Reactions of the dinuclear platina-β-diketone [Pt2{(COR)2H}2(μ-Cl)2]
(1) with K[(pz)3BH] and K[(3,5-Me2pz)3BH] (pz = pyrazolyl; 3,5-Me2pz = 3,5-dimethylpyrazolyl)
afforded neutral diacetyl(hydrido)platinum(IV) complexes [Pt(COMe)2H{(pz)3BH}] (4a) and [Pt(COMe)2H{(3,5-Me2pz)3BH}] (4b),
bearing κ3-bonded tris(pyrazolyl)borate (scorpionate)
ligands. These complexes were found to decompose in chloroform solution
under formation of the respective chlorido complexes [Pt(COMe)2Cl{(pz)3BH}] (5a) and [Pt(COMe)2Cl{(3,5-Me2pz)3BH}] (5b) as the initial step. Diacetylplatinum(II) complexes with κ2-coordinated scorpionate ligands (K[Pt(COMe)2{(pz)3BH}], 6a; K[Pt(COMe)2{(3,5-Me2pz)3BH}], 6b; K[Pt(COMe)2{(pz)4B}], 7; K[{Pt(COMe)2}2{(pz)4B}], 8) were obtained in ligand
exchange reactions of [Pt(COMe)2(NH2Bn)2] (3; Bn = benzyl) with the respective potassium
(pyrazolyl)borates. The deprotonation of the hydrido complexes 4 with potassium methoxide led also to the formation of 6. Diacetylplatinum(II) complexes 6a and 7 were found to react in oxidative addition reactions with
alkyl halides to yield diacetylplatinum(IV) complexes of the type
[Pt(COMe)2R{(pz)3BH)}] (R = Me, 9a; Et, 9b; Bn, 9c) and [Pt(COMe)2R{(pz)4B}] (R = Me, 10a; Et, 10b; Bn, 10c), respectively, with κ3-bonded
scorpionate ligands. The identities of all platinum complexes were
unambiguously proved by microanalyses or by high-resolution mass spectrometric
investigations, by NMR (1H, 13C, 195Pt) and IR spectroscopies, and by single-crystal X-ray diffraction
analyses (4a, 5a, 7·(18C6), 9c; 18C6 = 18-crown-6). The reactivity of the complexes is
discussed in terms of hemilability of the scorpionate ligands.
