Different C−C Coupling Reactions of Permethyltitanocene and Permethylzirconocene with Disubstituted 1,3-Butadiynes

Abstract

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 [Cp2*MCl2] (Cp* = C5Me5; M = Ti, Zr) with Mg in the presence of disubstituted butadiynes RC triple bond C-C triple bond 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' = tBu, the reaction gives, by a twofold activation of one pentamethylcyclopentadienyl ligand, the complex [Cp*Zr[-C(=C=CHtBu)-CHtBu-CH2-eta5-C5Me3-CH2-]] (3), containing a fulvene ligand that is coupled to the modified substrate (allenic subunit). When using the analogous permethyltitanocene fragment "Cp2*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[eta5-C5Me3-(CH2-CHR-eta2-C2-CHR'-CH2)]], is obtained with R = R' = tBu (4) and R = tBu, R' = SiMe3 (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 [[eta5-C5Me4(CH2)-]Ti[-C(=CHMe)-C(=CHMe)-CH2-eta5-C5Me4]] (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 [Cp2*ZrCl2] with MeC triple bond C-C triple bond CMe. Here the five-membered metallacyclocumulene complex [Cp2*Zr(eta4-1,2,3,4-MeC4Me)] (7) is obtained. The reaction paths found for R = R' = Me are identical to those formerly described for R = R' = Ph.

What Do Titano- and Zirconocenes Do with Diynes and Polyynes?

“…For R ) SiMe 3 , a titanacyclopropene, a η 2 -complex, is formed instead, probably due to steric reasons (Scheme 19). 31 Manifold C-H activations of the methyl groups of the pentamethylcyclopentadienyl ligand and C-C couplings with the particular diynes have been verified for M ) Zr, R ) t Bu; M ) Ti, R ) t Bu; and M ) Ti, R ) Me, Ph (Scheme 20).…”

Crystal structures of tribromo(η5-3,6-di-tert-butyl-9,10,11-trimethylbicyclo( 6.3.0)undeca-4-en-8,10-dienyl)titanium(IV), Ti(C22H35)Br3, and tribromo(η5-4,5-dibromo-3,6-di-tert-butyl-9,10,11-trimethylbicyclo( 6.3.0)undeca-8,10-dienyl)titanium(IV), Ti(C22H35Br2)Br3

“…For group 4decamethyltitanocenes and -zirconocenes manifold C-H bond activations of methyl groups of pentamethylcyclopentadienyl ligands with couplingr eactions with butadiynes RCºC-CºCR have been verified for M =Ti, R =Me, Ph, t-Buand M =Zr, R = t-Bu [2][3][4]. This is afacilemethod for functionalizing metallocenes to obtain chiral and non-chiral complexes [1,5].…”

“…This is afacilemethod for functionalizing metallocenes to obtain chiral and non-chiral complexes [1,5]. One examplefor this is aformal Ti(II) complex with one pentamethylcyclopentadienyl and one anellated trimethylcyclopentadienylcyclooctyne ligand [1][2][3][4][5]. Hydrogenation of this complex yields a Ti(II) complex with one pentamethylcyclopentadienyl and one anellated trimethylcyclopentadienyl-cyclooctene ligand, which is easily oxidized by bromine to aTi(IV) dibromide (1)with one pentamethylcyclopentadienyl and one anellatedt rimethylcyclopentadienylcyclooctene ligand [1].…”

Crystal structure of η5-3,6-di-tert-butyl-4-(tris(pentafluorophenyl)boranyloxycarbonyl)- 5-(η5-tetramethylcyclopentadienyl-methyl-9,10,11-trimethylbicyclo( 6.3.0)undeca-4-en-8,10-dienyl)titanium(III) toluene hemisolvate, Ti(C51H47BF15O2) · 0.5C7H8

“…Decamethylmetallocenes of titanium and zirconium couple under C-H bond activations of methyl groups of its pentamethylcyclopentadienyl ligands with butadiynes RCºC-CºCR,which has been verified for M =Ti, R =Me, Ph, t-Buand M =Zr, R = t-Bu [1][2][3]. Additionally, certain of these complexes insert carbon dioxide to give afurther facile method for functionalizing metallocenes [1].…”

“…Additionally, certain of these complexes insert carbon dioxide to give afurther facile method for functionalizing metallocenes [1]. The best investigated example is aformal Ti(II) complex with one pentamethylcyclopentadienyl and one anellated trimethylcyclopentadienyl-cyclooctyne ligand [1][2][3][4][5]. In the molecularstructure of the zwitterionic title complex, the titanium(III) is coordinated by two differently substituted cyclopentadienyl ligands.F rom the former pentamethylcyclopentadienyl ligand one methyl group is C-H activated and the formed methylene group couples with one of the former alkyne carbon atoms giving an alkenyl group.…”