John F. Nixon

Coordination chemistry of diphosphinoamine and cyclodiphosphazane ligands

The transition metal coordination and organometallic chemistry of acyclic diphosphazane ligands has grown rapidly in the last two decades and a stage has been reached that permits a delineation of similarities and contrasts with the chemistry of diphosphinomethane type ligands. Diphosphazane complexes of Group 10 metals (particularly those of Pd and Pt) have received much less attention than the analogous complexes of transition metals of other groups in the Periodic Table. The coordination chemistry of cyclodiphosphazanes has been investigated to a limited extent compared with that of their acyclic analogues. An attractive feature of the diphosphinoamine chemistry is the ease with which a range of ligands with different electronic and steric attributes can be synthesized by varying the substituents on both nitrogen and phosphorous.

Recent developments in the organometallic chemistry of phospha-alkynes, RCP

Abstract Recent developments in synthetic, structural and spectroscopic aspects Of novel organometallic compounds derived from phospha-alkynes are reviewed.

The microwave spectrum of 1-phosphapropyne, CH3CP: Molecular structure, dipole moment, and vibration-rotation analysis

Abstract The J = 4 ← 3 and J = 3 ← 2 rotational transitions of 1-phosphapropyne, CH3CP, between 26.5 and 40 GHz have been studied by microwave spectroscopy. The spectrum shows the characteristic vibration-rotation satellite patterns associated with a C3v symmetric rotor. Apart from the most abundant isotope variant, the species 12CD312C31P, 12CD2H12C31P, 12CH2D12C31P, 13CH312C31P, 12CH313C31P, 13CD312C31P, and 12CD313C31P have also been studied. For 12CH312C31P the rotational constants B0 = 4991.339 ± 0.003 MHz, DJ = 0.823 ± 0.092 kHz, DJK = 66.59 ± 0.18 kHz have been determined. From these data the following structural parameters have been derived: r s ( CH ) = 1.107 ± 0.001 A , ∠s(HCC) = 110.30 ± 0.09°, r s ( CC ) = 1.465 ± 0.003 A , r 0 ( CP ) = 1.544 ± 0.004 A . The dipole moment has been determined as 1.499 ± 0.001 D by analysis of the Stark effect of the J = 3 ← 2, |K| = 1 line. The vibrational satellites (vs = 1, 2, and 3) have been studied and various vibration-rotation parameters derived.

First structural characterisation of penta- and hexa-phosphorus analogues of ferrocene. Synthesis, crystal and molecular structure of the air-stable, sublimable iron sandwich compounds [Fe(η5-C2R2P3)2], and [Fe(η5-C3R3P2)(η5-C2R2P3)](R = But)

The first structurally characterised penta- and hexa-phosphorus analogues of ferrocene, bis-(η5–2,5-di-t-butyl-1,3,4-triphosphacyclopentadienyl)iron and (η5-2,4,5-tri-t-butyl-1,3-diphosphacyclopentadienyl)-(η5-2,5-di-t-butyl-1,3,4-triphosphacyclopentadienyl)iron, are described.

First example of cyclodimerisation of a phospha-alkyne to a 1,3-diphosphacyclobutadiene. Syntheses of complexes of the type [M(η5-C5R5){η4-(ButCP)2}] R = H or Me; M = Co, Rh, or Ir): crystal and molecular structure of η5-pentamethylcyclopentadienyl-2,4-di-t-butyl-1,3-diphosphacyclobutadienecobalt(I), [Co(η5-C5Me5){η4-(ButCP)2}]

Displacement of ethylene from [M(η5-C5R5)(C2H4)2], (R = H, M = Co or Rh; R = Me, M = Co, Rh, or Ir) by treatment with ButCP affords complexes containing the novel 2,4-di-t-butyl-1,3-diphosphacyclobutadiene ring.

Cleavage of the pc triple bond in a phospha-alkyne in the absence of a transition metal

Abstract The reaction of Bu t CP with Na/Hg in monoglyme results in the formation of the 2,5-di- t -butyl-1,3,4-triphosphacyclopentadienyl ( 1 ) and 2,4,5-tri- t -butyl-1,3-diphosphacyclopentadienyl ( 2 ) anions. The reaction has been carried out in the absence of [Ta(OAr) 2 Cl 3 ] (Ar = 4-Me,2,6- t -Bu 2 C 6 H 2 ), which proves that the formation of 1 and 2 does not involve the phosphide intermediate [TaP(OAr) 2 ] previously postulated by Cowley and Hall ( Polyhedron 1989, 8 , 849).

The detection of unstable molecules by microwave spectroscopy: phospha-alkenes CF2PH, CH2PCl, and CH2PH

The unstable phospha-alkenes CF2PH,CH2PCl, and CH2PH have been identified by microwave spectroscopy as products in the pyrolysis of CF3PH2, CH3PCl2, and (CH3)2PH, respectively.

The detection of the reactive molecule 1-phosphapropyne, CH3CP, by microwave spectroscopy

Abstract The reactive molecule 1-phosphapropyne, CH 3 CP, which is the phosphorus analogue of methylcyanide CH 3 CN, has been detected by microwave spectroscopy in the pyrolysis products of ethyldichlorophosphine CH 3 CH 2 PCl 2 . The J = 3 ← 2 and J = 4 ← 3 symmetric top transitions have been assigned and a value of B 0 = 4991.339 ± 0.010 MHz obtained. These results indicate that alkyl substituted analogues of phospha-acetylene, HCP can be produced by the pyrolysis of the appropriately substituted dichlorophosphine.

The First Delocalized Phosphole Containing a Planar Tricoordinate Phosphorus Atom: 1-[Bis(trimethylsilyl)methyl]-3,5-bis(trimethylsilyl)-1,2,4-triphosphole

The sterically demanding groups on the tricoordinate phosphorus atom, the π-electron acceptors substituted on the ring, and the dicoordinate phosphorus atoms within the ring are the most significant factors contributing to the planarity and aromaticity of the 1,2,4-triphosphole ring in 1. The Bird aromaticity index for 1 shows that it has the most pronounced aromatic character of all known phospholes.

New heptacoordinated tin complexes of 2,6-diacetylpyridine-bis(thiosemicarbazone), H2daptsc, and of 2,6-diacetylpyridine-bis(semicarbazone), H2dapsc. Crystal and molecular structures of [MeSnCl(Hdaptsc)]Cl·MeOH and [MeSnCl(H2dapsc)]Cl2·2H2O

Two new heptacoordinated organotin complexes, [MeSnCl(Hdaptsc)]Cl·MeOH (1) and MeSnCl(H2dapsc)]- Cl2·2H2O (2), have been prepared from MeSnCl3 and H2daptsc and H2dapsc, respectively. Single crystal X-ray diffraction studies showed them to be approximately pentagonal bipyramidal (PBP), with the organic ligands lying in the equatorial plane. H2daptsc and SnCl4 form a complex with the formula [ClSnCl(Hdaptsc)]Cl (3), which is presumed to have an analogous PBP structure. On the other hand, the complex obtained from H2dapsc and Me2SnCl2 is tentatively formulated as [(Me2SnCl2)2(H2dapsc)] (4), and 119Sn Mossbauer spectroscopic evidence suggests an octahedral coordination for the two tin atoms.