Double insertion of benzophenone into thorium-phosphorus bonds

Taming PH3: State of the Art and Future Directions in Synthesis

Appetite for reactions involving PH₃ has grown in the past few years. This in part is due to the ability to generate PH₃ cleanly and safely via digestion of cheap metal phosphides with acids, thus avoiding pressurized cylinders and specialized equipment. In this perspective we highlight current trends in forming new P–C/P–OC bonds with PH₃ and discuss the challenges involved with selectivity and product separation encumbering these reactions. We highlight the reactivity of PH₃ with main group reagents, building on the early pioneering work with transition metal complexes and PH₃. Additionally, we highlight the recent renewal of interest in alkali metal sources of H₂P^– which are proving to be useful synthons for chemistry across the periodic table. Such MPH₂ sources are being used to generate the desired products in a more controlled fashion and are allowing access to unexplored phosphorus-containing species.

Isocyanate Insertion into a La-P Phosphide Bond: A Versatile Route to Phosphaureate-Bridged Heterobimetallic Lanthanide-Coinage-Metal Complexes

A new route to heterobimetallic lanthanide-coinage-metal complexes is disclosed. The selective insertion of organic substrates such as phenyl iso(thio)cyanate into the La-P bond of the primary phosphido complex (PN)2La(PHMes) (1) (with PN- = (N-(2-(diisopropylphosphanyl)-4-methylphenyl)-2,4,6-trimethylanilide) yields the phospha(thio)ureate complexes (PN)2La(OC(NPh)(PHMes)) (2) and (PN)2La(SC(NPh)(PHMes)) (3) with retention of the PH protons. Subsequent deprotonation of the phosphaureate complex 2 with potassium hexamethyldisilazide (KHMDS, K[N(SiMe3)2]) leads to the polymeric complex [K{(PN)2La(OC(NPh)(PMes))}]n (4). Complex 4 was found to be an excellent precursor for salt metathesis reactions with copper(I) and gold(I) chlorides supported by an N-heterocyclic carbene (NHC, 5 and 6) or a cyclic alkyl amino carbene (CAAC, 7 and 8). This resulted in the unprecedented formation of heterobimetallic lanthanum-coinage-metal complexes, containing the first example of a μ,κ2(O,N):κ1(P)-phosphaureate bridging ligand. For an alternative route to complex 8 a direct protonolysis protocol between a new basic gold(I) precursor, namely (MeCAAC)Au(HMDS), and 2 was also investigated. The complexes have been characterized by multinuclear NMR spectroscopy, IR spectroscopy, and X-ray crystallography (except for 8).

Divergent uranium- versus phosphorus-based reduction of Me3SiN3 with steric modification of phosphido ligands

We describe an example of a two-electron metal- and ligand-based reduction of Me₃SiN₃ using uranium(iv) complexes with varying steric properties. Reaction of (C₅Me₅)₂U(CH₃)[P(SiMe₃)(Ph)] with Me₃SiN₃ produces the imidophosphorane complex, (C₅Me₅)₂U(CH₃)[N Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> P(SiMe₃)₂(Ph)] through oxidation of phosphorus. However, a similar reaction with a more sterically encumbering phosphido ligand, (C₅Me₅)₂U(CH₃)[P(SiMe₃)(Mes)] forms the U(iv) complex, (C₅Me₅)₂U[κ²-(N,N)–N(SiMe₃)P(Mes)N(SiMe₃)]. In probing the mechanism of this reaction, a U(vi) bis(imido) complex, (C₅Me₅)₂U(NSiMe₃){N[P(SiMe₃)(Mes)]} was isolated. DFT calculations show an intramolecular reductive cycloaddition reaction leads to the formation of the U(iv) bis(amido)phosphane from the U(vi) bis(imido) complex. This is a rare example of the isolation of a reaction intermediate in f element chemistry.

We describe an example of a two-electron metal- and ligand-based reduction of Me₃SiN₃ using uranium(iv) complexes with varying steric properties. With uranium-based reduction, a U(vi) intermediate is isolated.

Monoanionic Anilidophosphine Ligand in Lanthanide Chemistry: Scope, Reactivity, and Electrochemistry

We present the synthesis of a series of new lanthanide(III) complexes supported by a monoanionic bidentate anilidophosphine ligand (N-(2-(diisopropylphosphanyl)-4-methylphenyl)-2,4,6-trimethylanilide, short PN^-). The work comprises the characterization of a variety of heteroleptic complexes containing either one or two PN ligands as well as a study on further functionalization possibilities. The new heteroleptic complexes cover selected examples over the whole lanthanide(III) series including lanthanum, cerium, neodymium, gadolinium, terbium, dysprosium, and lutetium. In case of the two diamagnetic metal cations lanthanum(III) and lutetium(III), we have furthermore studied the influence of the lanthanide ion (early vs. late) on the reactivity of these complexes. Thereby we found that the radius of the lanthanide ion has a major influence on the reactivity. Using sterically demanding, multidentate ligand systems, e.g., cyclopentadienide (Cp^-), we found that the lanthanum complex La(PN)₂Cl (1-La) reacts well to the corresponding cyclopentadienide complex, while for Lu(PN)₂Cl (1-Lu) no reaction was observed under any conditions tested. On the contrary, employing monodentate ligands such as mesitolate, thiomesitolate, 2,4,6-trimethylanilide or 2,4,6-trimethylphenylphosphide, results in the clean formation of the desired complexes for both lanthanum and lutetium. All complexes have been studied by various techniques, including multi nuclear NMR spectroscopy and X-ray crystallography. ³¹P NMR spectroscopy was furthermore used to evaluate the presence of open coordination sites on the complexes using coordinating and noncoordinating solvents, and as a probe for estimating the Ce-P distance in the corresponding complexes. Additionally, we present cyclic voltammetry (CV) data for Ce(PN)₂Cl (1-Ce), La(PN)₂Cl (1-La), Ce(PN)(HMDS)₂ (8-Ce) and La(PN)(HMDS)₂ (8-La) (with HMDS = hexamethyldisilazide, (Me₃Si)₂N^-) exploring the potential of the anilidophosphane ligand framework to stabilize a potential Ce(IV) ion.

Thorium(IV) and Uranium(IV) Phosphaazaallenes

The synthesis of tetravalent thorium and uranium complexes with the phosphaazaallene moiety, [N(tBu)C=P(C6H5)]2−, is described. The reaction of the bis(phosphido) complexes, (C5Me5)2An[P(C6H5)(SiMe3)]2, An = Th, U, with two equivalents of tBuNC produces (C5Me5)2An(CNtBu)[η2-(N,C)-N(tBu)C=P(C6H5)] with concomitant formation of P(SiMe3)2(C6H5) via silyl migration. These complexes are characterized by NMR and IR spectroscopy, as well as structurally determined using X-ray crystallography.

Experimental and computational studies on a three-membered diphosphido thorium metallaheterocycle [η5-1,3-(Me3C)2C5H3]2Th[η2-P2(2,4,6-iPr3C6H2)2]

A three-membered diphosphido thorium metallaheterocycle complex was prepared and its reactivity was investigated.