Rhenium chemistry of azooximes: oxygen atom transfer, azoimine chelation, and imine-oxime contrast.

The concerned azooximes (L1OH, 1) are of type p-X-C6H4C(N2Ph)(NOH) (X = H, Me, Cl). The reaction of [Re(MeCN)Cl3(PPh3)2] with [Ag(L1OH)(L1O)] in cold dichloromethane-acetonitrile solvent has furnished the green colored ionized azoimine complex [ReV(O)Cl(PPh3)2(L1)](PF6), 2. In effect L1O- has undergone oxidative addition, the oxygen atom being transferred to the metal site.

Rhenium chemistry of diazabutadienes and derived iminoacetamides spanning the valence domain II-VI. Synthesis, characterization, and metal-promoted regiospecific imine oxidation.

The reaction of diazabutadienes of type R'N=C(R)-C(R)=NR', L (R = H, Me; R' = cycloalkyl, aryl) with Re(V)OCl(3)(AsPh(3))(2) has furnished Re(V)OCl(3)(L), 1, from which Re(III)(OPPh(3))Cl(3)(L), 2, and Re(V)(NAr)Cl(3)(L), 3, have been synthesized. Chemical oxidation of 2(R = H) by aqueous H(2)O(2) and of 3(R = H) by dilute HNO(3) has yielded Re(IV)(OPPh(3))Cl(3)(L'), 5, and Re(VI)(NAr)Cl(3)(L'), 4, respectively, where L' is the monoionized iminoacetamide ligand R'N=C(H)-C(=O)-NR'(-). Finally, the reaction of Re(V)O(OEt)X(2)(PPh(3))(2) with L has furnished bivalent species of type Re(II)X(2)(L)(2), 6(X = Cl, Br).

A family of vanadate esters of monoionized and diionized aromatic 1,2-diols: synthesis, structure, and redox activity.

The concerned diols (general abbreviation, H(2)L) are catechol (H(2)L(1)) and its 3,5-Bu(t)(2) derivative (H(2)L(2)). Esters of the type VO(xsal)(HL), 2, are obtained by reacting H(2)L with VO(xsal)(H(2)O) or VO(xsal)(OMe)(HOMe), where xsal(2-) is the diionized salicylaldimine of glycine (x = g), L-alanine (x = a), or L-valine (x = v). The reaction of VO(acac)(2) with H(2)L and the salicylaldimine (Hpsal) of 2-picolylamine has furnished VO(psal)(L), 3.

Pyridylazole chelation of oxorhenium(V) and imidorhenium(V). Rates and trends of oxygen atom transfer from Re(V)O to tertiary phosphines.

The concerned azoles are 2-(2-pyridyl)benzoxazole (pbo) and 2-(2-pyridyl)benzthiazole (pbt). These react with ReOCl(3)(PPh(3))(2) in benzene, affording Re(V)OCl(3)(pbo) and Re(V)OCl(3)(pbt), which undergo facile oxygen atom transfer to PPh(2)R (R = Ph, Me) in dichloromethane solution, furnishing Re(III)(OPPh(2)R)Cl(3)(pbo) and Re(III)(OPPh(2)R)Cl(3)(pbt). The oxo species react with aniline in toluene solution, yielding the imido complexes Re(V)(NPh)Cl(3)(pbo) and Re(V)(NPh)Cl(3)(pbt).

Regiospecific Oximato Coordination at the Oxygen Site: Ligand Design and Low-Spin Mn(II) and Fe(II/III) Species.

The (pyridylazo)oxime ligand (C(5)H(4)N)N=NC(=NOH)C(6)H(4)R(p), HRL (R = H, Me), has been synthesized with the objective of promoting the very rare mononuclear oximato-O coordination. The synthesis involves hydrazone nitrosation. HRL reacts with M(ClO(4))(2).

Carbohydrate Binding to VO(3+). Sugar Vanadate Esters Incorporating L-Amino Acid Schiff Bases as Coligands.

The glycosides methyl-2,6-dimethoxy-beta-D-galactopyranoside (beta-D-H(2)Me(3)GP), methyl-4,6-dimethoxy-alpha-D-mannopyranoside (alpha-D-H(2)Me(3)MP), and methyl-5-methoxy-beta-D-ribofuranoside (beta-D-H(2)Me(2)RF) have been synthesized, and their reaction with VO(L-Asal)(OMe)(OHMe) in dichloromethane has afforded esters of the type VO(beta-D-HMe(3)GP)(L-Asal), VO(alpha-D-HMe(3)MP)(L-Asal), and VO(beta-D-HMe(2)RF)(L-Asal) as dark-colored solids (red in solution). Here, L-Asal(2)(-) is the deprotonated salicylaldimine of L-alanine (A = a), L-valine (A = v), and L-phenylalanine (A = p). The X-ray structures of VO(beta-D-HMe(3)GP)(L-vsal).

Variable-Valent Re&tbd1;NAr Species. A Family of Re(VI)NAr Amide Complexes and Their Re(V)NAr Imine Precursors Related by Oxygen Atom Transfer.

Imide complexes of type Re(V)Cl(3)(X-SB)(NC(6)H(4)Y(p)), with X, Y= H, Me, OMe, Cl have been synthesized where X-SB is the Schiff base of pyridine-2-carboxaldehyde (the corresponding complex is 4), 2-acetylpyridine (5), 2-benzoylpyridine (6), and anilines, p-XC(6)H(4)NH(2). Treatment of 4 or 5 (but not 6) with aqueous nitric acid in acetonitrile afforded Re(VI)Cl(3)(X-PA)(NC(6)H(4)Y(p)), 7, via oxygen atom transfer (X-PA = monoanionic picolinamide). In the structures of 5(X=Cl,Y=Cl), 6(OMe,OMe), and 7(Me,Me), the chlorine atoms are meridionally disposed in a ReCl(3)N(3) coordination sphere.

A Triad of Variable-Valent Rhenium Aldimine and Amide Systems Interrelated by Successive Oxygen Atom Transfer.

The title systems are Re(V)OCl(3)(RA), 1, Re(III)(OPPh(3))Cl(3)(RA), 2, and Re(IV)(OPPh(3))Cl(3)(RB), 3, where RA is a 2-pyridinecarboxaldimine, p-RC(6)H(4)N=CHC(5)H(4)N, and RB(-) is the corresponding 2-picolinamide, p-RC(6)H(4)NC(=O)C(5)H(4)N(-) (R = H, Me, OMe, Cl). Controlled reaction of ReOCl(3)(PPh(3))(2) with RA affords 1, which is converted to 2 upon reaction with PPh(3). The oxidation of 2 in aqueous media by Ce(4+) or H(2)O(2) furnishes 3.

A Bis(azo-imine)palladium(II) System with 10 Ligand pi Electrons. Synthesis, Structure, Serial Redox, and Relationship to Bis(azooximates) and Other Species.

The first azo-imine chelate system, Pd(N(H)C(R)NNPh)(2) (Pd(RA)(2)), has been isolated in the form of diamagnetic solids by the 6e(-)-6H(+) reduction of bis(phenylazooximato)palladium(II), Pd(N(O)C(R)NNPh)(2) (abbreviated Pd(RB)(2)), with ascorbic acid in a mixed solvent (R = Ph, alpha-naphthyl). Selected spectral features are described. The X-ray structures of Pd(PhA)(2) and Pd(PhB)(2) have revealed trans-planar geometry consistent with metal oxidation state of +2.