Synthesis of Aryloxo Cyclopentadienyl Group 4 Metal-Containing Dendrimers

Abstract

A quantitative procedure for the hydrosilylation of allylic −SiMe3 protected phenols with Et3SiH and Si−H terminated carbosilane dendrimers of first, second, and fourth generations have been performed to give nG-[(CH2)3{C6H4 - r (OMe) r }OH] m . The subsequent treatment with [Ti(C5Me5)Cl2Me], [Ti(C5Me5)Me3], or [M(C5H5)2ClX] (M = Ti, X = Cl; M = Zr, X = H) afforded the corresponding organometallic metallodendrimers.

Synthesis of Half-Titanocene Complexes Containing π,π-Stacked Aryloxide Ligands, and Their Use as Catalysts for Ethylene (Co)polymerizations

“…In these two complexes, the Ti-O and O-C ipso bond distances are 1.7788(15) Å ( Ti1 ), 1.7794(18) Å ( Ti3 ) and 1.365(2) Å ( Ti1 ), 1.362(3) Å ( Ti3 ), respectively, which are quite similar to previously reported CpTiCl 2 (OAr) analogues that reveal Ti-O bond distances of 1.75-1.82 Å and O-C ipso bond distances of ca. 1.36 Å [ 34 , 42 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 ]. In contrast, they reveal much larger C ipso -O-Ti bond angles (158.09(13) o for Ti1 , 158.26(18) o for Ti3 ) when comparing half-titanocenes ligated with 2,6-unsubstituted aryloxide moieties that possess similar steric hindrance around the metal center, such as C ipso -O-Ti bond angle of 153.77(16) o in CpTiCl 2 (O(4- t BuPh) [ 59 ].…”

Ethylene polymerization behavior of monometallic complexes and metallodendrimers based on cyclopentadienyl-aryloxy titanium units

“…This result evidences the physical nature of the aggregation process and rules out the hydrolysis reaction mentioned above or other type of chemical aggregations. Interestingly, when [Ti(C 5 H 5 )Cl 2 ] was replaced by [Ti(C 5 Me 5 )Cl 2 ] or [Ti(C 5 H 5 ) 2 Cl] as peripheral units [5], and the toluene solutions were aged before activation with MAO, no aggregation and no changes in the catalytic activities, were observed. The activities found for all these systems are comparable to those obtained with the well established compounds [Ti(C 5 Me 5 )Cl 3 ] or [Ti(C 5 H 5 ) 2 Cl 2 ].…”

“…MAO was obtained from commercial sources (1.5 M toluene solution from Witco) and used as received. Dendrimers [4,5], [Si(CH 2 CH 2 CH 2 -SiMe 2 H) 4 ] [15] and [Ti(g 5 -C 5 H 5 )Cl 3 ] [17] were prepared according to reported methods. [Ti(g 5 -C 5 H 5 ) 2 Cl 2 ] and [Zr(g 5 -C 5 H 5 ) 2 Cl 2 ] were obtained from commercial sources and used as received.…”

“…In contrast, for some other homogeneous processes, higher activities respecting to the mononuclear counterparts have been observed [3]. Recently we have published the synthesis of aryloxo cyclopentadienyl titanium-containing carbosilane dendrimers [4,5] of type nG-Si[(CH 2 ) 3 [{C 6 H 4 À y (OMe) y }O]Ti(C 5 R 5 )Cl 2 ] x (see an example in Fig. 1) using as precursor 4-allyl-2-methoxyphenol (commonly called eugenol) or 4-allyl-2,6-dimethoxyphenol, although no catalytic applications were described.…”

Stereoselectivity and nonmigratory insertion mechanism of dimethylacetylene dicarboxylate into metallocene‐hydride of Cp2M(L)H [Cp =η5‐C5H5; M = Nb, V; L = CO, P (OMe)3]: A DFT study

“…Transition metal hydrides play a critical role in stoichiometric and catalytic transformations . They play important roles in various catalytic reactions, such as hydrogen exchange, hydrogen evolution and hydrogenation .…”