Bimetallic halides. Crystal structure of and ethylene polymerization by vanadium(II) chloride-zinc chloride-tetrahydrofuran (VCl2.ZnCl2.4THF)

Abstract

h e use of t h e diffractometer. The experimental assistance of J. M. Ball, C. L. Merritt, a n d Dr. S. N a n d a n a a n d Dr. R. Yamdagni's advice a n d help in obtaining spectroscopic data are gratefully acknowledged. We also t h a n k Dr. Scott Collins for helpful discussions.Registry No. meso-1, 97371-16-9; dl-1 (isomer I), 97371-17-0; 2, 81609-97-4; 3, 97295-68-6; [WC13(SMe)], 97295-72-2; [WCI,(SEt)], 97295-74-4; [ WCI,(SPh)], 97295-76-6; Me3Si(SMe), 3908-55-2; Me,Si(SEt), 5573-62-6; Me3Si(SPh), 4551-1 5-9; WCI,, 13283-01-7; WC14(Me2S)2, 53922-82-0; Et,SiH, 617-86-7

Generation of Versatile Reagents Derived from R2Zn and a Vanadium(III) or a Vanadium(IV) Complex and Their Application to Organic Synthesis

“…Thus, a nucleophilic attack of an alkylvanadium species to carbonyl compounds does not readily occur unless stabilizing additive such as HMPA is present . In our alkylation of carbonyl compounds mediated by a dialkylzinc−vanadium system, the reaction of vanadium(III) or -(IV) with R 2 Zn should afford an alkylated Zn−V hetero polymetallic complex similar to those reported by Thiele,3a which may contain both alkylzinc species and vanadium species. The real alkylating reagent may be the alkylzinc part, and the higher-valent vanadium part may function as an activator of the carbonyl compounds by coordination as a Lewis acid.…”

“…Although it is known that dialkylzinc reagents, R 2 Zn, are generally inert to carbonyl compounds, addition of a catalytic amount of an amino alcohol or certain transition metal complexes can enhance their nucleophilicity and make them reactive toward carbonyl compounds. It is reported that R 2 Zn can reduce vanadium(IV) complexes and produce low-valent vanadium(II) species, but application of the latter to organic synthesis has not appeared so far. During the course of our study to examine the reactivity of the combination of R 2 Zn and several vanadium complexes, we have found that reagents derived from R 2 Zn and VCl 4 or VCl 3 (thf) 3 showed different reactivity toward carbonyl compounds depending on the reaction conditions for preparation of the reagents.…”

Bis(pyrazolyl)pyridine vanadium(III) complexes as highly active ethylene polymerization catalysts

“…Studies of the oxidation state of vanadium catalysts for ethylene polymerization have generally revealed that V(III) and V(IV) precursors are often reduced to inactive V(II) species [9][10][11][12]. Alkyl vanadium(III) complexes bearing amidinate [13,14] and amide [15,16] ligands produce shortlived ethylene polymerization catalysts and are inactive in propene polymerization.…”

Synthesis and molecular structure of vanadium(III) dithiolate complexes: a new class of alkene polymerization catalysts

“…Studies of the oxidation state of active vanadium catalysts for ethylene polymerization by different investigators has led to the proposal that V iii and V ii represent the important oxidation states in the ethylene polymerization process. 8,9 Herein we report the synthesis, structural characterization and catalytic activity of the vanadium(iii) heterodinuclear complexes [V(m-DIPP) 2 {O(CH 2 CH 2 S) 2 }Li(L) 2 ] 1, 2 and the mononuclear complex 4) Å, within the range expected for V-S single bonds and comparable to other vanadium(iii) thiolato complexes. [12][13][14][15] The X-ray analysis of 3 reveals a mononuclear complex [V(DIPP){O(CH 2 CH 2 S) 2 }(py)] with slightly distorted trigonalbipyramidal coordination around the vanadium centre (Fig.…”