Klaus Eichele Publication Abstracts 1996

 

---

[UP]

K.V. Ramanathan, N. Suryaprakash, C.L. Khetrapal, E.D. Becker, K. Eichele and R.E. Wasylishen: 13C MAS NMR Spectra of cis,cis-Mucononitrile in Liquid Crystalline Media and the Solid State - Orientation of the Carbon Chemical Shift Tensors J. Magn. Reson. Ser. A 1996, 123, 196-200. DOI 10.1006/jmra.1996.0235

The spinning sidebands observed in the ¹³C MAS NMR spectra of cis,cis-mucononitrile oriented in liquid crystalline media and of the neat sample in the solid state are studied. There are differences in the sideband intensity patterns in the two cases. These differences arise because the order parameters which characterize the orientation of the solute in the liquid crystalline media differ. It is shown that, in general, the relative intensities of the sidebands contain information on the sign and magnitude of an effective chemical shift parameter which is a function of the sum of the products of the principal components of the chemical shift tensor and the corresponding order parameters with respect to the director. A method for obtaining the orientation of the carbon chemical shift tensor is proposed. The carbon chemical shift tensors obtained from gauge-including atomic orbitals (GIAO) calculations are also presented for comparison.

---

[UP]	K. Eichele, R.E. Wasylishen, R.W. Schurko, N. Burford and W.A. Whitla: An Unusually Large Value of 1J(31P,31P) for a Solid Triphenylphosphine Phosphoazonium Cationic Complex: Determination of the Sign of J from 2D Spin-Echo Experiments. Can. J. Chem. 1996, 74, 2372-2377.

Phosphorus-31 NMR spectra of a solid triphenylphosphine phosphoazonium salt, [Mes*NP-PPh₃][SO₃CF₃], have been acquired at 4.7 and 9.4 T. Analysis of the spectra obtained with magic-angle spinning indicates that the two phosphorus nuclei are strongly spin-spin coupled, ¹J(³¹P,³¹P) = 405(5) Hz, despite the unusually long P-P separation, r(P,P) = 2.625 Å. Two-dimensional spin-echo spectra provide convincing evidence that ¹J(³¹P,³¹P) is negative. Semi-empirical molecular orbital calculations at the INDO level support the negative sign for ¹J(³¹P,³¹P). A large span, 576 ppm, is observed for the chemical shift tensor of the two-coordinate phosphorus centre (δ₁₁ = 307 ppm, δ₂₂ = 174 ppm, δ₃₃ = -269 ppm), which is very similar to the value previously reported for the non-coordinated phosphorus centre in the free Lewis acid, [Mes*NP][AlCl₄]. The principal components and orientations of the phosphorus shielding tensors of these compounds are compared with those calculated for [HNP]⁺ and its phosphine adduct using the ab initio Gauge-Including Atomic Orbitals method. The phosphorus chemical shift tensor of the triphenylphosphine moiety has a relatively small span of 33 ppm.

---

[UP]

N. Burford, T.S. Cameron, J.A.C. Clyburne, K. Eichele, K.N. Robertson, S. Sereda, R.E. Wasylishen and W.A. Whitla: Nucleophilic Addition of CH, NH, and OH Bonds to the Phosphadiazonium Cation and Interpretation of 31P Chemical Shifts at Dicoordinate Phosphorus Centers. Inorg. Chem. 1996, 35, 5460-5467. DOI 10.1021/ic960131u

The phosphadiazonium cation, [Mes*NP]⁺, reacts quantitatively with the fluorenylide anion, Mes*NH₂, and Mes*OH (Mes* = 2,4,6-tri-tert-butylphenyl), resulting in formal insertion of the N-P moiety into the H-Y (Y = C, N, O) bonds. Specifically, reaction of Mes*NPCl with fluorenyllithium gives the aminofluorenylidenephosphine [crystal data: C₃₁H₃₈NP, monoclinic, P2₁/c, a = 9.586(8) Å, b = 24.25(2) Å, c = 11.77(1) Å, β = 101.38(8)°, Z = 4]. Similarly, reaction of [Mes*NP][GaCl₄] with Mes*NH₂ gives the diaminophosphenium salt [Mes*N(H)PN(H)Mes*][GaCl₄] [crystal data: C₃₆H₆₀Cl₄ GaN₂P, monoclinic, C2/c, a = 24.91(2) Å, b = 10.198(4) Å, c = 16.445(2) Å, β = 93.32(1)°, Z = 4], and reaction with Mes*OH gives the first example of an aminooxyphosphenium salt [Mes*N(H)POMes*][GaCl₄]. It is proposed that the reactions involve nucleophilic attack at phosphorus followed by a 1,3-hydrogen migration from Y to N. Experimental evidence for the formation of sigma-complex intermediates is provided by the isolation of [Mes*NP-PPh₃][SO₃CF₃] [crystal data: C₃₇H₄₄F₃NO ₃P₂ S, triclinic, P1-bar, a = 10.663(1) Å, b = 19.439(1) Å, c = 10.502(1) Å, α = 103.100(7)°, β = 113.311(7)°, γ = 93.401(7)°, Z = 2]. As part of the unequivocal characterization of the aminooxyphosphenium salt, detailed solid-state ³¹P NMR studies and GIAO calculations on the phosphenium cations have been performed. Contrary to popular belief, the phosphorus shielding in dicoordinate cations is not caused by the positive charge but results from efficient mixing between the phosphorus lone pair and π* orbitals.

---

[UP]	K. Eichele, R.E. Wasylishen, J.M. Kessler, L. Solujic and J.H. Nelson: Phosphorus Chemical Shift Tensors of Phosphole Derivatives Determined by 31P NMR Spectroscopy of Powder Samples. Inorg. Chem. 1996, 35, 3904-3912. DOI 10.1021/ic960095z

The results of a systematic solid-state ³¹P NMR study of 5-phenyldibenzophosphole, DBP, its chalcogenides and some of its transition metal complexes are reported. Phosphorus chemical shift tensors have been obtained from ³¹P NMR spectra of stationary samples and of samples spinning about the magic angle. The spans of the phosphorus chemical shift tensors for DBP and its chalcogenides are comparable to those of the corresponding compounds of triphenylphosphine; however, the asymmetry of the tensors for the DBP series reflects the reduced local symmetry at phosphorus. For the complexes (DBP)M(CO)₅ and cis-(DBP)₂M(CO)₄, where M is a group 6 transition metal (Cr, Mo, W), the most shielded component of the phosphorus shift tensor is found to be relatively independent of the metal or complex, δ₃₃ = -41(8) ppm, and is thought to lie along or close to the P-M bond axis direction. In contrast, δ₁₁ and δ₂₂ show considerable variation but decrease systematically on descending the group from Cr to W. Group 10 metal complexes, (DBP)₂MX₂, have also been investigated, including several trans geometric isomers of nickel, cis- and trans-isomers of palladium and cis-isomers of platinum. The phosphorus shift tensors are non-axially symmetric with spans in the range 50-150 ppm. The phosphorus shift tensors of the two DBP ligands of (DBP)₂PtX₂ (X = Cl, Br) exhibit quite different principal components. The intermediate component of the shift tensor is thought to lie along the Pt-P bond in these complexes. Some of the complexes exhibit interesting MAS-frequency dependent ³¹P NMR spectra.

---

[UP]	W.L. Wilson, J. Fischer, R.E. Wasylishen, K. Eichele, V.J. Catalano, J.H. Frederick and J.H. Nelson: Thermal Coupling Reactions of 1-Phenyl-3,4-dimethylphosphole within the Coordination Sphere of Palladium (II). Inorg. Chem. 1996, 35, 1486-1496. DOI 10.1021/ic951307f

The thermolyses of dihalobis(1-phenyl-3,4- dimethylphosphole)palladium(II) complexes [(DMPP)₂PdX₂, X = Cl, Br, I] were investigated in 1,1,2,2-tetrachloroethane solutions at 145 °C and in the crystalline state at 140 °C. For cis- (DMPP)₂PdCl₂ and cis- or trans-(DMPP)₂PdBr₂ four types of products were formed: (1) [4 + 2] cycloaddition products, (2) [2 + 2] cycloaddition products, (3) compounds that result from 1,5- hydrogen migration from a methyl group on one phosphole to the beta-carbon of an adjacent phosphole (exo-methylene), and (4) products that result from an intermolecular [4 + 2] coupling of two phospholes followed sequentially by phosphinidene elimination and intramolecular [4 + 2] cycloaddition to another phosphole to give diphosphatetracyclotetradecatrienes (DPTCT). trans-(DMPP)₂PdBr₂ undergoes thermal isomerization to cis-(DMPP)₂PdBr₂ in the solid state, and cis- and trans- (DMPP)₂PdBr₂ give the same products in both their solid- and solution-state thermolyses. In contrast, trans-(DMPP)₂PdI₂ neither isomerizes to the cis-isomer nor undergoes any of the phosphole coupling reactions in either the solution or solid state. The crystal structures of trans- (DMPP)₂PdX₂ (X = Br, I), {- (DMPP)₂[2 + 2]}PdBr₂, {(DMPP)₂(exo-methylene)}PdBr₂, and (DPTCT)PdCl₂ were determined. They crystallize in the monoclinic P2₁/c, triclinic P1-bar, monoclinic P2₁/c, monoclinic P2₁/n, and orthorhombic P2₁2₁2₁ space groups in unit cells of the following dimensions: a = 10.158 (3) Å, b = 14.876(4) Å, c = 16.829(5) Å, β = 104.25(2) °, Z = 4; a = 9.025(1) Å, b = 11.023(1) Å, c = 13.833(1) Å, α = 101.15(1) °, β = 98.82(1) °, γ = 105.30(1) °, Z = 2; a = 13.090(2) Å, b = 17.637(2) Å, c = 21.834(2) Å, β = 100.51(1) °, Z = 4; a = 10.721(1) Å, b = 16.929(1) Å, c = 14.675(1) Å, β = 97.86(1) °, Z = 4; and a = 15.532(3) Å, b = 19.401(4) Å, c = 9.910(2) Å, Z = 2, respectively. Least-squares refinements converged at final values of R(F) of 0.041, 0.0354, 0.0624, 0.0533, and 0.035 for 2770, 2672, 2729, 2159, and 2525 independent observed reflections, respectively. Kinetic studies suggest that the reaction mechanisms are the same in both the solid and solution states and that the reaction mechanisms are substantially different from those previously reported for the thermolyses of the analogous cis- (DMPP)₂PtX₂ complexes.

---

[UP]	I.V. Kourkine, M.B. Chapman, D.S. Glueck, K. Eichele, R.E. Wasylishen, G.P.A. Yap, L.M. Liable-Sands and A.L. Rheingold: Synthesis and Ligand Substitution Reactions of a Mesitylphosphido- Bridged Platinum(II) Dimer. Inorg. Chem. 1996, 35, 1478-1485. DOI 10.1021/ic951020i

The stable primary phosphine complexes trans-M(PH₂Mes*) ₂Cl₂ (1, M = Pd; 2, M = Pt; Mes* = 2,4,6-(tBu)₃C₆H₂) were prepared from Pd(PhCN)₂Cl₂ and K₂PtCl₄, respectively. Reaction of Pt(COD)Cl₂ (COD = 1,5-cyclooctadiene) with less bulky arylphosphines gives the unstable cis-Pt(PH₂Ar)₂Cl₂ (3, Ar = Is = 2,4,6-(i-Pr)₃C₆H₂; 4, Ar = Mes = 2,4,6-Me₃C₆H₂). Spontaneous dehydrochlorination of 4 or direct reaction of K₂PtCl₄ with 2 equiv of PH₂Mes gives the insoluble primary phosphido-bridged dimer [Pt(PH₂Mes)(mu-PHMes) Cl]₂ (5), which was characterized spectroscopically, including solid-state ³¹P NMR studies. The reversible reaction of 5 with PH₂Mes gives [Pt(PH₂Mes)₂(mu-PHMes)] ₂[Cl]₂ (6), while PEt₃ yields [Pt(PEt₃)₂(mu-PHMes)]₂[Cl] ₂(7), which on recrystallization forms [Pt(PEt₃)(mu-PHMes)Cl]₂ (8). Complex 5 and PPh₃ afford [Pt(PPh₃)(mu-PHMes)Cl]₂ (9). Addition of 1,2-bis(diphenylphosphino)ethane (dppe) to 5 gives the dicationic [Pt(dppe)(mu-PHMes)]₂[Cl]₂ (10-Cl), which was also obtained as the tetrafluoroborate salt 10-BF₄ by deprotonation of [Pt(dppe)(PH₂Mes)Cl][BF₄] (11) with Et₃N or by reaction of [Pt(dppe)(mu-OH)]₂[BF₄]₂ with 2 equiv of PH₂Mes. Complexes 8, 9, and 10-Cl · 2CH₂Cl₂ · 2H₂O were characterized crystallographically.