Carbosilane Molecules with Mono- and Bis(amino)arylmetal End Groups: Structures of {NiI[C6H2(CH2NMe2)2-2,6-SiMe3-4]} and Tetranuclear {[CH2Si(Me)2C6H3(CH2NMe2)-4-(PdCl)-3]2}2

Abstract

A set of model compounds have been designed in order to develop useful synthetic routes to novel dendritic carbosilane molecules functionalized with organometallic complexes derived from the monoanionic [C6H3(CH2NMe2)2-2,6]- (=NCN) and [C6H4(CH2NMe2)-2]- (=CN) ligands. Selective electrophilic palladation of both [C6H2(CH2NMe2)2-2,6-(SiMe3)2-1,4] (1) and [C6H4(CH2NMe2)-4-SiMe3-1] (6) using Pd(OAc)2 afforded, after addition of LiCl, [PdCl(C6H2{CH2NMe2}2-2,6-SiMe3-4)] (2) and dimeric [PdCl(C6H3{CH2NMe2}-2-SiMe3-5)]2 (7), respectively, in 98% and 84% yield. Lithiation of [C6H3(CH2NMe2)2-3,5-SiMe3-1] followed by transmetalation using 1 equiv of PtCl2(SEt2)2 in THF at room temperature yielded the platinated complex [PtCl(C6H2{CH2NMe2}2-2,6-SiMe3-4)] (3). Reaction of the iodinated analogue of 1, [IC6H2(CH2NMe2)2-2,6-SiMe3-4] (4), with an excess of Ni(PPh3)4 in THF at room temperature afforded the nickel complex [NiI(C6H2{CH2NMe}2-2,6-SiMe3-4)] (5). Similar synthetic approaches have also been applied to the (N)CN-substituted carbosilane ligand systems [CH2Si(Me)2C6H3(CH2NMe2)2-3,5]2 and [CH2Si(Me)2C6H4(CH2NMe2)-4]2 to give the bismetalated species [CH2Si(Me)2C6H2(CH2NMe2)2-3,5-(MX)-4]2 (MX = PdCl (9), PtCl (10), PdI (12)) and [CH2Si(Me)2C6H3(CH2NMe2)-4-(PdCl)-3]2 (13) in good yields. The molecular structures of 5 and bispalladated 13 have been determined. The molecular structure of 13 shows this species to be a centrosymmetric dimeric aggregate in the solid state, with the two bis(amino)arylpalladium carbosilane molecules held together via two terminal-terminal chlorine bridging atoms, thus forming a 26-membered macrocyclic ring.