Molybdenum-Mediated Insertion of Ketones into the P-P bond of cyclo-(P5 Ph5 ) and Formation of Trinuclear Molybdenum Complexes

The reaction of cyclopentaphosphine cyclo-(P5 Ph5 ) (1) with ketones (acetone and cyclooctanone) in the presence of [Mo(CO)4 (cod)] (cod=cycloocta-1,5-diene) led to air-stable trinuclear complexes in which the bis-phosphanido ligands (PPh-PPh-PPh-PPh-CMe2 O-PPh)2- (complex 2) and (PPh-PPh-PPh-PPh-C(CH2 )7 O-PPh)2- (complex 3) bridge a Mo(CO)3 -Mo(CO)3 unit. This extends the reaction of 1 with transition metal carbonyl complexes to further substrates and represents the first examples of insertion of carbonyl compounds into the P-P bond of cyclic oligophosphorus compounds. Complexes 2 and 3 have been characterized by 31 P NMR spectroscopy and single crystal X-ray diffraction. Furthermore, the thermal properties of the obtained complexes have been studied by differential scanning calorimetry (DSC) and fast scanning calorimetry (FSC).

Coordination Chemistry of Hepta-tert-butylnonaphosphane

Hepta-tert-butylnonaphosphane {cyclo-(P4tBu3)}2PtBu was employed as a ligand in transition metal complexes of iron(0) (1), cobalt(–I) (2), copper(I) (3) and rhodium(I) (4), which are readily formed in moderate to good yields,...

Gold(I) Complexes of Tetra-tert-butylcyclotetraphosphane

The reaction of tetra-tert-butylcyclotetraphosphane cyclo-(PtBu)4 (L) with one to four equivalents [AuCl(tht)] (tht = tetrahydrothiophene) leads to the gold(I) complexes [(AuCl)nL] (n = 1–4, 1–4) in which the ligand coordinates...

Hydrogen/Halogen Exchange of Phosphines for the Rapid Formation of Cyclopolyphosphines

The hydrogen/halogen exchange of phosphines has been exploited to establish a truly useable substrate scope and straightforward methodology for the formation of cyclopolyphosphines. Starting from a single dichlorophosphine, a sacrificial proton "donor phosphine" makes the rapid, mild synthesis of cyclopolyphosphines possible: reactions are complete within 10 min at room temperature. Novel (aryl)cyclopentaphosphines (ArP)₅ have been formed in good conversion, with the crystal structures presented. The use of catalytic quantities of iron(III) acetylacetonate provides significant improvements in conversion in the context of diphosphine (Ar₂P)₂ and alkyl-substituted cyclotetra- or cyclopentaphosphine ((AlkylP)_n, where n = 4 or 5) formation. Both iron-free and iron-mediated reactions show high levels of selectivity for one specific ring size. Finally, investigations into the reactivity of Fe(acac)₃ suggest that the iron species is acting as a sink for the hydrochloric acid byproduct of the reaction.

Versatile Coordination Chemistry of Hexa-tert-butyl-octaphosphine

The octaphosphine {cyclo-(P₄^tBu₃)}₂ (1) possesses a multifaceted coordination chemistry. The predominant binding mode is a P,P-chelate, e.g., in the monometallic chelate complex [MLL'(1-κ²P²,P^4')] in which the ligand 1 adopts a gauche conformation. Examples include square-planar (M = Rh^I, L = CO, L' = Cl (2), M = Pd^II, L = L' = Cl (3), M = Pt^II, L = L' = Cl (9)), tetrahedral (M = Co^-I, L = NO, L' = CO (4)), and trigonal-planar complexes [ML(1-κ²P²,P^4')] (M = Pd⁰, L = PPh₃, (5), M = Cu^I, L = Br (6)). With 2 equiv of [CuBr(SMe₂)], a dinuclear complex [(CuBr)₂(1-κ²P²,P^2',κ²P⁴,P^4')] (7) was obtained which features a synperiplanar conformation of the octaphosphine. A second coordination mode was also observed in [PtCl₂(1-κ²P¹,P^2')] (10) in which the bridge phosphorus atom in octaphosphine 1 is involved in the chelation, with the ligand in an antiperiplanar conformation. Thermolysis of selected complexes showed them to be suitable candidates for the generation of phosphorus-rich metal phosphides MP_x (x > 1).

Unexpected Isomerization of Hexa-tert-butyl-octaphosphane

Octaphosphane {cyclo-(P₄ tBu₃ )}₂ (1) undergoes an unexpected isomerization reaction to the constitutional isomer 2,2',2'',2''',3,3'-hexa-tert-butyl-bicyclo[3.3.0]octaphosphane (2) in the presence of Lewis acidic metal salts. The mechanism of this reaction is discussed and elucidated with DFT calculations. The results underline the fascinating similarity between phosphorus-rich and isolobal carbon compounds. The new bicyclic octaphosphane 2 shows a dynamic behavior in solution and reacts with [AuCl(tht)] (tht=tetrahydrothiophene) to give a mono- ([AuCl(2-κP³ )], 3) and a dinuclear complex ([(AuCl)₂ (2-κP³ ,κP^3' )], 4). With cis-[PdCl₂ (cod)] (cod=1,5-cyclooctadiene), the chelate complex ([PdCl₂ (2-κ² P² ,P^2' )], 5) with a different coordination mode of the ligand was obtained.