Supramolecular Organoplatinum(IV) Chemistry: Sequential Introduction of Amide Hydrogen Bonding Groups

Abstract

The self-assembly of organoplatinum(IV) complexes to give supramolecular polymers and network materials is described, using the ligand ethyl 5 0 -[(ethoxycarbonyl)amino]-2,2 0 -bipyridine-5-carboxylate (1), which contains the EtOC(dO)NH-hydrogen bonding donor group. Ligand 1 reacts with [Pt 2 Me 4 (μ-SMe 2 ) 2 ] to give [PtMe 2 (1)] (2), which forms a supramolecular polymer in the solid state through formation of intermolecular NH 3 3 3 OdC hydrogen bonds with further selfassembly to a sheet structure through π-stacking. Oxidative addition of bromomethyl compounds RCH 2 Br to complex 2 gave the corresponding organoplatinum(IV) complexes [PtBrMe 2 (CH 2 R)(1)], in which the group R could contain a further hydrogen bonding carboxamide group, and the organoplatinum(IV) complexes with two hydrogen-bond donor groups could form either supramolecular polymers or sheet structures through hydrogen bonding. As well as the anticipated NH 3 3 3 OdC hydrogen bonds, some complexes formed hydrogen bonds to solvent molecules NH 3 3 3 O (solvent) or to coordinated bromide NH 3 3 3 BrPt or a combination of π-stacking with CH 3 3 3 Br hydrogen bonding. New forms of self-assembly in organometallic compounds were identified, one involving polymerization through intermolecular NH 3 3 3 Br 3 3 3 HN supramolecular chelation and one involving a combination of NH 3 3 3 OdC and CH 3 3 3 Br hydrogen bonding along with π-stacking to form a network composed of multiply intercalated sheets.

(OC-6-35)-(2,2′-Bipyridine-κ2N,N′)dimethyl(3-sulfidopropionato-κ2S,O)platinum(IV)

“…2). The mean interplanar spacing between the bipyridine rings comprising the dimer unit is 3.36 Å, which is consistent with observed values of about 3.3 Å for platinum(IV) complexes of 2,2′-bipyridine (Au et al, 2009). The ring centroid(N3-pyridyl)•••ring centroid(N4-pyridyl) A distance = 3.611 (2) Å for A = -x, -y, 1-z.…”

“…For normal ranges of bond angles at platinum(IV) between cis ligands, see: Achar et al (1993); Aye et al (1988). For interplanar spacing between bipyridine rings in platinum(IV) complexes of 2,2 0 -bipyridine, see: Au et al (2009). For the preparation of dimethyl(2,2 0 -bipyridine)platinum(II), see: Monaghan & Puddephatt (1984).…”

Low-Dimensional Architectures in Isomeric cis-PtCl2{Ph2PCH2N(Ar)CH2PPh2} Complexes Using Regioselective-N(Aryl)-Group Manipulation

“…In continuation of these studies, we report here our work on the regioselective positioning of amide/hydroxy and methyl groups within a series of aminomethylphosphines, both as the free ligands and when coordinated to a square-planar Pt(II) metal centre. Our rationale for introducing an -C(O)NH-group is based on the known use of this functionality in supramolecular chemistry [23] and, furthermore, the recent interest in amide-modified phosphines for their variable coordination chemistry [24][25][26], binding nitroaromatics [27], and relevance to catalysis based on Pd [28]. Our choice of metal fragment in this work, "cis-PtCl2", is based on its capability to support a relatively small bite angle diphosphine ligand in a cis, six-membered ring conformation, and to provide up to two "acceptor" sites for potential H-bonding [29].…”

Self-Assembly of Chiral Organoplatinum(IV) Complexes with Both Carboxylic Acid and Amide Groups

“…Ligand substitution at platinum(II) or platinum(IV) is slower than in analogous palladium complexes, and this has limited the use of platinum compounds in self-assembly through dynamic coordination chemistry . However, the relative inertness of organoplatinum complexes can be an advantage in self-assembly by way of secondary bonding interactions, such as hydrogen bonding, and there have been impressive advances in the synthesis of complex organometallic structures using alkylplatinum complexes as building block molecules. − For example, a binuclear organoplatinum(II) complex cation [OC{4-C 6 H 4 Pt(PPh 3 ) 2 {3-C 5 H 4 NC(O)NH 2 )} 2 ] 2+ ( A , Chart ) forms a supramolecular polymer through hydrogen bonding between amide groups, while the diplatinum(IV) complex cation [{PtMe 2 (4-CH 2 C 6 H 4 CO 2 H)(bu 2 bipy)} 2 {μ-4-C 5 H 4 NCH 2 NHC(O)C(O)NHCH 2 -4-C 5 H 4 N}] 2+ ( B , Chart , NN=bu 2 bipy=4,4′-di- tert -butyl-2,2′-bipyridine) forms a double-stranded polymer through hydrogen bonding between both carboxylic acid and amide groups…”

“…Much of the known supramolecular organoplatinum(IV) chemistry has been based on the oxidative addition of functional alkyl bromide derivatives, RCH 2 Br, to the electron-rich platinum(II) complex [PtMe 2 (bu 2 bipy)] to give [PtBrMe 2 (CH 2 R)(bu 2 bipy)] . This reaction tolerates functional groups such as carboxylic acids or amides, but if only one such group is present, only supramolecular dimers can be formed.…”