Six-membered cyclometallated derivatives of platinum(II) derived from 2-benzylpyridines. Crystal and molecular structure of [Pt(L)(Ph3P)Cl] (HL = 2-(1-methylbenzyl)pyridine)
G. Minghetti, A. Zucca, S. Stoccoro
Nov 15, 1994
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19
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Journal
Journal of Organometallic Chemistry
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Key Takeaway Key Takeaway: Reaction of compounds 1 or 4 with AgBF 4 yields [Pt(L)(Ph3P)Cl] (HL = 2-(1-methylbenzyl)pyridine) and [Pt(L')(Ph3P)Cl] (HL = 2-benzylpyridine)
Abstract
Abstract The reaction of K 2 [PtCl 4 ] 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)(CNCH 2 SO 2 C 6 H 4 CH 3 -4)Cl] ( 7 ), [Pt(L)(acac)] (Hacac = 2,4-pentanedione) ( 8 ), [Pt(L)(dppm)][BF 4 ] (dppm = bis(diphenyl-phosphino)methane) ( 9 ), [Pt(L)(dppe)][BF 4 ] (dppe = bis(diphenylphosphino)ethane) ( 10 ) and [Pt(L)(dipy)][BF 4 ](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 AgBF 4 in acetonitrile affords [Pt(L)(CH 3 CN) 2 I BF 4 ] ( 14 ) or [Pt(L)(Ph 3 P)-(CH 3 CN)][BF 4 ] ( 15 ). From these, [Pt(L)(Ph 3 P) 2 ][BF 4 ] ( 16 ), [Pt(L)(Ph 3 P)(CO)][BF 4 ] ( 17 ) and [Pt(L)(Ph 3 P)(py)][BF 4 ] ( 18 ), can be obtained by displacement of the coordinated acetonitrile. The new complexes were characterized by IR , 1 H and 31 P NMR and FAB-MS spectroscopic techniques. The NMR spectra at room temperature of most of the species derived from HL give evidence for 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) A. The six-membered cyclometallated ring is in a boat conformation, with the CH 3 group in an equatorial position, i.e pointing away from the metal. Attempts to obtain [{Pt(L″)Cl} 2 ] (HL″ = 2-(dimethylbenzyl)pyridine), 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 ).