Sandwich and half-sandwich metal complexes derived from cross-conjugated 3-methylene-penta-1, 4-diynes. Issue 17 (5th January 2017)

• Record Type: Journal Article
• Authors: Vincent, Kevin B.; Gluyas, Josef B. G.; Zeng, Qiang; Yufit, Dmitry S.; Howard, Judith A. K.; Hartl, František; Low, Paul J.
• Is Part Of: Dalton transactions. Volume 46:Issue 17(2017)
• Page Start: 5522
• Page End: 5531
• Publication Date: 2017-01-05
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c6dt04470k
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : Mono-, di- and trimetallic derivatives of the cross-conjugated 3-methylene-penta-1, 4-diyne moiety have been prepared, and studied by (spectro)electrochemical methods. Abstract : The cross-conjugated ethynyl–vinylidene [Ph2 CC(CCH){C(H)CRu(PPh3 )2 Cp}]PF6 ([4a ]PF6 ), and [FcC(H)C(CCH){C(H)CRu(PPh3 )2 Cp}]PF6 ([4b ]PF6 ), and ethynyl–alkynyl Ph2 CC(CCH){CCRu(PPh3 )2 Cp} (5a ), and FcC(H)C(CCH){CCRu(PPh3 )2 Cp} (5b ) compounds (Cp = η 5 -cyclopentadienyl) have been prepared from reactions of the known 3-methylene-penta-1, 4-diynes Ph2 CC(CCH)2 (3a ) and [FcCHC(CCH)2 ] (3b ) with [RuCl(PPh3 )2 Cp]. The compounds derived from3b incorporating the more electron-rich alkene proved to be unstable during work-up, and attempts to prepare bis(ruthenium) complexes from3a and3b or from transmetallation reactions of the bis(alkynylgold) complex FcCHC(CCAuPPh3 )2 (7 ) with RuCl(PPh3 )2 Cp were unsuccessful. The related bis- and tris(ferrocenyl) derivatives Ph2 CC(CCFc)2 (6a ) and FcCHC(CCFc)2 (6b ) were more readily obtained from Pd(ii )/Cu(i ) catalysed cross-coupling reactions of FcCCH with the 1, 1-dibromo vinyl complexes PhCCBr2 (1a ) and FcC(H)CBr2 (1b ). Cyclic voltammetry of6a and6b using n -Bu4 N[PF6 ] as the supporting electrolyte shows broad, overlapping waves arising from the sequential oxidation of the ferrocenyl moieties in electronically and chemically similar environments. Electrostatic effects between the ferrocenyl moieties are enhanced in solutions of the weakly ion-pairing electrolyte n -Bu4 N[B{C6 H3 (CF3 )2 -3, 5}4 ], leading to better resolution of the individual electrochemical processes. The comparative IR spectroelectrochemical response of6a and6b suggest the vinyl ferrocene moiety in6b undergoes oxidation before the ethynyl ferrocene fragments. There is no evidence of electronic coupling between the metallocene moieties and [6a ] +, [6b ] n + ( n = 1, 2) are best described as Class I mixed-valence compounds.