Platinum(II) complexes of cyclic triphosphenium ions: a 31P NMR spectroscopic and computational study.

The first transition metal complexes of cyclic triphosphenium ions have been unequivocally identified in solution by (31)P NMR spectroscopy. The ligands coordinate to platinum(II) via the central phosphorus atom, but only when at least one of the outer phosphorus atoms has non-aromatic substituents. Depending on the system, either trans- (the kinetic reaction product) and/or cis- (the thermodynamic reaction product) complexes are formed. The (1)J coupling constants between (195)Pt and the central phosphorus atom of the CTI (P(A)) are small for both cis- and trans-isomers, between 900 and 1300 Hz, whereas other phosphanes in these complexes derived from the platinum(II) starting material show normal (1)J(PtP) values. These results suggest a possible long P-Pt bond between the overall positively charged ligand and the platinum(II) cation. Calculations including predicted (31)P NMR shifts for the CTIs and their Pt(II) complexes largely support our experimental findings.

Synthesis and characterisation of selected group 14 derivatives of the 2,5-(CF3)2C6H3 (Ar) ligand.

Selected group 14 tetrahalides EX(4) (E = Si, Ge or Sn; X = Cl or Br) have been reacted in various molar ratios with ArLi, where Ar = 2,5-(CF(3))(2)C(6)H(3). The compounds Ar(2)SiCl(2)1, Ar(3)SiF 3, Ar(2)Si(OH)(2)4, Ar(2)GeCl(2)7, Ar(2)Ge(Br)Ge(Br)Ar(2)8, Ar(3)SnCl 10, Ar(4)Sn 11 and Ar(3)SnBr 12 have been isolated, and characterised by single-crystal X-ray diffraction, elemental analysis and (19)F solution-state NMR spectroscopy.

The relative stabilities of cyclic dicationic derivatives of diphosphanes with three (3P) or four (4P) linked phosphorus atoms.

Reaction of a diphosphane with a chlorophosphane in the presence of SnCl(2) or AlCl(3) leads to the formation of dicationic heterocycles with three (3P) or four (4P) linked phosphorus atoms. Some 3P derivatives with small alkyl substituents may also be prepared by direct alkylation of cyclic triphosphenium ions. Several new species were prepared in solution, some of which were isolated and characterised by single-crystal X-ray diffraction. Investigations into the factors favouring formation of 3P or 4P species are described.

A dynamic disorder-linked reversible phase transition in a new chloroform solvate of cis-dichloridobis(triethylphosphane)platinum(II).

The title compound, cis-dichloridobis(triethylphosphane)platinum(II) chloroform monosolvate, [PtCl(2)(C(6)H(15)P)(2)]·CHCl(3), has been obtained from ligand scrambling in the cis-[PtCl(2)(Cyp(2)PCl)(PEt(3))] (Cyp = cyclopentyl) system in CHCl(3) solvent. Unlike the two previously reported unsolvated polymorphs, which are both monoclinic, the compound crystallizes in an orthorhombic setting. Furthermore, the system exhibits a reversible temperature-dependent structural phase transition, coupling a reduction in anisotropic displacement parameters and a reduction in crystallographic symmetry on cooling. The high-temperature phase adopts space group Pnma with the complex and solvent molecules sitting across a crystallographic mirror plane (Z' = 0.5). The low-temperature phase adopts the space group P2(1)2(1)2(1) with Z' = 1.

Stereochemically inactive lone pairs in phosphorus(III) compounds: the characterisation of some derivatives with the 2,5-(CF3)2C6H3 (Ar) substituent and their complexation behaviour towards Pt(II) species.

Some new phosphorus(III) derivatives Ar(2)PX (X = Br, Cl, F or H), ArPX(2) (X = Br or Cl), Ar(3)P and Ar(t)BuPCl, with the 2,5-bis(trifluoromethyl)phenyl (Ar) substituent on phosphorus, have been prepared, and characterised by (31)P and (19)F NMR solution-state spectroscopy. The complexing ability of Ar(2)PX, Ar(3)P and Ar(t)BuPCl towards the dimeric platinum(II) complexes [PtY(µ-Y)(PEt(3))](2) (Y = Cl or Br, the latter for X = Br only) has also been investigated. Single-crystal X-ray diffraction studies at low temperature have been carried out for Ar(3)P, Ar(2)PCl and the hydrolysis or oxidation products Ar(2)P(H)OH and Ar(2)P(O)OH. The structures of Ar(3)P and Ar(2)PCl are particularly interesting as in each compound the geometry around P is approximately octahedral. In Ar(3)P there are three short contacts to fluorine as well as the three bonded C atoms for both of the independent molecules in the unit cell. For Ar(2)PCl there are two short P-F contacts, and the octahedron is completed by a weak P-P interaction to a neighbouring molecule. In both instances the lone pair on the P(III) centre appears to be stereochemically inactive, and does not play a significant role in the structure.

Hydrogen bonding and short contacts in [2,4,6-tris(trifluoromethyl)phenyl]phosphinic acid.

In the title compound, C(9)H(4)F(9)O(2)P, molecules are linked by a single O-H...O hydrogen bond into chains related to those in phenylphosphinic acid. There are short intramolecular F...P contacts.

Alkyl and aryl dicationic derivatives of cyclic triphosphenium ions.

Direct alkylation of cyclic triphosphenium ions by triflates to give di-ium dications is only possible for small organic substituents on the attacking reagent. The dicationic products are not intrinsically unstable, however, and in many instances they may be synthesised by an alternative route, pioneered by Schmidpeter and co-workers. These species may be readily identified in solution by (31)P NMR spectroscopy. The crystal and molecular structures of five such derivatives have been ascertained for the first time by single crystal X-ray diffraction at 120 K. The results confirm that normal single P-P bond lengths are present in the dications, in contrast with the monocationic parent cyclic triphosphenium ions, where structural determinations have shown that the P-P bond lengths are intermediate between single and double bonds.

Novel (n + 1 + 1) cycloaddition reactions; the formation of cyclic tetraphosphonium dications with four linked phosphorus atoms and an organic backbone.

In the presence of SnCl(2), a novel cycloaddition of two moles of R'PCl(2) (R' = Et or Ph) to a diphosphane has been achieved, forming a cyclic dication with four linked phosphorus atoms and an organic backbone; two of these species have been characterised by single-crystal X-ray diffraction, and the mechanism of the reaction has been established.

The mechanism of formation of cyclic triphosphenium ions; detection of transient intermediates in solution.

The mechanism of formation of cyclic triphosphenium ions [-(CH(2))(n)P(R(2))PP(R(2))-](+) 3 from diphosphanes R(2)P(CH(2))(n)PR(2) and phosphorus(III) halides PX(3)(X = Cl or Br) has been unequivocally established for the six-membered heterocycles with R = Et, (i)Pr or c-Hex, n= 3, and for five-membered rings with R = Et, n= 2. The initial stage is the formation of an acyclic species, [R(2)P(CH(2))(n)P(R(2))PX(2)](+)X(-) 1. The cation of this species cyclises to a symmetrical dication [-R(2)P(CH(2))(n)P(R(2))P(X)-](2+) 2 by loss of halide, where the middle P atom has an X group attached and is still formally P(iii). The rate-determining step is then a redox reaction to form the final cyclic monocationic product 3, with a 'bare' middle P atom. Several transient intermediate species, including the precursor cyclic dication 2 in each case, have been identified by means of (31)P NMR solution-state spectroscopy.

trans-Di-mu-bromo-bis[bromo(triethylphosphine-kappaP)platinum(II)].

The title compound, [Pt2Br4(C6H15P)2], is a centrosymmetric dinuclear platinum(II) complex consisting of two square-planar platinum centres connected by two bridging Br atoms.