Unusual C–H bond activation—aldol condensation of aromatic aldehydes with the methyl group of a carbene-like triosmium cluster

Abstract

An unusual example of C-H bond activation in transition metal clusters is represented by the carbene-like aldol condensation of aromatic aldehydes with the organic ligand methyl group of a trinuclear osmium complex.

Triosmium compounds containing the oxametallacycle [Os(CO)3{C(R)CHC(O)CHC(H)C5H4FeC5H5}] moiety. Synthesis and electrochemical studies

“…1 depicts a view of the molecule of the major enantiomer. The C(11)-C (12) [1.341(5) Å ] and C(14)-C (15) [8] and [HOs 3 -(CO) 10 (g 3 ,g 1 ,g 1 -OC 4 H 2 CCHCHPh)] [9]. The coordination to one osmium atom of the ketonic group to generate a metallafurene, was observed by IR spectroscopy in KBr pellets (m C@O 1618 cm À1 ).…”

“…The new organic ligand oxidatively adds to the Os(1) atom towards an r-C coordination and to the Os(2) and Os (3) atoms towards a thiolate ligand. The S(1) atom bridges the two osmium atoms almost symmetrically [Os(2)-S(1) 2.4363 (9) and Os(3)-S(1) 2.4174(9) Å ]. In addition, the coordination of the ketonic group by an r-O bond to the Os(1) atom gives rise to a five-membered oxametallacycle.…”

“…In addition to compound 2 a small amount of the new compound [Os 3 (CO) 9 {l,g 3 -(SCH 2 CH 2 SC@CHC(O)CH @CH(C 5 H 4 )Fe(C 5 H 5 )}] (3) was separated as a second band by TLC. Analytical data as well as the presence in the FAB mass spectrum of the molecular peak (m/z 1179) and other peaks corresponding to the loss of nine carbonyls are in agreement with this formula.…”

The chemistry of the carbon–transition metal double and triple bond: annual survey covering the year 2002

“…Other studies of carbene complexes in this category are depicted in Scheme 68, and include: (1) formation of an aldol-like product (626) from the base-free coupling of triosmium carbene complex 625 with aldehydes [569]; and (2) [2+2]-cycloaddition reaction between ruthenium acetylides (e.g. 627) and tetracyanoethylene followed by opening to give a dienylruthenium species (e.g.…”

Interaction of 2-(2′,6′-dialkylphenylazo)-4-methylphenols with iridium. C–H activation and migration of alkyl group

“…Although an ortho methyl group in ligand L 1 was observed to undergo interesting elimination [53], migration [51] and oxidative migration [50], such a metal-carbon bond formation via methyl C-H bond activation of ligand L 1 was not experienced. It is also noteworthy that methyl C-H activation is less common than phenyl C-H activation [54][55][56][57][58][59][60][61][62]. This interesting reactivity of L 1 has prompted us to scrutinize reactions of two related 2-(2 0 ,6 0 -dialkylphenylazo)-4-methylphenols (L 2 and L 3 ) with iridium.…”