A Kumada Coupling Catalyst, [Ni{(Ph₂­P)₂N(CH₂)₃Si(OCH₃)₃‐P,P′}Cl₂], Bearing a Ligand for Direct Immobilization Onto Siliceous Mesoporous Molecular Sieves

Abstract

The ligand-exchange reaction between [Ni(PPh 3 ) 2 Cl 2 ] and (Ph 2 P) 2 N(CH 2 ) 3 Si(OCH 3 ) 3 afforded the novel Ni II complex [Ni{(Ph 2 P) 2 N(CH 2 ) 3 Si(OCH 3 ) 3 -P,PЈ}Cl 2 ] (1) in which the square-planar NiP 2 Cl 2 coordination sphere contains a fourmembered Ni-P-N-P ring. Comparison of the structure of 1 and related Ni II square-planar or Ni 0 tetrahedral complexes containing similar P-N-P ligands shows that the magnitude of the P-Ni-P angle is controlled by the presence of the Ni-P-N-P ring, irrespective of the geometry of the nickel coordi- [a]3038 nation sphere. Direct anchoring of 1 onto SBA-15 molecular sieves through the trimethoxysilyl end-group of the ligand afforded heterogeneous catalyst 1/SBA-15. Both 1 and 1/ SBA-15 catalyze Kumada cross-coupling reactions, exhibiting similar activity and a slightly higher product selectivity than the [Ni{Ph 2 P(CH 2 ) 3 PPh 2 -P,PЈ}Cl 2 ] and [Ni{(Ph 2 P) 2 N-(S)-CHMePh-P,PЈ}X 2 ] (X = Cl, Br) complexes described in the literature. The Grignard reagent employed is likely to induce leaching of the catalyst, which retains its activity in solution.

The novel [Ni{(Ph2P)2N(CH2)3Si(OCH3)3-P,P´}I2] complex: Structural features and catalytic reactivity in the oligomerization of ethylene

“…The chemical reagents (3-aminopropyl)trimethoxy silane (97%) and chlorodiphenylphosphine (97%) were purchased from Alfa Aesar, whereas triethylamine (99%) from Merck. The bis(phosphino)amine ligand (Ph 2 P) 2 N(CH 2 ) 3 Si(OCH 3 ) 3 [20] and complex 2 [17] were prepared according to published procedures.…”

“…Experiments employing higher ethylene pressure (10 bar) were performed in an autoclave reactor, under the experimental conditions described above. Ethylene oligomerization products were detected by GC-FID using a Varian L3800, fitted with a Varian WC07 fused silica capillary column, [17], respectively). It should be noted that this difference is significantly larger for complex 2, which exhibits the corresponding peak at 42.8 ppm [17].…”

“…Ethylene oligomerization products were detected by GC-FID using a Varian L3800, fitted with a Varian WC07 fused silica capillary column, [17], respectively). It should be noted that this difference is significantly larger for complex 2, which exhibits the corresponding peak at 42.8 ppm [17]. These observations would merit additional investigations.…”

“…However, the structure of [Ni{( i Pr 2 P) 2 NH-P,P´}I 2 ] (3) has been very recently reported in the literature. [25] The main bond lengths and angles of the later, along with those of complexes 1 and 2 [17], are listed in Table 2. It should be noted that the structure of one [Pd(P,P)I 2 ] complex (bearing one Me and three Ph as R groups and R′ = i Pr) [26] and two [Pt(P,P)I 2 ] complexes (R = Ph, R′ = C 6 H 4 (CO 2 CH 3 ) [27] or Ph [28]), have been reported and are available in the CSD.…”

“…For that reason, in the work presented herein, the synthesis and characterization of a Ni(II) complex of this type, namely [Ni{(Ph 2 P) 2 N(CH 2 ) 3 Si(OCH 3 ) 3 -P,P´}I 2 ] (1), is described. This compound bears the Si(OCH 3 ) 3 group, via which it can be immobilized onto solid supports, as it has recently been shown for the structurally characterized analogous X = Cl (2) compound, which is an active heterogenized catalyst for the Kumada C−C coupling reaction [17,18]. In an effort to probe the effects of the nature of the Ni(II)-coordinated halides X = Cl, I, the structural and spectroscopic properties of complex 1 was determined by X-ray crystallography and IR/NMR spectroscopies and compared with those of complex 2 [17].…”