Highly Strained Heterometallacycles of Group 4 Metallocenes with Bis(diphenylphosphino)amide Ligands

Abstract

A study regarding coordination chemistry of the bis(diphenylphosphino)amide ligand Ph2P‐N‐PPh2 at Group 4 metallocenes is presented herein. Coordination of N,N‐bis(diphenylphosphino)amine (1) to [(Cp2TiCl)2] (Cp=η5‐cyclopentadienyl) generated [Cp2Ti(Cl)P(Ph2)N(H)PPh2] (2). The heterometallacyclic complex [Cp2Ti(κ2‐P,P‐Ph2P‐N‐PPh2)] (3 Ti) can be prepared by reaction of 2 with n‐butyllithium as well as from the reaction of the known titanocene–alkyne complex [Cp2Ti(η2‐Me3SiC2SiMe3)] with the amine 1. Reactions of the lithium amide [(thf)3Li{N(PPh2)2}] with [Cp2MCl2] (M=Zr, Hf) yielded the corresponding zirconocene and hafnocene complexes [Cp2M(Cl){κ2‐N,P‐N(PPh2)2}] (4 Zr and 4 Hf). Reduction of 4 Zr with magnesium gave the highly strained heterometallacycle [Cp2Zr(κ2‐P,P‐Ph2P‐N‐PPh2)] (3 Zr). Complexes 2, 3 Ti, 4 Hf, and 3 Zr were characterized by X‐ray crystallography. The structures and bondings of all complexes were investigated by DFT calculations.

Triazenido Complexes of Titanocene(III)

“…The bis(trimethylsilyl)acetylene ligand is known to serve as a spectator ligand and can easily be released under mild reaction conditions to in situ generate the reactive 14 electron fragment [Cp 2 Ti II ], which can be utilised to trap reactive fragments and stabilise unusual coordination geometries and ligand motifs. [8a] By this approach, some of us succeeded in isolating several pnictogen containing metallacycles featuring the general structural motifs Cp 2 Ti[RNENR] and Cp 2 Ti[R 2 PNPR 2 ] with E = C, P, S as illustrated in Figure . Except for Cp 2 Ti[Me 3 SiNSNSiMe 3 ] ( F ), this approach mostly led to the formation of Ti III compounds.…”

“…Generation of nitrogen containing four‐membered titanacycles starting from Cp 2 Ti(η 2 ‐Me 3 SiC 2 SiMe 3 ) and E : SiMe 3 NCNSiMe 3 , F : Me 3 SiNSNSiMe 3 , G : [DippNPCl] 2 (Dipp = 2,6‐ i Pr 2 C 6 H 3 ), H : [Ph 2 PN(H)PPh 2 ] …”

Four‐Membered Heterometallacyclic d0 and d1 Complexes of Group 4 Metallocenes with Amidato Ligands

“…Hydrogen atoms are omitted for clarity. Selected bond lengths [] and angles [8]: Zr1ÀO1 2.2371(13), Zr1ÀN1 2.3122(15), Zr1À Cl1 2.4981(6), C1ÀO1 1.285(2), C1ÀN1 1.308(2); O1-Zr1-N1 56.67(5), O1-C1-N1 112.83(16), O1-Zr1-N1-C1 À1.92(10).…”

Highly Strained Heterometallacycles of Group 4 Metallocenes with Bis(diphenylphosphino)methanide Ligands

“…The paramagnetic metallocene complexes [Cp 2 M(κ 2 ‐ P , P ‐Ph 2 PNPPh 2 )] (M=Ti, Zr; Scheme , C ) are only stable for Ti III and Zr III . These complexes are stabilized by “in‐plane aromaticity”, which only arises when the metal center bears a single electron 6. Structural motif D is known for the zirconium complex [Zr(η 3 ‐L)(Cl)(κ 2 ‐ N , N ‐ t BuNPN t Bu)] (L=(PN t Bu) 2 (N t Bu) 2 ), as described by Roesky and co‐workers 7.…”

“…These complexes are stabilized by "in-plane aromaticity", which only arises when the metal center bears a single electron. [6] Structural motif D is known for the zirconium complex [ZrA C H T U N G T R E N N U N G (h 3 -L)(Cl)(k 2 -N,N-tBuNPNtBu)] (L = (PNtBu) 2 A C H T U N G T R E N N U N G (NtBu) 2 ), as described by Roesky and co-workers. [7] By using carbodiimides as substrates, diverse reactivity patterns are possible.…”