Compounds with Heteroatom Five-membered Ring Ligands

1 Compounds with Heteroatom Five-membered Ring Ligands 

Samarium chemistry with polydentate pyrrolyl ligands is also very diverse. Divalent and trivalent dinuclear samarium complexes supported by pyrrole-based tetradentate Schiff bases720 as well as Ln(n) and Ln(lll) meso- 

A reversible fixation of ethylene at a samarium center in a calixpyrrol-samarium complex has also been reported. Reduction of the Sm(m) complexes [(R8-calixpyrrol)ClSm Li(THF) 2 Li(THF)2 (/t3-Cl)] (R = Et or j-(CH2)5-(0.s) 

Like the decamethyllanthanidocenes, the bis(phospholyl)lanthanide(ll) sandwich complexes exhibit an interesting derivative chemistry. For example, addition of azobenzene to the samarium(ll) and thulium(ll) complexes resulted in 

Further treatment of Sc(P3C2But)3 with KCg in toluene at low temperature (—78 °C) produced a very deep blue solution, the color of which persisted at room temperature. Sublimation of the residue after removal of the volatiles gave very dark blue crystals of [Sc(P3C2But)2] containing formally divalent scandium. The complex is dimeric in the solid state and should best be described as a mixed oxidation state complex containing both Sc1 and Scm centers.733,73311 

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Intramolecular carbon-hydrogen insertion reactions have well known to be elTectively promoted by dirhodium(ll) catalysts [19-23]. Insertion into the y-position to form five-membered ring compounds is virtually exclusive, and in competitive experiments the expected reactivity for electrophilic carbene insertion (3°>2° 1°) is observed [49], as is heteroatom activation [50]. A recent theoretical treatment [51] confirmed the mechanistic proposal (Scheme 15.4) that C-C and C-H bond formation with the carbene carbon proceeds in a concerted fashion as the ligated metal dissociates [52]. Chemoselectivity is dependent on the catalyst ligands [53]. 

N-Substituents in hetarylazomethine ligands are represented by three-and five-membered rings with one heteroatom as well as azole and azine heterocycles. They may not always participate in the formation of metallacycles and thus play the role of coordination-active or inactive constituents of the hetarylazomethine ligands. A great majority of coordination compounds includes mononuclear complexes, although di- and oligonuclear structures are also known. 

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