Syntheses, Structure, and Molecular Cubic Hyperpolarizabilities of Systematically Varied Ethynylgold(I) Complexes

The reactions of Q[Au(acac)2] (Q = N(PPh3)2 (PPN; a), NPr4 (b); acac = acetylacetonato)
with terminal alkynes of the type HC⋮CC6H4R-4 in a 1:2 molar ratio affords the complexes
Q[Au(C⋮CC6H4R-4)2] (R = NO2 (1), C6H4NO2-4 (2), (E)-CHCHC6H4NO2-4 (3)). The same
alkynes react with [AuCl(CNBut)] in NEt3 to give the complexes [Au(C⋮CC6H4R-4)(CNBut)]
(R = NO2 (4), C6H4NO2-4 (5), (E)-CHCHC6H4NO2-4 (6)). When NHEt2 is used instead of
NEt3, attack of the secondary amine at the isonitrile ligand takes place and alkynyl carbene
complexes of the type [Au(C⋮CC6H4R-4){C(NHBut)(NEt2)}] (R = NO2 (7), C6H4NO2-4 (8),
(E)-CHCHC6H4NO2-4 (9)) are obtained. The crystal structures of 1a, 4, 7, and 9 have been
determined. The cubic hyperpolarizabilities of 1a,b, 4−6, 8, 9, and the related complexes
[Au(C⋮CC6H4R-4)(PPh3)] (R = H (10), NO2 (11), 4-C6H4NO2 (12), (E)-CHCHC6H4NO2-4
(13), C⋮CC6H4NO2-4 (14), (Z)-CHCHC6H4NO2-4 (15), (E)-NCHC6H4NO2-4 (16)) have been
determined by Z-scans at 800 nm. An increase in γreal is observed on replacing the coligand
ButNC by PPh3 (proceeding from 5 to 12 and from 6 to 13), introduction of the NO2 group
(proceeding from 10 to 11), extending the arylalkynyl π-bridge (proceeding from 11 to 12−15), and replacing (Z)-CHCH by the (E)-CHCH linking unit (proceeding from 15 to 13).