The dimolybdenum pentapivalate anion: X-ray crystal structure and dynamic solution behaviour and comments on the substitutional lability of containing compounds

Cayton, Roger H.; Chacon, Stephanie T.; Chisholm, Malcolm H.; Folting, Kirsten

doi:10.1016/s0277-5387(00)81746-5

Cited by 18 publications

(15 citation statements)

References 19 publications

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“…Despite the presence of excess HTiPB in the synthesis of 1, it does not undergo further substitution to tri-and tetra-substituted species under these conditions. The mechanism for substitution in [M 2 (O 2 CR) 4 ] complexes involves initial coordination of the incoming carboxylate ligand to the axial position [49], and it is likely that blocking this position with two bulky carboxylate ligands provides a kinetic barrier to further substitution.…”

Section: Synthesis and Characterisationmentioning

confidence: 99%

Unexpected structural and electronic effects of internal rotation in diruthenium paddlewheel complexes containing bulky carboxylate ligands

Gracia

Adams

Patmore

2010

Inorganica Chimica Acta

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Section: Synthesis and Characterisationmentioning

confidence: 99%

Unexpected structural and electronic effects of internal rotation in diruthenium paddlewheel complexes containing bulky carboxylate ligands

Gracia

Adams

Patmore

2010

Inorganica Chimica Acta

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“…16 (µ-η 1 ,η 1 -OAc) 2 ] in toluene, for example. 7 Here the Rh-Rh bonding electronic configuration is σ 2 π 4 δ 2 δ* 2 π* 4 and this may be compared with the kinetically inert t 2g 6 configuration seen in mononuclear octahedral complexes of Co 3ϩ , Rh 3ϩ , Ir 3ϩ and Pt 4ϩ which generally undergo substitution by dissociative, D, or interchangedissociative, I d , mechanisms. 8 In comparing the rates of solvent exchange in the [M 2 (OAc) 2 -(MeCN) 6 ][BF 4 ] 2 complexes we again observed kinetic lability for M = Mo and the inertness of the Rh complex which undergoes exchange of CH 3 CN for CD 3 CN (solvent) very much more slowly.…”

Section: Introductionmentioning

confidence: 99%

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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“…Ϫ anion, which has the solid-state molecular structure shown in 5, is fluxional on the NMR time-scale at room temperature in [ 2 H 8 ]toluene. 9 While we were inclined to view the lability of the Mo 2 4ϩ center in terms of its ability to enter into associative exchange processes with ligands such as carboxylates which have additional lone pairs, we were aware of the work of Andersen and co-workers 10 who had studied the phosphine exchange reactions shown in equation (1), where L = PMe 3 or PMe 2 Ph. These…”

mentioning

confidence: 99%

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

Chisholm¹,

McInnes²

1997

J. Chem. Soc., Dalton Trans.

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The dimolybdenum pentapivalate anion: X-ray crystal structure and dynamic solution behaviour and comments on the substitutional lability of containing compounds

Cited by 18 publications

References 19 publications

Unexpected structural and electronic effects of internal rotation in diruthenium paddlewheel complexes containing bulky carboxylate ligands

Unexpected structural and electronic effects of internal rotation in diruthenium paddlewheel complexes containing bulky carboxylate ligands

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

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

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