Coordination Properties of Multidentate Phosphanylborane Ligands in Tungsten Nitrosyl Complexes

Abstract

The ambiphilic and small‐bite‐angle diphosphanylborane ligands Ph2PCH(PPh2)CH2B(C8H14) (2) and Ph2PCH2CH[B(C8H14)]PPh2 (3) containing the Lewis acidic 9‐boranorbornyl group B(C8H14) have been prepared in one step by regioselective anti‐Markovnikov hydroborations of 1,1‐bis(diphenylphosphanyl)ethylene and 1,2‐bis(diphenylphosphanyl)ethylene with 9‐borabicyclo[3.3.1]nonane (9‐BBN) under relatively drastic reaction condition. The coordination properties of Ph2PCH2CH2B(C8H14) (1) and the newly prepared 2 and 3 towards the tungsten nitrosyl fragment {WNO}6 have been studied structurally and spectroscopically. Herein, we report the cis and trans tungsten nitrosyl complexes cis‐[W(CO)2(1)2(NO)(Cl)] (cis‐4a), cis‐[W(CO)2(1)2(NO)(H)] (cis‐4b), trans‐[W(CO)2(1)2(NO)(Cl)] (trans‐4a), trans‐[W(CO)2(1)2(NO)(H)] (trans‐4b), cis‐[W(CO)2(2)(NO)(Cl)] (cis‐5a), cis‐[W(CO)2(2)(NO)(H)] (cis‐5b), cis‐[W(CO)2(3)(NO)(Cl)] (cis‐6a), cis‐[W(CO)2(3)(NO)(H)] (cis‐6b), which were readily obtained from straightforward ligand‐substitution reactions of the tungsten carbonyl nitrosyl precursor [W(NO)(CO)4(ClAlCl3)] in tetrahydrofuran. The crystal structures of the tungsten chloride complexes cis‐4a, trans‐4a, and cis‐5a revealed that the trialkyl boron centers are free pendants in the secondary coordination spheres, whereas in the hydride complexes trans‐4b, cis‐5b, and cis‐6b the hydride ligand trans to the nitrosyl ligand is σ coordinated to the tethered B(C8H14) group and form three‐center, two‐electron (3c–2e) W–H–B bonds, which were observed in their crystal structures. The authenticity of the 3c–2e W–H–B bond in the tungsten hydride complex cis‐5b was further checked by a DFT structural optimization and natural bond order (NBO) analysis.

Main Group Lewis Acid-Mediated Transformations of Transition-Metal Hydride Complexes

“…50 The X-ray crystal structure of 15 (R = Me) instead indicates the presence of two bridging hydrides connecting W and Al, as shown in Scheme 9. 52 Berke and co-workers 53 Berke and co-workers 54 have also synthesized tungsten hydride complexes bearing an ambiphilic phosphanylborane ligand. Compound 18 was synthesized in two steps, with ligand substitution on the precursor [W(CO) 4 (NO)(ClAlCl 2.1.7.…”

“…Berke and co-workers have also synthesized tungsten hydride complexes bearing an ambiphilic phosphanylborane ligand. Compound 18 was synthesized in two steps, with ligand substitution on the precursor [W­(CO) 4 (NO)­(ClAlCl 3 )] followed by treatment with excess NaHBEt 3 (Scheme ) to install the hydride.…”

Nickel and Palladium Complexes of Ferrocene-Backbone Bisphosphine-Borane and Trisphosphine Ligands

“…Ambiphilic ligands, defined as those containing one or more conventional Lewis basic donors accompanied by a σ-acceptor group (e.g., a group 13 Lewis acid), have enjoyed increasing popularity over the last 10 years . Within this group, borane-containing ligands have played the dominant role and are either generated in situ , typically from a hydroborate or related anionic ligand complex, − or isolated prior to reaction with a metal precursor. − The most commonly employed borane-containing ligands are the H 3 –x B­(mt) x (mt = N -methylthioimidazolyl; x = 2 or 3) ligands pioneered by Hill and the R 3 –x B­{C 6 H 4 (PR 2 )- o } x ( x = 1–3) ligands developed by Bourissou. , …”

Synthesis, Structures and Coordination Chemistry of Singly Bridged Phosphane‐Boranes with Coordinately Unsaturated Platinum Group Metals

“…A key feature in both instances is the capacity of the pendant borane to stabilise the resulting formyl moiety (via O→B association); this has also been described more recently with diphosphanyl(organyl)boranes in the complexes [M(CO) 4 {κ 2 ‐ P,P ‐(PPh 2 ) 2 CH 2 B(C 8 H 14 )}Br] and [M(CO) 4 {κ 2 ‐ P,P ‐(Ph 2 P)CH(PPh 2 )CH 2 B(C 8 H 14 )}Br] (M = Mn, Re) 25. These ligands have also been employed in a series of group 6 nitrosyl complexes, in which the borane remains pendant 26…”