Reactivity Towards Acidic Protic Ligands of Cyclopalladated Di‐μ‐hydroxo Complexes

The dinuclear hydroxo complexes [{Pd(μ‐OH)(C∧N)}2] [C∧N = 2‐(2‐pyridyl)phenyl (Phpy) (I), 7,8‐benzoquinolyl (Bzq) (II) and 2‐(2‐oxazolinyl)phenyl (Phox) (III)] react in a 1:2 molar ratio with a wide variety of protic electrophiles H(L∧L) bearing different sets of donor atoms (L∧L = O∧O or O∧N) to give the mononuclear neutral palladium(II) derivatives with the general formula [Pd(L∧L)(C∧N)] [O∧O = salicylaldehydate (sal) (1), acetylacetonate (acac) (2) and benzoylacetonate (bzac) (3); O∧N = N‐phenylsalicylaldiminate (N‐Phsal) (4), N‐p‐chlorophenylsalicylaldiminate (N‐pClPhsal) (5), 2‐pyrrolecarbaldeydate (2‐pcal) (6), 8‐hydroxyquinolinate (oxin) (7)]. Structural characterisation of complexes I1, I3, I6, II4, II5and III5by X‐ray diffraction confirmed the proposed formulae. Dinuclear complexes [{Pd(μ‐N∧S)(C∧N)}2] [N∧S = 2‐pyridinethiolate (spy)] (8) were obtained when treating complexes I–IIIwith 2‐mercaptopyridine in the same molar ratio. A related process takes place when the three precursors react with ammonium O,O′‐diethyldithiophosphate under mild conditions and complexes [Pd{S(S)P(OEt)2}(C∧N)] (I9–III9) are obtained. Deprotonation of the secondary amine Et2NH by complexes I–IIIin the presence of carbon disulfideleads to the corresponding dithiocarbamate complexes [Pd(S2CNEt2)(C∧N)] (I10–III10). The new complexes were characterised by analytical and spectroscopic techniques (IR and 1H NMR).(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) The advantageous use of three PdIIdi‐μ‐hydroxo complexes as precursors containing a cyclometalated backbone is presented. Strong basic treatments were avoided supporting the unique characteristics of such complexes as starting materials in simple acid–base reactions with protic electrophiles or related ligands.