chemistry

Group 13/15 multiple bonds

Group 13/15 multiple bonds is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Group 13/15 multiple bonds rather than just read about it. In short: Heteroatomic multiple bonding between group 13 and group 15 elements are of great interest in synthetic chemistry due to their isoelectronicity with C-C multiple bonds. Nevertheless, the difference of electronegativity between group 13 and 15 leads to different character of bondings comparing to C-C multiple bonds.

Key takeaways

Group 13/15 multiple bonds belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Group 13/15 multiple bonds to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Group 13/15 multiple bonds from memory before moving on to harder problems.

Reference excerpt

Heteroatomic multiple bonding between group 13 and group 15 elements are of great interest in synthetic chemistry due to their isoelectronicity with C-C multiple bonds. Nevertheless, the difference of electronegativity between group 13 and 15 leads to different character of bondings comparing to C-C multiple bonds. Because of the ineffective overlap between p𝝅 orbitals and the inherent lewis acidity/basicity of group 13/15 elements, the synthesis of compounds containing such multiple bonds is challenging and subject to oligomerization. The most common example of compounds with 13/15 group multiple bonds are those with B=N units. The boron-nitrogen-hydride compounds are candidates for hydrogen storage. In contrast, multiple bonding between aluminium and nitrogen Al=N, Gallium and nitrogen (Ga=N), boron and phosphorus (B=P), or boron and arsenic (B=As) are less common.

Synthesis

Suitable precursors are crucial for the synthesis of group 13/15 multiple bond-containing species. In most successfully isolated structures, sterically demanding ligands are utilized to stabilize such bondings.

Boraphosphenes (P=B) Boraphosphenes, also known as phosphoboranes, was first reported by Cowley and co-workers in the 1980s. [(tmp)B=P(Ar)] (tmp= 2,2,6,6,-tetramethylpiperidina, Ar= 2,4,6-t-Bu3C6H2) was characterized by mass spectroscopy (EI MS), and the corresponding dimer, diphosphadiboretane, was characterized by X-ray crystallography. The Power and co-workers later reported the structure of [P(R)=BMes2Li(Et2O)2] (R = phenyl, cyclohexane, and mesitylene), which is the first B=P double bond observed in solid state. The synthesis of [P(R)=BMes2Li(Et2O)2] starts from treating in-situ generated Mes2BPHR with 1 equivalent of t-BuLi in Et2O, followed by crystallization at low temperature.

Cyclic system with P-B multiple bonds

Isomerization of four-member P-B cycles was investigated by Bourissou and Bertrand. It was reported that cycle-[R2PB(R')-B(R')-P(Ph)2] (R = phenyl, isopropyl; R'= tert-butyl, 2,3,5,6-tetramethyl phenyl) isomerize to form cycle-[R2P-B(R')=P(Ph)-B(R')(Ph)] upon irradiation. An example of five-membered ring was reported by Crossley suggesting that a reaction of 1,2-diphosphinobenzene with n-BuLi and Cl2BPh yielded a benzodiphosphaborolediide. Several six-membered ring systems involving P=B double bonds have been reported. One of the example is an analogue of borazine synthesizing from MesBBr2 and CyP(H)Li.

Arsinideneborates (As=B) A similar strategy to access litigated arsinideneborate was reported by Power and co-workers after the establishment of synthesizing litigated phosphinideneborates. Crystallizing [As(Ph)=BMes2Li(THF)3] with two equivalence of TMEDA yielded [As(Ph)=BMes2][Li(TMEDA)2]. Ring-systems containing As-B multiple bonds haven't been reported yet.

Group 13 imides (Al=N, Ga=N, In=N) Synthesis of group 13 imides usually starts with low valent group 13 species stabilized by bulky ligands. A [2+3] cycloaddition of monomeric [DipNacnc]Al or [DipNacnc]Ga (DipNacnc= HC{(CMe)(NDip)}2) compound with sterically bulky azide, TipTerN3 (TipTer = -C6H3-2,6-(C6H2-2,4,6-iPr3)2), gives the iminotrielenes [{DipNacnc}M=N-TipTer] (M=Al, Ga). Additionally, dimers of Ga(I) or In(I) were reported to form the iminotrielens [(DipTer)M=N-Mes'Ter] with Mes'TerN3 (M = Ga, In; Mes'Ter =C6H3-2,6(Xyl-4-tBu)2).

Al-N triple bonds

Transient Al≡N triple bond species were also investigated by reacting monomeric alanediyl precursor with organic azides. The unstable Al≡N triple bond species [iPr2TIPTerAl≡NR] (R = Ad, SiMe3) was not capture but further rearrange to tetrazole and amino-azide alone, respectively.

Phosphaalumenes and Arsaalumenes (P=Al, As=Al) The development of Al=P and Al=As species faced the difficulty due to the tendency of oligomerization of the lewis acidic Al and lewis basic P/As. In 2021, Hering-Junghans, Braunchweig, and co-workers reported the synthesis of phosphaalumens and arsaalumens with Al(I) precursors, [Al(I)Cp*]4 (Cp* = pentamethylcyclopentadiene). Reacting [Al(I)Cp*]4 with DipTer-AsPMe3 or DipTer-AsPMe3 at 1:4 ratio yielded the corresponding phosphaalumens/arsaalumens, which are stable and isolable.

Gallium-pnictogen double bonds (Ga=Pn)

Synthesis and characterization of Ga=Sb species was reported by Schulz and Cutsail III with the reaction of [DipNacnc]Ga (DipNacnc= HC{(CMe)(NDip)}2) with [Cp*SbCl2]. The resulting Sb radical species, [DipNacnc(Cl)Ga]2Sb, was then reduced by KC8 to give [DipNacncGa=Sb-Ga(Cl)DipNacnc]. Utilizing the similar reaction pathway, a Ga=As species, [DipNacncGa=AsCp*], was successfully synthesized and stabilized. Interestingly, no radical formation was observed comparing to the case of Ga=Sb species. With the rapid development of gallium pnictogen in the late 2010s, the first phosphagallene species was reported by Goicoechea and co-workers in 2020. The reaction of [(HC)2(NDip)2PPCO] with [DipNacncGa] gave the phosphagallene, [DipNacncGa=P-P(NDip)2(CH)2].

Reactivities

Reactivities of boraphosphenes B=P double bond species has been studied for bond activation. For example, C-F activation of tris(pentafluorophenyl)borane by NHC-stabilized phosphaboranes, [(tmp)(L)B=PMes*] (L = IMe4), was reported by Cowley and co-workers. The C-F bond activation takes place at the para position, leading to the formation of C-P bond. Reactions of phenyl acetylene with the dimer of [Mes*P=B(tmp)] give an analogue of cycle-butene, [Mes*P=C(Ph)-C(H)=B(tmp)], where C-C triple bond undergoes a [2+2]-cycloaddition to P=B double bond.

Phospha-bora Wittig reaction

Transient boraphosphene [(tmp)B=PMes*)] (tmp = 2,2,6,6-tetramethylpiperidine, Mes* = 2,4,6-tri-tert-butylphenyl) reacts with aldehyde, ketone, and esters to form phosphaboraoxetanes, which converts to phosphaalkenes [Mes*P=CRR'] and [(tmp)NBO]x heterocycles. This method provides direct access of phosphaalkenes from carbonyl compounds.

Reactivities of group 13 imides Compounds with group 13-N multiple bonds are capable of small molecule activation. Reactions of PhCCH or PhNH2 with NHC-stabilized iminoalane result in the addition of proton to N and -CCPh or -NHPh fragment to Al. The reaction with CO leads to the insertion of CO between the Al=N bond.

Reactivities of Ga=Pn species

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Group 13/15 multiple bonds

Start with the simplest possible case. Write down what Group 13/15 multiple bonds claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Group 13/15 multiple bonds before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Group 13/15 multiple bonds ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Group 13/15 multiple bonds

In research: Group 13/15 multiple bonds appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Group 13/15 multiple bonds in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Group 13/15 multiple bonds is common in secondary-school and first-year university syllabi. It links to neighbouring topics Chemical bond properties, so understanding it makes those chapters shorter.
In everyday life: Look for Group 13/15 multiple bonds outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Group 13/15 multiple bonds in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Group 13/15 multiple bonds means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Group 13/15 multiple bonds out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Group 13/15 multiple bonds in simple terms?

Why does Group 13/15 multiple bonds matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Group 13/15 multiple bonds?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Group 13/15 multiple bonds.