Trisilane-1,3-diolato Complexes of Ti and Zr:  Syntheses and X-ray Crystal Structures

Abstract

The syntheses and structures of zirconium and titanium complexes containing the novel chelating trisilane-1,3-diolate ligand [Me2Si(R2SiO)2]2- (R = SiMe3) (5)-H2 are reported. The chloride complexes [Me2Si(R2SiO)2]TiCl2 (7a) and [Me2Si(R2SiO)2]ZrCl2 x 2 THF (7b) were prepared by the reaction of MCl4 (M = Ti, Zr) with [Me2Si(R2SiO)2]2Ti (6a) and [Me2Si(R2SiO)2]2Zr (6b), which are derived from the reaction of 5 with M(NEt2)4, respectively. In the presence of TiCl4, complexes 6a and 7a undergo a ring-opening reaction to produce the dinuclear complex [Me2Si(R2SiO)2][TiCl3]2 (9). [Me2Si(R2SiO)2]TiMe2 (10) and [Me2Si(R2SiO)2]TiBnz2 (11) were prepared in moderate yields from reactions of 7a with 2 equiv of MeMgBr and BnzMgCl, respectively. According to NMR spectroscopic investigations, the reaction of the dimethyltitanium complex 10 with B(C6F5)3 led to full exchange of both methyl groups by C6F5 groups under quantitative formation of [Me2Si(R2SiO)2]Ti(C6F5)2 (12) and a mixture of B(C6F5)(3-n)Me(n), where n = 1-3. The structure of 12 is further evidenced by the preparation of an identical sample from the reaction of 7a with 2 equiv of C6F5MgBr. Refluxing an ether solution of 12 surprisingly gave [Me2Si(R2SiO)2]2TiC6F5]2O (13) as a result of ether cleavage. The structures of the complexes 7a, 7b, 9, 10, and 13 were determined by X-ray crystallography, and structural discussion of the bond parameters will be given.

5,5-Dimethyl-2,2-bis(pentafluorophenyl)-4,4,6,6-tetrakis(trimethylsilyl)-1,3-dioxa-4,5,6-trisila-2-titanacyclohexane

“…The titanium is coordinated in a chelate fashion [O1-Ti1-O2 106.33 (7) ] by the siloxide ligand, giving a nearly planar six-membered ring. The Ti-O distances [1.7503 (15), 1.7408 (15) Å ] in the ring are similar to those found in closely related cyclic siloxide complexes (Krempner et al, 2006).…”

“…B(C 6 F 5 ) 3 (Chernega et al, 1997) and (1) (Krempner et al, 2006) were prepared as previously described. Benzene-d 6 was dried over activated molecular sieves and stored in the glove box and n-pentane was distilled under argon from alkali metals prior to use.…”

“…Benzene-d 6 was dried over activated molecular sieves and stored in the glove box and n-pentane was distilled under argon from alkali metals prior to use. B(C 6 F 5 ) 3 (Chernega et al, 1997) and (1) (Krempner et al, 2006) were prepared as previously described. NMR: Bruker AC 250.…”

Synthesis and Structure of Cyclic Trinuclear Zinc Disiloxides

“…A rather straightforward strategy for the design of vicinal silanediols with an oligosilane backbone involves the use of phenyl-substituted metal silanides in salt metathesis reactions. In analogy to the synthesis of the trisilane-1,3-diol 2a previously reported, [5] treatment of Ph(Me 3 Si) 2 Si-K with BrCH 2 CH 2 Br provides easy access to the diphenyl oligosilane 1b in high yields. [6] This compound was treated with two equivalents of trifluoromethanesulfonic acid (TfOH) and subsequently hydrolyzed to give almost quantitatively the silanediol 2b as a colorless solid (Scheme 1).…”

“…[4] We have a long-term interest in the synthesis and structural characterization of cyclic five-and six-membered metal disiloxides, as these highly strained cycles might be useful for the selective ring insertion of metal species, which may form novel hetero-and homobimetallic complexes as we have shown recently for a dinuclear titanium disiloxide derived from a mononuclear cyclic species. [5] In this contribution we describe the preparation of a new disilane-1,2diol and we report on the synthesis of polycyclic trinuclear zinc disiloxides from reactions of ZnMe 2 with various sterically congested vicinal silanediols together with their solidstate structures.…”