Electrophilic behaviour of dicarbonylbis(pentamethylcyclopentadienyl)-dirhodium towards diazoalkanes and low-valent platinum compounds : X-ray crystal structure of [ PtRh2(µ-CO)2(CO)(PPh3)(η-C5Me5)2]
Abstract
The diazoalkanes R1R2CN2 react with the dirhodium compound [Rh2(µ-CO)2(η-C5Me5)2] to give the complexes [Rh2(µ-CR1R2)(CO)2(η-C5Me5)2](R1= R2= H or CF3; R1= H, R2= CO2Et; R1= H, R2= CH![[double bond, length as m-dash]](https://www.rsc.org/images/entities/char_e001.gif)
CH2), the i.r. and n.m.r. data for which are reported and discussed. The dirhodiumplatinum compounds [PtRh2(µ-CO)2(cod)(η-C5Me5)2](cod = cyclo-octa-1,5-diene), [PtRh2(µ-CO)2(CO)(PPh3)(η-C5Me5)2], and [PtRh2(µ-CO)2(CO)2(η-C5Me5)2] have been isolated from reactions between low-valent platinum species and [Rh2(µ-CO)2(η-C5Me5)2] or [Rh(CO)2(η-C5Me5)]. Spectroscopic properties are reported which are in accord with molecular structures in which PtL2 fragments are ′ complexed ′ with a [Rh2(µ-CO)2(η-C5Me5)2] molecule giving rise to a PtRh2 triangle semi-triply bridged by two CO ligands. This has been confirmed by an X-ray diffraction study on [PtRh2(µ3-CO)2(CO)(PPh3)(η-C5Me5)2], crystals of which are triclinic, space group P![[1 with combining macron]](https://www.rsc.org/images/entities/char_0031_0304.gif)
, in a unit cell with a= 11.185(3), b= 13.278(7), c= 15.443(9)Å, α= 102.98(5), β= 92.18(4), γ= 105.88(4)°, and Z= 2. The structure was solved to R 0.056 (R′ 0.058) from 4 285 observable independent reflections [I![[gt-or-equal]](https://www.rsc.org/images/entities/char_2a7e.gif)
3.0σ(I)] collected at 220 K in the range 2θ⩽ 50°. The molecule is based on a triangle of metal atoms [Rh–Rh 2.647(2), Pt–Rh 2.618(2) and 2.691(2)Å]. The platinum atom is in a planar environment with respect to the two rhodium atoms and the CO and the PPh3 ligands to which it is terminally bound. The longer Pt–Rh bond is essentially trans to CO. On either face of the metal triangle two other CO ligands bridge the Rh–Rh bond and lean towards the platinum in a semi-triply bridging manner [Pt–µ-CO (mean) 2.52 Å]. Each rhodium is η5-co-ordinated to a C5Me5 group, as expected. The reaction between [Ni(cod)2] and [Rh2(µ-CO)2(η-C5Me5)2] affords the thermally unstable and air sensitive complex [NiRh2(µ-CO)2(cod)(η-C5Me5)2], while the salt [PtRh2(µ-CO)(µ-NO)(cod)(η-C5Me5)2][PF6] has been prepared from [Rh2(µ-CO)(µ-NO)(η-C5Me5)2][PF6] and [Pt(cod)2]. The i.r. and n.m.r. data for these species are discussed.
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