Keith R. Dixon

Phosphorus to Bismuth

Phosphorus-31 is spin 1/2, 100% abundant and has a receptivity relative to the proton of 0.0663. In consequence, this is an easy nucleus to observe, and even prior to 1970 a great deal of information had been obtained for simple compounds using continuous wave instruments. The advent of pulsed NMR techniques has greatly accelerated development of the field (especially in coordination chemistry and biochemistry), and 31P is now one of the most common of all NMR experiments. With the additional constraints imposed by the dearth of recent comprehensive review literature, it is impossible to provide comprehensive coverage within a single chapter of limited length. I will aim at an outline of the main developments with sufficient lead references to enable individuals to trace details applicable to their own work; but I apologize in advance for the inevitable omissions and personal bias in the selection of material. Literature coverage in the present article extends to about the end of 1982 with minor additions during the prolonged development of the book.

Coordination chemistry of [CH{P(S)Ph2}2]−: X-ray diffraction studies of S,S-chelate complexes of iridium and rhodium

Reactions of the chloro-bridged complexes, [M2Cl2(cod)2], M  Ir or Rh, with CHR(P(S)Ph2)2, R  H or Me, provide a synthetic route to the cations, [M(cod){CHR(P(S)Ph2)2-S,S}]+, which are isolated as fluoroborate or perchlorate salts. Treatment of these products with sodium hydride results in facile deprotonation to the neutral complexes, [M(cod){CR(P(S)Ph2)2-S,S}], and when R  H, the neutral complexes are also accessible via reactions of [M2Cl2(cod)2] with Li[CH{P(S)Ph2)2]. The complexes, [Ir(cod){CH(P(S)Ph2)2-S,S}], and [Rh(cod){CH(P(S)Ph2)2-S,S}], crystallize in the P1 (No. 2) space group (Z = 2) with respective unit cells: a = 11.570(4), b = 15.122(2), c = 9.919(3) A, α = 79.86(4), β = 64.87(3), γ = 97.94(4)°; and α = 11.571(16), b = 15.078(2), c = 9.869(2) A, α = 100.16(1), β = 64.97(1), γ = 82.10(1)°. Both structures consist of puckered 6-membered rings formed by coordination of the disulfide ligands via two sulfur atoms to the metal center. The rings lie in distorted boat conformations with the prows occupied by one sulfur and one phosphorus and the metal atoms in one side.

Synthesis and 31P n.m.r. spectroscopy of platinum and palladium complexes containing side-bonded diphenyldiphosphene. The X-ray crystal and molecular structure of [Pd(PhPpph){bis(diphenyl-phosphino)ethane}]

The structure of [Pd(PhPPPh)(dppe)], dppe = bis(diphenylphosphino)ethane, obtained by a new and potentially general synthesis, is essentially plannar with only a 3° twist between the PdP2 planes and a P–P bond distance of 2.121(4)A; 31P n.m.r. data on the analogous platinum complexes show very small s-character in the Pt–P(diphosphene) bonds, suggesting that the structure is essentially a diphosphene bound to Pto rather that of a diphosphido(2–)ligand bound to PtII.

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)-PhPPPh}(Ph2PCH2CH2PPh2)] and [Pd{[(E)-PhPPPh][W(CO)5]2}(Ph2PCH2CH2PPh2)]

The complexes cis-[MCl2L2] react with Li2(PhPPPh) to give [M(PhPPPh)L2][M = Pd, L2= 1,2-bis(diphenylphosphanyl)ethane (dppe), (1); M = Pt, L2= dppe or (PPh3)2]. Complex (1) reacts with [W(CO)5(thf)](thf = tetrahydrofuran) to give [Pd{(PhPPPh)[W(CO)5]2}(dppe)](2). Complexes were characterized by 31P-{1H} 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 η2-[(E)-diphenyldiphosphene] ligands. In (2) the two diphosphene lone pairs co-ordinate to W(CO)5 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 η2-co-ordination.

Dynamic stereochemistry of cis-[PtH(SiR3)(PPh3)2]. Spontaneous ligand interchange with retentilon of nuclear spin–spin correlation

Above 0 °C in various solvents the complexes cis-[PtH(SiR3)(PPh3)2] with R = C6H5, p-ClC6H4, or p-MeC6H4 undergo spontaneous interchange of the PPh3 ligand position by a mechanism which retains P ⋯(Pt)⋯ H spin correlation and is thus intramolecular and non-dissociative within the limits of the n.m.r. experiment.

A new synthesis of platinum—carbon bonds

Abstract Syntheses of cis-[PtCl(CH2COCH3)(PEt3)2], cis-[PtCl(CH2NO2) (PEt3)2], and trans-[Pt(CCPh)2 (PEt3)2] are described. The procedure involves reaction of cis-[PtCl2(PEt3)2] with Ag2O and acidic CH bonds to precipitate AgC1 and generate a PtC bond. The method may represent a new general route to platinum—carbon bonds.

Coordination chemistry of [C(PPh2)P(S)Ph2)2]- : 31P NMR of rhodium, iridium and platinum complexes, and the crystal and molecular structures of [Rh(cod){C(PPh2)(P(S)Ph2)2-P,S}].CH2Cl2 and [RhI2(tBuNC)2{C(PPh2)P(S)Ph2)2-P,S}]

Complexes of the anionic ligand, [C(PPh2)(P(S)Ph2)2]−, are readily prepared under mild conditions by reactions of CH(PPh2)(P(S)Ph2)2, in the presence of base (NHEt2), with chlorobridged complexes, [M2Cl2(cod)2], M  Rh or Ir, cod = cycloocta-1,5-diene, [Pt2Cl4(PEt3)2], and [Pt2Cl2(MeOcod)2], MeOcod = 8-methoxy-cyclooct-4-ene-1-yl. The products are [M(cod){C(PPh2)(P(S)Ph2)2-P,S}], [PtCl(PEt3){C(PPh2)(P(S)Ph2)2-P,S}], and [Pt(MeOcod){C(PPh2)(P(S)Ph2)2-P,S}] respectively, and the platinum complexes are both mixtures of the two possible isomers. Subsequent reactions of [Rh(cod){C(PPh2)(P(S)Ph2)2-P,S}] with tBuNC followed by oxidative addition of I2 or benzyl bromide give [Rh(tBuNC)2{C(PPh2)(P(S)Ph2)2-P,S}], and isomeric mixtures of [RhI2(tBuNC)2{C(PPh2)(P(S)Ph2)2- P, S}] and [RhBr(Bz)(tBuNC)2{C(PPh2)(P(S)Ph2)2-P, S}]. The complexes were characterized primarily by 31P nuclear magnetic resonance (NMR) studies and by two crystal structure determinations. Complex 1a, [Rh(cod){C(PPh2)(P(S)Ph2)2-P,S}]·CH2Cl2 crystallized in the P21/c (No. 14) space group (Z = 4) with a = 12.294(3), b = 16.063(5), c = 21.384(5), A, β = 91.60(3)°. Complex 4a(i), [RhI2(tBuNC)2{C(PPh2)(P(S)Ph2)2-P,S}] crystallizes in the P421/c (No. 114) space group (Z = 8) with a = b = 30.174(3), c = 11.317(2) A. Both complexes contain bidentate P, S bonded ligands with the second PS group non-coordinated (“dangling”). In 1a, approximate square planar coordination about rhodium is completed by the two double bonds of a cod ligand, and in 4a(i), the P,S ligand and two cis iodides comprise the equatorial plane of an octahedron which is completed by two tBuNC ligands.

Formation of the novel bis(diphenylphosphino)methadane ligand by deprotonation of a coordinated bis(diphenyl- phosphino)methane. Crystal and molecular structure of chloro-triethylphosphine-bis(diphenylphosphino)methano- platinum(II)

Abstract [PtCl(PEt 3 )(Ph 2 PCHPPh 2 )], a complex containing the bis(diphenylphosphino)- methanide ligand, has been synthesized by reaction of NaH with [PtCl(PEt 3 )- (Ph 2 PCH 2 PPh 2 )] + and characterized by 31 P NMR and X-ray cystallography.

Fragmentation reactions of phosphido and sulphido bridged, trinuclear platinum and palladium clusters and formation of [M2(μ-PPh2)(μ-dppm)(PPh3)2]+, a new type of M(I) cation

Abstract Reactions of the trinuclear clusters, [M 3 (μ-X)(μ-PPh 2 ) 2 (PPh 3 ) 3 ] n + , M = Pd or Pt, X = H, Cl, S, SR, PPh 2 , n = 0 for S, n = 1 otherwise, with bis(diphenylphosphino)methane (dppm) and related ligands result in unusual cluster fragmentations to give a new type of M(I) cation, [M 2 (μ-PPh 2 )(μ-dppm)(PPh 3 ) 2 ] + , in which a metal—metal bond is supported by both dppm and phosphido bridges. The products indicate that the phosphido bridge is always the most robust of the set of bridging ligands.

Trifluoromethylthio and trifluorovinyl complexes of platinum(II): measurement of cis- and trans-influence by 31P and 19F nuclear magnetic resonance spectroscopy

Abstract 19 F and 31 P NMR data are reported for four series of complexes: (i) trans- [PtX(SCF 3 )(PEt 3 ) 2 ], X  C 6 H 5 , CH 3 , H, CF 3 , C 2 F 3 , CN, NO 2 , SCF 3 , N 3 , I, NCS, Br, Cl, and NO 3 . (ii) cis- [PtX(SCF 3 )(PEt 3 ) 2 ], X  CH 3 , NO 2 , SCF 3 , N 3 , NCS, NCO, and Cl. (iii) trans- [PtX(C 2 F 3 )(PEt 3 ) 2 ], X  CN, NO 2 , SCF 3 , N 3 I, Br, Cl, and NO 3 . (iv) trans- [Pt(C 2 F 3 )(PEt 3 ) 2 L][ClO 4 ], L  PEt 3 , P(OEt) 3 , P(OMe) 3 , P(OPh) 3 , PPh 3 , CO, and C 5 H 5 N. The results are used to establish scales of cis- and trans- influence for the X and L ligands and comparisons suggest that the cis- influence is much more sensitive to π-bonding, and possibly also to steric effects, than is the trans- influence. The π-bonding and steric effects are less evident when indirect coupling constants are used to measure the cis- influence and under these conditions rough inverse correlations with trans- influence may be obtained.