)-C(18)-C(17)
Rh(1)-C(18)-C(19)
Rh(1)-N(2)-C(15)
92.22(7)
97.08(5)
Experimental Section
Unless stated otherwise, synthetic procedures were per-
formed at room temperature (∼20 °C) using standard Schlenk
techniques under an atmosphere of dry Ar. The liquid imines
PhCH2NdCHPh and CH3NdCHPh from Aldrich were purified
by distillation; the solid imines PhCH2NdC(Me)Ph, PhCH2Nd
C(Me)-p-C6H4OMe, PhCH2NdCPh2, and PhNdCHPh, and the
liquid C6H11NdCHPh were synthesized in this laboratory
previously by Drs. D. E. Fogg, K. S. MacFarlane, and M. B.
Ezhova.18 The [Rh(COD)(PPh3)2]PF6 (1) and corresponding cis,-
trans,cis-[Rh(H)2(PPh3)2(solvent)2]PF6 (2, 2′) and cis-[Rh(PPh3)2-
(solvent)2]PF6 (3, 3′) precursors (solvent ) acetone, MeOH)
were prepared according to literature procedures.9,10 Other
reagents were purchased from commercial sources and used
as supplied. Solvents were dried over the appropriate agents
and distilled under N2 prior to use. NMR spectra were recorded
on Bruker AV 300 (300 MHz for 1H, 121 MHz for 31P{1H}, 75
1
MHz for 13C) and AV 400 (400 MHz for H, 162 MHz for 31P-
(18) (a) Fogg, D. E. Ph.D. Dissertation, The University of British
Columbia, Vancouver, 1994. (b) MacFarlane, K. S.; Ezhova, M. B.
Unpublished results.
(17) James, B. R. Catal. Today 1997, 37. 209.

1450 Organometallics, Vol. 24, No. 7, 2005
Marcazzan et al.
3
3
{1H}, 100 MHz for 13C) spectrometers. Residual solvent proton
(1H, relative to external SiMe4 δ 0.00) and external P(OMe)3
(31P{1H}, δ 141.00 versus external 85% aqueous H3PO4) were
used as references. All J values are given in Hz. Infrared
spectra were recorded on an ATLI Mattson Genesis Series
FTIR spectrophotometer, and IR bands (KBr pellet) are
reported in cm-1. Elemental analyses were performed by Mr.
P. Borda of this department using a Carlo Erba 1108 analyzer.
[N,o-C-(N-Benzylidenebenzylaminato)]hydrido(ace-
tone)bis(triphenylphosphine)rhodium(III) Hexafluoro-
phosphate, [Rh(H){PhCH2NdCH(o-C6H4)}(PPh3)2(ace-
tone)]PF6 (4). To a pale yellow solution of [Rh(H)2(PPh3)2-
(acetone)2]PF6 (2) (0.113 mmol) or a red solution of [Rh(PPh3)2-
(acetone)2]PF6 (3) (0.116 mmol) in acetone (3 mL) was added
PhCH2NdCHPh (22.0 µL, 0.116 mmol) under Ar and the
mixture stirred for 2 h. The volume was then reduced under
vacuum to ∼1 mL to afford spontaneous precipitation of an
off-white solid that was collected by filtration, washed with
Et2O (3 × 4 mL), and dried in vacuo. Yield: 0.090 g (75%).
C6H4), JHH ) 7), 6.65 (d, 1H, o-(o-C6H4), JHH ) 7), 6.80 (m,
1
2H, m-(o-C6H4)), 7.20-7.70 (m, 35H, aromatics), 8.00 (s, H,
dCH). R ) C6H11, R′ ) H (8): 31P{1H} NMR (acetone-d6): δ
1
38.40 (d, JRhP ) 117). H NMR (acetone-d6): δ -12.82 (ps q,
2
1H, Rh-H, JRhH ≈ JHP ) 13), 1.20-1.90 (m, 10H, C6(H)H10),
4.30 (pt, 1H, C6(H)H10, 3JHH ) 10), 6.45 (t, 1H, p-(o-C6H4), 3JHH
) 7), 6.52 (d, 1H, o-(o-C6H4), 3JHH ) 7), 6.95 (t, 1H, m-(o-C6H4),
3JHH ) 7), 7.05-7.90 (m, 31H, m-(o-C6H4) and aromatics), 8.10
(s, 1H, dCH). R ) PhCH2, R′ ) Me (9): 31P{1H} NMR
(acetone-d6): δ 40.33 (d, JRhP ) 117). 1H NMR (acetone-d6): δ
-12.42 (ps q, 1H, Rh(H), JRhH
≈
2JHP ) 13), 1.95 (s, 3H,
3
C(CH3)), 5.45 (s, 2H, CH2), 6.50 (t, 1H, p-(o-C6H4), JHH ) 7),
6.65 (d, 1H, o-(o-C6H4), 3JHH ) 7), 6.85 (m, 2H, m-(o-C6H4), 3JHH
) 7), 6.90-7.80 (m, 35H, aromatics). 9′, the CD3OD derivative
of 9, was made in situ in CD3OD from cis-[Rh(PPh3)2(CD3-
OD)2]+ and 1 equiv of PhCH2NdC(Me)Ph (see text); after one
week, a crystal that deposited from the solution was subjected
to X-ray analysis and determined to have the structure [Rh-
(H){PhCH2NdC(Me)(o-C6H4)}(PPh3)2(NH2CH2Ph)]PF6 (9*).
There was insufficient material for further characterization.
R ) PhCH2, R′ ) Ph (10): 31P{1H} NMR (acetone-d6): δ 38.54
(d, JRhP ) 118). 1H NMR (acetone-d6): δ -12.61 (ps q, 1H, Rh-
1
31P{1H} NMR (acetone-d6): δ 40.40 (d, JRhP ) 116). H NMR
(acetone-d6): δ -12.85 (ps q, 1H, Rh-H, JRhH
≈
2JHP ) 13),
2.10 (s, 6H, free CH3COCH3), 5.25 (s, 2H, CH2), 6.52 (t, 1H,
2JHP ) 13), 5.13 (s, 2H, CH2), 5.94 (d, 1H, o-(o-
3
3
(H), JRhH
≈
p-(o-C6H4), JHH ) 6.5), 6.72 (d, 1H, o-(o-C6H4), JHH ) 6.5),
3
3
3
C6H4), JHH ) 7), 6.40 (t, 1H, p-(o-C6H4), JHH ) 7), 6.45 (m,
6.95 (m, 2H, m-(o-C6H4), JHH ) 6.5), 7.01-7.79 (m, 35H,
3
2H, m-(o-C6H4), JHH ) 7), 7.00-7.75 (m, 40H, aromatics).
aromatics), 7.81 (s, 1H, dCH). IR (KBr): ν 2096 (Rh-H), 1660
(CdO), 1611, 1576 (CdN), Anal. Calcd for C53H49NOF6P3Rh:
C, 62.06; H, 4.81; N, 1.37. Found: C, 62.0; H, 4.9; N, 1.5.
{N,o-C-[N-(p-MeO-Phenylmethylbenzylaminato)]}-
hydrido(acetone)bis(triphenylphosphine)rhodium(III)
Hexafluorophosphate, [Rh(H){PhCH2NdC(Me)(o-C6H3-
p-OMe)}(PPh3)2(acetone)]PF6 (5). This complex was pre-
pared as a light brown solid from a solution of [Rh(H)2(PPh3)2-
(acetone)2]PF6 (2) (0.100 mmol) and the imine PhCH2Nd
C(Me)C6H4-p-OMe (0.024 g, 0.100 mmol) according to the
procedure given for 4. Yield: 0.070 g (65%). 31P{1H} NMR
(acetone-d6): δ 40.43 (d, JRhP ) 117). 1H NMR (acetone-d6): δ
Crystal Structure Determinations. Measurements were
made at 173(0.2) K on a Bruker X8 APEX and on a Rigaku/
ADSC CCD area detector diffractometer for 5 and 9*, respec-
tively, with graphite-monochromated Mo KR radiation (0.71073
Å). Some crystallographic data for 5 and 9* are shown in Table
1.
Data for 5 were collected and integrated using the Bruker
SAINT19 software package and corrected for absorption effects
using the multiscan technique (SADABS20). The material
crystallizes as a two-component twin, with the two components
related by a 2.2° rotation about the (1,0,0) axis. The structure
was solved by direct methods21 using an hklf4 format data set
including corrected twin overlaps, and final refinements were
carried out using an hklf5 format data set containing all
reflections for both twin components. The ratio of both twin
components is roughly 1:1. All non-hydrogen atoms were
refined anisotropically. Four F atoms of the PF6 anion were
disordered and were modeled in two orientations. The Rh-H
hydrogen atom was located in a difference map and refined
isotropically, while all other hydrogen atoms were included
in calculated positions but not refined. The material crystal-
lizes with one molecule of acetone in the asymmetric unit. The
final cycle of full-matrix least-squares refinement on F2 was
based on 30 620 reflections and 697 variable parameters (least-
2
-12.51 (ps q, 1H, Rh-H, JRhH ≈ JHP ) 13), 1.95 (s, 3H, C(CH3)),
2.10 (s, 6H, free CH3COCH3), 2.99 (s, 3H, p-OCH3), 5.40 (s,
2H, CH2), 6.08 (s, 1H, m-(o-C6H3-), 6.60 (d, 1H, o-(o-C6H3-),
3JHH ) 7), 6.85 (d, 1H, m-(o-C6H3-), 3JHH ) 7), 6.95-7.70 (m,
35H, aromatics). IR (KBr): ν 2105 (Rh-H), 1670 (CdO), 1600,
1576 (CdN). Anal. Calcd for C55H53NO2F6P3Rh: C, 61.75; H,
4.99; N, 1.31. Found: C, 61.35; H, 5.3; N, 1.7. An X-ray quality
crystal of 5 was obtained by slow evaporation of an acetone/
Et2O solution (1:1 vol) of the compound.
[N,o-C-(N-Benzylidenemethylaminato)]hydrido(ace-
tone)bis(triphenylphosphine)rhodium(III) Hexafluoro-
phosphate, [Rh(H){CH3NdCH(o-C6H4)}(PPh3)2(acetone)]-
PF6 (6). To a solution of [Rh(PPh3)2(acetone)2]PF6 (3) (0.096
mmol) in acetone (3 mL) was added CH3NdCHPh (12.0 µL,
0.097 mmol) under Ar and the mixture stirred for 2 h. The
volume was then reduced to ∼1 mL followed by addition of
Et2O (4 mL) to precipitate a creamy-white solid that was
collected by filtration, washed with Et2O (3 × 3 mL), and dried
in vacuo. Yield: 0.065 g (70%). 31P{1H} NMR (acetone-d6): δ
squares function minimized ∑w(Fo - Fc2)2, where w ) 1/[σ2-
2
(Fo ) + (0.0359P)2 + 0.00P] and P ) (Fo + 2Fc2)/3), and
converged to R1 ) 0.094, wR2 ) 0.104, GOF ) 0.94.
2
2
Data for 9* were collected and processed using the d*TREK22
program. The structure was again solved by direct methods21
and expanded using Fourier techniques.23 The material crys-
tallizes with 1.5 molecules of MeOH in the asymmetric unit.
All solvent atoms were refined isotropically, while the rest
were refined anisotropically. The N-H and Rh-H hydrogen
atoms were refined isotropically; the rest were included in fixed
positions. Neutral atom scattering factors were taken from
1
42.10 (d, JRhP ) 116). H NMR (acetone-d6): δ -12.58 (ps q,
2
1H, Rh-H, JRhH ≈ JHP ) 13), 2.10 (s, 6H, free CH3COCH3),
3.79 (s, 3H, CH3N), 6.54 (t, 1H, p-(o-C6H4), 3JHH ) 6.5), 6.83-
3
7.00 (m, 3H, m,o-(o-C6H4), JHH ) 6.5), 7.15-7.70 (m, 30H,
aromatics), 7.74 (s, 1H, dCH). IR (KBr): ν 2101 (Rh-H), 1666
(CdO), 1618, 1578 (CdN). Anal. Calcd for C47H45NO F6P3Rh:
C, 59.44; H, 4.78; N, 1.47. Found: C, 59.1; H, 4.9; N, 1.5.
In Situ Characterization of [Rh(H){RNdCR′(o-C6H4)}-
(PPh3)2(acetone-d6)]PF6. An NMR tube equipped with an
airtight J Young PTFE valve was charged with the precursor
cis-[Rh(PPh3)2(acetone-d6)2]PF6 (∼0.01 mmol) and a 1:1 mol
equiv of the respective imine, and the solvent was added via
vacuum-transfer. The resulting red solution was then analyzed
by NMR spectroscopy. R ) Ph, R′ ) H (7): 31P{1H} NMR
(acetone-d6): δ 39.91 (d, JRhP ) 116). 1H NMR (acetone-d6): δ
-13.12 (dt, 1H, Rh-H, JRhH ) 16, 2JHP ) 13), 6.40 (t, 1H, p-(o-
(19) SAINT: Version 6.02; Bruker AXS Inc.: Madison, WI, 1999.
(20) SADABS: Bruker Nonius area detector scaling and absorption
correction, Version 2.05; Bruker AXS Inc.: Madison, WI.
(21) SIR97: Altomare, A.; Burla, M. C.; Cammalli, G.; Cascarano,
M.; Giacovazzo, C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.;
Spagna, A. J. Appl. Cryst. 1999, 32, 115.
(22) d*TREK: Area Detector Software, version 4.13; Molecular
Structure Corporation: The Woodlands, TX, 1996-1998.
(23) DIRDIF94: Beurskens, P. T.; Admiraal, G.; Beurskens, G.;
Bosman, W. P.; de Gelder, R.; Israel, R.; Smits, J. M. M. The DIRDIF-
94 program system. Technical Report of the Crystallography Labora-
tory; University of Nijmegen, The Netherlands, 1994.

Rh(III)-Cyclometalated-Imine Complexes
Organometallics, Vol. 24, No. 7, 2005 1451
Cromer and Waber,24 and anomalous dispersion effects were
are stable as such in acetone solution (and show no
reactivity toward 1 atm H2), but in MeOH solution those
that contain a H atom at the imine-C are converted
partially to a cationic, mixed η1-N-imine/MeOH species
that provides a pathway for reaction of the orthometa-
lated complexes with H2; this reaction generates amine
in a stoichiometric reaction and is relevant in the Rh-
catalyzed hydrogenation of the imines, where we have
previously reported that a cationic, mixed η1-N-imine/
amine species is an important catalytic intermediate.
Characterized also is a cationic, Rh-orthometalated
imine complex containing also an amine ligand, the
amine being formed by hydrolysis of the imine. The
studies derive from our ongoing efforts to gain a more
detailed understanding of catalyzed imine hydrogena-
tions, particularly on the role of the solvent.
25
included in Fcalc
,
the values of ∆f ′ and ∆f ′′ being those of
Creagh and McAuley.26 Values for the mass attenuation
coefficients are those of Creagh and Hubbell,27 and all calcula-
tions were performed using the teXsan program.28 The final
cycle of full-matrix least-squares refinement on F2 was based
on 11 765 observed reflections (I > 0.00σ(I)) and 660 variable
parameters (using ∑w(Fo - Fc2)2, where w ) 1/σ2(Fo )) and
converged to R1 ) 0.056, wR2 ) 0.090, GOF ) 1.12.
2
2
Conclusions
Simple imines of the type RNdC(H)R′′ or RNdC(R′)-
R′′, where R, R′, and R′′ are solely alkyl or aryl
substituents, react in a 1:1 stoichiometry with cationic
Rh(I)-(PPh3)2 species to form (via the usual Cortho-H
activation) orthometalated complexes containing a five-
membered ring, when a suitable phenyl substituent (R′
or R′′) is available at the imine-C atom. The complexes
Acknowledgment. We thank the Natural Sciences
and Engineering Research Council of Canada (NSERC)
for funding.
(24) Cromer, D. T.; Waber, J. T. International Tables for X-ray
Crystallography, Vol. IV; The Kynoch Press: Birmingham, England,
Table 2.2 A, 1974.
(25) Ibers, J. A.; Hamilton, W. C. Acta Crystallogr. 1964, 17, 781.
(26) Creagh, D. C.; McAuley, W. J. In International Tables for
Crystallography, Vol. C; Wilson, A. J. C., Ed.; Kluwer Academic
Publishers: Boston, 1992; Table 4.2.6.8, pp 219-222.
Supporting Information Available: 31P{1H} and 1H
spectra of 4 in CD3OD at 298 and 253 K (Figure S1), and X-ray
crystallographic data for the structures of 5 and 9* in CIF
format. This material is available free of charge via the
Internet at http://pubs.acs.org.
(27) Creagh, D. C.; Hubbell, J. H. In International Tables for
Crystallography, Vol. C; Wilson, A. J. C., Ed.; Kluwer Academic
Publishers: Boston, 1992; Table 4.2.4.3, pp 200-206.
(28) teXsan: Crystal Structure Analysis Package; Molecular Struc-
ture Corporation: The Woodlands, TX, 1985 and 1992.
OM049121O