Photochemistry of a Tellurosilyl(carbonyl)iron(II) Complex. Generation of a Novel Te-Si-Fe Three-membered Cyclic Intermediate

Article abstract of DOI:10.1246/cl.2003.876

The tellurosilyliron complex Cp*(CO)₂FeSiMe ₂TePh (1) was synthesized by treatment of Cp*(CO) ₂FeSiMe₂Cl with LiTePh. Irradiation of complex 1 and acetone in toluene led to dissociation of a CO ligand and insertion of acetone into the silicon-tellurium bond to afford the five-membered metallacycle Cp*(CO)Fe{K²(Si,Te)-Me₂SiOCMe₂TePh}.

Full text of DOI:10.1246/cl.2003.876

876
Chemistry Letters Vol.32, No.9 (2003)
Photochemistry of a Tellurosilyl(carbonyl)iron(II) Complex.
Generation of a Novel Te–Si–Fe Three-membered Cyclic Intermediate
Hiroshi Okada, Masaaki Okazaki,ꢀ Hiromi Tobita,ꢀ and Hiroshi Ogino
Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578
(Received June 26, 2003; CL-030571)
The tellurosilyliron complex Cpꢀ(CO)2FeSiMe2TePh (1)
is attributable to the back-donation from the iron d orbital to
ꢂ
was synthesized by treatment of Cpꢀ(CO)2FeSiMe2Cl with
LiTePh. Irradiation of complex 1 and acetone in toluene led
to dissociation of a CO ligand and insertion of acetone into
the silicon–tellurium bond to afford the five-membered metalla-
cycle Cpꢀ(CO)Fe{ꢀ2(Si,Te)-Me2SiOCMe2TePh}.
the ꢃꢀ orbital of the silicon–tellurium bond.5,8 Consistently,
ꢀ
the bond length of Si–Te (2.568(2) A) is close to the longer limit
9
ꢀ
of the normal silicon–tellurium single bonds (2.47–2.57 A).
Various spectroscopic data also support the structure of 1.
The 29Si{1H} NMR spectrum shows a signal (ꢄ 47.4) in the nor-
mal region of silyliron complexes.1
Over the past few decades, a considerable number of stud-
ies have been made on the synthesis and properties of transition
metal silyl complexes, which could participate in various trans-
formation reactions of organosilicon compounds.1 Although a
large number of silyl complexes with alkyl and/or aryl substitu-
ents have been explored, little is known about the reactivity of
heteroatom-substituted silyl complexes. Pannell and we report-
ed that a coordinatively unsaturated disilanyl complex under-
goes 1,3-migration of a terminal silyl group to generate a silyl-
(silylene) complex.2,3 In particular, the photoreaction of disila-
nyl(carbonyl)metal complexes having an intramolecular donor
such as alkoxy or amino group gives donor-bridged bis(silylene)
complexes almost quantitatively (Scheme 1).4 Our recent inter-
est has been focusing on the syntheses and reactivities of
LnMSiMe2ERm compounds, in which the heteroatom (E) at
the ꢁ-position possesses a lone electron pair and could be coor-
dinated to an unsaturated metal center generated in the course of
the reactions.5 We report here the synthesis and photochemistry
of a tellurosilyliron(II) complex Cpꢀ(CO)2FeSiMe2TePh (1).
ꢀ
Figure 1. ORTEP drawing of 1. Selected interatomic distances (A)
and bond angles (ꢂ): Fe–Si 2.311(2), Te–Si 2.568(2), Te–C15
2.123(9), Si–Fe–C11 82.9(2), Si–Fe–C12 85.5(3), C11–Fe–C12
98.9(4), Fe–Si–Te 110.42(8), Si–Te–C15 94.8(2), Feꢃ ꢃ ꢃTe 4.009(2).
UV (ꢅ > 300 nm) irradiation of 1 in benzene-d6 gave a
complex mixture of Cpꢀ(CO)2FeTePh (2),10 [CpꢀFe(CO)2]2,
and unidentified products, all of them being in low yields. For-
mation of 2 and [CpꢀFe(CO)2]2 could be explained by assuming
the initial generation of three-membered metallacycle Cpꢀ(CO)-
Fe{ꢀ2(Si,Te)-Me2SiTePh} (3). Intermediate 3 then releases the
silylene moiety [:SiMe2], and the following coordination of CO
affords 2. Intermediate 3 can also release the tellurosilyl ligand
SiMe2TePh to give a [Cpꢀ(CO)Fe] fragment, which is smoothly
converted to [CpꢀFe(CO)2]2 through the coordination of CO
and dimerization. In addition, Tilley et al. reported the synthesis
and structure of thiasilairidacylcle [Cpꢀ(PMe3)Ir{ꢀ2(Si; S)-
Si(StBu)2StBu}](OTf) by the reaction of Cpꢀ(PMe3)Ir(Me)OTf
with HSi(StBu)3.11 This fact also supports the intermediate for-
mation of the tellurasilametallacycle 3.
To trap the intermediate 3, the photolysis of 1 was per-
formed in the presence of acetone. Thus, irradiation of 1 in
the presence of a large exess of acetone for 5 min afforded
the insertion product 4 (Eq 2). Crystallization of the residue
from hexane afforded brown crystals of 4 in 26% isolated
yield.12 The low yield is due to the sensitivity of 4 to irradiation.
In fact, monitoring the reaction by 1H NMR spectroscopy
showed decrease of the peak of 4 on prolonged irradiation.
Scheme 1.
A THF solution of Cpꢀ(CO)2FeSiMe2Cl was treated with
LiTePh, which was freshly prepared by the reaction of Ph2Te2
and LiBEt3H in THF (Eq 1). Workup of the mixture and crys-
tallization from toluene/hexane at ꢁ30 ꢂCafforded yellow crys-
tals of 1 in 69% isolated yield.6 The structure of 1 was deter-
mined by the X-ray diffraction study (Figure 1).7 Complex 1
adopts a normal piano-stool geometry; the iron center possesses
a pentamethylcyclopentadienyl ligand, two carbonyl ligands,
ꢀ
and a tellurosilyl ligand. The Fe–Si bond (2.311(2) A) is signif-
ꢀ
icantly shorter than the typical iron-silicon bond (2.32–2.37 A)
in LnFeSiR3 (R = alkyl, aryl),1 but is comparable to those of
the silyliron complexes with electron-withdrawing groups or
1
heteroatoms on the silicon atom (2.21–2.31 A). The shortening
ꢀ
Copyright Ó 2003 The Chemical Society of Japan

Chemistry Letters Vol.32, No.9 (2003)
877
The X-ray crystal structure analysis of 4 (Figure 2)7 re-
tone readily coordinates to the positively charged silylene sili-
con atom,16 and then the lone pair of the intramolecular
tellurolato ligand nucleophillically attacks the carbonyl carbon
atom of acetone to form 4.
ꢀ
vealed that the Fe–Si bond (2.296(1) A) is slightly shorter than
1
the normal iron–silicon single bonds (2.31–2.46 A) and is close
ꢀ
to the values for base-stabilized silylene complexes (2.21–
ꢀ
1
2.29 A). The Fe–Te bond (2.4407(9) A) is considerably shorter
ꢀ
References and Notes
than the previously reported Fe–Te bonds in telluroether com-
ꢀ
13
plexes (2.53–2.59 A). The bond lengths of Si–O1 and Te–
1
2
3
M. S. Eisen, in ‘‘The Chemistry of Organic Silicon Compounds Volume
2,’’ ed. by Z. Rappoport and W. Apeloig, John Willy & Sons, New York
(1998), Chap. 35.
a) K. H. Pannell, J. Cervantes, C. Hernandez, J. Casias, and S. Vincenti,
Organometallics, 5, 1056 (1986). b) H. K. Sharma and K. H. Pannell,
Chem. Rev., 95, 1351 (1995).
a) H. Tobita, K. Ueno, and H. Ogino, Chem. Lett., 1986, 1777. b) H.
Tobita, K. Ueno, and H. Ogino, Bull. Chem. Soc. Jpn., 61, 2797 (1988).
H. Ogino, Chem. Rec., 2, 291 (2002).
ꢀ
C11 are 1.708(4) A and 2.280(5) A, respectively, and are both
ꢀ
longer than the normal distances of the corresponding
ꢀ
14 13
single bonds [Si–O (ca. 1.63 A), Te–C(2.07–2.17 A) ]. Fur-
ꢀ
ꢀ
thermore, the bond distance of O1–C11 (1.387(6) A) is signifi-
14
ꢀ
cantly shorter than the normal C–O single bond (ca. 1.42 A).
These structural features suggest the significant contribution
of the acetone-stabilized benzenetellurolato(silylene) form A
in Figure 3.
4
5
a) M. Okazaki, M. Iwata, H. Tobita, and H. Ogino, Dalton Trans., 2003,
1114. b) J. S. McIndoe and B. K. Nicholson, J. Organomet. Chem., 648,
237 (2002).
6
7
Data for 1: 1H NMR (300 MHz, benzene-d6) ꢄ 1.01 (s, 6H, SiMe2), 1.50
(s, 15H, C5Me5), 6.94 (pseudo t, J ¼ 7 Hz, 2H, m-Ph), 7.05 (t,
J ¼ 7 Hz, 1H, p-Ph), 8.01 (d, J ¼ 7 Hz, 2H, o-Ph); 13CNMR
(75.5 MHz, benzene-d6) ꢄ 9.3 (SiMe2), 9.8 (C5Me5), 95.8 (C5Me5),
108.8, 127.1, 129.0, 142.0 (Ph), 216.6 (CO); 29Si NMR (59.6 MHz, ben-
zene-d6) ꢄ 47.4; IR (KBr) 1981, 1930 cmꢁ1 (ꢆCO); Anal. Calcd. for
C20H26FeO2SiTe: C, 47.11; H, 5.14%. Found: C, 47.31; H, 5.12%.
The structure was solved by direct methods (SIR92). The non-hydrogen
atoms were refined anisotropically. Hydrogen atoms were included but
not refined. Data for 1: C20H26FeO2SiTe, M ¼ 509:96, monoclinic,
ꢀ
ꢀ
ꢀ
P21=c (#14), a ¼ 8:779ð4Þ A, b ¼ 8:976ð5Þ A, c ¼ 27:637ð3Þ A, ꢁ ¼
ꢂ
ꢀ 3
92:42ð2Þ , V ¼ 2175ð1Þ A , Z ¼ 4, Dcalcd ¼ 1:557 g cmꢁ3, ꢇ(Mo Kꢈ)
= 20.71 cmꢁ1, R (Rw) = 0.045 (0.059) for 2324 unique data with
I > 3:0ꢃðIÞ. Data for 4: C22H32FeO2SiTe, M ¼ 540:03, monoclinic,
ꢀ
Figure 2. ORTEP drawing of 4. Selected bond lengths (A) and an-
ꢀ
ꢀ
ꢀ
P21=n (#14), a ¼ 9:815ð6Þ A, b ¼ 16:164ð6Þ A, c ¼ 15:020ð4Þ A,
gles (ꢂ): Fe–Si 2.296(1), Fe–Te 2.4407(9), Fe–C22 1.727(4), O2–
C22 1.158(5), Te–C11 2.280(5), O1–C11 1.387(6), Si–O1
1.708(4), Te–Fe–Si 82.34(4), Fe–Te–C11 98.0(1), Fe–Si–O1
108.3(1), Te–C11–O1 105.9(3), Si–O1–C11 125.4(3).
ꢁ ¼ 99:52ð3Þꢂ, V ¼ 2350ð1Þ A , Z ¼ 4, Dcalcd ¼ 1:526 g cmꢁ3
,
ꢀ 3
ꢇðMo KꢈÞ ¼ 19:22 cmꢁ1, R ðRwÞ ¼ 0:033 (0.043) for 3696 unique da-
ta with I > 3:0ꢃðIÞ. Crystallographic data have been deposited with
Cambridge Crystallographic Data Centre as no. CCDC-213434 for 1
and no. CCDC-213435 for 4.
8
9
H. Tobita, K. Ishiyama, Y. Kawano, S. Inomata, and H. Ogino, Orga-
nometallics, 17, 789 (1998).
a) P. J. Bonasia, D. E. Gindelberger, B. O. Dabbousi, and J. Arnold, J.
Am. Chem. Soc., 114, 5209 (1992). b) P. J. Bonasia and J. Arnold, In-
org. Chem., 31, 2508 (1992). c) D. E. Gindelberger and J. Arnold, In-
org. Chem., 32, 5813 (1993).
10 The tellurolato complex 2 was independently synthesized by refluxing
the toluene solution of [CpꢀFe(CO)2]2 and Ph2Te2. Green crystals of
2 were obtained in 63% isolated yield.
11 S. R. Klei, T. D. Tilley, and R. G. Bergman, Organometallics, 21, 3376
(2002).
12 Data for 4: 1H NMR (300 MHz, benzene-d6) ꢄ 0.67, 0.92 (s, 3H ꢄ 2,
SiMe2), 1.08, 1.93 (s, 3H ꢄ 2, CMe2), 1.68 (s, 15H, C5Me5), 7.02–
7.10 (m, 3H, m,p-Ph), 7.86 (m, 2H, o-Ph); 13CNMR (75.5 MHz, ben-
zene-d6) ꢄ 6.5, 11.6 (SiMe2), 11.1 (C5Me5), 34.7, 38.4 (CMe2), 79.9
(CMe2), 90.3 (C5Me5), 114.6, 129.2, 129.4, 137.5 (Ph), 220.3 (CO);
29Si NMR (59.6 MHz, benzene-d6) ꢄ 95.3; IR (KBr) 1880 (CO); Anal.
Calcd. for C22H32FeO2SiTe: C, 48.93; H, 5.97%. Found: C, 48.88; H,
5.73%.
Figure 3.
The NMR spectroscopic features of 4 are consistent with
the crystal structure. The signals of four Me groups on the
five-membered metallacycle appear inequivalently at 0.67,
0.93, 1.08, and 1.93 ppm. The 29Si{1H} NMR spectrum shows
a signal at 95.3 ppm. The chemical shift is characteristic of
the base-stabilized silylene complexes,1 supporting the contri-
bution of A.
13 a) H. Schumann, A. M. Arif, A. L. Rheingold, C. Janiak, R. Hoffmann,
and N. Kuhn, Inorg. Chem., 30, 1618 (1991). b) W.-F. Liaw, M.-H.
Chiang, C.-H. Lai, S.-J. Chiou, G.-H. Lee, and S.-M. Peng, Inorg.
Chem., 33, 2493 (1994).
14 A. J. Gordon and R. A. Ford, in ‘‘The Chemist’s Companion,’’ John
Willy & Sons, New York (1972).
Scheme 2.
15 Reactivity of some three-memebered silametallacycles has been report-
ed: a) E. K. Pham and R. West, Organometallics, 9, 1517 (1990). b) D.
H. Berry, J. Chey, H. S. Zipin, and P. J. Carroll, Polyhedron, 10, 1189
(1991). c) P. Hong, N. H. Damrauer, P. J. Carroll, and D. H. Berry, Or-
ganometallics, 12, 3698 (1993). d) T. S. Koloski, P. J. Carroll, and D.
H. Berry, J. Am. Chem. Soc., 112, 6405 (1990). e) B. K. Campion, R. H.
Heyn, and T. D. Tilley, J. Am. Chem. Soc., 112, 4079 (1990). f) L. J.
Procopio, P. J. Carroll, and D. H. Berry, Polyhedron, 14, 45 (1995).
16 M. Okazaki, H. Tobita, and H. Ogino, Dalton Trans., 2003, 493.
The formation of 4 can be considered to proceed through
the insertion of the C=O bond of acetone into the Si–Te bond
in tellurasilametallacycle 3. Since the precursor 1 does not react
with acetone at room temperature, this highly enhanced reactiv-
ity of 3 is attributable to the ring strain of the three-membered
ring15 and/or to a significant contribution of its open-form, tel-
lurolato(silylene) complex B (Scheme 2). The lone pair of ace-
Published on the web (Advance View) August 25, 2003; DOI 10.1246/cl.2003.876