Indenylnickel Imidato Complexes:  Synthesis, Characterization, and Reactivities

Abstract

The complex (1-Me-indenyl)Ni(PPh3)(phthalimidate) has been prepared and fully characterized by IR and 1H, 13C{1H}, and 31P{1H} NMR spectroscopy and single-crystal X-ray diffraction. The analogous 4,5-dichlorophthalimidato, maleimidato, and succinimidato complexes have also been prepared and characterized spectroscopically. These complexes are thermally stable, in contrast to the analogous Ni−amido species, which could not be prepared. Reactivity studies have shown that the Ni−imidato bond is fairly unreactive in insertion and nucleophilic reactions, and VT 1H NMR studies suggest that the rotation around the Ni−N bond in the maleimidato complex is hindered by ca. 11 kcal/mol. The solid-state structure of the phthalimidato derivative showed that the P, N, C1, and C3 atoms are arranged around the Ni atom in a distorted-square-planar coordination environment, while the C2 atom is within bonding distance above the main square plane. The phthalimidato ligand is η1(N)-coordinated to Ni; the Ni−N bond is relatively short (1.895(4) Å), and the orientation of the imidato ligand is such that the planes bearing the atoms P, Ni, N and C9, N, C16 are rotated by ca. 76° with respect to each other. The hapticity of the indenyl ligand is characterized by an allyl-ene distortion (η5↔η3) and a partial localization of bonding inside the indenyl ring (η3↔η1,η2). 1H and 13C{1H} NMR spectra indicate that the nonsymmetrical coordination of the indenyl ligand, which can be attributed to the different trans influences of the phthalimidato and PPh3 ligands, is maintained in the solution. The character of the Ni−imidato bond has been discussed in terms of electrostatic-covalent and π-bonding interactions.

Novel complexes of nickel with N-heterocyclic ligands and the hemilabile [2-(dimethylamino)ethyl]cyclopentadienyl group

“…But again, the product decomposed during removal of the solvent at ambient conditions. Similar observations have been reported for the analogous complexes [(1-MeInd)Ni(PPh 3 )(NR 2 )] [14]. In that latter case, Zargarian et al reported, that isolable compounds were obtained only when strongly electron-withdrawing groups were present at the N-atom, in particular the N-heterocyclic ligands L = phthalimidato, 4,5-dichlorophthalimidato, maleimidato and succinimidato.…”

“…In contrast to 3, the resolution of the 1 H and 13 C{ 1 H} NMR spectra of 4 and 5 suffer probably from paramagnetic species being present as minor components in equilibrium, quite similar as observed for the complex [Cp N Ni(acac)] [13c]. All signals in the 1 H NMR spectrum are very broad and are shifted towards lower field in comparison to the resonances reported for [(1-Me-Ind)Ni(PPh 3 )L] (L = maleimidato, phthalimidato) [14]. The proton shifts of the Cp N ligand are very similar in 4 and 5 and resemble those found for [Me 3 SiCp N NiI] as reference compound [13c].…”

“…A rotation out of this plane reduces these interaction and has been discussed in various imidato complexes similar to 5, e.g. the solid state structure of [(1-Me-indenyl)Ni(PPh 3 )(phthalimidato)] shows a rotation of 76° [14] and the square-planar d 8 -complexes like [Ir(CO)(PPh 3 )(maleinimidato)] adopt comparable spacial arrangements [16].…”

Novel nickel(II) complex bearing phthalimido ligands derived from oxime-mediated transformation of phthalonitrile

“…[Ni{trans-(L) 2 }(en) 2 ] {L = N-(5-chlorouracilato) [28], isothiocyanato [29] and salicylato [30]}. In contrast, the almost planar pti ligands in 2 are bound via the Ni1-N1 bond of 2.1235(13) Å that is significantly lengthened in comparison with the corresponding bond distances of 1.907(3) and 1.895(4) Å in [Ni{g 5 -(2-dimethylaminoethyl)cyclopentadienyl}(pti)] Á 0.5(C 7 H 8 ) [27] and [Ni(g 5 -1-methylindene)(pti)(PPh 3 )] [26], respectively, but comparable to that of ca. 2.102 Å encountered in the related [31].…”

“…The m(C@O) band is significantly shifted to a lower-energy region than that of free phthalimide [1744 cm À1 ] [25], although being comparable to those of related Ni complexes [i.e. 1654-1650 cm À1 ] bearing phthalimido moieties [26,27]. The positive FAB-MS spectrum of 2 shows the molecular ion [M] + peak with the expected isotopic pattern at the m/z value of 470.…”