The synthesis and study of main-group-element analogues of alkenes and alkynes containing genuine (p À p)p bonds involving p-block elements is a central theme of inorganic chemistry. [1,2] The prospect to "copy" the predictable and sophisticated reaction chemistry of C=C and CC bonds utilizing functional inorganic systems is particularly enticing. However, in many instances, the investigation of multiple bonds of heavy elements leads to fascinating, albeit unexpected, outcomes that reinforce the fundamental differences between the first and subsequent periods.Inspired by the intriguing analogy between P=C and C=C bonds in molecular chemistry, [3] we developed the addition polymerization of phosphaalkenes as a route to new functional phosphorus-containing polymers (Scheme 1). [4] Although the synthesis of phosphorus-containing macromolecules is of widespread interest because of their attractive properties and potential applications, [5] the study of the addition polymerization of P = C bonds remains in its infancy. Our studies showed that MesP=CPh 2 (1) and related monomers polymerize in the presence of radical or anionic initiators to afford poly(methylenephosphine) (Scheme 1). [6] The living anionic polymerization of 1 permits the formation of functional phosphine-containing block copolymers, [7,8] and the radical-initiated copolymerization of 1 with styrene affords random copolymers. [9] In order to explore the mechanism of radical addition to P = C bonds during polymerization, we investigated the reactions of monomer 1 with TEMPO-derived radical sources. Herein, we report the discovery of a fascinating isomerization polymerization of phosphaalkene 1 in the presence of radical alkoxyamine initiators. These striking results led to a revision of the proposed microstructure for poly(methylenephosphine) that was produced by a radical reaction.In an effort to understand the initiation step in the radical polymerization of 1, we investigated its reaction with TEMPO (1-2 equiv). 31 P NMR spectroscopic analysis of the reaction mixtures suggested the formation of multiple products, including radical species, which were detected by EPR spectroscopy. To date, none of these products have been successfully isolated or unambiguously identified. In contrast, employing the complex 1·AuCl [10,11] instead of 1 affords a single product with TEMPO. Specifically, treatment of a solution of 1·AuCl in toluene with TEMPO (1 equiv) resulted in 50 % conversion of 1·AuCl (d = 167.1) to a new species, as determined by 31 P NMR spectroscopy. Addition of more TEMPO (1 equiv, that is, 2 equiv total) resulted in complete conversion of 1·AuCl to two products in a ratio of approximately 1:3, which displayed 31 P signals at 135.6 ppm (d, J PH = 18 Hz) and 130.5 ppm (d, J PH = 18 Hz). The magnitudes of the 31 P-1 H coupling constants are not consistent with the expected product Mes(TEMPO)P(AuCl)-C-(TEMPO)Ph 2 .Colorless crystals were obtained by slow diffusion of hexanes into the reaction mixture at À30 8C. Analysis of the crystals by X-ray crys...

A series of symmetric and unsymmetric N,N-bis(diarylphosphino)amine ('PNP') ligands (Ar2PN(R)PNAr'2: R = Me, Ar2 = o-anisyl, Ar'2 = Ph, 1, R = Me, Ar2 = o-tolyl, Ar'2 = Ph, 2, R = Me, Ar2 = Ph(o-ethyl), Ar'2 = Ph, 3, R = Me, Ar2 = Ar'2 = o-anisyl, 4, R = iPr, Ar2 = Ar'2 = Ph, 5) and symmetric N,N'-bis(diarylphosphino)dimethylhydrazine ('PNNP') ligands (Ar2PN(Me)N(Me)PAr2: Ar2 = o-tolyl, 6, Ar2 = o-anisyl, 7) have been synthesised. Catalytic screening for ethene/styrene co-trimerisation and isoprene trimerisation was performed via the in situ complexation to [CrCl3(THF)3] followed by activation with methylaluminoxane (MAO). PNNP catalytic systems showed a significant increase in activity and selectivity over previously reported PNP systems in isoprene trimerisation. Comparing the symmetric and unsymmetric variants in ethene and styrene co-trimerisation resulted in a switch in selectivity, an unsymmetric catalytic (o-anisyl)2PN(Me)PPh2 (1) ligand system affording unique incorporation of two styrenic monomers into the co-trimer product distribution differing from the familiar two ethene and one styrene -substituted alkenes. Complexes of the type [(diphosphine)Cr(CO)4] 8-11 were also synthesised, the single-crystal X-ray diffraction of which are reported. We propose the mechanisms of these catalytic transformations and an insight into the effect of the ligand series on the chromacyclic catalytic intermediates.

The formation of odd-numbered olefins in chromiumcatalyzed ethylene oligomerization in which substoichiometric quantities of diphosphine ligand are used can be attributed to chain transfer between diphosphine-free chromium species and the AlMe 3 present in MAO cocatalysts.

Palladium complexes supported by a 2,3-diphenylcyclopropenylidene carbene ligand are efficient and robust catalysts for C−N coupling reactions.

The synthesis and study of main-group-element analogues of alkenes and alkynes containing genuine (p À p)p bonds involving p-block elements is a central theme of inorganic chemistry. [1,2] The prospect to "copy" the predictable and sophisticated reaction chemistry of C=C and CC bonds utilizing functional inorganic systems is particularly enticing. However, in many instances, the investigation of multiple bonds of heavy elements leads to fascinating, albeit unexpected, outcomes that reinforce the fundamental differences between the first and subsequent periods.Inspired by the intriguing analogy between P=C and C=C bonds in molecular chemistry, [3] we developed the addition polymerization of phosphaalkenes as a route to new functional phosphorus-containing polymers (Scheme 1). [4] Although the synthesis of phosphorus-containing macromolecules is of widespread interest because of their attractive properties and potential applications, [5] the study of the addition polymerization of P = C bonds remains in its infancy. Our studies showed that MesP=CPh 2 (1) and related monomers polymerize in the presence of radical or anionic initiators to afford poly(methylenephosphine) (Scheme 1). [6] The living anionic polymerization of 1 permits the formation of functional phosphine-containing block copolymers, [7,8] and the radical-initiated copolymerization of 1 with styrene affords random copolymers. [9] In order to explore the mechanism of radical addition to P = C bonds during polymerization, we investigated the reactions of monomer 1 with TEMPO-derived radical sources. Herein, we report the discovery of a fascinating isomerization polymerization of phosphaalkene 1 in the presence of radical alkoxyamine initiators. These striking results led to a revision of the proposed microstructure for poly(methylenephosphine) that was produced by a radical reaction.In an effort to understand the initiation step in the radical polymerization of 1, we investigated its reaction with TEMPO (1-2 equiv). 31 P NMR spectroscopic analysis of the reaction mixtures suggested the formation of multiple products, including radical species, which were detected by EPR spectroscopy. To date, none of these products have been successfully isolated or unambiguously identified. In contrast, employing the complex 1·AuCl [10,11] instead of 1 affords a single product with TEMPO. Specifically, treatment of a solution of 1·AuCl in toluene with TEMPO (1 equiv) resulted in 50 % conversion of 1·AuCl (d = 167.1) to a new species, as determined by 31 P NMR spectroscopy. Addition of more TEMPO (1 equiv, that is, 2 equiv total) resulted in complete conversion of 1·AuCl to two products in a ratio of approximately 1:3, which displayed 31 P signals at 135.6 ppm (d, J PH = 18 Hz) and 130.5 ppm (d, J PH = 18 Hz). The magnitudes of the 31 P-1 H coupling constants are not consistent with the expected product Mes(TEMPO)P(AuCl)-C-(TEMPO)Ph 2 .Colorless crystals were obtained by slow diffusion of hexanes into the reaction mixture at À30 8C. Analysis of the crystals by X-ray crys...