Fluorotrithiophosphate Abstraction from the Difluoropentathiodiphosphate Dianion: d8 and d6 Complexes of [η2-S3PF]2.

Coordinative heterolysis of the difluoropentathiodiphosphate dianion [S5P2F2]2- results in the formal elimination of [S2PF] by complexes of the group 10 divalent metals nickel, palladium, and platinum. The remaining fragment of this cleavage, [S3PF]2- coordinates as an η2-ligand. Several complexes with this novel fluorotrithiophosphate were characterized structurally and spectroscopically with X-ray diffraction (XRD), infrared (IR) spectroscopy, and 31P and 19F nuclear magnetic resonance (NMR). In addition to mononuclear η2 chelate complexes, bridging complexes with η2-µ2-S3PF configurations result in binuclear nickel and ruthenium adducts. Facile methylation with methyl triflate of the uncoordinated sulfur atom leads to a complex with the methylthiofluorodithiophosphate ligand in a cationic complex, which hydrolyses with loss of fluoride to give complexed [S2P(O)SMe]2-. Alternatively hydrolysis can also lead to a binuclear Ni2(dppe)2(S3PF)(S2POF) complex. Divalent ruthenium π-aryl's form fluorotrithiophosphate complexes rapidly at room temperature to give bridged dimers with complete chloride substitution.

The Sulfur Rich Fluorothiophosphate Dianions [S5 P2 F2 ]2- and [S3 PF]2- : Cluster and Chelation Control of P-S Heterolysis.

The sulfur rich difluoropentathiodiphosphate dianion [S5 P2 F2 ]2- , from fluoride addition to P4 S10 , has a somewhat checkered history and proves to be the main product of the reaction in acetonitrile. Its optimized synthesis, and structural characterization, as either a tetraphenylphosphonium or a tetrapropylammonium salt, [Nn Pr4 ]2 [S5 P2 F2 ] allows for the first coordination chemistry for this dianion. Reactions of [S5 P2 F2 ]2- with d10 metal ions of zinc(II), and cadmium(II), and d9 copper(II) resulted in a surprising diverse array of binding modes and structural motifs. In addition to the simple bis-chelate coordination of [S5 P2 F2 ]2- with zinc, cleavage of the P-S bond resulted in complexes with the unusual [S3 PF]2- fluorotrithiophosphate dianion. This was observed in two cluster complexes: a trinuclear cadmium complex with mixed [S5 P2 F2 ]2- /[S3 PF]2- ligands, [Cd3 (S5 P2 F2 )3 (S3 PF)2 ]4- as well as an octanuclear copper cluster, [Cu8 (S3 PF)6 ]4- which form rapidly at room temperature. These new metal/sulfur/ligand clusters are of relevance to understanding multimetal binding to metallothionines, and to potential capping strategies for the condensed nanoparticulate cadmium chalcogenide semiconductors CdS and CdSe.

Coordination Chemistry of the Parent Dithiocarbamate H2NCS2-: Organometallic Chemistry and Tris-Chelates of Group 9 Metals.

Two tris-chelate complexes of cobalt and rhodium and two complexes of Ru(II) of dithiocarbamate, [S2CNH2]-, were synthesized. The complexes were spectroscopically characterized by IR, NMR, UV-vis, and MS and structurally characterized by X-ray diffraction. The structural features of the rhodium complex were compared to those of other tris-chelate Rh(III) dithiocarbamate complexes and are characterized by a change in the ground-state geometry in comparison to expected octahedral tris-chelate complexes. This was confirmed both experimentally by X-ray diffraction and theoretically using DFT calculations. The inversion barriers of Rh(Bz2dtc)3, Ir(Bz2dtc)3, and Rh(Et2dtc)3 were determined using VT-NMR in DMSO. These barriers were found to be surprisingly low for heavy group 9 elements of d6 tris-chelate complexes: values of 16.7, 17.1, and 16.4 kcal/mol were calculated, respectively. By comparing structural features, we are able to determine that the activation barrier for the inversion of stereochemistry of Rh(H2dtc)3 must have a similarly low value. A modified version of the Bailar twist involving an intermediate with C3h geometry was proposed as the mechanism of inversion.

Separation of Isomers and Mechanisms of Inversion of Stereochemistry of Group 9 d6 Tris-Chelate Complexes of Hinokitiol.

Tris-chelate complexes of Co(III), Rh(III), and Ir(III) with 4-isopropyltropolone (hinokitiol or ß-thujaplicin) form by the substitution of carbonate and chloride ligands from group 9 trivalent metal salts. The new complexes are neutral, are readily soluble in most organic solvents, and are brightly colored with strong charge transfer bands. The fac isomers of Co(hino)3 and Rh(hino)3 were isolated from the mixture by fractional recrystallization from ethanol. The remaining mixtures were respectively enriched by 5:3 and 4.4:3 for the mer isomer. The 1H NMR data show that the complexes exhibit remarkable stereochemical lability, which is unusual for diamagnetic d6 group 9 metals, with rotational barriers of 14.2 and 18.2 kcal/mol found for the inversion of stereochemistry of Co(hino)3 and Rh(hino)3. The low activation barriers, as well as the analysis of some key structural parameters, suggest that the inversion of stereochemistry occurs via a trigonal-twist (Bailar) mechanism. Facile substitution of a single hinokitiol ligand in the cobalt complex with ethylenediamine to form [Co(en)(hino)2]Cl also indicates that the tris-chelates are substitutionally and configurationally labile.

Fluxionality in the Tropolone Hinokitiol Chelate.

Tropolonate complexes of Ru(II), Ru(III), and Os(II) with hinokitiol, also termed ß-thuljaplicin, or 4-isopropyltropolone, readily formed by chloride and triarylphosphine substitution in RuCl2(PPh3)3 and MHCl(CO)(PR3)3 (M = Ru, R = Ph; M = Os, R = Ph and p-tolyl). The resulting colorful complexes have variable and strong charge transfer bands and also have a surprising combination of stereochemical selectivity and lability. For the Os(II) d6 examples, the tropolone chelate has a fluxionality with a barrier of only 90 kJ/mol for the R = aryl examples, as determined by variable-temperature 31P NMR. Chlorination with N-chlorosuccinimide results in MCl(CO)(hino)(PPh3)2 (M = Ru and Os). Together these results quantify the fluxionality of this important chelate which in turn has consequences for its biochemistry.