CHEMISTRY OF P,N-LIGATED METHYLPALLADIUM(II) ALKOXIDE COMPLEXES - SYNTHESES, STRUCTURAL FEATURES IN THE SOLID-STATE AND IN SOLUTION, AND HYDROGEN-BOND FORMATION

The reaction of P,N-ligated dimethylpalladium(II) complexes [Pd(Me)(2) (P similar to N)] [P similar to N = o-(diphellylphosphino)-N,N-dimethy lbenzylamine (PCN), (diphenylphosphino)-N,N-dimethylethyleneamine (PN) ] with an equimolar amount of HOCH(CF3)(2) or HOCBH4-4-X (X = H, Cl, O Me, Me, CN, NO2, OH) affords methylpalladium(II) alkoxide and aryl oxi de complexes [Pd(Me)(OR)(P similar to N)] [R = CH(CF3)(2), C6H4-4-X; P similar to N = PCN, PN], which have been isolated in high yields as w hite or pale orange solids. NMR spectroscopic data indicate that the c omplexes have the alkoxide or aryl oxide ligand (OR) positioned trans with respect to the P-atom. Reaction of [Pd(Me)(2)(PCN)] with 2 equiv of phenol affords the phenol adduct [Pd-(Me)(OC6H5)(PCN)]. HOC6H5, whi ch has been isolated as a white solid. The transesterification reactio n of [Pd(Me)(OC6H5)(PCN)] with C6H5SC(O)Me affords the arenethiolate c omplex [Pd(Me)(SC6H5)(PCN)]. Furthermore, the alkoxide complex [Pd(Me) (OCH(CF3)(2))-(PN)] reacts with phenylacetylene to afford an isolable alkynylpalladium(II) complex [Pd(Me)(C (Me)C=CPh)(PN)]. Thermolysis of the latter complex results in reductive elimination of MeC=CPh in 98% yield. When this reductive elimination is performed under a CO atmosp here, MeC=CPh (87%) is formed together with small amounts of the inser tion product, MeC(O)C=CPh(3%). Crystals of [Pd(Me)OC6H5)(PCN)]. CH2Cl2 and its adduct with HOC6H5 have been subjected to X-ray diffraction s tudies. The molecular structure of the latter adduct shows an O-H ... O hydrogen bond between the phenol and the oxygen atom of the phenoxid e unit. The P-31 NMR chemical shift and (3)J(HP) for the Pd-CH3 group of the complexes [Pd-(Me)(OC6H4-4-X)(PN)] have been correlated with va rious Hammet substituent constants; the best linearity was achieved wi th parameters that represent the sum of resonance and inductive/field effects of the substituent X.