Generation and reactivity of {(ethane-1,2-diyl)-bis[diisopropylphosphine-κP]}-{[2,4,6-tri (tert-butyl)phenyl]phosphino-κP}rhodium ([Rh{PH(1Bu3C6H2)} (iPr2PCH2CH2P

Article abstract of DOI:10.1002/1522-2675(20011017)84:10<2958::AID-HLCA2958>3.0.CO;2-L

The complex [Rh(η³-benzyl)(dippe)] (1; dippe = bis(diisopropylphosphino)ethane = (ethane-1,2-diyl)bis-[diisopropylphosphine]) reacted cleanly with Mes*PH₂ (2; Mes* = 2.4,6-¹Bu₃C₆H₂) to prov

Full text of DOI:10.1002/1522-2675(20011017)84:10<2958::AID-HLCA2958>3.0.CO;2-L

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Helvetica Chimica Acta ± Vol. 84 (2001)
Generation and Reactivity of {(Ethane-1,2-diyl)-
bis[diisopropylphosphine-kP]}-{[2,4,6-tri(tert-butyl)phenyl]phosphino-
kP}rhodium ([Rh{PH(tBu3C6H2)}(iPr2PCH2CH2PiPr2)]):
Catalytic C P Bond Formation via Intramolecular C H/P H
Dehydrogenative Cross-Coupling
by Mark Stradiotto1), Kyle L. Fujdala, and T. Don Tilley*
Department of Chemistry University of California at Berkeley, Berkeley, CA 94720-1460, USA
(phone: (510)642-8939; fax: (510)642-8340; e-mail: tdtilley@socrates.berkeley.edu)
Dedicated to the memory of Professor Luigi M. Venanzi, an exceptional scholar, gentleman, mentor, and friend
The complex [Rh(h3-benzyl)(dippe)] (1; dippe ˆ bis(diisopropylphosphino)ethane ˆ (ethane-1,2-diyl)bis-
[diisopropylphosphine]) reacted cleanly with Mes*PH2 (2; Mes* ˆ 2,4,6-tBu3C6H2) to provide a new Rh species
[Rh(H)(dippe)(L)] (3), L being the 2,3-dihydro-3,3-dimethyl-1H-phosphindole ligand 4 (ˆtBu2C6H2(CMe2CH2PH))
(Scheme 1). Complex 3 was converted to the corresponding chloride [Rh(Cl)(dippe)(L)] (6) when treated with
CH2Cl2, whereas the dimeric species [Rh2{m-tBu2C6H2(CMe2CH2P)}(m-H)(dippe)2] (7) was formed upon
thermolysis in toluene (Scheme 2). The structures of 6 and 7 ´ C7H8 were determined by X-ray crystallography.
Complexes 1 and 3 served as catalyst precursors for the dehydrogenative coupling of C H and P H bonds in
the conversion of 2 to 4 (Scheme 3). Deuteration studies with Mes*PD2 exposed a complex series of bond-
activation pathways that appear to involve C H activation of the dippe ligand by the Rh-atom (Schemes 4
and 5)
Introduction. ± The activation of element-hydrogen bonds by transition-metal
fragments represents a fundamental step in a number of metal-catalyzed trans-
formations [1]. Studies that further our understanding of the way in which main-group
species are transformed within the coordination sphere of metal complexes are,
therefore, of particular relevance since these investigations may uncover novel reaction
pathways, and ultimately lead to new catalytic processes. In this context, activations of
multiple element-hydrogen bonds in a single substrate have attracted considerable
interest, leading to the genesis of dehydrocoupling methods [2].
Recently, we reported the first direct observation of 1,2-shifts (a-eliminations [3])
that convert silyl(transition metal) complexes [M(SiHR2)(L)n] into base-free (silanyl-
idene)hydridometals [M(H)(ˆ SiR2)Ln]. This intriguing intramolecular process was
initially observed for a cationic, three-coordinate silanylplatinum compound, in which a
1,2-hydride migration led to the formation of a more stable, four-coordinate square-
planar complex [4]. Cationic and zwitterionic (silylene)hydridoiridium complexes
possessing either octahedral [5] or three-legged piano-stool [6] geometries have also
been prepared via a-hydride elimination routes. It is noteworthy that in two cases,
1
)
Current address: Dalhousie University, Department of Chemistry, Halifax, Nova Scotia, Canada B3H 4J3
(e-mail: mark.stradiotto@dal.ca).

Helvetica Chimica Acta ± Vol. 84 (2001)
2959
transition-metal complexes with a silanylidene ligand resulted directly from the
sequential activation of two Si H fragments on a single R2SiH2 substrate [5][6].
In attempting to assess the generality of this 1,2-shift process as a route to multiple
bonds between main-group and transition-metal fragments LnMˆERm, neutral, three-
coordinate Group 9 metal complexes bearing reactive main-group substituents
represent important synthetic targets. Particularly appealing are phosphido derivatives
of the type [M(PHR)L2] (L ˆ 2-electron donor; M ˆ Group 9 metal), since a-hydride
elimination from the P-atom could lead to the formation of terminal phosphinidine
complexes [M(H)(ˆ PR)Ln], a hitherto elusive class of molecules2). Herein we re-
port on the reactivity of [Rh(PHMes*)(dippe)] (Mes* ˆ 2,4,6-tri(tert-butyl)phenyl;
dippeˆ bis(diisopropylphosphino)ethaneˆ (ethane-1,2-diyl)bis[diisopropylphosphine])
which is generated in situ by P H bond activation. This intermediate does not lead
to the late metal phosphinidine [Rh(H)(ˆ PMes*)-dippe)], but instead undergoes
intramolecular C H bond activation, leading to the formation of a new P C bond.
This stoichiometric process can be incorporated into a dehydrogenative catalytic
cycle.
Results and Discussion. ± For generation of a three-coordinate phosphidorhodium
complex of the type [Rh(PHR)L2], the reaction of [Rh(h3-benzyl)(dippe)] (1) [8] with
[2,4,6-tri(tert-butyl)phenyl]phosphine (Mes*PH2; 2) [9] was examined. It was thought
that this reaction might proceed via P H oxidative addition to the Rh-atom, followed
by reductive elimination of toluene. This combination of main-group and transition-
metal precursors seemed promising, since the dippe ligand is known to support square-
planar silylene complexes [4], while the Mes* fragment has proven efficient in
kinetically stabilizing metal-phosphorus multiple bonds in early metal phosphinidine
complexes [7].
Treatment of 1 with 1 equiv. of 2 rapidly resulted in the liberation of toluene and
clean formation of a new Rh complex 3 (Scheme 1), which was observed to contain
1
three nonequivalent P-centers and a Rh H fragment by 31P- and H-NMR spectro-
t
scopy. The complexity of the Bu signals, the appearance of new CH2 and PH
resonances in the 1H-NMR spectrum, as well as a low field 31P-NMR shift [7] attributed
to an aryl-substituted phosphine ( 23.9 ppm) suggested that 3 is a complex of the
known fused-ring-system phosphine 5,7-di(tert-butyl)-2,3-dihydro-3,3-dimethyl-1H-
phosphindole (4) [10], and not the desired (phosphinidine)rhodium complex 5. Metal
complexes ligated by 4 and its derivatives are known [11]; for example, Champion and
Cowley [11] reported that treatment of Mes*PˆCˆO with [Fe2(CO)9] leads to the
formation of [Fe(CO)4(4)]. These workers propose that [Fe(CO)4(4)] is generated
from the terminal-phosphinidine ligand of [Fe(CO)4(ˆ PMes*)]. Indeed, it is known
that ꢀMes*Pꢁ itself rearranges to 4 via insertion of the P-atom into one of the C
H
bonds of the ortho-positioned tBu group [10][12]. While it is plausible that 3 is similarly
derived from 5, an alternative mechanistic pathway leading from the inter-
mediate [Rh(PHMes*)(dippe)] to 3, involving C H oxidative addition and P C reduc-
tive elimination steps, is equally viable. No intermediates were observed when the reac-
2
)
While isolable, terminal-phosphinidine complexes of the early metals have been prepared, late-metal
derivatives have been generated only transiently, see [7].

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Helvetica Chimica Acta ± Vol. 84 (2001)
Scheme 1
tion of 1 and 2 was monitored by NMR spectroscopy at 808. Similarly, attempts to trap
transient low-valent species with but-2-yne and diphenylacetylene were unsuccessful.
The hydride 3 reacts with CH2Cl2 within 8 h, producing the corresponding
monomeric chlororhodium complex 6 (Scheme 2) in 89% yield, along with small
amounts of the known complex [RhCl(dippe)]2 [13]. Analogous reactions employing
either CCl4 or CHCl3 also led to 6, along with larger amounts of [RhCl(dippe)]2. The
structure of 6 was determined by X-ray-diffraction techniques (see Fig. 1), which

Helvetica Chimica Acta ± Vol. 84 (2001)
2961
indirectly confirmed the connectivity proposed for 3. Crystallographic data and
selected structural parameters are collected in Tables 1 and 2, respectively. The RhI
center in 6 exhibits a distorted square-planar geometry, with coordination sites
occupied by the dippe, chloro, and cyclic phosphine 4 ligands. Although a statistically
significant progression of Rh P bond lengths (Rh P(1) > Rh P(3) > Rh P(2)) is
observed, these distances fall within the previously observed range for Rh P bonds in
related systems3). The Rh Cl distance in 6 is also identical to those observed in
analogous ꢀ[RhClP3]ꢁ complexes4). The structural attributes of the phosphindole
moiety in 6 mirror those found in related crystallographically characterized species
[11]. The P(1) center is distorted considerably from ideal tetrahedral geometry.
Geometric distortions are also apparent at the aromatic C(18), which possesses angles
ranging from ca. 110 to 1318.
It was recently observed in the reaction of SiH2Mes2 (Mes ˆ 2,4,6-trimethylphenyl)
with [Ir(Cp*)(Me)(PMe3)](OSO2CF3) (Cp* ˆ pentamethylcyclopentadienyl) that a
cyclometallated species is formed as the kinetic product, which in turn isomerizes to the
Scheme 2
3
)
)
For a selection of crystallographically characterized [Rh(dippe)] complexes, see [14].
For a recent selection of crystallographically characterized ꢀ[RhClP3]ꢁ complexes, see [15].
4

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Helvetica Chimica Acta ± Vol. 84 (2001)
Fig. 1. Crystallographically determined structure of 6. Depicted with 50% thermal ellipsoids. Selected H-atoms
are omitted for clarity.
Table 1. Summary of Crystallographic Data
6
7 ´ C7H8
Empirical formula
Formula weight
Temperature
C32H61ClP3Rh
677.08
108(2)8
C53H101P5Rh2
1099.01
124(2)8
Crystal system
monoclinic
monoclinic
Lattice parameters
a ˆ 14.2475(5) Š
b ˆ 13.6514(6) Š
c ˆ 19.0902(4) Š
b ˆ 109.247(2)8
a ˆ 11.9099(7) Š
b ˆ 20.105(1) Š
c ˆ 12.0247(5) Š
b ˆ 90.746(2)8
3
3
Volume
3505.5(2) Š
2879.0(3) Š
Space group
P21/n
P21
Z
Dcalc
m(MoKa)
4
2
1.283 g/cm3
1.268 g/cm3
1
1
0.719 mm
0.743 mm
F000
1440
1168
q-range for data collection [8]
Reflections collected
Independent reflections
R(int)
1.87 to 25.60
15355
5880
1.69 to 25.60
12951
7308
0.0764
0.0545
Data/restraints/parameters
Goodness-of-fit on F2
R1 (I > 2.00s)
wR2 (I > 2.00s)
R1 (all data)
5735/0/337
0.702
0.0379
0.0461
0.1130
7200/1/551
0.967
0.0558
0.1162
0.1063
wR2 (all data)
Tmin, Tmax
Max peak in final diff. map
Min peak in final diff. map
0.0556
0.847, 0.962
0.479 e /Š
0.437 e /Š
0.1297
0.862, 0.939
0.735 e /Š
0.743 e /Š
3
3
3
3

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Table 2. Selected Bond Lengths [Š] and Angles [8] for 6 and 7 ´ C7H8
7 ´ C7H8
6
Bond distances:
Rh P(1)
Rh P(2)
Rh P(3)
Rh Cl
P(1) C(1)
P(1) C(18)
C(1) C(4)
C(5) C(18)
C(13) C(18)
2.323(1)
2.191(1)
2.261(1)
2.405(1)
1.839(4)
1.840(4)
1.522(5)
1.400(5)
1.420(5)
Rh Rh
3.157(1)
2.338(3)
2.209(3)
2.252(3)
2.342(3)
2.182(3)
2.262(3)
1.89(1)
Rh(1) P(1)
Rh(1) P(2)
Rh(1) P(3)
Rh(2) P(1)
Rh(2) P(4)
Rh(2) P(5)
P(1) C(1)
P(1) C(18)
1.92(1)
Bond angles:
P(1) Rh Cl
P(2) Rh Cl
P(3) Rh Cl
85.96(4)
172.53(4)
89.54(4)
97.87(5)
175.15(5)
86.41(4)
110.4(2)
125.6(2)
91.8(2)
P(1) Rh(1) P(2)
P(2) Rh(1) P(3)
P(1) Rh(1) P(3)
P(1) Rh(2) P(4)
P(1) Rh(2) P(5)
P(4) Rh(2) P(5)
C(1) P(1) Rh(1)
C(1) P(1) Rh(2)
C(1) P(1) C(18)
C(18) P(1) Rh(1)
C(18) P(1) Rh(2)
Rh(1) P(1) Rh(2)
105.1(1)
84.5(1)
169.2(1)
104.5(1)
168.8(1)
85.8(1)
118.1(4)
119.8(4)
89.9(5)
P(1) Rh P(2)
P(1) Rh P(3)
P(2) Rh P(3)
Rh P(1) C(1)
Rh P(1) C(18)
C(1) P(1) C(18)
P(1) C(18) C(5)
P(1) C(18) C(13)
C(5) C(18) C(13)
109.9(3)
131.0(3)
119.1(4)
123.8(3)
124.1(3)
84.8(1)
thermodynamic (silylene)iridium complex [6]. In an attempt to effect a similar
conversion of 3 to 5, a sample of the former was taken up in (D8)toluene and monitored
by NMR spectroscopy. Within 96 h at room temperature, slow decomposition of 3 to a
complex mixture of products was observed. However, heating solutions of 3 at 808 for
72 h resulted in the clean production of 0.5 equiv. each of the binuclear complex 7 and
the free phosphindole 4, along with varying amounts of H2. Consistent with the
structural formulation given in Scheme 2, compound 7 exhibits two 31P-NMR
resonances (85.8 and 90.1 ppm) attributed to the dippe ligand and a third resonance
(113.3 ppm) due to the bridging phosphido moiety. Features of the 1H-NMR spectrum
of 7 (including a rather complex m at 7.80 ppm) are also consistent with the proposed
structure. The solid-state structure of 7 (crystallized as the toluene solvate) was
determined by X-ray-diffraction techniques (see Fig. 2). Crystallographic data and
selected structural parameters are collected in Tables 1 and 2, respectively. Compound
7 is comprised of two edge-sharing distorted square planes bridged by phosphido and
hydrido ligands, and hinged at an angle of ca. 318 (least-squares planes defined by
Rh(1), P(1), P(2), P(3), H(1) and Rh(2), P(1), P(4), P(5), H(1)). The metal-metal
separation in 7 (3.157(1) Š) nears the limit commonly accepted for appreciable metal-
metal bonding (< 3.2 Š) [16], but the relatively low-field 31P-NMR chemical shift of
the phosphido ligand suggests no significant Rh Rh interaction [17]. The structure of
7 can be compared with the only other crystallographically characterized bi-
nuclear rhodium complex bridged exclusively by phosphido and hydrido ligands,
[Rh2(m-tBu2P)(m-H)(tBu2PH)2(CO)2], which is formulated as having a Rh Rh bond

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Fig. 2. Crystallographically determined structure of 7 ´ C7H8. Depicted with 30% thermal ellipsoids. The toluene
solvate, isopropyl Me groups, and selected H-atoms are omitted for clarity. Only the major components of the
disordered Rh2 and tert-butyl fragments are shown.
(2.906(2) Š) order of approximately one [18]. The Rh P bridging distances in this
latter complex (2.272(4) and 2.278(4) Š) are significantly shorter than those found in 7
(2.338(3) and 2.342(3) Š). As in 6, the P-center in the bridging phosphido moiety of 7
resides in a severely distorted tetrahedral environment.
Liberation of the cyclic phosphine 4 in the transformation 3 ! 7 suggested the
possibility that Mes*PH2 (2) may be catalytically cyclized to 4 in the presence of a RhI
compound. Indeed, complexes 1 and 3 function equally well as catalyst precursors for
the conversion of 2 to 4, which overall corresponds to the catalytic didehydro coupling
of alkyl C H and P H bonds to yield a new P C linkage (Scheme 3). In preliminary
experiments, ca. 10 mol-% of the Rh-catalyst precursor was employed for the
conversion of 60 mg of 2 in C6D6 (ca. 0.1m), and the progress of the reaction was
monitored by NMR spectroscopy. Although ca. 2 h were required to attain only three
turnover cycles under ambient conditions, the catalysis was found to proceed with

Helvetica Chimica Acta ± Vol. 84 (2001)
2965
Scheme 3
extremely high efficiency; only 2 and 4 were observed throughout, and after 72 h, ca.
90% conversion was attained. Upon completion of a catalytic run, the introduction of
additional substrate 2 led to continued catalysis, albeit with reduced activity. The crucial
role of the Rh-atom in this catalytic transformation was verified by the complete lack of
reactivity found when solutions of 2 were treated with dippe alone. Glueck and co-
workers [19] have examined related transformations in the Rh-catalyzed isomerization
of phosphacumulenes. Currently, there is considerable interest in the development of
new methods for the formation of P C bonds (for examples, see [20]), and routes
based on the dehydrocoupling of C H and P H bonds could be highly useful.
In an attempt to gain mechanistic insight into the aforementioned stoichiometric
and catalytic transformations, the reaction of 1 with Mes*PD2 in C6D6 was monitored
by NMR spectroscopy. Surprisingly, the stoichiometric reaction between 1 and
Mes*PD2 led to the formation of a product D1-3 that exhibited slightly broadened
1
isopropyl Me resonances in the H-NMR spectrum, and no detectable amount of D
incorporated at either P or Rh (Scheme 4). Deuteration of the dippe ligand was even
1
more prominent in the reaction of 1 with 5.0 equiv. of Mes*Pd2. H-NMR Data
acquired after 30 min indicated that substantial D-incorporation into the isopropyl Me
groups, along with partial deuteration of P and Rh, had occurred to give the Rh
complex Dn-3. The 1H- and 31P-NMR spectra of the reaction mixture also revealed the
presence of Mes*PD2, Mes*PDH, Mes*PH2 (2), the phosphindole 4, its deuterated
analogue D1-4, and small amounts of an unidentified species (d (31P) ˆ 24.3). After
an additional 8 h at room temperature, the D-containing free phosphines Mes*PD2,
Mes*PDH, and D1-4 were consumed. Finally, after a total reaction time of ca. 21 h, only
Dn-3, 4, and the unidentified impurity were detected, in keeping with the catalytic
dehydrogenation process depicted in Scheme 3. Throughout, neither deuteration of the
tBu groups nor productive activation of C6D6 was detected. The nearly exclusive
inclusion of D into the isopropyl Me groups of the dippe ligand was confirmed by the
2H-NMR data acquired upon completion of the reaction.
The facile Rh-mediated H/D exchange of D from Mes*PD2 at the C H units of the
isopropyl Me groups of the dippe ligand reveals the operation of a complex series of
reaction equilibria in this system. One simplified mechanistic rationale for the observed

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Helvetica Chimica Acta ± Vol. 84 (2001)
Scheme 4
i) 1.0 Mes*PD2, 10 min. ii) 5.0 Mes*PD2, 30 min.
D-scrambling is presented in Scheme 5. Treatment of 1 with Mes*PD2 presumably leads
to the deuterated intermediate [Rh(PDMes*)(dippe)], along with 1 equiv. of
(D1)toluene. Subsequent insertion into an isopropyl Me C H bond5), followed by
reductive elimination of P H could lead to the strained intermediate 86). Reaction of
this Rh-complex with the coordinated Mes*PDH fragment via P D oxidative
addition, followed by C D reductive elimination, Rh-insertion into a new isopropyl
C
H bond, and P H reductive elimination would generate Mes*PH2 (2) and a more
highly deuterated version of 8. The observed formation of Mes*PH2 from Mes*PD2 by
NMR spectroscopy (vide supra) suggests that such a P D/C H exchange process is
somewhat fast relative to the Rh-catalyzed P C bond-formation process depicted in
5
)
)
A related metallation process involving a PCP ꢀpincerꢁ complex of Rh has been observed [21].
A neutral three-coordinate alkylrhodium(I) complex has recently been reported [22].
6

Helvetica Chimica Acta ± Vol. 84 (2001)
2967
Scheme 5
Scheme 3. Dehydrogenative cyclization could then convert mixtures of Mes*PD2,
Mes*PDH, and Mes*PH2 (2), into the phosphindole 4 and its deuterated analogue D1-
4. Subsequent P D bond activation chemistry transforms D1-4 into 4. Alternatively, 8
could take up 1 equiv. of Mes*PD2, ultimately leading to deuteration of the P H and
Rh H groups in Dn-3. Whereas bond-activation pathways leading to D-incorporation
t
at the C H bonds of the ortho-positioned Bu group are also readily envisioned, the
2
1H- and H-NMR spectroscopic data suggest that such processes are not important.
In summary, the reactive intermediate [Rh(PHMes*)(dippe)], does not lead to an
isolable phosphinidine complex, but instead undergoes intramolecular C H bond
activation to afford the new hydridorhodium complex 3. This hydrido complex in turn
reacts with chlorinated solvents to yield 6 and, upon thermolysis, is converted to the
binuclear species 7. Complex 3 also serves as a catalyst precursor for the intramolecular
dehydrogenative coupling of P H and alkyl C H bonds in 2, leading to the
phosphindole 4. This latter transformation is of interest, as it corresponds to the
activation and coupling of two simple element-hydrogen bonds in a dehydrogenative
cross-coupling. Deuteration studies with Mes*PD2 revealed a complex series of
interconnected reaction manifolds that likely involve a dippe-metallated intermediate.
Future investigations will focus on exploring the generality and utility of Rh-catalyzed
C
H/P H dehydrogenative coupling, and on the synthesis of phosphinidine
complexes via a-migration processes.
Experimental Part
General. All manipulations were performed under N2 by means of Schlenk techniques or in a glove box.
Dry, O2-free solvents were employed throughout. Toluene was distilled from Na, and pentane from Na
benzophenone. (D6)Benzene and (D8)toluene were distilled from Na/K alloy, and CH2Cl2 and CD2Cl2 were

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Helvetica Chimica Acta ± Vol. 84 (2001)
dried over CaH2 and distilled prior to use. The compounds [Rh(h3-benzyl)(dippe)] [8] and Mes*PH2 (2) [9]
were prepared according to the literature, while LiAlD4 (Aldrich) was used as received. IR Spectra: Mattson
Infinity-60-MI-FTIR spectrometer; KBr pellets; in cm 1. NMR Spectra: at 500 (1H), 125 (13C{1H}), or 202 MHz
(
31P{1H}) and r.t., unless otherwise noted; Bruker DRX-500 spectrometer; chemical shifts d in ppm downfield of
SiMe4 (1H and 13C) or 85% H3PO4 (31P); J in Hz. Elemental analyses were performed by the Micro-Mass Facility
in the College of Chemistry at the University of California, Berkeley.
[5,7-Di(tert-butyl)-2,3-dihydro-3,3-dimethyl-1H-phosphindole-kP]{(ethane-1,2-diyl)bis[diisopropylphos-
phine-kP]}hydrorhodium (3). To a soln. of [Rh(h3-benzyl)(dippe)] (0.138 g, 0.303 mmol) in pentane (5 ml) was
added a soln. of Mes*PH2 (0.084 g, 0.303 mmol) in pentane (3 ml). After stirring the resulting deep red soln. at
r.t. for 30 min, the mixture was filtered through Celite ꢂ and stored at 308 for 24 h, producing 3 (0.169 g, 87%).
1
Anal. pure yellow powder. IR: 2226s (PH), 1767s (RhH). H-NMR ((D6)benzene, 258): 7.51 (m, 1 arom. H);
7.18 (m, 1 arom. H); 6.23 (dm, 1J(H,P) ˆ 272.5, PH); 2.48 (m, PHCH2CMe2); 2.02 (m, 2 H, Me2CHP); 1.88
(m, 2 H, Me2CHP); 1.80 (s, 1 tBu); 1.46 (s, 3 H, PHCH2CMe2); 1.29 (s, 1 tBu); 1.27 (s, 3 H, PHCH2CMe2); 1.23 ±
0.93 (m, 28 H, Me2CHP, PCH2CH2P); 4.61 (d, dꢀtꢁ, 1J(H,Rh) ˆ 112.3, 2J(H,Ptrans) ˆ 31.4, 2J(H,Pcis) ˆ 19.5,
RhH). 13C{1H}-NMR ((D6)benzene, 258): 156.8 (d, 2J(C,P) ˆ 9.7, arom. C); 152.8 (d, 2J(C,P) ˆ 9.7, arom. C);
152.3 (d, 4J(C,P) ˆ 1.3, arom. C); 134.8 (d, 1J(C,P) ˆ 32.1, arom. C); 122.7 (d, 3J(C,P) ˆ 7.5, arom. CH); 118.6
(d, 3J(C,P) ˆ 7.5, arom. CH); 45.3 (m, PHCH2CMe2); 42.7 (d, 1J(C,P) ˆ 27.9, PHCH2CMe2); 37.5 (s, Me3C); 35.4
(s, Me3C); 33.3 (d, 4J(C,P) ˆ 5.1, Me3C C(7)); 32.0 (s, Me3C C(5)); 30.8 (d, 4J(C,P) ˆ 5.3, PHCH2CMe2); 30.2
(s, PHCH2CMe2); 28.4 ± 26.6 (m, Me2CHP); 24.0 ± 23.6 (m, PCH2CH2P); 21.2 (m, Me2CHP); 20.9
(m, Me2CHP); 20.6 (m, Me2CHP); 20.4 (m, Me2CHP); 19.8 (m, Me2CHP); 19.7 (m, Me2CHP); 19.5
(m, Me2CHP); 19.1 (m, Me2CHP). 31P{1H}-NMR ((D6)benzene, 258): 102.9 (ddd, 2J(P,Ptrans) ˆ 318.7,
1J(P,Rh) ˆ 159.4, 2J(P,Pcis) ˆ 21.2, PCH2CH2P cis to H); 83.6 (ddd, 1J(P,Rh) ˆ 130.6, 2J(P,Pcis) ˆ 28.0,
1
2J(P,Pcis) ˆ 21.2, PCH2CH2P trans to H); 23.9 (ddd, 2J(P,Ptrans) ˆ 318.7, J(P,Rh) ˆ 149.2, 2J(P,Pcis) ˆ 28.0,
PH). Anal. calc. for C32H62P3Rh: C 59.81, H 9.72; found: C 60.06, H 9.83.
Chloro[5,7-di(tert-butyl)-2,3-dihydro-3,3-dimethyl-1H-phosphindole-kP]{(ethane-1,2-diyl)bis[diisopropyl-
phosphine-kP]}rhodium (6). To 3 (0.079 g, 0.123 mmol) was added CH2Cl2 (5 ml), followed by stirring for 8 h.
Subsequently, the mixture was evaporated and the remaining yellow residue extracted with pentane (2 Â 4 ml).
The extracts were then concentrated to ca. 3 ml and cooled to 308, producing 6 (0.074 g, 89%). Yellow prisms.
IR: 2282s (PH). 1H-NMR ((D6)benzene, 258) 7.54 (m, 1 arom. H); 7.18 (m, 1 arom. H); 5.76 (dm, 1J(H,P) ˆ
283.0, PH); 3.14 (m, 1 H, Me2CHP); 2.65 (m, 1 H, Me2CHP); 2.22 (m, 1 H, Me2CHP); 1.92 (m, 3 H, Me2CHP);
1.85 (s, 1 tBu); 1.58 (s, 3 H, PHCH2CMe2); 1.38 (m, 6 H, Me2CHP); 1.23 (s, 1 tBu); 1.20 (s, 3 H, PHCH2CMe2);
1.19 ± 0.81 (m, 22 H, Me2CHP, PCH2CH2P). 13C{1H}-NMR ((D6)benzene, 258); 158.9 (m, arom. C); 152.6
(m, arom. C); 152.5 (m, arom. C); 127.9 (m, arom. C); 122.6 (d, 3J(C,P) ˆ 8.3, arom. CH); 117.9 (d, 3J(C,P) ˆ
7.4, arom. CH); 45.0 (m, PHCH2CMe2); 39.1 (d, 1J(C,P) ˆ 26.8, Hz, PHCH2CMe2); 37.3 (s, Me3C); 35.0
(s, Me3C); 33.2 (d, 4J(C,P) ˆ 3.8, Me3C C(7)); 32.1 (s, Me3C C(5)); 31.1 (s, PHCH2CMe2); 30.9 (d, 4J(C,P) ˆ
6.7, PHCH2CMe2); 29.2 (m, Me2CHP); 27.1 ± 26.6 (m, Me2CHP); 25.2 ± 24.7 (m, PCH2CH2P); 24.2 ± 17.5
2
2
(m, Me2CHP). 31P{1H}-NMR ((D6)benzene, 258): 92.3 (ddd, 1J(P,Rh) ˆ 180.8, J(P,Pcis) ˆ 33.6, J(P,Pcis) ˆ 27.0,
PCH2CH2P trans to Cl); 90.6 (ddd, 2J(P,Ptrans) ˆ 363.0, J(P,Rh) ˆ 147.1, J(P,Pcis) ˆ 27.0, PCH2CH2P cis to Cl);
25.0 (ddd, 2J(P,Ptrans) ˆ 363.0, 1J(P,Rh) ˆ 126.8, 2J(P,Pcis) ˆ 33.6, PH). Anal. calc. for C32H61ClP3Rh: C 56.76,
H 9.08; found: C 56.61, H 9.26.
1
2
A crystalline sample (0.14 Â 0.14 Â 0.09 mm) of 6 generated by this methodology proved suitable for single-
crystal X-ray diffraction analysis.
{m-[5,7-Di(tert-butyl)-2,3-dihydro-3,3-dimethyl-1H-phosphindole-k2P]}bis{(ethane-1,2-diyl)bis[diisopropyl-
phosphine-kP]}(m-hydro)dirhodium (7). A reaction vessel equipped with a PTFE valve was charged with a soln.
of 3 (0.116 g, 0.180 mmol) in toluene (5 ml) and stored at 808 for 72 h. Upon cooling to r.t., the mixture was
concentrated to ca. 3 ml, filtered through Celiteꢀ, and stored at 308 for 48 h, producing orange-red crystals of
7 ´ C7H8 (0.088 g, 89%). Anal. pure samples of 7 were obtained free of solvent by recrystallization of 7 ´ C7H8
from pentane. 1H-NMR ((D6)benzene, 258): 7.41 (m, 1 arom. H); 7.18 (m, 1 arom. H); 2.70 (m, PCH2CMe2);
2.44 (m, 4 H, Me2CHP); 2.17 (m, 2 H, Me2CHP); 1.91 (m, 2 H, Me2CHP); 1.70 (s, 6 H, PCH2CMe2); 1.55
(s, 1 tBu); 1.43 (m, 9 H, Me2CHP); 1.35 (s, 1 tBu); 1.16 ± 1.12 (m, 29 H, Me2CHP, PCH2CH2P); 1.03 (m, 6 H,
Me2CHP); 0.92 (m, 6 H, Me2CHP); 0.74 (m, 6 H, Me2CHP); 7.80 (m, RhH). 13C{1H}-NMR ((D6)benzene,
258): 154.5 (m, arom. C); 150.9 (d, 2J(C,P) ˆ 7.5, arom. C); 148.6 (m, arom. C); 144.2 (m, arom. C); 122.9
(d, 3J(C,P) ˆ 7.0, arom. CH); 117.7 (d, 3J(C,P) ˆ 6.8, arom. CH); 44.4 (d, 2J(C,P) ˆ 4.9, Hz, PCH2CMe2); 41.5
(m, PCH2CMe2); 36.0 (s, Me3C); 34.9 (s, PCH2CMe2); 34.8 (s, Me3C); 34.6 (d, 4J(C,P) ˆ 4.2, Me3C C(7)); 31.6
(s, Me3C C(5)); 29.4 (m, Me2CHP); 29.1 (m, Me2CHP); 28.3 (m, Me2CHP); 25.3 (m, Me2CHP); 23.8
(m, PCH2CH2P); 23.2 (m, Me2CHP); 22.4 (m, Me2CHP); 22.0 (m, Me2CHP); 20.9 (m, Me2CHP); 20.0

Helvetica Chimica Acta ± Vol. 84 (2001)
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(m, Me2CHP); 19.7 (m, PCH2CH2P); 19.0 (m, Me2CHP); 18.0 (m, Me2CHP); 17.0 (m, Me2CHP). 31P{1H}-NMR
((D6)benzene, 258): 113.3 (m, RhPRh); 90.1 (m, PCH2CH2P cis to H); 85.8 (m, PCH2CH2P trans to H). Anal.
calc. for C46H93P5Rh2: C 54.87, H 9.31; found: C 54.68, H 9.40.
A crystalline sample (0.15 Â 0.13 Â 0.12 mm) of 7 ´ C7H8 proved suitable for single-crystal X-ray diffraction
analysis.
[2,4,6-Tri(tert-butyl)phenyl](D2)phosphine Mes*PD2. This compound was prepared as described for
Mes*PH2 (2) [9], with the exception that LiAlD4 (98 atom-%) was employed, and quenching of the reaction was
carried out with D2O in place of a 20% HCl soln. The resulting product was isolated as a ca. 85 :15 mixture of
Mes*PHD and Mes*PD2. 31P{1H}-NMR ((D6)benzene, 258): 131.5 (t, 1J(P,D) ˆ 32.4, Mes*PHD); 132.6
(quint., 1J(P,D) ˆ 32.4, Mes*PD2).
X-Ray Crystallography7). Single-crystal X-ray-diffraction data for 6 and 7 ´ C7H8 were collected from
samples mounted on a quartz fiber with Paratone N hydrocarbon oil. Data collection was carried out by means
of graphite-monochromated MoKa (l 0.71069 Š) radiation with a Siemens SMART diffractometer, equipped
with a CCD area detector. The preliminary orientation matrix and unit-cell parameters were determined by
collecting 60 10-s frames, followed by spot integration and least-squares refinement. A hemisphere of data was
collected with w scans of 0.38, counted for a total of 20 s per frame. Frame data were integrated (XY spot
spread ˆ 1.608; Z spot spread ˆ 0.608) and corrected for Lorentz and polarization effects with the program
SAINT [23]. The program SADABS [24] was utilized for the scaling of diffraction data and the application of an
empirical absorption correction based on redundant reflections. The structures were solved by direct methods
procedure in the Siemens SHELXTL [25] program library, and refinement was carried out by the full-matrix
least-squares method on F2. Apart from the exceptions noted below, anisotropic thermal parameters were used
for the non-H-atoms, and all C-bonded H-atoms were added at calculated positions and refined by means of a
riding model with isotropic displacement parameters equal to 1.2 (1.5 for Me groups) times the equivalent
isotropic displacement parameter of the attached C-atom. The H-atom bound to the P-atom in 6 was located in
the difference map and refined with a thermal parameter equal to 1.2 times the equivalent isotropic
displacement parameter of the attached P-atom. During the refinement of 7 ´ C7H8, alternative Rh-positions
(Rh(1A) and Rh(2A), offset along the Rh(1) Rh(2) vector) were identified and refined isotropically with a
fixed thermal parameter. The occupancy of the two Rh2 pairs was refined as a free variable (ca. 94 :6). No other
atomic positions associated with this minor disorder component were located. Although the heavy-atom core in
i
t
7 ´ C7H8 refined cleanly, significant disorder in the some of the Pr and Bu groups was encountered, and, thus,
C(16), C(15A), C(16A), C(17A), C(27), C(27A), C(28), C(28A), C(30), and C(30A) were refined
isotropically. The occupancy of two orientations of the tBu Me groups (C(15), C(16), C(17); C(15A), C(16A),
i
C(17A)) was refined as a free variable (ca. 67:33), whereas the disordered Pr C-atom positions (C(27),
C(27A); C(28), C(28A); C(30), C(30A)) were each fixed at 50% occupancy. H-Atoms were not added at
calculated positions for C(15A), C(16A), C(17A), C(27A), C(28A), and C(30A). During the refinement of 7 ´
C7H8, an electron-density peak located in a reasonable position between Rh(1) and Rh(2) was assigned as the
hydro ligand (H(1)) and not refined. No unusually close intermolecular contacts between the target molecule 7
and the toluene solvate were present. The final refined value of the absolute structure parameter ( 0.02(5))
confirmed the configuration chosen.
Acknowledgement is made to the National Science Foundation of its generous support of this work. M. S.
thanks the Natural Sciences and Engineering Research Council of Canada for financial support in the form of an
NSERC of Canada Postdoctoral Fellowship.
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)
Crystallographic data (excluding structure factors) for the structures reported in this paper have been
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CCDC-162113 (7 ´ C7H8). Copies of the data can be obtained, free of charge, on application to the CCDC,
12 Union Road, Cambridge CB2 1EZ UK (fax: ‡ 44 (1223) 336 033; e-mail: deposit@ccdc.cam.ac.uk).

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Received May 3, 2001