Monoanionic heteroallylic ligand systems [R−N−E−N−R]- (E = Si(R2), S(R2) or S(R), C(R), and P(R2)) are versatile chelating substituents both in main group and transition metal chemistry as they provide sufficient steric demand and solubility to the products. Their application is only limited by the rigid bite of the ligands as the N···N distance cannot be tuned to the various radii of different metals. In this paper we present the new concept of opening the ligand periphery to additional coordination. The NP(R2)N- chelate in classical aminoiminophosphoranates is extended by additional coordination sites in the organic substituents (e.g., 2-pyridyl (Py) instead of phenyl (Ph)). Py2P{N(H)SiMe3}(NSiMe3) (1) is the starting material for a new class of complexes as deprotonated 1 contains along with the NPN- chelate the pyridyl ring nitrogen atoms to generate a side-selective Janus face ligand. In [(THF)Sr{Py2P(NSiMe3)2}2] (2) and [(4,4‘-bipy)Ba{Py2P(NSiMe3)2}2] n (3) both pyridyl rings are involved in metal coordination but only one imido nitrogen atom. Hence, the classical NP(Ph2)N- chelating ligand is converted into a NP(Py2)N- tripodal ligand. In the coordination to zinc in the complex [Zn{Py2P(NSiMe3)2}2] (4) one pyridyl ring and one imido nitrogen atom is employed in metal coordination. Pyridyl substitution of the P(V) center gives not only access to new coordination modes but also changes the reactivity of aminoiminophophoranes considerably. [Li(Py2PNSiMe3)]2 (5) is a lithiated phosphanylamine derived from the reduction of 1 with lithium di(trimethylsilyl)amide. Reaction of 1 with lithium organics yields [(THF)2Li(Py2P)] (6). Pyridyl substitution facilitates single or even double PN bond cleavage, unprecedented in alkyl- or aryl-substituted aminoiminophosphoranes. This reduction of P(V) species to P(III) compounds supplies easy access to phosphanylamines and secondary phosphanes.

Lithiation of triphenyl(trimethylsilylimino)phosphorane Ph3P=NSiMe3 with MeLi gives the ortho‐metallated species [Li(o‐C6H4PPh2NSiMe3)]2·Et2O (1), which exhibits all the requirements of an organometallic ligand capable of side‐arm donation. The deprotonated ortho‐phenyl carbon atom gives access to metal–carbon σ bonds in transmetallation reactions, while the Ph2P=NSiMe3 moiety can donate to the same metal center through the imine nitrogen atom. In transmetallation reactions with CuBr, the dimeric organocopper complex [Cu(o‐C6H4PPh2NSiMe3)]2 (2) is obtained, while application of ZnCl2 yields the monomeric zinc complex [Zn(o‐C6H4PPh2NSiMe3)2] (3). Reaction with CuCl2 gives access to the new diiminophosphorane (o‐C6H4PPh2NSiMe3)2 (4) through oxidative coupling at the ortho positions. In all the metal complexes, the Ph2P=NSiMe3 residue acts as a side‐arm donating group through the nitrogen atom. The intermolecular N→Cu donor bond in 2 is as short as copper–amide bonds, while the N→Zn bond lengths in 3 are in the region normally found for donor bonds. Compound 4 is a molecule, possessing two Ph2P=NSiMe3 moieties bridged by a biphenylene group.

Lithiation of triphenyl(trimethylsilylimino)phosphorane Ph 3 PdNSiMe 3 with MeLi gives the ortho-metalated species [Li(o-C 6 H 4 PPh 2 NSiMe 3 )] 2 ‚Et 2 O (1). It has all the requirements of an organometallic ligand capable of side arm donation: the deprotonated ortho phenyl carbon atom leads to metal-carbon σ bonds in reactions with metal halides, and the Ph 2 Pd NSiMe 3 moiety donates an electron pair to that metal via the imine nitrogen atom. In reactions with SnCl 2 the Sn(II) organometallic complex [Sn(o-C 6 H 4 PPh 2 NSiMe 3 ) 2 ] (2) was obtained, while with PbCl 2 a new example of the rare lead(II) organometallic complexes was obtained. In [Pb(o-C 6 H 4 PPh 2 NSiMe 3 ) 2 ] (3) the lead(II) center is bonded to the two orthocarbon atoms and additionally stabilized by two PbrN donor bonds. In all metal complexes the Ph 2 PdNSiMe 3 unit acts as a side arm donating group via nitrogen.

Trimethylsilyliminotriphenylphosphoran Ph3P=NSiMe3 (1) reagiert mit metallischem Natrium in THF unter Spaltung einer P–CPhenyl‐Bindung zu Natriumdiphenylphosphanyltrimethylsilylamid [(THF)3Na(Ph2PNSiMe3)] (2). Anschließende Reaktion mit Ammoniumbromid oder Hydrolyse mit Wasser ergibt Diphenylphosphanyltrimethylsilylamin Ph2PN(H)SiMe3 (3) und bei der Hydrolyse mit Wasser in geringen Mengen das oxidierte Nebenprodukt [(THF)Na(OOPPh2)]n (4), das gezielt durch die Reaktion von Ph2POOH mit NaH in THF erhalten werden kann. Ph2PN(H)SiMe3 (3) reagiert mit einem Äquivalent Zn{N(SiMe3)2}2 zu [(Me3Si)2NZnPh2PNSiMe3]2 (5). Mit Caesium reagiert 3 unter Phosphor‐Phosphor‐Bindungsknüpfung in einer reduktiven Substituentenkopplungsreaktion zu [(THF)Cs2{Ph(NSiMe3)P}2]n (6). Phosphor(III) wird dabei zu Phosphor(II) reduziert. Phosphor‐Phosphor‐Bindungsknüpfung unter Oxidation der Phosphoratome von PIII zu PIV erfolgt bei der Darstellung von (Ph2PNSiMe3)2 (7) durch Lithiierung von 3 und anschließender Umsetzung mit Bismuttrichlorid.

Lithiation of triphenyl((trimethylsilyl)imino)phosphorane, Ph 3 PdNSiMe 3 (1), with MeLi gives the ortho-metalated species [Li(o-C 6 H 4 PPh 2 NSiMe 3 )] 2 ‚Et 2 O (2). It has all the requirements of an organometallic ligand capable of sidearm donation: the deprotonated ortho phenyl carbon atom leads to metal-carbon σ bonds in reactions with metal halides, and the Ph 2 PdNSiMe 3 moiety donates an electron pair to that metal via the imine nitrogen atom. In reactions with InCl 3 the In(III) organometallic complex [In(o-C 6 H 4 PPh 2 NSiMe 3 ) 3 ] (3) was obtained, while with FeCl 2 a new example of the rare iron(II) 14-VE complexes [Fe(o-C 6 H 4 -PPh 2 NSiMe 3 ) 2 ] (4) was obtained. Reaction of 2 with Ph 3 GeCl gave [Ph 3 Ge(o-C 6 H 4 PPh 2 -NSiMe 3 )] (5). While in 4 both imino sidearms coordinate to the metal, because of steric crowding only two of the three present coordinate in 3. Because of the low Lewis acidity of the tetraorganogermanium moiety the imino sidearm does not donate to the central germanium atom in 5.

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