Sodium complexes containing 2-iminopyrrolyl ligands: the influence of steric hindrance in the formation of coordination polymers

Abstract

Iminopyrrolyl complexes of sodium were prepared from the reaction of 2-arylformiminopyrrole ligand precursors (aryl = C(6)H(5) (I); 2,6-Me(2)C(6)H(3) (II); 2,4,6-Me(3)C(6)H(2) (III); 2,6-(i)Pr(2)C(6)H(3) (IV)) with one equivalent of sodium hydride. The resulting corresponding compounds 1-4, [{Na(mu(2):kappa(2)N,N'-iminopyrrolyl)}(2n)(OEt(2))(2x)] (n > or = 1; x = 0 or 1), were obtained in moderate to high yields and were characterised by NMR spectroscopy, high resolution mass spectrometry and X-ray diffraction, when suitable crystals were obtained. The X-ray structure of compound 1 (n >> 1; x = 0) reveals the formation of a coordination polymer with repeating units consisting of dimers that contain two iminopyrrolyl ligands chelating two sodium atoms, where both pyrrolyl rings exhibit bridging sigma + sigma coordination to the Na atoms within the dimer; the self-assembling of the polymer is established by additional pi-bonds (eta(5)-coordination) of each of the pyrrolyl rings to the sodium atoms of the adjacent dimer units. Conversely, the structure of complex D(IV) (n = x = 1) shows it as one of such dimers capped by two diethyl ether molecules, each coordinated to the sodium atoms (n = 2; x = 1). DFT calculations indicate that the differences between the structures 1-4 of arise from the increasing bulkiness imposed by the corresponding substituents of the iminic aryl groups.

Octahedral Co(III) complexes of 2-(phenylimino)pyrrolyl ligands: Synthesis and structural characterisation

“…Recently, we reported the synthesis and characterisation of a series of Na [7], Co(II) [8], Ni(II) [9], and Zn(II) [2a] complexes containing 2-aryliminopyrrolyl or 2-aryliminophenanthro [9,10-c]pyrrolyl ligands. Particularly, in the case of Co(II), the introduction of substituents with increasing bulkiness led to the formation of four-coordinate complexes with tetrahedral and square-planar geometries (Chart 1, B and C, respectively) [8a].…”

Alkali Blues: Blue‐Emissive Alkali Metal Pyrrolates

“…[53] The NaÀNa nd NaÀCd istances in [2] n agree well with those reported for similar [(NaL) 2 ] n oligomers (Scheme 1). [31,33,34,52] The aryl torsion angles of 2 in the solids tate are closer to ap lanar orientation with C5-N2-C6-C7 = 9.0(7)8 and C20-N4-C21-C22 = 13.6(11)8 compared with the lithium 2-iminopyrrolates. The Na1ÀNa2 distances are 3.471(4) and 3.525(4) .…”

“…[19,21,22] The C5-N2-C6-C7 aryl torsion angles of [1(CH 3 CN)] 2 and [1(H 2 NC(CH 3 )CHCN)] 2 amount to 35.96(15)8 and 27.76(14)8, respectively.S uch moderatet orsion angles are commonf or N,N'-chelated 2-iminopyrroles with sterically unhindereda rylimine substituents. [31] Sterically demanding aryl substituents, for example, 2,6-dimethylphenyl or 2,6-di(isopropyl)phenyl, enforce an almostp erpendicular orientation of the aryl substituents with torsion angles of 73.08 and 77.48,r espectively. [51] In contrast to the dimerica rrangements of [1(CH 3 CN)] 2 and [1(H 2 NC(CH 3 )CHCN)] 2 ,t he sodium salt 2 crystallizes as ap olymer in as taircasef ashion as [2] n in the monoclinic space group P2w ithout any contribution of solventm olecules (Figure 1c;S upporting Information, Ta blesS1a nd S3).…”

Bis{2-[(phenylimino)methyl]-1H-pyrrol-1-ido}palladium(II)

“…For structure analyses of the free ligand N-[(1H-pyrrol-2-yl)methylene]aniline, see: Gomes et al (2010); Crestani et al (2011). For the structure of a related nickel complex of the same imine ligand and an additional bipyridine ligand, see: Castro et al (1992).…”

“…E68, m1567 [doi:10.1107/S1600536812048143] Bis{2-[(phenylimino)methyl]-1H-pyrrol-1-ido}palladium(II) Wolfgang Imhof Comment In the course of a project related to the supramolecular structures of square planar nickel and palladium complexes of pyrrole-2-carbaldehyde based Schiff base ligands in comparison with the structures of the free ligands the molecular structure of the title compound was determined. The free ligands form inversion dimers via N-H···N hydrogen bondsbetween the pyrrole NH function and the imine nitrogen atom of a neighbouring molecule(Crestani et al, 2011;Gomes et al 2010).…”