X-Ray Structures

An Alane-Appended Analogue of DPPF and its Platinum Complexes

We recently prepared an alane-appended analogue of dppf (dppf is a wide bite-angle bis-phosphine ligand used extensively in late transition metal catalysis). The ligand, FcPPAl:

The FcPPAl ligand binds tenaciously to platinum in a range of oxidation states, yielding complexes with square pyramidal, T-shaped, and distorted square planar geometry. The CO and dihydride complexes also feature unusual multiceter bonding between the alane, platinum, and either a carbonyl or a hydride ligand.

A Borane-Appended Analogue of DPPF and its Platinum Complexes

We recently prepared a borane-appended analogue of dppf (dppf is a wide bite-angle bis-phosphine ligand used extensively in late transition metal catalysis). The ligand, FcPPB:

The FcPPB ligand η³BCC-coordinated to platinum:

The FcPPB ligand η²BC-coordinated to platinum:

The FcPPB ligand η¹B-coordinated to platinum:

Rhodium Halide and PF₆ Complexes of a Borane-Appended Ligand

The borane engages in a tight interaction to chloro or bromo co-ligands. By contrast, (a) there is only a weak interaction between the borane and iodo co-ligand, and (b) a fluoride co-ligand is completely abstracted to generate a zwitterionic complex in which the cationic rhodium center is now η²-coordinated to the ipso and ortho carbon atoms of one of the phenyl rings on boron:

When the halide is entirely abstracted from the metal center, the borane engages in an η²BC-interaction with rhodium:

Rhodium-Iron Heterobimetallic Complexes of the TXPB Ligand

Reaction of [RhCl(CO)(TXPB)] with K[CpFe(CO)₂] provided [(TXPB)Rh(μ-CO)₂Fe(CO)Cp] in which the borane is η³BCC-coordinated to rhodium:

Reaction of [(TXPB)Rh(μ-CO)₂Fe(CO)Cp] with isocyanides yields complexes featuring a bridging borataaminocarbyne (C–NR–BR₃) ligand:

Palladium Complexes of a Phosphine-Thioether-Borane Ligand

The borane of the TXPB ligand is η³BCC-coordinated to palladium:

The TXPB ligand is κ¹P-coordinated to palladium (the thioether and the borane are now uncoordinated):

One molecule of dba (dibenzylideneacetone) is bound between palladium and the borane of the TXPB ligand. The resulting complex is best described as a zwitterionic boratoxyallyl complexes in which the allyl unit is η³-coordinated to palladium:

One-electron reduction of [PdCl₂(TXPB)] yielded the bright red palladium dimer [{PdCl(TXPB)}₂] shown below:

Alkyl and Aryl Complexes of Borane-Appended Ligands

Reaction of TXPB with [PtMe₂(COD)] provided the complex shown below, [PtMePh(TXPB')], with one phenyl and one methyl group on platinum, and one phenyl and one methyl group on boron.:

Heating [PtMePh(TXPB')] resulted in exchange of the remaining phenyl group on boron with the remaining methyl group on platinum:

In solution, [PtMePh(TXPB')] exists in equilibrium with zwiterionic [PtMe(TXPB-Me)]. Neutral [PtMePh(TXPB')] is trapped by addition of 1 equivalent of P(OPh)₃, while zwitterionic [PtMe(TXPB-Me)] is trapped by addition of 2 equivalents of CNXyl:

Complexes of PS- and PSP-Donor Ligands

The PS- and PSP-ligands in the complexes below are borane-free analogues of our borane-containing TXPB ligand. Our primary interest in these complexes is for comparison of their structures and reactivities with TXPB analogues.

Vinylborane Complexes

This is the first η³BCC-coordinated vinylborane complexes. The first one below binds like an allyl ligand, with extensive delocalization within the BCC core of the ligand. The second one below binds like an alkyl anion with an attached borataalkene group.

This is the first complex of a vinylborane-containing ambiphilic ligand (it was formed in situ via the reaction of [Pt(FcPPB)] with HC₂Ph):

Rigid Ligand Thorium Complexes

Neutral thorium dialkyl complexes (in the dibenzyl complex, the hydrocarbyl ligands are η²- or η³-coordinated):

An unexpected adduct between [(BDPP)ThX₂] and MeMgX(OEt₂) where X = Cl or Br, and BDPP = an NNN-donor pincer ligand):

A rare example of a thorium alkyl cation (the 2nd view shows packing between the cations and B(C₆F₅)₄ anions):

A cationic thorium alkyl complex coordinated to a molecule of the neutral [(XA₂)Th(CH₂Ph)₂] starting material. The μ-η¹:η⁶-coordination mode in this structure is a previously unknown coordination mode for a benzyl ligand:

A thorium dication formed by double alkyl abstraction. The dictionic metal center is π-coordinated to two PhCH₂B(C₆F₅)₃ anions.

A very sterically hindered complex featuring two BDPP pincer ligand dianions coordinated to thorium(IV):

Rigid Ligand Uranium Complexes

Uranium(IV) halide complexes of rigid NON- and NSN-donor ligands (2 views of each):

Uranium(III) halide complexes of rigid NON- and NSN-donor ligands (2 views of each):

A representative uranium(IV) alkyl complex of our most commonly used NON-donor pincer ligand, XA₂:

Yttrium Complexes

We prepared the first acridanide-backbone pincer ligand (the AIm₂ monoanion). However, it was readily cyclometallated in the coordination sphere of yttrium, and then two ligands (the cyclometallated ligand and the intact ligand) are coupled together... The low thermal stability of the complexes stems from the imine donors, not the acridanide backbone...

Interesting Alkali Metal Complexes

Potassium-alkane interactions!!! (these are the first crystallographically characterized main group-alkane interactions):

An unexpected adduct between nBuLi and Li₂[XAT]:

Manganese Alkyl/Allyl Complexes

Volatile and thermally robust mixed alkyl / allyl complexes. Their thermal stability is remarkable given their high spin d⁵ configuration!

Dimetallic Copper and Zinc Complexes

The complexes below are formed as intermediates in the reactions of [CuL₂] (L = N-isopropyl-2-pyrrolylaldimine) with ZnEt₂ or AlMe₃ to deposit copper metal.