SITE-SELECTIVE PME3 ADDITION TO THE DONOR-ACCEPTOR COMPLEX RU-2(CO)(6)[(Z)-PH2PCH=CHPPH2] - X-RAY-DIFFRACTION STRUCTURE OF RU-2(CO)(5)(PME3)[(Z)-PH2PCH=CHPPH2]

The diphosphine-bridged ruthenium dimer Ru-2(CO)(6)[(Z)-Ph2PCH=CHPPh2] (1) reacts with added PMe3 under photochemical and thermal conditions and by Me3NO-induced activation at the phosphine-substituted rutheniu m center to give Ru-2(CO)(5)(PMe3)[(Z)-Ph2PCH=CHPPh2] (2). The enterin g PMe3 is found to adopt axial and equatorial sites in 2, as confirmed by solution H-1 and P-31 NMR spectroscopy measurements, The solid-sta te structure of the equatorially substituted isomer 2e has been establ ished by X-ray diffraction analysis. 2e crystallizes in the triclinic space group <P(1)over bar>: a=10.8602(7), b=11.1801(9), c=15.680(1) An gstrom, alpha=79.788(6), beta=82.838(6), gamma=66.450(5)degrees, V=171 4.6(2) Angstrom(3), Z=2, D-calc=1.578 g cm(-3); R=0.0574, R-w=0.0627 f or 3695 observed reflections with I>3 sigma(I). (C) 1998 Elsevier Scie nce S.A.