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Different C−C Coupling Reactions of Permethyltitanocene and Permethylzirconocene with Disubstituted 1,3‐Butadiynes
Author(s) -
Pellny PaulMichael,
Kirchbauer Frank G.,
Burlakov Vladimir V.,
Baumann Wolfgang,
Spannenberg Anke,
Rosenthal Uwe
Publication year - 2000
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/(sici)1521-3765(20000103)6:1<81::aid-chem81>3.0.co;2-9
Subject(s) - fulvene , cyclopentadienyl complex , ligand (biochemistry) , chemistry , ring (chemistry) , stereochemistry , coupling reaction , triple bond , substrate (aquarium) , steric effects , medicinal chemistry , double bond , catalysis , polymer chemistry , organic chemistry , biochemistry , oceanography , receptor , geology
Herein we describe different C−C coupling reactions of permethyltitanocene and ‐zirconocene with disubstituted 1,3‐butadiynes. The outcomes of these reactions vary depending on the metals and the diyne substituents. The reduction of [Cp 2 *MCl 2 ] (Cp*= C 5 Me 5 ; M=Ti, Zr) with Mg in the presence of disubstituted butadiynes RC≡C−C≡CR′ is suitable for the synthesis of different C−C coupling products of the diyne and the permethylmetallocenes, and provides a new method for the generation of functionalized pentamethyl‐cyclopentadienyl derivatives. For M=Zr and R=R′= t Bu, the reaction gives, by a twofold activation of one pentamethylcyclopentadienyl ligand, the complex [Cp*Zr{−C(=C=CH t Bu)−CH t Bu−CH 2 − η 5 ‐C 5 Me 3 −CH 2 −}] ( 3 ), containing a fulvene ligand that is coupled to the modified substrate (allenic subunit). When using the analogous permethyltitanocene fragment “Cp 2 *Ti”, the reaction depends strongly on the substituents R and R′. The coupling product of the butadiyne with two methyl groups of one of the pentamethylcyclopentadienyl ring systems, [Cp*Ti{ η 5 ‐C 5 Me 3 (CH 2 −CHR− η 2 ‐C 2 ‐CHR′−CH 2 )}], is obtained with R=R′= t Bu ( 4 ) and R= t Bu, R′=SiMe 3 ( 5 ). In these complexes one pentamethylcyclopentadienyl ligand is annellated to an eight‐membered ring with a C−C triple bond, which is coordinated to the titanium center. A different activation of both pentamethylcyclopentadienyl ligands is observed for R=R′=Me, resulting in the complex [{ η 5 ‐C 5 Me 4 (CH 2 )−}Ti{−C(=CHMe)−C(=CHMe)−CH 2 − η 5 ‐C 5 Me 4 }] ( 6 ), which displays a fulvene as well as a butadienyl‐substituted pentamethylcyclopentadienyl ligand. The influence exerted by the size of the metal is illustrated in the reaction of [Cp 2 *ZrCl 2 ] with MeC≡C−C≡CMe. Here the five‐membered metallacyclocumulene complex [Cp 2 *Zr( η 4 ‐1,2,3,4‐MeC 4 Me)] ( 7 ) is obtained. The reaction paths found for R=R′=Me are identical to those formerly described for R=R′=Ph.