Reaction of Carbon Monoxide with Hydridobis[di(tertiary phosphine)]rhodium(I) Complexes. Synthesis and Structure of the Metal-Metal Bonded Carbonyl-Bridged Dimers [Rh(CO)(diphosphine)]₂(μ-CO)₂

Reaction of the hydridorhodium(I) complexes RhH(P-P)₂ with carbon monoxide leads to formation of the dimeric carbonyl-bridged complexes [Rh(CO)(P-P)]₂(μ-CO)₂ with concomitant elimination of hydrogen, where P-P represents the di(tertiary phosphines): l,2-bis(diphenylphosphino)ethane, l,3-bis(diphenylphosphino)propane, and 2,3-Q-isopropylidene-2,3-dihydroxy-l,4-bis(diphenylphosphino)butane, abbreviated as dppe, dppp, and diop, respectively. The Rh2(dppp)2(CO)4-1/2CReaction of the hydridorhodium(I) complexes RhH(P-P)2 with carbon monoxide leads to formation of the dimeric carbonyl-bridged complexes [Rh(CO)(P-P)]2(μ-CO)2 with concomitant elimination of hydrogen, where P-P represents the di(tertiary phosphines): l,2-bis(diphenylphosphino)ethane, l,3-bis(diphenylphosphino)propane, and 2,3-Q-isopropylidene-2,3-dihydroxy-l,4-bis(diphenylphosphino)butane, abbreviated as dppe, dppp, and diop, respectively. The Rh2(dppp)2(CO)4-1/2C6H6 complex exists as two crystallographically independent binuclear molecules possessing approximate C2 symmetry (triclinic, space group PI, a = 17.222 (3) Å, b = 21.513 (4) Å, c = 15.479 (3) Å; α = 90.929 (11)°, ß = 108.358 (9)°, λ = 86.303 (12)°; Z = 4; R = 0.047 and Rw = 0.056 for 8068 reflections with I > 3σ(I)). The structure is described in terms of two square pyramids (with phosphorus apical) sharing an edge formed by the two bridging carbonyl ligands, the mean angle between basal planes being 82.6°; a formal metal-metal single bond is indicated. Important bond lengths are Rh-Rh = 2.725 (1) and 2.709 (1) Å, Rh-P(basal) = 2.340 (3)-2.399 (3) Å, Rh-P(apical) = 2.316 (3)-2.340 (3) Å, Rh-CO(bridging) = 2.036 (9)-2.067 (10) Å, and Rh-CO(terminal) = 1.920 (11)-1.944 (11) Å. Low-temperature 31P(Hj NMR spectra are consistent with the rigid structure; at room temperature the pairs of phosphorus atoms become chemically equivalent, probably via carbonyl site exchange since the 13C NMR spectrum is a single, broad resonance. Spectroscopic data for all three complexes indicate the same structure in each case. Like the corresponding bis(triphenylphosphine) species, the complexes are active catalysts for hydrogenation, isomerization, and hydroformylation of terminal olefins.₆H₆ complex exists as two crystallographically independent binuclear molecules possessing approximate C2 symmetry (triclinic, space group PI, a = 17.222 (3) Å, b = 21.513 (4) Å, c = 15.479 (3) Å; α = 90.929 (11)°, ß = 108.358 (9)°, λ = 86.303 (12)°; Z = 4; R = 0.047 and Rw = 0.056 for 8068 reflections with I > 3σ(I)). The structure is described in terms of two square pyramids (with phosphorus apical) sharing an edge formed by the two bridging carbonyl ligands, the mean angle between basal planes being 82.6°; a formal metal-metal single bond is indicated. Important bond lengths are Rh-Rh = 2.725 (1) and 2.709 (1) Å, Rh-P(basal) = 2.340 (3)-2.399 (3) Å, Rh-P(apical) = 2.316 (3)-2.340 (3) Å, Rh-CO(bridging) = 2.036 (9)-2.067 (10) Å, and Rh-CO(terminal) = 1.920 (11)-1.944 (11) Å. Low-temperature ³¹P(Hj NMR spectra are consistent with the rigid structure; at room temperature the pairs of phosphorus atoms become chemically equivalent, probably via carbonyl site exchange since the 13C NMR spectrum is a single, broad resonance. Spectroscopic data for all three complexes indicate the same structure in each case. Like the corresponding bis(triphenylphosphine) species, the complexes are active catalysts for hydrogenation, isomerization, and hydroformylation of terminal olefins.