RESUMEN
Oxidative addition of the P-P single bond of an ortho-carborane-derived 1,2-diphosphetane (1,2-C2(PMes)2B10H10) (Mes = 2,4,6-Me3C6H2) to cobalt(-i) and nickel(0) sources affords the first heteroleptic complexes of a carborane-bridged bis(phosphanido) ligand. The complexes also incorporate labile ligands suitable for further functionalisation. Thus, the cobalt(i) complex [K([18]crown-6)][Co{1,2-(PMes)2C2B10H10}(cod)] (cod = 1,5-cyclooctadiene) bearing a labile cyclooctadiene ligand undergoes facile ligand exchange reactions with isonitriles and tert-butyl phosphaalkyne with retention of the bis(phosphanido) ligand. However, in the reaction with one equivalent of P4, the electron-rich bis(phosphanido) moiety abstracts a single phosphorus atom with formation of a new P3 chain, while the remaining three P atoms derived from P4 form an η3-coordinating cyclo-P3 ligand. In contrast, when the same reaction is performed with two equivalents of the cobalt(i) complex, a dinuclear product is formed which features an unusual P4 chain in its molecular structure.
RESUMEN
Invited for the cover of this issue are the groups of Ruthâ M. Gschwind and Robert Wolf (University of Regensburg), Christian Müller (Freie Universität Berlin), and J.â Chris Slootweg (University of Amsterdam). The image depicts playing cards representing the reported reactions involving 1-phospha-7-bora-norbornadiene. Read the full text of the article at 10.1002/chem.202000266.
RESUMEN
Salt metathesis of 1-methyl-2,4,6-triphenylphosphacyclohexadienyl lithium and chlorobis(pentafluorophenyl)borane affords a 1-phospha-7-bora-norbornadiene derivative 2. The C≡N triple bonds of nitriles insert into the P-B bond of 2 with concomitant C-B bond cleavage, whereas the C≡C bonds of phenylacetylenes react with 2 to form λ4 -phosphabarrelenes. Even though 2 must formally be regarded as a classical Lewis adduct, the C≡N and C≡C activation processes observed (and the mild conditions under which they occur) are reminiscent of the reactivity of frustrated Lewis pairs. Indeed, NMR and computational studies give insight into the mechanism of the reactions and reveal the labile nature of the phosphorus-boron bond in 2, which is also suggested by detailed NMR spectroscopic studies on this compound. Nitrile insertion is thus preceded by ring opening of the bicycle of 2 through P-B bond splitting with a low energy barrier. By contrast, the reaction with alkynes involves formation of a reactive zwitterionic methylphosphininium borate intermediate, which readily undergoes alkyne 1,4-addition.
RESUMEN
New iron complexes [Cp*FeL]- (1-σ and 1-π, Cp*=C5 Me5 ) containing the chelating phosphinine ligand 2-(2'-pyridyl)-4,6-diphenylphosphinine (L) have been prepared, and found to undergo facile reaction with CO2 under ambient conditions. The outcome of this reaction depends on the coordination mode of the versatile ligand L. Interaction of CO2 with the isomer 1-π, in which L binds to Fe through the phosphinine moiety in an η5 fashion, leads to the formation of 3-π, in which CO2 has undergone electrophilic addition to the phosphinine group. In contrast, interaction with 1-σ-in which L acts as a σ-chelating [P,N] ligand-leads to product 3-σ in which one C=O bond has been completely broken. Such CO2 cleavage reactions are extremely rare for late 3d metals, and this represents the first such example mediated by a single Fe centre.
RESUMEN
Reduction of [CpArFe(µ-Br)]2 (1, CpAr = C5(C6H4-4-Et)5) by potassium napthalenide, followed by the addition of white phosphorus, affords [K(18-c-6){CpArFe(η4-P4)}] (2, 18-c-6 = [18]crown-6), which features a planar cyclo-P42- ligand. The related diiron complex [Na2(THF)5(CpArFe)2(µ,η4:4-P4)] (3) was obtained by reducing 1 with sodium amalgam in the presence of P4. Protonation of 3 affords [Na(THF)3][(CpArFe)2(µ,η4:4-P4)(H)] (4), while the reaction of 3 with trimethylchlorosilane gives the nortricyclane compound P7(SiMe3)3 as the main product.