Bis(diphenylphosphino)methane complexes of rhodium(III) halides as synthons for dinuclear rhodium(III) complexes

Abstract

Several rhodium(III) complexes have been synthesized by the reaction of dirhodium tetraacetate, Rh 2(O 2CCH 3) 4, with bis(diphenylphosphino)methane (dppm), in the presence of trimethylsilyl halides. Octahedral complexes of formula RhCl 3(dppm)(CH 3CN) ( 1) and RhI 3(dppm)(CH 3CN) ( 2) have been isolated as minor products in the reaction between Rh 2(O 2CCH 3) 4, dppm and Me 3SiCl or Me 3SiI, respectively. In addition, the tri-n-butylphosphine complex RhCl 3(dppm)(P-n-Bu 3) ( 3) has also been prepared either by treatment of 1 with P-n-Bu 3 or from the reaction of Rh 2Cl 6(P-n-Bu 3) 4 with dppm. Dimerization occurs upon heating 3 at 150 °C in vacuo for 2 h to form the Rh(II) complex Rh 2Cl 4(dppm) 2, which we have previously reported. X-ray crystallographic characterization of 1, 2 and 3 gave the following: for 1: space group I4̄, a=19.090(4), c=15.100(3) Å, V=5503(1) Å −3, Z=8; for 2: space group Cc, a=11.897(2), b=17.110(3), c=15.246(1)Å, β=106.04(9)°, V=2983(1) −3, Z=4; for 3: space group P2 12 12 1, a=15.914(4), b=19.819(6), c=12.207(3) Å, V=3850(2) Å 3, Z=4.