Bruce W. Royan

Nuclear magnetic resonance spectroscopic characterisation and the crystal and molecular structures of Ph3PSe·AlCl3and Ph3PSe·AlCl3: a classification of the co-ordinative bonding modes of the phosphine chalcogenides

A series of compounds with the general formula R3PE·AlCl3(R = Ph or NMe2, E = S or Se) has been examined by n.m.r. spectroscopy as a contribution toward the characterisation of the P–E bond and of the co-ordinate bond. Two derivatives, Ph3PS·AlCl3 and Ph3PSe·AlCl3, have been studied by X-ray crystallography. [Crystal data: C18H15AlCl3PS, monoclinic, space group, P21/n, a= 9.710(2), b= 9.464(1), c= 21.893(5)A, β= 95.15(2)°Z= 4, R= 0.042; C18H15AlCl3PSe, triclinic, space group, Pa= 8.967(2), b= 12.626(4), c= 18.242(4)A, α= 84.83(2), β= 89.02(2), γ= 85.67(2)°, Z= 4, R= 0.044.] In contrast to the oxygen analogues, the sulphur and selenium derivatives exhibit bent geometries [P–S–Al 109.62(8), P–Se–Al (mean)= 107.0(1)°]. The structures are maintained in solution, as demonstrated by the 27Al n.m.r. spectra. The 31P and 13C n.m.r. spectra are informative of the changes associated with adduct formation, and show the oxygen derivatives (E = O) to be unique. Disruption of the P–E π interaction due to adduct formation is more dramatic for the sulphur and selenium than for the oxygen derivatives. The extensive information available in the literature is re-evaluated in the light of the present results, and a classification for the co-ordinative bonding modes of the phosphine chalcogenides is proposed.

C–H activation and nitrile insertion reactions of a cationic niobium alkylidene complex

Oxidation of [Nb(η5-C5H4But)2(CH2Ph)2] yields the stable cationic benzylidene complex [Nb(η5-C5H4But)2(CHPh)(thf)]BPh4, which readily loses thf to form the C–H activation product [Nb(η5-C4H4But)(η5:η1-C5H4CMe2CH2)(η2–CH2Ph)]BPh4 and reacts with acetonitrile to give the double-insertion product [Nb(η5-C5H4But)2{η2-NC(Me)C(Ph)C(Me)NH}]BPh4.

Linear co-ordinative bonding at oxygen: a spectroscopic and structural study of phosphine oxide-Group 13 Lewis acid adducts

A number of adducts composed of phosphine oxides and Group 13 Lewis acids R3PO·EX3(R = Ph, NMe2, or PhO; E = B, Al, or Ga; X = F, Cl, or Br) have been spectroscopically characterised by multinuclear n.m.r. spectroscopy. Three isostructural derivatives have been structurally characterised by X-ray crystallography. Crystal data (all hexagonal, space group 3, Z= 6): Ph3PO·AlCl3, a= 13.663(2), c= 18.258(2)A, R= 0.062; Ph3PO·AlBr3, a= 14.021 (6), c= 18.387(3)A, R= 0.041; Ph3PO·GaCl3, a= 13.753(6), c= 18.345(6)A, R= 0.079. The structures show a uniquely linear or almost linear P–O–E backbone, which lies on the three-fold axis, in contrast to the bent structures observed for the corresponding BF3 adducts and other related systems. Short Al–O bonds [X = Cl, 1.733(4); Br, 1.736(7)A] are observed in both aluminium derivatives (E = Al). These compounds have narrow lines in the solution 27Al n.m.r. spectra, indicative of a highly symmetric environment for the aluminium centre, and consistent with a linear geometry in solution. The results provide experimental evidence for axially symmetric dative bonding by oxygen, support the triple-bond model for the phosphine oxide unit, and imply the possibility of a delocalised π interaction over the P–O–E framework.

Preparation and spectroscopic characterisation of dithia-arsolium and -stibolium cations: evidence for pπ-pπ bonding of sulphur with arsenic and antimony

5-Methyl-1,3,2-benzodithiarsolium and 5-methyl-1,3,2-benzodithiastibolium cations have been prepared and the naphthalenic nature of the compounds is strong is evidence for the presence of unique pπ-pπ bonding of sulphur to arsenic and antimony.

REACTION OF 1,3-DI-TERT-BUTYL-2,2-DIMETHYL-4,4-DICHLORO-1,3,2,4λ4-DIAZASILASTANNETIDINE WITH SILVER TRIFLUOROMETHANESULFONATE. THE CRYSTAL STRUCTURE OF POLYMERIC 1,3-DI-TERT-BUTYL-2,4-DIMETHYL-2,4-DITRIFLUOROMETHANESULFONATE-1,3,2,4λ5-DIAZASILASTANNETIDINE

Abstract When 1,3-di-tert-butyl-2,2-dimethyl-4,4-dichloro-1,3,2,λ2-diazasilastannetidine (1) is allowed to react with the chloride abstracting reagent AgCF3SO3 the chlorides are displaced by triflates forming 2. At the same time a rearrangement in the molecule takes place, one of the methyl groups on silicon migrating to tin in exchange of a triflate. In the solid the new compound 2 is a coordination polymer with trigonal bi-pyramidal tin centers, which exhibit quite unusual short Sn—N bonds in the axial plane (2.005 A) [X-ray structure determination, space group P2/l/n, a = 10.199(6)A, b = 13.532(9)A, c = 17.641(9)A, β = 99.13(9)°, Z = 4].

Synthesis of the unique 10π-electron 1,3,2-benzodithiaphospholium cation and a structural comparison with the phenyl phosphine derivative

The first example of a dithiaphospholium cation is a 10π-electron planar heterocycle, which exhibits thermodynamically stable 3pπ–3pπ bonding between phosphorus and sulphur.

pπ-pπ Bonding Between Sulfur and the Heavier Elements of Group 15

Abstract As a contribution to the development of general stable pπ-pπ bonding throughout the p-block, the first dithiaphosphenium cation la has been prepared. Stable dicoordinate phosphorus without the presence of at least one nitrogen or carbon ligand is unique. Moreover, this compound contains an unprecedented example of thermodynamically stable pπ-pπ bonding between phosphorus and sulfur. In addition, cation la contains a rare example of pπ-pπ bonding between the heavier elements of different groups of the Periodic Table. The analogous arsenic and antimony derivatives have been prepared, demonstrating that the system offers potential generality for genuine pπ-pπ bonding between all heavy (n > 2) non-metal elements.

The stability of Carbenic and Alkenic Phosphorus Environments

Abstract The factors responsible for the isolation or identification of (carbenic) phosphenium and (alkenic) tricoordinate phosphonium salts are discussed. Structural features, reactivity and observations of intramolecular rearrangement are presented, which illustrate some of the requirements for stability in each case.

Co-ordinatively unsaturated group 15 elements: the isolation and crystal structure of a novel dimeric dithiarsolidinium cation

The first example of a dithiarsolidinium cation has a novel dimeric structure, while the spirocyclic bis(ethanediyldithio)phosphonium cation has been isolated from attempts to obtain the corresponding dithiaphospholidinium cation, both observations illustrating the importance of supplemental stabilisation for low-co-ordinate group 15 elements.