POLYCARBON LIGANDS - SYNTHESIS AND CHARACTERIZATION OF THE PHOSPHINODIYNES PH(2)PC-C-C-CR (R=BU(T), PH, SIME(3)), THE MU-ETA(1),ETA(2)(ALPHA,BETA)-BUTADIYNYL COMPLEXES MU-PPH(2))(MU-ETA(1),ETA(2)(ALPHA,BETA)-C-C-C-CR), AND THE MOLECULAR-STRUCTURE OF A COBALT CARBONYL DERIVATIVE U-2(CO)(6)(MU-PPH(2))(MU-ETA(1),ETA(2)(ALPHA,BETA) TA(2),ETA(2)(GAMMA,DELTA)-C-C-C-CBU(T))CO-2(CO)(6)

The phosphino-diynes (PPh(2)C=C-C=CR) (R=Bu(t), Ph, SiMe(3)) are obtai ned in excellent yield from the corresponding diyne anions RC=C-C=C- b y quenching with PPh(2)Cl. Monosubstitution on Ru-3(CO)(12) yields the trinuclear clusters Ru-3(CO)(11)(PPh(2)C=C-C=CR), which upon thermoly sis afford the butadiynyl complexes Ru-2(CO)(6)(mu-eta(1), eta(alpha b eta)(2)-C=C-C=CR)(mu-PPh(2)) (R=Bu(t), 7a; R=Ph, 7b; R=SiMe(3), 7c) as the major products. The full characterization of the series of 2 comp ounds (7a-c) (mu-eta(1),eta(alpha,beta)(2)-C=C-C=CR)(mu-PPh(2)) is rep orted including an X-ray diffraction study of 7a. Crystals of 7a are m onoclinic, a=9.849(2), b=9.886(2), c=28.368(9) Angstrom, beta=95.18(2) degrees, space group P2(1)/n, and Z=4; refinement converged to R=0.024 3 (R(W)=0.0253). The structure shows that the tetracarbon chain is bon ded to the first metal atom by a simple M-C sigma bond and to the seco nd via a dative pi interaction leaving an outer alkyne unit uncoordina ted. In the reaction between 7a and cobalt carbonyl, a Co-2(CO)(6) moi ety becomes attached to the -CgammaCdelta- bond in a tetrahedral arran gement to give the tetranuclear mixed-metal species -eta(2),eta(gamma, delta)(2)-C=C-C=Bu(t))CO2(CO)(6) 8, as confirmed by X-ray crystallogra phy: triclinic, a=9.9969(9), b=11.3018(9), c=17.268(1) Angstrom, alpha =90.653(6)degrees, beta=100.911(6)degrees, gamma=110.465(5)degrees,spa ce group <P(1)over bar> and Z=2; refinement converged to R=0.0222(R(W) =0.0264).