Combined experimental and computational investigations of rhodium-catalysed C - H functionalisation of pyrazoles with alkenes.

Detailed experimental and computational studies have been carried out on the oxidative coupling of the alkenes C2 H3 Y (Y=CO2 Me (a), Ph (b), C(O)Me (c)) with 3-aryl-5-R-pyrazoles (R=Me (1 a), Ph (1 b), CF3 (1 c)) using a [Rh(MeCN)3 Cp*][PF6 ]2 /Cu(OAc)2 ⋅H2 O catalyst system. In the reaction of methyl acrylate with 1 a, up to five products (2 aa-6 aa) were formed, including the trans monovinyl product, either complexed within a novel Cu(I) dimer (2 aa) or as the free species (3 aa), and a divinyl species (6 aa); both 3 aa and 6 aa underwent cyclisation by an aza-Michael reaction to give fused heterocycles 4 aa and 5 aa, respectively. With styrene, only trans mono- and divinylation products were observed, whereas with methyl vinyl ketone, a stronger Michael acceptor, only cyclised oxidative coupling products were formed.

Combined experimental and computational investigations of rhodium- and ruthenium-catalyzed C-H functionalization of pyrazoles with alkynes.

Detailed experimental and computational studies are reported on the mechanism of the coupling of alkynes with 3-arylpyrazoles at [Rh(MeCN)3Cp*][PF6]2 and [RuCl2(p-cymene)]2 catalysts. Density functional theory (DFT) calculations indicate a mechanism involving sequential N-H and C-H bond activation, HOAc/alkyne exchange, migratory insertion, and C-N reductive coupling. For rhodium, C-H bond activation is a two-step process comprising κ(2)-κ(1) displacement of acetate to give an agostic intermediate which then undergoes C-H bond cleavage via proton transfer to acetate.

Bis(imino)quaterpyridine-bearing multimetallic late transition metal complexes as ethylene oligomerisation catalysts.

The bis(imino)quaterpyridine, 6,6'''-{(2,4,6-i-Pr(3)C(6)H(2))N=CMe}(2)-2,2':6',2'':6'',2'''-C(20)H(12)N(4) (L(tripp)), can be prepared in good yield by the condensation reaction of 6,6'''-bis(acetyl)quaterpyridine with 2,4,6-triisopropylaniline; the 2,6-diisopropylphenyl derivative 6,6'''-{(2,6-i-Pr(2)C(6)H(3))N=CMe}(2)-2,2':6',2'':6'',2'''-C(20)H(12)N(4) (L(dipp)) is also reported. Reactions of L(tripp) with 2.5 equivalents of MX(2) (MX(2) = CoCl(2), CoBr(2), (DME)(2)NiCl(2) and FeCl(2)) in n-butanol at 100 degrees C overnight results in self-assembly to form the paramagnetic salts [(L(tripp))M(2)X(3)](2)[MX(4)] [M = Co, X = Cl (1a); M = Co, X = Br (1b); M = Ni, X = Cl (2); M = Fe X = Cl (3)] in moderate yield.