Winfried Becker

ACYL- AND ALKYLIDENEPHOSPHINES. XXI.1 Acylphosphines and Their Derivatives with Phosphorus Atoms of Coordination Number 3, 2, and 1

Abstract The following article summarizes our work on acylphosphines and acylphosphides as well as on alkylidene- and alkylidynephosphines, most of which were thought only thirty years ago not to exist under ordinary conditions.

1,2- and 1,3-diphosphetanes from alkylidenephosphines

Abstract Alkyl- or arylbis(trimethylsilyl)phosphines as well as tris(trimethylsilyl)phosphine and the corresponding arsines react with acyl chlorides to give [1-(trimethylsiloxy)alkylidene]phosphines 1 and -arsines 2; most of their 2,2-dimethylpropylidene derivatives are thermally stable at room temperature. With the same class of phosphines as starting compounds and carbon disulfide [bis(trimethylsilylsulfano)methylidene]phosphines 3 are formed, whereas [(dialkylamino)methylidene]-4 and [diarylmethylidene]phosphines 5 or the corresponding arsines 6 and 7 can be obtained from acyl amides or ketones.1

Bis(2,4,6-trimethylbenzoyl)phosphan und -arsan : Synthese und Struktur (Acyl- und Alkylidenphosphane ; 31)

Aus Lithium-bis(trimethylsilyl)phosphid · 2THF1 oder Lithiumdihydrogenarsenid · 2THF und 2,4,6-Trimethylbenzoylchlorid im Molverhaltnis 3:2 zugangliches Lithium-bis(2,4,6-trimethylbenzoyl)phosphid · 2THF (1a) bzw. -arsenid · 2THF (1b) [16] setzen sich mit Tetrafluoroborsaure · Diethylether-Addukt in nahezu quantitativer Ausbeute unter Lithium-Wasserstoff-Austausch zu Bis(2,4,6-trimethylbenzoyl)phosphan (2a) sowie zum entsprechenden Arsan 2b um. Nach der Synthese einer nun groseren Zahl von Derivaten [19] lassen sich fur die zugehorigen Keto- und Enol-Tautomeren charakteristische NMR-Parameter angeben.Nach den Ergebnissen von Rontgenstrukturanalysen (Raumgruppe Fdd2; a = 1 486,1(4)/1 501,7(4); b = 2975,8(12)/3000,6(6); c = 827,9(2)/822,7(2) pm bei—100° ± 3°C; Z = 8; Rw = 0,034/0,040) liegen die beiden zueinander isotypen Verbindungen 2a und 2b im Festkorper als Enol-Tautomere mit sehr kurzer, symmetrischer O‥H‥O-Brucke (O‥O243/245 pm) vor. Die Molekule zeigen aufgrund ihrer speziellen Lage die Punktsymmetrie 2; charakteristische Bindungslangen und -winkel sind: P-C 177; As-C 190; C-O 126/128; C-C (Aren) 150/147; O-H 122/128 pm; C-P-C 98° C-As-C 97° P-C-O 125° As-C-O 123° P-C-C 117° As-C-C 118°; C-O-H 99°/116° O-H-O 173°/146°. Die unterschiedliche Geometrie der beiden Enolringe wird diskutiert. Lithium bis(2,4,6-trimethylbenzoyl)phosphide·2THF (1a) and the homologous arsenide 1b [16] are prepared from lithium bis(trimethylsilyl)phosphide·2THF1 and lithium dihydrogenarsenide·2THF, resp., and 2,4,6-trimethylbenzoyl chloride in a molar ratio of 3:2. Subsequent reaction with tetrafluoroboric acid·diethylether adduct results in an exchange of lithium with hydrogen and formation of bis(2,4,6-trimethylbenzoyl)phosphine (2a) and the corresponding arsine 2b in nearly quantitative yields. Characteristic nmr parameters for the keto and enol tautomer could be obtained from a larger number of derivatives [19].X-ray structure determination of the two isotypic compounds 2a and 2b (space group F d d 2; a =1 486.1(4)/1501.7(4); b = 2975.8(12)/3 000.6(6); c = 827.9(2)/822.7(2) pm at −100° ± 3° C; Z = 8; Rw = 0.034/0.040) show enol tautomers with very short symmetrical O‥H‥O-bridges (O‥O 243/245 pm) to be present in the solid state. Due to their special position the molecules are of point symmetry 2; characteristic bond lengths and angles are: P-C 177; As-C 190; C-O 126/128; C-C (arene) 150/147; O-H 122/128 pm; C-P-C 98deg;; C-As-C 97°; P-C-O 125°; As-C-O 123°; P-C-C 117°; As-C-C 118°; C-O-H 99°/116°; O-H-O 173°/146°. The different geometry of the two enol rings is discussed in detail.

Alkylidenephosphines and Diphosphetanes

Abstract In studies of the reactivity and thermal stability of various alkylidenephos-phines prepared from benzophenone and organylbis(trimethylsilyl)phosphines via a NaOH-catalyzed elimination of hexamethyldisiloxane (eq. la), detailed analyses of nmr-spectra and x-ray structure determinations prove the methyl derivative la to dimerize to an 1,3-diphosphetane (2a), whereas from the iso-propyl compound 1b the 1,2-diphosphetane 2b is obtained [1]. This observation confirms our hypothesis that the formation of 1,2- or 1,3-diphosphetanes is determined by the steric requirements of the substituent at phosphorus.

Adamant-1-ylmethylidynephosphine : a new, stable phosphaalkyne (Unusually coordinated phosphorus compounds ; 7)

The reaction of tris[trimethylsilyl]phosphine (4a) as well as of the lithium bis[trimethylsilyl]phosphide·; tetrahydrofuran complex (4b) with 1-adamantoyl chloride (5) results in the formation of the phosphaalkene 7 in 67% or 96% yield, respectively. Subsequent sodium hydroxide or tetra-n-butylammonium fluoride-catalysed elimination of hexamethyldisiloxane from 7 at 20/90 °C gives rise to the phosphaalkyne 8 in 83 or 71% yield. The phosphaalkyne 8 undergoes smooth [3 + 2]cycloaddition reactions with 1,3-dipoles such as the nitrile oxide 9, the diazo compounds 12a-c, and the azide 15 to produce the phospholes 11,14a-c, and 16, respectively. The phosphaalkene 7 reacts with the dipoles 9 and 12a to give the same cycloadducts 11 and 14a, respectively. In these two reactions, the primary adducts undergo spontaneous (10 → 11) or sodium hydroxide-catalysed (13 → 14a) elimination of hexamethyldisiloxane.

Molekül- und Kristallstruktur des 1,2-Di(tert-butyl)-3-dimethylamino-1-thio-4-trimethylsilylsulfano-1λ5,2λ3-diphosphet-3-ens (Acyl- und Alkylidenphosphane ; 25)

Die bei der Zersetzung von tert-Butyl(N,N-dimethylthiocarbamoyl)-trimethylsilylphosphan mit nahezu quantitativer Ausbeute gebildete Titelverbindung 1 kristallisiert orthorhombisch in der Raumgruppe P212121 mit {a = 1067,3(1); b = 1077,1(1); c = 1924,6(5) pm; Z = 4} bei + 20°C. Nach den Ergebnissen einer Rontgenstrukturanalyse (RG = 0,038) ordnen sich die beiden tert-Butylgruppen am vierfach (P1) und am dreifach koordinierten Phosphoratom (P2) trans zueinander an. Charakteristische Bindungslangen sind {endocycl.: P1–P2 221,9(1); P1–C4 177,7(3); P2–C3 185,1(4); C3–C4 136,0(5)} und {exocycl.: P1–S1 195,6(1); C3–N3 135,8(4); C4–S4 177,7(4); S4–Si4 216,1(2) pm}; die Ringinnenwinkel an den Atomen P1, P2, C3 und C4 betragen 79,0(1); 73,5(1); 105,0(3) und 102,2(3)°. The title compound 1 formed in a nearly quantitative yield by decomposition of tert-butyl(N,N-dimethylthiocarbamoyl)trimethylsilylphosphine, crystallizes in the orthorhombic space group P212121 with {a = 1067.3(1); b = 1077.1(1); c = 1924.6(5) pm; Z = 4} at +20°C. An X-ray structure determination (RG = 0.038) shows two tert-butyl groups at a four- (P1) and a three-coordinate phosphorus atom (P2) to be placed on different sides of the four membered ring. Characteristic bond lengths as well as the angles at the atoms P1, P2, C3, and C4 inside the ring have already been given above.

Acylphosphines and their derivatives with phosphorus atoms of coordination number 3, 2, and 1 (Acyl- and alkylidenphosphanes ; 21)

The following article summarizes our work on acylphosphines and acylphosphides as well as on alkylidene- and alkylidynephosphines, most of which were thought only thirty years ago not to exist under ordinary conditions.