REACTIONS OF THE DIRHENIUM(II) COMPLEXES RE2X4(MU-DPPM)(2) (X=CL, BR,DPPM=PH2PCH2PPH2) WITH ISOCYANIDES .13. IDENTIFICATION OF A NEW STRUCTURAL ISOMER OF THE DIRHENIUM CATION [RE2CL3(MU-DPPM)(2)(CO)(CNXYL)(2)](- STRUCTURAL CHARACTERIZATION OF (XYLNC)CLRE(MU-CL)(MU-CNXYL)(MU-DPPM)(2)RECL(CO)() AND ITS ISOMERIZATION BEHAVIOR )

A yellow form of the dirhenium salts of the type [Re2Cl3(mu-dppm)(2)(C O)(CNXyl)(2)]Y (Y = Cl, O3SCF3, PF6, ReO4) has been shown to have the mu-CNXyl-bridged structure lNC)-ClRe(mu-Cl)(mu-CNXyl)(mu-dppm)(2)ReCl( CO)](+) on the basis of an X-ray crystal structure determination of it s neutral paramagnetic congener. The Re-Re bond length in the structur e of Re2Cl3(mu-dppm)(2)(CO)(CNXyl)(2) is 2.7155(9) Angstrom, in accord with the presence of a formal Re-Re bond order of 1.5. This particula r cation constitutes the fourth isomer of [Re2Cl3(mu-dppm)(2)(CO)(CNXy l)(2)](+) to have been structurally characterized.