Organoamidometallics. I. Syntheses of [N,N′-Bis(Polyfluorophenyl)Ethane-1,2-Diaminato(2-)]Platinum(II) Complexes by Decarboxylation

Abstract

Reaction of PtCl2(en) (en = ethane-1,2-diamine) with thallous pentafluorobenzoate in hot pyridine ( py ) or 4-methylpyridine ( mepy ) yields the [N,N′- bis (2,3,5,6-tetrafluorophenyl)ethane-1,2-diaminato(2-)]platinum(II) complexes, Pt[N(p-HC6F4)CH2]2( py )2 (1a) and Pt[N(p- HC6F4)CH2]2( mepy )2 (1b). The route to (1a) is considered to involve formation of [Pt(en)( py )2](O2CC6F5)2 (2), decarboxylation of (2) into Pt(NHCH2)2( py )2 (1c) and pentafluorobenzene, and nucleophilic attack of (1c) on C6F5H. Complex (1a) has also been prepared by decarboxylation of (2), reaction of PtI2(en) and TlO2CC6F5, and reaction of PtCl2(en), C6F5H, and TlO2CC6F4H-p in boiling pyridine. From reaction of PtCl2(en), TlO2CC6F4H-p, and the appropriate polyfluorobenzene (RF) in boiling pyridine or 4-methylpyridine, the organoamidoplatinum compounds Pt(NRCH2)2L2(R = C6F5, p-MeC6F4, p-ClC6F4, p-BrC6F4, p-IC6F4, 2,3,5-F3C6H2, or p-C6F5C6F4, L = py and R = C6F5, L = mepy ) have been prepared. Analogous reactions of PtCl2( pn )( pn = propane-1,3-diamine) give the complexes Pt[NR(CH2)3NR]( py )2 (R = C6F5 or p-HC6F4). Spectroscopic evidence for the structures is discussed. The polyfluorophenyl groups confer stability to water on ethane-1,2-diaminato(2-)platinum(II) complexes, and this is attributable to delocalization of non-bonded lone pairs from the amido nitrogens into the polyfluorophenyl rings.

Syntheses and structures of N-polyfluorophenyl- and N,N′-bis(polyfluorophenyl)ethane-1,2-diaminato(1- or 2-)platinum(II) complexes

“…The substitution pattern for the fluorocarbon ring in 3a (Scheme 1, A) was evident from the 19 F chemical shifts which were close to those calculated from substituent chemical shifts (SCS) (shielding parameters) for H [29] and N(CH 2 -)Pt- [21], F6 (obs/calc): À123/ À127; F3 À144/À145; F2 À145/À143 ppm. By contrast, calculated values for the 2,3,4-trifluorophenyl substituted isomer differ greatly from those observed.…”

“…An analogous synthesis between [PtCl 2 (H 2 NCH 2 ) 2 ], Tl 2 CO 3 and pentafluorobenzene in 4-ethylpyridine gave [Pt{N(4-HC 6 F 4 )CH 2 } 2 (etpy) 2 ] (4). The first synthesis is noteworthy because previously it has been reported that [PtCl 2 (H 2 NCH 2 ) 2 ], C 6 F 4 H 2 -1,2 and either Tl(O 2 CC 6 F 4 H-p) [21] or Tl 2 CO 3 [25] in boiling pyridine gave dark coloured reaction mixtures, from which identifiable platinum complexes could not be isolated.…”

“…The 1 H NMR spectrum showed features associated with the backbone methylene protons, H4,5 of the polyfluorophenyl group, and the pyridine ligands. Assignment of H4 was based on the coincidence of the chemical shift with that of H4 of [Pt{N(4-HC 6 F 4 )CH 2 } 2 (py) 2 ] (3c) [21], whilst 3 J Pt,H (CH 2 or py) coupling constants of 3a and 3c are similar. The microanalysis sample of 3a analysed as a hydrate and this is supported by observation of a weak n(OH) infrared absorption.…”

“…The structure of (3) (R = 4-HC 6 F 4 ) has been examined since an earlier determination [27] suggested Pt-N(py) distances are shorter than Pt-N(amide) distances contrary to observations in related structures [22,24,25]. To further resolve this issue, the structure of the previously prepared [21,25] (3) (R = 4-BrC 6 F 4 ) has also been determined. Reaction of [PtX 2 (NH 2 CH 2 CH 2 NY 2 )] (X = Cl, Br, I) complexes with Tl 2 CO 3 and a polyfluoroarene provided class (1) and (2) complexes (Eq.…”

“…In addition, we report the synthesis of class (3) complexes (3a, 3b respectively) when 1,2,3,4-tetrafluorobenzene and 2-bromo-1,3,4,5-tetrafluorobenzene are used as the polyfluoroarene reactants and of [Pt(N(4-HC 6 F 4 )CH 2 ) 2 (etpy) 2 ] (4) when 4-ethylpyridine (etpy) is used as the solvent with C 6 F 5 H as the reactant. Previously, no organoamidoplatinum complex could be isolated from use of C 6 F 4 H 2 -1,2 in either reaction (2) [21] or reaction (3) [25]. Replacement of pyridine by etpy in complexes potentially enhances lipid solubility.…”