Butadiene-isocyanide

The nickel(II) complex 14 is also known as a catalyst for the polymerization of 1,3-butadiene. The versatility of this nickel catalyst was used in the synthesis of butadiene-isocyanide block copolymers [27]. In the so-called change of mechanism block copolymerization, 1,3-butadiene was initially polymerized with 14, yielding a butadiene polymer bearing living 773-allyl-nickel termini (Scheme 20). Addition of terf-butyl isocyanide to this living... 

The catalyst composed of [( -allyl)Ni(OCOCF3)]2 and hexafluoroacetone or hexachloroacetone polymerizes various monomers such as 1,3-butadiene, vinyl ethers, norbornene, isocyanide, styrene, and isoprene [91]. [(zr-Allyl) Ni(OCOCF3)]2 is used to synthesize butadiene-isocyanide diblock [92] and triblock copolymers (Scheme 8) [93]. 

Scheme 8 Synthesis of butadiene-isocyanide diblock and triblock copolymers...

One other reaction deserves mention. From bis(cyclooctadiene)nickel and butadiene (31), and in the presence of an isocyanide (RNC, R = cyclohexyl, phenyl, tcrt-butyl) two organic oligomeric products are obtained, 1 -acylimino-11 -vinyl-3,7-cycloundecadiene and 1 -acylimino-3,7,11 -cyclo-dodecatriene. In each, one isocyanide has been incorporated. An analogous reaction with carbon monoxide had been reported earlier. The proposed mechanism of these reactions, via a bis-7r-allyl complex of nickel, is probably related to the mechanism described for allylpalladium complexes above. 

Successive addition of 1,3-butadiene and isocyanide to the solution of the Ni catalyst forms a product with flexible polybutadiene blocks and rigid polyisocyanide blocks. Although the reaction of butadiene and isoprene in the presence of CoCl2/MAO causes homopolymerization of butadiene, the reaction catalyzed by CoCl2/MAO/PPh3 affords a copolymer with 1,2-butadiene and 3,4-isoprene units [94]. The monomer reactivity ratios indicate higher reactivity of butadiene than isoprene. 

Copolymerization of Allenes with 1,3-Butadiene, Propyne, and Isocyanides... 

Novak found the polymerization of allene catalyzed by [( -allyl)Ni (OCOCF3)]2 (Mw/Mn=1.23) and its copolymerization with propyne [138]. Although [(7r-allyl)Ni(OCOCF3)]2 does not initiate the homopolymerization of propyne, the copolymerization of allene with propyne is catalyzed by the complex to give the copolymer which has alignment of the allene-derived unit, -CH2-C(=CH2)-, and the propyne-derived unit, -CH=C(-CH3)-(Eq. 37) [139]. [(7r-Allyl)Ni(OCOCF3)]2 also initiates smooth polymerization of 1,3-butadiene [65] and isocyanides [140]. 

Endo and Tomita reported the copolymerization of allene with isocyanide [135, 141] and with 1,3-butadiene [142] to form AB-type block copolymers. The Pt-catalyzed hydrosilylation reaction of poly(allene-Msocyanide) occurs selectively at the C=CH2 group of the allene monomer unit to produce the polymer with silyl pendant groups (Eq. 38) [135]. The allene macromonomer... 

As, Sb, Bi) donor atoms, and with isocyanides. Reaction with butadiene to give the pale yellow tricarbonyl product (m.p. 19 C) is typical" ... 

In the catalytic formation of cyclododecatriene, the open chain species is cy-clized and displaced by entering butadiene with simultaneous reformation of the open chain species. When carbon monoxide is added to the complex, coupling takes place with incorporation of carbon monoxide to form cyclic ketone, namely 11-vinyl-3,7-cycloundecadien-l-one 128>. Isocyanide is isoelectronic with carbon monoxide, as described before thus isocyanide effects similar in-... 

Xantftpci/fin X. CisH,iN20 , Bis(p-hydroxybenzylidene)-ethylene isocyanide l,4-bis(p-hydroxyphenyl)-2,3 diisonitri-lo-l, 3-butadiene. R. = Rj = H. Structure Hagedorn,... 

Block copolymers can often offer properties that are unattainable with simple blends or random copolymers. This led to many efforts to combine dissimilar materials, like hydrophilic with hydrophobic, or hard with soft segments, as was shown earlier. A recent paper" describes the formation of block copolymers containing helical polyisocyanide and an elastomeric polybutadiene. Compound [(7 -C3H5>-Ni(OC(0)CF3)]2 was used to carry out living polymerization of butadiene and then followed by polymerization of rm-butyl isocyanide to a helical polymer. 

The nickel(O) complex Ni4(CNBu07 catalyzes reduction of acetylenes to olefins, isocyanides and cyanides to amines, as well as cyclotrimerization of acetylene and cyclodimerization of butadiene. Reduction of isocyanides is also catalyzed by other clusters (Chapter 13). Isocyanide copper compounds catalyze addition of CH2CIY (Y = COOR, COR, CN) to olefins leading to the formation of cyclopropane derivatives... 

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