868629-11-2Relevant academic research and scientific papers
A trithiol protio-ligand and its fixation to the periphery of a carbosilane dendrimer as scaffolds for polynuclear rhodium and iridium complexes and metallodendrimers
Camerano, Jose A.,Casado, Miguel A.,Ciriano, Miguel A.,Lahoz, Fernando J.,Oro, Luis A.
, p. 5147 - 5156 (2005)
Tris(methylenethiol)methane derivatives containing an allyl or benzyl linker (ROCH2C(CH2-SH)3; R = Bn(6a), CH 2=CHCH2(6b)), which could allow their fixation to carbosilane dendrimers, were synthesized through a multistep synthesis. Grafting the periphery of the core dendrimer Si[(CH2)3Si(Me) 2H]4 was achieved with the tosyl derivative CH 2=CHCH2OCH2-C(CH2OTs)3 by a hydrosilylation reaction to give selectively Si[(CH2) 3Si(Me)2(CH2)3OCH 2-C(CH2OTs)3]4 (G(0) OTs-12). This dendrimer was converted into the thiol-functionalized carbosilane dendrimer Si[(CH2)3Si(Me)2(CH 2)3OCH2C(CH2SH)3] 4 (G(0)SH-12) by reduction of the thiocyanate intermediate Si[(CH2)3Si(Me)2(CH2) 3OCH2C(CH2SCN)3]4 with LiAlH4. The trithiol compounds 6a and 6b protonated the complexes [Rh(μ-OMe)(cod)]2 and [Rh(acac)-diolefin] (M = Rh, diolefin = cod, nbd, tfb) to give the corresponding trinuclear complexes [Rh 3{μ-ROCH2c(ch2s)3}(diolefin) 3] (7-9). Their structure can be described as an adamantane-like entity, in which the metals are held together by the thiolate arms of the ligand, with the sulfurs bridging the metal atoms in a μ2 fashion, as shown for [Rh3{μ-BnOCH2C(CH2S) 3}-(nbd)3] by X-ray diffraction methods. Carbonylation of 7-9 under atmospheric pressure gave the carbonyl complexes with the thiolate tripod ligands [M3{μ-ROCH2C(CH2S) 3}(CO)6] (M = Rh, Ir), which were reacted with phosphorus donor ligands (PR3 = PPh3, P(OMe)3) to give [M3{μ-ROCH2C(CH2S)3}(CO) 3(PR)3] as a sole isomer of averaged C3v symmetry. The functional dendrimers were metalated by reaction of the core molecule Si[(CH2)3Si(Me)2-(CH2) 3OCH2C(CH2SH)3]4 (G(0)SH-12) by applying the synthetic protocols above-described for trinuclear complexes. Thus, the reactions of G(0)SH-12 with the complexes [M(acac)(diolefin)] (M = Rh, Ir; diolefin = cod, nbd, tfb) gave the metallodendrimers Si[(CH2)3Si(Me)2(CH 2)3-OCH2C(CH2S) 3{M(diolefin)}3]4 (G(0) M(dioiefin)-12) as insoluble solids. Soluble metallodendrimers, Si[(CH2)3Si(Me)2(CH2) 3OCH2C(CH2S)3{Rh(CO) 2}3]4 (G(0)Rh(CO)2-12) and Si[(CH2)3-Si(Me)2(CH2) 3OCH2C(CH2S)3{M(CO)(PPh 3)}3]4 (G(0)M(co)(PPh3)-12) were obtained either by carbonylation of the diolefin compounds or by the reaction of G(0)SH-12 with [M(acac)(CO)2] (M = Rh, Ir), and by further reaction with PPh3, respectively.
