Synthesis, structures, and electrochemistry of group 6 aminocarbenes with a P-chelating 1'-(Diphenylphosphino)ferrocenyl substituent

Ferrocene amides Ph(2)PfcC(O)NR2 (1; fc = ferrocene-1,1'-diyl, NR2 = NEt2 (a), morpholin-4-yl (b)) react with [Cr(CO)(5)](2-) in the presence of Me3SiCl to give easily separable mixtures of the respective P-chelated carbene [Cr(CO)(4)(Ph(2)PfcC(NR2)-kappa(2)C(1),P)] (2) and a phosphine complex, [Cr(CO)(5)(1-kappaP)] (3). A similar reaction between la and [W(CO)(5)](2-) is more complex, affording a mixture of the nonchelated carbene [Cr(CO)(4){Ph(2)PfcC(NEt)(2-)kappaC(1)}] (5), trimetallic carbene [(mu-1kappaC(1),2kappaP-Ph(2)PfcC(NEt2)){W(CO)(5)}(2)] (6), and the phosphine complex [W(CO)(5)-{1a-kappaP}] (4). Removal of 4 by chromatography and heating the mixture of 5 and 6 in toluene gives another mixture containing carbene analogous to 2, [W(CO)(4)(Ph(2)PfcC(NEt2)-kappa(2)C(1),P)] (7), unreacted 6, and [W(CO)(5){Ph(2)PfcCHO-kappaP}] (8) as a decomposition product. In contrast, the reaction of la with the iron carbonylate [Fe(CO)(4)](2-) under identical conditions yields solely [Fe(CO)(4){1a-kappaP}] (9). All compounds except for 5 were isolated and characterized by spectral methods. The structures of 2a(.)CH(2)Cl(2), 2b, 6(.)CHCl(3), 7, and 9 were determined by single-crystal X-ray diffraction. An electrochemical study showed that whereas compounds 1 and 3 behave as a simple system (ferrocene) and two localized redox systems (ferrocene and chromium), respectively, carbenes 2 are electronically delocalized systems, where the redox changes probably occur in the whole molecule.