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4319224 
Journal Article 
C-2-Symmetric Iron(II) Diphosphine-Dialkoxide Dicarbonyl and Related Complexes 
Lei, Hao; Royer, AM; Rauchfuss, TB; Gray, D 
2012 
1 
Organometallics
ISSN: 0276-7333
EISSN: 1520-6041 
31 
17 
6408-6414 
English 
WOS:000308513000054 
Reaction of Fe(bda)(CO)(3) (bda = benzylideneacetone) and Ph2P-2-C6H4CHO (PCHO) affords the bisphosphine bisalkoxide complex Fe[(Ph2PC6H4)(2)C2H2O2](CO)(2) (1) arising from the head-to-head coupling of two formyl groups concomitant with oxidation of Fe(0) to Fe(II). Crystallographic studies show that 1 features cis alkoxide ligands that are trans to CO; the two phosphine groups are mutually trans with a P-Fe-P angle of 167.44(4)degrees. The pathway leading to 1 was examined, starting with the adduct Fe(PCHO)(CO)(4) (2), which was obtained by addition of PCHO to Fe-2(CO)(9). Compound 2 decarbonylates to give tricarbonyl Fe(kappa(1),eta(2)-PCHO)(CO)(3) (3), which features a pi-bonded aldehyde. Photolysis of 2 gives a mixture of 3 and isomeric hydride HFe(kappa(2)-PCO)(CO)(3). Complex 3 reacts with an additional equivalent of PCHO to afford 1, whereas treatment with PPh3 afforded the substituted product Fe(kappa(1),eta(2)-PCHO)(PPh3)(CO)(2) (4). In 4, the phosphine ligands are trans and the aldehyde is pi-bonded. The geometry around Fe is pseudo trigonal bipyramidal. To gain insights into the mechanism and scope of the C C coupling reaction, complexes were prepared with the imine Ph(2)PC(6)H4CH=NC6H4Cl (abbreviated as PCHNAr), derived by condensation of 4-chloroaniline and PCHO. PCHNAr reacts with Fe-2(CO)(9) and with Fe(bda)(CO)(3) to afford the tetra- and tricarbonyl compounds Fe(PCHNAr)(CO)(4) (5) and Fe(PCHNAr)(CO)(3) (6), respectively. Treatment of 6 with PCHO gave the unsymmetrical C C coupling complex Fe[(Ph2PC6H4)(2)CH(O)CH(NAr)]-(CO)(2) (7). Compound 7 was also prepared by the reaction of 3 and PCHNAr. The solid-state structure of 7, as established by X-ray crystallography, is similar to that of 1 but with an amido group in place of one alkoxide. The deuterium-labeled phosphine aldehyde PCDO was prepared by the reaction of ortho-lithiated phosphine Ph2PC6H4-2-Li with DMF-d(7). Reaction of 6 with PCDO gave 7-d(1) with no scrambling of the deuterium label. Attempted oxidation of 1 with FcBF(4) (Fc(+) = ferrocenium) gave the adduct Fe[(Ph2PC6H4)(2)C2H2O2(BF3)(2)](CO)(2) (8). The structures of 1 and 8 are almost identical. Compound 8 was independently synthesized by treating 1 with BF3OEt2 via the intermediacy of the 1:1 adduct, which was detected spectroscopically. Qualitative tests showed that 1 also reversibly protonates with HOSO2CF3 and binds TiCl4.