Synthesis, Characterization, and Comparative Properties of [PPN]₂[Re₆C(CO)₁₈Mo(CO)₄] and [PPN]₂[Re₆C(CO)₁₈Ru(CO)₃]

Abstract

The reaction of [PPN](2)[Re(6)C(CO)(19)] with Mo(CO)(6) and Ru(3)(CO)(12) under sunlamp irradiation provided the new mixed-metal clusters [PPN](2)[Re(6)C(CO)(18)Mo(CO)(4)] and [PPN](2)[Re(6)C(CO)(18)Ru(CO)(3)], which were isolated in yields of 85% and 61%, respectively. The compound [PPN](2)[Re(6)C(CO)(18)Mo(CO)(4)] crystallizes in the monoclinic space group P2(1)/c with a = 20.190 (7) Å, b = 16.489 (7) Å, c = 27.778 (7) Å, beta = 101.48 (2) degrees, and Z = 4 (at T = -75 degrees C). The cluster anion is composed of a Re(6)C octahedral core with a face capped by a Mo(CO)(4) fragment. There are three terminal carbonyl ligands coordinated to each rhenium atom. The four carbonyl ligands on the molybdenum center are essentially terminal, with one pair of carbonyl ligands (C72-O72 and C74-O74) subtending a relatively large angle at molybdenum (C72-Mo-C74 = 147.2(9) degrees ), whereas the remaining pair of carbonyl ligands (C71-O71 and C73-O73) subtend a much smaller angle (C71-Mo-C73 = 100.5(9) degrees ). The (13)C NMR spectrum of (13)CO-enriched [PPN](2)[Re(6)C(CO)(18)Mo(CO)(4)] shows signals for four sets of carbonyl ligands at -40 degrees C, consistent with the solid state structure, but the carbonyl ligands undergo complete scrambling at ambient temperature. The (13)C NMR spectrum of (13)CO-enriched [PPN](2)[Re(6)C(CO)(18)Ru(CO)(3)] at 20 degrees C is consistent with the expected structure of an octahedral Re(6)C(CO)(18) core capped by a Ru(CO)(3) fragment. The visible spectrum of [PPN](2)[Re(6)C(CO)(18)Mo(CO)(4)] shows a broad, strong band at 670 nm (epsilon = 8100), whereas all of the absorptions of [PPN](2)[Re(6)C(CO)(18)Ru(CO)(3)] are at higher energy. An irreversible oxidation wave with E(p) at 0.34 V is observed for [PPN](2)[Re(6)C(CO)(18)Mo(CO)(4)], whereas two quasi-reversible oxidation waves with E(1/2) values of 0.21 and 0.61 V (vs Ag/AgCl) are observed for [PPN](2)[Re(6)C(CO)(18)Ru(CO)(3)]. The molybdenum cap in [Re(6)C(CO)(18)Mo(CO(4))](2-) is cleaved by heating in donor solvents, and by treatment with H(2), to give largely [H(2)Re(6)C(CO)(18)](2-). In contrast, [Re(6)C(CO)(18)Ru(CO)(3)](2-) shows no tendency to react under similar conditions.

The Redox Chemistry of [Co6C(CO)15]2–: A Synthetic Route to New Co-Carbide Carbonyl Clusters

“…A μ 3 -capped octahedron should possess 98 CVE, , as found in several M 7 C carbide clusters. − In this respect, [Co 7 C(CO) 15 ] 3– (100 CVE) is electron-rich, and the current electron-counting rules predict for it a capped trigonal prismatic structure, as found in [M 7 N(CO) 15 ] 2– (M = Co, Rh), [Ni 4 Os 3 C(CO) 15 ] 2– , and [Ni 7 C(CO) 12 ] 2– . Nonetheless, [Co 7 C(CO) 15 ] 3– adopts a capped octahedral structure, and to accommodate the two extra electrons, some Co–Co bonds are elongated, causing distortions in the metal polyhedron, as noticed above.…”

Hydride and Gold(triphenylphosphine) Derivatives of Hexarhenium Carbido Octadecacarbonyl

“…A variety of interesting cluster compounds results formally from the interaction of the octahedral [Re 6 (μ 6 -C)(CO) 18 ] 4- cluster core with one or more electrophilic moieties. − The set for one added electrophile (X + = H + , Re(CO) 3 + , M(CO) n 2+ , Re(CO) 3 L 3+ ) includes the clusters [HRe 6 C(CO) 18 ] 3- , [Re 7 C(CO) 21 ] 3- , [Re 6 C(CO) 18 M(CO) n ] 2- (M = Ru, n = 3; M = Mo, n = 4), and [Re 7 C(CO) 21 P(OPh) 3 ] 1- [HRe 7 C(CO) 21 ] 2- , , [Re 8 C(CO) 24 ] 2- , and [Re 7 C(CO) 21 ML n ] 2- (M = Rh, , Ir, 9,11 Pd, 9,12 Pt, Cu, Ag, Au, 6,13 Hg, Tl 15 ), and the only previously reported example of three added electrophiles (X + , Y + , Z + = H + , H + , Re(CO) 3 + ) is [H 2 Re 7 C(CO) 21 ] 1- …”

Synthesis of a Heptanuclear Rhenium−Iridium Carbido Carbonyl Cluster and of (Triphenylphosphine)gold(I) Derivatives

“…[1][2][3] For the systematic buildup of clusters, capping of triangular faces of anionic clusters by cationic or neutral mononuclear species has been widely used to form mixed-metal clusters having one or two more metal atoms than the original compounds. 4, 5 On the other hand, reactions of metal clusters with carbon monoxide, phosphines, or nitrogen-containing ligands frequently results in the removal of one metal vertex from a higher-nuclearity cluster compound. 6,7 As part of our continuing study of the synthesis 8 and reactivity 9 of a set of octanuclear mixed-metal clusters with the general formula [Re 7 (µ 6 -C)(CO) 21 ML n ] 2-, we observed that framework rearrangement of 1,4-bicapped [Re 7 (µ 6 -C)(CO) 21 Ir-(CO) 2 ] 2-generated [Re 5 Ir(µ 6 -C)(CO) 17 (µ 3 -Re(CO) 3 ) 2 ] 2-, a unique 1,3-bicapped isomer.…”

“…An important issue in studies of higher-nuclearity transition metal clusters is the controlled manipulation of nuclearity in cluster synthesis. − For the systematic buildup of clusters, capping of triangular faces of anionic clusters by cationic or neutral mononuclear species has been widely used to form mixed-metal clusters having one or two more metal atoms than the original compounds. , On the other hand, reactions of metal clusters with carbon monoxide, phosphines, or nitrogen-containing ligands frequently results in the removal of one metal vertex from a higher-nuclearity cluster compound. , …”