Nonclassical titanocene silyl hydrides.
The titanocene silyl hydride complexes [Ti(Cp)2(PMe3)(H)(SiR3)] [SiR3=SiMePhCl (6), SiPh2Cl (7), SiMeCl2 (8), SiCl3 (9)] were prepared by HSiR3 addition to [Ti(Cp)2(PMe3)2] and were studied by NMR and IR spectroscopy, X-ray diffraction (for 6, 8, and 9), and DFT calculations. Spectroscopic and struc...
| Main Authors: | , , , , , , |
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| Format: | Journal article |
| Language: | English |
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2004
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| _version_ | 1797059517825941504 |
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| author | Ignatov, S Rees, N Tyrrell, B Dubberley, SR Razuvaev, A Mountford, P Nikonov, G |
| author_facet | Ignatov, S Rees, N Tyrrell, B Dubberley, SR Razuvaev, A Mountford, P Nikonov, G |
| author_sort | Ignatov, S |
| collection | OXFORD |
| description | The titanocene silyl hydride complexes [Ti(Cp)2(PMe3)(H)(SiR3)] [SiR3=SiMePhCl (6), SiPh2Cl (7), SiMeCl2 (8), SiCl3 (9)] were prepared by HSiR3 addition to [Ti(Cp)2(PMe3)2] and were studied by NMR and IR spectroscopy, X-ray diffraction (for 6, 8, and 9), and DFT calculations. Spectroscopic and structural data established that these complexes exhibit nonclassical Ti-H-Si-Cl interligand hypervalent interactions. In particular, the observation of silicon-hydride coupling constants J(Si,H) in 6-9 in the range 22-40 Hz, the signs of which we found to be negative for 8 and 9, is conclusive evidence of the presence of a direct Si-H bond. The analogous reaction of [Ti(Cp)2(PMe3)2] with HSi(OEt)3 does not afford the expected classical silyl hydride complex [Ti(Cp)2(PMe3)(H)[Si(OEt)3]], and instead NMR-silent titanium (apparently TiIII) complex(es) and the silane redistribution product Si(OEt)4 are formed. The structural data and DFT calculations for the compounds [Ti(Cp)2(PMe3)(H)(SiR3)] show that the strength of interligand hypervalent interactions in the chlorosilyl complexes decreases as the number of chloro groups on silicon increases. However, in the absence of an Si-bound electron-withdrawing group trans to the Si-H moiety, a silane sigma complex is formed, characterized by a long Ti-Si bond of 2.658 A and short Si-H contact of 1.840 A in the model complex [Ti(Cp)2(PMe3)(H)(SiMe3)]. Both the silane sigma complexes and silyl hydride complexes with interligand hypervalent interactions exhibit bond paths between the silicon and hydride atoms in Atoms in Molecules (AIM) studies. To date a classical titanocene phosphane silyl hydride complex without any Si-H interaction has not been observed, and therefore titanocene silyl hydrides are, depending on the nature of the R groups on Si, either silane sigma complexes or compounds with an interligand hypervalent interaction. |
| first_indexed | 2024-03-06T20:05:25Z |
| format | Journal article |
| id | oxford-uuid:28bed5ee-91c4-4d75-8227-d0b8bbef03e3 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-06T20:05:25Z |
| publishDate | 2004 |
| record_format | dspace |
| spelling | oxford-uuid:28bed5ee-91c4-4d75-8227-d0b8bbef03e32022-03-26T12:14:46ZNonclassical titanocene silyl hydrides.Journal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:28bed5ee-91c4-4d75-8227-d0b8bbef03e3EnglishSymplectic Elements at Oxford2004Ignatov, SRees, NTyrrell, BDubberley, SRRazuvaev, AMountford, PNikonov, GThe titanocene silyl hydride complexes [Ti(Cp)2(PMe3)(H)(SiR3)] [SiR3=SiMePhCl (6), SiPh2Cl (7), SiMeCl2 (8), SiCl3 (9)] were prepared by HSiR3 addition to [Ti(Cp)2(PMe3)2] and were studied by NMR and IR spectroscopy, X-ray diffraction (for 6, 8, and 9), and DFT calculations. Spectroscopic and structural data established that these complexes exhibit nonclassical Ti-H-Si-Cl interligand hypervalent interactions. In particular, the observation of silicon-hydride coupling constants J(Si,H) in 6-9 in the range 22-40 Hz, the signs of which we found to be negative for 8 and 9, is conclusive evidence of the presence of a direct Si-H bond. The analogous reaction of [Ti(Cp)2(PMe3)2] with HSi(OEt)3 does not afford the expected classical silyl hydride complex [Ti(Cp)2(PMe3)(H)[Si(OEt)3]], and instead NMR-silent titanium (apparently TiIII) complex(es) and the silane redistribution product Si(OEt)4 are formed. The structural data and DFT calculations for the compounds [Ti(Cp)2(PMe3)(H)(SiR3)] show that the strength of interligand hypervalent interactions in the chlorosilyl complexes decreases as the number of chloro groups on silicon increases. However, in the absence of an Si-bound electron-withdrawing group trans to the Si-H moiety, a silane sigma complex is formed, characterized by a long Ti-Si bond of 2.658 A and short Si-H contact of 1.840 A in the model complex [Ti(Cp)2(PMe3)(H)(SiMe3)]. Both the silane sigma complexes and silyl hydride complexes with interligand hypervalent interactions exhibit bond paths between the silicon and hydride atoms in Atoms in Molecules (AIM) studies. To date a classical titanocene phosphane silyl hydride complex without any Si-H interaction has not been observed, and therefore titanocene silyl hydrides are, depending on the nature of the R groups on Si, either silane sigma complexes or compounds with an interligand hypervalent interaction. |
| spellingShingle | Ignatov, S Rees, N Tyrrell, B Dubberley, SR Razuvaev, A Mountford, P Nikonov, G Nonclassical titanocene silyl hydrides. |
| title | Nonclassical titanocene silyl hydrides. |
| title_full | Nonclassical titanocene silyl hydrides. |
| title_fullStr | Nonclassical titanocene silyl hydrides. |
| title_full_unstemmed | Nonclassical titanocene silyl hydrides. |
| title_short | Nonclassical titanocene silyl hydrides. |
| title_sort | nonclassical titanocene silyl hydrides |
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