Reactivity of [TiM2] (M = Rh, Ir) and [TiIr3] early-late heterobimetallic sulfido-bridged clusters

Abstract

Please cite this article as: M.A. Casado, M.A. Ciriano, F.J. Lahoz, L.A. Oro, J.J. Pérez-Torrente, Reactivity of [TiM2] (M = Rh, Ir) and [TiIr3] early-late heterobimetallic sulfido-bridged clusters, Journal of Organometallic Chemistry (2015), Early-late sulfido-bridged clusters with [TiM 2 ] cores (M = Rh, Ir) form hydroxo-bridged earlylate compounds upon protonation with aqueous HCl. The sulfido-bridged cluster of [TiIr 3 ] core reacts with alkynes at the metallic triangle. Abstract Treatment of heterobimetallic sulfido-bridged complexes [Cp(acac)Ti(µ 3 -S) 2 {M(cod)} 2 ] (M = Rh (1), Ir (2)) with the organic acids CX 3 COOH (X = F, H) forms the corresponding acetate derivatives [Cp(CX 3 COO)Ti(µ 3 -S) 2 {M(cod)} 2 ] (X = F, M = Rh (3), Ir (4); X = H, M = Rh (5), M = Ir (6)). While complex 3 was easily isolated, compounds 4-6 establish in solution the corresponding equilibria with the starting complexes 1 and 2. Treatment of 1 with a hydrochloric acid solution in THF generates the heterohexanuclear cationic cluster [{CpTi(µ 3 -S) 2 Rh 2 (cod) 2 } 2 (µ-OH)][Cl] (7), which is deprotonated with weak bases affording the oxo derivative [{CpTi(µ 3 -S) 2 {Rh(cod)} 2 } 2 (µ 2 -O)] (8). Cluster 8, and the analogous with the ligand methylcyclopentadienyl [{(CpMe)Ti(µ 3 -S) 2 {Rh(cod)} 2 } 2 (µ 2 -O)] (9), can be synthesized from reaction of the respective complexes [Cp 2 Ti(SH) 2 ] and [(CpMe) 2 Ti(SH) 2 ] with the methoxo-bridged dinuclear complex [{Rh(µ-OMe)(cod)} 2 ] in the presence of water. A preliminary study of the molecular structure of 9 confirmed the formation of an almost linear array of the "Ti-O-Ti" subunit, in which each titanium atom supports two "Rh(cod)" moieties through two sulfido bridges. Further, the heterotetranuclear cluster M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 2 [CpTi(µ 3 -S) 3 Ir 3 (µ 2 -CO)(CO) 3 (PMe 3 ) 3 ] (10) reacts with alkynes at the triiridium metallic triangle. The reactions with activated alkynes, such as dimethyl acetylenedicarboxylate (or diethyl acetylenedicarboxylate) afford clusters [CpTi(µ 3 -S) 3 Ir 3 (µ 2 -η 1 -RO 2 CC=CCO 2 R){C(O)RO 2 CC=CCO 2 R}(CO) 3 (PMe 3 ) 3 ] (R = Me (11), Et (12)), which incorporate two molecules of alkyne. The X-ray molecular structure of 11 shows that one alkyne is cis-metallated to the metal-metal bonded iridium centres whereas the other is taking part of a iridacyclobutenone moiety resulting from the CO migratory insertion into a iridium-alkyne bond at the third iridium centre. However, reaction of 10 with phenylacetylene stops at the cluster [CpTi(µ 3 -S) 3 Ir 3 (µ 2 -η 1 -PhCCH)(CO) 3 (PMe 3 ) 3 ] (13), which contains only a cis-metallated olefin to two metal-metal bonded iridium atoms. The X-ray molecular structure of [CpTi(µ 3 -S) 3 Ir 3 (µ 2 -η 1 -PhCCH)(H)(CO) 3 (PMe 3 ) 3 ][BF 4 ] (14), the product resulting from protonation of 13 with HBF 4 ·OEt 2 shows that the [TiIr 3 ]core remains intact and that the olefin is indeed cis-metallated to the two metal-metal bonded iridium atoms, while the third iridium atom from the metall...

Heterobimetallic Complexes of 1,1-Diphosphineamide Ligands

“…Complexes of these ligands have shown activity in homogeneous catalysis, with applications in reactions such as hydrogenation, hydroacylation, and hydrogen borrowing reactions . Moreover, we targeted an early/late transition metal combination for the potential of synergistic and cooperative reactivity of the two centers; ,− examples of homogeneous Ti–Rh bi- or multimetallic complexes have been reported − and used in catalysis, for example, hydrosilylation, hydroacylation, and hydrogenation reactions, with an observed enhanced reactivity of the bimetallic complex compared to their monometallic precursors.…”