Transcript P, As, Sb and Bi

The elements in group 15
Nitrogen
Phosphorus
Arsenic
Antimony
Bismuth
Introduction
• All are important elements
• Increasing trend to metallic
character and cationic behavior from
top to botom in the grroup
• Nitrogen is different with the other
elements, even phosphorus
1. The diminished ability to form p-p π
bond: radius, single bond
2. The possibility of utilizing the d orbitals:
d-p π bond , CN
Introduction (continue)
• All , but Bi, are important donor atoms in
their trivalent compounds
• Bismuth is a metal element, but sodium
bismuthate is a very strong oxidizing
agent: inert electron pair effect
Occurrence and Recovery of the Elements
Phosphorus
Principally obtained from phosphate rock
-remains of fossilized life forms
Ca5(PO4)3F and Ca5(PO4)3OH
Ca5(PO4)3F(s) + H2SO4(I)
2Ca3(PO4)2 + 6SiO2 + 10C
3H3PO4(l) + 5CaSO4(s) + HF(aq)
1500 °C
6CaSiO3 + 10CO + P4
Elemental Phosphorus
White Phosphorus:
•
•
Reaction on previous slide
Ignites spontaneously in air
• Stored under water
Red Phosphorus:
•Heat white phosphorus at
300 C in inert atm for several days
•Does not ignite in air
•Structure: contain linear chain
Black Phosphorus
•The most stable form
•Formed when P heated under high
pressure.
White Phosphorus
Black Phosphorus
Occurrence and Recovery of the Elements
Arsenic
Arsenic is found in nature in a number of minerals including
realgar (As4S4)
orpiment (As2S3)
arsenolite (As2O3)
iron minerals such as arsenopyrite (FeAsS)
loallingite (FeAs2).
Arsenic is made on an industrial scale by heating
appropriate minerals in the absence of air. The arsenic
is condensed out as a solid.
FeAsS (700°C)
FeS + As(g) + As(s)
Occurrence and Recovery of the Elements
Antimony
Antimony is found in nature in a number of minerals
including
stibnite (Sb2S3)
ullmanite (NiSbS).
Small amounts of native antimony have been found. Some
ores are treatable under reducing conditions to form Sb2S3.
The sulphide is removed to leave elemental antimony with
scrap iron.
Sb2S3 + 3Fe
2Sb + 3FeS
In antehr process, some ores can be heated to evolve the
oxide Sb2O3 and this in turn can be reduced by charcoal in
the presence of sodium sulphate, to ensure mixing, to form
elemental antimony.
2Sb O +3C
4Sb + 3CO
Occurrence and Recovery of the Elements
Bismuth
Bismuth is found in nature largely as
bismite (Bi2O3)
bismuthinite (Bi2S3)
bismutite [(BiO)2CO3].
However it is generally made as a byproduct of copper,
lead,tin, silver, gold, and zinc plants. The final step involves a
reduction of the oxide by charcoal.
Phosphine PH3
Typically prepared by the action of dilute acid on
calcium or aluminum phosphide or by pyrolysis of
H3PO3 or by reaction of KOH on white phosphorus
Pure phosphine is not spontaneously flammable but
often inflames due to the presence of trace P2H4 or P4
•Readily oxidized by air once ignited
•Sparingly soluble in water
•Very weak base pKb 1E-25 PH4+ is readily hydrolized
Extremely poisonous
Only phosphine of the lower Group 15 elements forms
subhydrides - P2H4
Used as a semiconductor dopant source
Arsine AsH3
Even more poisonous than phosphine
Readily decomposes to yeild elemental arsenic
-”arsenic mirror test”
Only know use as a semiconductor dopant source
Stibine SbH3 and Bismuthine BiH3
Limited stability makes these compounds of little
interest
•Bond energy (stability): NH3 >PH3 > AsH3 > SbH3 > BiH3
•Bond angle (HAH): NH3 >PH3 > AsH3 > SbH3 > BiH3
•Base strength in water: same as above
•Reduce ability: NH3 <PH3 < AsH3 < SbH3 < BiH3
Compounds of Group 15 Elements
Halides: PX3 PX5
Phosphorus Fluorides
PF3
colourless gas
•Melting point: -152°C
•Boiling point: -102°C
P2F4
colourless gas
•Melting point: -86.5
•Boiling point: -6.2
PF5
colourless gas
•Melting point: -94°C
•Boiling point: -85°C
2PCl3(l) + 3ZnF2(s)
2PF3(g) + 3ZnCl2(s)
Compounds of Group 15 Elements
Halides:
Arsenic Fluorides
AsF3 colourless liquid
•Melting point: -6°C
•Boiling point: 63°C
“Bridged” structure, but essentially molecular
AsF5
colourless gas
•Melting point: -79.8°C
•Boiling point: -52.8°C
Compounds of Group 15 Elements
Other Halides
AsCl3
AsBr3
AsCl5
Colourless liquid
•Melting point: -16°C
•Boiling point: 130°C
white to pale yellow crystalline solid
Melting point: 31°C
Boiling point: 221°C
AsI3
Decomp at –50 °C
Recall BrO4–
red crystalline solid
•Melting point: 141°C
•Boiling point: 400°C;
424°C
Compounds of Group 15 Elements
Halides:
Antimony Fluorides
SbF3 •colourless crystalline solid
•Melting point: 290°C
•Boiling point: 345°C
Actual structure has intermolecular contacts giving highly
distorted octahedral coordination
SbF5
•viscous liquid
•Melting point: 8.3°C
•Boiling point: 141°C
Forms tetrameric structure in the solid state
AsF3 and SbF3 are very useful as fluorinating agents
Compounds of Group 15 Elements
Other Halides
SbCl3
SbBr3
SbI3
white crystalline solid, SbCl
5
deliquescent
•Melting point:
73.4°C
•Boiling point: 223°C
white or yellow solid,
deliquescent crystals
•Melting point: 96°C
•Boiling point: 288°C
red crystalline solid
•Melting point: 170.5°C
•Boiling point: 401°C
colourless or yellow
liquid
•Melting point: 4°C
•Boiling point: 140°C
•Why liquid when
trichloride a solid?
Compounds of Group 15 Elements
Halides:
Bismuth Fluorides
grey-white crystalline solid
•Melting point: 649°C
•Boiling point: 900°C
What do the m.p. and b.p. imply?
BiF3
Ionic lattice
BiF5
white crystalline solid
•Melting point: 154°C
•Boiling point: 230°C
What do these m.p. and b.p imply?
Infinite linear BiF6 chains
Compounds of Group 15 Elements
Other Halides
BiCl5 Nonexistant
BiCl3 •white or yellowish white
crystalline solid,
•Melting point: 233.5°C
•Boiling point: 441°C
BiBr3
•yellow, golden crystalline
solid, deliquescent
•Melting point: 219°C
•Boiling point: 462°C
BiI3 green-black crystalline solid
•Melting point: 408.6°C
•Boiling point: 542°C
Bismuth Bromide
Structure
Reactions of PCl3
RCOCl
+ H3PO3
Cl3PS
Cl3P=NPCl2O
HCl + H3PO3 + H4P2O5
RCO2H
R3PO
N2O4
H2O
P(NCO)3 P(NCS)3
AgNCO
AgSCN
S
RMgX
Cl3PO
(RO)2PO ROH
O2
PCl3
ROH
P(OR)3 in base
(RO)2PHO
in absence of
base
RMgX, LiR
PR3, PR2Cl, PRCl
RH + O2
Ni(CO)4
RCl + AlCl3
RPOCl2 + HCl
NH3
[RPCl3]+[AlCl4]-
Ni(PCl3)4
H2O
P(NH2)3
RPOCl2
Reactions of
other MX3
Halides similar
Oxides of P, As, Sb and Bi
P4O10 a good drying and
detergent agent
Prepared by burning P in air
P4 + 5O2
P4O10
Limit the supply of oxygen and:
P4 + 3O2
P4O6
How to make an acid
P4O10 + 6H2O
P4O6 + 6H2O
4H3PO4
4H3PO3
Oxides of Arsenic, Antimony and Bismuth
Only As and Sb for (V) oxides, these are of limited
stability.
As, Sb and Bi oxides primarily (III) oxides
As2O3 Sb2O3 Bi2O3
Note: Acid-base property
Oxide-reduce property
Gas Phase of As and Sb oxides:
Sulphide
•
•
P4S3 P4S5 P4S7 P4S10… similar as oxides
Exclude P4S10, all contain at least one P–P
bond
• As2S3 As2S5 As4S4 …
• Sb2S3 Sb2S5
• Bi2S3 why ?
• Note:
1. Color: yellow to black. polarization
covalent
2. Solubility and oxidizing-reduce properties
3. Reaction with H+, OH–, S2–, Sx2–
Phosphorus Oxoanions:
Oxidation
Number
Formula
+1
H2PO2-
Name
Structure
H
Hypophosphit
e
P
H
H
+3
HPO32-
Phosphite
P
O
O
+5
+5
P2O64PO43P2O7
4-
Hypophosphat O O
e
P
O
Diphosphate O
P
O
O
O
O
O
O
O
O
Phosphate
Facile
Reducing
Agent
O
Facile
Reducing
Agent
O
Basic
P
P
+4
Remarks
O
O
O
Strongly Basic
O
P
O
O
Basic
Chain
variations
Structure and acidic strength of H3PO3
•
1.
2.
3.
•
1.
2.
3.
•
Pauling rule:
HnROm: represented as ROm-n(OH)n
pK = 7 – 5(m – n)
In same type: electronegativity
Application:
H3PO3
P(OH)3 pK = 7
Experimental: pK = 2
H3PO3
HPO(OH)2
P(OR)3
Poly- and cycle-phosphoric acid
(pyrophasphoric acid)
• [PnO3n+1](n+2)–
Ex. Na5P3O10
• [PnO3n]n–
• Ex. Na5P3O9
• Note:
1. Solubilities of different phasphorates
2. Reducing properties of Hypo-/phosphite
Phosphorus Nitrogen Compounds
The extra valence in N can make for some interesting
structures - Phosphazenes
R
P
R
N
N
R
PCl5 + nNH4Cl
(Cl2PN)n + 4nHCl
R N N
P
P
N P N
R
R
Substitutions by other Lewis
bases are common
(Cl2PN)n + 2nCF3CF2O-
[(CF3CF2O)2PN]n + 2nCl-
Polymeric structures common – rubber-like substances
-excellent low temperature properties
Hexachlorotriphosphazene
•
•
•
•
planar
N sp2, P sp3
d-p π
May form
polylimer
Complexes
•
•
•
•
•
PF6– AsF6– SbF6–
NaSb(OH)6
KH[Sb2(d-C4H2O6)2]
Common for Bi3+
Bi6O66+ Bi6O6(OH)33+
Bi6O6(OH)6