Ligand Design for the Assembly of Polynuclear Complexes: Syntheses and Structures of Trinuclear and Tetranuclear Aluminum Alkyl Complexes Bearing Tripodal Diamidoselenophosphinito Ligands and a Comparison to Related Tripodal Triamidophosphine Complexes

Controlled introduction of functional groups at one P atom in [Cp*Fe(η5-P5)] and release of functionalised phosphines

By salt metathesis reactions of the anionic complexes of the type [Cp*Fe(η⁴-P₅R)]^- (R = ^tBu (1a), Me (1b), -C[triple bond, length as m-dash]CPh (1c); Cp* = 1,2,3,4,5-pentamethylcyclopentadienyl) with organic electrophiles (XR^FG; X = halogen; R^FG = (CH₂)₃Br, (CH₂)₄Br, Me) a variety of organo-substituted polyphosphorus ligand complexes of the type [Cp*Fe(η⁴-P₅RR^FG)] (2) are obtained. Thereby, organic substituents with different functional groups (FG), such as halogens or nitriles, are introduced. In [Cp*Fe(η⁴-P₅RR')] (2a: R = ^tBu, R' = (CH₂)₃Br), the bromine substituent can be easily substituted, leading to functionalized complexes [{Cp*Fe(η⁴-P₅tBu)}(CH₂)₃{Cp*Fe(η⁴-P₅Me)}] (4) and [Cp*Fe(η⁴-P₅RR')] (5) (R = ^tBu, R' = (CH₂)₃PPh₂) or by abstraction of a phosphine to the asymmetric substituted phosphine tBu(Bn)P(CH₂)₃Bn (6). The reaction of the dianionic species [K(dme)₂]₂[Cp*Fe(η⁴-P₅)] (I') with bromo-nitriles leads to [Cp*Fe{η⁴-P₅((CH₂)₃CN)₂}] (7), allowing the introduction of two functional groups attached to one phosphorus atom. 7 reacts with ZnBr₂ in a self-assembly reaction to form the supramolecular compound [Cp*Fe{η⁴-P₅((CH₂)₃CN)₂}ZnBr₂]_n (8).

The Backbone of Success of P,N-Hybrid Ligands: Some Recent Developments

Organophosphorus ligands are an invaluable family of compounds that continue to underpin important roles in disciplines such as coordination chemistry and catalysis. Their success can routinely be traced back to facile tuneability thus enabling a high degree of control over, for example, electronic and steric properties. Diphosphines, phosphorus compounds bearing two separated P^III donor atoms, are also highly valued and impart their own unique features, for example excellent chelating properties upon metal complexation. In many classical ligands of this type, the backbone connectivity has been based on all carbon spacers only but there is growing interest in embedding other donor atoms such as additional nitrogen (–NH–, –NR–) sites. This review will collate some important examples of ligands in this field, illustrate their role as ligands in coordination chemistry and highlight some of their reactivities and applications. It will be shown that incorporation of a nitrogen-based group can impart unusual reactivities and important catalytic applications.

Diamagnetic molybdenum nitride complexes supported by diligating tripodal triamido-phosphine ligands as precursors to paramagnetic phosphine donors

The reaction of the ligand precursors P[CH2NHAr(R)]3 () with (Me2N)3Mo[triple bond, length as m-dash]N generated the complexes P(CH2NAr(R))3Mo[triple bond, length as m-dash]N (), where Ar(R) = 3,5-(CH3)2C6H3 (), Ph (), and 3,5-(CF3)2C6H3 (), with (Me2N)3Mo[triple bond, length as m-dash]N generated the complexes P(CH2NAr(R))3Mo[triple bond, length as m-dash]N (). Complex was obtained in poor yield, due to the formation of P(CH2N-3,5-(CF3)2C6H3)2(CH2NH-3,5-(CF3)2C6H3)(NMe2H)(NMe2)Mo[triple bond, length as m-dash]N () as the major product. Reaction of with VMes3THF generated the paramagnetic complexes P(CH2NAr(R))3Mo(μ-N)V(Mes)3 (). The reaction of with Ni(acac)2 generated the Ni(0) complexes Ni[P(CH2NAr(R))3Mo[triple bond, length as m-dash]N]4 () in poor yield. These complexes were synthesized in higher yields from the reaction of with Ni(COD)2, where COD = 1,5-cyclooctadiene. Reaction of either with V(Mes)3THF or with Ni(COD)2 generated the paramagnetic nonanuclear complex Ni[P(CH2NAr(R))3Mo(μ-N)VMes3]4 ().

A tripodal benzylene-linked trisamidophosphine ligand scaffold: synthesis and coordination chemistry with group(IV) metals

A new tripodal trisamidophosphine ligand (1) based on the trisbenzylphosphine backbone has been synthesized in three steps starting from NaPH2 and phthaloyl-protected 2-aminobenzyl bromide. At elevated temperatures, 1 reacts directly with M(NMe2)4 (M = Zr, Hf) to afford the dimethylamido complexes [PN3]M(NMe2) (M = Zr, Hf) (2), which are easily converted into the corresponding triflates [PN3]MOTf (M = Zr, Hf) (3) via reaction with triethylsilyl trifluoromethanesulfonate. The related titanium chloro complex [PN3]TiCl (4-Ti) is obtained from 1 and Bn3TiCl via protonolysis. Triple deprotonation of 1 with n-butyllithium affords the tris-lithium salt Li3[PN3] (1-Li), which serves as a common starting material for the preparation of all the group(IV) chlorides [PN3]MCl (M = Ti, Zr, Hf) (4). Upon treatment of 4-Ti with Bn2Mg(thf)2, formation of a benzyltitanium species is observed, which is converted cleanly into a ligand-CH-activated species (5-Ti).