New tridentate phosphine rhodium and iridium complexes, including a stable rhodium(I) silyl. Si-S activation and a strong effect of X in (PP2)M-X (X = H, Cl, Me) on Si-H activation

Article abstract of DOI:10.1021/om020120a

Rhodium and iridium complexes of the general formula (PP₂)MX bearing the new triphosphine ligand ⁱPr₂P(CH₂)₃P(Ph)(CH₂) ₃PⁱPr₂ (PP₂) have been synthesized. Reactivity of the PP₂MX complexes toward HSi(SEt)₃ was studied. Whereas (PP₂)RhCl and (PP₂)IrCl do not react with HSi(SEt)₃, (PP₂)RhH gives rise to the Rh(III) adduct [(PP₂)Rh(H)₂Si(SEt)₃], and (PP₂)RhMe (3) activates both the Si-H and the Si-S bonds of HSi(SEt)₃, affording the Rh(I) complexes (PP₂)RhSi(SEt)₃ (5) and (PP₂)RhSEt (6). Only a few stable Rh(I) silyl complexes are known, and Si-S bond activation by transition-metal complexes has been rarely observed. The X-ray crystal structure of 5 exhibits a considerable distortion from square-planar geometry, the average angle between the trans-disposed ligands being 152.5°. In contrast to 3, (PP₂)IrMe (8) forms a stable Ir(III) adduct with HSi(SEt)₃, fac-[(PP₂)Ir-(Me)(H)(Si(SEt)₃)] (9). No Si-S activation was observed with 8. Thus, the reactivity of (PP₂)-MX complexes toward HSi(SEt)₃ strongly depends on the nature of M and X.

Full text of DOI:10.1021/om020120a

5060
Organometallics 2002, 21, 5060-5065
New Tr id en ta te P h osp h in e Rh od iu m a n d Ir id iu m
Com p lexes, In clu d in g a Sta ble Rh od iu m (I) Silyl. Si-S
Activa tion a n d a Str on g Effect of X in (P P 2)M-X (X ) H,
Cl, Me) on Si-H Activa tion
Roman Goikhman, Michael Aizenberg, Yehoshoa Ben-David,
Linda J . W. Shimon, and David Milstein*
Department of Organic Chemistry, The Weizmann Institute of Science, Rehovot, Israel 76100
Received February 14, 2002
Rhodium and iridium complexes of the general formula (PP2)MX bearing the new
i
triphosphine ligand Pr2P(CH2)3P(Ph)(CH2)3PiPr2 (PP2) have been synthesized. Reactivity of
the PP2MX complexes toward HSi(SEt)3 was studied. Whereas (PP2)RhCl and (PP2)IrCl do
not react with HSi(SEt)3, (PP2)RhH gives rise to the Rh(III) adduct [(PP2)Rh(H)2Si(SEt)3],
and (PP2)RhMe (3) activates both the Si-H and the Si-S bonds of HSi(SEt)3, affording the
Rh(I) complexes (PP2)RhSi(SEt)3 (5) and (PP2)RhSEt (6). Only a few stable Rh(I) silyl
complexes are known, and Si-S bond activation by transition-metal complexes has been
rarely observed. The X-ray crystal structure of 5 exhibits a considerable distortion from
square-planar geometry, the average angle between the trans-disposed ligands being 152.5°.
In contrast to 3, (PP2)IrMe (8) forms a stable Ir(III) adduct with HSi(SEt)3, fac-[(PP2)Ir-
(Me)(H)(Si(SEt)3)] (9). No Si-S activation was observed with 8. Thus, the reactivity of (PP2)-
MX complexes toward HSi(SEt)3 strongly depends on the nature of M and X.
In tr od u ction
Resu lts a n d Discu ssion
Transition-metal-thiosilyl compounds, M-Si(SR)3,
are a relatively new group of silyl complexes.1,2 The
Si-S bond is relatively weak3 and is suitable for various
transformations. Various thiosilyl complexes have at-
tracted considerable attention in the past decade as
precursors for metallasilylenes (compounds having a
metal-silicon double bond) and other interesting tran-
sition-metal silyl derivatives.1 They have also been
utilized in mechanistic investigations.2
In continuation of our work on electron-rich late-metal
silyl complexes,2,4 we report here on the synthesis of Rh
and Ir complexes containing the new chelating triphos-
phine ligand iPr2P(CH2)3P(Ph)(CH2)3PiPr2 (PP2) and
describe their transformations and reactivity toward
tris(ethylthio)silane, HSi(SEt)3.5
The ligand PP2 was prepared using a procedure
analogous to that reported for the synthesis of Cy2P-
(CH2)3P(Ph)(CH2)3PCy2.6 Reaction of PP2 with the rho-
dium dimer [(COE)2RhCl]2 (COE ) cyclooctene, C8H14
)
at room temperature in THF afforded the complex (PP2)-
RhCl (1), which was used as a precursor for the
synthesis of other Rh(I) complexes. Upon treatment of
t
1 with BuLi, the hydrido complex (PP2)RhH (2) was
readily formed. Apparently, the reaction proceeded
through â-hydrogen elimination from the unobserved
intermediate (PP2)RhtBu. Isobutene formation was de-
1
tected by H NMR.
Another Rh(I) complex, (PP2)RhMe (3), was readily
prepared by treating complex 1 with MeLi.
The reactivity of complexes 1-3 toward the thiosilane
HSi(SEt)3 was examined.
* To whom correspondence should be addressed. Fax: 972-8-
9344142. E-mail: david.milstein@weizmann.ac.il.
(1) For example: (a) Grumbine, S. K.; Mitchell, G. P.; Straus, D.
A.; Tilley, T. D.; Rheingold, A. L. Organometallics 1998, 17, 5607 and
references therein. (b) Mitchell, G. P.; Tilley, T. D. J . Am. Chem. Soc.
1998, 120, 7635. (c) Grumbine, S. D.; Tilley, T. D.; Arnold, F. P.;
Rheingold, A. L. J . Am. Chem. Soc. 1993, 115, 7884.
(2) Aizenberg, M.; Goikhman, R.; Milstein, D. Organometallics 1996,
15, 1075.
(3) The BDE of the Si-S bond was estimated as 79 kcal/mol; see:
Baldwin, J . C.; Lappert, M. F.; Pedley, J . B.; Treverton, J . A. J . Chem.
Soc. A 1967, 1980.
(4) (a) Aizenberg, M.; Ott, J .; Elsevier, C. J .; Milstein, D. J .
Organomet. Chem. 1998, 551, 81. (b) Goikhman, R.; Aizenberg, M.;
Shimon, L. J . W.; Milstein, D. J . Am. Chem. Soc. 1996, 118, 10894. (c)
Aizenberg, M.; Milstein, D. Organometallics 1996, 15, 3317. (d)
Aizenberg, M.; Milstein, D. J . Am. Chem. Soc. 1995, 117, 6456. (e)
Goikhman, R.; Aizenberg, M.; Kraatz, H. B.; Milstein, D. J . Am. Chem.
Soc. 1995, 117, 5865. (f) Aizenberg, M.; Milstein, D. Angew. Chem.,
Int. Ed. Engl. 1994, 33, 317. (g) Aizenberg, M.; Milstein, D. Science
1994, 265, 359. (h) Zlota, A. A.; Frolow, F.; Milstein, D. J . Chem. Soc.,
Chem. Commun. 1989, 1826.
Unexpectedly, the 16e- Rh(I) chloride 1 did not
change upon addition of HSi(SEt)3 at room temperature,
as determined by NMR. In contrast, the Rh(I) hydride
2 reacted with HSi(SEt)3 at room temperature to yield
the stable Rh(III) dihydride complex mer,cis-PP2Rh-
(H)2Si(SEt)3 (4), which was unambiguously character-
ized by NMR spectroscopy. The 31P{1H} NMR spectrum
of 4 exhibits a doublet of triplets and a doublet of
doublets, indicating one unique phosphine and two
equal phosphines. Two hydride signals are observed in
1H NMR, a doublet of doublets of doublets of triplets at
(5) (a) Lambert, J . B.; Shulz, W. J . J . Am. Chem. Soc. 1988, 110,
2201. (b) Wolinsky, L.; Tieckelmann, H.; Post, H. W. J . Org. Chem.
1951, 16, 395.
(6) Uriarte, R.; Mazanec, T. J .; Tan, K. D.; Meek, D. W. Inorg. Chem.
1980, 19, 79.
10.1021/om020120a CCC: $22.00 © 2002 American Chemical Society
Publication on Web 10/08/2002

New Tridentate Phosphine Rh and Ir Complexes
Organometallics, Vol. 21, No. 23, 2002 5061
Sch em e 1
oxidative addition followed by C-H reductive elimina-
tion takes place, forming a Rh(I) silyl complex.
The fact that rhodium dihydrido silyl complexes are
thermodynamically stable, unlike the unobserved rho-
dium methyl hydrido silyls, was reported.4a
The result that (PP2)RhCl (1) does not add the silane,
whereas the analogous methyl and hydride complexes
readily undergo Si-H activation, is unexpected. Com-
paring complex 1 to a similar square-planar complex
bearing three alkylphosphine ligands and a chloride,
namely (Et3P)3RhCl, we observed that the latter com-
plex readily reacted with HSi(SEt)3 at room tempera-
ture, giving the Rh(III) adduct (Et3P)2Rh(Cl)(H)(Si-
(SEt)3) in quantitative yield and liberating 1 equiv of
Et3P (eq 1).8
To check whether the reason for the lack of observed
reactivity between the chloride complex 1 and the silane
is kinetic or thermodynamic, we tried to generate the
expected oxidative addition product (PP2)Rh(Cl)(H)(Si-
(SEt)3) by another route. Interestingly, treatment of
(PP2)Rh(Si(SEt)3) (5) with an HCl solution in dioxane
resulted in formation of the chloride complex 1 and free
thiosilane as the only products (eq 2), suggesting that
-9.05 ppm for the hydride trans to the unique phos-
phorus atom (2J H-Ptrans ) 123 Hz) and a multiplet
centered at -9.25 ppm for the hydride located cis to all
phosphorus atoms.
The methyl rhodium complex 3 slowly reacted with
HSi(SEt)3 in pentane solution at -20 °C to give the
Rh(I) silyl complex (PP2)Rh(Si(SEt)3) (5) as the main
product. Only a few Rh(I) silyl complexes are known.4a,g,7
The reaction apparently proceeded via the Rh(III)
intermediate [(PP2)Rh(Me)(H)(Si(SEt)3)] (unobserved),
which spontaneously eliminated methane (which was
detected by 1H NMR). Complex 4 was formed in a small
amount as a byproduct of this reaction. It was presum-
ably formed in two steps: (a) C-Si reductive elimination
from the intermediate, giving complex 2 and MeSi(SEt)3
the PP2 chloride adduct with the thiosilane is unstable,
unlike the Et3P-containing adduct. This may be due to
steric factors in the triphosphine complex, resulting in
phosphine dissociation in the case of the Et3P complex,
whereas the chelate effect disfavors chelate opening in
the case of the PP2 complex. Generation of free Et3P in
eq 1 as compared with elimination of the thiosilane
rather than one phosphine “arm” in eq 2 demonstrates
the high binding energy of the chelate.
Complex 5 slowly decomposes at room temperature.
It was crystallized from pentane at -30 °C as deep red
prisms. The crystal structure of 5 (Figure 1, Table 1)
exhibits a considerable distortion from square planarity,
the angles between the trans-disposed ligands being
substantially smaller than 180°. A similar distortion
was observed in a series of Rh(I) compounds having a
1
(an observed singlet at 0.63 ppm in H NMR probably
belongs to this compound), and (b) HSi(SEt)3 oxidative
addition to complex 2 to give the observed complex 4.
The product ratio 5:4 was about 8:1, indicating that
C-H reductive elimination significantly prevailed over
that of C-Si. This result is in accordance with our
previous finding that C-Si and C-H reductive elimina-
tion can be competitive, with the latter being the more
favorable process.4f
Scheme 1 briefly summarizes the synthesis and
transformations of the (PP2)Rh complexes.
Thus, complexes of the type PP2RhX react very
differently with HSi(SEt)3, depending on X. In the case
of X ) Cl no reaction is observed, with X ) H a stable
Rh(III) adduct is formed, and when X ) Me, Si-H
(8) A similar pathway was observed in the reaction of silanes with
(Ph3P)3RhCl and (iPr3P)2RhCl, leading to five-coordinated adducts: (a)
Nagashima, H.; Tatebe, K.; Ishibashi, T.; Nakaoka, A.; Sakakibara,
J .; Itoh, K. Organometallics 1995, 14, 2868. (b) Osakada, K.; Koizumi,
T.; Yamamoto, T. Organometallics 1997, 16, 2063. Although in the
latter paper the structures of the adducts are postulated as distorted
square pyramids, the reported Si-Rh-Cl angles of 111.1 and 126.4°
allows us to conclude that the structures are intermediate between
square pyramidal and TBP, probably closer to a TBP configuration.
(7) (a) Mitchell, G. P.; Straus, D. A.; Tilley, T. D.; Rheingold, A. L.
Organometallics 1998, 17, 2912. (b) Hofmann, P.; Meier, C.; Hiller,
W.; Heckel, M.; Riede, J .; Schmidt, M. U. J . Organomet. Chem. 1995,
490, 51. (c) Thorn, D. L.; Harlow, R. L. Inorg. Chem. 1990, 29, 2017.
(d) Hendriksen, D. E.; Oswald, A. A.; Ansell, G. B.; Leta, S.; Kastrup,
R. V. Organometallics 1989, 8, 1153. (e) J oslin, F. L.; Stobart, S. R. J .
Chem. Soc., Chem. Commun. 1989, 504

5062 Organometallics, Vol. 21, No. 23, 2002
Goikhman et al.
Ta ble 3. 31P {1H} NMR Da ta (C6D6; δ in p p m ,
J in Hz) for Com p lexes 1-6
PP2RhX
X )
Cl
(1)
X )
H
(2)
X )
Me
(3)
X )
X )
X )
(H)2Si(SEt)3 Si(SEt)3 SEt
(RhIII, 4)
(5)
(6)
δ(PP2), dt
1J P-Rh
21.5
173
15.7
125
49
9.2
125
44.2
145
41
2.4
118
23.2
145
46
8.3
85
33.6
94
-6.3
120
23.1
131
50
10.1
148
17.4
132
48
δ(PP2), dd
1J P-Rh
2J P-P
36
175, 164, and 156°, respectively. In complex 5 the
average value is 152.5°, which is comparable with the
value observed for [PP2*RhPEt3]+.9 The Rh-Si bond
distance of 2.375 Å in 5 is comparable to that observed
in the case of other Rh(I) silyls.4a,g,7
Reaction of 3 with HSi(SEt)3 at room temperature
proceeded less selectively than at -20 °C, resulting in
both Si-H and Si-S activation (Scheme 2). Si-H
oxidative addition prevailed, the product ratio 5:6 being
about 4:1. Complex 6, observed in the reaction mixture,
was synthesized independently from 3 and HSEt.
F igu r e 1. Perspective view (ORTEP) of 5. Hydrogen atoms
are omitted for clarity.
Ta ble 1. Selected Bon d Len gth s (Å) a n d An gles
(d eg) in a Molecu le of 5
1
Formation of MeSiH(SEt)2 was clearly observed by H
NMR (δ 5.31 ppm (q, 3J H-H ) 3.3 Hz, H-Si); δ 0.41 ppm
Rh(1)-P(2)
Rh(1)-P(4)
2.3107(10)
2.3221(9)
Rh(1)-P(3)
Rh(1)-Si(5)
2.2842(14)
2.3747(14)
3
(d, J H-H ) 3.3 Hz, CH3-Si)).
P(3)-Rh(1)-P(2)
P(2)-Rh(1)-P(4)
P(2)-Rh(1)-Si(5)
91.05(4) P(3)-Rh(1)-P(4)
91.86(4)
We are aware of only one example of Si-S oxidative
addition to a metal center, namely PhS-SiCl3 addition
to Pt(0) complexes.10
153.06(3) P(3)-Rh(1)-Si(5) 151.78(4)
93.57(4) P(4)-Rh(1)-Si(5) 96.40(4)
The 31P{1H} NMR data of the rhodium complexes is
presented in Table 3. All the complexes except for 4
Ta ble 2. Cr ysta llogr a p h ic P a r a m eter s for th e
Str u ctu r e of 5
1
exhibit J P-Rh coupling in the range of 118-173 Hz,
empirical formula
formula mass
color and habit
cryst size, mm
cryst syst
C30H61P3RhS3Si
741.88
red prism
0.5 × 0.5 × 0.4
triclinic
which is typical for Rh(I) compounds, whereas 31P NMR
1
of the Rh(III) complex 4 exhibits smaller J P-Rh (85 and
2
94 Hz) and J P-P (36 Hz) coupling constants. Complex
1 exhibits the signal of the unique P atom downfield
relative to the signal of the terminal P atoms, a result
of the lower chloride trans influence.
space group
a, Å
b, Å
P1h
10.818(2)
10.942(2)
17.750(4)
84.71(3)
c, Å
The reactivity of the rhodium(I) complexes was com-
pared with that of the corresponding iridium(I) ana-
logues. Similarly to the chloride Rh(I) complex 2, the
analogous unsaturated complex (PP2)IrCl (7), which was
prepared from [(COE)2IrCl]2 and the PP2 ligand in THF
at room temperature, did not exhibit reactivity with
HSi(SEt)3. This is remarkable, considering the normally
high propensity of electron-rich Ir(I) for Si-H oxidative
addition. (PP2)IrMe (8), which was synthesized from 7
analogously to the Rh methyl complex 3, selectively adds
the Si-H bond of HSi(SEt)3 at room temperature,
yielding the stable Ir(III) complex fac-(PP2)Ir(Me)(H)-
(Si(SEt)3) (9) (Scheme 3). As expected, C-H reductive
elimination from Ir(III) is more difficult than from Rh-
(III), resulting in a stable hydrido methyl complex.
Interestingly, in contrast to the addition of HSi(SEt)3
to the rhodium complex 3, no Si-S activation was
observed with 8.
R, deg
â, deg
72.57(3)
63.71(3)
1795.2(6)
2
1.372
γ, deg
V, Å3
Z
d(calcd), g/cm3
µ, mm-1
0.837
diffractometer
radiation (λ, Å)
monochromator
temp, K
Rigaku AFC5R
Mo KR (0.710 73)
graphite
120(2)
ω
16
mode
scan speed, deg/min
scan width, deg
collcn range, deg
hkl range
1.8
1.2 e θ e 27.5
-14 e h e 13, -14 e k e 7,
-23 e l e 22
no. of rflns
collected
indep
R1
wR2
8755
8187
0.0572
0.1458
(10) (a) Han, L.-B.; Tanaka, M. J . Am. Chem. Soc. 1998, 120, 8249.
similar triphosphine ligand, PhP(CH2CH2CH2PPh)2-
(PP2*).9 It was shown that the tetrahedral distortion
from planar geometry of PP2*RhX complexes depends
on the bulk of the X ligand: for X ) Cl, Py, PEt3, the
average angles between the trans-disposed ligands are
(b) For
a recent review on silane reactions with transition-metal
complexes, including other Si-X bond additions, see: Corey, J . Y.;
Braddock-Wilking, J . Chem. Rev. 1999, 99, 175. (c) We believe that
an alternative mechanism, involving addition of the Si-H bond
followed by intramolecular activation of the Si-S bond, is unlikely
because of the highly favored spontaneous elimination of methane from
the intermediate [(PP2)Rh(Me)(H)(Si(SEt)3)]. Additionally, intramo-
lecular bond activation in this saturated 18e- intermediate is expected
to be unfavorable.
(9) Christoph, G.; Blum, P.; Liu, W.; Elia, A.; Meek, D. W. Inorg.
Chem. 1979, 18, 894.

New Tridentate Phosphine Rh and Ir Complexes
Organometallics, Vol. 21, No. 23, 2002 5063
Sch em e 2
Sch em e 3
Exp er im en ta l Section
Gen er a l Con sid er a tion s. All the manipulations of air- and
moisture-sensitive compounds were carried out using a nitrogen-
filled Vacuum Atmospheres glovebox. Solvents were purified
by standard procedures, degassed, and stored over molecular
sieves in the glovebox. All the reagents were of reagent grade.
5
HSi(SEt)3 was prepared according to a literature procedure.
NMR spectra were obtained with a Bruker AMX 400 spec-
trometer at ambient probe temperature in C6D6 solutions
unless otherwise specified. NMR chemical shifts are reported
in ppm and are referenced to internal residual C6D5H at δ 7.15
(1H NMR, 400 MHz), external 85% H3PO4 in D2O at δ 0.0 (31P
NMR, 162 MHz), or internal C6D6 at δ 128.00 (13C NMR, 100
MHz). Abbreviations are as follows: s, singlet; d, doublet; t,
triplet; q, quartet; m, multiplet; v, virtual; ov, overlapped; ap,
apparent. Elemental analyses were performed by H. Kolbe,
Mikroanalytisches Laboratorium, Mulheim-an-der-Ruhr, Ger-
many.
iP r 2P (CH2)3P (P h )(CH2)3P iP r 2 (P P 2). This compound was
synthesized in analogy to a literature procedure reported for
Cy2P(CH2)3P(Ph)(CH2)3PCy2.6 A 31 g amount (0.28 mol) of
PhPH2 in dry degassed hexane was treated under argon with
450 mL of 1.475 M BuLi (0.66 mol) in hexane at room
temperature; this mixture was then refluxed for 1 h and cooled
to room temperature. The resulting yellow mixture was filtered
under argon, washed with dry pentane, and dried in vacuo to
give 34 g of PhPLi2 in quantitative yield. An 11.3 g amount
(0.093 mol) of PhPLi2 was suspended in 160 mL of freshly
distilled and degassed ether, and the suspension was added
under nitrogen over 1 h to 35.9 g (0.185 mol) of Cl(CH2)3PiPr2,
dissolved in 140 mL of ether, and cooled to 0 °C. The resulting
mixture was refluxed overnight and then hydrolyzed with 300
mL of distilled degassed water. The water layer was extracted
twice with 150 mL of ether, and the ether fractions were
combined and dried with anhydrous Na2SO4. The volatile
compounds and unreacted Cl(CH2)3PiPr2 were removed under
vacuum, and the residue was chromatographed over active
neutral Al2O3, using benzene as eluent. Removal of the
benzene in vacuo yielded 18 g (55%) of pure PP2. NMR
characterization (CDCl3) was as follows. 31P{1H} NMR: 2.9 s
Complex 9 was characterized by multinuclear NMR,
including 31P, 31P{1H}, 1H, 13C{1H}, and 31P-1H 2D
correlation. A proton-coupled 31P NMR spectrum defined
the signal of P trans to hydride. This signal is cross-
linked only with the isopropyl signals in a 31P-1H 2D
correlation (besides the hydride). Another 31P signal is
cross-linked only with the aromatic protons and was
assigned as trans to the silyl ligand. The third 31P signal
is cross-linked with both the isopropyl and methyl
signals in the 1H spectrum, being trans to the Me ligand.
It is noteworthy that the Me signal of the Ir(I) complex
8 appears in the 13C{1H} NMR spectrum at -5.7 ppm
2
as a doublet of triplets (2J CPtrans ) 60 Hz, J CPcis ) 11
Hz), whereas the Me signal of the Ir(III) complex 9 is
strongly high field shifted and appears at -33.6 ppm
2
2
(dt, J CPtrans ) 55 Hz, J CPcis ) 8 Hz).
In summary, a number of (PP2)RhX complexes with
a new tridentate phosphine ligand were synthesized.
The reactivity of the new Rh(I) complexes toward tris-
(ethylthio)silane was investigated. It was demonstrated
that the reaction pathway strongly depends on the X
ligand, showing lack of reactivity when X ) Cl, forma-
tion of a Rh(III) adduct as a result of Si-H oxidative
addition when X ) H, and both Si-H and Si-S bond
activation when X ) Me, resulting in Rh(I) products. A
rare example of an X-ray-characterized Rh(I)-silyl
complex was presented. Reactivities of the Rh(I) and
Ir(I) complexes toward the thiosilane were compared.
In contrast to the rhodium analogue, (PP2)IrMe oxida-
tively added the Si-H bond of HSi(SEt)3, giving rise to
a stable Ir(III) adduct with no evidence of Si-S activa-
tion.
1
(2P), -26.0 s (1P). H NMR: 7.33 m (P-Ph, 2H), 7.15 m (P-
Ph, 3H), 1.2-1.7 ov m (CH2 and CHMe2, 16H), 0.87 m (CH3,
24H). 13C{1H} NMR: 138.33 d (1J C-P ) 14.8 Hz, Ph-P), 132.18
d (2J C-P ) 18.8 Hz, Ph-P), 128.98 d (4J C-P ) 0.7 Hz, Ph-P),
128.0 d (3J C-P ) 6.9 Hz, Ph-P), 29.90 vt (J C-P ) 11.8 Hz, CH2),
3
24.33 dd (1J C-P ) 19.7 Hz, J C-P ) 14.5 Hz, CH2), 23.17 dd
(1J C-P ) 17.7 Hz, 3J C-P ) 11.3 Hz, CH2), 22.96 d (2J C-P ) 12.1
Hz, CH3), 19.89 d (1J C-P ) 15.7 Hz, CH), 19.83 d (1J C-P ) 15.5
Hz, CH), 18.56 d (2J C-P ) 9.5 Hz, CH3).
(P P 2)Rh Cl (1). A solution of 222 mg (0.31 mmol) of
[(C8H14)2RhCl]2 in 3 mL of THF was treated with 265 mg (0.62
mmol) of PP2. The mixture was stirred for 2 h at room
temperature, and then the solvent was removed under vacuum
to yield quantitatively 350 mg of pure compound 1 as a yellow-
brown solid. 31P{1H} NMR: 21.45 dt (1J P-Rh ) 173.0 Hz,

5064 Organometallics, Vol. 21, No. 23, 2002
Goikhman et al.
2
2J P-P ) 49 Hz, 1P), 15.72 dd (1J P-Rh ) 125.5 Hz, J P-P ) 49
Hz, 2P). 1H NMR: 8.17 m (Ph-P, 2H), 7.75 m (Ph-P, 1H),
7.17 m (Ph-P, 2H), 3.0 m (CH2, 2H), 2.18 m (CH2, 2H), 1.64
dvt (J ) 7.2 Hz, CH3CH-P, 6H), 1.49 dvt (J H ) 7.2 Hz, CH3-
CH-P, 6H), 1.03 dvt (J ) 6.9 Hz, CH3CH-P, 6H), 0.97 dvt
(J ) 6.2 Hz, CH3CH-P, 6H), signals of other CH2 and CH
groups appear as overlapped multiplets at 0.9-1.7 ppm. 13C-
{1H} NMR: 138.13 dd (1J C-P ) 35.8 Hz, 2J C-Rh ) 1.5 Hz, Ph-
P), 134.70 dd (2J C-P ) 11.5 Hz, 3J C-Rh ) 1.3 Hz, Ph-P), 129.78
d (4J C-P ) 2.2 Hz, Ph-P), 127.59 d (3J C-P ) 9.0 Hz, Ph-P),
CH-P), 20.87 s (CH3CH-P), 19.72 vt (2J C-P ) 4J C-Ptrans ) 1.9
Hz, CH3CH-P), 17.59 s (CH3CH-P), -6.76 ddt (1J C-Rh ) 22.3
2
2
Hz, J C-Ptrans ) 67 Hz, J C-Pcis ) 13.7 Hz). Anal. Calcd for
C
24H48P3Rh: C, 55.15; H, 8.89. Found: C, 55.25; H, 8.78.
m er -(P P 2)Rh (H2)(Si(SEt)3) (4). A solution of 16 mg (0.03
mmol) of 2 in 0.5 mL of C6D6 was treated at room temperature
with 6 µL (0.03 mmol) of HSi(SEt)3, forming the complex mer-
(PP2)Rh(H)2(Si(SEt)3) (4) within minutes as the major product
(85% by NMR). A brown viscous solid was formed after
evaporation of the solvent. 31P{1H} NMR: 33.7 dd (1J P-Rh
)
29.35 ddt (1J C-P ) 29.9 Hz, J C-P ) 5.3 Hz, J C-Rh ) 0.9 Hz,
3
2
93.5 Hz, 2J P-P ) 36 Hz, 2P), 8.3 dt (1J P-Rh ) 85 Hz, 2J P-P ) 36
Hz, 1P). 1H NMR: 8.18 m (Ph-P, 2H), 7.37 m (Ph-P, 1H),
7.06 m (Ph-P, 2H), 3.13 q (3J H-H ) 7.3 Hz, S-CH2, 6H), 3.09
m (CH2, 4H), 1.50 t (3J H-H ) 7.3 Hz, S-CH2CH3, 9H), 1.45
vdt (J ) 7.3 Hz, CH3CH-P, 6H), 1.29 vdt (J ) 7.3 Hz, CH3-
CH-P, 6H), 1.16 vdt (J ) 6.9 Hz, CH3CH-P, 6H), 1.04 vdt
(J ) 6.9 Hz, CH3CH-P, 6H), -9.05 dddt (1J H-Rh ) 15.2 Hz,
2J H-Ptrans ) 123 Hz, 2J H-Pcis ) 11.5 Hz, 2J H-H ) 1.9 Hz), -9.25
Ph-P-CH2), 27.35 vt (1J C-P ) J C-Ptrans ) 10.3 Hz, CH3CH-
3
P), 24.30 vt (1J C-P ) 3J C-Ptrans ) 12.1 Hz, CH3CH-P), 21.12 vt
(2J C-P
) )
4J C-Ptrans ) 2.9 Hz, CH3CH-P), 20.95 vt (2J C-P
4J C-Ptrans ) 2.2 Hz, CH3CH-P), 20.66 m (P-CH2CH2CH2-P),
19.46 vt (2J C-P ) J C-Ptrans ) 1.2 Hz, CH3CH-P), 19.09 m ((i-
4
Pr-P-CH2), 17.59 m (CH3CH-P). Anal. Calcd for C24H45ClP3-
Rh: C, 51.03; H 8.03. Found: C, 50.87; H, 7.91.
2
m (1J H-Rh ) 13.7 Hz, J H-H ) 1.9 Hz), signals of other CH2
(P P 2)Rh H (2). Complex 1 (113 mg, 0.2 mmol) was dissolved
in dry THF and the solution treated with 0.125 mL of a 1.6 M
tBuLi (0.2 mmol) solution in pentane at -30 °C and then
warmed to room temperature. After the mixture stood at room
temperature for 2 h, the solvents were evaporated in vacuo,
the residue was redissolved in pentane, and the solution
filtered. The filtrate was evaporated and dried in vacuo,
affording complex 2 as a dark brown, slightly viscous substance
in 88% yield (93 mg). 31P{1H} NMR: 44.2 dd (1J P-Rh ) 144.7
and CH groups appear as overlapped multiplets at 0.9-2.0
ppm. Each hydride signal was observed in 1H{31P} decoupled
1
measurements as a doublet of doublets (dd), and clear J H-Rh
2
and J H-H values were obtained from this experiment, proving
the dihydride structure.
The minor product (ca. 15%) formed in the synthesis of 4
had three different broad signals in 31P NMR (26.9 br d
(1J P-Rh ) 87 Hz, 1P), 13.7 br d (1J P-Rh ) 92 Hz, 1P), -0.8 dvt
Hz, J P-P ) 40.7 Hz, 2P), 9.2 dt (1J P-Rh ) 125.2 Hz, J P-P
)
2
2
2
(1J P-Rh ) 92 Hz, J P-P ) 30 Hz, 1P)), and two hydride (trans
40.7 Hz, 1P). 1H NMR: 8.04 m (Ph-P, 2H), 7.22 m (Ph-P,
2H), 7.12 m (Ph-P, 1H), 1.7-1.95 ov m (CH2CH2, 8H), 1.45
vdt. (J ) 7.4 Hz, CH3CH-P, 6H), 1.27 vdt (J ) 7.1 Hz, CH3-
CH-P, 6H), 1.19 vdt (J ) 6.7 Hz, CH3CH-P, 6H), 1.10 vdt
(J H ) 6.8 Hz, CH3CH-P, 6H), -4.51 ap dq (2J H-Ptrans ) 108
1
to P) signals in H NMR (-9.8 dm (2J H-P ) 131 Hz, 1H), -10.7
1
2
dm (2J H-Ptrans ) 109 Hz, J H-Rh ) 13 Hz, J H-H ) 6 Hz, 1H)).
The byproduct is likely to be a fac isomer of 4, which was also
supported by sufficient elemental analysis of the mixture.
Anal. Calcd for C30H62P3RhS3Si: C, 48.50; H, 8.41. Found: C,
48.55; H, 8.04.
1
2
Hz, J H-Rh ) J H-Pcis ) 20.0 Hz, H-Rh, 1H), signals of other
CH2 and CH groups appear as overlapped multiplets at 1.0-
(P P 2)Rh Si(SEt)3 (5). A solution of 44 mg (0.08 mmol) of 3
in 1 mL of pentane was treated at -20 °C with 16 µL (0.08
mmol) of HSi(SEt)3 and left standing at -20 °C. About 90%
conversion was observed after 3 weeks. The major product was
5 (80%). Small amounts of complexes 3 (starting compound)
and 4 were also observed. Methane and presumably MeSi-
(SEt)3 were detected by 1H NMR (singlets at 0.14 and 0.63
ppm, respectively). Complex 5 was isolated in 25% yield (15
mg) as deep red crystals after standing in concentrated
pentane solution at -20 °C for 1 month. The complex has a
limited stability at room temperature.
1.5 ppm. 13C{1H} NMR: 141.07 dd (1J C-P ) 21.2 Hz, J C-Rh
)
2
0.8 Hz, Ph-P), 134.59 dd (2J C-P ) 13.9 Hz, J C-Rh ) 0.8 Hz,
3
Ph-P), 129.27 d (4J C-P ) 1.8 Hz, Ph-P), 127.60 d (3J C-P
8.4 Hz, Ph-P), 30.13 dt (1J C-P ) 20.6 Hz, 3J C-P ) 4.9 Hz, Ph-
)
P-CH2), 28.52 vdt (1J C-P ) J C-Ptrans ) 9.9 Hz, J C-Rh ) 1.0
3
2
Hz, CH3CH-P), 27.89 vddt (1J C-P
)
3J C-Ptrans ) 13.1 Hz,
3J C-Pcis ) 3.6 Hz, J C-Rh ) 2.4 Hz, CH3CH-P), 23.50 ap dq
2
(1J C-P ) J C-Ptrans ) J C-Pcis ) 8.0 Hz, J C-Rh ) 0.8 Hz, Pr-
P-CH2), 21.58 m (P-CH2CH2CH2-P), 21.45 vdt (2J C-P
4J C-Ptrans ) 3.6 Hz, 2J C-Rh ) 1.0 Hz, CH3CH-P), 19.50 m (CH3-
3
3
2
i
)
CH-P), 19.32 m (CH3CH-P), 18.79 ap q (2J C-P ) 4J C-Ptrans
)
3J C-Rh ) 1.7 Hz, CH3CH-P). MS (ESI): m/z (%): 530 (30) [M+],
A room-temperature reaction of equimolar amounts of 3 (30
mg) and HSi(SEt)3 (11 µL) proceeded less selectively. Com-
plexes 4 (10%), 5 (65%), and 6 (15%) and small amounts of
several unidentified Rh(III) complexes were formed. New
529 (100) [M+ - H].
(P P 2)Rh Me (3). This complex was synthesized in analogy
to 2. A 170 mg amount (0.3 mmol) of 1 was dissolved in dry
THF and the solution treated with 0.24 mL of a 1.4 M ether
solution of MeLi (0.3 mmol) at -30 °C. This solution was
warmed to room temperature, and the solvent was evaporated
in vacuo. The residue was dissolved in pentane and filtered,
and the filtrate was evaporated and dried in vacuo, affording
1
signals assigned to MeSiH(SEt)2 were observed by H NMR:
3
3
5.31 (q, J H-H ) 3.3 Hz, H-Si); 0.41 (d, J H-H ) 3.3 Hz,
CH3-Si).
NMR data for 5 are as follows. 31P{1H} NMR: 23.1 dd
(1J P-Rh ) 131 Hz, J P-P ) 50 Hz, 2P), -6.3 dt (1J P-Rh ) 119.6
2
2
1
Hz, J P-P ) 50 Hz, 1P). H NMR: 8.13 m (Ph-P, 2H), 7.23 m
(Ph-P, 2H), 7.07 m (Ph-P, 1H), 3.67 m (CH2, 2H), 3.26 m
(CH2, 2H), 3.16 q (3J H-H ) 7.4 Hz, CH2-SSi, 6H), 1.50 t
(3J H-H ) 7.4 Hz, CH3CH2-SSi, 9H), 1.54 vdt (J ) 7.9 Hz, CH3-
CH-P, 6H), 1.27 vdt (J ) 8.1 Hz, CH3CH-P, 6H), 1.13 m (CH3-
CH-P, 6H), 1.07 m (CH3CH-P, 6H), signals of other CH2 and
CH groups appear as overlapped multiplets at 0.8-1.7 ppm.
Anal. Calcd for C30H60P3RhS3Si: C, 48.63; H 8.16. Found: C,
49.34; H, 7.95.
complex 3 as a brown slightly viscous substance in 85% yield
(140 mg). 31P{1H} NMR: 23.24 dd (1J P-Rh ) 145 Hz, J P-P
)
2
46 Hz, 2P), 2.39 dt (1J P-Rh ) 118 Hz, J P-P ) 46 Hz, 1P). H
NMR: 8.16 m (Ph-P, 2H), 7.19 m (Ph-P, 2H), 7.09 m (Ph-P,
1H), 2.39 m (CH2, 2H), 2.04 m (CH2, 2H), 1.8 ov m (CH2, 4H),
1.45 vdt (J ) 7.3 Hz, CH3CH-P, 6H), 1.31 vdt (J ) 6.9 Hz,
CH3CH-P, 6H), 1.05 vdt (J ) 6.6 Hz, CH3CH-P, 6H), 1.01 m
(CH3CH-P, 6H), 0.39 m (CH3-Rh, 3H), signals of other CH2
and CH groups appear as overlapped multiplets at 0.9-1.5
ppm. 13C{1H} NMR: 141.15 d (1J C-P ) 26.4 Hz, Ph-P), 134.6
d (2J C-P ) 12.5 Hz, Ph-P), 128.98 d (4J C-P ) 1.8 Hz, Ph-P),
127.34 d (3J C-P ) 8.3 Hz, Ph-P), 29.84 dvt (1J C-P ) 23.6 Hz,
2
1
Cr ysta l Str u ctu r e Deter m in a tion . Prismatic, red crystals
of 5 were mounted on a glass fiber and coated with inert oil.
They were then flash frozen in the liquid nitrogen gas stream.
Data were collected at 110 K on a Rigaku AFC-5R four-circle
diffractometer using graphite-monochromated Mo KR radia-
tion (λ ) 0.7107 Å) in the ω-scan mode. The unit cell
parameters were obtained from least-squares refinement of
3J C-P
)
2J C-Rh ) 4.3 Hz, Ph-P-CH2), 27.66 dvt (1J C-P
)
3J C-Ptrans ) 8.8 Hz, J C-Rh ) 0.9 Hz, CH3CH-P), 24.20 vtt
(1J C-P ) 3J C-Ptrans ) 11 Hz, 2J C-Rh ) 2J C-Pcis ) 1.4 Hz, CH3CH-
P), 21.55 m (iPr-P-CH2), 20.9 m (iPr-P-CH2), 20.90 s (CH3-
2

New Tridentate Phosphine Rh and Ir Complexes
Organometallics, Vol. 21, No. 23, 2002 5065
25 reflections, and all reflections in the range of 1.2° < 2θ <
27.5° were collected. Table 2 summarized crystal and refine-
ment data.
and CH groups appear as overlapped multiplets at 1.2-1.7
ppm. MS (ESI): m/z (%): 697 (19) [M + K+], 679 (13) [M +
Na+], 619 (100) [M+ - Cl].
The structure was solved using direct methods and refined
with the program SHELX-76. A full-matrix least-squares
refinement with anisotropic temperature factors was used for
all non-hydrogen atoms. Idealized hydrogen atoms were placed
in calculated positions and refined in the riding mode.
(P P 2)Rh SEt (6). A solution of 33 mg (0.06 mmol) of 3 in 1
mL of C6D6 was treated at room temperature with 4.5 µL (0.06
mmol) of HSEt. The reaction mixture was stirred for 30 min
to give 6 in 95% yield. Formation of methane was detected by
(P P 2)Ir Me (8). This complex was synthesized in analogy
to 3. A 130 mg amount (0.2 mmol) of 7 was dissolved in dry
THF and treated with 0.16 mL of a 1.4 M ether solution of
MeLi (0.2 mmol) at -30 °C. The solution was warmed to room
temperature, and the solvent was evaporated in vacuo. The
residue was dissolved in pentane and the solution filtered. The
filtrate was evaporated and dried in vacuo, affording orange
viscous compound 8 in 89% yield (112 mg). 31P{1H} NMR: 9.62
d (2J P-P ) 30.3 Hz, 2P), -17.62 t (2J P-P ) 30.3 Hz, 1P). 1H
NMR: 8.24 m (Ph-P, 2H), 7.22 m (Ph-P, 2H), 7.08 m (Ph-P,
1H), 2.55 m (CH2, 2H), 2.17 m (CH2, 2H), 2.05 m (CH2, 2H),
1.45 dvt (J ) 7.3 Hz, CH3CH-P, 6H), 1.30 dvt (J H ) 6.9 Hz,
2
NMR. 31P{1H} NMR: 17.4 dd (1J P-Rh ) 132.7 Hz, J P-P ) 48.1
2
1
Hz, 2P), 10.1 dt (1J P-Rh ) 147.5 Hz, J P-P ) 48.1 Hz, 1P). H
NMR: 8.15 m (Ph-P, 2H), 7.12 ov m (Ph-P, 3H), 2.92 dq
(3J H-H ) 7.3 Hz, 4J H-Ptrans ) 2.1 Hz, S-CH2, 2H), 2.67 m (CH2,
4H), 1.78 t (3J H-H ) 7.4 Hz, CH3CH2-S, 3H), 1.61 vdt (J )
7.3 Hz, CH3CH-P, 6H), 1.38 vdt (J ) 7.3 Hz, CH3CH-P, 6H),
1.14 vdt (J ) 6.4 Hz, CH3CH-P, 6H), 1.00 vdt (J ) 6.3 Hz,
CH3CH-P, 6H), signals of other CH2 and CH groups appear
as overlapped multiplets at 0.8-1.7 ppm. MS (ESI): m/z (%):
561 (86) [M+ - Et], 529 (100) [M+ - SEt].
3
CH3CH-P, 6H), 1.15 dt (3J H-Ptrans ) 5.5 Hz, J H-Pcis ) 7.2 Hz,
Ir-CH3, 3H), 1.07 dvt (J ) 6.7 Hz, CH3CH-P, 6H), 0.98 dvt
(J ) 6.0 Hz, CH3CH-P, 6H), signals of other CH2 and CH
groups appear as overlapped multiplets at 1.3-1.8 ppm. 13C-
2
{1H} NMR: -5.7 dt (2J C-Ptrans ) 60 Hz, J C-Pcis ) 11 Hz, Ir-
CH3). MS (ESI): m/z (%): 634 (6) [M+], 619 (92) [M+ - CH3].
fa c-[(P P 2)Ir (H)(Me)(Si(SEt)3)] (9). A solution of 19 mg
(0.03 mmol) of 8 in 0.5 mL of C6D6 was treated at 6 °C with 6
µL (0.03 mmol) of HSi(SEt)3. The complex fac-[(PP2)Ir(H)(Me)-
(Si(SEt)3)] (9) was readily formed. Removal of the solvent in
[(Et3P )2Rh (Cl)(H)(Si(SEt)3)]. A solution of 15 mg (0.03
mmol) of (Et3P)3RhCl in 0.5 mL of C6D6 was treated at room
temperature with 6 µL (0.03 mmol) of HSi(SEt)3. The complex
[(Et3P)2Rh(Cl)(H)(Si(SEt)3)] was formed within minutes, and
1 equiv of Et3P was liberated. Evaporation of the solution gave
18 mg of the yellow-orange viscous compound. The yield is
quantitative. The complex partially decomposes under high
vacuum. 31P{1H} NMR: 26.5 d (1J P-Rh) 112 Hz). 1H NMR: 3.03
q (3J H-H ) 7.5 Hz, SiS-CH2, 6H), 2.00 m (P-CH2, 12H), 1.35
vacuo gave an off-white residue of 9. 31P{1H} NMR: -33.83
2
dd (2J P-P ) 19.1 Hz, J P-P ) 22.5 Hz, 1P), -37.94 vt (2J P-P
)
19.1 Hz, 1P), -41.07 dd (2J P-P ) 19.1 Hz, J P-P ) 22.5 Hz,
2
1
1P). H NMR: 8.21 m (Ph-P, 2H), 7.36 m (Ph-P, 2H), 7.17 m
(Ph-P, 1H), 3.08 m (SiS-CH2, 6H), 2.48 m (CH2, 2H), 1.38 t
(3J H-H ) 7.4 Hz, SiS-CH2CH3, 9H), 0.81 m (Ir-CH3, 3H),
t (3J H-H ) 7.5 Hz, SiS-CH2CH3, 9H), 1.06 dt (3J H-P ) 15.2
-12.38 ddd (2J H-Ptrans ) 116.9 Hz, J H-Pcis ) 21.6 Hz,
2
3
Hz, J H-H ) 7.6 Hz, P-CH2CH3, 18H), -15.85 dt (1J H-Rh
)
2J H-Pcis ) 9.3 Hz), signals of other CH3, CH2, and CH groups
appear as overlapped multiplets at 0.9-2.1 ppm. 13C{1H}
2
23.7 Hz, J H-P ) 12.9 Hz, Rh-H, 1H).
2
Rea ction of (P P 2)Rh Si(SEt)3 (5) w ith HCl. A 9 mg
amount (0.012 mmol) of compound 5 was dissolved in C6D6
and treated with an equivalent amount (3 µL) of 4 M HCl
solution in 1,4-dioxane. Immediate quantitative formation of
(PP2)RhCl (1) and HSi(SEt)3 was detected by NMR.
NMR: -33.6 dt (2J C-Ptrans ) 55 Hz, J C-Pcis ) 8 Hz, Ir-CH3).
MS (ESI): m/z (%) 869 (21) [M + Na+], 769 (8) [M+ - CH4
SEt], 619 (100) [M+ - CH4 - Si(SEt)3].
-
Ack n ow led gm en t. This work was supported by the
Israel Science Foundation, J erusalem, Israel, and by the
Minerva Foundation, Munich, Germany. D.M. is the
Israel Matz Professorial Chair of Organic Chemistry.
(P P 2)Ir Cl (7). A solution of 180 mg (0.2 mmol) of [(cyclo-
octene)2IrCl]2 in 4 mL of THF was treated with 171 mg (0.4
mmol) of PP2. The mixture was stirred for 2 h at room
temperature, and the solvent was removed under vacuum to
yield quantitatively 262 mg of pure compound 7. 31P{1H}
NMR: 8.71 d (2J P-P ) 31 Hz, 2P), -15.94 t (2J P-P ) 31 Hz,
Su p p or tin g In for m a tion Ava ila ble: Tables giving crys-
tal data and structure refinement details, atomic coordinates
and equivalent isotropic displacement parameters, all bond
lengths and angles, anisotropic displacement parameters, and
hydrogen coordinates for 5. This material is available free of
charge via the Internet at http://pubs.acs.org.
1
1P). H NMR: 8.20 m (Ph-P, 2H), 7.19 m (Ph-P, 2H), 7.06 m
(Ph-P, 1H), 3.14 m (CH2, 2H), 2.27 m (CH2, 2H), 1.94 m (CH2,
2H), 1.63 dvt (J ) 7.5 Hz, CH3CH-P, 6H), 1.48 dvt (J H ) 7.1
Hz, CH3CH-P, 6H), 1.07 dvt (J ) 7.0 Hz, CH3CH-P, 6H),
0.95 dvt (J ) 6.3 Hz, CH3CH-P, 6H), signals of other CH2
OM020120A