Iron complexes of facially capping triphosphorus macrocycles

Abstract

Primary and secondary phosphine piano-stool complexes of the type [eta(5)-CpFeL3]+ (L = phenylphosphine, 3, (alpha-methyl)vinylphosphine, 4, allylphosphine, 5, (2-methylpropenyl)phosphine, 5b, allyl(phenyl)phosphine, 6) are described. The alkenyl phosphine complexes, 5 and 6, react by intramolecular hydrophosphination to give the corresponding [eta(5)-CpFe]+ complexes of 1,5,9-triphosphacyclododecane (12-aneP3R3, 2, R = H), 9 and 10 respectively. Alkylation of the secondary phosphines in 9 is achieved by hydrophosphinations with ethene to give the 12-aneP3R3 (R = Et) derivative 11. These complexes are also obtained by reaction of suitable [eta(5)-CpFe]+ containing precursor complexes with the corresponding free 12-aneP3R3 macrocycle as is the related [eta(5)-Cp*Fe]+ derivative, 8. Direct substitution of acetonitrile in [Fe(CH3CN)6][BF4]2 by 12-aneP3Et3, leads to the macrocycle piano-stool complex, [(12-aneP3Et3)Fe(CH3CN)3][BF4]2, 7. The crystal structures of selected primary phosphine, eta(5)-Cp, eta(5)-Cp* complexes and 7, allow a comparison of steric influences upon key macrocycle ring closure reactions and hence an insight into parameters required for the formation of smaller ring sizes by template based methods.

Template‐Controlled Formation of an [11]ane‐P2CNHC Macrocyclic Ligand at an Iron(II) Template

“…[5][6][7]13] From these we selected the Staudinger reaction for the conversion [5]PF 6 Ǟ [6]X (X = PF 6 -, Br -) employing the sterically demanding phosphane PPh 3 to prevent substitution of the isocyanide in [5]PF 6 . Complex [5]PF 6 was treated with PPh 3 in methanol, and the resulting iminophosphorane group was then hydrolyzed with HBr/H 2 O to lead to the complex with the 2-aminoethyl isocyanide ligand, which is not stable but reacts under intramolecular nucleophilic attack of the amino group at the isocyanide carbon atom with formation of complex [6]X.…”

“…Iron(II) has been used as template for the generation of P 3 macrocycles (B, Figure 1), which can be liberated from the metal center. [7] Here we describe the template-controlled formation of an [11]ane-P 2 C NHC macrocycle at a {CpFe II } template leading to complex [1]PF 6 .…”

Synthesis of a Ruthenium(II) Complex Containing an [11]ane-P2CNHC(NHC = Imidazolidin-2-ylidene) Macrocycle

“…More recently, complexes with macrocyclic P-donor ligands in the all-syn conformation have been obtained by metal template-controlled procedures . In selected cases it was possible to liberate the facially coordinated P 3 -donor macrocycle from the metal center and to coordinate it to another metal under conservation of the all-syn conformation. , The template synthesis proved advantageous since the separation of syn and anti ligand isomers could be avoided and the incorporation of different linkers within the macrocycle proved possible …”

Zirconium-Catalyzed Intermolecular Double Hydrophosphination of Alkynes with a Primary Phosphine

“…Secondary phosphines − and primary phosphines have been known to undergo hydrophosphination with ethylene, but so far there has been no report of hydrophosphination reactions involving acetylene. However, functionalization of the parent molecule offers an unparalleled opportunity for further synthesis of specialized diphosphines that are employed in an array of conventional transformations.…”