Water and protic acids as oxidants for platinum(II): Diorgano(hydrido)platinum(IV) and diorgano(hydroxo)platinum(IV) chemistry, including structural studies of poly(pyrazol-1-yl)borate complexes Pt(OH)R-2{(pz)(3)BH} (R=methyl, p-tolyl) and Pt(OH)Me-2{(pz)(4)B}·H2O