2 research outputs found
Partial Hydrogenation of a Tetranuclear Titanium Nitrido Complex with Ammonia Borane
No full textThe treatment of [{Ti(η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)}<sub>4</sub>(μ<sub>3</sub>-N)<sub>4</sub>] with NH<sub>3</sub>BH<sub>3</sub> leads to the paramagnetic
imidonitrido complex [{Ti(η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)}<sub>4</sub>(μ<sub>3</sub>-N)<sub>3</sub>(μ<sub>3</sub>-NH)], which can also be obtained by stepwise proton and electron
transfer with HOTf and [K(C<sub>5</sub>Me<sub>5</sub>)]
Group 4 Half-Sandwich Tris(trimethylsilylmethyl) Complexes: Thermal Decomposition and Reactivity with <i>N</i>,<i>N</i>‑Dimethylamine–Borane
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thermal decomposition of group 4 trimethylsilylmethyl derivatives
[M(η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>3</sub>] (M = Ti (<b>1</b>), Zr (<b>2</b>), Hf (<b>3</b>)) in solution and their reactivity
with <i>N</i>,<i>N</i>-dimethylamine–borane
were investigated. Heating of hydrocarbon solutions of compounds <b>2</b> and <b>3</b> at 130–200 °C results in
the elimination of SiMe<sub>4</sub> and the clean formation of the
singular alkylidene–alkylidyne zirconium and hafnium compounds
[{M(η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)}<sub>3</sub>{(μ-CH)<sub>3</sub>SiMe}(μ<sub>3</sub>-CSiMe<sub>3</sub>)] (M = Zr (<b>4</b>), Hf (<b>5</b>)). The reaction of <b>2</b> and <b>3</b> with NHMe<sub>2</sub>BH<sub>3</sub> (≥1 equiv) at
room temperature affords the dialkyl(dimethylamidoborane) complexes
[M(η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>2</sub>(NMe<sub>2</sub>BH<sub>3</sub>)] (M
= Zr (<b>6</b>), Hf (<b>7</b>)). Compounds <b>6</b> and <b>7</b> are unstable in solution and decompose with formation
of the alkyl(dimethylamino)borane [B(CH<sub>2</sub>SiMe<sub>3</sub>)H(NMe<sub>2</sub>)] (<b>8</b>), SiMe<sub>4</sub>, and other
minor byproducts, including the tetranuclear zirconium(III) octahydride
complex [{Zr(η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)}<sub>4</sub>(μ-H)<sub>8</sub>] (<b>9</b>) in the decomposition
of <b>6</b>. Addition of NHMe<sub>2</sub>BH<sub>3</sub> to the
titanium tris(trimethylsilylmethyl) derivative <b>1</b> gives
the trinuclear mixed valence Ti(II)/Ti(III) tetrahydride complex [{Ti(η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)(μ-H)}<sub>3</sub>(μ<sub>3</sub>-H)(μ<sub>3</sub>-NMe<sub>2</sub>BH<sub>2</sub>)] (<b>10</b>) at 45–65 °C. While the complete conversion
of <b>1</b> under argon atmosphere requires excess NHMe<sub>2</sub>BH<sub>3</sub> (up to 15 equiv), complex <b>10</b> is
readily prepared with 3 equiv of NHMe<sub>2</sub>BH<sub>3</sub> under
a hydrogen atmosphere indicating that the formation of <b>10</b> involves hydrogenolysis of <b>1</b> in the presence of (NMe<sub>2</sub>BH<sub>2</sub>)<sub>2</sub>. In absence of amine–borane,
the reaction of <b>1</b> with H<sub>2</sub> leads to the tetranuclear
titanium(III) octahydride [{Ti(η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)}<sub>4</sub>(μ-H)<sub>8</sub>] (<b>11</b>),
which upon addition of NHMe<sub>2</sub>BH<sub>3</sub> and subsequent
heating at 65 °C affords complex <b>10</b>. The X-ray crystal
structures of <b>2</b>, <b>4</b>, <b>5</b>, <b>10</b>, and <b>11</b> were determined
