C 2-symmetric iron(II) diphosphine-dialkoxide dicarbonyl and related complexes

Hao Lei; Aaron M. Royer; Thomas B. Rauchfuss; Danielle Gray

doi:10.1021/om300631a

C ₂-symmetric iron(II) diphosphine-dialkoxide dicarbonyl and related complexes

Hao Lei, Aaron M. Royer, Thomas B. Rauchfuss, Danielle Gray

Research output: Contribution to journal › Article › peer-review

Abstract

Reaction of Fe(bda)(CO) ₃ (bda = benzylideneacetone) and Ph ₂P-2-C ₆H ₄CHO (PCHO) affords the bisphosphine bisalkoxide complex Fe[(Ph ₂PC ₆H ₄) ₂C ₂H ₂O ₂](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)°. 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(κ ¹,η ²-PCHO)(CO) ₃ (3), which features a π-bonded aldehyde. Photolysis of 2 gives a mixture of 3 and isomeric hydride HFe(κ ²-PCO)(CO) ₃. Complex 3 reacts with an additional equivalent of PCHO to afford 1, whereas treatment with PPh ₃ afforded the substituted product Fe(κ ¹, η ²-PCHO)(PPh ₃)(CO) ₂ (4). In 4, the phosphine ligands are trans and the aldehyde is π-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 ₂PC ₆H ₄CH=NC ₆H ₄Cl (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[(Ph ₂PC ₆H ₄) ₂CH(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 Ph ₂PC ₆H ₄-2-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[(Ph ₂PC ₆H ₄) ₂C ₂H ₂O ₂(BF ₃) ₂](CO) ₂ (8). The structures of 1 and 8 are almost identical. Compound 8 was independently synthesized by treating 1 with BF ₃OEt ₂ via the intermediacy of the 1:1 adduct, which was detected spectroscopically. Qualitative tests showed that 1 also reversibly protonates with HOSO ₂CF ₃ and binds TiCl ₄.

Original language	English (US)
Pages (from-to)	6408-6414
Number of pages	7
Journal	Organometallics
Volume	31
Issue number	17
DOIs	https://doi.org/10.1021/om300631a
State	Published - Sep 10 2012

ASJC Scopus subject areas

Physical and Theoretical Chemistry
Organic Chemistry
Inorganic Chemistry

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@article{4158e60d3f3b405ca05c9b2ff89a9c4e,

title = "C 2-symmetric iron(II) diphosphine-dialkoxide dicarbonyl and related complexes",

abstract = "Reaction of Fe(bda)(CO) 3 (bda = benzylideneacetone) and Ph 2P-2-C 6H 4CHO (PCHO) affords the bisphosphine bisalkoxide complex Fe[(Ph 2PC 6H 4) 2C 2H 2O 2](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)°. 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(κ 1,η 2-PCHO)(CO) 3 (3), which features a π-bonded aldehyde. Photolysis of 2 gives a mixture of 3 and isomeric hydride HFe(κ 2-PCO)(CO) 3. Complex 3 reacts with an additional equivalent of PCHO to afford 1, whereas treatment with PPh 3 afforded the substituted product Fe(κ 1, η 2-PCHO)(PPh 3)(CO) 2 (4). In 4, the phosphine ligands are trans and the aldehyde is π-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 2PC 6H 4CH=NC 6H 4Cl (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[(Ph 2PC 6H 4) 2CH(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 Ph 2PC 6H 4-2-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[(Ph 2PC 6H 4) 2C 2H 2O 2(BF 3) 2](CO) 2 (8). The structures of 1 and 8 are almost identical. Compound 8 was independently synthesized by treating 1 with BF 3OEt 2 via the intermediacy of the 1:1 adduct, which was detected spectroscopically. Qualitative tests showed that 1 also reversibly protonates with HOSO 2CF 3 and binds TiCl 4.",

author = "Hao Lei and Royer, {Aaron M.} and Rauchfuss, {Thomas B.} and Danielle Gray",

year = "2012",

month = sep,

day = "10",

doi = "10.1021/om300631a",

language = "English (US)",

volume = "31",

pages = "6408--6414",

journal = "Organometallics",

issn = "0276-7333",

publisher = "American Chemical Society",

number = "17",

}

TY - JOUR

T1 - C 2-symmetric iron(II) diphosphine-dialkoxide dicarbonyl and related complexes

AU - Lei, Hao

AU - Royer, Aaron M.

AU - Rauchfuss, Thomas B.

AU - Gray, Danielle

PY - 2012/9/10

Y1 - 2012/9/10

N2 - Reaction of Fe(bda)(CO) 3 (bda = benzylideneacetone) and Ph 2P-2-C 6H 4CHO (PCHO) affords the bisphosphine bisalkoxide complex Fe[(Ph 2PC 6H 4) 2C 2H 2O 2](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)°. 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(κ 1,η 2-PCHO)(CO) 3 (3), which features a π-bonded aldehyde. Photolysis of 2 gives a mixture of 3 and isomeric hydride HFe(κ 2-PCO)(CO) 3. Complex 3 reacts with an additional equivalent of PCHO to afford 1, whereas treatment with PPh 3 afforded the substituted product Fe(κ 1, η 2-PCHO)(PPh 3)(CO) 2 (4). In 4, the phosphine ligands are trans and the aldehyde is π-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 2PC 6H 4CH=NC 6H 4Cl (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[(Ph 2PC 6H 4) 2CH(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 Ph 2PC 6H 4-2-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[(Ph 2PC 6H 4) 2C 2H 2O 2(BF 3) 2](CO) 2 (8). The structures of 1 and 8 are almost identical. Compound 8 was independently synthesized by treating 1 with BF 3OEt 2 via the intermediacy of the 1:1 adduct, which was detected spectroscopically. Qualitative tests showed that 1 also reversibly protonates with HOSO 2CF 3 and binds TiCl 4.

AB - Reaction of Fe(bda)(CO) 3 (bda = benzylideneacetone) and Ph 2P-2-C 6H 4CHO (PCHO) affords the bisphosphine bisalkoxide complex Fe[(Ph 2PC 6H 4) 2C 2H 2O 2](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)°. 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(κ 1,η 2-PCHO)(CO) 3 (3), which features a π-bonded aldehyde. Photolysis of 2 gives a mixture of 3 and isomeric hydride HFe(κ 2-PCO)(CO) 3. Complex 3 reacts with an additional equivalent of PCHO to afford 1, whereas treatment with PPh 3 afforded the substituted product Fe(κ 1, η 2-PCHO)(PPh 3)(CO) 2 (4). In 4, the phosphine ligands are trans and the aldehyde is π-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 2PC 6H 4CH=NC 6H 4Cl (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[(Ph 2PC 6H 4) 2CH(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 Ph 2PC 6H 4-2-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[(Ph 2PC 6H 4) 2C 2H 2O 2(BF 3) 2](CO) 2 (8). The structures of 1 and 8 are almost identical. Compound 8 was independently synthesized by treating 1 with BF 3OEt 2 via the intermediacy of the 1:1 adduct, which was detected spectroscopically. Qualitative tests showed that 1 also reversibly protonates with HOSO 2CF 3 and binds TiCl 4.

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