EARLY-LATE HETEROBIMETALLIC CHEMISTRY - REACTION OF A STABLE CARBENE ADDUCT OF [(C4ME4P)(2)YB](N) WITH RUTHENIUM HYDRIDES, TRANSIENT FORMATION OF A BIMETALLIC YB-RU HYDRIDE AND SYNTHESIS OF (C4ME4P)RUH(PPH3)(2)

The new complexes (tmp)(2)Yb(carbene) 1a and 1b (tmp = C4Me4P and carb ene = C2Me2((NPr)-Pr-i)(2)C and C2Me2(NMe2C)) have been synthesized fr om [(tmp)(2)Yb](n) and characterized by elemental analysis and by NMR (H-1, P-31). Complexes 1a and 1b are not stable in THF. Complex 1a rea cts in benzene-d(6) with RuH4(PPh3)(3) to give the moderately stable h eterobimetallic dihydride (PPh3)(2)RuH2-mu(tmp)(2)-Yb(carbene) 2a and with RuHCl(PPh3)(3) to give (tmp)RuH(PPh3)(2) 4. The formation of the analogous complex 2b is not observed when 1b is allowed to react with RuH4(PPh3)(3). The nature of 2a is established by NMR. After two days at room temperature, 2a is transformed into C2Me2((NPr)-Pr-i)(2)CH2 3a , 4 and (tmp)RuH(PPh3) (carbene) 4'. Complex 4 was obtained analytical ly pure from RuHCl(PPh3)(3) and tmpK whereas a mixture of 4 and 4' is obtained after addition of an excess of C2Me2((NPr)-Pr-i)(2)CH2 to a s olution of 4.