New Superhindered Polydentate Polyphosphine Ligands P(CH₂CH₂P^<i>t</i>Bu₂)₃, PhP(CH₂CH₂P^<i>t</i>Bu₂)₂, P(CH₂CH₂CH₂P^<i>t</i>Bu₂)₃, and their Ruthenium(II) Chloride Complexes

The synthesis and characterization of the extremely hindered phosphine ligands, P­(CH₂CH₂P^<i>t</i>Bu₂)₃ (P²P₃^<i>t</i>Bu, <b>1</b>), PhP­(CH₂CH₂P^<i>t</i>Bu₂)₂ (PhP²P₂^<i>t</i>Bu, <b>2</b>), and P­(CH₂CH₂CH₂P^<i>t</i>Bu₂)₃ (P³P₃^<i>t</i>Bu, <b>3</b>) are reported, along with the synthesis and characterization of ruthenium chloro complexes RuCl₂(P²P₃^<i>t</i>Bu) (<b>4</b>), RuCl₂(PhP²P₂^<i>t</i>Bu) (<b>5</b>), and RuCl₂(P³P₃^<i>t</i>Bu) (<b>6</b>). The bulky P²P₃^<i>t</i>Bu (<b>1</b>) and P³P₃^<i>t</i>Bu (<b>3</b>) ligands are the most sterically encumbered PP₃-type ligands so far synthesized, and in all cases, only three phosphorus donors are able to bind to the metal center. Complexes RuCl₂(PhP²P₂^<i>t</i>Bu) (<b>5</b>) and RuCl₂(P³P₃^<i>t</i>Bu) (<b>6</b>) were characterized by crystallography. Low temperature solution and solid state ³¹P­{¹H} NMR were used to demonstrate that the structure of RuCl₂(P²P₃^<i>t</i>Bu) (<b>4</b>) is probably analogous to that of RuCl₂(PhP²P₂^<i>t</i>Bu) (<b>5</b>) which had been structurally characterized