Helmut Keck

Synthesis, properties and structure of bis(dialkyldithiophosphinato)manganese(II) complexes

Abstract Reaction of Mn 2 (CO) 10 or powdered manganese with bis(diorganothiophosphoryl)disulfanes, R 2 P(S)- S 2 P(S)R 2 (R= Et, n -Pr) gives tetrahedral Mn(II)- dithiophosphinates, (R 2 PS 2 ) 2 Mn, which are dimerized in solution and in the solid state via ligand bridges. The crystal structure of the ethylcomplex is reported. Crystals are orthorhombic, space group Pbca with cell dimensions a = 20.164(4), b = 13.837(3) and c = 11.960(2) A.

The radical cation of trimethylphosphine oxide

Abstract The structure of the gaseous long-lived radical cation generated upon electron ionization of trimethylphosphine oxide, (CH 3 ) 3 PO, has been investigated by using ion-molecule reactions in a Fourier transform ion cyclotron resonance mass spectrometer. A radical cation with the connectivity of trimethylphosphine oxide is expected to react by facile electron transfer with triethylamine, pyridine and dimethyl disulfide since all these reactions are highly exothermic. However, no electron transfer reactions were observed. Instead, the radical cation transfers a proton to triethylamine and to pyridine, i.e., acts as a Bronsted acid. Further, the radical cation abstracts CH 3 S from dimethyl disulfide and hence demonstrates behavior characteristic of a distonic ion with a carbon radical center. This reactivity is unprecedented for a radical cation such as (CH 3 ) 3 P + -O with the odd spin located at an oxygen atom. These experimental results indicate that the initially generated radical cation (CH 3 ) 3 P + -O undergoes unimolecular isomerization to (CH 3 ) 2 P + (OH)CH 2 within a millisecond time frame. Ab initio molecular orbital calculations carried out at the unrestricted second-order Moller-Plesset (UMP2/6-31G** + ZPVE) level of theory support this conclusion by predicting that (CH 3 ) 2 P + (OH)CH 2 lies 23 kcal mol −1 lower in energy than (CH 3 ) 3 P + -O. The energy barrier for unimolecular [1,3]-hydrogen atom migration in (CH 3 ) 3 P + -O is estimated to be 24 kcal mol −1 . This study demonstrates that the PO moiety provides a very strong driving force for hydrogen shifts in phosphorus containing radical cations.

Ionic cluster dithiophosphinates [Mo3S4(R2PS2)3py3]+[MI3]−(M=Zn·py, Cd·py, Hg)

Abstract Reactions of clusters Mo 3 S 4 L 4 ( 2 ) (L=R 2 P(S)S − ; R=Et ( a ), Pr ( b )) with MI 2 (M=Zn, Cd, Hg) in the presence of pyridine yieided ionic clusters [Mo 3 S 4 L 3 py 3 ] + [MI 3 py] − (M=Zn ( 9 ), Cd ( 10 ); R=Et ( a ), Pr ( b )) and [Mo 3 S 4 L 3 py 3 ] + [HgI 3 ] − ( 11 ) (L=Pr 2 P(S)S − ), respectively. The cluster cations consist of a triangular array of Mo atoms which are bridged by three S atoms and capped by the fourth S atom. Each of the Mo atoms is chelated by one L and coordinated by one pyridine. 9a crystallizes in the monoclinic space group P 2 1 with Z =2 formula units in the unit cell of dimensions a =1120.9(2), b =1756.3(3), c =1447.3(2) pm, β=105.31(1)°, D c =1.98 mg/ mm 3 . The crystal structure was refined to R = 0.04 using 5599 observed reflections and consists of [Mo 3 S 4 (Et 2 PS) 3 py 3 ] + [ZnI 3 py] − . The coordination number of the Mo atoms is 8. The average distance MoMo is 276.6(2) pm. The Zn atom is coordinated tetrahedrally with average distance ZnI of 259.0(2) and ZnN of 208.8(11) pm.

Urea and Thiourea Derivatives of Bis(dimethyl-phosphinoylmethyl)-amine

A group of hitherto unknown 1-aryl-3,3-bis(dimethyl-phosphinoylmethyl)-, 1-benzyl-3,3-bis(dimethyl-phosphinoylmethyl)- and 1-cyclohexyl-3,3-bis(dimethyl-phosphinoylmethyl) ureas and thioureas 1-10 have been synthesized, characterized, and are reported in this article. The compounds were prepared via reaction of corresponding isocyanates or isothiocyanates with the secondary phosporus-containing amine: bis(dimethyl-phosphinoylmethyl)-amine. The composition of the novel compounds was proved by elemental analysis, corresponding structures were confirmed by IR, 1 H-, 31 P-, 31 P{ 1 H}-NMR spectroscopy and by mass spectrometry.

ZUR EXISTENZ VON “H3PS” UND SEINES RADIKALKATIONS IN DER GASPHASE

Abstract Radialkationen der Zusammensetzung [H3PS]+ (m/z66) entstehen beim EI-Zerfall (70eV) von ionisiertem Diethylphosphinsulfid Et2HP(S). Aus der Analyse des Stosaktivierungs(CA)-Massenspektrums der Ionen m/z 66 und aus thermochemischen Daten sowie den Ergebnissen semiempirischer MO-Rechnungen (MNDO) ergibt sich, das bei ihnen die Struktur [H2P-SH]+. (Cs) gegenuber [H3PS]+. (C3v) bzw. [HPSH2]+. (Cs) bevorzugt ist. Mittels der jungeren Technik der Neutralisations-Reionisations-Massenspektrometrie (NRMS) konnte gezeigt werden, das Ionen der Struktur [H2PSH]+. durch Neutralisation in Neutralmolekule H2P-SH ubergefuhrt werden konnen, die in der verdunnten Gasphase stabil sind.

SCHIFF BASES DERIVED FROM AMINOMETHYL-DIMETHYL-PHOSPHINE OXIDE

Abstract A group of Schiff bases 1-18 derived from aminomethyl-dimethyl-phosphine oxide with aromatic aldehydes have been synthesized. Structure and purity of the new compounds were determined by IR, 1H NMR and 31P{1H} NMR spectroscopy, mass spectrometry and elemental analysis.

THE PHOSPHOROTRITHIOUS ACID (HS)3P IS STABLE IN THE DILUTE GAS PHASE

Abstract Using the technique of neutralization-reionization mass spectrometry (NRMS) it could be shown that the elusive phosphorotrithious acid (HS)3P is a stable molecule in the rarefied gas phase. A triple propene elimination from the molecular ions of the dipropyl ester of propylphosphonotrithioic acid, PrP(S)(SPr)2, (70 eV EI) yields m/z 130 radical cations of composition “[H3PS3] +”. Analysis of their collisional activation (CA) mass spectrum using thermochemical data, shows that these “[H3PS3] +” ions have the structure [(HS)3P] + rather than that of the tautomer [(HS)2P(=S)H| +. Subjected to a NRMS experiment, these ions retain their structure and are cleanly reduced to (HS)3P. The results are entirely compatible with ab initio MO-calculations executed at the HF/3-21G∗ and HF/6-31G∗∗ levels of theory (GAUSSIAN 92 system of programs). The calculations predict that [(HS)3P] + and [(HS)2P(=S)H] + and their respective neutral counterparts are local minima which are separated by high potential energy ba...

Vierkernige Molybdän-Schwefel-Cluster mit Dithiophosphinatoliganden / Tetranuclear Molybdenum-Sulfur-Clusters with Dithiophosphinato Ligands

Tetranuclear clusters Mo4S4(R2PS2)6 (4) (a: R = Et, b: R = Pr) with cubane-like cores are conveniently obtained by reacting equimolar quantities of Mo3S4(Et2PS2)4, Mo(CO)6 and R2P(S)-S-S-P(S)R2. 31P NMR and MS data of 4 are reported and the magnetic properties are discussed. 4a crystallizes triclinically with a = 1159.41(6), b = 1162.77(7), c = 2228.54(14) pm, α = 102.660(3), β = 98.382(4), γ = 98.546(5)°. P1̅, Z = 2. The molecule consists of a distorted Mo4S4 cubane. Each Mo atom is coordinated by six S atoms: three within the cubane, two from a bidentate and one from a chelating dithiophosphinato ligand. Two Mo -Mo distances are short- ened by the chelate to an av. of 278.6 pm, while the av. of the remaining four Mo -Mo distances is 287.9 pm.

MASSENSPEKTROMETRISCHE UNTERSUCHUNGEN AN ORGANOPHOSPHORVERBINDUNGEN I Zum Massenspektrometrischen Fragmentierungsverhalten von Dithio- und Thiophosphonsäureanhydriden

Abstract 70 eV electron impact mass spectra of dimeric dithiophosphonic acid anhydrides [RP(S)S]2 (R = CH3, C6H5, p-CH3OC6H4, p-C2H5OC6H4, 2-Thienyl, 2-Naphthyl) and trimeric thiophosphonic acid anhydrides [RP(S)O]3 (R = CH3, C6H5, Cyclohexyl) are reported and discussed. General fragmentation patterns which are consistent with DADI metastable spectra are suggested for both classes of compounds. Molecular ions are observed in all cases. While in the earlier class ring fission followed by migration of R from phosphorus to sulphur is dominating, the –P–O–P– ring in the latter seems to be rather stable. Elektronenstos induzierte 70 eV Massenspektren der dimeren Dithiophosphonsaureanhydride [RP(S)S]2 (R = CH3, C6H5, p-CH3OC6H4, p-C2H5OC6H4, 2-Thienyl, 2-Naphthyl) und trimeren Thiophosphonsaureanhydride [RP(S)O]3 (R = CH3, C6H5, Cyclohexyl) werden aufgefuhrt und diskutiert. Allgemeine Fragmentierungsschemata, die durch Metastabilenspektren nach der Methode DADI erhartet worden sind, werden fur beide Verbindungs...

GASEOUS DIPHOSPHORUS AND TRIPHOSPHORUS SULFIDE: GENERATION AND IDENTIFICATION BY NEUTRALIZATION-REIONIZATION MASS SPECTROMETRY

Abstract The dissociative ionization by electron impact (70 eV) of tetraphosphorus trisulfide, P4S3, yields [P3S]+ and [PZS]+0 ions whose structures have been investigated by means of Coliisionai Activation (CA) mass spectra. Using the technique of Neutralization-Reionization mass spectrometry (NRMS) it is shown that both ions can be reduced to the corresponding neutral molecules. Thus, triphosphorus sulfide and diphosphorus sulfide are viable molecules in the rarefied gas phase. The results of ab initio MO calculations were used to interpret the experimental findings. Tetrahedral (C3v) and triangular (C2v) structures are proposed for the [P,S]+ and [PZS]+0 ions respectively.