METALLACUMULENES - ACTIVATION OF DIYNES AND FORMATION OF NEW ALLENYLIDENERUTHENIUM COMPLEXES - CRYSTAL-STRUCTURES OF PCH(2)PPH(2))(2)RU(=C=C=C(OME)CH=CPH(2))(2)](2+)() AND TRANS)

cis-RuCl2(Ph(2)PCH(2)PPh(2))(2) (1) reacts with pentadiynes XC=CC=CCPh (2)(OSiMe(3)) [2 (X = H) and 3 (X = Bu(3)Sn)], but in the presence of NaPF6, to afford (Ph(2)PCH(2)PPh(2))(2)(Cl)RuC=CC=CCPh(2)(OSiMe(3)) (4 ). On protonation with HBF4 complex 4 in methanol leads to allenyliden e (Ph(2)PCH(2)PPh(2))(2)(Cl)Ru=C=C=C(OMe)CH=CPh(2)]X (5a)(a: X = BF4) and in dichloromethane to h(2)PCH(2)PPh(2))(2)(Cl)Ru=C=C=CCH=C(Ph)(o-C 6H4)]X (6a) via electrophilic ortho-substitution within the metallacum ulene intermediate LnRu=C=C=C=C=CPh(2)]X (A). Alternatively, complex 1 and diyne 2 with NaPF6 afford in one step allenylidenes 5b (b: X = PF 6) in methanol and 6b in dichloromethane. Bis(diynyl) derivative (2)PC H(2)PPh(2))(2)Ru[(C=CC=CC(OSiMe(3))Ph(2)])(2) (7), obtained by reactio n of 2 with 1 and (HNPr2)-Pr-i, on protonation with HBF4 in methanol o ffered a direct route to the first bis(allenylidene) complex H(2)PPh(2 ))(2)Ru(=C=C=C(OMe)CH=CPh(2))(2)](BF4)(2) (8). The X-ray diffraction s tudies of two allenylidene complexes 6b and 8 are reported. The struct ure of 6b consists of two different allenylidene cations. That of 8 sh ows coplanar allenylidene ligands with a strong contribution of a ynyl resonance structure.