Formation and Structure of the First 7-Aza-1-phosphanorbornadiene Complex

Abstract

Dedicated to Professor Edgar Niecke on the occasion of his 60th birthdayThe chemistry of the norbornadienes (bicyclo[2.2.1]hepta-2,5-dienes) displays a variety of interesting aspects. One of these is the photochemical isomerization of norbornadienes to quadricyclanes [1] and its catalytic reversal. [2] Another is the synthesis, stability, and reactivity of heterocyclic analogues bearing a nitrogen or phosphorus atom at the 1-and/or 7-position (I ± III in Figure 1); particularly noteworthy results from this area concern the differences in stability between 7-aza- [3] and 7-phosphanorbornadienes (Type II), [4] (the latter can be stabilized and isolated by coordination of the phosphorus to a metal [5] ), and catalytic reactions [6] using 1-phosphanorbornadienes [7] (Type I) as novel ligands.

Partial Ring-Opening and Rearrangement Reactions of P,C-Cages to Yield Unusual Phosphinous Acids Stabilized by Pentacarbonyltungsten

“…Tetracyclic P,C-cage tungsten complexes 3a − c were obtained via thermolysis of P -C 5 Me 5 -substituted 2 H -azaphosphirene tungsten complex 1 in toluene in the presence of alkynyl esters. 31 P NMR spectroscopic reaction monitoring revealed that the formation of the polycyclic phosphirane derivatives 3a , b , c proceeded via intramolecular [4+2] cycloaddition reactions of transient 1 H -phosphirene tungsten complexes 2a − c (Scheme ).…”

“…31 P NMR spectroscopic reaction monitoring revealed that the formation of the polycyclic phosphirane derivatives 3a, 11 ) revealed that the cage structure is not significantly influenced by the different substituents on the phosphirane ring, so that bond lengths and angles observed in the cage are identical within the margins of error; although some bonds in the more congested derivative 3b appear to be marginally longer (3b: e.g., P-W: 2.464(1) A ˚; P-C4: 1.844(3) A ˚) than in 3a (P-W: 2.455(2) A ˚; P-C4: 1.839(7) A ˚) or 3c (P-W: 2.457(8) A ˚; P-C4: 1.836(3) A ˚). Typical structural features of these cage structures are small bond angle sums at phosphorus ( P -P(PR 3 )) of 195°(3a and 3c) or 196°(3b), thus yielding a strained, rigid cage that possesses a long P-C1 bond of 1.908(7) A ˚(3a), 1.916(3) A ˚(3b), or 1.924(3) (3c 12 ); for comparison, typical P(III)-C sp3 bond lengths are around 1.855 A ˚.13…”

A Novel N,P,C Cage Complex Formed by Rearrangement of a Tricyclic Phosphirane Complex: On the Importance of Non‐covalent Interactions

“…A versatile approach to a broad range of cage structures (e.g., VI )12 is based on the chemistry of highly reactive ligands bearing the P ‐pentamethylcyclopentadienyl group (Cp*) of bridging13 or terminal14 transition metal phosphinidene complexes, as well as on chemistry of P ‐Cp* oxaphosphirane complexes 15. In contrast, N,P,C cage formation involving transient cycloaddition reactions of 1,3‐dipoles such as nitrilium phosphane ylide complexes16 is rare,17 because the only established route to these transient 1,3‐dipole species relies on reactions of thermally formed electrophilic terminal phosphinidene complexes18 with nitriles at elevated temperatures 19.…”

Organphosphorus Compounds, Part 150; Imidovanadium(V)-Complexes as Reaction Partners for Kinetically Stabilized Phosphaalkynes. 1-Aza-2-phospha-4-vanada(V)-cyclobutenes: Precursors in the Synthesis of 1H-1,2-Azaphospholes

“…The bond lengths P(1)-C(2) [1.855(2) Å] and P(1)-C(6) [1.895(2) Å] are within the range of the experimentally determined average value (1.86 Å) 15 and are markedly longer than the corresponding bond lengths for C 3 14°], these bond length differences characterize the distortion of the norbornadiene skeleton. In addition, the nitrogen bridge is not positioned symmetrically between P(1) and C 4 15 A comparison of the geometric parameters of the bicyclic product 19e with those of a 1phosphanorbornadiene 16 or, of a tungsten-complexed azaphosphanorbornadiene 17 shows characteristic agreements for comparable structural increments. When the azaphosphanorbornadiene 19a is allowed to react with an equimolar amount of an oxidizing agent such as bis(trimethylsilyl) peroxide or sulfur in the presence of an equimolar amount of triethylamine, the respective chalcogen-containing bicyclic compounds 20 (58%) and 21 (71%) are obtained after workup (Scheme 7).…”