Lewis basicity of some difluorophosphines toward borane

Foester, R.; Cohn, Kim

doi:10.1021/ic50117a004

Cited by 29 publications

(6 citation statements)

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“…[28] Moreover, the magnitude of 1 J P,B coupling constants in phosphane-borane adducts serves as a qualitative measure of the strength of the P-B bond. [13,[29][30][31] Looking at the coupling constants via the P-B ( 1 J P,B ), P-CH 3 ( 1 J P,C ) and P-C(phenyl) bonds ( 1 J P,Ci ), there is always the same qualitative trend: all these coupling constants increase substantially upon attachment of chalcogeno substituents to the phosphorus centres of the parent molecules K(PPh 2 BH 3 ) (1), K(PtBu 2 BH 3 ) (6) and PPh 2 CH 3 (11). This effect is strongest for the oxo systems 2, 7 and 12 and decreases monotonously along the series O Ͼ S Ͼ Se Ͼ Te.…”

Section: Nmr Spectroscopymentioning

confidence: 99%

A Comparative Study of Chalcogenated Phosphanylborohydrides[EPR₂BH₃]^– (R = Ph, tBu) and Triorganophosphane Chalcogenides EPPh₂CH₃ (E = O, S, Se, Te)

et al. 2006

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Chalcogenation of the phosphanylborohydrides K(PPh2BH3) and K(PtBu2BH3) with N2O, S8, Se∞, and Te∞ leads to the corresponding species K(EPR2BH3) in excellent yield (E = O–Te; R = Ph, tBu). The parent systems as well as all the chalcogen derivatives have been structurally characterised as their 18‐crown‐6 adducts by X‐ray crystallography. In the case of [K(18‐c‐6)][EPPh2BH3] the anionic ligand binds to the K+ ion through both its E atom and its BH3 substituent. Significantly larger K–B distances together with shorter K–E contacts are observed in the sterically more congested tert‐butyl derivatives [K(18‐c‐6)][EPtBu2BH3]. Based on a comparison of characteristic NMR parameters (e.g. 1JP,B, 1JP,C) of K(EPPh2BH3) and EPPh2CH3, we come to the conclusion that the formal replacement of CH3+ by BH3 leads to a significant increase in the p character of the E–P bond, which therefore indicates that [PPh2BH3]– is better suited to direct electron density towards an acceptor atom than its triorganophosphane congener PPh2CH3. In line with this interpretation, displacement experiments between K(PPh2BH3) and EPPh2CH3 (E = S–Te) resulted in the quantitative formation of K(EPPh2BH3) and PPh2CH3. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

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Section: Nmr Spectroscopymentioning

confidence: 99%

A Comparative Study of Chalcogenated Phosphanylborohydrides[EPR₂BH₃]^– (R = Ph, tBu) and Triorganophosphane Chalcogenides EPPh₂CH₃ (E = O, S, Se, Te)

et al. 2006

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“…Despite of the fact that a quantitative assessment of these two competing factors is obviously difficult, an empirical correlation between the magnitude of 1 J PB and dative bond strength became evident from several studies on [BH 3 ] adducts of selected series employing smoothly varying phosphane ligands. [14,[30][31][32] Based on the development of 1 J PB coupling constants along the sequence 4H (42 Hz), 5H (55 Hz), and 9 (64 Hz) we therefore confidently assign the highest Lewis basicity to the phosphanylborohydride ligand [P(BH 3 )Ph 2 ]…”

Section: Introductionmentioning

confidence: 99%

Phosphanylborohydrides: First Assessment of the Relative Lewis Basicities of [BH₃PPh₂]^–, CH₃PPh₂, and HPPh₂

et al. 2006

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The compounds K[PPh2], HPPh2, CH3PPh2, BH3(H)PPh2, BBr3(H)PPh2, BH3(CH3)PPh2, BBr3(CH3)PPh2, [H2PPh2]I, [CH3(H)PPh2]I, [(CH3)2PPh2]I, and K[(BH3)2PPh2] have been investigated by NMR spectroscopy. In addition, X‐ray crystal structures have been determined for K(18‐crown‐6)[PPh2], BBr3(H)PPh2, BBr3(CH3)PPh2, [H2PPh2]I, [CH3(H)PPh2]I, [(CH3)2PPh2]I, and K(18‐crown‐6)[(BH3)2PPh2]. An evaluation of coupling constants (e.g. 1JPCi; Ci = ipso carbon atom of a phenyl ring) augmented by an inspection of key structural parameters (e.g. the angles Ci–P–Ci′) leads to the conclusion that dative bonds originating from ligand [BH3PPh2]– possess a significantly higher p character than dative bonds involving the ligands HPPh2 and CH3PPh2. The 1JPB values obtained for BH3(H)PPh2, BH3(CH3)PPh2, and [(BH3)2PPh2]– suggest [BH3PPh2]– to form the strongest [BH3] adduct of all three compounds which is in agreement with the results of displacement reactions employing the couples CH3PPh2/[(BH3)2PPh2]– and [BH3PPh2]–/BH3(CH3)PPh2. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

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“…1. 5 Hz for the sulphur compounds. It seems to be generally true that couplings across oxygen are anomalously small.…”

Section: Resultsmentioning

confidence: 99%

Instant ligands. Part 1. Preparation of some bidentate fluorophosphine ligands derived from straight chain organic substrates, and their reactions to form molybdenum complexes

Bell¹,

Rankin²

1986

J. Chem. Soc., Dalton Trans.

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The compounds (F,P)S(CH,),S(PF,) ( n = 2-6) and (F,P)O(CH,),O(PF,) ( n = 3-6) have been prepared by reactions of S ( PF,), with the appropriate dithiols and diols, and have been characterised by n.m.r. and i.r. spectroscopy. N.m.r. parameters for oxygen compounds with n = 7-1 0 and 1 2 have also been obtained. The compounds react with N-methylpyridinium pentacarbonyliodomolybdate to give compounds with two Mo( CO), units linked by the ligands. With tetracarbonyl (norbornadiene)molybdenum two types of products can be formed, depending on ligand chain length. The predominant products for n = 3-6 have two bidentate ligands bridging between two cis-Mo(CO), units. For n = 2, 3, or 4 monomeric species with a single chelating ligand on a cis-Mo(CO), unit are also generated, and their abundance depends on the concentrations of reactants. The metal complexes have been characterised by n.m.r., i.r., and mass spectroscopy.Many compounds containing -OPF, groups have been reportedand their chemistry has been studied in some detail. The majority of these compounds are simple organic derivatives, ROPF,, but species in which the oxygen is bound to other elements. such as silicon and phosphorus, are also known. In contrast very little work has been reported for the -SPF, analogues, and CH,SPF, is the only organic derivative described so far.3.s+6These fluorophosphines, whether bound to sulphur or oxygen, are all potential ligands, and we have therefore prepared a series of compounds containing two -OPF, or -SPF, groups, to be used as bidentate ligands. Most work with bidentate fluorophosphine ligands reported to date has concentrated on compounds of the type RN(PF,),,'.' in which the two phosphorus atoms are close together, such that they either chelate to a single metal atom or bridge between two adjacent metal atoms. The compounds we have prepared are (F,P)Y(CH,),Y( PF,), with Y = oxygen or sulphur and n being between 2 and 12. These bidentate ligands therefore have relatively large distances between the donor sites, and their chemistry depends on the number of intervening chain atoms.These new ligands can be prepared in a pure form or in solution in a few minutes by a one-step process, which is why we refer to them as 'instant ligands.' Samples of many different ligands can therefore be prepared when they are required, and it is only necessary to maintain a stock of S(PF,),. The compounds are thus particularly attractive for studies involving bidentate ligands with different distances or geometrical relationships between the co-ordinating groups. In this paper we describe compounds in which the chain linking the two phosphine groups is long and flexible.

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Lewis basicity of some difluorophosphines toward borane

Cited by 29 publications

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A Comparative Study of Chalcogenated Phosphanylborohydrides[EPR₂BH₃]^– (R = Ph, tBu) and Triorganophosphane Chalcogenides EPPh₂CH₃ (E = O, S, Se, Te)

A Comparative Study of Chalcogenated Phosphanylborohydrides[EPR₂BH₃]^– (R = Ph, tBu) and Triorganophosphane Chalcogenides EPPh₂CH₃ (E = O, S, Se, Te)

Phosphanylborohydrides: First Assessment of the Relative Lewis Basicities of [BH₃PPh₂]^–, CH₃PPh₂, and HPPh₂

Instant ligands. Part 1. Preparation of some bidentate fluorophosphine ligands derived from straight chain organic substrates, and their reactions to form molybdenum complexes

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Lewis basicity of some difluorophosphines toward borane

Cited by 29 publications

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A Comparative Study of Chalcogenated Phosphanylborohydrides[EPR2BH3]– (R = Ph, tBu) and Triorganophosphane Chalcogenides EPPh2CH3 (E = O, S, Se, Te)

A Comparative Study of Chalcogenated Phosphanylborohydrides[EPR2BH3]– (R = Ph, tBu) and Triorganophosphane Chalcogenides EPPh2CH3 (E = O, S, Se, Te)

Phosphanylborohydrides: First Assessment of the Relative Lewis Basicities of [BH3PPh2]–, CH3PPh2, and HPPh2

Instant ligands. Part 1. Preparation of some bidentate fluorophosphine ligands derived from straight chain organic substrates, and their reactions to form molybdenum complexes

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A Comparative Study of Chalcogenated Phosphanylborohydrides[EPR₂BH₃]^– (R = Ph, tBu) and Triorganophosphane Chalcogenides EPPh₂CH₃ (E = O, S, Se, Te)

A Comparative Study of Chalcogenated Phosphanylborohydrides[EPR₂BH₃]^– (R = Ph, tBu) and Triorganophosphane Chalcogenides EPPh₂CH₃ (E = O, S, Se, Te)

Phosphanylborohydrides: First Assessment of the Relative Lewis Basicities of [BH₃PPh₂]^–, CH₃PPh₂, and HPPh₂