Unsymmetrical complexes containing the linear tetraphosphine ligand DPPEPM

Nair, Arun K.; White, Colin; Anderson, Gordon K.; Rath, Nigam P.

doi:10.1016/j.jorganchem.2005.09.021

Cited by 15 publications

(8 citation statements)

References 34 publications

(53 reference statements)

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“…The configuration of [(DEPEPM)RhCl 2 ] + and [(DEPEPM)RhCl(CH 2 Cl)] + is cis-α . Palladium and platinum compounds of the perphenylated DPPEPM, on the other hand, are typically bimetallic, although monometallic complexes containing κ 2 - or κ 3 -DPPEPM can also be obtained under appropriate conditions . In group 8 chemistry, a related hexaphosphine ligand (Et 2 PCH 2 CH 2 ) 2 PCH 2 P(CH 2 CH 2 PEt 2 ) 2 (eHTP) coordinates in a tetradentate, cis-α configuration to Fe(II) .…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Monomeric Fe(II) and Ru(II) Complexes of Tetradentate Phosphines

Jana¹,

Ellern²,

Pestovsky³

et al. 2011

Inorg. Chem.

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rac-Bis [{(diphenylphosphino)ethyl}-phenylphosphino]methane (DPPEPM) reacts with iron(II) and ruthenium(II) halides to generate complexes with folded DPPEPM coordination. The paramagnetic, fivecoordinate Fe(DPPEPM)Cl2 (1) in CD2Cl2 features a tridentate binding mode as established by 31P{1H} NMR spectroscopy. Crystal structure analysis of the analogous bromo complex, Fe(DPPEPM)Br2 (2) revealed a pseudo-octahedral, cis-α geometry at iron with DPPEPM coordinated in a tetradentate fashion. However, in CD2Cl2solution, the coordination of DPPEPM in 2 is similar to that of 1 in that one of the external phosphorus atoms is dissociated resulting in a mixture of three tridentate complexes. The chloro ruthenium complex cis-Ru(κ4-DPPEPM)Cl2 Multidentate ligands are often used to provide stabilized coordination complexes through the chelate effect. At the same time, the structure of a polydentate ligand provides means to control the bite angle, chelate ring size, and stereochemistry. The resulting electronic and steric effects can be used to enhance the reactivity of a metal center. In well-studied organometallic examples, ansa-metallocenes 1-3 and constrained-geometry compounds 4-9 provide enhanced reactivity in olefin polymerization and bond activation, while inhibiting disproportionation reactions. Similarly, bidentate phosphines enforce cis coordination geometries, even though trans configurations might be sterically or electronically preferred, and tridentate phosphines such as MeSi (CH 2 24 and FeCl 2 (DHPePE) 2 (DHPePE = 1,2-bis(bis(hydroxypropyl)phosphino)ethane). 25 The trans geometry in these compounds may limit their reactivity by suppressing processes that require cis-disposed valencies, although cis-iron(II) complexes of bidentate and meso isomers of linear tetradentate phosphines are also formed on occasion. 23,[25][26][27][28][29][30] Ligand modifications can introduce strain, as well as control the geometry and configuration of late metal polyphosphine complexes. One approach involves replacing the central ethylene unit in DPPEPE with a methylene to shorten the ligand backbone and provide the ligand

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Section: Introductionmentioning

confidence: 99%

Synthesis of Monomeric Fe(II) and Ru(II) Complexes of Tetradentate Phosphines

Jana¹,

Ellern²,

Pestovsky³

et al. 2011

Inorg. Chem.

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“…Depending on reaction conditions, palladium(II) and platinum(II) yield mononuclear or binuclear complexes having meso-DPPEPM bonded in a κ 2 or κ 3 mode. [5][6][7] In a square pyramidal nickel complex Ni(CN) 2 (P 4 ) (P 4 = meso-Et 2 PCH 2 CH 2 P(Ph)(CH 2 )P(Ph)CH 2 CH 2 PEt 2 ) there are two strong P-Ni bonds in the equatorial plane, and a weak interaction between nickel and a third phosphorus located in the apical position. 3 These bonding patterns are in accord with the preferred square planar/pyramidal geometry of divalent group 10 metals.…”

Section: Discussionmentioning

confidence: 99%

“…These are predominantly bimetallic complexes that feature bidentate coordination of the ligand to each metal. [5][6][7] Also, an example of meso-Pd(II)(κ 3 -DPPEPM) was reported, but the compound was not structurally characterized. 5 In search of novel structures and chemistry of iron tetraphosphine complexes with possible utility in activation of small molecules, we have now explored the reaction of Fe(II) with meso-DPPEPM.…”

Section: Introductionmentioning

confidence: 99%

Unusual structural motif in a zwitterionic Fe(ii) complex of a tetradentate phosphine

et al. 2012

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The reaction of meso-DPPEPM (DPPEPM = bis(diphenylphosphino-ethylphenylphosphino)methane) with one equivalent of FeBr(2) in tetrahydrofuran generates a zwitterionic compound [FeBr(κ(2)-DPPEPM)(κ(3)-DPPEPM-FeBr(3))] (1). Compound 1 exhibits an unusual bonding arrangement with two meso-DPPEPM ligands and one bromide coordinated to a single Fe(II) center. One of the DPPEPM ligands binds to iron in a κ(2) mode via two central phosphorus atoms, leaving the terminal phosphines dangling. The second DPPEPM binds through three phosphines, whereas the fourth one coordinates to the iron center of an external FeBr(3)(-) unit. A 1 : 2 reaction of FeBr(2) and meso-DPPEPM in tetrahydrofuran generates [FeBr(κ(2)-DPPEPM)(κ(3)-DPPEPM)]Br ([2]Br) in which the positive charge on the pseudo-octahedral unit is balanced by free Br(-) as opposed to the phosphine-bound FeBr(3)(-) in 1. The compound [2]PF(6) was obtained from [2]Br and TlPF(6). Solution structures for 1, [2]Br and [2]PF(6) were assigned on the basis of (31)P NMR. For all three compounds the data are consistent with five phosphorus atoms bound to the metal.

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“…The residual solid was washed with diethyl ether and dried under reduced pressure to give a white powder. Recrystallization from dichloromethane/diethyl ether afforded 103.5 mg (49% yield) of 5 as colorless plates C,29.22;H,5.23. Found: C,29.59; H, 4.87%.…”

Section: Preparation Of [{Pd(g 3 -Allyl)} 2 (1)](sbf 6 ) 2 (5)mentioning

confidence: 99%