Synthese und Kristallstruktur von dimerem Dipyrazoldipyrazolato‐platin(II), [Pt(pz)₂(Hpz)₂]₂

Abstract

Der dimere Komplex [Pt(pz)2(Hpz)2]2 (Hpz = Pyrazol) entsteht in wäßriger Lösung aus [Pt(Hpz)4]2+ durch Zugabe von OH− oder pz−. Die in Wasser unlösliche, farblose Verbindung zersetzt sich bei 191°C in Pt(pz)2. Sie kristallisiert monoklin in der Raumgruppe C2/c mit den Gitterkonstanten a = 2 165,5, b = 972,0, c = 1 648,4 pm, β = 123,09°, Z = 4. Jedes Pt2+‐Ion ist von zwei Hpz‐Molekülen und zwei pz−‐Anionen quadratisch‐planar koordiniert. Die Dimerisierung erfolgt über vier symmetrische NHN‐Brücken zwischen den Hpz‐ und pz−‐Liganden beider Pt‐Atome, so daß ein vollständiger Ladungsausgleich zwischen den Liganden erreicht wird. Der Komplex besitzt die Symmetrie C2, wobei zwei der Brücken‐H‐Atome auf der Symmetrieachse liegen. Die PtN‐Abstände entsprechen mit 200 pm kovelanten Einfachbindungen. v(NH) wird bei 2 400 cm−1 als breite Absorption beobachtet.

Expected and Unconventional Ag+ Binding Modes in Heteronuclear Pt,Ag Coordination Polymers Derived from trans‐[Pt(methylamine)2(pyrazole)2]2+

“…It is analogous to the situation found in dinuclear [{Pt(pz) 2 (Hpz) 2 } 2 ], which is formed in aqueous solution,7c and reminiscent of intermolecular hydrogen bonding between free pyrazole molecules 16. Twofold deprotonation of 1 leads to the neutral complex trans ‐[Pt(ma) 2 (pz) 2 ] ( 1d ), which is poorly soluble in water.…”

“…This observation strongly suggests that the hemideprotonated complex 1c is stabilized prior to the second deprotonation step that leads to 1d . Based on the solid‐state structures of Pt II complexes that simultaneously contain Hpz and pz ligands, which reveal either intra‐ or intermolecular hydrogen‐bond formation between Hpz and pz ligands (hence pz ··· Hpz) depending on the mutual arrangement,7c,7e we propose that an intermolecular stabilization as sketched in Figure 4 is operative with 1c .…”

Lowest Electronic Excited States of Platinum(II) Diimine Complexes

“…This behavior is consistent with either MLCT or LMCT transitions. However, since Pt(pz) 2 (pzH) 2 and Pt(dmpz) 2 (dmpzH) 2 are colorless and have no similar low-lying transitions, the possibility of low-lying pyrazolate-localized or pyrazolate/Pt charge-transfer transitions is eliminated. By analogy to literature assignments for related Pt(diimine)X 2 (X = Cl, Br, I) systems, ,, we assign the higher-energy band to 1 MLCT[d(Pt)→π*(bpy)] excitation and the shoulder at lower energy to a transition to the corresponding triplet state.…”

Pyrazolato-Bridged Polynuclear Palladium and Platinum Complexes. Synthesis, Structure, and Reactivity

“…Reaction of [PtCl 2 (C 2 H 5 CN) 2 ] with pzH in the Presence of Et 3 N. To a propionitrile solution (100 mL) of [PtCl 2 (C 2 H 5 CN) 2 ] (189 mg, 0.50 mmol) were added pzH (103 mg, 1.52 mmol) and Et 3 N (155 mg, 1.54 mmol), and the solution was refluxed for 4 h. After filtration, the filtrate was concentrated under air. The colorless crystals, [Pt(pz) 2 (pzH) 2 ] 2 ( 7 ), appeared 2 weeks later and were collected, washed with acetonitrile, and dried in air. Yield: 23 mg (10%).…”