Lithioalkynyl iron(II) or ruthenium(II) complexes as precursors of novel alkynyl and vinylidene derivatives: heterobimetallic complexes containing a bridging ethynediyl system

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Abstract
Deprotonation of ethynyl complexes [Fe(CCH)(η5-C5H5)(dppm)]1a(dppm = Ph2PCH2PPh2) and [Ru(CCH)(η5-C9H7)L2][L2= 2PPh31b, Ph2PCH2CH2PPh2(dppe)1c or (PMe3)(PPh3)1d] with LiBut at –78 °C gave the lithiated complexes [Fe(CCLi)(η5-C5H5)(dppm)]2a and [Ru(CCLi)(η5-C9H7)L2]2b–2d, respectively. These species have been used in situ as precursors of novel alkynyl and vinylidene complexes by reactions with electrophiles. Treatment of complexes 2a–2d with MeOSO2CF3 at –78 °C gave vinylidene complexes [Fe(CCMe2)(η5C5H5)(dppm)][CF3SO3]3a and [Ru(CCMe2)(η5-C9H7)L2][CF3SO3][L2= 2PPh33b, dppe 3c or (PPh3)(PMe3)3d]. Iodoalkynyl complexes [Ru(CCl)(η5-C9H7)L2](L2= 2PPh34b or dppe 4c) have been obtained by reaction of [I(py)2][BF4](py = pyridine) with 2b and 2c, respectively. Reaction of 2a–2d with SnPh3Cl yielded the ethynediyl bridging bimetallic complexes [(η5-C5H5)(dppm)Fe–CC–SnPh3]5a and [(η5-C9H7)L2Ru–CC–SnPh3][L2= 2PPh35b, dppe 5c or (PPh3)(PMe3)5d]. Similar heterobimetallic complexes [(η5-C5H5)(dppm)Fe–CC–Au(PPh3)]6a and [(η5-C9H7)L2Ru–CC–Au(PPh3)]6b–6d have been obtained by treatment of ethynyl complexes 1a–1d with [AuCl(PPh3)] and TI(acac)(acac = acetylacetonate) in dichloromethane. Complexes 6a and 6b can alternatively be obtained by reaction of 5a and with 5b with [AuCl(PPh3)] in the presence of [PdCl2(MeCN)2]. The crystal structure of 5a has been determined by X-ray diffraction methods. It shows a typical three-legged piano-stool geometry. The iron atom is bonded to the cyclopentadienyl ring, the two phosphorus atoms of a chelating dppm ligand, with a narrow bite angle [74.90(5)°] and the terminal carbon of the triphenyltin acetylide group. The ethynyl bridge is bound to the iron and tin forming an CC–Sn angle of 162.8(4)° and an almost linear Fe–CC arrangement [178.0(3)°].

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