Rational Synthesis and Electronic Structure of Functionalized Trinuclear Pd Metal Sheet Sandwich Complexes

Abstract

In this article we present the rational synthesis and full characterization of molecular Pd 3 clusters sandwiched by imidazolium-and pyridinium-functionalized cycloheptatrienide ligands, of general formula [Pd 3 Br 3 (C 7 H 6 R) 2 ] + . From functionalized η 3 -cycloheptatrienide Pd complexes as starting materials, PdBr 2 (η 3 -C 7 H 6 R), a number of synthetic routes were tested and a generally applicable strategy was developed on the basis of the formation of dimeric "preclusters", [{PdBr(η 3 -C 7 H 6 R)} 2 (μ-Br)] + , which exhibit a Pd−Pd interaction. Spectroscopic and electrochemical results indicate a noninteger, common oxidation state of Pd in the trinuclear clusters, and crystallographic analysis reveals distinct differences in the binding properties of the Pd atoms in the solid state, suggesting that in certain environments there are even two discernible oxidation states, which is supported by computational analysis of the charge distribution.

Mechanistic Insight into H/D Exchange by a Pentanuclear Ni–H Cluster and Synthesis and Characterization of Structural Analogues of Potential Intermediates

“…The past decade has seen several reports of transition metal clusters , undergoing unprecedented bond transformations with traditionally inert bonds, − including the activation of C–C bonds in hydrocarbons such as benzene , and ethylene . This has spurred on the rational design of transition metal clusters and polynuclear complexes, − in an attempt to access similar cooperative reactivity. Interactions among proximal late transition metal centers could be envisioned to facilitate metal surface-like transformations.…”

A halide-free pyridinium-substituted η3-cycloheptatrienide–Pd complex

“…As the structure is very similar to previously reported complexes with other substituents on the cycloheptatrienide rings, it will only be discussed briefly. The allyl bonds are located in the -position (with respect to the distance of the central C atom from the substituent), as observed in the vast majority of reported monomeric and dimeric substituted 3 -cycloheptatrienide-Pd complexes (Mantas-Ö ktem et al, 2012;Jandl et al, 2014Jandl et al, , 2016Jandl et al, , 2017. The central Pd 2 Br 2 moiety is a distorted planar square, with Pd1-Br1 = 2.5392 (3) Å and Pd1-Br1a = 2.5769 (3) Å [symmetry code: (a) Àx + 1, Ày + 1, Àz + 1] and angles of Br1-Pd1-Br1a = 88.930 (9) and Pd1-Br1-Pd1a = 91.070 (9) .…”

“…It has also been shown that a partial exchange of halide ligands for noncoordinating anions, like hexafluorophosphate or tetrafluoroborate, gives rise to a range of dimeric complexes with bridging halides [see (a) in Fig. 1] (Mantas-Ö ktem et al, 2012;Jandl et al, 2014Jandl et al, , 2017. In one case, the co-existence of the dimer with a tetramer featuring a Pd 4 Br 4 macrocycle was observed [see (a) in Fig.…”

“…As pointed out in these reports, the dimeric complexes frequently exhibit intramolecular PdÁ Á ÁPd interactions. Thus, they were found to be useful precursors for the synthesis of molecular Pd clusters (Jandl et al, 2017). Inspired by the creation of PdÁ Á ÁPd contacts upon partial removal of halide ligands, we became interested in the structural effects that a complete exchange of halides for noncoordinating anions would have.…”

Investigation of Solvatomorphism and Its Photophysical Implications for Archetypal Trinuclear Au3(1-Methylimidazolate)3

“…In this context, having great interest in small organometallic clusters [ 21 , 22 ], closed-shell coinage-metal-based systems with fascinating photo-physical properties [ 23 , 24 ], we further consider the Au(I) imidazolate-type CTCs as a valuable platform to investigate the luminescence, inter- and intra-trimer metal-metal interactions and related supramolecular assembly. The simplest scaffold - Au 3 (MeIm) 3 was the first synthesized Au(I) imidazolate CTC by Burini in 1989 [ 7 ], but was not structurally determined until very recently by Ruiz et al in 2020 [ 20 ].…”