Synthesis, photophysical properties, and theoretical studies of hydride-alkynyl platinum(II) complexes.: Molecular structures of [trans-PtH(C=CC5H4N-2) (PPh3)2] and [Pt(η2-HC≡CCPh2OH) (PPh3)2]

A series of mononuclear, [trans-PtH(C=CR)(PPh3)(2)] (R = C5H4N-2 (1), (6-C=CH)C5H3N-2 (2), C6H4NH2-4 (3), (4-C=CH)C6H4 (4), (CH2)(5)C=CH (5)), and binuclear, [trans-(PPh3)(2)-HPt{mu-sigma:sigma-(C=C)(2)R}PtH(PPh3)(2)] (R = C5H3N-2 (7), C6H4-1,4(8)), hydride-alkynyl platinum complexes has been prepared in good to moderate yields from the reactions of [trans-PtHCl(PPh3)(2)] with an excess of the corresponding alkyne in the presence of an excess of NEt2H and from the reactions of [trans-PtHCl(PPh3)(2)] with 1 equiv of 2 or 4 in the presence of diethylamine. An analogous reaction with HC=CCPh2OH leads to a mixture of [trans-PtH-(C=CCPh2OH)(PPh3)(2)] (6a) and [Pt(eta (2)-HC=CCPh2OH)(PPh3)(2)] (6b). The binuclear diyne complex [{(PPh3)(2)Pt}(2){mu-eta (2):eta (2)-(C=CH)(2)C6H4-1,4) (9), prepared in high yield from [Pt(eta (2)-C2H4)(PPh3)(2)] and HC=CC6H4-1;4-C=CH (0.5 equiv), is also formed in the reaction leading to 8. Complexes 5, 7, and 8 have been used as precursors to form the mixed-valence Pt(II)-Pt(0) complexes 10-12. The spectroscopic characterization of the complexes and X-ray crystal structure determination of 1 and 6b are included. Their absorption and some selected emission spectra, examined on the basis of theoretical studies (EHMO), are also reported.