Further chemistry of trimethylphosphine complexes of rhodium(I): X-ray crystal structures of dodeca(trimethylphosphine)tetrarhodiumhexamercury, Hg6Rh4(PMe3)12, and trans-chlorobis(trimethylphosphine)(triphenylphosphine)rhodium(I)

Abstract

The interaction of sodium amalgam in tetrahydrofuran with [Rh(PMe₃)₄]Cl or RhCl(PMe₃)₃ yields Hg₆Rh₄(PMe₃)₁₂(1) in high yields. Similar reduction of [RhH₂(PMe₃)₄]Cl yields RhH(PMe₃)₄(2) and RhCl(CO)(PMe₃)₂ gives [RhH(CO)(PMe₃)₃]₂, (3). The syntheses of the following complexes are also reported: RhCl(PMe₂Ph)(PMe₃)₂, (4), Rh(η-C₅H₅)(PMe₃)₂, (5), RhMe(PMe₃)₃, (6), Rh(C₆H₄Me-3)(PMe₃)₃, (7), RhCllMe(PMe₃)₃, (8), RhCll(C₆H₅)(PMe₃)₃, (9), [Rh (O₂)(PMe₃)₄]PF₆, (10), and trans-RhCl(PPh₃)(PMe₃)₂, (11). The compounds have been studied by ¹H and ³¹P n.m.r. and i.r. spectroscopy and the structures of (1) and (11) have been determined by X-ray crystallography. Complex (1) is orthorhombic, space group Ccmm or Ccm2, with a= 12.909(2), b= 25.274 (4), c= 25.176(4)Å, and Z= 4. Complex (11) is monoclinic, space group P2₁/n, with a= 17.006(3), b= 11.821(2), c= 12.884(2)Å, β= 96.46(2)°, and Z= 4. The structures were determined using 2 448 and 3 708 observed intensities measured on an automatic diffractometer and refined to R values of 0.083 and 0.038 respectively. For compound (1) only the Hg, Rh, and P atom positions could be determined with any certainty. The Hg₆Rh₄P₁₂ cluster has the form of an Hg₆ octahedron with four tetrahedrally related faces capped by Rh(PMe₃)₃ units; Hg–Hg and Hg–Rh distances lie in the ranges 3.131(3)–3.149(3)Å and 2.690(4)–2.724(4)Å respectively. Compound (11) has the PPh₃ groups trans to the chloride. Bond distances and angles are similar to those in the tris PPh₃ and PMe₃ analogues.