The nature of the co-ordinate link. Part 11. Synthesis and phosphorus-31 nuclear magnetic resonance spectroscopy of platinum and palladium complexes containing side-bonded (E)-diphenyldiphosphene. X-Ray crystal and molecular structures of [Pd{(E)-PhPPPh}(Ph₂PCH₂CH₂PPh₂)] and [Pd{[(E)-PhPPPh][W(CO)₅]₂}(Ph₂PCH₂CH₂PPh₂)]

Abstract

The complexes cis-[MC12L2] react with Li,(PhPPPh) to give [M(PhP=PPh)L,] [M = Pd, L2 = 1,2-bis(diphenylphosphanyl)ethane (dppe), (1) ; M = Pt, L2 = dppe or (PPh3)2]. Complex (1) reacts with [W(CO),(thf)] (thf = tetrahydrofuran) to give [Pd{(PhP=PPh) [W(CO),],}(dppe)](2). Complexes were characterized by 31 P-{ H} n.m.r. spectroscopy. X-Ray crystal-structure determinations of complexes (1 ) and (2) reveal nearly identical and planar PdP4 moieties comprising the donor atoms of L2 and q2-[(€)-diphenyldiphosphene] ligands. In (2) the two diphosphene lone pairs co-ordinate to W(CO), groups and the W-P bonds are bent 32" away from the Pd atom. The diphosphene P-P bond in (2) [2.186(6) A] is 0.06 A longer than that in (1) [2.121(4) A], which is similar to that in other diphosphene complexes and is approximately mid-way between the P-P single and double bond lengths. Small values of the coupling constants 1J( PtP) and 2J( PP) involving the diphosphene ligand indicate that the diphosphene uses electrons of low s character in q2-co-ordination.Diorganodiphosphenes RP=PR tend to polymerize to cyclopolyphosphanes such as PhP(PPh)+ because the bond energy per phosphorus atom is smaller in the diphosphene (i.e. half the P=P bond energy) than in the polyphosphane (i.e. the P-P bond energy). Although px-pn bonding between elements X from the second and later rows of the Periodic Table leads to the expected maximum in the X2 bond dissociation energies at Group 5, the ratio of the bond energies per atom in X2 to that in the polymers containing single bond X-X is too small for the diatomic molecules X2 to be thermodynamically stable at 25 "C2 At high temperatures entropy favours the smaller molecules X2, and the n-bonded molecules X2 for most of the Main Group elements have been known for a long time. Recent success in the stabilization at room temperature of molecules RP=PR has been achieved by the use of bulky substituents R. In the (E)-configuration of the diphosphene the interaction between the two R groups is minimized, whereas the number and intensity of the steric interactions tend to be greater in the polymeric forms. With sufficiently bulky substituents R, the doubly-bonded molecules become thermodynamically stable at room temperature, and even when full thermodynamic stabilization is not achieved, the bulky R groups reduce the rate of polymerization or attack by other reagents. The molecules RP'PR have been prepared and studied for R = C6H2But3-2,4,6 and other bulky aryl group^,^-'^ C(Si Me3)3,599*1 9 l 2 N(SiMe3)2,13 and N(SiMe,Bu'),. l 3The early report l4 of the detection of monomeric and dimeric forms of PPh by 31P n.m.r. in melts of PhP(PPh)4 now n l l t 1,2-Bis(diphenylpho~phanyl)ethane[(E)-~~-dipheny~diphosphene]palladium(0) and 1-[1',2'-bis(diphenyIphosphanyl)ethane]- 2,2,2,2,2,3,3,3,3, 3-decacarbonyl-[(E)-CI-diphenyldiphosphene- P( Pd' W')P'( Pd W 3)]-palladium(0)d i tungsten(0) respectively. Supplementary data auailable(No. SUP 23947, 30 pp.): thermal parameters, H-atom co-ordinates, structure factors. See Instruc...

[Ni(NHC)2] as a Scaffold for Structurally Characterized trans [H−Ni−PR2] and trans [R2P−Ni−PR2] Complexes

“…X‐ray crystallography (Figure 5) showed, in both cases, a trans disposition of the two aryl substituents in the diphosphene ligand. The P−P bond lengths ( 18 : 2.1379(7) Å; 19 : 2.1342(7) Å) were in good agreement with those in [Ni(PEt 3 ) 2 ( trans ‐MesP=PMes)] (2.1355(9) Å), [Ni(PMe 2 Ph) 2 ( trans ‐MesP=PMes)] (2.137(1) Å), and [Pd(dppe)( trans ‐PhP=PPh)] (2.121(4) Å; dppe=1,2‐bis(diphenylphosphino)ethane), respectively [44,46] . The angles C1−Ni−C11 ( 18 , 104.62(6)°; 19 , 98.85(8)°) were larger than 90°, as expected for a pseudo three‐coordinated complex with small P−Ni−P angles ( 18 , 56.76(2)°; 19 , 56.89(2)°).…”

A selective route to aryl-triphosphiranes and their titanocene-induced fragmentation

“…η 2 -Diphosphene complexes of various transition metals have been known and were thoroughly reviewed by Weber 52. Noteworthy, is the formation of [(Ph 3 P) 2 M(P 2 {C 6 F 5 } 2 )] with an E -configured diphosphene ligand by the degradation of cyclic tetraphosphine P 4 (C 6 F 5 ) 4 in the presence of M(PPh 3 ) 4 (M = Pt,53 Pd54). Other known diphosphene complexes of group 4 include the anionic species [Cp 2 Zr(PPh) 2 Br] – with a P–P distance [2.145(3) Å] shorter than in 3a and 3b ,55 and the related Mes-substituted complex [Cp 2 Zr(P 2 Mes 2 )] with a similar P–P distance [2.188(3) Å] 56.…”

Reaktionen des [η2-{P-PtBu2}Pt(PPh3)2] und [η2-{P-PtBu2}Pt(dppe)] mit Metallcarbonylen. Bildung von [η2-{(CO)5M · PPtBu2}Pt(PPh3)2] (M = Cr, W) und [η2-{(CO)5Cr · PPtBu2}Pt(dppe)]

“…Der P±P-Abstand in der P 2 -Gruppe ist mit 216,4 pm angegeben [6]. Scherer et al [7] beschreiben die Bildung von [(TaL) 3 …”