Asymmetric Synthesis and Metal Complexes of aC3-Symmetric P-Stereogenic Triphosphine, (R)-MeSi(CH2PMe(t-Bu))3(MT-Siliphos)

Abstract

Asymmetric deprotonation of PMe2(t-Bu)(BH3) with s-BuLi/(−)-sparteine, followed by treatment with MeSiCl3, gave a 2.6:1 mixture of the C3- and C1-symmetric triphosphine–boranes MeSi(CH2PMe(t-Bu)(BH3))3 (3). Recrystallization gave highly diastereomerically and enantiomerically enriched C3-3. After deprotection with morpholine, the triphosphine (R)-MeSi(CH2PMe(t-Bu))3 (4; (Me, t-Bu)-Siliphos or MT-Siliphos) was used to prepare the metal complexes [Rh(MT-Siliphos)(norbornadiene)][OTf] (5), Ru(MT-Siliphos)(DMSO)Cl2 (6), [Ru(MT-Siliphos)(NCMe)3][OTf]2 (7), M(MT-Siliphos)(PPh3) (M = Pd (8), Pt (9)), Cu(MT-Siliphos)(Cl) (10), and polymeric [Cu2Cl2(μ-(κ2,κ1)-MT-Siliphos)]∞ (11). The crystal structures of C3-3 and of complexes 5, 7, and 11 were determined, and dynamic processes in 6 and 8 were characterized by variable-temperature NMR spectroscopy.