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Reacting white phosphorus (P4 ) with sterically encumbered aryl lithium reagents (aryl=2,6-dimesitylphenyl or 2,4,6-tBu3 C6 H2 ) and B(C6 F5 )3 gives the unique, isolable Lewis acid stabilized bicyclo[1.1.0]tetraphosphabutane anion. Subsequent alkylation of the nucleophilic site of the RP4 anion gives access to non-symmetrical disubstituted bicyclic tetraphosphorus compounds. This novel method enables PC bond formation in a controlled fashion using white phosphorus as starting material., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The preparation and comprehensive characterization of a series of homoleptic sandwich complexes containing diphosphacyclobutadiene ligands are reported. Compounds [K([18]crown-6)(thf)(2)][Fe(η(4)-P(2)C(2)tBu(2))(2)] (K1), [K([18]crown-6)(thf)(2)][Co(η(4)-P(2)C(2)tBu(2))(2)] (K2), and [K([18]crown-6)(thf)(2)][Co(η(4)-P(2)C(2)Ad(2))(2)] (K3, Ad = adamantyl) were obtained from reactions of [K([18]crown-6)(thf)(2)][M(η(4)-C(14)H(10))(2)] (M = Fe, Co) with tBuC[triple bond]P (1, 2), or with AdC[triple bond]P (3). Neutral sandwiches [M(η(4)-P(2)C(2)tBu(2))(2)] (4: M = Fe 5: M = Co) were obtained by oxidizing 1 and 2 with [Cp(2)Fe]PF(6). Cyclic voltammetry and spectro-electrochemistry indicate that the two [M(η(4)-P(2)C(2)tBu(2))(2)](-)/[M(η(4)-P(2)C(2)tBu(2))(2)] moieties can be reversibly interconverted by one electron oxidation and reduction, respectively. Complexes 1-5 were characterized by multinuclear NMR, EPR (1 and 5), UV/Vis, and Mössbauer spectroscopies (1 and 4), mass spectrometry (4 and 5), and microanalysis (1-3). The molecular structures of 1-5 were determined by using X-ray crystallography. Essentially D(2d)-symmetric structures were found for all five complexes, which show the two 1,3-diphosphacyclobutadiene rings in a staggered orientation. Density functional theory calculations revealed the importance of covalent metal-ligand π bonding in 1-5. Possible oxidation state assignments for the metal ions are discussed.

P makes it possible: The convenient oxidative synthesis of the 16-electron organophosphorus iron sandwich complex [Fe(eta(4)-P(2)C(2)tBu(2))(2)] (see structure) suggests that the elusive all-carbon complex [Fe(eta(4)-C(4)H(4))(2)] is a viable synthetic target.

1,2-Addition of transient W(CO)(5)-complexed phosphinidenes exo to hexamethyl Dewar benzene affords the novel 3-phosphatricyclo[3.2.0.0(2,4)]hept-6-ene complexes. The fused tricyclic phosphiranes are obtained as both the Z and the thermally less stable E isomers, the (31)P NMR chemical shifts of which differ by about 60 ppm. A computational investigation shows that the phosphorus pyramidalization and the presence of the gamma double bond are responsible for this effect. The semiquantitative results contribute to a more systematic understanding of the structural influences on (31)P chemical shieldings. The congested double bond of the Z isomer can be epoxidized with m-chloroperbenzoic acid (MCPBA) to afford a fused tetracyclic P,O bis-adduct.

Novel, highly stable, linear and branched mono- and diphospha[n]triangulanes were synthesized in high yields by the CuCl-catalyzed phosphinidene addition to spirocyclopropanated methylenecyclopropanes and bicyclopropylidenes. The effect of spirofusion on the electronic properties of these esthetically attractive phosphacycles is apparent from X-ray single crystal structure analyses, which reveals a tightening of the phosphirane ring on additional spirocyclopropanation, and from the NMR features that show deshielded chemical shifts for the ring-phosphorus and -carbon atoms. Steric factors play a role in the addition reaction when the substrate alkene carries a second sphere of spirocyclopropane rings and causes the formation of 2-phosphabicyclo[3.2.0]heptenes in small amounts. These by-products most probably result from addition of the [PhP(Cl)W(CO)(5)]-Cu-L (L=alkene or solvent) reagent to the spirocyclopropanated bicyclopropylidene to give an intermediate sigma-complex, which subsequently, facilitated by steric factors, undergoes a cyclopropylcarbinyl to cyclobutyl ring expansion followed by a [1,3]-sigmatropic shift.