Michal Sabat

A new approach to measuring absolute metal-ligand bond disruption enthalpies in organometallic compounds. The [(CH3)3SiC5H4]3 U-system

Absolute uranium—ligand bond disruption enthalpies in the series Cp3UR(Cp = η5-Me3SiC5H4) have been measured by halogenolytic isoperibol titration calorimetry of Cp3U/Cp3UI/Cp3UR ensembles. Derived D(Cp3UR) values in toluene solution are (kcal mol−1, R): 62.4(0.4), I; 28.9(1.7), n-Bu; 25.6(3.1), Bz; 39.3(2.3), CH2SiMe3; 44.8(1.1), Me; 48.5(2.2), vinyl; 86.7, CCPh. D(Cp3U ← L) values (kcal mol−1, 95% confidence limits) in toluene solution were also determined for L = CO [10.3(0.2)] and THF [9.8(0.2)]. The magnitudes of the D(UR) values appear to reflect a combination of steric and electronic factors, and suggest that D(UI) is less sensitive to ancillary ligation (more transferable) then D(U-alkoxide). The complex Cp3U(vinyl) crystallizes in the triclinic space group P with two molecules in a unit cell of dimensions a = 11.298(1), b = 13.997(2), c = 9.460(2) A, and α = 97.00(1), β = 105.98(1) and γ = 96.94(1)°. Least-squares refinement led to a value for the conventional R index (on F) of 0.0196 for 4373 reflections having 2θMo-Kα 3σ(I). The molecule possesses a conventional pseudotetrahedral Cp3MX geometry with UC(ring) = 2.759(4) A (average), UC(α, vinyl) = 2.436(4) A, < UC(α, vinyl)C(β, vinyl) = 137.7(3)°, < CgUCg = 116.4, 117.2, 120.0 and < CgUC(α, vinyl) = 95.1, 100.0, 100.1°. All hydrogen atoms were located and UH(Cα, vinyl) = 2.93(4) A. The metrical parameters evidence severe non-bonded repulsions between the vinyl ligand and the Cp ligands, as well as between different Cp ligands. The quantity D(MI)—D(MCH3) is proposed as a gauge of metal—ligand bonding.

The ketenylidene route to mixed-metal carbide clusters: [MnRu3C(CO)13]−, [MnOs3C(CO)13]−, [Cr2Ru3C(CO)16]2−, [Mo2Ru3C(CO)16]2−, [Rh3Ru3C(CO)15]−, [Ni3Ru3C(CO)13]2− and [Co3Ru3C(CO)15]−

Abstract Redox-condensation reactions between the ketenylidene clusters [M 3 (CO) 9 CCO] 2− (M = Ru, Os) and electrophilic transition-metal reagents provide a convenient route to the new carbido clusters [PPN][MnRu 3 C(CO) 13 ], [PPN][MnOs 3 C(CO) 13 ], [PPN] 2 [Cr 2 Ru 3 C(CO) 16 ], [PPN] 2 [Mo 2 Ru 3 C(CO) 16 ], [PPN][Rh 3 Ru 3 C(CO) 15 ], [PPN] 2 [Ni 3 Ru 3 C(CO) 13 ], and [PPN][Co 3 Ru 3 C(CO) 15 ]. These clusters have been characterized by elemental analysis, IR and variable-temperature 13 C NMR spectroscopy, and, in the case of [PPN][MnOs 3 C(CO) 13 ] and [PPN] 2 [Ni 3 Ru 3 C(CO) 13 ] by single-crystal X-ray diffraction studies. The [MnOs 3 C(CO) 13 ] − cluster consists of a butterfly array of metal atoms with the manganese occupying a hinge position. The structure of the [Ni 3 Ru 3 C(CO) 13 ] 2− is a distorted (opened) octahedron of metal atoms, with the three ruthenium atoms forming one closed face of the octahedron, and the carbide ligand occupying an interstitial site. 13 C NMR data indicate the octahedron closes in solution. For [PPN][MnRu 3 C(CO) 13 ] and [PPN][MnOs 3 C(CO) 13 ], the carbide ligands show variable temperature NMR behavior, which is best interpreted in terms of a two-bond spin-spin coupling of the carbide to the two endo carbonyls on the wingtip Ru or Os atoms. A similar two-bond coupling process may possibly also be operating in the [Cr 2 Ru 3 C(CO) 16 ] 2− cluster.

Isolation of [Cp(CO)(Ph3P)FeNCCH3]+BF−4 from a vinylidene precursor; an organometallic Beckmann rearrangement

The reaction of [Cp(CO)(Ph3P)FeCCH2]+ BF−4 with several hydrazine derivatives yielded the acetonitrile complex [Cp(CO)(Ph3P)Fe-NCCH3]+ BF−4 (4) (62–71%). The formation of this product is apparently the result of a facile Beckmann-type rearrangement.

Chemistry of carbonyl-derived ligands. Nucleophilic attack on anionic acetylide clusters

The broad range of reactions of anionic ketenylidene clusters is reviewed. We then describe some chemistry of the triiron nonacarbonyl acetylide clusters (PPN)[Fe3(CO)9CCOR] (Ia,Ib), (a: R = CH2CH3; b: R = C(O)CH3; PPN = bis(triphenylphosphine)iminium (1 +), (Ph3P)2N+), which are derived from the iron ketenylidene (PPN)2[Fe3(CO)9CCO]. The ethoxyacetylide cluster Ia adds a single phosphine to form a phosphonium alkyne (PPN)[Fe3(CO)9PMePh2CCOEt] (II). In contrast, Ib reacts with loss of acetate anion to form an unusual phosphonium acetylide cluster [Fe3(CO)9CCPMePh2] (III), which is also formed cleanly by protonation of II with one equivalent of triflic acid, HSO3CF3. Implications of the formation of these products on bonding and mechanism are considered. Clusters II and III are spectroscopically characterized, and a single crystal X-ray structure determination of II and III are reported. (PPN)[Fe3(CO)9PMePh2CCOEt] (II) crystallizes in the triclinic space group P1; a 9.910(1); b 16.920(2); c 17.372(2) A; α 74.83(1)°; β 84.65(1)°; γ 86.07(1)°; V 2796(1) A3; Z = 2. [Fe3(CO)9CCPMePh2] (III) crystallizes with an orthorhombic lattice; space group Pbca; a 7.898(1); b 19.885(2); c 31.906(5) A; V 5011(2) A3; Z = 8.

Nucleophilic attack on cluster-bound acetylide ligands derived from the iron ketenylidene, [Fe3(CO)9(CCO)]2−

Reaction of the iron ketenylidene (PPN)2[Fe3(CO)9CCO] [PPN =bis (triphenylphosphine)nitrogen(+1)] with trifluoroacetic anhydride forms a highly electrophilic acetylide cluster (PPN)[Fe3(CO)9CCOC(O)CF3] (lc), analogous to the known compounds (PPN)[Fe3(CO)9CCOR] [R=Et, (Ia); Ac, (Ib)] prepared from the reaction of ethyl triflate and acetyl chloride on the ketenylidene. Reaction of phosphines and (Ib, c) yield phosphonium acetylides [Fe3(CO)9CCPR3] [(II),R=Ph], with loss of (PPN)[CH3CO2] or (PPN)[CF3CO2]. Additionally, (Ic) and triphenylarsine react to give an analogous arsonium acetylide [Fe3(CO)9CCAsPh3] (III). No reaction occurs when an excess of arsine is added to (Ib). The reaction of (Ib, c) with anionic nucleophiles is reported, including reaction of Na[CpFe(CO)2] and (Ib) to afford an unusual metallated acetylide cluster (PPN) [Fe3(CO)9CCFe(CO)2Cp] (IV). Clusters (II), (III), and (IV) are spectroscopically characterized and a single crystal x-ray structure determination of (IV) is reported. (PPN)[Fe3(CO)9CCFe(CO)2Cp] (IV) crystallizes in the monoclinic space group P21/n;a=17.793(2) Å;b=16.108(3) Å;c=18.157(3) Å;β=107.62(1)0;V=4959(3) Å3;Z=4. Refinement of 469 variables on 5981 observed [I>3σ(I)] reflections converged toR=3.5% andRw=4.7%.

Mixed-metal butterfly acetamidediato clusters derived from a highly reactive ruthenium oxo cluster: synthesis and characterization of [(PPh3)2N][MRu3(CO)12(η2-μ3-NC(μ-O)CH3)], (M = Mn or Re)

Abstract Analogy with the isolable oxo cluster [Fe3(CO)9(μ3-O)]2−, which is structurally interesting and synthetically useful, prompted the present attempt to synthesize its ruthenium analog. Although the high reactivity of [Ru3(CO)9(μ3-O)]2− (I) prevented its isolation, the reaction of this species with [M(CO)3(NCCH3)]+, where M = Mn or Re, yields [PPN][MRu3(CO)12(η2-μ3-NC(μ-O)CH3]−. The high nucleophilicity of the oxo ligand in [Ru3(CO)9(μ3-O)]2− (I) appears to be responsible for the conversion of acetonitrile to an acetamidediato ligand and for the instability of I. The crystal structure of [PPN][MnRu3(CO)12(η2-μ3-NC(μ-O)CH3)]] reveals a hinged butterfly array of metal atoms in which the acetamidediato ligand bridges the two wings with μ3-N bonding to an Mn and two Ru atoms, and μ-O bonding to an Ru atom.