The reaction of tetraphenyldiphosphazane (Ph2P)2NH with mesityl azide 2,4,6‐Me3C6H2‐N3 affords a new [N,N′] chelating ligand, [HN(Ph2PN(2,4,6‐Me3C6H2))2] (LH). The ligand can be easily deprotonated by using nBuLi or Li[N(SiMe3)2] in Et2O to yield [{N(Ph2PN(2,4,6‐Me3C6H2))2}Li·OEt2] (1). The reaction of LH with AlMe3 and BH3·SMe2, respectively, gives the corresponding mononuclear complexes [{N(Ph2PN(2,4,6‐Me3C6H2))2}AlMe2] (2) and a rare borondihydride [{N(Ph2PN(2,4,6‐Me3C6H2))2}BH2] (3). Similarly, reaction of 1 with the trihalides, MX3, of group 13 elements afford the corresponding dihalo complexes, [{N(Ph2PN(2,4,6‐Me3C6H2))2}MX2] [M = B, X = F (4); M = Al, X = Cl (5); M = Ga, X = Cl (6); M = In, X = Br (7)]. All the complexes reported in this work have been isolated in good yields and are expected to serve as useful synthons in a number of reactions. The solid‐state structure of LH and 1–7 have been investigated by single‐crystal X‐ray structural analysis.

The influence of a sterically demanding iminophosphonamide ligand, [(2,6-iPr2C6H3N)P(Ph2)(NtBu)]H (LH), on the synthesis and stability of a heteroleptic germylene monochloride, [(2,6-iPr2C6H3N)P(Ph2)(NtBu)]GeCl (1), and its reaction chemistry has been discussed. Complex 1 behaves as a Lewis base to form an adduct with Fe(CO)4, namely [(2,6-iPr2C6H3N)P(Ph2)(NtBu)]Ge(Cl)Fe(CO)4 (2). Reaction of 1 with KOtBu or AgOSO2CF3 affords Ge(ii) compounds, [(2,6-iPr2C6H3N)P(Ph2)(NtBu)]GeR (R = OtBu (3), OSO2CF3 (4)). Treatment of complex 1 with elemental sulfur or selenium leads to heavier analogues of germaacid chlorides, [(2,6-iPr2C6H3N)P(Ph2)(NtBu)]Ge(E)Cl (E = S (5), Se (6)). Similarly, compound 3 on reaction with elemental sulfur or selenium produces heavier analogues of germaesters, [(2,6-iPr2C6H3N)P(Ph2)(NtBu)]Ge(E)OtBu (E = S (7), Se (8)). Complexes 1-8 were characterized using multinuclear NMR and EI-MS, and solid state structures of complexes 1-3, 5 and 8 have been elucidated using single crystal X-ray diffraction.

Reduction of the cyclodiphosphazane [(S=)ClP(μ-NtBu)]2 (1) with sodium metal in refluxing toluene proceeds via two different pathways. One is a Wurtz-type pathway involving elimination of NaCl from 1 followed by head-to-tail cyclization to give the hexameric macrocycle [(μ-S)P(μ-NtBu)2 P(=S)]6 (2). The other pathway involves reduction of the P=S bonds of 1 to generate colorless singlet biradicaloid dianion trans-[S-P(Cl)(μ-NtBu)]2 (2-) , which is observed in the polymeric structures of three-dimensional [{(S-)ClP(μ-NtBu)2 PCl(S)}Na(Na⋅THF2 )]n (3) and two dimensional [{(S-)ClP(μ-NtBu)2 PCl(S)} (Na⋅THF)2 ]n (4).

A sterically demanding iminophosphonamine ligand [(2,6-iPr2C6H3N)P(Ph2)(NtBu)]H (LH) and its lithium derivative [(2,6-iPr2C6H3N)P(Ph2)(NtBu)](Li·2THF) (1) were used to prepare complexes of group 13 elements. The reaction of LH with AlH3·NMe2Et and AlMe3 respectively, affords [LAlH2]2 (2) and LAlMe2 (3). The lithium derivative 1 when treated with the MCl3 compound of group 13 yields [(2,6-iPr2C6H3N)P(Ph2)(NtBu)]MCl2 (M = B (4); Al (5); and Ga (6). Compound 3 on reaction with a Lewis acid B(C6F5)3 generates the cationic complex [{(2,6-iPr2C6H3N)P(Ph2)(NtBu)}AlMe](+) [MeB(C6F5)3](-) (7) that slowly undergoes rearrangement to yield [(2,6-iPr2C6H3N)P(Ph2)(NtBu)]AlMe(C6F5) (8) and MeB(C6F5)2. Compounds 1-8 were characterized using multinuclear NMR, EI-MS and IR techniques and the solid state structure of 1-6 and 8 was elucidated by single crystal X-ray diffraction analyses.

The well-defined three coordinated electronically unsaturated cationic organoaluminum complex [({(2,6-iPr 2 C 6 H 3 N)P(Ph 2 )} 2 N) AlMe] + [MeB(C 6 F 5 ) 3 ] À (1), has been utilized to catalyze the cyanosilylation of aldehydes and ketones under mild and solvent-free conditions. Moreover, catalyst 1 showed high chemoselective cyanosilylation of aldehydes over ketones, nitriles and olefins. The multinuclear NMR investigations revealed that cyanosilylation proceeds via Lewis adduct formation between 1 and TMSCN thereby activating TMSCN (Si-CN bond) followed by nucleophilic attack of the carbonyl oxygen at the Si center of the activated silane and formation of the product.

New three-coordinate and electronically unsaturated aluminum hydride [LAlH] [HB(C F ) ] (LH=[{(2,6-iPr C H N)P(Ph )} N]H) and aluminum methyl [LAlMe] [MeB(C F ) ] cations have been prepared. The quantitative estimation of Lewis acidity by Gutmann-Beckett method revealed [LAlH] [HB(C F ) ] to be better Lewis acid than B(C F ) and AlCl making these compounds ideal catalysts for Lewis acid-mediated reactions. To highlight that the work is of fundamental importance, catalytic hydroboration of aliphatic and aromatic aldehydes and ketones have been demonstrated. Important steps of the catalytic cycle have been probed by using multinuclear NMR measurements, including successful characterization of the proposed aluminum benzyloxide cationic intermediate, [LAl-O-CH Ph] [HB(C F ) ] . The proposed catalytic cycle has been found to be consistent with experimental observations and computational studies clearly indicating the migration of hydride from cationic aluminum center to the carbonyl carbon is the rate-limiting step of the catalytic cycle.

The reaction of a recently synthesized dihydroboron species complexed with bis(phosphinimino)amide, LBH2 (), (L = [N(Ph2PN(2,4,6-Me3C6H2))2](-)) with 3 equivalents of BH2Cl·SMe2 or one equivalent of BCl3 affords the first stable monohydridoborenium ion, [LBH](+)[HBCl3](-) () that is stable without a weakly coordinating bulky anion. Compound can also be prepared directly by refluxing LH with 3 equivalents of BH2Cl·SMe2. Interestingly, reaction of LBH2 () with elemental sulfur and selenium involves oxidative addition of S and Se into B-H bonds and subsequent release of H2S (or H2Se) from the intermediate LB(SH)2 (or LB(SeH)2) species forming stable compounds with terminal boron-chalcogen double bonds LB[double bond, length as m-dash]S () and LB[double bond, length as m-dash]Se (). The electronic structures of compounds , and were elucidated by high resolution mass spectrometry, multi-nuclear NMR and single crystal X-ray diffraction studies. Ab initio calculations on are in excellent agreement with its experimental structure and clearly support the existence of the boron-sulfur double bond.

Reactions of bis(phosphinimino)amines LH and L'H with Me2 S⋅BH2 Cl afforded chloroborane complexes LBHCl (1) and L'BHCl (2), and the reaction of L'H with BH3 ⋅Me2 S gave a dihydridoborane complex L'BH2 (3) (LH=[{(2,4,6-Me3 C6 H2 N)P(Ph2 )}2 N]H and L'H=[{(2,6-iPr2 C6 H3 N)P(Ph2 )}2 N]H). Furthermore, abstraction of a hydride ion from L'BH2 (3) and LBH2 (4) mediated by Lewis acid B(C6 F5 )3 or the weakly coordinating ion pair [Ph3 C][B(C6 F5 )4 ] smoothly yielded a series of borenium hydride cations: [L'BH](+) [HB(C6 F5 )3 ](-) (5), [L'BH](+) [B(C6 F5 )4 ](-) (6), [LBH](+) [HB(C6 F5 )3 ](-) (7), and [LBH](+) [B(C6 F5 )4 ](-) (8). Synthesis of a chloroborenium species [LBCl](+) [BCl4 ](-) (9) without involvement of a weakly coordinating anion was also demonstrated from a reaction of LBH2 (4) with three equivalents of BCl3 . It is clear from this study that the sterically bulky strong donor bis(phosphinimino)amide ligand plays a crucial role in facilitating the synthesis and stabilization of these three-coordinated cationic species of boron. Therefore, the present synthetic approach is not dependent on the requirement of weakly coordinating anions; even simple BCl4 (-) can act as a counteranion with borenium cations. The high Lewis acidity of the boron atom in complex 8 enables the formation of an adduct with 4-dimethylaminopyridine (DMAP), [LBH⋅(DMAP)](+) [B(C6 F5 )4 ](-) (10). The solid-state structures of complexes 1, 5, and 9 were investigated by means of single-crystal X-ray structural analysis.