Synthesis and X-ray crystal structures of imido and ureato derivatives of titanium(iv) phthalocyanine and their application in the catalytic formation of carbodiimides by metathesis from isocyanates

Abstract

The imido titanium phthalocyanine complex [PcTi(NDip)] (Dip = 2,6-diisopropylphenyl) 2a was synthesized from [PcTiO] 1 and one eq. of DipNCO. Due to the steric demand of the Dip group, addition of another isocyanate molecule to the Ti = N functionality of 2a does not occur even at high molar ratios of DipNCO. However, 1 reacts with 2 eq. of arylisocyanates containing sterically less demanding aryl groups producing N,N'-diarylureatotitanium(iv)phthalocyanines [PcTi{κ(2)-(NR)C(O)(N'R)}] (R = p-tolyl (Tol) 3a or mesityl (Mes) 3b). The N,N' coordination (III) of the ureato ligand in 3a and 3b was proven by a single set of resonances for the aryl groups in their (1)H-NMR spectra. An N,O coordination (IV) can therefore be excluded. This is also confirmed by the X-ray crystal structure of 3a. Upon heating [PcTiO] and an excess of aryl isocyanates for 6 days, a steady evolution of CO(2) was observed and a white precipitate, identified as the corresponding diarylcarbodiimides (V), could be isolated. Therefore this reaction was applied in the metathetic conversion of two isocyanate molecules into diarylcarbodiimides (V) and CO(2). Additionally, imido titanium Pc's 2b (R = tBu) and 2c (R = Mes) were prepared by a more general synthetic strategy, reacting the potassium salt of the ligand PcK(2) with appropriate imido titanium precursors.

Redox non-innocence permits catalytic nitrene carbonylation by (dadi)TiNAd (Ad = adamantyl)

“…THF present to form (dadi)Ti(THF) ( 1 -THF) and CO 2 is calculated to be exergonic by Δ G ° = –19.2 kcal mol –1 (Δ H ° = –34.6 kcal mol –1 , Δ S ° = –51.6 eu). 36,37 Decomposition is observed, perhaps indicative of additional reactivity from liberated CO 2 ; further study is warranted. In addition, attempts to generate other (dadi)TiNR ( 2 NR) species 23–25 led to unanticipated reactivity, hence the adamantyl group protects the imide in (dadi)TiNAd ( 2 -Ad) such that group transfer can be realized.…”

“…36,37 The released CNAd is also favored to scavenge any (dadi)Ti ( 1 ) and provide (dadi)Ti(CNAd) with = –22.1 kcal mol –1 . It is likely that the barrier for OAT from AdNCO is sluggish compared to dinitrogen loss from (dadi)Ti(N 3 Ad) ( 1 -N 3 Ad) to form (dadi)TiNAd ( 2 -Ad), because the latter is exergonic by = –69.0 kcal mol –1 .…”

Recent development of synthetic preparation methods for guanidines via transition metal catalysis

“…This reaction can be accelerated by many catalysts including metal carbonyls or compounds containing the PQO moiety. [112][113][114][115] However, only symmetric carbodiimide can be prepared by condensation of isocyanate. The aza-Wittig reaction between iminophosphoranes (Ph 3 PQNR) and isocyanate is then developed, in which iminophosphoranes are used as imino transfer reagents in the reaction with isocyanate.…”

Indium(III) phthalocyanine eka-conjugated polymer as high-performance optical limiter upon nanosecond laser irradiation

“…33 1 H NMR spectrum of polymer (4) in DMSO-d 6 (Figure S1, supplemental data) shows only one singlet at 8.29 ppm for the aromatic protons in the 1,4-positions '-peripheral' of the Pc macrocycle. 26,34 The 1 H NMR spectra display pure compound free from any impurities or by-products.…”