Molecular Orbital Insights of Transition Metal-Stabilized Carbocations

Transition metal-stabilized carbocations are characterized by synthetically valuable interactions, yet, to date there are no comprehensive reports of the many bonding modes that can exist between a metal and carbocation. This review summarizes developments in these complexes to provide a clear picture of their properties and reactivities. In order to strategically exploit them, we propose this summary of the different bonding modes for transition metal-carbocation complexes. These models will help chemists understand the orbital interactions involved in these compounds so that they can approach their synthetic goals most effectively. Multiple transition metals and carbocations will be discussed.

Platinum organometallic compounds: classification and analysis of crystallographic and structural data of monomeric five and higher coordinated

Four hundred and twenty monomeric organoplatinum compounds, in which platinum atoms are five- and higher coordinated, are analyzed. The platinum atoms are found in the oxidation states +2, +3 and +4. The Pt(II) compounds by far prevail. There are wide varieties of the inner coordination spheres about the platinum centers. The Pt(II) compounds are five-coordinated (trigonal bipyramidal and square pyramidal), six-coordinated (different degrees of distortion), seven-coordinated (pentagonal bipyramidal, piano stool) and sandwiched (PtC10). The Pt(III) compound is square-planar. The Pt(IV) compounds are six- and eight-coordinated. There are several relationships between the Pt-L bond distances, covalent radii of the coordinated atom/ligand, and metallocycles, which are discussed. The trans-effect plays an important role in the inner coordination spheres about the Pt centers, especially on the Pt-L bond distances.

Cyclotriphosphorus complexes: solid-state structures and dynamic behavior of monoadducts with carbonyl fragments

Treatment of the cyclo-P3 complexes [(triphos)MP3] [triphos = 1,1,1-tris(diphenylphosphinomethyl)ethane; M = Co (1), Rh (2)] with stoichiometric amounts of [M'(CO)5(thf)]n+ (n = 0, M' = Cr, Mo, W; n = 1, M' = Re) and [W(CO)4(PPh3)(thf)] yields the compounds [[(triphos)M](mu,eta 3:1-P3) [M'(CO)5]] [M = Co; M' = Cr (3a), Mo (3b), W (3c). M = Rh; M' = W (4)], [[(triphos)Co](mu,eta 3:1-P3)[Re(CO5)]]BF4.C7H8 (5) and [[(triphos)Rh](mu,eta 3:1-P3)[W(CO)4PPh3]].2CH2Cl2 (6). The X-ray structures of 5 and 6 have been determined. Crystal data: 5, monoclinic space group P2(1)/n, a = 14.754(2) A, b = 24.886(4) A, c = 15.182(2) A, beta = 103.38(1) degrees, Z = 4; 6, monoclinic space group P2(1)/n, a = 14.872(3) A, b = 27.317(6) A, c = 16.992(4) A, beta = 111.75(5) degrees, Z = 4. The effects of eta 1 coordination on the MP3 core are discussed by comparing the MP3 skeletons in the above structures with those of the previously characterized bis and tris end-on adducts of organometallic fragments of 1. Variable temperature NMR data for the compounds provide evidence for fluxional processes in solution that may be interpreted as [(triphos)M] rotation about its C3 axis and [M'(CO)5] or [M'(CO)4PPh3] scrambling over the P3 cycle. The activation parameters of the fragment scrambling process are determined.