Stannous 2-ethylhexanoate

Two different mechanisms have been proposed for the ROP of (di)lactones depending on the nature of the organometalhc derivatives. Metal halides, oxides, and carboxylates would act as Lewis acid catalysts in an ROP actually initiated with a hydroxyl-containing compound, such as water, alcohol, or co-hydroxy acid the later would result more hkely from the in-situ hydrolysis of the (di)lac-tone [11]. Polymerization is assumed to proceed through an insertion mechanism, the details of which depends on the metal compound (Scheme la). The most frequently encountered Lewis acid catalyst is undoubtedly the stannous 2-ethylhexanoate, currently referred to as stannous octoate (Sn(Oct)2). On the other hand, when metal alkoxides containing free p-, d-, or f- orbitals of a favo-... 

The methanolysis catalyst is generally a base such as potassium carbonate, since the base catalyzed transesterification is generally lower in energy(5). For the transesterification of the hydroxymethylated fatty esters, however, a Lewis acid (stannous 2-ethylhexanoate) is employed. Although this catalyst requires higher temperatures to achieve rapid equilibrium, it has the benefit of not requiring removal... 

A similar method has been reported by Albertsson et al. [290], in which equimolar amounts of propane-1,3-diol and DEC were used, with stannous 2-ethylhexanoate as the transesterification catalyst, affording a yield of 53%. 

Synthetic routes include anionic, cationic, zwitterionic, and coordination polymerization. A wide range of organometallic compounds has been proven as effective initiators/catalysts for ROP of lactones Lewis acids (e.g., A1C13, BF3, and ZnCl2) [150], alkali metal compounds [160], organozinc compounds [161], tin compounds of which stannous octoate [also referred to as stannous-2-ethylhexanoate or tin(II) octoate] is the most well known [162-164], organo-acid rare earth compounds such as lanthanide complexes [165-168], and aluminum alkoxides [169]. Stannous-2-ethylhexanoate is one of the most extensively used initiators for the coordination polymerization of biomaterials, thanks to the ease of polymerization and because it has been approved by the FDA [170]. 

Of the large volume of tin compounds reported in the literature, possibly only ca 100 are commercially important. The most commercially significant inorganic compounds include stannic chloride, stannic oxide, potassium stannate, sodium stannate, stannous chloride, stannous fluoride, stannous fluoroborate, stannous oxide, stannous pyrophosphate, stannous sulfate, stannous 2-ethylhexanoate, and stannous oxalate. Also important are organotins of the dimethyl tin, dibutyltin, tributyltin, dioctyltin, triphenyltin, and tricyclohexyltin families. 

Stannous 2-Ethylhexanoate. Stannous 2-ethylhexanoate, Sn(C8H1502)2 (sometimes referred to as stannous octanoate, mol wt 405.1, sp gr 1.26), is a clear, very light yellow, and somewhat viscous liquid that is soluble in most oiganic solvents and in silicone oils (166). It is prepared by the reaction of stannous chloride or oxide with 2-ethylhexanoic acid. 

Stannous Octanoate (Stannous 2-Ethylhexanoate), Technical Data Sheet 176, M T Chemicals, Inc., Rahway, N.J., Dec. 1981. 

The advantage of the swelling method is that it is not limited by the crosslinking reactions of each phase so any interference from these will be limited. A good representative example is the synthesis developed by Hamurcu and Baysal [75]. They synthesized a bimodal PDMS (15 000 gmoD1)/ PDMS (75 000 g mol ) IPN with the same condensation curing system. First, the 75 000 g mol 1 PDMS network was formed from the corresponding a, tw-dihydroxypolydimethylsiloxane and tetraethylorthosilicate catalyzed by stannous 2-ethylhexanoate. It was then swollen in a 15 000 g mol 1 a,a>-dihydroxy-poly(dimethylsiloxane) monomer. The second monomer was then crosslinked via the same condensation cure. The sequential full IPN structure... 

Two sets of networks were prepared. In the first network, the M of the short chains was 660 g/mol (660-21.3 X 10 ), and in the second network, it was 880 g/ mol (880-21.3 X 10 ). The compositions of the networks are given in Table I. The chains were end linked with tetraethoxysilane, with stannous 2-ethylhexanoate as catalyst. The reactions were carried out for 2 days under a protective atmosphere of nitrogen at room temperature. Additional details are given elsewhere (7, 8, 14). All sample sheets thus prepared were gently extracted to remove the approximately 3 wt % soluble material they contained. 

The elastomers investigated were prepared by curing a silicone resin (supplied by Rhodia Silicones) containing a blend of ingredients polysiloxane-diols, small amounts of hydrogen-methyl polysiloxane, tetraalkoxy silane and fumed silica filler. An organotin ingredient, stannous 2-ethylhexanoate, supplied as a 77% w/w solution in 2-ethyl hexanoic acid, was used as a cure initiator. Typically, 5 wt. of initiator is mixed into the polysiloxane resin. After the initial cure, the material is post-cured at 70°C for 16 h in an air oven. 

EINECS 206-108-6 2-Ethylhexanoic acid tin(2-<-) salt Metacure T-9 NSC 75857 Nuocure 28 Stannous 2-ethylhexanoate Stannous 2-ethylhexoate Stannous octoate Tin 2-ethylhexanoate Tin bis(2-ethylhexanoate) Tin diocloate Tin ethylhexanoate Tin octoate Tin(2-r) 2-ethylhexanoate Tin(ll) 2-ethylhexanoate Tin(ll) 2-ethylhexylate Tin(ll) bis(2-ethylhexanoate). Catalyst used in production of PU coatings, adhesives, and sealants uniform activity and excellent stability. Arr Products Chemicals Inc. 

Lactide is produced by degradation reactions, mainly via intramolecular chain scission of the prepolymer. Lactide synthesis from a prepolymer with a DP in the range of 10-15 in the presence of various catalysts at 4-5 mbar and 190-245°C is reported by Noda and Okuyama [9]. The best performances were reported using 0.05-0.2 wt% tin catalysts and tin octoate (stannous 2-ethylhexanoate) in particular, which is widely available. The catalyst increases the rate of backbiting reactions from hydroxyl chain ends of prepolymers to form lactide molecules [9, 15]. The melt viscosity of the prepolymer increases because of the esterification reactions during the process, which results in decreased rate of mass transfer. 

ROP offers an alternate approach to the synthesis of polyanhydrides used for medical applications. Albertsson and coworkers prepared adipic acid polyanhydride from cyclic adipic anhydride (oxepane-2,7-dione) using cationic (e.g., AICI3 and BFjTCjHj) ), anionic (e.g., CHjCOO K and NaH), and coordination-type inhibitors snch as stannous-2-ethylhexanoate and dibutyltin oxide [24,25]. ROP takes place in two steps (1) preparation of the cyclic monomer and (2) polymerization of the cyclic monomers [26]. 

Stannous 2-ethylhexanoate Stannous-2-ethylhexoate. See Stannous octoate... 

Synonyms Sn-(ll)-ethylhexanoate Stannous 2-ethylhexanoate Stannous-2-ethylhexoate Tin octoate Tin-(ll)-octoate Empiricail CjsFIsoQiSn Formula Sn(C8H,sQ2)2... 

Stannous 2-ethylhexanoate sta-nos e-thol-. hek-s9- no-at (stannous octanoate) n. A polymerization catalyst for urethane foam. 

Ryner, M., et al., 2001. Mechanism of ring-opening polymerization of l,5-dioxepan-2-one and L-lactide with stannous 2-ethylhexanoate. A theoretical study. Macromolecules 34 (12), 3877-3881. 

Several polymerization methods, including melt, solution and emulsion have been applied to lactone monomers to form high molecular weight polymers. Typically, a catalyst such as a metal oxide or metal salt, stannous 2-ethylhexanoate or stannous chloride, is used along with a free hydroxy containing initiator such as water, an alcohol, hydroxy acid or ester to activate the lactone ring to initiate polymerization. 

Catalyst Systems A vast number of catalysts have been utilized in the ROP of lactide, of which the most studied are the carboxylates and alkoxides of Sn [111-120] and A1 [121-127]. Of these, stannous 2-ethylhexanoate (tin octanoate) is the most intensively studied. The polymerization mechanism is suggested to involve a preinitiation step, in which stannous 2-ethylhexanoate is converted to a stannous alkoxide by reaction with a hydroxyl-bearing compound. Then, the polymerization proceeds on the tin-oxygen bond of the alkoxide ligand, whereas the carboxylate itself is... 

---