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Group 4 Half-Sandwich Tris(trimethylsilylmethyl) Complexes: Thermal Decomposition and Reactivity with N,N‑Dimethylamine–Borane
The thermal decomposition of group 4 trimethylsilylmethyl derivatives [M(η5-C5Me5)(CH2SiMe3)3] (M = Ti (1), Zr (2), Hf (3)) in solution and their reactivity with N,N-dimethylamine–borane were investigated. Heating of hydrocarbon solutions of compounds 2 and 3 at 130–200 °C results in the eliminati...
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| Published in: | Inorganic chemistry 2017-09, Vol.56 (18), p.11220-11229 |
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| Main Authors: | , , , , , |
| Format: | Article |
| Language: | English |
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| Online Access: | Get full text |
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| Summary: | The thermal decomposition of group 4 trimethylsilylmethyl derivatives [M(η5-C5Me5)(CH2SiMe3)3] (M = Ti (1), Zr (2), Hf (3)) in solution and their reactivity with N,N-dimethylamine–borane were investigated. Heating of hydrocarbon solutions of compounds 2 and 3 at 130–200 °C results in the elimination of SiMe4 and the clean formation of the singular alkylidene–alkylidyne zirconium and hafnium compounds [{M(η5-C5Me5)}3{(μ-CH)3SiMe}(μ3-CSiMe3)] (M = Zr (4), Hf (5)). The reaction of 2 and 3 with NHMe2BH3 (≥1 equiv) at room temperature affords the dialkyl(dimethylamidoborane) complexes [M(η5-C5Me5)(CH2SiMe3)2(NMe2BH3)] (M = Zr (6), Hf (7)). Compounds 6 and 7 are unstable in solution and decompose with formation of the alkyl(dimethylamino)borane [B(CH2SiMe3)H(NMe2)] (8), SiMe4, and other minor byproducts, including the tetranuclear zirconium(III) octahydride complex [{Zr(η5-C5Me5)}4(μ-H)8] (9) in the decomposition of 6. Addition of NHMe2BH3 to the titanium tris(trimethylsilylmethyl) derivative 1 gives the trinuclear mixed valence Ti(II)/Ti(III) tetrahydride complex [{Ti(η5-C5Me5)(μ-H)}3(μ3-H)(μ3-NMe2BH2)] (10) at 45–65 °C. While the complete conversion of 1 under argon atmosphere requires excess NHMe2BH3 (up to 15 equiv), complex 10 is readily prepared with 3 equiv of NHMe2BH3 under a hydrogen atmosphere indicating that the formation of 10 involves hydrogenolysis of 1 in the presence of (NMe2BH2)2. In absence of amine–borane, the reaction of 1 with H2 leads to the tetranuclear titanium(III) octahydride [{Ti(η5-C5Me5)}4(μ-H)8] (11), which upon addition of NHMe2BH3 and subsequent heating at 65 °C affords complex 10. The X-ray crystal structures of 2, 4, 5, 10, and 11 were determined. |
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| ISSN: | 0020-1669 1520-510X |
| DOI: | 10.1021/acs.inorgchem.7b01607 |