Non-stoichiometry induced by differential oxygen/lone pair occupation in chiral bicyclic 1,1′-binaphthoxy cyclodiphosphazanes

Catechol and 1,2,4,5-tetrahydroxybenzene functionalized cyclodiphosphazane ligands: synthesis, structural studies, and transition metal complexes

This paper describes the syntheses of two novel cyclodiphosphazane derivatives and their coordination chemistry with Cu^I, Ru^II, Rh^I, Pd^II and Au^I is also described.

Cyclodiphosphazanes: options are endless

This short review describes the transition metal chemistry of cyclodiphosphazanes.

A versatile hard–soft N/S-ligand for metal coordination and cluster formation

The new ligand [S-P(μ-N^tBu)]₂²⁻ has adaptable hard–soft character with respect to the coordinated metal centre and can be used to construct large cage architectures.

Chiral ditopic cyclophosphazane (CycloP) ligands: synthesis, coordination chemistry, and application in asymmetric catalysis

A series of dichlorocyclophosphazanes [{ClP(μ-NR)}2 ] containing chiral and achiral R groups was obtained from simple commercially available amines and PCl3 . Their condensation reactions with axially chiral biaryl diols yielded ansa-bridged chiral cyclophosphazane (CycloP) ligands. This highly modular methodology allows extensive elaboration of the ligand set, in which the chirality can be introduced at the diol bridge and/or the amido R group. This provides the possibility to observe match and mismatch effects in catalysis. A series of twenty CycloP ligands was synthesized and characterized by multinuclear NMR spectroscopy, HRMS, elemental analysis, and in selected cases, single-crystal X-ray diffraction. These studies show that all of the ditopic CycloP ligands are C2 symmetric, rendering their metal coordination sites symmetry equivalent. Two well-established enantioselective reactions were explored by using late-transition metal CycloP complexes as catalysts; the gold-catalyzed hydroamination of γ-allenyl sulfonamides and the asymmetric nickel-catalyzed three-component coupling of a diene and an aldehyde. The steric demands of the CycloP ligands have a subtle influence on the reactivity and selectivity observed in both reactions. Good enantiomeric ratios (e.r.) as high as 89:11 in the gold-catalyzed reaction and 92:8 in the nickel-catalyzed bis-homoallylation reaction were observed.

The Phospha-Michael addition product {(t-BuNH)P(μ-N-t-Bu)(2)P(=N-t-Bu)-C(=CH(2))CH(p-CH(3)O-C(6)H(4))-P(O)[(OCH(2)C(CH(3))(2)CH(2)O)]}

The title compound, 2-{2-[1,3-di-tert-butyl-4-(tert-butyl-amino)-2-(tert-butyl-imino)-1,3,2λ(5),4-diaza-diphosphetidin-2-yl]-1-(4-meth-oxy-phen-yl)prop-2-en-1-yl}-5,5-dimethyl-1,3,2λ(5)-dioxaphosphinan-2-one, C(31)H(57)N(4)O(4)P(3), was synthesized from the Phospha-Michael addition reaction of cyclo-diphos-pha-zane [(t-BuNH)P(μ-Nt-Bu)](2) and allenyl-phospho-nate [(OCH(2)C(CH(3))(2)CH(2)O)P(O)C(p-CH(3)O-C(6)H(4))=C=CH(2)]. In the crystal, N-H⋯O and C-H⋯O hydrogen bonds link the mol-ecules. The structure exhibits pseudosymmetry but attempts to solve it in a higher (monoclinic) space group were unsuccessful.