Anti-Bredt N-heterocyclic carbene: an efficient ligand for the gold(I)-catalyzed hydroamination of terminal alkynes with parent hydrazine.

An anti-Bredt N-heterocyclic carbene gold(I) chloride complex was synthesized by taking advantage of the reversible insertion of the free carbene into the NH bond of hexamethyldisilazane. This precatalyst promotes the parent hydrazine hydroamination of terminal alkynes at room temperature.

The oxidative conversion of the N,S-bridged complexes [{RhLL'(µ-X)}2] to [(RhLL')3)(µ-X)2]+ (X = mt or taz): a comparison with the oxidation of N,N-bridged analogues.

The structures of [{RhLL'(µ-X)}(2)] [LL' = cod, (CO)(2), (CO)(PPh(3)) or {P(OPh)(3)}(2); X = mt or taz], prepared from [{RhLL'(µ-Cl)}(2)] and HX in the presence of NEt(3), depend on the auxiliary ligands LL'. The head-to-tail arrangement of the two N,S-bridges is accompanied by a rhodium-eclipsed conformation for the majority but the most hindered complex, [{Rh[P(OPh)(3)](2)(µ-taz)}(2)], uniquely adopts a sulfur-eclipsed structure. The least hindered complex, [{Rh(CO)(2)(µ-mt)}(2)], shows intermolecular stacking of mt rings in the solid state. The complexes [{RhLL'(µ-X)}(2)] are chemically oxidised to trinuclear cations, [(RhLL')(3)(µ-X)(2)](+), most probably via reaction of one molecule of the dimer, in the sulfur-eclipsed form, with the fragment [RhLL'](+) formed by oxidative cleavage of a second.

Potassium S2N-heteroscorpionates: structure and iridaboratrane formation.

The potassium salts of the new S(2)N-heteroscorpionate ligand hydrobis(methimazolyl)(3,5-dimethylpyrazolyl)borate [HB(mt)(2)(pz(3,5-Me))](-) and its known analogue hydrobis(methimazolyl)(pyrazolyl)borate [HB(mt)(2)(pz)](-) (prepared from KTp' or KTp and methimazole, Hmt), and the adduct KTp·Hmt have polymeric structures in the solid state (the first a ladder and the other two chains). The iridaboratranes [IrHLL'{B(mt)(2)X}] (X = pz(3,5-Me) or pz), prepared from the heteroscorpionate anion and [{Ir(cod)(µ-Cl)}(2)] (LL' = cod), subsequent carbonylation [LL' = (CO)(2)] and then reaction with phosphine [LL' = (CO)(PR(3)), R = Ph or Cy], have a pendant pyrazolyl ring and a bicyclo-[3.3.0] cage formed by an S(2)-bound B(mt)(2) fragment. The binuclear species [(cod)HIr{µ-B(mt)(3)}IrCl(cod)], the only isolated product of the reaction of KTm with [{Ir(cod)(µ-Cl)}(2)], also has an S(2)-bound iridaboratrane unit but with the third mt ring linked to square planar iridium(I).

Fluxional rhodium scorpionate complexes of the hydrotris(methimazolyl)borate (Tm) ligand and their static boratrane derivatives.

The reaction of potassium hydrotris(methimazolyl)borate {KTm = HB(mt)(3)} with [{Rh(cod)(mu-Cl)}(2)] gave [Rh(cod)Tm] while the complexes [Rh(CO)(PR(3))Tm] (R = Ph or NMe(2)) and [Rh{P(OPh)(3)}(2)Tm] were isolated from light-sensitive [Rh(CO)(2)Tm], prepared in situ from KTm and [{Rh(CO)(2)(mu-Cl)}(2)], and PR(3) or P(OPh)(3) under CO. The complexes [Rh(cod)Tm] and [Rh(CO)(PR(3))Tm] (R = Ph or NMe(2)) adopt kappa(3)-S(2)H structures in the solid state but in all cases rapid dynamic exchange processes render the three mt rings equivalent in solution. Oxidation of [Rh(CO)(PPh(3))Tm] with [Fe(eta-C(5)H(5))(2)][PF(6)] in the presence of NHPr(i)(2) gave a mixture containing two monocationic rhodaboratranes. One is assigned as [Rh(CO)(PPh(3)){B(mt)(3)}][PF(6)] on the basis of IR and NMR spectroscopy, with boron trans to the phosphine ligand. The second, structurally characterised as [Rh(PPh(3)){B(mt)(3)}][PF(6)], has boron trans to an empty coordination site, vacated by CO. Similar oxidation of [Rh(cod)Tm] gave small quantities of the boron-fluorinated bis(scorpionate) [Rh{FB(mt)(3)}(2)][PF(6)].

Photocontrolled ring-opening polymerization of strained dicarba[2]ferrocenophanes: a route to well-defined polyferrocenylethylene homopolymers and block copolymers.

The ring-opening polymerization (ROP) behavior of a variety of substituted 1,1'-ethylenylferrocenes, or dicarba[2]ferrocenophanes, is reported. The electronic absorption spectra and tilted solid-state structures of the monomers rac-[Fe(eta(5)-C(5)H(4))(2)(CHiPr)(2)] (7), [Fe(eta(5)-C(5)H(4))(2)(C(H)MeCH(2))] (8), and rac-[Fe(eta(5)-C(5)H(4))(2)(CHPh)(2)] (9) are consistent with the presence of substantial ring strain, which was exploited to synthesize soluble, well-defined polyferrocenylethylenes (PFEs) [Fe(eta(5)-C(5)H(4))(2)(C(H)MeCH(2))](n) (12) and [Fe(eta(5)-C(5)H(4))(2)(CHPh)(2)](n) (13) through photocontrolled ROP. Polymer chain lengths could be controlled by the monomer-to-initiator ratio up to about 50 repeat units and, consistent with the "living" nature of the polymerizations, sequential block copolymerization with a sila[1]ferrocenophane led to polyferrocenylethylene-polyferrocenylsilane (PFE-b-PFS) block copolymers (14 and 15). PFE polymers 12 and 13 showed two reversible oxidation waves, indicative of appreciable FeFe interactions along the polymer backbone. The diblock copolymers were characterized by NMR spectroscopy, GPC analysis, and cyclic voltammetry.