Versatile NS nickel-dithiolates as mono- and bridging bidentate, S-donor ligands to gold()

Development of square planar cis -dithiolate nickel complexes as metallo S-donor ligands focuses on the synthesis and structures of gold( i ) heterometallic clusters derived from assemblage with three NiN 2 S 2 complexes: Ni(bme-daco), Ni(bme-dach) and Ni(ema) 2− (bme-daco = (bismercaptoethanediazacyclooctane); bme-dach = bismercaptoethanediazacycloheptane; and ema = N , N ′-ethylenebis-2-mercaptoacetamide). With Ph 3 PAuCl as the gold source, examples of simple S-aurolation retaining the PPh 3 on Au + were obtained for [{Ni(bme-daco)}AuPPh 3 ] + Cl − and [{Ni(ema)} 2 Au 4 (PPh 3 ) 4 ], where the latter complex demonstrated unsupported aurophilic interactions between [{Ni(ema)}Au 2 (PPh 3 ) 2 ] units in its X-ray crystal structure (Au-Au = 3.054 and 3.127 Å). Three compounds containing fully-supported digold units with Au-Au distances in the aurophilic range of 3.11 to 3.13 Å were found as stair-step structures in which planar NiN 2 S 2 step treads are connected by planar S 2 Au 2 S 2 risers at ca. 90°: [{Ni(bme-daco)} 2 Au 2 ] 2+ (Cl − ) 2 ; [{Ni(bme-dach)} 2 Au 2 ] 2+ (Cl − ) 2 ; and (Et 4 N + ) 2 [{Ni(ema)} 2 Au 2 ] 2− . Electrochemical data from cyclic voltammograms demonstrated a positive shift in Ni II/I couples for the [{NiN 2 S 2 } x Au y ] complexes as compared to the NiN 2 S 2 precursors and a ca. 700 mV decrease in communication between multiple NiN 2 S 2 units as compared to [{NiN 2 S 2 } 2 Ni] 2+ analogues in slant chair conformation. The analogy between NiN 2 S 2 metallodithiolate ligands and diphosphine ligands holds here as in other examples of inorganic and organometallic complexes. The NiN 2 S 2 metallodithiolate ligands, Ni(bme-daco), Ni(bme-dach), and [Ni(ema)] 2- are shown as bidentate ligands to [Au 2 ] 2+ in "stair-step" configurations.