Synthesis of a Palladium Dimer Supported by a C-Bound Trifluoroacetonate Bridge Formed by Cleavage of a Hexafluoroacetylacetonate Ligand.

Palladium(II) hexafluoroacetylacetonate (Pd(Hfacac)2) is known to form adducts of bases, such as lutidine (2,6-dimethylpyridine). When treated with approximately 3 equiv of lutidine, Pd(Hfacac)2 yields a 1:1 complex as reported in the literature, Pd(O,O-Hfacac)(C-Hfacac)(lutidine), 1. However, when the amount of excess lutidine is increased, a new complex, 2, is formed. A single-crystal X-ray structure of 2 proves it is a rare example of a dimeric palladium complex containing two Pd(Hfacac)(lutidine) fragments bridged by a dianionic trifluoroacetonate ligand, µ-CHC(O)CF3. The formation of 2 is accompanied by a white precipitate determined to be a mixture of trans-Pd(O2CCF3)2(lutidine)2 (3), confirming the fate of the missing trifluoroacetate fragment from the cleavage of the Hfacac ligand, and [lutidinium][Hfacac] (4). Subsequent experiments revealed the determinative role that water played in this reaction. The mechanism of cleavage of the Hfacac ligand was explored by DFT methods.

Crosslinking Vinyl-Addition Polynorbornenes via Difunctional Diazirines to Generate Low Dielectric-Constant and Low Dielectric-Loss Thermosets.

Thermosets having low dielectric constant (Dk < 3) and low dielectric dissipation factor (Df < 0.003), high glass transition temperature (Tg > 150 °C), and good adhesion to copper are desirable for the low loss layers of the copper clad laminates (CCL) in next generation printed circuit boards. Three different difunctional diazirines are evaluated for both thermal and photochemical crosslinking of a high Tg vinyl-addition polynorbornene resin: poly(5-hexyl-1-norbornene) (poly(HNB)). The substrate polymer, crosslinked by the carbenes generated from the activated diazirines, forms thermosets with Dk < 2.3 and Df < 0.001 at 10 GHz depending on the identity of the diazirine and the loading. The Dk and Df values for one composition are stable for 1600 h at 125 °C in air and for 1400 h at 85 °C and 85% relative humidity, suggesting good long-term reliability of this thermoset. Adhesion of poly(HNB) to copper can be enhanced by priming the copper surface with a diazirine prior to high temperature lamination; peel strength values of greater than 7.5 N cm-1 are achieved. Negative-tone photopatterning of poly(HNB) with diazirines upon exposure to 365 nm light is demonstrated.

Formation of Phenoxynorbornane Pendant Groups by Acid-Catalyzed Hydroalkoxylation of Poly(hydroxystyrene) and Its Application to Photopatterning.

Poly(hydroxystyrene) (PHS) reacts with norbornene in the presence of acid to form a phenoxynorbornane pendent group through the hydroalkoxylation of the norbornene double bond by the phenol -OH group of PHS. Films of PHS, an aqueous base soluble polymer, containing norbornene derivatives and a photoacid generator (PAG) create a negative tone photopatternable composition. Acid generated in the exposed regions of the film promotes the hydroalkoxylation reaction generating the phenoxynorbornane pendent group, rendering the film insoluble in an aqueous base developer. Both dinorbornene and mononorbornene-functional additives were evaluated. In the case of the mononorbornene additive, a unique example of a negative tone photopatterned film that can be reworked after patterning by dissolution in a mild solvent at room temperature was demonstrated. Polymers containing aliphatic alcohol and carboxylic acid pendant functionalities could be photopatterned in the presence of dinorbornene additives showing the generality of this method.

Sugar-Functional Vinyl Addition Poly(norbornene)-Photopatternable Poly(norbornenyl gluconamide) Compositions Developed with Water.

The norbornenyl gluconamide (NBGA) monomer can be polymerized by a number of palladium catalysts to give water-soluble, vinyl addition poly(NBGA). Depending on the catalyst used, the reaction conditions, and the chain-transfer additives employed, high-molecular-weight polymers can be obtained. These polymers can be thermally cross-linked at ca. 190 °C or at ca. 150 °C when the difunctional glutaraldehyde is added. A photopatternable composition is formed by the addition of a water-soluble diazide when the poly(NBGA) molecular weight is sufficiently high. After image-wise exposure, negative-tone patterns are revealed by water development. A detailed analysis of NBGA monomer structures by high-resolution nuclear magnetic resonance techniques including pure shift is reported showing that two diastereomers of each endo- and exo-isomer are formed from the reaction of norbornene methylamine and δ-gluconolactone.

Synthesis and characterization of a new family of square-planar nickel(II) carbonyl derivatives.

The reaction of [NBu(4)](2)[Ni(C(6)F(5))(4)] (1) with solutions of dry HCl(g) in Et(2)O results in the protonolysis of two Nibond;C(6)F(5) bonds giving [NBu(4)](2)[[Ni(C(6)F(5))(2)](2)(mu-Cl)(2)] (2 a) together with the stoichiometrically required amount of C(6)F(5)H. Compound 2 a reacts with AgClO(4) in THF to give cis-[Ni(C(6)F(5))(2)(thf)(2)] (3). Reacting 3 with phosphonium halides, [PPh(3)Me]X, gives dinuclear compounds [PPh(3)Me](2)[[Ni(C(6)F(5))(2)](2)(mu-X)(2)] (X=Br (2 b) or I (2 c)). Solutions of compounds 2 in CH(2)Cl(2) at 0 degrees C do not react with excess CNtBu, but do react with CO (1 atm) to split the bridges and form a series of terminal Ni(II) carbonyl derivatives with general formula Qcis-[Ni(C(6)F(5))(2)X(CO)] (4). The nu(CO) stretching frequencies of 4 in CH(2)Cl(2) solution decrease in the order Cl (2090 cm(-1))>Br (2084 cm(-1))>I (2073 cm(-1)). Compounds 4 revert to the parent dinuclear species 2 on increasing the temperature or under reduced CO pressure. [NBu(4)]cis-[Ni(C(6)F(5))(2)Cl(CO)] (4 a) reacts with AgC(6)F(5) to give [NBu(4)][Ni(C(6)F(5))(3)(CO)] (5, nu(CO)(CH(2)Cl(2))=2070 cm(-1)). Compound 5 is also quantitatively formed ((19)F NMR spectroscopy) by 1:1 reaction of 1 with HCl(Et(2)O) in CO atmosphere. Complex 3 reacts with CO at -78 degrees C to give cis-[Ni(C(6)F(5))(2)(CO)(2)] (6, nu(CO)(CH(2)Cl(2))=2156, 2130 cm(-1)), which easily decomposes by reductive elimination of C(6)F(5)bond;C(6)F(5). Compounds 3 and 6 both react with CNtBu to give trans-[Ni(C(6)F(5))(2)(CNtBu)(2)] (7). The solid-state structures of compounds 3, 4 b, 6, and 7 have been established by X-ray diffraction methods. Complexes 4-6 are rare examples of square-planar Ni(II) carbonyl derivatives.