Diorganophosphanylphosphinidenes as complexed ligands: synthesis via an anionic terminal phosphide of niobium.
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Biomedical subjects
Christopher C Cummins
Publications and source records attributed to Christopher C Cummins.
Elucidation of a Sc(I) complex by DFT calculations and reactivity studies.
Sc(BrMgL)(2)Br (L = (R(2)NCH(2)CH(2)NCMe)(2)CH, R = H) was studied by DFT methods leading to the conclusion that this diamagnetic formal scandium(I) system enjoys stabilization of its Sc-based filled d(yz)() orbital by a delta-acceptor linear combination of BrMgL ring orbitals. Investigation of the reactivity of Sc(BrMgL)(2)Br (L = (R(2)NCH(2)CH(2)NCMe)(2)CH, R = Et) with H(2)O.B(C(6)F(5))(3) and (HOCH(2))(2)CMe(2), respectively, led to decomposition, with LMgBr being isolated in the latter case.
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Molybdenum chalcogenobenzimidato complexes: radical synthesis and nitrile extrusion via beta-EPh (E = S, Se, and Te) elimination.
Molybdenum chalcogenobenzimidates of formula (Ph[PhE]C=N)Mo(N[t-Bu]Ar)(3) (Ar = 3,5-C(6)H(3)Me(2)) have been obtained by treatment of Mo(N[t-Bu]Ar)(3) sequentially with benzonitrile and 0.5 equiv of PhEEPh (E = S, Se, and Te). Molecular structure determinations have been carried out for the S and Se variants. The Te variant extrudes PhCN forming structurally characterized (PhTe)Mo(N[t-Bu]Ar)(3) with facility assessed via stopped-flow kinetic measurements, while the Se and S analogues exhibit increasing stability. Quantum chemical calculations and solution calorimetry have been employed as an aid to interpretation of the PhCN extrusion reaction.
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Molybdenum-phosphorus triple bond stabilization by ancillary alkoxide ligation: synthesis and structure of a terminal phosphide tris-1-methylcyclohexanoxide complex.
Using alcoholysis, we converted terminal phosphide PMo(N[i-Pr]Ar)3 into a new, monomeric terminal phosphide PMo(OR)3, where R = 1-methylcyclohexyl or 1-adamantyl. Dimerization of the PMo unit was observed upon alcoholysis with 2,6-dimethylphenol, and the dimer [PMo(N[i-Pr]Ar)(O-2,6-C6H3Me2)2]2 was isolated and characterized by X-ray crystallography.
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The niobaziridine-hydride functional group: synthesis and divergent reactivity.
A multistep synthetic strategy enables the isolation of the niobaziridine-hydride complex Nb(H)(eta2-tBu(H)C=NAr)(N[Np]Ar)2 (1, Np = neopentyl, Ar = 3,5-C6H3Me2), which functions as a reactive synthon for its tautomer, the three-coordinate, trisamide species Nb(N[Np]Ar)3 (2). Treatment of 1 with various small molecules has demonstrated its capacity to effect two-electron reduction chemistry. Most noteworthy is the reaction between 1 and elemental phosphorus (P4), providing in high yield the bridging diphosphide complex (mu2:eta2,eta2-P2)[Nb(N[Np]Ar)3]2. However, unsaturated organic functionality including nitriles and aldehydes can insert into the Nb-H bond of 1, leaving the niobaziridine ring intact, thus demonstrating that dual pathways of reactivity are available to the niobaziridine-hydride functional group.
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Diuranium inverted sandwiches involving naphthalene and cyclooctatetraene.
Treatment of IU(DME)(NC[(t)Bu]Mes)(3) (2-I-DME) with 4 equiv of KC(8) and 0.5 equiv of naphthalene in DME allowed the isolation of a naphthalene-bridged compound, K(2)(mu-eta(6),eta(6)-C(10)H(8))[U(NC[(t)Bu]Mes)(3)](2) (K(2)-2(2)-mu-C(10)H(8)), in 60% yield as a dark brown powder. The twelve U-C distances are rather short, varying from 2.565(11) to 2.749(10) A. Treatment of M(2)-2(2)-mu-C(10)H(8) (M = Na, K) with 2 equiv of 1,3,5,7-cyclooctatetraene afforded a mixture of two products: M-2-COT and 2(2)-mu-COT. Compound 2(2)-mu-COT can be assembled independently in 90% yield by salt elimination upon reaction of M-2-COT with iodide 2-I-DME. The U-C(arene) distance in compound 2(2)-mu-COT is longer than that in its naphthalene counterpart K(2)-2(2)-mu-C(10)H(8)(2.822 vs 2.634 A), in accord with bonding considerations. A DFT study performed on model compounds for both M(2)-2(2)-mu-C(10)H(8) and 2(2)-mu-COT indicates that the delta bonds present in the former compound show better covalent overlap.
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Vanadium nitride functionalization and denitrogenation by carbon disulfide and dioxide.
A dramatic difference in behavior is observed for the dithiocarbamate and carbamate complexes [Ar(But)N]3V(NCE2)Na(THF)2(E = S or O, respectively), prepared from the corresponding nitride species ([Ar(But)N]3V identical to NNa)2 by way of a nucleophilic addition reaction involving carbon disulfide or dioxide, and is rationalized with the aid of DFT calculations.
Carbon Dioxide↗
Methine (CH) transfer via a chlorine atom abstraction/benzene-elimination strategy: molybdenum methylidyne synthesis and elaboration to a phosphaisocyanide complex.
Methine (CH) transfer to an open coordination site was achieved in one pot by titanium(III) abstraction of Cl from 7-chloronorbornadiene, radical capture by Mo, and benzene extrusion. This efficient Mo methylidyne synthesis permitted elaboration to an anionic phosphaisocyanide derivative upon deprotonation, functionalization with dichlorophenylphosphine, and ultimate reduction.
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