18 research outputs found
Ag<sub>13</sub>-Centered Cuboctahedral Architecture in Inorganic Cluster Chemistry: A DFT Investigation
The bonding in the [Ag<sub>13</sub>{Ī¼<sub>3</sub>-FeĀ(CO)<sub>4</sub>}<sub>8</sub>]<sup>3ā/5ā</sup> clusters, which exhibit an Ag<sub>13</sub>-centered cuboctahedral
core, has been analyzed and rationalized by DFT calculations. Not
considering the interaction with its encapsulated atom, the empty
[Ag<sub>12</sub>{Ī¼<sub>3</sub>-FeĀ(CO)<sub>4</sub>}<sub>8</sub>]<sup>4ā</sup> cage can be considered as the assembly of 12
linearly coordinated 14-electron Ag<sup>I</sup> metal centers. Adding
a supplementary Ag<sup>+</sup> at the center allows some covalent
delocalized bonding which to some extent tends to reduce the electron
deficiency of the 14-electron centers. Adding now two electrons strengthens
the delocalized bonding between the encapsulated atom and its host,
making [Ag<sub>13</sub>{Ī¼<sub>3</sub>-FeĀ(CO)<sub>4</sub>}<sub>8</sub>]<sup>5ā</sup> a superatom with two jellium (5s-type)
electrons. TDDFT calculations predict near-IR absorption for this
penta-anion, because of the presence of an a<sub>1g</sub> HOMO in
the middle of an energy gap. Luminescence in the same optical range
is also suggested. Other related cubococtahedral species, such as
[Ag<sub>23</sub>(SH)<sub>16</sub>]<sup>ā</sup>, a model for
the known 8-electron [Au<sub>23</sub>(SR)<sub>16</sub>]<sup>ā</sup> species which exhibits a bicapped centered dodecahedral kernel structure,
have also been investigated
Ag<sub>13</sub>-Centered Cuboctahedral Architecture in Inorganic Cluster Chemistry: A DFT Investigation
The bonding in the [Ag<sub>13</sub>{Ī¼<sub>3</sub>-FeĀ(CO)<sub>4</sub>}<sub>8</sub>]<sup>3ā/5ā</sup> clusters, which exhibit an Ag<sub>13</sub>-centered cuboctahedral
core, has been analyzed and rationalized by DFT calculations. Not
considering the interaction with its encapsulated atom, the empty
[Ag<sub>12</sub>{Ī¼<sub>3</sub>-FeĀ(CO)<sub>4</sub>}<sub>8</sub>]<sup>4ā</sup> cage can be considered as the assembly of 12
linearly coordinated 14-electron Ag<sup>I</sup> metal centers. Adding
a supplementary Ag<sup>+</sup> at the center allows some covalent
delocalized bonding which to some extent tends to reduce the electron
deficiency of the 14-electron centers. Adding now two electrons strengthens
the delocalized bonding between the encapsulated atom and its host,
making [Ag<sub>13</sub>{Ī¼<sub>3</sub>-FeĀ(CO)<sub>4</sub>}<sub>8</sub>]<sup>5ā</sup> a superatom with two jellium (5s-type)
electrons. TDDFT calculations predict near-IR absorption for this
penta-anion, because of the presence of an a<sub>1g</sub> HOMO in
the middle of an energy gap. Luminescence in the same optical range
is also suggested. Other related cubococtahedral species, such as
[Ag<sub>23</sub>(SH)<sub>16</sub>]<sup>ā</sup>, a model for
the known 8-electron [Au<sub>23</sub>(SR)<sub>16</sub>]<sup>ā</sup> species which exhibits a bicapped centered dodecahedral kernel structure,
have also been investigated
[M<sub>16</sub>Ni<sub>24</sub>(CO)<sub>40</sub>]<sup>4ā</sup>: Coinage Metal Tetrahedral Superatoms as Useful Building Blocks Related to Pyramidal Au<sub>20</sub> Clusters (M = Cu, Ag, Au). Electronic and Bonding Properties from Relativistic DFT Calculations
Characterization
of the tetrahedral Au<sub>20</sub> structure in
the gas phase remains a major landmark in gold cluster chemistry,
where further efforts to stabilize this bare 20-electron superatom
in solution to extend and understand its chemistry have failed so
far. Here, we account for the structural, electronic, and bonding
properties of [M<sub>16</sub>Ni<sub>24</sub>(CO)<sub>40</sub>]<sup>4ā</sup> (M = Cu, Ag, Au) observed in solution for gold and
silver. Our results show a direct electronic relationship with Au<sub>20</sub>, owing that such species share a common tetrahedral [M<sub>16</sub>]<sup>4ā</sup> central core with a 1S<sup>2</sup>1P<sup>6</sup>1D<sup>10</sup>2S<sup>2</sup> jellium configuration. In the
case of Au<sub>20</sub>, the [Au<sub>16</sub>]<sup>4ā</sup> core is capped by four Au<sup>+</sup> ions, whereas in [M<sub>16</sub>Ni<sub>24</sub>(CO)<sub>40</sub>]<sup>4ā</sup> it is capped
by four Ni<sub>6</sub>(CO)<sub>10</sub> units. In both cases, the
capping entities are a full part of the superatom entity, where it
appears that the free (uncapped) [M<sub>16</sub>]<sup>4ā</sup> species must be capped for further stabilization. It follows that
the Ni<sub>6</sub>(CO)<sub>10</sub> units in [M<sub>16</sub>Ni<sub>24</sub>(CO)<sub>40</sub>]<sup>4ā</sup> should not be considered
as external ligands as their bonding with the [M<sub>16</sub>]<sup>4ā</sup> core is mainly associated with a delocalization of
the 20 jellium electrons onto the Ni atoms. Thus, the [M<sub>16</sub>Ni<sub>24</sub>(CO)<sub>40</sub>]<sup>4ā</sup> species can
be seen as the solution version of tetrahedral M<sub>20</sub> clusters,
encouraging experimental efforts to further develop the chemistry
of such complexes as M(111) finite surface section structures, with
M = Ag and Au and, particularly promising, with M = Cu. Furthermore,
optical properties were simulated to assist future experimental characterization
New Main-Group-Element-Rich <i>nido</i>-Octahedral Cluster System: Synthesis and Characterization of [Et<sub>4</sub>N][Fe<sub>2</sub>(CO)<sub>6</sub>(Ī¼<sub>3</sub>āAs){Ī¼<sub>3</sub>āEFe(CO)<sub>4</sub>}<sub>2</sub>]
A series of clusters
of the form [Et<sub>4</sub>N]Ā[Fe<sub>2</sub>Ā(CO)<sub>6</sub>Ā(Ī¼<sub>3</sub>-As)}Ā(Ī¼<sub>3</sub>-EFeĀ(CO)<sub>4</sub>)], where E is either P or As, were synthesized from [Et<sub>4</sub>N]<sub>2</sub>Ā[HAsĀ{FeĀ(CO)<sub>4</sub>}<sub>3</sub>] and ECl<sub>3</sub>. AsCl<sub>3</sub> gives the As-only
compound; PCl<sub>3</sub> produces compounds having two As atoms with
one P atom, or one As atom and two P atoms, and they can exist as
two possible isomers, one of which is chiral. The As<sub>2</sub>P
and AsP<sub>2</sub> clusters cocrystallize, and their structure as
determined by single-crystal X-ray diffraction is given along with
the structure of the As-only cluster. Analytical data as well as density
functional theory calculations support the formation and geometries
of the new molecules
Neutron Diffraction Studies of a Four-Coordinated Hydride in Near Square-Planar Geometry
The
structure of a nanospheric polyhydrido copper cluster, [Cu<sub>20</sub>(H)<sub>11</sub>{S<sub>2</sub>PĀ(O<sup><i>i</i></sup>Pr)<sub>2</sub>}<sub>9</sub>], was determined by single-crystal neutron diffraction.
The Cu<sub>20</sub> cluster consists of an elongated triangular orthobicupola
constructed from 18 Cu atoms that encapsulate a [Cu<sub>2</sub>H<sub>5</sub>]<sup>3ā</sup> ion with an exceptionally short CuāCu
distance. The 11 hydrides in the cluster display three different coordination
modes to the Cu atoms: six Ī¼<sub>3</sub>-hydrides in a pyramidal
geometry, two Ī¼<sub>4</sub>-hydrides in a tetrahedral cavity,
and three Ī¼<sub>4</sub>-hydrides in an unprecedented near square-planar
geometry. The neutron data set was collected for 7 days on a small
crystal with dimensions of 0.20 mm Ć 0.50 mm Ć 0.65 mm using
the Spallation Neutron Source TOPAZ single-crystal time-of-flight
Laue diffractometer at Oak Ridge National Laboratory. The final <i>R</i>-factor was 8.63% for 16,014 reflections
Neutron Diffraction Studies of a Four-Coordinated Hydride in Near Square-Planar Geometry
The
structure of a nanospheric polyhydrido copper cluster, [Cu<sub>20</sub>(H)<sub>11</sub>{S<sub>2</sub>PĀ(O<sup><i>i</i></sup>Pr)<sub>2</sub>}<sub>9</sub>], was determined by single-crystal neutron diffraction.
The Cu<sub>20</sub> cluster consists of an elongated triangular orthobicupola
constructed from 18 Cu atoms that encapsulate a [Cu<sub>2</sub>H<sub>5</sub>]<sup>3ā</sup> ion with an exceptionally short CuāCu
distance. The 11 hydrides in the cluster display three different coordination
modes to the Cu atoms: six Ī¼<sub>3</sub>-hydrides in a pyramidal
geometry, two Ī¼<sub>4</sub>-hydrides in a tetrahedral cavity,
and three Ī¼<sub>4</sub>-hydrides in an unprecedented near square-planar
geometry. The neutron data set was collected for 7 days on a small
crystal with dimensions of 0.20 mm Ć 0.50 mm Ć 0.65 mm using
the Spallation Neutron Source TOPAZ single-crystal time-of-flight
Laue diffractometer at Oak Ridge National Laboratory. The final <i>R</i>-factor was 8.63% for 16,014 reflections
A Twelve-Coordinated Iodide in a Cuboctahedral Silver(I) Skeleton
Three new halide-centered
octanuclear silverĀ(I) complexes, [Ag<sub>8</sub>(X)Ā{S<sub>2</sub>PĀ(CH<sub>2</sub>CH<sub>2</sub>Ph)<sub>2</sub>}<sub>6</sub>]Ā(PF<sub>6</sub>), X = F<sup>ā</sup>, <b>1</b>; Cl<sup>ā</sup>, <b>2</b>; Br<sup>ā</sup>, <b>3</b>; were prepared
in the presence of the corresponding halide anions with silverĀ(I)
salts and dithiophosphinate ligands. Structure analyses displayed
that a Ag<sub>8</sub> cubic core can be modulated by the size effect
of the central halide; however, an iodide-centered Ag<sub>8</sub> cluster
was not found under similar reaction conditions. Interestingly, a
luminescent dodecanuclear silverĀ(I) cluster, [Ag<sub>12</sub>(Ī¼<sub>12</sub>-I)Ā(Ī¼<sub>3</sub>-I)<sub>4</sub>{S<sub>2</sub>PĀ(CH<sub>2</sub>CH<sub>2</sub>Ph)<sub>2</sub>}<sub>6</sub>]Ā(I), <b>4</b>; was then synthesized. The structure of <b>4</b> contains
a novel Ī¼<sub>12</sub>-I at the center of a cuboctahedral silverĀ(I)
atom cage, which is further stabilized by four additional Ī¼<sub>3</sub>-I and six dithiophosphinate ligands. To the best of our knowledge,
the Ī¼<sub>12</sub>-I revealed in <b>4</b> is the highest
coordination number for a halide ion authenticated by both experimental
and computational studies. Previously, the Ī¼<sub>12</sub>-I
was only observed in [PyH]Ā[{TpMoĀ(Ī¼<sub>3</sub>-S)<sub>4</sub>Cu<sub>3</sub>}<sub>4</sub>(Ī¼<sub>12</sub>-I)]. The synthetic
details, spectroscopic studies including multinuclear NMR and ESI-MS,
structure elucidations by single crystal X-ray diffraction, and photoluminescence
of <b>4</b> are reported herein
Hydrido Copper Clusters Supported by Dithiocarbamates: Oxidative Hydride Removal and Neutron Diffraction Analysis of [Cu<sub>7</sub>(H){S<sub>2</sub>C(aza-15-crown-5)}<sub>6</sub>]
Reactions of CuĀ(I) salts with NaĀ(S<sub>2</sub>CR) (R
= N<sup><i>n</i></sup>Pr<sub>2</sub>, NEt<sub>2</sub>, aza-15-crown-5),
and (Bu<sub>4</sub>N)Ā(BH<sub>4</sub>) in an 8:6:1 ratio in CH<sub>3</sub>CN solution at room temperature yield the monocationic hydride-centered
octanuclear Cu<sup>I</sup> clusters, [Cu<sub>8</sub>(H)Ā{S<sub>2</sub>CR}<sub>6</sub>]Ā(PF<sub>6</sub>) (R = N<sup><i>n</i></sup>Pr<sub>2</sub>, <b>1</b><sub><b>H</b></sub>; NEt<sub>2</sub>, <b>2</b><sub><b>H</b></sub>; aza-15-crown-5, <b>3</b><sub><b>H</b></sub>). Further reactions of [Cu<sub>8</sub>(H)Ā{S<sub>2</sub>CR}<sub>6</sub>]Ā(PF<sub>6</sub>) with 1 equiv
of (Bu<sub>4</sub>N)Ā(BH<sub>4</sub>) produced neutral heptanuclear
copper clusters, [Cu<sub>7</sub>(H)Ā{S<sub>2</sub>CR}<sub>6</sub>]
(R = N<sup><i>n</i></sup>Pr<sub>2</sub>, <b>4</b><sub><b>H</b></sub>; NEt<sub>2</sub>, <b>5</b><sub><b>H</b></sub>; aza-15-crown-5, <b>6</b><sub><b>H</b></sub>)
and clusters <b>4</b>ā<b>6</b> can also be generated
from the reaction of CuĀ(BF<sub>4</sub>)<sub>2</sub>, NaĀ(S<sub>2</sub>CR), and (Bu<sub>4</sub>N)Ā(BH<sub>4</sub>) in a 7:6:8 molar ratio
in CH<sub>3</sub>CN. Reformation of cationic Cu<sup>I</sup><sub>8</sub> clusters by adding 1 equiv of Cu<sup>I</sup> salt to the neutral
Cu<sub>7</sub> clusters in solution is observed. Intriguingly, the
central hydride in [Cu<sub>8</sub>(H)Ā{S<sub>2</sub>CN<sup><i>n</i></sup>Pr<sub>2</sub>}<sub>6</sub>]Ā(PF<sub>6</sub>) can
be oxidatively removed as H<sub>2</sub> by CeĀ(NO<sub>3</sub>)<sub>6</sub><sup>2ā</sup> to yield [Cu<sup>II</sup>(S<sub>2</sub>CN<sup><i>n</i></sup>Pr<sub>2</sub>)<sub>2</sub>] exploiting
the redox-tolerant nature of dithiocarbamates. Regeneration of hydride-centered
octanuclear copper clusters from the [Cu<sup>II</sup>(S<sub>2</sub>CN<sup><i>n</i></sup>Pr<sub>2</sub>)<sub>2</sub>] can be
achieved by reaction with CuĀ(I) ions and borohydride. The hydride
release and regeneration of Cu<sup>I</sup><sub>8</sub> was monitored
by UVāvisible titration experiments. To our knowledge, this
is the first time that hydride encapsulated within a copper cluster
can be released as H<sub>2</sub> via chemical means. All complexes
have been fully characterized by <sup>1</sup>H NMR, FT-IR, UVāvis,
and elemental analysis, and molecular structures of <b>1</b><sub><b>H</b></sub>, <b>2</b><sub><b>H</b></sub>, and <b>6</b><sub><b>H</b></sub> were clearly established
by single-crystal X-ray diffraction. Both <b>1</b><sub><b>H</b></sub> and <b>2</b><sub><b>H</b></sub> exhibit
a tetracapped tetrahedral Cu<sub>8</sub> skeleton, which is inscribed
within a S<sub>12</sub> icosahedron constituted by six dialkyl dithiocarbamate
ligands in a tetrametallic-tetraconnective (Ī¼<sub>2</sub>, Ī¼<sub>2</sub>) bonding mode. The copper framework of <b>6</b><sub><b>H</b></sub> is a tricapped distorted tetrahedron in which
the four-coordinate hydride is demonstrated to occupy the central
site by single crystal neutron diffraction. Compounds <b>1</b>ā<b>3</b> exhibit a yellow emission in both the solid
state and in solution under UV irradiation at 77 K, and the structureless
emission is assigned as a <sup>3</sup>metal to ligand charge transfer
(MLCT) excited state. Density functional theory (DFT) and time-dependent
density functional theory (TDDFT) calculations on model compounds
match the experimental structures and provide rationalization of their
bonding and optical properties
[Ag<sub>7</sub>(H){E<sub>2</sub>P(OR)<sub>2</sub>}<sub>6</sub>] (E = Se, S): Precursors for the Fabrication of Silver Nanoparticles
Reactions of AgĀ(I) salt, NH<sub>4</sub>(E<sub>2</sub>PĀ(OR)<sub>2</sub>) (R = <sup>i</sup>Pr, Et; E = Se, S), and NaBH<sub>4</sub> in a 7:6:1 ratio in CH<sub>2</sub>Cl<sub>2</sub> at room
temperature, led to the formation of hydride-centered heptanuclear
silver clusters, [Ag<sub>7</sub>(H)Ā{E<sub>2</sub>PĀ(OR)<sub>2</sub>}<sub>6</sub>] (R = <sup>i</sup>Pr, E = Se (<b>3</b>): R =
Et; E = SĀ(<b>4</b>). The reaction of [Ag<sub>10</sub>(E)Ā{E<sub>2</sub>PĀ(OR)<sub>2</sub>}<sub>8</sub>] with NaBH<sub>4</sub> in CH<sub>2</sub>Cl<sub>2</sub> produced [Ag<sub>8</sub>(H)Ā{E<sub>2</sub>PĀ(OR)<sub>2</sub>}<sub>6</sub>]Ā(PF<sub>6</sub>) (R = <sup>i</sup>Pr, E = Se
(<b>1</b>): R = Et; E = SĀ(<b>2</b>)), which can be converted
to clusters <b>3</b> and <b>4</b>, respectively, via the
addition of 1 equiv of borohydride. Intriguingly clusters <b>1</b> and <b>2</b> can be regenerated via adding 1 equiv of AgĀ(CH<sub>3</sub>CN)<sub>4</sub>PF<sub>6</sub> to the solution of compounds <b>3</b> and <b>4</b>, respectively. All complexes have been
fully characterized by NMR (<sup>1</sup>H, <sup>77</sup>Se, <sup>109</sup>Ag) spectroscopy, UVāvis, electrospray ionization mass spectrometry
(ESI-MS), FT-IR, thermogravimetric analysis (TGA), and elemental analysis,
and molecular structures of <b>3</b><sub><b>H</b></sub> and <b>4</b><sub><b>H</b></sub> were clearly established
by single crystal X-ray diffraction. Both <b>3</b><sub><b>H</b></sub> and <b>4</b><sub><b>H</b></sub> exhibit
a tricapped tetrahedral Ag<sub>7</sub> skeleton, which is inscribed
within an E<sub>12</sub> icosahedron constituted by six dialkyl dichalcogenophosphate
ligands in a tetrametallic-tetraconnective (Ī¼<sub>2</sub>, Ī¼<sub>2</sub>) bonding mode. Density functional theory (DFT) calculations
on the models [Ag<sub>7</sub>(H)Ā(E<sub>2</sub>PH<sub>2</sub>)<sub>6</sub>] (E = Se: <b>3ā²</b>; E = S: <b>4ā²</b>) yielded to a tricapped, slightly elongated tetrahedral silver skeleton,
and time-dependent DFT (TDDFT) calculations reproduce satisfyingly
the UVāvis spectrum with computed transitions at 452 and 423
nm for <b>3ā²</b> and 378 nm for <b>4ā²</b>. Intriguingly further reactions of [Ag<sub>7</sub>(H)Ā{E<sub>2</sub>PĀ(OR)<sub>2</sub>}<sub>6</sub>] with 8-fold excess amounts of NaBH<sub>4</sub> produced monodisperse silver nanoparticles with an averaged
particle size of 30 nm, which are characterized by scanning electron
microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, X-ray
diffraction (XRD), and UVāvis absorption spectrum
Hydrido Copper Clusters Supported by Dithiocarbamates: Oxidative Hydride Removal and Neutron Diffraction Analysis of [Cu<sub>7</sub>(H){S<sub>2</sub>C(aza-15-crown-5)}<sub>6</sub>]
Reactions of CuĀ(I) salts with NaĀ(S<sub>2</sub>CR) (R
= N<sup><i>n</i></sup>Pr<sub>2</sub>, NEt<sub>2</sub>, aza-15-crown-5),
and (Bu<sub>4</sub>N)Ā(BH<sub>4</sub>) in an 8:6:1 ratio in CH<sub>3</sub>CN solution at room temperature yield the monocationic hydride-centered
octanuclear Cu<sup>I</sup> clusters, [Cu<sub>8</sub>(H)Ā{S<sub>2</sub>CR}<sub>6</sub>]Ā(PF<sub>6</sub>) (R = N<sup><i>n</i></sup>Pr<sub>2</sub>, <b>1</b><sub><b>H</b></sub>; NEt<sub>2</sub>, <b>2</b><sub><b>H</b></sub>; aza-15-crown-5, <b>3</b><sub><b>H</b></sub>). Further reactions of [Cu<sub>8</sub>(H)Ā{S<sub>2</sub>CR}<sub>6</sub>]Ā(PF<sub>6</sub>) with 1 equiv
of (Bu<sub>4</sub>N)Ā(BH<sub>4</sub>) produced neutral heptanuclear
copper clusters, [Cu<sub>7</sub>(H)Ā{S<sub>2</sub>CR}<sub>6</sub>]
(R = N<sup><i>n</i></sup>Pr<sub>2</sub>, <b>4</b><sub><b>H</b></sub>; NEt<sub>2</sub>, <b>5</b><sub><b>H</b></sub>; aza-15-crown-5, <b>6</b><sub><b>H</b></sub>)
and clusters <b>4</b>ā<b>6</b> can also be generated
from the reaction of CuĀ(BF<sub>4</sub>)<sub>2</sub>, NaĀ(S<sub>2</sub>CR), and (Bu<sub>4</sub>N)Ā(BH<sub>4</sub>) in a 7:6:8 molar ratio
in CH<sub>3</sub>CN. Reformation of cationic Cu<sup>I</sup><sub>8</sub> clusters by adding 1 equiv of Cu<sup>I</sup> salt to the neutral
Cu<sub>7</sub> clusters in solution is observed. Intriguingly, the
central hydride in [Cu<sub>8</sub>(H)Ā{S<sub>2</sub>CN<sup><i>n</i></sup>Pr<sub>2</sub>}<sub>6</sub>]Ā(PF<sub>6</sub>) can
be oxidatively removed as H<sub>2</sub> by CeĀ(NO<sub>3</sub>)<sub>6</sub><sup>2ā</sup> to yield [Cu<sup>II</sup>(S<sub>2</sub>CN<sup><i>n</i></sup>Pr<sub>2</sub>)<sub>2</sub>] exploiting
the redox-tolerant nature of dithiocarbamates. Regeneration of hydride-centered
octanuclear copper clusters from the [Cu<sup>II</sup>(S<sub>2</sub>CN<sup><i>n</i></sup>Pr<sub>2</sub>)<sub>2</sub>] can be
achieved by reaction with CuĀ(I) ions and borohydride. The hydride
release and regeneration of Cu<sup>I</sup><sub>8</sub> was monitored
by UVāvisible titration experiments. To our knowledge, this
is the first time that hydride encapsulated within a copper cluster
can be released as H<sub>2</sub> via chemical means. All complexes
have been fully characterized by <sup>1</sup>H NMR, FT-IR, UVāvis,
and elemental analysis, and molecular structures of <b>1</b><sub><b>H</b></sub>, <b>2</b><sub><b>H</b></sub>, and <b>6</b><sub><b>H</b></sub> were clearly established
by single-crystal X-ray diffraction. Both <b>1</b><sub><b>H</b></sub> and <b>2</b><sub><b>H</b></sub> exhibit
a tetracapped tetrahedral Cu<sub>8</sub> skeleton, which is inscribed
within a S<sub>12</sub> icosahedron constituted by six dialkyl dithiocarbamate
ligands in a tetrametallic-tetraconnective (Ī¼<sub>2</sub>, Ī¼<sub>2</sub>) bonding mode. The copper framework of <b>6</b><sub><b>H</b></sub> is a tricapped distorted tetrahedron in which
the four-coordinate hydride is demonstrated to occupy the central
site by single crystal neutron diffraction. Compounds <b>1</b>ā<b>3</b> exhibit a yellow emission in both the solid
state and in solution under UV irradiation at 77 K, and the structureless
emission is assigned as a <sup>3</sup>metal to ligand charge transfer
(MLCT) excited state. Density functional theory (DFT) and time-dependent
density functional theory (TDDFT) calculations on model compounds
match the experimental structures and provide rationalization of their
bonding and optical properties