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Expected and Unconventional Ag + Binding Modes in Heteronuclear Pt,Ag Coordination Polymers Derived from trans ‐[Pt(methylamine) 2 (pyrazole) 2 ] 2+
Author(s) -
BrandiBlanco Pilar,
Sanz Miguel Pablo J.,
Lippert Bernhard
Publication year - 2012
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201101197
Subject(s) - chemistry , crystallography , pyrazole , methylamine , heteronuclear molecule , intramolecular force , ligand (biochemistry) , stereochemistry , nuclear magnetic resonance spectroscopy , organic chemistry , biochemistry , receptor
The combination of AgNO 3 and trans ‐[Pt(ma) 2 (Hpz) 2 ] 2+ ( 1 ; ma = methylamine; Hpz = neutral pyrazole) in water yields mixed Pt,Ag coordination polymers of different stoichiometries, depending on the ratio between Ag and Pt, as well as the pH. The products that were isolated and X‐ray structurally characterized display both conventional (Ag + coordination to pyrazole‐N) and unconventional Ag + binding modes (η 1 and η 2 binding to C atoms of the pyrazole/pyrazolate ligands; Pt → Ag dative bonds). Specifically, in trans ‐[Pt(ma) 2 (Hpz) 2 ]Ag 2 (NO 3 ) 4 ( 2 ) and in trans ‐[Pt(ma) 2 (pz) 2 ] 2 Ag 3 (NO 3 ) 3 ( 4 ), silver ions bind to C4 positions of Hpz ( 2 ) and pz – ( 4 ) ligands in η 1 fashions, with Ag–C distances of 2.574(4) and 2.643(16) Å, respectively. In 4 there is additional cross‐linking by a second Ag + of N2 sites of adjacent pz – rings, further reinforced by weak dative bonds from Pt to Ag. Ag–N coordination to both a neutral Hpz and an anionic pz – ligand is observed in trans ‐[Pt(ma) 2 (pz) 2 ]Ag 2 (Hpz) 2 (NO 3 ) 2 ( 5 ), with individual trinuclear PtAg 2 entities associated through weak η 2 contacts that involve the C3 and C4 positions of the neutral Hpz ligands. As in 4 , intramolecular Pt–Ag distances of 3.1374(6) Å suggest weak dative bond interactions between Pt and Ag. The acidities of the two Hpz ligands in 1 are distinctly different (p K a values of 7.25 and 9.08 in H 2 O), thereby suggesting a stabilization of the monodeprotonated species trans ‐[Pt(ma)(Hpz)(pz)] + ( 1c ) in solution, probably through intermolecular hydrogen‐bond formation between Hpz and pz – ligands.