P Ring Size Dependence on NHC-Induced Ring Contraction Reactions of [CoCp‴(η-P)], [Ta(CO)Cp″(η-P)], and [FeCp*(η-P)]: A DFT Study.

The facile ring contraction of [CoCp‴(η-P)] and [Ta(CO)Cp″(η-P)] to [CoCp‴(η-P)][(NHC)P] and [Ta(CO)Cp″(η-P)] [(NHC)P] induced by NHC and the absence of the ring contraction of [FeCp*(η-P)] under the same conditions are studied by density functional theory (DFT) computations. The latter is estimated to be thermodynamically the least favorable reaction and also has a very high energy barrier. The similar strain energies of P and P rings and the lower strain energy of the P ring play a decisive role in the ring contraction capability of these [TM-cyclo-P] complexes.

A Benzodiphosphaborolediide.

The first example of a diphosphaborolediide, the benzo-fused [C H P BPh] (1 ), is prepared from ortho-bis(phosphino)benzene (C H {PH }) and dichlorophenylborane, via a sequential lithiation approach. The dilithio-salt can be obtained as an oligomeric THF solvate or discrete TMEDA adduct, both of which are fully characterized, including by X-ray diffraction. Alongside NICS calculations, data strongly suggest some aromaticity within 1 , which is further supported by preliminary coordination studies that demonstrate η -coordination to a zerovalent molybdenum center, as observed crystallographically for the oligomeric [{Mo(CO) (η -1)}{μ-η -Mo(CO) (TMEDA)} ] ⋅ [μ-Li(THF)][μ-Li(TMEDA)].

Structure and bonding in stannadiphospholes and their dianions SnC2P2R2m (R=H, tBu m=0, -2): a comparative study with C5H5+ and C5H5- analogues.

The potential energy surfaces of both neutral and dianionic SnC(2)P(2)R(2) (R=H, tBu) ring systems have been explored at the B3PW91/LANL2DZ (Sn) and 6-311+G* (other atoms) level. In the neutral isomers the global minimum is a nido structure in which a 1,2-diphosphocyclobutadiene ring (1,2-DPCB) is capped by the Sn. Interestingly, the structure established by X-ray diffraction analysis, for R=tBu, is a 1,3-DPCB ring capped by Sn and it is 2.

Electronic structure and bonding in neutral and dianionic boradiphospholes: R'BC2P2R2 (R = H, tBu, R' = H, Ph).

Classical and non-classical isomers of both neutral and dianionic BC(2)P(2)H(3) species, which are isolobal to Cp(+) and Cp(-), are studied at both B3LYP/6-311++G(d,p) and G3B3 levels of theory. The global minimum structure given by B3LYP/6-311++G(d,p) for BC(2)P(2)H(3) is based on a vinylcyclopropenyl-type structure, whereas BC(2)P(2)H(3)(2-) has a planar aromatic cyclopentadienyl-ion-like structure. However, at the G3B3 level, there are three low-energy isomers for BC(2)P(2)H(3): 1) tricyclopentane, 2) nido and 3) vinylcyclopropenyl-type structures, all within 1.

Syntheses, structural studies, photoelectron spectra and density functional theory calculations of the "pseudo" tetraphospha-metallocenes [M(eta-P2C3Bu(t)3)(2)], (M = Ni, Pd, Pt).

Syntheses and structural characterization of the complexes [M(eta-P(2)C(3)Bu(t)(3))(2)], (M = Ni, Pd, Pt) are described. The nickel compound has an 18-electron [Ni(eta(5)-P(2)C(3)Bu(t)(3))(eta(3)-P(2)C(3)Bu(t)(3))] structure, whereas the palladium and platinum compounds both have a 16-electron [M(eta(3)-P(2)C(3)Bu(t)(3))(2)] structure (M = Pd, Pt).The electronic structure is examined and discussed using both photoelectron spectroscopy and DFT calculations.

Specific insertion reactions of a germylene, stannylene and plumbylene into the unique P-P bond of the hexaphospha-pentaprismane cage, P6C4tBu4: crystal and molecular structures of P6C4tBu4ER2 (E = Ge, Sn, R = N(SiMe3)2; E = Pb, R = (C6H3(NMe2)2 -2,6).

Treatment of the cage compound P6C4(t)Bu4 with M(N(SiMe3)2)2 (M = Ge or Sn) or Pb(C6H3(NMe2)2- 2,6) at room temperature results in their specific insertion into the P-P bond connecting the two 5-membered P3C2(t)Bu2 rings. The products were fully characterised by multinuclear NMR spectroscopy and single crystal X-ray diffraction studies.

Facile insertion and halogen migration reactions of the hexaphosphapentaprismane cage P6C4tBu4 with zerovalent and divalent platinum complexes.

The hexaphosphapentaprismane P(6)C(4)(t)Bu(4) undergoes specific insertion of the zerovalent platinum fragment [Pt(PPh(3))(2)] into the unique P-P bond between the 5-membered rings to afford [Pt(PPh(3))(2)P(6)C(4)(t)Bu(4)]. A similar reaction with the Pt(ii) complexes [{PtCl(2)(PMe(3))}(2)] and [PtCl(2)(eta(4)-COD)] results in both insertion and chlorine migration reactions. The complexes [Pt(PPh(3))(2)P(6)C(4)(t)Bu(4)], trans-[PtCl(PMe(3))P(6)C(4)(t)Bu(4)Cl], cis-,trans-[{PtCl(2)(PMe(3))}micro-{P(6)C(4)(t)Bu(4)}{PtCl(2)(PMe(3))}], [{PtClP(6)C(4)(t)Bu(4)Cl}(2)] and cis-[PtClP(6)C(4)(t)Bu(4)Cl(P(6)C(4)(t)Bu(4))] have been structurally characterized by single crystal X-ray diffraction and multinuclear NMR studies.

Copper(I) mediated oligomerisation of a phosphaalkyne.

The oligomerisation of tert-butylphosphaalkyne, tBuC[triple bond, length as m-dash]P, mediated by Cu(I) complexes yields an unprecedented C4P5 cage compound, which is stabilised in a matrix of copper(I) iodide.

Synthesis of the 2,4,5-tri-tert-butyl-1,3-diphospholide anion by phosphinidene elimination from 2,4,6-tri-tert-butyl-1,3,5-triphosphabenzene on treatment with the amide Li[NPh(SiMe3)].

Treatment of the lithium amide Li[NPh(SiMe3)] with 2,4,6-tri-tert-butyl-1,3,5-triphosphabenzene, P(3)C(3)tBu(3), in a 1:2 ratio afforded equimolar amounts of the lithium salt of the five-membered 2,4,5-tri-tert-butyl-1,3-diphospholide anion, LiP(2)C(3)tBu(3) (isolated as its N,N,N',N'-tetramethylethylenediamine (TMEDA) adduct), and the tricyclic compound 6-[phenyl(trimethylsilyl)amino]-3,5,7-tri-tert-butyl-1,2,4,6-tetraphosphatricyclo[3.2.0.

Electronic structure and bonding studies on triple-decker sandwich complexes with a P6 middle ring.

DFT and hybrid HF-DFT studies of structure and bonding of CpMP6MCp triple-decker sandwich complexes, ranging from 18-28 valence electrons (VE) with M=Sc, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W, show that the middle P6 ring complexes adopt symmetric planar (28 valence electron count [VEC]), asymmetric planar (26 VEC), and puckered (24 VEC) geometries. According to the mno Rule, 50 skeletal electrons are needed for these triple-decker cluster frameworks. For 28 VEC, this corresponds to 10 electrons more than the 50 electrons of the mno Rule if all VE of the metal are included.

The molecular structure of [Sn(P2C2But2)] using gas-phase electron diffraction and DFT calculations.

The molecular structure of 2,4-di-tert-butyl-eta4-1,3-diphosphacyclobutadiene tin has been determined in the gas phase by electron diffraction using both the DYNAMITE and SARACEN methods. The suitability of many different theoretical methods for the calculation of structures of half-sandwich main-group metal complexes has been investigated, and, by comparison of the results with the experimental structures, suggestions have been made as to the most suitable methods for this class of compound.

Synthesis of a eta 2-2,3-diphosphabutadiene complex of zerovalent platinum from the corresponding eta 2-phosphaalkyne complex.

Hydrozirconation of the eta 2-phosphaalkyne complex [Pt(dppe)(eta 2-tBuCP)] with [ZrHCl(eta 5-C5H5)2], followed by treatment with the chlorophosphaalkene ClP=C(SiMe3)2 affords the eta 2-2,3-diphosphabutadiene complex [Pt(dppe)(eta 2-tBuC(H)=PP=C(SiMe3)2]. In the presence of [Pt(PPh3)2] the latter undergoes an addition reaction with water to afford the structurally characterised Pt(II) complex [Pt(dppe)(tBuCH2P(O)HPC(SiMe3)2].

Hexaphosphapentaprismane: a new gateway to organophosphorus cage compound chemistry.

Several independent synthetic routes are described leading to the formation of a novel unsaturated tetracyclic phosphorus carbon cage compound tBu4C4P6 (1), which undergoes a light-induced valence isomerization to produce the first hexaphosphapentaprismane cage tBu4C4P6 (2). A second unsaturated isomer tBu4C4P6 (9) of 1 and the bis-[W(CO)5] complex 13 of 1 are stable towards similar isomerization reactions. Another starting material for the synthesis of the hexaphosphapentaprismane cage tBu4C4P6 (2) is the trimeric mercury complex [(tBu4C4P6)Hg]3 (11), which undergoes elimination of mercury to afford the title compound 2.

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.