OXIDATIVE ADDITION OF BR-2 TO RU(ETA(5)-C(5)ME(5))(ETA(4)-DIENE)BR COMPLEXES - EFFECT OF SUBSTITUENTS OF THE DIENE ON THE COURSE OF REACTION - FORMATION OF A NOVEL CATIONIC RUTHENIUM(IV) ETA(4)-DIENE COMPLEX

The products of bromine addition to RU(eta(5)-C(5)Me(5))(eta(4)-diene)Br (1) vary with the substituents of the diene moiety. In the case of 1,3-butadiene and 2-methyl-1,3-butadiene the corresponding Ru(eta(5)-C(5)Me(5))(eta(3)-allyl)Br-2 complexes (2) are readily formed. For 2,3-dimethyl-1,3-butadiene, in contrast, a eta(4)-diene Ru(TV) complex is obtained, which is unstable in solution and tentatively formulated as RU(eta(5)-C(5)Me(5))(eta(4)-CH(2)CMeCMeCH(2))Br-3 (3). Among the decomposition products the unusual complex [RU(eta(5)-C(5)Me(5))(eta(4)-CH(2)CMeCMeCH(2))Br-2][RU(eta(5) C(5)Me(5))Br-4] (5) is found. With AgCF3SO3, complex 3 affords, in a reversible reaction, the novel cationic complex [RU(eta(5)-C(5)R(5))(eta(4)-CH(2)CMeCMeCH(2))Br-2]CF3SO3 (4). By X-ray diffraction techniques, the molecular structures of 2b, 4, and 5 have been determined. 2b crystallizes in space group P2(1)/c (No. 14), with a = 12.910(4) Angstrom, b = 11.293(4) Angstrom, c = 12.615(4) Angstrom, beta = 105.05(1)degrees, V = 1776.1(10) Angstrom(3), and Z = 4. The structure was refined to R(F) = 0.045 (F greater than or equal to 4 sigma(F)). 4 crystallizes in space group Pnma (No. 62), with a = 17.424(4) Angstrom, b = 11.830(3) Angstrom, c = 10.550(3) Angstrom, V = 2174.6(10) Angstrom(3), and Z = 4. The structure was refined to R(F) = 0.039 (F greater than or equal to 4 sigma F)). 5 crystallizes in space group Pna2(1) (No. 33),with a = 28.239(8) Angstrom, b = 12.564(3) Angstrom, c = 9.006(2) Angstrom, V = 3195.3(14) Angstrom(3), and Z = 4. The structure was refined to R(F) = 0.049 (F greater than or equal to 4 sigma(F)).