Low Oxidation
State Iron(0), Iron(I), and Ruthenium(0) Dinitrogen Complexes with
a Very Bulky Neutral Phosphine Ligand
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Abstract
The
synthesis of a series of iron and ruthenium complexes with the ligand
P<sup>2</sup>P<sub>3</sub><sup>Cy</sup>, P(CH<sub>2</sub>CH<sub>2</sub>PCy<sub>2</sub>)<sub>3</sub> is described. The iron(0) and ruthenium(0)
complexes Fe(N<sub>2</sub>)(P<sup>2</sup>P<sub>3</sub><sup>Cy</sup>) (<b>1</b>) and Ru(N<sub>2</sub>)(P<sup>2</sup>P<sub>3</sub><sup>Cy</sup>) (<b>2</b>) were synthesized by treatment of
[FeCl(P<sup>2</sup>P<sub>3</sub><sup>Cy</sup>)]<sup>+</sup> and [RuCl(P<sup>2</sup>P<sub>3</sub><sup>Cy</sup>)]<sup>+</sup> with an excess of
potassium graphite under a nitrogen atmosphere. The Fe(I) and Ru(I)
species [Fe(N<sub>2</sub>)(P<sup>2</sup>P<sub>3</sub><sup>Cy</sup>)]<sup>+</sup> (<b>3</b>) and RuCl(P<sup>2</sup>P<sub>3</sub><sup>Cy</sup>) (<b>4</b>) were synthesized by treatment of
[FeCl(P<sup>2</sup>P<sub>3</sub><sup>Cy</sup>)]<sup>+</sup> and [RuCl(P<sup>2</sup>P<sub>3</sub><sup>Cy</sup>)]<sup>+</sup> with 1 equiv of potassium
graphite under a nitrogen atmosphere. The cationic dinitrogen species
[Fe(N<sub>2</sub>)H(P<sup>2</sup>P<sub>3</sub><sup>Cy</sup>)]<sup>+</sup> (<b>6</b>) and [Ru(N<sub>2</sub>)H(P<sup>2</sup>P<sub>3</sub><sup>Cy</sup>)]<sup>+</sup> (<b>7</b>) were formed by
treatment of <b>1</b> and <b>3</b>, respectively, with
1 equiv of a weak organic acid. The iron(II) complex Fe(H)<sub>2</sub>(P<sup>2</sup>P<sub>3</sub><sup>Cy</sup>) (<b>5</b>) was also
synthesized and characterized. Complexes [RuCl(P<sup>2</sup>P<sub>3</sub><sup>Cy</sup>)][BPh<sub>4</sub>], <b>1</b>, <b>2</b>, <b>3[BPh</b><sub><b>4</b></sub><b>]</b>, <b>4</b>, <b>5</b>, <b>6[BF</b><sub><b>4</b></sub><b>]</b>, and <b>7[BF</b><sub><b>4</b></sub><b>]</b> were characterized by X-ray crystallography. The Fe(I) and
Ru(I) complexes <b>3</b> and <b>4</b> were characterized
by electron paramagnetic resonance (EPR) spectroscopy, and the Fe(I)
complex has an EPR spectrum typical of a metal-centered radical
