Synthesis, characterisation and crystal structures of new nickel complexes in S4 coordination spheres; an unprecedented rearrangement during ligand synthesis

Abstract

Two new nickel() complexes were synthesized with an S 4 coordination environment. These complexes were synthesized by in situ deprotection of thiouronium salts in the presence of nickel(). The ligands used are 4-mercapto-3,3-methyl-1-phenyl-2-thiabutane (Hbsms) and α,αЈ-bis(4-mercapto-3,3-methyl-2-thiabutyl)-o-xylene (H 2 xbsms). The former is a didentate ligand containing one thioether and one thiolate group and the latter is a dithioether dithiolate tetradentate ligand. The differences between these ligands upon coordination to nickel have been investigated. During the synthesis of these ligands, an unprecedented spontaneous rearrangement occurs, which is very fast and selective to a single product. The complexes were characterized by analytical, spectroscopic and electrochemical methods. The geometry of the nickel complexes is square planar according to the single-crystal X-ray structures. In [Ni(bsms) 2 ] the two ligands are coordinated with the thiolates in trans positions towards each other; in [Ni(xbsms)] the thiolates are in enforced cis positions. [Ni(bsms) 2 ] crystallizes in the triclinic space group P1 and has one centrosymmetric molecule in the unit cell. [Ni(xbsms)] crystallizes in the monoclinic space group P2 1 /c with two independent molecules in the asymmetric unit, however, the differences between these two molecules are very small. The Ni-S distances are 2.1730(4)-2.1909(6) Å and in the common range for thiolates and chelating thioethers.

A molecular cage of nickel(ii) and copper(i): a [{Ni(L)2}2(CuI)6] cluster resembling the active site of nickel-containing enzymes

“…The focus of our attention is to study the chemistry involving the synthesis and reactivity of nickel thiolate complexes in relation with the structure and function of protein active sites, as described above. 1,3,[5][6][7][8] Herein, we report the synthesis of a new bidentate S 2 thioether-thiolate ligand (L),w the mononuclear low-spin nickel complex (1)w and the hetero-octanuclear nickel(II) copper(I) cluster complex [{Ni(L) 2 } 2 (CuI) 6 ] (2),z which contains two NiS 4 units, four trigonal-planar CuI 2 S and two tetrahedral CuI 2 S 2 sites.The reaction of Ni(acac) 2 with two equivalents of the thiouronium chloride salt of the ligand, in the presence of two equivalents of tetramethylammonium hydroxide, led to an immediate color change to deep brown and the new low-spin square-planar complex [Ni(L) 2 ] (1) was isolated as flocculent reddish-brown crystals in high yield (Scheme 1). Equimolar solutions of Ni(L) 2 (1) in dichloromethane and copper(I) iodide in acetonitrile were mixed under argon and stirred for an hour to yield a dark brown precipitate.…”

“…The focus of our attention is to study the chemistry involving the synthesis and reactivity of nickel thiolate complexes in relation with the structure and function of protein active sites, as described above. 1,3,[5][6][7][8] Herein, we report the synthesis of a new bidentate S 2 thioether-thiolate ligand (L),w the mononuclear low-spin nickel complex (1)w and the hetero-octanuclear nickel(II) copper(I) cluster complex [{Ni(L) 2 } 2 (CuI) 6 ] (2),z which contains two NiS 4 units, four trigonal-planar CuI 2 S and two tetrahedral CuI 2 S 2 sites.…”

Nickel Thiolate Complexes as Ligands for Copper and Zinc: Novel Additions to a Library of Binding Modes

“…These nickel ions are in a square-planar geometry with a small tetrahedral distortion defined by a dihedral angle of 5.44(7)°between the planes Ni(1)-S(6)-S(9) and Ni(1)-S(16)-S (19). The bonds of the thioether sulfur atoms and the thiolate sulfur atoms to Ni are slightly longer than in the parent nickel complex [Ni(xbsms)] [26] but are still unexceptional. Both thiolate sulfur atoms of the NiS 4 unit are bound as a chelating ligand to a single copper ion with one short Cu(2)-S(6) distance of 2.3010(12) Å and one long Cu(2)-S(16) distance of 2.6229(9) Å.…”

“…However, the molecule contains an approximate, non-crystallographic threefold rotation axis running through the apical copper ions that makes the differences between the three nickel ions, the three equatorial copper ions Cu eq and the two tetrahedrally coordinated copper ions Cu ap very small. The nickel-thiolate distances vary from 2.082 (17) [26] The Cu eq -thiolate distances vary from 2.2328(19) to 2.2775(18) Å, whereas the Cu ap -thiolate distances are slightly longer and vary from 2.3204(18) to 2.3548(18) Å. The Cu eq -iodide distances are 2.4860(10)-2.4903(10) Å and the Cu ap -iodide distances are 2.5775(9)-2.5801(9) Å.…”

“…[17][18][19] Recently, we have reported the mononuclear complexes [Ni(bsms) 2 ] and [Ni(xbsms)] in which the nickel ion is in an S 4 coordination environment [H 2 xbsms = α,αЈ-bis(4-mercapto-3,3-dimethyl-2-thiabutyl)-o-xylene; Hbsms = 4-mercapto-3,3-dimethyl-1-phenyl-2-thiabutane]. [26] The reactivity of these mononuclear complexes towards nickel and iron has been studied and the trinuclear nickel complexes [Ni 3 [15,27] The reactivity of these complexes towards copper(I) and zinc(II) salts has now been investigated, resulting in a number of novel aggregates with unprecedented structures that are described below.…”