Some complexes of rhodium(I), rhodium(II), and rhodium(III) containing tertiary t-butylphosphines as ligands

Abstract

Paramagnetic rhodium(II) complexes of the type trans-[RhCl2(PBut2R)2](R = Me, Et, or Prn) are formed rapidly by treating ethanolic rhodium(III) chloride trihydrate with the tertiary phosphine at 25 °C. The complexes have low magnetic moments in the solid state (<1·4 B.M.) but in solution trans-[RhCl2(PBut2Me)2] has the expected moment of ca. 2·12 B.M. Treatment of rhodium trichloride trihydrate with some t-butylphosphines (L = PButPrn2, PBut2Me, PBut2Et, or PBut2Prn) in refluxing propan-2-ol gives square pyramidal hydridorhodium(III) complexes [RhHCl2L2]. [RhHCl2(PButPrn2)2] reacts with some ligands Q [Q = MeNC, MeCN, pyridine, or P(OMe)3] to give complexes of type [RhHCl2(PButPrn2)2Q]. [RhHCl2(PBut2Me)2] reacts with hydrogen gas to give [RhH2Cl(PBut2Me)2], and trans-[RhCl2(PBut2Me)2] with hydrogen gas gives a ca. 1 : 1 mixture of [RhHCl2(PBut2Me)2] and [Rh2Cl(PBut2Me)2]. Treatment of rhodium chloride in propan-2-ol with tri-t-butylphosphine gives the five-co-ordinate dihydride [RhH2Cl(PBut3)2]. [RhH2Cl(PButMePh)3] was formed similarly as a mixture of enantiomers. Prolonged (7 days) treatment of hydrated rhodium trichloride in ethanol at 20 °C with di-t-butylalkylphosphines gives rhodium(I) carbonyl complexes trans-[RhCl(CO)(PBut2R)2](R = Me, Et, or Prn) in ca. 75% yield. Addition of a strong base (e.g., NaOMe) to solutions of complexes of the type [RhHCl2L2] in ethanol or methanol gives trans-[RhCl(CO)L2] within a few seconds. Ethanolic rhodium trichloride reacts with PHBut2 to give [RhCl(PHBut2)3]. 1H and 31P N.m.r., i.r., and electronic absorption spectral data are reported and discussed as are magnetic susceptibility data for the rhodium(II) complexes.