ORTHO- AND TA-(DIETHYNYLCYCLOPENTADIENYL)TRICARBONYLMANGANESE - BUILDING-BLOCKS TOWARD THE CONSTRUCTION OF METAL FRAGMENT SUPPORTED FULLERENYNES

Starting from [(trimethylsilyl)ethynyl]cymantrene (1), the two isomeri c 1,2- and 1,3-[bis-(trimethylsilyl)ethynyl]cymantrenes (3a, 4a) were prepared by a deprotonation/iodination/coupling sequence. The coupling reaction was performed on the mixed rtho-/meta-iodo[(trimethylsilyl)e thynyl]cymantrene (2) by using Stille methodology (tin alkynes and PdC l2(CH3CN)(2) as catalyst in ethyl ether/DMF). Separation of the isomer s (3a, 4a) is achieved by chromatography over flash silica gel. The or tho-diethynylcymantrene 3a is isolated in 42%, while the corresponding meta compound 4a is formed in 26%. If the deprotonation reaction of 1 in pentane/TMEDA is performed under carefully controlled conditions ( -78 degrees C), the formation of only ortho 2 is observed in 67% yield . Coupling with trimethylstannyl(trimethylsilyl)acetylene furnished 3a in 57%. Crystal structures have been carried out for complexes 3a (C2 /c; a = 29.923(1), b = 15.9145(7), c = 9.327(1) Angstrom, alpha = 90, beta = 102.920(7), gamma = 90 degrees; V = 4329.1(6) Angstrom(3); Z = 8; 2948 reflections with F > 3 sigma(F); R = 0.071, R(w) = 0.074) and 4a (P2(1)2(1)2(1); a = 17.027(3), b = 12.339(4), c = 10.235(2) Angstro m; alpha = beta = gamma = 90 degrees; V = 2150(1) Angstrom(3); Z = 4; 1392 reflections with F > 3 sigma(F); R = 0.059, R(w) = 0.058), Remova l of the alkyne-bound trimethylsilyl groups is achieved in yields of > 80% by treatment of 3a and 4a with potassium carbonate in methanol. Th e parent diethynylcymantrenes (3b, 4b) are stable compounds. Treatment of 1,2-diethynylcymantrene 3b under Hay conditions gives coupled mate rial, a polymer poly[(ortho-cymantrene)butadiynylene] (6) in 68% yield (M(n) = 9300). If the Hay reaction is conducted with 3b and an added capping reagent (ethynylcymantrene), a series of oligomeric butadiynyl enecymantrenes is isolated starting from the dimer up to the heptamer (dimer 7a, 8.2%; trimer 7b, 12.5%; tetramer 7c, 7.7%; pentamer 7d, 5.5 %; hexamer 7e, 3.6%; heptamer 7f, 2.5%; Sigma = 40%). The compounds we re separated by chromatography over flash silica gel or preparative HP LC. The oligomers 7 are unstable lemon yellow powders.