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The azides 2a-i undergo regiospecific [3+2]-cycloaddition with the phospha-alkyne 1 to form the l,2,3,4-triazaphospholes 3a-i; in the case of the reaction with 2J, an additional silyl shift occurs resulting in the formation of 4j. The latter product can by hydrolyzed to 6 which has also been prepared independently from 1 and hydrazoic acid(7). Flash vacuum pyrolyses of the 1,2,3,4-triazaphospholes 3c and 3e produce mixtures of the isomers 13a,b and 14a,b, respectively, from which the 1,2-azaphospholes 14 can be isolated as the major reaction products.

Syntheses of the anionic μ 3 -η 2 phosphaalkyne complexes [M 3 H(CO) 9 (Bu t CP)] − (M  Fe, Ru) are reported.

Syntheses of the phosphaalkyne complexes [Ni2(η5-C5H5)2(tBuCP)] and [CoNi(η5-C5H5)(CO)3(tBuCP)] are described. Adducts of the latter with [W(CO)5] and [Mn(CO)2(η5-C5H5)] are also reported. The reactions of tBuCP with [CoMn(CO)9] or [RuCo2(CO)11] lead to the disproportionation products [Co2(CO)6(tBuCP)] and [Mn2(CO)10] or [Ru3(CO)10], respectively.

Whereas tetrahedral alkyne complexes of the type [MM′(RCCR)], (M  Ni(η 5 -C 5 H 5 ), M′  Ni(η 5 -C 5 H 5 ); Co(CO) 3 ; Mo(CO) 2 (η 5 -C 5 H 5 )) react with [Fe 2 (CO) 9 ] to give cluster-expanded square pyramidal trimetallic complexes of the type (MM′Fe(CO) 3 (RCCR)], the tetrahedral phosphaalkyne complex [Mo 2 (CO) 4 (η 5 -C 5 H 5 ) 2 Bu t CP] reacts with [Fe 2 (CO) 9 ] or [W(CO) 5 THF] to give [Mo 2 (CO) 4 (η 5 -C 5 H 5 ) 2 (Bu t CP)Fe(CO) 4 ] and [Mo 2 (CO) 4 (η 5 -C 5 H 5 ) 2 (Bu t CP)W(CO) 5 ], respectively, in which the original tetrahedral cluster is intact. Structural features of these complexes and related alkyne and P 2 compounds are discussed.

Diazomethyl-Verbindungen (2a–h) addieren sich regiospezifisch an das Phosphaalkin 1 zu den Addukten 3, die durch spontane H-Verschiebung zu den 1,2,4-Diazaphospholen 4a–h isomerisieren. Nur bei der Reaktion 2i + 1 wird die H-Verschiebung zugunsten einer Trimethylsilyl-Wanderung (6i) unterdruckt. Auch bei der Addition von α-Diazoketonen 7a–e an 1 lassen sich Primarprodukte 8 nicht isolieren, da sie durch schnelle Acylverschiebung zu N-akzeptorsubstituierten Diazaphospholen (9a–e) isomerisieren. Im Fall von 7a–c kann daneben Isomerenbildung (11a–c) nachgewiesen werden. Die entsprechende Reaktionsfolge des Phosphaalkins 1 mit cyclischen α-Diazoketonen (12, 14, 16, 18) macht anellierte Vertreter des gleichen Strukturtyps (13, 15, 17, 19) leicht zuganglich. Phosphorylgruppen-Wanderungen sind fur die Bildung phosphorylierter 1,2,4-Diazaphosphole (24a–c) bei der Reaktion 1 + 20a–c verantwortlich. N-Acyl- und -Phosphorylgruppen der umgelagerten Cycloaddukte unterliegen leicht der Solvolyse (9a–e 4b, c, j, k; 24a–c 4b, c; 13 25). Phosphorus Compounds with Unusual Coordination, 191). – 1,2,4-Diazaphospholes by [3+2] Cycloaddition of Diazo Compounds onto a Stable Phosphaalkyne Diazomethyl compounds (2a–h) add regiospecifically onto the phosphaalkyne 1 to the adducts 3 which isomerize by spontaneous H-shift to the 1,2,4-diazaphospholes 4a–h. Only at the reaction 2i + 1 the H-shift is suppressed in favour of a trimethylsilyl migration (6i). Also at the addition of α-diazo ketones 7a–e onto 1 the primary adducts 8 cannot be isolated as they isomerize by fast acyl-shift to N-acceptor-substituted diazaphospholes (9a–e). In the case of 7a–c parallel to that formation of isomers (11a–c) can be demonstrated. The corresponding reaction sequence of the phosphaalkyne 1 with cyclic α-diazo ketones (12, 14, 16, 18) makes easily accessible annelated representatives of the same structural type (13, 15, 17, 19). Phosphoryl group migrations are responsible for the formation of phosphorylated 1,2,4-diazaphospholes (24–c) at the reaction 1 + 20a–c. N-Acyl and-phosphoryl groups of the rearranged cycloadducts are easily solvolysed (9a–e 4b, c, j, k; 24a–c 4b, c; 13 25).

Organophosphorus compounds have been applied in two ways in chemical synthesis. They can either be used as a reagent in a step of the synthesis (for example, in the Wittig reaction) or they can be incorporated directly into the target molecule. This second application, in particular, has expanded greatly in the last few years with the preparation of low-coordination phosphorus compounds. These include the phosphaalkynes, which are of great interest to organic and inorganic chemists. Phosphaalkynes have been employed in the synthesis of heterocyclic compounds, phosphaarenes and their valence isomers, and polycyclic compounds. Further applications have been the use of phosphaalkynes as new ligand systems in complex chemistry and their cyclooligomerization with organometallic reagents. While the chemical properties of phosphaalkynes have little in common with those of nitriles, they are in many ways very similar to those of the isoelectronic acetylenes.

Methylidynephosphane ( 2 ) is generated under flash pyrolytic conditions by cleavage of isobutene from the phosphaalkyne ( 1 ) or by elimination of hydrogen chloride from dichloromethylphosphine ( 3 ). It undergoes [3 + 2]-cycloaddition reactions with stable dipoles eq. diazo compounds ( 2 + 4a,b → 5a,b ), methyl azide ( 2 + 7 → 8 ), benzonitriloxide ( 2 + 10 → 12 , 1:2-adduct) and 3-methyl-2,4-diphenyl-1,3-oxazolium-5-olate ( 2 + 13 → 15 ) to give the corresponding phospholes. Silylated phosphaalkene ( 19 ) can be used as a synthetic substitute for 2 : the 5-trimethylsilyl-1 H -1,2,4-diazaphospholes ( 22 ), which result from the reaction of 19 and the diazo compounds 4 with chlorotrimethylsilane elimination, are desilylated to 5 by potassium fluoride in dimethyl formamide.

1,2,3-Oxadiazolium-5-olate (Sydnone) (2a–e) reagieren mit dem Phosphaalkin 1 unter [3 + 2]-Cycloaddition und nachfolgender Kohlendioxid-Cycloeliminierung zu den 1H-1,2,4-Diazaphospholen 5a–e. Nur bei der Umsetzung 1 + 2a kann auch das Regioisomere 6a als Nebenprodukt nachgewiesen werden. Von 1H-(bzw. 2H)-1,2,4-Diazaphospholen ausgehend, sind einige Vertreter der gleichen Reihe durch Lithiierung und anschliesende Methylierung zuganglich (7a–c 8a–c 5a, c, e). Das 1,3-Oxazolium-5-olat (Munchnon) 12 sowie das 1,3-Dithiolium-4-olat 14 reagieren analog mit 1 zum 1,3-Aza- bzw. 1,3-Thiaphosphol 13 bzw. 15. Konstitutionsisomere Thiazaphosphole (17, 18) werden bei der Umsetzung von 1 mit dem 1,3,2-Oxathiazolium-5-olat 16 gebildet. Phosphorus Compounds with Unusual Coordination, 211). –Cycloaddition of Mesoionic Compounds onto a Stable Phosphaalkyne – New Facilities in the Synthesis of Aza- and Thiaphospholes 1,2,3-Oxadiazolium-5-olates (sydnones) (2a–e) react with the phosphaalkyne 1 under [3 + 2] cycloaddition and following cycloelimination of carbon dioxide to give 1H-1,2,4-diazaphospholes 5a–e. Only in the reaction 1 + 2a the regioisomer 6a can also be detected as by-product. Starting with 1H(or 2H)-1,2,4-diazaphospholes some representatives of the same series are accessible by lithiation and subsequent methylation (7a–c 8a–c 5a, c, e). The 1,3-oxazolium-5-olate (munchnone) 12 as well as the 1,3-dithiolium-4-olate 14 react analogously with 1 to yield the 1,3-aza- and 1,3-thiaphosphole 13 and 15, respectively. Constitutional isomeric thiazaphospholes (17, 18) are formed in the reaction of 1 with the 1,3,2-oxathiazolium-5-olate 16.

The phosphaalkyne ligand in [Mo 2 (η-C 5 H 5 ) 2 (CO) 4 ( t BuCP)] can be used in transition metal cluster interlinkage.

Nonacarbonylbis(μ3-fluoromethylidyne)triiron, Fe3(CO)9(μ3-CF)2, and tetrafluoroferrole, (CO)3(Fe FeCFCFCFC F(CO)3, are obtained by the reaction of Fe(CO)5 with CFBr3. Fe3(CO)9(μ3-CF)2 was found to be a versatile starting material for the synthesis of other new clusters. Clusters containing a diferra-allyligand are formed by regioselective attack of alkynes on one μ3-CF ligand of Fe3(CO)9(μ3-CF)2 from the sterically less-hindered side. Replacement of fluorine by chlorine in Fe3(CO)9(μ3-CF)2 using aluminium chloride yields nonacarbonylbis(μ3-chloromethylidyne)triiron at ambient temperature. At elevated temperature or with aluminium bromide further attack of the cluster and substitution of three carbonyl ligands by benzene occurs, forming a cationic cluster, which reacts with nucleophiles such as alcohols, forming Fe3(CO)6(η6-C6H6)(μ3-CX)(μ3-CCOOR). The reaction of Fe3(CO)9(μ3-CF)2 with the phosphaalkyne t-C4H6CP results in the formation of a pentagonal bipyramidal cluster Fe2(CO)8[ FeCFC(C 4 H 9 )PC F], that contains a perfect planar FeCPCC five-membered ring system. In the cluster expansion reaction of Fe3(CO)9(μ3-CF)2 with Cp*Co(CO)2, carboncarbond bond formation with formation of a coordinated difluoroethyne ligand occurs. To our knowledge Cp*CoFe3(CO)9(μ4-η2-FCCF) is the first example of a coordinated difluoroethyne ligand.

The 1:1 molar reaction of the alkoxy(naphthyl)carbene-Cr complexes (I) with the phosphaalkyne (II) leads to the formation of the phosphaphenanthrenehydroquinone complexes (III) by connection of (II), the carbene ligand and one CO ligand.

Reactions of methylphosphaalkyne, P≡CMe, with a digermene, R" 2 Ge≡GeR" 2 (R" = -CH(SiMe 3 ) 2 ), and two distannenes, R" 2 Sn≡SnR" 2 and Ar' 2 Sn≡SnAr' 2 (Ar' = C 6 H 2 Pr i 3 -2,4,6), have given moderate to high yields of the first bridged 2,3,5,6-tetraphospha-1,4-dimethylidenecyclohexanes, [R 2 E{C(Me)(H)PC(≡CH 2 )P}] 2 (R = R" or Ar', E = Sn or Ge), all of which have been structurally characterized. Their mechanisms of formation are thought to involve successive [2 + 1] and [2 + 2] phosphaalkyne cycloaddition, heterocycle rearrangement, phosphaalkene/ vinylphosphine tautomerization, and intermolecular hydrophosphination reactions. In one reaction, two intermediates have been spectroscopically observed and one trapped by coordination to one or two W(CO) 5 fragments, yielding the first diphosphagermole complexes, {[W(CO) 5 } 1or2 {R" 2 Ge[C(Me)PC(Me)P]}], which have been structurally characterized. Differences between the reactivities of P=CMe and P≡CBu t are highlighted.

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1983, 501. DOI:10.1002/anie.198305010

The reaction of iminophosphanes, RPNR′ 1 with PCBu t 2 affords diphosphirenes R(R′N) PPC Bu t 3 , and by isomerization the azadiphosphetines R PN(R) PC Bu t 4 .