Synthesis of Bis(aliphatic amine)osmium(II), Bis(arylamido)osmium(IV), and Bis(imido)and Oxo(imido)osmium(VI) Porphyrins

The syntheses, characterization, and reactivity of a series of osmium porphyrins, Os^II(Por)(H₂NR)₂ [Por = dianions of octaethylporphyrinato (OEP), tetraphenylporphyrinato (TPP), meso-tetrakis(p-tolyl)porphyrinato (TTP), mesotetrakis(4-chlorophenyl)porphyrinato (4-Cl-TPP), meso-tetrakis(3,4,5-trimethoxyphenyl)porphyrinato (3,4,5-MeO-TPP). R = ^tBu; Por = TPP, R = ⁱPr], Os^II(Por)(HNEt₂)₂ (Por = TPP, 3,4,5-MeO-TPP), Os^IV(Por)(NHAr)₂ (Por = OEP, TPP, 3,4,5-MeO-TPP; Ar = Ph, 4-F-Ph). Os^VI(Por)(N^tBu)₂ (Por = TPP, TTP, 4-C1-TPP, 3,4,5-MeO-TPP), Os^VIO(Por)(N^tBu) (Por = TPP, TTP, 4-C1-TPP, 3,4,5-MeO-TPP), and Os^VIO(Por)(4-F-PhN) (Por = TPP, 3,4,5-MeO-TPP) are described. The complexes Os(Por)(HNAr)₂ are prepared from the reactions of Os(Por)-(N₂)(THF) with arylamines in aerobic tetrahydrofuran. Air oxidations of Os(Por)(H₂N^tBu)₂ in tetrahydrofuran and in the presence of H₂N^tBu give OsO(Por)(N^tBu) and Os(Por)(N^tBu)₂. The X-ray crystal structures of OsO-(TTP)(N^tBu)·EtOH and Os(4-Cl-TPP)(N^tBu)₂ have been determined. Crystal data for OsO(TTP)(N^tBu)·EtOH: monoclinic, space group P2_l/c, a = 13.546(6) Å, b = 23.180(3) Å, c - 16.817(3) Å, β = 90.84(2)°, V = 5279.7-(1.0) ų, Z = 4. Os(4-Cl-TPP)(N^tBu)₂: monoclinic, space group P2_l/c, a = 11.046(2) Å. b = 18.380(3) Å, c = 23.640(4) Å, β= 97.22(1)°, V = 4759.8(1.0) Å, Z = 4. The Os=O and Os=N^tBu distances in OsO(TTP)-(N^tBu)·EtOH are 1.772(7) and 1.759(9) Å, respectively. The Os=N^tBu distances in Os(4-Cl-TPP)(N^tBu)₂ average 1.775 Å. The imido angles range from 165.8(8) to 170.6(9)°. For the infrared spectra of these complexes, a discussion on the "oxidation state marker" band in the vicinity of 1000 cm^-1 is presented. The differences in the electronic properties of osmium porphyrins at various oxidation states are also described.