Novel T‐Shaped 14‐Electron Platinum(II) Complexes Stabilized by One Agostic Interaction

Abstract

The stereoelectronic properties of the PR2(2,6‐Me2C6H3) (R=Ph, Cy) ligand can be used to stabilize an unprecedented class of 14‐electron platinum(II) complexes. The X‐ray analysis of the cyclometalated cyclohexyl derivative reveals an agostic interaction between the Pt center and an o‐methyl moiety (see picture). The fast and reversible formation of three‐coordinate platinum–hydrido complexes occurs by reaction with H2, and is achieved through the cleavage of a platinum–carbon bond.

When Are Tricoordinated PdIISpecies Accessible? Stability Trends and Mechanistic Consequences

“…[17] Similar agostic coordinations have been found for related isoelectronic complexes of Ni II , [19] Pt II , [20][21][22] and Rh I . [23,24] Strictly speaking, counting the agostic coordination, these complexes are tetracoordinated.…”

Highly Efficient Deep‐Blue Emitters Based on cis and trans N‐Heterocyclic Carbene PtII Acetylide Complexes: Synthesis, Photophysical Properties, and Mechanistic Studies

“…Previous mechanistic studies on platinum complexes bearing phosphine or pyridine ligands have suggested that cis-trans isomerization either proceeds by a dissociative mechanism that involves loss of the phosphine, pyridine, or halide ligands leading to a three-coordinate T-shaped complex intermediate, or by an associative mechanism that involves coordination of the phosphine or pyridine ligand leading to a five-coordinate intermediate. [45] We found that the conversion of complex 5 a to 5 b proceeded efficiently when 5 a was heated in [D 8 ]toluene at 200 8C for 2 days in a J. Young NMR tube to give an isolated yield of 73 %.…”

Ligand Association/Dissociation Paths and Ill‐Defined Coordination Numbers

“…In [Ni( [14]ane-S 4 )]BF 4 (TTCDNI, Table 1) [36] and the perchlorate of a related macrocyclic complex (MAXSOT, Table 1), [37] moderate deviations from the octahedral shape result from relatively small differences between the bonded NiÀS distances (2.18 ) and the nonbonded contacts between the Ni atom and the BF 4…”

“…[9] The appreciation of the role that such secondary interactions may have led a group of researchers to say that a family of dithiolene copper complexes is "blessed with secondary coordination ability." [8] Other ways of referring to imprecise coordination numbers in transition-metal chemistry include the naming of some copper(I) complexes as "quasi-two-coordinate" to allude to the weak bonding of additional ligands, [10] or the use of the expression "semi-coordinating interaction," [11] not to mention the widely recognized "agostic interactions" or secondary coordination of ancillary groups [12] that may help, for example, stabilize low coordination numbers [13] or less common coordination geometries, such as a T-shaped tricoordination [14] or a seesaw tetracoordination. [15] Among the variety of examples that can be found in the literature, we choose to mention in more detail here only some illustrative ones.…”