Organometallic chemistry of selected third row metal complexes

A series of neutral platinum(IV) carboxamido complexes of the type Tp&feet;PtMe 2(C=O)NHR have been prepared via nucleophilic attack by a series of amide ions at the carbonyl carbon of Tp&feet;Me(CO) and subsequent addition of methyl iodide. Deprotonation of the carboxamido nitrogen atom, and subsequent acidification results in the formation of Tp&feet;Me2H by eliminating free isocyanate along the reaction pathway. Likewise, addition of methyl iodide upon deprotonation generates the corresponding Tp&feet;PtMe3 complex. This reaction sequence has shown promise as a recyclable route to synthesizing isocyanates from amines, as the Tp&feet;Me2H product is a precursor for the Tp&feet;Me(CO) starting material. Although a preliminary mechanism has been proposed, further studies on the mechanism of isocyanate elimination may provide additional insight into the analogous elimination of carbon dioxide in the water gas shift reaction.;Several square-planar platinum(II) aminotroponimate (ATI) complexes have been synthesized. The Pt(II) complex (N-tolyl-ATI)Pt(CH3)(&eegr; 2-C2H4) was synthesized via addition of ethylene to a mixture of [Li]+[N-tolyl-ATI]- and (Me)(Cl)Pt(SMe2)2 in THF, while (N-tolyl-ATI)Pt(Cl)(&eegr;2-C2H 4) was synthesized from the reaction of [Pt2(&eegr;2-C2H4)2(&mgr;-Cl)2Cl2] with [Li]+[N-tolyl-ATI]- in THF. Oxidative addition of MeOTf to (N-tolyl-ATI)Pt(CH 3)(n2-C2H4), and subsequent elimination of ethane presumably resulted in an equilibrium mixture of (N-tolyl-ATI)Pt(&eegr; 2-C2H4)(OTf) and its cationic aqua analogue, [(N-tolyl-ATI)Pt(&eegr;2-C2H4)(OH 2)][OTf]. Likewise, halide abstraction from (N-tolyl-ATI)Pt(Cl)(&eegr; 2-C2H4) with AgOTf resulted in the same equilibrium mixture.;The reaction of the neutral ATI ligand with Me4Pt2(&mgr;-SMe 2)2 in a solvent mixture containing n-pentane resulted in C-H activation of the solvent, followed by beta-hydride elimination to form a mixture of the dehydrogenation product (N-tolyl-ATI)Pt(H)(1-pentene) and (N-tolyl-ATI)PtMe(SMe2) byproduct. Attempts at exchanging the 1-pentene adduct with ethylene were unfruitful. Additionally, the complex (cod)PtMe 2 was capable of metallating the neutral ATI ligand, generating the downstream products, (N-tolyl-ATI)PtMe(CH3CN) and (N-tolyl-ATI)PtMe(py), with solvent incorporated into the coordination sphere. However, no C-H activation was observed utilizing alkane solvents.;The complexes W(acac)2(CO)(CNR)2[R = tBu; 2,6-dimethylphenyl] were synthesized successfully from W(CO)(acac)2(&eegr; 2-N≡CPh) via displacement of the &eegr;2-nitrile adduct with two equivalents of isocyanide. Attempts to induce C-C coupling or cross-coupling in the bis-isocyanide complexes utilizing various reducing agents, ranging from Zn(s) to sodium benzophenone, were unsuccessful. Different Lewis acids, including TMS reagents, were also employed in an effort to drive the reactions by taking advantage of the stability of Si-O or Si-N bonds in the proposed products. None of these conditions were found to initiate formation of an acetylene adduct, instead resulting only in decomposition of the acac ligands.