Hendrik Wilkens

Bond‐Selective Nitrile Insertion into the 2H‐Azaphosphirene Ring System as Induced by Tetracyanoethylene

Competitive reactions of 2H-azaphosphirene metal complexes 1a-c (M =Cr, Mo, W) with 1-piperidinonitrile and tetracyanoethylene in toluene have been observed at elevated temperatures. For the case of complex 1c, the delta5-1,2-azaphospholene complex 2c (as main product) and the 2H-1,4,2-diazaphosphole complex 3c (as by-product) were separated from the product mixture. At ambient temperature and using 1-piperidinonitrile as solvent, bond and regioselective insertion of 1-piperidinonitrile into the P-N bond of 2H-azaphosphirene metal complexes 1a-c (M = Cr, Mo, W) has been achieved in the presence of tetracyanoethylene (TCNE), yielding 2H-1,4,2-diazaphosphole metal complexes 3a-c, analogous reactions in benzo- or acetonitrile afforded the 2H-1,4,2-diazaphosphole tungsten complexes 3d, e. A preliminary study with the 2H-azaphosphirene tungsten complex 1c and 1-piperidinonitrile as solvent has revealed that substoichiometric amounts of TCNE (0.3 equiv) induce approximately 70% conversion of complex 1c. NMR data of the complexes 2c and 3a-e and the X-ray structure of complex 3c are discussed.

Syntheses, Structures, and Reactions of C-Methoxycarbonyl-Functionalized Small- and Medium-Sized P-Heterocycle Complexes

Thermal ring-opening of [{2-bis(trimethylsilyl)methyl-3- phenyl-2H-azaphosphirene-ĸP}pentacarbonyltungsten(0)] (8a) in the presence of dimethyl acetylenedicarboxylate (DMAD) led to the 2,3-bifunctionalized 1H-phosphirene complex 9a and the 4-phenyl-substituted 2H-1,2-azaphosphole complex 10a, the latter as a by-product. If a small amount of benzonitrile was added, complex 10a was obtained as the main product, along with a small amount of the decomplexed 2H-1,2-azaphosphole 11, which could not be isolated. Reaction of complex 10a with elemental sulfur furnished the corresponding PV sulfide 13. When the ring-opening of complex 8a was performed in the presence of two equivalents of DMAD and two equivalents of dimethyl cyanamide, we obtained the 4-dimethylamino-substituted 2H-1,2-azaphosphole complex 10b, together with the diastereomeric Δ3-1,3,2-oxazaphospholene complexes 14a,b. On reaction of [{2-pentamethylcyclopentadienyl-3-phenyl-2H-azaphosphirene-ĸP}pentacarbonyltungsten(0)] (8b) and DMAD in toluene, the corresponding 1H-phosphirene complex 9b was only formed as a transient species and the P-coordinated P,C-cage compound 15 was the final product. Using benzonitrile as solvent, the 4-phenyl-substituted 2H-1,2-azaphosphole complex 10c was obtained, together with the 7-aza-1-phosphanorbornadiene complex 16, the latter through partial decomposition of 10c coupled with rearrangement and a Diels–Alder reaction; the ratio 10c/16 was found to depend strongly on the molar ratio of complex 8b to DMAD. A cycloaddition reaction of the 2,3-bifunctionalized 1H-phosphirene complex 9a with 2,3-dimethylbutadiene furnished the bicyclic phosphirane complex 19, along with a small amount of the noncoordinated bicyclic phosphirane 20. Reaction of complex 9a with diethylamine yielded the phosphirane complex 21 as a 1,2-addition product, the diorganophosphane complex 22 through ring-opening of 9a, and the 3,4-functionalized 1,2-dihydro-1-phosphet-2-one complex 23 through an unprecedented ring-expansion reaction; the products 21, 22, 23 were formed in a ratio of ca. 1:1:1. The structures of the 1H-phosphirene complex 9a, the 4-dimethylamino-substituted 2H-1,2-azaphosphole complex 10b, the bicyclic phosphirane complex 19, the phosphirane complex 21, and the 1,2-dihydro-1-phosphet-2-one complex 23 have been determined by single-crystal X-ray diffraction analysis.

Bifunktionalisierte 1 H-Phosphiren- und g1-1-Phosphaallen-Wolframkomplexe

Der Wolfram(0)-Komplex [{(Me3Si)2HCPC(Ph)=N}W(CO)5] 1 reagiert beim Erwarmen mit den Acetylenderivaten 2 a–d in Toluol zu Benzonitril und den Komplexen [{(Me3Si)2HCPC(R)=COEt} · W(CO)5] 5 a–d (5 a: R = SiMe3; 5 b: R = SiPh3; 5 c: R = SnMe3; 5 d: R = SnPh3) und [{(Me3Si)2HCP=C=C(OEt)R} · W(CO)5] 6 a, b (6 a: R = SnMe3; 6 b: R = SnPh3), die chromatographisch gereinigt und bis auf 5 c und 6 a isoliert wurden, letztere wurden als Gemisch charakterisiert. Spektroskopische und massenspektrometrische Daten der Komplexe 5 a–d und 6 a, b werden angegeben und diskutiert. Die Struktur des Komplexes 5 a wurde durch Einkristall-Rontgenstrukturanalyse aufgeklart (5 a: Raumgruppe P21/n, Z = 4, a = 977,6(2) pm, b = 1814,6(4) pm, c = 1628,0(4) pm, β = 93,95(2)°). Bifunctionalized 1 H-Phosphirene and g1-1-Phosphaallene Tungsten Complexes The tungsten(0) complex [{(Me3Si)2HCPC(Ph)=N}W(CO)5] 1 reacts upon heating with acetylene derivatives 2 a–d in toluene to form benzonitrile and the complexes [{(Me3Si)2HCPC(R)=COEt} · W(CO)5] 5 a–d (5 a: R = SiMe3; 5 b: R = SiPh3; 5 c: R = SnMe3; 5 d: R = SnPh3) and [{(Me3Si)2HCP=C=C(OEt)R} · W(CO)5] 6 a, b (6 a: R = SnMe3; 6 b: R = SnPh3), which have been isolated by chromatography; complexes 5 c and 6 a have been characterized as mixtures. Spectroscopic and mass spectrometric data are discussed. The crystal structure of the compound 5 a was determined by X-ray single crystal structure analysis (5 a: space group P21/n, Z = 4, a = 977.6(2) pm, b = 1814.6(4) pm, c = 1628.0(4) pm, β = 93.95(2)°).

Synthesis of 1H-Diphosphirene, Phosphorus-Carbon Cage and 2,3-Dihydro-1,2,3-Triphosphete Tungsten Complexes

Abstract: New lH-diphosphirene and 2,3-dihydro-l,2,3-triphosphete tungsten complexes have been synthesized, by thermal decomposition of different 2H-azaphosphirene complexes in the presence of various phosphaalkynes. Novel phosphorus-carbon cage complexes were obtained, if a pentamethylcyclopentadienyl-substituted 2H-azaphosphirene complex and alkyl-substituted phosphaalkynes were employed.

Transylidation of a transiently formed nitrilium phosphane ylide complex

Thermal decomposition of the 3-phenyl-substituted 2H-azaphosphirene complex 1 in the presence of dimethyl cyanamide and dimethyl acetylenedicarboxylate (DMAD) yielded dimethylamino-substituted products, the 2H-1,2- azaphosphole complex 4b and the diastereoisomeric Δ3-1,3,2-oxazaphospholene complexes 5a,b; this represents the first example of 1,3-dipolar cycloaddition reactions of a nitrilium phosphane ylide complex that is generated in situ by transylidation.

Synthesis and Characterization of Some 2 H -1,4,2-Diazaphosphole-, 2 H -1,3,2-Diazaphosphole- and 2 H -1,2-Diazaphosphole- P -sulfide Derivatives

Abstract Partial decomplexation of 2H-1,4,2-diazaphosphole and 2H-1,2-azaphosphole complexes is observed upon prolonged heating in benzonitrile; the liberated heterocycles were detected spectroscopically, but could not be isolated. The first 2H-1,3,2-diazaphosphole derivative, formed by thermal decomplexation using o-xylene and 1,2-bis(diphenylphosphino)ethane, was isolated and characterized. In all three cases, the corresponding heterocyclic P(V)-sulfides were obtained by oxidative decomplexation using elemental sulfur. All products were characterized by NMR and MS spectroscopy and two, additionally, by X-ray diffraction.

Photochemically generated nitrilium phosphane-ylid tungsten complexes and their reactivity towards alkyne and nitrile derivatives

The photochemically generated nitrilium phosphane-ylid tungsten complex 2 reacts with different activated alkynes, dimethyl acetylenedicarboxylate (DMAD) (i) and ethyl acetylenecarboxylate (ii), and nitriles, ethyl cyanoformate (ECF) (iii) and 1-piperidinonitrile (iv), giving [3+2] cycloaddition products such as the 2H-1,2-azaphosphole complexes 3 (i) and 4 (ii), the 2H-1,4,2-diazaphosphole complex 5 (iii) and the 2H-1,3,2-diazaphosphole complex 7 in good to excellent yields, the latter complexes, 4–7, being formed regioselectively; the structure of the first ester-functionalized 2H-1,4,2-diazaphosphole complex 5 was established by X-ray analysis.

Synthesis and structure of the first 2H-1,3,2-diazaphosphole complex

Thermal decomposition of the 2H-azaphosphirene tungsten complex 1 in benzonitrile and in the presence of dimethylcyanamide yields the 2H-1,3,2-diazaphosphole tungsten complex 4, containing a novel five-membered heterocyclic ligand; the overall reaction may be described as a 1,3-dipolar cycloaddition of an in situ generated nitrilium phosphane ylide complex to benzonitrile.

Unexpected dimerisation of a 2H-azaphosphirene complex

Heating a 2H-azaphosphirene complex in the solid state afforded the first head-to-tail dimer, a 2,5-dihydro-2,5-diphosphapyrimidine complex, a η1-diphosphene complex and another complex having low-coordinated phosphorus centers; whereas the latter was detected only by 31P NMR spectroscopy, the dimer was isolated and structurally characterized.

Catalytic Reactions in Heterophosphole Complex Chemistry

Catalytic reaction of 2 H -azaphosphirene complex 1 with ortho -, meta -, and para -benzodinitrile ( 2a-c ) led in all cases to the 2 H -1,4,2-diazaphosphole complexes 3a-c if ferrocenium hexafluorophosphate was used as catalyst. In the case of the meta - and para -benzodinitriles 2b-c , the bis-2 H -1,4,2-diazaphosphole complexes 4b-c were additionally obtained. Under the same reaction conditions, acetone, diethylketone and cyclohexanone ( 5a-c ) reacted with complex 1 to yield j 3 -1,3,2-oxazaphospholene complexes 6a-c in good yields.