Accessing Ta/Cu Architectures via Metal‐Metal Salt Metatheses: Heterobimetallic C−H Bond Activation Affords μ‐Hydrides

Abstract

We employ a metal‐metal salt metathesis strategy to access low‐valent tantalum‐copper heterometallic architectures (Ta–µ2‐H2–Cu and Ta–µ3‐H2–Cu3) that emulate structural elements proposed for surface alloyed nanomaterials. Whereas cluster assembly with carbonylmetalates is well precedented, the use of the corresponding polyarene transition metal anions is underexplored, despite recognition of these highly reactive fragments as storable sources of atomic Mn–. Our application of this strategy provides structurally unique early‐late bimetallic species. These complexes incorporate bridging hydride ligands during their syntheses, the origin of which is elucidated via detailed isotopic labelling studies. Modification of ancillary ligand sterics and electronics alters the mechanism of bimetallic assembly; a trinuclear complex resulting from dinuclear C–H activation is demonstrated as an intermediate en route to formation of the bimetallic. Further validating the promise of this rational, bottom‐up approach, a unique tetranuclear species was synthesized, featuring a Ta centre bearing three Ta–Cu interactions.

π-Bonding of Group 11 Metals to a Tantalum Alkylidyne Alkyl Complex Promotes Unusual Tautomerism to Bis-alkylidene and CO2 to Ketenyl Transformation

“…A search in the CCDC database for Ta−Cu species, where the two metal centers are separated by 2.7 Å or less revealed only one recent study from Buss and Maiola, who reported hydride-bridged species, in which the Ta−Cu distances span the range [2.61− 2.90 Å]. 90 The Ta−Cu distance in 2-Cu (2.7018(8) Å) is falling in this range, which is in between the sum of the respective metallic radii (Ta: 1.343 Å; Cu: 1.173 Å; sum = 2.516 Å) 91 and covalent radii (Ta: 1.70 Å; Cu: 1.32 Å; sum = 3.02 Å). 92 This provides a potential avenue for metal−metal interactions.…”

“…Molecular compounds associating Ta and Cu are extremely rare in the literature, − and to our knowledge, there is no structurally characterized tantalum/copper molecular complex featuring an unsupported metal–metal interaction (i.e., without bridging ligands) reported to date. A search in the CCDC database for Ta–Cu species, where the two metal centers are separated by 2.7 Å or less revealed only one recent study from Buss and Maiola, who reported hydride-bridged species, in which the Ta–Cu distances span the range [2.61–2.90 Å] . The Ta–Cu distance in 2-Cu (2.7018(8) Å) is falling in this range, which is in between the sum of the respective metallic radii (Ta: 1.343 Å; Cu: 1.173 Å; sum = 2.516 Å) and covalent radii (Ta: 1.70 Å; Cu: 1.32 Å; sum = 3.02 Å) .…”

Cooperative activation of carbon–hydrogen bonds by heterobimetallic systems

“…10 ). 71 During the synthesis, bridging hydrides are incorporated in these heterometallic compounds. The origin of these hydrides was investigated by isotopic crossover experiments using either deuterated solvent (THF-d 8 or toluene-d 8 ) and deuterated naphtalenide.…”