Novel syntheses of heterodinuclear phosphaalkenyl complexes: X-ray structure of [Ru{P(AuPPh3)=CHBut}Cl2(CO)(PPh 3)2]

Article abstract of DOI:10.1039/a606987h

The reaction of [Ru(P=CHBu^t)Cl(CE)(PPh₃)₂] (E = O, S) with [AuX(PPh₃)] (X = Cl, C≡CC₆H₄Me-4), HgCl₂ or Hg₂Cl₂ leads via addition of the Au-X or Hg-Cl bonds

Full text of DOI:10.1039/a606987h

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Novel syntheses of heterodinuclear phosphaalkenyl complexes: X-ray structure
of [Ru{P(AuPPh3)NCHBut}Cl2(CO)(PPh3)2]
Robin B. Bedford,a Anthony F. Hill,*†a Cameron Jones,*‡b Andrew J. P. White,c David J. Williamsc and
James D. E. T. Wilton-Elya
a Department of Chemistry, Imperial College of Science, Technology and Medicine, South Kensington, London, UK SW7 2AY
b Department of Chemistry, University of Wales, Swansea Singleton Park, Swansea, UK SA2 8PP
c Chemical Crystallography Laboratory, Department of Chemistry, Imperial College of Science, Technology and Medicine, South
Kensington, London, UK SW7 2AY
The reaction of [Ru(PNCHBut)Cl(CE)(PPh3)2] (E = O, S)
with [AuX(PPh3)] (X = Cl, C·CC6H4Me-4), HgCl2 or
Hg2Cl2 leads via addition of the Au–X or Hg–Cl bonds
across the Ru–P linkage to the heterodinuclear phosphaal-
kene complexes [Ru{P(AuPPh3)NCHBut}ClX(CE)(PPh3)2]
and [Ru{P(HgCl)NCHBut}Cl2(CE)(PPh3)2].
spectroscopic§ and crystallographic¶ data (Scheme 2, Fig. 1).
Most informative amongst the spectroscopic data is the upfield
shift of the 31P NMR signal associated with the phosphaalkenyl
ligand from d 450.4 in 1a to d 319.4 in 3a. This resonance
appears as a double triplet as a result of coupling to the
phosphine phosphorus nuclei bound to gold [J(PP) 268.5 Hz]
and ruthenium [J(PPA) 29.6 Hz]. The former suggests an
essentially trans P–Au–P linkage, whilst the latter is con-
Mononuclear phosphaalkenyl complexes remain rare.1 Never-
theless, our recent observation2 that hydroruthenation of
phosphaalkynes provides an exceptionally facile entry into such
compounds should presage a substantial broadening of the field.
Polynuclear phosphaalkenyl complexes remain unknown, and
only one example of a dinuclear complex has been structurally
characterised, resulting from the reaction of the kinetically
stabilised phosphaalkene ClPNC(SiMe3)2 with Collman’s re-
agent.3 The remaining examples involve the reactions of
[W{PNC(R)SiMe3}(CO)3(h-C5H5)] (R = Ph, SiMe3) with
[Fe2(CO)9], [Ni(CO)4] or [AuCl(PPh3)].4 In these reactions the
lone pair of the phosphaalkenyl ligand coordinates to Fe(CO)4,
Ni(CO)3 or AuCl fragments via a simple dative two-electron
interaction. It is this aspect of phosphaalkenyl coordination
chemistry with which this report is concerned, in illustrating for
the first time the 1,2-addition of metal–halide and metal–carbon
bonds across the P–C multiple bond of a phosphaalkenyl
complex. This approach converts the three-electron phos-
phaalkenyl ligand into a formally neutral metallated phos-
phaalkene (Scheme 1). This has allowed the first structural
characterisation of a heterobimetallic phosphaalkenyl com-
plex.
R
L
L
R
EC
EC
Cl
P
P
H
i
Ru
L
Ru
L
Cl
Cl
ii
1
2
3
R
L
iii
EC
Cl
P
Au
Au
L
L
iv
Ru
L
Cl
R
R
L
L
EC
Cl
EC
P
Hg L
P
Ru
L
Ru
L
Cl
C
Cl
C
R'
5
4
Scheme 2 (L = PPh3, R = CMe3, RA = C6H4Me-4, E = O, S). Reagents
and conditions: i, HCl; ii, [AuCl(L)]; iii, [Au(C·CRA)L]; iv, Hg2Cl2 or
HgCl2.
The nucleophilicity of the phosphaalkenyl ligand in the
complex [Ru(PNCHBut)Cl(CO)(PPh3)2] 1a has been recently
demonstrated in its reactivity with HCl to provide the
phosphaalkene complex [Ru(HPNCHBut)Cl2(CO)(PPh3)2] 2.2
Over the last decade, guided by isolobal considerations the
+
fragment AuPPh3 has come to be viewed as the cluster
chemist’s proton. Within this context, it is therefore noteworthy
that the reaction of 1a with [AuCl(PPh3)] leads to the smooth
and high yield conversion of 1a to a complex formulated as
[Ru{P(AuPPh3)NCHBut}Cl2(CO)(PPh3)2] 3a on the basis of
P(45)
Cl(67)
P(20)
LnM
R
R
R
R
Cl(66)
P(1)
'MLn'
P
C
P
C
Ru
Au
(η-C5H5)(OC)3W
(η-C5H5)(OC)3W
C(64)
17 valence electron
metal centre
C(25)
O(65)
C(21)
LM'
R
H
R
H
C(23)
C(22)
C(24)
Cl–M'L
P(26)
P
C
P
C
(Ph3P)2(OC)ClRu
(Ph3P)2(OC)ClRu
Cl
15 valence electron
metal centre
Scheme 1 Phosphaalkenyl complexes as ligands; MLn
Ni(CO)3, AuCl; MAL = HgCl, AuPPh3
=
Fe(CO)4,
Fig. 1 Molecular geometry for [Ru{P(AuPPh3)NCHBut)Cl2(CO)(PPh3)2]
3a; phenyl groups omitted
Chem. Commun., 1997
179

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siderably larger than that found in the precursor 1a (10.0 Hz).
The resonances due to the phosphine ligands both show
coupling to the phosphaalkenyl phosphorus, however there is no
resolvable coupling between the phosphine resonances con-
sistent with the absence of an Ru–Au bond.
We gratefully acknowledge the generous loan of ruthenium
salts by Johnson Matthey Chemicals and the Nuffield Founda-
tion and the Engineering and Physical Sciences Research
Council (UK) for financial support and the provision of a
diffractometer.
The formulation was confirmed by a single-crystal X-ray
diffraction analysis,¶ the results of which are summarised in
Fig. 1. The geometry at ruthenium is essentially octahedral with
cis-interligand angles in the range 87.2(3)–93.0(1)°, whilst the
geometry at gold is close to linear [P(1)–Au–P(20) 177.6(1)°].
The two ruthenium chloride distances are 2.481(2) and 2.464(2)
Å indicating that the trans influence of the phosphaalkenyl
ligand is only marginally greater than that of the carbonyl
ligand. Interest focusses on the phosphaalkenyl bridge although
the novelty of 3a leaves us with little precedent for comparison.
It is noteworthy that the coordination at phosphorus is trigonal
[intersubstituent angles in the range 119.7(3)–120.2(3)°],
indeed this planarity extends to include Au, P(1), C(22) and the
equatorial ruthenium coordination plane [maximum deviation
from planarity of 0.085 Å by Cl(66)]. The P(20)–C(21) bond
length of 1.664(9) Å is clearly multiple in nature, and
comparable to that observed [1.640(4) Å] in [Fe{m-PNC(Si-
Me3)2}2(CO)6].3 The two Au–P distances differ only margin-
ally, with that to the phosphaalkenyl ligand [2.320(2) Å] being
the longer of the two. The Ru–P(20) separation of 2.296(2) Å is
however ca. 0.1 Å shorter than those to the phosphines [P(45)
2.397(2), P(26) 2.413(2) Å], indicating a p-acid role for the
phosphaalkenyl ligand when bound to a retrodative metal
centre. Finally the trans disposition of the ruthenium and the
butyl group about the PNC double bond confirms our earlier
suggestion that hydroruthenation of P·CBut to provide 1a
occurs in a regiospecifically trans manner.
The facility of the addition of [AuCl(PPh3)] to 1a bodes well
for the future elaboration of heterobimetallic phosphaalkenyl
complexes by the bridge-assisted methodology. Preliminary
results indicate that the gold acetylide [Au(C·CC6H4Me-
4)(PPh3)] also adds across the Ru–P bond to provide the
ruthenium acetylide complex [Ru{P(AuPPh3)NCHBut}-
(C·CC6H4Me-4)Cl(CO)(PPh3)3] 4a§ (Scheme 2). In a similar
manner both mercury-(i) and -(ii) chloride react with 1 to
provide [Ru{P(HgCl)NPHBut}Cl2(CO)(PPh3)2] 5a, the former
reaction being accompanied by deposition of elemental mer-
cury. Bis(alkynyl)mercurials [Hg(C·CR)2], however, fail to
react with 1a in contrast to [Au(C·CC6H4Me-4)(PPh3)].
Similar reactions, and the products [Ru{P(AuPPh3)NCH-
But}XCl(CS)(PPh3)2] [X = Cl 3b, C·CC6H4Me-4 4b] and
[Ru{P(HgCl)NPHBut}Cl2(CS)(PPh3)2] 5b are also observed
between these reagents and the thiocarbonyl complex
[Ru(PNCHBut)Cl(CS)(PPh3)2] 1b, obtained from the reaction of
[RuHCl(CS)(PPh3)3] and P·CBut.
Footnotes
† E-mail: a.hill@ic.ac.uk
‡ E-mail: c.a.jones@swansea.ac.uk
§ Spectral data: for 3a, IR/cm21 (Nujol) 1950 [n(CO)]; (CH2Cl2) 1960
[n(CO)]. NMR (CD2Cl2, 298 K) 1H: d 0.95 (s, 9 H, Me), 7.22, 7.53, 7.99 (m
3 3, 46 H, Ph + PNCH). 13C{1H}: d 199.4 [d, CO, J(PC) 10.7 Hz], 182.9
[d, PNC, J(PC) 19.6 Hz], 136–127 (Ph), 39.8 [d, CMe3, J(PC) 9.0 Hz], 32.3
[d, CH3, J(PC) 10.7 Hz]. 31P{1H}: d 319.4 [dt(br), PNC, J(PP) 268.5, J(PPA)
ca. 30 Hz], 37.8 [d, AuPPh3, J(PP) 265.8 Hz], 18.7 (d, RuPPh3, J 29.6 Hz).
FABMS: m/z (%) [assignment]; 1379(11) [Ru2Cl2(CO)2(PPh3)4]+,
1248(17) [M 2 HCl]+, 1148(0.5) [M 2 HPNCClCMe3], 1188(6) [H2-
Ru2Cl2(CO)2(PPh3)3]+, 987(11) [M 2 HCl 2 PPh3]+, 887(1) [M 2
HPNCClCMe3 2 PPh3]+, 689(4) [RuCl(CO)(PPh3)2]+, 654(11) [Ru-
(CO)(PPh3)2]+, 626 [HRu(PPh3)2]+, 459(20) [AuPPh3]+, 363(8) [RuPPh3]+,
263(18) [HPPh3]+.
4a, IR/cm21 (Nujol) 2094 [n(C·C)], 1953 [n(CO)], 817 [d(C6H4)];
(CH2Cl2) 2095 [n(C·C)], 1954 [n(CO)]. NMR (CD2Cl2, 298 K) 1H: d 0.98
[s, 9 H, C(CH3)3], 2.25 [s, 3 H, C6H4CH3], 6.79, 6.88 [(A B)2, 4 H, C6H4,
J(AB) 7.9 Hz], 7.55, 8.15 (m 3 2, 45 H, Ph), 7.64 [d, 1 H, PNCH, J(PH)
23.1 Hz]. 13C{1H}: d 200.4 [d, CO, J(PC) 10.7 Hz], 186.3 [s(br), PNC],
135.6–126.8 (Ph and RuC·C), 117.5 [d, RuC·C, J(PC) 19.4 Hz], 39.5 [d,
CMe3, J(PC) 14.3 Hz], 32.3 [d, C(CH3)3, J(PC) 11.1 Hz], 20.9 (C6H4CH3).
31P{1H}: d 312.8 [dt, PNC, J(PP) 227.5, J(PPA) 27.7 Hz], 40.0 [d, AuPPh3,
J(PP) 227.5 Hz], 26.4 (d, RuPPh3, 27.7 Hz). FABMS: m/z (%)
[assignment]; 1499(2) [M + nba 2 H2O]+, 1470(2) [M + nba 2 CO 2 H]+,
1364(0.3) [M]+, 1329(2) [M 2 Cl]+, 1248(4) [M 2 HCCC7H7]+, 1118(24)
[M 2 HCCC7H7 2 HPCHBut 2 CO]+. 5a, IR/cm21 (Nujol) 1981(sh), 1967
[n(CO)], 1260m, 1027m, 803m; (CH2Cl2) 1980 [n(CO)]. NMR (CD2Cl2,
298 K) 1H: d 0.85 [d, 9 H, CH3, J(PH) 2.2 Hz], 7.40–7.97 (m 3 4, 31 H,
PNCH and Ph). 13C{1H}: d 197.3 (m, CO), 178.2 [d, PNC, J(PC) 26.7 Hz],
127.2–134.8 (Ph), 40.6 [d, CMe3, J(PC) 14.3 Hz], 30.4 [d, CH3, J(PC) 14.2
Hz]. 31P{1H}: 257.9 [t, PNC, J(PP) 33.3, J(HgP) 7757 Hz], 18.2 (d, PPh3,
27.7 Hz). FABMS: m/z (%) [assignment]; 1025(1) [M 2 Cl]+, 689(14)
[RuCl(CO)(PPh3)2]+, 654(7) [Ru(CO)(PPh3)2]+, 625(7) [Ru(PPh3)2]+,
363(19) [RuPPh3]+.
¶ Crystal data for 3a: C60H55AuCl2OP4Ru·2CH2Cl2, M 1454.7,
monoclinic, space group P21/n, 10.276(3), b = 29.300(7),
=
a
=
c = 20.772(6) Å, b = 101.50(2)°, U = 6129(3) Å3, Z = 4, Dc = 1.577
g cm23, m(Mo-Ka) = 30.4 cm21, l = 0.710 73 Å, F(000) = 2896. A
yellow prism of dimensions 0.83 3 0.67 3 0.27 mm was used. Data were
measured on a Siemens P4/PC diffractometer with graphite monochromated
Mo-Ka radiation (w-scans). 7949 Independent reflections were measured
(2q @ 45°) of which 5644 had ıFoı > 4s(ıFoı) and were considered to be
observed. The structure was solved by direct methods and the non-hydrogen
atoms were refined anisotropically by full-matrix least squares based on F2
using absorption-corrected data to give R1 = 0.047, wR2 = 0.098 for the
observed data and 578 parameters. Atomic coordinates, bond lengths and
angles, and thermal parameters have been deposited at the Cambridge
Crystallographic Data Centre (CCDC). See Information for Authors, Issue
No. 1. Any request to the CCDC for this material should quote the full
literature citation and the reference number 182/308.
The chemistry described for the complexes 1 illustrates their
unusual nature which makes them distinct from other phospha-
alkenyl complexes for which the effective atomic number rule
holds domain. For such complexes, the linear three-electron
(electrophilic at P) or bent one-electron (nucleophilic at P) role
of the phosphaalkenyl ligand is distinctly dichotomous. We
have previously suggested2 that the complexes 1 represent a
special case: linearisation of the M = PNC linkage, and the
attendant reduction of the nucleophilicity of the phosphorus is
not apparently favoured by the 15-electron ‘RuCl(CE)(PPh3)2’
fragment. Such behaviour is typical of formally isoelectronic
nitrosyl complexes of the late-transition metals. This leads in
the unique case of 1 to the juxtaposition of a nucleophilic
phosphaalkenyl phosphorus adjacent to a coordinatively un-
saturated ruthenium centre, i.e. a 1,2-dipole predisposed to the
1,2-addition of dipolar reagents.
References
1 L. Weber, Angew. Chem., Int. Ed. Engl., 1996, 35, 271 and references
therein.
2 R. B. Bedford, A. F. Hill and C. Jones, Angew. Chem., Int. Ed. Engl.,
1996, 35, 547.
3 A. M. Arif, A. H. Cowley and S. Quashie, J. Chem. Soc., Chem.
Commun., 1985, 428.
4 E. Niecke, H.-J. Metternich, M. Nieger, D. Gudat, P. Wenderoth,
W. Malisch, C. Hahner and W. Reich, Chem. Ber., 1993, 126, 1299.
Received, 14th October 1996; Com. 6/06987H
180
Chem. Commun., 1997