Crystal structure of dicarbonyl[μ2-methylenebis(diphenylphosphane)-κ2 P:P′][μ2-2-(2,4,5-trimethylphenyl)-3-oxoprop-1-ene-1,3-diyl](triphenylphosphane-κP)ironplatinum(Fe—Pt)–dichloromethane–toluene (1/1/2), [(OC)2Fe(μ-dppm)(μ-C(=O)C(2,4,5-C6H2Me3)=CH)Pt(PPh3)]

The title compound, [(OC)2Fe(μ-dppm)(μ-C(=O)C(2,4,5-C6H2Me3)= CH)Pt(PPh3)], represents an example of a diphosphane-bridged heterobimetallic dimetallacyclopentenone complex resulting from a bimetallic activation of 1-ethynyl-2,4,5-trimethylbenzene and a metal-coordinated carbonyl ligand.


Chemical context
The coordination and transformation of alkynes on homobimetallic transition-metal complexes, in which the two metal centres are in close contact via a metal-metal bond, has been investigated intensively (Liddle, 2015). For example, during the course of a Pauson-Khand reaction, an acetylenic triple bond is added across [Co 2 (CO) 8 )], yielding a dimetallatetrahedrane [Co 2 (CO) 6 (-C 2 RR 0 )] (Bennett et al., 1992;Clé ment et al., 2007).

Structural commentary
The molecular structure of the title heterobimetallic complex is depicted in Fig. 2. It crystallized from CH 2 Cl 2 /toluene in the monoclinic crystal system, space group P2 1 /n, together with one molecule of CH 2 Cl 2 and two molecules of toluene. Selected bond lengths and bond angles are given in Table 1.
The Fe-Pt bond is bridged by a dppm ligand, forming a five-membered ring that adopts an envelope conformation, with angle P1-C45-P2 = 108.83 (17) , and the metalphosphorus bonds Pt-P2 and Fe-P1 being 2.2700 (9) and 2.1857 (11) Å , respectively. These structural features are in line with those of other related structures published by our Reaction scheme for the synthesis of the title compound.

Figure 2
The molecular structure of the title complex, with atom labelling. Displacement ellipsoids are drawn at the 30% probability level. For clarity, only H atom H1 has been included, and the solvent molecules have been omitted.  (Mohamed et al., 2019;Fontaine et al., 1988). When the metals are not spanned by a diphosphane ligand, the Fe-Pt bond distance is slightly longer, as in [(OC) with Fe-Pt distances of 2.608 (2) and 2.605 (2) Å , respectively (Yamazaki et al., 2005(Yamazaki et al., , 2006. Both metals are also incorporated in a dimetallacyclopentenone unit resulting from a carbon-carbon coupling reaction between CO and the terminal alkyne giving rise to an iron-acyl group [C12-O1 = 1.207 (4) Å ]. The geometry at Fe1 can be considered as distorted octahedral resulting from -coordination of the C1 C2 bond of the five-membered [FeC( O)CR C(H)Pt] unit [C1-Fe1 = 2.107 (3) and C2-Fe1 = 2.109 (4) Å ]. The C1 C2 bond length compares well with that of [(OC) 2 Fe{-C( O)C(o,p-C 6 H 3 -F 2 ) C(H)}(dppm)Pt(PPh 3 )] [1.386 (4) vs 1.382 (5) Å ; Jourdain et al., 2013]. The formation of the thermodynamic isomer, already evidenced by 1 H NMR spectroscopy, is indicated by the attachment of the aromatic C 6 H 2 Me 3 ring at the C2 atom in the position relative to platinum. The C( O)C(C 6 H 2 Me 3 ) C(H) moiety is -bonded to the platinum atom [C1-Pt1 = 2.023 (3) Å ], which adopts an irregular shape; see Table 1. The 4 descriptor for fourcoordination is 0.39 ( 4 = 0 for a perfect square-planar geometry and = 1 for a perfect tetrahedral geometry; for intermediate structures, including trigonal-pyramidal and seesaw, 4 falls within the range 0 to 1; Yang et al., 2007).

Supramolecular features
In the crystal, molecules are linked by a number of C-HÁ Á ÁO hydrogen bonds, forming layers parallel to the ab plane ( Fig. 3 and Table 2). There are also a number of intra-and inter-  A partial view along the c axis of the crystal packing of the title compound. The C-HÁ Á ÁO hydrogen bonds (Table 2) are shown as dashed lines. For clarity, only the H atoms (grey balls) involved in these interactions have been included. Colour code: the two toluene molecules are red and blue and the dichloromethane molecule is green.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3. All of the hydrogen atoms were placed in geometrically calculated positions (C-H = 0.93-0.98 Å ) and refined as riding on the parent C atom, with U iso (H) = 1.5U eq (C-methyl) and 1.2U eq (C) for other H atoms.

Funding information
We are grateful to the Deutsche Forschungsgemeinschaft (DFG) for financial support. LB thanks the Fonds der Chemischen Industrie (FCI) for doctoral fellowships.