The Butterfly Dimer [(tBu3SiO)Cr]2 (μ-OSitBu3)2 and Its Oxidative Cleavage to (tBu3SiO)2 Cr(=N-N=CPh2)2 and (tBu3SiO)2 Cr=N(2,6-Ph2-C6H3) Page: 2,008
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The Butterfly Dimer [(tBu3SiO)Cr]2(p-OSitBu3)2 and Its Oxidative
Cleavage to (tBu3SiO)2Cr(=N-N=CPh2)2 and
Orson L. Sydora,t David S. Kuiper,t Peter T. Wolczanski,*,t Emil B. Lobkovsky,t
Adriana Dinescu,* and Thomas R. Cundarit
Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University,
Ithaca, New York 14853, and Department of Chemistry, University of North Texas, Box 305070,
Denton, Texas 76203-5070
Received August 30, 2005
Treatment of CrCI2(THF)2 with NaOSitBu3 afforded the butterfly dimer [(tBu3SiO)Cr]2(u-OSitBu3)2 (12), whose d(CrCr)
of 2.658(31) A and magnetism were indicative of strong antiferromagnetic coupling. A Boltzmann distribution of
low-energy 1A,, 3B1, 5A1, 7B1, and 9A1 states obtained from calculations on [(HO)2Cr]2(uOH)2 (1'2) were used to
provide a reasonable fit of the ,eff vs T data. Cleavage of 12 with various L (L = 4-picoline, p-tolunitrile, tBuCN,
tBuNC, Ph2CO, and PMe3) generated (tBu3SiO)2CrL2 (1-L2). The dimer was oxidatively severed by Ph2CN2 to give
(tBu3SiO)2Cr(N2CPh2)2 (2) and by RN3 at 23 C to afford (silox)2Cr=NR (3-R) for bulky R (adamantyl (Ad), 2,6-
iPr2-C6H3, 2,4,6-Me3-C6H2 = Mes, 2,6-Ph2-C6H3) and (tBu3SiO)2Cr(=NR)2 (4-R) for smaller substituents (R =
1-Naph, 2-Anth). X-ray structural studies were conducted on 12, square planar 1-(OCPh2)2, pseudo-Td 2 and pseudo-
trigonal 3-(2,6-Ph2-C6H3), whose S = 1 ground state was discussed on the basis of calculations of (H3SiO)2Cr=
The generation of electronically and coordinatively un-
saturated transition metal fragments leaves them susceptible
to aggregation, but through the use of bulky ligands, low-
coordinate species can often be isolated. For example, the
bulky siloxide tBu3SiO- (silox) has been successfully
employed to stabilize low-coordinate mononuclear complexes
such as [(silox)3M]n (n = 0, M = Ti,1 V, NbL (L = PMe3,
4-picoline),2 Ta;3 n = 1-, M = Cr).4 These compounds have
been shown to be exceedingly reactive in CX bond activa-
tions,5 displaying chemistry as diverse as carbon monoxide
* To whom correspondence should be addressed. E-mail: ptw2@
t Cornell University.
I University of North Texas.
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10.1021/ic051481w CCC: $33.50 2006 American Chemical Society
Published on Web 01/12/2006
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Sydora, Orson L.; Kuiper, David S.; Wolczanski, Peter T.; Lobkovsky, Emil B.; Dinescu, Adriana & Cundari, Thomas R., 1964-. The Butterfly Dimer [(tBu3SiO)Cr]2 (μ-OSitBu3)2 and Its Oxidative Cleavage to (tBu3SiO)2 Cr(=N-N=CPh2)2 and (tBu3SiO)2 Cr=N(2,6-Ph2-C6H3), article, January 12, 2006; [Washington, DC]. (digital.library.unt.edu/ark:/67531/metadc75425/m1/1/: accessed February 20, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT College of Arts and Sciences.