VARIABLE-VALENT RE-NAR SPECIES - A FAMILY OF REVINAR AMIDE COMPLEXES AND THEIR REVNAR IMINE PRECURSORS RELATED BY OXYGEN-ATOM TRANSFER

Imide complexes of type (ReCl3)-Cl-V(X-SB)(NC6H4Y(p)), with X, Y = H, Me, OMe, Cl have been synthesized where X-SB is the Schiff base of pyr idine-2-carboxaldehyde (the corresponding complex is 4), 2-acetylpyrid ine (5), 2-benzoylpyridine (6), and anilines, p-XC6H4NH2. Treatment of 4 or 5 (but not 6) with aqueous nitric acid in acetonitrile afforded (ReCl3)-Cl-VI(X-PA)(NC6H4Y(p)), 7, via oxygen atom transfer (X-PA = mo noanionic 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 3N3 coordination sphere. The trans influence of the imide nitrogen con siderably lengthens the Re-N(pyridine) bond. The ReNC6H4Y(p) group has the triple-bonded linear moiety, Re equivalent to N-C. The amide grou p in 7(Me,Me) is planar. In 6(OMe,OMe) the two aryl rings on the imine function block water attack and hence amide formation. The rhenium(VI )-rhenium(V) E-1/2 values for 4-6 (0.7-1.0 V vs SCE) are much higher t han that for 7 (E-1/2 similar to 0.15 V), which displays the rhenium(V II)-rhenium(VI) couple near 1.6 V. Six EPR hyperfine lines are observe d for solutions of 7 at room temperature (g(iso) similar to 1.91; A(av ) similar to 490 G). Crystal data for the complexes are as follows: 5( Cl,Cl), empirical formula C19H15Cl5N3Re, crystal system monoclinic, sp ace group P2(1)/c, a = 13.360(6) Angstrom, b = 12.110(3) Angstrom, c = 14.954(9) Angstrom, beta = 111.41(4)degrees, V = 2252.4(1.7) Angstrom (3), Z = 4; 6(OMe,OMe), empirical formula C26H23Cl3N3O2Re, crystal sys tem orthorhombic, space group Pbca, a = 12.079(5) Angstrom, b = 17.083 (9) Angstrom, c = 26.049(9) Angstrom, V = 5375.4(4.0) Angstrom(3), Z = 8; 7(Me,Me), empirical formula C20H18Cl3N3ORe, crystal system monocli nic, space group P2(1)/c, a = 7.071(2) Angstrom, b = 17.541(6) Angstro m, c = 16.857(8) Angstrom, beta = 100.59(3)degrees, V = 2055.3(1.3) An gstrom(3), Z = 4.