Synthesis of carbosilane dendrimers containing peripheral (cyclopentadienyl)(aryloxy)titanium(IV) units

Treatment of [Ti(C5H5)Cl-3] with 4-allyl-2,6-dimethoxyphenol (II) gave the corresponding aryloxy complex [Ti(C5H5){OC6H2(OMe)(2)(C3H5)}Cl-2] (2), while hydrosilylation reactions of the allyl group of 4-allyl-2-methoxyphenol (eugenol; I) or 4-allyl-2,6-dimethoxyphenol (II) with HSiEt3 and subsequent reaction with [Ti(C5H5)Cl-3] led to the mononuclear compounds [Ti(C5H5){OCsH4-n(OMe)(n)(C3H6SiEt3)}Cl-2] (n = 1 (3), 2 (4)) in high yield. This synthetic procedure has been used as a model for the preparation of new peripheral carbosilane metallodendrimers. Series of carbosilane dendrimer generations G1, G2, and G4, with 4, 8, and 32 end groups, respectively, have been functionalized with these phenol groups on the surface. The divergent synthesis was accomplished via hydrosilylation of the olefinic group of the phenols with the corresponding silicon hydride terminated dendrimers, giving 4G-[(CH2)(3)(C6H3(OMe)}OH](32) (9), 1G-[(CH2)(3){C6H2(OMe)(2))OH](4) (10), 2G- [(CH2)(3){C6H2(OMe)(2)}OH](8) (11), and 4G-[(CH2)(3){C6H2(OMe)(2)}OH](32) (12) as oils in high yield. Reaction of 9-12 with [Ti(C5H5)Cl-3] afforded corresponding metallodendrimers containing (cyclopentadienyl)(aryloxy)titanium units at their periphery 4G-[(CH2)(3)[{C6H3(OMe))O]Ti(C5H5)Cl-2](32) (15), 1G-[(CH2)(3) [{C6H2(OMe)(2)}O] Ti(C5H5)Cl-2](4)(16), 2G-[(CH2)(3)[( C6H2(OMe)(2)}O] Ti(C5H5)Cl-2](8) (17), and 4G-[(CH2)(3) [{C6H2(OMe)(2)}O]Ti(C5H5)Cl-2](32) (18) The compounds have been characterized by H-1, C-13, and Si-29 NMR spectroscopy and elemental analysis and, up to the second generation of phenol-terminated dendrimers, by MALDI-TOF mass spectrometry. Gel permeation chromatography was used for all phenolic dendrimers, showing good linear relationships between calculated molecular weight and retention time.