95Mo NMR Spectroscopic Evidence for the Weak .pi.-Acceptor Ability of PCl3

Alyea, Elmer C.; Song, Shuquan

doi:10.1021/ic00119a006

Cited by 27 publications

(30 citation statements)

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“…The IR stretching frequencies for trans carbonyls of phosphite complexes are approximately the same, within experimental error, for each of the three geometries (see Table 3) I except that the f3-P(OPh), complex does have higher v,, (and force constant) values. The observation of this anomalous effect for P(OPh), is in agreement with the previous suggestion that the stretching frequency is more likely reflecting the weak a component (7). Only the A,(highest) mode is used here because of a higher precision (sharper line), the lack of ambiguity in its assignment, and its relation to (covering) all force constants.…”

Section: "Mo Nmr Spectral Parameterssupporting

confidence: 89%

“…As commonly accepted (7,8,12,13) which describes the multi-parameter dependencies of z (~~M o ) (or screening constant, up), in which 0, a , and IT are measures of steric, u, and IT components, respectively. An attempt to estimate the steric component in eq.…”

Section: "Mo Nmr Spectral Parametersmentioning

confidence: 99%

“…Applications of these steric parameters have mainly been qualitative due to the inherent uncertainty of each parameter and the overlapping effect of electronic components. Previous studies suggest that the steric effect exerts a significant influence on magnetic shielding of the transition metal nucleus (7), which can be measured to high precision, and therefore steric contributions to M-P bonding might be estimated more precisely from 9 5~o and 3 1~ NMR spectrometry if a wide range of bulky P(II1) ligands were investigated. This paper focuses on evaluations of the steric component in M-P bonding by analysis of 9 5~o NMR shielding parameters for a wide range of Mo(CO)~,(PY~), (n = 1-3) derivatives.…”

Section: Introductionmentioning

confidence: 99%

“…Data precision for the 9 5~o NMR spectral results has been described in related papers (7). To briefly summarize the line width data for the present Mo(CO)~,,(PY,), (n = 1-3) complexes, Wl12 had the following ranges: 5-120 Hz (n = l), 10-490 Hz (n = 2), and 5 4 0 Hz (n = 3).…”

Section: Introductionmentioning

confidence: 99%

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Steric effects of bulky phosphines on ⁹⁵Mo NMR shieldings

Song¹,

Alyea²

1996

Can. J. Chem.

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Three sets of substituted molybdenum carbonyl complexes of the type Mo(CO)~,(PY,), (n = 1-3) with a wide range of phosphorus ligands (Y = Ar, R, OR, NR,, C1, H) were synthesized and their respective 9 s~o NMR spectral data were collected, The steric effect of PY, plays an unexpectedly important role in the paramagnetic shielding term determining E(~'Mo), and is even observed in the least crowded M(CO),(PY,) complexes. It is deduced that the steric requirement reduces the commonly accepted a-ability of phosphites by weakening the M-P bonds, making 6 ( 9 5~~) positions move toward higher frequency in going from M(CO),(PY,) to fac-M(CO),(PY,),. A detailed correlation analysis in the case of phosphite ligands has shown that the free cone space to accommodate a PY, ligand may be as low as 95" in Mo(CO)~,(PY,), (n = 1-3) derivatives. The fair linearity of these correlations suggests indirectly that the a-component in phosphite bonding is relatively less important. These linear correlations of 6 ( 9 5~0 ) against the Tolman cone angle 9 provide an empirical estimation of the bulkiness of any phosphite ligand.

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Section: "Mo Nmr Spectral Parameterssupporting

confidence: 89%

Section: "Mo Nmr Spectral Parametersmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Steric effects of bulky phosphines on ⁹⁵Mo NMR shieldings

Song¹,

Alyea²

1996

Can. J. Chem.

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“…The 31 P NMR spectra of the complexes 4-11 consist of a doublet, indicative of the equivalence of the phosphorus nuclei in solution (Table 3) while for π-acceptor (also weak σ-donors) phosphites the chemical shift moves by a small amount toward high or low frequency upon coordination. 22 As far as the spin-spin coupling constants, 1 J(Rh-P), are concerned, they were found to be significantly larger for the phosphite- 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 The best known spectroscopic description of the electronic effects of trivalent phosphorus ligands is Tolman's electronic parameter (TEP). 20, 24 1 2 3 4 5 6 7 8 9 10 11 12 13...…”

Section: Complexmentioning

confidence: 99%

Tetrathiomolybdate Complexes of Rhodium(I) with Molybdenum–Rhodium Interactions

et al. 2016

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The synthesis and characterization of the tetrathiomolybdatorhodium(I) monoanionic complexes [L2Rh(μ-S)2MoS2](-) (L = CO (3), P(OPh)3 (4), P(O-o-Tol)3 (P(o-CH3C6H4)3; 5), P(OMe)3 (6), P(OEt)3 (7), P(O-i-Pr)3 (8); L2 = COD (1,5-cyclooctadiene; 2), cis-dppen (cis-Ph2PCH═CHPPh2; 9), dppe (Ph2PCH2CH2PPh2; 10), dppb (Ph2P(CH2)4PPh2; 11)) is presented. The complex 2 (NEt4(+) salt) was characterized by X-ray diffraction analysis. A detailed DFT study of the electronic structures of 2-4 and 6-8 has revealed the existence of extended electron delocalization over the four-membered Rh(μ-S)2Mo ring and hence the possibility of electronic communication between the metal centers. The electronic spectra were studied with TDDFT calculations, and the main absorption band in the visible region was assigned to ν(Rh→Mo) electron transfer transition, which is actually a HOMO-LUMO transition. The ν(Rh→Mo) transition was found to correlate linearly both with Tolman's electronic parameter of the phosphite ligands and the calculated HOMO-LUMO gap of the complexes, rendering it a well-defined ligand electronic parameter, which describes the net donating ability of monodentate and bidentate ligands (CO, COD, phosphites, diphosphines). The study of the variation of Δδ((31)P) and (1)J(Rh-P) of the phosphite complexes with respect to the QALE model electronic parameters χd, πp, and Ear has succeeded in the assessment of the σ and π effects on these NMR spectral parameters.

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