Heteroatom Donor Research Articles

Coordination Chemistry of a Tripodal S2ON Ligand: Syntheses, Structures, and Reactivity of the Molybdenum(VI) and Nickel(II) Complexes of Bis(2-mercaptoethyl)-2-amino-4-methylphenol (H3btap) and Comparison to VVO(btap)

The tripodal tetradentate ligand H3btap coordinates to VV, MoVI, and NiII via three different bonding modes to yield three complexes with unique ligand-based oxidation chemistry. For VV and MoVI (1), all four of the heteroatom donors are coordinated to the metal ion forming a trigonal bipyramidal complex with the oxovanadium(V) ion, VVO3+, and an octahedral complex with the cis-dioxomolybdenum(VI) ion, [MoO2]2+. Only three of the heteroatom donors of H3btap are used to coordinate to NiII (2), two thiolate sulfurs and the amine nitrogen, yielding a dimeric structure in which each nickel(II) ion has NS3 coordination. The ability of VVO(btap) to form η2-sulfenates, while [MoO2(btap)]- does not form stable η2-sulfenates, has been ascribed to the electron-deficient, π-accepting nature of VVO3+ relative to [MoVIO2]2+. Crystal data for 1 (C11H16NO4S2KMo): space group Pbcn, a = 6.6596(9) A, b = 13.7446(9) A, c = 32.992(2) A, α = β = γ = 90°, Z = 8. Crystal data for 2 (C24H38N2O4S4Ni): space group Pbcn, a = 12.0...

Laser Flash Photolysis Studies of Oxygen and Sulfur Atom Transfer Reactions from Oxiranes and Thiiranes to Singlet Carbenes1

Laser flash photolysis (UV-LFP) studies of benzylchlorodiazirine (1a), phenylchlorodiazirine (1b), phenylmethoxydiazirine (1c), 2,2-dimethoxy-5,5-dimethyl-Δ3-1,3,4-oxadiazoline (6a), 3,4-diaza-2,2-dimethoxy-1-oxa[4.3]spirooct-3-ene (6b), 5‘,5‘-dimethoxyspiro[adamantane]-2,2‘-[Δ3-1,3,4-oxadiazoline] (6c), and diazofluorene (DAF) in the presence of oxiranes and thiiranes are reported. These compounds, upon irradiation, afford benzylchlorocarbene (2a), phenylchlorocarbene (2b), methoxyphenylcarbene (2c), dimethylcarbene (8a), cyclobutylidene (8b), adamantylidene (8c), and fluorenylidene (FL), respectively. Absolute rate constants for the transfer of oxygen and sulfur atoms to these carbenes have been determined in both acetonitrile and cyclohexane solvents. These carbenes abstract oxygen and sulfur atoms with bimolecular rate constants ranging from 104 to 1010 M-1 s-1 at 22 °C. Ylides from attack of carbenes onto heteroatom donors were not observed for any of the heteroatom transfer reactions. It was found that the magnitudes of the rate constants for heteroatom transfer are dependent on the philicity of the carbene intermediate, and trends in the kinetic data suggest that oxygen and sulfur atom transfers occur by concerted mechanisms through ylide-like transition states. The reactions of dimethoxycarbene (14) with cyclohexene oxide and propylene sulfide have been studied by the thermolysis of 6a, in benzene, at 110 °C. It was found that dimethoxycarbene also abstracts oxygen and sulfur atoms, albeit in low yields. It is concluded that, for singlet carbenes, carbene electrophilicity is important in these heteroatom transfer processes.

Influence of heteroatom donors on the orders of relative gas-phase binding affinities of macrocyclic polyethers

The effects of the heteroatom donor on the complexation of various metal ions by macrocyclic polyethers were qualitatively examined by application of the ligand exchange technique in a quadruple ion trap mass spectrometer. The metal ions, including K+, Cs+, Al+, Mg+, Cu+ and Ni+, were generated by laser desorption and allowed to react with 12-crown-4 and its nitrogen and sulfur analogs, cyclen and 1,4,7,10-tetrathiacyclododecane. The orders of gas-phase basicities were established as a comparison. The relative K+ and Cs+ binding affinities of 12-crown-4 are greatest, whereas cyclen has the highest binding affinity for all the other metal ions and also the highest gas-phase basicity.

Synthesis and thermal decomposition of substituted [2-(acyloxy)alkyl]diorganotin compounds, Bu 2Sn(X)CH 2 CHR 1OCOR 2 (X  halogen 2,4-pentanedionate or OCOR), potential sources of organotin catalysts

Halido-, (2,4-pentadionato- O, O′) and (acyloxy[2-(acyloxy)ethyl]dibutylstannanes, Bu 2Sn(X)CH 2CHR 1OCOR 2 (X  halogen, 2,4- pentanedionate, or OCOR) have been prepared, either by hydrostannation of vinyl esters or by condensation of stannyllithium compounds with epoxides followed by esterification. These thermally unstable compounds are easily decomposed in diorganotin compounds with two heteroatom donors. Some are good catalyst sources for silicone curing and polyurethane preparation.

10,10′‐Bi(trispiro[2.0.2.0.2.1]decylidene): a Highly Nucleophilic Olefinic Hydrocarbon

The title compound 1 is a record olefin in more ways than one. Not only the four α-but also the two β-spirocyclopropane groups exert a donor effect on the double bond. The π-ionization potential of 7.3 eV and the oxidation potential of 0.74 V are the lowest values observed so far for monoolefins without heteroatom donor substituents.