o-Phenylenediamine and related complexes of chromium, vanadium and manganese

Abstract

Using the ligands (L–L)o-phenylenediamine, 4,5-dimethyl-o-phenylenediamine and phenanthrene-9,10-diamine, anionic chromium(III) complexes of the type [CrCl₄(L–L)]^–, have been isolated as quaternary phosphonium salts from interaction of CrCl₃(thf)₃(thf = tetrahydrofuran) and the ligand in the presence of [PPh₄]Cl or [PPh₃(CH₂Ph)]Cl. Interaction in the absence of quaternary phosphonium salts gives [CrCl₂(L–L)₂]Cl. A similar tetrachloro anion has been obtained using the chelating phosphine 1,2-(HPrⁱP)₂C₆H₄. Similar complexes obtained from VCl₃(thf)₃ have the form [VCl₄(L–L)]^– and [VCl₂(L–L)₂]Cl. Use of the dihalides leads to octahedral complexes trans-MCl₂(L–L)₂(M = V or Cr) and trans-MnI₂(L–L)₂. The interaction of [P(CH₂Ph)Ph₃][CrCl₄{(H₂N)₂C₆H₂Me₂}] with AgO₃SCF₃ and of [CrCl₂{(H₂N)₂C₆H₄}₂]Cl with trifluoromethanesulfonic acid and diethyl ether leads to the unusual chromium(IV) octahedral triflate compounds Cr(NH₂)(O₃SCF₃)₃[(H₂N)₂C₆H₂Me₂] and Cr(O₃SCF₃)₄[(H₂N)₂C₆H₄], respectively. The crystal structures of the compounds [PPh₃(CH₂Ph)][CrCl₄{(H₂N)₂C₆H₄}], Cr(NH₂)(O₃SCF₃)₃[(H₂N)₂C₆H₂Me₂], Cr(O₃SCF₃)₄[(H₂N)₂C₆H₄] and [PPh₄][VCl₄{(H₂N)₂C₆H₂Me₂}] have been determined. All have octahedral structures with chelating diamines. In the tetrachlorochromate(III) salt, the Cr–N distances are ca. 0.05 Å longer than those in the chromium(IV) compounds. The V^III–N distances [2.16(1)Å] are ca. 0.05 Å longer than the Cr^III–N distances [2.11(1)Å], as expected, but the vanadium complex shows a much greater diffrence in M–Cl distances trans to N [2.336(4)Å] or trans to Cl [2.381(4)Å] than in the chromium(III) complex [all 2.342–2.356(5)Å].