3.3.2. Crystal structure of [C2b]

The Mercury diagram of complex [C2b] with atom-lebeling scheme is shown in Fig. 2.
Although using a stoichiometric reaction of allyl Ni bromide with ligand L2 and TlPF6, if a mixture of CH2Cl2/ diethyl ether is used instead of CH2Cl2/n-hexane to crystallize the reaction product, a different compound is obtained. Its X-ray structure was measured and the molecular structure was determined. Suitable prismatic and orange single crystals of C2b were obtained by crystallization from CH2Cl2/diethyl ether. The complex C2b crystallizes in the orthorombic unit cell P2121 group (Table 1). Selected bond lengths and angles are listed in Table 2.

Table 2: Selected bond distances (Å) and angles (º) for complex C2 [Ni(η3-allyl)(L2)2]+PF6- …show more content…
Oligomerization of Styrene (ST)

The oligomerization reactions were carried out in Schlenk tubes immersed in a thermostatted oil bath controlled to 65°C / 110°C and with a stirring rate of 300 rpm. In a typical experiment, 5 mg of cationic complex was introduced to 2g of thermostatted styrene (2 g) without solvent. After 2 h, the reaction was terminated by flushing the solution with air to decompose the catalyst.
The decomposed catalyst and unreacted styrene and was removed from the reaction mixture by filtration on a fritted glass and washed it by 100 mL of methanol.
The oligomers were characterized by gel permeation chromatography, GPC/SEC analysis were performed by eluting THF solutions of the polymeric samples at 30 ºC (Waters oven) in two PolyPore columns (protected by a PolyPore guard column) (Polymer Labs) mounted on a Waters 1515 isocratic HPLC pump. Detection was performed by a Waters 2414 differential refractive index detector. The THF eluent was filtered through 0.45 µm PTFE Pall membrane filters and degassed in an ultrasound bath. Solution samples were filtered through 0.20 µm PTFE GVS filters. The system was calibrated with TSK Tosoh Co. polystyrene standards.

Table 3: Oligomerization styrene catalyzed by complexes C1 and …show more content…
The yields of recovered oligomer mixtures are acceptable, as shown in Table 3. In this Table we can appreciate that the oligomer mixtures have a very high content of styrene trimers. trimer contents are much similar when C2b catalysts are used at 65°C and 110°C. In the case of C2b catalyst, we obtained higher oligomers at lower temperature. The behaviour of the C1 and C2b is clearly different. C1 is not active as a catalyst of methylacrylate while was effective to get higher polystyrene. In contrast with the other entries in Table 3, the resulting oligomers at 65°C contain little styrene trimer, pentamer, hexamer and the main fraction corresponds to oligomers having Mn values of 349–1814. These values are almost similar to those obtained when the catalytic oligomerization of styrene is carried out at