OXIDATIVE ADDITION OF CARBON-CHLORIDE BONDS TO RHODIUM(I) COMPLEXES CONTAINING TERDENTATE NITROGEN LIGANDS - X-RAY ANALYSES OF RHODIUM(I) CHLORIDE AND RHODIUM(III) CHLOROMETHYL COMPLEXES

Potentially terdentate hemilabile 2,6-bis(R(2)-carbaldimino)pyridine a nd 2,6-bis(R(2)-ethylidyneimino)pyridine ligands (2,6-(C(R(1))=NR(2))( 2)C5H3N; R(1) = H, R(2) = i-Pr (1), t-Bu (2), cyclohexyl (3), p-anisyl (4); R(1) = Me, R(2) = p-anisyl (5), i-Pr (6)) have been used to prep are in high yields the novel and highly nucleophilic complexes [RhCl(2 ,6-(C(R(1)) = NR(2))(2)C5H3N)] (R(1) = H, R(2) = i-Pr (7), t-Bu (8), c yclohexyl (9), p-anisyl (10); R(1) = Me, R(2) = p-anisyl (11), i-Pr (1 2)) with [RhCl(alkene)(2)](2) (alkene = ethene, cyclooctene) as starti ng material. X-ray. analyses of 7, 8, and 12 show severe steric intera ctions between the R(2) group and the equatorial chloride atom, leadin g to out-of-plane bending of the chloride atom. The angle between the N-N-N plane and the Rh-Cl axis is 5.34(16)degrees for 7, 11.73(11)degr ees for 8, and 10.04(11)degrees for 12. Reaction of the Rh(I) complexe s with CH2Cl2, CHCl3, benzyl chloride, and alpha,alpha-dichlorotoluene led to Rh(III) complexes by C-Cl bond rupture. The Rh-C bonds of the chloromethyl complexes [RhCl2(CH2Cl)(2,6-(C(R(1))=NR(2))(2)C5H3N)] (R( 1) = H, R(2) = i-Pr (13), cyclohexyl (15)) are all short (2.052(5)-2.0 59(3) Angstrom), while the C-Cl bonds (range 1.728(4)-1.790(5) Angstro m) are rather long, which indicates the contribution of a Rh = CH2+Cl- resonance form. In solution all Rh(III) complexes exist as one isomer with the ligand bonded in a terdentate fashion (both H-1 and C-13 NMR ), except for the complexes [RhCl2(R(3))(2,6-(C(Me) = N-i-Pr)(2)C5H3N) ] (R(3) = CH2Cl (18), CH(2)Ph (24), CHClPh (27), Cl (33)), which all c ontain two interconverting isomers; one five-coordinate Rh(III) isomer has a Ligand which coordinates in a bidentate manner, while the other six-coordinate isomer has a ligand which coordinates in a terdentate fashion, as evidenced by low-temperature NMR measurements. Molecular m odeling has shown that the formation of the five-coordinate Rh(III) sp ecies is caused by the axial ligands, which force the equatorial Cl at om into the N-N-N plane, resulting in an increased steric interaction of R(2) and R(1). Reaction of the chloromethyl and dichloromethyl comp lexes 13-21 in boiling water with oxygen gave the trichloride complexe s [RhCl3(2,6-(C(R(1)) = NR(2))(2)C5H3N)] (R(1) = H, R(2) = i-Pr (28), t-Bu (29), cyclohexyl (30), p-anisyl (31); R(1) = Me, R(2) = p-anisyl (32), i-Pr (33)), while the chlorotolyl complex [RhCl2(CHClPh)(2,6-(C( Me) = N-i-Pr)(2)C5H3N)] 27 gave the complex 33, benzaldehyde, and H2O2 .