No abstract

With the intent to demonstrate that the charge of Ztype ligands can be used to modulate the electrophilic character and catalytic properties of coordinated transition metals,weare nowtargeting complexes bearing polycationic antimony-based Z-type ligands.T oward this end, the dangling phosphine arm of ((o-(Ph 2 P)C 6 H 4 ) 3 )SbCl 2 AuCl (1)was oxidized with hydrogen peroxidet oa fford[ ((o-(Ph 2 P)C 6 H 4 ) 2 (o-Ph 2 PO)C 6 H 4 )-SbAuCl 2 ] + ([2a] + )w hichw as readily converted into the dicationic complex [((o-(Ph 2 P)C 6 H 4 ) 2 (o-Ph 2 PO)C 6 H 4 )-SbAuCl] 2+ ([3] 2+ )b yt reatment with 2equiv AgNTf 2 .B oth experimental and computational results showthat [3] 2+ possess as trong Au!Sb interaction reinforced by the dicationic character of the antimony center.T he gold-bound chloride anion of [3] 2+ is rather inert and necessitates the addition of excess AgNTf 2 to undergo activation. The activated complex, referred to as [4] 2+ [((o-(Ph 2 P)C 6 H 4 ) 2 (o-Ph 2 PO)C 6 H 4 )-SbAuNTf 2 ] 2+ readily catalyzesb oth the polymerization and the hydroamination of styrene.T his atypical reactivity underscores the strong s-accepting properties of the dicationic antimony ligand and its activating impact on the gold center.

Facile ligand substitution is observed when the ruthenium azido complex (PPh 3 )[Ru]-N 3 (1; [Ru] ) Tp(PPh 3 )Ru) is treated with CH 3 CN, yielding the nitrile-substituted ruthenium azido complex (CH 3 CN)[Ru]-N 3 (2). Alkylation, [3 + 2] cycloaddition, and catalytic reactions of complex 2 have been investigated. In the case of [3 + 2] cycloaddition reactions, the metal-bound heterocyclic complexes (CH 3 CN)[Ru]-N 3 C 2 (CO 2 Me) 2 (3a), (CH 3 CN)[Ru]-N 3 C 2 HCO 2 Me (5), and (CH 3 CN)[Ru]-N 3 C 2 HCN (6) are obtained from dimethyl acetylenedicarboxylate, methyl propiolate, and fumaronitrile, respectively. The tetrazolato complex 8) is prepared from 2 and TCNE. Alkylation of 3a with organic bromides affords N-alkylated five-membered-ring organic triazoles. The reaction of CS 2 with 2 produces the thermally unstable thiothiatriazolate (CH 3 CN)[Ru]-N 3 CS(S) (10), which decomposes to the isothiocyanate (CH 3 CN)[Ru]-NCS (11). On the other hand, several cationic imine complexes {(CH 3 CN)[Ru]-(NHdCHR)} + (12a, R ) H; 12b, R ) CH 3 ; 12c, R ) HCdCH 2 ) are formed by the reaction of RCH 2 X with the negatively charged nitrogen atom of the azido ligand on Ru II . The reaction proceeds via formation of an alkylimido intermediate followed by N 2 evolution and proton transfer from the alkyl group to the imido nitrogen atom. Preliminary results on the catalytic activity of 2 are also presented. Interestingly, complex 2 catalyzes the dimerization of some terminal alkynes HCtCR in organic and aqueous medium. Whereas with R ) Ph, SiMe 3 , t-Bu isomeric mixtures of head-to-head and head-to-tail coupling products are obtained, in the case of R ) COOMe, E-selective head-to-head dimerization takes place exclusively. The structures of 1, 8, and 12c have been determined by X-ray diffraction analysis.