Syntheses, Properties and Structures of [{(C₅Me₅)₂Nb}₂NiTe₄] and [(tBuC₅H₄Nb)₂Ni₅Te₇(Ph₂PCH₂PPh₂)₂]: The Quest for Tetratelluronickelate Clusters

Abstract

International audienc

[{(C5Me5)2Nb}2PdTe4], a heterometallic palladium telluride cluster with a planar PdTe4 fragment

“…In contrast to the tetrahedral MTe 4 derivatives [{(tBuC 5 H 4 ) 2 NbTe 2 } 2 W AE W(CO) 4 ] (2) [8] and ½ðCp à 2 NbÞ 2 NiTe 4 (3) [6] the heavy atom core of 1 has a deck-chair like structure with angles of 160°between the planes Te1/Nb1/ Te2 and Te1/Te2/Pd (Fig. 2).…”

“…The obvious question is: is the symmetry of central MTe 4 unit governed by crystallographic requirements or by intrinsic properties of Ni versus Pd atoms? We have already described the electronic properties of [NiTe 4 ] 2À [6] for which no planar structure could be stabilised. Similar calculations with GAUSSIAN 03 [9] (DFT, B3LYP/3-21G * ) on [PdTe 4 ] 2À starting from slightly broken D 4h , D 2h , D 2d and T d geometries invariantly lead to the planar close to D 2h [PdTe 4 ] 2À ion.…”

“…The 1 H NMR spectrum of 1 reveals a singlet at d = 1.79 ppm (C 6 D 6 ) for the C 5 Me 5 rings. The trimetallic cluster 1 also forms in the presence of PEt 3 or when increasing the Pd/dppm ratio 2 ] and dppm in boiling toluene was also investigated in order to find analogies to the corresponding nickel telluride chemistry [6]. However, the only hint for the formation of larger Pd/Te clusters was provided by FD-MS, which reveals peaks at m/z 2098 and 2298 with isotope patterns typical of a polynuclear heavy atom skeleton, or part of it.…”

“…The calculated distance [d(Te-Te) = 2.970 Å ] is 0.18 Å shorter than that in 1, but the latter is still at the border of the wide range of compounds with Te-Te bonding interactions [1,6].…”

“…By contrast, comparatively little is known about palladium telluride complexes [4]. We have recently shown that use of ½Cp à 2 NbðTe 2 HÞ as tellurium transfer reagent [5] in the reaction with [Ni(COD) 2 ] in the presence of Ph 2 PCH 2 PPh 2 (dppm) provides access to the mixed early-late transition metal clusters ½ðCp à 2 NbÞ 2 NiTe 4 and [(Cp * Nb) 2 Ni 5-Te 7 (dppm) 2 ] [6]. Of particular interest for us has been the electronic structure of the tetratelluronickelate cluster.…”