Abstract Phosphinoformic acid is unstable like the N-analogue carbamic acid. We found however that the acid can be stabilized by coordination via P to a (CO)5Cr-moiety [1]. In accordance with the conclusions of Leiserowitz [2] about solid carboxylic acids the crystal formic acid consists of hydrogen of the Cr atom is a distorted bonds between 1.881 and 1.928 A bond of 2.335 A. The angular distortion is small as shown by a maximum deviation of about 2.3° fiom the ideal geometry. At the P atom all bonding angles involving the Cr atom are widened to a maximum of 124° and the other ones are reduced to a minimum of 95°. In the crystal structure two symmetry-related molecules are connected to each other by means of two equivalent hydrogen bonds 06… 07′ and 07… 06′ of 2.660 c length between the carboxylic groups. Because of a twofold disorder along the bond P-C6, proven by bond lengths of 1.269(2) A for C6–06 and 1.264(2) A for C6–07 as well as by the localization and refinement of two H atoms with an occupancy ...

Dissociative electron impact ionization (70 eV) of PhPBr2 yields [C-6,H-5,P](.+) ions with the PhP connectivity, as inferred from its collisional activation mass spectrum. Neutralization-Reionization experiments on this ion indicate that its neutral counterpart, phenylphosphinidene, Ph-P, is a stable species in the dilute gas phase.

EI fragmentation of trimethylphosphine sulfide (CH3)(3)P(S) (1) is reported and discussed. [1](+.) mainly retains the connectivity of the neutral molecule and no rearrangements to other long-lived isomeric farms occur. However, some [1](+.) ions undergo a unimolecular reaction by a [1,3]-hydrogen shift from carbon to sulfur atom to produce the short-lived carbon centered ylide radical [(CH3)(2)((CH2)-C-.)P+-SH]. Further, isomerization of the molecular ion by an [1,2]-shift of a methyl group from phosphorus to sulfur is suggested which leads to [(CH,),P-SCH3](+.). Compared to [1](+.) the coordination number at phosphorus in the latter ion is reduced from four to three. Structures of fragment ions [C-2,H-6,P,S](+) (m/z 93), [C-3,H-8,P](+) (m/z 75) and [C-2,H-6,P](+) (m/z 61) have been examined by collisional activation (CA) mass spectrometry. All. the even-electron ions exist with a phosphonium structure as dimethylthioxophosphonium- [(CH3)(2)P = S](+) (m/z 93), dimethyl-methylenephosphonium-[(CH3)(2)P = CH2](+) (m/z 75), and methyl-methylenephosphonium-ion [(CH3)HP = CH2](+) (m/z 61), respectively. The experimental findings are confirmed and complemented by the results of ab initio MO calculations. Copyright (C) 1999 John Whey & Sons, Ltd.

Abstract As members of the family of low-coordinated phosphorus compounds, the phosphinidenes (RP) containing subvalent phosphorus (σ1,λ1-P) are of current interest. Until now, no Organophosphiaidene RP (R=Alkyl, Aryl) is known to be stable in the condensed phase. As the results of trapping experiments are questioned, the formation of RP as intermediates is still doubtful [1]. The mass spectrometric decay of some organophosphorus compounds yields radical cations [C6,H5,P]+∗ m/z 108. For these species structures 1 and 2 are conceivable:

Crystal structure analysis of (CO)(5)CrPH2COOH (a = 1338.2, b = 622.6, c = 1161.5 pm, beta = 96,77 degrees, P2(1)/c, Z = 4, R = 0.0330) has shown the complex to be dimerized via hydrogen-bonds of the COOH group. Geometrical parameters of the hypothetical free ligand [H2PCOOH](2) were calculated using the HF/3-21 G*, HF/6-31 G** and MP2-FU/6-31 G** basis sets. Bond lengths and bond angles of the calculated free ligand are similar to those derived from the crystal structure analysis of the coordinated ligand and are not significantly influenced by coordination and/or intermolecular interactions.

Crystal structure analysis of (CO)5CrPH2COOH (a = 1338.2, b = 622.6, c = 1161.5 pm, β = 96,77°, P21/c, Z = 4, R = 0.0330) has shown the complex to be dimerized via hydrogen-bonds of the COOH group. Geometrical parameters of the hypothetical free ligand [H2PCOOH]2 were calculated using the HF/3-21 G*, HF/6-31G** and MP2-FU/6-31 G** basis sets. Bond lengths and bond angles of the calculated free ligand are similar to those derived from the crystal structure analysis of the coordinated ligand and are not significantly influenced by coordination and/or intermolecular interactions.

An ab initio study was made of the radical anions of thioxophosphane (H-PS) and thiohydroxyphosphinidene (H-S-P). Geometries were optimized at the UHF/3-21G∗, UHF/6-31G∗∗, UHF/6-31++G∗∗ and UMP2/6-31++G∗∗ levels of theory. Furthermore, the transition state between [H-P-S].− and [H-S-P].− was determined. The calculations show that [H-P-S].− is more stable than [H-S-P].−, with a significant barrier to isomerization. The opposite order of stability for the corresponding cations has been found previously.

The preparation of lithiumphosphinoformates R(2)PCOOLi 1 (R = Ph, c-Hexyl, i-Pr, Et) and RHPCOOLi 2 (R = Ph, c-Hexyl) from R(2)PLi or RPHLi and CO2 is described. In the latter reaction RP(COOLi)(2) 3 and RPH(2) are formed in addition to 2. In protic media 1-3 are rapidly decomposed with decarboxylation and formation of R(2)PH and RPH(2), respectively. Reactions of 1 with Mel, (MeO)(2)SO2, Me(3)SiCl and CS2 are similar to those of Ph(2)PCOONa and no significant influence of R was detected. With (MeO)(2)SO2 mixtures of 2 and 3 gave esters RHPCOOMe and RP(COOMe)(2) while with Me(3)SiCl RHPCOOSiMe(3) was obtained as the sole product. Ab initio MO calculations (GAUSSIAN 90 system of programs; HF/3-21G*, HF/6-31G** and MP2/6-31G** basis sets) showed the phosphinoformic acid to be less stable than its decomposition products, from which it is separated by a high barrier of isomerization. Therefore the acid should be stable in the rarefied gas phase.

The dissociative ionization by electron impact (70 eV) of tetraphosphorus trisulfide, P4S3, yields P3S2+ ions whose neutralization/reionization mass spectrum shows that the elusive P3S2. radical is a viable species in the rarefied gas phase. Ab initio molecular orbital calculations indicate that the structure of this radical is that of a planar five-membered PPSPS ring of C2v symmetry.

Using the technique of neutralization-reionization mass spectrometry (NRMS) we have shown that the elusive thioxophosphane H-P=S and its tautomer H-S-P, (thiohydroxy)phosphinidene, are stable molecules in the gas phase. H-S-P.+ radical cations, generated by electron impact ionization of diethylphosphine sulfide, (C2H5)2HP=S, are cleanly reduced to H-S-P; whereas H-P=S.- anions, generated in a negative chemical ionization (NCI) experiment with the diethylphosphine sulfide, are readily oxidized to H-P=S. Double collision experiments on the S-34 isotopomers of the two tautomeric species were used to confirm the connectivity of the atoms. H-S-P is the first example of a molecule of the composition "XPS" (e.g., X = F, Cl, or Br) in which P does not take the central position.

By neutralization–reionization mass spectrometry (NRMS), the parent compound of the phosphorus ylides, methylenephosphorane CH 2 PH 3 , can be generated and unequivocally characterized. This substance cannot be “bottled” but is stable under the conditions of the NRMS experiment, and its properties correspond with those proposed by theory.

Durch Neutralisations‐Reionisations‐Massenspektrometrie (NRMS)äß sich die Stammverbindung der Phosphor‐Ylide, Methylenphosphoran CH2PH3, erzeugen und eindeutig charakterisieren. Diese Substanz läß sich zwar nicht „auf Flaschen ziehen”︁, ist aber unter den Bedingungen des NRMS‐Experiments stabil. Ihre Eigenschaften stimmen mit den theoretisch vorhergesagten überein.

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