106040-32-8Relevant articles and documents
Synthesis and spectroscopic properties of tantalum μ-alkylidyne compounds containing bulky aryloxide ligands: X-ray structures of the asymmetric derivatives (Me2SiCH2)2 Ta(μ-CSiMe3)2Ta(CH2SiMe 3)(OAr-2,6-Ph2) and (Me2SiCH2)2Ta(μ-CSiMe ...
Fanwick, Phillip E.,Ogilvy, Ann E.,Rothwell, Ian P.
, p. 73 - 80 (2008/10/08)
Full title: Synthesis and spectroscopic properties of tantalum μ-alkylidyne compounds containing bulky aryloxide ligands: X-ray structures of the asymmetric derivatives (Me2SiCH2)2 Ta(μ-CSiMe3)2Ta(CH2SiMe 3)(OAr-2,6-Ph2) and (Me2SiCH2)2Ta(μ-CSiMe3) 2Ta(OAr-2,6-t-Bu2)2 (OAr-2,6-Ph2 = 2,6-diphenylphenoxide; OAr-2,6-t-Bu2 = 2,6-Di-tert-butylphenoxide). The reaction of the mixed alkyl-alkylidyne compound [(Me3SiCH2)2Ta(μ-CSiMe3)]2 (1) with a series of 2,6-disubstituted phenols has been investigated. 2,6-Dimethylphenol (HOAr-2,6-Me2) reacts with 1 to eventually produce the known Ta(OAr-2,6-t-Bu2)5 via a number of unidentified intermediates. With the more bulky 2,6-diphenylphenol (HOAr-2,6-Ph2) reaction proceeds by sequential loss of Me4Si to yield red mono- and disubstituted complexes 2 and 3 and to eventually give the green, tetrasubstituted derivative [(Ph2-2,6-ArO)2Ta(μ-CSiMes) 2]2 (4). Spectroscopic data on the disubstituted derivatives 3 is consistent with the presence of all three of the substitutional isomers possible for molecules with pseudotetrahedral geometry about the two tantalum metal atom centers. The 1,1-substitution and syn and anti forms of the 1,2-substitution isomers were present in essentially identical amounts. In contrast the use of 2,6-di-tert-butylphenol (HOAr-2,6-t-Bu2) was found to lead to only one of the possible disubstituted product isomers 5. Structural studies showed 5 to in fact be the 1,1-substituted isomer [(Me3SiCH2)2Ta(μ-CSiMe3) 2Ta(OAr-2,6-t-Bu2)2]. Both of the asymmetric derivatives 2 and 5 have been subjected to a single-crystal X-ray diffraction study. Both retain the initial dimetallocyclobutadiene Ta2(μ-CSiMe3)2 core with the terminal alkyl- and aryloxide donor atoms arranged in a pseudotetrahedral arrangement about each tantalum atom. The Ta-Ta distances of 2.8825 (6) and 2.9071 (4) A? for 2 and 5 are consistent with no metal-metal bond being present as expected for these d0-d0 dinuclear species. Crystal data for Ta2Si5OC38H64 (2) at 23°C are a = 10.343 (1) A?, b = 12.209 (2) A?, c = 37.411 (6) A?, β = 84.23 (1)° Z = 4, and dcalcd = 1.469 g cm-3 in space group P21/n. Of the 8690 unique data collected with Mo Kα, the 4597 with I > 3.0σ(I) were used in the least-squares refinement to give R = 0.042 and Rw = 0.056. Crystal data for Ta2Si4O2C44H82 at -160°C are a = 12.283 (6) A?, b = 23.692 (6) A?, c = 17.205 (6) A?, Z = 4, and dcalcd = 1.482g cm-3 in space group Pbcn. Of the 7306 unique data collected with Mo Kα, the 4118 with I > 3.0σ(I) were used in the least-squares refinement to give R = 0.038 and Rw = 0.056. The bis(phenoxide) 5 will undergo thermolysis to generate the known bis-cyclometalated derivative Ta(OC6H3-t-BuCMe2CH2) 2(CH2SiMe3) (OC6H3-t-BuCMe2CH2 = cyclometalated 2,6-di-tert-butylphenoxide), but only in very low yield.
