The phosphadiazonium cation [MesNP](+) reacts quantitatively with the fluorenylide anion, MesNH(2), and MesOH (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 MesNPCl with fluorenyllithium gives the aminofluorenylidenephosphine [crystal data: C(31)H(38)NP, monoclinic, P2(1)/c, a = 9.568(8) Å, b = 24.25(2) Å, c = 11.77(1) Å, beta = 101.38(8) degrees, Z = 4]. Similarly, reaction of [MesNP][GaCl(4)] with MesNH(2) gives the diaminophosphenium salt [MesN(H)PN(H)Mes][GaCl(4)] [crystal data: C(36)H(60)Cl(4)GaN(2)P, monoclinic, C2/c, a = 24.921(2) Å, b = 10.198(4) Å, c = 16.445(2) Å, beta = 93.32(1) degrees, Z = 4], and reaction with MesOH gives the first example of an aminooxyphosphenium salt [MesN(H)POMes][GaCl(4)]. 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 [MesNP-PPh(3)][SO(3)CF(3)] [crystal data: C(37)H(44)F(3)NO(3)P(2)S, triclinic, P&onemacr;, a = 10.663(1) Å, b = 19.439(1) Å, c = 10.502(1) Å, alpha = 103.100(7) degrees, beta = 113.311(7) degrees, gamma = 93.401(7) degrees, Z = 2]. As part of the unequivocal characterization of the aminooxyphosphenium salt, detailed solid-state (31)P 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 pi orbitals.

Several solid-state NMR techniques have been employed to characterize phosphorus chemical shift tensors and 31P−31P spin−spin coupling interactions for bisphosphine molybdenum complexes where only one phosphorus of the bisphosphine ligand is coordinated to the metal. The bisphosphine ligand of each complex was either tetraphenyldiphosphine, tpdp, or bis(diphenylphosphino)methane, dppm. For one compound, (OC)5Mo(η1-dppm), single crystals were examined by 31P NMR and X-ray diffraction. For the metal-bound phosphorus, the most shielded direction of the chemical shift tensor is near the Mo−P bond axis. For the non-coordinated phosphorus, the most shielded direction is oriented in the direction of the formal electron lone pair on phosphorus. For the other compounds, stationary powder samples were examined using dipolar-chemical shift and 2D spin−echo techniques. Powder samples were also examined under slow magic-angle spinning, variable-angle spinning, and rotational-resonance conditions. Analysis of these 31P NMR spectra suggested chemical shift tensor orientations analogous to those measured for the single crystal; however, in the case of powders only the relative orientations of the two chemical shift tensors with respect to the P−P axis can be determined. Our investigations indicate that spectra from powder samples should be analyzed at two or more applied magnetic fields. The 2D spin−echo experiment proved to be invaluable for obtaining the effective dipolar P,P coupling constant, R, and the relative signs of R and the indirect spin−spin coupling constant, J. Values of n J(31P,31P) measured in the solid state often differ significantly from the conformationally averaged values obtained in solution. The tpdp derivatives appear to have a reduced R, whereas for the dppm systems, R agrees very well with the value calculated from the known P,P separations.

Phosphorus chemical shift and spin-spin coupling tensors have been characterized for tetramethyldiphosphine disulfide (TMPS) by analysis of 31 P CP NMR spectra obtained at 4.7 T for a single crystal. In addition, 31 P CP NMR spectra of stationary powder and magic angle spinning (MAS) samples have been acquired at two applied magnetic fields (4.7 and 9.4 T) and analyzed independently using the dipolar-chemical shift method. A 2D spin-echo NMR spectrum was also obtained to independently determine the effective 31 P-31 P dipolar coupling constant. The crystal structure of TMPS (space group C2/m) consists of six molecules per unit cell. For two of the six molecules, the two phosphorus nuclei are related by an inversion center (site 1), while the remaining four molecules possess mirror planes containing the S-P-P-S bonds (site 2). The differences between the two sites are very subtle, as revealed by a redetermination of the X-ray crystal structure. The phosphorus chemical shift tensors obtained from both single-crystal and dipolar-chemical shift NMR methods are in excellent agreement. For site 1, δ 11 ) 91 ppm, δ 22 ) 75 ppm, and δ 33 ) -63 ppm with an error of (2 ppm for each component. The principal components of the phosphorus chemical shift tensor at site 2 are very similar; δ 11 ) 92 ppm, δ 22 ) 74 ppm, and δ 33 ) -59 ppm, again with errors of (2 ppm. The phosphorus chemical shift tensors for both sites are oriented such that the direction of highest shielding is closest to the P-S bond while the direction of least shielding is perpendicular to the plane containing the S-P-P-S bonds. Ab initio (RHF and DFT) calculations of the phosphorus chemical shift tensors for both sites are in good agreement with experiment.

Hyperpolarized (129)Xe NMR spectroscopy is used to establish the solid-state porosity of shape-persistent macrocycles with either an organic or metal-organic framework. These studies show that even upon removal of cocrystallized solvent molecules, the macrocycles maintain a porous or channeled structure. The technique can provide valuable information about systems for which X-ray crystallographic analysis is not feasible. [structure: see text]