Palladium complexes with Pd→B dative bonds: Analysis of the bonding in the palladaboratrane compound [κ⁴-B(mim^But)₃]Pd(PMe₃)

Abstract

The dinuclear complex {[mu-kappa(1),kappa(3)-B(mim(Bu(t)))(3)]Pd}(2), which features a Pd-->B dative bond, may be obtained by the reaction of [Tm(Bu(t))]K with Pd(OAc)(2); treatment of {[mu-kappa(1),kappa(3)-B(mim(Bu(t)))(3)]Pd}(2) with PMe(3) affords the mononuclear boratrane derivative [kappa(4)-B(mim(Bu(t)))(3)]Pd(PMe(3)), for which a molecular orbital analysis indicates that the palladium center possesses a d(8) configuration.

Crystal field arguments to explain the trans labilisation within transition metal–borane complexes

“…3. The trimethylphosphine ligand coordinated trans to boron in the trigonal bipyramidal palladium example has a bond distance 2.360 Å , indicating a moderate trans influence for the borane functional group [14]. In contrast, the rhodium-phosphine distances in the octahedral complex reveal a significant elongation of the ligand trans to the borane species [8].…”

“…This has been shown in a large number of examples that have been reported over the past few years. The majority of compounds, which have been provided by Hill [2][3][4][5][6][7][8][9][10][11][12] and others [13][14][15][16][17][18][19][20][21], contain either the flexible scorpionate ligand, Tm [hydrotris(2-methyl-1-imidazolyl)borate] or similar derivatives (Fig. 2).…”

Metallaboratranes Derived from a Triphosphanyl–Borane: Intrinsic C3 Symmetry Supported by a Z‐Type Ligand

“…The helical geometry of 2 most probably results from the presence of sp 3 -hybridized P and B atoms, and from the steric congestion between the phosphorus substituents of neighboring phosphanyl arms. In marked contrast, the related metallaboratranes featuring tris(methimazolyl)borane (Tm) ligands [23] [24] display approximately C 3v symmetry.…”

Coordination Chemistry of Neutral (Ln)–Z Amphoteric and Ambiphilic Ligands

“…Most complexes (55-61, 63-66, 68-77, 82, 90-95) adopt a pseudooctahedral geometry with a κ 4 -tris(methimazolyl)borane (κ 4 -oct), but few species (78-81) [65,68] can have the σ-acid ligand linked by two mim buttresses, as a κ 3 -bis(methimazolyl)borane framework (κ 3 -oct). A trigonal-bipyramidal geometry (κ 4 -pyr) was observed with Co (62), [62] Ni (83-86), [69][70] Pd (87) [71] and Pt (89) [72][73] complexes that can be described as having a d 9 and d 10 electronic configuration if the borane interaction is considered to be dative. However, this supposition has led to some debate (vide infra).…”

“…The Pd-S 3 bond from the lone fragment of the ligand bridging the two metallic fragments is significantly longer than the other Pd-S bonds from the chelating {κ 3 -B,S,SЈ-B(mim Me ) 3 } fragment (Pd-S 3 is 2.576 Å compared to an average of 2.341 Å for Pd-S 1 and Pd-S 2 ). In complex 67, one tris(methimazolyl)borane ligand is involved in what is a formal µ-κ 2 S,SЈ,κ 4 coordination, in which two of the sulfur atoms bridge two rhodium centres, [b] 9.5 75 [67] [71] µ-κ,κ 3 mim tBu Pd [e] 2.073(4) N.A. 89 [72- in addition to its usual κ 4 coordination.…”