A 1H and 195Pt NMR study of the protonation mediated interconversion of mono- ( S) versus bidentate S, O) co-ordination of Pt(II) by N−acyl- N′, N′-dialkylthioureas

• Published in: Polyhedron Vol. 17; no. 2; pp. 267 - 274
• Main Authors: Koch, Klaus R., Grimmbacher, Tarron, Sacht, Cheryl
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 1998
• Subjects: 195Pt NMR; isomerism; N-benzoyl- N′ N′-dialkylthiourea; platinum(II) complexes; protonation; 195Pt NMR; protonation; N-benzoyl- N′ N′-dialkylthiourea; platinum(II) complexes; isomerism
• ISSN: 0277-5387
• DOI: 10.1016/S0277-5387(97)00326-4

Treatment of
cis-[Pt(L−
S,
O)
2] in CDCl
3 solution, directly in an NMR tube with concentrated mineral acid HX and/or HY (X = Cl
−, Y = Br
−), leads to the reversible protonation of the co-ordinated ligand of these complexes across the aqueous-organic phase boundary; these processes have been followed by means of
195Pt and
1H NMR. Treatment with HCl yields of
cis- and
trans-[Pt(HL)−S
2
Cl
2] species, in addition to the partially-ring-opened [Pt(L
n
−
S,
O)(HL
n
−
S)Cl] complex in solution, the
cis-[Pt(HL−
S)
2Cl
2] complex predominating in solution at steady-state. These species are rapidly and reversibly converted back to only the
cis-[Pt(L−
S,
O)
2] complex on washing of the CDCl
3 solution with aqueous ammonia. Similar observations pertain to protonation by HBr, yielding the corresponding bromo complexes; treatment of
cis-[Pt(L−
S,
O)
2] in CDCl
3 with a mixture of HCl and HBr, leads to the formaiton of mixed-halide species of
cis- and
trans-[Pt(HL−
S)
2XY] in addition to the [Pt(HL−
S)
2)
2X
2] and [Pt(
HL
t-
S)
2Y
2] as well as the partially-ring-opened [Pt(L
n
−
S,
O)(HL
n
−
S)X/Y] complexes in solution, which revert to
cis-[Pt(
L−
S,
O)
2] on treatment with aqueous base. These observations clearly have important consequences in the use of
N-acyl-
N′
N′-dialkylthioureas for the solvent extraction of the platinum metals.