Alkyne or alkene binding versus hydrogenation in reactions with [Ir 2H(CO) 2 (μ-H) 2(Ph 2PCH 2PPh 2) 2] [BF 4]. Structure of [Ir 2(C 2H 4) (CO) 2(μ-H) (Ph 2PCH 2PPh 2) 2] [BF 4]

• Published in: Inorganica Chimica Acta 1997-06, Vol.259 (1), p.213-226
• Main Authors: Antwi-Nsiah, Fred H., Torkelson, Jeff R., Cowie, Martin
• Format: Article
• Language: English
• Subjects: Alkene complexes; Alkyne complexes; Crystal structures; Hydrido-bridged complexes; Hydrogenation; Iridium complexes
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/S0020-1693(97)05464-9

The reactions of [lr 2H(CO) 2(μ-H) 2(dppm) 2] [BF 4] (1) (dppm=Ph 2PCH 2PPh 2) with the alkynes, dimethyl acetyleredicarboxylate, hexafluoro-2-butyne or acetylene yield the respective products [Ir 2(H) 2(CO) 2(μ-H) (μ-RCCR) (dppm) 2] [BF 4] (R-CO 2Me, CF 3, H) in which the alkyne bridges the metals, bound in a parallel orientation. With tetrafluoroethylere the analogous olefin-bridged product [Ir 2(H) 2(CO) 2(μ-H) (μ-C 2.F 4) (dppm) 2] [BF 4] is obtained. The reactions of 1 with diphenylacetylene or ethylene result in hydrogenation, to yield cis-stilbene and ethane, respectively, with subsequent reaction of the resulting unsaturated intermediate with additional substrate to give [Ir 2(CO) 2(μ-H) (μ-PhCCPh) (dppm) 2] [BF 4] or [Ir 2(C 2H 4) (CO) 2(μ-H) (dppm) 2] [BF 4]. In the diphenylacetylene adduct this group is bound in a parallel position bridging the metals whereas the ethylene ligand binds to one metal in a terminal position opposite the Ir-Ir bond. The structure of this ethylene adduct has been determined by X-ray crystallography. This compound crystallizes in the monoclinic space group P2 1/ n, having a=13.6872(7), b=15.459(2), c=23.813(2) Å, β=97.870(5)° and Z=4. The carbonyl and ethylene ligands are disordered, but their positions have been adequately resolved and the structure has refined (on F 2) to R 1, ( F o ) =0.0344 (observed data) for 8699 unique reflections (6638 observations) and 653 parameters varied.