The reaction of [Na (thf) (P Mes )] (Mes=2,4,6-Me C H ) with cyclohexyl isocyanide (2:5) resulted in the formation of the heterocyclic N-(tetramesityltetraphosphacyclopentylidene)cyclohexylamine [cyclo-{P Mes C(NCy)}] (2) (30-35 %), the unusual 1,3,5-triphospha-1,4-pentadiene (3) (40-45 %), and small amounts of the dimeric iminomethylidenephosphane cyclo-{PMesC(NCy)} (4). With catalytic amounts of AgBF , 2 was the major product. The reaction of 2 with [CuBr(SMe )] (1:1) produced bromido-bridged dimeric Cu complex 5. Molecular structures of compounds 3, 4, and 5 were obtained.

The reaction of [Na 2 (thf ) 4 P 4 Mes 4 ] (1) (Mes = 2,4,6-Me 3 C 6 H 2 ) with 1,3-dimethylimidazolin-2-ylidene (Me 2 Im) or the corresponding imidazolium iodide ([Me 2 ImH]I) leads to P-P sible for their tendency to disproportionate in reactions with electrophiles such as protons and alkyl or silyl groups. [3] The disproportionation includes rearrangement via a four-centered transition state involving P-P bond formation, which results in shorter linear primary or secondary phosphanes and also cyclic phosphanes. [4,5] Recently, we have reported selective reactions of sodium tetraphosphanediides with electrophiles, namely, monoprotonation [3] and stannylation. [6] Stannylation of Na 2 (P 4 Mes 4 ) gave the desired product, P 4 Mes 4 (SnBu 3 ) 2 , with an intact P 4 chain, which, surprisingly, proved to be highly unreactive. [6] Protonation of Na 2 (P 4 Mes 4 ) gave the neutral tetraphosphane P 4 Mes 4 H 2 , which is stable in the solid state but disproportionates in solution. [3] Additionally, P-P bond cleavage in M 2 (P 4 Mes 4 ) (M = Na, K) was also observed in the reaction with nucleophiles such as nBuLi, leading to the unusual phosphaindazole anion (P 2 C 9 H 9 ) -. [7] N-heterocyclic carbenes (NHCs) and cyclic (alkyl)-(amino) carbenes (CAACs) were lately used to stabilize unusual and reactive compounds of main-group elements such as silicon, phosphorus, boron, and antimony, for example, disilicon(0) with a Si=Si bond, [8] diphosphorus(0) (P 2 ), [9a,9b] P 2 radical cations and dications, [9c] phosphorus mononitride and its radical cation, [9d] P 4 or P 12 , [10a-10c] phosphinidenes, [11] phosphen- [a] 620 be obtained free of charge via www.ccdc.cam.ac.uk/data_request/ cif. Crystal Data for 2: C 14 H 19 N 2 P, M = 246.28, monoclinic, space group Cc, a = 9.0092(5) Å, b = 13.3093(7) Å, c = 11.5430(7) Å, β = 96.439(6)°, V = 1375.4(1) Å 3 , Z = 4, ρ calcd. = 1.189 Mg m -3 , μ(Mo-K α ) = 0.181 mm -1 , θ max = 26.37°, R = 0.0700 and R w = 0.0968 (all data), absolute structure parameter 0.03(10).Supporting Information (see footnote on the first page of this article): In situ 31 P{ 1 H} NMR spectra, NMR spectra of 2, and details of the theoretical studies.

Substitution of the dicarbaundecaborate anion nido-7,8-C2B9H12(-) (1) by precise hydride abstraction followed by nucleophilic attack usually leads to symmetric products 10-R-nido-7,8-C2B9H11. However, thioacetamide (MeC(S)NH2) as nucleophile and acetone/AlCl3 as hydride abstractor gave asymmetric 9-[MeC(NHiPr)S]-nido-7,8-C2B9H11 (2), whereas N,N-dimethylthioacetamide (MeC(S)NMe2) gave the expected symmetric 10-[MeC(NMe2)S]-nido-7,8-C2B9H11 (4). For the formation of 2, acetone and thioacetamide are assumed to give the intermediate MeC(S)N(CMe2) (3), which then attacks 1 with formation of 2. Similarly, reaction of acetyliminium chloride [MeC(O)NH(CPh2)]Cl (5) with 1 in THF gave a mixture of 9- and 10-substituted [MeC(NHCHPh2)O]-nido-7,8-C2B9H11 (6 and 7, respectively). These reactions are the first examples in which compounds (here heterodienes) that unite the functionalities of both hydride acceptor and nucleophilic site react with 1 in a bimolecular fashion. Furthermore, the analogous reaction of 1 and 5 (in an equilibrium mixture with acetyl chloride and benzophenone imine) in MeCN afforded 10-[MeC(NCPh2)NH]-nido-7,8-C2B9H11 (8) and MeC(O)NHCHPh2 (9).

The chemistry of polyphosphorus cations has rapidly developed in recent years, but their coordination behavior has remained mostly unexplored. Herein, we describe the reactivity of [P5R2]+ cations with cyclopentadienyl metal complexes. The reaction of [CpArFe(μ‐Br)]2 (CpAr=C5(C6H4‐4‐Et)5) with [P5R2][GaCl4] (R=iPr and 2,4,6‐Me3C6H2 (Mes)) afforded bicyclo[1.1.0]pentaphosphanes (1‐R, R=iPr and Mes), showing an unsymmetric “butterfly” structure. The same products 1‐R were formed from K[CpAr] and [P5R2][GaCl4]. The cationic complexes [CpArCo(η4‐P5R2)][GaCl4] (2‐R[GaCl4], R=iPr and Cy) and [(CpArNi)2(η3:3‐P5R2)][GaCl4] (3‐R[GaCl4]) were obtained from [P5R2][GaCl4] and [CpArM(μ‐Br)]2 (M=Co and Ni) as well as by using low‐valent “CpArMI” sources. Anion metathesis of 2‐R[GaCl4] and 3‐R[GaCl4] was achieved with Na[BArF24]. The P5 framework of the resulting salts 2‐R[BArF24] can be further functionalized with nucleophiles. Thus reactions with [Et4N]X (X=CN and Cl) give unprecedented cyano‐ and chloro‐functionalized complexes, while organo‐functionalization was achieved with CyMgCl.

A straightforward synthetic route to a novel phosphorus–carbon heterocycle, namely, phosphaindazole, which is the phosphorus analogue of indazole or indene, was developed from sodium tetraphosphanediide [Na2(P4Mes4)](Mes = 2,4,6‐Me3C6H2) and nBuLi. A proposed intermediate in this reaction, the dimesityldiphosphanide dianion, could be isolated and structurally characterized as [Na8(thf)8(P2Mes2)4]·2THF.