Coordination chemistry and reactivity of new zwitterionic rhodium and iridium complexes featuring the tripodal phosphine ligand [PhB(CH 2PiPr2)3]-. Activation of H-H, Si-H, and ligand B-C bonds

Article abstract of DOI:10.1021/om030686e

The synthesis, characterization, and reactivity of zwitterionic rhodium and iridium complexes were carried out. The zwitterionic rhodium and iridium complexes contains tris(phosphino)borate ligand [PhB(CH₂P ⁱPr₂)₃] ^-([PhBP₃ ^']^-). The allyl complexes were prepared by reaction of [PhBP₃^']Li(THF) with the corresponding [(alkene) ₂IrCl)₂ complex. It was stated that the ligand B-C bond activation was shown to be a facile reaction pathway for [PhBP₃ ^']Rh complexes.

Full text of DOI:10.1021/om030686e

2488
Organometallics 2004, 23, 2488-2502
Coor d in a tion Ch em istr y a n d Rea ctivity of New
Zw itter ion ic Rh od iu m a n d Ir id iu m Com p lexes F ea tu r in g
th e Tr ip od a l P h osp h in e Liga n d [P h B(CH2P iP r 2)3]-.
Activa tion of H-H, Si-H, a n d Liga n d B-C Bon d s
Laura Turculet, J ay D. Feldman, and T. Don Tilley*
Department of Chemistry, University of California at Berkeley,
Berkeley, California 94720-1460
Received December 15, 2003
The synthesis, characterization, and reactivity of zwitterionic rhodium and iridium
complexes containing the tris(phosphino)borate ligand [PhB(CH2PiPr2)3]- ([PhBP3′]-) are
reported. The allyl complexes [PhBP3′]IrH(η3-C8H13) (3) and [PhBP3′]IrH(η3-C3H5) (4) were
prepared by reaction of [PhBP3′]Li(THF) (2) with the corresponding [(alkene)2IrCl]2 complex.
Complex 3 reacted with secondary silanes (H2SiR2, with R ) Et, Ph) to give silyl-capped
trihydride complexes of the type [PhBP3′]IrH3(SiHR2) (R ) Et, 5; Ph, 6) with concomitant
â-hydride elimination of 1,3-cyclooctadiene. Complex 5 underwent H/D exchange with D2 to
incorporate deuterium into both the Ir-H and Si-H positions. The reaction of 5 with 1
equiv of PMe3 resulted in elimination of Et2SiH2 to form the corresponding dihydride complex,
[PhBP3′]Ir(H)2(PMe3) (7). Complexes of the type [PhBP3′]Ir(H)2(L) (L ) PMe3, 7; PH2Cy, 8;
CO, 9) could also be prepared directly by the reaction of 3 with L. The observed reactivity
of [PhBP3′]Ir complexes is compared with that of the related [PhB(CH2PPh2)3]- ([PhBP3]-)
species. The Rh(I) complexes [κ2-PhBP3′]Rh(PMe3)2 (10) and [PhBP3′]Rh(CO)2 (11) are also
1
reported. Variable-temperature H and 31P NMR experiments did not reveal evidence for
κ2-κ3 interconversion for 10 and 11. However at elevated temperatures 10 was found to
engage in a dynamic equilibrium process involving dissociation of the PMe3 ligands and
reversible migration of a -CH2 group in the ligand backbone from B to Rh. The product of
this migration, [PhB(CH2PiPr2)2]RhCH2PiPr2 (12), was prepared independently by the
reaction of 2 with [RhCl(C2H4)2]2 and was structurally characterized by X-ray crystallography.
Complex 10 reacted with H2 to give the oxidative addition product [PhBP3′]Rh(H)2(PMe3)
(13). The reaction of 10 with 1 equiv of Ph2SiH2 resulted in loss of a ligand arm to give the
bis(phosphino)borane complex [PhB(CH2PiPr2)2]Rh(H)2(SiHPh2)(PMe3) (14). Complex 11
reacted with H2 in the presence of 1 equiv of Me3NO to give the oxidative addition product
[PhBP3′]Rh(H)2(CO) (15), with concomitant liberation of Me3N.
In tr od u ction
oxidative addition of Si-H bonds to the metal center;
however, considerable attention has focused on deter-
mining the extent to which further rearrangements of
the resulting metal silyl species may contribute to the
observed transformations.2
Along these lines, research in our group has focused
on elucidating the chemistry of transition metal-medi-
ated Si-H bond activation processes. Recently, we
reported the first direct observations of 1,2-hydride
shifts (R-eliminations) that convert transition metal silyl
complexes into base-free metal silylene hydrides.3 Given
the relative scarcity of isolable base-free metal silylene
complexes,2-4 as well as their potential to mediate new
The controlled activation of element-hydrogen bonds
by transition metal complexes represents a fundamental
step in a number of metal-catalyzed transformations.1
In particular, the activation of Si-H bonds by metal
fragments has been shown to be a key component of
olefin hydrosilylation and dehydrogenative silylation
processes, as well as in the dehydrocoupling of hydrosi-
lanes to polysilanes.2 For late transition metal com-
plexes, these bond activations generally involve the
(1) Elschenbrioch, C.; Salzer, A. Organometallics: A Concise Intro-
duction, Second Edition; VCH: New York, 1992; Chapter 17, p 411.
(2) (a) Tilley, T. D. In The Chemistry of Organic Silicon Compounds;
Patai, S., Rappoport, Z., Eds.; Wiley: New York, 1989; Chapter 24, p
1415. (b) Ojima, I. In The Chemistry of Organic Silicon Compounds;
Patai, S., Rappoport, Z., Eds.; Wiley: New York, 1989; Chapter 25, p
1479. (c) Tilley, T. D. Comments Inorg. Chem. 1990, 10, 37. (d) Tilley,
T. D. In The Silicon-Heteroatom Bond; Patai, S., Rappoport, Z., Eds.;
Wiley: New York, 1991; Chapters 9 and 10, pp 245-309. (e) Pannell,
K. H.; Sharma, H. Chem. Rev. 1995, 95, 1351. (f) Eisen, M. S. In The
Chemistry of Organic Silicon Compounds, Volume 2; Apeloig, Y.,
Rappoport, Z., Eds.; Wiley: New York, 1998; Chapter 35, p 2037. (g)
Corey, J . Y.; Braddock-Wilking, J . Chem. Rev. 1999, 99, 175.
(3) For examples of transition metal silylene complexes prepared
via R-hydride elimination routes, see: (a) Mitchell, G. P.; Tilley, T. D.
J . Am. Chem. Soc. 1998, 120, 7635. (b) Mitchell, G. P.; Tilley, T. D.
Angew. Chem., Int. Ed. 1998, 37, 2524. (c) Peters, J . C.; Feldman, J .
D.; Tilley, T. D. J . Am. Chem. Soc. 1999, 121, 9871. (d) Klei, S. R.;
Tilley, T. D.; Bergman, R. G. J . Am. Chem. Soc. 2000, 122, 1816. (e)
Mork, B. V.; Tilley, T. D. J . Am. Chem. Soc. 2001, 123, 9702. (f)
Feldman, J . D.; Peters, J . C.; Tilley, T. D. Organometallics 2002, 21,
4065.
10.1021/om030686e CCC: $27.50 © 2004 American Chemical Society
Publication on Web 04/07/2004

New Zwitterionic Rhodium and Iridium Complexes
Organometallics, Vol. 23, No. 10, 2004 2489
Sch em e 1
chemical transformations, we have sought to develop
reaction systems for which this R-hydride elimination
process is facile. In this context, we have previously
introduced the anionic, tripodal phosphino-borate ligand
[PhB(CH2PPh2)3]- ([PhBP3]-) and demonstrated its
utility in facilitating the preparation of zwitterionic,
base-free, iridium silylene and germylene complexes via
the sequential activation of two E-H (E ) Si, Ge)
fragments on a single R2EH2 substrate (eq 1).3c,f This
silylene extrusion reaction appears to involve 1,2-
hydride migrations between iridium and silicon and is
exceptional in that the direct conversion of secondary
silanes to silylene complexes was previously unknown.
laboratory has demonstrated that 2 is an effective
transfer reagent for the [PhBP3′]- ligand, which can be
used in the synthesis of unusual four-ccordinate [PhBP3′]-
Fe(II) silyl complexes.7 Additionally, Peters and co-work-
ers have recently reported the synthesis of [PhBP3′]Tl
and demonstrated novel dinitrogen activation chemistry
involving [PhBP3′]Fe and [PhBP3′]Co complexes.8 In this
contribution, we extend this chemistry to the synthesis
and bond activation reactivity of iridium complexes
supported by [PhBP3′]-. We also report for the first time
the synthesis and chemical reactivity of several rhodium
complexes featuring tris(phosphino)borate ligation.
The reactivity observed in our initial study of iridium
complexes featuring the [PhBP3]- ligand prompted us
to further examine the chemistry of this system and of
related metal species. One area of interest concerns
delineation of the steric and electronic factors that
influence reactivity in such phosphino-borate complexes.
In particular, we are interested in studying the effects
of a more electron-donating phosphino-borate ligand on
the bond activation chemistry of the corresponding
iridium complexes, as strongly electron-donating ligands
have been shown to promote transition metal-mediated
chemical transformations that are not accessible to less
electron-rich complexes.5 Additionally, our synthetic and
mechanistic investigations have revealed that the phen-
yl substituents on the phosphine donors of the [PhBP3]-
ligand are susceptible to intramolecular ortho-metala-
tion by the iridium center.3f,6 We therefore became
interested in replacing these phenyl groups with more
metalation-resistant substituents that would disfavor
such ligand activation processes.
Resu lts a n d Discu ssion
Syn th esis of [P h BP 3′]Ir Allyl Com p lexes. The
reaction of the salt [PhB(CH2PiPr2)3]Li(THF) (2) with
[(COE)2IrCl]2 (COE ) cyclooctene) provided high-yield
entry to the chemistry of [PhBP3′]Ir. This reaction
occurred readily at room temperature in benzene solvent
to give zwitterionic [PhBP3′]IrH(η3-C8H13) (3) via C-H
activation of a COE ligand (Scheme 1). The formation
1
of 3 was quantitative within 10 min by H NMR and
31P NMR spectroscopy (benzene-d6), and the product
was isolated in >90% yield. This transformation is
analogous to that used to prepare [PhBP3]IrH(η3-C8H13
)
(1),3c,6 as well as the hydridotris(pyrazolyl)borate (Tp)
analogue, TpIrH(η3-C8H13).9 Unlike the preparation of
1, however, no evidence for the formation of side-
products other than cyclooctene and lithium chloride
was observed, and the reaction mixture maintained a
golden orange color.
In the pursuit of a more electron-donating and meta-
lation-resistant analogue of [PhBP3]-, we recently de-
tailed the preparation of [PhB(CH2PiPr2)3]Li(THF)
([PhBP3′]Li(THF), 2; eq 2).7 Preliminary work in our
Complex 3 exhibits spectroscopic characteristics con-
sistent with the structure shown in Scheme 1. The 31P-
{1H} NMR spectrum of 3 (benzene-d6) contains a doublet
at 7.52 ppm (2J PP ) 21 Hz) and a triplet at -18.08 ppm
(2J PP ) 21 Hz) in a 2:1 ratio, consistent with a mirror
plane of symmetry that bisects the [PhBP3′] ligand. The
1H NMR spectrum of 3 (benzene-d6) is significantly
complicated by a large number of overlapping, intense
resonances in the alkyl region of the spectrum (2.5-
0.5 ppm) due to the ligand P-isopropyl substituents.
However, several diagnostic features of the spectrum
(4) For additional examples of base-free transition metal dialkyl and
diaryl silylene complexes prepared by routes other than R-hydride
elimination, see: (a) Grumbine, S. K.; Mitchell, G. P.; Straus, D. A.;
Tilley, T. D.; Rheingold, A. L. Organometallics 1998, 17, 5607. (b)
Wanandi, P. W.; Glaser, P. B.; Tilley, T. D. J . Am. Chem. Soc. 2000,
122, 972. (c) Feldman, J . D.; Mitchell, G. P.; Nolte, J .-O.; Tilley, T. D.
J . Am. Chem. Soc. 1998, 120, 11184.
(5) Werner, H. Angew. Chem., Int. Ed. Engl. 1983, 22, 927, and
references therein.
(6) Feldman, J . D.; Peters, J . C.; Tilley, T. D. Organometallics 2002,
21, 4050.
(8) (a) Betley, T. A.; Peters, J . C. Inorg Chem. 2003, 42, 5074. (b)
Betley, T. A.; Peters, J . C. J . Am. Chem. Soc. 2003, 125, 10782.
(9) (a) Tanke, R. S.; Crabtree, R. H. Inorg. Chem. 1989, 28, 3444.
(b) Fernandez, M. J .; Rodriguez, M. J .; Oro, L. A.; Lahoz, F. J . J . Chem.
Soc., Dalton Trans. 1989, 2073. (c) Alvarado, Y.; Boutry, O.; Gutierrez,
E.; Monge, A.; Nicasio, M. C.; Poveda, M. L.; Perez, P. J .; Ruiz, C.;
Bianchini, C.; Carmona, E. Chem., Eur. J . 1997, 3, 860.
(7) Turculet, L.; Feldman, J . D.; Tilley, T. D. Organometallics 2003,
22, 4627.

2490 Organometallics, Vol. 23, No. 10, 2004
Turculet et al.
are evident, such as the allyl methine resonances
(multiplets at 5.08 and 3.77 ppm) and an iridium
hydride resonance at -15.30 ppm that appears as a
doublet of triplets due to large trans-phosphine coupling
(2J HPtrans ) 120 Hz) and weaker coupling to the cis-
phosphine donors (2J HPcis ) 17 Hz).
The parent allyl complex [PhBP3′]IrH(η3-C3H5) (4)
was obtained by addition of [PhB(CH2PiPr2)3]Li(THF)
to a frozen THF solution of [(COE)2IrCl]2 that had been
saturated with propene (Scheme 1). Compound 4 was
isolated as an off-white crystalline solid in 67% yield
and exhibits spectroscopic characteristics analogous
with those of 3, consistent with a similar structure, as
shown in Scheme 1.
F igu r e 1. Crystallographically determined structure of
[PhB(CH2PiPr2)3]IrH3(SiHEt2) (5) depicted with 50% ther-
mal ellipsoids; all hydrogen atoms have been omitted for
clarity.
R ea ct ion s of [P h BP 3′]Ir Allyl Com p lexes w it h
Sila n es. Complex 3 reacted with secondary silanes (H2-
SiR2, with R ) Et, Ph) at 65 °C in benzene-d6 solution
to generate 1 equiv of 1,3-COD (COD ) cyclooctadiene)
and a new Ir-H species, [PhBP3′]IrH3(SiHR2) (eq 3, R
) Et, 5; R ) Ph, 6). The NMR characteristics of 5 and
6 are consistent with the 3-fold symmetric, silyl-capped
Ir(V) trihydride structure indicated in eq 3. Both 5 and
Ta ble 1. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for 5
(a) Bond Distances
Ir-P1
Ir-P2
2.382(2)
2.366(2)
Ir-P3
Ir-Si1
2.376(2)
2.413(3)
(b) Bond Angles
P1-Ir-P2
P1-Ir-P3
P2-Ir-P3
90.89(7)
89.13(7)
90.70(7)
P1-Ir-Si1
P2-Ir-Si1
P3-Ir-Si1
118.42(10)
129.72(9)
126.56(8)
The observed reactivity of 3 with H2SiPh2 and H2SiEt2
is surprisingly different from that observed for the
analogous complex [PhBP3]IrH(η3-C8H13) (1), which
reacted with secondary silanes (H2SiR2, with R ) Mes,
Ph, Et, Me) to generate 1 equiv of COE and the
corresponding silylene dihydride complexes, [PhBP3]Ir-
(H)2(dSiR2) (eq 1).3c,f On the basis of the observation of
1,3-COD as a byproduct in the reaction of 3 with silanes,
we postulate a mechanism involving â-hydride elimina-
tion, which can occur either from the η1-allyl complex I
(Scheme 2, path A) or alternatively from III, the product
of Si-H oxidative addition to I (Scheme 2, path B). The
former mechanistic path would generate an unsaturated
16 e- dihydride species “[PhBP3′]Ir(H)2” (II), which could
then oxidatively add an Si-H bond to give the observed
iridium silyl products (Scheme 2, path A). Elimination
of 1,3-COD from III would require that an open metal
coordination site become available, which could occur
via dissociation of a ligand arm, for example. By
comparison, the reaction of 1 with secondary silanes
proceeded via a path involving reductive elimination of
COE, which can be envisioned to occur via two possible
mechanisms (Scheme 2, paths B and C). One possibility
involves reductive elimination of COE from the Ir(III)
η1-allyl complex I to generate the η2-COE complex IV
(Scheme 2, path C). Reaction of IV with a silane Si-H
bond, followed by loss of COE, would generate the 16-
electron silyl intermediate V, which could then undergo
1,2-hydride migration to form the observed silylene
6 exhibit only one 31P{1H} NMR resonance, observed
at 7.53 and 7.85 ppm, respectively (benzene-d6, room
temperature). By 1H NMR spectroscopy, both complexes
exhibit an Ir-H resonance that integrates as three
2
hydrogens (for 5: -12.27 ppm, J HP ) 65 Hz; for 6:
2
-11.55 ppm, J HP ) 53 Hz), as well as an Si-H
1
resonance (for 5: 5.78 ppm, J SiH ) 193 Hz; for 6: 5.71
1
ppm, J SiH ) 245 Hz) that integrates as one hydrogen.
The 29Si NMR spectra for 5 and 6 contain a quartet at
-19.8 ppm (2J SiP ) 5 Hz) and -23.9 ppm (2J SiP ) 7 Hz),
respectively, consistent with coupling to three equiva-
lent phosphorus nuclei. This reaction was quantitative
1
by H and 31P NMR spectroscopy, and both complexes
were isolated in >90% yield. When the more sterically
hindered silane Mes2SiH2 (Mes ) 2,4,6-Me3C6H2) was
reacted with 3, little reaction of the silane was observed
in benzene-d6 solution at temperatures up to 100 °C.
Decomposition of 3 was observed under these conditions,
to give 1,3-COD and a mixture of unidentified iridium-
containing products.
The solid state structure of 5 was determined by X-ray
crystallography and is shown in Figure 1. Selected bond
lengths and angles are summarized in Table 1. The Si
atom is disordered over two positions, as is one of the
ethyl groups on silicon. All P-Ir-P angles are ap-
proximately 90°, while the P-Ir-Si angles range from
118° to 130°. Overall, the coordination geometry at
iridium is similar to that of the related complexes
[PhBP3]IrH3(SiMe3)3c and TpMe2IrH3(SiEt3)10,11 (TpMe2
) hydridotris(3,5-dimethylpyrazolyl)borate).
(11) A number of group 8 silyl-capped trihydride metal complexes
of the type MH3(SiR3)L3 have also been reported. Representative
examples include: (a) Knorr, M.; Gilvert, S.; Schubert, U. J . Orga-
nomet. Chem. 1988, 347, C17-C20. (b) Kono, H.; Wakao, N.; Ito, K.;
Nagai, Y. J . Organomet. Chem. 1977, 132, 53. (c) Procopio, L. J .; Berry,
D. H. J . Am. Chem. Soc. 1991, 113, 4039. (d) Buil, M.; Espinet, P.;
Esteruelas, M. A.; Lahoz, F. J .; Lledo´s, A.; Martinez-Ilarduya, J . M.;
Maseras, F.; Modrego, J .; On˜ate, E.; Oro, L. A.; Sola, E.; Valero, C.
Inorg. Chem. 1996, 35, 1250. (e) Rickard, C. E. F.; Roper, W. R.;
Woodgate, S. D.; Wright, L. J . J . Organomet. Chem. 2000, 609, 177.
(10) Gutierrez-Puebla, E.; Monge, A.; Paneque, M.; Poveda, M. L.;
Taboada, S.; Trujillo, M.; Carmona, E. J . Am. Chem. Soc. 1999, 121,
346.

New Zwitterionic Rhodium and Iridium Complexes
Organometallics, Vol. 23, No. 10, 2004 2491
Sch em e 2
product. Alternatively, as shown in path B, the η1-allyl
complex I could oxidatively add a silane Si-H bond to
give an Ir(V) intermediate (III). Reductive elimination
of COE from III followed by a 1,2-hydride migration
would give the final silylene product. However, these
two scenarios are further complicated in the case of 1
by the potential for rapid and reversible intramolecular
ortho-metalation of the P-phenyl groups on the PhBP3
ligand, which is implied by the facile incorporation of
deuterium into the ortho-positions of the P-phenyl
groups upon reaction of 1 with D2SiMes2.3f
ity of a fluxional process such as reversible elimination
of H2SiEt2. This possibility was confirmed by addition
of D2 (1 atm) to a benzene solution of 5, which resulted
in deuterium incorporation into both the Si-H and the
2
Ir-H positions (as indicated by H NMR spectroscopy)
after heating at 70 °C over the course of 14 h (eq 4).
It is interesting to note that although â-hydride
elimination was not observed in the reaction of 1 with
secondary silanes, evidence of â-hydride elimination
from 1 has been observed under certain other reaction
conditions. For example, analogous silyl-capped Ir spe-
cies [PhBP3]IrH3(SiR3) (R ) Et, Me) and 1,3-COD were
formed in the reaction of [PhBP3]IrH(η3-C8H13) with
tertiary silanes (HSiR3, where R ) Me, Et).3f Addition-
ally, [PhBP3]Ir(H)2(PMePh2) was formed, with concomi-
tant loss of 1,3-COD, upon addition of PMePh2 to
[PhBP3]IrH(η3-C8H13).6 Thus, while 1 can react via
either reductive elimination of COE or â-hydride elimi-
nation of 1,3-COD, replacing the P-phenyl substituents
with isopropyl groups appears to favor the latter path-
way and the formation of silyl-capped iridium trihydride
complexes in reactions of 3 with secondary silanes.
Reductive elimination from [PhBP3′]Ir complexes may
be disfavored as a result of a more electron-rich Ir center
relative to the analogous [PhBP3] complexes.
The related parent allyl complex, 4, did not react with
either Et2SiH2 or Ph2SiH2 under forcing conditions
(benzene-d6, 100 °C, 5 days). No decomposition of 4 was
observed under these reaction conditions. The inertness
of 4 is in agreement with the similar lack of reactivity
observed for its [PhBP3] counterpart, [PhBP3]IrH(η3-
C3H5),3f,6 and may reflect a reduced tendency for the
parent allyl ligand to undergo a change in hapticity (η3
to η1).
Elimination of H2SiEt2 from 5 was indeed observed upon
heating of a benzene-d6 solution of 3 (90 °C, 20 h) with
1 equiv of PMe3 (eq 5). This reaction resulted in the
quantitative formation of 1 equiv of H2SiEt2 and the
iridium phosphine complex [PhBP3′]Ir(H)2(PMe3) (7). On
the other hand, elimination of H2 from 5 would lead to
the coordinatively unsaturated 16 e- species [PhBP3′]-
IrH(SiHEt2) (V), which could then undergo a 1,2-hydride
shift from silicon to iridium to generate the correspond-
ing silylene complex, [PhBP3′]Ir(H)2(dSiEt2). However,
no direct evidence has been observed thus far for
reductive elimination of H2 from 5. No reaction was
observed upon heating of 5 alone or in the presence of
1 equiv of either tert-butylethylene or 1-hexene (benzene-
d6, 100 °C, 3 days). Similarly, no reaction was observed
upon photolysis of a benzene-d6 solution of 5 alone or
in the presence of 1 equiv of 1-hexene.
Syn th esis of [P h BP 3′]Ir (H)2L Com p lexes (L )
P Me3, P H2Cy, CO). In keeping with its propensity for
â-hydride elimination, compound 3 reacted with a
variety of neutral, two-electron-donor ligands to elimi-
The Si-H resonance observed in the room-tempera-
ture 1H NMR spectrum of the diethylsilyl iridium
trihydride complex (5) is broad, suggesting the possibil-

2492 Organometallics, Vol. 23, No. 10, 2004
Turculet et al.
Ta ble 2. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for 7‚(C7H8)0.5
(a) Bond Distances
Ir-P1
Ir-P2
2.303(1)
2.396(1)
Ir-P3
Ir-P4
2.376(1)
2.332(1)
(b) Bond Angles
P1-Ir-P2
P2-Ir-P3
P2-Ir-P4
P3-Ir-P4
101.24(5)
89.25(4)
91.56(5)
90.04(4)
P1-Ir-P3
P1-Ir-P4
H1-Ir-P3
H2-Ir-P2
105.23(4)
160.04(5)
80(1)
88(1)
Ir-P3 angles of 101.24(5)° and 105.23(4)°, respectively),
giving rise to a P1-Ir-P4 angle of 160.04(5)°. The Ir-P
distances reflect the greater trans influence of the
hydride ligands relative to the phosphine ligands, in
that the Ir-P2 and Ir-P3 distances (2.396(1) and 2.376-
(1) Å, respectively) are longer than the Ir-P1 and Ir-
P4 distances (2.303(1) and 2.332(1) Å, respectively).
F igu r e 2. Crystallographically determined structure of
[PhB(CH2PiPr2)3]Ir(H)2(PMe3)‚(C7H8)0.5 (7‚(C7H8)0.5) de-
picted with 50% thermal ellipsoids; all hydrogen atoms
have been omitted for clarity, with the exception of H1 and
H2.
nate 1,3-COD and form complexes of the type [PhBP3′]-
Ir(H)2L, where L ) PMe3, PH2Cy, or CO (eq 6). Heating
The reaction of CO (1 atm) with 3 in benzene solution
at 65 °C resulted in formation of [PhBP3′]Ir(H)2(CO) (9),
with the concomitant elimination of 1,3-COD. Com-
pound 9 was isolated in 97% yield and also exhibits Cs
symmetry in solution, consistent with a structure
similar to that observed for compounds 7 and 8. An
iridium hydride resonance is observed at -11.84 ppm
by 1H NMR spectroscopy (benzene-d6), and the 31P{1H}
NMR spectrum contains two resonances in a 1:2 ratio
2
at 11.47 ppm ([PhBP3′] trans to CO, J PP ) 24 Hz) and
2
3.75 ppm ([PhBP3′] cis to CO, J PP ) 24 Hz), respec-
tively. The IR spectrum of 9 (Nujol mull) contains a
characteristic CO stretch at 2003 cm-1. Additional
heating of 7 (90 °C, benzene-d6, 3 days) under an
atmosphere of CO did not lead to further reactivity.
of a benzene solution of 3 at 65 °C over the course of 16
h in the presence of 1 equiv of either PMe3 or PH2Cy
resulted in high-yield (>90%) formation of the phos-
phine complexes [PhBP3′]Ir(H)2(PMe3) (7) and [PhBP3′]-
Ir(H)2(PH2Cy) (8), respectively. The isolated complexes
exhibit Cs symmetry in solution, with a mirror plane
that contains the iridium center, a phosphorus donor
of the [PhBP3′] ligand, and the additional phosphine
ligand. Both 7 and 8 contain three sets of resonances
in their 31P{1H} NMR spectra, consistent with an A2-
MX pattern; the two [PhBP3′] phosphorus donors trans
to hydride ligands are observed as multiplets at -2.15
and -3.24 for 7 and 8, respectively, while the third
[PhBP3′] phosphine arm (doublet of triplets at 15.39
ppm (2J PPtrans ) 286 Hz, 2J PPcis ) 21 Hz) for 7 and 16.36
Compounds 7, 8, and 9 are analogous to the previ-
ously reported [PhBP3]Ir(H)2(PMePh2), which was pre-
pared by addition of 1 equiv of PMePh2 to 1, with similar
generation of 1,3-COD.6 The observation of 1,3-COD
suggests that these tris(phosphino)borate-Ir(H)2L com-
plexes are the products of â-hydride elimination from
3. Interestingly, the reaction of 1 with 1 equiv of PMe3
did not lead to formation of the â-hydride elimination
product [PhBP3]Ir(H)2(PMe3), but rather to the reduc-
tive elimination of COE and formation of {PhB[(CH2-
PPh2)2(CH2PPhC6H4)]}IrH(PMe3), the product of ortho-
metalation of a P-phenyl group. This suggests that in
the case of 1 ligand activation processes and concomi-
tant COE reductive elimination are competing with a
â-hydride elimination pathway.6 The reaction of 1 with
CO also led to reductive elimination of COE and to
formation of the Ir(I) complex [PhBP3]Ir(CO)2.6
2
ppm (2J PPtrans ) 284 Hz, J PPcis ) 20 Hz) for 8) and the
additional phosphine ligand are trans to one another
(doublet of triplets at -68.15 ppm (2J PPtrans ) 288 Hz,
2J PPcis ) 20 Hz) for 7 and a broad doublet at -64.06
ppm (2J PPtrans ) 287 Hz) for 8). The hydride ligands give
rise to a 1H NMR resonance at -13.50 ppm for 7 and
-13.25 ppm for 8 that integrates as two hydrogens for
each complex. Heating of benzene-d6 solutions of either
7 or 8 to 100 °C for up to 5 days did not result in any
further reaction. Photolysis of 7 (benzene-d6, 5 h) also
did not lead to any observed reaction.
The solid state structure of 7‚(C7H8)0.5 was determined
by X-ray crystallography and is shown in Figure 2.
Selected bond lengths and angles are summarized in
Table 2. Both hydride ligands were located, and their
positional coordinates were refined. The iridium center
exhibits distorted octahedral geometry, with the tripodal
phosphine ligand adopting the expected facial coordina-
tion featuring P-Ir-P angles of ca. 90°. The PMe3
ligand is significantly tilted away from the two bulky
isopropyl phosphine ligand arms (P1-Ir-P2 and P1-
In the absence of trapping ligands, thermolysis of 3
in benzene-d6 solvent (80 °C, 14 h) resulted in elimina-
tion of 1,3-COD, but no tractable Ir-H products were
formed. No precipitate indicative of a dimeric polyhy-
dride product6 was observed. Attempts to prepare poly-
hydride complexes by reaction of 3 with H2 (1 atm) in
benzene-d6 also did not lead to tractable Ir-H products,
suggesting that in the absence of a strongly coordinating
ligand, such as a phosphine or CO, the electronically
and coordinatively unsaturated intermediate “[PhBP3′]-
Ir(H)2” is highly reactive and does not form an isolable
dimeric species. By comparison, the highly insoluble
dihydride dimer {[PhBP3]Ir(H)(µ-H)}2 formed readily,
with concomitant elimination of COE, in the reaction
of 1 with H2.6

New Zwitterionic Rhodium and Iridium Complexes
Organometallics, Vol. 23, No. 10, 2004 2493
Ta ble 3. CO Str etch in g F r equ en cies for LRh (CO)2
Com p lexes in Hexa n es
Sch em e 3
complex
ν(CO), cm-1
[PhBP3′]Rh(CO)2
Cp*Rh(CO)2
2018, 1948
2026, 1964a
2054, 1981b
TpMe2Rh(CO)2
a
b
Ref 13. Ref 14.
Syn th esis a n d Ch a r a cter iza tion of [P h BP 3′]Rh -
(I) Com p lexes. The prominence of rhodium in E-H
bond activation chemistry2,12 prompted us to develop the
synthesis of tris(phosphino)borate-chelated rhodium
complexes. Accordingly, reactions of [PhBP3′]Li(THF)
with a number of Rh(I) starting materials were exam-
ined. It was found that [PhBP3′]Li(THF) reacted over
the course of a few minutes at room temperature with
(PMe3)4RhOTf to generate LiOTf, 2 equiv of PMe3, and
the 16 e- Rh(I) complex [κ2-PhB(CH2PiPr2)3]Rh(PMe3)2
F igu r e 3. Crystallographically determined structure of
[PhB(CH2PiPr2)3]Rh(CO)2 (11) depicted with 50% thermal
ellipsoids; all hydrogen atoms have been omitted for clarity.
1
(10, Scheme 3), which forms quantitatively by H and
Ta ble 4. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for 11
31P NMR spectroscopy (benzene-d6). Compound 10 was
isolated as an orange crystalline solid from pentane in
45% yield. The 31P{1H} NMR spectrum of 10 (benzene-
d6) exhibits three sets of resonances in the ratio 2:1:2;
the two [PhBP3′] phosphine donors chelating the rhod-
ium center are observed as a complex multiplet at 49.42
ppm, while the resonance corresponding to the two PMe3
ligands bound to rhodium is observed as a similar
complex multiplet at -23.14 ppm. By comparison, the
31P{1H} NMR resonance corresponding to the free arm
of [PhBP3′] is observed as a singlet at 1.93 ppm.
(a) Bond Distances
Rh-P1
Rh-P2
Rh-P3
2.3771(8)
2.4380(8)
2.3876(8)
Rh-C1
Rh-C2
1.889(3)
1.891(3)
(b) Bond Angles
P1-Rh-P2
P1-Rh-P3
P2-Rh-P3
C1-Rh-C2
C1-Rh-P1
89.36(3)
88.06(3)
90.27(3)
86.1(1)
C1-Rh-P2
C1-Rh-P3
C2-Rh-P1
C2-Rh-P2
C2-Rh-P3
103.48(10)
90.27(9)
89.95(10)
115.05(9)
154.58(10)
167.06(10)
shown in Table 3.13,14 The trend displayed by these
frequencies suggests that, to a general approximation,
[PhBP3′] is a more electron-donating ligand than both
TpMe2 and Cp*. A related cationic dicarbonyl complex,
[(triphos)Rh(CO)2][PF6], has CO stretching frequencies
of 2060 and 1995 cm-1 (measured in CH2Cl2),15 indicat-
ing that the zwitterionic complex 11 is a significantly
more electron-rich species.
The solid state structure of complex 11 was deter-
mined by X-ray crystallography and is shown in Figure
3. Selected bond lengths and angles are summarized in
Table 4. The metal center is five-coordinate, which is
consistent with increased Lewis acidity at rhodium
(relative to 10) caused by the electron-withdrawing
carbonyl ligands. The geometry at rhodium is that of a
distorted square-based pyramid, with two arms of the
[PhBP3′] ligand and two CO ligands occupying the basal
positions. Thus, P1 and C1 are trans to one another with
a P1-Rh-C1 angle of 167.06(10)°, and P3 and C2 are
also trans to each other with a somewhat compressed
P3-Rh-C2 angle of 154.58(10)°. The phosphine donors
trans to CO exhibit shorter Rh-P distances than the
apical phosphine (Rh-P1 2.3771(8) Å, Rh-P3 2.3876-
(8) Å, Rh-P2 2.4380(8) Å).
Compound 10 reacted instantly with CO (1 atm) at
room temperature in benzene-d6 solution to generate 2
equiv of PMe3 and [PhB(CH2PiPr2)3]Rh(CO)2 (11), in-
dicating that the PMe3 ligands of 10 are labile (Scheme
3). Compound 11 could also be prepared directly by the
reaction of [PhBP3′]Li(THF) with [(CO)2RhCl]2 (Scheme
1
3). Both reactions are quantitative by H and 31P NMR
spectroscopy. By the latter route, 11 was isolated in 64%
yield as a yellow crystalline solid. Unlike the bis-PMe3
complex (10), all three phosphine donors of the [PhBP3′]
ligand appear equivalent on the NMR time scale at room
temperature (benzene-d6 solution), with the 31P{1H}
NMR spectrum of 11 exhibiting only one resonance for
the rhodium-bound phosphorus atoms at δ 37.51 (1J PRh
) 97 Hz). Variable-temperature 31P NMR studies (tol-
uene-d8) indicate that this 3-fold symmetry is retained
at temperatures down to -80 °C. At room temperature,
the Rh-bound CO carbons are observed as a doublet of
quartets in the 13C{1H} NMR spectrum of 11 (benzene-
d6), consistent with coupling to three equivalent phos-
phorus nuclei (2J CP ) 23 Hz) and to the Rh center (1J CRh
) 56 Hz).
The IR stretching frequencies of the metal-bound
carbonyls for 11 and the analogous TpMe2 and Cp* (Cp*
) C5Me5) rhodium complexes (measured in hexanes) are
(13) Ghosh, C. K.; Graham, W. A. G. J . Am. Chem. Soc. 1987, 109,
4726.
(12) J ones, W. D.; Kakiuchi, F.; Murai, S. In Topics in Organome-
tallic Chemistry. Activation of Unreactive Bonds and Organic Synthesis;
Murai, S., Ed.; Springer: New York, 1999; Vol. 3, Chapters 2 and 3.
(14) J ohnston, G. G.; Baird, M. C. Organometallics 1989, 8, 1894.
(15) Ott, J .; Venanzi, L. M.; Ghilardi, C. A.; Midollini, S.; Orlandini,
A. J . Organomet. Chem. 1985, 291, 89.

2494 Organometallics, Vol. 23, No. 10, 2004
Turculet et al.
Sch em e 4
Complex 10 represents an interesting example of
bidentate coordination for a tris(phosphino)borate
ligand.16 Numerous examples of analogous complexes
featuring κ2 coordination of Tp-derived ligands have
been reported.17 For example, a series of related Rh(I)
bis(phosphine) complexes of the type TpiPrRhLL (LL )
dppm, dppe, dppp; TpiPr ) hydridotri(3,5-diisopropyl-
pyrazolyl)borate) were found to adopt square-planar
geometries in the solid state, featuring κ2-coordination
of the TpiPr ligand.17e In solution, studies have docu-
mented both κ2 and κ3 coordination for TpRRh(LL)
species, as well as cases of dynamic equilibria leading
to κ2-κ3 isomerism.17 The preference for bidentate or
tridentate coordination was found to depend on several
steric and electronic factors, including the nature of the
substituents on the pyrazolyl rings, the nature of the
donor ligands L, and the polarity of the solvent
employed.17c
Although low-temperature NMR experiments did not
provide evidence for κ2 coordination of the [PhBP3′]
ligand for complex 11, we pursued variable-temperature
NMR studies of 10 in order to determine if in this
instance κ2-κ3 interconversion is accessible on the NMR
time scale. While the 31P NMR spectrum of 10 is
consistent with κ2 coordination of the borate-derived
ligand at room temperature (vide supra), a different
species (12) was observed in toluene-d8 solution at 80
°C. Inspection of the NMR features observed for 12
indicate that this species is not simply the κ3-isomer of
10.
1H and 31P NMR spectroscopic features were observed
in the 20-80 °C temperature range in methylcyclohex-
ane-d14 solution, indicating that toluene activation is
likely not playing a role in the formation of 12.
To determine whether PMe3 dissociation from 10 was
indeed associated with the formation of 12, 2 equiv of
BPh3 was added to a benzene-d6 solution of 10.18
Precipitation of Ph3B(PMe3) was observed within 10
min, and the room-temperature 31P NMR spectrum of
the reaction mixture indicated resonances identical to
those observed for 12. Subsequent addition of 2 equiv
of PMe3 to this reaction mixture gave rise to the original
31P NMR spectrum observed for 10 at room tempera-
ture, confirming that 12 is indeed the product of PMe3
dissociation from 10. Furthermore, 12 could also be
prepared independently in the absence of PMe3 by the
reaction of 2 with [RhCl(C2H4)2]2 (Scheme 4).
In an NMR-tube reaction, addition of 0.5 equiv of
[RhCl(C2H4)2]2 to a benzene-d6 solution of 2 resulted in
an immediate color change from yellow to green-brown.
The 31P NMR spectrum of the reaction mixture indi-
cated complete consumption of 2 and formation of a new
Rh-containing product characterized by a 31P NMR
1
resonance at 59.40 ppm (2J RHP ) 126 Hz). The H NMR
spectrum of the reaction mixture did not exhibit reso-
nances that could be assigned to the Rh-bound ethylene,
although free ethylene was observed in solution. Over
the course of 1 h at room temperature, the color of the
reaction mixture changed from green-brown to orange.
The 31P NMR spectrum of the orange solution indicated
disappearance of the resonance at 59.40 ppm and
formation of a new Rh-containing species characterized
by 31P NMR features identical to those observed for 12.
This result confirms that the three phosphorus nuclei
observed in the 31P NMR spectrum of 12 are derived
only from the [PhBP3′] ligand.
The 31P NMR spectrum of 12 (generated in situ from
10 at 80 °C in toluene-d8) contains three multiplets at
76.99 (ddd, 2J PPcis ) 24 Hz, 2J PPcis ) 31 Hz, 1J RhP ) 171
Hz), 70.31 (ddd, 2J PPcis ) 24 Hz, 2J PPtrans ) 241 Hz, 1J RhP
2
2
) 187 Hz), and 13.92 (ddd, J PPcis ) 31 Hz, J PPtrans
)
1
241 Hz, J RhP ) 108 Hz) ppm in a 1:1:1 ratio. The
coupling constants measured for these three sets of
resonances are consistent with two cis-P-P couplings,
one trans-P-P coupling, and an additional coupling to
Rh for each multiplet. Coupling between these three
nuclei was further confirmed by 31P,31P-COSY NMR
spectroscopy (toluene-d8, 80 °C), which indicated off-
diagonal cross-peaks correlating all three multiplets.
Additionally, at 80 °C a broad resonance at -56 ppm
suggested that exchange between coordinated and free
PMe3 occurs on the NMR time scale. A 31P NMR
spectrum identical to that observed for 10 was obtained
upon cooling the solution back to room temperature,
indicating that the formation of 12 is reversible. At
intermediate temperatures, resonances corresponding
to both 10 and 12 were observed by 31P NMR spectro-
scopy with no indication of coalescence. Variable-tem-
perature 1H NMR studies of 10 (toluene-d8) provided
no evidence for the formation of rhodium hydrides in
the 20-80 °C temperature range. In addition, similar
On a preparative scale, a benzene solution of 2 and
0.5 equiv of [RhCl(C2H4)2]2 was allowed to stir at room
temperature for 1 h, after which the volatile components
of the reaction mixture were removed in vacuo. Crystal-
lization from Et2O afforded 12 as a red-orange crystal-
(16) Peters and co-workers have recently reported examples of
transition metal complexes featuring bis(phosphino)borate ligands: (a)
Thomas, J . C.; Peters, J . C. J . Am. Chem. Soc. 2001, 123, 5000. (b)
Lu, C. C.; Peters, J . C. J . Am. Chem. Soc. 2002, 124, 5272. (c) Thomas,
J . C.; Peters, J . C. J . Am. Chem. Soc. 2003, 125, 8870. (d) Thomas, J .
C.; Peters, J . C. Inorg. Chem. 2003, 42, 5055. (e) Betley, T. A.; Peters,
J . C. Angew. Chem., Int. Ed. 2003, 42, 2385.
(17) (a) Trofimenko, S. Chem. Rev. 1993, 93, 943. (b) Slugovc, C.;
Padilla-Martinez, I.; Sirol, S.; Carmona, E. Coord. Chem. Rev. 2001,
213, 129. (c) Bucher, U. E.; Currao, A.; Nesper, R.; Ru¨egger, H.;
Venanzi, L.; Younger, E. Inorg. Chem. 1995, 34, 66. (d) Oldham, W.
J ., J r.; Heinekey, D. M. Organometallics 1997, 16, 467. (e) Ohta, K.;
Hashimoto, M.; Takahashi, Y.; Hikichi, S.; Akita, M.; Moro-oka, Y.
Organometallics 1999, 18, 3234. (f) Kla¨ui, W.; Schramm, D.; Peters,
W.; Rheinwald, G.; Lang, H. Eur. J . Inorg. Chem. 2001, 1415. (g) Cˆırcu,
V.; Fernandes, M. A.; Carlton, L. Inorg. Chem. 2002, 41, 3859.
(18) Dioumaev, V. K.; Ploessl, K.; Carroll, P. J .; Berry, D. H.
Organometallics 2000, 19, 3374.

New Zwitterionic Rhodium and Iridium Complexes
Organometallics, Vol. 23, No. 10, 2004 2495
Ta ble 5. Selected Bon d Dista n ces(Å) a n d An gles
(d eg) for 12
(a) Bond Distances
Rh-P1
Rh-P2
Rh-P3
2.239(2)
2.240(2)
2.225(2)
Rh-C1
P1-C1
2.187(8)
1.760(8)
(b) Bond Angles
P1-Rh-P2
P1-Rh-P3
P1-Rh-C1
117.46(7)
144.56(8)
46.8(2)
P2-Rh-P3
C1-Rh-P2
C1-Rh-P3
97.95(7)
164.0(2)
97.7(2)
three-membered Rh-P-C ring. The Rh center is four-
coordinate and exhibits a distorted square planar
geometry. Due to the constrained nature of the Rh-
P1-C1 ring, the P1-Rh-C1 angle is compressed to
46.8(2)°. Accordingly, the remaining angles about the
Rh center are larger than expected for an ideal square
planar geometry (P1-Rh-P2 117.46(7)°, P2-Rh-P3
97.95(7)°, and C1-Rh-P3 97.7(2)°). The boron atom is
three-coordinate and planar, with the sum of the three
C-B-C angles summing to 359.8°. The Rh-B distance
of 3.83 Å is well out of the range for a Rh-B interac-
tion.22
The reaction of 2 with 0.5 equiv of [(COE)2RhCl]2 in
benzene-d6 solvent does not lead to formation of a Rh
analogue of 3. Rather, a mixture of 12 and additional
unidentified Rh-containing products was observed by 1H
and 31P NMR spectroscopy, with no indication for Rh-H
formation.
Rea ctivity of [P h BP 3′]Rh (I) Com p lexes. Evidence
for the facile dissociation of PMe3 ligands from the
coordinatively unsaturated Rh(I) center of complex 10
has been demonstrated by the ready conversion of 10
to the dicarbonyl complex, 11, as well as by the observa-
tion of thermally induced ligand B-C bond activation
leading to 12. The lability of the PMe3 ligands suggests
that, under suitable conditions, 10 may undergo facile
oxidative addition. However, reactions of 10 with polar
substrates such as MeI or Me3SiOTf in either benzene-
d6 or methylene chloride-d2 solvents did not lead to
formation of the oxidative addition products, possibly
due to preferential reaction of these substrates with the
free -CH2PiPr2 arm of the [PhBP3′] ligand.
F igu r e 4. Crystallographically determined structure of
[PhB(CH2PiPr2)2]RhCH2PiPr2 (12) depicted with 50% ther-
mal ellipsoids; all hydrogen atoms have been omitted for
clarity, with the exception of H1 and H2.
line solid (87% yield) that exhibits 31P NMR spectro-
scopic characteristics identical to those observed when
the complex was generated in situ. The 1H NMR
spectrum of isolated 12 (benzene-d6) shows no evidence
for a rhodium hydride; however, an unusual doublet is
observed at -0.11 ppm (J ) 10 Hz). This resonance
integrates as two hydrogens and is correlated to a 13C
NMR resonance at -19.9 ppm according to 1H,13C-
HMQC spectroscopy, suggesting the possibility of a Rh-
bound methylene group. Further insight into the struc-
ture of 12 was provided by its 11B NMR spectrum
(benzene-d6), which features a broad resonance at 74.9
ppm. The broad appearance of this resonance and its
downfield shift correspond to a three-coordinate boron
center, rather than the expected four-coordinate borate
of the [PhBP3′] ligand.19 By comparison, the 11B NMR
resonance for 10 (benzene-d6) is observed as a sharp
singlet at -16.16 ppm. These results suggest that 12 is
the product of an unusual migration of a ligand CH2
group from boron to rhodium (Scheme 4).20,21 Remark-
ably, this migration appears to be reversible in the
presence of PMe3, as observed in variable-temperature
NMR experiments with 10 (Scheme 4). This was con-
firmed by addition of 2 equiv of PMe3 to a benzene-d6
solution of isolated 12, which resulted in formation of
10. Thus, it appears that under certain reaction condi-
tions 12 functions effectively as a resting state for the
“[PhBP3′]Rh” fragment.
By comparison, 10 reacted with H2 (1 atm) at room
temperature to yield the oxidative addition product
[PhBP3′]Rh(H)2PMe3 (13) with loss of 1 equiv of PMe3
(Scheme 5). Attempts to monitor this reaction by NMR
spectroscopy (benzene-d6) were hindered by the presence
of 1 equiv of free PMe3 in solution, which appears to
1
exchange with coordinated PMe3, leading to broad H
and 31P NMR features. Compound 13 was isolated as
an off-white solid in 76% yield, and as in the case of
the Ir(III) complexes 7, 8, and 9, it exhibits Cs symmetry
in solution. The 31P{1H} NMR spectrum of 13 (benzene-
d6) contains three sets of resonances in a 1:2:1 ratio at
56.17 (ddt, [PhBP3′] trans to PMe3, J PPtrans ) 332 Hz,
J PPcis ) 25 Hz, J PRh ) 97 Hz), 32.00 (m, [PhBP3′] cis to
PMe3), and -22.06 (ddt, PMe3, J PPtrans ) 330 Hz, J PPcis
) 24 Hz, J PRh ) 100 Hz) ppm, respectively. A Rh-H
resonance integrating to two hydrogens is observed at
The structure of complex 12 was confirmed by X-ray
crystallography and is shown in Figure 4. Selected bond
lengths and angles are summarized in Table 5. The
complex is monomeric in the solid state and features a
(19) Kidd, R. G. NMR of Newly Accessible Nuclei; Academic Press:
New York, 1983; Vol. 2.
(20) A related example involving alkylation of a nickel center by a
tris((tert-butylthio)methyl)borate ligand has been reported: Schleber,
P. J .; Mandimutsira, B. S.; Riordan, C. G.; Liable-Sands, L. M.;
Incarvito, C. D.; Rheingold, A. L. J . Am. Chem. Soc. 2001, 123, 331.
The alkylated nickel product retained an intact tris((tert-butylthio)-
methyl)borate ligand set.
1
-11.08 ppm by H NMR spectroscopy (benzene-d6).
(21) Examples of intramolecular B-H bond activation in poly-
(pyrazolyl)borate metal chemistry have been reported: (a) Hill, A. F.;
Owen, G. R.; White, A. J . P.; Williams, D. J . Angew. Chem., Int. Ed.
1999, 38, 2759. (b) Yeston, J . S.; Bergman, R. G. Organometallics 2000,
19, 2947, and references therein.
(22) The sum of the van der Waals radii for Rh and B is 3.5 Å. For
comparison, the Rh-B distance for the Rh(I) σ-boryl complex (PMe3)4-
Rh(B(cat)) (cat ) 1,2-O2C6H4) has been reported as 2.047(2) Å: Dai,
C.; Stringer, G.; Marder, T. B.; Scott, A. J .; Clegg, W.; Norman, N. C.
Inorg. Chem. 1997, 36, 272.

2496 Organometallics, Vol. 23, No. 10, 2004
Turculet et al.
Sch em e 5
F igu r e 5. Crystallographically determined structure of
[PhB(CH2PiPr2)3]Rh(H)2PMe3 (13) depicted with 50% ther-
mal ellipsoids; all hydrogen atoms have been omitted for
clarity.
F igu r e 6. Crystallographically determined structure of
[PhB(CH2PiPr2)2]Rh(H)2(SiHPh2)(PMe3) (14) depicted with
50% thermal ellipsoids; all hydrogen atoms have been
omitted for clarity, with the exception of H1.
Ta ble 6. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for 13
(a) Bond Distances
Rh-P1
Rh-P2
2.377(3)
2.400(2)
Rh-P3
2.314(2)
2.301(2)
Ta ble 7. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for 14
Rh-P4
(b) Bond Angles
(a) Bond Distances
P1-Rh-P2
P1-Rh-P3
P1-Rh-P4
89.15(8)
90.13(9)
109.46(9)
P2-Rh-P3
P2-Rh-P4
P3-Rh-P4
91.60(8)
101.62(8)
156.28(9)
Rh-P1
Rh-P2
2.355(2)
2.353(2)
Rh-P3
Rh-Si1
2.341(2)
2.356(2)
(b) Bond Angles
The solid state structure of 13 was determined by
X-ray crystallography and is shown in Figure 5. Selected
bond lengths and angles are summarized in Table 6.
The metrical parameters for 13 mirror those obtained
for the Ir analogue, 7. The tripodal phosphine ligand
adopts the expected facial coordination featuring P-
Rh-P angles of ca. 90°. As in the structure of 7, the
PMe3 ligand is significantly tilted away from the two
bulky isopropyl phosphine ligand arms (P4-Rh-P1 and
P4-Rh-P2 angles of 109.46(9)° and 101.62(8)°, respec-
tively), resulting in a P4-Rh-P3 angle of 156.28(9)°.
Although the position of the hydride ligands was not
determined, their approximate location is indicated by
the open coordination sites trans to P1 and P2.
P1-Rh-P2
P1-Rh-P3
110.41(5)
104.52(5)
P2-Rh-P3
Si1-Rh-P3
94.90(5)
155.27(6)
sets of resonances in a 2:1 ratio. Two overlapping
multiplets integrating as two phosphorus nuclei are
observed at 38.59 ppm, while a third multiplet integrat-
ing as one phosphorus is observed at -30.85 ppm (1J PRh
) 99 Hz). Characteristic features of the 1H NMR
spectrum of 14 include a broad Si-H resonance at 5.81
ppm (1J SiH ) 152 Hz), as well as two Rh-H resonances
at -10.25 and -11.00 ppm integrating as one hydrogen
each. The 11B NMR spectrum of 14 contains a broad
downfield-shifted resonance at 74.6 ppm, indicating that
the ligand boron is three-coordinate.19 These results are
consistent with cleavage of a B-C bond in the ligand
backbone and formation of a bis(phosphino)borane
rhodium dihydride silyl complex that contains an ad-
ditional phosphine donor (Scheme 5).
The structure of 14 was confirmed by X-ray crystal-
lography and is shown in Figure 6. Selected bond
lengths and angles are summarized in Table 7. A
-CH2PiPr2 ligand arm has been lost, and as a result,
the boron atom is three-coordinate and planar, with the
sum of the three C-B-C angles totaling 359.9°. The
Rh-B distance is 3.94 Å, indicating that no bonding
interaction exists between these two atoms. The Rh
center is coordinated to the two phosphine arms of the
The reaction of 10 with secondary silanes (H2SiR2,
with R ) Et, Ph) in benzene-d6 solvent at room tem-
perature led to broad 1H and 31P NMR features, as
previously observed in the reaction of 10 with H2. A
1
broad resonance was observed at -10.6 ppm in the H
NMR spectrum of the reaction mixture, consistent with
the formation of a rhodium hydride species. On a
preparative scale, the reaction of 10 with H2SiPh2 was
allowed to stir at room temperature for 18 h, after which
the volatile components of the reaction mixture were
removed in vacuo. Upon crystallization from Et2O, a
yellow crystalline solid was isolated in <50% yield (14).
The 31P NMR spectrum of 14 (benzene-d6) contains two

New Zwitterionic Rhodium and Iridium Complexes
Organometallics, Vol. 23, No. 10, 2004 2497
1
bis(phosphino)borane ligand, as well as to a diphenyl-
silyl group and a PMe3 ligand. Although two rhodium
hydride ligands are observed in solution by 1H NMR
spectroscopy, the positions of these two ligands were not
determined in the solid state structure; their ap-
proximate location is indicated by the two empty
coordination sites trans to P1 and P2.
The isolation of complex 14 from the reaction of 10
with H2SiPh2 indicates that under some reaction condi-
tions the Rh-mediated B-C bond cleavage of the
[PhBP3′] ligand backbone may provide a facile decom-
position pathway for [PhBP3′]Rh complexes. Thus, while
10 appears stable indefinitely in benzene solution at
room temperature, heating at 90 °C for 1 h resulted in
decomposition to several unidentified Rh-containing
species and the formation of MePiPr2 (by 1H and 31P
NMR spectroscopy).
containing products was observed by H and 31P NMR
spectroscopy.
The reaction of 11 with secondary silanes (H2SiR2,
with R ) Et, Ph) in the presence of 1 equiv of Me3NO
(benzene-d6, 65 °C) leads to consumption of the silane
(after 1 week for R ) Ph, 12 h for R ) Et) and ca. 60%
conversion to the dihydride carbonyl complex 15. This
reaction appears to be complicated by the possibility of
direct or Rh-mediated reactions of the silane with Me3-
NO,23 as evidence for numerous silicon-containing prod-
ucts is observed by 29Si NMR analysis of the reaction
mixture. The 29Si NMR resonances observed fall in the
10 to -40 ppm region of the spectrum.
Con clu d in g Rem a r k s
This contribution describes the synthesis, character-
ization, and reactivity of zwitterionic rhodium and
iridium complexes featuring the tris(phosphino)borate
ligand [PhB(CH2PiPr2)3]- ([PhBP3′]-). The iridium allyl
complex [PhBP3′]IrH(η3-C8H13) (3) provided a conve-
nient entry to the chemistry of [PhBP3′]Ir. Unlike its
analogue [PhBP3]IrH(η3-C8H13) (1) (PhBP3 ) PhB(CH2-
PPh2)3), which features P-phenyl substituents, 3 does
not mediate “silylene extrusion” reactions; rather, the
chemistry of 3 is dominated by facile â-hydride elimina-
tion of 1,3-cyclooctadiene. Thus, in reactions with
secondary silanes, while 1 was found to reductively
eliminate cyclooctene and give silylene dihydride com-
plexes of the type [PhBP3]Ir(H)2(dSiR2), reactions of
compound 3 produced silyl-capped trihydride complexes
of the type [PhBP3′]Ir(H)3(SiHR2) with concomitant
elimination of 1,3-cyclooctadiene. While â-hydride elimi-
nation of 1,3-COD from 1 has been observed under
certain reaction conditions, this complex serves as a
source of “[PhBP3]Ir” in its reactions with secondary
silanes. By comparison, 3 has been found to react
exclusively as a source of “[PhBP3′]IrH2”. The observed
preference for â-hydride elimination from 3 over reduc-
tive elimination may be attributed to the electron-rich
nature of the iridium center, which should be less prone
to undergo reduction processes.
The dicarbonyl complex 11 did not react appreciably
with H2 (1 atm, benzene-d6) in the 20-70 °C tempera-
ture range or by photolysis (4 h). Heating of the reaction
mixture at 90 °C over the course of 12 h resulted in
decomposition to unidentified Rh-containing products.
The 1H NMR spectrum of the decomposition mixture
featured a broad Rh-H resonance at -8.9 ppm. Evi-
dence for the formation of MePiPr2 was also observed
under these conditions (by 1H and 31P NMR spectro-
scopy). The reaction of 11 with 1 equiv of H2SiPh2
(benzene-d6) was similarly sluggish. Heating of the
reaction mixture at 95 °C for 14 h resulted in a small
amount of decomposition (<10%) of the dicarbonyl
complex. Evidence was observed for the concomitant
1
formation of both MePiPr2 and Ph2HSiCH2PiPr2 (by H
and 31P NMR spectroscopy). No evidence of a rhodium
hydride complex was observed by 1H NMR spectroscopy.
Photolysis of the reaction mixture (6 h) also resulted in
minor decomposition of 11 (<10%) and trace formation
1
of MePiPr2 and Ph2HSiCH2PiPr2 (by H and 31P NMR
spectroscopy). Two rhodium hydride resonances were
1
observed at -8.6 and -9.0 ppm in the H NMR of this
decomposition product mixture. In the absence of a
secondary silane, photolysis of 11 in benzene-d6 solvent
for 4 h did not lead to any observed reaction.
The [PhBP3′]IrH2 fragment was readily trapped by
the reaction of 3 with neutral donor ligands such as
phosphines and CO. Interestingly, while previous re-
sults indicate that the [PhBP3]IrH2 fragment dimerizes
to form the isolable complex {[PhBP3]Ir(H)(µ-H)}2,
[PhBP3′]IrH2 does not appear to form an isolable dimer,
suggesting that the P-isopropyl-substituted ligand is
more sterically demanding than the P-phenyl analogue.
The [PhBP3′] ligand also provided access to the first
reported examples of tris(phosphino)borate-supported
rhodium complexes. Although rhodium allyl complexes
analogous to 3 do not appear to be accessible by
comparable synthetic routes, the Rh(I) complexes [κ2-
PhBP3′]Rh(PMe3)2 (10) and [PhBP3′]Rh(CO)2 were readily
prepared and isolated. Complex 10 is an unusual
example of κ2-coordination of a tris(phosphino)borate
ligand. By comparison, the dicarbonyl complex 11 is five-
coordinate in the solid state.
Although the CO ligands of 11 proved difficult to
displace thermally and photochemically, it was possible
to chemically remove CO from 11 via reaction with Me3-
NO. Thus, in the presence of 1 equiv of Me3NO, 11
reacted with H2 (1 atm) in benzene solvent at 65 °C to
form the dihydride carbonyl complex 15, with loss of
Me3N (eq 7). The formation of 15 was quantitative by
1H and 31P NMR spectroscopy. Complex 15 exhibits
spectroscopic features consistent with Cs symmetry in
solution, as previously observed for the analogous Ir
(23) Hydrosilanes are known to reduce sulfoxides and phosphine
oxides: (a) Fritzsche, H.; Hasserodt, U.; Korte, F. Chem. Ber. 1964,
97, 1988. (b) Naumann, K.; Zon, G.; Mislow, K. J . Am. Chem. Soc. 1969,
91, 2788. (c) Coumbe, T.; Lawrence, N. J .; Muhammad, F. Tetrahedron
Lett. 1994, 35, 625. (d) Horner, L.; Balzer, W. D. Tetrahedron Lett.
1965, 1157.
1
complex, 9. A Rh-H resonance is observed by H NMR
spectroscopy at -8.99 ppm. In the absence of H2, 11 did
not react with Me3NO in benzene solvent at 65 °C. At
higher temperatures, decomposition to unidentified Rh-

2498 Organometallics, Vol. 23, No. 10, 2004
Turculet et al.
added to a stirred, room-temperature suspension of [Ir-
(COE)2Cl]2 (0.20 g, 0.22 mmol) in ca. 5 mL of benzene. The
reaction mixture was allowed to stir at ambient temperature
for 1 h. The volatile components of the reaction mixture were
removed under vacuum, and the remaining yellow-orange
residue was extracted into ca. 10 mL of benzene and filtered
through Celite. The volatile material was removed under
vacuum to afford 3 (0.32 g, 91%) as an analytically pure off-
The CO ligands in complex 11 bind tightly to the
electron-rich metal center and are not readily displaced
thermally or photochemically. A comparison of the CO
stretching frequencies of 11 with the related dicarbonyl
complexes TpMe2Rh(CO)2 and Cp*Rh(CO)2 suggests that
[PhBP3′] is a stronger electron donor than both TpMe2
and Cp*. By comparison, the PMe3 ligands in complex
10 are labile in solution, and at temperatures above 20
°C evidence for an unusual dynamic process involving
reversible dissociation of PMe3 and migration of a ligand
-CH2PiPr2 group from B to Rh was observed. The
product of this bond migration, [PhB(CH2PiPr2)2]-
1
white solid. H NMR (400 MHz, benzene-d6): δ 7.97 (br m, 2
3
H, o-Harom), 7.59 (t, 2 H, m-Harom, J HH ) 7 Hz), 7.34 (t, 1 H,
3
p-Harom, J HH ) 7 Hz), 5.08 (m, 1 H, CH2CHCHCHCH2), 3.77
(m, 2 H, CH2CHCHCHCH2), 2.55 (br m, 4 H, CH2), 2.20 (m, 2
H, PCHMe2), 1.83 (m, 4 H, PCHMe2), 1.58-1.44 (br m, 6 H,
CH2), 1.30-1.15 (m, 24 H, PCHMe2), 0.98-0.90 (m, 16 H,
PCHMe2 + BCH2P), 0.67 (br m, 2 H, BCH2P), -15.30 (dt, 1 H,
RhCH2PiPr2 (12), can be isolated in high yield from the
reaction of 2 with 0.5 equiv of [RhCl(C2H4)2]2. This
ligand B-C bond activation appears to be a facile
reaction pathway for [PhBP3′]Rh complexes. Perhaps
most surprising is the observation that this bond
migration is reversible, depending on the reaction
conditions employed, which suggests that 12 may be a
viable masked source of “[PhBP3′]Rh”.
2
2
IrH, J HPtrans ) 120 Hz J HPcis ) 17 Hz). 13C{1H} NMR (125.8
MHz, benzene-d6): δ 132.1 (Carom), 127.6 (Carom), 123.8 (Carom),
86.0 (CH2CHCHCHCH2), 48.6 (CH2CHCHCHCH2), 38.8 (CH2-
CHCHCHCH2), 35.6 (m, PCHMe2), 34.2 (m, PCHMe2), 30.8
(CH2CHCHCHCH2), 30.0 (m, PCHMe2), 25.7 (CH2CHCHC-
HCH2), 20.7-18.7 (PCHMe2), 15.2 (br, BCH2P), 11.9 (br,
BCH2P). 31P{1H} NMR (162 MHz, benzene-d6): δ 7.52 (d, 2 P,
[PhBP3′] cis to H, 2J PP ) 21 Hz), -18.08 (t, 1 P, [PhBP3′] trans
2
to H, J PP ) 21 Hz). 11B NMR (160.46 MHz, benzene-d6): δ
-12.83. IR (cm-1): 2152 m (IrH). Anal. Calcd for C35H67BP3-
Exp er im en ta l Section
Ir: C, 53.63; H, 8.62. Found: C, 53.22; H, 8.89.
Gen er a l P r oced u r es. All experiments were conducted
under nitrogen in a Vacuum Atmospheres drybox or using
standard Schlenk techniques. Dry, oxygen-free solvents were
used unless otherwise indicated. Pentane was pretreated with
concentrated H2SO4, 0.5 N KMnO4 in 3 M H2SO4, and
saturated NaHCO3 solution, then dried over MgSO4, stored
over 4 Å molecular sieves, and distilled from potassium/
benzophenone ketyl under a nitrogen atmosphere. Diethyl
ether and THF were distilled under nitrogen from sodium/
benzophenone ketyl. Toluene and benzene were pretreated
with concentrated H2SO4, followed by saturated NaHCO3
solution, and then dried over MgSO4. Toluene was then
distilled from molten sodium under a nitrogen atmosphere.
Benzene was distilled from molten potassium under a nitrogen
atmosphere. Benzene-d6 and toluene-d8 were degassed and
stored over 4 Å molecular sieves. All NMR data were recorded
at room temperature, unless otherwise noted, using either a
Bruker AMX, AM, or DRX spectrometer. 1H NMR spectra were
referenced internally by the residual solvent proton signal
relative to tetramethylsilane. 13C NMR spectra were referenced
internally by the 13C signal of the NMR solvent relative to
tetramethylsilane. 29Si NMR spectra were referenced relative
to an external standard of tetramethylsilane. 11B NMR spectra
were referenced using a BF3‚OEt2 external standard. 31P NMR
spectra were referenced relative to an 85% aqueous H3PO4
external standard. In some cases, distortionless enhancement
by polarization transfer (DEPT) was used to assign the 13C
NMR resonances as CH3, CH2, CH, or C. Heteronuclear
multiple quantum coherence (HMQC) was used to identify 1H,
13C coupling. Infrared spectra were recorded as Nujol mulls
between NaCl plates using a Mattson FTIR spectrometer at a
resolution of 4 cm-1. Elemental analyses were performed by
the College of Chemistry Microanalytical Laboratory at the
University of California, Berkeley. Unless otherwise specified,
all reagents were purchased from commercial suppliers and
used without further purification. The compounds [Ir(COE)2-
[P h B(CH2P iP r 2)3]Ir (H)(η3-C3H5) (4). A thick-walled, 500
mL flask fitted with a PTFE stopcock was charged with [Ir-
(COE)2Cl]2 (0.49 g, 0.55 mmol), a magnetic stirbar, and ca. 100
mL of THF. The slurry was cooled to -78 °C, and the
headspace was evacuated. Propene (1 atm) was introduced and
allowed to saturate the solution for ca. 2 min, at which point
the flask was sealed and cooled with liquid nitrogen to give a
frozen yellow solution. A solution of [PhB(CH2PiPr2)3]Li(THF)
(0.50 g, 1.09 mmol) in 50 mL of THF was added to the frozen
solution, which was then allowed to warm to ambient tem-
perature and was stirred for 24 h. The volatile material was
removed under vacuum, and the solid residue was extracted
into ca. 10 mL of toluene. The toluene extracts were filtered
through Celite and concentrated to ca. 3 mL. Storage of this
solution at -35 °C for 24 h afforded 4 (0.52 g, 67%) as an off-
white crystalline solid. 1H NMR (500 MHz, benzene-d6): δ 7.97
3
(br m, 2 H, o-Harom), 7.58 (t, 2 H, m-Harom, J HH ) 8 Hz), 7.33
3
(t, 1 H, p-Harom, J HH ) 8 Hz), 4.51 (m, 1 H, CH2CHCH2), 2.72
(m, 2 H, CH2), 2.65 (m, 2 H, CH2), 2.15 (m, 2 H, PCHMe2),
1.80 (m, 4 H, PCHMe2), 1.32-1.09 (m, 24 H, PCHMe2), 0.98
(m, 4 H, BCH2P), 0.94-0.83 (m, 12 H, PCHMe2), 0.70 (m, 2 H,
2
2
BCH2P), -15.60 (dt, 1 H, IrH, J PHtrans ) 130 Hz, J PHcis ) 17
Hz). 13C{1H} NMR (125.8 MHz, benzene-d6): δ 132.1 (Carom),
123.9 (Carom), 85.5 (CH(CH2)2), 36.3 (m, PCHMe2), 34.4 (m,
PCHMe2), 30.3 (m, PCHMe2), 26.5 (CH(CH2)2), 21.3 (PCHMe2),
20.3 (PCHMe2), 20.2 (PCHMe2), 20.1 (PCHMe2), 19.7 (PCHMe2),
18.3 (PCHMe2), 15.7 (br, BCH2P), 11.5 (br, BCH2P). 31P{1H}
NMR (162 MHz, benzene-d6): δ 9.53 (d, 2 P, [PhBP3′] cis to
2
H, J PP ) 21 Hz), -20.15 (br m, 1 P, [PhBP3′] trans to H). 11B
NMR (160.46 MHz, benzene-d6): δ -12.31. IR (cm-1): 2100
m (IrH). Anal. Calcd for C30H59BP3Ir: C, 50.34; H, 8.31.
Found: C, 50.52; H, 8.58.
[P h B(CH2P iP r 2)3]Ir H3(SiHEt2) (5). Neat H2SiEt2 (0.023
g, 33 µL, 0.26 mmol) was added to a room-temperature benzene
solution (ca. 10 mL) of 3 (0.20 g, 0.26 mmol). The reaction
mixture was heated at 95 °C over the course of 14 h. The
resulting orange solution was filtered through Celite, and the
solvent was removed under vacuum to afford 5 as an off-white
solid (0.19 g, 96%). 1H NMR (400 MHz, benzene-d6): δ 7.92
Cl]2,24 (PMe3)4RhOTf,25 [Rh(C2H4)2Cl]2,26 and [Rh(CO)2Cl]2
26
were prepared according to literature procedures.
[P h B(CH2P iP r 2)3]Ir (H)(η3-C8H13) (3). A benzene (5 mL)
solution of [PhB(CH2PiPr2)3]Li(THF) (0.25 g, 0.45 mmol) was
3
(br m, 2 H, o-Harom), 7.59 (t, 2 H, m-Harom, J HH ) 8 Hz), 7.35
3
1
(24) Herde, J . L.; Lambert, J . C.; Senoff, C. V. Inorg. Synth. 1974,
15, 18.
(25) (a) Thorn, D. L. Organometallics 1982, 1, 197. (b) Thorn, D. L.
Organometallics 1985, 4, 192. (c) Aizenberg, M.; Milstein, D. J . Chem.
Soc., Chem. Commun. 1994, 411.
(t, 1 H, p-Harom, J HH ) 7 Hz), 5.78 (br s, 1 H, SiHEt2, J SiH )
193 Hz), 1.74 (m, 6 H, PCHMe2), 1.34-1.23 (m, 10 H, SiEt2),
1.16 (m, 18 H, PCHMe2), 1.05 (m, 18 H, PCHMe2), 0.87 (br m,
6 H, BCH2P), -12.27 (m, 3 H, IrH). 13C{1H} NMR (100.6 MHz,
benzene-d6): δ 132.0 (Carom), 127.7 (Carom), 124.1 (Carom), 32.3
(26) Cramer, R. Inorg. Synth. 1974, 15, 14.

New Zwitterionic Rhodium and Iridium Complexes
Organometallics, Vol. 23, No. 10, 2004 2499
(m, PCHMe2), 20.0 (PCHMe2), 18.9 (PCHMe2), 16.9 (SiCH2-
CH3), 13.4 (br m, BCH2P), 10.6 (SiCH2CH3). 31P{1H} NMR (162
MHz, benzene-d6): δ 7.53 (s). 29Si NMR (99.36 MHz, benzene-
m, 2 H, BCH2P), -13.25 (m, 2 H, Ir-H). 13C{1H} NMR (125.8
MHz): δ 132.2 (Carom), 127.6 (Carom), 123.8 (Carom), 38.5 (m,
PCy), 34.5 (m, PCHMe2), 33.6 (PCy), 32.0 (m, PCHMe2), 31.6
(m, PCHMe2), 27.2 (PCy), 26.4 (PCy), 21.4 (PCHMe2), 20.7
(PCHMe2), 19.6 (PCHMe2), 18.8 (PCHMe2), 18.7 (PCHMe2),
14.7 (br, BCH2P). 31P{1H} NMR (202 MHz, benzene-d6): δ
2
d6): δ -19.8 (br q, J SiP ) 5 Hz). 11B NMR (160.46 MHz,
benzene-d6): δ -11.48. IR (cm-1): 2070 (br, IrH), 2028 (SiH).
Anal. Calcd for C31H67BP3SiIr: C, 48.74; H, 8.84. Found: C,
48.73; H, 8.67.
2
16.36 (dt, 1 P, [PhBP3′] trans to PH2Cy, J PPtrans ) 283 Hz,
2J PPcis ) 20 Hz), -3.24 (m, 2 P, [PhBP3′] cis to PH2Cy), -64.06
(br d, 1 P, IrPH2Cy, 2J PPtrans ) 287 Hz). 11B NMR (160.46 MHz,
benzene-d6): δ -11.61. IR (cm-1): 2313 (PH), 2292 (PH), 2046
(IrH). Anal. Calcd for C33H68BP4Ir: C, 50.06; H, 8.66. Found:
C, 49.96; H, 8.76.
[P h B(CH2P iP r 2)3]Ir H3(SiHP h 2) (6). Neat H2SiPh2 (0.047
g, 47 µL, 0.26 mmol) was added to a room-temperature benzene
solution (ca. 10 mL) of 3 (0.20 g, 0.26 mmol). The reaction
mixture was heated at 65 °C over the course of 14 h. The
resulting orange solution was filtered through Celite, and the
solvent was removed under vacuum to afford 6 as an off-white
solid (0.20 g, 91%). 1H NMR (400 MHz, benzene-d6): δ 7.98
[P h B(CH2P iP r 2)3]Ir (H)2(CO) (9). A benzene solution (ca.
5 mL) of 3 (0.20 g, 0.26 mmol) was degassed via three freeze-
pump-thaw cycles, and CO (1 atm) was introduced. The
resulting orange solution was heated at 65 °C over the course
of 14 h. The reaction mixture was filtered through Celite, and
the solvent was removed under vacuum to afford 9 as a yellow
3
3
(d, 4 H, o-Harom, J HH ) 7 Hz), 7.90 (br d, 2 H, o-Harom, J HH
)
7 Hz), 7.57 (m, 2 H, p-Harom, overlapping with 2 H, m-Harom),
7.33 (t, 1 H, p-Harom, J HH ) 7 Hz), 7.25 (t, 4 H, m-Harom, J HH
) 7 Hz), 5.71 (s, 1 H, SiHPh2, J SiH ) 193 Hz), 1.72 (m, 6 H,
3
3
1
1
PCHMe2), 0.99 (m, 36 H, PCHMe2), 0.87 (br m, 6 H, BCH2P),
-11.55 (m, 3 H, IrH). 13C{1H} NMR (100.6 MHz, benzene-d6):
δ 145.8 (Carom), 136.2 (Carom), 134.8 (Carom), 131.9 (Carom), 130.0
(Carom), 127.4 (Carom), 127.0 (Carom), 32.2 (m, PCHMe2), 19.7
(PCHMe2), 19.0 (PCHMe2), 12.8 (br, BCH2P). 31P{1H} NMR
(162 MHz, benzene-d6): δ 7.85 (s). 29Si NMR (99.36 MHz,
solid (0.18 g, 97% yield). H NMR (400 MHz, benzene-d6): δ
3
7.89 (br m, 2 H, o-Harom), 7.58 (t, 2 H, m-Harom, J HH ) 8 Hz),
7.34 (m, 1 H, p-Harom), 2.00 (m, 2 H, PCHMe2), 1.69 (m, 2 H,
PCHMe2), 1.60 (m, 2 H, PCHMe2), 1.29-1.01 (m, 36 H,
PCHMe2), 0.87 (br m, 6 H, BCH2P), -11.84 (m, 2 H, Ir-H).
2
13C{1H} NMR (100.6 MHz): δ 178.4 (dt, IrCO, J CPtrans ) 97
2
2
benzene-d6): δ -23.9 (br q, J SiP ) 7 Hz). 11B NMR (160.46
Hz, J CPcis ) 5 Hz), 131.9 (Carom), 127.7 (Carom), 124.2 (Carom),
MHz, benzene-d6): δ -11.54. IR (cm-1): 2057 (br, IrH), 2025
(SiH). Anal. Calcd for C39H67BP3SiIr: C, 54.47; H, 7.85.
Found: C, 54.63; H, 7.94.
33.5 (m, PCHMe2), 33.2 (m, PCHMe2), 31.0 (m, PCHMe2), 20.8
(PCHMe2), 20.2 (PCHMe2), 20.0 (PCHMe2), 19.2 (PCHMe2),
18.6 (PCHMe2), 18.4 (PCHMe2), 13.17 (br, BCH2P). 31P{1H}
NMR (162 MHz, benzene-d6): δ 11.47 (t, 1 P, [PhBP3′] trans
[P h B(CH2P iP r 2)3]Ir (H)2(P Me3) (7). Neat PMe3 (26 µL,
0.019 g, 0.25 mmol) was added to a room-temperature benzene
(5 mL) solution of 3 (0.20 g, 0.25 mmol). The resulting solution
was heated at 60 °C for 24 h. The volatile material was
removed under vacuum, and the remaining residue was
extracted into ca. 3 mL of toluene. Storage of this solution at
-35 °C over 24 h afforded 7 (0.13 g, 69%) as a white crystalline
solid. 1H NMR (500 MHz, benzene-d6): δ 8.05 (br m, 2 H,
to CO, 2J PPcis ) 24 Hz), 3.75 (d, 2 P, [PhBP3′] cis to CO, 2J PP
)
24 Hz). 11B NMR (160.46 MHz, benzene-d6): δ -11.23. IR
(cm-1): 2003 (CO), 1939 (IrH), 1926 (IrH). Anal. Calcd for
C
28H55BP3OIr: C, 47.79; H, 7.88. Found: C, 48.18; H, 7.78.
[K2-P h B(CH 2P iP r 2)3]R h (P Me3)2 (10). A benzene (5 mL)
solution of [PhB(CH2PiPr2)3]Li(THF) (0.20 g, 0.36 mmol) was
added to a stirred, room-temperature suspension of Rh(PMe3)4-
OTf (0.20 g, 0.36 mmol) in ca. 5 mL of benzene. The resulting
orange solution was allowed to stir at room temperature for 1
h. The volatiles were removed under vacuum, and the remain-
ing orange residue was extracted into ca. 20 mL of pentane.
The pentane extracts were filtered through Celite, and the
volume was reduced by 50% under vacuum. Storage of this
solution at -35 °C for 24 h afforded 10 (0.12 g, 45%) as orange
o-Harom), 7.61 (t, 2 H, m-Harom
,
3J HH ) 8 Hz), 7.35 (tt, 1 H,
3J HH ) 7 Hz, J HH ) 2 Hz), 2.04 (m, 2 H, PCHMe2),
1.84 (m, 2 H, PCHMe2), 1.66 (m, 2 H, PCHMe2), 1.49 (dd, 9 H,
4
p-Harom
,
2
4
PMe3, J HP ) 8 Hz, J HPtrans ) 2 Hz), 1.38 (dd, 6 H, PCHMe2,
3J HH ) 14 Hz, 3J HP ) 7 Hz), 1.31 (dd, 6 H, PCHMe2, 3J HH ) 13
Hz, J HP ) 7 Hz), 1.23 (dd, 6 H, PCHMe2, J HH ) 17 Hz, J HP
) 9 Hz), 1.20-1.15 (m, 12 H, PCHMe2), 1.09 (br m, 4 H,
3
3
3
3
3
1
BCH2P), 0.98 (dd, 6 H, PCHMe2, J HH ) 13 Hz, J HP ) 8 Hz),
0.87 (br m, 2 H, BCH2P), -13.50 (m, 2 H, IrH). 13C{1H} NMR
(125.8 MHz, benzene-d6): δ 132.3 (Carom), 127.6 (Carom), 123.7
(Carom), 34.4 (m, PCHMe2), 32.1 (m, PCHMe2), 31.0 (m,
PCHMe2), 27.9 (m, PMe3), 21.3 (PCHMe2), 20.8 (PCHMe2), 20.7
(PCHMe2), 20.2 (PCHMe2), 18.8 (PCHMe2), 18.5 (PCHMe2),
14.6 (br, BCH2P). 31P{1H} NMR (162 MHz, benzene-d6): δ
15.39 (dt, 1 P, [PhBP3′] trans to PMe3, 2J PPtrans ) 286 Hz, 2J PPcis
) 21 Hz), -2.15 (m, 2 P, [PhBP3′] cis to PMe3), -68.15 (dt, 1
P, IrPMe3, 2J PPtrans ) 287 Hz, 2J ppcis ) 21 Hz). 11B NMR (160.46
MHz, benzene-d6): δ -12.21. IR (cm-1): 2106 (IrH), 2049 (IrH).
microcrystals. H NMR (500 MHz, benzene-d6): δ 8.05 (br m,
2 H, o-Harom), 7.50 (t, 2 H, m-Harom, 3J HH ) 8 Hz), 7.28 (m, 1 H,
p-Harom), 1.89 (m, 2 H, PCHMe2), 1.75 (m, 2 H, PCHMe2), 1.54
(m, 2 H, PCHMe2), 1.45-0.94 (m, 36 H, PCHMe2), 0.86 (br d,
20 H, RhPMe3 + BCH2P, J HP ) 8 Hz), 0.68 (br m, 4 H, BCH2P).
13C{1H} NMR (125.8 MHz, benzene-d6): δ 133.6 (Carom), 126.5
(Carom), 123.2 (Carom), 30.3 (m, PCHMe2), 29.5 (m, PCHMe2),
24.5 (m, PCHMe2), 21.8-19.9 (PCHMe2 + PMe3), 16.0 (br,
BCH2P), 13.39 (br, BCH2P). 31P{1H} NMR (162 MHz, benzene-
d6): δ 49.42 (m, 2 P, iPr2PRh), 1.93 (s, 1 P, BCH2PiPr2), -23.14
(m, 2 P, RhPMe3). 11B NMR (160.46 MHz, benzene-d6):
δ
Anal. Calcd for
Found: C, 50.51; H, 8.58.
C
30H64BP4Ir‚(C7H8)0.5
:
C, 50.43; H, 8.59.
-16.16. Anal. Calcd for C33H71BP5Rh: C, 53.82; H, 9.72.
Found: C, 53.87; H, 9.89.
[P h B(CH2P iP r 2)3]Ir (H)2P H2Cy (8). Neat PH2Cy (0.030 g,
34 µL, 0.26 mmol) was added to a room-temperature benzene
solution (ca. 5 mL) of 3 (0.20 g, 0.26 mmol). The resulting
orange solution was heated at 65 °C over the course of 14 h.
The reaction mixture was filtered through Celite, and the
solvent was removed under vacuum to afford 8 as an off-white
[P h B(CH2P iP r 2)3]Rh (CO)2 (11). Solid [RhCl(CO)2]2 (0.070
g, 0.18 mmol) was added to a room-temperature benzene
solution (ca. 15 mL) of [PhB(CH2PiPr2)3]Li(THF) (0.20 g, 0.36
mmol). The resulting orange solution was allowed to stir at
room temperature for 2 h. The solvent was removed under
vacuum, and the residue was extracted into ca. 30 mL of Et2O.
The Et2O extracts were filtered through Celite and concen-
trated to ca. 5 mL volume. The solution was then refrigerated
at -30 °C overnight to afford 11 (0.15 g, 64%) as a yellow
crystalline solid. Alternatively 11 can be prepared by treating
10 with 1 atm of CO at room temperature in benzene solution.
1H NMR (400 MHz, benzene-d6): δ 7.87 (br m, 2 H, o-Harom),
1
solid (0.19 g, 92% yield). H NMR (500 MHz, benzene-d6): δ
8.02 (br d, 2 H, o-Harom
,
3J HH ) 6 Hz), 7.61 (t, 2 H, m-Harom
,
3
3J HH ) 7 Hz), 7.35 (t, 1 H, p-Harom, J HH ) 8 Hz), 4.38 (br d, 2
1
H, PH2Cy, J HP ) 316 Hz), 2.18 (br m, 2 H, PCy), 2.06 (m, 2
H, PCHMe2), 1.83 (m, 2 H, PCHMe2), 1.66 (m, 5 H, PCHMe2
3
+ PCy), 1.46 (br m, 2 H, PCy), 1.40 (dd, 6 H, PCHMe2, J HH
)
3
3
3
3
15 Hz, J HP ) 7 Hz), 1.33 (dd, 6 H, PCHMe2, J HH ) 14 Hz,
7.56 (t, 2 H, m-Harom, J HH ) 8 Hz), 7.32 (t, 1 H, p-Harom, J HH
) 7 Hz), 1.75 (m, 6 H, PCHMe2), 1.22 (m, 18 H, PCHMe2),
1.07 (m, 18 H, PCHMe2), 0.80 (br m, 6 H, BCH2P). 13C NMR
3J HP ) 8 Hz), 1.22-1.10 (m, 26 H, PCHMe2 + PCy + BCH2P),
3
3
0.96 (dd, 6 H, PCHMe2, J HH ) 13 Hz, J HP ) 8 Hz), 0.86 (br

2500 Organometallics, Vol. 23, No. 10, 2004
Turculet et al.
1
1
(100.6 MHz, benzene-d6): δ 204.4 (dq, RhCO, J CRh ) 56 Hz,
crystalline solid (0.084 g, 44%). H NMR (500 MHz, benzene-
d6): δ 8.26 (br m, 4 H, o-Harom), 7.70 (d, 2 H, o-Harom, J HH ) 7
Hz), 7.34 (m, 7 H, Harom), 7.04 (m, 2 H, Harom), 5.81 (br s, 1 H,
2J CP ) 23 Hz), 131.8 (Carom), 127.7 (Carom), 124.1 (Carom), 32.8
(m, PCHMe2), 20.7 (PCHMe2), 19.1 (PCHMe2), 14.8 (br, BCH2P).
1
1
31P{1H} NMR (162 MHz, benzene-d6): δ 37.51 (d, J RhP ) 97
SiH, J HSi ) 152 Hz), 1.95-1.60 (br m, 4 H, PCHMe2), 1.27-
Hz). 11B NMR (160.46 MHz, benzene-d6): δ -13.89. IR (cm-1):
2007 (CO), 1935 (CO). Anal. Calcd for C29H53BP3O2Rh: C,
54.39; H, 8.34. Found: C, 54.55; H, 8.29.
0.81 (br m, 37 H, PCHMe2 + PMe3 + BCH2P), -10.25 (m, 1 H,
Rh-H), -11.00 (m, 1 H, Rh-H). 13C{1H} NMR (125.8 MHz,
benzene-d6): δ 136.2 (Carom), 136.0 (Carom), 133.8 (Carom), 132.3
(Carom), 127.4 (Carom), 127.1 (Carom), 126.6 (Carom), 31.0 (m,
PCHMe2), 28.4 (m, PCHMe2), 28.1 (m, PCHMe2), 26.9 (m,
PCHMe2), 24.0 (m, PMe3), 23.1-18.4 (PCHMe2), 18.0 (br,
BCH2P), 15.6 (br, BCH2P). 31P{1H} NMR (202 MHz, benzene-
d6): δ 38.59 (m, 2 P, BCH2PiPr2), -30.85 (m, 1 P, RhPMe3).
[P h B(CH2P iP r 2)2]Rh CH2P iP r 2 (12). Solid [RhCl(C2H4)2]2
(0.070 g, 0.18 mmol) was added to a room-temperature benzene
solution (ca. 15 mL) of [PhB(CH2PiPr2)3]Li(THF) (0.20 g, 0.36
mmol). The resulting green-brown solution was allowed to stir
at room temperature for 1 h. The solvent was removed under
vacuum, and the remaining residue was extracted into ca. 15
mL of Et2O. The Et2O extract was filtered through Celite,
concentrated to ca. 3 mL volume, and refrigerated at -30 °C
overnight to give 12 as a red crystalline solid (0.18 g, 87%
yield). 1H NMR (500 MHz, benzene-d6): δ 8.04 (m, 2 H,
o-Harom), 7.30 (m, 3 H, m-Harom + p-Harom), 2.22 (m, 2 H,
PCHMe2), 2.14 (m, 2 H, PCHMe2), 1.88 (m, 2 H, PCHMe2),
1.68 (m, 4 H, BCH2P), 1.26 (m, 12 H, PCHMe2), 1.17-1.03 (m,
24 H, PCHMe2), -0.11 (d, 2 H, J ) 10 Hz). 13C{1H} NMR (125.8
MHz, benzene-d6): δ 142.2 (Carom), 134.9 (Carom), 132.6 (Carom),
128.2 (Carom), 30.6 (m, PCHMe2), 30.1 (m, PCHMe2), 23.2 (br,
BCH2P), 21.9 (br, BCH2P), 21.6 (m, PCHMe2), 20.6 (PCHMe2),
20.2 (PCHMe2), 20.1 (PCHMe2), 20.0 (PCHMe2), 19.9 (PCHMe2),
19.2 (PCHMe2), 19.1 (PCHMe2), -19.9 (m, RhCH2). 31P{1H}
29Si NMR (99.36 MHz, benzene-d6): δ 19.6 (br d, J SiRh ) 239
1
Hz). 11B NMR (160.46 MHz, benzene-d6): δ 74.6. IR (cm-1):
2008, 1982, 1947. Anal. Calcd for C35H59BP3SiRh: C, 58.83;
H, 8.32. Found: C, 58.59; H, 8.08.
[P h B(CH2P iP r 2)3]Rh (H)2CO (15). A thick-walled, 100 mL
flask fitted with a PTFE stopcock was charged with 8 (0.12 g,
0.19 mmol), Me3NO (0.014 g, 0.19 mmol), a magnetic stirbar,
and ca. 10 mL of benzene. The resulting orange solution was
degassed via three freeze-pump-thaw cycles, and hydrogen
(1 atm) was introduced. The flask was sealed off, and the
reaction mixture was allowed to stir at 70 °C for 14 h. The
volatiles were removed under vacuum, and the remaining
yellow residue was extracted into Et2O (ca. 10 mL). The Et2O
extracts were filtered through Celite, concentrated to ca. 3 mL,
and refrigerated at -30 °C overnight to give off-white crystals
of 15 (0.10 g, 86%). 1H NMR (500 MHz, benzene-d6): δ 7.89
2
NMR (202 MHz, benzene-d6): δ 76.99 (ddd, 1 P, J PPcis ) 24
2
1
2
Hz, J PPcis ) 31 Hz, J RhP ) 171 Hz), 70.31 (ddd, 1 P, J PPcis
)
3
3
(d, 2 H, o-Harom, J HH ) 6 Hz), 7.57 (t, 2 H, m-Harom, J HH ) 7
2
1
24 Hz, J PPtrans ) 241 Hz, J RhP ) 187 Hz), 13.92 (ddd, 1 P,
Hz), 7.33 (t, 1 H, p-Harom, 3J HH ) 7 Hz), 1.86 (m, 2 H, PCHMe2),
2J PPcis ) 31 Hz, J PPtrans ) 241 Hz, J RhP ) 108 Hz). 11B NMR
2
1
3
1.56 (m, 4 H, PCHMe2), 1.28 (dd, 6 H, PCHMe2, J HH ) 7 Hz,
(160.46 MHz, benzene-d6): δ 74.9 (br). Anal. Calcd for C27H53
BP3Rh: C, 55.50; H, 9.14. Found: C, 55.70; H, 9.44.
-
3J HP ) 15 Hz), 1.22 (dd, 6 H, PCHMe2, 3J HH ) 7 Hz, 3J HP ) 15
Hz), 1.16 (dd, 6 H, PCHMe2, 3J HH ) 7 Hz, 3J HP ) 15 Hz), 1.11-
1.03 (m, 18 H, PCHMe2), 0.88 (br m, 2 H, BCH2P), 0.77 (br m,
4 H, BCH2P), -8.99 (m, 2 H, RhH). 13C{1H} NMR (100.6 MHz,
[P h B(CH2P iP r 2)3]Rh (H)2P Me3 (13). A thick-walled, 100
mL flask fitted with a PTFE stopcock was charged with 10
(0.66 g, 0.90 mmol), a magnetic stirbar, and ca. 10 mL of
benzene. The resulting orange solution was degassed via three
freeze-pump-thaw cycles, and hydrogen (1 atm) was intro-
duced. The flask was sealed off, and the resulting pale yellow
reaction mixture was allowed to stir at ambient temperature
for 24 h. The volatile material was removed under vacuum,
and the remaining pale yellow residue was washed with 3 ×
5 mL of pentane and dried under vacuum to give 13 (0.45 g,
76%) as an analytically and spectroscopically pure pale yellow
solid. 1H NMR (500 MHz, benzene-d6): δ 8.04 (br m, 2 H,
2
1
benzene-d6): δ 197.4 (ddt, RhCO, J CPtrans ) 107 Hz, J CRh
)
2
52 Hz, J CPcis ) 7 Hz), 131.8 (o-Carom), 127.1 (m-Carom), 124.1
(p-Carom), 33.5 (m, PCHMe2), 32.1 (m, PCHMe2), 30.5 (m,
PCHMe2), 20.7 (PCHMe2), 20.3 (PCHMe2), 20.0 (PCHMe2), 19.2
(PCHMe2), 19.0 (PCHMe2), 18.6 (PCHMe2), 14.4 (br, BCH2P).
31P{1H} NMR (162 MHz, benzene-d6): δ 53.34 (dt, 1 P, [PhBP3′]
trans to CO, 1J PRh ) 92 Hz, 2J PPcis ) 29 Hz), 36.58 (dd, [PhBP3′]
cis to CO, J PRh ) 78 Hz, J PPcis ) 29 Hz). 11B NMR (160.46
MHz, benzene-d6): δ -12.97. IR (cm-1): 2017 (RhCO), 1983
(RhH), 1950 (RhH). Anal. Calcd for C28H55OBP3Rh: C, 54.74;
H, 9.02. Found: C, 54.55; H, 9.17.
1
2
o-Harom), 7.60 (t, 2 H, m-Harom,
3J HH ) 7 Hz), 7.33 (t, 1 H,
3
p-Harom, J HH ) 7 Hz), 1.92 (m, 2 H, PCHMe2), 1.72 (m, 2 H,
X-r a y Str u ctu r e Deter m in a tion s. Single-crystal X-ray
diffraction data were collected from samples mounted on a
quartz fiber using Paratone N hydrocarbon oil. Data collection
was carried out using graphite-monochromated Mo KR (λ )
0.71069 Å) radiation on a Siemens SMART diffractometer
equipped with a CCD area detector. The preliminary orienta-
tion 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
using ω scans of 0.3° counted for a total of 30, 20, 10, 20, 30,
and 15 s per frame for 5, 7‚(C7H8)0.5, 11, 12, 13, and 14,
respectively. The frame data were integrated using the
program SAINT (SAX Area-Detector Integration Program;
V4.024; Siemens Industrial Automation, Inc.: Madison, WI,
1995). The program SADABS (Siemens Area Detector Absorp-
tion Corrections; Sheldrick, G. M., 1996) was utilized for
scaling of diffraction data and the application of an empirical
absorption correction based on redundant reflections. With the
exception of 13, the structures were solved using the teXsan
crystallographic software package of the Molecular Structure
Corp. using direct methods, and expanded with Fourier
techniques. The function minimized in the full-matrix least-
squares refinement was ∑w(|Fo| - |Fc|)2. In the case of 13, the
structure was solved using the direct methods procedure in
the Siemens SHELXTL (Sheldrick, G. M., Version 5.03;
PCHMe2), 1.61 (m, 2 H, PCHMe2), 1.38 (dd, 6 H, PCHMe2, 3J HH
3
) 7 Hz, J PH ) 15 Hz), 1.30 (m, 12 H, PCHMe2), 1.19 (m, 21
H, PCHMe2 + PMe3) 1.01 (dd, 6 H, PCHMe2, 3J HH ) 7 Hz, 3J HP
) 12 Hz), 0.94 (br m, 4 H, BCH2P), 0.78 (br m, 2 H, BCH2P),
-11.08 (m, 2 H, RhH). 13C{1H} NMR (125.8 MHz, benzene-
d6): δ 132.1 (Carom), 127.5 (Carom), 123.6 (Carom), 34.1 (m,
PCHMe2), 31.1 (m, PCHMe2), 30.7 (m, PCHMe2), 27.2 (m,
PMe3), 21.3 (PCHMe2), 20.9 (PCHMe2), 19.9 (PCHMe2), 19.1
(PCHMe2), 16.2 (br, BCH2P), 14.87 (br, BCH2P). 31P{1H} NMR
(162 MHz, benzene-d6): δ 56.17 (ddt, 1 P, [PhBP3′] trans to
PMe3, 2J PPtrans ) 332 Hz, 1J PRh ) 97 Hz, 2J PPcis ) 25 Hz), 32.00
(m, 2 P, [PhBP3′] cis to PMe3), -22.06 (ddt, 1 P, PMe3, 2J PPtrans
) 330 Hz, J PRh ) 100 Hz, J PPcis ) 24 Hz). 11B NMR (160.46
MHz, benzene-d6): δ -13.82. IR (cm-1): 2011 (RhH), 1945
(RhH). Anal. Calcd for C30H64BP4Rh: C, 54.39; H, 9.74.
Found: C, 54.51; H, 9.83.
[P h B(CH2P iP r 2)2]Rh (H)2(SiHP h 2)(P Me3) (14). Neat Ph2-
SiH2 (0.05 mL, 0.27 mmol) was added to a room-temperature
benzene (ca. 10 mL) solution of 10 (0.20 g, 0.27 mmol). The
reaction mixture was allowed to stand at room temperature
over the course of 18 h. The solution was filtered through
Celite, and the solvent was removed under vacuum. The
remaining residue was dissolved in ca. 3 mL of Et2O and
refrigerated at -30 °C overnight to give 14 as a pale yellow
1
2

New Zwitterionic Rhodium and Iridium Complexes
Organometallics, Vol. 23, No. 10, 2004 2501
Ta ble 8. Cr ysta llogr a p h ic Da ta for Com p ou n d s 5, 7‚(C7H8)0.5, 11, 12, a n d 14
5
7‚(C7H8)0.5
11
12
14
empirical formula
fw
IrP3SiC31H58
754.84
B
IrP4C33.5H64
793.80
B
RhP3C29H53O2B
640.37
RhP3C27H53
584.35
B
RhP3SiC35H57
712.56
B
cryst color, habit
cryst size (mm)
cryst syst
space group
a (Å)
off-white, plate
0.24 × 0.17 × 0.03
triclinic
pale yellow, plate
0.28 × 0.15 × 0.07
monoclinic
C2/c (#15)
36.527(3)
10.0508(7)
20.125(1)
90
92.273(2)
90
7382.7(8)
5346 (3.5-45°)
yellow, plate
0.25 × 0.20 × 0.14
monoclinic
P21/a (#14)
15.5038(8)
11.4661(6)
18.013(1)
90
92.326
90
3199.5(3)
6743 (3.5-45°)
red-orange, plate
0.29 × 0.27 × 0.05
monoclinic
P21/n (#14)
9.2758(5)
11.9315(7)
27.907(2)
90
pale yellow, plate
0.25 × 0.15 × 0.06
triclinic
P1h (#2)
9.3582(6)
11.1131(7)
18.206(1)
86.251(1)
86.214(1)
79.474(1)
P1h(#2)
10.1906(6)
12.8762(8)
14.0826(9)
88.929(1)
b (Å)
c (Å)
R (deg)
â (deg)
75.703(1)
87.422(1)
1788.8(2)
5064 (3.5-45°)
99.149(1)(2)
90
3049.3(3)
γ (deg)
V (Å3)
1854.7(2)
4218 (3.5-45°)
no. of orientation reflns
(2θ range)
Z value
5633 (3.5-45°)
2
8
4
4
2
D
calc (g/cm3)
1.401
770.00
39.28
SMART
1.428
3256.00
38.21
SMART
1.329
1352.00
7.06
1.273
1240.00
7.29
1.276
752.00
6.43
F000
µ (Mo KR) (cm-1
diffractometer
radiation
)
SMART
SMART
SMART
Mo KR (λ ) 0.71069 Å) graphite monochromated
temperature (°C)
scan type
scan rate (s)
2θmax (deg)
no. reflns measd
-149
-149
-130
ω (0.3° per frame)
10
-139
-99
30
49.5
total: 8949
unique: 5673
0.035
20
49.5
total: 18 547
unique: 6559
0.049
20
49.4
total: 14 738
unique: 5260
0.074
15
49.5
total: 9265
unique: 5864
0.040
49.4
total: 14 194
unique: 5588
0.038
Rint
transmn factors
structure solution
refinement method
no. of observations
no. of variables
reflns/param ratio
residuals: R; Rw; Rall
goodness of fit
T
min/Tmax ) 0.42
Tmin/Tmax ) 0.46
Tmin/Tmax ) 0.62
Tmin/Tmax ) 0.43
Tmin/Tmax ) 0.23
direct methods (SIR92)
full-matrix least-squares on F
4553
331
13.76
0.041; 0.048; 0.053
1.34
0.00
4918
354
13.89
0.030; 0.039; 0.039
1.13
0.00
4065
320
12.70
0.030; 0.037; 0.042
1.12
0.00
2659
290
9.17
0.041; 0.048; 0.077
1.08
0.00
4344
365
11.90
0.049; 0.060; 0.068
1.45
0.00
max. shift/error in final
cycle
max. and min. peaks in
1.50, -2.13
1.11, -1.70
0.63, -0.94
0.79, -1.17
1.20, -1.70
final diff map (e-/Å3)
Ta ble 9. Cr ysta llogr a p h ic Da ta for Com p ou n d 13
empirical formula
fw
RhP4C30H62
660.40
B
radiation
Mo KR (λ ) 0.71069 Å)
graphite monochromated
ω (0.3° per frame)
30 s
cryst color, habit
cryst size (mm)
cryst syst
space group
a (Å)
yellow, block
0.11 × 0.10 × 0.08
monoclinic
P21/c (#14)
10.993(2)
16.887(3)
18.951(4)
90
90.96(3)
90
3517.6(12)
2800 (3.5-45°)
scan type
scan rate
2θmax (deg)
no. reflns measd
48.08
total: 14147
unique: 5047
0.086
b (Å)
c (Å)
Rint
transmn factors
refinement method
structure solution
no. of observations
no. of variables
reflns/param ratio
Tmin/Tmax ) 0.48
R (deg)
full-matrix least-squares on F2
â (deg)
direct methods (SHELXS-86)
4044
320
γ (deg)
V (Å3)
no. of orientation reflns
(θ range)
Z value
12.64
4
final R indices (I > 2σ(I))
R indices (all data)
goodness of fit
max. shift/error in final
cycle
R1 ) 0.0604, wR2 ) 0.1414
D
calc (g/cm3)
1.247
1408.00
6.85
R1 ) 0.1085, wR2 ) 0.1655
F000
1.12
0.00
µ(Mo KR) (cm-1
)
diffractometer
SMART
max. and min. peaks in
1.452, -0.792
final diff map (e-/Å3)
temperature (°C)
-143
Siemens Crystallographic Research Systems: Madison, WI,
1994) program library, and refinement was carried out using
the full-matrix least-squares method on F2. Apart from noted
exceptions, non-hydrogen atoms were refined anisotropically,
with the exception of boron, which was refined isotropically.
Unless otherwise noted, hydrogen atoms were included in
calculated positions but not refined. The weighting scheme was
based on counting statistics and included a p-factor to down-
weight the intense reflections. Selected crystal and structure
refinement data are summarized in Tables 8 and 9.
F or 5. Crystals suitable for X-ray diffraction were obtained
from a diethyl ether solution at room temperature. The Si atom
of the SiHEt2 ligand was found to be disordered over two
positions (Si(1) and Si(2)). Si(1) was refined anisotropically
with 70% occupancy, while Si(2) was refined isotropically with
30% occupancy. Additionally, the ethyl group comprised of C(3)

2502 Organometallics, Vol. 23, No. 10, 2004
Turculet et al.
and C(4) was found to be disordered, exhibiting an alternate
orientation (C(32) and C(33)). C(3), C(4), C(32), and C(33) were
refined isotropically, with C(3) and C(4) at 70% occupancy,
while C(32) and C(33) were assigned 30% occupancy. All
remaining non-hydrogen atoms were refined anisotropically,
with the exception of the boron atom, B1, which was refined
isotropically. All carbon-bound hydrogen atoms were included
in geometrically calculated positions and not refined.
F or 7‚(C7H8)0.5. Crystals suitable for X-ray diffraction were
obtained from a toluene solution at -30 °C. The structure was
found to contain one molecule of the iridium complex and half
of a toluene molecule per asymmetric unit. The toluene
molecule is disordered over two positions that are related by
a crystallographically imposed mirror plane and was modeled
as seven half-occupancy carbon atoms (C31-C37), which were
refined isotropically. All remaining non-hydrogen atoms were
refined anisotropically, with the exception of the boron atom,
B1, which was refined isotropically. All hydrogen atoms were
included in geometrically calculated positions and not refined,
with the exception of H1 and H2, which were located in the
difference Fourier map and their positional coordinates were
refined.
F or 11. Crystals suitable for X-ray diffraction were obtained
from a diethyl ether solution at -30 °C. The structure was
found to contain one molecule of the rhodium complex per
asymmetric unit. All non-hydrogen atoms were refined aniso-
tropically, with the exception of the boron atom, B1, which
was refined isotropically. All hydrogen atoms were included
in geometrically calculated positions and not refined.
F or 12. Crystals suitable for X-ray diffraction were obtained
from a diethyl ether solution at -30 °C. The structure was
found to contain one molecule of the rhodium complex per
asymmetric unit. All non-hydrogen atoms were refined aniso-
tropically, with the exception of the boron atom, B1, which
was refined isotropically. All hydrogen atoms were included
in geometrically calculated positions and not refined, with the
exception of H1 and H2, which were located in the difference
Fourier map and their positional coordinates were refined.
F or 13. Crystals suitable for X-ray diffraction were obtained
from a toluene solution at -30 °C. The structure was found to
contain one molecule of the rhodium complex per asymmetric
unit. All non-hydrogen atoms were refined anisotropically,
with the exception of the boron atom, B1, which was refined
isotropically. All carbon-bound hydrogen atoms were included
in geometrically calculated positions and not refined.
F or 14. Crystals suitable for X-ray diffraction were obtained
from a diethyl ether solution at -30 °C. The structure was
found to contain one molecule of the rhodium complex per
asymmetric unit. All non-hydrogen atoms were refined aniso-
tropically, with the exception of the boron atom, B1, which
was refined isotropically. All carbon-bound hydrogen atoms
were included in geometrically calculated positions and not
refined, with the exception of H1, which was located in the
difference Fourier map and its positional coordinates were
refined.
Ack n ow led gm en t is made to the National Science
Foundation for their generous support of this work. We
thank Dr. Frederick J . Hollander and Dr. Allen G.
Oliver for assistance with the X-ray structure determi-
nations.
Su p p or tin g In for m a tion Ava ila ble: Summaries of crys-
tallographic data, bond distances and angles, atomic coordi-
nates, and anisotropic displacement parameters for 5, 7‚
(C7H8)0.5, 11, 12, 13, and 14. This material is available free of
charge via the Internet at http://pubs.acs.org.
OM030686E