www.elsevier.nl/locate/jorganchem Journal of Organometallic Chemistry 598 (2000) 222 – 227 Direct displacement of chlorine or iodine in reactions of (Me 3 Si) 3 CSiRRX with metal salts Kazem D. Safa *, Mohammad G. Asadi, Abdolreza Abri, Ali Mohammadpour, Hadi Kiae Faculty of Chemistry, Uniersity of Tabriz, Tabriz, Iran Received 1 December 1998; received in revised form 7 November 1999 Abstract Direct nucleophilic displacement of halide X (X =Cl or I) takes place when the compounds (Me 3 Si) 3 CSiRRX with R =Me, R =(C 6 H 4 Me-p ), (C 6 H 4 OMe-p ), CH 2 CH R =Bu, R =Cl, or R =Ph, R =Ph are treated with solutions of KOCN, KSCN, KCN, or NaN 3 in CH 3 CN or MeOH, and H 2 O in DMSO, or CH 3 CN. © 2000 Elsevier Science S.A. All rights reserved. Keywords: Silicon; Steric Hindrance; Trisyl 1. Introduction The effect of severe steric hindrance on direct nucleo- philic attack at functional silicon centres bearing the bulky trisyl group (denoted here by Tsi) or a related group has allowed the observation of previously inac- cessible mechanisms of reactions [1]. For example, un- usual rearrangement and migration in TsiSiR 2 X species take place through bridged silicocationic intermediates. When the steric hindrance at the functional silicon centres is reduced, or linear nucleophiles like N 3 - , SCN - , OCN - and CN - are used, direct biomolecular displacement takes place. Earlier work had indicated that nucleophilic substitution, while relatively easy for TsiSiMe 2 X, was very slow for TsiSiPh 2 I [2–5]. But we have now shown that under suitable conditions such substitution reactions provide a satisfactory route to TsiSiPh 2 X and some related species. We have also shown that with less hindered systems the chlorides can be satisfactorily used instead of iodides. For example, TsiSiMe(CHCH 2 )Cl and TsiSi- BuCl 2 undergo direct nucleophilic reactions to give the corresponding products. The chlorides (C 6 H 4 OMe-p )- SiMeHCl and (C 6 H 4 Me-p )SiMeHCl react with TsiLi to give trisyl derivatives containing a hydride substituent. The presence of even one hydride ligand reduces the steric hindrance considerably and we have seen that for such compounds nucleophilic substitution takes place fairly readily. In this work we synthesised new compounds with different groups and did some nucleophilic reactions on them with linear nucleophiles, namely N 3 - , SCN - , OCN - and CN - , to examine the ease of reactions on Si bearing the bulky trisyl group. 2. Results and discussion In our earlier work we have shown that the synthesis of TsiSiAn 2 I by the reaction of TsiSiAn 2 H with ICl was unsuccessful [1]. An attempt to make TsiSi (C 6 H 4 Me- p ) 2 F by reaction of TsiLi with (C 6 H 4 Me-p ) 2 SiF 2 was also unsuccessful. For that reason in order to reduce steric hinderance we have chosen methylanisyl and methyltolyl derivatives to prepare TsiSi(C 6 H 4 OMe- p )MeI and TsiSi(C 6 H 4 Me-p )MeI, respectively and stud- ied the reaction of the iodides with electrophiles, nucleophiles and alkoxides. When steric hinderance of the functional silicon centre is reduced or linear nucle- ophiles such as NCS - , NCO - , CN - are used, such bimolecular displacement reactions take place and no rearrangement is observed. * Corresponding author. E-mail address: g-asadi@ank.tabriz.ac.ir (K.D. Safa) 0022-328X/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved. PII:S0022-328X(99)00709-3