Crystal structure of acetopyruvato-κ2O,O'-dicarbonylrhodium(I), C8H7O6Rh

Abstract

Source of materialRhCl 3 ×3H 2 O(0.011 g, 0.043 mmol) was refluxed in 2mlofDMF until the red colour was observed to turn ab rilliant yellow (approx. 30 min). The solution was then cooled in an ice-bath before adding acetopyruvate (0.00738 g, 0.0512 mmol) to the reaction mixture. The yellow product was precipitated by the addition of ice-waterand wasthencollected bycentrifugation. Experimental detailsThemethylHatomswere placed in geometricallyidealized positionsand constrainedtorideontheir parent atoms,with C-H = 0.95 Åa nd U iso (H) =1 .5U eq (C). Theh ighest residual electron density waslocated 0.74 ÅfromRh1 andthe deepest hole was 0.85 Åfrom Rh1. DiscussionRhodium is one of the most studied transition metals due to its importance in various applications including catalysis and biological activity [1,2]. Our interest in rhodium chemistry forms part of an over-arching investigation into steric manipulation of various transition metal complexes for application in catalysis, radiopharmaceutical and separation technology [3][4][5][6][7][8][9][10].The title complex displays atypical square planar geometry with the rhodium centre surrounded by two carbonyl and a b-diketonato ligand. No significant distortion of the geometry is observed with the rhodium centre situated amere 0.046 Åabove the basal plane. There exists oxygen-oxygen contacts determined as 2.978(1) Åb etween the carbonyl groups of neighbouring molecules in aheadto-head configuration. Metallophilic interaction was observed between the rhodium centres of the molecules in the solid state. Metallophilicity hasbeendefined as theinteraction betweenelectron densitiesoflarge metal centres with an associated energy in thesameorderashydrogen-bonding [11].These metallophilic interactions often lead to the construction of 1-D metal chains and have been widely recognized for other square-planar Rh(I) molecules [12]. Therhodium complex reported here showed stacking in such away that the rhodium atomsofneighbouring complexes interact almost perpendicular to the coordination polyhedron, with Rh×××Rh distances of 3.124(2) Å. These values are slighly shorter than the Rh×××Rh distances reported for [Rh(acac)(CO) 2 ] (3.253a nd 3.271 Å) [13]. For the benzoyl-1,1,1-trifluoroacetonatodicarbonylrhodium(I) complex these distances were reported as 3.537 Å [14].Neighboring complexes arrange in ahead to tail mode with areported angle of 94.52°between the polyhedra of the rhodium centres. These interactions are the dominant force governing the packing of the molecules within the crystal structure. In contrast with previous structures the metallophillic interactions are only observed between two neighbouring rhodium centres and does not extend to form ainfinite chain as reported for similar complexes [10,13].

Rhodium-rhodium interactions in [Rh(β-diketonato)(CO)2] complexes

“…This holds true, except in cases where secondary interactions are found to disrupt this arrangement [40]. [34,41,42,43]. [46], and gas phase optimizations of related rhodium-βdiketonato complexes [34,35,47].…”