Synthesis and Characterization of Novel Rhenium(V) Tetradentate N₂O₂Schiff Base Monomer and Dimer Complexes

Abstract

Several rhenium(V) oxo complexes with tetradentate N(2)O(2) Schiff base ligands were synthesized and characterized. The general synthetic procedure involved reaction of [NBu(4)][ReOCl(4)] with a tetradentate Schiff base ligand (L(1) = N,N'-ethylenebis(acetylacetoneimine), (acac(2)en) or L(2) = N,N'-propylenebis(acetylacetoneimine) (acac(2)pn)) in ethanol solution to generate complexes of the form trans-ReOX(L) where X = Cl(-), MeO(-), ReO(4)(-), or H(2)O. The product isolated from the reaction was found to be dependent on the reaction conditions, in particular the presence or absence of water and/or base. The mu-oxo-Re(2)O(3)(L)(2) dimers were synthesized and characterized for chemical and structural comparison to the related monomers. Conversion of the monomer to its dimer analogue was followed qualitatively by spectrophotometry. The complexes were characterized by (1)H and (13)C NMR, UV-vis, and IR spectroscopy, elemental analysis, and single crystal X-ray diffraction. The crystallographic data reported for the structures are as follows: trans-[ReO(OH(2))(acac(2)en)]Cl (H(20)C(12)ClN(2)O(4)Re) 1, triclinic (Ponemacr;), a = 7.2888(6) A, b = 9.8299(8) A, c = 10.8195(9) A, alpha = 81.7670(10) degrees, beta = 77.1510(10) degrees, gamma = 87.6200(10) degrees, V = 747.96(11) A(3), Z = 2; trans-[ReO(OReO(3))(acac(2)en)] (H(18)C(12)N(2)O(7)Re(2)) 2, monoclinic (P2(1)/c), a = 7.5547(4) A, b = 8.7409(5) A, c= 25.7794(13) A, beta = 92.7780(10) degrees, V = 1700.34(16) A(3), Z = 4; trans-[ReOCl(acac(2)pn)] (H(20)C(13)N(2)O(3)ClRe) 3, monoclinic (P2(1)/c), a = 8.1628(5) A, b = 13.0699(8) A, c = 28.3902(17) A, beta = 97.5630(10) degrees, V = 3002.5(3) A(3), Z = 8; trans-[ReO(OMe)(acac(2)pn)] (H(23)C(14)N(2)O(4)Re) 4, monoclinic (P2(1)/c), a = 6.7104(8) A, b = 27.844(3) A, c = 8.2292(9) A, beta = 92.197(2) degrees, V = 1536.4(3) A(3), Z = 4; trans-[mu-oxo-Re(2)O(3)(acac(2)en)(2)] (H(36)C(24)N(4)O(7)Re(2)) 5, monoclinic (P2(1)/n), a = 9.0064(5) A, b = 12.2612(7) A, c = 12.3695(7) A, beta = 90.2853(10) degrees, V = 1365.94(13) A(3), Z = 2; and trans-[mu-oxo Re(2)O(3)(acac(2)pn)(2)] (H(40)C(26)N(4)O(7)Re(2)) 6, monoclinic (P2(1)/n), a = 9.1190(5) A, b = 12.2452(7) A, c = 12.8863(8) A, beta = 92.0510(10) degrees, V = 1438.01(14) A(3), Z = 2.

Synthesis and characterization of a neutral rhenium(V) complex containing a tridentate chelate with an imido donor atom

“…The Re-N(1) bond length of 2.169(3) Å is typical of Re V -N(imine) bonds [14], and the Re-O bond length of 1.928(2) Å falls at the lower end of the range normally observed for Re-O (phenolate) bonds [15]. The C(7)-N(1)-C(8) bond angle of 119.9(3) is close to the ideal for a sp 2 hybridized nitrogen atom and the C(7)-N(1) bond length of 1.292 (5) (2) Å ] found normally for Re(V) complexes containing phosphine ligands [16]. A weak intramolecular hydrogen bond exists between C(7)H(7) and Cl(1) [3.715(4) Å ].…”

Ligand-Enhanced Reduction of Perchlorate in Water with Heterogeneous Re−Pd/C Catalysts

“…Facile generation of perrhenate from exposure of lower-oxidation-state Re complexes to air and moisture, especially under acidic conditions, has been documented rather frequently. 15 Our second approach involved maintaining a constant hydrogen atmosphere for all operations. The ligand, NH 4 ReO 4 , and HCl were mixed with the Pd/C powder suspended in water, and adsorption of perrhenate was followed until completion.…”

A rhenium(V) complex containing a terdentate chelate with an imido donor atom: synthesis and structure of [Re(aps)I(PPh3)2]I (H3aps = N-(2-aminophenyl)-salicylideneimine)

“…These data intimate that the imido nitrogen atom is doubly, rather than triply, bonded to the rhenium. The Re-N(2) bond length of 2.185(5) Å (2.192(6) Å in B) is typical of Re(V)-N(imine) bonds [19]. The Re-O(1) bond length of 1.929(4) Å (1.910(4) Å in B) falls within the range normally observed for Re(V)-O (phenolic) bonds [19].…”