van't Hoff-Le Bel Stranger: Formation of a Phosphonium Cation with a Planar Tetracoordinate Phosphorus Atom

Abstract

A novel intriguing type of coordination mode in phosphorus chemistry has been established that is of fundamental interest in the understanding of chemical bonding. Besides the synthesis of the first planar phosphonium cation PR(4)(+) 1 by a surprisingly simple metathesis reaction, a potentially general experimental method that reaches the seemingly impossible high-energy region of basic molecular and isoelectronic ER(4) systems (E=B(-), C, N(+), Al(-), Si, P(+)) is provided.

New and Facile Entry to Nitrilium Phosphane Ylide Complex Chemistry by Using 7-Phosphanorbornadiene Complexes

“…[1,3] As also observed for pentacarbonyl[2-bis(trimethylsilyl)-methyl-3,4-bis(methoxycarbonyl)-5-dimethylamino-2H-1,2-azaphosphole-kP]tungsten(0) (6), [13] the molecular structure of complex 5 a (Figure 1) shows a planar five-membered ring (mean deviation 3 pm) with N1ÀC8 and C7ÀC6 bond lengths of 131.9(2) and of 135.0(2) pm, respectively, which are similar to those of complex 6 (NÀC: 131.2(5); CÀC: 133.8(6) [13] ). The different steric situation in the (OC) 5 WPR structural units of 5 a (R Me) and 6 (R CH(SiMe 3 ) 2 ) correlates with shortened bond lengths in 5 a (WÀP 249.96(5) and C9ÀP 181.4(2) pm; 6: WÀP 252.37 (11) and CÀP 183.6(4) pm [13] ) and a narrowing of the W-P-C6 bond angle in 5 a (114.97(6)8 vs 119.26(14)8 in 6 [13] ).…”

“…It is known that nitrilium phosphane ylide complexes II can be efficiently generated by thermally [1] or photochemically [2] induced ring opening of 2H-azaphosphirene complexes I (Scheme 1) and subsequently trapped by electronically activated p systems such as alkynes, [3] nitriles, [4] or phosphaalkynes, [5] thus providing access to a variety of new unsaturated N,P-heterocyclic ring systems. To develop the synthetic potential of this methodology, it was necessary to find a novel access to nitrilium phosphane ylide complexes II, thus providing N,P-heterocycles with more ubiquitous substituents 2': A solution of NaBPh 4 (2.01 g, 5.88 mmol) in THF (ca.…”

“…, o-CH), 6.94 (pseudo-t,3 J(H,H) 7.2 Hz, 8 H, m-CH), 6.80 (m, 4 H, p-CH), 0.40 (s, w 1/2 4 Hz, 36 H); 31 P NMR ([D 8 ]THF): d À 323.6 (s, w 1/2 90 Hz); 13 C{ 1 H} NMR ([D 8 ]THF): d 164.3 (q, C(1), 1 J(C,B) 49.4 Hz), 136.6 (q, C(3), 3 J(C,B) 1.2 Hz), 125.1 (q, C(2), 2 J(C,B) 3.0 Hz), 121.3 (s, C(4)), À 4.2 (s, w 1/2 11 Hz); 119 Sn{ 1 H} NMR ([D 8 ]THF): d 38.4 (s, w 1/2 180 Hz).…”

Perstannylated Ammonium and Phosphonium Ions: Organometallic Onium Ions That Are also Base-Stabilized Stannylium Ions

“…Elemental analysis calcd for (2.178) [b] (2.547) [d] [a] See reference [11]. It is known that nitrilium phosphane ylide complexes II can be efficiently generated by thermally [1] or photochemically [2] induced ring opening of 2H-azaphosphirene complexes I (Scheme 1) and subsequently trapped by electronically activated p systems such as alkynes, [3] nitriles, [4] or phosphaalkynes, [5] thus providing access to a variety of new unsaturated N,P-heterocyclic ring systems. To develop the synthetic potential of this methodology, it was necessary to find a novel access to nitrilium phosphane ylide complexes II, thus providing N,P-heterocycles with more ubiquitous substituents 2': A solution of NaBPh 4 (2.01 g, 5.88 mmol) in THF (ca.…”

“…[11] Similar Sn À N bond lengths are found in the ions [(Me 3 Sn) 2 NH 2 ] (av. 2.171(9) ) and [(Me 3 Sn) 3 NH] (2.168(3) ), [8] which clearly indicates that steric effects play only a subordinate role. This idea is supported by density functional calculations (DFT) on EL 3 and [EL 4 ] (E N, P; L silyl, stannyl) which show that in going from NL 3 to [NL 4 ] the MÀN bonds (M Si, Sn) become significantly longer than the corresponding MÀP bonds in the phosphorus analogues (Table 1).…”