Borane polymers

The preparation of phosphine-borane polymer (Figure 9.15) was reported. It was claimed to be a lire retardant but no lire test results were given98... 

Manners, I. and H. Dorn, 2002. Linear phosphine-borane polymers and methods of preparation therefore. U.S. Patent 6,372,873. 

Borane polymers were prepared by the Rohm and Haas Corp. by using the Friedel-Crafts addition to an olefinic linkage followed by a typical silicone hydrolytic polymerization. 

The borane polymers discussed were never fully developed because of several basic drawbacks. They were resinous and acted like strong reducing agents consequently, they could not be safely formulated with oxidants. A major development took place when the dicarbaclovododeca-borane (carborane) compounds were discovered because these materials were extremely stable and organophilic in character. (The formula —C-----C—is used for carborane to symbolize the delocalized bonding... 

The B—C bond may be reduced in the presence of Hj at high P and T to afford boranes, e.g., alkylboranes and arylboranes are converted to organodiboranes and, in the presence of amines, to amine boranes , and also in processes in which solid borane polymer is formed from liquid organoboranes and Hj at 200°C. Partial hydrogenation of trialkylboranes to dialkylboranes is effected by treatment of the borane with Hj gas at 30.4 MPa and 120-200°C. Amine complexes of haloboranes are reduced by Hj gas to R3NBH3 species and ultimately to diborane . Amine complexes of triorganoboranes are aJso converted to amineborane by reaction with Hj gas. Finally, tetrahalodiboranes(4) are converted to the dihaloboranes by reaction with Hj below 0°C. The HjBX species disproportionate to yield ultimately BjH and BX3. 

Borane—triethylamine complex (4) is used when slow Hberation of borane at elevated temperatures is advantageous, eg, in the cycHc hydroboration of trienes to avoid the formation of polymers (59). 

Chemical reduction is used extensively nowadays for the deposition of nickel or copper as the first stage in the electroplating of plastics. The most widely used plastic as a basis for electroplating is acrylonitrile-butadiene-styrene co-polymer (ABS). Immersion of the plastic in a chromic acid-sulphuric acid mixture causes the butadiene particles to be attacked and oxidised, whilst making the material hydrophilic at the same time. The activation process which follows is necessary to enable the subsequent electroless nickel or copper to be deposited, since this will only take place in the presence of certain catalytic metals (especially silver and palladium), which are adsorbed on to the surface of the plastic. The adsorbed metallic film is produced by a prior immersion in a stannous chloride solution, which reduces the palladium or silver ions to the metallic state. The solutions mostly employed are acid palladium chloride or ammoniacal silver nitrate. The etched plastic can also be immersed first in acidified palladium chloride and then in an alkylamine borane, which likewise form metallic palladium catalytic nuclei. Colloidal copper catalysts are of some interest, as they are cheaper and are also claimed to promote better coverage of electroless copper. 

Potential Non-Cvcllc Precursors of Preceramic Polymers. Boranes such as bis(trimethylsilyl(aminotrimethylsilylaminochloroboranes can be viewed as monomers for preceramic polymer and, ultimately, boron nitride production. Intermolecular dehydrohalogenation of this borane would be thus expected to yield either the dimer or the polymeric system. 

V. Polymers Derived from tris(A]kylamino)boranes 169... 

Grignard chemistry was used as an alternative to hydroboration reaction by the Chujo team in its search for new n-type conjugated polymers for utilization in polymer energy storage systems. By this route, the syntheses of 7r-conjugated poly(p-phenylene-boranes) (15)35 (Fig. 12) and poly(ethynylene-phenylene-ethynylene-borane)s were reported.36... 

Figure 14 rr-Conjugated dendritic polymers (18 and 19) obtained from tri-9-anthrylborane. The branched conducting polymer 20 was obtained from tris(JV-pyrrolyl)borane. (Adapted from refs. 38 and 39.)... 

A radical initiator based on the oxidation adduct of an alkyl-9-BBN (47) has been utilized to produce poly(methylmethacrylate) (48) (Fig. 31) from methylmethacrylate monomer by a living anionic polymerization route that does not require the mediation of a metal catalyst. The relatively broad molecular weight distribution (PDI = (MJM ) 2.5) compared with those in living anionic polymerization cases was attributed to the slow initiation of the polymerization.69 A similar radical polymerization route aided by 47 was utilized in the synthesis of functionalized syndiotactic polystyrene (PS) polymers by the copolymerization of styrene.70 The borane groups in the functionalized syndiotactic polystyrenes were transformed into free-radical initiators for the in situ free-radical graft polymerization to prepare s-PS-g-PMMA graft copolymers. 

The development of polypyrroles bearing supported diphosphine ligands protected from oxidation by borane groups has been reported.86 The polymer was produced by the electropolymerization of l-(7V-but-4-yl-pyrrol)-l,2-bis(diphenylphosphinoborane) (62) (Fig. 40). These preformed polymeric films lend themselves to the incorporation... 

Devaky and Rajasree have reported the production of a polymer-bound ethylenediamine-borane reagent (63) (Fig. 41) for use as a reducing agent for the reduction of aldehydes.87 The polymeric reagent was derived from a Merrifield resin and a 1,6-hexanediol diacrylate-cross-linked polystyrene resin (HDODA-PS). The borane reagent was incorporated in the polymer support by complexation with sodium borohydride. When this reducing agent was used in the competitive reduction of a 1 1 molar mixture of benzaldehyde and acetophenone, benzaldehyde was found to be selectively reduced to benzyl alcohol. 

Figure 41 The polymer-bound ethylenediamine-borane reagent (63) for use as a reducing agent for the reduction of aldehydes. (Adapted from ref. 87.)...

L Monomeric and Polymeric Organic Analogs of Boron Cluster Systems The polyhedral clusters of boranes and carboranes are groups of cluster systems that are present ubiquitously in organoboron polymers. As in the case with the... 

We have reported that the reaction of 2,4,6-tri(chloro)borazine CI3B3N3H3 with three equivalents of tris(isopropylamino)borane B(NHPr )3 led to the formation of 2,4,6-tri[bis(isopropylamino)boryl(isopropyl)amino]borazine 11 [Fig. 5(a)] in quantitative yield.26,27 The subsequent polycondensation carried out in vacuo up to 150°C, led to the formation of the polymer 12 containing B3N3 rings linked either through direct B—N interring bonds (minor pathway) or three-atoms —N—B—N— bridges... 

Hydroboration polymerization between diene monomers and 2,4,6-trimethylphenylborane (mesitylborane)6 or 2,4,6-triisopropylphenylborane (tripyl-borane)7 gave organoboron main-chain polymers (scheme 3). The polymerization was... 

Hydroboration reaction of the terminal double bond of polystyrene with thexyl-borane yielded a polymer bearing one organoboron unit at the center of the polymer... 

Poly(ethynylene-p-phenylene-ethynylene-borane)s were also prepared by polycondensations of bifunctional lithium acetylides and aryldimethoxyborane, as shown in scheme 35.61 The polymerization between dilithium 2,5-didodecyloxybenzene-1,4-diethynilide and tripyldimethoxyborane gave the corresponding polymer in 67%... 

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