Abstract:The molecule exhibits axial substitution of the ligand. N atoms in the ligand display planar geometry, with P-N bond lengths notably shortened.
“…Each complex possesses approximate C 3 v symmetry with the phosphine ligand occupying an axial position about the trigonal-bipyramidal iron, as expected, based on solution IR data and previously proposed π-back-bonding arguments . The P(1)−Fe(1)−C(1) angles for 7 , 9 , and 10 are 176.06(6)°, 174.48(10)°, and 178.64(11)°, respectively, and the Fe−C and C−O distances are similar to those commonly observed in axial-substituted Fe(CO) 4 (PR 3 ) complexes. ,,,− 2 (a) ORTEP drawing of Fe(CO) 4 ( 1 ) ( 7 ). Thermal ellipsoids are drawn at the 50% probability level.…”
Section: Resultssupporting
confidence: 80%
“…4 The P(1)-Fe(1)-C(1) angles for 7, 9, and 10 are 176.06(6)°, 174.48(10)°, and 178.64(11)°, respectively, and the Fe-C and C-O distances are similar to those commonly observed in axial-substituted Fe(CO) 4 (PR 3 ) complexes. 9,33,36,[38][39][40][41][42][43] The most striking feature of each structure is the short Fe-P bond distances of 7 (2.1539(5) Å), 9 (2.1970(8) Å), and 10 (2.1661(7) Å). Iron-phosphorus distances in axial-substituted Fe(CO) 4 (PR 3 ) complexes range 9,33,36,[38][39][40][41][42][43] from 2.158(3) Å in Fe(CO) 4 (ADPO) 33 to 2.364(1) Å in Fe(CO) 4 (P t Bu 3 ).…”
Variable-temperature (13)C NMR spectra for a series of Fe(CO)(4)(PR(3)) complexes ligated by phosphatri(3-methylindolyl)methane (1), phosphatri(pyrrolyl)methane (2), P(N-3-methylindolyl)(3) (3), and P(N-pyrrolyl)(3) (4) are reported. Ligand 2 was prepared by reaction of tri(pyrrolyl)methane with PCl(3) in THF and Et(3)N. Compound 2 is stable to methanolysis, hydrolysis, and aerial oxidation at room temperature. Reactions of 2 with selenium powder and Rh(acac)(CO)(2) yield phosphatri(pyrrolyl)methane selenide (5) and Rh(acac)(CO)(2) (6), respectively. The carbonyl stretching frequency in the IR spectrum of 6 and the magnitude of (1)J(Se)(-)(P) in the (31)P NMR spectrum of 5 indicate that 2 is a strong pi-acid and a weak sigma-base, commensurate with its lack of reactivity with CH(3)I. The trend in the decreasing basicity of 2 and related phosphines and phosphites was determined to be P(NMe(2))(3) > 3 > 4 > 1 > P(OPh)(3) > 2. IR data for a series of Rh(acac)(CO)(PR(3)) complexes indicate the trend in decreasing pi-acceptor ability to be 2 approximately 1 > 4 > P(OPh)(3) > 3 > PPh(3). Phosphines 1-4 were reacted with Fe(2)(CO)(9) to yield Fe(CO)(4)(1) (7), Fe(CO)(4)(2) (8), Fe(CO)(4)(3) (9), and Fe(CO)(4)(4) (10), respectively. IR data for 7-10 support the trend in pi-acidity listed above. Variable-temperature (13)C NMR spectra for compounds 8-10 show a single doublet resonance for the carbonyls in the temperature range from -80 to 20 degrees C indicative of rapid intramolecular rearrangement of carbonyls between axial and equatorial sites. However, the (13)C NMR spectrum for 7 shows slowed axial-equatorial carbonyl exchange at 20 degrees C. The limiting slow-exchange spectrum is observed at -20 degrees C. Hindered carbonyl exchange in 7 is attributed to the rigid 3-fold symmetry and steric bulk of 1. In addition to characterization of the new compounds by NMR ((1)H, (13)C, and (31)P) spectroscopy, IR spectroscopy, mass spectrometry, and elemental analysis, compounds 2, 7, 9, and 10 were further characterized by X-ray crystallography.
“…Each complex possesses approximate C 3 v symmetry with the phosphine ligand occupying an axial position about the trigonal-bipyramidal iron, as expected, based on solution IR data and previously proposed π-back-bonding arguments . The P(1)−Fe(1)−C(1) angles for 7 , 9 , and 10 are 176.06(6)°, 174.48(10)°, and 178.64(11)°, respectively, and the Fe−C and C−O distances are similar to those commonly observed in axial-substituted Fe(CO) 4 (PR 3 ) complexes. ,,,− 2 (a) ORTEP drawing of Fe(CO) 4 ( 1 ) ( 7 ). Thermal ellipsoids are drawn at the 50% probability level.…”
Section: Resultssupporting
confidence: 80%
“…4 The P(1)-Fe(1)-C(1) angles for 7, 9, and 10 are 176.06(6)°, 174.48(10)°, and 178.64(11)°, respectively, and the Fe-C and C-O distances are similar to those commonly observed in axial-substituted Fe(CO) 4 (PR 3 ) complexes. 9,33,36,[38][39][40][41][42][43] The most striking feature of each structure is the short Fe-P bond distances of 7 (2.1539(5) Å), 9 (2.1970(8) Å), and 10 (2.1661(7) Å). Iron-phosphorus distances in axial-substituted Fe(CO) 4 (PR 3 ) complexes range 9,33,36,[38][39][40][41][42][43] from 2.158(3) Å in Fe(CO) 4 (ADPO) 33 to 2.364(1) Å in Fe(CO) 4 (P t Bu 3 ).…”
Variable-temperature (13)C NMR spectra for a series of Fe(CO)(4)(PR(3)) complexes ligated by phosphatri(3-methylindolyl)methane (1), phosphatri(pyrrolyl)methane (2), P(N-3-methylindolyl)(3) (3), and P(N-pyrrolyl)(3) (4) are reported. Ligand 2 was prepared by reaction of tri(pyrrolyl)methane with PCl(3) in THF and Et(3)N. Compound 2 is stable to methanolysis, hydrolysis, and aerial oxidation at room temperature. Reactions of 2 with selenium powder and Rh(acac)(CO)(2) yield phosphatri(pyrrolyl)methane selenide (5) and Rh(acac)(CO)(2) (6), respectively. The carbonyl stretching frequency in the IR spectrum of 6 and the magnitude of (1)J(Se)(-)(P) in the (31)P NMR spectrum of 5 indicate that 2 is a strong pi-acid and a weak sigma-base, commensurate with its lack of reactivity with CH(3)I. The trend in the decreasing basicity of 2 and related phosphines and phosphites was determined to be P(NMe(2))(3) > 3 > 4 > 1 > P(OPh)(3) > 2. IR data for a series of Rh(acac)(CO)(PR(3)) complexes indicate the trend in decreasing pi-acceptor ability to be 2 approximately 1 > 4 > P(OPh)(3) > 3 > PPh(3). Phosphines 1-4 were reacted with Fe(2)(CO)(9) to yield Fe(CO)(4)(1) (7), Fe(CO)(4)(2) (8), Fe(CO)(4)(3) (9), and Fe(CO)(4)(4) (10), respectively. IR data for 7-10 support the trend in pi-acidity listed above. Variable-temperature (13)C NMR spectra for compounds 8-10 show a single doublet resonance for the carbonyls in the temperature range from -80 to 20 degrees C indicative of rapid intramolecular rearrangement of carbonyls between axial and equatorial sites. However, the (13)C NMR spectrum for 7 shows slowed axial-equatorial carbonyl exchange at 20 degrees C. The limiting slow-exchange spectrum is observed at -20 degrees C. Hindered carbonyl exchange in 7 is attributed to the rigid 3-fold symmetry and steric bulk of 1. In addition to characterization of the new compounds by NMR ((1)H, (13)C, and (31)P) spectroscopy, IR spectroscopy, mass spectrometry, and elemental analysis, compounds 2, 7, 9, and 10 were further characterized by X-ray crystallography.
“…The desirable ligand properties of heterocyclic phosphorus-nitrogen molecules were first demonstrated by the groups of Parry and Paine, who developed the coordination chemistry of diazaphospholidines (C) as cationic and neutral P-donor molecules. [33][34][35][36][37][38][39] Modified versions of these organic P-N heterocycles have been reported recently, and complexes bearing C 2 -symmetric ligands (D) have shown outstanding enantioselectivities. [40][41][42][43][44] Cyclic phosphines are not limited to organic ring compounds, of course, and we wondered if inorganic analogues might also be useful electron-rich spectator ligands.…”
Section: Introductionmentioning
confidence: 99%
“…This utility has created a sustained academic and industrial interest in the design and synthesis of these molecules, which is currently centered on their role as chiral auxiliaries. − Particularly effective for this purpose are cyclic, C 2 -symmetric bis(phosphines), − such as the bis(phosphetanes) (A) − and the bis(phospholanes) (B), which are shown in Chart . − Although the main reason for the adoption of cyclic structures was to create chirality, an added advantage of heterocycles is their greater compactness and electron-richness over conventional C 2 -symmetric bis(phosphines), most of which bear aryl groups. The desirable ligand properties of heterocyclic phosphorus−nitrogen molecules were first demonstrated by the groups of Parry and Paine, who developed the coordination chemistry of diazaphospholidines (C) as cationic and neutral P-donor molecules. − Modified versions of these organic P−N heterocycles have been reported recently, and complexes bearing C 2 -symmetric ligands (D) have shown outstanding enantioselectivities. − 1 …”
Synthesis and characterization of a new, highly electron-rich, chelating bis(phosphine), based on the ethanediyl-linked inorganic heterocycle [Me(2)Si(mu-N(t)Bu)(2)P], are reported. Treatment of nickel chloride with this bis(phosphine) afforded square-planar cis-[[Me(2)Si(mu-N(t)Bu)(2)PCH(2)](2)NiCl(2)], which features isometric nickel-chloride (2.2220(8) A) and nickel-phosphorus (2.1572(8) A) bonds. The ligand reacted with cis-[(piperidine)(2)Mo(CO)(4)] to form colorless cis-[[Me(2)Si(mu-N(t)Bu)(2)PCH(2)](2)Mo(CO)(4)], which has distorted octahedral geometry and long Mo-P bonds (2.5461(18) A). Because of its potential applications in hydrogenation catalysis cis-[[Me(2)Si(mu-N(t)()Bu)(2)PCH(2)](2)Rh(COD)]BF(4) was synthesized. This square-planar, cationic rhodium(I) complex, having symmetrical Rh-P (2.250(2) A) and Rh-C (2.305(6) A) bonds, is structurally related to bis(phospholano)- and bis(phosphetano)rhodium species.
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