Iron-57 NMR and structural study of [Fe(η5-Cp)(SnPh 3)(CO)(PR3)] (PR3 = phosphine, phosphite). Separation of steric and electronic σ and π effects

Article

pubs.acs.org/Organometallics

Iron-57 NMR and Structural Study of [Fe(η⁵‑Cp)(SnPh₃)(CO)(PR₃)] (PR₃

= Phosphine, Phosphite). Separation of Steric and Electronic σ and π

Eﬀects

Richard M. Mampa, Manuel A. Fernandes, and Laurence Carlton*

Molecular Science Institute, School of Chemistry, University of the Witwatersrand, Johannesburg 2050, Republic of South Africa

S

* Supporting Information

ABSTRACT: The complexes [Fe(Cp)(SnPh₃)(CO)(PR₃)] (PR₃= PMe₃(1), PⁿBu₃(2), PCy₃(3),

PMe₂Ph (4), PMePh₂(5), P(CH₂Ph)₃(6), PPh₃(7), P(4-MeC₆H₄)₃(8), P(4-MeOC₆H₄)₃(9), P(4-

FC₆H₄)₃(10), P(4-CF₃C₆H₄)₃(11), P(NMe₂)₃(12), P(OMe)₃(13), P(OPh)₃(14)), which have been

characterized by X-ray crystallography (except for 1 and 4), infrared spectroscopy (carbonyl stretching

frequency, ν_CO), and NMR spectroscopy (¹³C, ³¹P, ⁵⁷Fe, ¹¹⁹Sn) oﬀer some insight into the response of the

iron nucleus to changes in the electronic and steric properties of the PR₃ligand. A fairly good correlation is

found between the ⁵⁷Fe chemical shift and the Tolman cone angle θ for PR₃and a rather poorer correlation between δ(⁵⁷Fe) and

ν_CO. However, for the subseries of complexes 7−11 having PR₃= P(4-XC₆H₄)₃(X = H, Me, MeO, F, CF₃), the correlation

between δ(⁵⁷Fe) and ν_COis very good. Since the steric properties of these ligands, from the point of view of the metal, are

identical (θ = 145°), this provides a means of separating the steric and electronic contributions of PR₃to δ(⁵⁷Fe). The electronic

contribution of PR₃to δ(⁵⁷Fe) can be further separated into σ and π components by making use of the ﬁnding that the π

component of the Fe−P bond has a negligible inﬂuence on δ(⁵⁷Fe), unlike its inﬂuence on ν_CO. The ligands PMe_3,PⁿBu₃, PCy₃,

PMe₂Ph, PMePh₂, and P(NMe₂)₃are found to be “pure” σ donors, P(OMe)₃and P(OPh)₃are found to be π acceptors of

diﬀering strength, and P(4-XC₆H₄)₃is found to show weak but clearly distinguishable π acceptor properties.

commented on the methods of Drago²⁸and Suresh.²⁹

INTRODUCTION

■

Perspectives are given by Song and Alyea,³⁰Kuhl,³¹and York.³²

̈

The relative inﬂuences of ligand electronic and steric eﬀects on

the reactivity of transition-metal complexes are of foremost

Attempts to distinguish experimentally between the σ and π

components of the M−P bond would, at ﬁrst sight, appear to

require a parameter that reﬂects only σ eﬀects (neither pK_anor

importance in the design and optimization of homogeneous

catalysts for a wide range of reactions.¹The ligands that have

Kabachnik’s parameter is regarded as being entirely satisfactor-

proved to be most amenable to electronic and steric

modiﬁcation and are most commonly used are tertiary

phosphines and phosphites, but increasingly N-heterocyclic

y^27c,f,30b) or a parameter that, unlike the CO stretching

frequency or the redox potential, has a distinguishable

dependence on σ and π eﬀects. It has been shown by Alyea

carbenes are ﬁnding a role as their electron-donating ability

and Song,³³using ⁹⁵Mo NMR, that the transition-metal

extends beyond the range accessible to phosphines.²Measures

chemical shift can satisfy this requirement. In a number of

of steric properties of a tertiary phosphine ligand in a metal

complex include the widely used Tolman cone angle θ³and

studies phosphine electronic and steric eﬀects have been

more elaborate variants (ligand proﬁle,⁴cone angle radial

distinguished and quantiﬁed but either without the separation

of electronic σ and π eﬀects³⁴or with measurement only of the

proﬁle,⁵and solid angle⁶), Brown’s ligand repulsive energy,⁷the

electronic σ eﬀect.³⁵The complete separation and quantiﬁca-

tion of steric, σ, π, and pendent group eﬀects have been

demonstrated by Prock, Giering, and co-workers using QALE,

which avoids the need for a pure σ parameter.^27,36By means of

a graphical method^27cQALE can, in principle, distinguish

between pure σ and σ donor/π acceptor ligands. While the

diﬀering properties of phosphines and phosphites emerge

clearly from such a treatment, for ligands that are possible weak

π acceptors (such as PPh₃) the situation is less clear. The

authors point to the fact that data for complexes [Fe(Cp)-

(COMe)(CO)(PR₃)] (PR₃= P(4-XC₆H₄)₃) lie on a well-

deﬁned gradient predicted for pure σ donors and consequently

describe P(4-XC₆H₄)₃as having “...no appreciable π acidity”.^27e

accessible molecular surface (AMS) of Leitner and co-workers,⁸

Suresh’s molecular electrostatic potential,⁹Nolan’s percentage

buried volume,¹⁰an NMR method,¹¹and averaged values of X-

ray data obtained from searches of the Cambridge Structural

Database.¹²Electronic eﬀects have been quantiﬁed using

infrared spectroscopy (CO stretching frequency and Tolman’s

electronic parameter χ^3b,13), pK_a(of HPX₃), Kabachnik’s

parameter,¹⁵electrochemical,¹⁶kinetic,¹⁷and thermochemical¹⁸

measures, photoelectron spectroscopy,¹⁹NMR spectroscopy,²⁰

and computational methods.²¹The nature of the metal−

phosphorus bond has been analyzed in detail by computa-

tional²²(including Suresh’s molecular electrostatic poten-

tial^21b,23), structural,²⁴and a combined structural−computa-

tional approach²⁵and by the covalent/ionic method of Drago²⁶

and the more widely applicable quantitative analysis of ligand

eﬀects (QALE) of Prock and Giering,²⁷who have also

14

+

Received: November 28, 2013

A

dx.doi.org/10.1021/om4011593 | Organometallics XXXX, XXX, XXX−XXX

Organometallics

Article

However, this result, by itself, need not preclude a role for π

acceptance which, while weak, may remain fairly constant while

the eﬀects of varying X contribute largely to a change in σ

donor ability. A number of studies ﬁnd a signiﬁcant π

contribution to the bonding of P(4-XC₆H₄)₃to a metal.^22g,h,24a

In the present study of the steric and electronic inﬂuences of

PR₃(phosphine, phosphite) ligands on structural and NMR

parameters we have prepared a series of complexes [Fe(η⁵-

Cp)(SnPh₃)(CO)(PR₃)] that are sterically crowded, which

have a metal and coordination sphere that are amenable to

study by NMR spectroscopy (¹³C, ³¹P, ⁵⁷Fe, ¹¹⁹Sn) and contain

a CO ligand that can provide infrared data indicating the

relative level of electron density on the transition metal. In

addition to an examination of structural parameters, in

particular the Fe−P bond length, we have attempted to

separate the steric and electronic inﬂuences of PR₃on the ⁵⁷Fe

chemical shift and to distinguish between the electronic σ and π

eﬀects.

Cp)(SnPh₃)(PR₃)₂] was also formed and separated from the

desired product during crystallization. Of the series of

complexes studied, X-ray structures (Figures 1−12) were

found for all except the PMe₃and PMe₂Ph derivatives, for

which suitable crystals could not be grown. Crystal and

structure reﬁnement data are given in the Supporting

Information and selected bond lengths and angles in Table 1.

In all 12 structures the geometry at iron can best be

described as distorted octahedral, with the Cp ring occupying

three coordination sites, in the well-known “piano stool”

geometry. The largest angles are those between the Cp centroid

and the P, Sn, and C(O) substituents on iron. All are greater

than 115° with Cp−Fe−C(O) > Cp−Fe−P > Cp−Fe−Sn

(except for 2 and 3, where Cp−Fe−P is the largest angle). The

relative sizes of the angles between the “legs” (CO, PR₃, SnPh₃)

are P−Fe−Sn > P−Fe−C(O) > Sn−Fe−C(O) (except for 13

and 14), with the greatest degree of variation being found for

P−Fe−Sn, a range of 11.4° (from 89.5 to 100.9°). Variations in

P−Fe−C(O) (range 5.0°) and Sn−Fe−C(O) (range 5.6°) are

signiﬁcantly lower.

RESULTS AND DISCUSSION

■

The complexes [Fe(η⁵-Cp)(SnPh₃)(CO)(PR₃)] (Scheme 1)

Measurement of Steric Size of PR₃When Bound to a

Metal Atom. The size of a PR₃ligand in a metal complex has

been estimated in a variety of ways, the most well-known of

which is Tolman’s cone angle (θ),³in which a cone, with its

origin at a metal atom positioned at a distance of 2.28 Å from

the phosphorus, is drawn so as to enclose the substituents on

the phosphorus. The concept has been further developed by

Ferguson and co-workers^4a,bin the form of the ligand proﬁle,

which takes account of the interleaving of substituents of

adjacent ligands in sterically crowded environments in which

bulky phosphine ligands “...do not behave as regular solid cones

but are better described as irregular conic cogs.” A study by

were obtained in moderate to good yield as crystals or

a

Scheme 1

a

PR₃= PMe₃(1), PⁿBu₃(2), PCy₃(3), PMe₂Ph (4), PMePh₂(5),

P(CH₂Ph)₃(6), PPh₃(7), P(4-MeC₆H₄)₃(8), P(4-MeOC₆H₄)₃(9),

P(4-FC₆H₄)₃(10), P(4-CF₃C₆H₄)₃(11), P(NMe₂)₃(12), P(OMe)₃

(13), P(OPh)₃(14).

Muller and Mingos,¹²based on a survey of the Cambridge

̈

Structural Database, showed that, for a sample of 1507

structures of metal complexes containing PPh₃, values of the

cone angle (θ) for PPh₃(calculated using a method based on

that of Tolman) varied from 135 to 163°, with a mean value of

148.2° (standard deviation 4.9). In the same study complexes

of other phosphines showed a similar variation in θ, with mean

values (with the exception of that for PCy₃, for which the

crystalline powders (except for 4 which gave an oil), varying in

color from yellow to red, by photochemical reaction of [Fe(η⁵-

Cp)(SnPh₃)(CO)₂] with PR₃in toluene. With the phosphines

PMe₃and PMePh₂and phosphites P(OMe)₃and P(OPh)₃(all

of fairly low steric size) the disubstituted product [Fe(η⁵-

Figure 1. Molecular structure of [Fe(Cp)(SnPh₃)(CO)(PⁿBu₃)] (2). Thermal ellipsoids are shown at the 30% probability level.

B

dx.doi.org/10.1021/om4011593 | Organometallics XXXX, XXX, XXX−XXX

Organometallics

Article

Figure 2. Molecular structure of [Fe(Cp)(SnPh₃)(CO)(PCy₃)] (3). Thermal ellipsoids are shown at the 30% probability level.

Figure 3. Molecular structure of [Fe(Cp)(SnPh₃)(CO)(PMePh₂)] (5). Thermal ellipsoids are shown at the 30% probability level.

sample size was small) close to the values given by Tolman.

The values of cone angles calculated from crystallographic data

using the ligand proﬁle method show a variation (a range of

20−30°) similar to those of Mingos, as do values obtained

using the solid angle method, which, however, gives values of θ

signiﬁcantly lower than those of Tolman. The iron-57 chemical

shifts are measured from samples in solution. It is not

unreasonable to suppose that the cone angle θ of the PR₃

ligand in a dissolved complex takes an average value, with

conformations rapidly changing during molecular tumbling in

solution, that is approximated by the average of the values

obtained from solid-state data. The averaged solid-state data are

in generally good agreement with the Tolman values, and it is

on this basis that the Tolman values (Table 2) are used

throughout the following discussion.

phosphine and phosphite electronic properties in the form of

the Tolman electronic factor.^3b,13The CO stretching frequency

decreases as the σ-donor ability of the coligand (PR₃) increases

and increases as the π-acceptor ability of the coligand increases

and therefore, in the absence of other evidence, the value of ν_CO

does not permit a distinction between the eﬀects of diminished

σ donation and increased π acceptance (or vice versa). Values

of ν_COfor 1−14 are given in Table 2.

Iron−Phosphorus Bond Lengths. The iron−phosphorus

bond lengths for complexes 2, 3, and 5−14 are shown plotted

against the carbonyl stretching frequencies (ν_CO) in Figure 13

and against the Tolman cone angles θ for PR₃in Figure 14. The

general trend is for an increase in d(Fe−P) to be associated

with a decrease in ν_COand an increase in θ. The shortest Fe−P

bonds are found for the complexes of the phosphites 13 and 14,

where a signiﬁcant π contribution to the bond can be expected;

the longest Fe−P bond is found for the complex of the

sterically demanding PCy₃(3). On closer inspection of Figures

13 and 14, however, features are found which depart from these

general trends. In Figure 13 the PⁿBu₃complex 2 is found to

Measurement of Relative Electron-Donating Ability of

PR₃. The infrared stretching frequency of a carbonyl ligand

(ν_CO) has been widely used as a relative measure of the

electron-donating properties of a coligand in a transition-metal

complex and has found speciﬁc application in the assessment of

C

dx.doi.org/10.1021/om4011593 | Organometallics XXXX, XXX, XXX−XXX

Organometallics

Article

Figure 4. Molecular structure of [Fe(Cp)(SnPh₃)(CO)(P(CH₂Ph)₃)] (6). Thermal ellipsoids are shown at the 30% probability level. Two

cocrystallized dichloromethanes are omitted.

Figure 5. Molecular structure of [Fe(Cp)(SnPh₃)(CO)(PPh₃)] (7). Thermal ellipsoids are shown at the 30% probability level.

have a signiﬁcantly shorter d(Fe−P) than is found for

complexes 5−10 and 12, although sterically it is only slightly

smaller than 5 and electronically (ν_CO) it does not diﬀer from

5−10 and 12 (all eight complexes have ν_COvalues in the range

1900−1908 cm⁻¹). Complexes 5−10 and 12 form a cluster

lying within a narrow range of bond lengths (2.196−2.206 Å)

and ν_COin Figure 13, while the same complexes are found in

Figure 14 to occupy a fairly wide range of θ (from 136°

(PMePh₂) to 165° (P(CH₂Ph)₃)) for the same narrow range of

d(Fe−P), indicating that here the Fe−P bond length is largely

independent of the steric property (θ) of PR₃. In contrast to

this, a number of studies relating metal−phosphorus bond

length to the cone angle of the PR₃ligand have found a

moderate to good correlation between bond length and θ for

complexes of cobalt,³⁷molybdenum,³⁸and ruthenium.³⁹

The decrease in d(Fe−P) of 0.015 Å on going from 7 (PPh₃)

to 11 (P(4-CF₃C₆H₄)₃) almost exactly matches that found by

Prock, Giering, and co-workers for the same ligands in the

complexes [Fe(Cp)(COMe)(CO)(PR₃)], which is attributed

to a slight contraction of the phosphorus covalent radius as the

substituents on phosphorus become more electronegative.⁴⁰

For the complexes [Fe(Cp)(COMe)(CO)(PR₃)] it was found

that, although Fe−P bond lengths for the phosphite complexes

are signiﬁcantly shorter than for the phosphine complexes,

indicating the contribution of π acceptance in the former, the

correlation between Fe−P bond length and either Tolman χ or

θ was poor.⁴⁰The authors draw the conclusion that in the

absence of π bonding and steric encumbrance the length of the

M−P bond is essentially constant and independent of the

electron donor capacity of the ligand. From the foregoing

evidence it would seem clear that the use of metal−phosphorus

bond lengths in the analysis of ligand stereoelectronic

properties should be approached with caution.

D

dx.doi.org/10.1021/om4011593 | Organometallics XXXX, XXX, XXX−XXX

Organometallics

Article

Figure 6. Molecular structure of [Fe(Cp)(SnPh₃)(CO)(P(4-MeC₆H₄)₃)] (8). Thermal ellipsoids are shown at the 30% probability level.

Figure 7. Molecular structure of [Fe(Cp)(SnPh₃)(CO)(P(4-MeOC₆H₄)₃)] (9). Thermal ellipsoids are shown at the 30% probability level. Two

cocrystallized dichloromethanes are omitted.

Bond Angles. In Figure 13 the cluster of data points in the

region 2.20 ( 0.01) Å and 1900−1910 cm⁻¹(complexes 5−10

and 12, having PR₃= PMePh₂, P(CH₂Ph)₃, P(4-RC₆H₄)₃(R =

H, Me, MeO, F), P(NMe₂)₃), with the PⁿBu₃complex (2)

having a similar ν_COvalue (1901 cm⁻¹) but shorter Fe−P

distance, can be viewed as consisting of complexes having

phosphines with similar electronic properties. In a plot of P−

Fe−Sn bond angle against cone angle θ (Figure 15) four of

these complexes (PR₃= PⁿBu₃(2), P(4-MeC₆H₄)₃(8), P(4-

FC₆H₄)₃(10), P(NMe₂)₃(12)), their cone angles extending

from 132 to 157°, have values of P−Fe−Sn that fall within a

range of 0.87°. The cone angle of PR₃increases with very little

change in the Fe−P bond length (Figure 14) or the electronic

properties of the phosphine (ν_CO, Figure 13), and yet the P−

Fe−Sn bond angle (Figure 15) actually decreases slightly:

99.34(5)° (PⁿBu₃, θ = 132°) > 98.67(2)° (P(4-MeC₆H₄)₃, θ =

145°), 98.56(3)° (P(4-FC₆H₄)₃, θ = 145°) > 98.47(2)°

(P(NMe₂)₃, θ = 157°). While the diﬀerences are not large, it

is clear that there is no increase in the P−Fe−Sn bond angle

accompanying the increase in cone angle of the phosphines.

The increased volume of the phosphine is evidently taken up

elsewhere (see below). A prominent feature of Figure 15 is the

variation in P−Fe−Sn bond angle that is found as X is changed

in the complexes of P(4-XC₆H₄) (X = H (7), Me (8), OMe

(9), F (10), CF₃(11), extending from P−Fe−Sn =

96.501(17)° (R = OMe) to 100.95(2)° (R = H). Although

the cone angles are all regarded as being equal (145°), packing

forces in the solid state will vary according to the substituent X,

exerting an inﬂuence on the P−Fe−Sn angle amounting to

4.45° as X is varied. This is almost 40% of the full range

(11.40°) of variation in P−Fe−Sn. If this is the magnitude of

the contribution of packing forces to the observed geometry,

then a discussion of the inﬂuences of ligand electronic and

steric eﬀects on the geometry can, at best, be only approximate.

E

dx.doi.org/10.1021/om4011593 | Organometallics XXXX, XXX, XXX−XXX

Organometallics

Article

Figure 8. Molecular structure of [Fe(Cp)(SnPh₃)(CO)(P(4-FC₆H₄)₃)] (10). Thermal ellipsoids are shown at the 30% probability level.

Figure 9. Molecular structure of [Fe(Cp)(SnPh₃)(CO)(P(4-CF₃C₆H₄)₃)] (11). Thermal ellipsoids are shown at the 30% probability level.

Nevertheless, one or two structural trends are worthy of

comment.

taken as clear evidence of the relative contribution of packing

forces to the observed diﬀerences in structural parameters for

all of the complexes studied.

From these ﬁndings it would appear that the response of the

complex to changes in ligand size is not necessarily smooth and

continuous but may occur in steps, with one mode of change

(increasing bond angle) being superseded by another as the

ligand reaches a certain size.

The major geometrical changes which occur in the complex

as the phosphine is exchanged in the sequence PⁿBu₃(2), P(4-

MeC₆H₄)₃(8), P(4-FC₆H₄)₃(9), P(NMe₂)₃(12), for which

the P−Fe−Sn angle remains almost constant (Figure 15), are

an increase in the P−Fe−C(O) bond angle from 91.33(18)°

(2) to 96.10(6)° (12) (the full observed range of change of P−

Fe−C(O)) and a decrease in the Sn−Fe−C(O) bond angle

(from 89.31(16)° to 85.70(6)°) on going from the PⁿBu₃

complex (2) to the P(NMe₂)₂complex (12), as the cone angle

θ of PR₃is increased. Accompanying these changes is a

progressive change in the Cp−Fe−P bond angle, which for the

P(OMe)₃(13) complex (θ = 107°) has a value of 127.44(3)°,

decreasing as θ increases to a minimum (at a cone angle θ =

145°) and then increasing, with increasing θ, to a maximum of

128.73(5)° for the PCy₃complex (3) (Figure 16). In Figures

15 and 16 the range of variation arising from the diﬀering

substituents on the phosphines in complexes 7−11 can be

Inﬂuences on the ⁵⁷Fe Chemical Shift. The ⁵⁷Fe

chemical shifts (Table 3) of the 14 complexes under study

extend across a range of 542 ppm, demonstrating the high

sensitivity of the iron nucleus to its chemical environment.

Iron-57 NMR studies of a variety of organoiron complexes have

been reported by von Philipsborn,⁴¹Benn,⁴²and Wrack-

meyer,⁴³all of whom comment on the sensitivity of the ⁵⁷Fe

chemical shift to steric and electronic eﬀects. More generally,

for a transition-metal nucleus, inﬂuences on the chemical shift

that arise from a ligand such as PR₃can be rationalized as

follows. The inﬂuences are of two types: (i) σ donor/π acceptor

F

dx.doi.org/10.1021/om4011593 | Organometallics XXXX, XXX, XXX−XXX

Organometallics

Article

Figure 10. Molecular structure of [Fe(Cp)(SnPh₃)(CO)(P(NMe₂)₃)] (12). Thermal ellipsoids are shown at the 30% probability level.

Figure 11. Molecular structure of [Fe(Cp)(SnPh₃)(CO)(P(OMe)₃)] (13). Thermal ellipsoids are shown at the 30% probability level.

eﬀects and (ii) hard/soft (polarizability) eﬀects, the former

inﬂuencing the separation (ΔE) between occupied and

unoccupied orbitals on the metal and the latter inﬂuencing

the average d orbital radius (⟨r_d⟩). In a simpliﬁed form,⁴⁴

applicable when the oxidation state and coordination geometry

are eﬀectively constant, the chemical shift of the metal can be

represented as δ_M∝ ΔE⁻¹(⟨r_d⁻³⟩). It follows that ligands that

are good σ donors and/or poor π acceptors will increase the

chemical shift of the metal by decreasing ΔE (the ﬁlled orbitals

repel each other and their energy will rise) and soft/polarizable

ligands will decrease the chemical shift of the metal by

increasing ⟨r_d⟩. For a complex of a ligand such as PCy₃, which

exhibits both properties, there will be two opposing inﬂuences

on the chemical shift, the dominant eﬀect being the lowering of

ΔE and the consequent increase in δ_M(the PCy₃complex (9)

has the highest δ(⁵⁷Fe) value of the series). A complex of

P(OPh)₃(good π acceptor, low polarizability, leading to high

ΔE and low ⟨r_d⟩) will have a low δ_Mvalue (as seen for complex

14). A more advanced treatment of transition-metal chemical

shifts can be found in ref 45. In the discussion below, the

inﬂuences on the iron chemical shift that will be examined are

steric (leading to a realignment of bonding orbitals and

consequent change in ΔE), quantiﬁed in terms of the Tolman

cone angle θ for PR₃, and electronic, represented by the

carbonyl ligand CO stretching frequency, ν_CO. The possible

inﬂuence on the iron chemical shift of local magnetic ﬁelds

generated by ring currents in phenyl groups (where PR₃has

aryl substituents) was calculated, using dimensions from

structures, by means of the method of Pople.⁴⁶Ring current

eﬀects were found to inﬂuence the magnetic ﬁeld at iron to an

extent of less than 1 ppm.

Iron Chemical Shift and Steric and Electronic

Parameters. The relationship between the electronic proper-

ties of PR₃, as quantiﬁed by the value of ν_CO, for complexes 1−

14 and the iron chemical shift are shown in Figure 17. A

general trend is found from high ν_COand low δ(⁵⁷Fe) to low

G

dx.doi.org/10.1021/om4011593 | Organometallics XXXX, XXX, XXX−XXX

Organometallics

Article

Figure 12. Molecular structure of [Fe(Cp)(SnPh₃)(CO)(P(OPh)₃)] (14). Thermal ellipsoids are shown at the 30% probability level. A

cocrystallized toluene is omitted.

Table 1. Selected Bond Lengths (Å) and Angles (°) for Complexes [Fe(Cp)(SnPh₃)(CO)(PR₃)] (2, 3, 5−14)

2

3

5

6

7

8

PR₃

PⁿBu₃

PCy₃

PMePh₂

P(CH₂Ph)₃

2.2060(7)

2.5347(4)

1.728(3)

1.165(3)

97.76(2)

91.30(8)

83.98(8)

125.60(2)

119.66(2)

127.91(8)

PPh₃

P(4-MeC₆H₄)₃

2.2032(8)

2.5532(5)

1.730(3)

1.153(3)

98.67(2)

94.79(9)

86.90(9)

124.34(3)

116.70(2)

126.66(10)

14

Fe−P

Fe−Sn

Fe−C(O)

C−O

P−Fe−Sn

P−Fe−C(O)

Sn−Fe−C(O)

Cp−Fe−P

Cp−Fe−Sn

Cp−Fe−C(O)

2.1678(17)

2.5330(7)

1.745(5)

1.146(6)

99.34(5)

91.33(18)

89.31(16)

125.50(6)

117.64(3)

125.2(2)

9

2.2681(14)

2.5569(9)

1.729(6)

1.158(6)

99.80(4)

93.15(16)

86.87(16)

128.73(5)

115.21(4)

123.5(2)

10

2.1957(8)

2.5458(5)

1.738(3)

1.151(3)

94.13(2)

91.73(9)

89.63(9)

126.77(3)

116.20(2)

128.34(9)

2.1981(5)

2.5557(3)

1.735(2)

1.157(2)

100.95(2)

93.67(6)

87.64(7)

123.05(2)

116.62(1)

127.02(7)

11

12

13

PR₃

P(4-MeOC₆H₄)₃

2.1962(6)

2.5403(3)

1.732(2)

P(4-FC₆H₄)₃

2.1988(8)

2.5518(5)

1.727(3)

P(4-CF₃C₆H₄)₃

2.1831(13)

2.5417(7)

1.732(5)

P(NMe₂)₃

2.2034(9)

2.5299(7)

1.7215(16)

1.158(2)

P(OMe)₃

2.1204(8)

2.5236(4)

1.745(3)

P(OPh)₃

2.1079(8)

2.5487(5)

1.739(4)

Fe−P

Fe−Sn

Fe−C(O)

C−O

1.160(3)

1.166(3)

1.157(6)

1.142(4)

1.147(4)

P−Fe−Sn

P−Fe−C(O)

Sn−Fe−C(O)

Cp−Fe−P

Cp−Fe−Sn

Cp−Fe−C(O)

96.501(17)

94.09(8)

98.56(3)

100.37(4)

92.74(15)

84.57(15)

124.80(5)

117.35(3)

127.56(17)

98.47(2)

89.55(2)

91.70(2)

95.51(10)

87.48(11)

123.49(3)

117.02(2)

127.41(11)

96.10(6)

91.07(10)

88.12(11)

127.44(3)

118.82(2)

129.67(11)

96.11(11)

86.08(11)

125.82(3)

119.79(2)

126.37(11)

88.72(7)

85.70(6)

123.58(2)

118.78(1)

126.48(8)

124.50(2)

117.53(2)

125.50(5)

ν_COand high δ(⁵⁷Fe), with a cluster of data points in the middle

region with ν_COin the range 1900−1910 cm⁻¹, where there

appears to be little correlation. On closer inspection the data

points for complexes of P(4-XC₆H₄)₃(7−11) can be seen to

display, to a good approximation, a linear relationship between

ν_COand δ(⁵⁷Fe), which is examined in detail below. With the

exception of data points for complexes 1,2, and 4−6 (PR₃=

PMe₃, PⁿBu₃, PMe₂Ph, PMePh₂, P(CH₂Ph)₃), for which there

is no clear relationship between ν_COand δ(⁵⁷Fe), Figure 17

shows a clear trend extending from the phosphite complexes

(good π acceptors) via the P(4-XC₆H₄) complexes in order of

increasing σ donor ability, to the PCy₃complex (strong σ

donor).

Figure 18 shows a plot of δ(⁵⁷Fe) against Tolman θ for 1−

14. The plot shows a good (with the exception of the data

point for 6, discussed below) but in some ways deceptive

correlation in which δ(⁵⁷Fe) increases with increasing θ of PR₃.

The role played by electronic eﬀects can be clearly seen for

complexes 7−11 (P(4-XC₆H₄)₃), in which θ has a constant

value (in solution, at least) of 145°. Here δ(⁵⁷Fe) increases

from 541 ppm (X = CF₃) to 673 ppm (X = OMe). The role of

electronic eﬀects is less clearly seen for the phosphite

H

dx.doi.org/10.1021/om4011593 | Organometallics XXXX, XXX, XXX−XXX

Organometallics

Article

Table 2. Infrared (CO Stretching Frequency) and Steric Data (Cone Angle of PR₃) for Complexes [Fe(η⁵-

Cp)(SnPh₃)(CO)(PR₃)] (1−14)

1

2

3

4

5

6

7

PR₃

PMe₃

1903

118

PⁿBu₃

1901

132

9

PCy₃

1894

170

PMe₂Ph

1903

PMePh₂

1907

P(CH₂Ph)₃

1908

PPh₃

1904

145

14

a

ν_CO(cm⁻¹

)

b

θ (deg)

122

136

165

8

10

11

12

13

PR₃

ν_CO(cm⁻¹

θ (deg)

P(4-MeC₆H₄)₃

1904

P(4-MeOC₆H₄)₃

P(4-FC₆H₄)₃

1908

P(4-CF₃C₆H₄)₃

P(NMe₂)₃

1900

P(OMe)₃

P(OPh)₃

1936

)

1903

145

1914

145

1922

107

145

157

128

a

b

Recorded from chloroform solution. Tolman cone angle.^3b

Figure 13. Plot of ν_COagainst Fe−P bond length for [Fe(Cp)-

(SnPh₃)(CO)(PR₃)] (PR₃= PⁿBu₃(2), PCy₃(3), PMePh₂(5),

P(CH₂Ph)₃(6), PPh₃(7), P(4-MeC₆H₄)₃(8), P(4-MeOC₆H₄)₃(9),

P(4-FC₆H₄)₃(10), P(4-CF₃C₆H₄)₃(11), P(NMe₂)₃(12), P(OMe)₃

(13), P(OPh)₃(14)).

Figure 15. Plot of PR₃cone angle θ against P−Fe−Sn bond angle for

[Fe(Cp)(SnPh₃)(CO)(PR₃)] (PR₃= PⁿBu₃(2), PCy₃(3), PMePh₂

(5), P(CH₂Ph)₃(6), PPh₃(7), P(4-MeC₆H₄)₃(8), P(4-MeOC₆H₄)₃

(9), P(4-FC₆H₄)₃(10), P(4-CF₃C₆H₄)₃(11), P(NMe₂)₃(12),

P(OMe)₃(13), P(OPh)₃(14)).

Figure 16. Plot of PR₃cone angle θ against Cp−Fe-P bond angle for

[Fe(Cp)(SnPh₃)(CO)(PR₃)] (PR₃= PⁿBu₃(2), PCy₃(3), PMePh₂

(5), P(CH₂Ph)₃(6), PPh₃(7), P(4-MeC₆H₄)₃(8), P(4-MeOC₆H₄)₃

(9), P(4-FC₆H₄)₃(10), P(4-CF₃C₆H₄)₃(11), P(NMe₂)₃(12),

P(OMe)₃(13), P(OPh)₃(14)).

Figure 14. Plot of PR₃cone angle θ against Fe−P bond length for

[Fe(Cp)(SnPh₃)(CO)(PR₃)] (PR₃= PⁿBu₃(2), PCy₃(3), PMePh₂

(5), P(CH₂Ph)₃(6), PPh₃(7), P(4-MeC₆H₄)₃(8), P(4-MeOC₆H₄)₃

(9), P(4-FC₆H₄)₃(10), P(4-CF₃C₆H₄)₃(11), P(NMe₂)₃(12),

P(OMe)₃(13), P(OPh)₃(14)).

complexes. P(OPh)₃has a cone angle only 10° larger than that

of PMe₃, and the ⁵⁷Fe chemical shifts of their complexes are

almost identical, but in terms of electronic properties the

ligands diﬀer considerably, with complex 1 (PMe₃) having a

ν_COvalue of 1903 cm⁻¹and complex 14 (P(OPh)₃) a ν_COvalue

of 1936 cm⁻¹. A possible reason for the lack of impact of this

electronic diﬀerence on the iron chemical shift is discussed

below.

Also in Figure 18 one outlying point, arising from the

P(CH₂Ph)₃complex (6), appears a distance of ∼−250 pm in

I

dx.doi.org/10.1021/om4011593 | Organometallics XXXX, XXX, XXX−XXX

Organometallics

Article

Table 3. NMR Data for Complexes [Fe(Cp)(SnPh₃)(CO)(PR₃)]

a

b

c

d

e

f

complex

R

δ(¹³C)

δ(³¹P)

δ(⁵⁷Fe)

δ(¹¹⁹Sn)

J(³¹P,¹³C)

J(⁵⁷Fe,³¹P)

J(¹¹⁹Sn,³¹P)

1

PMe₃

PⁿBu₃

PCy₃

218.92

219.82

221.96

219.24

219.29

219.73

220.50

220.70

220.74

220.23

219.74

222.09

217.47

216.86

29.16

50.55

74.18

40.24

56.81

58.49

75.34

72.63

70.15

74.63

79.74

171.56

185.41

171.11

447

536

858

492

513

555

651

661

673

613

541

706

316

454

46.71

32.75

6.05

30.0

28.8

27.0

29.1

28.0

28.6

28.8

29.3

29.2

27.8

38.7

41.5

40.6

53

428

391

330

409

387

365

369

373

378

366

353

461

534

496

2

3

54

4

PMe₂Ph

44.12

34.77

24.98

9.29

53

5

PMePh₂

54

6

P(CH₂Ph)₃

PPh₃

56

7

56

8

P(4-MeC₆H₄)₃

P(4-MeOC₆H₄)₃

P(4-FC₆H₄)₃

P(4-CF₃C₆H₄)₃

P(NMe₂)₃

P(OMe)₃

10.36

9.81

56

9

55

10

11

12

13

14

10.30

14.08

17.79

47.76

46.65

57

59

73

100

102

P(OPh)₃

a

b

c

Solution (∼0.02 M) in CDCl₃at 300 K. Chemical shifts in ppm from zero deﬁned using CDCl₃at 77.00 ppm (TMS 0 ppm). Chemical shifts in

d

ppm from a frequency deﬁned by 85% H₃PO₄(external standard). Chemical shifts in ppm from a frequency deﬁned by Fe(CO)₅(neat liquid),

e

equivalent to an absolute frequency Ξ(⁵⁷Fe) = 3.237797 MHz (in a ﬁeld in which the protons of TMS resonate at exactly 100 MHz). Chemical shift

f

in ppm from a frequency deﬁned by SnMe₄(external standard). Coupling constants (absolute magnitude) in Hz. Signs are probably as follows:

47

42c

²J(³¹P,¹³C)_cispositive (as for [Fe(CO)_5‑x(PF₃)_x] ), J(⁵⁷Fe,³¹P) positive (as for [Fe(Cp)(H)(PR₃)₂] ), and J(¹¹⁹Sn,³¹P)_cispositive (as for cis-

1

2

[Pt(SnPh₃)₂(diphos)] and related compounds⁴⁸and for [Rh(NCBPh₃)(H)(SnPh₃)(PPh₃)₂(py)]⁴⁹).

Figure 17. Plot of ν_COagainst ⁵⁷Fe chemical shift for [Fe(Cp)-

(SnPh₃)(CO)(PR₃)] (PR₃= PMe₃(1), PⁿBu₃(2), PCy₃(3), PMe₂Ph

(4), PMePh₂(5), P(CH₂Ph)₃(6), PPh₃(7), P(4-MeC₆H₄)₃(8), P(4-

MeOC₆H₄)₃(9), P(4-FC₆H₄)₃(10), P(4-CF₃C₆H₄)₃(11), P(NMe₂)₃

(12), P(OMe)₃(13), P(OPh)₃(14)).

Figure 18. Plot of PR₃cone angle θ against ⁵⁷Fe chemical shift for

[Fe(Cp)(SnPh₃)(CO)(PR₃)] (PR₃= PMe₃(1), PⁿBu₃(2), PCy₃(3),

PMe₂Ph (4), PMePh₂(5), P(CH₂Ph)₃(6), PPh₃(7), P(4-MeC₆H₄)₃

(8), P(4-MeOC₆H₄)₃(9), P(4-FC₆H₄)₃(10), P(4-CF₃C₆H₄)₃(11),

P(NMe₂)₃(12), P(OMe)₃(13), P(OPh)₃(14)).

the ⁵⁷Fe chemical shift dimension and ∼+25° in the cone angle

dimension from the position which it might be expected to

occupy, in terms of the observed trend of the plot. A cone angle

of 137° is given for the P(CH₂Ph)₃ligand by a solid angle

calculation⁵⁰on the data for 6. Although calculated values for

phosphines in other complexes were similarly low, we ﬁnd

evidence from ¹³C and ⁵⁷Fe data (see below) that this value (θ

= 137°) may more accurately reﬂect the steric properties of

P(CH₂Ph)₃in 6 than Tolman’s value of 165°. A precedent for

the observed anomalous data point for the P(CH₂Ph)₃complex

(6) can be found in the results of the ¹⁰³Rh NMR study of

complexes [Rh(Cl)(cod)(PR₃)] reported by Elsevier and co-

workers.^34dIf ¹⁰³Rh chemical shifts from this work are plotted

against cone angle θ of PR₃, then the data point for the

tribenzylphosphine complex is found to be located ∼120 ppm

to lower chemical shift of the position at which it might be

expected according to the trend of the plot. In a diﬀerent

context another complex of P(CH₂Ph)₃has been found to

display anomalous behavior.^34cFor these reasons complex 6 is

omitted from a more detailed examination of the results of the

present study.

Separation of Steric and Electronic Eﬀects. The

separation of electronic and steric inﬂuences on the iron

chemical shift requires that, for a number of complexes, one of

the inﬂuences remains constant while the other is varied. It can

readily be seen that the subseries of complexes with ligands

P(4-XC₆H₄)₃(7−11) satisﬁes this requirement. The cone angle

θ of the phosphine remains constant at 145°, while the

electronic properties of the complexes vary according to the

substituent X. A plot of iron chemical shift against the observed

stretching frequency ν_COfor these complexes (Figure 19a) is

linear, with ν_COdecreasing and δ(⁵⁷Fe) increasing as the

substituent X becomes more strongly electron donating. On

going from X = CF₃to X = OMe the stretching frequency

decreases from 1914 to 1903 cm⁻¹and the chemical shift

increases by 132 ppm. The relationship between δ(⁵⁷Fe) and

J

dx.doi.org/10.1021/om4011593 | Organometallics XXXX, XXX, XXX−XXX

Organometallics

Article

(here 1900 cm⁻¹). A plot of δ(⁵⁷Fe)_stagainst cone angle θ of

PR₃for each complex (Figure 19b) shows the dependence of

the iron chemical shift on steric eﬀects alone. In Figure 19b

data points for the complexes 1−5 and 12 lie, to a good

approximation, on a straight line having a gradient from which

the relationship 5.9( 0.3) ppm per degree of θ can be

obtained. The iron chemical shift increases as the cone angle of

PR₃increases. Data points which lie a signiﬁcant distance from

this line are those corresponding to P(4-XC₆H₄)₃, P(OMe)₃,

and P(OPh)₃, for which the displacements from the gradient

(in ppm of δ(⁵⁷Fe)) are 67, 161, and 342, respectively. The data

points that deﬁne the line arise from complexes of ligands PR₃

that are considered to be either “pure” σ donors or very weak π

acceptors (PR₃= PMe₃(1), PⁿBu₃(2), PCy₃(3), PMe₂Ph (4),

PMePh₂(5), P(NMe₂)₃(12)). The discrepancies between the

data points for complexes of P(4-XC₆H₄)₃(7−11), P(OMe)₃

(13), and P(OPh)₃(14) and the gradient would appear to arise

from π eﬀects. The phosphites are generally regarded as being π

acceptor ligands, while the ligands P(4-XC₆H₄)₃have been

described as either pure σ donors^27c(a term taken by some

authors to imply a contribution of up to 20% π acceptance^22d

)

or weak π acceptors.^22h

In order to ensure that the gradient obtained using eq 1 and

Figure 19b is attributable to σ donor eﬀects alone (the gradient

in Figure 19a was obtained using data from complexes 7−11

with PR₃ligands (P(4-XC₆H₄)₃) now regarded as likely weak π

acceptors), data from complexes having the “pure” σ donor

ligands PMe₃(1), PⁿBu₃(2), PMe₂Ph (4), and P(NMe₂)₃(12)

were used in a plot (see Supporting Information) of δ(⁵⁷Fe)_obs

against θ. The four complexes have ν_COvalues lying in the

narrow range of 1900−1903 cm⁻¹, and so electronic diﬀerences

between their Fe−P bonds will be small. From the plot a value

of 6.4 ppm/deg is obtained, which considering that electronic

diﬀerences, although small, have not been taken into account is

a good match for the value of 5.9 ppm/deg obtained above. In

order to place the infrared data on a broader footing (data from

the sterically crowded complexes 1−14 might contain possible

steric inﬂuences), plots (see Supporting Information) of

Figure 19. Plots of (a) ν_COagainst ⁵⁷Fe chemical shift for

[Fe(Cp)(SnPh₃)(CO)(P(4-XC₆H₄)₃)] (X = H (7), Me (8), MeO

(9), F (10), CF₃(11)) and (b) PR₃cone angle θ against δ(⁵⁷Fe)_st(see

text) for [Fe(Cp)(SnPh₃)(CO)(PR₃)] (PR₃= PMe₃(1), PⁿBu₃(2),

PCy₃(3), PMe₂Ph (4), PMePh₂(5), 7−11 as for (a), P(NMe₂)₃(12),

P(OMe)₃(13), P(OPh)₃(14)).

3b

δ(⁵⁷Fe)_obsfor 7−10 against Tolman ν_COfor P(4-XC₆H₄)₃

ν_CO, obtained from the gradient, is −11.9( 0.6) ppm per

wavenumber. With the assumption that this conversion factor is

valid across the full range of stretching frequencies and

chemical shifts, it is then possible to compensate for diﬀerences

in the electronic inﬂuence of PR₃on the chemical shifts of the

complexes under study and to examine the steric inﬂuence in

isolation from the electronic inﬂuence.

and of δ(⁵⁷Fe)_obsagainst ν_COof the less sterically crowded

[Fe(Cp)(COMe)(CO){P(4-RC₆H₄)₃}]^27c(R = H, Me, OMe,

F, CF₃) give, to within 5%, the same gradient as that found in

Figure 19a.

Separation of σ and π Eﬀects. In a broad sense

information about the presence or absence of π eﬀects in a

metal−phosphorus bond can be obtained from CO stretching

frequencies and from metal−phosphorus bond lengths (the

former higher and the latter shorter where a signiﬁcant π

component is involved), but neither method can distinguish

between pure σ donors and weakly π accepting σ donors and,

with bond length information, anomalous data (as found for 2)

can further obscure the issue. The quantitative analysis of ligand

eﬀects (QALE) makes use of a combination of parameters,

This can be done by ﬁrst choosing a value of ν_COthat will

serve as a reference point, e.g. 1900 cm⁻¹, and subtracting this

value from the observed ν_COto give the diﬀerence Δν_CO, which

may be positive or negative. When this value is multiplied by

the conversion factor of −11.9 ppm/cm⁻¹, it gives the quantity

Δδ(⁵⁷Fe)_el(subscript indicating “electronic”), which can be

used to adjust the observed iron chemical shift δ(⁵⁷Fe)_obsso as

to exclude the electronic diﬀerences between the complexes.

+

This procedure is summarized in eq 1, where Δδ(⁵⁷Fe)_el

−11.9[Δν_CO].

=

including CO stretching frequencies, pK_avalues (for HPR₃),

reduction potentials, and enthalpies of reduction in the

examination of the M−P bond in complexes such as

[Fe(Cp)(COMe)(CO)(PZ₃)]^27c,eand identiﬁes the four

components θ (steric), σ, π, and E_ar(aryl or pendent group

eﬀect), which have been quantitatively separated. Transition-

metal NMR (⁹⁵Mo) has been used by Alyea and Song^33ain

conjunction with Kabachnik’s parameter to distinguish between

PCl₃and PF₃, among a series of related ligands, in complexes

fac-[Mo(CO)₃L₃]. The use of a two (or three³⁶)-dimensional

δ(⁵⁷Fe)_st= δ(⁵⁷Fe)_obs− Δδ(⁵⁷Fe)

(1)

el

The value of δ(⁵⁷Fe)_st(subscript indicating “steric”) reﬂects

relative steric diﬀerences in isolation from electronic inﬂuences

and should not be regarded as having absolute meaning, as its

value depends on the value of ν_COchosen as a reference point

K

dx.doi.org/10.1021/om4011593 | Organometallics XXXX, XXX, XXX−XXX

Organometallics

Article

approach can provide a basis for separating the σ and π

contributions to the metal−phosphorus bond. The transition-

metal chemical shift alone can be quite unhelpful with regard to

identifying the π contribution (see below).

for the complexes of the pure σ donors, this would imply that

for 7−11 the π contribution has a constant value and that the

measured diﬀerences between the ν_COvalues for these

complexes (7−11) arise from σ eﬀects alone.

A feature of the ⁵⁷Fe NMR data which requires some

comment is the fact that complexes having ligands PR₃with

similar cone angles but with very diﬀerent ν_COvalues can have

δ(⁵⁷Fe) values that diﬀer only slightly. This is clearly shown by

complexes 4 (PR₃= PMe₂Ph, θ = 122°, ν_CO1903 cm⁻¹, δ(⁵⁷Fe)

492 ppm) and 14 (PR₃= P(OPh)₃, θ = 128°, ν_CO1936 cm⁻¹,

δ(⁵⁷Fe) 454 ppm). In Figure 20, where steric inﬂuences have

been normalized, it can be seen that the iron chemical shift

appears to be entirely insensitive to the diﬀerence between 11

and 13 (Δν_CO= 4 cm⁻¹) or the diﬀerence between 2 and 10

(Δν_CO= 7 cm⁻¹), diﬀerences which in terms of ν_COare quite

signiﬁcant and are attributed to π-bonding eﬀects. This

phenomenon, seen for complexes which diﬀer only in the π-

bonding ability of a ligand (PR₃, P(OR)₃), has been observed

for [Os(p-cymene)Cl₂(PR₃)] (PR₃= PⁿBu₃(θ = 132°, Tolman

ν 2060.3 cm⁻¹, δ(¹⁸⁷Os) −2081 ppm), P(OⁱPr)₃(θ = 130°;

Tolman ν 2075.9 cm⁻¹, δ(¹⁸⁷Os) −2076 ppm))^34eand for

trans-[W(CO)₄(PPh₃)(PR₃)] (PR₃= PⁿBu₃(θ = 132°, Tolman

ν 2060.3 cm⁻¹, δ(¹⁸³W) 789 ppm), P(OPh)₃(θ = 128°, ν

2085.3 cm⁻¹, δ(¹⁸³W) 776 ppm)),⁵¹where large diﬀerences in

ν_CO(up to 25 cm⁻¹) translate into negligible diﬀerences in the

transition-metal chemical shift. The origin of the eﬀect has been

identiﬁed by von Philipsborn as being “...probably due to an

increase in the spectrochemical ΔE parameter caused by a

larger metal-ligand orbital interaction of more strongly π

accepting P(OR)₃ligands. This oﬀsets the deshielding eﬀect

expected by way of the associated decrease in the nephelauxetic

r_dparameter.”^34e,52Thus, an increase in π acceptance increases

ΔE (δ_metaldecreases) and the withdrawal of electron density

from the π-accepting phosphorus by its substituents (OR),

making it less polarizable, decreases ⟨r_d⟩ (δ_metalincreases). The

two eﬀects are related and can (see above) exactly match and

cancel each other.

The relative contribution of steric eﬀects to the iron chemical

shift can be excluded by making use of the relationship derived

from Figure 19b: namely that 1° of cone angle is equivalent to

5.9 ppm in the iron chemical shift. A value of θ can be chosen

as a reference point, e.g. 145°, and subtracted from the cone

angle of the PR₃ligand to give a diﬀerence Δθ. When

multiplied by the conversion factor of 5.9 ppm/deg, this gives

the quantity Δδ(⁵⁷Fe)_st, which can be used to adjust the iron

chemical shifts so as to exclude the inﬂuence of the steric

diﬀerences between the complexes. This is shown in eq 2,

where Δδ(⁵⁷Fe)_st= 5.9[Δθ].

δ(⁵⁷Fe)_el= δ(⁵⁷Fe)_obs− Δδ(⁵⁷Fe)_st

(2)

The value of δ(⁵⁷Fe)_elreﬂects relative electronic diﬀerences in

the absence of steric inﬂuences and has a numerical value that

varies with the choice of reference θ (here 145°). A plot of

δ(⁵⁷Fe)_elagainst observed ν_COis shown in Figure 20. In this

If the π contribution to the Fe−P bond does not inﬂuence

the observed iron chemical shift, then the diﬀerence in δ(⁵⁷Fe)

between any two complexes can be fully accounted for by steric

(θ) and σ (ν_CO) eﬀects. Since for some of the complexes π

eﬀects are clearly involved, a measure of the π contribution to

the Fe−P bond must come indirectly from the CO stretching

frequency via the empirical relationship Δδ(⁵⁷Fe)_el= −11.9-

[Δν_CO] (see above). The displacement of data points for 7−11,

13, and 14 from the gradient obtained from the complexes of

the pure σ donors in Figures 19b and 20 gives a measure of the

π contribution to the Fe−P bond expressed in ppm of iron

chemical shift (Figure 19b) or in wavenumbers of CO

stretching frequency (Figure 20). The relative contributions

of θ, σ, and π eﬀects, which are valid only for differences

between any two complexes, can then be calculated.

Figure 20. Plot of ν_COagainst δ(⁵⁷Fe)_el(see text) for [Fe(Cp)-

(SnPh₃)(CO)(PR₃)] (PR₃= PMe₃(1), PⁿBu₃(2), PCy₃(3), PMe₂Ph

(4), PMePh₂(5), P(CH₂Ph)₃(6), PPh₃(7), P(4-MeC₆H₄)₃(8), P(4-

MeOC₆H₄)₃(9), P(4-FC₆H₄)₃(10), P(4-CF₃C₆H₄)₃(11), P(NMe₂)₃

(12), P(OMe)₃(13), P(OPh)₃(14)).

ﬁgure two rows of data points deﬁne (to a good approximation)

equal gradients separated, in the ν_COdimension, by 5.5 cm⁻¹.

At higher wavenumbers are data points for complexes of the

phosphites 13 and 14, separated from the lower gradient by

13.3 and 28.5 cm⁻¹, respectively. The lower of the two parallel

gradients is deﬁned by data points for complexes of the PR₃

ligands regarded as pure σ donors (PMe₃(1), PⁿBu₃(2), PCy₃

(3), PMe₂Ph (4), PMePh₂(5), and P(NMe₂)₃(12)), and the

upper gradient by data points for complexes of P(4-XC₆H₄)₃

(X = H (7), Me (8), OMe (9), F (10), CF₃(11)).

Thus, on going from complex 1 (PMe₃: θ = 118°, ν_CO1903

cm⁻¹, δ(⁵⁷Fe) 447 ppm) to complex 13 (P(OMe)₃: θ = 107°,

ν_CO1922 cm⁻¹, δ(⁵⁷Fe) 316 ppm) the changes in the

contributions to the Fe−P bond, in terms of ⁵⁷Fe chemical

shift, are θ = −(118° − 107°) × 5.9 ppm/deg = −65 ppm, π =

−(Δν_CO(π) (=13.3 cm⁻¹from Figure 20) × 11.9 ppm/cm⁻¹

=

If the diﬀerences in ν_COand δ(⁵⁷Fe) that are associated with

complexes 1−5 and 12 in the lower gradient arise from purely

σ eﬀects, then it would appear reasonable to attribute any

further diﬀerences in ν_COto π eﬀects, as already noted for the

phosphites. In view of the fact that the gradient for the

complexes of P(4-XC₆H₄)₃(7−11) lies parallel to the gradient

−158 ppm, and σ = −(Δν_CO(obs) − Δν_CO(π)) × 11.9 ppm/

cm⁻¹= −68 ppm. The negative signs arise because the eﬀects

of decreased cone angle, of increased π acceptance, and of

decreased σ donation are all to reduce the magnitude of

δ(⁵⁷Fe). It can be seen that the θ and σ contributions (−65 and

L

dx.doi.org/10.1021/om4011593 | Organometallics XXXX, XXX, XXX−XXX

Organometallics

Article

−68 pm, respectively) to the iron chemical shift diﬀerence

between 1 and 13 combine to give −133 ppm, which is, within

experimental error, equal to the observed diﬀerence of −131

ppm. As noted above, the π contribution to the iron chemical

shift is, to a good approximation, exactly matched by a

counterbalancing inﬂuence, believed to originate in the

nephelauxetic eﬀect, which nulliﬁes the π contribution to the

metal (here iron) chemical shift but not, of course, to the Fe−P

bond. The relative contributions of θ, σ, and π eﬀects to the

Fe−P bond on going from 1 to 13, expressed as percentages,

are θ (22), σ (23), and π (55). Similarly, on going from 1 to 14

(P(OPh)₃) the relative contributions are θ (13), σ (12), and π

(75) and on going from 1 to 10 (P(4-MeOC₆H₄)₃) are θ (55),

σ (22.5), π (22.5).

the RO substituent on phosphorus (Fermi contact model of

spin coupling). In a plot (see the Supporting Information) of

J(¹¹⁹Sn,³¹P) against ν_COthe general trend in a poor correlation

is to higher J(¹¹⁹Sn,³¹P) with increasing ν_CO, but with a reverse

trend to lower J (as ν_COincreases) for complexes of P(4-

XC₆H₄)₃(7−11). On the other hand, the correlation between

J(¹¹⁹Sn,³¹P) and θ (Figure 22) is quite good if data points for

Carbon-13 Chemical Shift and Tin−phosphorus Spin

Coupling. The carbon-13 chemical shift of the carbonyl in 1−

14 shows a moderate correlation with cone angle θ (plot shown

in the Supporting Information). The correlation improves

considerably if data points for 6 (P(CH₂Ph)₃) and 14

(P(OPh)₃) are omitted (both appear ∼2 ppm to lower

chemical shift of positions that would match the trend of the

data). In Figure 21, which shows a plot of δ(⁵⁷Fe) against

Figure 22. Plot of PR₃cone angle θ against J(Sn,P) for [Fe(Cp)-

(SnPh₃)(CO)(PR₃)] (PR₃= PMe₃(1), PⁿBu₃(2), PCy₃(3), PMe₂Ph

(4), PMePh₂(5), P(CH₂Ph)₃(6), PPh₃(7), P(4-MeC₆H₄)₃(8), P(4-

MeOC₆H₄)₃(9), P(4-FC₆H₄)₃(10), P(4-CF₃C₆H₄)₃(11), P(NMe₂)₃

(12), P(OMe)₃(13), P(OPh)₃(14)).

12−14 are omitted, with J increasing as θ decreases. In Figure

22 the increase in J(¹¹⁹Sn,³¹P) that accompanies the change in

X from CF₃to OMe in the complexes of P(4-XC₄)₃(7−11)

can be seen to occur as the complexes become increasingly

electron rich.

CONCLUSION

■

The structural study of 12 of the complexes [Fe(Cp)(SnPh₃)-

(CO)(PR₃)] shows, other than for PR₃= PCy₃(longest Fe−P

bond) and PR₃= phosphite (shortest Fe−P bonds), a poor

correlation between Fe−P bond length and either Tolman θ or

infrared stretching frequency ν_CO. As the size of PR₃increases,

changes occur in bond angles, most notably P−Fe−Sn and

Cp−Fe−P, in a manner which is not in all cases smooth,

unidirectional, and continuous. The relative contributions of θ,

σ, and π eﬀects to changes in the iron chemical shift for

complexes 1−14 can be derived from plots of ⁵⁷Fe chemical

shift against Tolman θ (for PR₃) and against ν_CO. The ⁵⁷Fe

chemical shift is found to reﬂect changes in both the θ and σ

properties of PR₃but to be unresponsive to changes in the π-

acceptor ability of PR₃, unlike the CO stretching frequency,

thus permitting the separation of σ and π contributions to ν_CO

and, indirectly, to δ(⁵⁷Fe). It is found that the ligands PMe₃,

PⁿBu₃, PCy₃, PMe₂Ph, PMePh₂, and P(NMe₂)₃behave as

“pure” σ donors, P(OMe)₃and P(OPh)₃behave as π acceptors

of diﬀering strength, and P(4-XC₆H₄)₃behaves as having weak

but clearly distinguishable π acceptor properties which, within

the limits of experimental error, do not vary with X. The

relative contributions of θ, σ, and π eﬀects can be calculated as

differences between any two complexes. With PMe₃(complex

1) as a reference point, the contribution of π eﬀects to changes

in the Fe−P bond that occur on going from 1 to 7−11

(complexes of P(4-XC₆H₄)₃) is ∼20% (which varies as the σ

contribution independently varies with X).

Figure 21. Plot of CO δ(¹³C) against ⁵⁷Fe chemical shift for

[Fe(Cp)(SnPh₃)(CO)(PR₃)] (PR₃= PMe₃(1), PⁿBu₃(2), PCy₃(3),

PMe₂Ph (4), PMePh₂(5), P(CH₂Ph)₃(6), PPh₃(7), P(4-MeC₆H₄)₃

(8), P(4-MeOC₆H₄)₃(9), P(4-FC₆H₄)₃(10), P(4-CF₃C₆H₄)₃(11),

P(NMe₂)₃(12), P(OMe)₃(13), P(OPh)₃(14)).

δ(¹³C) of the carbonyl, if data points are considered only for

complexes of the P−C-bonded phosphines 1−11 and data for

complexes 12−14 are disregarded, a surprisingly good

correlation is found between the iron and carbon chemical

shifts. The data point for the P(CH₂Ph)₃complex 6 in Figure

21 now agrees well with the trend, indicating that the cause of

the discrepancies observed for the complex in plots of δ(⁵⁷Fe)

against θ and of δ(¹³C) against θ is likely to be steric in origin.

The tin-119 chemical shift correlates poorly with ν_COand only

moderately with θ (plots shown in Supporting Information),

δ(¹¹⁹Sn) decreasing with increasing θ.

The tin−phosphorus coupling constant is sensitive to the

electronic properties of PR₃, with much higher values for

complexes of the phosphites 13 and 14 than for complexes of

the phosphines. The greater magnitude of J(¹¹⁹Sn,³¹P) for the

phosphite complexes can be interpreted in terms of a greater

degree of s character in the phosphorus−iron bond induced by

M

dx.doi.org/10.1021/om4011593 | Organometallics XXXX, XXX, XXX−XXX

Organometallics

Article

1

3

cm⁻¹; H NMR (CDCl₃300 K) δ 7.59 (m, Sn sat. J_SnH∼35, 6H,

PhSn), 7.28−7.18 (m, 9H, PhSn), 4.99 (s, 5H, Cp), 1.52 (m, 3H,

CH₂), 0.80 (t, ³J_HH7.1, 9H, Me); ¹³C NMR (CDCl₃300 K) δ 219.82

EXPERIMENTAL SECTION

■

Materials. [Fe(η⁵-Cp)(SnPh₃)(CO)₂] was prepared from Na[Fe-

(Cp)(CO)₂] and SnClPh₃according to the method of Gorsich.⁵³

[Fe(Cp)(CO)₂]₂, SnClPh₃, phosphines, and phosphites were

purchased from Aldrich and from Fluka and were used without

further puriﬁcation. THF was distilled from sodium/benzophenone,

dichloromethane was distilled from P₂O₅, and toluene, n-hexane,

acetonitrile, and diethyl ether were distilled from calcium hydride. All

operations were performed under a nitrogen atmosphere.

2

(d, J_PC28.8, CO), 148.21 (s, PhSn), 137.26 (s, Sn sat. J_SnC32.1,

PhSn), 127.62 (s, Sn sat. J_SnC34.6, PhSn), 127.02 (s, Sn sat. J_SnC9.1

PhSn), 79.15 (s, Cp), 30.44 (d, J_PC25.4, CH₂α), 26.02 (d, J_PC2.4,

CH₂γ), 24.22 (d, J_PC12.5. CH₂β), 13.71 (s, Me). Anal. Calcd for

1

3

2

C₃₆H₄₇FeOPSn: C, 61.66 H, 6.76. Found: C, 61.94; H, 6.88.

Preparation of [Fe(η⁵-Cp)(SnPh₃)(CO)(PCy₃)] (3). A stirred

solution of [Fe(η⁵-Cp)(SnPh₃)(CO)₂] (0.059 g, 0.095 mmol) and

tricyclohexylphosphine (0.040 g, 0.14 mmol) in toluene (10 mL) at

room temperature was irradiated for 18 h, during which time a color

change from yellow to orange was observed. The solvent was removed

under vacuum, and the residue was extracted with dichloromethane.

The extract was concentrated and treated with hexane to give the

product as orange-red crystals: yield 0.047 g (60%); IR (chloroform)

ν(CO) 1894 cm⁻¹; H NMR (CDCl₃, 300 K) δ 7.64 (m, Sn. sat.³J_SnH

∼34, 6H, PhSn), 7.26−7.17 (m, 9H, PhSn), 4.58 (d, ³J_PH1.0, 5H, Cp),

1.89 (m, 3H, CH), 1.69 (m, 9H, CH₂), 1.58 (m, 6H, CH₂), 1.48 (m,

3H, CH₂), 1.27 (m, 3H, CH₂), 1.12 (m, 3H, CH₂), 1.90 (m, 6H CH₂);

¹³C NMR (CDCl₃300 K) δ 221.96 (d, ²J_PC27.0, CO), 148.87 (d, Sn

Synthetic Method. Complexes 1−14 were prepared by the widely

used photolytic method for displacement of a coordinated CO.

Reagents in toluene solution in sealed Schlenk tubes were irradiated by

means of a 400 W medium-pressure mercury UV lamp positioned at a

distance of ∼2 cm from the reaction vessel. Complex 7 has previously

been reported.⁵⁴

NMR Spectroscopy. Spectra were recorded on Bruker DRX 400

and Avance III 400 spectrometers equipped with 5 mm triple-

resonance inverse probes with dedicated ³¹P channel and extended

decoupler range operating at 400.13 MHz (¹H), 100.61 MHz (¹³C),

161.98 MHz (³¹P), 12.95 MHz (⁵⁷Fe), and 149.19 MHz (¹¹⁹Sn). Two-

dimensional ⁵⁷Fe−³¹P spectra were obtained using the pulse sequence

π/2(³¹P)−1/[2J(⁵⁷Fe,³¹P)]−π/2(⁵⁷Fe)−τ−π(³¹P)−τ−π/2(⁵⁷Fe)−1/

[2J(⁵⁷Fe,³¹P)]−Acq(³¹P).⁵⁵Chemical shifts were referenced to the

generally accepted standards of TMS (¹H), CDCl₃at 77.00 ppm

(¹³C), 85% H₃PO₄(external standard; ³¹P), Fe(CO)₅(external

standard; ⁵⁷Fe, equivalent to Ξ(⁵⁷Fe) = 3.237797 MHz), and SnMe₄

(external standard; ¹¹⁹Sn). Chemical shifts are reported in ppm and

coupling constants (J) in Hz.

3

1

sat. J_PC0.8, J_SnC224, PhSn), 137.39 (s, Sn sat. J_SnC30.0, PhSn),

127.53 (s, Sn sat. J_SnC33.4, PhSn), 126.80 (s, Sn sat. J_SnC8.7, PhSn),

78.73 (s, Cp), 39.04 (d, J_PC17.7, CH), 30.78 (s, CH₂), 29.47 (d, J_PC

2.2, CH₂), 27.34 (d, J_PC9.1, CH₂), 27.18 (d, J_PC10.2, CH₂), 26.42 (s,

CH₂). Anal. Calcd for C₄₃H₅₅FeOPSn: C, 64.72; H, 6.85. Found: C,

64.89, H, 6.76.

1

Preparation of [Fe(η⁵-Cp)(SnPh₃)(CO)(PMe₂Ph)]·CH₂Cl₂(4). A

stirred solution of [Fe(η⁵-Cp)(SnPh₃)(CO)₂] (0.075 g, 0.142 mmol)

and dimethylphenylphosphine (0.015 g, 0.109 mmol) in toluene (10

mL) at room temperature was irradiated for 8 h, during which time a

color change from yellow to orange was observed. The solvent was

removed under vacuum to give a sticky red-orange residue, which was

redissolved in dichloromethane. This mixture was centrifuged to

remove suspended solid and the solvent again removed to give a

viscous red oil: yield 0.056 g (55%). Attempts to crystallize the

product from CH₂Cl₂, benzene, toluene, Et₂O, and THF using hexane

were unsuccessful: IR (chloroform) ν(CO) 1903 cm⁻¹; ¹H NMR

(CDCl₃300 K) δ 7.75−7.15 (m, 20H, Ph), 4.32 (s, 5H, Cp), 1.62 (d,

Infrared Spectroscopy. Spectra were recorded on Bruker Vector

22 FT-IR and Varian FTS 800 FT-IR spectrometers from samples in

chloroform solution.

X-ray Structure Determination. Intensity data were collected on

Bruker SMART and APEX II CCD area detector diﬀractometers with

graphite-monochromated Mo Kα radiation (50 kV, 30 mA) using

respectively SMART-NT⁵⁶and APEX2⁵⁷data collection software. The

collection method involved ω scans of width 0.5° and 512 × 512 bit

data frames. Data reduction was carried out using the program

SAINT⁺,⁵⁸and face-indexed absorption corrections were made using

XPREP.⁵⁸The crystal structures were solved by direct methods using

SHELXTL.⁵⁹Non-hydrogen atoms were ﬁrst reﬁned isotropically,

followed by anisotropic reﬁnement by full-matrix least-squares

calculations based on F²using SHELXTL. Hydrogen atoms were

ﬁrst located in the diﬀerence map and then positioned geometrically

and allowed to ride on their respective parent atoms. Diagrams were

generated using ORTEP-3 for Windows.⁶⁰

²J_PH8.7, CH₃), 1.32 (d, J_PH8.9, CH₃′); ¹³C NMR (CDCl₃300 K) δ

219.24 (d, J_PC29.1, CO), 147.54 (s, Sn sat. J_SnC253, PhSn), 143.16

(d, J_PC39.5, PhP), 137.25 (s, Sn sat. J_SnC32.9, PhSn), 128.94 (d, J_PC

2.0, PhP), 128.80 (d, J_PC9.0, PhP), 128.43 (d, J_PC8.9, PhP), 127.74 (s,

2

1

Sn sat. J_SnC35.8, PhSn), 127.17 (s, Sn sat. J_SnC8.7, PhSn), 80.25 (s,

1

Cp), 21.29 (d, J_PC30.4, Me), 21.05 (d, J_PC33.0, Me′). Anal. Calcd

for C₃₃H₃₃Cl₂FeOPSn: C, 54.89; H, 4.61. Found: C, 55.22; H, 4.77.

Preparation of [Fe(η⁵-Cp)(SnPh₃)(CO)(PMePh₂)] (5). A stirred

solution of [Fe(η⁵-Cp)(SnPh₃)(CO)₂] (0.050 g, 0.095 mmol) and

methyldiphenylphosphine (0.040 g, 0.20 mmol) in toluene (10 mL) at

room temperature was irradiated for 20 h, during which time a color

change from yellow to orange was observed. The solvent was removed

under vacuum, and the residue was extracted with dichloromethane.

The extract was concentrated and treated with hexane to give the

product as a mixture of orange and red crystals, which were separated

by hand. The red product (0.021 g, 25%) was identiﬁed as the

disubstituted complex [Fe(η⁵-Cp)(SnPh₃)(PMePh₂)₂]: yield of orange

Preparation of [Fe(η⁵-Cp)(SnPh₃)(CO)(PMe₃)] (1). A stirred

solution of [Fe(η⁵-Cp)(SnPh₃)(CO)₂] (0.067 g, 0.127 mmol) and

trimethylphosphine (0.0076 g, 0.100 mmol) in toluene (10 mL) at

room temperature was irradiated for 15 h, during which time a color

change from yellow to orange was observed. The solution was

concentrated and treated with hexane to give the product as a yellow

microcrystalline powder: yield 0.034 g (59%); IR (chloroform) ν_CO

1903 cm⁻¹; ¹H NMR (CDCl₃300 K) δ 7.59 (m, Sn sat. ³J_SnH35, 6H,

2

PhSn), 7.30−7.21 (m, 9H, PhSn), 4.47 (s, 5H, Cp), 1.24 (d, J_PH9.0,

9H, Me); ¹³C NMR (CDCl₃300 K) δ 218.92 (d, J_PC30.0, CO),

2

3

product (5) 0.033 g (50%); IR (chloroform) ν(CO) 1907 cm⁻¹; H

1

147.68 (d, J_PC0.8, PhSn), 137.22 (s, Sn sat. J_SnC33.0, PhSn), 127.74

NMR (CDCl₃₂, 300 K) δ 7.9−6.9 (m, 35H, Ph), 4.36 (d, ³J_PH1.4, 5H,

Cp), 1.40 (d, J_PH8.4, Me); ¹³C NMR (CDCl₃, 300 K) δ 219.29 (d,

(s, Sn sat. J_SnC35.4, PhSn), 127.13 (s, Sn sat. J_SnC9.2, PhSn), 79.49 (s,

1

Cp), 23.22 (d J_PC29.7, Me). Anal. Calcd for C₂₇H₂₉FeOPSn: C,

²J_PC29.1, CO), 147.32 (s, Sn sat. J_SnC258, PhSn), 141.96 (d, J_PC

1

56.39; H, 5.08. Found: C, 56.50; H, 5.09. A low quantity of phosphine

(less than 1 equiv) was used in order to minimize the extent to which a

disubstituted product was formed.

1

40.9, PhP), 138.58 (d, J_PC39.3, Ph′P), 137.24 (s, Sn sat. J_SnC33.0,

PhSn), 131.71 (d, J_PC9.8, PhP), 131.05 (d, J_PC9.9, Ph′P), 129.77 (d,

J_PC2.2, PhP), 129.15 (d, J_PC2.0, Ph′P), 128.45 (d, J_PC9.3, PhP),

128.14 (d, J_PC9.4, Ph′P), 127.56 (s, Sn sat. J_SnC36,1, PhSn), 127.06 (s,

Preparation of [Fe(η⁵-Cp)(SnPh₃)(CO)(PⁿBu₃)] (2). A stirred

solution of [Fe(η⁵-Cp)(SnPh₃)(CO)₂] (0.053 g, 0.101 mmol) and tri-

n-butylphosphine (0.03 g, 0.15 mmol) in toluene (10 mL) at room

temperature was irradiated for 16 h, during which time a color change

from yellow to orange was observed. The solvent was removed under

vacuum, and the residue was extracted with dichloromethane. The

extract was concentrated and treated with hexane to give the product

as orange crystals: yield 0.061 g (87%); IR (chloroform) ν(CO) 1901

1

Sn sat. J_SnC8.8, PhSn), 80.91 (s, Cp), 19.66 (d, J_PC34.1, Me). Anal.

Calcd for C₂₂H₃₇FeOPSn: C, 63.57; H, 4.76. Found: C, 63.56; H, 4.84.

Preparation of [Fe(η⁵-Cp)(SnPh₃)(CO)(P(CH₂Ph)₃)] (6). A

stirred solution of [Fe(η⁵-Cp)(SnPh₃)(CO)₂] (0.058 g, 0110 mmol)

and tribenzylphosphine (0.035 g 0.115 mmol) in toluene (10 mL) at

room temperature was irradiated for 16 h, during which time a color

N

dx.doi.org/10.1021/om4011593 | Organometallics XXXX, XXX, XXX−XXX

Organometallics

Article

change from yellow to orange was observed. The solvent was removed

under vacuum, and the residue was extracted with dichloromethane.

The extract was concentrated and treated with hexane to give the

product as orange crystals: yield 0.075 g (85%); IR (chloroform) ν_CO

1908 cm⁻¹; ¹H NMR (CDCl₃₂300 K) δ7.9−6.9 (m, 25H, Ph), 3.99 (d,

solvent was removed under vacuum, and the residue was extracted

with dichloromethane. The extract was concentrated and treated with

hexane to give the product as red-brown crystals: yield 0.044 g (57%),

1

IR (chloroform) ν(CO) 1908 cm⁻¹; H NMR (CDCl₃300 K) δ 7.36

3

(m, Sn sat. J_SnH∼36, 6H, PhSn), 7.23−7.12 (m, 15H, Ar), 6.80 (m,

6H, C₆H₄P), 4.34 (s, 5H, Cp); ¹³C NMR (CDCl₃300 K) δ 220.23, (d,

2

³J_PH1.3, 5H, Cp), 3.12 (dd, J_HH14.6, J_PH9.7, 3H, CH₂), 2.86 (dd,

1

²J_PC29.2, CO), 163.41 (dd, J_FC252, J_PC2.4, C₆H₄P), 147.23 (s,

²J_HH14.6, ²J_PH6.4, 3H, CH₂); ¹³C NMR (CDCl₃300 K) δ 219.73 (d,

²J_PC28.0, CO), 148.01 (d, ³J_PC1.0, PhSn), 137.50 (s, Sn sat. J_SnC31.9,

PhSn), 135.36 (d, J_PC5.3, benzyl), 130.23 (d, J_PC5.3, benzyl), 128.49

(d, J_PC1.9, benzyl), 127.93 (s, Sn sat. J_SnC35.6, PhSn), 127.35 (s, Sn

sat. J_SnC9.0, PhSn), 126.67 (d, J_PC2.3, benzyl), 79.23 (s, Cp), 38.00 (d,

¹J_PC19.1, CH₂). Anal. Calcd for C₄₅H₄₁FeOPSn: C, 67.28; H, 5.14.

Found: C, 67.03; H, 5.15.

PhSn), 136.99 (s, Sn sat. J_SnC, 31.6, PhSn), 134.93 (dd, J_FC8.4, J_PC

11.6, C₆H₄P), 133.04 (dd, ¹J_PC47.4, J_FC3.6, C₆H₄P), 127.74 (s, Sn sat.

J_SnC36.3 PhSn), 127.09 (s, Sn sat. J_SnC8.8, PhSn), 115.27 (dd, J_FC

21.1, J_PC, 10.6, C₆H₄P), 81.68 (s, Cp). Anal. Calcd for

C₄₂H₃₂F₃FeOPSn: C, 61.88; H, 3.96. Found: C, 61.64; H, 3.94.

Preparation of [Fe(η⁵-Cp)(SnPh₃)(CO)(P(4-CF₃C₆H₄)₃)] (11). A

stirred solution of [Fe(η⁵-Cp)(SnPh₃)(CO)₂] (0.063 g, 0.120 mmol)

and tris(4-triﬂuoromethylphenyl)phosphine (0.058 g, 0.124 mmol) in

toluene (10 mL) at room temperature was irradiated for 16 h, during

which time a color change from yellow to orange was observed. The

solvent was removed under vacuum, and the residue was extracted

with dichloromethane. The extract was concentrated and treated with

hexane to give the product as orange crystals: yield 0.088 g (76%), IR

Preparation of [Fe(η⁵-Cp)(SnPh₃)(CO)(PPh₃)] (7). A stirred

solution of [Fe(η⁵-Cp)(SnPh₃)(CO)₂] (0.050 g, 0.095 mmol) and

triphenylphosphine (0.037 g, 0.141 mmol) in toluene (10 mL) at

room temperature was irradiated for 24 h, during which time a color

change from yellow to red-orange was observed. The solvent was

removed under vacuum, and the residue was extracted with

dichloromethane. The extract was concentrated and treated with

hexane to give the product as dark orange crystals: yield 0.038 g

1

(chloroform) 1914 cm⁻¹; H NMR (CDCl₃300 K) δ 7.4−7.15 (m,

3

27H, Ar), 4.38 (d, J_PH1.4, 5H, Cp); ¹³C NMR (CDCl₃300 K) δ

(50%); IR (chloroform) ν(CO) 1904 cm⁻¹; ¹H NMR (CDCl₃300 K)

2

3

1

219.74 (d, J_PC27.8, CO), 146.34 (d, J_PC0.9, PhSn), 140.61 (d, J_PC

40.0, C₆H₄P), 136.81 (s, Sn sat. J_SnC32.0, PhSn), 133.09 (d, J_PC10.8,

C₆H₄P), 131.90 (dq, J_PC2.3, J_FC32.8, C₆H₄P, 127.90 (s, Sn sat. J_SnC

37.7, PhSn), 127.40 (s, Sn sat. J_SnC9.6, PhSn), 125.15 (dq, J_PC9.8, J_FC

3

δ 7.49−7.05 (m, 30H, Ph), 4.33 (d, J

1.4, 5H, Cp); ¹³C NMR

PH

(CDCl₃300 K) δ 220.50 (d, ²J_PC28.6, CO), 147.90 (d, Sn sat. ³J_PC1.0,

¹J_SnC256, PhSn), 137.35 (d, J_PC40.4, PhP), 137.15 (s, Sn sat. J_SnC

1

31.8, PhSn), 133.12 (d, J_PC10.2, PhP), 129.44 (d, J_PC1.9, PhP),

127.89 (d, J_PC9.6, PhP), 127.54 (s, Sn sat. J_SnC35.8, PhSn), 126.81 (s,

Sn sat. J_SnC8.8, PhSn), 81.72 (s, Cp). Anal. Calcd for C₄₂H₃₅FeOPSn:

C, 66.27; H, 4.63. Found: C, 66.07; H, 4.74.

1

2

3.8, C₆H₄P), 123.47 (dq, J_PC1.0, J_FC272.7, CF₃), 81.83 (d, J_PC0.7,

Cp). Anal. Calcd for C₄₅H₃₂F₉FeOPSn: C, 55.99; H, 3.34. Found: C,

55.86; H, 3.41.

Preparation of [Fe(η⁵-Cp)(SnPh₃)(CO)(P(NMe₂)₃)] (12). A

stirred solution of [Fe(η⁵-Cp)(SnPh₃)(CO)₂] (0.050 g, 0.095

mmol) and tris(dimethylamine)phosphine (0.080 g, 0.50 mmol) in

toluene (10 mL) at room temperature was irradiated for 16 h, during

which time a color change from yellow to orange was observed. The

solvent was removed under vacuum, and the residue was extracted

with dichloromethane. The extract was concentrated and treated with

hexane to give the product as an orange microcrystalline powder: yield

0.065 g (95%). X-ray quality crystals were grown from a CH₂Cl₂/

Preparation of [Fe(η⁵-Cp)(SnPh₃)(CO)(P(4-MeC₆H₄)₃)] (8). A

stirred solution of [Fe(η⁵-Cp)(SnPh₃)(CO)₂] (0.050 g, 0.095 mmol)

and tris(p-tolyl)phosphine (0.043 g, 0.14 mmol) in toluene (10 mL) at

room temperature was irradiated for 20 h, during which time a color

change from yellow to red-orange was observed. The solvent was

removed under vacuum, and the residue was extracted with

dichloromethane. The extract was concentrated and treated with

hexane to give the product as red-orange crystals: yield 0.051 g (63%),

1

IR (chloroform) ν(CO) 1904 cm⁻¹; H NMR (CDCl₃300 K) δ 7.37

1

hexane solution at −20 °C: IR (chloroform) ν(CO) 1900 cm⁻¹; H

3

NMR (CDCl₃300 K) δ 7.57 (m, Sn sat. ³J_SnH∼34, 6H, PhSn), 7.28−

(m, Sn sat. J_SnH∼35, 6H, PhSn), 7.19−7.09 (m, 15H, Ar), 6.89, (m,

3

6H, C₆H₄P), 4.32 (d, J_PH1.4, 5H, Cp), 2.28 (s, 9H, Me); ¹³C NMR

7.17 (m, 9H, PhSn), 4.66 (s, 5H, Cp), 2.42 (d, ³J_PH9.2, 18H, Me); ¹³

C

(CDCl₃300 K) δ 220.70 (d, ²J_PC28.8, CO), 147.98 (d, Sn sat. ³J_PC1.1,

2

NMR (CDCl₃300 K) δ 222.09 (d, J_PC38.7, CO), 148.89 (d, Sn sat.

¹J_SnC250, PhSn), 139.32 (d, J_PC1.8, C₆H₄P), 137.18 (s, Sn sat. J_SnC

,

1

³J_PC2.1, J_SnC226, PhSn), 137.40 (s, Sn sat. J_SnC31.4, PhSn), 127.30

1

31.8, PhSn), 134.49 (d, J_PC44.4, C₆H₄P), 132.99 (d, J_PC10.3,

C₆H₄P), 128.56 (d, J_PC10.0, C₆H₄P), 127.41 (s, Sn sat. J_SnC35.4,

PhSn), 126.61 (s, Sn sat. J_SnC8.8, PhSn), 81.62 (s, Cp), 21.24 (s, Me).

Anal. Calcd for C₄₅H₄₁FeOPSn: C, 67.28 H, 5.14. Found: C, 67.30; H,

5.09.

(s, Sn sat. J_SnC34.0, PhSn), 126.74 (s, Sn sat. J_SnC8.8, PhSn), 79.23 (s,

2

Cp), 39.01 (d, J_PC4.2, Me). Anal. Calcd for C₃₀H₃₈FeN₃OPSn: C,

54.42; H, 5.78; N, 6.35. Found: C, 54.32; H, 5.89; N, 6.55.

Preparation of [Fe(η⁵-Cp)(SnPh₃)(CO)(P(OMe)₃)] (13). A stirred

solution of [Fe(η⁵-Cp)(SnPh₃)(CO)₂] (0.053 g, 0.106 mmol) and

trimethyl phosphite (0.013 g, 0.105 mmol) in toluene (10 mL) at

room temperature was irradiated for 20 h, during which time a color

change from yellow to light orange was observed. The solvent was

removed under vacuum, and the residue was extracted with

dichloromethane. The extract was concentrated and treated with

hexane to give the product as a bright yellow microcrystalline powder:

yield 0.025 g (40%). X-ray-quality crystals were grown from a CH₂Cl₂/

Preparation of [Fe(η⁵-Cp)(SnPh₃)(CO)(P(4-MeOC₆H₄)₃)] (9). A

stirred solution of [Fe(η⁵-Cp)(SnPh₃)(CO)₂] (0.050 g, 0.095 mmol)

and tris(4-methoxyphenyl)phosphine (0.050 g, 0.14 mmol) in toluene

(10 mL) at room temperature was irradiated for 20 h, during which

time a color change from yellow to red-orange was observed. The

solvent was removed under vacuum, and the residue was extracted

with dichloromethane. The extract was concentrated and treated with

hexane to give the product as orange crystals: yield 0.074 g (87%), IR

(chloroform) ν(CO) 1903 cm⁻¹; ¹H NMR (CDCl₃300 K) δ 7.38 (m,

1

hexane solution at −20 °C: IR (chloroform) ν(CO) 1922 cm⁻¹; H

NMR (CDCl₃300 K) δ 7.58 (m, Sn sat. ³J_SnH∼39, 6H, PhSn), 7.30−

7.20 (m, 9H, PhSn), 4.56 (d, ³J_PH0.7, 5H, Cp), 3.39 (d, ²J_PH11.4, 9H,

3

Sn sat. J_SnH∼35, 6H, PhSn), 7.19−7.08 (m, 15H, Ar), 6.60 (m, 6H,

3

C₆H₄P), 4.32 (d, J_PH1.4, 5H, Cp), 3.74 (s, 9H, Me); ¹³C NMR

2

Me); ¹³C NMR (CDCl₃300 K) δ 217.47 (d, J_PC41.5, CO), 147.53

3

1

(CDCl₃300 K) δ 220.74 (d, J_PC29.3, CO), 160.14 (d, J_PC1.6,

(d, Sn sat. J_PC1.8, J_SnC280, PhSn), 137.15 (s, Sn sat. J_SnC33.6,

PhSn), 127.48 (s, Sn sat. J_SnC38.1, PhSn), 127.02 (s, Sn sat. J_SnC9.5,

3

1

C₆H₄P), 148.08 (d, J_PC1.1, J_SnC247, PhSn), 137.07 (s, Sn sat. J_SnC

1

2

31.5, PhSn), 134.37 (d, J_PC11.6, C₆H₄P), 129.16 (d, J_PC47.1,

PhSn), 79.80 (s, Cp), 52.09 (d, J_PC6.1, Me). Anal. Calcd for

C₆H₄P), 127.36 (s, Sn sat. J_SnC35.2, PhSn), 126.59 (s, Sn sat. J_SnC8.9,

PhSn), 113.16 (d, J_PC10.6, C₆H₄P), 81.48 (s, Cp), 58.32 (s, Me). Anal.

Calcd for C₄₅H₄₁FeOPSn: C, 63.49; H, 4.86. Found: C, 63.35, H, 4.85.

Preparation of [Fe(η⁵-Cp)(SnPh₃)(CO)(P(4-FC₆H₄)₃)] (10). A

stirred solution of [Fe(η⁵-Cp)(SnPh₃)(CO)₂] (0.050 g, 0.095 mmol)

and tris(4-ﬂuorophenyl)phosphine (0.045 g, 0.14 mmol) in toluene

(10 mL) at room temperature was irradiated for 24 h, during which

time a color change from yellow to red-orange was observed. The

C₂₇H₂₉FeOPSn: C, 52.05; H, 4.69. Found: C, 51.94; H, 5.03.

Preparation of [Fe(η⁵-Cp)(SnPh₃)(CO)(P(OPh)₃)] (14). A stirred

solution of [Fe(η⁵-Cp)(SnPh₃)(CO)₂] (0.053 g, 0.106 mmol) and

P(OPh)₃(0.040 g, 0.129 mmol) in toluene at room temperature was

irradiated for 16 h, during which time a color change from yellow to

light orange was observed. The solvent was removed under vacuum,

and the residue was extracted with dichloromethane. The extract was

concentrated and treated with hexane to give the product as yellow

O

dx.doi.org/10.1021/om4011593 | Organometallics XXXX, XXX, XXX−XXX

Organometallics

Article

crystals: yield 0.056 g (62%); IR (chloroform) ν(CO) 1936 cm⁻¹; ¹H

Castarlenas, R.; Per

́

ez-Torrente, J. J.; Crucianelli, M.; Polo, V.; Sancho,

3

NMR (CDCl₃300 K) δ 7.63 (m, Sn sat. J_SnH∼40, 6H, PhSn), 7.25

R.; Lahoz, F. J.; Oro, L. A. J. Am. Chem. Soc. 2012, 134, 8171−8183.

(3) (a) Tolman, C. A. J. Am. Chem. Soc. 1970, 92, 2956−2965.

(b) Tolman, C. A. Chem. Rev. 1977, 77, 313−348. (c) Bunten, K. A.;

Chen, L.; Fernandez, A. L.; Poe, A. J. Coord. Chem. Rev. 2002, 233−

234, 41−51.

(4) (a) Alyea, E. C.; Dias, S. A.; Ferguson, G.; Restivo, R. J. Inorg.

Chem. 1977, 16, 2329−2334. (b) Ferguson, G.; Roberts, P. J.; Alyea, E.

C.; Khan, M. Inorg. Chem. 1978, 17, 2965−2967. (c) DeSanto, J. T.;

Mosbo, J. A.; Storhoff, B. N.; Bock, P. L.; Bloss, R. E. Inorg. Chem.

1980, 19, 3086−3092.

(5) Smith, J. M.; Taverner, B. C.; Coville, N. J. J. Organomet. Chem.

1997, 530, 131−140.

(6) (a) Immirzi, A.; Musco, A. Inorg. Chim. Acta 1977, 25, L41−L42.

(b) White, D.; Taverner, B. C.; Leach, P. G. L.; Coville, N. J. J.

Organomet. Chem. 1994, 478, 205−211. (c) White, D.; Taverner, B. C.;

Coville, N. J.; Wade, P. W. J. Organomet. Chem. 1995, 495, 41−51.

(d) Taverner, B. C. J. Comput. Chem. 1996, 17, 1612−1623. (e) Guzei,

I. A.; Wendt, M. Dalton Trans. 2006, 3991−3999.

(m, 9H, PhSn), 7.18 (m, 6H, PhO), 7.08 (m, 3H, PhO), 6.78 (m, 6H,

2

PhO), 4.26 (s, 5H, Cp); ¹³C NMR (CDCl₃300 K) δ 216.86 (d, J_PC

40.6, CO), 151.75 (d, J_PC10.6, PhO), 146.65 (s, PhSn), 137.30 (s, Sn

sat. J_SnC33.9, PhSn), 129.35 (s, PhO), 127.76 (s, Sn sat. J_SnC39.4,

PhSn), 127.28 (s, Sn sat. J_SnC9.8, PhSn), 124.03 (s, PhO), 121.38 (d,

J_PC4.2, PhO), 80.17 (s, Cp). Anal. Calcd for C₄₂H₃₅FeO₄PSn: C,

62.36; H, 4.36. Found: C, 62.38; H, 4.47.

̈

ASSOCIATED CONTENT

* Supporting Information

■

S

Tables giving crystal data and structure reﬁnement, ﬁgures

giving additional plots, and CIF ﬁles giving crystal coordinates

for compounds 2, 3, and 5−14. This material is available free of

charge via the Internet at http://pubs.acs.org. The CIF ﬁles can

also be obtained from the Cambridge Crystallographic Data

Centre (CCDC) as ﬁle numbers 973675−973686.

(7) (a) Brown, T. L. Inorg. Chem. 1992, 31, 1286−1294. (b) Brown,

T. L.; Lee, K. J. Coord. Chem. Rev. 1993, 128, 89−116. (c) Choi, M.-

G.; Brown, T. L. Inorg. Chem. 1993, 32, 5603−5610.

AUTHOR INFORMATION

Notes

The authors declare no competing ﬁnancial interest.

■

(8) Angermund, K.; Baumann, W.; Dinjus, E.; Fornika, R.; Gorls, H.;

̈

Kessler, M.; Kruger, C.; Leitner, W.; Lutz, F. Chem. Eur. J. 1997, 3,

̈

755−764.

ACKNOWLEDGMENTS

We thank the University of the Witwatersrand and the NRF for

ﬁnancial support.

■

(9) Suresh, C. H. Inorg. Chem. 2006, 45, 4982−4986.

(10) Clavier, H.; Nolan, S. P. Chem. Commun. 2010, 46, 841−861.

(11) Trogler, W. C.; Marzilli, L. G. J. Am. Chem. Soc. 1974, 96, 7589−

7591.

(12) Muller, T. E.; Mingos, D. M. P. Transition Met. Chem. 1995, 20,

REFERENCES

̈

■

533−539.

(1) (a) Heimbach, P.; Kluth, J.; Schenkluhn, H.; Weimann, B. Angew.

Chem., Int. Ed. 1980, 19, 569−570. (b) Heimbach, P.; Kluth, J.;

Schenkluhn, H.; Weimann, B. Angew. Chem., Int. Ed. 1980, 19, 570−

(13) Bartik, T.; Himmler, T.; Schultz, H.-G.; Seevogel, K. J.

Organomet. Chem. 1984, 272, 29−41.

(14) (a) Henderson, W. A.; Streuli, C. A. J. Am. Chem. Soc. 1960, 82,

5791−5794. (b) Allman, T.; Goel, R. G. Can. J. Chem. 1982, 60, 716−

722. (c) Moore, S. J.; Marzilli, L. G. Inorg. Chem. 1998, 37, 5329−

́

571. (c) Pruchnik, F. P.; Smolenski, P.; Wajda-Hermanowicz, K. J.

Organomet. Chem. 1998, 570, 63−69. (d) Serron, S.; Huang, J.; Nolan,

S. P. Organometallics 1998, 17, 534−539. (e) Hamann, B. C.; Hartwig,

J. F. J. Am. Chem. Soc. 1998, 120, 3694−3703. (f) Palo, D. R.; Erkey, C.

5335. (d) Babij, C.; Poe, A. J. J. Phys. Org. Chem. 2004, 17, 162−167.

̈

(15) Mastryukova, T. A.; Kabachnik, M. I. J. Org. Chem. 1971, 36,

1201−1205.

̀

Organometallics 2000, 19, 81−86. (g) Cavallo, L.; Sola, M. J. Am.

Chem. Soc. 2001, 123, 12294−12302. (h) von Schenk, H.; Åkermark,

B.; Svensson, M. Organometallics 2002, 21, 2248−2253. (i) Daura-

Oller, E.; Poblet, J. M.; Bo, C. Dalton Trans. 2003, 92−98. (j) Mann,

G.; Shelby, Q.; Roy, A. H.; Hartwig, J. F. Organometallics 2003, 22,

(16) (a) Lever, A. P. B. Inorg. Chem. 1990, 29, 1271−1285. (b) Lever,

A. P. B. Inorg. Chem. 1991, 30, 1980−1985.

́

(17) Amatore, C.; Carre, E.; Jutand, A.; M’Barki, M. A. Organo-

metallics 1995, 14, 1818−1826.

́

2775−2789. (k) Hegedus, C.; Madarasz, J.; Gergely, I.; Szollosy, A.;

̈ ̈

̈

(18) (a) Luo, L.; Nolan, S. P. Organometallics 1994, 13, 4781−4786.

(b) Serron, S.; Nolan, S. P.; Moloy, K. G. Organometallics 1996, 15,

4301−4306.

Monsees, A.; Riermeier, T.; Bakos, J. Tetrahedron: Asymmetry 2004,

15, 2507−2513. (l) Lautens, M.; Fagnou, K. Proc. Natl. Acad. Sci.

U.S.A. 2004, 101, 5455−5460. (m) DeVasher, R. B.; Spruell, J. M.;

Dixon, D. A.; Broker, G. A.; Griffin, S. T.; Rogers, R. D.; Shaughnessy,

(19) Weiner, M. A.; Lattman, M.; Grim, S. O. J. Org. Chem. 1975, 40,

1292−1294.

K. H. Organometallics 2005, 24, 962−971. (n) Hedberg, C.; Kallstrom,

̈

(20) (a) Cowley, A. H.; Damasco, M. C. J. Am. Chem. Soc. 1971, 93,

6815−6821. (b) Bodner, G. M. Inorg. Chem. 1975, 14, 1932−1935.

(c) Bodner, G. M. Inorg. Chem. 1975, 14, 2694−2699. (d) Bodner, G.

M.; May, M. P.; McKinney, L. E. Inorg. Chem. 1980, 19, 1951−1958.

(e) Allen, D. W.; Taylor, B. F. J. Chem. Soc., Dalton Trans. 1982, 51−

54. (f) Wang, S. P.; Richmond, M. G.; Schwartz, M. J. Am. Chem. Soc.

1992, 114, 7595−7596.

K.; Brandt, P.; Hansen, L. K.; Andersson, P. G. J. Am. Chem. Soc. 2006,

128, 2995−3001. (o) Cobley, C. J.; Froese, R. D. J.; Klosin, J.; Qin, C.;

Whiteker, G. T.; Abboud, K. A. Organometallics 2007, 26, 2986−2999.

(p) Sparta, M.; Børve, K. J.; Jensen, V. R. J. Am. Chem. Soc. 2007, 129,

8487−8499. (q) Moore, L. R.; Western, E. C.; Craciun, R.; Spruel, J.

M.; Dixon, D. A.; O’Halloran, K. P.; Shaughnessy, K. H. Organo-

metallics 2008, 27, 576−593. (r) Clarke, M. L.; Frew, J. J. R.

Organomet. Chem. 2009, 35, 19−46. (s) Grabulosa, A.; Frew, J. J. R.;

Fuentes, J. A.; Slawin, A. M. Z.; Clarke, M. L. J. Mol. Catal. A 2010,

330, 18−25. (t) Hanley, P. S.; Hartwig, J. F. J. Am. Chem. Soc. 2011,

133, 15661−15673. (u) Song, D.-P.; Shi, X.-C.; Wang, Y.-X.; Yang, J.-

X.; Li, Y.-S. Organometallics 2012, 31, 966−975. (v) Demchuk, O. M.;

(21) (a) Perrin, L.; Clot, E.; Eisenstein, O.; Loch, J.; Crabtree, R.

Inorg. Chem. 2001, 40, 5806−5811. (b) Suresh, C. H.; Koga, N. Inorg.

Chem. 2002, 41, 1573−1578.

(22) (a) Xiao, S.-X.; Trogler, W. C.; Ellis, D. E.; Berkovich-Yellin, Z.

J. Am. Chem. Soc. 1983, 105, 7033−7037. (b) Marynick, D. S. J. Am.

Chem. Soc. 1984, 106, 4064−4065. (c) Paccioni, G.; Bagus, P. S. Inorg.

́

Arlt, D.; Jasinski, R.; Pietrusiewicz, K. M. J. Phys. Org. Chem. 2012, 25,

́

Chem. 1992, 31, 4391−4398. (d) Gonzalez-Blanco, O.; Branchadell, V.

1006−1011. (w) Zingales, N. C.; Shaffer, A. R.; Schmidt, J. A. R.

Organometallics 2013, 32, 578−586. (x) Weickmann, D.; Frey, W.;

Plietker, B. Chem. Eur. J. 2013, 19, 2741−2748.

Organometallics 1997, 17, 5556−5562. (e) Landis, C. R.; Feldgus, S.;

Uddin, J.; Wozniak, C. E.; Moloy, K. G. Organometallics 2000, 19,

4878−4886. (f) Cooney, K. D.; Cundari, T. R.; Hoffman, N. W.;

Pittard, K. A.; Temple, M. D.; Zhao, Y. J. Am. Chem. Soc. 2003, 125,

4318−4324. (g) Leyssens, T.; Peeters, D.; Orpen, A. G.; Harvey, J. N.

New J. Chem. 2005, 29, 1424−1430. (h) Leyssens, T.; Peeters, D.;

Orpen, A. G.; Harvey, J. N. Organometallics 2007, 26, 2637−2645.

́

(2) (a) Díez-Gonzalez, S.; Nolan, S. P. Coord. Chem. Rev. 2007, 251,

874−883. (b) Mathew, J.; Suresh, C. H. Organometallics 2011, 30,

3106−3112. (c) Song, H.; Liu, Y.; Fan, D.; Zi, G. J. Organomet. Chem.

́

2011, 696, 3714−3720. (d) Grudzien, K.; Malinska, M.; Barbasiewicz,

M. Organometallics 2012, 31, 3636−3646. (e) Di Giuseppe, A.;

P

dx.doi.org/10.1021/om4011593 | Organometallics XXXX, XXX, XXX−XXX

Organometallics

Article

(23) Mathew, J.; Thomas, T.; Suresh, C. H. Inorg. Chem. 2007, 46,

10800−10809.

́

1996, 34, 1036−1042. (c) Meier, E. J. M.; Kozminski, W.; Linden, A.;

Lustenberger, P.; von Philipsborn, W. Organometallics 1996, 15,

2469−2477.

(24) (a) Orpen, A. G.; Connelly, N. G. Organometallics 1990, 9,

1206−1210. (b) Ernst, R. D.; Freeman, J. W.; Stahl, L.; Wilson, D. R.;

Arif, A. M.; Nuber, B.; Ziegler, M. L. J. Am. Chem. Soc. 1995, 117,

5075−5081. (c) Davies, M. S.; Aroney, M. J.; Buys, I. E.; Hambley, T.

W.; Calvert, J. L. Inorg. Chem. 1995, 34, 330−336.

(42) (a) Benn, R.; Brevard, C. J. Am. Chem. Soc. 1986, 108, 5622−

́

5624. (b) Benn, R.; Rufinska, A. Magn. Reson. Chem. 1988, 26, 895−

902. (c) Benn, R.; Brenneke, H.; Frings, A.; Lehmkuhl, H.; Mehler, G.;

Rufinska, A.; Wildt, T. J. Am. Chem. Soc. 1988, 110, 5661−5668.

(d) Benn, R.; Rufinska, A.; Kralik, M. S.; Ernst, R. D. J. Organomet.

́

(25) (a) Frenking, G.; Wichmann, K.; Frolich, N.; Grobe, J.; Golla,

̈

Chem. 1989, 375, 115−121.

W.; Le Van, D.; Krebs, B.; Lage, M. Organometallics 2002, 21, 2921−

̈

(43) (a) Wrackmeyer, B.; Ayazi, A.; Maisel, H. E.; Herberhold, M. J.

Organomet. Chem. 2001, 630, 263−265. (b) Wrackmeyer, B.; Tok, O.

L.; Ayazi, A.; Hertel, F.; Herberhold, M. Z. Naturforsch., B 2002, 57b,

305−308. (c) Wrackmeyer, B.; Tok, O. L.; Ayazi, A.; Maisel, H. E.;

Herberhold, M. Magn. Reson. Chem. 2004, 42, 827−830. (d) Wrack-

meyer, B.; Klimkina, E. V.; Maisel, H. E.; Tok, O. L.; Herberhold, M.

Magn. Reson. Chem. 2008, 46, S30−S35.

2930. (b) Fey, N.; Orpen, A. G.; Harvey, J. N. Coord. Chem. Rev. 2009,

253, 704−722.

(26) (a) Drago, R. S. Organometallics 1985, 14, 3408−3417.

(b) Drago, R. S.; Joerg, S. J. Am. Chem. Soc. 1996, 118, 2654−2663.

(c) Joerg, S.; Drago, R. S.; Sales, J. Organometallics 1998, 17, 589−599.

(27) (a) Golovin, M. N.; Rahman, Md. M.; Belmonte, J. E.; Giering,

W. P. Organometallics 1985, 4, 1981−1991. (b) Rahman, Md. M.; Liu,

H. Y.; Prock, A.; Giering, W. P. Organometallics 1987, 6, 650−658.

(c) Rahman, Md. M.; Liu, H.-Y.; Eriks, K.; Prock, A.; Giering, W. P.

Organometallics 1989, 8, 1−7. (d) Wilson, M. R.; Woska, D. C.; Prock,

A.; Giering, W. P. Organometallics 1993, 12, 1742−1752. (e) Fernan-

dez, A. L.; Reyes, C.; Prock, A.; Giering, W. P. J. Chem. Soc., Perkin

Trans 2 2000, 1033−1041. (f) Wilson, M. R.; Prock, A.; Giering, W.

P.; Fernandez, A. L.; Haar, C. M.; Nolan, S. P.; Foxman, B. M.

́

(44) Juranic, N. Coord. Chem. Rev. 1989, 96, 253−290.

(45) (a) Webb, G. A. In NMR and the Periodic Table; Harris, R. K.,

Mann, B. E., Eds.; Academic Press: London, 1978. (b) Webb, G. A. In

NMR of Newly Accessible Nuclei; Laszlo, P., Ed.; Academic Press: New

York, 1983. (c) Jameson, C. J.; Mason, J. In Multinuclear NMR;

Mason, J., Ed.; Plenum Press: New York, 1987. (d) Buhl, M.; Kaupp,

̈

M.; Malkina, O. L.; Malkin, V. G. J. Comput. Chem. 1999, 20, 91−105.

(e) Buhl, M. Annu. Rep. NMR Spectrosc. 2008, 64, 77−126.

̈

Organometallics 2002, 21, 2758−2763. (g) Poe, A. J. Dalton Trans.

̈

(46) (a) Pople, J. A. J. Chem. Phys. 1956, 24, 1111. (b) Bernstein, H.

J.; Schneider, W. G.; Pople, J. A. Proc. R. Soc. London 1956, 236, 515−

528. (c) Abraham, R. J.; Fisher, J.; Loftus, P. Introduction to NMR

Spectroscopy; Wiley: New York, 1988.

2009, 1999−2003.

(28) (a) Fernandez, A.; Reyes, C.; Wilson, M. R.; Woska, D. C.;

Prock, A.; Giering, W. P. Organometallics 1997, 16, 342−348.

(b) Fernandez, A. L.; Lee, T. Y.; Reyes, C.; Prock, A.; Giering, W.

P. Organometallics 1998, 17, 3169−3175.

(47) Mahnke, H.; Clark, R. J.; Rosanske, R.; Sheline, R. K. J. Chem.

Phys. 1974, 60, 2997−3004.

(48) McFarlane, W.; Rees, N. H. J. Chem. Soc., Dalton Trans. 1990,

3211−3214.

(49) Carlton, L. Annu. Rep. NMR Spectrosc. 2008, 63, 49−178.

(50) Guzei, I. A.; Wendt, M. Solid-G Version 0.25; University of

WisconsinMadison, Madison, WI, USA, 2006.

(51) Carlton, L.; Emdin, A.; Lemmerer, A.; Fernandes, M. A. Magn.

Reson. Chem. 2008, 46, S56−S62.

(52) Mason, J. Chem. Rev. 1987, 87, 1299−1312.

(53) Gorsich, R. D. J. Am. Chem. Soc. 1962, 84, 2486−2491.

(54) (a) Cullen, W. R.; Sams, J. R.; Thompson, J. A. J. Inorg. Chem.

1971, 10, 843−850. (b) Carlton, L.; Lindsell, W. E.; Preston, P. N. J.

Chem. Soc., Dalton Trans. 1982, 1483−1489.

(55) Bax, A.; Griffey, R. H.; Hawkins, B. L. J. Magn. Reson. 1983, 55,

301−315.

(56) SMART-NT version 5.050; Bruker AXS Inc., Madison, WI, USA,

1998.

(29) Giering, W. P.; Prock, A.; Fernandez, A. L. Inorg. Chem. 2003,

42, 8033−8037.

(30) (a) Alyea, E. C.; Song, S. Comments Inorg. Chem. 1996, 18, 145−

164. (b) Alyea, E. C.; Song, S. Comments Inorg. Chem. 1996, 18, 189−

221.

(31) Kuhl, O. Coord. Chem. Rev. 2005, 249, 693−704.

̈

(32) Morris, A. L.; York, J. T. J. Chem. Educ. 2009, 86, 1408−1411.

(33) (a) Alyea, E. C.; Song, S. Inorg. Chem. 1992, 31, 4909−4910.

(b) Alyea, E. C.; Song, S. Inorg. Chem. 1995, 34, 3864−3873.

(34) (a) Schenkluhn, H.; Scheidt, W.; Weimann, B.; Zahres, M.

̈

Angew. Chem., Int. Ed. 1979, 18, 401−402. (b) Berger, R.; Schenkluhn,

H.; Weimann, B. Transition Met. Chem. 1981, 6, 272−277. (c) Serron,

S. A.; Nolan, S. P. Organometallics 1995, 14, 4611−4616. (d) Elsevier,

C. J.; Kowall, B.; Kragten, H. Inorg. Chem. 1995, 34, 4836−4839.

́

(e) Bell, A. G.; Kozminski, W.; Linden, A.; von Philipsborn, W.

Organometallics 1996, 15, 3124−3135. (f) Huang, J.; Serron, S.; Nolan,

S. P. Organometallics 1998, 17, 4004−4008. (g) Haar, C. M.; Nolan, S.

P.; Marshall, W. J.; Moloy, K. G.; Prock, A.; Giering, W. P.

Organometallics 1999, 18, 474−479.

(57) APEX2 Version 2.0-1; Bruker AXS Inc., Madison, WI, USA,

2005.

(58) SAINT-Plus Version 6.0 (includes XPREP and SADABS); Bruker

AXS Inc., Madison, WI, USA, 2005.

(59) Sheldrick, G. M. Acta Crystallogr., Sect. A 2008, 64, 112−122.

(60) Farrugia, L. J. J. Appl. Crystallogr. 1997, 30, 565.

(35) (a) Zizelman, P. M.; Amatore, C.; Kochi, J. K. J. Am. Chem. Soc.

1984, 106, 3771−3784. (b) Dahlinger, K.; Falcone, F.; Poe, A. J. Inorg.

̈

Chem. 1986, 25, 2654−2658. (c) Brodie, N. M. J.; Chen, L.; Poe, A. J.

̈

Int. J. Chem. Kinet. 1988, 20, 467−491. (d) Poe, A. J. Pure Appl. Chem.

̈

1988, 60, 1209−1216. (e) Moreno, C.; Macazaga, M. J.; Delgado, S.

Organometallics 1991, 10, 1124−1130. (f) Poe, A. J.; Farrar, D. H.;

̈

Zheng, Y. J. Am. Chem. Soc. 1992, 114, 5146−5152.

(36) Babij, C.; Chen, H.; Chen, L.; Poe, A. J. Dalton Trans. 2003,

̈

3184−3191.

(37) (a) Bresciani-Pahor, N.; Calligaris, M.; Randaccio, L. Inorg.

Chim. Acta 1980, 39, 173−179. (b) Bresciani-Pahor, N.; Randaccio, L.;

Toscano, P. J. J. Chem. Soc., Dalton Trans. 1982, 1559−1563.

(38) Cotton, S. A.; Darensbourg, D. J.; Klein, S.; Kolthammer, B. W.

S. Inorg. Chem. 1982, 21, 294−299.

(39) Serron, S. A.; Luo, L.; Li, C.; Cucullu, M. E.; Stevens, E. D.;

Nolan, S. P. Organometallics 1995, 14, 5290−5297.

(40) Liu, H.-Y.; Eriks, K.; Prock, A.; Giering, W. P. Organometallics

1990, 9, 1758−1766.

(41) (a) Jenny, T.; von Philipsborn, W.; Kronenbitter, J.; Schwenk, A.

J. Organomet. Chem. 1981, 205, 211−222. (b) Hopp Rensch, G.; Nanz,

D.; Solana, I.; Stefanova, R.; von Philipsborn, W. Magn. Reson. Chem.

Q

dx.doi.org/10.1021/om4011593 | Organometallics XXXX, XXX, XXX−XXX

Article Doi

Iron-57 NMR and structural study of [Fe(η5-Cp)(SnPh 3)(CO)(PR3)] (PR3 = phosphine, phosphite). Separation of steric and electronic σ and π effects

DOI: 10.1021/om4011593

Source and publish data:

Authors:

Article abstract of DOI:10.1021/om4011593

Full text of DOI:10.1021/om4011593

Products guided by the article

R&D Labs maybe for 32661-67-9

Relevant to this article

Hot Product