Sulfido-Bridged Tetranuclear Titanium−Iridium Complexes with an Unconventional Tetrahedral Iridium Center

Abstract

A general route to the complexes [CpTi(μ3-S)3M3(diolefin)3] (M = Rh, diolefin = cod, nbd, tfbb; M = Ir, diolefin = cod) consists of the reactions of the anion [Cp2Ti2(μ-S)2(S)2]2-, obtained by mono-deprotonation of Cp2Ti(SH)2 with butyllithium in THF, with the appropriate complexes [{M(μ-Cl)(diolefin)}2]. Replacement of the diolefin by carbon monoxide in [CpTi(μ3-S)3M3(diolefin)3] gives the carbonyl derivatives [CpTi(μ3-S)3M3(CO)6]. Further reactions of the carbonyliridium complex with tertiary phosphine and phosphite ligands produce the 62-e valence clusters [CpTi(μ3-S)3Ir3(μ-CO)(CO)3(PR3)3] (PR3 = PPh3, PMe3, P(OMe)3, PMePh2). Remarkable features in the structure of these compounds, as found for [CpTi(μ3-S)3Ir3(μ-CO)(CO)3{P(OMe)3}] by X-ray diffraction studies, are a distorted tetrahedral metal framework with short Ir−Ir distances and a tetrahedral coordination of the iridium atom closest to the titanium. A delocalized bonding scheme can be proposed for the iridium triangle and, at least, an interaction between the tetrahedral iridium and the titanium atom. The complexes [CpTi(μ3-S)3Ir3(μ-CO)(CO)3(PR3)3] quickly exchange all their carbonyl ligands with 13CO under normal conditions to give the labeled complexes. Indeed, an equilibrium between the compounds [CpTi(μ3-S)3Ir3(μ-13CO)(13CO)3(PR3)3] and [CpTi(μ3-S)3Ir3(μ-13CO)(13CO)4(PR3)2] and free phosphine exists under an atmosphere of 13CO. In addition, these compounds are fluxional, since they exhibit a single carbonyl resonance in the low-temperature 13C{1H} NMR spectrum, probably due to very fast carbonyl scrambling. Furthermore, the reaction of [CpTi(μ3-S)3Ir3(μ-CO)(CO)3(PPh3)3] with HBF4 gives the unsymmetric and nonfluxional hydride of formula [CpTi(μ3-S)3Ir3(μ-CO)(H)(CO)3(PPh3)3]BF4.

Synthesis, characterization and soft transformation of some bis(cyclopentadienyl) Ti(IV) and Zr(IV) complexes of Schiff's base ligands to nano‐sized titania or zirconia materials

“…This observation is consistent with the literature reports that the elimination of Cp group takes place easily in the presence of protonic nucleophiles or electrofiles. 39,40 However, metathetical reactions of Cp 2 TiCl 2 or Cp 2 ZrCl 2 with the sodium salts of Schiff's bases in 1 : 1 and 1 : 2 molar ratios in anhydrous THF yielded complexes of the following type:…”

Early (Ti, Zr)-late (Rh, Ir) heteronuclear complexes with bridging sulphido ligands

“…As the latter hydridoiridium cluster can be obtained from [{Ir(µ-Cl)(cod)} 2 ] and NaHS or H 2 S, the titanium complex acts, in fact, as a source of hydrosulfido ligands for iridium, one of which produces the oxidative-addition of the S-H bond leading to the hydrido ligand. To avoid this [23]. The complexes were isolated as air stable crystalline solids.…”

“…Remarkable features in the structure of these compounds, as found for [CpTi(µ 3 -S) 3 Ir 3 (µ-CO)(CO) 3 {P(OMe 3 ) 3 }] by X-ray diffraction studies, are a distorted tetrahedral metal framework with short iridium-iridium distances and a tetrahedral coordination of the iridium atom closest to the titanium. The tetrahedral coordination of one iridium atom, together with the equatorial disposition of the phosphite ligands and consequent axial disposition for the carbonyl ligands, and the metal-metal bonding in the triiridium triangle are crucial in explaining the dynamic and chemical behaviour observed for these complexes [23]. While the bridging carbonyl group moves along the triangle, all the iridium centers are successively exchanging their stereochemistry, becoming tetrahedral and interacting with the titanium center.…”

“…However, when the electron-rich tetrahedral iridium center is protonated (Scheme 3) the carbonyl scrambling ceases [23].…”

The Anions [Cptt2Zr(μ-S)2M(CO)2]-(M = Rh, Ir) as Versatile Precursors for the Synthesis of Sulfido-Bridged Early−Late Heterotrimetallic (ELHT) Compounds

“…However, it has been established that sulfido ligands are able to stabilize early-late heterobimetallic compounds (ELHB) that contain dinuclear [TiM], 9 trinuclear [TiM 2 ] (M = Rh, Ir), 10 similar to the found in compound 4 which is a diagnostic for a staggered rotamer. 12a The interconversion of both rotamers, which was confirmed in the phase-sensitive NOESY spectrum, produces an equilibrium mixture in which the staggered rotamer 6a predominates (3:1).…”