New Superhindered Polydentate Polyphosphine Ligands P(CH2CH2PtBu2)3, PhP(CH2CH2PtBu2)2, P(CH2CH2CH2PtBu2)3, and their Ruthenium(II) Chloride Complexes

The synthesis and characterization of the extremely hindered phosphine ligands, P­(CH2CH2PtBu2)3 (P2P3tBu, 1), PhP­(CH2CH2PtBu2)2 (PhP2P2tBu, 2), and P­(CH2CH2CH2PtBu2)3 (P3P3tBu, 3) are reported, along with the synthesis and characterization of ruthenium chloro complexes RuCl2(P2P3tBu) (4), RuCl2(PhP2P2tBu) (5), and RuCl2(P3P3tBu) (6). The bulky P2P3tBu (1) and P3P3tBu (3) 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(PhP2P2tBu) (5) and RuCl2(P3P3tBu) (6) were characterized by crystallography. Low temperature solution and solid state 31P­{1H} NMR were used to demonstrate that the structure of RuCl2(P2P3tBu) (4) is probably analogous to that of RuCl2(PhP2P2tBu) (5) which had been structurally characterized.