Trimetallic Cubane-Type Clusters: Transition-Metal Variation as a Probe of the Roots of Hypoelectronic Metallaheteroboranes

Abstract

In an effort to synthesize chalcogen-rich metallaheteroborane clusters of group 5 metals, thermolysis of [Cp*TaCl] (Cp* = η-CMe) with thioborate ligand Li[BHS] was carried out, affording trimetallic clusters [(Cp*Ta)(μ-S)(μ-S)B(R)], 1-3 (1, R = H; 2, R = SH; and 3, R = Cl). Clusters 1-3 are illustrative examples of cubane-type organotantalum sulfido clusters in which one of the vertices of the cubane is missing. In parallel to the formation of 1-3, the reaction also yielded tetrametallic sulfido cluster [(Cp*Ta)(μ-S)(μ-S)(μ-O)], 6, having an adamantane core structure. Compound 6 is one of the rarest examples containing the μ-oxo unit with a heavier early transition metal, i.e., tantalum. In an effort to isolate selenium analogues of clusters 1-3, we have isolated the trimetallic cluster [(Cp*Ta)(μ-Se)(μ-Se)B(H)], 4, from the thermolytic reaction of [Cp*TaCl] and Li[BHSe]. In contrast, the thermolysis of [Cp*TaCl] with Li[BHTe] under the same reaction conditions yielded tantalum telluride complex [(Cp*Ta)(μ-Te)], 5. Compounds 1-4 are hypo-electronic clusters with an electron count of 50 cluster valence electrons. All these compounds have been characterized by H,B{H}, and C{H} NMR spectroscopy; infrared spectroscopy; mass spectrometry; and single-crystal X-ray crystallography. The density functional theory calculations were also carried out to provide insight into the bonding and electronic structures of these molecules.

Role of Metals and Thiolate Ligands in the Structures and Electronic Properties of Group 5 Bimetallic–Thiolate Complexes

“…The six-membered vanadacycle, comprising three sulfur atoms, two carbon atoms, and one vanadium atom, exists in chair form which is different from those of platinacycles, for example, [Pt­(PPh 3 ) 2 {(SCH 2 ) 2 SO}] and [Pt­(dppe)­{(SCH 2 ) 2 SO}] . The Cp* and one oxo ligand occupied the equatorial and axial positions, respectively, of the tri­thia­vanada­cyclo­hexane ring similar to [Cp*VOS 5 ] . The vanadium oxygen bond distance of 1.604(5) Å in 1 lies within the VO bond distance as reported for [Cp*VOS 5 ] (1.590 Å).…”

Metal Coordinated Tri‐ and Tetraborane Analogues

“…Two of the Ta−Ta bond distances in both 2 and 6 differ significantly from the other one. Although the observed Ta1−Ta1 distance of 2 (2.9622(15) Å) and Ta2−Ta2 distance of 6 (3.0865(19) Å) are consistent with normal Ta−Ta bond length, Ta1−Ta2 bond lengths of 2 (3.2192(12) Å) and 6 (3.3311(15) Å) are slightly higher [19,24] . This may be due to the presence of phenyl rings and an additional selenide group in 2 and 6 , respectively.…”

“…The 11 B{ 1 H} resonances of 1 at δ =31.8, −12.0, and −22.6 ppm are assigned to B1, B2, and B3, respectively, by means of calculated 11 B NMR [18] . The Ta−Ta bond distance of 2.763(6) Å in 1 is significantly shorter as compared to the Ta−Ta bond distances of [(TaCp*) 3 ( μ 3 ‐S) 3 (μ‐S) 3 B(SH)] [19] ( c.a . 3.106 Å) and [(TaCp*) 2 (μ‐H)(B 2 H 5 )(SCH 2 S) 2 ] [9a] (3.2903(8) Å).…”

Stabilization of dichalcogenide ligands in the coordination sphere of a ruthenium system

“…6a Further, the reaction of [Cp*MCl4] (M = Nb and Ta) with Li[BH2E3] (E = S, Se, or Te) yielded various metal chalcogenide complexes along with chalcogen rich trimetallic cubane type complexes. 7 Therefore over the years, the interest have grown to investigate the reactivity of Li[BH2E3] with heavier metal precursors. 8 To investigate the effect of the ancillary ligand as well as chalcogenide ligand on the stability of metal-chalcogenide complexes of ruthenium, we chose [(p-cymene)Ru(μ-Cl)Cl]2 as a suitable metal precursor.…”