Synthesis and reactions of mixed N,P ligands

Article abstract of DOI:10.1002/ejic.200400607

The gold complexes [RN=C(R′)CH(R)PPh₂(AuCl)] (6a, R′ = tBu; 6b, R′ = Ad; R = SiMe₃) were synthesised from the ketimines RN=C(R′)CH(R)PPh₂ (2a, R′ = tBu; 2b, R′ = Ad; R = SiMe₃) and Me₂SAuCl. The hydrolysis of the complexes to [H₂NC(R′)=CHPPh₂(AuCl)] (8a, R′ = tBu; 8b, R′ = Ad) in protic solvents was studied and the reaction intermediate [H(R) NC(tBu)=CHPPh₂(AuCl)] (7a) was isolated. The ketimines were further reacted with PhPCl₂ to the cyclic phosphonium salts [Ph₂PP(Ph)N(H)C(R′)=CH]X (3a, R′ = tBu, X = Cl; 3c, R′ = Ad, X = Cl; 3d, R′ = Ad, X = BPh₄) and in the case of 3a oxidised with sulfur to give the ring-opened β-keto thiophosphane oxide Ph₂P(S)CH₂C(O)tBu (9). All compounds were fully characterised by NMR spectroscopy and in the case of 6b, 8a and 9 by X-ray crystallography. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005).

Full text of DOI:10.1002/ejic.200400607

FULL PAPER
Synthesis and Reactions of Mixed N,P Ligands
Richard J. Bowen,*[a,b] Manuel A. Fernandes,[a] Patricia W. Gitari,[a] Marcus Layh,*[a] and
Richard M. Moutloali[a]
Keywords: Cyclic phosphonium salts / Gold phosphane complexes / β-Keto thiophosphane oxide / Keto-enol / Imine-
enamide tautomerism
The gold complexes [RN=C(RЈ)CH(R)PPh2(AuCl)] (6a, RЈ =
tBu; 6b, RЈ = Ad; R = SiMe3) were synthesised from the keti-
mines RN=C(RЈ)CH(R)PPh2 (2a, RЈ = tBu; 2b, RЈ = Ad; R =
SiMe3) and Me2SAuCl. The hydrolysis of the complexes to
[H2NC(RЈ)=CHPPh2(AuCl)] (8a, RЈ = tBu; 8b, RЈ = Ad) in pro-
tic solvents was studied and the reaction intermediate [H(R)
NC(tBu)=CHPPh2(AuCl)] (7a) was isolated. The ketimines
were further reacted with PhPCl2 to the cyclic phosphonium
salts [Ph2PP(Ph)N(H)C(RЈ)=CH]X (3a, RЈ = tBu, X = Cl; 3c, RЈ
= Ad, X = Cl; 3d, RЈ = Ad, X = BPh4) and in the case of 3a
oxidised with sulfur to give the ring-opened β-keto thiophos-
phane oxide Ph2P(S)CH2C(O)tBu (9). All compounds were
fully characterised by NMR spectroscopy and in the case of
6b, 8a and 9 by X-ray crystallography.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2005)
centred nucleophile to prepare adamantyl derivatives of 3.
This present study was stimulated by the emergence of
interest in lipophilic cations as a new class of antitumour
drugs with the potential to selectively target mitochondria
in tumour cells.[5] Several structurally diverse lipophilic cat-
ions have demonstrated strong activity by concentrating in
mitochondria, for example, rhodamine 123,[6] dequalin-
ium,[7] pyronine Y,[8] ditercalinium,[9] AA-1[10] and MKT-
077,[11] the latter having been advanced to phase I clinical
trials. Several classes of lipophilic cations have demon-
strated that antitumour selectivity is increased as the lipo-
philic-hydrophilic balance is varied (e.g. bisquaternary am-
monium heterocycles,[12] [Au(P-P)2]+, where P-P is a bis-
phosphane[5,13] and triarylalkylphosphonium salts[14]). Con-
sequently, herein the preparation of lipophilic cations is re-
ported, that is, the cyclic phosphonium salts derived from
1 and chlorophosphane precursors. The chemistry of for-
mation and stability of these compounds is presented with
a view of evaluating their potential as a new class of antitu-
mour agent.
Introduction
While the use of 1-azaallyllithium complexes as ligand
transfer agents has received considerable attention,[1] the
development of their utility in the context of phosphorus
chemistry is in its infancy. In two recent papers,[2,3] it was
shown that treatment of the ketimine Me3SiN=C(tBu)-
CH(SiMe3)PPh2 (2a) with RЈЈЈPCl2 or PCl3 gave the cyclic
phosphonium salts [Ph2PP(RЈЈЈ)N(H)C(tBu)=CH]Cl 3 (3a,
RЈЈЈ = Ph; 3b, RЈЈЈ = Et) and [Ph2PP(Cl)N(R)C(tBu)=CH]-
Cl (R = SiMe3) 4, respectively (Scheme 1). Conversely,
treatment of the related ketimine Me3SiN=C(tBu)-
CH(SiMe3)2 (2c) with PCl3 generated the trans-1,3,2,4-di-
azadiphosphetidine 5 in moderate yield (Scheme 1). The
key ketimines 2a and 2c were formed by the reactions of
the 1-azaallyl RNC(tBu)C(Li)HR (1a) with Ph2PCl or
CF3SO3R (R = SiMe3), respectively.[2] The successful prep-
aration of compounds such as 1 is dependent on the avail-
ability of suitable 1-azaallyl precursors which react prefer-
entially as C-centred rather than N-centred nucleophiles.[4]
For an ambidentate N,C-monoanionic ligand, C- over N-
centred nucleophilicity is often favoured by utilising sol-
vent-free 1-azaallyllithium precursors.[4] The presence of
donor solvents such as tetramethylethylenediamine signifi-
cantly enhances N-nucleophilicity. In preliminary studies,
the solvent-free 1-azaallyl, RNC(Ad)C(Li)HR (Ad = ada-
mantyl) (1b), was prepared by the reaction of LiCHR2 and
AdCN in pentane under ambient conditions.[1] Conse-
quently, it was envisaged that 1b could be utilised as a C-
Results and Discussion
Synthesis
In the present study, the solvent-free 1-azaallyllithium,
RNC(Ad)C(Li)HR (1b) was prepared in high yield by the
reaction of LiCHR2 (R = SiMe3) and AdCN (Ad = ada-
mantyl) in hexane at low temperature. This type of reaction
has previously been rationalised by insertion of the alkyl-
lithium reagent into the CN bond of the organonitrile to
form a lithioaldimine, followed by a 1,3-Me3Si shift to give
the 1-azaallyl.[4] Compound 1b, behaving as a C-centred nu-
[a] Molecular Sciences Institute, School of Chemistry, University
of the Witwatersrand,
Private Bag 3, Wits, 2050, Johannesburg, South Africa
[b] Project AuTEK, Mintek,
Private Bag X 3015, Randburg 2125, South Africa
Eur. J. Inorg. Chem. 2005, 1955–1963
DOI: 10.1002/ejic.200400607
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1955

R. J. Bowen, M. A. Fernandes, P. W. Gitari, M. Layh, R. M. Moutloali
FULL PAPER
Scheme 1. Reactions of ketimines with phosphorus halides.
cleophile, was reacted with the phosphanyl chloride, the complexes [H2NC(RЈ)=C(H)PPh2(AuCl)] (Scheme 2;
Ph2PCl, to give the novel ketimine RN=C(Ad)CH(R)PPh2 8a, RЈ = tBu; 8b, RЈ = Ad) in high yields. The structure of
(2b) (i, Scheme 2) in a yield comparable to the analogous the tBu derivative was confirmed by crystallographic analy-
reaction involving RNC(tBu)C(Li)HR and chlorodiphenyl- sis. The process presumably involves cleavage of the ter-
phosphane.[2] The purification of 2b by distillation was not minal trimethylsilyl group (Scheme 2, iii), followed by a 1,3
attempted owing to reports that the corresponding tBu de- trimethylsilyl shift from C to N (Scheme 2, iv) and isomeri-
rivative, RN=C(tBu)CH(R)PPh2 (2a) isomerised to give the sation of the ketimine (the sequence of rearrangement iv
(Z)-enamine upon heating under reduced pressure, while and isomerisation v may well be reversed or a simultaneous
subsequent irradiation of the (Z)-enamine using a medium- process) to the thermodynamically favoured enamine
pressure mercury lamp afforded an equilibrium mixture of (Scheme 2, v). The latter intermediate [H(SiMe3)-
the Z and E isomers [Equation (1)].[2] Owing to the stability NC(RЈ)=CHPPh2(AuCl)] was NMR spectroscopically
that a number of transition metals can afford to phos- identified for RЈ = tBu (7a) as the major product (with 6a
phanes, by σ-donation of the ligand and backbonding from and 8a as side products) when 6a was treated with a
the metal to the vacant d-orbitals of the phosphane, the AuI mixture of diethyl ether and hexane. Hydrolysis of the re-
complex of 2b was prepared (ii, Scheme 2). The expected maining trimethylsilyl group (Scheme 2, vi) completed a
stability and linear two-coordinate geometry of the complex template-assisted synthesis of novel bidentate ligands.
was observed (6b), allowing unambiguous assignment of 2b For
comparison
the
non-hydrolysable
ketimine
as a coordinated adduct by NMR and X-ray crystallo- Ph2PCH2C(Ph)=N(C6H3Me2-2,6)[15] was reacted with Me2-
graphic analysis. Similarly, [Me3SiN=C(tBu)CH(SiMe3)- SAuCl to synthesise a N-aryl analogue of 6. The gold com-
PPh2(AuCl)] (6a) was prepared in high yield from the reac- plex was isolated in good yield (66%) and found to exist
tion of Me3SiN=C(tBu)CH(SiMe3)PPh2 (2a) and in solution as a mixture of four isomers (two tautomers
ClAuSMe2 in THF. In both cases, the 1:1 complex was analogous to the ones shown for equilibrium v in Scheme 2
formed irrespective of stoichiometry, and an excess of li- and their respective Z/E isomers). No decomposition or
gand was typically used to ensure complete complexation. change in the isomer ratio was observed in acetone solution
While enhanced thermal stabilities of the ketimines were over a period of two weeks. The described synthesis of 8
achieved by coordination of P to AuI it was found that the represents a new route to mixed P, N donor ligands with
SiMe3 group attached to N was readily hydrolysed in the C–C backbone. Typically, ligands of this sort are generated
presence of moisture (treatment of 6 with methanol) to give by the AIBN-assisted free radical-catalysed[16] (or base-cat-
1956
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Eur. J. Inorg. Chem. 2005, 1955–1963

Synthesis and Reactions of Mixed N,P Ligands
FULL PAPER
Scheme 2. Synthesis of gold phosphane complexes.
alysed[17]) addition of P–H bonds to vinylamides [e.g. (2b) is likely to involve, firstly, N-centred nucleophilic attack
CH2=C(O)NH2] or possibly the reaction of N-nucleophiles of Me3SiN=C(Ad)CH(SiMe3)PPh2 at the P atom of
to ω-chloroalkylphosphanes. The procedure reported here, PhPCl2, yielding the ketimidophosphorous(iii) chloride
beginning with C-centred nucleophilic attack of a 1-azaallyl PhP(Cl)N=C(Ad)CH(R)PPh2 with concomitant Me3SiCl
on a phosphanyl chloride, followed by template-assisted hy- elimination. Secondly, cyclisation is invoked by a rearrange-
drolysis, not only provides a route to mixed P, N donor ment (1,3-SiMe3 shift from C to N) of PhP(Cl)N=C(Ad)-
ligands, but allows for further alkyl substitution at a single CH(R)PPh2 into the isomeric enamidophosphorus(iii) chlo-
carbon atom.
ride PhP(Cl)N(R)C(Ad)=C(R)PPh2 followed by intramo-
lecular nucleophilic displacement of the chloride to give the
cyclic phosphonium salt I. Hydrolysis completes the con-
version to [Ph2PP(Ph)N(H)C(Ad)=CH]Cl (3c). Alterna-
tively, the transformation could proceed through cyclisation
of the ketimidophosphorus(iii) chloride PhP(Cl)N=C(Ad)-
CH(R)PPh2, to give the cycloketimidophosphonylphos-
phonium salt [Ph2PP(Ph)N=C(Ad)CHR]Cl II, which sub-
sequently undergoes rearrangement to I and hydrolysis to
complete the process.
(1)
Since the reaction of Me3SiN=C(tBu)CH(SiMe3)PPh2
(2a) with RЈЈЈPCl2 proceeded to give the cyclic phospho-
nium salts [Ph2PP(RЈЈЈ)N(H)C(tBu)=CH]Cl (Scheme 1,
RЈЈЈ = Ph, 3a or Et, 3b),[2] the Ad-substituted analogue,
[Ph2PP(Ph)N(H)C(Ad)=CH]Cl (3c) was prepared by a sim-
ilar reaction involving Me3SiN=C(Ad)CH(SiMe3)PPh2 (2b)
Fulfilment of the requirement of stability is necessary be-
and PhPCl2, albeit in lower yield. In a process that was used fore proceeding with biological evaluations. While isolation
to rationalise the formation of the tBu-substituted cyclic and characterisation of the cyclic phosphonium salts were
phosphonium salts,[2] the formation of [Ph2PP(Ph)N(H)- possible under inert gas conditions, instability of the five-
C(Ad)=CH]Cl (3c) from Me3SiN=C(Ad)CH(SiMe3)PPh2 membered ring (a solution of 3c in CDCl3 decomposed
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R. J. Bowen, M. A. Fernandes, P. W. Gitari, M. Layh, R. M. Moutloali
FULL PAPER
within 24 h completely into two major products on expo- reformation is accompanied by the elimination of ammonia
sure to moist air) necessitated strategies to attempt to in- (Scheme 3, iv), with enol-keto tautomerism (Scheme 3, v)
duce stability. Consequently, metathesis reactions involving completing the envisaged reaction pathway involving the
replacement of the chloride with bulkier anions were under- formation of Ph2P(S)CH2C(O)tBu (9) from [Ph2PP(Ph)-
taken. The reaction of [Ph2PP(Ph)N(H)C(Ad)=CH]Cl (3c) N(H)C(tBu)=CH]Cl. Reaction of 3c with oxygen-free water
with NaBPh4 proceeded almost quantitatively to give in CH2Cl2 resulted in a solid that showed two major signals
[Ph2PP(Ph)N(H)C(Ad)=CH]BPh4 (3d), while the synthesis at δ = 22.5 and 23.3 ppm in the 31P NMR spectrum that
–
–
–
of related compounds with NO3 , CH3CO2 , BF4– or ClO4
were within 1 ppm identical to those found in the above-
as counterion from 3c and the corresponding silver salts mentioned decomposition study of 3c in CDCl3. This impli-
was unsuccessful. 31P NMR analysis of 3d, however, re- cates the reaction with water as a major reason for the in-
vealed that the instability under atmospheric conditions was stability of the phosphonium salts. Attempts to isolate the
persistent, with decomposition of the five-membered ring products were unsuccessful and a mass spectrum of the pro-
being particularly rapid in foetal calf serum (fcs) containing duct mixture was inconclusive. The further reaction of 3c
cell-culture medium. Subsequently, in an attempt to acquire with dry oxygen yielded after removal of the solvent a solid
an insight into the factors which were responsible for this that consisted of a mixture of numerous compounds with
decomposition, a reaction was undertaken with [Ph2PP- unreacted starting material being one of the major compo-
(Ph)N(H)C(tBu)=CH]Cl (3a) and one equivalent of sulfur nents. The mass spectrum of the mixture showed m/z values
in dichloromethane, since thiol-containing compounds are consistent with 3c and an oxygen analogue [Ph2P(O)-
constituents of fcs and the interaction with sulfur is a rea- CH2C(O)Ad] of 9. The persistent instability of the phos-
sonable comparison for the observed oxygen- and moisture- phonium salts under atmospheric conditions precluded fur-
facilitated decomposition pathways. Removal of the solvent ther biological testing and further development as potential
in vacuo, and recrystallisation of the crude product from antitumour drugs is at this stage doubtful.
propan-1-ol, gave colourless crystals in good yield. Crystal-
lographic analysis of the product revealed that a rare exam-
ple of a β-keto thiophosphane, i.e. Ph2P(S)CH2C(O)tBu (9)
was obtained. It is plausible that the formation of the β-
Solid-State Structures of Compounds 6b, 8a and 9
keto thiophosphane oxide involved initial sulfuration of the
The molecular structures of [RN=C(Ad)CH(R)-
quarternary P and concomitant P–P bond scission of the PPh2(AuCl)] (6b) (R = SiMe3) and [H2NC(tBu)=C(H)-
cyclic phosphonium salt [Ph2PP(Ph)N(H)C(tBu)=CH]Cl to PPh2(AuCl)] (8a) with the atom numbering scheme are
give an intermediary chlorophosphane Ph2P(S)CH=C- shown in Figure 1 and Figure 2, while selected bond lengths
(tBu)N(H)P(Ph)Cl (Scheme 3, i). Facile elimination of are compared in Table 1. Complex 6b crystallises as a dis-
ClPPhOPr or a related species (Scheme 3, ii), followed by crete monomer with the Au atom adopting a linear geome-
nucleophilic attack of water on the tBu-substituted carbon try [P–Au–Cl 178.74(9)°]. The Au–P and Au–Cl distances
in a Michael-type addition reaction (the related PIII com- of 2.245(2) and 2.296(2) Å are unexceptional and compare
pounds 8 in Scheme 2 are in contrast unreactive) produces well to those found in related two-coordinate phosphane
a zwitterionic intermediate (Scheme 3, iii) whose negative complexes
such
as
iBu3PAuCl,[18]
Et3PAuCl,[19]
charge is stabilised by the P=S double bond. Ethene bond Ph3PAuCl,[20] (2-Pyr)3PAuCl[21] or iPr3PAuCl.[22] The short
Scheme 3. Possible reaction mechanism for the formation of 9.
1958
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Eur. J. Inorg. Chem. 2005, 1955–1963

Synthesis and Reactions of Mixed N,P Ligands
FULL PAPER
C2–N [1.266(6) Å] and long C1–C2 [1.558(6) Å] distances Table 1. Selected bond lengths [Å] and angles [°] for compound 6b,
8a and 9.
are consistent with the alkyl substituent at P being an imi-
noalkyl. There is considerable steric repulsion between the
bulky adamantyl and trimethylsilyl groups attached to the
two sp2 hybridised atoms C2 and N, respectively, as is evi-
dent from the deviation of the angles C3–C2–N [123.9(4)°] P–C1
and C2–N–Si3 [151.9(4)°] from the idealised geometry of
Bond length/angle
6b
8a
9
Au/S–P
Au–Cl
2.245(2)
2.296(2)
1.825(6)
1.838(5)
1.830(6)
1.266(6)
1.558(6)
178.74(6)
2.243(2)
2.295(2)
1.777(7)
1.837(7)
1.819(6)
1.369(9)
1.361(9)
177.24(6)
1.9563(9)
–
1.822(2)
1.820(2)
1.821(2)
1.209(3)
1.523(3)
–
P–C[a]
P–C[b]
120°.
N/O–C2
C1–C2
P–Au–Cl
[a] C = carbon C19 (6b); carbon C7 (8a, 9). [b] C = carbon C25
(6b); carbon C13 (8a, 9).
veral recent papers[24] and a C–H···Cl distance of close to
3 Å has been suggested as reasonable.[24a] The closest con-
tact in compound 6b (C9–H9B···Cl: 2.94 Å, 148°) is in com-
parison considerably longer. In this context it is noteworthy
that the distance between the methyl group (C4) involved
in non-classical H-bonding and the central carbon atom of
the tBu group (C3) in 8a [1.54(1) Å] is longer than those to
the non-hydrogen-bonded methyl groups [1.52(1),
1.50(1) Å].
Figure 1. Molecular structure of ClAuPPh2CH(SiMe3)C(Ad)-
NSiMe3 (6b). Thermal ellipsoids are drawn at the 50% probability
level. H atoms have been omitted for clarity.
Figure 2. Molecular structure of ClAuPPh2CHC(tBu)NH2 (8a).
Thermal ellipsoids are drawn at the 50% probability level. H atoms
(except at N, C1) have been omitted for clarity.
Figure 3. H bonding and intermolecular contacts in compound 8a.
(For symmetry codes see Table 2).
Compound 8a crystallises as a centrosymmetric dimer
The bond lengths and geometry of the Au atom [Au–
(Figure 3) as a consequence of conventional hydrogen P: 2.243(2) Å, Au–Cl: 2.295(2) Å, P–Au–Cl 177.24(6)°] in
bonding between the Cl and NH2 groups of adjacent mole- complex 8a are similar to those in complex 6b. The short
cules hereby forming a 14-membered heterocycle R22(14). CN single bond [C1–N 1.369(9) Å] and comparatively long
The Cl···N contacts [3.345(7) Å] are close to the mean value CC double bond [C1–C2 1.361(9) Å] in the phosphane sub-
of 3.299(6) Å reported in the literature.[23] The dimers are stituent indicate considerable delocalisation within the en-
further weakly hydrogen-bonded by short C–H···Cl interac- amine backbone (Z isomer) of the ligand that may extend
tions (C4–H4···Cl: 2.76 Å, 172°) between the Cl atom and to some degree to the phosphorus atom (c.f. short P–C1 as
one of the methyl groups of the tBu substituent in the back- compared to long P–Ph distances).
bone of an adjacent dimer (Figure 3, Table 2). The existence
of C–H···Cl (H···A) interactions has been discussed in se- influence the solid-state structures of gold phosphane com-
Aurophilic Au···Au contacts[25] that have been found to
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R. J. Bowen, M. A. Fernandes, P. W. Gitari, M. Layh, R. M. Moutloali
FULL PAPER
Table 2. Intermolecular contact distances [Å] and angles [°] for plexes[26] in the case of less bulky phosphanes are not ob-
compounds 8a and 9.
served in compound 6b or 8a.
The molecular structure of compound 9 and the atom
numbering scheme is illustrated in Figure 4. The bond
lengths and angles (Table 1) are unexceptional and compare
well to the related dimethyl and diphenylphosphane sulfides
D–H···A
D–H
H···A
D···A
D–H···A
Compound 8a
N–H2B···Cl[a]
0.86
0.96
2.57
2.76
3.345(7)
3.717(13) 172
151
C4–H4···Cl[b]
Me2P(S)C(Me)OHC(O)Me,[27]
Me2P(S)C(Ph)OHC(O)-
Compound 9
Ph[27] and Ph2P(S)CHC(O)(CH2)4.[28] The PS and CO
groups are not coplanar as indicated by an angle of 71.5(2)°
between the two planes formed by the atoms S, P, Cl
and C1, C2, O. This facilitates weak intermolecular
C–H(Ph)···O and C–H(CH2)···S interactions (Table 2) be-
tween adjacent molecules of 9 (Figure 5). There is also a
close contact between C5 and O (C5···O: 3.130 Å).
C1–H1A···S[c]
0.99
0.95
2.80
2.42
3.755(2)
3.241(3)
163
145
C15–H15···O[d]
[a] Symmetry codes: –x + 1, –y + 1, –z. [b] x, 1 + y, z. [c] x, –y,
–1/2 + z. [d] 1/2 + x, –1/2 + y, z.
Experimental Section
All manipulations were carried out under argon, using standard
Schlenk techniques. Solvents were distilled from drying agents and
degassed. The NMR spectra were recorded in CDCl3, [D6]acetone
and [D6]DMSO at ambient probe temperature by using the follow-
ing Bruker instruments: DRX 400 (1H 400.13; 31P 161.9; 13C
100.6 MHz), Avance 300 (1H 300.13; 13C 75.5 MHz) or AC200 (1H
200.13 MHz) and referenced internally to residual solvent reso-
nances (chemical shift data in δ). 13C and 31P NMR spectra were
all proton-decoupled. Elemental analyses were determined by the
Institute for Soil, Climate and Water, Pretoria, South Africa. The
following abbreviations are used throughout the experimental sec-
tion: s = singlet, br. s = broad singlet, d = doublet, dd = doublet
of doublet, m = multiplet, mm = multiple multiplets. Coupling con-
stants (J) are given in Hz.
Synthesis of Me3SiNC(Ad)CH(SiMe3)PPh2 (2b): Ph2PCl (0.38 g,
1.71 mmol) in hexane (15 cm3) was added dropwise to a magneti-
cally stirred solution (–80 °C) of the 1-azaallyllithium complex 1b
(0.56 g, 1.71 mmol) in hexane (30 cm3). After stirring for 12 hours,
the solution was filtered and the solvent removed in vacuo to give
Figure 4. Molecular structure of Ph2P(S)CH2C(O)tBu (9). Thermal
ellipsoids are drawn at the 50% probability level. H atoms (except
at C1) have been omitted for clarity.
1
2b as a yellow oil (0.73 g, 80%). H NMR (CDCl3): δ = –0.04 (s,
9 H, CSiMe3), 0.28 (s, 9 H, NSiMe3), 1.25–1.83 (mm, 15 H, Ad),
2
3.95 [d, JH,P = 6.1 Hz, 1 H, CH] and 7.19–7.74 (mm, 10 H, Ph)
ppm. 31P NMR (CDCl3): δ = –2.1 ppm. 13C NMR (CDCl3): δ =
0.4 (s, CSiMe3), 0.5 (s, NSiMe3), 28.6 (s, CH-Ad), 36.5 (s, CH2-
1
Ad), 31.6 (s, ipso-C-Ad), 38.9 [d, JC,P = 27.3 Hz, CH], 39.5 (s,
CH2-Ad), 127.7 [d, 3JC,P = 7.1 Hz, m-Ph ], 128.2 [d, 3JC,P = 7.7 Hz,
2
m-Ph ], 128.5 (s, p-Ph), 129.0 (s, p-Ph), 134.3 [d, JC,P = 21.8 Hz,
2
1
o-Ph], 134.6 [d, JC,P = 19.1 Hz, o-Ph], 138.7 [d, JC,P = 16.3 Hz,
1
2
ipso-C], 140.3 [d, JC,P = 28.5 Hz, ipso-C] and 183.1 [d, JC,P
=
2.2 Hz, CN] ppm.
Synthesis of Ph2P+P(Ph)N(H)C(Ad)CH Cl– (3c): PhPCl2 (0.57 g,
3.16 mmol) was added to Me3SiN=C(Ad)CH(SiMe3)PPh2 (2b)
(1.60 g, 3.16 mmol). After complete addition, the mixture was
heated at 50 °C for 30 min. It liquefied as the ClSiMe3 was given
off. The mixture was then dried in vacuo to give a yellow solid
(1.43 g, 90%). C27H32ClNP2: calcd. C 69.30, H 6.85, N 2.99; found
C 68.52, H 6.87, N 2.47 (the compound incorporates varying
amounts of toluene). Pale yellow crystals were obtained from hot
1
toluene (0.40 g, 25%). H NMR (CDCl3): δ = 1.71–1.84 (mm, 15
2
H, Ad), 4.63 [d, JH,P = 15.6 Hz, 1 H, NH], 6.90–7.20 (mm, 5 H,
2
3
Ph), 7.38–7.87 (mm, 10 H, Ph) and 9.99 [dd, JH,P = 32.0, JH,P
=
=
21.2 Hz, 1 H, CH] ppm. 31P NMR (CDCl3): δ = 13.5 [d, JP,P
1
239.2 Hz, λ3P], 41.9 [d, JP,P = 239.2 Hz, λ4P+] ppm. 13C NMR
1
Figure 5. Intermolecular contacts in compound 9. (For symmetry
codes see Table 2).
3
(CDCl3): δ = 28.3 (s, CH-Ad), 36.2 (s, CH2-Ad), 40.4 [d, JC,P
=
1960
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2005, 1955–1963

Synthesis and Reactions of Mixed N,P Ligands
11.3 Hz, ipso-C-Ad], 41.0 (s, CH2-Ad), 64.1 [d, JC,P = 72.9 Hz,
FULL PAPER
1
1
3
8.5 Hz, CMe3], 86.4 [d, JC,P = 72.3 Hz, CH], 129.1 [d, JC,P
11.7 Hz, m-Ph], 131.2 [d, JC,P = 84.5 Hz, ipso-C], 131.4 [d, JC,P
=
1
2
1
4
CH], 118.1, [d, JC,P = 82.5 Hz, ipso-C ], 124.2 [dd, JC,P = 75.0,
3JC,P = 18.8 Hz, ipso-C], 125.2 (s, ipso-C), 128.7 (mm of aromatic
= 2.6 Hz, p-Ph], 133.2 [d, JC,P = 13.6 Hz, o-Ph] and 173.3 (s, CN)
2
2
3
C atoms) and 186.8 [overlapping dd, JC,P = 27.9, JC,P = 14.4 Hz,
ppm.
CN] ppm.
Synthesis of ClAuPPh2C(H)C(tBu)NH2 (8a): ClAuPPh2CHC(tBu)-
N(H)SiMe3 (7a) was dissolved in hot methanol. Colourless crys-
tals of 8a (0.06 g, 14%) were obtained after slow cooling of the
solution at room temperature. C18H22AuClNP: calcd. C 41.92, H
Synthesis of Ph2P+P(Ph)N(H)C(Ad)CH BPh4 (3d): NaBPh4
–
(0.37 g, 1.08 mmol) was added to a magnetically stirred solution of
CH2Cl2 (20 cm3) and Ph2P+P(Ph)N(H)C(Ad)CH Cl– (3c) (0.54 g,
1.07 mmol) at –30 °C. The reaction mixture was stirred for 12 hours
and warmed to room temperature giving an off-white solution. It
was filtered and the solvent removed in vacuo to give a yellow solid.
Various recrystallisation attempts led to the decomposition of the
1
4.30, N 2.72; found C 41.20, H 4.33, N 2.70. H NMR (CDCl3): δ
2
= 1.23 (s, 9 H, tBu), 4.32 [d, JH–P = 8.8 Hz, 1 H, CH], 4.82 (br. s,
2 H, NH2), 7.44 (6 H, Ph) and 7.57–7.63 (mm, 4 H, Ph) ppm. 31P
NMR (CDCl3): δ = 7.1 ppm. 13C NMR (CDCl3): δ = 29.1 (s,
3
1
1
CMe3), 37.2 [d, JC,P = 9.8 Hz, CMe3], 72.8 [d, JC,P = 71.9 Hz,
compound. 3d (crude: 0.76 g, 92%). H NMR (CDCl3): δ = 1.57–
3
4
1.89 (mm, 15 H, Ad), 4.64 [d, 1 H, 2JH,P = 15.3 Hz, NH], 6.00 [dd,
CH], 129.0 [d, JC,P = 11.7 Hz, m-Ph], 131.2 [d, JC,P = 2.3 Hz, p-
Ph], 131.9 [s, ipso-C], 132.9 [d, JC,P = 13.5 Hz], o-Phand 168.9 (s,
2
2JH,P = 22.0, JH,P = 8.0 Hz, 1 H, CH], 6.84–7.10 (mm, 5 H, Ph)
3
and 7.36–7.64 (mm, 10 H, Ph) ppm. 31P NMR (CDCl3): δ = 10.8
CN) ppm.
[d, 1JP,P = 241.4 Hz, λ3P], 43.8 [d, 1JP,P = 241.4 Hz, λ4P+] ppm. 13
C
Crude 6a (0.45 g, 0.68 mmol) was dissolved in methanol (20 cm3)
and after a period of 5 minutes a white precipitate started to form.
After stirring the reaction mixture for 30 minutes at room tempera-
ture the solvent was carefully decanted and the residue dried in
vacuo to give 0.31 g (88%) of 8a.
NMR (CDCl3): δ = 28.0 (s, CH-Ad), 36.0 (s, CH2-Ad), 39.8 (s,
1
ipso-C-Ad), 41.0 (s, CH2-Ad), 66.4 [d, JC,P = 71.4 Hz, CH], 117.3
1
1
[d, JC,P = 81.0 Hz, ipso-C], 121.7 (s, BPh), 122.4 [d, JC,P
=
32.5 Hz, ipso-C], 125.5 (s, BPh), 129.2 [d, JC,P = 5.6 Hz, Ph], 129.5
[d, JC,P = 19.0 Hz, Ph], 130.3 [d, JC,P = 12.6 Hz, Ph], 132.8 [d, JC,P
= 10.4 Hz, Ph], 136.3 (s, BPh), 164.2 [q, JC,B = 49.3 Hz, ipso-C]
Synthesis of ClAuPPh2C(H)C(Ad)NH2 (8b): ClAuPPh2CH(SiMe3)
C(Ad)NSiMe3 (6b) was dissolved in hot methanol. It was cooled
slowly and yielded 8b (0.13 g, 65%) as a pale yellow powder.
1
2
and 184.8 [d, JC,P = 13.0 Hz, CN] ppm.
Synthesis
ClAuSMe2
of
ClAuPPh2CH(SiMe3)C(tBu)NSiMe3
(6a): C24H28AuClNP: calcd. C 48.50, H 4.75, N 2.36; found C 48.33, H
[29]
(0.24 g, 0.82 mmol) was added to a solution of
4.85, N 2.27. 1H NMR (CDCl3): δ = 1.67–1.83 (mm, 15 H, ada-
2
Ph2PCH(SiMe3)C(tBu)NSiMe3 (2a) (0.30 g, 0.85 mmol) in THF mantyl), 4.28 [d, JH–P = 9.1 Hz, 1 H, CH], 4.81 (br. s, 2 H, NH2),
(10 cm3) at 0 °C. The solution was stirred at 0 °C for 10 minutes,
warmed to room temperature and stirred for further 15 minutes.
The solvent was removed in vacuo to yield a sticky yellow com-
7.42–7.44 (mm, 6 H, Ph) and 7.56–7.64 (mm, 4 H, Ph) ppm. 31P
NMR (CDCl3): δ = 7.1 ppm. 13C NMR (CDCl3): δ = 28.4 (s, CH-
Ad), 36.5 (s, CH2-Ad), 38.9 [d, 3JC,P = 9.5 Hz, ipso-C, Ad), 40.9 (s,
pound (6a, 0.45g, 83%). 1H NMR (CDCl3): δ = 0.17 (s, 9 H, CH2-Ad), 72.5 [d, JC,P = 72.0 Hz, CH], 129.0 [d, JC,P = 11.8 Hz,
1
3
2
4
CSiMe3), 0.33 (s, 9 H, NSiMe3), 0.88 (s, 9 H, tBu), 4.46 [d, JH,P m-Ph], 131.2 [d, JC,P = 2.5 Hz, p-Ph], 132.1 (s, ipso-C), 132.9 [d,
= 15.8 Hz, 1 H, CH] and 7.44 –7.81 (mm, 10 H, Ph) ppm. 31P
2JC,P = 13.4 Hz, o-Ph] and 169.1 (s, CN) ppm.
Synthesis of ClAuPPh2CH2C(Ph)N(C6H3Me2-2,6):
ClAuPPh2CH2C(Ph)N(C6H3Me2-2,6) was obtained from
NMR (CDCl3): δ = 40.7 ppm. 13C NMR (CDCl3): δ = 0.8 [d, 3JC,P
1
= 4.3 Hz, CSiMe3], 3.1 (s, NSiMe3), 29.0 (s, CMe3), 38.8 [d, JC,P
= 30.4 Hz, CH], 43.6 (s, CMe3), 128.5 [d, JC,P = 11.6 Hz, o-Ph],
131.0 [d, JC,P = 9.9 Hz, m-Ph], 131.8 [d, JC,P = 2.4 Hz, , p-Ph],
132.8 [d, 1JC,P = 79.0 Hz, ipso-C] and 179.4 [d, 2JC,P = 6.0 Hz, CN]
ppm.
2
PPh2CH2C(Ph)N(C6H3Me2-2,6)[15] (0.18 g, 0.44 mmol) and
ClAu(SMe2) (0.11 g, 0.38 mmol) following the same procedure as
described for compound 6. The solvent was removed and the resi-
due recrystallised by layering a toluene solution of the title com-
3
4
pound
with
hexane
(approx.
ratio
a
1:4)
yielding
Synthesis
ClAuSMe2
of
ClAuPPh2CH(SiMe3)C(Ad)NSiMe3
(6b):
[29]
ClAuPPh2CH2C(Ph)N(C6H3Me2-2,6) as
colourless powder
(0.30 g, 1.02 mmol) was added to a solution of
(0.16 g, 66%). In solution the compound was found to exist as a
mixture of two tautomers and their respective Z/E isomers (the
ratio is given in bracket):
Ph2PCH(SiMe3)C(Ad)NSiMe3 (2b) (0.78 g, 1.54 mmol) in THF
(20 cm3) at 0 °C. The solution was stirred for 15 minutes and the
solvent was removed in vacuo to yield a yellow solid. Colourless
crystals of 6b (0.25 g, 33%) were obtained from CH2Cl2 at –60 °C.
ClAuPPh2CH2C(Ph)=N(C6H3Me2-2,6). Major Isomer (4): 1H
1H NMR (CDCl3): δ = 0.07 (s, 9 H, CSiMe3), 0.25 (s, 9 H,
2
NMR (CDCl3): δ = 1.73 (s, 6 H, Me), 3.86 (d, JH–P = 13.5 Hz, 2
2
H, CH) ppm. 31P NMR (CDCl3): δ = 23.8 ppm. 13C NMR ([D6]
NSiMe3), 1.26–1.86 (mm, 15 H, adamantyl), 4.37 (d, JH,P
=
1
15.9 Hz, 1 H, CH), 7.41–7.43 (mm, 6 H, Ph), 7.71–7.74 (mm, 2 H,
acetone) (only CH2 and CN are assigned): δ = 39.9 [d, JC,P
=
Ph) and 7.92–7.98 (mm, 2 H, Ph) ppm. 31P NMR (CDCl3): δ =
44 Hz, CH], 165.5 (s, CN) ppm. Minor Isomer (3): 1H NMR
3
40.9 ppm. 13C NMR (CDCl3): δ = 1.0 [d, JC,P = 4.0 Hz, CSiMe3],
2
(CDCl3): δ = 1.88 (s, 6 H, Me), 4.24 (d, JH–P = 9.9 Hz, 2 H, CH)
1
ppm. 31P NMR (CDCl3): δ = 25.8 ppm. 13C NMR ([D6]acetone):
3.7 (s, NSiMe3), 28.5 (s, CH-Ad), 36.2 (s, CH2-Ad), 37.6 [d, JC,P
= 30.2 Hz, CH], 39.6 (s, CH2-Ad), ipso-C-Ad not observed, 128.5
not observed.
3
4
[d, JC,P = 11.7 Hz, m-Ph], 131.3 [d, JC,P = 2.8 Hz, p-Ph], 132.3
ClAuPPh2CH=C(Ph)N(H)(C6H3Me2-2,6). Major Isomer (8): 1H
NMR (CDCl3): δ = 2.33 (s, 6 H, Me), 4.33 (d, 2JH–P = 5.3 Hz, 1 H,
CH), 5.64 (d, 4JH–P = 3.3 Hz, 1 H, NH) ppm. 31P NMR (CDCl3): δ
= 17.9 ppm. 13C NMR ([D6]acetone) (only CH and CN are as-
1
2
[d, JC,P = 79.9 Hz, ipso-C], 134.3 [d, JC,P = 14.2 Hz, o-Ph] and
179.5 (s, CN) ppm.
Synthesis of ClAuPPh2CHC(tBu)N(H)SiMe3 (7a): ClAuPPh2CH-
(SiMe3)C(tBu)NSiMe3 (6a) was dissolved in a mixture of ether/
1
2
signed): δ = 78.9 [d, JC,P = 87 Hz, CH], 163.3 (d, JC,P = 21 Hz,
hexane. A yellow powder of 7a (0.37 g, 66%) was obtained at CN) ppm. Minor Isomer (1.2): 1H NMR (CDCl3): δ = 2.11 (s, 6 H,
1
–60 °C. H NMR (CDCl3): δ = 0.14 (s, 9 H, SiMe3), 1.23 (s, 9 H,
Me), 4.74 (d, 2JH–P = 9.9 Hz, 1 H, CH), 6.55 (br. s, 1 H, NH) ppm.
tBu), 4.33 [d, 2JH–P = 5.6 Hz, 1 H, CH], 4.81 [br. s, 1 H, NH], 7.42– 31P NMR (CDCl3): δ = 8.8 ppm. 13C NMR ([D6]acetone): not ob-
7.69 (mm, 10 H, Ph) ppm. 31P NMR (CDCl3): δ = 10.6 ppm. 13C
served. FAB-Mass spectrum: m/z (%) = 1243 (21) [(M+)2 – Cl], 639
3
NMR (CDCl3): δ = 2.5 (s, SiMe3), 29.8 (s, CMe3), 38.3 [d, JC,P
=
(20) [M+], 604 (92) [M+ – Cl].
Eur. J. Inorg. Chem. 2005, 1955–1963
www.eurjic.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1961

R. J. Bowen, M. A. Fernandes, P. W. Gitari, M. Layh, R. M. Moutloali
FULL PAPER
Table 3. Crystal data and refinement for compounds 6b, 8a and 9.
Compound
6b
8a
9
Empirical formula
M
C30H44AuClNPSi2
738.23
C18H22AuClNP
515.75
C18H21OPS
316.38
T [K]
Wavelength [Å]
293(2)
0.71073
293(2)
0.71073
173(2) K
0.71073
Crystal system
Space group
monoclinic
P21/n
triclinic
P-1
monoclinic
Cc
a [Å]
b [Å]
c [Å]
α [°]
13.630(3)
16.154(3)
14.574(3)
90
93.783(4)
90
3201.9(11)
4
8.841(6)
16.2497(19)
9.8721(11)
10.9257(12)
90
98.304(2)
90
1734.3(3)
4
1.212
10.228(7)
11.224(7)
68.113(11)
89.650(12)
86.744(12)
940.1(11)
2
β [°]
γ [°]
V [Å3]
Z
D(calcd.) [Mg/m3]
1.531
4.822
1.822
8.047
μ [mm–1]
0.276
F(000)
1480
0.36×0.09×0.06
18516
6273 [R(int.) = 0.074]
6273/0/332
0.932
496
672
Crystal size [mm3]
Reflections collected
Independent reflections
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I Ͼ 2σ(I)]
0.26×0.22×0.04
6345
4426 [R(int.) = 0.062]
4426/0/202
1.032
0.56×0.10×0.09
5906
3054 [R(int.) = 0.024]
3054/2/193
0.971
R1 = 0.030, wR2 =
0.064
R1 = 0.037, wR2 = 0.075
R1 = 0.040, wR2 = 0.099
R indices (all data)
R1 = 0.072, wR2 = 0.084
R1 = 0.052, wR2 = 0.105
R1 = 0.039, wR2 =
0.067
Extinction coefficient
–
–
0.04(6)
0.26 and –0.16
Largest diff. peak and hole [e·Å–3]
1.25 and –0.80
2.34 and –1.24
Synthesis of Ph2P(S)CH2C(O)tBu (9): Sulfur (0.026 g, 0.81 mmol)
was added to a magnetically stirred solution of Ph2P+P(Ph)N(H)
C(tBu)CH Cl– (3a) (0.33 g, 0.77 mmol) in CH2Cl2 (15 cm3) at
–30 °C. The colourless solution was stirred for 12 hours at room
temperature; the solvent was then removed in vacuo to yield a white
compound. Colourless crystals of 9 (0.15 g, 61%) were obtained
from propanol at –60 °C. Melting point: 210–212 °C. Mass spec-
trum: m/z = 316 (85) [M+], 259 (15) [M+ – tBu], 231 (65)
[Ph2PSCH2]. 1H NMR (DMSO): δ = 1.07 (s, 9 H, tBu), 4.32 [d,
2JH–P = 13.1 Hz, 2 H, CH2], 7.47–7.52 (mm, 6 H, Ph) and 7.88–
7.95 (mm, 4 H, Ph) ppm. 31P NMR (DMSO): δ = 38.9 ppm. 13C
NMR (DMSO): δ = 25.3 (s, CMe3), 26.1 [d, 1JC,P = 76.1 Hz, CH2],
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
Acknowledgments
The authors thank CANSA, Mintek (project AuTEK) and the
University of the Witwatersrand for financial support.
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graphic data are summarised in Table 3. Diagrams and publication
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ORTEP3.[33]
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© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2005, 1955–1963

Synthesis and Reactions of Mixed N,P Ligands
FULL PAPER
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Received: July 14, 2004
Eur. J. Inorg. Chem. 2005, 1955–1963
www.eurjic.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1963