Bridged and Unbridged Nickel–Nickel Bonds Supported by Cyclopentadienyl and Phosphine Ligand Sets

Abstract

A series of Ni complexes [Ni­(Cl)2(PR3)2] with R = Me (1-Me), n Pr (1- n Pr), and n Bu (1- n Bu) and nickelocenes [Ni­(η5-C5H4R′)2] with R′ = H (2-H), Me (2-Me), and SiMe3 (2-SiMe 3 ) were synthesized and characterized. From these complexes, the synthesis of the Ni complexes [NiCl­(PR3)­(η5-C5H4R′)] R = Me, R′ = H (3-Me), R= n Bu, R′ = H (3- n Bu), R = n Pr, R′ = H (3- n Pr), R = Et, R′ = Me (4), and R = Et, R′ = SiMe3 (5) was achieved. All complexes were fully characterized, including single crystal X-ray crystallography. Complexes 3-R, 4, and 5 were then used to obtain homobimetallic Ni complexes with rare examples of unbridged Ni–Ni bonds [{Ni­(η5-C5H5)­(PR3)}2], with R = Me (7-Me) and R = n Pr (7- n Pr) being structurally characterized by single crystal X-ray diffraction. In order to probe the effect of bridging ligands on the Ni–Ni bond, the bridged complex [{Ni­(μ:η5-C5H4CH2CH2P­( t Bu)2)}2] (8) was synthesized from the monomeric precursor [Ni­(Cl)­(κ1-η5-C5H4CH2CH2P t Bu2)] (6). The Ni–Ni distances in 7-Me, 7- n Pr, and 8 were found to be 2.407(1), 2.3931(6), and 2.6027(17) Å, respectively, the latter seemingly lengthened compared to the other two due to the tethered nature of the bridging ligand. DFT calculations confirm the presence of unbridged σ-bonds between the Ni atoms in 7-Me and 7- n Pr and show that the bridging ligand in 8 has a minimal effect on the character of the Ni–Ni bond.

Unmasking the constitution and bonding of the proposed lithium nickelate “Li3NiPh3(solv)3”: revealing the hidden C6H4ligand

“…Importantly, the bridging C–C bond in the C 6 H 4 moiety (1.449(6) Å) is significantly longer than the analogous bond in a previously reported 4,5-difluorobenzyne complex [{(PEt 3 ) 2 Ni} 2 (μ-η 2 :η 2 -C 6 H 2 -4,5-F 2 )] (1.390(3) Å) 32 and the mononuclear Ni–benzyne complex [(Cy 2 PCH 2 CH 2 PCy 2 )Ni(η 2 -C 6 H 2 )] (1.331(3) Å) 33 ( Scheme 2 ). Compared to dinickel complexes, where Ni–Ni bond distances tend to be around 2.5 Å, and in a rare case 2.6027(17) Å, 34 the Ni⋯Ni distance of 2.7117(8) Å is very long and is similar to the 2.7242(3) Å observed in [{(PEt 3 ) 2 Ni} 2 (μ-η 2 :η 2 -C 6 H 2 -4,5-F 2 )]. 32 In that case, Ni⋯Ni interactions were not studied.…”

New nickel(ii) Schiff base complexes as potential tools against SARS-CoV-2 Omicron target proteins: an in silico approach

“…50 The square planar Ni(II) complex (2) often stacks with relatively short NiÁ Á ÁNi distances. 60,61 The NiÁ Á ÁNi separation is 3.317 Å (Fig. S25 and S26, ESI †) in the Ni(II) complex (2).…”

A phenoxy-bridged trinuclear Ni(ii) complex: synthesis, structural elucidation and molecular docking with viral proteins

“…None of these distances falls outside the range of average Ni-O(phenoxo) distances observed in other hexacoordinated trinuclear Ni( ii ) complexes reported [1.971(2)–2.102(7) Å]. 54 The Ni(1)⋯Ni(2), Ni(1) i ⋯Ni(2) and Ni(1)⋯Ni(1) i distances within the trimeric complex are 2.075, 3.087 and 4.455 Å, respectively. The detailed structural analysis and non-covalent supramolecular interactions are also investigated by single crystal structure analysis.…”