Synthesis and structure of indenyl rhodium(I) complexes containing unsaturated phosphines: Catalyst precursors for alkene hydroboration

Article abstract of DOI:10.1039/b812259h

The indenyl compound (η⁵-C₉H₇)Rh(coe) ₂ (1, coe = cis-cyclooctene) has been prepared as a thermally stable alternative to the diethylene derivative (η⁵-C₉H ₇)Rh(η²-H₂CCH₂)₂. Compound 1 reacts with unsaturated phosphines Ph₂PR (R = CHCH ₂, 2; CH₂CHCH₂, 3; and CC-tert-Bu, 4) to give complexes of the type (η⁵-C₉H₇)Rh(Ph ₂PR)₂, where bonding occurs through the phosphorus atom. Addition of Ph₂PCCPPh₂ to 1 gave the dimer [(η⁵-C₉H₇)Rh(μ-Ph₂PCCPPh ₂)]₂ (5). Solution and solid state data showed that these new phosphine complexes have only a moderate amount of distortion within the indenyl ring. These compounds were found to catalyse the hydroboration of vinylarenes and the first example of an internal hydroboration of diphenylvinylphosphine has been reported. The Royal Society of Chemistry 2009.

Full text of DOI:10.1039/b812259h

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PAPER
www.rsc.org/dalton | Dalton Transactions
Synthesis and structure of indenyl rhodium(I) complexes containing
unsaturated phosphines: catalyst precursors for alkene hydroboration†
Christian N. Garon,a Daniel I. McIsaac,a Christopher M. Vogels,a Andreas Decken,b Ian D. Williams,c
Christian Kleeberg,d Todd B. Marder*d and Stephen A. Westcott*a
Received 17th July 2008, Accepted 12th November 2008
First published as an Advance Article on the web 20th January 2009
DOI: 10.1039/b812259h
5
The indenyl compound (h -C9H7)Rh(coe)2 (1, coe = cis-cyclooctene) has been prepared as a thermally
5
2
=
stable alternative to the diethylene derivative (h -C9H7)Rh(h -H2C CH2)2. Compound 1 reacts with
=
=
∫
unsaturated phosphines Ph2PR (R = CH CH2, 2; CH2CH CH2, 3; and C C-tert-Bu, 4) to give
5
complexes of the type (h -C9H7)Rh(Ph2PR)2, where bonding occurs through the phosphorus atom.
5
∫
∫
Addition of Ph2PC CPPh2 to 1 gave the dimer [(h -C9H7)Rh(m-Ph2PC CPPh2)]2 (5). Solution and solid
state data showed that these new phosphine complexes have only a moderate amount of distortion
within the indenyl ring. These compounds were found to catalyse the hydroboration of vinylarenes and
the first example of an internal hydroboration of diphenylvinylphosphine has been reported.
Introduction
There has been considerable interest in the use of late metal
indenyl complexes arising from their enhanced catalytic activities,
as compared to their cyclopentadienyl analogues, for a number
of important organic reactions.1 This enhanced reactivity has
been termed the ‘indenyl effect’ and it is known to occur in both
associative (SN2) and dissociative (SN1) reaction pathways.2 A low
5
3
energy barrier associated with an h →h ring slippage (Fig. 1) is
commonly attributed to the associative reaction pathway, where
the metal centre avoids an unfavourable 20-electron transition
5
state. Interestingly, DFT calculations on [(h -C9H7)MoL2(CO)2]+
Fig. 1 Two of the possible bonding modes in indenyl metal complexes
with numbering scheme for the indenyl ring.
(L = NCR, CNR) show that the indenyl ring starts to slip when
the incoming ligand is approaching the metal centre at a distance
of ca. 400 pm.2c This haptotropic rearrangement has also been
rationalized via a ground state effect where three of the five
metal carbon bonds are shorter than the other two to give a
distinct h :h -indenyl bonding mode.3 Recent results by Chirik
and co-workers have shown that the indenyl ring can even bind
to transition metals through all of the carbon atoms as shown in
complexes of the type (h -C9H5-1,3-R2)(h -C9H5-1,3-R2)Zr (R =
SiMe3, CHMe2).4 A significant amount of research has therefore
focussed on examining the structure and bonding in indenyl metal
complexes. As part of our ongoing investigation in this area5
rhodium complexes containing unsaturated phosphines and their
ability to catalyse the hydroboration of vinylarenes.
Results and discussion
3
2
5
2
=
Although (h -C9H7)Rh(h -H2C CH2)2 is frequently used as a
starting material in ligand substitution reactions owing to the
labile ethylene groups, we have prepared the thermally stable
9
5
5
analogue (h -C9H7)Rh(coe)2 (1, coe = cis-cyclooctene) as an alter-
native to this ethylene precursor. Complex 1 was prepared by the
room temperature addition of lithium indenide to [RhCl(coe)2]2 in
66% yield. The 1H NMR spectrum of 1 shows a distinctive quartet
for the indenyl H(2) peak at d 6.01 ppm with coupling to H(1,3)
5
we have prepared a number of (h -C9H7)RhL2 complexes and
3
2
investigated the role the ancillary ligands play in this h :h -indenyl
bonding mode.6 We report herein on the synthesis of indenyl
3
and the rhodium metal of JHH = JRhH = 2.2 Hz. The degree
of distortion of the indenyl ring in solution has been measured
previously by 13C{ H} NMR spectroscopy.2d,5,7 The 13C{ H} NMR
1
1
aDepartment of Chemistry, Mount Allison University, Sackville, NB E4L
1G8, Canada. E-mail: swestcott@mta.ca; Fax: +1 506 364-2313; Tel: +1
506 364 2372
5
data suggest a small distortion away from the h bonding mode,
as evidenced by the chemical shift of the ring junction carbons
bDepartment of Chemistry, University of New Brunswick, Fredericton, NB
E3B 5A3, Canada
C(3a,7a) of 114.5 ppm. For comparison, the analogous ethylene
5
2
cDepartment of Chemistry, Hong Kong University of Science and Technology,
Clear Water Bay, Kowloon, Hong Kong
=
complex (h -C9H7)Rh(h -H2C CH2)2 has a chemical shift of
112.2 ppm.8 Complex 1 has also been characterized by single
crystal X-ray diffraction; the molecular structure, selected bond
distances and angles, are given in Fig. 2. Details of the data
collection, structure solution and refinement are presented in
Table 1.
dDepartment of Chemistry, Durham University, South Road, Durham, UK
DH1 3LE. E-mail: todd.marder@durham.ac.uk; Fax: +44 191 384 4737;
Tel: +44 191 334 2037
† CCDC reference numbers 686222–686224 and 708194. For crystallo-
graphic data in CIF or other electronic format see DOI: 10.1039/b812259h
1624 | Dalton Trans., 2009, 1624–1631
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Table 1 Crystallographic data collection parameters for 1, 2, 4 and 5
Complex
1
2
4
5
Chemical formula
Formula mass
Crystal dimensions (mm3)
Crystal system
Space group
C25H35Rh
438.44
0.60 ¥ 0.225 ¥ 0.175
Orthorhombic
P212121
4
7.3306(6)
13.4620(12)
20.7134(19)
90
90
90
2044.1(3)
1.425
173(1)
C37H33P2Rh
642.48
C45H45P2Rh
750.66
0.40 ¥ 0.275 ¥ 0.20
Triclinic
P-1
2
11.0600(6)
11.8418(7)
17.1608(10)
108.854(1)
92.464(1)
112.489(1)
1929.21(19)
1.292
C70H54P4Rh2
1224.83
0.15 ¥ 0.12 ¥ 0.05
Triclinic
P-1
2
11.6644(2)
13.4814(2)
19.1415(3)
102.0975(5)
92.9700(6)
106.4690(5)
2802.52(8)
1.451
120(2)
MoKa (0.71073 A)
0.746
43145
0.40 ¥ 0.35 ¥ 0.025
Monoclinic
P21/c
Z
a (A)
b (A)
4
˚
˚
˚
17.385(4)
10.162(2)
17.492(4)
90
103.055(4)
90
3010.4(12)
1.418
173(1)
c (A)
a (◦)
b (◦)
g (◦)
3
˚
Volume (A )
Dcalcd (Mg m-3)
T (K)
198(1)
˚
˚
˚
˚
Radiation
MoKa (l = 0.71073 A)
MoKa (l = 0.71073 A)
MoKa (l = 0.71073 A)
m (mm-1)
0.841
0.698
0.555
Total reflections collected
Total unique reflections
No. of variables
q (◦)
14137
4575
235
1.80–27.49
1.038
0.0240
0.0195
0.0497
0.795, -0.275
19545
6710
361
1.20–27.50
1.098
0.0580
0.0477
0.1374
1.514, -1.284
13395
8406
439
1.94–27.50
1.091
0.0174
0.0332
0.0922
1.473, -0.463
12873
685
1.10–27.50
1.021
0.0337
0.0297
0.0757
1.261, -0.654
GoF on F2
Rint
R1[I > 2s(I)]a
wR2 (all data)b
-3
˚
Largest diff peak and hole (A )
ꢀ
ꢀ
ꢀ
ꢀ
a R1 = ꢀFo| - |Fcꢀ/ |Fo|. b wR2 = ( [w(Fo - Fc2)2]/ [Fo4])1/2, where w = 1/[s (Fo2) + (0.0306P)2 + (0.3037P)] (1), 1/[s (Fo2) + (0.0447P)2 +
2
2
2
(8.3225P)] (2), 1/[s (Fo2) + (0.059P)2 + (0.2619P)] (4) and w = 1/[s (Fo2) + (0.0349P)2 + (2.0246P)] (5), where P = (max (Fo2, 0) + 2Fc2)/3.
2
2
still bonding between the rhodium and ring junction carbons C3a
and C1a, as required to attain an 18 electron configuration at the
˚
metal. The value of this slip-distortion is D = 0.180(2) A, where
D = d(average Rh–C3a,1a) - d(average Rh–C1,3). The fold angle (FA)
of 9.11(8)◦ is the angle between planes defined by C(1), C(2), C(3)
and C(7a), C(7), C(6), C(5), C(4), C(3a), and this also indicates a
small distortion towards the allylic bonding mode.
The coordination chemistry of phosphines bearing alkenyl
or alkynyl substituents is an area of considerable interest, ow-
ing to the use of these ligands in the structural architecture
of multinuclear species.10,11 We therefore decided to examine
the reactivity of 1 with such phosphines.6l,m Addition of two
=
equivalents of diphenylvinylphosphine (Ph2PCH CH2) to 1 gave
Fig. 2 Perspective view of molecule of 1 with atom labelling scheme.
5
=
Thermal ellipsoids are drawn at 50% probability level with hydrog◦en
(h -C9H7)Rh(Ph2PCH CH2)2 (2) in moderate yield (Scheme 1).
˚
atoms omitted for clarity. Selected bond distances (A) and angles ( ):
Compound 2 has been characterized by a number of physical
methods including multinuclear NMR spectroscopy. The 31P{ H}
1
Rh–C(9) 2.1495(19), Rh–C(16) 2.1513(19), Rh–C(8) 2.1520(19), Rh–C(17)
2.1659(19), Rh–C(1) 2.230(2), Rh–C(3) 2.2385(19), Rh–C(2) 2.245(2),
Rh–C(1A) 2.4126(18), Rh–C(3A) 2.4148(17), C(8)–C(9) 1.408(3),
C(16)–C(17) 1.405(3); C(1)–Rh–C(3) 61.76(8), ethene centroid–Rh–ethene
centroid 93.2.
NMR spectrum for 2 shows a doublet at d 43.9 ppm with a
coupling constant of JRhP = 220 Hz, suggesting that the ligands
are, not surprisingly, bound to the metal via the soft phosphorus
1
atom. This observation is confirmed by the H NMR data, as
no significant change is observed for the vinyl peaks in 2, as
The rhodium alkene bond distances of 2.1495(19), 2.1513(19),
=
compared to free Ph2PCH CH2. The ring junction carbons within
˚
˚
2.1520(19), and 2.1659(19) A (Rh–Cave = 2.1547(19) A) are similar
to those reported for related systems9 and a distinct lengthening
˚
=
of the C C bonds (C–Cave = 1.407(3) A) of the alkene is also
observed, arising from p-back bonding from the metal centre.
As expected, there are three ‘short’ (Rh–C(1) 2.230(2), Rh–C(3)
˚
2.2385(19), and Rh–C(2) 2.245(2) A) and two ‘long’ (Rh–C(1A)
˚
2.4126(18) and Rh–C(3A) 2.4148(17) A) rhodium–carbon bond
distances within the indenyl ring. These values clearly indicate a
slip-fold distortion towards an allylic bonding mode, but there is
Scheme 1 Synthesis of indenyl rhodium phosphine complexes 2–4.
Dalton Trans., 2009, 1624–1631 | 1625
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1
the indenyl ring appear at d 118.8 ppm in the 13C{ H} spectrum
and again suggest only a moderate amount of slip distortion
in solution. Compound 2 has also been characterized by X-ray
diffraction, the molecular structure of which is shown in Fig. 3. The
˚
ground state slip distortion in 2 is D = 0.207(4) A, slightly larger
than what is observed in 1, with a FA of 10.1(4)◦. The rhodium
phosphorus bond lengths of Rh(1)–P(1) 2.2243(13) and Rh(1)–
˚
P(2) 2.2194(13) A are similar to those observed in other indenyl
phosphine systems.5b,12 For example, rhodium phosphorus bond
˚
lengths of 2.213(1) and 2.210(1) A were reported for the complex
5
(h -C9H7)Rh(PMe3)2.5b
Fig. 4 Perspective view of molecule of 4 with atom labelling scheme.
Thermal ellipsoids are drawn at 50% probability level with hydrogen atoms
◦
˚
omitted for clarity. Selected bond distances (A) and angles ( ): Rh–P(1)
2.1938(5), Rh–P(2) 2.2083(5), Rh–C(1) 2.226(2), Rh–C(2) 2.253(2),
Rh–C(3) 2.257(2), Rh–C(7A) 2.390(2), Rh–C(3A) 2.423(2), C(20)–C(21)
1.195(3), C(38)–C(39) 1.195(3); P(1)–Rh–P(2) 94.30(2), C(1)–Rh–C(3)
62.03(9).
Fig. 3 Perspective view of molecule of 2 with atom labelling scheme.
Thermal ellipsoids are drawn at 50% probability level with hydrogen atoms
◦
˚
omitted for clarity. Selected bond distances (A) and angles ( ): Rh(1)–P(2)
2.2194(13), Rh(1)–P(1) 2.2243(13), Rh(1)–C(2) 2.228(5), Rh(1)–C(3)
2.230(4), Rh(1)–C(1) 2.235(4), Rh(1)–C(3A) 2.435(4), Rh(1)–C(7A)
2.443(5), C(20)–C(21) 1.315(7), C(34)–C(35) 1.303(8); P(2)–Rh(1)–P(1)
96.10(4), C(3)–Rh(1)–C(1) 62.15(18).
Scheme 2 Synthesis of indenyl rhodium dimer 5.
crystal X-ray diffraction study confirms the dimeric structure for
complex 5 (Fig. 5) with diphosphine ligands coordinating in a
P–P¢ bridging mode. This coordination mode is known for similar
complexes of other transition metals.13,14 In contrast, the only pre-
viously characterized rhodium complex of this ligand comprises
a polymer.15 One molecule of 5 constitutes the asymmetric unit
showing no molecular symmetry. This is especially apparent in the
different rhodium-indenyl bonding situations at Rh(1) and Rh◦(1B)
We have also prepared the allyldiphenylphosphine compound 3
and the alkynyldiphenylphosphine derivative 4 via a similar route.
1
Both compounds show the characteristic doublet in the 31P{ H}
NMR spectra, signifying that bonding is once again occurring
through the phosphorus atoms and with coupling to rhodium of
JRhP = 220 Hz and JRhP = 227 Hz, respectively. The ring junction
1
carbons appear in the 13C{ H} NMR spectra at d 120.2 ppm for 3
characterized by values of D = 0.146(3) A and a FA of 9.2(1) for
˚
◦
˚
and d 117.7 ppm for 4. Compound 4 has also been characterized
by single crystal X-ray diffraction (Fig. 4). The ground state slip
distortion in 4 is unusually small for a bis(phosphine) system with
Rh(1) and D = 0.185(3) A and a FA of 8.7(1) for Rh(1B). This
is (on average) in good agreement with the results obtained for
◦
˚
the related compound 4 with D = 0.165(2) A and a FA of 9.2(3) .
˚
˚
D = 0.165(2) A, which is actually less than that observed for 1.
The rhodium phosphorus bond length of Rh(1)–P(1) 2.196(1) A
˚
˚
˚
By comparison, a distortion of D = 0.201 A was observed in the
and Rh(1)–P(2B) 2.212(1) A and Rh(1B)–P(2) 2.192(1) A, and
trimethylphosphine analogue (h -C9H7)Rh(PMe3)2.5b A fold angle
Rh(1B)–P(1B) 2.208(1) A respectively, are similar and typical
5
˚
of 9.2(3)◦ is also observed for 4. The rhodium phosphorus bond
for these complexes. Interestingly, the two alkynyldiphosphine
moieties in the solid state structure of 5 have different geometries,
one is almost linear (P(1B)–C(20B)–C(21B) 179.0(2)◦ and P(2B)–
C(21B)–C(20B) 175.9(2)◦) whilst the other one is considerably bent
(P(2)–C(21)–C(20) 168.5(2)◦ and P(1)–C(20)–C(21) 165.5(2)◦). In
˚
lengths of Rh–P(1) 2.1938(5) and Rh–P(2) 2.2083(5) A are again
typical for these complexes.
Addition of one equivalent of the linear diphosphine
∫
Ph2PC CPPh2 to 1 led to the formation of dimeric 5 in moderate
1
yield (Scheme 2). Compound 5 displays a doublet in the 31P{ H}
both ligands, the carbon–carbon triple bond lengths of 1.205(3) A
˚
˚
NMR spectra at d 26.1 ppm with JRhP = 220 Hz. The ring
(C(20)–C(21)) and 1.202(3) A (C(20B)–C(21B)) are normal. The
junction carbons appear in the 13C{ H} NMR spectra at d
bending of one bridging alkynyldiphosphine is well documented
in related complexes.14 Additionally compound 5 was studied by
1
117.9 ppm, suggesting minimal distortion in solution. A single
1626 | Dalton Trans., 2009, 1624–1631
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Scheme 3 Indenyl rhodium catalysed hydroboration of 4-vinylanisole
and diphenylvinylphosphine.
indenyl ligand has been borylated, as observed by multinuclear
NMR spectroscopy and GC-MS analyses, and replaced by the
Bcat2- anion which has coordinated to the rhodium via one of the
aryl groups. These zwitterionic systems are remarkably active and
selective hydroboration catalysts for a wide range of alkenes, and
are well known to give the selective formation of the branched
product in hydroborations of vinylarenes using HBcat.18 As the
phosphines also contain a site of unsaturation, it is highly probable
that the ligands are also being reduced in these catalytic runs. To
test this hypothesis we examined the ability of 2 to add HBcat
Fig.
5
Perspective view of molecule of 5 with atom labelling
scheme. Thermal ellipsoids are drawn at 50% probability level with
hydrogen atoms and non-ipso phenyl carbon atoms omitted for clarity.
Selected bond distances (A) and angles (◦): Rh(1)–P(1) 2.196(1),
˚
Rh(1)–P(2B) 2.212(1), Rh(1)–C(1) 2.207(2), Rh(1)–C(2) 2.251(2),
Rh(1)–C(3) 2.246(2), Rh(1)–C(7A) 2.368(2), Rh(1)–C(3A) 2.395(2),
C(20)–C(21) 1.205(3), Rh(1B)–P(1B) 2.208(1), Rh(1B)–P(2) 2.192(1),
Rh(1B)–C(1B) 2.212(2), Rh(1B)–C(2B) 2.234(2), Rh(1B)–C(3B) 2.251(2),
Rh(1B)–C(7AB) 2.404(2), Rh(1B)–C(3AB) 2.431(2), C(20B)–C(21B)
1.202(3); P(1)–Rh(1)–P(2B) 95.41(2), C(1)–Rh(1)–C(3) 62.00(9),
P(1B)–Rh(1B)–P(2) 94.82(2), C(1B)–Rh(1B)–C(3B) 61.79(9).
=
to Ph2PCH CH2. Although conversion of the starting alkene was
only 75% using one equivalent of HBcat, we have found that these
reactions proceed to give a mixture of the expected linear product
Ph2PCH2CH2(Bcat) (11, 20%) along with the unusual branched
product Ph2PCH(Bcat)CH3 (12, 15%). While derivatives of 11
have recently been prepared and examined for their ability to act
as ambiphilic ligands or donor–acceptor systems,20 the generation
of 12 represents the first example of a metal catalysed addition
of a borane to diphenylvinylphosphine to give this branched
product. The ability to generate 12 selectively and enantiomerically
pure will prove to be a valuable method of synthesising chiral
monodentate phosphine ligands.21 While the vinyl boronate ester
mass spectroscopy, but neither ionisation by EI nor by MALDI
(in positive and negative ion mode) resulted in helpful data.
Interestingly, addition of 2 equivalents of this phosphine to 1 led
to an unidentified mixture of rhodium phosphine species.
As indenyl complexes are known to catalyse the addition of
catecholborane (HBcat, cat = 1,2-O2C6H4) to alkenes,1i,k we have
examined complexes 1–5 for their potential to act as catalyst
precursors in this important reaction.16 Although reactions using
catalytic amounts of 1 (5 mol%) to facilitate the addition of
=
Ph2PCH CH(Bcat) 13 was not observed to any extent, the
corresponding diborated product Ph2PCH(Bcat)CH2(Bcat) 14
was observed as the major boron containing product (65%).
Interestingly, no hydrogenation product was observed in this
reaction. We are in the process of examining this reaction further
in an effort to improve selectivities and will report our findings in
due course.
=
HBcat to 4-vinylanisole (4-MeOC6H4CH CH2) gave a mixture of
hydroboration products 4-MeOC6H4CH2CH2(Bcat) (6, 18%) and
4-MeOC6H4CH(Bcat)CH3 (7, 3%), as ascertained by multinuclear
NMR spectroscopy, products derived from a competing dehydro-
genative borylation pathway were also observed.17 Dehydrogena-
tive borylation is believed to proceed via initial oxidative addition
of the borane to the metal centre, followed by coordination and
insertion of the alkene into the Rh–B bond with a subsequent, and
selective, b-hydride elimination to give a vinyl boronate product
along with an active rhodium dihydride species. Indeed, the
Experimental
General
=
vinyl boronate ester 4-MeOC6H4CH CH(Bcat) (8) was the major
Reagents and solvents were purchased from Aldrich Chemicals
and used as received. Lithium indenide22 and [RhCl(coe)2]223 were
boron-containing product observed in 37% yield. Interestingly,
the diborated product 4-MeOC6H4CH(Bcat)CH2(Bcat) (9) was
also generated in this reaction, albeit in minor amounts (2%).
This latter product18b,c,e,19 presumably arises from a selective
hydroboration of 8. A considerable amount (40%) of hydrogenated
starting material, 4-MeOC6H4CH2CH3 (10), is also observed in
these reactions.
We then examined catalytic hydroboration reactions using the
indenyl phosphine complexes 2–5 and found that all gave predom-
inant formation of the internal isomer 7 (ca. 95%, Scheme 3)
along with only a minor amount (5%) of products derived
from the dehydrogenative borylation pathway. The fate of the
catalyst system upon completion of these reactions appears to
∫
synthesized as previously reported. The phosphines Ph2PC C-
24
∫
tert-butyl and Ph2PC CPPh2 were donated as a generous gift
from Dr J. F. Corrigan. NMR spectra were recorded on a JEOL
JNM-GSX270 FT NMR (1H 270 MHz; 11B 87 MHz; 13C 68 MHz;
31P 109 MHz) spectrometer. Chemical shifts (d) are reported in
ppm [relative to residual solvent peaks (1H and 13C) or external
BF3·OEt2 (11B), and H3PO4 (31P)] and coupling constants (J) in
Hz. Multiplicities are reported as singlet (s), doublet (d), triplet
(t), quartet (q), sextet (sext), multiplet (m), broad (br), apparent
(app), and overlapping (ov). Melting points were determined using
a Mel-Temp apparatus and are uncorrected. Elemental analyses
were performed by Guelph Chemical Laboratories (Guelph, ON).
Reactions were performed under an atmosphere of dinitrogen.
6
be zwitterionic complexes of the type (h -catBcat)RhP2, where the
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(g5-C9H7)Rh(coe)2 (1). To a stirred toluene (10 mL) solution
of [RhCl(coe)2]2 (1.00 g, 1.39 mmol) was added lithium indenide
(0.35 g, 2.86 mmol) as a solid. The reaction was allowed to proceed
at RT for 18 h at which point the solution was passed through
multiple plugs of silica until the solution became clear orange.
The removal of solvent under vacuum afforded 1 as an orange
solid. Yield: 0.80 g (66%); m.p.: 120 ◦C (decomp.) NMR (C6D6):
1H d 7.13 (s, 4H, H4–7), 6.01 (q, JHH = JRhH = 2.2 Hz, 1H, H2), 4.74
added a THF (3 mL) solution of Ph2PC C-tert-butyl (0.25 g,
0.94 mmol). The reaction was allowed to proceed at RT for 18 h
at which point the solvent was removed under vacuum and the
resulting orange solid was washed with hexane (2 ¥ 2 mL) to afford
4. Yield: 0.24 g (70%); m.p.: 115 ◦C (decomp.). NMR (C6D6): 1H
d 7.78 (br m, 8H, Ar), 7.17–7.02 (ov m, 14H, Ar & H4,7), 6.74 (t,
JHH = 3.0 Hz, 2H, H5,6), 6.43 (q, JHH = JRhH = 2.7 Hz, 1H, H2),
∫
4.55 (d, JHH = 2.7 Hz, 2H, H1,3), 0.85 (s, 18H, tert-butyl); 13C{ H}
1
(d, JHH = 2.2 Hz, 2H, H1,3), 2.12–2.08 (ov m, 4H, CH2), 1.79–1.51
d 141.0 (t, J = 24.6 Hz, ArCP), 132.7 (t, J = 6.7 Hz, Ar), 128.6
(s, Ar), 127.5 (t, J = 5.1 Hz, Ar), 121.1 (s, C4,7), 117.7 (s, C3a,7a),
115.8 (s, C5,6), 113.5 (t, J = 5.1 Hz, PC∫C), 95.9 (d, JRhC = 5.6 Hz,
1
(ov m, 16H, CH2 & CH), 1.40–1.21 (ov m, 8H, CH2); 13C{ H} d
=
122.9 (s, C4,7), 119.3 (s, C5,6), 114.5 (d, JRhC = 1.9 Hz, C3a,7a), 94.9
∫
(d, JRhC = 5.4 Hz, C2), 83.1 (d, JRhC = 4.6 Hz, C1,3), 69.9 (d, JRhC
=
C2), 77.9–76.1 (ov m, C1,3 and PC C), 29.9 (s, C(CH3)3), 28.1 (s,
1
13.7 Hz, C C), 32.4 (d, JRhC = 3.5 Hz, CH2), 32.1 (d, JRhC = 1.2 Hz,
CH2), 26.7 (s, CH2). Anal. Calcd. (%) for C25H35Rh (438.50): C,
68.47; H, 8.06. Found: C, 68.38; H, 7.90.
C(CH3)3); 31P{ H} d 25.1 (d, JRhP = 227 Hz). Anal. Calcd. (%) for
=
C45H45P2Rh (750.75): C, 71.99; H, 6.05. Found: C, 72.35; H, 6.11.
5
∫
[(g -C9H7)Rh(l-Ph2PC CPPh2)]2 (5). To a stirred toluene
(5 mL) solution of (h -C9H7)Rh(coe)2 (0.20 g, 0.46 mmol) was
added a toluene (5 mL) solution of Ph2PC CPPh2 (0.18 g,
5
5
=
(g -C9H7)Rh(Ph2PCH CH2)2 (2). To a stirred THF (5 mL)
5
∫
solution of (h -C9H7)Rh(coe)2 (0.20 g, 0.46 mmol) was added
a THF (3 mL) solution of diphenylvinylphosphine (0.20 g,
0.94 mmol). The reaction was allowed to proceed at RT for 18 h
at which point the solvent was removed under vacuum and the
resulting orange solid was washed with hexane (2 ¥ 1 mL) to afford
2. Yield: 0.19 g (65%); m.p.: 110 ◦C (decomp.). NMR (C6D6): 1H
d 7.46 (br m, 8H, Ar), 7.07–6.99 (ov m, 14H, Ar & H4,7), 6.72 (t,
JHH = 3.0 Hz, 2H, H5,6), 6.52 (q, JHH = JRhH = 2.6 Hz, 1H, H2), 6.15
(ov dddd, JHH = 17.6, 11.1, Hz, JPH = 17.3 Hz, JRhH = 2.1 Hz, 2H,
0.46 mmol). The reaction was allowed to proceed at RT for 18 h
at which point an orange precipitate was collected by suction
filtration and washed with hexane (2 ¥ 2 mL) to afford 5. Yield:
0.13 g (46%); m.p.: decomposes above 215 ◦C. NMR (C6D6): 1H d
7.48 (br m, 16H, Ar), 7.02–6.92 (ov m, 28H, Ar & H4,7), 6.73 (m,
4H, H5,6), 6.34 (q, JHH = JRhH = 2.7 Hz, 2H, H2), 4.61 (d, JHH
=
1
2.7 Hz, 4H, H1,3); 13C{ H} d 138.6 (t, J = 25.1 Hz, ArCP), 132.0
(t, J = 8.2 Hz, Ar), 128.7 (s, Ar), 127.7 (t, J = 5.1 Hz, Ar), 121.7 (s,
=
=
∫
RhPCH CH2), 5.41 (d, JHH = 17.6 Hz, 2H, CH CHH), 5.34 (ddd,
C4,7), 117.9 (s, C3a,7a), 116.0 (s, C5,6), 102.8 (app t, J = 31.7 Hz, C C),
1
JPH = 29.4 Hz, JHH = 11.1 Hz, JRhH = 2.2 Hz, 2H, CH CHH),
95.4 (d, JRhC = 6.1 Hz, C2), 77.3–77.1 (m, C1,3); 31P{ H} d 26.1 (d,
=
1
4.65 (d, JHH = 2.6 Hz, 2H, H1,3); 13C{ H} d 139.0 (t, J = 27.0 Hz,
JRhP = 220 Hz). Anal. Calcd. (%) for C70H54P4Rh2 (1225.04): C,
ArCP), 136.8 (t, J = 25.5 Hz, PCH), 133.5 (t, J = 8.2 Hz, Ar)
128.6 (s, Ar), 128.3 (s, CHCH2), 127.5 (t, J = 4.6 Hz, Ar), 121.2 (s,
68.63; H, 4.45. Found: C, 68.98; H, 4.20.
General procedure for the hydroboration of 4-vinylanisole. To
a stirred C6D6 (0.5 mL) solution of 4-vinylanisole (50 mg,
0.37 mmol) and the desired catalyst (1–5) (5 mol%), was
added a C6D6 solution (0.5 mL) catecholborane (44 mg,
0.37 mmol). After 18 h the reaction was monitored by
multinuclear NMR spectroscopy. Selected NMR spectroscopic
data for: 4-MeOC6H4CH2CH2(Bcat), 6: 2.79 (t, J = 7.9 Hz,
CH2CH2(Bcat)), 1.42 (t, J = 7.9 Hz, CH2CH2(Bcat)); 4-
MeOC6H4CH(Bcat)CH3, 7: 2.74 (q, J = 7.7 Hz, CH(Bcat)CH3),
C4,7), 118.8 (s, C3a,7a), 115.8 (s, C5,6), 96.1 (d, JRhC = 8.6 Hz, C2), 76.1
(dt, JRhC = 3.8 Hz, JPC = 10.6 Hz, C1,3); 31P{ H} d 43.9 (d, JRhP
=
1
220 Hz). Anal. Calcd. (%) for C37H33P2Rh (642.55): C, 69.16; H,
5.19. Found: C, 69.46; H, 5.49.
5
=
(g -C9H7)Rh(Ph2PCH2CH CH2)2 (3). To a stirred toluene
5
(5 mL) solution of (h -C9H7)Rh(coe)2 (0.20 g, 0.46 mmol) was
added a toluene (3 mL) solution of allyldiphenylphosphine (0.21 g,
0.94 mmol). The reaction was allowed to proceed at RT for 18 h
at which point the solvent was removed under vacuum and the
resulting orange solid was dissolved in hexane (10 mL) and stored
at -30 ◦C. An orange precipitate was collected by suction filtration
and washed with cold hexane (2 ¥ 1 mL) to afford 3. Yield: 0.14 g
=
1.48 (d, J = 7.7 Hz, CH(Bcat)CH3); 4-MeOC6H4CH CH(Bcat),
=
8: 7.82 (d, J = 18.3 Hz, CH CH(Bcat)), 6.34 (d, J = 18.3 Hz,
=
CH CH(Bcat)); 4-MeOC6H4CH(Bcat)CH2(Bcat), 9: 2.09 (dd, J =
16.1, 9.1 Hz, CH(Bcat)CHH(Bcat), 1.82 (dd, J = 16.1 Hz, 7.1 Hz,
CH(Bcat)CHH(Bcat); 4-MeOC6H4CH2CH3, 10: 2.45 (q, J =
7.7 Hz, CH2CH3), 1.10 (t, J = 7.7 Hz, CH2CH3).
◦
1
(45%); m.p.: 93–95 C. NMR (C6D6): H d 7.38 (br m, 8H, Ar),
7.06 (app t, JHH = 3.0 Hz, 2H, H4,7), 7.02–6.96 (ov m, 12H, Ar),
6.88 (t, JHH = 3.0 Hz, 2H, H5,6), 6.55 (q, JHH = JRhH = 2.7 Hz,
Hydroboration of diphenylvinylphosphine using 2 as a precatalyst.
To a stirred C6D6 (0.5 mL) solution of diphenylvinylphosphine
(50 mg, 0.24 mmol) and the catalyst (2) (3 mg, 2 mol%), was
added a C6D6 solution (0.5 mL) of catecholborane (31 mg,
0.26 mmol). After 18 h the reaction was monitored by multi-
nuclear NMR spectroscopy. Selected NMR spectroscopic data
for: Ph2PCH2CH2(Bcat), 11: 1H d 2.20 (t, J = 8.2 Hz,
PCH2CH2(Bcat)), 1.28 (dt, JHP = 12.2 Hz, JHH = 8.2 Hz,
=
1H, H2), 5.92 (m, 2H, CH CH2), 4.92 (d, JHH = 10.2 Hz, 2H,
=
=
CH CHH), 4.81 (d, JHH = 13.1 Hz, 2H, CH CHH), 4.79 (d,
JHH = 2.7 Hz, 2H, H1,3), 2.52 (app t, JHH = 7.2 Hz, 4H, PCH2);
13
1
=
C{ H} d 140.1 (t, J = 18.4 Hz, ArCP), 134.9 (s, CH CH2), 133.1
(t, J = 5.9 Hz, Ar), 128.6 (s, Ar), 127.2 (t, J = 4.6 Hz, Ar), 121.1
(s, C4,7), 120.2 (s, C3a,7a), 116.5 (t, J = 5.6 Hz, PCH2CH), 115.6 (s,
C5,6), 96.4 (d, JRhC = 6.1 Hz, C2), 74.8–74.5 (m, C1,3), 38.7 (t, J =
11.8 Hz, PCH2); 31P{ H} d 38.0 (d, JRhP = 220 Hz). Anal. Calcd.
1
1
1
CH2CH2(Bcat)); 31P{ H} d: -10.1; Ph2PCH(Bcat)CH3, 12: H d
(%) for C39H37P2Rh (670.66): C, 69.84; H, 5.57. Found: C, 70.11;
H, 5.41.
2.39 (qd, JHH = 7.4, JHP = 3.0 Hz, PCH(Bcat)CH3), 1.36 (dd,
JHP = 16.1, JHH = 7.4 Hz, PCH(Bcat)CH3); 31P{ H} d: -1.2;
1
5
1
∫
(g -C9H7)Rh(Ph2PC C-tert-butyl)2 (4). To a stirred THF
Ph2PCH(Bcat)CH2(Bcat), 14: H d 2.93 (ddd, JHH = 10.6, 5.2,
5
(5 mL) solution of (h -C9H7)Rh(coe)2 (0.20 g, 0.46 mmol) was
JHP = 2.2 Hz, PCH(Bcat)CH2(Bcat)), 1.99 (ov ddd, JHH = 16.8,
1628 | Dalton Trans., 2009, 1624–1631
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The Royal Society of Chemistry 2009
©

View Article Online
10.6, JHP = 11.8 Hz, PCH(Bcat)CHH(Bcat)), 1.76 (ddd, JHH
=
Chem. Soc., 1994, 116, 8793; (h) M. A. Schmid, H. G. Alt and W.
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1
16.8, 5.2, JHP = 11.1 Hz, PCH(Bcat)CHH(Bcat)); 31P{ H} d: 2.0.
X-Ray crystallography†
Crystals of 1 were grown from saturated diethyl ether solutions, 2
from saturated C6D6 solutions at room temperature, and 4 from
saturated THF solutions layered with hexanes at -30 ◦C. Crystals
of 5 were grown by diffusion of n-hexane into a solution of
5 in benzene at room temperature. Single crystals were coated
with Paratone-N oil or Perfluoropolyether oil, mounted using
a glass fibre or human hair and frozen in the cold stream
of the goniometer. A hemisphere of data were collected on a
Bruker AXS P4/SMART 1000 diffractometer using w and q
scans with a scan width of 0.3◦ and exposure times of 10 s
(1 and 4) and 30 s (2). The detector distances were 5 cm.
In the case of 5 more than a hemisphere was collected on a
Bruker SMART 6K CCD using w scans (0.3◦ width), a detector
distance of 4.85 cm and an exposure time of 15 s. The data were
reduced (SAINT) and corrected for absorption (SADABS).25 The
structures were solved by direct methods and refined by full-
matrix least squares on F2(SHELXTL). All non-hydrogen atoms
were refined using anisotropic displacement parameters. Hydrogen
atoms were included in calculated positions and refined using a
riding model.
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Conclusions
5
We have prepared (h -C9H7)Rh(coe)2 (1, coe = cis-cyclooctene)
5
as a thermally stable alternative to the diethylene derivative (h -
2
=
C9H7)Rh(h -H2C CH2)2. Compound 1 reacts with unsaturated
5
phosphines to give complexes of the type (h -C9H7)RhP2, where
bonding occurs through the phosphorus atom. Solution and solid
state data showed that these new phosphine complexes have
only a moderate amount of distortion within the indenyl ring.
These compounds were found to catalyse the hydroboration of
vinylarenes, and the first example of an internal hydroboration of
diphenylvinylphosphine has been reported.
Acknowledgements
Thanks are gratefully extended to the Canada Research Chairs
Programme, Canadian Foundation for Innovation-Atlantic Inno-
vation Fund, Natural Science and Engineering Research Council
of Canada, and Mount Allison University for financial support.
We also thank Roger Smith and Dan Durant (MtA) for expert
technical assistance. Support for C. Kleeberg by the Deutsche
Forschungsgemeinschaft (DFG) is gratefully acknowledged. We
thank the team of the EPSRC National Mass Spectrometry Service
Centre (Swansea) and anonymous reviewers for helpful comments.
Notes and references
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