Control of S-based aggregation: designed synthesis of NiM2 and Ni2M trinuclear complexes.

Modification of the nickel dithiolate metalloligand, Ni(bme-daco) [where bme-daco = bis(mercaptoethyl)diazacyclooctane] or Ni-1, by oxygenation of one thiolate into a sulfinate, Ni(mese-daco) [where mese-daco = (mercaptoethyl)(sulfinatoethyl)diazacyclooctane] or Ni-2, restricts the ligating ability to monodentate and is expected to reduce the donor ability of the remaining thiolate S. Nevertheless, the Ni-2 complex forms a stable thiolate S-bound adduct of W0(CO)5, (Ni-2)W(CO)5, a complex whose upsilon(CO) IR spectrum reports insignificant differences in the donor abilities of Ni-1 and Ni-2 in (eta1-NiN2S2)W(CO)5 complexes. In the presence of the strong sulfophile CuI, a CuNi2 trimetallic, (Ni-2)2CuBr, was isolated.

NiN(2)S(2) complexes as metallodithiolate ligands to Rh(I), Rh(II) and Rh(III).

Three molecular structures are reported which utilize the NiN(2)S(2) ligands -, (bis(mercaptoethyl)diazacyclooctane)nickel and -', bis(mercaptoethyl)diazacycloheptane)nickel, as metallodithiolate ligands to rhodium in oxidation states i, ii and iii. For the Rh(I) complex, the NiN(2)S(2) unit behaves as a bidentate ligand to a square planar Rh(I)(CO)(PPh(3))(+) moiety with a hinge or dihedral angle (defined as the intersection of NiN(2)S(2) and S(2)Rh(C)(P) planes) of 115 degrees . Supported by -' ligands, the Rh(II) oxidation state occurs in a dirhodium C(4) paddlewheel complex wherein four NiN(2)S(2) units serve as bidentate bridging ligands to two singly-bonded Rh(II) ions at 2.

A nickel tripeptide as a metallodithiolate ligand anchor for resin-bound organometallics.

The molecular structure of the acetyl CoA synthase enzyme has clarified the role of individual nickel atoms in the dinickel active site which mediates C-C and C-S coupling reactions. The NiN2S2 portion of the biocatalyst (N2S2 = a cysteine-glycine-cysteine or CGC4- tripeptide ligand) serves as an S-donor ligand comparable to classical bidentate ligands operative in organometallic chemistry, ligating the second nickel which is redox and catalytically active. Inspired by this biological catalyst, the synthesis of NiN2S2 metalloligands, including the solid-phase synthesis of resin-bound Ni(CGC)2-, and sulfur-based derivatization with W(CO)5 and Rh(CO)2+ have been carried out.

Characterization of steric and electronic properties of NiN2S2 complexes as S-donor metallodithiolate ligands.

The physical properties and structures of a series of six complexes of the type (NiN(2)S(2))W(CO)(4) have been used to establish electronic and steric parameters for square planar NiN(2)S(2) complexes as bidentate, S-donor ligands. According to the nu(CO) stretching frequencies and associated computed Cotton-Kraihanzel force constants of the tungsten carbonyl adducts, there is little difference in donor abilities of the five neutral NiN(2)S(2) metallodithiolate ligands in the series. The dianionic Ni(ema)(2)(-) (ema = N,N'-ethylenebis(2-mercaptoacetamide)) complex transfers more electron density onto the W(CO)(4) moiety.

Metallodithiolato ligands as bridges in multiply bonded dimolybdenum complexes.

For the first time, a NiN2S2 metallothiolate ligand is used as a bidentate bridging ligand for a multiply bonded dimetal unit.