SYNTHESIS AND REACTIVITY OF TITANOCENE COMPOUNDS (ETA(5)-C5H4SIME3)(2)TI(C C-C-C CR)(2) AND (ETA(5)-C5H4SIME3)(2)TI(C C-SIME2-C CSIME3)(2) CRYSTAL-STRUCTURE OF [(ETA(5)-C5H4SIME3)(2)TI (C C-C CC2H5)(2)]PD(PPH3)

The reaction of [Ti]Cl-2 (1) {[Ti] = (eta(5)-C5H4SiMe3)(2)Ti} with two equivalents of LiC=C-C=CR (2a: R = C2H5, 2b: R = SiMe3) produces the bis[(sigma)-1,3-butadiyne-1-yl] titanocenes [Ti](C=C-C=CR)(2) (3a: R = C2H5, 3b: R = SiMe3) in high yield; with LiC=CSiMe2-C=C-SiMe3 (4) the bis[(sigma)-1,4-pentadiyne-1-yl) titanocene [Ti](C=C-SiMe2-C=CSiMe3)( 2) (5) is formed. Compounds 3 and 5 afford with equimolar amounts of N i(CO)(4) (6) the heterobimetallic nickel-titanium complexes {[Ti](C=C- C=CR)(2)})Ni(CO) (7a: R = C2H5, 7b: R = SiMe3) and {[Ti](C=C-SiMe2-C=C SiMe3)(2)}Ni(CO) (8) in quantitative yields. On treatment of molecule 8 with two mole equivalents of Co-2(CO)(8) (9) compound =C-SiMe2-[(eta (2)-C=CSiMe3)Co-2(CO)(6)])(2)}Ni(CO) (10) is formed in which the inner C=C triple bonds of the 1,4-pentadiyne-1-yl groupings are pi-bonded t o a low-valent Ni(CO) building block, whereas the outer C=C triple bon ds are each eta(2)-coordinated to a Co-2(CO)(6) transition metal fragm ent. Moreover, the reaction of molecule 5 with Co-2(CO)(8) (9) yields, depending on the amount of Co-2(CO)(8) used, different products: {[Ti ]{(C=C-SiMe2-C=CSiMe3)(2)}Co(CO)\degrees (11), =CSiMe3){C=C-Me2Si-[(et a(2)-C=CSiMe3)Co-2(CO)(6)]} (12), [Ti]{C=C-SiMe2-[(eta(2)-C=CSiMe3)Co- 2(CO)(6)]}(2) (13) as well as 2(CO)(6)]-SiMe2-[(eta(2)-C=CSiMe3)Co-2(C O)(6)]}(2) (14). On treatment of titanocenes 3a or 5 with Pd(PPh3)(4) (17) or Pt(PPh3)(2)(H2C=CH2) (18) the heterobimetallic complexes {[Ti] (C=C-C=CC2H5)(2)}M(PPh3) (19a: M = Pd, 19b: M = Pt) and {[Ti](C=C-SiMe 2-C=CSiMe3)(2)}Pd(PPh3) (20) are produced. In compounds 7, 8, 10, 19 a nd 20 a low-valent Ni(CO) or M(PPh3) (M = Pd, Pt) moiety is complexed by the inner C=C triple bonds of the C=C-C=CR or C=C-SiMe2-C=CSiMe3 li gands. The result of the X-ray structure analysis of {[Ti](C=C-C=CC2H5 )(2)}Pd(PPh3) (19a) is reported. Compound 19a crystallizes in the tric linic space group <P(1)over bar> with the cell parameters a=12.356(7), b=13.111(4), c=14.52(2) Angstrom, alpha=91.42(8), beta=112.21(8), gam ma=95.72(4)degrees, V=2161.9(3) Angstrom(3) and Z=2.