Rhodium-hydrido-benzylamine-triphenylphosphine complexes: Solid-state and solution structures and implications in catalyzed imine hydrogenation

Article abstract of DOI:10.1021/ic049227b

The complexes cis,trans,cis-[Rh(H)₂(PPh₃) ₂(NH₂CH₂Ph)₂]PF₆ (1) and cis-[Rh(PPh₃)₂(NH₂CH₂Ph) ₂]PF₆ (2) are characterized by X-ray crystallography; the structures are maintained in CH₂Cl₂ where the species are in equilibrium under H₂. In MeOH and in acetone, loss of amine and/or H₂ can occur. Traces of 1 and 2 are present after a Rh-catalyzed H₂-hydrogenation of PhCH=NCH₂Ph in MeOH, where the amine is generated by hydrolysis of the imine substrate through adventitious water. The findings are relevant to catalyst poisoning in the catalytic process.

Full text of DOI:10.1021/ic049227b

Inorg. Chem. 2004, 43, 6838−6841
Rhodium−Hydrido−Benzylamine−Triphenylphosphine Complexes:
Solid-State and Solution Structures and Implications in Catalyzed Imine
Hydrogenation
Paolo Marcazzan, Brian O. Patrick, and Brian R. James*
Department of Chemistry, The UniVersity of British Columbia, VancouVer,
British Columbia, Canada V6T 1Z1
Received June 14, 2004
The complexes cis,trans,cis-[Rh(H)2(PPh3)2(NH2CH2Ph)2]PF6 (1) and cis-[Rh(PPh3)2(NH2CH2Ph)2]PF6 (2) are
characterized by X-ray crystallography; the structures are maintained in CH2Cl2 where the species are in equilibrium
under H2. In MeOH and in acetone, loss of amine and/or H2 can occur. Traces of 1 and 2 are present after a
Rh-catalyzed H2-hydrogenation of PhCHdNCH2Ph in MeOH, where the amine is generated by hydrolysis of the
imine substrate through adventitious water. The findings are relevant to catalyst poisoning in the catalytic process.
Introduction
Experimental Section
The cis,trans,cis-[Rh(H)2(PPh3)2(MeOH)2]PF6 (3) precur-
sor, readily formed from [Rh(COD)(PPh3)2]PF6 and 1 atm
H2 at room temperature (room temperature, ∼20 °C),
catalyzes homogeneously the H2-hydrogenation of benzylide-
neamines (PhCHdNR, R ) alkyl, aryl) in MeOH at ambient
conditions.1,2 We have shown recently that, for the imine
PhCHdNCH2Ph, the mixed imine-amine complex cis-[Rh-
(PPh3)2(PhCHdNCH2Ph)(PhCH2NH2)]PF6 (4) is the species
that reacts with H2 in the key step of the catalytic cycle; the
benzylamine is generated via a Rh-promoted hydrolysis of
the imine, the source of the adventitious water possibly being
the liquid imine.2 At the end of the catalysis, trace amounts
of Rh species were detected by 31P NMR. These have now
been identified as cis,trans,cis-[Rh(H)2(PPh3)2(NH2CH2Ph)2]-
PF6 (1) and cis-[Rh(PPh3)2(NH2CH2Ph)2]PF6 (2); this article
describes the characterization of 1 and 2 in the solid state
and their solution structures in CH2Cl2, MeOH, and acetone.
More generally, catalyzed imine hydrogenation is very
solvent-dependent1 and can be subject to catalyst poisoning
by amines,2 and so, the findings are important in this area
that has industrial significance.3
General. General experimental procedures were carried out, and
reagents were obtained, as described recently elsewhere.2
Syntheses. cis,trans,cis-[Rh(H)2(PPh3)2(NH2CH2Ph)2]PF6 (1).
A yellow suspension of [Rh(COD)(PPh3)2]PF6 (85 mg, 0.100 mmol)
in MeOH (6 mL) was stirred under 1 atm H2 for 2 h. To the resultant
pale yellow solution was added the amine (27 µL, 0.250 mmol)
under H2, and the mixture was stirred for 15 min to afford
spontaneous precipitation of a white solid that was collected, washed
with hexanes (3 mL) and Et2O (3 × 3 mL), and dried in vacuo.
Yield: 50 mg (51%). Anal. Calcd for C50H50N2P3F6Rh: C, 60.74;
H, 5.10; N, 2.83. Found: C, 60.38; H, 4.87; N, 2.78. 31P{1H} NMR
(CD2Cl2): δ 49.55 (d, JRhP ) 116). 1H NMR (CD2Cl2): δ -17.55
2
(pseudo-q, 2H, Rh(H)2, JRhH ≈ JHP ) 14), 2.20 (m, 4H, -NH2),
2.80 (m, 4H, -CH2), 6.20 (d, 4H, -CH2(o-C6H5), 3JHH ) 5), 6.95-
7.60 (m, 36H, arom-H). IR (KBr pellet): ν 2050, 2090 (Rh-H,
m), 3336 (N-H, m).
cis-[Rh(PPh3)2(PhCH2NH2)2]PF6 (2)‚0.5MeOH. To a red solu-
tion of [Rh2(PPh3)4][PF6]2 (85 mg, 0.110 mmol Rh)4 in MeOH (4
mL) under Ar was added the amine (27 µL, 0.250 mmol), and the
resultant yellow solution was stirred for 2 h. The volume was then
reduced to ∼1 mL to afford precipitation of a yellow solid that
was collected, washed with hexanes (3 mL) and Et2O (3 × 3 mL),
and dried in vacuo. Yield: 60 mg (55%). Anal. Calcd for
C50H48N2P3F6Rh‚(0.5CH3OH): C, 60.48; H, 4.99; N, 2.79. Found:
C, 60.27; H, 4.90; N, 2.80. 31P{1H} NMR (CD2Cl2): δ 51.81 (d,
* To whom correspondence should be addressed. E-mail: brj@
chem.ubc.ca.
(1) For reviews on imine hydrogenation, see: James, B. R. Catal. Today
1997, 37, 209. Kobayashi, S.; Ishitani, H. Chem. ReV. 1999, 99, 1069.
Tang, W.; Zhang, X. Chem. ReV. 2003, 103, 3029.
(2) Marcazzan, P.; Abu-Gnim, C.; Seneviratne, K. N.; James, B. R. Inorg.
Chem. 2004, 43, 4820. Marcazzan, P.; Patrick, B. O.; James, B. R.
Organometallics 2003, 22, 1177.
(3) Blaser, H.-U.; Malan, C.; Pugin, B.; Spindler, F.; Steiner, H.; Studer,
M. AdV. Synth. Catal. 2003, 345, 103.
(4) Marcazzan, P.; Ezhova, M. B.; Patrick, B. O.; James, B. R. C. R.
Chim. 2002, 5, 373 (J. A. Osborn Memorial Volume).
6838 Inorganic Chemistry, Vol. 43, No. 21, 2004
10.1021/ic049227b CCC: $27.50
© 2004 American Chemical Society
Published on Web 09/21/2004

Rh-Hydrido-Benzylamine-Triphenylphosphine Complexes
Table 1. Crystallographic Data for 1 and 2
1
2
formula
fw
C52H54N2F6P3Cl4Rh
1158.59
C50.5H50N2O0.5F6P3Rh
1002.74
cryst color, habit colorless, chip
red, blocks
0.38 × 0.30 × 0.25
C2/c (No. 15)
29.3124(7)
21.0184(5)
18.1676(4)
124.853(2)
9185.2(4)
8
0.540
40023
9302
0.057
cryst size (mm3)
space group
a (Å)
0.15 × 0.15 × 0.10
C2/c (No. 15)
13.7776(9)
21.9566(14)
19.2997(14)
95.948(4)
5806.9(7)
4
0.614
27616
6625
0.071
b (Å)
c (Å)
â (deg)
V (Å3)
Z
µ (mm-1
)
total reflns
unique reflns
Rint
no. variables
R1 (I > 2σ(I))
wR2
349
590
0.060 (4488 obsd reflns) 0.042 (7083 obsd reflns)
0.168 (all data)a
0.96 (all data)
0.120 (all data)b
1.03 (all data)
GOF
Figure 1. ORTEP diagram of the cation cis,trans,cis-[Rh(H)2(PPh3)2(NH2-
CH2Ph)2]+ (1) with 50% probability thermal ellipsoids.
a w ) 1/[σ2(Fo ) + (0.0996P)2], where P ) (max(Fo , 0) + 2Fc )/3. b w
2
2
2
) 1/[σ2(Fo ) + (0.0588P)2 + 0.5327P], where P ) (max(Fo , 0) + 2Fc )/
2
2
2
3.
for 1, and on 9302 observed reflections (I > 0.00σ(I)) and 590
variables for 2. All calculations were performed using the teXsan10
crystallographic software package and SHELXL-97.11
JRhP ) 177). In CD3OD: δ 52.21 (d, JRhP ) 176). 1H NMR (CD2-
Cl2): δ 2.50 (br t, 4H, -NH2), 3.45 (br t, 4H, -CH2), 6.90-7.70
(m, 40H, arom-H).
Results and Discussion
X-ray Crystallographic Analysis. X-ray quality crystals of 1
and 2, respectively, were grown from CH2Cl2/hexanes and from
MeOH solutions of the complexes. Measurements were made at
173(2) K on a Rigaku/ADSC CCD area detector with graphite
monochromated Mo KR radiation (0.71073 Å). Some crystal-
lographic data for 1 and 2 are shown in Table 1. Data were collected
and processed using the d*TREK program.5 The final unit-cell
parameters for 1 and 2 were based on 14423 (3.7° < 2θ < 55.7°)
and 22397 (5.9° < 2θ < 55.9°) reflections, respectively. The
structures were solved by direct methods6 and expanded using
Fourier techniques.7 Compound 1 crystallizes with a CH2Cl2
molecule in the asymmetric unit; additional residual electron density
peaks were found but could not be modeled as either CH2Cl2 or
hexane. The SQUEEZE function8 in PLATON9 was used to correct
the raw data for the residual density. All non-H-atoms of the cations
of 1 and 2 were refined anisotropically. Within 1, the N-H and
Rh-H H-atoms were refined isotropically, while other H-atoms
were included in fixed positions. Within 2, the associated PF6
counterion resides on two positions with one-half PF3 on each; one
PF3 fragment is disordered and was modeled in two orientations.
In addition, one-half molecule of MeOH also crystallized in the
asymmetric unit of 2. Some atoms in the disordered PF3 fragment
were refined isotropically, while the H-atoms of the MeOH involved
in H-bonding were refined isotropically, but all other H-atoms were
included in calculated positions. The final cycle of full-matrix least-
Reaction of a MeOH solution of cis,trans,cis-[Rh(H)2-
(PPh3)2(MeOH)2]PF6 (3), generated in situ from [Rh(COD)-
(PPh3)2]PF6,12 with ∼2 equiv of PhCH2NH2 at room tem-
perature under 1 atm H2 for 15 min results in the displacement
of the MeOH ligands and the formation of cis,trans,cis-[Rh-
(H)2(PPh3)2(NH2CH2Ph)2]PF6 (1) in ∼50% isolated yield
(Scheme 1).
The structure of the cation is shown in Figure 1, with
selected bond lengths and angles given in Table 2. The
complex resides on a 2-fold rotation axis, and the geometry
at the Rh(III) is close to octahedral. The Rh-P distance
within the trans-PPh3 ligands (2.293 Å) and the Rh-H bond
length (1.47 Å) are typical of those found in Rh(III)
complexes,13,14 while the phosphine ligands are bent towards
the hydrides as indicated by the P-Rh-H angles (86.9° and
82.4 °) and the P-Rh-P angle (165.6 °). The Rh-N distance
(2.239 Å) is ∼0.2 Å longer than an estimated average
RhIII-N bond length,15 presumably because the amine is trans
to the high trans-influence hydride ligand.16 The geometry
of the coordinated amine is essentially identical to that in
the mixed RhI-imine-amine complex such as 4 (see
Introduction) but where the phosphine is P(p-tolyl)3 and the
2
squares refinement (function minimized: ∑w(Fo - Fc2)2) was
(10) teXsan: Crystal Structure Analysis Package; Molecular Structure
Corporation: The Woodlands, TX, 1985 and 1992.
(11) Sheldrick, G. M. SHELXL-97; University of Go¨ttingen: Go¨ttingen,
Germany, 1997.
(12) Shapley, J. R.; Schrock, R. R.; Osborn, J. A. J. Am. Chem. Soc. 1969,
91, 2816. Schrock, R. R.; Osborn, J. A. J. Am. Chem. Soc. 1971, 93,
2397. Haines, L. M.; Singleton, E. J. Chem. Soc., Dalton Trans. 1972,
1891.
based on 6625 observed reflections (I > 0.00σ(I)) and 349 variables
(5) d*TREK: Area Detector Software, version 7.11; Molecular Structure
Corporation: The Woodlands, TX, 2001.
(6) SIR97: Altomare, A.; Burla, M. C.; Cammalli, G.; Cascarano, M.;
Giacovazzo, C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.;
Spagna, A. J. Appl. Crystallogr. 1999, 32, 115.
(7) 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 Laboratory; Univer-
sity of Nijmegen: Nijmegen, The Netherlands, 1994.
(8) SQUEEZE: Sluis, P. v. d.; Spek, A. L. Acta Crystallogr., Sect. A 1990,
46, 194.
(13) Yu, X.-Y; Maekawa, M.; Morita, T.; Chang, H.-C.; Kitagawa, S.; Jin,
G.-X. Polyhedron 2002, 21, 1613.
(14) 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).
(15) Orpen, A. G.; Brammer, L.; Allen, F. H.; Kennard, O.; Watson, D. J.
Chem. Soc., Dalton Trans. 1989, S1.
(16) Kaesz, H. D.; Saillant, R. B. Chem. ReV. 1972, 72, 231.
(9) PLATON: Spek, A. L. A Multipurpose Crystallographic Tool; Utrecht
University: Utrecht, The Netherlands, 1998.
Inorganic Chemistry, Vol. 43, No. 21, 2004 6839

Marcazzan et al.
Scheme 1. Reaction Scheme for the Formation of cis,trans,cis-[Rh(H)2(PPh3)2(NH2CH2Ph)2]PF6 (1) and cis-[Rh(PPh3)2(NH2CH2Ph)2]PF6 (2)
Table 2. Selected Bond Distances and Angles for
cis,trans,cis-[Rh(H)2(PPh3)2(NH2CH2Ph)2]PF6 (1) with Estimated
Standard Deviations in Parentheses
Table 3. Selected Bond Distances and Angles for
cis-[Rh(PPh3)2(NH2CH2Ph)2]PF6 (2) with Estimated Standard Deviations
in Parentheses
bond
length (Å)
bond
angle (deg)
bond
length (Å)
bond
angle (deg)
Rh(1)-P(1)
Rh(1)-N(1)
Rh(1)-H(1)
N(1)-C(1)
C(1)-C(2)
2.2927(10)
2.239(3)
1.47(3)
1.489(5)
1.513(5)
P(1)-Rh(1)-N(1)
N(1)-Rh(1)-N(1*)
P(1)-Rh(1)-P(1*)
N(1)-Rh(1)-H(1)
N(1*)-Rh(1)-H(1)
P(1)-Rh(1)-H(1)
P(1*)-Rh(1)-H(1)
P(1)-Rh(1)-N(1*)
C(1)-N(1)-Rh(1)
91.76(11)
94.33(19)
165.63(5)
174.5(12)
91.1(12)
86.9(13)
82.4(13)
98.01(11)
114.7(2)
Rh(1)-P(1)
Rh(1)-P(2)
Rh(1)-N(1)
Rh(1)-N(2)
N(1)-C(37)
N(2)-C(44)
2.2063(8)
2.2483(8)
2.202(3)
2.146(3)
1.486(4)
1.475(6)
P(1)-Rh(1)-N(1)
P(2)-Rh(1)-N(2)
P(1)-Rh(1)-P(2)
P(1)-Rh(1)-N(2)
P(2)-Rh(1)-N(1)
C(37)-N(1)-Rh(1)
C(44)-N(2)-Rh(1)
N(1)-Rh(1)-N(2)
178.17(10)
173.47(11)
93.88(3)
92.50(10)
87.70(10)
120.0(2)
120.0(3)
85.95(14)
0.03-0.09 Å shorter than those in complex 1. The Rh-N-C
angles of 2, compared to those of 1, have opened up by
∼5 °, presumably because of less steric constraint.
The structure of 2 is retained in CD2Cl2 and in CD3OD
solutions, where a 31P{1H} doublet is seen in the room
temperature NMR spectra, the JRhP value of ∼175 Hz being
typical for cis-PPh3 ligands coupled to Rh.3,12 The corre-
sponding 1H NMR spectra also identify 2 as the only species
present in solution.
amine is trans to the phosphine; in this mixed complex, the
Rh-N distance is 2.209 Å.2 For complex 1, IR bands are
seen for ν(Rh-H) and ν(N-H).
The structure of 1 is maintained in CH2Cl2 under H2 (see
additional details elsewhere in this paper) as shown by room
temperature NMR data: the 31P{1H} doublet (δP 49.55, JRhP
) 116) is typical for trans-PPh3 ligands coupled to Rh,12
1
while the high-field H resonance for the equivalent cis-
2
hydrides (δH -17.55, JRhH ≈ JPH ) 14) appears as a pseudo-
Complex 1 on dissolution at room temperature in CD3-
OD under Ar undergoes partial (reversible) loss of H2 to
quartet instead of the expected doublet of triplets. This
overlapping of triplets has been seen previously with
corresponding dihyride complexes containing unsaturated
N-donor ligands.13,17 The more downfield δH shift for the
hydrides of 1 versus that of the analogous bis-alcohol
complex 3 (δH -21.20) is consistent with the relative trans-
form 2, and a trans-Rh(PPh3)2 species (δP 46.09 d, JRhP
)
118 Hz). This is almost certainly the amine-MeOH species
cis,trans,cis-[Rh(H)2(PPh3)2(NH2CH2Ph)(MeOH)]PF6 (5), as
in the presence of excess amine this species is reconverted
to 1. Of note, the high-field hydride resonances for 1 and 5
are not seen in CD3OD, presumably because of hydride
exchange with the solvent (an intermediate with hydrogen-
bonding between cis-disposed hydride and MeOH ligands
1
influence of the ligands (RNH2 > ROH).16 The H NMR
doublet at δ 6.20 (3JHH ) 5) is assigned to the ortho-H atoms
of the amine benzylic rings, likely involved in a π-arene
interaction with one phosphine-Ph group: a similar assign-
ment was made for the imine-amine complex 4, where a
1H-13C HETCOR NMR experiment established that these
protons correlate with aromatic C-atoms.2
Complex 1 in CD2Cl2 under Ar loses H2 reversibly to
generate cis-[Rh(PPh3)2(NH2CH2Ph)2]PF6 (2) (Scheme 1), a
species that was more readily isolated from reaction of 2
equiv of PhCH2NH2 with cis-[Rh(PPh3)2(MeOH)2]PF6, this
being generated in situ by dissolution of [Rh2(PPh3)4][PF6]2
in MeOH.4 The reaction is again simple replacement of
MeOH ligands by amines. The structure of the cation of 2
(Figure 2, Table 3) reveals the expected, essentially square-
planar geometry at the Rh(I) center. The RhI-P distances
are within (0.05 Å of those found in other Rh(I) complexes
containing cis-PPh3 ligands3,4 while the RhI-N lengths are
(17) Albinati, A.; Auklin, C. G.; Gunazzoli, F.; Ruegg, H.; Pregosin, P. S.
Inorg. Chem. 1987, 26, 503. Ghedini, M.; Neve, F.; Manotti Lanfredi,
A. M.; Ugozzoli, F. Inorg. Chim. Acta 1988, 147, 243. Al-Najjar, I.
M.; El-Baih, F. E. M.; Abu-Loha, F. M.; Gomaa, Z. Transition Met.
Chem. 1994, 19, 325.
Figure 2. ORTEP diagram of the cation cis-[Rh(PPh3)2(NH2CH2Ph)2]+
(2) with 50% probability thermal ellipsoids.
6840 Inorganic Chemistry, Vol. 43, No. 21, 2004

Rh-Hydrido-Benzylamine-Triphenylphosphine Complexes
is readily envisioned). Thus, the fact that 1 dissolved in
MeOH (the favored solvent for catalyzed imine hydrogena-
tion)2,3 exists as a mixture of 1, 2, and 5 certainly shows
that benzylamine may compete for (i.e., poison) the Rh
catalyst. When PhCHdNCH2Ph is added (Rh/imine ) 1:1)
to a CD3OD solution of 2 stored under Ar, the imine-amine
complex 42 (∼30% formation), unreacted imine, and 2 are
detected. Exposure of this solution to 1 atm H2 for 5 min
results in complete conversion of the imine to the dibenzy-
lamine product and generation of 1. Similarly, if excess imine
(10 equiv) is added to 2 (or 1) in CD3OD under H2, catalytic
hydrogenation occurs via complete formation of 4 as
described elsewhere,2 although here 1 is the final species
remaining in solution. Thus in MeOH, the presence of up to
2 equiv of benzylamine per Rh is innocuous to the catalysis,
and indeed 1 equiv is essential for formation of the key
imine-amine species. Addition of >2 equiv of PhCH2NH2,
however, does inhibit the catalysis.2
The 8-line AMX pattern seen in the 31P{1H} NMR spectrum
reveals inequivalent cis phosphines, each trans to a different
ligand, and both protons within each of the CH2 and NH2
1
groups of the coordinated amine are inequivalent in the H
NMR, presumably because of restricted rotation about the
Rh-N bond.2 An upfield-shifted doublet resonance for 2
protons in the aromatic region (δ 6.23) is similar to that
observed for 1 and could be assigned to the o-protons of the
benzylamine moiety of the mixed amine/acetone species, in
which case the downfield resonance would be assigned to
the P-atom trans to acetone, and the upfield resonance to
the P-atom trans to the amine.19 However, in situ 6 in acetone
was unreactive toward 1 atm H2 or 1 equiv of PhCHdNCH2-
Ph, and no catalyzed imine hydrogenation was observed in
this solvent. As the bis(amine) and bis(acetone)12 species
readily oxidatively add H2, nonreactivity of the amine/acetone
species toward H2 would be surprising. Thus, 6 is more likely
a bidentate benzylamine adduct containing η2-coordination
of the phenyl group, in which case the δ 6.23 signal would
be assigned to the protons of the η2-moiety.
Acetone is clearly a stronger donor ligand than MeOH
within these Rh systems and does not allow for ready
formation of the mixed imine-amine species that is neces-
sary for the catalytic hydrogenation.2 Further, dihydrides are
readily formed at 1 atm H2 by Rh(I)-bis(amine) and
Rh(I)-amine(solvent) species in MeOH, but not in acetone.
Such marked solvent effects, coupled with the requirement
for adventitious water, make optimization of conditions for
hydrogenation of PhCHdNCH2Ph a nontrivial problem. The
generality of such findings within other imine substrates
remains to be established.
Addition of 1 equiv of PhCHdNCH2Ph to a CD2Cl2
solution of 2 under Ar again results in partial formation
(∼50%) of the mixed species 4. Exposure of this solution
to 1 atm H2, however, results in the hydrogenation of only
the imine contained in complex 4, with complete conversion
of all the Rh into 1; consistent with this, there is no reaction
of 1 with 1 equiv of imine. These observations indicate
further that, although 2 (and 1) are themselves a “dead-end”
for catalysis, hydrogenation can still occur if the mixed
species is formed.
In acetone solution at rt under Ar, 1 and 2 display behavior
very different from that in CD2Cl2 and CD3OD: both
complexes quantitatively rearrange (via loss of H2 and/or
amine) into a species 6 that is either cis-[Rh(PPh3)2(NH2-
CH2Ph)(acetone)]PF6 or cis-[Rh(PPh3)2{NH2CH2(η2-C6H5)}]-
PF6 (eq 1).18 Free benzylamine and H2, displaced from either
1 or 2, were detected in the 1H NMR spectrum [δ(CH2) 4.55
s, δ(H2) 4.15], but attempts to isolate 6 were unsuccessful.
Acknowledgment. We thank the Natural Sciences and
Engineering Research Council of Canada for financial
support.
Supporting Information Available: X-ray crystallographic data
for the structures of 1 and 2 in CIF format. This material is available
free of charge at http://pubs.acs.org.
IC049227B
(18) The in situ characterization of species 6 follows. 31P{1H} NMR
(acetone-d6): δ 47.46 (dd, JRhP ) 167, 2JPP ) 49), 52.44 (dd, JRhP
)
2
2
183, JPP ) 49). 1H NMR (acetone-d6): δ 2.90 (d, 1H, JHH ) 12,
2
2
-NH2), 3.16 (d, 1H, JHH ) 12, -NH2), 4.50 (d, 1H, JHH ) 12,
-CH2), 4.75 (d, 1H, 2JHH ) 12, -CH2), 6.23 (d, 2H, 3JHH ) 8, -CH2-
(o-C6H5) or η2-Ph, see text), 7.05-7.65 (m, 33H, arom-H).
(19) Marcazzan, P. Ph.D. Thesis, The University of British Columbia,
Vancouver, Canada, 2002. Becalski, A. G.; Cullen, W. R.; Fryzuk,
M. D.; James, B. R.; Kang, G.-J.; Rettig, S. J. Inorg. Chem. 1991, 30,
5002.
Inorganic Chemistry, Vol. 43, No. 21, 2004 6841