Pyridylazole Chelation of Oxorhenium(V) and Imidorhenium(V). Rates and Trends of Oxygen Atom Transfer from Re^VO to Tertiary Phosphines

Abstract

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). The X-ray structures of pbt, ReOCl(3)(pbt), Re(OPPh(3))Cl(3)(pbt), and Re(NPh)Cl(3)(pbo) are reported. The lattice of pbt consists of stacked dimers. In all the complexes the azole ligand is N,N-chelated and the ReCl(3) moiety is meridionally disposed. In ReOCl(3)(pbt) the metal-oxo bond length is 1.607(9) A. The second-order rates and the associated activation parameters of the oxygen atom transfer reactions of the Re(V)O chelates with PPh(2)R are reported. The large and negative entropy of activation (approximately -24 eu) is consistent with an associative pathway involving nucleophilic phosphine attack. The rate increases with phosphine basicity (PPh(2)Me > PPh(3)) and azole heteroatom electronegativity (O(pbo) > S(pbt)). Logarithmic rate constants for ReOCl(3)(pbo), ReOCl(3)(pbt), and ReOCl(3)(pal) are found to correlate linearly with Re(VI)O/Re(V)O reduction potentials (pal is pyridine-2-(N-p-tolyl)aldimine). The relatively low rate constant of ReOCl(3)(pbt) compared to that of ReOCl(3)(pal) is consistent with the observed shortness of the metal-oxo bond in the former. Crystal data are as follows: (pbt) empirical formula C(12)H(8)N(2)S, crystal system orthorhombic, space group Pca2(1), a = 13.762(9) A, b = 12.952(8) A, c = 11.077(4) A, V = 1974(2) A(3), Z = 8; (ReOCl(3)(pbt)) empirical formula C(12)H(8)Cl(3)N(2)OSRe, crystal system monoclinic, space group P2(1)/c, a = 11.174(7) A, b = 16.403(10) A, c = 7.751(2) A, beta = 99.35(4) degrees, V = 1401.8(13) A(3), Z = 4; (Re(NPh)Cl(3)(pbo)) empirical formula C(18)H(13)Cl(3)N(3)ORe, crystal system monoclinic, space group P2(1)/c, a = 9.566(6) A, b = 16.082(8) A, c = 11.841(5) A, beta = 94.03(4) degrees, V = 1817(2) A(3), Z = 4.

Synthesis and electrochemical study of 2-(2-pyridyl)benzothiazole complexes with transition metals (CoII, NiII, and CuII). Molecular structure of aquabis[2-(2-pyridyl)benzothiazole]copper(II) diperchlorate

“…g The peak is weakly pronounced and is not always reproducible. C (6) electron withdrawing group into the thiazole ring may impart the ability to be reduced at the thiazole ring. 15 Electrochemical reduction of benzothiazolium salts oc curs at the N=C bond.…”

Oxidorhenium(V) Complexes of a Family of Bipyridine‐Like Ligands Including Pyridyltriazines and Pyrazinyltriazine: Oxygen‐Atom Transfer, Metal Redox and Correlations

“…As expected, the 1 H NMR spectra of the complexes are paramagnetically shifted. [14,17,19,30] Although no direct structural characterisation was possible due to lack of single crystals, our previous work [11][12][13][14][15][16][17][18]31] on related systems strongly supports the gross geometry of the phosphane oxide complexes to be 6.…”

“…The reaction is thus second order in nature, see Equation (2). Rates for all the complexes were determined at 303 K ( [10,17] where initial attack involves the phosphane lone pair and ReϵO π*-orbitals.…”

“…Although a beginning in this direction was recently made with pyridylazole ligands, [17,18] the logical starting point would be the familiar didentate pyridyl aza-aromatic, viz. bipyridine (bpy).…”

Synthesis and crystal structure determination of copper(II) and iron(III) complexes of 2-(2-pyridyl)benzothiazole

“…In the preferred conformation of the pbt molecule, as revealed by its X-ray diffraction analysis [20], the N=C-C=N moiety is anti; so pbt needs a 180°con-formational rotation of the pyridyl moiety to enable N,Nchelation of the metal centres. Pbt is expected to bind to soft acceptor centres in S,N-chelating mode [25], but the only observed binding mode of pbt is N,N-chelation [23,[25][26][27][28]. A key to the explanation of this behaviour comes from the comparison of IR spectra of pbt and its complexes.…”