Tertiary phosphine ligand-exchange reactions involving the M&gt;M quadruply bonded complexes M2Cl4L4, where L = PMe3, PEt3, PBun3 or PMe2Ph

Chisholm, Malcolm H.; McInnes, Jacqueline M.

doi:10.1039/a701222e

Cited by 12 publications

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References 24 publications

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“…A similar pattern for the dangling dmpe ligands was observed in the 31 P{ 1 H} NMR spectrum of 6 ( −0.39 and −48.07 ppm). This result is in accord with the data reported before, although the signals do not have exactly the same chemical shifts because the spectra were recorded at different temperatures.…”

Section: Resultssupporting

confidence: 93%

“…Recently, it has been found by Chisholm and McInnes that the substitution of monophosphines (PR 3 = PEt 3 , PMe 2 Ph) in a complex Mo 2 Cl 4 (PR 3 ) 4 by dmpe gave a compound that they formulated as Mo 2 Cl 4 (η 1 -dmpe) 4 on the basis of 31 P NMR data. We can now offer further evidence that compounds of that type really exist, and we report here the crystal structure of Mo 2 Cl 4 (η 1 -dmpm) 4 where all four potentially bidentate dmpm ligands are coordinated as monodentate groups.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Mixed Chloride/Amine Complexes of Dimolybdenum(II,II). 2. Reactions of Mo₂Cl₄(NHEt₂)₄with Monodentate and Bidentate Phosphines. New Type of Compounds Mo₂Cl₄(diphosphine)₄

Herrero

1999

Inorg. Chem.

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The complex Mo(2)Cl(4)(NHEt(2))(4) (1) undergoes facile substitution reactions of the amine ligands by phosphines to give compounds with the same core structure, Mo(2)Cl(4)(phosphine)(4), where the phosphine is PMe(3) (2), PMe(2)Ph (3), PHEt(2) (4), dmpm (bis(dimethylphosphino)methane) (5), or dmpe (1,2-bis(dimethylphosphino)ethane) (6). Complexes of the type M(2)X(4)L(4) are well-known with monodentate ligands, but there is no previous crystallographically verified example of the M(2)X(4)L(4) type of compound in which L is a potentially bidentate ligand acting as a unidentate ligand. Mo(2)Cl(4)(eta(1)-dmpm)(4) (5) can be isolated in good yield as the kinetic product of the substitution reaction at room temperature. When a solution of 5 in THF is heated, transformation into the more stable compound Mo(2)Cl(4)(&mgr;-dmpm)(2) (7) takes place. Mo(2)Cl(4)(eta(1)-dmpe)(4) (6) is stable in solution in the presence of free phosphine and can be detected by NMR. Over time it converts to a polymeric material which precipitates from the solution. For dppm (bis(diphenylphosphino)methane) (8) and dppa (bis(diphenylphosphino)amine) (9), only products of the stoichiometry Mo(2)Cl(4)(diphosphine)(2) were obtained. The crystal structures of the complexes 4 and 5 have been investigated by X-ray diffraction. The crystallographic parameters for them are as follows: for 4, orthorhombic space group Pbcn with a = 7. 6015(8) Å, b = 20.120(8) Å, c = 19.070(6) Å, and Z = 4; for 5, hexagonal space group P6(4)22 with a = 12.396(1) Å, c = 21.960(2) Å, and Z = 3. Both structures have a Mo(2)Cl(4)P(4) core where the phosphorus atoms are trans one to another on each metal center. The Mo-Mo distances of 2.137(1) Å (4) and 2.137(1) Å (5) are consistent with quadruple bonding.

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Section: Resultssupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Mixed Chloride/Amine Complexes of Dimolybdenum(II,II). 2. Reactions of Mo₂Cl₄(NHEt₂)₄with Monodentate and Bidentate Phosphines. New Type of Compounds Mo₂Cl₄(diphosphine)₄

Herrero

1999

Inorg. Chem.

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“…In this regard the mechanism is similar to that for M-PR 3 substitution by PR 3 Ј ligands in M 2 Cl 4 (PR 3 ) 4 compounds described previously in this journal. 14 The ability of certain chelating ligands such as dppe, dppm, 2,2Ј-bipyridine, 1,10-phenanthroline to catalyze the exchange of equatorial CH 3 CN ligands for CD 3 CN solvent molecules implies the rapid and reversible formation of an activated complex that is kinetically labile yet not directly on the path of the substitution chemistry described here. We have previ- ously suggested the possibility of the reversible formation of a mixed valence complex Rh III -Rh I wherein the Rh() center is kinetically labile.…”

Section: Discussionmentioning

confidence: 92%

Some studies of the substitution chemistry of [Rh2(OAc)2(CH3CN)4][BF4]2 with monodentate and bidentate tertiary phosphines †

Chisholm

Huffman

Iyer

2000

J. Chem. Soc., Dalton Trans.

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2 (dppm) have been studied by 1 H and 31 P{ 1 H} NMR spectroscopy in CD 3 CN. The chelating phosphines dppe and dppm catalyze the exchange of coordinated CH 3 CN for solvent CD 3 CN exchange prior to any other observable substitution chemistry. The monodentate phosphines initially form kinetically labile biaxially ligated complexes, [Rh 2 (OAc) 2 (CH 3 CN) 4 (PR 3 ) 2 ][BF 4 ] 2 prior to substitution of the equatorial CH 3 CN by PR 3 . Over time, the biaxial complex rearranges to form the monoaxial, monoequatorial complex, involving displacement of a single equatorial CH 3 CN ligand. For PCy 3 the complex [Rh 2 (OAc) 2 (CH 3 CN) 3 (PCy 3 ) 2 ][BF 4 ] 2 has been characterized by 1 H and 31 P{ 1 H} NMR spectroscopy. With time, a further reaction occurs leading to the cleavage of the Rh-Rh bond and the monomeric complex [Rh(CH 3 CN) 2 (PCy 3 ) 2 ][BF 4 ] has been identified. Crystal data at ϩ25 ЊC: space group P2 1 nm, a = 9.879(1) Å, b = 13.275(1) Å, c = 16.705(1) Å and Z = 4. A similar reaction sequence is observed with PMe 3 but more isomers of formula [Rh 2 (OAc) 2 (CH 3 CN) 3 (PMe 3 ) 2 ][BF 4 ] 2 are observed by 31 P{ 1 H} NMR spectroscopy. Reactions involving dppe lead to axial and equatorial Rh-P bonded complexes. Based on 31 P{ 1 H} NMR data, the bisequatorial complex formulated as [Rh 2 (OAc) 2 (CH 3 CN) 2 (dppe)][BF 4 ] 2 is formed. The formation of the latter, which has been followed from 35 to 80 ЊC, is evidently reversible since all attempts to crystallize the complex yielded only the acetonitrile salt [Rh 2 (OAc) 2 (CH 3 CN) 4 ][BF 4 ] 2 and free dppe. With dppm, only axial ligation is observed while for dmpm and dmpe the substitutional behavior is more complex and has not been evaluated in detail. The activation parameters for the conversion of the biaxial [Rh 2 (OAc) 2 (S) 4 (L) 2 ][BF 4 ] 2 to the monoaxial, monoequatorial [Rh 2 (OAc) 2 (S) 3 (L) 2 ][BF 4 ] 2 complex (S = CH 3 CN and L = phosphine) have been determined. For L = PMe 3 , ∆H ‡ = 16(1) kcal mol Ϫ1 and ∆S ‡ = Ϫ9(3) cal K Ϫ1 mol Ϫ1 and for L = PCy 3 , ∆H ‡ = 21(1) kcal mol Ϫ1 and ∆S ‡ = ϩ2(3) cal K Ϫ1 mol Ϫ1 . For dppe, the 1 : 1 adduct shows only one type of 31 P signal for the initial axial complex indicative of rapid exchange of free and bound PPh 2 groups. The rearrangement to the equatorialaxial isomer [Rh 2 (OAc) 2 (S) 3 (dppe)][BF 4 ] 2 occurs with ∆H ‡ = 26(1) kcal mol Ϫ1 and ∆S ‡ = ϩ12(1) cal K Ϫ1 mol Ϫ1 . Collectively these data show that substitution at the Rh 2 4ϩ -center proceeds via an initial reversible associative process followed by an interchange of labile axial for inert equatorial sites. These results are compared with earlier studies of the substitution of M 2 4ϩ -containing complexes, where M = Mo, Ru and Rh.

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“…93 Based on Hückel analysis of the bonding, metallic behavior is expected. 97 The results of the phosphine ligand exchange studies suggest that the exchange reactions proceed by an interchange dissociative mechanism, with the entering group within the W 2 4+ coordination sphere at the axial coordination site before the rate-determining phosphine displacement step. 97 Another synthetic method 86 4 is performed by reduction of WCl 4 by either KC 8 or NaBEt 3 H at low temperature in THF, followed by the addition of the amine.…”

Section: 89mentioning

confidence: 98%

“…97 The results of the phosphine ligand exchange studies suggest that the exchange reactions proceed by an interchange dissociative mechanism, with the entering group within the W 2 4+ coordination sphere at the axial coordination site before the rate-determining phosphine displacement step. 97 Another synthetic method 86 4 is performed by reduction of WCl 4 by either KC 8 or NaBEt 3 H at low temperature in THF, followed by the addition of the amine. A similar reaction occurs with either pyridine derivatives, 4-tert-butylpyridine and 3-n-butylpyridine, 28 or primary amines resulting in W 2 Cl 4 (NH 2 R) 4 complexes where R is Pr n , Bu t , or Cy.…”

Section: 89mentioning

confidence: 98%

Tungsten Compounds

Eglin¹

Multiple Bonds Between Metal Atoms

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Tertiary phosphine ligand-exchange reactions involving the M>M quadruply bonded complexes M2Cl4L4, where L = PMe3, PEt3, PBun3 or PMe2Ph

Cited by 12 publications

References 24 publications

Mixed Chloride/Amine Complexes of Dimolybdenum(II,II). 2. Reactions of Mo₂Cl₄(NHEt₂)₄with Monodentate and Bidentate Phosphines. New Type of Compounds Mo₂Cl₄(diphosphine)₄

Mixed Chloride/Amine Complexes of Dimolybdenum(II,II). 2. Reactions of Mo₂Cl₄(NHEt₂)₄with Monodentate and Bidentate Phosphines. New Type of Compounds Mo₂Cl₄(diphosphine)₄

Some studies of the substitution chemistry of [Rh2(OAc)2(CH3CN)4][BF4]2 with monodentate and bidentate tertiary phosphines †

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Tertiary phosphine ligand-exchange reactions involving the M>M quadruply bonded complexes M2Cl4L4, where L = PMe3, PEt3, PBun3 or PMe2Ph

Cited by 12 publications

References 24 publications

Mixed Chloride/Amine Complexes of Dimolybdenum(II,II). 2. Reactions of Mo2Cl4(NHEt2)4with Monodentate and Bidentate Phosphines. New Type of Compounds Mo2Cl4(diphosphine)4

Mixed Chloride/Amine Complexes of Dimolybdenum(II,II). 2. Reactions of Mo2Cl4(NHEt2)4with Monodentate and Bidentate Phosphines. New Type of Compounds Mo2Cl4(diphosphine)4

Some studies of the substitution chemistry of [Rh2(OAc)2(CH3CN)4][BF4]2 with monodentate and bidentate tertiary phosphines †

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Mixed Chloride/Amine Complexes of Dimolybdenum(II,II). 2. Reactions of Mo₂Cl₄(NHEt₂)₄with Monodentate and Bidentate Phosphines. New Type of Compounds Mo₂Cl₄(diphosphine)₄

Mixed Chloride/Amine Complexes of Dimolybdenum(II,II). 2. Reactions of Mo₂Cl₄(NHEt₂)₄with Monodentate and Bidentate Phosphines. New Type of Compounds Mo₂Cl₄(diphosphine)₄