dl ‐Selective Pinacol‐Type Coupling Using Zinc, Chlorosilane, and Catalytic Amounts of Cp ₂ VCl ₂ ; dl ‐1,2‐dicyclohexylethanediol

Abstract

Dichlorodicyclopentadienylvanadium Chlorotrimethylsilane Cyclohexanecarboxaldehyde 1,2‐Cyclohexylethanediol

Titanocene(IV) and vanadocene(IV) complexes of dicyanomethanidobenzoate

“…These reactions give two types of the complexes. The reaction with titanocene dichloride (1) forms Cp 2 Ti(dcmb) 2 (3) that have both dcmb ligands bonded through the oxygen atoms. Bonding of the dcmb ligands .…”

“…Its recrystallization from wet MeCN gives dcmbHÁH 2 O that was used for the reactions with bent metallocenes. The X-ray diffraction analysis of dcmbHÁH 2 O has shown that the dcmb is protonated at oxygen atom (see Fig. 1).…”

“…Bent metallocene complexes of the type [Cp 2 MCl 2 ] (Cp = g 5 -C 5 H 5 ; M = early transition metal) are currently under comprehensive investigation due to their promising catalytic [1,2] and biological activity [3,4]. Although metallocene complexes of linear pseudohalide ligands [Cp 2 MX 2 ] (X = NCO, NCS, NCSe, N 3 , CN) are known for long time [5][6][7], their analogues containing non-linear pseudohalides were described recently (X = dca, tcm, dcnm) [8][9][10].…”

“…The only difference was observed when the reactions are carried out in an aqueous solution. In this case, several titanocene complexes give dimers with two bis-cyclopentadienyl titanium(IV) units connected via oxygen bridging [(Cp 2 TiX) 2 O] [9,11,12].…”

“…It is a pseudohalide analogue of benzoate containing dicyanomethanide groups (@C(CN) 2 ) instead of carbonyl oxygen (@O). The reactions with titanocene dichloride (1: Cp 2 TiCl 2 ) and vanadocene dichlorides (2a: Cp 2 VCl 2 , 2b: (g 5 -C 5 H 4 Me) 2 VCl 2 ) show the bonding ability of the dcmb ligand. It can be coordinated through oxygen or nitrogen atom as was proposed based on the contribution structures depicted in Scheme 1.…”