REACTIVITY OF THE DIRUTHENIUM(I) DIPHOSPHINE-BRIDGED AND ACETATE-BRIDGED SPECIES [RU-2(CO)(4)(MU-O(2)CME)(MU-DPPM)(2)][BF4]

Reactions of the cationic singly bridged A-frame complex [Ru-2(CO)(4)( mu-O(2)CMe)(mu-DPPM)(2)](+) (2) with I-, N-3(-), and Pz'(-), via HPz'/ Et(3)N (HPz' 3,5-dimethylpyrazole), in MeOH yield two types of neutral dibridged A-frame products, [Ru-2(CO)(2)(mu-CO)(mu-X)X(mu-DPPM)(2)] ( X = I (3), N-3 (4)) and [Ru-2(CO)(3)(mu-Pz')H(mu-DPPM)(2)] (10). Compl exes 3, 4, and 10 have been characterized by spectroscopic data and X- ray crystallography: 3 . Et(2)O, a = 12.779(4) Angstrom, b = 27.447(11 ) Angstrom, c = 15.487(4) Angstrom, beta = 95.676(23)degrees, V = 5405 (3) Angstrom(3), monoclinic, P2(1)/c; Z = 4, refined to R = 0.041 R(w) = 0.034, and GOF = 1.33 4 . CH2Cl2, a = 19.764(2) Angstrom, b = 14.64 7(2) Angstrom, c = 20.033(2) Angstrom, beta = 97.532(8)degrees, V = 57 49(1) Angstrom(3), monoclinic, P2(1)/c; Z = 4, refined to R = 0.058, R (w) = 0.086, and GOF = 1.16; 10 . CH2Cl2, a 13.046(2) Angstrom, b = 15 .179(3) Angstrom, c = 28.226(5) Angstrom, beta = 95.93(1)degrees, V = 5559(1) Angstrom(3), monoclinic, P2(1)/c; Z = 4, refined to R = 0.074, R(w) = 0.081, and GOF = 1.70. The Ru-Ru distance is 3.0147(15) Angstr om in 3, 3.020(1) Angstrom in 4, and 2.891(3) Angstrom in 10. Complex 3 reacts with PMe(3) and P(OMe)(3) to give [Ru-2(CO)(3)I-2(PMe(3))(mu- DPPM)(2)] (8) and [RU(2)(CO)(3)I-2(P(OMe)(3)}(mu-DPPM)(2)] (9), respec tively, whereas no reaction between 4 and these phosphine ligands was observed even under forcing conditions. This difference in reactivity, accompanied with the spectral evidences of 8 and 9, reflects apparent ly the greater importance of a facile switch from a bridging to termin al group relative to the cleavage of the dative Ru-Ru bond in the doub le-bridged A-frame complexes such as 3 and 4 to form isolable adducts such as 8 and 9.