The Versatile Reactivity of cyclo‐(P₅tBu₄)⁻ with Complexes of the Nickel Triad

Abstract

Na[cyclo-(P(5)tBu(4))] (1) reacts with [NiCl(2)(PEt(3))(2)] and [PdCl(2)(PMe(2)Ph)(2)] with elimination of tBuCl and formation of the corresponding metal(0) cyclopentaphosphene complexes [Ni{cyclo-(P(5)tBu(3))}(PEt(3))(2)] (2) and [Pd{cyclo-(P(5)tBu(3))}(PMe(2)Ph)(2)] (3). In contrast, complexes with the more labile triphenylphosphane ligand, such as [MCl(2)(PPh(3))(2)] (M=Ni, Pd), react with 1 with formation of [NiCl{cyclo-(P(5)tBu(4))}(PPh(3))] (4) and [Pd{cyclo-(P(5)tBu(4))}(2)] (5), respectively, in which the cyclo-(P(5)tBu(4)) ligand is intact. In the case of palladium, the cyclopentaphosphene complex [Pd{cyclo-(P(5)tBu(3))}(PPh(3))(2)] (6) in trace amounts is also formed. However, [Ni{cyclo-(P(5)tBu(4))}(2)] (7) is easily obtained by reaction of two equivalents of 1 and one equivalent of [NiCl(2)(bipy)] at room temperature. Complex 7 rearranges on heating in n-hexane or toluene to the previously unknown [Ni{cyclo-(P(5)tBu(4))PtBu}{cyclo-(P(4)tBu(3))}] (8), which presumably is formed via the intermediate [Ni{cyclo-(P(5)tBu(4))}{cyclo-(P(4)tBu(3))PtBu}], which, after an unexpected and unprecedented phosphanediide migration, gives 8, but always as an inseparable mixture with 7. In the reaction of 1 with [PtCl(2)(PPh(3))(2)], ring contraction and formation of [PtCl{cyclo-(P(4)tBu(3))PtBu}(PMe(2)Ph)] (9) is observed. Complexes 3-5 and 7-9 were characterised by (31)P NMR spectroscopy, and X-ray structures were obtained for 5-9.

Ring Contraction by NHC‐Induced Pnictogen Abstraction

“…Thermally induced rearrangements are another method for ring contractions. For instance, this was shown for the formation of B (Scheme ), which is obtained by heating a solution of [Ni( t Bu 4 P 5 ) 2 ] . We recently found that the complexes [(LCo) 2 ( μ 2 , η 2:2 ‐E 4 )] (L=CH{C(Me)N(Dipp)} 2 ; E=P, As) undergo a thermally induced elimination of a pnictogen atom leading to the triple‐decker complexes [(LCo) 2 ( μ 2 , η 3:3 ‐E 3 )] ( C ) with an E 3 middle deck…”

The unusual coordination chemistry of phosphorus-rich linear and cyclic oligophosphanide anions

“…Thus, complexes with the cyclo-(P 5 Bu t 3 ) ligand and two coordinated phosphanes (67, 71 and 73) show an AA BB CDD spin system with a large (absolute) coupling constant 1 J(P A , P A ) of ca. 470 Hz, which indicates multiple-bond character between P A and P A [57]. On the other hand, the 31 P{ 1 H} NMR spectra of the homoleptic complexes 68 and 72 exhibit five multiplets for an AA BB CC DD EE spin system.…”

“…An ABCDEF spin system (ratio 1:1:2:1:1) was observed in the 31 P{ 1 H} NMR spectrum of 70, while the spectrum of 74 showed a typical first-order ABCDEF spin system with 132 lines in which phosphorus atom A appeared at ca. −125 ppm, due to the "small-ring effect" which shifts all signals to higher field [57].…”

“…2(3) 231 . (2) [Pt(P4Mes4)(dppe)] (56) 219.5(3) 233.8 (2) AA BCXX [50] 221.4(3) 234.7(2) 223. 6(3) [Pt(P4Mes4)(C NBu t )2] (57) 221.3(2) 231. 9(1) g [50] 221.3 (2) 233.9(1) 222.1 (2) [Pt(P4Mes4)(C NCy)2] (58) 221.1(2) 233.1 (2) g [50] 221.…”

Synthesis and Thermolysis of the Homoleptic Iron(II) Complex [Fe{cyclo‐(P5tBu4)}2]

“…The reactions between [Na(thf) 4 { cyclo ‐(P 5 t Bu 4 )}]13 and transition metal complexes gave phosphorus‐rich transition metal complexes in which 1) the cyclo ‐(P 5 t Bu 4 ) – ring stays intact, as in [M{ cyclo ‐(P 5 t Bu 4 )} 2 ] (M = Pd, Ni),14 [Rh{ cyclo ‐(P 5 t Bu 4 )}(PPh 3 ) 2 ]15 and [Au{ cyclo ‐(P 5 t Bu 4 )}(PCyp 3 )],16 2) formation of cyclo ‐(P 5 t Bu 3 ) occurs with elimination of t BuCl, e.g., [Ni{ cyclo ‐(P 5 t Bu 3 )}(PEt 3 ) 2 ]13 or 3) rearrangement to [{ cyclo ‐(P 4 t Bu 3 )}P t Bu] – occurs, which shows different bonding modes, for instance, bidentate chelating in [PtCl{ cyclo ‐(P 4 t Bu 3 )P t Bu}(PMe 2 Ph)],14 bis‐bidentate chelating in [Mn 2 (μ‐Br){ cyclo ‐(P 4 t Bu 3 )P t Bu}(CO) 6 ]17 and bridging (via the exocyclic P t Bu group) in [M 4 { cyclo ‐(P 4 t Bu 3 )P t Bu} 4 ] (M = Cu, Ag, Au) 18. Herein we report the first iron(II) complex [Fe{ cyclo ‐(P 5 t Bu 4 )} 2 ] ( 2 ) in which two cyclo ‐(P 5 t Bu 4 ) – ligands exhibit tridentate coordination to the iron atom thus forming an 18‐electron complex.…”