Silylenediamido [(CH3)2Si(NTs)2 2-; Ts = p-CH3C6H4SO2] complexes of iridium: Synthesis, structures and facile Si-N bond cleavage

Article abstract of DOI:10.1039/b709930b

The N,N′-bis(sulfonyl)diaminosilane TsdmsinH₂ (TsdmsinH₂ = (CH₃)₂Si(NHTs)₂, Ts = p-CH₃C₆H₄SO₂) reacted with [Cp*IrCl₂]₂ (Cp* = η⁵-C ₅(CH₃)₅) in the presence of a base to give the coordinatively unsaturated (silylenediamido)iridium complex [Cp* Ir(Tsdmsin)] (2), which was further converted to the 18e adducts [Cp*Ir(Tsdmsin)L] (L = P(C₆H₅)₃ (3a), P(OC₂H₅)₃, CO); the reactions of 2 and 3a with water led to the formation of the imido-bridged dinuclear complex [Cp*Ir(₂-NTs)₂IrCp*] and the bis(amido) complex [Cp*Ir(NHTs)₂{P(C₆H₅) ₃}], respectively. The Royal Society of Chemistry.

Full text of DOI:10.1039/b709930b

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2−
Silylenediamido [(CH3)2Si(NTs)2 ; Ts = p-CH3C6H4SO2] complexes of
iridium: synthesis, structures and facile Si–N bond cleavage†‡
Koji Ishiwata, Shigeki Kuwata* and Takao Ikariya*
Received 29th June 2007, Accepted 2nd July 2007
First published as an Advance Article on the web 17th July 2007
DOI: 10.1039/b709930b
The
N,Nꢀ-bis(sulfonyl)diaminosilane
TsdmsinH2
Treatment of [Cp*IrCl2]2 with two equiv. of 1 in the presence of
triethylamine and CaH2 as a water scavenger cleanly afforded the
16e silylenediamido complex [Cp*Ir(Tsdmsin)] (2) as shown in
eqn (2).§
(TsdmsinH2 = (CH3)2Si(NHTs)2, Ts = p-CH3C6H4SO2)
5
reacted with [Cp*IrCl2]2 (Cp* = g -C5(CH3)5) in the presence
of a base to give the coordinatively unsaturated (silylene-
diamido)iridium complex [Cp*Ir(Tsdmsin)] (2), which was
further converted to the 18e adducts [Cp*Ir(Tsdmsin)L] (L =
P(C6H5)3 (3a), P(OC2H5)3, CO); the reactions of 2 and 3a with
water led to the formation of the imido-bridged dinuclear
complex [Cp*Ir(l2-NTs)2IrCp*] and the bis(amido) complex
[Cp*Ir(NHTs)2{P(C6H5)3}], respectively.
(2)
The coordinatively unsaturated nature of 2 was evidenced by its
facile reactions with various two-electron donor ligands, giving the
corresponding 18e adducts [Cp*Ir(Tsdmsin)L] (3a: L = P(C6H5)3;
3b: L = P(OC2H5)3; 3c: L = CO) quantitatively (eqn (3)).§
The Si–N linkage has been a useful component in designing
chelating amido ligands such as ansa-monocyclopentadienyl–
amido ligands in a certain type of polymerization catalysts1
and Fryzuk’s [PxNy]-type mixed donor ligands.2 The silylamido
moiety in the chelate backbone of these ligands facilitates ligand
synthesis and gives electronic perturbation to the metal center by
its weak dative pp–dp bonding between the nitrogen and metal in
comparison with the alkylamido congeners.3 Our extensive studies
on metal/NH bifunctional catalysts bearing chelating amine
ligands4 revealed that modification of the amine ligand greatly
effects the catalyst performance. For example, hydrogenolysis of
epoxides is accelerated by using phosphinoethylamines in place of
(3)
Among the P donor ligands, only the phosphine ligand in 3a
proved to be so labile that the dissociation of triphenylphos-
phine was observed in a C6D6 solution of 3a. Fig. 1 depicts
the crystal structures of 2 and 3a.¶ The Ir–Si distances in
5
1,2-diamines in the Cp*Ru(chelating amine) catalyst (Cp* = g -
C5(CH3)5).5 As an extension of these studies, we became interested
in silylenediamido (R2Si(NRꢀ)22−) complexes, in which the chelate
backbone of the diamine ligand is replaced by an Si atom. This type
of ligand has been used mainly in early transition metal chemistry,6
and its coordination to late transition metal centers remains
undeveloped.7 We report here the synthesis and structures of the
(silylenediamido)iridium complexes, which undergo unexpectedly
facile and selective hydrolysis of the Si–N bond.
˚
2 and 3 (2.896(2)–2.9794(15) A; Table 1), which are much
longer than those in the reported (silyl)iridium complexes
8
˚
(2.235–2.454 A), indicate no apparent direct Ir–Si bonding
˚
interactions. The Ir–NTs distances in 2 (2.034 A, mean) are
slightly longer than those in the related coordinatively unsat-
urated complexes [Cp*Ir{H2NCH(C6H5)CH(C6H5)NTs}][B{3,5-
The silylenediamine ligand TsdmsinH2 (1; TsdmsinH2
=
9
˚
(CF3)2C6H3}4] (1.984(4) A) and [Cp*Ir{N(Ts)CH2CO2}]
(CH3)2Si(NHTs)2, Ts = p-CH3C6H4SO2), having an electron-
withdrawing sulfonyl substituent, was prepared by the reaction
of the dichlorosilane and lithium sulfonylamidate as the corre-
sponding di(arylamino)silanes (eqn (1)).§
10
˚
(1.981(7) A), but still shorter than those in the 18e complexes
˚
3 (2.128(4)–2.179(5) A). Thus considerable p-donation from the
N atoms in 2 is suggested despite the presence of the electron-
withdrawing sulfonyl substituents on the N atoms. The IrNSiN
four-membered ring in 2 is almost planar, whereas that in 3a is
puckered with the Ir–N(1)–N(2)–Si dihedral angle of 150.0(3)◦ to
avoid steric congestion between the Si(CH3)2 group and the phos-
phine ligand. Coordination of the two-electron donors renders the
two methyl groups on the Si atom in 3 inequivalent in the 1H NMR
spectra. The CO stretching band, 2036 cm−1, of 3c is comparable
with that in the related N,Nꢀ-bis(tosyl)ethylenediamido complex
[Cp*Ir(TsNCH2CH2NTs)(CO)] (2042 cm−1).11
−−−→
(CH3)2SiCl2 + 2LiNHTs
(CH3)2Si(NHTs)2
(1)
THF
1, 58%
Department of Applied Chemistry, Graduate School of Science and Engineer-
ing, Tokyo Institute of Technology, O-okayama, Meguro-ku, Tokyo, 152-
8552, Japan. E-mail: skuwata@apc.titech.ac.jp; tikariya@apc.titech.ac.jp;
Fax: +81 3 5734 2637; Tel: +81 3 5734 2150
† CCDC reference numbers 647948–647952. For crystallographic data in
CIF or other electronic format see DOI: 10.1039/b709930b
Treatment of the coordinatively unsaturated complex 2 with
water in the presence of KOH resulted in cleavage of the Si–N
‡ Electronic supplementary information (ESI) available: Experimental
details. See DOI: 10.1039/b709930b
3606 | Dalton Trans., 2007, 3606–3608
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◦
˚
Table 1 Selected interatomic distances (A) and angles ( ) in 2 and 3
2
3a
3b
3c
Ir–Si
2.913a
2.896(2)
2.171
69.4(2)
354.8
2.9794(15)
2.156
69.82(14)
358.6
2.9657(17)
2.129
70.03(17)
359.2
Ir–Na
2.034
N–Ir–N
72.0a
Sum of the bond angles around Na
Ir–N–N–Si torsion angle
359.8
177.0a
150.0(3)
166.0(2)
172.8(2)
a Mean values.
(5)
1
The presence of the amide protons in 5 is suggested by the H
NMR (d 2.65) and IR spectrum (mNH = 3346, 3281 cm−1). An X-
ray analysis revealed the presence of an intramolecular hydrogen
bond between an amido proton and a sulfonyl oxygen atom
˚
with an N(1)–O(4) distance of 2.925(7) A, although the amine
hydrogens could not be located in the difference Fourier map
(Fig. 2).¶ The hydrolysis of 3a was suppressed by addition of
P(C6H5)3, and the hydrolysis of 3b bearing the inert phosphite
ligand did not proceed under the same conditions; nevertheless,
the parent coordinatively unsaturated complex 2 itself failed to
react with water in the absence of the base. These observations
suggest that the initial coordination of water and subsequent
deprotonation by the dissociated phosphine should occur in
the hydrolysis of 3a. The resultant anionic hydroxo species
[Cp*Ir(OH)(Tsdmsin)]− (6) also seems to be involved in the
hydrolysis of 2 shown in eqn (4). A similar (hydroxo)ruthenium
intermediate has recently been proposed in the controlled hydrol-
ysis of the PNP complex [Ru{N[Si(CH3)2CH2P(t-C4H9)2]2}(OTf)]
to the bis(siloxo)complex [Ru{OSi(CH3)2CH2P(t-C4H9)2}2] by
Caulton and co-workers.2e For the selective hydrolysis of 2 and 3a,
Fig. 1 Crystal structures of 2 and 3a. Hydrogen atoms are omitted for
clarity, and one of the two crystallographically independent units in 2 is
shown. Thermal ellipsoids are drawn at the 30% probability.
and Ir–N bonds and formation of the imido-bridged dinuclear
complex [Cp*Ir(l2-NTs)2IrCp*] (4)12 quantitatively (eqn (4)).
(4)
In contrast, the two Si–N bonds in the 18e silylenediamido
complex 3a underwent hydrolysis even in the absence of the base to
afford the novel bis(amido) complex [Cp*Ir(NHTs)2{P(C6H5)3}]
(5; eqn (5)).§
Fig. 2 Crystal structure of 5·CH2Cl2. Hydrogen atoms and the solvating
CH2Cl2 are omitted for clarity. Thermal ellipsoids are drawn at the 30%
◦
˚
probability. Selected bond distances (A) and angle ( ): Ir–N(1), 2.130(5);
Ir–N(2), 2.148(5); N(1)–Ir–N(2), 84.0(2).
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the following intramolecular nucleophilic attack of the hydroxo
ligand to the Si atom in 6 would lead to Si–N bond fission.13
Subsequently, the Ir–N or Si–N bond would be cleaved depending
upon the availability of an external proton.
34.25 cm−1, T = 193 K, 38467 reflections measured (Rint = 0.065),
final R indices (2h < 55◦) for 9542 unique reflections (546 parameters)
are R1 = 0.053 [I > 2r(I)], wR2 = 0.123 (all data), GOF = 1.001.
For 5·CH2Cl2: C43H48Cl2IrN2O4PS2 (1015.08), orthorhombic, Pbca, a =
3
˚
˚
14.832(5), b = 19.130(7), c = 30.389(11) A, U = 8622.6(55) A , Z =
8, qcalc = 1.564 g cm−3, l(MoKa) = 34.06 cm−1, T = 193 K, 92390
reflections measured (Rint = 0.091), final R indices (2h < 55◦) for 9869
unique reflections (542 parameters) are R1 = 0.039 [I > 2r(I)], wR2 =
0.103 (all data), GOF = 1.000.
Facile and selective hydrolysis of 3a to 5 highlights the silylene
moiety as a protecting group of the mononuclear M(NHR)2
functionality without chelation, which is scarce14 probably because
it tends to decompose to the terminal or bridging imido species
by a-elimination of amine.15 Indeed, we could not obtain the
bis(amido) complex 5 by the simple salt-elimination reaction of
[Cp*IrCl2{P(C6H5)3}] and LiNHTs. We expect 5 to be a useful
precursor for the imido-bridged heterodinuclear Lewis acid–
Brønsted base bifunctional catalysts,4 featuring a delicate balance
of the basicity of the N atom and the stability of the complex
owing to the electron-withdrawing sulfonyl substituent.12
In summary, we have revealed that the silylenediamido com-
plexes of a late transition metal undergo selective hydrolysis of the
Si–N bond in two modes with high yields. Further studies are now
under way to clarify the detailed mechanism of the hydrolysis as
well as the reactivities of the silylenediamido complexes.
This work was supported by a Grant-in-Aid for Scientific
Research on Priority Areas (No. 18065007, “Chemistry of Con-
certo Catalysis”) from the Ministry of Education, Culture, Sports,
Science and Technology, Japan and the Asahi Glass Foundation
(S.K.).
1 A. L. McKnight and R. M. Waymouth, Chem. Rev., 1998, 98, 2587–
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1530–1543; (b) B. A. MacKay and M. D. Fryzuk, Chem. Rev., 2004, 104,
385–402; (c) M. D. Fryzuk, Chem. Rec., 2003, 3, 2–11; (d) O. V. Ozerov,
L. A. Walstrom, M. Pink and K. G. Caulton, J. Am. Chem. Soc., 2007,
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Chem., 2006, 45, 5617–5620; (f) L. H. Gade, Chem. Commun., 2000,
173–181.
3 R. A. Andersen, K. Faegri, Jr., J. C. Green, A. Haaland, M. F. Lappert,
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7119.
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393–406; M. Ito, A. Sakaguchi, C. Kobayashi and T. Ikariya, J. Am.
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Ikariya, Org. Lett., 2007, 9, 1821–1824.
5 M. Ito, M. Hirakawa, A. Osaku and T. Ikariya, Organometallics, 2003,
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6 Recent examples: L. Zhou, Y. Yao, C. Li, Y. Zhang and Q. Shen,
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Notes and references
§ Spectral data for 1: dH(300 MHz; CDCl3) 7.75, 7.28 (d, 4H each, 3JHH
=
8.4 Hz, SO2C6H4CH3), 4.98 (br, 2H, NH), 2.42 (s, 6H, SO2C6H4CH3),
0.44 (s, 6H, Si(CH3)2). For 2: dH(300 MHz; C6D6) 7.98, 6.82 (d, 4H each,
3JHH = 8.1 Hz, SO2C6H4CH3), 1.95 (s, 6H, SO2C6H4CH3), 1.25 (s, 15H,
Cp*), 0.60 (s, 6H, Si(CH3)2). For 3a: dH(300 MHz; C6D6) 7.95–6.63 (m,
7 H. Chen, R. A. Bartlett, H. V. R. Dias, M. M. Olmstead and P. P.
Power, Inorg. Chem., 1991, 30, 2487–2494.
8 Y.-K. Sau, H.-K. Lee, I. D. Williams and W.-H. Leung, Chem.–Eur. J.,
2006, 12, 9323–9335.
9 Z. M. Heiden and T. B. Rauchfuss, J. Am. Chem. Soc., 2006, 128,
13048–13049.
3
15H, aryl), 7.24, 6.59 (d, 4H each, JHH = 8.1 Hz, SO2C6H4CH3), 1.89
(s, 6H, SO2C6H4CH3), 1.62 (d, 15H, 4JPH = 2.0 Hz, Cp*), 0.95, −0.75 (s,
3H each, Si(CH3)2). dP(122 MHz; C6D6) 16.6 (s). For 3b: dH(300 MHz;
C6D6) 8.02, 6.84 (d, 4H each, 3JHH = 8.1 Hz, SO2C6H4CH3), 3.82 (dq, 6H,
3
3JPH = JHH = 7.1 Hz, P(OCH2CH3)3), 1.96 (s, 6H, SO2C6H4CH3), 1.77
(d, 15H, 4JPH = 3.4 Hz, Cp*), 1.04 (t, 9H, 3JHH = 7.1 Hz, P(OCH2CH3)3),
0.52, 0.42 (s, 3H each, Si(CH3)2). dP(122 MHz; C6D6) 79.2 (s). For 3c:
dH(300 MHz; C6D6) 7.88, 6.81 (d, 4H each, 3JHH = 8.1 Hz, SO2C6H4CH3),
1.86 (s, 6H, SO2C6H4CH3), 1.57 (s, 15H, Cp*), 0.77, 0.58 (s, 3H each,
Si(CH3)2). mmax(KBr)/cm−1 2036 (CO). For 5: dH(300 MHz; C6D6) 7.52,
6.99 (br, 15H, aryl), 7.44, 6.65 (d, 4H each, 3JHH = 8.1 Hz, SO2C6H4CH3),
2.65 (d, 2H, 3JPH = 3.4 Hz, NH), 1.97 (s, 6H, SO2C6H4CH3), 1.56 (d, 15H,
4JPH = 2.4 Hz, Cp*). dP(122 MHz; C6D6) 7.3 (s). mmax(KBr)/cm−1 3346,
3281 (NH).
10 D. B. Grotjahn and T. L. Groy, Organometallics, 1995, 14, 3669–
3682.
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12 K. Ishiwata, S. Kuwata and T. Ikariya, Organometallics, 2006, 25, 5847–
5849.
13 For related Si–N bond cleavage reactions, see: M. D. Fryzuk and P. A.
MacNeil, J. Am. Chem. Soc., 1984, 106, 6993–6999; W. A. Herrmann
and W. Baratta, J. Organomet. Chem., 1996, 506, 357–361; O. V. Ozerov,
H. F. Gerard, L. A. Watson, J. C. Huffman and K. G. Caulton, Inorg.
Chem., 2002, 41, 5615–5625; M. D. Fryzuk, M. P. Shaver and B. O.
Patrick, Inorg. Chim. Acta, 2003, 350, 293–298.
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D. A. Kissounko, A. Epshteyn, J. C. Fettinger and L. R. Sita,
Organometallics, 2006, 25, 1076–1078.
¶ Crystal data for 2: C26H35IrN2O4S2Si (724.00), monoclinic, P21/a, a =
◦
˚
14.045(4), b = 18.430(5), c = 22.740(6) A, b = 98.606(3) , U = 5820.0(25)
A , Z = 8, qcalc = 1.652 g cm−3, l(MoKa) = 48.19 cm−1, T = 193 K,
3
˚
52747 reflections measured (Rint = 0.059), final R indices (2h < 55◦) for
13188 unique reflections (719 parameters) are R1 = 0.039 [I > 2r(I)],
wR2 = 0.130 (all data), GOF = 1.005. For 3a: C44H50IrN2O4PS2Si (986.29),
˚
monoclin◦ic, P21/c, a = 10.474(4), b = 19.550(7), c = 20.356(7) A, b =
15 D. S. Glueck, J. Wu, F. J. Hollander and R. G. Bergman, J. Am. Chem.
Soc., 1991, 113, 2041–2054.
91.550(5) , U = 4166.9(25) A , Z = 4, qcalc = 1.572 g cm−3, l(MoKa) =
3
˚
3608 | Dalton Trans., 2007, 3606–3608
This journal is
The Royal Society of Chemistry 2007
©