Peter F. Barron

Lewis base adducts of Group 11 metal compounds. Part 24. Co-ordination of triphenylphosphine with silver nitrate. A solid-state cross-polarization magic angle spinning 31P nuclear magnetic resonance, crystal structure, and infrared spectroscopic study of Ag(PPh3)nNO3(n= 1–4)

Solid-state cross-polarization magic angle spinning 31P n.m.r. spectroscopy, single-crystal X-ray structure determination, and i.r. spectroscopy have been used to investigate the properties of the adducts of triphenylphosphine with silver(I) nitrate: Ag(PPh3)NO3, (1); Ag(PPh3)2NO3, (2); Ag(PPh3)3NO3, (3); and Ag(PPh3)4NO3, (4). The value of 1J(Ag–P) decreases with increasing co-ordination number: (1), 780; (2), 470; (3), 310; and (4),190 Hz, paralleling solution results. Single-crystal X-ray structure determinations of compounds (2)–(4) have been performed: (2), triclinic, space group P, a= 11.821(3), b= 11.990(3), c= 13.660(3)A, α= 102.05(2), β= 112.80(2), and γ= 105.30(2)°, yielding R= 0.036 for 4 090 ‘observed’ reflections; Ag–P 2.443(1) and 2.440(1)A, P–Ag–P 138.21(5)°(3), monoclinic, space group P21/n, a= 18.984(5), b= 13.710(3), c= 17.900(4)A, and β= 94.94(2)°, yielding R= 0.053 for 5126 reflections; Ag–P 2.630(2), 2.525(1), and 2.545(2)A, P–Ag–P 118.37(5),112.07(4), and 116.44(5)°; (4), trigonal, space group R, a= 19.07(2), and α= 43.77(5)°, yielding R= 0.060 for 1 903 observed reflections; Ag–P 2.643(3) and 2.671(4)A, P–Ag–P 109.49(12) and 109.45(10)°. Structures (2) and (3)[and (1)] are isomorphous with the analogous triphenylarsine compounds. In all cases the nitrate group is only weakly co-ordinated [and is ionic in (4)]: Ag–O 2.464(4) and 2.649(4) in (2), 2.684(6) and 2.775(6)A in (3). These weak interactions are reflected in the small splitting observed for the asymmetric N–O stretching vibrational mode compared to the analogous copper(I) compounds.

Lewis-base adducts of group 11 metal (I) compounds. XXVI: Solid-state cross-polarization magic-angle-spinning 31P n.m.r. and structural studies on 1:1 adducts of triphenylphosphine with gold (I) salts

Linear, two-coordinate compounds of molecular formula (PPh3) AuX have been characterized by solid-state and solution 31P n.m.r. spectroscopy, and single-crystal X-ray diffraction techniques. The solid state n.m.r. spectra reveal single, broad resonance lines for X = NO3 (chemical shift 19 ppm , ref. 85% H3PO4), CH3C02 (24 ppm), SCN (36ppm), CN (37 ppm ) and CH3 (47 ppm ) and doublets for X = Cl (27, 33 ppm ), Br (28, 36 ppm ) and I (34, 38 ppm ), the latter three spectra being recorded at 121.47 MHz and 161.96 MHz. Solution spectra show relatively sharp single resonances for each compound with 6 values generally slightly higher than in the solid state. Crystal data are reported for X = NO3, space gro )p P21/c, a 8 895(9), b 10.117(8), c 19.57(2) A; β 97.43(8)o, Au-P,O = 2.199(5), 2.02(1) A. Crystals of compounds with X = Br, I and SCN are isomorphous with the AuCl compound, belonging to space group 212121. For X = Br, a 12.479(5), b 13.45(1), c 10.0!2(8) A; Au-P, Br = 2.252(6), 2.407(2) A. For X = I, a 12.529(8), b 13.870(5), c 10.188(4) A; Au-P, I = 2.254(5), 2.556(2) A. For X = SCN, a 12.257(5), b 13.776(8), c 10.754(6) A; Au-P, S = 2.252(7), 2.304(7) A.

Application of the DEPT pulse sequence for the generation of 13CHn subspectra of coal-derived oils

Abstract The application of the recently developed DEPT pulse sequence for the generation of 13 CH n subspectra of coal-derived oils is determined. The technique is able to generate subspectra with accurate cancellation of signals of unwanted multiplicity for complex oil mixtures containing broad and overlapping resonances. However, the use of signal intensities in DEPT subspectra to determine quantitatively the amounts of CH n groups present in oil mixtures suffers in accuracy due to variable polarization transfer and relaxation rates.

29 Si Spin–lattice relaxation in aluminosilicates

29 Si N.m.r. spin–lattice relaxation times have been measured in some layer aluminosilicates and found to vary over three orders of magnitude, demonstrating that, in contrast to results reported to date, 29Si T1s may be extremely long in aluminosilicates.

Differences in structure of organic matter in two soils as demonstrated by 13C cross polarisation nuclear magnetic resonance spectroscopy with magic angle spinning

Abstract Spectra of two whole soils have been recorded by cross polarisation n.m.r. spectroscopy with magic angle spinning. Magic angle spinning allows detailed structural comparisons between the types of organic carbon in whole soils to be made. Sufficient resolution is achieved to show that the two soils differ considerably in polysaccharide content.

Solid state 13C NMR of mercuric(II) acetate: scalar 13c199Hg coupling and crystal structure

Abstract Solid state 13 C CP/MAS spectra of crystalline mercuric(II) acetate have been obtained. Scalar 13 C 199 Hg couplings are observed in contrast to solution 13 C spectra where rapid acetate group exchange prevents detection of coupling. Two and three bond couplings are compared with typical values found in solution. Two major resonances are observed for both the methyl and carboxyl carbons. This can be rationalized by available crystal structure data which indicates non-equivalence of the two acetate groups attached to mercury.

1H and 199Hg NMR spectra of methylmercury(II) complexes. Effects of basicity and ortho substitution in pyridines(L) in complexes [MeHgL]NO3

Abstract Linear complexes [MeHgL]NO3 (L = substituted pyridine) have been prepared and their 1H and 199Hg NMR spectra measured and compared with other complexes of this series reported previously. The coupling constant J(1H−199Hg) correlates directly with pKa and with the gas phase enthalpy of ionization [ΔGi(g)] of LH+; with J(1H−199Hg) decreasing with increasing pKa or ΔGi(g). The chemical shift, δ, for 199Hg does not correlate with either pKa or ΔGi(g). Complexes without substituents in the 2 position of pyridine have δ199Hg ca. 80–100 ppm downfield from MeHgNO3, those with one methyl group in the 2 position ca. 125–150 ppm, and those with methyl groups in the 2 and 6 position (or benzyl or 3′-methylpyridyl groups in the 2 position) ca. 160–200 ppm downfield from MeHgNO3. The coupling constant J(1H−199Hg) is found to be more useful than δ199Hg in determination of solution structures of MeHg(II) complexes of this type of ligand.

Variable temperature carbon-13 and mercury-199 NMR examination of cyclohexylmercury systems

Abstract The variable temperature carbon-13 and mercury-199 nmr spectra of some cyclohexylmercurials. C 6 H 11 HgX (X = -OCOCH 3 . -CN, -C 6 H 11 and -C 6 H 5 ) have been recorded and assigned by consideration of chemical shifts, 199 Hg- 13 C coupling constants and comparisons with the data For 4-methylcyclohexyl derivatives of established constitution. These studies confirm the axial preference for the mercury groups (HgX) examined, although X does influence the conformational equilibrium to a minor extent. For dicyclohexylmercury, three arrangements about mercury are possible and anticipated ( a , a ; e , e ; a , e ), and at low temperatures signals appropriate for the three species are detected in the 13 C spectra. Some 199 Hg chemical shifts for related miscellaneous compounds are also presented, and equatorial mercury groups resonate 80–100 ppm to higher field of the corresponding axial groups.

A 199Hg NMR spectroscopic study of two and three-coordinate methylmercury(II) complexes, [MeHgL]NO3

Abstract 199 Hg NMR spectra are reported for the complexes [MeHgL]NO 3 containing either two- (e.g. L = pyridine) or three-coordinate mercury (e.g. L = 2,2′-bipyridyl). For unidentate and bidentate ligands of similar basicity chelation with bidentate ligands to give three-coordinate mercury results in upfield shifts of 199 Hg resonances from that of the linear complexes. For complexes of unidentate ligands shifts correlate with changes in base strength of the ligands, and methyl substitution in the 2 position of pyridine appears to result in an upfield shift of ca. 30 ppm. Effects of substitution in the 2 position are very strong in complexes of unidentate 2-benzylpyridine and 3,3′-dimethyl-2,2′-bipyridyl. Comparison of the 199 Hg shifts with J( 1 H- 199 Hg) shows the coupling constant to be insensitive to substitution in the 2 position in linear complexes and is a function only of the ligand base strength.

Oxythallation and oxymercuration. Carbon-13 NMR examination of some norbornene derivatives

Abstract Natural abundance 13 C NMR spectra of a number of oxythallation adducts of norbornenes have been obtained and assigned by considerations of SFORD spectra, chemical shifts, comparisons of spectra at different frequencies, T 1 values and some aspects of 203,205 Tl 13 C couplings. The substituent induced shifts (α, β, γ effects) at various carbons have been calculated and compared with those for the analogous mercury(II) compounds. 203,205 Tl 13 C and 199 Hg 13 C couplings have been measured, and for vicinal ( 3 J ) couplings, a dihedral angle dependence (of the Karplus type) is demonstrated.