Mechanistic studies of an unusual epoxide-forming elimination of a beta-hydroxyalkyl rhodium porphyrin

A new and remarkably facile sp3-C-O bond forming reaction of beta-hydroxyalkyl Rh porphyrins to form epoxides has been discovered and its mechanism investigated.     

Platinum(II) Complexes of Cyclic Triphosphenium Ions: a (31)P NMR Spectroscopic and Computational Study

The first transition metal complexes of cyclic triphosphenium ions have been unequivocally identified in solution by (31)P NMR spectroscopy. The ligands coordinate to platinum(II) via the central phosphorus atom, but only when at least one of the outer phosphorus atoms has non-aromatic substituents. Depending on the system, either trans- (the kinetic reaction product) and/or cis- (the thermodynamic reaction product) complexes are formed. The (1)J coupling constants between (195)Pt and the central phosphorus atom of the CTI (P(A)) are small for both cis- and trans-isomers, between 900 and 1300 Hz, whereas other phosphanes in these complexes derived from the platinum(II) starting material show normal (1)J(PtP) values. These results suggest a possible long P-Pt bond between the overall positively charged ligand and the platinum(II) cation. Calculations including predicted (31)P NMR shifts for the CTIs and their Pt(II) complexes largely support our experimental findings.     

The building block approach to extended solids: 3,5-pyrazoledicarboxylate coordination compounds of increasing dimensionality

A series of M(II) complexes with the ligand 3,5-pyrazoledicarboxylic acid (H3dcp) has been synthesised mainly via hydrothermal reactions and their structures have been characterised. Simple mononuclear [Ni(Hdcp)(H2O)4] (1), Na2(mu-H2O)2(H2O)8[Ni(Hdcp)2(H2O)2] (2), [M(H2dcp)2(H2O)2] x 2H2O [M = Co (3), Zn (4) and Cu (5)] and dinuclear (Et3NH)2[Cu2(dcp)2(H2O)2] (9) building blocks have been isolated and subsequently linked into 1-D chains [Mn(Hdcp)(H2O)2]infinity (6), [[Mn(H2O)4][Mn(Hdcp)2(H2O)2] x 4H2O]infinity (7), [Ni2(Hdcp)2(mu-H2O)2(H2O)2]infinity (8), [[Ni(H2O)4][Ni2(dcp)2(H2O)4]]infinity (11), or 3-D arrays [[Na2(mu-H2O)2][Cu2(dcp)2]]infinity (10), [Cu3(dcp)2(H2O)4]infinity (12), utilising novel bridging modes of the H3dcp ligand. In the unprecedented 1-D Ni(II) chain 8, rarely reported double aqua-bridges link the Ni(II) ions to form an inter-linked double stranded chain. The magnetic properties of these compounds have been measured and reveal a variety of antiferromagnetic coupling behaviours induced by the ligand bridging modes.     

Crystal and molecular structures of some six‐coordinate tin(IV) halogeno complexes with phosphorus‐containing ligands

Six new complexes of tin(IV) halides with phosphorus‐containing ligands have been fully characterized by single‐crystal X‐ray diffraction at low temperature. Three of the compounds, derived from the diphosphanes bis‐(diphenylphosphino)methane or bis‐(dicyclohexylphosphino)methane, have a novel zwitterionic structure, with five Cl ligands and one unidentate phosphorus‐containing ligand on tin, together with a proton on the second phosphorus atom of the potentially bidentate ligand; these are Cl₅Sn⁻P(Ph₂)CH₂PPh₂H⁺ ( 1 ), Cl₅Sn⁻OP(Ph₂)CH₂‐PPh₂H⁺ ( 2 ), and Cl₅Sn⁻OP(cy₂)CH₂Pcy₂H⁺ ( 3 ). The other three complexes have a bidentate donor attached to the SnX₄ moiety; they comprise Cl₄SnOP(Ph₂)‐(CH₂)₂PPh₂O ( 4 ), a derivative of bis‐(diphenylphosphino)ethane dioxide, I₄SnOP(Ph₂)CH₂PPh₂O ( 5 ), a similar derivative of bis‐(diphenylphosphino)‐methane dioxide, and the very unusual Br₄SnAs‐(Ph₂)(CH₂)₂PPh₂O ( 6 ), with coordination to tin by As and O. Since the starting material for the last compound was Ph₂As(CH₂)₂PPh₂, this result illustrates well the more facile oxidation of P(III) than As(III). © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:136–143, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20525     

A Synthetic High‐Spin Oxoiron(IV) Complex: Generation,Spectroscopic Characterization,and Reactivity

High versus low : The high‐yield generation of a synthetic high‐spin oxoiron(IV) complex, [Fe^IV(O)(TMG₃tren)]²⁺ (see picture, TMG₃tren = 1,1,1‐tris{2‐[N2‐(1,1,3,3‐tetramethylguanidino)]ethyl}amine), has been achieved by using the very bulky tetradentate TMG₃tren ligand, in order to both sterically protect the oxoiron(IV) moiety and enforce a trigonal bipyramidal geometry at the iron center, for which an S=2 ground state is favored.

     

Easily assembled,modular N,O-chelating ligands for Ta(V) complexation: a comparative study of ligand effects in hydroaminoalkylation with N-methylaniline and 4-methoxy-N-methylaniline

The influence of structurally related N,O-chelating ligands with additional heteroatoms (N, O, P, S) on the reactivity of in situ generated tantalum complexes for the hydroaminoalkylation of amines has been explored. Reactivity was probed by evaluating the catalytic ability of these N,O-chelating systems with N-methylaniline and 4-methoxy-N-methylaniline substrates. Enhanced reactivity is observed with amide proligands bearing an ortho-methoxyphenyl group on the nitrogen. 4-Methoxy-N-methylaniline is found to be more prone to undergo C–H functionalization via hydroaminoalkylation than N-methylaniline. The use of the related substrate 2-methoxy-N-methylaniline is not tolerated, and instead C(sp³)–O bond cleavage was observed.     

Sensitive resist systems based on acid-catalyzed polymer reactions

Acid-catalyzed polymer reactions have been successfully utilized in the design of chemical amplification resist systems for semiconductor manufacturing. In this paper are described preparation and acid-catalyzed depolymerization reactions of α-substituted polystyrenes.