First X-ray structures and metal oxidation state dependence on cage isomerism for U-EMFs.

The synthesis and characterization of a series of novel iron complexes has been accomplished using a monoanionic pincer bis­(carbene) ligand framework. Metalation first proceeded through an isolated Fe­(II) zwitterionic intermediate that was subsequently reduced in situ to Fe(0) to facilitate oxidative addition of the aryl C–H bond, generating the FeII–H complexes. Varying the L-type ligand on these complexes exhibited profound effects, as observed by IR and 1H NMR spectroscopy. Higher oxidation states of Fe could also be supported in this ligand framework, as evidenced by the isolation of two Fe­(III) complexes. Treating an FeII–H complex with CO2 generated an Fe–formate complex (κ2-OOCH) from insertion into the FeII–H bond. The independent synthesis of this molecule was accomplished by treating FeII–Cl with excess NaOOCH.

Herein we report the synthesis and characterization of a linear, two-coordinate Pt(II) ketimide complex, Pt(N=C t Bu2)2 (1), formed via reaction of PtCl2(1,5-COD) with 2 equiv of Li(N=C t Bu2). Also generated in the reaction is the bimetallic complex, [(t Bu2C=N)Pt(µ-N,C-N=C(t Bu)C(Me)2CH2)Pt(N=C t Bu2)] (2). Both complexes 1 and 2 have been characterized by NMR spectroscopy and X-ray crystallography. Notably, complex 1 exhibits short Pt-N distances (av. Pt-N = 1.817 Å) and an unusually deshielded 195 Pt chemical shift (δPt =-629 ppm) with a large 1 J(195 Pt, 14 N) coupling constant (537 Hz). These data, in combination with a detailed DFT electronic structure analysis, reveal the presence of highly covalent Pt=N multiple bonds formed by a combination of σ-donation, π-donation, and π-backdonation.

γ-Agostic interactions in(MesCCC)Fe–Mes(L) complexes were observed in the crystal structures, NMR data, and DFT calculations.

No abstract