facilitate the isomerization.27 If the interconversion for Cp-
[ToMeBenz]ZrCl2 and Cp[TmMe]ZrCl2 were to proceed via a
common mechanism, the observation of a more facile process
for the [O3] ligand would be consistent with a mechanism that
involves direct ‘‘inversion’’ at the chalcogen, since barriers to
inversion are typically lower for second row rather than third
row elements.28 In this regard, calculations on [TmH]ZnCl and
[TmH]Mn(CO)3 predict an increase in M–S–C bond angle upon
accessing the transition state in which the [TmH] ligand has local
5 F. Armbruster, I. Fernandez and F. Breher, Dalton Trans., 2009, 5612.
´
6 (a) W. Klaui, H. O. Asbahr, G. Schramm and U. Englert, Chem.
¨
Ber., 1997, 130, 1223–1229; (b) W.-H. Leung, Q.-F. Zhang and
X.-Y. Yi, Coord. Chem. Rev., 2007, 251, 2266; (c) W. Klaui, Angew.
Chem., Int. Ed. Engl., 1990, 29, 627.
¨
7 (a) A. A. Barney, A. F. Heyduk and D. G. Nocera, Chem.
Commun., 1999, 2379; (b) J. C. Peters, J. D. Feldman and
T. D. Tilley, J. Am. Chem. Soc., 1999, 121, 9871.
8 (a) M. D. Spicer and J. Reglinski, Eur. J. Inorg. Chem., 2009, 1553;
(b) G. Parkin, New J. Chem., 2007, 31, 1996; (c) J. M. Smith,
Comments Inorg. Chem., 2008, 29, 189.
9 C. G. Riordan, Coord. Chem. Rev., 2010, 254, 1815.
C
3v symmetry,27b and so the tendency of two-coordinate oxygen
10 (a) M. Minoura, V. K. Landry, J. G. Melnick, K. Pang, L. Marchio
and G. Parkin, Chem. Commun., 2006, 3990; (b) V. K. Landry,
K. Pang, S. M. Quan and G. Parkin, Dalton Trans., 2007, 820.
11 The tris(phthalimidyl)hydroborato ligand has been reported. How-
ever, since there is no structural verification of either the ligand or
its complexes, the true nature of these compounds remains
unknown. See: S. A. A. Zaidi, M. Jaria and Z. A. Siddiqi, Synth.
React. Inorg., Met.-Org., Nano-Met. Chem., 1986, 16, 1067.
12 (a) V. Salinier, J. M. Corker, F. Lefebvre, F. Bayard, V. Dufaud
and J. M. Basset, Adv. Synth. Catal., 2009, 351, 2155;
(b) V. Salinier, G. P. Niccolai, V. Dufaud and J. M. Basset, Adv.
to adopt larger bond angles than sulfur would be expected
to facilitate the concerted isomerization process. Supporting
this suggestion, the Zr–O–C angles for Cp[ToMeBenz]ZrCl2
[1321–1371] are significantly greater than the Zr–S–C angles
for Cp[TmMe]ZrCl2 [1071–1141].25 It is, therefore, evident that
[ToR] ligands are more flexible than [TmR] ligands.
In addition to its application to zirconium chemistry,
[ToMeBenz]Na has also been used to synthesize derivatives of
less oxophilic metals such as zinc, cobalt and iron. Thus,
[ToMeBenz]Na reacts with (i) ZnI2 to give tetrahedral [ToMeBenz]-
ZnI and (ii) CoCl2 and FeCl2 to give octahedral
[ToMeBenz]2Co and [ToMeBenz]2Fe, respectively. The molecular
structures of [ToMeBenz]ZnI and [ToMeBenz]2M (M = Fe, Co)
have been determined by X-ray diffraction. In each case, the
[ToMeBenz] ligand adopts a k3-coordination mode that resembles
the coordination mode of the [TmMe] ligands in similar
compounds, e.g. [TmMe]ZnI29 and [TmMe]2Fe.30 The formation
of [ToMeBenz]2Co, however, is particularly noteworthy because
(i) the [TmMe]2Co counterpart has not been isolated31,32 and
(ii) [TmPh]2Co adopts a type of structure that is totally
different to that of [ToMeBenz]2Co. Specifically, while both
[ToMeBenz]2Fe and [ToMeBenz]2Co adopt octahedral structures
with k3-O3 coordination of the ligand, [TmPh]2Fe and
[TmPh]2Co exhibit coordination via only two of the sulfur
donors of each ligand, with the coordination sphere being
completed by interaction with the two B–H groups.33
Synth. Catal., 2009, 351, 2168.
t
13 X-Ray diffraction indicates that [ToBu ]Na is dinuclear in the solid state.
14 T. E. Muller andD. M. P. Mingos, Transition Met. Chem., 1995, 20, 533.
¨
15 K. Yurkerwich and G. Parkin, unpublished results.
16 For compilations of IR spectroscopic data on (L2X)Re(CO)3 and
(L2X)Mn(CO)3 compounds, see ref. 10b, references therein and:
(a) R. Garcia, A. Paulo and I. Santos, Inorg. Chim. Acta, 2009, 362,
4315; (b) L. A. Graham, A. R. Fout, K. R. Kuehne, J. L. White,
B. Mookherji, F. M. Marks, G. P. A. Yap, L. N. Zakharov,
A. L. Rheingold and D. Rabinovich, Dalton Trans., 2005, 171.
17 M. H. Chisholm, E. R. Davidson, J. C. Huffman and
K. B. Quinlan, J. Am. Chem. Soc., 2001, 123, 9652.
18 J. A. McCleverty, Chem. Soc. Rev., 1983, 12, 331.
19 (a) M. Schwalbe, P. C. Andrikopoulos, D. R. Armstrong,
J. Reglinski and M. D. Spicer, Eur. J. Inorg. Chem., 2007, 1351;
(b) M. Garner, M. A. Lehmann, J. Reglinski and M. D. Spicer,
Organometallics, 2001, 20, 5233.
20 L. A. Graham, A. R. Fout, K. R. Kuehne, J. L. White,
B. Mookherji, F. M. Marks, G. P. A. Yap, L. N. Zakharov,
A. L. Rheingold and D. Rabinovich, Dalton Trans., 2005, 171.
21 R. Garcia, A. Paulo and I. Santos, Inorg. Chim. Acta, 2009, 362, 4315.
22 T. R. Ward, S. Duclos, B. Therrien and K. Schenk, Organome-
tallics, 1998, 17, 2490.
In summary, a new class of tripodal L2X ligands that feature
23 (a) T. Repo, M. Klinga, I. Mutikainen, Y. C. Su, M. Leskela and
¨
t
three oxygen donors, namely [ToBu ] and [ToMeBenz], has been
M. Polamo, Acta Chem. Scand., 1996, 50, 1116; (b) J. Y. Corey,
X.-H. Zhu, L. Brammer and N. P. Rath, Acta Crystallogr., Sect. C:
Cryst. Struct. Commun., 1995, 51, 565.
synthesized via the respective reactions of NaBH4 with 1-tert-
butylimidazolone and 1-methyl-2-benzimidazolinone. These
ligands are substantially more sterically demanding than
related [O3] donor ligands and offer potential for providing
counterparts of metallocenes in an oxygen rich environment.
We thank the U. S. Department of Energy, Office of Basic
Energy Sciences (DE-FG02-93ER14339) and the National
Science Foundation (CHE-0749674) for support of this research.
A.A.-H. thanks the government of Saudi Arabia for a scholarship.
24 K. Mislow, D. Gust, P. Finocchiaro and R. J. Boettcher, Top.
Curr. Chem., 1974, 47, 1.
25 D. Buccella, A. Shultz, J. G. Melnick, F. Konopka and G. Parkin,
Organometallics, 2006, 25, 5496.
26 Differences in barriers to enantiomer interconversion due to geome-
trical changes at sulfur and oxygen have been observed previously.
See,forexample:P.GhoshandG.Parkin,Chem. Commun., 1998, 413.
27 (a) M. R. St.-J. Foreman, A. F. Hill, A. J. P. White and D. J. Williams,
Organometallics, 2003, 22, 3831; (b) P. J. Bailey, A. Dawson,
C. McCormack, S. A. Moggach, I. D. H. Oswald, S. Parsons, D. W.
H. Rankin and A. Turner, Inorg. Chem., 2005, 44, 8884.
28 Alternatively, if isomerization were to require dissociation of one
of the arms, it is likely that the barrier would be greater for the [O3]
ligand, assuming that the Zr–O bonds are stronger than the
corresponding Zr–S bonds.
29 I. Cassidy, M. Garner, A. R. Kennedy, G. B. S. Potts, J. Reglinski,
P. A. Slavin and M. D. Spicer, Eur. J. Inorg. Chem., 2002, 1235.
30 M. Garner, K. Lewinski, A. Pattek-Janczyk, J. Reglinski, B. Sieklucka,
M. D. Spicer and M. Szaleniec, Dalton Trans., 2003, 1181.
31 C. A. Dodds, M. A. Lehmann, J. F. Ojo, J. Reglinski and
M. D. Spicer, Inorg. Chem., 2004, 43, 4927.
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c
This journal is The Royal Society of Chemistry 2011
Chem. Commun., 2011, 47, 3123–3125 3125