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

Abstract

-3,6-di-tert-butyl-9,10,11-trimethylbicyclo(6.3.0)undeca-4-en-8,10-dienyl)titanium(IV), Ti(C 22 H 35 )Br 3 , and tribromo(h 5 -4,5-dibromo-3,6-di-tert-butyl-9,10,11-trimethylbicyclo(6.3.0)undeca-8,10-dienyl)titanium(IV), Ti Source of materialDibromo-pentamethylcyclopentadienyl-trimethylcyclopentadienyl-cyclooctene-Ti(IV) [1] (1;1 25 mg, 0.195 mmol) was dissolved in 20 ml of n-hexane under argon and treated with an excess(0.3 ml) of bromine. Standing at room temperature for 20 h and concentration of the orange-red solution in vacuum to 2ml gave amixture of red crystals of complexes Cp*TiBr 3,t he title compounds (2 and 3)inamolar ratio of 35:35:30 as identified by NMR. Fractional recrystallization from n-hexane gave small amounts of individual complex 2 (20 mg) and complex 3 (30 mg) whichwere separated from the mother liquor, washed with cold n-hexane and dried in vacuum. DiscussionFor 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]. 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]. In the crystal structures of the title compounds, the h 5 -coordinated Cp ligand and three bromine ligands form a" piano-stool"-like coordination. As in the case of the startingcomplex 1 and their chloridecongener the cyclooctene unit is oriented away from the metal. There is no hint for any interaction of the double bond with the metal in 2.This was expectedfor the electronically saturated Ti(IV). The bromine substituents in 3 are in an anti conformation to each other.