6-MEMBERED CYCLOMETALATED DERIVATIVES OF PLATINUM(II) DERIVED FROM 2-BENZYLPYRIDINES - CRYSTAL-STRUCTURE AND MOLECULAR-STRUCTURE OF [PT(L)(PH(3)P)CL] (HL=2-(1-METHYLBENZYL)PYRIDINE)

The reaction of K-2[PtCl4] with 2-(1-methylbenzyl)pyridine, HL, and 2-benzylpyridine, HL', affords the cyclometallated species [{Pt(L)Cl}(2)] (1) and [{Pt(L')Cl}(2)] (2), respectively. The chloride bridge in complex 1 can be split by neutral or anionic species to give the monomeric, [Pt(L)(Ph(3)P)Cl], as two isomers, trans-P-Pt-C (3) and trans-P-Pt-N, (4), [Pt(L)(py)Cl] (5), [Pt(L)(CO)Cl] (6), [Pt(L)CNCH2SO2C6H4CH3-4)Cl] (7), [Pt(L)(acac)] (Hacac = 2,4-pentanedione) (8), [Pt(L)(dppm)][BF4] (dppm = bis(diphenyl-phosphino)methane) (9), [Pt(L)(dppe)][BF4] (dppe = bis(diphenylphosphino)ethane) (10) and [Pt(L)(dipy)][BF4](dipy = 2,2'-dipyridine) (11). Similarly, compound 2, by reaction with Ph(3)P, affords [Pt(L')(Ph(3)P)Cl], as two isomers, trans-P-Pt-C (12) and trans-P-Pt-N (13). Reaction of compounds 1 or 4 with AgBF4 in acetonitrile affords [Pt(L)CH3CN)(2)][BF4] (14) or [Pt(L)(Ph(3)P)-(CH3CN)][BF4] (15). From these, [Pt(L)Ph(3)P)(2)][BF4] (16), [Pt(L)(Ph(3)P)(CO)][BF4] (17) and [Pt(L)(Ph(3)P)(py)][BF4] (18), can be obtained by displacement of the coordinated acetonitrile. The new complexes were characterized by IR, H-1 and P-31 NMR and FAB-MS spectroscopic techniques. The NMR spectra at room temperature of most of the species derived from HL give evidence far the presence in solution of two diastereomers a and b. The structure of one diastereomer of complex 4 has been solved by single crystal X-ray diffraction, 4b. The platinum atom is in an almost square planar geometry with a P-Pt-N trans arrangement: Pt-N = 2.095(3), Pt-C = 1.998(4), Pt-P = 2.226(1) and Pt-Cl = 2.400(1) Angstrom. The six-membered cyclometallated ring is in a boat conformation, with the CH, group in an equatorial position, ie pointing away from the metal. Attempts to obtain [{Pt(L'')Cl}(2)] (HL'' = 2-(dimethylbenzylpyridine), afforded an insoluble product heavily contaminated by platinum metal; treatment of this crude material with Ph(3)P gave [Pt(L'')(Ph(3)P)Cl] (19).