Organic chemistry of dinuclear metal centres. Part 7. Ylides in the synthesis of organodiruthenium complexes: X-ray crystal structure of [Ru2(CO)2(µ-CO)(µ-CH2)(η-C5H5)2]
Abstract
Heating [Ru2(CO)(µ-CO){µ-C(O)C2Ph2}(η-C5H5)2] with an ylide Ph3P![[double bond, length as m-dash]](https://www.rsc.org/images/entities/char_e001.gif)
CHR in toluene at reflux rapidly yields µ-alkylidene complexes [Ru2(CO)2(µ-CO)(µ-CHR)(η-C5H5)2](R = H, 70%; Me, 35%; Et, 28%; or Ph, 57%). A similar reaction with Ph3PCHCHCH2 gives only a 13% yield of the analogous product [Ru2(CO)2(µ-CO)(µ-CHCHCH2)(η-C5H5)2], the major product (33%) being the isomeric substituted allyl complex [Ru(CO){η3-C3H4[Ru(CO)2(η-C5H5)]-1}(η-C5H5)]. Upon u.v. irradiation the latter undergoes rearrangement, with Ru–Ru bond formation, to give the former, believed to proceed via a 16-electron σ-allyl species. Further u.v. irradiation of [Ru2(CO)2(µ-CO)(µ-CHCHCH2)(η-C5H5)2] releases a CO ligand and brings the alkylidene vinyl substituent into co-ordination, forming [Ru2(CO)(µ-CO)(µ-CHCHCH2)(η-C5H5)2] in high yield. The two metal atoms in the complex [Ru(CO){η3-C3H4[Ru(CO)2(η-C5H5)]-1]}(η-C5H5)] are also brought into bonding with one another when the allyl is protonated, yielding the methylvinyl cation [Ru2(CO)2(µ-CO)(µ-CHCHMe)(η-C5H5)2]+. Treatment of the cation with NaBH4 results in hydride addition to the β-carbon of the vinyl, producing [Ru2(CO)2(µ-CO)(µ-CHEt)(η-C5H5)2] in good yield. The µ-CH2 complex [Ru2(CO)2(µ-CO)(µ-CH2)(η-C5H5)2] is not formed when [Ru2(CO)(µ-CO){µ-C(O)C2Ph2}(η-C5H5)2] and CH2N2 are heated together, but thermally more robust diazoalkanes, CH(CO2Et)N2 and Ph2CN2, afford [Ru2(CO)2(µ-CO){µ-CH(CO2Et)}(η-C5H5)2] and [Ru2(CO)2(µ-CO)(µ-CPh2)(η-C5H5)2] respectively. The latter suffers from steric crowding and readily ejects a CO to give [Ru2(CO)(µ-CO)(µ-CPh2)(η-C5H5)2], in which a double bond of one phenyl ring is co-ordinated to ruthenium. Under CO pressure this transformation is reversed. The complex [Ru2(CO)2(µ-CO)(µ-SO2)(η-C5H5)2] is formed in high yield when SO2 is bubbled through a boiling toluene solution of [Ru2(CO)(µ-CO){µ-C(O)C2Ph2(η-C5H5)2]. Crystals of [Ru2CO)2(µ-CO)(µ-CH2(η-C5H5)2] are triclinic, space group P![[1 with combining macron]](https://www.rsc.org/images/entities/char_0031_0304.gif)
, with Z= 2 in a unit cell for which a= 6.771(2), b= 9.315(2), c= 11.864(5)Å, α= 103.12(3), β= 100.61(3), and γ= 103.40(2)°. The structure has been solved by heavy-atom methods and refined to R0.0365 (R′ 0.0359) for 2 725 independent intensities. The two Ru(CO)(η-C5H5) moieties are held together by a single Ru–Ru bond [2.707(1)Å] which is symmetrically bridged by CO and CH2 groups. The interplanar angle between the two bridge systems is 161° with the convex side facing the terminal (cis) carbonyl groups. The molecule has idealised Cs(m) symmetry.
Please wait while we load your content...
