RESUMEN
Iron(II) complexes containing ligands with a R2 P-P-PR2 unit were synthesized by metathesis reactions. With R=tBu, a mixture of two isomers is formed; in one of them, the terminal phosphorus binds to the Fe center (ylidic structure), while in the other one, the central P atom is linked to Fe. Starting from differently functionalized parent triphosphanes and corresponding functionalized Fe complexes, the ratio of isomers does not change. The outcome of the reaction and therefore the binding modes of the triphosphane ligands in the resulting compounds can be influenced by the size of the substituents. In the case of R=iPr a chelate complex is formed (both terminal P atoms are linked to the Fe center). Applying the mixed-substituted triphosphane, the ylidic structure of the resulting complex is preferred. The new compounds were characterized by NMR spectroscopy in solution and single-crystal X-ray diffraction in solid-state. The synthetic work was supported by DFT calculations.
RESUMEN
The influence of substituents on α-borylated phosphorus ylides (α-BCPs) has been investigated in a combined experimental and quantum chemical approach. The synthesis and characterization of Me3 PC(H)B(iBu)2 (1), consisting of small Me substituents on phosphorous and iBu residues on boron, is reported. Compound 1 is accessible through a novel synthetic approach, which has been further elucidated through DFT studies. The reactivity of 1 towards various small molecules was probed and compared with that of a previously published derivative, Ph3 PC(Me)BEt2 (2). Both α-BCPs react with NH3 to undergo heterolytic N-H bond cleavage. Different di- and trimeric ring structures were observed in the reaction products of 1 with CO and CO2 . With PhNCO and PHNCS, the expected insertion products [Me3 PC(H)(PhNCO)B(iBu)2 ] and [Me3 PC(H)(PhNCS)B(iBu)2 ], respectively, were isolated.