No abstract

The square planar complex (BINAP)Rh(CO)Cl (BINAP = 2,2‘-bis(diphenylphosphino)-1,1‘-binaphthyl) was synthesized from [Rh(COD)Cl]2 (COD = 1,5 cyclooctadiene) and BINAP under a CO atmosphere. It reacts with oxygen to form the square planar (BINAP(O))Rh(CO)Cl in approximately 50% yield, along with molar equivalents of free BINAP dioxide (BINAP(O)2) and CO2. The oxygen atom of the BINAP(O) was shown crystallographically to be trans to the CO ligand. In the presence of excess BINAP under CO/O2 gas mixtures, the reaction is catalytic with a TOF of 0.16 h-1 at ambient temperature in chloroform. The kinetics of this transformation were investigated and conditions for optimum selectivity for BINAP(O) formation suggested. A stoichiometric mechanism is proposed that involves initial formation of an O2 adduct, followed by oxygen atom transfer to both phosphorus atoms of BINAP or to one phosphorus atom and the CO ligand trans to it. These processes might be concerted, or stepwise with intermediate RhO species. To the best of our knowledge, this chemistry represents the first example of a reaction exhibiting oxygen atom addition from O2 either to both phosphorus atoms in a bisphosphine ligand or to one phosphorus atom and a CO ligand in the same complex.

Synthesis of a variety of 2,5- and 2,6-diethynylpyridine based organic and PtII-σ-acetylide monomers and polymers is reported. Quaternization of pyridine nitrogen via solution nucleophilic substitution reactions with methyl iodide and methyl triflate yields stable pyridinium analogs and is accompanied by strong red shifts in the UV−vis absorption spectra. The latter is indicative of enhanced π-electron delocalization along the backbone upon quaternization. These compounds exhibit strong fluorescence with quantum yields of 0.015−0.058 for the monomers and 0.060−0.223 for the polymers. Quaternization leads to enhanced fluorescence intensities and quantum efficiencies. These polymers are insulators in the ground state, however, and, upon doping with iodine, they exhibit semiconducting behavior.

Chelation kinetics of the complexes Ru(CO) 4 (η 1 -(P-P)) have been studied in heptane, where P-P ) Ph 2 P(CH 2 ) n PPh 2 (n ) 1, 2, 3, or 4, i.e., dppm, dppe, dppp, or dppb), Ph 2 P(NMe)PPh 2 (dppma), Ph 2 P(o-C 6 H 4 )PPh 2 (dpp-benzene), or R 2 P(CH 2 ) 2 PR 2 (R ) Me or Cy, i.e., dmpe or dcpe). The complexes were prepared in situ by reaction of the bidentate ligands with Ru-(CO) 4 (C 2 H 4 ), which itself was prepared in situ by photolysis of Ru 3 (CO) 12 under C 2 H 4 . The initially formed Ru(CO) 4 (η 1 -(P-P)) complexes react cleanly to form axial-equatorial Ru-(CO) 3 (η 2 -(P-P)), as shown by the crystallographic structures of the products when P-P ) dppe, dmpe, and dpp-benzene and the close similarity of their FTIR spectra to those of the other products. The chelated products undergo further reaction in solution or the solid state, and the product when P-P ) dppma has been characterized by crystallography as Ru 2 -(CO) 3 (µ-PPh 2 )(µ-Ph 2 PNMePPh 2 ). The kinetics of the displacement of CO from Ru(CO) 4 (η 1 -(P-P)) in n-heptane are characterized by ∆H q values that are lower by up to 9 kcal mol -1 than those of their monodentate P-donor analogues. ∆S q values range from quite positive to slightly negative and suggest a trend from purely dissociative to appreciably associative mechanisms along the series P-P ) dpp-benzene < dcpe < dmpe < dppp e dppm ≈ dppbu ≈ dppe , dppma. This contrasts with the CO-dissociative reactions of analogous Ru(CO) 4 L complexes when L ) monodentate P-donor ligands.

P-Donor nucleophiles of cone angle >or=145 degrees are known to react with Os3(CO)9(mu-C4Ph4) quite differently from those with cone angles