Low-Valent Titanium Bis(phospholyl) Chemistry:  A Configurationally Stable Chiral Phosphatitanocene

Abstract

The first example of a low-valent phosphatitanocene has been prepared and structurally characterized, and a chiral Ti(II) phosphametallocene was prepared and was found to have a significantly higher barrier to isomerization than the Ti(IV) analogue. Descriptions of the molecular orbitals of the two complexes offer an explanation of the difference.

Cycloheptatrienyl Zirconium Sandwich Complexes with Lewis Basic Phospholyl Ligands (Phosphatrozircenes): Synthesis, Structure, Bonding and Coordination Chemistry

“…[5,35] Additionally, few theoretical experiments on phospholyl complexes are present in the literature, [12,36] with landmark molecular orbital calculations on phosphaferrocenes probably being the most important.…”

“…These two possibilities are crucial for the isomerisation of chiral Group 4 phosphametallocenes by an h 5 !h 1 !h 5 slipinversion mechanism, [11] which seems to be easier for d 0 than d 2 complexes. [12] Alternatively, the cyclopentadienyl system can also be extended by one or more CH units. Following extensive studies by Green and Ng in the 1990s, [13] independent reports from the groups of Braunschweig, [14] Elschenbroich, [15] Girolami [16] and Tamm [17] have recently revitalised interest in early-transition-metal complexes containing the cycloheptatrienyl (Cht) ligand.…”

Synthesis and Properties of [NiCp*(2,5‐tBu2PC4H2)], a 20‐Valence‐Electron Phosphanickelocene

“…[50] However, both in Ephritikhines [7] and our work it has been possible to observe 18 ve nickel-containing structures that are formally the products of an h 5 -to h 1 -ring shift occurring in a phosphanickelocene structure. [51][52][53] The X-ray data suggesting that the carbon atoms preferentially peel away from the metal centre upon moving from phosphaferrocene 17 to phosphanickelocene 2, and the DFT results showing the high electron density at the phosphorus atom of 2, seem to indicate that the preferred structure for a simple unencumbered "monophosphanickelocene" will be a dimer such as 18. The 20ve configuration will become stable when the hindrance in the coordination sphere rises sufficiently to prevent the phospholyl ligand from adopting an orientation favourable to bridging: a situation that clearly exists in the structure found for 4.…”

Phosphines and Related Tervalent Phosphorus Systems

“…823,824 Palladium 825 and gallium 826 complexes of diphosphaferrocenes, involving s-donation from phosphorus, have also been prepared. Phosphametallocenes in which the phospholide anion is p-bonded to a transition metal other than iron have also generated much interest, reports having appeared concerning the chemistry of phosphatitanocenes, 827,828 phosphazirconocenes, 829 phospharuthenocenes, 830,831 and a phosphacymantrene. 832 Main group phospholide systems have also been reported, involving sodium, potassium, rubidium and caesium, 833 and also phospholides involving the f-block elements samarium and thulium.…”