Novel chemistry of rhodium induced by a new type of ligand, a phosphino-N-benzoylhydrazone: Crystal structure of [Rh(CO){C(CO2Me)=CHCO2Me}{PPh2CH[C(CO 2Me)=C(CO2Me)]C-(But)=N-N=C(Ph)O}]

Article abstract of DOI:10.1039/a702196h

Treatment of the phosphino-N,N-dimethylhydrazone Z-PPh₂CH₂C(Bu^t)=NNMe₂ with benzohydrazide in the presence of acetic acid gave the phosphino-N-benzoylhydrazone PPh₂CH₂C(Bu^t)=NNHC(=O)Ph I. Treatment of the phosphine I with 0.5 equivalent of [{RhCl(CO)₂}₂] gave the rhodium(I) complex [Rh(CO){PPh₂CH₂C(Bu^t)=N-N=C(Ph)O}] 1 containing two fused five-membered chelate rings. Complex 1 readily reacted with Br₂ to give the dibromorhodium(III) complex [AhBr₂(CO){PPh₂CH₂C(Bu ^t)=N-N=C(Ph)O}] 2. Similarly, it underwent oxidative-addition reactions with MeI or HC=CCH₂Cl to give rhodium(III) complexes of type [RhX(R)(CO){PPh₂CH₂C(Bu^t)=N-N=C(Ph)O}] (R = Me, X = I 3; R = CH=C=CH₂, X = Cl 4). In contrast, treatment of 1 with allyl bromide caused loss of the carbon monoxide ligand to give the η³-allylrhodium(III) complex [RhBr(η-3-C₃H₅){PPh₂CH₂C(Bu ^t)=N-N=C(Ph)O}] 5. Treatment of 1 with MeO₂CC=CCO₂Me gave the cyclometallated alkenylrhodium(III) complex [Rh(CO){C(CO₂Me)=CHCO₂Me}{PPh₂CH[C(CO ₂Me)=C(CO₂Me)]C(Bu^t)=N-N=C(Ph)O}] 6, in which the phosphine ligand is tetradentate through P, N, O and C; in the formation of 6 one alkyne has attacked the methylene carbon of the phosphine ligand and the second has added to Rh-H to give RhC(CO₂Me)=CH(CO₂Me). On the prolonged heating 6 isomerised to give the rhodium(III) complex 7; in this isomer the C(CO₂Me)=CH(CO₂Me) ligand is trans to phosphorus whereas in 6 it is cis. The crystal structure of 6 has been determined.

Full text of DOI:10.1039/a702196h

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Novel chemistry of rhodium induced by a new type of ligand,
a phosphino-N-benzoylhydrazone: crystal structure of
[Rh(CO){C(CO Me)᎐CHCO Me}{PPh CH[C(CO Me)᎐C(CO Me)]C-
᎐
᎐
2
2
2
2
2
(But)᎐N᎐N᎐C(Ph)O}]
᎐
᎐
Mustaffa Ahmad, Sarath D. Perera, Bernard L. Shaw* and Mark Thornton-Pett
School of Chemistry, University of Leeds, Leeds, UK LS2 9JT
Treatment of the phosphino-N,N-dimethylhydrazone Z-PPh CH C(But)᎐NNMe with benzohydrazide in
᎐
2
2
2
the presence of acetic acid gave the phosphino-N-benzoylhydrazone PPh CH C(But)᎐NNHC(᎐O)Ph I.
᎐
᎐
2
2
Treatment of the phosphine I with 0.5 equivalent of [{RhCl(CO)2}2] gave the rhodium() complex
[Rh(CO){PPh CH C(But)᎐N᎐N᎐C(Ph)O}] 1 containing two fused five-membered chelate rings. Complex 1
᎐
᎐
2
2
readily reacted with Br to give the dibromorhodium() complex [RhBr (CO){PPh CH C(But)᎐N᎐N᎐C(Ph)O}] 2.
᎐
᎐
2
2
2
2
᎐
Similarly, it underwent oxidative-addition reactions with MeI or HC᎐CCH Cl to give rhodium()
᎐
2
complexes of type [RhX(R)(CO){PPh CH C(But)᎐N᎐N᎐C(Ph)O}] (R = Me, X = I 3; R = CH᎐C᎐CH ,
᎐
᎐
᎐ ᎐
2
2
2
X = Cl 4). In contrast, treatment of 1 with allyl bromide caused loss of the carbon monoxide ligand
to give the η3-allylrhodium() complex [RhBr(η-3-C H ){PPh CH C(But)᎐N᎐N᎐C(Ph)O}] 5.
᎐
᎐
3
5
2
2
᎐
Treatment of 1 with MeO CC᎐CCO Me gave the cyclometallated alkenylrhodium() complex
᎐
2
2
[Rh(CO){C(CO Me)᎐CHCO Me}{PPh CH[C(CO Me)᎐C(CO Me)]C(But)᎐N᎐N᎐C(Ph)O}] 6,
᎐
᎐
᎐
᎐
2
2
2
2
2
in which the phosphine ligand is tetradentate through P, N, O and C; in the formation of 6 one alkyne
has attacked the methylene carbon of the phosphine ligand and the second has added to Rh᎐H to give
RhC(CO Me)᎐CH(CO Me). On the prolonged heating 6 isomerised to give the rhodium() complex 7;
᎐
2
2
in this isomer the C(CO Me)᎐CH(CO Me) ligand is trans to phosphorus whereas in 6 it is cis. The crystal
᎐
2
2
structure of 6 has been determined.
The direct synthesis of hydrazones R1R2C(᎐NNH ) from a
᎐
Me
Ph2
2
ketone and hydrazine is often difficult since an azine R1R2C᎐
᎐
Br
Ph2
P
CO
N᎐N᎐CR1R2 may form preferentially. A method of synthesiz-
CH=C=CH2
Ph2
᎐
Rh
I
P
CO
O
ing hydrazones R1R2C(᎐NNH ) was devised by Newkome
᎐
2
But
(ii)
N
O
P
CO
Rh
Br
and Fishel1 which was to make the N,N-dimethylhydrazone
Rh
Cl
But
N
N
R1R2C(᎐NNMe ) first and then to carry out an exchange reac-
᎐
But
N
O
3
2
N
Ph
N
4
tion with hydrazine using acid as catalyst. We have used this
Ph
2
Ph
approach to synthesize the phosphino hydrazone Z-PPh2-
(iii)
(iv)
CH C(But)᎐NNH by heating the readily prepared Z-PPh2-
᎐
᎐
2
2
CH C(But)᎐NNMe with hydrazine in the presence of acetic
Ph
N
Ph2
P
Rh
2
2
O
H
Ph2
P
Rh
acid as catalyst.2 The compound Z-PPh CH C(But)᎐NNH and
CO
᎐
2
2
2
(v)
(i)
its derivatives have a very extensive chemistry.2–12
N
But
N
O
But
N
O
Hydrazides of carboxylic acids, viz. of type RCONHNH2,
are readily prepared and available and we reasoned that such
hydrazides might also effect acid-catalysed displacement of
H2NNMe2 from PPh CH C(But)᎐NNMe to give (diphenyl-
Br
N
PPh2
N
But
Ph
1
5
I
Ph
᎐
2
2
2
Scheme 1 (i) 0.5 equivalent [{RhCl(CO)2}2]; (ii) Br2; (iii) MeI; (iv)
propargyl chloride; (v) allyl bromide
phosphino)acylhydrazones of type PPh CH C(But)᎐NNHC-
᎐
2
2
(᎐O)R, which would show interesting properties as ligands.
᎐
Some acylhydrazones13–15 have been used as ligands, e.g. for
CuII,13 FeIII 14 and SnIV,15 but none of these contained a tertiary
phosphine moiety. We thought that the monodeprotonated
form of the (diphenylphosphino)acylhydrazone, viz. of type
PPh CH C(But)᎐N᎐N᎐C(R)OϪ, might act as a terdentate
(᎐O)Ph I was prepared by heating the phosphino-N,N-dimethyl-
᎐
2
hydrazone Z-PPh CH C(But)᎐NNMe with an excess of
᎐
2
2
2
benzohydrazide NH NHC(᎐O)Ph in hot ethanol for several
᎐
2
hours in the presence of acetic acid as catalyst. We have used
this compound to generate new chemistry from rhodium car-
bonyls and the various reactions of I and of the rhodium com-
plexes are summarised in Schemes 1 and 2. Characterising micro-
analytical and mass spectral data are in the Experimental sec-
tion, IR and 31P-{1H} NMR data are in Table 1, 1H NMR data
in Table 2, and selected 13C-{1H} NMR data in the Experi-
mental section. The 31P-{1H} NMR spectrum of I showed a
singlet at δ Ϫ22.4 and the IR spectrum showed bands at 3165
᎐
᎐
2
2
ligand co-ordinating through P, N and O. We also thought that
breakage of the oxygen–metal bond of the chelate might occur
rapidly and reversibly and that the resultant bidentate ligand
complexes show some interesting organometallic/co-ordination
chemistry. We are finding this to be the case and in this paper we
describe the synthesis of the new compound PPh CH C(But)᎐
᎐
2
2
NNHC(᎐O)Ph and some chemistry generated from it with
rhodium-() and -() carbonyls.
᎐
and 1665 cmϪ1 for ν(N᎐H) and ν(C᎐O), respectively.15 The pro-
᎐
ton resonance at δ 9.57 was assigned to the NH proton which
exchanged with D2O. We suggest that this phosphine I has the Z
Results and Discussion
The phosphino-N-benzoylhydrazone PPh CH C(But)᎐NNHC-
configuration around the C᎐N bond, as do the phosphino-
᎐
hydrazones of type PPh CH C(But)᎐NNR , R = H or Me.2
᎐
᎐
2
2
2
2
2
J. Chem. Soc., Dalton Trans., 1997, Pages 2607–2612
2607

View Article Online
We reasoned that treatment of the very substitution-labile
rhodium() carbonyl complex [Rh2Cl2(CO)4]16 with I (1 equiv-
alent per rhodium atom) ought to give a neutral rhodium()
carbonyl complex in which the monodeprotonated I would
bind to the rhodium as a terdentate ligand. Indeed in
dichloromethane solution at 20 ЊC evolution of carbon mon-
oxide occurred and the hoped for rhodium() complex
Table 1 Infrared a and 31P-{1H} NMR b data
Compound
I c
1
2
ν(C᎐O)
δP
1J(RhP)/Hz
᎐
᎐
—
Ϫ22.4
52.3
45.2
54.0
51.7
53.3
85.5
98.8
—
1974s
2097s
2060s
2088s
—
165
101
121
118
125
112
66
3
[Rh(CO){PPh CH C(But)᎐N᎐N᎐C(Ph)O}]
1 was obtained
4d
5
᎐
᎐
2
2
Characterising microanalytical, mass and NMR spectral data
6e
7f
2084s
2070s
are in the Experimental section and Tables 1 and 2. In the IR
spectrum there was a strong band at 1974 cmϪ1 due to ν(C᎐O),
᎐
᎐
a
As KBr disc, in cmϪ1, s = strong. b Recorded at 36.2 MHz in CDCl3,
unless otherwise indicated; chemical shifts (δ) are in ppm relative to
85% H3PO4. c ν(N᎐H) 3165w and ν(C᎐O) 1665s cmϪ1 d ν(C᎐C᎐C)
a value typical of a rhodium() carbonyl.4,10,17 In the 31P-{1H}
1
NMR spectrum the high value of J(RhP) = 165 Hz is typical
.
᎐
᎐ ᎐
for phosphorus co-ordinated to rhodium() and trans to a co-
ordinated oxygen (an electronegative donor atom).10,18,19 In the
1H NMR spectrum (Table 2), the resonance of the CH2P pro-
tons was a doublet at δ 3.99 with 2J(PH) = 10.7 Hz. In the
1935m cmϪ1 e ν(C᎐O) 1720s cmϪ1 f ν(C᎐O) 1700s cmϪ1
. . .
᎐ ᎐
co-ordinated to rhodium(), in addition there was a strong
᎐ ᎐
13
1
C-{ H} NMR spectrum the resonance of the C᎐O ligand
band at 1935 cmϪ1 due to ν(C᎐C᎐C).10 The 13C-{1H} NMR
᎐
᎐
2
was a doublet of doublets at δ 191.7 with J(PC) = 19.1 and
spectrum of 4 also supported the allenic structure and the
᎐ ᎐
1
J(RhC) = 72.2 Hz, typical values for Rh᎐C᎐O.4,10 The chemical
central allenic carbon (C᎐C᎐C) gave a singlet at δ 204.8.10,27
᎐
᎐
shift of the methylene carbon (CH2P), δ 47.9 with 1J(PC) = 29.9
Treatment of complex 1 with allyl bromide gave a single
Hz, is typical of a methylene carbon in a five-membered chelate
ring.3,20 In six-membered chelate rings involving azine or hydra-
zone phosphine–metal complexes methylene carbons absorb at
ca. δ 25.3,4,8–11,20 In forming the two five-membered chelate rings
product which showed no band in the IR spectrum correspond-
ing to ν(C᎐O) and in the 13C-{1H} NMR spectrum there was
᎐
᎐
᎐
no resonance corresponding to C᎐O. We observed a similar
᎐
decarbonylation reaction when we treated allyl chloride with
[Rh(CO){PPh CH C(But)᎐N᎐N᎐CH[C H O(OMe) ]}].10 We
isomerisation around the C᎐N bond from Z to E has occurred.
᎐
᎐
᎐
2
2
6
2
2
formulate this complex as an η3-allylrhodium() adduct of
We have found such isomerisation to be common in azine or
hydrazone phosphine–metal complexes.2,3,20–22
stereochemistry 5. The 31P-{1H} NMR spectrum of 5 showed a
1
doublet at δ 53.3 with J(RhP) = 125 Hz. In the 1H NMR spec-
A reaction of some rhodium()–tertiary phosphine com-
plexes is oxidative addition to give rhodium()–tertiary phos-
phine complexes. However, rhodium() shows less tendency to
undergo oxidative addition than does iridium(), for example
trans-[RhCl(CO)(PPh3)2] has less tendency to undergo oxid-
ative addition than does the well known trans-[IrCl(CO)-
trum, the terminal anti protons of the η3-allyl group each gave
a doublet, one at δ 2.16 [3J(HH) = 10.0 Hz] and the other at
3
δ 3.85 [3J(HH) = 12.2 Hz]; the large value of J(HH) is typical
for trans-vicinal coupling. The syn-protons gave multiplets, at
δ 2.35 and 4.49. In the 13C-{1H} NMR spectrum the methyl-
ene carbon (CH2P) gave a doublet resonance at δ 48.0 with
1J(PC) = 36.8 Hz. The resonances at δ 53.5, 63.3 and 98.3 were
(PPh3)2].17,23,24 We have investigated the behaviour of
1
towards oxidative addition. A solution of it in dichloro-
methane reacted immediately with bromine (in approxim-
ately two-fold excess) to give a single product (as evidenced
by the 31P-{1H} NMR spectrum). We formulate this as
assigned to the two ᎐CH carbons and the ᎐CH carbon of the
᎐
᎐
2
η3-allyl group.28
᎐
MeO CC᎐CCO Me
᎐
2 2
Dimethyl
acetylenedicarboxylate,
[RhBr (CO){PPh CH C(But)᎐N᎐N᎐C(Ph)O}] 2. In the 1H
(dmad), is an electronegative acetylene and often forms adducts
with metals which are in a low valency state. Sometimes such
an interaction is followed by carbon–carbon bond formation
giving, for example, a metallacyclopentadiene, sometimes
carbon–carbon bond formation continues and hexa(methoxy-
carbonyl)benzene is formed catalytically, e.g. by treatment of
trans-[RhCl(CO)(PPh3)2] with dmad.29
᎐
᎐
2
2
2
NMR spectrum (Table 2) the methylene protons were equiv-
alent as were the two sets of PPh2 hydrogens, i.e. the two brom-
Ϫ1
᎐
ine atoms have added trans. The ν(C᎐O) value of 2097 cm
᎐
is similar to values reported for rhodium() carbonyl com-
plexes.17,24
Methyl iodide also added to complex 1 to give a single prod-
uct which we formulate as having the stereochemistry 3. The
characterising proton NMR data in Table 2 show non-
equivalent methylene hydrogens. The RhCH3 hydrogens in the
1H-{31P} NMR spectrum were coupled to rhodium,
2J(RhCH3) = 2.2 Hz and in the 13C-{1H} NMR spectrum the
resonance of the RhMe carbon was a doublet of doublets at δ
16.7, 2J(PC) = 2.8 and 1J(RhC) = 19.9 Hz. The carbonyl carbon
We treated the carbonylrhodium() complex 1 with an excess
of dmad at 20 ЊC in dichloromethane solution and followed the
progress of the reaction by 31P-{1H} NMR spectroscopy. We
found conversion of 1 to give a single new product, character-
1
ised by a doublet at δ 85.5 J(RhP) = 112 Hz. After 2 h 1,
1
characterised by the doublet at δ 52.3 J(RhP) = 165 Hz, had
essentially all reacted to give the new product which was isol-
ated as pale yellow crystals. Elemental analysis and the mass
spectrum (m/z 816, Mϩ) of this product showed that 1 had
taken up 2 mol of dmad. The crystal structure of this product
was determined and is shown in Fig. 1 and diagrammatically as
6 in Scheme 2. It shows that one acetylenic carbon of dmad has
attacked the CH2 carbon of the terdentate (P,N,O) ligand in 1
and the other acetylenic carbon is bonded to rhodium to give a
tetradentate (P,N,O,C) ligand with three fused five-membered
chelate rings. The second dmad has become bonded to rhodium
1
gave a doublet of doublets at δ 187.0, J(RhC) = 58.4 Hz, and
2
the relatively small value of J(PC) = 13.8 Hz showed that the
carbonyl ligand was cis to P. It is well established that addition
of MeI usually goes so that the methyl and iodide ligands finish
up mutually trans in the adducts of tertiary phosphine com-
plexes of RhI, IrI and PtII and we tentatively formulate our
adduct as having stereochemistry 3.
Oxidative addition of propargyl (prop-2-ynyl) chloride
᎐
(HC᎐CCH Cl) to iridium() usually gives allenyl complexes
᎐
2
containing a moiety CH ᎐C᎐CHM (M = metal), i.e. nucleo-
as a C(CO Me)᎐CH(CO Me) moiety in which the Rh and
᎐
2 2
2᎐ ᎐
᎐
philic attack by the metal presumably occurs at the HC᎐C car-
hydrogen are mutually cis around the C᎐C bond. The crystal
᎐
᎐
bon and not at the CH2Cl carbon.10,25,26 Such an addition to
structure also showed that in the P,N,O part the P and O are
co-ordinated in mutually trans positions, as they were in 1.
The infrared spectrum of complex 6 showed a strong band at
give an allenic complex 4 occurred when we treated 1 with
31
1
᎐
HC᎐CCH Cl. A single product was formed ( P-{ H} NMR
᎐
2
evidence) and isolated as a yellow solid. This showed in its IR
1720 cmϪ1 due to the ν(C᎐O) and a strong band at 2084 cmϪ1
᎐
spectrum a very intense band at 2088 cmϪ1, typical for a C᎐O
due to ν(C᎐O). The H NMR spectrum showed four singlets of
1
᎐
᎐
᎐
᎐
2608
J. Chem. Soc., Dalton Trans., 1997, Pages 2607–2612

View Article Online
Table 2 Proton NMR data a
δ(But)
δ(CH2P)/δ(CHP)
Others
9.57 (1 H, br, NH)c
I b
1b
2
1.50 (9 H, s)
1.50 (9 H, s)
1.61 (9 H, s)
1.62 (9 H, s)
3.17 (2 H, s)
3.99 [2 H, d, 2J(PH) 10.7]
4.43 [2 H, d, 2J(PH) 12.6]
3
4.31 [1 H, dd, 2J(HH) 12.5, 2J(PH) 13.3]
4.34 [1 H, dd, 2J(HH) 12.5, 2J(PH) 11.4]
4.34 [1 H, dd, 2J(PH) 13.2, 2J(HH) 18.5]
4.36 [1 H, dd, 2J(PH) 11.9, 2J(HH) 18.5]
0.86 [3 H, t, 3J(PH) 2.2, 2J(RhH) 2.2, RhMe]
4
1.62 (9 H, s)
3.62 [1 H, ddd, 2J(HH) 7.8, 4J(HH) 6.0, 4J(RhH) 1.3, ᎐CH2], 4.03 [1 H,
᎐
ddd, 2J(HH) 7.8, 4J(HH) 6.0, 4J(RhH) 1.3, ᎐CH2], 4.95 [1 H, m, 4J(HH) 6.0,
᎐
2J(RhH) 4.3, 3J(PH) 2.5, RhCH]
3
3
5
6
7
1.66 (9 H, s)
1.62 (9 H, s)
1.15 (9 H, s)
4.08 [1 H, dd, 2J(PH) 13.9, 2J(HH) 18.1]
4.25 [1 H, dd, 2J(PH) 10.2, 2J(HH) 18.1]
5.58 [1 H, d, 2J(PH) 12.8, CHP]
2.16 [1 H, d, J(HH) 10.0, Hanti], 2.35 (1 H, m, Hsyn), 3.85 [1 H, d, J(HH)
12.2, Hanti], 4.49 (1 H, m, Hsyn), 4.51 (1 H, m, CHRh)
3.38 (3 H, s, OMe), 3.59 (3 H, s, OMe), 3.68 (3 H, s, OMe), 3.75 (3 H, s,
OMe), 4.99 [1 H, d, 3J(RhH) 1.0, C᎐CH]
᎐
5.50 [1 H, d, 2J(PH) 11.5, CHP]
3.55 (3 H, s, OMe), 3.69 (3 H, s, OMe), 3.74 (3 H, s, OMe), 3.79 (3 H, s,
OMe), 5.45 [1 H, dd, 3J(RhH) 2.0, 4J(PH) 12.5, C᎐CH]
᎐
a
Recorded at 250 MHz, chemical shifts δ relative to SiMe4, solvent CDCl3 unless stated; coupling constants J in Hz; s = singlet, d = doublet,
br = broad, m = multiplet, ddd = double doublet of doublets and t = triplet; phenyl protons were observed between δ 7.03 and 7.89. b Recorded at 100
MHz. c D2O exchange.
was isomeric with 6. We tentatively formulate it as the structure
7 on the basis of the following spectroscopic data. The infrared
MeO2C
CO2Me
spectrum showed the ν(C᎐O) at 1700 cmϪ1 whilst the high value
Ph2
P
Rh
Ph2
P
Rh
᎐
CO
O
H
CO
O
Ϫ1
(i)
᎐
of ν(C᎐O) at 2070 cm indicates the ϩ3 oxidation state for
᎐
rhodium.24 The 1H and 13C-{1H} NMR data are similar to
those of 6. The methyl protons of the CO2Me groups gave four
singlets at δ 3.55, 3.69, 3.74 and 3.79. The CHP proton gave a
But
N
But
N
N
N
1
Ph
Ph
H
2
doublet at δ 5.50 with J(PH) = 11.5 Hz. The resonance of the
alkenyl proton was a doublet of doublets at δ 5.45 with a sizable
MeO2C
CO2Me
3
five-bond coupling of 12.5 Hz to phosphorus and J(RhH) = 2
6
Hz, suggesting that the alkenyl group was probably trans to the
phosphorus atom since for complex 6 the five-bond coupling to
phosphorus was too small to be resolved. In the 13C-{1H} NMR
(ii)
᎐
MeO2C
spectrum of 7 the resonance of the RhC᎐O carbon was a doub-
CO2Me
᎐
1
let of doublets at δ 185.2 [2J(PC) = 7.6 and J(RhC) = 61.0 Hz];
Ph2
P
2
᎐
the small value J(PC᎐O) of 7.6 Hz indicates that the carbonyl
᎐
H
CO
H
2
ligand is cis to P. The resonance at δ 164.9 with J(PC) = 125.9
and J(RhC) = 27.8 Hz was assigned to the RhC᎐CHCO Me
carbon. Such a large J(PC) value of 125.9 Hz is expected for
Rh
O
1
But
N
᎐
2
2
CO2Me
N
CO2Me
a carbon trans to a phosphorus atom; similar values have
Ph
2
been found for some transition-metal complexes, e.g. J(P᎐M᎐
7
Ctrans) ≈ 75–130 Hz where M = Pt, Ir or Ru.6,9,30
᎐
Scheme 2 (i) MeO2CC᎐CCO2Me; (ii) heat
᎐
We suggest two possible sequences of steps for the conversion
of complex 1 into 6 (see Scheme 3). We have shown previously
with iridium chemistry of the azine diphosphine Z,Z-PPh2-
CH C(But)᎐N᎐N᎐C(But)CH PPh that reversible migration
equal intensity at δ 3.38, 3.59, 3.68 and 3.75 for the four OMe
groups. The methine proton (CHP) resonated at δ 5.58 as a
doublet with J(PH) = 12.8 Hz, and the resonance of the alk-
᎐
᎐
2
2
2
2
of a methylene hydrogen to iridium to give an iridium()
enyl proton appeared at δ 4.99 with coupling to rhodium
[3J(RhH) = 1.0 Hz]; the coupling to phosphorus was too small
to be resolved. The 13C-{1H} NMR spectrum was recorded
and the carbon resonances were assigned with the aid of an
hydride could occur rapidly, possibly via PPh CH᎐C(But)-
᎐
2
NH᎐N᎐C(But)CH PPh and oxidative addition of N᎐H to
᎐
2
2
iridium().31,32 We suggest a similar process is involved in the
conversion of 1 into the (ene–hydrazone)rhodium hydride 8.
Co-ordination of dmad to 8 followed by cis migration of
hydride to the β-carbon of the co-ordinated dmad then gives 9.
Michael-type attack on the second mol of dmad by the ene–
hydrazone carbon followed by attack of the second dmad car-
bon on rhodium (see 10) then gives 6. Alternatively, Michael-
type attack on dmad by 8 might occur first to give 11 and then
12; 12 is then attacked by a second mol of dmad with hydride
migration to give 6.
attached proton test (APT) and by two-dimensional H᎐13C-
1
{1H} COSY (correlation spectroscopy) experiments. The
᎐
resonance of the C᎐O carbon was a doublet of doublets at
᎐
δ 186.8 [2J(PC) = 12.3 and J(RhC) = 58.2 Hz], whilst the two
1
singlets at δ 171.2 and 177.7 were assigned as resonances of
the two RhC᎐CCO Me carbons. The resonances of the two
᎐
2
RhCCO2Me carbons were doublets at δ 174.5 and 175.6. The
doublet of doublets at δ 170.9 with 2J(PC) = 3.1 Hz and
1J(RhC) = 23.3 Hz and a doublet at δ 187.9 with 1J(RhC) = 20.0
We tentatively suggest that in the conversion of complex 6
into 7 a Rh᎐O bond breaks to give a five-co-ordinated inter-
mediate which rearranges and when the Rh᎐O bond reforms
isomer 7 is preferred.
Hz were assigned to the two RhC᎐C carbons. The smaller
᎐
2J(PC) values (3.1 and 0 Hz) indicate that the carbon atoms are
cis to the phosphorus atom.
When we heated complex 6 in benzene solution at 78 ЊC for
55 h the 31P-{1H} NMR spectrum indicated its complete con-
version into a new compound which resonated at δ 98.8 with
1J(RhP) = 66 Hz. This new species was readily isolated as a
yellow solid. The microanalytical and mass spectral data for
this new complex (see Experimental section) established that it
The crystal structure of the rhodium() complex 6 was
determined and is shown in Fig. 1. Important features are: (i)
an acetylenic carbon of a dmad has attacked the carbon of the
activated CH2, the other acetylenic carbon becoming directly
bonded to rhodium; thus the original P,N,O terdentate ligand
is transformed into a P,N,O,C tetradentate ligand; (ii) the
J. Chem. Soc., Dalton Trans., 1997, Pages 2607–2612
2609

View Article Online
Table 3 Selected interatomic distances (Å) and angles (Њ) with e.s.d.s in parentheses
Rh᎐C(13)
Rh᎐O(6)
Rh᎐C(14)
P᎐C(111)
P᎐C(2)
C(2)᎐C(7)
N(4)᎐N(5)
C(6)᎐O(6)
C(7)᎐C(11)
1.942(8)
2.108(4)
2.128(6)
1.826(7)
1.871(7)
1.571(8)
1.399(7)
1.316(7)
1.487(9)
Rh᎐N(4)
Rh᎐C(8)
Rh᎐P
P᎐C(121)
C(2)᎐C(3)
C(3)᎐N(4)
N(5)᎐C(6)
C(7)᎐C(8)
C(8)᎐C(9)
2.054(5)
2.116(6)
2.299(2)
1.829(6)
1.513(9)
1.331(8)
1.372(8)
1.387(9)
1.509(9)
C(9)᎐O(9)
1.211(8)
1.484(8)
1.348(9)
1.144(8)
1.517(9)
1.349(8)
1.476(9)
1.389(8)
C(9)᎐O(10)
C(11)᎐O(11)
O(12)᎐C(12)
C(14)᎐C(17)
C(15)᎐O(15)
O(16)᎐C(16)
C(18)᎐O(18)
O(19)᎐C(19)
1.348(8)
1.224(9)
1.457(9)
1.359(9)
1.197(8)
1.500(9)
1.211(9)
1.447(9)
O(10)᎐C(10)
C(11)᎐O(12)
C(13)᎐O(13)
C(14)᎐C(15)
C(15)᎐O(16)
C(17)᎐C(18)
C(18)᎐O(19)
C(13)᎐Rh᎐N(4)
N(4)᎐Rh᎐O(6)
N(4)᎐Rh᎐C(8)
C(13)᎐Rh᎐C(14)
176.6(3)
79.6(2)
81.3(2)
93.2(3)
C(13)᎐Rh᎐O(6)
C(13)᎐Rh᎐C(8)
O(6)᎐Rh᎐C(8)
N(4)᎐Rh᎐C(14)
101.4(2)
95.4(3)
97.6(2)
90.1(2)
O(6)᎐Rh᎐C(14)
C(13)᎐Rh᎐P
O(6)᎐Rh᎐P
83.6(2)
97.3(2)
161.19(12)
97.4(2)
C(8)᎐Rh᎐C(14)
N(4)᎐Rh᎐P
C(8)᎐Rh᎐P
170.9(2)
81.7(2)
78.6(2)
C(14)᎐Rh᎐P
C(3)᎐C(2)᎐C(7)
C(7)᎐C(2)᎐P
C(3)᎐N(4)᎐N(5) 122.9(5)
N(5)᎐N(4)᎐Rh 114.1(4)
O(6)᎐C(6)᎐N(5) 128.1(6)
N(5)᎐C(6)᎐C(61) 118.3(5)
C(8)᎐C(7)᎐C(11) 126.7(6)
C(11)᎐C(7)᎐C(2) 115.9(6)
107.4(5)
98.0(4)
C(3)᎐C(2)᎐P
N(4)᎐C(3)᎐C(2) 110.1(5)
C(3)᎐N(4)᎐Rh 122.7(4)
C(6)᎐N(5)᎐N(4) 109.4(5)
O(6)᎐C(6)᎐C(61) 113.6(5)
C(6)᎐O(6)᎐Rh
C(8)᎐C(7)᎐C(2)
C(7)᎐C(8)᎐C(9)
C(9)᎐C(8)᎐Rh
O(9)᎐C(9)᎐C(8)
108.6(4)
O(10)᎐C(9)᎐C(8)
O(11)᎐C(11)᎐O(12) 124.6(7)
O(12)᎐C(11)᎐C(7)
O(13)᎐C(13)᎐Rh
C(17)᎐C(14)᎐Rh
111.8(6)
C(9)᎐O(10)᎐C(10)
O(11)᎐C(11)᎐C(7)
C(11)᎐O(12)᎐C(12)
C(17)᎐C(14)᎐C(15)
C(15)᎐C(14)᎐Rh
O(15)᎐C(15)᎐C(14)
C(15)᎐O(16)᎐C(16)
O(18)᎐C(18)᎐O(19) 125.1(6)
O(19)᎐C(18)᎐C(17) 109.0(6)
115.5(6)
124.7(7)
115.2(7)
122.6(6)
115.4(4)
123.5(7)
117.4(6)
110.7(7)
175.9(6)
122.0(5)
106.0(4)
117.4(5)
127.1(6)
119.6(5)
125.8(6)
O(15)᎐C(15)᎐O(16) 123.1(7)
O(16)᎐C(15)᎐C(14)
C(14)᎐C(17)᎐C(18)
O(18)᎐C(18)᎐C(17)
C(18)᎐O(19)᎐C(19)
113.3(6)
124.1(6)
125.8(7)
116.5(6)
C(7)᎐C(8)᎐Rh
O(9)᎐C(9)᎐O(10) 122.2(6)
113.1(4)
Ph2
P
H
CO
O
Ph2
P
H
H
Ph2
P
Rh
Rh
..
CO
O
(i)
(ii)
But
N
RhH(CO)
..
N
But
N
O
But
N
Ph
N
N
H
Ph
8
MeO2C
1
Ph
(iii)
CO2Me
MeO2C
MeO2C
CO2Me
Ph2
9
CO2Me
Ph2
P
(iii)
H
H
P
CO
Rh
RhH(CO)
O
..
But
But
N
N
O
MeO2C
CO2Me
N
N
Ph2
P
Ph
Ph
11
H
H
CO
O
MeO2C
CO2Me
MeO2C
Rh
..
CO2Me
But
N
6
Ph2
P
(iii)
N
H
RhH(CO)
O
Ph
H
But
N
MeO2C
10
N
CO2Me
12
Ph
Scheme 3 Possible mechanism(s) for the conversion of complex 1 into 6. (i) 1,3-Proton shift and N᎐H addition; (ii) dmad co-ordination and
hydrogen migration; (iii) dmad
second dmda has interacted with Rh᎐H to give an E-RhC-
1H and 31P, 99.5 and 40.25 MHz), a Bruker ARX-250 (operat-
ing frequencies for 1H and 13C, 250.13 and 62.9 MHz) or a
(CO Me)᎐CH(CO Me) moiety, i.e. effectively Rh᎐H has added
᎐
2
2
cis to the ᎐C᎐C᎐; (iii) the C᎐O ligand remains trans to nitrogen
Bruker AM-400 spectrometer (operating frequencies for 1H, 31
P
᎐
᎐
᎐
᎐
as it was in the starting square-planar rhodium() complex 1.
Selected bond distances and angles are given in Table 3 whilst
crystal data and details of refinement are given in Table 4. The
bond lengths Rh᎐P [2.299(2)], Rh᎐N(4) [2.054(5)] and Rh᎐O(6)
[2.108(4)] are similar to such bond lengths previously reported
for rhodium() complexes.28,33–36 The bond angles N(4)᎐Rh᎐
O(6) [79.6(2)], N(4)᎐Rh᎐C(8) [81.3(2)] and N(4)᎐Rh(1)᎐P
[81.7(2)Њ] are all considerably less than 90Њ because of restric-
tions imposed by the tetradentate ligand.
and 13C, 400.13, 161.9 and 100.6 MHz). The 1H and 13C chem-
ical shifts are relative to tetramethylsilane and 31P shifts to 85%
phosphoric acid. Infrared spectra were recorded using a Perkin-
Elmer model 257 grating spectrometer (4000–600 cmϪ1) or a
Philips Scientific SP2000 (4000–200 cmϪ1) spectrometer, fast
atom bombardment (FAB) mass spectra using a VG Autospec
spectrometer with 8 kV acceleration.
The phosphine Z-PPh CH C(But)᎐NNMe was prepared as
᎐
2
2
2
reported.2
Preparations
Experimental
Z-PPh CH C(But)᎐NNHC(᎐O)Ph I. A solution of the phos-
phino-N,N-dimethylhydrazone
(6.07 g, 18.6 mmol), benzohydrazide (9.03 g, 66.0 mmol) and
acetic acid (10 cm3) in ethanol (90 cm3) was heated under reflux
for 12 h. Water (25 cm3) was then added to the mixture to give
᎐
᎐
2
2
All the reactions were carried out in an inert atmosphere of
dry nitrogen. The NMR spectra were recorded using a JEOL
Z-PPh CH C(But)᎐NNMe
᎐
2 2 2
FX-90Q (operating frequencies for H and 31P, 89.5 and 36.2
1
MHz, respectively), a JEOL FX-100 (operating frequencies for
2610
J. Chem. Soc., Dalton Trans., 1997, Pages 2607–2612

View Article Online
3
CDCl3): δ 28.7 (3 C, s, CMe3), 38.8 [1 C, d, J(PC) 9.9, CMe3],
47.9 [1 C, d, 1J(PC) 29.9, CH2P], 176.0 [1 C, dd, J(PC) or
Table 4 Crystal data and details of refinement for compound 6
J(RhC) 1.8 or 5.6, C᎐N], 176.6 [1 C, d, J(PC) or J(RhC) 1.8,
᎐
2
1
Empirical formula
M
T/K
Crystal system
Space group
a/Å
b/Å
c/Å
C38H38N2O10PRhؒ0.5C6H6
᎐
C᎐N] and 191.7 [1 C, dd, J(PC) 19.1, J(RhC) 72.2 Hz, C᎐O].
᎐
᎐
855.64a
200
[RhBr (CO){PPh CH C(But)᎐N᎐N᎐C(Ph)O}] 2. A solution
Triclinic
᎐
᎐
2
2
2
¯
P1
containing complex 1 (692 mg, 0.13 mmol) in dichloromethane
(5 cm3) was treated with an excess of bromine solution in car-
bon tetrachloride (0.32 cm3, 0.751 mol dmϪ3, 0.24 mmol) and
was put aside for 1 h. The solvent was then evaporated to low
volume under reduced pressure and methanol added to the
residue to give 2 as an orange solid. Yield 51 mg, 57% (Found:
C, 43.35; H, 3.75; N, 3.75. C26H26Br2N2O2PRhؒ0.5CH2Cl2
requires C, 43.35; H, 3.7; N, 3.8%). m/z (FAB, for 103Rh and
79Br) 693 (M ϩ 3), 665 (M ϩ 3 Ϫ CO) and 583 (M Ϫ CO Ϫ Br).
9.624(2)
14.720(3)
16.265(3)
105.917(10)
92.517(10)
103.004(12)
2145.3(7)
2
α/Њ
β/Њ
γ/Њ
U/Å3
Z
Dc/Mg mϪ3
1.325
0.491
µ/mmϪ1
F(000)
882
[RhMe(I)(CO){PPh CH C(But)᎐N᎐N᎐C(Ph)O}] 3. A solu-
Absorption correction
Maximum, minimum transmission
factors
Crystal size/mm
θmin, θmax/Њ
Empirical via ψ scans
0.833, 0.730
᎐
᎐
2
2
tion containing complex 1 (73 mg, 0.13 mmol) in dichloro-
methane (5 cm3) was treated with an excess of methyl iodide
(0.3 cm3) and was put aside for 3 h. The solvent was then evap-
orated to low volume under reduced pressure and methanol
added to the residue to give 3 as a reddish brown solid. Yield 69
mg, 75% (Found: C, 47.9; H, 4.3; I, 18.9; N, 4.2. C27H30IN2O2-
PRh requires C, 48.0; H, 4.5; I, 18.8; N, 4.15%). m/z (FAB, for
103Rh) 675 (Mϩ) and 547 (M Ϫ HI). 13C-{1H} NMR (62.9
MHz, CDCl3): δ 16.7 [1 C, dd, 2J(PC) 2.8, 1J(RhC) 19.9,
0.15 × 0.12 × 0.08
3.62, 66.39
Ϫ11, 10; Ϫ17, 16; 0, 19
7280
3860
0.0600
7280, 60, 489
1.002
0.050
0.142
0.841, Ϫ1.036
hkl Ranges
Independent reflections, p
Reflections with Fo2 > 2σFo
2
Weighting scheme parameter a b
Data, restraints, parameters (n)
Goodness of fit on F 2, S c
R1d
3
wR2e
RhMe], 28.9 (3 C, s, CMe3), 38.9 [1 C, d, J(PC) 10.5, CMe3],
47.0 [1 C, d, 1J(PC) 35.5, CH P], 170.3 (1 C, s, C᎐N), 176.3 [1 C,
Largest difference map peak and
᎐
2
hole/e ÅϪ3
2
d, J(PC) or J(RhC) 2.1, C᎐N] and 187.0 [1 C, dd, J(PC) 13.8,
᎐
1
a
Includes solvate molecule. b w = [σ2(Fo)2 ϩ aP2]Ϫ1
,
where P =
¹
᎐
J(RhC) 58.4 Hz, C᎐O].
᎐
(Fo2 ϩ 2Fc )/3 overall scale factor. c S = [Σw(Fo2 Ϫ Fc )2/(n Ϫ p)]². d R1 =
2
2
¹
Σ||Fo| Ϫ |Fc||/Σ|Fo|. e wR2 = [Σw(Fo2 Ϫ Fc )2/Σ(Fo2)2]².
2
[RhCl(CH᎐C᎐CH )(CO){PPh CH C(But)᎐N᎐N᎐C(Ph)O}]
᎐ ᎐
᎐
᎐
2
2
2
4. A solution containing complex 1 (73 mg, 0.14 mmol) in
dichloromethane (5 cm3) was treated with an excess of prop-
argyl chloride (0.3 cm3) and put aside for 24 h. The solvent was
then evaporated to low volume under reduced pressure and
methanol added to the residue to give 4 as a yellow solid. Yield
44 mg, 52% (Found: C, 56.4; H, 4.7; N, 4.5. C29H29ClN2O2PRhؒ
0.2CH2Cl2 requires C, 56.2; H, 4.75; N, 4.5%). m/z (FAB, for
103Rh and 35Cl) 542 (M Ϫ CO Ϫ HCl). 13C-{1H} NMR (62.9
3
MHz, CDCl3): δ 28.7 (3 C, s, CMe3), 39.1 [1 C, d, J(PC) 9.7,
1
CMe ], 45.9 [1 C, d, J(PC) 33.9, CH P], 72.1 (1 C, s, ᎐CH ),
᎐
3
2
2
1
2
81.5 [1 C, dd, J(RhC) 28.0, J(PC) 6.0, RhCH], 170.0 (1 C, s,
C᎐N), 176.0 (1 C, s, C᎐N), 184.1 [1 C, dd, 2J(PC) 13.8, 1J(RhC)
᎐
᎐
᎐
58.0 Hz, C᎐O] and 204.8 (1 C, s, C᎐C᎐C).
᎐
᎐ ᎐
[RhBr(ç3-C H ){PPh CH C(But)᎐N᎐N᎐C(Ph)O}] 5. A solu-
᎐
᎐
3
5
2
2
tion containing complex 1 (66 mg, 0.12 mmol) in dichloro-
methane (5 cm3) was treated with an excess of allyl bromide (0.3
cm3) and put aside for 0.5 h. The solvent was then evaporated to
low volume under reduced pressure and methanol added to the
residue to give 5 as a yellow solid. Yield 59 mg, 73% (Found: C,
52.05; H, 4.75; N, 4.1. C28H31BrN2OPRhؒ0.25CH2Cl2 requires
C, 52.35; H, 4.95; N, 4.35%). m/z (FAB, for 103Rh and 79Br) 545
(M Ϫ Br). 13C-{1H} NMR (62.9 MHz, CDCl3): δ 28.9 (3 C, s,
CMe3), 39.2 [1 C, d, 3J(PC) 9.7, CMe3], 48.0 [1 C, d, 1J(PC) 36.8,
CH2P], 53.5 [1 C, d, 1J(RhC) 13.1, RhCH2], 63.3 [1 C, d,
1J(RhC) 7.1, RhCH2], 98.3 [1 C, d, 1J(RhC) 4.7, RhCH], 171.0
Fig. 1 Crystal structure of the bis(dimethylacetylenedicarboxylate)
adduct 6
the required phosphine I as a white solid. Yield 4.90 g, 65%
(Found: C, 74.4; H, 6.6; N, 6.9. C25H27N2OP requires C,
74.6; H, 6.8; N, 6.95%). m/z (electron impact, EI) 400 (M Ϫ 2).
13C-{1H} NMR (100.6 MHz, CDCl3): δ 27.6 [1 C, d, 1J(PC) 48.3
Hz, CH2P], 28.3 (3 C, s, CMe3), 39.4 (1 C, s, CMe3), 162.4 (1 C,
s, C᎐N) and 168.2 (1 C, s, C᎐O).
᎐
᎐
(1 C, s, C᎐N) and 174.9 [1 C, d, J(PC) 3.7 Hz, C᎐N].
᎐
᎐
[Rh(CO){PPh CH C(But)᎐N᎐N᎐C(Ph)O}] 1.
A
solution
᎐
᎐
2
2
[Rh(CO){C(CO Me)᎐CHCO Me}{PPh CH[C(CO Me)᎐C-
᎐
᎐
2
2
2
2
containing the phosphine
I (481 mg, 1.19 mmol) and
(CO Me)]C(But)᎐N᎐N᎐C(Ph)O}] 6. A solution containing
[{RhCl(CO)2}2] (233 mg, 0.59 mmol) in dichloromethane (5
cm3) was put aside for 3 h. The solvent was then evaporated to
low volume under reduced pressure and methanol added to the
residue to give complex 1 as a yellow solid. Yield 263 mg, 41%
(Found: C, 57.45; H, 4.9; N, 5.0. C26H26N2O2PRhؒ0.2CH2Cl2
requires C, 57.3; H, 4.8; N, 5.1%). m/z (FAB, for 103Rh) 533
(M ϩ 1) and 505 (M ϩ 1 Ϫ CO). 13C-{1H} NMR (62.9 MHz,
᎐
᎐
2
complex 1 (46 mg, 0.02 mmol) in dichloromethane (5 cm3) was
treated with an excess of dimethyl acetylenedicarboxylate
(0.018 cm3, 0.15 mmol) and put aside for 2 h. The solvent was
then evaporated to low volume under reduced pressure and
methanol added to the residue to give 6 as a yellow solid. Yield
59 mg, 73% (Found: C, 53.95; H, 4.6; N, 3.25. C38H38N2O10-
J. Chem. Soc., Dalton Trans., 1997, Pages 2607–2612
2611

View Article Online
PRhؒ0.5CH2Cl2 requires C, 53.85; H, 4.6; N, 3.25%). m/z (FAB,
for 103Rh) 816 (Mϩ). 13C-{1H} NMR (62.9 MHz, CDCl3): δ 29.6
(3 C, s, CMe3), 39.2 [1 C, d, J(PC) 8.1, CMe3], 50.1 (1 C, s,
References
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10 K. K. Hii, S. D. Perera and B. L. Shaw, J. Chem. Soc., Dalton Trans.,
1994, 3589.
11 K. K. Hii, S. D. Perera and B. L. Shaw, J. Chem. Soc., Dalton Trans.,
1995, 625.
12 S. D. Perera, M. Shamsuddin and B. L. Shaw, Can. J. Chem., 1995,
73, 1010.
13 P. Domiano, A. Musatti, M. Nardelli, C. Pelizzi and G. Predieri,
J. Chem. Soc., Dalton Trans., 1979, 1266 and refs. therein.
14 A. Bonardi, C. Merlo, C. Pelizzi, G. Pelizzi, P. Tarasconi and
F. Cavatorta, J. Chem. Soc., Dalton Trans., 1991, 1063 and refs.
therein.
15 L. Labib, T. E. Khalil, M. F. Iskander and L. S. Refaat, Polyhedron,
1996, 15, 3697 and refs. therein.
16 J. A. McCleverty and G. Wilkinson, Inorg. Synth., 1966, 8, 211.
17 A. J. Deeming and B. L. Shaw, J. Chem. Soc. A, 1969, 597 and refs.
therein.
3
OMe), 50.2 (1 C, s, OMe), 51.8 (1 C, s, OMe), 52.4 (1 C, s,
1
2
OMe), 63.1 [1 C, dd, J(PC) 32.4, J(RhC) 2.1, CHP], 123.4 [1
C, d, J(PC) or J(RhC) 6.1, HC᎐CRh], 128.4 (1 C, s, C᎐CRh),
᎐
᎐
161.2 [1 C, dd, J(PC) or J(RhC) 8.8 or 1.2, C᎐N], 163.5 [1 C, d,
᎐
J(PC) or J(RhC) 1.6, C᎐N], 170.9 [1 C, dd, 1J(RhC) 23.3,
᎐
2J(PC) 3.1, RhC᎐C], 171.2 (1 C, s, RhC᎐CCO Me), 174.5 [1 C,
᎐
᎐
2
d, J(PC) or J(RhC) 1.6, RhCCOMe], 175.6 [1 C, d, J(PC) or
J(RhC) 1.6, RhCCO Me], 177.7 (1 C, s, RhC᎐CCO Me), 186.8
᎐
2
2
1
[C, dd, 2J(PC) 12.3, J(RhC) 58.2, C᎐O] and 187.9 [1 C, d,
᎐
᎐
1J(RhC) 20.0 Hz, RhC᎐C].
᎐
[Rh(CO){C(CO Me)᎐CHCO Me}{PPh CH[C(CO Me)᎐C-
᎐
᎐
2
2
2
2
(CO Me)]C(But)᎐N᎐N᎐C(Ph)O}] 7. A solution containing
᎐
᎐
2
complex 6 (189 mg, 0.23 mmol) in benzene (5 cm3) was heated
at 78 ЊC for 3 d. The solvent was then evaporated to low volume
under reduced pressure and methanol added to the residue to
give 7 as a yellow solid. Yield 154 mg, 82% (Found: C, 56.05;
H, 4.6; N, 2.9. C38H38N2O10PRh requires C, 55.9; H, 4.7, N,
3.45%). m/z (FAB, for 103Rh) 816 (Mϩ). 13C-{1H} NMR (62.9
3
MHz, CDCl3): δ 27.6 (3 C, s, CMe3), 38.7 [1 C, d, J(PC) 2.5,
CMe3], 51.1 (1 C, s, OMe), 51.3 (1 C, s, OMe), 51.9 (1 C, s,
1
2
OMe), 52.6 (1 C, s, OMe), 61.4 [1 C, dd, J(PC) 33.2, J(RhC)
2.9, CHP], 125.4 [1 C, d, J(PC) or J(RhC) 1.7, HC᎐CRh],
᎐
128.8 (1 C, s, C᎐CRh), 161.6 [1 C, dd, J(PC) or J(RhC) 8.8 or
᎐
1.2, C᎐N], 163.7 [1 C, dd, J(PC) or J(RhC) 2.7 or 15.3, C᎐N],
᎐
᎐
18 G. C. Cristoph, P. Blum, W. C. Liu, A. Elia and D. W. Meek, Inorg.
Chem., 1979, 18, 894.
19 E. M. Hyde, J. D. Kennedy, B. L. Shaw and W. MacFarlane,
J. Chem. Soc., Dalton Trans., 1977, 1591.
1
2
164.9 [1 C, dd, J(RhC) 27.8, J(PC) 125.9, RhC᎐C], 171.9 (1
᎐
C, s, RhC᎐CCO Me), 172.0 [1 C, d, J(PC) or J(RhC) 6.5,
᎐
2
1
RhCCO Me], 172.4 [1 C, d, J(RhC) 24.5, RhC᎐C], 174.1 (1
᎐
2
20 U. U. Ike, S. D. Perera, B. L. Shaw and M. Thornton-Pett, J. Chem.
Soc., Dalton Trans., 1995, 2057.
21 S. D. Perera, B. L. Shaw and M. Thornton-Pett, J. Chem. Soc.,
Dalton Trans., 1992, 1469.
C, s, RhC᎐CCO Me), 175.0 [1 C, d, J(PC) or J(RhC) 5.4,
᎐
2
2
1
RhCCO2Me] and 185.2 [1 C, dd, J(PC) 7.6, J(RhC) 61.0 Hz,
᎐
C᎐O].
᎐
22 S. D. Perera, B. L. Shaw and M. Thornton-Pett, J. Chem. Soc.,
Dalton Trans., 1991, 1183.
Crystallography
23 J. P. Collman and L. S. Hegedus, Principles and Applications of
Organotransition Metal Chemistry, University Science Books, Mill
Valley, CF, 1980, p. 210; A. G. Constable, C. R. Langrick, B.
Shabanzadeh and B. L. Shaw, Inorg. Chim. Acta, 1982, 65, L151.
24 J. Chatt and B. L. Shaw, J. Chem. Soc. A, 1966, 1437; R. F. Heck,
J. Am. Chem. Soc., 1964, 86, 2796; M. C. Baird, J. T. Mague, J. A.
Osborn and G. Wilkinson, J. Chem. Soc. A, 1967, 1347.
25 J. P. Collman, J. N. Cawse and J. W. Kang, Inorg. Chem., 1969, 8,
2574.
26 M. D. Johnson and C. Mayle, Chem. Commun., 1969, 192.
27 P. Sohar, NMR Spectroscopy, CRC Press, Boca Raton, FL, 1983,
vol. 2, p. 179.
28 K. Ossalaka, J.-C. Choi, T. Koizumi, I. Yamaguchi and
T. Yamamoto, Organometallics, 1995, 14, 4962.
29 J. P. Collman and J. W. Kang, J. Am. Chem. Soc., 1967, 89, 844.
30 J. D. Vessey and R. J. Mawby, J. Chem. Soc., Dalton Trans., 1993, 51.
31 S. D. Perera and B. L. Shaw, J. Chem. Soc., Chem. Commun., 1995,
865.
32 S. D. Perera, B. L. Shaw and M. Thornton-Pett, J. Chem. Soc.,
Dalton Trans., 1996, 3111.
33 M. Cano, J. V. Heras, M. A. Lobo, E. Pinilla and M. A. Monge,
Polyhedron, 1992, 11, 2679.
34 M. Cano, J. V. Heras, M. A. Lobo, M. Martinez, E. Pinilla and
M. A. Monge, Polyhedron, 1991, 10, 187.
Crystallisation of complex 6 from C6H6–EtOH gave a suitable
crystal as a benzene solvate. All crystallographic measurements
were made on a Stoe STADI4 diffractometer operating in the
ω–θ scan mode using graphite-monochromated Cu-Kα radi-
ation (λ = 1.541 84 Å). Crystal data are given in Table 4
together with refinement details. Cell dimensions were refined
from the values of 40 selected reflections (together with their
Freidel opposites) measured at ±2θ in order to minimise sys-
tematic errors.
The structure was solved by heavy-atom methods using
SHELXS 8637 and developed by full-matrix least-squares
refinement (on F 2) using SHELXL 93.38 The unit cell also con-
tains a benzene solvate molecule which is positioned across
the inversion centre at (1.0 Ϫ x, y, 1.0 Ϫ z). All non-hydrogen
atoms were refined with anisotropic displacement parameters,
including those of the solvate molecule. Restraints were applied
to the phenyl rings so that they remained flat with overall C2v
symmetry. All hydrogen atoms were constrained to idealised
positions with a riding model including free rotation of methyl
groups. Selected bond lengths and angles are in Table 3.
Atomic coordinates, thermal parameters, and bond lengths
and angles have been deposited at the Cambridge Crystallo-
graphic Data Centre (CCDC). See Instructions for Authors,
J. Chem. Soc., Dalton Trans., 1997, Issue 1. Any request to the
CCDC for this material should quote the full literature citation
and the reference number 186/548.
35 M. Cano, J. V. Heras, M. A. Lobo, E. Pinilla, E. Gutierrez and
M. A. Monge, Polyhedron, 1989, 8, 2727.
36 K. G. van Aswegen, J. G. Leipoldt, I. M. Potgieter, G. J. Lamprecht,
A. Roodt and G. J. van Zyl, Transition Met. Chem., 1991, 16, 369.
37 G. M. Sheldrick, Acta Crystallogr., Sect. A, 1990, 46, 467.
38 G. M. Sheldrick, SHELXL 93, Program for refinement of crystal
structures, University of Göttingen, 1993.
Acknowledgements
We thank Johnson Matthey plc for a generous loan of rhodium
salts, the EPSRC for a Fellowship (to S. D. P.) and for other
support, and the Universiti Sains Malaysia for a scholarship
(to M. A.).
Received 1st April 1997; Paper 7/02196H
2612
J. Chem. Soc., Dalton Trans., 1997, Pages 2607–2612