Phosphorus-Bridged Dinuclear Tungsten Amino(aryl)carbene Complexes – New Precursors for (2H-Azaphosphirene)tungsten Complexes bearing a σ-P-Bonded Cp* Group☆
✍ Scribed by Rainer Streubel; Udo Rohde; Jörg Jeske; Frank Ruthe; Peter G. Jones
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 238 KB
- Volume
- 1998
- Category
- Article
- ISSN
- 1434-1948
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✦ Synopsis
The first syntheses of pentacarbonyl [2-(pentamethyl-2,4case, a dinuclear carbene complex with a P(Cp*)-O-P(Cp*) bridging unit was isolated. Under ordinary reaction cyclopentadien-1-yl)-2H-azaphosphirene]tungsten complexes are reported, using a one-pot reaction of dichloro(pen-conditions 2H-azaphosphirene complexes are slowly transformed into {pentacarbonyl[chloro(pentamethyl-2,4-tamethyl-2,4-cyclopentadien-1-yl)phosphane (Cp*PCl 2 ) with triethylamine and {[amino(aryl)carbene]pentcarbonyltung-cyclopentadien-1-yl)phosphane]tungsten(0)}. NMR-spectroscopic and single-crystal X-ray structural data of some sten(0)}. [Pentamethyl-2,4-cyclopentadien-1-yl]phosphanediyl-bridged dinuclear carbene complexes are formed as dinuclear carbene complexes and 2-(pentamethyl-2,4cyclopentadien-1-yl)-2H-azaphosphirene complexes are long-lived intermediates, which, by elimination and rearrangement reactions, led to the final products. If traces presented. of water were present, then by-products were formed; in one
The chemistry of (2H-azaphosphirene)tungsten com-subsequent transformations (paths a and b) must have occurred very fast, because the mono-condensation products plexes has recently been the subject of increased interest, because of their widespread applicability in the synthesis of 3 could not be detected. Instead, the first products formed in these reactions were the (Cp*-phosphanediyl)-bridged di-three-, [2] four- [3] and five-membered [4] heterocycles. Therefore, our interest in further synthetic investigations was en-nuclear (carbene)metal complexes 4aϪe, aside with small amounts of the 2H-azaphosphirene complexes 6a؊e and hanced, and one of our most important aims was to develop a new access to 2H-azaphosphirene complexes using complex 7. 4aϪe were most probably formed, according to the two pathways a, b depicted in Scheme 1. Path a de-amino(aryl)carbene complexes, a base and dichloro(organo)phosphanes. Compared to [bis(trimethylsilyl)methy-scribes a further condensation, yielding 4aϪe, whereas a base-induced hydrogen chloride elimination, followed by lene]chlorophosphane, which was used in our initial synthetic approach, [5] the advantages should be: the ease of addition of one equivalent of 1 to the short-lived intermediates 5 (cf. ref. [9] ), would also explain the generation of the accessibility, the option of introducing P-functional groups into 2H-azaphosphirene complexes and the potential exten-complexes 4aϪe (path b). Interestingly, upon prolonged reaction, complexes 4aϪe eliminated 1 yielding the 2H-aza-sion of this method to condensation reactions of other dichloro(organo)element compounds of group-15 elements. phosphirene complexes 6aϪe, probably by unspecified rearrangements of 5; this elimination reaction has been pro-Furthermore, in order to mimic the bulkyness of the bis(trimethylsilyl)methyl substituent, which is useful for kinetic ven for the case of 4c by treating a pure sample of 4c with triethylamine yielding 6c. We observed that one of the fac-stabilization, we chose pentamethyl-2,4-cyclopentadien-1-yl (denoted hereafter as Cp*) and the corresponding dichloro-tors that limited the yields of 6aϪe was the rate of the reaction of complexes 6aϪe with triethylammonium chloride, phosphane, [6] Cp*PCl 2 .
Our first attempts to treat amino(aryl)carbene complexes which led to [{Cp*P(H)Cl}W(CO) 5 ] (7) in all cases (Scheme 1). This latter reaction was found to depend strongly on the 1a, b, [7] c, [8] d, e [7] with Cp*Cl 2 (2) at ambient temperature in ether with an excess of triethylamine failed. Therefore, nature of the para-phenyl substituent, the concentration and, most importantly, on the reaction temperature. There-we switched to the more polar solvent dichloromethane for the reactions reported hereafter. According to 31 P-NMR-fore, the temperature had to be kept between 0 and 18°C throughout the reactions and subsequent manipulations. spectroscopic investigations, the first condensation step and Apart from complexes 4aϪe, 6aϪe and 7, two other un- [᭛] Part 12: See ref. [1] .
identified products (amounts < 5%) were formed transi-