Aileen A. Frew

Synthesis and 31P NMR spectra of some platinum(II) complexes of the phospha-alkene, (mesityl)P=CPh2: Crystal and molecular structure of cis-[PtCl2(PEt3)(C6H2Me3P=CPh2)]·CHCl3

Abstract Syntheses of the phospha-alkene complexes cis - and trans -[PtCl 2 (PEt 3 )(mesityl)P=CPh 2 ], and cis - [PtX 2 {(Mesityl)P=CPh 2 } 2 ](X=Cl, I, Me) complexes are reported. 31 P NMR spectra indicate that bonding of the phospha-alkene to the metal is via the phosphorus lone pair and this is confirmed by a single crystal X-ray diffraction study of cis -[PtCl 2 (PEt 3 ){(mesityl)P=CPh 2 }]CHCl 3 .

The di-µ-bis(diphenylphosphino)methane-µ-hydrido-bis[methylplatinum(II)] cation: synthesis, molecular structure, and chemical properties

The binuclear title complex [Pt2Me2(µ-H)(µ-dppm)2][PF6], dppm = Ph2PCH2PPh2, has been prepared and characterized by lH and 31P n.m.r. spectroscopy and by an X-ray structure determination. Crystals are monoclinic, with space group P21/c, a= 10.640(3), b= 20.341(3), c= 23.201(3)A, β= 91.88(2)° and Z= 4. The structure has been solved by the heavy-atom method and refined to R= 0.053 for 5 374 reflections withl 3σ(I). The cation has the ‘A-frame’ structure with a Pt–Pt separation of 2.932(1)A; a closed three-centre two-electron Pt2(µ-H) bonding system is proposed. The complex undergoes slow reductive elimination of methane induced by added PMe2Ph and is photochemically decomposed, but it has high thermal stability.

Dimerisation of a diplatinum to a tetraplatinum complex during catalysis of the water gas shift reaction: the X-ray crystal structure of [Pt4(µ2-CO)2(µ2-Ph2PCH2PPh2)3{Ph2PCH2P(:O)Ph2}]

The binuclear complex [Pt2H2(µ-dppm)2][PF6], dppm = Ph2PCH2PPh2, is an active catalyst precursor for the water gas shift reaction, especially at low pressures of carbon monoxide; the catalytic solutions are shown to contain cluster complexes such as the tetranuclear [Pt4(µ-CO)2(µ-dppm)3{Ph2PCH2P(:O)Ph2}], whose ‘butterfly’ structure has been determined by X-ray crystallography.

Multiple methylene insertion reactions: the crystal structure of a complex formed by insertion of methylene into a Pt–P bond

Up to three methylene groups from diazomethane may be incorporated into hydridodiplatinum(I) complexes by insertion into Pt–Pt. Pt–H and, in one case, a Pt–P bond; X-ray structure determination establishes the an M2(µ-CH2) group with no M–M bond are reported.

Synthesis, solution and solid-state structure (X-ray analysis), and some reactions of the dimer [PtMe3(µ-Ph2PCH2PPh2)]2

The new dimer [Pt2Me4(µ-dppm)2](dppm = Ph2PCH2PPh2) has been prepared and its conformation both in the solid state and in solution has been studied; it is thermodynamically less stable than the monomeric form and is much less reactive than the monomer towards oxidative addition.

Donor–acceptor metal–metal bond in the dinuclear platinum(II) complex [Pt2Me3(µ-Ph2PCH2PPh2)2][PF6]

An X-ray diffraction study of the title compound reveals that it contains a PtII→PtII donor–acceptor bond and confirms the other features of its novel structure previously deduced from n.m.r. evidence.

Synthesis and structure of a dimethyl(μ-hydrido)di-platinum(II) complex

The complex [Pt 2 Me 2 (μ-H)(μ-dppm) 2 ][PF 6 ] (I, dppm = Ph 2 PCH 2 PPh 2 ) has been prepared and characterised by 1 H and 31 P NMR spectroscopy and by a full molecular structure determination by X-ray methods. The complex undergoes only slow reductive elimination of methane induced by added tertiary phosphine at 70°C.

Cross and parallel cyclisation–rearrangement of face proximate π-2p-C cations generated in polycyclic olefins

Partially dechlorinated and other derivatives of the cyclodiene pesticides have been made and their behaviour in strongly acid media investigated with a view to correlating structure with cyclisation geometry. The X-ray crystal structure of one key compound unambiguously indicates that in the absence of the dichloromethano-bridge characteristic of the parent pesticides aldrin and isodrin, cross rather than parallel cyclisation is preferred in strongly acid conditions. Successive thermal rearrangements of 1,2,3.4-tetrachlorocyclopentadiene used here in synthesis of useful model compounds is briefly discussed together with certain other acid-catalysed transformations of isodrin and dieldrin analogues. Simple Huckel MO calculations accord with experimental observation.